MEDICAL 
 
HUMAN PHYSIOLOGY, 
 
 STATICAL AND DYNAMICAL; 
 
 OB, 
 
 THE CONDITIONS AND COURSE 
 
 OF THE 
 
 LIFE Or MAN. 
 
 JOHH iLiAM DRAPER, 10., LL.D., 
 
 PROFESSOR OF CHEMISTRY AND PHYSIOLOGY IN THE UNIVERSITY OF NEW YORK; 
 AUTHOR OF A "HISTORY OF THE INTELLECTUAL DEVELOPMENT OF EUROPE," 
 
 WITH NEARLY 300 WOOD ENGRAVINGS. 
 
 SEVENTH EDITION. 
 
 NEW YORK: 
 
 HARPER & BROTHERS, PUBLISHERS, 
 
 FRANKLIN SQUARE. 
 
 1873. 
 
 R 
 

 Entered, according .tq Ac 
 
 t of Congress, in the year one thousand eight hundred and 
 
 ' 
 
 : H A IWVEy & jB TJJ ER . . . 
 in the Clerk's Office of the District Court of the Southern District of New York. 
 
PREFACE TO THE SEVENTH EDITION. 
 
 ANOTHER edition of this work being required, I take the opportunity 
 of returning my thanks to the medical profession and the public for 
 their continued favor. 
 
 A recent and thorough examination of it enables me to say that I be- 
 lieve it will be found to present the Science of Physiology in its most 
 modern form. 
 
 It is intended to give an exposition of the Physiology of Man, con- 
 sidered as an individual, and may be looked upon in that respect as a 
 work complete in itself. 
 
 But man is also a member of society, and, as has been remarked in 
 previous editions, History is in truth only a branch of Physiology. 
 This is the point of view from which I have regarded the subject in my 
 " History of the Intellectual Development of Europe," a work which, 
 taken together with this, is intended as a treatise on the entire range of 
 human relations, individual and social. 
 
 The remarkable favor with which that portion of the work has also 
 been received, both in America and Europe, several editions, transla- 
 tions, and reprints having been called for in the course of a few months, 
 satisfies me that the views here indicated meet with approval. 
 
 For the encouragement so shown to these works I again return my 
 sincere thanks. 
 
 New York, 1865. 
 
PREFACE TO THE SECOND EDITION. 
 
 Two years ago the first edition of this work was published. Since 
 that time several thousand copies have been disposed of; it has been in- 
 troduced as a text-book in many of our medical schools, and has been 
 very favorably received by the profession and the public. 
 
 I have therefore felt it necessary to submit it to a careful examination, 
 for the purpose of removing any errors it may contain, and improving it 
 as far as its present form admits. The revision it has undergone will, I 
 hope, make it worthy of the continued patronage of those who have hith- 
 erto shown it so much encouragement. 
 
 In these corrections I have availed myself of many of the suggestions 
 made in various reviews of the original work, and take this occasion to 
 express my thanks for the consideration shown toward it both in Amer- 
 ica and Europe. JSTo one knew better than myself how numerous were 
 its imperfections. The manner in which they have been overlooked has 
 served to convince me that those who were judges of the science, and 
 could deal authoritatively with it, were disposed to encourage any at- 
 tempt at its improvement, even though that attempt was marked by 
 many conspicuous shortcomings. 
 
 For doubtless they saw that this book aimed at much more than was 
 directly expressed upon its pages. To- treat Physiology as a branch of 
 Physical Science ; to exclude from it all purely speculative doctrines and 
 ideas, the relics of a philosophy (if such it can be called) which flourished 
 in the Middle Ages, though now fast dying out, and from which the more 
 advanced subjects of human knowledge, such as Astronomy and Chem- 
 istry, have long ago made themselves free to do this, amounts, in reality, 
 to a reorganization and reconstruction : a task of extreme difficulty, and 
 for complete success demanding the conjoint labors of many philosophers 
 and many physicians. 
 
 At the best, therefore, such an attempt, embracing the whole science, 
 made by a single individual, must needs be unsatisfactory, if any thing 
 like a rigorous criticism be applied. And yet it may be truly said that 
 the interest of the medical profession at the present time requires that 
 such encouragement as this work has received should be extended to 
 every undertaking of the kind. I hope that the success which has in 
 
VI PREFACE. 
 
 this manner attended my labors may prove an encouragement to others 
 to devote themselves with better results to a similar task. 
 
 To physicians I would earnestly address myself, in the hope of ob- 
 taining their continued aid and hearty patronage for every such attempt. 
 I would ask them why it is that we never hear of empiricism in Natural 
 Philosophy, Engineering, Astronomy ? Is it not because the principles 
 upon which those subjects rest have ceased to be speculative, and are 
 restricted to the demonstrative, the experimental, the practical? In 
 Philosophy, sects only arise while principles are uncertain ; in Medicine, 
 the quack only exists because there is a doubt. And considering the 
 condition to which the medical profession in our times has come, consid- 
 ering its decline in social estimation, and its shortcomings even in its 
 own judgment is it not the duty of every physician to inquire into the 
 causes of such a state ? 
 
 If a watch is to be mended, or a steam-engine repaired, do we not ap- 
 ply the principles of common sense to the case ? Who ever heard of sects 
 among watchmakers, or quacks among engineers ? If we will only apply 
 ourselves in a right spirit to its study, there is nothing more mysterious 
 or incomprehensible in a living organism than there is in such mechanical 
 contrivances. There is nothing in the structure of man which the intel- 
 lect of man can not understand. It is this, indeed, which constitutes his 
 chief glory, and makes him a worthy representative of the wisdom and 
 power of his Creator. 
 
 As in any mechanical contrivance, so in ourselves, imperfections and 
 disarrangements can only be repaired by a knowledge of the construction 
 of the parts, and their manner of working. The practice of Medicine 
 must rest on an exact Anatomy and a sound Physiology. As soon as 
 it is brought to this, empiricism will disappear of itself; it will need no 
 legal enactments, no ethical codes for its destruction. And for this rea- 
 son, if there were no others, it is the bounden duty of every physician to 
 encourage to the utmost within his own sphere of influence every attempt 
 to realize such a state of things. The encouragement which has been 
 given to this book I regard as a token that these principles are profound- 
 ly recognized by the medical profession of our country. 
 
 To students of Medicine I may be permitted, on this occasion, to say 
 a few words. It was chiefly with the hope of influencing them, and 
 guiding them into the paths of scientific Physiology, that I was first in- 
 duced to write this book. I would impress on them the importance of 
 cultivating habits of thought arising from the exact and practical sci- 
 ences. A great revolution is impending over the profession to which 
 they have devoted themselves. If they design to take a leading posi- 
 tion, not merely following it as an industrial pursuit, but regarding it as 
 one of the most dignified and noble of human occupations, they must 
 
PREFACE. Vll 
 
 prepare themselves in a manner consistent with the modes of thought 
 that must prevail in the times now quickly approaching. It may be too 
 much for us to expect that our contemporaries, who have been educated 
 in the ideas of the past, should unlearn so much of what they have learn- 
 ed, should in so many things begin their studies again ; but we may de- 
 mand a right preparation from those who are only now commencing. 
 In offering to them this book, I do not present an untried work. It is 
 the result of an experience in teaching for many years, an attempt to set 
 forth in plain language the great features of the science, and to give in 
 sufficient detail a representation of the present state of Physiology. For 
 the purpose of facilitating its study, I have divided the whole subject 
 into two branches, Statical and Dynamical. The expediency of this has 
 been impressed upon my attention by the necessity of conforming the 
 course of lectures of which these pages are an abstract, to the wants of 
 a medical class. The physician is chiefly concerned with the conditions 
 of life the organic functions, as digestion, respiration, secretion, etc. 
 The doctrines of development and the career of an organic form are of 
 less pressing interest ; but it was very soon found that other advantages 
 were derived from this subdivision, as might have been expected from its 
 conformity to the usages of writers on other branches of Physical Science. 
 
 To the general reader I may remark that I have endeavored to carry 
 put in the following pages the spirit of what is contained in the preced- 
 ing paragraphs. I have devoted more than twenty years not merely to 
 the study, but also to the experimental determination of physiological 
 questions, of which only a summary could here be offered. It was not 
 possible to give my own results more in detail in a formal text-book on 
 the entire science, but it may not perhaps be improper here to say that 
 opinions sometimes delivered in a few lines have cost me many days, or 
 even weeks, of expensive and laborious experiment. 
 
 Among the contemporary works I have used as authorities are Dr. 
 Carpenter's different treatises, Todd and Bowman's Physiological Anat- 
 omy, and Kirke's and Paget's Hand-book. As respects monographs, the 
 language of the authors themselves has been employed wherever it was 
 possible. A list of wood-cuts is annexed, in which reference is given to 
 the sources from which those not original have been derived. In the 
 explanation of these engravings the description used is that of the au- 
 thors themselves in most cases, and it is incorporated in the text, as, 
 for instance, in Book I., Chapter XVII., in which, the engravings being 
 derived from the Neurology of Leveille and Hirschfield, the accompany- 
 ing descriptions are merely translations from the French ; or, again, in 
 Book II., Chapter VII. , in Dr. Prichard's statements of the methods ot 
 examining the skull. With respect to the original engravings, it will be 
 seen that many have been obtained by the aid of microscopic photog- 
 
Vlll PREFACE. 
 
 raphy, the process having been so far improved by me as to be made very 
 available for these uses. For several of the specimens from which pho- 
 tographs have been taken I am indebted to Mr. Abbott. 
 
 In this work I have therefore endeavored to treat of man according to 
 the methods accepted in Physical Science, but still of man as an individ- 
 ual only. Physiology, however, in its most general acceptation, has an- 
 other department connected with problems of the highest interest. Man 
 must be studied not merely in the individual, but also in the race. 
 There is an analogy between his advance from infancy through child- 
 hood, youth, manhood, to old age, and his progress through the stages of 
 civilization. In the whole range of human study there are no topics of 
 greater importance, or more profound, than those dealt with in this sec- 
 ond department or division. It is also capable of being treated in the 
 same spirit and upon the same principles as the first. I 'have nearly 
 completed a volume, which will serve as a companion to this, in which 
 in that manner the subject is discussed, and the laws which preside over 
 the career of nations established, and would bespeak for it the considera- 
 tion of the reader. 
 
 JOHN W. DRAPER. 
 
 University, Neio York, July 1st, 1858. 
 
CONTENTS, 
 
 BOOK I. 
 
 STATICAL PHYSIOLOGY. 
 CONDITIONS OF LIFE. 
 
 CHAPTER I. 
 
 Conditions of Life. Nature and Sources of Substances supplied to the Body. Annual Quantities 
 required. Table of Physiological Standards. Animals do not create, but transform Substan- 
 ces. Properties and Quantities of Matters received by the System. Properties and Quantities 
 of those it restores. Heat of the Body arises from Combustion. Cooling Agencies in an An- 
 imal. Necessity of Repairs in the System. Physical Aspect of Man. The Soul. The Vital 
 Principle. Importance of Physical Science to Physiology Page 9 
 
 CHAPTER U. 
 OP FOOD. 
 
 The natural Subdivisions of Physiology. Of Food: its Sources and Classification its Value not 
 altogether dependent on its Composition. Of Milk: its Composition, and Use of its Water, 
 Casein, Sugar, Butter, and Salts. Variations in the Composition of Milk. Of Bread. Of 
 mixed Diets. Of the embryonic Food of Birds. Nutrition of carnivorous and herbivorous 
 Animals. Food formed by Plants and destroyed by Animals. Uses of mixed Food and Cook- 
 ing. Absolute Amount of Food 26 
 
 CHAPTER III. 
 
 OF DIGESTION. 
 TISSUE-MAKING OR HISTOGENETIC DIGESTION. 
 
 Nature of Digestion. The Mouth, Teeth, Stomach. The Salivary Glands. Different Kinds of 
 Saliva. Properties of mixed Saliva : its Quantity, Composition, and Functions. Relation of 
 the Salivary Glands and Kidneys. The digestive Tract. The Stomach. Gastric Juice. 
 Organs for its Preparation. Manner of producing Chyme. Influence of the Nerves. Artifi- 
 cial Digestion. Preparation and Properties of Pepsin. Regional and functional Divisions of 
 the Stomach in Animals and in Man. Object of Stomach Digestion. Peptones. Use of Salt. 
 Digestibility of various Articles of Food 40 
 
 CHAPTER IV. 
 
 OF CALORIFACIENT OR INTESTINAL DIGESTION. 
 
 Nature of Intestinal Digestion. Structure of the Intestine. Digestive Fluids of the Intestine. 
 The Pancreatic Juice. The Enteric Juice. Juice of Lieberkuhn. Secretion of Peyer's 
 . Glands. Bile. Digestion of the Carbohydrates and Hydrocarbons. Properties and Varie- 
 ties of Lactic Acid. Doctrine of the Effects of Acidity and Alkalinity of the Digestive Juices. 
 Illustration of Intestinal Digestion from the making of Wine. Making of Bread. Influence 
 of Heat over Ferments. Comparison of Gastric and Intestinal Digestion. Changes of the In- 
 testinal Contents. The Fcecal Residues 67 
 
X CONTENTS. 
 
 CHAPTER V. 
 OF ABSORPTION. 
 
 Double Mechanism for Absorption. The Lacteals and Veins. Lacteal Absorption. Descrip- 
 tion of a Vittus. Analogies in Plants. Introduction of Fat by the Villi. The Chyle. 
 Causes of the Flow of Chyle,. Intermediate Changes on its Passage to the Blood. Action of 
 Peyer's Bodies. Lymphatic Absorption. Nature of Lymph. Structure of the Lymphatic 
 System. Comparison of Chyle, Lymph, and Serum. Function of the Lymphatic System. 
 Production of Fibrin. Cutaneous Absorption. Causes of the Flow of Lymph. Apparent se- 
 lecting power of the Absorbents. Connection of the Lacteals and Lymphatics with the Locomo- 
 tive and Respiratory Mechanism Page. 84 
 
 CHAPTER VI. 
 ABSORPTION BY THE BLOOD-VESSELS. 
 
 Proof of Absorption by the Blood Capillaries. Occurs as a physical Necessity. Nature of Cap- 
 illary Attraction. Its Phenomena in the Rise and Depression of Liquids. Conditions for 
 producing a Flow in a Capillary Tube. Passage of Liquids through minute Pores. General 
 Propositions respecting Capillary Attraction. Endosmosis and Exosmosis. They depend on 
 Capillary Attraction. Force against which these Movements may take place. Illustrations of 
 selecting Power. General View of the entire Function of Absorption, lacteal and venous.... 102 
 
 CHAPTER VII. 
 OF THE BLOOD. 
 
 The Offices and Relation of Blood in the System. The Plasma and Cells. General Properties 
 and Composition of the Blood. Quantity in the Body. Coagulation. Blood-cells. Their suc- 
 cessive Forms. The perfect Cell. Hozmatin : its Properties. Number of Blood-cells. Plas- 
 ma : its Composition, and Variations of its Ingredients. Albumen, Fibrin, Fat, Sugar. Min- 
 eral Ingredients of the Cells and Plasma compared. Gases of the Blood. ^Changes occurring 
 during the Circulation. General Functions of the different Ingredients of the Blood. Introduc- 
 tion of Oxygen by the Cells. Their transient Duration Ill 
 
 CHAPTER Vm. 
 
 OF THE CIRCULATION OF THE BLOOD. 
 
 The Heart as a Machine. Inadequacy of Harvey's doctrine of the Circulation. Physical Prin- 
 ciple, of the Circulation ; applied in the case of a Nucleated Cell, Pervious Tissue, Motion of 
 Sap and of Blood. Dependence of the Circulation on Respiration. Forms of Circulation : 
 Systemic, Pulmonary, Portal. Description of the Heart ; its Movements.- Their Force, Num- 
 ber, and Value. Sounds of the Heart. Cause of its Contractions. Description of the Arte- 
 ries, Capillaries, Veins. Explanation of the Circulation of the Blood. Facts supporting it. 
 The First Breath , 129 
 
 CHAPTER DL 
 OF RESPIRATION. 
 
 Respiration introduces and removes aerial Substances. Coalescence of Respiratory and Urinary 
 Organs in Fishes. Physical and chemical Conditions of Respiration. Interstitial Movements 
 of Solids, Liquids, and Gases. Condition of Equilibrium in the Diffusion of Gases. Con- 
 densing Action of Membranes. Forms of Respiratory Mechanism. The Lungs of Man. 
 Three Stages in the Introduction of Air : Atmospheric Pressure, Diffusion of Gases, and 
 Condensation by Membranes. Exchange of Carbonic Acid for Oxygen. Divisions oftheCon- 
 
 . tents of the Lungs. Variations in the expired Air. Removal of Water. Effect ofirrespira- 
 bk Gases. Experiments qfRegnault and Reiset. Nervous Influence concerned in Respiration. 
 Results of Respiration 149 
 
CONTENTS. xi 
 
 CHAPTER X. 
 
 OF ANIMAL HEAT. 
 
 Participation of Organic Forms in external Variations of Temperature. Mechanism for counter- 
 balancing these Variations. Development of Heat in Plants at Germination and Inflorescence. 
 Its Cause is Oxidation. Connection of Respiration and Heat. Temperature of Man. His 
 Power of Resistance. The diurnal Variations of Heat. Connection of these Variations with 
 organic Periodicities. Annual Variations of Heat. Control over them by Food, Clothing, and 
 Shelter. Source of Animal Heat. Effect of Variations in the Food and in the respired Me- 
 dium, both as respects its future and Rarefaction. Hibernation. Starvation. Artificial Re- 
 duction of Temperature by Blood-letting. Principles of Reduction of Temperature. Radia- 
 tion. Contact. Evaporation. Their Balance with the Heating Processes. Local Varia- 
 tions eliminated by the Circulation. Control by the Nervous System. Its physical Nature. 
 Allotropism of Organic Bodies Page 175 
 
 CHAPTER XL 
 
 OF SECRETION. 
 SEROUS, MUCOUS, AND HEPATIC SECRETIONS. 
 
 Object of Secretion. Type of secreting Mechanism. Filtration and Cell Action. Of Serous 
 Membranes and their Secretions. Of Mucous Membranes and their Secretions. Of Hepatic Se- 
 cretions. The Liver: its Development and Structure. Source, Quantity, Composition, Uses, 
 and Flow of the Bile. Existence of biliary Ingredients in the Blood. Production of Sugar and 
 Fat in the Liver. Changes of the Blood-cells in it. General Summary of the four-fold Action 
 of the Liver: it produces Sugar and Fat, eliminates Bile, is the Seat of the final Destruction 
 of old Blood-cells, and of the Completion of new Ones. Of the ductless Glands. The Spleen: 
 its Functions 189 
 
 CHAPTER XII. 
 
 OF EXCRETION. 
 THE URINE, MILK, AND CUTANEOUS EXCRETIONS. 
 
 Secretion and Excretion. 
 
 Of the Kidney: its Structure and Functions. The Malpighian Circulation. The Urine: its In- 
 gredients, their Variations and Sources. Abnormal Substances in it. The Water and Salts 
 exude by Filtration. The Cells remove unoxidized Bodies. Manner of Removal of the Liquid 
 from the Malpighian Sac. 
 
 Of the Mammary Gland: its Structure. Colostrum and Milk. Ingredients of Milk and their 
 Variations. Influence of Diet. Inquiry into the Origin of the Ingredients of the Milk, its Fat, 
 Casein, Salts, Sugar. Manner of Action of the Gland by Strainage. 
 
 Of the Skin. Structure of its Epiderma and Derma. -Sudoriparous and Sebaceous Glands. 
 Nails. Hair. Ingredients of Perspiration. Exhalation: its Amount. Causes of the Vari- 
 able, Action of the Skin. Its Double Action. Absorption by the Skin. General Summary of 
 the Cutaneous Functions 213 
 
 CHAPTER XHI. 
 
 OF DECAY AND NUTRITION. 
 
 Of Decay : Loss of Weight in Starvation. Interstitial Death. Effect of Allotropism. 
 
 Of Nutrition: Nutrition for Repair and Nutrition for Remodeling, illustrated in the cases of Fat 
 and Bone respectively. 
 
 Of Fat: Its Peculiarities, modes of Occurrence, and Origin. Inquiry whether Animals ever form 
 Fat. Artificial Production of it. Animals both collect it and make it. Accumulation of it 
 expends Nitrogenized Tissue. Conditions of the Fattening of Animals. Summary of the 
 Sources, Deposit, and manner of Removal of Fat. Its partial Oxidations. Summary of its 
 Uses. Nitrogenized Nutrition. 
 
Xll CONTENTS. 
 
 Of Bone: The Skeleton. Structure and Chemical Composition of Bone. Sources of its Con- 
 stituents. The Process of Ossification. Experiments on the Growth of Bone. Influence of 
 Physical Agents on Development and Nutrition Page 243 
 
 CHAPTER XIV. 
 
 OF THE NERVOUS SYSTEM. 
 
 Divisions of the Nervous System. Cerebro-spinal and Sympathetic. Fibrous and Vesicular. 
 
 Structure and Functions of Nerve Fibres. Centripetal and Centrifugal. Rate of Conductibility. 
 
 Anatomical Examination of 'the Structure and Functions of Nerve Vesicles. They diffuse Influ- 
 ences, are Magazines of Force. Element of Time introduced by Registering Ganglia. Oxida- 
 tion necessary to Nerve Activity. Necessity of Repair and Rest. Electrical Examination of 
 the Functions of Vesicles. Anatomical and Electrical Examinations agree. 
 
 Automatic Nerve Arc. Cellated Nerve Arc. Multiple Arcs. Commissures. Registering Nerve 
 Arcs. Sensorium. Influential Arc. 
 
 Suggestions derived from cerebral Structure respecting the Soul. Its independent Existence and 
 Immortality. 
 
 Ideas of Time and Space. Objective, subjemive, and impersonal Operations. Vestiges of Im- 
 pressions and their Interpretation. Finite Nature of Knowledge. Mental Emotions 258 
 
 CHAPTER XV. 
 
 THE SPINAL AXIS. 
 
 Primitive Development of Nervous System. Itsflnal Condition in different Vertebrates. 
 
 The Spinal Cord: its Structure. Its Membranes. Its Thirty-one Pairs of Nerves. Proper- 
 ties of their Roots. Functions of the Cord. BeWs Discovery. Transmission of Longitudinal 
 and Transverse Influences. Reflex Action of the Cord. Nature of Reflex Action. Motor and 
 Sensory Tracts of the Cord. Summary of its Functions. 
 
 The Medulla Oblongata : its Structure and Functions. 
 
 The Pons Varolii : its Structure and Functions. 
 
 Dr. Carpenter's Views of the Analogy between the Spinal Cord of Vertebrates and the Ventral 
 Cord of Articulates 291 
 
 CHAPTER XVI. 
 
 OF THE BRAIN. 
 
 The Brain: its Structure. Its Motor and Sensory Parts, Hemispheres, and Commissures. 
 The Sensorium. Variations of the Hemispheres in Size and Weight. Instrumental Nature 
 of Cerebrum. The Cerebellum : its Structure and Functions. Co-ordinates muscular Motions. 
 Connection with Amativeness. Phrenology. Conditions of Action of Brain. 
 Symmetrical Doubleness of the Brain. Function of each Half, and of both conjointly. Independ- 
 ence and Insubordination of each Hemisphere. Double Thought. Alternate Thought. Senti- 
 of Pre-existence. Loss of Perception of Time 313 
 
 CHAPTER XVII. 
 
 OF THE CRANIAL NERVES AND THE GREAT SYMPATHETIC. 
 
 Enumeration of the Cranial Nerves. The Third Pair, or Oculo-motor. The Fourth Pair, orPa- 
 thetici. The Fifth Pair, or Trigemini. The Sixth Pair, or Abducentes. Illustrations of the 
 Third, Fourth, Fifth, and Sixth Pairs. The Seventh Pair, or Facial Illustration of the 
 Facial. The Ninth Pair, or Glosso-pharyngeal. Illustration of the Glosso-pharyngeal. The 
 Tenth Pair, or Pneumogastric. Illustration of the Pneumogastric. Illustration of the Laryn- 
 geals. The Eleventh Pair, or Spinal Accessory. The Twelfth Pair, or Hypoglossal. Il- 
 lustration of the Hypoglossal. 
 
 The Phrenic Nerve. 
 
 Of the Great Sympathetic System. Position, Structure, and Origin of the Sympathetic. Its Re- 
 lation with the Pneumogastric. Its Connection with the Spinal System. Its Plexuses. Its 
 
CONTENTS. Xlil 
 
 Ganglia. They are Reservoirs of Force. Summary of the Functions of the Sympathetic. 
 Illustration of the Sympathetic. The Abdominal Plexuses. 'The Solar Plexus. TheMesen- 
 teric Plexuses Page 333 
 
 CHAPTER XVHI. 
 
 OF THE VOICE. 
 
 Origin of the Voice. Comparative Physiology of Noise, Song, Voice. Distinction between Song 
 and Speech. The Larynx, and its Action in Singing. Mutter's Explanation of the Action of 
 the Vocal Organs. Speaking Animals and Machines. 
 Nature of Words and their constituent Sounds. Vowels and Consonants. Whispering. Use 
 
 of the Voice of Animals. 
 
 Of Languages: their Duration, Character, History. Registry of Sounds by Writing and Print- 
 ing. Musical Signs. Alphabetic Writing 351 
 
 CHAPTER XIX. 
 
 OF HEARING. 
 
 The Senses : General Remarks upon. Five Organs of Sense. Necessity of Apparatus for the 
 Appreciation of Time, Space, Pressure, Temperature, and Chemical Qualities. 
 
 Of Hearing. General Structure of the Organ of Hearing. Physical Peculiarities of Sounds, In- 
 tensity, Time of Vibration, and Quality. The Tympanum, Cochlea, and Semicircular Canals 
 are for the Appreciation of these peculiarities. 
 
 Structure and Functions of the Tympanum, or Measurement of Intensity. 
 
 Structure of the Cochlea, its Spiral Lamina and Scalar. Measures the Time of Vibration. Ac- 
 complishment of Interference in the Scalce. Comparative Anatomy of the Cochlea. 
 
 Structure of the Semicircular Canals. They estimate the Quality of Sounds. 
 
 Comparative Anatomy of the Auditory Mechanism. Its Progress in Development. Imperfection 
 of the Doctrine of Means and Ends 359 
 
 CHAPTER XX. 
 
 OF VISION. 
 
 Analogy between Sound and Light. Comparative Anatomy of Vision. Perception of Warmth. 
 Structure of Ocelli. Use of Lenses. Physical Principle of the Organ of Vision. 
 
 Description of the Human Eye. Optical Action of its Parts. Spherical and Chromatic Aberra- 
 tion. Receiving Screen of the Eye is the black Pigment. Long and short Sight, and their 
 Correction. Limits of Vision are included in one Octave. Limit in estimating the Brightness 
 of Light. 
 
 Nervous Mechanism of the Eye : its Structure and Functions. Manner of Perception by the 
 Retina. The black Pigment absorbs the Rays. Single and double Vision. Duration of Im- 
 pressions. Ocular Spectra. Erect Vision. Idea of the Solidity of Bodies. Hypothesis of 
 the Action of the Retina. 
 
 Accessory Apparatus of the Eye. The Eyebrows. Eyelids. Lachrymal Apparatus. Muscles 
 of the Ball 379 
 
 CHAPTER XXI. 
 OF CEREBRAL SIGHT OR INVERSE VISION. 
 
 Difference between ordinary Vision and cerebral Sight. Inverse Vision depends on the Vestiges 
 of Impressions existing in the Brain. 
 
 Condition of our perceiving these Impressions is that they must be equal in Intensity to present 
 Sensations. Two Methods of accomplishing this Equalization : 1st, by re-enforcing the old Im- 
 pressions ; 2d, by diminishing the present Sensations. 
 
 Emergence of old Impressions in Sleep, Fever, Death. Artificial Emergence of such Vestiges by 
 Protoxide of Nitrogen, Opium, etc. 
 
 Cerebral Sight used teleologically to indicate the Immortality of the Soul. 401 
 
CONTENTS. 
 
 CHAPTER XXII. 
 
 OF TOUCH, AND THE DETERMINATION OF PRESSURES AND TEMPERATURES. 
 Functions of the tactile Mechanism : its Structure. Regions of different Sensitiveness. Compar- 
 ative Physiology of Touch. Estimate of physical Qualities. 
 Perception of Temperature. Subjective Sensations of Temperature Page 417 
 
 CHAPTER XXHL 
 
 OF SMELLING, AND THE MEANS OF DISTINGUISHING GASEOUS AND VAPOROUS SUB- 
 STANCES. 
 
 Structure of the Organ of Smell. Its proper Instrument the First Pair of Nerves. Limited Re- 
 gion of Smell. Conditions of its perfect Action. Duration of Odors. Their localization. 
 Subjective Odors 423 
 
 CHAPTER XXTV. 
 OF TASTE. 
 
 Conditions for Taste. Structure and Functions of the Tongue. Tactile and Gustative Regions 
 of the Tongue. Complementary Tastes. Subjective Tastes 427 
 
 CHAPTER XXV. 
 
 OF ANIMAL MOTION. 
 
 Ciliary and Muscular Motion. Description of Cilia and the Manner of Action. 
 
 Muscular Fibre : its Forms, Non-striated and Striated. Muscle Juice. Manner of Contraction 
 of a Muscle : its supply of Blood-vessels and Nerves. Its Chemical Change during Activity. 
 Its Rise of Temperature. Effect of Electrical Currents. Duration of Contractility. 
 
 Doctrine that Muscle Contraction is the result of Muscle Disintegration. Manner in which ordi- 
 nary Cohesion is brought into play. Manner of Restoration. Removal of the Heat and Oxi- 
 dized Bodies. 
 
 Rigor Mortis. Connection of Muscle for Locomotion. Of Standing. Walking. Running. 431 
 
 BOOK II. 
 
 DYNAMICAL PHYSIOLOGY. 
 COURSE OF LIFE. 
 
 CHAPTER I. 
 OF THE PRINCIPLE OF ORGANIZATION, OR PLASTIC POWER. 
 
 Remarks on the Subdivision of Physiology. 
 
 Career of an Organic Form. Three Modes of Development. 
 
 Inquiry respecting the special Principle of Organization. Illustration from the Growth of a Plant 
 
 in Darkness and Light. Inference respecting Plastic Power : its Nature and Properties. 
 
 Of the ordinary Growth of a Plant, and the Sources from which its Materials are derived. 
 Relation of all Organisms to each other. 
 Correction of the Doctrine of a Plastic Power, from Considerations regarding the Individuality 
 
 of a Plant. Plants are Operations, not Individuals. Physical Illustration of this View. 
 Conclusion respecting the Nature of the Plastic Power: that it is a continued Manifestation of an 
 
 antecedent physical Impression ^56 
 
CONTENTS. XV 
 
 CHAPTER H. 
 OF THE INFLUENCE OF PHYSICAL AGENTS ON THE ORGANIC SERIES. 
 
 Of the Geography of Plants: their horizontal and vertical Localization. Influence of Heat on or- 
 ganic Distribution : isotheral and isochimenal Conditions. Effects of Variations in the Dens- 
 ity of the Air, Moisture, Soil, Sunlight, Length of Day. Definite Quantity of Heat required 
 by Plants. 
 
 Secular Perturbations in the Species of Plants. Long Periods of Time required. Secular geo- 
 logical Changes. 
 
 Inverse Problem of the Investigation of the Earth's History from her fossil Flora. Two great 
 terrestrial Epochs : Change in the Constitution of the Air, and Localization of Organisms 
 through Decline of the Earth's Interior Heat. 
 
 Difference between abrupt and gradual Impressions. Invariable Causes may produce abrupt 
 Crises. 
 
 Extension of the above Principles to the Case of Animals. Case of the Inca Indians. 
 
 General Argument supported by the Extinction of Forms. Development is under the Influence of 
 Law. Rudimentary Organs and Excesses of Development. The Idea of Development by 
 Law consistent with natural Facts Page 472 
 
 CHAPTER HI. 
 
 OF THE ORGANIC CELL : ITS DEVELOPMENT. REPRODUCTION, AND DIFFERENTIATION 
 OF STRUCTURE AND FUNCTION. 
 
 Simple and Nucleated Cells. The Simple Cell: its Parts and Functions. The Nucleated Cell: 
 its Parts and Functions. Activity of the Nucleus. Other Forms of Cells. Cells arise by 
 Self-origination and Reproduction. Reproduction by Subdivision and Endogenously. 
 
 The Animal Cell. Forms of Cellular Tissue. Forms of Vascular Tissue. Spiral Vessels, 
 Ducts, etc. 
 
 Differentiation of Cells. Acquisition of new Functions. Differentiation of the Animal Cell. 
 Depends on Physical Causes. Influence of Heat and Air. Epoch of Differentiation.... 492 
 
 CHAPTER IV. 
 OF REPRODUCTION AND DEVELOPMENT. 
 
 Relation of Organic Beings : they come from a similar Cell and develop to different Points. 
 Their Division by Classification is fictitious. Development and Differentiation. Homogenesis 
 and Heterogenesis. They depend on physical Conditions. The reproductive State closes De- 
 velopment. 
 
 Development is from the General to the Special. Law of Von Bar. Invariable Sequence in 
 Differentiation. 
 
 OF REPRODUCTION: 1st. By Generation. Conjugation and Filaments. The Sperm-cell: its 
 Production. Spermatozoa. The Germ-cell: its Production. 
 
 Ovum in the Ovary. Its Structure. Corpus Luteum. 
 
 Ovum in the Oviduct. Mulberry Mass. Germinal Membrane. The Chorion. 
 
 Ovum in the Uterus. Membrana Decidua. Placenta. Development of the Embryo. Types 
 of Nutrition. Of Conception. Of Gestation. Of Parturition. Influence of both Parents. 
 
 2d. By Gemmation. Budding of Plants and Animals. Of Grafting. Limit of Gemmation. 
 Influence of Temperature on Gemmation. 
 
 Alternations of Generation. Its Explanation 505 
 
 CHAPTER V. 
 
 THE GROWTH OF MAN. 
 
 Infancy. Weight and Size of the Infant. Weight and Size at subsequent Periods. Develop- 
 ment of the Intellect. Maturity of Man. Tendency to Crime. Maxima of Physical and Men- 
 tal Strength. 
 
XVI CONTENTS. 
 
 Mental and Physical Decline. Mortality at different Periods of Life. Comparative Structure, 
 
 Functions, and Mortality of the two Sexes. 
 Artificial Epochs of Life. Gradual Change in the Mental Qualities. Independent Existence of 
 
 the Soul. '. Page 538 
 
 CHAPTER VI. 
 
 OF SLEEP AND DEATH. 
 
 Causes of the Necessity for Sleep. Its Duration and Manner of Approach. Manner of Awak- 
 ing. Cause of Night-sleep. Increased Warmth required. Connection of Sleep and Food. 
 
 Of Dreams: their Origin and Phenomena. Somnambulism. Nightmare. 
 
 Of Death. Old Age. Internal Causes of Decline. Death by Accident and by Old Age. The 
 Hippocratic Face. Final Insensibility 551 
 
 CHAPTER VII. 
 
 ON THE INFLUENCE OF PHYSICAL AGENTS ON THE ASPECT AND FORM OF MAN AND 
 ON HIS INTELLECTUAL QUALITIES. 
 
 Differences in Form, Habits, and Color of Men. Ideal Type of Man. Its Ascent and Descent. 
 Causes of these Variations. 
 
 Doctrine of the Unity of the Human Race. Doctrine of its Origin from many Centres. 
 
 Influence of Heat on Complexion. Cause of Climate Variations. Influence of Heat illustrated 
 by the cases of the Indo-Europeans, the Mongols, the American Indians, and the Africans. 
 Distribution of Complexion in the Tropical Races. 
 
 Variations in the Skeleton. Four Modes of examining the Skull. Connection of the Shape of 
 the Skull and Manner of Life. Physical Causes of Variation of the Skull. 
 
 Influence of the Action of the Liver on Complexion. Influence of the Action of the Liver on the 
 Form of the Skull. Base Form of Skull arising from Low as well as High Temperatures. 
 Disappearance of the Red-haired and Blue-eyed Men in Europe. 
 
 The Intellectual Qualities of Nations. Synthetical Mind of the Asiatic. Analytical Mind of the 
 European. Their respective Contributions to Human Civilization. Spread of Mohammedan- 
 ism in Africa. Spread of Christianity in America. Manner of the Progress of all Nations 
 in Civilization 563 
 
 CHAPTER VIH. 
 SOCIAL MECHANICS. 
 
 Comparative Sociology. Connection of Structure and Habit. Connection of History and Phys- 
 iology. Insect Society. Descartes' 's Doctrine that Insects are Automata. Necessity of a 
 Mechanism of Registry for Instinct, Reason, and Civilization. 
 
 Nature of Man. Influence of surrounding Circumstances on him. Dejiniteness of his Career. 
 
 GENERAL FACTS OP EUROPEAN HISTORY. Introduction of Egyptian Civilization into Europe. 
 The Registry of Facts by Writing. Egyptian Philosophy in the Greek Schools. The Persian 
 Empire: its Influence. Analytical Quality of the European Mind. Influence of the Greek 
 Schools on modern Philosophy. 
 
 Origin of European Commerce. Discovery of the Straits of Gibraltar. Macedonian Campaign. 
 Reconstruction of Monarchy in Egypt. 
 
 The Roman Empire : its centralizing and civilizing Power. Fall of European Paganism. In- 
 fluence of the Christian Church. The Sabbath Day. The Reformation. 
 
 Influence of Mohammedanism on Europe. The Arab physical Science. The Crusades. Dis- 
 covery of America by the Spaniards. Fall of the Spanish Power. 
 
 Later Mental Changes in Europe. Disappearance of Credulity. Physiological Change of Eu- 
 ropeans. Effect of Mohammedanism in changing the Centre of Intellect of Europe. Analyt- 
 ical Tendency of the European Mind. Advantages resulting therefrom 602 
 
LIST OF ILLUSTRATIONS. 
 
 l! The lower Jaw Wilson 41 
 
 2. Section of Stomach Author 42 
 
 3. Digestive Tract Harrison 48 
 
 4. Mucous Membrane of Stomach Wilson 50 
 
 5. Stomach Follicles and Tubes Todd and Bowman 50 
 
 6. Section of Stomach Tubes " " 51 
 
 7. The Hydra 51 
 
 8. Digestive Tract of Beetle Milne Edwards 58 
 
 9. Mucous Membrane of Beetle's Stomach Photograph by Author 58 
 
 10. Digestive Tract of Fowl " " 58 
 
 11. Stomach of African Ostrich Cuvier 59 
 
 of Dormouse " 59 
 
 ofCapeHyrax " 59 
 
 ofPorqppine " 59 
 
 ofPorpoise " 59 
 
 ofKangaroo " 59 
 
 12. 
 13. 
 14. 
 15. 
 16. 
 
 17. of a Ruminant " 59 
 
 18. Posterior View of human Stomach Retzius 61 
 
 19. Posterior View of Duodenum Bourgery 68 
 
 20. Diagram of Brunner's Glands Author 69 
 
 21. Diagram of Follicles of Lieberkuhn " 69 
 
 22. Peyerian Glands Thomson 70 
 
 23. Section of Heum Wall Kolliker 85 
 
 24. Villi of Monkey Camera Lucida by Author 85 
 
 25. Villi of Duodenum Author 85 
 
 26. ViUi of Jejunum " 85 
 
 27. Section of Villi " 86 
 
 28. Villi of Squirrel " 88 
 
 29. Principle of Venturi " 90 
 
 30. Thoracic Duct Wilson 90 
 
 31. Chyle Corpuscles with Blood-cells Photograph by Author 93 
 
 32. " " " Water Author 94 
 
 33. " " " Acetic Acid " 94 
 
 34. Lymphatics of large Intestine Bourgery 97 
 
 35. Diagram of Lymph Gland Goodsir 97 
 
 36. Evolution of Lymph Cells " 97 
 
 37. Capillary" Depression of a Liquid Author 104 
 
 38. Capillary Elevation of a Liquid " 104 
 
 39. Passage of Water through a Crevice " 105 
 
 40. Endosmometer " 106 
 
 41. Selecting Power of a Membrane " 108 
 
 42. Human Blood-cells Photograph by Author 116 
 
 43. Elliptic Blood-cells " " 116 
 
 44. Action of Water on elliptic Cells " " 116 
 
 45. Action of Acetic Acid " " 117 
 
 > 46. Reptile Blood-cells " 117 
 
 47. Human Blood-crystals Lehmann 119 
 
 A 
 
LIST OF ILLUSTKATTONS. 
 
 PAS! 
 
 48. Blood-crystals of Guinea-pig Lehmann 119 
 
 49. Blood-crystals of Squirrel " 120 
 
 50. Stellated Blood-cells Photograph by Author 127 
 
 61. Capillary Motion Author 131 
 
 52. Motion in Cells " 132 
 
 53. Circulation in Tradescantia " 132 
 
 54. Diagram of Fish Circulation Milne Edwards.... 135 
 
 55. Rudimentary Heart Thomson 135 
 
 56. Diagram of single Heart Roget 136 
 
 67. Heart of Dugong Home 136 
 
 58. Human Heart on right Side Wilson 136 
 
 59. Human Heart on left Side " 137 
 
 60. Muscular Fibres of Heart ...Author 137 
 
 61. Vessels of Mucous Membrane of Stomach " 142 
 
 62. Vessels of Villi of Duodenum " 142 
 
 63. Capillary Circulation of Frog's Foot Wagner 142 
 
 64. White Corpuscles in the still Layer " 143 
 
 65. Valves of Veins open Roget 143 
 
 66. Valves of Veins shut " 143 
 
 67. Diffusion of Gases Author 152 
 
 68. Diffusion through Earthenware " 152 
 
 69. Diffusion through India-rubber " 153 
 
 70. Passage through Films " * 153 
 
 71. Force of Filtration " 155 
 
 72. Air Vesicles of Insect Fabricius 157 
 
 73. Spiracle of Insect Photograph by Author 157 
 
 74. Air Sac of Fish Blasius 157 
 
 75. Lung of Reptile Flourens 158 
 
 76. Lungs of Frog " 159 
 
 77. Human Air-tubes Wagner 160 
 
 78. Heart and Lungs " 160 
 
 79. Capillaries on Lungs Rathke 160 
 
 80. Mechanism of Respiration Author 161 
 
 81. Experiments on Respiration Regnault and Reiset 170 
 
 82. Hepatic Coecum of Cray-fish Leidy 198 
 
 83. Bile-ducts entering the Duodenum Paxton 199 
 
 84. Hepatic Veins in the Lobules of the Liver Kiernan 199 
 
 85. Origin of Hepatic Veins " 200 
 
 86. Origin of Bile-ducts " 200 
 
 87. Hepatic Cells " 201 
 
 88. Section of Kidney .....Wilson 215 
 
 89. Diagram of Malpighian Corpuscle Kolliker 216 
 
 90. Glomerulus of horse " 216 
 
 91. Cilia on Uriniferous Tube Bowman 216 
 
 92. Diagram of Malpighian Circulation " 217 
 
 93. Malpighian Tuft Isaacs .' 217 
 
 94. Ruptured Malpighian Coil of Deer " 217 
 
 95. Nucleated Cells on Coil " 217 
 
 96. Development of Mammary Gland Kolliker 225 
 
 97. Section of human Mamma 225 
 
 98. Colostral Corpuscles Photograph by Author 225 
 
 99. Epidermis of Dog " " 235 
 
 100. Section of Skin Kolliker 235 
 
 101. Under Surface of Cuticle Todd and Bowman 235 
 
 102. Papillae of Palm " " 235 
 
 103. Skin of Palm , " 236 
 
LIST OF ILLUSTRATIONS. 3 
 
 104. Section of Hair Todd and Bowman 236 
 
 105. Transverse Section of Hair Photograph by Author 237 
 
 106. Sudoriparous Gland Wagner 237 
 
 107. Fat-cell Schwann 246 
 
 108. Adipose and areolar Tissue Berres 246 
 
 109. Transverse Section of Bone Photograph by Author 254 
 
 110. Lucunae and Canaliculi Author 254 
 
 111. Ossifying Cartilage Kolliker : 255 
 
 112. Ossifying Cartilage Photograph by Author 256 
 
 113. Ossifying Femur Kolliker 256 
 
 114. Axis Cylinder Author 261 
 
 115. Subdivision of Nerve Fibres Kolliker 262 
 
 116. Nerve-cells " 263 
 
 117. Bipolar Nerve-cells " 264 
 
 118. Multipolar Nerve-cell Author 264 
 
 119. Nerve Cells and Tubes Wagner 264 
 
 120. Nerve Cells and Tubes Purkinje.. 264 
 
 121. Dorsal Ganglion of Mouse Valentin 267 
 
 122. Simple automatic Arc Author 277 
 
 123. Simple cellated Arc " v 278 
 
 124. Multiple Nerve Arcs " 278 
 
 125. Commissured Arcs " 279 
 
 126. Nervous System of Larva of Sphinx Ligustri ....Newport 279 
 
 127. Nervous System of Pupa of Sphinx Ligustri " 279 
 
 128. Nervous System of Imago of Sphinx Ligustri.... " 279 
 
 129. Nervous System of Asterias Tiedemann. 279 
 
 130. Nervous System of Patella Cuvier 279 
 
 131. Nervous System of Octopus " 279 
 
 132. Nervous System of Aplysia " 280 
 
 133. Registering Nerve Arc Author . 281 
 
 134. Suppression of Centrifugal Branch....' " 281 
 
 135. Influential Arc 282 
 
 136. Primitive Trace Bischoff 293 
 
 137. Origin of Brain on Spinal Cord " 293 
 
 138. Spinal Cord Photograph from Leveille 295 
 
 295 
 
 " " 296 
 
 " " 297 
 
 " " . 297 
 
 u n 297 
 
 144. Portion of Cord of Spirostreptus Newport : 301 
 
 145. Front of Medulla Oblongata Photograph from Leveille 305 
 
 146. Back of Medulla Oblongata " " " 305 
 
 147. Interior of Medulla and Pons " " " 305 
 
 148. Posterior View of Medulla Oblongata Todd and Bowman 306 
 
 149. Nervous System of Larva of Sphinx Ligustri ....Newport 308 
 
 150. Ganglion of Polydesmus Maculatus " 309 
 
 151. Ganglion of Centipede " 312 
 
 152. Thoracic Portion of Cord of Sphinx Ligustri.... " 313 
 
 153. Respiratory and locomotive Ganglia " 313 
 
 154. External lateral Face of Brain Photograph from Leveille 316 
 
 155. Superior Aspect of Brain " " " 316 
 
 156. Internal lateral Face of Brain " " " 317 
 
 157. Base of Brain Photograph by Author 317 
 
 158. Diagram of Brain Mayo 318 
 
 159. The Motor Tract..., ...Bell... 319 
 
 139. Section of Spinal Cord 
 
 140. Spinal Dura Mater 
 
 141. Origin of anterior Roots of Nerves 
 
 142. Origin of posterior Roots , 
 
 143. Origin of both Roots 
 
LIST OF ILLUSTRATIONS. 
 
 FIG. 
 
 160. 
 
 161. 
 
 162. 
 
 163. 
 
 164. 
 
 165. 
 
 166. 
 
 167. 
 
 168. 
 
 169. 
 
 170. 
 
 171. 
 
 172. 
 
 173. 
 
 174. 
 
 175. 
 
 176. 
 
 177. 
 
 178. 
 
 179. 
 
 180. 
 
 181. 
 
 182. 
 
 183. 
 
 184. 
 
 185. 
 
 186. 
 
 187. 
 
 188. 
 
 189. 
 
 190. 
 
 191. 
 
 192. 
 
 193, 
 
 194. 
 
 195. 
 
 196. 
 
 197. 
 
 198. 
 
 199. 
 
 200. 
 
 201. 
 
 202. 
 
 203. 
 
 204. 
 
 205. 
 
 206. 
 
 207. 
 
 208. 
 
 209. 
 
 210. 
 
 211. 
 
 212. 
 
 213. 
 
 214. 
 
 215. 
 
 PAGE 
 
 The Sensory Tract Bell 320 
 
 Nerves of the Orbit Photograph from Leveille 334 
 
 Nerves in the Orbital Cavity 335 
 
 Diagram of the Fifth Nerve " 335 
 
 335 
 
 .. 336 
 
 Ganglion of Gasser 
 
 The Fifth Nerve 
 
 The inferior Maxillary 
 
 The Facial Nerve 
 
 The Glosso-pharyngeal Nerve. 
 
 Diagram of Anastomoses 
 
 The left Pneumogastric 
 
 Pulmonary Ganglia 
 
 The inferior Laryngeals......... 
 
 The Hypoglossal Nerve......... 
 
 The Phrenic Nerve... 
 
 337 
 
 339 
 
 339 
 
 341 
 
 -342 
 
 342 
 
 343 
 
 344 
 
 Relation of the Sympathetic and Spinal Todd and Bowman 345 
 
 The Great Sympathetic Photograph from Leveille. 
 
 Abdominal Plexuses " " " 
 
 The Solar Plexus " " " 
 
 The Mesenteric Plexuses " " " 
 
 Spiracle of Insect : .Photograph by Author 
 
 Profile of Larynx Leveille 
 
 Posterior View of Larynx " 
 
 External, middle, and internal Ear " 
 
 Tympanic Cavity " 
 
 Facial in the Aqueduct of Fallopius " 
 
 Interior of Cochlea 
 
 Section of Cochlea 
 
 Magnified Section of Cochlea 
 
 Cochlear Nerve 
 
 Auditory Nerve 
 
 Ossicles and their Muscles 
 
 Tympanic Face of Labyrinth " 
 
 Cranial Face of Labyrinth " 
 
 Interior of ^Labyrinth " 
 
 Interior of Labyrinth " 
 
 Profile of Eye " , 
 
 Front View of Eye " 
 
 Section of Eye ,. " , 
 
 Veins of the Choroid " 
 
 Arteries of the Choroid " , 
 
 Yellow Spot of Soemmering Soemmering 
 
 Membrane of Jacob Jacob 
 
 Simple Papillae , Todd and Bowman 
 
 Compound Papillae Kolliker 
 
 Olfactory Nerve Leveill^ 
 
 Olfactory Nerve " 
 
 The Tongue Photograph from Leveille, 
 
 Ciliated Cells Author , 
 
 Ciliated Animalcule Ehrenberg 
 
 Hydra walking Trembley , 
 
 Striated muscular Fasciculi Photograph by Author , 
 
 Human Sarcolemma Bowman 
 
 Sarcolemma of Fish , " 
 
 Ultimate muscular Fibre Photograph by Author 
 
 Unstriped muscular Fibre Author 
 
 , 348 
 , 349 
 350 
 350 
 352 
 354 
 354 
 362 
 362 
 362 
 369 
 369 
 370 
 370 
 370 
 370 
 374 
 374 
 375 
 375 
 383 
 383 
 383 
 385 
 385 
 386 
 390 
 420 
 420 
 424 
 424 
 428 
 431 
 432 
 432 
 433 
 433 
 433 
 433 
 435 
 
LIST OF ILLUSTEATIONS. 5 
 
 216. Unstriped Fibres in Acetic Acid Author 435 
 
 217. Muscle Cells Kolliker 435 
 
 218. Muscular Fasciculi torn in Discs Bowman 436 
 
 219. Transverse Section of human Muscle " 437 
 
 220. Transverse Section of Muscle of Teal " 437 
 
 221. Non-fibrillated Insect Fasciculi Photograph by Author 437 
 
 222. Non-fibrillated Insect Fasciculi* " " 437 
 
 223. Contracting Muscle of Dytiscus Bowman 438 
 
 224. Sarcolemma raised in BulL *. Todd and Bowman 438 
 
 225. Fasciculus contracting " " 439 
 
 226. Distribution of muscular Capillaries Berres 439 
 
 227. Muscular Arteries and Veins Kolliker 440 
 
 228. Distribution of muscular Nerves Burdach 440 
 
 229. Volume of contracting Muscle Author 450 
 
 230. Hasmatococcus Binalis Hassall -494 
 
 231. Conferva glomerata Mohl 495 
 
 232. Simple Cellular Tissue Photograph by Author 497 
 
 233. Muriform Cellular Tissue " " 497 
 
 234. Fibro-cellular Tissue " " 497 
 
 235. Spiral Vessels of Cactus " - " 498 
 
 236. Spiral Vessels of Banana " " 498 
 
 237. Woody Fibre of Pine " " 498 
 
 238. Yellow Fibrous Tissue ; Author 499 
 
 239. White Fibrous Tissue " 499 
 
 240. Areolar Tissue " 499 
 
 241. Development of Frog Rusconi 509 
 
 242. Frog ; 510 
 
 243. Development of Crab Couch 510 
 
 244. Development of Insects Straus Durckheim 510 
 
 245. Zygnema Quinmum Kiitzing 515 
 
 246. Testis Arnold 517 
 
 247. Development of Spermatozoa Wagner 518 
 
 248. Section of Ovary Kolliker 521 
 
 249. Section of Graafian Vesicle Von Bar 521 
 
 250. Ovum Barry 521 
 
 251. Diagram of Graafian Vesicle ..Kirkes and Paget 521 
 
 252. Corpora Lutea Patterson and Montgomery 522 
 
 253. Ovarian Ovum 523 
 
 254. Ovarian Ovum 523 
 
 255. Segmentation of Ovum Bischoff 524 
 
 256. Segmentation of Ovum Kolliker andBagg.1 524 
 
 257. Uterine Tubes Weber 525 
 
 258. Layers of Germinal Membrane Bischoff 527 
 
 259. Primitive Groove " 527 
 
 260. Origin of Brain " 528 
 
 261. Production of Vessels Wagner 529 
 
 262. Production of Lymphatics Kolliker 529 
 
 263. Rudimentary Heart Thomson 529 
 
 264. Foetal Heart Von Bar 530 
 
 265. Hydra budding Trembley 534 
 
 266. Newton Photograph from Principia 563 
 
 267. Australian D'Urville. Photographed from Prichard 563 
 
 268. Australians D'Urville. " " 564 
 
 269. Brahmin Branwhite. " " " 573 
 
 270. Chinese " " 574 
 
 271. Kamtschatdale... " " " .. 575 
 
6 LIST OF ILLUSTRATIONS. 
 
 no. PIOB 
 
 272. Sac Indian Catlin. Photographed from Pilchard 575 
 
 273. Cherokee Indian Catlin. 
 
 274. California Indian Choris. 
 
 275. California Indians Choris. 
 
 276. Abyssinian D'Abbadie. 
 
 576 
 
 576 
 
 576 
 
 ..... 577 
 
 577 
 
 .. 578 
 
 277. Native of Madagascar 
 
 278. Native of Mozambique " 
 
 279. Negro of Guinea Author 579 
 
 280. Philippine Negro Choris. Photographed from Prichard 579 
 
 281 . Skeleton of Man, Chimpanzee, and Orang Photograph by Author 581 
 
 282. Skull of European ....Prichard 582 
 
 283. Skull of Negro " 582 
 
 284. Skull of Chimpanzee " 582 
 
 285. Skull of Orang " 582 
 
 286. Caucasian Skull " 583 
 
 287. Mongol Skull " 583 
 
 288. Negro Skull " 584 
 
 289. Titicacan Skull " 584 
 
 290. Base of human Skull " 584 
 
 291. Base of Orang Skull " 584 
 
 292. Esquimaux Skull " 585 
 
 293. Negro Skull.. Author 587 
 
 294. Trench Skull " 587 
 
 295. Cephalic Ganglia Newport 607 
 
 296. Thoracic Portion of Ventral Cord " 607 
 
HUM AIT PHYSIOLOGY, 
 
 STATICAL AND DYNAMICAL 
 
HUMAI PHYSIOLOGY. 
 
 BOOK FIRST. 
 
 STATICAL PHYSIOLOGY, 
 
 CONDITIONS OF LIFE. 
 
 CHAPTER I. 
 
 Conditions of Life. Nature and Sources of Substances supplied to the Body. Annual Quantities 
 required. Table of Physiological Standards. Animals do not create, but transform Substan- 
 ces. Properties and Quantities of Matters received by the System. Properties and Quantities 
 of those it restores. Heat of the Body arises from Combustion. Cooling Agencies in an An- 
 imal. Necessity of Repairs in the System. Physical Aspect of Man. The SouL The Vital 
 Principle. Importance of Physical Science to Physiology. 
 
 FOR the maintenance of the life of man three chemical conditions must 
 be complied with. He must be furnished with air, water, and combusti- 
 ble matter. 
 
 Under the same conditions, also, all animals exist. Even in those 
 which seem to furnish us with instances of departure from this Three condi- 
 general rule, the exceptions are rather apparent than real. To tions oflife - 
 breathe, to drink, to eat, are the indispensable requisites of life. If there 
 be among insects some which seem never to take water, or among fishes 
 some which never taste solid food, these peculiarities disappear as soon 
 as we understand them properly. Where a high development has been 
 attained, as in man, experience assures us that the same inevitable result 
 awaits a cessation of respiration for a few moments, an abstinence from 
 water for a few hours, or from food for a few days. 
 
 The supply of a part of these necessaries of life is adjusted to the ur- 
 gency of the want. The act of breathing is incapable of de- Sources of sup- 
 lay, but the air is accordingly every where present, and al- ply of material, 
 ways fit for use. We can bear with thirst for a little time, and the earth 
 here and there furnishes her springs and other stores of water. But far 
 otherwise is it in the obtaining of food. It is the lot of all animals to 
 secure nourishment by labor, and even of men the larger proportion, both 
 
10- EQUILIBRIUM OF LIFE. 
 
 in civilized and savage countries, submit to a hard destiny. To obtain 
 their daily bread is the great object of life. 
 
 What is the philosophical explanation of this necessity for a supply 
 of air, of water, of food ? Why is it that the system will bear so little 
 delay ? 
 
 The answer which Physiology gives to these questions is an answer 
 Life de ends ^ ommous import, but the whole science is a commentary on 
 on destruction its truth. The condition of life is death. No part of a liv- 
 of material. ^ mecnan i sm can ac t without wearing away, and for the 
 continuance of its functions there is therefore an absolute necessity for 
 repair. 
 
 It has been greatly to the detriment of physiology and the practice of 
 medicine that this conception has not been thoroughly realized until late 
 times. The aspect of identity which an animal presents is an illusion, 
 hiding from us the true state of the case. It has been the fruitful source 
 of errors which have retarded the progress of these sciences. What could 
 their career possibly be when men had persuaded themselves that a liv- 
 ing being possesses a capacity for resisting any change, and that organic 
 structures never yield to external physical influences until after death ? 
 
 But life, far from being a condition of immobility, is a condition of 
 ceaseless change. An organism, no matter of what grade it may be, is 
 only a temporary form, which myriads of particles, passing through a de- 
 terminate career, give rise to. It is like the flame of a lamp, which pre- 
 sents for a long time the same aspect, being ceaselessly fed as it ceaselessly 
 wastes away. But we never permit ourselves to be deceived by the sim- 
 ulated unchangeableness which such a natural appearance offers. We 
 recognize it as only a form arising from the course which the disappear- 
 ing particles take. And so it is even with man. He is fed with more 
 than a ton weight of material in a year, and in the same time wastes more 
 than a ton away. 
 
 There is, therefore, a general condition of equilibrium which every an- 
 Conditions of * ma ^ P resem X depending upon its receipts and its wastes, a 
 equilibrium in proper knowledge of the conditions of which is at the founda- 
 tion of Physiology. That we may approach this problem un- 
 der its simplest form, free it from all unnecessary complications, and make 
 it of most interest to the special object of this book, the remarks now 
 to be made will be confined to our own species, and, except when oth- 
 erwise stated, to a condition of health, and to the adult period of life. 
 
 To have a uniform standard of reference, we may assume one hundred 
 and forty pounds as the weight of an adult healthy man. Now the con- 
 stant consumption of food, water, and atmospheric air tends steadily to 
 increase that weight, and even in a very short time a disturbance arising 
 from these sources would be perceptible, w^ere there not some causes of 
 
ANNUAL RECEIPTS AND WASTE IN MAN. 11 
 
 compensation. But even after a year, if a state of health is maintained, 
 the weight may remain precisely what it was, and this may continue year 
 after year in succession. The consumption of large quantities of solid, 
 liquid, and gaseous matter does not therefore necessarily add to the 
 weight. 
 
 There are two periods of life for which this observation will not hold 
 good. They are infancy and old age. During the former the weight in- 
 creases from day to day, and during the latter it slowly declines. 
 
 If there be thus causes for the increase of weight of the living system, 
 there are also causes for its diminution. Setting aside the minor ones, 
 these may be chiefly enumerated as loss by urine, by faeces, by transpired 
 and expired matters. By transpired matters, are meant such as escape 
 under the form of liquids and gases from the skin, and by expired mat- 
 ters, vapors and gases escaping from the lungs. There is, therefore, a 
 tendency to an increase and a tendency to a diminution of the weight, 
 and, in the condition of equilibrium we are considering, these must bal- 
 ance one another. 
 
 If a man of the standard weight abstains from the taking of water and 
 food, a good balance will prove that in the course of less than an hour he 
 has become lighter. If he still persists, it needs no instrument to detect 
 what is going on ; the eye perceives it, for emaciation ensues. 
 
 How, then, is it possible for a living being to continue at its standard, 
 except the causes of increase are precisely equal in effect to the causes 
 of diminution? Overlooking minor ones, we may therefore assert that 
 the sum total of food, water, and atmospheric air taken in a given period 
 of time is precisely equal to the sum total of all the losses by urine, fae- 
 ces, transpired, and expired matters ; for if the receipts were greater, the 
 weight must increase if the losses were greater, the weight must dimin- 
 ish. Persistency in this respect proves equality, and the case is just as 
 simple as in the common affairs of life ; he who pays less than he receives 
 grows rich ; if his payments are more than his receipts, he becomes poor ; 
 but his condition is unchanged if his payments and receipts are equal. 
 Infancy, old age, and manhood answer to these circumstances respect- 
 ively. 
 
 From the army and navy diet scales of France and England, which of 
 course are based upon the recognized necessities of large Quantity of 
 numbers of men in active life, it is inferred that about 2 J 
 pounds avoirdupois of dry food per day are required for each year, 
 individual ; of this about three quarters are vegetable and the rest animal. 
 At the close of an entire year the amount is upward of 800 pounds. 
 Enumerating under the title of water all the various drinks coffee, tea, 
 alcohol, wine, &c. its estimated quantity is about 1500 pounds per an- 
 num. That for oxygen may be taken at 800 pounds. 
 
12 ANNUAL RECEIPTS AND WASTE IN MAN. 
 
 With these figures before us, we are able to see how the case stands. 
 The food, water, and air which a man receives amount in the aggregate 
 to more than 3000 pounds a year ; that is, to about a ton and a half, or to 
 more than twenty times his weight. This enormous mass may well at- 
 tract our attention to the expenditure of material which is required for 
 supporting life. It reveals to us the fact that the old physiological doc- 
 trine, that a living being is not influenced by external agents, is altogether 
 a fallacy. A living being is the result and representative of change on a 
 prodigious scale. 
 
 The condition of equilibrium which has just been set forth, moreover, 
 Quantity of leads to the conclusion that the aggregate weight of urine, 
 i^manTifa 601 ^ eces ? transpired, and expired matter is the same for the 
 year. same period of time. In round numbers, we may take it at 
 
 a ton and a half. 
 
 It can not be questioned that the materials which are rendered back to 
 the external world, after having subserved the purpose of the animal and 
 passed through its system, are compounds of those which were originally 
 received as food, drink, and air, though they may have assumed in their 
 course other, and perhaps, in our estimation, viler forms. Eecognizing 
 as indisputable the physical fact that not an atom can be created any 
 more than it can be destroyed, we should expect to discover in the sub- 
 stances thus dismissed from the system every particle that had been 
 taken in. 
 
 What, then, is man ? Is he not a form, as is the flame of a lamp, the 
 temporary result and representative of myriads of atoms that are fast 
 passing through states of change a mechanism, the parts of which are 
 unceasingly taken asunder and as unceasingly replaced ? The appear- 
 ance of corporeal identity he presents year after year is only an illusion. 
 He begins to die the moment he begins to breathe. One particle after 
 another is removed away, interstitial death occurring even in the inmost 
 recesses of the body. 
 
 From these general considerations we infer that the essential condition 
 Great extent of of life is waste of the body ; and this not only of the body 
 the system of** in tne aggregate, but even of each of its particular parts, 
 man. Whatever part it may be that is exercised is wearing away, 
 
 and wherever there is activity there is death. And since parts that are 
 dead are useless, or even injurious to the economy, the necessities simul- 
 taneously arjse for their removal and for repair. Much of the compli- 
 cated mechanism of animal structures is for the accomplishment of this 
 double duty. 
 
 For an organic being to live, its parts must die. The amount of activ- 
 ity it displays is measured by the amount of death, and in this regard 
 every member of the animal series stands on the same level. Here, at 
 
FIXED STANDARDS OF PHYSIOLOGY. 13 
 
 the very outset of our science, we must dismiss the vulgar error that the 
 physical conditions of existence vary in different tribes, and that man is 
 not to be compared with lower forms. We must steadily keep in view 
 the interconnection of all, a doctrine which is the guiding light of modern 
 physiology, and which authorizes us to appeal to the structure and func- 
 tions of one animal for an explanation of the structure and functions of 
 another. The more steadily we keep before us this philosophical con- 
 ception of the interconnection of all organic forms, the clearer will be our 
 physiological views. There has never been created such a thing as an 
 isolated living being. 
 
 From the manner in which these general considerations of the mechan- 
 ical and chemical equilibrium of the system of man have been Necessity and 
 introduced, it will doubtless be seen that it is the first busi- p^gioiogkfi 
 ness of the physiologist to disentangle the variable results standards. 
 which that system presents, as far as may be possible, and offer them un- 
 der a standard estimate ; that at the basis of this science there should 
 be a table setting forth with the utmost exactness all the quantities con- 
 cerned in such a standard type. Thus, assuming the weight of an adult 
 man at 140 pounds, as we have done, it should show the diurnal consump- 
 tion of combustible matter or food, of water, of air the diurnal loss by 
 evaporation, by secretion, by respiration. In contrast with this it should 
 also give the nocturnal. It should also represent the quantity of bile, 
 of saliva, of pancreatic juice ; the weight of each one of the various salts 
 and organic bodies they contain, the diurnal and nocturnal production of 
 heat, &c. 
 
 For the purpose of the practice of medicine, a standard of 140 pounds 
 will perhaps be found most convenient, but in a scientific point of view, 
 and especially for comparative physiology, a standard of 1000 parts is 
 best assumed. I now present an attempt at the construction of such ta- 
 bles, it being perhaps scarcely necessary to apologize for their extreme 
 imperfection. Though offering the results at present received as most 
 trustworthy, a very superficial examination will show how full they are 
 of errors and contradictions. Perhaps it would not be too much to say 
 that it will require the labor of many physicians, continued for centuries, 
 to bring such tables to the truth. Yet the approach to precision in these 
 hypothetical constants will in all times be a measure of the exactness of 
 physiology, and it may be added, also, of the practice of medicine. The 
 time is at hand when such a typical standard must be the starting-point 
 for pathology, and no rational practice can exist without it. The passage 
 of physiology, from a speculative to a positive science, is the signal for a 
 revolution in the practice of medicine. 
 
 Moreover, physiology should furnish formulas for the computation of 
 variations in these tabular numbers under variable conditions ; as, for in- 
 
14 FIXED STANDAEDS OF PHYSIOLOGY. 
 
 stance, under low and high aerial temperatures, change of atmospheric 
 pressures, absolute quiescence, or the near approach thereto, the effect of 
 a determined amount of locomotion, or other muscular exertion, &c. As 
 the science becomes more perfect, it should likewise attempt to embrace 
 pathological states ; as, for instance, the diurnal or periodic production of 
 heat in fevers, the effect of the hygienic system of the bedroom. 
 
 Physiology having attained to this high condition, the practice of med- 
 icine in its great department of diagnosis will consist, in reality, in the 
 solution of inverse problems. Given the variations from the standard ex- 
 isting in any case, to determine the cause of those variations. At this 
 point diagnosis becomes a science, and ceases to be an art. 
 
 As in painting and statuary, the artist has an ideal model in his mind, 
 Illustration of a ^7P^ ca ^ standard which no living being has perfectly reach- 
 the following ed, though some of the most beautiful may have approached 
 thereto, so in physiology the standard or typical man pre- 
 sents the combined and mean values of all the human race. 
 
 A less comprehensive view presents us with distinct national standards, 
 instead of this universal one, for every country has its own peculiarities. 
 Eesults of the highest interest are to be perceived when these national 
 standards are compared with one another. Even the same nation must 
 offer, from age to age, modifications in its type expressive of the secular 
 perturbations it is undergoing, as it advances or descends in a knowledge 
 of the arts of life and civilization. 
 
 Moreover, there are typical standards of a still lower order, having ref- 
 erence to the conditions of sex and the period of life. Of these six may 
 be designated the infant, the adult, the aged, of the male and female sex 
 respectively. 
 
 As illustrations of these remarks, and examples of the determination of 
 the fundamental element of such a general physiological table, the stand- 
 ard weight of the body, we may take the following estimates. An ex- 
 amination of 20,000 infants, at the Maternite in Paris, gives for the weight 
 of the new-born 6 Jibs. ; the same mean value obtains for the city of Brus- 
 sels. For about a week after birth this weight undergoes an actual dim- 
 inution, owing to the tissue destruction which ensues through the estab- 
 lishment of aerial respiration, and which for the time exceeds the gain 
 from nutrition. For the same age the male infant is heavier than the fe- 
 male, but this difference gradually diminishes, and at twelve years their 
 weight is sensibly the same. Three years later, at the period of puberty, 
 the weight is one half of what it is finally to be, when full development 
 is reached. The maximum weight eventually attained is a little more 
 than twenty times that at birth, this holding good for both sexes ; but 
 since the new-born female weighs less than the standard, and the new- 
 born male more, the weight of the adult male is 136^^- Ibs., and of the 
 
PHYSIOLOGICAL TABLES. 
 
 15 
 
 adult female 121^^^ Ibs. The mean weight of a man, irrespective of his 
 period of life, is 103^^ Ibs., and of a woman 93^^^- Ibs. The mean 
 weight of a human being, without reference either to age or sex, is 
 
 For the preceding numbers we are indebted to the researches of M. 
 Quetelet, who likewise has in an interesting manner extended the meth- 
 ods of statistics to the illustration of the physical and moral career of 
 man, and impressed us with the facts that in the discussion of the phe- 
 nomena which masses present, individual peculiarity disappears and gen- 
 eral laws emerge. The actions which seem to be the result of free will 
 in the individual, assume the guise of necessity in the community. Just 
 as we are sure that man is born, develops, and dies under the operation 
 of laws that are absolutely invariable, so communities seem to be under 
 the influence of unchangeable laws. " In communities man commits the 
 same number of murders each year, and does it with the same weapons. 
 We might enumerate beforehand how many individuals will imbrue their 
 hands in the blood of their kind, how many will forge, how many poison, 
 very nearly as we enumerate beforehand how many births and deaths will 
 take place." 
 
 PHYSIOLOGICAL STANDAKD TABLES. 
 
 Diurnal Ingesta, Secretions, and Excretions of a Man whose 
 eight is 140 Ibs. avoirdupois. 
 
 Diurnal Ingesta, Secretions, and Excretions of a Man whosa 
 weight is 1000 parts. 
 
 Weight of body 140.000 
 
 fWater 4.109 
 
 I Oxygen 2.192 
 
 ] Dry vegetable food. . . 1.687 
 
 S I Dry animal food 563 
 
 Saliva 3.300 
 
 Gastric j uice 14. 080 
 
 Pancreatic juice 440 
 
 Bile 3.500 
 
 5 Carbon from lungs . . . .500 
 
 j3 Intestinal juice 440 
 
 Loss of water by lungs 1.440 
 " skin. 2.234 
 
 Fseces OT8 
 
 Urine 2.180, consisting of 
 
 Water 2.034 
 
 Urea 065 
 
 Uric acid 002 
 
 Lactic acid 037 
 
 Sulphuric acid 007 
 
 Phosphoric acid 008 
 
 Chloride of sodium . .009 
 Alkalies and earths . . 016 
 
 Other bodies 002 
 
 TBlcod . . . 17.000, consisting of 
 
 Water 13.328 
 
 Albumen 1.190 
 
 Fibrin i... .037 
 
 Discs 2.227 
 
 Fats 022 
 
 Chloride of sodium .061 
 Chloride of potass . . 006 
 Phosphate of soda . .003 
 Carbonate of soda . .012 
 Sulphate of soda. . . .004 
 Phos. lime and mag .004 
 Oxide and phos. iron .008 
 Other bodies 098 
 
 In this table the estimate is in the 
 pound and decimals thereof. 
 
 ivoirdupois 
 
 Weight of body 1000.000 
 
 tfWater 29.350 
 J Oxygen .' 15.057 
 _ | Dry vegetable food . . 12.050 
 
 w I Dry animal food 4. 021 
 
 Saliva 23.576 
 
 Gastric j uice 100.571 
 
 Pancreatic j uice 3. 143 
 
 Bile 25.000 
 
 Carbon from lungs. . . 3.571 
 
 :E Intestinal juice 3.143 
 
 2 Loss of water by lungs 10. 286 
 8 " " skin. 15.957 
 
 a Faeces 557 
 
 Urine 15.571, consisting of 
 
 Water 14.529 
 
 Urea 464 
 
 Uric acid 014 
 
 Lactic acid 264 
 
 Sulphuric acid 050 
 
 Phosphoric acid ... .057 
 Chloride of sodium . 064 
 Alkalies and earths .114 
 
 Other bodies 014 
 
 121.429, consisting of 
 
 Water 95.200 
 
 Albumen 8.500 
 
 Fibrin 264 
 
 Discs 15.907 
 
 Fats 157 
 
 Chloride of sodium . . 436 
 Chloride of potass . . .043 
 Phosphate of soda . . .021 
 Carbonate of soda . . .OSM 
 
 Sulphate of soda 029 
 
 Phos. lime and mag. .029 
 Oxide and phos. iron .057 
 
 Other bodies 700 
 
 In this table the estimate is upon one thousand 
 parts. 
 
 It is to be received as a doctrine admitting no controversy, that or- 
 
16 NATURE OF MATTERS RECEIVED. 
 
 ganic systems, whether vegetable or animal, whether humble or elaborate- 
 An animal ere- \y developed, possess no power of creating material. Their 
 buToSy trfns- function is of necessity limited to the mere transformation of 
 
 forms the sub- substances furnished to them. From this it follows, even in 
 ceives. the case of man, that the substances dismissed from the sys- 
 
 tem are metamorphosed forms of those which have been received, and 
 that, whatever their appearance may be, they must have arisen from the 
 reaction of the food, water, and air upon one another. 
 
 This reaction we may proceed to view as a purely chemical result ; 
 for, casting aside all the vain hypotheses of the older physiology, and per- 
 mitting ourselves to be guided by the harmonies of nature, we should ex- 
 pect to recognize in the changes taking place in organic systems, and in 
 the phenomena which attend those changes, the same results which arise 
 in the artificial or experimental reaction of food, water, and air on each 
 other. A very superficial examination of the facts shows at once the 
 The chemical correctness of this expectation. On such an examination we 
 mauersre-^ now enter > premising it with some general remarks needful for 
 ceived. our purpose on the nature and properties of food, water, and air. 
 
 1st. OF FOOD. No article is suitable for food except it be of a com- 
 bustible nature. Its chemical constitution must be such that if its tem- 
 perature be raised to a proper degree with a due access of atmospheric air 
 it will take fire and burn, and the products of its combustion must be car- 
 bonic acid gas and water, or those substances with nitrogen or its com- 
 pounds. 
 
 2d. OF WATER. This may be taken as the type and representative 
 of all the various liquids used as drinks. It evaporates at any tempera- 
 ture, even at those which are lower than its freezing point, and in this 
 evaporation produces cold. Water vaporizing from the skin absorbs 1114 
 degrees of heat, and hence exerts a most powerful refrigerating action. 
 Over saline substances there are few bodies which exercise so general a 
 solvent effect. In virtue of this property, it is enabled to introduce in 
 the dissolved state such compounds as are wanted for the nutrition of the 
 system, and in the same manner to carry away the wasted products of 
 decay. 
 
 3d. OF ATMOSPHERIC AIR. The active principle of the air is oxygen 
 gas, the effects of which are moderated by the presence of a large quanti- 
 ty of nitrogen- four fifths of the air consisting of this latter substance. 
 Physiologically, we often use the terms atmospheric air and oxygen syn- 
 oifymously. 
 
 The chief materials which a living being receives from the external 
 world are, therefore, COMBUSTIBLE MATTER, WATER, OXYGEN GAS ; and out 
 of the action of these upon one another all the physical phenomena of its 
 life arise. 
 
NATUEE OF MATTEES EESTOEED. 17 
 
 Such being the nature and properties of the things received, we may 
 now examine in the same general manner those which are Properties of 
 dismissed from the system. Here, at the very outset, we en- substances 
 
 . -,. -, dismissed bv 
 
 counter the important fact that they are oxidized or burned the system." 
 bodies. 
 
 1st. As respects the urine and its constituents. Its liquid part, wa- 
 ter, is an oxide of hydrogen, of which, though the greater portion may 
 not have been produced in the economy, yet a certain quantity unques- 
 tionably has. In it, too, are to be found sulphuric acid, which is an ox- 
 ide of sulphur ; phosphoric acid, which is an oxide of phosphorus ; and its 
 leading solid constituent, urea, is the representative of bodies which arise 
 when processes of oxidation have been going on. 
 
 2d. The expired and transpired matters present similar burned com- 
 pounds. At the head of these products stand carbonic acid gas, which is 
 an oxide of carbon, and water, which, as we have already said, is an ox- 
 ide of hydrogen. We here omit any consideration of the nature or con- 
 stitution of the fecal matter, because much of it has never been properly 
 in the interior of the system, though it has passed through the intestine. 
 
 The general result at which we arrive is, then, that the food consists of 
 combustible matter, and that the substances dismissed from the economy 
 are oxidized bodies. A burning must, therefore, have been go- c om k ust j on 
 ing on, and this could only have been accomplished by the air occurs in the 
 introduced by breathing acting upon the substance of the body oc y ' 
 itself and its contents, and,* to repair the waste which must have ensued, 
 a due weight of food has been required. Since this, in its turn, as a 
 part of the living mechanism, is destined to undergo the like destructive 
 action, we may present the entire series of facts under consideration cor- 
 rectly by regarding them as arising remotely from the action of the air 
 upon the food. 
 
 With this statement before us, we next inquire what ensues when sub- 
 stances appropriate for food are exposed in artificial experiments at a cer- 
 tain temperature to the action of atmospheric air. 
 
 A piece of flesh, or even of any vegetable body, consisting of carbon, 
 hydrogen, oxygen, and nitrogen, submitted to those condi- Results of arti- 
 tions, undergoes combustion. Its carbon, by uniting with ox- fi . cial combus- 
 
 \ J & tion the same 
 
 ygen, produces carbonic acid, its hydrogen for the most part as that in the 
 water, but a residue thereof, combining with the nitrogen, may bodjr - 
 give rise to the production of ammonia. If there be any sulphur and 
 phosphorus present, they also burn, and salts of sulphuric and phosphoric 
 acids are the result. 
 
 Such is what occurs outside of the body in a common case of artificial 
 combustion where atmospheric air has access. The constituents of which 
 the food is composed thus satisfy their chemical affinities, and the com- 
 
 B 
 
18 PEODUCTION OF HEAT. 
 
 pounds we have mentioned arise. Now it is a fact of the utmost signifi- 
 cance that the compounds thus originating from the direct artificial "burn- 
 ing of matters proper for food are the very same that are dismissed from 
 the animal system in which food has been submitted to the air introduced 
 by respiration. They are such substances as carbonic acid, water, am- 
 monia, sulphates and phosphates. 
 
 It may impress these truths more deeply upon us to learn that the 
 facts at which we have thus arrived may also be recognized m the 
 changes of destruction presented by the vegetable kingdom. The leaves 
 of trees, after they have fallen in autumn, quickly decay, and even the 
 heart- wood itself has a limit beyond which it does not last. Sooner or 
 later every part of a plant is destroyed by the atmospheric air. Such 
 limits of duration in animal structures are short. A very brief time, per- 
 haps only a few hours, is all that is wanted for putrefaction to set in, and 
 the entire mass, undergoing dissolution, is lost in the surrounding air. 
 
 This final disappearance of all organized structures is brought about 
 by the action of that energetic element, oxygen. If by any contrivance 
 its influence is prevented and its presence avoided, these changes do not 
 take place. Putrefaction and decay are slow combustions, true burnings 
 taking time. There equally arise from the fallen leaf and from the de- 
 caying body carbonic acid, water, and ammonia, the self-same substances 
 dismissed from the economy during the continuance of life. 
 
 Processes of combustion and processes of decay are therefore both due 
 to the action of atmospheric oxygen on the changing substance. They 
 differ chiefly from one another in the relative rapidity with which they 
 are accomplished. 
 
 The facts thus set forth wan-ant the following statements. The mat- 
 ters which a man receives as food are combustible bodies ; those dismissed 
 Production of from his system have been burned. To that, as to any other 
 animal heat. g^^ burning, oxygen gas is absolutely requisite. There is, 
 therefore, a plain conclusion before us, which, in its far-reaching conse- 
 quences, covers the whole science of physiology, and betrays to us the 
 function which every animal discharges, viz., that oxidation is incessant- 
 ly going on in the interior of the system through the agency of atmos- 
 pheric air introduced by the process of breathing. 
 
 An animal, in this point of view, is an oxidizing machine, into the in- 
 terior of which atmospheric air is constantly introduced. The active con- 
 stituent, oxygen, satisfies its chemical affinities at the expense of those 
 parts of the system which are wasting away. And as the act of breath- 
 ing, that is, the introduction of this gas, takes place day and night, wak- 
 ing and sleeping, so too must the production of burned bodies ; a part 
 escaping by the lungs, a part by the skin, a part in the urine. To com- 
 pensate the loss which ensues s nearly 1000 pounds weight of combustible 
 
PRODUCTION OF HEAT. 19 
 
 matter must be used in the course of a year, and, for reasons to be exam- 
 ined in detail presently, three quarters of a ton of water. But this is a 
 very different conclusion to the notion of the ancient physicians, that an 
 animal during its life is exempt from participating in external changes, 
 and is an enduring monument of the power possessed by the VITAL FORCE 
 of resisting all physical influences. 
 
 But carbon by uniting with oxygen can not turn into carbonic acid, 
 nor can hydrogen turn into water, nor nitrogen into ammonia, without 
 heat being produced. The very meaning we attach to the term indicates 
 that every process of burning is attended with the liberation of heat. 
 
 In domestic economy, we protect ourselves from the cold weather of 
 winter, or attain any high temperature we want by the oxidation of some 
 of the forms of carbon, such as wood or coal, in fire-places or stoves. 
 "We know that for the production of a given quantity of heat a given 
 weight of combustible matter and of air is required, and that by employ- 
 ing various mechanical contrivances for increasing the draught we can ac- 
 celerate* the burning. 
 
 Moreover, if in our laboratories we require the very highest tempera- 
 ture that can be artificially obtained, we resort to the burning of hydro- 
 gen. There are instruments, such as the compound blow-pipe, construct- 
 ed on this principle. In the flame which arises in this combustion the 
 most refractory substances melt or are deflagrated. 
 
 But it may be said that though when a substance is rapidly oxid- 
 izing it must be evolving heat, there is perhaps a slower Production of 
 kind of combination, in which the particles unite without any ^^ J^ re " 
 disturbance of temperature. What proof could be offered, for decay, 
 example, that a mouldering leaf is disengaging heat ? 
 
 In answer to this it is not necessary to bring forward refined or direct 
 experiments. Every leaf when it moulders is literally burning away. 
 The extrication of warmth begins even when it is ready to fall. What 
 does the farmer expect in making his hay, if he puts the grass up in too 
 moist a state, or in too large a mass ? The temperature does not stop at 
 the stage of bituminous fermentation, but the stack most probably takes 
 fire. Of course what is going on in the whole mass is going on in each 
 separate leaf, undistinguishable, it is true, in the latter case, because the 
 heat of a single decaying leaf, taken alone, may be carried off by the cold 
 surrounding air, or by the contact of good conducting bodies, and so be 
 lost to examination. 
 
 From agricultural operations we may also learn that what holds good 
 for vegetable bodies is true for animal substances. Heaps of manure or 
 of offal of any kind, if due access of air be given, exhibit the extrication 
 of carbonic acid, steam, and ammonia, and the temperature promptly rises. 
 The gardener avails himself of this fact. He uses the heat, as it is slowly 
 
20, REGULATION OF HEAT. 
 
 set free by the putrefaction of manure in his forcing frames, to bring forth 
 plants in the early spring. There is no kind of decay, or putrefaction, or 
 oxidation of organic matters, however slow it may be, that is not marked 
 by the production of warmth. 
 
 Man, in a state of health, maintains a nearly uniform temperature. 
 Heat of man: Neglecting slight variations, to be hereafter critically exam- 
 its cause. wed, it is 98 degrees. For the most part, it is immaterial 
 in what climate of the earth he may reside, whether in the cold polar re- 
 gions or the hot tropic ; he is so constituted that, either through the pro- 
 visions of his own organization, or by resorting to the adventitious aid of 
 clothing, or to special articles of food, he can maintain himself at about 
 the same degree ; and as all this heat arises from interstitial oxidation 
 continually taking place, it is obvious that within certain limits he has 
 control over it. Thus, in the winter he sometimes resorts to violent mus- 
 cular action in order to increase the rapidity of respiration and the de- 
 struction of muscular tissue ; for the greater the quantity of air intro- 
 duced in a given period of time, the higher the temperature rises, just 
 as when we close the door of a stove, or place a blower on an anthracite 
 fire, an increased draught is occasioned and the quantity of heat is in- 
 creased. To breathe with rapidity and depth is certain to raise the tem- 
 perature. 
 
 On the contrary, in summer, when the heat is oppressive, we instinct- 
 ively abstain from muscular exertion, tranquil and slow respiration goes 
 on, and the temperature is kept down. Again, there are means of occa- 
 sioning an increased liberation of heat by changing the nature of the food 
 and using highly combustible material, such as the various kinds of alco- 
 holic preparations. The chemical constitution of alcohol is such that in 
 the act of burning carbonic acid and water are produced with the libera- 
 tion of so much heat that chemists find it one of the most suitable means 
 of attaining a high temperature. On taking preparations of this substance, 
 such as distilled liquors or wines, the first effect is the production of a 
 genial warmth all over the body, intoxication eventually coming on as a 
 secondary result. 
 
 These remarks are not limited in their application to our own species, 
 the whole animal world furnishes us with commentaries on their truth. 
 Man maintaining a temperature, as has been said, of about 98 degrees, 
 other animals are at other degrees, some being cold-blooded and some hot. 
 The particular point they reach depends, as direct observation shows, on 
 the quantity of oxygen they consume, or, in other words, on their respira- 
 tion. Birds, whose breathing mechanism is by far the most elaborate 
 and extensively developed, have by far the highest temperature. The 
 snake or the tortoise, whose rate of respiration is very slow, and which 
 consume but little oxygen, have a correspondingly low degree of heat. 
 

 USES OF WATER. 21 
 
 And in those creatures which at one period of the year are in full activity, 
 but at another lie dormant or hibernate, as they begin to respire more 
 slowly their temperature begins to decline, and when they have sunk into 
 their winter's sleep their breathing is scarcely perceptible, and their 
 warmth scarcely above that of the surrounding air. 
 
 In what has been thus far said we have been considering those oper- 
 ations of the system which tend to the production of heat, causes of cooi- 
 and the maintenance of the whole mass of the body at a tern- ing of the body. 
 perature above that of the surrounding air. But it is obvious that pro- 
 vision must be made to prevent any undue rise, so that between those 
 causes of elevation and these of depression a due equilibrium may be main- 
 tained. If a very large quantity of combustible matter, under the form of 
 food, and about an equal weight of oxygen, are necessary for obtaining a 
 proper heat, we should also recollect that nearly three quarters of a ton of 
 water are consumed each year. The duty which this water 
 
 J J Uses of water. 
 
 discharges we may next consider. 
 
 That duty is twofold. 1st. The removal of solid material in a state 
 of solution ; and, 2d. The production of cold by evaporation. It is the 
 cooling agency which is of most interest to us in our present inquiry, but 
 a few remarks as regards the removal of solid matter may not here be 
 misplaced. 
 
 1st. Water, then, exerts its solvent power for the removal of all those 
 substances which, arising incessantly in the animal system, can its solvent 
 not assume either the vaporous or gaseous state. In this con- P wer - 
 dition are the different saline bodies, such as the sulphates which are com- 
 ing from the destruction of the muscular tissues, as voluntary and invol- 
 untary motions are performed ; or the phosphates which are produced by 
 the destruction of cerebral and nervous 'matter. In the same condition 
 starid nearly all the nitrogenized results of the destruction of the soft 
 parts, and which are to a great extent to be removed as urea. Water dis- 
 solving with more or less facility these various bodies permits their escape 
 from the system by the secreting action of the kidneys, which, strain- 
 ing or filtering them from the blood, dismiss them to the bladder, from 
 which they are periodically removed. 
 
 The skin is no inefficient auxiliary to the kidneys in effecting this re- 
 moval of water charged with soluble matters. All over its surface are 
 scattered in profusion the ducts of the perspiratory glands, which consist 
 of a convoluted tubing abundantly supplied with blood-vessels. The final 
 mode of action of these glands depends on extraneous circumstances. 
 Most commonly the fluid is carried away under the form of a vapor or in- 
 sensible perspiration, but when the secretion goes on more rapidly, or the 
 dew-point of the surrounding air is high, it then accumulates as drops of 
 sweat. The amount of water thus removed, even by insensible perspira- 
 
?2 COOLING BY EVAPORATION. 
 
 tion, is greater than might be supposed, yet it corresponds with the ex- 
 tent of the provision. The length of the water-secreting tubing in the 
 skin of a man is about twenty-eight miles. 
 
 Thus by the action of the kidneys and the skin large quantities of wa- 
 ter are dismissed, either under the liquid or vaporous form. A third or- 
 gan is concerned in this important duty. It is the lungs. These, how- 
 ever, are limited in their operation to its exhalation as vapor or steam. 
 That water abundantly escapes from them is plainly shown when the days 
 are cold, the moisture as it comes from the respiratory passages condens- 
 ing into a visible cloud when it encounters the air. It is estimated that 
 the loss of water by the skin and lungs conjointly is about 18 grains in 
 a minute, of which 11 pass off from the skin and 7 from the lungs. Mak- 
 ing due allowance for the variable action of the skin as dependent on the 
 dew-point and other such causes, we can scarcely set down the entire 
 quantity at less than 1000 pounds a year. In the same period the quan- 
 tity of water lost as urine may be taken at 900 pounds. It may perhaps 
 be remarked, that here we are assuming a loss of 1900 pounds, when the 
 quantity of water annually taken is only 1500 pounds. But it is to be 
 recollected that not only does water form a very prominent constituent of 
 the solid food, whether vegetable or animal, but also that much arises 
 from the oxidation of hydrogen in the interior of the system. 
 
 2d. Water also exerts a cooling influence, arising from its evapora- 
 Cooling influ- tion from the surface of the skin and the cells of the lungs, 
 ence of water, rpj^ diff erence between water in the state of an invisible va- 
 por and in the liquid condition consists in this, that the vapor contains 
 1114 degrees of heat which the liquid does not. When, therefore, it 
 evaporates from a surface of any kind, as from the skin, it obtains there- 
 from that large amount of latent heat, and so tends to cause the tempera- 
 ture to decline. Not that this is the only cooling agency at work. * Ka- 
 diation might also be mentioned ; for, just as a warm inorganic body cools 
 by the escape of radiant heat from it, so too does a living being. 
 
 These considerations explain how an equilibrium of temperature is es- 
 Equiiibrium of tablished. By the process of respiration there is a constant 
 heat in man. tendency to increase the heat ; but by evaporation of water, 
 radiation, and other cooling causes, tllere is a constant-tendency to dimin- 
 ish it. A balance is struck between the two processes, and in man a 
 temperature of 98 degrees is kept up. 
 
 This average temperature is, however, easily departed from. Through 
 some trivial cause the cooling agencies may be interfered with, and then, 
 the heating processes getting the superiority, a high temperature or fe- 
 ver comes on. Or the reverse may ensue. In Asiatic cholera, the con- 
 stitution of the blood is so changed that its cells can no longer carry ox- 
 ygen into the system, the heat-making processes are put a stop to, and> 
 
PHYSICAL MECHANISM OF MAN. 23 
 
 the temperature declining, the body becomes of a marble coldness charac- 
 teristic of that terrible disease. 
 
 The animal mechanism is thus the focus of intense chemical changes, 
 and great quantities of material are required in- very brief Necessity of re- 
 spaces of time for its support. We have seen what is the {^^ft* 1 **" 
 use of the combustible matter employed as food, what of the wastes. 
 water, what of the air, how, these reacting on one another, a high but reg- 
 ulated temperature is kept up. 
 
 Much of what has been thus far said has had reference only to the de- 
 struction of tissues. This waste of matter arises for a double reason, 
 partly to give origin to the heat which animals require, and partly as a 
 consequence of intellectual activity and muscular motion ; for no move- 
 ment can be made without a destruction of muscular fibre, and all mental 
 and nervous actions imply the waste of a certain quantity of vesicular 
 substance. For this reason, after an animal has undergone violent mus- 
 cular exercise, the quantity of urea and sulphuric acid in the urine is in- 
 creased, this being the channel through which those results of the de- 
 struction of muscular, fibre are removed ; or, after severe mental or intel- 
 lectual duty, there is more phosphoric acid than usual in the urine, be- 
 cause of the greater oxidation of phosphorus which has taken place in 
 the brain. 
 
 But of course this destruction of tissue must be compensated by a re- 
 pair if a normal condition and health are preserved. The action of the air 
 is not directly upon the food, for intermediately and temporarily the food 
 is converted into the living mechanism. The dead material is awakened 
 into life, and for a time, though only for a time, becomes a portion of the 
 living and feeling mass. 
 
 The functions and actions we have been considering imply the provi- 
 sion of many complicated mechanisms. There must be means various mech- 
 for effecting the introduction of the air ; these, in man, depend anisms wanted 
 
 iv - , ,. .. A { A i f r removal of 
 
 on calling into operation its pressure. A system of tubes is waste and for 
 necessary for its distribution to the points at which it is re- repair, 
 quired, and in like manner a system is required for carrying away the 
 wasted products of decay. The new material which is destined to re- 
 place the parts which are thus disappearing, and to keep the economy in 
 repair, must be submitted to such processes of mechanical and chemical 
 preparation that it may be dissolved in the blood, and carried wherever it 
 is wanted. It must therefore be cut and crushed by teeth driven by pow- 
 erful muscles, dissolved by acid and alkaline juices in digestive cavities 
 set apart for that purpose. From these it must be taken by arrange- 
 ments which can absorb it and carry it into the torrent of the circulation. 
 Physical means must be resorted to, not only for the impulsion of these 
 newly-absorbed nutritive juices, but likewise to drive the blood in its 
 
24 THE SOUL. 
 
 proper career of circulation. It is needless here to dwell on the manner 
 in which the most refined principles of hydraulics are brought into play, 
 or to speak of the manner in which forces of compression and elasticity 
 are introduced ; how that there are valves which open only in one way 
 to let the current pass, or how some of these, as in the like human con- 
 trivances, are tied down in their action by cords. Moreover, since it is 
 required that the animal shall go in search of its food, muscles of loco- 
 motion, which act upon purely mechanical principles on the bony skele- 
 ton, must be resorted to, and so the animal structure becomes a most 
 elaborate and complicated machine. 
 
 In this regard the human body may be spoken of as a mere instrument 
 Physical as- or engine, which acts in accordance with the principles of me- 
 pectofman. c h an i ca l an d chemical philosophy, the bones being levers, the 
 blood-vessels hydraulic tubes, the soft parts generally the seats of oxida- 
 tion. But if we limit our view to such a description, it presents to us 
 man in a most incomplete and unworthy aspect. There animates this 
 machine a self-conscious and immortal principle the soul. 
 
 Though in the most enlarged acceptation it would fall under the prov- 
 Thesoui- its * nce ^ P^7 s ^g7 to * reat of this immortal principle, and to 
 nature and re- consider its powers and responsibilities, these constitute a 
 ies ' subject at once so boundless and so important, that the phys- 
 iologist is constrained to surrender it to the psychologist and theologian, 
 and the more so since the proper and profitable treatment of it becomes 
 inseparably involved with things that lie outside of his domain. 
 
 Yet under these circumstances, considering the ever-increasing control 
 which scientific truth exerts over the masses of men, considering too how 
 much the welfare of the human family depends on the precision and 
 soundness of its religious views, it is the duty of the physiologist, if for 
 the reasons that have been specified he yields this great subject to others, 
 to leave no ambiguity in the expression of the conclusion to which his 
 own science brings him. Especially is it for him, whenever the oppor- 
 tunity offers, to assert and to uphold the doctrine of the oneness, the im- 
 mortality, the accountability of the soul, and to enforce those paramount 
 truths with whatever evidence the structure of the body can furnish. 
 
 For this reason, he can not recall but with regret the existing use of 
 many terms, such as mind, intellect, vital principle, spirit, which, though 
 they were at first doubtless employed as expressions of the function's or 
 qualities of the soul, have in the course of time gathered other meanings 
 and confused the popular ideas. They have brought about a condition 
 of things in science not unlike that which prevailed in theology during 
 the reign of polytheism. Constrained, perhaps, himself by the necessities 
 of language to use such phraseology, it is for him at the outset to leave 
 no doubt of the views he entertains, and, as far as he can, prevent such 
 
THE VITAL PRINCIPLE. 25 
 
 expressions from frittering away the great truth that, as there is but one 
 God in the universe, so there is but one spirit in man. 
 
 On one of these terms, the vital principle, I may make a few remarks, 
 since, from being a mere expression of convenience, it has by de- The vital 
 grees risen among physicians and physiologists to the rank of P rmci P le - 
 designating an existing agent, by some regarded as of the same kind as 
 light, heat, electricity, or gravitation nay, even superior to them, since it 
 is its peculiar attribute to hold them all in check. Animated by this ex- 
 traordinary power, organic substances are supposed to withstand every 
 external influence, and to submit to physical agents only after this prin- 
 ciple has left them. Such a preposterous doctrine will not bear the 
 touch of exact science for a moment. It is only a relic of the old meta- 
 physical system of philosophizing, which accepted a name in lieu of an 
 explanation, which preferred the dogma of the horror of a vacuum to the 
 more simple but material view of the pressure of the air. By the aid of 
 this imaginary principle, complete physiological systems have been wov- 
 en, in which every act and every condition of the animal economy is spon- 
 taneously explained, and nothing remains for solution. But by the stu- 
 dent of nature, whose mind has been trained in positive science, the im- 
 posture is detected. He sees at a glance that this is not the style of the 
 Great Artist. The problems of organization are not to be solved by em- 
 pirical schemes ; they require the patient application of all importance of 
 the aids that can be furnished by all other branches of hu- 
 man knowledge, and even then the solution comes tardily, ology. 
 Yet there is no cause for us to adopt those quick but visionary specula- 
 tions, or to despair of giving the true explanation of all physiological 
 facts. Since it is given us to know our own existence, and be conscious 
 of our own individuality, we may rest assured that we have what is in 
 reality a far less wonderful power, the capacity of comprehending all the 
 conditions of our life. God has framed our understanding to grasp all 
 these things. For my own part, I have no sympathy with those who 
 say of this or that physiological problem, it is above our reason. My 
 faith in the power of the intellect of man is profound. Far from suppos- 
 ing that there are many things in the structure and functions of the body 
 which we can never comprehend, I believe there is nothing in it that we 
 shall not at last explain. Then, and not till then, will man be a perfect 
 monument of the wisdom and power of his Maker, a created being know- 
 ing his own existence, and capable of explaining it. In the application 
 of exact science to physiology, I look for the rise of that great and noble 
 practice of medicine which, in a future age, will rival in precision the me- 
 chanical engineering of my times. In it, too, are my hopes of the final 
 K extinction of empiricism. Even now this method is attended with results 
 rhich must commend it to every thoughtful mind, since it is connecting 
 
26 SUBDIVISIONS OF PHYSIOLOGY. 
 
 itself with, those great truths which concern the human family most 
 closely, and is bringing into the region of physical demonstration the ex- 
 istence and immortality of the soul of man, and furnishing conspicuous 
 illustrations of the attributes of God. 
 
 CHAPTEE II. 
 
 OF FOOD. 
 
 The natural Subdivisions of Physiology. Of Food: its Sources and Classification its Value not 
 altogether dependent on its Composition. Of Milk: its Composition, and Use of its Water, 
 Casein, Sugar, Butter, and Salts. Variations in the Composition of Milk. Of Bread. Of 
 mixed Diets. Of the embryonic Food of Birds. Nutrition of carnivorous and herbivorous 
 Animals. Food formed by Plants and destroyed by Animals. Uses of mixed Food and Cook- 
 ing. Absolute Amount of Food. 
 
 PHYSIOLOGY possesses a very great advantage over many other sciences 
 Subdivisions of in offering its leading problems and doctrines in a certain 
 physiology. well-marked order or sequence, a connected whole, with only 
 here and there points of digression, but those points often of very striking 
 interest. Thus pursuing the train of reflections entered on in the pre- 
 ceding chapter, we should have to consider the nature of the food, the 
 manner, of its preparation by the process of digestion, the mechanism by 
 which it is taken up from the cavities in which it has been so prepared, 
 and that by which it is distributed to every part. We should have to 
 show the way in which it becomes incorporated as a portion of the living 
 mass, its duration in that condition, and the manner of its decay. We 
 should have to show by what physical means and through what mecha- 
 nism the air is introduced to effect the destruction of the dying parts, and 
 how, as the consequence of this, a fixed temperature is maintained. The 
 causes which lead to variations of this temperature, and the manner in 
 which the wasted products are removed by the skin, the lungs, the kid- 
 neys, might next obtain our attention. The complicated machinery nec- 
 essary to accomplish all these purposes requires to be made to act in uni- 
 son in all its different parts, a condition which introduces to us the nerv- 
 ous system. A consideration of the structure and gradual development 
 of this system leads to the structure of the various organs of sense, and 
 to the operations of the intellectual principle itself. Thus in succession 
 we should have to treat of digestion, absorption, circulation, respiration, 
 secretion, nutrition, and innervation, and to close the whole with the con- 
 sideration of reproduction. This is the order which I propose to follow, 
 and shall devote this chapter to the nature and qualities of the food. 
 
HISTOGENETIC AND CALORIFACIENT FOOD. 27 
 
 The supply of food to animals requires a more complicated provision 
 than it does to plants, in which the elaborating organs, the Sourcesoffood 
 leaves, presenting themselves superficially, are always in for animals and 
 contact with the air, from which much of their nutrition is p a 
 derived. And as one portion after another becomes exhausted, it is re- 
 newed by simple mechanical agencies, such as the trembling of the leaf, 
 the warmth of the sun, or the winds. 
 
 Food, therefore, comes spontaneously to plants, which need no powers 
 of locomotion. And though, as we shall hereafter find, muscular move- 
 ment requires as its essential condition the waste of tissue, it is not nec- 
 essary for their nutrition that plants should destroy organized substance. 
 But an animal must seek its food, and for this purpose is endowed with 
 locomotion, involving the destruction of tissue. In a chemical point of 
 view, plants are organizing, and animals destroying machines. Nor is 
 this general assertion controverted by the apparent exceptions which are 
 here and there presented, as, for example, that the herbivora can form 
 sugar and fat from food in which those substances did not pre-exist, and 
 the salts of the biliary acids, which are never found in plants. 
 
 To obtain for animals the necessary supply of nutriment, the resources 
 of nature are displayed in the most wonderful contrivances. According 
 as their modes of life may be, one takes its food with its teeth, another 
 with its lips, another with its fore member, another winds around it its 
 whole body. The geometrical spider weaves a net, and lies in wait for 
 his prey ; the ant lion digs a pit in the sand. Some rely upon labor, 
 some upon force, some upon fraud. Man depends upon all. 
 
 Viewed as regards its physiological distinction, the food is generally 
 considered as of two kinds : Histogenetic or tissue-making, and classification 
 Calorifacient or heat-making. Histogenetic food furnishes the f food int . 
 chemical substances carbon, hydrogen, oxygen, nitrogen, sul- a ndcaiorifa- 
 phur, chlorine, phosphorus, iron, potash, soda, lime, &c. Ca- cient - 
 lorifacient food furnishes carbon and hydrogen mainly. In consequence 
 of this chemical constitution, tissue-making food is sometimes called ni- 
 trogenized, and heat -making non-nitrogenized food. The former is also 
 sometimes designated nutritive, and the latter respiratory. 
 
 It is, however, to be distinctly understood that these divisions are only 
 adopted for the sake of convenience, and that they have no natural foun- 
 dation. Thus it will be found, when we examine the functions which 
 the fats discharge, that though they are non-nitrogenized bodies, and are, 
 therefore, considered as belonging to the class of respiratory food, there 
 is every reason to believe that they are essentially necessary to tissue 
 development, and that the metamorphoses of nitrogenized bodies can 
 only go on in their presence. They are, therefore, as truly essential to 
 nutrition as are the latter substances. 
 
28 CLASSIFICATION OP FOOD. 
 
 So, too, as respects the albumenoid bodies, of which it would be incor- 
 rect to speak as though they were limited to nutrition. In their decay 
 or descending metamorphosis in the organism, they give rise to the evo- 
 lution of heat, and are at last dismissed under the aspect of products of 
 oxidation. They are, therefore, as far as this goes, as much respiratory 
 food as are the fats themselves. 
 
 Other ciassifi- Perhaps the most convenient subdivision of food articles 
 cations of food. j s presented in the four following groups : 
 
 1st. Carbohydrates, or compounds in which carbon is united with 
 hydrogen and oxygen, their proportion being that for forming water. 
 Starch, sugar, gum, cellulose, are examples. 
 
 2d. Hydrocarbons. Compounds containing unoxidized hydrogen. 
 The oils, fats, and alcohol, are examples. 
 
 3d. Albumenoid bodies. These contain nitrogen. Albumen, fibrin, 
 casein, are examples. 
 
 4th. Salts. Any classification of food articles which does not con- 
 tain this group is imperfect ; for salts are not only absolutely essential 
 to organic processes, but also to the construction of many tissues. As 
 an example of the former case, the chloride of sodium may be mentioned ; 
 and of the latter, the phosphate of lime. 
 
 It has been supposed that the tissue-making power of any kind of 
 Value of food food depends on the quantity of nitrogen it contains, and 
 does not de- that .jfs value may therefore be determined by chemical anal- 
 
 pend wholly on . ^ . J 
 
 its composi- ysis. Upon this principle tables have been constructed, 
 tlon - showing the agricultural worth of different articles of forage 
 
 for domestic animals. But, as will be found hereafter, when we consider 
 the physiological effect of the allotropism of bodies, these tables are not of 
 the use supposed. Without entering into details at present, the case of 
 gelatin may be taken as an example ; this, though a substance abounding 
 in nitrogen, possesses no tissue-making value, but in reality belongs to the 
 calorifacient class, and therefore its administration in the sick-room, under 
 the various well-known forms of jellies, soups, etc., is altogether deceptive 
 as regards any nutritive power, since it undergoes speedy oxidation in 
 the system, and the products of its change escape by the kidneys and the 
 lungs. The value of food is not only dependent on the occurrence of 
 certain chemical elements ; they must also be present in certain allotropic 
 states. 
 
 The same remark applies to the tables which have been constructed, 
 showing the amount of caloric furnished by different varieties of heat- 
 making food. The quantity of heat set free during the combustion of a 
 substance depends not only on the nature of the elements composing it, 
 but also on the particular states in which they occur. Combustibles may 
 have the same chemical composition, but very different heating power. 
 
COMPOSITION OF MILK. 29 
 
 Food which is typically perfect, is presented by nature to the young 
 of various animals. In milk, or in the egg, we should ex- Miikasanarti- 
 pect to find whatever is necessary for the growth of the tis- cic of food: its 
 
 i f .1 f *MI' * - M* A composition. 
 
 sues, and for the performance 01 the junctions. An exam- 
 ination of milk will therefore illustrate the essential characters of the 
 different elements of food. 
 
 Composition of JUiffc. 
 
 Water 873. 
 
 Casein 48. 
 
 Sugar of milk 44. 
 
 Butter 30. 
 
 Phosphate of lime 2.30 
 
 Other salts 2.70 
 
 1000.00 
 
 In this we notice, first, the large proportion of water present, almost 
 nine tenths of the whole amount. The double duty of this The water of 
 water has already been mentioned, to remove from the sys- milk - 
 tern effete substances which are not of a vaporous or gaseous form, and 
 which can not escape through the lungs, and to regulate the temperature 
 by evaporation. We might have added to these that it imparts a due 
 fluidity to the blood. These are conditions as necessary to the infant 
 as to the adult, and it should be remembered that two thirds of the 
 weight of the body are water. 
 
 Next follows the nitrogenized principle casein, which is closely re- 
 lated in composition to muscular flesh. It is the tissue-mak- The casein of 
 ing, histogenetic, or nutritive element of the milk, and has been milk - 
 elaborated from the albumenoid substances of the mother's system. It 
 is to be converted into the muscular, gelatinous, and other soft tissues of 
 the infant. 
 
 Casein is one of a group designated as the neutral nitrogenized bodies, 
 of which some of the more prominent are albumen, fibrin, Nature of pro- 
 and globulin. From an opinion that these all contain the tein bodies - 
 same organic radical, they are often termed the protein bodies. They 
 appear to exist in two different physical conditions, soluble and insolu- 
 ble in water; they all contain sulphur, and exhibit. a proneness to pass 
 into the putrefactive fermentation. As this takes place when they have 
 reached a certain stage of decay, they act upon other bodies as ferments. 
 Their constitution is represented in common by the formula 
 
 C 48 H 36 M N, 
 
 Of the whole group, albumen may be taken as the type and most import- 
 ant member. Indeed, as will be found hereafter, in the process 
 of digestion the others are invariably converted into it. The 
 white of the egg and the serum of the blood are usually referred to as 
 examples of albumen, though they differ in several particulars from one 
 
30 CASEIN AND FIBEIN. 
 
 another. Albumen forms basic, neutral, and acid compounds. It is a 
 basic albuminate of soda which is found in the egg and in serum of 
 blood. In certain diseased conditions the blood contains the neutral al- 
 buminate. 
 
 Casein presents nearly the same constitution as albumen, but differs 
 from it in its physical properties ; for, while a solution of albumen 
 is coagulable by heat, one of casein is not, but lactic and acetic 
 acids coagulate it, -though they have no such effect on albumen. While, 
 so far as their protein nucleus is concerned, the two substances agree in 
 composition, they differ in this respect, that casein appears to contain a 
 less proportion of sulphur, and no phosphorus. It is interesting to re-* 
 mark that, during incubation, casein arises from albumen in the eggs of 
 birds. 
 
 Closely allied to albumen and casein, and having the same protein nu- 
 cleus, is fibrin, which likewise exists in two states, soluble and 
 insoluble. Its solidification or coagulation can be produced by 
 the action of sulphuric ether, which does not affect albumen. Moreover, 
 in the coagulated state fibrin decomposes the deutoxide of hydrogen, 
 but albumen does not. The most important difference between them is, 
 that in the act of coagulation albumen shows no disposition to assume a 
 definite structure, but fibrin does fibrillating, as it is termed. The 
 analogy of constitution and closeness of relation of the two substances is 
 demonstrated by the fact that y nitrate of potash coagulated fibrin may 
 be changed into albumen, and the same conversion is accomplished in the 
 stomach by the digestive juices. 
 
 It is generally supposed, however, that fibrin contains a larger pro- 
 portion of oxygen than albumen, a conclusion which seems to be confirm- 
 ed by physiological considerations respecting its origin. For this reason, 
 Mulder describes it as a higher oxide of his hypothetical protein. It al- 
 ways is associated with fat, or, perhaps more correctly, with soaps of 
 ammonia and lime. 
 
 Fibrin is found in the chyle, lymph, and blood. In the latter fluid 
 its quantity varies in different parts of the circulation. The blood of the 
 portal vein yields it in smaller proportion than that of the jugular. It is 
 also affected very much by diet : thus Lehmann found that under an ani- 
 mal diet there was much more fibrin in his blood than under a vegeta- 
 ble one, a result which has been confirmed by experiments on dogs. It 
 has also been observed that its quantity is increased during starvation. 
 But the blood of herbivorous animals contains more than that of carnivo- 
 rous ones, and that of birds contains the most of all. 
 
 These remarks on the composition and physical properties of casein, 
 albumen, and fibrin, have been introduced for the purpose of illustrating 
 the facility with which these bodies are mutually convertible, and more 
 

 OF THE SALTS, BUTTEE, AND CUED OF MILK. 31 
 
 particularly for showing that there is nothing whatever mysterious in 
 the casein or curd of milk arising from -the albuminous serum of the 
 mother's blood, and being transmuted into the fibrin structure of the 
 muscular tissues of the infant. 
 
 Returning now to our examination of the composition of milk, as set 
 forth in the preceding table, we find that two respiratory el- The sugar and 
 ements are next upon the list : 1st. Sugar of milk, which is butter of milk - 
 to be converted into lactic acid, partly by the agency of the saliva, and 
 chiefly in intestinal digestion ; 2d. Butter, which is the oleaginous or 
 fatty portion, and of which a part is to be deposited in the adipose tis- 
 sues for a time of need, and a part, along with the lactic acid and excess 
 of sugar, is to be burned at once for the production of heat. 
 
 The inorganic body, phosphate of lime, is necessary for the earthy por- 
 tion of the skeleton, and probably the reason of the introduction The ^^ of 
 of casein, to the exclusion of other protein compounds, depends milk, particu- 
 on the power it possesses of holding phosphate of lime in solu- eaSh^nd" 
 tion, not less than 6 per cent, of its weight of this earthy body chloride of so- 
 being often obtainable from it. Among the other salts of 
 the milk, chloride of sodium may be pointed out as of special importance. 
 It undergoes decomposition in the system of the infant, its hydrochloric 
 acid giving acidity to the gastric juice, its soda entering into the compo- 
 sition of the bile and various salivary secretions. It also imparts solu- 
 bility to albumen, and, in some degree, regulates the facility with which 
 that substance coagulates. It impedes the coagulation of fibrin. 
 
 Milk is not a chemical compound, but a variable mixture of different 
 ingredients, which, under proper circumstances, may be sepa- Making of 
 rated. When the fluid is allowed to rest for some hours at the butter - 
 ordinary temperature, the fat-globules rise to the surface as cream, Vhich, 
 submitted to a strong agitation with air in the process of churning, forms 
 butter. 
 
 The casein of milk can be readily coagulated by rennet (which is the 
 mucous membrane of the stomach of the calf) at a temperature Making of 
 of 120. If parted from the residual whey, mixed with a little cheese - 
 salt and yellow coloring matter, and subjected to the action of a suitable 
 press, it is formed into cheese. No better examples of the tissue-mak- 
 ing and heat-making elements of food can be offered than cheese and 
 butter respectively. 
 
 When milk is exposed to the air, its sugar, under the influence of the 
 casein or curd, gradually disappears, turning into lactic acid, Lactic acid in 
 and the milk becomes sour. The composition of sugar and sour milk - 
 lactic acid is such, that we might, without much error, say that an atom 
 of sugar symmetrically bisected will yield two atoms of lactic acid. This 
 effect is produced by the casein commencing to pass into a state of de- 
 
32 VARIOUS KINDS OP MILK. 
 
 cay under the influence of the atmospheric air. It is likewise produced 
 during digestion by the saliva, and also by the pancreatic juice. The 
 turning sour of milk on the stomach is due to the transmutation of its 
 sugar into lactic acid. 
 
 An infant finds in its mother's milk whatever it wants for the growth 
 Physiological of its own body. In its system the curd resumes the form 
 uses of milk. O f albumen, or passes into the condition of fibrin or syntonin, 
 and in this manner its muscular and gelatinous tissues are made. The 
 butter is deposited in the adipose cells, or burned at once for the pro- 
 duction of animal heat, a part of it, however, being incidentally consumed, 
 as will be hereafter explained, in the fabrication of fibrin and for other 
 histogenetic purposes. The phosphate of lime is carried to the osseous 
 system, now in a state of rapid increase, and bone is formed from it. 
 
 But though milk is so well adapted to the wants of infantile life, it is 
 unsuited to the adult. Its nitrogenized principle, casein, though in suf- 
 ficient quantity for the repair of muscular waste and development at the 
 former period, is inadequate to these purposes at the latter, when de- 
 struction, arising from the incessant activity of the muscular system, is 
 V ri k* d so g rea ^7 increased. It is interesting to remark how the 
 of milk for dif- composition of milk is modified when there is a necessity to 
 
 nt animals. meet these indications, its nitrogenized principle being in- 
 creased in the case of animals such as the cow and horse, the young 
 of which commence locomotion almost at birth, or at a far earlier period 
 than the human infant. This excess of casein is necessary for the re- 
 pair of the resulting waste. 
 
 The Constitution of Mlk. 
 
 Source. 
 
 Casein. 
 
 Sugar. 
 
 Butter. 
 
 Goat's milk 
 
 80 
 
 40 
 
 40 
 
 Cow's milk 
 
 63 
 
 28 
 
 40 
 
 
 32 
 
 36 
 
 29 
 
 This table presents an explanation of the unsuitableness which is 
 sometimes remarked in the milk of the cow when used for the nourish- 
 ment of children. Milk which is adapted to the wants of the calf is not 
 adapted to the functional wants of the child. Experience has taught the 
 nurse that these difficulties may in part be removed by diluting it with 
 water and sweetening it with sugar, the effect of this being to -reduce the 
 percentage of the nitrogenized element, the- casein, and to increase that of 
 the respiratory, and so approximate the composition more closely to that 
 of human milk. 
 
 Moreover, milk is not suitable as the sole nourishment of adult life, 
 since it does not contain in sufficient quantity those phosphorized com- 
 pounds which are necessary for the repair of the waste of the cerebral and 
 nervous tissues, which at this period are much more active than in infancy. 
 
OF BREAD. 
 
 33 
 
 Variations in the composition of milk from its normal standard are ob- 
 served to depend upon age and bodily health. Young fe- influence of 
 males, from fifteen to twenty, yield a milk more rich in sol- ?&!!& 
 ids than that which is given at thirty-five or forty. Gesta- sition of milk. 
 tion at a late period increases the solid portions. The following table 
 of Vernois and Becquerel illustrates the influence of disease : 
 
 
 
 Influence of Disease on the Constitution of Milk. 
 
 
 In Health. 
 
 Acute Disease. 
 
 Chronic Disease. 
 
 Water 
 
 889.08 
 
 884.91 
 
 885.50 
 
 Casein and extractive... 
 Sugar ... 
 
 39.24 
 43.64 
 
 50.40 
 33.10 
 
 37.06 
 43.37 
 
 Butter 
 
 26 66 
 
 29.86 
 
 32.57 
 
 Salts 
 
 1.38 
 
 1.73 
 
 1.50 
 
 
 1000.00 
 
 1000.00 
 
 1000.00 
 
 From this consideration of the nature and properties of the food of in- 
 fancy, we may pass to the examination of that of the mature period. 
 
 Experience has shown that, of all articles of food, bread made from 
 wheaten flour meets best the requirements of the adult life of 
 
 T, ^ 11 ,1 , f A Of bread. 
 
 man. It seems to contain all that is necessary lor support. A 
 
 very simple analysis will show how it presents both the respiratory and 
 
 nutritive elements. 
 
 If such flour be made into a paste with water, and be gradually washed 
 with a larger quantity, an elastic coherent mass is left, and Examination 
 the water assumes a milky turbidity. After a time it be- ^atandof 
 comes clear, through the settling of a white precipitate, which other grains. 
 is starch, the leading member of the respiratory group. The elastic sub- 
 stance is gluten, which is a true vegetable fibrin, mixed with another 
 nitrogenized body, gliadine, which may be removed, along with a certain 
 quantity of oil, by washing with ether and alcohol. 
 
 Thus, simply by washing in water, flour may be separated into two 
 physiological elements, respiratory and nutritive, the former being the 
 starch, and the latter the gluten. The relative quantity of tlicse substan- 
 ces differs in different samples of flour, and, other things being equal, the 
 greater the amount of gluten the more valuable the sample, because the 
 more nutritious. It is interesting to remark that the liquid from which 
 the starch has settled, if brought to the boiling pointy becomes turbid 
 again, from the coagulation of the vegetable albumen it contains. 
 
 Other grains, treated in the same manner, yield similar results. The 
 flour of barley and of the oat, when washed with water, do not, however, 
 yield gluten, but a pure fibrin, with a separation of starch. 
 
 The fibrin occurring in these grains is replaced in other nutritious 
 seeds, such as peas and beans, by legumin, which, like the casein of milk, 
 does not coagulate by boiling, but merely forms tenacious skins as it is 
 evaporated. These may be removed by skimming. This substance, 
 
 C 
 
34 OF MIXED DIETS. 
 
 which presents many analogies to casein, is coagulable by acetic acid 
 and alcohol, and, if mixed with sugar, turns curdy, and becomes sour 
 from the presence of lactic acid. It differs from casein in not dissolving 
 in concentrated acetic acid, and, when precipitated by an acid, being un- 
 acted on by carbonate of lime. It is, however, coagulated by rennet. 
 
 Thus, when we use bread made of any of the common varieties of flour, 
 we find in it both kinds of food, the respiratory and nutritive the former 
 as starch, and the latter as fibrin. 
 
 But civilized man has greatly improved on the simple diet which Na- 
 Use of butter ture furnishes, and, without knowing the immediate or philo- 
 on bread. sophical reason, has added articles which increase the respira- 
 tory element. The proverb says, "It is good to have bread, but it is 
 better to have bread and butter." Let us examine why it is so. 
 
 Wheaten flour, in its relations to the animal system, is defective in one 
 point its respiratory element, the starch. Now the constitution of starch 
 is, that in its dry state it contains much more than half its weight of wa- 
 ter, none of its hydrogen being free, but all oxidized. It is, therefore, 
 only by the use of very considerable quantities of bread that the neces- 
 sary amount of respiratory food can be had for keeping up the tempera- 
 ture to the proper degree. But if butter be put upon the bread, the effect 
 is different. In common with all oleaginous bodies, butter contains an 
 excess of hydrogen, and therefore, under the same weight, possesses a 
 very high heating power. The defect of the flour is thus compensated, 
 and by the use of quite a moderate quantity a high temperature can be 
 maintained. 
 
 It would be very interesting to examine in this way the physiological 
 relations of the diets adopted by communities of men, and the great 
 changes which, at quite a recent period, have taken place through the in- 
 troduction of tea, coffee, and chocolate on an extensive scale among civ- 
 ilized nations. Before the discovery of the passage to the East by the 
 Cape of Good Hope, and the establishment of direct commercial relations 
 between Western Europe and China, the general diet of the agricultural 
 classes consisted chiefly of the common products of the farm and sub- 
 Of mixed di- stances readily obtained in domestic economy, such as bread, 
 cheese 8 and^' an( l*cheese, and beer. In a theoretical point of view, we can 
 beer. scarcely conceive of a diet more conducive to the sustenance 
 
 of the bodily frame. The constitution of wheat flour shows that it con- 
 tains the elements necessary for life ; and cheese, which may be regarded 
 as the preserved curd of milk, is an excellent flesh-producing body, the 
 casein of which it consists being readily convertible into muscle-fibrin. 
 The common salt used in its preparation promotes the function of diges- 
 tion, by furnishing hydrochloric acid and soda. In addition, there are 
 also in the beer, an alcoholic and intoxicating liquid, all the advantages 
 
EMBRYONIC FOOD OF BIRDS. 35 
 
 of a highly combustible body for the purposes of respiration. 'Whatever, 
 therefore, is requisite for the well-being of the animal economy is present 
 in abundance in such a diet. 
 
 From an examination of the diet-scales of the educational and invalid 
 establishments of London, the prisons and the hospitals, Beneke obtains 
 the result that the nitrogenized should be to the non-nitrogenized food in 
 weight as one to five. From other data, Frerichs calculates Ratio of nitro- 
 that the diurnal consumption should be 2.17 oz. avoirdupois non-ntoo"en- 
 of nitrogenized, and 15.54 oz. avoirdupois of non-nitrogen- izedfood. 
 ized food, that is, about as one to seven. Whatever is taken more than 
 this is superfluous. 
 
 The peculiar advantages arising from the use of casein, which in a solu- 
 ble form possesses the quality of dissolving large quantities of phosphate 
 of lime, unquestionably determine its employment as a constituent of 
 milk. But there are circumstances under which a necessity arises for 
 the use of other nitrogenized compounds, such as albumen, in early nu- 
 trition ; and then it is remarkable by what indirect methods the difficulty 
 of its want of solvent power over that earthy body is compensated for. 
 The foetal period of the life of birds furnishes an example. In the egg 
 there is, of course, whatever is wanted for the development Development 
 of the young animal ; for, merely by the process of incuba- th* e g^ori"in 
 tion, or submitting the egg to a due temperature for a suita- of its parts. 
 ble length of time, with the access of atmospheric air, the young chicken 
 forms, with all its parts complete its bony, muscular, nervous systems, 
 feathers, beak, claws. The phosphate of lime required for the skeleton 
 is not present as such, but is formed as incubation goes on ; for in the 
 yolk there is free phosphorus, to which the air finds access through the 
 pervious shell, and, effecting its oxidation, phosphoric acid is the result. 
 This reacts on the "carbonate of lime, of which the shell consists, decom- 
 poses it, and the phosphate of lime forms. For this reason we observe, 
 as the incubation proceeds, that the shell becomes lighter and thinner. 
 The albuminous fluid which constitutes the white of the egg has little 
 power of holding bone-earth in solution ; but by manufacturing the salt 
 in this manner, as it is wanted, the development of the young bird goes 
 on without difficulty. To insure the due supply of oxygen, an air-bub- 
 ble is placed at the broad end of the egg, so that, should any transient 
 circumstance interfere with the passage of air through the pores of the 
 shell, there is a little reservoir of that material on which to rely. 
 
 The mammalia find in milk all that they need in their infantile life 
 for their nutritive purposes. In the same manner birds, in their foetal 
 life, have whatever they require in the egg. For the former, casein is 
 the nutritive element ; for the latter, albumen. In both cases a ready 
 transmutation of that element into muscle-fibrin occurs. 
 
36 FOOD OF CAENIVORA AND HERBIVORA. 
 
 At a mtiturer period of life, animals may be divided into two groups, 
 carnivorous and herbivorous, or those which feed exclusively on flesh, 
 and those which feed on vegetable substances. Between these may, 
 perhaps, be introduced a minor group, partaking of the manner of life of 
 both. 
 
 The carnivorous animal finds in its prey all that is 'required for nutri- 
 Nutrition of tion ' anc * t ^ ie discharge f i ts functions. Digestion under these 
 carnivorous circumstances is reduced to its simplest conditions, and is 
 a s> scarcely more than a process of solution. In the stomach the 
 fibrin is brought into a soluble form ; in the duodenum the fats are re- 
 duced to an emulsion. The digestive apparatus has but little complexi- 
 ty. The stomach maybe regarded as a mere enlargement or pouch upon 
 the alimentary canal, having, along with the intestine, the office of bring- 
 ing the food into such a condition that it can be taken up by the veins 
 and lacteals, and so pass into the circulation. The various constituents 
 now revert into the same state in which they were before digestion be- 
 gan, the fibrin aiding in the repair of the wasted muscular tissues, and 
 the fats being deposited in the adipose cells. The bones, feathers, and 
 other such matters as have not been dissolved by digestion, are cast out. 
 
 In the production of heat and motion the carnivorous animal consumes 
 itself, and, through the oxidation incessantly going on by means of the 
 air introduced by respiration, carbonic acid, ammonia, water, sulphuric 
 and phosphoric acids are constantly forming. 
 
 On a superficial view it might be supposed that in the other group, 
 Nutrition of ^ e h^ivorous, * ne case * s quite different. These seem to 
 herbivorous spend all their lives in obtaining food. The ox or the horse, 
 put out into the pastures, is all the day long cropping the 
 grass. On a comparison of the quality and nature of the food which 
 they take with the substances of which their bodies consist, there seems 
 to be nothing in common. It was not, therefore, without reason that the 
 earlier physiologists imputed to the digestive organs of this class the 
 power of forming flesh and blood from vegetable matters. When, how- 
 ever, we come to a critical examination of the facts, we find that there is 
 no essential difference between them and the carnivora. 
 
 When the expressed juice of vegetables is permitted to stand for a 
 time, though it may have been clear at first, a turbidity sets in, and a flaky 
 material is deposited. The substance thus possessing the power of spon- 
 taneous coagulation is identical in that property, and in composition, with 
 animal fibrin. After its deposit, if the clear liquid be warmed to near the 
 boiling point, it* again becomes turbid, and a second nitrogenized sub- 
 stance subsides, which, from its quality of coagulating by rise of tempera- 
 ture and its analysis, is inferred to be identical with animal albumen. 
 When this has been separated by filtration or otherwise, and the juice is 
 
NUTRIENT MATTERS PEE-EXIST IN PLANTS. 37 
 
 slowly evaporated, there come on its surface skins of a body having the 
 same qualities as casein ; so fibrin, albumen, and casein pre-exist in plants. 
 
 Fatty matters of every description may also be extracted from vege- 
 table products. From leaves, seeds, bark, wood, etc., oleaginous bodies 
 can be obtained by the action of sulphuric ether, which removes the fat, 
 and leaves it on subsequent evaporation. 
 
 It being thus understood that the food of the graminivorous animals 
 contains nitrogenized bodies and fats ready formed, we have clearer views 
 of the function of digestion in those tribes. It is not necessary to im- 
 pute to their digestive organs the power of creating flesh and fat from 
 vegetable matter. The office of the animal is merely to collect. The 
 two groups being compared together, the carnivorous animal receives un- 
 der less compass the required amount of nutrition, and its digestive ap- 
 paratus is more compact. But the graminivorous animal must all the 
 day long collect large quantities of food, out of which it may extract the 
 little nutrient matter they contain. The carcass of an animal, seized by 
 a lion, is almost all digestible, but it would require a very large amount 
 of herbage or of grain to be supplied to an ox to make up the same quan- 
 tity of albumen .or fat. Hence the necessary complexity and size of the 
 digestive organs of the herbivorous group, and hence many of their hab- 
 its of life. 
 
 Moreover, we see that even in this apparently extreme case the ani- 
 mal system does not clearly exhibit any quality of exerting Food formed 
 a formative action, nor of grouping atoms into a state of Destroyed by* 
 higher organization. It possesses no special power of mak- animals, 
 ing flesh. To the vegetable world we have to look as the great forma- 
 tive agent. In the organism of plants the various compounds wanted 
 by animals are fabricated. Animals destroy those compounds, and in 
 so doing maintain a high temperature, irrespective of atmospheric con- 
 ditions, and give rise to the phenomena of motion and intellectuality. 
 
 Universal experience, as well as direct experiment, proves that in the 
 case of man health can not be maintained on a uniform diet, however it 
 may be with animals. A mixed food, which varies from time to time, 
 seems to be essential; and there can not be a doubt that the changes 
 which physicians have recognized in the nature of the predominating dis- 
 eases, from century to century, are connected with changes which have 
 taken place in the nature of the diet. The introduction of tea, coffee, 
 the potatoe, arid tobacco, must have made a marked impression in these 
 respects. 
 
 Undue excesses of albumen, oil, or starch, in the diet of an individual, 
 produce a liability to arthritic, bilious, and rheumatic affec- Necessity of a 
 tions. An abstinence from fresh vegetables and fruits devel- ^an^us? * 
 ops scorbutic, and a deficiency of oleaginous materials scrofu- of cooking. 
 
38 ABSOLUTE QUANTITY OF FOOD. 
 
 lous disease. It is evident that a control over these affections may be ob- 
 tained, or even their cure, to a considerable extent, accomplished, by suit- 
 able changes in the nature of the food. This is strikingly seen in the 
 improvement of the health of sailors during long voyages, since the intro- 
 duction of vegetable preparations or acid juices. In 1726, Admiral Ho- 
 * sier sailed from England to the West Indies with seven ships of the 
 line, and lost his whole crew twice by scurvy. The circumnavigation 
 of the globe is now often accomplished without the loss of a single man. 
 
 I have already remarked the insufficiency of the tables setting forth 
 the value of articles of food as dependent on their chemical constitution. 
 Such tables are of little use, agriculturally, in the case of animals, and 
 still less, physiologically, in the case of man. The art of cooking does 
 not minister alone to the gratification of the palate, it lends a real assist- 
 ance to the operation of digestion. New elements may not have been 
 added, nor existing ones removed in submitting the food to the action 
 of a high temperature, yet such a change is thereby impressed upon it 
 that it becomes more capable of digestion, and more subservient to the 
 wants of the economy. 
 
 In determining the absolute quantities of nutrient substances required 
 The absolute ^7 * ne system, Lehmann observes that there are three mag- 
 quantity of nitudes which we are especially called upon to consider : the 
 first is, the quantity of food requisite to prevent the animal 
 sinking from starvation ; the second is, that which affords the right sup- 
 ply of nourishment for the perfect accomplishment of the functions ; and 
 the last is, that which indicates the amount of nutrient matter which 
 may, under the most favorable circumstances, be subjected to metamor- 
 phosis in the blood. The method of finding the minimum of food nec- 
 essary to support life by stopping all supplies without, and determining 
 the quantities of matters which the organism uses by the excretion of 
 urine, fasces, expired and transpired products, though it has yielded re- 
 sults of the utmost importance to science, is nevertheless not altogether 
 reliable, for in such a state of inanition the system is brought into a 
 morbid condition, or, at all events, is not acting in'a normal way. More- 
 over, much depends on the activity with which the various functions are 
 carried forward, a necessity for nourishment increasing with increase of 
 external activity. And as to the amount of food demanded for the 
 maintenance of the system at its standard, it must be borne in mind 
 that of the four classes, the carbohydrates, the fats, the albuminous mat- 
 ters, and the salts, no one alone will answer the purpose, but all must 
 be employed together, and this in variable proportion, according as the 
 local, and therefore variable, wastes of the system may have been. These 
 considerations indicate how complicated the problem we have in view 
 really is. 
 
QUANTITY OF FOOD REQUIRED. 39 
 
 From the experiments of Boussingault with reference to fat, and of 
 Bidder and Schmidt with reference to the albuminates, and Maximum lim- 
 of Yon Becker with reference to the carbohydrates, we learn J^SStS 
 that only definite quantities of these substances can be ab- mentsoffood. 
 sorbed by the intestine in definite periods of time. This maximum limit 
 is, however, far more than the necessities of the system require ; hence in 
 overfeeding, though much of the excess of food passes away with the ex- 
 crement, a very large portion is, as it were, needlessly absorbed, and, un- 
 dergoing metamorphosis in the blood, is removed by the kidneys. To 
 this portion Lehmann applies the designation introduced by Schmidt, 
 luxus consumption, or superfluous consumption. Of course, the simplest 
 condition under which we can investigate the normal quantity of food 
 required is that of an invariable weight, and the difficulties of the inquiry 
 are increased when growth, corpulence, pregnancy, or other such states, 
 are included. 
 
 Though we are very far from being able to offer a complete solution 
 of the problem of the amount of food required, in its most general sense, 
 yet, through the labors of many chemists, we have accumulated several 
 facts which have a bearing on this question. Thus it is known that albu- 
 minous substances alone can not be absorbed in quantity enough to com- 
 pensate for the loss of carbon by respiration. A duck, as is shown by 
 Boussingault, expires in one hour 1.25 grammes of carbon, but can only 
 absorb of carbon in albuminates 1. 00 gramme. So, in like manner, fat alone 
 is inadequate, for of this substance 0.84 gramme, containing about 0.70 
 gramme of carbon, can only be taken up in an hour, and this is not much 
 more than half of what the respiratory operation demands. The carbo- 
 hydrates, however, can be absorbed in sufficient proportion, and in this 
 mixed manner are all the requirements satisfied. Boussingault makes 
 the curious remark that, in the quantity of starch, 5.26 parts, and the 
 quantity of sugar, 5.62 parts, which this bird can absorb in one hour, 
 there are nearly the same quantities, 2.37, of carbon. 
 
 Among the special investigations which have been made to determine 
 the amount of food used and the amount of educts from the Amount of 
 system, should be mentioned that of Valentin upon himself, food, and 
 His weight was 117 Ibs. ; his diurnal consumption of food, 
 6.451 Ibs.; solid excrement, .42 lb.; urine, 4.686 Ibs.; and 2.751 Ibs. 
 perspiration. From the more recent and very exact experiments of Bar- 
 ral, it is inferred that of 100 grammes of carbon which have been ab- 
 sorbed into the organism, 91.59 escape as carbonic acid through the lungs 
 and skin, 4.58 appear, in the urine, and 3.83 are re-excreted and appear 
 in the fasces. Upon similar principles, Lehmann computes, from the 
 data furnished by Barral, that for every 100 parts of absorbed nitrogen, 
 49.6 parts are removed through the skin and lungs, 42.07 are found in 
 
40 OF DIGESTION. 
 
 the urine, and 8.33 are re-excreted into the faeces. As a general result, 
 it follows, from these experiments, that an adult man oxidizes, on an 
 average, 289 grammes of carbon, and 18.6 grammes of hydrogen in 
 twenty-four hours. 
 
 CHAPTER III. 
 
 OF DIGESTION. 
 
 TISSUE-MAKING OR HISTOGENETIC DIGESTION. 
 
 Nature of Digestion. The Mouth, Teeth, Stomach. The Salivary Glands. Different Kinds of 
 Saliva. Properties of mixed Saliva : its Quantity, Composition, and Functions. Relation of 
 the Salivary Glands and Kidneys. The digestive Tract. The Stomach. Gastric Juice. 
 Organs for its Preparation. Manner of producing Chyme. Influence of the Nerves. Artifi- 
 cial Digestion. Preparation and Properties of Pepsin. Regional and functional Divisions of 
 the Stomach in Animals and in Man. Object of Stomach Digestion. Peptones. Use of Salt. 
 Digestibility of various Articles of Food. 
 
 BEFORE the food can be absorbed and carried to all parts of the sys- 
 Nature of t em it must be submitted to certain preparatory operations, 
 digestion. gi nC e it is either to be dissolved in the blood or transported as 
 chyle through the lacteal vessels, it is absolutely necessary to bring it 
 into a condition of solution in water, or at least into a state of minute 
 suspension in that liquid. Eeceived in masses of a certain size, it is 
 first cut and crushed into smaller portions by the teeth, and then brought 
 from an insoluble into a soluble or suspended state by the chemical ac- 
 tion of the digestive juices. 
 
 In the mouth the food is submitted to a twofold preparation. It is 
 Functions of divided by the mechanical action of the teeth, and also simul- 
 the mouth, taneously mingled with liquids secreted from the salivary 
 glands. 
 
 The animal series present us with numberless contrivances for accom- 
 plishing this comminution. The teeth, though of a bony nature, are not 
 to be regarded as appertaining to the skeleton, but rather to the digestive 
 mechanism. Their structure, number, and position differ veiy much in 
 different tribes. In certain fishes the mouth is almost lined with them. 
 In crabs they extend to the stomach, but in other cases they are restrict- 
 ed to the pharynx, or are wholly absent ; this being the case, for instance, 
 among the ant-eaters. Those insects whose food is of a fluid nature have 
 Instruments of no need of teeth ; but those which use solid material are ac- 
 in^ariou^ani- comm dated with suitable instruments of abrasion, such as 
 mals. borers, chisels, saws, nippers, the particular mechanism re- 
 
THE TEETH. 41 
 
 sorted to being adapted to the nature of the food. It is to be understood 
 that these mechanical terms are not mere metaphors, they indicate the 
 actual nature of the apparatus. The object aimed at is to obtain the food 
 in such small portions, and in such a bruised or pulpy condition, that di- 
 gestion can be accomplished promptly. In man the number of _ 
 
 , . r r . ^ ; . m T The teeth. 
 
 temporary teeth is twenty, ten in each jaw. They are arranged 
 in three classes four incisors, two canines, and four molars for the up- 
 per and under jaw respectively. The permanent teeth, which are eventu- 
 ally substituted for these temporary ones, are thirty-two in number, class- 
 p . 1 ified for each jaw as four incisors, two ca- 
 
 nines, four bicuspids, and six molars. 
 Their arrangement is exemplified in Fig. 
 1, representing the lower jaw, in which 
 i is the middle and lateral incisor, c the 
 canine, b the two bicuspids, and m the 
 three molars. 
 
 The movements of the teeth, aided by 
 those of the tongue, accomplish a due 
 abrasion of the food, and simultaneously 
 
 The human lower jaw. . . _. . . 
 
 incorporate it with the saliva, llus is, 
 
 therefore, a purely mechanical operation. It is analogous to Mechanical na _ 
 the methods to which chemists resort in their laboratories ture of mastica- 
 when they prepare solid materials for exposure to reagents. 
 
 The mingling of food with saliva, or insalivation, effects a double ob- 
 ject. Coated over with a glairy juice, the bruised substance passes 
 along the resophageal tube into the stomach ; but there are also certain 
 chemical changes, which, commencing in the mouth, are of essential im- 
 portance to the completion of digestion. 
 
 The stomach is an expansion of the alimentary canal between the 
 oesophagus and duodenum, of a conical figure, the base of D escr i pt i on of 
 which is to the left. It communicates with the oesophagus the human 
 by its cardiac orifice, and by its pyloric with the duodenum. 
 It consists of three coats or tunics the serous or peritoneal, which is 
 exterior ; the muscular, which is intermediate ; and the mucous, which is 
 interior. They are connected with each other by cellular tissue. The 
 fibres of the muscular coat run in three different directions, constituting 
 three layers ; the superficial ones are longitudinal, radiating from the oesoph- 
 agus over the surface of the organ ; those of the middle layer are circular, 
 or ring-like ; they are well developed about the middle of the stomach, 
 and by their contractions sometimes make it assume a divided appear- 
 ance, as though composed of two compartments. Toward the pylorus 
 they are also greatly re-enforced. The fibres of the third layer take, for 
 the most part, an oblique direction. The interior or mucous coat is some- 
 
42 THE STOMACH^ 
 
 times termed the villous, from its velvety appearance. Its color is very 
 variable ; it is folded into rugas, which admit of variations in the disten- 
 tion of the stomach, without interference with the structure or functions 
 of the membranes of which they are a part. The cardiac orifice is pli- 
 cated, and the opening into the duodenum is through a circular fold with 
 a central aperture the pyloric valve, which being surrounded with a 
 band of muscular fibres, acting as a sphincter, the passage from the stom- 
 ach to the intestine may be entirely obstructed. 
 
 The stomach is seen in 
 section Fig. 2, a being the 
 oesophagus ; b, the greater 
 extremity ; c, the smaller 
 curvature; d, the great 
 curvature; e, the pyloric 
 or less end ; /, A, the du- 
 odenum ; <7, place of entry 
 of the ductus communis 
 choledochus and pancre- 
 atic duct. The place of 
 
 Section of the human stomach showing its mucous interior. J 
 
 is the cardiac region: the 
 
 membrane is there plicated. The place of junction of the duodenum is 
 the pyloric region. , 
 
 The typical form of the digestive apparatus is a sac with one aperture, 
 Types of the winch serves the double purpose of affording an entrance to 
 stomach. nutritive material, and an outlet to undigested remains. In a 
 higher condition it may be conceived of as a tube open at both ends, and 
 having a sac-like swelling on its middle part. The portion of the tube 
 anterior to the sac is the type of the oesophagus, its aperture answering 
 to the mouth, the sac-like swelling being the type of the stomach, and the 
 tube leading from it representing the intestinal canal. In the more ele- 
 mentary of such forms, vessels arise from the walls of the digestive cav- 
 ity, and pass to all other parts of the system. These serve to convey the 
 elaborated material. Certain appendages are soon to be discovered in 
 connection with this simple digestive mechanism. They are for the 
 preparation of salivary, gastric, pancreatic,' or biliary juices. In size or 
 development they vary with the habits of life of the animal, or with the 
 nature of its food. Indeed, the same remark may be made as respects 
 the entire digestive tract of the highest tribes. Thus, in the bat the 
 length of the intestine is to that of the body as three to one, but in the 
 sheep as twenty-eight to one. The ruminants generally have an intes- 
 tinal tube of great length. In man and in monkeys the proportion is 
 about five or six to one. Again, as regards construction, there are many 
 
 
DIFFERENT KINDS OF SALIVA. 43 
 
 diversities, the number of digestive dilatations and their size correspond- 
 ing in some measure to the nature of the food. 
 
 Three pairs of glands, the parotid, submaxillary, and sublingual, se- 
 crete saliva. Of these organs the parotid is the largest ; its Different kinds 
 secretion is delivered through the duct of Steno. The sub- of saliva - 
 maxillary duct is Wharton's, but the sublingual pours its fluid through 
 many small apertures near the frenum linguae Besides these proper sali- 
 vas, the lining membrane of the mouth yields a fluid, the buccal mucus. 
 
 The parotid saliva is thin and watery, limpid and colorless, inodorous 
 and tasteless. Secreted during fasting or under the use of The parotid sa- 
 stimulating food, it is denser. It contains so large a quanti- liva - 
 ty of lime that, on exposure to the air, it becomes covered with an in- 
 crustation of the carbonate of that substance. It also contains sulpho- 
 cyanide of potassium. Its organic ingredient, if not albuminate of soda, 
 closely resembles that body. 
 
 From the chemical constitution of the saliva of the parotids, the phys- 
 iological function of those glands, as aquiparous organs, is established. 
 They yield a certain quantity of watery juice, which, by reason of its 
 thinness or fluidity, is readily incorporated with the food by the teeth. 
 Parotid saliva appears to have no power of transmuting starch into sugar. 
 
 The submaxillary saliva is also colorless and limpid, tasteless and in- 
 odorous. It contains no morphological elements. It is The submaxil- 
 lighter than the parotid, less alkaline, and contains less lime. lai r saliva. 
 For this reason, when exposed to the air, it does not become incrusted 
 with carbonate of that earth. It contains sulphocyanide of potassium. 
 It is so viscid and glutinous that it may be drawn into threads. From 
 this physical property it probably, facilitates deglutition by furnishing a 
 kind of anti-friction coating. 
 
 The .sublingual saliva is thin and watery, containing, like the parotid, 
 but a small percentage of solid matter, and probably dis- The sublingual 
 charging a similar function. saliva. 
 
 Besides the special salivary juices, the lining membrane of the mouth 
 pours forth a liquid the buccal mucus a thick and tena- The buccal mu- 
 cious substance, having many epithelial cells. It is alkaline cus - 
 in its reaction, does not coagulate on heating, its insoluble salts contain- 
 ing no carbonate of lime. It has been obtained for examination by tying 
 the ducts of Steno and Wharton, keeping the nostrils open and the head 
 inclined, so that, the animal being unable to swallow, the mucus flows out 
 of the mouth. 
 
 The buccal mucus, if mixed with parotid saliva, does not appear to 
 
 )ssess the power of turning starch into sugar, but, if mixed with the 
 submaxillary secretion, it accomplishes that transmutation with facility. 
 
 The saliva, as obtained from the mouth, is therefore a mixture of the 
 
44 PROPERTIES OF MIXED SALIVA. 
 
 secretions of the various salivary glands. It may be doubted whether 
 Properties of the method of obtaining it sometimes recommended, by mak- 
 mixed salivas. j n g pressure under the chin and tickling the fauces with a 
 feather, yields it of normal constitution. It is described as an alkaline 
 juice, of a bluish color or colorless, in consistency glairy, readily froth- 
 ing, and therefore well adapted for entrapping atmospheric air. It con- 
 tains, of solid matter, from 0.348 to 0.841 per cent. Its alkali appears, 
 for the most part, to be combined with an organic substance, ptyaline, 
 from which it may be separated by the weakest acids, such as carbonic. 
 In the ash of saliva the alkali occurs chiefly as phosphate : this arises from 
 rearrangement of the constituents during incineration. The saliva con- 
 tains but a trace of alkaline sulphates, the chlorides of sodium and potas- 
 sium preponderating over all the other mineral ingredients. 
 
 On standing, saliva separates into two layers : a transparent one, which 
 is supernatant, and a grayish turbid one below, which consists of a de- 
 posit of particles of pavement epithelium and mucus corpuscles, derived 
 from the lining membrane of the mouth and the salivary ducts. Its 
 chemical reaction varies to some extent with the state of the system ; thus, 
 after long-continued fasting, from being alkaline, it may approach the neu- 
 tral state. By some it is asserted that under these conditions it may 
 even become acid. There is no proof that this is owing to the appear- 
 ance of lactic acid : it may be due to butyric acid, or even the acid phos- 
 phate of soda. In morbid conditions this reaction is by no means infre- 
 quent : it has been commonly observed in intestinal inflammation, acute 
 rheumatism, intermittent fever. Donne and Frerichs assert that acidity 
 of the saliva depends on an irritation of the buccal mucous membrane. 
 
 The specific gravity of mixed saliva varies from 1.004 to 1.009. These 
 variations depend on many different causes, there being a diminution after 
 the taking of drink, and a greater increase after taking food, than even is 
 observed in the fasting state. An animal diet especially increases it. 
 
 Under ordinary circumstances, the saliva is secreted to an amount of 
 Quantity of from 15 to 20 ounces daily. The exudation is more copious 
 saliva. during mastication, speaking, reading, more being produced by 
 the use of hard than soft food. Mental emotions exert a control over its 
 flow, sometimes diminishing it, as in moments of anxiety, sometimes in- 
 creasing it, as by the anticipation of food. After eating, the flow contin- 
 ues to a considerable extent ; it is also provoked by the use of aromatics. 
 On irritation of the interior of the stomach through a gastric fistula, the 
 flow is simultaneous with that of the gastric juice. 
 
 The movements of the jaw and the pressure of the food give rise to va- 
 riations in the quantity of saliva. It is perhaps for these, reasons that the 
 parotid gland on that side of the mouth which is most used in mastication 
 secretes more than the other. Of the proportion of the different kinds of 
 
CONSTITUTION OF SALIVA. 45 
 
 saliva in the mixed secretion, nothing is known with certainty in the case 
 of man, but it is said that in horses the parotids furnish two thirds, the 
 submaxillaries one twentieth, and the sublinguals and mucous follicles 
 the rest. The secretion of the saliva goes on during sleep. 
 
 To the active organic substance of the saliva the designation of ptya- 
 line has been given. It is regarded as a ferment, possessing in 
 several respects the properties of diastase, and hence has been t>a 
 called by Mialhe diastase salivaire. 
 
 For the purpose of analysis, saliva should be obtained in a perfectly 
 fresh state, a condition not easily fulfilled, for it decomposes or changes 
 with rapidity. 
 
 During these changes, alkaline carbonates, for example, are formed in 
 abundance, though they may have existed but to a small extent at first. 
 We have already seen that in this way parotid saliva, ex- Constitution of 
 posed to the air, yields crystals of carbonate of lime. The saliva - 
 following table is presented as offering an example of the average consti- 
 tution of mixed saliva. 
 
 Constitution of the Saliva (Frerichs). 
 
 Water 994.10 
 
 Epithelium and mucus 2.13 
 
 Fat 07 
 
 Ptyaline and alcohol extract 1.41 
 
 Sulphocyanide of potassium 10 
 
 Fixed salts 2.19 
 
 1000.00 
 
 Of the fixed salts the chief are, the phosphates of soda, lime, and mag- 
 nesia, and the chlorides of sodium and potassium. The sulphocyanide 
 of potassium varies in amount considerably : it increases after meals, and 
 .especially after the use of condiments, salt, pepper, spices. Those arti- 
 cles wiuch contain sulphur, as mustard, garlic, radishes, increase its amount 
 in a very marked manner. 
 
 Not only does the saliva, as derived from the different glands, present 
 differences of constitution ; it likewise differs in various ani- Modifications 
 mals, and in the same animal according to its age. This is of saliva - 
 observed even in the case of man. The saliva of an infant at the breast 
 possesses very little power of saccharizing starch, a transmutation which 
 that of the adult accomplishes with energy. 
 
 The action of this secretion appears to be limited to starch, and certain 
 kinds of sugar, which first yield lactic and then butyric acid. It does not 
 exert any influence in transforming albuminous matter. 
 
 The saliva discharges many functions. It is a necessary intermedium 
 in the sense of taste, for substances to be sapid must be more Functions of 
 or less soluble in this juice. If insoluble, they are tasteless. SJfliva - 
 It also moistens the interior of the mouth, and prevents the sensation of 
 
46 SALIVARY DIGESTION IN THE STOMACH. 
 
 dryness. But its chief duty seems to be that of promoting the digestive 
 operation ; for, though the food remains in the mouth but a short time, 
 the action of the saliva is prolonged after the masticated mass has been 
 deposited in the stomach. Though the direct admixture of saliva with 
 gastric juice injures the power of the latter, this effect does not ensue in 
 the stomach, since they act for the most part separately. The action of 
 the gastric juice is superficial, and two distinct operations are therefore 
 conducted at the same moment, the surface of the food changing under 
 Action of the the influence of the' gastric juice} and the inner portion under 
 dnued^the that of tlie saliva ' l Mieve that in this manner the salivary 
 stomach. juice lends itself to stomach digestion, for it is well known 
 that by its aid starch changes into grape sugar, and the transmutation 
 does not stop at that point, but goes on to the production of lactic acid. 
 An acid juice is essential to stomach digestion. 
 
 After the administration of balls of starch to animals in which gastric 
 Production of fistulas have been established, sugar may be detected in the 
 sugar from stomach in the course of ten or fifteen minutes. It does 
 stomach bythe n ot appear that there is any relation between the quantity 
 saliva. O f sa li v a incorporated by mastication and the quantity of 
 
 starch in the food. Animals which swallow their food without mastica- 
 tion have either no parotids, or those organs exist in only a rudimentary 
 state ; commonly, however, their submaxillary glands are large. Un- 
 der the most favorable circumstances, the digestion of starchy food is 
 scarcely ever complete, a considerable portion being found in the excre- 
 ment. The true function of the saliva has been well illustrated by in- 
 serting amylaceous food into the stomach of dogs with gastric fistula?, 
 after tying the salivary ducts, in which case no sugar can be detected. 
 
 It has been suggested that the eventual arrest of the action of saliva 
 on reaching the stomach may be due to the digestion of its ptyaline by 
 the gastric juice. In artificial experiments, however, such a digestion 
 or destruction can not be accomplished. 
 
 The double digestion, partly salivary and partly gastric, occurring in 
 the stomach, is doubtless one of the causes of those differences which 
 have been noticed between the natural action of that organ and the arti- 
 ficial imitations of it. The influence of the saliva, even under these, 
 which may seem at first sight to be unfavorable circumstances, is far 
 from being trivial, an effect which is well illustrated by the instantane- 
 ous manner in which a solution of starch in water, mixed with an equal 
 quantity of saliva and agitated, is transmuted into a solution of sugar. 
 In a few moments its viscidity is lost, it fails to give the blue reaction 
 with iodine, becomes sweet to the taste, and readily answers to Trom- 
 mer's test. 
 * Besides the duties which have been mentioned, the saliva incidentally 
 
RELATION OF THE SALIVARY GLANDS AND KIDNEYS. 47 
 
 accomplishes a secondary object by its power of retaining gasefe in its 
 froth or foam. Atmospheric oxygen by this means is incor- Saliva carr i es 
 porated with the food during mastication, and is thus enabled air into the 
 to exert an important influence in promoting the action of 
 the gastric juice. For to the inception of the change which that juice 
 impresses on the food, oxygen is necessary. It is brought into the cav- 
 ity of the stomach entangled or dissolved in the saliva. 
 
 It has just been mentioned that the action of saliva on starch is not re- 
 stricted to the production of sugar, but that it may end in the Lactic acid 
 
 formation of lactic acid. If, therefore, any thing intervenes to 
 
 check the supply of hydrochloric acid, which usually gives drochioric. 
 acidity to the gastric juice, the system possesses vathin itself the means 
 of compensating for the difficulty.. In the interior of the digesting mass 
 lactic acid is being set free. This acid, as has long been known, can re- 
 place hydrochloric acid in its physiological duty. 
 
 Though so large a quantity of saliva as 20 ounces may be secreted in 
 a day, this being about one half of the urinary discharge, it is to be re- 
 membered that the water is not lost to the system, as in the latter case. 
 When the impure habit of profuse spitting is indulged in, it D isgusting e f_ 
 is interesting to remark the reflected effect which takes place feet of profuse 
 in the reduced quantity of the urine, and an instinctive desire 
 for water, a kind of perpetual thirst. It is probable that, under these dis- 
 gusting circumstances, the percentage amount of saline substances in the 
 saliva is increased, and that, so far as that class of bodies is concerned, 
 the salivary glands act vicariously for the kidneys, and the mouth is thus 
 partially converted into a urinary aqueduct. 
 
 The relation between the salivary glands and the kidneys is very well 
 shown after the administration of such substances as the Relation of the 
 iodide of potassium. If five grains of this salt be taken in and^hlkid" S 
 pills, and the mouth be then thoroughly washed, in the course neys. 
 of a quarter of an hour the saliva will readily strike a blue tint when 
 tested with nitric acid and starch, but the urine will not show that reac- 
 tion until after a considerable interval, perhaps even an hour or more. It 
 w.ould therefore appear that such a salt must pass again and again through 
 the salivary glands before it is finally disposed of by the kidneys, which 
 oifer the only outlet for its total removal. 
 
 Among the functions of the saliva we ought not to overlook the influ- 
 ence which its rapid secretion must exert on the state of tension of the 
 blood-vessels, an influence which probably favors the absorption going on 
 in the stomach and intestines. 
 
 Thus prepared by mastication and in,salivation, the food descends into 
 the stomach, passing along the pharynx, which dilates to receive it. The 
 rima glottidis spontaneously closes, and additional security is given to the 
 
48 
 
 THE DIGESTIVE TEACT. 
 
 tract. 
 
 Fig. 3. 
 
 respiratory passage by the valve-like shutting of the epiglottis. Through 
 the oesophagus the morsel advances "by the contraction of the muscular 
 coat, with a wave-like or undulating motion onward. The food is now de- 
 livered at the cardiac orifice of the stomach, and, entering that organ, is sub- 
 mitted to the gastric juice, which is exuding from the mucous membrane. 
 The digestive tract may be considered as presenting six prominent re- 
 iiiustration of ^ ons ^e mou t n > tne pharynx, the oesophagus, the stomach, 
 the digestive the small intestine, the large intestine. Their relative posi- 
 tion and subdivisions are illustrated in Figure 3. 1, the 
 tongue ; 2, 2, the pharynx ; 3, 3, the 
 oesophagus; 4, the velum pendulum 
 palati ; 5, section of the larynx ; 6, the 
 palate ; 7, the epiglottis ; 8, the thy- 
 roid cartilage; 9, the medulla spina- 
 lis; 10, 10, bodies of vertebra3; 11, 
 12, spinous processes of ditto ; 13, 
 cardiac orifice of stomach ; 14, splenic 
 extremity; 15, pyloric extremity; 16, 
 16, greater curvature; 17, the less 
 curvature ; 18, pylorus ; 19, superior 
 transverse portion of duodenum ; 20, 
 middle or perpendicular portion ; 21, 
 inferior transverse portion ; 22, gall- 
 bladder ; 23, cystic duct ; 24, hepatic 
 duct; 25, ductus communis choledo- 
 chus; 26, its aperture in the duode- 
 num ; 27, duct of the pancreas, empty- 
 ing into the duodenum near to the place 
 of entry of the ductus communis chole- 
 dochus ; 28, commencement of jeju- . 
 num ; 29, 29, 29, jejunum ; 30, 30, 30, 
 ileum; 31, ileum opening into great 
 intestine ; 32, ileo-colic valve ; 33, il- 
 eo-ccecal valve; 34, ccecum; 35, ap- 
 pendix vermiformis ; 36, 36, the as- 
 cending colon ; 37, transverse arch of 
 colon ; 38, descending colon ; 39, sig- 
 moid flexure ; 40, rectum ; 41, anus. 
 
 From the interior or mucous coat of 
 the stomach the gastric juice exudes. 
 This fluid may be best obtained for ex- 
 amination by gastric fistulas artificially 
 The h Uman digestive tract. established in animals. As respects the 
 
THE GASTRIC JUICE. 49 
 
 aspect of the interior of the stomach, Dr. Beaumont, who had an opportuni- 
 ty of examining it in the case of Alexis St. Martin, describes Aspect of inte- 
 it as of a light pink color, its velvety surface Ibeing coated nor of stomach. 
 over with mucus. On the introduction of food or any irritant, lucid 
 points protrude from the mucous coat ; these are the mouths of the folli- 
 cles from which the juice exudes. When in activity, the temperature 
 of the interior of the organ is about 100 Fahr. 
 
 The gastric juice is a viscid fluid, with an acid reaction and faint odor. 
 After filtration through paper it is clear and transparent, and The gastric 
 possesses all its physiological qualities. The impurities thus J uice - 
 separated from it are merely old undigested residues, on which, in no re- 
 spect, its qualities depend. It does not become turbid at 212, remains 
 long undecomposed, and retains its digestive power even after it has be- 
 come mouldy. It does not accumulate in the stomach while fasting, but 
 requires a stimulus for its ejection, and even then is produced in a limit- 
 ed quantity only. It is secreted by the follicles of the mucous membrane 
 of the stomach, which follicles may be described as cup-shaped cavities, 
 about the two hundredth of an inch in diameter, from the bottom of which 
 project two or more parallel tubes, the mouth of the cup open- i t i ssec retedby 
 ing into the stomach, and the tubes ending in a closed term- follicles, 
 ination in the tissue beneath. Toward the pylorus the cups become deep- 
 er, so as to assume the form of a cylinder, and the projecting tubes are 
 shorter. Between these follicles blood-vessels pass. They are ramifica- 
 tions from the cceliac axis, and discharge a double function. As the ar- 
 terial branches invest the roots of the tubes, they furnish nutrition for the 
 cells which are produced in crowds at that part of the arrangement ; but 
 when they have gained the interior of the mucous membrane, and are in 
 the ridges between the follicles, having assumed the character of veins, 
 they act as absorbents, conducting the material which is sufficiently di- 
 gested into the portal circulation. Agreeably to this, these vessels have 
 a larger diameter than capillaries generally. It seems, therefore, that the 
 function of the tube is the production of cells, which, originating from 
 germs at the bottom and sides of each tube, become perfected as they pass 
 forward, and soon after their extension burst or deliquesce, and as the 
 material they discharge does not possess the acid reaction, it is probably 
 the pepsin element of the gastric juice. 
 
 Constitution of the Gastric Juice of the Dog. 
 
 
 Gastric j uice, 
 without saliva. 
 
 Gastric juice, 
 with saliva. 
 
 Water . 
 
 973 062 
 
 971 171 
 
 Pepsin 
 
 17.127 
 
 17336 
 
 Hydrochloric acid 
 
 3 050 
 
 2 337 
 
 Chlorides of pot., sod., calc., amm 
 Phosphates of lime, magn., iron 
 
 4.724 
 2.037 
 
 6.418 
 2.738 
 
 
 1000.000 
 
 1000.000 
 
 D 
 
50 
 
 STOMACH FOLLICLES. 
 
 The preceding table, from Hublbenet, shows that nearly two thirds of 
 Pro erties of ^ ie s0 ^ matcr ^ ^ ^ e gastric juice is pepsin. Exposure 
 
 the gastric 
 juice. 
 
 to a very low temperature does not deteriorate the properties 
 of this substance, for it will resume its activity even after be- 
 ing frozen. But, on the contrary, a temperature approaching ebullition 
 destroys its solvent power, and the same effect ensues when it is neutral- 
 ized by an alkali. 
 
 The gastric juice acts on iron or zinc with evolution of hydrogen, an 
 effect which the acid phosphate of lime can not produce. This seems 
 to be decisive against the views of those physiologists who have imputed 
 its reaction to the latter substance. 
 
 The digestive power of this juice is impeded by the presence of almost 
 any alkaline salt. To this remark common salt offers no exception. It 
 is owing to its alkalinity that saliva injures the digesting power of gas- 
 tric juice. On the contrary, that power is very much increased by the 
 Fig. 4 presence of fat, which promotes the conversion 
 
 of protein bodies into peptones. 
 
 The mucous membrane of the stomach pre- 
 sents a reticulated appearance, as shown in Fig. 
 Stomach foiii- 4. At the bottom of each compart- 
 
 Mucous membrane of the stomach 
 magnified TO diameters. 
 
 and functions ' foUideS, the size and depth of wllidl 
 
 increase toward the pylorus. Their exterior is 
 partly covered with columnar epithelium, which extends over the inter- 
 vening ridges ; the residue is glandular, and continu- 
 ally gives origin to granules. The upper part of 
 each follicle, as well as the entire surface of the mu- 
 cous membrane, is usually covered with mucus. 
 
 In Fig. 5 is a representation, given by Todd and 
 Bowman, of stomach follicles and their tubes in a 
 vertical section. The specimen is from the dog after 
 twelve hours fasting. A represents these structures 
 in the middle region of the stomach ; B in the pylor- 
 ic region ; a a, orifices of the follicles on the inner 
 surface* of the stomach ; b b, different depths at which 
 the columnar epithelium is exchanged for glandular ; 
 d, pyloric tubes terminating variously, and lined to 
 their extremities with columnar epithelium. 
 
 Fig. 6, A, horizontal section of a stomach folli- 
 cle a little way within its orifice ; <z, basement mem- 
 brane ; b y columnar epithelium. All but the centre 
 of the cavity of the cell is occupied by a transparent mucus, which seems 
 to have oozed from the open extremities of the epithelial particles ; c, 
 
 Vertical section of stomach 
 follicles and tubes magni- 
 fied 150 diameters. 
 
HYDROID STRUCTURE OF THE STOMACH. 
 
 51 
 
 Fig. 6. 
 
 fibrous matrix surrounding and supporting the basement membrane ; d, 
 small blood-vessels. 
 
 B, horizontal section of a set of stomach tubes 
 proceeding from a single cell. The letters refer 
 to corresponding parts. The epithelium is glan- 
 dular, the nuclei very delicate, and the cavity of 
 -the tubes very small, and in some cases not visi- 
 ble. (From the dog, by Todd and Bowman, after 
 twelve hours' fasting.) 
 
 It thus appears that there are at least two dis- 
 tinct classes of stomach follicles, differ- Varieties of 
 ing from each other in anatomical con- stomach foi- 
 struction, and, as there is now reason to ] 
 believe, also in physiological function, those which 
 are near the pylorus yielding a secretion which, 
 taken by itself, exerts only a tardy action in pro- 
 ducing the solution of protein bodies, but those 
 from the middle and other portions of the organ 
 
 Horizontal section of stomach fol- T i ,1 i , ,1 T, 
 
 licles and tubes magnified 200 di- accomplishing that Solution promptly. It IS SUS- 
 
 pected that the acid of the gastric juice is yielded 
 by one class of these structures, and the 
 pepsin by the other. 
 
 A general idea of the structure of these 
 secreting follicles may perhaps be obtained 
 by likening each of them to a little glove, 
 the hand of which opens into the stomach, 
 and the fingers project upon the submucous 
 tissue beneath. From the sides and tip of 
 each finger, cells may be supposed to arise 
 continually, and, as they are crowded for- 
 ward, they undergo development, leaving 
 the hand in a perfect condition, and deli- 
 quescing as they pass into the stomach. 
 
 Though we have spoken of these folli- 
 cles as excavations or cup-like depressions 
 in the mucous tissue, according to the de- 
 scription usually given of them Hydroidcon . 
 by anatomists, it is to be under- struction of 
 stood that this view of their con- t] 
 struction is philosophically incorrect, for 
 each, instead of being a mere excavation, is 
 truly a distinct organism, analogous in struc- 
 The hydra. ture and many of its functions to a polype. 
 
52 QUANTITY OF GASTRIC JUICE. 
 
 The hydra, a fresh-water polype, may be taken as the type of this organ- 
 ism. This animal, Fig. 7, consists of a bag or digestive sac, a a, end- 
 ing in a cylinder, #, the opening to which is furnished with numerous 
 tentacles, c c c ; the tentacles enfold in their grasp objects on which the 
 hydra feeds, and by their contractions carry them to the sac. Into the 
 interior of the sac a juice exudes possessing digestive powers, and soon 
 dissolving food. 
 
 We may therefore regard the follicular structure of the stomach as a 
 colony of polypes, the tentacles of which are converged into a muscular 
 tube, constituting the oesophagus. In a stomach of ordinary size there 
 are probably a million of these organisms. Digestion is undoubtedly 
 conducted on the same physical principles in both cases, though in the 
 polype the food matter enters the follicular cavity of which the body of 
 the animal consists, but in man is contained in the stomach, into which 
 the follicles open, and pour forth their digestive fluid. 
 
 With respect to the acid constituent of the gastric juice, it appears to 
 be hydrochloric or lactic. The latter has probably originated in the man- 
 ner just described by the action of the saliva on amylaceous bodies ; the 
 former undoubtedly comes from the common salt ingested. Perhaps, un- 
 der a deficiency of common salt, lactic acid discharges the entire duty. 
 Schmidt regards the digestive principle as a conjugated acid, the nega- 
 tive constituent being hydrochloric acid, and pepsin being the adjunct, 
 the compound being analogous to ligno-sulphuric acid. About twenty 
 Quantity of parts of gastric juice are required to digest one part of dry al- 
 gastric juice. ]oumen, and about 70 ounces are secreted in a day. If the 
 hourly destruction of fibrin in average muscular action is 62 grains, about 
 60 ounces of gastric juice would be required each day for muscular repair. 
 A very large demand is therefore made upon the water in the system for 
 this use. But here the same remark is to be made as in the case of the 
 saliva ; the water, after accomplishing its object, is not lost to the econ- 
 omy, but is immediately reabsorbed. 
 
 It was remarked, in speaking of the salivary glands, that their secre- 
 Re eated as ** on P asses repeatedly through them, the saliva, as it exudes, 
 sage of extra- being swallowed, reabsorbed, and so secreted over and over 
 through the a g am ' ^ n these repeated passages, many salt substances, 
 stomach foiii- such as the iodide and bromide of potassium, will accompany 
 it, the kidneys, however, eventually removing such extraneous 
 bodies. In like manner, heterogeneous matters will make a repeated cir- 
 culation through the gastric follicles before a final removal by the kid- 
 neys. When the latter organs have been extirpated, the constituents of 
 their secretion, such as urea, may appear in the stomach. 
 
 On the deposit of the food in the stomach, a movement of translation 
 is given to it by the alternate contraction and relaxation of the fibres of 
 
SUMMARY OF STOMACH DIGESTION. 53 
 
 the muscular coat, aided to a considerable extent by the respiratory 
 movements of the abdominal walls. The course of this ro- Motions of * the 
 tation commonly is, that after passing the cardiac orifice the food in the 
 food moves from right to left round the great extremity, and S1 
 then along the large curvature from left to right, returning along the small 
 curvature, and occupying from one to three minutes to perform this revo- 
 lution, the motion continuing for a few minutes at a time. 
 
 While this is going forward digestion is rapidly taking place, and the 
 portions which have suffered complete action are oozing through the py- 
 loric valve into the intestine as a semi-fluid and apparently Formation of 
 homogeneous material called chyme. This process has fairly chvme - 
 set in in the course of an hour, and is usually finished in about four. 
 In consistency, color, and chemical reaction, the chyme varies with the 
 nature of the food, its chemical constitution, and its quantity ; but under 
 common circumstances it presents the acid reaction, for it is to be remem- 
 bered that the diurnal supply of hydrochloric acid to the stomach is about 
 the fifth of an ounce. Arrived in the intestine, the chyme is pushed for- 
 ward by the peristaltic movements, and soon after its appearance in the 
 duodenum is mixed with several important fluids the bile, which is fur- 
 nished by the liver, the secretion of the pancreas, and the enteric juice 
 which is exuding from Brunner's glands. 
 
 The digestion of the albuminous part of the food commences in the 
 stomach, and in that cavity advances far toward completion. Summary of 
 The action is not merely for the purpose of bringing those dige^n1n 
 substances into a state of solution in water, but also of modi- the stomach, 
 fying them chemically. This change is so well marked that it has been 
 found expedient to indicate it by a designation, and hence we speak of 
 albumen peptone, fibrin* peptone, casein peptone. These peptones are, 
 for the most part, absorbed by the blood capillaries, though a portion of 
 them enters the circulation as a constituent of chyle. In the system, 
 whatever their origin may have been, they seem to revert to the state of 
 blood albumen. But, though the production of these peptones is accom- 
 plished to the extent that has been mentioned in the stomach by the gas- 
 tric juice, the action is continued and brought to its completion in the 
 small intestine by the aid of the intestinal juice. It does not appear that 
 the large intestine participates in this duty, since portions of coagulated 
 albumen, or of flesh introduced into it through fistulous openings, are 
 voided through the rectum. 
 
 Such is the general description of the act of digestion. We have next 
 to enter on a physical examination of what it is that really Influence O f 
 takes place in the stomach. It was formerly supposed that the nerves on 
 
 d,. i j , . .(. ,, digestion, 
 
 igestion is entirely due to nervous agency, since, if the prieu- 
 
 mogastric nerves be divided, the process is very much interfered with. 
 
54 ARTIFICIAL DIGESTION. 
 
 But this interference takes place only in an indirect way, for the section 
 of* those nerves is attended with such a paralysis of the stomach that 
 those movements which so well serve to mix up the food with the gas- 
 tric juice, and expel it through the pyloric valve, are put an end to. 
 
 Bidder and Schmidt, from an examination of four dogs with gastric 
 Effect of section fistnlge, demonstrated that the section of the pneumogastric 
 of the pneumo- nerves does not exert that influence on the secretion of the 
 gastric juice which had been formerly supposed, for both in 
 quantity and composition it remained the same. Even in those cases in 
 which both they and others have observed a diminution in its amount, 
 the result ought, probably, to be referred to the shock given to the entire 
 system by the severity of the operation. 
 
 The acidulating material of the gastric juice is hydrochloric acid. Is 
 it possible by artificial mixtures containing that substance to reduce 
 food articles to a digested condition ? This inquiry introduces a descrip- 
 tion of the experimental investigations which have been made in artificial 
 digestion. 
 
 When water acidulated with hydrochloric acid is kept in contact with 
 Artificial di- albumen, no action is perceptible at ordinary temperatures in a 
 gestion. moderate period of time. If the temperature is raised to about 
 150 a slow dissolution ensues, which becomes better marked as the heat 
 rises toward 212. 
 
 f But if to the weak hydrochloric acid thus made to act on albumen, 
 pepsin is added, the solution takes place with rapidity at moderate tem- 
 peratures. An ounce of water, mixed with twelve drops of hydrochloric 
 acid to which one grain of pepsin has been added, will completely dis- 
 solve the white of an egg in two hours at a temperature of 100. It 
 acts in the same manner on cheese or flesh, these nitrogenized articles 
 being converted into soluble non-coagulable bodies. The acid does not 
 enter into chemical combination with the dissolving organic matter. It 
 may be recovered from the solution by resorting to proper processes. 
 
 When striated muscular tissue is submitted to artificial digestion, it is 
 Artificial di- ^ rst divided into its constituent fasciculi, and the transverse 
 gestion of mus- stride then disappear, the sarcolemma being destroyed. The 
 course of the action seems to be the same in natural diges- 
 tion. In the fcecal matter, shreds of muscular fasciculi still bearing their 
 striation may be discerned. These, having by chance escaped solution 
 during their sojourn in the stomach, have passed through the whole 
 length of the digestive tube unchanged. 
 
 Pepsin the substance resorted to in these experiments may be ob- 
 tained by macerating the mucous membrane of the stomach 
 
 Pepsin, prep- ' & 1-1 
 
 aration and for a short time in lukewarm water. This water, along with 
 properties of. a ^^ O f t ne pepsin, removes various impurities ; it may there- 
 
FUNCTIONS OF PEPSIN. 55 
 
 fore be cast away $ the maceration being then continued with a fresh por- 
 tion of cold water, and this being submitted to nitration, and subsequent- 
 ly evaporated at a low temperature to dry ness, yields the pepsin as a 
 gummy mass. From its solutions pepsin may be precipitated by corro- 
 sive sublimate or acetate of lead, and it may be separated from those 
 combinations by sulphureted hydrogen. Wasmann availed himself of 
 this fact to obtain it in a pure state. 
 
 Composition of Pepsin. (From Schmidt.*) 
 
 Carbon 530.00 
 
 Hydrogen 67.00 
 
 Nitrogen 178.00 
 
 Oxygen 225.00 
 
 1000.00 
 
 From this it would appear that it contains less carbon and more nitro- 
 gen than the members of the protein group. 
 
 A weak acid therefore possesses at a high temperature the power of 
 
 bringing into a state of solution the various nitrogenized food _ 
 
 -II -. o -1 <> i - Pepsm re- 
 
 matters, and at lower degrees fails of that property ; but in places a high 
 
 the presence of pepsin the solvent powers are assumed un- tem P eratur e. 
 der the latter circumstances, and therefore it is said of this substance 
 that it replaces a high temperature. By its aid, hydrochloric or lactic 
 acids present in the stomach reduce the food to a uniform pulpy mass 
 the chyme. Of all acids, these, however, alone arc capable of forming 
 digestive fluids. 
 
 Formerly it was supposed that the act of digestion was simply me- 
 chanical, the food being ground down to chyme by the mo- R ex 
 tions of the stomach. Reaumur's experiments showed the perimcntswith 
 error of this supposition. He took small hollow silver balls, Sllver balls * 
 perforated with holes, and, having filled them with meat, caused them to 
 be swallowed by a dog. When they had remained in the animal's stom- 
 ach a suitable length of time, they were withdrawn by a thread which 
 had been previously attached to them. Now if the stomach acted by a 
 triturating or grinding power, the material within the ball would be en- 
 tirely protected, but if by a solvent power exerted by the gastric juice, 
 the digestion should at most be only delayed. Accordingly, it was found 
 that this was what actually took place, digestion being fully, though more 
 slowly accomplished, the action commencing on the outside of the mate- 
 rial, and gradually reaching its centre. If the balls were kept in the 
 stomach long enough, they came out quite empty at last. 
 
 The idea that there is something more than a simple solution of the 
 food effected in the stomach, that some mysterious change is Chief object of 
 impressed upon it by the vitality of that organ, may there- tSrthe^oiu" 
 fore be abandoned. It does not appear that there is any es- tionofthefood. 
 
56 NUTEITIVE MATTER IS DISSOLVED. 
 
 sential difference between natural digestion and the artificial imitation of 
 it, either as respects the order of action or the final result. Moreover, 
 the anatomical consideration that the food is yet outside the body, though 
 it is inside the stomach, should be sufficient to remove all errors of that 
 kind. A living surface, such as the skin, never exerts any chemical ac- 
 tion at a distance ; and the lining membrane of the stomach, both as re- 
 gards its physiological origin and its anatomical relation, is nothing more 
 than a reflected continuation of the skin. The act of digestion is com- 
 pleted long before the nutrient material is taken up by the lacteals and 
 veins, and thrown into the torrent of the circulation. But then, and not 
 till then, is the food fairly in the interior of the body. 
 
 The lacteals and veins can not exert their absorbent action on a sub- 
 stance presented to them unless it is dissolved in water. If not abso- 
 lutely dissolved, at least it must be in that condition of minute subdivis- 
 ion which we see in emulsions. Though it has been stated that insolu- 
 ble substances, such as charcoal, can find their way into the circulation 
 in the solid state, there does not appear to be a sufficient weight of evi- 
 dence to support such an improbability. In the economy of plants, it is 
 In plants, all a general rule that nothing can have access to the interior of 
 nutrient mate- t} ie i r system except it be dissolved in water. All the vari- 
 
 rial must be in ITT i 
 
 solution in \va- ous gases and saline substances they require are obtained in 
 ter - a state of solution ; the former are introduced, for the most 
 
 part, through the leaves, the latter through the roots. The object aimed 
 at in the construction of the digestive apparatus of the animal mechanism 
 is absolutely the same. Plants use as their food inorganic matter only ; 
 the chief materials on which they depend, such as the salts of ammonia 
 and carbonic acid, are abundantly soluble in water. The ascending sap 
 obtains the former from decaying organic residues in the ground ; the at- 
 mosphere presents the latter unceasingly to the leaves ; and since the 
 economy of many plants requires earthy salts, as silicates and phos- 
 phates, which are of sparing solubility in water, the difficulty arising from 
 that want of solubility is avoided by the introduction of an immense quan- 
 tity of water, which, after bringing into the plant the needful amount of 
 mineral material, is evaporated off at the leaves. But the food of animals 
 is essentially organic, and this, before it can be received into their blood, 
 must be brought into the dissolved state. It must be submitted to a pre- 
 paratory operation or series of operations. However complicated these 
 The operations or the niechanism which accomplishes them may be, the end 
 on the food are aimed at is clear. The action begins by the cutting, tearing, 
 
 purely chemic- , 11-11 i j 
 
 aland median- and crushing movements of the teeth, which break down all 
 ical> the larger portions, and carry on the process as far as it is 
 
 possible by mechanical means. The stomach then continues the subdi- 
 vision by chemical agency, to the end that a condition of solution may be 
 
OBJECTS OF DIGESTION. 57 
 
 attained. Digestion is not, therefore, to vitalize the food, as the ancients 
 supposed, nor to communicate to it any new or obscure properties ; it is 
 for the purpose of comminuting, subdividing, dissolving, or bringing it 
 into that minutely suspended state that it can without difficulty submit 
 to the absorbing action of the lacteals and veins. There is a complete 
 analogy between this operation and the artificial processes to which the 
 chemist resorts in his laboratory for the solution of various bodies. He, 
 too, uses mechanical implements the mortar and pestle to grind, the ham- 
 mer to crush, the rasp to abrade. When these have carried the subdi- 
 vision sufficiently far, he resorts to acids or other solvents, and thus 
 breaks down the compactness of the hardest minerals, and brings them 
 into the dissolved state. The animal world presents us with a thousand 
 illustrations of the principles here set forth, mechanical contrivances curi- 
 ously arranged. For instance, birds, whose plan of organization is such 
 as to meet the case of locomotion through the air, could not have the an- 
 terior part of their bodies loaded with teeth, accompanied as they must 
 have been with a powerful muscular apparatus. Such a mechanism 
 would have rendered the animal top-heavy, and would have been totally 
 inconsistent with flying. But, to avoid this difficulty, that which might 
 truly be regarded as the mouth is lodged in the interior of the body, nearer 
 the centre of gravity. It is the gizzard. Instinct teaches the bird to 
 swallow small angular stones, and the food, rasped between powerful mus- 
 cular surfaces, is soon brought into a fit condition for the action of the 
 stomach. The chemist, too, puts fragments of glass or of quartz into the 
 
 mortar in which he is conducting the reduction of a tough or resisting 
 
 o o o 
 
 substance. 
 
 The first object of digestion is, therefore, the subdivision of the food. 
 The operation begins in the mouth by a resort to mechanical implements, 
 and when these have carried the process as far as they can, the stomach 
 continues the duty. In its cavity, when in full activity, the temperature 
 is 100 ; a periodically increasing and relaxing motion of revolution is 
 kept up, gastric juice exudes in definite quantity, the hydrochloric and 
 lactic acids exert their action, and in the course of three or four hours 
 a complete reduction is accomplished. 
 
 Allusion has been made to the probability that different portions of 
 the mucous membrane of the stomaeh discharge functions Regional divis- 
 which are wholly distinct, one portion being devoted to the ^iSaSS^' 
 elaboration of pepsin, another to the secretion of hydrochlo- ent functions. 
 ric acid, another to the preparation of a special mucus. This view de- 
 rives considerable support from many facts in comparative physiology. 
 In those cases in which the food approaches, in its mechanical and chem- 
 ical condition, to the form which it is destined to assume as a part of the 
 body of the animal receiving it, the stomach is simple in construction, 
 
58 
 
 DIGESTION IN INSECTS AND BIRDS. 
 
 Fig. 8. 
 
 and is little more than a mere dilatation of the alimentary canal. But 
 Analogous ar- when, as among the herbivora and granivora, 
 SffS*ni? there is a g reat differ ence Between the form 
 mais. of the food received and the form of the tis- 
 
 sues to be made, the digestive sac no longer presents 
 such a simple structure, but is parted off into distinct 
 regions, or is actually converted into distinct organs. 
 Thus, in the insect digestive tract shown in Fig. 8, 
 
 Digestives- a is the P hal 7 nx > * the oesophagus, lead- 
 partmcnts of ing into a crop or insalivatory pouch, c, and 
 this into the gizzard, d, the function of which 
 is to rasp up and abrade the more resisting portions of 
 the food, which, when this is accomplished, passes into 
 the true stomach, e, and from thence into the intestine, g. 
 The delicate vessels about f are supposed to be biliary 
 tubes, and h glandular secreting organs. 
 
 T-, , f i Digestive tract of a car- 
 
 Even in these cases of minute organization, the mu- nivorous beetle. 
 
 cous structure remains the same as in larger animals of the same mode 
 
 of life. The photographic represetita- 
 tion in Fig. 9 displays the same retic- 
 ulated appearance in the stomach of 
 the carnivorous beetle as has been de- 
 scribed in the case of that of man; 
 and undoubtedly, with similarity of 
 structure there is similarity in the man- 
 ner of action. 
 
 A regional division of 
 the digestive apparatus 
 is also presented in the 
 case of many birds, as 
 is shown in the photo- 
 graphic representation, 
 
 Fig. 10, in which we have the digestive tract of the corn- 
 Digestive com- mon fow1 ' a be?in S the oesophag* 8 leadin g 
 into the insalivating pouch or crop, 
 
 which empties into the stomach, c, 
 and this into the gizzard, d. In the stomach, 
 which is relatively small, the digesting material 
 is mingled with the gastric juice before being 
 submitted to the action of the gizzard. From 
 the gizzard it is passed into the small intestine 
 y, f. In the figure, e is the liver, # , g, the cceca, 
 and h the cloaca. Dlgcstive tract of th: common fowl 
 
 Fig. 10. 
 
 Mucousmembraoeachofacarnivo- 
 
 partments of 
 
EEGIONAL SUBDIVISIONS OF THE STOMACH. 
 
 59 
 
 In the ostrich, as shown \nFig. 11, the local distribution of the glan- 
 Fi d- n- _ duke very obviously marks out a regional dis- 
 
 tribution of function. C is the cardiac cav- 
 ity, the mucous membrane of which is stud- 
 ded here and there with glands ; G G are the 
 surfaces of the gizzard. Among the higher 
 quadrupeds, the evidences of a similar divis- 
 
 Fig. 12. Fiy. 13. 
 
 Interior of stomach of African ostrich. Stomach of dormouse. Stomach of Cape hyrax. 
 
 ion of function are presented. Thus, in the dormouse, fig. 12, there are 
 two compartments : a cardiac, C, and a pyloric, P ; the same Digestive com . 
 being exhibited more perfectly in the Cape hyrax, Fig. 13. partments of 
 In these -cases the cardiac compartment is often lined with 
 cuticle, but the pyloric not. An increase in the number of these cavities 
 occurs as the food becomes more heterogeneous. In the porcupine, Fig. 
 14, there are four, and in the porpoise, Fig. 15, five. The stomach of 
 
 Fig. 14. Fig. 15. Fig. 10. 
 
 Stomach of porcupine. Stomach of porpoise. Stomach of kangaroo. 
 
 the kangaroo, as shown in Fig. 16, possesses a multitude of these cham- 
 bers or compartments, and therefore offers a good illustration of the sub- 
 divisions of stomach digestion. 
 
 . IT. The case of ruminants 
 
 possesses a special inter- 
 est. In these there- are 
 what might be termed 
 four different digestive 
 chambers, as is shown in 
 Fig. 17, in which a is the 
 
 Digestive cavities of a ruminant. O3SOphagUS ; b, the inglu- 
 
60 DIGESTION IN EUMINANTS. 
 
 vies or paunch; c, the reticulum or honey-comb stomach; d, the omasum, 
 Di estive com- man 7pli es or third stomach ; e, abomasum, reed, or fourth 
 
 partments of stomach ; and y, the pylorus. The food, roughly triturated 
 in the mouth, enters the ingluvies, in which it is moistened; 
 it then passes into the honey-comb or second stomach, which likewise 
 receives directly the water that has been taken, and, after it has been 
 thoroughly moistened therewith, it is returned to the mouth in small 
 portions, to undergo a more complete mastication and insalivation. Be- 
 ing swallowed again, it is now directed into the third stomach, from 
 which it passes into the fourth. In this it is submitted to a true acid 
 digestion, a gastric juice being secreted from the walls of this cavity. It 
 is the mucous lining of this cavity which yields rennet. That these com- 
 plicated motions and these successive actions of the different cavities are 
 for the purpose of preparation for the true digestion of the fourth stom- 
 ach, is clearly proved by the fact that in the calf the milk passes directly 
 into the abomasum. 
 
 Since fishes and water animals generally have no salivary glands, or 
 Digestion on ty rudimentary ones, some physiologists have inferred that the 
 in fishes. use o f the saliva is for the commingling of the food with a due 
 portion of water. This would reduce the importance of insalivation very 
 greatly, and, indeed, is scarcely consistent with the elaborate mechanism 
 which has been just described in the case of ruminant animals. It is 
 worthy of remark that, even among fishes, there are some which exhibit 
 a true rumination, as, for example, the carp. This is not alone for the 
 purpose of resubmitting the food to the abrading action of the pharyngeal 
 teeth, but likewise for commingling it with the secretion of the pharyn- 
 geal cavity. 
 
 In view of the preceding facts, it may be concluded that, so far from 
 there being any thing in contradiction to the doctrine that different por- 
 tions of the digestive surface of the mucous membrane of the stomach are 
 devoted to different duties, there is strong evidence in support of its truth, 
 derived partly frpm the instances furnished by comparative anatomy, and 
 partly from the anatomical structure of the gastric mucous membrane. 
 The four separate digesting chambers of the ruminating herbivora are 
 merely an elaboration of the structure which is presented by an appar- 
 ently homogeneous mucous surface in man. But that this mucous sur- 
 face is in reality heterogeneous, and in different regions possesses differ- 
 ent powers, is shown by the fact that at one part it presents mucous fol- 
 Reo-ionai func- ^ c ^ es at another pepsin follicles, at another follicles for the 
 tions of human secretion of hydrochloric acid. As we approach toward the 
 pylorus, the existence of a new function is betrayed by the 
 appearance of a new mechanism the villi, which have been so well stud- 
 ied by Dr. Neill, and this is even indicated externally in the posterior 
 
EEGIONAL DIVISIONS OF THE HUMAN STOMACH. 
 
 61 
 
 Posterior view of human stomach. 
 
 of the well-known plicse fimbriatse. 
 
 Flg ' 18 ' view of the human stomach, Fig. 
 
 18, showing, according to Profess- 
 or Retzius, that the antram py- 
 lori of the older anatomists is re- 
 ally a special compartment of the 
 general cavity. The figure is 
 derived from numerous examin- 
 ations of the stomach in bodies 
 of middle-aged women, and, as 
 represented at c c, d d, indicates 
 the antrum pylori, a being the 
 oesophagus, b the cardiac orifice. 
 The antrum pylori is distinguish- 
 ed by greater thickness of its mus- 
 cular coat, more copious glandu- 
 lar development, and the presence 
 The commencement of the duode- 
 num also forms a special rounded cavity, which Professor Retzius pro- 
 poses to name antrum duodeni, characterized internally by the absence 
 of valvulae conniventes, and by the dense array of Brunner's glands be- 
 neath its mucous membrane. This part constitutes what has been called 
 the fourth stomach in the porpoise and some other cetaceans. The so- 
 called ligaments of the pylorus are connected with the formation of the 
 antrum pylori. 
 
 It has been remarked that the first aim of digestion is the procuring of 
 the food either in a dissolved state, or, at all events, in a con- Di gest ion ac- 
 dition approaching thereto. But, in .addition to this, pro- compiishes so- 
 found changes in the very nature of the digested material metamorphosis 
 must, in an incidental way, be constantly occurring. Thus of the food - 
 the action of saliva is to produce lactic acid from starch, and thus, in 
 the stomach itself, starch is transmuted into sugar. In some cases the 
 first stage of digestion seems to be actually the reverse of what has been 
 here set forth. Milk, when received into the stomach, undergoes coagu- 
 lation, and, in like manner, so also does soluble albumen. But these are 
 only incidental changes, the temporary solids thus produced soon lique- 
 fying as proper digestion sets in. There is reason to believe that all the 
 protein bodies are passed into the condition of albuminose, and this though 
 they may have been introduced in the liquid state. Even soups and 
 broths require to be digested. A solution of gelatine, after G t . 
 it has been in the stomach, refuses to gelatinize, a solution ges of the food 
 of albumen to coagulate. The circumstance that gases may di^iJons^an?" 
 be evolved from digesting material, both in the stomach and assimilation of 
 intestine, is a sufficient proof that that material is undergoing water< 
 
62 USE OF COMMON SALT. 
 
 a more or less extensive change. But these changes are altogether insig- 
 nificant when compared with those great metamorphoses which the nu- 
 trient material passes through after it has been absorbed from the digest- 
 ive cavities ; and doubtless, at the most, they are only mere subdivisions, 
 of which the splitting of the sugar or starch atom into lactic acid may be 
 taken as the type, or mere unions with water, of which the passage of 
 cane sugar into milk sugar is an example. 
 
 The gastric juice, therefore, not only dissolves, but also, in an incipient 
 Production of an< l indirect manner, modifies the food. Protein bodies and 
 peptones. gelatinous matters yield substances after its action of the 
 same composition as their own, but with different physical and chemical 
 properties, being readily soluble in water, and even in diluted alcohol, and 
 not forming insoluble compounds with metalline salts. By Lehmann, 
 who has examined these substances, they have been designated as pep- 
 tones ; and since they may arise without the evolution or absorption of 
 any gas, and the quantity of sulphur they contain is the same as that in 
 the bodies from which they were derived, he infers that the action is real- 
 ly an assimilation of water, the other ingredients remaining unchanged. 
 
 Turning our attention now to the origin of the gastric juice, it is inter- 
 esting; to observe the economical manner in which its hydro- 
 Use and man- . . . , . 
 agement of chloric acid element is managed. To the proper understanding 
 jommon s t. Q ^j^ ^ j s necessary to anticipate what will have to be more 
 fully considered in describing the bile, a uniform ingredient of which is 
 the oxide of sodium, or soda. The hydrochloric acid of the gastric juice 
 and the soda of the bile are derived from the same source common salt, 
 which is either present in the food, or purposely added as a condiment. 
 It undergoes decomposition easily, yielding the two products specified, 
 that is, hydrochloric acid and soda, and is readily formed by the reunion 
 of these substances. 
 
 There exists in the action of the kidneys a special provision for prevent- 
 ing the quantity of chloride of sodium present in the blood from rising 
 over 41 parts in 10,000. This, of course, controls the amount diffused 
 through the tissues. The necessity of such a regulation becomes appar- 
 ent when we consider that the rate of the solubility of albumen and ca- 
 sein in water is governed by the presence of that substance, as is also the 
 quickness with which the coagulation of fibrin takes place, and the re- 
 pair of the waste of the muscles. 
 
 Common salt introduced into the system undergoes decomposition, 
 furnishing hydrochloric acid to the gastric juice, and soda to the bile. 
 Considering the large quantity of these secretions produced in a short 
 space of time, it is clear that the drain of common salt must be great 
 not less than a third of an ounce a day ; yet the quantities consumed, at 
 most, are only small. 
 
SUMMARY OF DIGESTION. 63 
 
 How, then, is this to be explained? Assuredly there is no other 
 source from which these bodies can come than the one indicated the 
 common salt, and yet it seems to be totally inadequate. 
 
 I think that this difficulty ?s rather imaginary than real. Things are 
 so arranged that a limited quantity of salt can produce unlimited quanti- 
 ties of gastric juice and bile ; for the former, associated with the food it 
 has digested, scarcely escapes from the pyloric valve before it encounters 
 the bile and pancreatic juices discharging into the duodenum, and through 
 the length of the upper portion of the small intestines these secretions, 
 together with the food they have acted upon, are brought into complete 
 contact. The reproduction of chloride of sodium is therefore constantly 
 taking place in intestinal digestion, and it returns back to the system 
 through the absorbents. Again it undergoes decomposition, its acid re- 
 appearing in the gastric juice, and its alkali in the pancreatic juice and 
 bile. By thus using a small amount over and over again, great effects 
 can be produced, and it is then only necessary to restore those small por- 
 tions that are wasted in carrying out the general scheme. 
 
 In the low-pressure marine steam-engine we have an example of the 
 same kind. A certain quantity of water is vaporized in the boiler and 
 condensed in the engine ; pumped back into the boiler to be vaporized, 
 arid then recondensed in the engine. Comparatively little is required to 
 supply the wants of the machine, and long voyages can be made with 
 only as much water as will compensate for the necessary waste arising 
 in the working. 
 
 For the sake of presenting the consideration of the function of diges- 
 tion with clearness, it is customary to leave out of consider- Stomach di 
 ation the subordinate actions taking place both in the stom- gestion is his- 
 ach and intestine. This, however, involves a certain amount JeftlnafdLes- 
 of error, since respiratory or non-nitrogenized digestion oc- tion is caiorifa- 
 cuf s in the former cavity, and nutritive or nitrogenized in the 
 latter. Nevertheless, there can be no doubt that if our view is restricted 
 to the more imposing characters, we are justified in accepting the dogma 
 that " stomach digestion is histogenetic or nitrogenized, and intestinal 
 digestion is calorifacient." 
 
 Under the most comprehensive point of view, examining the action of 
 the entire digestive tract from the mouth to the rectum, we General sum . 
 discover a recurrent periodicity. In the mouth, the transi- mary of diges- 
 tory digestion taking place is wholly expended upon the ca- 
 lorifacient food ; in the stomach it is the nutritive portion which is chiefly 
 attacked ; in the duodenum there is a return to the calorifacient, and in 
 the ccecum of animals a resumption of the nutritive. This last is less 
 apparent in man, for in him the ccecum exists only in a rudimentary state, 
 represented by the appendix vermiformis. 
 
64 DIGESTION OF GELATINE. 
 
 As the alteration takes place from calorifacient to nutritive digestion, 
 the active fluid changes its chemical relations. In the mouth and duo- 
 denum, alkaline juices are resorted to ; in the stomach and coecum, acid 
 ones. Whenever there is an accidental inversion of these conditions, the 
 result correspondingly changes ; so when bile, which is alkaline, regur- 
 gitates into the stomach, the digestion of nutritive food is instantly ar- 
 rested. 
 
 In each of these cases the object is the same: it is to obtain the nutri- 
 ent material under such forms that the absorbent vessels can readily take 
 it up ; this, as we have seen, often involves a metamorphosis of the ele- 
 ments of the food where mechanical subdivision would be insufficient. 
 Fibrin has to be brought into a soluble state, and, indeed, albumen itself 
 must be modified. If it has been taken uncoagulated or glairy, it be- 
 comes opalescent, and passes into the allied form known as albuminose. 
 In this condition it is neither precipitated by heat nor by nitric acid, 
 though it is by corrosive sublimate. The cause of this transformation 
 probably has reference to the relative facility with which albuminose can 
 transude into the venous capillaries compared with albumen. 
 
 There is thus reason to suppose that the result of stomach digestion 
 is the reduction of the various nitrogenized constituents of the food to 
 the condition of albuminose. It is plain that fibrin must come into this 
 or some analogous condition, for it can not be absorbed as fibrin, and, ac- 
 cordingly, it is found that the blood of the gastric and mesenteric veins 
 abounds in albuminose. 
 
 Intermediate between the classes of calorifacient and histogenetic food, 
 Case of gela- belonging, by its composition and conditions of digestion, to 
 tine - the latter, but by the function it discharges to the former, is 
 
 gelatine, a nitrogenized substance. It appears to be always derived from 
 albumen, and any portion which may have been received in the food is 
 never directly assimilated or used for the fabrication of tissue, but solely 
 ministers to the production of heat. Though thus a calorifacient body, 
 its place of digestion is the stomach. After it has suffered the action of 
 that organ it has lost its power of gelatinizing, can no longer be precip- 
 itated by chlorine, nor give the leather precipitate with tannin. The use 
 of it under the form of jellies, soups, etc., is always attended with the ap- 
 pearance of an unusual quantity of urea in the urine, and hence the ad- 
 ministration of those domestic preparations, under an idea of their great 
 nutritive value, is to be looked upon as only a popular error. In an in- 
 direct way, however, under the conditions of restricted diet, usually met 
 with in the sick-room, gelatine doubtless maintains an interesting relation 
 to the albumenoid bodies in this, that it protects them from destruction 
 by undergoing oxidation itself, and so satisfying the requirements of the 
 respiratory mechanism ; for, were there not such a substance present to 
 
EELATIVE DIGESTIBILITY OF FOOD. 65 
 
 receive the attack, the respired oxygen would rapidly bring on the waste 
 of the proper nitrogenized tissues. 
 
 In relation to the gelatigenous tissues, it may be remarked that gela- 
 tine is not an actual constituent of them, but arises from them Gelatine not 
 by boiling with water. By a like process, sufficiently pro- e^n^ 
 longed, a similar substance may be obtained from cartilage, ent. 
 designated cartilage-gelatine, or chondrine. In these cases the material 
 unites with water in the same manner that starch does in producing glu- 
 cose. 
 
 The food must therefore pass through various stages before it can be 
 fitted for introduction into the circulation, and carried to all parts of the 
 system. It is procured in portions of a suitable size either by the fin- 
 gers, or, in civilized life, by resorting to artificial implements, the knife 
 and fork. The incisor teeth next cut it up, and the molars crush or grind 
 it, being worked for this purpose by a powerful system of muscles ; mean- 
 time it is incorporated with saliva and atmospheric air. Passing into 
 the stomach under the condition of a coarse pulpy mass, the gastric juice 
 carries the process still farther, a more intimate disintegration of its 
 structure ensues, and it is eventually brought into a soluble and changed 
 form. The time required to produce this effect varies with Dio . estibilit 
 the nature of the food. Thus it has been noticed that beef of different ar- 
 is much 'more quickly acted on than mutton, and mutton t] 
 sooner than pork. 
 
 Statements respecting the digestibility of different articles of food 
 must, however, be received with many restrictions. If, as circumstances 
 the earlier physiologists believed, the stomach was the sole interfering 
 digestive cavity, and the intestine only for the purpose of ab- O f digestibiii- 
 sorption, they would doubtless be much nearer to the truth. t 7- 
 But when we recall that the digestion of fats does not even begin until 
 the intestine is reached, and that the digestion of the nitrogenized sub- 
 stances is only in part accomplished by the gastric juice, but goes on 
 under the influence of the intestinal juice throughout the whole length of 
 the small intestine, we see at once how imperfect and even incorrect are 
 the indications afforded by such experiments as those of Spallanzani, 
 who introduced food articles into the stomach through the oesophagus in 
 perforated silver vessels, or those of Beaumont, who availed himself of a 
 gastric fistula. Neither can we take, in all instances, the time which an 
 article of food will remain in the stomach as a measure of its digestibil- 
 ity, for this is known to vary with many conditions, as, for instance, the 
 quantity introduced at a time, and the condition of the organ itself. As 
 general illustrations of the digestibility of some of the ordinary elements 
 of food, the examples, however, being more or less open to the preceding 
 criticisms, the following facts may be offered. The white of an egg, rep- 
 
 E 
 
66 RELATIVE DIGESTIBILITY OF FOOD. 
 
 resenting soluble albumen, if introduced into the stomach of a fasting dog 
 through a gastric fistula, will disappear in less than an hour ; but if the 
 whites of eight eggs be introduced, portions thereof can be recognized 
 after four hours. Lehmann, who made these observations, adds that 
 blood fibrin varies in its time for gastric solution according as it is in a 
 finely comminuted or a massive state ; in the former instance disappear- 
 ing from the stomach of a dog in an hour and a half, but the same weight 
 in the latter condition requiring almost twice the time. Coagulated al- 
 bumen indicates the commencement of digestion, and even its local com- 
 pletion, in from five minutes to a quarter of an hour ; but here again much 
 depends on the condition of the stomach and the general state of the sys- 
 tem, whether the animal has been fasting, and whether the gastric juice 
 is exuding in a dilute or concentrated state. 
 
 So far as such examinations go, they do not exhibit any marked dif- 
 Kespiratory di- ference between albumen, fibrin, and casein. Gelatine, how- 
 gestion, as of ever> { s acted on with remarkable rapidity. Beaumont ob- 
 gln in the served that in an hour 150 grammes of jelly had disappeared, 
 stomach. The, experiments which have been made on the digestibility 
 
 of vegetable food introduced through gastric fistula? are obviously of no 
 use, since the chief constituents thereof, such as starch and fat, are not 
 even influenced in those circumstances until they have reached the intes- 
 tine. Their passage from the stomach in this unchanged state, or 
 changed only so far as their nitrogenized ingredients are concerned, may 
 teach us the important fact, which should in these inquiries be always 
 borne in mind, that disappearance from the stomach is one thing and di- 
 gestion another, and that even though a substance may have passed the 
 pyloric valve, its digestion, far from having been completed, may not as 
 yet have commenced. 
 
 The digestion of nutritive or nitrogenized material histogenetic diges- 
 tion is therefore carried on in the stomach mainly ; and though first 
 mechanical, and then chemical agencies are resorted to, the object is 
 throughout the same to obtain the food in such a divided and changed 
 state that it can pass, dissolved in water, into the capillary vessels. 
 
INTESTINAL DIGESTION. 67 
 
 CHAPTER IV. 
 
 OF CALORIFACIENT OB INTESTINAL DIGESTION. 
 
 Nature of Intestinal Digestion. Structure of the Intestine. Digestive Fluids of the Intestine. 
 The Pancreatic Juice. The Enteric Juice. Juice of Lieberkuhn. Secretion of Peyer's 
 Glands. Bik. Digestion of the Carbohydrates and Hydrocarbons. ^-Properties and Varie- 
 ties of Lactic Add. Doctrine of the Effects of Acidity and Alkalinity of the Digestive Juices. 
 Illustration of Intestinal Digestion from the making of Wine. MaJdng of Bread. Influence 
 of Heat over Ferments. Comparison of Gastric and Intestinal Digestion. Changes of the In- 
 testinal Contents. The Fozcal Residues. 
 
 
 AFTER the chyme formed in the stomach has passed through the py- 
 loric valve into the small intestine, the influence of the gastric juice 
 continues for a certain time, even after the bile and pancreatic juices 
 have been reached. Since their action must be necessarily, in the first 
 instance, superficial, the interior of the mass is still undergoing stomach 
 digestion. 
 
 But, setting aside this incidental result, which at the most can not be 
 of long duration, the digestive operation taking place in the ^ ature of in 
 part of the intestinal tract now under consideration is di- testinai diges- 
 rected to the heat-making food. 
 
 The organ in which calorifacient digestion takes place may be de- 
 scribed as a tube bounded by two valves, the pyloric above structure of 
 and the ileo-coecal below. Its length may be estimated at the intestine, 
 about twenty feet. The digestive surface, making a due allowance for 
 its increase by reason of its valvular structure presently to be described, 
 can not be much under 3500 square inches. The dimensions of the ca- 
 lorifacient digesting surface are therefore far rreater than those of the 
 nutritive. 
 
 The interior and acting portion of this tube presents two different 
 systems of apparatus, and is occupied in the discharge of two D 
 totally distinct functions, digestion and absorption. It is, ratus of intes- 
 perhaps, this double duty which demands so extensive a sur- tine ' 
 face, and not the necessities of heat-making digestion alone. 
 
 Like the stomach, this tube consists of three coats a serous, a mus- 
 cular, and a mucous. The latter is gathered up in its inte- . 
 
 . 11 c 11 i 11 , Action of the 
 
 nor into numberless projecting folds the valvular conniven- vaivuise conni- 
 tes. These serve to increase the surface to which the food ventes - 
 is exposed, and perhaps afford a mechanical obstacle to its passing too 
 quickly forward. They tend also to break the continuous motion, and 
 bring the interior parts of the chyme to the surface. The onward move- 
 
68 INTESTINAL DIGESTIVE FLUIDS. 
 
 ment is of course due to the pressure exerted conjointly by the straight 
 and circular fibres of the muscular coat. Anatomists divide the tube 
 into three portions the duodenum, jejunum, and ileum. 
 
 Fig. 19. In Fig. 19 we have a pos- 
 
 terior view of the duodenum, 
 a being its superior or pyloric 
 extremity, b the middle por- 
 tion, o the jejunum, d the gall- 
 bladder, i the cystic duct, p 
 hepatic duct, c the ductus com- 
 munis, m pancreatic duct. 
 
 Soon after the chyme has 
 escaped through .the pyloric 
 valve into the duodenum, it 
 Posterior view of the duodenum. comes under the influence of 
 
 the bile and pancreatic juices, which are sometimes discharged upon it 
 at a common point, and sometimes at a little distance apart. 
 
 Digestive flu- r , . . 
 
 ids of the in- Almost simultaneously it is submitted to the mechanical ac- 
 tion of the valvula? conniventes, which make their appearance 
 in the vertical portion of the duodenum, and continue in large numbers 
 until within the last two or three feet of the end of the tube. As the 
 intestine is distended, these project w4th a certain degree of turgidity, 
 and accomplish their mechanical object. 
 
 But, besides the pancreatic and biliary fluids, there are other juices 
 thrown upon the passing chyme the enteric juice, which comes from 
 Brunner's glands, and a liquid oozing from the follicles of Lieberkuhn. 
 Moreover, the organisms known as Peyer's glands are affecting the con- 
 tents of the tube. Of each of these it is necessary therefore to speak. 
 
 1st. The pancre'atic juice, secreted by the pancreas, an organ bearing a 
 Pancreatic resemblance in its anatomical construction to the salivary 
 tion e and n prop- gl an ^ s > an( * hence usually regarded as one of that group. 
 erties of. The juice itself is analogous to saliva, being viscid, and in its 
 
 reaction alkaline: its specific gravity is about 1.008. Alcohol coagulates 
 it. It is said to contain no sulphocyanide nor any suspended particles. 
 It acts upon starch even more energetically than saliva, transmuting it 
 into sugar and lactic acid, and upon fats by forming them into an emul- 
 sion, so that they are readily absorbed. This has been found to take 
 place in artificial experiments by submitting fat substances to the juice 
 at a temperature of 100. 
 
 Constitution of Pancreatic Juice of Dog. (From Schmidt.') 
 
 Water 900.76 
 
 Organic matter 90.38 
 
 Inorganic " 8.86 
 
 1000.00 
 
ENTEEIC JUICE AND SECRETION OF LIEBERKUHN. 
 
 69 
 
 As would be inferred from the difference of emulsifying power between 
 the saliva and tjiis juice, its organic matter differs from ptyaline. It is 
 estimated that the standard secretion of it is from five to seven ounces 
 per diem. 
 
 The action of the pancreatic juice appears to be limited to the upper 
 half of the intestine, for it is in that region only that butyric acid is de- 
 veloped from butter. 
 
 2d. The enteric juice is secreted by the organs known as Brunner's 
 glands, the structure of which has a certain analogy to the 
 
 T i TM i -ITI 11 IT Enteric juice. 
 
 preceding, and, like it, these doubtless belong to the salivary 
 group. Brunner's glands occur chiefly in the upper part of the small in- 
 testine, presenting themselves in the submucous tissue thereof as little 
 bodies, commonly compared by anatomists to hemp-seeds. They consist 
 of lobules with ducts communicating with a common outlet. Their se- 
 cretion possesses a more energetic power when mixed with bile and pan- 
 creatic juice, than the pancreatic juice alone, in producing fatty emulsions. 
 In the opinion of Bidder and Schmidt, the intestinal juice, which they 
 describe as being invariably alkaline, not only metamorphoses starch as 
 Fig. 20. rapidly as the saliva or pancreatic juice, but 
 
 also exerts as powerful an action on flesh, 
 albumen, and other protein bodies as that 
 which occurs in the stomach itself. 
 
 In Fig. 20, which is a half diagram of 
 one of these glands, a a represents the mu- 
 cous surface of the intestine, and b the 
 lobulated gland, discharging its secretion 
 through a common duct. 
 
 3d. The secretion of the follicles of Lieberkuhn, which, as shown in 
 Fig. 21, are straight, narrow coecal de- Secretion of 
 pressions of the mucous membrane, found follicles of 
 all over the small intestine, and in a gen- Lieberkuhn - 
 eral manner analogous to the tubular follicles of the 
 stomach. Their interior is lined with columnar 
 epithelium, and in depth they are equal to the thick- 
 ness of the mucous membrane, their closed ends be- 
 ing therefore in contact with the submucous tissue, 
 and their mouths opening into the intestine. In a 
 state of health they contain a clear mucus-like secre- 
 tion. In inflammations of the part they are filled 
 with a more opaque, whitish liquid. From their re- 
 semblance to the follicles of the stomach which secrete pepsin, it may be 
 presumed that they possess a somewhat similar function; but in the 
 stomach, the resulting secretion is brought in relation with acids ; in the 
 
 Diagram of Brunner's glands. 
 
 Fig. 21. 
 
 Diagram of follic 
 kuhn. 
 
 of Lieber- 
 
70 PETER'S BODIES AND THE- BILE. 
 
 intestine, with alkaline bodies ; and hence the physiological action may 
 differ in the two positions, though the structure and primary function 
 may be the same. 
 
 4th. The secretion of Peyer's glands. These may be described as cir- 
 Secretion from cular spots, of a whitish color, and about the tenth of an inch 
 Peyer's glands. j n diameter, constituting glandular patches full of cell germs, 
 but without any excretory duct opening into the intestine. It is sup- 
 posed that they discharge their contents by rupturing at a certain stage 
 of their development. The solitary and agminate glands appear to be- 
 Ftg. 22. long to the same physiological group. 
 
 The two conditions of the Peyerian glands 
 are shown in Fig. 22, the right one being 
 empty, its contents having been discharged, 
 the left one still full. By some it is denied 
 that these bodies are connected with intes- 
 tinal digestion. The facts that vascular 
 loops pass into their granular contents, and 
 Peyenan glands. that the lacfeals bear a definite relation to 
 
 them, seem to indicate that they are rather portions of the absorbent 
 mechanism. 
 
 5th. The bile. Of this it is not now necessary to give a detailed 
 description, since that will occur more appropriately in treat- 
 ing of the functions of the liver. For the present purpose, it 
 is sufficient to state that bile is a greenish-yellow liquid, of bitter taste 
 and alkaline reaction. It is soluble in water, changes with rapidity 
 under the influence of the air, or even spontaneously. Its specific grav- 
 ity is about 1.028. An ultimate analysis of its organic material shows 
 C 76 , H 66 , O 22 , N 2 , with sulphur. Its aspect is therefore that of a hydro- 
 carbon, and it stands in strong contrast with the nitrogenized bodies. 
 It is a significant fact that, even in the lower tribes of life, it is uniformly 
 discharged into the upper part of the intestine. Bidder and Schmidt 
 estimate the diurnal quantity of bile at 54 ounces, containing 5 per 
 cent, of solid matter ; they also give the following table of the diurnal 
 amounts of the various digestive fluids secreted by a man of the stand- 
 ard weight, 140 pounds : 
 
 Diurnal Amount of Digestive Secretions. 
 
 Saliva 3.30 Ibs., containing solid matter 1. per cent. 
 
 Bile 3.30 " " " " 5. " 
 
 Gastric Juice 14.08 " " " " 3. " 
 
 Pancreatic Juice ... .44 " " " " .1 " 
 
 Intestinal Juices ... .44 " " " " 1.5 " 
 
 The bile does not appear to exert any agency in effecting the digestion 
 of either nitrogenized or amylaceous bodies. The period of its max- 
 
POWER OF PANCREATIC JUICE. 71 
 
 imum production, which is 13 or 14 hours after a meal, does not coincide 
 with the period of most energetic digestion. 
 
 With these statements of the nature of the various juices which pass 
 into the small intestine, we may proceed to investigate the phenomena 
 of the digestion carried on in that tube. 
 
 In 1832, Dr. Bright, to whom medicine is so much indebted for his 
 discoveries in relation to the pathology of the kidney, pub- Emulsifvin(r 
 lished three cases of disease of the pancreas, attended by the power of pan- 
 appearance of a large quantity of fat in the faeces, and drew c 
 the inference that in such morbid states the fats are imperfectly digested. 
 More recently, M. Bernard has published experimental evidence to prove 
 that the digestion of the fats consists in bringing them into the condition 
 of an emulsion, and that the pancreatic juice accomplishes this object. 
 
 Whatever influence the pancreatic and enteric juices can exert on 
 starch and oil outside of the body, in artificial experiments, they un- 
 doubtedly exert it in the small intestine as long as the temperature is 
 the same. On starch, the action, as has already been stated, is to effect 
 its conversion into sugar, and then into lactic acid. The oils are turned 
 into emulsions. The constitutional relation between starch and lactic 
 acid is such, that if, in presence of water, one atom of the g ubdiv i s i on O f 
 former be equally and systematically split or divided into starch into lac- 
 two portions, those portions are atoms of lactic acid. And 
 since this substance contains no nitrogen, its oxidation either artificially 
 or in the interior of the system gives origin to carbonic acid and water 
 bodies which can at once b removed by the action of the skin, or the 
 lungs, or the kidneys. 
 
 Respecting the digestion of the carbohydrates cellulose, gum, starch, 
 and the different kinds of sugars, it may be remarked, that eel- Digggfon of 
 lulose, of which the pith of elder is an example, and which the carbohy- 
 occurs in a pure form in Swedish filtering-paper, not only re- 
 sists, in artificial experiments, the action of the digestive juices, but also 
 it would appear to do so naturally in the higher tribes, and hence it is 
 abundantly found in the excrement of the herbivora. To this statement, 
 perhaps, however, the case of the beaver affords an exception, Digestion of 
 there being reason to suppose that this animal possesses the cellulose, 
 power of digesting cellulose. 
 
 There can be no doubt, moreover, that many insects have the same 
 power, for chitin, which may be obtained from their wing-cases, and which 
 retains the appearance of the structure of the part, may be considered as 
 cellulose united with a nitrogenized body, having the constitution of in- 
 sect muscular fibre. This substance not only constitutes the skeleton 
 of insects, their scales, hairs, and enters into the construction of their 
 tracheae, but even forms one of the coats of their intestinal canal. Since 
 
72 DIGESTION OF CAEBOHYDEATES. 
 
 it does not appear that they can metamorphose other carbohydrates into 
 this body, we may infer, as would indeed seem probable, considering the 
 nature of the food of many of them, that they can digest woody fibre. 
 The digestive apparatus of man, however, can not exert such a power. 
 
 Neither does it appear that gum undergoes either digestion or absorp- 
 Digestion of ti n ' I n artificial experiments it also resists the action of di- 
 gum. gestive fluids, and is not changed when present during the 
 
 fermentation of other bodies, even though its exposure thereto be contin- 
 ued for several days. Administered to animals, it is almost entirely 
 voided with the excrement. Thus Boussingault, having given to a duck 
 fifty grammes of gum-arabic, obtained forty-six grammes from the ex- 
 crements in nine hours. In an experiment upon an old rabbit, to which, 
 with a diet of cabbage-leaves, ten grammes of gum-arabic were daily given 
 by Lehmann, the gum being administered in solution in water by injec- 
 tion into the stomach, no trace whatever of gum could be detected in 
 the urine, none in the chyle of the thoracic duct, and none in the blood, 
 but it was easily enough recognized in the excrement. From this he 
 infers that the preparations of gum, which are such favorite medicines 
 with some physicians, yield to the animal organism only an extremely 
 small quantity of material of a nature to support the respiratory process, 
 and that their uses, if they are of any use, can be merely negative in 
 acute diseases. 
 
 Of the carbohydrates, starch is perhaps the most important, occurring 
 Digestion of as ^ does in abundance in vegetable food. It can not be made 
 starch. use O f j n ^he system without fifst being transmuted into dex- 
 trine, sugar, and eventually lactic acid, these changes being greatly ex- 
 pedited if it has been previously prepared by boiling in water, or other 
 equivalent operations of cooking. The saliva commences the action, 
 which in man is even prolonged in the stomach, and in the herbivora still 
 more decisively in the paunch, in birds in the crop. On gaining the stom- 
 ach, the farther transmutation of the starch is arrested by the gastric 
 juice, but after reaching the duodenum it is resumed with greater energy 
 than ever, under the influence of the pancreatic juice. Reaching the ile- 
 um, the intestinal juice continues the action, though with less vigor. In 
 this passage to the large intestine, the starch is gradually assuming the 
 condition of dextrine and sugar, the former substance passing into the 
 latter with such facility that it can only be recognized transiently. 
 Doubtless the sugar thus arising is in great part directly absorbed, though 
 some, before the ccecum is reached, is transmuted into lactic acid, and oth- 
 er portions, after passing through the ileo-coecal valve, into butyric acid. 
 
 From what has been observed respecting starch, it may be inferred how 
 Digestion of important sugar is, since through the condition of sugar alone 
 sugar. i s starch available for the uses of the system. It is to be rec- 
 
DIGESTION OF SUGAR. 73 
 
 ollected, however, that sugar itself is only an intermediate or transitory 
 stage, through which the carbohydrate is passing, a consideration which 
 explains the circumstance that it does not occur even in the portal blood 
 to such an extent as might be expected, nor yet in the chyle. Some 
 have been led to infer from these facts that this substance, like gum, is 
 in reality only very tardily absorbed, an opinion which they suppose to 
 be strengthened by the circumstance that glucose or any other kind of 
 sugar, introduced into the jugular vein, runs through the course of the 
 circulation, and is secreted unchanged by the kidneys. But it is to be 
 remembered that portal blood is very different from the proper systemic 
 blood, and that there are many changes, beyond all question, which can 
 take place with rapidity in the former, but which do not take place in the 
 latter. 
 
 Sugar, whether it has been received as an ingredient of the food, or 
 arisen from the metamorphosis of starch, is, as we have said, only a tem- 
 porary form, which passes quickly onward to the state of lactic acid. To 
 this we must impute the acid reaction which is observed throughout the 
 length of the small intestine, and which can not be attributed to the gas- 
 tric juice, a reaction occurring in spite of the alkalinity of the bile and 
 pancreatic secretion. This pushing of the carbohydrate forward to the 
 state of lactic acid is very generally imputed to the intestinal juice, which 
 greatly re-enforces the power of the saliva and pancreatic fluid; some have 
 even supposed that the bile aids in producing this effect. Of this, how- 
 ever, there is no satisfactory proof. 
 
 From the experiments of Von Becker, who injected saccharine solu- 
 tions at intervals of a quarter of an hour into the stomach of rabbits, it 
 was found that 4.5 parts of sugar were absorbed each hour for every 1000 
 parts weight of the animal. Whatever may have been the form of sugar 
 administered, as, for instance, cane-sugar, it quickly passes into the con- 
 dition of glucose in the intestine, and from that to lactic acid. Thus sug- 
 ar of milk may be traced in an hour as far as the coecum, communica- 
 ting to the contents of the small intestine an intense acid reaction. 
 
 Since lactic acid discharges very important offices in the animal econ-. 
 omy, it may be worth while to observe its properties, and p roduct i onand 
 the circumstances under which it is produced. Very many properties of 
 liquids containing organic matter yield it abundantly: thus it '' 
 is found in sauer kraut, a preparation of cabbage. It is, however, more 
 conveniently obtained from milk, and hence the term lactic acid. The 
 diluted solution obtained from this source, being concentrated by evap- 
 oration, furnishes a sirupy liquid, heavier than water, having an intense- 
 ly sour taste, a great affinity for water, and therefore attracting it from 
 the air, and dissolving freely in it. With metallic oxides it forms solu- 
 ble salts, and in the concentrated sirupy state has the remarkable con- 
 
74 LACTIC ACID. 
 
 stitution that it contains six atoms of each of its elements, carbon, hy- 
 drogen, and oxygen. 
 
 The production of this acid in organic substances is very common. 
 It depends on the same principle as presented in duodenal digestion, 
 which it therefore very strikingly illustrates. As an example deserving 
 of attentive consideration, its development in milk may be offered. 
 
 When milk is exposed to the air it eventually turns sour, the sour- 
 ness being due to the appearance of lactic acid. In its sweet state, the 
 milk may be regarded as consisting of casein, or the curdy principle, a 
 substance belonging to the protein group, insoluble in pure water, but 
 abundantly soluble if a little free or carbonated alkali be present ; of milk 
 sugar, dissolved, and of butter held in suspension in water. The ac- 
 Production of ^ on ta ^ m S P^ ace during the souring is as follows : Under 
 lactic acid the influence of atmospheric oxygen, which for this purpose 
 rom milk. mus t liswQ access, the nitrogenized principle, the casein, be- 
 gins to change, and, for reasons presently to be more particularly exam- 
 ined, impresses a change on the sugar, splitting its atom so as to give 
 rise to the production of lactic acid. As this forms, it renders the casein 
 insoluble, and the milk begins to coagulate, to prevent which a little car- 
 bonate of soda may from time to time be added. All the sugar origin- 
 ally present in the milk is soon acidified, but a much stronger solution 
 can be made by adding more milk sugar as the process of exhaustion 
 goes on, and the change can be thus kept up until the casein itself is 
 quite consumed. 
 
 On examining this process critically, we observe that every thing de- 
 pends on the change occurring in the nitrogenized principle, the casein. 
 This, under the circumstances, takes on an incipient oxidation, and com- 
 pels the sugar atom so to divide as to give rise to the production of lac- 
 tic acid. This ceases the moment the casein ceases to change, and re- 
 commences the moment the casein is permitted to reoxidize. The de- 
 struction taking place in the casein is propagated to the sugar, the 
 physical peculiarity being that the atom of sugar is merely divided, fis- 
 sured, or split, and gives rise to the production of lactic acid, and no 
 other substance. The whole process is therefore essentially one of sub- 
 division, a conclusion which should be carefully borne in mind in apply- 
 ing these experimental principles to the physiological function of diges- 
 tion. So far as the result is concerned, the two cases are the same. 
 
 Many other organic liquids furnish similar illustrations. Thus, in 
 Production of ^ e P era tion of making starch for commercial purposes, con- 
 lactic acid siderable quantities of that substance are turned into lactic 
 >m starch. &C Q cons tit u ting what the manufacturers term sour liquor. 
 Nor is it even requisite that so much water should be present as to give 
 the liquid condition ; for if wheat flour be made into a paste, and kept for 
 
LACTIC ACID IN THE SYSTEM. 75 
 
 some days in a warm place, its gluten induces such a change that the 
 starcft turns into lactic acid, and the paste becomes sour. 
 
 Of lactic acid there are two kinds ; that derived, as hereafter stated, 
 from muscle juice, is the alpha lactic acid, and that from the Alpha and beta 
 fermentation of sugar the beta lactic acid. As it occurs in lactic acid - 
 the gastric juice, associated with or replacing hydrochloric acid, it is of 
 the beta variety. Whatever may have been the source of this portion 
 of it, whether it has been derived by gastric secretion or through the 
 transmutation of amylaceous food by the saliva, its abundant occurrence 
 in the contents of both the small and large intestines, in which it is rec- 
 ognized by the peculiarities of its zinc and magnesia salts, confirm the 
 conclusion that in this case, at least, the beta form arises from the opera- 
 tion of the digestive juices. 
 
 Lactic acid undergoes rapid absorption through the intestine, and is 
 as rapidly disposed of in the system. Thus Lehmann found, after tak- 
 ing half an ounce of dry lactate of soda, that in thirteen minutes his 
 urine had become alkaline. On injecting the same salt into the jugular 
 vein, it appeared in from five to twelve minutes as carbonate of soda in 
 the urine. 
 
 Berzelius first discovered the existence of lactic acid in the juice of the 
 muscles. Liebig showed that, in quantity, there is more p r0( j u ction of 
 present in this source than is sufficient to neutralize the alkali lactic acid by 
 of all the other liquids or juices of the body. Muscle lac- * 
 tic acid is removed away with rapidity by the lymphatics. Berzelius 
 concluded that its quantity increases in proportion to the exercise the 
 muscle has undergone ; and this would lead to the inference that it is 
 one of the chief products of muscular waste ; for it is not to be supposed 
 that its appearance in muscle juice is because those organs attract it 
 from the blood, in which it pre-exists, derived, perhaps, from the trans- 
 formation of amylaceous substances in the intestine, for the muscles of the 
 carnivora yield as much of it as those of the herbivora ; and though it can 
 not be artificially made directly from albuminous material, yet it would 
 seem that, with urea and ammonia, it might arise from the breaking up 
 of creatine. From glycerine lactic acid may be also developed. When- 
 ever an excess of it is produced in the system, either by muscular action, 
 unusual diet, or imperfect oxidation in the blood, it may be detected in 
 the urine. Under ordinary circumstances, doubtless, very large quanti- 
 ties of it are destroyed in the circulation, giving rise to the production of 
 carbonic acid and water with a disengagement of heat. 
 
 We can not here fail to remark how the process of comminuting the 
 food is carried forward to such an extent that the absorbent These digest- 
 vessels are able to take it up. The action first begins, as has 
 been shown in detail, by cutting and crushing implements, ions. 
 
76 DIGESTION OF FAT. 
 
 the teeth, and when these have carried the subdivision as far as mechanical 
 means can, it is continued by chemical agents. Upon these principles, 
 the pancreatic juice divides starch into lactic acid in duodenal digestion 
 a product which, without difficulty, finds its way at once into the system. 
 
 Besides starch and sugar, there is another group of bodies belonging 
 Digestion of to the class of calorifacient food, which, in the case of carniv- 
 fafc - orous animals, seems to be exclusively employed. The fats 
 
 and oils constitute this group. 
 
 The action of the pancreatic and enteric juices upon these bodies, in 
 bringing them into the condition of an emulsion, has already been stated. 
 That this occurs in the intestine appears from the fact that if the pan- 
 creatic duct be tied, no emulsion forms, and the chyle in the laeteals 
 is limpid instead of being milky. In the rabbit this duct opens much 
 lower in the intestine than the biliary, and it is observed that it is only 
 after the food has passed that point that it becomes emulsioned. The 
 place for pancreatic digestion seems to be very constant in tribes that are 
 far apart in habits of life. Thus, in fishes, the pancreas consists of a cor- 
 onet of coecal tubes, surrounding the pyloric extremity of the intestine, 
 each opening into that organ by a separate mouth. 
 
 The fats reach the duodenum without undergoing any change. There, 
 under the influence of the pancreatic juice, they become subdivided into 
 extremely minute portions, which, absorbed by the laeteals, give to the 
 chyle its characteristic aspect. Beyond this condition of subdivision 
 no other change is thus far impressed, the fat of the laeteals being abso- 
 lutely the same as that of the chyme. To the introduction of fat into 
 the laeteals, the presence of bile seems to be necessary, or, if not absolute- 
 ly necessary, absorption is greatly facilitated by it. 
 
 The gastric and pancreatic juices stand in a remarkable relation to one 
 Bernard's doc ano ^ ner the former being an acid liquid, having the power 
 trine of the ef- of bringing into a state of solution nitrogenized bodies, such 
 and alkalinity as ^ Tm 5 tne latter alkaline, without action on nitrogenized 
 in the digest- bodies, but operating energetically on starch, sugar, and oils. 
 
 J U1< From this it might be supposed that the intrinsic qualities of 
 
 these juices are different, and that they act in this manner because of a 
 special dissimilarity of constitution. 
 
 Attempts have been made to prove that this difference of action de- 
 pends wholly on the chemical relations of the juice itself. If pancreatic 
 juice or saliva be purposely acidulated with hydrochloric acid, it is said 
 that it loses at once the power of acting on calorifacient food, but can 
 bring about the solution of the histogenetic. On the other hand, if gas- 
 tric juice be rendered alkaline by admixture with soda, it no longer dis- 
 solves fibrin or coagulated albumen, but gains the power of acting on 
 starch and sugar. Since, then, it thus appears that the same organic body 
 
ORGANIC PRINCIPLE OF DIGESTIVE JUICES. 77 
 
 becomes endowed with one or other of these properties, according as it is 
 acidulated or alkalinized, the function of digestion is presented to us un- 
 der a simple aspect. It is upon these principles that we may explain 
 the fact that the presence of bile in the stomach suspends or arrests the 
 digestion going on in that organ. 
 
 Though the views here expressed are such as are received among many 
 chemists, yet it is still open for consideration whether the The nature of 
 nature of the result which is reached in these cases does not, the or s anic in - 
 
 . gredient more 
 
 to a great extent, depend upon the nature of the organic important than 
 changing body, the ferment, which first sets up the action. the reaction - 
 Many circumstances would lead us to infer that this must be the case, 
 and that, as with differences of temperature, so also with these differences, 
 the final result may present distinct variations, though they may be with- 
 in a certain range or limit. Thus, though the saliva and pancreatic juice 
 are both alkaline, and both impress in a general way the same digestive 
 change on starch and sugar, a minute examination of the results of their 
 action would doubtless lead to the detection of shades of difference va- 
 riations which could only be attributed to the difference between the act- 
 ive organic principle of the pancreatic juice, and ptyaline, the correspond- 
 ing principle of the saliva. 
 
 The imputed control which the alkalinity or acidity of the digesting 
 juices exerts in determining the result, illustrates the import- j> e ] at j n f 
 ant function discharged by common salt, which furnishes to common salt in 
 the juices of the stomach and intestine the characteristic in- dl estlon - 
 gredients they require by breaking up readily into hydrochloric acid and 
 soda, and re-forming at once whenever these materials are brought in 
 contact. There is, therefore, an important reason for the instinct which 
 animals display in resorting to the use of this substance, as in the buffa- 
 lo licks at the West, and the necessity which men experience to add it 
 as a condiment to their food. But though, by furnishing an acid or al- 
 kali, as the case may be, it determines the nature of the work which the 
 secreting juices perform, it is not to be regarded as the prime mover of 
 the change. It guides rather than works. The efficient principle bring- 
 ing about digestion appears always to be a nitrogenized body, acidulated, 
 perhaps, for the production of one duty, and rendered alkaline for the per- 
 formance of another. 
 
 Directing our attention now more particularly to the phenomena dis- 
 played by such a changing nitrogenized principle, the folio wing, illustra- 
 tions will serve to show that there is nothing mysterious in its operation. 
 Out of many cases which might be selected, those now to ]be offered are 
 more particularly interesting, since they refer to substances extensively 
 used in the diet of man. 
 
 First, of wine. A grape, if perfectly sound, will keep for a consider- 
 
78 ILLUSTRATIONS FROM WINE AND BREAD. 
 
 Illustration a ^ e l en gth ^ tmie without undergoing any change ; but if 
 from the mak- a puncture be made in it to give the air access, it rapidly de- 
 ine ' teriorates. The precise change taking place is perhaps bet- 
 ter understood by observations on the expressed juice of this fruit. If 
 grapes be pressed beneath the surface of quicksilver, and the juice be col- 
 lected in an inverted jar, without ever coming in contact with the atmos- 
 pheric air, it may be kept for a long time without any apparent change ; 
 but if a small quantity of air, or only a single bubble of oxygen is per- 
 mitted to enter the jar, and the temperature is that of a summer's day, an 
 intestine commotion or fermentation at once ensues, carbonic acid escapes, 
 alcohol arises in the liquid, and the sugar which was in the grape-juice 
 disappears. But the quantity of sugar thus capable of being destroyed 
 is limited, and a point is eventually reached at which no. more sugar can 
 be decomposed, and no more carbonic acid set free. 
 
 The juice of the grape contains a nitrogenized principle resembling al- 
 bumen. It is this which is in reality the active body. So long as ox- 
 ygen is excluded, this nitrogenized substance remains unaltered, but the 
 moment the air finds access, a change begins. The sugar which is pres- 
 ent in the juice becomes involved in the movement going on, which is 
 propagated by degrees to all its atoms, dividing each into two well-known 
 and well-marked bodies. The period at which no farther change takes 
 place in portions of sugar 'which may have been purposely added is 
 when the nitrogenized principle has disappeared. 
 
 Carbonic acid and alcohol are the two substances arising in this de- 
 composition. Their mode of origin is obvious when it is understood 
 that one atom of sugar can be so divided as to yield four of carbonic acid 
 and two of alcohol. In this artificial instance, the subdivision is even 
 more complex than that which occurs in duodenal digestion, in which the 
 sugar atom is subdivided into two equal and symmetrical parts, two 
 atoms of lactic acid. In the following formulas, (1) represents the case 
 of vinous production, (2) that of duodenal digestion : 
 
 (1) ..... C 12 H 12 13 =4 (C0 2 )+2 (C 4 H 6 OJ. 
 
 (2) ..... C 13 H 13 13 =2(C 6 H 6 6 ). 
 
 Second, of bread. If, in the preceding case, a transmuting nitrogen- 
 T11 ized body breaks the sugar atom so that alcohol is one of the 
 
 Illustration J ,. & .., -,,. 
 
 from making products, and upon this principle all wines and intoxicating 
 bread. liq uors are made, the instance now presented is of far more 
 interest to the well-being of man. The use of wine undoubtedly adds 
 not only to social enjoyment, but sometimes conduces to health a ben- 
 efit, alas ! often attended with a thousand ills. Not so with bread, em- 
 phatically and truly described as the staff of life. 
 
 The making of wine and of leavened bread are two of the oldest chem- 
 
ILLUSTRATION FROM THE MAKING OF BREAB. 79 
 
 ical processes. Their origin is lost in a remote antiquity, and so uni- 
 versally are their benefits acknowledged that their use is diffused all over 
 the world. 
 
 Experience proves that the best bread is made from fine wheaten flour, 
 mixed into a paste with a due proportion of water. A certain quantity 
 of a nitrogenized substance undergoing incipient oxidation, termed yeast, 
 is added, and the whole submitted to a gentle temperature. All flour 
 contains a small quantity of sugar ; on this the yeast immediately acts, 
 dividing it, as in the former case, into carbonic acid and alcohol. If 
 enough sugar is not present, more under the circumstances is formed from 
 starch. The acid gas, as it is set free, can not extricate itself from the 
 surrounding dough, but expands into a thousand little vesicles or bub- 
 bles, which give that peculiar porosity for which this kind of bread is so 
 highly prized. At this period, before baking, the other substance which 
 has arisen from the destruction of the sugar the alcohol is contained 
 in the dough, and is expelled therefrom along with the excess of water 
 by the high temperature of the oven, which also, by increasing the expan- 
 sion of the included gas, adds to the porosity of the bread. In some 
 baking establishments arrangements have occasionally been made to con- 
 dense the alcohol as it rises from the bread. The good and evil of life 
 are often closely intermixed. The advocate of total abstinence from al- 
 cohol may with reason look upon half-baked bread distrustfully. The 
 enemy is lying in ambush for him. 
 
 On some occasions, instead of using yeast, a piece of leaven, that is, 
 dough in a state of incipient putrefaction, is employed. The mode of 
 action is, however, the same. The use of this material well illustrates 
 the progressive nature of these changes, and how the action gradually 
 passes from point to point of the entire mass. It is written, "A little 
 leaven leaveneth the whole lump." 
 
 In the cases here presented the action is one of subdivision. A com- 
 plex atom has its constitution broken up, and is separated These actions, 
 into distinct parts. When such a change is once commenced ^^^are dl ~ 
 in a mass, there is a liability for the whole to become in- subdivisions, 
 volved, just as, when we ignite one point in a pile of combustibles, the 
 fire spreads throughout ; or as, when on one part of a piece of fresh meat 
 a small portion in a putrescent state is laid, the corruption, with measured 
 rapidity, proceeds from part to part, until the whole is decayed. One 
 after another, the particles submit in succession. 
 
 Over all these subdividing actions heat exerts the most extraordinary 
 influence, so that for a given effect to be produced it is abso- influence of 
 lutely necessary that a given temperature should be main- gubdMSng 686 
 tained. Thus, if we take the saccharine juice of almost any actions, 
 kind of fruit, and cause it to be acted on by a changing nitrogenized body, 
 
80 ^EFFECTS OF TEMPERATURE ON FERMENTS. 
 
 it will yield, as just stated, alcohol and carbonic -acid so long as the tem- 
 perature ranges about 75 ; but, every thing remaining the same, if 
 the temperature be raised to 100 or 120, neither alcohol nor carbonic 
 acid is formed, but in their stead other products arise, such as lactic acid, 
 gum," and manna. Though, therefore, decomposition will go on through- 
 out all this range of temperature, the products will vary very much, al- 
 cohol being formed at a low, and lactic acid at a high degree. 
 
 Again, the decomposition of milk furnishes a very instructive instance. 
 When the temperature ranges from 50 to 75, the liquid turns sour, 
 owing to the formation of lactic acid ; but if the temperature is over 90, 
 the products are different, for now a true vinous fermentation sets in, al- 
 cohol and carbonic acid appearing. It is on this principle that the Tar- 
 tars make an intoxicating liquid from mare's milk. The fermentation of 
 milk, therefore, yields lactic acid at a low, and alcohol at a high degree. 
 
 On comparing these illustrations, the results stand in direct contrast, 
 but both show the great influence which a specific degree of heat exer- 
 cises over such subdivisions ; and, as a consequence of this principle, 
 which obtains equally in the physiological case, we recognize the neqes- 
 sity of maintaining the cavity of the stomach and intestine uniformly 
 at a temperature which is fixed, otherwise there would cease to be any 
 uniformity in the subdivision of the food, occasioned by the digestion 
 there going on. These principles, moreover, lead to the explanation of 
 the action of such stimulating substances as alcoholic liquids,- pepper, 
 etc., which at once determine a local elevation of temperature ; they also 
 explain the injurious effects which may ensue from intemperate draughts 
 of ice-cold water. 
 
 A nitrogenized substance, in a state of change, can thus bring about a 
 definite action on fibrin, coagulated albumen, or casein in the stomach, 
 or on starch in the intestine, so long as a temperature of 100 is main- 
 Loss of power tained, but in every known instance this transmuting power 
 l\ttTmpe * s tota % destroyed by exposure to a very low or very high 
 ature. degree of heat. Large masses of animal matter whole car- 
 
 casses may be preserved for many centuries unchanged if the tempera- 
 ture is kept down to 32. A striking example of this occurs in the case 
 of the extinct elephants which are occasionally thrown on the shores of 
 the Polar Sea from icebergs, in which they have been entombed for 
 many thousand years, their flesh remaining in a perfectly fresh and un- 
 decayed state. And as respects a high temperature, an exposure to 212 
 totally destroys the power. On this principle, all kinds of meat or veg- 
 etable substances may be indefinitely preserved. If such are inclosed in 
 metallic canisters, so as totally to exclude the atmospheric air, and ex- 
 posed to a bath of boiling water, they may then be carried around the 
 world without undergoing any change. 
 
AETIFICIAL PRODUCTION OF FAT. 81 
 
 One of these illustrative cases still remains. It belongs to the class 
 of changes now under consideration, and deserves a prominent examina- 
 tion from its connection with duodenal digestion. It is the production 
 of fatty bodies from starch and sugar. 
 
 Physiological considerations assure us that there are circumstances 
 under which oils and fats can be formed from starch and p roduction of 
 sugar in the system. Animals can be fattened by feeding fats from ear- 
 on potatoes, or other such food, in which the quantity of oil y rj 
 is quite insignificant. Bees can make wax, which strictly belongs to the 
 group of fats, though they are fed on pure white sugar. 
 
 Such results can be artificially imitated. If a strong solution of sugar 
 be mixed with a small quantity of casein and powdered chalk, and ex- 
 posed to a temperature of more than 80, carbonic acid and hydrogen are 
 evolved, and butyric acid forms as the butyrate of lime. This acid sub- 
 stance is a colorless oily liquid, having the odor of rancid butter, in 
 which indeed it exists. 
 
 From a review of all the preceding facts, we may conclude that a nitro- 
 genized substance secreted by the follicles of the stomach, Contrast of 
 and undergoing incipient oxidation, acidulated with hydro- 
 chloric acid obtained by the decomposition of common salt, tion. 
 or with lactic acid produced by a continuation of salivary digestion, has 
 the power of dissolving coagulated albumen, and generally those articles 
 of food which belong to the nitrogenized class ; that -this goes on in 
 the stomach, it being the function of that organ to effect the digestion of 
 this kind of food, and thereby contribute to the general nutrition of the 
 system. The muscular tissues are supplied from this source, and by the 
 stomach their waste is repaired. 
 
 Another and distinct digestion takes place in the intestine, commenc- 
 ing immediately after the food gains the duodenum. It too is brought 
 about by the action of a special liquid, a mixture of the pancreatic and 
 intestinal juices. The chemical reaction of this juice is alkaline ; in this 
 respect it is therefore antagonistic to the gastric juice. This quality is 
 due to the soda it contains, a substance derived co-ordinately with hy- 
 drochloric acid from the decomposition of common salt. The digestion 
 of starchy and saccharine bodies is thus effected by dividing them so as 
 to produce lactic acid. 
 
 This done, common salt is reproduced by the commingling of the gas- 
 tric, biliary, and pancreatic products together. The salt is carried by the 
 absorbents into the interior of the system, to be again decomposed. 
 
 Moreover, the pancreatic and enteric juices reduce the oleaginous and 
 fatty bodies to the condition of an emulsion, or, if they be not present 
 in the food, give origin to them in the way just described. 
 
 The reaction of the intestinal contents not only differs in different por- 
 
 F 
 
82 SALTS AND GASES OF THE INTESTINE. 
 
 Successive tions of the tube, but in the same region, in different parts 
 tmSt^ouoi! of tne mass ' its exterior ma 7 te alkaline, its interior acid, or 
 the intestine, the converse. The acidity which has been imparted by the 
 gastric juice seems generally to have disappeared some time before the 
 large intestine is reached. In this an alkaline reaction is observed. The 
 causes of this prolonged acidity are very various. In part it depends on 
 the nature of the food, in part upon the gastric juice, as has just been 
 stated, and in part upon the production of lactic, butyric, and other acids. 
 The resinous ingredients of the bile may be detected as far as the lower 
 extremity of the ileum. Glucose, originating in the action of the pancre- 
 atic and intestinal juices on starch, may be recognized throughout the 
 whole length of the canal, but that which has been introduced in the 
 food seems to be absorbed in the stomach itself; thus, in milk-fed ani- 
 mals, sugar does not appear to descend beyond the jejunum. 'The trans- 
 mutation and reabsorption of biliary matter commences in the small in- 
 testine and proceeds continuously, so that by the time the middle of that 
 portion of the tube is reached, half the bile is gone. 
 
 Since the intestinal absorbents can only take up a definite proportion 
 of fat, it might be expected, as is really the case, that after an unusually 
 fatty diet, fat substances will be found in the excrement. Indeed, a cer- 
 tain small proportion always so occurs. 
 
 Of the salt substances usually occurring in the food, most disappear 
 Salts of the in- during their passage through the intestine, and hence but lit- 
 testine. tie is found in the faeces ; more particularly is this the case 
 
 with those of a very soluble kind. Of the sulphates and chlorides of the 
 food, not even a trace may occur in the excrement. If these substances 
 should not be required for the uses of the system, they are promptly re- 
 moved by the kidneys, and in the same manner are disposed of any ab- 
 normal salt substances which may have been purposely administered, as, 
 for instance, iodide of potassium. 
 
 The gaseous contents of the intestine originate in part from the air 
 Gases of the that has been introduced during the mastication of the food, in 
 intestine. p ar f r0 m fermentative processes occurring after certain articles 
 have been used which are only imperfectly digested, and in part from the 
 endosmosis of gas from the blood through the walls of the intestinal cap- 
 illaries. As compared with atmospheric air, though the composition 
 must necessarily be very various, the intestinal gas shows a great excess 
 of carbonic acid and nitrogen, a diminution and sometimes even a total 
 absence of oxygen, the presence of pure hydrogen, and of its carburets 
 and sulphurets. The quantity of this latter gas is less than might be 
 expected from its odor, and, as would be anticipated from the circum- 
 stances, the accumulation of gas is much more abundant in the large than 
 in the small intestine. 
 
FORMATION OF F^CES. 83 
 
 Schmidt shows that the intermediate circulation of water toward the 
 intestine is far more considerable than its final excretion, and Water furnish- 
 amounts in one day to nearly one fourth of the whole quan- |^ 1] 
 tity of water in the body. 
 
 As the digested mass passes onward, driven by the peristaltic motions 
 through the convolutions of the intestine, it becomes of a Complex chan- 
 more solid consistency, as the absorbents gradually remove testinai^on^" 
 its liquid portions. By the time it has reached the coacum, tents, 
 the same effect which arose in the stomach from salivary digestion is 
 repeated, for the traces of unabsorbed lactic acid cause nutritive diges- 
 tion to be again feebly resumed, at all events in herbivorous animals, if 
 not in man, whose ccecum is rudimentary, under the form of the appen- 
 dix vermiformis. From Peyer's glands a secretion has exuded, which 
 perhaps gives to the mass the characteristic odor it is now assuming, if, 
 indeed, these organs are not connected with absorption. The effete re- 
 mains are finally voided as fasces, which, due allowance being made for 
 the water they contain, amounting to about 75 per cent., may be rep- 
 resented as averaging about 1J ounce per day. These excrementitious 
 remains, colored yellow by the coloring material of the bile, are partly de- 
 rived from the residues of the food which have been unacted upon, and 
 partly from the decay of the system itself. The microscopt shows the 
 remains of cell membranes, and the walls of vegetable vas- Formation 
 cular tissues, starch granules, and chlorophyll, the relics of car- of faeces ' 
 tilaginous and fibrous tissues, shreds of muscular fibre, fat-cells. From 
 the digestive tract there have been derived mucus corpuscles, epithelial 
 cells, and the coloring matter of the bile. Perhaps, too, much of the wa- 
 ter which gives consistency to the fasces has been derived from the intes- 
 tinal walls, for in quantity, under certain circumstances, it may exceed 
 the amount that has been used as drink. 
 
 In its passage through the intestine, that portion of the bile which has 
 not been absorbed undergoes- considerable changes, its conju- Disappearance 
 gated acids degenerating into dyslysin, which may be recog- of the blle - 
 nized in the fseces, as is also the case with the modified pigmentary mat- 
 ters ; the soluble mineral constituents are, for the most part, absorbed. 
 
 The reducing agencies in the intestine, and the manner in which sub- 
 stances can find their way into the urinary secretion, is well Incidental re- 
 illustrated by the administration of indigo, which undergoes fnSntts? 11 
 deoxidation into the condition of suboxide of isatine, and will, tine, 
 notwithstanding the agency of arterial blood, appear in that condition in 
 the urine, to which, upon contact of the air, it imparts a blue tint, becom- 
 ing more intense under a prolonged exposure, and eventually indigo-blue 
 being deposited. Such a result not only shows how energetic are the re- 
 ducing agencies in the intestine, but also with what facility very oxidiz- 
 
84 ABSOKPTION. 
 
 able material may, under certain conditions, be exposed to arterial blood 
 without oxidation. Yet that this want of action is wholly due to inci- 
 dental circumstances is shown from the fact that salts of organic acids 
 are much more quickly oxidized in the blood than they are in the open 
 air. 
 
 It is interesting thus to observe how the death of one part of the body 
 Advanta e mm i sters to the life of the rest ; for the nitrogenized and act- 
 taken 'of the ive principles of t!^ juices secreted for the accomplishment of 
 portion toor- digestion are on the descending career, and are truly dying 
 ganize an- matter. The incipient stage of decay through which they are 
 passing reacts on the food, and prepares it in a temporary 
 manner to replace those parts of the body which are ceasing from activ- 
 ity, and about to be removed. 
 
 CHAPTER V. 
 
 OF ABSORPTION. 
 
 Double Mechanism for Absorption. The Lacteals and Veins. Lacteal Absorption. Descrip- 
 tion of a Villus. Analogies in Plants. Introduction of Fat by the Villi. The Chyle. 
 Causes of the Flow of Chyle. Intermediate Changes on its Passage to the Blood. Action of 
 Peyer's Bodies. Lymphatic Absorption. Nature of Lymph. Structure of the Lymphatic 
 System. Comparison of Chyle, Lymph, and Serum. Function of the Lymphatic System. 
 Production of Fibrin. Cutaneous Absorption. Causes of the Flow of Lymph. Apparent se- 
 lecting power of the Absorbents. Connection of the Lacteals and Lymphatics with the Locomo- 
 tive and Respiratory Mechanism. 
 
 THE food, after digestion, though in the alimentary tract, is exterior to 
 Double mech- ^ e anniia l system. Means have therefore to be resorted to 
 anism for ab- for its introduction into the circulation, and its distribution 
 to every part. This is accomplished by a double mechanism, 
 one portion of which is adapted to the digestion which has been going on 
 in the stomach, the other to that which is completed in the intestine. 
 The veins which are profusely spread on the walls of the digestive cav- 
 ity constitute the former apparatus, the lacteal vessels the latter. 
 
 The lacteal vessels may be described as delicate tubes, conveying ma- 
 Description of terials absorbed from the intestine into the blood. Their 
 a villas. mode of origin may be understood by considering them as 
 
 projecting with a fine but blunt end upon the inner coat of the intestine. 
 This projection is covered over with smooth muscle cells and a plexus of 
 blood-vessels, a continuation, as it were, of those of the mucous coat of 
 the intestine itself; they are held together by connective tissue, and over 
 that is cast a covering of cylindric epithelium. This construction con- 
 
DISTRIBUTION OF BLOOD-VESSELS TO THE VILLI. 
 
 85 
 
 stitutes what is called a villus, the shape of which is conical, or perhaps 
 cylindrical. The villus may then be regarded as a process of mucous 
 membrane. 
 
 Fig. 23 is a section of the wall of the ileum, 
 a being the villi ; b, glands of Lie- Structure of 
 berkuhn ; <?, muscular layer of mu- -the intestinal 
 cous membrane ; d, follicles of a Pey- T 
 er's patch ; 0, remainder of submucous tissue be- 
 neath them; y, circular muscles; g h, longitu- 
 dinal muscles. (Kolliker.) 
 fig. 24 represents the .distribution of blood- 
 vessels to the villi of the intestine of the mon- 
 
 Fvj. 24. 
 
 Section of wall of ileum magnified 
 50 diameters. 
 
 Distribution of arteries and veins on villi of 
 monkey. 
 
 key. The figure was drawn by the camera lucida, a a being the arteries, 
 b b the veins. 
 
 The form of the villi differs in different regions of the intestine. In 
 the duodenum thev are less elevated, laminated, and broad- 
 
 t - , T . t T -i --i Forms of villi. 
 
 er, Fig. 25. In the jejunum, more projecting or cylmdroicl, 
 
 Fig. 25. 
 
 Fig. 20. 
 
 Distribution of blood-vessels on the villi of the 
 duodenum. 
 
 Distribution of blood-vctesels on the villi of the je- 
 junum. 
 
 Fig. 26. In all cases, however, they are abundantly supplied with blood- 
 
86 STRUCTURE OF THE VILLI. 
 
 vessels. Their epithelial covering of cylindroid cells is shown in the 
 sectional diagram, Fig. 27, a a ; at b b is the origin of the lacteal aris- 
 ing obscurely. ' Fig. 27. 
 
 So amply are the villi supplied 
 with blood-vessels, that if, after in- 
 Various opin- jection with coloring 
 
 materia1 ' their c J lin - 
 
 cells. dric epithelium be re- 
 
 moved, they seem to be tinged all 
 over. Each cell of the epithelium 
 appears to be filled with granular 
 matter, and to have a well-marked 
 
 nucleus. Some anatomists assert Conical villi in section, with cylindroid epithelium. 
 
 that that end of these cells nearest the cavity of the intestine is in reality 
 open, and in this manner they account for the ready passage of oil glob- 
 ules into them, and also for the appearance of solid foreign bodies, as Os- 
 terlein observed. 
 
 Though we have described the lacteal as a vessel projecting into the 
 Origin of the interior of the intestine, it is by some viewed rather as 'a mere 
 lacteal. excavation in the villus. The villi impart to the mucous mem- 
 
 brane an aspect sometimes likened to the pile of velvet. On an average, 
 their number upon a square inch is about 10,000. The entire number 
 of these organisms must, therefore, amount to many millions. At one 
 time it was supposed that the lacteals open directly into the intestine an 
 opinion which is now universally abandoned. The action of each villus is 
 doubtless more complicated than is generally represented, for the organic 
 fibre cells it contains give to it the power of executing rhythmic motions. 
 
 When the operation of the lacteal vessels as absorbents was first de- 
 The lacteals tected, it was believed that all nutriment is introduced by 
 
 Sfc^anfef t ^ ieir means - But tnere are man j animals wholly destitute 
 absorption. of this system of tubes, for instance, the invertebrates. Even 
 in many fishes the villi are absent. In such cases absorption must nec- 
 essarily be conducted by the veins. Moreover, though there are no lac- 
 teals on the walls of the stomach, nor, indeed, on that part of the intes- 
 tinal tube which is higher than the place of introduction of the biliary 
 and pancreatic ducts, there are many substances freely absorbed from the 
 gastric cavity when its pyloric orifice is tied. It has already been men- 
 tioned that the stomach absorbs water with remarkable rapidity. The 
 doctrine that the lacteals are the exclusive organs of absorption must, 
 therefore, be abandoned, for it is plain that the venous system participates 
 in this duty. 
 
 The function of absorption has therefore to be examined from two 
 points of view. As there are two digestions, one producing a perfect so- 
 
ABSORPTION IN PLANTS. 87 
 
 lution, and the other an emulsioned, but not dissolved state Conditions of 
 of the food, so there are two absorbent systems, the lacteals 
 and the veins. The lacteals introduce such substances as are tion. 
 not absolutely dissolved, particularly the oils and fats. The veins ap- 
 pear to take up those substances only which are completely dissolved in 
 water. 
 
 As in many other cases in physiology, so in this, a correct interpreta- 
 tion of the functions of the animal mechanism may be ob- Abgor tion in 
 tained by examining the corresponding structures and func-^ plants, their 
 tions in plants. In the more perfect of these, the absorption a 
 of watery material from the ground, constituting the ascending sap, is 
 brought about by the agency of collections of soft cells, which are placed 
 at the extremity of each rootlet. They are designated spongioles. By 
 their action the fluid is forced up through the tubes of the sap-wood into 
 the leaves, and there exposed to the conjoint agency of the sun and air. 
 A change is thus accomplished, and, from being crude, it turns into elab- 
 orated sap, and now descends through the bark, to be distributed to every 
 part of the plant. Its ascent is caused by the cells of the spongioles, its 
 descent by the chemical changes occurring among the cells which are 
 found in the structure of the leaves. 
 
 These cells both of the roots and of the leaves are far from contin- 
 uing their action for an unlimited period of time. At the most, their 
 existence is transient. Those of the roots are gradually lost by decay, 
 or converted into solid structure, as the elongation of the organs through 
 the ground goes on. Those of the leaves are equally transitory. At 
 periodic intervals, both in deciduous and evergreen plants, the fall of the 
 leaf occurs a new organism succeeding in another summer to make up 
 for the one which has passed away. 
 
 Whatever nutrient material is taken from the soil in the case of plants 
 is introduced by the aid of a cellular structure, and the cells die after ac- 
 complishing their duty. 
 
 It was once a saying among physiologists that the lacteals are the 
 roots of animals, and in this there is, in reality, a great deal Analogy be- 
 of truth, for between the rootlet of a plant and the lacteal of 
 an animal there is a conspicuous relation, not only in struc- roots, 
 ture, but also in function. As is seen in Fig. 27, upon each villus of 
 the intestinal tube there is a layer of cylindric cells, underneath which the 
 lacteal vessel takes its rise, for it does not open by a free orifice on the 
 interior of the intestine, but its flask-shaped, loop-like, or convoluted or- 
 igin is obscurely seen in the midst of the cells. The aspect which the 
 villi present, from its doubtful nature, has led to the erroneous conclusion 
 that, as soon as active digestion goes forward, cells rapidly develop with- 
 in the epithelium, and continue to do so as long as the intestine contains 
 
88 INTRODUCTION OF FAT. 
 
 digested matter ; that they become turgid with chyle, and have a diame- 
 ter of about the yJ^- of an inch ; that, as they select material, they 
 throw it into the lacteal tube, either by bursting or deliquescing, and at 
 the same time set free broods of germs from which new cells are developed. 
 So far, therefore, as their duration is concerned, if this be their true histo- 
 ry, they are even more transitory than the corresponding cells of plants. 
 
 That the lacteals are connected with respiratory digestion seems to be 
 Fat is intro- plainly indicated by the circumstances of their occurrence, 
 facteais Into 6 ^ one ^ them are found upon the stomach, nor even on that 
 the blood. part of the duodenum which is above the entrance of the he- 
 patic and pancreatic ducts, but below that point they are scattered in pro- 
 fusion all over the small intestine. The digestion of fatty bodies not 
 taking place until the food has gained the duodenum, vessels for the ab- 
 sorption of the emulsions to which that digestion gives rise are not re- 
 quired until after that point is passed. Correctly speaking, however, 
 the lacteals are only lymphatics which are taking up oil presented to 
 them. In view of the use which the oils subserve in the animal economy, 
 the lacteals are in reality an appendix to the respiratory system. There 
 can be no doubt that through their channel oils and fats, under the form of 
 emulsions, are transmitted to the blood. The analysis of the chyle shows 
 that it is always rich in fat, and, indeed, it is supposed by some physi- 
 ologists that the objects just described. as cells, surrounding the origin of 
 the lacteals, are nothing more than oil or fat globules accumulated there 
 and waiting to be taken up, or that the disappearance and exuviation of 
 the so-called cells is an optical deception, due to their walls becoming 
 permeated with oil. 
 
 The manner in which oil globules collect round the villus I have re- 
 marked as being very strikingly displayed 
 in the case of the gray squirrel after feed- 
 ing on fatty nuts. As shown in Fig. 28, 
 the whole structure looks as if it were dis- 
 tended with oil globules, a a, in the midst 
 of which the origin of the lacteal, b b b, may 
 be doubtfully and dimly discerned. 
 
 Although it can not be admitted that the 
 Evolution and production and deliquescence 
 
 function of the / .1 n c MV i Half-diagram of villi of the gray squirrel 
 
 cells of the * " ie Ce -" S * ^"" 1S a demon- after feeding on nuts. 
 
 villi. strated fact, and that on this the action of the lacteals as ab- 
 
 sorbent vessels for the most part depends, the rapid evolution and disap- 
 pearance of these cells is by no means a physiological impossibility. Bot- 
 anists assert that, in a single night, the Bo vista giganteum, a puff-ball, 
 can develop from a mere point to such a size that it must contain fifty 
 thousand millions of cells a number that seems almost incredible. The 
 
THE MESENTERIC GLANDS. 89 
 
 development of cells in the villi of the intestinal tube, in countless 
 crowds, may therefore be within the bounds of possibility. 
 
 If this be the case, the cells which thus come rapidly into existence 
 in the villi appropriate those articles of respiratory food which are of 
 imperfect solubility in water. To this class the oils belong. Each cell 
 then, as it dies, yields up its contents to the lacteal tube. In the white 
 fluid, the chyle, which flows along those tubes, are many pale or color- 
 less corpuscles continually coming into existence. These seem to im- 
 press a change upon the chyle, and, to give a full opportunity for such 
 action, that fluid is compelled to flow gradually through long and sinuous 
 channels, for the glands in the mesentery may be regarded as convoluted 
 windings, or rather plexuses of tubes, to which that particular form is 
 given for the sake of closeness of package. From the enveloping cap- 
 sule of fibrous tissue of the glands thin sheets are projected, Structure of 
 and so internetted as to divide the whole gland into many the mesenteric 
 alveoli. These are filled with a pulpy material supplied s ar 
 with delicate blood-vessels. The chyle either oozing through this ma- 
 terial eventually escapes from the gland by the efferent vessels, or makes 
 the passage in its own thin tube. In reptiles, in which there are no 
 such glands, the lacteals are extended to a very great length. 
 
 The manner in which the chyle passes through the mesenteric glands 
 is therefore explained differently, according to the view Modeofaction 
 which is taken of the structure of those organs. If they ofthemesentc- 
 are considered as mere dilatations of the lacteal vessel, from nc s al 
 the sides of which partition processes are sent off, the interspaces being 
 filled with granular material, through which delicate blood-vessels pass, 
 the chyle is to be considered as oozing through this granular structure, 
 and crossing directly in contact with it. But if we accept the doctrine 
 that the chyle is conducted through the gland in a plexus arising from 
 the incoming lacteal, the granular material being outside, then the influ- 
 ence of that material, in whatever it may consist, takes effect through 
 the delicate walls of the plexus. The like remarks apply to the lym- 
 phatic glands. Physically, however, the condition in both cases is the 
 .same ; the incoming liquid is simultaneously exposed in the gland to 
 the influence of the granular pulp and to arterial blood. 
 
 The chyle, delivered into the lacteal tube, is propelled by the conjoint 
 action of several different forces. The constant accumulation Causes of lhe 
 of liquid at the origin of the vessel produces a pressure which flow of the 
 can only be relieved by motion through the tube, and at the chyle ' 
 mouth, where the lacteal empties into a vein, as sooner or later all do, 
 either directly or through the intervention of the thoracic duct, a suction 
 force is exerted on the contents of the lacteal by the passing current of 
 the venous blood, upon the well-known hydraulic principle of Yenturi, 
 
90 
 
 MOTION OF THE CHYLE. 
 
 blood-vessels. 
 
 that if into a tube, a b,Fig. 29, through which a current of water is stead- 
 
 ily flowing, another tube, c d, opens, its 
 more distant end being in communication 
 with a reservoir of water, e, through this 
 tube a current will likewise be establish- 
 ed, and the reservoir be emptied of its 
 contents. The effect is still greater, as 
 Bernouilli demonstrated, when the main 
 current is flowing toward the wide end 
 of a conical pipe. Moreover, the lacteal 
 tubes are elastic, and furnished with valves, 
 which open to let the fluid pass toward 
 the veins, but close in the opposite way. 
 
 Principle of venturi. This valvular mechanism renders available 
 
 any pressure arising either from the contractility of the vessels them- 
 Mechanism for selves, or from those various muscular movements, respira- 
 transfemng torv or voluntary* which affect the abdominal walls. The 
 
 chyle from the J , . f 
 
 viiius to the manner of introduction of the great lacteal trunk the tho- 
 racic duct at the angle of junction of the left subclavian and 
 f. DO. jugular veins, is also very felicitous, for the suc- 
 
 tion force of those large vessels is there conjoin- 
 ed, and the effect is at a maximum. The con- 
 trol of the blood motion on the chyle motion is 
 obvious from this, that as soon as the circula- 
 tion stops the chyle stops, and this not so much 
 from the engorgement of the venous trunks, 
 which renders it difficult for the chyle to make 
 its way into them, as from the cessation of that 
 tractile force, which solicits the chyle to move 
 into the blood. 
 
 Fig. 30 represents the position and course of 
 the thoracic duct, and its manner of introduction 
 of the chyle into the blood circulation. (Wil- 
 son.) 
 
 1, Arch of aorta ; 2, thoracic aorta ; 3, abdom- 
 inal aorta ; 4, arteria innominata, dividing into 
 right carotid and right subclavian arteries ; 5, 
 left carotid ; 6, left subclavian ; 7, superior cava, 
 formed by the junction of, 8, the two vena? in- 
 nominata?, and these* by the junction, 9, of the in- 
 ternal jugular and subclavian on each side ; 10, 
 the greater vena azygos ; 11, the termination of 
 The thoracic duct. the lesser in the greater vena azygos ; 12, recep- 
 
INTRODUCTION OF FAT. 91 
 
 taculum chyli, several lymphatic trunks opening into it ; 13, the thoracic 
 duct, dividing opposite the middle of the dorsal vertebra? into two branch- 
 es, which soon reunite ; the course of the duct behind the arch of the 
 aorta and left subclavian artery is shown by a dotted line ; 14, the duct, 
 making its turn at the root of the neck, and receiving several lymphatic 
 trunks previously to terminating in the posterior aspect of the junction 
 of the internal jugular and subclavian vein ; 15, the termination of the 
 trunk of the ductus lymphaticus dexter. 
 
 As to the manner in which digested fat finds its way into the lacteals, 
 it seems to be as follows: In the interior of the epithelial Mannerofthe 
 cells oil-drops are detected, while on the outer part the sur- introduction of 
 face presents a pearly aspect, from other portions of oil wait- fat ' 
 ing to enter. By degrees, all the cells upon the exterior of the villus ex- 
 hibit the same appearance, the particles gradually finding their way 
 through the parenchyma of the villus, and so entering the lacteal tube. 
 If, with some anatomists, we regard the lacteal at its origin as not being 
 a true vessel, but only an excavation in that parenchyma, much of the 
 obscurity which surrounds the explanation of the manner of the entry 
 of oleaginous material into the lacteal is removed. If, moreover, with 
 other anatomists, we represent the intestinal end of the cylindric cells to 
 be wanting, and the cells themselves to be truly cup-shaped forms, filled 
 with a peculiar secretion, through which fat particles and even solid sub- 
 stances may pierce their way, this likewise would remove much of the 
 difficulty. But, after all, even if the general opinion of the structure of 
 a villus is adopted, that the lacteal commences with a blind pouch or 
 blunt tube surrounded by a network of blood-vessels, and over this an 
 epithelium cast, there being no mouths, or pores, or apertures of discov- 
 erable size leading into the lacteal through its own wall and enveloping 
 structures, we should also remember the extreme minuteness of the oily 
 particles suspended in the chyle, and still more particularly that even 
 this size, small as it is, is deceptive ; for, in passing through interstices 
 too minute to be seen even by optical aid, the oil particles may be press- 
 ed out into long, thread-like forms, which, as soon as they escape into the 
 free cavity of the lacteal, assume the spheroidal appearance by reason of 
 their own cohesion, just as a blood-cell can pass through a vessel of a 
 diameter far less than its own by lengthening itself out into a linear 
 shape, and reassuming its original figure as soon as it escapes from con- 
 finement and pressure. Though, therefore, the lacteals commence upon 
 the intestinal walls as closed tubes, this, in reality, offers no obstacle to 
 their absorbing power when their molecular porosity is considered. 
 
 Perhaps this infiltration or intrusion of oily material is, to a consid- 
 erable extent, aided by the presence of the bile, or, rather, its oily con- 
 stituent. It is capable of easy demonstration that oil will rise much 
 
92 
 
 CHANGES OF THE CHYLE. 
 
 higher in a capillary glass tube, the inside of which has been coated over 
 with bile, than in the one which has not been so prepared. 
 
 The liquid which has been gathered into the lacteals from the intes- 
 tine pursues its course to the veins, and ultimately enters them. The 
 special changes which are impressed on it during this passage will new 
 be explained. 
 
 The constitution of the chyle varies with the physiological conditions 
 Constitution ^ ^ e S 7 stem - After a period of fasting it is colorless, and 
 and changes in presents the general aspect of lymph, hereafter to be de- 
 scribed, but during digestion it is a whitish milky fluid, 
 whence its name. This milkiness depends on the suspension of minute 
 fat or oil globules in it. Their diameter is commonly stated at the 
 "3 ToTo of an inch. Of course, the composition of the chyle varies in dif- 
 ferent animals, and even in the same animal under different diets. 
 
 Composition of Clujlc, 
 
 
 Horse. 
 
 Ass. 
 
 Cat. 
 
 Man. 
 
 Water 
 
 935.00 
 
 902.37 
 
 905.70 
 
 904.80 
 
 Fat 
 
 15.00 
 
 36.01 
 
 32.70 
 
 9 20 
 
 Fibrin 
 
 .75 
 
 3.70 
 
 1.30 
 
 ) 
 
 Albumen . . 
 
 35.00 
 
 35.16 
 
 
 > 70.80 
 
 Extractive 
 
 6.25 
 
 15.65 
 
 48.90 
 
 10.80 
 
 Salts 
 
 8.00 
 
 7.11 
 
 11.40 
 
 4 40 
 
 
 
 
 
 
 
 1000.00 
 
 1000.00 
 
 1000.00 
 
 1000.00 
 
 With so many causes of variation, such a table as the preceding is 
 only valuable as giving a general idea of the nature of the chyle. We 
 learn from it that the predominating solid constituents are fat and albtK 
 men. The percentage amount of the first of these in the sample of hu- 
 man chyle is very low, a fact due to the circumstance that the subject 
 from which it was obtained an executed criminal had eaten but little 
 for some time before his death. In like manner, the chyle of horses 
 which have been kept without food has been observed to exhibit a dim-' 
 inution of its fat to such an extent as to be less than one tenth of the 
 normal amount. It is to be remarked that the saline ingredients of the 
 chyle closely represent those of the blood, both in constitution and 
 amount. 
 
 The composition of the chyle varies at different points on its passage 
 Constitution of to the veins, there being a gradual diminution of the albu- 
 chyie at vari- men an( j an j ncrease O f the fibrin. After the passage through 
 its course. the mesenteric glands it becomes capable of coagulation, 
 and will separate into a serum and a clot. Examined near the villi, it 
 may be regarded as ah albuminous liquid, in which are suspended glob- 
 ules of fat of various sizes, down to the degree of minuteness just speci- 
 fied. The nature of these globules is determined by the action of sul- 
 phuric ether, which readily dissolves them. After passing through the 
 
CHANGES IN THE CHYLE. 
 
 93 
 
 mesenteric glands, the percentage amount of albumen declines, and the 
 fat globules diminish in number. Simultaneously the special cells, to 
 which the name of chyle corpuscles is given, make their appearance, and 
 the liquid is now capable .of coagulating, owing to the production of 
 fibrin. These characters become more strikingly developed as the chyle 
 advances in the thoracic duct. The chyle corpuscles are eventually de- 
 veloped into red blood-cells. 
 
 .It should be borne in mind, in all discussions respecting the composi- 
 tion of chyle in different parts of its course, that it must re- ,, . 
 
 r -,11 It is affected by 
 
 ceive transuded matters from the blood, and that this must transudation 
 more particularly occur on its passage through the mesen- fromtheblood - 
 teric glands. Owing to this, it is quite probable that, even though there 
 should be an actual consumption of albumen in accomplishing the meta- 
 morphoses which are taking place, the apparent percentage amount of 
 that ingredient may increase by transudation from the blood. It ap- 
 pears to me quite probable that the albuminous material in the lacteal, at 
 its very origin in the villus, has been derived to quite as great an extent 
 by transudation from the plexus of blood-vessels as by absorption from 
 the digested food. 
 
 Whatever may be the special manner by which the fats pass from the 
 intestine into the lacteals, they have scarcely gained those saponificatiou 
 vessels before they undergo a change. The quantity of free of the fat - 
 fat diminishes, and that of saponified fat increases ; this is probably ac- 
 complished by soda obtained from the blood. * 
 
 As to the fibrin, it can scarcely be supposed that the imperfectly co- 
 agulable variety which the chyle contains should have been Difference be- 
 derived by transudation through the vessels of the strongly ^^^^~ 
 contractile kind contained in the blood ; and, in view of all chyle-fibrin, 
 the circumstances of the case, it would appear that the explanation we shall 
 
 offer of its direct origination from the 
 chyle albumen by oxidation is correct. 
 The chyle corpuscles are readily 
 distinguished from the blood- _. 
 
 Nature of 
 
 cells, not only by their white chyle cor- 
 appearance, but also by their actTo^^ 
 form. They are spheroidal, reagentson 
 and either homogeneous or 
 granular. Those of the frog are seen 
 in Fig. 31, at a a, sparsely scattered 
 among the elliptical blood-cells. The 
 photograph from which the engraving is 
 taken exhibits nearly the average pro- 
 
 Chyle corpuscles with blood -cells, magnified 250 ,. ,, , -, ,. 
 
 portion of these bodies in that animal. 
 
 diameters. 
 
94 
 
 CHYLE COKPUSCLES. 
 
 By the action of water, the nucleus of the chyle-cell becomes more dis- 
 tinct, its increased granular aspect making it more visible, as in Fig. 32. 
 
 Fig. 32. Fig. 33. 
 
 Chyle corpuscles with water, magnif ed 
 500 diameters. 
 
 Chyle corpuscles with acetic acid, mag- 
 nified 500 diameters. 
 
 tern. 
 
 By acetic acid the nucleus is greatly contracted, as in Fig. 33, and some- 
 times even escapes from the cell. 
 
 In embryonic life, the first appearance of chyle corpuscles commonly 
 coincides with a change in the arrangement of the respiratory mechan* 
 ism, as the closing of the branchial fissures, indicating a connection be- 
 tween their production and the activity of interstitial oxidation. 
 
 It has been previously stated that the bodies known as Peyer's glands 
 Fever's bodies are to be regarded as belonging to the absorbent rather than 
 ^ ie Digestive apparatus. In structure they are analogous to 
 the lymphatic and lacteal glands, consisting of a capsule 
 containing granular material, in which loops of capillary blood-vessels 
 are laid. From these proceed many lacteal vessels, as may be very 
 plainly observed during digestion. Their functions would therefore seem 
 to be the submitting of the chyle to the simultaneous influence of the 
 blood brought by the arterial capillaries, and the pulpy material or gran- 
 ular plasma they contain. They are, in reality, dilatations of the absorb- 
 ent vessels, accomplishing in a small space a result which would other- 
 wise demand a very long lacteal tube, and probably not impressing any 
 other change on the chyle than that which would have occurred in such 
 a tube, if of sufficient length. 
 
 It is not possible clearly to understand the functions of the lacteals 
 . without a description of the structure and functions of the 
 
 Structure and r 
 
 functions of the lymphatics, for these vessels conspire in their action. 
 
 tlcs * Anatomical, chemical, and physiological considerations 
 
 lead us to conclude that the formation of the LYMPHATIC SYSTEM is 
 closely allied to that of the LACTEAL. The two classes of vessels make 
 their appearance together in fishes ; the lymphatics originate in a net- 
 work of delicate tubes, but are disseminated through all the soft tissues 
 except the nervous, and are found especially in the skin. The fine ini- 
 
PROPERTIES OF LYMPH. 
 
 95 
 
 tial tubes gradually coalesce, producing those that are of a larger diame- 
 ter, and these pass through glands, which might indeed be regarded as 
 mere plexuses, and eventually empty into the veins. 
 
 A few minutes after if has been drawn, the lymph coagulates into a 
 colorless clot, and then exhibits contraction. Compared with p rop erties of 
 blood in like circumstances, the clot of lymph is small in re- iymp h - 
 lation to the serous portion. In other respects there is a general resem- 
 blance between lymph and blood free from its red cells, the fibrin and 
 the albumen being apparently the same in the two cases* The saline 
 constituents are not only the same, but bear the same ratio to one an- 
 other in the two fluids. Their absolute percentage amount differs, be- 
 cause the lymph contains a larger proportion of water than the blood. 
 
 The lymph arising, as we shall find, by transudation from the capil- 
 laries, must obviously vary in different parts, those parts taking from 
 the blood the materials they require for their nutrition, and yielding to 
 it the products that have arisen during their waste. Whatever in this 
 manner changes the composition of the blood, must also occasion a change 
 in the transuded liquid. Thus Schmidt has shown that protein bodies 
 transude through the capillaries of the pleura most copiously ; through 
 those of the peritoneum not to half that amount ; through those of the 
 brain and those of the subcutaneous areolar tissue to a less and less ex- 
 tent. Not only must the material thus oozing from the capillaries vary in 
 different regions, because of variations in the mechanical constitution of 
 
 ose vessels, but it must also change even in the same locality, through 
 temporary accidents, such as changes in the velocity with which the blood 
 is flowing. An attempt has been made to show that the transudation will 
 be richest in albumen as the blood current in the capillaries is slower. 
 
 When the contents of the lymphatic vessels are submitted to analysis, 
 and compared with the chyle, a striking difference is appar- composition of 
 ent. The chyle contains, as has been already stated, large b rm P h - 
 but variable proportions of fat or oil in an extremely subdivided state, 
 from which the lymph is free. The leading solid constituent of the 
 lymph is albumen, and this indicates the use of the system. 
 
 Composition of Lymph. 
 
 
 Horse. 
 
 Ass. 
 
 Man. 
 
 Water 
 
 950 00 
 
 965 36 
 
 961 00 
 
 Fat 
 
 .09 
 
 
 
 Fibrin 
 
 ) 
 
 1 20 
 
 2 50 
 
 Albumen 
 
 J- 39.11 
 
 1200 
 
 27 50 
 
 Extractive 
 
 4 88 
 
 15 59 
 
 6 90 
 
 Salts 
 
 5 92 
 
 5 85 
 
 2 10 
 
 
 
 
 
 
 1000.00 
 
 1000.00 
 
 1000.00 
 
 The functional connection between the lacteals and lymph vessels is 
 very well illustrated by the following analysis, which ex- Fasting chyle 
 hibits the composition of chyle obtained from the thoracic 
 
96 COMPAEISON OF LYMPH, CHYLE, AND SERUM. 
 
 duct of a man who died from softening of the brain, and who took noth- 
 ing but a little water for 30 hours preceding his death. (L'Heritier.) 
 
 Composition of CJiyle after Fasting. 
 
 Water ,... 924.3G 
 
 Fat 5.10 
 
 Fibrin 3.20 
 
 Albumen 60.02 
 
 Salts 7.32 
 
 1000.00 
 
 The constitution of the chyle so nearly approaches that of the lymph, 
 Comparison of ^ iat we aie autnor i ze ^ to conclude that, during fasting, the 
 lymph and lacteals transmit lymph, and the conclusion gives force to 
 the observation already made, that the albumen of chyle is 
 derived rather from the blood capillaries than from the digested food. 
 Comparison of ^ n com P arm g together the salts of the serum of the blood 
 the lymph and and those of the lymph as obtained from the horse, they ap- 
 pear to coincide. 
 
 Salts of Serum and Lymph. 
 
 
 Scrum. 
 
 Lymph. 
 
 Alkaline chlorides 
 
 4 055 
 
 4 123 
 
 Alkaline carbonates 
 
 1.130 
 
 1 135 
 
 Alkaline sulphates 
 
 311 
 
 233 
 
 Alkaline phosphates 
 
 .115 
 
 120 
 
 
 
 
 
 5.611 
 
 5.611 
 
 From the indications presented in these tables, there can be no doubt 
 that the office of the lymphatics is to collect the albuminous 
 
 Office of the x 
 
 lymphatic sys- matters which have every where transuded from the blood- 
 vessels, or been set free by changes going on in the soft 
 parts. Such matters, though they may be regarded as being in one 
 sense dead, are yet as applicable for the further support of the mechan- 
 ism as are the albumenoid bodies introduced as food, and said to be 
 taken up by the lacteals. The last table shows that the lymph is really 
 nothing but a diluted serum. A mechanism is therefore resorted to to 
 turn this collected albumen into fibrin, and thus arises a lymphatic gland 
 a contrivance which tends greatly to compactness. This structure is 
 Structure of ^ ie countei T art ^ tne mesenteric or lacteal gland. It may be 
 lymphatic described as originating from the coalescence of two or three 
 lymph vessels, which, casting off their external coat as they 
 enter the gland, anastomose with one another in various ways, so as to 
 form plexuses and convolutions. The capsule of the gland, strengthen- 
 ed by the coat it has received from the entering vessels, sends forth par- 
 tition-like processes, which dip down into the grayish pulpy material 
 filling the interstices. On their emergence from the gland the vessels 
 recover from it their external coat, and, during their passage through it 
 in their naked state, blood-vessels are distributed upon them. The ob- 
 
THE LYMPHATIC SYSTEM. 
 
 97 
 
 ymphatics of the largo intestine. 
 
 ject of the arrangement seems to be to submit the liquid contained in 
 the lymph vessel to the action of the pulpy material of the gland and ar- 
 terial blood under the most favorable circumstances, the thinness of the 
 wall and the convolved plexus being well adapted to that end. 
 
 Fig. 34 illustrates the lymphat- 
 ics of the large intestine, the ad- 
 joining parts being cut or displaced 
 to display them ; <2, <z, ascending 
 and transverse colon drawn aside; 
 &, , descending colon and its sig- 
 moid flexure drawn aside ; <?, cce- 
 cum; d, stomach; e, duodenum; 
 y, jejunum cut ; <?, A, i, lymphatics 
 and their glands. In such an ar- 
 rangement as this, the lymph is far 
 more perfectly exposed to the in- 
 fluences to which it has to be sub- 
 mitted than it could possibly be in 
 straight tubes. In reptiles, how- 
 ever, this package is not resorted 
 to, and the tubes, being spread out, 
 give the false appearance of a great- 
 eT'cfevelopment to this system than in the higher tribes. In the mam- 
 malia, according to Professor Goodsir, wherever the lymph tube enters 
 the gland, it changes its internal constitution, losing the scale-like cover- 
 ing that its inner coat presented, and offering a numerbus development 
 of nucleated cells, many of which adhere to the membrane beneath, but 
 many float away and drift with the lymph in its course. There is a 
 constant reproduction of these organisms, and they seem to be connected 
 with a diange in the albumenoid constituent of the lymph, Production of 
 turning it into fibrin. And thus, if examination is made of fibrin in lymph 
 the lymph before it enters a gland and after it has passed s lands - 
 through, in the former instance it seems to differ but little from the liquor 
 sanguinis, or serous portion of the blood, as has been already shown, but 
 in the latter fibrin begins to abound. 
 
 Professor Goodsir's view is represented in the diagram, Fig. 35, show- 
 ing the scale-like ep- 
 ithelial cells of the 
 lymphatic tube chang- 
 ing into the nucleated 
 cells of the gland. 
 
 Diagram of a lymph gland. Evolution of cells in lymph gland. Fig. 36 illustrates 
 
 the generation of broods of cells, some being attached and some free. 
 
 G 
 
 Fig. 85. 
 
 Fig. 36. 
 
98 PRODUCTION OF FIBRIN. 
 
 Some chemists, adopting the views of Liebig respecting the essential 
 Fibrin not an difference "between blood fibrin and muscle fibrin, look upon 
 effete body. ^Q f orme r substance, not as a histogenetic, but as an effete 
 body, a conclusion which, of course, would have an important bearing 
 upon the interpretation of the function of the glands as here given, as like- 
 wise upon that in the corresponding case of the chyle. The weight of 
 physiological evidence is, however, so strongly against this doctrine, that 
 we are constrained to retain the old one, and therefore to regard the pro- 
 duction of fibrin as one of the important duties of the lymphatic system. 
 
 The absorbent vessels, whether lacteals or lymphatics, have therefore 
 its mode of a common duty f changing albuminose or albumen into 
 production and fibrin, and thereby of compensating for the constant waste of 
 that substance which is going on in the wear and tear of 
 the muscular system. The constitution of the urine proves that the 
 amount of muscular fibrin destroyed in short periods of time is very 
 great. "We can not estimate the hourly consumption at less than 62 
 grains. Such a waste must demand an equivalent compensation, if 
 the animal mechanism is to be kept up unimpaired, and every^ care is 
 therefore taken to omit no means which may incidentally offer for hus- 
 banding the necessary materials. The action of the lymphatics illus- 
 trates this principle significantly. Passing through all the soft solids 
 where exudation of albumen from the blood-vessels can take place, they 
 collect the materials that would otherwise go to waste, and add thereto 
 many of the products arising from the disintegration and decay of the 
 soft parts themselves. Receiving all these, they transmit them through 
 their windings in the glands, and thus submit them to the action of the 
 innumerable cells which are there coming into existence. As in the egg 
 of a bird, in which, as the albumen slowly disappears, the muscular tis- 
 sues of the young chicken arise, so here the serous portion disappears, 
 and fibrin comes in its stead, and this is hurried forward to the torrent 
 of the circulation, and thrown into the blood-vessels, to be by them dis- 
 tributed to all parts of the mechanism, wherever the muscular tissues are 
 in want of repair. 
 
 But, besides this function of the elaboration of fibrin, there can be no 
 Cutaneous question that the lymphatics have other incidental uses, 
 lymphatic ab- Many facts are known which prove that those of the skin 
 exert a powerful agency in absorbing liquid material. Thus 
 a person who has abstained from water will, after he has immersed his 
 body in a bath, not only find his weight increased, but the sensation of 
 thirst abated. Instances of the kind are on record where sailors, in open 
 boats without fresh water, have assuaged the torments of thirst by im- 
 mersing their bodies in the sea. Nay, it is even asserted that in certain 
 conditions water may thus be obtained from the atmospheric air, and in 
 
SELECTING POWEK OF THE ABSORBENTS. 99 
 
 all such cases every thing points out that the lymphatic vessels are the 
 avenues through which the liquid is introduced. 
 
 In what manner does the lymph move? In reptiles there are found 
 what are termed lymphatic hearts, which are merely dilated cause of the 
 portions of a tube exhibiting pulsation. Of these, in the flow of lymph, 
 frog, two pairs may be discovered, one behind the hip-joint, and situated 
 so superficially that the motions can be plainly seen ; the other is at the 
 anterior part of the chest. The pulsating movements of these organs, of 
 course, impel the liquid acted on in the direction determined by the valves 
 with which the vessels are so profusely supplied, that is, to the general 
 circulation, and the lymph finally enters the blood-vessels. 
 
 But in the higher tribes these organs of impulsion are absent, and the 
 circulation through the vessels is determined by the agencies mentioned 
 in the case of the lacteals. 1st. By the constant accumulation of liquid 
 at the origin of the tube ; 2d. By every muscular movement, either vol- 
 untary or involuntary, which produces a compression of the tube, the 
 valves all opening one way, and therefore causing the included liquid to 
 pass in one direction only ; 3d. By the exhaustive action at the mouth 
 of the lymphatic, arising from the passage of the blood. It ought, per- 
 haps, t^ be prominently pointed out, as belonging to the second of these 
 es, that the pulsation of the arterial trunks adjacent to any lym- 
 phatic brings the power of the heart itself into operation in an indirect 
 way. 
 
 Though the absorbents will receive many different bodies and transmit 
 them to the veins, the action does not take place in an in- A arent ge 
 discriminate manner. Certain substances, such as the fats lecting power 
 and albumen, find a ready entrance, but admission to others of abs( 
 is wholly denied. Thus it has long been known that if coloring matter 
 be introduced into the intestine, it by no means follows that the chyle 
 will be tinged. If an animal be compelled to take litmus-water, the 
 chyle will still be found colorless or white. On such facts was founded 
 the old doctrine that these organs possess a low species of intelligence, 
 distinguishing among different substances, permitting some to enter 
 them, and refusing a passage to others. Many years ago I showed that 
 these fanciful cases are capable of a simple physical explanation. Thus 
 I found that if blue litmus water was tied up in a bladder, or a piece of 
 peritoneum, and sunk in a vessel of alcohol, though the water would rap- 
 idly infiltrate into the alcohol, the coloring matter would be stopped just 
 as- it is in the intestine. But, in reality, there is no need of such experi- 
 ments to satisfy us of the fictitious nature of this selecting power. If 
 we fill a lamp half full of oil and'lult cf water, : and' immerse KriYa wick 
 long enough to dip into both,- if the wick be previously soaked in oil, it 
 will withdraw from the l#mb oil' alone, and continue to fro' 1 so 'until the 
 
100 FORMATION OF FIBRIN. 
 
 lamp ceases to burn ; but if it be first soaked in water, it will wholly 
 refuse to take the oil, and remove the water alone, until all is escaped by 
 evaporation. But did ever any one impute to the wick of a lamp a 
 "power of intellectuality, no matter how obscure, or suppose that there 
 is any thing mysterious in such a selecting operation ? A perpetual refer- 
 ence of the most common facts to mysterious agencies has been the great 
 barrier to the advance of medical science. This system was introduced 
 by the alchemists and quacks of the Middle Ages, and even now it will 
 take many books and many years before physiology can be rescued from 
 such visionary theories. 
 
 From the point to which our descriptions have brought us, we have 
 
 Connection of to re S ar( ^ tn ^ s P art ^ tne absorbent mechanism as connected 
 lacteaisand with two great animal functions, motion^and respiration. 
 with motion Both its divisions, the lymphatics and the lacteals, in prepar- 
 and respira- ing fibrin from albumen, make provision for the repair of the 
 muscular tissues, and are therefore to be regarded as a portion 
 of the motive apparatus. But the lacteals are charged with a farther 
 duty, and in a double manner are connected with the respiratory mechan- 
 ism, for they not only introduce fats into the system, but give origin to 
 the cells of the blood, which are the carriers of oxygen. 
 
 We may therefore close this chapter with a few remarks, 1st. On the 
 connection of the absorbent system with the provisions for motion ; 2d. 
 On its connection with the respiratory function, as more particularly dis- 
 played by the preparation of blood-cells. 
 
 1st. The connection of the absorbent system with the provisions for 
 motion is through its function of preparing fibrin from albumen. 
 
 From the membrane which lines the plexus of tubes of which the mes- 
 Fabrication enteric and lymphatic glands are composed, crowds of nucleated 
 of fibrin. ce n s are continually arising. As to the function of these cells, 
 there can be little doubt that it is in part to effect the translation of a 
 portion of albumen, which has been introduced along with the oil glob- 
 ules, into fibrin, and accordingly we find that the chyle, analyzed 'at dif- 
 ferent parts of its course, yields different products. As has been stated 
 already, intercepted before its passage through these glands, very little 
 fibrin is found, but collected from points beyond, the quantity of fibrin 
 steadily increases and that of albumen declines. The plexus of tubes 
 has therefore for its object to expose its contents to the influence of the 
 cells. 
 
 Now what are the chemical conditions under which the transmutation 
 of albumen into fibrin takes place ? The ^problem is most clearly pre- 
 sented in !tae case, of r 'the 'incubation of a : bird's egg. The white of the 
 egg, consisting chiefly ^of albumen, gradually loses that form, and passes 
 into the Bfattf bi* fibrin as the \5evelo|!>nient of the muscular tissues of the 
 
FORMATION OF BLOOD-CELLS. 101 
 
 young chicken is effected ; but the change can not take place except ox- 
 ygen be received through the shell ; and, indeed, in all cases in which al- 
 bumen passes into fibrin, it does so only in the presence of oxygen. 
 
 But in the case of the absorbent glands, from what source does the 
 requisite oxygen come ? These glands have just been de- Manner in 
 scribed as plexuses of the absorbent tubes, among the rami- y hich oxygen 
 fications of which arteries and veins are abundantly distrib- the making of 
 uted, the blood not getting access to the interior of the ab- fibrin * 
 sorbent, but running in its own vessels, as it were, side by side, and 
 branching on the naked walls of the plexus ; and, just as in the placen- 
 tal circulation the arterial blood of the mother vivifies or furnishes oxy- 
 gen to the foatal blood, so in this instance the arterial blood enables the 
 cells to discharge their duty of converting the albumen into fibrin, which 
 passes onward to the general circulation for the renovation of the muscu- 
 lar tissues. 
 
 Since the hourly consumption of fibrin may be taken at 62 grains, 
 the quantity produced by the action of these cells must be the same. 
 We may therefore affirm that the fibrin-producing mechanism yields 
 aboutjone grain in each minute of time. 
 
 Contemporaneously with the elaboration of fibrin is the develop- 
 ment of the proper chyle corpuscles. Through the evolution Formation of 
 of these and the absorption, of fat, the chyle vessels present a Wood-cells, 
 connection with the respiratory apparatus. 
 
 If any weight is to be given to the views of Ascherson, the occurrence 
 of fat globules in the chyle is essential to these cellular productions. 
 He found that when globules of oil are placed in a solution of albumen, 
 they become coated over with a film of that substance in a coagulated 
 state, and hence was led to infer that this is the starting-point of cell pro- 
 duction generally. 
 
 The chyle corpuscles are the embryos of the true red blood-cells, the 
 latter being derived from them by gradual development. As will appear 
 more in detail when we come to the description of the blood, in verte- 
 brated animals there are two distinct classes of red blood- Twosuccessive 
 cells, which appertain to distinct periods of life. The first, forms of biood- 
 which are found in man previously to the time of formation Cl 
 of the chyle and lymph, are nucleated, and have the power of reproduc- 
 tion by fissuring of the nucleus. 
 
 But a distinct set gradually replaces the preceding. These cells have 
 no nucleus ; they are flattened, bi-concave, and in man circular. They 
 possess no power of reproduction either by fissuring or otherwise. Their 
 origin is from the chyle corpuscle, the granular interior of which clears 
 up, and is succeeded by a deep red tint. The transition from the first 
 to the second of these forms takes place at an early period, and may be 
 
102 ABSORPTION BY THE BLOOD-VESSELS. 
 
 regarded as complete in the human embryo of two months old. After 
 that time "blood-cells are generated upon the second plan, from the chyle 
 corpuscles alone. 
 
 It is a significant circumstance that this transition from the reproduc- 
 tive to the non-reproductive blood-cell is coincident usually with the dis- 
 appearance of the external branchia3, or the closing of the branchial fis- 
 sures. There can be no question that the destined function of the per- 
 fect blood-cell is the introduction of oxygen to the system. In their or- 
 igin and in their object they are therefore in relation with the respiratory 
 mechanism. 
 
 CHAPTER VI. 
 
 ABSOKPTION BY THE BLOOD-VESSELS. 
 
 Proof of Absorption by the Blood Capillaries. Occurs as a physical Necessity. Nature of Cap- 
 illary Attraction. Its Phenomena in the Rise and Depression of Liquids. Conditions for 
 producing a Flow in a Capillary Tube. Passage of Liquids through minute Pores. General 
 Propositions respecting Capillary Attraction. Endosmosis and Exosmosis. They depend on 
 Capillary Attraction. Force against which these Movements may take place. Illustrations of 
 selecting Power. General View of the entire Function of Absorption, lacteal and venous. 
 
 THAT the blood-vessels of the stomach and intestinal tube participate 
 Substances are in the function of absorption is demonstrated by many dif- 
 the^bbodX- ferent facts * Medicaments placed in the stomach after its 
 iiiaries. pyloric orifice has been tied will produce their specific effect 
 
 almost as rapidly as under natural circumstances ; and, since there are 
 no proper lacteals upon that organ, and its lymphatics seem to be inade- 
 quate, the absorption of these agents can have taken place through the 
 blood-vessels only. 
 
 This conclusion is substantiated by an examination of the blood of 
 the gastric and mesenteric veins. It varies with the 'stage of diges- 
 tion and the nature of the food. At first there is a general lowering of 
 the percentage amount of the solid ingredients, this being evidently the 
 result of the absorption of water. At a more advanced period, the rela- 
 tive proportion of albumen, or rather of albuminose, rises, and along with 
 it the extractive, gelatine, and sugar increase. As with the chyle in the 
 lacteals, so with the blood in the mesenteric veins, coagulation takes 
 place imperfectly, or perhaps not at all. It is stated that the mesen- 
 teric blood of a fasting animal does not differ from the ordinary venous 
 blood. 
 
 The position of the blood-vessels, both on the mucous surface of the 
 stomach and particularly on the villi of the intestine, is favorable to the 
 
PHYSICAL NECESSITY OF VASCULAR ABSORPTION. 103 
 
 discharge of this function. The term venous absorption, employed to 
 express it, is perhaps somewhat incorrect, since there is no reason that a 
 venous capillary should have any advantage over an arterial one in this 
 respect. The rapidity with which substances in a state of solution are 
 taken up from these cavities has been well demonstrated by such in- 
 stances as those of the detection of the ferrocyanide of potassium in the 
 urine within 2 J minutes of its having been deposited in the stomach, or 
 by the death of dogs in a similar short period after strong alcohol had 
 been administered to them, their blood being found to be charged with 
 that combustible substance. 
 
 Among substances thus finding their way into the circulation by di- 
 rect vascular absorption may be enumerated such soluble salts as have 
 little affinity for the tissues, mineral and organic acids, alcohol, ether, 
 volatile oils, vegetable alkaloids, and coloring matters, as those of rhu- 
 barb, madder, gamboge. 
 
 In fact, if there were not these physiological considerations, we should 
 have to admit absorption by the blood-vessels as a mat- Absorption by 
 ter of physical necessity ; for, under the circumstances of the Wood-ves- 
 
 . /^r . i ' t -i se ^ s occurs as a 
 
 theirsituation, they must take up soluble matters presented physical neces- 
 to them. Through the pores of their delicate structure sub- sit - y - 
 stances in the liquid state will pass to mingle with the blood. 
 
 Though we have treated of respiratoiy or lacteal absorption as specif- 
 ically distinct from absorption by the blood-vessels, the circumstances 
 here alluded to evidently point out that the resulting action of the villi 
 of the intestines is of a mixed kind ; for, though the epithelial cells and 
 the commencing pouch of the lacteal may exert a definite influence, the 
 network of blood-vessels which lies immediately beneath the epithelium 
 must be engaged in precisely the same manner as the network of blood- 
 vessels between the gastric follicles. The permeation of the walls of 
 these tubes by substances in a state of solution is dependent, as we are 
 now to see, upon a purely physical principle, which is just as applicable 
 in the one case as it is in the other. The leading solid ingredients of 
 the chyle being fat and albumen, the former is perhaps introduced by the 
 proper lacteal structure, and the latter, taken up by the vascular network, 
 exudes in part again from it into the lacteal arrangement. 
 
 In the case of absorption, as in that of respiration, hereafter to be de- 
 scribed, there is a physical principle in operation which it is necessaiy 
 to understand. I shall proceed to explain it on this occasion as far as is 
 needful for the present purpose, and complete the description in the chap- 
 ter on the function of respiration. The peculiar views here set forth, 
 so far as they differ from those ordinarily expressed, I believe to be 
 warranted by my own experiments elsewhere published. 
 
 The absorbent action of the blood-vessels depends on the force known 
 
104 
 
 CAPILLAEY ELEVATIONS AND DEPRESSIONS. 
 
 Fig. ST. 
 
 Capillary among physical writers as CAPILLARY ATTRACTION. Its nature 
 attraction. may -fo e illustrated as follows : 
 
 If a piece of glass be laid on the surface of quicksilver, it is so power- 
 fully attracted thereto as to require the exertion of considerable force to 
 lift it off. Natural philosophers generally regard this as a force sui ge- 
 neris, and speak of it under the title of capillary attraction. I believe it 
 is nothing but an ordinary electrical phenomenon, since, if the glass be 
 examined, it will be found to be in a positively electrified state, and the 
 quicksilver negative, and under the general law of electricity, known as 
 that of Dufay, attraction must be the result. 
 
 If the glass be laid upon the surface of water, there is 
 an attraction as before. On lifting it, however, there is 
 no electrical manifestation; The reason of this is plain. 
 On examining this glass, it will be found that no true 
 separation of it from the water has taken place. A film 
 of water is still attached to it, or, in other words, it is 
 wetted. 
 
 If a slender glass tube, , Fig. 37,be dippedinto a liquid, 
 Elevation and a, a, which can not wet it, as, for example, 
 ilqSlrca^. quicksilver, the liquid is depressed as at c, 
 maiy tubes, and does not rise to its proper hydrostatic Depression of a non . 
 level, or, perhaps, altogether refuses to enter the tube. wetting liquid. 
 
 Fig. ss. If a slender glass tube, b, Fig. 38, be dipped into 
 
 a liquid, , #, which can wet it, as, for example, water, 
 the liquid at once rises in the tube, as at c, to a height 
 which is greater in proportion as the diameter of the 
 tube is less. It is this phenomenon which has given 
 the designation capillary attraction, because it is 
 best seen in tubes as fine as a hair (capillus). 
 
 Now if there be a tube of such a diameter that it 
 could thus lift water ten inches, and it be broken off 
 so as to be only six inches long, we might inquire 
 whether the water would overflow from its top, or 
 simply remain suspended. 
 Mathematical considerations as well as direct experiments prove that, 
 in such a case, there would be no overflow. A capillary tube under 
 these circumstances simply lifts the water, but can not produce a contin- 
 uous current. 
 
 But if a removal of the water at the top of the tube takes place in any 
 Conditions for manner as > f r instance, by evaporation, or by being dissolved 
 producing a away, then a continuous current is produced. This fact ex- 
 plains the phenomena of endosmosis, presently to be de- 
 scribed. 
 
 Elevation of a wetting 
 liquid. 
 
PASSAGE OF WATER THROUGH CREVICES. 105 
 
 As illustrative of the production of a continuous flow, we may cite the 
 case of a spirit-lamp, the wick of which may "be regarded as a bundle of 
 capillary tubes. If the cover of the lamp be taken off, all the spirit will 
 pass up the wick and escape by evaporation. Or in an oil-lamp, the wick 
 of which becomes readily saturated with the liquid, but never exhibits 
 any overflow, on the lamp being kindled, the oil is burned off, and a cur- 
 rent is at once established. 
 
 I have shown that water will pass through a crevice, the width of which 
 is less than one half of the millionth of an inch. Pores or Liquids pass 
 crevices of such a dimension are invisible even with a micro- ^inut^crev 7 
 
 SCOpe. ices or pores. 
 
 The evidence in proof of this is very readily obtained experimentally. 
 Fig. 39. If -we take a convex lens, a, a, of 
 
 Passage of water through a crertce. point of Contact, C, On looking down 
 
 upon the arrangement, a black spot surrounded by a series of variously 
 colored^oireentric circles, the appearance being well known among op- 
 tical writers underlie name of Newton's colored rings. At the point 
 of apparent contact, <?, the lens and the plane are, as Newton has shown, 
 a distance apart of about the one half of the millionth of an inch, and 
 from this central point, proceeding outwardly, the distance between the 
 glasses, of course, increases. If any where at the outer portion a drop 
 of water be introduced, it extends itself instantly across all the colored 
 rings, reaching even across the central black spot. 
 
 The three following general propositions present those phe- General propo- 
 nomena of capillary attraction which are most interesting in j^^uiyry*' 
 a physiological point of view. attraction. 
 
 1st. If the force of attraction of the particles of a solid for those of a 
 liquid be not equal to half the cohesive force of the latter for each other, 
 the liquid will refuse to pass through a pore of that solid substance, and, 
 in a capillary tube consisting of it, will be depressed below its hydro- 
 static level. 
 
 2d. If the force of attraction of the particles of a solid for those of a 
 liquid exceeds half the cohesive force of the latter for each other, but is 
 not equal to the whole force, the liquid will pass through a pore of that 
 solid substance, and, in a capillary tube of it, will rise above its hydro- 
 static level. 
 
 3d. If the force of attraction of the particles of a solid for those of a 
 liquid exceeds the whole cohesive force of the latter, chemical union be- 
 tween them ensues. 
 
 It would not be consistent with the plan of this work to offer a dem- 
 onstration of these propositions ; nevertheless, they are capable of rigor- 
 
106 ENDOSMOSIS AND EXOSMOSIS. 
 
 ous mathematical and physical proof. The views I am here presenting 
 enable us to include the pressures between solids and liquids, the rise or 
 depression of liquids in capillary tubes, and the phenomena of chemical 
 affinity in the same general expression. And such a co-ordination is the 
 more valuable, since there has been a disposition among physiologists to 
 regard the introduction of material through the pores of organized textures 
 as dependent on some ill-defined or mysterious principle. 
 
 The phenomena of endosmosis, first brought to general notice in the 
 Endosmosis case of liquid substances by M. Dutrochet, may be explain- 
 and exosmosis. e( j as follows : If some alcohol be placed in a bladder, the 
 neck of which is tightly tied, and the bladder be sunk in a vessel of 
 water, a percolation ensues, so that the bladder distends to its utmost 
 capacity, and might even be burst. Or, which is a better method of 
 showing the result, if, instead of tying the mouth of the bladder, a glass 
 tube, open at both ends, and a foot or two long, be fastened into it with- 
 out leakage, as the water introduces itself through the pores of the blad- 
 der to mingle with the alcohol, the liquid rises in the glass tube, sup- 
 posed to be left in a vertical position, and, when it has reached the top of 
 
 it, overflows. To express this inward pas- 
 sage of the water the term endosmosis was 
 introduced, and since a little of the alcohol 
 simultaneously passes outward to mix with 
 the water, it is said to exhibit exosmosis. 
 
 In Fig. 40 is represented the endosmome- 
 ter of Dutrochet. It consists of a small blad- 
 der, #, tightly tied to a tube, d, which is open 
 at both ends, and bent, as seen in the figure 
 at c ; the bladder being completely filled with 
 alcohol, and the tube to some such point as 
 d, the arrangement is to be placed in a ves- 
 sel of water, e e; almost immediately the level 
 of ^ jig^ w {\\ fa seen to be rising, the 
 bend of the tube is reached, and one drop after another falls from the open 
 end into the glass, b. And this continues until the liquids inside and 
 outside of the bladder are uniformly commingled. 
 
 It is to be regretted that the terms endosmosis and exosmosis have 
 These move- "been accepted by physiological writers, for in these results 
 ments are de- fa QrQ ^ nothing more than what we* should expect from the 
 
 pendent on ca- . , ^ .,, . mi e 
 
 piliary attrac- known principles of capillary attraction. The pores 01 a 
 tlon - bladder, or of any other such organic texture, are nothing but 
 
 short capillary tubes into which water readily finds its way, because it 
 can wet the substance surrounding the pore. If the bladder be distended 
 with air, and sunk under water, although the water will fill the pores, it 
 
FORCE OF ENDOSMOTIC MOVEMENT. 107 
 
 will not exude from them, and accumulate in the interior of the viscus, 
 for, as we have seen, a capillary tube can not establish a continued cur- 
 rent or flow. But the case becomes totally different when the bladder is 
 filled with alcohol ; for then, as fast as the water presents itself on the in- 
 ner end of the pore, it is dissolved away by the alcohol, and the necessary 
 condition for a continuous flow is complied with. Meantime, through . 
 the pore itself a little alcohol passes in the opposite way by infiltrating 
 through the incoming water, provided that the current be not too strong, 
 and so endosmosis of the water and exosmosis of the alcohol take place, 
 the current of the former greatly preponderating over that of the latter, 
 and an accumulation of liquid in the interior of the bladder ensues. 
 
 That in all this there is nothing specially dependent on the organic 
 texture employed is obvious from the fact that the same results arise 
 when any inorganic porous body is used. Vessels of unglazed earthen- 
 ware, pieces of baked slate or stucco, answer the purpose very well, as 
 will also a^glass vessel with a minute fissure or crack in it. 
 
 An incorrect representation of the conditions under which endosmosis 
 takes place is often made. It is said to depend on the relative specific 
 gravity of the liquids. Thus it is stated that the lighter liquid always 
 moves toward the denser, more abundantly than the denser to the lighter. 
 The error of this is readily shown by many simple illustrations. Thus 
 water endosmoses equally well to alcohol, which is lighter than it, and 4o 
 gum water or salt water, which are heavier. The relation of specific 
 gravity has nothing whatever to do with the action. 
 
 The force with which a liquid will thus pass through a pore to mingle 
 with another liquid beyond is very great. I have observed -p orce against 
 these motions occurring against a pressure of many atmos- which these 
 
 A-,.,,.. , ^ movements 
 
 pneres. And, indeed, in practice we have no means of measur- ma y take 
 ing its actual intensity ; for when a pressure of a certain de- P lace - 
 gree has accumulated, hydraulic leakage takes place backward through 
 the pore, and conceals the true action. 
 
 From the preceding statements respecting capillary attraction and en- 
 dosmosis, we may therefore conclude that, whenever a liquid is in con- 
 tact with a porous body the substance of which it can wet, it will freely 
 pass into the pores thereof, and, if the necessary conditions for its re- 
 moval are present, will percolate or transfuse with very great mechanical 
 power ; that this will take place through pores that are not only invis- 
 ible to the eye, but imperceptible by the aid of the microscope ; that 
 some liquids pass thus with more readiness, some with less, some not at 
 all the result in these respects depending on the electro-chemical rela- 
 tions subsisting between them and the solid they are in contact with, 
 and their own force of cohesion; that organic membranes present no 
 peculiarities, their action arising, not because they are organic, but be- 
 
108 
 
 SELECTING POWER OF MEMBRANES. 
 
 cause they arc porous ; that the so-called selecting power is purely 
 Fig. 41. physical, as are the separations and apparent decomposi- 
 
 tions to which it gives rise. When a drop of colored 
 water is put upon chalk, the water sinks in, but the color 
 is left on the surface. When weak alcohol is tied up 
 in a bladder, the water will escape through the pores, 
 and the spirit become anhydrous at last. 
 
 If we take a glass tube, <2, a, Fig. 41, over the lower 
 end of which a piece of peritoneum, or other delicate 
 membrane, &, &, is tightly tied, and half fill it with litmus- 
 water, and then place it in a glass of alcohol, c, c, the 
 level of the liquids inside and outside being adjusted ac- 
 cording to their specific gravity, so that there may be no 
 hydrostatic pressure either one way or the other through 
 the pores of the peritoneum as soon as the arrangement 
 is completed, if the observer be so placed as to view it by 
 transmitted light, he will see the water descending from 
 the pores of the peritoneum in stride and streams through 
 
 Selecting power of a r r 
 
 membrane. the alcohol in a perfectly colorless state. Th6 membrane, 
 therefore, has absorbed and transmitted the water, but has refused to 
 the coloring matter a passage. It is to this particular experiment that 
 a^usion was made when speaking of the non-coloration of the chyle 
 when certain coloring material had been mixed with the food. Such 
 illustrations may therefore satisfy us that the selecting power of organic 
 porous textures, like that of inorganic ones, is dependent on simple 
 physical circumstances, and for these reasons I exclude from the mech- 
 anism of animal absorption the influence of any vital or other mysterious 
 principle, and adopt the sentiment of the Abbe Hauy, that "those specious 
 causes and imaginary powers, to which, in the Middle Ages, all natural 
 phenomena, even those of an astronomical kind, were referred, but which, 
 through the genius of Newton and Laplace, have been banished from the 
 celestial spaces, have taken their last refuge in the recesses of organic 
 beings, and from these retreats positive philosophy is preparing to expel 
 them." 
 
 In view of all the preceding facts, I therefore regard absorption by the 
 Summary of blood-vessels as taking place of necessity, because of the po- 
 tts nature of rous structure of those tubes ; for, though the pores may be 
 too small to be discerned even by microscopic aid, they are 
 abundantly large enough to permit such a percolation. Whatever ma- 
 terial is existing in the chyme in a state of solution in water and also 
 soluble in the blood, passes through the walls of the vessels, and is moved 
 toward the liver, its percolation being greatly facilitated by the onward 
 motion of the blood, in which liquid it is dissolved as fast as it presents 
 
COURSE OF ABSORBED MATERIAL. 109 
 
 itself. The double condition here specified must be complied with ; the 
 material to be introduced must be dissolved in water, and must be sol- 
 uble in the blood. If the latter condition be wanting, the vessels seem 
 to manifest a selecting power, absorption not taking place, as in the case 
 of litmus, presented above as an illustration a coloring matter which, 
 though soluble in water, is not soluble in alcohol, and so can not, under 
 those circumstances, pass through a piece of bladder. 
 
 While thus there is an introduction of digested material from the stom- 
 ach and intestine into the blood, the physical principles which are guid- 
 ing us in our explanation teach us that there must be a percolation of 
 the more watery portions of the blood in the opposite direction that is, 
 into the digestive cavity. There is every reason to believe that this 
 percolation is to a far greater amount than is generally supposed. Under 
 certain circumstances, it is a matter of ordinary observation that the wa- 
 ter discharged from the intestine is more in quantity than that which has 
 been taken as drink^ 
 
 Turning our attention now to the course which is followed by the liq- 
 uid which has been introduced from the digestive cavity Course of the 
 into the blood-vessels, we must bear in mind that the con- absorbed mate- 
 tent of those vessels is composed of two distinct portions, "** ^dificaT" 
 the matter thus recently introduced, and the original venous tions it under- 
 blood. These together make their way through the portal goes 
 vein to the liver, a gland of double function, and, as we may say in this 
 respect, of double structure ; for, though it has a duct for the disposal 
 of the products which arise from its action on one portion of the material 
 thus brought to it, the venous blood, it is ductless as regards the other 
 portion, which has been received from the digestive cavity. This portion, 
 under the influence of the cell structure of the liver, undergoes profound 
 modification ; for instance, liver-sugar makes its appearance, though none 
 existed before. It is not necessary for us to specify these changes par- 
 ticularly here, since we shall have to examine them more in detail in a 
 subsequent chapter ; but it may be observed that the anatomical pe- 
 culiarity of the liver in this branch of its duty is, that it simply impresses 
 a change on the compounds thus brought to it, gives rise to no excretions, 
 and therefore has no channel or duct of escape, unless indeed we say, as 
 we are actually justified in doing, that the hepatic veins themselves are 
 the ducts of the liver in this respect. 
 
 Though it does not strictly appertain to the subject of which we are 
 now speaking, absorption, we may, for the sake of completeness, describe, 
 in a superficial manner, what occurs to the other constituent of the portal 
 blood, its proper venous portion. This, brought into the liver, is acted 
 upon by that organ and decomposed into two portions, one of which, con- 
 stituting the bile, is brought back eventually through the proper bile duct 
 
110 SUMMARY OF ABSORPTION. 
 
 into the intestine. The other is carried into the blood circulation. I be- 
 lieve that this separation is of a purely physical kind, and is accomplish- 
 ed by mere filtration, the elements of the bile all pre-existing in the blood. 
 However that may be, the separation in a chemical sense is very distinct, 
 for the nitrogenized ingredients are saved to the system, and earned into 
 the general circulation through the hepatic veins ; but the biliary mate- 
 Return of a Ild ^ Brought k ac k i nt tne intestine is a hydrocarbon tinctured 
 part to the with a little coloring matter, which, being on a rapid career of 
 retrograde metamorphosis, is prone to act as a ferment, and 
 therefore unfit to remain in the system ; accordingly, it is removed with 
 the excrement. The other portion, the hydrocarbon, which has been 
 brought into the intestine, is not yet done with ; advantageous use can 
 still be made of it. It can aid in the introduction of fats through the 
 villi into the lacteals, and, from its combustible nature, is of an equal value 
 to the system with the oils it thus helps to introduce. We may advan- 
 tageously trace the course which it follows, for in so doing we shall com- 
 plete our description of the function of absorption in its most general 
 sense. 
 
 The fat matters which have been subdivided into portions of micro- 
 Manner of sc pi ca l minuteness, small globules, each of which is coated 
 action of over with a delicate film of albumen, and all brought therefore 
 *' into the state of an emulsion, can make their way by reason of 
 the peculiar properties of the investiture which thus covers them through 
 the pores of the villi into the lacteal. For my own part, I do not believe 
 that there is any passage through the epithelial cells, but that it is en- 
 tirely interstitial, and that it is not unlikely that the biliary constituent 
 aids in this progress. It signifies nothing that the spaces through which 
 the fat globules have to go are less than their own diameter ; they can 
 elongate into worm-like forms, just as, under the same circumstances, 
 blood-cells can do, and, the moment they reach the cavity of the lacteal, 
 reassume their sphericity by reason of their cohesion. The albumen 
 that now accompanies them in the liquid form, as the other chief ingre- 
 dient of the chyle, comes, for the most part, from the blood-vessels of 
 the villi. The chyle moves onward to the mesenteric glands, and makes 
 its passage through them either in naked tubes or through their pulpy 
 structure, is submitted to cell action and to arterial blood, undergoes the 
 morphological changes which have been described in the preceding chap- 
 ter, and, gaining the thoracic duct, is brought into the general circula- 
 tion. 
 
 In the description here offered of the function of absorption, the agen- 
 cy of physical forces alone has been considered, and these I conceive to 
 be abundantly sufficient to enable us to account for all the phenomena. 
 
THE BLOOD. Ill 
 
 CHAPTER VII. 
 
 OF THE BLOOD. 
 
 The Offices and Relation of Blood in the System. The Plasma and Cells. General Properties 
 and Composition of the Blood. Quantity in the Body. Coagulation. Blood-cells. Their suc- 
 cessive Forms. TJie perfect Cell. Hcematin: its Properties. Number of Blood-cells. Plas- 
 ma : its Composition, and Variations of its Ingredients. Albumen, Fibrin, Fat, Sugar. Min- 
 eral Ingredients of the Cells and Plasma compared. Gases of the Blood. Changes occurring 
 during the Circulation. General Functions of the different Ingredients oftheBhod. Introduc- 
 tion of Oxygen by the Cells. Tlieir transient Duration. 
 
 IT is necessary for the functional activity of every organized being that 
 there shall circulale-throjigh all parts of it a nutritive liquid. In plants, 
 it is the sap ; in animals, the blood. 
 
 Since the life of plants manifests itself, for the most part, in a purely 
 formative result, and involves little or no destruction of parts, The blood: its 
 the circulating current is devoted almost entirely to nutrition, functions. 
 But in animals, whose conditions of existence involve extensive and un- 
 ceasing destruction, the current is burdened with another duty. It is 
 also the means of removal of dying or wasted portions. 
 
 In the first chapter it was shown that about a ton and a half of mate- 
 rial is required by a man in the course of a year, and that in introduction 
 the same period a like amount is removed from the system, ^grki'bythe 
 When we reflect that the introduction and removal of this blood, 
 immense mass is accomplished through the agency of the circulating 
 blood, it is obvious that that fluid must be undergoing the most rapid 
 changes. The rapidity with which dying matters are removed is strik- 
 ingly illustrated by the minute extent to which they are permitted to ac- 
 cumulate in a healthy state. These elements of decay are strained off 
 or exhaled as quickly as they arise. That fancied power, the " vis med- 
 icatrix naturae," is only an ideal expression of the perfection with which 
 the various eliminating mechanisms work. Poisonous agents, whether 
 they have been introduced from without or have originated from morbid 
 actions within, like all other useless or noxious products, find their prop- 
 er channel of escape, and the system will thus rid itself of intoxicating 
 liquids and narcotic drugs if their quantity does not exceed the amount 
 that it can destroy or excrete in a special period of time. 
 
 Considered in its relation to nutrition, the circulating liquid presents 
 many interesting aspects. Each of the thousand variously-constituted 
 parts of the body is withdrawing the supplies it needs : the muscular, the 
 
112 PKOPERTIES OF THE BLOOD. 
 
 interconnect nervous, the cartilaginous, the bony ; and hence there arises 
 thro^h^hiT* 8 a g enera ^ balance in the system, each part making its demand 
 circulation. at a certain rate, and each observing a complementary ac- 
 tion to all the rest. Many of those phenomena which, in the infancy of 
 physiology, were regarded as instances of sympathy between different 
 parts, are clearly dependent on these conditions ; for the development of 
 one part, by abstracting special material from the circulating liquid, per- 
 mits the co-ordinate development of another, or perhaps puts a stop to 
 it. The minutest portion of the mechanism is thus indissolubly con- 
 nected with all the rest through the medium of the blood. 
 
 Seen as it circulates in the vessels, the blood consists of a colorless 
 The plasma liquid containing corpuscles. In man, some of these corpuscles 
 and cells. are w hite and others red. , To the liquid in which they float, 
 the designation of the plasma is given ; the colored corpuscles, from their 
 Properties of shape, are called discs or cells. The specific gravity of the 
 the blood. blood varies from 1.050 to 1.059, the variation being, to a con- 
 siderable extent, due to variations in the quantity of the cells. The 
 temperature is about 100 Fahr., the reaction always alkaline ; there is 
 also a faint sickly odor, which differs in different animals. The capacity 
 of blood for heat is in direct proportion to its density. The cells give to 
 the blood its tint of color, and this, in the systemic arteries, is crimson, in 
 the veins, deep blue. However, the color of arterial blood depends con- 
 siderably on the condition of respiration. An imperfect introduction of 
 oxygen, as in hot climates, causes the arterial blood to assume a dark color, 
 and the same is observed when chloroform, ether, or diluted irrespirable 
 gases are breathed. The blood of the male sex is heavier than that of 
 the female. 
 
 Constitution of tKe Blood. 
 
 Water 784.00 
 
 Albumen 70.00 
 
 Fibrin 2.20 
 
 (Globulin 123.50 
 
 DlSCS tEfematin 7.50 
 
 f Cholesterine 0.08 
 
 Cerebrine 0.40 
 
 _, J Seroline 0.02 
 
 I Oleic and margaric acid J 
 
 Volatile and odorous fatty acid > 0.80 
 
 I Fat containing phosphorus 3 
 
 Chloride of sodium 3.60 
 
 Chloride of potassium 0.36 
 
 Tribasic phosphate of soda 0.20 
 
 Salts ^ Carbonate of soda 0.84 
 
 Sulphate of soda 0.28 
 
 Phosphates of lime and magnesia 0.25 
 
 Oxide and phosphate of iron 0.50 
 
 Extract, salivary matter, urea, biliary coloring > - , ~ 
 
 matter, accidental substances ) 
 
 1000.00 
 
QUANTITY OF BLOOD. 113 
 
 Elementary Composition of dried Ox Blood. 
 
 Carbon 519.50 
 
 Hydrogen 71.70 
 
 Nitrogen 150.70 
 
 Oxygen 213.90 
 
 Ashes 44.20 
 
 1000.00 
 
 This table leads to the hypothetical formula of the ultimate constitu- 
 tion of blood: ' 
 
 ^48 H 39 ^6 15 
 
 As to the quantity of blood in the circulation, it has been variously es- 
 timated. It may perhaps be taken at one eighth of the weight Q uantit of 
 of the body, a number which is agreed upon by several authors, blood in the 
 and in support of which Lehmann mentions the following in- y " 
 teresting observation: "My friend, E. Weber, determined, with my co- 
 operation, the weights of two criminals before and after decapitation. The 
 quantity of blood which escaped from the body was determined in the 
 following manner : Water was injected into the vessels of the trunk and 
 head until the fluid escaping from the veins had only a pale red or yel- 
 low color. The quantity of blood remaining in the body was then calcu- 
 lated by instituting a comparison between the solid residue of this pale red 
 aqueous fluid and that of the blood which first escaped. By way of illus- 
 tration, I subjoin the results yielded by one of the experiments. The living 
 body of one of the criminals weighed 60, 140 grammes ; and the same body, 
 after the decapitation, 54,600 grammes; consequently, 5540 grammes of 
 blood had escaped. 28.560 grammes of this blood yielded 5.36 grammes 
 of solid residue ; 60.5 grammes of sanguineous water collected after the 
 injection contained 3.724 grammes of solid substances. 6050 grammes 
 of the sanguineous water that returned from the veins were collected, and 
 these contained 37.24 grammes of solid residue, which corresponds to 
 1980 grammes of blood; consequently, the body contained 7520 grammes 
 of blood (5540 escaping in the act of decapitation, and 1980 remaining in 
 the body) ; hence the weight of the whole blood was to that of the body 
 nearly in the ratio of one to eight. The other experiment yielded a pre- 
 cisely similar result." 
 
 A short time after it has been drawn, the blood undergoes coagulation, 
 and is then said to be composed of the serum and the clot. Spontaneous 
 In this state it is sometimes spoken of as dead. The plasma seramand t0 
 of living blood differs from the serum of dead in containing clot, 
 fibrin. 
 
 The coagulation of the blood commences within about ten minutes 
 after it has been drawn, and the clot undergoes a subsequent The coaguia- 
 condensation during one or two days. To understand the tlon of blood - 
 physical nature of this singular change, we may conveniently regard the 
 
 H 
 
114 COAGULATION OF THE BLOOD. 
 
 living blood as containing three leading constituents an albuminousjiq- 
 uid, fibrin dissolved therein, and the cells. The coagulation arises from 
 the tendency of the fibrin particles to agglutinate together. As this takes 
 place, the cells are caught in the meshes of the network that arises, and 
 a voluminous red clot is the result. So the serum of dead blood con- 
 tains no fibrin, and differs from the plasma of living blood in that impor- 
 tant particular. 
 
 It has been observed that exposure to cold retards coagulation, as does 
 likewise the absence of air, or covering the blood over with a film of oil. 
 The condition of rest promotes it, as also does the presence of rough or 
 angular bodies. Blood will yield up its fibrin readily when stirred with 
 The buffy a stick. When, for any reason, the cells sink more rapidly than 
 coat usual from the surface of the blood, the fibrin of the supernatant 
 portion coagulates alone, giving rise to a stratum free from the red color, 
 and designated the bufiy coat, and on the subsequent contraction, since 
 there are no cells to hinder the fibrin, its parts upon this stratum are 
 drawn more closely together, and the clot becomes cupped. 
 
 By those who accept figurative expressions as an explanation of phys- 
 Expianationof iological facts, the coagulation of the blood is said to be due 
 coagulation, f j{ s d ea th ; some, however, have regarded it as an abortive 
 attempt at organization, and therefore a manifestation of life. Such con- 
 tradictory explanations lose much of their interest when we examine the 
 facts of the case critically. I believe that nothing more takes place in 
 blood which has been drawn into a cup than would have taken place had 
 it remained in the body. In either case the fibrin would have equally 
 coagulated. The entrapping of the cells is a mere accident. The hourly 
 demand for fibrin amounts to 62 grains ; a simple arithmetical calculation 
 will show that the entire mass of the blood would be exhausted of all 
 the fibrin it contains in about four hours, so that the solidification of 
 fibrin must be taking place at just as rapid a rate in the system as after 
 it has been withdrawn. No clot forms in the blood-vessels, because the 
 fibrin is picked out by the muscular tissues for their nourishment as fast 
 as it is presented, nor would any clot form in a cup if we could by any 
 means remove the fibrin granules as fast as they solidified. 
 
 That blood-fibrin differs from muscle-fibrin in certain respects is to be 
 admitted, but it does not follow that blood-fibrin is in a condition of ret- 
 rograde metamorphosis. It may require modification before it can be 
 received as the syntonin of muscles, but that such a conversion actually 
 takes place I think there can be no doubt. 
 
 In entering on a detailed examination of the constitution and func- 
 tions of the blood, our attention will have to be directed, in the first 
 place, to the cells. It is sufficient to arrest our thoughts at once when 
 we learn that for every beat of the pulse nearly twenty millions of these 
 
SUCCESSIVE FORMS OF BLOOD-CELLS. 115 
 
 organisms die ! Physiology has its passing wonders as well as astron- 
 omy. 
 
 In the life of man there are three periods distinguished from each other 
 by the nature or structure of the blood-cells. Those of the Successivc 
 first period originate simultaneously with, or even previously races of blood- 
 to, the heart. These are sometimes designated as embryo ^ 
 cells, and in that view bear the same relation to those of the second pe- 
 riod as do the lymph corpuscles to those of the third. They are color- 
 less and spherical cells, containing granules of fatty material, and having 
 a central nucleus. These are developed, by a process of internal deli- 
 quescence, into cells of the second period, which have acquired a red col- 
 or, and in oviparous vertebrates an elliptical form, though in man they 
 are circular. They are flat or disc-like in shape, have a diameter of 
 about 2-^-Q of an inch, with a central nucleus of half that size. Some- 
 times they appear to undergo multiplication by division of the nucleus. 
 
 These cells of the second period are replaced by those of the third, the 
 transition being clearly connected with the production of lymph and chyle 
 corpuscles. By the end of the second month of foetal existence the re- 
 placement is complete, and the class of cells or discs that has now arisen 
 is continued during life. The mode of their production, according to Mr. 
 Paget, is this. The chyle or lymph corpuscle loses its granular aspect, 
 and acquires a pale red color, which gradually deepens ; the corpuscle be- 
 comes smooth, loses its spherical form, and, condensing, takes on a con- 
 vex lenticular shape, and eventually a bi-concave. While this change 
 of structure is going on, the specific gravity increases through the con- 
 densation, and the development closes by the spherical, white, granular, 
 lymph corpuscle becoming a red, bi-concave, non-nucleated, circular, small, 
 and heavy blood disc. 
 
 The cell of the first period is therefore spherical, white, and nucleated ; 
 that of the second, red, disc-shaped, and nucleated ; that of the third, red, 
 disc-shaped, bi-concave, and non-nucleated. 
 
 The primordial cell advances in development to different points in dif- 
 ferent orders of living beings. The blood of invertebrated Development 
 animals contains coarse granule cells, which pass forward to ^th^atiS 
 the condition of the fine granule cells, and reach the utmost series, 
 perfection they are there to attain in the colorless nucleated cell of the 
 first period of man. In oviparous vertebrated animals the development 
 is carried a step farther, the red nucleated cell arising, and in them it 
 stops at this, the second period. In mammals the third stage is reached 
 in the red, non-nucleated disc, which is therefore the most perfect form. 
 
 This perfect form of blood cell, as it occurs in man, may be described 
 as presenting a flattened shape ; the bright spot, which is sometimes seen 
 in the centre, arising from a refraction of light due to the form of the 
 
116 
 
 CIECULAR AND ELLIPTIC CELLS. 
 
 disc and not to a nucleus. The sac of each disc is elastic, so that it can 
 Pro erties and ^ e swo ^ en ^7 water until it becomes convex or even globu- 
 sizeoftheper- lar, or by immersion in thick sirup may be made to shrink, 
 :el ' effects arising from the endosmotic infiltration or exudation 
 through its wall. When passing through the fine capillaries in the 
 course of the circulation, the cell, by reason of this elasticity, can make 
 its way through very difficult passages, extending itself into a cylindroid 
 form, or by bending, but it recovers its original shape as soon as relieved 
 from pressure. The average diameter of the cell is estimated at 32 * OQ of 
 Fig. 42. an incn the extremes being ^J^, and-^^i^. 
 
 The thickness of the cell is about -12400 of 
 an inch. The cell owes its color to ha3ma- 
 tin, which exists in its interior in a state of 
 solution, and associated with globulin. 
 
 The facts mentioned in the preceding par- 
 agraph are illustrated by the annexed en- 
 graved photographs. Fig. 42 represents hu- 
 man blood-ceils. Their form is circular : they 
 have a central depression, but no nucleus. 
 Fig. 43 represents the elliptic nucleated 
 blood-cells of the frog, with here and there, 
 Fig. 44 represents .the endosmotic action of 
 
 Human blood-cells magnified 500 diam 
 eters. 
 
 at a a, chyle corpuscles. 
 
 Fig. 43. 
 
 Fig. 44. 
 
 Elliptic blood-cells of frog magnified 250 diame- 
 ters. 
 
 Action of vrater on elliptic cells. 
 
 water on these cells. Fig. 45, the action of acetic acid in darkening or 
 concentrating the nucleus. In Fig. 46 we have an illustration of the 
 size and appearance of the blood-cell in a reptile, the photograph from 
 which this figure was taken having been made under the same magni- 
 fying power as that employed in obtaining the photograph of human 
 blood. 
 
FOEMS OF BLOOD-CELLS. 
 
 117 
 
 Fig. 45. 
 
 Fig. 40. 
 
 Action of acetic acid on elliptic cells. 
 
 Reptile blood-cells magnified 500 diameters. 
 
 The mammals in which the blood corpuscles are not round, but ellip- 
 tic and bi-convex, are the camel, the dromedary, and the llama. In 
 birds and amphibia they are oval. The difference in the shape and size 
 of these cells is of the more importance, since observations and measure- 
 ments by the microscope may lead us to a correct reference of a sample 
 of blood to its origin when chemical analysis would afford us no assist- 
 ance. It is not to be forgotten, however, that both in size and form a 
 blood-cell undergoes changes according to unequal pressures Variations Q f 
 exerted upon it, or to the physical circumstances under which the form of 
 it is placed, liquid readily finding its way into its interior or blo ills ' 
 exuding therefrom according to the laws of endosmosis, the elastic sac 
 perfectly accommodating itself to these changes. As a consequence of 
 these modifications, there will, of course, follow variations of specific grav- 
 ity in the cell, differences in its tendency to sink in the plasma which 
 surrounds it, and also differences in its tint of color. 
 
 By Mr. Wharton Jones, the colored blood-disc of the mammalian is 
 regarded as being homologous with the nucleus of the color- Human blood 
 less corpuscle of the same blood, and it may therefore be disc is a ceii^- 
 spoken of as a free cellseform nucleus, the cell itself having form nucleus - 
 deliquesced or become disintegrated, and the nucleus, filled with globulin 
 and coloring matter, remaining. 
 
 The cell wall of the blood-cells is generally admitted to be fibrin, or 
 some substance allied thereto ; but there has been much dif- Nature of the 
 ference of opinion respecting the constitution of the nucleus cell walls and 
 of those cells which possess it. By some, this also has been 
 regarded as fibrin ; by others, as fat ; and by others, as a species of horn, 
 to which the designation of nucleine has been given. 
 
 The cell wall of the white corpuscles does not appear to be elastic. 
 It is viscid, and hence these bodies, tend to agglutinate with one another : 
 
118 COMPOSITION OF BLOOD-CELLS. 
 
 in aspect it is granular. The contents appear to be an albuminous so- 
 lution, in which, fine granules are' suspended. 
 
 Though we have described the mesenteric glands as the original place 
 of formation of the blood-cells, it is to be understood that 
 these become perfected in the circulation of the blood ; and 
 from what will be said respecting the function of the liver, it may be in- 
 ferred that that gland is the seat of a most important change : there 
 probably they receive their iron. That no special organ is exclusively 
 charged with the duty of forming them appears from this, that the first 
 form of blood-cells arises in the germinal area of the embryo when there 
 is, as yet, no gland. 
 
 Composition of Blood-cells. 
 
 Water 688.00 
 
 Haematin (including iron) 16.75 
 
 Globulin and cell membrane 282.22 
 
 Fat 2.31 
 
 Extractive 2.60 
 
 Mineral substances 8.12 
 
 1000.00 
 
 Leaving the water out of consideration, the predominating ingredients 
 of blood-cells are therefore globulin and ha3matin. The former is a sub- 
 stance approaching, in properties, to casein, or perhaps intermediate be- 
 tween casein and albumen. Its constituents, as determined by an ulti- 
 mate analysis, are the same as in the case of those bodies. 
 
 Ha3matin is distinguished by its red color. When isolated, it exhibits 
 Changes of col- the changes of tint characteristic of arterialization in a doubt- 
 or depending f u l manner. There are, however, many facts which lead to 
 t^ C forn?oftne the supposition that the color of arterial and venous blood 
 cells. does no t depend so much on a chemical change in the ha3ma- 
 
 tin as on an alteration of the figure of the discs. 
 
 The constitution of hasmatin is C 44 , H 22 , N 3 , O 6 , Fe. It exists under 
 Properties of two forms, soluble and coagulated. It has hitherto been stud- 
 hrcmatin. } e( j O11 }y i n the latter state, and is soluble in weak alcohol 
 acidulated with sulphuric or hydrochloric acid, but not in water. Its 
 solution is therefore precipitated by the addition of that liquid. In weak 
 solutions of alkalies it readily dissolves. Formerly its characteristic red 
 color was attributed to the iron it contains, but that metal may be en- 
 tirely removed from it without changing its tint. The amount of iron it 
 yields is about seven per cent. 
 
 Ha3matin occurs in the blood-cells associated with globulin, and would 
 seem to owe its origin to the action of the wall of the cell, if it be true 
 that the red cells originate from the white ones. In this formation of 
 ha3matin there are several reasons which lead us to infer that fat takes 
 an essential share. 
 
COMPOSITION OF REMATIN. 119 
 
 Ultimate Analysis of flcematin. 
 
 Carbon C53.47 
 
 Hydrogen 54.45 
 
 Nitrogen 103.9G 
 
 Oxygen 118.81 
 
 Iron 69.31 
 
 1000.00 
 
 The remarkable feature in the composition of this "body is the large 
 quantity of iron it contains. The percentage amount of this i ron in the 
 metal in the blood of the foetus is much greater than in that of cells - 
 the mother. After birth the proportion declines, but it rises again at 
 puberty. These variations in the amount of the iron are, however, de- 
 pendent on corresponding variations in the amount of cells. 
 
 The importance of the remark, when we arrive at the study of the 
 bile, justifies us in repeating that the iron of the blood belongs to the 
 haematin of the cells, its percentage proportion varying with their condi- 
 tion, and also with the region of the circulation from which they have 
 been drawn. As derived from different animals, the cells present differ- 
 ent quantities of this metal. Thus Schmidt found in 100 parts of dry 
 blood-cells in man, 0.4348 ; in the ox, 0.509 ; in the pig, 0.448 ; and in 
 the hen, 0.329. 
 
 The crystalline substance of blood occurs under three dmercnt forms, 
 in prisms, tetrahedra, and hexagonal tablets. In the pris- Cr stalline 
 matic form it is derived from human blood, that of fishes, substance of 
 and of some mammals ; in the tetrahedral form it is obtained blood ' 
 
 Fin. 4i. 
 
 Fig. 48. 
 
 Human bK>ou-c;-ystals. 
 
 Blood-crystals o:' Guinea-pig. 
 
 from Guinea-pigs, rats, and mice; in the hexagonal' form, from squir- 
 rels. Blood-crystals are of a red color, without smell or taste, losing 
 their water of crystallization under exposure to the air, the different forms 
 presenting different rates of solubility ; the tetrahedral being soluble 
 
120 
 
 BLOOD-CRYSTALS. 
 
 in 600 parts of water, the prismatic 
 in 90 parts only; the solution in 
 the former case being pinkish, that 
 of the latter, dark red. They are 
 also dissolved by acetic acid, the red 
 prussiate of potash producing a pre- 
 cipitate therefrom, as in the case of 
 ^ other protein bodies. Chlorine de- 
 colorizes their solutions and gives a 
 white flaky precipitate. The crys- 
 tals, when heated, swell, yield an 
 odor like burnt horn, and, after com- 
 bustion, leave a small quantity of 
 Biood-crystais of squirrel. as h. From the difficulty of obtain- 
 
 ing blood-crystals in a state of purity, their constitution is not known 
 with absolute certainty. The ash which they yield consists of about 72 
 per cent, of oxide of iron, and 21 per cent, of phosphoric acid, the protein 
 constituent being apparently identical with other protein bodies. The 
 Mode of ob- crystals may be obtained for examination by covering a mi- 
 taining blood- nute drop of blood with a glass slide, and, after adding water, 
 alcohol, or ether, to permit a gradual evaporation to ensue. 
 The amount thus produced depends very much upon the presence of light; 
 thus Lehmann found that while he could only obtain two per cent, of 
 crystals from the blood of the Guinea-pig in the dark, he could obtain 
 more than seven per cent, in the sunlight. 
 
 Lehmann believes that the crystalline substance is not a mixture of a 
 pigment and a protein body, but a pure chemical compound, having either 
 a salt-like or conjugated constitution. 
 
 The color of the blood, as dependent upon the tint of its cells, is, ac- 
 Coior of blood- cording to the views of Henle, connected to a considerable 
 degree with the form of those organisms as they vary from a 
 concave to a convex surface, and not with the state of the 
 hsematin. When they are more concave they are of a crimson, when 
 of a more convex, of a darker hue. Moreover, during these variations 
 their investing membrane must necessarily change in thickness, and this 
 likewise must alter their mode of transmitting light. 
 
 Among the causes which can impress a change on the figure of the 
 blood-cells ought particularly to be specified exposure to oxygen and 
 carbonic acid respectively, the latter causing them to become more opaque 
 in their centre, broader upon their edge, the cell distending ; an opposite 
 effect ensuing under exposure to the former. In the case of the blood- 
 cells of frogs exposed to oxygen, the long and short diameters both di- 
 minish, and the wall becomes granular ; after exposure to carbonic acid 
 they increase, the wall becoming pellucid. 
 
 cells may de- 
 pend on their 
 form. 
 
NUMBER OF BLOOD-CELLS. 121 
 
 Constituted thus of an elastic sac filled with globulin and hsematin, the 
 cells float in the plasma. They are nourished at its expense, and when 
 they die, deliver up their contents Iby deliquescence to it. Accompany- 
 ing them are the white corpuscles, from which new generations are to 
 arise. It is usually stated that for every 50 red discs there The white 
 is one white corpuscle. They may be readily discovered dur- cor P uscle s- 
 ing the circulation by the microscope, many of them occupying the exte- 
 rior of the current, as though they had a special relation to the soft tis- 
 sues. It may perhaps be erroneous to regard these large white corpus- 
 cles as the embryos of the red discs. Reasons could be assigned in sup- 
 port of the doctrine that the same primitive germ going onward to devel- 
 opment may, at a certain point, diverge in two directions ; if it passes 
 through one, it will perfect itself as a white cell; if through the other, as a 
 red disc. 
 
 The proportional number of blood corpuscles in different animals va- 
 ries considerably. Generally cold-blooded mammals present Number of cells 
 fewer than warm-blooded ones, birds having more than quad- 
 rupeds, and among these the carnivora more than the herbiv- 
 ora. Of different domestic animals, the pig, the dog, the ox, the horse, 
 the cat, the sheep, the goat, possess them in the order in which their 
 names have been mentioned, the goat having only 86 to 145 in the pig. 
 Their proportional number also varies in different regions of the circula- 
 tion ; thus it is said that arterial blood contains fewer than venous, the 
 portal blood fewer than the jugular, the hepatic more than the portal. It 
 is not, however, to be overlooked, that in all these determinations the 
 quantity of water which chances to be present controls the estimates, and 
 that therefore, as thus offered, they are really of less interest than might 
 at first sight be supposed. 
 
 We have next to speak of the plasma. It may be described as a clear 
 and slightly yellowish colored fluid, consisting, as all animal composition 
 juices do, for the most part of water, holding in suspension or of plasma, 
 solution albumen, fibrin, fats, and various mineral bodies, as the follow- 
 ing analysis shows. 
 
 Proximate Composition of the Plasma. 
 
 Water 902.90 
 
 Albumen 78.84 
 
 Fibrin 4.05 
 
 Fat 1.72 
 
 Extractive 3.94 
 
 Mineral substances 8.55 
 
 1000.00 
 
 Of the water it may be remarked, that the usual percent- Water of the 
 age estimate made of its quantity, as regards the entire blood, whole blood : 
 is from 700 to 790 parts in 1000. Within these limits it is its variations - 
 
122 VARIATIONS IN WATER, ALBUMEN, AND FIBRIN. 
 
 liable to rapid variations, as dependent on the condition of thirst or the 
 recent indulgence in drinks. It does not increase in proportion to the 
 amount which has been imbibed, for the Malpighian bodies of the kidney, 
 as will hereafter appear, strain it off with great rapidity. When the 
 blood-vessels are distended to a certain degree, they refuse an entrance to 
 it. The necessity of these provisions arises from the fact that there is a 
 certain state of viscidity which the blood must possess for its proper cir- 
 culation. 
 
 Eespecting variations in the amount of water in the blood, it may be 
 stated that that of women contains more water than that of men. Among 
 different animals, the serum of the amphibia contains the largest quantity; 
 and among mammals, that of the herbivora more than that of the car- 
 nivora. Obtained from different vessels, the arterial has more than 
 venous blood, but the serum of the portal vein contains more than that 
 of any other vein, the proportion depending on the amount and time of 
 the ingestion of water. 
 
 The albumen varies in quantity from 60 to 70 in 1000. It is prob- 
 Variations in a ^ v associated or combined with soda. It exists in the 
 quantity of ai- blood of the splenic and hepatic veins as the neutral albumi- 
 nate of soda. It does not appear to contain any phosphorus, 
 as was at one time supposed. It is the plastic material from which all 
 the soft tissues are nourished, and by it the cells themselves grow. 
 Fibrin arises from it in the blood in the same manner as it does during 
 the incubation of an egg ; every care is taken to economize it in the sys- 
 tem, and it is never excreted except in disease. 
 
 The quantity of albumen is greater in venous than in arterial blood, 
 the proportion increasing during digestion. It also presents variations 
 in different states of disease. Its condition varies in various parts of the 
 circulation, a circumstance, to a considerable extent, due to the nature of 
 the salts, or to the quantities of alkali with which it is associated. 
 
 The fibrin is usually estimated at 2 or 3 parts in 1000 of blood. It 
 
 Vari tions in mav ^1 as ^ ow as ^ or r ^ se as high a s 7 j. There is a con- 
 the quantity of stant drain upon it for the nutrition of the muscular tissues ; 
 and since it originates in the action of oxygen upon albu- 
 men, we should expect, as is really the case, that arterial blood would be 
 richer in it than venous. The portal blood contains it in minimum quan- 
 tity. Its percentage rises if oxygen be inhaled, or the respiratory pro- 
 cess be quickened ; for similar reasons, it uniformly increases in acute 
 inflammations. The ultimate analyses of fibrin seem to show that it con- 
 tains more oxygen than albumen, and this corresponds with its mode of 
 origin. It is an important practical observation, that though it is easy 
 to regulate the quantity of cells by variations of diet, the amount of 
 fibrin can not so readily be changed in that manner, nor its development 
 
FIBKIN, FAT, AND SUGAR OF BLOOD. 123 
 
 checked by venesection. There is less fibrin in the blood of the camiv- 
 ora than in that of the herbivora. 
 
 It has been asserted, as was mentioned before, that there is so wide a 
 difference between the fibrin of blood and muscular fibre, Fibrin is a his- 
 that we can no longer regard the latter as arising from the togeneticbody. 
 former, but must consider it merely as coagulated albumen ; and that, 
 since the action of acetic acid upon it shows its relation to gelatine, it is 
 probably more nearly related to the fibro-gelatinous than to the cellulo- 
 albuminous tissues. But, although the fact that fibrin contains more 
 oxygen than albumen seems to lend weight to such views, since oxida- 
 tion appertains to the retrograde rather than to the ascending metamor- 
 phosis, there are so many arguments in favor of the old doctrine, that 
 I think it may be regarded as thus far unshaken. Moreover, it is now 
 established beyond any doubt, that by nitrate of potash, and other salts, 
 fibrin may be transmuted into a substance analogous to albumen. 
 
 The fats vary very much in quantity at different times. The amount 
 is usually stated at from 1.4 to 3.3 in 1000 of blood. After a meal the 
 plasma may be actually milky, through the fat globules y ariationsin 
 brought in by the chyle. We have already shown that the quantity of 
 starch will give origin to fat, and oily substances can be ob- at ' 
 tained from lactic acid itself. The nitrogenized bodies, during their de- 
 struction, likewise yield them, and it is a normal function of the liver to 
 effect the production of fat. 
 
 The serum contains only an insignificant quantity of free fat ; but 
 there is a large proportion of saponified fat in it, as well as the lipoids 
 cholesterine and serolin. 
 
 The view heretofore taken, that this class of substances is not histo- 
 genetic, but only respiratory, requires to be modified. There Uses of the fats 
 is reason to believe that the blood-cells themselves can not of blood - 
 be formed except in presence of oil, which is also necessary to enable ni- 
 trogenized bodies to assume the ferment action. The nuclei of cells con- 
 tain fats, as do also embryonic structures generally. Cholesterine, or 
 liver-fat, is not saponifiable. It appears as a product of disintegration, 
 increasing in quantity during acute diseases. The proportion of this sub- 
 stance increases after 40 years ; it also forms a principal ingredient in 
 biliary concretions. 
 
 Among the special constituents of certain portions of the venous blood 
 not mentioned in the preceding tables, we ought not to over- 
 
 ,., . . T? ,*I-I-IT Liver-sugar. 
 
 look sugar, which exists as a constant ingredient of the blood 
 contained in that part of the circulation intervening between the liver and . 
 the lungs. This, which is known as liver-sugar, may have originated in 
 the transmutation of cane-sugar, or from the metamorphosis of the mus- 
 cular tissues. It is to be remarked that the blood contains no gelatine. 
 
124 
 
 THE MINERAL CONSTITUENTS OF BLOOD. 
 
 Comparison of To the mineral substances in the cells and plasma of the 
 constituents of Wood respectively, attention should be particularly directed, 
 the cells and smce they indicate the functions of these portions. 
 
 plasma. 
 
 Mineral Constituents in 1000 Parts of the Blood. 
 
 
 (Jells. 
 
 Plasma. 
 
 Chlorine 
 
 1 686 
 
 (\AA 
 
 Sulphuric acid 
 
 066 
 
 O-I-IK 
 
 Phosphoric acid 
 
 1 134 
 
 0101 
 
 Potassium 
 
 3 328 
 
 39$ 
 
 Sodium 
 
 1 052 
 
 q 041 
 
 Oxvcren . 
 
 667 
 
 4-03 
 
 Phosphate of lime 
 
 114 
 
 n qi i 
 
 Phosphate of magnesia 
 
 073 
 
 222 
 
 Iron excluded 
 
 
 
 
 
 ****** 
 
 
 8.120 
 
 8.550 
 
 The amount of inorganic matter in the cells and plasma, respectively, 
 of 1000 parts of blood being nearly the same, the table shows that there 
 is more than twice as much chlorine, and more than three times as much 
 sodium in the plasma as in the cells. It may thence be inferred that the 
 chloride of sodium is, for the most part, in the plasma. Moreover, there 
 is six times as much phosphorus, and more than ten times as much po- 
 tassium, in the cells as in the plasma ; and therefore it may be inferred, 
 since potash is required to so great an extent in the nutrition of the mus- 
 cular system, and phosphorus as an element of the phosphorized oils in 
 the nervous, that the cells have a direct functional relation to those im- 
 portant mechanisms, and this in addition to their duty of introducing 
 oxygen. 
 
 The mineral constituents of the blood discharge very different duties, 
 Functions of some, either directly or indirectly, acting functionally, others 
 consTituenfsof as histogenetic bodies. Thus the alkaline properties of the 
 the blood. blood are due to the presence of the carbonate and phosphate 
 of soda, and this latter substance enables the serum to hold in solution 
 carbonic acid, and thus it maintains a relation in the respiratory opera- 
 tion. But the phosphate of lime discharges a true histogenetic function, 
 since upon it the bony system depends for its nutrition. The mutual 
 relations of these substances are, of course, very complex, though often 
 of importance. Thus, of the two just mentioned, the phosphate of soda 
 enables the serum to hold the phosphate of lime in solution. 
 
 The tawny coloring matter of serum diifers from cholepyrrhin in not 
 Coloring mat- yielding the characteristic reaction of that body. The tint 
 ter of serum, sometimes becomes quite deep, owing to several different 
 .causes, such as the undue accumulation of the coloring matter of urine, 
 through disturbance of renal action, or from bile pigment, as in icterus. 
 
 The gases which can be disengaged from the blood occur in the cells, 
 according to Magnus, a statement which, however, is very far from being 
 
FUNCTIONS OF THE CONSTITUENTS OF BLOOD. 125 
 
 substantiated : they are carbonic acid, oxygen, and nitrogen. Gases of the 
 He found that this liquid can absorb once and a half its vol- blood - 
 ume of carbonic acid, and that in arterial blood the proportion of that 
 acid to oxygen is as 16 to 6, in venous as 16 to 4. That the oxygen 
 is very loosely retained is shown by the circumstance that it may for 
 the most part be removed by exposure in a vacuum. The other gases 
 may be withdrawn by a stream of hydrogen. 
 
 At a temperature of 98, water absorbs scarcely one per cent, of its 
 volume of oxygen gas, but the blood can take up from 10 to 13 times as 
 much. This is accomplished by the coloring material. The amount is 
 independent of variations in the pressure of the air, which would not be 
 the case if the gas were received into the circulating fluid by mere solu- 
 tion. This is the opinion of Liebig, by whom it is regarded as being to 
 some extent substantiated by the fact that the respiration is accomplished 
 with nearly the same result, so far as the absorption of oxygen is con- 
 cerned, at considerable heights above and at the level of the sea, and that 
 no more oxygen is received from an atmosphere very rich in that gas 
 than from the ordinary air. However correct this view may be, the facts 
 cited in its support are very far from being undeniable. 
 
 The preceding chemical examination of the special constituents of the 
 blood leads us next to consider the general functions of this liquid in the 
 aggregate. 
 
 In this general sense, the blood discharges the following offices. Its 
 albumen has the duty of giving origin to all the plastic tis- General state 
 sues of the system. From it, for example, by cell action, as ment of the 
 explained in treating of lacteal absorption, fibrin arises theliiffkrent 
 fibrin, which is used for the renovation and repair of the mus- constituents of 
 cular tissues. The discs have a relation with the function of 
 respiration; they obtain oxygen in the pulmonary circulation, and carry 
 it through the system. They contribute, moreover, to the development 
 of muscular fibre, and also nervous material, and this not alone as regards 
 the coloring matter of those tissues. The fats are necessary in the pro- 
 duction of fibrin and for the nuclei of cells ; but, besides these histoge- 
 netic relations, they eventually, with the exception of liver-fat, undergo 
 oxidation, and so minister to the support of a high temperature. Of the^ 
 saline substances, common salt promotes digestion by aiding in the prep- 
 aration of gastric and pancreatic juices ; the phosphate of soda enables 
 the plasma to hold carbonic acid in solution, and carry it to the lungs. 
 
 It is interesting to observe the limits of variation which the blood may 
 present in disturbed or diseased conditions. In inflammations, the fibrin 
 may increase fourfold ; in typhoid fevers it may diminish to less than 
 one half, and from these variations special results may arise. Thus 
 diminution of its fibrin disposes the blood to preternatural oozing or fa- 
 
126 CHANGES IN THE CIRCULATION. 
 
 cility of escape. So also the cells have been known, in cases of chloro- 
 sis, to sink to one fifth of the healthy amount. The albumen, too, ex- 
 hibits like variations. In Bright's disease it greatly diminishes, much 
 of it escaping in the urine by the straining action of the kidneys. 
 
 Thus constituted, the blood, by a mechanism to be described in the 
 Chan es occur next cna P ter passes from the heart alternately to all parts 
 ring during the of the system, and alternately to the cells of the lungs, giv- 
 circuiation. -^ T ^ Q ^ Q what have been termed the greater and less cir- 
 culation, or the systemic and the pulmonary. In the systemic circula- 
 tion, the blood, which leaves the heart in an arterialized condition, or as- 
 sociated with atmospheric oxygen, gives up that element to the various 
 tissues as it pervades them, and accomplishes a double result: the re- 
 moval of all those particles which, having discharged their duty and un- 
 dergone partial or perfect interstitial death, are ready to pass away, and 
 also the liberation of a great amount of heat by the destructive oxidation ; 
 so, at the same time, the wasted matter is removed and advantage taken 
 of it to raise the temperature of the body. This done, the blood makes 
 its way back to the heart, following the channel of the veins as they suc- 
 cessively converge into trunks that are larger and larger. At the mo- 
 ment of surrendering its oxygen and receiving the various products of 
 combustion, a change of color occursr The bright crimson turns to a 
 deep blue, and the blood presents itself of that color at the heart. 
 
 It now undergoes the less or pulmonary circulation. Leaving the 
 heart, it passes over the air-cells of the lungs, and is there exposed to the 
 aerating action of the atmosphere. From the interior of the cells the 
 discs receive their supply of oxygen, the plasma surrendering up carbonic 
 acid and the vapor of water. The color now changes back from the 
 blue to the scarlet. In this condition it returns to the heart, to be dis- 
 tributed in the systemic circulation once more. 
 
 During this double round an incessant change is taking place in the 
 Less obvious constitution of the'blood: it is undergoing a continuous met- 
 but important amorphosis. In some respects, as, for instance, in color, 
 this is obvious enough. But the invisible changes infinite- 
 ly exceed in importance and amount those that are obvious to the eye. 
 
 All the soft tissues, since they are wasting away, require repair. 
 This, inasmuch as it is accomplished either directly or indirectly by the 
 albumen of the blood, gives rise to a constant drain of that substance, 
 and demands a constant supply, which is provided by nutrition or stom- 
 ach digestion. 
 
 The cells, which constitute the other chief portions of the blood, are 
 Translation of necessai T * tne production of a high temperature, by con- 
 oxygen by th stantly transferring oxygen from the cells of the lungs to 
 cells. every part of the body ; carriers of oxygen they have been 
 
GRADUAL DESTRUCTION OP BLOOD-CELLS. 127 
 
 truly called. That this is one of their duties has been proved experi- 
 mentally, for a solution of albumen or the serum has but little power of 
 absorbing oxygen, scarcely exceeding water itself in that respect, but 
 the discs condense it at once. The change of color they exhibit as they 
 alternately gain or lose that element, is in itself a proof of this fact, as 
 is also the action of serum or blood-discs respectively on a measured 
 volume of air contained in a jar. If the discs be in the venous or pur- 
 ple condition, they quickly absorb oxygen from the confined air, which 
 therefore at once diminishes in amount, but the serum, or a solution of 
 albumen, produces no such effect. The plasma serves, therefore, for the 
 general nutrition of the system, and the discs, by transferring oxygen 
 from point to point, discharge that part of their duty which is connect- 
 ed with the production of heat. 
 
 But the discs, though of a flattened form, are truly cells, and all that 
 obtains in the case of cell life and cell action obtains for , 
 
 Transitory du- 
 
 them. They have not a duration at all comparable to the ration of the 
 duration of the system, but are constantly coming into ex- cells * 
 istence and disappearing. Each is an individual having its own partic- 
 ular history, its time of birth, its time of maturity, its time of death. 
 Each passes through a series of incidents proper to itself. Originating 
 as has been described, they grow at the expense of the plasma, and in 
 this regard it serves for their nutrition as well as for that of the body 
 generally. 
 
 On exposing blood-cells to oxygen and carbonic acid gases alternately, 
 there is not only a change in their shape, which becomes corrugated and 
 star-like, but also in their chemical constitution, so that, after such an 
 exposure of nine or ten times, they are entirely destroyed. Such alter- 
 nations occurring in the system doubtless lead to the same result, though 
 more slowly, since the oxygen is presented in a diluted condition. 
 
 The corrugated and star-like blood-cells abound in the blood of the 
 portal, though not in that of the hepatic vein. If their aspect 
 arises from their tendency to disintegration, this is no more ym 
 
 than might be expected in view of the func- 
 tions of the liver. That the stellated aspect 
 is an indication of a commencing disorganiza- 
 tion, or other profound change, may be illus- 
 trated by an examination of the action of wa- 
 ter on normal blood-cells, which, if they be 
 exposed to that liquid, undergo a distention ; 
 their thicknels increasing more rapidly than 
 their diameter, they lose their concavity, be- 
 come convex, and at last appear as spheres 
 
 Stellated blollsagnified 500 Qf fl ^ ^ thaR ^ original <J iscs . 
 
 
128 ASSOCIATION OF H^MATIN AND OXYGEN. 
 
 the quantity of water they have received has distended them to their ut- 
 most capacity, they then are invisible ; but when it is withdrawn from 
 them by establishing exosmosis through the addition of saline sub- 
 stances, they may reappear in the corrugated or star shape, as seen in 
 the photograph, Fig. 50. 
 
 With respect to the action of the hsematin, it may be observed, that 
 Action of hsem ot ^ ier nitrogenized coloring materials present a similar rela- 
 atin illustrated tion to oxygen. As an example, indigo may be mentioned, 
 by mdigo. j cons ^ er that the properties of this substance illustrate in 
 a significant manner the properties of hasmatin in the system. Indigo 
 occurs in the leaves of the plant which yields it in a yellow and soluble 
 state. It is easily extracted from them by maceration in water. Ex- 
 posed to the air, it absorbs oxygen, becomes insoluble, and simultane- 
 ously, gains a deep blue tint. So lightly is the oxygen thus united to 
 it, that by exposure to very feeble agents it surrenders it up, and repasses 
 into the yellow and soluble condition. Once more exposed to the air, 
 it turns blue, and once more may have that color removed from it by tak- 
 ing its oxygen away. For many times in succession its tint may be 
 thus changed, and made yellow or blue at pleasure. 
 
 From this we perceive in what a loose manner oxygen is held by such 
 a coloring material ; how readily it surrenders it, and how readily it re- 
 covers it. Such a union can scarcely be called an oxidation or a com- 
 bination ; it is rather an association. 
 
 All this is precisely what occurs in the case of hasmatin. It takes up 
 Feeble union of Ox 7g en w ^ n rapidity as it goes over the cells of the lungs, 
 oxygen and and turns scarlet ; it surrenders that oxygen with equal fa- 
 cility as it passes the systemic capillaries, and turns blue. 
 This change of color is incessantly taking place ; it is now red, and now 
 blue, as the cells are passing in the greater and the less circulation. 
 
 Formerly it was supposed that, in the act of respiration, oxygen from 
 Eeception and the air united with carbon of the blood or of the cells, and 
 ofTx^genty car ko n i c acid formed, a combination or perfect oxidation 
 the blood-cells, taking place in the lung. But, , if this were true, the tem- 
 perature of those organs should be higher than that of the rest of the 
 body, and this is by all admitted not to be the case. 
 
 The cells are therefore carriers of oxygen. They receive that vivify- 
 ing principle as they move over the respiratory cells, and, freighted with 
 it, pass to all parts of the body, not united with it, nor disorganized, nor 
 burnt up by it, but holding it loosely, and ready to give it up and go 
 back again for a fresh supply. * 
 
 The sac containing the haematin offers no kind of resistance to these 
 exchanges. It will be fully demonstrated in the chapter on respiration 
 that this is the case. Thick pieces of India-rubber, stout animal mem- 
 
CIRCULATION OF THE BLOOD. 129 
 
 branes, or even masses of stucco, present no obstacle to the passage of 
 gases. The delicate wall of these cells, a tissue of almost inconceivable 
 tenuity, can offer no resistance. The gas passes in and out without im- 
 pediment or restraint. 
 
 But though in this manner these little organisms perform their duty, 
 it is only for a time. They may take oxygen from the air- Summar of 
 cells and give it up in the system, and do this perhaps many the function of 
 thousand times, but it comes to an end at last. The inces- b 
 sant motion stops, and the worn and exhausted disc is brought to its term. 
 By degrees, as old age steals over it, it becomes corrugated and relaxed, 
 is unable to withstand chemical reagents, as its younger comrades can 
 do. Through the microscope it seems puckered and attenuated. The 
 red color of its interior deteriorates into a tawny tint. As with a leaf in 
 the autumn, the natural color of which disappears, and yellowness or 
 other change precedes its fall, so with the dying disc. Unable any 
 longer to discharge its duties, its existence is brought to a close, the de- 
 cayed ha^matin is shed out to give a transient tawny tint to the plasma, 
 but is presently strained off as one of the constituents of bile by the liver. 
 Nor is the illustration here used wholly metaphorical, for, in the case of 
 herbivorous animals, Berzelius has shown that the coloring matter of their 
 bile is identical with chlorophyll, the coloring matter of leaves. 
 
 CHAPTER VIII. 
 
 OF THE CIRCULATION OF THE BLOOD. 
 
 The Heart as a Machine. Inadequacy of Harvey's doctrine of the Circulation. Physical Prin- 
 ciple of the Circulation ; applied in the case of a Nucleated Cell, Pervious Tissue, Motion of 
 Sap and of Blood. Dependence of the Circulation on Respiration. Forms of Circulation : 
 Systemic, Pulmonary, Portal. Description of the Heart : its Movements. Their Force, Num- 
 ber, and Value. Sounds of the Heart. Cause of its Contractions. Description of the Arte- 
 ries, Capillaries, Veins. Explanation of the Circulation of the Blood. Facts supporting it. 
 The First Breath. 
 
 No function of the animal mechanism illustrates more strikingly the 
 doctrine that we must rely on physical agents for physiological explana- 
 tions than that which we have now to consider, the circulation of the 
 blood. 
 
 We surrender some of the most beautiful recollections of classical 
 mythology, and some of the most cherished popular illusions The heart as 
 of our own times. The heart, which in the higher classes of an en s ine - 
 life is the central organ of impulse of the circulation, is to be degraded 
 into a mere engine. We have to speak of its valves, its cords, its pipes. 
 
 I 
 
130 CIRCULATION OF THE BLOOD. 
 
 We have to consider its exhausting and its forcing action to deal with 
 it just as we should deal with any hydraulic apparatus. In the old 
 times this organ was looked upon as the seat of the thoughts and the 
 passions ; it was the centre of all good and evil, purity and uncleanness, 
 devotion and love. In the modern system the brain has succeeded to 
 the functions which were once imputed to it. 
 
 The heart, then, is no longer, an altar on which flames are burning, no 
 longer the seat of the passions and the source of love. It is a machine, 
 but what kind of a machine ? How great is the admiration we may ex- 
 press at its exquisite construction ! This little organ can execute three 
 thousand millions of beats without a stop ! In the course of a life, such 
 as we sometimes meet with, it has propelled half a million tons of blood, 
 and, though momentarily wasting, has repaired its own waste all the time. 
 The mathematical rhythm of its four moving cavities, the perfect closure 
 of its mitral and semilunar valves, and the regurgitating play of its tri- 
 cuspid, have never failed it. To the eye of the intellect there is nothing 
 lost in transferring it from the regions of metaphor and speculation to 
 the domain of physical science. 
 
 The doctrine of the circulation of the blood was first propounded by 
 Harvey's doc- Dr. HARVEY about two hundred years ago. It originated 
 cuiTtionof the * n t ^ ie discovering of the valves of the veins by Fabricius ab 
 blood. Aquapendente. After many years of discussion, it was re- 
 
 luctantly received by the medical profession. 
 
 In this doctrine the circulation is referred to causes that are purely 
 mechanical, in the strictest acceptation of that term. The contraction 
 of the walls of the heart propels the blood through the arterial tubes, 
 and even through the veins, the direction of its movement being insured 
 by a proper arrangement of valves. 
 
 But when comparative anatomy and physiological botany were more 
 Its imperfec- extensively cultivated, it was seen that this doctrine is insuf- 
 tions. ficient, for the unity of nature forbids us to believe that nu- 
 
 tritious juices are circulated in different tribes of life by different forces. 
 And though it may be that the contractions of that central impelling 
 mechanism regulate the circulation in those organisms which have a heart, 
 what is to be made of those countless numbers which have none ? In 
 this group we find the whole vegetable creation, and a majority of the 
 animal. 
 
 There is a physical principle which has long appeared to me sufficient. 
 Physical prin- Its use in an explanation of the motion of nutritive juices in 
 iSecaptilary organized systems of every class I have taught in the Uni- 
 circulation. " versity for many years. It possesses the advantage of gen- 
 erality, since it is applicable in every case, from the circulation taking 
 place in a closed cell up to that of man. 
 
PHYSICAL PKINCIPLE OF THE CIPtCULATION. 131 
 
 In Chapter VI. is a general statement of the phenomena and laws of 
 capillary attraction ; the principle now to be employed is closely connect- 
 ed therewith. It may be stated as follows : 
 
 If two liquids communicate with one another in a capillary tube, for 
 the substance -of which they have affinities of different intensities, move- 
 ment will ensue : the liquid having the highest affinity will occupy the 
 tube, and may even drive the other before it. The same eifect will en- 
 sue in a porous structure. 
 
 Fig. 51. Thus, let &, #, Fig. 51, be a capillary tube 
 
 of any kind, which is occupied conjointly by 
 
 Motion in a capillary tube. two liquids, a and v, meeting each other in 
 its middle, c; a having a high and v but little affinity for the substance 
 of which the tube consists, a will occupy the tube, pressing out v before 
 it. Of course, it is to be understood that the liquids a and v respect- 
 ively communicate with reservoirs that can furnish them a necessary 
 supply. 
 
 The various phenomena described under the designation of endosmo- 
 sis* are experimental illustrations of the same kind. Thus, A Hed to thc 
 when water is put on one side of a piece of bladder, and al- explanation of 
 cohol on the other, the water, having the highest affinity for ei 
 the substance of which the bladder consists, occupies the pores thereof, 
 and expels the alcohol. Nor would any of the latter substance find its 
 way in the opposite direction, back into the water, were it not so soluble 
 or diffusible in that liquid. Exosmosis therefore takes place through 
 the water, and constitutes a very subordinate or feeble current. 
 
 Now it is precisely relations of this kind that are observed in the case 
 of the circulating and nutritive juices of all organic beings. 
 
 The simplest instance is presented by the fluid contents of certain nu- 
 cleated cells, both among animals and plants, in which a cur- Circulation iu 
 rent moves toward, and then from, the nucleus, coming back nucleated 
 in a returning path. The fluid which the cell contains yields c 
 to the nucleus, in which seems to be concentrated all the activity of the 
 organism, the nutritive material it requires, and, this done, passes on to 
 make way for other portions. The act of nutrition, therefore, is followed 
 by motion, and this upon the above simple principle ; for the liquid, be- 
 fore it approaches to the nucleus, is charged with material which the nu- 
 cleus can attract ; but immediately after contact has taken place, and the 
 material has been removed, the liquid maintains no longer any relation with 
 the nucleus, the affinity or attraction is satisfied, and, so to speak, it loses 
 its hold thereupon, and is pressed off by new-coming portions. Before its 
 approach, and after its departure, the liquid has opposite relations to the 
 nucleus, and in this respect may be regarded as representing two liquids, 
 the one having a high affinity, and the other none, for the nucleus. The 
 
132 
 
 CIRCULATION IN CELLS. 
 
 Circulation in vegetable cells. 
 
 Circulation in Tradescantia. 
 
 Fi 9- 52 - circulation in vegetable cells is shown by the di- 
 
 rection of the arrows in Fig. 52. The course taken 
 by the current may be determined under the mi- 
 croscope by the minute floating, or, rather, drifting 
 granules. It is to and then from the nucleus. 
 
 fig. 53 represents one of Fig. 53. 
 
 the jointed hairs from the 
 Tradescantia Yirginica. The 
 engraving is from the view 
 given by Mr. Slack, correct- 
 ed, however, by the aid of a 
 photograph of a similar ob- 
 ject, a, ^ c, d are the suc- 
 cessive cells of the hair. The 
 dotted lines show the direction of the current to 
 and from the nucleus. 
 
 The juice which is about to nourish a part has 
 Circulation ^ or *^at P art a certam affinity, but, with the accomplishment 
 through per- of that nutrition, the affinity is at once lost. Thus, for in- 
 us parts. gtance? i n the systemic circulation, the parts to be nourished 
 have a certain affinity for the arterial blood ; they take from it whatever 
 their purposes require, and, that done, the relation at once ceases ; the 
 blood, become venous, has lost its hold upon them, and is pressed off. 
 We may conveniently describe this effect as a pressure of the unchanged 
 upon the changed liquid. 
 
 The motions of the sap in plants are clearly dependent on this prin- 
 Expianation of ciple. Leaving out of consideration the minor movements 
 scenTof tbfslp w ^ cn ta ^e place for special purposes, or at specific epochs 
 of plants. in the development, it may be truly said that the nutritive 
 changes occurring in the leaf are the primary cause of the motion ; for, as 
 the ascending sap presents itself on the sky face of the leaf, it receives 
 carbon, under the influence of the sunlight, from the air, and becomes con- 
 verted into a gummy, glutinous liquid. And just as in the pores of a 
 bladder, or in those of any pervious mineral, pure water will drive out 
 gum-water, and occupy the pore, so will the ascending sap expel the 
 gummy solution from the capillary tubes or intercellular spaces of the 
 leaf. As fast as this takes place, the active liquid becomes inactive, by 
 itself changing into a gummy solution, and the movement is perpetuated. 
 And this ensues not only in the leaf, but in every part of the plant ; the 
 liquid to be changed presses upon that which has changed, and forces 
 it onward. In this manner, motions in various parts and of very great 
 intricacy will ensue, but all of them, if duly considered, no matter 
 whether their seat be in the root or in the bark, in the flowers or in the 
 
CAUSE OF THE CAPILLARY CIRCULATION. 133 
 
 leaves, no matter whether they take place in the height of summer or 
 just at the close of winter, when the sap first rises, or even in the germ- 
 inating seed which is under the ground, and has never yet been exposed 
 to the light, may, without difficulty, be referred to the nutritive change 
 earned on in the leaves of the plant under examination, or its parent, by 
 the influence of the rays of the sun. 
 
 All this holds good, not only in the nutrition of a cell, the more com- 
 plicated nutrition of the various parts of a flowering plant, or Explanation of 
 even of an animal, but likewise in those destructive changes circuSionof 
 restricted to the latter class, and arising in interstitial decay ; animals, 
 for the blood has a double duty to perform : it not only serves for nutri- 
 tion, but also for the removal of effete and dying parts. These it effects 
 the oxidation of, their carbon passing into carbonic acid, their hydrogen 
 into water ; and this is accomplished by the oxygen which has been ob- 
 tained in the process of respiration. The scarlet or arterial blood, charged 
 with its oxygen, passes to all parts of the economy in search of organic 
 particles ready to be removed; it effects their disorganization, and, becom- 
 ing thereby venous, is pressed onward. And now, if we recall that nu- 
 trition in animals depends on the access of air even fibrin can not arise 
 from albumen except under that condition we can not avoid the con- 
 clusion that all operations of repair and all operations of waste are made 
 to conspire together for the production of movement ; and though every 
 part offers its own special cause, as depending on nutrition, or disente- 
 gration, or secretion, they may be all grouped together as the necessary 
 results of one more primitive operation, which is the supply of oxygen 
 to the blood in the respiratory mechanism. 
 
 In my view of this subject, it is therefore the arterialization of the 
 blood in the lungs which is the cause of the circulation in De en(ience of 
 man. I consider the circulation as the consequence of res- circulation in 
 piration ; and though, in one sense, the minor causes are the res P iratlon - 
 numerous, each portion of nervous material, each muscular fibre, every 
 secreting cell working its own way, these subordinate actions are all 
 referable to one primordial act, and that is the exposure of the blood to 
 the air. 
 
 Whatever, therefore, interferes with respiration, interferes with circula- 
 tion. If an irrespirable gas is thrown into the cells of the lungs, the 
 passage of the blood is instantly arrested, and asphyxia ensues. Or, if 
 the access of the air is cut off, as in drowning, in vain the heart exerts 
 its utmost convulsive throb it is unable to drive forward the Case of res- 
 blood; and in those cases, by no means infrequent, yet un- deathT^" 1 
 doubtedly the most surprising occurring in the practice of drowning. 
 medicine restoration from death after drowning, the whole success turns 
 on one condition, the re-establishment of the arterialization of the blood. 
 
134 COURSE OP THE CIRCULATING BLOOD. 
 
 If that be accomplished, the circulation is restored, and the heart pro- 
 ceeds with its duty. And for these reasons, I believe that in many cases 
 success would be had, where failures are now experienced, if, instead of 
 resorting to atmospheric air, pure oxygen gas or protoxide of nitrogen 
 were administered. 
 
 In the more highly-developed organisms the objects of the circulation 
 are threefold : 1st. To minister to the nutrition of the system ; 2d. To 
 introduce oxygen ; 3d. To remove the products of waste. In man, these 
 various results are accomplished by several different arrangements : 1st. 
 Different ^ e g reater or systemic circulation ; 2d. The less, or pulmo- 
 ciasses of nary circulation ; 3d. The portal circulation ; 4th. The Malpi- 
 
 circulation. g^ circulatioilj &c . 
 
 The course taken by the blood is as follows. Leaving the left ventri- 
 Courseofthe c ^ e of the heart, it passes into the aorta, and is distributed 
 blood in its sys- by the ramifications thereof, constituting the systemic arte- 
 
 temic and pul- . -,-, f .-, T , 1,11 
 
 monaiy circu- nes > to all parts of the system. It moves onward through 
 lations. the capillaries, which may at once be considered as the term- 
 
 inal ramifications of the arteries and the commencing tubelets of the 
 veins. These, converging into larger and larger venous trunks, the sys- 
 temic veins, deliver it into the ascending and descending vense cavas, from 
 which it flows into the right auricle, and from thence into the right ven- 
 tricle of the heart. From thence it is driven into the pulmonary artery, 
 to be distributed to the lungs, and, coming therefrom along the pulmo- 
 nary veins, reaches the left auricle, and from thence it gains the left ven- 
 tricle, which was its starting-point. 
 
 In the pulmonary veins, the left cavities of the heart, and in the sys- 
 Dristribution of temic arteries, the blood is crimson. In the systemic veins, 
 crimson and of the right cavities of the heart, and pulmonary artery and its 
 branches, it is blue. The change from crimson to blue takes 
 place in the systemic capillaries, and from blue to crimson in the pulmo- 
 nary. The systemic, or greater circulation, is considered as beginning 
 at the left ventricle and ending at the right auricle ; the pulmonary, or 
 less circulation, begins at the right ventricle and ends at the left auri- 
 cle. This double course is sometimes, among authors, illustrated by 
 likening it to the figure 8, the upper loop representing the pulmonary, 
 the lower the systemic circulation, and the heart placed at the nodal point. 
 
 As has just been remarked, there are other subordinate circulations, 
 The portal but of these only one need attract our attention at present it 
 circulation. j s tne portal. This originates in a system of capillaries, the 
 veins belonging to the digestive apparatus, which, converging rapidly to- 
 gether, form a common trunk, the portal vein. This at once ramifies 
 like an artery in the substance of the liver. From the resulting capilla- 
 ries, the portal blood passes into the commencing capillaries of the hepat* 
 
ORIGIN OF THE HEART. 
 
 135 
 
 ic veins, which empty into the inferior vena cava, and so it reaches 
 the general circulation. The physical peculiarity of the portal cir- 
 culation is, that it commences in a capillary system, and ends in one, 
 without the intervention of any central organ of impulse, or heart. At a 
 very early period, comparative anatomists were struck with Portal circuia- 
 the analogy between the portal circulation in man and the J^^j^t^fa* 1 
 systemic circulation of fishes, both being carried on in the fish, 
 same way, that is, without a heart. In fishes, the heart is a branchial, 
 respiratory, or pulmonary one. Their systemic circulation, or circula- 
 tion of crimson blood, commences in the capillaries of the respiratory ap- 
 paratus, the gills ; a convergence takes place into an aorta, which ramifies 
 into systemic capillaries. So the great circulation in these tubes is ac- 
 complished without any heart. It is scarcely necessary to point out the 
 bearing of such a fact on the theories of the movement of the blood. 
 
 In Fig. 54 is a diagram of the circulation of a fish ; a, 
 is the auricle ; , the ventricle ; c, the branchial or pulmo- 
 nary artery; , e, the branchial or pulmonary veins, bring- 
 ing blood from d, the branchiae, and converging directly to 
 /", the aorta, which distributes the systemic blood. This 
 is collected into a vena cava, <?, and so brought to the au- 
 ricle, a. There is therefore no systemic heart. 
 
 The further discussion of this subject will be continued 
 as follows : We shall describe, 1st, the construction and 
 action of the heart ; 2d, of the arteries ; 3d, of the capil- 
 laries ; 4th, of the veins. We shall then present a view 
 of the combined result of these various mechanisms. 
 
 1st, The Heart. The first appearance of the heart is as 
 a cavity arising in a collection of cells, by cleli- 
 
 J , AX The heart. 
 
 quescence or separation of the central ones. At 
 this early period, and even before the cavity has fairly formed, pulsation 
 may be observed. The organ soon assumes a tubular form ; and this, 
 
 becoming curved, as shown in Fig. 
 55, differentiates into three compart- 
 ments, with arterial and venous con- 
 nections ; 1, the venous trunks ; 2, 
 the auricle ; 3, the ventricle ; 4, the 
 bulbus arteriosus. The form to be 
 eventually assumed is foreshadowed in the manner in which the curved 
 tube develops, the arch of the curve, 2, bulging so as to form a conical 
 ventricle. This tri-chambered heart remains permanent in fishes, as seen 
 in the preceding figure (54), of which c is the third chamber. But in birds 
 and mammals, the aortic bulb merges into the ventricle, through which, 
 as well as through the auricle, a septum or partition is established, and 
 
 Diagram of fisli 
 circulation. 
 
 Fig. 55. 
 
 Rudimentary heart 
 
136 
 
 STRUCTURE OF THE HEART. 
 
 Diagram of single heart. 
 
 Fig. 56. thus a double heart, or one of four cham- 
 
 bers, arises. 
 
 The diagram, Fig. 56, represents a 
 double-chambered heart, d being its auri- 
 cle, e the ventricle, c, <?, the veins converg- 
 ing to the auricle, a the aorta or main arte- 
 ry passing from the ventricle. The course 
 of the blood is indicated by the arrows. 
 
 The heart with four cavities may be 
 considered as arising from the conjunction 
 of a pair of the preceding form, with their 
 efferent and afferent tubes, or arteries 
 and veins, so modified or arranged that 
 the right heart receives its blood from the 
 system in an auricle, from which it passes into a ventricle, and thence to 
 
 the lungs. From the lungs, after aeration, 
 this blood is brought to the auricle of the 
 left heart, thence into its ventricle, and 
 thence to the aorta. Though all four cham- 
 bers are generally coalesced into one conic- 
 al form, the heart of the dugong, Fig. 57, 
 presents the true typical structure; E is 
 the right or pulmonary ventricle, L the left 
 or systemic ventricle, their apices being 
 quite apart ; D is the right or systemic au- 
 ricle, F the pulmonary artery, K the left or 
 Heart of the dugong. pulmonary auricle, and A the aorta. 
 
 Fig. 58 is the anatomy of the human heart as viewed upon the right 
 
 side, the figure and description being 
 from Dr. E. Wilson. 1, the cavity of 
 the right auricle ; 2, the appendix au- 
 ricuke ; 3, the superior vena cava, 
 opening into the upper part of the 
 right auricle; 4, inferior vena cava; 
 5, the fossa ovalis ; the prominent 
 ridge surrounding it is the annulus 
 ovalis; 6, the Eustachian valve; 7, the 
 o opening of the coronary vein ; 8, the 
 coronary valve ; 9, the entrance of the 
 auriculo- ventricular opening; a, the 
 right ventricle ; &, c, the cavity of the 
 
 Human heart on the right side. right Ventricle, On the walls of which 
 
 the columnce earner are seen ; c is placed in the channel leading upward 
 
STRUCTURE OF THE HEART. 
 
 137 
 
 to the pulmonary artery, d; e,f, the tricuspid valve : e is placed on the 
 anterior curtain, and/* on the right curtain ; #, the long columna carnea, 
 to the apex of which the anterior and right curtains of the tricuspid 
 valve are connected by the chordaa tendineas; h, the long moderator 
 band ; i, the two columnse carneaa of the right curtain ; &, the attach- 
 ment by chorda3 tendinea3 of the left limb of the anterior curtain ; I, I, 
 chorda3 tendinese of the fixed curtain of the valve ; m, the valve of the 
 pulmonary artery : the letter of reference is placed on the inferior semi- 
 lunar segment ; n, the apex of the right appendix auriculas ; o, the left 
 ventricle ; JP, the ascending aorta ; #, its arch, with the three arterial 
 trunks which arise from the arch ; r, the descending aorta. 
 
 Fig. 59 exhibits the view of the organ on its left side. Like the pre- 
 Fig 59 ceding, the figure and description 
 
 are from Dr. Wilson. 1, cavity 
 of the left auricle : the number 
 is placed on that portion of the 
 septum auricularum correspond- 
 i n g Tftifa the centre of the fossa 
 ovalis ; 2, cavity of the appendix 
 auriculas ; 3, opening of the two 
 right pulmonary veins ; 4, the 
 sinus into which the left pulmo- 
 nary veins open ; 5, the left pul- 
 monary veins ; 6, the auriculo- 
 ventricular opening; 7, the coro- 
 nary vein, lying in the auriculo-ventricular groove ; 8, the left ventricle ; 
 9, 9, the cavity of the left ventricle. The numbers rest on the septum 
 ventriculorum. a, the mitral valve : its flaps are connected by chordaa 
 tendineas to , , b, the columnaa carneaa ; c, c, fixed columnas carneae, form- 
 ing part of the internal surface of the ventricle ; d, the arch of the aorta, 
 from the summit of which the three arterial trunks of the head and up- 
 per extremities are seen arising ; -0, the pulmonary artery ; f, the oblit- 
 erated ductus arteriosus ; g, the left pulmonary artery ; A, the right ven- 
 tricle ; i, the point of the appendix of the right auricle. 
 
 Externally, the heart is covered by a serous membrane, pericardium, 
 
 and in its interior is sheathed by the 
 endocardium, an extension of the inte- 
 rior coat of the great blood-vessels. 
 Though its movements are wholly in- 
 voluntary, its muscular fibres are of the 
 transversely striated kind. They are 
 about one third less in diameter than 
 Muscular fibres of the heart. those of voluntary muscles generally, 
 
 Human heart on the left side. 
 
138 COUESE OF THE BLOOD IN THE HEART. 
 
 and are especially characterized by their disposition to anastomose with 
 one another, as represented in Fig. 60. In the ventricles, the arrange- 
 ment is such that the fibres of the external and internal surfaces decus- 
 sate. 
 
 The motions of the heart consist in the relaxations and contractions of 
 Eelaxations the muscular walls of its cavities. The two auricles contract 
 dons^fThe" at tf 16 same moment, as do also the two ventricles, but the 
 heart. contractions of the auricles coincide with the relaxations of the 
 
 ventricles. 
 
 The course of the blood through the heart is this. The venous blood, 
 Course of the brought by the ascending and descending cava3, flows into 
 blood in the the right auricle as it is dilating, and for the moment pushes 
 movements of forward to the ventricle, but the auricle, being of less capac- 
 the valves. fry t h an ^Q ventricle, is rilled to distention first ; at this in- 
 stant it contracts, forcing its contents past the tricuspid valve into the 
 ventricle, and fills it completely. The blood can not regurgitate into the 
 veins to any extent while this is going on, because of the almost perfect 
 closure of their valves. The right ventricle now commences to contract ; 
 its fleshy columns shorten so as to pull upon the tendinous cords attach- 
 ed to the flaps of the tricuspid valve : this enables the blood to get be- 
 hind them, and they quietly close the aperture between the auricle and 
 ventricle ; the closure is riot, however, under all circumstances, perfect, 
 the mechanism being such as to permit leakage or regurgitation to a lim- 
 ited extent. The blood now rushes into the pulmonary artery, passing 
 by its semilunar valves, which, the moment the ventricular pressure 
 ceases, shut, so as to prevent any return to the heart. 
 
 Having passed through the lungs and been submitted to the air, the 
 blood now returns to the left auricle, which forces it into the left ventri- 
 cle, the action on this side of the heart being the same as on the other; 
 the mitral valve, which closes the opening from the auricle into the ven- 
 tricle, is worked in the same manner as the tricuspid, and the blood is 
 pressed into the aorta, the semilunar valves of which, at that instant, 
 shut abruptly with an audible sound, and prevent any regurgitation. In 
 this manner the distribution to the system is accomplished. 
 
 On both sides of the heart, as soon as the auricles have finished their 
 contraction, they begin to dilate, and continue to do so during the peri- 
 od that the ventricles are contracting. Thus there is an accumulation 
 in them when the ventricles are ready to dilate, and, as soon as that oc- 
 curs, the blood flows freely forward into those cavities, the complete dis- 
 tention of which is then accomplished by the contraction of the auricles, 
 as before explained. 
 
 Movements of The mode of action of the two sets of cavities is different, 
 and ventricles. Tlie auricle s contract suddenly, first at the place of junction 
 
MOVEMENTS OF THE HEART. 139 
 
 of their veins, the effect passing quickly forward ; the ventricles con- 
 tract more slowly, but simultaneously in every part. 
 
 During each beat of the heart two sounds may be heard, followed by 
 a silence. The first sound is dull ; the second, which fol- Sounds of the 
 lows it quickly, is sharp. They may be imitated by artic- heart - 
 ulating the syllables lubb, dup. The first is due to the contraction 
 of the muscular fibres of the ventricles, and the striking of the apex of 
 the heart against the wall of the chest ; to a certain extent, the opening 
 of the semilunar valves, and the rush of the blood into the pulmonary 
 artery and aorta contribute to it. The second sound is due to the shut- 
 ting of the semilunar valves of the aorta and pulmonary artery. 
 
 At each contraction of the ventricles the heart strikes against the walls 
 of the chest, usually between the fifth and sixth ribs, and an inch or two 
 to the left of the sternum. This motion is partly due to the action of 
 the spiral muscular fibres of the ventricles, which, gives a tilt to the 
 heart, and partly to the globular form which the whole organ suddenly 
 assumes. 
 
 The number of pulsations made by the heart differs very much at dif- 
 ferent periods of life: at birth it is from 130 to 140 per Number of pui- 
 minute ; at the seventh year, from 80 to 85 ; during mature sations. 
 life, from 70 to 75 ; and in old age, from 50 to 65. In females it is 
 more frequent than in males. It observes a general relation with the 
 number of respirations, five pulsations commonly occurring during one 
 respiration. It varies with incidental circumstances. During sleep it 
 declines in frequency ; after eating, or during exercise, it is quickened. 
 Examined from morning to evening, it becomes slower by degrees. Ly- 
 ing down, the pulse is slower ; in a sitting posture, more frequent ; and 
 still more so when standing, the variations depending on muscular exer- 
 tion. In conditions of disease, the ratio between the number of pulsa- 
 tions and respirations is variable. 
 
 The walls of the left ventricle are twice as thick as those of the right, 
 and the force of its contractions is about double. The ca- Structure and 
 pacity of the two ventricles is nearly the same, and is taken power of the 
 at about three ounces. The active force with which the au- walls ' 
 ricles dilate is feeble, and wholly incompetent to exert any thing like the 
 suction power at one time supposed, yet that they are not distended by 
 the mere influx of the blood is satisfactorily proved by their dilatation 
 after the heart has been cut out. 
 
 With respect to the absolute force which the left ventricle exerts for 
 the propulsion of the blood into the systemic arteries, it is stated to be 
 13 Ibs. This result is derived from the consideration that the pressure 
 of the blood in the aorta is about 4 Ibs. 3 oz. 
 
 That the motions of the heart can not be referred to the presence of the 
 
140 CAUSE OF THE MOTIONS OF THE HEART. 
 
 Cause of the kl oc) d> or an 7 re fl ex action arising from the cerebro-spinal 
 motions of the system, but must be attributed to the organ itself, is proved 
 by their continuance after its excision from the body, or even 
 after it has been cut in pieces. Some have supposed that the minute 
 sympathetic ganglia with which it is furnished are the source of the mo- 
 tive power ; others are disposed to impute it to a self-contractile power 
 of its muscular fibres, irrespective of any nervous agency. Of course, it 
 is admitted by all that the brain and spinal cord can influence these 
 movements, but such effects are superadded and not uniform. 
 
 Of these opinions, we shall find many reasons for preferring the first 
 when we come to the description of the nervous mechanism. It will be 
 then seen that one of the prominent functions of nervous ganglia of a cer- 
 tain order, and particularly the ganglia of the sympathetic, is the storing 
 up of impressions they have received, and thus becoming reservoirs or 
 magazines of force. The power thus engendered or contained in them 
 is by no means always delivered out in totality at once, but it may be 
 in small portions, at intervals, for a long time ; and doubtless in this 
 way the minute sympathetic ganglia of the substance of the heart retain 
 a power of keeping up the motions of that organ for a certain period of 
 time, even though great lesions or morbid changes may have supervened. 
 Such a mechanism recalls the manner in which chronometers are kept 
 going during the short time that the action of the main-spring is taken 
 off when the watch is wound up. 
 
 2d. The arteries are tubes consisting of different tunics or layers va- 
 Description of rioTisly numbered by anatomists, but which may be suffi- 
 the arteries. ciently described as, 1st. The exterior tunic, containing fibres 
 generally running lengthwise, connective and elastic tissue : it is of about 
 the same thickness as the tunic below ; 2d. The middle tunic, character- 
 ized by being composed of non-striated muscular fibres circularly ar- 
 ranged ; 3d. The interior tunic, which is thin, and consists of a cellular 
 or epithelial layer, smooth and polished, to permit of the ready passage 
 of the blood. 
 
 The elasticity of the arteries enables them to sustain the sudden action 
 of the heart by distending to a certain degree as the blood is driven into 
 them, and by their gradual collapse when the ventricles cease their pres- 
 sure, the jetting or intermitting flow is converted eventually into a con- 
 tinuous stream. The mechanical influence of the heart is thus decom- 
 posed into two portions : one, which is of momentary duration, or, at all 
 events, lasting only so long as the ventricle contracts ; and a second, 
 which is occupied in distending the elastic arterial tube; but this por- 
 tion is not lost to the circulation, since the tube, as it contracts, yields 
 it back again to the blood. The momentary impulse of the heart is thus 
 spread over a considerable duration without loss. 
 
ACTION OF THE AKTERIES. 141. 
 
 The muscularity of the arteries is shown by their contraction on ex- 
 posure, their subsequent dilatation being due to their elasticity, this con- 
 tractile property being continued for some time after death. It is also 
 proved by the great diminution of diameter which arteries exhibit when 
 under the influence of an electric current. The quantity of muscular 
 and elastic tissue in different arterial tubes is usually in an inverse pro- 
 portion. In the great arteries the elastic tissue abounds, in the smaller 
 the muscular increases. By their muscular coat the quantity of blood 
 in these tubes can, within certain limits, be regulated. 
 
 At each injection of blood into it an artery distends. It then con- 
 tracts, and thus gives origin to a pulsation. Its increase is Action of the 
 both in diameter and length, the tendency being to lift it at arteries. 
 each pulsation. The distention does not occur at the same instant in 
 all these tubes, but those nearest to the heart yield first, and the more 
 distant a little later. There is therefore what may be termed a wave of 
 distention passing throughout the length of each arterial tube, and an- 
 other actual wave in the blood itself. These pass onward at different 
 rates of speed. The interval of wave-motion from the heart to the 
 wrist is about one seventh of a second. Of course this wave-motion is 
 to be distinguished from the absolute movement of the blood, which is 
 much slower. In the carotid artery the flow of the blood is about one 
 foot in one second. 
 
 A pressure or impact, communicated to a liquid in a long tube, is 
 transmitted to the more distant end with vastly more rapidity than the 
 liquid itself could flow through the same distance. Thus, if we were to 
 suppose a very long metal tube to be filled completely with water, its 
 two ends having been tightly closed by tying pieces of bladder over 
 them, the tap of a finger on one of the pieces of bladder would be almost 
 instantly felt by a finger laid on the other. Indeed, it has been pro- 
 posed to establish telegraphic communication on this principle, though 
 such attempts would prove abortive from the interference of collateral 
 circumstances. This example may serve, however, to illustrate the es- 
 sential difference between the flow of a liquid in a tube and the passage 
 of a pulsation through such a liquid contained in such a tube. 
 
 The capillaries may be regarded as tubular continuations of the arte- 
 ries and the commencement of the veins. They ramify 
 
 , . J .. J The capillaries. 
 
 through the organic structures. They are of pretty uniform 
 diameter, and may therefore be looked upon as cylinders. Their usual 
 size is about -g-^-Q of an inch ; their mode of distribution varies with the 
 structure and functions of the part they occur in : thus, in muscles they 
 run parallel ; in the papillas they are looped. 
 
 They consist essentially of a delicate structureless membrane, analo- 
 gous to cell membrane, and the sarcolemma of voluntary muscles. It 
 
142 
 
 THE CAPILLAEIES. 
 
 possesses a certain degree of elasticity, and presents here and there cell 
 nuclei. 
 
 Fig. 61. Fig. 62. 
 
 Capillary distribution to mucous membrane of 
 stomach. 
 
 Capillary distribution to villi of duodenum. 
 
 Fig. 63. 
 
 The interspaces between adjacent capillaries vary much in size and 
 Size of inter- shape, the latter variation being dependent on the mode of 
 spaces. distribution, whether parallel, reticulated, looped, &c. ; as to 
 
 size, in the liver the interspaces are of less diameter than the capillaries, 
 in the choroid coat still smaller, but in the cellular coat of the arteries 
 they are ten times larger than the vessels. These interstitial spaces are 
 nourished by the matter which exudes through the thin walls of the cap- 
 illaries. 
 
 Fig. 63 represents 
 the capillary circula- 
 tion in the web of the 
 frog's foot : a, venous 
 trunk ; , #, branches 
 of venous trunk ; c, c, 
 pigment cells. The 
 elliptical blood- discs 
 are seen in outline in 
 the interior of the ves- 
 sels. 
 
 The blood flows 
 through the capilla- 
 ries in an uninterrupt- 
 ed stream, its jetting 
 motion being entirely 
 lost. The rate of cir- 
 culation through the 
 
 Capillary circulation of frog's foot. SVStemic Capillaries is 
 
STRUCTURE OF THE VEINS. 
 
 143 
 
 taken at three inches per minute, that through the pulmo- Motion of the 
 nary being five times as quick, the length of the capillary tube blood in the 
 to be passed -^ of an inch, so that the passage from the ar- ca P lllanes - 
 tery to the vein may be accomplished in less than one second. It is to 
 be remarked, however, that all parts of the cylindrical stream do not 
 move with equal rapidity. Those parts which are nearest to the wall of 
 the vessel are spoken of as the still layer, from their tardy movement. 
 It is in this that the white corpuscles may be seen. 
 
 fig. 64. Fig. 64 shows a portion of a small 
 
 vessel from a frog's foot: <z, <z, red blood 
 elliptic cells, occupying the axis of the 
 vessel, and exterior to them, moving 
 more slowly, or occupying the still lay- 
 er, the white spherical cells ; b, b, nucle- 
 ated epithelium. 
 
 4th. The veins have a structure in 
 some respects different from The veins : 
 that of the arteries. Their their structure. 
 -, elastic coat is by no means so much de- 
 veloped, and their muscularity less dis- 
 tinct. With the exception of those of 
 the lungs, abdominal viscera, and brain, 
 their interior is furnished with valves of single, double, or triple flaps, in 
 all instances opening toward the heart. The blood flows equably in 
 them, the pulsating action of the ventricles having disappeared in the 
 capillaries. Since they present an aggregate capacity two or three times 
 that of the arteries, the motion of the circulation in them is proportion- 
 ally slower. Fig. 65 is a diagram showing the manner in which the 
 valves open when the blood flows in the course indicated by the arrows. 
 
 Fig. 66. 
 
 Fig. 65. 
 
 Valves of veins open. 
 
 White corpuscles in the still layer. 
 
 Valves of veins shut. 
 
 Fig. 66 shows their application to each other, or to the sides of the vein, 
 and the consequent bulging of that vessel when the current, as indicated 
 by the arrows, is in the opposite direction. 
 
 Having now described the structure and action of the heart, the arte- 
 ries, capillaries, and veins respectively, as far as is necessary, it remains 
 to group those actions together, and present the theory of the circulation 
 at one view. 
 
 But, before entering on this, it is proper to offer an ar- Error of the doc- 
 gument against the doctrine of those physiologists who still h eart is t h e sole 
 maintain that the circulation is wholly dependent on the heart, cause of the cir - 
 
 . . T . culation. 
 
 and fhnt that orcran is entirely competent to carry it on. 
 
144 ACTION OF THE HEART. 
 
 The majority of the circulations we examine in organic forms are ac- 
 complished without any heart. Plants have none ; fishes have no sys- 
 temic heart ; even in man, at the first period of embryonic existence, there 
 is no such central organ ; in his adult condition the portal circulation has 
 none. The current of blood in the capillaries, seen under the microscope, 
 exhibits no jetting movements, but, on the contrary, a steadiness of 
 flow, sometimes for long in one channel, then a cessation, then perhaps 
 a retrogradation, and then a new path. It looks as though the blood 
 was flowing spontaneously, and not by any force acting behind. The 
 heart of an animal may be suddenly cut out, and yet the capillary motion 
 may go on in the same direction as before. After death the arterial 
 tubes are most commonly found empty : a result which is a mechanical 
 impossibility on the supposition that the heart alone drives the blood, 
 but which ensues as a necessary consequence if the capillaries draw it. 
 In acardiac monsters the blood circulates without difficulty, and, though 
 it was at one time supposed that in these twins the hearted foetus drove 
 the blood through the heartless one, this is now demonstrated not to be 
 the case. The circulation, moreover, varies locally, and at special epochs, 
 as in the development of the generative organs, the mammary glands, the 
 flow to the erectile tissues. Ubi irritatio ibi fluxus is an old medical 
 aphorism, and these local variations are incompatible with the action of 
 one central unvarying force. In cases of spontaneous gangrene, it some- 
 times occurs that the circulation through the part has declined, while the 
 capillaries are all open, as subsequent examination proves. The applica- 
 tion of cold to a part checks the circulation through it, and this not 
 through any contraction of the vessels ; so, likewise, does a jet of carbon- 
 ic acid gas directed upon them. Moreover, any retardation in the supply 
 of air to the lungs restrains the circulation, and this not alone in the 
 pulmonary vessels, but also in the systemic capillaries, producing an in- 
 creased pressure in the arterial tubes, a diminished one simultaneously 
 occurring in the veins ; and if, in the various cases now mentioned, the 
 propulsive action of the ventricles can not be relied on to explain the dif- 
 ficulties, neither can any supposed suction or exhausting action of the 
 auricles. When a ligature is tied round a vein, the action of the auricle 
 is cut off, but the vein distends beyond the obstruction, showing that 
 there is a force acting from the capillaries. Flexible tubes, such as are 
 those vessels, would at once collapse under the exertion of a very moder- 
 ate suction power, far less in intensity than would be necessary to draw 
 the blood in the veins. 
 
 In spasmodic asthma, and in all pulmonary congestions, the right side 
 of the heart circulates, the blood with difficulty through the lungs, show- 
 ing the existence of a great obstruction to its motion through the pulmo- 
 aary capillaries. An examination of the condition of the various por- 
 
CIRCULATION OF THE BLOOD. 145 
 
 tions of the circulatory apparatus after death presents facts utterly inex- 
 plicable on the doctrine of the sufficiency of the heart. I have alrtady 
 mentioned the empty state of the systemic arteries ; to this may be add- 
 ed what is often witnessed the distended condition of the pulmonary 
 artery, into which the blood has been forced by the expiring beats of the 
 right ventricle, but has been unable to get through the pulmonary capil- 
 laries because of the cessation of respiration ; but in other cases, where 
 respiration has come to an end more tranquilly or slowly, the left auricle 
 is full of blood, which must have been driven into it by the pulmonary 
 capillaries. In sudden death, as by hanging and drowning, the right 
 heart is excessively distended, as is also the pulmonary artery. 
 
 I might proceed to add to these other facts exhibiting local variations 
 of the supply of blood in the periodicities of the system. There is a cer- 
 tain amount sent to the brain during the day, and a less during the re- 
 pose of the night ; in the muscular system, during the time of its action, 
 the quantity demanded is greater ; in its state of inactivity, less. A con- 
 stant and invariable acting machine, such as is the heart, could by no 
 possibility adjust these variable supplies. But the cases here offered are 
 more than enough, and it remains to be added that, though, not one of 
 them can be explained on the doctrine of the sufficiency of the heart, 
 there is not one which does not follow as a necessary consequence of the 
 doctrine now to be presented. 
 
 On this view, Ae circulation is conducted in the following manner: 
 The left ventricle of the heart impels the blood into all the Ex lanationof 
 aortic branches, any backward regurgitation into the auricle the circulation 
 being prevented by the shutting of the mitral valve; the oftheblood - 
 force employed is decomposed into two portions, one part exerting an in- 
 stantaneous effect on the blood in pressing it forward, and ceasing in- 
 stantaneously, and thus giving origin to the pulse ; the second distend- 
 ing the arterial tubes, but not being lost thereby, since their elasticity 
 causes them to contract, and the semilunar valves at the origin of the 
 aorta being at this period shut, a steady, onward pressure is exerted on 
 the blood ; so the quickly-ending action of the ventricle gives origin to 
 two distinct mechanical results a sudden impact and a continuous press- 
 ure. This suffices to bring the blood to the arterial origin of the capil- 
 laries, and beyond that point the action of the heart may be considered 
 not to extend. 
 
 The relation between the interspaces of the capillaries and the blood 
 thus introduced to them continues the current. The particular mode in 
 which this relation is manifested differs in different parts. The oxidiz- 
 ing arterial blood has a high affinity for those portions that have beqpme 
 wasted : it effects their disintegration, and then its affinity is lost. The 
 various tissues require repair ; they have an affinity for one or other of 
 
 K 
 
146 CIRCULATION OF THE BLOOD. 
 
 the constituents of the blood ; they take the material they need and their 
 anHity is satisfied ; or secreting cells originate a drain upon the blood, 
 and the moment they have removed from it the substance to be secreted, 
 they have no longer any relation with it. So processes of oxidation, and 
 processes of nutrition, and processes of secretion, all conspire to draw the 
 current onward from the arteries, and to push it out toward the veins ; 
 and though these processes may present themselves in many various as- 
 pects, they are all modifications of the same simple physical principle. 
 
 The blood has now reached the veins, and is forced onward in them by 
 the power that has thus originated in the capillaries. The influence of 
 the heart is here unfelt, the exhausting action of its right auricle is un- 
 appreciable, and, thus pushed onward from the capillaries, it reaches the 
 heart, completing its systemic or greater circulation. This circulation 
 may therefore be said to be due to the high affinity which arterial blood 
 has for the tissues, venous blood having none ; and the action of the heart 
 is confined to the filling of the arterial tubes, and presenting fresh por- 
 tions of blood to the capillaries. 
 
 Arrived at the right auricle, the blood flows continuously into it and 
 the right ventricle for a moment, but the ventricle holding more than the 
 auricle, the latter cavity is fully distended first. At that instant it con- 
 tracts, the valves in the veins shutting, and the blood, driven thus forcibly 
 into the ventricle, distends it to the utmost. The ventricle, in its turn, 
 now contracts, the tricuspid valve shutting, and th*blood issues forth 
 through the pulmonary artery, its valves then closing. At this moment 
 an event occurs which, in these descriptions, is generally overlooked an 
 action analogous to that of the hydraulic ram. On the shutting of the 
 tricuspid, the whole column of venous blood would be brought to a stop 
 if the tubes containing it were unyielding, and a great force would be gen- 
 erated from this stopping of its momentum ; but the auricle is ready to 
 dilate, and into its cavity the blood, which would be otherwise checked, 
 flows. I consider that this safety action of the auricle is one of its prime 
 functions. The rapidity with which the dilatations and contractions are 
 taking place furnish no argument against the occurrence of this action. 
 I have a hydraulic ram, the pulsations of which may be so adjusted as 
 to exceed greatly in frequency those of the heart, and, indeed, to give rise 
 to a low murmuring sound, and yet, under these circumstances, the lat- 
 eral force is so great as to throw a column of water more than forty feet 
 high. If it were not for the dilatability of the auricles and their yield- 
 ing texture, the veins would burst on the shutting of the tricuspid valve. 
 
 The ramifications of the pulmonary artery bring the blood to the cap- 
 illaries of the lungs, but beyond that the influence of the heart is not felt, 
 for now the physical principle heretofore described comes again into ac- 
 tion. The venous blood has a high affinity for the oxygen of the air, an 
 
THE HEART'S ACTION. 147 
 
 affinity which is satisfied as soon as the Hood presents itself in the cells 
 of the lungs. Arterialization "being accomplished, the portions to Ibe 
 changed exert a pressure on those that have changed, and the blood, mov- 
 ing forward in the pulmonary veins, reaches the left auricle of the heart. 
 
 For a moment it passes into the left auricle and ventricle continuously, 
 but the auricle, being of less capacity, fills first. It contracts as soon 
 as it is completely full, and drives its contents into the left ventricle, dis- 
 tending it to the utmost. The ventricle now contracts, shutting the mi- 
 tral valve, and the ram-like action is repeated on this side of the heart. 
 But the blood expelled from the ventricle is urged into the aorta, its force 
 being decomposed, as before described, one part acting instantaneously 
 as an impact on the blood, the other on the arterial walls, and on the 
 first moment of the recession of the walls of the ventricle the semilu- 
 nar valves of the aorta shut, and this act completes one tour of the cir- 
 culation of the blood. 
 
 In this description I have said nothing of the circulation in the sub- 
 stance of the heart itself, since it would have led to a needless complica- 
 tion. It should be remembered, as an illustration of the working of the 
 physical principle here explained, that the motion of the blood is contrary 
 in the greater and less circulations, compared together. In the former, 
 the current is from the crimson to the blue, in the latter, from the blue 
 to the crimson side. 
 
 The action of the heart is therefore limited to the filling of the arterial 
 tubes, so as to present to the capillaries a constant supply of Correct state _ 
 blood. There seems to be but little suction force exerted ment of the 
 by the- auricular cavities for the emptying of the veins. The heart ' s action< 
 valvular construction of these vessels economizes every pressure that the 
 muscles may exert on them in favor of the circulation, for every such 
 pressure must, by reason of the valves^ force the blood onward to the 
 heart. This is, however, only an incidental result of the same character 
 a's the influence which the motions of respiration exert. They may be 
 properly overlooked in a general statement of the causes of the circulation. 
 
 By regarding the affinity between the blood and the tissues with which 
 it is in contact as the great primary cause of the circulation, , Various facts 
 we assign a reason for those various phenomena which can supporting this 
 not be accounted for on Harvey's doctrine : the motions in ex P lanatlon - 
 the embryo ; the periodic and local variations ; the portal circulation ; 
 the changes in the current, as seen under the microscope ; the movement 
 in the capillaries after the heart is cut out ; the empty condition of the 
 arteries after death ; the phenomena of acardiac foetuses ; local inflam- 
 mations and congestions ; the gangrene of parts while their capillaries 
 are pervious ; the retardation of the current On the application of cold or 
 cf carbonic acid gas ; the results of asphyxia and death by drowning or 
 
148 THE FIEST BREATH. 
 
 hanging ; the changes of pressure in the arteries and veins respectively 
 during a check on the respiration ; the vis a tergo of the veins ; the effects 
 of a ligature on those vessels ; the action of irrespirable gases when 
 breathed, and the opposite conditions when oxygen gas or protoxide of 
 nitrogen are used. 
 
 Among the striking proofs of the truth of this doctrine, that the pri- 
 mary cause of the circulation is the aeration of the Tblood, I 
 would particularly direct attention to the effects which en- 
 sue in the moment of birth at the first breath. That intercommunication 
 between the two sides of the heart, established through the foramen ovale 
 and through the ductus arteriosus, is suddenly put an end to. But this 
 is not through any change in the mechanism of the heart itself, nor be- 
 cause of any interruption in the action of the placenta. It is solely be- 
 cause of the calling into operation of the principle we have been here en- 
 forcing. Through the contact of the cold air, or other causes which might 
 be assigned, the inspiratory muscles make their first contraction and dis- 
 tend the lungs. At that instant, the commencing arterialization produces 
 a pressure, in the manner I have explained, of the venous upon the now 
 arterialized blood in the vessels of the pulmonary cells. There is no 
 other possible issue to such an action than an instant drain upon the 
 heart. The pulmonary or less circulation sets in with full vigor. The 
 blood is not driven by the heart to the lungs, but drained by the lungs 
 from the heart. If it were the heart's action that occasioned this sudden 
 increase of force, because of the strain thrown upon it through the shut- 
 ting off of the influence of the placenta, it is inconceivable why the cur- 
 rent should not continue to move through the great avenues already open 
 to it from the right to the left auricle through the foramen ovale, and 
 from the right ventricle into the aorta through the ductus arteriosus. 
 The arrest of its motion through these channels distinctly establishes that 
 the seat of the new action is in the lungs, and the final closure of the 
 foramen and shriveling of the duct confirm the correctness of this con- 
 clusion. 
 
 Though it does not strictly belong to the subject now under consid- 
 eration, I can not avoid impressing on the reader the suddenness of the 
 effect that thus ensues on the taking of the first breath. It is a crisis in 
 the history of development. Of these changes by crisis much more will 
 be said in the second book, and their important bearings on the theory 
 of physiology pointed out. It is enough for the present purpose to com- 
 mend to the attention of those naturalists who deny that physiological 
 crises ever occur, the facts which have been considered in the preceding 
 paragraph. 
 
 A doctrine which accounts with simplicity for such a long list of mis- 
 cellaneous facts commends itself to our attention at once. There are, 
 
OP RESPIRATION. 149 
 
 however, considerations of a still weightier character, which must compel 
 us to adopt it. The affinity between the blood and the parts with which 
 it is brought in contact is a chemical fact beyond contradiction. The 
 pressures and motions I have been speaking of follow as the inevitable 
 consequences of that affinity. We can not, therefore, gainsay their ex- 
 istence in the living mechanism, and the only doubt we can entertain is 
 as to whether they are of competent power to produce all the effects be- 
 fore us. But after what has been already said respecting the energy of 
 endosmotic movements displayed against pressures of many atmospheres, 
 we may abandon those doubts ; and since we have here a force of uni- 
 versality enough, and intensity enough, and in every instance acting in 
 the right direction, it would be unphilosophical to look farther, since such 
 a force must, under these conditions, exist in the physical necessity of 
 the case. 
 
 CHAPTER IX. 
 
 OF RESPIRATION. 
 
 Respiration introduces and removes aerial Substances. Coalescence of Respiratory and Urinary 
 Organs in Fishes. Physical and chemical Conditions of Respiration. Interstitial Movements 
 of Solids, Liquids, and Gases. Condition of Equilibrium in the Diffusion of Gases. Con- 
 densing Action of Membranes. Forms of Respiratory Mechanism. The Lungs of Man. 
 Three Stages in the Introduction of Air: Atmospheric Pressure, Diffusion of Gases, and 
 Condensation by Membranes. Exchange of Carbonic Add for Oxygen. Divisions of the Con- 
 tents of the Lungs. Variations in the expired Air. Removal of Water. Effect ofirrespira- 
 ble Gases. Experiments ofRegnault and Reiset. Nervous Influence concerned in Respiration. 
 Results of Respiration. 
 
 SINCE it is essentially necessary to the life of all animals that the 
 blood should pass to every part of the system, provision must objects of 
 be made for securing aeration. The breathing apparatus is the res P irati on. 
 skin, or some extension, reflection, or modification of it. 
 
 Besides the great duty of originating the circulation, respiration is con- 
 nected with others of equal importance. The functional activity of the 
 nervous and muscular tissues is dependent on their- oxidation, and this 
 implies the introduction of air. In each tribe, moreover, it is necessary 
 to keep the temperature up to a specific point. This also is accomplished 
 by oxidation, either of the disintegrating material which is passing to 
 w^aste, or of combustible substances, such as sugar or fat. 
 
 All organic material, at its death, eventually gives origin, .p. 
 under the action of the air, to two products with which the of tissue meta- 
 function of respiration is mainly concerned. These products mor P hosis - 
 are carbonic acid and water. With the exception of gelatin, the other 
 
150 NATURE OF RESPIRATION. 
 
 respiratory elements of food fat, sugar, starch, &c., yield these two pro- 
 ducts alone. The nutritive elements give rise to nitrogenized compounds 
 in addition. The conditions of life are such that carbonic acid can not 
 be permitted to accumulate in the system, and means have therefore to 
 be resorted to for its removal. The introduction of oxygen and excre- 
 tion of carbonic acid are accomplished by the same mechanism, the lungs, 
 the action of which is 'dependent on a physical principle. 
 
 Under its simplest condition, respiration consists in the passing of car- 
 Respiration is b om * c ac id with the vapor of water from the system, and the 
 connected tvith reception of oxygen in exchange. The construction of the 
 porous maker apparatus which accomplishes this double duty in atmos- 
 on b"- pheric animals is such that it can deal with substances in 
 
 the aerial state alone. Nothing can be introduced through the lungs or 
 escape therefrom except it be in the gaseous or vaporous form. All 
 those products of disorganization which are not presented under this con- 
 dition must therefore be removed by other organs, and this is more par- 
 ticularly done by the kidneys. 
 
 But in aquatic animals, as in fishes generally, there is not this restric- 
 Coaiescence of tion or concentration of function, for the gill, being in contact 
 and^rhmrv^r- w ^ n water, offers a channel for the passing away of many 
 gans in fishes, products of waste which, from their non-aerial state, could 
 never escape through a lung, and so I regard this organ, the gill, as in a 
 measure sharing the duty of a kidney in eliminating nitrogenized and 
 perhaps saline matters. Comparative anatomists have long recognized 
 that the so-called kidney in fishes approaches in character the Wolffian 
 bodies largely developed in the foetal condition of man. I am disposed 
 to believe that the physical interpretation of this depends on the fact now 
 before us, and that the gill in fishes, and the placenta, in part, in mam- 
 mals, discharge at once the double office of a respiratory and urinary or- 
 gan. It is consistent with the scheme of organic design that there should 
 be this separation and concentration of function as development takes 
 place. 
 
 These considerations would therefore lead us to expect that we should 
 find in the respiration of air-breathing animals that function in its purest 
 and least complicated form, and this is accordingly the case. If it be 
 merely the skin that is relied on,' as in the low orders of aerial life, or if 
 the mechanism be constructed on the type of carrying the air to the 
 blood, as in insects, or that of carrying the blood to the air, as in man, 
 the operation consists essentially in the escape of carbonic acid and 
 steam, and the reception of oxygen in return. 
 
 Respiration, like circulation, furnishes us with a signal instance of 
 the employment of purely physical principles for the accomplishment of 
 physiological purposes. It is with the pressure of the atmosphere, the 
 
INTERSTITIAL MOVEMENTS OF SOLIDS, LIQUIDS, GASES. 151 
 
 diffusion of gases, and the condensing action of membranes, _ 
 
 rrn -i Physical prm- 
 
 that we have now to deal. These give us so precise and per- cipies alone re- 
 
 spicuous an explanation of the act of breathing that it is 
 
 needless to look beyond them ; yet on that act depend the respiratory en- 
 
 highest operations of life. In this particular the Scriptures glne 
 
 have summed up the deductions of modern physiology in a single line 
 
 no metaphorical expression, but the simple assertion of a truth : He 
 
 " breathed into his nostrils the breath of life, and man became a living 
 
 soul." 
 
 Of the physical principles now to be dealt with, it is unnecessary to 
 say any thing respecting the pressure of the atmosphere, since that is 
 well understood; but not so with the phenomena of the diffusion of gas- 
 es, and the condensing action of membranes. Though these are subjects 
 which have been particularly examined by American physicians, the facts 
 they have elicited are little known abroad. For example, the error of 
 Valentin's statement respecting the diffusion exchanges of carbonic acid 
 and oxygen, and the uselessness of the elaborate discussions which have 
 originated therefrom, would at once have been recognized, had attention 
 been directed to the facts developed here almost twenty years ago. 
 , Interstitial motions are exhibited by solids, liquids, and gases. I 
 have had occasion to examine Roman silver coins, from the interstitial 
 interior of which the copper originally present had made its ^Ji^widK^ 
 way out to the surface, forming the greenish incrustation uids. 
 known as patina by antiquarians, the silver being left almost pure. In 
 speaking of absorption by the blood-vessels in Chapter VI., we had oc- 
 casion to dwell upon the same propensity as shown by liquids, the en- 
 dosmosis of Dutrochet being an example of it. The ready mobility of 
 this group of bodies, arising from their diminished cohesion, greatly pro- 
 motes these effects. Mr. Boyle collected a number of cases of solid move- 
 ments in his tract on the languid motions of bodies. 
 
 Gases and vapors, by reason of their total want of cohesion, present the 
 most striking examples of these effects. Their propensity to intermin- 
 gle with each other is manifested, even though they be obliged to pass 
 through crevices or winding passages. One of the first instances to which 
 attention was directed occurred under the observation of Dr. Priestley's ob- 
 Priestley, who found, on passing steam through an earthen 
 tube placed in a furnace, that air would be delivered at the of gases. 
 farther end. For some time he supposed that this experiment demon- 
 strated the conversion of water into air by a great heat f but eventually 
 traced it to its proper cause the escape of the steam outward through 
 the pores of the earthen tube, and the intrusion in the opposite direc- 
 tion of air from the furnace. This singular experiment may be well 
 shown by attempting to pass steam through a red-hot tobacco-pipe, the 
 
152 
 
 EXPEEIMENTS OF DALTON AND GRAHAM. 
 
 
 Graham's ex 
 
 
 end of which dips beneath some water. A torrent of gas bubbles will 
 escape. 
 
 Mr. Dalton demonstrated that if a light gas be placed above a heavy 
 Daiton'sexper- gas in a suitable apparatus, the former, notwithstanding its 
 ^~ nt . on t ? e levity will descend, and the latter, notwithstanding * its 
 
 diiiusion 01 f~ 
 
 gases. weight, will rise, and a complete and uniform intermixture 
 
 will result. By such experiments he was led to believe that 
 gases act as vacua to one another, and correctly explained the 
 uniform composition of the atmosphere on this property of dif- 
 fusion, or tendency of its constituents to intermix. 
 
 Thus, if a vial filled with hydrogen be placed with its 
 mouth downward over the mouth of a vial of the same size 
 containing carbonic acid gas, as shown at A, <?, Fig. 67, in the 
 course of a few moments the diffusion will be complete, and 
 if the mixture in either vial be examined, it will be found to 
 contain equal quantities of the gases. 
 
 Professor Graham extended Dr. Priestley's observations on 
 the passage through porous barriers. The sub- 
 stance he chiefly employed was a mass of dry 
 plaster of Paris. This enabled him to prove that Di ini5ion of 
 in the case of different gases diffusion takes place at different 
 rates, which are dependent on the density of the gas. Per- 
 haps the most satisfactory method of illustrating this class of 
 Diffusion results is by taking a porous earthenware cup, 
 throughporous a a; Fig. 68, such as is used in Grove's voltaic 
 battery, drying it perfectly, and cementing into 
 its mouth an open glass tube, b, three quarters of an inch 
 in diameter, and a foot or more long. A wide-mouthed bot- 
 tle, c c, being placed as a temporary cover over the porous 
 cup, it may be filled with hydrogen gas by displacement ; 
 and if the end of the glass tube be put into water contained 
 in a reservoir, d, the water will rush up the moment the 
 bottle is removed. When this motion is completed, if a jar 
 of hydrogen be held over the porous cup, the water will be 
 driven down with great rapidity, and a number of air-bub- 
 bles quickly escape. The extraordinary speed with which 
 a gas will flow in and out of pores could not be better dis- 
 played. This rapidity of motion is an element with which 
 the physiologist has to deal, as we shall presently find. 
 
 Even when the texture of the substance is much closer, and the pores 
 Diffusion of extreme minuteness, similar results can be obtained, as was 
 through in- shown in the experiments of Dr. Mitchell, of Philadelphia, who 
 employed thin sheets of India-rubber. If, over the mouth of 
 
 Fig. 68. 
 
 through 
 earthenware. 
 
 
PASSAGE OF GASES THROUGH POROUS FILMS. 
 
 153 
 
 Diffusion through India-rubber. 
 
 a glass bottle, such a thin tissue be tightly tied, and the bottle placed 
 in an atmosphere of carbonic acid gas, movement at once takes place, a 
 little air flowing out of the bottle into the carbonic acid, and so large a 
 Fig. 69. quantity of the acid passing the opposite way 
 
 that the India-rubber soon swells outward^ 
 and eventually caps the bottle like a dome, as 
 in Fig. 69, at b. Or, if the conditions be re- 
 versed, the bottle being filled with carbonic 
 acid, and then exposed to the atmosphere, the 
 India-rubber will be depressed, as at #, and 
 stretch so as almost fo sink to the bottom. 
 Such experiments therefore prove that, even 
 though barriers of a very close texture should 
 intervene, gases will pass through them, and 
 with so much force, as Dr. Mitchell showed, that many inches of mercury 
 may be lifted, nor does the movement cease until the gases on both sides 
 of the membrane have the same composition. 
 
 Other substances having a close texture may be thus 'readily permea- 
 ted. I found that a little bladder of shellac, blown on the Experiments 
 end of a glass tube, permitted the passage of the vapor aris- ^anTii^' 
 
 ing f rom water of ammonia. The "ids. 
 instantaneousness of these motions is, how- 
 ever, most -beautifully illustrated by employ- 
 ing soap-bubbles, the liquid nature of which 
 excludes the idea of pores in the strict accepta- 
 tion of that term. If a bottle, a a, Fig. 70, be 
 rinsed out with amponia, and then, by means 
 of a piece of glass tube, b b, a soap-bubble, <?, 
 be blown therein, the air from the bubble be- 
 ing immediately drawn into the mouth with- 
 out a moment's delay, the strong taste of the 
 ammonia is perceived. Or if a rod, dipped in 
 hydrochloric acid, be presented to the projecting end of the glass tube, 
 copious white fumes arise. This therefore shows that vapors will pass 
 through barriers having no proper pores, the transit taking place instan- 
 taneously. 
 
 Soap films enable us to demonstrate the endosmosis of gases in a very 
 advantageous manner, owing to their cohesiveness and thinness. If the 
 finger be dipped in soap-water, and then rapidly passed over the mouth 
 of an empty bottle, so as to leave a horizontal film attached across, on 
 exposing the bottle to carbonic acid gas, the horizontally of the film is 
 immediately disturbed, and it soon swells up into an almost spherical 
 dome. Or if the bottle be filled with carbonic acid, and then exposed 
 
 Instantaneous passage of gases 
 through films. 
 
154 PASSAGE OF GASES THROUGH POROUS FILMS. 
 
 to the air, the film is promptly depressed into a deep concavity, and 
 bursts. By these methods the passage of all kinds of vapors and gases 
 may be demonstrated, oxygen, hydrogen, carbonic acid, protoxide of ni- 
 trogen, the vapors of peppermint, lavender, and various essential oils. 
 
 By many experiments on such different substances, I found that the 
 Law of e uilib- ^ aw ^ &|fc$*l#iaHi f r gases and vapors is the same as for 
 rium, and ex- liquids. No matter what the thickness or thinness of a po- 
 f lfc ' rous barrier may be, movement takes place through it, un- 
 til the media on its opposite sides have the same chemical composition. 
 The observed action, in particular cases, will therefore altogether depend 
 on the circumstances untler which the experiment is made. A soap-bub- 
 ble full of carbonic acid, exposed to the air in a closed bottle, collapses 
 only to a certain extent, when the percentage constitution of the air it 
 contains is the same as that of the air in the bottle, contaminated with 
 the carbonic acid which the bubble has yielded it. But if the bubble be 
 exposed to the free atmosphere, it collapses almost completely, for now 
 the carbonic acid escapes finally away. 
 
 One of the most interesting facts connected with these results is the 
 Action throu h P er ^ ect manner in which a film of excessive tenuity will dis- 
 fiims of ex- charge these mechanical functions. With a little care, a 
 Ult7 ' film may be obtained so thin as to be invisible except in 
 certain lights, when it presents a velvety black aspect. In this condi- 
 tion, as Newton has proved, it is not thicker than three eighths of a 
 millionth of an inch, yet endosmosis takes place perfectly through it : it 
 expands and collapses, rises up into a dome, or is depressed into a con- 
 cavity, as the circumstances of its exposure may be. And this should 
 prepare us to admit that in organic tissues of the utmost degree of tenu- 
 ity these physical phenomena may occur, and that even under these most 
 unlikely circumstances such tissues may give origin to mechanical forces 
 of the greatest intensity, as we shall now prove. 
 
 Graham's law of the diffusion of gases has but a very limited physio- 
 logical application. The introduction of it in cases to which 
 of Graham's it does not properly apply has led to several errors. There 
 js nothing common in the result of the movement of gases 
 exposed freely to one another, and exposed with the intervention of a 
 close-pored tissue. The tissue itself gives origin to mechanical force of 
 such intensity as not only to modify the diffusion rate, but, in a great 
 many of the most important cases, absolutely to invert the direction of 
 the motion. Thus, through a stucco plug, in which the pores are of 
 sensible size, atmospheric air passes more rapidly to carbonic acid than 
 carbonic acid does to it, but through the thinnest film of water just the 
 reverse takes place. A bubble full of that acid, exposed to the air, lets 
 it escape with so much rapidity that in a few moments a complete col- 
 
FORCE OF PASSAGE THROUGH MEMBRANES. 
 
 155 
 
 lapse lias occurred. If the law of diffusion here held good, the bubble 
 should rapidly distend. 
 
 Moist membranes and films of water, by reason of their chemical affin- 
 ity for gaseous substances, and their consequent condensing Condensingac . 
 action, become the origin of great mechanical power. Under tion of mem- 
 such conditions, I have seen carbonic acid pass into atmos- 
 pheric air, driven, as it were, by the ; action of the membrane against a 
 pressure of ten atmospheres, and sulphureted hydrogen against a pres- 
 sure of twenty-five atmospheres, and, even against these great resistances, 
 the passage is accomplished with so much promptness as to lead to the 
 inference that a membrane will cause one gas to diffuse into another, even 
 though the apparent resistance be indefinitely great. 
 mg. 7i. In Fig. 71 is given a representation of the arrangement by 
 which these results were obtained. It consists of a strong 
 glass tube, seven inches or more in length and half an inch in 
 diameter, hermetically closed at one end, through which a pair 
 of platina wires, , <?, pass into the interior of the tube parallel 
 but not touching. The other end, a a, has a lip or rim turned 
 on it. Between the platina wires, a gauge-tube, d, is dropped, 
 to show the amount of condensation. On the top of the gauge- 
 tube a small test-tube, f, is placed, to contain a reagent suited 
 to the gas under trial, as lime-water for carbonic acid, acetate 
 of lead for sulphureted hydrogen, litmus-water for sulphurous 
 acid. Sometimes, instead of this test-tube, a piece of paper, 
 soaked in the proper reagent, was employed. The Measure of the 
 large tube was then filled with water to the height force of infii- 
 e e. Its lip or rim, a a, being next smeared with 
 burnt India-rubber, to insure absolute freedom from leakage, 
 a thin sheet of India-rubber was tied tightly over it, and over 
 
 Great force of . ' . J . 
 
 infiltration, this again, to give strength, a very stout piece of silk. Every 
 thing being thus arranged, the projecting wires, , c, were connected with 
 a voltaic pile, decomposition of the water ensued, oxygen and hydrogen 
 being disengaged, and a condensed mixture of atmospheric air and those 
 gases accumulated in the space a a e e, the gauge-tube showing the ex- 
 tent to which the condensation had gone. Now if the little tube, f, had 
 been filled previously with lime-water, and the whole arrangement was 
 introduced into, a jar of carbonic acid gas, the upper part of the lime- 
 water presently became milky, and after a time a copious precipitate of 
 carbonate of lime subsided. This would readily take place when the 
 gauge was indicating a pressure of ten atmospheres. In like manner, 
 when a piece of paper imbued with carbonate of lead had been introduced 
 into the tube, and a pressure of 24| atmospheres accumulated, on intro- 
 ducing the instrument into a vessel of sulphureted hydrogen, the paper 
 
156 GENERAL PRINCIPLE OF DIFFUSION. 
 
 quickly became brown. So sulphureted hydrogen can pass through a 
 sheet of India-rubber and diffuse into an atmosphere of oxygen, hydro- 
 gen, and atmospheric air beyond, though it is resisted by a pressure equal 
 to that of 800 feet of water. 
 
 The method of condensation here employed, because of its freedom from 
 mechanical concussions, enabled me to continue these researches up to 
 pressures of 50 atmospheres without leakage, in comparatively slender 
 tubes, and even under these circumstances gaseous diffusion seemed to 
 take place without any restraint. 
 
 It would lead me too far from my present object to pursue the con- 
 General facts sideration f these facts, and I must therefore be content to 
 connected with refer the reader to the memoirs in which they have been spe- 
 diffusion. cia j lv di scusse( k* i t i s sufficient to understand, 1st. That 
 gases simply exposed to each other inter-diffuse with great rapidity, and 
 at a rate inversely proportioned to the square root of their densities ; 2d. 
 That the same takes place through stucco plugs, or diaphragms with open 
 pores ; 3d. That a gas dissolved in a liquid, or held in a condensed state 
 by a solid mass, will exchange by inter-diffusion with any atmosphere 
 to which it may be exposed, in these cases the liquid or the solid mass 
 becoming a source of force ; 4th. That through a liquid, which, of course, 
 has no pores, gases arranged on its opposite sides will diffuse, but their 
 rate is no longer expressed by Graham's law ; 5th. That a liquid hold- 
 ing a gas in solution permits it to diffuse with another gas held by an- 
 other liquid in solution. 
 
 On the first of these principles, the fresh air of the bronchial tubes ex- 
 changes with the respired air of the pulmonary cells, the case being that 
 of a gas exposed to a gas. On the third of these principles, arterializa- 
 tion of the blood takes place, the case being that of a dissolved gas ex- 
 changing with a free gas ; and on the fifth of these principles, aquatic or 
 gill respiration depends, the case being that of a dissolved gas exchang- 
 ing with another dissolved gas. 
 
 Under its simplest aspect, the act of breathing consists in the elimina- 
 Various forms ^ on ^ car b oiu ' c acid from the system, and the introduction 
 of respiratory of oxygen. The manner in which the respiratory surface 
 itself from the former, and secures new supplies of the 
 
 mechanism. 
 
 latter, differs very greatly. In the lower orders which lead an aquatic 
 life, currents are established in the water by the aid of ciliary motion, and 
 by these the necessary changes are made. In others, in which respira- 
 tion is conducted by the skin, incessant locomotion is relied on ; and 
 again, in others, the water is drawn into the stomach and intestinal canal, 
 and every part bathed with the aerating medium. 
 
 In insects, the type of carrying air to the blood is developed to the ut- 
 * American Journal of Medical Sciences, May, 1838. 
 
RESPIRATION OF INSECTS AND FISHES. 
 
 157 
 
 most degree, there being great numbers of tracheal tubes pervading all 
 the soft parts. These occasionally present dilatations, acting as reser- 
 voirs the foreshadowing of the respiratory cavities of the higher tribes. 
 Of such, Fig. 72, representing the air-sacs or tracheal dilatations of the 
 
 Air-sacs of insects. 
 
 Spiracle of insect 
 
 scolia liortorum, is an illustration. The tracheal tubes Respiration of 
 communicate with the external air through openings which insects. 
 maybe obstructed by a valvular arrangement, as represented in Fig. 73. 
 The photograph from which this figure was taken shows such a spiracle 
 magnified 75 diameters. These organs may be seen arranged in rows 
 on each side of the body ; thus, in the common caterpillar, there are ten 
 pairs. The mode of guarding the orifice varies in different cases, some- 
 times tufts of hair being resorted to, and sometimes, as in the figure, 
 valves. 
 
 The true lung is first recognized in the swimming bladder of fishes as 
 a simple sac. In the carp, the tendency to a multi-chambered construc- 
 tion already appears under the form of two such bladders, #, #, communi- 
 
 eating with each oth- 
 er through a narrow 
 tube. These are con- 
 nected with the oesoph- 
 agus, 0, by means of 
 the pipe c d, the fish 
 being thus enabled to 
 remove at pleasure a part of the air contained in the sacs by muscular 
 compression. Though this mechanism is, as we have said, a rudiment- 
 ary lung, it does not properly subserve the duty of such an organ, but is 
 .employed for producing variations in the specific gravity of the animal 
 by compression or rarefaction of the included air. In these Respiration of 
 tribes the gills are the mechanism for aeration, which is ac- fishes - 
 
 Air-sac of fish. 
 
158 
 
 RESPIRATION OF FISHES AND REPTILES. 
 
 complished in the following manner : The mouth is periodically filled 
 with water, which is driven past the gills by muscular compression, and 
 thereby the carbonic acid is removed from the blood which circulates in 
 those organs, and oxygen is obtained in return. For this reason, a fish 
 dies very quickly when its mouth is kept open. The angler knows that 
 it is not owing to any loss of blood, nor to any injurious lesion that the 
 hook may cause, but simply to suffocation, the water no longer lifting the 
 gill covers, but merely passing out through the open mouth. 
 
 The experiments of Humboldt and Prove^al clearly demonstrate the 
 analogy between aquatic and aerial respirations ; for water is not de- 
 composed by the breathing of fishes : it is the air dissolved in it that is 
 used. In the sample examined by these chemists, there was 20.3 per 
 cent, of its volume of air, consisting of oxygen 29.8, nitrogen 66.2, and 
 carbonic acid 4.0, in the hundred parts. After the fishes had remained 
 in it for a due time, it still contained 17.6 per cent, of its volume of air, 
 but this in 100 parts now consisted of oxygen 2.3, nitrogen 63.9, and 
 carbonic acict 33.8. There had therefore been a consumption of oxygen 
 and evolution of carbonic acid, together with a slight removal of nitrogen, 
 this being the general result witnessed in aerial respiration. In a sim- 
 ilar course of experiments on the breathing of gold fishes, 
 made by myself, the result corresponds to the preceding 
 statement, only the water I used was richer in oxygen gas, 
 and the transposition into carbonic acid did not seem by 
 any means to be so complete. I also remarked the same 
 diminution in the quantity of nitrogen, but am disposed to 
 attribute it not so much to the consumption of that gas by 
 the fishes as to its diffusion from the water into the atmo- 
 sphere, the solvent power having changed by the substitu- 
 tion of carbonic acid for oxygen. 
 
 In reptiles the lung presents the sac-like form, as in Fig. 
 Respiration of 75, a pulmonary artery passing on one side, 
 reptiles. an( j a pulmonary vein returning on the other : 
 
 a is the trachea ; #, its bifurcation ; <?, pulmonary artery ; 
 d, d, pulmonary vein. It often occurs that. '"the two lungs 
 are not equally developed, one of them, B, being rudiment- 
 ary as compared with the other, A. Into such a sac in ser- 
 pents the air is forced by muscular contraction, a kind of 
 swallowing. It is expelled from them by the contraction 
 of the abdominal muscles, and hence the hissing sound 
 which it emits during its expulsion. From the simple sac 
 to the cellular lung the advance is made by degrees, a de- 
 velopment of parietal cells upon the inner surface taking 
 place. At the intermediate stage, between the simple sac 
 
STRUCTURE OF THE LUNGS. 159 
 
 and the highly subdivided respiratory organ of the mammals, the condi- 
 Fig. T6. tion of things is well illustrated by the lungs 
 
 of the frog. In Fig. 76, a is the hyoid appa- 
 ratus ; b, cartilaginous ring at the root of the 
 lungs ; c, the pulmonary vessels ; and d, d, the 
 pulmonary sacs. 
 
 Of all tribes, the respiratory mechanism is 
 most highly developed in birds, Respiration of 
 which, besides being provided with birds - 
 lungs, have air-sacs between the muscles, and 
 respiratory membranes spread on the interior 
 of the hollow bones. It is in consequence of 
 this that a bird is killed so readily, even by a 
 Lungs of frog. Yerv small shot, since it is scarcely possible to 
 
 make a perforation into any part of the body without opening the respi- 
 ratory cavity. 
 
 In man, the bronchial tube, as it passes into each lung, branches forth 
 like a tree, the walls of the tubelets thus arising having car- 
 
 , .-, . - . (, , . Lungs of man. 
 
 tilagmous rings to preserve their form under compression, 
 circular organic muscular fibres to enable them to contract, and longitu- 
 gitudinal fasces of elastic tissue to shorten them after extension. In 
 their interior they are covered with mucous membrane provided with 
 cilia. When the proper degree of minuteness, about -^ of an inch, is 
 reached, they consist alone of elastic membrane, interspersed with mus- 
 cular fibres, and upon their sides the air-cells open ; sometimes single 
 ones, or sometimes many cells communicating with one another, discharge 
 through the same orifice, the tubelet itself ending in a cell. The air- 
 cells have various dimensions, from JL to 1 2 * tf of an inch. Their struc- 
 ture is like that of the tubelet. The pulmonary capillaries are spread 
 so closely upon them that the spaces between them are less than their 
 own diameters, which, on an average, are 3-^-3- of an inch. As the cells 
 are close together, the blood-vessels passing between them are brought 
 in communication with the air. on both sides, and arterialization is thus 
 rapidly and completely performed. Each tubelet, with the air-cells thus 
 clustered upon it, is a miniature representation of the lung of a reptile. 
 These cells themselves communicate by lateral apertures with one an- 
 other. The membrane which lines their interior is sharply folded at the 
 apertures, and there are reasons for supposing that it contains organic 
 muscular fibres. It is stated that each terminal bronchus has nearly 
 20,000 air-cells clustered upon it, and that the total number is 600 
 millions. 
 
 The mode of distribution of the air-tubes is represented in Fig. 77. 
 a is the larynx ; b b, the trachea, the upper letter corresponding to the 
 
160 
 
 STRUCTURE OF THE LUNGS. 
 
 cricoid cartilage ; c, the left bronchus ; d, the right bronchus ; e,f, g, its 
 ramifications in the right lung, j j ; A, i, ramifications of the left bron- 
 chus in the left lung, k L 
 
 Fig. 77. Fig. 78. 
 
 Human air-tubes. 
 
 The heart and lungs. 
 
 Fig. 78, arrangement of the heart and lungs, the latter in part section. 
 1, left auricle of the heart ; 2, right auricle ; 3, left ventricle ; 4, right 
 ventricle ; 5, pulmonary artery ; 6, aorta ; 7, superior vena cava ; 8, in- 
 nominata; 9, left primitive carotid; 10, left subclavian, ; 11, 12, upper 
 rings of trachea and cartilages of the larynx ; 13, upper lobe of right 
 lung; 14, upper lobe of left lung; 15, right pulmonary artery; 16, 16, 
 lower lobes of lungs. 
 
 Fig. 79 illustrates the manner of 
 distribution of blood-vessels on the 
 air-cells of the lungs. 
 
 As the blood to be arterialized 
 passes through the pulmonary capil- 
 laries, its discs can only move in sin- 
 gle files, and even then probably un- 
 dergo a compression which changes 
 their form. As soon, however, as 
 they escape into the larger vessels, 
 their elasticity enables them to recov- 
 
 Distribution of capillaries on air-cells of the lungs. er their or igmal shape. 
 
 By the aid of this elaborately constructed mechanism the air is brought 
 Three stages in to tne blood. There are three distinct stages through which 
 the introluc- Jt has to pass. The first is the filling of the trachea and 
 larger ramifications of the bronchial tubes : this is accom- 
 plished by atmospheric pressure, brought into play by muscular contrac- 
 
MOVEMENTS OF KESPIRATION. 
 
 161 
 
 Fig. SO. 
 
 tion. The second stage is the translation of the fresh air from the larger 
 bronchial tubes to the ultimate air-cells : this is accomplished on the 
 principle of gaseous diffusion. The third stage is the passage from the 
 air-cells into the blood : this is through the wall of the cell, the wall of 
 the blood-vessel, and the sac of the blood disc ; it involves passage 
 through membranes, and implies their condensing action. Each of these 
 three stages we have now to consider. 
 
 1st. The introduction of fresh air into the trachea and larger ramifi- 
 cations of the bronchial tubes is accomplished by muscular The effect of the 
 contraction, which calls into operation atmospheric pressure, pressure of the 
 In tranquil respiration the diaphragm is nearly sufficient for 
 this purpose. This muscle, forming the convex floor of the chest, as soon 
 as it contracts, assumes more nearly a plane figure, thereby increasing 
 the content of that cavity ; and, just as in a common bellows, when the 
 lower board is depressed, the air flows in through the pipe, so^on the de- 
 scent of the diaphragm, the air flows in through the trachea, forced by 
 the external pressure. 
 
 An experimental illustration of the manner in 
 which the air is introduced into the cavity of the 
 lungs by the descent of the floor of the chest, 
 and then expelled by its elevation, is represented 
 in Fig. 80, in which a a is a tube of glass half 
 an inch or more in diameter, and six or eight 
 inches long, to the lower end of which a blad- 
 der, b, is tightly attached. The tube is passed 
 through the neck of a bell-jar, c <?, air tight. A 
 large glass reservoir of water, filled to the height 
 d d, receives the bell-jar, as shown in the figure. 
 When the jar is depressed in the water the air 
 is expelled from the bladder, and when the jar 
 is raised the air flows in. By alternately ele- 
 vating and depressing the bell, the bladder exe- 
 cutes movements like those of the lungs, of which, 
 indeed, it is a representation; the glass tube be- 
 ing the trachea, the bell-jar the walls of the chest, 
 and the rising and falling water-level the rising 
 In this illustration the bladder is, of course, per- 
 
 Mechanism of respiration. 
 
 and falling diaphragm. 
 
 fectly passive, as was at one time supposed to be the case with the lungs : 
 an erroneous opinion, which will presently be corrected. 
 
 In the mature period of life, and especially in deep respiration, the ac- 
 tion of the diaphragm is insufficient for the introduction of air, Manner of in _ 
 and a still farther volume is obtained by raising the ribs, which troducing the 
 increases the dimensions of the chest from right to left, and air> 
 
162 MOVEMENTS OF EESPIEATIOX. 
 
 also from front to back. In men, this effect* takes place more particular- 
 ly through the movements of the lower ribs, and this form of respiration 
 is therefore sometimes called the inferior-costal ; but in women the upper 
 jibs are more movable, the dilatation of the chest is there greater, and 
 the respiration therefore designated as the superior -costal. In these 
 movements of the ribs, and especially in violent respiration, many mus- 
 cles are involved. 
 
 In the reverse act, that is, in expiration, or the expulsion of air through 
 the trachea, the floor of the chest is raised. The diaphragm, when it 
 contracted, made pressure upon the viscera of the abdomen, and forced 
 the muscular walls of that cavity outward ; but, as soon as the diaphragm 
 relaxes, the abdominal muscles contract, and thus an antagonizing force 
 is originated which tends to expel the air. In this the elasticity of the 
 lungs and of the walls of the thorax itself affords a great assistance. 
 Owing to Jhis elasticity, the muscular exertion required for the introduc- 
 tion of the air greatly exceeds that required for its expulsion. 
 
 In tranquil respiration, we may regard the changing of the air to be 
 accomplished by the alternate depression and elevation of the diaphrag- 
 matic floor of the chest. On an average, this takes place 1 7 times in a 
 minute, and in an adult of the standard size we may assume that 17 
 cubic inches of air are introduced at each inspiration. Of every five 
 breaths one is usually deeper than the other four. The statement often 
 made, that five pulsations correspond to one respiration, must be received 
 with a certain restriction. In pneumonia, the respirations may be to 
 the pulsations as 1 to 2 ; in typhoid fevers, as 1 to 8 ; and even in a 
 state of health there may be considerable variations. 
 
 By muscular movements, which thus call into action atmospheric pres- 
 sure, the air is drawn, but not forced, into the respiratory apparatus. 
 Considering, however, the solid contents of the lungs, which can not be 
 taken at less than 200 cubic inches, it is clear that the amount is not 
 more than sufficient to fill the nasal passages, the trachea, and the larger 
 ramifications of the bronchial tubes. Lying nearest to the outlet, it 
 would be the first to be expelled by the act of expiration. There could 
 be no exchange of the fresh for the foul air, unless some additional means 
 were employed for accomplishing its transference from the larger ramifi- 
 cations of the bronchial tubes to the remotest air-cells. 
 
 2d. The transference of fresh air to the cells is accomplished by re- 
 sorting to two different principles, the diffusion of free gases into one an- 
 other, and muscular contraction. 
 
 An estimate of the relative share which each of these takes is arrived 
 Effect of gase- at by an examination of the absolute velocity with which 
 Us^oforganic S ases diffuse into one another. The statement that gases 
 muscle fibres, act as vacua to each other has led to some very erroneous 
 
PASSAGE OF OXYGEN TO THE BLOOD. 163 
 
 conclusions. It has "been taken for granted that the actual diffusion is 
 very rapid, perhaps approaching to the velocity with which gases rush 
 into a void. But I have shown* that this is altogether a misconception, 
 and that the transit of fresh air from the bronchi, exchanging with foul 
 air from the cells, if conducted on that principle alone, would require a 
 period greatly beyond the time occupied for one respiratory act, which is 
 about three seconds and a half. 
 
 To an additional agent we must therefore look for a complete explana- 
 tion, and this, I think, is presented in the circular organic fibres of the 
 bronchial tubes and cells. It has long been understood that these pos- 
 sess the power of varying the capacity of the tubes. 
 
 With this agency in view, this second stage of the process is accom- 
 plished as follows : The carbonic acid, vapor of water, and excess of ni- 
 trogen, if any, that have accumulated in the cells belonging to any given 
 bronchial tree, are expelled therefrom by the muscular contraction of the 
 circular organic fibres, and are delivered into the larger bronchial tubes, 
 in which diffusion at once takes place with the air just introduced. As 
 soon as the expiration is completed, relaxation of the muscular fibres oc- 
 curs, and the passages and cells dilating, both through their own elastic- 
 ity and the exhaustive effect arising from the simultaneous contraction of 
 other bronchial trees, fresh air is drawn into them, the alternate expulsion 
 and introduction being accomplished by muscular contraction and elas- 
 ticity, the different bronchial trees coming into action at different periods 
 of time, some being contracting while others are dilating. 
 
 3d. The third stage is the passage of oxygen from the cells to the blood: 
 it is through the wall of the cell, the wall of the blood-vessel, Passage of ox- 
 and the sac of the blood disc. The carbonic acid issues from gen thr u s h 
 
 the membranes 
 
 the plasma, and passes through the wall of the blood-vessel to the blood. 
 and the wall of the cell. 
 
 Many physiologists have supposed that this exchange of oxygen for 
 carbonic acid takes place on the principle of diffusion. On Exchan e of 
 the authority of Valentin and Brunner, it has been asserted carbonic acid 
 that the proportional exchange actually observed is 1174 of 
 oxygen for 1000 of carbonic acid, these being the theoretical quantities 
 under the law of diffusion ; but there is no difficulty in proving that this 
 is a physical impossibility, for the exchange is not merely that of oxy- 
 gen and carbonic acid; it is much more complicated. The lungs regu- 
 late the quantity of free nitrogen in the system, and there is a constant 
 escape of the vapor of water. These bodies, moreover, are not present- 
 ed in the gaseous state, but in that of liquid solution ; and the wall of 
 the cell, of the pulmonary capillary, and of the blood disc, by their con- 
 densing action, totally disturb the conditions of diffusion. 
 * American Journal of Med. Sciences, April, 1852. 
 
164 ESCAPE OF CARBONIC ACID FROM THE BLOOD. 
 
 If an aqueous film, not more than three eighths of a millionth of an inch 
 in thickness, can completely disturb the law of diffusion by the condens- 
 ing action it exerts on carbonic acid and oxygen, what may be expected 
 from the moist walls of the air-cells and pulmonary artery, which con- 
 jointly must be more than a thousand times as thick ? 
 
 From these complications, it is not possible to assign any definite ratio 
 as expressing the gaseous exchange between the interior of the cells and 
 the blood, for, so far from this being a case of exchange between two gas- 
 es without any obstruction intervening, the condition under which alone 
 the law of diffusion applies, the nitrogen is doubtless in a state of solu- 
 tion in the blood, the steam in the liquid condition of water ; and re- 
 specting the carbonic acid, nothing certain is known whether it be in so- 
 lution or chemically combined. Perhaps it is united with soda in the 
 blood as a bi-carbonate. From this latter substance hydrogen gas will 
 expel one half of its carbonic acid, and in like manner a stream of hy- 
 drogen gas passed through blood deprived of its fibrin removes carbonic 
 acid. Upon such principles it has been supposed that atmospheric oxy- 
 gen removes carbonic acid from the blood during respiration, just as would 
 a stream of hydrogen rernove half the acid from a solution of bi-carbon- 
 ate of soda. 
 
 The generation of carbonic acid in the system is commonly localized 
 Place of the ^y referring it to the soft tissues. But, though doubtless 
 generation of much originates in this way, as is illustrated by the case of 
 Cld ' insects, in which the air is carried directly to the parenchyma 
 of the organs without the intervention of any proper oxidizing blood, 
 there can be no doubt that in man, as in all the higher tribes, a very 
 large proportion is generated in the blood itself. If there were no other 
 reason to bring us to this conclusion, it would be sufficient to recall that 
 ultimate oxidation by no means occurs at 6nce, but that the various 
 wasted products pass from stage to stage in their retrograde career. 
 Thus, between the syntonin of muscular fibre and the urea of the urine, 
 many steps or stages intervene, and that much of these changes is ac- 
 complished in the blood itself is demonstrated by what occurs in the 
 use of excesses of starch, albumen, or gelatine in the food. Such sub- 
 stances, finding access through the absorbents in a modified form, but not 
 wanted for the repair of any part, are dismissed without ever entering 
 into the composition of any organ, by the lungs or the kidneys as prod- 
 ucts of oxidation or derivatives thereof. 
 
 The act of respiration in man is therefore accomplished in the follow- 
 Generai state- ing way. The air, introduced by atmospheric pressure, 
 process of res- brought into play by the action of the diaphragm and other 
 piration. respiratory muscles, fills the nasal passages, the trachea, and 
 
 larger ramifications of the bronchial tubes. Between it and the gas 
 
GENERAL STATEMENT OF THE KESPIEATOEY ACT. 165 
 
 coming from the pulmonary vesicles, diffusion steadily takes place, tend- 
 ing to remove the cell gas into the atmosphere; but this gas is not 
 brought from the vesicles by diffusion alone, which could not act with 
 sufficient speed, but by the contraction of the circular organic muscles of 
 the bronchial tubelets and of the cells, the different bronchial trees not 
 acting simultaneously, but successively. As soon as contraction is over, 
 the tubes expand by their elasticity, and the air is drawn into the cells, 
 each bronchial tree, by its contraction, aiding the expansion of the adja- 
 cent ones. The lungs are therefore not altogether passive during respi- 
 ration, as is sometimes said. The exchange between the gas in the cells 
 and that in the blood does not take place through simple diffusion, or in 
 quantities proportional to the diffusion volumes of oxygen and carbonic 
 acid. It is a complex diffusion, in which the disturbances arise from the 
 gases in the blood being either dissolved or combined, and through sev- 
 eral intervening membranes, that of the air-cells, that of the pulmonary 
 artery, and that of the blood disc, all of which exert a condensing action, 
 of the result of which it is impossible to furnish any numerical estimate. 
 The process ends by the expulsion of the foul air which has accumulated 
 in the larger bronchi and trachea, by the diminution which takes place 
 in the capacity of the chest during expiration, occasioned by the contrac- 
 tion of the expiratory muscles, the elasticity of the walls of the chest, 
 and of the lungs themselves. 
 
 Such is the arrangement by which fresh air is constantly presented to 
 the blood, and the gases and vapors exhaling from it are removed. The 
 degree of exhaustion occurring in the chest scarcely justifies the ex- 
 pression sometimes used, "a tendency to a vacuum," since it is rarely 
 more than competent to raise water a single inch. This may be readily 
 proved by dipping a glass tube, open at both ends, and half an inch in 
 diameter, into a cup of water, and placing the projecting extremity be- 
 tween the lips, taking care to keep the muscles of the mouth at complete 
 rest. It will then be seen that at each inspiration the water rises about 
 an inch, and at each expiration is depressed to a similar extent. Its 
 movements indicate the degree of rarefaction or compression occurring in 
 the chest. 
 
 It has been found convenient to consider the gaseous contents of the 
 lungs under several different titles : 1st. The residual air is Divisions of 
 that portion which can not be removed by the most power- content, e( of S tiie 
 fill expiration ; 2d. The supplemental air remains after tran- lungs. 
 quil respiration, but can be removed at will ; 3d. The breathing or tidal 
 air is that portion which changes by tranquil inspiration and expiration ; 
 4th. The complemental air is that which can be inhaled by the deepest 
 inspiration, over and above that introduced by ordinary breathing. 
 These are terms introduced by Mr. Jeffreys. 
 
166 
 
 VOLUME AND CHANGES OF THE GAS. 
 
 "The amount of air that can be expelled by the deepest expiration 
 Connection be- after the fullest inspiration" bears a singular relation to the 
 tiIn e and Pira ~ hei S lli of the individual, as was discovered by Dr. Hutch- 
 height, inson. " For every inch of stature from five to six feet, 
 eight additional cubic inches of air at 60 Fahr. may be thus given out." 
 The quantity of air which can be thus expelled for the stature of five feet 
 one inch is 174 cubic inches, and for six feet, 262. It is independent of 
 the absolute capacity of the chest. 
 
 The diurnal amount of air introduced into the lungs has been variously 
 Volun- and estimated from 226 to 399 cubic feet. A part, from 4 to 6 
 changes of the per cent., of the oxygen thus introduced disappears in the 
 respired gas. J U ngs, anc i the expired air is charged with from 3 to 5 per 
 cent, of carbonic acid. But that nothing analogous to combustion occurs 
 in those organs is proved by their temperature, which is not higher than 
 that of other parts of the system. Moreover, carbonic acid can be with- 
 drawn from venous blood in a Torricellian vacuum, and still better by 
 agitating the blood with such gases as hydrogen and nitrogen, proving 
 that that gas pre-exists in the venous blood before its entiy into the 
 lungs, and is not formed in those organs, unless, indeed, it exists as a bi- 
 carbonate, as already mentioned. The quantity of carbonic acid thus 
 disengaged is less than the quantity of oxygen absorbed, because much 
 of the latter is consumed in the production of sulphuric and phosphoric 
 acids, which escape in the urinary secretion, as indeed does a large quan- 
 tity of carbonic acid itself. 
 
 The experiments of Vierordt show that the expiration, in a state of 
 Vierordt's rest, contains 4.334 per cent, of carbonic acid; that, as the 
 experiments, number of respirations per minute increases, the percentage 
 amount of carbonic acid diminishes ; and that for every expiration, with- 
 out reference to its duration, there is a constant amount of carbonic acid, 
 namely, 2.5 per cent., to which we must add a second value, expressing 
 the quantity of carbonic acid, and which is exactly proportional to the 
 duration of the respiration, as is shown in the following table. 
 
 Eespirations 
 per minute. 
 
 Percentage of 
 carbonic acid. 
 
 Constants. 
 
 Augmentation of the percentage 
 of the carbonic acid for the 
 duration of the respiration. 
 
 6 
 12 
 24 
 
 48 
 96 
 
 5.7 
 4.1 
 3.3 
 2.9 
 
 2.7 
 
 2.5 
 2.5 
 2.5 
 2.5 
 2.5 
 
 3.2 
 1.6 
 0.8 
 0.4 
 0.2 
 
 Vierordt also estimates that, for the entire removal of the carbonic 
 acid from the blood, more than three hundred respiratory acts per minute 
 would be required. To some extent, the depth of the respiration will 
 compensate for want of frequency. Thus he shows that in an expiration 
 of double the usual volume, the quantity of carbonic acid removed is 
 
RATIO OF INSPIRED AND EXPIRED OXYGEN. 167 
 
 nearly equal to that which would be exhaled by respirations of three 
 times the normal frequency, and on examining a single respiration, he 
 demonstrates what, however, would obviously be foreseen from a consid- 
 eration of the circumstances of the case, that the last portions of the ex- 
 piration are the richest in carbonic acid. Thus the first half of a respi- 
 ration contained only 3.72 per cent, of carbonic acid, the last half 5.44 
 per cent.. 
 
 With respect to the ratio between the quantity of oxygen inspired and 
 that contained in the expired carbonic acid, a variation will K at i ooflhein 
 be observed, depending on many conditions, as, for example, spired and ex- 
 on the nature of the food. Thus, with a carbohydrate, the pired oxygen ' 
 quantity of oxygen in the carbonic acid will always be less than that in- 
 spired, a portion being employed in the destruction of the systemic nitro- 
 genized material which is undergoing decay. This destruction of nitro- 
 genized material is not sufficient for the support of animal heat, and 
 hence either carbohydrates introduced by 'the food, or fat already exist- 
 ing in the system, must be resorted to for the purpose of making up the 
 deficiency. With such variations in the requirements of the system, 
 and variations in the nature of the food, the ratio of the oxygen intro- 
 duced to that in the carbonic acid removed must also vary. 
 
 For the perfect oxidation of the different elements of food, very differ- 
 ent quantities of oxygen are required ; thus, for the oxidation of 100 
 parts of fat, it would require 292.14 of oxygen; for that of starch, 118.52; 
 for that of muscle, 147.04. 
 
 For reasons to be considered when we treat of the production of heat, 
 the quantity of carbonic acid disengaged varies with external Variations in 
 circumstances. When the weather is cold it is greater than the respired 
 when it is warm. Thus at 68 there is twice as much lib- air ' 
 erated as at 106. It increases during exercise and after eating, but 
 diminishes during sleep. More is set free by men than by women ; it 
 also varies with age, the proportion rising from eight years to thirty, re- 
 maining stationary to forty, and then declining. It changes with the 
 frequency of the respirations. The total quantity of carbon daily re- 
 moved by respiration may be estimated at eight ounces. 
 
 Besides the carbonic acid removed, a large quantity of water is ex- 
 creted by the lungs, for the expired air may be regarded as Water removed 
 saturated, or containing the maximum quantity of water for in espiration. 
 94. For the vaporization of this water much heat is consumed, as is 
 likewise the case for the warming of the introduced air, which, no mat- 
 ter wha"t the external temperature may have been, is brought to that of 
 the lungs. 
 
 With respect to the absolute amount of air expired, and also the quan- 
 tity of water removed by the lungs, some experiments have recently been 
 
168 QUANTITY OF AIR AND WATER. 
 
 made by my son, Dr. J. C. l)raper ; the principle upon which they were 
 Quantit of air con( lucted may be thus briefly stated. The air from the 
 expired per lungs, which has a dew-point of 94, was passed by a wide 
 tube through a metallic condenser kept at 32, care being 
 taken to have as little obstruction as possible to its egress. The weight 
 of the water collected in the condenser furnished the means of calculating, 
 by a simple formula, the quantity of air which had been expired, for the 
 vapor, leaving the respiratory passages at 94, and that leaving the con- 
 denser at 32, were at their maximum densities. Computations exe- 
 cuted upon data obtained on this principle furnish the following, among 
 other interesting results : 
 
 1. On making sixteen respirations in the minute, and continuing the 
 experiment for twenty minutes, the average of five different series of ex- 
 periments gives 622 cubic inches of air expired each minute. 
 
 2. On making six respirations in a minute, and continuing the trial 
 for twenty minutes, the average of three series of experiments gives 511 
 cubic inches for the air expired each minute. 
 
 3. On making thirty-three respirations in a minute, and continuing the 
 experiment for twenty minutes, the average amount of air is 1077 cubic 
 inches for the air expired in each minute. 
 
 On comparing these three statements, it appears that, the first repre- 
 senting normal, the second very slow, the third very quick respiration, 
 the absolute amount of air removed from the lungs is directly proportion- 
 al to the number of respiratory acts in a given period of time, and this 
 notwithstanding such variations in the depth of the inspirations as un- 
 der such circumstances are likely to occur. 
 
 With respect to the quantity of water removed from the lungs, he also 
 shows, 
 
 Quantit of wa ^' 1^ ia *' at an atmospheric temperature of 55, the dew- 
 ter exhaled per point being 49, the number of expirations sixteen per minute, 
 the quantity of water removed per minute is 4.416 grains. 
 
 5. The other conditions remaining the same, but the respirations re- 
 duced to six per minute, the amount of water removed per minute is 
 3.586 grains. 
 
 6. The other conditions remaining as before, but the number of res- 
 pirations increased to thirty-three per minute, the amount of water re- 
 moved p'er minute is 7.560 grains. 
 
 From these statements it therefore appears that the quantity of water 
 removed from the blood by respiration increases- with the frequency of 
 the respiratory acts, and this notwithstanding variations which, under 
 such circumstances, must take place in their depth. Theoretically, it is 
 also obvious that the absolute amount thus expired is dependent on the 
 existing dew-point of the air. In the general table, given on page 15, 
 
EFFECT OF RESPIRATION ON THE BLOOD. 169 
 
 the amount of water is calculated from Seguin's experiments, but it ap- 
 pears from these results, which are obtained by a much more accurate 
 process, that the number there given is undoubtedly too high. 
 
 The time of exposure of the blood to the air is only a second or two. 
 The color changes, as has been described before, from blue to crimson, 
 and the temperature rises a degree or two, as is shown by an examina- 
 tion of the left cavities of the heart. The water thus removed is not 
 pure, but contains animal matter in a state of decay. 
 
 Though we have treated of the act of respiration as consisting of two 
 separate and consecutive stages, inspiration and expiration, Respiration is 
 in reality it proceeds continuously. At the respiratory sur- 
 face, which is the wall of the air-cell, the passage of oxygen ing. 
 inward, and of carbonic acid and steam outward, takes place in a steady 
 and unvarying manner. The periodicity under which it has been conven- 
 ient to speak of this function concerns only the introduction and removal 
 of gases from the large air-ways. 
 
 Considering, therefore, the continuous loss of water which the venous 
 blood brought by the pulmonary arterial branches undergoes, Effect of respi- 
 it must give rise necessarily to a greater density in the blood 
 on the left side as compared with that of the right side of blood, 
 the heart. The total quantity of blood passing through the lungs in one 
 minute is 225 ounces, and the loss of water from this in the same time 
 can not be more than 7 grains. This, therefore, shows that the actual 
 loss of water by the blood during its passage over the air-cells is about 
 15 ^ QO part, a quantity which is altogether inappreciable, so far as its in- 
 fluence on the specific gravity is concerned, and showing us that the ob- 
 servations which some experimenters have made on this point, with a 
 view of demonstrating an increased spissitude, density, or cohesiveness 
 of the blood on the left side of the heart, from the giving up of its water 
 as it passed through the respiratory organ, are either exaggerated or af- 
 fected by some deceptive cause. 
 
 The introduction of an irrespirable gas into the lungs, or the prevention 
 of the access of the atmosphere, brings the circulation of the Effect of the in- 
 blood to a stop ; for that movement depends, as I have shown, 
 on the aeration taking place in the pulmonary capillaries. In gases. 
 such cases there will be an engorgement of the right heart and vessels 
 arising therefrom, but, if the stoppage has not lasted too long, the current 
 may be re-established by re-establishing the respiration. Death com- 
 monly ensues on an exclusion of the air for five minutes, and, in cases 
 of drowning, it is rare for restoration to be effected if the immersion has 
 lasted more than four. 
 
 In the respiration of protoxide of nitrogen, a gas which is an energetic 
 supporter of combustion, and acting more powerfully on the animal sys- 
 
Fig. 81. 
 
 170 EXPERIMENTS OF REGNAULT AND EEISET. 
 
 Effect of rot tem wnen res pi re( l tnan even oxygen itself, on account of its 
 oxide of nitro- ready condensibility by pressure, or by membranes, and sol- 
 ubility in water, the circulation is greatly quickened at first, 
 and a state of exhilaration ensues ; but this is soon followed by a con- 
 dition of depression, or even of coma, for the quantity of carbonic acid 
 produced in the system is now so great that the lungs are wholly inade- 
 quate to effect its removal, and all the symptoms of poisoning by car- 
 bonic acid come on. 
 
 Zimmerman found that a rabbit exhaled 12 J grains of carbonic acid 
 per hour when breathing atmospheric air, but that the quantity rose at 
 once to 20 grains per hour when it was caused to breathe protoxide of 
 nitrogen. But by far the most complete and important series of experi- 
 Summary of ments yet made in regard to the relations of the aerial me- 
 Regnauit's and dium and the respiring animal is that of MM. Eegnault and 
 iments or; res- Reiset, published in the Annales de Chimie, Juillet, 1849, of 
 piration. which, since it may be taken as a model of physiological in- 
 
 vestigation, a brief abstract is here given. 
 
 The apparatus they 
 employed is represented 
 in Fig. 81. It possesses 
 the great advantage over 
 all experimental arrange- 
 ments heretofore employ- 
 ed in permitting an ani- 
 mal to be kept even for 
 many days in a limited 
 volume of air, but under 
 such circumstances that 
 
 Experiments on respiration. that ail* WaS Constantly 
 
 kept at its normal composition by the automatic motions of the instru- 
 ment itself: oxygen being thus furnished as it was required, and car- 
 bonic acid removed. 
 
 The arrangement consists of three parts : 1st, a chamber or bell, Z, for 
 inclosing the animal, surrounded by a jar filled with water, the tempera- 
 ture of which could be ascertained by a thermometer, L In the interior 
 of the bell was a platform perforated with holes, by the aid of which the 
 'excretions could be collected. On one side, at^>, was a pressure gauge, 
 connected with the bell by a tube, and showing the condition of conden- 
 sation or rarefaction of the included atmosphere. 2d. At the same side, 
 the bell communicated, by means of India-rubber tubes, m, n, with two 
 cylindric vessels, q, r, filled with a solution of caustic potassa, and which 
 were driven by the aid of powerful clock-work in such a way that the 
 one alternately rose and the other descended, the flexible tube s permit- 
 
EXPEEIMENTS OF EEGNAULT AND EEISET. 171 
 
 ting this motion. The result of this was that a portion of the air of the 
 bell was alternately drawn into each of the cylindric vessels, its carbon- 
 ic acid removed by the potash, and then it was returned ; so, as fast as 
 the animal produced that gas by breathing, the potash removed it, giving 
 rise, therefore, to a tendency to a certain amount of rarefaction in the air 
 of the bell ; but, 3d, on the opposite side of the bell were placed three 
 receptacles, e, e', e", filled with pure oxygen gas, which flowed into the 
 bell through the tubes fh, fh, f'h, to compensate for that rarefaction, 
 coming in by a bubble at a time through the little potash flask i, the 
 oxygen being pressed out of the reservoirs by a solution of chloride of 
 calcium descending through a stop-cock, c, from a reservoir, b b', kept at 
 a constant level in the usual manner by the flasks a, a', a". As fast as 
 one receptacle was exhausted, the pressure tube was successively con- 
 nected with the others, and so the supply kept up. Attached to the 
 stand supporting the animal was a eudiometer, o, which enabled a small 
 quantity of air to be withdrawn from the bell at any moment for the 
 purpose of analytical examination. For other details of this apparatus, 
 and the particulars of its method of use, reference may be made to the 
 original memoir itself. It is sufficient for the present purpose to under- 
 stand that an animal could be kept in the interior of this bell for several 
 days without showing any signs of discomfort, pure oxygen being sup- 
 plied to it, and the carbonic acid produced by breathing removed by the 
 play of the machine itself. 
 
 The following is an abstract of the results obtained : 
 
 1st. Hot-blooded animals, mammalia and birds, under their ordinary 
 diet, always disengage a little nitrogen by respiration, the Hot blooded 
 amount varying from less than y-J-^- to jfe of the weight of animals on an 
 the oxygen they consume. 
 
 2d. When these animals are fasting, they often absorb nitrogen in pro- 
 portions similar to the preceding. In like manner, an absorp- The same 
 tion of nitrogen was observed after starving the animal, and then fasting. 
 submitting him to a diet very different from his ordinary one, and also 
 during sickness. 
 
 3d. The ratio between the quantity of oxygen contained in the car- 
 bonic acid and the quantity consumed depends more on the Influence of 
 nature of the food than on the class to which the animal be- food and fast- 
 longs, being, when the animals are starving, the same as it is ing * 
 when they are fed upon meat, or perhaps a trifle less. From this the 
 interesting conclusion may be drawn that a starving animal furnishes to 
 the air of respiration his own substance, which is of course of the same 
 nature as the flesh he eats when dieted on meat. All hot-blooded ani- 
 mals present, when they are starving, the respiration of carnivora. The 
 ratio for the same animal varies from 0.62 to 1.04, according to the na- 
 ture of the diet. 
 
172 EXPEEIMENTS OF REGNAULT AND EEISET. 
 
 
 4th. In fowls, submitted to their usual diet of grain, there is often 
 Respiration more oxygen in the carbonic acid disengaged than was furnished 
 of birds. j n f nc a i r }^y respiration. The surplus of course comes from 
 the food. 
 
 5th. The quantity of oxygen consumed in a given time varies with 
 f the state of digestion, motion, and other circumstances. Com- 
 motion, age, pared together, the consumption is greater among the young 
 than among adults, greater among those that are lean but in 
 good health than among those that are fat. 
 
 6th. If we take an equal weight of the animals under examination, the 
 influence of quantity of oxygen varies much with their absolute size ; 
 the size of ani- thus it is ten times greater among little birds, such as spar- 
 rows and green-finches, than among common fowls. This 
 is owing to the fact that, since these different species have the same tem- 
 perature, and the little ones present relatively a greater surface to the 
 ambient air, they must consume relatively more oxygen to keep up their 
 heat to the standard degree. 
 
 7th. Hibernating animals, such as marmots, when perfectly awake, ex- 
 Res iration of ^ibit no peculiarity, but when fast asleep often absorb nitro- 
 hibemating gen. The ratio of the oxygen contained in the carbonic acid 
 to that inspired is very low, scarcely amounting to 0.4, the 
 missing oxygen escaping in the compounds of the urinary secretion ; 
 but since this removal takes place only periodically, the sleeping marmot 
 exhibits the remarkable phenomenon of increasing in weight by respira- 
 tion alone. 
 
 8th. The consumption of oxygen by sleeping marmots is very small, 
 scarcely -^ of what they require when awake. At the moment they 
 awaken from their lethargy, their respiration becomes extremely active, 
 and during the period of their awakening they consume much more oxy- 
 gen than when they are completely awake. Their temperature rises rap- 
 idly, and their members gradually lose their stiffened state. While tor- 
 pid they can remain without difficulty in an atmosphere which would 
 suffocate them in a few moments if awake. 
 
 9th. Cold-blooded animals, for an equal weight, consume much less 
 Res iration of ox yg en * nan hot-blooded. Frogs with their lungs cut out 
 cold-blooded continue to breathe with nearly the same activity as before, 
 often living for several days, the proportions of the gases 
 absorbed and disengaged differing little from what is observed in the 
 case of uninjured frogs. This shows that their respiration can be con- 
 ducted by the skin. The respiration of earthworms is the same as that 
 of frogs, as regards the quantity of oxygen consumed, when they are com- 
 pared under an equal weight. 
 
 10th. The respiration of insects, such as May-bugs and silk-worms, 
 
NERVES OF RESPIRATION. 173 
 
 is much more active than that of reptiles. Under an equal Respiration of 
 weight they consume nearly as much oxygen as mammalia : insects - 
 the comparative lowness of their temperature is due to the relatively 
 great surface and moist exterior they present to the air. It is to be re- 
 marked that we are here comparing the respiration of insects with that 
 of mammalia whose weights may lie from 2000 to 10,000 times as 
 great. 
 
 llth. The respiration of animals of different classes, in an air con- 
 taining two or three times as much oxygen as the atmos- Effect of in- 
 phere, does not differ from existing respiration ; indeed, the creasin s tj 6 
 animals do not appear to perceive that they are in a medium ygen. 
 different from the ordinary atmosphere. 
 
 12th. The respiration of animals in a medium in which, for the most 
 part, hydrogen replaces the nitrogen of our atmosphere, scarcely differs 
 from existing respiration ; only there is remarked a greater consumption 
 of oxygen, due perhaps to the necessity of compensating for the increased 
 cooling arising from the contact of hydrogen gas. 
 
 The introduction of air into the system is, to a certain extent, auto- 
 matic, and, to a certain extent, dependent on the will. In tranquil res- 
 piration we are wholly unconscious of the motion ; the ex- Nerves in 
 citing impression is made on the pneumogastric nerves, and, voived in re& 
 being conveyed to the respiratory ganglion, the medulla ob- piratlon - 
 longata, is there so reflected that through the agency of the phrenic nerve 
 motion takes place in the diaphragm. The automatic, and therefore un- 
 conscious movement, to a certain extent, occurs in that way. But there 
 is no doubt that the brain also participates in the function. No other 
 evidence of this is required than that we can " hold the breath," and the 
 relative share that the voluntary and automatic mechanisms take is illus- 
 trated by the circumstance that this holding of the breath can only be 
 persisted in for a certain time, when the necessity for respiring becomes 
 altogether uncontrollable. 
 
 It is not, however, to be supposed that so important a condition as 
 that of the introduction of the air is only slenderly provided for. Many 
 other nerves, besides those mentioned, take part in it directly or indi- 
 rectly ; the fifth pair, the nerves of the general surface, and also the great 
 sympathetic, the intercostals, the spinal accessory, which probably gives 
 its motor property to the pneumogastric. Opinion has differed respect- 
 ing the cause which produces the necessary impression on the receiving 
 nerves, some referring it to the presence of venous blood in the capilla- 
 ries of tke lungs, and some to the carbonic acid in the cells. Moreover, 
 there is reason to believe that the presence of an abnormal amount of 
 venous blood in the respiratory ganglions will of itself give rise to res- 
 piratory movements through the proper centrifugal nerves. 
 
174 RESULTS OF RESPIRATION. 
 
 
 The control possessed by the will over the introduction of air stands 
 Respiration in a close relation to the production of articulate or other 
 tar^and^art- soun ^ s an ^ therefore to intercommunication between indi- 
 ly automatic, viduals by speech. This involves not merely a general con- 
 trol alone, but also a particular one, which is reached by regulating the 
 movements of the glottis by the agency of the superior and inferior laryn- 
 geal nerves. But though the will for these important purposes exercises 
 so marked a power of regulation, it is to be looked upon as superadded 
 or incidental, and during sleep, coma, and that larger portion of life which 
 is spent in total inattention to the carrying on of this function, it is dis- 
 charged in a purely automatic way. 
 
 The mechanism which accomplishes the surprising results of respira- 
 Results of res- tion may therefore well challenge our admiration. As a 
 piration. self-acting or automatic contrivance, over which we have not 
 a necessary control, it originates in a single year nearly nine millions of 
 separate motions of breathing. It never fatigues us ; indeed, we are 
 never conscious of its action. In the same time, a hundred thousand 
 cubic feet of air have been introduced and expelled, and more than thir- 
 ty-five hundred tons of blood have been aerated. In a future page we 
 shall have to present the wonderful mechanism by which aerial currents, 
 as they pass in and out of the respiratory apparatus, are incidentally em- 
 ployed as a means of producing musical notes or articulate sounds, and 
 of thus establishing a relation and communication between different in- 
 dividuals. By these the feelings and thoughts are diffused, and in a 
 mechanical origin commence those bonds which hold society together. 
 
ANIMAL HEAT. 175 
 
 CHAPTER X. 
 
 OF ANIMAL HEAT. 
 
 Participation of Organic Forms in external Variations of Temperature. Mechanism for counter* 
 balancing these Variations. Development of Heat in Plants at Germination and Inflorescence. 
 Its Cause is Oxidation. Connection of Respiration and Heat. Temperature of Man. His 
 Power of Resistance. The diurnal Variations of Heat. Connection of these Variations with 
 organic Periodicities. Annual Variations of Heat. Control over them by Food, Clothing, and 
 Shelter. Source of Animal Heat. Effect of Variations in the Food and in the respired Me- 
 dium, both as respects its Nature and Rarefaction. Hybernation. Starvation. Artificial Re- 
 duction of Temperature by Blood-letting. Principles of Reduction of Temperature. Radia- 
 tion. Contact. Evaporation. Their Balance with the Heating Processes. Local Varia- 
 tions eliminated by the Circulation. Control by the Nervous System. Its physical Nature. 
 Allotropism of Organic Bodies. 
 
 OWING to the earth's diurnal rotation on its axis, and its annual move- 
 ment of translation round the sun in an orbit inclined to the , 7 . 
 
 Variations of 
 
 equator, variations of temperature arise, the vicissitudes of external tem- 
 summer and winter, day and night. perature. 
 
 In these variations all objects upon the surface of the planet partici- 
 pate ; organic forms are no exception. As the heat of the medium in 
 which they live ascends or descends, theirs follows it at a rate depend- 
 ent on their conductibility. 
 
 Like mineral substances, the more lowly forms of life submit to these 
 changes. They have no provision for check or compensation. Organic forms 
 In summer, the temperature of the stem of a tree rises with- t^ ^-^. 111 
 out any restraint; in winter it declines; and, should the tions. 
 point be reached at which those nutritive changes that give motion to the 
 sap cease, nothing is done to arrest the descent, and the whole organism 
 passes into a state of torpor, hybernation, or temporary death. 
 
 Now, since this following of atmospheric temperatures must take place 
 in every organism as well as in every mineral body, the con- Compensating 
 struction of one having a uniform mode of existence in all 
 climates and all seasons implies a resort to some subsidiary tribes. 
 mechanism, which, though it may not check, may yet compensate for 
 these vicissitudes. Accordingly, so nearly is this equalization accom- 
 plished in the highly-developed tribes, and a standard temperature so 
 nearly attained for them, that many physiologists, misled by imperfect 
 observations, have concluded that such living beings are emancipated by 
 nature from the operation of physical laws : an erroneous conclusion, for 
 in them that action is only concealed. 
 
176 THE HEAT OF PLANTS. 
 
 In different races, the mechanism by which these variations of atmos- 
 pheric temperature are balanced acts with different degrees of perfection, 
 d hot ^ n ^ s a subdivision has been founded, and animals classi- 
 Mooded ani- fied as the cold and hot blooded. We are not, however, to 
 mals - attach much importance to such an arrangement : it is rather 
 
 imaginary than founded on any real distinction. In man, the tempera- 
 ture is near 100 ; in fishes, it is about that of the water in w^hich they 
 live. Insects, in their larva and pupa condition, are cold-blooded; in 
 their perfect condition, hot. 
 
 We have now to explain what physical principles are resorted to in 
 solving the problem of maintaining an organic form at a constant tem- 
 perature in a medium the heat of which is variable ; and as we may 
 reasonably anticipate that these principles are the same in every tribe of 
 life, it will facilitate our investigations to commence with the simplest 
 cases first. 
 
 There are two periods in the life of a plant during which it simulates 
 Two periods of the functions of an animal in ^maintaining a temperature 
 heat in plants, higher than that of the surrounding air. These periods are, 
 1st, at the germination of the seed ; 2d, during the functional activity of 
 the flower. 
 
 If a mass of seeds be laid together, as in the making of malt, the op- 
 Heat of germ- eration being conducted at a gentle temperature, and with the 
 ination. access of atmospheric air, oxygen disappears, carbonic acid is 
 
 set free, and the temperature rises forty or fifty degrees. A process of 
 oxidation must therefore have been carried into effect, and to it we trace 
 the heat disengaged, for carbon can not produce carbonic acid without a 
 rise of temperature ensuing. The loss of weight which a seed exhibits 
 is therefore due to its loss of carbon, and the whole effect is explained in 
 the statement that atmospheric oxygen has united with a portion of car- 
 bon contained in the seed, producing carbonic acid gas and an evolution 
 of heat. 
 
 Again, during flowering, the same action is repeated. The flower re- 
 Heat of inflo- moves from the surrounding air a portion of the oxygen it 
 rescence. contains, and replaces it with carbonic acid, the temperature 
 rising, as accurate experiments have proved, in absolute correspondence 
 with the quantity of oxygen consumed. Nor is this elevation insignifi- 
 cant. A mass of flowers has been observed to raise the thermometer from 
 66 to 121. 
 
 If thus the disengagement of warmth is the result of oxidation, it must 
 Oxidation the depend on the presence of air, and be regulated by the rapidity 
 e^vation^of 6 wit ^ which oxygen can be supplied. As we pass from the 
 temperature, consideration of plants to that of animals, we discover that the 
 production of heat must be connected with the power and precision with 
 
CONNECTION OF RESPIKAT10N AND HEAT. 177 
 
 which the respiratory apparatus works, for it is through its agency that air 
 is introduced. Extensive observation accordingly establishes a close cor- 
 respondence in each animal tribe between the quantity of heat produced and 
 the capability of respiratory apparatus. The lower tribes breathe sfbw- 
 ly and are cold. Earthworms are only a degree or two warmer than the 
 ground ; and even among vertebrates, fishes are only two or three degrees 
 warmer than the water, a lowness of temperature in a great ^measure de- 
 pending on the high cooling agencies which that liquid ex- Connection of 
 erts, its specific heat, and the facility with which currents are respiration and 
 established in it. However, even in these cases the produc- L 
 tion of heat depends on the power of the respiratory engine. The bonito 
 can keep its heat 20 above that of the sea, and the narwhal maintains 
 a steady temperature at 96. 
 
 The organic operations involved in nutrition, and also the retrograde 
 changes of decay, can only go on at their accustomed rates so invariability 
 long as standard limits of temperature are observed. The of organic ac- 
 
 , . m-f T T " OT implies a 
 
 proper progress of the actions of life implies a corresponding definite tem- 
 adjustment of heat, and this irrespective of the mere size of P erature - 
 the animal. Even those that are microscopic must come under this rule. 
 When the temperature of a liquid containing infusorials is caused to de- 
 scend to the freezing point gradually, the last portions which solidify are 
 those which surround each of these little forms ; a drop is kept liquid by 
 the heat they disengage. In the same individual, the absolute tempera- 
 ture will depend on its respiratory condition ; thus insects, in passing 
 through each of their stages of metamorphosis, present a definite condi- 
 tion as to their heat: the larva of the bee may be only two degrees above 
 the air, while the perfect insect is 10. Whatever accelerates the in- 
 troduction and expulsion of the air, increases the warmth; Variations of 
 so a bee shaken in a bottle, and kept in a state of constant ^0^0* d 
 muscular exertion, will raise the temperature contained there- tion. 
 in far higher than if he remains inactive. Among insects, those having 
 the largest organs of respiration have always the highest temperature ; 
 and, since muscular motion implies destruction of muscular tissue by ox- 
 idation, and therefore development of heat, we should expect to find, as 
 is actually the case, that animals possessing the highest powers of loco- 
 motion will possess also the highest temperature. Of all, therefore, birds, 
 the endurance and energy of whose powers of flight result from the per- 
 fection of their respiratory mechanism, have the highest temperature. It 
 is about 110. Yet even here there are differences : the sluggish barn- 
 door fowl has not the heat of the energetic swallow. 
 
 The standard temperature of man is usually stated to be 98, but from 
 this mean it ranges within certain limits upward and down. Temperature 
 Much depends on the state of the health; of course, every thing of man - 
 
 M 
 
178 DIUENAL VAEIATIONS OF HEAT. 
 
 on the respiration. In fevers it will rise to 105 ; in tetanus it may reach 
 110; the contrary in asthma, when it may sink to 82, owing to imper- 
 fect access of air ; in cyanosis to 77, owing to imperfect aeration of the 
 blood ; in Asiatic cholera to 75, owing to the non-reception of oxygen by 
 the cells in their diseased state. It also varies with the period of life : 
 in the new-born infant it is 100 ; it presently sinks to 99, and rises 
 during childhood to 102. Mental exercise in the adult increases it, 
 bodily exertion still more. The special degree varies with the point on 
 which the observation is made : the limbs are colder than the trunk, and 
 this is the more marked as the point is more remote. On the leg the 
 temperature may be 93 ; on the sole of the foot, 90 ; while that of the 
 viscera is 101. 
 
 In his residence in different climates, man is exposed to variations of 
 Resistance of temperature which extend over a scale of 200. Toward 
 
 1 anHrTtT ex" ^ P* GS ^ co ^ ^ winter ^ s ^ ten 60 ; in the tropics 
 tremes of tem- the heat of summer +130. For a short period his power of 
 perature. resistance is greatly beyond what these numbers would in- 
 dicate; he can enter with impunity an oven heated to 600, provided the 
 air is dry. In these cases, though excessive evaporation from the skin 
 moderates the effect and keeps it within bounds, there is always a mark- 
 ed rise of temperature of the whole body. In a corresponding manner, 
 exposure to cold produces depression, as shown in Dr. Davy's observa- 
 tions. At 92 of the air, a thermometer under the tongue stood at 100 J ; 
 at 73 it stood at 99 ; at. 60 it stood at 97J . 
 
 Among these variations there is one class which calls for critical at- 
 Diurnal varia- t ent i n - I* ^ the diurnal variation ; less marked in man, 
 tion in the heat who instinctively makes provision against it, but well shown 
 in the case of fasting animals. This illustrates, in an inter- 
 esting manner, the controlling influence of external conditions ; for if ex- 
 posure to a high temperature, as that of an oven, compels a ^rise of the 
 heat of the whole body, in spite of the conservative arrangements, and 
 exposure to extreme cold compels a descent, we ought to expect that ex- 
 posure to more moderate degrees would, in like manner, produce an im- 
 pression. 
 
 The old astrologers were therefore not altogether wrong when they af- 
 firmed the doctrine of planetary influences. The diurnal temperatures 
 of a locality, as dependent on the position of the sun, are expressed in 
 the system of man. The minimum of heat for the night, and the max- 
 imum for the day, find a correspondence in the decline of animal temper- 
 ature at the former, and its rise at the latter period. The experiments 
 of M. Chossat on birds submitted to absolute starvation showed that, 
 though in their normal state, at the commencement, the variation between 
 midnight and noon was only 1J, it gradually increased to 6, until at 
 
CALORIFIC INFLUENCE OF FOOD. 179 
 
 last, the generation of heat wholly ceasing, the temperature gave way 
 rapidly just previous to death. 
 
 If, therefore, it was possible for life to continue without the evolution 
 of animal heat, it would be with the body as it is with the stem of a tree. 
 It would follow the thermometric variations in the air, the maxima of 
 heat and cold being somewhat later than the aerial ones, and within nar- 
 rower limits, by reason of the low conducting power. The nearest ap- 
 proach to this is in cases of absolute starvation, and though in man the 
 effect is masked by the due taking of food, it none the less exists. In 
 human communities there is some reason beyond mere cus- influence of 
 torn which has led to the mode of distributing the daily 
 meals. A savage may dispatch his gluttonous repast, and ature. 
 then starve for want of food ; but the more delicate constitution of the 
 civilized man demands a perfect adjustment of the supply to the wants 
 of the system, and that not only as respects the kind, but also the time. 
 It seems to be against our instinct to commence the morning with a 
 heavy meal. We break fast, as it is significantly termed, but we do 
 no more, postponing the taking of the chief supply until dinner, at the 
 middle or after part of the day. If men were only guided by views of 
 economy of time saved for the pursuits of business, or if, on this occasion, 
 they put in practice the rule they observe on so many others, of never 
 postponing the gratification of their desires, the first affair of the morn- 
 ing would have been an abundant repast. But against this something 
 within us revolts, and that in all classes, the laboring, the intellectual, 
 the idle. I think there are many, reasons for supposing, when we recall 
 the time which must elapse between the taking of food and the comple- 
 tion of respiratory digestion, that this distribution of meals is not so 
 much a matter of custom as an instinctive preparation for the systemic 
 rise and fall of temperature attending on the maxima and minima of daily 
 heat. The light breakfast has a preparatory reference to noonday, the 
 solid dinner to midnight. 
 
 Once more I would remark, that we must not be deceived by the 
 masked aspect which the system in this matter presents, connection of 
 Its diurnal variations are concealed by agencies brought variations of 
 
 . . , iL L-ut j. heat with or- 
 
 specially into operation for that purpose, but they exist in gan i c p er iodi- 
 the physical necessities of the case ; and herein, I believe, cities - 
 we have a first glimpse of the cause of those periodicities, which physi- 
 cians from the earliest times have remarked ; for, though the nervous 
 system, both in a state of health and disease, may seem to be their ori- 
 gin, it is not impossible that its changes are connected with variations 
 thus taking place in the external world. 
 
 We have next to consider the effect of the annual varia- Annual varia- 
 tions of temperature, which reach their maximum soon after tions of heat - 
 
180 EFFECT OF ANNUAL VARIATIONS OF HEAT. 
 
 mid-summer and their minimum soon after mid- winter, the manner in 
 which the system comports itself under them, and the means which in- 
 stinct and experience teach us to employ in providing against them. 
 
 The tables of mortality show that there is a loss of life at the annual 
 imu rnax i mum an d minimum of temperature which greatly ex- 
 ai variations ceeds the average of any other period. In England and Bel- 
 gium, where the mean temperature of the summer months is 
 moderate, this is not so strikingly marked for those months, and the chief 
 loss falls upon the winter ; but in New York, which has a summer cor- 
 responding to that of the south of Europe and a winter like that of the 
 north, the effect of these extremes becomes so obvious as even to be 
 popularly connected with the position of the thermometer above or below 
 55. Among infants and the aged, whose controlling powers over tem- 
 perature are imperfect, these effects are most distinctly witnessed ; but 
 among healthy adults, and even in Europe, we can detect them on crit- 
 ical examination. Thus, in Brussels, the monthly mortality for January 
 being taken as 105, that for July is 91, for August 96, and for October 
 93 ; and it is to be recollected that these are the residual traces of the 
 operation of cold and heat after all the precautions have been used to 
 ward them off. I might make here the same remark that was made 
 when considering diurnal variations, that the true effect is so masked and 
 concealed that we are liable to undervalue it, and do not properly appre- 
 ciate this tax put upon the system. 
 
 These annual variations of external temperature are chiefly combated 
 Control over ty food, clothing, and shelter. The dietetic changes we make 
 annual varia- between winter and summer are founded upon the principle 
 
 tions by food, - ' . , .-ri ./ - i - 1* j -11 
 
 clothing, shel- of using more combustible food for the former, and less com- 
 bustible for the latter season ; and, since the calorific ef- 
 fect of an article of food greatly depends on the quantity of oxidizable 
 hydrogen it contains, the winter diet has more of that element than the 
 .summer. Partly thus by varying the nature, and partly by varying the 
 quantity of the food, we can effect a compensation to a certain extent. 
 
 Of the manner in which the diet-compensation is aided by variations 
 in clothing little needs to be said. The experiments of Count Eumford 
 established the fact that the conductibility of summer clothing is greater 
 than that of winter, and therefore its resistance to the escape of heat is 
 less. It is sufficient merely to allude to the control which is gained by 
 difference of thickness in the garments, and by their amount or quan- 
 tity. We instinctively make these adjustments to meet the existing ex- 
 igencies, and, as far as may be, in this manner aim at a medium effect. 
 
 The check upon external temperature by the use of clothing was doubt- 
 less one of the first contrivances of the human race. Even of savage life 
 it is a cardinal feature. The check by adjustment of diet belongs to a 
 
IMPERFECTIONS OF SHELTER. 181 
 
 civilized state, since it implies a certain control over the animal appetite 
 and personal self-denial. Though great improvements in both of these 
 will doubtless hereafter be made, when the principles of their operation 
 -are more generally and better understood, they must, even in their pres- 
 ent condition, be regarded as having reached a higher perfection than the 
 check by resorting to shelter. The art of constructing dwelling-houses 
 may be said to be yet in its infancy in all parts of the world, E . . 
 and yet in no particular is the physical condition of females perfections of 
 and children, and especially of the sick, more nearly touched. shelter - 
 It is only within our own times that attention has been drawn to the 
 proper methods for the admission of warmth, and air, and light ; the hy- 
 gienic influences of furniture and decoration are unknown, beyond, per- 
 haps, a popular impression that it is unhealthy to be in a recently-paint- 
 ed apartment, inexpedient to sleep in a chamber where there are flowers, 
 and unpleasant in summer to have a carpet on the floor, because it looks 
 warm, and is thought to generate dust. The owner of a palace, on which 
 wealth has been fruitlessly lavished, finds, on a cold day, that he can 
 not obtain from his parlor fire the necessary warmth unless by alternate- 
 ly turning round and round. The testy valetudinarian sits in his easy- 
 chair, tormented by drafts coming in from every quarter. In his vain 
 attempts to stop the offending crevices, it never occurs to him that his 
 chimney is a great exhausting machine, which is drawing the air out of 
 the room, and that his means of warming and ventilation are the most 
 miserable that could be resorted to, since radiation can warm only one 
 side of a thing at a time, and fresh air under those conditions can only 
 be introduced by drafts. 
 
 To warm rooms by contrivances such as the open fire-place or stove 
 is obviously unphilosophical, since the effect of these is to ex- of artificial 
 haust the air of the apartment. The modern method of warm- warmth, 
 ing by furnaces, which act by throwing air duly moistened and of the 
 right temperature into the rooms, and therefore by condensation, is clear- 
 ly a better system, since it not only puts an end to all drafts, the 
 tendency being to force air out through every crevice instead of drawing 
 it in, but it possesses the inappreciable advantages of giving uniformity 
 of warmth, a perfect control over the degree of heat, and likewise over the 
 nature of the air, which need not be drawn from the cellar, or the con- 
 taminated impurity of the street, but by suitable flues from the free and 
 clear air above. Ventilating contrivances which can cheaply and effectu- 
 ally force a supply of artificially cooled air in the summer, and warm air 
 in the winter, into dwelling-houses, are still a great desideratum. 
 
 By the aid of diet, clothing, and shelter, we are able to effect an almost 
 complete compensation for the changes of diurnal and annual temper- 
 atures, and even to occupy any climate of the globe. It is the manage- 
 
182 EFFECT OF COMBUSTIBLE ALIMENT. 
 
 ment of caloric which makes man what he is, and constitutes his special 
 prerogative ; his degree of skill therein is the measure of his civilization. 
 The distribution of plants and animals, or, rather, their limitation within 
 fixed boundaries, depends on the distribution of heat, but from these re- 
 straints man is free, because he can control temperatures. 
 
 From these considerations of the effect of external heat on the human 
 mechanism, we return to a more critical examination of the modes by 
 which heat is generated, and its degree regulated in the body. 
 
 In every instance we assert that the production of animal heat is due 
 Source of ani- to oxidation taking place in the economy, and giving rise to 
 mal heat. carbonic acid, water, and other collateral products. It is not 
 necessary to attach any weight to the experiments of Dulong, which seem- 
 ed to indicate that not more than four fifths of the heat actually pro- 
 duced could be owing to the oxidation of carbon, nor to those of a like 
 kind of Despretz. The method they resorted to for the measurement of 
 the disengaged heat was open to error ; the numbers they employed as 
 representing the combustion heats were incorrect ; nor did they make any 
 allowance for other substances, such as sulphur and phosphorus, which 
 are simultaneously oxidizing, and the products of their combustion escap- 
 ing by the kidneys. 
 
 Eeduced to its ultimate conditions, the evolution of animal heat de- 
 Effect of more pends on the reaction taking place between the air intro- 
 aiSient^w^ai- ^ uce ^ ^7 respiration and the food, and as either one or other 
 cohoi. of these is touched, the result may be predicted. If, for ex- 
 
 ample, into the digestive canal alcoholic preparations be introduced, they 
 are absorbed, by reason of their liquid condition and diffusibility, with 
 readiness. The combustibility of alcohol, and the amount of heat it 
 yields, are so great, that the primary effect of the oxidation which ensues 
 is a warmth or feverish sensation. By reason of the changes which are 
 now taking place so actively in it, the blood circulates with unwonted 
 rapidity, and the supply to the brain increasing, that organ exhibits an 
 unusual functional activity. But this display of intellection is only tem- 
 porary, and an opposite condition soon comes on, for, more carbonic acid 
 accumulating in the blood than the lungs can get rid of, the depressing 
 effects of that body commence, and eventually the symptoms of poison- 
 ing by it ensue. 
 
 Not unlike this is the train of effects which arise when, instead of va- 
 Effectofamore rying the nature of the article ingested, we vary that of the 
 porter of respi- & as respired. An energetic supporter of combustion, like the 
 ration than air. protoxide of nitrogen, gives rise to a feverish glow, cerebral 
 activity, to be followed eventually by a deep depression, the poisonous 
 influence of the carbonic acid produced being exhibited. After a while 
 the system casts it off, and recovers its condition of health completely. 
 
EFFECT OF RAREFIED AIR. 183 
 
 If there be an abstinence from food, since the introduction of air by 
 respiration goes on without abatement, the body itself must A starvin 
 undergo oxidation, lose weight, and emaciation occur. Its imai dies of 
 tendency to follow the diurnal variations of temperature be- c 
 come more and more strikingly marked as the process of starvation goes 
 on, and finally a rapid and unchecked decline of the heat ensues. Yet 
 even then life may be preserved by the application of sufficient external 
 warmth, and from an extreme condition of attenuation an animal may be 
 rescued by the use of food ; but for such a recovery the external warmth 
 must be continued until there has been time for digestion and absorption 
 to take place. If, however, such an extraneous aid be not duly applied, 
 the temperature of the starving animal goes on diminishing, and he dies 
 of cold. 
 
 The doctrine we are here inculcating, that animal heat is due to oxida- 
 tion in the system, is still further strikingly illustrated by Effectofre . 
 what might be termed starving the respiration. As cold is spiring rarefied 
 felt from want of food, so also it is from want of air. In as- air ' 
 cending high mountains, the effect upon the system has been graphically 
 expressed as " a cold to the marrow of the bones ;" a difficulty of making 
 muscular exertion is experienced ; the strongest man can scarcely take a 
 few steps without resting; the operations of the brain are interfered with ; 
 there is a propensity to sleep. The explanation of all this is very clear. 
 In the accustomed volume of air received at each inspiration, there is a 
 less quantity of oxygen in proportion as the altitude gained is higher. 
 Fires can scarce be made to burn on such mountain-tops ; the air is too 
 thin and rare to support them ; and so those combustions, which should 
 go on at a measured rate in the interior of the body, are greatly re- 
 duced in intensity, and hence the sense of a penetrating cold. Such 
 journeys, moreover, illustrate how completely the action of the muscular 
 system, and also of the brain, is dependent on the introduction of air ; 
 and under the opposite condition of things, where men descend in diving- 
 bells, though surrounded by the chilly influences of the water, they ex- 
 perience no corresponding sensation of cold, because they are breathing a 
 compressed and condensed atmosphere. 
 
 The respiratory apparatus of certain animals permits a reduction in the 
 amount of air introduced under exposure to a due degree of _,, 
 
 . fo Phenomena of 
 
 cold. Such animals are said to hybernate. At the com- hybemating 
 ing on of winter their adipose tissues are engorged with fat. animals - 
 As they pass into their annual sleep, the rate of their respiration falls. 
 The marmot, which in activity will make 140 respirations in a minute, 
 makes now but 3 or 4; the temperature of the body descends, and combus- 
 tion of the store of fat goes on more slowly. Yet it does go on, for, toward 
 spring, the animal has become very lean ; sufficient heat is disengaged to 
 
184 COOLING AGENCIES. 
 
 permit the blood slowly to circulate, and so "barely to keep up the func- 
 tions of life. If, however, the stock of material available for combustion 
 is insufficient, the animal dies. 
 
 Although we can not interfere with the rate of respiration, we can 
 Reduction of affect the quantity of air introduced into the system by arti- 
 temperatureby c i a l means, as in the operation of blood-letting ; for though, 
 
 blood-letting ' r 
 
 and in morbid alter Diooa nas been drawn, we may make the normal mini- 
 states. k er of respirations, 17 in a minute, and for each introduce 
 17 cubic inches of air, we have diminished the number of discs, which 
 are the carriers of oxygen ; and, as the experience of physicians in all 
 times has shown, there is no method so effectual in reducing any unusual 
 or febrile temperature. So, in like manner, in Asiatic cholera, the marble 
 coldness which the body presents is attributable to the loss of function 
 of the discs, and the consequent abatement in the quantity of oxygen in- 
 troduced. 
 
 Thus far we have considered the means which the animal mechanism 
 ,, , . ' possesses for raising its own temperature ; it remains to show 
 reducing the how it can also regulate it. For any thing that has thus far 
 are * been said to the contrary, the combustions or oxidations 
 which are continually going forward should establish a constant rise, and 
 there must therefore be some principle of restraining such a rise within 
 due bounds. Considering also the incessant vicissitudes of atmospheric 
 temperature, a constant degree could not be maintained unless the sys- 
 tem possessed the means of depressing as well as elevating its heat. 
 
 That the means of regulating the heat are purely physical, we should 
 Effect of cov- expect for many very obvious reasons. Economy of heat is 
 s'ecte^onduct- a ccomplished by non-conducting material. On this princi- 
 ibiiity. pie, hair, wool, and feathers act by excluding the contact of 
 
 the atmosphere, their low conductibility being brought into operation. 
 In many cases, the manner in which this is done is clearly intentional. 
 Thus the down which is placed on the breast of a water-fowl is to screen 
 off the chilling influence of the water, which is there chiefly felt as the 
 bird swims on the surface. The deposits of fat in whales, their blubber, 
 at once affords a protection through its imperfect conductibility, and is 
 also a store of combustible material for the purpose of respiration. 
 
 The chief cooling agencies in animals are, 1st. Radiation ; 2d. Loss 
 General cool- f neat by warming the expired air ; 3d. Loss by contact of 
 ing agencies, the cold external air ; 4th. Evaporation. The circulation of 
 the blood tends to establish an interior equalization, so that local varia- 
 tions are soon obliterated ; for, through whatever part the blood may flow, 
 it attains the temperature thereof, and, passing in succession from part to 
 part, equalizes the heat of all. 
 
 It would be useless to offer any proof that a living being, like an in- 
 
COOLING AGENCIES. ' 185 
 
 organic mass, loses or gains heat, as the case may be, by radi- 
 
 ~. 3 . ,_ 11 Of radiation, 
 
 ation. bince, however, in man, the temperature is usually 
 
 higher than that of the surrounding medium, the result of this action is 
 that cooling takes place. With regard to loss of heat by warming the 
 expired air, it may be observed that, whatever the temperature of the ex- 
 ternal air may be, it is raised to that of the lungs after it has been brought 
 into the respiratory passages. This constitutes, therefore, a cooling 
 agency of variable power, for the loss will be greater as the external heat 
 is lower : if the atmospheric temperature rose to 98, loss in this manner 
 would cease. Becalling what has been said respecting the mode in which 
 air is introduced, it is plain that this loss will chiefly fall Heat given to 
 upon the nasal passages, the trachea, and larger ramifications the expired air. 
 of the bronchial tubes ; for, by the time the volume inspired has made its 
 way beyond that limit, its temperature must be nearly that of the body. 
 The contact of the cold surrounding air, and more particular- contact of the 
 ly of currents which may be occurring in it, act chiefly upon surrounding 
 the skin, and it is in preventing this loss that clothing be- 
 comes so efficient. The difference we so frequently notice between the 
 indications of the thermometer and our own sensations are, for the most 
 part, dependent on these currents. A temperature of 50 below zero can 
 be sustained without much inconvenience if the air is perfectly calm, 
 but not so if there is any wind. Of all the cooling agencies, evaporation 
 is, however, by far the most energetic. From the skin and Coolino . b 
 the air cavities, large quantities of the vapor of water are ex- evaporation of 
 haled. As the external heat rises, the sudoriparous tubes act* water< 
 with increased energy, and pour out their excretion as drops of sweat 
 faster than it can be removed. Their length has been estimated at 28 
 miles. Since, at the temperature of the body, the heat of elasticity of the 
 vapor of water is 1114, this continued vaporization from the skin and 
 lungs is one of the most powerful sources of refrigeration. 
 
 It may be well to direct a closer attention to the special action of the 
 air passages and skin as concerned in these cooling process- Variabilit in 
 es. The diurnal loss of water, by both organs conjointly, is the action of 
 usually estimated at 3 Ibs., of which the pulmonary exha- theskin - 
 lation constitutes about one third, and the cutaneous about two thirds. 
 The skin acts in a variable manner, losing more or less water as the ex- 
 ternal air is dryer or more damp. The removal of water therefore be- 
 comes a complex operation, in which three different organs are concerned 
 the skin, the lungs, and the kidneys. Of these, the skin acts meteoro- 
 logically and variably, as has been just remarked, and the respiratory or- 
 gans for the most part uniformly. But since it is requisite, in the nor- 
 mal operations of the system, that the diurnal average of water should be 
 removed, the variable action of the skin throws a variable action upon 
 
186 ' BALANCE BETWEEN HEATING AND COOLING. 
 
 v< . the kidneys, for the excess that the skin can not evaporate 
 
 tionofthekid- must be strained off Iby these organs. In this regard the 
 
 kidneys act, therefore, vicariously for the skin ; and in hot 
 weather, when the cutaneous losses are great, but little urine is discharged ; 
 but in cold weather, when the cutaneous loss is diminished, the quantity 
 of the urine is increased. 
 
 I think, however, that as regards the respiratory organs, a distinction 
 
 should be made in their mode of action. In reality, they 
 
 Evaporation in J ' > 
 
 the air pas- operate in a double way. 1st. They act, so far as the nasal 
 passages, the trachea, and larger ramifications of the bron- 
 chial tubes are concerned, meteorologically, and therefore variably, for 
 the introduced air possesses the existing atmospheric temperature ; is at 
 one time warm, and at another cold ; yet, since it always leaves these 
 passages at 94, it removes from their surfaces sometimes less and some- 
 times more heat ; but it is not so with the action going on in the air- 
 cells, the temperature of which, and of the air they contain, is always 
 uniform ; and as water vaporizes into them, it must always do it at a uni- 
 form rate, and remove as its caloric of elasticity a uniform amount of 
 heat. I therefore decompose the loss of heat by the respiratory organs 
 into two portions : one, which is constant, and taking place in the cells ; 
 the other, variable, occurring in the large air-ways, and, being meteoro- 
 logical, coincides in this respect with the cutaneous loss. In consider- 
 ing the diseases of the respiratory organs, it is well to keep this distinc- 
 tion in mind. 
 
 The establishment of the equilibrium of temperature in an animal is 
 Balance be- effected* by the mutual operation of the heating and cooling 
 ingandkooMng arr angements. More or less heat, as the system requires, 
 arrangements, may be furnished by promoting or retarding the oxidation 
 of respiratory material ; and since a living being, like an inorganic mass, 
 is subject to every external influence, its temperature tending to rise or 
 fall as diurnal, or annual, or seasonal changes may be, these, as well as 
 Elimination of its own interior variations, are held in check by the cooling 
 local variations or wa rming powers it can exert. Local differences within 
 tion of the itself are eliminated in an indirect, but still very effectual 
 blood. manner, by the circulation of the blood ; and, considering 
 
 the range of variation to which it is exposed, and the frequency of the 
 changes, the required equilibrium is admirably secured. 
 
 I have reserved for a more special and prominent consideration the in- 
 Controi of the fl uence which the nervous system exerts over animal heat, 
 nervous sys- since it is upon this that many have been disposed to deny 
 the great truth that the heat of the body arises from oxida- 
 tion. They say that it is produced by the nerves. Even a mental emo- 
 tion gives rise to disturbance of temperature, and the face may be cover- 
 
INFLUENCE OF THE NEEVOUS SYSTEM. 187 
 
 ed with blushes. Moreover, as experiments have proved, on cutting a 
 nerve the temperature of the parts it supplies declines ; on injuring the 
 great nerve centres the temperature of the whole system lowers, even 
 though artificial respiration may "be kept up. In cases of paralysis, the 
 temperature of the disabled part may be very much lower than that of 
 the sound. A paralyzed arm has shown a surface heat of 70 only, 
 while the sound one has been at 92. It is also said of decapitated ani- 
 mals that they cool quicker when artificial respiration is kept up than 
 when they are let alone. 
 
 All this may be very true, yet it is very far from proving that the 
 nerves are the generators of animal heat. The engineer of a locomotive 
 can regulate the speed of his train and control the production of steam by 
 throwing more or less fuel on the fire, or by supplying it with more or less 
 air ; but does any one impute the production of the heat to him ? If 
 an accident should throw him off, thereby establishing a sort of analogy 
 between his machine and the decapitated animals we have referred to, the 
 stoppage that would soon ensue, and the dying out of the fire, would by 
 no means prove that he made the heat ! 
 
 And so with the nervous system, its function is not a generative, but 
 a controlling one. It determines in what way the combustive or oxidiz- 
 ing actions shall go on, but that is a totally different affair from forming 
 the heat. 
 
 Before specifying more particularly the views I entertain on this sub- 
 ject, I will remark, that the most superficial consideration satisfies us 
 that oxidation in the system goes on in a regulated way. There is not 
 an indiscriminate attack made by the arterial blood on whatever is next 
 before it, but those particles only are removed which the needs of the 
 system require. This therefore implies some overriding or superintend- 
 ing agency, which can save one atom from destruction and surrender an- 
 other. The portion assaulted may, to all appearances, be identical in 
 physical aspect and chemical constitution to an adjacent one that is pass- 
 ed by. There seems to be an arrest or suspension of affinity in one case, 
 and its ready satisfaction in the other. 
 
 There are some well-known facts in natural philosophy which throw 
 a flood of light on this obscurity. If a piece of pure zinc physical anal- 
 be placed in a glass of acidulated water beside a piece of s ies to this 
 
 , 111 ^ i control of the 
 
 copper, so long as the metals are kept apart no action what- nervous sys- 
 ever ensues ; but if a conducting thread is laid from one to tem * 
 the other, the zinc instantly begins to oxidize, clouds of hydrogen gas 
 bubbles rise from the copper, and the thread becomes at once red-hot and 
 magnetic. On lifting the communicating thread all these actions cease ; 
 on restoring it they instantly recur. We think we explain them by say- 
 ing that they are all due to the decomposition of water by the zinc. But 
 
188 ALLOTEOPISM OF OEGANIC BODIES. 
 
 why was the zinc passive when alone, and why did it assume this activ- 
 ity when merely touched by another metal ? Does not all this serve to 
 show that substances may be, as it were, in a quiescent state, and on the 
 application of what may perhaps seem the most insignificant cause, may 
 suddenly assume activity, and forthwith satisfy their chemical affinities ? 
 There is nothing in the graduated oxidations going on in the system 
 more obscure or more unaccountable than the phenomena of a simple 
 Voltaic circle. Their effects are almost parallel. 
 
 All elementary substances appear to have the quality of assuming active 
 Allotropism of and passive conditions. Carbon, moreover, presents many 
 bodies. intermediate forms. As diamond it is extremely incombus- 
 
 tible, and is set on fire with difficulty even in oxygen gas ; as lampblack 
 it will kindle spontaneously. With these differences in its relations with 
 oxygen, it also exhibits great variations in its optical, calorific, mechan- 
 ical, and other properties. These transitions of state may be induced by 
 various causes, especially by the agency of what are called the impon- 
 derable principles, as by rise of temperature, and exposure to the sun- 
 light. Thus, in the case of chlorine, I have shown that, though it re- 
 fuses to combine with hydrogen so long as it is in the dark, an exposure 
 to indigo-colored light will cause it to unite with explosive energy with 
 that substance ; and these peculiarities are retained by bodies when 
 they go into union with each other. Thus there are two forms of phos- 
 phorus; the one active and shining in the dark, and therefore readily oxi- 
 dizable ; the other passive, not shining in the dark, and with therefore a 
 less affinity for oxygen ; and these severally give rise to two varieties 
 of phosphureted hydrogen, which, though having the same composition, 
 yet differ in thi's respect, that the one containing the active form of phos- 
 phorus is spontaneously combustible in the air, but the other, which con- 
 tains the passive form, is not spontaneously combustible. Phosphorus 
 is thrown from the active to the inactive state by mere exposure to the 
 more refrangible rays of the sun. 
 
 The properties here spoken of have been designated by Berzelius as 
 Allotropism of ^ ie a ^otropism of bodies. I have endeavored to prove that 
 organized bod- allotropism is the true cause of many of the obscure facts 
 which we meet with in the animal mechanism ; for it is very 
 clear that something so modifies the relations of the tissues to oxygen 
 that they are not indiscriminately destroyed by it, but these parts yield 
 in a measured or regulated way ; and since, in inorganic substances, the 
 influence of the imponderables can compel the assumption of an active or 
 passive state, there is nothing contradictory in imputing to the nervous 
 system a similar power. 
 
 In this manner we may therefore conclude that, so far as tissue de- 
 struction is concerned, the nervous system possesses a governing or con- 
 
OF SECRETION. 189 
 
 trolling power ; that by keeping parts in states answering to the passive 
 and active conditions of inorganic chemistry, it can suspend the action of 
 the respired oxygen or permit it to take effect. This controlling power 
 is, however, altogether distinct from a generative one, and all the heat dis- 
 engaged is due to oxidation. It is also possible that not only are these 
 states of activity or passivity impressed on the tissues by the agency of 
 the nerves, but also upon the respired oxygen itself, since that gas is no 
 exception to the rule ; it also exhibits allotropism. Its passive state is 
 Priestley's oxygen, its active is Ozone. In its transit from the air-cells 
 into the blood it may experience such a change, and have at once com- 
 municated to it a high degree of activity. 
 
 - 
 CHAPTER XL ; 
 
 OF SECRETION. 
 
 SEROUS, MUCOUS, AND HEPATIC SECRETIONS. 
 
 of Secretion. Type of secreting Mechanism. Filtration and Cell Action. Of Serous 
 Membranes and their Secretions. Of Mucous Membranes and their Secretions. Of Hepatic Se- 
 cretions. The Liver: its Development and Structure. Source, Quantity, Composition, Uses, 
 and Flow of the Bile. Existence of biliary Ingredients in the Blood. Production of Sugar and 
 Fat in the Liver. Changes of the Blood-cells in it. General Summary of the four-fold Action 
 of the Liver: it produces Sugar and Fat, eliminates Bile, is the Seat of the final Destruction 
 of old Blood-cells, and of the Completion of new Ones. Of the ductless Glands. The Spleen: 
 its Functions. 
 
 Two classes of substances occur in the blood the products of decay 
 and the elements of nutrition. The equilibrium of the system requires 
 that the former should be removed and the latter appropriated. 
 
 The primary object of the function of secretion is this dismissal and 
 appropriation, and therefore, through the latter duty, secre- object of secre- 
 tion becomes connected with nutrition. tion - 
 
 The elementary type of a gland or organ of secretion consists ot a sac, 
 on the interior of the wall of which a network of arterial ramifi- Type of a 
 cations is spread ; this delivers its blood into a similar network e land - 
 of veins. The matter which the gland is destined to separate oozes 
 from the arterial capillaries into the interior of the sac, and is delivered 
 through the neck or mouth thereof, which may be spoken of as the duct. 
 It will be presently shown that the material which thus finds its way 
 into the interior of the sac is not fabricated by that organism, but is 
 brought to it pre-existing in the affluent current of arterial blood. As 
 our knowledge of the functions of glandular structures becomes more 
 
190 VICARIOUS SECRETION. 
 
 precise, the less and less does it appear probable that the secreted matter 
 is in any way engendered by the gland itself. 
 
 Since, with the exception of the lungs, which excrete carbonic acid and 
 
 . vapor of water, all the great glands remove the material they 
 
 glandular are concerned with in a state of liquid solution, it follows of 
 
 necessity that the blood of the artery supplying the gland, and 
 
 that removed by the vein from the gland, differ in two respects : 1st. In 
 
 the peculiar material constituting the solid secreted ; and, 2d. In the 
 
 quantity of water. From the latter cause it must follow that the venous 
 
 blood will have a greater spissitude than the arterial. 
 
 This elementary or typical form of a gland is but very little departed 
 from in those cases in which the sac is elongated into a tube ; and even 
 where this has been extended to an exaggerated degree, the essential 
 principle of action still remains the same. 
 
 From the constancy of aspect which glands present, we might be led 
 Influence of at first to suppose that their peculiarities of construction de- 
 by'viSous a<> termme their physiological action, that the liver secretes bile, 
 tion. and the kidney urine, because they have the special organ- 
 
 ization which is needful for such purposes. Such a supposition, how- 
 ever, has to be received with much limitation, as is proved by number- 
 less cases of vicarious action. Thus, in morbid difficulties of the liver, 
 the skin will discharge its duty for it in the elimination of the bile ; and 
 in derangements of the kidneys, the mammary gland, the mucous mem- 
 brane of the nose, or even the stomach, will discharge urine. Construct- 
 ive arrangements have therefore for their object the facilitating of a secre- 
 tion, but they do not produce it. Thus the liver is far better fitted for 
 separating bile, or the kidney urine, than is the skin for each of these re- 
 spectively ; but if they become incapacitated, the skin is able to act vica- 
 riously for them. 
 
 Though such vicarious action has been denied by some physiologists 
 Connection of as being totally incompatible with anatomical indications, a 
 tioiuinTdevel- more profound conception of the law of development of these 
 opment. structures may satisfy us that it is in reality a physiological 
 
 probability, apart from the evidence we have often derived from interest- 
 ing instances of its actual occurrence. It will be seen, when we treat of 
 the primitive appearance of the different secreting organs, that they are, 
 in reality, all evolved, as it were, from a common surface or membrane ; 
 that this primitive surface discharged, though perhaps in a confused way, 
 all their functions collectively ; and that in development the ruling idea 
 seems to be the separating out, or localizing upon a determinate spot or 
 region, structures which should have the duty, in a special manner at- 
 tached to them, of removing this or that particular substance, a central- 
 ization or concentration of action thus occurring. There is therefore 
 
FILTEATION AND CELL ACTION. 191 
 
 nothing extraordinary that, under the pressure of circumstances, one of 
 the special structures should, in an imperfect way, resume the action 
 which it once enjoyed, while it was yet a part of the common structure ; 
 but, however this may be, the cases of vicarious action are too numer- 
 ous and too well authenticated to admit of any doubt. 
 
 Though these vicarious actions may be in a certain degree imperfect, 
 they are of the highest importance physiologically, since they indicate the 
 true nature of the function, and place the influence of structure in its 
 proper attitude. 
 
 The separation of material from the blood may, however, for the pres- 
 ent, be considered as conducted in two different ways ; 1st, by filtration ; 
 2d, by cell action. 
 
 Secretion by filtration is, of course, a purely physical act. The trans- 
 udation of water charged with saline substances, or with more Separation of 
 or less of albumen, seems to imply nothing but the escape of ^f^oo^by 
 pre-existing bodies through pervious or porous membranes, filtration. 
 Such a result is presented in the case of the lachrymal gland, the duty 
 of which is to accomplish a definite mechanical operation for the eye in 
 keeping the cornea clear and transparent. This mechanical function is 
 again observed in the case of the serous membranes, and particularly the 
 synovial ones, in which the relief of friction of movable parts seems to be 
 the object aimed at. 
 
 As long as the material secreted clearly pre-exists in the blood, it is 
 needless to refer secretion to any other principle than the simple one of 
 transudation or filtration. It would be unphilosophical to suppose that 
 the lachrymal gland exercises any property for the formation or produc- 
 tion of water when by mere transudation copious supplies of that sub- 
 stance can be obtained from the blood. 
 
 But secretion is, moreover, perhaps connected with cell life. On the 
 upper part of the intestine of the young chick, a few cells secretion by 
 make their appearance about the fourth day of incubation, cell action. 
 They are eventually recognized as bile-containing cells from the color of 
 their contents. As the process goes on, the spot they occupy buds off, 
 as it were, so as to produce a blind pouch. This offshoot, with its ex- 
 terior cells, is eventually, when perfect development is reached, the liver. 
 Secreting organs of this glandular class, and also membranes, possess a 
 general analogy: they consist of a structureless basement membrane, with 
 cells upon its surface, and a supply of blood-vessels. The cells are not 
 persistent, but lead a very transitory life, apparently elaborating the ma- 
 terial with which they are charged, and then undergoing rupture or deli- 
 quescence. 
 
 Our conclusion respecting the mode of action of secreting cells turns 
 altogether upon the evidence of the power they possess of preparing ma- 
 
192 FILTEATION AND CELL ACTION. 
 
 terial which did not pre-exist in the blood. Thus, if it should be. shown 
 that, under normal circumstances, the elements of bile are not found in the 
 blood, the inference might be drawn that the hepatic cells display a com- 
 bining, or, as it were, a preparing power ; and so likewise in the case of 
 other secreting cells ; but the weight to be attached to such evidence is 
 greatly affected by the consideration that the action of each gland or se- 
 Difficuityofde- creting apparatus masks what is really going on in the sys- 
 
 of C sec?etio"in S tem * ^ * s P 088 ^ 6 tnat we ma 7 l e scarcely able to discov- 
 the blood. er the traces of substances in the blood, and yet a tendency 
 may exist for their accumulation to a great extent. Thus there can be 
 no doubt that urea would abound through the disintegration of the mus- 
 cular structures, and the use of nitrogenized food, if it were not for the 
 action of the kidneys. It is the very perfection of that action which so 
 diminishes the amount in the circulation as to prevent us, except with 
 difficulty, from detecting the presence of the ingredient. 
 
 Nor is this all, for it ought to be remembered that many of the prod- 
 ucts of secretion are substances undergoing retrograde metamorphoses, 
 and have therefore, as it were, in themselves, an interior principle of 
 change. It is conceivable that things which did not pre-exist in the 
 blood may yet occur in the secretions, coming tnere, not through the 
 agency of cell-life, but because of the downward course toward an inor- 
 ganic condition through which the secretion is spontaneously passing. 
 
 Of the more prominent substances in the chief secretions, many indis- 
 putably pre-exist in the blood. Urea, cholesterine, casein, are examples. 
 Wherever this occurs, the removal is unquestionably due to mere filtra- 
 tion. Why should it be supposed that the cells of the kidneys have any 
 duty of combining material presented to them into urea, or those (if the 
 liver into cholesterine, or those of the mammary glands into casein ? As 
 our methods of examining the blood become more perfect, this formative 
 or grouping action, once so largely imputed to the secreting cells, be- 
 comes more and more restricted. 
 
 The cases in which the influence of cells is indisputable are those which 
 Conditions of ^ er to us com ^ ma tions of progressive metamorphosis. Of 
 filtration and these, the most striking instance is the preparation of the sper- 
 of cell action. matic ^^ Perhaps we should not be very far from the truth 
 if we considered all those secretions in which the materials are in a state of 
 retrograde metamorphosis, or in a descending career, as arising by mere 
 filtration, and those which are ascending to a higher grade as due to cell 
 agency; between the two there being an intermediate class, the phase of 
 which is stationary, and in which cells may or may not be necessarily 
 involved, as, for instance, the transmutation of one fat into another, or 
 the preparation of sugar from albumenoid bodies. 
 
 The apparatus for secretion is generally conveniently treated of under 
 
SECRETIONS OF SEROUS MEMBRANES. 193 
 
 two heads : 1st. Membranes, such as the serous and mucous ; 2d. Glands, 
 as the liver, kidney. This division is, however, not founded either on 
 structural or functional differences, and is to be preserved merely for the 
 sake of convenience. 
 
 A secreting membrane consists essentially of a tunic of connective tis- 
 sue, affording a nidus for vessels and nerves. Upon this, in the opinion 
 of many anatomists, a thin basement membrane is laid, the existence of 
 which is denied by others. Upon the surface of the basement membrane 
 there is a layer of cells, the form and arrangement of which differ in 
 different regions. In some places the cells are flat, in others cylindroid. 
 Their duration is temporary, one brood succeeding another from germs on 
 the basement membrane. The superficial, and, therefore, the older cells, 
 desquamate or deliquesce, and are replaced by others from beneath. It 
 is usually said that the serous membranes, with the exception O f serous mem 
 of the peritoneum, are all closed sacs, the peritoneum being branes and 
 perforated where the fimbriated extremities of the Fallopian their secretion ' 
 tubes open into the abdominal cavity in the mammalia, and in fishes 
 through the lateral anal openings. The generality of this view is now 
 called in question, both as regards the sy no vial sacs and bursse mucosas, 
 which all belong to this group. Thus Kolliker regards the synovial 
 structures as tubes open at both ends, and attached by their edges round 
 the articular surfaces of the bones. 
 
 However this may be, even the peritoneum is practically a shut sac. 
 Accumulations of water within it do not escape through the apertures of 
 the Fallopian tubes, nor can air be injected the opposite way. 
 
 The fluid exuding from the serous surfaces is a dilute albuminous so- 
 lution, more dilute as it is presented in the ventricles of the _ 
 
 n T . , i Serous fluids. 
 
 brain, and more concentrated in the synovia! cavities, its con- 
 sistency in the latter case being such that it may sometimes be drawn 
 out in tenacious threads. The mechanical qualities of these various ex- 
 udations permit a certain freedom of motion in the parts to which they 
 are applied. Thus the secretion of the peritoneum facilitates the move- 
 ments of the abdominal viscera ; those of the pericardium and pleura, of 
 the heart and lungs ; those of the synovial membranes and bursa3 mu- 
 cos03, of the joints and tendons. 
 
 The nature of serous secretions may be illustrated by the cases of 
 fluids collected from the abdominal and thoracic cavities, &c. They 
 are usually of a faint yellowish color, clear or turbid, reaction alkaline, 
 and sometimes containing so much albumen as to coagulate readily on 
 heating. 
 
 N 
 
194 CONSTITUTION OF SEROUS FLUIDS. 
 
 TABLE I. 
 fluid of Asdtes. (From Marchand.') 
 
 Water 952.30 
 
 Albumen 23.80 
 
 Urea 4.20 
 
 Chloride of sodium 8.10 ^ 
 
 Carbonate of soda 2.10 
 
 Phosphate and traces of sulphate of soda 0.60 
 
 A viscid substance 8.90 
 
 1000.00 
 
 TABLE II. 
 Asdtes with Suppuration of both Kidneys. (From Simon?) 
 
 Water 978.00 
 
 Fat containing cholesterine 1.00 
 
 Albumen 8.40 
 
 Alcohol extract 0.30 
 
 Spirit extract 1.70 
 
 Carbonate of soda and phosphate of lime 1 .20 
 
 Chloride of sodium and lactate of soda 6. 80 
 
 Urea 1.20 
 
 Loss 1.40 
 
 1000.00 
 
 TABLE in. 
 Pleural Effusion. (From Simon.') 
 
 Water 934.72 
 
 Fibrin 1.02 
 
 Fat 1.05 
 
 Alcohol extract, with salts 1.35 
 
 Spirit extract, with salts. 10.64 
 
 Albuminate of soda 17.86 
 
 Albumen 31.00 
 
 Fixed salts :.. 9.50 
 
 Gain in analysis 7.14 
 
 1000.00 
 
 To the above may be added the following interesting instances of fluid 
 of hydrocele, in which attention should be particularly directed to the oc- 
 currence of cholesterine and other bile constituents. In the case pre- 
 sented in Table IV., the fluid was observed to sparkle when shaken, in 
 consequence of the numberless crystals of cholesterine : 
 
 TABLE IV. 
 Fluid of Hydrocele. (From Simon.*) 
 
 Water 860.00 
 
 Cholesterine, with a little margarine and oleic acid 8.40 
 
 Albumen 48.30 
 
 Albuminate of soda and extractive matter 6.88 
 
 Extractive matter soluble in alcohol 2.30 
 
 Chlorides of sodium and calcium, a little sul- > <-9 -<> 
 
 phate and traces of phosphate of lime 
 
 Phosphate of lime and traces of peroxide of iron... .70 
 
 Loss 0.90 
 
 1000.00 
 
FEE-EXISTENCE OF SECRETED PRODUCTS. 195 
 
 TABLE V. 
 Fluid of Hydrocele. (From Heller.) 
 
 Water 919.20 
 
 Albumen 58.00 
 
 Free fat 1.60 
 
 Soda soap, biliphaein, haemato-globulm, dissolved ) 
 
 hsematin, and extractive \ 
 
 Fixed salts 7.30 
 
 1000.00 
 
 TABLE VI. 
 Fluid of Hydrocele. (From Heller.) 
 
 Water 906.36 
 
 Albumen 60.00 
 
 Fat containing cholesterine 0.23 
 
 Extractive matters, biliphaein, soda soap 24.04 
 
 Fixed salts, chiefly chloride of sodium 9.37 
 
 1000.00 
 
 TABLE VII. 
 Synovial Fluid. (From Frerichs.) 
 
 Water 948.00 
 
 Mucus and epithelium 5.00 
 
 Fat 0.70 
 
 Albumen and extractive 35.00 
 
 Salts 9.00 
 
 Loss 2.30 
 
 1000.00 
 
 I have introduced these tables not only for the purpose of exhibiting 
 the nature of the fluid yielded by membranes of the serous Products of ee- 
 group, but also for the sake of the important evidence they j^ n . P ^ x ~ 
 offer as regards the function of secretion itself. In the jn- blood, 
 fancy of physiology it was universally believed that the special function 
 of each gland arose from its peculiarity of construction ; that thus, by^he 
 liver, out of blood in which they did not pre-exist, cholesterine and its 
 allied bile compounds were made ; that thus, by the kidney, urea was 
 formed. Even in more recent times a modification of this doctrine has 
 prevailed, and to the cells of which glands are so largely composed, the 
 duty has been attributed of forming special products. In this way, we 
 still constantly speak of the bile-secreting cells of the liver; but the pre- 
 ceding tables indisputably show that these very compounds, cholester- 
 ine, biliphaein, urea, etc., may make their appearance in distant places, 
 oozing from surfaces wholly devoid of the supposed special mechanism. 
 In cases in which there occurs structural degeneration of the kidneys, 
 for instance, urea at once makes its appearance in unaccustomed places, 
 as though, when the readiest avenues through which it might have es- 
 caped have failed, it bursts forth or oozes out at the weakest point. 
 With such results, the idea of leakage or straining seems to be insepara- 
 
196 OF ELECTIVE FILTEATION. 
 
 bly connected ; and, moreover, an enlarged view of the operation of cell 
 life seems to indicate that the general action of those organisms is to 
 produce a formative result, the grouping of amorphous into organized 
 material, and the elaboration of that material into more complicated and 
 higher forms. But many of the most important constituents of the va- 
 rious secretions are indisputably things which are on the downward ca- 
 reer, fast passing to the inorganic state. Many of them, as presented in 
 the bile or in the urine, run through a series of spontaneous changes, 
 which end in the appearance of truly inorganic bodies. For the fabrica- 
 tion of such substances, half inorganic themselves, it is scarcely to be 
 thought that cell life should be necessary ; and these, with many other 
 such considerations, recall the observation I made a few pages back, that 
 the more profoundly we study the composition and constitution of se- 
 creted fluids, and the more accurately we understand the function of se- 
 cretion itself, the less are we disposed to invoke the agency of cell life, 
 and to rely the more on the ordinary mechanical act of strainage. 
 
 That the different secreting surfaces exercise an elective elimination on 
 Elective filtra- materials existing in the blood, some permitting the escape 
 tlon * of one, and some of another ingredient more readily, may be 
 
 demonstrated from their action on saline substances purposely introduced 
 into the blood. Thus the iodide of potassium was detected by Bernard 
 in the saliva, pancreatic juice, and the tears in less than one minute, 
 but in the urine and bile not until after an hour. The ferrocyanide of 
 potassium could be recognized in the urine in seven minutes, but not at 
 all. in the saliva. In like manner, cane-sugar and grape-sugar appear in 
 the secretions of the kidneys and liver, but not in those of the pancreas 
 and salivary glands. The lactate of iron, injected into the veins, fur- 
 nishes no iron to the saliva, but both iodine and iron can be recognized 
 in Jliat secretion after the administration of the iodide of iron. 
 
 Upon the whole, we may therefore conclude that very many substances 
 are strained from the blood in which they naturally occur by membranes 
 and glands, which, from the circumstance that they are of various con- 
 struction and possess a different physical nature, are better adapted, some 
 for the removal of one, and some for the removal of another compound. 
 
 Among secreting surfaces the mucous membranes are usually enumer- 
 Of mucous ated. Strictly speaking, however, they are scarcely so much 
 mfdtheir^secre- secretm g surfaces as the seat of numberless secreting organ- 
 tion. isms. They line the interior of the digestive, respiratory, 
 
 urinary, and generative apparatuses, and are characterized by extreme vas- 
 cularity. In structure they consist of several different layers or regions, 
 the undermost being submucous cellular tissue, upon which is spread the 
 proper mucous membrane, containing connective and elastic tissue, which 
 affords a nidus for blood-vessels and nerves. Upon this is the basement 
 
PROPERTIES OF MUCUS. 197 
 
 membrane, covered with epithelial cells. In many regions this compound 
 structure rises into elevations, as in the intestinal villi, or sinks into de- 
 pressions, as in the follicles. 
 
 The epithelial cells are of different kinds, sometimes flat, giving origin 
 to tesselated or pavement epithelium, and sometimes cylin- 
 
 T ., i n - i -i -n , Epithelial cells. 
 
 droid, each cell, in this case, being set vertically upon the 
 basement membrane. In many instances, the cylindroid nucleated cells 
 are furnished upon their outer extremity with vibrating cilia, constituting 
 ciliated cylindroid epithelium. Both forms of epithelium, the tesselated 
 and the cylindroid, coexist in glandular ducts. The origin of the cells 
 is in the basement membrane, from germs arising there ; and as the older 
 and therefore superficial cells exuviate or deliquesce, new ones arise to 
 take their places. 
 
 After what has been said, it is not necessary to give a detailed de- 
 scription of mucous surfaces farther than to state that from properties 
 them there is furnished a viscid, glairy fluid, of different shades * of mucus, 
 of color from white to yellow, denser than water, and insoluble therein. 
 Examined by the microscope, it contains granular corpuscles and epithe- 
 lial cells. Its reaction is alkaline, and its proximate constituent is a sub- 
 stance to which the name of mucin has been given. Derived from dif- 
 ferent sources, as the nasal, bronchial, and pulmonary surfaces, the in- 
 testinal canal, and the urinary and gall bladders, it exhibits specific dif- 
 ferences. Its quantity is often greatly increased by morbid causes, as, 
 for example, in catarrh, its composition likewise varying at different 
 stages of the same disease. Its use, for the most part, seems to be the 
 protection of the delicate structure which secretes it. In some positions, 
 as in the intestinal canal, it likewise probably acts in the way of reliev- 
 ing friction of the substances passing over surfaces. 
 
 Of secreting Glands. The typical form of secreting cell-gland is a 
 single cell, with its nucleus at the lower end, the other end simple sac-like 
 having become open by deliquescence or dehiscence, and thus cell-gland, 
 constituting a sac. From the nucleus thus situated at the end of the 
 cavity broods of young cells arise. These become more perfect as they 
 advance toward the mouth of the sac. The outer wall, and especially 
 the region of the nucleus, is furnished copiously with blood-vessels. 
 
 Of such structures, variously modified, the different glands are com- 
 posed. We shall now proceed to the description of the more important 
 of these, as the liver, kidneys, mammary gland, &c., again impressing 
 the remark that, though all these glands are the seats of myriads of cells, 
 cell life is for increased organization, and secretion is in many instances 
 nothing more than filtration or strainage. We shall endeavor, as the 
 occasion arises, to show, in the case of each gland, what part of its action 
 is due to cell influence, and what to such mechanical permeation. 
 
198 
 
 DEVELOPMENT OF THE LIVER. 
 
 OF THE LIVER. 
 
 The first appearance of a bile-secreting organ is the occurrence of yel- 
 Rudiment of l w CQ ^ S variously scattered upon the lining membrane of the 
 the liver. digestive cavity, as in the hydra. A concentration or local- 
 ization next ensues, such yellow cells being grouped upon the wall of the 
 intestin3 at a definite spot. A ccecal projection, in the higher tribes, 
 seems next to force out the yellow cells, bearing them on its exterior, as 
 in the nudibranchiate gasteropods ; and as these cceca are prolonged 
 more and more, so, in a more definite manner, does the rudimentary liver 
 appear. In molluscs this partition is sufficiently distinct. The special 
 form which the hepatic apparatus presents in different tribes varies very 
 greatly, though doubtless the principle of construction and of action is 
 always the same. Thus, in insects, the liver con- 
 sists of long tubes of delicate membrane, covered 
 with secreting cells, small and germ-like near the 
 distant end of the tube, but more perfect at the 
 mouth. These tubes are in relation with an adi- 
 pose mass, which is probably connected with the 
 origin of the cells. The different condition of 
 these cells, when compared at the bottom and at 
 the mouth of the bile-sac, is well seen in the 
 case of crustaceans, as in Fig. 82, one of the he- 
 patic coeca of the cray-fish. The letters at the 
 side show the state of the cells in different posi- 
 tions toward the mouth of the follicle. At a they 
 contain yellow biliary matter only ; at b, oil glob- 
 ules are appearing in them, which become more 
 distinct at c / and toward d and e they present 
 the appearance of ordinary fat-cells. Thus, ex- 
 amined at the bottom of the follicle, the cells are 
 Biliary, an d as we Advance to the mouth they be- 
 
 ^' 
 
 i of cray-fish. 
 
 Hepatic 
 
 come fatty. (Leiby.} 
 
 The comparative anatomy of the liver is repeated in its order of devel- 
 Development opment in the high vertebrated animals. In them it is first 
 of the liver, detected in an evolution of cells upon the intestinal wall, at 
 the point which is eventually to be the place of discharge of the common 
 bile-duct. This agglomeration of bile-cells is next seen to project or bud 
 off through the intrusion of a coecal pouch. In the amphioxus the con- 
 dition thus reached remains permanent, and is the counterpart of the liver 
 of a fowl about the fourth day of incubation. The coecal pouch next 
 sends forth ramifications, which are likewise accommodated with cells, 
 and these, branching again, give origin to a complicated structure. In 
 
STRUCTURE OF THE LIVER. 
 
 199 
 
 . sa 
 
 this condition, the mouth of the ccecum becomes drawn out and narrowed 
 down, and so forms the rudiment of an hepatic duct. 
 
 In man, the liver is the largest gland in the body : it is of a reddish- 
 brown color, dense, and from three to five pounds in weight ; Description of 
 convex on its upper, and concave on its inferior surface. It the liver - 
 has five lobes : the right lobe, the left lobe, the lobus quadratus, the lo- 
 bus spigelii, and lobus caudatus.. It is held in its position by dupli- 
 catures of peritoneum and by a fibrous cord termed its ligaments. Its 
 peritoneal envelope is the cause of its glossy appearance ; its cellular en- 
 velope extends into the interior as sheaths for the vessels. Five classes 
 of vessels are found within it : the branches of the portal vein, those of 
 the hepatic artery, those of the hepatic veins, the lymphatics, and the he- 
 patic ducts ; the latter, converging eventually into a trunk, the hepatic 
 duct, joins with the cystic duct to form the ductus communis choledo- 
 
 chus, which discharges its contents 
 into the duodenum, as seen in Fig. 
 83, in which a is the gall-bladder, 
 which constitutes a temporary recep- 
 tacle for the bile, b the cystic duct, 
 d the hepatic duct, c its branches, e 
 the ductus choledochus, and h its 
 opening into the duodenum. 
 
 The bile-ducts entering the duodenum. The gaU^^der ls Wanting in in- 
 
 vertebrated animals, and first makes its appearance in a rudimentary 
 condition as a dilatation of the bile-duct : it is absent in the horse, pres- 
 ent in the ox ; in the camelopard it was absent in one individual, and 
 the next that happened to be examined had two. 
 
 The intimate structure of the liver in man is, in many particulars, still 
 imperfectly known, though the attention of the most eminent Intimate struc 
 anatomists has been devoted to it. It may, however, be un- ture of the HV- 
 derstood that each hepatic vein, commencing in the substance 
 of the liver, bears upon its capillaries small portions called lobules, from 
 the -J0- to the -fa of an inch in diameter, in a manner which calls to mind 
 
 the arrangement of leaves on a branch, or 
 a bunch of grapes, as represented in Fig. 
 84, a being the vein, #, , , leaf-like lob- 
 ules on its branches. Excluding the lym- 
 phatics, it may be said that four different 
 systems of vessels are engaged in the liver, 
 the portal vein and hepatic artery, the bile- 
 ducts and hepatic veins. The first pair 
 Hepatic veins in the lobules of the liver. are a ff eren t, the second pair efferent ves- 
 sels. The portal vein brings the blood from which bile is to be secre- 
 
200 
 
 STRUCTURE OF THE LIVER. 
 
 Fig. 85. 
 
 Origin of hepatic veins in the liver lobules. 
 
 ted ; the hepatic artery brings aerated Wood for the nourishment of the 
 gland ; the bile-ducts carry away the biliary secretion which has been 
 separated from the portal blood, and the residue, taken charge of by the 
 hepatic veins, is eventually carried back into the general circulation 
 through the vena cava. 
 
 A general idea of the mode of arrangement of the four vessels in the 
 
 liver may be obtained by recalling 
 the illustration just given, that the 
 lobules are placed on the commence- 
 ment of the hepatic veins, like grapes 
 on their stalks. The vein originates 
 in the centre of each lobule, as shown 
 at a a, in Fig. 85, and exhibits there 
 a ray-like kind of divergence. On 
 the periphery of each lobule, at #, 5, #, 
 as it were on the surface of the 
 grape, the other three vessels ram- 
 ify. Of them the portal veinlets dip 
 down into the substance of the lob- 
 ule. The hepatic arteries likewise 
 enter for the purpose of giving nutri- 
 tion to the parts. In Fig. 86, #, a are the commencing hepatic or intra- 
 
 lobular veins of two lobules ; , #, 
 the biliary ducts ; c, interlobular 
 tissue ; d d, parenchyma of the lob- 
 ules. With respect to the bile- 
 ducts, which are prominently rep- 
 resented in this figure, it is not pos- 
 itively known whether they pro- 
 ceed beyond the surface, and the 
 manner in which they are related 
 to the secreting cells, and receive 
 the liquid yielded by them, is a sub- 
 ject of controversy. The inter- 
 spaces between the capillaries that have entered the lobules are filled up 
 with these cells. 
 
 It is not known whether the hepatic artery discharges its blood into 
 
 He atic cells ^ P orta ^ capillaries, or into those of the hepatic vein, and, 
 
 for this reason, it is doubtful whether that blood takes part 
 
 in the secretion of the bile. The secreting cells have nucleolated nuclei, 
 
 and are about the - 2 * 6 of an inch in diameter. 
 
 In Fig. 87, at <z, #, #, their normal state is shown. They are filled 
 with a yellowish, granular soft substance ; at b b is the appearance of fat 
 
 I T> 
 
 Origin of bile-ducts on the liver lobules. 
 
COURSE OF THE BILE. 201 
 
 globules, which increase in number and size at c, , <?, c. They thus con- 
 tain both biliary material and oil globules, the quantity of the latter vary- 
 ST. ing with the nature of the food, and 
 
 ffi\ sf^&i * n certani Diseased conditions occur- 
 '.?..\ ('.-i^K* rm g to so g rea t an extent as to give 
 rise to the aspect known as "fatty 
 .liver." This accumulation of fat is 
 connected with the respiratory func- 
 tion, not only in conditions of dis- 
 ease, but even in a state of health ; 
 
 Hepatic cells magnified 400 diame'ters. f Qr? t ^ e more ener g e ti c the rCSpira- 
 
 tion, the more free is the liver from fat. 
 
 As the chyle passes through the mesenteric glands before it is dis- 
 charged into the circulation, so do the matters which have been taken up 
 by the vascular absorbents pass to the liver. In Chapter IV. the bile, 
 which is secreted from the portal blood, is treated of as taking part in the 
 function of digestion ; but there is another aspect under which we have 
 now to regard it. 
 
 We speak of the circulation of the blood, because, setting out from the 
 heart, it conies back thereto, pursuing a course which returns H r othetical 
 upon itself. In the same metaphorical manner, according to spiral course of 
 the views of some, we might speak of the spiral motion of t 
 the bile ; for those of its constituents, which are first taken from the stom- 
 ach and small intestine by their veins, appear to pass in the portal circu- 
 lation to the liver. In that gland a preliminary partition of the constitu- 
 ents of the portal blood ensues, one stream setting off to the general cir- 
 culation through the hepatic veins, and another, the bile itself, returning 
 to the intestine. In the intestine another partition ensues ; the coloring 
 matter of the bile is dismissed with the faeces, and the residue, taken up 
 by the lacteals, passes through the mesenteric glands, and, either by the 
 thoracic duct or otherwise, gets into the blood circulation. It may there- 
 fore be perhaps thought that the constituents of the bile have been twice, 
 in close succession, in the digestive cavity, and have been twice absorb- 
 ed, first by the veins, and then by the lacteals ; and that, as it were, a 
 spiral course has been pursued. 
 
 The question at once arises, what is the object of such a course ? Why 
 is there this return to the digestive cavity? The answer commonly given 
 is, the bile takes part in promoting the operation of digestion. But the 
 return may perhaps be, not for the purpose of inducing digestion, but for 
 the purpose of being acted on or digested itself. The separation of its 
 coloring matter, just alluded to, is a significant fact. 
 
 The portal blood, as it is preparing to enter the liver, may be regarded 
 as systemic venous blood, the constitution of which has been altered 
 
202 SOURCE OF THE BILE. 
 
 through the additions made to it by absorption of matters from the stom- 
 ach and intestine. We may overlook for the present those 
 
 beparation or '.** 
 
 the portal blood contributions it receives from the veins of the spleen and oth- 
 m the liver. er S0urce3> Regarding it, therefore, as systemic venous blood, 
 charged with certain of the products of digestion, it enters the liver to be 
 acted upon by that gland. The first effect upon it is, in a chemical point 
 of view, well marked. The stream which sets off to the general circula- 
 tion through the hepatic veins may be said to carry away the whole of the 
 nitrogenized material ; for the bile, which is at this point parted out and 
 sent back to the intestine through the biliary ducts, does not contain more 
 than 4 per cent, of nitrogen, and this exclusive of the water which im- 
 Course and P arts * ^ ^ ts liquid condition. Arrived in the intestine, a rep- 
 separation of etition of the same process of partition takes place, the color- 
 ing matter, which contains nearly the whole of this residual ni- 
 trogen, being dismissed with the faeces, and the remaining hydrocarbon 
 taken up by the lacteals along with other fats. 
 
 The first duty of the liver is therefore a separation of the nitrogenized 
 principles of the portal blood, which are forthwith carried into the gen- 
 eral circulation through the hepatic veins and the vena cava. The result 
 is, that there is returned to the intestine a sulphureted hydrocarbon, still 
 containing so much* nitrogen as to form a very unstable product, prone 
 even to spontaneous decomposition. In the intestine its nitrogen is whol- 
 ly removed from it, and the combustible hydrocarbon is then absorbed. 
 
 The portal blood, regarded under the aspect here presented, is obvi- 
 From what ous ty composed of two constituents : 1st. Systemic venous 
 source is the blood ; 2d. Matters obtained from the digestive cavity. We 
 
 bile derived? next inquire from which O f these ^ ft\ Q is rea H y derived. 
 
 Besides the presumptive evidence arising from the consideration that 
 if the bile originated from matters which had been just absorbed from 
 the digestive cavity, it would be inconceivable why it should be returned 
 forthwith thereto, its quality of extreme instability marks it out; as a sub- 
 stance fast approaching to final disorganization and decomposition. It 
 bears no aspect of a histogenetic or formative body, but, on the contrary, 
 it is on the downward course. We should scarcely expect to recognize 
 it as a primary product of the digestive action, but should seek its prob- 
 able origin in some source of decay. 
 
 Whatever weight may attach to such considerations, we have, in addi- 
 tion, direct evidence which places the source of the bile beyond doubt by 
 referring it to the systemic venous blood, and not to the matters just ob- 
 tained from the digestive cavity. 
 
 During foetal life, the digestive organs are in an inactive state, but the 
 liver, which is largely developed, discharges its secretion into the intes- 
 tine. This secretion, which is known as the meconium, is a true bile, as 
 the following analysis proves. 
 
BILE IS DERIVED FROM VENOUS BLOOD. 203 
 
 Composition of Meconium. (From Simon.) 
 
 Cholesterine 160.00 
 
 Extractive and bilifellinic acid 140.00 
 
 Casein 340.00 
 
 Bilifellinic acid and bilin 60.00 
 
 Biliverdin and bilifellinic acid 40.00 
 
 Cells, mucus, albumen 260.00 
 
 1000.00 
 
 Dr. Davy found that the ash left after the incineration of a sample of 
 rneconium is of a reddish color, consisting chiefly of peroxide of iron and 
 magnesia, with a trace of phosphate of lime and chloride of sodium. 
 
 During foetal life the liver is therefore discharging the same function 
 that it does after aerial respiration has commenced, that is it does not 
 to say, it secretes bile (meconium) into the intestine ; but at 
 this period, since there is no true digestion, the -bile can products. 
 come from one source alone, and that source is the systemic venous 
 blood. There therefore can remain no doubt that, in after life, the same 
 effect takes place, and that the bile is never derived from materials which 
 have just been brought from the digestive cavities. 
 
 I therefore regard the bile as an excretion of materials which are de- 
 composing and ready to be removed from the system. I in- It comeg from 
 cline to the supposition that much of it is derived from the the venous 
 cells of the blood, the life of which is only temporary, for the blood * 
 casein of the meconium is nothing but the globulin of the cells, the two 
 substances being chemically allied, and the predominance of iron in the 
 ash of meconium seems to establish a connection with hasmatrn. More- 
 over, this opinion is supported by the remarkable stability of many of 
 the nitrogenized coloring, matters, the analogies between hasmatin and 
 chlorophyl, and particularly by the fact that in the herbivora the coloring 
 matter of the bile is undistinguishable from chlorophyl, and in most oth- 
 er tribes closely allied thereto. 
 
 In any discussion of the action of the liver, it is thus to be constantly 
 borne in mind that the portal blood consists of two distinct portions, sys- 
 temic venous blood and matters absorbed from the digestive apparatus. 
 Derived from the first of these portions, we trace the origin of the bile to 
 the waste of the tissues, or to the blood-cells on their downward career ; 
 and hence we arrive at the important conclusion that every proximate 
 constituent of the bile pre-exists in the systemic venous blood. 
 
 Lehmann, inclining to the view that the formation of the bile occurs 
 in the liver itself, quotes the experiments of Miiller and Attempts to de- 
 Kune, who, after tying the portal vein and applying liga- tect cholic acid 
 tures to all the points of attachment of the liver in frogs, ex- mentinthf" 
 tirpated that organ, and collected the blood of those which blood - 
 survived the operation for two or three days, by amputating their thighs. 
 
204 CONSTITUTION OF BILE. 
 
 It was expected that in this blood, bile pigment and cholic acid would 
 be found if the original formation of those substances took place exter- 
 nally to the liver. Such did not prove to be the case. It may, however, 
 be justly inferred that no reliable conclusion can be drawn after opera- 
 tions of such magnitude and severity. 
 
 The alleged inability to detect the constituents of the bile in the blood 
 Cause of this of the portal vein is probably due to the defects of our ana- 
 Scting'biie in~ ty^ processes, for it is very clear from the circumstance 
 the blood. that the bile which is poured into the intestine must be reab- 
 sorbed, with the exception of its coloring material, either by the lacteals 
 or the veins, or by both, since it is not found in the excrement. Through 
 whichever of these channels it passes, it must therefore regain the gen- 
 eral circulation, for it can not be supposed that in the short period of its 
 course it could have undergone complete metamorphosis. 
 
 We may therefore assume that the proximate ingredients of bile pre- 
 exist in the blood, and this conclusion is enforced by the fact that, after 
 tying the vena porta, bile, though in a diminished quantity, is still se- 
 creted. The same also occurs in those cases of malformation in which 
 that vessel, instead of ramifying into the liver, empties directly into the 
 vena cava. When there is any failure or delay in the removal of bile 
 from the system, the effects are such as might even be predicted, nervous 
 disturbance ensuing, and eventually all- the symptoms of poisoning. The 
 circumstance that this last effect often takes place suddenly, has been by 
 some supposed to be dependent on the necessity for the bile to accumu- 
 late, to a certain extent, but it is much more likely that it is determined 
 by the metamorphosis of the decomposing bile having reached a certain 
 point, when special poisonous products have spontaneously arisen from it. 
 
 Bile, from whatever animal it may have been derived, contains a resin- 
 Constitution of ous soda salt, a coloring material, cholesterine, and mucus, 
 bile. rj^g ac - ( j Q t j ie g0( ^ a ga | t - g fa Q taurocholic or glycocho- 
 
 lic. The coloring matter in carnivorous and omnivorous animals is 
 brown, the cholepyrrhin of Berzelius ; but in birds, fishes, and amphibia, 
 it is green, biliverdin. Strecker makes the curious remark respecting the 
 bile of fishes, that in those which are of salt water, potash salts predom- 
 inate ; and in those of fresh water, soda salts. Among the ultimate ele- 
 ments occurring in the bile, and being of special interest, may be men- 
 Constitution of tioned sulphur, which exists in taurine, of which the com- 
 taurine. position is C 4 , H 7 , N, S 2 , O 6 . It may be obtained from ox- 
 
 gall ; it has likewise been made artificially by Strecker from the isethi- 
 onate of ammonia. It is distinguished by evolving sulphurous acid 
 when burnt in the open air. It does not exist in the bile in an insu- 
 lated condition, but probably as an adjunct to cholic acid, and has been 
 found in that secretion of both hot and cold-blooded animals. It has, 
 
QUANTITY OF BILE. 205 
 
 however, been asserted that sulphur, and therefore taurocholic acid, does 
 not exist in the bile of the hog. 
 
 The bile is secreted more slowly during a long period of fasting, and 
 more rapidly during normal nutrition. To a certain extent, production of 
 this variable rate depends on the general principle that a bile - 
 gland acts more energetically in proportion as the supply of blood sent 
 to it is greater. If not wanted for the present purpose, the product is 
 stored up, for a time, in the gall-bladder. 
 
 When the bile has been long retained in the gall-bladder, it becomes 
 concentrated through the removal of a portion of its water : change of bile 
 it also undergoes a change of color. In animals whose he- after retention, 
 patic bile is yellow or brown, the cystic bile has a tendency to green, a 
 change of color dependent on partial oxidation, occasioned by the arte- 
 rial blood. 
 
 The flow of bile takes place with different degrees of rapidity at dif- 
 ferent diurnal periods : thus it reaches its maximum in from p eriod of max 
 thirteen to fifteen hours after the last full meal, and then imum flow of 
 rapidly diminishes. 
 
 Bidder and Schmidt estimate the diurnal secretion in an adult at 54 
 oz., containing 5 per cent, of solid matter, an estimate which is undoubt- 
 edly too high, so far as an average diet and state of health are implied. 
 It is asserted that a diet of flesh tends to produce more bile than one of 
 a purely amylaceous kind. Even the use of a large quantity of water 
 increases its amount, and this as regards its solid constituents. Reme- 
 dial agents act in various ways. Calomel increases the fluid, but di- 
 minishes the solid constituents. Carbonate of soda diminishes both. 
 Again, there are great variations in the rate of its production: the circum- 
 stance just mentioned, that its maximum flow is several hours after the 
 maximum digestion, is important as regards the explanation of its forma- 
 tion, showing significantly that it is not directly produced from matters 
 recently absorbed from the intestine, but from the systemic venous blood. 
 
 But the liver has other duties to discharge besides the separation of 
 bile. It gives origin to sugar and fat, as is proved by the Other duties of 
 circumstance that the blood of the hepatic veins is richer in 
 those ingredients than the blood of the portal. In this re- ing bile, 
 spect its action seems more particularly to be that it converts other sug- 
 ars into the particular form known as liver-sugar, which it can also pro- 
 duce from the transforming albuminous bodies ; it forms fat from sugar, 
 and makes from certain other fats the special one known as liver-fat. In 
 this duty of forming sugar and fat, it exhibits an inverse power of action ; 
 as the production of the one predominates, that of the other declines. 
 
 From the .point of view which we have now reached through this de- 
 scription, we are able to see the double duty which this great gland dis- 
 
206 BILE BEHOVED FROM BLOOD BY FILTRATION. 
 
 The liver does charges, and must correct, to a certain extent, the popular 
 not form bile, theory of its action. Does the liver really secrete bile ? Is 
 it the business of the so-called bile-secreting cells to withdraw the constit- 
 uents of that liquid from the blood, and combine them together into this 
 viscid yellow liquid ? I think not ; for it is a matter of demonstration that 
 not only every constituent of the bile, but the bile itself, pre-exists in the 
 blood, and it is just as unphilosophical to burden those cells with the 
 duty of forming it as it would be to believe that a like agency is needful 
 for the appearance of urea in the kidney. Moreover, we must constantly 
 bear in mind the extreme instability of this substance, how readily the 
 yellow bile, of carnivorous animals becomes green by partial oxidation, 
 and the green bile of the herbivora yellow by deoxidation. It spontane- 
 ously changes in its downward career, and any differences in quality or 
 character which we might impute to the action of the cells upon it may 
 be equally well attributed to its own inherent principle of change. 
 
 For these reasons, I believe that the bile simply transudes from the 
 Manner of blood, and that the cells of the lobules have no special relation 
 removing it. to j t beyond this, that it oozes past their interstices, or, perhaps, 
 by *physical imbibition, finds access to their interior. I see no reason 
 that these cells should form it when it pre-exists in the blood, nor does 
 the state of the affluent and effluent blood offer any contradiction to this 
 conclusion. In all discussions of the functions of this organ founded 
 upon a comparison of the portal and hepatic venous blood, the relative 
 quantity of water which they contain, and its great and even rapid fluc- 
 tuations, should always be borne in mind. As might be expected, portal 
 blood contains far more water, and, even after abundant drinking, the 
 amount in the hepatic venous blood has by no means increased to the 
 extent that might have been expected. It is for these reasons that the 
 bile varies so greatly at different periods in its specific gravity and 
 fluidity. 
 
 The blood of the portal vein is, moreover, periodically varying in its 
 Variation in constitution, according to the state of activity of the organs 
 
 tfoVorfoeJor- from wllich i1: is tefog derived - In tlie first sta g es of diges- 
 tai blood. tion the stomach is supplying it in unusual quantities, and 
 with the ingredients which its veins have been absorbing from the result 
 of histogenetic digestion. A little later, the same thing occurs with the 
 intestine. At another period the supply from the spleen varies. 
 
 The explanation which Mr. Handfield Jones has recently given of the 
 Function of the function of the hepatic cells that they manufacture liver- 
 hepatic cells, sugar deserves attentive consideration, more particularly if 
 we likewise impute to them the production of liver-fat ; for this would at- 
 tach them rather to the ramifications of the hepatic veins as a part of their 
 instrumental mechanism, and assign them only a very indirect relation to 
 
PRODUCTION OF FAT AND SUGAR. 207 
 
 
 
 the bile-ducts. The contradictory statements whicii have been made by 
 the most eminent anatomists respecting the connection of the bile-ducts 
 and the bile-cells some believing that the bile-ducts are covered inte- 
 riorly with the cells ; others, that the ducts end on the outside of the 
 lobules ; others, that the passages reported to have been seen among the 
 cells are interstitial channels and not proper vessels make it just as 
 probable, anatomically, that the cells belong to the hepatic veins as that 
 they belong to the biliary ducts. 
 
 It is true that there may be a mixed action, and that presence of bil- 
 iary matter may be necessary to the sugar and fat producing agency. 
 This interworking and mutual dependency of functions is not without a 
 parallel. Thus the lung, viewed as a secreting or excreting gland, has 
 for its object the removal of carbonic acid from the system ; but it also 
 discharges another duty, which is dependent for its accomplishment 
 upon the physical or chemical qualities of the hsematin of venous blood, 
 the introduction of oxygen by aerating or arterializing. But the excre- 
 tion of carbonic acid and the introduction of oxygen, though separate 
 physiological events, and to be spoken of as distinct functions of the 
 lung, are yet nevertheless interconnected ; the one is essential for the ac- 
 complishment of the other, and the one effect is made the means by 
 which the other is brought about. 
 
 So it may be in the liver: the contact of bile with the secreting cells 
 may be essential to their sugar or fat producing action. 
 
 The deposit of fat and the production of bile seem to be inversely as 
 each other. Bidder and Schmidt found that fat animals Relation of the 
 yield less bile than lean ones, and that when they were fed 
 on fat the quantity was smaller than in the case of animals of bile, 
 fed on a less fatty diet. From such facts, the inference has been drawn 
 that the accumulation of fat is in consequence of a diminution of the se- 
 cretion of bile, and not that the diminution is the consequence of the an- 
 imal being fat. In such discussions it should, however, be recollected, 
 that the fats do not furnish all the substances required for the produc- 
 tion of bile, but only a limited portion thereof. Thus there are reasons 
 for the belief that sugar, lactic acid, or some other allied body is essen- 
 tial to that process, and it is very clear that so too are the materials 
 furnished from the decay of the cells of the blood. 
 
 With respect to the production of sugar in the liver, it may be re- 
 marked, that the quantity of that substance in the solid res- p roduction of 
 idue of the serum of hepatic blood is from ten to sixteen sugar and fat 
 times greater than in the same residue from the portal blood ; 1] 
 
 id in animals undergoing starvation, though no sugar could be found in 
 
 >rtal blood, it occurred to such an extent in the corresponding hepatic 
 
 lous blood, that Lehmann found that its quantity could be determined 
 
208 INFLUENCE OF PNEUMOGASTRIC NERVE. 
 
 
 
 Iby fermentation. FrDm this there can be no doubt that, in the changes 
 which are occurring during the passage of the blood through the liver, 
 there is a production of sugar, and this seems to be connected with a dim- 
 inution in the quantity of fat ; for if an excess of fat and a deficiency 
 of sugar enter that organ, and their quantities are inversely changed at 
 their emergence from it, it would appear that fat may be decomposed act- 
 ually, as we know is possible hypothetically, into cholic acid and sugar. 
 
 But with respect to taurine, the adjunct of the cholic acid, since it is a 
 
 Taurine comes m 'trogenized body, we are obliged to seek for it in some oth- 
 
 from blood- er source, and this, it would appear from the facts set forth, 
 
 must be the regressive metamorphosis of the blood-cells. 
 
 Taurine has not as yet been detected in the portal blood. It can not be 
 
 supposed that the sulphuric acid of the portal blood is used by deoxida- 
 
 tion in the preparation of free sulphur for the taurine, since, if any thing, 
 
 the quantity of that acid in the hepatic venous blood is increased. From 
 
 'whatever source it may have been derived, the sulphur of taurine entered 
 
 the liver in an unoxidized state. 
 
 When we reflect that the bile is the product of decay, that it pre-ex- 
 ists in the blood, that on its arrival in the intestine a part of it is cast 
 out with the fa3cal matter, it seems very unlikely that an immense cell 
 apparatus, constituting the largest gland in the whole system, should be 
 Analogies in necessary for its removal. But when we moreover reflect 
 dlTdnglugar " that in tte mechanism of plants, from gum, or rather from 
 and fat. carbonic acid and water, under the agency of cells in the 
 
 leaves or other structures, both sugar and oils are formed, we recognize 
 that there is a connection between those organisms and these products. 
 
 M. Bernard's experiments seem to show that the sugar-forming func- 
 Influence of tion of the liver may be morbidly increased by wounding the 
 the pneumo- medulla oblongata near the origin of the pneumogastric nerve, 
 
 gastric nerve . _ r 
 
 on the quanti- or by the application of galvanism to the same part, an arti- 
 ty of sugar. c i a l diabetes ensuing, and this within a few minutes after 
 the operation, but it usually ceases after two or three days. It is accom- 
 panied by a great derangement of respiration, a lowering of the tempera- 
 ture, and a venous condition of the arterial blood. It by no means fol- 
 lows, however, that the excess of sugar observed in Bernard's experi- 
 ments arises from an increased action of the liver, or an increased energy 
 of the sympathetic nerve : it may be, as Reynoso asserts, attributable to 
 the injury inflicted on the pneumogastric, and diminished respiration. 
 The administration of ether and chloroform, the conditions of old age and 
 foetal life, the influence of many diseases, as chronic bronchitis, asthma, 
 pleurisy, all present a tendency to the accumulation of sugar in the urine, 
 the sources in each of these cases being attributable to respiratory dis- 
 turbance ; for if any thing occurs to retard or delay the destruction by 
 
DESTRUCTION OF BLOOD-CELLS IN THE LIVER. 209 
 
 oxidation of the sugar, constantly formed by the liver, the accumulation 
 will make its appearance in the urine. The appearance of saccharine 
 matter in that secretion may be equally well attributed to its non-de- 
 struction in the system generally as to its over-production by the liver. 
 
 This gland, besides producing sugar and fat, is the seat in which the 
 worn-out blood-cells are finally disintegrated, and probably Destruction O f 
 the young ones pushed forward through a certain stage of blood-cells in 
 their development ; advantage, moreover, being incidentally t 
 taken of the secreted bile, which possesses properties useful though not 
 essential for promoting the digestion and absorption of fatty material, 
 perhaps, also, of imparting a definite course to the transmutation of the 
 semi-digested material in the intestine, and this both as regards nitro- 
 genized ? amylaceous, and fatty bodies. Of the influence of the bile in 
 promoting the absorption of fat, the physical experiments which have 
 been alluded to leave no doubt; but that these uses are of a secondary 
 or non-essential kind, and are only taken advantage of in an indirectly eco- 
 nomical way, is established beyond all possibility of a doubt by the fact 
 that animals can live for a long time, even for months, without the pas- 
 sage of bile into the intestine, provision having been made for its escape 
 externally through an artificial fistulous orifice. 
 
 These conclusions respecting the functions of the liver are in harmony 
 with the appearances presented by the blood leaving and entering it : 
 the predominance of colorless blood-cells, and of young cells well ad- 
 vanced toward perfection in the former, and of wasted, worn-out ones in 
 the latter ; with the fact that the maximum secretion of bile does not 
 take place until more than half a day after the ingestion of food ; and 
 that during foetal life, in which there is no food, either in the stomach or 
 intestine, to be digested, the liver is nevertheless in high activity, and 
 bile is secreted. 
 
 In view of all the preceding facts, we may therefore finally conclude 
 that there are at least four distinct operations conducted in the liver; 1. 
 The production of sugar and fat ; 2. The separation of the bile ; 3. The 
 destruction of old blood-cells ; 4. The completion or perfection of young 
 blood-cells, perhaps by receiving their iron. With respect to these it 
 may be remarked, 
 
 First. The formation of sugar and fat, either from carbohydrates, or 
 what, in this instance, is more probable, from albumenoid bod- General sum- 
 ies brought by the portal vein, can no longer be doubted. 
 The prevalence of liver-sugar and liver-fat in all that region er. 
 of the venous circulation included between the liver and the lungs must 
 be attributed to this source. That the sugar undergoes rapid metamor- 
 phosis in the pulmonary organs is plainly proved by the effects of irri- 
 tation of the pneumogastrics, which, interfering with the function of rcs- 
 
 O 
 
210 SUMMARY OF THE ACTION OF THE LIVER. 
 
 piration, permit this substance to reach the aortic circulation, from which 
 it is removed by the kidneys, a diabetes arising. So far as the prepara- 
 tion and course of this sugar is concerned, the liver is a ductless gland, 
 and, with Mr. Handfield Jones, I believe that the cells of the liver are the 
 agents which accomplish this duty. The production of fat appears to be 
 inversely as that of sugar. In the crustacean bile-sac, Fig. 82, we see 
 the gradual stages of its appearance ; and the production of both bodies 
 .is well illustrated in the life of plants. 
 
 Second. The bile is separated from the blood portion of the portal 
 blood, and not from the products of digestion obtained from the chylo- 
 poietic viscera. The elements of bile I believe to pre-exist in the blood, 
 and to escape from the portal veinlets to the biliary ducts by mere filtra- 
 tion or strainage. The precise source from which the bile is derived 
 is probably the blood- cells, and in the changes which they are under- 
 going the spleen is perhaps concerned. If this be so, the bile-duct is 
 as much a duct for the spleen as it is for the liver itself. The bile may 
 almost be looked upon as a hydrocarbon, containing a very changeable 
 and therefore noxious coloring material, which, when the secretion reach- 
 es the intestine, is parted from it and dismissed with the fteces, the prop- 
 er hydrocarbon being taken up by the absorbing arrangement for hydro- 
 carbons, the lacteals, and so sent through the thoracic duct. Perhaps, 
 also, by reason of its special adaptedness for that purpose, it aids in the 
 absorption of other fats. 
 
 At this point it may be remarked that the view here presented of the 
 sugar-forming and bile-straining functions of the liver appears to be 
 greatly strengthened by the anatomical construction of that organ. 
 There is no obvious communication between the portal and hepatic vein- 
 lets save through cells, but the portal veins and the bile-ducts run in 
 their ramifications side by side. 
 
 Third. Whatever part of the disintegration of old blood-cells takes 
 place in the spleen, their final destruction is doubtless accomplished in 
 the liver, this being the immediate source from which the bile itself is 
 derived. Though these metamorphoses are, to a greater or less extent, 
 occurring throughout the circulation, it is in these two great glands that 
 an opportunity is afforded for the destruction to reach it's completion, and 
 the resulting product of waste to be removed ; nor is there any thing in 
 this view at all contradictory to the opinion I have enforced, that all the 
 constituents of the bile may be found in the general circulation. 
 
 Fourth. The liver also aids in the preparation or maturation of young 
 blood-cells in an indirect way. There are certain of the mineral constit- 
 uents of the disintegrated cells too valuable to be cast away, since they 
 can subserve the duty of entering into the composition of young cells 
 passing toward perfection. As such a substance may be mentioned iron. 
 
THE DUCTLESS GLANDS. 211 
 
 This view of the action of the liver appears also to "be sustained by the 
 large number of star-like and corrugated blood-cells occurring in the 
 pgrtal blood of fasting animals, and which are replaced by such as appear 
 to be young and perfect in the blood of the hepatic veins. It is not, 
 however, to be supposed that all the iron is economized in this manner ; 
 a considerable portion of it accompanies the pigment as an essential in- 
 gredient, and is finally discharged through the intestine. 
 
 OF THE DUCTLESS GLAOT)S. 
 
 The salivary and sudoriparous glands discharge their secretion directly 
 through ducts. The liver and kidneys have upon their ducts The ductless 
 an additional mechanism, the gall bladder in the one case, and glands. 
 the urinary in the other, which serve as receptacles for storing up the 
 product of action in a temporary manner, and so converting the continu- 
 ous effect of the gland into a periodical result. In each of these instances 
 we may arrive at conclusions of a certain degree of exactness respecting 
 the functions and use of the gland from a study of the secretion it yields ; 
 but there are in the system other glandular organs which differ essen- 
 tially from all the preceding in not being furnished with ducts. These 
 are the spleen, the thymus and thyroid glands, and the supra-renal cap- 
 sules. 
 
 Much diversity of opinion prevails respecting the true nature and ac- 
 tion of these bodies. From their structure bearing a resent Their supposed 
 blance to that of the preceding, with the exception of the ab- functions, 
 sence of a duct, many have thought that, like them, they are really secret- 
 ing organs. Others have supposed that they have a relation to the nu- 
 trition of the system, in giving origin to the development of cells, or that 
 they are connected with the organization of the blood itself; and that 
 such is their duty is perhaps rendered probable by the circumstance that 
 some of them, as the thymus and thyroid, exhibit their utmost develop-, 
 ment when the body is rapidly growing, and diminish when maturity is 
 reached. That they enjoy a community of action, or that their function 
 can be vicariously discharged by other organs, has been clearly estab- 
 lished by the result of operations in which one or other of them has been 
 extirpated. 
 
 With respect to the spleen, the views of Professor Kolliker are sup- 
 ported by many facts. He supposes that one of the chief func- Function of 
 tions of that gland is the dissolution of the disorganizing blood- the s P leen - 
 cells preparatory to the action of the liver, in which ha3matin is to be 
 converted into the coloring matter of the bile. In the discussion entered 
 into respecting the origin of the bile, we have come to the conclusion 
 that it is derived from the systemic venous blood, and in the supposition 
 here presented respecting the function of the spleen there is nothing con- 
 
212 
 
 THE SPLEEN. 
 
 tradictory, for it is to be remembered that the blood of the spleen is a 
 constituent of the portal circulation. It also appears to be a general 
 Opinion that the spleen likewise maintains a mechanical relation to the 
 portal mechanism by serving as a receptacle for any excess of blood, 
 and thus relieving the vessels of pressure, or by acting in like manner 
 when there is any obstruction to the passage of blood through the liver. 
 
 As our knowledge of the action of the ordinary glands becomes more 
 Analogy of the accurate, the function of the ductless glands loses much of 
 S^ttMdncfe- its P eculiarit 7- As we have already stated, in a certain 
 less. sense the liver itself may be said to be a ductless gland, for 
 
 it appears to be one of the constant duties of that organ to prepare sugar 
 from materials in which it did not pre-exist. And this sugar does not 
 escape through the hepatic ducts in company with the bile, but is taken 
 directly into the system through the hepatic veins. But this principle 
 of action is identically what occurs in the case of every ductless gland, 
 and hence it may be inferred that the changes which these impress on the 
 blood are necessary for the development and nutrition of the system. If 
 the doctrine of Kolliker, be correct, the spleen is only an appendix to the 
 liver, and the same duct answers as a common outlet for both. 
 
 The views here alluded to are enforced by the examinations which 
 Nature of have been made of the blood of the splenic vein. The fol- 
 spienic blood. l ow i n g table exhibits the contrast between it, that of the ex- 
 ternal jugular, and that of the mammary artery. 
 
 Constitution of Splenic Blood. (From Scherer.") 
 
 
 Mammary Artery. 
 
 Ext. Jugular. 
 
 Splenic Vein. 
 
 Water 
 
 750.60 
 
 778.90 
 
 746 30 
 
 Albumen 
 
 89.50 
 
 79.40 
 
 124.40 
 
 Corpuscles and Fibrin.... 
 Loss 
 
 159.90 
 
 141.70 
 
 128.90 
 .40 
 
 
 
 
 
 
 1000.00 
 
 1000.00 
 
 1000,00 
 
 ,. From which it appears that the blood, after circulating through the 
 spleen, has lost a- large portion of its cells, the relative quantity of its 
 albumen is greatly increased, and, moreover, from being the basic albu- 
 minate of soda, the form under which it ordinarily occurs in the blood, 
 it has become the neutral albuminate, as is proved by a turbid appear- 
 ance on the addition of water, and this state it seems to retain during 
 the portal circulation, for the blood of the hepatic veins exhibits the same 
 peculiarity. 
 
OF EXCRETION. 213 
 
 CHAPTER XII. 
 
 OF EXCRETION. 
 
 THE URINE, MILK, AND CUTANEOUS EXCRETIONS. 
 
 Secretion and Excretion. 
 
 Of the Kidney: its Structure and Functions. The Malpighian Circulation. The Urine: its In- 
 gredients, their Variations and Sources. Abnormal Substances in it. The Water and Salts 
 exude by Filtration. The Cells remove unoxidized Bodies. Manner of Removal of the Liquid 
 from the Malpighian Sac. 
 
 Of the Mammary Gland: its Structure. Colostrum and Milk. Ingredients of Milk and their 
 Variations. Influence of Diet. Inquiry into the Origin of the Ingredients of the Milk, its Fat, 
 Casein, Salts, Sugar. Manner of Action of the Gland by Strainage. 
 
 Of the Skin. Structure of its Epiderma and Derma. Sudoriparous and Sebaceous Glands. 
 Nails. Hair. Ingredients of Perspiration. Exhalation: its Amount. Causes of the Vari- 
 able Action of the Skin. Its Double Action. Absorption by the Skin. General Summary of 
 the Cutaneous Functions. + 
 
 THE function of secretion is very commonly treated of by physiolo- 
 gists under two divisions, secretion and excretion. The Di s t i nct ; on be 
 former refers to the separation from the blood of those fluids tween secretion 
 which are required for the uses of the body, and which are 
 therefore still retained ; the latter, to those which are effete, and to be 
 cast out as excrementitious matter. Of secretions, the saliva or the pan- 
 creatic juice may be taken as examples ; of excretions, the urine. 4 
 
 But this subdivision is only one of convenience, and has no natural 
 foundation. The so-called secretions are, in many instances, far from 
 being more highly elaborated bodies ; in reality, they are often on their 
 descending career. And among excretions, if milk be enumerated, as it 
 ought to be, since it is a dismissed product of the system preparing it, 
 we have, instead of an excrementitious, a pre-eminently nutritive body. 
 
 Nevertheless, since this manner of considering the subject offers con- 
 siderable conveniences, I have resorted to it for the preceding and pres- 
 ent chapters. In this I shall accordingly treat of the urine, the milk, 
 and the products removed by the skin. 
 
 OF THE KIDNEYS. 
 
 The products of waste arising from oxidation in the functional activity 
 of the system, and which are of a non-gaseous kind, the use- , 
 
 J ' . Physical func- 
 
 less materials, saline or otherwise, which have been absorb- tion ofthekid- 
 ed in the digestive tract, and carried into the circulation, ne7 ' 
 must be removed. Gaseous substances and vapors may pass away 
 through the lungs, but solid material must be excreted in a state of so- 
 
214 STRUCTURE OF THE KIDNEY. 
 
 lution in water. To accomplish tins object, a special mechanism, the 
 kidney, is introduced. 
 
 From this manner of considering the functional duty of the kidney, it 
 is very clear that a special relation must exist between this excreting or- 
 gan and the respiratory mechanism, for in the case of animals which 
 breathe by gills, or in those which, though subsequently atmospheric 
 breathers, receive their supply of aerated blood before birth by a placenta, 
 the conditions under which aeration takes place are such as permit the 
 removal of solid material by the respiratory mechanism. The urinary 
 excreting apparatus of an animal breathing air is therefore necessarily 
 burdened with an exclusive duty, which is shared by the gills and the 
 skin in a water-breather. 
 
 In fishes, the renal apparatus is constructed under the condition here 
 The kidnev in indicated, an d though in many it appears to be greatly de- 
 birds, fishes, veloped, extending as a tubular arrangement from the skull 
 
 cts, etc. through the abdominal cavity, it is to be regarded as analo- 
 gous to theWollfian bodies rather than to the true kidney. In reptiles 
 the proper kidneys appear ; in birds they are well developed, but their 
 secretion is, for the most part, a semi-solid substance, chiefly urate of 
 ammonia. The tubular form is presented in both insects and arachni- 
 dans, discharging its secretion into a cloaca. 
 
 In man the kidneys may be described as a pair of dark-red ovoid bod- 
 The kidneys in i es ? placed one on each side of the vertebral column, in the 
 man - lumbar region, the right kidney being a little lower than the 
 
 left. In the adult the kidney is four or five inches in length, and is en- 
 veloped in a mass of fat. Blood is brought from the aorta to supply the 
 organ by the renal or emulgent artery, and is carried back by the emul- 
 gent vein into the inferior vena cava. During its passage through the 
 kidney there is removed from the Wood a liquid secretion, the urine, 
 which*, flowing down a long channel, the ureter, is emptied into the blad- 
 der, from which it may be periodically removed. 
 
 The supra-renal capsules are bodies of a yellow-red color placed above 
 Supra-renal the kidneys. They are much larger in the foetus than in the 
 capsules. adult, and doubtless have a reference to the peculiar conditions 
 of respiration obtaining at that time, for, as we have just observed, the 
 renal and respiratory mechanisms are necessarily interconnected. 
 
 The substance of the kidney is described as consisting of two por- 
 Minute strnc- ^^ ons tne cortical and the medullary or tubular, as seen in 
 ture of the kid- Fig. 88, in which 1 is the supra-renal capsule ; 2, the vascu- 
 lar portion of the kidney; 3, 3, tubular portion grouped into 
 cones ; 4, 4, papillae projecting into calices ; 5, 5, 5, the three infundi- 
 bula ; 6, the pelvis ; 7, the ureter. (Wilson.) From which it appears 
 that the cortical substance is the external portion, and the tubular is 
 
 
THE MALPIGHIAN CORPUSCLES. 
 
 215 
 
 Section 
 
 grouped into cones, the base of each cone being 
 outward, and the point toward the pelvis of the 
 kidney. The cortical substance, however, envel- 
 ops the cones nearly to their points. It is of a 
 red color, and is the seat of the secreting action. 
 The urine, as it arises, passes along the fine con- 
 vergent vessels, the uriniferous tubes, and these, 
 coalescing as they approach the points of the cones, 
 give origin to what are termed the ducts of Bellini. 
 From these the secretion passes into the calices, 
 thence into the pelvis, and so along the ureter into 
 the bladder. In the cortical substance there are 
 large numbers of dark points, the Malpighian bod- 
 kidney. i es . Their diameter is about -j-Lj- of an inch. 
 Mr. Bowman has demonstrated that the minute structure of the cortical 
 portion is as follows : The uriniferous tubes, as they approach it, under- 
 go bifurcation in such a way that the branches continually arising have, 
 for the most part, a diameter of about -^-$ of an inch. As they enter it 
 they are contorted, and at their ends present small capsules or flask- 
 shaped sacs. Each of the capsules is entered by a twig of Str * uctureofthe 
 the renal artery, which at once divides into loop-like branch- Malpighian 
 es constituting a tuft, and which delivers the blood to a cor P us 
 vein originating in the interior of each tuft. These structures are known 
 as the Malpighian corpuscles. The vein and artery pass out of the cor- 
 puscles usually at the same point ; the vein, however, instead of deliv- 
 ering its blood at once to the renal vein, forms a plexus on the sides of 
 a uriniferous tube, in this simulating the mechanism of the portal vein, 
 which begins in a capillary system and ends in one. It is supposed that 
 the exudation of the water of the urine takes place in the Malpighian 
 body, and the secretion of the solid portions from the cells which cover 
 the uriniferous tubes. 
 
 The chief feature of this structure is, therefore, that in a sac formed 
 upon a uriniferous tube, a tuft of capillaries, the walls of which are of ex- 
 treme tenuity, permits water to escape from the blood supplied by the 
 emulgent artery. The blood, thus concentrated by loss of its water, 
 passes into the veinlets which originate in the interior of the tuft ; these, 
 converging into a little trunk, less in diameter than the twig Circulation of 
 of the emulgent artery, escape along with that vessel from thebioodinthe 
 the capsule ; but, instead of discharging its contents into the kidne ^- 
 renal vein, it ramifies in a plexus on the walls of a uriniferous tube, thus 
 affording a miniature representation of the portal vein, beginning in a 
 capillary system and ending in one. From the plexus the commencing 
 capillaries of the renal veins arise. 
 
216 
 
 THE MALPIGHIAN CORPUSCLES. 
 
 90. 
 
 Some anatomists suppose that the Malpighian capsule is not, in reality, 
 a flask-like expansion of the uriniferous tube, 
 but that the tube, dilating, folds over the blood 
 capillaries, and so receives them. However 
 that may be, they form a loose ball in its in- 
 terior, fastened to it only by the arterial twigs 
 and its corresponding and juxtaposed vein. 
 
 The foregoing description is illustrated by 
 the annexed figures, Fig. 89 being half dia- 
 grammatic, from Kolliker. 1, a Malpighian 
 capsule, A, with the tubulus uriniferus, B, C, 
 springing from it ; a, membrane of Malpighian 
 body, continuous at b with the membrana pro- 
 pria of convoluted tubule; c, epithelium of 
 Malpighian corpuscle; d, that of tubule; e, 
 detached epithelium ; f, vas afferens ; g, vas 
 efferens ; A, glomerulus Malpighianus : 2, three 
 naif diagram of human Malpighian epithelial cells from convoluted tubule, magni- 
 
 corpuscle, magnified 300 diameters. fied g 5 Q diameters OD6 with oil drops. 
 
 Fig. 90, Glomerulus, or tuft of blood-vessels from the innermost part 
 of the cortex of the kidney of the horse: #, 
 arteria interlobularis ; a/, vas afferens ; m m, 
 glomerulus ; ef, vas efferens ; b, divisions of 
 arteriola recta in the medullary substance. 
 
 Fig. 91 shows the ciliated epithelium of the 
 uriniferous tube in the frog: a, cavity of the 
 uriniferous tube ; 5, its epithelium ; b', ciliated 
 portion thereof; b", de- 
 tached ciliated epithelial 
 cell ; c, basement mem- 
 brane of the tube ; cf, 
 that of the capsule ; m, 
 capillaries of the tuft ; 
 t, adjacent uriniferous 
 tube. 
 
 Mr. Bowman's expla- 
 nation of the Malpighi- 
 an circulation is repre- 
 sented in Fig. 92. a, 
 branch of renal artery ; 
 of, afferent vessels ; m, 
 m, Malpighian tufts ; ef, 
 eft efferent vessels ; p, 
 
 Fig. 91. 
 
 Glomerulus from the horse, magni- 
 
 Cilia on uriniferous tube of frog. 
 
THE MALPIGHIAN CORPUSCLES. 
 
 217 
 
 Fig. 92. 
 
 Diagram of Malpjghian circu- T . . . 
 
 lation. es. Dr. Isaacs s in- 
 
 vestigations are entirely confirmatory of 
 Mr. Bowman's views, so far as structure 
 is concerned. Fig. 93 is a view obtained 
 by agitating scrapings of the kidney of a 
 
 ~ 04 
 
 their plexus upon the uriniferous tube ; st, straight 
 tube ; ct, convoluted tube. 
 
 I am indebted to Dr. Isaacs for the following in- 
 structive figures and descriptions from his paper read 
 before the Academy of Medicine. His method of 
 examination of the Fig. 93. 
 
 minute mechanism 
 of the kidney, by 
 rendering small por- 
 tions of it transpa- 
 rent, greatly facili- 
 tates these research- 
 
 tuft with uriniferous tube, 
 
 nified 75 diameters. 
 
 Ruptured Malpighian coil of the deer, magnified 80 diameters. 
 
 Fig. 95 
 
 Nucleated cells c i coil, magnified 80 diameters. 
 
 sheep (which had pre- 
 viously been injected 
 with chrome yellow 
 and sulphuric ether) in 
 a test-tube with water. 
 The portion on the left 
 shows the tuft alone, 
 that on the right its 
 reception in the urinif- 
 erous capsule. 
 
 Fig. 94 shows the 
 artery, filled with in- 
 jection, and the Mal- 
 pighian coil or tuft rup- 
 tured in the capsule. 
 The injected material 
 lies in broken portions. 
 Fragments of the in- 
 
218 THE UEINE. 
 
 jected vessels of the coil are seen passing down the tube. From the 
 kidney of the deer. 
 
 A difference of opinion prevails among anatomists as to the existence 
 of nucleated cells upon the Malpighian tuft or coil in the case of the higher 
 animals. This question is finally settled by Dr. Isaacs in the following 
 manner. An ethereal or watery-colored solution is injected into the ure- 
 ter, so as to distend the tubes, burst, and throw off the capsule. The 
 cells can then be seen upon the naked tuft or coil. Fig. 95 shows the 
 Malpighian body and uriniferous tube of the kidney of the black bear. 
 The artery had been first partially filled with injection, which had broken 
 the coil in pieces. The injection from the ureter ruptured the capsule, 
 which is seen in shreds. Nucleated cells are seen on the naked coil or tuft. 
 In the upper part of the figure, to the left, is a broken tuft, on the right of 
 which the ruptured capsule is perceived, and nucleated cells upon the 
 uncovered tuft. In the upper part of the figure, to the right, are the 
 fragments of a Malpighian tuft, with nucleated cells adhering to it. The 
 capsule had been torn off with a fine needle. All the above drawings 
 were made under the microscope. 
 
 The urine of man is a clear, amber-yellow liquid, the average specific 
 The urine its g^^ty f which may be taken at 1.020, giving an acid re- 
 properties and action when first voided, but gradually becoming alkaline 
 and turbid. Its composition varies greatly with preceding 
 states of the system, and the nature and quantity of the food. It 
 amounts, in the course of a day, to from 20 to 50 ounces ; this, however, 
 depending on the quantity of water that has been taken, and on the ac- 
 tivity of the skin. Its solid ingredients vary from 20 to 70 parts in 1000 
 of the urine, the leading substances being urea, uric acid, lactic acid, ves- 
 ical mucus, epithelial debris, extractive, and salts. 
 
 The urine of carnivorous differs from that of herbivorous animals, the 
 latter being turbid, and having an alkaline reaction ; that of the former 
 transparent, pale yellow, and acid. 
 
 From Winter's experiments, it appears that for every thousand parts 
 of his weight a man discharges 25.9 parts of urine per diem, the max- 
 imum being 46.8, the minimum 14.0. A child, reduced to the same 
 standard, discharges 47.4 parts ; but a cat, fed on a flesh diet, 91.036. 
 The quantity of water thus removed depends, to a very great extent, on 
 the existing conditions of the system ; sometimes it is far less than would 
 answer to the amount that has been taken ; sometimes, on the contrary, 
 more. The solid material likewise exhibits very great fluctuations. 
 
 Viewed as a group, the constituents of the urine are evidently the ox- 
 Ori in of the idized residues of the system, which, unable, from their not 
 other urine possessing the vaporous or gaseous form, to escape through 
 constituents. t j ie lungSj ^^ from t i }e ^ so i u ]bility in water, readily removed 
 
COMPOSITION OF THE UKINE. 219 
 
 by the kidneys. The urea and uric acid are derived from muscular de- 
 cay ; perhaps, of -the two, the uric acid first arises, and is subsequently 
 converted into urea ; this is not, however, its exclusive source, since the 
 quantity of urea increases by the use of highly nitrogenized food. The 
 mucus and epithelial debris are derived from the mucous membrane lin- 
 ing the interior of the urinary apparatus. Of the salts, there are two of 
 unusual interest, the sulphates and phosphates, each having, like the 
 urea, a double origin, the food and tissue decay. Leaving out of consid- 
 eration that part which has been supplied by the food, we recognize in 
 the sulphates the final disposal of that sulphur which was once secreted 
 by the liver, and subsequently reabsorbed. In the phosphates we recog- 
 nize the oxidation of the free phosphorus of the nervous Constitution of 
 vesicles during their period of activity. That portion of the urine - 
 solid constituents of the urine which is due to decay or retrograde met- 
 amorphosis is shown when an animal is exclusively fed on sugar. 
 
 Composition of Urine. (From Berzelius.} 
 
 Water 933.00 
 
 Urea 30.10 
 
 Uric acid 1.00 
 
 Lactic acid, lactate of ammonia, and extractive 1 7. 14 
 
 Mucus 00.32 
 
 Sulphate of potash 3.71 
 
 Sulphate of soda , 3.16 
 
 Phosphate of soda 2.94 
 
 Bi-phosphate of ammonia 1.65 
 
 Chloride of sodium 4,45 
 
 Muriate of ammonia 1.50 
 
 Phosphates of lime and magnesia 1.00 
 
 Silica 0.03 
 
 1000.00 
 
 The composition of urine is not only disturbed by variations in the 
 amount of its normal ingredients, but likewise, in morbid states, by the 
 appearance of unusual ones. Among these may be more particularly 
 mentioned sugar, albumen, blood, bile, pus, fat. The presence of such 
 abnormal ingredients is determined by chemical tests or microscopic ob- 
 servations. 
 
 Since the urinary apparatus is the sewer of the system, tables, like the 
 preceding, which purport to set forth the composition of its y ariabil ity O f 
 excretion, can only be received as general illustrations. In its constitu- 
 the urine must occur whatever materials have been gener- 
 ated in the complicated disintegration of the economy, and whatever use- 
 less substances have found their way in through the absorbents by rea- 
 son of their solubility in water. 
 
 Eespecting the substances thus occurring, either normally or unusu- 
 ally, in the urine, the following are observations of interest : 
 
 The quantity of urea excreted depends more upon the nature of the 
 
220 OEIGIN AND VARIATIONS OF UEEA. 
 
 food than upon any other condition. It reaches its maxi- 
 
 Variahons in -,11 , -,. -, . 
 
 the quantity mum under an absolute animal diet, and its minimum under 
 a non-nitrogenized one. It still appears during fasting, and 
 about to the same extent as during a non-nitrogenized diet. Its sources, 
 therefore, are partly the waste of the tissues and partly the food. 
 
 By several observers, urea has been detected in the blood under ordi- 
 nary circumstances. After extirpation of the kidneys it has been re- 
 peatedly recognized in that of the lower animals. It is removed with 
 such rapidity by the kidneys that its quantity is probably never per- 
 mitted to exceed a fiftieth of one per cent, of the circulating blood. Its 
 origin has generally been attributed to the waste of muscular tissue, 
 though it has not yet been detected in muscle juice ; but then rt should 
 be remembered that creatine and inosic acid may produce it during their 
 descending metamorphosis. Under this view, the seat of its production 
 would be the blood itself, a conclusion which is enforced by the circum- 
 stance that caffeine also increases its amount. 
 
 In his inaugural dissertation, entitled, " Is muscular Motion the Cause 
 Origin of the of the Production of Urea ?" Dr. John C. Draper, by experi- 
 urea. ments on the urine of persons in different conditions of motion 
 
 and rest, and by an examination of the diurnal and nocturnal variations 
 in the amount of urea voided, compared with an invariable standard, 
 gives reasons for concluding that the differences in the amount of urea 
 excreted are almost entirely attributable to the influence of the food, an 
 individual in such a state of comparative rest as is observed during treat- 
 ment for a fractured leg not excreting by any means so much less urea 
 as might have been anticipated when compared with another individual 
 who walked thirteen miles at the rate of four and a half miles an hour. 
 
 But, on examining the influence of food, it appears to be well marked. 
 The greatest amount of urea is excreted within a few hours after dinner. 
 Another maximum also occurs just after breakfast ; but during the eight 
 night hours far less is excreted than during the same period in the aft- 
 ernoon. 
 
 The ingestion of food thus exercising so rapid and marked an influ- 
 ence on the quantity of urea, he refers to it as the cause of the increased 
 excretion of that substance during the course of the day rather than to 
 the increased motion of exercise then indulged in; and in view of this 
 conclusion, it becomes probable that the nitrogen of the wasting muscu- 
 lar tissues escapes, not under the form of urea through the kidneys, but 
 through the skin, or perhaps even as free nitrogen from the lungs. 
 
 Of the variations of the sulphates, it may be observed that the aver- 
 Variations of a ge diurnal excretion of sulphuric acid per thousand parts of 
 the sulphates. man b e i n g 0.050 of a part, an increase is observed during di- 
 gestion, a diminution occurring during the night, the minimum being 
 
EXTKACTIVE AND SALTS. 221 
 
 reached in the forenoon. Exercise to a moderate degree does not seem 
 to influence it, though that of a more violent kind, and also mental ex- 
 citement, do. Fasting for one day does not diminish it. Copious 
 drafts of water increase it, but it subsequently declines. The admin- 
 istration of sulphur, and of the sulphates of potash, soda, and magnesia, 
 also increases it, the latter salts being removed from the system through 
 the kidneys. 
 
 The quantity of extractive matter excreted by children is much more 
 than that excreted by adults, when estimated, as all such Q uantit ofex 
 observations ought to be, by reduction to a common stand- tractive in 
 ard. Thus Scherer found that for every thousand parts of T 
 weight a child excreted 0.346 of a part of extractive per diem, but an 
 adult, for each thousand parts of weight, excreted 0.156 of a part, which 
 is less than half as much. . 
 
 The quantity of chlorine in the urine, as chlorides of sodium and po- 
 tassium, undergoes many variations. Hegar shows that it y ariations in 
 is at a maximum in the afternoon, at a minimum in the the chloride of 
 night, and rising toward morning. Its quantity is increased Sl 
 after taking water, and then diminishes. Muscular exercise also in- 
 creases it. It is interesting to remark that, in inflammatory conditions 
 accompanied by copious exudations, the chlorides in the urine are so 
 much diminished that that secretion in its fresh state will yield no pre- 
 cipitate with nitrate of silver. In 80 cases of pneumonia observed by 
 Kedtenbacher, the acidified urine did not become turbid with nitrate of 
 silver, but as the inflammatory action subsided the chlorides reappeared. 
 
 Of medicaments and other unusual substances introduced into the or- 
 ganism, those which are soluble in water, and have little Egca e of unu 
 affinity for the constituent matters of the body, are removed sual salts in 
 in the urine. In this list are found a great number of salts t] 
 which escape in this manner without undergoing any change ; such, for 
 example, as carbonate of potash, nitrate of potash, bromide of sodium. 
 Other substances undergo change previously to their elimination, as, for 
 instance, the alkaline sulphides, which become oxidized, and are then 
 finally removed as alkaline sulphates. Dr. Bence Jones has satisfactori- 
 ly shown that, when ammonia is taken, it is removed as nitric acid in the 
 urine. Under the administration of the neutral alkaline salts of vegeta- 
 ble acicls, alkaline carbonates in excess appear, owing to the oxidation 
 of their acid in the blood. That this is the true seat of the oxidation, 
 and that it takes place with great rapidity, is demonstrated by the in- 
 jection of such salts into the jugular vein, which very soon are found as 
 carbonates in the urine. 
 
 When oxalate of lime is introduced into the stomach, it does not make 
 its appearance in the urine, perhaps because of its insolubility present- 
 
222 HIPPUEIC ACID, LACTATES, PROTEIN BODIES. 
 
 ing a difficulty to its absorption. In the case of some animals it occurs 
 Production of naturally in the excrement. When, in man, it is found in the 
 dSturbe^re^ 1 urme * ts occurrence may be often traced to a disturbance 
 piration. of the respiratory function, or to abnormal metamorphosis 
 occurring in the blood. Under such circumstances it presents itself in 
 convalescence from typhus. That it can arise from such metamorphosis 
 is proved by the circumstance that it is found in the urine after the in- 
 jection of urates into the veins. When the kidneys act vicariously for 
 the lungs, there thus appears to be a tendency to the removal of carbon 
 under the form of oxalic instead of carbonic acid. 
 
 Hippuric acid may arise in the organism from the metamorphosis of 
 Occurrence of benzoic and cinnamic acids, the administration of these sub- 
 hippuric acid, stances being followed by its excretion in the urine. If any 
 thing was necessary to prove that the seat of its origin is the blood, its 
 discovery therein, in the case of the ox, by Verdeil and Dollfass would 
 be sufficient. Its general occurrence in the urine of graminivorous ani- 
 mals, and its absence in that of the carnivora, indicate that its normal 
 production is connected with the nature of the food. However, among 
 some of the lower animals it is still excreted while they are in a state of 
 starvation, and it has been recognized in the urine of diabetic patients 
 under a strict animal diet. 
 
 After the injection of alkaline lactates into the jugular, the urine be- 
 Disappearance comes alkaline in the course of a quarter of an hour. If 
 tates^from the tnev nave ^ een taken into the stomach, in about double that 
 blood. time. The passage of other salts is sometimes even more 
 
 rapid ; thus the ferrocyanide of potassium has been detected in the urine 
 in less than two minutes. 
 
 The excess of protein bodies absorbed from the digestive canal, and 
 Excess of ro- unnece ssary for the repair of the system, is removed as urea 
 tein bodies re- and uric acid ; and, in like manner, the sulphur and phos- 
 phorus introduced by those bodies are, after oxidation, dis- 
 charged as sulphates and phosphates. Under the use of a strictly ani- 
 mal diet, the urine resembles that of carnivorous animals in color, acid 
 reaction, and freedom from lactic and hippuric acids. 
 Disappearance ^e Phosphate of lime often almost totally disappears 
 of phosphate of during pregnancy, and fractures unite at that period with 
 difficulty. -. 
 
 Many circumstances regulate the length of time that extraneous sub- 
 Period that ex- stances will remain in the system ; thus it sometimes occurs 
 traneous sub- that, after the administration of alkaline salts of organic acids, 
 main in the the alkalinity of the urine will disappear in the course of 
 system. j^f a ^ av? w hji e on O ther occEsions it will continue for sev- 
 
 eral days. The period also varies very much with different individuals. 
 
REMOVAL OF URINE SALTS. 223 
 
 When the substance administered is of such a chemical nature that it 
 can unite with any tissue, it may remain in the system for a very long 
 time. 
 
 The anatomical construction of the Malpighian bodies has led physi- 
 ologists to infer that there are two distinct stages in the se- Manner of se- 
 cretion of urine. These have already been pointed out in jfiJlto ij 
 the remark that the Malpighian bodies separate water from filtration, 
 the blood, but that the solid ingredients are secreted from that delicate 
 plexus of vessels which covers the walls of the urinary tubes. Before 
 accepting this opinion, we may, however, observe, that the chief solid con- 
 stituents of the urine, as urea, uric acid, sulphates, and phosphates, pre- 
 exist in the blood, and are all soluble in water. It is not to be supposed 
 that the water which oozes through the delicate walls of the Malpighian 
 tufts should leave such substances behind it. That the loss of water 
 actually takes place in the tuft circulation appears to be proved by the 
 fact that the vessel emerging from the tuft is less than the one entering 
 it ; the volume of blood is less by the amount of abstracted water. 
 
 We must, moreover, take care that we are not deceived by a name. 
 The vessel emerging from the tufts may be conveniently ThQ arterial 
 enough called a vein, but is there any proof that such is its quality retain- 
 physiological attitude? ' There is no reason to believe that ed in the tufts ' 
 the blood has lost its arterial character while it has been in the tuft. At 
 the most, it can only have lost the elements of urine. It is not until it 
 is distributed in the plexus on the walls of the uriniferous tubes that it 
 really gains the venous character, and then through nourishing those ves- 
 sels, and particularly the cells of their interior. 
 
 These considerations therefore lead me to the suggestion that the inor- 
 ganic bodies, as urea, uric acid, sulphates, and phosphates, which may all 
 be regarded as products of final oxidation, pass out with the water in 
 which they are dissolved while the blood is yet circulating in the Mal- 
 pighian tuft. The loss of velocity in the current by the arterial twig 
 breaking up into so many vessels must, as Mr. Bowman states, greatly 
 favor this transudation, as does also the pressure that must arise, from the 
 blood having to pass through a narrow channel of exit, and still more 
 through another capillary system just beyond. It was arterial blood that 
 entered the tuft, and it is arterial blood that emerges, to be then directed 
 upon the walls of the uriniferous tubes. 
 
 And now the question may arise, What is the object of this second cap- 
 illary circulation ? Though the statement is often made that The cells re- 
 the. constituents of the urine are the results of oxidation, it ^Jdw^" 
 is very far from being strictly true. The analysis of urine stances, 
 shows that a very large proportion of them, classed as extractive, are real- 
 ly combustible bodies, and not far advanced in their retrograde meta- 
 
224 THE MAMMARY GLANDS. 
 
 morphosis. They retain still, as it were, the traces of organization ; 
 they belong rather to the hydrocarbon family than to the nitrogenized. 
 It may be that, for the removal of these, cell action is necessary. 
 
 Whatever importance may be attached to such a suggestion, it is very 
 Modeofremov- clear that, notwithstanding the extreme thinness of the walls 
 from\hVS of the tuft vessels the relaxation in the speed of the blood 
 pighian sac. current through them, and the pressure brought to bear upon 
 them, that water could not be separated by oozing through them unless 
 there was an additional provision. The sac into which the exudation is 
 to take place is already full, and it may be questioned whether ciliary mo- 
 tion in the uriniferous tubes would exert a sufficient exhaustion to relieve 
 the interior of the capsule from pressure ; but the introduction of a liquid 
 of a different nature into the uriniferous tube may call at once into oper- 
 ation the principle described at page 131 as acting in the capillary circu- 
 lation of the blood, and thus the contents of the Malpighian sac are drawn 
 forward into the uriniferous tube, just in the same manner that water is 
 drawn from the inside of a bladder through the pores thereof by alcohol 
 on the outside. 
 
 THE MAMMARY GLANDS. 
 
 The mammary glands are situated on various portions of the abdom- 
 inal and thoracic surfaces of animals of the class mammalia. 
 
 Description of 
 
 the mammary In the higher members of this class they present the appear- 
 ance of racemose glands, rudimentary in the males, but well 
 developed in the adult females, especially after parturition. They separ- 
 ate from the blood the white secretion, milk. 
 
 In the ornithorynchus the mammary gland consists of an obtuse cone 
 of coecal follicles, ending upon an areolar surface. There is no nipple. 
 The milk is expelled, both in these and the marsupials, by direct mus- 
 cular pressure. In cetaceans the nipple is included in a cleft of the in- 
 its compara- tegument, but in the higher mammalia it projects, so that, be- 
 tive anatomy. ' n g rece i ve <j i n ^ o the mouth of the young, and suction being 
 made, the pressure of the air takes effect upon the surface of the gland 
 and expels the milk. 
 
 In different cases the number of mammas differs. In the human spe- 
 cies there are but two, placed upon the thoracic surface, and from their 
 position favoring the care and nursing of the child. Among other ani- 
 mals the number seems to have a relation to the number of young brought 
 forth at a birth, there usually being a pair for each one. Many excep- 
 tions to this rule, however, occur. 
 
 The mammary gland corresponds in anatomical structure to the paro- 
 
 Its stru P t ^ anc * P ancreas - I* cons i sts of 15 or 20 lobes, each from J 
 
 to 1 inch in width ; these are composed of lobules, and these, 
 
 again, of coecal vesicles. The excretory ducts are lined with tesselated 
 
STRUCTUEE OF MAMMARY GLAND. 
 
 225 
 
 Fig. 96. 
 
 epithelium. The ducts converge toward tKe nipple, opening upon it by 
 10 or 15 apertures, and in their course dilating into ampullae, of small 
 capacity in women, but in the cow capable of holding a quart. 
 
 As regards its development, the mammary 
 gland originates in the fourth or fifth j ts develop- 
 month as a papillary projection of the ment - 
 mucous layer of the epidermis, as shown in Fig. 
 96, in which 1 is the rudimentary gland in the 
 male embryo of five months, a being the horny, 
 b, mucous layer of the epidermis ; c, process of 
 the latter, the rudiment of the gland ; d, fibrous 
 membrane round it. At 2 is the lacteal gland 
 of a female embryo of seven months, een from 
 above : a, central substance of the gland ; b, <?, 
 budding outgrowths, the rudiments of the gland 
 lobes. (Kolliker.) 
 
 Fig. 97, vertical section of the human mam- 
 a, its pectoral surface ; b, b, skin on surface of the gland ; 
 c, skin of nipple ; d, lobules and lobes of gland ; e, lac- 
 tiferous tubes passing from the lobules to the nipple. 
 
 As pregnancy advances, the cells of the gland begin 
 to contain fat, in a manner not unlike that which is re- 
 marked in the cells of the sebaceous follicles of the skin. 
 When the gland becomes active after parturition, it is 
 stated that the first-formed milk-cells break up in the 
 lactiferous ducts into milk globules, their membrane and 
 nucleus disappearing. The milk globules are minute 
 
 Development of the mammary 
 gland. 
 
 mary gland 
 
 Fig. 97. 
 
 section of the human 
 
 mammary gland. 
 
 particles, varying in their diameter from the 
 
 
 to the iSQQQ of an inch. They con- 
 sist of oily material inclosed in an envelope, as is shown by the fact that, 
 though they will resist for a short time the action of sulphuric ether, 
 Fig. 98. they are finally dissolved by that substance. Be- 
 
 sides these milk globules, there are other exceed- 
 ingly minute fat particles present. The milk 
 which is first secreted after delivery contains cor- 
 puscles of considerable size, and of a granulated 
 appearance, as seen in the photograph, Fig. 98. 
 They are called colostrum corpuscles. 
 
 r 111- ,1 i ^i f Colostrum. 
 
 They are soluble in ether, and therefore 
 Miik with coiostrai corpuscles. con tain fat. There is reason to suppose that all 
 the fat globules of the milk are inclosed in cyst-like pellicles of casein. 
 
 In the chapter on food (Chapter II.), a general description of the char- 
 acter and constitution of milk has been given, together with its physio- 
 
 P 
 
226 
 
 COLOSTRUM AND MILK. 
 
 Properties of logical relations in nutrition. It may now be added that fresh 
 milk. milk presents an alkaline reaction, which continues longer in 
 
 the milk of women than in that of cows. Left to itself, and the more 
 quickly the warmer the air, milk turns sour through the production of 
 lactic acid, the casein undergoing coagulation. That the oil globules just 
 spoken of are coated with a film of a coagulated protein body appears 
 from the circumstance that it may be dissolved by acetic acid, and the in- 
 cluded butter is then set free. 
 
 One of the simplest methods for the analysis of milk consists in coag- 
 Anaiysis of ulating it at a temperature of 212 with pulverized gypsum ; 
 milk - the mass, being then evaporated to dryness, is pulverized, the 
 butter being extracted by ether, and the sugar and soluble salts by hot 
 alcohol. * The amount of the soluble salts thus obtained may be determ- 
 ined by incineration ; and since their amount is to that of the insoluble 
 salts as 5 to 7, an approximate determination of the latter may be made, 
 and thereby the weight of the sugar and casein corrected. This is the 
 method of Haidlen. 
 
 It would appear, from examinations that have been made of the secre- 
 T> i * f tion of the mammary gland previous to parturition, that it 
 lostrum and contains albumen in the place of casein, the casein gradually 
 appearing as the period of parturition approaches, but not 
 reaching its maximum until a few days after that event. Colostral milk 
 differs essentially from the subsequent ordinary secretion, as the follow- 
 ing table shows : 
 
 Constitution of Colostrum and Milk. (From Simon.') 
 
 
 Colostrum. 
 
 Milk. 
 
 Water 
 
 828 00 
 
 887 60 
 
 Fat...... 
 
 50.00 
 
 25 30 
 
 Casein. 
 
 40 00 
 
 34 30 
 
 
 70.00 
 
 4820 
 
 Ash ; . . 
 
 3 10 
 
 2 30 
 
 Loss 
 
 8.90 
 
 2.30 
 
 
 1000.00 
 
 1000.00 
 
 The specimens here presented were obtained from the same individual ; 
 and from the table it appears that the colostrum contains a much larger 
 proportion of solid material than the milk. The quantity of fat is near- 
 ly double ; the quantity of sugar is likewise much greater, but the rela- 
 tive quantity of casein is less, this being in accordance with the state- 
 ment that the production of that substance approaches gradually to a 
 maximum which is not attained till a few days after parturition. 
 
 The composition of milk varies with many circumstances. Thus, 
 Variability in among cows, it is well known that there are certain breeds 
 its composition. w hi c h yi^a a m $k { n wn i c h butter predominates ; in others, 
 a milk in which there is an excess of casein. It is in reference to this 
 that such are, among agricultural people, often described as good butter 
 
VARIATIONS IN MILK. 
 
 227 
 
 cows, or good cheese cows, as the case may be. Such variations are 
 likewise often popularly referred to peculiarities in the color of these ani- 
 mals ; and, indeed, there is a general impression of the same kind as re- 
 spects the milk of women, that that of fair women is inferior to that of 
 brunettes. L'Heritier, who has examined into this matter, selected two 
 females of the same age, 22 years, and caused them to adopt the same 
 diet and the same mode of life. The one was a blonde, the other a bru- 
 nette. The following table exhibits the most marked of his results 
 
 Milk of Women of different Temperaments. (From UHeritierS) 
 
 
 The Blonde. 
 
 The Brunette. 
 
 "Water 
 
 892.00 
 
 853 30 
 
 Butter 
 
 35.50 
 
 54 80 
 
 
 10.00 
 
 16.20 
 
 Sugar of xnilk 
 
 58.50 
 
 71.20 
 
 Salts ' 
 
 4.00 
 
 4.50 
 
 
 
 
 
 1000.00 
 
 1000.00 
 
 The average of the various analyses he made shows the same general re- 
 sult, though not so strikingly, the number being for the solid constitu- 
 ents, in the case of the blonde, 120, and for that of the brunette, 134. 
 
 As would be expected, the constitution of the milk varies greatly with 
 the diet. Simon found that in the case of a very poor woman, influence of 
 who had been almost deprived of the necessaries of life, the diet on milk - 
 quantity of solid material was only 8.6 per cent. On giving her a nutri- 
 tious meat diet it rose to 11.9 per cent. Being again reduced, by cir- 
 cumstances, to the utmost destitution, the solid residue sank to 9.8 per 
 cent. ; and on once more being supplied with a nutritious meat diet, the 
 percentage rose to 12.6. These results illustrate in a striking manner, 
 as will be presently seen, the function of the mammary gland. Simon 
 also found, in this particular case, that the relative quantities of casein 
 and sugar do not greatly vary with these extreme dietary variations, but 
 that the absolute quantity of butter does. On the two occa- Qri in of the 
 sions of starvation, it was as low as 8 parts in 1000 of milk, casein and of 
 and on the two of full nutritious diet, it rose to 34 and 37 thebutter - 
 respectively. From this it seems to follow that while the amount of 
 butter in milk is determined by the quantity and quality of the food, the 
 amounts of casein and sugar are, to a considerable degree, independent 
 thereof, and hence I believe their origin is to be attributed to changes 
 taking place in the system, and that these substances are more immedi- 
 ately furnished from metamorphoses of its structures. 
 
 The casein and the sugar are reciprocally related to each other, the 
 quantity of casein steadily increasing from the time of par- Relative uan 
 turition until a fixed proportion is attained. At parturition tity of casein 
 the quantity of sugar is at its maximum, a gradual decline a sugar ' 
 then occurring until its proportion likewise becomes nearly constant. 
 
228 ACTION OF THE MAMMARY GLAND. 
 
 Saline substances administered by the stomach or rectum do not al- 
 Extraneous ways appear in the milk ; thus the ferrocyanide of potassi- 
 saits in milk. unlj w hich may be quickly detected in the urine, can not be 
 found in the milk. It is curious, that when iodide of potassium has been 
 administered to the mother, in doses, for example, of three grains thrice 
 a day, it can be readily detected in the urine of the infant by the usual 
 test of starch and nitric acid. 
 
 The diurnal quantity of milk yielded by the human female has been 
 Diurnal quan- estimated at from 32 to 64 ounces. This estimate is made 
 tity of milk, ^y determining the weight of the infant before and after suck- 
 ling. Although a certain proportion is present in the gland, the secre- 
 tion appears to take place for the most part with great rapidity. On the 
 application of the infant the blood flows suddenly, and the milk pours 
 into the ducts, constituting what is termed the draft. 
 
 We now enter on a consideration of the function of the mammary 
 
 Mode of action g^ an< ^ w ^ n a v ^ ew ^ determining whether it acts in virtue 
 
 of the mamma- of its special construction, whether it fabricates in itself, by 
 
 the agency of cells, the proximate constituents of milk, or 
 
 whether it merely strains them from the blood in which they pre-exist. 
 
 Due weight should here be given to the fact that, unlike the excretions 
 of the lungs, the kidneys, or even the liver, the milk contains a very large 
 percentage of histogenetic or formative bodies. Its casein can not be 
 considered as in the career of retrograde transformation, since in the body 
 of the infant it is presently changed into albumen. Such a fact might 
 even lead us to suspect that we should detect some essential structural 
 and functional differences between the mammas and other glands. 
 
 The influence of special structure is, however, disposed of by the nu- 
 livfluence of merous well-authenticated cases now on record, in which por- 
 speciai struc- tions of the skin, or the stomach, the navel, intestines, the ax- 
 illa, and glands in the groin have assumed a vicarious action, 
 and secreted milk ; and though it has been said of the latter instance that 
 it may be nothing more than an obscure manifestation of an attempt in 
 the human species at a repetition of the mammary gland in a region near 
 which it is normally present in the lower mammals, such a remark has 
 no application in the other cases. We may therefore infer that the proxi- 
 mate constituents of the milk are not manufactured by reason of any 
 special structure of the gland which secretes them, since other structures 
 can assume a vicarious action. 
 
 This therefore narrows our inquiry down to the point, Does the mam- 
 mary gland merely filter off from the blood substances already existing 
 in it, or, those substances not so pre-existing, are they made in this or- 
 gan by cells ? 
 
 Of the proximate elements of milk, many, such as the entire group 
 
SOURCE OP THE BUTTER OF MILK. 229 
 
 of its salts, are acknowledged on all hands to pre-exist in the The galtg of 
 blood ; and these, constituting about -^ of its solid ingredi- milk exist in 
 ents, must be admitted to pass into the secretion by strainage 
 only. Of the other solid ingredients, the fat, which constitutes about one 
 fourth, also exists in the blood, being derived by lacteal absorption from 
 the food. 
 
 Do milk-giving animals, then, find in their ordinary dief a sufficient 
 quantity of oleaginous material to supply the drain establish- The hydrocar . 
 ed through the mammary gland, and the calorifacient de- bons pre-exist 
 mand, supposing none to be made in the system ? The re- 
 searches of Dumas have definitely settled this question. Of these the 
 following is an abridgment : 
 
 Fat in Articles of Forage. 
 
 Indian corn 8.75 per cent. 
 
 Kice 1.00 
 
 Oats 3.30 
 
 Eye 1.75 
 
 Wheat 2.10 
 
 Dry hay 2.00 
 
 Clover in flower 4.00 
 
 Wheat straw 3.20 
 
 Oat straw 5.10 
 
 Beet root 0.05 
 
 Potatoes 0.08 " " 
 
 A cow in good condition, eating 100 pounds of dry hay, will furnish 21 
 quarts of milk, from which there can be obtained 1J pounds Quantity of fat 
 of butter. If this butter was obtained exclusively from the in fora s e - 
 food, and none made in the system, we ought to find in the 100 pounds 
 of dry hay 1J pounds of fatty matter; but sulphuric ether can remove 
 from such hay 2 pounds, and in several specimens of clover cut in flow- 
 er, M. Boussingault found the proportion as high as 4 per cent. We 
 may therefore affirm, relying on the universal experience of farmers, that 
 the hay eaten by a milch cow contains more fat matter than the milk 
 which she yields. Thus far, therefore, we are not authorized to regard 
 the animal as capable of producing the butter found in its milk, but, on 
 the contrary, we may be led to suppose that the whole of it is taken 
 from the food. 
 
 In a physiological point of view, a single experiment of this kind is 
 insufficient. Errors may arise in comparing together hay taken by 
 chance, and the produce of milk taken by chance. It would doubtless 
 be far better to establish a direct experiment, giving the proportion of 
 butter, determined by analysis, relatively to the proportion of fat matter 
 consumed by a cow. This experiment has been made on such a scale 
 and with so much care as to be very convincing. It lasted for a year, 
 and was conducted on 7 milch cows, the milk, drawn twice a day, being 
 
230 SOUECE OF THE BUTTER OF MILK. 
 
 carefully measured. The 7 cows furnished 17,576 quarts of milk; its 
 weight was 36,382 pounds. Being analyzed from time to time, it was 
 found to yield 3.7 per cent, of butter, completely deprived of water. 
 From this it follows that these 7 cows furnished during the year 1346 
 pounds of butter. 
 
 During this time they ate 30 pounds of hay, clover, and grass each 
 day; that is to say, the 7 cows consumed during the year 77,650 Ibs. 
 
 Now if in 100 pounds of hay there are 1.8 of fat, the 77,650 pounds 
 represent 1378 ; recollecting, however, the use of clover, which is richer 
 in fat, the amount should rise to more than 2000 pounds. But the but- 
 ter obtained was only 1346 pounds. 
 
 From this experiment, therefore, we gather, that a cow which is giving 
 milk finds much more fat in the fodder she eats than is subsequently 
 yielded in her butter. We may therefore conclude that such an animal 
 extracts from her food most of the fat it contains, and that she either 
 stores it up in her adipose cells, uses it for the production of heat, or con- 
 verts it into butter. 
 
 In the argument, as thus presented by M. Dumas, the question is con- 
 sidered in its quantitative aspect, no allowance being made, however, for 
 the amount of oily material accompanying the fasces, and no estimate of- 
 fered of the proportion destroyed for the sake of producing heat. It 
 might be that the entire amount of fat escapes in the former of these 
 ways, and that, though a sufficiency occurs in the food, it is not absorbed 
 therefrom into the system. 
 
 There are many facts which show that the identical fat occurring in 
 The identical the food is actually delivered by the mammary gland with 
 [sfomid^i/the raan y f its quantities unchanged. Thus, if by chance cows 
 milk. should eat the tender shoots of pine-trees, or wild onions, or 
 
 other strong-smelling herbs, the milk is at once contaminated with the 
 special flavor of their oils. The same, too, takes place when turnips are 
 introduced in their diet. If half the allowance of hay for a cow is re- 
 placed by an equivalent quantity of linseed-cake, rich in oil, the cow 
 maintains herself in good condition, but the milk produces a butter more 
 than usually soft, and tainted with a peculiar flavor derived from the lin- 
 seed oil. 
 
 To the preceding facts it is unnecessary to add any observations in re- 
 lation to the carnivorous mammals, which obviously find in their prey 
 large quantities of 'fat. In the chapter on calorifacient digestion, and in 
 that on the functions of the liver, the evidence was presented both as 
 regards the reception of oily material from the food, and likewise its fabri- 
 Sufficient cation in the system. From these sources conjointly it may 
 of fat therefore be plainly seen that fats of various kinds must al- 
 
 ways exist in the blood. A simple arithmetical computation, 
 
CASEIN FEE-EXISTS IN BLOOD. 231 
 
 founded on the data furnished by the tables of the constitution of blood and 
 of milk respectively, will show that there is at any moment a sufficient 
 supply of fatty matters in the blood to furnish two thirds of the diurnal 
 amount of milk. It does not seem, therefore, philosophical, under these 
 circumstances, to impute to the mammary gland a power of forming but- 
 ter. It doubtless obtains that substance directly from the blood ; and it 
 may be that those bodies which are conceived of as cells, and which are 
 supposed to arise in the lobules of the gland in successive broods, which 
 run a rapid living career, coming into existence, reaching maturity, dying 
 and deliquescing with incredible rapidity, are, in reality, nothing more 
 than oil globules which have coated themselves over with a cyst of coag- 
 ulated casein, as in Ascherson's experiment, or just as they become coat- 
 ed with a similar film immediately on passing from the intestine into the 
 lacteal vessels ; and this, accordingly, is the opinion I entertain of their 
 nature. 
 
 Next of the casein. There has been much controversy among chem- 
 ists respecting the existence of casein as a normal ingredi- Reasons for in- 
 cut in the blood. Theoretically there does not appear any jSbSl? > 
 solid reason for denying that it may be one of those constit- blood, 
 uents, considering the analogy of constitution which it shows with albu- 
 men. The evidence is much more distinct and positive in the case of 
 puerperal blood, and is greatly strengthened by the recognized tendency 
 to the occurrence of kiestine in the urine during gestation. This sub- 
 stance, to which much attention has of late been devoted, makes its ap- 
 pearance in such urine as a pellicle or membrane, which gradu- 
 ally increases in thickness. It is not commonly seen before 30 
 hours after the urine is passed, nor later than the eighth day. Though 
 sometimes appearing at an earlier period of gestation, it is more frequent 
 in the seventh, eighth, or ninth months. The fact is not without signifi- 
 cance for our present purpose, that it may reappear in the urine after par- 
 turition if any thing occurs to check the secretion of milk. Moreover, 
 Prout noticed it in the urine of a delicate child which was fed chiefly on 
 milk. An examination of it shows that kiestine is composed of casein, a 
 butyric fat, and the phosphate of magnesia. Such a constitution betrays 
 at once its relation to the secretion of the mammary gland. 
 
 Lehmann, who inclines to the belief that kiestine is nothing else but 
 the formation of crystals of triple phosphate and fungoid and confervoid 
 growths, which take place when the urine becomes alkaline, admits that, 
 unless it has been the basic albuminate of soda which has been mistaken 
 for it, casein does occasionally occur in the urine. From the acknowl- 
 edged fact that the acid interstitial juice of muscle fibre contains casein, 
 there can not be any doubt, I think, that that substance must pre-exist 
 in the blood. 
 
232 SOUECE OP THE CASEIN OF MILK. 
 
 The occurrence of casein under the form of kiestine in the urine, in 
 quantity increasing as gestation advances, indicates therefore that the 
 system is assuming a propensity for the generation of this substance from 
 its albumenoid compounds ; and since, in cases of starvation, the percent- 
 age of casein in the milk does not seem to be materially affected, we are 
 to attribute its immediate source to the system rather than to the food. 
 In this respect it differs from the oily constituent, butter, the percentage 
 amount of which is instantly affected by variations in the nature and 
 quantity of the food. It would seem, indeed, that, from the same plastic 
 ingredient, albumen, the soft tissues of both mother and infant are fabri- 
 cated, with this difference, that in the latter case the temporary condition 
 of casein is intermediately assumed. We have already remarked on the 
 identity of constitution of albumen, casein, and fibrin, so far as their car- 
 bon, hydrogen, nitrogen, and oxygen are concerned ; and, indeed, these 
 compounds differ far less in their physical characters from one another 
 than albumen in its coagulated and uncoagulated state ; yet that differ- 
 ence in physical quality may be readily brought about by so trifling an 
 agency as rise of temperature through only a few degrees, and is proba- 
 bly dependent upon the different allotropic forms which the carbon con- 
 stituent is prone to assume. Giving due weight to these various consid- 
 erations, we shall find reason to conclude that this constituent of the 
 milk, the casein, is directly derived from the system, which can manufac- 
 ture it at a rate of about 30 grains per hour, this being about one half 
 the quantity of fibrin generated in the same period of time for the sup- 
 port of the muscular tissues. Chemically, the transition from albumen 
 to casein is not to be regarded either as an ascending or declining meta- 
 morphosis, but only as the temporary assumption of a state of passage 
 onward to the condition of fibrin. 
 
 With respect to the constitution of casein there is considerable doubt. 
 Complex na- The substance commonly passing under this title seems to 
 ture of casein. cons i s t O f a t least two different bodies ; at all events, it may 
 be separated into two parts, one containing sulphur, and the other not ; 
 moreover, if to milk, which has been perfectly freed from butter, there be 
 added dilute hydrochloric acid, the ordinary precipitate is yielded, but 
 there still remains in solution an analogous body, which does not precipi- 
 tate until the mixture is boiled. In milk, though much of the casein is 
 held in solution, much also exists in the coagulated state, forming the 
 wall of the milk globules. Its existence under this membranous form 
 may be demonstrated by the action of acetic acid on milk globules un- 
 der the microscope, and also by shaking new milk with ether, which pro- 
 duces very little change ; whereas, if the milk were only an emulsion, the 
 ether should take up the fat and hold it in solution. Now, on the addi- 
 tion of potash or its carbonate to milk before the action of ether, those 
 
THE ACTION OF THE MAMMARY GLAND. 233 
 
 substances dissolve the membrane, and then the ether takes up the fat 
 and forms a dimly-clear solution. We may therefore conclude that the 
 substance we designate as casein consists of two ingredients, the protein 
 compound, which exists in a state of solution in milk, and also that 
 which forms the membrane of the fat corpuscles. 
 
 Many of the remarks just made respecting the origin of casein are ap- 
 plicable to the saccharine constituent of the milk, the origin origin of the 
 of which is not to be attributed so much to the food directly sugar of milk. 
 as to the system ; for, in starvation, the sugar, like the casein, still con- 
 tinues to form to nearly the normal amount. I think it is probable that 
 its production is due to the liver, and is, in reality, nothing more than an 
 indication of the continued action of that gland, one of the prime func- 
 tions of which is the generation of saccharine compounds. 
 
 From the data now before us respecting the origin of the different con- 
 stituents of the milk, the casein, the butter, the sugar, and T ' he mammary 
 the salts, we are able to come to a definite conclusion re- gland acts by 
 garding the physiological action of the mammary gland. I 
 have entered on this long disquisition from the important bearing which 
 the decision we arrive at has upon the whole theory of secretion ; for if 
 there be a gland in the body in which we should expect to find proofs 
 of formative power, through the agency of cell life or otherwise, in giving 
 rise to products that did not pre-exist in the blood, it is certainly the 
 mammary. But now, as it appears that all the constituents which its 
 secretion contains are found in the blood, we can scarcely suppose that 
 the gland itself does more than merely strain them out ; of course, in com- 
 mon with all such structures, it possesses what might aptly be termed 
 an elective filtrating power ; thus it permits the exudation of the iodide 
 of potassium from the blood, but refuses a passage to the ferrocyanide. 
 And, finally, the conclusion to which, we thus come recalls the remark 
 heretofore made, that the more thoroughly we study the secretions deliv- 
 ered by the various glands, and the more perfectly we identify the sources 
 from which their constituent ingredients have been derived, the more we 
 should be disposed to impute glandular action to the physical process of 
 elective filtration, and the less to the agency of cell life. 
 
 OF THE SKIN. 
 
 The skin is composed of two layers, the epidermis or cuticle, and the 
 derma or cutis. It contains tw9 systems of glands, one for the removal 
 of water, and another for that of oily substances. It also presents sub- 
 sidiary parts or appendages, such as the nails and hair. 
 
 The epidermis, which is the exterior portion of the skin, originates from 
 the cutis. It has a different thickness in different parts; The epidermis : 
 the contrast, in this respect, being very well shown upon the its structure. 
 
234 THE KETE MUCOSUM AND THE TRUE SKIN. 
 
 soles of the feet and the eyelids. In this respect its use is mechanical. 
 It serves as a protective covering to the parts it envelops, being thick 
 where pressure and hard usage have to be provided for, and thinner where 
 there is a necessity for motion. It consists of an aggregation of nucle- 
 ated particles adhering together, the deepest being granules, the inter- 
 mediate more perfect cells, which gradually become flattened scales as 
 they are examined nearer the surface. They undergo constant exuvia- 
 tion, and are as constantly replaced from beneath, the superficial ones 
 becoming dry and horny, thus furnishing a resisting tegument, the oper- 
 ation of which is very well displayed by the action of vesicating agents : 
 a watery discharge from the vessels of the cutis soaks through the lower 
 substance of the cuticle, and raises the dry layers above. The chemical 
 composition of these dry scales is the same as that of nail, hair, horn, 
 and is C 48 , H 39 , N 7 , O 18 . 
 
 At one time it was supposed that the rete mucosum, or layer of Mal- 
 pighi, which is the lowest portion of the cuticle, and there- 
 
 liete mucosum * o .... 
 
 and its color- fore resting on the cutis, is a distinct structure. It is, how- 
 ing matter. everj me rely the most recently-formed portion of the cuticle. 
 The netted appearance it presents originates in the eminences of the pap- 
 illary structure below. Many of its constituent particles contain col- 
 oring matter, especially in the dark races. The pigment seems to be 
 produced by the agency of the sunlight and continued high temperature, 
 though it disappears gradually as the cells containing it approach the 
 surface. It yields a very large percentage of carbon. 
 
 Beneath the epidermis is the derma or true skin. It is composed of 
 The derma ^rous tissue, which also serves to connect it with the parts 
 its construe- beneath, blood-vessels, lymphatics, and nerves. In its areolar 
 lon ' tissue both the white and yellow fibrous elements are found, 
 
 the proportion of each varying according to the mechanical function the 
 part has to discharge, the yellow predominating where elasticity is re- 
 quired, and the white where a resistance to pressure. The derma also 
 contains organic muscular fibres, to which its property of corrugation, as 
 in cutis anserina, is due. On different parts it is of different thickness, 
 being thinnest where motion has to be provided for. A deposit of fatty 
 material, lodged beneath, gives it a yielding support. Its outer surface 
 presents a papillary structure, which is the instrument of touch. This is 
 more perfectly developed on the inner surface of the palm of the hand and 
 fingers. The furrowed aspect of the cutis arises from this. A farther 
 consideration of the mechanism and functions of the papillge is deferred to 
 the description of the sense of touch. 
 
 The photographic engraving, Fig. 99, represents a thin section of the 
 epidermis of the foot of the dog. 
 
 The general method of arrangement of the constituent portions of the 
 
THE CUTICLE. 
 
 235 
 
 Fig. 99. 
 
 Fig. 100. 
 
 Perpendicular section of skin of 
 
 ear, magnified 10 diameters. 
 Epidermis of dog, magnified 20 diameters. 
 
 skin may be gathered from the perpendicular section of that of the ex- 
 ternal auditory meatus in Fig. 100. <z, the derma ; , rete mucosum ; 
 , horny layer of epiderma ; d, coil of ceruminous glands ; 6, their excre- 
 tory ducts ; y, their apertures ; <?, hair-sacs ; A, sebaceous glands ; 2, 
 masses of fat. (Kolliker.) 
 
 Fig. 101 shows the under surface of the cuticle detached by macera- 
 tion from the palm, exhibiting double rows of depressions, in which the 
 papillae have been lodged, with the hard epithelium lining the sudoripa- 
 rous ducts in their course through the cutis. Some of them are con- 
 torted at the end, where they have entered the sweat gland. (Todd and 
 Fig. 101. Bowman.) 
 
 Fig. 102, papilla? of the 
 palm, the cuticle being de- 
 tached. (Todd and Bow- 
 man.) 
 
 Fig. 102. 
 
 Under surface of the cuticle. 
 
 Papillse of palm, magnified 35 
 diameters. 
 
 Fig. 103, surface of the 
 skin of the palm, showing the 
 ridges, furrows, cross grooves, 
 and orifices of the sweat - 
 ducts. The scaly texture of 
 the cuticle is indicated by the 
 irregular lines on the surface. 
 (Todd and Bowman.) 
 
236 
 
 THE NAILS AND HAIE. 
 
 Fig. 103. 
 
 The nails. 
 
 The NAILS constitute one of the appendages 
 
 of the epiderma. They are horny 
 
 coverings protecting the extremities 
 of the fingers and the toes. They originate 
 in a fold of the cutis, and become free at their 
 outer extremity. The nail grows from its 
 roots, increasing in length, and simultaneously 
 in thickness. Its rate of growth depends upon 
 the general rate of nutrition. During periods 
 of sickness or abstinence, its growth in both 
 directions is retarded, as is indicated by a mark 
 or impression on its surface, and so the nail 
 becomes a register of the condition of nutrition 
 during the period of its own existence. The 
 
 thumb nail is Said tO OCCUpy about 20 Weeks Skin of palm, magnified 20 diameters. 
 
 in its growth from the root to the extremity ; that of the great toe about 
 two years an estimate which is probably too long. 
 
 THE HAIE. Each hair originates in a flask-shaped follicle, formed by 
 a depression of the cutis, and lined by a continuation of the cu- 
 ticle, and, like it, presenting scales on its superficies and round 
 cells beneath. The bottom of the follicle is the place of origin. The 
 hair consists of two portions, the outer or cortical, and the inner or me- 
 dullary, the proportions of which differ very much in different cases. 
 The surface of the hair presents a layer of imbricated scales, within which, 
 at the lower part, are minute cells, but farther from the root the cells be- 
 come larger and begin to contain pigment, the coloring matter being dis- 
 tributed unequally, sometimes producing a tubular appearance in the axis. 
 The hair grows by constant prolongation from 
 the follicle, its color being due to a peculiar col- 
 ored oil ; and in the black varieties, iron predom- 
 inates. The diameter of the hairs varies from 
 rh> to TsVo of an inch. 
 
 In Fig. 104, the structure of the root of a hair 
 and part of its shaft is displayed. Bulb of a 
 small black hair from the scrotum, seen in sec- 
 tion : # , basement membrane of the follicle ; &, 
 layer of epidermic cells resting upon it, and be- 
 coming more scaly as they approach c, a layer of 
 imbricated cells forming the outer lamina or cor- 
 tex of the hair : they are more flattened and com- 
 pressed the higher they are traced on the bulb. 
 Within the cortex is the proper substance of the 
 Human hair in section. hair, consisting, at the base, where it rests on 
 
 Fig. 104. 
 
OF THE SUDORIPAROUS GLANDS. 
 
 237 
 
 Transverse section of human hair, magnified 
 200 diameters. 
 
 the basement membrane, of small angular cells, scarcely larger than their 
 Fig. 106. nuclei. At d these cells are more bulky, 
 
 and the bulb consequently thicker : there 
 is also pigment developed in them ; above 
 d they assume a decidedly fibrous char- 
 acter, and become condensed ; 0, a mass of 
 cells in the axis of the hair, much loaded 
 with pigment. (Todd and Bowman.) 
 
 Fig. 105 is an engraving of a photo- 
 graph of a transverse section of human 
 hair from the head. The outer line 
 shows the cortex ; in some the pigment- 
 ary axis is seen ; in most, however, it is 
 absent. 
 
 The SUDORIPAROUS GLANDS originate in depressions of the cutis or 
 tissues beneath, occurring in some parts, as in the axilla, The SU( ioripa- 
 more numerously than in others. They consist of a tube rous glands. 
 wound on itself, and sometimes dividing in convoluted* branches. The 
 knot thus arising is contained in a cell, the wall of which is copiously 
 supplied with blood-vessels : the duct passes through the superjacent tis- 
 sues. The tube is formed of a cylinder of basement mem- 
 brane lined with epithelium. The basement membrane 
 may be considered to be derived from the outer surface of 
 the papillae, and the epithelium is an external projection of 
 the cuticle. The duct, on its passage outward, loses its 
 basement membrane as it escapes between the papilla; 
 and it has a spiral or helical aspect, an arrangement prob- 
 ably intended to keep the calibre open. It is estimated 
 that the number of sudoriparous glands is about seven mill- 
 ions, and the total length of their tubing about 28 miles. 
 
 Fig. 106 is a sudoriparous gland from the palm of the 
 hand : <z, a, knot of tubes with two excretory ducts, b, b, 
 uniting into a helical canal, which perforates the epidermis 
 at , and opens on its surface at d : the gland is imbedded 
 in fat vesicles at e, e, e, e. (Wagner.) 
 
 The SEBACEOUS GLANDS are distributed in different 
 ed2o giand, abundance in various parts, their office being The sebaceous 
 
 to lubricate the hair, to keep the skin in a flex- s lands - 
 ible condition, and avoid the inconveniences of friction. Their ducts 
 open either into the hair follicles or upon the cuticular surface ; the gland 
 consisting of basement membrane lined with epithelium, the cells of 
 which, as they reach maturity, become filled with a sebaceous or oily ma- 
 terial. The ear glands of this class secrete a waxy matter. 
 
238 OF THE SEBACEOUS GLANDS. 
 
 Such being the construction of the skin, we have next to speak of its 
 action. It discharges a double function : 1st, as an excreting, and, 2d, 
 as an absorbing organ. In this respect it has an analogy with the mu- 
 cous membrane, which, indeed, is a reflection or continuation of it. 
 
 Of the excreting action of the skin. The skin permits water, saline 
 Different kinds an ^ fatty substances, to escape from it in quantities which 
 of perspiration, differ on different portions of its surface, the nature of the se- 
 cretions varying to meet local requirements. In the examination which 
 we are now entering upon, we shall speak of these substances and their 
 proportions in a general way, overlooking, for the time, the particular va- 
 riations. Yet that such variations exist is clear on the most superficial 
 observation. The sweat of the feet differs from that of the general sur- 
 face, as, again, does that of the arm-pits. 
 
 It has been usual to distinguish the watery transudation into two por- 
 Quantityof tions, that which escapes from the perspiratory ducts, and 
 water through that passing through the surface of the cuticle. It has even 
 
 the cuticle and , r . , J? - ,* i j i . e 
 
 from the ducts been said that the true glandular secretion passing from the 
 compared. ducts is not more than one sixth of the total cutaneous ex- 
 udation ; but this, I believe, is altogether erroneous. When we recall 
 the impermeable nature of the horny and dried scales which constitute the 
 outer portion of the cuticle, and that these are constantly coated over with 
 an oily varnish issuing from the sebaceous glands, we may infer that the 
 cutaneous surface between the mouths of the perspiratory ducts is con- 
 structed rather for the hinderance of evaporation than for its promotion ; 
 and though the oily matter with which the skin is thus imbued is justly 
 regarded as having for one of its functions the prevention of injury from 
 the admission of external moisture, it must be equally effectual in stop- 
 ping the escape of water from within. The tardy manner in which wa- 
 ter thus escapes is illustrated by the operation of blisters. 
 
 Under the form of steam, water continually escapes from the skin. It 
 also, on certain occasions, issues in the liquid state as drops 
 and perspira- of sweat. To its escape under the form of steam the desig- 
 nation of exhalation or insensible perspiration is given ; but if 
 under the form of sweat, that of sensible perspiration. 
 
 OF EXHALATION. On condensing the vapors which arise from the 
 skin, they are found to consist of water containing a little acetate of am- 
 monia. With the water likewise escapes carbonic acid gas. With a 
 view of ascertaining the weight of the matters thus lost, Seguin inclosed 
 Experiments m 'mself in an air-tight bag, the mouth of which was gummed 
 to ascertain the upon his face in such a way as to permit the access of air to 
 tCTescapin g" tn respiratory organs. He then determined the weight of 
 through the his body and the bag together. After several hours, on re- 
 weighing, he ascertained the amount of loss by pulmonary 
 
OP PERSPIRATION. 239 
 
 exhalation. Then, taking off the air-tight bag, he was weighed again, 
 and after another interval once more. The difference between the two 
 last weighings is the amount of the pulmonary and cutaneous exhalation 
 together, and from these data, by a simple arithmetical calculation, the 
 value of each may be determined. By these experiments it appeared 
 that the loss by pulmonary and cutaneous exhalation together is, on an 
 average, eighteen grains per minute, of which seven issue from the lungs 
 and eleven from the skin. The variable action of the skin is, however, 
 well illustrated by the extreme numbers observed, the minimum being 
 eleven grains, and the maximum thirty-two. From the experiments of 
 Valentin, the average of loss through the skin is two pounds and nearly 
 half an ounce a day. Seguin's experiments would make it two pounds 
 and three quarters. It has been shown in Chapter X. that Causesofthe 
 the action of the skin is partly meteorological : the amount variable action 
 of water passing through it depends on the dew-point, the 
 atmospheric temperature, the conductibility and perviousness of the cloth- 
 ing. Whatever physical circumstances promote surface evaporation cor- 
 respondingly promote the action of the skin. Moreover, this membrane 
 acts vicariously with the kidneys, and this not only as regards the water, 
 but also as regards the solid matter, a large amount of which is thrown 
 off in the course of the day. 
 
 In all computations of the quantity of water eliminated by the skin, 
 it should not be overlooked that any inclosing barrier or bag must neces- 
 sarily occasion a complete alteration in the conditions under which the 
 action is occurring. On the whole, it is perhaps most probable that the 
 ratio of the matters expired through the skin and those expired by the 
 lungs is as 9 to 5. 
 
 Besides the water secreted by the sudoriparous glands, carbonic acid 
 and nitrogen escape. Their relative proportion is variable, Transpiration 
 and seems to depend, among other things, upon the nature of of gases. 
 the food, the carbonic acid increasing under a vegetable, and the nitrogen 
 under an animal diet. From the experiments of Dr. J. C. Draper, above 
 referred to, it appears that the absolute amount of these gases is influ- 
 enced by exercise. 
 
 OF PERSPIRATION. When the atmospheric temperature is high, and 
 more particularly if muscular exertion be resorted to, the ingredients of 
 quantity of water issuing from the perspiratory ducts is so perspiration, 
 great that it can not be evaporated. It then exudes as drops of sweat, 
 which become mingled with the oily secretion prepared by the sebaceous 
 glands. From this commingling it is scarcely possible to obtain the 
 sweat, in an uncontaminated condition, suitable for analysis, or even to 
 exclude the detritus of the cuticle itself. In a thousand parts of sweat 
 there are from five to twelve and a half parts of solid material. Thenard, 
 
240 EXCRETION OP FAT BY THE SKIN. 
 
 by resorting to the expedient of wearing for some days a flannel shirt 
 which had been thoroughly washed in distilled water, ascertained, after 
 it had again been washed in distilled water, that it had become imbued 
 with the chloride of sodium, acetic acid, phosphate of soda, phosphate of 
 lime, oxide of iron, and an animal substance. Berzelius found in the 
 sweat of the forehead chloride of sodium, lactic acid, and muriate of am- 
 monia. Besides these, other chemists have found butyric acid, the car- 
 bonates and sulphates of potash and soda, and the carbonate of lime. 
 That sweat contains sulphur is proved by keeping a portion of it : when 
 putrefaction ensues, the sulphide of ammonium is disengaged. 
 
 Fourcroy first detected urea in perspiration, an observation subse- 
 quently confirmed by Landerer and others. That the skin can, under 
 certain circumstances, excrete urea, is proved by the interesting fact that 
 this substance sometimes occurs as a bluish powdery material on the 
 bodies of those who have died from cholera. 
 
 In the perspiration formic acid also exists, and in certain conditions 
 Occurrence of ^ disease, as > f r instance, intermittent, it occurs in consid- 
 formic acid in erable quantity. Its origin may be from lactic acid, which 
 perspiration. p asses through this combination in gradually proceeding to 
 its.final destruction into carbonic acid and water. It has been asserted 
 that the increased acidity of rheumatic sweats is due to a concentration 
 from evaporation. 
 
 The sudoriparous glands secrete a portion of fat, as is demonstrated by 
 Experiment of the experiment of Krause, who removed from the palm of the 
 Krause. hand, on which there are no sebaceous glands, loose epithe- 
 
 lial scales and fat by means of ether and friction, and then placed upon a 
 square inch of it several thicknesses of filtering .paper, which was kept 
 in contact for one night, and properly protected externally. The paper 
 yielded to the action of ether a fatty substance, which contained marga- 
 rine and oil, in quantity sufficient to make tissue paper translucent. 
 
 But, besides the saline substances thus dissolved in water, the skin, 
 Secretion of fat through the action of its sebaceous glands, secretes oleagin- 
 and oil from ous material. The nature of this fatty substance differs on 
 different regions, or according to the purposes to which it is 
 to be applied. Where the ducts of the sebaceous glands open into the 
 hair follicles, the fat is of a liquid or oily nature. Sometimes stearine 
 and margarine, sometimes cholesterine is set free. Before birth, this last 
 substance is the chief constituent of the vernix caseosa, coating the sur- 
 face of the skin. In this manner, sometimes the saponifiable and some- 
 times the non-saponifiable fats or lipoids are used. 
 
 In the midst of these complex actions a very important principle may 
 Double action be discerned. I have spoken of the double action of the kid- 
 of the skin. nev? i tg mechanism f or removing saline solutions, and also 
 
ABSORPTION BY THE SKIN. 241 
 
 that for combustible material. I have now to present the skin under the 
 same aspect. It is not a mere analogy that exists between the action of 
 these organs ; the occurrence of urea and of the salt substances, the names 
 of which have been specified in both secretions, is a fact of the utmost sig- 
 nificance. I believe that the sudoriparous glands are the counterparts 
 of the Malpighian bodies, and the sebaceous glands, in their function, are 
 the counterparts of the uriniferous tubes. Indeed, this double action is 
 also distinguished in the case of the mucous membranes, which possess 
 one instrumental arrangement for the transit of saline solutions, and an- 
 other for that of fats. And since the skin, the mucous membrane, and 
 the great glands connected with it, are all to be regarded as developments 
 of one original tissue, we should expect to discover, even in their concen- 
 tration or specialization of function, the traces of their original and com- 
 mon property. Development takes place from the general to the special ; 
 and hence, in parts which have arisen from the same primordial structure, 
 though they may be charged with the accomplishment of functions which, 
 in appearance, differ essentially, there may be, both in their action and 
 in their construction, the traces of their original identity. It is in this 
 manner that the kidneys, and skin, and mucous membrane, possess the 
 property of acting vicariously for one another. The kidney can dis- 
 charge water for the skin, or the skin urea for the kidney. The com- 
 bustible matter, known as extractive in the urine, can be set free under 
 diminished renal action by the sebaceous glands, and the saline solutions, 
 eliminated by the convoluted tubing of the tufts of Malpighi, can be set 
 free by the convoluted tubing of the sudoriparous glands. In connection 
 with the views I am here impressing, I would recall the structural and 
 functional analogy there is between the transuding mechanism of the 
 kidney and the transuding mechanism of the skin. Both are arrange- 
 ments of thin convoluted tubes, and the same may be remarked as re- 
 gards the elimination of combustible material, which is probably accom- 
 plished by cell action in the uriniferous tubes, and again by cell action 
 in the sebaceous glands. 
 
 Besides exercising the functions of exhalation and perspiration, nu- 
 merous facts demonstrate that the skin exerts an absorbent Absorption by 
 action. The endermic application of remedial agents estab- of g 
 lishes this in a satisfactory manner. That water can find liquids, 
 access in this way is shown by the assuaging of the thirst which may 
 occur on taking a bath ; nor is the amount insignificant, since it may 
 give rise to a considerable increase of weight. Thus lizards, which have 
 been kept in a dry atmosphere, and thereby suffered a diminution, recov- 
 er their original weight after immersion in water ; nor is it necessary 
 that the whole .skin should be brought into contact with that liquid ; 
 the same result is obtained if merely the tail and hinder parts are im- 
 
 Q 
 
242 FUNCTIONS OF THE SKIN. 
 
 mersed. Gaseous substances also find entrance through the skin. If 
 the hand be put into a bell-jar containing oxygen, nitrogen, or carbonic 
 acid at the pneumatic trough, absorption of those gases ensues. Proba- 
 bly it is a standard function of the skin to permit a partial arterialization 
 of the blood, atmospheric oxygen being exchanged for carbonic acid 
 through it, an action the residual trace of the community of function be- 
 tween the skin and mucous membrane. In the case of some animals 
 this cutaneous respiration is well marked. 
 
 Kecapitulating now the more important actions of the skin, the folio w- 
 Summarv of & statement raa 7 ^ e ma( ^ e : ^ regulates, to a certain extent, 
 the functions the amount of water in the system, disposing of it, as the case 
 of the skm. m ^ -^ e ^h er ag sensible or insensible transpiration. The 
 water doubtless maintains its liquid condition until it presents itself at 
 the mouths of the sudoriparous ducts, moistening the general surface of 
 the skin, and then being evaporated ; or, if the supply be greater than 
 can be thus removed, it accumulates as drops of sweat. There appears 
 to be no substantial reason for believing that any portion of water trans- 
 udes directly through the structure of the cuticle, since the scales' which 
 compose it are of an impervious and almost horny nature, and their in- 
 terspaces are fortified against any such leakage by the oily exudations 
 of the sebaceous glands. With the water thus presenting on the surface 
 are many compounds which are also constituents of the urinary secre- 
 tion. Among these, urea may be particularly pointed out, thus indicating 
 a similarity of instrumental action between this organ and the kidneys, 
 and this is farther substantiated by both containing provisions for the 
 elimination and escape of the hydrocarbons ; but besides these direct 
 functions there are other very important collateral agencies which the 
 skin exerts, and particularly as a regulator of temperature. In this re- 
 spect the action is, to a certain extent, meteorological. But this has been 
 previously treated of so much in detail that it is unnecessary to resume 
 the consideration of it now. 
 
DECAY AND NUTRITION. 243 
 
 CHAPTER XIII. 
 
 OF DECAY AND NUTRITION. 
 
 Of Decay : Loss of Weight in Starvation. Interstitial Death. Effect of Allotropism. 
 
 Of Nutrition : Nutrition for Repair and Nutrition for Remodeling, illustrated in the cases of Fat 
 and Bone respectively. 
 
 Of Fat: Its Peculiarities, modes of Occurrence, and Origin. Inquiry whether Animals ever form 
 Fat. Artificial Production of it. Animals both collect it and make it. Accumulation of it 
 expends Nitrogenized Tissue. Conditions of the Fattening of Animals. Summary of the 
 Sources, Deposit, and manner of Removal of Fat. Its partial Oxidations. Summary of its 
 Uses. Nitrogenized Nutrition. 
 
 Of Bone: The Skeleton. Structure and Chemical Composition of Bone. Sources of its Con- 
 stituents. The Process of Ossification. Experiments on the Growth of Bone. Influence of 
 Physical Agents on Development and Nutrition. 
 
 OF DECAY. 
 
 THE animal mechanism, as a condition of its activity, is constantly 
 giving rise to wasted products, its parts in succession passing Retro rade 
 through retrograde metamorphosis or decay. From the elab- metamorpho- 
 orate organization which they have maintained, they go by 
 degrees through a descending course, which brings them nearer and 
 nearer to the inorganic state. Thus the fats, falling from one step to an- 
 other, finally emerge from the system as -carbonic acid and water, and 
 thus the complex atom of protein degenerates into those substances and 
 ammonia. 
 
 To this steady wasting away we offer no resistance. Having no in* 
 terior principle of conservation, the organism delivers itself LOSS of weight 
 up unresistingly, and, if its necessary supplies be withheld, in starvati n. 
 very soon succumbs. The experiments of Chossat show that, taking the 
 mean of forty-eight cases> including rabbits, Guinea-pigs, turtle-doves, 
 pigeons, hens, and crows, the body loses 39.7 per cent, of its weight be- 
 fore death by starvation ensues ; that mammals, during the process of 
 inanition, lose daily 4.0 per cent, of their weight ; and birds, as indeed 
 might be expected from their higher rate of respiration, 4.4 per cent. It 
 follows, therefore, that such animals, under these circumstances, lose one 
 twenty-fourth part of their weight per diem by destruction of tissue, a 
 result which corresponds with that of Schmidt's experiments, which lead 
 to the inference that the daily amount of properly-selected food which an 
 animal requires must amount at least to one twenty-third of its bodily 
 weight. 
 
 That the functional activity of a part implies destruction is very well 
 
244 INTERSTITIAL DEATH. 
 
 illustrated by the gradual waste of the muscles under use ; that nervous 
 Necessity of activity is also dependent on oxidation is indicated by the 
 repair. appearance of alkaline phosphates in the urine. Generally, 
 the more active the function, the shorter the life of a part ; but even the 
 hair, the teeth, the cuticle, the activity of which is very low, are no ex- 
 ceptions, for they, too, have a limit of duration, and provisions for repair 
 or renewal. Thus, as the surface of the cuticle abrades, it is restored by 
 the development of new cells below, and their gradual drying up into 
 scales ; and as regards the teeth, the second set arise, as it may be said, 
 from germs which have been left by the first, so that when the crown of 
 the deciduous tooth dies, and its fang and vascular arrangement are ab- 
 sorbed, the new tooth is ready to take its place. 
 
 Since it is not merely superficial parts, as the hair, the teeth, or the 
 Interstitial cuticle, but also the deep-seated or interior ones, that undergo 
 death. these changes, the appropriate designation of interstitial death 
 has been introduced. The removal of the effete material is accomplish- 
 ed by the aid of the blood, which occasions partial or perfect oxidation, 
 with a corresponding liberation of heat, and then, dissolving the products 
 that have arisen, carries them away. We have heretofore discussed the 
 question how it is that this oxidizing action of the arterial blood is lim- 
 ited to the dying parts, and how those which are yet capable of taking a 
 share in organization are protected. It appears to me that we are obliged 
 Deca de end * a dmit, ^ n the niechanism of living beings, those peculiar 
 ent on aiiotrop- conditions which both simple and compound bodies may as- 
 sume, and which are known as allotropic states in chemistry. 
 The indifference to oxidation which carbon, under the form of diamond, 
 presents, contrasts strikingly with the extreme combustibility of lamp- 
 black. The ready oxidibility of phosphorus, which causes the shining 
 from which it has derived its name, is no longer recognized in that other 
 phosphorus which has been acted on by the more refrangible rays of the 
 sun. And these are qualities which elementary atoms carry with them 
 when they go into union with other bodies, as is well displayed by the 
 two distinct forms of phosphureted hydrogen gas, bodies having the 
 same composition, but the one spontaneously combustible and the other 
 not. Some reasons have also been offered for imputing to the nervous 
 system a control over these allotropic changes, and under this point of 
 view we must regard it as having, for one of its prime duties, the regu- 
 lation of decay. These conclusions receive weight from the considera- 
 tion that in plants, in the economy of which no interstitial deaths are 
 taking place, no nervous system is found. 
 
USE, SOURCE, AND DEPOSIT OF FAT. 245 
 
 OF NUTRITION. 
 
 Interstitial death and retrograde metamorphosis imply removal ; but, 
 besides the removals of wasted material, on account of its in- Nutrition for 
 ability to be any longer subservient to the uses of the econ- J^mon ^^ u ' 
 omy, there are also subordinate removals, which are con- modeling. 
 nected with the necessary remodeling of parts. Thus, during the growth 
 of the skeleton, bone earth is transferred from one point to another, the 
 osseous cavities enlarged or altered, and the substance taken from them 
 is carried to other points where it is needed. Under such circumstances, 
 the disappearing part is not, in reality, giving rise to useless products. 
 The substance thus taken from the position it occupied is as valuable as 
 it ever was, and accordingly it is employed over again. 
 
 The restoration of material in the place of that which is being con- 
 sumed for use, and even the preservation of excesses which may be of 
 value at a future time, is very well illustrated by the deposit of fat in the 
 adipose tissue. Transference from point to point of material which has 
 undergone no deterioration may be studied in the history of the growth 
 and development of bone. To these cases in succession I propose to 
 direct attention. 
 
 First. Of the use, sources, and manner of deposit of the fat. 
 
 The use of fat in the animal economy doubtless depends on its heat- 
 making power ; for, though there are many different varieties Physiological 
 of this substance, solid and liquid, they are all characterized relations of fat. 
 by an analogy of composition, all containing a great excess of unoxidized 
 hydrogen. It is, indeed, on this peculiarity that their employment in 
 domestic economy depends. They are all highly combustible, and evolve 
 so much heat as to be very available for the production of flame. 
 
 For the better understanding of the functions discharged by fatty sub- 
 stances, we may perhaps profitably offer the following statement of their 
 chemical relations. 
 
 When a fat or oil is acted upon by an alkali, in contact with water at 
 its boiling-point, decomposition ensues, a fatty acid and gly- Chemical 
 cerine being disengaged, and the acid, uniting with the alkali, cuiiarities of 
 gives origin to a soap. During this action no oxygen is ab- at ' 
 sorbed, but, since the compounds arising present an increase of weight, it 
 is evident that there has been an assimilation of water. In view of these 
 facts, it is therefore inferred that the oils and fats are composed of a fatty 
 acid united with the oxide of a radical, to which the designation of lipyl 
 has been given, and which, when it is displaced, combining with water, 
 gives origin to glycerine. 
 
 Glycerine, which is a substance of considerable physiological import- 
 ance, is a pale yellow liquid, of a sweetish taste, and attracting moisture 
 
246 
 
 PROPERTIES OF FAT. 
 
 from the air. If fermented in a large quantity of water with yeast, it is 
 converted into metacetonic acid. It occurs in the yolk of the egg, and 
 also in the fats of the brain. By gradual oxidation it can give rise to 
 lactic acid. 
 
 The physical properties of the fats depend, for the most part, on the 
 nature of their acids. The fats derived from animals are of various de- 
 grees of consistency ; they are colorless or white, lighter than water, bad 
 conductors of heat. They are insoluble in water, and burn, in the pres- 
 ence of air, into carbonic acid and water, with the evolution of much heat. 
 By the action of certain nitrogenized ferments they may be separated into 
 their acid and glycerine, and by the action of pancreatic juice, as ex- 
 plained previously, may be brought into the condition of an emulsion. 
 The more important of the animal fats are stearine, margarine, and oleine. 
 Places of occur- They are inclosed in cells accumulated in various parts of 
 rence of fat. the system, such as in the orbit of the eye, around the heart, 
 and among the muscles of the face, under the cutis, and within the bones. 
 In morbid states they sometimes abound in the kidneys, liver, and spleen. 
 They are also discovered in some of the animal fluids : thus they commu- 
 nicate to the chyle its characteristic property, and therefore likewise oc- 
 cur in the blood. In their relative amount they vary at different periods 
 of life, being in a larger proportion in childhood, and again after the mid- 
 dle period. Their quantity likewise changes with physical changes, di- 
 minishing, for instance, after continued muscular exertion, and also by 
 long exposure to cold. 
 
 Though the amount of fat in the blood varies with the nature of the 
 Quantity of fat f od > it can not, however, be increased, in a state of health, 
 in the blood, beyond a certain point, owing to the inability of the absorb- 
 ents to receive more than a definite quantity. The serum of arterial con- 
 tains less fat than the serum of venous blood; the blood of women more 
 than that of men. 
 
 The manner of occurrence of fat in 
 
 organized structures is twofold : oft- 
 
 en it occurs in the free state, but also 
 
 is very commonly inclosed in the in- 
 
 terior of cells, as shown in Fig. 107, 
 
 which is a fat-cell, a being the adi- 
 
 pose membrane, and b the nucleus. 
 Fig. 108, adipose and areolar tissue: a, #, fat- 
 cells ; &, &, fibres of areolar tissue. 
 
 Respecting the origin of the fat substances in 
 Fats arise from plants there can be no question. They 
 
 are derived fr o m the decomposition of Adi P se and areolar tissue ' 
 
 pig. ios. 
 
 Fat-ceii. 
 
 turning thereto, carbonic acid and water by those organisms under the in- 
 
ARTIFICIAL FORMATION OF FAT. 247 
 
 fluence of the rays of the sun. It is interesting to remark that to these 
 same binary bodies do the fats return after accomplishing the successive 
 stages of their metamorphosis in the economy of animals. From car- 
 bonic acid and water they come ; to carbonic acid and water they return. 
 
 But the origin of the fatty substances of animals is by no means so 
 clear. One of the questions which have been debated in chem- ~ 
 ical physiology is, Do animals collect from their food all the collect or fab- 
 fat they require, or have they the power of making it for them- ricate at - 
 selves ? In the preceding chapter, under the description of the origin of 
 the butter of milk, we have, in part, anticipated the facts which might 
 here be presented. Referring, therefore, to what has there been said, it 
 will be sufficient now to admit the general conclusion that fats and oils 
 very abundantly occur in plants. 
 
 But instances are not wanting which show that from other sources 
 than the vegetable kingdom, and by processes very different to those ex- 
 ecuted by plants, fats may be made from substances in which they did 
 not pre-exist. We select some of these which have been offered by chem- 
 ists who have asserted the power of the animal system for such a form- 
 ation of fat. 
 
 1st. When an animal body is buried under certain circumstances, it 
 does not undergo putrefaction, but changes into a fatty or soapy gu oged Jn 
 substance, adipocire. Attention was first directed to this fact stances of its 
 on the occasion of exhuming many bodies from the cemetery formatlon - 
 of Innocents in Paris. Those which lay a certain depth beneath the 
 ground were found to have undergone the change in question ; but that 
 it does not altogether depend on the condition of the earth of the grave, 
 as respects moisture or other such physical state, I have myself had the 
 opportunity of verifying in the case of a subject which had been buried 
 for nineteen years, and which was disinterred in a condition of perfect 
 preservation, so far as exterior appearance went, but which had been 
 wholly converted into adipocire. Yet, from the same burying-ground, 
 many other bodies were disinterred, but none had undergone a like change. 
 
 2d. When nitric acid is made to act on fibrin apparently deprived of 
 its fat, an oily substance is disengaged. 
 
 3d. During the action of nitric acid on starch, in the preparation of 
 oxalic acid, a like effect takes place, oily matter being set free. 
 
 4th. As has been described in a preceding chapter, butyric acid may be 
 prepared from sugar, through the influence of casein, in the presence of 
 carbonate of lime. 
 
 Though the conversion of albumenoid bodies into fat has not thus far 
 been distinctly accomplished in an artificial way, no doubt Production of 
 can exist that it is possible. Indeed, the experiments of fat from aibu- 
 Quain and Virchow respecting the origin of adipocire have menoid bodies - 
 
248 FORMATION OF FAT BY ANIMALS. 
 
 led them to regard it as, at all events to some extent, arising from the 
 albuminous constituents of the muscles being decomposed into fatty acids 
 and ammoniacal salts. Wagner, Donders, Burdach, and others, have fur- 
 nished many interesting experiments on the apparent transmutation of 
 various bodies, such as pieces of coagulated albumen, crystalline lenses, 
 etc., in the abdominal cavities of birds. These extraneous objects after a 
 time become enveloped in, and in some cases permeated by, fatty mate- 
 rial. But that this does not arise from metamorphosis of the protein 
 body introduced was well proved by the last observer, who employed 
 pieces of wood and the pith of elder with the same result. 
 
 Whatever, therefore, may be the conclusion arrived at on the cases 
 The carnivora kere m * r duced whether, during a special metamorphosis, 
 find fat in their muscular tissue can pass into adipocire ; whether from fibrin 
 or starch, by the action of nitric acid, fats may be made, or 
 whether these substances pre-existed in the material from which they ap- 
 pear to arise, and are only disengaged or set free there can be no question 
 as regards one great group of animals, the carnivora, that they find in their 
 food a sufficiency of these hydrocarbons to meet all their wants. It is 
 as respects the other group, the herbivora, that this question of the arti- 
 ficial formation of fats from substances in which they did not pre-exist. 
 Do the herbiv an( ^ particularly fr m albumenoid bodies, becomes interest- 
 ora ever make ing. Do the herbivora find in their food all the fat they re- 
 quire, or are they obliged to fabricate a part ? 
 
 The question whether there exists in the animal mechanism a capabil- 
 Formation of ity of forming fat from material in which it did not pre-exist 
 fat by bees. ma y -fo G considered as finally settled in the affirmative, after 
 much discussion, by the repetition of Gundelach's experiment by Dumas 
 and Milne Edwards. This experiment consisted in the feeding of bees 
 with honey nearly free from wax, and determining the quantity of fat in 
 their bodies at the beginning and end of the experiment, and also the 
 quantity of wax in the comb that they made. The following table gives 
 the result : 
 
 Gramme. 
 
 Fat found in the body of each bee at the beginning 0.0018 
 
 Wax each bee consumed with the honey, not exceeding 0.0003 
 
 Whole amount of fat derived from food 0.0022 
 
 Wax secreted by each bee 0.0064 
 
 Fat and wax in the body of each bee at end of experiment 0.0042 
 
 From which it appears that a very large quantity of fat and wax had 
 been produced. 
 
 Admitting thus that the animal system possesses the power of form- 
 The system * n & ^ at ^ * s P r bable that, under all circumstances, it carries 
 continually forward that function, though it may be at different rates on 
 generates fat. c | ifferent occas i ons< g uc h a production of fat probably com- 
 
PLANTS FURNISH FAT. 249 
 
 mences in the intestinal tube, the material from which it originates being 
 both nitrogenized and non-nitrogenized. Thus, when ducks have been 
 fed on albumen containing but little fat, the digested material in the in- 
 testine yields a larger proportion of fat than when they have been fed on 
 clay, or even on starch. If the glands of the intestine secreted fat from 
 the blood, it would be detected after feeding the birds with clay, and 
 hence we may conclude that the source of the increase observed is from 
 the albumen. 
 
 But, in addition to the part they thus make, a large portion of the fat 
 of animals is undoubtedly obtained from the food. This is obviously the 
 case with carnivora, and the same may, indeed, be said of the herbivora. 
 Very many of the oleaginous bodies have a close chemical relationship 
 to one another, so that they may be regarded as affording a series, the 
 terms or members of "which arise from successive partial oxidations ; 
 and since the fats are soluble in one another, they freely mix together, 
 and therefore many of them may be found co-existing in the adipose tis- 
 sues, some of them less and some of them more advanced in their prog- 
 ress of oxidation. Whether they have been derived from pi an ts furnish 
 the food or by indirect processes made in the system, it is fatorthemate- 
 
 . , , . , -, . " . rials from 
 
 equally true in both instances that their primary source was w hich it is 
 in the vegetable kingdom. In the former case they occur- made ' 
 red in the plant-structure as hydrocarbons, in the latter as amylaceous 
 or nitrogenized bodies. Under the influence of the sunlight the vegeta- 
 ble tissues obtain them by decomposing carbonic acid and water, and to 
 those two substances they return after they have undergone destruction 
 in the animal organs, thus presenting a significant instance of the alter- 
 nate passage of atoms from the inorganic to the organic state, and back 
 again. 
 
 The primary source of all fat substances is therefore in plants, which 
 obtain them from the decomposition of the inorganic constituents of the 
 air. The excess of hydrogen which characterizes this group of bodies in 
 most instances is undoubtedly derived from the decomposition of water, 
 and this explains the fact, frequently noticed, that the development of 
 such hydrocarbons in plants is often accompanied by the simultaneous 
 appearance of acids, for the hydrogen being appropriated by the former 
 class, the residual oxygen gives origin to acids or is set free. 
 
 The quantity of fatty matter formed in the ordinary articles of food 
 used by domestic animals seems to be amply sufficient to Quantity of fat 
 meet all their wants. If a calculation be made of the amount 
 of such materials consumed by cattle during the process of mais. 
 fattening, it will be ascertained that the quantity used not only contains 
 sufficient to account for the increase of weight, but also furnishes an am- 
 ple supply for the portion which is destroyed by respiration. The fats 
 
250 CONDITIONS OF FATTENING. 
 
 thus contained in plants are often absorbed with but little alteration. 
 The fattening of cattle with linseed-cake gives rise to an accumulation 
 in their adipose tissues of an oily material of unusual fluidity, and it is 
 a matter of common observation, as previously mentioned, that when 
 strong-smelling oils have been accidentally used, their flavor will be im- 
 parted to the secretion of the mammary gland. 
 
 The quantity of fat in articles of food is commonly estimated by the 
 solvent action of sulphuric ether. It should, however, be understood 
 that we can not with correctness regard all the matters extracted by that 
 menstruum from plants as fat. 
 
 Thus, either by forming or by collecting from the food, a supply of fat 
 The accumula- is obtained, and this is absorbed by the lacteal system in the 
 Uro- 16 " manner already described. But where fat is administered 
 tissue, in excess, so that large quantities of it are retained in the 
 system, a proportionate cell formation arises for the purpose of affording 
 it a receptacle. The walls of such cells are composed of nitrogenized 
 material, and herein is displayed the connection between the two groups 
 of bodies, the albumenoid substance and the fats. There is reason to 
 suppose that when, from the food, a sufficient quantity of nitrogenized 
 material for this purpose can not be obtained, resort is actually had to 
 the muscular fibre of the system itself, but when this also fails the fat 
 accumulates in the blood. 
 
 In the artificial fattening of animals, the indications to be complied 
 General condi- with are very obvious : They are, 1st. To furnish an abund- 
 fattrni^golan- ant ^PP 1 / of oleaginous material in the food; 2d. To pre- 
 imais. vent, as far as possible, waste by oxidation. 
 
 The first indication is satisfied by the purposed employment of oleag- 
 inous articles, as, for instance, linseed-cake, or by the selection, among 
 ordinary food substances, of those which, like Indian corn, abound in oil. 
 It is to be remarked that the increase of weight of an animal may take 
 place in two ways : 1st. By adding fat to the deposit in the adipose tis- 
 sues ; or, 2d. By development of the muscles. It might perhaps be ad- 
 missible to speak of the former as adipose fattening, the latter as albu- 
 menized. According as it has been subjected to one or other of these 
 processes, an animal will be very differently prepared for undergoing se- 
 vere exercise. A horse fed with Indian corn can not, under those cir- 
 cumstances, maintain himself as well as if he had been fed on oats. In 
 the former case his adipose tissues have been developed, in the latter his 
 muscular. 
 
 The second indication is met by resorting to every expedient which 
 can restrain the action of the respired oxygen. A state of perfect quies- 
 cence is therefore to be observed. Muscular movement of every kind in- 
 creases the activity of respiration. On the contrary, rest diminishes it. 
 
SOURCES, DEPOSIT, AND REMOVAL OF FAT. 251 
 
 If, in addition to this state of quiet or rest, sleep likewise be indulged in, 
 the object is still more perfectly attained ; and if a high temperature be 
 resorted to, since this checks the oxidation needful for maintaining the 
 system at its due temperature, this also diminishes the waste of the fat. 
 
 Under such circumstances, where every thing is done to give a supply 
 of fat, and every thing to prevent -its consumption, it may be caused to 
 accumulate in the tissues to an extraordinary amount. But The liver affect 
 this very soon interferes with the action of the liver, one of ed in that oper- 
 the functions of which we have seen is the preparation of fat. atlon ' 
 And it may also be remarked that many of the diseases of that organ, 
 especially those occurring in hot climates, meet their explanation on the 
 principles we are here inculcating, the state of rest produced by lassitude, 
 the warm and therefore expanded air that is breathed, and the improper 
 resort to oleaginous articles of food. 
 
 In view of the preceding facts, it may therefore be concluded that the 
 interior source from which the adipose tissues are supplied Summar of 
 is the fat contained in the plasma of the blood, into which it the sources, 
 has been poured through the thoracic duct, or otherwise ob- ^^and^an- 
 tained from the digestion of food in the small intestine ; and ner of removal 
 since the blood-cells contain a higher percentage of oily ma- 
 terial than the plasma (2.2 per cent, may be extracted from them by ether, 
 either as a phosphorized fat or glycero-phosphoric acid), they constitute 
 reservoirs of supply to meet the exigencies of the system, there being a 
 necessary relation between the quantity they can thus retain in store 
 and the quantity contemporaneously existing in the plasma, a diminution 
 of which at once establishes a drain upon the cells. Thus charged with 
 these hydrocarbons, the plasma passes wherever there are adipose cell- 
 germs, furnishing to them the special nutriment they require for their 
 development 'into fat-cells, the wall and nucleus of which are derived from 
 the blood, or, as we have mentioned, in certain cases actually from the 
 muscular tissues. The amount of fat which can thus be held in reserve 
 depends in part on the number of germs, in part on the supply of fat 
 from the digestive organs, and in part on the supply of appropriate ma- 
 terial for the walls and nuclei. 
 
 When the fat thus stored up is wanted, the cell wall in many cases 
 deliquesces or wastes away, surrendering its contents back to the plasma, 
 but probably much more frequently a transudation of the hydrocarbon 
 takes place through it, analogous to what has been described as occur- 
 ring in the blood-cells themselves. This demand upon the adipose tis- 
 sues may originate for many reasons, since there may be a necessity for 
 fat in the accomplishment of the various histogenetic operations going 
 forward, or for those of retrograde metamorphosis, or for the maintenance 
 of a normal state of the blood as respects its oleaginous ingredient, or for 
 
252 USES OF FAT. 
 
 the production of heat by immediate and final oxidation into carbonic 
 acid and water. 
 
 It is not to be supposed, however, that this final oxidation into car- 
 Fats undergo bonic acid and water always takes place at once or abrupt- 
 ^nslVthe a " ly* Every thing shows that fats pass through successive 
 system. gradations of retrograde metamorphosis, perhaps gradually 
 
 losing by oxidation two atoms of carbon and hydrogen ; and, indeed, 
 there is reason to believe that, on special occasions, the opposite changes 
 happen. Thus stearic acid may arise from margaric acid by deoxidation. 
 It does not occur to any considerable extent in vegetable food, having 
 thus far been only found in cacao butter. 
 
 In a summary of the uses of fatty substances may be mentioned the 
 Summary of production of a high temperature by oxidation ; their agency 
 the uses of fat. j n metamorphosis, as displayed by the assistance they lend 
 in gastric digestion; the function they seem to discharge in cell life, 
 which would appear to be important if it be true that the nuclei of some 
 cells are composed of fat ; their relation in the formation of bile, and their 
 probable connection with the production of haematin. Among, their phys- 
 ical uses may be mentioned the equable manner in which they propagate 
 pressures in all directions when they are in the liquid state, as is often 
 the case ; the manner in which they fill up vacuities, and communicate a 
 roundness and solidity to the system ; their low conducting power as 
 respects heat, which enables them to economize the warmth of the body ; 
 their diminishing of friction among moving parts, as in the case of the 
 muscles ; and that they discharge some highly important function as 
 respects the nervous system is proved by the manner in which they 
 uniformly occur in tubular nervous tissue. In the general metamorph- 
 oses of the system they seem to take an important part. This may 
 be inferred from the fact of their presence wherever cells or fibres are 
 forming. 
 
 From what has been said respecting the connection of the fats with 
 the metamorphoses of the system, it is obviously incorrect to regard them 
 as constituting a purely respiratory element. 
 
 Conclusions similar to those which have been stated respecting the 
 Nutrition of ve g eta ^ e source of the fats might also be arrived at as re- 
 the nitrogen- gards the source of the nitrogenized constituents of the sys- 
 tem. These likewise are found in plants ; and thus, therefore, 
 though the carnivorous animal may be said to be nourished by the car- 
 cass on which it feeds, it is nevertheless strictly true that its nutrient 
 material is all from the vegetable world. 
 
 The repair of muscles, of nerves, of the skin, or other such highly or- 
 ganized parts, is dependent on the agency of cells. Since these are un- 
 distinguishable, or to all appearance perfectly alike, it becomes a matter 
 
STEUCTUEE OF BONE. 253 
 
 of curious inquiry how they should be able to occupy exactly the places 
 and discharge with precision the functions of those which they are re- 
 placing? or, in the case of growth and development, why they should 
 combine so as to take on a determinate, and, as it were, predestined form ? 
 How is it that such a variety of structures spring up from the same orig- 
 inal cell ? How is it that the two halves of the body have such a sym- 
 metrical conformation in a majority of instances, the one being the exact 
 counterpart of the other, peculiarities which are often continued even 
 after the supervening of morbid conditions, as shown in such cases as 
 are known by the term of symmetrical diseases, in which a structural 
 change affecting one side of the body affects also the corresponding part 
 of the other side ? It appears to me that these and other such instances 
 of nutrition, growth^ and development can only be explained by admit- 
 ting, as a great and fundamental principle in physiology, that the primor- 
 dial germ being in all instances alike, its mode of development will de- 
 pend on the physical agents and conditions to which it is exposed : a 
 principle which, though it may seem of little moment at the first view, 
 carries with it consequences of the utmost importance at last. 
 
 Second. Of the structure and development of bone. 
 
 The skeleton in man is composed of 246 bones, which are usually di- 
 vided into three groups, the Ions:, flat, and irregular. Their 
 
 . & , , & The skeleton. 
 
 uses are purely mechanical, such as to give support to the 
 
 soft parts ; to serve as levers on which the muscles, by their contractions, 
 
 may act. 
 
 In structure bone offers an imperfect division into the compact and 
 spongy. ' The compact is, however, a porous mass full of cells structure of 
 and passages. Through it there pass, more particularly in bone< 
 the longitudinal direction, canals for containing blood-vessels and nerves : 
 they are called haversian canals. These, which are well seen in a thin, 
 transverse section of bone as irregular circular openings, are surrounded 
 with lamellae, and in the basis substance occur hollow spaces, the lacuna?, 
 which, presenting a dark aspect, were formerly mistaken for solid corpus- 
 cles ; they are, however, cavities from which proceed minute channels or 
 canaliculi. In form the lacunas are irregularly oval ; the canaliculi of 
 those nearest to the haversian canal communicate directly with its cav- 
 ity, and there is so complete an inosculation between adjacent lacunas, 
 by means of these delicate tubes, that the whole so-called compact struc- 
 ture of the bone may be said to present a connected system of lacunas 
 and canaliculi. 
 
 The diameter of these delicate channels of intercommunication is much 
 too small to permit the passage of blood-cells, yet through them the 
 plasma readily finds its way and thus carries forward the nutrition of 
 the entire bone. 
 
254 COMPOSITION OF BONE. 
 
 Fig. 109 is a photograph of a transverse section of part of human fe- 
 mur, showing the haversian canals surrounded by their concentric lamel- 
 la, lacuna, and canaliculi. The complete perviousness of the structure 
 is demonstrated. 
 
 Fig. 109. Fig. 110. 
 
 Transverse section of bone, magnified 50 diameters. Lacunae and canaliculi from frontal bone. 
 
 Fig. 110, lacunae and canaliculi of human frontal bone. 
 
 In chemical constitution, bone may be considered to be composed of 
 Chemical com- two P ort i ns > organic and mineral : the former is gluten, and 
 position of in the latter phosphate of lime greatly predominates, as the 
 )ne> following analysis by Berzelius shows : 
 
 Analysis of Bone. (Berzelius.) 
 
 Cartilage (or gluten) 32.17 
 
 Blood-vessels 1.13 
 
 Phosphate of lime .51.04 
 
 Carbonate of lime 11.30 
 
 Fluoride of calcium 2.00 
 
 Phosphate of magnesia 1.16 
 
 Soda, chloride of sodium ...*..... ,. 1.20 
 
 100.00 
 
 An instructive separation of bone into its leading constituents may be 
 Se aration of accom pli sne d by the action of hydrochloric acid or by cal- 
 its organic and cination respectively. When a bone is soaked in dilute hy- 
 y ases. d r ochloric acid for a due length of time, its mineral constitu- 
 ent is removed, and the organic gluten is left in the shape of the original 
 bone ; or, if the bone be calcined in the open fire with free access of air, 
 the organic material is consumed and the mineral material remains. A 
 more . critical examination shows that these constituents are not merely 
 associated together they are, in reality, chemically combined. 
 
 The different degrees of softness and hardness which bones from dif- 
 ferent animals present depend very considerably on the amount of wa- 
 ter they contain. The gluten is doubtless, in all instances, derived from 
 
OF OSSIFICATION. 255 
 
 the metamorphosis of albumenoid bodies, a conclusion which Orf . Q of the 
 is well illustrated by what we observe in the case of the in- organic and 
 cubating egg. In the adult the source of the bone-earth is earthy matter - 
 twofold : in part it is derived from the food, and in part obtained from 
 the remodeling and changes of the bones themselves. In speaking of 
 the composition of milk, we have already described how, through the ca- 
 sein of that secretion, a supply of phosphate of lime is secured for in- 
 fant life. 
 
 At its first formation, bone consists of a gelatinous material, which grad- 
 ually becomes condensed and cellular, presenting what is termed the carti- 
 laginous state. In this material vascular canals arise, which, The process of 
 concentrating toward one spot, give origin to the point or ossification, 
 centre of ossification. Simultaneously, the structure of the cartilage be- 
 comes modified, its nucleated cells are elongated, nucleoli arising, and 
 smaller cells forming. These reach maturity, and are separated from 
 one another by the material derived from the deliquescence of their pa- 
 rent cells, which has simultaneously been taking place. The progress of 
 these changes may be studied by examining the calcifying cartilage near- 
 er and nearer to the point of ossification, to which, as we approach, we 
 find that the cells become more and more numerous, a general arrange- 
 ment into a columnar form being now apparent. 
 
 The deposit of mineral material commences at the point of ossification, 
 and proceeds between the columnar arrangement of cells, lateral branch- 
 es between the individual cells being successively given off, a bony net- 
 work thus arising which is pervious in every part. In the human em- 
 bryo the cartilaginous stage is completed in the sixth week, and ossifi- 
 cation commences first in the clavicle during the seventh. 
 
 Fig, in, Fig. Ill, perpendicular section of the ossifying 
 
 border of the shaft of the femur of a child a fortnight 
 old : a, cartilage in which the cells, the nearer they 
 are to the ossifying border, are in more extended 
 longitudinal rows; , ossifying border: the dark 
 streaks indicate the progressive ossification of the 
 intercellular substance, the clear ones the cartilage 
 cells, which ossify subsequently; c, compact layer 
 of bone near the ossifying border ; d, the substantia 
 spongiosa formed in the osseous substance by ab- 
 sorption, with cancelli, e 1 e, the contents of which are 
 not shown. (Kolliker.) 
 
 Fig. 112, photograph of ossifying cartilage, the 
 dark portions showing the region of complete ossifi- 
 
 Ossifying cartilage, magni- .mi i j. * . i. .L-I 
 
 fied 10 diameters. cation. The columnar arrangement of the cartilage 
 cells s is very apparent. 
 
256 
 
 GROWTH OF BONE. 
 
 Fig. 112. 
 
 Fig. 113. 
 
 Ossifying femur. 
 
 Ossifying cartilage, magnified 50 diameters. 
 
 Fig. 113, femur of a child a fortnight old, natu- 
 ral size : #, substantia compacta of the shaft ; b, 
 medullary cavity ; c, substantia spongiosa of the 
 shaft ; d, cartilaginous epiphysis, with vascular ca- 
 nals ; e, osseous nucleus in the inferior epiphysis. 
 (Kolliker.) 
 
 When silver rings are placed upon the shaft of 
 Growth of a growing bone at a measured dis- 
 siiverrings^nd tance > subsequent examination shows 
 madder. that that distance still remains the 
 
 same, though the bone may have become much 
 longer. If such a ring be permitted to remain a sufficient period of time, 
 it will eventually be found in the interior of the bone. When madder 
 is mixed with the food of pigs, its coloring matter so unites with the 
 phosphate of lime of their bones as to impart to them a red tint. If the 
 animal submitted to the experiment be very young, the whole skeleton 
 may be tinged in a single day, a more close examination showing, how- 
 ever, as might be expected, that the portion most completely acted upon 
 is that nearest to the vascular surface. In older animals the coloring 
 goes on more slowly ; the portion which shows the effect most striking- 
 ly is between the shaft and extremities, more particularly upon the sur- 
 face. If the madder be given, periodically and then withheld, alternate 
 layers of a red and white appearance are produced. 
 
 From these experiments, it may be inferred that the growth of a bone 
 Conclusions is not uniform in all parts. Young bones grow chiefly toward 
 such" ex f peri- ^ e extremities ; nor is the growth cumulative, the parts al- 
 ments. ready deposited being ever after preserved ; for, if that were 
 
 the case, it would not be possible for a ring placed in such a manner as 
 has been described to find its way into the medullary canal. For that to 
 
OF NUTRITION. 257 
 
 occur, there must have been an absorption or removal of the pre-existing 
 parts. The tinging by madder shows that growth is taking place wher- 
 ever the plasma of the blood can have access, and this not alone upon 
 the proper vascular surfaces, but also interstitially. 
 
 It thus appears that bone, solid and dense as it is, is the seat of con- 
 tinual changes, which, though they may go on with more activity in the 
 growing state, take place also when the structure has reached maturity 
 or apparent perfection. From one portion a part is removed, on another 
 additions are made, the method by which this is accomplished being 
 through the access of the blood-plasma, which finds its way to every 
 part by reason of the pervious structure of the mass. 
 
 As to the sources from which the phosphate of lime is derived, though 
 doubtless the food offers it in considerable quantity, there are gources from 
 many reasons for inferring that the identical portion which which material 
 has been removed from one part is used for the extension 1S denved - 
 of another ; and thus we may say that there is a plastic operation con- 
 tinually going forward, a remodeling, so as to adapt the structure to its 
 new conditions if in a growing animal, or to maintain it in good repair 
 if in an adult. 
 
 Turning from the two cases with which we have been thus occupied, 
 the development and maintenance of the adipose and osseous tissues, to 
 the phenomena of nutrition generally, we may conclude that there are 
 several sources from which material for these purposes may be derived : 
 a part may be obtained by absorption directly from the food ; a part may 
 be manufactured or fabricated in the system itself, or may be taken from 
 some locality therein in which it has become redundant or useless, and 
 transferred elsewhere to the point at which it is required. 
 
 The medium through which these additions and exchanges for the pur- 
 pose of development or remodeling are accomplished is of course the 
 blood. It bears with it, wherever it circulates, the substances that are 
 demanded fibrin for muscles, bone-earth for the skeleton, fat for the ad- 
 ipose tissues. 
 
 It remains for us to inquire into the laws of deposit and development 
 involved in these processes, that is to say, why, for example, Partg are de _ 
 is phosphate of lime laid down at the points where the phos- veioped and 
 phate of lime has been, or, if growth be taking place, why Se^fluenL 
 are the accretions arranged in a definite way both as respects of physical 
 size and shape ? Upon this mquiry I do not propose at pres- 
 ent to enter, since it is closely connected with the general doctrine of de- 
 velopment, which will have to be considered in detail in the next book. 
 We shall then find that reasons may be assigned for the deposit of given 
 substances in places that have been vacated by others of the same kind, 
 as in the nutrition of muscles. We shall also then have to consider the 
 
258 OF THE NERVOUS SYSTEM. 
 
 laws of development from a much more extensive point of view, intro- 
 ducing the doctrine of the paramount influence of physical causes in this 
 respect, and perhaps we shall find ourselves brought to the conclusion 
 that the progressive career of a cell is absolutely dependent on the phys- 
 ical conditions to which it is exposed, and that there is nothing extraor- 
 dinary in the circumstance that two cells placed under conditions which 
 are alike will develop alike ; that, therefore, a part which is being repaired 
 will have its additions made in the same places, of the same material, to 
 the same extent, and of the same form as the part which has been re- 
 moved. 
 
 CHAPTER XIV. 
 
 OF THE NERVOUS SYSTEM. 
 
 Divisions of the Nervous System. Cerebro-spinal and Sympathetic. Fibrous and Vesicular. 
 
 Structure and Functions of Nerve Fibres. Centripetal and Centrifugal. Rate of Conductlbillty. 
 
 Anatomical Examination of the Structure and Functions of Nerve Vesicles. They diffuse Influ- 
 ences, are Magazines of Force. Element of Time Introduced by Registering Ganglia. Oxida- 
 tion necessary to Nerve Activity. Necessity of Repair and Rest. Electrical Examination of 
 the Functions of Vesicles. Anatomical and Electrical Examinations agree. 
 
 Automatic Nerve Arc. Cellated Nerve Arc. Multiple Arcs. Commissures. Registering Nerve 
 Arcs. Sensorlum. Influential Arc. 
 
 Suggestions derived from cerebral Structure respecting the Soul. Its Independent Existence and 
 Immortality. 
 
 Ideas of Time and Space. Objective, subjective, and Impersonal Operations. Vestiges of Im- 
 pressions and their Interpretation. Finite Nature of Knowledge. Mental Emotions. 
 
 THE parts and functions which have been thus far described stand in 
 Im ortanceof subordination to the important system on the study of which 
 the nervous we now enter. It may be truly said that the position of any 
 animal in the scale of life is directly dependent on the de- 
 gree of development of its nervous system. Through this it is brought 
 in relation with the external world, deriving sensations or impressions 
 therefrom ; through this, also, all voluntary muscular contraction takes 
 place. Whatever the grade of intelligence may be, the degree of devel- 
 opment or expansion of the nervous system is in close correspondence 
 thereto, from the lowest conditions in which it is first making its appear- 
 ance in tribes which are scarcely distinguishable from vegetable forms, 
 up to its highest elaboration in the cerebro-spinal system of man. 
 
 The physiologist has to confess that in this, which is, without doubt, 
 imperfect con- ^ e mo ^ t important part of his science, the amount of what is 
 dition of the known with exactness is limited : indeed, so great an obscu- 
 BU Je rity rests upon the functions of the nervous system that he 
 
 has to content himself rather with the description of structure than offer 
 
DIVISIONS OF THE NERVOUS SYSTEM. 259 
 
 the explanation of action. Yet even now a few leading facts have been 
 determined, which foreshadow the attitude in which the whole subject 
 will stand when it comes to be better understood. Among these may 
 be numbered the localization of special functions in special parts of the 
 nervous centres, as was observed by Gall ; the double office of the spinal 
 nerves, first recognized by Bell, that their anterior roots are motor and 
 posterior sensory ; the conversion of impressions made at the periphery 
 into motions, reflex action, as it has been termed, first clearly recognized 
 by Hall ; the relation of the ganglia at the base of the brain to the cere- 
 brum and the spinal cord, as shown by Carpenter ; and particularly the 
 general condition on which the activity of the entire system depends, 
 that it undergoes oxidation or waste, and, among other products, gives 
 origin to salts of phosphoric acid. 
 
 For the sake of convenience of description, the nervous system is usu- 
 ally regarded as consisting of two portions, the cerebro-spi- Di v i s i on O f t h e 
 nal and sympathetic. The former is composed of the spi- nervous system 
 nal cord, the brain, the nerves proceeding from them, and S p ma i &ri ~ 
 their ganglia; the sympathetic is composed of a series of sympathetic, 
 ganglia, united by intercommunicating threads on each side of the ver- 
 tebral column, and supplying branches to the coats of the blood-vessels 
 and viscera of the great cavities. Both portions contain two kinds of 
 structure, a fibrous and a vesicular. The latter is found in _.. 
 
 \ f Fibrous and 
 
 various situations ; the former serves to connect those mass- vesicular stmc- 
 es with one another, or to furnish means of communication *' 
 from point to point ; the office of the ganglia, or nervous centres, is for 
 the reception of impressions and the origination of motions. In the 
 brain the impressions of external circumstances are, as it were, registered, 
 and from it originate the processes of intellection. 
 
 The study of this portion of the mechanism of man brings us therefore 
 in contact with metaphysical science, and some of its funda- Connection of 
 mental dogmas we have to consider. Nearly all philoso- metaphysical 
 phers who have cultivated, in recent times, that branch of phl1 
 knowledge, have viewed with apprehension the rapid advances of physi- 
 ology, foreseeing that it would attempt the final solution of problems 
 which have exercised the ingenuity of the last twenty centuries. In 
 this they are not mistaken. Certainly it is desirable that some new 
 method should be introduced, which may give point and precision to 
 whatever metaphysical truths exist, and enable us to distinguish, sepa- 
 rate, and dismiss what are only vain and empty speculations. 
 
 So far from philosophy being a forbidden domain to the physiologist, 
 it may be asserted that the time has now come when no one is entitled 
 to express an opinion in philosophy, except he has first studied physiol- 
 ogy. It has hitherto been to the detriment of truth that these processes 
 
260 RELATIONS OF PHYSIOLOGY TO METAPHYSICS. 
 
 of positive investigation have been repudiated. If from the construction 
 of the human brain we may demonstrate the existence of a soul, is not 
 that a gain? for there are many who are open to arguments of this 
 class, on whom speculative reasoning or a mere dictum fall without any 
 weight. Why should we cast aside the solid facts presented to us by 
 material objects ? In his communications throughout the universe with 
 us, God ever materializes. He equally speaks to us through the thou- 
 sands of graceful organic forms which are scattered in profusion over the 
 surface of the earth, and through the motions and appearances presented 
 by the celestial orbs. Our noblest and clearest conceptions of his attri- 
 butes have been obtained from these material things. I am persuaded 
 that the only possible route to truth in mental philosophy is through a 
 study of the nervous mechanism. The experience of 2500 years, and 
 the writings of the great metaphysical intellects, attest with a melancholy 
 emphasis the vanity of all other means. 
 
 Whatever may be said by speculative philosophers to the contrary, 
 the advancement of metaphysics is through the study of physiology. 
 What sort of a science would optics have been among men who had pur- 
 posely put out their own eyes ? What would have been the progress of 
 astronomy among those who disdained to look at the heavens ? Yet that 
 is the preposterous course which has been followed by the so-called phi- 
 losophers. They have given us imposing doctrines of the nature and 
 attributes of the mind, in absolute ignorance of. its material substratum. 
 Of the great authors who have thus succeeded one another in ephemeral 
 celebrity, how many made themselves acquainted with the structure of 
 the human brain ? Doubtless some had been so unfortunate as never to 
 see one ! yet that wonderful organ was the basis of all their speculations. 
 In voluntarily isolating themselves from every solid fact which might 
 serve to be a landmark to them, they may be truly said to have sailed 
 upon a shoreless sea from which the fog never lifts. The only fact which 
 they teach us with certainty is that they know nothing with certainty. 
 It is the inherent difficulty of their method that it must lead to unsub- 
 stantial results. What is not founded on a material substratum is nec- 
 essarily a castle in the air. 
 
 Returning now to the general description of the nervous mechanism, 
 and following the division above indicated, we shall consider, first, the 
 fibrous element of the nervous system, and, second, the vesicular. 
 
 First. Of the fibrous there are two varieties, one belonging to the 
 Fibrous or tu- cerebro-spinal, and the other to the sympathetic. The for- 
 buiar portion. mer mav -fo Q described as a delicate membranous tube contain- 
 ing a semi-fluid material, and presenting under the microscope a pellucid 
 glassy appearance when examined in the recent state ; a spontaneous 
 separation or partition, however, soon ensues, a white material or medul- 
 
NERVE FIBRES OR TUBES. 261 
 
 la appearing immediately within the membranous tube, and affording a 
 contrast to the portions which are toward the centre or axis. In this 
 state the nerve-tube presents the appearance of parallel lines toward its 
 periphery, the outer one corresponding to the membranous Membrane, 
 sheath, and the inner to the internal limit of the coagulated J^ l * tance 
 material. In this condition the tube is very prone to as- axis cylinder, 
 sume a beaded appearance, either by the influence of pressure, or even 
 spontaneously. Names have been given to distinguish these parts from 
 each other ; the central grayish portion is called the axis cylinder or axis 
 band, since it may be of a flattened shape ; and the material which sur- 
 rounds it, intervening between it and the membranous investment, is des- 
 ignated the medulla or white substance of Schwann. There can be no 
 doubt that the membranous tube, the white substance, and the axis cyl- 
 inder discharge different physiological functions. In chemical composi- 
 tion they also differ : the tube is a nitrogenized structure, the white sub- 
 stance oleaginous, and the axis cylinder is supposed to be nitrogenized 
 also. In the first development, the axis cylinder is first formed, and the 
 white substance then cast round if. 
 
 If a portion of a nerve, a, Fig. 114, be placed 
 in concentrated acetic acid, the axis cylinders of 
 its included tubes will, in the course of a day 
 Axis cylinder of nerveiT or ^ ^ geen protruding in a brush-like form, 
 as at , the effect being very well shown when the nerve is sufficiently 
 slender to be subsequently examined by the microscope. 
 
 The nerve fibres run in a direct course to their point of distribution. 
 Of their manner of termination we shall speak subsequently ; Terminal 
 here, however, it may be remarked, that occasionally they ex- branchings of 
 hibit preparatory terminal branchings, as shown in Fig. 115, 
 p. 262, observed by Kolliker in the case of the frog : tf, a being bifurca- 
 tions, b a trifurcation of a small twig from the cutaneous thoracic muscle. 
 Similar subdivisions of the ultimate ramifications have been noticed in the 
 amphioxus, fishes, insects, and it is certain that they also occur in man. 
 
 The sheath of the nerve fibres is an elastic membrane, which is nei- 
 ther acted on by dilute alkalies nor by boiling, but is solu- Chemical reac- 
 ble in concentrated acetic acid and strong solutions of pot- 
 ash and soda. By nitric acid it is stained yellow, and, though fibres, 
 not identical with elastic tissue, has a certain resemblance thereto, ap- 
 proaching, however, more nearly to a protein substance. The axis cyl- 
 inder is, as is shown by its behavior with reagents, a protein substance, 
 differing, however, from syntonin and also from blood fibrin. From the 
 latter substance it is distinguished both by the difficulty with which it 
 dissolves in acetic acid and in a solution of nitre, from the former by its 
 insolubility in hydrochloric acid. 
 
262 
 
 NERVE FIBRES OR TUBES. 
 
 .Fig. 115. 
 
 Subdivision of nerve fibres in the frog, magnified 350 diameters. 
 
 Of such fibres, arranged parallel to each other in bundles, the bundles 
 united by fibro-cellular tissue, nerves are composed, the tissue not only 
 accomplishing that mechanical object, but also affording a nidus for blood- 
 vessels, which run in a course parallel to the nerve fibres. Though we 
 Form and size have spoken of those fibres as cylinders, they, in reality, ap- 
 of nerve fibres, proach more nearly to the figure of acute cones, since, though 
 
 their diameter is from the 2^0 o" 
 
 Wo 
 
 an 
 
 * n 
 
 nerve 
 
 trunks, they diminish to the 10 ^ QO or the T4 ^ OQ of an inch as they reach 
 the nerve centres, and, in the same manner, their diameter becomes less 
 as they branch off in their peripheral distribution. In the brain, as they 
 pass through the medulla to the cortical part, they exhibit a similar dim- 
 inution. 
 
 The sympathetic fibres differ from the preceding in appearance. Being 
 Character of ^ a y e U wis h-g ra y color, and only about half as large, they 
 sympathetic do not show the separation into an axis cylinder and white 
 investment after death, as is the case with cerebro- spinal 
 fibres ; they may therefore be regarded as being more homogeneous in 
 their construction, or possessing a constitution like that of the other kind 
 of fibres when they undergo diminution and approach their central or 
 peripheral termination. Even in the cerebro-spinal fibres the quantity 
 of white substance present is very variable ; the retina, the olfactory or- 
 gan, and the Pacinian corpuscles furnish instances of its absence. The 
 sympathetic, gray, or gelatinous fibres, as they are indifferently called, 
 contain many nucleated corpuscles, which may be rendered very distinct 
 by the action of acetic acid. 
 
NERVE VESICLES. 263 
 
 Nerve fibres terminate in various ways. Their ends may tliin out and 
 become free, or they may form a loop, and so return back in Manner of 
 their course. Each nerve runs in an unbroken line from its termination of 
 origin to its termination, but between the adjacent ones in- 
 tercommunication is established by the formation of plexuses. On the 
 other hand, as the fibres are preparing to enter the nervous centres, the 
 membranous tube dilates so as to receive a nerve vesicle, Manner of re _ 
 with which the diaphanous axis cylinder is thus brought in ceptionofvesi- 
 contact. Where corpuscles are received into the membran- cles ' 
 ous sheath, it is not always certain but that the fibre has some other 
 termination beyond. Some have supposed that sensitive fibres differ 
 from the motor ones in the circumstance that the former alone are 
 brought in connection with the corpuscles, but this is very unKkely. 
 
 Second. The vesicular nervous substance is composed of nucleated 
 cells containing a granular substance, with which there are The vesicular 
 intermixed, especially near the nuclei, pigment granules. P rtion - 
 These granules, however, are sometimes absent, as in the vertebrata. 
 The nucleus of each ganglionic vesicle often presents a nucleolus ; the 
 diameter of the vesicle varies from -g-J^ to 1 2 * 5 Q of an inch. These ves- 
 icles are found in the nerve centres, their coloring material communicat- 
 ing to those parts the peculiar tint they display. In shape they vary 
 very much, some being spherical, some ovoid, and others caudate, ex- 
 hibiting processes which are filled with granules, or which, becoming 
 eventually transparent, communicate with similar processes from other 
 cells, or are continuous with the axis cylinders of the nerve-tubes. Ac- 
 cording to Axmann, the axis cylinder is a continuation of the nucleus 
 of the cell. The ganglion vesicles, as they are termed, are character- 
 Fi 116 ized by containing a large amount of phosphor- 
 
 ized oil, and it is probable that the oxidation of 
 this material is a condition of their functional ac- 
 tivity. 
 
 Fig. 116, ganglion globules (nerve-cells), from 
 the Gasserian ganglion of the cat. 1. Cell, with 
 short pale process, showing the origin of a fibre ; 
 <z, sheath of the cell and nerve-tube, containing nu- 
 clei ; b, cell membrane of the nerve-cell. 2. Cell, 
 with the origin of a fibre without sheath ; b, cell 
 membrane of the nerve-cell. 3. Nerve-cell, de- 
 prived, in the preparation of it, of its membrane 
 Nerve W magnified awdi- and external sheath. (Kolliker.) 
 
 Fig. 117, p. 264, bipolar nerve-cell of the pike, 
 
 continued at each end into nerve-tubes, a, sheath of the nerve-cell ; b, 
 sheath of the nerve ; c, medulla ; d, axis cylinder continuous with the 
 
264 
 
 BIPOLAR AND MULTIPOLAR NERVE-CELLS. 
 
 contents of the nerve-cell, e, which have shrunk away 
 from the sheath after action by arsenious acid. (Kol- 
 liker.) 
 
 Fig. 118, caudate nerve vesicle of the multiple 
 kind: a, the nucleated vesicle; b, its processes. 
 
 Fig. 118. 
 
 Bipolar nerve-cell, magni- 
 fied 350 diameters. 
 
 Fig. 119. 
 
 Multipoint nerve-cells, magnified 200 diameters. 
 
 These probably are continuous with the axis cylin- 
 ders of the nerves, in connection with the vesicle. 
 Fig. 119, tubules and nerve-cells : A, from sympa- 
 thetic ganglion ; *, a sepa- 
 rate cell, showing its pellu- 
 cid nucleus and nucleolus : 
 B, from the gray substance 
 of human cerebellum: <z, b, 
 plexus of primitive fibres ; 
 <?, nucleated globules ; *, 
 a separate cell from hu- 
 man ganglion of Gasser. 
 (Wagner.) 
 
 Fig. 120, tubules and 
 nerve-cells of human brain : A, 
 nerve-cells lying in the midst 
 of varicose nerve -tubes and 
 blood-vessels in the substance 
 of the optic thalamus : #, glob- 
 ule more enlarged ; , small vas- 
 cular trunk: B, B, multipolar 
 nerve-cells from the dark por- 
 tion of the eras cerebri. (Pur- 
 kinje.) 
 
 Such being the construction 
 of the fibrous and vesicular ma- 
 terial, we may next inquire into 
 their functions. 
 
 Nerve cells and tubes, magnified 353 diameters. 
 
 B 
 
 Human nerve tubules and cells. 
 
CENTRIPETAL AND CENTRIFUGAL FIBRES. 265 
 
 FUNCTIONS OF NERVE FIBRES. 
 
 That the function of nerve-tubes is to conduct impressions, is proved 
 by many different facts. On putting a ligature round a nerve, Functions of 
 or cutting it across, it no longer transmits the usual influ- nerve fibres - 
 ences. A more critical examination shows that impressions made on 
 the external extremities of a nerve are conveyed by it to the centres, 
 and the influences originating in the nervous centres are conducted along 
 such trunks to the parts to which they are distributed. This double 
 duty therefore implies that there are two classes of tubes, the centripetal 
 and centrifugal, though thus far no structural difference between them 
 has been detected. They can not of themselves either originate impres- 
 sions or motions, these in every instance arising from external or central 
 agency. The centrifugal fibres, when cut across, may show Centri etal * 
 no effect if the part still remaining attached to the nerve cen- and centrifu- 
 tre is irritated ; but if the other part connected with the pe- gal fibres ' 
 riphery be pressed upon or pinched, muscular contraction, that is, mo- 
 tion, results. If centripetal fibres be examined in like manner, the part 
 connected with the periphery being irritated, no result arises ; but if 
 the part connected with the centre be irritated, sensations, general or 
 special, as the case may be, are perceived. These several effects ensue 
 when the motor or sensory nerve is intact ; for, on irritating the one or 
 the other, motion or sensation, as the case may be, is produced. If the 
 whole trunk of a centripetal nerve be irritated, the mind refers the sen- 
 sation to all those parts to which the branches of that nerve are distrib- 
 uted ; if a part only, then the sensation is limited to those portions to 
 which the fibrils of that part go ; but, besides this, the mind also recog- 
 nizes the particular spot upon the trunk to which the irritation has been 
 applied. In like manner, when the entire trunk of a centrifugal nerve is 
 irritated, all the muscles which it supplies contract ; or, if only a part, 
 then those muscles which are supplied from that part. From the ana- 
 tomical fact that a nerve-tube does not anastomose with its neighbors, 
 the influences which it conveys are transmitted along it without any lat- 
 eral diffusion, and every fibre discharges one duty, and one Unity of func _ 
 alone. The centripetral can never assume the function of tion in the 
 the centrifugal ; and in the case of nerves of special sense, 
 there is the same restriction: the optic nerve can not transmit the im- 
 pressions of sounds, nor the auditory the vibrations of light ; the nerves 
 of common sensation are affected neither by one or the other, but they 
 are by variations of temperature. The velocity with which Rate of con _ 
 these influences pass along nerve fibres is indefinitely less ductitility in 
 than that with which electricity moves in a metal conductor. nerves - 
 Thus far, however, no satisfactory measure of it has been obtained. 
 
266 ANALOGY OF NERVES AND ELECTRIC CONDUCTORS. 
 
 The experiments of Helmlioltz give, for the rate of propagation, from 83 
 to 88 feet per second in the frog, and in man 200 feet, the velocity ris- 
 ing with the mean animal heat. At one time it was thought that there 
 are perceptible differences in this rate in the same nerve of different indi- 
 viduals, or in different nerves in the same individual, but these conclu- 
 sions are admitted to be erroneous, or to be explained upon another prin- 
 ciple. It can not be denied that there is a general resemblance between 
 the manner in which a nervous fibril transmits its influences and that in 
 which a conducting medium conveys an electric current, though the ve- 
 Resembiance locity may be very different. There is a resemblance be- 
 between the tween the arrangement of the axis cylinder surrounded by 
 trical conduct-" ^s white substance and membranous tube, and that of a met- 
 ors - alline wire wrapped round with silk, or other non-conduct- 
 
 ing material in many electrical arrangements. An electric current arti- 
 ficially transmitted along a nerve trunk will, as the nature of that trunk 
 may be, give rise to muscular contraction, or produce general or special 
 sensations, or originate reflex action. For these reasons, it has long been 
 supposed, by many physiologists, that the influence which passes along 
 nervous fibres is analogous to electricity, if it be not identical therewith ; 
 but all attempts to prove the existence of an electric current, either in the 
 centripetal or centrifugal fibres, have thus far been abortive. It may, 
 however, be remarked, that the arguments which are commonly present- 
 ed against the hypothesis of the identity of the nervous agent and elec- 
 tricity are but of little weight when critically examined. Thus it is said 
 that an electric current, passing along a nerve fibre, spreads laterally, 
 whereas the nervous agent never does ; but this is all dependent upon 
 that quality formerly known among electricians as intensity. There is 
 no reason to suppose that a thermo-electric current, the intensity of which 
 is very low, would exhibit such a lateral propagation ; whereas a voltaic 
 current, whose intensity is high, does it without difficulty. Moreover, 
 though it has been stated that the electric conductibility of a nervous 
 trunk is indefinitely worse than that of a metal, even lower than that of 
 a bundle of muscular fibre, it should be remembered in these discussions 
 that the conducting power is in the axis cylinder, and no attempt has 
 ever yet been made by any experimenter to isolate that structure and sub- 
 mit it to proper examination. It is just the same as though we should 
 take a bundle of copper wires, each one of which is separated from its 
 neighbors by a layer of non-conducting fat ; that we should cut out a sec- 
 tion of such a construction with a pair of scissors, and then attempt to 
 determine its conductibility. That, under any circumstances, would be 
 low enough ; and the chances are that the non-conducting material would 
 be smeared over the ends in the act of making the section, and the speci- 
 men refuse to conduct at all. In a similar manner, we may dispose of 
 
OF NERVE-CELLS. 
 
 267 
 
 all those experiments which have been brought to prove the dissimilari- 
 ty of electricity and the nervous agent, by intervening a piece of metal 
 between a section of a nervous trunk, it having been found that under 
 such circumstances the nervous influence does not pass. 
 
 The physical condition upon which the activity of the nervous mech- 
 anism depends is the supply of arterial blood ; for, although Nervous activ 
 the nerve fibres never receive or are penetrated by blood cap- ity depends on 
 illaries-, these latter run in company with them in the nerv- artenal b 
 ous fasciculi. It would appear, however, that the supply of arterial blood 
 is of far less moment in the function of the nerve fibres than it is in that 
 of the nerve centres. This is shown by the limited supply given to the 
 former, and the abundant one to the latter ; by the comparative effect of 
 a stoppage of the blood circulation, in which case the action of the nerve 
 centres is instantly arrested, whereas that of the fibres may continue for 
 a long time. On the whole, there are strong reasons for believing that 
 the conductibility of the nerve fibres is as purely physical as is that of a 
 metal wire, and that the supply of blood that they receive is only for the 
 purpose of maintaining their construction in a perfect state. 
 
 We have stated that there are nerves the functions of which are essen- 
 tially different, such as the centripetal .or sensory, and the identification 
 centrifugal or motor. The identification of the class to of the class of 
 which a nerve under examination belongs, may sometimes 
 be made by examining its manner of distribution, or its ganglionic con- 
 nection ; sometimes by experiment, by making a section and irritating 
 the cut extremities. In these cases, however, caution has to be exer- 
 cised in coming to a conclusion. 
 
 FUNCTIONS OF NERVE-CELLS. 
 
 .The neTvous fibres having for their duty the conduction of external 
 impressions and the transmission of nervous influences, the Function of 
 
 Fig. 121. nerve-cells or nerve vesicles - 
 
 ^ ' ' vesicles are for the re- 
 
 ception of those impres- 
 sions and the origination 
 of those influences. The 
 nerve centres or ganglia 
 are made up of vesicles, 
 granules, and nerve-tubes 
 ft conjointly. 
 
 Fig. 121, dorsal gan- 
 glion of the sympathetic 
 nerve of a mouse. $, b, 
 
 Dorsal ganglion of mouse. COl'ds of Connection With 
 
268 VESICLES ARE MAGAZINES OF FORCE. 
 
 adjacent ganglia ; <?, c, c t <?, branches to the viscera and spinal nerves ; d, 
 nerve-cells ; e, nerve-tubes traversing the ganglion. (Valentin.) 
 
 For the explanation of the function of the nerve centres, it is essential- 
 Function of ly necessary that we should have clear views of the function 
 Sedanatom- ofthe nerv<3 vesicles. It has appeared to me that their duty 
 icaiiy. is manifested by their anatomical relations. The influence, 
 
 whatever it may be, which passes along a nervous cord, is completely 
 isolated therein, and never leaves the fibril in which it is passing from 
 its origin to its termination. It is isolated by the white substance of 
 They permit Schwann. But it is very plain, as a thousand phenomena 
 esca^ 'intcT * ^ ^ ie nervous system prove, that there are places of escape 
 new channels, for this influence, although it may be confined in the nerve- 
 tube, and these places can be no other than the vesicles. Their caudate 
 aspect, or multipolar form, as it is often termed, will bear no other inter- 
 pretation. The disturbing influence, coming along the axis cylinder of a 
 nerve-tube, finds itself delivered into the granular material in the interior 
 of a vesicle, a material physically continuous, in the opinion of many 
 physiologists, with the structure of the axis cylinder. Through this 
 granular material the influence is transmitted, and if the vesicle should 
 have on its distant contour two or more nerve-tubes connected with it, 
 it would seem to be the necessary result of such a state of things that 
 the influence will pass down all those channels. For these reasons I re- 
 gard the nerve vesicles as being constructions for the purpose of 'opening 
 out the closed nerve tubules, and permitting them to deliver their energy 
 into new tracts. 
 
 But more than this. Whatever may be the manner in which the 
 Diffusion of in- nervous influence is propagated, or conducted from point 
 granular mate! * P om * ^ tne granular material within the vesicle, there 
 rial. must be now, since there is no structure to prevent it, a lat-* 
 
 eral spreading of effect. It is not to be supposed that the passage is 
 made in a direct line, from the terminus of the centripetal to the origin 
 ofthe centrifugal fibre, across these caudate vesicles, and restricted there- 
 to. There is no isolator to confine it in any such track, and it seems to 
 follow of necessity that the whole contents of the vesicle must be affect- 
 Vesicles retain ed, and this irrespective of its magnitude. Such a condition 
 ad r arTma'-a- ^ tnm g s introduces the suspicion of a second great duty 
 zines of force, which the vesicles may discharge in retaining within them- 
 selves, at all events for a short period, the influences that have thus es- 
 caped laterally, and thus they become temporary magazines of power. 
 Unipolar, bi- And perhaps this may be the true interpretation ofthe action 
 polar, muitipo- of unipolar and bipolar vesicles; the unipolar being a capsule 
 for the collection and conservation of the entire delivered in- 
 fluence, the bipolar to admit of the passage onward of a large portion of 
 
RETENTION AND INTEEFEEENCE OF IMPEESSIONS. 2G9 
 
 the force, but by lateral diffusion to preserve or delay a part, and the 
 multipolar at once permitting of conservation and of a discharge into, 
 perhaps, a multitude of new channels. 
 
 Upon the same principle that multicaudate vesicles permit of the es- 
 cape of nervous influence from the single channel in which it interference of 
 has been coming into many new ways, so likewise they impressions, 
 must be the seats of the interference of influences delivered into them 
 from many centripetal fibres at the same time. Thus we may imagine 
 a tricaudate vesicle into the granular material of which an influence is 
 delivered simultaneously by two centripetal fibrils, and these, reacting on 
 one another in the interior of the vesicle, give rise to a resultant which 
 may differ from them both, and this is passed on through the third, the 
 centrifugal fibril. 
 
 Regarded in this way, the function of a nerve vesicle may therefore be 
 stated to be, 1st. To permit the escape of an entering influence out of the 
 solitary channel in which it has been isolated into any number of diverg- 
 ing tracts ; 2d. -To combine influences which are entering it from various 
 directions into a common or new result ; 3d. By permitting of lateral dif- 
 fusion to take off and keep in store for a certain duration a part of the 
 passing influence. 
 
 Our attention can not fail to be arrested by this last effect ; for if there 
 be a property which is characteristic of the nervous mechan- ^ 
 
 . n, . Retention of 
 
 ism in its utmost degree ot development, it is this of retain- the vestiges of 
 ing the relics or traces of impressions which have formerly im P ressions - 
 been made upon it. As it goes on increasing in perplexity as we rise 
 through the animal series, the provision for the retention of such impres- 
 sions becomes more and more strikingly marked. Ganglionic masses, 
 which, from their position and structure, are marked out for this duty, 
 appear in that ascending scale in increasing magnitude. To these we 
 may aptly apply the designation of registering ganglia, since Registering 
 they truly store up the traces of ancient impressions and keep ganglia. 
 them in reserve. These ganglia must, moreover, be the scenes of the in- 
 teraction and interference of the impressions they thus contain. 
 
 The registering ganglia thus introduce the element of time into the ac- 
 tion of the nervous mechanism. The impression which T 
 
 <"*" i -i -i i Introduction 
 
 without them would have forthwith ended in action is de- of the element 
 layed for a season, nay, perhaps even as long, though it may me< 
 be in a declining way, as the structure itself endures ; and with the in- 
 troduction of this condition of duration come all those important effects 
 which ensue from the various action of many received impressions, old 
 and new, upon one another. 
 
 This internal origination of new results through the interaction of im- 
 pressions retained in the registering ganglia is too important a phenom- 
 
270 VARIABLE EFFECTS FROM INVARIABLE CAUSES. 
 
 enon to "be passed lightly by, more especially when we consider the sur- 
 prising results to which it eventually leads in the higher forms of life. I 
 Illustration of sna ^ therefore, without any apology, digress briefly for the 
 the production sa k e o f illustrating my meaning, by showing how, even in 
 suits^yinvari- the material world, from conditions which are as fixed as fate, 
 able causes. through interaction of consequences variable results arise. 
 
 The laws of nature, being founded on pure reason, are absolutely un- 
 changeable. Of the things which are presented to our contemplation, 
 they alone are invariable. Material substances of every kind wear by 
 time, and exhibit incessant alterations, and this the same whether they 
 are of a terrestrial or a celestial kind. There are tides, eclipses, seasons, 
 births, deaths. Throughout the universe there is no monument that re- 
 tains its primordial condition; for all material aggregations are only 
 forms, and every form, in the process of time, must perish. There are 
 changes of the surface of the earth, changes in its position as to the sun, 
 changes in the places of systems of worlds as to one another. Every 
 thing is at every moment in motion ; but in the midst of all, every law 
 of nature, as, for example, the law of gravitation, endures without varia- 
 tion for an instant, and is never for an instant suspended. 
 
 This invariability of natural laws from age to age, even under circum- 
 stances in which we might suspect a change, is illustrated by the parallel 
 which may be traced between the development of the most recent em- 
 bryos, as of man, and those of the ancient geological times, or between 
 human development and that of the whole animal series. In all these 
 cases such a phenomenon is never witnessed as that of a part springing 
 from nothing : it conies out of something existing before, and exists as a 
 consequence of some preceding act. The order in which part arises from 
 part is the same now as it has been in all times the same in organ- 
 isms which are most distinct from each other in structure or position in 
 the natural scale ; and thus we see that development is not only the con- 
 sequence of law, but of law which is unchangeable and universal in its 
 application. 
 
 As with these phenomena of development and all natural facts, so with 
 the operations of the mind. There is no such thing as a spontaneous or 
 self-originating thought. Every intellectual act is the consequence of 
 some preceding act. It conies into existence in virtue of something that 
 has gone before. Two minds constituted precisely alike, and placed 
 under the influence of precisely the same external physical circumstances, 
 must give birth to precisely the same thought. Such is plainly the 
 consequence of that invariability and universality of the laws of nature 
 on which I have been insisting, which is illustrated by the fact we so often 
 witness in our daily affairs, and strikingly in the case of philosophical 
 discoveries, the same idea occurring to many persons at the same time. 
 
REGISTERING GANGLION. 271 
 
 It is this sameness of action to which we allude in that popular expres- 
 sion, common sense a term full of meaning. In the origination of a 
 thought there are two distinct conditions involved the state of the mind 
 as dependent on antecedent impressions, and the existing physical cir- 
 cumstances. The brain is the instrument on which external circum- 
 stances play ; but in the same manner that the course of time presents 
 us with natural vicissitudes, such as night and day, the seasons, the tides, 
 spring and neap, with their ebb and flow, variations of events may ensue, 
 notwithstanding the fate-like aspect of the acting law, and this through 
 the interaction of consequences. So the earth revolves round the sun 
 as a consequence of gravity, and for the same reason does the moon re- 
 volve round the earth ; for the same cause do the tides flow and ebb in 
 the sea ; yet there will be spring tides when the sun and moon draw in 
 one direction, and neap tides when they draw in opposite ways. Out of 
 the invariable the variable may therefore arise. 
 
 To return from this digression to the phenomena displayed by regis- 
 tering ganglia, in continuation of the views offered, I may pre- Illustration of 
 sent as an example the manner in which I should be disposed ^ 8 yjj in 
 to regard in this respect the entire nervous system of the ar- sects. 
 ticulata. Constructed as these animals are upon an axis, the nerves 
 which are given off from the ganglia upon that axis right and left, a pair 
 for each segment, are primarily purely automatic, and act therefore pri- 
 marily in a purely reflex way ; an impression made on the peripheral ex- 
 tremity of one of their centripetal fibres is conducted to the ganglion, 
 passes through it, escapes along the centrifugal fibre, and a motion oc- 
 curs. But the whole influence is not thus promptly disposed of. A part 
 of it is conducted by commissural strands to the cephalic ganglia, and 
 there held in reserve. And the same thing holds good for ev- Function of 
 ery one of the ganglia of the ventral cord, so that for them all the cephalic 
 the cephalic become a point of common convergence, or, in my gang ia ' 
 view, the common register for them all. Here, at this focal point, are 
 stored up the relics of whatever impressions have been made upon the 
 common peripheral nerves, and here are received those which are brought 
 from the structures of special sense the visual, the auditory, the olfac- 
 tory, if any. There does not, then, appear any great difficulty in ex- 
 plaining the well-marked deviations from automatism which these ani- 
 mals may present. 
 
 The action of every ganglionic mechanism depends upon the existence 
 of certain physical conditions, among which, as being of par- Nerve centres 
 
 -, -, . ^ T , . , i -J can not act ex- 
 
 amount importance, one may be discerned. It is the due cept by ox j ( i a . 
 supply of arterialized blood. If this be stopped but for a tion - 
 moment, the nerve mechanism loses its power, or if diminished, the dis- 
 play of its characteristic phenomena correspondingly declines. If, on 
 
272 WASTE AND REPAIR OF NERVOUS MATTER. 
 
 the contrary, the supply be unduly great, or its oxidizing power artificial- 
 ly increased, there is a more energetic action. This latter condition of 
 things is presented in the earlier stages of the respiration of protoxide of 
 nitrogen, an increased muscular power, and an exaggeration of the pro- 
 cesses of intellection. The opposite state is witnessed when carbonic 
 acid, more or less dilute, is breathed, from that blunting of the intellectual 
 faculties and indisposition for muscular exertion which is felt in ill-ven- 
 tilated apartments where carbonic acid is permitted to accumulate, to the 
 profound torpor and insensibility experienced when it is in a more con- 
 centrated state. These exaltations and depressions of the capabilities of 
 the nervous instrument are, therefore, clearly of a chemical kind, and may 
 be produced artificially and at pleasure by the respiration of appropriate 
 gases or the administration of certain drugs. Nay, even the accumula- 
 tions of the effete products of the economy are sufficient to give rise to 
 such diminutions of power, as we see when bile or urea is permitted to 
 accumulate in the blood. The therapeutical and toxicological influences 
 of certain medicaments are illustrations of these principles. Of such 
 substances, some act on the sensorial and some on the motor powers, 
 
 The copious distribution of arterial blood to the nervous centres indi- 
 Necessityofre- cates that they undergo a rapid waste. That supply can 
 pair and rest. no ^ -j^ f or ^he mere purposes of growth alone, since, when 
 once maturity is reached, the nervous mechanism presents but little ex- 
 pansion. The provision for nutrition assures us that that action must 
 be rapidly going on ; but the equilibrium of the system betrays that such 
 nutrition is not for development, but for the repair of waste ; and, in- 
 deed, this waste proceeds at such a rate that there arises in some portions 
 of this system a necessity for periodic repose, a time for the restoration 
 of the parts. If any arguments were required to establish beyond dis- 
 pute that such a disintegration of the material of the nerve centres does 
 occur, it would be furnished by an examination of the urine ; for, in nerv- 
 ous substance, phosphorus occurring as a characteristic ingredient, it 
 must give rise to the production of phosphoric acid, or salts thereof, in 
 Destruction of the supposed periods of activity. Moreover, in this meta- 
 nervous mate- morphosis of the vesicular structure ammonia must eventu- 
 portiontonerv- ally arise, from the cell walls if from no other source, and 
 ous activity, accordingly we find in the urine that characteristic double 
 salt, the phosphate of soda and ammonia. The amount of these alkaline 
 phosphates has long been known to be in proportion to the activity of 
 the nervous system, particularly in the case of individuals, such as cler- 
 gymen, whose mental powers are taxed unduly at stated intervals. The 
 general fact that the degree of energy which this system exhibits is de- 
 pendent on the activity of respiration in different tribes of life might be 
 established from many familiar instances. 
 
COMPOSITION OF NERVOUS MATTER. 
 
 273 
 
 More precise ideas would be arrived at regarding the waste of the nerv- 
 ous mechanism if we possessed a more accurate knowledge of its chem- 
 ical constitution. The examinations hitherto made are far ~ 
 
 Composition of 
 
 from agreeing with one another, and this, to a certain extent, nervous mate- 
 is due to the difficulty of obtaining the true nervous tissue in nal ' 
 an isolated state, or unmingled with other intervening structures. * The 
 following tables will give, however, a general idea of its composition at 
 different periods or in different conditions. 
 
 Analysis of Brain of different Conditions of Life. (From L'Heritier.) 
 
 
 Infants. 
 
 Youths. 
 
 Adults. 
 
 Aged. 
 
 Idiots. 
 
 Water 
 
 827 90 
 
 742.60 
 
 725.10 
 
 738 50 
 
 709 30 
 
 Albumen 
 
 70.00 
 
 102.00 
 
 94.00 
 
 86.50 
 
 84 00 
 
 Fat 
 
 34 50 
 
 53.00 
 
 61.00" 
 
 43.20 
 
 50 00 
 
 Osmazome and salts 
 Phosphorus 
 
 59.60 
 8.00 
 
 85.90 
 16.50 
 
 101.90 
 18.00 
 
 121.80 
 10.00 
 
 148.20 
 8.50 
 
 
 1000.00 
 
 1000.00 
 
 1000.00 
 
 1000.00 
 
 1000.00 
 
 Composition of Spinal Cord of Adult. (From L'Seritier.") 
 
 Water 710.50 
 
 Albumen 73.00 
 
 Fat 82.50 
 
 Osmazome 115.00 
 
 Phosphorus 19.00 
 
 1000.00 
 
 Analysis of Medullary and Cortical Substance of Brain of Idiot. (From Lassaigne.) 
 
 
 Cortical and Med- 
 ullary together. 
 
 Cortical. 
 
 Medullary. 
 
 Water 
 
 770.00 
 
 850.00 
 
 730.00 
 
 
 96.00 
 
 75.00 
 
 99.00 
 
 Colorless fat 
 
 72.00 
 
 10.00 
 
 139.00 
 
 Red fat 
 
 31.00 
 
 37.00 
 
 9.00 
 
 Extractive, lactic acid, and salts... 
 Phosphates of lime, magnesia, and 
 peroxide of iron 
 
 20.00 
 11.00 
 
 14.00 
 12.00 
 
 10.00 
 13.00 
 
 
 1000.00 
 
 998.00 
 
 1000.00 
 
 From which it would appear that the percentage of water is greatest in 
 the early periods of life, and that of phosphorus in the adult. Attention 
 may also be drawn to the fact that the percentage of phosphorus in the 
 brain of idiots is very low. It also appears that the constitution of the 
 white and gray portions of the brain is different, as might have been an- 
 ticipated from tlieir appearance, the color of the latter being due to a 
 brown fat. By some it is supposed that the non-saponifiable fat cho- 
 lesterine arises as a product of waste, and that the phosphorized oils, as 
 they are termed, constitute the white enveloping cylinder known as the 
 white substance of Schwann, and that the interior cylinder is a nitrogen- 
 ized but non-phosphorized body ; but there are reasons for suspecting 
 that the white substance of Schwann is a non-phosphorized fat, and that 
 .the axis cylinder contains the phosphorus in an unoxidized state, prob- 
 ably as a highly phosphorized protein body. Every thing seems to in- 
 
 S 
 
274 VESICULAR MATTER. 
 
 dicate that Schwann's substance only discharges the physical duty of 
 an isolator. The coincidence between the varying activity of the nerv- 
 ous mechanism and the varying quantity of oxidized compounds of phos- 
 phorus in the urine indicates in a significant manner that this chemical 
 element bears something more than a passive relation to the processes 
 going* forward ; and its known occurrence in the vesicular structures, to- 
 gether with its extraordinary chemical relations, would prepare us to ex- 
 pect that it is, in reality, intimately concerned in all these phenomena. 
 Vesicular nervous material contains much less fatty matter than the 
 . tubular, but much more water. Thus HaufF and Walther 
 
 Composition of 
 
 vesicular mat- found in the gray substance of the brain from 85 to 86 per 
 ter ' cent, of water, and only from 4.8 to 4.9 of fat; but in the 
 
 corpus callosum they found 70.2 per cent, of water, and from 14.5 to 
 15.5 of fat. From such facts it would appear that the presence of fat in 
 nervous material is functionally connected with its property of conduc- 
 tion or transmission of nervous influence. In the brain of a child which 
 died at birth, Schlossberger found that the corpus callosum contained as 
 much water as the gray matter, and that, compared with the brain of 
 adults, that of new-born infants is richer in water and poorer in fat. Von 
 Bibra ascertained that, within certain limits, the quantity of fat is con- 
 stant in the brain ; that a diminution or increase of fat in other parts of 
 the system is not accompanied by any change in the quantity of brain- 
 fat ; that the proportion of fat in the brain of man, other mammals, birds, 
 amphibia, and fishes, diminishes in the order in which their names are 
 here mentioned ; that the medulla oblongata contains the largest per- 
 centage of fat ; that the quantity of brain-fat in old men is a little less 
 than that of adults in the prime of life. He also concludes that the 
 amount of phosphorus in brain-fat is nearly the same in man, other mam- 
 mals, and birds ; that its percentage in the brain of the insane does not 
 exceed thef mean amount ; that the vesicular matter contains more phos- 
 phorus than the white; and that there is no special connection .between 
 the intelligence and the amount of phosphorus ; that the amount of fat in 
 the brain of the foetus is much less than that of the adult, the difference 
 being made up by an excess of water, but that a great and sudden aug- 
 mentation of fat occurs toward the end of foetal existence. 
 
 Our attention may next be directed to the methods of repair of the 
 Mode of re air ves ^ cu ^ ar structures. Their waste, as just established, im- 
 of nervous plies their repair. Here, as in the muscular tissues, the 
 blood-vessels conduct both operations, and the mode of dis- 
 tribution of the capillaries is such as to bring the circulating current into 
 the most favorable position for discharging this duty. The vesicles are 
 included in the midst of a network of capillaries, and it is believed that 
 there, is a resemblance between their mode of growth and that of the cells 
 
CHOLESTERINE AND PHOSPHORUS. 275 
 
 of the epidermis ; that is to say, they arise from nuclei on the spaces 
 which are nearest to the supply of "blood, and gradually undergo devel- 
 opment as they prepare for connection with the tubular tissue, assuming 
 the place of cells that have discharged their function and are undergoing 
 disintegration. This gradual passing onward and wearing away recalls 
 the changes in the structure of the cuticle. 
 
 To two of the substances thus met with in these examinations of the 
 nervous system our attention may be profitably directed. Chole rin 
 These are cholesterine and phosphorus. Of the former we and phospho- 
 can not have failed to remark that it is a constant ingredient rus * 
 in the product of the action of the liver. It is a lipoid, and is found in 
 biliary calculi ; and though it may be regarded in one sense as an excre- 
 mentitious body, since it occurs in faecal matter, yet it also appears as 
 a normal constituent of the blood. It may therefore be inferred, if the 
 opinion of its existence in the white substance of Schwann be correct, 
 that it is one among the various functions of the liver to prepare this 
 body. Of phosphorus it might be said, that it, among the chemical 
 elements, is most strikingly characterized in its active state by the in- 
 tensity of its affinity for oxygen. On this depends its quality of shining 
 in the dark, a quality which has given it a name ; but by many agents, 
 such, for example, as exposure to a particular temperature, and especially 
 to the light of the sun, it may be thrown into a condition so completely 
 passive that its chemical energies disappear. The doctrine that was pre- 
 sented in explanation of the destruction of one part of the system by the 
 air introduced by respiration while another is protected therefrom, as de- 
 pendent on the allotropic condition of those parts, is presented here again 
 in discussing the destruction and repair of the nervous tissue ; for it is 
 only when it is ready to be removed that the phosphorized constituent 
 assumes the active state, and in so doing gives rise to the development 
 of force. On this view, it would appear that such phosphorized com- 
 pounds are obtained from the vegetable kingdom in the food in a passive 
 state, the tissues of plants having deoxidized them under the influence 
 of the sunlight, which simultaneously has thrown them into the condi- 
 tion of inactivity, and perhaps it is the assumption of that very condition 
 that is the fundamental cause of their deoxidation. 
 
 By the aid of the conclusions to which we have come respecting the 
 function of nerve-tubes and vesicles, as betrayed by their an- Functions of 
 atomical structure, we shall not have much difficulty in ex- n ^ e 1 ^ e " o s n and 
 plaining the offices of nervous arcs presently to be described, sidered eiec- 
 The results at which we thus arrive, from a consideration of tricall y- 
 those cells, are singularly fortified by the electrical experiments of Gal- 
 vani, Volta, Nobili, and especially those of Volkmann. Among these, 
 the three following are of primary importance : 
 
276 VOLKMANN'S ELECTEICAL EXPERIMENTS. 
 
 1st. When a continuous electrical current is passed along a centrifu- 
 Voikmann's g a ^ nerve, contraction of the muscles which that nerve supplies 
 results. takes place, and continues as long as the electric current pass- 
 es, without relaxation, but ceases the moment the current is stopped. 
 
 2d. When a continuous electric current is passed through a ganglion, 
 contraction of the muscles supplied by the centrifugal nerves of that gan- 
 glion ensues. These contractions do not .alternate with relaxation, and 
 on stopping the current the contraction does not cease as in the preced- 
 ing case, but is continued for a period of time. 
 
 3d. When a continuous electric current is passed down a centripetal 
 nerve, muscular contraction of the parts supplied by the corresponding 
 centrifugal nerves occurs, and these contractions alternate with relax- 
 ations. 
 
 In view of these facts, we are brought to two conclusions : First, that 
 there is a property in the ganglion which enables it to hold in reserve a 
 portion of the influence brought into it, so as to keep up the action for a 
 period of time after the original disturbing causes have ceased. Second, 
 that the structure of the ganglion is such as to permit the escape of the 
 coming influence by lateral ways, either periodically or otherwise, and so 
 to produce from a continuous influence an intermitting effect. 
 
 Kecalling the fact that a ganglion is made up of nerve-tubes and vesi- 
 cles conjointly, these electrical results must find their solution in the el- 
 ementary structure of the ganglion, that is to say, in its vesicular por- 
 tion ; for it is not to be supposed that a current of electricity, such as we 
 are here considering, would ever have an opportunity of escaping from 
 the axis cylinder along which it passes. The isolating quality of the 
 white cylinder of Schwann would prevent any such effect. It is not nec- 
 essary that we should embarrass ourselves here with the fact that elec- 
 tric currents of sufficient intensity could make their way out from the in- 
 terior channel in spite of its insulating investiture, since it is only with 
 those of a far less power that we have to deal. Arrived in the vesicle, 
 the current at once diffuses itself throughout the granular material, just 
 in the same manner that it would diffuse throughout a spherical conduct- 
 ing mass if brought to it by a wire, and escape therefrom through any 
 number of similar wires that might chance to be in contact with the con- 
 ducting mass beyond ; and though the main body of the current would, 
 as may be readily proved, under these circumstances move in a direct 
 line from the point of entry to the point of exit, there would be neverthe- 
 less a diffusion of part of it through the conducting mass, no portion 
 thereof remaining unaffected. In a good conductor, such as a metal, this 
 laterally diverging current would instantly escape, but the case becomes 
 very different in the less perfectly conducting material, the granular sub- 
 stance within the cell. As in the secondary piles of Bitter, which, when 
 
ANATOMICAL AND ELECTRICAL EXAMINATION. 277 
 
 brought into contact with an active voltaic circle, participate Analofr with 
 in all its qualities, physiological and chemical, give shocks, the secondary 
 produce decompositions, and continue to do so for a time aft- plles of Rltter - 
 er the original influence has ceased, so a similar conservation occurs in the 
 interior of the vesicle ; and this I consider to "be the consequence of the 
 difference of structure of the fibrous axis cylinder and the granular vesi- 
 cle contents. The continuous lines along which the influence has been 
 coming terminate on reaching the vesicle, and are replaced by a divided 
 and inferior conveying structure, a structure which recalls at once the sec- 
 ondary piles of Hitter just alluded to. 
 
 We may therefore truly say that these electrical experiments offer a 
 striking confirmation of the truth of the conclusions to Coincidence of 
 which we have come from the study of the anatomical struc- anelectrical 
 ture of a nervous arc. They assure us that a vesicle, and examination, 
 therefore a ganglion, has a double office to perform, the stopping, reserv- 
 ing, storing up a part of the influence which is brought to it, and also 
 the conveying of that incident influence into many new channels. These 
 conclusions are altogether independent of any conception of the nature of 
 the nervous agent : it may be identical with, or allied to, electricity, or it 
 may be a totally different principle. It is not that question which we 
 are concerning ourselves with now. We are dealing with structure and 
 its interpretation. Whatever our views may be of the nature of inner va- 
 tion, we shall find ourselves constrained to infer that the delays, diver- 
 gences, detentions, and subsequent surrender, the opportunity of diverg- 
 ing from one into many new channels, or conversely the convergence fro in 
 many lines of entry into a single one of exit, with all the accompanying 
 interferences and reactions, must be common to both the electrical and 
 the nervous agent, for they depend, not upon the qualities of those prin- 
 ciples, but upon the anatomical structure through which they are passing. 
 With these remarks I proceed to an exposition of the typical construc- 
 tion of the nervous system, pointing out its successive com- Hypothetical 
 plications. The hypothetical diagrams which I shall now SS2^2*2 
 present are chiefly for the sake of impressing the conclu- anism. 
 sions at which we have arrived from a consideration of the structure of 
 the nervous elements, fibrous and vesicular, the experimental determina- 
 tion of those functions, and their electrical phenomena. That these dia- 
 grams are, however, somewhat more than imaginary 
 sketches, will be obvious from a consideration of the 
 nervous mechanism of the articulata, which offers 
 striking illustrations of them. 
 
 The simple automatic nerve arc, Fig. 122, consists 
 of an afferent or centripetal fibre, #, connected contin- 
 uously with an efferent or centrifugal fibre, e. An 
 
278 
 
 SIMPLE AND MULTIPLE ARCS. 
 
 impression made on the free extremity of a instantly produces a con- 
 Fia 128. traction in the muscular fibre m, which the effe- 
 
 rent branch e supplies. The whole force is at 
 once consumed, no portion of it remaining. 
 
 The simple cellated nerve arc, Fig. 123, con- 
 sists of a centripetal fibre, <z, which, receiving 
 impressions on its free extremity, conveys them 
 to the vesicle v, from which the influence passes 
 forward along the centrifugal fibre 6, causing the 
 simple ceiiated arc. muscular fibre m, which the nerve supplies, to 
 
 contract. An impression made at a therefore produces motion at m. 
 The action is purely automatic, and a part of the force is stored up or 
 remains in the vesicle. 
 
 In the figures here given, the centripetal and centrifugal fibres are rep- 
 resented apart. In fact, however, they may be considered as bound to- 
 gether, for the sake of compactness, without there being any fusion or 
 coalescence of structure or functions. It is also to be understood that 
 the free extremity of the centripetal fibre is connected with some special 
 mechanism adapted to the influence it is to receive. Thus its axis cyl- 
 inder may be naked, or connected with a vesicle, or with an apparatus 
 for the reception of light, or sound, or heat, or pressure, &c. 
 
 Multiple automatic nerve arcs arise from an arrangement of many such 
 simple arcs in succession longitudinally, as in Fig. 
 124, or it may be in a circular order. The former 
 case is presented in the articulata, the latter in the ra- 
 diata. Each symmetrical portion of the animal has 
 its own nervous arc, but as such symmetrical portions 
 are not destined to live an independent life, but to act 
 in unison with the others, a necessity arises for each 
 arc to be brought in relation and maintain a connec- 
 tion with the others, and this is done by extending 
 from ganglion to ganglion fibres of communication, <?, <?, which may here 
 Commissurai be called commissural fibres. So the circle of ganglia which 
 fibres. surrounds the mouth of the radiata is not a circular arrange- 
 
 ment of isolated ganglia, but a ring of ganglia and commissures conjoint- 
 ly. Where the nervous system is planned symmetrically on the two 
 sides of the mesial plane, the ganglia are commissured across the plane 
 to insure a reciprocity of action. In the molluscs, whose organs of ani- 
 mal life show this bilateral symmetry, and which have three such gan- 
 glia, the cephalic, pedal, and parieto-splanchnic, each is commissured with 
 its colleague on the other side of the plane, or they are brought up to the 
 plane and juxtaposed, the commissure then disappearing, but their bi- 
 lobed aspect betraying their separate construction. The coalescence fre- 
 
 Fig. 124. 
 
 Multiple nerve arcs. 
 
COMMISSURAL ACTION. 
 
 279 
 
 Fig. 125. 
 
 Pairs of arcs commissure*. 
 
 quently becomes more intimate, and all traces of the 
 original double construction disappear. 
 
 The letters remaining the same as in the preced- 
 ing diagrams, Fig. 125 represents the manner of 
 commissuring across the mesial plane. 
 
 As illustrations of the manner in which these 
 mechanical principles are carried out, the following 
 
 Fig. 12T. 
 
 Fig. i2s. 
 
 Fig. 126, nervous system of the larva of the sphinx li- 
 gustri, showing the successive arrangement of mul- IU trations 
 tiple nerve-arcs from 1 to 11, commissured with from various 
 one another, and all with the cephalic ganglion animals - 
 17, which is their common register. 
 
 Fig. 127, the pupa condition of 
 the same insect, and Fig. 128 the 
 imago. (Newport.) 
 
 Fig. 129, nervous system of the 
 asterias, in its elementary parts. 
 It consists of a series of five gan- 
 glia, gr, g, circularly arranged round 
 
 Fig. 129. 
 
 I 
 
 Nervous system Nervous system of Nervous system of 
 of larva of pupa of sphinx li- imago of sphinx li- 
 
 sphinx ligustri. gustri. gustri. 
 
 the mouth of the animal, and giving forth 
 to each ray a pair of nerves. (Tiedemann.) 
 Fig. 130, nervous system 
 of patella : Z, Z, lateral ganglia, 
 commissured with the cephal- 
 ic, which is between them ; t, 
 the transverse or'subossopha- 
 system of g eal ganglion, commissured in 
 patella - like manner. (Cuvier.) 
 
 Fig. 131, nervous system of sepia octo- 
 pus : C 9 cephalic ganglion ; 0, 0, optic gan- 
 glia ; <?, suboesophageal ganglion ; 1 9 Z, lat- 
 eral stellate ganglia ; a, abdominal or vis- 
 ceral ganglion. (Cuvier.) 
 
 Nervous system of asterias. 
 Fig. 131. 
 
 Nervous system of octopus. 
 
280 
 
 COMMISSUEAL ACTION. 
 
 Fig. 132, nervous system of aplysia : a, an- 
 terior ganglion ; c, cephalic ; I, I, lateral ; g, 
 abdominal. 
 
 In the mechanical interpretation of the nerv- 
 Function of ous system, the action of commis- 
 commissures. SU ral strands is a point of primary 
 importance. It may Ibe said that they are for 
 the purpose of drawing off from the nerve arc a 
 part of the influence which is coming along the 
 centripetal fibre, and directing it into a new chan- 
 nel. If such coarse illustrations are permissi- 
 ble, the vesicles act like a three-way cock, or 
 perhaps like a piece of looking-glass with a 
 
 part of the foil removed from its midst; a Nervous system of apiysia. 
 beam of light impinging upon it is in part reflected, and part escapes be- 
 hind through the uncovered space. Though I have described the simple 
 cellated nerve arc as containing essentially a ganglion or vesicle, it is not 
 to be supposed that such a structure necessarily impresses any change 
 on the incoming influence. Since, if we irritate a centripetal fibre, mus- 
 cular motion may ensue from propagation of that irritation through the 
 ganglion, and if we irritate a centrifugal fibre, muscular motion equally 
 ensues, it is quite clear that in the so-called action of reflection by the 
 ganglion there is, in reality, no change in the influence which has been 
 brought along the centripetal fibre. The same impression on any part 
 of the nervous arc, no matter on which side of the ganglion it may be 
 made, will produce the same muscular result. 
 
 Such considerations therefore lead us to suspect that nothing takes 
 Actofreflec- place in the ganglion which justifies such an expression as 
 don. u ac t of reflexion" or "reflex action," terms which convey an 
 
 idea that the influence which passes in the two branches of the nerve 
 arc is different, the difference having been established or brought on by 
 the ganglion. They confirm the opinion that the ganglion has, for one of 
 its primary duties, the function of permitting an escape of the influence 
 passing in the interior of the centripetal fibre into new channels for the 
 establishment of new results. 
 
 In the simple automatic nerve arc the impression and the effect are in- 
 instantaneous stantaneous. An irritation of the centripetal branch pro- 
 action of the duces, without any sensible interval of time, muscular con- 
 traction through the action of the centrifugal branch, and that 
 contraction ceases the moment the impression is over. But the open- 
 Reserved action ing out of the nerve arcs by the introduction of a vesicle 
 of cellated arcs, permits a part of the influence, whatever it may be, to be 
 drawn off, and this, now passing along the commissural line, may be dis- 
 
REGISTERING NERVE ARC. 
 
 281 
 
 posed of in two different ways : 1st. The influence thus drawn off may 
 be instantaneously consumed or utilized by exciting, through adjacent 
 simple arcs, synchronous movements ; or, 2d. It may be held in reserve 
 for future use by being carried along the commissure to a receiving, or, 
 as I may term it, registering ganglion. 
 
 This, therefore, introduces a more complex mechanism, which may be 
 designated as, 
 
 The registering nerve arc, the typical construction of which is repre- 
 133. sented in Fig. 133. In this we have the Registering 
 
 centripetal, a, and centrifugal fibre, 6, as be- nerve arcs - 
 fore, in connection with their central vesicle, v ; but, 
 passing from that central vesicle, a commissural fibre, 
 c, offers a channel of escape of a part of the influence 
 which so reaches the registering ganglion, r, and makes 
 a permanent impression upon it by disturbing its con- 
 dition physically or chemically; and, since many nerv- 
 ous arcs may be thus commissured upon the same registering ganglion, it 
 thus becomes for them all a central point of deposit and a centre of com- 
 mon action. And in this manner not only is a temporary Variable ef- 
 influence converted into a permanent impression, but, from f ectsansefrom 
 
 x _ invariable im- 
 
 the interaction of such impressions upon one another, new pressions. 
 and variable results arise. Some illustrations were given a few pages 
 back of the development of the variable from the invariable in the case 
 of certain ordinary physical phenomena, and these may be profitably re- 
 ferred to again. 
 
 A modification of the registering nerve arc is presented in Fig. 134, 
 Fig. is*, which exhibits the suppression of the centrifugal gu ression of 
 branch, the whole influence received passing along centrifugal 
 the commissural line to the registering ganglion. branch - 
 This condition of things may occur when the centripetal branch 
 at its free extremity is involved in a mechanism of special 
 sense, olfactive, ophthalmic, or auditory. No part of the im- 
 pression thus received is necessarily expended at once ; the 
 whole may be thus retained, and utilized at a future time, 
 gai branch. The introduction of the registering ganglion is thus the in- 
 troduction of the element of time in a living mechanism. In the lower 
 forms of arc an impression is instantaneously expended, in this it is pre- 
 served. 
 
 The common centre or register of whatever impressions have been re- 
 ceived by the special sense instruments, olfactive, ophthalmic, or auditory, 
 as well as impressions of a general tactile kind, is doubtless 
 to be properly regarded as the sensorium. Though animals 
 constituted on this type accomplish many variable actions, that variabil- 
 
 suppresson 
 
 of centrifu- 
 
 
282 THE INFLUENTIAL AEG. 
 
 ity is essentially and purely automatic. As such may be regarded the 
 instinctive actions of bees, any two of which, if placed under the same 
 circumstances, act with undeviating certainty in the same way. The 
 whole career of life of one of these insects is the whole career of any oth- 
 er. They build their combs now in the same way that they did a thou- 
 sand years ago ; their daily doings are the same as they have ever been. 
 Except as repccts a particular, hereafter to be pointed out, they may be 
 regarded as automatons. 
 
 The introduction of a registering ganglion necessarily gives rise to an 
 Effect of the in- extension of the physical relations of an animal by connect- 
 regis U t C erhTg 0f * & its P resent existence with antecedent facts, for the gan- 
 gangiion. glion at any moment contains the relics of all the impres- 
 sions that have been made on it up to that time, and these exert their in- 
 fluence on any action it is about to set up. In virtue of them, the nerv- 
 ous mechanism has now the power of modifying whatever impressions 
 may be made on its centripetal nerves, and, within certain limits, of con- 
 verting them into different results. Yet still the automatic condition is 
 none the less distinct, and still the immediate source of every action is to 
 be found in external impressions. 
 
 An increasing complexity of nervous structure is next evidenced by a 
 Sensory and division of the registering ganglion into two portions, which, 
 motor lobes. w j t jj some incorrectness, may be designated sensory and mo- 
 tor lobes, a division which is preparatory to, and, indeed, obviously con- 
 nected with, the introduction of a totally new method of action and source 
 of power. 
 
 In Fig. 135 we have an ideal sketch of this new condition of things. 
 Fig 135 '^ ne letters used in the preceding cases, in this refer again 
 to the same parts. But now it is seen in addition that 
 the registering ganglion has assumed a bilobed aspect, 
 s ra, the letters respectively indicating its sensory and mo- 
 tor portions, or, to use the language of human anatomy, a 
 thalamus and corpus striatum. From these there branch 
 off commissural lines, radiating to a hemispherical collec- 
 tion of vesicular matter, c c, the representative of a cere- 
 brum. 
 
 Assuming the registering ganglion as a centre, the arc- 
 like arrangement on either side of it is symmetrical, as is shown in Fig. 
 Theinfluen- 135. And since it will facilitate our consideration to intro- 
 tiai arc. ^ uce ^.g distinctive terms, I shall designate the external arc, 
 which is in relation with the external world, as the automatic arc, and 
 the inner one, which is in relation with the cerebrum, the influential arc. 
 Throughout this work I have constantly assumed the existence of an 
 intellectual principle, spirit, or soul, whose links of connection with the 
 
OF THE EXISTENCE OF THE SOUL. 283 
 
 external world are the sensory ganglia and the cerebral Evidence of the 
 hemispheres. We may now profitably inquire whether any existence of the 
 
 j. -u i, if f ^ t. soul derived 
 
 argument in behalf of the existence of such an agent may f r0 m cerebral 
 be gathered from the anatomical and physiological facts just structure - 
 presented, or whether we must assume it as a postulate, relying for proof 
 on evidences of a totally different character to those which are presented 
 by the science now engaging our attention. It is to be greatly regretted 
 that evidence drawn from structural arrangement has hitherto, by very 
 high authority, either been totally cast aside or held in very light esteem. 
 It is still more deeply to be regretted that those who should have known 
 better have conceded the argument that from no consideration based 
 upon anatomical or structural arrangement could proof be obtained of 
 the existence of an immaterial principle. Even by such, the study of 
 physiology has been designated as leading to materialism, and, with an 
 injustice which can not be too emphatically reprobated, the scandal has 
 often been quoted, that where there are three physicians there are two 
 atheists. 
 
 But what if it should turn out that, from the study of the cerebral 
 mechanism, distinct proof can be obtained on this point proof of just as 
 cogent a nature in support of the doctrine of the existence of the soul 
 as that which we have of the existence of the external world, and of pre- 
 cisely the same character? Without, therefore, occupying -myself with 
 such other evidence as might be drawn from theological or metaphysical 
 sources, and which are therefore extraneous to the object of this work, I 
 shall proceed to point out such considerations as naturally offer them- 
 selves to our minds when we recall the general structure of the nervous 
 apparatus. Eepeating, therefore, such facts as may be necessary for the 
 proper understanding of this interesting argument, I present it as follows : 
 
 The simple cellated nervous arc consists essentially of these portions, 
 a centripetal fibre, a vesicle, and a centrifugal fibre ; the cen- Automatic 
 tripetal fibre may have at its outward or receiving extremity mechanism of 
 vesicular or cellular material. Thus constituted, this mech- 
 anism is ready to receive external impressions, which, if such language 
 may be appropriately used, are converted or reflected in part by the gan- 
 glion into motions, and the residue retained. But the arc, viewed by it- 
 self, is a mere instrument, ready, it is true, for action, but possessing no 
 interior power of its own. It is as automatic as any mechanical con- 
 trivance in which, before a given motion can be made, a certain spring 
 must be touched. 
 
 The essential condition of the activity of such a nervous arc is there- 
 fore the presence and influence of an external agent a some- Re uireg an 
 thing which can commence the primitive impression, for with- external agent 
 out it the mechanism can display no kind of result. More- for actlon * 
 
2k* INVERSE PHYSIOLOGICAL PROBLEMS. 
 
 over, there must be an adaptation between the nature of that agent and 
 the structure thus brought in relation with it, as is strikingly illustrated 
 by each of the organs of sense. Thus the peripheral extremities of the 
 fibrils of the optic nerve are involved in a combination of a purely phys- 
 ical kind, having relation to the properties of light : the convex surface 
 of the cornea, the unequicurved lens, the diaphragmatic iris, the interior 
 investiture of black pigment, these are all structures the object of which 
 we clearly understand. We know that the rays of light must undergo 
 refraction at the curved surfaces upon which they are incident, and de- 
 pict the images of external forms on the retina or black pigment, the iris 
 expanding or contracting, as the case may be, to regulate the entrance of 
 Adaptation be- the light. So completely do we admit this principle of an 
 !* adaptation of structure to the nature of the agent which is 
 to set it in activity, that in this particular instance, without 
 any hesitation, we class the eye among optical instruments, and include 
 its description in our optical treatises. But in the same manner that, 
 starting from the well-known properties of light, we advance to the ex- 
 planation of the uses of each of the various parts of the eye, there can be 
 no doubt that the converse of this method of reasoning would be possi- 
 ble to an intellect of sufficient power, who, from a full consideration of 
 the structure of the eye, might determine the properties of light, guided 
 in doing this by the principle that there must be an adaptation between 
 such structures and such properties ; and, in the same manner, a man 
 deaf and dumb, but of an intellect of great capacity, might doubtless, 
 from the critical study of the construction of the ear, determine the na- 
 ture of sounds. Nay, even more, it is not impossible that he should be 
 able to compare together the physical peculiarity of the movements which 
 constitute light or sound respectively, and to demonstrate that these 
 originate in normal, and those in transverse vibrations. 
 
 So, therefore, these problems present themselves under a double aspect, 
 Nature of in- and are capable both of a direct and an inverse solution : 
 Mcai h prob- Given * ne nature of light, to determine what must necessarily 
 lems. be the construction of the organ of vision ; or, Given the con- 
 
 struction of the eye, to determine what is the nature of light ; and the 
 same might be said of the organ of hearing. This inverse method of 
 treating natural agents is still in its infancy, because of the extreme im- 
 perfection of our knowledge ; but doubtless what has been said will re- 
 call to the mind of the reader the parallel example which is furnished by 
 astronomy, and which, within a few years past, has yielded such a splen- 
 did result. The mass of a planet being known, the perturbations which 
 it can cause in another are capable of direct computation, but it was re- 
 served for Leverrier to discuss the inverse problem, and from the per- 
 turbations to find the place of the planet. The discovery of Neptune 
 was the result. 
 
OF THE EXISTENCE OF THE SOUL. 
 
 Now the problem we are dealing with is of this inverse kind. It may 
 be stated, Given the structure of the cerebrum, to determine the nature 
 of the agent that sets it in action. And herein the fact which chiefly 
 guides us is the absolute analogy in construction between the elementary 
 arrangement of the cerebrum and any other nervous arc. In it we plainly 
 recognize the centripetal and centrifugal fibres, and their con- External influ- 
 vergence to the sensory ganglia, the corpus striatum and f^ 
 optic thalamus ; we notice the vesicular material at their tial arc. 
 external periphery as presented in the convolutions of the human brain ; 
 and if in other nervous arcs the structure is merely automatic, and can 
 display no phenomena of itself, but requires the influence of an external 
 agent if the optical apparatus be inert and without value save under 
 the influences of light if the auditory apparatus yields no result save 
 under the impressions of sound since there is between these structures 
 and the elementary structure of the cerebrum a perfect analogy, we are 
 entitled to come to the same conclusion in this instance as in those, and, 
 asserting the absolute inertness of the cerebral structure in itself, 
 to impute the phenomena it displays to an agent as perfectly 
 external to the body and as independent of it as are light and sound, 
 and that agent is the soul. 
 
 It would not comport with the object of this work to pursue this ar- 
 gument in its details, yet I can not forbear observing that, even so far as 
 we have already advanced, the point which, after all, is of the utmost 
 importance, is completely attained. Those who have accused physiology 
 of tending toward materialism have never duly weighed the accusation 
 they make, and certainly have never understood the nature of the argu- 
 ments it can present ; for such as the one here imperfectly set forth, from 
 their tangible nature, will commend themselves to many minds who do 
 not appreciate the strength of purely metaphysical arguments, and herein 
 they may become subservient to the highest and most enduring interests 
 of our race. 
 
 And thus it may be proved that those actions which we term intellectual 
 do not spring from mere matter alone, nor are they functions Inde endence 
 of mere material combinations ; for though it is indisputably and immortal- 
 true that the mind seems to grow with the bodily structure, lty J 
 and declines with it, exhibiting the full perfection of its powers at the 
 period of bodily maturity, it may be demonstrated that all this arises 
 from the increase, perfection, and diminution of the instrument through 
 which it is working. An accomplished artisan can not display his power 
 through an imperfect tool, nor, if the tool should be broken, or become 
 useless through impairment, is it any proof that the artisan has ceased to 
 exist ; and so, though we admit that there is a correspondence between 
 the development of the mind and the growth of the body, we deny that 
 
286 OPINIONS RESPECTING THE SOUL. 
 
 it follows from that, either that the mind did not pre-exist, or that the 
 death of the body implies its annihilation. 
 
 If it fell within the compass of our plan, we might proceed to consider 
 how far, since the mind can act upon external nature through 
 
 Opinions re- f 
 
 specting the the intervention of the bodily mechanism, the converse is 
 soui^ntertain- P 088 ^ 6 ; how, since the face of things around us can be 
 ed by different changed by our voluntary exertions, the intellectual faculties 
 may be changed by the action of external nature through the 
 bodily mechanism. And since we have established the existence of the 
 intellectual principle as external to the body, we might proceed, for now 
 we are entitled so to do, to reason respecting its nature from the phenom- 
 ena it displays. I do not, however, propose to enter on those considera- 
 tions now, and shall close these remarks with a reference to some doc- 
 trines proposed by the most highly-advanced and intellectual portions of 
 the human family. 
 
 It is said that the spirit of man is created in the image of God, an ob- 
 servation strikingly illustrated by the fact that, as regards both, two es- 
 sentially different doctrines have been held the pantheistic, by some of 
 the most highly advanced of the Asiatics, and the anthropomorphic, by 
 the Europeans. The pantheistic supposes the human soul to be a part 
 of the Deity, and therefore devoid of form ; the anthropomorphic as hav- 
 ing the likeness of the body. The Asiatics, then, regarding the Deity as 
 a principle diffused in and throughout nature, consider the spirit of man 
 as a part or portion thereof, and often use such illustrative allusions as 
 those of a drop of water in the ocean, a spark of a universal and vital 
 flame ; or, if they do not accept this view of a oneness in 'the nature of 
 spirit and Deity, they regard the former as arising in some manner from 
 the latter, just as waves may exist upon the sea, or sounds may arise in 
 the air. They believe that at death there is, as it were, a reunion of the 
 part with the whole, as every drop of water sooner or later finds its way 
 back to the sea, or waves become quiet and disappear, or sounds die away 
 in the air. 
 
 But with European nations there has been, from their very infancy, a 
 tendency to the anthropomorphic conception. The barbarians before the 
 Roman empire, in their legendary fables, accepted the idea of disembod- 
 ied spirits under the shape of men, and through the intervening ages up 
 to our own times, such notions, under various forms, have been held. 
 The rural populations entertain an undoubted faith in fairies and ghosts, 
 so that it might be asserted that this manner of viewing the thing is 
 almost natural to us. We instinctively represent to ourselves in this 
 way the immaterial principle, and in the case of each individual expect a 
 correspondence between it and his bodily form. Whatever may be our 
 authority for arriving at such a conclusion, there can be no doubt that it 
 
ORGANS OF SPACE AND 'TIME. 287 
 
 so specializes and intensifies our ideas, and is so connected with many 
 of our most highly cherished recollections, that, even were the evidence 
 in its behalf far weaker than it actually is, we should look without favor 
 on any attempt to invalidate the doctrine, and, if forced to do so, should 
 abandon it with regret. The pantheistic is a grand but cold philosoph- 
 ical idea ; the anthropomorphic embodies our recollections, and restores 
 to us our dead. The one is the dream of the intellect, the other is the 
 hope of the heart. 
 
 We have thus traced out the essential elements of the nervous ma- 
 chine in its highest complexity, and shown its gradual rise imperfection 
 from the purely automatic to the influential. We may there- jj 
 fore comprehend the difficulties under which metaphysicians tions. 
 labor, who confound all these parts and all these functions together, and 
 pass over as of no account the guiding indications which are furnished 
 by the study of structure. It is not difficult for the physiologist, en- 
 lightened by the knowledge he possesses, to recognize the various points 
 at which these philosophers go astray the point at which their theories 
 cease to be representations of the truth. He acknowledges the existence 
 of an external nature, and equally the existence of an immaterial spirit, 
 and to their action on or relation to each other he traces the resulting 
 phenomena. He admits that, among certain classes of life, every motion 
 and every sensation is due to external nature alone, but to these purely 
 automatic groups man does not belong. He repudiates the doctrines of 
 the idealist, because, though they may maintain themselves in the uncer- 
 tainties of metaphysical argument, they are dissipated at once in the more 
 severe trial of anatomical discussion. 
 
 There are two fundamental ideas essentially attached to all our per- 
 ceptions of external things: they are SPACE and TIME, and Pro vision in the 
 for these an early provision is made in the nervous mechan- ^^^lf tfim 
 ism, while yet it is in an almost rudimentary state. The space and time. 
 development of the eye and the ear, as we shall more particularly find 
 when we come to the description of these organs, is for this purpose. In 
 a philosophical respect the eye is the organ of space, and the ear of time ; 
 the perceptions of which, by the elaborate mechanism of these structures, 
 become infinitely more precise than would be possible if the sense of 
 touch alone were resorted to. The indications thus gathered are trans- 
 mitted by the optic and auditory nerves respectively to the brain. 
 
 In its highest condition of development, the nervous mechanism has a 
 threefold operation, objective, subjective, and impersonal. Objective, sub- 
 Objective ideas arise in external facts ; subjective in register- fa tl er&maio 
 ed impressions ; the impersonal, as, for example, the abstract erations. 
 truths of geometry, issue of pure reason, and are therefore to be attrib- 
 uted to the essential nature of the soul. Of these three elementary con- 
 stituents all human knowledge consists. 
 
288 VESTIGES OF GANGLIONIC IMPRESSIONS. 
 
 As respects subjective or registered impressions, a few remarks may 
 be here made. There can not be a doubt that the registry 
 
 Illustrations of / 
 
 the vestiges of of impressions involves an actual structural change in the 
 impressions. g an glion, which is of a permanent character. These changes 
 may be rudely and imperfectly illustrated by experiments, such as I pub- 
 lished years ago, of which the following may be taken as examples : If, 
 on a cold, polished piece of metal, any object, as a wafer, is laid, and the 
 metal then be breathed upon, and, when the moisture has had time to 
 disappear, the wafer be thrown ofT, though now upon the polished surface 
 the most critical inspection can discover no trace of any form, if we 
 breathe upon it a spectral figure of the wafer comes into view, and this 
 may be done again and again. Nay, even more ; if the polished metal be 
 carefully put aside where nothing can deteriorate its surface, and be so 
 kept for many months (I have witnessed it even after a year), on breath- 
 ing again upon it, the shadowy form emerges ; or, if a sheet of paper on 
 which a key or other object is laid be carried for a few moments into the 
 sunshine, and then instantaneously viewed in the dark, the key being 
 simultaneously removed, a fading spectre of the key on the paper will be 
 seen ; and if the paper be put away where nothing can disturb it, and 
 so kept for many months, at the end thereof, if it be carried into a dark 
 place and laid on a piece of hot metal, the spectre of the key will come 
 forth. In the case of bodies more highly phosphorescent than paper, the 
 spectres of many different objects which may have been in succession 
 laid originally thereupon will, on warming, emerge in their proper order. 
 I introduce these illustrations for the purpose of showing how trivial 
 are the impressions which may be thus registered and preserved. In- 
 deed, I believe that a shadow never falls upon a wall without leaving 
 thereupon its permanent trace a trace which might be made visible by 
 resorting to proper processes. All kinds of photographic drawing are in 
 their degree examples of the kind. Of the moral consequences of such 
 facts it is not my object here to speak. The world would be none the 
 worse if every secret action might thus be made plain. But if on such 
 inorganic surfaces impressions may in this way be preserved, how much 
 more likely is it that the same thing occurs in the purposely-constituted 
 ganglion ! Not that there is any necessary coincidence between an ex- 
 ternal form and its ganglionic impression any more than there is be- 
 tween the letters of a message delivered in a telegraphic office and the sig- 
 interpretation na ^ s wn i cn tne telegraph gives to the distant station, yet these 
 ofsuchves- signals are easily retranslated into the original words no 
 more than there is between the letters of a printed page and 
 the acts or scenes they may chance to describe, but those letters call up 
 with clearness in the mind of the reader the events and scenes. Indeed, 
 the quickness with which the mind interprets such traces or impressions 
 
SPONTANEOUS FUNCTIONS OF GANGLIA. 289 
 
 in its registering ganglia is illustrated by the rapidity with which we 
 gather the sense of a printed page without individualizing each of the 
 letters it contains, or as a skillful accountant runs his jeye over a long 
 column of figures, and seems to come by intuition at once to the correct 
 sum. The capability which we thus possess of determining a final per- 
 ception or judgment of results, without dwelling on the intermediate 
 traces or steps, is also illustrated by our appreciation of music without 
 concentrating our thoughts on the time and intensities of vibration or in- 
 terferences of the notes, though these mathematical relations are at the 
 very bottom of the harmony ; and conspicuously does the Supreme In- 
 telligence, God, reach with unerring truth to every final result without 
 any necessary concern in the intermediate steps. 
 
 From the preceding considerations we may infer that there is a neces- 
 sary limitation of the amount of impressions capable of being Finite nature 
 registered in the organism, and therefore, in this regard, all of human 
 human knowledge is finite. Yet its term is much farther off kn<mle(J g e - 
 than might at first sight appear. A library of a given size may only be 
 able to contain a given number of books upon its shelves, but the amount 
 of information it is capable of containing may be made to vary with the 
 condensation and perspicuity of the books. /. 
 
 In the hypothetical language of physiology, the nervous centres are 
 spoken of as the origin of the nervous influence or force. A conclusion re- 
 close examination of the phenomena they display leads us, specting the 
 however, to receive such a doctrine with a certain amount function of 
 of limitation. Most of the ganglia produce no motor im- s an s lia - 
 pulses except under the action of external impression, and under the el- 
 ementary view we have just presented regarding the function of the 
 brain, the same remark applies even to it, since the immaterial principle, 
 whose instrument it is, must be regarded as an agent distinct from it, 
 and in that respect external. Indeed, the cases in which the nervous 
 centres seem to display the quality of spontaneously originating force are 
 so few, and in their nature so doubtful, that we are almost entitled to dis- 
 regard them. For example, the ganglia of the heart are by some sup- 
 posed to cause, by their own inherent power, the contractions of that or- 
 gan, which in cold-blooded animals, long after it has been excised, will 
 continue its rhythmic motions. But it is far more agreeable to the anal- 
 ogies of the nervous system to regard these cardiac ganglia, not as orig- 
 inators of power, but as merely depositories, reservoirs, or magazines of 
 it. There is nothing more extraordinary in then: ability to keep up the 
 motions of the organ with which they are connected than there is in the 
 subsidiary spring of a chronometer, which maintains the movement of 
 that instrument for the period during which the action of the mainspring 
 is taken off while it is being wound up. Yet the mainspring, and the 
 
 T 
 
290 MENTAL EMOTIONS. 
 
 subsidiary spring too, derive their mechanical power originally from the 
 force which has wound up the chronometer. In this particular of the 
 storing up of power for its utilization in the time of need, the whole gan- 
 glionic or sympathetic system of nerves may be taken as the great ex- 
 ample. 
 
 The conveyance of an impression through the great nervous centres is 
 more complicated than it is through the nerve trunks. It 
 
 Nature of the r ./.<. 
 
 action of nerve may be conducted, ii oi sufficient intensity, through one gan- 
 res ' glion after another in succession. The intermedium through 
 
 which this is done is probably the nerve-tubes in a majority of instances, 
 though perhaps, in those cases in which a longer period of time is occu- 
 pied, it may be rather from vesicle to vesicle than through the tubes. 
 Impressions may be thus transferred from one set of tubes to others, or 
 Conveyance of they may be diffused from a nerve centre to many tubes 
 IhroughTn- around and so produce a wider circle of influence. That 
 tres. transfer of impressions from centripetal to centrifugal fibres 
 
 which has been previously described as reflex action, though commonly 
 involuntary, may in many instances be governed by a direct exertion of 
 the will. Thus the respiratory movements for the introduction of air 
 may be controlled to a certain extent, as in holding the breath, but this 
 is only during a short time, for the necessity of permitting the normal 
 action to occur presently becomes insuperable. Of reflex actions, the 
 majority are obviously for the accomplishment of some special object so 
 long as the system is in health they are means for an end ; but in dis- 
 eased conditions they very often occur in an objectless or useless way. 
 
 In its most perfect condition, the nervous system thus consists of two 
 Nature of men- separate mechanisms, the automatic and the influential, and 
 tai emotions, these are so related that they can mutually act on one an- 
 other. The will can exert a control over the so-called reflecting func- 
 tion of the automatic part, and external impressions which have been 
 received by that part can exert a reaction upon the wilL It is in this 
 way that mental emotions may be explained, the power of external influ- 
 ences which antagonize or even overcome the will. 
 
THE SPINAL AXIS. 291 
 
 CHAPTER XV. 
 
 THE SPINAL AXIS. 
 
 Primitive Development of Nervous System. Itsjinal Condition in different Vertebrates. 
 
 The Spinal Cord: its Structure. Its Membranes. Its Thirty-one Pairs of Nerves. Proper- 
 ties of their Hoots. Functions of the Cord. Bell's Discovery. Transmission of Longitudinal 
 and Transverse Influences. Reflex Action of the Cord. Nature of Reflex Action. Motor and 
 Sensory Tracts of the Cord. Summary of its Functions.. 
 
 The Medulla Oblongata : its Structure and Functions. 
 
 The Pons Varolii: its Structure and Functions. 
 
 Dr. Carpenter's Views of the Analogy between tlie Spinal Cord of Vertebrates and the Ventral 
 Cord of Articulates. 
 
 WE now commence a more detailed examination of the nervous sys- 
 tem, presenting a description of its structure as far as may Subdivisions 
 be necessary for the understanding of its functions. We of the sub J* ect - 
 shall follow the usual division of this subject as adopted by authors. 
 This will therefore lead us to speak in succession of the spinal cord and 
 medulla oblongata, of the sensory ganglia, of the cerebellum and cere*- 
 brum, of the nerves generally, and, lastly, of the sympathetic system. 
 
 The important position occupied by the nervous mechanism in the an- 
 imal body will always draw to it the closest attention of the physiol- 
 ogist, and yet it must be admitted that hitherto it is the least ad- 
 vanced portion of the science. If metaphysicians are to be blamed for 
 casting away the advantages which arise from a study of Advantages de- 
 structure, the earlier physiologists were almost equally in 
 error in confining themselves to human anatomy alone, 
 They did this under an impression that there is an essential and intrinsic 
 difference between the functions of this system in man and in the lower 
 animals. 
 
 There is an analogy of construction in all the forms of nervous system 
 presented by the different animal tribes, which, in the infancy of the sci- 
 ences of organization, was attributed to a unity of design pervading the 
 plan of Nature, but which, when seen from a higher and more philosoph- 
 ical point of view, is plainly the necessary result of a universal and un- 
 varying law of development. This conclusion, which, when better un- 
 derstood, is doubtless destined to become one of the most important sug- 
 gestions ever furnished by science respecting the management of the 
 world, is strikingly enforced by the analogies between the Advant<> esde- 
 successive transitory stages of development of this system rived from de- 
 at different epochs in the life of man, and the permanent vel P ment - 
 form it assumes in members of the entire animal series. Since there can 
 
292 DEVELOPMENT OF THE CEEEBRO-SPINAL AXIS. 
 
 be no doubt that every animal function, from the automatic motions of 
 the obscurest living form up to processes of intellection of man, depend 
 upon this structure as on an instrument, we may, by a due comparison of 
 the habits, instincts, or other phenomena in such cases with the existing 
 nervous development, arrive at 'true conclusions of the connection between 
 its structure and its functions. :. We shall therefore indicate, in a general 
 manner, the order of development of this system in man, and then its 
 permanent stages in the animaL series. 
 
 The nervous system first n:i.kes its appearance in the serous lamina 
 Course of de- of the germinal membrane and in the midst of the pellucid 
 veiopment of area ag ^ e p r j m itiy e trace, a delicate and pale- white line ris- 
 ous system, ing somewhat above the general surface of the germinal area. 
 This line soon presents a conical' aspect ; the thicker portion is destined 
 to become the head of the embryo. After a short interval, the membrane 
 is gathered into a fold on each side of the primitive trace, and these folds, 
 advancing toward each other, constitute the dorsal laminse, which, when 
 their edges have met and coalesced, form a tubular cavity a. rudimentary 
 preparation for the vertebral column. Beneath the tube so arising may 
 be discovered, at this stage, a line of nucleated cells the chorda dorsalis. 
 As the edges of the dorsal laminae approach each other, they assume a wavy 
 form, and simultaneously a bending forward or curvature of the embryo 
 occurs, so that the vertebral tube becomes arched. In the middle wavy 
 portion are now to be seen rectangular plates, the elements of the future 
 vertebras. The coalescence of the middle part of the dorsal laminas 
 takes place first, the ends as yet diverging in the portions which corre- 
 spond respectively to the head and the sacrum. The spinal marrow and 
 the brain thus arise at the primitive trace, the brain being a superposed 
 or additional structure to the spinal marrow ; for now the wavy edges of 
 the anterior extremity are gradually seen to give origin to three cells by 
 their juxtaposition : 1st. The epencephalpn, a single cell, to produce the 
 medulla oblongata : its' cavity is to be the fourth ventricle ; 2d. The mes- 
 encephalon, also a single cell, for the corpora quadrigemina : its cavity 
 is to be the ventricle of Sylvius ; 3d. The. deutencephalon, a single cell, 
 for the optic thalami : its cavity is to be the third ventricle. Though at 
 first transparent and fluid, the nervous matter becomes by degrees more 
 consistent and covered over with a thin layer of membrane, the indica- 
 tion of its future investitures. The rudiment of an eye, under the form 
 of a protrusion, now appears from the most anterior cell ; and in like 
 manner the auditory apparatus emerges from the cell of the medulla ob- 
 longata, from the anterior part of which, by the coalescence of a pair of 
 fasciculi which have arisen, the cerebellum begins to form. At this peri- 
 od, through the continued curvature of the embryo, the cell of the cor- 
 pora quadrigemina has become most anterior. 
 
DEVELOPMENT OF THE CEEEBRO-SPINAL AXIS. 293 
 
 The origin of the spinal cord and brain is illustrated in the annexed 
 figures from Bischoff. Fig. 136 shows upon a dark ground Ori . Q of thg 
 a portion of the germinal membrane, in the midst of which is spinal cord and 
 the area pellucida and primitive trace : #, the area pellucida ; the bram> 
 , the dorsal laminse ; c, the primitive trace. 
 
 Fig. 136. Fig. 137. 
 
 The primitive trace, magnified 8 diameters. Origin of the brain upon the spinal cord, magnified 
 
 8 diameters. 
 
 Fig. 137, the same at a later stage, preparation for the brain being 
 made. The dorsal Iamina3 are approaching each other, particularly to- 
 ward the middle: , the dilated upper extremity or cephalic end, the 
 three cells appearing : the epencephalon, mesencephalon, and deutenceph- 
 alon ; b, chorda dorsalis along the bottom of the groove ; c, rudiments of 
 vertebra ; . d, lancet-shaped dilatation. In both figures the pale borders 
 along the primitive trace are pellucid nerve substance. 
 
 The dorsal cord, which is only a transitory structure, now disappears, 
 the spinal marrow commencing to exhibit a division into four strands, 
 right and left, upper and under. The medulla oblongata flattens next 
 in its upper part, its fasciculi parting from each other; the interval so 
 arising between them is to be the fourth ventricle. The hemispheres 
 now appear as a double cell, the prosencephalon, and as development goes 
 on, they soon exceed the corpora quadrigemina in size, and, as they ad- 
 vance, force these bodies backward and under them. 
 
 From this it appears that the type of construction of the nervous sys- 
 tem is, that upon the rudimentary spinal marrow a series of vesicles is 
 developed. They constitute eventually the medulla oblongata, the cer- 
 ebellum, the corpora quadrigemina, the thalami optici, the corpora striata, 
 the olfactive ganglia, and in front of all, but destined to cover the anterior 
 portions over, the hemispheres. 
 
 Turning now to the animal series, we find in the lowest members of 
 
294 THE SPINAL COED. 
 
 the vertebrata, as in the amphioxus, the spinal cord, medulla 
 
 Comparative ' 
 
 nervous system oblongata, and the elementary representatives of the sensory 
 in vertebrates. g an gii a a l ne, and as, in succession, we pass to the higher 
 ones, we recognize a cerebellum appearing over the medulla oblongata, 
 and cerebral hemispheres over the sensory ganglia. These organs in 
 the upward career become more and more developed, the hemispheres, for 
 example, soon equaling in size the quadrigemina, and then greatly sur- 
 passing them, and with this increase of size a higher grade of intelligence 
 is reached. In fishes there are four ganglia, corresponding respectively 
 to the cerebellum, quadrigemina, cerebral hemispheres, and olfactive gan- 
 glia. In reptiles the number of ganglia and their order of occurrence is 
 the same, but the cerebral hemispheres have now greatly increased, an 
 increase which is even better marked in birds, for in them the hem- 
 ispheres have expanded in front so as to cover the olfactive ganglia, and 
 posteriorly the optic, a condition of things analogous to that presented 
 by the human brain at about the close of the third month of foatal life, 
 and approaching that permanently exhibited by the lower mammals, as, 
 for instance, the marsupials. It is to be understood that what is here 
 spoken of as the hemispheres answers in reality only to the anterior lobe 
 of the cerebrum of man ; and as in him, during the fourth and fifth months, 
 the middle lobes are developed in the upward and backward direction 
 from the anterior, and still later the posterior lobes from the posterior of 
 these, the same course is followed in the animal series, the final type of 
 development, the trilobed cerebrum, being only reached by the highest 
 carnivora and quadrumanous animals. 
 
 Commencing now more particularly with human nervous anatomy 
 
 STRUCTURE OF THE SPINAL CORD. 
 
 The spinal cord is placed in the midst of the vertebral canal. In form 
 Description of it is cylmdroid, its section being elliptical, the lateral diame- 
 the spinal cord. ter teing the long on ^ Longitudinally it shows two en- 
 largements, one about its upper third, the other toward its termination. 
 Exteriorly it is white, but its section shows a gray substance, arranged 
 in the form of two crescents connected by an isthmus. Above, it is con- 
 tinuous with the brain, which, indeed, is a development upon it, and be- 
 low it terminates at the cauda equina. Its relative length is much great- 
 er in foetal life, at the third month of which it extends into the sacrum. 
 In adult life it only occupies about the upper two thirds of the verte- 
 bral canal ; it is generally stated that its termination is about the first 
 or second lumbar vertebra. Moreover, it does not fill the vertebral ca- 
 nal, being, by reason of the transverse dimensions of that cavity, rather 
 suspended in than confined by it. The rest of the space, amount- 
 ing to about one third, is occupied by the roots 'of the nerves, liga- 
 
THE SPINAL CORD. 
 
 295 
 
 fig. 138. 
 
 The spinal cord. 
 
 Fig. 139. 
 
 ments, the investitures of the cord, blood-vessels, and a 
 liquid. 
 
 Fig. 138, A, A, shows the front view of the spinal 
 cord, with the medulla oblongata ; B, B, the posterior 
 view % ; and C, C, the decussation of its strands, from 
 which it appears that the organ is composed of two equi- 
 lateral portions. They are united by an interior com- 
 missure, but separated in front by the anterior, and be- 
 hind by the posterior fissure. Of these the posterior 
 fissure is the deeper, the anterior being wider. Besides 
 these regional divisions, the cord also presents longi- 
 tudinal furrows, two for each side, dividing it into the 
 anterior, the middle or lateral, and posterior columns or 
 tracts, as shown in the figures. 
 
 With respect to the interior constitution of the cord, 
 it has already been stated that it is composed exteriorly 
 of white, and interiorly of gray material. The relative 
 quantities of these, and the particular form and distribu- 
 tion of the gray substance, may, perhaps, be best understood from the 
 
 sections given in Fig. 139, 
 from one to nineteen, 1 show- 
 ing a transverse section as 
 high as the cerebral pedun- 
 cles ; 2, through the medulla 
 oblongata; and the remaining 
 figures, to 19, at lower and 
 lower points. 
 
 In the first of these sec- 
 tions, 1 is the interpeduncu- 
 lar space ; 2, 2, inferior tract ; 
 o 9 3, 3, middle tract ; 4, 4, locus 
 
 ^H^l &* %. y/rf^WVr^ ^S^iJ^V J ---*" rr TT'*w 
 
 dl n &i & 10 $$ m& niger ; 5, 5, superior tract ; 6, 
 
 section of the aqueduct of 
 Sylvius ; 7, 7, section of the 
 superior peduncles of the cer- 
 ebellum ; 8, 8, section of the 
 two tubercula quadrigemina. 
 In the second section: 1, 1, 
 the pyramidal bodies; 2, 2, 
 olivary bodies ; 3, 3, resti- 
 form ; 4, 4, section of middle strands ; 5, floor of fourth ventricle. 
 
 In the fourth of these sections : 1, the right half of the cord ; 2, left 
 half; 3, anterior median fissure; 4, posterior median fissure; 5, 5, pos- 
 
 16 
 
 17 
 
 18 
 
 Sections of the spinal cord. 
 
296 
 
 STRUCTURE OF THE SPINAL CORD. 
 
 terior furrows : 6, white or anterior commissure ; 7, gray or posterior 
 commissure ; 8, anterior horn of right crescent ; 9, posterior horn of dit- 
 to : it is prolonged to the posterior furrow ; 10, antero-lateral columns ; 
 11, 11, posterior columns: these are all of white tubular substance. The 
 symmetrical reference numbers on one side are omitted for the sake of 
 clearness. 
 
 The spinal cord is surrounded by three membranes, continuous with 
 Membranes of those of the cranium : the dura mater, the arachnoid, and the 
 the spinal cord. pi a mater. The latter embraces the cord so closely as to ex- 
 ert a compression upon it. This is shown on slightly wounding it,' when 
 the white substance protrudes through the orifice. Fig. 140. 
 
 Fig. 140 : 1, spinal dura mater laid open and drawn 
 aside ; 2, 2, sheaths formed by this membrane round 
 the roots and spinal ganglia; 3, spinal arachnoid; 
 4, 4, sheaths formed by the arachnoid around the 
 roots of the nerves and dentated ligament ; 5, 5, points 
 of communication of the visceral layer -of the arach- 
 noid, with its parietal layer ; 6, pia mater ; 7, denta- 
 ted ligament separating the anterior roots from the 
 posterior roots of the spinal nerves, and serving as a 
 communication between the dura mater and pia mater. 
 
 From the spinal cord there arise thirty-one pairs 
 The spinal f nerves, each nerve having two roots, an 
 nerves. anterior or motor, and a posterior or sensory. 
 
 The anterior roots issue from the anterior furrow, 
 Roots of the the posterior from the posterior furrow, 
 spinal nerves. w here the gray substance emerges. Of 
 the two the latter are the larger, and have more radicles. They also 
 have, in the intervertebral foramen, a ganglion. Beyond the ganglion the 
 two roots coalesce, and the resulting nerve trunk, passing through the 
 intervertebral foramen, divides into an anterior and posterior branch, for 
 the anterior and posterior portions of the body. To this general descrip- 
 tion there are, however, some exceptions. Thus the posterior root of the 
 first cervical nerve is smaller than the anterior, and very often it has no 
 ganglion. The spinal nerves are enumerated as eight cervical, twelve 
 dorsal, five lumbar, and six sacral pairs. The cervical pass off to their 
 distribution transversely, the dorsal obliquely, and the lumbar and sacral 
 vertically. The latter constitute the cauda equina. 
 
 Fig. 141 illustrates the origin of the anterior roots of the spinal 
 nerves. 1, pons varolii; 2, large and small root of the fifth pair; 3, 
 sixth pair; 4, facial nerve; 5, auditory nerve; 6, intermedian nerve; 
 7, glosso-pharyngeal ; 8, pneumogastric ; 9, spinal accessory ; 10, hypo- 
 glossal. 
 
 Spinal dura mater laid 
 open. 
 
STRUCTURE OF THE SPINAL CORD. 
 
 297 
 
 Origin of anterior 
 roots of nerves. 
 
 From 11 to 11, the eight anterior roots of the cervical 
 nerves ; from 12 downward, the same roots of the dorsal 
 nerves : those of the lumbar and sacral are not shown in 
 the figure. As at 15, are shown the anterior branches of 
 the spinal nerves ; as at 16, their posterior branches ; at 
 17, spinal ganglia formed on the posterior roots ; 18, ante- 
 rior roots cut ; 19, anterior roots cut beyond the ganglion ; 
 20, dentated ligament, separating anterior from posterior 
 roots ; 21, insertion of this ligament on dura mater by its 
 dentated edge ; 22, insertion of same ligament on the pia 
 mater. 
 
 Fig. 142 illustrates the origin of the posterior roots of 
 the spinal nerves. 1, tubercnla quadrigemina ; 2, trian- 
 gular band ; 3, 3, superior peduncles of the cerebellum ; 
 4, 4, middle peduncles of cerebellum ; 5, 5, inferior pedun- 
 cles of cerebellum ; 6, anterior wall of fourth ventricle ; 7, 
 glosso-pharyngeal ; 8, pneumogastric ; 9, spinal accessory ; 
 from 10 to 10, posterior roots of eight cervical pairs : the 
 dorsal, the lumbar, and the sacral below 11 are not shown 
 in the figure. From 14 downward, a dotted line arising 
 from the tearing away of the posterior roots ; 15, 15, an- 
 terior roots of spinal nerves, the dentated ligament being 
 visible through the removal of the posterior roots ; 16, spi- 
 nal ganglia, of which there are thirty pairs, the first pair 
 of nerves not being furnished with them ; 17, 17, anterior 
 branches of spinal nerves ; 18, 18, posterior branches; 
 19, 19, dentated ligament, placed between the posterior 
 and anterior roots ; 20, same ligament brought into view. 
 
 Fig. 143 shows a portion of the spinal cord mgm 143- 
 surrounded by its envelopes, and seen in pro- 
 file, so as to display at once the origin of the 
 anterior and posterior roots. 1,1, posterior 
 roots of spinal nerves and their ganglia ; 2, 2, anterior roots 
 of the same nerves anastomosing with the anterior portions 
 of these ganglia; 3, 4, anterior and posterior roots cut; 
 5, dentated ligament ; 6, dura mater, preserved to show the 
 sheaths which it forms around these ganglia and the branches 
 of the spinal nerves ; 7, vertical section of the sheath of the 
 anterior and posterior roots, to show the little lamella which 
 separates the one root from the other; 8, 8, interior face. of 
 the dura mater, which is drawn aside to show the smooth 
 aspect which it possesses, owing to the parietal layer of the rior rootSt 
 arachnoid which covers it. 
 
 J.gin of posterior 
 roots of nerves. 
 
298 LONGITUDINAL TRANSMISSION IN THE CORD. 
 
 The white or fibrous portion of the spinal cord is composed in part of 
 the spinal nerve fibres and in part of commissural ones. At one time it 
 was supposed that every one of the preceding continued uninterruptedly 
 to the brain. On this point, however, the weight of evidence will lead 
 us to infer that the vertical distance through which these fibres pass is 
 not very great, and that they are soon brought in connection with the 
 interior vesicular substance. If all the fibres passed uninterruptedly to 
 the brain, we should expect that the cord would increase in thickness by a 
 regular progression upward ; but this, as is shown in Fig. 138, is not the 
 case. Its enlargements correspond to the number of nerve roots given 
 off from the localities in which they occur. Thus, where many nerve 
 roots are required for the upper extremities, and again for the lower ones, 
 we notice such corresponding enlargements. The experiments of Volk- 
 mann show that these dilatations are as much owing to an increase of 
 the vesicular material as to an increased number of fibres. In the view 
 presented in the preceding chapter respecting nerve-arcs and the functions 
 of nerve-cells, we should be led to infer that every centrifugal and cen- 
 tripetal fibre of the cord is brought in connection with such a cell of the 
 gray material, and that it does not extend very far from its point of exit 
 or entrance. 
 
 FUNCTIONS OF THE SPINAL CORD. The determination of the func- 
 Functions of tions of the roots of the spinal nerves by Bell has already 
 the spinal cord. k een referred to as one of the great discoveries of physiol- 
 ogy, and as furnishing a solid foundation for an exact knowledge of the 
 functions of the nervous system. The evidence of the truth of the doc- 
 trine that the anterior roots of these nerves are motor and the posterior 
 Bell's dis- sensory, is complete. Thus, if the anterior root of one of these 
 covery. nerves be divided, all those parts which are supplied by that 
 nerve will exhibit loss of motion, though their sensation is unimpaired ; 
 if the posterior root be divided, the sensibility of the parts is lost, though 
 the power of motion is unaffected. Similar evidence may also be ob- 
 tained by irritating the ends of the divided roots, muscular motion or 
 pain, as the case may be, being correspondingly observed. 
 
 The spinal cord transmits impressions from the periphery to the brain, 
 Lon itudinai an< ^ converse ty enables the brain to bring into action the 
 transmission of motor nerves. Division of it at once causes an interruption 
 ifluences. Q vo i un t ai y mo tion and sensation in those parts supplied 
 by nerves below the place of the operation, the functions of the parts 
 above remaining unimpaired. But, though the influence of the brain in 
 exciting voluntary motion, and its capability of receiving sensations, is 
 thus cut off, the severed portion of the cord still possesses an automatic 
 power. 
 
 This transmission of influences upward or downward is doubtless, to 
 
TEANSVEESE TEANSMISSION. 299 
 
 a considerable degree, accomplished through the vesicular substance, the 
 quality of which, in this respect, has been explained in the preceding 
 chapter. But, besides this, the exterior fibrous structures possess a like 
 function, correspondingly as they are connected with the motor or sen- 
 sory roots of the nerves, the anterior columns being motor, and the pos- 
 terior apparently sensory. 
 
 The spinal cord not only permits the passage of influences in its longi- 
 tudinal, tut also in its transverse direction. This is what Transverse 
 might be anticipated from the structure and functions of the transmission of 
 cells of its gray interior. If the cord be cut half through in u 
 a given place, and again be cut half through on the opposite side, at a 
 little distance above or below, impressions may be conducted through 
 the intermediate portion, the vesicular material being then their only 
 channel. 
 
 In a memoir on the distribution of the fibres of the sensitive roots, and 
 on the transmission of impressions in the spinal cord, Dr. Brown . Se uard 
 Brown-Sequard, referring to the two theories entertained at on the conduc- 
 present 1st. That sensitive impressions reaching the cord tlonofthecord - 
 pass in totality to the brain along the posterior columns ; 2d. That such 
 impressions so arriving pass directly to the central gray substance, which 
 transmits them upward offers reasons for supposing that both these 
 theories, and especially the first, are contradicted by facts. 
 
 It is his opinion that sensitive impressions reaching the cord pass in 
 different directions, some ascending, others descending, but both going in 
 part by the posterior columns, and in part by the posterior gray horns, 
 and perhaps by the lateral columns, to penetrate, after a short distance, 
 the gray central substance by which, or in which, they are transmitted 
 to the brain. 
 
 He also shows that sensitive impressions of one lateral half of the 
 body are transmitted principally in a crossed manner, that is to say, that 
 they follow more particularly the opposite half of the cord to reach the 
 brain ; that the decussation of the conducting elements for sensitive im- 
 pressions is not made, as is commonly said, at the anterior extremity of 
 the pons ; that the gray substance does not possess the property of 
 transmitting sensitive impressions in every direction, as some have sup- 
 posed ; that most, if not all the conducting elements for sensitive im- 
 pressions decussate in the spinal cord, the decussation occurring in part 
 almost immediately on their entry into the cord, but that a few make 
 their decussation at a certain distance above the point of entry, the ma- 
 jority, however, descending in the cord, and making their decussation 
 below the point of entry ; that if there are conducting elements for sen- 
 sitive impressions which ascend throughout the entire length of the cord 
 to make their decussation in the brain, their number must be very small ; 
 
300 REFLEX ACTION. 
 
 and that alterations capable of producing a paralysis of sensibility, and 
 situated upon any point of a lateral half of the cerebro-spinal axis, al- 
 ways produce a paralysis of sensibility on the opposite half of the body, 
 and that there is no difference between the brain and the spinal marrow 
 in this respect. 
 
 Thus constructed, the spinal cord, as we shall presently show from 
 Analoo- with ^ r * Carpenter, evidently agrees with the gangliated ventral 
 ventral cord cord of the articulata, each portion x of it from which a pair of 
 lata ' nerves is given off representing each ganglion of that ventral 
 cord, the difference in the two structures being, that in the spinal col- 
 umn the ganglia are commissured, so as to form, in appearance, one con- 
 tinuous mass, and agreeably to this view of its construction are the 
 circumstances under which its enlargements occur. In those animal 
 forms in which the entire trunk is concerned in locomotion, as in snakes 
 and eels, the cord is nearly cylindrical; but as soon as special members 
 for locomotion are developed, a corresponding increase of diameter is ob- 
 served. Thus, in birds, the ganglionic enlargement corresponds with the 
 region from which the nerves for the wings are given off; but in that tribe, 
 as in the ostrich, the mode of locomotion of which is by the legs rather 
 than by the wings, a corresponding posterior enlargement occurs. The 
 same observations may even be more distinctly made during metamorph- 
 oses ; thus, in frogs, while they are in the tadpole state the spinal cord is 
 cylindrical, but bulging ensues in it anteriorly and posteriorly as soon as 
 the anterior and posterior members are developed. 
 
 The translation of impressions which have been brought along the 
 Reflex action centripetal fibres into motions, the exciting influence of which 
 of the cord. { s conveyed along the centrifugal fibres, includes what is un- 
 derstood as the reflex action of the spinal cord as developed by Dr. Hall. 
 Its essential condition is its independence of the agency of the brain, and 
 therefore unconscious nature. As general examples may be mentioned 
 the movements which occur in swallowing ; for after the food has been 
 carried by voluntary action into the fauces, its passage onward to the 
 stomach is perfectly involuntary. In like manner, the introduction of air 
 into the lungs in ordinary respiration is involuntary ; for though it may 
 be, to a certain extent, under the control of the will, yet that extent is 
 limited, a necessity for the motion presently arising, which soon becomes 
 uncontrollable. The action of the valvular arrangements at the cardiac 
 and pyloric orifices of the stomach, and the constant contraction of the 
 sphincter *ani, are farther illustrations. To these may be added those 
 impulsive movements which we instinctively make on the approach of 
 danger or in the act of falling, and perhaps, too, automatic walking, as 
 we go from place to place in a state of mental abstraction, paying no at- 
 tention to the course we take. 
 
REFLEX ACTION. 
 
 301 
 
 The cord is to be regarded as a longitudinal series of simple automatic 
 nerve arcs, or, as we have termed it, a multiple automatic Automatic ac- 
 arc. Each segment of it has therefore an independent action tionofthecord. 
 of its own, but can conspire with its neighbors or be influenced by the 
 
 brain, by means of its commissural 
 fibres, an arrangement of which num- 
 berless interesting instances might be 
 furnished. The one represented in 
 Fig. 144, which is from the cord of 
 spirostreptus, may, however, suffice: 
 A, under surface of a portion ; B, up- 
 per surface; a, inferior longitudinal 
 fibres ; e, superior longitudinal fibres ; 
 y, fibres of re-enforcement, seen also 
 at b and c\ g, commissural fibres, seen 
 also at d. 
 
 The power which the cord displays 
 in this simple action is most striking- 
 ly seen when it is cut off from its 
 cranial connections. The decapitated 
 frog props himself up stiffly on his 
 legs, and, if his cutaneous surface be 
 irritated, exhibits antagonizing mo- 
 tions ; such motions are all of the reflex character, and are commonly 
 much more strikingly seen in cold than in warm-blooded animals ; but 
 even in man precisely the same results are witnessed during periods of 
 the suspension of the activity of the brain, as, when the palm of the hand 
 of a sleeping child is touched with the finger, the finger is at once grasped. 
 As above stated, this reflex function of the cord is therefore independ- 
 ent of the brain, though the brain can control it, and this Reflex action 
 the more perfectly the higher the organization of the animal, independent of 
 Breathing can go on, whether we pay attention to it or not, * 
 but we can arrest it if we choose for a time ; and since in man this in- 
 troduction of air is incidentally used for very refined purposes, by volun- 
 tary exertion we moderate or regulate it, as in the production of musical 
 sounds in singing or of articulate sounds in speech. 
 
 In a general way, there is not much difficulty in distinguishing be- 
 tween simple actions of the cord and those in which the brain Distinction be- 
 is participating. In the former, no weariness or fatigue is ^cerebral 
 ever experienced ; in the latter it is ; and perhaps, even in action, 
 these last, involving voluntary muscular action, though the control is to 
 be attributed to the brain, the source of the force is in the cord. 
 
 These normal phenomena which the cord displays become greatly ex- 
 
 Portion of cord of spirostreptus. 
 
302 [RELATIONS OF THE SPINAL CORD AND BRAIN. N 
 
 Increase of aggerated in certain conditions of disease, as, for example, in 
 spinal action, tetanus, in which the slightest peripheral irritation may be 
 followed by violent convulsive movement, or the same occurs by the 
 agency of powerful poisonous substances, as strychnine. In these cases 
 the action may be either limited simply to the cord, as in the tetanus 
 brought on by opium in frogs, or the brain may be involved in it, as in 
 cases of hydrophobia, in which the sound or sight of water, operating 
 through the cerebrum, will produce spasmodic convulsions. 
 
 From the facts presented by the lower animals, it may be inferred that 
 the spinal cord does not act as a single organ, but rather should be re- 
 garded as a collection of ganglia, special duties being discharged by spe- 
 cial parts of it. 
 
 With respect to the commissural action of the spinal cord, reference has 
 Connection of a ^ rea ^7 ^ een ma de to the structural connection between the 
 the cord and cord and the nervous regions above it, and in referring to the 
 old anatomical doctrine that each of the spinal nerves is con- 
 nected by continuous fibres with the brain, due weight has been given 
 to the fact that the cord does not increase in thickness as it approaches 
 the brain, but that its bulgings correspond to the regions from which it is 
 necessary that an unusual supply of nerves should be given off. The 
 force of this argument is, however, considerably diminished when we 
 recollect that the nerve-tubes are by no means of uniform diameter, but 
 are doubly conical in shape. Even, therefore, with a diminished diame- 
 ter of the spinal cord, there might be an upward continuation of spinal 
 fibres, the diameter of which is becoming less and less ; and this seems 
 to be rendered more likely from the analogy of the structure of the ven- 
 tral cord of the articulata, in which fibres are sent to the cephalic gan- 
 glia for the purpose of establishing a communication between them and 
 the roots of the nerves. But, however that may be, there can be no 
 question of the influence of the brain over spinal action, and this, of course, 
 implies structural connection of some kind an intercommunication 
 which, if it does not take place solely through the white columns, must 
 take place through the gray material. It is, however, important to ob- 
 serve that the gray material has no direct communication with that of 
 the cerebrum, but, passing through the optic thalamus, ends in the cor- 
 pus striatum, extending therefore in one continued mass through the cord, 
 and terminating in that ganglionic organ. By one or both of these chan- 
 nels, white or gray, the impressions which are made upon the spinal 
 sensitive nerves are presented to the brain, and in a similar manner the 
 influences which produce voluntary motions are transmitted down. A 
 Effect of le sect ^ on ^ an 7 P art ^ tne s P ma l cor< l at once incapacitates the 
 sionsofthe will from acting upon the parts beyond, the motions of which 
 cord< become therefore purely automatic, though the parts above still 
 
FUNCTIONS OF THE SPINAL CORD. 303 
 
 display their customary phenomena. These effects are sometimes in- 
 structively witnessed in man when lesions of the cord have occurred 
 through disease. 
 
 If the view that has been presented respecting the continuation of 
 fibres from the cord to the brain be correct, these fibres dis- ,, . 
 
 1 Motor and sen- 
 
 charge a commissural duty. This would lead us to sup- sory tracts of 
 
 pose that there is a correspondence between the functions of { 
 the columns of the cord and those of the roots of the spinal nerves, the 
 anterior columns being motiferous, or in unison with the motor root of 
 the nerves, the posterior being sensiferous, or in unison with the sensory 
 root of the nerves. Agreeably to this, if the anterior columns be irri- 
 tated, motions are excited in all those parts which are supplied with 
 nerves beyond the irritated point ; and if the posterior columns be irri- 
 tated, in like manner pain is experienced. In this instance, however, a 
 certain amount of motion is occasionally observed, but this has common- 
 ly been explained by referring it to reflexion within the cord. It has 
 also been observed, as strengthening these views, that if the posterior 
 columns be irritated after complete section of the cord, the result will de- 
 pend on which of the cut portions be disturbed ; if it be the lower, there 
 will be no effect. An examination, under the same circumstances, of the 
 anterior columns, demonstrates that, if the upper section be irritated, there 
 is no effect produced ; if the lower, there are convulsive movements of 
 the parts supplied with nerves beyond. 
 
 From these results we should infer that the physiological functions of 
 the anterior and posterior roots of the spinal nerves are participated in 
 by the anterior and posterior columns of the cord, and might therefore 
 expect that those functions would be continued in the higher distribu- 
 tion of the columns above the medulla oblongata. 
 
 From the point of view under which we have thus presented it, the 
 action of the spinal cord is therefore simple, or it is disturb- General funo 
 ed by the agency of the brain ; in the first case it offers it- tions of the 
 self purely as an automatic instrument ; in the latter, its com- 
 missural connections with the brain make a compound apparatus. The 
 former state is closely represented in the construction of the amphioxus, 
 the nervous system of which has no rudiment of a cerebrum or cerebel- 
 lum ; in this animal, therefore, since also the sensory ganglia are merely 
 in a rudimentary state, the mode of life must be purely mechanical, just 
 as it is with an artificial automaton, of which, when a given spring is 
 touched, a given motion is made. Even among the highest vertebrated 
 animals, man himself at the periodic times of quiescence of the cerebrum, 
 as in sleep, when the cerebral influence over other portions is, to a certain 
 extent, suspended, an approach to a similar condition occurs ; but in 
 periods of activity of the cerebrum, it can hold the spinal cord in check, 
 
304 THE MEDULLA OBLONGATA. 
 
 controlling, and in some cases arresting its action, and this is done through 
 influences propagated along the tubular structures of the posterior and an- 
 terior columns, which therefore are to be regarded, in this respect, as 
 commissures to the brain. 
 
 OF THE MEDULLA OBLONGATA. 
 
 The medulla oblongata is a conical body, lying between the spinal cord 
 Limits of the an< ^ ^ e brain. ^ * s generally understood to be bounded at 
 medulla obion- its upper portion by the pons varolii, but this is not a true 
 limit, since its structure extends through the pons varolii to 
 the crura of the brain. There is the same indefiniteness of limit as re- 
 spects its lower boundary, which is generally said to be marked by some 
 decussating fibres which appear on its front. Like the spinal cord, it 
 Its subdivis- has an anterior and posterior fissure, which divide it into two 
 ions. symmetrical lateral halves ; the former is a continuation of 
 
 the anterior spinal fissure, the latter of the posterior, and ends in the ca- 
 lamus scriptorius above. The lateral halves thus produced are marked 
 by three grooves, producing four eminences, which pass under the follow- 
 ing names : 1st. The anterior pyramids ; 2d. The olivary bodies ; 3d. 
 The restiform bodies ; 4th. The posterior pyramids. The anterior fis- 
 sure is crossed about an inch below the pons varolii by decussating fibres, 
 and hence injuries on one side of the brain produce nervous effects on the 
 opposite side of the body. 
 
 First. The anterior pyramids consist of white fibres originating near 
 The anterior tne decussating fasciculi. They have a compound structure, 
 pyramids. f or each contains fibres arising from the inner side of the op- 
 posite anterior column of the cord, and also fibres from its own side : 
 they pass through the pons varolii into the crus cerebri. From these 
 pyramids curved fibres pass round the olivary body, and are lost in the 
 restiform. They are called arciform fibres. 
 
 Second. The corpora olivaria receive their name from their olive shape. 
 The olivary They are separated by a groove from the preceding in front, 
 bodies. an( j by another groove from the restiform bodies behind. Ex- 
 ternally, they are formed of white tubular tissue, which incloses a vesic- 
 ular mass, the olivary ganglion, which connects with the vesicular struc- 
 ture of the pons above, and that of the cord below. The fibres of these 
 ganglia are called the olivary tracts. They are continuous with the cen- 
 tral part of the medulla oblongata, passing behind the pyramids, extend- 
 ing upward along the posterior part of the crura cerebri to the optic thai- 
 ami and tubercula quadrigemina. The olivary bodies exist only in man 
 and the monkey tribe. 
 
 Third. The restiform bodies are separated from the olivary by a 
 groove. They are continuous with the posterior and antero-lateral col- 
 
THE MEDULLA OBLOXGATA. 
 
 145. 
 
 umns of the cord. Ascending, they enter the cerebellum, and The restifbrm 
 are continuous with the inner part of its cms. They there- k die s- 
 fore are a tract of communication from the spinal cord to the cerebellum. 
 They each inclose a gray nucleus, which is the ganglion of the pneumo- 
 gastric nerves, and of some of the roots of the glosso-pharyngeal. 
 
 Fourth. The posterior pyramids are doubtfully marked off from the 
 restiform bodies in front, and are separated from each other The posterior 
 by the posterior fissure. Superiorly, their fibres are contin- pyramid*. 
 uous with the sensory tract of the crura cerebri : their gray nuclei are 
 the ganglia of the auditory nerves. 
 
 The structure of the medulla oblongata is exempli- 
 fied in the annexed figures. 
 
 Fig. 145: 1, chiasm of the optic nerves; 2, crus cere- 
 bri ; 3, tuber cinereum ; 4, corpora albicantia ; 5, locus 
 .perforatus ; 6, pons varolii ; 7, section of the middle 
 peduncle of cerebellum ; 8, transverse fissure, separa- 
 ting the medulla from the pons ; 9, first enlargement 
 of the cord, or medulla oblongata ; 10, anterior pyra- 
 mid; 11, olivary body; 12, anterior portion of resti- 
 form body ; 13, neck of the medulla oblongata; from 
 16 downward is the anterior median fissure; from 17 
 downward, the anterior lateral furrow. 
 
 Fig. 146: 1, section of optic 
 tract; 2, tubercula quadrigemina ; 
 3, triangular band ; 4, section of crus cerebelli ; 5, 
 medulla oblongata ; 6, anterior floor of the fourth ven- 
 tricle ; 7, median fissure of the fourth ventricle, aid- 
 ing to form the calamus scriptorius ; 8, mammillary 
 swelling near the nib of the pen ; 9, posterior portion 
 of the restiform body; from 12 down- 
 ward, posterior median fissure ; from 
 13 downward, lateral furrow ; from 14 
 downward, posterior furrow. 
 
 T-T. * i / ^ t> , i 
 
 Juig. 147: o, anterior column ot the 
 cord, divided superiorly into two portions, of which the 
 most internal one contributes to the formation of the cor- 
 responding pyramid; 7, middle or lateral column, di- 
 vided superiorly into three or four portions, decussating 
 with as many portions of the column of the opposite side, 
 the decussation taking place both laterally and antero- 
 posteriorly : it is the origin of the internal two thirds 
 of the pyramid ; 8, 8, pyramids ; 9, white fibres of the 
 pyramid, traversing the pons, and continuing to the crus 
 'U 
 
 Fig. 140. 
 
 Front of medulla ob- 
 longata. 
 
 Fig. 147. 
 
 Posterior view of medulla 
 
306 
 
 THE MEDULLA OBLONGATA. 
 
 Fig. 148. 
 
 Posterior view of medulla oblongata. 
 
 cerebri ; 10, superficial section of the trans- 
 verse fibres of the pons ; 11, deeper section 
 of the transverse fibres of the pons ; 12, oli- 
 vary body ; 13, right olivary body, brought 
 into view by removal of the corresponding 
 pyramid. 
 
 Fig. 148 is a posterior view of the me- 
 dulla oblongata : p, p, posterior pyramids, 
 separated by a posterior fissure ; r, r, resti- 
 form bodies, composed of, <?, c, posterior col- 
 umns, and </, d, part of antero-lateral col- 
 umns of the cord ; <2, #, olivary columns, as 
 seen on the floor of the fourth ventricle, sep- 
 arated by s, the median fissure, and crossed 
 by some fibres of origin of, n, ft, the seventh 
 pair of nerves. 
 
 FUNCTIONS OF THE MEDULLA OBLONGATA. 
 
 Viewed as a superposed continuation of the spinal cord, the medulla 
 Functions of oblongata is the tract of communication between that organ 
 
 the medulla : an( j the brain : the anterior pyramids and olivary tracts con- 
 it is a tract of . , .... J , 
 communica- vey motor influences, and the resmorm tracts and posterior 
 
 tion - pyramids sensations. By experiments similar to those which 
 
 have been performed upon the cord, these conclusions have been main- 
 tained. 
 
 But, besides this function of conduction, the medulla oblongata dis- 
 charges a most important duty as a nervous centre ; on it depend respi- 
 ration and deglutition. The brain may be wholly removed above, and 
 the spinal cord below, as far as the origin of the phrenic nerve, without 
 death necessarily ensuing, but on wounding the medulla oblongata, the 
 muscular movements necessary for the introduction of air are necessarily 
 stopped. 
 
 Moreover, the medulla oblongata exhibits the property of reflex action. 
 Its relations to So far as the function of respiration is concerned, its chief 
 respiration. centripetal nerve is the pneumogastric, but the power which 
 it possesses is participated in by many others, perhaps by reason of the 
 venous condition into which the blood is brought from want of proper 
 aeration. The violent respiratory movements by the sudden application 
 of cold to the skin, the shower-bath, or dashing cold water on the face, 
 are converted by it into respiratory muscular motions. From it also 
 arise the movements required in the act of deglutition. 
 
 Under this view of the functions of the medulla oblongata, it is to be 
 regarded as an exclusively automatic instrument, which can continue its 
 
THE PONS VAEOLII. 307 
 
 operation after the excision of the brain. As with the spinal cord, so 
 with it : its simple action may continue though its commissural action 
 has ceased, and this either through conditions of disease or by the ad- 
 ministration of drugs. In lesions of the brain respiration may still con- 
 tinue, as it may also when sensation and voluntary motion have been ar- 
 rested by the breathing of chloroform. 
 
 OF THE PONS VAKOLH. 
 
 The pons varolii consists of a loop of fibres passing from one crus 
 cerebelli to the other, around the tracts of communication structure of the 
 between the cord and the brain. As shown in Fig. 145, P ns varolii. 
 they do not form a continuous superficial commissure, but, at a certain 
 distance below, interlace with the fibres of the pyramids ; moreover, 
 among their deeper fibres gray vesicular matter occurs. That they con- 
 stitute mainly a commissure for the cerebellum is apparent from the cir- 
 cumstance that, in those animals which have the median cerebellar lobe 
 only, there is no p'ons, and in other cases its relative magnitude is in 
 proportion to the size of the cerebellar hemispheres. 
 
 FUNCTIONS OF THE PONS VAKOLH. 
 
 The functions of the pons varolii are therefore twofold: it acts as a 
 conductor, and also as a nerve centre. In the first respect, it Functions of 
 is the channel from the spinal column to the cerebrum and the P ns - 
 cerebellum, and also between the cerebellar halves, and experiments upon 
 it, in giving rise to sensations and motions, are in conformity with what 
 we should anticipate from the structure and functions of the spinal cord. 
 
 In the second respect, as a nervous centre, it has been stated that, when 
 the cerebrum and cerebellum are removed, but the pons left untouched, 
 an animal gives tokens of sensation when pinched or irritated, and like- 
 wise executes motions which have an object ; these, however, were no 
 longer observed after the removal of the pons. 
 
 We have had repeated occasion already to mention that the surest 
 guide which can be followed in interpretations of the func- 
 
 . (. , , . T ^ Dr. Carpen- 
 
 tions of the nervous system is comparative physiology. Our te r's views of 
 views of the action of the spinal cord, medulla oblongata, J^^H!" 
 and even portions above, hereafter to be described, will be nai cord of ver- 
 rendered clear by a knowledge of the structure and func- jeentrai d 
 tions of the ventral cord of the articulata, the analogy of cord of articu- 
 which to the parts we have had under consideration was { 
 first correctly pointed out by Dr. Carpenter. I therefore transcribe from 
 his General and Comparative Physiology the following paragraphs, which 
 present his views with perspicuity. 
 
 " The plan on which the nervous system is distributed in the sub- 
 
308 
 
 FUNCTIONS OF THE CORD. 
 
 Fig. 149. 
 
 kingdom articulata exhibits a remarkable uniformity throughout the 
 whole series, while its character gradually becomes more elevated as we 
 trace it from the lowest to the highest diyisions of the group. It usu- 
 ally consists of a double nervous cord studded .with ganglia at intervals, 
 and the more alike the different segments, the more equal are these gan- 
 glia. The two filaments of the nervous cord are sometimes 
 at a considerable distance from one another, and the ganglia 
 are distinct, but more frequently they are in close apposition, 
 and their ganglia appear single and common to both. That 
 which may seem as the typical conformation of the nervous 
 system of this group is seen in the ganglionic cord of scolo- 
 pendra, or in that of the larvae of most insects, such as that 
 of the sphinx ligustri, Fig. 149. Here we see the nervous 
 cord nearly uniform throughout, its two halves being sepa- 
 rated, however, in the anterior portion of the body. The 
 ganglia are disposed at tolerably regular intervals, are simi- 
 lar to each other in size (with the exception of the last, 
 which is formed by the coalescence of two), and every one 
 supplies its own segment, and has little connection with any 
 other. The two filaments of the cord diverge behind the 
 head to inclose the oesophagus, above which we find a pair 
 of ganglia that receive the nerves of the eyes and antennas. 
 We shall find that in the higher classes the inequality in the 
 formation and office of the different segments, and the in- 
 creased powers, of special sensation, involve a considerable 
 change in the nervous system, which is concentrated about 
 the head and thorax. In the simplest vermiform tribes, on 
 the other hand, we lose all trace of separate ganglia, the nervous cord 
 passing without evident enlargement from one extremity to the other. 
 Whatever may be the degree of multiplication of the ganglia of the 
 trunk, they seem but repetitions of one another, the functions of each 
 segment being the same with those of the rest. The cephalic ganglia, 
 however, are always larger and more important. They are connected 
 with the organs of special sense, and they evidently possess a power of 
 directing and controlling the movements of the entire body, while the 
 power of each ganglion of the trunk is confined to its own segment. 
 
 " The longitudinal ganglionic cord of the articulata occupies a position 
 which seems at first sight altogether different from that of the nervous 
 system of vertebrated animals, being found in the neighborhood of the 
 ventral or inferior surface of their bodies, instead of lying just beneath 
 their dorsal or upper surface. From the history of their development, 
 however, and from some other considerations, it has been suggested that 
 the whole body of these animals may be considered as in an inverted po- 
 
 sphinx Hgustri. 
 
FUNCTIONS OF THE CORD. 309 
 
 t 
 
 sition, the part in which the segmentation is first distinguished in insects 
 being the equivalent of the dorsal region in vertebrata, and that over 
 which the germinal membrane is last to close in, being homologous with 
 the ventral region. This view applies also to the position of the dorsal 
 vessel, which would then be on the ventral side of the axis, as in verte- 
 brata. Eegarded under this aspect, the longitudinal nervous tract of ar- 
 ticulata corresponds with the spinal cord of vertebrated animals in posi- 
 tion, as we shall find it does in function. 
 
 " When the structure of the chain of ganglia is more particularly in- 
 quired into, it is found to consist of two distinct tracts, one of which is 
 composed of nerve fibres only, and passes backward from the cephalic 
 ganglia over the surface of all the ganglia of the trunk, giving off 
 branches to the nerves that proceed from them, while the other includes 
 the ganglia themselves. Hence, as in the mollusca, every part of the 
 body has two sets of nervous connections, one with the cephalic ganglia, 
 and the other with the ganglion of its own segment. Impressions made 
 upon the afferent fibres which proceed from any part of the body to the 
 cephalic ganglia become sensations when conveyed to the latter, while in 
 respondence to these, the consensual impulses, operating through the ce- 
 phalic ganglia, harmonize and direct the general movements of the body 
 by means of the efferent nerves proceeding from them. For the purely 
 reflex operations, on the other hand, the ganglia of the ventral cord are 
 sufficient, each one ministering to the actions of its own segment, and to 
 a certain extent, also, to those of other segments. It has been ascertained 
 by t"he careful dissections of Mr. Newport, to whom we owe all our most 
 accurate knowledge of the nervous system in articulated animals, that of 
 the fibres constituting the roots by which the nerves are implanted in 
 the ganglia, some pass into the vesicular matter of the ganglion, and, after 
 coming into relation with its vesicular substance, pass out again on the 
 same side (Fig. 150, /*, &), while a second set, after traversing the vesic- 
 ular matter, pass out by the trunks proceeding from the opposite side of 
 the same ganglion, and a third set run along the portion of the cord which 
 
 connects the ganglia of different segments, 
 and enter the nervous trunks that issue from 
 them at a distance of one or more ganglia 
 above or below. 
 
 "Fig. 150, from ganglionic tract of poly- 
 desmus maculatus. &, interganglionic cord ; 
 c, anterior nerves ; d, posterior ; f, Jc, fibres 
 of reflex action ; </, A, commissural fibres ; i, 
 longitudinal fibres, softened and enlarged as 
 they pass through the ganglionic matter. 
 Ganglion of poiydesmus macuiatna. " Thus it appears that an imrrassion con- 
 
310 FUNCTIONS OF THE CORD. 
 
 veyed by an afferent fibre to any ganglion may excite motion in the mus- 
 cles of the same side of its own segment, or in those of the opposite side, 
 or in those of segments at a greater or less distance, according to the 
 point at which the efferent fibres leave the cord ; and as the function of 
 these ganglia is altogether related to the locomotive actions of the seg- 
 ments, we may regard them as so many repetitions of the pedal ganglia 
 of the mollusca, their multiplication being in precise accordance with that 
 of the instruments which they supply. 
 
 " The general conformation of articulated animals, and the arrangement 
 of the parts of their nervous systems, render them peculiarly favorable 
 subjects for the study of the reflex actions, some of the principal phe- 
 nomena of which will now be described. The mantis religiosa custom- 
 arily places itself in a curious position, especially when threatened or at- 
 tacked, resting on its two posterior pairs of legs, and elevating its thorax 
 with the anterior pair, which are armed with powerful claws ; now if the 
 anterior segment of the thorax, with its attached members, be removed, 
 the posterior part of the body will still remain balanced upon the four 
 legs which belong to it, resisting any attempts to overthrow it, recover- 
 ing its position when disturbed, and performing the same agitated move- 
 ments of the wings and elytra as when the unmutilated insect is irritated ; 
 on the other hand, the detached portion of the thorax, which contains a 
 ganglion, will, when separated from the head, set in motion its long arms, 
 and impress their hooks on the fingers which hold it. If the head of a 
 centipede be cut off while it is in motion, the body will continue to move 
 onward by the action of the legs, and the same will take place in the 
 separate parts if the body be divided into several distinct portions. 
 After these actions have come to an end, they may be excited again by 
 irritating any part of the nervous centres, or the cut extremity of the 
 nervous cord. The body is moved forward by the regular and successive 
 action of the legs, as in the natural state, but its movements are always 
 forward, never backward, and are only directed to one side when the for- 
 ward movement is checked by an interposed obstacle. Hence, though 
 they might seem to indicate consciousness and a guiding will, they do 
 not so in reality, for they are carried on, as it were, mechanically, and 
 show no direction of object, no avoidance of danger. If the body be op- 
 posed in its progress by an obstacle of not more than half of its own 
 height, it mounts over it, and moves directly onward as. in its natural 
 state ; but if the obstacle be equal to its own height, its progress is arrest- 
 ed, and the cut extremity of the body remains forced up against the op- 
 posing substance, the legs still continuing to move. If, again, the nerv- 
 ous cord of a centipede be divided in the middle of the trunk, so that the 
 hinder legs are cut off from connection with the cephalic ganglia, they 
 will continue to move, but not in harmony with those of the fore part of* 
 
FUNCTIONS OF THE CORD. 311 
 
 the body, being completely paralyzed, so far as the animal's controlling 
 power is concerned, though still capable of performing reflex movements 
 by the influence of their own ganglia, which may thus continue to propel 
 the body in opposition to the determinations of the animal itself. The 
 case is still more remarkable when the nervous cord is not merely di- 
 vided, but a portion of it is entirely removed from the middle of the trunk ; 
 for the anterior legs still remain obedient to the animal's control, the legs 
 of the segments from which the nervous cord has been removed are alto- 
 gether motionless, while those of the posterior segments continue to act 
 through the reflex powers of their own ganglia, in a manner which shows 
 that the animal has no power of checking or directing them. 
 
 " The stimulus to the reflex movements of the legs in the foregoing 
 cases appears to be given by the contact of the extremities with the solid 
 surface on which they rest. In other instances the appropriate impression 
 can only be made by the contact of liquid. Thus a dytiscus (a kind of 
 water-beetle), having had its cephalic ganglia removed, remained motion- 
 less as long as it rested upon a dry surface, but when cast into water it 
 executed the usual swimming motions with great energy and rapidity, 
 striking all its comrades to one side by its violence, and persisting in 
 these for more than half an hour. Other movements again may be ex- 
 cited through the respiratory surface. Thus, if the head of a centipede 
 be cut off, and, while it remains at rest, some irritating vapor (such as 
 that of ammonia or muriatic acid) be caused to enter the air-tubes on one 
 side of the trunk, the body will be immediately bent in the opposite direc- 
 tion, so as to withdraw itself as much as possible from the influence of 
 the vapor ; if the same irritation be then applied to the other side, the re- 
 verse movement will take place, and the body may be caused to bend in 
 two or three different curves by bringing the irritating vapor into the 
 neighborhood of different parts of either side. This movement is evi- 
 dently a reflex one, and serves to withdraw the entrances of the air-tubes 
 from the source of irritation, in the same manner as the acts of coughing 
 and sneezing in the higher animals cause the expulsion from the air-pas- 
 sages of solid, liquid, or gaseous irritating matters which may have found 
 their way into them. 
 
 "From these and similar facts, it appears that the ordinary movements 
 of the legs and wings of articulated animals are of a reflex nature, and 
 may be effected solely through the ganglia with which these organs are 
 severally connected ; while, in the perfect being, they are harmonized, 
 controlled, and directed by impulses which act through the cephalic gan- 
 glia, and the nerves proceeding from them. There is strong reaeon to 
 believe that the operations to which these ganglia are subservient are al- 
 most entirely of a consensual nature, being immediately prompted by 
 sensations, chiefly those of sight, and seldom or never by any processes 
 
312 FUNCTIONS OF THE CORD. 
 
 of a truly rational character. When we attentively consider the habits 
 of these animals, we find that their actions, though evidently directed to 
 the attainment of certain ends, are very far from being of the same spon- 
 taneous nature, or from possessing the same designed adaptation of means 
 to ends as those performed by ourselves, or by the more intelligent ver- 
 tebrata under like circumstances. We judge of this by their unvarying 
 character, the different individuals of the same species executing pre- 
 cisely the same movements when the circumstances are the same, and 
 by the very elaborate nature of the mental emotions which would be re- 
 quired in many instances to arrive at the same results by an effort of 
 reason. Of such we can not have a more remarkable example than is 
 to be found in the operations of bees, wasps, and other social insects, 
 which construct habitations for themselves upon a plan which the most 
 enlightened human intelligence, working according to the most refined 
 geometrical principles, could not surpass, but which yet do so without 
 education communicated by their parents or progressive attempts of their 
 own, and with no trace of hesitation, confusion, or interruption, the dif- 
 ferent individuals of the community all laboring effectively to one pur- 
 pose, because their automatic impulses (producing what are usually term- 
 ed instinctive actions) are all of the same nature. 
 
 " Not only are the locomotive ganglia multiplied in accordance with the 
 repetition of segments and members, but the respiratory ganglia are mul- 
 tiplied in like manner in accordance with a repetition of respiratory or- 
 gans. The respiratory division of the nervous system consists of a chain 
 of minute ganglia lying upon the larger cord, and sending off its delicate 
 nerves between those that proceed from the ganglia of the latter, as seen 
 in Fig. 151. These respiratory ganglia and their nerves are best seen in 
 the thoracic portion of the cord, where the cords of communication be- 
 tween the pedal ganglia diverge or separate from one another ; and this 
 is particularly the case in the pupa state, when the whole cord is being 
 shortened and their divergence is increased. The thoracic portion of the 
 cord is shown in Fig. 152, B, which represents the second, third, and 
 fourth double ganglia of the ventral cord, the cords of connection between 
 them here widely diverging laterally, and the small respiratory ganglia 
 which are connected with each other by delicate filaments that pass over 
 Fig. 151. the ganglia of the ventral cord, and which send off lateral 
 branches that are distributed to the air-tubes and other 
 parts of the respiratory apparatus, and communicate with 
 those of the other system." 
 
 Illustrations of the nervous system of the articulata. 
 Fig. 151, A, single ganglion of centipede, much enlarged, 
 showing the distinctness of the purely fibrous tract, b, from 
 
 Ganglion of centi- ,-\ . . -, -y-j. ., _,- -pj . / .1 
 
 pede. the ganghonic column, a. Fig. 152, B, portion of the 
 
THE BRAIN. 
 
 313 
 
 Fig. 152. 'double cord from the thorax of 
 
 the pupa of sphinx ligustri, 
 showing the respiratory gan- 
 glia and nerves between the 
 ganglia 2, 3, 4, and the sepa- 
 rated cords of the locomotive 
 system. Fig. 153, C, view 
 of the two systems combined, 
 showing their arrangement in 
 the larva : , ganglion of the 
 ventral cord ; , fibrous tract 
 passing over it ; c, <?, respira- 
 tory system of nerves, distinct 
 from both. 
 
 Having thus presented the views of Dr. Carpen- 
 ter respecting the analogy between the ventral cord 
 of the articulata and the spinal cord of the verte- 
 brata, I should next continue the explanations 
 which this pjiysiologist has offered of the connec- 
 tions and relations of the sensory ganglia ; but this 
 can not be conveniently done until we have passed 
 through the description of the organs at the base of 
 the brain. 
 
 Thoracic portion of cord of 
 sphinx ligustri. 
 
 CHAPTER XVI. 
 
 OF THE BRAIN. 
 
 The Brain: its Structure. Its Motor and Sensory Parts, Hemispheres, and Commissures. 
 The Sensorium. Variations of the Hemispheres in Size and Weight. Instrumental Nature 
 of Cerebrum. The Cerebellum: its Structure and Functions. Co-ordinates muscular Motions. 
 Connection with Amativeness. Phrenology. Conditions of Action of Brain. 
 
 Symmetrical Doubleness of the Brain. Function of each Half, and of both conjointly. Independ- 
 ence and Insubordination of each Hemisphere. Double Thought. Alternate Thought. Senti- 
 ment of Pre-existence. Loss of Perception of Time. 
 
 THE cerebrum and cerebellum, being organs additional to the spinal 
 cord, and developed, as has been shown in the last chapter, n 
 
 . \ ' . ' General view 
 
 upon it, the cord being able to discharge its own functions of structure of 
 independently of them, we shall find it at once the most brain> 
 natural and most commodious method to consider their structures as 
 arising out of its structure, and their functions as having relation to its 
 functions. 
 
 A general idea of the structure of the brain as an appendage to the 
 
314 / THE BRAIN. 
 
 spinal cord may be gathered by considering that a bifurcation of the 
 fibres takes place in the medulla oblongata, and upon one of the re- 
 sulting bundles, the eras cerebri, the cerebrum is formed, on the other 
 the cerebellum. The crus cerebri is composed of three strands : an infe- 
 rior, the fibres of which have come from the anterior pyramids, and in 
 part from the olivary bodies. This strand ends in the corpus striatum, 
 its fibres not, however, blending abruptly with the vesicular matter, but 
 passing into it in bundles. It is essentially motor. A superior, which 
 is derived from the posterior pyramids, and terminates in the thalamus. 
 It is essentially sensory. Between these, constituting the third portion 
 strand it can scarcely with propriety be called is a layer of dark vesic- 
 ular material, the locus niger. It is to be understood that the motor 
 strands of the opposite sides decussate in the medulla oblongata ; the 
 sensory strands decussate in the mesocephalon. 
 
 The other bundle, arising in the original bifurcation, assumes the des- 
 Formation of ignation of crus cerebelli. On it the cerebellum is devel- 
 the cerebellum. O p Q ^ t It consists essentially of fibres from the restiform 
 bodies, re-enforced by others which have come from the anterior pyramids 
 under the name of arciform fibres. These together make their way to 
 the interior ganglion of the cerebellum, the corpus dentatum, and there 
 they end. But the crus cerebelli contains likewise two other great 
 strands : an inferior, which constitutes the commissure of the two cere- 
 bellar hemispheres, and which, running round the entire prolongations of 
 the spinal cord, forms the pons varolii ; a superior, the processus cere- 
 belli ad testes, which unites the cerebellum and cerebrum. 
 
 Of the portions of the spinal cord on which the cerebrum is to be de- 
 veloped, those which are sensory end in the optic thalamus, those which 
 are motor in the corpus striatum. The thalamus and striatum of each 
 side may be regarded as one compound ganglion, since, like the columns 
 of the cord, they are united by a gray and a white commissure. Of the 
 portions on which the cerebellum is to be developed, the termination is 
 in the central ganglion of the cerebellum, the corpus dentatum. 
 
 At the place of bifurcation of the constituent strands of the crus cere- 
 bri and crus cerebelli from each other in the medulla oblon- 
 
 " ar} y ' gata, there is intercalated or included a ganglion, which, with 
 its apparatus, constitutes the olivary body, the fibres of which make 
 their way upward between the two preceding bundles, and, having bi- 
 furcated, one branch goes to the quadrigemina and the other to the op- 
 tic thalamus, the latter constituting, as has been said, a part of the 
 crus cerebri. The seat of power of the medulla oblongata is in this 
 ganglion. 
 
 Such being the anatomical construction of the crus cerebri, it may be 
 physiologically regarded as a compound- strand, the anterior portion of 
 
THE BRAIN. 315 
 
 which is motor, the posterior sensory ; and between these a Nerves of the 
 dark vesicular deposit, the locus niger, which is continuous ^^^ifdsre^ 
 between the vesicular matter in the spinal cord and that of spectiveiy. 
 the thalamus and corpus striatum. From the lowest extremity of the 
 cord to these great ganglia there is, therefore, an unbroken vesicular 
 channel. In its progress onward to the corpus striatum, the anterior 
 strand yields roots of the spinal accessory, hypoglossal, facial, abducens, 
 the small root of the fifth, the trochlearis, and the oculo-motor nerves. 
 If there were no other proof of the motor character of this strand, the 
 motor property of all these nerves would be sufficient to determine it. 
 In like manner, the posterior strand yields the pneumogastric, the glosso- 
 pharyngeal, and the sensory root of the fifth, from the sensory functions 
 of which its sensory character is established. 
 
 The layer of vesicular matter which is found upon the cerebral convo- 
 lutions, and which is doubtless the seat of the higher intel- Relation of the 
 lectual qualities, has therefore no communication with the ^roftoe hem- 
 vesicular matter of the spinal axis, by contact or continua- ispheres. 
 tion, but only through the intervention of fibres which radiate upon it in 
 all directions from the thalamus and striatum, or rather through some 
 which radiate from the great sensory centre, the thalamus, to the periph- 
 ery of the cerebrum, and others which converge from that periphery to 
 the great motor centre, the striatum. If the diameter of these fibres be 
 assumed to be 10 ooo of an inch, there must be many millions of them 
 in the aggregate. The vesicular matter of the hemisphere is arranged 
 on the superficies instead of centrally, on account of the necessities of 
 their structure and condition of activity, for thereby a great surface is 
 obtained, which is further increased by the artifice of convolutions, a ve- 
 sicular surface which, counting in that of the cerebellum, has been esti- 
 mated at 670 square inches, and blood can be copiously supplied and 
 freely removed. 
 
 But the thalamus and striatum are only two of a chain of ganglia be- 
 neath the cerebral hemispheres. Anteriorly we find the ol- Gapglia at the 
 factive ganglia, or bulbs of the olfactory nerves, which are base of the 
 seated upon peduncles, though their character is manifest from 
 the gray matter they contain. Behind these are the tubercula quadri- 
 gemina, to which the optic nerves run, and which are therefore their gan- 
 glionic centres. What answers to the auditory ganglion is lodged at a 
 distance back, at the fourth ventricle, and the gustatory ganglion is in 
 the medulla oblongata. These are the ganglia of special sense, and to 
 be regarded as subordinate to the thalamus, 'which is their common 
 register. 
 
 All these parts are commissured with one another, and with their fel- 
 lows of the opposite half of the brain. Indeed, so likewise are all its 
 
316 
 
 THE BRAIN. 
 
 Commissures of parts, the different cerebral lobes, the opposite hemispheres, 
 the brain. adjacent and distant convolutions, the cerebrum with the 
 cerebellum. Hence arises a structure of extreme complexity. Among 
 the commissural apparatus may be more particularly mentioned the cor- 
 pus callosum, the fornix, the anterior, the posterior, the soft, and the su- 
 perior longitudinal commissures. 
 
 For the sake of a clear conception of the structure of the brain, so far 
 Aspects of the as is required for physiological purposes, the annexed repre- 
 brain. sentations of its superficial aspects are given. These are a 
 
 preparation for the diagrammatic sketches which follow, and which ena- 
 ble us to understand the relation and dependence of the more prominent 
 parts. It need scarcely be added that the uses and functions of nearly 
 all the subordinate parts are at present wholly unknown. For the time 
 being, they are therefore objects of interest to the anatomist rather than 
 to the physiologist. 
 
 Fig. 154, external lateral face of the right half of the brain : 1, me- 
 dulla oblongata; 2, pons varolii; 3, cerebellum; 4, pneumogastric lob- 
 ule ; 5, frontal convolutions ; 6, parietal convolutions ; 7, occipital con- 
 volutions ; 8, fissure of Sylvius ; 9, 9, its two branches. 
 
 Fig. 154. 
 
 Fig. 155. 
 
 Superior aspect of the brain. 
 
 External lateral face of the brain. 
 
 Fig. 155, superior aspect of the brain: 
 1, 1, anterior lobes ; 2, 2, posterior lobes ; 
 3, 3, great median fissure ; 4, 4, fissures 
 of Eolando ; 5, 5, anterior parietal convolutions ; 6, 6, posterior parietal 
 convolutions ; 7, 7, rudimentary parietal convolutions ; 8, 8, frontal con- 
 volutions ; 9, 9, occipital convolutions. 
 
 Fig. 156, internal lateral face of the right half of the brain : 1, half 
 of medulla oblongata ; 2, half of pons varolii ; 3, half of eras cerebri ; 4, 
 arbor vita? of cerebellum ; 5, aqueduct of Sylvius ; 6, half of the valve 
 of Vieussens ; 7, two of the tubercula quadrigemina; 8, half of the pin- 
 eal gland ; 9, its inferior peduncle ; 10, its anterior peduncle ; 11, trans- 
 verse portion of the fissure of Bichat : 12, superior face of the optic tract ; 
 
THE BRAIN. 
 
 317 
 
 Internal lateral face of the brain. 
 
 13, its internal face; 14, commis- 
 suramollis; 15, infundibulum; 16, 
 portion of pituitary gland ; 17, por- 
 tion of tuber cinereum ; 18, pisiform 
 tubercle; 19, locus perforatus; 20, 
 oculo-inotor nerve ; 21, portion of 
 optic nerve ; 22, anterior cerebral 
 commissure ; 23, foramen of Mon- 
 roe ; 24, fornix ; 25, septum luci- 
 dum ; 26, corpus callosum ; 27, 
 splenium ; 28, genu ; 29, sinus of 
 the corpus callosum ; 30, gyrus 
 fornicatus ; 31, internal convolu- 
 tion of the anterior lobe ; 32, deep anfractuosity ; 33, convolution of pos- 
 terior lobe ; 34, anfractuosity. 
 
 Fig. 157, base of the brain, photo- 
 graphed from a wax cast : 1, 1, anteri- 
 or lobes ; 2, 2, middle lobes ; 3, 3, pos- 
 terior lobes; 4, anterior portion of great 
 median fissure; 5, its posterior portion; 
 6, 6, fissures of Sylvius ; 7, 7, antero- 
 posterior portions of the great fissure 
 of Bichat ; 8, tuber cinereum ; 9, 9, 
 corpora albicantia; 10, locus perforatus 
 medius ; 11, 11, crura cerebri; 12, pons 
 varolii; 13, medulla oblongata; 14, 
 14, anterior pyramids; 15, 15, olivary 
 bodies; 16, 16, restiform bodies; 17, 
 17, lateral lobes of the cerebellum ; 18, 
 Base of the brain. portion of its middle lobe ; 19, 19, 
 
 two small antero-posterior convolutions of the frontal lobe, separated by 
 the groove of the olfactory nerve ; 20, oblique convolution, limiting the 
 fissure of Sylvius ; 21, convolution of the great cerebral fissure ; 22, ol- 
 factory nerve ; 23, its bulb ; 24, 24, optic nerves and their chiasm ; 25, 
 25, oculo-motor nerves ; 26, 26, pathetici ; 27, 27, great and small roots 
 of the trifacial; 28, 28, external oculo-motor nerves; 29, 29, facial nerves ; 
 30, 30, auditory; 31, 31, glosso-pharyngeal ; 32, 32, pneumogastric 
 nerves ; 33, 33, spinal accessory ; 34, 34, great hypoglossal. In this 
 engraving several of the symmetrical numbers are not repeated, for the 
 sake of clearness. 
 
 Fig. 158 is an analytical diagram of the brain in a vertical section 
 (from Mayo). It serves to impress on the mind the foregoing structure of 
 structural descriptions, s, Spinal cord preparing for bifurca- t ? e brain - 
 
318 
 
 STRUCTURE OF THE BEAIN. 
 
 Fig. 158. 
 
 Diagram of the structure of the brain. 
 
 tion ; r, restiform bodies passing to <?, the cerebellum ; d, corpus denta- 
 tum of the cerebellum ; 0, intercalation of the olivary body ; f, columns 
 continuous with the olivary bodies and central part of the medulla ob- 
 longata, and ascending to the tubercula quadrigemina and optic thalami ; 
 JP, anterior pyramids : v, pons varolii ; n, b, tubercula quadrigemina ; 
 <7, geniculate body of the optic thalamus ; , processus cerebelli ad testes; 
 #, anterior lobe of the brain ; q, posterior lobe of the brain. 
 
 Fig. 159, the motor tract (from Sir C. Bell). A, A, fibres of the hem- 
 ispheres converging to form the anterior portion of the crus cerebri ; B, 
 the same tract when passing the crus cerebri ; C, the right pyramidal 
 body, a little above the point of decussation ; D, the remaining part of 
 the pons varolii, a portion having been dissected off to expose B. 1, 
 olfactory nerve in outline ; 2, union of optic nerves ; 3, 3, motor oculi ; 
 4, 4, patheticus ; 5, 5, trigeminus ; 6, 6, its muscular division ; 7, 7, its 
 sensory root ; 8, origin of sensory root from the posterior part of the me- 
 dulla oblongata ; 9, abducens oculi ; 10, auditory nerve; 11, facial nerve; 
 
THE MOTOR TRACT. 
 Fig. 159. 
 
 319 
 
 The motor tract. 
 
 12, eighth pair ; 13, hypoglossal ; 14, spinal nerves ; 15, spinal acces- 
 sory of right side, separated from par vagum and glosso-pharyngeal. 
 
 Fig. 160 (on the following page), the sensory tract (from Sir C. Bell). 
 A, pons varolii ; B, B, sensory tract separated ; C, union of posterior 
 columns ; D, D, posterior roots of spinal nerves ; E, sensory roots of the 
 fifth pair. 
 
 The ganglia at the base of the brain are regarded by Dr. Carpenter as 
 constituting the true sensorium. a doctrine which he has es- . 
 
 i i t Thesensonum. 
 
 tablished by many weighty arguments, and which is doubt- 
 less one of the most important thus far introduced by any physiologist. 
 
 The idea here intended to be conveyed is, that the thalami, striata, 
 sensory ganglia, and nervous arrangements below, constitute an isolated 
 apparatus ; distinct from which, and superadded, are the cerebral hem- 
 ispheres. 
 
 From observations on the animal series, the conclusion seems to be un- 
 
320 THE SENSORY TRACT. 
 
 Fig. 160. 
 
 D 
 
 The sensory tract. 
 
 avoidable that the chain of ganglia now under consideration must con- 
 stitute a sensorium, the centripetal fibres communicating their impression 
 and motion ensuing, the impressions being attended with consciousness. 
 This view is moreover substantiated by observations made after excision 
 of the cerebrum, a certain degree of consciousness remaining, not unlike 
 that exhibited by a man who is half asleep. This condition of things is 
 naturally presented in the amphioxus. 
 
 But after the cerebral hemispheres are added, an impression received 
 Effect of the ad u P (:)n ^ ne thalamus, whether it has come in through the sen- 
 dition of the sory ganglia, or any other sensory part of the cranio-spinal 
 axis, is transmitted to the convolutions along the radiating 
 fibres. From the convolutions, the influence which is to produce mo- 
 tion descends along the converging fibres to the striatum, thence along 
 the inferior layers of the crus, through the mesocephalon to the anterior 
 pyramids, and by their decussation to the opposite side of the cord. 
 
 Such is the view which Dr. Carpenter presents of the functions of the 
 sensory ganglia and spinal axis ; or, employing the terms we have pre- 
 viously defined, the cord alone is a longitudinal series of automatic arcs ; 
 on the addition of the thalamus and striatum, it becomes a compound 
 registering arc, the cerebral hemispheres finally annexed to it constitut- 
 ing an influential arc. 
 
 In a simple arc, an impression is at once converted into motion, and 
 leaves behind it no traces ; its expenditure is instantaneous and complete. 
 In a registering arc, a part of the impression is stored up or remains 
 
THE CEREBRUM. 321 
 
 nay, even the whole of it may be so received and retained. It is not to 
 be overlooked that, as soon as this effect occurs, the evidences of sensation 
 arise ; and, since sensation necessarily implies the existence of ideas, 
 ideas themselves are doubtless dependent on this partial retention or reg- 
 istry of impressions. We may therefore adopt the doctrine of Dr. Car- 
 penter, as regards the sensorial functions of the cranio-spinal apparatus, 
 not only from the arguments he has presented, but also from other con- 
 siderations. 
 
 There can be no doubt that the cerebral hemispheres constitute the in- 
 strument through which the mind exerts its influences on the General result 
 body. Any injury of sufficient severity inflicted upon them of variations 
 
 j. ^ J J - A l_ x 1 1 f x 11 in the Size and 
 
 is at once attended with a total loss of intellectual power; weight of the 
 any malformation or lesion by disease is attended by a dete- hemis P here s- 
 rioration below the customary mental standard; any unusual develop- 
 ment with correspondingly increased powers of intellection ; and this not 
 only as regards animals of different tribes, or individuals at special peri- 
 ods of their lives, but also of different men when compared with one an- 
 other. The general impression is founded in fact that those who have 
 distinguished themselves for mental attainments or intellectual power 
 have been marked by the unusual development of their cerebral hemi- 
 spheres. 
 
 It is to be understood that, in thus asserting a correspondence between 
 the development of the cerebrum and intellectual capability, i nstrumental 
 we are not to overlook the instrumental nature of that organ, nature of cere- 
 Though imperfections in it may produce a manifest inferior- brum ' 
 Ity, that inferiority is by no means to be referred to the intellectual prin- 
 ciple itself. The mode of action being by an instrument, if that instru- 
 ment becomes imperfect the action becomes imperfect too. Under such 
 circumstances, in any human contrivance, we should never think of im- 
 puting inferiority to the prime mover. 
 
 From this point of view we may therefore consider the intellectual prin- 
 ciple as possessing powers, properties, and faculties of its own ; as being 
 acted on by impressions existing in the thalamus, and delivered through 
 the intervening fibrous structures to the vesicular material of the convolu- 
 tions of the cerebral hemispheres. In this region they act upon the in- 
 tellectual principle and are acted upon by it, the returning influence, if 
 any, coming down through the converging tubular structures to the cor- 
 pus striatum, and by its commissural connections sent off to particular 
 ganglia, passing along the inferior strand of the crus through the meso- 
 cephalon to the anterior pyramids, and by their decussation to the oppo- 
 site side of the cord. 
 
 Having thus spoken of the sensory ganglia and the cerebral hemi- 
 spheres, it remains to add some remarks respecting the cerebellum. It 
 
 X 
 
322 STRUCTURE OF THE CEREBELLUM. 
 
 The cerebel- arises, as has been stated, from the triple strand of the eras 
 lum. cerebelli, of which one layer of fibres is connected with the 
 
 corpora quadrigemina, and through them with the optic thalami ; a sec- 
 ond with the restiform bodies ; and the third is commissural, and passes 
 forward as the pons varolii. 
 
 Like the cerebrum, this organ is vesicular on its surface, which pre- 
 sents a number of parallel lines, which are fissures descending to the in- 
 terior. Their object is apparently the same as that of the convolutions 
 of the brain, the augmentation of surface. Of these fissures, the deep 
 are termed the primary : they divide the organ into lobes. Those which 
 descend to a less depth are termed secondary : the divisions they give 
 rise to are lobules. The gray vesicular material does not, however, de- 
 scend to the bottom of the primary fissures, and in this respect they dif- 
 fer from the cerebral convolutions. Moreover, from this circumstance, 
 that material is not continuous all over the cerebellum, but is in divided 
 portions. 
 
 Such are the appearances presented on an exterior examination of 
 Structure of ^ ie cerebellum. Viewed as a development upon the crura 
 the cerebellum, cerebelli, it may be described as consisting of a median lobe 
 and two hemispheres ; the former is, however, found existing alone in fish- 
 es and reptiles, the latter being subsequently added in the higher tribes. 
 From the central column of each hemisphere white fibrous planes are 
 given off, and from these, again, secondary, and again, tertiary planes 
 proceed. The planes are covered with vesicular matter, and thus give 
 rise to the appearance spoken of in the preceding paragraph, in the exte- 
 rior examination of the cerebellum, as primary and secondary fissures.' 
 They are lined with pia mater. The median lobe is formed on the same 
 plan. Its fibrous stem comes from the processus cerebelli ad testes, or, 
 more properly, from the optic thalamus. The weight of the cerebellum, 
 compared with that of the cerebrum, is usually stated as being about 1 to 8. 
 
 Much diversity of opinion prevails respecting the true function of the 
 cerebellum, some supposing that it is the centre of common sensation, 
 others that it is for the purpose of co-ordinating muscular movement, 
 and others that it is the seat of sexual instinct. 
 
 That the cerebellum is one of the sensory ganglia may be inferred from 
 Function of the the history of its development and its anatomical connec- 
 cerebeiium. tions. Its median lobe is the first to appear, as in fishes, 
 and the hemispheres arise subsequently as appendages thereto, as in 
 birds. The size which these eventually attain gives them a deceptive 
 prominence, and hides their subordinate character. Regarding the lobe, 
 therefore, as the essential and fundamental portion of the structure, the 
 significance of its cerebral connection with the thalamus through the pro- 
 cessus ad testes is too obvious to be overlooked. As by this its senso- 
 
FUNCTIONS OF THE CEREBELLUM. 323 
 
 ry character is displayed, so the same holds good for the hemispheres, 
 their relations with the spinal cord through the restiform bodies being 
 also of a sensory nature. It seems probable that the superficial vesicu- 
 lar material is in anatomical connection with the thalamus, and the cor- 
 pus dentatum or inner ganglia with the posterior or sensory columns of 
 the cord. 
 
 The arguments which have been brought forward by those who sup- 
 pose the cerebellum to have for its office the co-ordination of The doctrine 
 general muscular movement, may be briefly quoted as fol- 
 lows : There appears to be a general correspondence between motion, 
 its size and the degree of energy and complication of the motor powers 
 in various animals. Thus, in fishes, and likewise in birds, those tribes 
 which excel in their powers of motion, or are distinguished by the com- 
 plication of their movements, are characterized by the manner in which 
 this organ is developed ; and the same may be said even of the mamma- 
 lia, quadrupeds whose locomotive mechanism is simple possessing it in 
 a lower state of development than those which either temporarily or 
 constantly move on the posterior extremities. Among apes, those which 
 more frequently assume the erect posture, which is normal to man, have 
 their cerebellum of a size more closely approaching to his. 
 
 On examining such facts, it appears that it is not so much muscular 
 power as the quality of co-ordinating and governing minute muscular 
 motions. To maintain the standing position motionless, there are, in re- 
 ality, a great many muscular movements required, which serve to antag- 
 onize all the little incidents producing a tendency to fall ; and if this be 
 so in standing, how much more difficult must such antagonizing and 
 compensating actions become in walking, running, and such movements. 
 Theoretically, it might be expected that some special organ is necessary 
 to combine such various actions, and that organ seems to be the cere- 
 bellum. 
 
 In confirmation of this are the experimental results which have been 
 obtained. The cerebellum, on irritation, gives rise to no Results of ex- 
 convulsive motions, nor to sensations. If removed by de- ft"corebei^ 
 grees in successive slices, the motions of the animal become lum. 
 irregular, and, finally, it loses all power of walking or of maintaining its 
 equilibrium. Though the powers of the animal in bringing its muscles 
 into contraction seem not to have suffered, it can not co-ordinate or com- 
 bine the necessary muscular exertions, and, as is graphically stated, stag- 
 gers and falls over like a drunken man, still making efforts to maintain 
 its balance. Such experiments have been repeatedly made in the case of 
 different animals, and with the same results. 
 
 Connected with these results of experimental lesions of the cerebellum 
 are the rotations, as they are termed, which occur, for example, when one 
 
324 DOCTRINE OF PHRENOLOGY. 
 
 Rotary motions of the crura cerebelli is cut, the animal rolling upon its lon- 
 of animals. gitudinal axis for a long time and with great rapidity. 
 From such facts, it has therefore, been concluded that the function of the 
 cerebellum is neither for sensation nor intellection, nor is it the source of 
 voluntary movements, but that it is for the government or control of 
 combined muscular action. This is the view of M. Flourens. 
 
 M. Foville supposes that the cerebellum is for the perception of the 
 Doctrine that sensations derived from the muscles, and enabling the mind 
 cerebellum is to exert a guiding action. The facts which support the pre- 
 
 for the percep- .. . , ,, . -, ,, , . . 7, . 
 
 tion of muscu- ceding view support this also, there being, moreover, in this 
 lar sensations. case? an additional argument derived from the connection 
 which the cerebellum has been shown to maintain with the sensory col- 
 umns of the cord, and the pain experienced on irritating the restiform 
 columns. It has likewise been pointed out that this hypothesis illus- 
 trates the connection between the cerebellum and the optic ganglia, as if 
 it were for the purpose of bringing the organs of sight to the aid of this 
 co-ordination of muscular motion. 
 
 A third hypothesis, to which allusion has been made, is, that the cere- 
 Doctrine that k e ^ um * s t ^ ie or g an f sexual instinct, or of amativeness, as 
 it is the organ it is termed by phrenologists. The evidence of this, when 
 of amativeness. feidy . examine a, fe, however, ve ry far from affording a full 
 
 proof; indeed, in many instances the facts are in direct opposition to 
 the doctrine. In castrated animals the cerebellum undergoes no dimi- 
 nution. There is no coincidence between the intensity of that instinct 
 in the different animal tribes and the degree of development of this or- 
 gan ; and where it has been in a diseased condition, there has not been a 
 necessary correspondence between the lesion and the loss of the instinct. 
 This view of the function of the cerebellum is connected with the doc- 
 trine of special localization, or phrenology, which may therefore bejiere 
 briefly considered ; the general expression of this doctrine being that par- 
 ticular regions of the brain are devoted to special functions, 
 ' and that by an inspection of the exterior of the cranium men- 
 tal peculiarities may be detected. Drs. Gall and Spurzheim considered 
 that this view is supported by the fact that the specialization of function 
 in the brain is agreeable to the general mechanism of the system, in 
 which particular organs are charged with particular duties ; that, in any 
 individual, the mental powers are not equally or proportionally developed, 
 but some at one and some at another period of life, and so likewise of their 
 decline, some remaining at their original strength, while others may have 
 Arguments in become seriously impaired. It does not appear how such 
 Foc^zationof 1 ^ acts can ^ e explained upon the hypothesis that the whole 
 functions. brain acts as a unit. They may be readily understood if it 
 be supposed to act by parts which are developed in succession. The 
 
WEIGHT OP THE BRAIN. 325 
 
 same conclusion is arrived at from well-known facts connected with in- 
 sanity, in which it very frequently happens that some of the faculties 
 alone are deranged, while the others retain their power, and some may 
 even become more perfect than before ; so, likewise, in dreaming, some 
 of the faculties retain their activity, while others have become torpid ; 
 and so, likewise, when different individuals are compared, some exhibit a 
 superiority in one, and some in another mental particular ; and it is as- 
 serted that where the same peculiarity has predominated in different in- 
 dividuals, it has always been attended by an unusual development of a 
 special locality of the brain. Nor is there, in these views, any thing that 
 stands in contradiction to the general plan upon which the nervous sys- 
 tem itself is constituted, as is manifested by the different sensory gan- 
 glia for vision, hearing, or smell, or the arrangement for motion or sensa- 
 tion presented by the spinal cord ; and, moreover, they are supported by 
 the comparative anatomy of this system ; for, whatever grade of animal 
 life we may consider, the appearance of a new function or of a new in~ 
 stinct is certain to be connected with a new and contemporaneous devel- 
 opment of some part of the nervous system. 
 
 The facts which have been observed in cases where one cerebral hem- 
 isphere has either suffered lesions or lost its functions, do not present 
 any contradiction to the preceding doctrines ; for, though the remaining 
 hemisphere may seem to act equally well alone, as did both together, we 
 are very apt to deceive ourselves as regards the actual facts, a statement 
 which may be illustrated by recollecting how easily we persuade our- 
 selves that we see with one eye as well as with two. No doubt, in many 
 of the ordinary cases, one hemisphere of the brain may, like one eye, seem 
 to act well enough, but a more critical examination proves that in other 
 cases this is far from being true. That the two hemispheres act sever- 
 ally and separately is clear from what sometimes ensues in diseased con- 
 ditions of one of them, or when, perhaps, there is a want of symmetry 
 between them, those remarkable forms of mental derangement, some- 
 times known under the designation of double life or duality of mind, 
 then ensuing. 
 
 In man, the weight of the brain averages about fifty ounces ; in fe- 
 males, about forty-five ; the maximum being about sixty-four, weight of the 
 and the minimum about twenty ; in the case of idiots, the brain - 
 mean specific gravity of the gray matter is stated by Dr. Sankey to be, 
 in both sexes, 1.034, but somewhat less early and late in life. The 
 specific gravity of the white is 1.041, and this varies less with sex and 
 time of life than the former. 
 
 The functional activity of the brain depends on the copious supply of 
 arterial blood. It is computed that one fifth of the whole quantity in 
 the circulation is sent to this organ. It is delivered through the two 
 
326 PRESSURE ON THE BRAIN. 
 
 internal carotid and two vertebral arteries. The impetus of 
 
 Supply of .11111- 
 
 blood "to the the current is checked Toy the sinuous course these vessels 
 brain - take, or "by their breaking promptly into capillary branches. 
 
 A freedom of anastomosis among them, as is well displayed in the circle 
 of Willis, affords abundant provision for accidental stoppages or re- 
 straints. 
 
 Although the brain is inclosed in an unyielding cavity, it is subject to 
 Atmos heric ^ pressure of the air, a fact which, though it has been de- 
 pressure on the nied by some physiologists, follows from ordinary physical 
 principles. And since the quantity of blood present at any 
 moment in the organ varies with the contemporaneous functional activ- 
 ity, being greater as that activity is greater, the cerebro-spinal fluid also 
 varies in amount. Through this fluid an equality of pressure is there- 
 fore insured, no matter what may be the quantity of blood in the brain. 
 
 The cerebro-spinal fluid, the quantity of which has been estimated at 
 Cerebro-spinal two ounces, is readily absorbed and as readily reproduced. 
 fluid - The act of adjustment between it and the blood requiring a 
 
 certain period for its completion, the brain can not instantaneously be 
 brought to its maximum action. Thus, as all persons observe, when we 
 undertake any unusual intellectual duty, there is a certain preparatory 
 period to be passed through, as the common expression is, " for compos- 
 ing the thoughts." t 
 
 Pressure upon the brain, either applied mechanically or through acci- 
 Effect of me- dental effusions, produces at once functional inactivity, prob- 
 
 chanicai pres- a ^j ty interference with the due circulation of the blood ; 
 changes in the and, in like manner, any marked change in the chemical re- 
 blood. lations of that fluid exerts on the brain a corresponding ef- 
 
 fect. Thus, when oxygen gas is breathed, or, still better, protoxide of 
 nitrogen, which is more soluble in the blood, the processes of intellection 
 go on in an exaggerated way, and ideas in rapid succession, and in unu- 
 sual forms of combination, flit through the mind ; but, as the consequence 
 of this, since the lungs can not remove with the necessary promptness 
 the carbonic acid which is arising, the narcotic effects of that body are 
 soon experienced ; and this is also the case in alcoholic intoxication, in 
 the advanced stages of which the accumulation of carbonic acid in the 
 blood gives rise to the same result. 
 
 That different regions of the brain have independent though mutually 
 Effect of size commissured faculties, is fully established by the phenomena 
 tion onhe" f the nery es of sense, nor can there be any doubt that these 
 brain. differences of physiological function are directly dependent on 
 
 differences of anatomical structure. It is, indeed, to structural differences 
 that we should impute the greater or less efficiency of the whole organ, 
 as much as to differences of its weight. Because of a higher elaboration, 
 
DOUBLENESS OP THE NERVOUS SYSTEM. 327 
 
 the brain of one person may be more energetic than that of another, even 
 though its weight may be less. It is not to be denied, however, that there 
 is a connection between mental power and the quantity of cerebral matter, 
 when individuals of the same kind are compared, or that in the animal 
 series the psychical powers decline as the cerebrum diminishes in size. 
 
 Few topics are more worthy of the attention of the physiologist than 
 that of the variable psychical powers of man, and yet few have Ilg variable 
 been more overlooked. By variable psychical powers I mean psychical . 
 those periodicities of increase and diminution in our intellect- p<rv 
 ual efficiency, which may be noticed not only in diseased, but abo in 
 healthy states. On the principles we have presented, these find their 
 explanation in the temporary physical states of the organ, such as its 
 condition of repair, its existing facility for oxidation, and the constitution 
 of the blood as respects a proper arterialization. 
 
 The most striking structural characteristic of the nervous system is its 
 symmetrical doubleness, the cranial and spinal nerves com- Symmetrical 
 ing forth by pairs to their distribution on the right and left ^l { 
 sides of the body. The manner of development from the tem. 
 spinal axis laterally implies such a construction, and, indeed, gives ori- 
 gin to two halves so equal and alike that it has often been said each 
 person consists of two separate individuals. Examining those organs 
 which, by reason of the elaborateness of their mechanism and principles 
 of action, enable us to determine with satisfactory precision Fun ction of 
 the function discharged by each one of the members of the each lateral 
 pair, as in the case of the eye or the ear, we may corne to the organ 
 following conclusions : Each is a distinct organ in itself, capable of its 
 meeting the requirements of the economy in a sufficiently satisfactory 
 manner, and therefore forms a distinct whole ; but the pair can likewise 
 act simultaneously, re-enforcing, to a certain degree, each oth- Con . ointl 
 er's power, though in this double action there by no means double organs 
 arises a double intensity of effect. The closure of one ear jjj^j J 
 to a sound does not diminish the loudness by one half, nor crease 'their 
 does the shutting of one eye reduce to one half the bright- pre ' 
 ness of a light ; but, though there is not such a doubling of effect when 
 both eyes or both ears are employed, there is a degree of precision in the 
 resulting indication which is not to be gained by the use of one of these 
 organs alone In such a double organ, then, the result is not so much 
 a heightening of the final impression as the giving to it of a greater de- 
 gree of precision. 
 
 Moreover, each organ seems to exert a compensating influence over its 
 fellow in any deficiencies or imperfections it may possess. Compensation 
 Tims it is rare that both eyes are of an equal optical good- of defects - 
 ness, as most individuals wiH find on making a personal examination; 
 

 328 INDEPENDENT ACTION OF EACH HEMISPHERE. 
 
 but in vision with both eyes the faults of the more imperfect one are 
 merged in the indications of the better, and the same might be remark- 
 ed of the ear ; from which it would appear that this doubleness of or- 
 gans is rather for the purpose of introducing a principle of compensation 
 than one of conspiring action, the object intended to be gained being a 
 justness of perception rather than an increase of effect. 
 
 These observations apply to double organs in their normal states, or, 
 Effect of tem- if not their normal, their habitual ones ; but if to the eye, 
 porary disturb- f QY exam pl e a temporary disturbance is given, as by press- 
 
 anceofoneor- f . , . , ,. , n 
 
 gan. ure which renders its optical axis oblique, the fellow organ 
 
 being permitted to retain its usual position, double sight is the result. 
 It is true that, in the habitual divergence of strabismus, such is not the 
 effect, one of the images disappearing, or perhaps the mind, accommodat- 
 ing itself to the habitual condition, combines the two into one. These 
 circumstances indicate that each member of a double organ can, under 
 conditions of disturbance, exercise an independent and even opposing ac- 
 tion to its fellow. 
 
 It has by some been supposed that the mind pays attention to the im- 
 The indications pressions of only one of the pair of organs at a time ; thus, 
 contem fated *^at we see ^ ie ^ ma g es furnished by only one eye, though we 
 at a time. can with very great quickness direct attention to those fur- 
 nished by the other, and therefore, deceived by the rapidity with which 
 this alternation of attention can be accomplished, our belief in the syn- 
 chronous use of both organs is an error. If two differently colored ob- 
 jects, such as differently tinted wafers, be so placed as to be separately 
 and yet simultaneously viewed by both eyes, the mind vainly attempts 
 to combine the two images together. We do not see the resulting form 
 of a green tint, but we see, according as our attention is given to the 
 right or left, a blue or a yellow, if these have been the colors of the wa- 
 fers, and these colors can quickly merge into one another, like dissolving 
 Illustrative views. There is a simple experiment which serves to support 
 experiment. t m ' s view, and which any one may readily make. If the open 
 hand be placed along the nose, so as to divide the right eye from the left, 
 and we look upon the surface of a uniformly-illuminated sheet of paper 
 covered with writing, it will be found that we can only read with one 
 eye at a time, but that the mind can with great rapidity determine which 
 eye it will use. In this little experiment, we have, moreover, the means 
 of estimating the relative sensitiveness of the two eyes, and other of their 
 optical peculiarities ; thus it will be commonly remarked that, though the 
 paper be, as we have said, uniformly illuminated, that part of it which is 
 regarded by one eye is brighter than that seen by the other, this being 
 due to a difference in their sensibility. It will also frequently occur 
 that the two portions of the page will present different shades of tint, 
 
DOUBLE TRAINS OF THOUGHT. 329 
 
 the one, perhaps, being a faint greenish gray, while the other is of a yel- 
 lowish white, the proper color given to it by the candle or lamp Tby which 
 it is seen. 
 
 In this feature of double construction the brain itself participates, pre- 
 senting a right and left half approaching one another in form, without 
 being absolutely identical. Much, therefore, of what has been said re- 
 specting the mutual relations of the right and left eye, and the right and 
 left ear, must apply to the right and left hemispheres of the brain ; and 
 it is under this point of view that Dr. Wigan has regarded it in Indc endent 
 his work on the Duality of the Mind. Nor can there be any action of each 
 doubt that each hemisphere is a distinct organ, having the hemis P here - 
 power of carrying on its functions independently of its fellow; that, though 
 each can thus act separately, both can act simultaneously ; and, judg- 
 ing from the cases that have just been presented, it would seem that we 
 are justified in inferring that the common action of the two hemispheres 
 is not for the purpose of a heightening of effect, but only for greater pre- 
 cision, and that in the same manner as it is a rare thing to find two eyes 
 or two ears of equal goodness, so also it is unusual to have two hemi- 
 spheres which are precisely alike. The defects of the one may i nsubor <ji na - 
 be compensated by the superiorities of the other, and thus tion of one 
 a mean result be attained ; and as one eye or one ear can, 
 under the proper circumstances, overpower its fellow, so likewise can one 
 hemisphere of the brain, except in certain cases, which have been some- 
 what imaginatively described as insubordination of one of the hemi- 
 spheres, when insanity is the result, the healthy half being unable to 
 control the diseased one ; and for this reason, we often observe of the 
 insane that they have synchronously, or, at all events, in a very rapid al- 
 ternation, two distinct trains of thought, and, consequently, Double train of 
 two distinct utterances, each of which may, so to speak, be thou s ht - 
 perfectly continuous and even sane by itself, but the incongruities that 
 arise from the mingling of the two betray the condition of such persons. 
 In fhis case doubleness of action is seen in its most exaggerated aspect, 
 but in a less degree, it may be remarked, in the thinking operations of 
 those whose minds are perfectly sound. Thus there is no student but 
 must have observed, when busily engaged in reading, that his mind will 
 wander off to other things, though he may mechanically cast his eyes 
 over page after page ; and the same may occur in listening to a lecture 
 or sermon. But, though the insane man may indulge in two synchro- 
 nous trains of thought, he never indulges in three, for the simple reason 
 that he has not three hemispheres to do it with, the same remark apply- 
 ing to the sane man in the accidental wanderings of his thoughts. 
 
 The overcoming of this insubordination of one of the hemispheres may, 
 to a very considerable degree, be accomplished by education, of which 
 
330 CASTLE-BUILDING. 
 
 Effect of edu- one of the chief results is that it exercises us in the habit of 
 cation. thinking of one thing at a time, of thinking therefore with- 
 
 out confusion, and of arriving at conclusions with precision and decision. 
 And these considerations should also, in Dr.Wigan's view, be our chief 
 guide in the cure of insanity, doing all in our power to invigorate the ac- 
 tion of the healthy hemisphere, and enable it to subdue the insubordina- 
 tion of the diseased one. If both hemispheres are diseased, the case is 
 almost hopeless. 
 
 Of the independent and yet complete action of each of the cerebral hem- 
 Perfect action i s P neres we ^ ave abundant and interesting proof. Mental 
 of a single operations can be carried on in a profoundly diseased state of 
 hemisphere. Qne Q f fi^Q organs, as multitudes of well-authenticated cases 
 attest nay, even when the lesion has gone so far as to amount to an 
 absolute and entire disorganization of one of the hemispheres. Similar 
 evidence is also furnished by those interesting cases in which, by accident, 
 as by gunshot wound, destruction of one side has occurred. 
 
 Even in a state of health we have numerous examples of this inde- 
 Intermixed ac P en ^ ent action of each hemisphere. While engaged in ordi- 
 tion of the two nary pursuits which imply a continued mental occupation, 
 hemispheres. we afe occas i ona ]iy troubled with suggestions of a different 
 kind. A strain of music, or even a few notes, may be perpetually ob- 
 truding, and such an occurrence we could scarcely explain save upon the 
 principle of the separate action of these organs, the one interfering with 
 the other. That precision which we have remarked as arising from the 
 conjoint use of two eyes and two ears is doubtless also attained where 
 the two hemispheres are acting in unison. We can, moreover, volunta- 
 rily permit one to rest while the other continues its duty, as we can vol- 
 untarily make use of one eye, disregarding the indications of the other ; 
 but where it is necessary to execute a critical comparison or arrive at an 
 accurate judgment of things, both hemispheres are brought into action, 
 as are both eyes when we intently consider an object. 
 
 Among other phenomena, Dr. Wigan calls attention to the operation 
 Castle- of castle-building, as it is designated, as illustrating the volunta- 
 buiidmg. ry manner i n w hich we permit one hemisphere to act, presenting 
 fanciful delusions ; the other, as it were, watching with satisfaction the 
 operation, and in this respect lending itself to it. Not that for a moment 
 we suppose there is any truth in the ideas suggested, and in this the 
 phenomenon differs essentially from that of dreaming, in which it never 
 occurs to us that the scenes and actions are unsubstantial. 
 
 Still more strikingly do those singular cases, which from time to time 
 Double or ai- P resent themselves to the physician, of double or alternate 
 ternate con- consciousness, illustrate this isolated function of the hemi- 
 spheres. In some of these, which have been carefully ob- 
 
SENTIMENT OP FEE-EXISTENCE. 331 
 
 served and authentically recorded, each of these portions of the brain has 
 continued its action for a period of days, or even weeks, and then, relaps- 
 ing into a quiescent state, has been succeeded by the other, thus present- 
 ing in some degree an analogy of what is observed in ordinary cases of 
 insanity, so far as the reciprocating action of the two organs is concerned, 
 but differing in the period of duration of their function ; and thus, if one 
 of them should have undergone deterioration, or have suffered lesion, so 
 that it has been reduced to what might be termed an infantile state, the 
 impressions formerly stored up in it having been for the most part lost, 
 or there being an incapacity in it to make use of them, the patient will 
 alternately exhibit what has been aptly termed child life and mature life. 
 For a few days, or perhaps weeks, he will conduct himself in the ordi- 
 nary manner of an adult, reading, reasoning, and acting, and then, for a 
 similar period, will pass into a condition in which he does not even know 
 his letters, and reasons and acts like a child. These phenomena of al- 
 ternate and double intellection are interesting in the highest degree, and 
 seem to be explicable on no other principle than that which this author 
 suggests. 
 
 But I do not think that the explanation which he offers of the senti- 
 ment of pre-existence is correct. By this term is under- Sentiment of 
 stood that strange impression, which all persons have occa- P re -existence. 
 sionally observed in the course of their lives, that some incident or scene 
 at the moment occurring to them, it may be of quite a trivial nature, 
 has been witnessed by them once before, and is in an instant recognized. 
 Though this opinion that we have seen a present incident once before 
 sometimes occurs in cases where the circumstances are of profound in- 
 terest to us, the experience of most persons assures us that it is more fre- 
 quently in trivial events. Dr. Wigan's view is, that it arises from the 
 almost contemporaneous action of the two hemispheres, and that, under 
 the circumstances, we have a confusion of memory, and are led to be- 
 lieve that there has been an interval of indefinite duration, when, in 
 point of fact, it was an impression in each hemisphere closely coincident 
 in point of time. This explanation turns on the assumption that this 
 sentiment of pre-existence occurs but once. He denies that we ever 
 suppose that we have seen the thing twice before. But I believe that 
 the experience of many individuals assures them that this is not the case, 
 , and that they are under a firm persuasion that they have witnessed the 
 same incidents more than once before, nay, perhaps even many times. 
 The instance which this author furnishes as occurring to himself, in 
 which, on the occasion of attending the funeral of an exalted personage, 
 and at the time of the coffin being deposited in the vault, with the strik- 
 ing solemnities of the occasion there rushed upon his mind the idea that 
 he had been present at this same scene once before, a thing which was, 
 
332 LOSS OF PERCEPTION OF TIME. 
 
 of course, an impossibility, is very instructive. But the difficulty in the 
 way of his hypothesis lies in the fact that it offers us no explanation of 
 those cases in which we are perfectly persuaded that we have witnessed 
 the thing more than once before, though it may answer in the particular 
 Loss of a true i ns * ance here cited. Perhaps we may appropriately recall the 
 perception of well-known fact offered to us in dreaming, and to which at- 
 tention hereafter will be more particularly directed, that there 
 are circumstances under which our mental operations are carried forward 
 with the most marvelous speed. Thus a sudden sound, which awakes 
 us, or even a flash of lightning, which is over in a moment, may be in- 
 corporated or expanded into a long dream, diversified with a various 
 multitude of incidents, all appearing to follow one another in an appro- 
 priate order, and occupying, as we judge, quite a long time, yet all nec- 
 essarily arising in an instantaneous manner, for we awake at the moment 
 of the disturbance. Of the same kind is that remarkable deception, 
 which is authentically related by those who have recovered from death 
 by drowning, that in the last moment of their agony all the various 
 events of their past life, even those of a trivial kind, have come rushing 
 before them with miraculous clearness. Mental operations, therefore, 
 both as regards old recollections and new suggestions, may take effect 
 with wonderful rapidity, and if the sentiment of pre-existence is to be 
 explained on the principle of the double action of the brain, it must like- 
 wise be dependent upon the fact here presented. 
 
THE CRANIAL NERVES. 333 
 
 CHAPTER XVII. 
 
 OF THE CRANIAL NERVES AND THE GREAT SYMPATHETIC. 
 
 Enumeration of the Cranial Nerves. The Third Pair, or Oculo-motor. The Fourth Pair, orPa- 
 thetid. The Fifth Pair, or Trigemini. The Sixth Pair, or Abducentes. Illustrations of the 
 Third, Fourth, Fifth, and Sixth Pairs. The Seventh Pair, or Facial. Illustration of the 
 Facial. The Ninth Pair, or Glosso-pharyngeal. Illustration of the Glosso-pharyngeal. The 
 Tenth Pair, or Pneumogastric. Illustration of the Pneumogastric. Illustration of the Laryn- 
 geals. The Eleventh Pair, or Spinal Accessory. The Twelfth Pair, or Hypoglossal. Il- 
 lustration of the Hypoglossal. 
 
 The Phrenic Nerve. 
 
 Of the Great Sympathetic System. Position, Structure, and Origin of the Sympathetic. Its Re- 
 lation with the Pneumogastric. Its Connection with the Spinal System. Its Plexuses. Its 
 Ganglia. They are Reservoirs of Force. Summary of the Functions of the Sympathetic. 
 Illustration of the Sympathetic. The Abdominal Plexuses. The Solar Plexus. The Mesen- 
 teric Plexuses. 
 
 THERE are twelve pairs of cranial nerves : 1st. The olfactory; 2d. The 
 optic ; 3d. The oculo-motor ; 4th. The pathetic ; 5th. The tri- The cranial 
 facial; 6th. The abducent ; 7th. The facial; 8th. The audito- nerves - 
 ry ; 9th. The glosso-pharyngeal ; 10th. The pneumogastric ; llth. The 
 spinal accessory ; 12th. The hypoglossal. 
 
 Of these, the first, the second, and the eighth, being nerves of special 
 sensation, may be more conveniently studied in connection with the or- 
 gans of special sense the nose, the eye, the ear. 
 
 OF THE THIRD PAIR, OR OCULO-MOTOR NERVES. 
 
 The motor-oculi nerve arises from the inner side of the crus cerebri', 
 near to the pons varolii, some of its fibres passing into the The third pair, 
 gray substance of the crus. Advancing forward, it divides or oculo-motor. 
 into two branches, one of which supplies the superior rectus andlevator 
 palpebrae, the other the internal rectus, inferior rectus, and inferior ob- 
 lique. Considering the place of origin, it would be expected that this 
 nerve is wholly motor, and this is confirmed by experiment. When the 
 nerve is irritated the muscles which it supplies are convulsed, and when 
 it is divided they are paralyzed. Through its connection with the len- 
 ticular ganglion, it furnishes motor filaments to the iris. The optic 
 nerve, the corpora quadrigemina, and this nerve together constitute a 
 complete nervous arc, and impressions made on the retina occasion mo- 
 tions in the iris. 
 
334 THE FOURTH, FIFTH, AND SIXTH PAIRS. 
 
 OF THE FOURTH PAIR, PATHETICI, OR TROCHLEAR NERVES. 
 
 This nerve arises from the valve of Yieussens, near the testis, and, 
 The fourth pair, passing around the cms cerebri, enters the orbit, and is dis- 
 or pathetic!. tributed to the orbital surface of the superior oblique, or 
 trochlear muscle, for which it is the motor nerve. When it is irritated 
 that muscle is convulsed. 
 
 OF THE FIFTH PAIR, TRIFACIAL, OR TRIGEMINI. 
 
 The fifth nerve has a construction so closely analogous to that of the 
 The fifth pair, spinal nerves, that it has been designated the spinal, nerve of 
 or trigemini. ^he head. It arises by two roots, the anterior of which is 
 the smaller, the posterior having a large ganglion, the ganglion of Gas- 
 ser ; with this ganglion the anterior root is in contact, but not in con- 
 nection: it passes forward to the inferior maxillary nerve. From the 
 ganglion three branches diverge, the ophthalmic, the superior maxillary, 
 and inferior maxillary, the first proceeding from the upper angle of the 
 ganglion, the second from the middle, the third from the inferior angle. 
 This last receives the motor portion of the nerve ; the first and second 
 branches are sensory, the third is sensory and motor also. From the 
 sensory portions the anterior and most of the antero-lateral portions of 
 the head are furnished, as also the organs of special sense themselves, so 
 far as their common sensation is concerned. The motor branch supplies 
 the muscles of mastication. 
 
 OF THE SIXTH PAIR, OR ABDUCENTES. 
 
 This nerve arises by several filaments from the upper part of the cor- 
 The sixth pair, pus pyramidale, near to the pons varolii, and is distributed 
 or abducentes. to tne external rectus. From its origin, distribution, and 
 from experiments made upon it, it is known to be a motor nerve. 
 
 ILLUSTRATIONS OF THE THIRD, FOURTH, FIFTH, AND SIXTH PAIRS OF NERVES. 
 
 Fig.\\\ 1, chiasm of optic nerves; 2, 
 third pair ; 3, nasal nerve ; 4, external oculo- 
 motor; 5, ganglion of Gasser; 6, nasal nerve 
 and its two branches, internal and external ; 
 7, nerve of obliquus inferior ; 8, ophthalmic 
 ganglion ; 9, ciliary nerves ; #, portion of ld- 
 vator palpebrae superioris and rectus superi- 
 or ; , rectus inter nus ; c, rectus extern us ; d, 
 fibrous ring of the recti muscles. 
 
 NERVES IN THE ORBITAL CAVITY. 
 
 NemTs of the orbit. Fig. 162 i 1, 1, optic nerve and globe of the 
 
THE FIFTH NERVE. 
 
 335 
 
 Fig. 162. 
 
 8 7 dJO b 
 
 Nerves in the orbital cavity. 
 
 eye; 2, third nerve ; 3, superior branch ; 
 4, nerve of obliquus inferior; 5, external 
 oculo-motor ; 6, ganglion of Gasser ; 7, 
 ophthalmic branch ; 8, nasal nerve ; 9, 
 ophthalmic ganglion; 10, short root of 
 ophthalmic ganglion; 11, ciliary nerves ; 
 12, frontal nerve ; #, levator palpebras 
 superioris and rectus superior ; Z>, rectus 
 inferior ; c, obliquus inferior ; d, rectus 
 extemus ; e, ring of the recti muscles. 
 
 DIAGRAM OF THE FIFTH NERYE. 
 
 Fig. 163. 
 
 Fig. 163 : 1, ganglion of Gasser ; 
 2, ophthalmic ganglion ; 3, its long 
 root furnished by the nasal branch; 
 4, short root ; 5, sympathetic, from 
 the plexus surrounding the inter- 
 nal carotid ; 6, ciliary nerves trav- 
 ersing the sclerotic ; 7, ciliary gan- 
 glion ; 8, ganglion of Meckel ; 9, 
 its sensory roots from the superior 
 maxillary ; 10, petrous branch of 
 vidian nerve, or motor root of the 
 ganglion of Meckel ; 11, its sym- 
 pathetic root ; 12, naso- palatine 
 
 Diagram of the fifth nerve. ganglion, receiving at its upper an- 
 
 gle the naso-palatine nerve, and at its inferior the anterior palatine ; 13, 
 otic ganglion ; 14, small superficial petrosal ; 15, submaxillary ganglion ; 
 16, sublingual ganglion ; 17, geniculated ganglion; 18, cavernous ganglion. 
 
 GANGLION OF GASSER AND ADJACENT PARTS. 
 
 Fig. 164. _ Fig. 164 : 1, ganglion of Gas- 
 
 ser; 2, ophthalmic nerve; 3, front- 
 al branch ; 4, lachrymal ; 5, nasal ; 
 6, opthalmic ganglion; 7, superior 
 maxillary nerve ; 8, orbital branch ; 
 9, ganglion of Meckel ; 10, petrosal 
 branch of vidian nerve; 11. palatine 
 nerves ; 12, anastomosis of the gan- 
 glion *of Meckel with the nervous 
 plexus surrounding the internal max- 
 illary artery ; 13, posterior and su- 
 perior dental nerves ; 14, suborbital nerve, its anastomoses with facial 
 
 Ganglion of Gasser. 
 
336 
 
 THE FIFTH NERVE. 
 
 and nasal; 15, inferior maxillary, receiving the motor portion of the fifth 
 pair ; 16, superficial auriculo-temporal nerve ; 17, buccal nerve ; 18, sec- 
 tion of other collateral branches of inferior maxillary ; 19, inferior den- 
 tal ; 20, mental nerve ; 21, lingual ; 22, chorda tympani ; 23, facial 
 nerve ; A, external carotid artery ; B, facial artery ; C, temporal artery ; 
 D, internal maxillary ; E, its dental branch ; F, middle meningeal ; a, 
 membrana tympani ; #, glenoid cavity ; <?, orbicularis oris ; d, buccina- 
 tor ; , pterygoideus internus ; /, pterygoideus externus ; g, digastric ; 
 h sterno-cleido-mastoid muscle. 
 
 THE FIFTH NERVE, THE GANGLION OF GASSER BEING REMOVED. 
 
 Fig. 165. Fig. 165 : 1, ophthalmic, cut ; 2, 
 
 superior maxillary, cut at both ex- 
 tremities ; 3, ganglion of Meckel ; 4, 
 petrosal and carotid branch of vidian 
 nerve ; 5, abducent ; 6, nerve of Ja- 
 cobson ; 7, superior and posterior 
 dental nerves ; 8, anterior and supe- 
 rior dental nerve ; 9, otic ganglion ; 
 10, gustatory nerve ; 11, chorda tym- 
 pani ; 12, submaxillary ganglion ; 
 13, anastomosis of lingual with hy- 
 poglossal ; 14, sublingual plexus ; 15, terminal branches of gustatory or 
 lingual nerve ; 16, inferior dental ; 17, mylo-hyoid branch ; 18, mental ; 
 19, incisive nerve ; 20, ganglion of glosso-pharyngeal ; 21, facial, in the 
 aqueduct of Fallopius ; 22, hypoglossal ; a, superior maxillary bone ; b, 
 cartilages of the nose ; , internal wall of tympanic cavity ; d, ptery- 
 goideus internus muscle ; , buccinator, cut ; y, mylo-hyoid muscle ; g, 
 part of anterior belly of digastric ; A, sterno-cleido-mastoid, turned aside. 
 
 The fifth nerve. 
 
 ILLUSTRATION OF THE TERMINAL BRANCHES OF THE 
 INFERIOR MAXILLARY NERVE. 
 
 Fig. 166 : 1, motor and sensory roots 
 of ganglion of Gasser ; 2, junction of mo- 
 tor root with inferior maxillary; 3, auricu- 
 lo-temporal nerve ; 5, buccal nerve ; 6, 
 pterygoid nerves ; 7, cut branches of tem- 
 poral and masseteric nerves ; 8, gustatory 
 nerve; 9, chorda tympani; 10, facial; 11, 
 anastomosis of gustatory and inferior den- 
 tal nerves ; 12, tonsillar branch ; 13, sub- 
 
 The inferior maxiiiary. maxillary ganglion ; 14, sublingual plex- 
 
 us; 15, anastomosis of gustatory and hypoglossal nerves; 16, branches 
 
THE FACIAL NERVE. 
 
 337 
 
 of gustatory; 17, inferior dental; 18, mylo-hyoid nerve; 19, incisive 
 branch of dental nerve; 20, branch of mental, cut; <z, pterygoideus in- 
 ternus ; b, part of pterygoideus externus muscle ; c, mylo-hyoid muscle ; 
 d, portion of anterior belly of the digastric ; e, hypoglossal muscle ; J\ 
 portion of submaxillary gland. 
 
 OF THE SEVENTH PAIR, THE FACIAL NERVE. 
 
 This nerve arises from the upper part of the groove between the oli- 
 vary and restiform bodies, and near the pons. varolii. With The seventh 
 the auditory nerve, or portio mollis, it constitutes the seventh P air > or facial, 
 nerve in the nomenclature of Willis, and derives the name portio dura, 
 under which it sometimes passes, from the density and closeness of its 
 texture. It supplies all the muscles of the face except those of mastica- 
 tion, which are supplied by the fifth nerve, those of the palate, the sta- 
 pedius, laxator tympani, and tensor tympani ; also the muscles of the ex- 
 ternal ear, and some of those of the tongue. The facial is a centrifugal 
 nerve. If irritated near its origin, there is no sensation of pain ; but sub- 
 sequently it obtains fibres from other sources, as from the fifth and the 
 pneumogastric. After it has been joined by these, irritation is acutely 
 felt. It is therefore to be regarded as the general motor nerve of the 
 face, influencing the function of respiration through reflex action, but not 
 being connected with the function of mastication. Injury of it produces 
 paralysis of the parts to which it is distributed, as, for example, the orbic- 
 ularis palpebrarum, causing inflammation of the eye and opacity of the 
 cornea, through inability of that organ to free itself from dust and spread 
 the lachrymal secretion over its surface. In like manner, the sense of 
 hearing may be injured through loss of control over the muscular struc- 
 tures of the ear, and the acuteness of the sense of smell diminished from 
 Fig.iw. inability to introduce the air in a 
 
 strong current, or the sense of taste, 
 if the point of injury be previous to 
 the giving off of the chorda tympani. 
 In paralysis of the facial nerve the 
 muscles of the face become powerless, 
 and the countenance, therefore, dis- 
 torted. 
 
 ILLUSTRATION OF THE FACIAL NERVE. 
 
 Fig. 167 : 1, trunk of the facial 
 at its emergence from the aqueduct 
 of Fallopius ; 2, occipito- auricular 
 branch ; 3, auricular of the cervical 
 plexus ; 4, twig of the occipital mus- 
 
 The facial nerve. 
 
338 THE GLOSSO-PHARYNGEAL NERVE. 
 
 cle ; 5, twig of the posterior auricular muscle ; 6, twig of the superior 
 auricular ; 7, anastomosis of the facial with the auricular of the cervical 
 plexus ; 8, branch for the stylo-hyoid and posterior belly of the digastric ; 
 9, temporo-facial anastomosis with the superficial auriculo-temporal of 
 the fifth pair ; 10, temporal ramifications of the facial ; 11, frontal twigs ; 
 12, superior palpebral twigs ; 13, middle palpebral twigs ; 14, inferior 
 or motor palpebral twigs; 15, suborbital twigs ; 16, suborbital plexus; 
 17, superior buccal; 18, cervico-facial branch; 19, buccal branches, anas- 
 tomosing 'with, 20, buccal nerve of fifth pair; 21, mental twigs, forming 
 with, 22, mental nerve of fifth pair, the mental plexus ; 23, cervical 
 branches ; 24, transverse cervical branch of cervical plexus ; 25, parotid 
 branches of the superficial auriculo-temporal ; 26, parotid branches of the 
 facial ; #, frontal muscle ; b, occipital muscle ; c, anterior auricular ; d, 
 superior auricular ; 0, posterior auricular; f, orbicularis palpebrarum; ^, 
 zygomaticus, major ; -A, buccinator ; ^orbicularis oris ; &, masseter; , 
 parotid gland ; m, platysma ; n, stylo-hyoid and posterior belly of di- 
 gastric ; o, sterno-cleido-mastoid ; j?, trapezius. 
 
 OF THE NINTH PAIR, OR GLOSSO-PHARYNGEAL. 
 
 This nerve arises by five or six filaments from the groove between 
 The ninth pair, ^ ie ^ var 7 an ^ restiform bodies. Its origin may be traced 
 or giosso-pha- to the vesicular substance in the floor of the fourth ventricle : 
 passing forward, it is distributed to the mucous membrane 
 of the base of the tongue and fauces. While in the jugular fossa it 
 forms two ganglia, a small one produced by its posterior fibres, and call- 
 ed the superior ganglion ; a second, much larger, termed the inferior, or 
 ganglion of Andersch. The branches given off by the glosso-pharyngeal 
 are the muscular, the tympanic or Jacobson's nerve, which is distributed 
 to the inner wall of the tympanum and interior portions of the ear ; the 
 pharyngeal, which supplies the pharynx, and, with branches of the pneu- 
 mogastric and sympathetic, forms the pharyngeal plexus ; the lingual 
 supplies the mucous membrane of the sides and base of the tongue ; 
 the tonsillitic, which supplies the mucous membrane of the fauces and 
 soft palate, and forms a plexus round the base of the tonsil. Besides 
 these, the glosso-pharyngeal anastomoses with the facial, pneumogastric, 
 accessory, and sympathetic. 
 
 Examined in the usual way, the glosso-pharyngeal proves to be a cen- 
 tripetal nerve, having the power of producing reflex motions through the 
 nerves of deglutition, its motor influence being chiefly due to its con- 
 nections with the pneumogastric and accessory. Though thus a sen- 
 sory nerve, it is doubtful whether it be the only nerve of taste, or whether 
 that function is not likewise participated in by the lingual branch of the 
 fifth pair. It is certain that section of the lingual does not destroy the 
 
THE GLOSSOPHARYNGEAL NERVE. 
 
 339 
 
 sense of taste, and also that those parts of the tongue to which the 
 glosso-pharyngeal is distributed present that sense in the most marked 
 manner. The inference which is usually drawn is that this nerve and the 
 lingual are both tactile and gustative, and this renders appropriate its 
 description in this place rather than among the nerves of special sense. 
 
 ILLUSTRATION OF THE GLOSSO-PHARYNGEAL. 
 
 Fig. 168. 
 
 Fig. 168 : 1, origin of the glosso-pharyngeal 
 between, 2, the pneumogastric, and, 3, the facial.; 
 4, ganglion of Andersch; 5, pharyngeal branches; 
 6, anastomosis of the glosso-pharyngeal with the 
 lingual branch of the facial ; 7, application of the 
 spinal to the superior ganglion of the pneumo- 
 gastric ; 8, branch of jugular fossa ; 9, plexiform 
 ganglion of par vagum ; 10, carotid branch ; 11, 
 superior laryngeal nerve ; 12, external laryngeal; 
 13, inferior or recurrent laryngeal ; 14, cervical 
 branch of the spinal ; 15, bulbar branch of same 
 the union of these forms a trunk which 
 
 nerve 
 
 The glosso-pharyngeal. 
 
 divides into two branches ; 16, external branch ; 
 17, internal branch ; 18, cervical portion of sym- 
 
 pathetic ; 19, hypoglossal, cut. 
 
 DIAGRAM OP GLOSSO-PHARYNGEAL. 
 
 Fig. 169. 
 
 Fig. 169 : 1, facial ; 2, glosso-pharyngeal; 3, pneumo- 
 gastric ; 4, spinal ; 5, hypoglossal ; 6, superior cervical 
 ganglion ; 7, 7, anterior branches of the two first cervical 
 pairs ; 8, plexus enveloping the internal carotid artery ; 
 9, Jacobson's nerve ; 10, its anastomotic branch with the 
 carotid plexus ; 11, small deep petrosal, which passes into 
 the great superficial petrosal; 13, otic ganglion ; 14, anas- 
 tomosis of glosso-pharyngeal with lingual branch of the 
 facial; 15, anastomosis of glosso-pharyngeal and pneumo- 
 gastric ; 16, anastomosis of the pharyngeal of the glosso- 
 pharyngeal with that of the pneumogastric and of the 
 spinal ; 17, auricular twig of Arnold ; 18, application of 
 
 Diagram O f anasto- the trunk of the s P inal to tlie superior ganglion of the 
 moses. pneumogastric ; 19, anastomosis of internal branch of the 
 
 spinal with the ganglion of the trunk of the par vagum ; 20, anastomosis 
 of pneumogastric and hypoglossal ; 21, anastomosis of hypoglossal with 
 the loop formed by first and second cervical ; 22, 22, anastomosis of the 
 two first pairs with the cervical ganglion ; 23, pharyngeal plexus ; 24, 
 laryngeal plexus ; 25, anastomosis of the external branch of the spinal 
 with the anterior branch of the third cervical pair. 
 
MO THE PNEUMOGASTRIC NERVE. 
 
 OF THE TENTH PAIR, THE PAR VAGUM, OR PNEUMOGASTRIC NERVE. 
 
 The pneumogastric nerve arises by six or eight filaments from the 
 groove between the olivary and restiform bodies below the glosso-pha- 
 ryngeal, and, like it, may be traced to the vesicular material of the floor 
 The tenth air ^ tne fo urtn ventricle. It first presents a small ganglion, 
 or pneumogas- and soon after a second, nearly an inch in length, called the 
 plexus gangliformis. The nerve then descends the neck in 
 the sheath of the carotid vessels, and in its course differs on the right 
 and left sides respectively. On the right side it passes between the sub- 
 clavian artery and vein, descending toward the stomach and solar plexus 
 on the posterior portion of the oesophagus ; on the left it enters the chest 
 nearly parallel with the left subclavian, and passes to the stomach and 
 solar plexus along the anterior portion of the oesophagus. 
 
 The chief branches of the pneumogastric are the auricular, the pharyn- 
 geal, the superior laryngeal, the cardiac, the inferior laryngeal or recur- 
 rent, the anterior pulmonary, the posterior pulmonary, the cesophageal, 
 and the gastric. 
 
 The pneumogastric presents several plexuses in its course, and, even 
 when distributed on the stomach, exhibits flat, membraniform ganglia. 
 It supplies three great classes of organs : 1st. The digestive, as the pha- 
 rynx, oesophagus, stomach, liver; 2d. Respiratory, as the larynx, trachea, 
 lungs ; 3d. Circulatory, as the heart and great vessels. It associates it- 
 self intimately with the sympathetic, and aids it in forming several great 
 plexuses. 
 
 At its root the pneumogastric is sensory, but in its trunk it possesses 
 a double function, arising from its intermingling with other nerves, as the 
 spinal accessory and sympathetic. Though the trunk, if irritated, gives 
 rise to pain, we are not, under ordinary circumstances, conscious of indi- 
 cations, as, for example, in the act of breathing, in which we do not per- 
 ceive the necessity of respiration, except the access of the air be too long 
 delayed. The pharyngeal branch is the chief motor nerve of the pharynx 
 and palate. The superior laryngeal is the sensory nerve of the larynx, 
 the inferior laryngeal being the motor. Considered along with the spi- 
 nal accessory, the pneumogastric presents an analogy to a spinal nerve ; 
 the accessory constituting the anterior or motor root, and the pneumo- 
 gastric, with its ganglion, the sensory root. 
 
 The pneumogastric nerve was formerly regarded as taking an influen- 
 tial part in the action of the stomach during digestion. The precise na- 
 ture of its agency in this, respect has been already alluded to. In addi- 
 tion, it may be remarked that probably through this nerve is the sensa- 
 tion of hunger conveyed to the mind. 
 
THE PNEUMOGASTRIC NERVE. 
 
 341 
 
 Fig. 170. 
 
 ILLUSTRATION OF THE LEFT TNEUMOGASTRIC NERVE. 
 
 Fig. 170 : 1, 1, 1, the pneumogastric nerve ; 2, anastomosis of it with 
 the hypoglossal ; 3, anastomosis of plexiform ganglion with internal 
 branch of the spinal ; 4, pharyngeal, passing in front of the internal car- 
 otid artery ; 5, superior laryngeal, behind the internal carotid artery ; 6, 
 external laryngeal ; 7, laryngeal plexus, formed by external laryngeal 
 and great sympathetic ; 8, superior cardiac ; 9, middle cardiac ; 10, 10, 
 
 inferior laryngeal, or recurrent, 
 forming a curve round the arch 
 of the aorta ; 11, pulmonary gan- 
 glion ; 12, its anastomosis with 
 the great sympathetic ; 13, pos- 
 terior pulmonary plexus ; 14, 
 cesophageal plexus; 15, curves 
 formed around the oesophagus 
 by the right and left pneumo- 
 gastrics; 16, cesophageal strand 
 traversing the diaphragm ; 17, 
 plexus formed by the strand 
 upon the anterior face of the car- 
 diac end; 18, branches for the 
 great end of the stomach; 19, 
 branches for the small curva- 
 ture ; 20, branches for the ante- 
 rior face of the stomach ; 21, 
 hepatic branches commingling 
 with the hepatic plexus of the 
 great sympathetic, and ramify- 
 ing in the substance of the liver, 
 22, glosso- pharyngeal. 23, its 
 lingual branch , 24, pharyngeal 
 branch ; 25, branch for the sty- 
 lo-pharyngeal muscle; 26, spi- 
 nal ; 27, internal branch, aiding 
 to form the pharyngeal nerve ; 
 28, external branch; 29, twig 
 
 The left pneumogastric nerve. o f external branch anastomos- 
 
 ing with the third cervical ; 30, anastomosis with trapezian branch of 
 the fourth cervical ; 31, cervical portion of great sympathetic ; 32, 32, 
 thoracic portion ; a, thyroid body ; b, trachea ; c, left lung, drawn to the 
 right ; d, liver, raised ; e, oesophagus ; /, great end of the stomach, 
 drawn to the left ; g, arch of the aorta ; the carotid, and subclavian ar- 
 teries, cut. 
 
342 
 
 THE SPINAL ACCESSORY NERVE. 
 
 Fig. 171. 
 
 ILLUSTRATION OF PULMONARY GANGLIA. 
 
 Fig. 172. 
 
 Fig. 171 : 1,1, pulmonary ganglia ; 2, median anas- 
 tomoses of these ganglia at the posterior face of the 
 trachea, and origin of the bronchi ; 3, left laryngeal 
 nerve, aiding to form the bronchial plexus ; 4, anas- 
 tomoses of the two pneumogastrics on the posterior 
 
 Pulmonary ganglia. faCC of the O3SOphagUS. 
 ILLUSTRATION OF INFERIOR LARYNGEALS, ANTERIOR PULMONARY, AND CARDIAC PLEXUS. 
 
 Fig. 172, 1, 1, pneumogastric ; 2, 2, superior laryngeal; 3, 3, exter- 
 nal laryngeal ; 4, superior car- 
 diac nerve; 5, 5, middle cardiac 
 nerves ; 6, inferior cardiacs ; 7, 
 cardiac ganglion and plexus ; 8, 8, 
 nerves from this plexus surround- 
 ing the coronary plexus ; 9, 9, an- 
 terior pulmonary plexus ; 10, 10, 
 inferior laryngeal-: the left em- 
 bracing the arch of the aorta, the 
 right the subclavian artery, both 
 go to the posterior face of the 
 larynx; 11, tracheal branches; 
 A, pulmonary artery ; B, its left 
 branch ; C, its right branch ; D, 
 arch of the aorta ; E, fibrous cord 
 arising from obliteration of the 
 ductus arteriosus ; F, left subclavian ; G, G, left primitive carotid ; H, 
 brachio-cephalic trunk, cut to show cardiac nerves ; I, vena cava supe- 
 rior ; K, left coronary artery and vein ; L, right coronary artery and 
 vein , #, os hyoides ; 5, projecting portion of the larynx ; <?, trachea ; d, 
 thyro-hyoid muscle ; e, c, crico-thyroid ; /*, /*, scalenus anticus ; #, <?, 
 thyroid body ; A, A, diaphragm ; ?, ?", pericardium, cut away. 
 
 OF THE ELEVENTH PAIR, OR SPINAL ACCESSORY NERVE. 
 
 The spinal accessory arises by several filaments from the side of the 
 The eleventh s P ma ^ cord, as low as the fifth or sixth cervical nerve. In 
 pair, or spinal its upward course it communicates with the posterior roots 
 of the first cervical. It then divides into two branches, the 
 smaller joining the pneumogastric, the main trunk passing onward, and 
 being eventually distributed to the trapezius muscle, and also furnishing 
 supplies to the sterno-mastoid. 
 
 The spinal accessory is a motor nerve, as appears from the usual evi- 
 
 The inferior laryngeals. 
 
THE HYPOGLOSSAL AND PHRENIC NERVES. 343 
 
 dence of irritation, and also from its origin and distribution. Its action 
 is not essential in ordinary or involuntary respiration. In voluntary res- 
 piration it is brought into play. 
 
 OF THE TWELFTH PAIR, OR HYPOGLOSSAL NERVE. 
 
 This nerve arises in the groove between the pyramidal and olivary 
 bodies, by 8 or 10 filaments, which are collected into two The twelfth 
 bundles. It next passes forward and crosses inward, pur- pair, or hypo- 
 sues a course which is concave upward, and supplies the gossal< 
 genio-hyoglossus and muscles of the tongue generally, giving off the 
 following branches in its course : the descendens noni, the thyro-hyoid, 
 and filaments connecting the gustative nerve. It also anastomoses with 
 the pneumogastric, spinal accessory, first and second cervical nerves, and 
 sympathetic. 
 
 The hypoglossal is the motor nerve of the tongue, irritation of it giv- 
 ing rise to movements throughout that organ, the lingual branch of 
 the fifth being the sensory. The hypoglossal causes the muscles of the 
 neck to aid in the movements necessary for articulate speech. 
 
 ILLUSTRATION OF THE HYPOGLOSSAL NERVE. 
 
 1, medulla oblongata; 2, glosso-pharyngeal ; 3, pneumo- 
 gastric ; 4, superior laryngeal ; 5, spi- 
 nal ; 6, first cervical pair ; 7, second 
 pair ; 8, third pair ; 9, fourth pair ; 
 10, lingual; 11, origin of hypoglos- 
 sal ; 12, anastomosis of hypoglossal 
 with first cervical; 13, anastomosis 
 with nervous loop of two first cervi- 
 cals ; 14, descending branch of hy- 
 poglossal, anastomosing with, 15, de- 
 scending branches of cervical plexus ; 
 16, twig of thyro-hyoid muscle; 17, 
 The hypogiossai nerve, branches of hyoglossus ; 18, recur- 
 
 rent branch of stylo-glossus ; 19, branches of genio-hyoid ; 20, plexiform 
 branches of hypoglossal ; 21, anastomotic branch with the lingual ; 22, 
 branch for submaxillary ganglion ; A, vertebral artery ; B, external car- 
 otid ; C, lingual ; D, temporal ; E, internal maxillary ; #, portion of the 
 condyle of the occipital bone ; , median section of atlas ; c, styloid pro- 
 cess ; d, stylo-glossus ; e, stylo-pharyngeus ; /*, hyoglossus ; <?, genio- 
 glossus ; A, pterygoideus externus ; ?, pterygoideus internus. 
 
 OF THE PHRENIC NERVE. 
 
 Although the phrenic, or internal respiratory nerve is not strictly in- 
 
344 
 
 THE GEEAT SYMPATHETIC. 
 
 The phrenic eluded in the group now under consideration, yet, considering 
 nerve. its important connection with the motions of respiration, it is 
 
 proper to describe and illustrate it here. 
 
 It arises from the third and fourth cervical nerves, aided by a branch 
 from the fifth, or from the brachial plexus, and from the sympathetic. 
 In its descent it communicates with the lower cervical ganglion, enters 
 the thorax between the subclavian vein and artery, and, passing along 
 the side of the pericardium, descends to the diaphragm, the right phrenic 
 being perpendicular, and the left running obliquely round the apex of the 
 heart. It is distributed, for the most part, to both faces of the diaphragm, 
 superior and inferior. It is the motor nerve of the diaphragm. 
 
 Fig. 174 
 
 The phrenic nerve. 
 
 ILLUSTRATION OF THE PHRENIC NERVE. 
 
 Fig. 174: 1,1, root of the phrenic 
 nerve, furnished by the fourth cervi- 
 cal ; 2, 2, roots from the brachial 
 plexus ; anastomosis of this nerve 
 with branch of the subclavian ; 4, 
 anastomosis with the inferior cer- 
 vical ganglion ; 5, 5, curve of the 
 hypoglossal, cut, sending a twig to 
 the phrenic nerve ; 6, 6, pericardiac 
 branches of the phrenic nerve ; 7, 
 7, branches to the superior face of 
 the diaphragm; 8, 8, branches to 
 the inferior face of the diaphragm ; 
 9, anastomoses . of these branches 
 with, 10, the solar plexus ; 11, 
 transverse communication of the 
 phrenic nerves. 
 
 OF THE GREAT SYMPATHETIC NERVE. 
 
 Under the designations of sympathetic, visceral, toisplanchnic, gangli- 
 Position and on * c ' i ntercosta ^ or nerve of organic life, passes a series of 
 structure of the reddish or gray ganglia, interconnected by nervous strands, 
 sympathetic, extending along each side of the vertebral column, from the 
 head to the coccyx, communicating with all other nerves of the body, 
 and distributing branches to the internal viscera, or organs of involunta- 
 ry function. These ganglia are less numerous than the vertebrae ; the 
 chain on each side communicates with its colleague through plexuses, 
 and the ganglion impar is the common uniting point on the coccyx be- 
 low. By some it is supposed that the ganglion of Ribes, and by others 
 that the pituitary body has the same function in the cranium above. 
 
CONNECTION OF SYMPATHETIC AND SPINAL. 
 
 345 
 
 What are here spoken of as nervous strands are perhaps more correctly 
 prolongations of the ganglia themselves. 
 
 The origin of the sympathetic has been long a subject of dispute, some 
 supposing that it is a special system, of which the ganglia are origin of the 
 so many independent centres, establishing incidental commu- sympathetic, 
 nications with the cerebro-spinal ; others, that its origin is in the internal 
 viscera, and its termination in the cerebro-spinal system, this opinion be- 
 ing supported by the alleged facts that the sympathetic, in its develop- 
 ment, appears before the other parts of the nervous system, and simulta- 
 neously with the splanchnic organs, and that it has been found in mon- 
 sters without a brain or spinal cord ; others, again, suppose that it orig- 
 inates from the roots of the cerebro-spinal system, and terminates in the 
 interior organs. Regarding it in this light, some have imputed its origin 
 to all the spinal, and fifth and sixth cranial conjointly ; others have lim- 
 ited it to the two latter. 
 
 The pneumogastric nerve aids it in forming three of its plexuses, the 
 pharyngeal, cardiac, and solar. In certain respects the pneu- Eelations of 
 mogastric and sympathetic seem to exhibit a reciprocal de- 
 velopment, in some of the lower animals the former pre- pathetic, 
 dominating over, and supplying the place of the latter; and this replace- 
 ment, it is said, goes on in the descending series until, in the cephalopo- 
 dous mollusks, the sympathetic has disappeared, and the pneumogastric 
 takes its place. 
 
 Fig. 175 illustrates the relation 
 of the sympathetic and spinal nerves : 
 c, c, anterior fissure of the spinal 
 cord ; , anterior root of a dorsal 
 spinal nerve ; p, posterior root, with 
 its ganglion ; #', anterior branch ; p' 9 
 posterior branch ; s, sympathetic ; <?, 
 its double junction with the anterior 
 branch of the spinal nerve by a white 
 and a gray filament. 
 
 The sympathetic chain therefore 
 establishes connections Connection of 
 with the cerebro-spinal SfgSfe 
 system. Each spinal tem. 
 nerve is brought into relation with 
 it through two strands, a tubular or 
 white, and a gelatinous or gray. 
 The tubular or white strand may be 
 regarded as actually arising from the 
 spinal cord, and consisting of motor 
 
 Relation of the sympathetic and spinal. an( J Se nSOry filaments. It makes its 
 
 Fiy. 1T5. 
 
346 THE GKEAT SYMPATHETIC. 
 
 way to the ganglion of the sympathetic, passes over and through it, its 
 fibres conjoining themselves with gray ones, which they have gathered in 
 the ganglion. The gray or gelatinous root is to "be viewed as having its 
 origin in the ganglion of the sympathetic, and ^sending its fibres chiefly 
 to the ganglion on the posterior root of the spinal nerve, but few of them 
 doubtfully communicating with the anterior root. The fibres which seem 
 to enter the cord are probably for the supply of blood-vessels. Each of 
 these sympathetic ganglia is, therefore, a nervous centre, sending forth 
 strands in three directions : 1st. To join the spinal fibres in their distri- 
 bution ; 2d. To the spinal cord itself, or chiefly to the ganglia on the pos- 
 terior roots of its nerves ; 3d. To the next sympathetic ganglion above. 
 Sympathetic In the various plexuses of the sympathetic, vesicles are found, 
 plexuses. f rom w hi cn g^y fibres seem to originate. The branches which 
 supply the viscera constantly form plexuses ; the arteries are surrounded 
 with such a net-work. The splanchnic ganglia, with their interconnect- 
 ing strands, and supplies from the cerebro-spinal, give rise to four great 
 plexuses: the pharyngeal, the cardiac, the solar, and the hypogastric. 
 The first and last of these are in symmetrical pairs ; the other two are 
 single, and placed on the median line. 
 
 From its construction the sympathetic can not be regarded as an iso- 
 Ph -sical effects ^ ate ^ or self-acting system, since all its branches contain 
 of sympathetic fibres derived from the cerebro-spinal. In function it must 
 therefore be adjuvant to that system, and it must be admit- 
 ted that the motor and sensory qualities of the included spinal fibres, ac- 
 cording as they have been derived from the anterior or posterior columns 
 of the cord, are continued in their association with the sympathetic. 
 Hence, in so far as being a compound nerve, it possesses both those func- 
 tions, and this conclusion is corroborated by such facts as those of the 
 distribution of the sympathetic both to muscular portions, as to the heart, 
 and also to sensitive ones ; by the circumstance that the intestinal canal 
 from the stomach to the end of the colon receives its nervous supply 
 from this source alone. Experiments on the sympathetic ganglia estab- 
 lish a similar conclusion, irritation of the cceliac ganglion, for instance, 
 giving rise to increased peristaltic motions, and pathological observations 
 furnishing like evidence as regards the sensory function. Compared 
 with other nerve trunks, the sympathetic is much less active in these re- 
 spects, a high irritation of the parts supplied by it often being required 
 to cause pain, and, in like manner, its motor fibres are little under the in- 
 fluence of the will. 
 
 The sympathetic transmits sensations so tardily that it has been sup- 
 posed that one office of its ganglia is for the purpose of cutting off such 
 impressions ; and, in like manner, when motor fibres of the cerebro-spi- 
 nal system pass through its ganglia, their conducting power appears to 
 
THE GREAT SYMPATHETIC. 347 
 
 be impaired. There does not seem to be any decisive proof that any of 
 the fibres of the sympathetic, properly speaking, are motor or sensory, or 
 that its ganglia produce reflex action, the agency which it exerts in these 
 respects on the muscular structure of the heart, blood-vessels, digestive 
 or urinary organs, being due to the associated cerebro-spinal fibres. 
 
 In this manner, by its distribution to the arteries, the sympathetic, as 
 a compound nerve, exerts a power over the passage of the blood through 
 them by influencing their contractility, and thereby their diameter. In 
 virtue of this, it therefore affects the rapidity of secretion, and also regu- 
 lates the rate of nutrition. The entire digestive tract, with its dependen- 
 cies are thus brought under its influence, the salivary glands, pharynx, 
 oesophagus, stomach, intestine, nasal, bronchial, and pulmonary sur- 
 faces, etc. 
 
 The view of the function of ganglia presented on preceding pages is 
 strongly supported by the mechanism and phenomena of the Itg an Ha are 
 sympathetic nerve. Its ganglia permit the influence passing reservoirs of 
 along the nervous cords to escape therefrom into new chan- ( 
 nels, and also retain and store up nervous power. They become, there- 
 fore, magazines of force, and are hence capable of sustaining rhythmic 
 movements. Even after organs have been exsected, they will still exhib- 
 it, under the influence of these ganglia, their accustomed motion, as is the 
 case with the heart, which, in some of the cold-blooded animals, will con- 
 tinue its contractions for many hours after it has been cut out of the body. 
 
 I therefore regard the sympathetic system as having for one of it& 
 main functions the equalization or balancing of the nervous Conclusion 
 force, storing up all transient excesses of it, and furnishing f^Sn^ftiL 
 all transient deficiencies. As in a mechanical contrivance, sympathetic. 
 in which the prime mover works in an irregular way, the fly-wheel har- 
 monizes all such variations, storing up or supplying power as the cir- 
 cumstances may require, so does this complicated apparatus act in the 
 mechanism of innervation. And it is worthy of remark, that some such 
 arrangement would seem to be necessary, since the organs of digestion, to 
 which the sympathetic is so largely directed, are periodically in activity 
 and periodically quiescent. 
 
 It is to be greatly regretted that the term sympathetic has been ap- 
 plied to this important nerve, since that term, as defining function, has 
 led to the promulgation of theoretical views which have exerted an influ- 
 ence to the disadvantage of the progress of physiology views which will 
 not bear the test of anatomical criticism, and which are therefore incor- 
 rect. It is always much better to give designations in allusion to struc- 
 ture or position than to function, especially where the function is doubt- 
 ful. For this reason, the title of intercostal is much preferable to that 
 of nerve of organic life, and trisplanchnic better than sympathetic an 
 
348 
 
 THE GKEAT SYMPATHETIC. 
 
 imposing but mysterious epithet, which has been a source of injury to 
 the science, and which it would be well even now to replace by such a 
 term as vincular or moniliform nerve, or some title of equivalent import. 
 
 ILLUSTRATION OF THE GREAT SYMPATHETIC. 
 
 Fig - m ' Fig. 176: 1, globe of the eye, 
 
 dissected so as to show the ciliary 
 nerves ; 2, branch of the inferior ob- 
 lique and the motor root of the oph- 
 thalmic ganglion ; 3, 3, 3, the three 
 branches of the trifacial, in connec- 
 tion with most of the cranial gan- 
 glia, that is, with, 4, ophthalmic gan- 
 glion, 5, spheno-palatine, 6, otic, 7, 
 submaxillary, and, 8, sublingual ; 
 9, external motor oculi; 10, facial 
 and its anastomoses with the sphe- 
 no-palatine and otic ganglia ; 11, 
 glosso - pharyngeal ; 12, 12, right 
 pneumogastric ; 13, left pneumo- 
 gastric; 14, spinal; 15, hypoglos- 
 sal; 16, 16, cervical plexus; 17, 
 brachial plexus ; 18, 18, intercostal 
 nerves ; 19, 19, lumbar plexus ; 
 20, sacral plexus ; 21, superior cer- 
 vical ganglion, furnishing two caro- 
 tid branches, forming the carotid 
 plexus around the artery of that 
 name, and from which arise the 
 anastomoses with, 22, nerve of Ja- 
 cobson, 23, carotid branch of vid- 
 ian nerve, 24, external motor oc- 
 uli, 25, ophthalmic ganglion ; 26, 
 twig for the pituitary gland; 27, 
 anastomosis of superior cervical 
 ganglion with the first cervical 
 pairs ; 28, carotid and" pharyngeal 
 branches ; 29, pharyngeal and in- 
 tercarotid plexus ; 30, laryngeal 
 branch, anastomosed with the external laryngeal of the pneumogastric ; 
 31, superior cardiac nerve ; 32, strands of junction of the superior cervi- 
 cal ganglion with, 33, middle cervical ganglion : among the internal 
 branches of the latter are, 34, the anastomotic with, 35, the recurrent 
 
 The great sympathetic nerve. 
 
THE ABDOMINAL PLEXUSES. 
 
 349 
 
 nerve, 36, middle cardiac nerve ; 37, strand of junction of middle cervical 
 ganglion with, 38, inferior cervical ganglion ; 40, twigs furnished by in- 
 ferior cervical ganglion around the subclavian and vertebral arteries ; 41, 
 anastomotic branch with the first intercostal nerve ; 42, cardiac plexus 
 and ganglion ; 43, 44, secondary plexuses of right and left coronary ar- 
 teries ; from 45 to 46, thoracic ganglionary chain ; 47, the great splanch- 
 nic traversing the diaphragm, and going to, 48, semilunar ganglion ; 49, 
 little splanchnic ; 50, solar plexus, receiving, 51, anastomosis of pneu- 
 mogastric, 52, phrenic nerve; 53, gastric coronary; 54, hepatic; 55, sple- 
 nic ; 56, superior mesenteric, enveloping the arteries of those names ; 57, 
 renal plexus ; from 58 to 58, lumbar ganglionic chain; 59, lumbo-aortic 
 plexus, presenting two enlargements, one, 60, above, the other, 61, below 
 the bifurcation of the aorta; 62, spermatic plexus ; 63, inferior mesenteric; 
 64, hypogastric plexus ; 65 to 65, sacral ganglionic chain ; 66, terminal 
 coccygeal ganglion ; A, heart, slightly turned aside to show the cardiac 
 plexus ; B, arch of the aorta, also drawn aside by hook ; C, innominata ; 
 D, subclavian, cut, to show inferior cervical ganglion ; E, inferior thy> 
 roid; F, portion of external carotid; G, internal carotid; H, thoracic 
 aorta ; I, abdominal aorta ; J, primitive iliac ; K, intercostals ; L, pul- 
 monary artery, of which the right branch is cut ; M, superior vena cava, 
 cut at its origin ; N, vena cava inferior ; O, pulmonary veins ; #, lach- 
 rymal gland ; &, sublingual gland ; c, submaxillary gland ; d, thyroid 
 body ; e, trachea ; f, oesophagus, going to, g, the stomach ; A, several in- 
 testinal loops with superior mesenteric plexus ; i, transverse colon ; j 9 
 sigmoid flexure ; &, rectum ; Z, bladder ; m, ureter ; ft, prostate ; o, ve- 
 Fi 9- - sicula seminalis ; p, vas deferens ; , sperm- 
 
 atic cord; r, r, diaphragm. 
 
 THE ABDOMINAL PLEXUSES. 
 
 The abdominal plexuses. 
 
 Fig. 177: 1, 1, 1, 1, portion of the right 
 and left ganglionic chain ; 2, coccygeal gan- 
 glion ; 3, median anastomoses of the two 
 sacral cords ; 4, 4, great splanchnic, right 
 and left, traversing the diaphragm, and go- 
 ing to, 5, 5, semilunar ganglia ; 6, solar 
 plexus ; 7, splenic plexus ; 8, hepatic plex- 
 us ; 9, coronary plexus of stomach ; 10, 
 anastomoses of the two pneumogastrics, 
 right and left, with solar plexus and gastric 
 coronary; 11, diaphragmatic plexus and su- 
 perior capsular; 12, anastomoses of these 
 two plexuses with the phrenic nerve ; 13, 
 middle capsular plexus ; 14, inferior capsu- 
 
350 
 
 THE SOLAR PLEXUS. 
 
 lar plexus, coming from, 15, renal plexus ; 16, 16, lesser splanchnics, 
 traversing the diaphragm; 17, superior mesenteric plexus; 18, sperm- 
 atic plexus, arising from three sources, the renal, lumbo-aortic, and hypo- 
 gastric; from 19 to 19, lumbo-aortic plexus; 20, 20, its bifurcations; 
 21, inferior mesenteric plexus ; 22, 22, its anastomoses with, 23, 23, 
 hypogastric plexus on each side ; 24, 24, sacral plexus ; , diaphragm, 
 cut ; , portion of stomach and oesophagus ; c, spleen ; d, kidney and its 
 supra-renal capsule ; e, testicle ; /*, ureter, cut ; A, A, aorta. 
 
 THE SOLAR PLEXUS. 
 
 Fig. 178: 1, solar plexus, furnishing, 2, hepatic plexus; 3, gastric 
 coronary plexus, and, 4, splenic plexus ; 5, anastomoses of right and left 
 pneumogastric with the solar plexus and gastric coronary ; 6, branches 
 of pneumogastric going to the liver ; 7, plexus of biliary ducts; 8, origin 
 of superior mesenteric plexus ; 9, renal plexus ; 10, capsular plexus ; 
 11, 11, spermatic plexus; 12, commencement of lumbo-aortic plexus; 
 13, portion of inferior mesenteric plexus ; a, the liver, raised ; , the stom- 
 ach, cut at its great end ; , the spleen ; d, the kidney ; e, kidney, cut ; 
 f, supra-renal capsule ; <7, <?, ureters ; . Fig. ITO. 
 
 \ duodenum ; i, i, pancreas. 
 
 11 a tt 
 
 The solar plexus. 
 
 The mesenteric plexuses. 
 
 SUPERIOR MESENTERIC AND INFERIOR MESENTERIC PLEXUS. 
 
 Fig. 179: 1, superior mesenteric plexus, surrounding the divisions of 
 the artery of the same name, and offering many flat ganglia ; 2, portion 
 of inferior mesenteric plexus ; #, ccecum and appendix vermiformis ; b, b, 
 transverse colon ; <?, portion of small intestine. 
 
THE VOICE. 351 
 
 CHAPTER XVIII. 
 
 OF THE VOICE. 
 
 Origin of the Voice. Comparative Physiology of Noise, Song, Voice. Distinction between Song 
 and Speech. The Larynx, and its Action in Singing. Mutter's Explanation of the Action of 
 the Vocal Organs. Speaking Animals and Machines. 
 
 Nature of Words and their constituent Sounds. Vowels and Consonants. Whispering. Use 
 of the Voice of Animals. 
 
 Of Languages: their Duration, Character, History. Registry of Sounds by Writing and Print- 
 ing. Musical Signs. Alphabetic Writing. 
 
 FOR the production of the sounds necessary for intercommunication 
 among the higher animals, and particularly for the speech of Voice arises 
 man, it might be supposed that some complicated and elab- p^ults^of 
 orate contrivance must needs be resorted to. This object is, respiration, 
 however, accomplished by merely employing, on its escape from the sys- 
 tem, the wasted product of respiration, the breath, which, as it issues out- 
 ward through the respiratory passages, sets in motion a simple mechan- 
 ism, and thereby originates all the exquisite modulations of song, and 
 all the impressive utterances of speech. Is it not to be admired that 
 thus, out of dead and dismissed matter, results of so high an order, ma- 
 terially and mentally, are obtained? 
 
 What might be termed the comparative physiology of the voice is very 
 simple. It appears* first in invertebrate animals as a mo- Com arative 
 notonous noise or cry, which gradually, in higher tribes, be- physiology of 
 comes more varied in loudness and note. It is worthy of ' 
 remark that, in the different stages of his existence man himself furnishes 
 an illustration of this course. Voiceless before birth, with a piteous or 
 monotonous cry in early infancy, articulate speech and song are the re- 
 sult of education, and through these the power is eventually gained of 
 expressing the most refined emotions and the most elevated ideas. The 
 solitary bell-like sound which the nudibranchiate gasteropods emit, thus 
 produces, by its successive improvements, a wonderful result at last. 
 
 Among insects the modes of producing sounds are very various, some 
 effecting it by percussion, some by the friction of horny or- Production of 
 gans. In others, the extremity of the trachea, through rudimentary 
 which the air escapes, is accommodated with vibrating mem- sounds - 
 branes. According to Burmeister, the contractions of the muscles of the 
 wings, which are brought vigorously into action during flying, occasion 
 
352 RUDIMENTARY SOUNDS. 
 
 an alternate pressure and relaxation 
 upon the tracheal tubes. The air, 
 thus passing in and out, throws into 
 vibration the valves of the spiracle, 
 which, as seen in Fig. 180, are sus- 
 pended upon a dozen or more flexible 
 supports ; but their free edges, ap- 
 proaching within a certain distance of 
 each other, are thrown into quick vi- 
 bration by the passing current, in the 
 same manner as is the vibrating spring 
 of the accordeon. These vibrating 
 plates of insects are the rudiments of 
 
 Spiracle of insect what ^ become fa perfect ^ ap _ 
 
 paratus in man. Again, in others, the swiftly-recurring beating of the 
 wings produces a sound, as, for example, in the musquito. Among ver- 
 tebrated animals, those which breathe the air are vocal, nearly all fishes 
 Sounds of rep- being mute. From fishes, as we pass upward, the sound 
 tiles and birds. an( j t ne instrument which makes it increase together in com- 
 plexity. Through a simple chink, the air expelled from the respiratory 
 sacs of snakes, by the contraction of their abdominal muscles, issues 
 forth as a mere hiss, the sound being increased in the frog by the devel- 
 opment of resonant cavities. From these simple noises we are conduct- 
 .ed to the musical notes of birds, some of which are of exquisite purity 
 and sweetness. In these, the vocal glottis is situated at the bifurcation 
 of the trachea, another glottis being above for the final es- 
 cape of the air. These vertebrated animals first introduce 
 us to the mechanism for articulate speech, the rav&n and parrot being 
 able to pronounce words with distinctness. The articulation is effected, 
 as in man, by the motions of the tongue and other portions of the mouth. 
 For the further consideration of this subject, it is necessary to under- 
 Distinction be- s ^ an( ^ tnat there i g a distinction between song and speech, 
 tween song and Song is produced by the glottis, speech by the mouth; or, 
 speech. perhaps, a more correct statement would be, that the larynx 
 
 is the organ of song, the mouth of that form of speech which we call 
 whispering, and for which nothing is required but a stream of air issuing 
 from the fauces, the tongue and other organs giving it articulation ; but 
 for audible speech, a noise is created in the larynx, and modified by ar- 
 ticulation in the mouth. 
 
 The double larynx of birds is replaced by a single larynx in man, 
 which serves at the same time for the entrance and exit of air, and like- 
 wise for vocalization. Those birds in which the lower larynx is absent 
 are voiceless. A general idea of the construction of the organ of voice 
 
ACTION OF THE VOCAL COEDS. 353 
 
 in man may be gathered by supposing it to be composed of three por- 
 tions, the trachea, the larynx, and the mouth. The trachea Description of 
 is the tube by which air is brought from the lungs and de- the lar J nx - 
 livered into the larynx, which is a superposed structure, arranged upon 
 the cricoid cartilage, on which is articulated the thyroid cartilage by its 
 lower horns, around which a certain degree of rotation can be accomplish- 
 ed, so that the front of the thyroid may be elevated or depressed with a 
 kind of bowing motion. Posteriorly, on the cricoid cartilage are placed 
 the arytenoid cartilages, which can be approached or separated from each 
 other, and from their summits pass to the front of the thyroid cartilage 
 the inferior laryngeal ligaments or vocal cords. These constitute the 
 essential organ of sound. The thyroid cartilage, by its motions, can de- 
 termine the strain put upon them, and the arytenoids can either bring 
 them into parallelism, or place them at an acute angle. The chink or fis- 
 sure between them is the rima glottidis : its figure and width vary with 
 the recession or approximation of the vocal cords, which, as the air passes 
 by them, are thrown into vibration in the same manner as the reed in mu- 
 sical instruments. The epiglottis cartilage, which is above, guards the 
 passage, and may also be supposed, by its descent, to deaden the sounds. 
 
 The slowness or rapidity of the vibration is dependent on the stretch 
 of the vocal cords. The manner in which various degrees Regulation of 
 of tension can be given to the cords is readily understood by the vocai cords, 
 considering their attachments. In front, as we have said, they are fast- 
 ened to the thyroid cartilage, posteriorly to the arytenoids. When the 
 thyroid cartilage executes a bowing motion forward, the vocal cords are 
 put upon the stretch, and similar variations of their tension and also of 
 their position can be given by the movements of the arytenoid cartilages 
 behind. When the air is moving in and out without giving rise to any 
 sound, the chink of the glottis is angular, its point being forward, and 
 from that the cords diverge posteriorly. For the production of sound, 
 the cords must be brought parallel, or even inclining toward each other. 
 If they incline away from each other, no sound will be produced. The 
 pitch of the note will be determined by the stretch of the cords, and this, 
 in its turn, will be determined by the contraction of the vocal muscles. 
 The crico-thyroid and sterno-thyroid bow the front of the thyroid cartil- 
 age down, the thyro-arytenoid and thyro-hyoid carry it back ; the for- 
 mer therefore stretch the cords, and the latter relax them. The opening 
 of the glottis is likewise determined by other muscles, the posterior cri- 
 co-arytenoid dilating it, and the lateral crico-arytenoid and the transverse 
 arytenoid closing it. 
 
 Fig. 181, p. 354, is the larynx, seen in profile : <z, a, half of the hyoid 
 bone ; b, thyroid cartilage, cut ; c, thyro-hyoid membrane ; <#, cricoid 
 cartilage ; e, trachea ; f, oesophagus ; g, epiglottis ; A, great horn of the 
 
 Z 
 
354 
 
 ACTION OF THE VOCAL ORGANS. 
 
 Fig. 181. 
 
 of larynx. 
 
 Posterior view of 
 larynx. 
 
 thyroid cartilage, united to, t, the great horn of the os hy- 
 oides by, &, the lateral thyro-hyoid ligament ; Z, thyro-hyoid 
 membrane, traversed by the superior laryngeal nerve ; m, 
 posterior crico-arytenoid muscle ; ft, lateral crico-arytenoid ; 
 1, inferior laryngeal nerve; 2, posterior crico-arytenoid 
 twigs ; 3, lateral crico-arytenoid twigs ; 4, thyro-arytenoid 
 twigs ; 5, arytenoid twig. 
 
 Fig. 182 is the posterior view of the lar- 
 ynx : a, base of the tongue ; , posterior bor- 
 der of the thyroid cartilage ; c, <?, thyroid body ; d, pos- 
 terior crico-arytenoid muscle ; 0, arytenoid muscle ; 1,1, 
 superior laryngeal, traversing the superior thyro-hyoid 
 membrane, and giving off lingual and epiglottic branches, 
 and others to the mucous membrane covering the poste- 
 rior face of the larynx ; 2, twig for the arytenoid muscle ; 
 3, anastomotic of Galien ; 4, inferior laryngeal ; 5, tra- 
 cheal branches ; 6, twig for the posterior crico-arytenoid 
 muscle ; 7, twig for the arytenoid muscle ; 8, branch for the lateral crico- 
 arytenoid and posterior crico-arytenoid muscles. 
 
 The researches of Miiller furnish the best account we possess of the 
 Midler's ex- action of the vocal organs. He has shown that the larynx 
 the action of the * s essentially a reed instrument with a double membranous 
 vocal organs, tongue. That the rima glottidis is the seat of the origin of 
 the sound is proved by the fact that when an aperture exists in the tra- 
 chea below the glottis the voice disappears, but if above the glottis there 
 is no effect. Magendie records the case of a man who had a fistulous 
 opening in his trachea, and who could not speak unless he closed it or 
 wore a tight cravat. Moreover, the human or animal larynx can be made 
 to produce its characteristic sounds with more or less distinctness, after it 
 has been removed from the body, by directing a current of air through 
 the trachea. Cases have occurred which have afforded the opportunity 
 of observing the condition of the glottis while emitting sounds. The 
 vocal cords are brought into parallelism with one another, and separated 
 by an interval of scarcely more than from the y^ to the y|^ of an inch ; 
 but when the air is moving in and out silently, the fissure assumes a di- 
 vergent or triangular form. 
 
 Professor Miiller gives the following account of the mode of produc- 
 tion of the notes of the natural voice. " The vocal ligaments vibrate in 
 their entire length, and with them the surrounding membranes and the 
 thyro-arytenoid muscles. For the deepest notes, the vocal ligaments are 
 much relaxed by the approximation of the thyroid to the arytenoid car- 
 tilages. The lips of the glottis are, in this state of the larynx, not only 
 quite devoid of tension j they are, when at rest, even wrinkled and pli- 
 
OF SINGING. 355 
 
 cated, "but they become stretched "by the current of air, and thus acquire 
 the degree of tension necessary for vibration. From the deepest note 
 thus produced, the vocal sounds may be raised about an octave by al- 
 lowing the vocal cords to have a slight degree of tension, which the elas- 
 tic crico-thyroid ligament can give them by drawing the thyroid cartilage 
 toward the cricoid. The medium state, in which the cords are neither 
 relaxed and wrinkled nor stretched, is the condition for the middle notes 
 of the natural register, those which are most easily produced. The or- 
 dinary tones of the voice in speaking are intermediate between these and 
 the deep bass notes. The higher notes are produced and the correspond- 
 ing falsetto notes avoided by the lateral compression of the vocal cords, 
 and by the narrowing of the space beneath them by means of the thyro- 
 arytenoid muscles, and farther by increasing the force of the current of 
 air ; the muscular tension given to the lips of the glottis by the muscles 
 above mentioned must also be taken into account, as contributing to the 
 production of the notes of the natural register." 
 
 An artificial larynx, constructed in such a way as to represent more 
 or less perfectly the preceding conditions, will give rise to Artificial la- 
 sounds analogous to those of the human larynx. Such have r y nx - 
 been made of leather, and, better still, of caoutchouc. 
 
 The narrower the glottis is made, and the more tightly the cords are 
 strained, the more rapidly they will vibrate, and the higher will be the 
 musical note emitted. In an individual the range of the Relations of the 
 voice is rarely three octaves, but the male and female voice, larynx in sing- 
 taken together, may be considered as reaching to four. Gen- mg ' 
 erally, the lowest female note is about an octave higher than the lowest 
 male, a similar remark applying to their highest notes respectively. 
 They differ also intrinsically from each other, just as different wind in- 
 struments sounding the same note give it of a different quality. More- 
 over, in each sex there arc different voices : in the male, the base and the 
 tenor ; in the female, the contralto and soprano. The base usually reach- 
 es lower notes than the tenor, and the tenor higher than the base ; the 
 contralto reaches usually lower notes than the soprano, and the soprano 
 higher ones than the contralto, though these distinctions are by no means 
 uniform. There are, again, intermediate complications : thus the bary- 
 tone intervenes between the base and the tenor, and the mezzo soprano 
 between the contralto and soprano. The chief reason for the difference 
 between the voice in the sexes is in the difference of the length of their 
 vocal cords, which are in men and women* respectively in the proportion 
 of three to two ; but besides this, those personal peculiarities which we 
 so readily recognize in the voices of individuals are due to differences in 
 the structure of the tissues forming the vocal mechanism, or peculiarities 
 in the size and condition of the resonant cavities. Frequently the same 
 
356 NATURE OF VOCAL SOUNDS. 
 
 individual is capable of singing in two different voices, known as chest 
 notes and falsetto notes. The chest notes are produced by the ordinary 
 mode of vibration ; the falsetto notes, which are purer or more fluty, are 
 considered to be probably due to vibrations of the harmonic subdivisions 
 of the column of air in the trachea, or to vibrations of the inner borders 
 of the vocal cords. 
 
 While thus song is laryngeal, speech, which is a modification thereof, 
 Speaking ani- * s ora *' or P ro duced ^7 tne mouth. Man is not alone endow- 
 mais and ma- ed with the faculty of uttering articulate sounds : there are 
 several other animals which, by education, may be taught to 
 express them. Ingenious mechanics have also repeatedly invented in- 
 struments, the construction of which, being upon the same principle as 
 that of the vocal organs, has combined the sounds of letters into words, 
 and even into sentences, a convincing proof not only of the mechanical 
 nature of articulate sounds, but also of the perfect manner in which the 
 natural mechanism is understood. Animals which have been taught to 
 speak may also be regarded as automata, for they have no comprehen- 
 sion of what it is they are uttering, and never produce articulate com- 
 binations spontaneously, but only as the result of instruction. 
 
 Like the automata just alluded to, the human voice expresses words 
 Words originate ^ v com bining their constituent letters together. Gramma- 
 by combining rians divide letters into two groups, vowels and consonants, 
 defining the vowel as a sound that can be uttered by itself, 
 the consonant taking its name' from the fact that it can only be uttered 
 consonantly with a vowel. By personal experiment, it may be easily 
 proved that the vowel is a continuous sound, which may be kept up just 
 as long as the breath will enable, and, on examining the position of the 
 Consonants tongue and other movable portions of the mouth, the particular 
 and vowels, arrangement necessary for pronouncing the letters #, 0, z, o, u, 
 or the sixteen or eighteen vowel sounds of the Continental languages, will 
 be detected. It will be found that the determining condition is, for the 
 most part, the peculiar modification of the oral apertures. It will also 
 be discovered that articulation is wholly independent of the larynx, since 
 merely by expelling the air through the mouth, without permitting any 
 laryngeal sound to be formed, all the letters may be articulated in a whis- 
 per. M. Deleau has illustrated this fact in an ingenious way by put- 
 ting an India-rubber tube through the nostril, so as to reach the poste- 
 rior portion of the mouth, and causing another individual to blow gently 
 through it ; while the organs of the mouth are silently thrown into those 
 Nature of whis- positions necessary for the utterance of any particular sound, 
 penng. t ^at ar ti c ulate sound will at once appear in whispers ; but 
 
 if, while this is being done, the larynx is permitted to yield a sound, two 
 voices then are heard, one in audible speech and one in a whisper, the 
 
NATURE OF LANGUAGES. 357 
 
 former belonging to the individual who is making the experiment, and 
 the other arising from the air which his companion is blowing into the 
 tube. There is no kind of difficulty in constructing a simple kind of in- 
 strument from which the sounds of the vowels can be produced by gen- 
 tly blowing air into it. 
 
 The consonants are of two kinds, the explosive and continuous. The 
 former arise from an abrupt and momentary action, and dis- Explosive and 
 appear at once; as examples of these, the letters b, d,p, in continuous con- 
 which it may be remarked that the characteristic of the 
 sound disappears in an instant ; hence the term explosive ; and if any 
 attempt be made to continue it, it issues in the utterance of the vowel e ; 
 but in the continuous consonants this does not take place, as in the let- 
 ters n,f, s. In the case of the consonants, as in that of the vowels, the 
 peculiar arrangement of the parts of the mouth, though difficult to de- 
 scribe, may be readily ascertained by personal experiment. 
 
 Of vocal sounds thus originating, it may be remarked, .that in the low- 
 er tribes of animals, their chief use seems to have reference to Use of the 
 the perpetuation of the race. Even in the highest, the changes voice of ani- 
 of the reproductive and vocal organs often occur contempora- 
 neously ; but, though this may be true of mere sounds, the modulated 
 variations thereof have a far more general use. Of languages it may be 
 said that they are the creation of groups or nations of .men, not of indi- 
 viduals, and hence they reach beyond the compass of indi- of languages: 
 vidual life, in some instances having endured for thousands their duration, 
 of years. Moreover, if critically considered, each often contains the his- 
 tory of the race by which it is spoken, and even manifests the broader 
 features of its character ; so our own tongue contains the indications of 
 the two chief political events which have befallen the English nation, at 
 least so far as foreign relations are concerned the conquest of Britain by 
 the Komans, and, a thousand years after, by the French. In conse- 
 quence of the first of these events, the language became, so far as com- 
 mon expressions are concerned, almost bi-lingual. Such simple illustra- 
 tions as the words God, deity ; fatherly, paternal ; motherly, maternal ; 
 heavenly, celestial ; earthly, terrestrial ; hellish, infernal ; womanly, fem- 
 inine, may serve as examples. So well recognized are these principles 
 among linguists that they are resorted to for the decision of pre-historic- 
 al questions. The best and most precise evidence that we have of the 
 Indian origin of the German nations is derived from the occurrence of 
 Sanscrit roots in their vocabulary, and analogies in their grammar. The 
 names of many domestic animals, of farming implements, and of many 
 common objects, are the same in Sanscrit, Latin, Greek, and German. 
 
 Nay, even more than this, from the structure of a language, collated 
 with the history of the people by which it is spoken, we can often judge 
 
358 NATURE OF LANGUAGES. 
 
 Connection of f tne influence of events more perfectly than in any other 
 language with wav so in the two instances which we are referring to as 
 toitie^Sd 011 " illustrations of these remarks, the French conquest did not 
 history. make that deep and abiding impression which the Roman one 
 
 had done. - A thousand years had elapsed between the invasion of Ca3sar 
 and that of William of Normandy, eight hundred only from the latter 
 event to our times, yet the influence of the masculine and civilizing Ro- 
 man has reached through that long interval, has made the deepest im- 
 pression en the national character, and is manifested in almost one half 
 of the sentences that we utter. 
 
 Connected with articulate speech, it may not be out of place to allude 
 Registry of briefly to those great advances which have been made by the 
 in^a^d^rtnf" g enms ^ man i n tne permanent record or registering by 
 ing. written signs ; and as sounds are of two kinds, musical and 
 
 articulate, so we have two distinct methods of writing ; and this, leaving 
 out all the earlier and more imperfect forms, a method for music and one 
 for speech. Of the former, it is scarcely necessary to remark that it is 
 universal ; the combination of sounds designed to be conveyed is com- 
 prehended at once by men of every nation ; but in the writing for speech, 
 various methods have been employed at different times and by different 
 Different meth nat i ns > ^ rom mere picture writing, each sign of which called 
 ods of express- forth in different languages different sounds, through the hi- 
 ing language. er0 giyphi c and Chinese methods up to that most splendid 
 invention of later ages, alphabetic writing, the principle of which is ab- 
 solutely perfect, because it is natural, being to decompose each word into 
 each constituent vowel or consonant sound which it contains, and to 
 write a mark or letter representing each of those sounds. Though many 
 circumstances have contributed to the advancement of the human race, it 
 can not be doubted that this invention has exceeded all others in power, 
 and that alphabetic writing has been the great instrument of civilization. 
 
OF THE SENSES. 359 
 
 CHAPTER XIX. 
 
 OF HEAEING. 
 
 The Senses: General Remarks upon. Five Organs of Sense. Necessity of Apparatus for the 
 Appreciation of Time, Space, Pressure, Temperature, and Chemical Qualities. 
 
 Of Hearing. General Structure of the Organ of Hearing. Physical Peculiarities of Sounds, In- 
 tensity, Time of Vibration, and Quality. The Tympanum, Cochlea, and Semicircular Canals 
 are for the Appreciation of these peculiarities. 
 
 Structure and Functions of the Tympanum, or Measurement of Intensity. 
 
 Structure of the Cochlea, its Spiral Lamina and Scalce. Measures the Time of Vibration. Ac- 
 complishment of Interference in the Scalce. Comparative Anatomy of the Cochlea. 
 
 Structure of the Semicircular Canals. They estimate the Quality of Sounds. 
 
 Comparative Anatomy of the Auditory Mechanism. Its Progress in Development. Imperfection 
 of the Doctrine of Means and Ends. 
 
 OF THE SENSES. 
 
 THE organs and functions which have thus far been described have 
 reference, for the most part, to the conservation of the indi- Function of 
 vidual being, maintaining its structure unimpaired, notwith- the senses - 
 standing the waste it is perpetually undergoing, or conducting its devel- 
 opment. We now enter on the consideration of a totally distinct ap- 
 paratus, the object of which is to put the individual in relation with ex- 
 ternal nature, and to which, therefore, the designation of mechanism of 
 external relation may be appropriately given. 
 
 For the sentient being in its highest development, means must be pro- 
 vided for the perception of time, space, force, and quality. Five organs 
 This is accomplished by what are termed the organs of sense. of sense - 
 They are five in number : 1st. The organ of hearing ; 2d. That of see- 
 ing ; 3d. That of touching ; 4th. That of smelling ; 5th. That of tasting. 
 In the further description of the senses, it will be found that the ear is 
 the organ of time ; the eye that of space ; the tactile apparatus is for the 
 perception offeree ; and that the mechanism for smelling and tasting con- 
 jointly determine the chemical qualities of bodies ; that of smelling ad- 
 dressing itself to substances which are in the vaporous and gaseous state ; 
 and that of tasting, to such as are liquid or dissolved in water. 
 
 We shall pursue the description of the senses in the order in which 
 they have been just enumerated, premising of them respect- The ear is the 
 ively that, the function of hearing being the reception of the or s an of time - 
 succession of sounds, periods of silence, musical notes, and their modu- 
 lations, together with the peculiarities of articulate speech, things which 
 are all inherently and essentially connected with the lapse of time, the 
 
360 OF HEARING. 
 
 The eye is the ear is in a philosophical sense the time organ ; that, the func- 
 organ of space, ^ion of the eye being the estimation of extents, the position 
 of objects, their sizes and apparent distances, this apparatus is, in reality, 
 the space organ, its indications in this particular being rendered more 
 perspicuous and more intense by its quality of being affected by varia- 
 tions of color ; that as the tactile mechanism is affected by extraneous 
 Touch is for ^ orces sucn as pressures, estimating their degree of power, and 
 pressure and being likewise influenced by things which are at a distance, 
 temperature. ^ tem p eratures O f wn i cn are different from the standard 
 which it observes, but not by electrical, magnetic, or luminous agencies, 
 we may infer that its functions are limited to a relation with mechanical 
 Smell and taste powers, strictly speaking, and to heat; that smell and taste, 
 
 for chemical though conveniently treated of as separate functions, de- 
 qualities of gas- . * . ' 
 es and liquids pendent on separate organs, are, in reality, allied in the de- 
 
 respectiveiy. termination of the chemical peculiarities of bodies, and re- 
 spectively adapted to the appreciation of those peculiarities, according as 
 the substance presented may have the gaseous or liquid form. 
 
 OF HEAEING. 
 
 The organ of hearing is composed of three parts, the external ear, the 
 tympanic cavity or tympanum, and the labyrinth. 
 
 The external ear consists of, 1st. The pinna, which is for the purpose 
 Oftheexter- f collecting soniferous waves, and directing them into, 2d. 
 nal ear. The meatus auditorius or auditory canal, a tube about an inch 
 long, and extending to the tympanum. It is not perfectly cylindrical, 
 its vertical diameter being the greatest, and it is curved so as to be con- 
 cave downward. The interior is protected by hairs, and by a waxy se- 
 cretion of the ceruminous glands. 
 
 The tympanum, tympanic cavity, or middle ear, is within the petrous 
 Ofthetympa- tone. It is bounded exteriorly by a thin oval membrane, 
 num - the membrana tympani, which is placed obliquely across the 
 
 meatus, at an angle of about 45 degrees, its outward plane looking down- 
 ward. Across the tympanum there is a chain of three small bones, the 
 malleus or hammer,, the incus or anvil, and the stapes or stirrup. The 
 malleus is attached by its handle to the membrana tympani, and the 
 stapes, which is at the other extreme of the chain, is fastened by its foot- 
 plate to the membrane of the fenestra ovalis. To the short process of 
 the malleus, the tendon of the tensor tympani is attached, and to the neck 
 of the stapes the stapedius. Besides these, other muscles of the tympa- 
 nic cavity may be doubtfully mentioned, as the external muscle or laxa- 
 tor tympani, and the laxator tympani minor. Into the tympanic cavity 
 there are ten openings, of which the more important ones are, 1st. That of 
 the meatus auditorius ; 2d. The fenestra ovalis, which is of an elliptic 
 
STRUCTURE OF THE EAK. 361 
 
 shape and opposite the preceding, the foot-plate of the stapes, as has been 
 said, being placed upon it ; it is also sometimes called fenestra vestibuli ; 
 3d. Fenestra rotunda, which is below the preceding, and separated from 
 it by the promontory. From the circumstance that it leads from the 
 tympanum to the cochlea, it is also called fenestra cochlea? : like the pre- 
 ceding, it is closed by a double membrane ; 4th. The Eustachian tube, 
 which extends from the anterior of the tympanum to the pharynx ; and, 
 5th. The mastoid cells. The smaller openings are for the passage of va- 
 rious nerves and muscles. 
 
 The labyrinth, called likewise the internal ear, consists of three parts, 
 .the vestibule, the semicircular canals, and the cochlea. 
 
 The vestibule has three corners, an anterior, a superior, and a poste- 
 rior, termed its ventricles. There open into it the fenestra oftheiaby- 
 ovalis, the scala vestibuli, and the five openings of the three sem- rinth - 
 icircular canals. Besides these there are some smaller ones, as the aque- 
 duct of the vestibule, and foramina for small arteries, and for the branch- 
 es of the auditory nerve. The semicircular canals are three bony semi- 
 circles opening into the vestibule : upon one of the branches of each there 
 is a dilatation, the ampulla. The three canals are respectively placed in 
 planes at right angles to each other. The cochlea is a spiral bony canal 
 raised upon a central axis, the modiolus : its interior is divided into two 
 passages or scalar by the lamina spiralis. These communicate at the 
 apex of the cochlea through a small aperture, their other extremities 
 opening differently ; the scala vestibuli into the anterior ventricle of the 
 vestibule, and the scala tympani through the fenestra rotunda into the 
 tympanum. The labyrinth contains interiorly a membrane, the mem- 
 branous labyrinth. Between the membranous labyrinth and the bony, 
 a liquid, the perilymph, intervenes ; the membranous labyrinth being 
 also filled with liquid, the endolymph. There is no perilymph in the 
 cochlea. 
 
 Of the three portions of the ear, the external canal is, of course, full 
 of air, as is also the tympanic cavity or drum ; but the labyrinth, as we 
 have seen, is filled with a liquid, and in this the terminal filaments of 
 the auditory nerve are placed. 
 
 The essential part of the mechanism of hearing is the auditory nerve, 
 which arises from the anterior wall of the fourth ventricle, of the audi- 
 and then, joining the facial, passes forward upon the crus cer- ' tor J -nerve. 
 ebelli ; reaching tha meatus, it divides into two portions, the cochlear and 
 vestibular nerves, which subdivide again, and are distributed to the ves- 
 tibule and cochlea respectively in the manner hereafter explained. 
 
 VIEW OF EXTERNAL, MIDDLE, AND INTERNAL EAR. 
 
 Fig. 183 : #, #, pavilion and external auditory canal, or external ear ; 
 
362 
 
 STRUCTURE OF THE EAR. 
 
 Fig. 1S3. 
 
 External, middle, and internal ear. 
 
 #, tympanic cavity, containing the bones ; 
 
 c, hammer and its three muscles, viz., 
 
 d, internal muscle, lodged in the thick- 
 ness of the superior wall of Eustachian 
 tube, and bending at a right angle to be 
 inserted in superior part of handle of 
 hammer ; e, anterior muscle of 'hammer; 
 jf, external muscle of hammer ; g, inte- 
 rior half of membrana tympani, holding 
 the handle of the hammer ; A, tube of 
 Eustachius ; i, internal ear or labyrinth. 
 
 Tympanic cavity. 
 
 TYMPANIC CAVITY, ITS BONES, MUSCLES, AND NERVES. 
 
 Pig. 184 : , hammer, holding, by the anterior and superior part of its 
 
 handle, and by its round extremity, #, the 
 membrana tympani ; <?, internal muscle of 
 hammer ; d, stirrup upon fenestra ovalis ; 
 0, muscle of stirrup ; 1, facial nerve, com- 
 municating with, 2, great superficial pe- 
 trosal, and, 3, little superficial petrosal ; 
 4, chorda tympani ; 5, 5, nervous twig of 
 internal muscle of hammer, arising from 
 motor portion of fifth pair, and traversing otic ganglion ; 6, nervous twig, 
 arising from facial and going to muscle of stirrup ; 7, ganglion of Gasser. 
 
 DIAGRAM SHOWING THE FACIAL IN THE AQUEDUCT OF FALLOPIUS AND ITS ANASTOMOSES. 
 
 Fig. 185 : 1, facial ; 2, nerve of Wrisberg ; 3, petrosal twig of vidian 
 Fig. 185. nerve ; 4, ganglion of Meckel ; 5, little 
 
 petrosal of Longet ; 6, twig of muscle of 
 stirrup; 7, auricular twig of Arnold ; 8, 
 chorda tympani, cut ; 9, ganglion of An- 
 dersch ; 10, nerve of Jacobson, divided 
 into six twigs, viz., 11, twig anastomos- 
 ing with, 12, carotid plexus, 13, twig 
 anastomosing with great superficial pe- 
 Faciai in the aqueduct of Faiiopius. trosal (little deep petrosal of Arnold), 14, 
 little superficial of Arnold, uniting with little petrosal of Longet to form 
 15, a common trunk, which goes to 16, otic ganglion ; 17, twig of fenes- 
 tra rotunda ; 18, twig of fenestra ovalis ; 19, twig of tube of Eustachius. 
 The explanation usually given of the functions of these various parts 
 Common hy- is as follows : The waves of sound, moving through the at- 
 functSn of the Biosphere, pass down the exterior canal and strike upon the 
 auditory parts, membrane of the drum, which is thrown into vibration there- 
 
PEOPERTIES OF SOUND. 363 
 
 by. The little bones which form a chain from this membrane to the oval 
 one at the back of the drum participate in this movement, and, indeed, 
 serve to convey it, without much loss, across the cavity. It is consider- 
 ed that this is their function, since it may be proved experimentally that 
 wave sounds going through such a solid combination, surrounded by at- 
 mospheric air, pass with but very little loss of intensity. Under the im- 
 pulses thus communicated to it, the oval membrane commences to vi- 
 brate, and in those movements the water in the labyrinth joins ; and so 
 the filaments of the auditory nerve become aifected, and the sensation of 
 sound is transmitted to the brain. It is supposed that the three semi- 
 circular canals, which are set at right angles to one another, as it were, 
 occupying the three adjoining faces of a cube, are for the purpose of de- 
 termining in what direction the sound is coming whether upward, down- 
 ward, or laterally. Moreover, it is believed that the little muscles winch 
 operate on the membrane of the drum have the duty of tightening or 
 slackening it so as to receive the sounding waves in the most available 
 way. 
 
 It is not necessary to enter on a lengthy criticism of this explanation. 
 Physiologists have long regretted that it assigns no use for Criticisms on 
 many of the most complicated and delicate arrangements con- this hypothe- 
 nected with the ear, offers no explanation of the manner in S1S ' 
 which that intricate organ is enabled to present to the mind the various 
 relations of sound, and is inconsistent with many of the facts of compar- 
 ative anatomy. Indeed, it is very plain that a true interpretation of the 
 action of the different regions and structures of the ear can only be given 
 from a conjoint study of the physical nature and properties of sounds, of 
 the peculiarities of the soniferous waves which it is necessary p r0 permodeof 
 for us to perceive, of the comparative anatomy of the ear as obtaining a 
 
 i 11 , -1 ri't* i ^ , t true interpret- 
 
 presented in all tribes ol liie ; and, since mere must be a cor- a tion of these 
 respondence among the lower tribes perhaps we might have functions - 
 said the higher too between the organs of voice and the organs of audi- 
 tion, the obscure points in the structure of the latter may be illustrated 
 by what is known of the former. To these might be added the study of 
 its embryonic development. It is by the aid of these different means 
 that I pass to the description of the function of audition. 
 
 What, then, are the physical peculiarities existing in the waves of 
 sound which we actually perceive? They are these three, Three hvsical 
 1st. The intensity, that is, loudness or feebleness of the peculiarities of 
 sound; 2d. Its note or pitch; 3d. Its quality; for two sounds s< 
 of the same intensity and note may differ characteristically. The sound 
 of the violin differs from that of the flute, and this, again, from that of 
 the human voice. Our organ of audition is so constructed that it is af- 
 fected by each of these peculiarities, and transmits them to the mind. 
 
364 STKUCTUEE OF THE DEUM. 
 
 In this respect we may speak of it as a perfect organ ; for all mathemati- 
 cians who have written on the subject of sound agree in setting forth the 
 three peculiarities that have "been mentioned, intensity, note,' quality, as 
 the grand features of waves of sound, and this upon a mere abstract dis- 
 cussion of acoustics. Now these three essential, abstract, or theoretical 
 peculiarities of sound-waves are the very three which the organ of hear- 
 ing seizes upon, and so we are justified in saying that, in this respect, it 
 is perfect in its construction. Premising the remark that mathemati- 
 cians have abundantly proved that the intensity of sounds depends upon 
 the amplitude of excursion of the vibrating particles, and the pitch or note 
 upon wave length, I shall now proceed to offer some arguments in proof of 
 the proposition that the triple function of the ear is discharged in the fol- 
 Functionofthe l wm g wa y : 1^. That the drum is for the measurement of 
 drum, cochlea, intensity; 2d. The cochlea for the recognition of wave length; 
 
 canals. ^ ^ Q semicircular canals for the appreciation of quality. 
 I shall endeavor to show that the ear is not a homogeneous organ, as the 
 older hypothesis supposed, but that one or other of these instrumental 
 parts may be absent, and with it will disappear its' special function, forti- 
 fying this view with facts presented by comparative anatomy, by embry- 
 onic development, and also by the relations of the voice, and showing 
 the parallel between the structure and functions of the ear, the organ for 
 normal vibrations, and of the eye, the organ for transverse ones ; and the 
 analogy and the identity of their embryonic development ; that, for in- 
 stance, the drum is the equivalent of the iris, and the cochlea of the ret- 
 ina and its adjacent parts. 
 
 1st. On the measurement of the intensity of sound, structure of the 
 tympanic cavity or drum, and its functions. 
 
 The tympanic cavity or drum of the ear, as we have briefly described, 
 Structure of * s an a ^ r cav ^7 ^ a cylindroid and flattened shape, in the 
 the drum and petrous portion of the temporal bone. Outwardly it is 
 its functions. bounded ^y the membrana tympani, and on other sides by 
 the petrous bone : it is crossed by a chain of bones, three in number, and 
 named the malleus or hammer-bone, the incus or anvil, and the stapes 
 or stirrup. The Eustachian tube affords a channel of communication 
 from the interior of the drum to the pharynx. Moreover, there is a com- 
 munication with the mastoid cells, but the Eustachian tube is the only 
 outlet to the atmosphere. The whole cavity of the tympanum is lined 
 with mucous membrane and ciliated epithelium, which is also reflected 
 over the bony chain. Upon the inner wall of the tympanum are two 
 chief apertures, the fenestra ovalis and the fenestra rotunda, each closed 
 by membrane. The chain of bones is attached at one end by the handle 
 of the malleus to the membrana tympani, at the other by the foot of the 
 stirrup to the membrane of the fenestra ovalis. 
 
ACTION OF THE EAR MUSCLES. 365 
 
 It is to be remarked that the membrana tympani is placed obliquely 
 at the bottom of the external canal. In a hollow bony cone, Action of the 
 rising upon the interior wall of the tympanum, and called the tensor'tym-* 
 pyramid, the stapedius muscle is placed. Through a little pani. 
 aperture at the apex of the pyramid its tendon goes out, and is inserted 
 in the neck of the stapes. Its action seems to be to make pressure on 
 the membrane of the fenestra ovalis, but as it does this, it tilts the stapes 
 into an oblique position. A second muscle, the Censor tympani, is at- 
 tached in front to the under surface of the petrous bone, and is inserted 
 in the short process of the malleus ; when it contracts it makes tension 
 upon the membrana tympani, drawing it more tightly inward. It is to 
 be especially remarked of both these muscles that they are voluntary ; 
 that is, of the striated variety. Two other muscles are described by 
 some anatomists, and have been indicated in Fig. 183 and 184. Their 
 existence, however, is disputed by others. 
 
 In the opinion of Mr. Toynbee, the action of the two voluntary mus- 
 cles of the ear is as follows. By the tensor tympani the Mr.Toynbee's 
 base of the stapes is pressed inward to ward the vestibule, as views of the ac- 
 
 _. r n _ , , tionof the sta- 
 
 is a piston in its cylinder, and, as soon as the muscle ceases pediusandten- 
 to act, the elastic ligaments which attach the circumference sor ^P* 111 - 
 of the base of the stapes to that of the fenestra ovalis draw it out again. 
 The stapes is moved by two muscles, the tensor tympani and the stape- 
 dius, it being commonly supposed that the latter. aids the former in press- 
 ing the stapes inward, but he shows that it rotates' the base of the stapes 
 and withdraws it from the cavity of the vestibule. This may be demon- 
 strated by pulling the stapediusj when the fluid in the scala vestibuli 
 will be found to move correspondingly. He therefore asserts that the 
 stapedius is the antagonist of the tensor, the former relaxing the laby- 
 rinthine fluid, membrana rotunda, and membrana tympani, the latter 
 rendering them more tense. Agreeably to this, the stapedius is supplied 
 from the portio dura, and the tensor from the otic ganglion. This con- 
 struction might lead to the supposition that the tensor affords protection 
 from loud sounds, and the stapedius enables the most delicate whisper to 
 be heard, as in listening. Together they regulate the amount of sono- 
 rous vibrations which enter the labyrinth. Hence the effect of the de- 
 struction of the membrana tympani is to make sounds unendurable. In 
 confirmation of this is quoted the case of a patient who, under those cir- 
 cumstances, could not bear the whistling of another patient in an adjoin- 
 ing bed, and the observation of Cheselden that a dog, in which both 
 membrana3 tympani had been destroyed, for some time received strong 
 sounds with horror. 
 
 We shall now present some reasons for supposing that the function 
 of the tympanum is for determining the first property of sounding waves, 
 that is, their intensity. 
 
366 EFFECTS OF TENSION OF THE TYMPANUM. 
 
 It has been proved by the experiments of Savart and Miiller, that 
 Ofthedeterm- when the tension of the membrana tympani is increased, so- 
 ination of the norous undulations pass with less readiness through it. In- 
 
 intensity of so- 
 
 niferouswaves. deed, this may be yenned by personal experiment, as when, 
 by a strong effort of .expiration or inspiration, the mouth and nostrils be- 
 ing closed, we compress air into the tympanic cavity or withdraw it there- 
 from through the Eustachian tube, and thereby stretch the membrana 
 tympani outwardly or inwardly, the hearing at once becomes indistinct, 
 and sounds are enfeebled. The same ensues on going down in a diving- 
 bell, or suddenly ascending in a balloon. Of the former effect, Dr. Col- 
 Deafness in the ladon gives the following account during a descent in a div- 
 diving-beii. ing-bell at Howth in 1820. "We descended," says he, 
 " so slowly that we did not notice the motion of the bell ; but as soon 
 as the bell was immersed in water, we felt about the ears and forehead a 
 sense of pressure, which continued increasing during some minutes. I did 
 not, however, experience any pain in the ears, but my companion suffered 
 so much that we were obliged to stop our descent for a short time. To 
 remedy. that inconvenience, the workmen instructed us, after having closed 
 our nostrils and mouth, to endeavor to swallow, and to restrain our respi- 
 ration for some moments, in order that, by this exertion, the external air 
 might act on the Eustachian tube. My companion, however, having tried 
 it, found himself very little relieved by this remedy. After some minutes 
 we resumed our descent. My friend suffered considerably : he was pale ; 
 his lips were totally discolored ; his appearance was that of a man on the 
 point of fainting ; he was in involuntary low spirits, owing perhaps to the 
 violence of the pain, added to that kind of apprehension which our situa- 
 tion unavoidably inspired. This appeared to me the more remarkable, as 
 my case was totally the reverse. I was in a state of excitement resem- 
 bling the effect of some spirituous liquor. I suffered no pain. I expe- 
 rienced only a strong pressure around my head, as if an iron circle had 
 been bound about it. I spoke with the workmen, and had some diffi- 
 culty in hearing them. This difficulty of hearing rose to such a height 
 that during three or four minutes I could not hear them speak. I could 
 not, indeed, hear myself speak, though I spoke as loudly as possible, 
 nor did even the great noise caused by the violence of the current against 
 the sides of -the bell reach my ears." 
 
 Under natural circumstances, a stretching of the membrane inwardly 
 Action of the * s accom pli sne( l by the contraction of the tensor tympani mus- 
 musciesofthe cle, the stapedius holding tight contemporaneously on the 
 loop of the stirrup, and preventing disturbance of position of 
 the bony chain at that end, and hindering any outward bulging of the 
 membrane of the fenestra ovalis. When, therefore, the soniferous waves 
 impinge upon the membrana tympani, they tend to throw it into vibra- 
 
THE EUSTACHIAN TUBE. 367 
 
 tion ; the tensor tympani contracts to such an extent as to bring the 
 membrane to a standard of tension, and, since this muscle is of the vol- 
 untary kind, the mind judges of fhe degree of force which is required to 
 produce that result just as, when we lift from the ground bodies of dif- 
 ferent weights, we judge with a certain precision of the degree of force 
 necessary to be put forth. The condition of contraction of the tensor 
 tympani therefore enables the mind to measure the intensity of the sound- 
 ing waves. 
 
 But this muscular contraction is strictly a reflex act, and is therefore 
 preceded, as all such acts are, by an impression. That impression is 
 made, as we shall presently find, primarily on the auditory nerve. But 
 since these reflected acts are not sensory, the mind has no knowledge of 
 the effect impressed in this respect upon the auditory nerve, and only be- 
 comes sensible of it in an indirect way, through the contractions which 
 have ensued in the tensor tympani muscle. 
 
 In this view of the case, the use of the Eustachian tube becomes ob- 
 vious ; it is to form a ready passage for the air inwardly or tlseoftheEus- 
 outwardly, so that no condensation or rarefaction shall occur tachian tube - 
 within the tympanic cavity ; for such rarefactions and condensations 
 would disturb the action of the contracting muscle, and make it yield a 
 false estimate. Besides this, the Eustachian tube, as has long been 
 known, affords an outlet for mucus. 
 
 In the explanation here presented, the function of the ossicles is rather 
 for the purpose of tension than of conduction, though it is Function of the 
 not denied that sounds may pass readily along them. They ossicles - 
 are to be regarded as aiding in the perfection of auditory perceptions, but 
 yet not as being absolutely essential to the appreciation of sounds, or 
 even of their finer modifications. Whatever affects the facility of vibra- 
 tion of the membrana tympani, such as its thickening, or stiffening, or 
 unusual dryness, will render the hearing dull, but the membrane itself 
 may be perforated, or even undergo extensive lesions, without any appar- 
 ently corresponding effect. But if the stapes be injured or be removed, 
 deafness is at once the result. 
 
 There is nothing remarkable in the precision with which the contrac- 
 tions of the two muscles which stretch the membrane of the Precision in es- 
 drum are made. The same precision is illustrated in the timatingthe 
 
 ,, , , i i f i i -i rm contraction of 
 
 case of the muscles which adjust the vocal cords. The state the auditory 
 of these may be determined to the - llr ^ 00 part of an inch. scies. 
 
 It might perhaps be inquired, Why should not the function of determ- 
 ining the intensity of sounds, as well as their wave length, be imputed 
 directly to the auditory nerve ? It is with the ear as with the eye, the 
 mechanism for determining wave length can only act with uniformity 
 when the agent to be measured is reduced to a standard intensity. A 
 
368 STRUCTURE OF THE COCHLEA. 
 
 bright light falling upon the eye brings on a contraction of the pupil. 
 And so with the ear. A partial deafening must be established to adjust 
 the intensity of sound, that the auditoly nerve may act under standard 
 circumstances. The primary impression therefore made upon that nerve 
 by the loudness of sounds is, so to speak, consumed by being converted 
 as a reflex act into motion, because there is a necessity that the tensor 
 and stapedius should move, and reflex acts do not affect the mind, but 
 it instantly perceives the condition of contraction of those muscles, and 
 so estimates the intensity of the sound. 
 
 2d. On the measurement of wave length, or time of vibration of sounds. 
 Structure of the cochlea and its functions. 
 
 The structure of the cochlea is so significant that its true function 
 Structure of has been long ago more or less distinctly recognized. Thus 
 the cochlea, p^ Young speaks of it as a micrometer of sound. Many 
 physiologists regard it as determining the flote or pitch. Any one who 
 remarks the gradually decreasing width of its spiral lamina, and the 
 manner in which the ultimate filaments of the auditory nerve are spread 
 thereon, becoming shorter and shorter as they ascend the scale who re- 
 calls the structure of the harp, or gradually shorter strings of the piano- 
 forte, could scarcely fail of being impressed with the truth of this conclu- 
 sion. The function of the cochlea is the determining of wave length, 
 that is, the time of vibration or note of sounds. 
 
 The cochlea has been described as resembling a snail's shell in appear- 
 ance. It is a conical tube, wound spirally, and making two and a half 
 turns. The interior of this conical and spirally- winding tube is divided 
 throughout its length into two portions by means of a transverse parti- 
 tion, which, following the spiral winding of the tube, has had the name 
 of lamina spiralis bestowed on it. The two partitions produced by the 
 intervention of this lamina are called scala vestibuli and 
 
 The two scalce. . 
 
 scala tympani. At the top or point of the helix the two 
 scalas communicate through a little hole, from the cessation of the lamina 
 spiralis. To this opening or deficiency the name of helicotrema is given. 
 Considering the two scalse as separate tubes, their mouths open differ- 
 ently ; the scala vestibuli opens into the vestibule of the labyrinth, and 
 we may therefore regard the membrane of the fenestra ovalis as being 
 virtually its boundary or closure, but the mouth of the scala tympani is 
 against the fenestra rotunda, and is closed by the membrane of that aper- 
 ture. As their names therefore indicate, the scala vestibuli opens into 
 the vestibule, and the scala tympani into the tympanum. 
 
 Passing directly through the body of the cochlea, and being, as it 
 introduction were tne core upon which that structure is built, is a bony 
 of the auditory cone, called the modiolus. Indeed, the bony part of the 
 
 transverse plate which separates the tube of the cochlea into 
 
THE SPIRAL LAMINA. 
 
 369 
 
 Fig. 186. 
 
 Interior of the cochlea. 
 
 Fig. 1ST. 
 
 Section of the cochlea. 
 
 its two scalar, might be regarded as a spiral process of the modiolus. 
 Through the modiolus and its spiral process, or lamina spiralis, the au- 
 ditory nerve gains access, through suitable channels, to the interior of 
 the scalas. 
 
 Fig. 186, interior of the cochlea, rendered 
 visible by the removal of half of the outer wall: 
 
 a, a, lamina spiralis, turning by its inner edge, 
 
 b, around the axis of the cochlea ; <?, infundib- 
 ulum ; d, aperture of communication between 
 two scalaB; e, e, section of the outer wall; 
 fi f-> ft inferior or tympanic scala ; <?, g, g^ su- 
 perior or vestibular scala. 
 
 Fig. 187, section of the cochlea in the direc- 
 tion of its axis : #, canals of the axis, or of 
 the columella, for the passage of the vascular 
 and nervous ramifications; , infundibulum ; 
 c, base of the modiolus, or columella ; d, d, d, 
 section of spiral lamina ; 6, e, 6, section of the 
 outer wall; f,f,fi inferior scala; <7, <?, superior 
 scala. 
 
 It is necessary to understand the structure of the lamina spiralis more 
 particularly. As we have said, it divides the helical tube into The spiral 
 the two scake by extending transversely across it. Its bony por- lamina. 
 tion does not, however, extend more than about one third of the distance, 
 the rest of it being made up in part of a delicate membranous portion, 
 and completed by a muscular structure ; so that, if we consider the lam- 
 ina spiralis at any point, the region of it near the modiolus is bone, the 
 intermediate portion membranous, and the residual is muscular. Or, 
 considering the lamina spiralis in the aggregate, we might say that it 
 consists of a helix of bone, membrane, and muscle. To the muscle the 
 name of the cochlearis is given. Its obvious function is to tighten the 
 membranous region. Moreover, considered thus in the aggregate, the 
 lamina spiralis is a triangular plate wound round upon a central conical 
 core, and which, therefore, is broadest at the base of the cochlea, and 
 gradually tapers off toward the apex. It is to be understood that the 
 cochlea, like all other portions of the labyrinth, is filled with water. 
 
 Upon the spiral lamina, issuing forth through its bony portion, are 
 placed the ultimate filaments of the auditory nerve. These, having cast 
 off their white substance r come into relation with elongated vesicles, 
 and are thus distributed upon the membranous portion, the membrane 
 being kept uniformly tense by the action of the cochlearis muscle. 
 
 Fig. 188, p.. 370, section of the cochlea through its axis, magnified four 
 diameters, and showing the cochlear branch of the auditory nerve, ac- 
 
 AA 
 
370 
 
 STRUCTURE OF THE COCHLEA. 
 
 Fig. 1S8. 
 
 Magnified section of cochlea. 
 
 companied "by some vascular ramifica- 
 tions across the conduits of the colu- 
 mella to the spiral lamina. 
 
 Fig. 189, section of the cochlea, mag- 
 nified six diameters, to show the dis- 
 tribution of the cochlear branch of the 
 auditory nerve from its perforation of 
 the columella to its termination on the 
 spiral lamina. 
 
 Figs. 190, 191, showing the middle 
 and internal ear by a section of the 
 superior face of the petrous bone, and 
 principally the entire distribution of 
 the auditory nerve : ., #, hammer, 
 holding, &, &, &, its internal muscle ; c, 
 
 Fig. 189. 
 
 Fig. 190. 
 
 Distribution of cochlear nerve. 
 
 c, c, its anterior muscle ; and, d, its 
 external muscle ; e, e, anvil ; /", len- 
 ticular bone ; g, stirrup ; h, muscle 
 thereof; i, chorda tympani; j, fa- 
 cial nerve, receiving, &, great su- 
 
 Ftn. 1C1. 
 
 The ossicles and their muscles. 
 
 General distribution of auditory nerve. 
 
 perficial petrosal ; Z, cochlea ; m, auditory nerve; n, its cochlear branch ; 
 and, o, its vestibular branch, furnishing,^, branch of posterior vertical 
 
FUNCTION OF THE COCHLEA. 371 
 
 canal ; q, branch of sacculus ; 7 1 , branch of utricle ; s, branch of horizon- 
 tal canal ; t, t, branch of superior vertical canal. 
 
 We proceed now to the consideration of the functions of the cochlea. 
 
 The principles of acoustics would lead us to infer that sounds entering 
 the cochlea throw into vibration its spiral lamina, an inference Functions of 
 which is supported by anatomical considerations in regard to the cochlea, 
 the position and function of the cochlearis muscle in keeping the mem- 
 branous portion of the lamina at a due degree of tension. We should 
 also infer that each external sound does not throw the lamina into vi- 
 bration throughout its whole length, but only on a special and corre- 
 sponding point, and thereby affects solely the filament of the auditory 
 nerve in connection with that point ; that sounds which are low will act 
 upon the broader portions of the membrane, near the mouth of the coch- 
 lea, and those which are high, the narrower portions near the apex. In 
 this respect, therefore, the function of hearing should have two limits, 
 one for low and the other for high notes, as experience proves to us is 
 actually the case ; but possibly the scale is, so to speak, enlarged through 
 the various degrees of tenseness which may be given by the contractions 
 of the cochlearis muscle. A general idea of the nature of this limited 
 vibration may be obtained by recalling the effect which is Physical iiius- 
 produced when one musical instrument is played in the vi- ^J^"^^^ 16 
 cinity of another, as when, for example, a flute is played cochlea. 
 near to a piano-forte, the strings of the latter are thrown into sympathetic 
 vibration, and the piano emits a note answering to each note of the flute. 
 All the strings are not thrown into vibration at once, but for each note 
 of the flute that string of the piano vibrates, the length and tension of 
 which are duly adjusted. The same thing, again, may be seen when 
 musical sounds are originated near a stretched membrane, the surface of 
 which has been dusted over with grains of dry sand. The whole sheet 
 of the membrane is not cast into vibration at once, but some parts move 
 and some remain at rest, and so the sand-grains dance up and down on 
 the vibrating parts, and soon, being cast therefrom, accumulate on the 
 parts that are still, and mark out what are termed nodal lines. These 
 nodal lines, or places which are motionless, are frequently of remarkable 
 complexity and symmetry, as may be seen from the figures of them given 
 in any of the books on natural philosophy. m 
 
 It is immaterial in what manner the sound has reached the cochlea, 
 whether through the auditory canal or through the bones of Course of 
 the skull generally; the effect, as far as the spiral lamina is sounds to the 
 concerned, will be the same in both cases. That sounds can cochlea - 
 efficiently reach the auditory nerve, and produce thereupon their proper 
 effect, without ever having passed through the auditory canal or the drum, 
 is manifested by a great many familiar facts. We still continue to hear 
 
372 INTERFERENCE OF SOUNDS. 
 
 distinctly, though not so plainly, when the external canal is closed by 
 some obstruction nay, even when the sound-giving object, as a watch, 
 is put into the mouth. So it would appear that the function of the coch- 
 lea is, in a certain sense, independent of the drum, though we have to 
 admit that, for the precision and perfection of hearing, the latter is nec- 
 essary. 
 
 In the view here presented, I consider that each external musical note 
 The cochlea causes a special portion of the spiral lamina to vibrate, and 
 HEKfiL that the particular nerve fibril supplying that portion is af- 
 tion of sounds, fected thereby, and thus a distinct sensation is communi- 
 cated to the brain, the nerve fibrils to the right and left of the one af- 
 fected lying at rest. It may probably be that the denticulate structure 
 -described by Drs. Todd and Bowman has for its duty the more perfect 
 production of this isolated effect, or that the teeth thereof act like the 
 dampers of a musical instrument, and restrain the vibration. Notes the 
 wave length of which is great, or, what is the same thing, the times of 
 the vibrations of which are long, affect those portions of the spiral lamina 
 which are broad and near to the base of the cochlea, but notes whose wave 
 lengths are short, and times of vibration correspondingly brief, affect 
 those portions near to the apex. But probably the scale is changed, as 
 before said, by the tension of the cochlearis muscle, and thus the same 
 part of the lamina can take charge of a range of many octaves. 
 
 It may be inquired how it is that a sound passing through the audi- 
 tory canal, the bones of the tympanum, the membrane of the 
 an interference fenestra ovalis, and thus affecting its destined portion of the 
 mechanism. l am i naj does not give rise to an idea in the mind of repeti- 
 tion or reverberation by moving back and forth through the two scala3, 
 and affecting its proper nerve fibril at each passage. Is there not a ne- 
 cessity for the existence of some mechanism of interference which shall 
 destroy the wave after it has once done its work ? Admitting the force 
 of such inquiries, we can not avoid being impressed with the fact 'that 
 the two scala3 into which the cochlear tube is divided present all the as- 
 pects of a mechanism constructed for the discharge of such a duty. For 
 interference to take place among undulations of any kind, waves upon 
 water, sounds in the air, or the ethereal undulations which constitute light, 
 the essential condition is that they shall run through paths of unequal 
 length, the inequality being one of a series of numbers. They must also 
 be brought, for a full practical effect, to their common point of encounter 
 under a very acute angle, and these conditions are represented in the 
 scala vestibuli and the scala tympani, which are of unequal length, placed 
 at such an acute angle to one another that they might almost be said to 
 be parallel, occupied by a fluid of the same density, and through both at 
 the same moment are passing the undulations which constitute the same 
 
FUNCTION OF THE COCHLEA. 373 
 
 sound, one having been communicated by the fenestra ovalis, the other 
 through the fenestra rotunda, their common point of convergence, and 
 perhaps of mutual destruction, being at the helicotrema, the aperture at 
 the apex through which they intercommunicate. Nor can we fail to be 
 struck by the circumstance, if this explanation of the function of the 
 scalse be correct, in what an admirable manner the whole in- . d . tment of 
 strument is provided with self-adjusting power, since, when the length of 
 the stirrup forces in the membrane of the fenestra ovalis, the t] 
 pressure which is communicated through the water pushes out the mem- 
 brane of the fenestra rotunda, and thereby the relative length of the two 
 scalas has changed, the one having become longer by as much as the 
 other has become shorter, an adjustment necessary to bring about total 
 interference at the helicotrema. And we might add that. such a con- 
 struction is all the more interesting, for, since it is the intensity of the 
 waves that is to be destroyed, reliance is had upon the intensity instru- 
 ment, the drum, to produce that effect, and it is done by the contractions 
 of the tensor tympani and stapedius muscles. Perhaps the perfect ac- 
 complishment of this interference is the standard, to which allusion has 
 been made before, by which the mind judges of the power which has been 
 put forth by those muscles, and thereby of the intensity of the sound. 
 
 From the comparative anatomy of the cochlea and the character of the 
 vocal organs, JVI. Duges formerly came to the conclusion that Com arative 
 the cochlea has for its function the determining of the pitch anatomy of the 
 of sounds. In man, whose vocal powers are most varied, it Cl 
 exists in the highest perfection ; in birds, whose vocal powers are more 
 restricted, it is reduced to a short and slightly curved tube, but still di- 
 vided by a longitudinal septum ; in reptiles, it exists only in a rudiment- 
 ary state. 
 
 The necessary existence in the ear of some mechanism for the purpose 
 of preventing reverberation or repercussion has long been recognized 
 both by writers on acoustics and by physiologists. Thus an explana- 
 tion of the functions of the semicircular canals and of the cochlea upon 
 this principle is given by Dr. Koget, in his Bridgewater Treatise ; and, 
 in like manner, Professor Jackson, of Philadelphia, has for several years 
 taught a similar doctrine in his lectures. Since 1840, 1 have in my pub- 
 lic lectures presented the explanation given in the preceding paragraphs. 
 It differs essentially from that of my friend, Professor Jackson (of which 
 a brief statement may be found in Dr. Smith's edition of Carpenter's 
 Physiology, Philadelphia, 1855), in this, that it limits the accomplish- 
 ment of interference to the cochlea. The view which I entertain respect- 
 ing the function of the semicircular canals will be immediately set forth : 
 it does not appear to me that they are in any way connected with the in- 
 terference mechanism. 
 
374 
 
 STRUCTURE OF THE SEMICIRCULAR CANALS. 
 
 3d. On the determination of the quality of sounds, the structure of the 
 semicircular canals, and their function. 
 
 The semicircular canals are cylindroid tubes, developed, as it were, 
 ureofthe ^ rom the vestibule, and of a figure which has suggested their 
 semicircular name. They are three in number, and placed at right angles 
 to one another : two of them are vertical, the third horizon- 
 tal ; they all open into the vestibule, the adjacent branches of two of 
 them coalescing first. On one of the branches of each of them there is 
 a dilatation just before it joins the vestibule ; to this dilatation the des- 
 ignation of ampulla is given. The vestibule of the labyrinth may there- 
 fore be regarded as the common mouth of the semicircular canals, and of 
 the scala vestibuli of the cochlea ; or, considering its order of develop- 
 ment, the vestibule may be regarded as the essential portion of the lab- 
 yrinth, and the semicircular canals and cochlea appendices that have 
 branched forth from it. 
 
 The vestibule and semicircular canals are lined with a membrane 
 which, of course, copies their shape, yet it is not in contact with their 
 bony walls, but is parted therefrom by a stratum of water, to which, as 
 has been said, the name of perilymph is given ; their interior is also 
 filled with a liquid the endolymph, it is called. The bony structure is 
 called the bony labyrinth ; this structure is the membranous labyrinth. 
 A portion of the auditory nerve divides into three main branches, which 
 present themselves for the supply of the ampullae : the brush-like termi- 
 nations of these are accommodated with an otolith. 
 
 ILLUSTRATIONS OF LABYRINTH OF LEFT SIDE. 
 
 EXTERNAL, OB TYMPANIC FACE OF LABYRINTH. 
 
 Fig. 192. 
 
 Tympanic face of the labyrinth. 
 
 Fig. 192 : #, external wall of vestibule, on which 
 is seen, &, fenestra ovalis ; , fenestra rotunda, 
 and, d, tract of the facial nerve ; 0, superior semi- 
 circular canal ; /*, posterior semicircular canal ; <?, 
 horizontal semicircular canal ; i, i, i, wall of coch- 
 lea ; j, aqueduct of cochlea ; &, portion of petrous 
 
 Fig. 193. 
 
 INTERNAL, OR CRANIAL FACE OF LABYRINTH. 
 
 Fig. 193 : a, internal wall of vestibule ; b, aque- 
 duct of vestibule ; c, base of cochlea ; d , aqueduct 
 of cochlea ; e, /*, conduit, at the bottom of which 
 are several holes for the passage of facia) and au- 
 ditory nerves; g, superior semicircular canal; A, 
 cranial face of the labyrinth, posterior semicircular canal ; i, horizontal semicir- 
 cular canal. 
 
FUNCTION OF THE SEMICIRCULAR CANALS. 375 
 
 INTERIOR OF LABYRINTH, SEEN ON ITS EXTERNAL OR TYMPANIC FACE. 
 
 Fig. ic4. Fig. 194 : #, vestibule, into which open the semi- 
 
 circular canals by five orifices, and the vestibular 
 scala of the cochlea ; b, b, section of the wall of the 
 cochlea ; <?, c, bony portion of spiral lamina, dividing 
 the conoid cavity of the cochlea into scala vestibuli 
 interior of labyrinth. and scala tympani ; d, orifice at summit of cochlea. 
 
 INTERIOR OF LABYRINTH, SEEN ON ITS INTERNAL OR CRANIAL FACE. 
 
 Fig. ic5. Fig. 195 : #, vestibular cavity, into which open the 
 
 cavities of the semicircular canals and the cochlear cav- 
 ity ; b, bottom of internal auditory canal, answering to 
 base of cochlea, 'and partly to internal wall of vestibule ; 
 , simple foramen for facial nerve ; d, many openings 
 interior of labyrinth. f or auditory nerve. 
 
 The explanation usually given of the function of the semicircular ca- 
 nals is, that they serve to determine the direction of sounds, Criticism on 
 an idea which has arisen from their remarkable rectangular the expiana- 
 position. However, this is accomplished in almost all cases ^"^life 
 by directing the external canal toward the point from which function of the 
 the sound is coming, and judging of its place by the varia- 
 tions of its intensity. Animals commonly direct the external ear toward 
 the sounding point, guided doubtless in the same way. Some physiolo- 
 gists have restricted the use of the semicircular canals to the collection 
 of those sounds which strike upon the skull, but, besides the preceding 
 considerations, there are others derived from comparative anatomy which 
 seem to indicate that this can scarcely be their duty. 
 
 The intensity of sounds is judged of by the tympanum ; their pitch 
 or wave length is determined by the cochlea, and therefore They are for 
 there arises a strong presumption that the semicircular ca- q S u 4 a t atl "f tt 
 nals must have the function of distinguishing the third char- sounds. 
 acteristic of sounds, that is, their quality ; since, if this be not the case, 
 there seems to be no other portion of the auditory mechanism to which 
 that office could be assigned. 
 
 The suspicion which we are thus led to entertain, that the semicircu- 
 lar canals are for appreciating the quality of sounds, is strengthened in 
 no common degree by facts of comparative physiology. Unfortunately, 
 we know so little of the mechanical peculiarity on which distinctions of 
 quality depend, that we are wholly unable to trace out the structural con- 
 ditions of an organ which should be calculated for seizing on them. We 
 know that the quality of a note emitted by a violin is different from that 
 emitted by a flute, though the intensity and pitch may be the same, but 
 
376 COMPARATIVE ANATOMY OF THE EAR. 
 
 we can not tell why. In the case before us, we therefore can expect no 
 assistance in the way of arguments from mechanical philosophy, and are 
 limited to the use of those which may "be drawn from comparative anat- 
 omy and physiology. 
 
 Examining, therefore, what appears to be the primitive plan of the con- 
 Illustration of struction of this mechanism, we find it to consist of a nerve 
 thisexpiana- fibril .in connection with an otolith, or little stony body. 
 
 tion from com- ^ . j i i i i r 
 
 parative anat- Such a construction, included in a bag 01 water, constitutes, 
 m y- in point of fact, the organ of "hearing of some of the lower 
 
 tribes, as the gasteropodous molluscs. These animals can have no per- 
 ception of the pitch of sounds or musical notes, and only an imperfect one 
 of intensities. But what they do distinguish is one noise from another. 
 Now the idea conveyed to the mind by difference of noises is precisely 
 the distinction that we are dwelling on, that of quality. 
 
 If, instead of restricting our examination to the semicircular canals, we 
 General view exten( ^ & * tne whole organ of hearing, and consider to- 
 of the auditory gether, in the case of each animal tribe, its requirements, and 
 sm ' the manner in which those requirements are satisfied, we 
 shall meet with a surprising confirmation of the preceding views. The 
 lowest requirement we can conceive of is the appreciating of noises ; an 
 advance upon this is the determination of their direction ; a higher ad- 
 vance, the determination of their intensity ; and a still higher, the rec- 
 ognition of those combinations of impulses which constitute a musical 
 sound. For each of these successive requirements the auditory mech- 
 anism must necessarily become more complex ; and thus it first ap- 
 pears, as we have just stated, as a sac of water, containing a stony grain 
 or otolith imbedded in the cesophageal collar. A noise agitates the oto- 
 Com arative ^^' an< ^ ^7 i ts movement the perception of a sound ensues, 
 anatomy of the In cephalopodous molluscs the auditory sac is detached, and 
 the intercommunicating thread represents the rudiment of 
 what, in the higher grade of development, will be the auditory nerve. 
 With another advance the sac is lodged in a cartilaginous cavity. Thus, 
 in the cuttle-fish, a simple cartilaginous vestibule exists, having within 
 it a membranous bag or auditory capsule, filled with fluid, and upon the 
 capsule the filaments of the auditory nerve are spread. An otolith or 
 ear-stone is placed within, and this constitutes the entire apparatus, while 
 yet there is no vibrating membrane and no fenestral aperture. 
 
 Even in still higher conditions the purely mechanical character of the 
 structure is manifest, and so, in some of those in which the sac opens ex- 
 teriorly, grains of sand, that have been introduced by chance from without, 
 rest on the hair like filaments which the auditory sac contains, each fila- 
 ment apparently including a nerve fibril. In a still higher condition of 
 advance, as, for example, in the lobster, a portion of the shelly wall which 
 
COMPARATIVE ANATOMY OF THE EAR. 377 
 
 forms the boundary of the auditory cavity is unconsolidated, and a mem- 
 brane which stretches over the otherwise vacant space presents the first 
 rudiment of the fenestra ovalis. With the exception of the amphioxus, 
 all vertebrated animals have a special organ of hearing, which, in suc- 
 cessive tribes, presents an interesting increase of complexity, beginning in 
 the cyclostomes with a sac in the cranial cartilages filled with water, 
 nerve fibrils distributed on its walls, and an otolith included, but no ex- 
 ternal communicating aperture. From this, in succession, the various 
 portions which are to be developed in perfection in the higher races grad- 
 ually appear: the myxine has one semicircular canal arising from the 
 vestibule, the lamprey has two, the higher forms have three. As the case 
 may be, a portion of the cartilage or bony parietes is deficient, and, again, 
 the fenestra ovalis is the result. Though in the osseous fishes there is 
 neither tympanum or cochlea, in some few the rudiments of the former 
 begin to exist. The naked amphibia have no cochlea, and only one fe- 
 nestra, answering to the ovalis : to this is fitted a stapes ; but in lizards 
 and scaly serpents there is a general advance, these having a conical 
 cochlea. As we pass through them the plan is earned out ; the tympan- 
 ic cavity and its chain of bones, the Eustachian tube, and cochlea ap- 
 pear; and with the rudiment of the cochlea there is presented in the tym- 
 panic cavity a second aperture, answering to the fenestra rotunda. In 
 birds the structure offers a continued improvement, commencing on a 
 plan analogous to that of the scaly amphibia, but exhibiting a speedy 
 development. . The membrana tympani is composed of several layers ; 
 the cavity of the drum communicates with cells in the cranial bones, the 
 analogues of the mastoid cells ; a bony Eustachian tube crosses to meet 
 its fellow of the opposite side, and open in a common aperture. The os- 
 sicles consist of a malleus, a staff-shaped intermediate bone, and a flat 
 stapes, resting on the fenestra ovalis. As if to show a tendency to the 
 form it is eventually to assume, this bone sometimes presents a forked 
 appearance, the preparation for a stirrup shape. As regards this bone, 
 birds and mammals may be said to overlap, for in its more developed 
 condition in birds it bifurcates, but in the lower mammals, as the kanga- 
 roo, it is still cylindric. In birds of prey the semicircular canals are 
 large, the cochlea fairly developed, though as a straight or slightly-curved 
 tube, containing its scake and vibrating lamina : the vestibule has ear- 
 stones. Through the monotremata this condition of construction is con- 
 tinued into the perfect mammals : all the aerial tribes have external ears, 
 and full development is reached in the auditory mechanism of man. 
 
 Now if we collate the facts here presented with the requirement of the 
 condition of life which each of these successive races seems to demand, we 
 shall find that the remark heretofore made, that the semicircular canals 
 are for the recognition of the qualities of sound, is strikingly borne out, 
 
378 DEVELOPMENT OP THE EAR. 
 
 though, from our ignorance of what it is in which quality consists, we are 
 wholly unable to offer an explanation of the precise mode of action of 
 that part of the auditory mechanism. 
 
 We are so prone to extend our ideas of our own perceptions to the 
 Partial deaf case ^ otner animals that it may not here be unprofitable to 
 ness of inferior offer a remark which may serve to correct such views. To 
 many of the sounds with which we are familiar, birds and oth- 
 er lower tribes are totally deaf; they can not appreciate, except within a 
 narrow range, the notes of music, and, indeed, to all those in which there 
 is no cochlea such notes are inaudible. - In the lower grades nothing more 
 than a noise can be detected, and that doubtless in a very indefinite way. 
 We can therefore understand how, through imperfection of construction, 
 they are cut off from the perception of an infinite number of occurrences 
 which are obvious enough to us. Even among our domestic animals, to 
 which we so often speak or sing in the way we do to one another, the in- 
 tellectual obtuseness which we think we recognize doubtless originates 
 in an incapacity to receive those expressions, because of faulty structural 
 condition. 
 
 In closing these remarks on the sense of hearing, it is necessary to 
 , direct attention to the order of development of the organ in 
 
 Order of devel- ,.,,,,,,, . r & 
 
 opment of the the individual of the human species, as we have done in the 
 case of the successive tribes of animals ; and here it may be 
 affirmed that the ear of man passes in a transient succession through all 
 these permanent animal forms. It originates at first from a budding 
 forth of the vesicle of the medulla oblongata, the issuing cell becoming 
 by degrees pear-shaped, and connected with the parent cavity by a thread 
 or stalk. The pear-shaped cavity is the rudiment of what is eventually 
 to be the vestibule ; the pedicle will become the auditory nerve. Even 
 at this early period the cavity contains an otolith. By degrees there 
 arises from the folding in of the walls of the vestibule the curved forms 
 that are to become the semicircular canals, and, at a period a little later, 
 in an analogous way, the cochlea. At one stage of this development the 
 membranous labyrinth presents an almost identical aspect with that of 
 the retina at the time, both being composed of a fibrous network inter- 
 spersed with granules and nucleated cells, the shadowing forth of the 
 parallelism of construction which may be traced in the two organs when 
 they have reached their utmost development, the one for the cognizance 
 of normal and the other for transverse vibrations. 
 
 And so it appears that, as respects the organ of hearing, its order of 
 illustration of development in the individual is identically the same as its 
 the imperfec- order of development in successive tribes taken in the ag- 
 
 tionofthedoc- _ r _ _ . 
 
 trine of means gregate. In the latter case, we constantly regard its con- 
 and ends. dition of construction as arising from a purposed adaptation 
 
VISION. 379 
 
 to the wants of the animal. We consider it as affording a series of il- 
 lustrative instances of the use of means for the production of definite 
 ends, and therefore as exhibiting the evidences of design ; but what are 
 we to make of the other, the parallel, the individual case, in which, in 
 succession, the organ presents each one of these particular forms, and in 
 which not one is ever used, save only the most complete, the last? 
 There would seem here to be little of adaptation, little of means to an 
 end, nothing of design. But does not this prove to us (and the other 
 organs of sense will furnish a similar argument) that the development of 
 the various animal tribes, and of each individual of those tribes, takes 
 place under the operation of a far-reaching and common law, and that the 
 particular condition which any species presents, or even any individual 
 at some special period of his existence, is a manifestation of the degree 
 or extent to which that law has been carried out ? 
 
 CHAPTER XX. 
 
 OF VISION. 
 
 Analogy between Sound and Light. Comparative Anatomy of Vision. Perception of Warmth. 
 Structure of Ocelli. Use of Lenses. Physical Principle of the Organ of Vision. 
 
 Description of the Human Eye. Optical Action of its Parts. Spherical and Chromatic Aberra- 
 tion: Receiving Screen of the Eye is the black Pigment. Long and short Sight, and their 
 Correction. Limits of Vision are included in one Octave. Limit in estimating the Brightness 
 of Light. 
 
 Nervous Mechanism of the Eye : its Structure and Functions. Manner of Perception by the 
 Retina. The black Pigment absorbs the Rays. Single and double Vision. Duration of Im- 
 pressions. Ocular Spectra. Erect Vision. Idea of the Solidity of Bodies. Hypothesis of 
 the Action of the Retina. 
 
 Accessory Apparatus of the Eye. The Eyebroios. Eyelids. Lachrymal Apparatus. Muscles 
 of the Ball. 
 
 THE physical difference between waves of sound and waves of light 
 has been already stated to consist in this, that the vibrations . 
 which give rise to the former coincide with the direction in tween sound 
 which the wave passes, but those of the latter are transverse. and llght ' 
 There is, however, notwithstanding this difference, a general analogy be- 
 tween the structure of the ear and that of the eye, and provision must 
 be made in the case of the organ of sight for determining the fundamental 
 peculiarities which are necessary to be determined in the case of the or- 
 gan of sound ; that is to say, intensity, wave length, or time of vibra- 
 tion, and, in addition thereto, the requirements of this particular prob- 
 lem demand that means should be included for ascertaining with exact- 
 ness the shape of objects and their relative positions. 
 
380 PERCEPTIONS OF WARMTH. 
 
 Of the different methods which we might follow in the discussion of 
 Importance of the mechanism of the eye, none, perhaps, is more satisfacto- 
 the compara- Qr j ea( j s to clearer conclusions, than that which is pre- 
 
 tive anatomy J ' ' 
 
 of vision. sented by comparative anatomy. It is just as difficult to 
 take a complicated organ, such as the eye of man, and from the study 
 of it to deduce the significance of its various parts, as it would be to take 
 a complicated human contrivance and determine from it the properties of 
 its mechanical elements. It is scarcely from the watch or other delicate 
 machine that we should expect to make plain the properties of the lever 
 or the wheel, and experience shows that it is only by the attentive study 
 of the cases presented by comparative physiology those experiments 
 made for us by nature, as CUVIER has called them that we can hope to 
 advance to the perfect solution of this problem. 
 
 Treating the subject, therefore, in this way, we observe that, in the an- 
 Confused er * ma ^ ser ^ es ' ^ on S Before an y thing like a distinct organ of vis- 
 ception of ion can be detected, there is yet a perception of light and 
 warmth. darkness. The hydra, a fresh-water polype, offers an exam- 
 ple, for this animal seeks the sunny side of the vessel in which it is 
 placed, preferring it to the shade. In the absence of every vestige of a 
 visual organ, there can not be a doubt that its 'movements depend on the 
 perception of warmth, just as when a man who is totally blind passes 
 from the sun into the shade, his feelings at once notify him of the change. 
 In a physiological sense, it is of no interest to us to inquire into the phys- 
 ical nature of this effect, whether light is identical with heat, or whether, 
 when light falls upon a body, it turns into heat. We have only to ac- 
 cept it as a fact capable of abundant experimental proof, that, whenever 
 rays of light fall on a surface, that surface becomes warm. This, as we 
 shall now find, is the key of all the explanations we have to give. 
 
 Dr. Franklin made an experiment to the following effect. He placed 
 Dr. Franklin's on the snow, on a sunshiny winter day, pieces of cloth of dif- 
 experiment. ferent colors black, yellow, white, etc., etc. in such a posi- 
 tion that the sun's rays fell equally on them. After a certain length of 
 time, on examining them, he found that the black cloth had melted its 
 way deeply into the snow, the yellow to a less depth, and the white 
 scarcely at all. He therefore drew the conclusion that, when they are 
 receiving light, surfaces become warm in proportion to the depth of their 
 tint, and that, of all surfaces, one having a velvety blackness is most sen- 
 sitive, because it can exert the most powerful absorbent agency. 
 
 On this principle seem to be constructed the ocelli of the lower tribes. 
 Ocelli of lower These consist of a collection of pigment granules, usually 
 animals con- O f a re( j bi ac k or <j ar k co lor, seated on the expansion of a 
 
 structedon . n . 
 
 Franklin's nervous thread. The principle which is clearly contained in 
 principle. ^ s mechanism j s that of relieving the general surface from 
 
OPTICAL PRINCIPLES OF THE EYE.' 381 
 
 the impression of light, or rather of rendering it more intense by central- 
 izing it upon a special locality. Such a construction involves at once a 
 change in the nervous mechanism, by devoting a particular system of 
 nerve tubules to the new duty. But, notwithstanding this increasing 
 complexity of structure, the physical principle is still as simple as be- 
 fore. It is indeed almost as though a blind man should paint upon his 
 skin a black space, so that, as in Franklin's experiment, it might be 
 more sensitive to the sun. With this devotion to a new duty the nerv- 
 ous tubules doubtless assume an isolated function, and thus there arises 
 a nerve of special sense. The ocelli of the lower animals are sometimes 
 quite numerous. Fronl this a new power is at once derived, the power 
 of determining the position of the source of light, a property which doubt- 
 less becomes more perfectly marked in proportion to the number and 
 symmetry of arrangement of the ocelli. As we ascend the animal series 
 in our examination, we soon find that complexity is being introduced. 
 A membranous hood, arising from a little fold of the external tegument, 
 shadows forth the rudiment of an eyelid, and seems to indicate to us that, 
 even in these low grades, the condition which we shall eventually find 
 so strikingly marked in the high ones already exists, that functional ac- 
 tivity involves destruction, and that the sensory mechanism must have 
 its period of repose. 
 
 Approaching the more highly-developed conditions of the organ of 
 vision, we may next consider the cases presented by the i ntroduction of 
 eyes of insects and the eyes of higher mammalia. In these converging me- 
 a new physical principle has been introduced, the optical ia ' 
 property of the convex lens, a transparent solid, having one or both of 
 its surfaces curved, and obtaining therefrom the power of forming repre- 
 sentations, or images of objects which may be in front of it, at a certain 
 focal distance behind. Such images are seen when we take a magnify- 
 ing glass or a convex lens, and, holding a piece of paper be- The focus and 
 hind it at a particular point, there will be depicted upon the its variations 
 paper the inverted forms of whatever objects may be in front. 
 That distance is the focal length of the lens. But we may farther no- 
 tice, and to this observation our attention will be required hereafter, that 
 the focal length is variable. If the object be near, the focal length is 
 greater ; if distant, it is less. 
 
 The instrument known as the camera obscura represents the optical 
 construction of the eye. Upon a receiving surface or screen, The camera 
 placed at the focal distance behind its lens, images are depicted obscura. 
 of whatever objects may chance to be in front ; but and this is a remark 
 of interest to us now the visual range, or field of view, is quite limited. 
 In animals, the perfection of whose vision requires that, instead of being 
 restricted, in their view to a narrow space, they should be able, as it 
 
382 STRUCTURE OF THE EYE. 
 
 were, to take in almost a hemisphere at a glance, this extension of the 
 visual function can only be accomplished in one of two different ways. 
 rent con ^ use ^ e illustration we have been employing, it may be 
 trivances for reached by having innumerable cameras pointing in innumer- 
 iSger field of a ^ e directions, and conveying the resulting images to one 
 view by the common surface, or by having one, or at most two, camerse 
 set upon a movable stand, which can quickly point them in 
 any direction, and so enable them to inspect successive fields of view 
 with almost instantaneous rapidity. The former plan is resorted to in 
 most insects, the latter in man. In insects, the immobility of the head 
 upon the trunk would interfere with any rapid rotation of the visual or- 
 gan ; in man, the facility with which rotation can take place upon the 
 neck as on an axis, and the movement of the eye in its orbit, accom- 
 plishes the object without any kind of difficulty. 
 
 In continuing an investigation of the structure of the eye, it is con- 
 venient to consider it under three heads : 1st. Its optical mechanism ; 
 2d. Its nervous mechanism ; 3d. Its accessory apparatus. 
 
 1st. Of the Optical Mechanism of the Eye. 
 
 The human eye is of a globular form, and about one inch in diameter. 
 The human I* * s no ' t perfectly spherical, its lateral diameter being shorter 
 e 3 Te - than its antero-posterior by about one twentieth part. It may 
 
 be described as consisting of three coats, which, forming a shell, contain 
 transparent media and the optical apparatus. It might also be consid- 
 ered as arising from an expansion of the optic nerve into an almost 
 spherical cavity, and which, being fortified by certain tissues behind, 
 has a dioptric mechanism in front. 
 
 The coats of the eye are three in number : the sclerotic, the choroid, 
 and the retina. The sclerotic, which is the exterior, is a white fibrous 
 membrane, very tough, and possessing the necessary resistance to give 
 mechanical protection to the parts within. Within this is the choroid, a 
 vascular layer or tunic, presenting on its interior the black pigment which 
 darkens the interior of the eye. The innermost coat is the retina, an ex- 
 pansion of the optic nerve. The sclerotic coat is perforated in front, and 
 into the circular aperture so arising the transparent cornea is let, like a 
 watch-glass. . Many anatomists, however, consider that the cornea is 
 absolutely continuous with the sclerotic, and a part of it ; the sclerotic 
 and the choroid are united round the edge of the cornea by the ciliary 
 ligament. The iris is perforated in its centre, the aperture being desig- 
 nated as the pupil. Posterior to the iris is the crystalline lens, the space 
 between the lens and the cornea being filled with the aqueous humor, in 
 which the iris floats, dividing it into two regions, called, from their posi- 
 tion, the anterior and posterior chambers. All the rest of the ,globe be- 
 
STRUCTURE OP THE EYE. 383 
 
 tween the back of the lens and the retina is filled with a substance ex- 
 tremely transparent, and known as the vitreous humor. The aqueous 
 humor, the crystalline lens, and the vitreous humor, by reason of their 
 transparency, offer, therefore, no obstacle to the passage of light. 
 
 ILLUSTRATIONS OF THE EYE. 
 
 Fig. 196 : #, a, sclerotic, turned over ; &, choroid ; c, <?, ciliary nerves 
 traversing sclerotic, and going between it and choroid ; d, retina ; 0, vit- 
 reous body ; f, crystalline ; g, middle section of iris ; A, middle section 
 of cornea ; i t anterior chamber ; j 9 posterior chamber ; &, canal of Fonta- 
 196. na, between the ciliary circle and iris 
 
 on one side, and sclerotic and cornea on 
 the other. 
 
 Fig. 197. 
 
 Profile view of the eye. Front view of the eye. 
 
 Fig. 197 : <z, transparent cornea ; , &, sclerotic ; , iris ; d, pupil ; 6, 
 ciliary circle ; /*, choroid, on which is seen the dichotomous termination 
 of the ciliary nerves ; <?, ciliary processes ; A, crystalline. 
 
 SECTION OF THE EYE. 
 
 fig. 198 : a, upper eyelid ; &, lower eyelid, showing the different lay- 
 
 ers composing them ; c, c, conjunc- 
 tiva, reflected from posterior face of 
 eyelid upon the anterior face of the 
 globe of the eye ; d, d, orbito-oc- 
 ular aponeurosis, prolonged upon, 
 e, the sheath of the optic nerve, and 
 sending sheaths to the muscles ; f, 
 the superior rectus ; </, the inferior 
 rectus ; A, A, sclerotic, re-enforced 
 behind by sheath of optic nerve, 
 
 section of the eye. and in front by aponeurotic expan- 
 
 sion of recti muscles ; ', transparent cornea, cut to show its lamellar tex- 
 ture ; j, j, choroid ; &, ciliary circle ; Z, ciliary body and processes ; m, 
 iris and pupil ; n, n, canal of Fontana ; o, o, retina, continuous with sub- 
 
384 STRUCTURE OF THE EYE. 
 
 stance of optic nerve ; j?, ciliary circle of Zinn ; q, g, hyaloid mem- 
 brane ; r, capsular artery, lodged in hyaloid canal ; s, s, vitreous humor 
 and its cells ; t, crystalline and its capsule ; u, u, canal of Petit ; v, an- 
 terior chamber ; #, posterior chamber. 
 
 To this general description of the conformation of the eye may be add- 
 ed a few remarks on each of its constituent parts. 
 
 The sclerotic coat consists of white fibrous tissue, which, in addition 
 The sclerotic to the use before mentioned, affords the means of insertion of 
 coat. the muscular mechanism for moving the ball. It is thicker 
 
 behind than in front, its relative thickness differing in different animals 
 according to the mechanical circumstances to which they have to be ex- 
 posed. In the whale, which has to resist the pressure of a deep sea, the 
 sclerotic is an inch thick. In some instances cartilage is included in it, 
 in others bone. Besides the aperture in front, into which the cornea is 
 let, there is another behind for the passage of the optic nerve. This 
 method of description, though very convenient, is, however, scarcely cor- 
 rect, if we consider the coats of the eye as arising from expansions of the 
 optic nerve, for then the sclerotic answers to the exterior investiture, and 
 the tubules of the nerve gain access to the interior of the eye without 
 passing through an aperture, properly speaking. The place at which 
 the nerve enters is not in the optical axis, but at a distance of about its 
 own diameter on the interior side. The aperture is smaller on the in- 
 side of the sclerotic than on the outside; thus it presents a conical shape. 
 It is not a single hole, but rather a collection of sieve-like openings, 
 through which the optic tubules pass. 
 
 The cornea, which is let into the sclerotic in front, is of greater curva- 
 ture than the sclerotic. Its front and back faces are parallel. 
 
 The cornea, m. , .. , ,, . -. , ., , . J . 
 
 Though it seems to be pellucid as glass, it has a very intri- 
 cate construction, being composed of at least five separate layers ; the 
 innermost one, or cornea proper, consisting, it is said, of more than sixty 
 lamellae. 
 
 The choroid coat is arranged, like the sclerotic, for the passage of the 
 Thechoroid: optic nerve. The iris is commonly described as a process 
 its arrange- O f ft. The choroid is a sheet of blood capillaries arranged 
 
 ment for intro- . , . , , . , 
 
 during and re- m two layers, an arterial and a venous, in such a way as to 
 moving blood. gj ve ^6 u tmost freedom of access for the arterial blood to 
 the retina within. The veins which remove this blood are placed in 
 curved forms, and are designated vasa vorticosa ; from the choroid also 
 the dark pigment is secreted. Those animals in which it is absent are 
 called albinos. Near to the iris the choroid merges in the ciliary liga- 
 ment, and gives forth the ciliary processes, being covered in front by the 
 ciliary muscle. 
 
 Fig. 199 : a, a, section of sclerotic ; , exterior surface of the choroid, 
 
THE IRIS, RETINA, AND HUMORS. 
 
 385 
 
 on which are seen, c, c, the vasa vorticosa ; <#, d, ciliary nerves ; 0, ciliary 
 ligaments ; /*, anterior face of iris ; <7, pupil. 
 
 Fig. 199. Fig. 200. 
 
 The veins of the choroid. The arteries of the choroid. 
 
 Fig. 200: a, a, exterior surface of the choroid and the iris, showing the 
 arterial network of these two membranes, supplied by the ciliary arteries, 
 which, after having traversed the sclerotic, divide into, 5, , posterior cili- 
 aries for the choroid, and <?, c, anterior ciliaries for the iris. 
 
 The iris, though arising, as has been said, from the choroid, is con- 
 structed in a different way, its tissue mainly consisting of un- 
 striped muscular fibre, except in the case of birds, which present 
 the striped variety. It is extremely vascular, its arteries being derived 
 from the ciliary. The color of the eye depends on the color of the front 
 of the iris ; the posterior portion is covered with black pigment. 
 
 The ciliary muscle, for such it has been proved to be by Dr. Wallace, 
 of New York, is of the unstriped kind ; its action is to move the lens. 
 In birds it is of the striped variety. 
 
 The retina intervenes between the vitreous humor and the choroid 
 coat ; it arises from the tubules of the optic nerve, which have _ 
 
 -, . . . -, . , i , The retina. 
 
 cast off their covering investitures on their passage through the 
 sclerotic. It extends forward to the ciliary body ; is perfectly trans- 
 parent during life, though it soon becomes semi-transparent. Its struc- 
 ture, a knowledge of which is of the utmost importance in the theory of 
 vision, will be presently described. 
 
 201. In the optical axis of the eye there is upon the ret- 
 
 ina a spot of about the twentieth of an inch in diam- 
 eter, called the yellow spot of Soemmering. Its posi- 
 tion is shown in Fig. 201. The entrance of the optic 
 nerve is at the blind spot which is marked at some dis- 
 tance on one side. The vitreous humor is contained in 
 spot of soem- a delicate mesh of transparent tissue, which The vitreous 
 
 causes it, when removed, to present the aspect humor - 
 of a jelly. In front it receives the crystalline lens, which is contained 
 in a closed capsule. Eound the lens there is a passage, known as the 
 canal of Petit, which enables the ciliary muscle to move the lens. The 
 
 BB 
 
386 OPTICAL ACTION OF THE EYE. 
 
 Analysis of the vitreous humor shows that it consists of water contain- 
 ing about one and a third per cent, of common salt, with a trace of al- 
 bumen. 
 
 The crystalline lens is a double convex of unequal curvatures, the an- 
 The crystalline terior surface being the flattest, the shape changing with the 
 lens. period of life, as also does the density of its parts, its cen- 
 
 tral portions being always the most dense. In construction it is ex- 
 tremely complex, being made up of fibres ranged side by side, and so 
 forming successive lamina. The fibres are about the -^fa-^ part of an 
 inch thick. The refracting power of the lens differs at the centre and 
 circumference : in the former region it is greater. In chemical composi- 
 tion, the lens consists of about fifty-eight per cent, of water, and thirty- 
 six per cent, of a form of albumen known as globulin. 
 
 The aqueous humor fills up the space between the lens and the cornea : 
 Aqueous humor. ** * s c m posed of water containing about one per cent, of 
 common salt. 
 
 Of the Optical Action of the Eye. 
 
 It is the province of the works on natural philosophy to explain how, 
 Formation of wnen ravs ^ % nt &H upon a convex lens, or upon combi- 
 images by nations of such lenses, an image of the object will form at the 
 proper focal distance. For the purposes of physiology, it is 
 sufficient to receive this as a fact, which may be easily illustrated by ob- 
 serving the images of external objects depicted upon a sheet of white 
 paper when a convex lens or magnifying-glass is held at a particular 
 distance between the object and the paper. 
 
 In making such an experiment, some other facts which concern the 
 Effect of dis- physiologist may be readily demonstrated: 1st. That the 
 tanceoftheob- focal distance, that is, the distance between the lens and the 
 
 ject and curv- . .,,.. /> - 
 
 ature of the paper, is variable : it is greater for objects that are near, less 
 for those that are remote ; 2d. That lenses of different curv- 
 atures being compared together, the flatter ones have the longest focus 
 for objects at the same distance ; 3d. That lenses of the same focus, but 
 of different diameters, give images unequally sharp, an indefiniteness be- 
 ing perceived in the image given by the lens of large diameter. This in- 
 distinctness is due to the spherical figure of the lens, and would not have 
 Spherical and occurred had the surface been ground to another conic sec- 
 chromatic aber- tion. It is called spherical aberration ; 4th. Unless the 
 lens be of very long focus, or its aperture or diameter be 
 very small, the edges of the images it yields will be fringed with rainbow 
 colors, and thereby a second cause of indistinctness arises. It is called 
 chromatic aberration. This aberration may be destroyed by properly 
 combining together lenses made of different refracting media, and with 
 
THE RECEIVING SCREEN. 387 
 
 surfaces of suitable curvatures ; a combination in which this has been ef- 
 fected is termed an achromatic lens ; and if, at the same time, by proper 
 arrangements, the spherical aberration has been destroyed, the lens is 
 termed aplanatic. 
 
 Now the aqueous humor, as bounded by the cornea in front and the 
 crystalline lens behind, acts as a convex, and therefore con- Conver ent 
 verging lens, and to this effect the crystalline itself adds pow- media of the 
 erfully, the two conjointly causing the images of external ob- eye ' 
 jects to form upon the black pigment. These images are, of course, in- 
 verted. 
 
 The adjustment of the eye for perfect vision of objects at different dis- 
 tances is accomplished by the action of the ciliary muscle, ^d'ustment b 
 the requisite movement being to draw the lens farther from the ciliary mus- 
 the black pigment when the object is near. There has been c 
 much controversy as to the manner by which this adjustment for dis- 
 tance is effected, but it is generally now agreed that it is done in the 
 manner just mentioned. There has also been a difference of opinion as 
 respects the actual screen upon which the images form. Some of the 
 early optical writers regarded the black pigment as being The receiving 
 that receiving surface, an opinion which has been universal- screen V 3 the 
 ly abandoned, the function having been of late attributed to aMnoUhe ret- 
 the retina, but, as it appears to me, on totally insufficient ina - 
 grounds. The arguments against the retina, both optical and anatom- 
 ical, are perfectly unanswerable. During life it is a transparent medium, 
 as incapable of receiving an image as a sheet of clear glass, or the at- 
 mospheric air itself; and, as will presently be found, when we come to 
 describe its structure, its sensory surface is its exterior one, that is, the 
 one nearest to the choroid coat. But the black pigment, from its perfect 
 opacity, not only completely absorbs the rays of light, turning them, if 
 such a phrase may be used, into heat, no matter how faint they may be, 
 but also discharges the well-known duty of darkening the interior of the 
 eye, and therefore preventing indistinctness through the straying of the 
 rays of light. Perfection of vision requires that the images should form 
 on a mathematical superficies, and not in the midst of a transparent me- 
 dium. The black pigment satisfies that condition, the retina does not. 
 
 Spherical aberration is compensated for partly by the increasing dens- 
 ity of the lens toward its centre, and partly by the action Correction for 
 of the iris, which stops such rays of light as are at any con- spherical aber- 
 siderable distance from the axis of the eye, acting in the 
 same manner as a perforated plate or diaphragm in ordinary optical in- 
 struments. 
 
 It does not appear that there is any attempt at correcting the chromat- 
 ic aberration of the eye, though it is popularly supposed that the cornea, 
 
388 LONG AND SHOET SIGHT. 
 
 the aqueous humor, the lens, and the vitreous humor act to- 
 Chromatic ab- ^ . . 
 erration is un- gether in the same manner as the different pieces of glass in 
 
 corrected. an acnroma tic arrangement. Optical reasons, however, found- 
 ed upon the constitution and refractive powers of those substances, lead 
 us to abandon that view, and in a theoretical respect to regard the eye 
 as imperfect in this particular. 
 
 Adjustment for the variable intensity of light is effected by the dilata- 
 tions and contractions of the iris, the pupillary opening; of 
 
 Adjustment for . 7 i P i -, 
 
 the intensity which varies from the -?fc to the -J of an inch in diameter. 
 We are thus enabled to bring to the same degree of illumin- 
 ating effect upon the retina lights which differ in brilliancy in the pro- 
 portion of one to forty-five. The means by which this is accomplished 
 will be more particularly described when we speak of the nervous mech- 
 anism of the eye. 
 
 It has been already observed that the actual field of view at a given 
 moment is quite limited. We are liable to deceive ourselves on this 
 point from the rapidity with which the eyeball can be directed to differ- 
 ent parts in succession. 
 
 In what has been said, reference is made to a perfect eye ; but imper- 
 Long and short fections are very common. Two may be more particularly 
 cSre^donb'y 11 P ointed out long-sightedness and short-sightedness. In 
 spectacles. the former, objects, to be seen distinctly, must be placed 
 farther off than the usual distance ; in the latter they must be brought 
 nearer. Long-sightedness arises from the flatness of the lens or cornea, 
 so that the focal images given do not fall truly on the black pigment, but 
 would be, at a certain distance, exterior to it ; hence the indistinctness 
 that results. Short-sightedness is due to an excess of curvature in the 
 cornea or lens, the rays forming their focal images before the black pig- 
 ment is reached. The former defect may be removed by the use of con- 
 vex lenses as spectacles, the latter by concave. It is often said that 
 short-sightedness is a defect of early life, long-sightedness of old age. 
 However this may be in another respect, it is not so optically. Indeed, 
 cases sometimes occur in which one eye is affected with the former and 
 the other with the latter difficulty. Very frequently the two eyes, com- 
 pared together, will be found differently advanced in their degree of im- 
 perfection, and hence the difficulty of obtaining a pair of spectacles, 
 though the selection is attempted to be made out of a large assortment. 
 In such cases, each eye should be accommodated with a lens to suit it- 
 self. 
 
 Compared with the organ of hearing, the eye is much more limited in its 
 Limit of vision action ; for, while the ear can distinguish sounds which vary 
 is one octave, through many octaves, the eye can only perceive vibrations 
 which, to use the language of acoustics, differ by a single octave only. 
 
EFFECTS OF HEAT. 389 
 
 To one octave, therefore, its range is limited. The extreme red ray, which 
 is emitted by a substance just becoming red hot at a temperature of 
 1026 Fahr., and which is the least refrangible that can affect the eye, 
 is caused by vibrations that are exactly half as frequent as the extreme 
 violet ray emitted by the sun. It is important, in the explanations we 
 are giving, to understand that, in a perfect solar spectrum, the distribution 
 of the colored spaces is totally different from what it is in the case of the 
 prismatic. In such a spectrum, as produced by the interference of rays 
 passing through a surface of glass on which have been ruled with a point 
 of a diamond parallel lines the yfl-J-g-g- ^ an mcn apart, the yellow occu- 
 pies the middle region, and from this the light grades off, terminating at 
 equal distances with the extreme red on one side and the extreme violet 
 on the other. The circumstances of such an experiment prove that, the 
 wave length for the red light being compared with that for the yellow, 
 and also for that of the violet, they bear to one another the extraordinary 
 and simple relation of 1, 1J, 2, establishing the assertion just made, 
 that the extreme limit of perception of the eye is comprised in a single 
 octave. 
 
 I may refer to the experiments published by myself on this point, and 
 also to those both antecedently and subsequently published 
 by M. Melloni, in proof of the unreliability of the method of colored rays is 
 examining the solar spectrum by the prism in the manner jeinu? 
 introduced by Newton. More particularly to the discussion minating pow- 
 now before us does this remark apply ; for the prism, as er * 
 may be gathered from what has just been said, spreads out the colors of 
 light unduly, and gives false indications respecting the distribution of 
 heat. There can now remain no doubt, although the prism indicates the 
 contrary, that the yellow, or brightest ray of light, is the hottest, and 
 that the warming power of the others, orange, green, &c., follows in the 
 order of their luminous < intensity. When we have finished a descrip- 
 tion of the nervous mechanism of the eye, we shall find that the expla- 
 nation of its function turns on the admission of this fact. 
 
 The eye is limited in another respect ; it can not simultaneously com- 
 pare lights which differ from one another in brilliancy if the Limit in the 
 one should be upward of 64 times as bright as the other. 
 The more luminous overpowers or extinguishes the feebler, of lights. 
 We can not see the light of a candle if we hold it up against the sun. I 
 may again refer to the experiments I have published, establishing that 
 upon this fact is founded the most exact method of photometry yet 
 known. 
 
 2d. Of the Nervous Mechanism of the Eye. 
 In the preceding description it was stated that the retina, commonly 
 
390 STEUCTUEE OF THE EETINA. 
 
 described as an expansion of the optic nerve, intervenes between the vit- 
 reous humor and the choroid coat. 
 
 Regarding it as composed of distinct layers, the innermost of which, 
 Construction in contact with the hyaloid membrane, is called the fibrous 
 f nd Jacobs S ra 7 ^ a 7 er ' ar i ges fr m tne tubules of the optic nerve, which 
 membrane, have cast off the white substance of Schwann ; and in pass- 
 ing, we may dwell emphatically upon the point that at that spot, where 
 it exists alone, that is to say, where the optic nerve is entering the eye, 
 vision can not be performed. Beneath, or outside this fibrous layer, 
 comes the gray vesicular layer: it is analogous to the vesicular matter 
 of the brain. The two layers thus far described are served with capillary 
 blood-vessels of extreme minuteness. Outside of the gray vesicular lay- 
 er is the granular layer, which, as its name imports, consists of a conge- 
 ries of granules, which are puobably the origin of the vesicles, new ones 
 arising from this layer continually. Yet again, outside of the granular 
 layer, comes a delicate sheet, known as the membrane of Jacob, but which 
 is formed, in reality, from the juxtaposition of a set of rod-shaped and 
 conical bodies, the thicker ends of the rods being outward, the thinner 
 inward. 
 
 ig. 202. Fig. 202 shows the partial detachment of 
 
 the membrane of Jacob from the exterior of the 
 retina. The membrane appears as delicate 
 shreds, and may be advantageously demon- 
 strated after the removal of the choroid, the 
 specimen being placed under water. 
 
 In the preceding description I have followed 
 the course usually taken by former anatomists, 
 who describe the retina as consisting of suc- 
 cessive layers or strata, but much more philo- 
 Membrane of Jacob. sophical views are obtained by considering it in 
 
 Per endicuiar ^e manner introduced by H. Miiller, that is to say, in its 
 examination radial section. From this it appears that the four strata 
 of the retina. ^ QyQ ^^0,^^ y^ \ t Jacob's layer of rods and cones ; 2. 
 The granular layer ; 3. The vesicular layer ; 4. The fibres of the optic 
 nerve, are, in reality, all connected in such a way that, passing in a radial 
 direction as respects the globe of the eye, all these different elements are 
 successively combined, constituting what is termed the radiated fibre 
 system. Thus from each of the proper fibres of the optic nerve a thread- 
 Eadial fibre like body passes radially through the thickness of the retina, 
 system. including in its outward passage a vesicle, and again, beyond 
 that, a granule, and, still farther, a cone, and terminating in a rod ; so 
 that from the extremity of the rod there is a continuous communication 
 through the thickness of the retina to the fibres of the optic nerve ; the 
 
THE OPTIC NERVES. 391 
 
 rods are therefore to be regarded as the termination of the optic fibres. 
 In the opinion of Miiller and Kolliker, the rods and cones composing 
 Jacob's membrane are the true percipients of light, communicating their 
 condition to the fibres of the optic nerve by means of the connection 
 which they thus maintain with it ; or, perhaps, the rods and cones are 
 conductors of the luminous impressions to the nerve-cells of the retina, 
 which constitute a ganglion capable of perceiving light, and the fibres of 
 the optic nerve merely communicate those impressions to the sensorium. 
 
 Whichever of these descriptions we may follow, the physiological fact 
 which I desire to present with emphasis still remains the same. It is, 
 that the sentient or receiving part of the retina is the posterior, that 
 which is in contact with the black pigment. 
 
 The second pair of nerves, from which the retina is thus derived, are, 
 from their function, designated the optic nerves. They do The optic 
 not enter the sclerotic in its optical axis, but at a little dis- nerves : their 
 
 * . . . chiasm and 
 
 tance on one side, and obliquely a provision doubtless in- passage to the 
 tended, in a measure, to avoid the occurrence of the blind bram< 
 spot on the centre of the field of vision, and to place it unsy in metrically 
 in the two eyes, so that each eye shall compensate the defect of the oth- 
 er. The nerves from each eye converge to their chiasm, which is a com- 
 missure consisting of three distinct systems of tubules an anterior set, 
 which are commissures between the two retinas, a posterior set, commis- 
 sures between the two optic thalami, and an interior set, the proper tu- 
 bules of the optic nerve, which cross, those from the right eye going to 
 the left side of the brain, and those from the left eye going to the right 
 side of the brain. The chiasm is therefore to be regarded as a complex 
 structure, its posterior region being independent of the other parts, and 
 existing in animals in which the optic nerve is not found, as, for exam- 
 ple, in the mole. 
 
 Besides the optic nerve, which is exclusively the nerve of vision, the 
 collateral parts of the eye are supplied from various sources. 
 The third pair, or motores-oculorum, supply the superior, in- eye-ball and 
 ferior, and internal recti muscles, the inferior oblique, and the annexe P arts - 
 levator palpebrae. The fourth pair, or pathetici, supply the superior ob- 
 lique or trochlear muscles. Of the fifth pair, supplies are derived from 
 the frontal branch, lachrymal, the ciliary, and the infra-trochlear. The 
 sixth pair, or abducent, pass to the external recti : supplies are also de- 
 rived from the sympathetic. Of these nerves, the functions are very va- 
 rious ; some are for the movement of the ball, or for general sensibility 
 of the surface, or for the movements of the eyelids, or for those of the iris, 
 and some for the lachrymal apparatus. 
 
392 NERVOUS ffliCHANISM OF THE EYE. 
 
 Of the Function of the Nervous Mechanism of the Eye. 
 
 The reasons have already been given for considering that it is the 
 The black pig- black pigment which acts as the receiving eft optical screen, 
 ment, and not and no t the retina. If no other argument was adduced for 
 the receiving departing from the opinion usually expressed, which attrib- 
 screen. u ^es this function to the retina, the thickness of that struc- 
 
 ture would be sufficient ; images can only form with precision or sharp- 
 ness upon an abrupt surface. And since it is now indisputably ascer- 
 tained that both the chemical effect and the heating effect of the rays of 
 light depend upon their absorption, those effects being in direct propor- 
 tion to the completeness with which absorption is taking place, we are 
 justified in inferring that, since the eye is sensible to rays of so low a 
 degree of intensity, and to each of the colored ones equally, its screen of 
 reception must not only be a superficies, but likewise a black one. Such 
 a surface the black pigment is. In the case of albinos, and animals in 
 which the black pigment is imperfectly developed, the receiving surface 
 or screen is still the interior of the choroid. Under such circumstances, 
 vision must be indistinct. 
 
 Recalling what has been said respecting the diffuse sensibility of the 
 Heating effect lower members of the animal series to light, and the struc- 
 on the pigment, ture of ocelli, it accords well therewith to consider that the 
 primary effect of the rays of light upon the black pigment is to raise its 
 temperature, and this to a degree which is in relation to their intensity 
 and intrinsic color ; light which is of a yellow tint exerting, as has 
 been said, the most energetic action, and rays which correspond to the 
 extreme red and the extreme violet the feeblest. The varied images of 
 external objects which are thus painted upon the black pigment raise its 
 temperature in becoming extinguished, and that in the order of their brill- 
 iancy and color ; the pigment thus discharging a double duty, as a sur- 
 face of extreme sensibility for calorific impressions, and also as darken- 
 ing the interior of the globe. 
 
 In this local disturbance of temperature, in my opinion, the act of 
 Manner of er- v^ 011 commences, this doctrine being in perfect harmony 
 ception by the with the anatomical structure of the retina, the posterior 
 surface of which is its sensory surface, and not the anterior, 
 as it ought to be if the explanation usually given of the nature of vision 
 is correct ; and therefore, as when we pass the tip of the finger over 
 the surfaces of bodies, and recognize warm and cold spaces thereupon, 
 the same occurs with infinitely more delicacy in the eye. The club- 
 shaped particles of Jacob's membrane are truly tactile organs, which 
 communicate to the sensory surface of the retina the condition of tern' 
 peratura. of the black pigment. 
 
PHOTOGRAPHIC RELATIONS OF THE EYE. 393 
 
 But this communication of a variation of temperature implies a varia- 
 tion in the waste and repair of the retina itself, for there can be no doubt 
 that all such changes are accelerated by an increase of heat, and dimin- 
 ished by its decrease. And though in this manner the origin of the ac- 
 tion which has been set up is calorific, and therefore physical, it imme- 
 diately becomes converted into a physiological equivalent in the meta- 
 morphosis and destruction of a nervous tissue. 
 
 The eye can not perceive rays which come from a luminous source 
 the temperature of which is lower than 1000 F., for such rays can not 
 pass through a stratum of water or through the humors of the eye. 
 Natural philosophers, in making a distinction between light and heat, 
 have too often overlooked the fact that, though thermometers are sensi- 
 tive to rays of every sort, the eye is not. Its indications are complicated 
 by the necessary introduction of absorbent media, which stop all rays 
 the refrangibility of which is low. 
 
 Many years ago, Count Rumford, from a limited examination of cases, 
 concluded that all photographic effects are the effects of Photographic 
 a high temperature. From an examination, continued for ff? t g ts f "tfh 
 many years, of numerous phenomena of the same class, which temperature. 
 have since been described, I have come to the same conclusion. The 
 impinging of a ray of light on a point raises the temperature of that 
 point to the same degree as that possessed by the source from which the 
 ray comes, but an immediate descent takes place through conduction to 
 the neighboring particles. This conducted heat, by reason of its indef- 
 initely lower intensity, ceases to have any chemical effect, and hence 
 photographic images are perfectly sharp on their edges. It may be dem- 
 onstrated that the same thing takes place in vision, and in this respect 
 it might almost be said that vision is a photographic effect, the receiving 
 surface being a mathematical superficies, acting under the preceding con- 
 dition. All objects will therefore be definite, and sharply defined upon 
 it, nor can there be any thing like a lateral spreading. If vision took 
 place in the retina as a receiving medium, all objects would be nebulous 
 on the edges. This sharpness and grading off are happily illustrated by 
 the metal daguerreotype and paper photograph respectively. 
 
 Perhaps it might be thought that the sharpness of impressions upon 
 collodion or albumen stands in opposition to what is here Absorption nee- 
 said respecting the inefficiency of translucent media. Those 
 substances, however, would be totally inert unless there had tion 
 been purposely mingled with them some compound of easy decomposi- 
 bility, capable of absorbing the "blue rays, which are in these cases the 
 effective photographic ones. Such a compound must commonly be of a 
 yellow color. In these substances the absorption takes place with en- 
 ergy the moment the light has entered their surface. In the Philosoph- 
 
394 FUNCTION OF THE EETINA AND CHOROID. 
 
 ical Magazine, September, 1840, 1 have given proofs that the essential 
 condition of the chemical activity of a ray of light is its being thus ab- 
 sorbed. As an illustration may be given the well-known result, that if 
 chlorine and hydrogen be exposed to the sun, they unite with a violent 
 explosion, but, under the same circumstances, oxygen and hydrogen will 
 utterly refuse to unite, no matter how long the period of exposure may 
 be, nor what the brilliancy of the light ; and the difference in the two 
 cases is merely this, that the chlorine, being of a yellowish color, can ab- 
 sorb the violet light, and therefore be influenced by it ; but the oxygen, 
 being uncolored, can not. For photographic effects, as well as calorific, 
 the essential condition is absorption. A medium like the retina, which 
 is without absorbing action, permits rays to pass through it without any 
 kind of effect, but a surface like the black pigment, which receives them 
 all equally, whatever their color may be, and absorbs them all equally, 
 is equally affected by them all. 
 
 The impression arising from the disturbed condition of the retinal 
 Function of the vesicles is carried by the optic tubules to the chiasm of the 
 
 two chief lay- ^wo nerves. Apart from the general facts elsewhere pre- 
 
 ers of the reti- -,.1 , . />ITT 
 
 naandthecho- sented by physiology, the existence of a bund spot at the 
 entrance of the optic nerve, where there is a necessary ab- 
 sence of vesicular structure, is a clear proof of the insensibility of the 
 tubular structure to the influence of light. Considering, therefore, the 
 retina as typically composed of three layers, one of tubules, one of vesi- 
 cles, and one of granules, and these in health being perfectly transparent, 
 the luminous beams pass through them just as they do through the at- 
 mosphere, without exerting the slightest effect ; and as, when those rays 
 strike the opaque surface of the earth, or are absorbed by the sea, heat is 
 disengaged and effects ensue, so likewise, when they have reached the 
 black pigment, the changes I have been designating arise. The vesicu- 
 lar layer undergoes rapid metamorphosis, the effect of that change is 
 transmitted by the tubular layer, and in the granular the germs are con- 
 stantly arising from which the waste of the middle layer is repaired. So, 
 therefore, the tubular layer is for conduction, the vesicular layer for waste, 
 the granular layer for repair ; and now appears the significance of the 
 construction and proximity of the choroid coat, for the waste of the ve- 
 sicular layer can not occur save under the oxidizing influence of the ar- 
 terial blood, nor can the nutrition of the granular layer be accomplished 
 except under the same condition. Moreover, the resulting products of 
 waste require to be quickly removed, and it is not possible to conceive 
 the construction of an arrangement better adapted for this triple object 
 than that which the choroid presents. On the old view of the nature of 
 vision, the construction of the choroid seems to be without significance. 
 The analogy between the mechanism of the retina and that of the 
 
SINGLE VISION. 395 
 
 skin, so far as waste and restoration are concerned, can not fail to be 
 noticed. 
 
 The effect which has thus been communicated to the vesicular layer 
 of the retina, through the intervention of Jacob's rods and T 
 
 . interconnection 
 
 cones, is now earned along the nervous tubules out of the of the right and 
 globe of the eye. The nerves from each eye, converging, e fc cye> 
 encounter one another at the chiasm, the triple structure of which has 
 already been described. Here it is, however, to be understood that, 
 while the proper optic tubules of the right eye go to the left brain, and 
 of the left eye to the right brain, the anterior band of commissural tu- 
 bules brings the two eyes into a special relation with one another, the 
 right side of one eye corresponding with the rignt of the other, and the 
 left with the left ; or, to put the same statement under a more simple yet 
 more instructive form, the outer side of one eye corresponds with the in- 
 ner of the other, and in this manner the two retinas become as if they 
 were virtually incased the one within the shell of the other, an arrange- 
 ment which obviously, as has been already remarked, compensates in a 
 degree for the blind spot of each eye, and, indeed, eliminates the effect of 
 all accidental irregularities, for numberless such irregularities must exist, 
 there being a necessity, for example, that blood-vessels should cross 
 through the sensitive to the conducting structures, and such blood-ves- 
 sels give rise to lines of inertness. 
 
 From this commissural arrangement it comes to pass that each retina 
 possesses regions of symmetry with the other, and on this single and 
 singleness of vision depends ; each point of the outer portion double vision, 
 of the retina of the right eye has its point of symmetry in an inner portion 
 of the left, and when from a distant object rays fall on these symmetrical 
 points, that object will be seen single ; but if, by the pressure of the fin- 
 ger or otherwise, we compel the image to fall in one of the eyes upon 
 another, and, therefore, non-symmetrical point, the object at once becomes 
 double. It should be remarked that this exchange of symmetry concerns 
 only the lateral divisions, for the upper portion of one eye corresponds 
 with the upper portion of the other, and the lower with the lower. 
 
 If the view which I have presented respecting the scal^e of the laby- 
 rinth of the ear be correct, that singular structure finds its Analo be _ 
 equivalent in the black pigment of the eye ; for though we tween the scalse 
 only know in an indistinct manner the physical condition of and P. 1 s ment - 
 black opacity, we may be certain that it arises from total interference of 
 rays, and such, it is presumed, is the office of the scalaa of the ear. 
 
 Impressions made upon the retina do not disappear instantly, but grad- 
 ually fade away, and in so doing occupy a certain period of Duration of 
 time, which varies with the brightness of the original light, the impressions 
 existing condition of the eye, and the illumination to which it 
 
396 ERECT VISION. 
 
 is exposed. This duration of impressions is commonly estimated at 
 about one third of a second. It is a phenomenon analogous to that of the 
 continuance of sound in the ear, and subserves an important purpose of 
 keeping vision continuous and distinct during the winking of the eyelids. 
 Commonly it is illustrated by referring to the familiar experiment of a 
 stick lighted at one end and twirled rapidly round, which gives rise to 
 the appearance of a continuous fiery circle. Many ingenious and interest- 
 ing toys, such as the thaumatrope or wonder-turner, act on this principle. 
 
 When the eye, particularly after a period of repose, as when we first 
 Ocular spectra wake in the morning, is turned to the window or some bright 
 %^t, an( ^ ^ en c l se d> a spectral impression is for a long 
 time presented to the mind. If, instead of closing the eyes 
 after looking at a bright light, they are directed to some white surface, a 
 dark spectral appearance of the luminous object is seen. The explana- 
 tion of this is evidently that those parts of the retina which have just 
 undergone change are less fit to be acted upon by the more moderate 
 light to which they are now exposed than those which have hitherto been 
 unaffected. Under similar circumstances arise what are termed comple- 
 mentary colors. Thus, if we intently regard a red wafer on which the 
 sun-rays are brightly shining, and then turn our eyes away to a feebly 
 illuminated white wall, a green spectre of the wafer will be seen ; and so 
 of other colors. The complementary tint is that color which, added to 
 the original one, forms white light. The explanation of these colored 
 spectra depends upon the principle just mentioned. 
 
 There have been few optical problems more warmly contested than 
 that of erect vision. The image at the bottom of the eye is 
 
 Erect vision. . 11. t n , 
 
 inverted, but we see the object upright. Some have supposed 
 that we really see things upside down, but have learned to correct the 
 error by the sense of touch. Doubtless the true explanation is to be 
 found in the anatomical construction of the eye. It should be borne in 
 mind that there is a very wide difference between the image formed at 
 the bottom of an eye as we look at it, and, if such an expression may be 
 used, as the eye itself looks at it. We see it from behind, the retina 
 sees it from the front. Or, to put the statement perhaps more clearly, 
 it is one thing to look at the images on the ground glass of a camera ob- 
 scura from behind the instrument, and another to see them, as it were, 
 from the interior of the box. The two positions are upon the opposite 
 sides of a vertical axis, round which we may consider that we have turn- 
 ed, and hence the lateral inversion is corrected. That portion of the im- 
 age which, seen from behind, was on the right of the spectator, is on his 
 left if seen in front. A similar event must ensue in the case of the ret- 
 ina. As we have seen, it is its posterior face, looking at the black pig- 
 ment, which is its sensitive surface. It sees, as it were, looking back- 
 
IDEAS OF SOLIDITY. 397 
 
 ward, but not forward, and hence there arises a correction for Lateral inver , 
 the lateral inversion. This, of course, implies the existence sion corrected 
 of some structural arrangement which shall either correspond- y 
 ingly correct the vertical inversion, or bring back the lateral to its orig- 
 inal erroneous state, and thereby establish a harmony of position in the 
 two directions ; and if, in the retina itself, the means exist for the cor- 
 rection of inversion, vertical as well as lateral, by changing the direction 
 of the conducting tubules, it necessarily must be that that place of cor- 
 rection is where the retina is intersected by the optical axis of the eye. 
 I think it is to be greatly regretted that we are not bet- Suggestion re- 
 ter acquainted with the construction of the yellow spot of JSJjJj^Jfjl 
 Soemmering, which occurs at this very point. The ridge- Soemmering. 
 like form it presents, the thin, uncolored spot in its centre, its more def- 
 inite occurrence in those animals, as man, the quadrumana, and some 
 saurians, the axes of whose eyes are nearly parallel to one another, seem 
 to indicate, in a very significant manner, that at this place the correction 
 in question is made. There are many ways in which we may conceive 
 this to be done by varying the direction of the nervous tubules. As an 
 illustration, it may be remarked that if, through a small hole made in a 
 sheet of paper, a number of threads, the end of each of which is fasten- 
 ed to the back of the sheet, be caused to pass, under the condition that 
 they do not cross one another in the hole, but leave its aperture open, 
 their direction in space as they retire from the hole will be inverted as 
 respects the direction in which they approached to it. The analogy be- 
 tween such an aperture and the foramen of Soemmering is too striking to 
 be overlooked. 
 
 The stereoscope, invented by Professor Wheatstone, shows to what an 
 extent our ideas of the solidity of objects depend on the dif- 
 ferences of the images in each eye. By reason of their dif- 
 ference of position, each of the two eyes will have a different picture upon 
 its black pigment of any solid object, and the mind, combining these dis- 
 similar pictures into one, gathers therefrom the idea of solidity. If thus 
 we offer to the eyes two pictures of a given object, presenting the same 
 form as that object would have done when seen from each eye respect- 
 ively, the mind combines these flat pictures together, and can not divest 
 itself of the idea of a solid body. This is the principle of the stereo- 
 scope. It is shown by this instrument that, when two such pictures of 
 different sizes are used, the mind combines them into one of intermediate 
 magnitude. Probably this effect is involved in the circumstance that, 
 when we look at an object unequally distant from the two eyes, we still 
 see it single. When two images of different colors are employed, the 
 mind can not combine them, but sees first the one and then the other, 
 the brightest one continuing the longest. 
 
398 SUBJECTIVE IMAGES. 
 
 The eye is adjusted to the varying intensities of light by the motions 
 of the iris, which admits more or fewer rays according to its 
 
 Adjustment to . . > 
 
 variations of state of contraction, an action which, on certain occasions, is 
 brightness. a i(j e( j by the orbicularis palpebrarum, which, "by bringing 
 the eyelids together, limits the number of rays passing to the pupil. In 
 man, the muscular fibres of the iris are of the unstriped form ; in birds 
 they are striped. Our perceptions of the intensities of light, as gather- 
 ed from the state of the iris, can never be so distinct as the indications 
 for sound yielded by the tensor tympani and stapedius muscles. In 
 birds, however, it is probably different. We gather, to a great extent, 
 our notion of the brilliancy of light from the rapidity of structural change 
 taking place in the retina itself. 
 
 Although many images may be simultaneously existing upon the ret- 
 Concentration * na ' ^ e mm( ^ possesses the power of singling any one of them 
 of attention on out and fastening attention upon it, just as among a number 
 of musical instruments simultaneously played, one, and that 
 perhaps the feeblest, may be selected, and its notes exclusively followed. 
 These phenomena, however, are not dependent upon any peculiarity of 
 construction of any of the organs of sense ; and as the mind can perceive 
 the images of external things, so can it give rise to spectral illusions 
 which may simulate perfectly the aspect of external forms. The anec- 
 dotes of such occurrences which are to be found among all people are not 
 the fabrications commonly supposed. The mind can be readily deceived, 
 even in spite of itself, as the phenomena of the stereoscope prove ; and 
 spectres, having their origin in natural or diseased conditions of the brain, 
 may accurately replace images that have been painted in the eye. It is 
 Sub'ective im sa ^' however, that we may readily distinguish, by means of 
 ages, and test a simple optical test, a true external apparition, if any ex- 
 ists, from a phantom of diseased imagination ; for by press- 
 ing duly with the finger on the ball of one of the eyes, external objects 
 are at once doubled, but it is not so with a mental illusion ; and we may 
 therefore suspect that, even in the best authenticated cases of the ap- 
 pearances of these unnatural forms, had this test been applied, their true 
 character would have been ascertained ; and that, since none of them 
 would have undergone duplication, they would at once have been detect- 
 ed as mere hallucinations of the mind. 
 
 The explanation of the function of vision which I have given on the 
 preceding pages might be termed the calorific hypothesis, since it rests 
 essentially on the fact that the temperature of the receiving screen of the 
 eye is raised by the impinging of light upon it. The result thus far is of 
 a purely physical nature, but it becomes physiological when we farther 
 admit that changes of constitution ensue in the vesicular structure of the 
 retina. These changes are rendered more rapid as the temperature is 
 
ACCESSORY APPARATUS. 399 
 
 higher. It remains now to add that this is only one manner of looking 
 at the thing. According as our hypothesis of the nature of light, of its 
 relations to heat, and of its manner of establishing chemical changes may 
 be, the special explanations we give of the functions of the eye will differ ; 
 yet there is such a relationship among these hypotheses that Translation of 
 we can, without any difficulty, convert an explanation derived the calorific 
 
 n . i i * i / -i T hypothesis to 
 
 irom one into an explanation derived from another. It re- other forms of 
 ally comes to little more than a translation of phraseology. ex P ression - 
 I have found the calorific hypothesis convenient, because we are led to it 
 by the comparative anatomy of the eye in starting from the ocelli of the 
 lower forms ; yet, with almost equal convenience, the function might have 
 been treated otherwise, viewing light as arising from ethereal undulations, 
 the additional advantage then being obtained of establishing a parallel- 
 ism between the action of the organ of sight and that of hearing. Or, 
 in like manner, the case might have been viewed in its purely chemical 
 aspect, photographically, as it might be said, the destruction of the vesic- 
 ular structure of the retina through the agency of arterial oxygen being 
 taken as the primary physical act. But this, again, amounts only to a 
 different mode of stating the same effect, since, as I have shown (London 
 and Edinburgh Philosophical Magazine, May, 1851), all chemical changes 
 accomplished in material substances are occasioned by the establishment 
 of vibratory motions therein, and Ampere has already demonstrated that 
 all the phenomena of heat may be explained upon the doctrine of the vi- 
 brations of the constituent molecules of bodies. 
 
 Divesting ourselves, therefore, of any farther concern in making a se- 
 lection among the various hypotheses, we have adopted the view that the 
 change of the retina originates in a calorific disturbance, because it ap- 
 pears to be somewhat more convenient for our use. 
 
 It is to be understood that the sensation of light is, however, purely 
 mental, and whatever can disturb the nutrition or waste of The sensation 
 the retina will give rise to luminous impressions. The press- of light purely 
 ure of the finger on the ball of the eye, a blow, the passage n 
 of an electric current, and divers other causes, will at once produce the 
 appearance of light, and even of colors. Heat is only one out of a mul- 
 titude of agents that can disturb the retina. 
 
 3d. Of the Accessory Apparatus of the Eye. 
 
 The accessory apparatus of the eye consists chiefly of the eyebrows, 
 the eyelids, the Meibomian glands, the lachrymal mechanism, and the 
 muscles for the movement of the ball. 
 
 The eyebrows are two arches of integument, covered with hair, on the 
 upper edge of the orbit. They are usually classed with the The eyebrows 
 appendages of the eye upon the supposition that they protect and eyelids. 
 
400 THE LACHRYMAL APPARATUS. 
 
 that organ from undue intensity of light, or preserve it from the ingress 
 of drops of sweat. They aid greatly in the expression of mental emo- 
 tions, but perhaps should rather be looked upon as among the remaining 
 vestiges of the hairy tegument which affords a protection to the entire 
 skin of other mammals below man in the animal series. The eyelids 
 may be described as a pair of valves, the upper one having a much great- 
 er latitude of motion than the lower. Their use is to afford protection 
 to the eye by closing entirely over it, more particularly during sleep ; to 
 keep its optical surface moist and free from dust by their winking mo- 
 tion. They are brought into action by the contact of air or of irritating 
 particles, through the fibres of the fifth and facial nerves, or by the agency 
 of light upon the retina. The edges of the lids are furnished with rows 
 of curved hairs, the eyelashes, which add greatly to the protection of the 
 delicate organ beneath, while permitting vision to take place to a certain 
 extent. Opening upon the edges of the eyelids are the foramina of the 
 Meibomian glands, in the upper lid there being about thirty, in the low- 
 er somewhat fewer. The glands themselves are imbedded on the in- 
 ternal surface of the cartilage of the lids, and afford an oily secretion, 
 which discharges the double duty of preventing adhesion of the lids, and, 
 by its relation of capillary attraction, hindering the overflow of the water 
 which moistens the eye upon the cheek. 
 
 Of the lachrymal apparatus, it may be said that in the same manner 
 The lachrymal tna * we breathe upon a spectacle glass and wipe it that its 
 apparatus. surface may be perfectly clean, so it is necessary for the op- 
 tical action of the cornea that its surface should be constantly washed, 
 and even more so, for its lamellated- structure is such that, if it be not 
 kept constantly damp, it loses much of its transparency. This therefore 
 renders it necessary that there should be a mechanism for the supply of 
 water, another for spreading that water uniformly over the surface of the 
 cornea, and a waste-pipe for carrying any surplus away. The lachrymal 
 gland discharges the first of these duties. It is situated in the upper 
 and outer angle of the orbit ; its secretion, which is a bitter and some- 
 what saline water, is brought to the surface of the conjunctiva by eight or 
 ten little ducts arranged in a row for the purpose of equalizing their dis- 
 charge. The spreading of this fluid over the eye, and the simultaneous 
 wiping of the surface, is accomplished by the eyelids. Usually the wa- 
 ter that has been employed is dissipated by evaporation into the air; but 
 if, by reason of meteorological circumstances, such as the dampness of 
 the atmosphere, or by the supply being too abundant, there should arise 
 an excess, it is carried off through two minute orifices which are upon the 
 edge of the eyelids, the puncta lachrymalia. These draw off any collection 
 of water that may have accumulated in the lachrymal lake, and, carrying 
 it into the lachrymal sac, discharge it through the nasal duct into the 
 
CEREBRAL SIGHT. 401 
 
 cavity of the nose. From this it is removed by evaporation, the current 
 of air alternately introduced and expired affording the means of accom- 
 plishing that object in a remarkable manner. But should the secretion 
 of water from the lachrymal gland become excessive, as in weeping, this 
 draining mechanism is insufficient, and the water is discharged as tears 
 down the cheek. 
 
 Of the muscles for the 'movement of the eye, the description has, in 
 part, been given under that of the nerves. It may, how- Motions of the 
 ever, be here remarked that the eyeball is moved by six eyeball, 
 muscles, the four straight and the two oblique. The straight muscles 
 arise at the optic foramen, and are inserted into the sclerotic in the four 
 quadrantal positions above, below, right, and left. The action of each 
 of these muscles is to turn the eyeball toward itself; when they contract 
 all together, they fix it. The superior oblique muscle arises from the 
 same place, passes through a pulley beneath the internal angular process 
 of the frontal bone, its tendon being inserted into the sclerotic near to 
 the entrance of the optic nerve. The inferior oblique rises from the in- 
 ner margin of the superior maxillary bone, passes beneath the inferior 
 straight muscle, and is inserted into the sclerotic on its outer and pos- 
 terior part, near the entrance of the optic nerve. The superior oblique 
 rolls the globe inward and forward, the inferior rolls it outward and back- 
 ward ; acting together, they draw the globe forward and converge the 
 axes of the eyes. The nervous supply for these various muscles has al- 
 ready been specified in page 334. 
 
 CHAPTEE XXI. 
 
 OF CEREBRAL SIGHT OR INVERSE VISION. 
 
 Difference, between ordinary Vision and cerebral Sight. Inverse Vision depends on the Vestiges 
 of Impressions existing in the Brain. 
 
 Condition of our perceiving these Impressions is that they must be equal in Intensity to present 
 Sensations. Two Methods of accomplishing this Equalization: 1st, by re-enforcing the old Im- 
 pressions ; 2d, by diminishing the present Sensations. 
 
 Emergence of old Impressions in Sleep, Fever, Death. Artificial Emergence of such Vestiges by 
 Protoxide of Nitrogen, Opium, etc. 
 
 Cerebral Sight used tekologically to indicate the Immortality of the Soul. 
 
 THE perception of external objects depends on the rays of light enter- 
 ing the eye, and converging so as to produce images which make an im- 
 pression on the retina, and, through the optic nerve, are recognized by 
 the brain. The direction of the influences, so far as the observer is con- 
 cerned, is from without to within, from the object to the brain. 
 
 Cc 
 
402 INVEESE VISION. 
 
 But the inverse of this is possible. Impressions already existing in 
 the brain may take, as it were, an outward direction, and be projected 
 or localized among external forms ; or if the eyes be closed, or the ob- 
 server is in darkness, they will fill up the empty space before him with 
 scenery of their own. 
 
 Inverse vision depends primarily on the condition that former impres- 
 sions, which are inclosed in the optic thalami or registering ganglia at 
 the base of the brain, assume such a degree of relative intensity that 
 they can arrest the attention of the mind. The moment that an equal- 
 ity is established between the intensity of these vestiges and sensations 
 contemporaneously received from the outer world, or that the latter are 
 wholly extinguished, as in sleep, inverse vision occurs, presenting itself, 
 as the conditions may vary, under different forms, apparitions, visions, 
 dreams. 
 
 From the moral effect to which these give rise, we are very liable to 
 regard them as connected with the supernatural. In truth, however, 
 they are the natural result of the action of the nervous mechanism, which 
 of necessity produces them whenever it is placed, either by normal, or 
 morbid, or artificial causes, in the proper condition. It can act either di- 
 rectly, as in ordinary vision, or inversely, as in cerebral sight, and in this 
 respect resembles those instruments which equally yield a musical note 
 whether the air is blown through them or drawn in. 
 
 The hours of sleep constantly present us, in a state of perfect health, 
 Difference be- illusions which appear to address themselves to the eye rath- 
 aii^wakin^^f er ^ nan ^ an 7 other sense, and these commonly combine into 
 lusions. moving and acting sceneries, a dream being truly a drama 
 
 of the night. In certain states, appearances of a like nature intrude 
 themselves before us even in the open day, but these, being corrected by 
 the realities with which they are surrounded, impress us very differently 
 to the phantoms of our sleep. The want of unison between such im- 
 ages and the things among which they have intruded themselves, the 
 anachronism of their advent, or other obvious incongruities, restrain the 
 mind from delivering itself up to that absolute belief in their reality 
 which so completely possesses us in our dreams. Yet, nevertheless, 
 such is the constitution of man, the bravest and the wisest encounter 
 these fictions of their own organization with awe. 
 
 If we measure the importance of events occurring to us by their fre- 
 Frequencyof ( l uenc 7 the depth of the impression they make, the influ- 
 mentaihaiiuci- ence they exert on our own individual career, or have ex- 
 erted on the progress of the whole human race, there are 
 very few more deserving the discussions of physiology than visual hal- 
 lucinations. With respect to frequency, it may be reasonably said that, 
 if images arise in the mind by night as numerously as sensible forms 
 
EFFECT OF THESE ILLUSIONS. 403 
 
 present themselves by day, it is not likely that they should be better 
 borne in memory ; but of the thousands of objects we encounter every 
 day of our lives, how few there are that we can distinctly recollect at its 
 close. We think we explain this wonderful forgetfulness by saying we 
 have paid no attention to them ; and, in like manner, the dreams we re- 
 member are perhaps only a very insignificant proportion of those which 
 have been presented to the mind. 
 
 It has been said that a belief in apparitions is natural to every man. 
 However much we may dissent from the correctness of such a T heir moral 
 general assertion, there can be no doubt that it has a founda- effecfc - 
 tion in truth. The faith of a child in this particular is only gradually 
 sapped as he grows up to be a man. Nay, even in mature life there may 
 always be found those who have an unwavering confidence in the reality 
 of these illusions, and many of these are persons characterized by their 
 moral courage and love of truth. I have just remarked that few things 
 have exerted a greater influence on the career of the human race than a 
 firm belief in these spiritual visitations. The visions of the Arabian 
 prophet have ended in tincturing the daily life of half the people of Asia 
 and Africa for a thousand years. A spectre that came into the camp at 
 Sardis unnerved the heart of Brutus, and thereby put an end to the po- 
 litical system that had made the great republic the arbiter of the world. 
 Another, that appeared to Constantine, strengthened his hand to the ac- 
 complishment of that most difficult of all the tasks of a statesman, the 
 destruction of an ancient faith. 
 
 But these were all impostures, it may be said. Not so ; they were 
 no impostures of the persons to whom they are reported to have occurred, 
 and who assuredly firmly believed in the real existence of what they 
 thought they saw. To the two or three instances mentioned above, 
 scores of a like kind might be added, which have issued in the commit- 
 ting of men to the most earnest kind of work. So often do historians 
 notice an element of this kind mingling in the career of those who have 
 made the deepest mark on our race, that some are to be found who as- 
 sert the necessity of such a condition to any widespread and permanent 
 political event. Whatever we may think of such a conclusion, the prem- 
 ises on which it is founded are well worthy of our consideration. The 
 physiologist is not at liberty to deny that lunatic and delirious men have 
 faith in what they see. Their senses may deceive them, but they are 
 not impostors. It is for him to consider how phantoms may arise in 
 conditions of apparent health as well as in states of disease ; in the tran- 
 quillity of the solitary man as well as in the feverish excitement of the 
 enthusiast. 
 
 Visual hallucinations are of two kinds, those which are seen when the 
 eyes are open, and those perceived when they are closed. To the for- 
 
404 RETINAL DISTURBANCE. 
 
 Apparitions mer, the designation of apparitions ; to the latter, that of vis- 
 and visions. j ons ma y be given. Dreams therefore come under the latter 
 
 class. 
 
 The simplest form of apparition is that known among physicians as 
 Muscse voli- muscse volitantes. These are dark specks, like flies, which 
 tantes. seem to be floating in a devious course in the air. They are 
 owing to disturbances or changes in the retina. They often appear to 
 occupy the dying. 
 
 Of visions the most common, because they can be voluntarily pro- 
 Remains of op- duced, are those which depend on the remains of impressions 
 tic impressions. j[ n the retina and optic centres. If, when we awake in the 
 morning, our eyes are turned for a moment to a window or other bright 
 object, and then closed, there still appears to the mind a spectral repre- 
 sentation of the. object, which gradually fades away. These illusions can 
 be caused to have, as it were, a movement in the dark, space before us, 
 answering to the voluntary rotation of the eyeball. Sometimes, when 
 the light is not sufficiently intense, or the nervous organs not sensitive 
 enough, the vision does not make its appearance on the closing of the 
 eyelids, but, after fastening the attention on the position in which it is ex- 
 geatofa ari- P ecte< ^ to.come, it slowly emerges at last. That it consists 
 tions and vis- in a real impression which has been made on those organs, 
 )ns ' and is not a mere product of the unaided imagination, is very 
 
 clear from the fact that we may discern, by attentively considering it, 
 many little peculiarities which we have not had' time to notice in the 
 original object ; thus, if there has been a lace curtain, or other such well- 
 marked body before us, we can not only see in the vision the places 
 where its folds intersect the windows, but likewise, if the impression be 
 a good one, all the peculiarities of its figured pattern ; and that our 
 conclusions in these respects are correct is proved as soon as we re-open 
 our eyes. 
 
 Between apparitions and visions is an intermediate class, of which it 
 is not my object now to say much; they may, however, be 
 
 Deceptions. .. J . J \ . 7 . / . J 
 
 styled deceptions. These take their origin in some outward 
 existing reality, and are exaggerations of the fancy. They are commonly 
 encountered in the evening twilight, or in places feebly illuminated. Sir 
 W. Scott says of children that lying is natural to them, and that to tell 
 the truth is an acquired habit. If they are thus by nature prone to de- 
 ceive those around them, they are none the less prone to deceive them- 
 selves. To them, a white object, faintly descried in the obscurity, is 
 easily expanded into a moving and supernatural thing. 
 
 In a physiological sense I consider that simple apparitions arise from 
 disturbances or disease of the retina ; visions from the traces of im- 
 pressions inclosed at a former time in the corpora quadrigemina and op- 
 
RETINAL DISTURBANCE. 405 
 
 tic thalami. In their most highly-marked state the former may "be 
 treated of as results of insanity of the retina, the latter as of cerebral 
 vision. 
 
 Disturbance of the retina, brought on by any cause whatever, may give 
 rise to simple spectral apparitions, which, as the circumstances A aritions 
 change, will have an indefinite contour or a definite form ; nor from retinal 
 are they merely shades and shadows : they may be presented disturbance - 
 in colors, which, however, are usually dim or subdued. Thus, if, the eye- 
 lids being closed, we press gently with the tip of the finger on the inner 
 or outer angle of one of the eyes, a gray spot surrounded by colors makes 
 its appearance on the opposite side of the same eye, and dances about as 
 the pressure of the finger varies. With a more extensive and heavier 
 pressure clouds of various rainbow tints fill up all the imaginary space 
 before us. In like manner, the passage of an electric current from a vol- 
 taic pair induces a flash of light of considerable brilliancy. Internal 
 pressures and spontaneous variations in the rate of metamorphosis and 
 nutrition of the retina act in a manner analogous to external disturbances. 
 
 From the muscge volitantes, which may be regarded as the first rudi- 
 ments of apparitions, it is but a step to the intercalation of simple or even 
 grotesque images among the real objects at which we are looking ; and, 
 indeed, this is the manner in which they always offer themselves, as rest- 
 ing or moving among the actually existing things. I do not undertake 
 to say how far we are liable to practice deception upon ourselves, after 
 the manner we have spoken of in children, when we have once detected 
 the fact that we are liable to this infirmity. An inanimate object for in- 
 stance, a stick is seen upon the floor; we go to take it up; we find there 
 is nothing there ; we return to our first position, but we can observe no 
 shadow or other reality that can be offered as an explanation of what we 
 have seen. An event of this kind predisposes us, perhaps, to return to 
 that disposition of exaggeration so natural to our early life, and the next 
 time the retina deceives us we involuntarily give to the hallucination mo- 
 tion and a more definite form. 
 
 Insects flying in the air, or, rather, floating in vacancy before us, pre- 
 sent the incipient form of retinal malady. It may be provoked by un- 
 due use of the eyes, as reading by lamp-light. I remark it constantly, 
 in my own case, after prolonged use of the microscope. In a more ag- 
 gravated form, it less frequently occurs as producing stars or sparks of 
 light. From the earliest times, physicians have observed that it is a 
 "bad sign" when the patient localizes these images. " If the sick man 
 says there be little holes in the curtains, or black spots on his bed- 
 clothes, then is it plain that his end is at hand." 
 
 Under the title of pseudoblepsis, or false vision, medical authors enu- 
 merate several varieties of the foregoing phenomena ; but when, as is 
 
406 HALLUCINATIONS OCCASIONED BY DRUGS. 
 
 Co-existence most commonly the case, the derangement which gives origin 
 of retinal in- t these appearances is not limited to the retina, but, arising 
 
 sanity and cer- , . 
 
 ebrai sight. in some constitutional affection, involves more or less com- 
 pletely the entire nervous apparatus of the eye, retinal insanity and cerebral 
 vision occur together. In those cases which have been investigated in 
 a philosophical manner by the patients themselves, this complication is 
 often distinctly recognized. Thus Nicolai, the Prussian bookseller, who 
 published in the Memoirs of the Royal Academy of Berlin an interesting 
 account of his own sufferings, states that, of the apparitions of men and 
 women with which he was troubled, there were some which disappeared 
 on shutting the eyes, but some did not. In such a case there can be no 
 doubt that the disease affected the corpora quadrigemina and the optic 
 thalami as well as the retina. 
 
 This condition, in which the receiving centres and registering ganglia 
 at the base of the brain are engaged, is the one which yields the most 
 striking instances of hallucinations in which apparitions and visions co- 
 Brought on ar- exist. It can, like the less complicated forms, be brought 
 tificiaiiy by ai- artificially, as in the delirium tremens which follows a 
 
 conol, opium, > 7 
 
 &c. cessation from the customary use of alcohol, or in the exalt- 
 
 ation by the purposed administration of opium or other drugs. In this, 
 as in those forms, it is the localization of the phantom among the bodies 
 and things around us that begins to give power to the illusion. The 
 form of a cloud no bigger than the hand is perhaps first seen floating 
 over the carpet, but this, as the eye follows it, takes on a sharp contour 
 and definite shape, and the sufferer sees with dismay a moping raven on 
 some of the more distant articles of furniture. Or, out of an indistinct 
 cloud, faces, sometimes of surprising loveliness, emerge, one face succeed- 
 ing as another dies away. The mind, ever ready to practice imposture 
 upon itself, will at last accompany the illusion with grotesque or even 
 dreadful inventions. A sarcophagus, painted after the manner of the 
 Egyptians, distresses the visionary with the rolling of its eyes. Martin 
 Luther thus more than once saw the devil under the well-known form 
 popularly assigned to him in the Middle Ages. 
 
 As the nervous centres have been more profoundly involved, these 
 Visions of false v i s i ons Become more impressive. Instead of a solitary 
 or exaggerated phantom intruding itself among recognized realities, as the 
 shade of a deceased friend qpens the door and noiselessly 
 steps in, the complicated scenes of a true drama are displayed. The 
 brain becomes, as it were, a theatre. According as the travel or the 
 reading of the sick man may have been, the illusion takes a style : black 
 vistas of Oriental architecture, that stretch away into infinite night; tem- 
 ples, and fanes, and the battlemented walls of cities ; colossal Pharaohs, 
 sitting in everlasting silence, with their hands upon their knees. " ] 
 
FORMS OF SPECTKES. 407 
 
 saw," says De Quincey, in his Confessions of an Opium-eater, " as I lay 
 awake in bed, vast processions, that passed along in mournful pomp ; 
 friezes of never-ending stories, that to my feelings were as sad and sol- 
 emn as if they were stories drawn from times before (Edipus or Priam, 
 before Tyre, before Memphis ; and, at the same time, a corresponding 
 change took place in my dreams ; a theatre seemed suddenly opened 
 and lighted up within my brain, which presented nightly spectacles of 
 more than earthly splendor." 
 
 Apparitions are the result of a false interpretation of impressions con- 
 temporaneously made on the retina ; visions are a presentment of the 
 relics of old ones which yet remain in the registering ganglia of the 
 brain. We convince ourselves of the truth of this general assertion not 
 so well from an examination of one or more well-related or authenticated 
 cases as from what may be termed the natural history of ghosts.. The 
 Greeks and Eomans of antiquity were just as much liable to Secular varia- 
 disorders of the nervous system as we are, but to them su- ^ecT^nd^os^" 
 pernatural appearances came under mythologic forms, Venus, tume of spirits. 
 and Mars, and Minerva. The places of these were taken in the dreams 
 of the ascetics of the Middle Ages by phantoms of the Virgin and of the 
 saints. At a still later time, in Northern Europe, and even in England, 
 where the old pagan superstitions are scarcely yet rooted out of the vul- 
 gar mind, even though the Reformation has broken the system of ecclesi- 
 astical thought, fairies, and brownies, and Robin Goodfellow survive. 
 The form of phantoms has changed with change of the creeds of commu- 
 nities, and we may therefore, with good Reginald Scot, inquire, " If the 
 apparitions which have been seen by true men and brave men in all ages 
 of the world were real existences, what has become of the swarms of 
 them in these latter times ?" 
 
 One class of apparitions perhaps it was the first to exist, as it is the 
 last to remain has survived all these changes survived them because 
 it is connected with a thing that never varies the affection of the hu- 
 man heart. To the people of every age the images of their dead have 
 appeared. They are not infrequent even in our own times. It would 
 be an ungracious task to enter on an examination of the best authenti- 
 cated of such anecdotes. Inquiries of this kind can scarcely be freed 
 from the liability to an imputation on personal veracity, perceptive pow- 
 er, or moral courage ; and, after all, it is not necessary to entangle our- 
 selves with these causes of offense. It is enough for us to perceive that 
 even here incongruities may be pointed out. The Roman saw the shade 
 of his friend clothed in the well-known toga ; the European sees his in 
 our own grotesque garb. The spirit of Maupertuis, which stood by the 
 bay window of the library at Berlin, had on knee-breeches, silk stock- 
 ings, and shoes with large silver buckles. To the philosopher it may 
 
408 SPECTRES ORIGINATE IN PAST EVENTS. 
 
 perhaps occur that it is very doubtful if, among the awful solemnities of 
 the other world, the fashions ever vary. Let us pause before we carry 
 the vanities of life beyond the grave. 
 
 From such reflections as the preceding, I think it may therefore be 
 concluded that there are two sources from which spectral appearances are 
 derived : 1st. Disturbance of the retina, which presents masses of light 
 and shade or colors to the mind, and these are worked by the fancy into 
 definite forms on the same principle that we figure to ourselves pictures 
 of faces among glowing embers. This constitutes retinal insanity. 2d. 
 Gradual emergence from the registering ganglia of the brain of old im- 
 pressions, which are rendered as intense and distinct as contemporaneous 
 sensations. The two forms may, however, coexist. Of the latter, I may 
 observe that the views of Dr. Hibbert, in his work on Apparitions, appear 
 to me to approach nearer to the truth than those of any other author. It 
 will be perceived, however, after perusing his interesting book, that I. have 
 not laid the stress he has done on the mechanical influence of the circu- 
 lation of the blood, but view the effect as of a more purely nervous kind. 
 
 As the emergence of old images which have been registered in the op- 
 tic thalami is not only connected with the physiological explanations we 
 have given of the functions of the brain, but also occurs under circum- 
 stances of such singularity as to border upon the supernatural, we may 
 pursue the consideration of it a little farther. It may, I think, be broad- 
 Alls ectrala ^ asser ^ e( l that all spectral appearances refer to things that 
 pearances refer are past, persons who are dead, events which have taken 
 place, scenes that we have visited ; or, if we have not seen 
 the actual reality, then pictures, statues, or other such representations 
 thereof. It has never yet occurred that any one has seen a phantom the 
 indications of the bodily presence or representation of which, until that 
 moment, he had never known. Thus, in the Middle Ages, the spectres 
 of African negroes were common enough, but no man ever witnessed one 
 of an American Indian, yet these, in their turn, prevailed after the voy- 
 age of Columbus. They were no strangers to the early colonial settlers. 
 The same may be said of all kinds of inanimate objects. 
 
 As illustrating the manner in which impressions of the past may 
 . emerge from the registering ganglia, I shall here famish an 
 the emergence instance which borders closely upon the supernatural, and 
 lions i a.*' ^ a ^7 represents the most marvelous of these psychological 
 etition of phenomena. It occurred to a physician, who related it in 
 my hearing to a circle whose conversation had turned on the 
 subject of personal fear. " What you are saying," he remarked, " may 
 be very true, but I can assure you that the sentiment of fear, in its ut- 
 most degree, is much less common than you suppose ; and, though you 
 may be surprised to hear me say it, I know from personal experience that 
 
EMERGENCE OF OLD IMPEESSIONS. 409 
 
 this is certainly so. When I was five or six years old, I dreamed that I 
 was passing by a large pond of water in a very solitary place. On the 
 opposite side of it there stood a great tree, that looked as if it had been 
 struck by lightning ; and in the pond, at another part, an old fallen trunk, 
 on one of the prone limbs of which there was a turtle sunning himself. 
 On a sudden a wind arose, which forced me into the pond, and in my dy- 
 ing struggles to extricate myself from its green and slimy waters, I awoke, 
 trembling with terror. 
 
 "About eight years subsequently, while recovering from a nearly fatal 
 attack of scarlet fever, this dream presented itself to me, identical in all 
 respects, again. Even up to this time I do not think I had ever seen 
 a living tortoise or turtle, but I indistinctly remembered there was the 
 picture of one in the first spelling-book that had been given me. Per- 
 haps, on account of my critical condition, this second dream impressed me 
 more dreadfully than the first. 
 
 " A dozen years more elapsed. I had become a physician, and was 
 now actively pursuing my professional duties in one of the Southern 
 states. It so fell out that one July afternoon I had to take a long and 
 wearisome ride on horseback. It was Sunday, and extremely hot ; the 
 path was solitary, and not a house for miles. The forest had that in- 
 tense silence which is so characteristic of this part of the day ; all the 
 wild animals and birds seemed to have gone to their retreats, to be rid of 
 the heat of the sun. Suddenly, at one point of the road I came upon a 
 great stagnant water-pool, and, casting my eyes across it, there stood a 
 pine-tree blasted by lightning, and on a log that was nearly even with 
 the surface, a turtle was basking in the sun. The dream of my infancy 
 was upon me ; the bridle fell from my hands ; an unutterable fear over- 
 shadowed me as I slunk away from the accursed place. 
 
 " Though business occasionally afterward would have drawn me that 
 way, I could not summon the resolution to go, and actually have taken 
 roundabout paths. It seemed to me profoundly amazing that the dream 
 that I had had should, after twenty years, be realized without respect to 
 difference of scenery, or climate, or age. A good clergyman of my ac- 
 quaintance took the opportunity of improving the circumstance to my 
 spiritual advantage ; and in his kind enthusiasm, for he knew that I had 
 more than once been brought to the point of death by such fevers, inter- 
 preted my dream that I should die of marsh miasm. 
 
 " Most persons have doubtless observed that they suddenly encounter 
 circumstances or events of a trivial nature in their course of life of which 
 they have an indistinct recollection that they have dreamed before. It 
 seemed for a long time to me that this was a case of that kind, and that 
 it might be set down among the mysterious and unaccountable. How 
 wonderful it is that we so often fail to see the simple explanation of 
 
410 IMPRESSIONS AND SENSATIONS EQUALIZED. 
 
 things, when that explanation is actually intruding itself before us. And 
 so in this case ; it was long "before the truth gleamed in upon me, before 
 my reasoning powers shook off the delusive impressions" of my senses. 
 But it occurred at last ; for I said to myself, Is it more probable that 
 such a mystery is true, or that I have dreamed for the third time that 
 which I had already dreamed of twice before ? Have I really seen the 
 blasted tree and the sunning turtle ? Are a weary ride of fifty miles, 
 the noontide heat, the silence that could almost be felt, no provocatives 
 to a dream ? I have ridden under such circumstances many a mile, fast 
 asleep, and have awoke and known it; and so I resolved that if ever 
 circumstances carried me to those parts again, I would satisfy myself as 
 to the matter. 
 
 "Accordingly, when, after a few years, an incident led me to travel 
 there, I revisited the well-remembered scene. There still was the stag- 
 nant pool, but the blasted pine-tree was gone ; and after I had pushed 
 my horse through the marshy thicket as far as I could force him, and 
 then dismounted, and pursued a close investigation on foot in every di- 
 rection round the spot, I was clearly convinced that no pine-tree had ever 
 grown there ; not a stump, nor any token of its remains, could be seen ; 
 and so now I have concluded that, at the glimpse of the water, with the 
 readiness of those who are falling asleep, I had adopted an external fact 
 into a dream ; that it had aroused the trains of thought which, in former 
 years, had occupied me ; and that, in fine, the mystery was all a delusion, 
 and that I had been frightened with less than a shadow. " 
 
 The instructive story of this physician teaches us how readily, and yet 
 how impressively, the remains of old ideas may be recalled ; how they 
 may, as it were, be projected into the space beyond us, and take a posi- 
 tion among existing realities. That such images arise from a physical 
 impression, which has formerly been made in the registering ganglia, it 
 is impossible to doubt, and that for their emergence from their dormant 
 state it is necessary that there should be a dulling or blunting of con- 
 Equalization of temporaneous sensations, so that these latent relics may 
 old impressions present themselves with a relatively equal force. This 
 
 and new sensa- ,. . . -, -, 
 
 tions necessary equalization of the intensity of an old impression with a 
 for visions. present sensation may be brought about in two different 
 ways : 1st. By Diminishing the force of present sensations, as when we 
 Modes of ac- are in a reverie, or have fallen asleep, or by breathing vapors 
 that^quaii? unsuited for the support of respiration ; 2d. By increasing the 
 zation. activity of those parts of the brain in which the old impres- 
 sions are stored up. On each of these a few remarks may be made. 
 
 Cerebral vision depends on an equalization in intensity between pres- 
 ent sensations and old impressions. So long as the former predominate 
 in power, the latter excite no attention or are wholly overlooked. This 
 
EMERGENCE OF OLD IMPRESSIONS. 411 
 
 condition is illustrated by such facts as that the flame of Illustrations of 
 a candle, held against the sun, is utterly overpowered and ^e^o^erin^ 
 imperceptible, but is seen of its proper brightness when it each other, 
 is in presence only of another flame like itself; or as the stars, which 
 are concealed by day, are plain enough when the sun sets. Ancient im- 
 pressions, harbored in the optic thalami, can not make themselves felt 
 against sensations just establishing themselves ; for as, when we have 
 looked at a bright window and then closed our eyes, the retinal phantom 
 we see becomes paler and paler, and after a while dies out, so do cerebral 
 images undergo a diminution of intensity with lapse of time, though it 
 may be questioned whether they ever entirely wear out. The law 
 which obtains in our economy for other organs of sense applies in these 
 cases too. Even in contemporaneously-occurring sensations, unless there 
 is something like an equality between them, the weaker makes no im- 
 pression upon us. In the presence of a bright light, a less brilliant one 
 can not be seen ; a feeble sound is made inaudible by an intensely loud 
 one ; minute variations of temperature become imperceptible when we 
 are submitted to a great heat or cold. Ideas are no more than the ves- 
 tiges of what were once sensations, and are subjected to the same phys- 
 ical law. For them to become embodied, and to cheat the mind into a 
 belief of their re-existence, equivalent in all regards to outward and actu- 
 ally-existing things, the impressions of these latter must be diminished 
 in their power, or the vigor of the former must be re-enforced. 
 
 So, when we are passing away in sleep, the organs of sense no longer 
 convey their special impressions with the clearness and force Emero . ence of 
 that they did in our waking hours, and this gives to the de- old impressions 
 caying traces which are stored in the registering ganglia the 
 power of drawing upon themselves the attention of the mind. 
 
 So, likewise, in the delirium of fevers, the spectral phantoms which 
 trouble the sick are first seen when the apartment is dark- Emer ence of 
 ened and kept silent, and especially when the patient closes old impressions 
 his eyes. Until the senses are more completely overwhelm- offe^ers^nTin 
 ed, these shadows will disappear on brightly illuminating the article of 
 the room or on opening the eyes. And so, too, in the hour 
 of death, when outer things are losing their force upon the dim eye, and 
 dull ear, and worn-out body, images that have reference to the manner 
 of our past life emerge ; the innocent and good being attended in their 
 solemn journey by visions in unison with their prior actions and thoughts, 
 the evil with scenes of terror and despair ; and it is right that it should 
 Be so. 
 
 The enfeebling of sensations which we are in the act of receiving 
 from external sources, so as to bring them on an equality with those 
 which have been long ago impressed, not only occurs in the condition 
 
412 ACTION OF PROTOXIDE OF NITEOGEN. 
 
 Emergence of of sleep, and in the article of death, but may, in a temporary 
 old impressions manner fog established by resorting to certain physical 
 
 by artificial <* o ^ r J 
 
 means. agents and drugs. Pressure upon the brain, either accident- 
 
 ally or purposely applied, is well known to produce such a result, and, 
 in like manner, the inhalation of various agents, such as pure hydrogen 
 gas, the vapor of ether or chloroform, or other non-supporters of respira- 
 tion. On breathing these substances, anaesthesia is soon induced ; the 
 external world disappears ; and, on carrying forward the operation to a 
 due extent, the mind and the brain are literally left to themselves. Opium 
 acts in like manner, more particularly in the case of those who have ac- 
 customed themselves to its undue use. It, however, not only blunts 
 the force of new impressions, but exerts a positive agency in intensifying 
 the decaying, remains of old ones. Under its full influence, the true re- 
 lations of space and of time disappear : a century of events is lived 
 through in a single night ; the vision can comprehend distances ap- 
 proaching to the infinite ; and yet, under these circumstances, the mind 
 does not perceive a riot of incongruous combinations, but every thing is 
 presented in a methodical and orderly way pictures, all the parts of 
 which are in just proportions and severe keeping to each other, and long 
 sequences of events which maintain a mutual harmony. 
 
 But, as I have just remarked, the equalization of new sensations with 
 Artificially in- old impressions, which is necessary for phantom appearances, 
 creased func- an( j fa Q incarnation and outward localization of ideas that 
 
 tional activity . ,,.. ,.,..,. 
 
 of the brain in- is, cerebral vision may take place by heightening or re-en- 
 creases them. f orc i n g the old impressions, as well as by diminishing the 
 intensity of the new sensations ; and as in the former case, so in this, the 
 result can be reached in many different ways. Whatever will cause in- 
 creased functional activity of the cerebral structure may recall these old 
 images in force. It is almost unnecessary to allude to the delirium 
 which attends inflammatory states of the brain. Artificial experiments 
 are more instructive. 
 
 For the purpose of increasing the functional activity of the cerebral 
 Case of protox- structure, protoxide of nitrogen, by reason of its greater solu- 
 ide of nitrogen, bility in the blood, exceeds in power even oxygen gas itself. 
 This substance, when respired, at once awakens long trains of vivid ideas, 
 the recollection of all kinds of former scenes. Its action is divisible into 
 two periods, the first corresponding to the heightened sensibility arising 
 from the increased oxidation it is establishing in the economy, the sec- 
 ond to the depression which soon comes on through the consequent ac- 
 cumulation of carbonic acid, and which the lungs and skin are unable 
 with sufficient quickness to remove. Sir H. Davy, who first recognized 
 its physiological power, has given us a graphic description of these ef- 
 fects. He says, "A thrilling, extending from the chest to the extremir 
 
REGISTERED IMPRESSIONS. 413 
 
 ties, was almost immediately produced. I felt a sense of tangible exten- 
 sion, highly pleasurable, in every limb. My visible impressions were 
 dazzling and apparently magnified. I heard distinctly every sound in 
 the room, and was perfectly aware of my situation. By degrees, as 
 the pleasurable sensation increased, I lost all connection with external 
 things ; trains of vivid visible images rapidly passed through my mind, 
 and were connected with words in such a manner as to produce sensa- 
 tions perfectly novel. I existed in a world of newly-connected and 
 newly-modified ideas. When I was awakened from this semi-delirious 
 trance by Dr. Kinglake, who took the bag from my mouth, indignation 
 and pride were the first feelings produced by the sight of the persons 
 about me. My emotions were enthusiastic and sublime, and for a mo- 
 ment I walked round the room perfectly regardless of what was said to 
 me. As I recovered my former state of mind, I felt an inclination to 
 communicate the discoveries I had made during the experiment. I en- 
 deavored to recall the ideas ; they were feeble and indistinct. One rec- 
 ollection of terms, however, presented itself, and with the most intense 
 belief and prophetic manner I exclaimed to Dr. Kinglake, ' Nothing ex- 
 ists but thoughts ; the universe is composed of impressions, ideas, pleas- 
 ures, and pains.'" 
 
 In like manner, the intoxication that arises from alcohol has two dis- 
 tinct stages, depending on entirely different phases of its chemical action. 
 At first there is an exaltation of effects, because of the increased function- 
 al activity established ; but this, after a time, is succeeded by a dullness, 
 or even stupefaction, attributable to the impression which the carbonic 
 acid arising from the oxidation of the alcohol is making upon the nerv- 
 ous centres. 
 
 By two different methods, therefore, ancient impressions TWO methods of 
 may be equalized, as respects intensity, with new sensations, equalization of 
 
 r - / ,1 r i T .ii /*> , / old impressions 
 
 The vigor of the former may be increased, or the effect of and existing 
 the latter diminished. sensations. 
 
 Equalized in any way in their force, the mind is ready to confound its 
 own ideas and external forms together. A cause which, perhaps, might 
 seem to be trivial, fastens the attention, and at once a solitary form, or 
 even the machinery of a long drama, emerges. It is no more possible for 
 us to say why the thought runs in one course rather than another, and 
 lays hold of image after image in succession, than we can foretell the 
 way of a spark that moves darkling, on the ashes of a piece of burned pa- 
 per. Yet it too runs in connected lines. 
 
 No better evidence can be given that the images we are speaking of 
 are impressions of past events registered in the brain, and which gain 
 the power of drawing upon themselves the attention of the mind, either 
 by their assuming an unwonted intensity, or by the diminution of the in- 
 
414 KEGISTEKED IMPEESSIONS. 
 
 fluence of newly-arriving sensations, than the philosophical 
 
 Proof of the ex- . J -, j i /. , , 
 
 istence of im- observations which have been made by some of those who 
 pressions in the j iaye ^ een ji^le | o these infirmities on their own cases. 
 
 registering gan- 
 glia and their Thus, in such a case recorded in Nicholson's Philosophical 
 emergence. Journa i ? and a u u d e d to by Dr. Hibbert : "I had a visit," 
 said the patient, "from Dr. C , to whom, among other remarks, I ob- 
 served that I then enjoyed the satisfaction of having cultivated my mor- 
 al habits, and particularly in having always endeavored to avoid being 
 the slave of fear. ' I think,' said I, 'that this is the breaking up of the 
 system, and that it is now in progress to speedy destruction. In this 
 state, when the senses have become confused, and no longer tell me the 
 truth, they still present me with pleasing fictions, and my sufferings are 
 mitigated by that calmness which allows me to find amusement in what 
 are probably the concluding scenes of life.' I give these self-congratula- 
 tions without scruple, more particularly because they led to an observa- 
 tion of fact which deserves notice. When the doctor left me, my relax- 
 ed attention turned to the phantasms, and some time afterward, instead 
 of a pleasing face, a visage of extreme rage appeared, which presented a 
 gun at me, and made me start ; but it remained the usual time, and then 
 gradually faded away. This immediately showed me the probability of 
 some connection between my thoughts and these images, for I ascribed 
 the angry phantasm to the general reflection I had formed in conversa- 
 tion with Dr. C . I recollected some disquisitions of Locke, in his 
 
 treatise on the Conduct of the Mind, where he endeavors to account for 
 the appearance of faces to persons of nervous habits. It seemed to me 
 as if faces in all their modifications, being so associated with our recol- 
 lections of the affections of passions, would be most likely to offer them- 
 selves in delirium; but I now thought it probable that other objects 
 could be seen, if previously meditated upon. With this motive it was 
 that I reflected upon landscapes and scenes of architectural grandeur 
 while the faces were flashing before me, and after a considerable interval 
 of time, of which I can form no precise judgment, a rural scene of hills, 
 valleys, and fields appeared before me, which was succeeded by another 
 and another in ceaseless succession, the manner and times of their respect- 
 ive appearance, duration, and vanishing being not sensibly different from 
 that of the faces. All the scenes were calm and still, without any strong 
 light or glare, and delightfully calculated to inspire notions of retirement, 
 of tranquillity, and happy meditation." The same writer adds in anoth- 
 er place, " The figures returned, but now they consisted either of books, 
 or parchments, or papers containing printed matter. I do not know 
 whether I read any of them, but am at present inclined to think that they 
 were not either distinctly legible, or did not remain a sufficient time be- 
 fore they vanished. I was now so well aware of the connection of thought 
 
USE OF INVERSE VISION. 415 
 
 with their appearances, that, by fixing my mind on the consideration of 
 manuscript instead of printed type, the paper appeared, after a time, only 
 with manuscript writing ; and afterward, by the same process, instead of 
 being erect, they were all inverted, or appeared upside down." 
 
 We can not fail to remark the close resemblance between these illu- 
 sions, arising from a fixed meditation on recollected scenery, E . , j j 
 and the phantoms which are witnessed after our gaze has izatkmofphan- 
 been steadily directed to some brightly-illuminated object, asms> 
 as a window, when we first awake. In both there is the same subdued 
 and uncertain brilliancy of effect ; in both the same gradual fading away ; 
 in both the mind does not refer the image it contemplates to an inward 
 point or place, but sets it forth outwardly, projecting it into the empty 
 or occupied region beyond. In inverse as in ordinary vision, the law of 
 the line of visible direction is enforced, and this reference of cerebral im- 
 ages to a definite point in outer space is a phenomenon of the same kind 
 as the appearance of the invisible coin on pouring water into a basin, the 
 lifting of ships into the air by atmospheric refraction, the appearance of 
 the sun and moon every day above the horizon before they have actu- 
 ally risen and after they have set, and many other optical illusions that 
 might be mentioned. 
 
 Physiology, though full of teleological illustrations that is, examples 
 of the use of means for the accomplishment of an end has ,, 
 
 ^ Ine nervous 
 
 none more worthy of our consideration than this of inverse mechanism con- 
 vision. Men in every part of the world, even among na- dkate e fheim" 
 tions the most abject and barbarous, have an abiding faith mortality of the 
 not only in the existence of a spirit that animates us, but 
 also in its immortality. Of these there are multitudes who have been 
 shut out from all communion with civilized countries, who have never 
 been enlightened by revelation, and who are mentally incapable of rea- 
 soning out for themselves arguments in support of those great truths. 
 Under such circumstances, it is not very likely that the uncertainties of 
 tradition derived from remote ages could be any guide to them, for tra- 
 ditions soon disappear except they be connected with the wants of daily 
 life. Can there be, in a philosophical view, any thing more interesting 
 than the manner in which these defects have been provided for, by im- 
 planting in the very organization of every man the means of constantly 
 admonishing him of these facts, of recalling them with an unexpected 
 vividness before him, even after they have become 'so faint as almost to 
 die out? Let him be as debased and benighted a savage as he may, 
 shut out from all communion with races whom Providence has placed in 
 happier circumstances, he has still the same organization, and is liable to 
 the same physiological incidents as ourselves. Like us, he sees in his 
 visions the fading forms of landscapes, which are, perhaps, connected with 
 
416 USE OF INVERSE VISION. 
 
 some of his most grateful recollections ; and what other conclusion can 
 he possibly derive from these unreal pictures than that they are the fore- 
 shadowings of another land beyond that in which his lot is cast ? Like 
 us, he is visited at intervals by the resemblances of those whom he has 
 loved or hated while they were alive ; nor can he ever be so brutalized as 
 not to discern in such manifestations suggestions which to him are in- 
 controvertible proofs of the existence and immortality of the soul. Even 
 in the most refined social conditions we are never able to shake off the 
 impression of these occurrences, and are perpetually drawing from them 
 the same conclusions as did our uncivilized ancestors. Our more ele- 
 vated condition of life in no respect relieves us from the inevitable con- 
 sequences of our own organization any more than it relieves us from in- 
 firmities and disease. In these respects, all over the globe, we are on an 
 equality. Savage or civilized, we carry about within us a mechanism in- 
 tended to present us with mementoes of the most solemn facts with which 
 we can be concerned, -and the voice of history tells us that it has ever been 
 true to its design. It wants only moments of repose or of sickness, when 
 the influence of external things is diminished, to come into full play, and 
 these are precisely the moments when we are best prepared for the truths 
 it is going to suggest. Such a mechanism is in keeping with the man- 
 ner in which the course of nature is fulfilled, and bears in its very style 
 the impress of invariability of action. It is no respecter of persons. It 
 neither permits the haughtiest to be free from the monitions, nor leaves 
 the humblest without the consolation of a knowledge of another life. 
 Liable to no mischances, open to no opportunities of being tampered with 
 by the designing or interested, requiring no extraneous human agency for 
 its effect, but always present with each man, wherever he may go, it 
 marvelously extracts from vestiges of the impressions of the past over- 
 whelming proofs of the reality of the future, and, gathering its power from 
 what would seem to be a most unlikely source, it insensibly leads us, 
 no matter who or where we may be, to a profound belief in the immortal 
 and imperishable, from phantoms which have scarcely made their appear- 
 ance before they are ready to vanish away. 
 
 It is scarcely necessary for me to do more than barely refer to the as- 
 sertions of those who would have it believed that they look upon all 
 these appearances as fictions and deliberate impostures. What is to be- 
 come of all history if such a doctrine could be maintained ? Human ev- 
 idence must be regarded as utterly worthless. Moreover, no one denies 
 the existence of dreams, and the phenomena we have been here treating 
 of are philosophically of the same order. 
 
OF TOUCH. 417 
 
 CHAPTER XXII. 
 
 OF TOUCH, AND THE DETERMINATION OF PRESSURES AND TEMPERA- 
 TURES. 
 
 Functions of the tactile Mechanism: its Structure. Regions of different Sensitiveness. Compar- 
 ative Physiology of Touch. Estimate of physical Qualities. 
 Perception of Temperature. Subjective Sensations of Temperature. 
 
 THE tactile organ is the skin, or some part, modification, or append- 
 age of it. The general functions of the skin have Ibeen al- Functions of 
 ready described. It remains to speak of it in connection with mecifanism 
 the sense of touch. 
 
 An impression has long prevailed among physiologists that this sense 
 should be considered as offering several subdivisions. Thus, for in- 
 stance, we have a consciousness of the general condition of the muscular 
 system muscular sense, as it might be termed and this, in some cases, 
 is exquisitely perfect, as may be gathered from what has been said re- 
 garding the tensor tympani and stapedius muscles in the chapter on 
 hearing. Distinct from this is our appreciation of pain or pleasure, and 
 so also our estimation of temperatures. Adelon has indeed maintained 
 that the cognizance of temperatures is the primary or chief function of 
 this sense. It will be sufficient, however, for our purpose, leaving out 
 these minor subdivisions, to direct our attention to the more important, 
 and to consider the tactile organ as devoted to two uses : 1st, the appre- 
 ciation of pressures ; 2d, of temperatures. Pressures doubtless act upon 
 the skin in a purely mechanical way ; temperatures operate by inducing 
 a variation in the rate of waste and nutrition. .At a certain point, even 
 this distinction ceases, for pressures, when they reach a sufficient intensi- 
 ty, interfere with the supply of arterial blood or the removal of venous, 
 and thereby change the rate of nutrition and waste, acting, as far as 
 this goes, in a manner not unlike that of the variations of temperature. 
 
 In man, the skin possesses tactility to a different degree in different 
 regions. On the tips of the fingers and on the lips the sen- Re ional dif 
 sory perception is most acute, while it is at a minimum on ference in tac- 
 the trunk and thigh. In other mammals, which are covered tx lty ' 
 with hair or wool, the sense of touch is much more restricted. Its 
 proper organ is to be regarded as arising from a concentration of general 
 sensibility of the skin upon a special construction, the papillary body, 
 as it is termed. The organs of vision and hearing consist essentially of 
 
 DD 
 
418 THE ORGAN OF TOUCH. 
 
 two portions, a receiving and a nervous, the former being constructed on 
 the principles of optics in the one case, and of acoustics in the other. A 
 similar doubleness of structure may be recognized in the instance now 
 before us, though with a difference of effect, for in those cases the outer 
 or receiving organ is for the purpose of more powerfully concentrating 
 the influence received, but in touch it is the reverse. The office of the 
 cuticle, which covers over the true skin, is to render it less sensitive to 
 external impressions, and for this reason, therefore, it varies in thick- 
 ness in different regions, being less developed on those portions that are 
 more particularly devoted to tactile sensibility. Considering the hand, 
 Structure of or- or perhaps, more correctly, the tips of the ringers, as being 
 gan of touch, chiefly devoted to the purposes of touch, no construction 
 could be conceived of better adapted to that end. Placed at the extrem- 
 ity of the arm, a lever which is jointed at its middle, the elbow, and the 
 fore part of which has a motion of partial rotation, pronation, and supina- 
 tion upon its own axis, the hand being carried so that its palm presents 
 upward or downward, or in any of the intermediate positions included in 
 the half-circular motion -jointed again by the bones of the wrist, so as 
 to obtain a hinge-like movement, the hand may be flexed or extended 
 almost 180 degrees upon the forearm. Its bony structure, subdivided 
 into suitable pieces, is clothed with a multitude of muscles or their ten- 
 dons. In the fingers and thumb the structure breaks up into five sep- 
 arate pieces, possessed of an incredible firmness when we consider the 
 numberless motions which can be accomplished. The position and ar- 
 ticulation of the thumb, which enables it to set itself in opposition to 
 the other four digits, a feature which constitutes a hand, properly speak- 
 ing, gives the power of grasping things perfectly, and makes the whole 
 organ a perfect mechanism of prehension. The papillary structure, de- 
 veloped in its utmost refinement on the tips of the fingers, and fortified 
 behind by the nails, which present moderate resistance to pressures, com- 
 pletes this contrivance, which, from its perfect adaptation to 'the 'uses to 
 which it is devoted, its power, its delicacy, and the infinite movements 
 which it can accomplish, is not surpassed as an example of the adapta- 
 tion of means for the accomplishment of an end by any other structure 
 of the body. There have been authors who have asserted that the su- 
 periority of man over other animals may be entirely accounted for by his 
 possession of a hand a statement which, though it can not be main- 
 tained in its generality, is yet a very good proof of the appreciation in 
 which this wonderful instrument is held by those who have studied its 
 construction and functions most closely. 
 
 Between the indications that have to be dealt with by the hand as 
 an organ of touch, and those dealt with by the eye and ear, there is an 
 essential, difference. The eye, for example, receives the pictures of ex- 
 
EXAMINATION OF SOLIDITY. 419 
 
 ternal objects upon a surface, but the hand examines the so- Examination 
 lidity of bodies. The former is occupied with length and of solidity by 
 breadth ; the latter with all three dimensions, length, breadth, the hand ' 
 and thickness conjointly. Our notions of solidity are to no little extent 
 obtained in this way, as was proved in the case of Cheselden's patient, 
 who had been blind from birth, and to whom vision was given by a suc- 
 cessful operation for cataract, and still more recently by a similar case 
 of Franz. In this instance, "a solid cube and a sphere, each of four 
 inches diameter, were placed before the patient, at the distance of three 
 feet, and on a level with the eye. After attentively examining these 
 bodies, he said he saw a quadrangular and a circular figure, and, after 
 some consideration, he pronounced the one a square and the other a disk. 
 His eye being then closed, the cube was taken away, and a disk of equal 
 size substituted, and placed next to the sphere. On again opening his 
 eye, he observed no difference in these objects, but regarded them both 
 as disks. The solid cube was now placed in a somewhat oblique posi- 
 tion before the eye, and, close beside it, a figure cut out of pasteboard, 
 representing a plain outline prospect of the cube when in this position : 
 both objects he took to be somewhat like a flat quadrate. A pyramid 
 placed before him, with one of its sides turned toward his eye, he saw as 
 a plain triangle. This object was now turned a little, so as to present 
 two of its sides to view, but rather more of one side than of the other : 
 after considering and examining it for a long time, he said that this was 
 a very extraordinary figure ; it was neither a triangle, nor a quadrangle, 
 nor a circle he had no idea of it, and could not describe it : 'in fact,' 
 said he, 'I must give it up.' An example of the close association which 
 exists between the sense of touch and that of sight, in enabling the mind 
 to form a correct idea of an object, is afforded in the statement of this 
 patient, that, although by the sense of sight he could detect a difference 
 in the cube and sphere, and perceive that they were not drawings, yet 
 he could not form from them the idea of a square and a disk until he 
 perceived a sensation of what he saw in the points of his fingers as if he 
 really touched the objects/ When he took the sphere, cube, and pyra- 
 mid into his hand, he was astonished that he had not recognized them asf 
 such by sight, being well acquainted with them by touch." 
 
 The mechanism for touch, as distinguished from the general dermoid 
 sensibility, is the papilla, which may be described as conical Structure of 
 eminences on the cutis, at once solid and flexible, sometimes papillae of 
 clavate in form, and sometimes having numerous points. They 
 are about the T J^ of an inch in height, and the -% J^ of an inch in diam- 
 eter at their base, these dimensions varying, however, very greatly with 
 the situation. They contain a loop of blood-vessels and a twig of a 
 sensory nerve, for all the centripetal nerves, with the exception of those 
 
420 THE PACINIAN BODIES. 
 
 devoted to the special senses, may be regarded as concerned in this func- 
 tion. The papilla? contain an elastic substance axile body, as it is term- 
 ed w hich serves to heighten the sense, and the yielding structure of the 
 
 skin aids in the same effect. The papilla? are covered over with the cuti- 
 cle, through which, therefore, all *** 204 - 
 action on them must take place. 
 
 Fig. 203. 
 
 Simple papillae, magnified 35 diameters. Compound papillae, magnified 60 diameters. 
 
 Fig. 203 (Todd and Bowman) represents simple papilla? of the palm, 
 the cuticle having been detached. Fig. 204 (Kolliker), compound papil- 
 ke, with two, three, or four points : a, base of a papilla ; #, , , separate 
 processes ; c, c 9 c, processes of papilla? whose bases are not visible. 
 
 The mode in which the nerve fibre terminates in the papilla is as yet 
 The Pacinian doubtful, some asserting that it is arranged as a returning 
 bodies. loop, and some that it is by a pointed extremity. This lat- 
 
 ter mode is thought to be illustrated by the structure of the bodies term- 
 ed Pacinian, which are ovoid in form, -^ to -^ of an inch in length, -^ to 
 -g 1 ^ in breadth, and attached by a pedicle to many of the cerebro-spinal 
 and sympathetic nerve branches. Each consists of many concentric 
 membranous layers, arranged like the coats of an onion, the interior ones 
 closer than the exterior. They have a central cavity, distended by a 
 fluid, which also intervenes between the coats. Across this cavity, and 
 occupying exactly its axis, a nerve fibre, which has cast off its white 
 sheath, passes, terminating at the other end either in branches or a knob. 
 The use of these bodies is wholly unknown, and even their structure is 
 doubtful, the existence of the central liquid referred to being denied by 
 some anatomists. 
 
 The sensitiveness of a part is in proportion to the number of papilla? 
 The sensitive- ** contams - Tables have been constructed setting forth the 
 ness of differ- relations of different regions, as determined by placing a pair 
 regions. Q com p asseSj t j ie p i n t s O f which were covered with cork, on 
 the parts to be tried, the eyes being shut, and closing the compasses un- 
 til the pieces of cork could no longer be distinguished as separate. It 
 appears that this will take place on the tip of the tongue when the points 
 are the -^ of an inch apart ; on the tip of the third phalanx, at the -fa 
 of an inch ; on the lips, the one sixth of an inch ; tip of the great toe, 
 half an inch ; the lower part of the occiput, 1 inch ; and on the middle 
 of the thigh, 2 J inches. 
 
 No part of the skin is entirely devoid of sensitiveness, as Kolliker has 
 
NEEVES OF THE PAPILLA. 421 
 
 shown by examinations with a fine needle. At first he ,, 
 
 Jbvery part of 
 
 thought he had found some places which were quite insensi- the skin is sen- 
 ble, while in others the slightest touch produced sensation ; 8Itlve * 
 but on carrying the investigation farther, it appeared that the very same 
 place was sometimes sensible and sometimes not, so that finally he came 
 to the conclusion that the very smallest portions of the skin are sensi- 
 tive. But since, even in the palm of the hand, the papillae containing 
 nerves are widely dispersed, and in other places occur but rarely, or 
 even not at all, he infers that it is necessary to assume the existence of 
 non-medullated fibres in all the papillae, or to have recourse to the nerv- 
 ous plexus at their base, since he believes it is not possible to demon- 
 strate nerves in eveiy one of those bodies. 
 
 The nerves supplying the papillae may perhaps be said to ascend 
 through the cutis, continually branching, and forming eventu- papillary 
 ally terminal plexuses. The primitive tubules themselves di- nerves. 
 viding at an acute angle into two, and entering the papillae, they are 
 united at their extremities in a loop. Of course, this construction in- 
 volves the fact that they have freed themselves from the white substance 
 of Schwann. The impression made on these exposed nervous fibrils is 
 by many regarded as of a purely mechanical kind. They may be affect- 
 ed not merely by vertical pressures, but likewise by those exerted in the 
 direction of the plane of the skin, and this accounts for tactile sensation 
 on portions of that surface which are either sparsely or not at all sup- 
 plied with nerve fibrils. To this effect the unyielding and horny texture 
 of the cuticle doubtless contributes. 
 
 No papillae are found in invertebrate animals. Among vertebrates 
 they are variously disposed. In lizards they occur under TQ^ j n other 
 the toes ; in the chameleon, and some of the ant-eaters, which vertebrates. 
 use their tails for tactile purposes, they are found upon that organ. In 
 the spring season of the year they are temporarily developed on the thumb 
 of the frog. Among birds they are found upon the toes, or, if web-foot- 
 ed, upon the web ; in the mole on the tip of the snout. In the tapir and 
 elephant they occur upon the trunk ; among the quadrumana, on the 
 hands and feet, and in some also upon the tail. The whiskers of the cat, 
 the rat, the rabbit, may be regarded as appendages to the tactile organs, 
 enabling them to find their way through narrow passages in the dark. 
 Among articulata the antennae have doubtless, with their other functions, 
 a similar use. Men who have become blind often guide their steps by 
 means of a stick, judging from the sensations which its contact with sur- 
 rounding bodies imparts to the hand : it is in all respects a temporary 
 antenna. 
 
 Our estimates of the hardness and softness, roughness and smoothness 
 of bodies, is primarily dependent on indications derived from the sense 
 
422 FEELING AND TOUCHING. 
 
 Estimate of ^ toucn ' We should make a distinction, however, with 
 physical quail- Magendie, between feeling and touching, the former being 
 essentially passive, the latter active; and though we usu- 
 
 su PP ose that, ^ a ^ our senses, touch is the most reli- 
 and touching, able, it often conveys to the mind illusory impressions, as, 
 for instance, in the well-known experiment of Aristotle, when the tips of. 
 the fingers are crossed over each other, and a pea rolled beneath them, it 
 seems as if there were two peas, one under each finger. The indications 
 of touch are generally more correct than those of feeling. Thus, if we 
 close our eyes, and another person moves the tip of our finger over an 
 unknown surface, he can completely deceive us by duly varying the press- 
 ure, and make us believe that it is concave or convex, whereas it may be 
 flat ; but if we pass our fingers over the surface ourselves, we very quick- 
 ly come to a true conclusion, because now we are conscious of the exer- 
 tion of muscular power ; and from what has been said respecting hearing, 
 we may infer how delicate our estimate of muscular exertion is. The 
 former is therefore an example of feeling, the latter .of touch. 
 
 Connected with this distinction are the singular phenomena of tick- 
 ling ; the regions most readily affected by this are those of low 
 tactile sensibility. A person can not tickle himself, though it 
 is said that cases are upon record in which one has been tickled to death 
 by another. As in the other cases, the mind can direct attention exclu- 
 sively, for the time being, to some one indication of touch, which, though 
 it may be apparently insignificant in itself, becomes, after a while, per- 
 fectly intolerable, as the pressure of a hair, a gentle draught, or the fall- 
 Remains of im- m g f water, drop by drop, on the top of the head ; and, as 
 pressious. w ith them, an impression which is made does not instanta- 
 neously disappear, but will sometimes continue for quite a considerable 
 time. A ring or other article that has been long worn will leave a sen- 
 sation, though it may have been removed. 
 
 Besides affording an estimate of external pressures, the sensory organ 
 enables us to discover variations of temperature. It may therefore be 
 thus effected by bodies upon contact or by bodies at a distance ; and 
 Perception of though we usually confound the two indications together, 
 temperature there is, in reality, a distinction between them ; thus, in cer- 
 
 distmctfrom . . J ,.,.,.. _ , 
 
 that of press- tain conditions of paralysis, the indications of the contact of 
 bodies may remain, but those of heat and cold may have to- 
 tally disappeared. On examining a surface from which the skin has 
 been removed, it does not appear capable of distinguishing hot from cold 
 bodies, but only communicates to the mind an indefinite sensation of 
 Ideas of heat pain ; nor can we create sensations of heat or cold by any ir- 
 nof arise Trd- ritati( > n ^ the nerves. The measure of temperature by the 
 ficiaiiy. agency of the skin is very far from being exact, as has been 
 
OF SMELLING. 423 
 
 proved by the simple experiment of dipping the finger into very warm 
 water, and then the whole hand into water many degrees cooler. The 
 increased extent of surface seems to overcompensate for the Dece tions 
 lower temperature, and we come to the erroneous conclusion the sense of 
 that the cooler specimen is the warmer of the two samples. 
 
 As sounds may be heard which have no reality, but merely originate 
 in the brain, or spectral illusions may be seen, so the sense Subjective sen- 
 of touch is subject to similar hallucinations, as a sensation 
 of pressure or weight, or the crawling of insects on the skin ; ture. 
 and though we can not, by artificial irritation of the nerves, give rise to 
 impressions of heat and cold, those effects very frequently occur in this 
 interior or subjective way. 
 
 CHAPTEE XXIII. 
 
 OF SMELLING, AND THE MEANS OF DISTINGUISHING GASEOUS AND VA- 
 POEOUS SUBSTANCES. 
 
 Structure of the Organ of Smell. Its proper Instrument the First Pair of Nerves. Limited Re- 
 gion of Smell. Conditions of its perfect Action. Duration of Odors. TJieir Localization. 
 Subjective Odors. 
 
 BY the sense of smell we are able to distinguish many gaseous and 
 vaporous substances from one another. They enter the nos- gensc of gmell 
 trils with the respiratory current, and are brought in con- for gases and 
 tact with the olfactory or Schneiderian membrane. Though va P rs - 
 received at first in the elastic state, they become dissolved in the mucus 
 which moistens that membrane. It does not follow, however, that all 
 vaporous substances give rise to the perception of an odor ; for example, 
 water itself communicates no sensation whatever. Again, there are other 
 bodies, as, for instance, musk, which yield an odor far more Deiicacj-oftMs 
 powerful than corresponds to their loss of weight. Thus it perception, 
 is said that.that substance may be exposed for years in an apartment, dif- 
 fusing all the time its penetrating emanations, and yet not becoming 
 lighter. Such statements are, however, on their face, exaggerations. 
 There can be no doubt that the olfactory organs detect extremely minute 
 portions of matter. In most cases, elevation of the temperature of a 
 body increases its odorous effect. 
 
 The primary uses of the function of smell are for a discrimination of 
 the qualities of food, or its condition, and also for enabling 
 
 , .,, p !. -i , ic -,T T Uses of smell. 
 
 an animal with greater lacility to provide it sen with supplies. 
 Hence the development of this structure takes place in the utmost per- 
 fection among the carnivora, which often depend almost exclusively upon 
 
424 THE OLFACTOKY ORGAN. 
 
 this faculty for the pursuit of their prey. But even in the herbivora it 
 is well marked, and furnishes them, though less exactly, similar indica- 
 tions. In man, though this sense is less acutely developed, it applies 
 itself to a greater variety of objects, and doubtless enables him to appre- 
 ciate differences among odors in a more correct manner than in the case 
 of the lower animals. 
 
 The general principle involved in the construction of the organ of smell 
 Mechanism of * s to ex P ose an extensive and constantly moistened surface 
 the olfactory to the air brought in by the respiratory current. Of course, 
 other things being equal, the larger the surface, the more per- 
 fect the sense. The object of gaining a great extent of superficial ex- 
 posure under a relatively small volume is accomplished by spreading 
 the sensitive mucous membrane on projections or shelves, which also 
 serve the purpose of intercepting the incoming current of air. It is in 
 reptiles and birds that turbinated processes first make their appearance. 
 In air-breathing animals, the organ of smell is essentially an appendix 
 to the respiratory mechanism, its action depending entirely upon the 
 play thereof. But, though the material submitted to the olfactory mem- 
 brane in this manner is presented in the vaporous or gaseous state, it is 
 intermediately dissolved, as has been stated, in the liquid mucus which 
 covers that membrane, before it can affect the ramifications of the olfac- 
 tory nerve. 
 
 The nose, thus constituting the commencement of the respiratory 
 tract, forms a characteristic feature of the countenance. It is composed 
 in part of bones and in part of cartilages, covered over with muscles and 
 integument. Its five cartilages give to it shape in its inferior portion, 
 and, by their elasticity, enable it to resist external injury. The whole 
 surface of the nasal cavities is covered over with mucous membrane, to 
 which the names of pituitary or Schneiderian membrane have been given. 
 This mucous membrane likewise extends into the maxillary antrum, 
 ethmoid, and sphenoid cells, or sinuses which are adjacent, and open into 
 the same nasal cavity. The Schneiderian membrane is highly vascular, 
 and receives its nervous supply from the nasal branches of the fifth 
 pair, which give it common sensibility, but its olfactory function de- 
 205. Fig. 206. pends on the distribution which a 
 
 certain portion of it receives from 
 the first, or olfactory nerve. 
 
 Fig. 205 illustrates the distribu- 
 tion of the olfactory nerve on the 
 septum of the nose. Fig. 206 is 
 its distribution on the outer wall of 
 the nasal fossa. 
 
 That the function of the first pair of nerves is olfactory is proved by 
 
THE OLFACTORY NERVES. 425 
 
 many facts. Animals in which these nerves have been di- Functionofthe 
 vided are no longer affected by odors of any kind, and, gen- first pair of 
 erally speaking, the greater the development of these nerves, nerves - 
 the acuter is the sense of smell. In persons in whom this sense has 
 been defective or totally absent, or in those who have been troubled with 
 unpleasant odors of a subjective kind, post-mortem examinations have 
 shown a corresponding absence or lesion of these nerves. 
 
 In man, the proper olfactory organ is formed by the distribution of the 
 olfactory, or first' pair of nerves, on the mucous membrane which covers 
 the upper part of the nose, the internal set of filaments being disposed 
 on that of the septum, the external on that of the superior and middle 
 spongy bones. The membrane is very vascular, and covered with a thick, 
 pulpy epithelium. The filaments distributed to it have lost the white 
 substance of Schwann. It is those parts alone to which these filaments 
 are distributed which possess the sense of smell, the adjacent cavities, 
 as, for example, the frontal sinuses, not participating in the function, as 
 has been proved by the injecting of the vapor of camphor or other odo- 
 riferous bodies into them. It seems to be necessary for the vaporous or 
 gaseous substances to be dissolved in the moisture which covers the ol- 
 factory membrane in order to their exerting a proper effect. If, by 
 chance, the membrane is too dry, the sense of smell is temporarily lost, 
 and the same likewise occurs if it be unusually moist. 
 
 From the mode of distribution of the olfactory nerve, it follows that* 
 the sense of smelling is restricted to the upper portion of Limited re ion 
 the nasal cavity ; and, for this reason, when we desire to de- for the sense of 
 tect odors with unusual precision, the air is drawn violently smell> 
 into that region by sniffing. On the contrary, we avoid the perception 
 of odors by breathing through the mouth, or, as the common Conditions for 
 phrase is, by holding the nose. Since the perfection of the its perfect ac- 
 sense requires that the olfactory surface shall neither be too i 
 dry nor too cold, an advantage is gained by placing it high in the cav- 
 ity, where it is free from the disturbing effects of the dry air introduced 
 by inspiration, which becomes moistened and warm before it reaches the 
 place of action. 
 
 Just as we make a distinction between a musical sound and a noise, 
 so should we distinguish between an odor and such impres- Distinction be _ 
 sions as arise from tickling, pressures, the use of snuff, mus- tween odors 
 tard, pepper, and pungent bodies, for these act as mere irri- 
 tants, and many of them can produce analogous effects on other portions 
 of the surface of the skin. Odors do not give rise to the impressions of 
 pain, and, indeed, the nervous mechanism having charge of the action is 
 totally different in the two cases. Odors operate, as we have said, upon 
 the olfactory nerve, but these other impressions are made upon the nasal 
 
426 DURATION AND LOCALIZATION OF ODORS. 
 
 supplies from the fifth pair. The upper part of the nasal cavity is there- 
 fore devoted to the proper sense of smell, the lower portion to general 
 sensation. 
 
 In one respect there is a striking difference between this sense and 
 Duration of vision and hearing. We can perceive many luminous im- 
 odors. pressions at the same time, or hear many sounds in rapid suc- 
 cession ; but not so with odors. We can smell only one thing at a time, 
 or, at all events, the impression remains long upon the olfactory appara- 
 tus, perhaps because the odoriferous substance remains dissolved in the 
 attached moisture. The identification of substances by their odor nec- 
 essarily implies a resort to recollection or memory, and sometimes we 
 have to apply the fragrant object again and again to the nose, before we 
 can recall with satisfactory precision its name. 
 
 In the lower animals the sense of smell is probably localized in some 
 parts of the skin ; many of them display instincts which seem 
 anatomy of to imply the possession of such a sense. Insects also, by 
 smell, are often led to their food or to one another. 
 
 The variable current of air introduced by respiration compensates in 
 some degree for the want of mobility of the nose, which may be regard- 
 ed, in air-breathing vertebrated animals, as consisting of a diverticulum 
 from the respiratory passages. In fishes, however, the olfactory cavity is 
 not connected with the respiratory passages : there are no posterior nares. 
 'The circumstance of their living under water disables them from appreci- 
 ating the odorous peculiarities of gases and vapors. In the whale the or- 
 gan is altogether absent, being replaced by the mechanism for receiving 
 air and blowing out water. In other tribes the acuteness of the sense 
 is in proportion to the development of the olfactory ganglia : in reptiles 
 it is feeble ; in birds, more developed ; in carnivorous animals, still more. 
 But here again it exhibits a special restriction, since there is reason for 
 supposing that carnivorous animals are insensible to the perfume of flow- 
 ers, while herbivorous ones distinguish them perfectly. In man, as we 
 have said, the sense is less developed, but it has a wider range. 
 
 The localization of odors is effected in a much less perfect manner than 
 Localization the localization of sounds. The principle by which it is ac- 
 of odors. complished is obviously that of determining the direction, of 
 maximum intensity, and this involves necessarily the constant exercise 
 of memory and comparison. The surprising manner in which this can 
 be accomplished by animals whose sense of smell is acute, as, for exam- 
 ple, by the dog, is extremely interesting. From the different manner in 
 which various odors affect different individuals, there is no general stand- 
 ard of comparison to which they may be referred, as there is in the case 
 of colors and of sound. Scents which may be highly disagreeable to one 
 are acceptable to another person. By constant exposure, the faculty may 
 
OP TASTE. 427 
 
 become so benumbed as to be unable to distinguish some altogether. 
 Thus Turner found "that the flower -of the iris persica was Various effects 
 pronounced of pleasant odor by forty-one out of fifty-four of odorous im- 
 persons, by four to have little scent, and by one to be ill- P rtessions - 
 scented. Of thirty persons, twenty-three held the anemone nemorosa 
 agreeable in its perfume, and seven did not think that it smelled at all." 
 Diseases of the central organs will sometimes give rise to the percep- 
 tion of subjective odors, just as they do to spectral illusions or subjective 
 sounds in the ears. odors. 
 
 CHAPTER XXIV. 
 
 OF TASTE. 
 
 Conditions for Taste. Structure and Functions of the Tongue. Tactile and Gustative Regions 
 of the Tongue. Complementary Tastes. Subjective Tastes. 
 
 THOUGH the function is participated in by other portions of the oral 
 cavity, the tongue is to be regarded as the organ of taste. Conditions for 
 The physical conditions under which savors are perceived is taste - 
 that the substance shall be presented in solution in water, or, at all 
 events, in the saliva. From vision, hearing, and smell, the sense of taste 
 differs in the circumstance that it requires the contact of the acting body; 
 and, to a certain extent, the same distinction which has been made re- 
 garding such substances as can act on the olfactory mechanism might 
 also be made here ; that is to say, that there are two classes of agents 
 which affect the organ those which produce a mere pungent sensation, 
 and those which excite savors, properly speaking, for the irritations and 
 former will frequently give rise to specific action when ap- savors- 
 plied to other portions of the surface of the skin. 
 
 Sensations of taste are very frequently conjoined with olfactory per- 
 ceptions, so that we mistake the one for the other. There Connection of 
 are many substances, reputed to have a powerful flavor, ceptkmTand" 
 which become tasteless when the nose is held ; and this re- tastes. 
 mark applies more particularly to such as are at the same time volatile 
 and soluble in water. However, irrespectively of this, some of those 
 bodies which produce the most intense and permanent impression on the 
 organs of taste do so merely in virtue of their solubility, as, for exam- 
 ple, quinine, which is a non-volatile body. The intensity of such action 
 depends on the duration of contact and the degree of exposure of the 
 substance to the tongue, so that the papilla? may, as it were, become 
 thoroughly permeated. 
 
428 PAPILLA OF THE TON&UE. 
 
 The idea of taste may arise irrespectively of the presence of any actual 
 substance. A sharp blow will produce it, as also the passage 
 ent on acci- of a feeble voltaic current. It was, indeed, in this way that 
 dental agents. ^ fa s j. O "b serva ti n in galvanic electricity was made. A 
 narrow jet of air directed upon the tongue causes a taste resembling that 
 of saltpetre. If the tongue be dry and parched, its power of discrim- 
 inating tastes is greatly enfeebled, and the same thing takes place if its 
 temperature is very much changed, either by elevation or depression, 
 as by keeping it for a short time in contact with hot or very cold water. 
 
 The action of the tongue, as the organ of taste, depends upon the pa- 
 e pillae which are on its surface. These structures give to the 
 
 Structure of r ^ ... & 
 
 the papiii* of upper portion of the tongue its rough appearance. They are 
 of three kinds : 1st. The conical papillae, which are the most 
 numerous ; 2d. The circumvallate papillae, which are situate near the 
 base of the organ, and which are from -^ to -^ of an inch in diameter, 
 with a crater-like depression, round the edge of which is a groove, and 
 again a circular elevation; 3d. The fungiform papillae, which are chiefly 
 on the sides and tip, their shape being conical, the narrow end of the cone 
 being downward. The epithelium of the tongue is less dense over the 
 fungiform papillae, and hence their projecting appearance : it is more dense 
 over the conical papillae, and projects from them in processes which pre- 
 sent an aspect like that of hairs. Some of them contain hair-tubes. 
 Besides these, the surface of the tongue presents a papillary structure 
 resembling that of the skin secondary papillae, as they are termed. It 
 is supposed that the conical papillae are chiefly organs of prehension ; the 
 others are organs of taste, but that function is participated in by other 
 portions of the surface of the mouth, as, for example, the soft palate, its 
 arches, and the tonsils. 
 
 Fig. 207 represents the surface of the tongue and the adjacent parts : 
 #, a, lingual papillae ; , b, circumvallate papil- 
 lae, disposed along two converging lines form- 
 ing the lingual V; c, foramen ccecum ; d, d^ 
 fungiform papillae ; e, 6, filiform papillae ; /", 
 fraenum epiglottidis ; g, epiglottis ; 7z, anterior 
 pillar of velum ; i, stylo-glossus ; Z, isthmus 
 of the fauces ; ra, uvula ; n, velum pendulum 
 palati ; 0, hard palate ; p, raphe ; , , orifices 
 of the excretory ducts of the palatine glands ; 
 f, palatine glands, the mucous membrane be- 
 ing removed ; , palatine glandules ; , mu- 
 cous membrane covering the same glands ; u, 
 palatine tubercle ; i?, v, section of the lower 
 
 The tongue. J a W. 
 
NERVES OF THE TONGUE. 429 
 
 The organ of taste is placed at the commencement of the digestive ca- 
 nal; hence the characters of substances may be examined usesofthe 
 with deliberation while they are yet under the control of the sense of taste - 
 will, for when once a body has entered the oesophagus it is swallowed in- 
 voluntarily. The tongue, therefore, gives warning of the presence of del- 
 eterious substances, and in no small degree excites the appetite by receiv- 
 ing the impression of pleasant flavors. The essential condition under 
 which it acts is a moist state of its surface, for the dry tongue, though it 
 enjoys common sensibility, after the manner of any portion of the exter- 
 nal tegument, does not enjoy taste. One of the duties of the salivary 
 glands is incidentally to maintain this moistened condition. To a cer- 
 tain degree, taste may be regarded as a refinement on touch. It differs 
 from vision and hearing in the peculiarity that there is no sin- serves of the 
 gle nerve of special sense individually devoted to it, for the tongue, 
 front of the tongue is supplied by the lingual branch of the fifth pair, 
 and the back by the glosso-pharyngeal. Its entire nervous supply is 
 derived from four different sources: the lingual, the hypoglossal, the 
 glosso-pharyngeal, and the sympathetic, representing therefore special 
 sensibility, muscular motion, common sensibility, and sympathetic rela- 
 tion. That the hypoglossal is the nerve of motion, or muscular nerve, is 
 proved beyond doubt by its section, after which the motions of the tongue 
 are destroyed, but taste. and touch remain. The individual duty dis- 
 charged by the glosso-pharyngeal, and the lingual branch of the fifth pair 
 respectively, is not so clearly determined. Section of the former is at- 
 tended with loss of taste, though it is not yet proved that there is a loss 
 of all kinds of taste. If the lingual branch of the fifth be divided, com- 
 mon sensation at the tip of the tongue is destroyed, and there is evidence 
 that with this the appreciation of certain tastes disappears. The glosso- 
 pharyngeal is distributed to the circumvallate papillae, and it is said that 
 in some birds the lingual is suppressed. Upon the whole, therefore, it 
 may be concluded that these nerves are conjointly engaged in the sense 
 of taste, the glosso-pharyngeal being engaged with those flavors which 
 affect the back part of the tongue, the lingual with those which affect 
 the tip. 
 
 Illustrations of the distribution of the hypoglossal nerve have already 
 been given in its description, under the title of the twelfth pair. 
 
 The surface of the tongue presents the tactile and gustative powers in 
 an inverse manner. Examined by the method described in Tactile and 
 the chapter on touch, the compasses must be opened to a great l^* 1 ^ the" 
 extent, as we pass from the tip toward the back of the tongue, tongue. 
 in order that a double impression may be perceived. This condition ap- 
 pears to be in accordance with the requirements of the organ, common 
 tactile sensibility being most necessary at its outer extremity, and this 
 
430 COMPLEMENTARY AND SUBJECTIVE TASTES. 
 
 gradually passing off into the refinement of taste. The action of any 
 given substance may be increased by motion and pressure, as when it is 
 rolled over the tongue, or held thereby. Its sense of discrimination may 
 be rendered more acute by education. 
 
 As with the organs of the other senses, so with this, an impression 
 Duration of made upon it does not instantaneously cease, but remains for 
 tastes. a certain period of time, indeed, in this instance longer than 
 
 in those. Hence many substances acting in rapid succession give rise 
 to a confused effect, though it is said that, out of such interminglings, an 
 accomplished epicure can fasten his attention on one, and continue to 
 recognize it just as we recognize and follow the sound of one instrument 
 in an orchestra. No explanation has as yet been given of the manner 
 of action of different tastes, though it is asserted that some act upon one, 
 and some upon another set of the papillae. After-tastes are also observed, 
 Complement- which are occasionally of a complementary kind, as, for in- 
 ary tastes. stance, the intensely bitter taste of tannin is followed by a 
 sweetness. These after effects modify the taste of substances which may 
 be taken while they last. They therefore form an ample subject for the 
 profound contemplation of the epicure, and should occupy the serious at- 
 tention of the cook. They may be illustrated in a general manner by the 
 injurious effect of sweet substances upon the flavor of delicate wines. 
 
 It has been mentioned that the passage of a voltaic current through 
 Electrical and ^ e ton g ue causes an alkaline or acid taste. Some experi- 
 subjective menters deny the correctness of this statement, and assert 
 that the impression is merely metallic. The effect, however, 
 depends upon the intensity of the current employed, or on the nature of 
 the pieces of metal used. If the current has power enough to decom- 
 pose the salts of the saliva, acid or alkaline tastes will be detected, ac- 
 cording as the direction of the current is made to vary, and the acid or 
 alkaline body is disengaged on the upper or under side of the tongue. 
 Subjective tastes arise in diseases of the nervous centres, but these are 
 often rendered obscure by the exudations and furred condition of the 
 tongue. Dogs, into the blood-vessels of which milk has been injected, 
 have been observed to lick their lips ; and from this it has been inferred 
 that the presence of substances artificially introduced into the circulato- 
 ry current may be detected by the organ of taste. 
 
ANIMAL MOTION. 431 
 
 CHAPTER XXV. 
 
 OF ANIMAL MOTION. 
 
 Ciliary and Muscular Motion. Description of Cilia and ike Manner of Action. 
 
 Muscular Fibre : its Forms, Non-striated and Striated. Muscle Juice. Manner of Contraction 
 of a Muscle : its supply of Blood-vessels and Nerves. Its Chemical Change during Activity. 
 Its Rise of Temperature. Effect of Electrical Currents. Duration of Contractility. 
 
 Doctrine that Muscle Contraction is the result of Muscle Disintegration. Manner in which ordi- 
 nary Cohesion is brought into play. Manner of Restoration. Removal of the Heat and Oxi- 
 dized Bodies. 
 
 Rigor Mortis. Connection of Muscle for Locomotion. Of Standing. Walking. Running. 
 
 IT was formerly held that animals are distinguished from plants by 
 the possession of the power of locomotion, a doctrine which . 
 
 r J J T A i -u Animal motion. 
 
 can now no longer be regarded as true. It was also be- 
 lieved that the muscular movements of animals are due to the influence 
 of the nerves, and that a muscular fibre contracts only when stimulated 
 to do so by a nerve. This makes the possession of a nervous system 
 essential to the motions of animals. These doctrines also are erroneous. 
 Animal motion is of two different kinds : 1st. It is accomplished by 
 vibrating cilia ; 2d. By the contraction of cells arranged in the form of a 
 fibre. 
 
 OP CILIARY MOTION. . 
 
 The epithelial cells of the cylindrical and of the tesselated kind are 
 occasionally arranged with delicate projecting strige on their Description of 
 free extremities. The length of these varies from the - 6 -J-Q cilia and their 
 to the XQOQQ of an inch. These stria? are termed cilia, and 
 the cells are said to be ciliated. Examples are presented by the mucous 
 Fig. 208 membrane of the respiratory surface and of the nasal 
 
 cavities ; an illustration is given in Fig. 208. The 
 cilia may be regarded as prolongations of the cell wall 
 itself. They exhibit a vibrating motion back and 
 forth, which recalls the movements of stalks of grain 
 in a field as the wind is passing over it, the ears bend- 
 
 Ciliated cells. , , . . . r . , , 
 
 ing down and rising again in the breeze, and throwing 
 the whole surface into waves. The cilia also exhibit a movement like 
 that known as the feathering of an oar, or sometimes as turning round 
 upon the point of attachment, as upon a centre, giving rise to a sort of 
 conical motion, the free end describing a circle. These motions seem to 
 
432 
 
 CILIARY MOTION. 
 
 20 9. 
 
 be perfectly involuntary, for they not only take place long after death, 
 
 but even in detached portions, the ciliary cell being uninjured and entire. 
 
 The seats of ciliary action are always moistened surfaces. The condi- 
 
 tion for the continuance of the motion after death is accordingly that the 
 
 surface shall be kept moist, but it is also necessary that a certain tem- 
 
 perature should be observed, which in warm-blooded animals must not 
 
 fall below 42 F. Even after the motion has completely ceased, a solu- 
 
 tion of carbonate of potash re-excites it, but this does not take place 'with 
 
 ammonia, because it injures the ciliated cells. 
 
 Ciliary motion is independent of nervous agency. The control of tem- 
 
 perature and of chemical reagents over it shows that it is of a physical 
 
 nature. 
 
 In the lower orders of life ciliary movement is relied on both for the 
 
 Uses of ciliary purposes of locomotion and prehension. 
 
 motion. " pig % 209 illustrates this in the case of 
 
 a vorticella, the upper edge of which shows such a 
 
 mechanism. It is often stated that in the higher an- 
 
 imals the object is to determine a movement of the 
 
 liquid which moistens the ciliated cells in the direc- 
 
 tion of the outlet of the tube, or other surface which 
 
 they line. In this way the action of the cilia may 
 
 tend to the expulsion of material from the air-cells 
 
 of the lungs into the bronchial tubes. In reptiles, 
 
 whose urinary tubelets are furnished with this mech- ciliated animalcule. 
 
 anism, the secretion may be urged thereby in the proper direction. 
 The contractile tissue which enables such animals as the hydra (Fig. 
 
 Embryonic ^^) to execute movements of prehension and locomotion 
 
 contractile tis- may perhaps be regarded as the rudimentary state of the 
 structures next to be described. The annexed sketch, from 
 
 Trembley, illustrates the 
 manner of progression of 
 this animal. No trace of 
 a proper muscular fibre, 
 and none of a nervous 
 Hydra walking. system, have hitherto been 
 
 detected in it. 
 
 Of Muscular Motion. 
 
 The muscular system consists of muscular fibres, tendons, bones, to- 
 gether with various accessory parts, such as ligaments, sheaths, bursa3 
 mucosiE, synovial capsules, fascia. Its action depends on the primary 
 fact that, under appropriate influences, muscular fibre shortens. 
 
 Each voluntary muscle consists of a collection of fasciculi, which ex- 
 
MUSCULAR FASCICULI AND FIBRILS. 
 
 433 
 
 Fig. 211. 
 
 hibit the characteristic appearance 
 of transverse striation, as in the 
 
 Fig. 212. 
 
 Striated muscular fasciculi, magnified K5 diameters. 
 
 Sarcolemma of fish. 
 
 photograph of muscular structure of the frog (Fig. 211). voluntary mus- 
 The primary fasciculi are collected into larger bundles, cuiar fasciculi. 
 secondary muscular fasciculi, held together by connective tissue, and 
 these, again, into still larger, the tertiary. 
 
 The primitive fasciculus is enveloped in a delicate sheath, the sarco- 
 lemma, as shown in. Fig. 212, in which the fasciculus, though torn across, 
 is held together by the sarcolemma. The specimen is from the human 
 muscle. Fig. 213 is a good representation of the same fact. It is given 
 by Todd and Bowman from the skate. The sarcolemma is a delicate 
 membrane, which, though of great tenuity in man, may be made visible 
 by the action of acetic acid or alkalies. Within the sarcolemma the 
 primitive fasciculus is seen to be composed of many parallel fibrils, 
 which may, by maceration or chemical agents, be separated from one an- 
 other. These fibrils present a beaded aspect, and, since their constituent 
 elements are arranged side by side in parallel planes, they ultimate mus- 
 give to the fasciculus the appearance of striation it presents. cular fibril - 
 
 The longitudinal striation of the fas- 
 ciculus arises from the fibrils them- 
 selves. Here and there, in the inte- 
 rior of the sarcolemma, nuclei occur ir- 
 regularly, and with them fat granules. 
 The fibrils, with the fat and a liquid, 
 fill the sarcolemma, without leaving 
 any central canal or hollow axis. 
 
 Fig. 214 is a photograph of ulti- 
 mate muscular fibre of the pig, from 
 one of Mr.Lealand's preparations. The 
 rectangular form of the constituent 
 
 Ultimate muscuuTfi^HI^d 200 diameters. Cells IS Well Seen at 0, a, a. At , 
 
 EE 
 
 - 214 - 
 
434 MUSCLE JUICE. 
 
 probably by reason of a twist, tension, or undue strain, a spiral appear- 
 ance is presented ; c, c are the primitive fasciculi. 
 
 A fluid surrounds the fibres of striped muscles, and the fibre cells of 
 
 smooth ones, which is wholly different from the plasma of 
 
 Muscle juice. ^ ^^ The exper i ments O f Schultz show-that this fluid 
 
 contains a large amount of casein, a conclusion of considerable import- 
 ance, since, if there were any doubt of the occurrence of that substance 
 in the blood, this fact, at all events, renders it certain that the mammary 
 gland is not necessary to its formation. That the substance thus occur- 
 ring is casein is proved by the action of rennet. 
 
 Muscle juice undoubtedly arises within the sarcolemma through which 
 it exudes. Each fibre therefore presents four objects : the syntonin, the 
 nucleus, the sarcolemma, and the muscle juice. That the muscle juice 
 arises in part from the functional activity of the fibre, and is immediate- 
 ly derived from the waste of its syntonin, and that, in its turn, the syn- 
 tonin is closely allied to the substance of the nucleus, is shown by their 
 exhibiting almost the same chemical reactions with alkalies, acids, etc. 
 
 The sarcolemma is not, however, filled with syntonin; it contains be- 
 sides, as stated above, a certain quantity of fat, as may be demonstrated 
 by removing from the sarcolemma its syntonin by acids, when a granu- 
 lar material will be left. That this is fat is proved by its solubility in 
 sulphuric ether. 
 
 The sarcolemma does not belong to the protein class of bodies, but is 
 Sarcolem- rather analogous to elastic tissue. The color of muscle appears 
 ma - to be not so much due to the blood as to a special pigment, 
 
 which, perhaps, adheres in a free state to the fibrils. The muscle juice 
 contains relatively far more potash salts and phosphates than the blood, 
 as is shown by the following table from Liebig. 
 
 For one hundred parts of soda there occur, 
 
 In the hen, 40.8 of potash in the blood, and 381 in the muscle juice. 
 " 'ox, 5.9 " " " 279 " " 
 
 " horse, 9.5 " " " 285 " " 
 
 " fox, " " " 214: " " 
 
 " pike, " " " 497 " " 
 
 It is commonly stated that muscular motion is accomplished by fibres 
 Two forms of of .two different kinds: 1st. The simple, non-striated, un- 
 fibre n^n stri P e <^ or organic fibre ; 2d. The striated, striped, or volun- 
 stria'ted and tary fibre just described. Though this subdivision may be 
 convenient, it can scarcely be regarded as accurate, since the 
 former variety passes by insensible degrees during development into the 
 latter, and cases, indeed, are not wanting in which the same fasciculus 
 presents in different parts both conditions at once. 
 
 The non-striated muscular fibre. Fig. 215, consists of translucent bands 
 
FORMS OF MUSCLE. 
 
 of a soft granular material, varying from the -^QQ to 
 
 Fig. 215. Fig. 21C. 
 
 an 
 
 435 
 
 m 
 
 Unstriped fibres. 
 
 Unstriped fibres in acetic acid. 
 
 Fig. 'ill. 
 
 Muscle 
 cells, 
 
 breadth, and exhibiting here and there the traces of Non-stria- 
 nuclei, particularly after the fibre has been acted on by ted fibre - 
 acetic acid, as is shown in Fig. 216. Each fibre may be re- 
 garded as an arrangement of nucleated cells, the nucleus be- 
 ing of a cylindroid or spindle form. The contractile content 
 within is syntonin. Non-striated fibre is not usually attach- 
 ed to fixed points, as to bone, but by being collected into par- 
 allel bundles, different bundles interlacing with one another, 
 contractile planes or surfaces are formed, such as the cylindri- 
 cal coat of muscular structure of the digestive tube, or the 
 contractile layer of the urinary bladder. Similar fibres, im- 
 bedded in the skin and connective tissues, communicate to 
 them the quality of corrugation or contractility. The fascic- 
 uli are bathed externally with an acid juice, characterized by con- 
 taining salts of potash, phosphoric acid, creatinc, nnd inosite. The 
 general appearance of fibre cells of this class is given in Fig. 217 : 
 a is from the small intestine of man ; , from the fibrous invest- 
 ment of the spleen of the dog. (Kolliker.) 
 
 Contractile fibre cells present the following reactions : Acetic 
 acid causes the fibre to swell, and makes the nucleus more contractile 
 visible ; it occasions a complete dissolution when in a fibre - cell s- 
 concentrated state. Dilute hydrochloric acts in a similar manner, 
 the effect in this instance being the same with the fibres of. both 
 smooth and striped muscle. The examinations thus far made have 
 shown no difference in ultimate composition between these forms. 
 The. striated muscular fibre consists therefore of fasciculi, with 
 an elastic investment of sarcolemma, collected into bundles, striated 
 and invested with perimysium. The contractile constituent . fibre - 
 
436 STRUCTURE OF MUSCLE. 
 
 is syntonin ; and though the general rule is that the primitive bundles 
 shall run isolatedly and parallel to each other, in certain cases they anas- 
 tomose, Fig. 60. In its ultimate construction, the form of fibre may be 
 regarded as consisting of a series -of cells, as shown \nFig. 214, the di- 
 ameter of which varies according to the actual condition of the muscle, 
 whether it is in the contracted or relaxed state, but which may be taken, 
 on an average, at the Yoiy o"o f an i ncn - The cells are placed end to end, 
 the boundary walls upon the end presenting the appearance of a delicate 
 transverse line. Each cell consists of two portions, a central spot and 
 a pellucid border. The pellucid border is considered by Dr. Carpenter, 
 whose views of muscular structure we are here presenting, to be the cell 
 wall, the central space being the cavity of the cell filled with some* highly 
 refracting substance. Dr. Carpenter speaks of the central spot as dark ; 
 an inspection of the photograph, Fig. 214, proves that it may be light if 
 exactly in focus. When the fibril is in a relaxed state the longest axis 
 of each cell coincides with the length of the fibril, but when contraction 
 occurs this axis shortens, and a shortening of the entire fibril is the re- 
 sult. A number of these fibrils, placed side by side, constitute a fascicu- 
 lus ; indeed, there may be many hundreds of them thus bound together. 
 When such a fasciculus is forcibly ruptured it presents different appear- 
 ances, according as the ends or sides of its constituent cells have cohered 
 most strongly together. If the lateral cohesion is weakest, the fascicu- 
 lus tears into its constituent fibrils, as was shown in Fig. 214, but if the 
 end cohesion is the weakest, it will tear into discs or plates, as in Fig. 
 Fig. 218. 218. The fasciculus is thus a bundle of fibrils, its 
 
 diameter varying very greatly, and being, in man, 
 from the -^ $ to the -g-^ of an inch ; in females it 
 is, on an average, smaller. Each fibril is a linear 
 series of coalesced cells. The cells, as they form 
 the fibril, lose their rounded and assume a rectan- 
 gular appearance, as shown at a, <z, Fig. 214. It 
 
 Muscular fasciculi torn & , ./. -, i PI -i . i 
 
 in discs. therefore appears that each fibril must have its own 
 
 investing sheath, the representative of the walls of the little cells which 
 have coalesced, and this, though not usually admitted by anatomists, ap- 
 pears plainly in the photograph from which that figure is taken. In 
 length, muscular fasciculi vary fromtthe sixth of an inch to two feet. 
 The larger animals furnish some that are even much longer. The nor- 
 mal form is doubtless cylindrical, but this is constantly departed from, 
 each accommodating itself to the pressure of the adjacent ones. The 
 sarcolemma serves as a partition between its included fibrils and the cap- 
 illary blood-vessels and nerves, which imbed themselves in the rounded 
 angular spaces between adjacent bundles. The cross section of a por- 
 tion of muscle shows the manner in which the sarcolemma and the fibres 
 
STRUCTURE OF MUSCLE. 
 
 437 
 
 are arranged. Fig. 219 is from the human biceps, and Fig. 220 from 
 
 Fig. 219. 
 
 Fig. 220. 
 
 Hansverse section of human muscle. 
 
 Muscular fas- the pectoral 
 cicuii. muscle of the 
 
 teal. Since it is in the 
 interspaces between the 
 rounded fasciculi that 
 
 the blood-VeSSels lie, the Transverse section of muscle of teal. 
 
 tissue is more vascular as its fasciculi are of less diameter. 
 
 It has already been stated, in connection with Fig. 211, that the stri- 
 ated form of muscular fibre derived its name from the circumstance that, 
 when examined by a sufficiently high power, it appears to be crossed by 
 delicate transverse lines, the longitudinal separations between the fibrils 
 being also visible. This is seen in the specimen of insect muscle repre- 
 sented in the photograph, Fig. 221, and under a still higher magnifying 
 
 Fig. 221. 
 
 Fig. 222. 
 
 Non-fibrillated insect fasciculi, magnified 50 diameters. 
 
 power in that of Fig. 222. The dis- 
 tance between the transverse stria3 va- 
 ries with the condition of the muscle, 
 but on an average it is represented as N 0n -fibriiiated insect fasciculi, magnified 200 
 being about the ^ of an inch. Many 
 
 more stria3 are crowded together when contraction takes place, and they 
 retire from each other as soon as relaxation occurs. 
 
 It is said that the voluntary muscles contain in their muscle juice 
 more acid than is enough to neutralize all the alkali of the 
 
 blood. The electro-chemical relations of this interfascicular 
 
 Muscle juice. 
 
438 
 
 MANNER OF MUSCULAR CONTRACTION. 
 
 acid juice and the alkaline plasma of the blood are doubtless the cause 
 of the production of those electric currents which have been demonstrated 
 in the muscles. It does not follow, therefore, that these currents occur 
 in the natural state : they may be the result of the experimental arrange- 
 ment for their own detection, since it has long been known that an acid 
 and an alkaline juice, separated from each other by a conducting organic 
 body, will form an effective voltaic circle. 
 
 Of the contractile element of muscular fibre, syntonin, it may be re- 
 marked that it can be dissolved by the aid of dilute hydrochlo- 
 ric acid, and that it differs from fibrin of blood not only in that 
 respect, but also both in its ultimate composition and physical and chem- 
 ical qualities. In certain cases it seems to degenerate into fatty sub- 
 stance. In the growth of a muscle, the constituent fibrils increase in 
 number and in length, their diameter remaining, however, nearly the 
 same as in the early periods of life. The thickening of a muscle is, 
 therefore, not so much due to the thickening of its constituent fibrils as 
 to their increase of number. 
 
 The contraction of a muscular fibre does not take place throughout its 
 Manner of con wno ^ e l en gth at once ; it generally begins at the end, a change 
 traction of a of aspect arising from the approach of the opaque centres of 
 Hie cells to one another, and this occurring simultaneously 
 across the whole fibre. This approach may, however, ensue in different 
 parts of the length at the same time, the sarcolemma being raised up in 
 bulla3 as the contraction takes- place. This effect is shown in Fig. 223, 
 
 Fig. 223. 
 
 Contracting muscle of Dytiscus. 
 
 in which the thickened portion of the contracted middle space of the mus- 
 cle is surrounded with the sarcolem- 
 mic bullas. 
 
 Fig. 224. 
 
 The same is demon- 
 strated in Fig. 224, which repre- 
 sents the border of a muscular fas- 
 ciculus in a young crab, with a spot 
 of contraction, and the sarcolemma 
 elevated along the edge. In these 
 cases the contraction is brought on 
 by the action of water, which, in 
 some measure, may exaggerate or disturb the phenomena. Fig. 225 
 exhibits, under the same circumstances, a fasciculus from the eel, a being 
 the uncontracted, b the contracted part, on the edge of which the sarco- 
 
 Sarcolemma raised in bullse. 
 
ATTACHMENT OF MUSCLE TO BONE. 439 
 
 Fig. 225. lemma, is again raised up. The two 
 
 latter illustrations are from Todd and 
 Bowman. 
 
 Different portions of the length of 
 the fibre assume this condition at dif- 
 ferent moments, and hence the whole 
 
 Fasciculus contacting. structure is thrown into a form which 
 
 recalls the motion of a worm. The zigzag appearance pointed out by 
 Prevost and Dumas arises from the circumstance that when relaxa- 
 tion of the fibre occurs all its parts are not brought at once into the 
 same state, but while some are contracted others are in the opposite con- 
 dition. A muscle, during its contraction, appears to have nearly the 
 same solid dimensions which it had during its relaxation. This has led 
 to the deceptive conclusion that whatever it has lost in length it has 
 gained in thickness. There must, however, be a diminution correspond- 
 ing to the recognized amount of waste, for it is well known that destruc- 
 tion of a portion of its tissue is the essential condition of the activity of 
 a muscle. The various degrees of energy with which the contraction 
 takes place at different times is to be explained not so much by the 
 more or less energetic shortening of the cells as by the varying number 
 of fibres which are simultaneously contracting, or by the different frac- 
 tional portion of each which is going into action at once. As the mus- 
 cular effect is more energetic, so will the sense of fatigue be more speedy, 
 for while one fibre is acting another is resting, and the same remark ap- 
 plies to different parts of even the same fibre. It is to this reciproca- 
 tion of motion that the sound usually emitted while the muscle is in ac- 
 tion, a low ringing sound, is to be attributed. 
 
 Striated muscle is often attached to bone, or other substance on which 
 it has to exert its mechanical power, by intervening fibrous jj usc i e at t a ch 
 tissue constituting tendon. These fibres are collected in ed to bone by 
 groups, so as to present primary, secondary, and tertiary fas- 
 ciculi. The tendinous fibres are brought in relation with the sarcolem- 
 ma, and thus form a sheath connected with adjacent ones by other de- 
 tached fibres. These may be considered as converging from all parts of 
 the muscle to its extremities, and thus giving rise to its tendon. In 
 - 226 - some instances the muscular fibres attach them- 
 
 selves to the side of the tendon, which does not 
 then undergo subdivision. 
 
 From the peculiar structure of muscular tis- 
 sue, .the capillary vessels which are distributed 
 to it must run in a direction for the most part 
 parallel to its fibres, as in Fig. 226. Their 
 Distribution of muscular capillaries. mo <3 e O f branching, transverse and longitudinal, 
 
440 
 
 DISTRIBUTION OF VESSELS AND NERVES. 
 
 Muscular arteries and veins. 
 
 They never penetrate 
 
 is shown in Fig. 227, a being .the artery, b the ^ 227. 
 
 . vein, c, capillary plexus. Each ar- 
 
 Distribution of ' ' r J r 
 
 blood-vessels to tenal branch has usually two vena3 
 muscle. comites, and the supply of these 
 
 capillaries has a general correspondence to the 
 number of fibrils. The lymphatics are not nu- 
 merous. Vascular distribution to the tendons 
 is much more sparing. By the muscular blood- 
 vessels a triple function has to be discharged: 
 they furnish oxidized blood, on which the action 
 of the muscle depends ; they remove the waste 
 which arises as the consequence of that activity ; 
 they also repair that waste by presenting the 
 elements of nutrition. The younger Liebig has 
 demonstrated that a muscle can not contract ex- 
 cept it be furnished with oxygen, and that, as 
 long as the capacity for contraction continues, it 
 absorbs oxygen and yields carbonic acid. 
 
 In the same general manner that the blood- 
 vessels are distributed, so likewise are the 
 nerves. An example of this is seen in Fig. 228. 
 , the sarcolemma, 
 
 Distribution of 
 
 nerves to mus- but run ill close 
 
 contiguity with 
 it, their distribution to dif- 
 ferent parts of the fasciculi 
 being very unequal, some 
 parts being quite scantily fur- 
 nished, the nerve filaments 
 coming in contact, as it were, 
 at occasional points. The 
 opinion is generally maintain- 
 ed among physiologists that 
 the nerves present toward 
 their extremities a looped arrangement, as shown in Fig. 228, but by 
 some it is asserted that the termination is in an extremely delicate point, 
 or bifid, or trifid, without exhibiting any return. Of the two forms of 
 muscular tissue, the striated is, for the most part, supplied from the cere- 
 bro-spinal system, the non-striated from the sympathetic. 
 
 The manner of development of muscular fasciculus seems to be, that 
 Development the sarcolemma is first produced as a thin and delicate tube 
 of muscle. ^ fa Q coa lescence of cells arranged linearly, the walls of which, 
 where they come in contact at the ends, are obliterated, giving origin to 
 
 Distribution of muscular nerves. 
 
COMPOSITION OP MUSCLE. 
 
 441 
 
 an elongated band. A granular material then occupies the interior of 
 the tube. Viewing the sarcolemma as the sum of the coalesced cell walls, 
 the fibrils are to be regarded as a development from the granular cell con- 
 tents. They form, by a sort of endogenous process, from without to 
 within. The nuclei, as has already been remarked, are on the inner sur- 
 face of the sarcolemma, and not within the cells. The structure is not 
 evident until after the end of the second month of foetal life, but by the 
 fourth month it has so much advanced that the muscle assumes a pale 
 red aspect; the tendons, which have already begun to be distinctly dif- 
 ferentiated, are gray. At birth the structure has become so far com- 
 pleted that the fibres can be isolated. The condition which the non- 
 striated fibre presents is, therefore, that beyond which the striated fibre 
 has passed, and in this respect the former may be regarded as an embry- 
 onic state of the latter. In some insect muscles an instructive interme- 
 diate condition is seen ; fibres may be found striated toward the middle, 
 and non-striated at the ends, as though imperfectly developed. The 
 thoracic muscles of insects, which offer a beautiful example of muscular 
 structure, are not, however, to be regarded as presenting primitive fibrils, 
 but rather non-fibrillated primitive bundles. This I consider to be the 
 case with the specimens from which the photographs, Figs. 221, 222, 
 were taken. Though not so apparent, nuclei exist in the striated fibre 
 even of adult life, and discharge an active function. At this period, the 
 increase of thickness of the muscles is to be attributed to an increase in 
 the number of the contained fibrils, which individually have about the 
 same dimensions as before birth. 
 
 Composition of Ox Muscle. 
 
 
 Herzelius. 
 
 Braconnot. 
 
 Marchand. 
 
 Water 
 
 771.70 
 
 770.30 
 
 766.00 
 
 Fibrin, cells, vessels, and nerves... 
 Albumen and hsemato-globulin ... 
 Alcohol extract and salts 
 
 177.00 
 
 22.00 
 18.00 
 
 181.80 
 27.00 
 19.40 
 
 180.00 
 25.00 
 17.00 
 
 
 10.50 
 
 11.50 
 
 11.00 
 
 Phosphates of lime and albumen.. 
 
 00.80 
 
 
 1.00 
 
 
 1000.00 
 
 1010.00 
 
 1000.00. 
 
 Composition of Human Muscle. 
 
 
 Marchand. 
 
 L'Heritier. 
 
 
 780.00 
 
 771.00 
 
 Matter insoluble in cold water 
 
 170.00 
 
 158.00 
 
 Soluble albumen and coloring matter.... 
 Alcohol extract with salts 
 
 23.00 
 16.00 
 
 34.00 
 12.00 
 
 
 10.00 
 
 25.00 
 
 Phosphate of lime with albumen 
 
 1.00 
 
 
 
 1000.00 
 
 1000.00 
 
 The result of the chemical change which muscular fibre undergoes dur- 
 ing the periods of its activity is eventually manifested by the Chemical 
 appearance of carbonic acid and urea, and also salts of sulphuric ^Sct^ity 
 acid, the two latter escaping from the system through the uri- of muscle. 
 
442 FUNCTION OF MUSCULAR FIBRE. 
 
 nary apparatus ; the former, in part, through the lungs. That these prod- 
 ucts are to be attributed to muscular waste is inferred from their in- 
 crease or diminution with increases or diminutions of muscular exertion. 
 In the voluntary fibres there is commonly a necessity for repose, during 
 which repair of the waste is taking place ; but in those organs which 
 are in ceaseless action, as the heart and diaphragm, the repair or nutri- 
 tion goes forward at an equal rate with the waste, and no period of rest 
 is required. It necessarily happens, during the destruction of this tis- 
 eo f tem er sue by t ne arterial blood, that a rise of temperature must 
 atureinmus- ensue, and such a rise has been actually observed to the 
 L0n * amount of a degree or more, notwithstanding the constant 
 tendency to the removal of the heat by the constant current of venous 
 blood flowing from the muscle. There is no necessity to attribute the 
 elevation of temperature to friction among muscular fibres, and, indeed, 
 the amount that could arise in that way must be very 'insignificant, and 
 not to be for a moment compared with that due to the oxidation. Even 
 in muscles which have been removed from the body, and made to con- 
 tract by the aid of magneto-electric currents, changes of composition may 
 be detected. 
 
 OF THE FUNCTION OF MUSCULAR FIBRE. 
 
 The mechanical action of muscular fibre depends, as we have seen, on 
 Nature of the shortening of the long axis of the cells of which the fibres 
 contractility. are composed. To this result the designation of contractility 
 is given, and the property by which the fibre is enabled to exhibit this 
 shortening is designated, agreeably to the metaphysical system of the old 
 physiologists, who were content to accept a word as an explanation of 
 a fact, by the term irritability ; this, as being useless, may be discarded ; 
 the former we may continue to employ. 
 
 At one time it was supposed that the contraction of a muscular fibre 
 Contractility depends so completely upon the agency of the nervous system 
 enf on^hf" that it; mi g nt ^ e considered as the direct function thereof; but 
 nerves. a more critical examination of the circumstances of the short- 
 ening of the fibre cells shows that it possesses many features in common 
 with the same contraction of the cells of plants, which have no nervous 
 system. The influence passing along the nerve fibrils is only one out of 
 many which can cause muscular contraction. There is abundant evi- 
 dence in support of the position that contractility is the result of the 
 structure of the muscular fibre, and that it belongs to it, and is not a spe- 
 cial function of nerves. 
 
 When muscular fibres are touched by a pointed instrument, they ex- 
 hibit contraction even after they have been detached from the body, pro- 
 vided that too long a period of time has not elapsed. If it be of the stria- 
 
CONTEACTION OF MUSCULAR FIBRE. 443 
 
 ted variety, the bundle that has been disturbed alone contracts, ~ 
 
 -, 1P ' Difference in 
 
 and presently alter relaxes ; but there is no lateral spread or the contrac- 
 diffusion of the effect to adjacent bundles, except in the case teTlndton-" 
 of the heart, in which it would appear that the contraction of striated mus- 
 one part is diffused laterally, and a single disturbance is fol- cles ' 
 lowed by many alternating contractions and relaxations, simulating, as it 
 were, the normal function of the whole organ. But where the non-stria- 
 ted form is in like manner examined, the contraction takes place more 
 slowly, spreads laterally to a wider extent, and is followed by a relaxa- 
 tion. The effect of an intermitting magneto-electric current is different 
 in the two forms of tissue, the striated contracting and keeping Effect of 
 contracted as long as the action is kept up, but the effect ceasing electrical 
 when the current stops. In the non-striated the action is tardy, 
 and relaxations may ensue even while the current is passing, and con- 
 tractions continue to occur after it has stopped. The effect becomes of 
 more interest when a weak, continuous electrical current is passed through 
 the centrifugal nerves supplying any muscle, for then the whole muscle 
 contracts, and remains in that state as long as the current flows. If the 
 current be passed through the ganglionic centre of those nerves contrac- 
 tion again ensues, and is maintained for a time even after the current has 
 ceased. If the current be sent through the centripetal fibre, alternate 
 contractions and relaxations of the muscle are the result. The interpret- 
 ation of these different cases has already been given (p. 276). 
 
 The capability of contracting continues in muscle fibre for a certain 
 time after death, a period which is shorter as the rate of res- Experiments 
 piration is higher, and hence these effects were first observed of Gaivani. 
 by Gaivani and others in the case of the frog and cold-blooded animals. 
 Even after it has disappeared, it may be re-established by Ex eriments 
 continuing the supply of arterial blood, as Dr. Brown- Sequard of Brown-Se- 
 has shown : a fact which illustrates in a striking manner the quai ' 
 independence of the muscular contraction of the nervous system. Of 
 course, as would have been expected, whatever interferes with due arte- 
 rialization* interferes with muscular power. This is the reason of the 
 inability for exertion which is experienced in the thin air of mountain 
 tops, the relaxation of the muscular system in asphyxia, the same con- 
 dition in the respiration of the vapors of ether or of chloroform ; it is also 
 to a great extent the cause of the wayward and staggering gait of the 
 drunkard. The converse of this likewise holds good : the higher the rate 
 of respiration, the more energetic the muscular power ; and therefore, in 
 birds, which respire most perfectly, muscular contractility is exhibited 
 with the greatest energy. 
 
 The contractility of the muscular tissues, as being independent of the 
 activity of the nervous system, is well illustrated by the remarkable ob- 
 
444 DOCTRINE OF MUSCULAR CONTRACTION. 
 
 Experiments servations of Dr. Dowler, of New Orleans, on the automatic 
 of Dr. Dowler. movements that sometimes take place after death by yellow 
 fever. After respiration had ceased, each hand in succession was car- 
 ried to the throat, and then to the crown of the head, and so back again 
 to the breast. In another instance, on being stimulated by a blow, the 
 arm was extended upward, and the hand could even be made to slap the 
 mouth ; or when the leg hung down, if the flexors of the hamstring were 
 struck, the heel was drawn upward. These manifestations continued 
 for between three and four hours, and even occurred in amputated limbs. 
 
 Contractility lasts for a different period, not only in different animals, 
 Duration of but even in different parts of the same animal. Thus, in man, 
 contractility, ft declines in the following order: in the left ventricle first, 
 then in the intestines and stomach, the urinary bladder, right ventricle, 
 oesophagus, iris, in the voluntary muscles of the trunk, lower and upper 
 extremities, and, finally, in the left and right auricle of the heart. 
 
 Assuming that the diameter of each muscular fibre is, on an average, 
 Distance at the 10 Q 00 of an inch, and that each fasciculus is the -^ of 
 which a muscle an inch, it may be inferred that each fasciculus contains about 
 enced by^a U 650 fibres. Now, since the nerves do not penetrate the sar- 
 nerve. colemma, the influence which they exhibit must be efficacious 
 
 at a distance; and if we take the maximum measurements which have 
 been made of muscular fasciculus, we may safely conclude that that in- 
 fluence extends at least through a distance of -^J-g- part of an inch. 
 
 It is not necessary for us, in this place, to enter on a discussion of the 
 T functions of nerve fibres, whether they exert a magnetic 
 
 that muscular agency, or act by rise of temperature, or, from an abrupt po- 
 suHsTronimus- ^ ar termmat i n deprived of its white substance of Schwann 
 cuiar disinte- permit the escape of their current into the muscle fibril, and 
 thence into the corresponding denuded pole of a centripetal 
 nerve beyond, the current being determined through the muscle by rea- 
 son of the better conducting power of that structure. The immediate 
 cause of muscular contraction is to be sought for in the muscles them- 
 selves, and this, I think, is much more obvious than is generally sup- 
 posed. So far from there being any thing mysterious or incomprehen- 
 sible about it, as some writers insist, we probably shall not be very far 
 from the truth if we assert that muscular contraction is the necessary 
 physical result of muscular disintegration, and without here consider- 
 ing the various ways by which that muscular disintegration may be 
 brought about, such is the doctrine that I now present. 
 
 Reviewing the various conditions under which contraction occurs, I re- 
 
 Change in mus- S ar( ^ destructive metamorphosis as the primary and leading 
 
 cie after con- one. Every thing seems to indicate that the contraction of 
 
 a fibril can not take place without the loss of a part of its 
 
CHANGE IN MUSCLE BY CONTRACTION. 
 
 445 
 
 substance, and this ensues even in the artificial motions that are estab- 
 lished by electric currents in amputated muscles, as is satisfactorily shown 
 by the experiments of Helmholtz. Of these the following synopsis is 
 given by Dr. Day : 
 
 " Powerful muscular contractions were induced by passing an electric 
 current through the amputated leg of a frog as long as convulsions con- 
 tinued to be manifested. The flesh of both legs was then analyzed. 
 The albumen was apparently scarcely affected, the mean of six experi- 
 ments giving 210 per 10,000 of albumen in the electrized, and 213 in 
 the non-electrized flesh. With regard to the extractive matters, it ap- 
 peared that in all the experiments, without a single exception, the water 
 extract in the electrized flesh was diminished, while on the other the 
 spirit and alcohol extracts were increased. The results are expressed in 
 the following tables : 
 
 Change in Muscle after Ekctric Contraction. 
 Alcohol extract from 100 parts recent frog's flesh. 
 
 Exp. 
 
 a. In electrized portion. 
 
 b. In non-electrized portion. 
 
 a: b 
 
 1 
 2 
 3 
 4 
 5 
 
 6 
 
 7 
 8 
 9 
 Mean 
 
 0.752 
 0.569 
 0.664 
 0.652 
 0.575 
 
 0.606 
 0.427 
 0.481 
 0.493 
 0.433 
 
 .24:1 
 .33:1 
 .38:1 
 .32:1 
 .33:1 
 
 Extracted with alcohol of 95 per cent. 
 
 1.020 
 
 0.748 
 
 1.36 : 1 
 
 Water extract. 
 
 Spirit extract. 
 
 a. 
 
 b. 
 
 a: b 
 
 a. 
 
 6. 
 
 a:b 
 
 1.21 
 0.93 
 0.72 
 0.95 
 
 1.63 
 1.23 
 0.90 
 1.25 
 
 0.79 : 1 
 0.76 : 1 
 0.80 : 1 
 0.78 : 1 
 
 1.69 
 1.65 
 1.76 
 1.70 
 
 1.50 
 1.35 
 1.53 
 1.46 
 
 1.13:1 
 1.22:1 
 1.15:1 
 1.16:1 
 
 " The amount of fat was unaffected. No urea could be found in the 
 alcohol extract. 
 
 "There is great difficulty in performing experiments of this nature on 
 warm-blooded animals, in consequence of the rapidity with which iso- 
 lated portions of the muscle lose their contractility. 
 
 " The best results were obtained with decapitated pigeons : 
 
 
 a. In electrized muscle. 
 
 b. In non-electrized muscle. 
 
 a:b 
 
 Albumen 
 Water extract 
 Spirit extract. 
 
 2.04 
 0.64 
 1.68 
 
 2.13 
 0.73 
 1.58 
 
 .88 : 1 
 1.06:1 
 
 " The above facts sufficiently show that muscular action is always ac- 
 companied by a chemical change in the composition of the acting mus- 
 cle." It appears that after electrization the alcohol extract increases be- 
 tween 24 and 38 per cent. ; the water extract diminishes between 24 and 
 20 per cent. ; the spirit extract increases between 13 and 22 per cent. 
 
 I therefore regard disintegration of the muscular structure as the prim- 
 itive act, so far as the fibril itself is concerned, and contraction as the 
 
446 MANNER OF CONTRACTION. 
 
 Balanced state necessary consequence, that disintegration being brought 
 of a muscle a bout by the oxidizing agency of arterial blood. It must, 
 
 through waste J i i 
 
 and repair. however, be borne in mind that this waste is masked by its 
 incessant repair, and that its condition at any moment of its action repre- 
 sents the actual balancing at that instant of the waste and repair re- 
 spectively ; and since the repair does not proceed with the same rapidity 
 as the destruction, it needs must follow that, sooner or later, a point will 
 be arrived at when there is an absolute necessity for repose to give to 
 the renovating processes the opportunity or time for effecting* a complete 
 restoration. 
 
 Accepting, therefore, the fact that a fibre can not contract without loss 
 Manner in ^ * ts substance, an ^ regarding that loss as the cause and the 
 which contrac- contraction as the effect, it is plain that whatever influence 
 ccurs ' can accomplish an oxidation will produce a shortening of the 
 fibre. Perhaps it may be that the nerve tubule does it by occasioning a 
 rise* of temperature; perhaps it may be, if nerves do not end in loops, 
 but in denuded points, by the current escaping into the muscle from 
 those points, and occasioning such an allotropic change in the contents 
 of the muscle cells as enables the blood to destroy them, in the manner 
 set forth in Chapter X. With such theories we need not now embar- 
 rass ourselves, but confine our attention to the result with which we are 
 concerned, that is to say, the destruction of the material contained in the 
 muscle cells, which destruction is practically brought about by the ac- 
 cess of arterial blood. When this takes place, the cell affected under- 
 goes an actual diminution of size, through loss of part of its contained 
 material, its longer axis shortening from no other cause than the cohe- 
 sion of its included granules thus suddenly brought into play. The cell 
 which we have under consideration, like an entire muscular fasciculus, 
 Restoration of P ossesses no power of active dilatation, and so remains with- 
 the contracted out change until it is stretched by similar contractions tak- 
 ing place in the components of other and perhaps distant 
 antagonist muscles. Coincident, however, with this destruction of its 
 interior substance, and loss of its prolate form, is the act of repair, the 
 nucleus of the cell reproducing other granules from materials furnished 
 by the blood ; for the arterial capillaries not only bring the means of 
 oxidation, but they bring the plastic elements of nutrition, and so per- 
 mit the cell to recover its dimensions, and to be stretched to its orig- 
 inal shape by the contraction of antagonist fibres. The destruction was 
 almost instantaneous ; the repair is an affair of a little longer time, and 
 thus, while one part is resting, other portions of the muscular mass take 
 up the action in succession, one after another contracting. Such is the 
 first series of changes ; let us now examine the second. 
 
 For, as the result of that first stage, there has been a liberation of prod- 
 
PRODUCTS OF MUSCULAR WASTE. 447 
 
 nets of oxidation, which are eventually to find their way into the urinary 
 secretion, or to escape by the respiratory surfaces. It is immaterial what 
 the first aspect of these substances may be, creatine, urea, extractive, etc. ; 
 this much is absolutely certain, that they are on the downward career, 
 and will end as urea, sulphuric, carbonic acids, etc. The experiments 
 both of Reymond and Liebig prove that the muscles, when at Products of 
 rest, contain no acid juice, and during their activity it is known muscular 
 that the degree of acidity is proportional to the energy with * 
 which they have been contracting. It can not for a moment be sup- 
 posed that this acidity is the cause of the contraction ; on the contrary, 
 it is its result. 
 
 Among the products arising during muscular action may be more par- 
 ticularly mentioned inosite, or muscle sugar, which is isomeric inosite and 
 with glucose, and creatine, which, though it contains so large creatine - 
 a proportion of nitrogen, must be regarded as a product of the waste go- 
 ing on. By the loss of two atoms of the element of water, it gives origin 
 to creatinine, which is accordingly found in the muscle juice, the blood, 
 and the urine. Indeed, these two substances seem to be inversely pro- 
 portional to each other. 
 
 The partial oxidation which has given rise to these various products 
 can not occur without an elevation of temperature. A second stage of 
 the process of muscular action consists in the removal of the heat and 
 of the partially oxidized bodies. 
 
 We have only to look at the minute anatomy of the parts under con- 
 sideration to recognize the manner in which this double re- Removal of the 
 moval is accomplished. The arterial capillaries, when they ^zed^dies by 
 break up for their final distribution, run parallel with the the blood. 
 muscular fibres, as also do the attendant veins. From one to the other, 
 at short intervals, as seen in Fig. 227, intercommunicating vessels trans- 
 versely pass, the whole being arranged on such a system as to afford 
 the readiest means of removal of the blood as fast as it becomes venous 
 a facility of removal of the last importance for carrying off the wasted 
 products of oxidation ; and in this manner, those products, whatever they 
 may in the first instance be, find a ready means of escape, and so the 
 muscular fibre by degrees is relieved from these results of functional ac- 
 tivity. 
 
 As for the heat which has arisen in a secondary way from the meta- 
 morphosis which has been going on in the fibre, that is in like manner 
 extracted. It is difficult to conceive of a more effective method by which 
 the heat could be taken away from the wasted fibre, or indeed we might 
 say from the interior of the whole mass of the muscle. The current of 
 vendus blood bears away with it not only the products that have arisen 
 in the oxidation, but likewise the heat. 
 
448 . RHYTHMIC CONTRACTION. 
 
 It is probable that one cause of cessation of muscular contraction in 
 Effect of accu- any one point of a fibre is the momentary accumulation of 
 mulation or wa sted material, as might be illustrated in a coarse manner 
 rial. by the difficulty of causing a fire to continue burning when 
 
 the ashes are permitted to accumulate, and the necessity of their removal 
 before the combustion can go on. Two separate events have to occur 
 before a fibril that has been in contraction is ready to contract again : 
 these are the removal of the oxidized products, and the renovation of the 
 interior of the cells. The two probably go on coincidently, the veins 
 taking one part of the duty, and the arterial capillaries the other. 
 
 In non-striated muscular fibre, in which the supply of blood-vessels is 
 Peculiarity in much less copious, there is a possibility for a lateral propa- 
 S^onltrilted g ati on of effect, because of the possibility of the lateral prop- 
 fibre, agation of the heat, either supplied directly from the nerve 
 tubule or arising from the oxidation going on. The sluggishness of its 
 first contraction, the longer continuance, the propagation from fibre to 
 fibre laterally until the effect wears out or is re-enforced by some new 
 stimulus, might almost seem to be the necessary result of the imperfect 
 supply of arterial blood, the sluggish removal of the products of waste, 
 and the more perfect opportunity for the diffusion of heat. This doc- 
 trine therefore meets with a very happy illustration in the phenomenon 
 displayed by the contraction of the two kinds of fibre. 
 
 It may still farther illustrate these views to examine that other variety 
 Rhythmic con- of contraction, rhythmic in its nature, which is exhibited, for 
 tractions. example, by the heart, of which it may be said that the fibres 
 show a simultaneous contraction alternating with periods of repose, con- 
 traction and relaxation succeeding each other at definite intervals. If, 
 as we have just said, the cessation of contractility arises from the mo- 
 mentary accumulation of products of waste, and the capacity for its re- 
 newal is due to restoration of the original state by nutrition, rhythmic ac- 
 tion may follow as the consequence of an arrangement of muscular fibrils 
 with an adjusted supply of arterial and venous capillaries. An original 
 excitation producing a contraction can not act in a permanent way, for 
 the result of that contraction is an accumulation of wasted material which 
 must be removed. It may require but a moment for the removal to take 
 place to a sufficient extent to enable the original disturbance to act once 
 more, and be checked in its action again. Whatever value there may 
 be in such explanations as these, they undoubtedly gather a deep inter- 
 est from thus enabling us to comprehend that it is possible to resolve 
 such mysterious phenomena as rhythmic periodicities into the results of 
 ordinary mechanical laws. 
 
 But the question returns upon us. Admitting the descriptions that 
 have now been given to be a true representation of the facts, and also of 
 
CONTRACTION OF MUSCLE. 449 
 
 their natural sequence, what is the actual physical cause of 
 
 the shortening of the muscular fibril? All that we have extensive mus- 
 
 thus far said can Ibe received at the best as only a statement cuiar contrac- 
 
 f tion by slight 
 
 of a succession or order of facts. To say that that shorten- muscular 
 ing is the direct consequence of loss of material involves us waste * 
 at once in the inquiry whether it be possible, through the destruction of 
 so small an amount of material as we know to occur, that any thing like 
 the required extent of motion could be produced. Could a muscle be 
 made to shorten several inches, and, upon these principles, lose only an 
 insignificant amount of weight, the shortening being nevertheless the 
 consequence of that loss of weight or destruction of substance ? To an- 
 swer this inquiry, we have, in the first place, to recall the fact that a 
 whole muscle is never in contraction at once, but only an insignificant 
 portion thereof, one bundle of fibrils after another taking up the action in 
 succession, and each particular fibril undergoing change, not throughout 
 its whole length, but only in isolated portions here and there. We have, 
 moreover, to recall the insignificant weight of these fibrils, for a simple 
 computation will show that thirty thousand of them a foot long weigh 
 only a single grain. To these recollections we should add the intense 
 energy of the molecular force of attraction, as displayed at such distances 
 as those which we have here under consideration distances which we 
 may regard as being virtually inappreciable, and these recollections place 
 the problem in its true light, and set it in its proper attitude before us. 
 
 For it is capable of demonstration that muscular contraction ensues as 
 the direct consequence of destruction of muscular substance, and that a 
 great linear extent of movement may be accomplished by the removal of 
 an insignificant amount of substance. If 100,000 fibrils lost one third 
 of their entire substance -a thing which, of course, could scarcely take 
 place the diminution of weight would only amount to a single grain. 
 Our conception of this action may perhaps be rendered clearer by an il- 
 lustration. If we had an iron thread of excessive tenuity, illustration of 
 composed, for instance, of a single row of iron atoms set end ofa^usTte^ 
 to end, and could, by suitable processes, effect the removal, fibre. 
 here and there, of atoms in the line, an instantaneous contraction would 
 be the result, the thread shortening in proportion to the number of atoms 
 removed, but shortening with an energy commensurate with the cohesive 
 force of the iron itself, and yet ready to return to its original length the 
 moment that fresh iron atoms present themselves to be introduced in the 
 place of the abstracted ones ; and so with muscular fibre, the molecular 
 force of cohesion developed here and there by the removal of tissue is to 
 be measured only by the cohesion of the fibre, though the loss of mate- 
 rial which may have been the cause of that force coming into play may 
 be very small indeed; nor does the quickness of relaxation present any 
 
 FF 
 
450 VOLUME OF CONTEACTING MUSCLE. 
 
 difficulty when we consider the rapidity with which interstitial nutrition 
 takes place, and the small quantity of matter to be supplied. 
 
 We have now analyzed the phenomenon of muscular contraction, and 
 set forth the conditions on which it depends. These we may 
 ment of this here reproduce together for the more distinct continuation of 
 doctrine. ^ Q ar g umen t. The primary act is the destruction of the 
 muscular material by the agency of arterial blood; an incipient oxidation 
 setting in, the wasting particles can no longer retain the places they have 
 occupied. They have lost their hold on the particles with which they 
 were associated. At that instant molecular attraction comes into play, 
 and shortening of the fibre is the result. The wasted material is already 
 being absorbed by the venous capillaries, and already repair is taking 
 place by the introduction of new fibrinous material from the arterial 
 blood; but the renewal or repair proceeds much more slowly than the 
 removal of the waste ; the latter effect, as might be inferred from what 
 has been said under the head of absorption, occurs almost instantly, the 
 former gradually; and thus muscular contraction presents itself as a 
 composite result, depending, under normal circumstances, partly on oxi- 
 dation, partly on removal of waste, partly on repair by nutrition, yet so 
 that if any one of these conditions be interfered with it can not take place 
 at aU. 
 
 I can not at this point avoid offering a criticism on the experiments 
 Volume of a ^7 which it has been attempted to prove that a muscle, when 
 
 muscle after it contracts, loses none of its bulk ; the loss that does in real- 
 contraction. .. ., . . , , 
 
 ity occur is, it is true, very minute, perhaps so minute that, in 
 
 the coarse apparatus which has been resorted to in these experiments, it 
 Fig. 229. . would be altogether inappreciable. Such a contrivance is 
 represented in Fig. 229, in which <z, a is a wide tube for 
 containing the muscle, g; it is also to be filled with water, 
 and from its side a narrow tube, d, projects, the water 
 reaching to some such point as e. The tube, a, a, being 
 closed at both its extremities water-tight by means of corks, 
 #, <?, whenever the muscle is made to contract by an elec- 
 tric current, applied by means of the spring wires, /", f, or 
 otherwise, if enlargement occurred the water would rise at 
 0, and if diminution it would descend ; but as, upon trial, 
 it is found that no movement whatever takes place, it has 
 been inferred that the volume of the muscle remains un- 
 changed. But no compensation whatever for temperature 
 is provided ! Yet it is positively known that when a mus- 
 cle contracts it becomes warm, and, doubtless, these in- 
 
 Volume of contract- J -/.-IT -, i i -i ^ -i , , i 
 
 * ing muscle. struments, if delicate enough, would have led to the pre- 
 posterous conclusion that a muscle after contraction is larger than it was 
 
CONTRACTION BY WATER. 451 
 
 before. But, even setting disturbances of temperature aside, such ex- 
 periments are of no kind of value, since they contain no provision for the 
 removal of the wasted material of the muscle, which still continues a part 
 thereof, though it has become, to all intents and purposes, extraneous, 
 and would, if in the living system, have been instantly removed by the 
 veins. 
 
 And now, by the aid of these doctrines, we may comprehend the full 
 significance of those conditions, which have been long known 
 to physiologists, which have cast such a mystery over muscu- of partial hy- 
 lar contraction, and led to such a diversity of views as re- P theses - + 
 spects its true explanation. We see that they were right who asserted 
 that muscular contraction is a function of nutrition, though they were 
 wrong in saying that it is therefore of a vital, and consequently of an 
 inexplicable nature. They, too, were right who asserted that muscular 
 contraction depends on respiration, and that the higher the rate of that 
 function the more energetic the muscular power will be. They, too, were 
 right who asserted that muscular contraction is manifested by a waste 
 of tissue, and that that waste may be measured, if certain corrections are 
 applied, by the quantity of urea and sulphuric acid in the urine. They, 
 too, were right who asserted that there is a connection between the co- 
 agulability of the blood and the energy of muscular contraction in the 
 various tribes of life, for the speed of repair depends on the percentage 
 of fibrin in the blood, and so, too, does the speed of coagulation. They, 
 too, were right who asserted the connection between muscular contrac- 
 tion and the speed or slowness of the circulation of the blood. All these, 
 and many other partial hypotheses, are the necessary consequences of the 
 more general doctrine, that muscular contraction is the result of loss of 
 muscular substance. 
 
 There remains a phenomenon to which our attention has to be direct- 
 ed in the conclusion of this subject. It is the contractions _ t 
 
 . . . -,-, nil- -i. r Contraction 
 
 which may be observed under the microscope when a lascicu- produced by 
 lus is submitted to water. These contractions commence in water ' 
 isolated places, from which they spread in all directions, and so move 
 about from end to end, often interfering with one another, the fasciculus 
 thickening where the contraction is greatest, and eventually the whole 
 length becoming involved. The ultimate degree of contraction that can 
 be reached reduces the fasciculus to one third of its original length. With 
 this contraction, through the agency of water or other such liquids, we 
 may connect those contractions which ensue under the pressure or dis- 
 turbance of some hard body, as by the touch of a pin. 
 
 From these cases it might be supposed that muscular contractility can 
 take place independently of chemical destruction, but a more critical ex- 
 amination of them will satisfy us that they ensue as the natural conse- 
 
452 RIGOR MORTIS. 
 
 quences of the preceding views. They are not to be regarded as pure or 
 uncomplicated manifestations of the qualities of muscular fibre itself, but 
 as the consequences of the impression that has been made upon it by the 
 treatment through which it has passed. The preparation of a fasciculus 
 can not be made without cutting or rending the parts, mutilating the 
 nerves of supply, and totally destroying the functions of the arteries and 
 veins. In the act of exsecting such a fasciculus, the disturbance im- 
 pressed upon it, however great it may be, is never fully answered to by 
 the due amount of contraction ; for with the destruction of the vascular 
 mechanism there are no means of removing the products of waste, and con- 
 traction can not go on to its full completion, but in this condition the 
 fasciculus, placed in water, gradually gives up here and there the prod- 
 ucts of waste, and with their removal the opportunity arises for the re- 
 maining muscular elements to approach one another, and, finally, com- 
 plete contraction ensues ; a contraction not due to the immediate action 
 of the water, but to the change impressed upon the fasciculus by the op- 
 eration for its exsection. 
 
 So as regards disturbance by the touch of foreign bodies, we might 
 Contraction recall those numerous instances known in chemistry, in which 
 by touch, decompositions or other mechanical results are brought about 
 in a similar way. The different compounds which undergo explosive de- 
 composition by the lightest friction might furnish us with illustrations ; 
 but, in this instance, the effect is more purely mechanical, and arises from 
 the forced equilibrium into which the fasciculus has fallen by the act of 
 exsecting it being more or less perfectly overcome. The elements of a 
 part of a fasciculus are brought by that touch within a nearer range of 
 one another, the products of waste which had failed to escape because of 
 the destruction of the absorbent function of the veins are pressed aside, 
 one motion gives rise to another, a worm-like action spreads here and 
 there irregularly through the length, and ends in a final contraction.* 
 
 Connected with the phenomena described in the preceding paragraph 
 is that general rigidity of the muscles which occurs a certain 
 
 Rigor mortis. . -, , , 
 
 time after death, and hence known as rigor mortis. This 
 usually commences in the lower jaw and neck, invading next the upper 
 extremities, and reaching eventually the lower ones. After continuing 
 for a period longer in proportion to the lateness of its beginning, relaxa- 
 tion ensues, the parts being affected in the same order as they were made 
 rigid. The rigor mortis sometimes begins as soon as ten minutes after 
 death, sometimes it is postponed as long as seven hours. In those who 
 have died of chronic diseases it occurs and ceases very quickly. Both 
 classes of muscles, striped and unstriped, are affected by it, and when it 
 is over they present an unresisting and lax condition, and putrefactive 
 change presently sets in. Even after cadaveric rigidity has been as- 
 
OF STANDING AND WALKING. 453 
 
 sumed, the contractile power of muscles may be restored by furnishing 
 them, through a suitable arrangement, arterial blood; for this fact we 
 are indebted to Dr. Brown- Sequard, his experiments having been made 
 both upon man and animals. The arterial blood employed assumed, 
 during its passage through the limb which was the subject of the trial, 
 the venous character, and issued of a dark color. This restoration of 
 contractility was by no means imperfect or transient ; in one instance it 
 continued for two hours. 
 
 By means of tendon the muscles are attached to the skeleton, which 
 constitutes the solid framework of the system. Operating Connection of 
 thus through the skeleton, the muscles are enabled to keep muscle for lo- 
 the entire body in the erect or standing position, and also to 
 give it locomotion. The conditions of standing and locomotion have been 
 well studied by the brothers Weber, the following being a brief synopsis 
 of their statements. 
 
 In man, the power of standing implies the conservation of the line of 
 direction of the whole body within the narrow basis covered by 
 
 mi i i i Of standing. 
 
 the feet and between them. The head is balanced on the at- 
 las so nearly under its centre of gravity that no ligamentum nuchse is 
 required, as in the case of other animals, to prevent it from falling for- 
 ward. Nevertheless, a forward motion can be executed, amounting to 
 about 75 degrees from the perpendicular, and a lateral motion right and 
 left of from 45 to 50 degrees. In standing, the weight of the entire body 
 is transmitted perpendicularly to the feet. These rest on the heel and 
 the. fore ends of the metatarsal bones, especially of the great and little 
 toes, and on the points of the toes. The general centre of gravity of the 
 entire body is a little above the transverse axis connecting the heads 
 of the thigh bones, and for equilibrium to be maintained, a perpendicular 
 line drawn from this centre must always fall within the basis inclosed by 
 the contour of the feet. 
 
 Even in the most perfect condition of rest that we can assume while 
 maintaining the standing position, a great many separate muscular acts 
 are necessarily required. Apart from those little voluntary changes 
 which are incessantly occurring, the rhythmic action of the muscles in- 
 volved in respiration, especially those of the abdominal walls, is perpet- 
 ually changing the position of the centre of gravity, and therefore those 
 muscles which are employed in keeping the spine erect are obliged to 
 assume an antagonizing rhythmic action. This is at once the reason of 
 the fatigue we experience in long standing, and of the difficulty which 
 infants encounter in their, attempts to maintain the erect position. 
 
 In walking, the legs act like a pair of pendulums. The head of the 
 thigh bone, which is their centre of motion, is held in its sock- 
 et, not by muscular exertion, nor by its ligamentous arrange- 
 
454 OF. RUNNING. 
 
 
 merits, but by the pressure of the air, a fact that may be proved by very 
 simple experiments. If the pressure of the air be removed, as in an ex- 
 hausted receiver, spontaneous dislocation ensues. The trunk of the body 
 is like a rod balanced on an axis passing through the hip joints, and ad- 
 vancing with the movement of the legs like a rod balanced on the tip of 
 the finger. It is inclined forward or backward in correspondence with 
 the motion or with the resistance of the wind ; if the wind blows in front, 
 we lean forward; if behind, we lean backward; the angle of inclination be- 
 ing in proportion to its force. In walking there are two distinct periods : 
 the body is first poised on one of the limbs, and then rests for a moment 
 on both. The advancing limb swings like a pendulum, bending at the 
 knee so as to be shortened one ninth ; the other straightening at the knee 
 and hip joint, and so pushing the pelvis and trunk forward to be received 
 on the limb that has just advanced. It is only in slow walking that the 
 whole arc of motion is swung through, the time occupied being two thirds 
 of a second. In quick walking and running only half a vibration is ac- 
 complished, and this in half a second of time. In slow walking each foot 
 rests upon the ground one third of a second. The longest step made is 
 half the entire span of the two extremities. To prevent swaying from 
 side to side, the arms swing with the legs. 
 
 In running there is a moment when both feet are off the ground at 
 once, and the body actually projected into the air. In walk- 
 '' ing there is a moment when both feet are on the ground to- 
 gether, the one not being raised till the other is planted. In running the 
 steps are, on an average, twice as long as in walking ; and the number 
 of steps made in a given time in running and walking respectively is as 
 3 to 2. 
 
HUMAI PHYSIOLOGY. 
 
 BOOK SECOND. 
 
 DYNAMICAL PHYSIOLOGY. 
 
 COURSE OF LIFE. 
 
 CHAPTER I. 
 
 OF THE PRINCIPLE OF ORGANIZATION, OR PLASTIC POWER. 
 
 Remarks on the Subdivision of Physiology. 
 
 Career of an Organic Form. Three Modes of Development. 
 
 Inquiry respecting the special Principle of Organization. Illustration from the Growth of a Plant 
 in Darkness and Light. Inference respecting Plastic Power : its Nature and Properties. 
 Of the ordinary Growth of a Plant, and the Sources from which its Materials are derived. 
 
 Relation of all Organisms to each other. 
 
 Correction of the Doctrine of a Plastic Power, from Considerations regarding the Individuality 
 of a Plant. Plants are Operations, not Individuals. Physical Illustration of this View. 
 
 Conclusion respecting the Nature of the Plastic Power : that it is a continued Manifestation of an 
 
 REGARDING physiology as a branch of natural philosophy, I have been 
 led in this work to introduce the methods of considering it Divisions of 
 which are familiar to writers on mechanics ; for, as there are physiology, 
 two distinct divisions of that subject, according as we treat of the equi- 
 librium or the motion of inorganic bodies, so likewise there must be in 
 physiology a statical and dynamical branch, the one including the con- 
 ditions of equilibrium of an organized form, the other those of its devel- 
 opment development being no more than its motion. 
 
 If we establish this subdivision in physiology, similar advantages will 
 doubtless be obtained for this science as those which so Advantages of 
 quickly accrued to mechanics after Galileo had formally in- this division. 
 troduced the same partition therein. Moreover, in this case there are 
 collateral reasons not applying to that. Whatever may be the views 
 which the advance of science causes us to take of the various functions 
 maintaining a living animal in its normal state whatever may b the 
 
456 CAREER OF AN ORGANIC FORM. 
 
 general conception we entertain of the nature of its equilibrium, it is 
 scarcely possible to present the subject in a manner that will coincide 
 with the diversified views of the profession. It is almost exclusively 
 with statical physiology that the physician has to deal. The healthy 
 and diseased states of the apparatus for digestion, absorption, respira- 
 tion, circulation, innervation, etc., are the things with which he is con- 
 cerned. It is respecting these that his mind is filled with the early prej- 
 udices of his education, and that his social necessities compel him to ex- 
 press with decision opinions unsuited to a close philosophical examina- 
 tion. He is to be pardoned for the mystification which circumstances 
 oblige him to cast upon the subjects of his study ; for resorting to the 
 vital principle as an explanation of his difficulties ; and for throwing upon 
 the nervous system the burden of every thing for which the imperfect 
 state of physiology does not enable him to account. He is not to be 
 blamed that the circumstances under which he is placed compel him to 
 appear to know more socially than he actually does know philosophically ; 
 and where, under such a false position of things, men have been spend- 
 ing their lives, it is not at all extraordinary that they should resist any 
 attempt at a reformation which strikes at the very existence of the doc- 
 trines they have adopted, and to which they stand committed. The old 
 physician must have his vital principle and his nervous agent, or he 
 must begin the alphabet of his studies again. If, therefore, statical phys- 
 iology stood alone, it must depend for its progress in the gradual removal 
 of error and introduction of truth upon one generation of physicians suc- 
 ceeding another ; but, fortunately, there is a circumstance which aids it 
 in this march, for the great branch on which we are now entering pre- 
 sents connections and considerations of a more purely philosophical kind; 
 free, at all events, from the entanglements of professional interests. Ca- 
 pable of being treated in the rigid manner of the positive sciences, and re- 
 moved, by reason of the nature of the topics with which it is concerned, 
 from the strifes of medical sectarianism, this noble subject can develop 
 itself in silence, without disturbance and without restraint ; and yet such 
 an advance can not take place without compelling a reflected effect to 
 ensue in statical physiology, and hastening the time when, by the united 
 consent of all physicians, it, too, will be cleared from every mystification, 
 and brought within the pale of exact and positive science. 
 
 In the preceding book we have investigated the conditions of the 
 Career of an or- equilibrium of the animal mechanism: in this, therefore, we 
 game form. have ^ Q ftQ&i of its motion or career. Indeed, we might gen- 
 eralize our expression, and include the vegetable along with the animal, 
 for the two are so inseparably connected that we can not speak of the 
 one without, at the same time, dealing with the other. Viewed as re- 
 spects, its motion or career, an organism presents us with the striking 
 
GEOMETRICAL MODES OF DEVELOPMENT. 457 
 
 fact that it passes through a definite series of changes. Commencing at 
 first as a simple cell, to which what might be termed a momentum of de- 
 velopment has been imparted, it assumes one form after another in suc- 
 cession, but is ever ready, like the moving bodies of mechanics, to obey 
 the impulses which extraneous forces may impress upon it. Properly 
 speaking, we can never say of an organized being that it is in a condi- 
 tion of rest. In truth, it is always in motion. It has a past and a fu- 
 ture coming from one state and going to another ; and though, to use 
 the language of mechanics, the inertia that it has at any moment must 
 tend to continue it in the state at which it is then found, since it varies 
 by degrees from one condition to another, we are obliged to look upon it 
 in these variations just as we should upon an inorganic mass under sim- 
 ilar circumstances, and, guided by the incontrovertible law of physics, 
 that (jyery change of motion is to be attributed to the influence of a force, 
 we must impute its passage from state to state to the intervention of a 
 like agency. In this respect, the career of an organic combination, in its 
 two conditions of maintaining for a time a similarity or passing through 
 metamorphoses, presents a general analogy to the uniform rectilinear, and 
 to the varied motion of mechanics. 
 
 As we have just remarked, the most elementary organic combination 
 appears to be a simple cell. This, under circumstances Tllree 
 which we shall presently consider, may pass into develop- rical modes of 
 ment by multiplication in three different ways, geometrical- 
 ly distinct. Its development may be in one, two, or three dimensions 
 linear, superficial, or solid. As illustrations may be offered the proto- 
 coccus, which is a simple cell ; the linear conferva?, consisting of a row 
 of cells which perpetually undergo terminal extension, the line becoming 
 longer and longer as development of new cells at the end goes on ; the 
 ulvas, in which increase takes place simultaneously in length and breadth ; 
 and any of the higher forms, which grow simultaneously in length, 
 breadth, and thickness. Whatever the manner of development may be, 
 or whatever the condition presented as the combination passes from 
 phase to phase, no doubt can be entertained that it takes place in conse- 
 quence of the agency of forces which are acting under definite laws ; and 
 though, even in the case of organisms low in the series, a geometrical 
 definition of their form is impossible, this is because of the imperfection 
 of our knowledge, and is no kind of indication that there has been any 
 irregularity or wantonness of play in the forces at work. 
 
 Asserting thus in the broadest manner the influence of physical forces 
 over development, and seeing that dynamical physiology must i nqu i ry into 
 be committed to those conditions, and those alone, which are the existence 
 universally recognized in positive science, I shall proceed, in priLlpJe'of 
 this chapter, to set forth the views we entertain respecting the r s aniz ation. 
 
458 GERMINATION OF A SEED. 
 
 existence and nature of a special principle of organization. The conclu- 
 sions at which we shall arrive, though apparently very different from 
 what we might have expected, are the necessary consequences of the 
 physical doctrine. 
 
 It may, perhaps, aid the reader if I give, at the outset, a synopsis of 
 Outline of the ^ e argument. Selecting as a general illustration the famil- 
 argument. ia r case O f the germination of a seed and the growth of a 
 plant, we shall investigate the results of growth, in light and darkness, 
 with their attendant phenomena. From this we shall draw apparent ev- 
 idence of the existence of a special principle of organization, or plastic 
 power, and ascertain, in a general way, its functions ; but, from an ex- 
 amination of the attitude in which the resulting organism stands, as re- 
 spects its individuality, we shall learn to correct that view, and reach the 
 final conclusion that that plastic power is not an agent, but a condition 
 of things, the result or the manifestation of antecedent physical influ- 
 ences. 
 
 Every living being springs from a germ. The animal and vegetable 
 Primordial kingdoms present us with numberless forms, differing from one 
 cel1 - another in aspect, in construction, and in function ; but the or- 
 
 igin of all is the same a cell or vesicle, which, under the influence of 
 external circumstances, develops into a determinate shape. 
 
 A seed may be kept in a dry place for many years without undergo- 
 ing any visible change, or losing its power of germination. It may be 
 exposed to all the annual variations of temperature occurring in the dif- 
 ferent seasons ; it may have the free access of atmospheric air. Its vi- 
 tality is dormant ; there is no attempt at evolving its parts. 
 
 But if some water be supplied, and a certain degree of dampness be 
 Germination thereby communicated, the seed does not fail, as soon as the 
 of a seed. temperature reaches that of a summer's day, to germinate. 
 Under the influence of air, heat, and moisture, the embryo consumes the 
 nourishment stored up for it in the seed, a gradual unfolding of its parts 
 ensues, a root is put forth, a stem rises from the ground, and leaves 
 make their appearance : so heat, air, and water have enabled the seed to 
 become a plant. 
 
 These physical agents are not, however, sufficient to carry the growth 
 Effects of sun- forward to its full extent. Another is essential : it is light ; 
 light. f or if g row th be conducted in darkness, heat, air, and water 
 
 can not cause the young plant to add any thing to its substance. It is 
 feeding on the seed. Indeed, when the experiment is carefully made, it 
 is found that there is an actual loss of substance, the resulting plant, if 
 dried, weighing less then than the dry seed from which it came. 
 
CONSUMPTION OF LIGHT BY PLANTS. 459 
 
 In a dark place, then, it is possible for a seed to grow, but it grows in 
 a certain way, and only to a certain extent. Its stem and its leaves are 
 of a sickly yellowish hue: exposure to the sunshine soon produces a 
 green color in these parts, and the weight of the plant increases. Growth 
 in darkness leads to one result, and growth in the sunshine to another. 
 
 From these facts it therefore might appear, from a superficial considx 
 eration of the thing, that the development of a plant depends p art i a i infer- 
 on two distinct conditions an innate power which resides ence respecting 
 
 -T 1,1 ,- P-I.-I-I T the existence 
 
 in the germ, by the action of which the matters previously ofapiastio 
 stored up in the- seed by the parent plant are regrouped, and P wer - 
 so arranged as to constitute a new organization ; but this power does not 
 extend tg the obtaining of new material; it is only a power of arrange- 
 ment a PLASTIC POWER. Whatever new material is required must be 
 furnished by a totally distinct agency, the sunlight; and just as the 
 plastic power can not collect, the sunlight can not arrange. Each has 
 its own sphere of duty. The one gives the substance, the other 
 moulds it. 
 
 Every flowering plant, no matter how humble it may be, is, then, a rep- 
 resentative of the action of these double influences, and, when Consumption 
 properly considered, may well extend the views we ought to yegetabie* 
 entertain of the system of nature. The supplying or furnish- development, 
 ing agent, the light, comes from a star which is at a distance of almost a 
 hundred millions of miles, and is the pivot of all the planetary motions. 
 Without this extraneous, this foreign force, the whole surface of the earth 
 would be a desolate waste, presenting no semblance of life. The leaf, 
 the flower, the bud, the stem, the root, are all made of substance that has 
 been given by the sun, derived, it is true, from one of the constituents 
 of the air, but forced to take on the special state which suits the needs 
 of the plastic power by that distant agent ; and, in order for this to oc- 
 cur, it is plain, from mechanical considerations, that there must have been 
 an expenditure of power, or of the acting principle itself, for light can 
 not produce these effects without losing its own peculiar form. For the 
 decomposition of a given weight of carbonic acid, and the formation of a 
 given weight of gum, a fixed and invariable quantity of light is required ; 
 just as it is necessary, in moving a mass of a certain weight, to expend an 
 equivalent and definite 'force. So the substance of which plant-organs 
 consist has been brought into an available state by the consumption of 
 a definite quantity of light perhaps its incorporation, under some other 
 form, in the resulting mass. It may be pent up and imprisoned in the 
 organic structure for any imaginable time, even for centuries, but is ever 
 ready to resume its primitive state when favorable circumstances exist. 
 The coal-fields which furnish us with fuel are the remains of primeval 
 forests which grew in the ultra-tropical climate of the secondary times, 
 
460 NATURE OF THE PLASTIC POWER. 
 
 and the light and heat we derive from them are the same that came from 
 the sun in those ancient days. 
 
 If, then, our earth does not possess in herself the power of sustaining 
 is the plastic tne varied forms of vegetable life, but borrows it from an ex- 
 power a uni- traneous source ; if light, in producing these effects, never 
 fiSagenV undergoes destruction, but only modifies its state for nei- 
 like the ether? her force nor matter can be annihilated, though they may be 
 changed what shall we say of the plastic power which we have thus 
 assumed to reside in the germ, the co-worker with the luminous agent ? 
 Does their partnership in action indicate a resemblance in position or na- 
 ture ? If the one consists of motion arising in an ethereal, intangible, and 
 weightless medium, diffused throughout the universe, may we, suppose 
 that the other is the manifestation of a similarly diffused principle? 
 There is no necessity, as many have thought, to impute to the first-crea- 
 ted germ a formative power for all its successors, as though whatever 
 force or qualities they possess were originally concentrated and included 
 in it. It is possible that countless millions of organic beings may have 
 originated from one primordial germ, just as we see an extensive confla- 
 gration originating from a single spark. 
 
 That such a plastic principle exists has long been admitted by philos- 
 ophers, both speculative and experimental. It is a doctrine which seems 
 to have arisen in the infancy of human knowledge, and is to be met with 
 in almost all the old Asiatic and European systems. The archeus and 
 soul of the world of the alchemists were only the reproduction of a very 
 ancient idea. The term " vital spark" was once something more than 
 a mere metaphorical expression ; and, indeed, there is a classic* noble- 
 ness in the thought which recognizes a universal spirit diffused every 
 where. In different countries and by different authors, the nature and 
 function of this principle are variously represented ; imperfect concep- 
 tions of what is so significantly but briefly set forth in the opening words 
 of the Sacred Scriptures, which plainly recognize the true conditions un- 
 der which all vegetable organisms, arose formless matter, the sunlight, 
 and a brooding spirit. 
 
 I shall continue to speak of this principle under the designation of the 
 plastic power, because that expression points out aptly the function dis- 
 charged, and to assume that all those organisms which possess the qual- 
 ity of converting inorganic bodies into organic structures do so under the 
 double influence of light and of this interior principle. This, of course, 
 
 Principio coelum ac terras camposque liquentes, 
 
 Lucentemque globum Lunaa, Titaniaque astra, 
 
 Spiritus intus alit, totamque infusa per artus 
 
 Mens agitat molem, et magho se corpore miscet. 
 
 Inde hominum pecudumque genus vitseque volantum, 
 
 Et quae marmoreo fert monstra sub aequore pontus. VIRG. JEN., 1 vi , 724. 
 
ACTION OF DIFFERENT RAYS. 461 
 
 includes nearly all vegetable forms, for we may leave out of considera- 
 tion the fungi, a group which stands intermediately between plants and 
 animals. The distinctive character of a plant is to form, from carbonic 
 acid of the air, solid organic structures. The distinctive character of an 
 animal is, by the oxidizing processes going on in it, to restore the or- 
 ganic bodies which have served it as food to their original formless state. 
 The group referred to differs from true plants in feeding on matter al- 
 ready organized, and breathing like animals. It therefore does not re- 
 quire the influence of light to collect material for it, and bring it to the 
 proper state. In the development of this group the plastic principle is 
 alone concerned. 
 
 Since the sunlight is composed of many differently colored rays and 
 different principles, it becomes an interesting inquiry which Powe * of dif 
 of these is the immediate agent in ministering to the nutri- ferent colored 
 tion of plants. In 1843, by causing plants to effect the de- ra y sofli s ht - 
 composition of carbonic acid in the prismatic spectrum, I found that the 
 yellow is by far the most effective, the relative power of the various col- 
 ors being as follows : 
 
 Yellow, Blue, 
 
 Green, Indigo, 
 
 Orange, Violet. 
 Bed, 
 
 My experiments on the production of hydrochloric acid by the direct 
 union of chlorine and hydrogen under the influence of light, Phenomena of 
 both artificial and solar, and also on the decomposition of ihe action of 
 pe'roxalate of iron, from which carbonic acid is readily disen- growth of & 
 gaged, conclusively establish the fact that the primary con- P lants - 
 dition essential for the chemical action of light is the absorption of some 
 particular ray. If the physical condition of substances otherwise easily 
 decomposable is such that they transmit light without absorbing any, no 
 chemical change ever ensues in them, and the same condition obtains in 
 cases of combination. Thus oxygen and hydrogen can not be made to 
 unite, even by the most intense radiation, because neither of them ex- 
 ert any absorptive action ; but chlorine and hydrogen unite with energy, 
 because the chlorine absorbs the indigo ray. 
 
 The same experiments prove that the amount of decomposition or oth- 
 er work done by light is always proportional to its quantity ; hence, by 
 the aid of converging mirrors and lenses, chemical changes can be ac- 
 complished with great rapidity. These instruments, however, when even 
 of the largest size, are unable to produce any other effect than would be 
 brought about by a feebler ray if applied sufficiently long. The great- 
 ly increased intensity of light which they can present does not enable us 
 either to bring about combinations or decompositions of substances which 
 
462 PLANTS LIBERATE OXYGEN. 
 
 are unacted upon by rays of a more moderate brilliancy, for the general 
 rule under which the chemical action of light occurs is, the amount of 
 chemical change is as the quantity of light absorbed. 
 
 These facts are of importance in all discussions respecting the prim- 
 itive formation of organic matter by plants. Guided by them, we infer 
 that, though vegetation may greatly differ in its luxuriance in different 
 climates of the globe, the manner of action of the light is always the 
 same. Nothing is gained under the brilliancy of the tropical skies be- 
 yond a shortening of the time required for the accomplishment of a given 
 amount of work. No substances are there decomposed, even in the or- 
 ganisms of plants, which could not equally well be decomposed by the 
 feebler light of more temperate climates, only in these it would demand 
 more time. The oils and other substances, almost or quite free from 
 oxygen, which abound in the plants of the torrid zone, are not excep- 
 tions to, but illustrations of, the doctrine here set forth. 
 
 It is proper here to correct the statement which is usually made by 
 it is not the vegetable physiologists, that the decomposition of carbonic 
 green parts of ac i(j fty plants is accomplished by their srreen parts. A 
 
 plants which J , * j j I.- i. t, 
 
 decompose car- plant which has been etiolated, or, indeed, one which has 
 bonic acid. been raised from a seed in total darkness, when brought into 
 the sunshine, decomposes carbonic acid, liberates oxygen, and its pale 
 and sickly leaves presently turn green. This, therefore, demonstrates 
 that the green portions are not the seat nor the origin of the decomposi- 
 tion, but are, properly speaking, its effect. 
 
 Thus, under the influence of sunshine, the leaves of plants decompose 
 Plants liberate carbonic acid, liberate its oxygen, which, for the most part, 
 oxygen. escapes into the atmosphere, the amount of gas decomposed 
 
 depending primarily on the quantity of light supplied, and therefore, 
 among other conditions, on the surface of exposure of the leaves, and 
 not upon their thickness or' mass. But I found, on an examination of 
 the gas thus evolved, that it is never pure oxygen, but always contains 
 a certain though variable proportion of nitrogen. From this it follows 
 that a part of the oxygen appertaining to the carbonic acid is appropri- 
 ated for the uses of the plant. 
 
 Such, in a general way, is what takes place in the daytime, but at 
 night the process is to a certain degree inverted, a plant absorbing oxy- 
 gen from the air, and yielding carbonic acid. The explanation which 
 Liebig offers of this state of things is doubtless correct, that the evolu- 
 tion of carbonic acid is a purely physical process, and the absorption of 
 oxygen due to the chemical action of the various deoxidized bodies 
 which have been accumulating during the day. 
 
 As respects the sources from which the various constituents of the 
 plant organism are derived, they are sufficiently obvious. The carbon 
 
SOURCES OF THE CONSTITUENTS OF PLANTS. 463 
 
 may doubtless be entirely attributed to carbonic acid, ob- s ources f rom 
 tained either directly from the atmosphere or furnished by which the con- 
 the gradual decay of humus in the soil. For the hydrogen plant" are de- 
 a double source may be assigned water and ammonia. rived - Ofcar- 
 The abundant occurrence of resins, oils, fats, in which this 
 
 element preponderates, conclusively establishes the fact that 
 the supply of ammonia, as indicated by the nitrogenized compounds' 
 which have been formed, is insufficient to account for the quantity of hy- 
 drogen, and for which there would appear no other source than water ; 
 and though the most brilliant light, even though concentrated by a pow- 
 erful burning-glass, can not alone eifect the decomposition of this liquid, 
 there will be no difficulty in admitting that such a decomposition does 
 take place, when we recall that carbon is being presented in what might 
 be termed its nascent state. 
 
 Of the nitrogen necessary for the formation of the protein bodies of 
 plants, it is generally concluded that ammonia is the only 
 source, and that these organisms do not directly obtain that 
 element from the atmospheric air; moreover, it occurs apparently to a 
 sufficient extent in their sap, having been introduced by absorption 
 through the roots. As essential to the production of the same group 
 of bodies, the protein substances, both sulphur and phosphorus are in- 
 troduced through the same channel, from the soil, as sul- of sulphur and 
 phates and phosphates, which undergo decomposition and phosphorus. 
 deoxidation within the organism, so as to yield the sulphur and phos- 
 phorus in an unoxidized state. 
 
 We can not overlook the saline substances, or mineral bodies, which 
 occur in different parts of plants, and which obviously are of saline sub- 
 absolutely essential to their constitution. The circumstance stances. 
 that, in any given plant, they are found fixed in their nature, definite in 
 their quantity, and deposited in determinate regions, is sufficient to es- 
 tablish that conclusion. As is very well known, we can not judge of 
 their nature or condition during the life of the plant from the aspect they 
 present when its ash is examined. Thus those which have been exist- 
 ing as neutral or acid salts of organic acids must appear in the ash as 
 carbonates ; and though it has been established that basic and mineral 
 substances generally will to some degree replace one another nay, that 
 even the plant itself, by generating vegetable alkaloids, may dispense 
 with bases of the mineral kind, the extent to which this can be carried 
 is as yet undetermined. The occurrence of sulphates and phosphates 
 in the leaves and seeds, and wherever organic activity has to be dis- 
 played, and protein bodies are found, is sufficient to establish a con- 
 nection between those substances and the neutral nitrogenized bodies, 
 though of the manner in which, from carbonic acid, water, ammoniaj 
 
464 ACTION OF PLANTS ON THE AIE. 
 
 sulphates, and phosphates, those bodies are formed, we are as yet alto- 
 gether ignorant. 
 
 By some chemists it has been supposed that the decomposition of car- 
 The decompo- bpnic acid by plants in the sunshine is not instantaneously 
 sition of car- complete, but that a gradual process of reduction takes place, 
 
 bonic acid is , , , , .,, i v,,! , -, 
 
 not partial, but the carbon losing by little and little its oxygen, but never, 
 total. perhaps, losing it all. My own experiments, previously al- 
 
 luded to, which show that the quantity of oxygen set free is never quite 
 equal to that of the carbonic acid consumed, have been used in support 
 of this view. But this, I think, is an interpretation which they will 
 scarcely bear. There are many facts connected with the chemical action 
 of light which might be cited as offering abundant proof that the decom- 
 position in question is, on the contrary, instantaneous and complete, and 
 in that I am led to believe really consists the primary function of the 
 light, the carbon thus obtained being subsequently employed in accom- 
 plishing the decomposition of water, and other processes of reduction 
 known to go on in the vegetable organism, but with which, under the 
 circumstances of the case, it is impossible that the sunlight should be di- 
 rectly concerned. I separate as distinct factors in the life of a plant 
 the obtaining of carbon from the air, which is accomplished by the influ- 
 ence of an external agent, and the moulding or modifying it with other 
 ingredients into organized material, which we have thus far imputed to a 
 plastic power in the plant itself, and respecting which more will be pres- 
 ently said. Free carbon once obtained, we- can easily conceive that all 
 other operations of reduction may follow, and that this division of the 
 action of plants into two distinct stages or factors, as we have just term- 
 ed them, is not a mere speculation, but represents what in reality occurs, 
 will perhaps be admitted on recalling what has been remarked on growth 
 in the sunshine and in darkness respectively. 
 
 As a summary of the action of vegetation on the air, it is on all hands 
 Summary of admitted that plants tend, by the removal of carbonic acid 
 SLfcforTthe therefrom and the return of oxygen thereto, to compensate for 
 atmosphere, the disturbance occasioned by animals, which is to the oppo- 
 site effect. In this way, through very many centuries, the same percent- 
 age constitution of the atmosphere is maintained, the sum total of veg- 
 etable being automatically adjusted to the sum total of animal life ; auto- 
 matically, and not by any interference of Providence ; for if we admit, 
 what has been conclusively established by direct experiment, that plants 
 would grow more luxuriantly in an atmosphere somewhat richer in car- 
 bonic acid than the existing one, we may see how upon this condition de- 
 pends a principle of conservation, which must forever retain the air at its 
 present constitution, no matter how animal life may vary. The proofs 
 that are sometimes offered that there has been no change in this respect 
 
CONDITIONS OF GROWTH. 465 
 
 for at least 2000 years, and which are drawn from an examination of the 
 aerial contents of vessels said to have been obtained from Pompeii or 
 Herculaneum, are of very little account. We have only to recollect how 
 easily diffusion takes place through crevices, and even almost invisible 
 pores. But there are proofs of a far higher order, and of a much more 
 general kind, which might be brought forward, if this were the proper 
 place, establishing beyond all possibility of contradiction the fact that in 
 a slow manner, through countless ages, the constitution of the atmosphere 
 has changed, and that now, through the operation of conditions which 
 have spontaneously arisen, it has come into a condition of apparent 
 equilibrium. 
 
 When, therefore, a seed is placed in the ground in the warm season of 
 the year, the germ it contains develops, and, after a few days, makes its 
 appearance as a young plant at the surface. If the growing structure is 
 examined during its passage through the soil, it presents a pale yellow- 
 ish aspect, which is exchanged for a bright green tint as soon as it 
 escapes from its confinement, and unfolds itself to the sunlight and the air. 
 
 From the first moment, until the green color is assumed, the young 
 plant is nourished, as we have seen, at the expense of the Infantile and 
 seed. In anticipation of this, the parent had laid up a stock adult life of 
 of nutritive material. On this the embryo draws, consuming P lant f- 
 a part in the support of its life, and incorporating the residue in its 
 structure ; but as soon as the surface of the soil is gained, this life of de- 
 pendence ends ; the plant weans itself, and, abandoning its temporary 
 support, commences to collect from the air and the earth tfie materials of 
 which it is to consist. Its infantile seed-life has closed ; its independ- 
 ent aerial life has begun. 
 
 In this aerial life, which is the mode of existence destined to continue 
 until absolute death occurs, the two essential conditions to g umma O f 
 which we have drawn attention are recognized. There must the conditions 
 be a steady supply of material for the building up of the grox 
 growing structures, and this has to be derived from external sources. 
 There must also be a capability of so grouping or moulding the material 
 thus acquired that the various parts that are wanted leaves or fruits, 
 flowers or thorns, may be made. 
 
 The manner in which these conditions are satisfied presents to a re- 
 flecting mind one of the most wonderful examples of the system of na- 
 ture. We have already shown that the power of moulding and group- 
 ing is inherent in the plant. In virtue of this, while it was yet in the 
 ground, and therefore in the dark, the germ could put up its stem and 
 fashion its imperfect leaves, but it did not possess any power to gather 
 nourishment beyond that which was stored up in the seed, and had that 
 stock been exhausted before it reached the surface, it must have died. 
 
 GG 
 
466 RELATION OF ORGANIC FORMS. 
 
 We have also shown that the supply of new material is always fur- 
 nished by the sun. In the absence of his rays the plant may organize, 
 but can not increase, and, indeed, it was to the influence of light that the 
 green color of the first leaflets was due. All the day long, and with the 
 more activity as the day is brighter, the leaves, which are the collecting 
 organs, are absorbing material from the air ; they cease to do it at night. 
 The sunbeam enables them to take from the air carbon, hydrogen, and 
 nitrogen. They feed by day and fast at night. 
 
 Astronomers say that the sun is the most sublime object the eye of 
 man can contemplate. They speak of his prodigious mass, and describe 
 how he compels the planets to move in obedient circles around him. To 
 the physiologist he is not less sublime. The most insignificant moss 
 that grows on the wall was called into existence by his heat, and is daily 
 fed by his light. The sunbeam is the finger of God. 
 
 The nutrition of plants is therefore dependent on physical causes. 
 The carbonic acid required being brought to them by aerial currents, oc- 
 casioned partly by the warming influence of the sun on their leaves and 
 partly by the winds, the tendency of gases to diffuse into one another 
 aids in producing the same result. In this manner, as they exhaust the 
 surrounding air, fresh quantities are supplied, the separation of carbon 
 from it being brought about by the agency of the yellow rays. The 
 leaves, also, sometimes follow the motion of the sun, or present themselves 
 in the most favorable position under the influence of the indigo rays. 
 
 The water requisite is obtained from the soil by the spongioles of the 
 roots. With *t there are carried into the interior of the plant the saline 
 and inorganic substances necessary for its structure. These, since they 
 are often of sparing solubility in water, will require large quantities of 
 that liquid to effect their introduction to a proper amount. During the 
 course of a summer there may pass through the system of the plant 
 perhaps many hundred times its weight of water a prodigious amount 
 when the phenomenon is considered on the great scale. 
 
 Cuvier speaks of the inferior organisms as furnishing us with a series 
 Relation of or ^ ex P er i ments made by the hand of Nature, an idea often 
 ganisms to quoted and often admired, but which is, perhaps, scarcely con- 
 each other. gistent with enlarged conceptions of the system of the world. 
 An organism, no matter how high or low, is not in an attitude of isola^ 
 tion. It is connected by intimate bonds with those above and those be- 
 neath. It is no product of an experimental attempt, which, either on the 
 part of Nature or otherwise, has ended in failure or only partial success. 
 
 The organic series an expression which is full of significance and full 
 of truth, for it implies the interconnection of all organic forms the or- 
 ganic series is not the result of numberless creative blunders, abortive at- 
 tempts, or freaks of Nature. It presents a far nobler aspect. Every 
 
RELATION OF ORGANIC FORMS. 467 
 
 member of it, even the humblest plant, is perfect in itself. From a com- 
 mon origin, a simple cell, all have arisen : there is no perceptible micro- 
 scopic difference between the primordial vesicle which is to produce the 
 lowest plant, and that which is to produce the highest ; but the one, un- 
 der the favoring circumstances to which it has been exposed, has contin- 
 ued in the march of development, the career of the other has been stop- 
 ped at an earlier point. The organic aspect at last assumed The forms of 
 is the strict representation of the physical agencies which have organization 
 
 , i TT j .0. * j i depend on 
 
 been at work. Had these for any reason varied, that varia- physical 
 tion would at once have been expressed in the resulting form, a s ents - 
 which is, therefore, actually a geometrical embodiment of the antecedent 
 physical conditions. For what reason is an offspring like its parent, 
 except that it has been exposed, during development, to the same condi- 
 tions as was its parent ? Comparative physiology is not a fortuitous col- 
 lection of experiments. Our -noblest conception of it is the conception 
 we have of analytical geometry, and, speaking in mathematical language, 
 each member of the organic series is an embodied result of a discussion 
 of the equation of life for one special case. Nay, I would present the 
 whole system of Nature as included in the same idea. The inorganic 
 and lifeless combinations which are all around us are,, to my mind, in 
 truth, in that equation of life, the analogues of the imaginary solutions of 
 the calculus. 
 
 It was a felicitous thought of Descartes that we may represent a geo- 
 metrical form in an algebraical equation, and, by the proper Illustration of 
 consideration and discussion of such an expression, determ- the relation of 
 ine and delineate all the peculiarities of such a form ; that here Jf? 8 
 it should become concave and there convex, here it should analytical ge- 
 run out to infinity, there have a cusp. The equation determ- 
 ines all the peculiarities of the form, and enables us to construct it. But 
 if the original conditions are inconsistent with one another, the construc- 
 tion can not be fulfilled, it having become impossible. In the same man- 
 ner are all living and lifeless forms related : an increase in the value of 
 one condition carries development forward in one direction, and increase 
 in the value of another condition determines development in another way, 
 and these variations give rise in their succession to the whole organic 
 series. But in these, as in the other case, if inconsistent conditions have 
 existed, their presence is indicated in the resulting solution, which can 
 not be constructed as an organic form, but is represented as a lifeless 
 mass. 
 
 "God ever geometrizes," ajid, it might be added, ever materializes. 
 Every organism is the result of the development of a vesicle under given 
 conditions, carried out into material execution. It is the incarnation, the 
 embodiment, the lasting register of physical influences ; for, if such Ian- 
 
468 NATUKE OF INDIVIDUALITY. 
 
 guage may be with propriety used, the consequences of the action of nat- 
 ural agents do not remain as a barren idea in the creative mind, but are 
 presented as a material and tangible result. 
 
 Such a mathematical conception of the relations of the various forms 
 around us obliterates at once the line of demarcation which natural his- 
 tory has thus far vainly attempted to define with correctness between 
 the organic and inorganic worlds. In the system of creation no such 
 boundary exists ; neither does one exist between the vegetable and ani- 
 mal groups. On every form, all existing influences have exerted their 
 sway: gravitation, heat, electricity; the result is the issue of their action. 
 The shape of any great mountain is thus the record of every thing that 
 has affected its mass since it was first uplifted. Its ancient peaks are 
 the register of every summer's sun, every frost, every falling rain, every 
 lightning stroke. It is what it is because of them ; and so also of the 
 lichen which unfolds itself on some favorable spot on the rock. "Would 
 it be there at all, or would it have the special aspect it presents, if there 
 was not a due proportion of sunshine, a proper supply of moisture, a 
 suitable temperature ? It is such conditions which have called it forth. 
 It is what it is because of them. In this respect, between the inorganic 
 and organic, there is no difference. 
 
 The preceding elementary examination of the circumstances under 
 Correction of which plants grow has led us to the inference that in their 
 _ f germ there resides a plastic power whose function it is to 
 model the organic matter, as it is furnished by the sunlight, 
 into definite shapes or organs. We now proceed to correct the concep- 
 tion we have thus formed, and to show that it is more philosophical to 
 decline the idea of an agent and to accept that of a condition. 
 
 Perhaps the most simple method of illustrating this idea is from con- 
 siderations connected with the individuality of the organisms which have 
 thus arisen. Directing their attention to plants', botanists have occupied 
 themselves in endeavoring to determine what is the attitude in which 
 Considerations they stand. They have tried to find out wherein the indi- 
 iSviduaiit he "^duality of a plant consists, for this question of individual- 
 of a plant. ity lies truly at the basis of the position which those struc- 
 tures occupy. There are oaks that have lasted a thousand years, but are 
 they to be regarded as individuals that are a thousand years old ? Is 
 not such a tree rather like a nation, a collection or colony of individuals, 
 the individuality belonging to each bud, to each leaf it has borne ; for 
 there is a close analogy, if not an absolute identity, between the process 
 of development of a seed in the ground and of a bud upon a branch ; 
 both have their infantile, both their aerial life. The leaves of the oak, 
 which expand in the spring, fall in the autumn. Their origin and du- 
 ties are connected with astronomical events. Each annual generation, 
 
NATURE OF INDIVIDUALITY. 469 
 
 while it lasted, carried forward all the functions of the tree, as, in a na- 
 tion that may have endured for a thousand years, each generation of men 
 has borne its part in the general scheme, and made provision for its suc- 
 cessors. The individuality therefore lies not in the tree, but, perhaps, 
 as thus far considered, should be referred to the bud. 
 
 But, moreover, when we consider the modes by which a tree may be 
 propagated, as, for instance, in the horticultural processes of budding or 
 grafting, our views of this question of individuality must again be modi- 
 fied. By these artificial operations an original stock may be multiplied 
 again and again, and each of the plants so arising is undistinguishable from 
 any other that may have come in the same way. Setting aside the inci- 
 dental difference that, through the intervention of artificial means, the buds 
 from which two such plants have originated have been brought under the 
 condition of physical independence of one another, the one, perhaps, grow- 
 ing in America, the other in Europe, is there any absolute and essential 
 difference between them more than there would have been had they been 
 permitted to remain upon the parent stock, and to develop themselves into 
 two branches thereof? Such facts suggest to us that individuality does 
 not belong to plants, as they thus present themselves to us, and that 
 perhaps we ought to assume an individuality of a higher order a race 
 individuality, as it were. In this manner, all weeping willows in Europe 
 and in America are one individual, because they have all been derived 
 from one original imported Babylonian stock ; and the same might be 
 said of every one of our cultivated fruits. But of these, if a seed be plant- 
 ed, the general aspect of the resulting growth may possibly be the same 
 as that derived from a graft, and how shall we then make a distinction 
 between the one and the other? for, though by seed development the 
 plant may chance to run back to a wilder form or to produce a new va- 
 riety, this result is by no means absolutely necessary. 
 
 From similar considerations, some physiologists have been led to deny 
 individuality to the bud and the seed, and to refer it to the primary cell ; 
 but here, again, precisely the same difficulties are encountered. A cell 
 may multiply itself by fissure through its nucleus, as well as in an en- 
 dogenous way ; moreover, cells arise from granular material. Individu- 
 ality, therefore, except it be that of a lower order, can not be attributed 
 to them, and the question of the determination of it rests precisely where 
 we found it. 
 
 In truth, are not all such discussions, in their very nature, illusory, so 
 long as we have no more definite idea of the term individu- The idea of in- 
 ality ? If a natural philosopher were to occupy himself with 
 similar discussions respecting the flame of a lamp, he too, piahts. 
 doubtless, would be led to precisely the same empty conclusion. He 
 might show how, in such a flame, there are separate, well-marked re- 
 
470 ANALOGY BETWEEN A PLANT AND A FLAME. 
 
 gions, some of which were present at the first moment of its existence, 
 and remain to its end, as, for example, the blue portion which is at its 
 under part. He might show how every one of these flames tends to as- 
 sume a definite or determinate form conical, for instance and proceed 
 to argue that this is the result of the interaction of external causes, as the 
 passage of currents in the air, and some interior principle or power pos- 
 sessed by the flame itself. He might consider how that from one flame 
 another can be kindled, in all respects like its parent in qualities or 
 shape ; and how, in succession, from one original, myriads upon myriads 
 might so arise. He might engage himself in disquisitions as to the man- 
 ner in which such an extraordinary result is to be explained, and as to 
 the source to which he should impute with exactness the origin of each 
 of these independent flames, and their mutual interrelation. He might 
 inquire if the force which each possesses was originally contained in the 
 original flame, and how it came to give it forth without loss of any of its 
 own power. He might also amuse himself with questions of individu- 
 ality, and, in doing all this, it would be no more than physiologists have 
 done before. Between the case of the trees and flames, of which we 
 have been speaking, it is not difficult to see that there is an analogy. 
 
 Are plants, in truth, then, nothing more than temporary states through 
 Plants are o - w ^ cn material substance is passing, because of some original 
 erations, not physical impression made upon it, and the present operation 
 als ' of external circumstances ? Can individuality be applied to 
 them any more than to a flame ? Instead of being individuals, are they 
 not rather the transitory results of an operation? 
 
 The lamp, which we have been using as an illustration, may serve to 
 Analo"- ' be enlighten our path a little farther. In the infancy of chemis- 
 tween a plant try, it might have been said of it that it possessed a burning 
 me ' power, which enabled it to dispose of the matter with which 
 it was fed, just as we say of a plant, in the infancy of physiology, that it 
 possesses a plastic power, which groups into definite forms the substance 
 with which it is furnished. The so-called burning power was derived 
 from another flame, in all respects analogous to that which manifests it, 
 and is nothing more than an extension of a physical operation, the tend- 
 ency of which, so far from being to check, is to continue as iong as the 
 proper material is furnished. The lighting of a second flame is essen- 
 tially the same condition as the continued combustion in the first. The 
 fact of separateness changes the phenomenon in no respect whatever ; the 
 relation of two separate flames is the same as that of two different parts 
 of the same flame ; and so the derivation of a plastic power by a plant 
 from its' ancestor is essentially the same thing as the manifestation of a 
 similar power in different parts of its own system. 
 
 Though it may therefore be convenient to speak hypothetically of this 
 
NATURE OF THE PLASTIC POWER. 471 
 
 principle which accomplishes in a plant the grouping of its parts as if it 
 were an agent, the foregoing illustrations show us that all the facts of the 
 case are equally well satisfied on the supposition that it is the continua- 
 tion of an operation. A multitude of parallel instances present them- 
 selves. In the making of leavened bread, all the phenomena would seem 
 to be accounted for either upon the hypothesis that there resides in the 
 leaven or ferment an agent, whose quality it is to determine a specific 
 change in the flour,, or that there is an operation which, because of the 
 chemical conditions existing, is gradually spreading, and which will not 
 cease until all the material submitted to it has been affected, and this no 
 matter whether it be in the same mass or in successive portions. Of 
 such hypotheses, the first is merely an elementary idea, the latter in- 
 volves a philosophical conception. 
 
 In this way, therefore, the so-called plastic power of a cell or the germ 
 of a seed may be regarded as the continued manifestation Nature O f the 
 of an antecedent impression long ago made, and which, un- plastic power. 
 der the existing conditions, has no liability to wear out or die away; 
 and that impression may have been purely physical in its nature. 
 
 Viewed in this attitude, the life of plants is a physical phenomenon. 
 The parts of which they are composed are furnished to them The life of 
 by influences of a mechanical kind : their carbon is taken by p h an s ^ai & 
 a true chemical decomposition from the carbonic acid of the phenomenon. 
 air ; their nitrogen comes from ammonia or from the atmosphere. Wa- 
 ter is drawn by capillary attraction from the ground. In virtue of its 
 chemical qualities, it carries into the growing system the various saline 
 bodies present in the soil, and which are needful for the economy. The 
 sunlight, heat, rain, winds, are the supplying and nurturing powers, and 
 the grouping agencies residing in the plant are of the same mechanical 
 derivation or order. 
 
 The germination of a seed and the growth of a plant, as thus consid- 
 ered, show us to what an extent physical forces are concerned in vege- 
 table organization. The conclusion thus indicated is enforced in no 
 common manner when we direct our attention to the series instead of to 
 a single plant. This is what I propose to do in the following chapter. 
 
472 GEOGRAPHY OF PLANTS. 
 
 CHAPTER II. 
 
 ON THE INFLUENCE OF PHYSICAL AGENTS ON THE ORGANIC SERIES. 
 
 Of the Geography of Plants: their horizontal and vertical Localization. Influence of Heat on or- 
 ganic Distribution : isotheral and isochimenal Conditions. Effects of Variations in the Dens- 
 ity of the Air, Moisture, Soil, Sunlight, Length of Day. Definite Quantity of Heat required 
 by Plants. 
 
 Secular Perturbations in the Species of Plants. Long Periods of Time required. Secular geo- 
 logical Changes. 
 
 Inverse Problem of the Investigation of the Earth's History from her fossil Flora. Two great 
 terrestrial Epochs : Change in the Constitution of the Air, and Localization of Organisms 
 through Decline of the Earth's Interior Heat. 
 
 Difference between abrupt and gradual Impressions. Invariable Causes may produce abrupt 
 Crises. , 
 
 Extension of the above Principles to the Case of Animals. Case of the Inca Indians. 
 
 General Argument supported by the Extinction of Forms. Development is under the Influence of 
 Law. Rudimentary Organs and Excesses of Development. The Idea of Development by 
 Law consistent with natural Facts. 
 
 THE publication of HUMBOLDT'S Essay on the Geography of Plants 
 Geo ra hical ^ rst f rma ^y drew the attention of botanists to the connec- 
 distribution of tion between the distribution of vegetables and the distribu- 
 tion of heat on the surface of the globe. Starting from the 
 equator and advancing to the pole, in either hemisphere, the mean annual 
 temperature declines as the latitude becomes greater, and in succession a 
 series of vegetable zones, merging gradually into each other, though each, 
 where best marked, perfectly distinguished from the succeeding, is encoun- 
 tered. In the tropics we have the palms, which give so striking a charac- 
 teristic to the forests, the broad-leaved bananas, and the great climbing 
 plants, which throw themselves from stem to stem like the rigging of a 
 ship. Next follows a zone described as that of evergreen woods, in which 
 the orange and the citron come to perfection. Beyond this, another of 
 deciduous trees the oak, the chestnut, and the fruit-trees with which, 
 in this climate, we are so well acquainted, and here the great climbers of 
 the tropics are replaced by the hop and the ivy. Still farther advanc- 
 ing, we pass through a belt of conifers firs, larches, pines, and other 
 needle-leaved trees, and these, leading through a range of birches, which 
 become more and more stunted, introduce us to a region of mosses and 
 saxifrages, but which at length has no tree nor shrub ; and finally, as 
 the perpetual polar ices are reached, the red snow-alga is the last trace 
 of vegetable organization. 
 
 A similar series of facts had been observed by Tournefort in an ascent 
 
GEOGEAPHY OF PLANTS. 473 
 
 of Mount Ararat. He found that the distribution of the veg- y ertical dis _ 
 etation from the base to the top of the mountain bore a gen- tribution of 
 eral resemblance to the distribution from the base toward the p a 
 Arctic regions. These facts by subsequent observers were generalized, 
 it having been established that there exists an analogy between horizon- 
 tal distribution on the surface of the globe and vertical distribution at 
 different altitudes above the level of the sea. Even in the tropics, if a 
 mountain be sufficiently high, a very short ascent suffices to carry us 
 from the characteristic endogenous growths at its foot, in succession, 
 through a zone of evergreens into one of deciduous 1 trees, and this, again, 
 into one of conifers, the vegetation declining through mosses and lichens 
 as we reach the region of perpetual snow. 
 
 In these two cases of horizontal and vertical distribution respectively, 
 which thus present such a striking botanical resemblance, Distribution 
 there is likewise so clear a meteorological analogy that it is ofheatdeterm- 
 
 , . , , ines the distri- 
 
 impossible to avoid coming to the conclusion that the dis- button of 
 tribution of plants depends on the distribution of heat. The P lants - 
 same climate variation encountered on a surface journey directed from 
 the equator toward the poles is again encountered as we leave the foot 
 of a tropical mountain and go toward its summit ; for it is a well-ascer- 
 tained fact that the temperature of the atmosphere declines as we rise to 
 greater altitudes, and that, no matter how high the summer heat may be, 
 we may, by a vertical -ascent at any locality, come to a region where 
 the temperature is never above 32 Fahr., and where ice and snow, there- 
 fore, never melt. If, in any locality, the mountain ranges are of sufficient 
 height to gain that region, their tops will be covered with perpetual 
 snow. The vertical ascent thus to be made is less as the latitude is 
 greater. At the equator it is 15,200 feet, and at the eightieth degree it 
 is within 450 feet of the ground. Beyond this, the surface itself is per- 
 petually frozen. 
 
 The mean temperature of a place determines its vegetable growth, and 
 hence there will ever be a resemblance between the vegetation of places 
 of the same mean temperature, though they may be geographically very 
 wide apart. But this, though a resemblance, is very far from being an 
 identity. We can not always designate by name the particular plants of 
 a high latitude which should be found at a corresponding elevation in the 
 mountains of the tropics. There may be the general resemblance of 
 which we have been speaking, and yet the genera and species of plants 
 in the two places may be quite distinct. But this fact, far from affecting 
 the truth to which we have arrived of the control of a physical agent 
 such as heat over the distribution of plants, leads us to ex- Influence of 
 tend it, and teaches us that, though we might expect, in other physical 
 places far apart, identically the same vegetable growths if conditions - 
 
474 INFLUENCE OF PHYSICAL CONDITIONS. 
 
 all the physical conditions were identical, yet, since heat is only one of 
 these conditions, it alone is insufficient, and that differences in the press- 
 ure of the air, the amount of moisture, the quantity of carbonic acid, as 
 also variations in the constitution of the soil, must have their effect. In- 
 stead, then, of limiting our views to the control of temperature over the 
 occurrence of plants, we must enlarge them in such a way as to include 
 divers other influences, some of which are those just mentioned, and all 
 are equally of a physical kind. 
 
 This therefore brings before us, in an impressive manner, the subject to 
 which this chapter is devoted, the influence of physical agents generally 
 over organization. 
 
 That the conditions of temperature alone are insufficient to account for 
 the occurrence and distribution of plants may be clearly established by 
 the aid of another series of facts. Throughout the old continent, with 
 the exception of its torrid zone, from the south of Africa to the north of 
 Europe, heaths abound, their species being very numerous in the south- 
 ern latitudes, less so in the northern, but the individuals increasing in 
 number as the species diminish. At the extreme north the common 
 heather remains as the sole representative of the whole group, and so 
 universally covers the surface as to give a characteristic feature to the 
 landscape. But in America, which reaches through all corresponding 
 degrees of latitude, and has in its proper localities the same mean tem- 
 peratures, not a single heath ever occurs. Again, in the New World, 
 through forty degrees on each side of the equator, the cactus tribe of all 
 kinds of grotesque forms abounds, but in Africa, though there are local- 
 ities of corresponding temperature, not a single cactus is to be seen. The 
 spurges there make their appearance. So, again, in Australia, the forests 
 present a melancholy and shadeless character from their leafless casuari 4 - 
 nas, acacias, and eucalypti, whereas, if temperature alone were concern- 
 ed, they should offer the same aspect as the forests of North America 
 and Europe. 
 
 Restricting our examination for the present to the influence of heat, it 
 Influence of may be observed that this is by no means so simple as might 
 h^atTand win- at ^ rst a PP ear - I* s distribution does not correspond with 
 ter colds. the latitude, the lines of equal mean temperature, isothermal 
 lines, not coinciding with the parallels of latitude. If we examine the 
 zones of plant distribution just described, we find that they follow the 
 isothermal lines much more closely than the latitudes ; but even here, 
 again, there are very great deviations deviations which, however, are to 
 some extent understood when we recall that it is not so much with the 
 mean annual temperature that plants are concerned as with the special 
 temperature of particular moments of the year. For the most part they 
 are affected by the heat of the summer season, which is their period of 
 
INFLUENCE OF THE AIR AND MOISTUKE. 475 
 
 growth, and though two localities may have the same mean annual tem- 
 perature, it does not follow that their maximum of cold for the winter, 
 and their maximum of heat for the summer, should coincide. It was 
 such considerations that led to the construction of isotheral lines, or those 
 of equal summer heat, and isochimenal lines, or those of equal winter 
 cold. 
 
 Into the causes which bring about this difference of heat distribution 
 it is not necessary for us here to inquire minutely. They Causes of the 
 
 are very various. The prevalent winds at different seasons S " 
 
 of the year, ocean currents, the geological structure of a coun- heat. 
 try, even what might be termed its optical qualities, that is, its power of 
 absorbing the rays of the sun (for instance, the great Desert of Sahara 
 disturbs the temperature of all Europe), and upon like principles must 
 act the removal of extensive forests, and their substitution by equivalent 
 surfaces of cultivated, differently colored, and differently absorbing lands, 
 elevation above the sea level, for the higher the country the lower its 
 temperature : these, and a multitude of other such conditions, impress 
 an effect upon the distribution of heat. The mean annual temperature 
 represents these and all other such influences, and includes all the varia- 
 tions, diurnal and nocturnal, monthly and seasonal, for the year. 
 
 The organic functions of a plant demand particular temperatures at 
 particular times. There is, doubtless,^ special degree best suited to the 
 period of germination, another to the period of aerial growth, another to 
 the period of fertilization, and another to that of ripening the seeds ; and 
 these degrees differ in the case of different plants. Where the require- 
 ments become so complicated, it would be erroneous to expect that the 
 mean annual temperature should satisfy them all. 
 
 Connected in part with temperature, and in part with elevation above 
 the sea, are the variations in the density of the air. These influence of va- 
 control, to a certain extent, the aerial supply to plants, the riations in the 
 
 . i . . , T density of the 
 
 quantity presented to their leaves diminishing as the density air moisture, 
 becomes less. etc ' 
 
 The same observation may be made respecting moisture, which, as is 
 very well known, constitutes one of the most influential conditions in de- 
 termining the growth of plants, and this in a double way, either as va- 
 por contained in the air or as rain. The effect of rain in this respect is 
 twofold : it diminishes the quantity of atmospheric carbonic acid by 
 exerting over it a solvent power, carrying it into the ground, and thereby 
 reducing, by sometimes as much as one half, the supply on which the 
 leaves are depending ; it also brings in larger quantities to the interior 
 of the plant the saline constituents of the soil which are requisite for tis- 
 sue development. 
 
 To variations in the temperature, the density of the air, and its moist- 
 
476 INFLUENCE OF THE SOIL AND LIGHT. . 
 
 Influence of ure, as affecting the well-being of plants, may be added the 
 the soil. chemical constitution of the soil upon which they grow. Lime- 
 plants can never be developed except on soils in which that earth abund- 
 antly occurs, and the same may be said of potash or soda plants, or, in 
 short, of any which demand some special mineral ingredient. Thus, for 
 instance, the salsolas and salicornias, which grow abundantly on the At- 
 lantic shores of France, and which require for their development the 
 saline ingredients of the sea, are nowhere to be seen throughout Central 
 Europe, though they reappear on the salt steppes of Russia, and abound 
 around the Caspian. We should scarcely expect that sea-weeds, into 
 the composition of which bromine and iodine abundantly enter, should 
 ever grow in waters from which these chemical elements are totally ab- 
 sent. Upon these principles, the vegetation of extensive tracts of coun- 
 try has undergone a change in an artificial way. Thus, for instance, in 
 Virginia and other Southern States, we may pass for miles in succession 
 through tracts in which the ancient forest-growths have been replaced 
 by the Pinus teeda, or old field pine. These are tracts from which the 
 potash salts have been removed, to a great extent, by the culture of to- 
 bacco. And of the indigenous trees, this pine requires the smallest pro- 
 portion of those salts. It therefore can flourish where -the others can 
 not exist. 
 
 From what has been said in tjie last chapter, it may be inferred that 
 Influence of among the various conditions thus influencing the growth of 
 the sun's light. a pl an t, none are of greater importance than the amount of 
 light furnished to it. Through this agent the decomposition of carbonic 
 acid is effected, and the plant obtains from the air the carbon it requires, 
 out of which its solid structures are for the most part built. The rapid- 
 ity with which the reduction of the carbonic acid takes place depends 
 upon the brilliancy of the light, and the amount of carbon thus obtained 
 upon that condition and the time of exposure conjointly. The amount of 
 light received from the sun in any locality depends in a general way, as 
 does the heat, upon the latitude ; but in both cases a multitude of disturb- 
 ing agencies intervene. Variations of moisture control the supply of light 
 by permitting a translucency, or establishing its opposite, a cloudiness or 
 murkiness of the air. Other meteorological causes, as, for example, winds, 
 by condensing or removing moisture, act in like manner ; so also do as- 
 influence of tronomical conditions, especially by influencing the relative 
 the position of length of the day and night ; for, as we advance toward the 
 
 the sun and , fo . J . b _ . . . _ , . 
 
 length of the pole, the summer sun is above the horizon longer and longer. 
 da y- I n Northern Europe, during the month of June, he never sets, 
 
 but remains all night, if night it can be called, above the horizon ; and, 
 as Berzelius well remarks, "Under the influence of this midnight sun of 
 the North, the life of plants runs through the same cycle of change in 
 
DEFINITE QUANTITY OF HEAT REQUIRED. 477 
 
 six weeks which it takes four or five months to accomplish in beautiful 
 Italy." 
 
 Attempts have been made to establish the doctrine that every plant 
 requires, from the time of its germination to the close of its Definite quan- 
 organic activity, a definite amount of heat. The following quf r ed by^ ' 
 example, in the case of barley, is furnished by Schleiden. plants. 
 " In Egypt, on the banks of the Nile, barley is sown at the end of No- 
 vember, and harvested at the end of February ; the period of vegetation, 
 therefore, amounts to about 90 days, and the meail temperature of this 
 season is 69 48'. ,In Tuqueres, near to Cumbal, under the equator, the 
 time of sowing in the mountains for barley is about the 1st of June, the 
 time of harvest the middle of November ; the mean temperature of this 
 vegetating season of 168 days is 50 12'. At Santa Fe de Bogota they 
 number 122 days between seed-time and harvest, with a mean tempera- 
 ture of 57 24'. If, now, the number of days is multiplied by the figures 
 of the mean temperature, we obtain 6282 for Egypt, 8433-|^ for Tuque- 
 res, for Santa Fe 6489-|-J ; therefore as nearly the same number as the 
 uncertainty in the estimate of the days, the accurate mean temperature, 
 and the want of knowledge whether or not the same kind of barley is 
 cultivated in all the places, will allow us to expect. Similar results are 
 obtained for wheat, maize, the potato, and other cultivated plants. We 
 may express these results thus : Every cultivated plant requires a cer- 
 tain quantity of heat for its development, but it is the same thing wheth- 
 er this heat is distributed over a shorter or longer space of time, so that 
 certain limits are not exceeded ; for where the mean temperature sinks be- 
 low 36 24', or where it rises above 71 36', barley will no longer ripen. 
 Consequently, to define accurately the conditions of temperature which a 
 plant requires to maintain it in a flourishing condition, we must state 
 within what limits its period of vegetation may vary, and what quantity 
 of heat it requires. This most remarkable circumstance was first ob- 
 served by Boussingault, but, unfortunately, we as yet possess not nearly 
 sufficiently accurate accounts of the conditions of culture in the various 
 regions of the earth to enable us to follow out this ingenious view in all 
 its details." 
 
 Respecting the calculations offered in the preceding paragraph, the re- 
 mark may be made that they contain an element which vi- xhe effect of 
 tiates their correctness, and that, if the proper data were re- the intensity 
 
 , , , . . , . -i -i T -i -i an( i quantity 
 
 sorted to, the general principle intended to be demonstrated O f heat consid- 
 would be far more clearly established. The degrees of the ered - 
 thermometer are not the data required, for that instrument indicates the 
 intensity, but not the quantity of heat. If some form of calorimeter were 
 substituted for it, the result would turn out very differently. As an illus- 
 tration, if a mass of ice of constant surface was exposed to the warmth in 
 
478 GENERATION OF HEAT. 
 
 each of these various cases, the quantity of water arising from its melt- 
 ing should be the same at the close of the specified number of days. In 
 this case the true element is introduced the element of quantity, as de-' 
 termined by one of the ordinary calorimetric methods. 
 
 It is not, however, to be inferred from this criticism that the peculiar 
 quality of heat which we recognize indifferently by the terms intensity, 
 temperature, or degree, is without significance in the case of plants : the 
 limiting maxima and minima between which a given plant can exist 
 prove that both conditions exert an influence, though they exert it in a 
 different way. Doubtless a plant, from the time of its germination to 
 that of the completion of its organic life, must have a definite quantity 
 of heat measured out to it, but its organic functions might be fatally in- 
 terfered with if the temperature should rise above a limiting maximum, 
 or sink beneath a minimum. 
 
 The definite quantity of heat in this manner demanded by each plant 
 is probably connected with a purely mechanical effect the necessity for 
 the evaporation of a definite quantity of water by the leaves. The inor- 
 ganic salt substances required by every plant are introduced through its 
 roots in a state of solution in water, and, since these salts are mostly of 
 sparing solubility, a great quantity of water is required to accomplish 
 the object. Nevertheless, they are dissolved at a given heat-degree in 
 an invariable proportion in the liquid, and are required by the plant in a 
 determinate proportion as compared with its mass ; so that, were there 
 no other reason, this doubtless would be sufficient to account for the cir- x 
 cumstance under consideration. 
 
 It should also be remembered that every plant generates a certain 
 Disturbance amount of heat, which varies with its organic condition at the 
 arising from time. The experiments of Professor Paine present this in an 
 tion ofheat interesting point of view. The following extract is from the 
 in plants. Medical and Physiological Commentaries, vol. ii., p. 75 : 
 
 "On the 9th of April, 1839, we repaired to a forest in New Jersey, 
 Prof. Paine's provided with very delicate thermometers, of Fahrenheit's 
 experiments. sca l e) constructed for our object. The bulbs were no larger 
 than the stem, the range of the mercury extensive, and the degrees 
 marked upon the glass. The stems filled exactly the bore of a small 
 spiral auger, and when the glass was introduced the air was excluded by 
 applying a silk handkerchief around the hole. The perforations were all 
 made on the northern side of the trees. Fifteen minutes, at least, were 
 allowed for the subsidence of the heat that arose from the friction of the 
 perforator, and the thermometer was generally reapplied at different in- 
 tervals afterward. The perforations were made about four feet above the 
 ground, and the diameters of the trees were ascertained at this point. 
 When the diameter was five inches or more, the perforations were made 
 
VARIATIONS IN THE SPECIES. 
 
 479 
 
 to the depth of two and a half inches. When the diameter was less than 
 five inches, the thermometer was introduced as far as the centre of the 
 tree." 
 
 Of the tables given by Professor Paine I select the following : 
 " Range of thermometer in the shade during the observations, which 
 lasted six hours, from 38 to 52 : near freezing at sunrise. 
 
 "A dead upright dry tree was selected as a standard of comparison. 
 Its diameter was twelve inches. The temperature of this tree, at the 
 close of our observations, was 45 at the centre and in all other parts. 
 
 " Juglans squamosa, diameter 10 inches, 48 Buds slightly enlarging, 
 do. d6. '6 " 49 do. 
 
 Fagus sylvatica, 
 Quercus tinctoria, A 
 Castanea Americana, 
 Betula nigra, 
 Salix Babylonica, 
 do. do. 
 
 ' 10 " 
 
 t 7 u 
 
 12 " 
 . 4 " 
 18 " 
 
 18 " 
 
 49 Buds swelling. 
 49 No budding. 
 50 do. 
 51 Elowering. 
 53 Buds unfolded. 
 53 do. 
 
 Pinus Canadensis, 
 Platanus Occidentalis, 
 do. do. 
 
 ' 18 " 
 < 18 " 
 *;: 6 " 
 
 54 
 50 No budding. 
 54 do. 
 
 do. do. 
 
 < 4 ' 
 
 55 do. 
 
 Juniperus Viginiana, 
 Kobinia pseudacacia, 
 Populus Ia3vigata, 
 do. do. 
 
 : _ 4 
 B " 
 4 " 
 4 " 
 
 55 
 62 do. 
 62 In bloom. 
 64 do. 
 
 do. do. 
 
 3 " 
 
 63 do. 
 
 do. do. " 3 " 
 
 65 do. 
 
 do. do. " 2 
 
 67 do. 
 
 do. do. 1| " 
 
 68 do." 
 
 The 'heat which is thus liberated by plants stands in the stead of a 
 certain amount of atmospheric heat, and therefore complicates the preced- 
 ing considerations. 
 
 By such facts as those which have now been presented, we may be 
 satisfied that the well-being of plants is affected, and even Accomplish- 
 their existence determined by the influence of external agents, "onsinthe sp&. 
 and that, in this manner, they are capable of having changes cies of plants, 
 impressed upon them even in an artificial way. If we furnish to them 
 those materials or conditions which their circumstances require, they will 
 grow with luxuriance, or under an opposite state of things will dwarf 
 away ; and where, for a long period of time, such conditions are imposed 
 upon successive generations of them, a permanent change may be effect- 
 ed, those which have appeared as varieties assuming the more definite 
 form and persistency of sub-species. The general impression alluded to 
 in the last chapter, that such peculiarities are only to be extended by 
 budding or other equivalent operations, and that those which we regard 
 as different individuals are truly fragments or parts of the same individ- 
 ual, does not here properly apply. A like propagation of peculiarity is, 
 
480 SECULAR CHANGES IN PLANTS. 
 
 in a multitude of instances, accomplished by the use of seeds, and this 
 precisely in the instance in which we should be led to expect it. Of 
 our kitchen-garden plants, the carrot, the beet, the turnip, the cabbage, the 
 pea, etc., we propagate the expected kind without any uncertainty by the 
 use of seeds, never supposing that they will run back to the wild stock, 
 or give origin to plants different to those from which they were derived. 
 The care of man, exerted for many years upon these vegetables, has, then, 
 impressed upon them a change very far from ephemeral in its nature, and 
 enabled them to pass from the condition of mere varieties into that of 
 actual sub-species. 
 
 Acknowledging, therefore, the influence which physical agents exert on 
 Necessity of the growth and development of plants, and admitting that 
 time forchan^ f avorm g circumstances will bring on a modification of form, 
 ing plants. especially if applied long enough, and that man himself, by 
 his arts of culture, can, without difficulty, establish similar variations, we 
 might be led to expect that more profound changes in external circum- 
 stances, if steadily applied through extended periods of time, would give 
 origin to more striking results. A variation in the constitution of the air, 
 in the brilliancy of light, in the mean temperature, moisture, or chemical 
 constitution of the soil, if kept up for thousands of years, or permanent- 
 ly established, could not fail to exert a prodigious effect upon the whole 
 vegetable world. If, for example, the brilliancy of the sun in the slow 
 lapse of centuries should gradually decline, or the mean temperature of 
 the surface of the earth should descend, or enormous quantities of car- 
 bonic acid be permanently removed from the air and replaced by equiva- 
 lent volumes of oxygen gas ; if carbonate of lime, to an extent sufficient 
 for the formation of geological strata, were removed from the waters, in 
 which it could no longer be held in solution because of the withdrawal 
 of carbonio acid from the atmosphere, it must follow, as a matter of inev- 
 itable necessity, that the whole vegetable world would feel the change. 
 Plants that at one time existed could exist no more ; others, by gradu- 
 ally accommodating themselves to the slow revolution, would exhibit 
 here the development of one part, there the development of another, and 
 some, which perhaps maintain themselves with difficulty under the old 
 state of things, would now begin to develop themselves in a more luxu- 
 riant way. 
 
 The changes here spoken of hypothetically have, however, actually oc- 
 Secuiar changes cur *ed in the history of the earth. We can not shut our 
 occurring to the eyes to the corresponding!; march which vegetation has made, 
 
 earth and occa- J . .* ,? i i A - vo_ ^.i. 
 
 commencing in the earliest geological times with the stem- 
 
 turns in plants. i ess cryptogamia, followed by those provided with stems 
 and leaves, the gymnospores, such as the conifers and cycadeas, next 
 making their appearance, after these, monocotyledons, and at last the 
 
EPOCHS OF THE GLOBE. 481 
 
 dicotyledons a steady progression from those which we may term of a 
 lower to those of a more elevated organization, and all this was produced 
 Iby the influence of physical agents. 
 
 On so firm a footing may we regard this doctrine as now placed, that 
 we can use it for the purpose of determining from the ascer- . ,. .. 
 tained botanical condition of our planet at any period the these principles 
 physical conditions under which she then existed, and this inverse1 ^- 
 with a precision constantly becoming greater. Among the more impor- 
 tant facts which have been distinctly made out, a few may be cited as 
 illustrations of the subject now treated of. For example, 1st. The ex- 
 istence of a tropical climate in regions of very high latitude, as is proved 
 by the occurrence of fossil tropical plants therein ; 2d. That all over the 
 globe the temperature was once nearly uniform, nothing answering to 
 what we now term climates existing, as is proved by the uniformity of 
 the vegetable growths preserved as coal from the equator to near the polar 
 circles great arborescent cryptogamia, exceeding in size the arborescent 
 ferns now growing in the Pacific islands under the equinoctial line. 
 From such a botanical fact, we reason without error to the Succession of 
 conclusion that in those times the influence of the sun, so climates on the 
 far as the supply of heat was concerned, must have been ined from its 
 wholly overpowered, the intrinsic temperature of the planet fossil flora - 
 obliterating all climate subdivisions. 3d. That these climate subdivis- 
 ions, which are now presented as existing side by side in zones upon the 
 planet, were introduced for each latitude in an order of succession as to 
 time ; that even the frigid zone, by reason of the cooling of the earth, 
 has passed through an ultra-tropical, a tropical, and a temperate degree 
 of heat to reach its present state ; 4th. That the extinction of the old 
 vegetable forms was accomplished by an inability of those organisms to 
 maintain themselves in the physical revolution that was gradually taking 
 place. Among such may be mentioned the dying out of gigantic equi- 
 setums or horsetails twenty feet high, club mosses rivaling forest trees, 
 calamites and stigmarias, these, as they disappeared, being replaced by 
 cycadacese, and coniferge, and tree-like liliacese. Even long after the de- 
 posit of the coal there flourished in England innumerable palms, which 
 maintained themselves, with their tropical associates, into the tertiary 
 times. 
 
 Among the physical events which geological researches disclose, there 
 are two of surpassing importance in the history of the globe, Two epochs in 
 and both of them immediately connected with the doctrine the history of 
 we have under discussion ; these are the change impressed * e g 
 on the atmosphere by the withdrawal from it of those enormous masses 
 of carbon deposited under the different forms of coal, and the localiza- 
 tion of plants and animals in climate distribution as the sun's rays be- 
 
 HH 
 
482 LOCALIZATION OF PLANTS. 
 
 gan to assert their influence through the lowering of the surface temper- 
 Change in the ature of the globe. The first of these events was not alone 
 tbTa7mos n f l iimte d in i ts effect to a Disturbance of the organic functions 
 phere. of plants by diminishing the amount of gaseous material from 
 
 which they gathered their support in the air : its influence was also felt 
 in animal life by rendering that possible which was not possible before 
 the existence of the quickly-respiring and hot-blooded tribes ; for it fol- 
 lows as a chemical necessity that, under the circumstances of the case, 
 the removal of the carbonic acid was attended with the evolution of an 
 equal volume of oxygen gas. As respects the influence of the sun, which 
 gradually led to the establishment of climates, first in an order of time, 
 and then in an order of place, this was the signal for the localization of 
 Definite locaii- P^ ants an( l animals i* 1 definite regions. From many coun- 
 zation of plants tries which they had thus far inhabited they were now ex- 
 and animals, p^^ an( j "barriers of temperature placed around them which 
 they could never again overpass. And as these great changes occurred, 
 they were attended by the extinction of countless forms in both king- 
 doms, which were utterly unable to maintain themselves in the new cir- 
 cumstances around them, their places being occupied by the extension 
 of contemporaneous forms, or by the appearance of others that were whol- 
 ly new. 
 
 As an illustration of the manner in which a vegetable organism may 
 
 Exam le of the ^ e use( ^ * n ^^ s i nverse Wa 7 f r tne determination of physic- 
 inverse method al conditions, I may introduce the following quotation from 
 len * Schleiden : " The gradual conversion of the universal trop- 
 ical climate into the present climatal zones may be shown in another 
 very interesting manner in quite a special instance. All ligneous trunks 
 of coniferous trees continually increase in thickness at all parts of their 
 circumference. In the equatorial regions, where the climate retains the 
 same character uninterruptedly throughout the year, this thickening of 
 the trunk proceeds without interruption and homogeneously ; no mark 
 betrays, in a smooth, transverse section of the stem, the time which was 
 required for its formation. As we proceed toward the north, however, 
 as the climatal conditions produce continually-increasing diversity in the 
 particular seasons, the corresponding growth in thickness shows itself to 
 have been furthered by the favorable season, and restrained or altogether 
 interrupted by the unpropitious times. In a cross section of a stem are 
 seen, the higher the latitude in which it has grown, the greater differ- 
 ences in the structure of the successive portions of the wood, until final- 
 ly, in the latitudes where there is a severe alternation of winter and sum- 
 mer, so striking becomes the difference between the wood last formed in 
 summer and that first produced in the next spring, that we may count, 
 in the number of annular marks thus produced in a cross section, with 
 
ABRUPT AND GRADUAL IMPRESSIONS. 483 
 
 great certainty and accuracy, the number of years which have been oc- 
 cupied in the formation of the trunk. The circular lines upon the cross 
 section, well known to every forester, are thence called annual rings. 
 When, fortified with the knowledge of this fact, we compare with each 
 other the trunks of the conifers which we obtain from the various epochs 
 of formation, we find that the oldest remains exhibit no trace whatever 
 of annual rings, but, in the course of time, they become continually more 
 defined, so that lastly, in the most recent formations for instance, in the 
 upper brown coal they appear marked just as distinctly as in the trees 
 now living in the same localities." 
 
 In speaking of artificial changes impressed by culture upon domestic 
 plants which have been converted from varieties into sub- Difference be- 
 species, the importance of the element of time was insisted * w een abrupt 
 
 T i -ti 1*11 an( l gradual 
 
 upon. In the same manner, in the changes which have oc- impressions on 
 curred during geological periods, the successive replacement P lants - 
 of one class of vegetable forms by another, that element again obtrudes 
 itself upon our notice. If a few years serve to establish such minor 
 changes as the perpetuation of varieties into sub-species, what should be 
 expected from the enduring influence of innumerable centuries ? More- 
 over, in these artificial results there is a necessary abruptness in the appli- 
 cation of the disturbance, which can not but exert an unfavorable influ- 
 ence. No time is afforded to the organism to suit itself gradually to the 
 force exerted upon it, none for acclimating itself to the external variation. 
 It must either yield at once or perish. But how different as respects 
 the method of application in the case of the organic series ! If it be de- 
 cline of temperature that we consider, how shall we enumerate the suc- 
 cessive centuries that must have elapsed as the descent was made from 
 degree to degree ? In these later times, as is admitted on all hands, the 
 mean temperature of the surface could not decline the tenth part of a 
 Fahrenheit degree in the lapse of 10,000 years. Yet the interval has 
 transpired during which there has been a gradual descent from those 
 high thermometric points at which the existence of organic life was bare- 
 ly possible, and, in truth, through a far greater range than that. It sig- 
 nifies nothing that this descent might have been more rapid the higher 
 the degree ; in any case, it implies a prodigious interval of time. Or, if 
 we consider variations in the light of the sun, either because of his being 
 a variable star, or because of the gradual clearing up and improving 
 transparency of the atmosphere, we are brought again to the same re- 
 sult long periods of time ; for, though there may be among the fixed 
 stars some whose periods of variation, as respects brilliancy, are short, 
 included perhaps within a few days, or even hours, if we had no better 
 evidence, history assures that our sun is not one of that quickly-varying 
 group. Or, again, if we consider the changes which have indisputably 
 
484 SECULAR PHYSICAL CHANGES. 
 
 occurred in the chemical constitution of the air, the diminution of its an- 
 cient amount of carbonic acid, the reduction of the mean percentage of 
 its vapor of water, the increase of its oxygen, these again are changes of 
 a secular kind, the time required for the accomplishment of which is 
 wholly beyond our finite comprehension. In such a gradual advance, 
 organisms for many generations might show but little change, yet, in 
 the end, the effect must come to be profound. Indeed, all the great nat- 
 ural effects we witness are accomplished in this quiet and gradual way : 
 the traces of tempests and other catastrophes are very soon effaced, no 
 matter how violent the original commotion may have been ; but warmth, 
 and light, and moisture causes which act so gently that we might over- 
 look them are the agents which control the universal aspect of things. 
 In this, as in other respects, the strong are always the silent ; and in the 
 Secular phys- s l w l a P se f many centuries, by the gradual operation of 
 icai changes at- universal forces thus gently applied, organic forms had an 
 
 tended by pro- . ,, j / v - 
 
 ductions and opportunity oi accommodating or acclimating themselves to 
 extinctions. fa Q new gtate, or, if they failed to do so through some want 
 of correspondence in their structure, they gradually passed away and be- 
 came extinct. It is no argument against the transmutation of species, 
 or even of genera, that we have never witnessed such an event. We can 
 never witness the necessary combination of circumstances which should 
 bring it about, above all, as regards the needful lapse of time, the slow 
 yielding and accommodation which such a change implies. In this, as 
 in those great modifications that have occurred in the stratification of 
 the globe, the like of which has never been seen in the periods of human 
 record, our want of familiarity with them is a matter of very little mo- 
 ment. The remark of an eminent geologist applies with equal force in 
 both cases : " Changes that are rare in time become frequent in eter- 
 nity." 
 
 But it may be said that if by external influences the successive spe- 
 Graduai change cies and genera in this manner arose, we ought to find, 
 produ^effeSs even Between those which are most closely allied, many in- 
 by abrupt crises, termediate forms ; for, since the active causes were gradual 
 in their operation, one organism should pass into another by slow de- 
 grees- so insensibly, indeed, that it would perhaps be impossible to indi- 
 cate the point at which the proper transition was made. Such an ex- 
 pectation is, however, founded upon a total misconception of the charac- 
 ter of these progresses, for a force applied for thousands of years may 
 show no effect, but at last may manifest itself by an instant crisis. Mul- 
 titudes of illustrations might be furnished of this principle ; for instance, 
 the motion of a comet may be toward the sun in a path which is almost 
 a straight line for scores of centuries, but on a sudden it assumes a curvi- 
 linear course, and accomplishes its perihelion passage in perhaps a few 
 
MECHANICAL ILLUSTRATION OF CRISES. 485 
 
 hours, and then, receding from that luminary, takes a course not sensi- 
 bly differing from a straight line, and occupying perhaps centuries in its 
 accomplishment. The variations of direction and of velocity are, how- 
 ever, the necessary results of the conditions under which its movement 
 is taking place, and may be truly said to have been originally included 
 therein. 
 
 This instantaneous or critical assumption of a new phase may also be 
 illustrated by the functions of organic beings. Thus the Illustratio n 
 foetal mammal, though provided with lungs, a mechanism in from the life 
 all respects ready for aerial respiration, does not pass by 
 graduated steps from placental, which is truly aquatic breathing, but the 
 change takes place on a sudden at the moment of birth. These and 
 other such instances may therefore satisfy us that what an imperfect in- 
 duction would lead us to look upon as a departure from the existing rule, 
 or as a breach of the law, may, in reality, be nothing more than the im- 
 mediate or legitimate consequence of it. They may teach us that, in 
 the natural progress of things, variations do not necessarily always take 
 place in so gradual a manner as to be un distinguishable from stage to 
 stage, but sometimes instantaneously, and, as it were, by a crisis. 
 
 Again, this variation by crises may be illustrated by many familiar 
 mechanical contrivances. The case of the common seconds Mechanical ii- 
 striking clock may furnish an example. Let us trace the lustrations. 
 successive conclusions to which an ingenious man might have come at 
 the first introduction of this instrument, his investigation of it being sup- 
 posed to exclude an inspection of its parts. After listening for a length 
 of time to the beats of its pendulum, he would observe that these suc- 
 ceeded at precisely regular intervals, and after extending his examination 
 through two or three thousand of such occurrences, he would doubtless 
 feel justified in coming to the conclusion that the construction was of 
 such a nature that the passage of successive small intervals of time was 
 indicated by the occurrence of a brief, dull sound. His first conclusion, 
 therefore, would be, that the instrument would go on doing this continu- 
 ously. 
 
 At the close of -3600 such observations, when the truth of his in- 
 duction appeared to have become irresistible, his attention would be ar- 
 rested, and his faith in the correctness and completeness of the extensive 
 inductive conclusion he had just drawn would be shaken by hearing one 
 loud stroke upon a bell. Now, probably, he would suspect that the struc- 
 ture of the instrument was such that it indicated the lapse of each 3600 
 minor beats by one louder stroke. This would be his second and more 
 improved induction. 
 
 Setting himself to verify the truth of this hypothesis, he would watch 
 the instrument through 3600 beats more, confidently expecting that, at 
 
486 MECHANICAL ILLUSTKATION OF CRISES. 
 
 the conclusion thereof, the hypothesis to which he had thus hastened 
 would be confirmed. True to the time, the bell would again strike, but, 
 instead of striking only once, it would strike twice. Admonished of the 
 hastiness of his hypothesis, our philosopher might now be induced to 
 pause before he generalized again, and, after watching through 3600 more 
 beats, the clock would strike thrice. 
 
 Now, surely, he would feel absolutely certain of having reached the 
 tfde interpretation of the action of the machine at last. His third and 
 corrected conclusion would be that each group of 3600 beats was register- 
 ed by the bell, the number of strokes upon which indicated the number 
 of such groups, and that this it would do continuously. 
 
 Patiently listening through many thousand beats, he would find that 
 every thing confirmed his new and improved induction. He would hear, 
 in their regular succession, ten, eleven, and twelve strokes made by the 
 clock. Of course, his expectation would now be confirmed that at the 
 next time the clock struck it would be thirteen. How great would be 
 his surprise to find it was only one ! 
 
 Perseveringly continuing his examination, he would reach, at last, the 
 true law regulating the indications of the machine, and would find that 
 the partial conclusions to which he had successively arrived, and which 
 he had thought, at the time, to be substantiated by a superfluity of facts, 
 were in themselves incomplete, and in that respect erroneous ; but he 
 would also observe that whatever truth there was in them was embraced 
 in the final induction that the machine was not as simple as he had at 
 first supposed, and that the critical variations which in succession had 
 surprised him were all embraced in the original plan of its construction. 
 Our imaginary philosopher has passed through a mental exercise precise- 
 ly like that which is befalling modern comparative physiologists. From 
 his labors, disappointments, and eventual success, they may gather en- 
 couragement. The clock of the universe does not forever go on vibrat- 
 ing monotonously. A thousand years upon it are only as the beat of a 
 pendulum ; but it, too, has its periods of critical variation variations that 
 were included in its original device. 
 
 The point which I wish to impress by these illustrations is, that there 
 A lication of * s a definite career which an organism must follow, accord- 
 the preceding ing to its exposure to existing physical conditions, and that, 
 lon< though this career may seem to be continuous, it by no means 
 follows that it shall not exhibit an instantaneous and critical change, and 
 that, on a sudden, the organism may assume a specifically new aspect ; 
 and though, in what has thus far been said, reference has been had chief- 
 Influence of ly to plants, these observations all apply, in like manner, to 
 ainma l s - I do not propose, however, to enter on that branch 
 of the inquiry now, but, as an illustration of the influence of 
 
THE INC A INDIANS. 487 
 
 physical agents, even on the highest man himself shall offer the fol- 
 lowing example : 
 
 M. D'Orbigny, in his description of the Inca Indians of South Amer- 
 ica, remarks, " It has always been observed that the trunk is case of the 
 longer in proportion than among other Americans, and that, Inca Indians. 
 for the same reason, the extremities are, on the contrary, shorter. We 
 endeavored, at the same time, to explain this fact by the greater devel- 
 opment of the chest. It would appear that any part of the body may 
 take a greater extension from any adequate cause, while other parts fol- 
 low the ordinary course. An evident proof of this fact may be found in 
 the phenomena of imperfect conformation, in which a certain part of the 
 body, in consequence of deformity, does not assume, in external appear- 
 ance, its complete natural development, as we see in the trunk of a dwarf, 
 while this defect does not prevent the extremities from acquiring those 
 proportions that they would have had if the trunk had received its full 
 growth. This accounts for the want of symmetry in the persons of 
 dwarfs, and for that length of the upper and lower limbs so much out of 
 proportion to the body. If we admit this fact, difficult to contest, why, 
 in the case in question, may we not as well admit that the chest, from a 
 cause which we shall explain, having acquired a more than ordinary ex- 
 tension, might naturally lengthen the trunk without causing the extrem- 
 ities to lose their normal proportion, which would make it appear, as in- 
 deed it would be, longer than among other men where no accident can 
 have altered the form common to the race ? 
 
 " Let us return to the causes which occasion in the Incas the great 
 volume of chest which has been observed in them. Many considera- 
 tions have led us to attribute it to the influence of the elevated regions 
 in which they live, and to the modifications occasioned by the extreme 
 expansion of the air. The plateaux which they inhabit are always com- 
 prised between the limits of 7500 to 15,000 feet above the level of the 
 sea. There the air is so rarefied that a much greater quantity must be 
 inhaled at each inspiration than at the level of the ocean. The lungs 
 require, in consequence of their great necessary volume, and of their 
 greater dilatation in breathing, a cavity larger than in the lower regions. 
 This cavity receives from infancy and during the time of its growth a 
 great development entirely independent of that of the other parts. "We 
 were desirous of determining whether, as we might suppose a priori, the 
 lungs, in consequence of their great size, were not subject to extraordi- 
 nary modifications. Inhabiting the city of La Paz, upward of 11,000 
 feet above the level of the ocean, and being informed that in the hospital 
 there were constantly Indians from the populous plateaux still more ele- 
 vated, we had recourse to the kindness of our countryman, M. Burnier, 
 physician to the hospital, and he permitted us to make a post mortem 
 
488 EXTINCTION OF FORMS. 
 
 examination of some of these Indians from the highest regions. In these 
 we have, as we expected, found the lungs of an extraordinary dimension, 
 which the external form of the chest clearly indicated. We remarked 
 that the cells were much larger and more in number than in those of the 
 luHgs we had dissected in France ; a condition very necessary to increase 
 the surface in contact with the ambient fluid. To conclude, we have 
 discovered, 1st. That the cells were more dilated ; 2d. That their dilata- 
 tion increases considerably the volume of the lungs ; 3d. That, conse- 
 quently, they must have to contain them a larger cavity; 4th. That, 
 therefore, the chest has a much larger capacity than in the normal state ; 
 5th. That this great development of the chest elongates the trunk beyond 
 its natural proportions, and places it almost out of harmony with the 
 length of the extremities, this remaining the same as if the chest had 
 preserved its natural dimensions." 
 
 With respect to the doctrine of the influence of physical agents on or- 
 Ar umentfrom g aju>za tion generally, we admit without hesitation that the 
 the extinction extinction of forms has been accomplished through outward 
 causes, decline of heat, etc. These extinctions are intimate- 
 ly connected with the appearance of new organisms, and, indeed, are to 
 be regarded as being, with them, essential parts of a common plan. It 
 would not appear agreeable to the mode in which the scheme of Nature 
 is carried out to invoke one class of influences for the removal of the 
 vanishing forms, and a totally different one for the introduction of the 
 new-comers. There seems to be a better harmony in the supposition that 
 all these things are managed upon similar principles, and that, since it is 
 the failure of congenial conditions which closes the term of life of a race, it 
 was the suitability of those conditions, or their conspiring together, which 
 gave it origin. 
 
 The influence of decline of temperature appears when we examine par- 
 influence of ticular individuals or particular species either of plants or of 
 decline of tem- animals. Thus the Virginia cherry attains the height of 100 
 feet in the Southern States, and is dwarfed to a shrub of not 
 more than five feet at the great Slave Lake ; the nasturtium, which is a 
 woody shrub in warm climates, becomes a succulent annual in cold. Or, 
 if we examine some special tribe of life, as Milne Edwards has done in 
 the case of crustaceans, the higher the temperature, the greater the lia- 
 bility to variations of species, the more numerous also the differences of 
 form, and the attainment of a greater individual size. That these varia- 
 tions are the actual consequences of the physical conditions, and not 
 merely collateral results, is shown by supplying the condition that is 
 wanting. We can imitate the natural result, in an artificial way, in hot- 
 houses ; the plants of the warmest climate may be grown, and the effects 
 of summer imitated at any season of the year. What better proof could 
 
METAMORPHOSIS OF ORGANISMS. i 489 
 
 we have of the control of the agent heat over development, than the well- 
 ascertained fact that the time of emersion of larvas depends upon the 
 temperature ? The silk-grower, by placing the eggs of the insect in an 
 ice-house, retards them as long as he pleases. The amputated limbs of 
 the water-newt can only be reproduced at a temperature from 58 to 75. 
 The tadpole, kept in the dark, does not pass on to development as a frog. 
 In decaying organic solutions, animalcules do not appear if light be ex- 
 cluded. 
 
 Upon the whole, therefore, we conclude that organisms of every kind, 
 so far from presenting any resistance to change, are. im- Changes of or- 
 pressed without any difficulty by every exterior condition ; ^nd^n hiva" 
 and since existing natural circumstances have been main- riabie laws, 
 tained for a long time without any apparent change, their sameness pro- 
 duces a sameness in the order and manner of development. But it should 
 be borne in mind that this idea of, sameness can be entertained only on 
 an imperfect view of the state of Nature, for there is scarce one of those 
 conditions, to the sameness of which we have been referring, which has 
 not, in reality, undergone slow secular variations ; and with those changes 
 there have been changes in the manner of development. 
 
 In truth, as I have on a former page observed, the only things which 
 are absolutely unchangeable are the laws of Nature, such, for instance, 
 as that of gravitation ; every thing else is to be looked upon as an effect, 
 or as a changeable phenomenon arising from the operation of those laws. 
 So, therefore, though, in this chapter, the terms physical in- Successive met- 
 fluences and natural conditions have been repeatedly used, cons^uence^f 
 yet a higher and more philosophical view of the case brings invariable law. 
 us inevitably at last to the idea of law ; and therefore I accept the in- 
 terpretation of all these facts, which has of late years been impressing 
 itself more and more strongly and clearly on the minds of physiologists, 
 that the development of every organism, from a primordial cell to its 
 final condition, however elevated that condition may be, is the inevitable 
 consequence of the operation of a universal, invariable, and eternal law. 
 
 All animals, no matter what position they occupy in the scale of na- 
 ture, unquestionably arise in the first instance from a cell, which, possess- 
 ing the power of giving birth to other cells, a congeries at last arises, the 
 size and form of which is determined wholly by external circumstances. 
 In all cases, the material from which these cells are formed is obtained 
 from without, and, whatever the eventual shape of the structure may be, 
 the first cell is in all instances alike. There is no perceptible difference 
 between the primordial cell which is to produce the lowest plant and 
 that which is to evolve itself into the most elaborate animal. The mode 
 of growth, and the arrangement of the new cells as they come into exist- 
 ence, determining not only the form, but also the functions of the new 
 
490 . METAMORPHOSIS OF ORGANISMS. 
 
 being, depend on the particular physical conditions under which the 
 growth is taking place. The germ which is to produce a lichen obtains 
 from materials around it the substances it wants as best it may; but 
 the germ which is to end in the development of man is brought in suc- 
 cession under the influence of many distinct states. As a consequence 
 of this, it gives rise in succession to a series of animated forms, which, as- 
 suming by degrees a higher complexity, end at last in the perfect human 
 being. At one time it was believed that these metamorphoses, as they 
 are termed, are limited to insects and frogs : the insect, which at first 
 appears under the form of a caterpillar as it comes from the egg, and, 
 passing through the pupa state, at last takes its true position as a wing- 
 ed being ; the frog, which, appearing at first from the ovum as a true 
 fish, whose respiration is carried forward by gills, and whose life is lim- 
 ited to the water, at last assumes a new constitution and a new organi- 
 zation, breathes by lungs, and becomes an amphibious reptile. But it 
 is now known that these, so far from being exceptions, are only instances 
 of a general rule, which is, that all organized beings shall begin existence 
 at the bottom of the scale, and, taking on one type of life after another, in 
 more or less rapid succession, end, finally, in assuming a size and form 
 analogous to those of the parent which gave them birth. 
 
 There is a general resemblance between the life of an individual and 
 the life of a species. Each has its time of birth, its time of maturity, 
 its time of decline ; each also has its embryonic states. The fossil forms 
 of the early geological ages are in many cases the embryos of existing 
 animals. Upon each all natural agents have exerted their effects, push- 
 ing forward or retarding development ; and this applies not only to an- 
 imals, but also to plants : it is in accordance with the principles we are 
 setting forth that over the whole domain of life natural forces exert 
 their sway. Change the conditions under which growth is taking place, 
 and you at once change resulting form and function. It is in this man- 
 ner that, on a small scale, the horticulturist works in furnishing us what 
 are called improved varieties of flowers and fruits. It is in this manner 
 that animals, known to have been indisputably of the same original kind, 
 assume such different forms and characters in various climates. It is 
 true, we can not expect in an abrupt mariner to bring about such strik- 
 ing modifications in a solitary individual, for the life of an individual is 
 readily destroyed, but not so the life of a race ; and Nature, carrying on 
 her operations in the slow lapse of centuries, and dealing with races 
 rather than individuals, forces them up to any point of development she 
 may desire, but still the impress of the laws under which they have been 
 brought to that condition is upon them, and each betrays, in the embry- 
 onic and foetal forms, a manifestation of the metamorphoses through 
 which his race has run. 
 
RUDIMENTARY ORGANS. 491 
 
 Our attention might here be directed to that interesting class of phe- 
 nomena known to comparative anatomists under the title of Rudimentary 
 rudimentary organsthat is to say, organs which exist in an thfh^inter- 
 apparently undeveloped and useless condition, such, for in- pretation. 
 stance, as the mammas of the male mammalian, or the subcutaneous feet 
 of certain snakes for these are facts intimately connected with the sub- 
 ject before us. It looks as if Nature stopped short in her attempt at 
 reaching perfection, but it preves to us the constancy of the plans on 
 which she works. In the case of the whale, which, though apparently 
 belonging to the fishes, is a warm-blooded mammal and suckles its young, 
 the general type of its class is observed even down to minute particulars ; 
 it is the attribute of those belonging to it that they shall have seven cer- 
 vical vertebras, and this is equally the case with the camelopard, with 
 its long, graceful neck, and the* mole, which seems to have no neck at 
 all. In the whale, which conforms to that general rule, the teeth are, 
 moreover, found in the jaw, in the earlier period of life, uncut, precisely 
 as we find them at birth in the human infant. In this last instance we 
 think we see a wise provision and foresight of nature, which does not 
 give to man these masticating organs before the time they are wanted ; 
 but what are we to make of the former case ? Man is not always a true 
 interpreter of the works of God. Shut up, as they are, in the interior of 
 the bony mass of the jaw, never to be developed and never to be used, 
 does not that look to a careless observer something like a work of super- 
 erogation ? Or, in the case of such snakes as the anguis, typhlops, and 
 amphisbasna, why is it that Nature has placed under the skin the bony 
 representatives of the extremities : the mode of progression of those an- 
 imals is by the use of the ribs, and organs such as feet are never wanted. 
 
 We may also turn to the other department of physiology, the vegeta-^ 
 ble world, and what do we there see ? Rudimentary organs and excess 
 of development are .every where presented. An attentive examination 
 of any flower proves that we may with truth regard it as a transformed 
 branch, the law of development being such that that which might have 
 passed forward to the condition of a branch has turned to the condition 
 of a flower ; or, in still minuter particulars, we witness the same prin- 
 ciple : that which might have evolved into a leaf turns indifferently, as 
 circumstances may direct, into a sepal, a petal, or a stamen. 
 
 But is it possible that there is all this confusion and want of precision 
 in the works , of Nature ? Not so. If we consider rightly, Appearance of 
 we shall come to the conclusion that Nature never works rudimentary 
 
 , , organs the con- 
 
 COntingently, nor resorts to a sudden contnvance to meet an sequence of 
 
 exigency. All her operations are carried forward under far- law - 
 reaching and universal laws. These rudimentary and perhaps useless 
 organs come into existence through a general plan, of which they are 
 
492 OF THE ORGANIC CELL. 
 
 witnesses to us, if they subserve no other duty. They tell the same 
 great fact which is so loudly proclaimed by all the phenomena of the res- 
 toration of parts and renovation of tissues, that the grouping of orga- 
 nized matter into definite and special forms is not a wanton or chance ef- 
 fect, but is the direct and inevitable consequence of invariable physical 
 laws. 
 
 Expedients are for the vacillating and weak, law is for the strong. It 
 takes from the merit of any human contrivance if the engineer has to be 
 constantly tampering with it to keep it going ; we admire the machine 
 that continues its movements without variation after it has left its 
 maker's hand. I think we can have no nobler conception of the great 
 Author of the wonderful forms around us than to regard them all, the 
 vegetable and animal, the living and lifeless, the earth, and the stars, and 
 the numberless worlds that are beyond our vision, as the offspring of 
 one primitive idea, and the consequences of one primordial law. 
 
 CHAPTER III. 
 
 OF THE ORGANIC CELL : ITS DEVELOPMENT, REPRODUCTION, AND DIF- 
 FERENTIATION OF STRUCTURE AND FUNCTION. 
 
 Simple and Nucleated Cells. The Simple Cell: its Parts and Functions. The Nucleated Cell: 
 its Parts and Functions. Activity of the Nucleus. Other Forms of Cells. Cells arise by 
 Self-origination and Reproduction. Reproduction by Subdivision and Endogenously. 
 
 The Animal Cell. Forms of Cellular Tissue. Forms of Vascular Tissue. Spiral Vessels, 
 Ducts, etc. 
 
 Differentiation of Cells. Acquisition of new Functions. Differentiation of the Animal Cell. 
 
 Depends on Physical Causes. Influence of Heat and Air. Epoch of Differentiation. 
 
 
 
 THE organic cell, which is the starting-point of every organism, veg- 
 Simpieandnu- etable or animal, consists of a vesicle or shell, with included 
 cieated cells, contents. If the vesicle be of uniform thickness all over, 
 the cell is a simple one ; but if there be upon some portion of it a thick- 
 ened granular spot, the cell is said to be nucleated. 
 
 The vesicle of the SIMPLE VEGETABLE CELL, more closely examined, 
 The simple ^ s found to be composed of different laminas or strata. The 
 vegetable cell: innermost, designated the primordial utricle, consists of an 
 
 its wall, utri- . ' _ & /. , 
 
 cie, and endo- azotized substance, a member 01 the protein group. On the 
 chrome. exterior of this pellicle, and, as it were, arising from its sur- 
 
 face, lies the cell wall, which serves to give protection to the parts with- 
 in. The cell wall is not a mere extension by thickening of the primor- 
 dial utricle, as is proved by its chemical constitution ; for, though it may 
 vary in physical condition from a mere glairy mucus to a firm woody 
 
THE NUCLEATED CELL. 493 
 
 texture, it uniformly consists of a non-nitrogenized body, gummy, amy- 
 laceous, or ligneous. Indeed, though the vegetable cell is usually said 
 to have two concentric investitures, the nitrogenized primordial utricle 
 and the non-nitrogenized wall, it is more exact to describe the latter as 
 consisting of several pellicles, which have been generated in succession 
 from the outside surface of the utricle, and these differ from one another 
 in their physical qualities, according as they are nearer to the surface of 
 the utricle or nearer to the general exterior, recalling, in this respect, the 
 analogous condition of the cuticle under circumstances that are some- 
 what parallel. 
 
 Within the primordial utricle, the cell contents present themselves of 
 a different nature and different form, according as the species of the cell 
 may be. In different cases they are colored of various tints, and are of 
 various consistency, more solid or more liquid. To the cell-contents the 
 convenient designation of endochrome is given. This interior content is 
 not to be understoodas having a homogenous constitution, since sometimes 
 even its colored portions are separated out and arranged in dots or spiral 
 lines, which are very distinct from the remaining uncolored material. 
 
 The active portion of such a cell consists of the utricle and endochrome 
 conjointly, the cell wall only discharging a mechanical office. In the 
 simple cell, all parts of the utricle appear to be endowed with equal pow- 
 er for carrying on the functions of the organism. 
 
 But in those cells which possess a nucleus, the energy is no longer dif- 
 fused with uniformity, the nucleus concentrating much of , 
 the power in itself, and serving as a centre of activity. Its activity of its 
 nitrogenized constitution indicates that it is in relation with nucleus - 
 the primordial utricle, and not with the cell wall ; a conclusion which is 
 corroborated by its physiological activity, as also by the fact that in those 
 nucleated cells which exhibit currents, the nucleus appears to be the 
 starting-point from which they diverge in various directions. 
 
 There are subordinate species of cells, as the spiral and the dotted. 
 These exhibit points of re-enforcement or thickening, such Subordinate 
 as the appearance of a thread wound spirally, or in dots here forms of cells - 
 and there on the interior of the wall. There would seem to be a tend- 
 ency during the development of a cell for these parts to assume a spiral 
 arrangement. Even the endochrome shows this peculiarity, the green 
 material being often arranged in a spiral course on the interior of the cell. 
 
 Thus constituted, each cell runs through a definite cycle or career, hav- 
 ing its moment of birth, its period of maturity, its time of death. Dur- 
 ing its mature life it discharges with activity the special function to which 
 it is devoted, but in so doing becomes eventually worn out and old. 
 The period of activity of cells of different species is very different, some 
 passing away quickly, and others having a longer duration. 
 
494 REPRODUCTION BY SUBDIVISION. 
 
 The commencement of cells is either, 1st, by self-origination, or, 2d, 
 by reproduction. 1st. Cells arise in an obscure manner from 
 
 Origin of cells J r t n 
 
 byseif-origina- homogeneous particles floating in a protoplasma, which, tak- 
 tion. j n g on Development, have a vesicle thrown over them, and, 
 
 being of a spherical shape, present the aspect of a cell wall and cavity. 
 The granular content by degrees increases as the young cell grows in all 
 its dimensions. From that granular content new cells may arise. 
 
 Though this process is spoken of as one of self-origination, it is quite 
 probable that the spherical and homogeneous particles floating in the 
 protoplasma, and which were the points of origin of the cells that have 
 arisen, were themselves nothing more than germs which had been pre- 
 pared by an antecedent generation of cells. This is the opinion com- 
 monly entertained of their nature, though its truth has never yet been 
 demonstrated by actual observation. It is adopted because of its proba- 
 bility, for we usually observe that every new organism is the descendant 
 of an older one ; yet it should not be forgotten that there must have been 
 a time when the first organic cell arose from inorganic material, and it is 
 not unphilosophical to suppose that what must have occurred once may 
 occur again. 
 
 Origin of cells . 2d. Cells are reproduced from antecedent ones of the 
 by reproduction. same kind by subdivision, by budding, by endogenous gen- 
 eration. 
 
 The reproduction of cells by subdivision is strikingly illustrated by 
 Reproduction theHasmatococcus binalis. The manner of the process seems 
 by subdivision. f b e as follows. The endochrome of the original spherical 
 
 cell, , Fig. 230, begins to undergo bi-par- 
 tition as at b, and as the dividing portions 
 recede from one another the primordial utri- 
 cle bends round them. Next a layer of per- 
 manent ce ll wall, of a mucous character on 
 its exterior, is produced, which accompanies 
 the inflection of the primordial utricle as at 
 } e c, and, after a while, the bi-partition is com- 
 plete, and the separated portions constitute 
 distinct individual cells. The subdivision 
 may be repeated as at d. The seat of the 
 
 Reproduction of H^matococcus binalis. primarv acti(m fe gaid to be in the endo _ 
 
 chrome ; but of this there may be reasonable doubt, since generally the 
 primordial utricle is the place of energy of the cell ; and where nucleated 
 cells undergo multiplication by this process of fissure, the nucleus di- 
 vides along with the endochrome, so that both the resulting portions pos- 
 sess a part of it. But if the utricle, with its nucleus, was inert during 
 this operation, it would seem that the vesicle should tear any where 
 
KEPRODUCTION BY BUDDING. 
 
 495 
 
 rather than through that thickened and stronger place. The phenomena 
 are equally well accounted for by imputing the first action to the utricle 
 itself, which, exerting a constrictive pressure upon the endochrome in the 
 direction of one of the great circles of the cell, divides it in the manner 
 that we see. 
 
 This process of multiplication is exhibited in Fig. 231, in Conferva 
 
 Fig. 231. 
 
 Cell reproduction in Conferva glomerata. 
 
 glomerata, which consists of a system of cells arranged in a filament. At 
 A two states are shown, complete partition at , and incomplete at a / at 
 B, C, D, the successive steps of partition, a being the primordial utricle, 
 b the endochrome, c cell membrane, d mucous investment. At E the 
 primordial utricles are separated, and the cell membrane intervenes. At 
 F the membrane is completed so as to exhibit lamina. 
 
 The cells which have thus arisen by subdivision soon grow to the 
 size of the one from which they were derived, and are ready for subdi- 
 vision in their turn. Indeed, it often happens that traces of incipient 
 subdivision may be detected long before the cell has reached its mature 
 dimensions. 
 
 The reproduction of cells by budding may be illustrated by the vesi- 
 cles of the yeast-plant ; and though, in those cases in which the budding 
 cell possesses a nucleus, the nucleus is not necessarily involved, yet the 
 conclusion indicated in the preceding paragraph is greatly strengthened, 
 for we must clearly attribute the result which now takes place to an in- 
 creased nutrition of the primordial utricle upon a restricted portion of 
 its surface, and not to a distention arising from a pressure of the endo- 
 chrome within. So closely does this resemble the preceding mode of re- 
 production, that they are commonly said to be really of the same kind, 
 or, rather, to offer no other distinction than this, that in the former the 
 
496 THE ANIMAL CELL. 
 
 cell divides into portions which are sensibly equal, in this into unequal 
 parts. 
 
 Cells are said to arise from endogenous generation when they make 
 their first appearance in the cavity of a former cell, of which 
 
 Endogenous Jrir . *. . . 
 
 generation of the endochrome exhibits a disposition to divide into many 
 small portions, at first doubtfully, then more distinctly, and 
 each one of these portions obtaining a covering investiture or primordial 
 utricle for itself. The process continues until the young brood of cells 
 has reached a certain degree of perfection, when they -escape from their 
 confinement, either by the fissuring or deliquescence of the old cell wall. 
 The young cells may now lead an independent life and grow rapidly. 
 In this manner zoospores arise, which are young cells having for a time 
 a power of locomotion, from cilia which have been developed from their 
 walls, or for other reasons. 
 
 The reproduction of cells l>y endogenous generation is commonly at- 
 tributed to an action arising in the endochrome which brings on its sub- 
 division into portions. From the fact that these portions are eventually 
 found clothed with a primordial utricle, we might be led to suspect that 
 the original seat of the action is in this, as in the preceding cases, that 
 portion of the original cell which, undergoing projection internally, di- 
 vides the endochrome and incloses the portions in its meshes. Such 
 membranous projections may be difficult of detection in the first instance, 
 because of their extreme tenuity ; nor is the fact that the zoospores 
 move freely in the cavity of the mother cell just before their escape at 
 all in contradiction to this. 
 
 THE ANIMAL CELL presents a structural arrangement diifering from 
 Peculiarity of the vegetable in this, that it does not possess a proper cell 
 the animal cell. wa ll, but consists of a primordial utricle and interior con- 
 tent alone. Its manner of reproduction is of three kinds : 1st. From 
 germs ; 2d. By fissure ; 3d. Endogenously. Where animal cells orig- 
 inate from germs, these seem to be granules of a substance analogous to 
 fibrin, which are floating in the formative liquid. In duplication by sub- 
 division, the import of the nucleus is shown by the fact that the action 
 begins at it. It may be said of animal cells that the nucleus maintains 
 a more conspicuous relation than it does in the case of vegetable ones. 
 Reproduction in the endogenous manner is carried forward in the case of 
 these cells in the manner described in a preceding paragraph. 
 
 OP THE CONSTRUCTION OP CELLULAR AND VASCULAR TISSUES. 
 
 By their development and juxtaposition with one another, cells give 
 
 Cellular tissue r * se to coirt inuous fabrics of various kinds, or cellular tissue. 
 
 its various If the development of new cells occurs in a space where there 
 
 is freedom from pressure, the cells maintain their original 
 
CELLULAR TISSUE. 
 
 497 
 
 Fig. 232. 
 
 spherical form, as seen in the photograph, Fig. 232. But should the 
 
 development occur in a confined space, 
 or under circumstances of pressure, the 
 intercellular spaces which necessarily ex- 
 ist in the former case by reason of the 
 spherical shape, are now encroached upon, 
 and the cells assume various angular 
 forms, such as parallelopipedons, rhom- 
 bic dodecahedrons, &c. Of the former 
 we have an example in the photograph, 
 Fig. 233, which represents a section of 
 muriform cellular tissue. In other,cases, 
 with a view of giving resistance to press- 
 simple cellular tissue, magnified 50 diameters. ^ the i nte rior of each O f the Cells is 
 
 fortified by a fibre, and thus arises the tissue of which we have an exam- 
 
 Fig. 23.4. 
 Fig. 233. 
 
 Muriform cellular tissue, magnified 50 diameters. 
 
 Fibro-cellular tissue, magnified 50 diameters. 
 
 pie in the photograph, Fig. 234. Two or more fibres may, in this man- 
 ner, be employed, and when such is the case, it is observed that they do 
 not cross one another, the one winding from right to left, the other from 
 left to right, but they are laid parallel to each other, and form a com- 
 pound strand. In other cases the constituent cells of the tissue assume 
 much more complicated forms, as, for instance, in the stellate variety. 
 These more complicated forms prove that it is not altogether through 
 the influence of a force of compression that cells assume modified shapes, 
 but that on many occasions the disposition of their primordial utricle to 
 branch in various directions, of which mention has been made in a pre- 
 ceding paragraph, is the true cause of the variations in question. 
 
 This disposition to grow spontaneously in one direction rather than in 
 another is the cause of the production of the different kinds of vascular 
 tissue. A cell undergoing extreme elongation in one direction, either by 
 
 II 
 
498 
 
 VASCULAE TISSUE. 
 
 reason of this quality of its primordial utricle, or through un- 
 Vascular tissue * 
 
 and its modifi- equal nutrition, or other cause, gives origin to a tube. And 
 if, of several cells thus elongated, and placed end to end on 
 each other, the terminal portions should be obliterated either by rup- 
 ture or absorption, a vessel permeable throughout is the result. In this 
 manner vascular tissue arises. These vessels still exhibit the structural 
 peculiarity of the cells from which they have originated in this, that they 
 may be fortified in their interior with fibres wound in a spiral, and so 
 constituting a spiral vessel ; or wound in rings, and forming annular 
 ducts. In like manner, through similar modifications, the varieties known 
 as reticulated and dotted ducts arise. In these fibre-vascular tissues it 
 frequently happens that the fortifying thread is double or even quadru- 
 ple. Of spiral vessels derived from a cactus we have an example in the 
 photograph, Fig. 235, and in those from the banana in that of Fig. 236. 
 
 Fig. 236. 
 
 Fig, 235. 
 
 Spiral vessels of cactus, magnified 50 diameters. 
 
 Spiral vessels of banana, magnified 50 dinmctcrs. 
 
 The spiral vessels of plants Contain air. Other tubes are for the 
 Spiral vessels, conveyance of liquid; the laticiferous vessels, for example, 
 v "f'co- which are branching tubes Fi ,. 237 . 
 
 nifers. for transmitting the latex 
 
 of plants. Again, in other cases, the 
 interior of the vessel is more or less 
 completely filled up by a gradual de- 
 posit of solid material, it being in 
 this manner that proper woody fibre 
 is formed from long, spindle-shaped 
 cells. Vascular tissue in coniferous 
 plants presents a peculiar dotted, as- 
 pect from disc-like forms, exhibiting 
 a pair of concentric circles, which are 
 set at regular intervals upon it, as 
 shown in the photograph, Fig. 237, 
 
 Woody fibre of pine, magnified 50 diameters. 
 
YELLOW AND WHITE FIBROUS TISSUE. 
 
 499 
 
 which is dotted woody fibre from pine. The circular discs or glands run 
 in single rows except in one place, where a double row is seen. Among 
 true living^ pines more than two rows are not met with. In the Arauca- 
 ria the rows are sometimes triple or even quadruple. 
 
 Animal vascular tissue arises in the same manner as vegetable, by the 
 conjunction of elongated cells and the obliteration of their v ,, 
 
 . Yellow and 
 
 terminations. The physiological purposes these vessels sub- white fibrous 
 serve are, as in the other instance, the conveyance of gases or tlssue< 
 liquids. But fibres may form in animal fabrics without the previous in- 
 termedium of cells, either directly from fibrin, the parts of which possess 
 the quality of agglutinating into threads, or from the coalescence under 
 like circumstances of substances allied to gelatine, which yield the varie- 
 ties of fibrous tissue known respectively as the yellow and the white, 
 the former being composed of branching filaments, as seen in Fig. 238. 
 It is unacted upon by warm acetic acid, and, from its extraordinary elas- 
 
 Fig. 23S.' Fig. 289. 
 
 represented i 
 
 Yellow fibrous tissue, magnified 300 diameters. White fibrous tissue, magnified 300 diameters. 
 
 ticity, is used wherever that quality is required. The latter, which is 
 . 239, shows strands of a wavy appearance: it is inelas- 
 240. tic, softens under the action of acetic acid, 
 
 being thereby distinguished from the pre- 
 ceding, and is employed on account of 
 its tenacity wherever resistance to exten- 
 sion is required, as, for example, in the 
 ligaments of the joints. The solid ani- 
 mal fibres are therefore employed where 
 physical qualities are necessary, the hol- 
 low tubes for organic processes. By 
 some physiologists it is believed that 
 both yellow and white fibrous tissue arise 
 from cells. 
 
 Areolar tissue, magnified 25 diameters. Areolai* 01' Connective tisSUC. Fig. 240, 
 
50Q DIFFERENTIATION OF CELLS. 
 
 is composed of the two preceding elements, the yellow and white fibrous, 
 interwoven with each other so as to constitute a porous structure, with a 
 multitude of intercommunicating spaces. It is to be understood that 
 these interstices are wholly distinct from cells; hence the inapplicability 
 of the term cellular, sometimes employed for this tissue. Areolar tissue 
 is employed for uniting the various animal parts. Its interspaces are 
 filled with a fluid, which, when in jexcess, is spoken of as dropsical effu- 
 sion. Air, artificially or accidentally introduced at any point into it, may 
 pass to every part, as is illustrated in cases of emphysema. The speci- 
 men from which the figure is taken was in this manner inflated. 
 
 By the differentiation of cells is meant the assumption of a variation 
 Differentiation in their structure from which follows, as a consequence, the 
 of cells. capacity of discharging new functions. When the red snow- 
 
 alga multiplies, as previously described, each of the young cells resem- 
 bles that from which it was derived in structure, and discharges a simi- 
 lar office. In such a case there is development, but not differentiation. 
 When, on the contrary, a lichen grows on a rock, though the original 
 tendency in development may have been for the production of cells from 
 the first germ absolutely similar in all directions, yet the circumstances 
 of growth are such that very soon the physical conditions under which 
 the cells of different parts of the growing mass are generated become dif- 
 ferent. Those which are next to the rock are screened by the superin- 
 cumbent ones from the sunlight and the air ; they are therefore develop- 
 ed in a comparative obscurity, and in the presence of moisture holding in 
 Acquisition of solution inorganic salts. Under such circumstances, it is to 
 new functions, "foe expected that a modification will ensue in their construc- 
 tion, and that they will be different from those which are developing on 
 the exterior in contact with the dry air ; and, since a change of structure 
 invariably implies a change of function, we might expect, as in reality is 
 the case, that the outer cells are for the obtaining of carbon from the air, 
 being acted upon by the sunlight, and the under cells for procuring moist- 
 ure and such saline substances as may be wanted from the rock surface 
 below. In such a case as this there is a differentiation both of structure 
 and of function. 
 
 Structural differentiation is to be received as the cause of functional 
 Differentiation differentiation, which is its consequence. The former, in 
 in a regular se- every instance, arises from the changed circumstances under 
 
 quenceappears J . \. i-t^- i c - 
 
 to be determ- which cells are being generated, and if this change of circum- 
 med by law. stances follows a regular order or sequence, the differentia- 
 tion will assume the appearance of being guided by a fixed law. Many 
 physiologists, who have not been disposed to accord to physical agents a 
 due influence in this respect, have therefore imputed to the developing 
 cell a power or property of spontaneously pursuing a determinate career. 
 
DIFFERENTIATION OF ANIMALS. 501 
 
 It is clear that the facts are capable of interpretation either upon the doc- 
 trine that external conditions guide or compel the cell in its development- 
 al career, or that it, by reason of an innate power, spontaneously pursues 
 a determinate course in spite of them ; determinate, because that power 
 is acting under a law. The mixed doctrine, which imputes the career of 
 development in part to the innate power of the cell, and in part to the in- 
 fluence of external conditions, it is needless for us here to consider. 
 
 No doubt can be entertained of the fact that a cell or congeries of cells 
 will differentiate when submitted to new physical conditions while in the 
 act of development. Thus certain lichens pass into forms analogous to 
 algae if the normal conditions of their production be reversed if, instead 
 of developing in places that are dry and brightly illuminated, they are 
 supplied with moisture, and made to grow in obscurity; and, in like man- 
 ner, some of the fungi will simulate algse if they are compelled to vege- 
 tate in water. 
 
 The separation of the organ for the reception of water and that for the 
 reception of carbon, which is first shadowed forth in the under and outer 
 surface of the lichens, is manifested in perfection by highly-developed 
 plants, in which the root discharges the former, and the leaves the latter 
 duty, and these are separated widely apart from each other by the as- 
 cending axis or stem. 
 
 The remarks here made respecting plants might be repeated as re- 
 gards animals, which, during their development, exhibit the Differentiation 
 principle of differentiation even in a more striking way. of the animal 
 Thus, in the protozoa, as in the protophyta, cells undergo cel1 ' 
 duplication, and, by development in new positions, or under changed cir- 
 cumstances, exhibit differentiation. The trivial circumstances under 
 which new functions are assumed are well shown in Trembley's experi- 
 ments with the hydra* This polype, which is nothing more Experiments 
 than a gastric sac furnished with prehensile tentacles, re- with the hydra, 
 spires on its outer surface and digests on its inner; but so closely are 
 these functions blended together that, if the animal be turned inside out, 
 the surface that did respire will now digest, and that which did digest 
 will now respire. Indeed, we may in an ideal manner con- Ideal differen _ 
 ceive of the production of the more elementary animal forms tiation of ani- 
 as arising from a simple sac or bag, which, furnishing a start- 
 ing-point, exhibits its first acquirement of localization of function by the 
 doubling of one half into the other, thereby giving rise to a cup or pocket 
 shaped form, so that respiration and digestion, which were confusedly and 
 conjointly carried forw'ard upon the same surface, are now parted from 
 each other, the outside of the cup being devoted to the one, and the in- 
 side to the other. Increased endowments are obtained by crimping or 
 dividing the edge of the cup, prehensile organs of less or greater length 
 
502 CAUSE OF DIFFERENTIATION. 
 
 and power thereby arising ; and this, in reality, is the structure of the 
 hydra just alluded to. Another advance is made by the preparation of 
 new and complicated structures, fashioned out in the substance between 
 the inner and the outer wall, and in this manner arise the various mech- 
 anisms for respiration and reproduction. Such a state of things is pre- 
 sented by the Actinia. 
 
 It will be found, when we describe the development of the higher ani- 
 Individuai and mals, that a parallelism is observed between the career of 
 race develop- Q^h individual and that of the series to which it belongs, 
 niais by differ- The evidence furnished by natural history and paleontology 
 entiation. proves that, in the development of animal species, there has 
 been an orderly progress, not so much from those of a lower to those of 
 a higher form, as from the general to the special ; a gradual parting out 
 of structures and functions that were once commingled and coalesced, an 
 elaboration which may be attributed either to a melioration of the cir- 
 cumstances under which species were successively forming, or to the 
 innate power possessed by the organic structure itself. Even at the pres- 
 ent time our knowledge of the order of geological change is sufficiently 
 exact to enable us to institute an inquiry into the probability of the cor- 
 Differentiation rectness of each of these hypotheses, upon the principle that, 
 d h P 8?crfdr smce there is that parallelism between the career of individ- 
 cumstances. ual development and race development, there should also be 
 an analogy in the physical circumstances under which they have taken 
 place. Among conditions in animal development, two prominent ones 
 may be mentioned ; they are the degree of temperature at which the pro- 
 cess is carried forward, and the quality or nature of the medium supplied 
 for respiration. No doubt can now exist that, as regards the former, 
 there has been a gradual diminution from the early times, and that, as 
 respects the latter, the quantity of oxygen furnished in the medium of 
 respiration has been increased. It has long been observed, in a general 
 way, that there is a correspondence between the activity of respiration 
 and the degree of animal endowment, both as regards the individual and 
 Influence of ^ e race> The provision made for the more perfect conduc- 
 the aerial tion of the process from the moment that the embryo exhibits 
 any arterialization of its blood, is always attended with, if it 
 is not the cause of, increasing animal power. The supply of oxygen at 
 the first period is very imperfect, but instrumental means are introduced 
 in succession to increase the amount. When a mere membrane has be- 
 come insufficient to meet the requirements, branchiaB are resorted to, and 
 these, in their turn, are replaced by lungs. In a' double way, therefore, 
 an increased supply is secured, by alterations in the mechanism obtain- 
 ing it, which gradually becomes more and more adapted to the end in 
 view, or by variations in the chemical constitution of the medium which 
 
INFLUENCE OF EXTERNAL AGENTS. 503 
 
 furnishes it. Thus, in the development of a mammal, the first and lim- 
 ited supply of oxygen is from the portion contained in the liquids of the 
 ovum ; a far more copious one, at a later period, is derived from the pla- 
 cental mechanism ; but these subordinate states eventually give place to 
 the direct respiration of the open atmospheric air. As this gradual march 
 in the evolution of the. respiratory function is going forward, it is attend- 
 ed by a corresponding development of all the animal capabilities. 
 
 So, too, on the great scale with genera and species. In the impure at- 
 mosphere of the earliest geological times, it was not possible that energet- 
 ic respiration could be carried on either by aquatic or by aerial animals. 
 Both may be included in the remark, for it is demonstrable that, on ordi- 
 nary physical principles, there must ever be a correspondence between the 
 chemical constitution of the atmospheric air and the gas of respiration 
 dissolved in the sea, or other natural waters. Abundant geological evi- 
 dence is before us to the effect that the entire respiratory medium, both 
 atmospheric and aquatic, has passed through a gradual amelioration, the 
 percentage amount of its irrespirable elements declining, and that of its 
 oxygen correspondingly increasing. The removal of those prodigious 
 masses of carbon deposited as coal satisfactorily establishes this point ; 
 and, therefore, as far as that medium is concerned, there is a general re- 
 semblance between the conditions under which the entire animal series 
 and the single individual have been placed. 
 
 We might include in these remarks the vegetable as well as the ani- 
 mal series ; for, as respects flowering plants, it is the special function 
 of their floral or reproductive apparatus to discharge at a particular epoch 
 the functions of an animal in taking oxygen from the air, and replacing 
 it by carbonic acid. There would, therefore, be no cause for surprise if, 
 in that ancient carbonated atmosphere, cryptogamic plants alone could 
 maintain themselves, and that the flowering tribes could only appear after 
 a due change in the aerial constitution, which also gave to hot-blooded 
 animals the opportunity of coming forth. That change, as we have said, 
 consisted essentially in the appearance of a great excess of oxygen gas. 
 Such a superficial examination of the question shows that there is a par- 
 allelism between the physical conditions under which the animal series, 
 in the lapse of countless centuries, has been placed, and those to which, 
 in the shorter period of its history, the developing individual is submit- 
 ted, at least as respects the respiratory function. But it is to be re- 
 membered that respiration is the prime function in the animal economy. 
 
 As regards the influence of heat, it has been remarked in the preceding 
 chapter that, at the period of the first appearance of organic i n fl uen ce of 
 forms, there was not only a high, but likewise a uniform tern- heat - 
 perature all over the globe. The evidence establishing this is already 
 given ; but if thus, in what might be termed the infancy of the organic 
 
504 EPOCHS OF DIFFEKENTIATIOX. 
 
 series, such a perfect uniformity in the condition of temperature obtain- 
 ed, the same is often observed in the first periods of individual develop- 
 ment. The circumstances under which the ovum commences its career, 
 even in the highest tribes, insure for it a perfect relief from every varia- 
 tion of heat. Included in the body of the female, it is cut off from all 
 external causes of disturbance, and kept at the temperature of her body, 
 whatever that temperature may be. In those cases, as in birds, in which 
 the embryo is developed under circumstances of necessary exposure, a 
 strong instinct is called into operation, and, by the incubation of the pa- 
 rent, the necessary uniformity is secured. Again, in other instances, as 
 in the ova of insects, which, by reason of their minuteness and their fre- 
 quently exposed position, although they may run through their earlier 
 changes with relatively great rapidity, some accomplishing them in the 
 almost uniform warmth of a summer's day, development never does nor 
 can occur until the required condition, even if it be temporary, as to uni- 
 formity of temperature, is reached. 
 
 These considerations, though not affording an absolute proof that the 
 career of development is guided by the influence of external physical 
 conditions, are sufficiently significant to cast an air of probability over 
 that doctrine ; and even if we adopt the view that the developing germ 
 possesses a plastic power, which spontaneously compels it to run forward 
 from stage to stage in a predestined career if we recall what has already- 
 been said respecting that plastic power, that perhaps it is itself nothing 
 more than a manifestation of the remains of antecedent physical impres- 
 sions, we are really brought back to the same starting-point ; and, under 
 any hypothesis, we encounter, sooner or later, as a necessary postulate, 
 the grand doctrine that, directly or indirectly, development is a function 
 of external physical condition. 
 
 It is not to be supposed that differentiation takes place with equal 
 Epochs of dif- ease at a H periods of the history of organic forms, whether 
 ferentiation. we consider them in the great scale, as constituting the ani- 
 mal series, or* on the small, in the individual. There are undoubtedly 
 epochs in each of their histories at which the exertion of an external in- 
 fluence will produce an effect infinitely greater than that which would 
 occur at any other moment. If we may be permitted to use such a me- 
 chanical illustration, the career of an organism recalls the flight of a 
 heavy projectile, as a shell, thrown upward, which, at the first moments 
 of its ascent and the last of its descent, pursues its way irresistibly, but 
 when it is at the top of its flight, and the momentum which had been im- 
 parted to it is just ceasing, the slightest breath of air, or the exertion of 
 any other insignificant force, will divert it into a path different from that 
 in which it would have gone ; and so, in the career of an organism, there 
 are moments when forces, which, at another time, would have been unfelt, 
 
REPRODUCTION AND DEVELOPMENT. 505 
 
 can bring on differentiation, and, through it, call into existence new func- 
 tions, and thereby forever determine a new course, through which it must 
 pass. It is because a due weight has not been given to this considera- 
 tion that many physiologists have depreciated the influence of external 
 circumstances, or even denied it altogether, for they have assumed that, 
 since we can not produce a more marked change than we do in the way 
 of accomplishing a variation in species by artificially altering the condi- 
 tions under which they exist, such conditions can have had but little 
 power in bringing them to their present state. 
 
 Upon the whole, there can be no doubt that differentiation will occur 
 in a more marked manner according as the exciting impres- Organic chan- 
 sion is made at an earlier period of the organic career. Con- S^^/finft 
 versely, the more advanced the organism, the less the prob- periods of life, 
 ability of differentiation. For this reason it is that striking changes of 
 this kind are rarely witnessed in individual life : they occur chiefly in 
 the first embryonic states, and therefore, for the most part, require for 
 their full manifestation generation after generation. Great organic varia- 
 tions are not, then, to be expected in the individual, though they may be 
 distinctly manifested in the course of time by the race to which it be- 
 longs. 
 
 CHAPTER IV. 
 
 OF REPRODUCTION AND DEVELOPMENT. 
 
 Relation of Organic Beings : they come from a similar Cell and develop to different Points. 
 Their Division by Classification is fictitious.- Development and Differentiation. Homogenesis 
 and Heterogenesis. They depend on physical Conditions. The reproductive State closes De- 
 velopment. 
 
 Development is from the General to the Special. Law of Von Bar. Invariable Sequence in 
 
 OF REPRODUCTION: 1st. By Generation. Conjugation and Filaments. The Sperm-cell: its 
 
 Production. Spermatozoa. The Germ-cell: its Production. 
 Ovum in the Ovary. Its Structure. Corpus Luteum. 
 
 Ovum in the Oviduct. Mulberry Mass. Germinal Membrane. The CJiorion. 
 Ovum in the Uterus. Membrana Decidua. Placenta. Development of the Embryo. Types 
 
 of Nutrition. Of Conception. Of Gestation. Of Parturition. Influence of both Parents. 
 2d. By Gemmation. Budding of Plants and Animals. Of Grafting. Limit of Gemmation. 
 
 Influence of Temperature on Gemmation. 
 Alternations of Generation. Its Explanation. 
 
 IN the popular view of the organic world, each individual being is re- 
 garded as maintaining an existence independent and irre- Popular view 
 spective of all others, or, at most, only connected with those pJSenSXfo*. 
 of its own race or kind. Without any apparent disturb- ganic beings. 
 
506 THE PRIMORDIAL GERM. 
 
 ance of the general system, this or that species or genus might never 
 have existed, since it stands in no relation as being the product of others, 
 nor as having been concerned in giving origin to others. 
 
 But these superficial conceptions are now to .be replaced by others of 
 
 a far more general and philosophical order, which present to us 
 
 organic creation under an aspect of sublime grandeur, each class 
 
 of beings standing in an intercommunication or connection with others 
 
 a part of a plan, the manifestations of which are not limited to the forms 
 
 now existing, but also include those presented by the ancient geological 
 
 times. These views cast a flood of light not only upon the relations of 
 
 the various races of life to one another, but also of the human family to 
 
 them, illustrating the course through which man has hitherto passed, and 
 
 indicating that through which, in future ages, he is to go. 
 
 Starting from a solitary cell, development takes place, and, according 
 All organic be- as extraneous forces may be brought into action, variable in 
 thf\ame tf erm tne ^ r nature, and differing in their intensity, the resulting or- 
 or cell. ganisms will differ. If such language may be used, the aim 
 
 of Nature is to reach a certain ideal model or archetype. As the pas- 
 sage toward this ideal model is more or less perfectly accomplished, form 
 after form, in varied succession, arises. The original substratum or ma- 
 terial is in every instance alike ; for it matters not what may be the class 
 of animals or of plants, the primordial germ, as far as investigation has 
 gone, is in every instance the same. The microscope shows no differ- 
 ence, but, on the contrary, demonstrates the identity of the first cell, 
 which, if it passes but a little way on its forward course, ends in pre- 
 senting the obscure cryptogamic plant, or, if it runs forward toward 
 reaching the archetype, ends in the production of man. The diversity 
 of form that is eventually presented depends then, not upon the consti- 
 tution or aspect of the primitive cell, but upon the influence of the many 
 surrounding agencies to which it is exposed. In one instance, through 
 The primitive the interworking of these agencies perhaps by cessation of 
 ward^oTiffer- one or P erna P s by ^ s increased intensity development 
 ent points. comes up rapidly to a certain point, and there stops. In 
 another case, through change in the conditions, it runs to a farther de- 
 gree, and there stops. Organic beings are, therefore, the materialized 
 embodiment of what must take place through the action of given forces, 
 of a given intensity, and under given conditions, on an evolving cell ; 
 The ciassifica- and, though it may suit the purposes of description to classify 
 Siy anTfic- t ^ iem * nto or ^ ers J genera, species, or other such subdivisions, 
 titious. . it must never be forgotten that these are artificial fictions, 
 
 and have no real foundation in nature. 
 
 Not only is the primordial cell in all instances the same, but the first 
 stages of its career are in all instances identical, and this whether we 
 
VALUE OF EMBRYONIC FORMS. 507 
 
 consider it in the lowest or the highest cases, belonging either to the veg- 
 etable or the animal kingdom. It is a process of repetition or reproduc- 
 tion, cell arising from cell. And here at once we may correct the lan- 
 guage so often used indeed, which we have ourselves just used in this 
 respect, for such terms as high and low are only to be employed in a very 
 restricted sense. The evolving cell gives rise to other- cells, but for a pe- 
 riod of time no indication is presented as to which of the two kingdoms 
 it is to belong, animal or plant. By degrees, as the develop- Development 
 ment goes on, that point is determined, and so, one after an- is attended by 
 other, the unfolding mass gradually reveals the class, order, evolving of pe- 
 family, genus, species, and, finally, its sex and individual pe- culiarities - 
 culiarities. In all this there is an evolving of the special out of the gen- 
 eral ; one after another, peculiarities, which are more and more minute, 
 arise ; and thus we are not to regard the progress of development as tak- 
 ing place from the lower to the higher, forms that are more and more com- 
 plex arising in succession, but we are to regard it as the gradual unfold- 
 ing of the special from the general. 
 
 This career of development applies equally to the case of any individ- 
 ual animal, or any race of animals. Thus man himself, in Analogy of de- 
 succession, passes through a great variety of forms, from the ^faSSidual 
 condition of a simple cell; these forms merging by degrees andin the race, 
 into one another, the form of tlie serpent, of the fish, of the bird, and this 
 not only as regards the entire system in the aggregate, but also as re- 
 gards each one of its constituent mechanisms the nervous system, the 
 circulatory, the digestive. Now, on the passage onward, these forms are 
 to be regarded, as has been well expressed, each one as the scaffolding 
 by which the next is built ; and just as man, in his embryonic transit, 
 presents these successive aspects on the small scale, so does the entire 
 animal series present them in the world on the great scale. Kaces of 
 animals are not to be compared as though they were more perfect or low- 
 er than one another, but as having advanced more or less in the direction 
 from the general to the special ; and therefore, in this philosophical view, 
 we are justified in regarding those animated forms which heretofore have 
 been spoken of as lower in the animal scale as being, in reality, the em- 
 bryos of those that are higher ; and this should lead us to a juster esti- 
 mate of their relation of value toward one another, since we are very apt 
 to contrast them in that respect. In the case of an individ- Value of em- 
 ual, as in man, we put at once a true interpretation on the kryonic forms, 
 value of the various transitory conditions through which he has passed, 
 estimating these as of but little intrinsic importance; as being, as it were, 
 no more than links in a chain ; and this may teach us a more just appre- 
 ciation of the relations of animal races to one another and to the human 
 species. It may teach us the folly of comparing, as some have endeav- 
 
508 DEVELOPMENT OF THE SPECIAL FROM THE GENERAL. 
 
 ored to do, the animal tribes with ourselves ; of measuring their instincts 
 with our mental operations ; things which are different terms of two dif- 
 ferent series, and things which are incommensurable. 
 
 There are three cases in which we might consider this career. These 
 are, first, in the development of particular organs, as the digestive, res- 
 piratory, or circulatory ; second, in the development of individual beings, 
 which pass in their onward progress, as we have said, through various 
 forms in succession; third, in the development of species, presenting 
 what have been formerly designated as successive stages of increasing 
 perfection. For all these various cases a single illustration may suffice, 
 illustration of Thus, in the primitive period of life, a single membrane dis- 
 the unfolding charges promiscuously and contemporaneously all the va- 
 
 of the special f . f ,. ., -,. . .. . . 
 
 from the gen- nous organic functions it digests, it respires, it secretes ; 
 eral - but, a little .advance onward, special portions of it are allot- 
 
 ted for one and another of these uses, and a localization, a centralization 
 of function ensues, and things that were mixed in confusion become sep- 
 arate and distinct. As the passage onward is made, still farther special- 
 izations are introduced, and so on in succession. Thus at the two ex- 
 tremes we may contemplate the single germinal membrane of the ovum, 
 which is discharging contemporaneously every function digesting, ab- 
 sorbing, respiring, etc. and the complete organic apparatus of man, the 
 stQmach, the lungs, the skin, the kidneys, and the liver mechanisms 
 set apart each for the discharge of a special duty, yet each having arisen, 
 as we know positively from watching their order of development, from 
 that simple germinal membrane. We must not, therefore, permit our- 
 selves to be deceived by the appearance of complexity they exhibit, 
 since, intricate as may be their construction, they have all arisen through 
 gradual centralization, one duty being separated from another, and hav- 
 ing an appropriate mechanism for itself; and so, at last, it comes to pass 
 that even the minutest conditions are discharged by a special part. 
 Thus, in the kidney, the salts are removed by one portion of the struc- 
 ture and the organic constituents by another ; yet, even in these ut- 
 most conditions of refinement, the primitive condition is at all times 
 ready to be reproduced, and, when driven to it, each of these structures 
 can act vicariously for the others, and discharge for the others their 
 duty. 
 
 It is unnecessary for our purpose to multiply instances, since every 
 page of natural history, comparative anatomy, and embryology presents 
 them in abundance ; but it may be to the purpose to remark that this 
 doctrine leads to more worthy conceptions of the system of nature ; 
 for if we suppose that there has been, in the case of the animal series, 
 a passage from things that are less perfect to things that are more so, 
 though this may be agreeable to our own experience, which is essen- 
 
ILLUSTRATIONS OF DEVELOPMENT. 509 
 
 tially tentative, it gives us very base notions of the manner Base nature of 
 in which natural operations are conducted, since we can not ^ew oniw or- 
 divest ourselves of the idea that such a passage from imper- ganic world. 
 fection to perfection implies trial, verification, and improvement : a pro- 
 cess which, though it is suited to the limited knowledge of man, is not 
 in accordance with the precision, perfection, and energy of Nature, and is 
 to "be rejected the moment we consider that we deal with the acts of 
 Omniscience and Omnipotence. Moreover, that erroneous view leads to 
 fallacious estimates, both in the animal series and in the individual, of 
 the character of transitory forms, conferring on them too much inde- 
 pendence, and therefore too much dignity; for the transitory forms of 
 embryonic life and the forms of animal species are the equivalents of 
 each other. 
 
 Every living being, therefore, springs from a germ, which will develop 
 itself into the likeness of its parent, provided it is submit- career and stop- 
 ted to the same conditions through which, its parent pass- P a s e of a devel - 
 ed ; but if the conditions be changed, it will either take pen ds on exter- 
 on a new aspect, or if they have become incompatible, it nal condltlons - 
 will cease to exist. Similarity of development depends on similarity of 
 condition, as is abundantly proved by such instances as the almost per- 
 fect resemblance of the two sides of the body, which, in reality, may be 
 regarded as distinct individual forms. To the proof thus derived from 
 bilateral symmetiy as occurring in man might be added such suggestions 
 as arise from the well-known resemblance of twins ; and as identity of 
 condition will thus give origin to analogy of development, so we may 
 fairly infer that difference of condition, no matter in what respect the dif- 
 ference may be, will give rise to difference of structure ; thus experienced 
 gardeners have shown that the sex of flowers is, to a very great extent, 
 determined by the brilliancy of the light in which they grow. Differ- 
 ence in the supply of nutritive material removes the spines from one 
 plant, or doubles the flowers of another, by changing its stamens . into 
 petals, or alters the cycle of career, and makes annuals into biennials. 
 As illustrations of the complete changes of form during development, 
 241. the three following cases may be 
 
 presented : in Fig. 241 are shown 
 the ova of the frog, which are trans- 
 parent spherical bodies, containing 
 a dark globule. From this, by de- 
 velopment, the tadpole, which is a 
 true fish, breathing by gills, arises. 
 
 Development of the frog. The figures represent a side and 
 
 upper view. After growth has taken place to a certain degree, a change 
 of structure becomes apparent, limbs gradually emerging, and the ani- 
 
510 
 
 ILLUSTRATIONS OF DEVELOPMENT. 
 
 Fig- 242, mal, after passing through an inter- 
 
 mediate state, eventually loses its 
 gills and tail, ceases its aquatic, and 
 commences aerial respiration, and 
 shows the aspect, Fig. 242, of the 
 perfect frog. 
 
 Fig. 243 represents the success- 
 ive metamorphoses of the Carcinus 
 mamas, or edible crab, as given by Mr. Couch. A represents the animal 
 
 Fig. 243. 
 
 Development of the crab. 
 
 on its emergence from the egg. It has a hemispherical shield on the 
 head and thorax, with a projecting spine, a tail formed of six segments, 
 the two last being joined laterally. The second form, at B, exhibits a 
 great change: the spine has disappeared, the shield is depressed, the 
 eyes on footstalks ; there are claws, and the tail is often carried bent 
 under the body. When this shell, like its predecessor, has been cast, 
 the third form, C, is assumed, the transition adapting the animal for 
 walking rather than swimming. The final form, D, is taken on at the 
 next moult, and now development ceases, and growth only takes place. 
 Fig. 244 illustrates the metamorphoses of a lepidopterous insect, the 
 
 Bombyx mori, or moth 
 of the silk- worm. From 
 the eggs there arises a 
 caterpillar, which not on- 
 ly possesses the means of 
 locomotion by feet, etc., 
 but also contains within 
 it the rudiments of the 
 organs to be eventually 
 assumed. In this state 
 
 Development of insects. the insect passes under 
 
 the name of a larva, because it is covered with a series of teguments, 
 
GROWTH, DIFFERENTIATION, DEVELOPMENT. 511 
 
 which, like masks, conceal the interior structure. These, in succession, 
 are cast off. 
 
 After many such successive castings of the skin, the insect enters into 
 the pupa or chrysalis state. It has no organs of locomotion, and, as it 
 has been, with some degree of imagination, said, becomes an egg again. 
 After resting in this state for a certain time, it bursts its confinement, 
 and assumes the form of an aerial, swift-moving winged insect. This is 
 its imago state. 
 
 It will now be convenient to give a more precise definition to terms 
 which have been hitherto used with a certain latitude. 
 
 By the term growth is to be understood the increase in size of a struc- 
 ture, without its assuming any variation as respects the na- Definition of 
 ture of its fabric or of the functions it discharges. SS^ and 
 
 By differentiation is meant an increase involving modifica- development, 
 tion of fabric and the assumption of new function. 
 
 By development is meant a differentiation of a higher order, or com- 
 pound differentiation. Usually it implies growth and differentiation con- 
 jointly. 
 
 As illustrations of the preceding definitions, it may be said that a crys- 
 tal grows, its enlargement presenting no structural variation and no new 
 quality. Cells differentiate from their normal spherical form, and, assum- 
 ing a cylindroid figure, give origin to vascular tissue, the vessels so aris- 
 ing serving for new purposes, as for the conveyance of gases or liquids. 
 A seed develops, for the organism to which it gives rise not only offers 
 continually increasing dimensions, but at all points the origination of 
 novel structures, arising by differentiation from adjacent and pre-existing 
 ones, these new structures having also new functions. 
 
 By homogenesis is meant the production of an organism in all respects 
 like its parent ; by heterogenesis, the production of an or- Homoo . enesis 
 ganism unlike its parent. and heterogen- 
 
 For the sake of brevity and simplicity, we may suppose esis ' 
 that there resides in every germ, and, therefore, in every organism, a prin- 
 ciple or quality which governs the collocation or grouping of new parts, 
 the same to which allusion has heretofore been made under the designa- 
 tion of plastic power. It is unnecessary for us here to burden our con- 
 ceptions of such a power with any hypotheses respecting its nature, it 
 being understood that we use the title of this supposed agent only as an 
 expression of convenience. 
 
 The production of every organism appears, as far as existing observa- 
 tions and experiments go, to be referable to a previously ex- An organ ,- c 
 isting organism. This being admitted, generation and repro- molecule the 
 duction imply, as their starting-point, an organic molecule. pou 
 Such a combination, furnished with nutrition, grows, its plastic power 
 
512 HOMOGENESIS AND HETEKOGENESIS. 
 
 grouping the new material. But such a growth can not take place to any 
 extent without a variation being encountered in the surrounding condi- 
 tions, and the instant that this occurs, differentiation ensues as its neces- 
 sary consequence. Growth under changed circumstances is then differ- 
 entiation. If the order of variation, as regards condition, is exactly the 
 Condition for same m tne case ^ two growing and differentiating combi- 
 simiiarity of nations, their career of development will be exactly alike, and 
 2nt * the* forms they will present at the same epoch of their course 
 will be the same. According as the career is short, the probabilities of 
 identity are greater, since the chances of variation, which might be en- 
 countered in the two cases, are less. But where the career is more pro- 
 tracted, and many conditions in succession must be encountered, it can 
 not happen that there will be an exact resemblance in the course of two 
 organic combinations, and therefore there never can be an absolute iden- 
 tity in the aspect of any two resulting forms. 
 
 The general result of every development is heterogenesis. No parent 
 Development organism ever reproduces another absolutely like itself, un- 
 tendTtohete- ^ ess ** ^ e * n ^ e ^ owest developed types, in which the oppor- 
 rogenesis. tunity for change is at a minimum. Homogenesis is only ap- 
 proached as the conditions bringing on differentiation approach similari- 
 ty; it therefore sinks into a special case coming under a more general 
 law, and, indeed, speaking with exactness, we might say that in the nat- 
 ural world it never occurs, the prevalent notion which regards it as the 
 rule and heterogenesis as the exception being altogether illusory. Ev- 
 ery grade of organism, vegetable and animal, furnishes us with examples 
 of this truth. Let us look for a moment at the highest tribes ; and in 
 them reproduction never takes place except by pairs of individuals of dif- 
 ferent sexes. Eigorously, therefore, the births should also be by pairs of 
 different sexes. Moreover, if it be necessary in these general and super- 
 ficial considerations, let us direct our attention to the special case of man. 
 The infant necessarily differs from one of its parents in sex, and from 
 both in size, weight, endowments, and' physical attributes. It is like 
 neither of them. The popular notion may suggest that a closer resem- 
 blance will be reached, perhaps, after the lapse of thirty or forty years, 
 when a nearer approach to the form of one of the parents may be offered 
 with elements incorporated from the lineaments of the other ; but even 
 m this case a rigorous examination compels us to admit that like has not 
 produced like. 
 
 Eeflecting on this popular illustration more profoundly, we discern 
 Cycles of pro- wherein the error consists. Instead of comparing cycles of 
 C ared and 00 " P rocess we ^ ave ^ een blundering with isolated forms, which 
 individual arise at different epochs therein. Without going into tedi- 
 ous details, man presents, as regards the most important of 
 
REPRODUCTIVE STATE ENDS DEVELOPMENT. 513 
 
 his constituent structures, his nervous system, the successive character- 
 istics of an avertebrated animal, a fish, a turtle, a bird, a quadruped, a 
 quadrumanous animal, before he assumes the special human character- 
 istics. This is his cycle of life, and it is the same cycle in one case as 
 in another. 
 
 But the moment that our view is thus enlarged, we see that it is not 
 the individual with which we should deal, for an individual we can scarce- 
 ly define, since he is continually differing from himself. It is with a cy- 
 cle of proceeding, or a course of operations that we are engaged, a series 
 of forms being the outward manifestation of the succeeding periods of 
 that cycle or course. 
 
 An infant, though unlike both its parents in form, has run through a 
 career like that passed through by them both. Sexual differentiation, 
 which indeed is one of the last differentiations occurring, offers no excep- 
 tion to the truth of this remark. The similitude lies in the career, not 
 in the form taken at different epochs. 
 
 The essential principle, then, is, not that an organism produces a like 
 organism, but it produces a germ which, being placed under The reproduct _ 
 similar circumstances, passes through a like career of devel- iv e state closes 
 opment, and at successive periods offers an orderly series of 
 forms. The career is commonly observed to close as soon as the capac- 
 ity for reproduction is assumed. Hence, in every organism, the assump- 
 tion of the reproductive state is the signal that the end of development 
 is at hand. 
 
 It does not plainly appear what are the circumstances which give rise 
 to the assumption of this capacity ; nevertheless, it may take place at 
 any moment of the career. In the Volvox globator it occurs almost at 
 the close of the first stage, for the germ only reaches the condition de- 
 scribed hereafter as the mulberry mass when it becomes capable of re- 
 production ; but in man the developing organism has a long journey to 
 perform beyond this first step. Except in the condition here dwelt upon, 
 he differs in no respect from his humbler comrade at this point. The 
 tendency to a gliding off into the reproductive phase is in him repressed, 
 and therefore differentiation and development continue to go on. 
 
 During the development of any new organism, the new parts uniformly 
 arise from the old ones ; they are not built from foreign mate- All the parts of 
 rials depositing themselves upon new centres, but are educed an . organism 
 by the unfolding, enlarging, and modeling of parts already 
 
 common cen- 
 
 existing. An organism is not developed as we enlarge a tral origin- 
 house, by building part to part, but it all expands from one common or 
 single centre. As the sphere of its expansion becomes greater, the op- 
 portunity arises for devoting different regions to different uses, and thus 
 offices which were confusedly intermingled become separated out, and, 
 
 KK 
 
514 LAW OF VON BAR. 
 
 as, in social undertakings, the division of labor gives greater perfection to 
 the work, so in this, functions which, because they were blended, were 
 imperfectly discharged, now assume precision and power, because they 
 are disentangled from what were perhaps countervailing conditions. 
 By these considerations, we are gradually led to the general law of de- 
 velopment, first recognized by Yon Bar, and passing under 
 
 LawofVonBar. r rrn J ? i 
 
 his name. This is somewhat obscurely enunciated in the 
 following terms : " The heterogeneous arises from the homogeneous by a 
 gradual process of change." By this it is meant that, in the process of 
 development, the stages are not from forms that are of a degraded to those 
 of a higher type, but that from the general the special, which was therein 
 included, is gradually evolved. 
 
 In conclusion of these preliminary remarks on reproduction, it may be 
 Invariable se- ^served that, even in the highest and most elaborate types, 
 quence and dif- the causes which bring on differentiation follow each other in 
 such a predetermined sequence, that the whole phenomenon 
 might be said to be under the dominion of mathematical conditions. As 
 a striking instance of this may be mentioned, in the case of man, the nu- 
 merical equality of the sexes ; and that this singular result is determined 
 by the alternate preponderance of conditions which are otherwise nicely 
 balanced, is shown by the interesting instances occurring among insects 
 of dimidiate and quadrate hermaphroditism, in .the former of which 
 the resulting insect is of different sexes on the .two sides of its body, 
 and in the latter the male and female portions are quadrantally arranged. 
 If the left side of the head and thorax are those of a male- insect, the 
 right half of the abdomen is of the same kind, the intervening portions 
 being of the other sex. The neuter state might even be imagined to 
 arise from the more precise blending, balancing, and confusing of such 
 conditions as here give evidence of an incipient tendency to separate from 
 one another. 
 
 In the farther discussion of reproduction we shall find it conveniently 
 Divisions of considered under two distinct divisions; first, generation; 
 reproduction. secon <3 ? gemmation. Our attention may, then, be profitably 
 directed to the singular facts known under the designation of alternation 
 of generations. As illustrations of the terms here employed, it may be 
 stated that the production of a seed and the development of a plant there- 
 from are to be considered in connection with generation, and that the ob- 
 taining of new plants and trees by budding and grafting, and the pro- 
 duction of many new hydras by their sprouting forth from an old one, 
 are to be considered under gemmation. By the alternation of genera- 
 tions is meant that an organism, A, will give rise to a second one, B, 
 wholly unlike itself, and that this second organism, B, will give rise to a 
 third, C, unlike itself, but C shall resemble A. This singular condition 
 
GENERATION. 
 
 515 
 
 of things will be shown to originate in the periodical alternation of gen- 
 eration and gemmation respectively. 
 
 1ST. OP GENERATION. 
 
 Eeproduction by generation is accomplished on two different types : 
 1st. By the conjugation of two similar cells ; 2d. By filaments. 
 
 In the first, that is, by the conjugation of two similar cells, a third 
 body, called a sporangium, results. Of this process there Three modifi 
 appear to be three different modifications : 1st. The two sim- cations of con- 
 ilar conjugating cells discharge their endochrome, or coloring J u s atlon - 
 material, each voiding itself completely, and the sporangium arises from 
 the mixture ; 2d. A dilatation forms on the point of union of the two 
 conjugating cells, and into this dilatation the endochromes of both cells 
 are passed ; 3d. The endochrome of one cell is wholly retained, and that 
 of the other is added to it, the one becoming void, and in the other the 
 sporangium being produced. This, occurring in the lowest vegetables, 
 among which it was for a long time supposed that the type of reproduc- 
 tion is totally different from that of flowering plants and animals, pre- 
 sents us with the first traces of what is eventually displayed as differ- 
 ence of sex. 
 
 This shadowing forth of the difference of sexes is illustrated in a very 
 instructive manner by the Zygnema quininum, a fresh-water conferva. 
 Its manner of growth is what has been already described in the case of 
 the Conferva glomerata, Fig. 231. In the annexed Fig. 245 is repre- 
 
 . Development and reproduction of Zygnema quininum. 
 
 sented at A the process of growth by the subdivision of cells, a b c repre- 
 senting three such cells, the middle one, 5, being in the act of subdivision. 
 At B two threads are in the act of conjugation. The endochromes of 
 both are spirally arranged, and dilatations reaching from one to the other 
 are here and there seen. At C the endochromes of one thread, <z, have 
 wholly passed over to the other thread, b, and the round bodies, or spo- 
 
516 SPERM-CELLS. 
 
 rangia, are the result. It is this passage from one thread to the other 
 which betrays the first indications of sex. 
 
 In the second, that is, by filaments, two cells are again necessary, 
 which, differing in construction and also in function, are des- 
 tionsbyfiia- ignated the sperm-cell and germ-cell respectively. Of this 
 ments. ^^ Q there are two modifications : 1st. Reproduction by mov- 
 
 ing filaments, as presented in the higher algse and ferns ; 2d. By elon- 
 gating filaments, as in flowering plants. The moving filaments, which 
 were discovered in the case of animals soon after the introduction of the 
 microscope, were regarded as animalcules, and passed under the designa- 
 tion of spermatozoa. The germ which arises in the first of these modi- 
 fications is, in the lower tribes, unprovided with any nutritive supply ; 
 in the higher, a stock of food is prepared for it by the parent. In. the 
 second, the sperm-cell, or, as it is frequently termed, pollen grain, does 
 not produce a moving filament, but elongates itself into a delicate tube 
 until it reaches the germ-cell. A stock of nutritious matter is placed 
 around the resulting embryo, and this is the ordinary construction of 
 seeds. 
 
 Eestricting our description to the case which more immediately inter- 
 ests us, we shall first consider the mode of origin and nature of the 
 sperm-cell and its filaments in animals, and then of the germ-cell and its 
 process of development when fertilized. 
 
 1st. Of the Sperm-cell. The testes are the organs in which the 
 sperm-cells and filaments arise in man. They are of an ovoid fbrm ; 
 each is covered with a white envelope, the tunica albuginea. A serous 
 membrane, folded as a shut sac, overlies this tunic. From the inner 
 surface a number of delicate projections arise, which divide the organ into 
 several compartments. In these compartments are lodged lobules aris- 
 ing from the tubuli seminiferi and their supplying blood-vessels. There 
 Production of are a ^ out 450 lobules in each testis ; their shape is conical, 
 sperm-ceils by the diameter of the tubes of which they are composed about 
 the 2-^0- of an inch. The total length of this tubular struc- 
 ture is about three quarters of a mile. Before the tubuli of each lobule 
 reach the rete testis, they cease to be convoluted, and bundles of them, 
 uniting into larger vessels, are designated tubuli recti. In the rete tes- 
 tis there are from half a dozen to a dozen of these tubes, which various- 
 ly anastomose with one another and divide. They empty into the vasa 
 efferentia, which, from being straight, become convoluted, a series of 
 cones arising, which together form the globus major of the epididymis. 
 This is a convoluted canal, of about twenty feet in length, which, de- 
 scending, receives beyond its globus minor the vasculum aberrans. It 
 then empties into the vas deferens. 
 
 Fig. 246, human testis : , testis ; , lobes ; <?, tubuli recti ; d, rete 
 
THE TESTIS. 
 
 517 
 
 Fig. 246. 
 
 The testis. 
 
 vasculosum ; e, vasa efferentia ; y, 
 coni vasculosi ; <7, epididymis ; A, 
 vas deferens ; i, vas aberrans ; ?ft, 
 branches of the spermatica inter- 
 na of the testis and epididymis ; 
 w, ramification on the testis ; 0, ar- 
 teria deferentialis ; p, anastomosis 
 with a branch of the spermatic. 
 (Arnold.) 
 
 The secretion of the testis must 
 be taken for examination from the 
 vas defe'rens or epididymis, before 
 it has been mixed with the fluid of 
 the prostate and Cowper's glands, 
 or with mucus. It may be min- 
 gled with a little albumen or se- 
 rum for the purpose of dilution, and, 
 when examined with a power of 
 500 diameters, exhibits multitudes 
 of moving bodies. These are the 
 seminal animalcules, or spermato- 
 zoa. Among them are to be seen, here and there, round granular bod- 
 ies, the seminal granules. These, with the spermatozoa, are sustained 
 in a clear and transparent liquid. The examination of these different 
 constituents is conducted with difficulty, since they can not be separated 
 from one another by means of filtration. The spermatozoa arise from 
 the seminal granules. 
 
 The spermatozoa are found in the spermatic fluid of all animals after 
 puberty, their form being different in different classes and spermatozoa, 
 species. Generally they may be described' as consisting of description of. 
 a little oval-shaped head, from which a delicate filament or tail projects. 
 The motion of the spermatozoa is accomplished by means of their fil- 
 ament. It takes place in different ways, sometimes the filament vibrat- 
 ing like a whip, sometimes rotating like a screw, and sometimes a spin- 
 ning round, as it were, upon a pivot, occurs, the filament having been 
 coiled like a watch-spring. The rate of motion seems under the micro- 
 scope to be rapid ; it is, however, estimated at an inch in thirteen min- 
 utes. In man, their entire length may be estimated at about the -g-L of 
 an inch, the length of the head being about the 3^^, and its Human sper- 
 breadth the Io jj 00 . They continue to exhibit motion in matozoa - 
 birds for fifteen or twenty minutes after death ; in cold-blooded animals 
 even after days. They withstand, for a time, the action of solutions of 
 sugar and salt, but are destroyed at once by alcohol and dilute acids, 
 
518 SPEKMATOZOA. 
 
 which appear to affect their organization. Strychnia, opium, and hy- 
 drocyanic acid likewise stop their motions, but without causing any 
 change in their form. 
 
 The production of spermatozoa is best studied in the case of birds. 
 Spermatozoa For this purpose Wagner recommends that one of the order 
 in birds. of Passeres be taken in the pairing time. The condition of 
 the testes indicates the state of evolution of the spermatozoa. In win- 
 ter those organs are of the size of a pin's head, but in spring they have 
 increased twenty or thirty fold. Exteriorly they exhibit convolutions like 
 those of the brain, and contain granules and seminal globules. After 
 pairing time is over, they relapse to their original diminutive state. The 
 seminal globules appear to be derived from the epithelial cells lining the 
 tubuli seminiferi. They are developed into what are termed primary 
 cells, each of which contains a number of secondary cells or vesicles of 
 evolution. In the interior of these vesicles the spermatozoa originate, 
 as a derivation or development from the nucleus, each vesicle giving rise 
 Evolution of to one spermatozoon. When this has reached perfection, the 
 spermatozoa, vesicle deliquesces and sets it free. There are from one to 
 twenty vesicles of evolution in each primary cell. In birds the filaments 
 may be retained for a length of time in the primary cell after deliquescence 
 of the vesicle, but in mammals, as soon as the filament is mature it es- 
 capes. In the former case the filaments aggregate into bundles, but they 
 break up into individuals when the primary cell deliquesces. 
 
 24L Fig. 247, spermatozoic filaments, develop- 
 
 ing in Certhea vulgaris : #, seminal granule ; 
 , cyst, with two vesicles of evolution, many 
 granules, and a bundle of spermatozoa ; , oval 
 cyst, with spermatozoa coiled up. (Wagner. ) 
 Of the formation of spermatic filaments 
 Dr. Burnett gives an account somewhat dif- 
 ferent from the preceding. According to him, 
 "the morphological changes in the sperm- 
 
 Development of spermatozoa. ^ preceding the formation of the Spermatic 
 
 filaments are identical in their character with the changes in the ovum 
 which are antecedent to the formation of the new being. When the gen- 
 erative function begins to be developed, the character of the epithelial 
 cells lining the tubules is modified. The cells pass to a higher degree 
 in function, but do not undergo any change in structure, except a slight 
 increase in size. In this condition they divide and subdivide, by a pro- 
 cess similar to the segmentation of the yolk, until they are entirely con- 
 verted into a mulberry mass. A liquefaction of the segmented contents 
 into a minute granular blastema then ensues, and from this the spermatic 
 filaments are developed. In the Plagiostomes, Dr. Burnett was able to 
 
THE GERM-CELL. 519 
 
 observe the disappearance of the mulberry mass, and its replacement by 
 a fasciculus of spermatic filaments, although the exact metamorphosis by 
 which the granular cellular mass formed the bodies of the spermatozoids 
 could not be detected. The spermatic filaments, Dr. Burnett thinks, are 
 not formed, as stated by Kolliker, by a deposit from the contents of the 
 sperm-cell or nucleus, but by an elongation of the nucleus itself. The 
 body of the spermatozoid is developed from the cell, while the tail is 
 probably subsequently formed by an accumulation of minute particles." 
 (Kolliker, Am. ed., p. 625.) 
 
 In man, the production of spermatozoa commences between the four- 
 teenth and sixteenth year, the time of puberty, and continues until the 
 sixty-fifth or seventieth, or even much longer. This period of commence- 
 ment is marked by a great change in the physical and moral constitution. 
 
 The spermatic fluid of mule animals contains no spermatozoa. This 
 fact has been established in an interesting manner by Wagner in the case 
 of birds, of which many of those which are domesticated readily cross. 
 There can be no doubt that these bodies are the essential portion of the 
 fluid, and that it is their action upon the ovum which establishes its fer- 
 tilization. 
 
 There has been much controversy whether the spermatozoa present 
 traces of organization, properly speaking. Though it is convenient to 
 designate their dilated portion as the head, and the filament as the tail, 
 it has never yet been established that any thing answering to a true 
 structural arrangement exists, and, upon the whole, it may be concluded 
 that the appearances which have been by some supposed to indicate or- 
 ganization are, in reality, only an optical illusion. 
 
 2d. Of the Germ-cell. In mammals the female reproductive appara- 
 tus consists essentially of the ovaries, oviduct, and uterus. Female 
 
 The ovaries are two ovoid bodies situated on either side ductive appa- 
 of the uterus. They consist of a stroma in which vesicles r 
 are imbedded : these vesicles give origin to the ova. In the manner to 
 be presently described, the ova, being received at the fimbriated extrem- 
 ities of the Fallopian tubes, those tubes being therefore appropriately 
 termed oviducts, are carried into the cavity of the uterus. 
 
 At the time of puberty in the human female, which occurs between 
 the 14th and 16th year, a physical and moral change takes 
 
 i . ^ C-Vt. t: i j n j i . The catamenia. 
 
 place, answering to that which has been already alluded to 
 as occurring in the male. From this period a sanguinolent discharge 
 makes its appearance monthly : it is the catamenia. The interval from 
 time to time is commonly estimated at four weeks ; it varies, however, 
 with individuals, and it is said also with climates, the discharge occurring 
 in the hotter more frequently, and in greater quantity. It is essentially 
 blood, which has been deprived of its quality of coagulating by inter- 
 
520 OVUM IN THE OVARY. 
 
 mixture with acid mucus of the vagina. So long as these periods con- 
 tinue, the individual possesses the reproductive power, the first appear- 
 ance of the catamenia indicating the capacity for conception, and the dis- 
 appearance, at about the 45th year, its end. During gestation the cata- 
 menia are suspended, and, indeed, it is this event which is usually taken 
 as the indication that conception has occurred. 
 
 The periodical occurrence of this discharge in the human female, though 
 more frequent, is essentially the same as the periodically occurring heat 
 of other animals, which is also attended with a sero-sanguinolent dis- 
 charge. In other respects, likewise, the analogy is maintained, for in 
 those animals, the appearance of this discharge and its attendant phe- 
 nomena constituting an indication of a simultaneous capacity for con- 
 ception, in women the same thing holds good, conception occurring in 
 them at the time of the close of the menstrual discharge. 
 
 I. Ovum in the Ovary. 
 
 The ovary is the organism in which the ova are prepared, these bodies 
 arising in the following way : 
 
 In the stroma of the ovary there occur at a time ten, twenty, or many 
 Production more cells, which have received the designation of Graafian ves- 
 of ova. j c i es or O visacs. These originate in the interior of the ovary, 
 and, as they become perfected, pass to its surface, presenting themselves 
 thereupon as prominences which are covered over exteriorly with peri- 
 toneum. Each of these vesicles has a membranous envelope connecting 
 it with the substance of the ovary exteriorly, and covered interiorly with 
 a layer of nucleated cells, designated membrana granulosa. It is filled 
 with a fluid in which multitudes of granules float, and in its centre is the 
 ovule. This, as it becomes mature, is pushed up toward the surface of 
 the ovisac by an accumulation of liquid in the lower part thereof, and 
 is so brought into close relation with the membrana granulosa at the 
 place where it is upon the surface of the ovary. At this point there col- 
 lects on the ovum a zone of granules, to which the designation of discus 
 proligerus is given. 
 
 Fig. 248, transverse section through the ovary of a woman dead in 
 the fifth month of pregnancy : <z, Graafian follicle of inferior, and, , of 
 superior surface ; c, peritoneal lamella of ligamentum latum, continued 
 Upon the ovary, and coalescing with, d, the tunica albuginea : in the in- 
 terior two corpora albicantia (old corpora lutea) are visible; , stroma of 
 the ovary. (Kolliker.) 
 
 Fig. 249, section of the Graafian vesicle : 1, stroma of ovary, with 
 blood-vessels ; 2, peritoneum ; 3 and 5, layers of the external coat of the 
 Graafian vesicle ; 4, membrana granulosa ; 6, fluid of the vesicle ; 7, gran- 
 ular zone, or discus proligerus ; 8, the ovum. (Von Bar.) 
 
Fig. 250. 
 
 521 
 
 Section of Graafian vesicle. 
 
 Ovum. 
 
 Section of ovary. 
 
 Fig. 250, ovum of the sow : 1, germinal spot ; 2, germinal vesicle ; 
 3, yolk ; 4, zona pellucida ; 5, discus proligerus ; 6, adherent granules or 
 cells. (Barry.) 
 
 The diameter of the human ovum varies from the yj-^ to the -^g- of 
 an inch. It consists of an exterior transparent membrane, Description of 
 the Y^fr o" f an i nc k * n thickness, which, when compressed the ovum - 
 for the purpose of examination, appears like a diaphanous circle, and hence 
 called zona pellucida. Within this zone, and inclosed by it, is the yolk, 
 a granular material suspended in or intermingled with fluid, the granules 
 being of different sizes ; those near the pellucid zone are the largest. For 
 the most part, the yolk consists of albumen and oil globules. ' Its condi- 
 tion, as regards liquidity, varies in different animals ; in some it is al- 
 most a soft solid, so that, when water percolates through the zona pellu- 
 cida, it isolates the yolk by surrounding it on all sides, and parting it off 
 from the zone. Within the substance of the yolk is a distinct cell, the 
 germinal vesicle, which gradually makes its way from the interior to the 
 place of peritoneal contact. As it advances to perfection, it consists of a 
 delicate spherical membrane containing a liquid, in which granules are 
 suspended. Upon that portion of it nearest to the place of peritoneal 
 
 contact is its nucleus, the germinal 
 spot, about the - 8 * of an inch 
 in diameter, and consisting of yel- 
 low granules. 
 
 Fig. 251, diagram of a Graa- 
 fian vesicle and ovum : 1, stroma 
 of ovary ; 2, 3, external and in- 
 ternal tunics of the Graafian ves- 
 icle ; 4, cavity of vesicle ; 5, thick 
 tunic of the ovum or yolk-sac ; 6, 
 the yolk ; 7, the germinal vesicle ; 
 8, the germinal spot. 
 
 The most mature ova are near- 
 est the surface of the ovary, but 
 Diagram of Graafian vesicle. are separated from its peritoneum 
 
 251. 
 
522 
 
 COEPUS LUTEUM. 
 
 Corpus luteum. 
 
 by a thin, fibrous layer of stroma. The Graafian vesicle is, there- 
 fore, the parent of the ovum. Periodically, as development is going on, 
 the Graafian vesicle bursts, and the ovum is set free. This effect arises, 
 in part, from the circumstance that, the space between the vesicle and 
 ovum being filled with cells, those near the surface of the ovary disap- 
 pear, and an albuminous liquid, which accumulates below, pushes the 
 ovum up. This extrusion of ova occurs even in childhood. The ovisac, 
 or Graafian vesicle, thus changed into a follicle, is gradually filled up, its 
 walls wrinkling, and red-colored material, arising from the membrana 
 
 granulosa, being deposited in it until it is almost filled. 
 
 This deposit gradually turns yellow, and is eventually com- 
 posed of cells interiorly, and fibres arising therefrom exteriorly. When 
 the deposit is completed, a stellated cicatrix is observed in its midst. 
 The yellow body thus arising passes under the designation of corpus lu- 
 teum. If impregnation does not occur, the yellow substance forms to 
 but a small extent, and after a time disappears. It is relatively more 
 abundant in animals than in women. Attempts have been made to use 
 the indications of the corpus luteum for determining the question of preg- 
 nancy. The following points are presented by Dr. Dalton as offering 
 characteristics by which the corpora lutea of pregnancy and menstruation 
 may be distinguished : " The corpus luteum of pregnancy arrives more 
 slowly at its maximum development, and afterward remains for a long 
 time as a noticeable tumor instead of undergoing rapid atrophy. It re- 
 tains a globular or only slightly flattened form, and gives to the touch a 
 sense of resistance and solidity. It has a more advanced organization 
 than the other kind, and its convoluted wall is much thicker. Its color 
 is not of so decided a yellow, but of a more dusky hue, and if the period 
 of pregnancy is at all advanced, it is not found, like the other, in com- 
 pany with unruptured vesicles in active process of development." 
 
 Fig. 252, corpora lutea of different periods : a, corpus luteum two 
 
 Fig. 252. 
 
 Corpora lutea. 
 
 days after delivery ; I, corpus luteum of about sixth week after impreg- 
 nation, showing its plicated form at that period ; 1, substance of ovary ; 
 2, substance of corpus luteum ; 3, grayish coagulum in its cavity ; d, in 
 
OVUM IN THE OVIDUCT. 523 
 
 the twelfth week after delivery, (a and b, Dr. Patterson ; d. Dr. Mont- 
 gomery.) 
 
 II. Fertilized Ovum in the Oviduct. 
 
 Such being a description of the ordinary or unfertilized ovum, we have 
 next to follow the changes which ensue if fertilization has taken place. 
 
 The spermatozoa having become enveloped in the pellucid zone or 
 passing through it, the ovum is received by the iimbriated extremities 
 of the Fallopian tube, along which it is carried by peristaltic contraction 
 or ciliary motion. The first change which takes place in it is the disap- 
 pearance of its germinal vesicle and germinal spot. This disappearance 
 is, however, stated by some to be preceded by a development of cells 
 originating in the nucleus or germinal spot ; nor is it the result of fertil- 
 ization, since it occurs in the unimpregnated ovum. The Chano . es of the 
 cells of the membrana granulosa, which surround the ovum, fertilized ovum 
 become first of a conical shape, but their rounded form is re- 
 sumed on passing into the tube. 
 
 Fig. 253. Fig. 253, ovarian ovum of dog, exhibiting the 
 
 elongated form and stellate arrangement of the 
 cells of the discus proligerus round the zona pel- 
 lucida. 
 
 Fig. 254, same ovum after the 
 removal of most of the club- 
 shaped cells. 
 
 The yolk is next observed to 
 ovarian ovum. contract so as to leave a clear 
 
 space between it and the zona pellucida. As the pas- 
 sage along the tube is taking place, the zona assumes 
 a coating of albuminous material, which is what is call- 
 ed in birds the white of the egg. It eventually becomes the chorion. 
 Meantime, after the disappearance of the germinal vesicle, a new cell, the 
 embryo cell, arises, and this undergoes subdivision or segmentation, an 
 effect in which the yolk itself presently becomes involved, each new or 
 daughter embryo cell so arising assuming a part of the yolk. A constant 
 process of bisection is thus established, the yolk dividing first into two 
 portions, then into four, eight, sixteen, etc., each division containing a 
 nucleated cell. At this period may be seen the spermatozoa involved in 
 the zona pellucida, and, as the process of bisection goes on, The mulberry 
 the mass assumes a mulberry aspect, and finally becomes mass - 
 granular. This is, for the most part, finished by the time the ovum en- 
 ters the uterus. 
 
 Fig. 255, ova of the dog in various stages : a, from the oviduct, half 
 an inch from the uterus, spermatozoids being in the pellucid zone, the yolk 
 
524 
 
 SEGMENTATION OF OVUM. 
 
 bisected ; b, cells of tunica granulosa have disappeared, and the yolk is 
 in four segments ; c, continued advance in segmentation ; d, the zona 
 has become thicker, and the segmentation more complete ; e, ovum burst 
 by. compression : some of the segments have escaped ; each shows a 
 bright spot or vesicle. 
 
 Fig. 255. 
 
 Segmentation of ovum. 
 
 Fig. 256, cleavage of the yolk after fecundation : #, an ovum of As- 
 caris nigrovenosa, the yolk of which is divided into two equal portions ; 
 the upper portion contains a cell with a large nucleus, the lower a sim- 
 ilar cell with two small nuclei ; &, ovum subdivided into four portions ; 
 c, the subdivision has reached sixteen, each possessing a mono-nucleated 
 cell ; d, ovum of Ascaris acuminata, showing the stages of subdivision, 
 the portions becoming very small ; 6, the portions preparing to be mould- 
 ed into the young worm, (#, &, c, Kolliker ; d, e, Bagge.) 
 
 Fig. 256. 
 
 Segmentation of ovum. 
 
 As the ovum is about to enter the uterus, each portion which has arisen 
 from the segmentation of the yolk has become a perfect cell. This cell 
 formation having been accomplished at the surface of the yolk first, the 
 cells there begin to coalesce into a membrane, with an aspect like that 
 of hexagonal pavement epithelium, and, as the change passes toward the 
 centre, the cells, as they form, come toward the membrane and thicken 
 it, leaving a clear liquid within. In this manner a secondary vesicle 
 forms within the zona pellucida : it is the blastodermic vesicle : it is the 
 
UTERINE NUTRITION. 525 
 
 temporary stomach of the embryo. Its wall constitutes the germinal 
 membrane, upon which the embryo arises. New cells being constantly 
 added, the membrane increases in thickness ; and here it may ^he germinal 
 be remarked that, in most types, the yolk is to be considered membrane, 
 as presenting two portions the germ-yolk and the food-yolk ; the for- 
 mer being immediately employed in the development of the embryo, and 
 the latter being a stock for more advanced supply. In mammals, for 
 whom other means of nutrition are quickly provided, the food-yolk is im- 
 perceptible, and, moreover, in them the albuminous coating of the zona 
 pellucida is small ; but in birds, the embryo of which has to be nourish- 
 ed independently of the parent, the quantity is necessarily large. As we 
 have sai'd, this albuminous covering and the zona together constitute the 
 chorion, the exterior of which presents a rugged aspect, from the appear- 
 ance of absorbing radicles, which, becoming imbedded or dove- 
 tailed in the deciduous membrane, presently to be described, 
 establishes the necessary connection for tuft nutrition, and thereby ob- 
 taining albumen from the parent. 
 
 III. Fertilized Ovum in the Uterus. 
 
 While the ovum is passing through the Fallopian tube or oviduct, it 
 obtains a coating of albuminous material outside of its zona pellucida, as 
 has been said. This coating becomes the means of attachment to the 
 uterus, and thereby of the absorption of nutriment in the following way. 
 The outside surface of the incipient chorion presents a layer of cells, 
 and soon after assumes a fibrous structure. In this condi- uterine nutri- 
 257. tion the ovum makes its appearance in tion - 
 
 the uterus, on the interior of the surface of which the 
 mouths of a great number of follicles open. These 
 follicles are not unlike those which the stomach 
 presents. Their general appearance is illustrated by 
 Fig. 257; d, csecal terminations of glands; e, their 
 tubes ; , mouths on interior of uterus. The con- 
 stitutional disturbance which is at this time taking 
 place, enhanced by the presence of the ovum in the 
 organ, at once increases its vascularity ; the follicles 
 become larger, cells are abundantly developed in 
 them, and the uterine cavity is filled with a liquid 
 containing many nucleated cells. This plastic semi- 
 fluid material receives the fringes of the villous coat 
 of the chorion, which are now being developed ; and 
 these even find their way into the mouths of the 
 ** glandular tubes ; from this exudation or secretion 
 uterine tubes. the membrana decidua forms, though by some it is 
 
526 MEMBRANA DECIDUA AND PLACENTA. 
 
 Formation of represented as being a metamorphosis of the mucous mem- 
 membrana de- brane itself. Meantime the ovum is itself coated over with a 
 corresponding membrane, designated membrana reflexa, be- 
 cause it was believed by Mr. Hunter to originate in the circumstance 
 that, when the ovum reached the uterine mouth of the Fallopian tube, it 
 there encountered the proper membrana decidua, and, not perforating it, 
 but bearing it onward, gathered a fold, covering, or envelope, which, 
 from its having thus been formed by a reflexion, was appropriately des- 
 ignated by the term specified. It is, however, now admitted that this 
 description of the formation of the membrana reflexa is erroneous, for in 
 reality the ovum is at no time on the outside of the mucous membrane, 
 which is continuous from the cavity of the uterus through the Fallopian 
 tube. The following, therefore, seems to be the more correct description. 
 The presence of the ovum gives rise to an increased development of cells, 
 which rapidly spread around it, and coat it all over, their points of origin 
 being those portions of the uterine mucous membrane with which the 
 ovum is in contact. In this way it receives its deciduous envelope, 
 which, participating duly in its growth, is at the end of the third month 
 in contact with the uterine decidua all over. 
 
 At the stage we are now considering, the nutrition of the embryo is 
 conducted in a special but very temporary way. The yolk of the ovum 
 has no stock of food to maintain the nutritive processes beyond the brief 
 space which transpires in the passage through the Fallopian tube. The 
 duty of nutrition is at this moment assumed by the villous coat of the 
 chorion, which absorbs fluid exuding from the uterine decidua very 
 much after the manner of the spongioles of a plant ; but almost imme- 
 diately the necessity arises of diverting more directly the albumenoid 
 material to the quickly-growing embryo from the yolk-bag, to which it 
 would have gone, and this new destination implies the introduction of 
 new channels of transport, which, under the form of a vascular appara- 
 tus, are now provided. 
 
 About the close of the second month, a proper vascular apparatus for 
 the combined purposes of nutrition, secretion, and respiration 
 
 The placenta. , '. . , , _ . f . . 
 
 makes its appearance: it is the placenta. Its origin is in 
 the little blood-tubes which form in the tufts of the chorion, in man at 
 one point, in ruminants simultaneously at several, giving rise in the for- 
 mer case to one organ, the placenta, as has been said, in the other to 
 many such, or, at all events, to one of a composite structure, the cotyle- 
 dons. The foetal vessels thus arising in the villi of the chorion become 
 intermingled with vessels contemporaneously arising from the uterus ; 
 and though, in some cases, this intermingling is less complicated, so that 
 the maternal and fostal portions are separable, in man the internetting is 
 complete, the principle being to bring the foetal vascular tufts in such a 
 
DIVISION OF THE GERMINAL MEMBRANE. 
 
 527 
 
 relation with the maternal blood-sinuses, by the tufts dipping Functions of 
 down or being enveloped therein, that the completest con- the P lacen t a - 
 tact and facility of exchange, but not of intermixture, may be insured. 
 Things are arranged in such a way that the maternal and foetal blood do 
 not intermingle, each being confined in vessels of its own, through the thin 
 walls of which nutritious matter may pass and excrementitious matter re- 
 pass. Every foetal tuft has a deciduous layer upon it, and the blood 
 brought by the curling arteries of'the uterus furnishes to the foetus its ox- 
 ygen, and receives back carbonic acid, with other excrementitious matters. 
 In this respect, respiration is carried on by the aid of a mechanism which 
 answers to the gills of fishes, the maternal arterial blood standing for the 
 aerated water ; but, besides this, the tufts have another duty to dis- 
 charge the obtaining of albumenoid material from the maternal blood. 
 The placental mechanism is therefore much more perfect in its action 
 than the. tuft mechanism which preceded it. 
 
 The germinal membrane, formed as has been described, already ex- 
 hibits at one spot an opaque area of a roundish shape, con- change* in the 
 
 Fiq 258 Sisting Of Cells and granules. To germinal mem- 
 
 ^ G brane,andpro- 
 
 this the designation of germinal duction of lay- 
 area is given. At this area the ers - 
 membrane next becomes divisible into t\vo 
 laminaa, and eventually throughout its whole 
 extent, as seen in Fig. 258. Of these lam- 
 inae, the exterior, which is nearer to the zona 
 pellucida, is the serous layer. It is the raised 
 membrane of the figure, and in it are to be 
 developed the nervous and muscular systems 
 of the embryo. The interior is designated the mucous layer, and from 
 Fig. 259. this arise the digestive organs. 
 
 The germinal area by degrees 
 loses its circular form and becomes 
 oval, its central portions clearing 
 off and giving rise to the area pel- 
 lucida. Around this the opacity 
 is increased, and in it blood-ves- 
 sels appear; hence to this dark cir- 
 cle the designation of area vascu- 
 losa is applied. In the pellucid 
 zone is next seen a delicate line, 
 the primitive groove, T ' he primitive 
 
 Fig. 259. It OCCUrS groove and 
 
 in the serous layer dorsal laminie ' 
 
 The primitive groove, magnified 8 diameters. Only, IS Wider at one end than at 
 
528 
 
 VERTEBRAL COLUMN. 
 
 Fig. 260. 
 
 Origin of the train upon the spinal cord, magnified 8 
 diameters. 
 
 the other, the wider part being destined for the head of the embryo. 
 On each side of the primitive groove two oval areas of cells emerge : 
 they are the dorsal laminae. They rise up to cover in the primitive 
 groove, so as to convert it into a tube, with three bead-like swellings at 
 its wider end, the elements of the prosencephalon, mesencephalon, and 
 
 epencephalon, Fig. 260. The ex- 
 planation of this and the preced- 
 ing figure have already been given 
 on p. 293. On the internal part 
 of the lamina nervous matter be- 
 gins to form, the rudiment of the 
 cerebro-spinal axis. In the bot- 
 tom of the groove is the trace, 
 chorda dorsalis. The groove it- 
 self, converted into a tube, con- 
 stitutes the central canal of that 
 axis, its completion into the tu- 
 bular shape occurring first in the 
 middle, and then up and down. 
 The form of the lateral masses va- 
 ries as development goes on. 
 A line of cells running lengthwise in the primitive groove is the origin 
 Chorda dorsa- of the chorda dorsalis, on which the rudiments of the verte- 
 and~^vascuiar kral c l umn appear. In the amphioxus and myxenoid fishes 
 system. development in this direction stops at this point, the chorda 
 
 dorsalis being the permanent structure. The vertebrse now emerge un- 
 der the aspect of square plates, and the dorsal laminse, prolonging them- 
 selves outward and downward, as it were, by an offshoot, produce the 
 ventral laminse, which close in the abdominal walls, and so form the 
 boundaries of the trunk. Simultaneously a new layer of cells arises be- 
 tween the serous and mucous layer of the germinal membrane, at the area 
 vasculosa, and in this intercalated lamina the vascular system forms and 
 blood corpuscles appear, capillary vessels arising from the coalescence of 
 nucleated cells, the touching ends of which become pervious. As the 
 process goes forward, a network of such vessels is constructed, and it is 
 to be particularly remarked that this takes place and that the blood is in 
 circulation prior to the existence of the heart. Around the extending 
 blood-vessels or vascular area runs a circular capillary called the terminal 
 sinus in the first stage of the process, but this disappears as the vessels 
 extend all over the germinal membrane. The extension of these vessels 
 is in part accomplished by the cells from which they have arisen elon- 
 gating themselves into processes. 
 
 Fig. 261, first appearance of blood-vessels in vascular layer of germ- 
 
PRODUCTION OF VESSELS. 
 
 529 
 
 Production of vessels. 
 
 Fig. 261. inal membrane of a fowl at thirty-sixth hour of in- 
 
 cubation. (Wagner.) 
 
 The formation of vessels from the coalescence 
 of nucleated cells, the touching ends becoming 
 pervious or elongating, is continued to a much 
 later period of development, as is demonstrated by 
 Fig. 262. 
 
 Capillary lymphatic from the tail of the tadpole : #, membrane ; b, 
 Fig- 262. processes formed by it ; c, re- 
 
 mains of the contents of the 
 cells forming these vessels, in 
 which nuclei are concealed; 0, 
 ccecal terminations of the ves- 
 sels ; jf, one of these termina- 
 tions still recognizable as a form- 
 ative cell ; g, isolated formative 
 cells about to join with actual 
 vessels, magnified 350 diame- 
 ters. (Kolliker.) 
 
 It is at this tirns that nutri- 
 tion by cells ceases, and vascu- 
 lar nutrition commences, as pre- 
 viously described. The embryo 
 has now become too large for 
 promiscuous cell nutrition to an- 
 swer ; moreover, development is 
 required to take place at differ- 
 
 Production of vessels) capillary lymphatic, magnified 350 Cnt rateS at isolated and Special 
 
 points. The formation of the 
 amnion coincides with these events. 
 
 The heart appears first as a canal or tube, arising in the vascular 
 layer from a columnar mass of cells, of which the inner ones Development 
 have deliquesced to form a tube. This then becomes tri- of the heart - 
 chambered, containing an auricle, a ventricle, and the bulbus arteriosus, 
 Fig 263 Fig. 263, of which a description is 
 
 given on p. 135. Subsequently the 
 auricle and ventricle are each divi- 
 ded by septa, that in the ventricle 
 being commenced about the fourth, 
 and finished about the eighth week. 
 The auricular septum is not completed until after birth. 
 
 Fig. 264, page 530, shows the human heart at about the fifth week : 
 A, the heart opened on the abdominal aspect; 1,. the bulbus arteriosus; 
 
 LL 
 
 Rudimentary heart. 
 
530 THE AMNION. 
 
 2, 2, two aortic arches, uniting posteriorly 
 to form the aorta ; 3, the auricle ; 4, the 
 opening from the auricle into the ventricle, 
 6, which is laid open ; 5, the septum rising 
 from the lowest part of the cavity of the ven- 
 tricle ; 7, the vena cava inferior : B, view 
 from behind ; 1, the trachea ; 2, the lungs ; 
 
 3, the ventricle ; 4, 5, the large atrium cor- 
 Fcetai heart. dis, or auricle ; 6, the diaphragm ; 7, the 
 
 aorta descendens; 8, the pneumogastric ; 9, its branches ; 10, its continu- 
 ation. (Von Bar.) 
 
 As soon as the capillary system is fairly established, the change in 
 the character of the function of nutrition alluded to is accomplished, and 
 in those animals which depend for their development on a food yolk, it 
 is eventually entirely covered with ramifications of these vessels. The 
 blood-cells of the first order or series are evolved from the nuclei of the 
 cells which coalesced for the formation of blood-vessels. 
 
 The development of the embryo still continuing, it assumes a form 
 Elevation of which has been aptly described as resembling that of a boat 
 the embryo. pi ace( j U p S i(J e down, the bottom of the boat rising higher and 
 higher above the surface of the germinal membrane, and lifting with it 
 that portion of the membrane to which it is attached. The two ends of 
 the boat-shaped body bend under toward one another ; the larger of the 
 two is destined to become the head of the embryo. As this elevation 
 takes place, the embryo becomes separated by a constricted space from 
 the surrounding germinal membrane, its abdominal parietes being still 
 open and in contact with the yolk. From the layer which thus lines 
 the interior of the cavity of the embryo, the intestinal canal arises as a 
 tube from the coalescence of a pair of lateral ridges, and the surrounding 
 and exterior portions of the germinal membrane, elevating themselves 
 above the constricted space, coalesce over the back of the embryo, and 
 thus inclose it in a sac. This sac constitutes the amnion, 
 
 Theammon. . . ' 
 
 and in this manner, by folding, the interior of the germinal 
 membrane is used as a digestive surface, the outer as one for secretion. 
 The umbilical cord obtains a sheath from the amnion, which at one end 
 is continuous with the skin of the foetus, and the other is reflected over 
 the surface of the placenta. The amnion therefore constitutes a closed 
 sac, which contains a fluid, the liquor amnii. 
 
 The place at which the germinal membrane is constricted, so as to be 
 able to act as a digestive surface to the embryo, though linear at first, is 
 gradually narrowed down, and constitutes the umbilicus. This .con- 
 stricted part is now the omphalo-mesenteric duct, which of course com- 
 municates with the cayity of the yolk-sac, which, at this stage of devel- 
 
THE CIRCULATORY SYSTEM. 531 
 
 opment in mammalia, is the umbilical vesicle. In birds, the yolk-sac is 
 carried completely into the abdomen through the umbilical opening ; in 
 mammals it remains exterior. It does not appear that the contents of 
 the yolk are directly absorbed from the cavity of the sac, but they are 
 carried by the ramifying vessels to the liver. These vessels are there- 
 fore counterparts of the mesenteric. Eventually folds arise on the lin- 
 ing membrane of the yolk-sac over which these vessels pass, and which 
 facilitate absorption. In fish, at this stage, the yolk-bag hangs down, 
 and respiration takes place upon its surface. 
 
 From the caudal extremity of the embryo the allantois emerges as a 
 mass of cells, of which the interior liquefy, and the exterior* 
 
 T . * . <7 ' , .. , The allantois. 
 
 then constitute a sac. In birds and in reptiles it reaches 
 considerable development ; in the former extending entirely over the 
 yolk-sac, but in mammals it is soon replaced and shrivels up. It dis- 
 charges the function of a urinary bladder, and, indeed, a portion of it 
 continues to do so in man. Its disappearance is the signal that the em- 
 bryo is now depending on the placenta. 
 
 To return now to the development of the circulatory system. At 
 about the end of the eighth week, as we have seen, the ven- Development 
 tricle is divided by a septum, the division of the auricle not of the circuia- 
 occurring till a little after, and even then not being perfect, tory syst ' 
 an aperture, the foramen fcvale, existing. This is the state of things at 
 about the twelfth week: of the five branchial arches two disappear, 
 the aortic bulb then divides into two tubes, which .are to be the aorta 
 and pulmonary artery respectively. Next, one of the branchial arches 
 forms the subclavian and carotid arteries. Of the middle pair, the right 
 is obliterated, but the left remains to constitute the arch of the aorta. 
 Of the lowest pair, the right forms the right and left pulmonary arteries, 
 and the left constitutes the ductus arteriosus. 
 
 The blood-system having reached its full development, the foetal circu- 
 lation may be described us follows : From the placenta ox- The f^i c j r . 
 idized blood is brought through the umbilical vein, a part cuiation. 
 passing into the ascending cava through the ductus venosus, and the rest 
 into the liver through the vena portas, from which, by the hepatic vein, 
 it also reaches the ascending cava. In its passage to the heart it be- 
 comes adulterated with blood derived from the trunk and lower extrem- 
 ities. It next gains into the right auricle, and, to some extent, is kept 
 from contamination with the venous blood coining through the descend- 
 ing cava by means of the Eustachian valve, which directs the arteri- 
 alized blood through the foramen ovale into the left auricle, from which 
 it gains the left ventricle, and also directs the venous blood of the de- 
 scending cava into the right ventricle. The blood which is in the left 
 ventricle is driven therefrom into the ascending aorta, and supplies the 
 
532 TYPES OF NUTRITION. 
 
 head ; but the venous blood which is in the right ventricle is driven 
 therefrom through the pulmonary artery and ductus arteriosus into the 
 descending aorta, and, mingling with the arterial blood therein, passes 
 to the trunk and legs. Of this blood a portion is then carried to the 
 placenta to be arterialized. 
 
 At the moment of birth a change takes place in the manner of the cir- 
 culation, which is now arranged upon the type described at page 134. 
 This is accomplished as described at page 148. 
 
 From the description which has thus been given, it may be gathered 
 Three types of ^ at U P to ^ G period of birth, three distinct types of nutri- 
 nutrition. tion have been followed. They may, with sufficient accura- 
 cy, be designated, 1st. Yolk nutrition ; 2d. Tuft nutrition ; 3d. Placental 
 nutrition. To these may be added the two followed at a later period : 
 4th. Lactation, and, after the dental mechanism is supplied, 5th. The diet 
 of mature life. 
 
 Respecting the development of special organs, it may be remarked that 
 The vertebral f those which are permanent, the vertebral column is one of 
 column. the first to appear ; it shows itself under the form of isolated 
 quadrangular elements. The gelatinous cellular structure, chorda dorsa- 
 lis, acquires a sheath, which assumes a fibrous structure, and from this, 
 in the lower vertebrates, the vertebrae are evolved. In man, the ele- 
 mentary quadrangular plates are considered tcfhave an independent ori- 
 gin. As they increase in number and size they surround the chorda, 
 and projections springing from their superior surface form arches to en- 
 velop the spinal cord. Each vertebra, therefore, is constructed by the 
 union of two pieces, one on either side. These first assume the condi- 
 tion of cartilage, and, later, the body and arches ossify from separate 
 points. The chorda dorsalis, which has, during this development, been 
 gradually evolved in the bodies of the vertebrae, disappears. 
 
 The bones of the skull are metamorphosed vertebras, of which, accord- 
 ing to Professor Owen, four appear to have undergone change. To these 
 the auditory, gustative, optic, and olfactory nerves are respectively re- 
 lated, in the same manner that the spinal nerves are to their vertebra. 
 
 In the descriptions given in the preceding part of this work, incident- 
 Development al allusion to a sufficient extent has been made to the devel- 
 tus^f organic P ment ^ most of the apparatus of organic and also animal 
 life. life. It may therefore here be briefly stated that the ali- 
 
 mentary canal originates in the pinching off of a part of the blastodermic 
 vesicle below the spinal column. At first it is a straight tube, which 
 communicates about its middle with that vesicle, but after a time shows 
 its eventual division into oesophagus, stomach, large and small intestines, 
 assuming an oblique position on the part to be occupied by the stomach, 
 and then curving in the region of the intestine. From a part of this tube 
 
INDICATIONS OF CONCEPTION. 533 
 
 the liver emerges as a thickened deposit of cells, into which the wall of 
 the intestine bulges so as to form a kind of sac, and from this rudiment 
 a ramified structure arises, which at last recedes from its place of origin, 
 and is connected with the intestine by the hepatic duct. The commence- 
 ment of this structure is about the third week, but it proceeds with so 
 much rapidity that in the third month it nearly fills the abdominal cav- 
 ity. The functions of the liver at this period have already been pointed 
 out, the meconium it secretes being modified bile (page 202). In like 
 manner, from the digestive tract, the pancreas and salivary glands orig- 
 inate from masses of cells, ducts being formed by deliquescence of por- 
 tions within. From the alimentary canal, also by budding and deliques- 
 cence, the lungs arise, their cavity communicating at first by several aper- 
 tures with the pharynx. This occurs about the sixth week. These organs 
 are gradually removed from the place of origin, as in the case of the liver. 
 
 The Wolffian bodies are temporary urinary organs, which precede the 
 kidneys and eventually disappear. They are of an ovoid The Wolffian 
 shape, and consist of a duct from which transverse canals todies. 
 branch forth, the duct discharging into the sinus urogenitalis. They 
 originate about the end of the first month, and commence to degenerate 
 in the third. In fishes they remain as the permanent urinary apparatus. 
 The testes or ovaries arise from the inner margin of the Wolffian body, 
 the former being guided into the scrotum by the gubernaculum. This 
 descent commences between the fourth and fifth month, and is completed 
 at birth or shortly after. 
 
 Among the indications that conception has occurred are usually enu- 
 merated, stoppage of the menses, the placental murmur, the indications of 
 development of the mammary gland, its sense of pain or ten- conception, 
 derness, the color of the areola, the turgescence of the areola and nipple, 
 irritability of the stomach. Quickening, as it is termed, usually occurs 
 about the eighteenth week, and parturition in the fortieth, or at the close 
 of 280 days. With respect to this, it is admitted that the term may be 
 possibly .prolonged, in very rare cases, by 40 days. The French laws le- 
 gitimatize a child born within 300 days ; and that such variations of the 
 proper term may occur is proved by observations made upon domestic 
 animals, in which the duration of pregnancy can be ascertain- p er iod of ges- 
 ed with precision. In the cow, which has the same period of **&<>* 
 gestation as the human female, the shortest period hitherto observed is 
 213 days, the longest 336. The shortest period at which human par- 
 turition can occur, consistent with the viability of the child, appears to 
 be about 23 weeks. 
 
 The act of parturition in its first stage is to be referred to a contrac- 
 tion of the muscular fibres of the fundus and body of the Mechanism of 
 uterus with a synchronous relaxation of those of the cervix, parturition. 
 
534 GEMMATION. 
 
 At a later period the contraction of the expiratory muscles assists. After 
 birth is accomplished, the mouths of the uterine vessels are closed through 
 the contraction of the organ, the lochial discharge carrying with it any 
 disintegrated residues of the deciduous membrane, and also large quanti- 
 ties of fat, derived probably from the degeneration of the uterine struc- 
 ture itself. 
 
 That both parents are concerned in imparting characteristics to the 
 Influence of child there can be no doubt : it is fully established where they 
 both parents. are O f different races, as white and black, or white and red ; 
 and equally in the case of animals, as in mules, produced by the mix- 
 ture of different kinds. It is scarcely necessary to remark that this ex- 
 tends to the communication of more refined peculiarities, the resemblance 
 of countenance, figure, gesture, and even mental qualities, family like- 
 nesses which we daily observe. These impressions are of a much more 
 profound character than might at first be supposed, as is proved by the 
 fact that the third generation will exhibit peculiarities belonging to its 
 progenitors, though those peculiarities have not occurred in the second. 
 Even after parturition is over there still remains impressed upon the fe- 
 male a definite change : this is illustrated by the well-known case of a 
 mare which had borne a colt by a quagga, her subsequent colts by horses 
 being distinctly marked like the first ; and in the human female cases 
 are of common occurrence in which the offspring of a widow, who has 
 been married a second time, resemble her first husband. Marriage pro- 
 duces in this respect a permanent change in the female, a constitutional 
 impression not disappearing in any length of time, the influence of the 
 first husband reappearing in the children of a subsequent contract. 
 
 2D. GEMMATION. 
 
 The ascending axis of a plant is terminated by a differentiating part, 
 Gemmation of surr ounded by protecting structures. From this, as growth 
 plants and ani- takes place, leaves or their modifications are produced. This 
 differentiating part is a bud. In like manner may.be found 
 in the axils of leaves similar buds, which pass by development into 
 branches, but sooner or later the terminal buds are checked in their lon- 
 gitudinal increase, and the parts to which they would have given origin 
 Fig. 265. spirally being compressed into circles, a flower arises, 
 
 and further development ceases, the reproductive phase 
 being now assumed. 
 
 Among the lower animals propagation by buds is 
 also observed. Thus the hydra exhibits this manner 
 of increase, as seen in Fig. 265 ; and even upon the 
 buds thus produced, other buds, of a second order or 
 Hydra budding. generation, are found. 
 
METHODS OF GRAFTING. 535 
 
 Propagation through the agency of buds is termed gemmation. It 
 may be accomplished either by the natural or artificial separation of the 
 buds from the parent stock. Thus, in the hydra, the buds may spon- 
 taneously be separated from the parent, and thereby give rise to free in- 
 dividuals, or they may be purposely cut off with the same result. In 
 the case of plants, artificial separation is constantly resorted to, as in the 
 various methods of budding and grafting employed by horticulturists for 
 obtaining the finer varieties of flowers or fruits. It consists Methods of 
 essentially in placing a bud of the plant which it is desired to g raftin g- 
 propagate upon a stock of a different kind, in such a way that, as devel- 
 opment of the bud or scion takes place, union or incorporation with the 
 stock shall occur. There are many different ways in which grafting may 
 be performed ; they all depend for their success, however, upon causing 
 the alburnum of the scion to coincide with that of the stock, so that the 
 vessels of the former may receive the sap arising from those of the latter. 
 When the parts are thus adjusted, they are to be retained in their posi- 
 tion by bandages or other suitable means, and protected from the air and 
 rain by means of clay or wax. The most suitable time for this opera- 
 tion is in the spring, just previous to the rising of the sap. 
 
 There are certain limits within which the operation of grafting must 
 be performed. The stock and the scion must be nearly re- Limits of gem- 
 lated to each other. If species of different natural orders be mation ' 
 grafted they will not take, but the species of the same genus may. 
 
 If in this manner we take a bud, and graft it on a stock of an allied 
 kind, it will continue to grow and develop in the same man- Nature of 
 ner that it might have done without detachment from the propagation 
 parent plant, and in the same manner from the new plant that. bygem 
 has thus arisen, by a repetition of the process, plant after plant, for many 
 generations, can be secured. Experience has taught us that, whatever 
 might have been the peculiarities of the original from which the first bud 
 was taken, those peculiarities, whether of odor, taste, color, or shape, will 
 reappear in the product ; but experience has also taught us that thereds 
 a limit beyond which these repetitions can not be conducted. The val- 
 ued fruits and flowers of the old times have thus disappeared. Propaga- 
 tion by gemmation is therefore considered as tending to exhaust the orig- 
 inal plastic power. But it is to be remarked that, if from these artificial 
 growths seeds be taken and caused to germinate, the plants so arising no 
 longer present the special, and, perhaps, valued peculiarity, but in many 
 instances run back at once to the original and wild stock. 
 
 We are apt to attach to propagation by gemmation more importance 
 than it really deserves in a philosophical point of view when it thus ap- 
 pears to have given rise to new and successive generations of individuals. 
 But, after all, wherein does it differ essentially from what goes on natur- 
 
536 SPONTANEOUS GEMMATION. 
 
 ally ? The manner of extension of any given plant is by bud after bud 
 in succession, either terminal or axillary ; but this extension does not go 
 on indefinitely ; it reaches a limit both as respects size and duration. 
 We never notice in the development of a bud which remains attached to 
 its parent stock the spontaneous appearance of novel qualities. The 
 flowers and fruits are like all the others upon the same plant. If such 
 a bud, then, removed from its parent seat, be permitted, under favorable 
 conditions, to grow elsewhere, it might be expected, as is actually the case, 
 that it would go on in its development without exhibiting any alterations. 
 
 Essentially of an exhausting nature, reproduction by gemmation is 
 limited. It can only be repeated a definite number of times. At the 
 most, all that we do in this artificial process is to obtain a part of an old 
 individual under a new and isolated form. We thereby relieve such 
 new growth from the chance of those accidents which may befall the 
 original stock ; but both for the one and for the other there is a definite 
 term of life. When that term is approached, though we may take sci- 
 ons or buds, and treat them with every care in the usual operation of 
 grafting or budding, the operation will fail. 
 
 There is a certain analogy between this incorporation of the parts of 
 different plants and the so-called grafting or Taliacotian operations which 
 are sometimes performed on the parts of animals, as the transplantation 
 of the spur of one bird on the top of the comb of another, or many of the 
 plastic operations of surgery ; but these parts do not necessarily perish 
 in the manner which has been indicated by Butler in his Hudibras. 
 
 Propagation by gemmation and reproduction by generation are, in 
 many instances in the animal series, resorted to alternately for the con- 
 tinuation of the race. Thus, during the summer season, propagation by 
 gemmation may serve to increase the number of a given kind, but if these 
 should be unable to maintain themselves during the cold of winter, the 
 race would inevitably become extinct, unless reproduction by ova were 
 resorted to ; for though the developed animal may not be able to with- 
 Influence of stand the decline of temperature, the ova may. Thus, in 
 spontaneous 011 a hydra, propagation by gemmation continues until the ex- 
 gemmation, ternal temperature lowers to a certain degree, and that at 
 once brings on a reversion to the other process. The same thing has 
 been observed in the case of the aphis, which multiplies by gemmation 
 until there is a reduction of temperature, and then it multiplies by gener- 
 ation. We have already dwelt at length on the control which external 
 circumstances have over development; it is, therefore, no more than might 
 be expected that they should, in like manner, determine the processes of 
 propagation and reproduction. 
 
 Gemmation occurs only in a very doubtful way and under special cir- 
 cumstances among the more advanced members of the animal series. In 
 
ALTERNATION OF GENERATIONS. 537 
 
 man, there is reason to suppose that gemmation can only take place in 
 the earliest periods of existence, perhaps at the epoch of the formation of 
 the mulberry mass. Upon this principle an explanation of the occur- 
 rence of double monsters has been given. 
 
 3D. ALTERNATION OP GENERATIONS. 
 
 It has been already explained that by this phrase is meant that a pa- 
 rent plant or animal will give origin to a form wholly unlike Alternate em 
 itself, and this form, perhaps after the lapse of years, will mation and 
 give origin to another unlike itself, but similar to the original S eneratlon - 
 progenitor. Thus the Salpse present themselves under two different as- 
 pects, the solitary and the aggregated, the latter being produced from the 
 former by being Thudded off in an internal stolon, the individuals being 
 united to one another in an aggregation or chain after they have been 
 separated from the parent. These aggregated salpas alone have sexual 
 organs and produce ova. From each ovum a solitary salpa arises, which 
 repeats the process described again. The solitary salpa, therefore, mul- 
 tiplies by gemmation, the aggregate by generation. Nor is this process 
 confined to animals ; it is also observed in the case of plants. Thus, 
 in ferns, the spore produces the prothallium, which becomes a distinct or- 
 ganism, separated from its parent, and carrying on its nutritive processes 
 independently for itself. From it arises by generation a fern like the 
 original, which, like it, by gemmation, produces prothallia, but never 
 directly produces a fern. Therefore between each fern and its descend- 
 ant a prothallium intervenes, the prothallium arising by gemmation from 
 the fern, and a fern arising by generation from the prothallium. 
 
 After a careful examination of Steenstrup's doctrine of alternations of 
 generation, Dr.. Carpenter concludes that it can not be re- ,, , 
 
 L Explanation 
 
 ceived in the form originally presented, since we should re- of alternations 
 gard a generation as embracing the entire product from gen- of s eneratlon - 
 erative act to act. Indeed, the intermediate forms are often nothing 
 more than sexual organs, furnished or not with an apparatus of locomo- 
 tion, or, in "the more complicated cases, having a mechanism of nutrition 
 attached sufficient for their purpose. The correctness of this interpreta- 
 tion may be illustrated by such cases as the development of medusa buds, 
 which, being first attached to the parent, gradually exhibit the formation 
 of an independent digestive apparatus, and when this has reached a cer- 
 tain degree of perfection, they are separated and swim off, generative or- 
 gans then arising in these buds by which true ova are formed. In the 
 Sentularidas buds are developed in ovarian capsules, and these reproduce 
 in their turn ova by generation. The rate at which gemmation goes on 
 in many of these instances is obviously connected with physical condi- 
 tions, more particularly the degree of temperature and the supply of food. 
 
538 GROWTH OF MAN. 
 
 The fact of the apparent dissimilarity between the product of gemma- 
 tion and the product of generation ceases to have any force as soon as 
 we consider the former in the attitude which it really ought to occupy, 
 as not constituting a distinct individual, but merely a part, a derivative, 
 or an appendix of the product of generation ; and this view of Dr. Car- 
 penter's seems, therefore, to be the proper interpretation of the whole case. 
 
 CHAPTER V. 
 
 THE GROWTH OF MAN. 
 
 Infancy. Weight and Size of the Infant. Weight and Size at subsequent Periods. Develop- 
 ment of the Intellect. Maturity of Man. Tendency to Crime. Maxima of Physical and Men- 
 tal Strength. 
 
 Mental and Physical Decline. Mortality at different Periods of Life. Comparative Structure, 
 Functions, and Mortality of the two Sexes. 
 
 Artificial Epochs of Life. Gradual Change in the Mental Qualities. Independent Existence of 
 the Soul. 
 
 IN the last chapter the successive stages of embryonic development 
 were described. It was shown that at one period nutrition is solely at 
 the expense of the yolk of the ovum, which is appropriated, by a simple 
 surface-imbibition ; and that this, in due time, is succeeded by what has 
 been designated tuft nutrition. At a later period, this mode, in its turn, 
 is replaced by another, depending on a vascular arrangement, the pla- 
 infancy of centa. For a considerable period after birth a fourth system is 
 man. relied on, nourishment by milk ; and it is only by degrees, when 
 the necessary changes have been made in the digestive mechanism, the 
 teeth being cut, that the final mode of nutrition is assumed. Even after 
 this the human infant leads a dependent life, because of its own weak- 
 ness and imbecility, irrespectively of any peculiarities of our social state. 
 So far, therefore, from man not exhibiting those metamorphoses which 
 are undergone by the lower members of the animal series, he of all dis- 
 plays them in the most marked way, for they do not cease at the period 
 of birth, but reach through many subsequent years a gradual develop- 
 ment of the body, attended by a gradual change in the manifestations of 
 the mind. 
 
 At birth, the human infant is the very representative of weakness and 
 imbecility. Though, unlike many other mammals, it opens its eyes at 
 once, it exhibits no token of visual perceptions ; though it may be sub- 
 jected to sounds or noises of various kinds, it takes no notice whatever 
 of them. This condition of inertness is followed by a condition of con- 
 fused sensation, which by degrees is succeeded by a capability of ap- 
 
THE TEETH. 539 
 
 predating special ideas. Buffon has very truly said that the earliest 
 period of conscious existence is a scene of pain, the life of the infant "be- 
 ing divided between sleep and crying ; from its slumbers it is awakened 
 only by the pains of hunger ; nor is it until after the lapse of many days, 
 or even weeks, that the first smile is seen. It is too feeble to turn from 
 side to side, but remains in the position in which it was placed. Its 
 skin, which at birth was covered over with a whitish incrustation, the 
 vernix caseosa, becomes reddish, the depth of this tint, however, shortly 
 passing away. At this period, moreover, life is purely vegetative, the in- 
 fant feeding and sleeping. The biliary matter, meconium, which had ac- 
 cumulated in its intestine during foetal life, is discharged in the course of 
 a day or so after birth, and the digestive apparatus enters on its functions 
 with activity. 
 
 It is said that the infant smiles soon after it is forty days old ; though 
 it can cry it can not shed tears. Before long it gives indications of its 
 satisfactions and dislikes. The power of moving in an erect posture is 
 gained by it in the course of a year, and by the close of that time it can 
 masticate. Of its teeth, the central incisors appear about the 
 seventh month, those of the lower jaw first ; the lateral incisors 
 about the eight or tenth, the anterior molars about the twelfth, and the ca- 
 nines about the eighteenth, the posterior molars being cut between that 
 time and three years. The average date of the appearance of the perma- 
 nent teeth is, the front molars about the seventh year ; middle incisors, 
 eighth ; lateral incisors, ninth ; anterior bicuspids, tenth ; second bicuspids, 
 eleventh ; canines, twelfth to thirteenth ; second molars, twelfth to four- 
 teenth; and the last molars from the seventeenth to the twenty-firs, t year. 
 
 The power of articulate speech is displayed within twelve or fifteen 
 months, some letters being more easily gained than others ; among 
 themareA,B,P,M. 
 
 From henceforth the mind emerges with rapidity from the confusion 
 of a multitude of impressions, and learns to concentrate itself Concentration 
 at pleasure upon one. This capability of mental abstraction of the atten- 
 is a process of specialization, and is a manifestation of the tlon ' 
 law of Von Bar. The intellectual difference which we eventually observe 
 between one man and another is, to no inconsiderable degree, dependent 
 upon such an ability of concentrating thought. He who conceives of a 
 thing distinctly is very likely to express -himself of it clearly. 
 
 Throughout infancy and childhood, the features, and even the gestures, 
 indicate the profound constitutional changes which are going on. The 
 countenance, instead of expressing pleasure and pain in the aggregate by 
 smiling or crying, as was the case at first, gains the faculty of represent- 
 ing every grade of feeling. Long before maturity is reached we read 
 without difficulty the thoughts which are passing in the mind from the 
 
540 MAXIMUM AND MINIMUM OF HEIGHT. 
 
 movements of the lip or the eye, and the painter can express every shade 
 of feeling, and every emotion, by the mere configuration of the outward 
 form. 
 
 The monthly growth of the foetus for six months before birth is es- 
 Mean length tablished at two inches. At birth, the mean length of boys 
 of the infant. j s jgi. j ncneS) an d of girls 18 inches, the former being there- 
 fore a little the longer. 
 
 At sixteen or seventeen years the growth of girls is relatively as much 
 Growth of boys advanced as that of youths of eighteen or nineteen. For 
 and girls. the most part, the inhabitants of towns are taller than those 
 of the country. The full height is not reached, in some instances, until 
 twenty-five years ^ in very warm and very cold climates it is more quick- 
 ly attained. The recumbent position is regarded as being favorable to 
 growth, and, influenced by his own weight, an individual is shorter in 
 the evening than when he first rises from bed in the morning. 
 
 With regard to the rate of growth, it may be observed that it is most 
 rapid immediately after birth, and continually diminishes until about five 
 years, the epoch of maximum of probable life. It then remains equable 
 to about sixteen years, the annual growth being 2-^ inches. After pu- 
 berty it declines, being, from sixteen to seventeen years, 1J inches, and 
 during the next two 1 inch only. The annual increment relatively to 
 the height then attained continually diminishes from birth. The foetus 
 grows as much in length in a month as the child from 6 to 16 years 
 does in a year. The limits of growth of the two sexes are unequal, be- 
 cause women are smaller than men, terminate their growth sooner, and 
 annualjy grow less. Individuals in affluent circumstances may often 
 surpass the standard height, but misery and fatigue are liable to produce 
 the opposite effect. Longevity is generally less for persons of great 
 height. 
 
 As to the maximum and minimum of height, it may be remarked that 
 Maximum and Frederick the Great had a Swedish body-guard whose height 
 minimum was eight feet three inches ; and, on the other hand, Birch 
 ian ' states that there was an individual, 37 years old, whose 
 height was sixteen inches. In view of these and other such facts, 
 Quetelet fixes on 8 feet 3 inches as the maximum, and 1 foot 5 inches 
 as the minimum of height ; he gives as the mean 5 feet 4 inches. Half 
 the men of France, at the age of conscription, are between 5 feet 2 inches 
 and 5 feet 6 inches, but the wars incident on the great Revolution made 
 a permanent impression on the French in this respect by lowering the 
 standard through the consumption of the taller men. M. Quetelet more- 
 over remarks, that in ten millions of men there is but one more than 6 
 feet 8 inches, and one less than 4 feet. There is reason, however, to be- 
 lieve that this statement will not hold good of America. 
 
WEIGHT AND HEIGHT. 541 
 
 As regards weight, new-born boys are heavier than girls. An average 
 taken from 20,000 gives 6 Ibs. as the weight at birth; the weight of 
 maxima and minima have been 10 J Ibs. and 2 J Ibs. For about infan ts. 
 a week after birth the weight diminishes, owing to the effect of aerial 
 respiration. The difference in weight between the two sexes gradually 
 diminishes until about the twelfth year, when an equality is reached. 
 The maximum w*eight is attained about 40, and as 60 is ap- We - tt at dif _ 
 proached a diminution is perceived, which reaches 12 Ibs. ferent periods 
 at about 80 years, the stature likewise correspondingly di- 
 minishing by about 2| inches ; the female reaches her maximum weight 
 somewhat later, at about 50 years. The extreme limits of weight in 
 men are 108 Ibs. and 216 Ibs. ; in women, 87J Ibs. and 206 Ibs. The 
 mean weight at nineteen is nearly that of old age in both sexes. At full 
 development the male and female weigh almost exactly 20 times as much 
 as at birth. In the first year the infant of both sexes triples its weight. 
 It requires six years more to double that, and thirteen to quadruple it. 
 Immediately after puberty both sexes have half their ultimate weight. 
 Between the ages of 25 and 40 the mean weight of the male is 136J Ibs., 
 and of the female 120f Ibs. 
 
 With respect to the relation between weight and height, if man increased 
 equally in all his dimensions, the weight would be as the cube Eelation of 
 of the height ; but since this is not so, development taking place height and 
 unequally, the proportion is not observed, and it is found that weig fc * 
 from the end of the first year to puberty the weights are as the squares 
 of the heights. M. Quetelet gives as an approximate rule that during 
 development the squares of the weights at different ages are as the fifth 
 power of the heights, the transverse growth being less than the growth 
 in height. The mean weight of a male, without reference to age, is 103f 
 Ibs. ; of a female, 93f . A similar calculation for the population of the 
 United States as that which has been given by this philosopher for Brus- 
 sels would give for the total weight of all Americans two thousand six 
 hundred and thirteen millions of pounds. 
 
 The weight of an individual, considered without reference to age or 
 sex, is 98J Ibs. 
 
 From birth until puberty the mode of life is essentially vegetative, all 
 the instincts having relation to the individual and corporeal development. 
 Except through the intervention of education, the desires of the child are 
 chiefly directed to the pleasures of mere vegetative existence, eating and 
 drinking ; and this, in savage races, is witnessed in a much more mark- 
 ed manner than in those that are civilized, in whom the manner of life is 
 affected through the intervention of parental care. In this particular it 
 may be remarked that maternal love is divisible into an in- Maternal love 
 stinctive and a moral affection, the former of a lower and of two kinds. 
 
542 MATURITY OF MAN. 
 
 more animal kind, the latter of a higher and intellectual ; the former lim- 
 ited to the period of infantile helplessness and dependence, and succeed- 
 ed by the latter as maturer years are attained. In savage races, howev- 
 er, instinctive affection seems alone to exist, and the intensity of moral 
 affection is, to a certain extent, a measure of civilization. Throughout 
 Character of t ^ ie ^ rst ^ teen y ears of life, with the gradual development 
 the life of chil- of the body there is also a steady intellectual progress, the 
 dren ' gains of which seem to be greatest at the earlier periods, and 
 
 less and less marked as maturity is approached. When we recall the 
 wonderful advance accomplished in the first years, embracing the acqui- 
 sition of speech, and a knowledge of the nature and qualities of a thou- 
 sand surrounding objects, we might be led to suppose that our mental 
 acquisitions decline with the progress of life ; but this is altogether de- 
 ceptive ; for, though the acquirements of later years be less obvious, they 
 are none the less important and none the less profound. 
 
 Through the successive changes to which allusion has now been made, 
 The maturity each of which is a strict metamorphosis, and each of which, 
 of man. w ^ n its special structures, has its special functions, man at last 
 reaches maturity. In some cases, as we have seen, the stature contin- 
 ues increasing until after the twenty-fifth year, and throughout the whole 
 mature period, even after what has been termed the meridian of life is 
 gained, the weight also becomes greater. This increase of weight, how- 
 ever, has not so much a relation to the muscular as to the respiratory sys- 
 tem, for the former reaches its perfection at a much earlier date, the in- 
 creasing development of the middle period of life being due to a continued 
 tendency to the accumulation of fat. At this period, moreover, the object 
 of life has undergone an entire change ; the vegetative propensity, or that 
 for the exclusive development of the individual, has declined in prom- 
 inence, and the reproductive has been assumed. With this there have 
 been awakened new sentiments and new emotions, affording still another 
 corroborative proof of the connection of mental habitudes and structural 
 condition. The psychical powers are now advancing toward maturity, 
 an advance which they continue to make until about the fiftieth year. 
 Throughout this whole period, and even at this extreme date, we still 
 notice how much intellectual capacity is connected with the perfection of 
 corporeal development. It needs but a little experience for us to de- 
 termine at a glance the intelligent from the obtuse, and to read even the 
 minor shades of character in the aspect of the face. Without being 
 aware of it, we are constantly putting into requisition the principles of 
 phrenology and physiognomy, and drawing conclusions respecting char- 
 acter to a certain degree correct, from the expression of the eyes, the lin- 
 eaments of the countenance, or the configuration of the head. 
 
 The actions of man are closely connected with the physical and moral 
 
TENDENCY TO CRIME. 543 
 
 circumstances under which he is placed. The greatest nura- The tendency 
 ber of crimes against persons and property is among the inhab- to crime in 
 itants of river-banks. The period of the maximum of crimes n 
 against persons coincides with that which is the minimum against prop- 
 erty, and is the summer season. As respects each individual, his tend- 
 ency to crime is at first against property, and this reaches its maximum 
 at about 25 years of age, whereas the tendency to crime against persons 
 commences later than that against property, and increases with the in- 
 crease of strength. In crime, man, as he grows older, substitutes strata- 
 gem for force. If brought up in a liberal profession, his tendency in 
 crime is against persons, but that of the workman is against property. 
 Elementary instruction, so far as reading and writing go, does not lead 
 to the diminution, but rather to the increase of crime : a very Pre j udicial efL 
 important conclusion, more particularly in the United States, feet of low ed- 
 in many portions of which this kind of education is chiefly 
 patronized by government, to the exclusion, to a certain extent, of that 
 which is of a higher grade, and which serves to correct this important 
 defect.. Moreover, superficial education makes the mind a ready recep- 
 tacle for every kind of imposture, and has been the cause of the rapid 
 spread of many modern delusions, such as spiritualism and homoeopathy. 
 As regards women, their tendency to crime, when compared with that 
 of men, is as 23 to 100 ; at least this is the case in France. _ 
 
 Ine tendency 
 
 Their tendency for the perpetration of crimes against persons to crime in 
 is less than that for crimes against property in the proper- ^ 
 tion of 16 to 26. It is interesting to observe that the physical force of 
 woman, as compared with that of man, is also as 16 to 26. From such 
 considerations, it may therefore, perhaps, be concluded that the morality 
 of women is about the same as that of men, their physical feebleness and 
 modesty being taken into account. In woman, the maximum tendency 
 for crime occurs at about 30 years, but then she relinquishes that dispo- 
 sition sooner than man. Her tendency to theft, however, begins early, 
 and lasts through life. When she desires to commit murder, she em- 
 ploys, by preference, poison. In this may be discerned the influence of 
 her constitutional element, physical feebleness. Timid at explosions and 
 at the sight of blood, if driven to the extremity of self-destruction, she 
 instinctively resorts to drowning. Women, like men, who are the res- 
 idents of towns, are much less moral than those who live in the country. 
 This may be inferred from such facts as that the annual percentage of 
 still-births occurring in the former is very near double of that occurring 
 in the latter case ; and though this may be, to a certain extent, connect- 
 ed with the fashionable restraints of clothing and social dissipations, it 
 is far more due to female depravity. The illegitimate births of towns 
 compared with those of the country are as 23 to 7. Among the still- 
 
544 MAXIMA OP STRENGTH. 
 
 "born, the illegitimates are to the legitimates as 5 to 3. In the city of 
 Berlin, the illegitimate still-births are to the legitimate in as high a pro- 
 portion as 3 to 1. 
 
 The passions of man are gratified in a manner that seems to be inde^ 
 pendent of religious profession. The open dissoluteness of one country- 
 is counterpoised by the secret crime of another. Protestant England 
 and Catholic France exhibit a striking illustration. In the former, in 
 1845, the number of illegitimates was 70 per thousand of the whole num- 
 ber of children born. In France it was about 71. 
 
 During the process of the development of the intellect of man, various 
 Succession of P s y c ^ ca l persuasions in succession arise, which are frequent- 
 psychical per- ly imputed to education or tradition, but of which the origin 
 is undoubtedly to be traced to the organization. Those gen- 
 eral ideas that are found all over the world, among all races of mankind, 
 whatever may be the climate in which they live, their social condition, 
 or religious opinions ideas of what is good and evil, of virtue, of the 
 efficacy of penance and of prayer, of rewards and punishments, and of 
 another world : these, from the uniformity of their existence in all ages 
 and in all places, must be imputed to the stamp that has been put upon 
 our cerebral organization. In the same light we must view, as Dr. Prich- 
 ard has said, the delusions and fictions which are universal, such as 
 ghosts and genii, giants and pigmies. Universal opinions are not the 
 result of accident, nor always of tradition. They are often creations of 
 the mind, arising from peculiarities of its constitution. 
 
 Arrived at maturity, the system of man commences at once to decline, 
 Successive max- the epochs of the maximum of physical and mental strength 
 and mental S1< l not however, coinciding ; that for the former occurring at 
 strength. about the 25th year, as previously remarked, but that for 
 
 the latter not until between the 45th and 50th year. At this period, 
 when the powers of imagination and reason have reached their highest 
 degree, the liability to mental alienation and insanity is also at its max- 
 Order of men- i mum< Somewhat later, the physical system plainly be- 
 tai and physi- trays that it is pursuing its downward course, retracing the 
 steps through which it passed forward to development. Soon 
 there is an evident decrease of weight, the nutritive operations being no 
 longer able to repair the waste of the body. There is also a diminution 
 of the height. This corporeal decay is the signal for a depression of the 
 mental powers, the first which begins to yield being probably that of con- 
 centrating or abstracting the thought. As years pass on, external im- 
 pressions exert a diminished influence, and he who at an earlier period 
 reached the meaning of things, as it were, almost by intuition, now casts 
 his eyes over page after page without an idea being communicated to his 
 mind. The old man querulously complains that he reads his book, but 
 
LONGEVITY. 545 
 
 does not understand what it means. With this failure of per- Extreme old 
 ception the powers of memory decline, recent events fading a s e - 
 away first, "but those of early life being recollected last. The present no 
 longer possesses an interest, for the brain is less capable of receiving any 
 new impressions. One after another, the organs of sense fail to discharge 
 their functions ; the sight becomes misty, the hearing dull ; there is an 
 indisposition for exertion, a desire for repose. The white-bearded pa- 
 triarch of a hundred years sits quietly by the fireside, resting his hands 
 on the top of his staff. 
 
 Instances of Longevity. 
 
 Yean. 
 
 Attila 124 
 
 Margaret Patten 137 
 
 The Countess of Desmond 145 
 
 Thomas Parr 152 
 
 Thomas Damme 154 
 
 John Kovin > 172 
 
 His wife.... > .-. 164 
 
 Peter Torton 185 
 
 The mortality of towns is greater than that of the country. As we 
 advance from the midst of the temperate region toward the i j0ca i raor . 
 equator or toward the poles, it also increases : thus, in the tali< y- 
 northern portions of Europe, the annual mortality is as 1 to 41 ; that of 
 Central Europe, 1 to 40^ ; that of Southern Europe, 1 to 33^. Con- 
 sidered as respects different periods of life, the rate of mor- Mortality at 
 tality varies very much. Of both sexes, 22 per cent, die different peri- 
 before they are one year old, and 37 per cent, before they 
 are five years old. Male infants are, however, more liable to die imme- 
 diately after birth than female, but at the close of about two years their 
 mortality is the same. Nine twentieths of the whole number born die 
 before they are fifteen years of age, that is, before they have become use- 
 ful to the community. 
 
 The mortality among girls increases between 14 and 18, and among 
 men between 21 and 26. In France and Belgium, from 26 Relative raor . 
 to 30 is the epoch of marriage, and at this period the mortal- tality of the 
 ity is the same in both sexes. It then increases for the s 
 women during the years of childbearing, and afterward again becomes 
 equal for both. At 25 years half the births are dead. The mean life 
 may be estimated at 33 years. The maximum expectancy of life is at 
 5 years, at which age the risk of mortality is suddenly reduced, and be- 
 comes small till puberty, when, especially among girls, it becomes great. 
 From 60 to 65 the chances of life are again at a minimum. 
 
 To the foregoing statements, in which contrasts have been drawn be- 
 tween the male and female, the following may be added : Not only is 
 there a difference in the entire stature, but the different portions of the 
 
 M M 
 
546 PECULIAEITIES OF THE FEMALE. 
 
 Comparison of body have not the same relative size. The capacity of the 
 *f Vemale and s ^ u ^ * n * ne f ema ^ e is ^ ess tne body is longer ; the lower ex- 
 female, tremities shorter ; the pelvis of greater size, especially in its 
 transverse diameter; the heads of the thigh bones, therefore, farther apart, 
 and the bones themselves including a larger angle than in the case of the 
 male ; the chest and the abdomen are respectively more convex ; the trans- 
 verse diameter at the shoulders smaller, and the upper extremities, like 
 the lower, shorter ; the hands and feet, fingers and toes, of less size. The 
 surface presents a more elegantly rounded form, without angularities ; 
 the skin thinner and more translucent ; the hair of the head is longer 
 and finer, but other portions of the skin less covered with hair ; the nails 
 smaller and thinner. 
 
 The strength of the female is to that of the male as 16 to 26. Her 
 Functional e musc ^ es contract with less energy, and are more easily wea- 
 cuiiarities of ried. The peculiarities of the construction of the bones of 
 
 female. j^ p e } v i s an( j cnes t respectively give rise to peculiarities in 
 the movements of the lower and upper extremities ; hence the character- 
 istic manner of walking and movement of the arm in attempting to throw 
 a stone. In the chapter on the voice we have already pointed out the 
 female peculiarities in speaking and singing, and its more acute quality. 
 
 With respect to her moral and intellectual peculiarities, these are man- 
 Her moral and ^ este ^ ^ rom * ne earliest infancy in the sports and games 
 intellectual pe- which she instinctively follows. Coming to maturity more 
 rapidly than the male, she abandons these, though they may 
 still be enjoyed by boys of her own age, whom, for the course of a year 
 or two, she regards with neglect or even disrespect, a feeling soon after 
 to be followed by timidity. Education and the position in which she 
 may have been placed may, to a certain extent, control or disguise her 
 habits, but they can never wholly obliterate the striking predominance 
 of her moral over her intellectual qualities, as compared with man. Es- 
 sentially religious, her faith is applied to almost all the ordinary affairs 
 of life, though when she finds that she has been deceived she is ever dis- 
 trustful. From the earliest times it has been remarked that her revenge, 
 more particularly when it concerns wounded pride, is implacable. Much 
 more than the male she is delighted with the adornments of dress. Her 
 reasoning powers are less vigorous, though her sensations are more acute, 
 yet she bears pain with more resignation than man. Her judgment is 
 not so evenly balanced, and is often perverted by the preponderance of 
 her feelings. It has been asserted that these moral and intellectual pe- 
 culiarities which she presents when compared with man are distinctly 
 traceable to the phrenological predominance of the moral over the intel- 
 lectual regions of the brain. 
 
 The physiologist who is thus obliged to speak of the constitutional 
 
EPOCHS OF LIFE. 547 
 
 and mental imperfections of the female, may be permitted to turn with 
 delight from the dry details of statistics and anatomy to the family and 
 social relations, for it is therein that her beautiful qualities shine forth. 
 At the close of a long life, checkered with pleasures and misfortunes, 
 how often does the aged man with emotion confess that, though all the 
 ephemeral acquaintances and attachments of his career have ended in dis- 
 appointment and alienation, the wife of his youth is still his friend. In 
 a world from which every thing else seems to be passing away, her affec- 
 tion alone is unchanged ; true to him in sickness as in health, in misfor- 
 tune as in prosperity, true in the hour of death. When the schemes that 
 occupied his active years have vanished, or, if realized, are now no more 
 to him than vanities which hardly fasten his thoughts ; when, in the 
 feeble extremity of age, every thing is a burden to him, and the pass- 
 ing excitements of others can not even arouse his attention, the echo of 
 those prayers is still heard which his unskillful tongue first learned at his 
 mother's knee. The stern, the avaricious, the hard-hearted, the intellect- 
 ual, all are equally brought to confess who was their first and who is their 
 last true friend. 
 
 The necessities of society have led to the establishment of artificial 
 epochs in the life of man. In most countries, the first recog- Artificial 
 nized movements of the foetus are taken as the period from e P chs of life - 
 which independent life begins, and the twenty-first year is fixed as the 
 time of maturity. These arbitrary dates answer the purpose very well, 
 but they have not that physiological significance which is commonly sup- 
 posed, for neither of them coincides with any great change in the mode 
 of life. Of the metamorphoses through which we pass, the final one, oc- 
 curring at puberty, which separates the merely vegetative from the re- 
 productive period of life, is, under the circumstances of the case, with the 
 exception of the assumption of aerial respiration at birth, the only obvious 
 one. The change which then ensues is in no respect less marked than 
 the passage to the perfect or imago state by insects. Development sud- 
 denly takes on a new phase, and with the physical change correspond- 
 ingly occur changes in the psychical endowments modesty and woman- 
 ly sentiments in the one sex, courage, the perception of honor, and manly 
 qualities in the other, the capability of mutual love in both. Even among 
 animals under the same conditions, analogous results are presented, though 
 in a less refined way. 
 
 The human species is no exception to the observation long ago made, 
 that the undue extension of the vegetative period of life into Encroachment 
 the reproductive is at the expense of the latter. In the same 
 manner that a tree overladen with foliage presents its flow- life. 
 ers scantily, so a love for the pleasures of the table and a predominating 
 epicurean turn is often the indication of incapability. 
 
548 CHANGE OF MENTAL QUALITIES. 
 
 Up to the fourteenth year, the human being lives solely for itself; its 
 Gradual instincts are for the gratification of its present wants, and 
 change in the t j lose wan ts are, for the most part, connected with its vegeta- 
 ties. tive development. After that period its life is for the future, 
 
 and is in relation to the race. With this more elevated condition, new 
 emotions and passions have been awakened ; there is a gradual unfolding 
 of the mental powers, and a balancing arising from increased knowledge 
 and increased experience ; yet, even now, the mental qualities that are 
 most marked are only the extension of those the germ of which may be 
 discovered at the first dawn of reason, and the same may be said even 
 of our intellectual impressions. The ideas we have gathered as members 
 of a family are reproduced and expanded in our religious views, and the 
 government of GOD is presented to the human heart less acceptably when 
 he is set forth as the Almighty Maker of the world than as the Universal 
 Father and Giver of all good. 
 
 In a preceding chapter I have already shown how the existence of the 
 Parallel of cor- immaterial spirit of man may be investigated physiologically, 
 mental Tevel- ^ ma 7 no * ^ e out of place here to dispose of an argument 
 opment. that some have insisted on, that, since the development of 
 
 the mind proceeds in an equal step with the development of the body, 
 each expanding or declining with the other, the dissolution of the animal 
 fabric is the token of the death of the soul. Against this doctrine the 
 whole human family, in all ages, has borne its testimony, and, if univer- 
 sal ^impressions arise from physical constitution far more than they do 
 from tradition, it may be truly said that that doctrine is incompatible 
 with the organization of man. Probably there is no question which has 
 received a greater amount of individual and general attention none 
 which has more deeply exercised the thought of the profoundest intellect ; 
 and what is the actual result ? Whatever may be the social state, bar- 
 barous or polished, whatever the manner of life, whatever the climate, 
 whatever the form of religion, the assertion of the existence of the spirit 
 after death is so universal, that it may be termed one of the organic dog- 
 mas of our race. Indeed, we may affirm that the mind has to be edu- 
 cated, trained, or strained before it becomes capable of an opposite view, 
 which, even then, will be doubtingly entertained. 
 
 If there is a point in natural philosophy which may be regarded as 
 independent ^ na ^7 settled, it is the imperishability of the chemical ele- 
 existence of ments and the everlasting duration of force. With the sys- 
 tem of nature existing as it is, we can not admit that an atom 
 of any kind can ever be destroyed ; and a like assertion may be made 
 of force. Heat may give rise to motion, motion to electricity, electricity 
 to heat : one kind of force may be converted into another, there being a 
 perfect correlation or quality of substitution among them. The quan- 
 
THE SOUL. 549 
 
 tity of power is now the same as it ever was. Its variations are analo- 
 gous to the apparent transmutations of ponderable material. They are 
 mere metamorphoses. 
 
 Matter and force are equally incapable of destruction. Each constitu- 
 ent atom of the animal mechanism, though it may be dismissed for the 
 time as useless, is not lost, but sooner or later is economized in some 
 organic form again. The heat which seems to arise from the most in- 
 significant muscular contraction has been, so to speak, many a time in 
 existence before, and after it has escaped from the system is not lost to 
 the world, but discharges one function after another forever ; and if thus 
 neither matter nor force can die, it would be a great anomaly if the prin- 
 ciple of conscious identity were capable of annihilation. Like them, it 
 may be capable of modification or change, and, like them, it is not capa- 
 ble of loss of existence. The creeds of various nations recognize this 
 great truth ; they differ only in their ideas of what that future state of 
 modification may be. 
 
 Perhaps in some age hereafter physiology will find herself sufficiently 
 advanced to offer her opinion on this profound topic, for I can not think 
 that GOD has left us without a witness in this matter, even in the struc- 
 ture and development of the body itself. From the moment that we see 
 the first traces of the nervous mechanism lying in the primitive groove, 
 we recognize the subordination of every other part to that mechanism. 
 For it, and because of it, are introduced the digestive, the circulatory, 
 the secretory, the respiratory apparatus. They are merely its ministers. 
 And, fastening our attention on the course which it pursues, we see that 
 it is at once a course of concentration and development. The special is 
 at each instant coming out of the more general, and, from the beginning 
 to the end, the whole aim is at psychical development. The germinal 
 membrane is cast away as soon as a stomach can be prepared, aquatic 
 respiration ceases as soon as aerial can be maintained. The scaffolding 
 that was of use at one moment is thrown aside as soon as a new eleva- 
 tion is reached. The germ, the embryo, the infant, are only successive 
 points in a progress which at every instant displays this casting away 
 of the means that have been used as soon as they are done with. That 
 is the style in which the work is carried on. The principle which ob- 
 scurely animated the germ is the same which in a higher way animates 
 the embryo, and this again is the same which, in a more exalted condi- 
 tion, animates the infant and the man. The cloudy speck which ushers 
 in the phantasmagoria of life expands as the great Artist directs until 
 every lineament has become visible. 
 
 That active agent which was first laid in a fold of the germinal mem- 
 brane was not annihilated when its type of life was changed to placental 
 and therefore aquatic respiration. It withstood the shock when again, 
 
550 THE SOUL. 
 
 after a due season, it was suddenly made to breathe the air. Arrived at 
 the mature condition, there is not in its companion-body a single particle 
 that was present at birth. All has changed. And, what is still more 
 important, not only has there been this interstitial removal, but, in suc- 
 cession, the very nature of every one of its organs has changed. It is 
 needless now to repeat how many different systems of nutrition it has 
 depended on how many sorts of stomachs in succession it has had 
 how it has breathed by a membrane, by gills, and by lungs how it has 
 carried on its circulation without a heart, with a heart of one cavity, and 
 finally with one of four. Through all these losses and changes the im- 
 material principle has passed unscathed, and even gathering strength. 
 In the broadest manner that a fact can be set forth, we see herein the 
 complete subordination of structure and the enduring character of spirit. 
 Whatever may be the mechanism that is wanted, it is in readiness for its 
 time ; and when it has finished its duty, is neglected and disappears. 
 There is, therefore, a sound reason in the conclusion to which mankind, 
 perhaps from a mere instinctive impression, have come, that the soul will 
 exist after death, for, after surviving so many mutations, the removal of 
 so many of what seemed to be its firm and essential supports, we are jus- 
 tified in expecting that it will bear without ruin the entire withdrawal of 
 the whole scaffolding. 
 
 As I have pointed out, we have precisely the same reason for believ- 
 ing the existence of the immortal spirit that we have for knowing that 
 there is an external world. The two facts are of the same order. Of 
 the future continuance of that external world, irrespective of ourselves, 
 we entertain no doubt ; indeed, in certain cases, as in those presented by 
 astronomy, we are able to tell its state a thousand years hence. So long 
 as our attention was confined to statical physiology, every thing connect- 
 ed with the subject now under consideration was enveloped in darkness, 
 but it will be very different when dynamical physiology begins to be 
 cultivated dynamical physiology, which speaks of the course of life, 
 of organs, individuals, and races. The law of development will guide 
 us to an interpretation of many things which are now shrouded in ob- 
 scurity, and teach us, from a consideration of what we have learned of 
 our past, and what we know of our present, what we may expect of our 
 future state ; and then it will appear that the universal opinion of the 
 ages and nations is not a vulgar illusion, but a solemn philosophical fact. 
 
 So, therefore, the decline of the mental faculties with advancing years 
 is no indication of the hebetude of the spirit, or premonitory to its final 
 dissolution. It is only the gradual wearing out of the instrument, the 
 intervention of which has established relations with the outer world. 
 When a tool becomes blunted and old, the workman can no longer man- 
 ifest his former skill ; but the skill may nevertheless remain. Though 
 
OF SLEEP. 551 
 
 the apparatus for the reception of external impressions, as well as that 
 for voluntary action, may be failing, it implies nothing as regards the 
 prime mover. The eye may be dim, the ear dull, and touch imperfect, 
 the voice may be feeble, and the limbs trembling, but all this indicates 
 nothing more than that what has been passed through so often before 
 is about to be passed through again. The organs that have done their 
 duty are to be cast away, but the result of their action is to remain. 
 
 It may not, perhaps, fall within the proper compass of a treatise on 
 physiology to speak of that future condition, and yet so deeply The future 
 interesting are these subjects to all men that a single observa- state - 
 tion may in this place be excused. The whole course of life, from its 
 very beginning, has been one of development and concentration. We 
 comprehend this the more perfectly as we extend our views beyond our 
 present state, and examine what we have in succession been, and in what 
 manner our existing condition was reached. It is not credible that that 
 system is to be all at once abandoned, or replaced by a contradictory one. 
 Such is not the style in which the affairs of the organic world are at any 
 time carried on. The slowly emerging consequences of the primitive 
 law ccme forth one after the other in their proper and unvarying sequence, 
 and the law holds on inexorably forever. And since we may say that, 
 throughout those prior states, the idea aimed at is the isolation of a con- 
 scious intelligence, every organ being shaped and every function bent to 
 that end, we are reasonably led to the expectation that in a future state 
 that archetype will be completely reached. It would be strange indeed 
 if a blank oblivion should crown such a work. 
 
 CHAPTER VI. 
 
 OF SLEEP AND DEATH. 
 
 Causes of the Necessity for Sleep. Its Duration and Manner of Approach. Manner of Awak- 
 ing. Cause of Night-sleep. Increased Warmth required. Connection of Sleep and Pood. 
 
 Of Dreams : their Origin and Phenomena. Somnambulism. Nightmare. 
 
 Of Death. Old Age. Internal Causes of Decline. Death by Accident and by Old Age. The 
 Hippocratic Face. Final Insensibility. 
 
 Isx. OF SLEEP. 
 
 ONE third of the life of man is spent in sleep, a condition of modified 
 sensibility, in which the mind performs its functions in an im- 
 perfect way, and voluntary motion is nearly suspended. This 
 state, occupying so large a portion of the short period of time allotted to 
 us, is therefore well deserving of the consideration of the physiologist, 
 
552 APPROACH OF SLEEP. 
 
 and the more so since it presents, in the various phenomena of dreams, 
 significant illustrations of the manner of action of the nervous system. 
 
 All animals sleep. Many, perhaps most,- dream. The necessity for a 
 season of repose arises from the preponderance of the waste of the sys- 
 tem ove/ its repair during our waking hours. By bringing the animal 
 functions into a condition of rest, an opportunity is afforded for renova- 
 tion, and the equilibrium can be maintained. 
 
 In early infancy, when it is necessary for the nutritive operations to be 
 . ., carried forward with the utmost vigor, and attended with as 
 
 Causes of the &. 
 
 necessity for little waste as possible, the whole time is spent in sleeping 
 and eating. The waking period is gradually increased as the 
 child advances, but not so as to make it continuous, for the day is broken 
 into intervals of sleep. Even at three or four years of age we sleep more 
 Duration and tnan once a ^ a j- ^ n mature life eight hours are on an aver- 
 depth of sleep. a g e required, but the precise time varies with different indi- 
 viduals, and even with the same individual in different constitutional 
 states. The time is not, however, always a true measure of the amount 
 of rest, for sleep varies very much in the degree of its completeness or 
 intensity ; there is a slumber so disturbed that we are unrefreshed by it, 
 and a sleep so profound that we awake weary. Old age, as it advances, 
 admonishes us to spare the system as much as we may, for repair is con- 
 ducted with difficulty ; and this period, characterized by its resemblance 
 in so many respects to childhood, like it, is often marked by frequently- 
 recurring and prolonged slumber. Moreover, various accidental and 
 other circumstances are liable at all times to disturb its proper periodic- 
 ity a warm afternoon, a hearty dinner, an ill-ventilated apartment, mo- 
 notonous sounds, the attention devoted to one object, bodily quiescence, 
 ceasing to think, the use of narcotics, extreme cold, a horizontal posi- 
 tion, &c. 
 
 Sleep is commonly preceded by a sense of drowsiness of more or less 
 Approach of intensity, which is gradually followed by a loss of sensibility, 
 sleep. Objects cease to make an impression on the eyes, the lids be- 
 
 come heavy and close. If we are not in the horizontal position, but re- 
 quire muscular support, as in sitting, the head droops, and the hands seek 
 a support. Successively the senses of smelling, hearing, and touch pass 
 away, as the sight has done ; but, before this progress is completed, we 
 start at any sound or disturbance, voluntary muscular action being in- 
 stantly assumed, though in the midst of a surprise. "We are nodding. If 
 we are in the horizontal position, as in bed, the body is thrown into a 
 form requiring the least muscular exertion the limbs are semiflexed. 
 As sight, smell, hearing, touch, again in succession fail, all voluntary mo- 
 tions cease, those which are now executed being of a purely automatic 
 kind. The eyes are turned upward and inward, the iris is contracted, 
 
MANNER OF AWAKENING. 553 
 
 the heart and the lungs act more slowly but more powerfully ; a gentle 
 delirium, which exists while the centres of the special senses are coming 
 into repose, introduces us to profound and unconscious sleep. 
 
 This condition of profound sleep, though it may be quickly, is yet 
 gradually reached by passing through certain well-marked p rog ress of 
 stages. Once gained, we sleep with heaviness in the early night-sleep. 
 part of the night, and more and more lightly as morning approaches. 
 It would, however, be erroneous to suppose that this falling into insensi- 
 bility and awakening are perfectly continuous events ; there are, undoubt- 
 edly, subordinate periods of more and less complete repose, but under 
 no circumstances are we ever aware that we are asleep. 
 
 At any time of the night sleep may be abruptly broken, the mind re- 
 suming its power after passing through a momentary interval Manner of 
 of confusion. Toward the close of the customary time, the awakening, 
 senses resume their power in an order inverse to that in which they lost 
 it the touch, the hearing, the smell, the sight. For a short period after 
 awakening, the organs seem to be in a state of unusual acuteness, more 
 particularly that of sight an effect arising from the obliteration of the 
 vestiges of old impressions. From profound sleep we pass to the wak- 
 ing state through an intermediate condition of slumber. In the former, 
 the movements which we may execute, under the influence of external 
 impressions, are wholly of an automatic kind, such as turning in bed in 
 various positions. The -length of time spent in sleep and slumber re- 
 spectively is by no means constant, many causes increasing the one at 
 the expense of the other. On awakening, we are apt to indulge in cer- 
 tain muscular movements we rub our eyes, stretch, and yawn. If we 
 are suddenly aroused, our motions are feeble and uncertain on attempt- 
 ing to walk at once ; but if we spontaneously awake at an unusual period, 
 and more particularly if it be toward the morning, we commonly remark 
 a clearness of intellect or mental power. Many of our most judicious 
 and correct conclusions occur to us under these circumstances. 
 
 Though it is said that the sleep of man lasts about eight hours, there 
 are many variations. Authentic cases are on record in which M aximuin and 
 individuals have, for a considerable time and apparently with- minimum 
 out injury, slept only for one hour, and others in which that engt 
 state has been prolonged for an entire week. Man shows much greater 
 differences than other animals ; birds, for instance, sleep lightly, and cold- 
 blooded animals generally profoundly. Since the object of sleep is to 
 afford an opportunity for repairing the waste of the system, the length 
 of the needful time depends on conditions that are themselves variable : 
 the extent of the antecedent waste, and the rapidity of the repair. In 
 winter we sleep longer and usually deeper than in summer, for the hour- 
 ly waste in winter is greater. Habit, however, controls us very much. 
 
554 NIGHT-SLEEP. 
 
 It has been supposed by some that it is to habit that our tendency to 
 Cause of night- sleep at night is to be imputed. It is, however, more properly 
 sleep. to be attributed to the ordinary circumstances of our life the 
 
 day being spent in muscular or mental exercise, since we can then see 
 to perform our duties, and this tax upon the system being necessarily 
 followed by a feeling of weariness. Those animals which seek their food 
 in the dark sleep by day. It is not, therefore, to any external physical 
 condition that we should impute our nocturnal sleep, but to the interior 
 condition of our system, though it is quite true that physical agents, 
 such as cold, and others that have been mentioned, will provoke a sensa- 
 tion of drowsiness. 
 
 In sleep we require additional warmth, and this we obtain by instinct- 
 Increased ively using more clothing for the purpose of economizing the 
 warmth re- animal heat. The amount of caloric generated in the system 
 eep * is diminished through the cessation of muscular exercise, 
 and therefore reduction of decay. The same may be said, to a certain 
 extent, of the waste of the brain through its intellectual acts, and of the 
 nervous system generally. This diminished amount of interstitial death 
 corresponds with a diminished respiration, the hourly amount of oxygen 
 consumed exhibiting a decline. The negro, who is much more sensitive 
 than the white man to this decline of temperature, instinctively envelops 
 his head with clothing, so that the air may be warmed by its conta'et 
 therewith before it enters the respiratory organs. For the same reason, 
 he sleeps with his head toward the fire, while the white man sleeps with 
 his away. On similar principles we may account for the control which 
 food has over sleep, the one seeming, to a certain degree, to replace the 
 other. The French proverb says, "He who sleeps, dines," and this is 
 Uniformity of true ; for during sleep the waste of the system is reduced to 
 ed wiSTmii-*" a mm i m um, and the necessity for food correspondingly di- 
 formityoffood. minished. The quality of the food likewise exerts an influ- 
 ence on the length of sleep, for that which is of a nutritious kind, and 
 easily assimilated, can more speedily execute whatever repairs the sys- 
 tem may demand. It is probably owing to his variable diet that, even 
 in a state of perfect health, man is so variable a sleeper, and that ani- 
 mals, the nature of whose food is so constant, sleep with so much uni- 
 formity. 
 
 By some it has been supposed that the amount of sleep required by 
 different animals is dependent upon the size of their brain; but if we 
 keep in view that the object of sleep is the repair of waste, and that this 
 is accomplished by the agency of the different mechanisms involved in 
 organic life, we can easily see that such a statement can not be true. Its 
 fallacy appears from common observation, apart from any physiological 
 considerations. The brain of a turtle or of a serpent is relatively small, 
 
OF DEEAMS. 555 
 
 and yet those animals sleep long and profoundly ; but if we reflect on 
 how many different conditions, external and internal, the repair of waste 
 depends, we shall see that the time of sleep can not have any such arbi- 
 trary measure as that of the size of the brain. Among external causes 
 which influence the rate of repair may be mentioned the digestibility of 
 the food, some varieties of which, by reason of their chemical or physi- 
 cal qualities, yield more slowly than others. The internal causes are very 
 numerous : the size of the digestive organs in relation to the Conditiong of 
 body, and the energy with which their function is accom- the duration of 
 plished ; the condition of development of the absorbent sys- s eep * 
 tern, and the rapidity of its action ; the rate of the circulation of the 
 blood, which hurries the nutritive supply in its course ; the amount of 
 oxygen introduced into the system by the respiratory apparatus, which 
 discharges, as we have elsewhere explained, the double function of re- 
 moving the wasted products of decay, and of grouping into appropriate 
 forms, so as to be available for their uses, the elements of nutrition that 
 are being introduced. All these, and other conditions that might be 
 named, determine the rate at which repair can be executed, and therefore 
 the necessary duration of sleep. If, out of these various elements, we 
 were to select one which would represent it, the activity of the respira- 
 tory organs would afford a more accurate measure than the size of the 
 brain. 
 
 As the necessary repairs are accomplished, we pass through a condi- 
 tion of slumber, and our organs gradually awake in the manner that has 
 been described. It is during this intermediate passage, that is, toward 
 the morning chiefly, as the brain is resuming its functions, of dreams : 
 that dreams occur. They may, however, happen at any other their s> 
 period of the night, though then they are liable to present greater in- 
 congruities and more obvious violations of the proper order of events. 
 It is quite correct that morning dreams are more likely to be prophetic, 
 for they are more likely to be in themselves true. 
 
 Dreams never strike us with surprise, no matter what may be the ex- 
 traordinary scenery they present no matter how great the violations of 
 truth and reality. The dead may appear with the most astonishing clear- 
 ness ; their voices, perhaps long forgotten, may be heard ; we may be 
 transported to places where we have spent past years of our lives ; com- 
 binations of the most grotesque and impossible kinds may be spread be- 
 fore us : we accept all as reality, perhaps not even suspecting that we 
 dream. The germs from which have originated all these strange com- 
 binations are impressions stored up in the registering ganglia of the brain, 
 more particularly in its optic thalami. These, as outward impressions 
 have for the time ceased, are enabled to attract the attention of the mind, 
 and emerge from their latent state. That all dreams originate in such 
 
556 OF DREAMS. 
 
 impressions is illustrated by the history of the blind, who still dream 
 of things that they formerly saw. Thus it is stated that Huber, after 
 he had been blind for fifty years, still dreamed of things he had seen 
 when a boy. But little explanation can be given of the manner in which 
 these vestiges may be grouped a grouping which is so frequently in vi- 
 olation of all correctness that a dream which presents us with a logical 
 sequence of events,* and which we recognize on awakening to be natu- 
 rally true, is sure to be an impressive one ; and yet we can not doubt 
 that the causes which suggest dreams are often purely physical, as when, 
 in dropsy of the chest, the dreamer fancies he is drowning, or even suf- 
 fers under the same delusion when his hand is dipped in water ; or when 
 a candle is earned into the room, and he awakens stricken with terror 
 that the house is on fire ; or, on the occurrence of noise, he believes that 
 he is in a thunder-storm, or, perhaps, on a field of battle. Hence arises 
 an automatism which becomes most striking when the dreamer answers 
 questions put in a whisper to him, an incident of which cases are record- 
 ed in which individuals have revealed important events of their lives, 
 which, when waking, they would never have divulged. 
 
 Automatic actions are usually considered as occurring without sensa- 
 tion, but this, in some instances, as in those now before us, can not be 
 regarded as altogether true. 
 
 Suggested thus by external circumstances, or arising spontaneously 
 Deceptive ap- without any obvious cause, dreams pass before us with an 
 pearance of a ir of truthfulness so imposing that we never suspect their 
 
 truth in dreams. ,, T ^ , A , - 1 .,1 ,1 i i 
 
 fallacies. It may be truly said that they have a logic ot 
 their own. Indeed, so complete is the illusion, that instances are not 
 wanting, and many have been recorded, in which, at the moment of 
 awakening, the sleeper has been struck with the correctness of the con- 
 clusions at which he had arrived, and it was not until he had recovered 
 from the delirious confusion of the moment, and reason had resumed her 
 sway, that he perceived how incorrect they were. Thus great mathe- 
 maticians have thought they had solved difficult problems, poets that 
 they had composed stanzas of force and beauty ; but these, on a mo- 
 ment's reflection, they have discovered to be an inconsequent flow of 
 ideas, and mere nonsense. A few exceptions undoubtedly have occur- 
 red, as in the case of Mr. Coleridge, who affirms that, under these cir- 
 cumstances, he composed Kublai Khan, and remembered it in part on 
 awaking. The French mathematician, Condorcet, makes the same state- 
 ment with respect to several of his writings. 
 
 One of the most extraordinary phenomena presented in the dreaming 
 instantaneous state is the instantaneous manner in which a long series ot 
 aTo^g'trainof events mav be offered to the mind, the exciting cause being 
 events. truly of only a momentary duration. Some sudden noise 
 
FORGETFULNESS OF DREAMS. 557 
 
 arouses us, and, in the act of waking, a long drama connected with that 
 noise appears before us ; or, in like manner, we are disturbed perhaps by 
 a flash of lightning, and with that flash occurs a dream which seems to 
 us to occupy a space of hours or even days, so many are the incidents 
 with which it is filled. It has long been known that a like peculiarity 
 has offered itself to those who have suffered by drowning, and have been 
 subsequently restored. They have related that in their moment of su- 
 preme agony, the whole series of events of their past life has, as- it were, 
 flowed in an instant upon them with the most appalling vividness, their 
 good and evil works, and even the most trifling incidents presenting 
 themselves with distinctness a tide of memory. And doubtless it is 
 owing to like causes that, under the influence of opium or other narcotic 
 drugs, the relations of space and time are so totally destroyed that we 
 seem to live through a century in a single night, or to take in our view 
 scenery, the distances and magnitudes of which are utterly beyond the 
 reach of mortal vision. It has been truly said that the province of 
 dreams is one of intense exaggeration. It is so in a double sense, for 
 with equal facility we spread out a single and perhaps in- The g readin(r 
 significant circumstance, so that it occupies the entire night, of one idea over 
 or we crowd a thousand strange, though perhaps connected, a ong time ' 
 representations into the twinkling of an eye. Nor is it by any means 
 the least extraordinary part of these wonderful facts that the mind occu- 
 pies itself in an undiverted and unbroken manner for so long a time, 
 with an insignificant idea in the one case, and perceives, with miraculous 
 perspicuity, the rapidly disappearing occurrences in the other ; that of a 
 majority of dreams it retains no precise recollection, though they may 
 have been presented with an intense energy, as we are assured from the 
 impression of dread or melancholy, or even the physical results they 
 have left, as when we awake and feel the heart throbbing Forgetfuiness 
 violently and the whole frame trembling with terror, yet can of dreams, 
 not, with the utmost exertion of memory, recollect what it wds that we 
 saw. The remembrance of dreams by no means, therefore, depends on 
 the intensity of the impression that they made for the time ; doubtless 
 the majority of them are forgotten and can never be recalled. In some 
 instances, which almost every one can recall, we dream a second time the 
 same dream which we failed to remember when awake, and, it is said, 
 even occasionally dream that we are dreaming. 
 
 Our mental capability for recalling the scenes that have occupied us 
 in our sleep is therefore dependent upon something more than the depth 
 of the impression they have made. Whether it be, as some suppose, 
 through an inertness of the mind, an incapability or indisposition of pay- 
 ing attention to the things thus presented to it, or whether it be that, 
 through accidental causes, the vestiges of impressions remaining in the 
 
558 SOMNAMBULISM. 
 
 optic thalami are brought out sometimes with more and sometimes with 
 less force, there is every grade of intensity presented, from those floating 
 indistinct aerial scenes, which seem scarcely to leave the slightest trace 
 behind them, to those which, in spite of their outraging all reality, and 
 even all probability, leave us in a horror-stricken state ; such as, for ex- 
 ample, the celebrated dream of the Emperor Caligula, in which he thought 
 that the sea spoke to him. Yet there can be no doubt that in all these 
 cases, no matter how indistinct or energetic, how false or how true, hoAV 
 
 d* i n un narmon ^ ous as a whole, or how contradictory and grotesque, 
 der which the elements of which all dreams are composed are impres- 
 dreams arise. g ' ons Q ^ings t h at we have seen or heard, or which have 
 been otherwise submitted to the senses, the traces of which still remain 
 imprinted in the registering ganglia of the brain. During the day, while 
 we are exposed to light, and sounds, and other sources of disturbance, the 
 impressions arising therefrom totally overpower, by reason of their new- 
 ness and intensity, these ancient residues, so that the attention of the 
 mind, in a state of health, is never directed to them ; but when we close 
 our eyes in the silence of night, all such external impressions are at an 
 end, the organs of sense, sight, hearing, smell, and touch, are successive- 
 ly benumbed, and there is nothing to prevent the mind thus separated 
 from outer things from occupying itself with these old impressions, any 
 one or more of which, through accidental circumstances, presents itself 
 in vigor, and a dream is the result. 
 
 The phenomena of dreams therefore illustrate, in a significant manner, 
 the remarks that we have made respecting the functions of the cephalic 
 ganglia of insects as magazines for the registry of impressions received 
 by the organs of sense. No explanation of dreaming can be possibly 
 given without admitting for a part of the human brain a like duty. The 
 important advantages which accrue to our physiological explanations of 
 the action of the human mind from the admission of this doctrine have 
 already been dwelt upon. 
 
 Connected with dreams, and being, indeed, a dream carried into action, 
 Somnambu- i g somnambulism, or sleep-walking, of which there are several 
 iism. grades, from mere sleep-conversation and sleep-crying to the 
 
 actual performance of difficult and even hazardous feats. The young in- 
 fant evinces its discomforts by crying in its slumber, yet it can be com- 
 forted without awaking by the well-known voice of its mother. Chil- 
 dren often show a propensity to talking in their sleep, and can sometimes 
 be brought to give a few rational replies to inquiries put to them. At 
 their time of life, the disposition is more frequently manifested to get out 
 of bed and move about the house, or even out into the open air under the 
 influence of a dream. When sleep-walking occurs in the adult, it is lia- 
 ble to be accompanied by actions of an apparently connected kind, though 
 
NIGHTMARE. 559 
 
 their object may be quite trivial, and in its attainment considerable risks 
 may be run. In these cases it seems as if the mind was absolutely wrap- 
 ped up in one idea, and wholly unable to comprehend any thing else. If 
 the eyes of the somnambulist are wide open, he sees nothing, and even 
 though a bright light be presented before him, the iris will not contract, 
 yet he moves about in a manner as if he were, in one respect, guided by 
 understanding, the air of his movements being as if he knew what he 
 was about, yet in another respect as though he was impelled by the 
 most unaccountable folly, walking along the roof of the house, seating 
 himself on the chimney, and finding his way in safety over precipitous 
 places, past which it would be impossible he should go if awake, no mat- 
 ter how steady his head might be. Besides this complete condition of 
 somnambulism there are intermediate forms, during which the various 
 senses of seeing, hearing, etc., are in partial activity. There are also 
 differences in the intensity or depth of the state, as is shown by the ease 
 or difficulty with which the individual is aroused ; sometimes to speak 
 to him is enough, sometimes he must be violently shaken or otherwise 
 roughly treated. It has been observed in some cases that where the pa- 
 tient spontaneously wakens under circumstances that affright him, he is 
 at once broken of the habit. 
 
 With dreams and somnambulism is also to be classed that sensation 
 which often surprises and disturbs us when we are just passing Sensation 
 into sleep, a sensation as though we were suddenly falling down of fallin s- 
 stairs. This, with some persons, is of almost nightly occurrence. Its 
 opposite, an inability to move, as though we were oppressed by some 
 great weight, or spell-bound in some incomprehensible way, is nightmare. 
 In this distressing affection there is a sense of oppression at Nightmare : 
 the epigastrium, and a difficulty, or rather impossibility, of its causes - 
 moving or speaking. A frightful dream, in which some alarming object 
 is depicted with intolerable distinctness, accompanies these symptoms, 
 the attack terminating by a struggle to shake off the object of dread, or 
 to escape by flight, or to speak. On awaking, the sufferer finds himself 
 trembling with terror, the respiration hurried, and the heart throbbing 
 violently. The intellectual faculties are on different occasions in vari- 
 ous states of activity, and sometimes the dream, and our actions conse- 
 quent upon it, offer no violation of reason. Indeed, some individuals are 
 affected by this trouble during the daytime, when they are wide awake 
 and perfectly aware of what is going on ; but, whether it occurs by night 
 or by day, the sentiment with which it oppresses is that of unspeakable 
 dread. Even at night we sometimes are conscious of its approach, when 
 we are in the intermediate state between sleeping and waking. 
 
 The cause of nightmare, in all its variety of forms, is disturbance of 
 the respiratory function, which, by interfering with the arterialization of 
 
560 OF DEATH. 
 
 the blood, affects the brain. This disturbance may be brought on in 
 many ways, as by the pressure of the stomach after a hearty supper, or 
 in diseased conditions, such as hydrothorax ; but it is popularly supposed, 
 where these morbid conditions are not obviously concerned, to be attrib- 
 uted to sleeping on the back. Though- this is undoubtedly true in a 
 great many instances, it is very far from being an essential condition, for 
 nightmare may occur in any position that the sleeper may possibly as- 
 sume. The restraint upon the arterialization of the blood, which appears 
 to be its essential condition, interferes with the circulation through the 
 lungs on the principles that have been described in a preceding chapter, 
 nor can the heart force a passage, however violently it may throb. The 
 effect depends not so much upon the apparent rate and power with which 
 the respiration is going on, for any embarrassment or difficulty in the in- 
 troduction of air merely leads to snoring, which is in no manner connected 
 with nightmare. The cause of this latter affection is to be sought for in 
 the air-cells, which are unable to rid themselves, with their accustomed 
 facility, of the carbonic acid and other effete products of respiration which 
 they contain. 
 
 2D. OF DEATH. 
 
 At all periods of life, the functional activity of the system occasions a 
 Condition of waste ^ ^ s tissues by the interstitial death of their parts, and 
 healthy equi- therefore involves a necessity of repair. So long as the repa- 
 ration balances the waste, a healthy equilibrium is maintained ; 
 but when the nutritive powers decline, as old age approaches, a gradual 
 deterioration of the system ensues. 
 
 The period of greatest activity is also that of greatest waste, and of 
 the most active and perfect repair, interstitial death and the removal of 
 decayed material then occurring in the most rapid manner. The energy 
 of life is thus dependent on the amount and completeness of death. 
 
 At a later period, with advancing years, although the loss of substance 
 through functional activity may be lessened, the renewal and restoration 
 of the portions which are necessarily consumed are far more than corre- 
 spondingly diminished. We thus become incapacitated corporeally and 
 mentally, and, if no accident intervenes, we die through mere old age. 
 
 On several occasions we have already noticed the analogy between the 
 Death of a ^ Q f individuals and that of species. An analogy also may 
 molecule, of an "j^ traced in the circumstances and causes of their death, for 
 
 individual or-,-. ,, 1111 11 t 
 
 ganism,ofa the discoveries of geology abundantly show that thousands 
 species. O f sp ec i es j n the organic series have become extinct. The 
 
 death of a constituent molecule in an animal body, the death of the in- 
 dividual animal itself, the death of the species to which it belongs, are 
 all philosophical facts of the same kind, though presenting, perhaps, in 
 
GEADUAL DEATH. 561 
 
 their aspect a difference of interest and importance. The death of indi- 
 viduals, as has been said, may occur in two ways, by acci- Death from ac _ 
 dent or by old age. But death from old age is very unusual, cident and by 
 for even in the cases of those who are very far advanced in 
 life, its close is ordinarily brought about by some lesion or derangement 
 of the vital organs, thus, in reality, constituting accidental death. 
 
 Most men desire that their final scene may be attended with as little 
 derangement as possible of their ordinary mental powers, and 
 
 *. *, . . Euthanasia. 
 
 that it may be very brief. If this constitute the euthanasia, 
 or happy death, it certainly can not be thought that extreme old age is 
 desirable, constituting, as it does, a long-continued and dreary disease. 
 The senses fail us in the same manner and in the same order that they 
 do when we are falling asleep, their gradual deterioration bringing us back 
 to the helplessness and imbecility of infancy. In the long interval dur- 
 ing which this is going on, the aged man is not only a burden to himself, 
 but a sad spectacle to every one around him ; his perceptions arc being 
 gradually blunted ; and though he is, as it were, by degrees passing into 
 a final slumber, it is in that disturbed way which all have experienced when 
 they fall asleep after severe fatigue. 
 
 The different portions of the body die in succession : the system of 
 animal life before that of organic, and of the former the sens- f 
 
 .-.,_ , . ... Gradual death. 
 
 ory functions fail first, voluntary motion next, while the pow- 
 er of muscular contraction under external stimulus still feebly continues. 
 The blood, in gradual death, first ceases to reach the extremities, its pulsa- 
 tions becoming less and less energetic, so that, failing to gain the periph- 
 ery, it passes but a little way from the heart ; the feet and hands become 
 cold as the circulating fluid leaves them, the decline of temperature gradu- 
 ally invading the interior. No one has ever yet offered a more accurate 
 picture of the appearance of the dying than that presented by Hippocrates : 
 " If the patient lies on his back, his arms stretched out, and his legs 
 hanging down, it is a sign of great weakness ; when he slides down in 
 the bed it denotes death. If, in a burning fever, he is continually feel- 
 ing about with his hands and fingers, and moves them up before his face 
 and eyes as if he were going to take away something before them, or on 
 his bed-covering as if he was picking or searching for little straws, or 
 taking away some speck, or drawing out little flocks of wool, all this is 
 a sign that he is delirious, and that he will die. When his lips hang 
 relaxed and cold, when he can not bear the light, when he sheds tears 
 involuntarily, when, dozing, some part of the white of the eye is seen, un- 
 less he usually sleeps in that manner, these signs prognosticate danger. 
 When his eyes are sparkling, fierce, and fixed, he is delirious, The Hippo- 
 or soon will be so ; when they are deadened, as it were, with cratic face - 
 a mist spread over them, or their brightness lost, it presages death or 
 
562 THE AGONY. 
 
 great weakness. When the patient has his nose sharp, his eyes sunk, 
 his temples hollow, his ears cold and contracted, the skin of his forehead 
 tense and dry, and the color of his face tending to a pale green or leaden 
 tint, one may give out for certain that death is very near, unless the 
 strength of the patient has been exhausted all at once by long watchings, 
 or by a looseness, or being a long time without eating." 
 
 Even after death some of the organic functions continue for a time, 
 Post-mortem more particularly secretion and the development of heat. In 
 t^nT^d^as- a * rmer chapter, page 444, the capability of extraordinary 
 sions. muscular motions has been referred to. From other inter- 
 
 esting observations on those who have been instantaneously decapitated 
 by the guillotine, it has been asserted that the body can display what 
 has been termed post-mortem passion and resentment. It may, however, 
 be doubted whether this is really true. Perhaps these effects are only 
 analogous to those convulsive manifestations which may be easily pro- 
 duced, in an intensely interesting way, by the application of voltaic bat- 
 teries to those who have been dead for some time. 
 
 Physiologists often quote the sentiment of Montaigne, " With how 
 insensibilit IM 6 anxiety do we lose the consciousness of light and of 
 before the final ourselves." By this they would convey the idea that the 
 act of dying is as painless as the act of falling asleep, and 
 also as little perceived. They recall the fact which seems to support 
 this view, that those who have been recovered after apparent death from 
 drowning, and after sensation has been totally lost, report that they have 
 experienced no pain ; and, indeed, when we reflect that the sensory pow-' 
 ers are the first to decline, the eye and the ear, at an early period in the 
 article of death, failing to discharge their duty, and the general sense of 
 touch becoming rapidly more and more obtuse, we can scarcely put any 
 otner interpretation upon the final struggles which constitute what is so 
 significantly called the agony, than that they are purely automatic and 
 therefore unfelt. Doubtless the mind, in this solemn moment, is some- 
 times occupied with an instantaneous review of impressions long before 
 made upon the brain, and which offer themselves with clearness and 
 energy now that present circumstances are failing to excite its attention, 
 through loss of sensorial power of the peripheral organs, this state of 
 things having also been testified to by those who have been recovered 
 from drowning. 
 
 Life closes at last in various ways. Some pass away as though they 
 were really falling asleep ; others with a deep sigh or groan ; others with 
 a gasp ; and some with a convulsive struggle. 
 
DIFFERENCES IN MEN. 
 
 563 
 
 CHAPTER VII. 
 
 ON THE INFLUENCE OF PHYSICAL AGENTS ON THE ASPECT AND FORM 
 OF MAN AND ON IHS INTELLECTUAL QUALITIES. 
 
 Differences in Form, Habits, and Color of Men. Ideal Type of Man. Its Ascent and Descent. 
 ^-Causes of these Variations. 
 
 Doctrine of the Unity of the Human Race. Doctrine of its Origin from many Centres. 
 
 Influence of Heat on Complexion. Cause of Climate Variations. Influence of Heat illustrated 
 by the cases of the Indo-Europeans, the Mongols, the American Indians, and the Africans. 
 Distribution of Complexion in the Tropical Races. 
 
 Variations in the Skeleton. Four Modes of examining the Skull. Connection of the Shape of 
 the Skull and Manner of Life. Physical Causes of Variation of the Skull. 
 
 Influence of the Action of the Liver on Complexion. Influence of the Action of the Liver on the 
 Form of the Skull. Base Form of Skull arising from Low as well as High Temperatures. 
 Disappearance of the Red-haired and Blue-eyed Men in Europe. 
 
 The Intellectual Qualities of Nations. Synthetical Mind of the Asiatic. Analytical Mind of the 
 European. Their respective Contributions to Human Civilization. Spread of Mohammedan- 
 ism in Africa. Spread of Christianity in America. Manner of the Progress of all Nations 
 in Civilization. 
 
 THERE are great differences in the aspect of men. 
 
 The portrait of Newton is from the frontispiece of his immortal Prin- 
 
 Fifj. 266. cipia. " Does he eat, Differences in 
 
 and drink, and sleep, * " f d 
 like other people ?" ask- men. 
 
 Fig. 207. 
 
 Sir Isaac Newton. Australian. 
 
 ed the Marquis de I'Hopital, himself a great contemporary French math- 
 
564 DIFFERENCES IN MEN. 
 
 ematician: " I represent him to myself as a celestial genius entirely dis- 
 engaged from matter." And, truly, transcendent intellect shines out in 
 every lineament of that noble countenance. 
 
 What a contrast between the astronomer, of whom the human race 
 may be justly proud, and the Australian savage whose portrait Dr. Prich- 
 ard has furnished! This man lives in a hollow tree, which he has in 
 part excavated by fire, and obtains a precarious support from shell-fish, 
 or bruised ants and grass. He can make a hook of a piece of oyster, 
 and can fasten a line to it. He is lost in filth and vermin. His life is 
 like that of a beast ; it is concerned only with to-day. The early navi- 
 gators accused him of cannibalism. We can not say that his features 
 acquit him of the charge. 
 
 History teaches us that a nation may pass through an ascending or 
 descending career. It may, by long-continued mental culture, exhibit a 
 general mental advance, and under such circumstances may produce, here 
 and there, an intellect of the first order ; or it may go through a course 
 of degradation until it reaches conditions inconsistent with its continued 
 existence, and then it dies out. 
 
 Man is accordingly distributed over the face of the earth in various con- 
 Fig. 268. ^bls^ ditions. Here he presents 
 
 the civilization of the Euro- 
 pean, there the abject mise- 
 ry of the Australian. What 
 more humiliating spectacle 
 could be offered to us than 
 the annexed engraving, Fig- 
 ure 268, from M. d'Urville? 
 Even a negro of Guinea 
 might look down on such a 
 specimen of human imbecil- 
 ity and physical weakness 
 with contempt, and refuse 
 to recognize such a being as 
 a man at all. 
 
 W r hat is it that has 
 brought this man and his 
 companion to such a pass? 
 
 Australians. . An almost tropical sun, a 
 
 Causes of these pestilential climate, starvation, nakedness, the want of shel- 
 differences. ter, personal fear : these have done their work on the suc- 
 cessive generations of his miserable ancestors, who have been forced from 
 step to step in a descending career, and here is the result. 
 
 Among the causes which influence the aspect of man, there are two 
 
IDEAL TYPE OF MAN. 565 
 
 which are pre-eminent : heat determines his complexion ; social condi- 
 tion the form of his Tbrain, and, therefore, that of his skull. 
 
 The aspect of man in form and color oscillates between two extremes. 
 Submitted for a due time to a high temperature, any race, Ascenfc and de 
 irrespectively of its original colos, will become dark ; or if to scent of human 
 a low temperature, it will become fair. Under such condi- or s aniz 
 tions as will be set forth in this chapter, it will pass to the elliptical ; un- 
 der others, to the prognathous form of skull. No race is in a state of 
 absolute equilibrium, or able successfully to maintain its present physi- 
 ognomy, if the circumstances under which it lives undergo a change. It 
 holds itself ready, with equal facility, to descend to a baser, or rise to a 
 more elevated state, in correspondence with those circumstances. 
 
 I think that this principle has not been recognized with sufficient dis- 
 tinctness by those who have studied the natural history of man. They 
 have occupied themselves too completely with the idea of fixity in the 
 aspect of human families, and have treated of them as though they were 
 perfectly and definitely distinct, or in a condition of equilibrium. They 
 have described them as they are found in the various countries of the 
 globe, and since these descriptions remain correct during a long time, the 
 general inference of an invariability has gathered strength, until some 
 writers are to be found who suppose that there have been as many sep- 
 arate creations of man as there are races which can be distinguished from 
 each other. We are perpetually mistaking the slow movements of Na- 
 ture for absolute rest. "We confound temporary equilibration with final 
 equilibrium. 
 
 Man can not occupy a new climate without an organic change occur- 
 ring in his economy, which by degrees comes to a corre- Corres on( j ence 
 spondence with the conditions by which it is surrounded, of climate and 
 In this career, each individual, as a member of one genera- organi 
 tion$ may only make a partial advance, for differentiation most commonly 
 occurs in the early periods of embryonic life, as described at page 505; 
 but, since all individual peculiarities are liable to hereditary transmission, 
 the cumulative effect becomes strongly marked at last. So dominating 
 is the control which physical influences exert over us, that invariability 
 of our aspect for several generations may be received as a proof that those 
 influences have been stationary in kind and degree. In such a perfect 
 manner is that aspect dependent on them that it is truly their represent- 
 ative. If they change, it must change too. 
 
 I do not, therefore, contemplate the human race as consisting of vari- 
 eties, much less of distinct species, but rather as offering numberless rep- 
 resentations of the different forms which an ideal type can be made to as- 
 sume under exposure to different conditions. I believe that that id ea i type 
 ideal type may still be recognized, even in cases that offer, when of man - 
 
566 HABITS OF NATIONS. 
 
 compared together, complete discordances ; and that, if such an illustra- 
 tion be permissible, it is like a general expression in algebra, which gives 
 rise to different results .according as we assign different values to its 
 quantities, yet in every one of those results the original expression exists. 
 
 From this it therefore follows that there is a capability of metamor- 
 phosis or transmutation from form to form ; that the human system pos- 
 sesses no inherent resistance to change, no physiological inertia, but will 
 pass indifferently upward and downward, toward perfection or toward 
 degradation, as circumstances overrule, yet is it the same human system 
 throughout. Nor is it of any consequence that the progress of these 
 re uired cnan S es ma 7 ^e, as we term them, tardy, and that for their 
 for physiolog- completion a long time may be required. Even a mass of 
 
 change, inorganic matter a rock transferred from the equator 
 toward the pole, or from the pole to the equator, would not change 
 its temperature to that of the new locality at once ; it would come to 
 its destined equilibrium in a gradual way, in a time depending en its 
 mass and conducting power. We should not impute its slow manner 
 of yielding to any inherent principle of resistance which it possessed. 
 The physiological metamorphosis of man is an affair of centuries. The 
 universal recognition of the principle that such changes are possible lies 
 at the bottom of all our attempts to elevate communities by ameliorating 
 their social condition and by education. 
 
 In the remarks which follow, it will therefore be understood that I re- 
 ceive the classifications of Blumenbach and other authors as offering a 
 convenience in description, but do not attach to them any essential sig- 
 nificance. 
 
 Though plants and animals are limited to certain localities of the earth's 
 Habits of dif- surface, some species being formed in one and some in an- 
 ferent nations. O ther region, the human family lives indifferently all over the 
 surface of the globe. It occupies countries where the thermometer falls 
 to 50 below zero, or where the temperature of the midday sun is 160. 
 In these different climates, the most marked differences in color, stature, 
 conformation, and habits are exhibited, there being every shade, from 
 a jet black to a fair white ; every stature, from the pigmy Esquimaux 
 and Laplanders to the tall Patagonian ; every variety of facial angle, from 
 that acute one which characterizes the ape to the classical aspect of the 
 Greek, which is more than 90 ; every pursuit of life, hunting, fishing, 
 the keeping of flocks, agriculture, commerce, and the arts of civilized so- 
 ciety. To these might be added the use of every variety of food, from a 
 wretched subsistence on worms and roots scratched out of the ground to 
 the luxurious habits of the epicure ; every grade of locomotion, from 
 those who never leave the hill or valley where they were born to those 
 who are perpetually wandering all over a continent, nay, even all over 
 
REALMS OF PLANTS AND ANIMALS. 567 
 
 the globe. There might, too, be added every variety of character and 
 every degree, of intellectuality. Among these differences, the variations 
 of language are by no means the least important. It is estimated that 
 more than three thousand dialects are spoken. 
 
 Among these races certain common traditions prevail, historical rem- 
 iniscences handed down from one generation to another, Traditions of 
 which convey the deeds of former great men who have either B ation s> 
 distinguished themselves by their achievements in war or by their in- 
 ventions in the peaceful arts ; traditions which have also communicated 
 the religion or the superstition of the ancient times, and which, among 
 people inhabiting countries remote from one another, present such an as- 
 pect of sameness, that we must either refer them to one common and more 
 ancient source, or regard them as arising from analogous peculiarities in 
 the mental structure of the whole race. 
 
 There can not be a doubt that in the lapse of many ages the influ- 
 ence of external physical agents must have made a marked i nfluenceofex 
 impression upon the original characters of men. Few ques- temai agents 
 tions have been more critically discussed than the extent to 
 which this change of aspect by physical agents can go, many naturalists 
 believing that the sole cause of national difference is the influence of cli- 
 mate or temperature an influence which is sufficient to account for all 
 other organic peculiarities we have just specified ; for if we admit that 
 the same original germ may develop itself into countless forms, accord- 
 ing as it has been exposed to different physical agents, much more is it 
 probable that the various races composing the human family, exposed as 
 they have been to different physical circumstances, may by degrees have 
 assumed the discordant features they present, although they have de- 
 scended from one original stock. 
 
 Here we shall have to consider the weight which should be attached 
 to a very remarkable observation which has of late been Geographical 
 made as respects the distribution of man. -With regard to 'JSJ^'* 
 plants, it has long been known that they are grouped round mais,andman. 
 certain centres, which may be regarded as their foci of origin, and one of 
 such groups compared with another presents striking contrasts ; the veg- 
 etation of Central Africa is wholly distinct from that of Europe, the veg- 
 etation of Europe distinct from that of North America, and this, again, 
 from New Holland. There are no lauringe in Central Africa, no heaths 
 in the New World. The forests of New Holland gain their most strik- 
 ing features from their leafless acacias and eucalypti. So, in like man- 
 ner, there are foci of origin and circles of distribution as regards animal 
 life. The fauna of Asia is wholly dissimilar from that of Europe, the 
 fauna of Europe is dissimilar from that of North America, and this, again, 
 from that of Africa and New Holland. Without specifying details, we 
 
568 ORIGIN OF NATIONS. 
 
 may recall that the hippopotamus and camelopard are natives of Africa, 
 and are restricted to it ; the tiger is a native of India ; the armadillos 
 and ant-eaters, of South America ; the kangaroo and ornithorhynchus, of 
 New Holland. The earth's surface might thus be divided into regions 
 or realms, each possessing its own special flora and fauna. And more 
 than this, the oceans, too, might in like manner be parted off, and this 
 not only as regards their surface, but also in strata at different depths. 
 Now these botanical centres and circles are coincident with the zoological 
 centres and circles, and hence there has arisen the idea that such centres 
 have been truly points of original development, both for one and the oth- 
 er of these natural kingdoms, and that the globe has not been filled by a 
 process of dispersion or diffusion from one point, but co-ordinately, and, 
 perhaps, contemporaneously from many such foci, and that we can still 
 recognize the position of these foci by a critical study of animals and 
 plants. 
 
 As to the discussions which have of late years arisen on this question, 
 The IAVO hy- the reader may refer to the work of Drs. Nott and Gliddon 
 orMrfof na the on ^ ie tv P es ^ ma nkind for arguments in support of a mul- 
 tions. titude of centres of human origin, and to that of Dr. Prich- 
 
 ard on the natural history of man for those in behalf of the unity of the 
 race. In these works, respectively, will be found most of the facts hith- 
 erto brought forward. 
 
 In the former of these works, Professor Agassiz draws attention to the 
 Doctrine of circumstance that all around the Arctic circle, and therefore in 
 Professor every longitude, is to be found one race offering characters that 
 Agassiz. are strikingly homogeneous in aspect, intellect, and habits of life, 
 represented in America by the Esquimaux, in Europe by the Laplanders, 
 and in Asia by the Samoiedes. These live in a region of which the 
 Floral faunai ^ auna an( ^ ^ ora are likewise homogeneous. It has every where 
 and human ' the same dreary expanses, covered with dwarf birches, moss- 
 es, and lichens ; .in its waters there are the same fishes, as 
 the salmon, and the same molluscs and echinoderms. In the air it has 
 the same birds. Among its mammals found thus with uniformity, the 
 white bear, the reindeer, the walrus, and the whale may be mentioned. 
 With a special fauna thus coinciding with a special flora, there is also a 
 special variety of man. 
 
 What has here been said respecting Arctic life may be generalized. 
 Each of the coincident floral and faunai circles has its own species of 
 man. 
 
 Thus, in the temperate zone, may be distinguished three such primary 
 realms, each of which is distinct as regards its botany and zoology ; and, 
 in correspondence, we find that in the first, in the country of the Mongo- 
 lians, to the east beyond the Caspian Sea, there are nations whose com- 
 
HABITS OF NATIONS. 569 
 
 plexion is yellow ; in the second, upon the shore of the Mediterranean 
 and throughout Europe, there are others whose complexion is white ; in 
 the third, in America, others whose complexion is red; and though 
 these three widely-extended races touch, upon their north boundary, the 
 homogenous Arctic inhabitants, in every respect they may be distin- 
 guished from them. The temperature of the zone in which they live 
 ranges from 32 to 74 ; it permits the growth of pines, nut and fruit 
 trees, and among its animals might be mentioned the bear, the wolf, the 
 otter, the deer, the squirrel, and the rat; these animals, however, respect- 
 ively exhibiting striking differences characteristic of their three focal cen- 
 tres : the black bear belongs to North America, the brown bear to Europe, 
 and the bear of Thibet to Asia. The European stag finds its American 
 analogue in the wapiti, and in Asia in the musk deer. The wild ox of 
 Lithuania differs from the North American buffalo, and this, again, from 
 the Mongolian yak. Even among plants the same differences may be 
 traced ; the pines of Europe are not the same as the pines of America, 
 and thus it would appear that each of the three great organic circles be- 
 longing to the temperate zone has a flora, a fauna, and a human species 
 of its own. 
 
 The same general result might be established for the tropical regions, 
 and special centres assigned for Africa, Malaya, and Polynesia. 
 
 In view of this distribution as connected with habits, Dr. Prichard thus 
 expresses himself in his Natural History of Man : " Let us Habits of na- 
 imagine, for a moment, a stranger from another planet to visit tions - 
 our globe, and to contemplate and compare the manners of its inhabit- 
 ants, and let him first witness some brilliant spectacle in- one of the high- 
 ly-civilized countries of Europe : the coronation of a monarch, the in- 
 stallation of St. Louis on the throne of his ancestors, surrounded by an 
 august assembly of peers, and barons, and mitred abbots, anointed from 
 the cruise of sacred oil brought by an angel to ratify the divine privilege 
 of kings ; let the same person be carried into a hamlet in Negroland, in 
 the hour when -the sable race recreate themselves with dancing and bar- 
 barous music; let him then be transported to the saline plains over 
 which bald and tawny Mongols roam, differing but little in hue from the 
 yellow soil of their steppes, brightened by the saffron flowers of the iris 
 and tulip ; let him be placed near the solitary den of the Bushman, where 
 the lean and hungry savage crouches in silence like a beast of prey, watch- 
 ing with fixed eyes the creatures which enter his pitfall, or the insects 
 and reptiles which chance brings within his grasp ; let the traveler be 
 carried into the midst of an Australian forest, where the squalid con> 
 panions of kangaroos may be seen crawling in procession in imitation of 
 quadrupeds ; can it be supposed that such a person would conclude the 
 various groups of beings whom he had surveyed to be of one nature, one 
 
570 RESEMBLANCES OF NATIONS. 
 
 tribe, or the offspring of the same original stock ? It is much more prob- 
 able that he would arrive at an opposite conclusion." 
 
 On this it may be remarked that much would depend on the previous 
 training of the illustrious stranger. If his mind had been imbued with 
 a better philosophy than that which prevails in this our lower world, he 
 might look with an equal eye on the transitory fashions before him, and 
 penetrate to the first principles of things through the false glare of pomp 
 or through debasement and degradation, and so arrive at a conclusion 
 precisely the opposite of the foregoing, in the same manner as has Dr. 
 Prichard himself. 
 
 For, from such an elevated point of view, the plumed pageant of civ- 
 ilized life might only appear to be a modified phase of the ceremonials 
 of equinoctial Africa, where the inhabitants, on their festive occasions, 
 adorn their naked bodies with leaves, and present oblations of palm oil 
 with many genuflexions to their chiefs and enchanters. Beneath the 
 feathers in the one case, and the leaves in the other, he might discern the 
 same ruling idea, and detect the same human nature ; or, if his vision 
 could reach into the past, and recall the credulous Greek worshiping be- 
 fore the exquisitely perfect statues of the deities of his country, beseeching 
 them for sunshine or for rain, and then turn to the savage Amaiman, who 
 commences his fasts by taking a vomit, and, for want of a better goddess, 
 adores a dried cow's tail, imploring it for all earthly goods, and particu- 
 larly to pay his 'debts again the same principle would emerge, only il- 
 lustrated by the circumstance that the savage is more thorough, more 
 earnest in his work. 
 
 In fact, wherever we look, man is the same. Stripped of exterior cov- 
 Resembiances erings, there is in every climate a common body and a com- 
 among nations. mon mm( j. Are not all of us liable to the same diseases ? 
 Have not all a tendency to exist the same length of time ? Is it the 
 temperature of our body, the beat of the pulse, the respiration that we 
 observe are they not every where alike ? Or, turning to the manifesta- 
 tions of the mind, is there not, among all the tribes of oui* race, a belief 
 in the existence and goodness of God ? in unseen agents, intermediate 
 between him and ourselves ? and in a future life ? Do we not all put a 
 reliance in the efficacy of prayers ? and all, in our youth, have a dread of 
 ghosts ? How many of us, in all parts of the world, attach a value to 
 pilgrimages, sacrificial offerings, fastings, and unlucky days, and in our 
 worldly proceedings are guided by codes of law and ideas of the nature 
 of property ! Have we not all the same fears, the same delights, the 
 same aversions, and do we not resort to the use of fire, domestic animals, 
 and weapons ? Do we not all expect that the differences which surround 
 us here will be balanced hereafter, and that there are rewards and punish- 
 ments ? Is there not a common interpretation of all the varied forms of 
 
LOCAL TEMPERATURES. 571 
 
 funeral ceremonies? a common sentiment of the sacredness of the tomb? 
 Have we not always, and do we not every where set apart a sacerdotal 
 order, who may mediate for us ? In our less advanced civilization, do we 
 not all believe in sorceries, witches, and charms ? It signifies nothing 
 in what particular form our mental conceptions are embodied ; it is the 
 conception that concerns us, and not the aspect it has assumed. Thus 
 equally do the views of the various nations demonstrate their innate be- 
 lief of a future world the undisturbed Hunting-ground of the American 
 Indian, the voluptuous Paradise and society of the houris of the Ara- 
 bian, or the snow hut of the Esquimaux, in which the righteous feed on 
 the blubber of whales. 
 
 Turning our attention to the influence of temperature, it may be ob- 
 served that the development of coloring matter in the skin de- influence of 
 pends on the heat to which we are exposed. Generally, it ^JJIe'com^ 
 might therefore appear that there should be a correspondence piexion. 
 between the complexion and the latitude of the place of our abode, the 
 skin being darker as we approach the equator, and fairer toward the 
 poles, because, since all the heat that we receive comes from the sun, 
 the amount which is furnished to us depends upon the obliquity of his 
 rays, and therefore upon the latitude. But this is true only in a very 
 general way, and many exceptions at once spontaneously suggest them- 
 selves. I may point out some of these variations. 
 
 The temperature of a place depends on three leading circumstances, 
 its latitude, its elevation above the sea, and on meteorolog- causes of local 
 ical conditions. Kespecting the latitude, nothing need be temperatures. 
 added to the remarks already offered ; and as regards the influence of 
 elevation above the sea, it is to be remembered that there is a decline of 
 temperature as we ascend in the atmosphere from any point of the globe, 
 and for this reason, as has been already explained at page 473, even un- 
 der the equator there will be an arrangement answering to climates on 
 every high mountain, its top, if sufficiently elevated, being covered with 
 perpetual snow. Of meteorological conditions, it may be said that they 
 are so numerous as to render it almost impossible to give a full and yet 
 brief statement of them, but as illustrations may be mentioned the prox- 
 imity of the sea, or of great desert tracts, ocean currents, the prevailing 
 winds ; thus, in our hemisphere, a north wind predominating lowers the 
 mean temperature of the place, a south wind tends to raise it ; and thus, 
 also, the great desert of Sahara and the American Gulf Stream increase 
 by many degrees the temperature of Europe. 
 
 For such reasons, therefore, the lines of equal heat do not correspond 
 to the parallels of latitude, but, as an inspection of a chart of them will 
 show, deviate greatly therefrom. 
 
 In treating of the influence of heat on plants, it was shown that, when 
 
572 RELATIONS OF HEAT. 
 
 we make our examination in a critical manner, the problem is not so sim- 
 ple as appears at first sight, and that there are several different relations 
 of the heat which must be considered. Thus the geography of plants is 
 not wholly determined by the mean temperature of the whole year, nor 
 by the greatest heat of the summer, nor the greatest cold of winter ; that 
 is to say, it neither follows the isothermal, isotheral, nor isochimenal lines. 
 Moreover, the luxuriance of vegetation is not so much dependent upon 
 the temperature or intensity of heat as it is upon the quantity. These 
 remarks apply with much force to the case now before us, 
 
 Intensity and jr.r / 
 
 quantity of for the change of complexion is not so much dependent upon 
 heat compared. tte i ntens i tv O f l iea t determined by the thermometer as it is 
 upon the absolute annual quantity ; for, though these conditions of in- 
 tensity and quantity of heat are essentially distinct, yet it will generally 
 happen that they may increase or diminish together, without there being 
 an absolute correspondence between them. There can be no doubt that 
 the quantity of heat annually furnished in Guinea vastly exceeds the 
 quantity annually furnished to any part of tropical America. It is upon 
 this condition, and not upon the height of the thermometer, that the dark- 
 ening of the human complexion depends. 
 
 To the reader who is not familiar with the technicalities of Natural 
 Philosophy, an explanatory illustration of the statement here made may 
 be of value. If he will suppose that he examines a wine-glass of water, 
 boiling hot, and a gallon of tepid water by a thermometer, he will find 
 that that instrument will stand much higher in the wine-glass than in 
 the gallon. But if he proceeds to determine how much ice the two por- 
 tions of water will" respectively melt, he will find that the greatest effect 
 is produced by the lukewarm water. We say, therefore, that though the 
 thermometer has indicated the intensity of the heat in the two portions 
 of water respectively, that is to say, their temperatures, it has not indi- 
 cated tlie quantity present in each, but the melting of the ice has revealed 
 the fact that the tepid water, by reason of its larger proportion, contains 
 a larger quantity of heat. 
 
 It may be repeated, therefore, that the absolute quantity of heat an- 
 nually furnished to any locality is by no means -indicated by the maxi- 
 mum height to which the thermometer will rise in the summer season, 
 yet it is upon that condition, quantity, that the tint of the complexion 
 depends. 
 
 That climate does thus influence color is clearly demonstrated by the 
 Quantity of ^ act ^at a f am ^7 f men, indisputably derived from a corn- 
 heat influences mon stock, have different complexions in different countries. 
 The Jews of the north of Europe are fair men, often having 
 red beards and blue eyes. As we trace them in their southeasterly dis- 
 tribution, their color deepens by degrees. In their original country they 
 
INDO-EUROPEANS. 
 
 573 
 
 are tawny, still farther on they are deep brown, and in Malabar almost 
 black. A more interesting and more general instance is offered by tho 
 race to which we belong, the Indo-European, which reaches, in one un- 
 broken column, across Western Asia, through Europe, from Hindostan to 
 the British Islands. That this is one homogeneous family, derived from 
 a common stock, is proved beyond all possibility of a doubt by the affin- 
 ities of its languages, all showing a relation to the ancient Sanscrit, 
 and even betraying, by their varied designations of certain objects, in an 
 approximate manner, the time at which the progress of this column was 
 made that it was anterior to the introduction of the metals, in the age 
 of stone, as some authors have designated it, when weapons and imple- 
 ments of that material alone were employed, for the names of the metals 
 are different in many of the different languages of this race. 
 
 But how is it as regards the complexion of the Indo-European s ? To 
 the northwest it is light, but it darkens toward the extreme Variations im- 
 southeast in India, the distribution in this respect having 
 been doubtless much better marked in former times, before race, 
 it was disturbed by the influences of civilization. Thus the Eoman au- 
 thors speak of the northern Germans, of the Britons, and the Gauls, as 
 being red-haired, blue-eyed, and very light in their complexion. It is 
 riot to be understood, however, that the tint deepens through various 
 shades of olive and brown by a steady progress as we pass toward India, 
 for the physical principles on which we have been dwelling would pre- 
 pare us to expect that, whenever we reach regions more elevated above 
 
 the level of the sea, the com- 
 plexion of the natives will be 
 lighter. For this reason, the 
 inhabitants of the range of the 
 Caucasus, and again those of 
 the great elevations of the Him- 
 malaya Mountains and sour- 
 ces of the Ganges, are as light 
 a as the southern Europeans, 
 H| and there very frequently is 
 jji seen the auburn-bearded, and 
 blue or gray eyed man. 
 
 While the complexion thus 
 depends on the heat, the form 
 of the skull is determined by 
 the condition of development 
 of the brain, and this is the 
 more perfect where life is main- 
 Brahmin, tained in circumstances of 
 
 Fig. 269. 
 
574 
 
 MONGOLS. 
 
 plenty, indolence, luxury, ease. In Hindostan, among the natives of 
 high caste, have from time to time arisen men whose mental endowments 
 have been in no respect inferior to those of Europeans statesmen, poets, 
 soldiers, astronomers, mathematicians. Complexion apart, the portrait 
 of Ram Ruttum, a Brahmin, Fig. 269, taken Iby Mr. Branwhite, presents 
 an intelligent and agreeable countenance, though, perhaps, with an air of 
 effeminacy. 
 
 Let us examine a second of our subdivisions, the Mongol, character- 
 ized as descending; from a common stock by the affinities of 
 
 Variations im- f .... 
 
 pressed on the its languages, though having a geographical distribution from 
 Mongol race. the Indian Q cean to tlie tfioKs of the Polar Sea. As with 
 the Indo-European race, so with this, the color becomes darker as the 
 tropic is approached so dark, indeed, that, in the lowest latitudes to 
 which its nations reach, they may be said to be black. From this they 
 pass through various shades of brown and olive as a progress to the 
 higher latitudes is made, the pale countenance reappearing in North Tar- 
 tary, and attaining to whiteness in the fish-feeding tribes, Samoiedes, on 
 the shores of the Icy Sea. But here, again, the complexion and the lati- 
 tude are not in correspondence : on the low shores of China the natives are 
 tawny, but in the mountainous regions of the northwest of that country 
 there are tribes spoken of by those who have seen them as of surprising 
 whiteness, and a similar circumstance occurs among the Tartar tribes of 
 the very elevated plateaux of Central Asia. 
 
 Although the Chinese countenance, both of the indigenous race and the 
 
 dominant Tartars, is very characteris- 
 tic, as seen in the annexed portrait, 
 Fig. 270, from Dr. Prichard, the form 
 of the skull expresses a high intellec- 
 tual culture, of which also their civil- 
 ization and their polity are a surpris- 
 ing proof. The difficulties of govern- 
 ing masses of men concentrated in a 
 narrow space seem, by the statesmen 
 of that nation, to have been in a great 
 measure overcome. On the Chinese 
 rivers there are many great cities, vast- 
 ly outnumbering in their population 
 the largest European capitals. Under 
 the government of the emperor, it is said that there live, in security and 
 repose, one third of the human race! Such a spectacle may impress 
 even the philosopher with sentiments of respect and admiration. 
 
 The hardships of life have left their impression on the form of the skull 
 of the North Asiatic, whose energies have to be directed to the support of 
 
 Fig. 270. 
 
 Chinese. 
 
AMERICAN INDIANS. 
 
 575 
 
 Fig. 271. 
 
 animal existence. The portrait 
 of a Kamtschatdale, Fig. 271, 
 selected by Dr. Prichard as an 
 example, shows the projecting 
 muzzle, that invariable index of 
 want, and true animal feature. 
 The complexion is nevertheless 
 in correspondence with the low 
 temperature of the country. 
 A like examination of a third 
 
 of the subdivisions Variations im- 
 
 Kamtschatdale. 
 
 Fig. 272. 
 
 Can, equally Well il- dian race. 
 
 lustrates the influence of heat. 
 These, though popularly spoken 
 of as red, and often regarded as presenting the same color from the North 
 Polar Sea to Terra del Fuego, are very far from offering such a uniform- 
 ity. The Esquimaux on the north, and the Fuegians on the south, are 
 light, the tint of the native races deepening, to a certain degree, as the 
 equator is approached a gradual deepening, much better marked in 
 South than in North America, and on the Pacific than on the Atlantic 
 
 slope. As examples of the 
 North American Indians, 
 we may take the portraits, 
 by Mr. Catlin, of Black 
 Hawk, Fig. 272, and Tuch- 
 te,Fig. 273, page 576; the 
 former a Sac, the latter a 
 Cherokee. It is sufficient 
 to compare the counte- 
 nances of these Indians 
 with those of California, as 
 figured in the Voyage Pit- 
 toresque of Choris, Fig. 
 274, page 576, to realize 
 how erroneous is the preva- 
 lent statement that all the 
 American tribes, both of 
 the north and south conti- 
 tinent, are alike. The ol- 
 ive-black Indians of the Pacific slope, though their lips are thick and 
 their noses flat, have lank and not woolly hair, Fig. 275, page 576. On 
 the Atlantic shore, as is well known, the temperature, in passing to lower 
 
 ^^^) 
 
 American Indian. 
 
576 
 
 AMEKICAN INDIANS. 
 
 Fig. 27C 
 
 latitudes, docs not so rapidly vary ; 
 and on the Pacific the mean heat is* 
 much higher than on the Atlantic 
 
 Fig. 274. 
 
 American Indian. 
 
 for the same parallel of latitude. 
 
 Calrornla Indian. 
 
 Fig. 2T5. 
 
 California Indians. 
 
 In South America, the so-called red race, as we have just observed, is 
 deeper in complexion as we pass from Terra del Fuego and Patagonia 
 northward toward the line. The Chilians are darker than the Fuegians, 
 and the Peruvians darker than the Chilians. As the topographical con- 
 struction of that continent would lead us to infer, there is an analogous 
 distribution from west to east, crossing the preceding at right angles ; 
 the Inca race, who inhabit the plateaux of the Andes, are lighter than 
 
AFRICANS. 
 
 577 
 
 corresponds to the latitude ; but from this point, passing to the east, the 
 -Brazilio-Guarani are darker as we approach the Atlantic Ocean. It may 
 with truth be said that the intervention of the Gulf of Mexico and Ca- 
 ribbean Sea has lightened the complexion of the aboriginal tribes of 
 North and South America. 
 
 In the last place, we may consider, in like manner, the African races. 
 These are, as we should expect from the high temperature y . . 
 of that continent, all dark, yet not equally so, for the Berbers pressed on the 
 toward the Mediterranean shore, and the Hottentots and Kaf- African races * 
 firs adjacent to the Cape of Good Hope, are of a lighter hue. In this 
 class we ought also to enumerate, as an example of no common interest, 
 the native Egyptians, who are, perhaps, the lightest of all. It does not 
 appear that there has been any marked change in the complexion of the 
 aboriginal Egyptian for the last three thousand years, so far as can be 
 judged from a comparison of the descriptions and paintings which have 
 descended to our times, with the existing Copts. Leaving the Mediter- 
 ranean shore, and advancing to the south, we pass through bands of pop- 
 ulation sensibly becoming darker, save where a disturbance arises by rea- 
 son of the elevation of the mountain ranges. On the north of the equa- 
 tor the negro land is not reached until we are within 10 lati- The negro 
 tude. The true negro occupies a zone crossing through the con- zone - 
 tinent west and east. If our examination be made meridionally, in the 
 manner just supposed, but along the Eed Sea coast, the complexion of 
 the inhabitants is observed to darken through Upper Egypt and in Abys- 
 synia. Of this country it is interesting to remark that it still retains the 
 Christian faith as delivered to it in the remotest times of the Church. 
 
 The portrait of an Abyssinian, 
 Fig. 276, from M. d'Abbadie, shows 
 
 Fig. 276. 
 
 Abyssinian. Native of Madagascar. 
 
 an admixture of the Arab lineaments, though there is no reason to suppose 
 
 Go 
 
578 
 
 AFRICANS. 
 
 that this is due to the admixture of Arab blood. Of the two classes 
 of Abyssinians, those who inhabit the more southerly parts have a coun- 
 tenance much more approaching to the negro. They are, indeed, an in- 
 trusive race, who conquered in more recent times the regions in which 
 they are settled. It is said that the Amharic, the language of the true 
 Abyssinians, is singularly analogous to the Hebrew. 
 
 As resembling the Abyssinians in many respects, though on the op- 
 posite side of the equator, may be mentioned the natives of Madagascar, 
 Fig. 277, p. 577. Presenting, in some particulars, the traces of Arab in- 
 fluence, it has nevertheless been inferred, partly from their language and 
 partly from their features, that the most numerous class is of Malay ori- 
 gin. Though among the inferior tribes there are some which are black, 
 the complexion of this is olive, and the hair is not woolly, though it 
 curls. 
 
 It should be constantly borne in mind that the resemblance of features 
 Evidences from is no proof of a community of origin. The influence of cli- 
 countTnance ma t e and of manner of life is so great that in a due period 
 and language, of time the most diverse tribes will show similar lineaments. 
 Analogy in the structure of languages and identity in vocabulary is 
 much better evidence, though even this must be received with caution. In 
 reference to this, it has been very significantly remarked that birds of the 
 Fig. 2T8. same kind sing the same notes 
 
 in all countries, even though 
 under such circumstances as to 
 exclude the possibility of their 
 having been taught by their 
 parents. 
 
 The annexed figure, 278, is 
 given by Dr. Prichard as a 
 specimen of the natives of Mo- 
 zambique. The expression is 
 undoubtedly much superior to 
 that prevailing on the West ' 
 African coast. Of some of 
 these tribes it is said that the 
 Native of Mozambique. hair is not woolly, but merely 
 
 frizzled. It grows long, and hangs in slender curls. 
 
 Examining the zone designated as negro land, we find that the negro 
 Amelioration character of its inhabitants is not in all parts developed with 
 typeto^he equal intensity. The maximum is shown in the Guinea 
 east. countries, and from thence across the continent to the east 
 
 the physiognomy improves. The negro characteristics may be specified 
 as intense blackness of the skin, woolly hair, thick lips, gaping nostrils, 
 
THE NEGRO. 
 
 579 
 
 Fig. 279. 
 
 Negro of Guinea. 
 
 Fig. 280. 
 
 and a prognathous skull. But the negro 
 aspect is not limited to the African con- 
 tinent ; it is prolonged or projected through 
 the Indian into the Pacific Ocean, north 
 and south of the equator, in a zone of 'many- 
 degrees. Sumatra, Borneo, Celebes, New 
 Guinea, and part of Australia, lie in this 
 zone. In these various countries, one or 
 another of the characteristics we have men- 
 tioned predominate, in part through the in- 
 fluence of climate, and in part through ad- 
 mixture of blood. In some of these people 
 the hair is not woolly ; in some, the lips 
 are thin, and the nose projecting ; in some, 
 the form of the skull indicates a great su- 
 periority over the West African tribes. But, whatever these modifica- 
 tions may be, the black races of the Pacific present in their general ap- 
 pearance so predominating a negro as- 
 pect that they have by all travelers 
 been classed with that tribe. Of one 
 of these nations, Dampier, the early 
 navigator, speaks as " shock, curl-pa- 
 ted, New Guinea negroes. " The por- 
 trait, Fig. 280, from Choris's Voyage 
 Pittoresque, of a girl of the island of 
 Luzon, one of the Philippines, may il- 
 lustrate this remark ; for, though the 
 form of the head shows a very great 
 advance upon that of the Guinea ne- 
 gro, the facial angle, respecting which 
 more will shortly be said, being much 
 larger, and the relative size of the 
 brain therefore increased, the counte- 
 nance is essentially that of tropical 
 Africa. 
 
 The projection of the African type into the Pacific is crossed at a cer- 
 tain point by a like projection of the dark Asiatic type, and y ariations im 
 in the region of this intersection or commingling we find the pressed on the 
 most degraded specimens of humanity. Pacific race ' 
 
 From these regions, as we pass eastwardly toward the American con- 
 tinent, the improvement becomes very striking; thus tne Amelioration of 
 natives of the Society Islands, though living within the the Pelagian 
 tropic, are of a clear olive or brunette. In the opinion of type to the east> 
 
 Philippine negro. 
 
580 COMPARISON OF THE SKELETON. 
 
 some, if it were not for a slight thickness of the lips and spreading of 
 the nostrils, the countenance would be European. The men are de- 
 scribed as "tall, strong, well-limbed, and finely shaped." Many of the 
 children have flaxen hair ; and sailors, who are generally competent 
 judges of such matters, universally yield a tribute of admiration to the 
 prettiness of the women. Captain Bligh attributed the mutiny in his 
 ship to that interesting cause. 
 
 We may next consider variations in the form of the skeleton. 
 
 Here, more particularly in the classification of the forms of skulls, I 
 Comparison adopt the division introduced by Dr. Prichard, from whose 
 of skeletons, work, above alluded to, the following passages are extracted : 
 
 " In all other races, compared with Europeans, the limbs are more 
 crooked and badly formed. In the negro the bones of the leg are 
 eg ' bent outward. Soemmering and Lawrence have observed that 
 the tibia and fibula in the negro are more convex in front than in Eu- 
 ropeans ; the calves of the legs are very high, so as to encroach upon the 
 hams ; the feet and hands, but particularly the former^ are flat ; the os 
 calcis, instead of being arched, is continued nearly in a straight line with 
 the other bones of the foot, which is remarkably broad." 
 
 " It was observed by White, and has been generally believed, that 
 the length of the forearm is so much greater in the negro than 
 
 The arm. . & 
 
 in the European as to constitute a real approximation to the 
 character of the ape. Facts, however, prove but a very slight difference, 
 and by no means greater than the varieties which are every day to be 
 observed on comparing many individuals of any race or nation. On the 
 other hand, the difference between adult apes and men in the length of 
 the extremities is so great as to render all such comparisons very remote, 
 and of very doubtful importance with respect to any ulterior conclusion. 
 According to Mr. Owen, the arms of the orang reach to the heel, or at 
 least to the ankle-joint, while in the chimpanzee, or troglodyte, they ex- 
 tend below the knee-joint. This is a most decided and widely-marked dif- 
 ference between the most anthropoid apes and the uncultivated races of 
 men. Yet even the slightest approach to the former shape would be a 
 curious circumstance ; if it could be fully established, it would tend, with 
 other facts, to imply that the savage races of mankind have somewhat 
 more of the animal, even in their physical conformation, than the more 
 cultivated races, or those whose improvement by civilization may be 
 dated from a very remote era in the history of the world." 
 
 "It has been a general opinion, since the time pf Soemmering, that 
 
 The foramen *^ e head of the negro is placed so much farther backward on 
 
 magnum of the the vertebral column as to occasion a material difference in 
 
 the figure of the whole body. It was observed by Dauben- 
 
 ton that the foramen magnum is placed in quadrupeds behind the centre 
 
FOUR METHODS OF EXAMINING THE SKULL. 
 
 581 
 
 Fig. 281 
 
 of gravity, whence an important difference arises in the relative position 
 of the head and trunk in man and in inferior animals. The extent of 
 this difference, when the human skeleton is compared with that of the 
 simias, has been most fully made known by Mr. Owen, who has shown 
 that it is much greater in respect to the adult ape than it has hitherto 
 been supposed. But there is, in reality, no difference in human races. 
 The foramen magnum is only posterior in the negro skull to its place 
 in the European, in consequence of the projection of the upper jaw, par- 
 ticularly of the alveolar process." 
 
 In illustration of the statement of Mr. Owen respecting the relative 
 
 length of the arm in man 
 and in the more anthropoid 
 apes, I give the annexed 
 photograph, Fig. 281, of 
 the human skeleton and 
 those of the chimpanzee 
 and orang. Of the chim- 
 panzee it should be ob- 
 served that the specimen 
 was young. They are all 
 brought nearly to the same 
 size by adjusting the dis- 
 tances at which they were 
 taken. The human skele- 
 
 Skeleton of man, chimpanzee, and orang. fOU Was that of a man more 
 
 than six feet in height. 
 
 There are four different views from which an examination ^ 
 
 K our modes of 
 
 of the skull of man and animals may be made : 1st. The lat- examining the 
 eral ; 2d. The vertical ; 3d. The basilar ; 4th. The front. skulL 
 
 1st. The lateral view, or Camper's method, is thus described by the 
 anatomist who introduced, it, and whose name it bears. 
 
 "The basis on which a distinction of nations is founded may be dis- 
 played by two straight lines, one of which is to be drawn The lateral 
 through the meatus auditorius to the base of the nose, and view, or Cam- 
 the other touching the prominent centre of the forehead, and per s n 
 falling thence on the most advancing part of the upper jaw-bone, the 
 head being viewed in profile. In the angle produced by these two lines 
 may be said to consist not only the distinctions between the skulls of 
 the several species of animals, but also those which are found to exist 
 between different nations ; and it might be concluded that Nature has 
 availed herself, at the same time, of this angle to mark out the diversi- 
 ties of the animal kingdom, and to establish a sort of scale from the in- 
 ferior tribes up to the most beautiful forms which are found in the human 
 
582 
 
 THE LATERAL VIEW, OR CAMPER'S METHOD. 
 
 species. Thus it will be found that the heads of birds display the small- 
 est angle, and that it always becomes of greater extent in proportion as 
 the animal approaches more nearly the human figure. Thus there is 
 one species of the ape tribe in which the head has a facial angle of forty- 
 two degrees ; in another, of the same family, which is one of those simige 
 most approximating in figure to mankind, the facial angle contains ex- 
 actly fifty degrees. Next to this is the head of the African negro, which, 
 as well as that of the Kalmuck, forms an angle of seventy degrees, while 
 the angle discovered in the heads of Europeans contains eighty degrees. 
 On this difference of ten degrees in the facial angle the superior beauty 
 of the European depends ; while that character of sublime beauty, which 
 is so striking in some works of ancient statuary, as in the head of Apollo 
 and in the Medusa of Sisocles, is given by an angle which amounts to 
 one hundred degrees." 
 
 As illustrations of this view, the subjoined profiles of the skull of the 
 European, Fig. 282, the negro, Fig. 283, the chimpanzee, Fig. 284, and 
 
 Fig. 282. Fig. 283. 
 
 European. 
 
 the orang, Fig. 285, are given. 
 
 Fig. 284 
 
 Negro. 
 
 Of the latter, which, of apes, are among 
 
 Fig. 285. 
 
 Chimpanzee. 
 
 those most closely approaching to man, 
 the chimpanzee is a native of tropical 
 Africa, and the orang of the Indian 
 Archipelago. 
 
 2d. The vertical view, or Blumenbach's method, 
 
 Orang, 
 
THE VERTICAL VIEW, OR BLUMENBACIl'S METHOD. 583 
 
 " Blumenbacli gives the following account of the way of describing 
 heads, which, he says, is the result of his own observations The vertical 
 in a long and constant study of his collections of the skulls menb^ch? 1U ' 
 of different nations : He remarks that the comparison of the method, 
 breadth of the head, particularly of the vertex, points out the principal 
 and most strongly-marked differences in the general configuration of the 
 cranium. He adds that the whole cranium is susceptible of so many va- 
 rieties in its form, the parts which contribute more or less to determine 
 the national character displaying such different proportions and direc- 
 tions, that it is 'impossible t6 subject all these diversities to the measure- 
 ment of any lines or angles. In comparing and arranging skulls accord- 
 ing to the varieties in their shape, it is preferable to survey them in that 
 method which presents at one view the greatest number of characteristic 
 peculiarities. t The best way of obtaining this end is to place a series 
 of skulls with the cheek-bones on the same horizontal line, resting on the 
 lower jaws, and then, viewing them from behind, and fixing the eye on 
 the vertex of each, to mark all the varieties in the shape of parts that 
 contribute most to the national character, whether they consist in the di- 
 rection of the maxillary -and malar bones, in the breadth or narrowness 
 of the oval figure presented by the vertex, or in the flattened or vaulted 
 form of the frontal bone.' " 
 
 By this means of comparison Blumenbach obtains a division of skulls 
 into three classes, the Caucasian, Mongol, and Negro. They are repre- 
 sented in Fig. 286, Fig. 287, Fig. 288, and Dr. Prichard has added to 
 these figures Fig. 289, the artificially elongated skull of an ancient Pe- 
 ruvian, from the burial-places of Titicaca. 
 
 Fig. 286. p- ig , 287. 
 
 3. The basilar view, or Owen's method. 
 
 " No single view of the skull determines so much in regard to its gen- 
 eral configuration as that of the basis. * The importance of The basilar 
 this manner of examining the bony structure of the head view, or Owen's 
 has been demonstrated in the fullest manner by Mr. Owen, 
 
584 THE BASILAE, OR OWENS METHOD. 
 
 Fig. 2SS. Fig. 289. 
 
 Negro. 
 
 in his excellent memoir on the struc- 
 ture of the orang and chimpanzee. 
 
 The relative proportions and extent, and the peculiarities of formation 
 of the different parts of the cranium, are more fully discovered by this 
 mode of comparison, which has hitherto been much neglected, than by 
 any other method." 
 
 Fig- 200. mn 291< 
 
 Skull of orang. 
 
 Human skull. 
 
 " It may be observed, in this view of the cranium, that the antero- 
 posterior diameter of the basis of the skull is in the orang very much 
 larger than in man. The most striking circumstance which displays 
 this difference is the situation occupied by the zygomatic arch in the 
 plane of the basis of the skull. In all races of men, and even in human 
 idiots, the entire zygoma is included in the anterior half of the basis cra- 
 nii ; in the head of the adult troglodyte, or chimpanzee, as well as in that 
 of the satyr, or orang, the zygoma is situated in the middle region of the 
 skull, and in the basis occupies just one third part of the entire length 
 of its diameter. Posterior to the zygomata, the petrous portions have, 
 in the simian, a larger development in the antero-posterior direction. 
 
THE FEONT VIEW, OE PEICHAED'S METHOD. 585 
 
 Another most remarkable character, in respect to which those anatomists 
 have been greatly deceived who compared only young troglodytes with 
 man, is the great occipital foramen, a feature most important as to the 
 general character of structure and to the habits of the whole being. 
 This foramen, in the human head, is very near the middle of the basis 
 of the skull, or, rather, it is situated immediately behind the middle 
 transverse diameter, while in the adult chimpanzee it is placed in the 
 middle of the posterior third of the basis cranii. A third characteristic 
 in the ape is the greater size and development of the bony palate, in con- 
 sequence of which the teeth are much larger and more spread, and want 
 that continuity which is, generally speaking, a characteristic of man; and 
 intervals between the laniary, cutting, and bicuspid teeth admit, as in 
 the lower tribes of animals, the apices of teeth belonging to the opposite 
 jaws. Fourthly, the basis of the skull is flat, owing to the want of that 
 'downward development of the brain, and of the bony case connected with 
 the greater dimension which the cerebral organ acquires in the human 
 being compared with the lower tribes." 
 4. The front view, or Prichard's method. 
 
 "Neither the facial angle of Camper, nor the method of viewing the 
 skull proposed by Blumenbach, affords a satisfactory display T^efrontview 
 of the characteristics of the pyramidal or lozenge-faced skull." or Prichard's 
 . 292, which is the drawing of the skull of an method ' 
 Fig, 292. Esquimaux, the lines drawn from the 
 
 zygomatic arch, touching the temples, 
 meeting over the forehead, form with 
 the basis a triangular figure. * These 
 two lines in well -formed European 
 heads are parallel, the forehead being 
 very much broader than in the heads 
 of Esquimaux, and other races whose 
 skulls belong to the same great division 
 of human crania, among whom are the 
 Mongolians, and other nomadic nations 
 of Northern Asia. The most striking 
 characteristic of these skulls is the great 
 Esquimaux. lateral or outward projection of the zyg- 
 
 omatic arch. The cheek-bones, rising from under the middle of the or- 
 bit, do not project forward and downward under the eyes, as in the prog- 
 nathous skull of the negro, but take a direction laterally or outward, and 
 turn backward to meet a corresponding projection of the process of the 
 temporal bone, and form with it a large, rounded sweep or segment of a 
 circle. The orbits are large and deep. The upper part of the face being 
 remarkably plane or flat, the nose flat, and the nasal bones, as well as the 
 
586 CLASSIFICATION OF SKULLS. 
 
 space between the eyebrows, nearly on the same plane with the cheek- 
 bones, the triangular space described by the lines (drawn on the wood- 
 cut) may be compared to one of the faces of a pyramid. The whole face, 
 instead of an oval form, as in most Europeans and many Africans, is of 
 a lozenge shape." 
 
 " Another characteristic in most of the pyramidal skulls, or, rather, in 
 the form of the face to which this configuration of the skull gives rise, 
 is the apparently angular position of the aperture of the eyelids. There 
 is no want of parallelism in the orbits, or, rather, of coincidence in the 
 transverse sections of the orbital cavities. The obliquity consists in 
 the structure of the lids themselves ; the skin, being tightly drawn over 
 the large protuberance of the malar bone, under the outer angle of the 
 eye, and at the inner extremity smoothly extended over the lower nasal 
 bones, while the bridge of the nose is scarcely elevated above the plane 
 of the suborbital spaces, gives to the eye the appearance of being placed 
 with the inner angle downward." 
 
 " The oval or elliptical form is that of Europeans, and the southern 
 Asiatics who resemble them ; the zygomatic bones and the jaws being 
 less protuberant, the entire outline of the head, viewed from above, has 
 no projecting angular parts, and is defined by an oval circumference. But 
 in that oval figure, or rather ellipse, the two diameters vary considera- 
 bly in proportion ; in other words, some nations have rounder, others more 
 elongated heads. The shape of the brain, and of the skull at its basis, 
 is in the rounder heads more like that of the pyramidal skull, or the 
 cranium of the northern Asiatics ; in the narrower heads it approaches 
 the figure of the elongated, or negro head." 
 
 We may therefore conveniently classify skulls in three divisions : 
 
 1st. The prognathous, which is represented in Fig. 293, being the 
 Classification skull O f a negro of very forbidding aspect. This form is 
 of skulls. marked by a forward projection of the jaws, the brain being 
 therefore, as it were, thrown backward as respects the face, the forehead 
 being more horizontal and low. 
 
 2d. The pyramidal, Fig. 292, which gives rise, as has been stated 
 above, to the lozenge-shaped face. 
 
 3d. The elliptical or oval, which, viewed from above, has an oval con- 
 tour without projecting parts, and in the profile shows a large facial an- 
 gle, as in the French skull, Fig. 294. 
 
 These forms of skull seem to be connected very closely with habits 
 Connection of of life : the prognathous with the savage state, or that of 
 the skuTand ^ untm g > the pyramidal with a wandering pastoral life ; and 
 manner of life, the elliptical with that of civilization. 
 
 With respect to the form of the pelvis in different nations, the varia- 
 tions are by no means so significant as in the case of the cranium, inas- 
 
EFFECTS OF WANT AND DEGRADATION. 
 
 Fig. 293. Fig. 294. 
 
 587 
 
 Negro. 
 
 French. 
 
 much as they are of indiscriminate oc- 
 currence. It may perhaps be maintained in a general way, 
 that in the less advanced tribes, as in the female Hottentot, 
 there is an approximation to the form exhibited by the simiae, the iliac 
 bones being more vertical, and the whole structure characterized by its 
 length and narrowness. Professor Weber, who has examined this sub- 
 ject with care, concludes that no particular figure of the pelvis is a char- 
 acteristic of any one race. 
 
 The remarks which have been made respecting variations of complex- 
 ion, as exhibited in different climates, might almost be re- The physical 
 peated as respects variations of the form of the skull, origi- a^^inthe* 1 ' 
 nating in difference of physical circumstances ; for as the skull, 
 complexion varies in different temperatures, so does the figure of the 
 skull in different social conditions. The elliptical skull, which beyond 
 all doubt is that which belongs to man in his most civilized state, may 
 be deteriorated and degraded even to the lowest prognathous form. 
 Want and squalid misery will produce this result. Igno- its degradation 
 ranee, mere animal life, social degradation, lead to its ap- b 7 want - 
 proach in varied degrees. Even in the large European cities we recog- 
 nize the incipient stages of it in those classes who follow a precarious 
 life the projecting jaw, the retreating forehead, the mouth habitually 
 open, or the lips parted so as to show the teeth. Mr. Thackrah, in his 
 work on the Effects of Arts, Trades, etc., on Health and Longevity, says, 
 " I stood in Oxford Road, Manchester, and observed the stream of oper- 
 atives as they left the mills at twelve o'clock. The children were almost 
 universally ill-looking, small, sickly, barefoot, and ill-clad. Many ap- 
 peared to be no older than seven. The men, generally from sixteen to 
 twenty-four, and none aged, were almost as pallid and thin as the chil- 
 dren. The women were the most respectable in appearance, but I saw 
 no fresh, fine-looking individuals among them. Here I saw, or thought 
 I saw, a degenerate race human beings stunted, enfeebled, depraved." 
 Under the opposite circumstances, where life is maintained in indolence 
 
588 PROGNATHOUS AND ELLIPTICAL SKULLS. 
 
 and plenty, the converse effects may take place. Of this, perhaps the 
 its rectification most striking illustration is that pointed out by Dr. Prichard 
 by luxury. of the loss of the pyramidal form of skull by the European 
 Turks, a form which appertained to their Asiatic ancestors, and the as- 
 sumption of the elliptical, the skull not of a wandering, but of a station- 
 ary and civilized race. Nor has this transmutation taken place in them, 
 in the short period since they made their European conquest, because of 
 the influence exercised by the Circassian and Georgian women intro- 
 duced into their harems, for this has been upon too small a scale to pro- 
 duce such a general result, and is a luxury which can only be indulged 
 in by the wealthier classes. 
 
 As a descent is made to the skull of the prognathous form, the coun- 
 Contrast be- tenance loses those features which we regard as being beau- 
 nlt e hous h and e t tiful and assumes a baser cast. When it has reached the 
 liptical skulls. limit in that direction, it is actually hideous, recalling at 
 once the detestable aspect of the ape. In this state, in the tropical cli- 
 mates, the lips are thick, the hair woolly, the nostrils gaping. The in- 
 tellectual powers are correspondingly depressed ; the dullness of the eye, 
 its porcelain-like sclerotic contrasting with the blackness of the skin, is 
 in correspondence with the low and degraded mental power. On the 
 contrary, when the passage is made toward the elliptical form, the coun- 
 tenance becomes more beautiful and interesting, capable of expressing the 
 most refined mental emotions. The eyes, in an indescribable but sig- 
 nificant manner, manifest the exalted powers of the mind, and the lips 
 are composed or compressed. 
 
 If I am not mistaken, darkness of the skin and a prognathous form of 
 Mode in which skull may be dependent in the dark tribes on the same cir- 
 dark P comp C iex- cumstance. Functionally the liver is in connection with the 
 in. calorifacient apparatus, its secretion, the bile, as shown in 
 
 Chapter XL, coinciding in habitudes with a hydrocarbon. Much of it 
 is therefore reabsorbed, and eventually devoted for the support of a high 
 temperature. But, besides this combustible material, the bile likewise 
 contains a coloring matter, which is in all respects an effete body, and 
 useless to the system. This pigment is derived from the blood-discs, 
 or, rather, from their hasmatin, as is proved by the fact that it occurs in 
 the meconium of the new-born infant, and likewise, like hgematin, it is 
 rich in iron. Its source is, therefore, not immediately from the food. 
 To remove this useless material is thus one of the primary functions of 
 the liver. 
 
 Now there is no organ which is more quickly disturbed in its duty by 
 Influence of the a high temperature than the liver. Whether such a high 
 the 6 temperature produces its effect through a disturbance of the 
 
 complexion. action of the lungs, or through an impression on the skin, is 
 
ORIGIN OF COLOR. 589 
 
 quite immaterial. If the organ be in any manner enfeebled in its duty, 
 and no other avenue is open through which the degenerating hasmatin 
 may escape, it must accumulate in the circulation, and be deposited here 
 and there in suitable places. Under such circumstances, there arises a 
 tendency for its accumulation in a temporary manner in the lower and 
 more spherical cells of the cuticle, from which it is removed by their 
 gradual exuviation and destruction as they become superficial. The 
 temporary deposit of the coloring matter in tins situation imparts to the 
 skin a shade more or less deep. It may amount to a perfect blackness ; 
 for the origin of the black pigment of the negro is the same as The color of the 
 that of the black pigment of the eye in all races, and the pre- skin derived 
 
 , . . t L. T i -. from the h*- 
 
 dominating percentage 01 iron it presents plainly betrays ma tin of the 
 that it arises from a degenerating haimatin, in which the kiood. 
 same metal abounds. 
 
 I believe, therefore, that the coloration of the skin, whatever the par- 
 ticular tint may be, tawny-yellow, olive-red, or black, is connected with 
 the manner in which the liver is discharging its function. That de- 
 posits of black pigment can normally arise in the way of a true secretion 
 by cell action is satisfactorily proved by their occurrence in angular and 
 ramified patches in the skin of such animals as the frog ; and that hae- 
 matin, in its degeneration, may give rise to many different tints, is sub- 
 stantiated by the colors exhibited by ecchymoses. 
 
 It is not to be forgotten that coloration of the skin, though apparently 
 persistent, is tending continually to a removal, because of Constant re- 
 the oxidation which is taking place as the pigment cells ap- ^^fof ^ 6 
 proach the surface of the cuticle in their process of desquama- skin, 
 tion ; but as this goes on, new cells and new pigment are perpetually 
 forming beneath, to undergo destruction in their turn. Under this point 
 of view, the complexion of the skin is an index of the energy with which 
 that tissue is addressing itself for the removal of metamorphosing ha3- 
 matin. In accomplishing this removal, the liver, in the fair races of man- 
 kind, exerts a sufficient activity; but in hot climates, the habitation of 
 the black races, either through a diminished power of that gland, or be- 
 cause of an increased production of effete pigment, the skin has to lend 
 its aid, and the degree to which it does this is betrayed by the depth of 
 its hue. 
 
 Having thus traced the coloration of the skin to existing peculiarities 
 of hepatic action, I may repeat the remark already made, influence of the 
 that it is not improbable that, in the most degraded negro efon^he form^f 
 type, the prognathous form of the skull may be attributed the skull. 
 to the same cause. 
 
 Not that this alone is always the cause, for a prognathous skull can 
 by degrees arise, as we have seen, in any race, even the white, from a 
 
590 EFFECT OF TEMPERATURE ON THE SKULL. 
 
 variety of causes, such as misery, want, or an oppressed social state. It 
 is, however, on all hands admitted that nothing so quickly disturbs the 
 brain in its action as functional disturbance of the liver. If, through a 
 partial failure in the operation of that great gland, the products which it 
 should normally secrete begin to accumulate in the blood, or have to 
 seek new channels for their escape, the vigor of the intellect is at once 
 impaired. It is with the brain as it is with any other organ, a decline 
 in its activity is soon followed by a deterioration or diminution of its 
 structure, and we must not forget that it is not the brain which accom- 
 modates itself to the capacity of the skull, but the skull which accommo- 
 dates itself to the shape and size of the brain. Whatever the causes may 
 be, and of course they are very numerous, which tend to lessen the en- 
 tire cerebral mass, or by inequality in their effect produce the develop- 
 ment of one part with the contemporaneous diminution of another, they 
 will inevitably give rise to a modification in the figure of the skull ; 
 and observation, as well as phrenological considerations, would cause us 
 to anticipate that, if the effect takes place in such a way as to involve the 
 higher powers of intellection, the skull, answering in its change thereto, 
 will assume the prognathous cast. 
 
 From what I have said respecting the relationship of different nations 
 Hereditar of men, it will be gathered that the peculiarities on which we 
 transmission have been dwelling, the complexion and form of the skull, as 
 of variations. Dependent upon hepatic action, are capable of hereditary trans- 
 mission ; for such a modified glandular action, in whatever manner it 
 may have been occasioned, can be propagated in that way. 
 
 In these remarks it will be perceived that I have mainly had in view 
 Base form of that degradation from the more perfect standard of man which 
 from low Tern- * s encount ered in hot climates, and which finds its expression 
 peraturc. in a blackness of the skin and a base form of the skull. But 
 there is likewise a white degraded form. It is that which we meet in 
 the highest latitudes, and it is therefore dependent upon climate, that is 
 to say, temperature. Here no such tax is thrown upon the skin as is 
 the case in the torrid zone, but here the intellectual powers are greatly 
 enfeebled, if for no other reason, at least because of the hardships under 
 which life must be maintained. It is not, therefore, in very high or very 
 low latitudes that we should expect to find man in his best estate, and 
 this is corroborated by the history of all races. It is true that, by the 
 artificial control which we have obtained over temperature by the aid of 
 clothing and improved modes of shelter, we have, in some degree, with- 
 drawn ourselves from the absolute dominion of climate; but, putting 
 these disturbances of civilization aside, and looking only to our natural 
 state, we shall be constrained to admit that the man of maximum intel- 
 lectual capacity is of a faint brown hue. Nor was it through any acci- 
 
DISAPPEARANCE OF THE FAIR RACES. 591 
 
 dental circumstance, but because of physiological conditions, Maximum of 
 that civilization arose in Egypt and in the Mesopotamian J^falntbTovm 
 countries. It was for a like physiological reason that it races. 
 spread next through the nations on the north shore of the Mediterranean, 
 and never spontaneously originated in Arctic Europe or Tropical Africa. 
 
 Moreover, it must be observed how forcibly the doctrine here urged of 
 the passage of man from one complexion to another, and Disappearance 
 through successively different forms of skull in the course of of the red-hair- 
 ages, is illustrated by the singular circumstance to which at- e yed people in 
 tention has of late years been directed, of the gradual disap- Eur P e - 
 pearance of the red-haired and blue-eyed men from Europe. Less than 
 two thousand years ago, the Homan authors bear their concurrent testi- 
 mony to the fact that the inhabitants of Britain, Gaul, and a large portion 
 of Germany were of that kind. But no one would accept such a descrip- 
 tion as correct in our times. By some writers, who have not taken en- 
 larged physiological views, this curious circumstance has been attempted 
 to be explained on the hypothesis of a more prolific power of the brown 
 or black haired and darker man. That this is correct not a shadow of 
 evidence can be offered. The supplanting of the red by the black haired 
 man is neither on account of any insidious or involuntary extermination, 
 nor because of the numerical pressure alluded to. The true Cause of thig 
 reason is that the red-haired man has himself been slowly apparent dis- 
 changing to get into correspondence with the conditions that appea 
 have been introduced through the gradual spread of civilization condi- 
 tions of a purely physical kind, and with which the darker man was more 
 nearly in unison ; for though it might be shown that the climate of 
 Europe, by reason of the removal of forests, and other causes, chiefly agri- 
 cultural in their nature, has undergone a change, this is nothing compared 
 with the changes that have been accomplished in domestic economy by 
 better clothing, and more comfortable lodging and food, and these are par- 
 allel to actual changes in climate. What a contrast between the starved, 
 naked, and almost houseless peasant-savages of the times of Ca3sar, and 
 the well-fed, well-clothed, and well-housed agricultural laborers or manur 
 facturing operatives of ours, who, though they may be living in the same 
 geographical region, are literally in a warmer and more genial climate a 
 climate with which man is only in correspondence when his skin is of a 
 darker shade, and his hair of a brown or black color ! 
 
 From these investigations of the anatomical peculiarities of the nations 
 of men, we may turn to those of a mental kind, which, in- O f the intellect 
 deed, are derivatives thereof. Doubtless the intellectual uai qualities of 
 qualities are manifested in the expression of the countenance natlons - 
 and in the capacity and. form of the skull. 
 
 Considering, for the sake of convenience, groups of nations as they 
 
592 MENTAL QUALITIES OF THE EUKOPEAN AND ASIATIC. 
 
 are distributed geographically, though, as we have seen, this is a divis- 
 ion which has no philosophical foundation, we may proceed to an exam- 
 ination of the psychical state of the European and Asiatic, whose history 
 furnishes us abundant materials for this purpose. The black nations of 
 Africa and the red tribes of America, from the imperfect advances they 
 have made toward civilization, can supply but few facts for such an in- 
 vestigation. 
 
 We can not read the histories of Europe and Asia we can not exam- 
 Synthetical me the present condition of those continents, without coming 
 mind of the to the conclusion that the people inhabiting them possess a 
 lyticai mind of different mental constitution. After what has been said re- 
 the European. S p ec ting the influence of physical circumstances on the or- 
 ganization of man, it is unnecessary for us to inquire here in what that 
 difference has originated. It is, perhaps, most significantly expressed 
 if we say that the mind of the Asiatic is essentially synthetic, that of the 
 European analytic. The former is the creator of systems of theology, 
 law, science, some of which have endured for thousands of years, and 
 have been adopted by a large portion of the human race. The latter 
 pursues his course in a way less grand, but which, since it has a better 
 ascertained foundation, leads to more certain, and, in the course of cen- 
 turies, will show more powerful, widespread, and equally lasting results. 
 The intellectual peculiarity of the Asiatic has been attended with the ad- 
 vantage of producing an almost definite social state. In Asia the cus- 
 toms remain invariable ; every thing is in a state, as we might term it, 
 of stagnation, or, as they consider it, of repose. On the other hand, the 
 analytical tendency of the European has led to the intellectual and polit- 
 ical anarchy of our times, when fundamental doctrines of every kind are 
 called in question, and scarcely two men can be found whose views on re- 
 ligious, political, and social questions coincide. In Asia there are no 
 questions, but only affirmations. Europe, except when the Church for 
 a thousand years enforced the Asiatic system, has ever been prone to ask 
 questions. Since the fourteenth century, when she returned to this pro- 
 pensity, she has been passing through a chaos of doubt in the innumer- 
 able answers she receives. 
 
 With an intellect of this analytical kind, it may be doubtful whether 
 Necessity of the European could ever have spontaneously entered on the 
 Europ^aiTdv- career f civilization. The contact of the Asiatic was essen- 
 iiization. tial to him, as giving him the material on which to work. 
 Nor was it of importance whether the basis from which he thus started, 
 and the additions which, from time to time, he has received, were true or 
 false ; they furnished him with the essential condition that was wanting. 
 The dissector must have his subject. The history of Europe, whether 
 as regards philosophical, religious, or political affairs, bears the impress 
 
INFLUENCE OF EUEOPE AND ASIA ON AFKICA. 593 
 
 of the analytical mind of the white man. In Asia, on all these points 
 they tend to the homogeneous. In Europe, every day makes us more 
 and more heterogeneous. 
 
 Thus compared with that of the Asiatic, it can not be denied that the 
 mind of the European is of the higher order. Moreover, though Comparison 
 our moral qualities are not equal to our intellectual, the man- J^Euro^ean 
 ner in which we act in the conditions in which we are placed intellect, 
 asserts our superiority even in that regard. The instances are many in 
 which we do not dare to cany our convictions into execution, and each 
 of these illustrates the inequality here set forth. To "be content with the 
 chances of things, to suffer the events of life uncomplainingly, is surely 
 not so worthy a character as to demand a reason, and to accept the con- 
 sequences of resistance. 
 
 The intellectual superiority of the European over the Asiatic is strik- 
 ingly illustrated by their relative power over the African, who Th . 
 is confessedly, in this respect, beneath them both. To go no ive influence 
 farther back than the last ten centuries, both have, in their on Afnca - 
 special way, exerted their influence. Here and there, on the outskirts 
 of that great continent, the European has made a faint, but, at the best, 
 only a transitory impression : the Asiatic has pervaded it through and 
 through. Of the promising churches, which, in the early days of Chris- 
 tianity, fringed the northern coast, scarce any vestige now remains ; the 
 faith of Arabia has not only supplanted them, but is spreading even to- 
 ward the Cape of Good Hope, and this, as it would appear, spontaneous- 
 ly. On the other hand, the European, with that universal charity which 
 is his noblest attribute, has spared no exertions and no expense to dif- 
 fuse the blessings which have been conferred by Providence upon him ; 
 and yet it would seem to be in vain, though enforced by the great exam- 
 ple of his civilization and power. In this we see the affinity of the mind 
 of Africa with that of Asia, of which it is an exaggeration, and its incon- 
 gruity with that of Europe. It can not, in its present state, appreciate 
 our manner of thinking ; it can not embrace our conceptions of truth, but 
 delivers itself unresistingly to the dogmas of the East, with all their er- 
 rors of faith and all their imperfections of polity. * 
 
 Since I have been drawn into a psychical comparison of the Asiatic 
 and European in the foregoing particulars, it may not be p ositionof 
 amiss to consider the two races in another important respect, women in Asia 
 the condition of their females. In the barbarous state, the a 
 woman is the slave of the man ; the Mohammedan makes her his toy, the 
 European his companion. The avarice of the former for beauty is re- 
 placed in the latter by an avarice for wealth. The treasures of the one 
 are placed in a harem ; those of the other are perhaps invested in the 
 public stocks. 
 
 PP 
 
594 POLYGAMY AND MONOGAMY. 
 
 The natural position of the female sex in this respect is indicated at 
 once by the relation of numbers. In Europe, for every 106 male births 
 there are 100 female, and as the sex of offspring is influenced by the 
 relative ages of the parents, the older parent giving a tendency to its own 
 sex, we may reasonably suppose that in the infants born of polygamy 
 the males will preponderate, reversing the result which is observed in the 
 great cities of Western Europe, in which the ratio of female births rises 
 above its true mean by nearly four per cent, when those births are ille- 
 gitimate. In that term of the market, four per cent., what a volume of 
 information is here conveyed ! It tells us that the European female does 
 not fall at once ; that there intervene years of resistance to temptation, a 
 struggle of virtue against penury and distress, but it also reveals the 
 precocious wickedness of man ! 
 
 Considering, therefore, the near equality of male and female births, we 
 may truly assert that monogamy is the proper condition of our species, 
 and that, apart from its social evils and criminality, polygamy is an un- 
 natural state. I shall pass, as unworthy of notice, the assertion of those 
 who, in this Christian country, practice so shameful a vice, that we might 
 as well divide the number of square acres on the face of the globe by the 
 number of its inhabitants, and declare it to be immoral in any one to 
 possess a larger estate than corresponds to the quotient thereof. Ac- 
 knowledging the natural depravity of the human heart, I accept with 
 humiliation the rebuke that the most enlightened communities exhibit 
 in these respects a deplorable spectacle, and that the vices of the Mo- 
 hammedan harems find their full counterpoise in the general, the awful, 
 and, in many places, the legalized prostitution of Christian cities. 
 
 Europe has adopted as the fundamental basis of its religious: system 
 Effects of o- *ke S ran ^ Asiatic truth of the unity of God, but in its family 
 lygamy and system it has rejected the immemorial and widespread Asi- 
 mogamy. ^^ p ract j ce O f polygamy. That circumstance has made it 
 what it is. The monogamous habit has tended to draw the family tie 
 more firmly, and has led to the accumulation and transmission of wealth 
 from generation to generation in the same house. "With this have arisen 
 a liability to concentration of power in castes, and the use of surnames 
 which have perpetuated family interests and family pride. In Europe 
 the career of improvement is in the society ; in Asia it is in the individ- 
 ual ; the unknown, starving, illiterate, but strong-willed soldier of to-day 
 is the Pasha, the Caliph, the Emperor to-morrow. The castes of India 
 The respective form but a trifling exception to the fact that, in the midst of 
 STandEu- a uinversa l despotism, the primest democratic element is 
 rope. concealed, for the career is open to talent. Through this, 
 
 Asia has asserted her superiority again and again. Europe has never 
 produced a great lawgiver ; Asia has produced many. Generations of 
 
ASIATIC CONTRIBUTIONS TO CIVILIZATION. 595 
 
 three hundred millions of men have followed the maxims of Confucius for 
 two thousand years, three hundred millions are the followers of Moham- 
 med. The faiths which govern the daily life of two thirds of the human 
 race may well be an awful spectacle to us the more awful because we 
 know that they are a delusion. The only approach to these great results 
 in the Western Continent is in the supremacy of the Italian Church ; but 
 Rome owed the origin of her system to Asiatic missionaries ; nor was it 
 the completed work of the hand of one man, it was the offspring of cen- 
 turies, the joint issue of a long line of illustrious sacerdotal kings. In 
 military life the highest qualities shine forth. If the talent for command 
 and the capacity of a statesman are to be measured by the grandeur of un- 
 dertakings and their success, it still remains for Europe to produce a sol- 
 dier the equal of Genghis Khan, and a king like Tamerlane. These great 
 captains held almost all Asia in their iron grasp. The opinions we com- 
 monly hold respecting these illustrious men have come to us through 
 perverted channels. Such prodigious successes as theirs imply the high- 
 est intellectual powers. Their true character appears when we compare 
 them with their European contemporaries. At the same time that 
 Charles VII. of France was mystifying his people with the imposture of 
 Joan of Arc, and Henry VI. of England was engaged in the burning of 
 necromancers who had attempted his life by melting an enchanted wax 
 image before the fire, Ulug Beg, the grandson of Tamerlane, was de- 
 termining with precision the latitude of Samarcand, his capital, with a 
 mural quadrant of 180 feet radius, and making a catalogue of the stars 
 from his own observations, which more than 200 years subsequently was 
 printed at the University of Oxford. 
 
 If the European wishes to know how much he owes to the Asiatic, he 
 has only to cast a glance at an hour of his daily life. The Contributions 
 clock which summons him from his bed in the morning was * Em-^ean 
 -the invention of the East, as were also clepsydras and sun- civilization, 
 dials. The prayer for his daily bread which he has said from his in- 
 fancy first rose from the side of a Syrian mountain. The linens and 
 cottons with which he clothes himself, though they may be very fine, are 
 inferior to those which have been made time immemorial in the looms of 
 India. The silk was stolen by some missionaries, for his benefit, from 
 China. He could buy better steel than that with which he shaves him- 
 self in the old city of Damascus, where it was first invented. The cof- 
 fee he expects at breakfast was first grown by the Arabians, and the na- 
 tives of Upper India prepared the sugar with which he sweetens it, a 
 schoolboy can tell the meaning of the Sanscrit words sacchara canda. 
 If his tastes are light, and lie prefers tea, the virtues of that excellent 
 leaf were first pointed out by the industrious Chinese. They also 
 taught him how to make and use the cup and saucer in which to serve 
 
596 ASIATIC CONTRIBUTIONS TO ART AND SCIENCE. 
 
 it. His breakfast- tray was lacquered in Japan. There is a tradition 
 that leavened bread was first made of the waters of the Ganges. The 
 egg he is breaking was laid by a fowl whose ancestors were domesticated 
 by the Malaccans, unless she may have been, though that will not alter 
 the case, a modern Shanghai. If there are preserves and fruits on his 
 board, let him remember with thankfulness that Persia first gave him 
 the .cherry, the peach, the plum. If in any of those delicate preparations 
 he detects the flavor of alcohol, let it remind him that that substance was 
 first distilled by the Arabians, who have set him the praiseworthy exam- 
 ple, which it will be for his benefit to follow, of abstaining from its use. 
 When he talks about coffee and alcohol, he is using Arabic words. A 
 thousand years before it had occurred to him to enact laws of restriction 
 on the use of intoxicating drinks, the Prophet of Mecca had accomplish- 
 ed the same object, and, what is more to the purpose, has compelled, to 
 this day, all Asia and Africa to obey it. We gratify our taste for per- 
 sonal ornament in the way the Orientals have taught us, with pearls, ru- 
 bies, sapphires, diamonds. Of public amusements it is -the same : the 
 most magnificent fireworks are still to be seen in India and China ; and 
 as regards the pastimes of private life, Europe has produced no invention 
 Asiatic contri- which can rival the game of chess. We have no hydraulic 
 buttons in art. constructions as great as the Chinese canal no fortifications 
 as extensive as the Chinese wall ; we have no artesian wells that can at 
 all approach in depth some of theirs ; we have not yet resorted to the 
 practice of obtaining coal-gas from the interior of the earth : they have 
 borings for that purpose more than 3000 feet deep. 
 
 Similar observations may be made if we examine the Asiatic contribu- 
 Asiatic contri ^ ons to sc i ence While the learned of Europe were forbid- 
 butions in sci- ding, as a heresy, the doctrine of the globular figure of the 
 earth, the Caliph Al Maimon was measuring the length of a 
 degree along the shore of the Eed Sea. He and his successors repeat- 
 edly determined the obliquity of the ecliptic. A Saracen constructed the 
 first table of sines, another explained the nature of twilight, and showed 
 the importance of allowing for atmospheric refraction in astronomical ob- 
 servations. Algebra itself was invented and brought into Europe by the 
 Mohammedans, who gave it the name it bears. The same may be said 
 of chemistry. It is needless to pursue these statements, for whoever will 
 take the trouble to look into the history of any branch of science existing 
 in the seventeenth century will find how deep are its obligations to Asia. 
 I shall therefore add but one fact more, the invention of the figures of 
 arithmetic, which in reality gave birth to that science, and laid knowl- 
 edge and commerce equally under obligations. From its simplicity, 
 beauty, and universality, this invention alone is enough to command the 
 gratitude of the human race. The manner of using the cipher and 
 
SPEEAD OF MOHAMMEDANISM IN AFEICA. 597 
 
 placing the figures is one of the happiest suggestions of the genius of 
 man. 
 
 I shall not set in contrast with these statements a catalogue of the 
 contributions of the European. We know our own doings well enough ; 
 but such facts as the preceding may serve to remind us that the Euro- 
 pean is no more justified in ignoring the obligations he is under to the 
 Asiatic than the Asiatic is justified in regarding him as a barbarian. 
 In the advance of our common humanity, both have taken and still are 
 taking their share. The European has brought to the new continent he 
 discovered his religion, his laws, his literature, his science, and it may be 
 a profitable subject of reflection to him that under them the Indian is dy- 
 ing away. The Asiatic has likewise carried the Koran into The g rpad of 
 Africa. Our prejudices and education ought not to conceal Mohammedan- 
 from us that there must surely be some adaptedness, even lsm 
 if it be in a sensual respect, between its doctrines and the ideas of many 
 climates, many nations, many colors. The light of the Arabian crescent 
 shines on all countries from the Gulf of Guinea to the Chinese wall. In 
 those pestilential and sun-burnt forests under the equinoctial line, cit- 
 ies are springing up with their ten, their twenty, their fifty thousand in- 
 habitants. That implies subordination, law, civilization. It may be 
 that this is not a course of events which would have been chosen by 
 the French on the north, with their military colonies ; the English on the 
 south, with their commercial establishments ; the Americans on the west, 
 with their political institutions ; but it is the course of Providence. Let 
 us be thankful if the African is rescued from the abyss of barbarism, and 
 brought to a knowledge of our higher morality and holier religion, as 
 brought he will be at last, even though it be by the hand of the Prophet. 
 
 In the following chapter I shall have some remarks to make respect- 
 ing the manner in which the civilization of Europe was ac- p ectiv 
 complished, and shall offer reasons for supposing that its es- civilization of 
 sential condition was a physiological change in the inhabit- 
 ants. Without troubling the reader with details, I may here incident- 
 ally observe that the spread of Mohammedanism in Africa is altogether 
 owing to its having been introduced in the right direction. It appears to 
 me hopeless to attempt the amelioration of that continent from its west- 
 ern shore. Whatever is done must be done from the East. In power 
 of intellect, and in a disposition to appreciate our civilization, the inhab- 
 itants of the countries bordering on the Red Sea are far superior to 
 those on the Atlantic. It does not seem well to begin with those who 
 are the least prepared. We do not commonly expect success from 
 operations conducted at an eccentric point. The Koran has spread be- 
 cause it has availed itself of the great lines of trade, which reach from 
 the Red Sea to the interior of the continent; it has spread, not because 
 
598 SPREAD OF CHRISTIANITY IN AMERICA. 
 
 of its doctrinal theology or theoretical politics, but because it is concern- 
 ed in the amendment of the social condition of the people. That is pre- 
 cisely the principle which accomplished the civilization of Europe ; and, 
 with regard to the capacity of those nations to receive Christianity, we 
 may, even to our shame, recall the circumstance that the Abyssinians are 
 yet a Christian people, still retaining the ancient faith delivered to them 
 in the apostolic ages, when our forefathers were pagan barbarians. Sur- 
 rounded by the most depressing and antagonizing influences, they have 
 held fast to their faith for nearly eighteen centuries. The hoary Abys- 
 sinian Church carries us back beyond the Council of Chalcedon and the 
 disputes of the Eutychians ; its literature is full of the questions which 
 exercised the faithful in the primitive times of the brethren at Jerusalem 
 circumcision, things strangled, meats prohibited by the law of Moses ; 
 and yet, to the discredit of the European and American, it must be said 
 that this Church, full of incidents of the most singular and touching in- 
 terest, has scarcely had (with one exception) any sympathy extended to 
 it by other Christian people. 
 
 From these considerations of the effects of Asiatic civilization upon 
 Spread of Africa, we may profitably turn to a brief statement of that of 
 ^/t^Amer" Eur P e u P on tne red races of America. This result in the 
 icas. two continents, north and south, is, that in the latter, out of 
 
 almost 1,700,000 aborigines, nearly 1,600,000 have embraced Christian- 
 ity, less than 100,000 remaining in the savage state. No such favorable 
 impression has been made upon the aborigines of the northern continent, 
 who, as is well known, are steadily diminishing in numbers, and many 
 tribes that were once numerous have disappeared. This has taken place 
 notwithstanding the care which has been manifested by the government 
 of the United States for all those who are within its territories. It does 
 not appear that the conclusion which has been drawn by some eminent 
 authors in view of these facts can be maintained, that " this considera- 
 tion, if we can separate it from the events of the Spanish conquest, for 
 which it is to be hoped that the soldiers, and not the ministers of relig- 
 ion, are responsible, must be allowed to reflect honor on the Eoman Cath- 
 olic Church, and cast a deep shade on the history of Protestantism." 
 
 That this conclusion is incorrect is shown at once by the very tables 
 that are relied on for its support. Out of the 100,000 aborigines of 
 South America who remain heathen, more than 66,000, that is to say, 
 two thirds, belong to the Araucanian and Patagonian branches, who are 
 the counterparts for that continent of the Indians of the United States 
 and British American territories in this. Upon these it may be truly 
 said that no impression whatever has been made: Of the Patagonian 
 branch, estimated at more than 32,000, only 100 individuals are stated 
 to have embraced Christianity, and of the Araucanian branch, consisting 
 
EFFECT OF CLIMATE ON CIVILIZATION. 599 
 
 of 34,000, not one. It is by bringing into these discussions the singu- 
 lar and widespread error that all the aboriginal American tribes are 
 alike, and by not making due allowance for their habits of life, their 
 physical and mental endowments, that this mistake has arisen; but 
 whoever will consider the facts as they actually stand must come to the 
 conclusion that there are just as well-marked differences among these 
 people as there are in the climates and circumstances in which they live. 
 Intellectually, there is even a greater difference between the Indian of 
 the United States and the Indian of Peru than there is in their physical 
 aspect. The one is an intractable savage, the other docile and easily 
 led; the one has never yet been enslaved, the other prospers and in- 
 creases in number, though he has sustained all the consequences of the 
 atrocities of the Spanish Conquest. By chance, or perhaps, as we should 
 more truly say, through Providence, the field of Catholic labor has been 
 among the more docile races, that of Protestant among the more untam- 
 able, and the result is exactly such as, under those circumstances, the 
 philosopher would be led to expect. 
 
 I can not here avoid recalling to the attention of the reader what I have 
 said respecting the comparative progress of Christianity and Mohammed- 
 anism in Africa, for we find upon our own continent a repetition of the 
 facts which were presented to us there. The chances, if such a term can, 
 on this occasion, with propriety be used, of the diffusion of Christian civ- 
 ilization, are directly proportional to the existing intellectual development 
 of the community among whom the attempt is made. Mohammedanism 
 has diffused itself in Africa for precisely the same reason that Catholi- 
 cism has succeeded in America because its operation was commenced 
 upon those tribes best prepared to receive it. 
 
 We can not have a more striking instance of the effect of climate on 
 civilization than that which is offered by the American In- Illustration of 
 dians. As is well known, though throughout all those lati- 
 tudes in which life is maintained with difficulty, by reason iiizatkm. 
 of their inclemency, all the tribes, both of the north and south continent, 
 were in a barbarous state, yet in those more pleasant countries toward 
 the equator, in which, by reason of the natural fertility of the soil and a 
 higher mean temperature, the inhabitants had little occasion to work, and 
 passed their lives in comparative plenty and ease, a special civilization 
 had arisen. It is of no little interest to observe how the main features 
 of Asiatic and European civilization were presented in this case, doubt- 
 less without any communication with those continents, for it shows how 
 the human mind is ever prone to unfold itself in the same way, to give 
 birth to the same ideas and to the same inventions. The . .,. 
 
 Civilization of 
 
 civilized Americans of Mexico and Peru were organized in the tropical in- 
 communities not unlike those with which the white man is dians * 
 
(300 EXTINCTION OF THE INDIANS. 
 
 elsewhere familiar, living in cities which were regulated by municipal 
 laws familiar enough to us, maintaining among their social institutions, 
 fixed ideas respecting property and family rights, having a national relig- 
 ion, an established priesthood, and the means of recording events, which, 
 though imperfect, were not unlike those which obtained in the earlier pe- 
 riods of our own civilization.. If they had not a knowledge of iron and 
 the plow, they had already fallen upon the early Asiatic plan of subju- 
 gating and domesticating such animals as were suitable for their pur- 
 poses. Civilization arose among these people in similar localities and 
 under similar circumstances of life as it had arisen among our ancestors 
 in the Old World, and, such is the sameness of constitution of the human 
 mind, was advancing in exactly the same way. 
 
 Although, for a time, among the degenerate descendants of the Span- 
 Gradual ex- iards, the South American Indian may maintain himself, but 
 tinction f the little doubt can be entertained that the same destiny awaits 
 temperate him which has befallen his North American brother. He 
 
 zone. 
 
 can not withstand that enterprise and activity which are 
 leading to the extension of the white invaders of his native soil. Even 
 though the age of cruelty to these unfortunates has passed away, never 
 more to return, and enlightened governments, animated by sentiments 
 into which no mercenary consideration enters, interest themselves in their 
 welfare, it is not to be supposed that nations depending on such an arti- 
 ficial support can long continue to exist. In this inevitable decline, the 
 tropical races may far more worthily excite our commiseration than those 
 of the higher latitudes ; nor is their departure unavenged : they leave 
 behind them two curses, tobacco and syphilis. 
 
 In conclusion of this partial examination of the progress of the human 
 Manner of family under varied circumstances, we may remark a repeti- 
 natlo^rin^v- ^ on ^ a ^6 series of changes to those which have been 
 ilization. traced in the psychical career of the individual, and this, 
 whether we consider the progress in theology, policy, philosophy, or any 
 other respect. It is a continued passage from the general to the special 
 from the homogeneous to the heterogeneous. The history of any of 
 the ancient nations might be brought forward as an example. Emerging 
 from the barbarous state, they shake off their Fetichism, that union of 
 the supernatural with the natural, which gives to every wood, every tree, 
 every river, its presiding genius ; to families, their Penates ; to the city, 
 and even to the road, their Lares ; to stars, and to stones, and to med- 
 icines, their spirits ; to the night, its apparitions and fairies. It is in 
 vain that we say these are the subjects of African credulity. They are 
 found in the origin of all people. Our forefathers once cherished the il- 
 lusions which still occupy the negro mind. The time came when intel- 
 lectual development outgrew such base superstitions, and for a crowd of 
 
PROGRESS OF CIVILIZATION. 601 
 
 imaginary inanities were substituted the chosen forms of Polytheism. It 
 is true that, among Egyptians, Hindoos, or Greeks, there were deities 
 enough, but the process of specialization may be nevertheless plainly dis- 
 cerned. The Fetich stage, the Polytheistic stage, are necessarily in- 
 cluded in the onward progress to a pure metaphysical Monotheistic con- 
 ception. In this it is to be remarked that the Asiatic races Their religious 
 of men have led the way, both in the priority and strictness P ersu asions. 
 of their views. The great statesmen of China, of India, of Arabia, and 
 of Judea, centuries ago, seized upon this as the pivot of their intellectu- 
 al and even political systems. To the last country, Europe itself, as 
 history proves, is indebted for this noble idea. 
 
 European Monotheism is not indigenous, but imported from the He- 
 brews, an Asiatic race. The intellectual condition of the nations among 
 whom it was introduced was but little advanced, and hence among some 
 it came to be degraded mixed up with the remains of popular and an- 
 thropomorphic conceptions, which otherwise were gradually dying out. 
 For a length of time the pagan creeds maintained a conflict with it, and 
 with difficulty it disentangled itself from the base features w T hich they 
 endeavored to impress upon it, as with the Hebrews themselves of old, 
 the people seemed to be reluctant to surrender altogether their Polythe- 
 istic ideas. 
 
 These remarks are to be understood as not applying to individuals, 
 for in every age and nation great men have arisen, whose views on these 
 and other subjects of like vital importance were far in advance of their 
 times. In their best days, both in Greece and Kome, there were men 
 who had attained to the standard here alluded to, but their teaching was 
 without effect on the popular mass. There was a want of equivalency 
 between the individual attainment and the race attainment. Though 
 individuals may be progressive, races are essentially conservative ; and 
 hence there will constantly arise against individual attempts at an ad- 
 vance discountenance and resistance, an opposition which in too many 
 instances becomes a tyranny. Masses of men are not like inorganic mass- 
 es, which resist a change by their inertia alone. The biography of ev- 
 ery great reformer shows that the popular mind resents any disturbance 
 of its repose. [Resistance has to be overcome in the moving of things, 
 resentment is added in the moving of men. 
 
 To the philanthropist it is a most delightful spectacle that the various 
 nations, in spite of the difference of their interests, their Existence of a 
 creeds, and their politics, can yet present certain great prin- ^iTty wit'dis- 
 ciples which they recognize in common, and this is becom- cordant creeds. 
 ing more and more marked with the onward advance of the world. In 
 the course of events, the special is ever coming out of the general, and 
 the great principles of a common morality are gradually disentangling and 
 
602 SOCIAL MECHANICS. 
 
 unfolding themselves from contradictory forms of faith. The Chinese, 
 the Hindoo, or the Turk, though they may not coincide with the Amer- 
 ican or European as to what is to be looked upon as true, will yet agree 
 as to what is just. The sentiment of honor, the ideas of personal integ- 
 rity, are fast becoming universal. 
 
 Yet even in these later ages, there is in this respect nothing new. The 
 tendency of the human mind, whether individual or collective, to the same 
 direction is continually manifest a premarked and predestined course 
 in which it must go. Our most refined notions of rectitude contain noth- 
 ing more than is to be found in the little epitome of the ancient lawgiv- 
 er; for if we strike from the ten commandments \vhatever is explanatory 
 or threatening, retaining the mandatory parts alone, there remains what 
 commends itself to the understanding of intelligent men even of the 
 most diverse nations the acknowledgment of the unity of God, the ven- 
 eration due to him, the expediency of a day of rest for the laborer, the 
 duty of filial affection, the enormity of murder, the sin of adultery, the 
 crime of stealing, the shame of lying, and a strict regard for the property 
 of another : these are things which exact for themselves a spontaneous 
 and universal assent. 
 
 CHAPTER VIII. 
 
 SOCIAL MECHANICS. 
 
 Comparative Sociology. Connection of Structure and Habit. Connection of History and Phys- 
 iology. Insect Society. Descartes 's Doctrine that Insects are Automata. Necessity of a 
 Mechanism of Registry for Instinct, Reason, and Civilization. 
 
 Nature of Man. Influence of surrounding Circumstances on him. Deflniteness of his Career. 
 
 GENERAL FACTS OF EUROPEAN HISTORY. Introduction of Egyptian Civilization into Europe. 
 The Registry of Facts by Writing. Egyptian Philosophy in the Greek Schools. The Persian 
 Empire : its Influence. Analytical Quality of the European Mind. Influence of the Greek 
 Schools on modern Philosophy. 
 
 Origin of European Commerce. Discovery of the Straits of Gibraltar. Macedonian Campaign. 
 Reconstruction of Monarchy in Egypt. 
 
 The Roman Empire: its centralizing and civilizing Power. Fall of European Paganism. In- 
 fluence of the Christian Church. The Sabbath Day. The Reformation. 
 
 Influence of Mohammedanism on Europe. The Arab physical Science. TJie Crusades. Dis- 
 covery of America by the Spaniards. Fall of the Spanish Power. 
 
 Later Mental Changes in Europe. Disappearance of Credulity. Physiological Change of Eu- 
 ropeans. Effect of Mohammedanism in changing the Centre of Intellect of Europe. Analyt- 
 ical Tendency of the European Mind. Advantages resulting therefrom. 
 
 HAVING described man as an individual, we have next to consider him 
 
 Dependency of * n m ' s soc ^ relations ; for so closely are his actions connect- 
 
 sociai career on ed with his organization, that it may be said that universal 
 
 history is only a chapter of physiology. It is acknowledged, 
 
COMPARATIVE SOCIOLOGY. 603 
 
 even by those who have given but a superficial attention to the subject, 
 that there is a connection between corporeal development and historical 
 career ; that those races who have led the way in the course of civiliza- 
 tion, and those who still remain in the savage state, are characterized by 
 striking anatomical peculiarities, particularly in the size and development 
 of their cerebral hemispheres. Such general conclusions are strengthened 
 by our observations on the animal series, the lower members of which 
 offer together a sameness of structure and an identity in their course of 
 life. In those the metamorphoses of which have been stud- Structure and 
 led, it is always noticed that every change of structure is at habit in the 
 once/ollowed by a change of habit, yet, during the continuance case of msects - 
 of a given condition, their manner of life is without any variation. The 
 actions of one insect are for the most part the actions of another of the 
 same kind and in the same state, whether larva, pupa, or imago. But 
 in the midst of all this automatism there are, however, the glimmerings 
 of a free will. The animal world presents forcible illustrations on every 
 hand on the connection of structure and habit. 
 
 Philosophical views of human sociology are only to be attained by 
 treating that great problem in the same manner that we have comparative 
 learned to treat so many others in physiology. We must in- sociology. 
 elude in our discussion all other animal races, and not close our eyes to 
 the fact that there is such a thing as comparative sociology. We ob- 
 serve the republican propensities of the ant, the monarchical life of bees, 
 the solitary habit of other tribes. Is it not, at least in part, because of 
 cerebral peculiarities that one kind of bird is polygamous, and another 
 observes an annual or perpetual monogamy ; that the buffalo delights in 
 the society of his kind, but the lion will tolerate no neighbor ; that the 
 horse runs in herds, and adopts an organized system, submitting to a cap- 
 tain whose motions he follows ? We can not suppose that these habits 
 are the sole result of a present and immediately active external influence 
 which calls them forth ; an internal influence is also at work, an internal 
 influence dependent on organization. 
 
 A discussion of the problem of human sociology could, therefore, only 
 be completed after a study of the same problem in the entire animal se- 
 ries a task requiring varied and profound knowledge of natural his- 
 tory and comparative anatomy. Indeed, the present state of these sci- 
 ences does not enable us to accomplish it. The remarks I am about to 
 make are, therefore, of a very imperfect kind. The social problems pre- 
 sented to us by animals are a fitting introduction to the social problems 
 of man. 
 
 For the clearer understanding of what follows, it may Distinction be _ 
 therefore be observed that we may receive the term instinct tween instinct 
 as indicating a faculty incapable of improvement, and possess- 
 
604 COMPARATIVE SOCIOLOGY. 
 
 ed by each individual exhibiting it spontaneously, without experience 
 or imitation. The suggestions of instinct are often instantaneous and 
 always unvarying ; those of reason involve deliberation, and into them 
 the element of time enters. They also involve error. Animals which, 
 for a thousand years, nay, indeed, through all time, have never invented, 
 never improved, never varied, all of the same kind being equally skill- 
 ful, are to be considered as actuated by instinct, not by reason. Those 
 of which it may be said that they perceive, remember, think, compare, 
 and then form a judgment, are to be considered as possessing reason, and 
 this the more as they the more perfectly accomplish that end. In this 
 respect, man is approached by the quadrumana, the elephant, the. dog, 
 but the immense interval which separates him from them is at once in- 
 dicated by the fact that they appreciate only good and evil, so far as in- 
 volved in pleasure and pain ; but he contemplates equally the good, the 
 beautiful, and the true. 
 
 The historian may perhaps view with resentment an attempt on the 
 Connection of P art ^ P n y s ilgi sts * accomplish the annexation of the ter- 
 history and ritory in which he labors. With difficulty will he be brought 
 physiology. ^ o a j m ' t fae dogma that the history of men and of nations 
 is only a chapter of physiology. He doubtless will smile at the absurd- 
 ities of a doctrine which places under a common point of view the doings 
 of caterpillars, ants, and wasps, with the high resolves of senates and 
 emperors which undertakes to consider how, out of the most obscure, 
 the most august may proceed. 
 
 But it is none the less true that there exists a comparative sociology, 
 as well as a comparative anatomy and a comparative physiology. Struc- 
 ture, function, and career are all inseparably connected. 
 
 When we were considering, in a former chapter, the nervous mechan- 
 ism of insects, we saw how that, from the purely automatic, the volun- 
 tary is gradually produced by the development on the ventral cord of an 
 apparatus for the registry of impressions, the cephalic ganglia. These 
 registered impressions are the cause of the most surprising psychical re- 
 sults. 
 
 The action of barbarian communities is as purely automatic as the ac- 
 Barbarism and tion of an insect, which never had, or from which there have 
 civilization. k een rem oved, the registering ganglia. Irritate the decap- 
 itated wasp, it will sting. The uninjured wasp has a choice of action ; 
 it may possibly fly away. The action of civilized communities is of a 
 far higher kind : they are guided in what they do by experience. In the 
 progress of civilization there have arisen the means of permanently re- 
 cording past events. Such records influence us in deciding how we shall 
 act. They constitute knowledge. 
 
 If we may compare small things with great, is there not an analogy 
 
INSECT SOCIETY. 605 
 
 between the manner in which the registering mechanism of Analogy be- 
 
 an insect or other animal is evolved, and the manner in tween i 
 which the means of perpetuating and disseminating a knowl- ment and social 
 edge of events have arisen in human society ? The one, it is career - 
 true, appertains to individual life ; but is there any fact more clearly 
 made manifest by physiology than that of the parallelism of race life and 
 individual life, no matter how lowly that individual life may be? 
 
 An insect presents us with surprising actions, because it possesses 
 within itself the means of registering the events which occur in its little 
 circle. Nations act wisely and well, according as they are guided by 
 their store of experience. 
 
 If our pride can be so far overcome as to admit that in the history of 
 the life, even of an insect, the progress of mankind is shadowed forth, 
 that is to say, universal history is seen in a microscopic manner, it will 
 not be too much to hope that we shall then entertain physical or mechan- 
 ical ideas of the social career, that society advances in a definite way, has 
 its laws of equilibrium and movement, its centre of intelligence, its centre 
 of power, in short its statics and dynamics. 
 
 Though it is only one out of many instances that might be presented, 
 let us briefly consider social life in the inferior tribe to which reference 
 has been made ; let us also look at some of the individual peculiarities 
 of insects. Our sentiments of exclusiveness and pride may be corrected 
 thereby. 
 
 Insects form societies for mutual assistance, defense, invasion, emigra- 
 tion, mere pleasure societies which undoubtedly arise in 
 
 . /. T 1 T /. s^<* ,1 Insect society. 
 
 the experience ot passions, such as love and tear. Ut these 
 the duration is variable ; some last through the larva state only, some are 
 confined to the imago, some are maintained through life. The organiza- 
 tion by which their object is accomplished is various, monarchical, re- 
 publican. The caterpillars of the processionary moths are guided in 
 their march by a leader ; the termites obey at once a king and a queen. 
 The lust of power is not alone felt among human monarchs ; the queen 
 bee never rests till she lias assassinated her rival. All insects of the 
 same kind are not born equal, nor do all pursue the same occupation ; 
 some follow a life of leisure, some devote themselves to the profession of 
 arms, some are laborers. When the metropolis of the termites is attack- 
 ed, the laborers, as non-combatants, retire, but the soldiers come out. 
 The ants, with which w r e are more familiar, engage in military and filli- 
 bustering expeditions ; they make reconnoissances, set sentinels, march in 
 a definite order, the van alternately falling to the rear ; their lines of com- 
 munication are maintained, and, if necessary, swift couriers are disp&tch- 
 ed for re-enforcements. If successful, they not only carry off the ene- 
 mies' stores, but reduce the vanquished to actual servitude, compelling 
 
606 HABITS OF INSECTS. 
 
 them to work as slaves. They have notions of property, and, though 
 some of them practice cannibalism, they will amuse themselves in more 
 pleasant occupations, tumbling and playing together like kittens or pup- 
 Habits of pi es - With a sentiment of strict justice, the wasp who has re- 
 insects, turned from a successful foray divides his booty among the 
 males, females, and the laborers who have been working in the vespiary ; 
 nor is the sentinel, who is doing duty at the door, forgotten. If, through 
 the chances of war or by accident, any one has sustained a grave injury, 
 in some tribes the most devoted sympathy is shown : the ant will carry 
 his wounded friend out of the hot of the fight ; in other tribes a more 
 than Roman firmness is displayed : the sufferer is put out of pain by his 
 companion. Expecting an attack, some insects will shut their doors at 
 night, and barricade them within, or, if the danger is continual, will build 
 masked gateways in succession, with interior walls that command them. 
 They are no contemptible engineers. They can construct and maintain 
 roads of great length, with paths branching from them, which, if neces- 
 sary, they keep mown. They cross streams by throwing themselves 
 into floating bridges, and the damage done to their premises by an in- 
 vader they show the most singular skill and alacrity in repairing. How 
 many are the contrivances to which insects resort to carry out their pur- 
 poses ! The caterpillar of the cabbage butterfly makes a ladder and goes 
 up it ; the geometrical caterpillar lets down a rope, and, for fear of hurt- 
 ing himself, drops a foot at a time. The gossamer spider sends forth a 
 thread fine enough to act like a balloon, and, floating in the air, he de- 
 scends or rises by winding it up or letting it out. There are other in- 
 sects which make diving-bells, and go under the water. No bird makes 
 a net, no beast a pitfall : men and insects do both. A gang of sailors 
 will carry a spar by supporting it on alternate sides on their shoulders ; 
 a gang of ants will, in like manner, carry a straw or a long worm. There 
 are spiders which show as much dexterity as an Indian in sneaking for- 
 ward to get in reach of their prey. 
 
 In their domestic economy, how wonderful ! Some build their houses 
 of artificial stone, some of pasteboard which they make. Some cover 
 their rooms with tapestry, some lay carpets of silk on the floor, some 
 hang their doors on silk hinges, so that they shut by their own weight. 
 They make arches, domes, 'colonnades, stair-cases. They practice con- 
 cealment of food. Ray, an accurate observer and a very pious man, says 
 of a sand-wasp that it carried a caterpillar fifteen feet, removed a pellet 
 that closed the mouth of a hole, deposited its booty therein, came out, 
 and rolled the pellet back on the hole, scratched dust thereon like a dog, 
 went for rosin to agglutinate it, leveled the ground, and put two pine 
 leaves to mark the place. However much we may smile at this anec- 
 dote, it may satisfy us of the high opinion entertained of the accom- 
 
THE CEPHALIC GANGLIA. 
 
 607 
 
 plishments of insects by those who have been close observers of their 
 habits. 
 
 Dr. Laycock remarks, when speaking of the cephalic ganglia of insects 
 (Med. Chir. Rev., July, 1853) : " On what structures de- instincts of in- 
 pend, if not on these cephalic ganglia, all those wonderful Jj^? ^hanc" 
 instincts which mimic in their operation the arts of man? ganglia. 
 There is hardly a mechanical pursuit in which insects do not excel. They 
 are excellent weavers, house-builders, architects. They make diving- 
 bells, bore galleries, raise vaults, construct bridges. They line their 
 houses with tapestry, clean them, ventilate them, and close them with 
 admirably-fitted swing-doors. They build and store warehouses, con- 
 struct traps in the greatest variety, hunt skillfully, rob, and plunder. 
 They poison, sabre, and stab their enemies. They have social laws, a 
 common language, divisions of labor, and gradations of rank. They 
 maintain armies, go to war, send out scouts, appoint sentinels, carry off 
 prisoners, keep slaves, and tend domestic animals. In short, they are 
 mentally a miniature copy of man." 
 
 The surprising character of some of these facts might disappear were 
 we acquainted with what may be termed the spring of the action. It 
 has been said by Dr. Whateley that the building of a comb is like the 
 provisioning of a city, in which, through the desire of the dealers to get 
 wealth, is solved what is probably the most intricate of social problems. 
 It is done by no design of theirs, and yet they advance to it as if im- 
 pelled by gravitation or some other insuperable force. A printer may 
 put types together to get money without ever troubling himself about 
 the diffusion of knowledge. A bee may find gratification in what he is 
 doing without any concern about the final use of the comb. 
 Of the cephalic ganglia spoken of in the preceding paragraphs, Fig. 
 295 is an illustration from Mr. Newport, in the case of 
 the imago of the Sphinx ligustri : <z, cephalic ganglia ; , 
 , eyes ; <?, anterior median ganglia ; d, d, posterior lat- 
 eral ganglia of the stomato-gastric system ; Nervous system 
 e,f, large ganglionic masses in the thorax, f insects, 
 giving nerves to the legs and wings. It is Fig. 296. 
 to be understood that upon these ganglia 
 the voluntary action of insects depends. 
 They are the places of reception of the im- 
 pressions on the organs of special sense and 
 cephalic ganglia, the seat of memory. The automatic or in- 
 voluntary apparatus is in part seen at Fig. 296, which is the 
 thoracic portion of the nervous system of the pupa of the same 
 insect : <z, #, c, three ganglia of the ventral cord ; d, d, their 
 
 Thoracic portion 
 
 connecting trunks; e, , respiratory ganglia. The entire of ventral C0 rd. 
 
 Fig. 295. 
 
608 MEMOEY OF INSECTS. 
 
 nervous mechanism for the larva state has been shown in Fig. 126 ; for 
 the pupa, 127 ; for the imago, 128 ; from which it will be recognized 
 that the nervous system of insects, as they pass through their metamor- 
 Changes in the phoses, undergoes change. In the larva state, the nerves, as 
 nervous system they branch forth from the ventral cord, indicate by their uni- 
 mTtTmorp^o- formity the equality of the segments of the body. In many 
 sis - cases the cord is separated throughout its whole length into 
 
 its two constituent strands, and the cephalic ganglia are minute because 
 of the imperfect condition of the organs of sense. In the .pupa state 
 there is a general approach of the ventral ganglia, an increase of the 
 cephalic, and a thickening of the strands which connect that organ with 
 the suboesophageal. In the imago state the cephalic ganglia have still 
 farther increased to a size which corresponds to the great development 
 of the organs of sense ; the ventral ganglia appear to have coalesced in 
 the thorax. The general result of these changes during metamorphosis 
 is therefore to effect a concentration of the nervous centres in the head 
 and in the thorax, the ganglia of special sensation coalescing in the for- 
 mer, and those of motion in the latter region. We may remark that 
 these modifications strikingly illustrate the observation that change in 
 habits of life is always preceded by change of the nervous system. 
 
 Besides being the repository of the impressions of the special senses, 
 Seat of mem- tne cephalic ganglia discharge a function of a more general 
 ory in insects. an c[ most important kind, since doubtless they are the seat of 
 memory. That insects of the more elevated kind have the power of 
 recollection there can not be any doubt. If there were no other fact, 
 their recognition of their homes would be sufficient to establish this. A 
 thousand trivial incidents offer indirect, but instructive and interesting 
 proofs of the same thing. When a spider who has been disturbed feigns 
 death in order to avoid the cause of his alarm, he proves his capacity of 
 recollection, as also when he has been brought out from his concealment 
 by touching his web, and, discovering the nature of the imposition that 
 has been practiced upon him, refuses to come forth upon a repetition of 
 the trial. The quality which the cephalic ganglia thus possess of bear- 
 ing upon themselves the enduring traces of impressions received through 
 the sensory organs scarcely requires here to be more particularly exam- 
 ined. In the preceding book, in the chapter on inverse vision, various 
 facts have been mentioned which illustrate the faculty possessed by the 
 optic centres in man of retaining visual impressions for a considerable 
 period of time ; as, for instance, if, when we awake in the morning, our 
 eyes are directed to the bright window and then closed, a representation 
 thereof will still continue to be seen in its natural colors and relations, a 
 representation which gradually fades away; and, in like manner, the 
 cephalic ganglia register the impressions they receive from the optic, 
 
DESCARTES'S DOCTRINE. 609 
 
 the auditory, olfactive, and other nerves that pass to them, The ce halLc 
 and preserve the vestiges thereof; for, if this be not the case, ganglia are 
 it is wholly impossible to explain how insects should have the W8 ^ ef8f 
 power of remembering, even though it be indistinctly or imperfectly, 
 things that are past : those things or effects must have left upon them 
 an enduring mark. 
 
 The ganglia of the ventral cord, with their related nerve trunks, con- 
 stitute a series of automatic nerve arcs, their immediate ob- ... - .. 
 
 ' f Action oi the 
 
 ject being locomotion. As has been said, the impression of ventral cord 
 the surface upon which the insect rests gives rise, under or- a 
 dinary circumstances, to muscular contraction, and thereby motion, and 
 the same thing occurs under circumstances of unusual experimental dis- 
 turbance, as when irritation of any kind for instance, the pungent va- 
 por of ammonia is applied to one side of a centipede, the body is flex- 
 ed in such a way as to get rid, as far as possible, of the noxious fume. 
 These movements are purely reflex, and in their production the cephalic 
 ganglia are in no manner concerned. 
 
 Guiding and controlling these purely reflex operations, the cephalic 
 ganglia, by means of the fibres which they send in -company Controlling 
 with the trunks of the ventral cord, can exert their influence actl n of the 
 
 cephalic gan- 
 
 in the remotest part of the body. That influence we distin- glia. 
 guish as being of a twofold nature : in part it is due to impressions 
 which are being at that moment received through the various organs of 
 sense the eye, the ear, or whatever other such organ the insect under 
 consideration may possess, and in part arising from the residues of old 
 impressions which the ganglion has formerly received. It does not 
 therefore seem possible, at least as regards the more perfect of these 
 tribes, to accept the views of Descartes, who regarded all insects as mere 
 automata. They are automata only so far as the action of Descartes's 
 their ventral cord and that portion of their cephalic ganglia ^jg Vrctu- 
 which deals with contemporaneous impressions is concerned, tomata. 
 but they are not automata, since they are under the influence of those 
 ganglia as the registers of past impressions. 
 
 What has been said respecting insects applies to all higher tribes of 
 life. Man himself is no exception. In the preceding book we have shown 
 that, so far as his spinal nervous system is concerned, he is simply an 
 automaton, and that it is the development of a brain thereupon which 
 makes him capable of voluntary action. We have seen that in his indi- 
 vidual progress part is evolved from part, an ever-increasing complexity 
 and an ever-continuing improvement. Cerebral mech 
 
 It is the same, also, with the group to which he belongs anism in ani- 
 the vertebrates. Just in proportion to the advance of their 
 cerebral mechanism are their psychical powers. The amphi- powers. 
 
 QQ 
 
WRITING* AS A RECORD. 
 
 oxus, which has no cerebral hemispheres, represents the condition of man 
 when the action of his brain is suspended in sleep ; the fish, the reptile, 
 the bird, follow in an ascending order an order which man himself passes 
 through in his individual progress of development. 
 
 And man in the aggregate in society in the race does the same, his 
 
 historical career being a transcript of his individual career. Generation 
 
 after generation leads a purely automatic life, the life of barbarism ; but, 
 
 by degrees, there is evolved in such conditions the means of registry or 
 
 record. The acts and thoughts of one age can then be trans- 
 
 Writing is the ' . . c 
 
 means of record mitted to another, and can influence its acts and thoughts. 
 Civilization can not exist without writing, or the means of 
 record in some shape. 
 
 Writing once invented, the advance in society is again precisely as it 
 is in the individual. In part it is regulated by the physical circum- 
 stances around, in part by the interior the acquired principle. 
 
 In the superficial sketch which I intend now to give of the progress 
 of European civilization, there are certain facts which, from their promi- 
 nence, can not fail to arrest our attention. They are, 
 
 1. Europe remained in the barbarous state until it obtained the means 
 General facts ^ P er P etua ^ n S i^ eas ? tnat i g * Sa 7> until it learned the art of 
 
 of European writing. 
 
 2. The progress of civilization in Europe was attended by 
 an absolute physiological change in its inhabitants. They were brought 
 nearer to the condition of the inhabitants of a more temperate climate. 
 On this point, however, we have dwelt to a sufficient extent in the pre- 
 ceding chapter. 
 
 3. The European mind is analytic, that of Asia is synthetic. In Eu- 
 rope, the action in philosophy, in religion, in politics, tends to the inces- 
 sant decomposition of a thing into its parts, and their separate discus- 
 sion. The results of this tendency are seen in many of the practical social 
 difficulties of modern times. 
 
 Before entering on this, the conclusion of his work, the author may 
 recall by a few passing remarks the general views which have been in- 
 cidentally scattered through preceding pages respecting the nature of 
 man, the influence of surrounding circumstances over him, his social posi- 
 tion, the definiteness of his career, a definiteness which authorizes us to 
 treat his history, not as though it were composed of chance events, but 
 as a fitting subject for the contemplation of physiology. 
 
 Man is every where constructed upon the same essential type, and 
 hence, in one sense, he acts in an invariable manner, but that type passes 
 forward in development to many different aspects, and hence, in another 
 sense, he exhibits differences in his determinations and movements. 
 
 With the form and size of the brain, the intellectual capacity of man 
 
NATURE OF MAN. 611 
 
 varies. In a state of nature, his mental powers are in close relation with 
 the climate in which he lives, attaining their greatest perfection in the 
 wanner portion of the temperate zone ; but under the artificial condition 
 of civilization, in which the vicissitudes of the seasons are compensated 
 for by food, fire, shelter, and clothing, properly adjusted, he gains his 
 maximum development in a somewhat higher latitude. 
 
 After what has been said in the last chapter respecting the influence 
 of physical circumstances on the structure of man, producing modified 
 development in our typical form, and thereby giving rise to many dis- 
 tinct families, it will be anticipated that those circumstances must con- 
 sequently modify our mental operations, our manner of thinking and act- 
 ing, that is to say, must leave their marks on our history as nations. 
 For a long time this has been recognized in a general manner : the mount- 
 aineer thinks differently and acts differently to the native of the low- 
 lands ; he whose life is spent on the borders of the sea to him who lives 
 in the great plains in the interior of continents. But it is not to these 
 influences as operating by association on the individual that I now refer ; 
 it is rather to the profound effect they have had in producing a special 
 cerebral, and, therefore, mental organization in the course of many gen- 
 erations on races and nations. 
 
 Let us always remember that there is a common principle which un- 
 derlies the varied movements and determinations of men every where a 
 principle from which no one can disentangle himself. At the bottom of 
 even the most diverse actions it may be discerned, just as we can detect 
 the fundamental type of our organization under the most varied forms. 
 
 As from the physical point of view there is a standard man who, in 
 weight, height, strength, and other such like particulars, rep- 
 
 , 5 , r Nature of man. 
 
 resents the entire human family, so, in an intellectual point 
 of view, there is a standard man who, in mental progress, manner of 
 thinking and of acting, represents the whole race. There are also sub- 
 ordinate standards, the representatives of particular groups or nations. 
 It is to these standards that we are continually appealing in arriving at 
 a judgment of the acts of individuals. The special history of these 
 phases constitutes, in a philosophical sense, national history. The rec- 
 ord of the development of the fundamental type constitutes universal 
 history. 
 
 I have already remarked that universal history is only a chapter in 
 physiology. Since, by reason of the similarity of construction of the 
 cerebral apparatus, the actions of men will present a uniformity when 
 under the influence of similar motives or impulses, there is not only a 
 resemblance between such actions among different persons, influence of 
 but also it may be discerned when nation is compared with 
 nation, and race with race ; for the movements of communi- on him. 
 
612 CAREER OF MAN. 
 
 ties depend on the same motives as the movements of individuals, being 
 indeed the sum of individual determinations. But when multitudes and 
 masses are thus brought under our consideration, the element of free-will 
 seems for the most part to disappear, and events assume an air of pre- 
 destination. To this principle it is that history owes its chief value, and 
 truly becomes, as is often said, philosophy teaching by example. The 
 intelligent man who lived twenty centuries ago would doubtless have 
 come to the same decision which is reached by the intelligent man of our 
 times ; the same propositions being submitted to both, both guiding 
 themselves by similar principles to a like result. The logic of truth is 
 eternal, for it is the expression of the manner of action of our cerebral ap- 
 paratus, the type of which never changes ; and since there is thus no 
 essential change in the typical construction of man, and therefore none 
 in the manner of operation of his mental processes, since physical nature 
 Definiteness of i g unvarying, and the events of life spring one out of another 
 his career. j n a regular order or sequence, there must arise those same 
 analogies in the history of race compared with race, and nation compared 
 with nation, that are so obvious when individual is compared with indi- 
 vidual. Of every great future event there is therefore a past history, for 
 every such event has had its precedent in other histories, and therefore 
 its prognostic. Things will follow in a definite order so long as the in- 
 fluences of external nature are the same, and so long as the construction 
 of the human brain is the same. 
 
 The political foresight of the most eminent statesmen depends on a 
 gift of appreciating national mental types, like that possessed by great 
 sculptors or painters of appreciating a standard of beauty. It is this 
 which enables them to foresee the probable consequences of events, and 
 to realize the expected action of individuals, and even of masses of 
 men. In such actions there is far more uniformity than is commonly 
 supposed. The same general conditions which yield to the post-office 
 a definite percentage of misdirected letters every year which, with mar- 
 velous fidelity, give to the hospitals, the jails, the bills of mortality, their 
 expected numbers, operate from age to age, and in one nation as in an- 
 other, and hence arises that appearance of fate in the action of masses 
 to which we have alluded; hence also it is that the same cycle of 
 events re-occurs again and again, diversified, perhaps, but never essen- 
 tially changed by the influence of individual free-will. As the compar- 
 ative anatomist exhibits, in the different members of the living series, 
 their common points of resemblance that this organ in one animal is 
 the homologue of that in another, and this function the analogue of that, 
 so the philosophical statesman, acknowledging the essential principle of 
 comparative history, reasons from nation to nation and from age to age. 
 
PRIMITIVE STATE OF EUROPE. 013 
 
 CHIEF EVENTS IN THE CIVILIZATION OF EUROPE. 
 
 The Odyssey presents us a vivid picture of the state of Europe a 
 thousand years before the birth of Christ. A twilight was Euro e emer _ 
 breaking on the most eastern verge in the countries adjoin- ing from bar- 
 ing the Hellespont, but the West and the North were im- b 
 mersed in a night of barbarism. The unfolding mind is ever prone to 
 fill darkness with imaginary creations, and it was with the white race at 
 that period as it is with a child. Every shore of the Mediterranean 
 and Black Seas was full of prodigies. To the Greek no fiction was too 
 marvelous for belief if- it was separated from his view by a hundred 
 years or a hundred miles, the exaggeration of tradition confirming it in 
 the one case, and the difficulties of travel in the other. His horizon was 
 crowded with enchantresses like Circe, sorcerers like Tiresias, monsters 
 like the Cyclops. Gods and goddesses were perpetually flying through 
 the air ; every hill had its supernatural legend, every forest its phantom. 
 Even the mouth of hell was on the farther side of the Euxine. 
 
 A religion of superstition is very liable to be connected with a life 
 of evil works. The maritime enterprise of those days seems to have re- 
 ceived no little incitement from the temptations of piracy a profession 
 to which, even at a later period, the Greek appears instinctively to turn ; 
 nor were these felonious expeditions restricted to the taking of goods ; they 
 drew an additional profit from the stealing of men. The evidences of 
 even a still darker crime may also be discerned, since there were people 
 accused by common fame of eating the captives who fell into their hands. 
 The white man, therefore, emerges from his state of barbarism a pirate, 
 a slaver, a cannibal, cruel in his moment of power, and debased by an 
 incredible superstition in his moment of fear. 
 
 Unable to originate his civilization for himself, he drew the elements 
 of it from another country. By the concurring testimony of Civilizatio 
 all authors, as well as the internal evidences of ancient history, originated 
 that great blessing is the gift of Egypt. For thirty-four cen- X1 
 turies before our era that country was governed by dynasties of kings, 
 succeeding each other without interruption. Its soil, proverbially fer- 
 tile, sustained a population, estimated, in the most prosperous times, at 
 about seven millions ; and repeated military expeditions into Asia and 
 Ethiopia had, in the course of ages, concentrated in it immense wealth, 
 the spoils of conquered nations, and crowded with captives and slaves 
 the Valley of the Nile. 
 
 For this long continuance of the Egyptian polity satisfactory reasons 
 may be assigned. In early ages, when maritime expeditions Ancient condi- 
 were necessarily feeble, the country was open to invasion tion of Egypt, 
 only across a narrow neck of land on the east, and was protected from 
 any attack on the west by impassable and interminable deserts. Under 
 
614 THE EGYPTIANS. 
 
 the military system of remote antiquity Egypt was almost inaccessible ; 
 but through the changes of later times, and ever since naval expeditions 
 have been carried to any extent, her position has been that of extreme 
 weakness. The uniform experience of twenty-five centuries, from the 
 Persian wars to those of the French ^Revolution, has shown that the pos- 
 session of the mouths of the river is equivalent to the conquest of the 
 country. 
 
 In the security of this inaccessible retreat, and under political institu- 
 tions of a favorable character, the civilization which was to be conferred 
 on the white man originated. For a succession of centuries, industrial 
 art, and its parent, natural knowledge, appear to have undergone a steady 
 development ; perhaps, as in other countries at a later time, advancing in 
 the more prosperous political seasons, and becoming stationary in the 
 decay of the empire. The statements furnished to us by Greek authors 
 are of very little value, for as long a period of time intervened between 
 the first Egyptian kings and them as from them until now. It is rather 
 from the monuments of the Egyptians that we must judge. Each year 
 since their country has been open to investigation, and their hieroglyphic 
 system understood, the impressions we have received of their intellectual 
 advancement have been more and more favorable. The vocal statue of 
 Memnon at Thebes, it is said, emitted a musical sound when touched by 
 the rays of the sun. In the light of modern criticism, every obelisk and 
 monument in those desolated palaces is finding a voice. 
 
 The public works attest to this day the greatness and permanence of 
 Manners of the the Egyptian monarchy, and the peculiarities of the Egyp- 
 Egyptians. ^ian mind. From the statues and ruins of the temples of 
 the Greeks we see what a vivid perception that people had of the beauti- 
 ful. The statues, and tombs, and temples of the Egyptians offer a strik- 
 ing contrast ; the useful every where predominates. The vases of the one 
 were adorned with emblematical and graceful forms ; the tombs of the oth- 
 er were covered with sculptures and paintings, commemorating the ordi- 
 nary pursuits of life, and various processes in the arts and manufactures. 
 
 These sculptures and paintings show to what an extent the physical 
 sciences and arts depending on them had been cultivated. They set be- 
 fore us the domestic life and daily business and trades of the people : 
 cookery, confectionery, glass-blowing, weaving, pottery-making, manu- 
 facture of cotton, painting on wood and stone, staining of glass, and a 
 hundred other occupations. Among the pictured representations, a chem- 
 ist sees with pleasure the apparatus of his art, siphons, bellows, blow- 
 pipes, etc. 
 
 Shut up by its political system from the Mediterranean nations in the 
 same manner that the Chinese and Japanese empires have been in later 
 times from other states, Egypt was to the Greek a land of mystery and 
 
INTRODUCTION OF WRITING. 615 
 
 marvels. The exaggerated legends which had been brought from it at 
 distant intervals by those who had escaped by stealth, or in troublous 
 times had, like Cecrops and Danaus, led forth colonies of emigrants, lost 
 none of their wonders in the traditions of successive generations, but 
 were rather verified by the roving pirates who had seen the pyramids, 
 obelisks, and sphinxes, and the great temples on the banks of the Nile. 
 
 The first step in civilization is the invention of some system of per- 
 manent record some method of writing. Without this, it i ntroduct i on 
 may be truly said that law can not exist. Law can not main- of writing from 
 tain itself in the uncertainties of tradition law, without Egypt * 
 which we can not conceive of society. The legendary history of Europe 
 is doubtless correct in referring to some of these Egyptian fugitives or 
 emigrants the contemporaneous introduction of writing, and a system of 
 jurisprudence. Even if the former was derived from Phrenicia, accord- 
 ing to the story of Cadmus, the Phoenicians had originally borrowed it 
 from Egypt. It is an interesting illustration of the tendency of the Eu- 
 ropean mind to analysis, that of the forms of writing known in those 
 times, the ideographic or picture-writing, the syllabic or the representa- 
 tion of syllable sounds by signs, and the alphabetic, the latter alone 
 maintained its foothold in Europe. This form, as described at page 356, 
 essentially consists in decomposing articulate expressions into their con- 
 stituent vowel and consonant sounds, and assigning for each of those 
 sounds a letter. 
 
 About seven hundred years before Christ, events took place which led 
 to the extension of Egyptian" civilization to Europe. The an- j ntro d uc tion 
 cient power of the kings had declined, through disputes and of Egyptian 
 compromises occurring between them and the priesthood. Be- 
 tween the priests and the military caste there was an open quarrel, many 
 of the former having been deprived of their lands. These rivalries broke 
 out in revolts and insurrections, and for two years the country was in a 
 state of anarchy, from which a partial respite was obtained by an entire 
 change in its institutions. Twelve of the most influential persons divided 
 it among them, each having a province which he ruled as an independent 
 king. The old monarchy had degenerated into an oligarchy, and it was 
 this revolution which introduced African science into Europe. 
 
 Psammetichus, one of the twelve, had for his province the country which 
 borders on the Mediterranean Sea. Availing himself of his position, he 
 established an intercourse with the neighboring nations, particularly the 
 Greeks and Phoenicians, and amassed from it so much wealth that his 
 colleagues, jealous of his increasing power, resolved to dispossess him. 
 Until this time, all foreigners had been held in the utmost contempt, and 
 rigidly excluded. Psammetichus called in the aid of Ionian pirates, and 
 other Mediterranean adventurers, and, having collected a sufficient body 
 
616 THE PERSIAN EMPIRE. 
 
 of such mercenaries, defeated his colleagues at the battle of Momemphis, 
 and "became sole ruler of the whole country. 
 
 By the aid of a foreign force the revolution had been ended, but the 
 Opening of the position of Psammetichus was essentially different from that 
 ports of Egypt. o f a ll preceding princes. A foreign force had given him the 
 throne, and a foreign force alone could maintain him on it. Under such 
 circumstances, he took his most politic course, and, breaking through the 
 traditions of twenty-five centuries, opened the ports of Egypt. 
 
 This event necessarily led to a closer intercourse among the Mediter- 
 ranean nations, and insured communication between Europe and Africa. 
 The foreign element quickly made its influence manifest. In the very 
 next reign the Cape of Good Hope was doubled, and Africa circumnavi- 
 gated, and in the course of a very few years we find Pythagoras, Solon, 
 and Thales visiting Egypt, and bringing from thence to Europe the ele- 
 ments of law and natural science. 
 
 The Persian empire in the mean time had attained an attitude of su- 
 The Persian P r emacy in Western Asia. Following the inspirations of its 
 empire: its in- Babylonian predecessors, it was engaged in continual wars 
 with its African neighbor. From the battle of Pelusium, 
 and the conquest of Egypt by Cambyses, the political interests of that 
 country and Greece became essentially the same. The Persian con- 
 querors, operating alternately on the north and south shores of the Medi- 
 terranean, betrayed a determination to extend their rule around that sea, 
 and make it a Persian lake. On the one hand they were resisted by the 
 Greeks, on the other by the Egyptians, between whom active communi- 
 cations were kept up. For several centuries these operations were con- 
 ducted with various success. The kings of Persia, several of whom 
 seem to have been men of great capacity, comprehended the political ad- 
 vantages which would arise from the possession of the sea, and would 
 have doubtless carried out their plans as respects the south shore, if the 
 Phoenicians had not opposed obstacles for the sake of their colony at 
 Carthage. And though the Greek historians, with a pardonable motive, 
 speak of the various movements on the north as failures, there are many 
 circumstances which lead us to receive their accounts with allowances. 
 If Memphis was sacked, Athens also was burned ; and even at the open- 
 ing of the Macedonian expedition, Greek history is full of Persian inci- 
 dents and intrigues. 
 
 In speaking of the Egyptian cultivators of philosophy as priests, the 
 Introduction of signification which is now attached to that word gives us an 
 Egyptian phi- erroneous idea of what they really were. The colleges at 
 Memphis, Thebes, Heliopolis, and Sais, were, in reality, each 
 the head-quarters of a fraternity of artists and professional men, and bore 
 no sort t>f resemblance to our modern ecclesiastical institutions. Among 
 
THE GREEK SCHOOLS. 617 
 
 them were architects, lawyers, physicians, painters, chemists, astrono- 
 mers. These men were, moreover, the great landowners ; not only were 
 the temples richly endowed as corporations, but the individual members 
 were persons of wealth. They enjoyed monopolies of all kinds ; for in- 
 stance, among other things they had extensive factories for cottons, and 
 laboratories for the preparation of chemical products. 
 
 From these institutions the Greek philosophers brought natural sci- 
 ence. Pythagoras had resided at Thebes, Thales and Democ- The Greek 
 ritus at Memphis, Plato at Heliopolis, Solon at Sais. They schools - 
 did at first little more than expound the doctrines they had learned. 
 Their mode of instruction seems to have been, in many instances, found- 
 ed on the Egyptian model. The Pythagorean establishment at Crotona 
 may be regarded as a partial imitation of the African colleges. 
 
 It is not my intention to enter on an examination, or even enumera- 
 tion, of ancient philosophical opinions, nor to show that many of the doc- 
 trines which have been brought forward within the last thtee centuries 
 existed in embryo in those times. It may, however, be observed that, 
 in the midst of much error, there were those who held just views of the 
 various problems of theology, law, politics, philosophy, and particularly 
 of the fundamental doctrines of natural science, the constitution of the so- 
 lar system, the geological history of the earth, the nature of chemical 
 forces, the physiological relations of animals and plants. 
 
 It is supposed by many, whose attention has been casually drawn to 
 the philosophical opinions of antiquity, that the doctrines which we still 
 retain as true came to the knowledge of the old philosophers not so much 
 by processes of legitimate investigation as by mere guessing or crude 
 speculation, for which there was an equal chance whether they were right 
 or wrong ; but a closer examination will show that many of them must 
 have depended on results previously determined or observed by the Af- 
 ricans or Asiatics, and thus they seem to indicate that the human mind 
 has undergone in twenty centuries but little change in its manner of ac- 
 tion, and that, commencing with the same data, it always comes to the 
 same conclusions. Nor is this at all dependent on any inherent logic of 
 truth. Very many of the errors of antiquity have reappeared in our 
 times. If the Greek schools were infected with materialism, pantheism, 
 and atheism, the later progress of philosophy has shown the same char- 
 acters. To a certain extent, such doctrines will receive an impression 
 from the prevailing creeds, but the arguments which have been appealed 
 to in their favor have always been the same. The distinction between 
 these heresies in ancient and modern times lies chiefly in the grosser 
 characters which they formerly assumed, arising partly from the reflected 
 influence of the existing mythology, and partly from the imperfections 
 of exact knowledge. Even the errors of early antiquity are venerable. 
 
618 ANALYTICAL MIND OF THE EUROPEAN. 
 
 We must judge our predecessors by the same rules that we hope pos- 
 terity will judge us, making a generous allowance for the imperfections 
 of reason, the infirmities of character, and especially for the prejudices 
 of the times. To have devoutly believed in the existence of a human 
 soul, to have looked forward to its continuing after the death of the 
 body, to have expected a future state of rewards and punishments, and 
 to have drawn therefrom, as a philosophical conclusion, the necessity of 
 leading a virtuous life these, though they may be enveloped in a cloud 
 of errors, are noble results of the intellect of man. 
 
 The analytical quality of the European mind already manifested itself 
 Analytical in this decomposition of knowledge derived from foreign coun- 
 Eurcfean **"* tries, in this establishment of a host of schools, this examina- 
 mind. tion and discussion of the fundamental elements of the im- 
 
 ported philosophy. As there are differences in the physiognomy of 
 races, so there are differences in their intellectual endowments, which, 
 arising in peculiarities of cerebral construction, communicate peculiarities 
 to the processes of thinking. The physical science of Egypt, transported 
 to Greece, rapidly degenerated into speculative philosophy, and in so 
 doing produced an instability of opinion which entailed as its conse- 
 quence a laxity of morals. Such a social condition led naturally to the 
 results which history indicates. It is not surprising that the most em- 
 inent men were open to bribery, and that the glory of those ages was so 
 often the brilliancy of corruplion. These are the necessary results at- 
 tending such political conditions. Too often it fell out that the great 
 men of Greece accused, and too often convicted each other of being in- 
 fluenced by Persian intrigues and Persian gold. In the general demor- 
 alization, they seem to have taken for their guide a perverted interpreta- 
 tion of the admirable precept of Solon, " In every thing thou doest, con- 
 sider the end." 
 
 Added to this, the public faith in things once implicitly believed was 
 shaken. Xerxes in a very unceremonious way violated the temples and 
 carried off their treasures, showing the same contempt for the gods of 
 Europe that Cambyses had shown for those of Africa. If there lingered 
 in the minds of the philosophers any latent belief in the national faith, a 
 relic of the impressions of childhood or of popular opinion, such a prac- 
 Greek irre- tical demonstration could scarcely be lost. During the fifty 
 ligion. years of that war, the philosophical opinions of the Persians 
 had full opportunity to find their way among a class of men quite open 
 to receive them, and from this time we perceive a striking similarity be- 
 tween many of the doctrines of the schools and the well-known dogmas 
 of the Orientals. The Greeks, like the Hindoos, in the possession of the 
 mere rudiments of science, passed at once to the discussion of the most 
 important and elevated problems with which the human mind can be en- 
 
ORIGIN OF EUROPEAN COMMERCE. 619 
 
 gaged, and, as an inevitable consequence, were led away from true phi- 
 losophy into sophistry and irreligion. 
 
 It has been remarked a few pages back, that in the progress of nations 
 events follow in repeating cycles, and that for any one we may generally 
 find its precursor, and therefore its prognostic. Greece dealt with the 
 philosophy she had received from the southern people, African or Asi- 
 atic, exactly in the same manner that Europe dealt with Italian theology 
 the moment that liberty of action was permitted by the Reformation. In 
 each case the issue was not the prompt and final substitution of a sys- 
 tem correcting apparent and acknowledged defects, a system in unison 
 with the existing tone of thought. There was no such stoppage of ac- 
 tion ; but from the bosom of each principle and sect many other princi- 
 ples and sects arose, until there seemed to be no end to the subdivision. 
 
 If thus we consider the political position of Greece, the condition of 
 Asia Minor, occupied by Persian troops, the destruction that influence of the 
 had overtaken Egypt, the excitements and calamities of a war ^mod'eraphi- 
 of half a century, we can readily understand that this was losophy. 
 not a season when the tedious and slow processes of true philosophy were 
 likely to flourish, and that it was far more conducive to imposture than 
 to science. The seeds of knowledge which had been brought from 
 Egypt shot up into a rank growth, and Europe did not free herself of 
 these weeds for sixteen centuries. The character of a long train of 
 events is often determined at its inception ; for this reason, I have dwelt 
 in detail on those times, and it is well worthy of remark that the posi- 
 tive science of the European was not fairly established until after three 
 distinct impulses from Egypt : once, as we have seen, under her Pha- 
 raohs ; again, under her Ptolemies ; and still again, under her Caliphs 
 and Sultans. 
 
 While these events were taking place in the southeast of Europe, do- 
 mestic and foreign commerce were preparing the way for a Ori - n of Eu 
 gradual diffusion of civilization. A trade with the countries ropean coin- 
 bordering on the Baltic Sea for the amber which is found on J 
 those shores had gradually arisen, and, in like manner, another with 
 Spain, France, and England for tin. The tin of Cornwall was carried 
 through France and shipped by the Phoenicians at Marseilles, a certain 
 quantity of the same metal being also obtained from the Spanish mines. 
 Early in their history the Phoenicians had established colonies on several 
 points of the Black Sea, and from these depots they brought the various 
 products of those countries, among which may be mentioned gold, which 
 had apparently been originally derived from the washing of the Uralian 
 deposits. This Black Sea commerce seems, however, to have been event- 
 ually abandoned for the more profitable Spanish trade, and on the with- 
 drawal of the Phoenicians from the Euxine, the Greeks occupied their 
 
620 THE MACEDONIAN CAMPAIGN. 
 
 Discover of P^ ace * Meantime the enterprise of the Tyrian sailors had 
 the straits of carried them through the Straits of Gibraltar, and enabled 
 Gibraltar. them to have direct access with the tin and amber countries 
 without the intervention of any overland traffic. It was doubtless the 
 discovery of this outlet to the Atlantic which led to the destruction of 
 the Gaulish trade in tin and the German trade in amber. So greatly 
 was this latter substance prized, that the overland commerce in it had 
 many ramifications : thus amber was carried into Italy by the Etruscans, 
 who had a sacred road under the protection of the adjacent tribes to the 
 Baltic Sea. 
 
 With their commerce the Phoenicians disseminated a knowledge of 
 many inventions peculiar to themselves, among which may be mentioned 
 the use of stamped metallic coinage. Their great African colony, Car- 
 thage, exerted in these movements eventually a more powerful influence 
 than even the parent country. 
 
 Emulating the enterprise of the Phoenicians, the Greek mariners un- 
 dertook expeditions both to the east and to the west, succeeding, as we 
 have seen, in establishing themselves on the shores of the Euxine, and 
 eventually passing, under Colceus of Samos, through the Straits of Gib- 
 raltar into the Atlantic Ocean; but even up to the time of the Mace- 
 The Macedoni- donian expedition, their geographical ideas were very crude 
 an campaign. an( j f u n O f errors. Of the expedition of Alexander, Hum- 
 boldt remarks that it partook as much of the character of a scientific as 
 of a military undertaking, and its consequences, both immediate and re- 
 mote, upon Europe can scarcely be exaggerated. That great commander 
 surrounded himself with whatever talent was to be found in Greece, and 
 made his military successes for a time subservient to the science of his 
 native country. It was through this that Aristotle obtained that com- 
 manding influence which not only gave him an authority over the active 
 mind of his own times, but which was felt even until the introduction of 
 the Baconian system of philosophy. The campaigns of Alexander doub- 
 led the geography of the Greeks in longitude, opened to their investi- 
 gation new countries even to the tropics, brought them acquainted with 
 races of men who had been the depositaries of science, as it then existed, 
 for thousands of years, and, in short, added Asiatic to Grecian knowl- 
 edge. It is a significant fact that, after the taking of Babylon, Alexander 
 sent to Aristotle a series of astronomical observations reaching back 
 through 1903 years. 
 
 The Macedonian expedition not only made a profound impression on 
 
 Restoration of ^ e European mind by its immediate results its influence is 
 
 monarchy in equally palpable in its remoter consequences. It would be 
 
 impossible, in such a sketch as this, to do justice to that great 
 
 event in all its details ; for nations can not be thus brought in contact 
 
THE PTOLEMIES. 621 
 
 without prodigious mental results, the extinction of old, and the appear- 
 ance of new ideas. But of the influences which thus arose, there is, how- 
 ever, one which deserves to fasten our attention, and the more so since 
 we have had already, and shall have again, the occasion for alluding to 
 it. It was the establishment of a regal government in Egypt. Under 
 the Ptolemies, who may "be truly characterized as the most 
 
 T , J , The Ptolemies. 
 
 illustrious kings of antiquity, that ancient country recovered 
 her pristine glory. Among the works accomplished by these great men 
 may be mentioned, as examples of their high-toned policy, the sending 
 out an exploring expedition to equinoctial Africa ; the establishment of 
 menageries and zoological gardens at Bruchium ; their attempts at determ- 
 ining the cause of the overflow of the Nile ; the library at Alexandria ; 
 the museum at Ehakotis ; the measurement of a degree on the earth's 
 surface between Alexandria and Syene ; the ascertaining of the prodigious 
 distance of the region of the fixed stars ; the recognition of the motion 
 of rotation of the earth upon her axis, and of her translation around the 
 sun ; the precession of the equinoxes ; the attempt at constructing a map 
 of the world by the aid of degrees, based on lunar observations and on 
 shadows ; the improvement of the methods of astronomical observation 
 by the invention of water-clocks, and instruments for the more accurate 
 measurement of angles. Along with these, Baron Humboldt, in his Cos- 
 mos, has enumerated many other philosophical works of the Ptolemies, 
 which exerted a profound influence both upon the knowledge and intel- 
 lect of Europe. Greece now repaid what she had formerly borrowed ; 
 her schools of philosophy were translated to Alexandria, and the great 
 names of Euclid, Apollonius, and Archimedes testify to the return of 
 those ages to exact science. 
 
 The decline of Greece and her final absorption into the Roman em- 
 pire was the necessary consequence of her mode of life. In Decline of 
 policy as in philosophy, her essential tendency was to sub- rise e of'the d Ro- 
 division, and therefore to weakness. In her external rela- man empire, 
 tions she had ever been far more closely connected with Asia than with 
 Europe. For a long time she was little more than an outlying territory 
 of Persia, respecting and fearing the highly-civilized nations in her front, 
 but scarcely concerning herself with the barbarians at her back. Very 
 different was it with Rome, her great supplanter and successor, who, 
 thoroughly European in her whole history, exercised an active, interven- 
 tion in the affairs of adjacent nations an influence perpetually felt 
 through Spain, Germany, Gaul, and Britain. 
 
 It is difficult to estimate fully the influence of the Roman empire on 
 the intellect of Europe. Its power lay not in the origination of what was 
 new, but in the development and dissemination of what was derived from 
 other sources. The contributions of the Roman emperors to the stock 
 
622 THE ROMAN EMPIRE. 
 
 of positive knowledge bear no kind of comparison to that of the Ptole- 
 mies just mentioned; indeed, their works have reference chiefly to military 
 purposes and material aggrandizement. In this manner we must look 
 upon the surveys and itineraries which they caused to be made of vari- 
 ous parts of the empire. Nevertheless, through their influence the idea 
 of civilization was gradually made to find its way through Central and 
 Northern Europe. 
 
 The function of Rome in our history is very distinct. From small 
 Centralizing beginnings she steadily pursued the same progress. The 
 pote^ 11 ^ c 011 *! 1168 * an ^ absorption of town after town, which was the 
 Home. history of her earlier times, was carried out in the annexation 
 
 of nations in her day of strength. From the moment that she gained 
 the control of the Mediterranean Sea, which was the grand epoch of her 
 life, she inexorably forced all the conterminous nations to acknowledge 
 Italian centralization. It is no metaphorical expression that she became 
 their centre of gravity. No circumstance could occur to her which did 
 not instantly influence them all. As far more than an equivalent for 
 subjugation and loss of independence, she made them into a common 
 race, harmonizing their actions, and giving them common ideas. The 
 Roman empire was the organizing agent of the white man. 
 
 The acts of man, though they may have the aspect of free-will as re- 
 gards himself, are automatic as regards the race. He is employed in 
 achieving a result of which he is utterly ignorant ; he is concerned in a 
 work of the effects of which he is unconscious. He is like a bee, which 
 doubtless experiences a certain pleasure in flying from flower to flower, 
 the gratification of an obscure desire in constructing cell after cell, its 
 individual delight ministering to a public good of the nature of which it 
 is wholly unconscious. 
 
 In such a manner we may look upon the career of the Roman with 
 satisfaction. He was pursuing a life of evil deeds, and accumulating in 
 his great and dissipated capital the spoils of wasted provinces, gratifying 
 his wanton luxuries by a systematic resort to war, that most awful of 
 the curses that afflict our race. It was the temporary lust of individual 
 interest that he was pursuing. Providence was bringing out of it a uni- 
 versal good. 
 
 If Rome was cruel in her national acts, she was majestic in her policy. 
 The fall of Eu ^ e decimated nations that she might bind them into one 
 ropean pagan- family. With remorseless vigor she extinguished every 
 trace of independent action, and with a contradictory but 
 noble liberality, domesticated the worship of every conquered people 
 round the Capitol. There was no god whose image she could not show, 
 no faith of which she was not the patroness. It may serve as an exam- 
 ple of the manner in which her policy led to definite results of which she 
 
THE PAPAL GOVERNMENT. 623 
 
 was unaware, or, if aware, of the manner in which the strong hand of 
 Providence inverted her designs, that by this, her system of universal 
 toleration of every ancient faith, /she absolutely destroyed them all. 
 Brought thus to bear upon one another at a common central point, their 
 contradictions, inconsistencies, fallacy, and emptiness became apparent. 
 The men of capacity first made the detection, their opinions spreading 
 by degrees through society. Well might St. Chrysostom say that the 
 error of idolatry vanished of itself, and that paganism seemed in his day 
 " like a conquered city, whose walls were overthrown, her halls, theatres, 
 and public buildings consumed by fire, her defenders slain, and here and 
 there a few old men and children lingering among the ruins. Even 
 these were soon found no more." 
 
 It is sometimes said that the Boman empire was essentially composed 
 of cities ; that at its fall its fragments were cities ; and that it left nothing 
 to posterity but its municipal system. Such a statement is not true. 
 Its legacy was of a far higher order. It left the religion it had adopted, 
 the civil law, and the foreshadowing of the great deeds that might be ac- 
 complished by the white man organized and united. To this, in a more 
 perfect way, the affairs of our times are still conspicuously tending. We 
 begin to hear of the opinion of Europe, the public law of Europe, expres- 
 sions which are gaining each day more and more significance. 
 
 In that phantasmagorial. exhibition which we call history, events give 
 birth to events as in dissolving views, the phantoms of the i nfluenceoftlie 
 actors stalking one after another. It is not always possible empire in its 
 for us, with the slender information we possess, to determine 
 the time of origin of etch incident, or its true and actual bearings. The 
 secret history of antiquity is almost unknown. Nearly every circum- 
 stance in the decline of the Roman empire was fraught with important 
 consequences for modern times. Among the more obvious facts which 
 attract our attention are the dislocation of the centre of the empire by 
 the translation of the seat of government to Constantinople, the conse- 
 quent acquisition of power by the bishops of Home in the West, the in- 
 cessant emigrations and invasions of barbarians from the North, the con- 
 quests of the Saracens, from whom it seemed af one time that Europe 
 would hardly escape, and that the threat of Muza would come to pass, 
 that the name of Mohammed should be proclaimed in the Vatican ; the 
 consolidation of ecclesiastical policy, and the repeated attempts of the 
 Church to suppress barbarism attempts so signally successful that by 
 the end of the eighth century many of those nations had written systems 
 of law ; the separation of the Greek and Latin Churches, the The Papal 
 different phases which the latter assumed as she was affected government, 
 by existing circumstances, how she extricated herself from an almost 
 barbarous state after the empire had failed her, how she asserted the in- 
 
624 SUPPRESSION OF PHILOSOPHY. 
 
 dependence of the spiritual order, how she kept her grasp upon mankind 
 by the establishment of monastic institutions ; how, after the death of 
 Charlemagne, who had done so much for her, she adopted the feudal 
 system, which was the legitimate offspring of barbarism ; how, as knowl- 
 edge began to spread, she tried to render it tributary to her by councils, 
 convocations, federations ; how, finding it likely to become uncontrollable, 
 she took the alarm, and in an evil hour attempted its repression ; how 
 for a little while she became the autocrat of Europe, and in the plenitude 
 of her power so greatly forgot her duty that, in the time of Leo X., it 
 was doubted in Rome whether the soul be immaterial and immortal, 
 Erasmus testifying with horror that he heard it proved that there is 
 no difference between the soul of a man and that of a beast of a truth 
 it was said that the Eternal City teemed at once with all crime and all 
 the glories of art how, against the moral and intellectual revolt which 
 she encountered the Reformation the Church made a stand by the aid 
 of the Society of the Jesuits and the establishment of the Inquisition, 
 Its attem t at an< ^' w ^ a quick sense of her true position, attempted to 
 suppressing guide children through education by the former, and to check 
 philosophy. men ^ the terrors of the i a tter; h OWj as if ^ i ns tinct, she 
 
 detected the antagonism of exact science, and on the one hand published 
 her Index of prohibited books, and on the other allied herself with art, 
 cultivating it so eminently as to compel even her enemies to confess that 
 she had produced true miracles at last in architecture, sculpture, paint- 
 ing, music. Pius IV. was justified in comparing some of her grand 
 masses to the strains of Paradise. 
 
 The mistake committed by the Italian governmftnt in thus attempting 
 the compression of human thought was in its imperfect appreciation of 
 the qualities of the European mind and the existing philosophical tend- 
 ency. Up to a certain point opinion may be coerced by force. It is 
 altogether a vulgar error that persecution never attains its ends. In 
 nine cases out often it does attain them, provided it is applied with suf- 
 ficient severity and for a sufficient time, as is proved by the history of 
 almost any nation ; but in the tenth it fails. 
 
 Judging from the experience of twenty centuries, for that was nearly 
 Failure of that the period during which the European had been philosophiz- 
 attempt. j n g ? the popes were justified in coming to the conclusion that 
 they did. Those centuries had produced no philosophy of a sure and 
 permanent kind. The only fruit which they had borne was the meta- 
 physical uncertainties of the schools. There seemed no prospect that the 
 human mind would ever do more than flounder in doubt ; that sect after 
 sect, and doctrine after doctrine, would emerge into prominence and disap- 
 pear. In such a state of things, it was not to be supposed that any peril 
 could arise from attempting to control opinion by authority, and to extin- 
 guish the spirit of inquiry by asserting the paramount efficacy of faith. 
 
THE REFORMATION. 625 
 
 In thus failing to recognize the fact that things were coming to that 
 condition in which the elements of certainty and absolute philosophical 
 truth would be shortly attained, the popes committed the Church to an 
 irreparable error. They periled her authenticity in an unequal conflict. 
 It might do for a little time to deny and denounce the globular figure of 
 the earth, but the demonstration of the truth came irresistibly at last ; 
 and so with the doctrines of the antipodes, the daily rotation on an axis, 
 <ind the annual translation round the sun. It enhanced the folly of these 
 proceedings that they were, in reality, insincere. Of the great ecclesias- 
 tics there probably were none who did not privately admit the truth of 
 what was thus condemned. When the bark Vittoria, of Magellan's 
 squadron, made the first voyage of circumnavigation round the globe, it 
 was a high Church dignitary, Cardinal Contarini, who gave the true ex- 
 planation of the circumstance, then first remarked, of the loss of one 
 whole day in her reckoning. Such insincerity, and the issue of these 
 and other like questions, could end in no other way they sapped the 
 prestige of the Church. How different would it have been if she had 
 taken the lead, and directed the human mind in the channels through 
 which it was destined to pass, instead of opposing herself as an obstacle! 
 She might have guided, but she could not resist. 
 
 It is to be remarked that the men who, from the twelfth to the six- 
 teenth century, distinguished themselves in precipitating the The Reforma- 
 result, were mostly ecclesiastics. Roger Bacon may be taken tion< 
 as the type of them all. Their labors had no little connection with 
 the Eeformation which was headed by Luther. Though we are accus- 
 tomed to regard this with the most profound interest, a more philosoph- 
 ical view of the state of things may perhaps suggest that it is, in real- 
 ity, only one act of a great drama. We should not mistake an episode 
 for the main event. The Reformation soon reached its full expression 
 in dividing Christendom. Geographically it culminated in 1648, at the 
 treaty of Westphalia. By the philosopher it will ever be contemplated 
 with unalloyed satisfaction, for it asserted as its chief doctrine the right 
 of the human mind to judge for itself, a doctrine so unspeakably precious 
 as to make of no account the inconveniences which arise in its practical 
 application from the continual multiplication of sects. 
 
 In the history of the European, from the time of the Emperor Con- 
 stantine to the eighteenth century, the ecclesiastical element i n fl ue nce of 
 so greatly preponderates as to constitute its almost essential the Christian 
 feature ; and, after all, it is impossible to do justice to the ropean civffi- 
 effects which ensued on the establishment of Christianity, zation - 
 and its adoption by the white man as his religion. The civil law exert- 
 ed an exterior power in human relations ; this produced an interior and 
 moral change. The idea of an ultimate accountability for personal deeds, 
 
 RE 
 
626 THE CHRISTIAN CHURCH. 
 
 of which the old Europeans had an indistinct perception, became intense 
 and precise ; the sentiment of universal charity was exemplified not only 
 in individual acts, the remembrance of which soon passes away, but in the 
 more permanent institution of establishments for the relief of affliction, 
 the spread of knowledge, the propagation of truth. Of the great ecclesias- 
 tics, many had risen from the humblest ranks of society, and these men, 
 true to their democratic instincts, were often found to be the inflexible 
 supporters of right against might. Eventually coming to be the deposi- 
 taries of the knowledge that then existed, they opposed intellect to brute 
 force, in many instances successfully, and, by the example of the organi- 
 zation of the Church, which was essentially republican, they showed how 
 representative, systems may be introduced into the state. Nor was it 
 over communities and nations that the Church displayed her chief power. 
 Never in the world before was there such a system. From her central 
 seat at Eome her all-seeing eye, like that of Providence itself, could equal- 
 ly take in a hemisphere at a glance, or examine the private life of any 
 individual. Her boundless influences enveloped kings in their palaces, 
 or relieved the beggar at the monastery gate. In all Europe there was 
 not a man too obscure, too insignificant, or too desolate for her. Sur- 
 rounded by her solemnities, every one received his name at her altar ; her 
 bells chimed at his marriage, her knell tolled at his funeral. She ex- 
 torted from him the secrets of his life at her confessionals, and punished 
 his faults by her penances. In his hour of sickness and trouble her serv- 
 ants sought him out, teaching him by her exquisite litanies and prayers 
 to place his reliance on God, or strengthening him for the trials of life 
 by the example of the holy and just. Her prayers had an efficacy to 
 give repose to the soul of his dead. When even to his friends his life- 
 less body had become an offense, in the name of God she received it into 
 her consecrated ground, and under her shadow he rested till the great 
 reckoning day. From little better than a slave she raised his wife to be 
 his equal, and, forbidding him to have more than one, met her recompense 
 for those noble deeds in a firm friend at every fireside. Discountenancing 
 all impure love, she put round that fireside the children of one mother, 
 and made that mother little less than sacred in their eyes. In ages of 
 lawlessness and rapine, among people but a step above savages, she vin- 
 dicated the inviolability of her precincts against the hand of power, and 
 made her temples a refuge and sanctuary for the despairing and oppress- 
 ed. Truly she was the shadow of a great rock in many a weary land ! 
 
 The civilization of the European, so far as it has yet advanced, has 
 been accomplished by the agency of many different causes, foreign and 
 domestic ; but among all these, the institution of the Christian Church 
 stands pre-eminent by reason of the moral power it exerted, its duration, 
 and the social benefits it has conferred. 
 
THE SABBATH DAY. 627 
 
 Out of the numberless blessings which have thus been conferred on our 
 race by the Church, the physiologist may be permitted to se- The Sabbath 
 lect one for remark, which, in an eminent manner, has con- da ^- 
 duced to our physical and moral well-being. It is the institution of the 
 Sabbath day. Not that this originated with, or is peculiar to the Chris- 
 tian faith, since, as is known to all, it dates from the remotest times, and 
 was directly adopted from the Hebrew ceremonial. Its sanctification and 
 enforcement by the Church was at once an object important in the high- 
 est degree in ecclesiastical polity, and a boon to all classes of men ; for 
 in whatever position of life we may be placed, it is needful for us to have 
 an opportunity of rest. No man can for any length of time pursue one 
 avocation or one train of thought without mental, and, therefore, bodily 
 injury nay, without insanity. The constitution of the brain is such 
 that it must have its time of repose. Periodicity is stamped Necessity of 
 upon it. Nor is it enough that it is awake and in action by P eri <> d sofrest. 
 day, and in the silence of night obtains rest and repair; that same perio- 
 dicity which belongs to it as a whole, belongs to all its constituent parts. 
 One portion of it can not be called into incessant activity without the 
 risk of injury. Its different regions, devoted to different functions, must 
 have their separate times of rest. The excitement of one part must be 
 coincident with a pause in the action of another. It is not possible for 
 mental equilibrium to be maintained with one idea, or one monotonous 
 mode of life. There is a necessity even for men of great intellectual en- 
 dowments, whose minds are often strained to the utmost, to fall back on 
 other pursuits, and thus it will always be that one seeks refuge in the 
 pleasures of quiet country life, another in foreign travel, another in social 
 amusements. Pitt sought a relaxation from the cares of politics in the 
 excitement of the chase ; Davy found a relief and consolation in the rod 
 and line ; and among men whose lot is cast in the lowliest condition, whose 
 hard destiny it is to spend their whole lives in the pursuit of their daily 
 bread, with one train of thought and one unvarying course of events, the 
 same principle imperiously applies. It is often said that the pleasures 
 of religion are wholly prospective, and to be realized only in another 
 world ; but in this there is a mistake, for those consolations commence 
 even here, and temper the bitterness of fate. The virtuous laborer, though 
 he may be ground down with the oppressions of his social condition, is 
 not without his relief: at the anvil, the loom, or even the bottom of the 
 mine, he is leading a double existence the miseries of the body find a 
 contrast in the calm of the soul, the warfare without is compensated by 
 the peace within, the dark night of life here serves only to brighten the 
 glories of the prospect beyond. Hope is the daughter of Despair. And 
 thus a kind Providence so overrules events that it matters not in what 
 station we may be, wealthy or poor, intellectual or lowly, a refuge is al- 
 
628 PUBLIC WORSHIP. 
 
 ways at hand, and the mind, worn out with one thing, turns to another, 
 and its physical excitement is followed by physical repose. 
 
 By the enforcement of the observance of the Sabbath the Church gave 
 Influence of effect to this providential system of physical and mental re- 
 public worship. Ji e J have already said that her chief strength lay in this, 
 that she concerned herself with the common man, who never in the 
 world's history before had had any to watch over or to care for him. 
 She humanized him by the devotional solemnities of a sacred day a 
 day of entire relief from toil. Ignorant and rude though he might be, 
 it was not possible for him to enter her hoary temples without being 
 made a better man. The atmosphere of rest, the twilight streaming 
 through the painted windows, the prayer in an unknown tongue, the slow 
 chanting of old hymns, or the swelling forth of those noble strains of 
 music, which, once heard, are graven in remembrance forever these she 
 had made, with more than worldly wisdom, the elements or incidents of 
 public worship. She gratified the manly sense by asserting before her 
 altar the equality of all men, by making the vain and transitory grada- 
 tions of society disappear, and by teaching the rich and the poor, the 
 great and the humble, their common dependence on the mercy of God. 
 Under her powerful influence, inarticulate Nature, as if spellbound, seem- 
 ed to acquiesce in the tranquillity of the Sabbath day, and to assume 
 an air of rest. In the cottage they rose at a later hour. The father 
 cleansed himself with more than usual care, and, if it was the custom 
 of his country, shaved his face, perhaps sadly neglected in the interven- 
 ing week, and dressed himself in his better clothing. His honest pride 
 found a gratification in the neatness of his wife and children. His table 
 was more bountifully supplied, his heart humanized by the grateful re- 
 lief from labor, and the society and converse of those dearest to him. 
 Physically and mentally he rests, and by that rest is enabled to sustain 
 the cares of a life of toil. It is not without a reason which we may turn 
 to our profit, that the Scriptures have placed upon lasting record that 
 the Great Head of the Church has taught us both by precept and personal 
 example how to use this day ; and that, for the sake of the many gen- 
 erations of laboring and weary men who were to follow him, he inflexibly 
 resisted every attempt at encroachment upon it by the grim bigots and 
 hypocrites of his times. 
 
 Though Kome did little for Europe in the production of knowledge, 
 The civil s ^ e ^ us serve< ^ * ts i n terests well in the most vital respects. 
 She gave it her system of law and her religion. With the 
 introduction of Roman usages among barbarians came the Roman law, 
 modifying or abrogating the existent imperfect polities. To a consider- 
 able extent, its spread was due to the influence of the ecclesiastics and 
 the wants of the rising municipalities. 
 
INFLUENCE OF THE ARABS. 629 
 
 The influence exerted by the Koman empire on the social condition of 
 Europe in the two particulars to which reference has been Influence of the 
 made, the introduction of the civil law, and the establish- Mohammedans 
 ment of the Christian Church, occurred in the' period of its 
 decline, and was therefore contemporaneous with the spread of Moham- 
 medanism through the north of Africa, and the occupancy of Spain by 
 the Arabs. To a very considerable degree, the practical character which 
 European thought has exhibited in later centuries is to be attributed to 
 the Arabians, who have justly been termed the founders of physical sci- 
 ence ; for though, through them, the literature of Greece was intro- 
 duced into Western Europe, the writings of Aristotle, for example, being 
 made known through an Arabic translation, they imparted to what they 
 thus gave their own particular impress. Being the first founders of or- 
 ganized institutions for the cultivation of medical pursuits, answering 
 completely to our modern medical colleges, they attached to those pro- 
 fessional studies their own peculiar methods. It was therefore in this 
 way that botany and chemistry were particularly cultivated, be- The Arab 
 cause they were regarded as the foundation of Materia Medica. schools. 
 Humboldt remarks, that while the Europeans have been disposed to con- 
 nect the physical sciences with theology, the Arabians connected them 
 with medicine, and that through their medical colleges they ruled the 
 Christian schools, who looked up to Avicenna and Averroes as the great 
 authorities on these subjects. The most important applications of the 
 mathematical sciences to the purposes of life were made by the Arabs. 
 Of this it is sufficient to mention the introduction of the notation of arith- 
 metic and many instruments of navigation, the former not only fur- 
 nishing an invaluable aid in the computations required by the wants of 
 a commerce which reached from the north of Europe to Madagascar, and 
 from the Atlantic islands to China, but, what was of even more import- 
 ance, in the progress of mathematical science itself, the latter through the 
 aid afforded in astronomical observations permitting the successful ac- 
 complishment of voyages in seas which even to that time had been little 
 frequented. 
 
 It would extend this chapter unduly if we were to enter into any de- 
 tail of the special contributions of the Arabs to the stock of Eu- Arab discov- 
 ropean knowledge. It may, however, be briefly remarked, that eries - 
 we owe to them our system of universal arithmetic, and even the title 
 under which it now passes, algebra. Their discovery of the strong acids, 
 nitric, sulphuric, and also aqua regia, constitutes an epoch in chemistry. 
 The cultivation of that science also was stimulated in no small degree 
 by their attempts at the transmutation of the baser metals into gold, and 
 the discovery of the means of indefinitely prolonging life the philoso- 
 pher's stone and the elixir vita?. In the science of optics, the work of 
 
(330 THE CRUSADES. 
 
 Alhazen on refraction demonstrates their cultivation of the methods of 
 physical experiment and observation, and their application of the pendu- 
 lum to the measurement of time is even yet acknowledged to be the most 
 perfect contrivance for that purpose. 
 
 In estimating the value of the influence which the Mohammedans ex- 
 erted upon the European mind, we recognize its specific similarity to 
 that which, more than a thousand years before, had been communicated 
 from the schools of Egypt under its Macedonian kings, and even, still 
 centuries before that, at the time of the opening of the Egyptian ports. 
 In all three cases the tendency imparted was to the cultivation of the 
 physical sciences, then in their infancy, and thereby to the increase of 
 the material power of the race. In a very short time, inventions which 
 have been of the utmost importance made their appearance, such as gun- 
 powder, the mariner's compass, and various optical instruments. It is 
 of no moment whether these were introduced by the enterprise of the 
 Arabs from Asia or whether they were of indigenous origin ; there can 
 be no doubt that the intellect of Europe had reached that peculiar phase, 
 and the tendency of thought was in that particular direction that, even 
 if these discoveries had not been communicated from abroad, they would 
 very soon have been made at home. 
 
 The Mohammedan attacks on Europe were retaliated by the Crusades. 
 These strange wars, into which the white race plunged, were 
 
 The Crusades. . -, -, , -A 111 
 
 instigated by the Koman government toward the close ot 
 the eleventh century, and were followed by consequences which their pro- 
 jectors never expected. They precipitated barbarian Europe upon Asia, 
 under the pretense of rescuing the Savior's tomb from the infidel, but in 
 reality to keep back the threatened tide of Saracenic invasion, and to di- 
 vert from Italy the restless military spirit that was every where engen- 
 dering. No other motive than the one thus ostensibly put forth could 
 have brought the ferociously independent hordes of Europe to act to- 
 gether. It had been well if, in ancient times, the emperors had been in 
 possession of so useful a device ; it might have saved the city from some 
 sieges and sacks. As it was, the turbulent stream was thrown upon the 
 Byzantine monarchs to their utter perplexity. The Saracens received 
 it with amazement. The ostensible causes which had set in motion such 
 a countless rabble of stupid barbarians were absolutely incomprehensi- 
 ble by them. In their invasions of Europe they had carried the light 
 of such science as they possessed, but in this counter invasion of Asia 
 they were repaid with the most besotted ignorance. 
 
 The Crusaders found that the infidel they had come so far to encoun- 
 influeaceofthe ter w ^ nout provocation was valiant and polished, in many 
 Crusades ou cases merciful and just. Their ideas of the Asiatics under- 
 went a great change after they had been in contact with 
 
EFFECTS OF THE CRUSADES. 631 
 
 them for a time. Those who lived to return to their homes from the 
 successive expeditions spread abroad a more enlarged and correct con- 
 ception of Oriental countries, events, and men, the influence of which 
 was not lost to civilization. In his imprisonment in the fortress of 
 Dierstein, the lion-hearted Richard of England doubtless reflected that 
 there was more honor in the infidel Saladin than in many a Christian 
 king. It has not escaped the observation of historians that the frequent 
 communication which these events established between all parts of Eu- 
 rope and the Italian court served often to disturb the sentiment of piety. 
 The visitors at Rome saw things which had been better concealed. Their 
 unaffected simplicity was shocked by the dissipation and immoralities in 
 high places. They carried the shameful story to their homes. 
 
 Among the unexpected and lasting advantages arising from the Cru- 
 sades, not one of which had been contemplated by the Ital- Advantages 
 ian court, may be enumerated more enlarged and liberal views derived from 
 of foreign nations, and the importation of Asiatic discoveries. 
 From the remote parts of that continent embassadors came to Italy, and 
 enterprising European travelers, like Marco Polo, wandered in return all 
 over it. In this manner the knowledge of the mariner's compass was 
 obtained. From having learned to employ their ships in warlike expe- 
 ditions, the Western nations were induced to enter on that career of mar- 
 itime commerce which soon led them to the discovery of America and 
 the doubling of the Cape of Good Hope, and which, in these times, con- 
 stitutes the chief feature of their life*. Trade, which until then had been 
 overland or terrestrial, became maritime a change important to the last 
 degree, since it eventually gave rise to the prodigious development of 
 manufacturing industry. Heavy masses of goods can never be trans- 
 ported by caravans, though they can easily in ships. The geographical 
 value of countries was changed. Egypt, for instance, lost her position, 
 not to be recovered again until the invention of the locomotive, which 
 will restore land-transport to its former state. Wealth poured into the 
 maritime states, and markets were sought for all over the globe. More- 
 over, the separate principalities and kingdoms were taught to act in uni- 
 son, and the idea of Europe united Europe was made manifest. As 
 a present advantage was realized the downfall of the feudal system, and, 
 as a direct consequence thereof, a redistribution of the population. To 
 this system, in its flourishing period, some have been disposed to impute 
 many benefits that it originated our domestic manners, gave birth to 
 the sentiment of loyalty and honor, cherished independence, and elevated 
 the female sex ; but these are misconceptions or exaggerations. In the 
 last particular, the advancement of women, the merit is strictly due to 
 the Church ; for, had there been no other reason, the universal preva- 
 lence of Mariolatry throughout Christendom, by diffusing a most accept- 
 
632 SPANISH DISCOVERY OF AMERICA. 
 
 able and even adorable image of female loveliness and virtue, would have 
 led to that result. 
 
 But far exceeding the Crusades in effect, more distinct in its origin, 
 Discover of s i nce ^ directly resulted. from the tone of thought which the 
 America by Arabs had introduced, lasting in the influence that it has ex- 
 
 the Spaniards. ^^ and ^ forever exert on the d est i n i es Q f ^ w j lite 
 
 race, was the discovery of America by the Spaniards in 1492. This con- 
 tinent, four hundred years before, had been visited repeatedly by the Ice- 
 landers and Norwegians ; but the shores they discovered being less hos- 
 pitable and less tempting, their expeditions unsupported by a powerful 
 home government, and the results little attractive, the very remembrance 
 of them seems almost to have passed away. Had it not been for the 
 magnetic needle, and other instruments of navigation introduced from the 
 East, the passage of the tropical Atlantic could never have been accom- 
 plished, and probably would never have been attempted. Moreover, we 
 must not overlook the fact that the rapid conquests of the Saracens, and 
 even the Crusades themselves, had introduced a largeness of conception, 
 and had familiarized the public mind with undertakings to be accom- 
 plished in regions that were very remote. The successful return of Co- 
 lumbus from his first voyage found all Europe ready to rush into West- 
 ern enterprises, and this event may be truly regarded as a grand epoch 
 in the history of the white race, since it more than quadrupled the geo- 
 graphical surface over which they might spread, and presented to. their 
 unmolested occupation climates from the equator to the extreme north 
 and south. 
 
 In the prodigious emigration that ensued, Spain led the way, and did 
 Colonial em- so to her ruin. In vain she received and scattered over Eu- 
 pire of Spain. r0 pe the wealth of Mexico and Peru ; she gave in exchange 
 for it what was to her of infinitely more value the most enterprising 
 and bravest of her people. The drain of this class produced an effect 
 from which she has never recovered. It left her without energy and im- 
 becile. In vain she founded a greater, and, for the time, more prosperous 
 colonial empire than history has ever recorded, carrying her influences 
 through a large part of South and much of North America, from the At- 
 lantic to the Pacific Ocean. Her emigrants, unable to withstand the in- 
 fluences of a tropical climate, and intermarriages and connections with 
 the native races among whom they were thrown, soon lost the enterprise 
 that had once distinguished them, and the descendants of the Spaniard 
 in America exemplify at this day the universal imbecility that is exhib- 
 ited in the mother country. 
 
 In her pursuit of the wealth of America Spain was a fearful oppress- 
 The fan of the or. Bartholomew de las Casas, the Bishop of Chiapa, to use 
 Spanish power. kj s QWn ex p ress i on , charged her "before the tribunal of the 
 
POPULAR PHILOSOPHICAL BELIEF. 633 
 
 Universe," with destroying more than fifteen millions of natives during 
 his time. " The acrimony of his style was complained of, but the fact 
 was never denied." No nation can practice such atrocities with impu- 
 nity. The day of reckoning may be a little postponed, but it brings its 
 inexorable verdict in the end. The broad hand of an overruling Provi- 
 dence is at last plainly discovered, imposing with an unerring justice the 
 penalty of national crime. There is no need for God to hasten, he has 
 the centuries and eternity to work in. Even now, is not the Spaniard in 
 the hands of an avenger for the Indian blood that cries for retribution 
 from the silver mines of Mexico ? For the failings of the individual 
 there is mercy, but in the ways of eternal justice no mediator is provided 
 for the crimes of society. There is an inflexible recompense of good for 
 good and evil for evil. 
 
 The step which the intellect of the white man has made since the Ref- 
 ormation is very strikingly discerned by comparing the nat- T helatermen _ 
 ural philosophy of the fifteenth with that of the nineteenth cen- tai changes in 
 tury. Its passage to its present condition has been mark- 
 ed by a continual casting away of the marvelous. It is almost impossi- 
 ble for us now to realize the fictions which occupied the minds of our 
 predecessors. To pejietrate "the secrets of nature" is with us a meta- 
 phorical expression ; with them, a portentous and solemn reality, most 
 readily accomplished by the help of familiars and imps, whose services 
 might be secured by forbidden enchantments. The laboratory of an al- 
 chemist was ill furnished which did not possess in the shape of an un- 
 gainly and deformed dwarf such an aid, and who, if not the incarnation 
 of a devil, was at least possessed by one. Operations for the discovery 
 of the philosopher's stone, the powder of projection, and elixir of life, 
 were necessarily commenced by exorcism, invocations, and a favorable 
 aspect of astrological combinations. There were seven planets, and also 
 seven metals, and the guiding spirits which resided in the former exer- 
 cised their influence over the latter, communicating to them their specific 
 virtues. The expressions have lost their significance, though they have 
 descended to' our times, when we call a certain metal mercury, and a salt 
 lunar caustic. 
 
 As Mr. D'Israeli, in bis " Curiosities of Literature," remarks, whoever 
 had been a witness of the miracles of these philosophers might well be 
 prepared to believe any of their declarations. He who had visited the 
 dark chamber of Baptista Porta, and seen with his own eyes its fairy 
 but inverted landscapes, its fields, and rocks, and rivers, and the moving 
 forms of men and animals in their proper colors and indescribable charm 
 of light and shade, the clouds and sky, the magical spectres of things 
 which the fingers could not grasp, a perfect but artificial day-dream, might 
 surely feel justified in also believing in the enchanted mirror upon which, 
 
634 DISAPPEARANCE OF CREDULITY. 
 
 if a man looked, he would find reflected all the future events of his life. 
 He who had seen the phantasmagoria cast upon smoke in these myste- 
 rious laboratories, now so little that the eye could scarcely discern their 
 form, and now expanding to a gigantic stature and rushing forth, was 
 duly prepared to credit the legends of brazen men who could speak and 
 even prophesy, nay, whose limbs would continue to grow unless the de- 
 mon that possessed them was cast out. A vial of that which we call 
 ammonia, the mere smelling of which can recall one from a swoon, was 
 a very fair earnest of the elixir of life. JSTo prodigy was too great to be 
 believed. As in dreams, nothing was too impossible, nothing too con- 
 tradictory. Men who could make themselves invisible even without the 
 romantic aid of a ring ; incombustible sages who could wash themselves 
 in melted copper, and sit at their ease in flaming straw ; alchemists in 
 possession of the philosopher's stone, but their stomachs as empty as their 
 bellows ; monks carrying about fairies shut up in glass vials, into which 
 Gr d l disa they had been decoyed by distilled dew ; salamanders which 
 pearance of ere- had been engendered in a fire maintained without ever go- 
 ing out for forty years ; a rain in Egypt in which there fell 
 multitudes of little men of less than one span, clothed in black garments, 
 and with mitres like bishops : these were all facts in the philosophy of 
 that day. The explosions and choke-damp of mines were not disentan- 
 gled from spectres and faces of abominable appearance which had been 
 seen in those subterranean solitudes by numberless witnesses until the 
 dawn of pneumatic chemistry. The palingenesis, or resurrection of roses 
 and apparitions of flowers, so acceptable in doctrinal theology, continued 
 to be received until crystallography was cultivated. These wonders have 
 all passed away. 
 
 The character which marks this change is the gradual dropping of mys- 
 tery and the supernatural. The same career is followed from infancy to 
 maturity, both in the individual and in society. 
 
 It is not necessary to pursue any further this historical outline. It 
 would bring us to events which can scarcely be spoken of with correct- 
 ness and impartiality, on account of their nearness to our own times. 
 Here, therefore, we may pause, to collect such inferences and present such 
 reflections as the facts we have offered suggest. 
 
 It may, then, be observed, that the old white inhabitants of Europe 
 Ph siolo ical were no * a ^ e * commence their civilization from their own 
 change of Eu- interior resources, but were thrown into that career by the ex- 
 ample and aid of a more southern and darker people, whose 
 climate was more favorable. The artificial change which spread by de- 
 grees over Europe, through the introduction of more comfortable modes 
 of life, at last compensated for the natural climate defect, and the Euro- 
 pean entered on the course of advancement, undergoing, as we have seen 
 in the last chapter, a physical as well as a mental change. 
 
EFFECT OF MOHAMMEDANISM OX EUROPE. 635 
 
 Contemporaneous with the commencement of this physiological and 
 psychical change was the introduction of a method of record Eesult of the 
 by writing, which at once aided, in the most marked manner, introduction of 
 the dissemination of this improving condition, especially by * 
 leading to the consolidation of society through the introduction of durable 
 systems of law. By this, the influence of men and of generations was 
 indefinitely extended. The opinions and thoughts of those times have 
 actually, in many instances, descended to us. Elsewhere we have dwelt 
 on the fact that these effects in the progress of humanity are foreshadow- 
 ed and illustrated in the course of individual development. A high psy- 
 chical condition demands as its essential, both in the individual and in 
 the race, a mechanism of registry. 
 
 From the preceding imperfect narration we may moreover gather that 
 the progress of civilization in Europe has not been in the way Centre of intel- 
 of a diffusion from a central point, but that there has been a lect of Eur P e - 
 shifting of the centre of intellect. For a length of time it was in Greece ; 
 then it passed to Italy ; in our times it is still more to the west. In a 
 philosophical respect, the result of Mohammedanism on Europe has been, 
 through the introduction 'of physical science by the Arabians, to coalesce 
 the centre of intellect and the centre of force. Henceforth upon that 
 continent physical power must be subordinate to intellectual. 
 
 In this we see what is the true interpretation of the influence which 
 Mohammedanism has exerted on Europe an influence which, Effect of Mo _ 
 though popularly, is very unworthily represented as an oc- hammedanism 
 
 ? o r / /^ *rt on the centre 
 
 cupation of Spam for a few centuries and the capture of Con- O f intellect of 
 stantinople. In truth, it was of a far higher and very dif- Eur P e - 
 ferent order. The Koran of the Arabians failed to make its way through 
 Europe, but it was very different with the physical science of the Arabi- 
 ans. Its spread was the true foundation of modern national power, for 
 it at once occupied itself with the development of material resources and 
 the introduction of useful inventions. The manner of thought it engen- 
 dered lies really at the basis of the great intellectual controversy of our 
 times. The translation of the centre of intellect from Italy to the West 
 is the legitimate issue of the Moorish invasion of Spain. 
 
 As regards that propensity to the decomposition of every thing into 
 its constituent elements which is the tendency of the Euro- Eesult of the 
 pean, though doubtless it has its disadvantages, we are not enc^n^Eu" 
 to suppose that it leads of necessity to an intellectual chaos, ropean mind. 
 Those authors who view with dismay our present state, who represent 
 us as though, both in polity and religion, we were crumbling to pieces, 
 and that the multiplicity of opinions and sects, which are ever on the 
 increase, is the precursor of a universal anarchy, have never duly con- 
 sidered that out of such a state it is possible in. an instant for fixed 
 
636 CONDITION OF EUROPEAN IMPROVEMENT. 
 
 principles of order to emerge, and this not by any process of compression 
 or suppression, but spontaneously in the natural course of events. In 
 the outset of this brief historical description I have alluded to the adop- 
 tion of alphabetic writing in Europe as a signal illustration of the mental 
 peculiarity of the inhabitants ; this may also serve to make clear the 
 paradoxical assertion that systems founded on indefinite subdivision 
 may suddenly free themselves from complexity and become simple and 
 perspicuous. On a superficial consideration of the thing, one might im- 
 agine that to decompose articulate sounds into their constituent syllables, 
 with a view of representing those syllables by symbols, would be at- 
 tended with a prodigious complication, and that such is the case the Chi- 
 nese have found, who have pursued this plan in its details until it is 
 said that their alphabet contains 80,000 letters ; but still more would it 
 be supposed that if those syllables were in their turn decomposed into 
 their constituent parts, the required elements would be utterly unman- 
 ageable by reason of their number, and the art of writing utterly imprac- 
 ticable ; yet do we not find, on the contrary and it may be an instruct- 
 ive lesson to us that when the decomposition is thus pushed to its ex- 
 treme, instead of myriads of characters b$ing required, as we might have 
 plausibly expected, an alphabet of 20 or 30 letters is all we want ? The 
 state of opinion in Europe is illustrated by the state of writing in China. 
 
 In view of the facts presented in this and the foregoing chapter, we 
 may come to the general conclusion that the extremes of humanity, which 
 are represented by a prognathous aspect and by a complexion either very 
 dark or very fair, are equally unfavorable to intellect, which reaches its 
 greatest perfection in the intermediate phase ; that, even in the condition 
 which was presented by the inhabitants of Europe three thousand years 
 ago, no advance in civilization was possible, save by first accomplishing 
 Conditions of an ^solute physical change in their constitution through 
 European im- modifications in their habits of life equivalent to a true cli- 
 3nt * mate change a preparation for a higher mental development 
 by an amelioration of their condition of life. 
 
 The civilization of the European could never have been accomplished 
 save by preparing the way through such a physical change. It followed 
 that change in the manner that effect follows its cause. Its incident was 
 the transformation of the fair race which then occupied all Europe to an- 
 other of a darker hue ; the extinction of the disappearing people not be- 
 ing accomplished by such means as an extermination, after the manner 
 in which the North American Indian is dying out, but by a slow and true 
 metamorphosis into another form. 
 
 Advance in civilization takes place during such a metamorphosis. Asia, 
 Stationary con- which, at an early period, must have exhibited a mental de- 
 
 tion of Asia, yelopment of great rapidity, has long ago become stationary. 
 
ADVANTAGES OF THE ANALYTICAL MIND. 637 
 
 In her physical life there is no change, and hence none in her intellect- 
 ual. Her wandering central tribes encamp on the steppes in the same 
 felt huts that their ancestors did two thousand years ago ; her southern 
 people never vary their customs. That which, in a philosophical respect, 
 is the most important condition, domestic economy, has undergone no 
 kind of modification. 
 
 But with us, how different ! The hardships of life have to a very great 
 extent been removed, and we are familiar with a degree of comfort to 
 which our predecessors were wholly strangers. Not that we have been 
 freed from all trials ; it has only been an exchange of bodily sufferings 
 for mental anxieties. Our higher condition has created new wants and 
 new sources of pain. 
 
 With the transformations through which, as a race, we have passed, 
 and with the assumption of that analytical mental character Advantages 
 to which I have referred, there has been gained a capability arising from an 
 
 < i * . i -!{ 1 j i /* c analytical and 
 
 oi indefinitely modifying our state, and, therefore, ot improv- mental consti- 
 ing it. It is this which pre-eminently distinguishes the Eu- tution - 
 ropean ; that whatever scientific discovery he makes, or whatever inven- 
 tion occurs to him, he forthwith applies it to economic advantage, and is 
 thereby perpetually impressing a change on his own state. In this re- 
 spect, even a single generation often suffices to show the advances which 
 are made. We have only to recall the greatly improved means of loco- 
 motion ; the instantaneous transmission of intelligence through many 
 thousand miles ; the development of industrial art, and the rendering 
 available mechanical powers for many new purposes, which have been 
 achieved in less than a single century. Nor does there seem to be any 
 possible limit to human advance in this path. 
 
 Since thus the mind of the European is essentially analytic, his ad- 
 vance in civilization, as it were in a geometrical progression, is the neces- 
 sary consequence thereof. If we examine his career in subordinate par- 
 ticulars, it illustrates equally his mental physiognomy ; it is the same 
 whether we look to his passage in philosophy, science, politics, or religion. 
 If I may be permitted without offense so to say, his divergence from a 
 single form of faith, the springing up of those numberless denominations 
 and sects which constitute the most observable feature of his present re- 
 ligious state, is a result which he can not help, for it is the consequence 
 of his organization. Things which were possible in the eighth century 
 had become impossible in the new state of the sixteenth. And so, too, 
 it is in his political relations. 
 
 Herein consists the superiority of the analytical over the synthetical 
 mind. To the work of him who pulls to pieces there is no end, but he 
 who puts things together comes to an end of his task. 
 
INDEX. 
 
 ABDUCENTES, 334. 
 
 Aberration, chromatic and spherical, 386. 
 
 Abrupt and gradual impressions, 483. 
 
 Absorbed material, course of, 109. 
 
 ABSORPTION, forces of, 110 ; by blood-vessels, 
 49, 84, 102 ; nutritive, 84 ; double mecha- 
 nism for, 84 ; in plants, 86 ; summary of, 
 108 ; by lacteals, 84, 86 ; by lungs, 163 ; 
 by general surface, 98 ; by skin, 98, 241 ; 
 two kinds of, 86 ; interstitial, 98 ; selecting 
 power in, 99. 
 
 Abyssinian, 577. 
 
 Acid, hydrochloric, use of, 52. 
 
 Activity of the brain depends on arterializa- 
 tion, 326. 
 
 Affinity for tissues the cause of circulation, 
 133, 147. 
 
 Africa, influence of Europe and Asia on, 593 ; 
 prospective civilization of, 597 ; inhabit- 
 ants of, 577. 
 
 Agassiz on origin of nations, 568. 
 
 Age, influence of, 61, 172 ; old, 545. 
 
 Agents, external, influence of, on man, 567. 
 
 Agony, final, 562. 
 
 Air, introduction of, 160; expired per min- 
 ute, 168 : passages, evaporation from, 186. 
 
 Air-cells of lungs, 159, 160. 
 
 Albumen, 29 ; transformation of, into fibrin, 
 100 ; quantity of, 121. 
 
 Albuminose, 61, 64. 
 
 Alcohol, use of, in supporting heat, 20 ; effect 
 of, 182, 406. 
 
 Alexander, expedition of, 620. 
 
 Alexandria, library of, 624. 
 
 Aliment, necessity for, 10. 
 
 Allan tois, 531. 
 
 Allotropism of bodies, 188 ; decay depends 
 on, 244. 
 
 Alpha and Beta lactic acid, 75. 
 
 Alphabetic writing, 358. 
 
 Alternate consciousness, 330. 
 
 Alternation of generations, 514, 537. 
 
 Amber, trade in, 619. 
 
 Amelioration of negro, 578. 
 
 America, discovery of, 632 ; spread of Chris- 
 tianity in, 598 ; Indians, 575. 
 
 Amnion, 530. 
 
 Amphibia, blood of, 121. 
 
 Analogy of spinal and ventral cord, 308. 
 
 Analytical mind of European, 592 ; advan- 
 tages of, 618, 635, 637. 
 
 Animal, capillary circulation of, 133 ; heat 
 illustrated by locomotive, 187 ; makes fat, 
 247; motion, 431. 
 
 Animal kingdom, subdivisions of, 176. 
 
 Anterior roots of spinal cord, 296. 
 
 Anthropomorphism, 286. 
 
 Antrum duodeni, 61 ; pylori, 61. 
 
 Ants, habits of, 605. 
 
 Aplysia, 280. 
 
 Apparitions, 402. 
 
 Appendix vermiformis, 63. 
 
 Approach of sleep, 532. 
 
 Aqueous humor, 386. 
 
 Arabs, discoveries of, 629 ; influence of, 629. 
 
 Araucanians, 598. 
 
 Arc, automatic, 277 ; cellated, 278 ; influen- 
 tial, 282; commissured,279; multiple, 278; 
 registering, 281. 
 
 Aristotle, 620. 
 
 Arm, 580. 
 
 Art, contributions of Asia to, 595. 
 
 Arteries, coats of, 140 ; contractility of, 141 ; 
 structure of, 140. 
 
 Article of death, 411. 
 
 Artificial larynx, 355. 
 
 Ascaris acuminata, 524 ; nigrovenosa, 524. 
 
 Ascent of sap, causes of, 87. 
 
 Ascherson on use of fat, 101. 
 
 Asia, stationary condition of, 636. 
 
 Asiatic contributions, 595. 
 
 Asterias, nervous system of, 279. 
 
 Astrology, 178. 
 
 Atmosphere, action of, on plants, 464, 482. 
 
 Attraction, capillary, 104. 
 
 AUDITORY MECHANISM, general view of, 
 376. 
 
 Auditory muscles, estimate of contraction of, 
 367; nerve," 361. 
 
 Auricles of heart, 138, 146. 
 
 Australian, 563 ; forests, 474. 
 
 Automata, insects are, 609. 
 
 Automatic arc, 277, 283 ; registering, 281. 
 
 Awakening, 553. 
 
 Axmann on nerves, 263. 
 
 B. 
 
 BACON, ROGER, 625. 
 
 Balance between heating and cooling, 186. 
 Barbarism, 604. 
 Barral on food distribution, 39. 
 Basilar view of skull, 584. 
 Beaumont on food, 66. 
 Becquerel, table from, 33. 
 Bee, formation of fat by, 248. 
 Beef, digestibility of, 65. 
 Bell, discoveries of, 259, 298, 318. 
 Beneke on hospital diet, 35. 
 Bernard on digestion, 76 ; on fat, 71 ; on sali- 
 va, 196 ; on liver-sugar, 208. 
 i Bernouilli, principle of, 90. 
 
640 
 
 INDEX. 
 
 Berzelius on lactic acid, 75; on perspiration, 
 240. 
 
 Bibra, Von, on brain fat, 274. 
 
 Bidder on albuminates, 39 ; on section of 
 pneumogastric, 54. 
 
 Bidder and Schmidt on intestinal juice, 69 ; 
 on bile, 70 ; table by, 70. 
 
 BILE, secretion of, 70, 110, 202 ; composition 
 of, 204; formed from venous blood, 110, 
 303 ; sources of, 202 ; aids in introducing 
 fat, 91; spiral course of, 201; change by 
 retention of, 205 ;' period of maximum flow 
 of, 205 ; not formed in the liver, 206 ; man- 
 ner of removal of, 206. 
 
 Bipolar nerve-cell, 264, 268. 
 
 Bird, digestive tract of, 58; respiration and 
 heat of, 159 ; talking, 352. 
 
 Bishop of Chiapa, his accusation, 632. 
 
 Black pigment, 387. 
 
 Black Sea trade, 619. 
 
 Blastodermic vesicle, 524. 
 
 Bligh on Pelagians, 580. 
 
 BLOOD, 111; properties of, 112 ; composition 
 of, 112 ; total amount in body, 113 ; coag- 
 ulation of, 113 ; buffy coat of, 114 ; changes 
 produced in by respiration, 120, 126, 134 ; 
 excretion of carbonic acid from, 126, 167 ; 
 changes of color of, 169 ; density of, 169 ; 
 salts of, 124 ; gases of, 125 ; functions of 
 constituents, 125 ; course of, 134 ; distribu- 
 tion of, 144 ; glandular change of, 190. 
 
 Blood of spleen, 212. 
 
 Blood-cells, form of, 1 15 ; constitution of, 
 118; origin of, 94, 115; destruction of, 
 209 ; increase of, 125 ; diminution of, 126 ; 
 short life of, 127; changes in form, 117; 
 cell wall of, is fibrin, 117. 
 
 Blood, colorless, corpuscles of, 115, 120. 
 
 Blood crystals, 119. 
 
 Bloodletting, reduction of temperature by, 
 184. 
 
 Blood-vessels, origin of, 528. 
 
 Blumenbach's method of examining the skull, 
 582. 
 
 Bone, 253; sources of, 257; composition, 254 ; 
 growth of, 256. 
 
 Bonito, 177. 
 
 Boussingault on expiration, 39 ; on gum, 72 ; 
 on fat, 39, 229. 
 
 Bovista giganteum, 88. 
 
 Bowman on kidney, 223. 
 
 Brahmin, 573. 
 
 Brain, 313. See Cerebrum and Cerebellum. 
 
 Brazen men, 634. 
 
 Bread, 33 ; use of butter on, 34 ; making of, 
 illustrates digestion, 78 ; sets free alcohol, 
 79. 
 
 Breath, the first, 148. 
 
 Breathing, act of, 156. 
 
 Bright on pancreas, 71. 
 
 Bronchial tubes, 159. 
 
 Brown-Sequard on muscle, 443 ; on rigor 
 mortis, 453 ; on spinal cord, 299. 
 
 Bruchium, gardens of, 621. 
 
 Bud, its nature, 469. 
 
 Budding, 469, 535 ; reproduction by, 495, 535. 
 Buffon on infancy, 539. 
 
 Buffy coat, 114. 
 Burning lenses, 461. 
 Butter, making of, 31. 
 
 CALIFORNIANS, 576. 
 
 Calorific hypothesis of vision, 599. 
 
 Calorifacient digestion, 63. 
 
 Camelopard, 491. 
 
 Camera obscura, 381. 
 
 Camper's method of examining skulls, 581. 
 
 Canaliculi, 253. 
 
 Canals, semicircular, 375. 
 
 Cape of Good Hope, discovery of, 34, 631. 
 
 Cape Hyrax, stomach of, 59. 
 
 CAPILLARY VESSELS, 39, 141, 160; move- 
 ment of blood in, 145 ; of muscle, 459. 
 
 Capillary absorption, 103 ; attraction, 104 ; 
 propositions respecting, 105 ; motion, 131. 
 
 Capillary circulation, 142 ; phenomena of, 
 145 ; in acardiac foetus, 144 ; in asphyxia, 
 145; local excitement, 144. 
 
 Carbohydrates, 71 ; turn into fat, 81 ; make 
 up deficit of albumen, 39. 
 
 Carbonic acid excretion, 164; sources of, 164, 
 252; introduces oxygen, 165 ; decomposed 
 by light, 461. v 
 
 Carcinus msenas, 510. 
 
 Career of man, 612 ; of organic form, 456. 
 
 Carnivora consume themselves, 36 ; fibrin of 
 their blood, 123 ; find fat in their food, 248. 
 
 Carp, lung of, 157. 
 
 Carpenter on nervous system, 259 ; on sen- 
 sorium, 319 ; on analogy between spinal 
 and ventral cords, 307 ; on generation, 
 537. 
 
 CASEIN, 30, 31, 231 ; pre-exists in plants, 36 ; 
 changes into fibrin, 35 ; dissolves phos- 
 phate of lime, 35. 
 
 Castle building, 330. 
 
 Catamenia, 519. 
 
 Caudate vesicles, 264. 
 
 Causes of sleep, 552. 
 
 CELLS, primordial, 458 ; simple and nucle- 
 ated, 492; animal, 496 ; circulation in, 132. 
 
 Cells of blood, 116; uses of, 129; numbers 
 of, in different animals, 121. 
 
 Cells of kidney remove unoxidized bodies, 
 
 223. 
 
 Cells in lungs, 159. 
 
 Cells, nerve, 264. 
 
 Cellulose, 71. 
 
 Centre of intellect, 635. 
 
 Centres of nerves, 290. 
 
 Centripetal and centrifugal fibres, 265. 
 
 Cephalic ganglia, 271, 607. 
 
 CEREBELLUM, 322; development of, 314 ex- 
 periments on, 323 ; structure and function 
 of, 322. 
 
 Cerebral sight, 401. 
 
 Cerebro-spinal fluid, 326. 
 
 CEREBRUM, structure of, 317; development 
 of, 314; aspects of, 316 ; tracts of, 318; 
 ganglia at base, 319; weight of, 325; at- 
 mospheric pressure on, 326. 
 Cheese, making of, 31. 
 
INDEX. 
 
 641 
 
 Cheselden's case of cataract, 419 ; on the ear, 
 365. 
 
 Chest, type of, 161. 
 
 Chilians, 576. 
 
 Chimpanzee, 581. 
 
 Chinese, 574 ; writing, 636. 
 
 Chitin in wings of insects, 71. 
 
 Chlorine and hydrogen, 471. 
 
 Cholepyrrhin, 124. 
 
 Cholera, effect of, 22. 
 
 Cholesterine, 275. 
 
 Chorda dorsalis, 528. 
 
 Chorion, 523 ; changes in, 525. 
 
 Choroid coat, 384 ; function of, 394. 
 
 Chossat on inanition, 178, 243. 
 
 CHBISTIAN CHURCH, 626 ; spread of, in Amer- 
 ica, 598. 
 
 Chromatic aberration, 386. 
 
 Chronometer, illustration of heart by, 140. 
 
 CHYLE, 53 ; absorption of, 87 ; causes of the 
 flow of, 89 ; composition of, 92 ; corpuscles, 
 first appearance of, 94 ; action of water and 
 acetic acid on, 94. 
 
 Chyme, 53. 
 
 Cilia, 431. 
 
 Ciliated animacule, 432. 
 
 CIRCULATION, 145 ; objects of, 111, 134 ; 
 changes during, 126 ; course of, 134 ; in 
 plants, 132 ; in lower animals, 135 ; action 
 of heart in, 138 ; sounds of heart in, 139 ; 
 nervous influence on, 140 ; foetal, 531 ; pla- 
 cental, 527; portal, 134; connection of 
 parts by, 112 ; dependence of, on respira- 
 tion, 133. 
 
 Civil law, 628. 
 
 Civilization, effect of climate on, 599 ; com- 
 pared with barbarism, 604. 
 
 Classification of natural history, 506 ; of 
 skulls, 586. 
 
 Climates, botanical, 481. 
 
 Clock, illustration from, 485. 
 
 Coagulation of blood, 113. 
 
 Cochlea, 364, 368 ; comparative anatomy of, 
 373. 
 
 Cceliac axis, ramifications of, 49. 
 
 Coinage, introduction of, 620. 
 
 Cold-blooded animals, 172, 176. 
 
 Coleridge on dreams, 556. 
 
 Colladon on diving-bell, 366. 
 
 Color, origin of, 589. 
 
 Colored rays, effect of, 461. 
 
 Colostrum, 225. 
 
 Combustion, artificial, 17 ; organic, 17, 18. 
 
 Commerce, origin of European, 619. 
 
 Comminution instruments, 40. 
 
 Commissures, function of nervous, 280. 
 
 Comparative history, 612. 
 
 Compartments of ruminant's stomach, 60. 
 
 Complemental air, 165. 
 
 Complexion of man, 571, 572. 
 
 Conception, 530. 
 
 Condensing action of membranes, 155. 
 
 Condition of dreams, 558. 
 
 Condorcet on dreams, 556. 
 
 Conductibility in nerves, 265. 
 
 Conferva, 495. 
 
 Congelation, perpetual, 473. 
 
 s 
 
 Conjugation, modification of, 515. 
 Consonants, 356 ; explosive and continuous, 
 
 357. 
 
 Constant temperature, problem of, 176. 
 Constituents of plants, sources of, 4G3 ; of the 
 
 blood, functions of, 125. 
 Contarini, Cardinal, on circumnavigation, 625. 
 Contractile fibre-cells, 435. 
 CONTRACTILITY of muscle, 442, 449 ; nature 
 
 of, 442. 
 Contraction, hypothesis of, 451 ; by water, 
 
 451 ; by touch, 452 ; after death, 444. 
 Control of heat by nerves, 186. 
 Converging media, 381. 
 Cooling agencies, 184. 
 Cord, spinal, 294 ; conduction by, 299. 
 Cornea, 384. 
 Corpuscles, of milk, 225 ; of fat, 246 ; of 
 
 blood, 116; origin of, 101, 115; colorless, 
 
 93, 115 ; of chyle, 93, 143 ; proportion of, 
 
 125. 
 
 Cotyledons, 526. 
 Couch on metamorphosis, 510. 
 Course of the bile, 202. 
 Crab, edible, 510. 
 Cranial nerves, 333. 
 Creatine, 447. 
 
 Crevice, passage of water through, 105. 
 Crime, tendency to, 543. 
 Crises, change by, 148, 484. 
 Crus cerebri, 314 ; cerebelli, 314. 
 Crusades, 630. 
 Crystalline lens, 386. 
 Crystals of blood, 119. 
 Cutaneous absorption, 98. 
 Cuvier on organisms, 466. 
 Cycles of progress, 512. 
 
 D. 
 
 DALTON on corpus luteum, 522 ; on diffusion, 
 152. 
 
 Daubenton on skull, 580. 
 
 Davy on animal heat, 178; on meconium, 
 203 ; on protoxide of nitrogen, 412. 
 
 Deafness in diving-bell, 366 ; partial, of infe- 
 rior animals, 377. 
 
 Death, 560 ; from accident and old age, 561. 
 
 Decay, 243. 
 
 Deception, 404 ; of touch, 421. 
 
 Deleau on the voice, 356. 
 
 Descartes on insects, 609. 
 
 Descent of dhp, causes of, 87, 132. 
 
 Despretz on animal heat, 182. 
 
 Deutencephalon, 292. 
 
 DEVELOPMENT, 505 ; of the ear, 378; of the 
 eye, 380 ; of muscle, 440 ; geometrical 
 modes, 447 ; of bird, 35 ; of heart, 135. 
 
 Diaphragm movements, 161. 
 
 Diastose salivaire, 45. 
 
 Diet, 34. 
 
 Differences in men, 563. 
 
 DIFFERENTIATION, 500 ; causes of, 502 ; in- 
 fluence of heat on, 503 ; epochs of, 504 ; 
 defined, 511. 
 
 DIFFUSION of gases, 152 ; force of, 153, 156; 
 general facts of, 156 ; effect of, 162. 
 
 S 
 
642 
 
 INDEX. 
 
 Diffusion of influence in granular nerve ma- 
 terial, 268. 
 
 DIGESTION, nature of, 16, 40, 52, 63 ; object of, 
 61,66; histogenetic, 63 ; calorifacient, 63 ; 
 is mechanical and chemical, 57 ; double, 
 46 ; processes of, as insalivation, 40, 46 ; 
 deglutition, 46 ; passage into duodenum, 
 52, 67 ; passage along intestine, 67. 
 
 Digestion, artificial, 52, 54. 
 
 Digestion of gum, 71 ; of cellulose, 71 ; of 
 starch, 72 ; of sugar, 72 ; of fat, 76 ; intes- 
 tinal and stomach, contrasted, 81. 
 
 Digestive tract, divisions of, 48 ; of insect, 
 58 ; of various animals, 59 ; juices, their or- 
 ganic ingredient, 77 ; power injured by sal- 
 iva, 50. 
 
 Discs of muscular fasciculi, 436 ; of blood, 
 see Cells. 
 
 Discus proligerus, 520. 
 
 Distribution, vertical, of plants, 473 ; of heat, 
 473. 
 
 Diurnal amount of air used, 166. 
 
 Diurnal variations of heat, 178. 
 
 Donne on saliva, 44. 
 
 D'Orbigny on Inca Indians, 487. 
 
 Dormouse, stomach of, 59. 
 
 Dorsal cord, 293 ; lamina, 527. 
 
 Double trains of thought, 329. 
 
 Doubleness of brain, 327. 
 
 Dowler's experiments, 444. 
 
 Draper, J. C., on respiration, 168, 239 ; on 
 urea, 220. 
 
 Dreaming, 555. 
 
 Drowning, restoration from, 133. 
 
 Drum of ear, 364. 
 
 Duality of mind, 329. 
 
 Duct, thoracic, 90. . 
 
 Ductless glands, 211. 
 
 Ducts, dotted, 498. 
 
 Dufay, law of, 104. 
 
 Dugong, heart of, 136. 
 
 Dulong on animal heat, 182. 
 
 Dumas on fat, 248. 
 
 Dutrochet on endosmosis, 106. 
 
 Dyslysin, 83. 
 
 Dytiscus, 438. 
 
 E. 
 
 EAR, structure of, 376 ; external, 360 ; action 
 
 of, 359 ; auditory nerve of, 368 ; labyrinth 
 
 of, 375 ; tympanum of, 365. 
 Education, effect of, 330, 543. . 
 Edwards, Milne, on crustaceans, 488 : on fat, 
 
 248. 
 
 Egg, development of bird from, 35. 
 Egypt, 613, 614. 
 Elasticity, heat of, 185. 
 Elective filtration, 196. 
 Electrical tastes, 430 ; currents in muscles, 
 
 443 ; conductors, nerves resemble, 266. 
 Electricity, 275. 
 Eleventh pair, 342. 
 Elixir of life, 633. 
 Elliptical skull, 586. 
 EMBRYO, 538 ; germinal membrane of, 525 ; 
 
 vertebral column of, 532 ; vascular area of, 
 
 527 ; allantois, 538 ; circulation, 531 ; in- 
 fluence of mother, 534 ; size and weight of, 
 at birth, 540, 541 j viability of, 545. 
 
 Embryonic development of brain, 313 ; of 
 circulating apparatus, 531 ; forms, 507. 
 
 Emergence of impressions from brain, 408. 
 
 Emotions, mental, 290. 
 
 Empiricism, extinction of, 25. 
 
 Endocardium, 137. 
 
 Endochrome, 493. 
 
 Endogenous generation, 496. 
 
 Endosmosis, 105, 107, 131 ; through films, 
 154 ; through stucco, 107 ; force of, 107, 
 153. 
 
 Enteric juice, 369. 
 
 Epencephalon, 292, 528. 
 
 Epidermis, 233 ; functions, 234. 
 
 Epithelium, 197, 234 ; cylindric, tesselated, 
 ciliated, 197. 
 
 Epochs of globe, 481 ; of life, 547. 
 
 Equilibrium, conditions of, 10, 22, 560. 
 
 Erect vision, 396. 
 
 Esquimaux, 568. 
 
 Europe, primitive state of, 613. 
 
 European history, 610. 
 
 Eustachian tube, 367. 
 
 Euthanasia, 561. 
 
 Evaporation, 185. 
 
 Excretion, 213. 
 
 Exhalation by lungs, 21, 22. 
 
 Exosmosis, 106, 131. 
 
 Expectoration, 47. 
 
 Explosive consonants, 357. 
 
 Extinction of Indians, 600. 
 
 Extinctions, 484, 488. 
 
 EYE, structure of, 382 ; nervous mechanism 
 of, 389, 394 ; accessary apparatus of, 399. 
 
 Eyeball, motions of, 401. 
 
 Eyebrows, 399. 
 
 Eyelids, 399. 
 
 F. 
 
 FABRICIUS AB AQUAPENDENTE on veins, 130. 
 
 Faeces, 83. 
 
 Fair races, disappearance of, 591, 636. 
 
 Falling, sensation of, 559. 
 
 Fasciculi of muscle, 433, 436 ; digestion of, 
 54. 
 
 FAT, 246 ; oxidizes gradually, 252 ; relation 
 of, to bile, 207 ; to nitrogenized tissue, 250 ; 
 in articles of forage, 229 ; emulsifying of, 
 71 ; produced from carbohydrates, 81 ; in- 
 troduction into villi, 91 ; saponification of, 
 93. 
 
 Faunal groups, 568. 
 
 Feeling and touching, distinction between, 
 422. 
 
 Female and male compared, 546. 
 
 Fenestra ovalis and rotunda, 361. 
 
 Ferments, 45, 80. 
 
 Feudal system, 631. 
 
 FIBRIN, 30, 93, 97, 114; loss of, 52; vegeta- 
 ble, 33 ; not an effete body, 98 ; organiza- 
 tion, 113; difference of, in blood and mus~ 
 cle, 114; variations in quantity, 122. 
 
 Fifth pair of nerves, 334. 
 
INDEX. 
 
 643 
 
 Filtering action of glands, 191. 
 
 Filtration, elective, 196. 
 
 Final agony, 562. 
 
 Finite nature of knowledge, 289. 
 
 Fire-place, exhausting nature of, 181. 
 
 First breath, 485. 
 
 First pair of nerves, 425. 
 
 Fishes, digestion of, 60 ; circulation in, 135 ; 
 respiration of, 150, 157. 
 
 Flame and plant, analogy between, 470. 
 
 Floral groups, 568. 
 
 Flour, 33. 
 
 Foetus, circulation in, 531. See Embryo. 
 
 Follicles, gastric, 49, 50 ; varieties of, 51. 
 
 FOOD, 16, 26 ; sources of, 27 ; classification 
 of, 27 ; value of, 28 ; different kinds of, 27, 
 28; of carnivora, 36 ; of herbivora, 36, 37 ; 
 nitrogen, 27, 35 ; movements of, 53 ; ad- 
 justs temperature, 179 ; demand for, 179 ; 
 allowance of, 11 ; digestibility of, 36, 66 ; 
 formed by plants and destroyed by animals, 
 37 ; minimum quantity of, 38. 
 
 Foramen magnum, 580. 
 
 Force of endosmosis, 107. 
 
 Forge tfulness of dreams, 557. 
 
 Formic acid, 240. 
 
 Fourcroy on perspiration, 240. 
 
 Fourth pair of nerves, 334. 
 
 Fowl, digestive tract of, 58. 
 
 Franklin on heat, 380. 
 
 Frerichs on food, 35 ; on saliva, 44. 
 
 Frog, lungs of, 159 ; development of, 509. 
 
 Front view of skull, 585. 
 
 Future state, 551. 
 
 G. 
 
 GALILEO, 455. 
 
 Gall on brain, 259. 
 
 Gall-bladder, 199. 
 
 Galvani, experiments of, 443. 
 
 GANGLIA, structure of, 263 ; spontaneous func- 
 tion, 289 ; of sympathetic, 140, 264 ; of 
 special sense, 315 ; cephalic, 607. 
 
 Gases of intestine, 82. 
 
 GASTRIC changes are subdivisions and assim- 
 ilation of water, 62. 
 
 Gastric juice, 49, 50 ; quantity of, 52 ; acid 
 of, 52, 54 ; relation of nervous influence to, 
 54. 
 
 Gelatine, 64, 65. 
 
 Gemmation, 534. 
 
 GENERATION, 515, 516 ; spermatozoa in, 517, 
 518. 
 
 Geographical distribution, 567. 
 
 Geography of plants, 472. 
 
 Geological changes, 480. 
 
 Geometrical modes of development, 457. 
 
 Germ-cell, 519. 
 
 Germinal membrane, 525 ; its layers, 527 ; 
 vesicle and spot, 521. 
 
 Germination, 458; heat of, 176. 
 
 Gestation, 533. 
 
 Gibraltar, Straits of, 620. 
 
 Gills, 135, 150, 157. 
 
 GLAND, 189 ; type of, 189, 197 ; vicarious ac- 
 tion of, 190 ; filtering action of, 190 ; par- 
 
 otid, 43 ; salivary, 43 ; submaxillary, 43 ; 
 
 sublingual, 43 ; mesenteric, 89 ; ductless, 
 
 211 ; mammary, 225. 
 Glandular blood, change in, 190. 
 Globulin, 118. 
 
 Glosso-pharyngeal nerve, 338. 
 Glucose, 73. 
 Gluten, 33. 
 Glycerine, 245. 
 Goodsir on lymphatics, 97. 
 Graafian follicle, 521. 
 Gradual death, 561. 
 Grafting, 469, 535. 
 Graham on diffusion, 152, 154. 
 Greeks, 613 ; schools of, 617. 
 Growth, 511, 538, 540 ; conditions of, 465. 
 Guinea, negro of, 579. 
 Gum, digestion of, 71. 
 Gundelach on fat, 248. 
 
 H. 
 
 HABITS OF NATIONS, 566, 569 ; of insects, 
 605. 
 
 Hsematin, 118 ; analysis of, 119. 
 
 Hsematococcus binalis, 494. 
 
 Hair, 236. 
 
 Hall, discoveries of, 259. 
 
 Hallucination, 402. 
 
 Harvey on circulation, 130. 
 
 HEARING, sense of, 359 ; structure of organ 
 of, 360 ; use of tympanum in, 364 ; audi- 
 tory nerve of, 368. 
 
 HEART, 135 ; fibres of, 137 ; valves of, 138 ; 
 development of, 135 ; of dugong, 136 ; ac- 
 tion of nerves on, 140 ; statement of action 
 of, 147 ; number of beats of, 130. 
 
 HEAT, 17, 18, 19, 20; check upon, 21, 22, 184 ; 
 equilibrium of, 22 ; animal, 175, 177; car- 
 bonic acid, relation to, 19, 20, 176 ; varia- 
 tions, 178; diurnal, 178 ; extreme, endura- 
 ble, 178; annual, 179; source of, 182; of 
 light rays, 389 ; removed from muscle, 447 ; 
 quantity for plants, 477 ; intensity and 
 quantity of, 477 ; decline of, 488 ; relations 
 of, 572 ; effect of, on skull, 590. 
 
 Heaths, absence of, from America, 474. 
 
 Height of man, 541. 
 
 Helmholtz on nerve, 266 ; on muscle, 445. 
 
 Hepatic artery, 200 ; cells, duct, vein, 200, 
 206. 
 
 Herbivora, 36. 
 
 Herculaneum, 465. 
 
 Hereditary transmission, 590. 
 
 Hermaphroditism, 574. 
 
 Hibbert on apparitions, 408. 
 
 Hippocratic face, 561. 
 
 Histogenetic digestion, 40, 63. 
 
 HISTORY a branch of Physiology, 604 ; Euro- 
 pean, 610 ; universal, 611 ; prognostics in, 
 612 ; comparative, 612. 
 
 Homogenesis and heterogenesis, 511. 
 
 Hot-blooded animals, 176. 
 
 Hottentots, 577. 
 
 Hubbenet, table by, 49. 
 
 Huber, 556. 
 
 Human groups, 568. 
 
644 
 
 INDEX. 
 
 Humboldt on respiration, 158 ; on plants, 471. 
 
 Humors of the eye, 386. 
 
 Hunter on reflexa, 596. 
 
 Hutchison on respiration, 166. 
 
 Hybernating animals, 172, 183. 
 
 Hydra, 5 1,52, 432, 501, 534. 
 
 Hydraulic action of auricle, 146. 
 
 Hydrochloric acid, 52, 62. 
 
 Hydrogen, use of, 17, 19. 
 
 Hypoglossal nerve, 343. 
 
 I. 
 
 IDEAL type of man, 565. 
 
 Idiot, composition of brain of, 273. 
 
 Illusions, 402. 
 
 Imago, 5.11. 
 
 Immortality of the soul, 415. 
 
 Impersonal operations,. 287. 
 
 Impressions, vestiges of, 288. 
 
 Improvability of man, 15. 
 
 Inanition, experiments on, 178, 243. 
 
 Inca Indians, 487. 
 
 Incombustible men, 634. 
 
 Independence and immortality of the soul, 
 285. 
 
 Independent action of each half of the brain, 
 328. 
 
 Index of prohibited books, 624. 
 
 Indians, 575 ; extinction of, 600. 
 
 India-rubber, diffusion through, 152. 
 
 Individuality, nature of, 468. 
 
 Indo-Europeans, 573. 
 
 Infancy of man, 538. . 
 
 Inflorescence, heat of, 176. 
 
 Influence of agents on man, 563, 567, 571 ; 
 of parent on child, 534. 
 
 Influential arc, 282. 
 
 Infusorials, heat of, 177. 
 
 Inosite, 447. 
 
 Inquisition, establishment of, 624. 
 
 Insalivation, 40. 
 
 Insanity of retina, 406. 
 
 INSECT, digestive tract of, 58 ; cephalic gan- 
 glia, 271 ; nervous system, 271 ; respira- 
 tion of, 157; development of, 510; struc- 
 ture and habit of, 603, 605 ; memory and 
 metamorphoses of, 608. 
 
 Instantaneousness of dreams, 556. 
 
 Instinct distinguished from reason, 603. 
 
 Insubordination of one hemisphere, 329. 
 
 Intellect, maximum of, 591 ; centre of, 635. 
 
 Intensity, adjustment for variations of, in 
 eye, 388. 
 
 Intensity of heat, 477, 572. 
 
 Interference, mechanism of, in ear, 372 ; of 
 nervous impressions, 269. 
 
 Interstitial death, 244 ; movements, 151. 
 
 INTESTINE, length of, 42 ; salts and gases of, 
 82 ; digestion in, 63, 68, 81 ; contents, 
 changes of, 83 ; section of wall of, 85 ; per- 
 istaltic movements of, 68 ; passage of food 
 through, 67, 81 : glands and secretion of, 
 69, 70; 
 
 Inverse problems, 284, 482. 
 
 INVERSE VISION, 401 ; use of, 416. 
 
 Iris, 385. 
 
 Iron acted on by gastric juice, 50 ; source of, 
 
 in blood-cells, 118. 
 Irrespirable gas, action of, 133, 169. 
 Isaacs on kidney, 217. 
 
 J. 
 
 JACKSON on the ear, 373. 
 
 Jacob's membrane, 390. 
 
 Jeffreys on respiration, 165. 
 
 Jesuits, 624. 
 
 Jones, Bence, on urine, 221. 
 
 Jones, Handfield, on hepatic cells, 206. 
 
 Jones, W., on blood-cells, 117. 
 
 K. 
 
 KAFFIRS, 577. 
 
 Kamtschatdale, 575. 
 
 Kangaroo, 59. 
 
 Kidney, 213 ; structure of, 214 ; tubuli uri- 
 niferi of, 215 ; circulation in, 215 ; devel- 
 opment of, 214 ; vicarious action, 186. 
 
 Kiestine, 231. 
 
 Kolliker on skin, 420 ; on retina, 391 ; spleen, 
 211. 
 
 Koumiss, 80. 
 
 Krause on sebaceous secretion, 240. 
 
 Kreatine, 447. 
 
 Kune on bile, 203. 
 
 L. 
 
 LABYRINTH, 361. 
 
 Lachrymal gland, 400. 
 
 Lacteals, 84, 86, 87, 91, 111 ; function of, 85 ; 
 and lymphatics, connection of, with respi- 
 ration, 100. 
 
 Lactic acid, 47, 52, 73, 74, 75. 
 
 Lacunas of bone, 253. 
 
 Lamina spiralis, 359. 
 
 Landerer on perspiration, 240. 
 
 Languages, 357. 
 
 Laplander, 568. 
 
 Larva, 510. 
 
 Larynx, 353 ; double, of birds, 352 ; artificial, 
 355. 
 
 Lateral inversion, 397. 
 
 Lateral view of skull, 581. 
 
 Law, civil, 628. 
 
 Lawrence on the leg, 580. 
 
 Laycock on cephalic ganglia, 607. 
 
 Leg, 580. 
 
 Legumin, 33. 
 
 Lehmann on absorbed nitrogen, 39 ; pep- 
 tones, 62 ; gastric solution, 66 ; gum, 72 ; 
 urine, 75 ; quantity of blood, 113 ; blood 
 crystals, 120; bile, 203 ; kiestine, 231. 
 
 Leidy on liver, 198. 
 
 Length of infant, 540 ; of sleep, 553. 
 
 L'Heritier on chyle, 96. 
 
 Lieberkuhn, follicles of, 69. 
 
 Liebig on lactic acid, 75; on fibrin, 98; on 
 blood gases, 125. 
 
 Life, conditions of, 9, 12. 
 
 Light, nature of, 399 ; influence of, 459. 
 
 Lime, phosphate of, 35. 
 
INDEX. 
 
 645 
 
 Liquor, sanguinis, 121 ; amnii, 530. 
 
 LIVER, 209 ; structure of, 199, 200, 201 ; de- 
 velopment of, 191, 198 ; secretion, 203, 
 205 ; sugar, 123 ; production of sugar and 
 fat in, 207 ; destruction of blood-cells in, 
 209 ; absorbed material goes to, 107 ; effect 
 of, on complexion, 588. See Bile. 
 
 Localization of functions in brain, 324^ of 
 plants and animals, 482. 
 
 Longevity, 545. 
 
 Loss of perception of time, 332. 
 
 LUNGS, structure of, 157, 159, 160; capillaries 
 of, 160; capacity of, 162 ; organic fibres of, 
 163 ; chemical changes in, 163. See Res- 
 piration. 
 
 Luther, Martin, vision of, 406. 
 
 Luxury, effect of, on skull,. 588. 
 
 Lymph, 95 ; salts of, 96 ; flow of, 99. 
 
 Lymphatic glands, 94. 
 
 LYMPHATICS, distribution of, 97 ; function of, 
 96, 98 ; origin of, 529. 
 
 M. 
 
 MACEDONIAN CAMPAIGN, 620. 
 
 Machines, speaking, 356. 
 
 Madagascar, native of, 577. 
 
 Madder in bone, 256. 
 
 Magellan, voyage of, 624. 
 
 Male and female, comparison of, 546. 
 
 Malpighian bodies, 215 ; sac, removal of li- 
 quid from, 224. 
 
 Mammary gland, 224 ; development of, 225 ; 
 action, 233. 
 
 Man, physical aspect of, 24 ; soul of, 25 ; ma- 
 turity of, 542. 
 
 Margarine, 246. 
 
 Mariolatry, 631. 
 
 Marmots, 172. 
 
 Mastication, 40. 
 
 Matters received, 16 ; dismissed, 17. 
 
 Maturity of man, 542. 
 
 Meconium, 202. 
 
 Medulla oblongata, 304 ; functions of, 306. 
 
 Melloni on light, 389. 
 
 Membrana granulosa, 520 ; decidua, 525, 526. 
 
 Membranes, selecting power of, 107. 
 
 Memory of insects, 608. 
 
 Menstruation, 519. 
 
 Mental emotions, nature of, 290. 
 
 Mental hallucination, 402. 
 
 Mental qualities of different nations, 592. 
 
 Mental strength, maximum of, 544. 
 
 Mesencephalon, 292, 528. 
 
 Mesenteric glands, structure of, 89 ; plexuses, 
 350. 
 
 Metacetonic acid, 246. 
 
 Metamorphosis, 490. 
 
 Metamorphosis of batrachians, 509. 
 
 Metaphysics, 259. 
 
 Midnight sun, 476. 
 
 MILK, 29, 31, 32 ; casein of, 29, 227, 231 ; 
 sugar of, 31, 227, 233 ; butter of, 31 ; salts 
 of, 31, 228 ; lactic acid of, 31 ; effect of 
 disease of, 33 ; composition of, 225, 226 ; 
 analysis of, 226 vicarious secretion of, 228. 
 
 Mind, 24. 
 
 Miracles, true, 624. 
 
 Mitchell on diffusion, 152. 
 
 Mohammedanism, influence of, 629 ; spread 
 of, in Africa, 597. 
 
 Moisture, influence of, 475. 
 
 Mongols, 574. 
 
 Monogamy, 594. 
 
 Monotheism, 601. 
 
 Mortality, 545. 
 
 Motion, ciliary, 431 ; muscular, 432. 
 
 Motor oculi nerve, 391. 
 
 Motor tract of brain, 319; of cord, 303. 
 
 Mouth, functions of, 40. 
 
 Mozambique, native of, 578, 
 
 Mucous membrane, 196 ; layer, 527. 
 
 Mucus, 43, 197; buccal, 43. 
 
 Mulberry mass, 523. 
 
 Miiller on bile, 203; on vision, 391 ; on voice, 
 354. 
 
 Multipolar nerve-cell, 264, 268. 
 
 Municipal system, 623. 
 
 Muscse volitantes, 404. 
 
 Muscle juice, 434, 437. 
 
 MUSCULAR FIBRE, structure of, 433 ; non-stri- 
 ated, 435,; motion of, 432 ; movements, co- 
 ordination of, 323 ; contraction of, 436 ; 
 reparation of, 446 ; blood-vessels of, 440 ; 
 contraction of, after death, 444 ; develop- 
 ment of, 440 ; analysis of, 441 ; capillaries 
 of, 439 ; effects of electricity on, 443. 
 
 Muza, his threat, 623. 
 
 N. 
 
 NAILS, 236. 
 
 Narwhal, 177. 
 
 Nations, origin of, 568 ; habits of, 569 ; prog- 
 ress of, 600. 
 
 Natural history, classification of, 506. 
 
 Negro, 579. 
 
 Neill on villi, 60. 
 
 NERVES, division of, 259 ; rate of conduction 
 in, 265 ; sheath of, 261 ; fibres of, 262 ; 
 function of fibres, 265 ; function of vesicles, 
 267 ; necessity of rest for, 272. 
 
 Nervous agency, magazines of, 268 ; trans- 
 mission of, 265 ; retention of, 269 ; inter- 
 ference of, 269. 
 
 Nervous arcs, 277 ; condition for action, 283 ; 
 centres, 290. 
 
 Nervous system, 258 ; controls heat, 186 ; de- 
 velopment of, 292 ; metamorphosis of, 608 ; 
 structure and functions of, 293. 
 
 Nervous vesicular matter, 260 ; ganglia, 263 ; 
 activity, 267; tissue, composition of, 273; 
 regeneration, 274. 
 
 Newport on insects, 309. 
 
 Newton, colored rings of, 105. 
 
 Nicolai on apparitions, 406. 
 
 Nightmare, 559. 
 
 Night sleep, 554. 
 
 Ninth pair of nerves, 338. 
 
 Nitrogen, use of, 16 ; in respiration, 171 ; prot- 
 oxide of, 412. 
 
 Nodal lines, 371. 
 
 Non-striated fibre, 435. 
 
 Nose, 424. 
 
646 
 
 INDEX. 
 
 Nucleated cells, circulation in, 131. 
 
 Nucleine, 117. 
 
 Nucleus, 493. 
 
 NUTRITION, 245, 252 ; connection with nerv- 
 ous agency, 186, 244 ; selecting power in, 
 245 ; three types of, 532 ; of carnivora and 
 herbivora, 36. 
 
 O. 
 
 OBJECTIVE OPERATIONS, 287. 
 
 Ocelli, 380. 
 
 Octopus, nervous system of, 279. 
 
 Ocular spectra, 396. 
 
 Oculo-motor nerve, 333. 
 
 ODORS, sensibility to, 424 ; localization of, 
 426. 
 
 Odyssey, 613. 
 
 Oil, emulsifying of, 71 ; globules on villus, 88. 
 
 Old age, 545. 
 
 Oleaginous principles of food, 36, 81. 
 
 Oleine, 246. 
 
 Olfactory organ, mechanism of, 424. 
 
 Olivary bodies, 304, 314. 
 
 Omphalo-mesenteric duct, 530 ; vessels, 531, 
 
 Operations, plants are, 470. 
 
 Opium, effects of, 406. 
 
 Optic nerve, 391. 
 
 Orang, 581. 
 
 ORGANIC FORM, career of, 456. 
 
 Organic life, nerve of, 344. 
 
 Organic periodicities connected with heat, 
 179. 
 
 Organisms, metamorphosis of, 489. 
 
 Organization, principle of, 457. 
 
 Organized bodies, allotropism of, 188. 
 
 Organs of sense, 359. 
 
 Origin of nations, 568. 
 
 Ornithorynchus, 224. 
 
 Ossicles, 367. 
 
 Ossification, 255. 
 
 Osterlein on villi, 86. 
 
 Ostrich, stomach of, 59. 
 
 Oval skull, 586. 
 
 Ovarium, origin of ova in, 520 ; corpus lute- 
 urn of, 522. 
 
 Ovisac, 520. 
 
 OVUM, 521 ; discharge of from ovary, 523 ; 
 changes of, 524 ; segmentation of, 524. 
 
 Owen on the arm, 380 ; on skull, 532, 584. 
 
 Oxalic acid in urine, 222. 
 
 OXYGEN, uses of, 47, 101, 134 ; in respiration, 
 134, 163, 182 ; influence of, on blood, 126 ; 
 changes albumen into fibrin, 101, 176 ; lib- 
 erated by plants, 461. 
 
 P. 
 
 PACINIAN BODIES, 420. 
 
 Paganism, fall of, 622. 
 
 Paine, Professor, on plants, 478. 
 
 Pale people, disappearance of, in Europe, 634. 
 
 Palingenesis, 634. 
 
 Pancreas, 68 ; juice of, 68. 
 
 Pantheism, 288. 
 
 Papal government, 623. 
 
 Papillae of skin, 419 ; of tongue, 428. 
 
 Parotid gland, 43. 
 
 Parturition, 533. 
 
 Par vagum, 340 ; influence of, on liver, 208. 
 
 Patagonians, 578. 
 
 Patella, nervous system of, 279. 
 
 Pathetici, 334. 
 
 Patina, 151. 
 
 Pelagian type, 579. 
 
 Pepsin, 49, 54, 55. 
 
 Peptones, 50, 53, 62. 
 
 Perception of time, loss of, 332. 
 
 Pericardium, 137. 
 
 Peristaltic movements, 53. 
 
 Peroxalate of iron decomposed by light, 461. 
 
 Persecution, result of, 624. 
 
 Persian empire, 616. 
 
 Perspiration, 238. 
 
 Persuasions, 544. 
 
 Peruvian, 576. 
 
 Peyer's bodies, 70, 94. 
 
 Phantasms, localization of, 415. 
 
 Philippine negro, 578. 
 
 Philosopher's stone, 633. 
 
 Philosophy, suppression of, 624. 
 
 Phrenicians, 619. 
 
 Phosphorus, 17, 23, 27, 32, 275. 
 
 Photographic effects of temperature, 393. 
 
 Phrenic nerve, 344. 
 
 Phrenology, 324. 
 
 PHYSIOLOGY, subdivisions of, 26 ; statical, 9 ; 
 dynamical, 455. 
 
 Piles of Bitter, 277. 
 
 Pine, woody fibre of, 498. 
 
 Placenta, 526. 
 
 PLANTS, individuality of, 468 ; quantity of 
 heat for, 467 ; secular changes of, 480 ; lo- 
 calization, 482. 
 
 Plasma, 121. 
 
 Plastic power, 459, 471. 
 
 Pneumogastric nerve, 340. 
 
 Polygamy, 594. 
 
 Polype, 51. 
 
 Polytheism, 601. 
 i Pompeii, 465. 
 : Pons varolii, 307. 
 i Porcupine, 59. 
 
 Porpoise, stomach of, 59. 
 ' Portal circulation, 119, 134, 201, 202. 
 
 Ports of Egypt, opening of, 616. 
 
 Posterior roots of spinal nerves, 296. 
 
 Potassium, iodide of, experiments with, 47, 
 52. 
 
 Powder of projection, 633. 
 
 Pre-existence, sentiment of, 331. 
 
 Prevost and Dumas on muscle, 439. 
 
 Prichard on habits of men, 569 ; on skull, 
 580, 585. 
 
 Priestley on gaseous endosmosis, 151. 
 
 Primitive trace, 293, 527. 
 
 Primordial cell, 458. 
 
 Principle of organization, 457. 
 
 Printing, 358. 
 
 Prognathous skull, 586. 
 
 Protein bodies removed by urine, 220, 222. 
 
 Provencal on respiration, 155. 
 
 Psammetichus, 615. 
 
 Psychical powers, 327. 
 
INDEX. 
 
 647 
 
 Ptolemies, 621. 
 
 Ptyaline, 45. 
 
 Pulsation of heart, 138 ; of arteries, 141. 
 
 Pulse, 139. 
 
 Pupa, 511. 
 
 Pyramidal skull, 586. 
 
 Pyramids, anterior and posterior, 304. 
 
 Q- 
 
 QUAIN ON ADIPOCIRE, 247. 
 
 Quality of sounds, estimation of, 375. 
 Quantity of heat, 477. 
 Quetelet, researches of, 15, 540. 
 Quick respiration, effect of, 168. 
 Quincey, De, on opium, 407. 
 
 R. 
 
 EADIAL fibre system, 390. 
 
 Radiation of heat, 185. 
 
 Ramlike action of heart, 147. 
 
 Rarefied air, effect of, 183. 
 
 Ray on insect habits, 606. 
 
 Reaumur on digestion, 55. 
 
 Reduction of temperature, 184. 
 
 Reflex action, 280 ; of insects, 609. 
 
 Reformation, 619, 625. 
 
 Registered impressions, 414. 
 
 Registering ganglia, 259 ; nerve arc, 281 , 282. 
 
 Registry of sounds, 358. 
 
 Regnault and Reiset on respiration, 170. 
 
 Repair, necessity of, 244. 
 
 Reparation, 23. 
 
 REPRODUCTION of cells, 494 ; and develop- 
 ment, 505 ; closes development, 513. 
 
 Reptile respiration, 158. 
 
 Residual air, 165. 
 
 RESPIRATION, 151, 156, 157, 170, 171, 174; 
 water removed by, 168 ; gases of, 163, 167, 
 171,176; movements in, 162; movements 
 of air in, 163 ; number of movements, 162 ; 
 influence of nervous agents on, 173; gen- 
 eral statement of, 174. 
 
 Respiratory digestion, 63. 
 
 Restiform bodies, 304. 
 
 Resurrection of roses, 634. 
 
 RETINA, 390, 392, 394 ; structure of, 385, 390 ; 
 disturbance of, 405. 
 
 Retzius on stomach, 61. 
 
 Reynoso on sugar, 208. 
 
 Rhakotis, 621. 
 
 Rhythmic contractions, 448. 
 
 Rigor mortis, 452. 
 
 Roman coins, 151. 
 
 Roman empire, 622. 
 
 Rotation of animals, 324. 
 
 Rudimentary organs, 491. 
 
 Rudimentary sounds, 325. 
 
 Rumford on clothing, 180. 
 
 Ruminant, stomach of, 59. 
 
 Running, 454. 
 
 S. 
 
 SABBATH DAY, 627. 
 Sahara, Desert of, 475. 
 
 Saladin, 631. 
 
 SALIVA, 43; action of, 46; quantity of, 44, 
 
 47 ; specific gravity of, 44 ; composition of 
 
 45 ; action of, in stomach, 46, 50 ; aeration 
 
 by, 47. 
 
 Salivary glands, 43. 
 Salpse, 537. 
 Salt, use of, 62. 
 Samoiedes, 568. 
 Sankey on brain, 325. 
 Sap, ascending, 87, 132. 
 Sarcolemma, 433, 438. 
 Scalse of ear, 368. 
 Scherer on urine, 221. 
 Schlossberger on brain, 274. 
 Schmidt on albuminates, 39 ; on blood-cells, 
 
 119 ; on pneumogastric, 54 ; on pepsin, 55 ; 
 
 on pancreatic juice, 68 ; on intestinal wa- 
 ter, 83 ; on transudation, 95. 
 Schneiderian membrane, 424. 
 Schultz on muscle juice, 434. 
 Schwann on nerves, 261. 
 Science, contributions of Asia to, 596. 
 Sclerotic, 384. 
 
 Scot, Reginald, on spirits, 407. 
 Scott, Walter, on lying, 404. 
 Sebaceous glands, 227. 
 
 Secreted matters pre-exist in blood, 192, 195. 
 Secretion, 189 ; structures for, 193 ; by serous 
 
 membranes, 193 ; by mucous, 196. 
 Seeing. See Vision. 
 Seguin on exhalation, 238. 
 Selecting power, 99. 
 Semicircular canals, 361, 364, 374. 
 Sensation of falling, 559. 
 Senses, 359. 
 Sensorium, 281,319. 
 Sensory tract of cord, 303, 320 ; of brain, 320 ; 
 
 ganglia, 282. 
 
 Sentiment of pre-existence, 331. 
 SEROUS fluids, 193. 
 Serous layer, 527. 
 Serous membrane, 193. 
 Serpents, legs of, 491. 
 Serum, salts of, 96. 
 Seventh pair, 337. 
 Sexes, mortality of, 545. 
 Shelter, imperfections of, 181. 
 Sight, cerebral, 401. 
 Silk-worm, 489. 
 Silver balls in digestion, 55. 
 Singing, 355. 
 Single vision, 395. 
 Sisocles, 582. 
 Sixth pair, 334. 
 Skeleton, 253, 580. 
 SKIN, 233 ; absorption by, 241 ; transpiration 
 
 from, 185, 237 ; glands of, 235 ; exudation 
 
 of, 185, 239. 
 SKULLS, examination of, 581 ; forms of, 582; 
 
 classification of, 586 ; effect of heat on, 
 
 590. 
 
 Slack on circulation in cells, 132. 
 Sleep, 551. 
 
 Slow respiration, 168. 
 Smell, 423 ; condition of, 425. 
 Soap-bubble, dilf i-ion through, 153. 
 
648 
 
 INDEX. 
 
 Social mechanics, 602. 
 
 Society of insects, 604. 
 
 Sociology, comparative, 602. 
 
 Sodium, chloride of, 62 ; use of, 77. 
 
 Soemmering on leg, 580 ; spot of, 385, 397. 
 
 Soil, influence of, 476. 
 
 Solar plexus, 350. 
 
 Somnambulism, 557. 
 
 Song and speech, distinctions of, 352. 
 
 SOUL, existence of, 283 ; independence of, 
 285, 548. 
 
 SOUND, peculiarities of, 361 ; analogy of, to 
 light, 379 ; articulate, 539. 
 
 Spain, colonial empire of, 632. 
 
 Spallanzani on food, 65. 
 
 Speaking machines, 356. 
 
 Species of plants, 479 ; changes in, 480, 484. 
 
 Speech, 539. 
 
 Spermatic fluid, 517. 
 
 Spermatozoa, 517 ; development of, 518. 
 
 Sperm-cell, 516. 
 
 Spherical aberration, 386. 
 
 Sphinx ligustri, 279, 308, 313, 607. 
 
 Spinal axis, 291. 
 
 SPINAL CORD, 294, 296 ; reflex action of, 300 ; 
 comparative anatomy of, 300 ; divisions of, 
 296 ; connection of, with brain, 302 ; func- 
 tions of, 303. 
 
 Spinal nerves, roots of, 303. 
 
 Spiracle of insect, 157, 352. 
 
 Spiral vessels, 498. 
 
 Spirit, 24. 
 
 Spirostreptus, 301. 
 
 Spissitude of blood, 169, 190. 
 
 Spitting, habit of, 47. 
 
 Spleen, 211. 
 
 Spongioles, 87, 466. 
 
 Spontaneous gemmation, 536. 
 
 Stages in introduction of air, 160. 
 
 Standards, fixed physiological, 13 ; tables of, 
 15. 
 
 Standing, 453. 
 
 Stapedius, 365. 
 
 Starch, 71. 
 
 Starvation, 182. 
 
 Stearine, 246. 
 
 Steenstrup on generation, 537. 
 
 Steno, duct of, 43. 
 
 Stereoscope, 397. 
 
 Still layer, 143. 
 
 STOMACH, 41, 42; types of, 42 ; temperature 
 of, 49 ; regions of, 60 ; histogenetic diges- 
 tion of, 63 ; blood-vessels of, 102 ; mucous 
 surface of, 50, 58 ; follicles of, 50 ; hydroid 
 nature of, 51 ; trituration by, 55 ; secre- 
 tions of, 48 ; various forms of, 59 ; move- 
 ments of, 52. 
 
 Stove, warming by, 181. 
 
 Strecker on bile, 204. 
 
 Striated muscular fibre, 433, 436. 
 
 Stucco, endosmosis through, 107, 152. 
 
 Subdivisions influenced by heat, 79. 
 
 Subjective operations, 287 ; images, 398. 
 
 Submaxillary saliva, 43. 
 
 Suction, act of, 228. 
 
 Sudoriparous glands, 237, 238. 
 
 Sulphocyanide of potassium, 43. 
 
 Sulphur, 17, 23, 27. 
 
 Sunlight, 458 ; consumption of, 459 ; uses of, 
 
 466 ;' variation of, 483. 
 Supplemental air, 165. 
 Supra-renal capsules, 214. 
 Swimming bladder, 157. 
 SYMPATHETIC SYSTEM, 344; peculiar fibres 
 
 of, 262 ; origin of, 345 ; connected with 
 
 spinal, 345 ; ganglia of, 346. 
 Sympathy depends on circulation, 112. 
 Synthetical mind of Asiatic, 592. 
 Syntonin, 438. 
 Systemic circulation, 134. 
 
 T. 
 
 TADPOLE, experiments with, 489. 
 
 Talking birds, 352. 
 
 Taste, 427 ; nerves of, 429. 
 
 Taurine, 204, 208. 
 
 Teeth, 40 ; development of, 539. 
 
 Teleology, 415. 
 
 TEMPERATURE, effect of, on body, 177 on 
 skull, 590 ; extremes, 178. 
 
 Tendons, 439. 
 
 Tensor tympani, 365. 
 
 Tenth pair of nerves, 340. 
 
 Testis, 516; secretion of, 517. 
 
 Thackrah on effect of want, 587. 
 
 Thenard on perspiration, 240. 
 
 Third pair of nerves, 333. 
 
 Thoracic duct, 90. 
 
 Tickling, 422. 
 
 Tidal air, 165. 
 
 Time, introduction of, into nervous mecha- 
 nism, 269, 287. 
 
 Tin, trade in, 619. 
 
 TISSUE, cellular, 497; mnriform, 497 ; fibro- 
 cellular, 497; vascular, 498 ; yellow fibrous, 
 499 ; white fibrous, 499 ; areolar, 499. 
 
 Tongue, 428. 
 
 TOUCH, structure of organ of, 417, 418 ; acute- 
 ness of, 420; in animals, 421 ; connected 
 with vision, 419. 
 
 Tournefort on plants, 472. 
 
 Toynbee on ear, 365. 
 
 Tracts of spinal cord, 303 ; of brain, 318. 
 
 Tradescantia Virginica, circulation in, 132. 
 
 Traditions, 567. 
 
 Trains of thought, 329. 
 
 Transverse transmission in spinal cord, 298. 
 
 Trembley on hydra, 501. 
 
 Trigemini, 334. 
 
 Trisplanchnic nerve, 344. 
 
 Turner on smell, 427. 
 
 Twelfth pair, 343. 
 
 Twins, similarity of, 509. 
 
 Tympanum, 360, 365. 
 
 Type, ideal, of man, 565, 611. 
 
 U. 
 
 UNIPOLAR NERVE-CELLS, 263, 268. 
 Universal history, 611. 
 Urea, 447. 
 
 URINE, 218 ; composition of, 219 ; urea con- 
 tained in it, 220 ; hippuric acid in, 222 ; 
 
INDEX. 
 
 649 
 
 variability of, 219 ; sulphates in, 220; in- 
 fluence of diet on, 220 ; saline matter of, 
 220. 
 
 Uterine nutrition, 525 ; tubes, 525. 
 
 Utricle, 416. 
 
 V. 
 
 VACUUM, tendency to a, in respiration, 165. 
 Valentin on diffusion, 163 ; on perspiration, 
 
 229 ; on food, 39. 
 
 Valves of the heart, 138 ; sounds of, 139. 
 Valvulae conniventes, 67. 
 Variable results from invariable causes, 270, 
 
 281. 
 Variations of heat, 179 ; effect of, on man, 
 
 180 ; of species of plants, 479. 
 VASCULAR area, 528 ; lamina, 528 ; system, 
 
 origin of, 528. 
 
 Vegetable cells, circulation in, 132, 466. 
 Veins, absorption by, 84, 143. 
 Ventral cord, 300, 307, 609. 
 Ventricles, 138 ; force of, 139. 
 Venturi, principle of, 90. 
 Vermiform appendix, 63. 
 Vernois, table from, 53. 
 Vertebra, 528. 
 Vertebral canal, 294. 
 Vertebrata, 294. 
 Vertical view of skull, 582. 
 VESICULAR matter, composition of, 274 ; re- 
 lations of, 315. 
 Vestibule, 374. 
 
 Vestiges of nervous impressions, 269, 288. 
 Vibration of sound, time measured by, 372. 
 Vicarious action, 47, 190. 
 Vierordt, 164. 
 Villi, 84, 86, 87, 110 ; cells of, 88 ; action of, 
 
 110. 
 
 Virchow on adipocire, 247. 
 VISION, 379 ; comparative anatomy of, 380 ; 
 
 single and double, 395 ; inverse, 401. 
 Visions, 404 ; conditions of, 410. 
 Visual hallucinations, 403. 
 Vital principle, 24, 25, 55, 108, 456. 
 Vital spark, 460. 
 Vitreous humor, 385. 
 Vocal sounds, 352, 354. 
 Voice, 351 ; artificial larynx, 355 ; pitch of, 
 
 356. 
 
 Volkmann on muscular contraction, 276. 
 
 Volume of contracting muscle, 450. 
 
 Volvox globator, 513. 
 
 Von Bar, law of, 514. 
 
 Von Becker on carbohydrates, 39 ; on sugar, 
 
 73. 
 Vowels, 356. 
 
 W. 
 
 WALKING, 453. 
 
 Wallace on eye, 385. 
 
 Want, effect of, 587. 
 
 Warmth, artificial, 181 ; increased quantity 
 
 required in sleep, 554. 
 Wasmann on pepsin, 55. 
 Wasp, habits of, 606. 
 Waste of tissue, 12, 23, 52. 
 WATER, use of, 16, 21, 22 ; solvent power of, 
 
 21 ; use in milk, 29 ; absorption of, 52 ; 
 
 quantity exhaled, 168 j cooling effect of, 
 
 185; of blood, 121. 
 Wave in blood, 141. 
 Weaning of plants, 465. 
 Weber on pelvis, 587 ; on quantity of blood, 
 
 113 ; on standing, 453. 
 Weight of man, 13, 14, 541 ; of infants, 14. 
 Whale, 491. 
 Wheatstone, 397. 
 Whispering, 356. 
 White on arm, 580. 
 Wigan on duality of mind, 329, 331. 
 Willow, 469. 
 Wilson on heart, 136. 
 Wine-making, 78. 
 Wolffian bodies, 150, 533. 
 Women in Asia and Europe, 593. 
 Words, origin of, 356. 
 Worship, public, influence of, 628. 
 Writing, 358, 610, 615, 635. 
 
 ZIGZAG appearance of muscle, 439. 
 Zimmerman on respiration, 170. 
 Zinc acted on by gastric juice, 50. 
 Zona pellucida, 523, 525. 
 Zoospores, 496. 
 Zygnema quininum, 515. 
 
 THE END. 
 
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