-^. hJf ¥ BL 262 .B87 1838 Burnett, Charles Mountf ord. 1807-1866. The power, wisdom , and <->( ,-^ /^ /-^ K. <:?nr? c rs ^ rir\!^ POWER, WISDOM, AND GOODNESS GOD, LONDON: PRINTED BY LEVEY, KOBSON, AND FRANKLYN, 46 St. Martin's Lane. THE POWER, WISDOM, AND GOODNESS GOD, AS DISPLAYED IN THE ANIMAL CREATION; SHEWING THE REMARKABLE AGREEMENT BETWEEN THIS DEPARTMENT OF NATURE AND REVELATION. IN A SERIES OF LETTERS. y By C. M. BURNETT, Esq. MEMBER OF THE ROYAL COLLEGE OF SURGEONS. LONDON: JAMES BURNS, 17 PORTMAN STREET, PORTMAN SQUARE. M.DCCC. XXXVIII. PREFACE. That branch of natural theology which shews forth the wisdom of God in the animate creation, lias of late years been placed in a position highly injurious to the cause of revealed religion, which this science purjDoses to support ; and one, therefore, from which it behoves the friends of that cause to exert themselves to rescue it. Whether the facts which are supposed to warrant the taking up of the position in question are indisputably proved, or whether, granting that they are so, they bear out the conclusions derived from them, are questions which deserve serious consideration. The views to which I allude are principally to be found in the department of knowledge called Geology, — a science which, since it owes the greater part of its general propositions to comparative anatomy and conchology, might more properly be called Zoogeology. The geological opinions which appear to me to be contradictory to revelation are supported in a popular, and certainly an ingenious manner ; not a few able men have adopted them, and are indefatigable in their diffu- sion. It would, therefore, be a neglect of duty for those who entertain contrary opinions, to abstain from pointing out the fallacies couched beneath the seemingly demon- VI PREFACE. strated theories of Geolog5^ The errors in question ought not to be let alone^ in the expectation that they will die away of themselves, and that any exposure of them would but cause their more extensive pronudgation. They are not confined, like the old philosophical theories, to a small and select body, but are carefully fitted for com- mon comprehension and reception. So that unless they are met by a similar method of discussion, it must be anticipated that they will gain wider and wider currency, sapping, in their unobserved progress, the foundations on which belief in revelation and in the distinctive doctrines of Christianity has hitherto I'ested. The rapid progress of Geology as a science, and much of the conclusiveness which it appears to possess, are mainly owing to the fact that comparative anatomy has undertaken to answer, in a manner which to the general reader wears the character of certainty, questions which, in the present state of that science, are quite incapable of satisfactory solution. Being convinced that many geological phenomena are susceptible of explanations widely different from those anti-scriptural ones too commonly received, 1 have de- voted the two introductory Letters to the consideration of some of the many difficulties which stand in the way of those who, by the theories they have advanced, have compromised the truths of revelation. I have there endeavoured to shew, that the relative increase and de- parture from its original type of each species of animal, according to fixed laws appointed for its regvdation, afford explanations of all the geological appearances hitherto PREFACE. Vll observed, at once satisfactory in a scientific point of view, and confirmatory of the statements of revelation. It is right that I should here mention, that in the Third Letter, page 127^ I have given the most popular theory of respiration, namely, that of Lavoisier j and it was not until after this part of the work had gone to press that the public were put in possession of the more recent experiments of Bischoff, Bertuch, Magnus, and others, noticed in the second part of Baly^s translation of Miiller's Physiology* It is now decided, that the chief object which the respiratory process is intended to accom- plish is the absorption of oxygen from the atmosphere into the blood, which conveys that gas to the different parts of the body. In this process carbonic acid is removed; but the experiments above mentioned prove that this is not the main object of the function. In refu- tation of Lavoisier's theory of combustion, Muller says : " The fact of more oxygen disappearing than is accounted for by the carbonic acid formed, does not justify the assumption of Lavoisier, Laplace, Dulong, and Despretz, that this portion of oxygen which is lost goes to form the watery vapour, by combining with the hydrogen of the blood. The hypothesis that the watery vapour exhaled from the lungs is formed in them by the direct combina- tion of its elements, is quite gratuitous ; for under the existing external conditions, water must evaporate from moist animal surfaces, particularly at the temperature of \varm-blooded animals.^' So that no part of the great quantity of oxygen which the blood extracts from the air in the process of respiration unites with the hydrogen in Vm PREFACE. the blood to form water, as Lavoisier maintained; the oxygen is wholly absorbed, and acts as a stimulus upon the different organic parts. I must also in this place acknowledge the attentions which I have received from Mr. Owen, and the facilities he has afforded me in completing the plates attached to this Work. CONTENTS. LETTER I.— (Introductory.) Organised bodies a material evidence of the existence and the unity of a God. Man is endowed with facilities which enable him to compare this e\'idence with that which has been revealed in the Scriptures. Remarkable confirmation of the one by the other. Proofs of uniformity in design, drawn from the skeletons of animals. Consideration of the arguments used by geologists to prove a succession of crea- tions. Doubtful tendency of those arguments. Miracle of creation. Impossibility of estimating the extent of change thus induced in the materials of the earth. Argument of Mr. G. Penn. Consideration of the deluge. This catastrophe thought by some to be incapable of explaining the number and variety of fossil remains. Groundlessness of such doubts. Our inability to estimate the extent of the destruction effected by the deluge. Difficulty of reconciling a succession of crea- tions with revelation. Truths of reUgion and of science can never be at variance. Difficulties of opposing the Mosaic record. Universality of the deluge. Theories of a succes- sion of creations and of a transmutation of species have no foundation Pages 1-50 LETTER II. — (Introductory.) Impossibility of ascertaining what animals were taken by Noah into the ark. Some great cause has determined the structure of every species which is capable of being modified by climate, food, locality, &c. Absurdity of the doctrine which teaches CONTENTS. that the characteristics of animals are referrible to second causes alone. We are unable to acquire a perfect knowledge of all the characteristics which distinguish the different genera and species of animals ; and still more unable to determine the laws on which those characteristics are dependent. Many animals have become extinct ; we cannot therefore infer that they did not form part of the creation recorded by Moses. Causes of extinction now in operation. Influence of man in altering the relative position of animals. The incorrectness of the opinion, that man came into existence at a compara- tively recent period, proved from geological data. Fossil bones already discovered comparatively very few. Human bones have been found with those of extinct animals. As in the beginning of creation the animals belonging to the lowest orders increased with the greatest rapidity, so these form the great bulk of discovered animal remains. Arguments of some geologists in favour of a succession of creations refuted by the clearest evidence. The method of estimating the age of a rock by the animal remains which it contains entirely conjec- tural. Cuvier's theory of the strata of the Paris basin. In- superable difficulties in the way of this theory. ImiDOSsibility of determining whether a shell is marine or fresh water. The probable relative increase of various animals during the earlier periods of the earth's existence, sufficient to account for the vast number of fossil shells in the strata of the earth, and the comparative paucity of the remains of higher animals. The record of Moses is therefore literally true. . . 51-107 LETTER III. Difficulty of explaining the structure and functions of living bodies. Outline to be pursued. Wonders disclosed to us by tlie improvements in the microscope. Explanation of terms used in zoology. Classification of animals. The sys- tems of Linuccus, Blumenbach, and Cuvier. Impossibility of CONTENTS. XI arranging animals in a graduated chain. Composition of animal bodies. Solids contained in the fluids. Changes in their composition. Apparatus for transmitting the blood. Most complicated in the higher animals. Adapted in all to the circumstances in which they are placed. The absorbent system ; its character and office. The nervous system. The muscular and bony systems .... 108-138 LETTER IV. Inquiry into the principle called life. Distinction between soul and spirit. First proof of the existence of the vital principle in animals. Impossibility of physically explaining the cause of the construction of organic bodies. Remarkable protective influence of the vital principle in opposition to the laws of nature. The wonderful power which it holds over heat, one of the most powerful inorganic agents . . . 137-152 LETTER V. Electricity. Its resemblance to the vital principle. Is given out by many animals. Aids the vital functions. All vital pheno- mena traced to the stimulating power of the oxygen which is conveyed to the blood through the lungs. Electricity is governed by the vital principle, and has been bestowed in diff'erent degrees on various bodily structures. . 153-169 LETTER VI. Physical conformation of man . Proof from this that he is destined to hold a superiority over the creatures which surround him. Advantages derived from his reason, which enables him to apply the structure of his body to many artificial purposes. Obscurity of writers on the true cause which distinguishes man from animals. Distinguishing characteristics of man divided into two classes, intellectual and physical. The re- Xll CONTENTS. markable power which mind exercises over matter. Exam- ples. The brain ; larger in man than in any other animal. It is a complicated organ, made up of many different parts. Their relative sizes compared in man and the lower animals. Inference thence deduced. Large part of the brain of man devoted to the service of the mind. The mind is manifested through this organ. Arguments against materialism. Proofs of the separate existence of the soul. Arguments drawn from the writings of Moses and St. Paul in support of this doc- trine. The existence of a soul as demonstrable as that of the body. Importance of the faculty of speech to man. Proofs that it results from his reason .... 170-212 LETTER VII. Physical distinctions of man. His erect stature and biped pro- gression. Form of his upper and lower limbs contrasted with those of other animals. His spinal column. The hand ; its compound office. This organ rendered a mighty instrument by the aid of reason. Man omnivorous ; the construction of his digestive apparatus enables him to be so. Design in his slow growth and long infancy. Peculiar construction of his skin adapted to facilitate his extension over all parts of the earth. Proofs that man is a distinct genus. His varieties are not more diversified than those which exist in many other species of animals. Proofs of this drawn from the different varieties of swine. Proofs that man has power to subdue every creature .... 213-249 LETTER VIII. The adaptation of all creatures to their various stations. Rational deduction that the Being which formed them must have cre- ated all things. Remarkable connexion in their organisation. Secondary causes influence their distribution. The operation CONTENTS. XUl of a first cause equally obvious. The internal construction of animals made subservient to their different stations. Won- derful proofs of this in the low^er animals. The locomotive organisation of animals adapting them to take their different spheres, exemplified in various instances. . . 250-283 LETTER IX. The digestive apparatus of animals adapts them to take their sta- tions in different parts of the earth. Benevolence of that law in the creation vs^hich ordains that some animals should serve as food for others. Great diversity in the food of ani- mals requires a corresponding change in the structure of the digestive orsrans. The stomachs of various animals. Other D O parts of the organisation of animals facilitate their obtaining food. The form and structure of their teeth bear an intimate relation to the different food on which they subsist. The circulatory apparatus fitted to enable animals to inhabit every part of the globe. Numerous examples of wisdom and con- trivance. The law of hybernation. Many lower animals capable of subsisting without breathing. The existence of toads in the heart of trees and in solid rocks thus explained. Wise adaptation of these organs in the amphibia 284-319 LETTER X. The structure of birds, and its adaptation to the air. Nature of that fluid. The contrivance by which birds are capable of being rendered lighter than the specific gravity of the atmo- sphere. Peculiar formation of their lungs. Use of their wings, and wonderful power of migration. The construc- tion of the air-cells of birds. The law which confines these volatile animals to particular parts of the globe. The great wisdom of God in their distribution shewn in the locality of the vtJture and the secretary bird . . . 320-348 XIV CONTENTS. LETTER XL Structure of fishes formed in relation to the element which they inhabit. The nature and relative position of the sea. Wise jorovision by which animals are suspended in the water. Contrivance in the argonaut. Respiratory organs in fishes. Variety in their contrivance. Low vitality in fishes. Their organisation not the less indicative of design. Proof of this in the construction of their teeth. External coverings of their bodies. Wisdom in placing the skeleton externally instead of internally in many of the lower animals. Complete defence against danger incompatible with the scheme of Providence 349-379 LETTER XIL The five external senses and their organs. The use of ordi- nary sensation exemplified. Advantages of the external senses. Consequences of the loss of one or more of the external senses. Uses of the several nerves of sense, and their comparative development in various animals. The eye. The laws and phenomena of light. Structure and functions of the eye. Its application to the different spheres in which animals exist. The nictitating membrane. The ear. Tlie subtle nature of sound. The structure and functions of the ear. Wisdom shewn in the diversity of arrangements in the different parts of the ear of various animals. Sense of touch. Its situation in various animals. Its use. Taste and smell. Its great development in some animals, particularly the herbi- vora. Importance of these senses to many animals 380-431 LETTER XIII. Inferences drawn from the skeletons of animals. Their primary uses. Importance ofan internal articulate skeleton. Materials of which it is composed. Their wise arrangement exemplified CONTENTS. XV in the bony covering of the brain. Bony protection to the nerv- ous system of the lovi^er animals. Beautiful contrivance and use of the spinal column. Its wonderful adaptation in all ani- mals. Use and adaptation of the ribs of various animals. Uni- formity of design clearly to be traced in the w^hole. 432-453 LETTER XIV. Instinct in animals a power added to organisation. Subservient to three inherent principles. Manifest in all the grades of the sentient creation. It is independent of reason. Examples of instinct in various animals. Instinct a faculty in many respects superior to reason. Argument to prove their differ- ence. That instinct is independent of experience, proved by the mathematical skill displayed by many of the lower animals. Instinct characterised by a blind impetuosity. Example to prove this. Instinct intimately connected with the organisa- tion of animals ; both having a mutual dependence, of which the animal cannot be conscious. Instinct confers upon ani- mals some degree of foreknowledge . . . 454-482 LEITER XV. Inquiry into the mental constitution of animals. Some species possess faculties common to aU ; others peculiar to individual species. Probable design intended by this. Animals have innate faculties capable of being defined. They have the faculty of perception ; they have simple ideas, but they cannot combine them. Animals have memory. Of the feeUng of attachment in animals. Of the means adopted by the Creator where this feeling is absent in animals. Animals have caution or cunning. Of the propensity to construct in animals. Of the propensity to imitate. Of the power of locality. Of the propensity to destroy . . . , . 483-528 Conclusion, 529-530 ERRATA. P. 10, line 12, for " it was," read, " they were." P. 129, note*, /or "Fig. X" read "Fig. 2;" note t,/o»' " Figs. 2 and 3," read "Fig. 3." P. 2!».?, line 1, ajter " mouse kind," insert as note, " See Plate II. Fig. 3." P. 293, note f, fur " Plate III. Fig. 2," read " Plate IV. Fig. 2." LETTER I. INTRODUCTORY. " The real use of natural theology is to shew the strong pro- bability of that being true which revelation declares." — Sumner's Records of Creation, vol. i. p. 11. The creation of organised bodies, with all the phenomena of their diversified existence, furnishes to our minds a field of inquiry scarcely to be ex- ceeded in interest by any other ; and its contem- plation affords us material evidence of the exist- ence and attributes of Him who hath not left him- self without witness, by whom " were all things created that are in heaven and that are in earth, visible and invisible."* In surveying the animate works of the Creator, we are not less surprised at the phenomena which they present, resulting from that principle of life with which they are endowed, or at the perfect adaptation of every creature, even in the minutest particular, to the station which it holds, than at that all-pervading benevolence which has prepared for their enjoyment so many varieties of the surface and productions of the earth on which they are placed. How far the physical * Col. i. 16. " For the invisible things of Him from the creation of the world are clearly seen, being understood by the things that are made." — Rom. i. 20. B L LETTER I. evidence of the Divine power, wisdom, and good- ness, arising from these considerations, is in accord- ance with what has been revealed to ns upon these subjects by Divine inspiration, must be a most inte- resting inquiry to every reflecting mind. The marks of design which animals exhibit, and the inferences to be drawn from their confor- mation, are every day furnishing us with fresh proofs of that Divine wisdom which was employed in framing their constitution. That the laws which have governed this constitution have not varied in the least, from the period of their first institution up to the present time, and therefore, that the same Being who established them has ever presided over and maintained them, and does so now, can be satisfactorily proved. We have abun- dant evidence which, while it demonstrates the existence of one presiding Power, declares that power to be unchangeable. Were it not for this uniformity in the works of the Creator, we should be deprived of all proofs, apart from revelation, of the unity of the Supreme Being ; and it is therefore a fact of great importance, and one which ought to be universally known and understood. And there can be little doubt, that as man, the only being in this creation which has a consciousness of the con- ditions of its existence, has been endowed with reasoning faculties capable of discovering and com- prehending the laws which God has made to go- vern the universe, and of tracing the relations LETTER I. 3 which connect, as one harmonious whole, all the objects with which he is acquainted, it was intended by this means that he should acquire a knowledge confirmatory of those facts which have been re- vealed in God's word, though in a manner wholly independent of science or of learning.* And in- deed it must be admitted, even by the most deter- mined advocates for considering the subject of God's creative wisdom apart from revelation, that nothing can contribute so powerfully to seal the truth of the sacred Scriptures as this fact, which has never been disproved, namely, that though the Scriptures were penned by men, many of whom were wholly unacquainted with rules of science, as * " Suppose it granted, for the present, that a Creator exists, it is difficult to believe that such a world, and such beings as it contains, were created without any definite and assignable object; that its intelligent inhabitants were summoned into life, and then immediately abandoned by their Maker, retaining no connexion with him, either during the short period of their earthly existence, or after it. But if we reject this idea as inconsistent with all reasoning as to the probable operations of Divine intelligence, then it becomes natural and almost necessary to conclude, that the Creator would have some memorial of himself in a world which, as forming a part in the comprehensive scheme of his providence, he beholds with regard and interest. It is evident, however, that as mankind alone, of all the inhabitants of the earth, are gifted with intelligence, mankind alone can hold any connexion with an intelligent Creator. To these, therefore, we must look as the chief objects of creation, and as the depositories with whom the records of it, supposing such an event to have taken place, would be left, to be handed down by them from age to age." — Records of Creation, vol. i. p. 60. 1 LETTER 1. they of themselves testify, yet does the record stand boldly out in its own strength, unrefuted by the discoveries of modern science,* as it is mishaken by the most subtle metaphysical arguments. De- prive the revealed word of the confirmation which it receives from the physical sciences, and we at once strike at the grandest arguments which can be ad- duced to substantiate the truths it contains. Without attempting to establish the authenticity of the Old Testament Scripture, or discussing the question of its strictly literal intei^pretation, I shall assume the truth of the Bible upon, first, its strong internal evidence ; secondly, its having been cited literally so many times by our Saviour and his apostles ;f and thirdly, its containing several pre- dictions which have been literally and circumstan- tially accomplished. " As to the nature of the history" (Mosaic), says Sumner, " it has not been * No fact places this truth in a stronger hght than this, that, after the lapse of two thousand years, during which time science has exerted all her power to ascertain the nature and properties of the blood, the researches of Hunter, Hewson, Magendie, Berze- lius, and many others, have not disproved the statement made by Moses, that the blood of the animal is the life ; but, on the con- trary, have confirmed it in the strongest manner, by proving that the blood itself is alive. Vide vol. i. of Dr. S. Smith's Philosophy of Health. t At least twenty-seven passages have been cited, word for word, from the Pentateuch, by our Saviour and his apostles. Besides which, we are bound to give a literal interpretation to this part of Scripture from many prophecies herein related having received a literal fulfilment. LETTER I. b unusual for some real and pretended friends of revelation, startled at the difficulties which seemed to oppose them in the early chapters of Genesis — difficulties, it must be remembered, which are com- monly magnified to support their hypotheses — to give an allegorical interpretation to those parts of Scripture which they cannot be persuaded to un- derstand literally. Two unanswerable reasons must prevent us, however pressed with difficulties, from resorting to this explanation of them : first, these passages are referred to in other parts of Scripture as of historical authority (2 Cor. xi. 3 ; 1 Tim. ii. 14) ; secondly, it would seem altogether unjustifi- able in an author, professing to relate matters of fact, and to sanction, on their authority, his legis- lative character, to introduce allegory into the most important subject of his narration. Sir Wil- liam Jones saw this in a strong light : ' Either the first eleven chapters of Genesis,' he says, * all due allowance being made for an eastern style, are true, or the whole fabric of our national religion is false.' — (Asiat. Resear. i. 225.) My inquiry, there- fore, supposes the Mosaic account not allegory, but fact — fact, of which Moses derived his knowledge either by inspiration delivered immediately to him- self, or from information originally revealed and preserved from the earliest times, and afterwards incorporated with the Hebrew law by the Divine direction."* * Records of Creation, vol. i. p. 69, et seq. 6 LETTER I. Nothing in the economy of animated existences bears more evident marks of design, and of subjec- tion to constant and universally operating laws, than the skeleton — that admirably devised frame- work, which serves so many important purposes in the formation of the higher classes of animals. This firm foundation is so constructed as to be fitted for the accomplishment of the most opposite ends, and thus accommodates itself to all the pe- culiarities which distinguish the various tribes of animals, enabling them so appropriately to take their several places, and to perform their various and complicated movements with the facility and regularity which characterises them all.* We read here a depth of ingenuity and an extension of thought, which the laboured inven- tions of man can but faintly imitate. Here is no * " Independently of this variation in the structure of hones, fitting them for the office in which they are employed, they are also adapted to the medium in which the animal is placed ; for instance, the bones of all swimming animals are light. This pro- perty is acquired in very different ways ; one is, by a small pro- portion of phosphate of hme being contained in the bones, as in those of the cartilaginous fishes. In the whale tribe, where it becomes necessary that the bones should have strength as well as extent of surface, they are rendered light by the internal cavity of the bone being filled with oil. In one species, the spermaceti whale, there is a very large cavity in the upper part of the skull entirely filled with spermaceti, which renders the head of this enormous animal sufficiently buoyant to keep the blow-holes above the surface of the water." — Sir E. Home's Lectures on Comparative Anatomy, vol. i. p. 7f). LETTER I. 7 weak or defenceless part — no error in the com- plicate machinery — no want of mutual connexion; but all is wisely united to meet every contingency. And yet, amidst the endless variety of form, there is such a unity of purpose,* such a conspicuous * Connected with this wonderful feature in the animal king- dom is that remarkable discovery of Goethe, of that symmetrj^ in all the parts of vegetable and animal life, proving that the several types which are assumed, in order to adapt those parts to the circumstances for which they are designed, must have originated from one model. The principle upon which this metamorphosis depends may be explained in the following manner : that all the varieties in the different members of the same plant or animal, originating from one model, are modified according to the degree of vitahty or development of the production. In order to give some idea of this principle as applied to plants, Mr. Whewell says, " it will not be difficult, if the reader will imagine to him- self a flower — for instance, a common dog-rose, or the blossom of an apple-tree — as consisting of a series of parts disposed in whorls («. e. encircling the stem like a ring), placed one over another on an axis, or stem : the lowest whorl is the calyx with its five sepals (or divisions) ; above this is the corolla, with its five petals ; above this are a multitude of stamens, which may be considered as separate whorls of five, each often repeated ; above these is a whorl composed of the ovaries, or what become the seed-vessels in the fruit, which are five, and united together in the apple, but indefinite in number, and separate, in the rose. Now, the morphological view is this : that the numbers of each of these whorls are in their nature identical, and the same as if they were whorls of ordinary leaves, brought together by shortening their common axis, and modified in form by the successive elaboration of their nutriment." — History of the Inductive Sciences, vol. iii. p. 436. Now, in the animal kingdom, Goethe shewed that the skeleton, which in all animals is determined in its frame- work by 8 LETTER I. keeping throughout the whole, that we are imper- ceptibly led to the behef, as we pursue the inquiry, that He who planned the construction of one, must have been the sole agent in the construction of all. A httle insight into anatomy will prove this, con- firming the truth of revelation, which so loudly declares that there is but one God, who created and who governs the earth. A greater proof of this uniformity of design, and of the unchangeable nature of those bodies, which alike bear the impress of one and the same Creator, we cannot advance than the following: " A skeleton is dug up which has lain under many fathoms of rock, being the bones of an animal which lived antecedent to the formation of that rock, and at a time when the earth's surface must have been in a condition very different from what it is now. These remains prove that all animals have been formed of the same element, and have had analogous organs ; that they received new matter by digestion, and were nourished by means of a circulating fluid ; that they possessed feeling through a nervous system, and were moved by the the peculiar form of the nervous system, undergoes a similar metamorphosis. He shewed that the bony head of beasts is formed out of six bones, similar in type to those which form the spinal column ; and although subsequent researches have shewn that only three vertebrae are thus expanded, as it were, to encircle the brain, as Spix has clearly laid down in his elaborate work {Cephalogenesis), yet the discovery of this uniformity of plan is due to Gee the. LETTER I. 9 action of muscles ; that their organs of digestion, circulation, and respiration, were modified by cir- cumstances, as in the animals now alive, and in accordance with their habits and modes of living. The changes in the organs are but variations in the great system by which new matter is assimi- lated to the animal body ; and however remarkable these may be, they always bear a certain relation to the original type, as part of the same great design. In examining these bones of the ancient world* so regularly are they formed on the same prin- ciple which is evident in the animals now inhabit- ing the earth, that on observing their shape, and the processes (or more prominent parts) of bone by which their muscles were attached, we can reduce the animals to which they belonged to their order, genera, and species, with as much pre- cision as if the recent bodies had been submitted to the eye of the anatomist. Not only can we demonstrate that their feet were adapted to the sohd ground, or to the oozy bed of rivers, for speed, or for grasping and tearing ; but, judging by these indications of the habits of the animal, we acquire a knowledge of the condition of the earth during their period of existence ; that it was suited at one time to the scaly tribe of the lacertae (hzards), with languid motion ; at another, to animals of a higher organisation, with more varied and lively habits ; and finally, we learn that, at any period previous 10 LETTER I. to man's existence, the surface of the earth would have been unsuited to hhn."* Observations hke these, which abound in the writings of the present day, are intended to shew that there really is such a harmony and unity of purpose in the works of the Creator, that a single bone of an animal will point, with undeviating accuracy, even to the particular species to which it belonged. It is, however, very doubtful whether, in our present imperfect knowledge of the adapta- tion of similar structures in different animals to all the varied purposes for which it was formed, we can, in every instance, speak with such certainty. It is only necessary to know what diversified means are employed in every combination of struc- ture, to be impressed with a sense of human insuf- ficiency,— a sense forced upon us in surveying the endless resources of organised bodies, where so much simihtude, extending even to the smallest bone, characterises those bodies which, of all others, appear the most dissimilar. As though it were intended to satisfy the doubts of some as to the unity of the plan of creation, and, resting on this, as to the unity of the Creator, this cha- racter has been impressed upon all the works of God ; so that, in the words of Dr. Roget, " amidst endless diversity in the details of structure and of processes, the same general purpose is usually accomphshed by similar organs and in similar * Sir C. Bell on the Hand, p. 26. LETTER I. 11 modes. So firmly is this principle established, that we may ventvire with confidence to predict many circumstances relating to an unknown ani- mal, of which only a few fragments are presented to us, from our general knowledge of the character and economy of the tribe or family, or the type on which it has been modelled. Thus, the discovery of a mutilated portion of the skeleton of a fossil animal gives, to the physiologist who is conversant with the details of comparative anatomy, a know- ledge of the general structure and habits of that animal, though all other traces of its existence may have been swept away amidst the primeval revolutions of the globe."* This uniformity of * Roget, Animal Physiology, vol. i. p. 50 ; and Cuvier, Dis- cours sur les Revolutions de la Surface du Globe, p. 47. " The next thing admirable in the composition of the skeleton is the relation of its parts ; the manner in which they are aU cast at once, forming a system which, in our method of proceeding, we are apt to forget. In studying the individual bones with great minuteness, we neglect the relation which is established betwixt all the parts of the skeleton of any one animal. To exemplify this : if an anatomist and naturalist should pick up a bone of the leg of some animal, he may observe that it is not formed to turn with that extent of motion which belongs to an animal having the paw and the toes free. He will then conclude that the bones of the foot were embraced with a hoof, and not armed with claws. He will reflect that, as there were no claws, neither could there be carnivorous teeth. Ascertainmg the form of the teeth, he in a manner knows the corresponding form of the jaws ; and if of the jaws, the muscles which move them ; and if the muscles of the jaws, the form of the head. Returning to the contemplation of the bone he has picked up, he will tind in 12 LETTER I. design is more clearly to be traced in that division of animals denominated vertebrated, which comprises all those possessing an internal articulated skele- ton. Roget observes, " that a remarkable affinity of structm-e prevails throughout the whole of this extensive assemblage of beings. Whatever may be the size or external form of these animals ; whatever the activity or sluggishness of their movements ; whether they be inhabitants of the land, the water, or the air ; — a striking similitude may be traced, both in the disposition of their vital organs and in the construction of the solid framework, or skeleton, which sustains and pro- tects their fabric. The quadruped, the bird, the tortoise, the serpent, and the fish, however they may differ in subordinate details of organisation, are yet constructed upon one uniform principle, and appear like varied copies from the same ori- ginal model. In no instance do they present structures which are altogether isolated, or can be regarded as the results of separate and inde- pendent formation."* Two great purposes appear to be answered by this arrangement, in addition to those to which it that the proof of a restrained position and limited motion, and of its belonging to a limb directly under the animal, for locomotion only, or for swiftness. He will know the form of the shoulder- joint, the form of the spine, the form of the extremities, and the form of the head." — Bell's Anatomy, vol. i. p. 10. * Animal Physiology, vol. i. p. 362. LETTER I. 13 is immediately subservient, and which concern the preservation and enjoyment of those beings in whose structures it is manifest. First, in the law of variety we are presented with a striking and indisputable proof of the interminable resources of the Creator, and thus become impressed with the conviction that his wisdom and power are infinite, and far beyond our comprehension ; and secondly, by the law of conformity, or resemblance, (which prevails not only among all the tribes of animals now existing, but extends to those extinct races with which we have become acquainted by means of their fossil remains, and thus links together the two extremes of existence,) it is demonstrated, that the Creator of all that now have life is the Creator of all that have ever lived; and we are thus taught to rise to the conclusion, that there is but one God, and that he was before all worlds. Although it would lead us far beyond the limits of this work, were we to dwell upon the extensive subject which such reasoning as this naturally forces upon us, yet the 07'der and succes- sion of organic remains, as they are found in the different strata of the earth, have given rise to so many conflicting and undigested theories, tending to weaken man's belief in the statements of Scrip- ture, that it is necessary to make some observa- tions upon this point, and endeavour to shew the incorrectness of many current opinions connected with it. There is one assumption made by geolo- 14 LETTER T, gists which appears to be wholly gratuitous, viz. that, judging from the present condition of the earth, more especially with reference to fossil re- mains, there must have been a series of creations antecedent to that recorded by Moses ; and they maintain that the creation of man, and other animals with him, did not take place at the same time as the creation of the earth, but was a sub- sequent, and comparatively quite a recent event, being accompanied by a mere revolution of the globe, or by the adaptation of its surface to the accommodation of man and the other races cre- ated at the same time. This theory is so clearly inconsistent with the Scriptural account of the creation, that various attempts have been made to pervert the obvious meaning of that narrative, in order to obviate the objection that might hence be taken to the theory, and to give to it the sanction of revelation. " A strange and singular argument," says Bab- bage, " has frequently been brought against the truth of the facts presented to us by geology — facts which every instructed person may confirm by the evidence of his senses. It has been stated that they cannot be true, because, if admitted, they lead inevitably to the conclusion that the earth has existed for an enormous period, ex- tending, perhaps, over millions of years ; whereas it was supposed, from the history of the creation as delivered by Moses, that the world was first LETTER I. 15 created about six thousand years ago. A different interpretation has been lately put upon that pas- sage of the sacred writings ; and, according to the highest authorities of the present time, it was not the intention of the writer of the book of Genesis to assign this date to the creation of our globe, but only to that of its most favoured inhabitants."* We shall not here stop to point out the rea- sons which render this interpretation untenable, but proceed to make some observations upon the theory to support which it is hazarded. There is, in our opinion, little real difference between this theory (that of the extreme antiquity of the earth), and that which recognises no First Cause, but teaches the eternity of matter. Those who hold the former admit, it is true, the exist- ence of the Deity, and the creation of the material universe by him ; yet, by placing the origin of that universe at a period far beyond all human calcula- tion, or even imagination, they necessarily lead the mind to doubt whether it ever had a beginning ; since that which exceeds the power of calculation appears to be infinite, and in the mass of mankind this is a power exceedingly limited. The supporters of the other openly deny the creation of matter, or the existence of a creative Intelligence, and thus appear to inculcate a far more dangerous belief. For the reason above given, however, it may be doubted whether the practical results of this are * The Ninth Bridgewater Treatise, p. 63. 16 LETTER I. worse than those of the less bold, but more insi- nuating theory. The opinion of the successionist is founded on his imperfect observation of, and fal- lible reasonings upon, the phenomena of nature, without reference, nay, in opposition, to God's re- vealed word ; while that of the sceptic proceeds from ignorance even of those phenomena, or from perverted reasonings respecting them. To the former class of men we would recom- mend less confidence in human judgment, and greater reverence for the declarations of Scripture ; and would observe, in the language of Whewell, that " all palaetiological sciences, all speculations which attempt to ascend from the present to the remote past by the chain of causation, do also, by an inevitable consequence, urge us to look for the beginning of the state of things which we thus con- template ; but in none of these cases have men been able, by the aid of science, to arrive at a beginning which is homogeneous with the known cause of events. The first origin of language, of civilisation, of law and government, cannot be clearly made out by reasoning and research ; and just as little, we may expect, will a knowledge of the existing and extinct species of plants and animals be the result of physiological and geo- logical investigation."* * History of the Inductive Sciences, vol. iii. The hypo- thetical speculations of geologists are innumerable, yet none of them can be said to throw any light upon the true theory of the LETTER I. 17 To those who assert the eternity of the earth we would address the whole of this book, to prove that throughout nature the evidences of design, of omnipotent power, and of infinite wisdom, are so numerous and so convincing, that a candid and unprejudiced mind cannot, when they are fairly brought before it, but infer from them the exist- ence of an intelligent and almighty First Cause. earth. The opinion that the world has existed from all eternity, subject to successive catastrophes and revolutions, -was main- tained by some of the most ancient philosophers, and may, with great truth, be called a native heathen idea. Many of the ancient sects of astronomers and mathematicians held that the changes in the interior of the earth were caused by alternate conflagrations and inundations. The early cos- mologies are fuU of such hypotheses ; and up to the period of the Christian era almost universal error prevailed upon this point. The following apologue may be taken as an ingenious illustration of the anti- scriptural hypothesis we are combating. " Mohammed Kazwini, towards the close of the thirteenth cen- tury, wrote a manuscript entitled ' The Wonders of Nature,' in which he introduces an allegorical personage, who records the following narrative : — 'I passed one day by a very ancient and wonderfully populous city, and asked one of its inhabitants how long it had been founded. ' It is a mighty city,' replied he ; ' we know not how long it has existed, and our ancestors were on this subject as ignorant as ourselves.' Five centuries afterwards, as I passed by the same place, I could not perceive the shghtest vestige of the city. I demanded of a peasant who was gathering herbs upon its former site, how long it had been destroyed ? ' In sooth, a strange question,' replied he ; ' the ground here has never been different from what you now behold it.' ' Was there not of old,' said I, ' a splendid city here ?' ' Never,' answered he, ' so far as we have seen ; and never did C 18 LETTER 1. Let US now examine the evidences of the miracle of creation. Vain indeed must be every attempt to give a physical definition or explanation of this greatest of all miracles ; to tell how the Ancient of Days called out of nothing all those materials which now constitute our globe, and gave life, and breath, and all things. " No rational natu- ralist," says Sumner, " would attempt to describe, either from the brief narrative in Genesis or other- wise, the process by which our system was brought from confusion into a regular and habitable state. No rational theologian will direct his hostility against any theory which acknowledges the agency of the Creator, and only attempts to point out the secondary instruments he has employed. Hitherto, our fathers speak to us of any such.' On my return there five hundred years afterwards, I found the sea hi the same place, and on its shores were a party of fishermen ; of them I inquired how long the land had heen covered hy the waters ? ' Is this a ques- tion,' said they, ' for a man like you ? This spot has always been where it is now.' I again returned, five hundred years after- wards, and the sea had disappeared. I inquired of a man who stood alone upon the spot, how long ago this change had taken place ; and he gave me the same answer as I had received before. Lastly, on coming back again, after an equal lapse of time, I found there a flourishing city, more populoiis and more rich in beautiful buildings than the city I had seen the first time. And when I would fain have informed myself concerning its origin, the inhabitants answered me, ' Its rise is lost in remote anti- quity ; we are ignorant how long it has existed ; and our fathers were on this subject as ignorant as ourselves.' " — Lyell's Geology, vol. i. p. 34. LETTER I. 19 indeed, those theories have had the fate of the monsters of antiquity, and been destroyed by one another ; leaving the only record to which any cer- tain reference can be made to triumph over their fate."* St. Paul says, " through faith we understand that the worlds were framed by the word of God, so that things which are seen were not made of things which do appear." Heb. xi. 3. Again, St. Peter says, " for this they willingly are ignorant of, that by the word of God the heavens were of old." If we trust to revelation, nothing can be more certain than that the creation of every thing living was at first the result of a direct miracle ; for it tells us that " God made every creature, and cattle, and creeping thing, and beast of the earth ; and every fowl of the air, and moving creature which the waters bring forth ; and every plant of the field before it was in the earth, and every herb of the field before it grew." Gen. i. 21, 24, 25, 30 ; ii. 5. So that the attempt to discover the process by which the world was made, or even to trace its various stages, by the investiga- tion of the existing forms of matter, we may, from these passages, be assured is both fruitless and presumptuous. The observations of Mr. Gran- ville Penn upon this subject are very original, and worthy of notice. He thinks that the conclusion of geologists, that the phenomena of rocks indicate * Records of Creation, vol. i. p. 356. 20 LETTER I. their former existence in a chaotic ocean, from which they were separated during an undeter- minate series of years, and consohdated, as we find them in the present day, is unfounded, being opposed to the great principles of Newton, as well as to the Mosaic tradition, both which authorities assign these phenomena to the fiat of the Almighty. The remarkable analogy existing in the three great departments of creation, namely, the animal, vegetable, and mineral kingdoms, and their mutual dependence one upon the other, leads us to infer that they have a community of purpose essential to the present state of things ; the earth being adapted to the support and nourishment of vege- tables, and they in their turn serving for food to the animated creation, and at the same time de- riving from animal matter much valuable nourish- ment. Each of these, therefore, constitutes a part of one great whole ; and the formation of them all must, of consequence, be referred to the same cause. If, then, we can prove that one of these has been created immediately by God, it must follow, as a necessary consequence, that the others have been formed in the same way — namely, by the fiat of the Almighty. Mr. Penn proceeds to argue that, as animals were first created at once without the intervention of any secondary cause, so also were the other two divisions of nature. Keeping this analogy between, and mutual de- pendence of, the several departments of creation LETTER I. 21 in view, he endeavours to ascend to the origin of man. If we trace our species back, we must ulti- mately arrive at tlie first man, the parent of all. Supposing this first man to have been formed with a bodily structure like our own, its soft parts would be supported in a similar manner by bone, and this bone would have the same structure as that of any other human being. So that if a bone of the first man were presented to an anatomist, there would be nothing in it to prevent the conclu- sion, that it was secreted and produced by some animal body similarly constructed to those now existing. When bone is first formed, it is soft and yielding, in order that it may accommodate itself to the dimensions of those organs which it is subsequently to protect ; and it is only by degrees that the bones become perfectly hard. Now, if we were to say that the bone of the first man was originally made soft, and gradually became firm and hard, because this is the natural process in the growth of bone, we should make an assertion of which we have no physical proof, and which would also be contrary to Scripture ; for there we learn that man was created perfect at once. In like manner, the geologist who, observing the chemical transformations effected by the action of heat, water, electricity, and the other great agents of nature, upon the various materials of which the earth is composed, maintains that these agents were employed in the original formation of the 22 LETTER I. globe, wanders not less widely from sound rea- soning,— unless, indeed, he at once denies the omnipotence of God, — than the anatomist would do in the supposed case, and opposes his own fallible conclusions to the declarations of Holy Writ. Mr. Penn argues in the same manner respect- ing the origin of the first tree. As every tree proceeds from a root, and in the early stages of its existence is soft and tender, gradually be- coming hard by time, we might be induced to infer that the first tree was the result of the same process : but this is not true, for the first tree was formed a tree at once ; and yet, if we could behold a portion of it, there would be nothing in its appearance to suggest that it had not arrived at maturity slowly and gradually, in the natural way : in the same manner as geologists can see nothing in the nature of rocks, and of the other materials of the earth, to lead them to believe that they have not all arisen from solutions or fusions, caused by the agency of water or fire.* The Bible opens with a record of the fact, that God brought into existence all the elements of matter, impressed them with certain invariable properties, and established their mutual relations ; that, moreover, to some of his creatures he gave the incomprehensible power of life ; and that all * See Penn's Comparative Estimate of the Mineral and Mosaic Geologies, passim. LETTER I. 23 these events took place, not in six unlimited pe- riods of time, but in six days. Now, we would ask. Is all this to be explained by physical causes ? We answer, that it cannot be explained by such causes. We do not dispute the miracle.* We know that to accomplish all this by means, or by no means at all, is the same to Him who is as independent of time and space, and the materials developed by that time or contained in that space, as He is of the crash of worlds ; who " upholdeth all things by the word of his power," keeping to- gether the materials of the earth by the same power that called them into existence. Those geologists who argue as though they did not consider that the act of creation was fol- lowed by any displacement of the earth's crust, will do well to observe, with Mr. Penn, that though the earth was created on the first day, it was "without form and void," and that the sea continued to cover the rocks till the third day, when God said, " Let the waters under the hea- vens be gathered together into one place, and let the dry land appear;" from which he very pro- perly infers that a violent disruption and depres- sion of the solid crust of the earth must have taken place, in order to create a bed for the ocean. This first revolution, or rather change, in the * "He spake, and they were made; He commanded, and they were created." " He said. Let them be ; and it was so." Psalm cxlviii. 5 (old translation) ; Gen. i. 24 LETTER I. position of the materials of the earth, when many- rocks must have been subverted, fractured, and displaced, it will be remembered must have hap- pened before the creation of plants or animals. It therefore explains the circumstance, that none of their remains are to be found in the primi- tive rocks.* According to Mr. Penn's argument, no more surprise ought to be felt in viewing the distinct character and the arrangement of the beds in which we now find rocks disposed, than what would naturally arise in observing the regu- larity which must have existed in the plates of the * Mr. Penn considers that the beautiful passage in the civth Psalm, from the fifth to the ninth verse, t relates exclusively to the deluge. Bishop Home says (Commentary on the Psalms, vol. ii. p. 213), " the process at the creation vi'as so exactly similar to that of the deluge, vs^ith regard to the circumstances here mentioned, that it matters not to which we apply the beau- tiful and poetical passage before us." But it w^ill be seen that, if this passage at all applies to the creation, the vi^ords in the latter part of the ninth verse, " that they turn not again to cover the earth," w^ould not bear ; for at the deluge the " fountains of the great deep vi^ere broken up, and the waters prevailed exceed- ingly upon the earth, and all the high hills that were under the whole heaven were covered ;" which could not have taken place if it had been decreed at the time of the creation that the waters were not as-ain to cover the earth. f "Who laid the foundations of the earth, that it should not be removed for ever. Thou coveredst it with the deep as with a garment : the waters stood above the mountains. At thy rebuke they fled ; at the voice of thy thunder they hasted away. They go up by the mountains ; they go down by the valleys unto the place which thou hast founded for them. Thou hast set a bound that they may not pass over ; that they turn not agairi to cover the earth." LETTER I. 25 skin of the first lizard, or in the colours of the tail of the first peacock ; for surely there can be no more difficulty in explaining why chalk is white, or basalt black — why marble differs from clay, or flint from iron, — than there would be in deter- mining how it came to pass that the skin of one animal was originally black, while that of another was white ; why one was striped, and another spotted ; why one was covered with a hard case of shell, another with a thick covering of fur, while a third was provided with quills.* We cannot, therefore, believe that all the phenomena which the earth discloses may be explained by the laws now in operation. Neither does the Mosaic tradition oblige us to believe that all the revolutions which the earth has undergone are referrible to the single act of creation. It tells us that, after the lapse of many hundred years, the earth was deluged with water ; that the fountains of the great deep were broken up ; and that, with the exception of Noah, and those who were with him in the ark, " all flesh died that moved upon the earth, both of fowl, and of cattle, and of beast, and of every creeping thing that creepeth upon the earth, and every man." " A single day's convulsion and inundation would have been sufficient to extinguish human life. The facts, that the effusions from the skies lasted forty days, — that the waters continued rising * Comparative Estimate, vol. i. p. 137. 26 LETTER I. and prevailing for one hundred and fifty, — and that one hundred and fifty more days were afterwards occupied in the retiring and subsidence of the watery fluid, — announce to us that a great process was then in operation, for other objects than the death of the subsisting population. These objects must have related to the state and structure of the earth itself in its habitable surface ; and as geo- logical investigations shew that the present rocks and masses of our surface are formations from the fragments of earlier ones, and have been preceded or accompanied by great changes, and convulsions, and dislocations, it is our duty, and the dictate of our common sense, to remember that we have here, in the dikivian catastrophe, an actual period historically recorded, in which the events and agi- tations of this character are attested to have taken place."* * Sharon Turner's Sacred History of the World, vol. ii. p. 305. There is no nation in the world that does not possess some faint tradition of the deluge of Noah; which is a most powerful evidence of the truth of the sacred historian. Cuvier, the greatest naturalist that ever lived, arrived at the conclusion that the deluge of Noah took place within a very few years of the time mentioned in the hook of Moses ; a conclusion which cer- tainly adds to the authority of that naiTative, inasmuch as it was derived from physical evidence only. For a more detailed account of this tradition, as it has been handed down to different nations, we must refer our readers to the second volume of Turner's " Sacred History of the World;" and for the physical evidence, confirmatory of the facts here briefly noticed, to Mr. Penn's second volume of the " Mosaic and Mineral Geology." LETTER I. 27 But it is contended that this aqueous destruc- tion of the earth will not account for the number and variety of fossil animal remains; as, reason- ing upon the principle of analogy, which we have before shewn to exist throughout the whole animal creation, those remains must have belonged to animals adapted to a condition of the earth's sur- face different from that which existed previously to the deluge ; neither is it thought sufficient to ex- plain the consecutive order and arrangement of those fossil remains which the earth discloses in every direction. Let us consider these two diffi- culties. Living creatures, as we shall hereafter prove, are formed with the strictest reference to the media and habitations in which they are placed; and the bones of extinct animals — those ancient records of creation — shew that, as those media and habitations have varied, there has been a corresponding change in the organisation of ani- mals ; that, in fact, the same creative Wisdom has at all periods been manifested, in the perfect adap- tation of animals to the circumstances in which they exist. From the quotations which we have lately made, and from many other passages to the same purport, v>^hich abound in the popular works of the day, we gather this fact, that the bones of all animals, whether living or extinct, are the most durable evidences of that God who created and animated every living thing ; and hence much 28 LETTER I. valuable information is to be derived from these imperishable monuments.* The great divisions of the living creation are all marked with an accuracy which does not per- mit us to doubt that a graduated scale of beings * " Bone is composed of animal and earthy matter, in different proportions, according to the nature of every animal. This com- bination enables it, better than aU other substances, to resist the operation of the most powerful agents in nature, such as heat, the atmosphere, &c., and thus to record those facts which other- wise must have been lost amidst the revolutions of the earth. If bone be submitted to an intense heat, it will part with the animal matter, but retain the earthy, together with its form. Now, if fossil bones be submitted to chemical analysis, they are found to be destitute of animal matter, but to have retained their earthy constituents. Hence they resemble, in this respect, bones that have been burnt. Mr. Hatchett, who examined some fossil bones brought from Gibraltar, first discovered this. The phos- phate of lime remained ; but the interstices, which, in the recent state of the bones, would have contained animal matter, were found to be filled up with carbonate of lime, thereby giving them the most durable properties, while they at the same time retain their original shaj)e. This change in the composition of fossil bones particularly demands attention ; for it would seem to shew that they had been acted on by some powerful chemical agent. Mere putrefaction and burying in the earth does not destroy the animal part of bone ; for Mr. H. examined a humerus (arm-bone) taken from a Saxon tomb at Hythe, in Kent, and found it con- tained nearly as complete a residuum of animal matter as a recent bone. " Another circumstance which cannot fail to excite atten- tion, in considering the history of organic remains, is the matter, or substance, of which they consist. They are termed LETTER I. 29 formed part of the Divine plan. Yet, though we firmly beheve that the boundaries of their habitations were all appointed, it is certain we should be drawing a much wider inference than is warranted, were we to attempt to localise every species of animal according to the particular shape and construction of the skeleton. The informa- tion we may derive from the skeleton, however correct, will only extend to certain general points of distinction, beyond which any conclusion drawn petrifactions, — a compound word, signifying made stone; be- cause they are actually converted into a mineral substance, the quality of which is determined by that of the rock in which they are contained. In some instances, the animal or vege- table matter has been entirely dissolved or removed, and the mi- neral matter of the rock so nicely substituted, as to assume the perfect form of the internal structure, even to the minutest vessel or fibre of the plant or animal. Sometimes the process of petri- faction has been carried no further than the infiltration of the stony matter into the pores of the organised body. In other cases, again, the animal and vegetable substance has been wholly presei-ved, and the plant or animal has undergone no other change than the removal of such parts as are the most liable to dissolu- tion and decay. The process of petrifaction is usually the most perfect among the older strata; while among the more recent, and generally throughout all the tertiary group, the contained relics have sustained little alteration. This principle, however, is so far from holding universally, that among the old red sandstone and other secondary strata, remains are found where no substitu- tion has taken place ; where, for example, fish-scales occur in the greatest abundance, possessing still their pearly lustre, and the other qualities by which they are characterised." — Mr. Anderson's paper in Scottish Christian Herald, No. V. 30 LETTER I. from it must be unsubstantiated and unsafe. Nu- merous circumstances, quite independent of osseous structure, we may safely affirm, might have caused animals of the same species to inhabit widely dif- ferent climates : we must therefore proceed with the greatest caution, in speaking of the peculiari- ties of species which formerly existed, when we have no other circumstances to guide us than the mere structure of the skeleton.* If, for instance, we had nothing but the skeleton of the horse to inform us as to the variety of climate which this animal is known to exist in, is it probable that we should have concluded that it was fitted to live as well in the polar as in the tropical regions ? We should therefore receive with caution all those theories of geographical distribution, which merely take into consideration the degree of temperature in which the animal may be thought to exist. Never- theless, the number and the variety of ossific relics give us a plentiful assurance that the surface of * " The fossil remains of quadrupeds can indeed reveal to us what animals once lived, by shewing us what animals have perished; and thus we may, therefore, collect what genera or what species are become extinct. But this is the utmost extent of the instruction imparted by fossils extraneous to the sea." — Penn's Comparative Estimate, &c. vol. ii. p. 147. What part of the skeleton of the Semnopithecus entellus would have told us, if this animal had become extinct, that it was the only known monkey of the old world having no cheek-pouches, or that its stomach was so elaborately or so differently contrived from the same organ in other animals } (See Plate III. Fig. 4.) LETTER I. 31 the earth has been completely altered, and that great changes have taken place in the relative position of sea and land. To give this subject the consideration which it demands, let us see how far these changes can be referred to the great diluvial catastrophe recorded in the book of Genesis. Possessing that history, we do not require to be told by geology that the earth has been sub- jected to a great catastrophic change, the effects of which, neither our present knowledge of the extent of action of physical laws,* nor the nar- ration of it given by Moses, enables us to esti- mate with accuracy. For who is bold enough to * We do not wish to deny the unde^dating uniformity of secondary causes ; we believe that those causes have operated ever since the earth was created. But are we bound to beheve that such a vast and extraordinary event as the deluge was brought about simply by those causes ? Sumner says : " the importance which Moses attached to the fact of the deluge is evident from the manner of his narration. He represents it as scarcely less vast and extraordinary than the creation itself, and as requiring equally the immediate exertion of the Creator's power. He relates it very particularly. He prepares us for the account of it by a solemn deliberation on the part of the moral Governor of the world, and closes the history of it by an assur- ance to mankind that the globe they inhabit should never again be subjected to a similar catastrophe." — Records of Creation, vol. i. p. 349. Thus, in making geological deductions, we should take into consideration effects which could only proceed from catastrophic causes, as well as effects which may be said to be produced by natural causes. 32 LETTER I. say what was the result of that immeasurable vacuum and displacement which must have taken place in the bowels of the earth, when the foun- tains of the great deep were broken up, and when, for many months, the waters returned from off the earth continually, to take their stations again in those fountains from which they had been summoned ? When to this we add the con- flicting operation of a great subterranean fire, which is in continual active operation at the present time, as is proved by the existence of many hundred volcanic craters,* through which it makes its escape beneath the bed of the ocean,f * " During the last century," says Lyell, " about fifty erup- tions are recorded of the five European volcanic districts of Vesu- vius, Etna, Volcano, Santorin, and Iceland ; but many beneath the sea, in the Grecian Archipelago, and near Iceland, may doubtless have passed unnoticed. If some of them produced no lava, others, on the contrary, like that of Skaptar Tokul, in 1783, poured out melted matter for five or six years consecutively ; which cases, being reckoned as single eruptions, vv^ill compensate for those of inferior strength. Now, if we consider the active volcanoes of Europe to constitute a fortieth part of those already known on the globe, and calculate that, one vdth another, they are about equal in activity to the burning mountains in other districts, we may then compute that there happen on the earth about two thousand eruptions in the course of a century, or about twenty every year." — Principles of Geology, vol. ii. p. 179. t " It can only have been since historical times, and by mere accident, that instances of volcanoes forcing themselves from be- neath the sea could have been recorded. Now, the power of man to do this is so recent, that we may conclude such occur- rences to have been far from rare ; and that, even in the present LETTER I* 33 as well as on the surface of the earth, we think there is some reason to believe that the deluge was not a mere aqueous deposit, but a mighty- convulsion, calculated not only to shake and dis- locate the whole materials of the globe, but to de- stroy every thing living on its surface."* " It is a problem of very difficult solution, to determine how much of that appearance of in- ternal and external ruin which the earth uniformly exhibits is to be referred to the effects of this catastrophe. To ascertain this point with any approach to probability, we ought to be acquainted with the means employed. The operation by which the submersion was caused is, however, de- scribed by the historian in the most general terms. day, they may happen in remote regions, into which civilised man rarely, if ever, enters, and therefore they remain unknown. Tliere are numerous islands in the ocean composed almost entirely of volcanic matter, and in which active volcanoes still exist, that may have been thus formed ; the dome, or cone, not giving way before the pressure of the water, but gradually accumulating a mass of lava, cinders, and ashes, so that the islands have become firm, and even of considerable size. Owhyhee, or Hawaii, is perhaps a magnificent example of such an island. The whole mass, estimated as exposing a surface of 4000 square miles, is composed of lava and other volcanic matter, which rises, in the peaks of Mouna Roa and Mouna Kaah, to the height of between fifteen and sixteen thousand feet above the level of the sea." — De LA Beche's Manual of Geology, p. 113. * For an account of the earthquake at Chili in 1835, when flames rose from the sea through a depth of sixty-nine fathoms of water, see Lyell's Geology, vol. ii. D 34 LETTER I. Nothing, surely, short of the complete subversion of the whole globe, could raise the sea a perpen- dicular height of at least 20,000 feet beyond its ordinary level, or cause an equivalent subsidence of the land. Even if we diminish, in any allow- able proportion, the height of the antediluvian hills, still such an overthrow of the system could neither have been effected without violence, nor have taken place without corresponding devas- tation. When we call to mind the destruction which is occasioned by a sudden alteration in the level of a very inconsiderable collection of water, even to the extent of fifty or a hundred feet, we cannot easily assign limits to the effect of a body of waters like the ocean pouring in over the land, when its level was destroyed ; we are at a loss to conceive what the power of such a machine might be, when once in operation. Were it allow- able to risk a conjecture as to the secondary agents employed in this supernatural revolution, it might seem a p7io7i probable that subterraneous fire would be principally concerned in effecting it. The reasons are obvious : the known existence of nearly two hundred volcanic openings is sufficient proof of the extent of internal fire. The vast dis- tance at which their shocks have been sensibly felt gives some idea of the extent of their force, which even an intervening ocean cannot restrain. The volcanoes of Etna and Vesuvius attest their in- ternal communication by their simultaneous erup- LETTER I. 35 tions : the convulsions which shook Italy have been accompanied by similar convulsions in Ice- land. Their accompaniments are earthquakes, agitations of the sea, and inundations ; their consequences are destruction. The earthquake that overwhelmed Callao may have represented, on a small and partial scale, the universal deluge. If we multiply that partial submersion of nature to the extent required in order to raise the sea to the level of the highest mountains, we may form some conception of the magnitude of the convul- sion ; though it would be impossible for us, even then, to determine what effect such a total dis- ruption and submersion of all the parts which form the fabric of our globe might occasion upon the materials of which it is composed. St. Peter, alluding to the deluge, seems clearly to have enter- tained the idea of a complete overthrow of the parts of the globe. ' The world that then was, being overflowed with water, perished.' The term world would not necessarily carry this argument with it without the succeeding verse, in which the apostle proceeds to add, ' but the heavens and the earth which are now, by the same word are kept in store, reserved unto fire against the day of judg- ment.' The contrast in the latter verse explains the ambiguous term in the former. 2 Pet. iii. 6, 7. From these considerations, it would appear ante- cedently not improbable that the crust of the earth should exhibit traces of the agency, perhaps I 36 LETTER I. may add of the destructive agency, of water and fire ; and whicli may be best explained, in some instances, if we suppose those powerful agents to have been simultaneously employed."* We shall therefore require to see the wane of many more theories, before we disturb the Mosaic account, or regard it as in any respect inadequate to explain the changes which the earth has under- gone since the creation of man. Assuredly we shall not do so merely because men, reasoning upon the facts discovered by digging in a few arbitrarily se- lected spots on the earth's surface, have found them- selves unable to connect those facts with the events relcited in the Scripture, as effects with causes. The theorists of the day would doubtless rejoice to be thus rid of a difficulty which is always in their way, reflecting on their folly, and dissipating their baseless fabrics into thin air. But in the present day we are required to receive with many modi- fications the truths of revelation ; and in reference to the awfully remarkable change in the state of our globe which we have been considering, we are told, that the discussion of the several re- volutions to which our earth has been exposed is a subject which must be conducted entirely apart from revelation, and that " the highest demands of truth, and the best interests of mankind, are inva- riably sacrificed, when rehgion is introduced into * Records of Creation, vol. i. p. 352. LETTER I. 61 questions of science and civil policy."* So that, if the record of an event which has come down to us through a source which, we are told (not from tradition alone, be it remembered), and believe, conveys the sentiment, if I may so say, of the Almighty himself, is irreconcilable with any one of the thousand ephemeral and half-digested theories of the day, — which, like the bubble- blown hypotheses of the heathen philosophers, are here one moment and gone the next, — we are to cancel revelation, by giving it an allego- rical interpretation, in order that it may coincide with the current opinions of the time ; or else, like some natural theologians, we are to give to the words of the Mosaic account an extent of meaning which they are quite unable to bear, * Review of Buckland's Bridgewater Treatise in Edinburgh Review, April 1837. " In the dark ages of geology, her science rested on the two assumptioiis — that the world was made in six days, and afterwards overwhelmed in the waters of an universal deluge ; and hence arose a series of erroneous positions impreg- nable to human reason, because guarded with aU the sanctities of religious belief. The primitive waters of the globe were held to be an universal menstruum, capable of dissolving the most refrac- tory substances, and the primitive mountains themselves. The metalhc ores, the hardest gems, and even adamant itself, were supposed to be chemical precipitates from this chaotic fluid. In this way did the rude architects of our planet sm-round its nucleus v^dth a succession of universal formations, like the coats of an onion, and hand it over to the apprentice -skiU of diurnal opera- tions, to fashion it into the picturesque, the beautiful, and the sublime." — Edinburgh Review, p. 4. 38 LETTER I. and which can be supported only by the most chnnsy devices and the boldest perversions of their obvious meaning ; and thus the narrative is deprived of all its authority, and we are lost in the endless speculations of heathen darkness.* We may indeed say, " Who is this that darkeneth counsel by words without knowledge ?"f The words of revelation would naturally teach us to infer, that the deluge of Noah was a mighty convulsion, in no respect inferior in its effects to that of the third day of creation, when " the waters were gathered together into one place, and the dry land appeared ;" and not, as the suc- cessionists express it, the tranquil, peaceful deluge of the Scriptures. " We cannot fail to perceive that a repetition of the same process, a renewal of the same Divine operation which produced the former earth, was alone requisite to bring to light another earth to replace it, now that the counsels of its Creator had determined to remove it. We have already seen that in the first great revolution or modification of the primitive formation of our globe, which took place in the third day of the progress of creation, one vast division of its sub- * We quite think, with Krummacher, that " the prevailing spirit of our times is that of infidelity and apostacy ; a spirit of pretended illumination, but, in reality, the blindest presumption ; a spirit of opposition to the plain word of God ; a spirit of idola- trous exaltation of mere natural reason above the revealed wisdom of God." — Elijah the Tishbite, p. 152. ] Job, xxxviii. 2. LETTER I. 39 aqueous surface was suddenly and violently frac- tured and depressed, in order to form a bed suf- ficiently profound to receive and confine the con- gregated waters of the universal abyss ; which waters, drawn down into that bed from off the other division of the subaqueous surface, left it exposed, undisturbed, and fitted for the growth of vegetation, and the habitation of animals and of man. That exposed and hitherto undisturbed division was now to sink and disappear. By a similar fracture and depression of its surface, which should reduce it below the level of the first depressed part, or basin of the sea, the waters, flowing down into a still lower level, would leave that basin empty, ex- posed, and dry ; and would thus render it, in its turn, an habitable earth, applicable to all the same uses as the former earth, which had been obtained by a similar drainage of the waters. We are en- joined by sound philosophy to refer similar effects to similar causes; and the effects which we are considering being in both cases similar, we are accordingly to refer them to similar causes. And since the record contains nothing that opposes the application of this principle to the case in question, we are authorised by reason to conclude, that the production of a second earth was effected by means exactly corresponding to those which had produced di first earth; the evidence which the mind is enabled to apprehend of the means by which a first earth was produced, becoming 40 LETTER I. conclusive evidence to the reason that a second earth might be produced by similar means, and therefore directing it to look to those means for its production. Among those means or secondary agencies^ we have found the strongest reasons for assuming the instrumentality of volcanic action. That powerful agency, rendered extensively ope- rative at two successive and distant periods, would probably have left correspondent and permanent vestiges of its operation, during both those periods, in the materials of the crust of the globe; and accordingly, the mineral geology has found, that in some regions of the earth ' the principal seat of the subterraneous fires appears to be beneath the transition, or fragmentary rocks,'* " that is, be- neath those rocks which were first fractured to form the primitive sea-bed ; whilst, in other re- gions, ' the volcanic formations appear to have been formed between the epochas of the secon- dary and tertiary formations,'f that is, between the last tranquil sedimentary formations in the primi- tive sea, and the tumultuary formations during the diluvial transfusion of that sea.";|; It has been well said, that the trutlis of religion and of science can never be at variance, and that whenever they appear to be so, the cause is to be sought for in the ignorance or errors of men, occa- sioning belief in that which is false, or has no ex- * Humboldt's Superpos. of Hocks, p. 33. t I^- P- "116. \ Penii's Comparative Estimate, vol. ii. pp. 21, 23. LETTER I. 41 istence. But since we have an unerring guide to Q-eligious truth in Divine revelation, whereas we have no means of discovering scientific truth ex- cept our own weak reason informed by fallible sense, it is certainly more reasonable, in the case of any such apparent variance, to seek for the error which gives rise to it in the department of science, rather than in that of religion. When, for example, Moses, directed by the Spirit of God, records the fact, that " In the beginning God created the heaven and the earth. And the earth was without form and void ; and darkness was upon the face of the deep ;" are we, because this statement contradicts our geological theories, jus- tified in assuming that the historian intended to say. In the beginning God created the heavens and the earth. And the earth was not without form, neither was it void ; but hght and hfe were vipon the face of the deep ? For, in order to make the Bible accord with those falsely called truths of geology, nothing short of this perversion of mean- ing will suffice. But by setting aside the Mosaic tradition, or rather, by assuming that the events narrated in it extended over a long and indefinite period of time, the successionists lay themselves open to the most obvious and insurmountable objections. Thus, they say that " the darkness described on the evening of the first day was a temporary darkness, produced by an accumulation of dense vapours upon the face of the deep," and 42 LETTER I. that " an incipient dispersion of these vapours may- have re-admitted hght to the earth upon the first day, whilst the exciting cause of hght was still ob- scured."* But we must here ask, if light existed previously to the Adamic creation, what was the purpose of withdrawing it at that time ? for it was not with- drawn at the deluge. And if the Adamic creation was only a mere revolution of the globe, effected in order to accommodate it to the service of man, as geologists believe, darkness would no more have been induced then than at the deluge ; which we might reasonably have supposed would produce an accumulation of dense vapour quite sufficient to cause darkness upon the face of the deep, but which we know had not this effect. If, then, we admit, as we must do, that before the Adamic creation no light shone upon the earth, all doubts are removed about a succession of creations : for, in the first place, we cannot suppose that animals could exist at all without light ; and, in the next place, we actually find in some of the lowest strata (which, according to geologists, are the oldest) remains of animals pos- sessing visual organs ; and since these could serve no other purpose than to convey sensations of hght, it necessarily follows, that light existed when these animals were created ; and thence we con- clude, that they must have been called into being * Buckland's Geology, p. 30. LETTER I. 43 at the same time as man. But assuming that these animals enjoyed hght before the Adamic creation, it is absurd to suppose that darkness preceded that event ; since, if it was a mere geo- logical revolution, it could not have produced darkness, any more than the effect of the deluge was to produce darkness. The important truth disclosed by De Luc, that light was not first shed upon the earth by the sun, is certainly one which speaks louder for the integrity of the first chapter of Genesis than any other known fact ; for no one will presume to say that, if unassisted reason could have conceived the idea that hght was created before the sun, such an apparent incon- sistency would have stood the test of ages, in opposition to all seeming probabihty. We are quite of opinion that a '' geological truth must command our assent as powerfully as that of the existence of our own minds, or of the Deity himself; and any revelation that stands opposed to such truths must be false."* It is, however, a piece of presumption to call every crude hy- pothesis, founded, perhaps, on a few doubtftd facts in geology, a truth ; for thousands of facts in the history of this science teach us that our conclusions upon many points have been hmited and premature. We may therefore turn round and say, with less arrogance, that any geo- logical deductions which stand opposed to the re- * Edinburgh Review, No. 131, p. 16. 44 LETTER I. vealed word of God must be false. We cannot, then, go on to say, with the reviewer, " the geo- logist, therefore, has nothing to do with revealed religion in his scientific inquiries."* So far from agreeing with this, we believe that it is only when men are wise enough to take the compass of God's sacred word on board their frail geological barks, that they have the prospect of arriving at any safe anchorage. It is a favourite opinion with those who have lately written upon natural theology, that, because Scripture is silent upon many subjects not imme- diately relating to God's moral government of the world, they are therefore at liberty to draw their own conclusions as to the physical condition and early history of our planet, without any reference to Scripture. But, in the first place, the Scrip- tures are not entirely silent upon the physical con- dition of our earth ; and, in the next place, there are many circumstances which, though not actually alluded to in Scripture, must be allowed to have too close a connexion with God's moral govern- ment of the world, to admit of being discussed with a freedom wholly regardless of revelation. Thus, it is argued by Prichard, that, because some animals " seem to have had the origin of their ex- istence in distant regions, as Australia and South America, therefore they could not have descended from a stock that was preserved in Noah's ark, be- * Edinburgh Review, No. 131, p. 16. LETTER I. 45 cause, in that case, they must all have been con- gregated in one spot, — a supposition which can hardly be reconciled with geological researches."* He considers that there is no necessity for making any such assumption, as it is no where asserted in the Mosaic history. So that we see it has been thought that the silence of Scripture upon such a matter as a fresli creation of animals is of little con- sequence ; although we should think that, if such a re-creation did take place, so important a fact as the formation of a new type of beings would no more have been omitted by the sacred historian than the original creation of man. Again, though Scripture is silent upon many subjects relating to natural phenomena, still it is most important that our explanations of those phenomena, which we may think were not required to be mentioned in * History of Mankind, vol. i. p. 31. Other writers have concurred in this opinion. " Some persons," says Swainson, " will object to this hypothesis, that it assumes positions not laid down in the sacred narrative, such as a partial creation subse- quent to the deluge. This must be granted ; and the proofs of such position must be sought, not in Scripture history, but in external phenomena. The silence of the Scriptures in respect to such facts seems to be of little consequence. It is not to be pre- sumed that these sacred books contain a narrative of all that it has pleased Divine Providence to effect in the physical creation, but only of his dispensations to mankind, and of the facts with which man is concerned ; and it was of no importance for man to be informed at what era Australia began to contain kangaroos, or the woods of Paraguay ant-eaters and armadillos." — Geography of Animals, p. 6. 46 LETTER I. Scripture, should accord with what has been re- vealed ; otherwise it places that revelation in a false position. When once we have determined to deny the physical possibility of all created animals, after their kind, being taken into the ark,* because their habits, organisation, or geographical distribution are opposed to such an idea, there must be an end generally to behef, and every modification of be- lief in Divine revelation; and unassisted reason cuts the knot which was so long held together by faith. If revelation tells us that, at the time of the deluge, God said unto Noah, " the end of all flesh is come before me ; " and, after that deluge had subsided, again said, " I will not again smite * Independently of the supposed zoological impossibility, that representatives of all the animals could be brought before Adam in the first instance, and subsequently be collected in the ark, maintained by Prichard, Lawrence, and others — it has been thought that the dimensions of that vessel were not ample enough to accommodate so large a number of beings. Now, if we take, with Shuckford, the common cubit, or one foot and a half, which is the shortest measure of the three cubits which were made use of by the Hebrews, we then have an ark measuring 450 feet in length, 75 feet in breadth, and 45 in height. Reck- oning the cubit after this manner. Hales says the ark must have been of the burden of 45,413 tons. A first rate man-of-war is of between 2,200 and 2,300 tons ; and consequently the ark had the capacity or strength of eighteen such ships, the largest in present use, and might carry 20,000 men, with provisions for six months, besides the weight of 1,800 cannons and of all military stores. Can we then doubt its abihty to contain eight persons and LETTER I. 47 every thing livivg as I have done ;"* surely there can be no truth in the supposition of a partial deluge of the earth at the time Noah entered the ark, when " all flesh died that moved upon the earth/' and " Noah only remained alive, and they that were with him in the ark."f A remarkable proof of the universality of this catastrophe is fm-nished by those caves which contain together the bones of the rein-deer, an animal inhabiting the coldest regions of the north, and those of the rhinoceros, which is confined to the torrid regions. Cuvier saw, in a cave in France, the bones of a rhinoceros and those of a rein-deer side by side ',% and again, the bones of the spotted a few thousand animals, with sufficient food for all ? But to the objectors who refuse their assent to the hteral truths of Scripture, because they are zoologically or physically impossible, we may re- mark, that the geometrical cubit of nine feet will increase the above dimensions five times, and will give 212,065 tons, or a storage equal to ninety of our largest ships ; a space sufficiently large to obviate all the doubts and difficulties of the most uncompro- mising sceptic ; while to those who believe that the creatures were all brought into the ark by the Creator's immediate in- terposition, I need scarcely say that they " went two and two unto Noah into the ark." Scott observes, " there must have been a very extraordinary miracle viTought, perhaps by the ministration of angels (the idea of many learned divines), in bringing two of every species, and of every clean beast by sevens, to Noah, and rendering them submissive to him, and peaceable with each other." (See Commentary, note to Gen. vii. 2.) * Gen. vi. 13, and viii. 21. f lb. vii. 21, 23. X Theory of the Earth, p. 287. 48 LETTER I. hyaena, a native of the Cape of Good Hope, have been found mingled with those of the ghitton, a native of Lapland. No argimients founded upon a change of temperature alone can account for this mixture of animals, which, in their habits and in- stincts, must have occupied widely different spheres. If the account of the Noachial deluge be true, it is the opinion of some naturalists that there has been a succession of creations subsequently to that event, or else a transmutation of species has been going on. We do not believe that there is any real evidence to prove that there have been several distinct and successive acts of creation and extinction of species, as some geologists suppose. If, since the first creation, animals have become extinct, we have no proof that they did not form part of the first creation ; and their extinction has arisen from the circumstance that they were no longer fitted to the existing condition of the earth's surface, being only adapted to a state of the earth antecedent to their extinction. If, on the other hand, new species appear to have arisen since the creation, it is because some kinds of animals vary their species to the extent to which each is suscep- tible of change, under different circumstances ; and those circumstances have not all been sub- mitted to the observation of man. Thus, it is by no means necessary to assume that new species must have been brought into existence subse- quently to the first creation, merely because, as LETTER I. 49 our acquaintance with the surface of the earth becomes more extensive and complete, animals previously unknown are discovered. The varia- tion in the laws which govern the economy of every species, as we shall presently shew, would operate, amongst many other causes, to render their relative numbers so difficult to be ascer- tained, that the fact of some species not having been presented to our notice may be owing to the circumstance of the laws which govern that particular species not being favourable to its in- crease or distribution at the early period of the earth's history. The doctrine of a transmutation of species, which supposes that the organised spe- cies of one epoch were changed into others by the long-continued agency of natural causes, is a theory, to use the words of Professor Sedgewick, '' no better than a frensied dream ;" and there can be no doubt that the changes of which each species is susceptible are confined to certain fixed and impassable hmits. " It may be considered," says Whewell, " as determined by the overbalance of physiological authority, that there is a capacity in all species to accommodate themselves, to a cer- tain extent, to a change of external circumstances, — this extent varying greatly, according to the species. There may thus arise changes of appear- ance and structure, and some of these changes are transmissible to the offspring ; but the mutations thus superinduced are governed by constant laws, E 50 LETTER I. and confined within certain limits."* Indefinite divergence from the original type is not possible ; and the extreme limit of possible variation may usually be reached in a short period of time ; in short, species have a real existence i?i 7iature — trans- mutation from one to another does not exist. Thus, for example, Cuvier remarks,f that notwith- standing all the differences of size, appearance, and habits, which we find in the dogs of various races and countries, and though we have, in the Egyp- tian mummies, skeletons of this animal as it ex- isted three thousand years ago, the relation of the bones to each other remains essentially the same ; and, with all the varieties of their shape and size, there are characters which resist all the influences both of external nature, of human intercourse, and of time." J * Whether the differences in some of our species are capable of taking place, as coining within the fixed laws which govern the genus, is not determined by physiological evidence. t Ossem. Foss. Disc. Prelim, p. 61. X Whewell's Inductive Sciences, vol. iii. p. 576. LETTER 11. INTRODUCTORY. " The real use of natural theology is to shew the strong pro- bability of that being true which revelation declares." — Sumner's Records of Creation, vol. i. p. 11. We will now proceed to shew that there is neither improbability nor inconsistency in the sa- cred narrative ; and the proofs which we shall hereafter adduce, to shew that the various or- ganic changes in the forms of living bodies are all the results of the operation of peculiar laws, which regulate every individual species, will be as subversive of the Jicfio?i of a succession of crea- tions as of a transmutation of species ; and these arguments will apply to the position of animals before the deluge, as well as subsequently to that event. When Noah entered the ark, he was told to take with him " two of every kind of fowls after their kind, and of cattle after their kind, and of every creeping thing of the earth after his kind."* Now, the classification of animals, according to the very best human authority, has proved to be an undertaking attended with difficulties which, in spite of the most profound knowledge and persevering application, must, in the present im- perfect state of our knowledge of the earth, be * Gen. vi. 20. 52 LETTER II. considered insurmountable. The fact, that many extensive portions of the earth remain to this day unexplored, gives sufficient ground for asserting that the classifications of Linnaeus, of Cuvier, and of Blumenbach, are intrinsically incomplete.* The effect of this deficiency, whether from geo- graphical or other causes, has been either to add new animals to our catalogues, or to alter the arrangement of those which had already been comprised in them.f And we have no doubt this * The more limited classifications of Geoffroy, lUiger, La- marck, Spix, Gmelin, Buffon, Pallas, and many others, have less to recommend them either as general or partial systems of zoo- logy. Speaking of some of the partial systems which preceded his last great " Tableau des Animaux," Cuvier shews us the difficulties he had to overcome in the great task which he had undertaken. He says, " I not only found that the species were either grouped or distributed in defiance of common sense, but I saw that many of the species were by no means positively esta- blished by the characters attributed to them, or by the figures and descriptions given of them." — Preface to the first edition of the Rrgne Animal. t " Both French and foreign naturalists seem to have felt the necessity of estal)lishing divisions in those immense genera in which such incongruous s^Decies were formerly heaped together : their groups are now precise and well defined, their descrijotions sufficiently detailed, their figures scrupulously exact, even to the most minute characters, and very frequently of the greatest beauty as specimens of art. There now remains scarcely any difficulty in fixing the identity of their species ; they had only to establish an understanding about the nomenclature. Unfortu- nately, that object of care was the one which they most neglected. The names of the same genera and of the same species are multi- LETTER II. 53 must continue to be the case, to a greater or less extent, as long as the circumstances of the earth, and man's relation to them, remain what they are now. It appears, then, that there is ample reason for the belief, that to this day we do not know what may have been comprehended in the com- mand to Noah, that every animal, after its kind, should be taken into the ark ; and that many kinds of animals yet unknown to man as distinct kinds, and consequently not duly recognised, or perhaps not even contained in his classifications, might have been received by Noah. It must also be understood, that the word " kind" is not by any means synonymous with species. In our classifi- cations, we make many individual and minute dif- ferences in the details of comparative anatomy to constitute a distinct species ; but, as it will be pre- sently shewn, it is not probable that those differ- ences were recognised by Noah, nor indeed that all of them existed.* With these facts before us, plied as often as an author speaks of them ; and in consequence of this disagreement, the same chaos will spring up in all its former confusion, though arising from altogether a different cause." — Preface to the second edition of Cuvier's RPgne Animal. * As the command to Noah was, that he should take with him into the ark two of every kind, and the researches of some of our geologists have shewn that many genera and species have passed away, it is not improbable that some animals had become extinct before the period of our deluge. That the extinction of 54 LETTER II. it must be admitted that those who assert that a new creation must have taken place, because some animal is brought under their notice which they had never before seen, make an assumption wholly gratuitous ; since we do not certainly know that it did not constitute part of the original creation. With regard to the varieties of animals, in their kind as well as in their species, many circum- stances press upon our consideration which have been very unfairly represented by different writers. And after we have shewn that some first cause must have operated to fix the species, it will not be difficult to prove that many causes of a se- condary nature, such as climate, food, locality, &c., are important agents in effecting those dif- ferences which are observable in animals of the same species, and v/hich are regulated by the pe- cuhar circumstances of their situation.* many animals is a law of nature now in active operation, we shall presently be able to demonstrate. * " The opinion, that those conditions which regulate the geographical distribution of species are limited to circumstances connected with temperature, food, situation, and foes, is totally insufficient to account for the phenomena of animal geography. We know, indeed, that these causes, either singly or collectively, have great influence on local distribution ; but they have nothing to do with the geographic distribution of animals indigenous to large continents, nor will they ever explain the local distribution of some of the commonest birds. It may be said, indeed, that the absence of the nightingale in Northumberland and Scotland is to be attributed to the greater coldness of those parts, compared with the milder air of southern England. But how are we to LETTER II. 55 We have already given some proof of the adaptation of all animals to their appointed sta- tions ; and in the course of the following pages we shall be able to extend those proofs by many interesting particulars. Now, as the surface of the earth has from time to time undergone very great changes, and the temperature, food, locality, and other circumstances which modify the forms of animals, have consequently all been altered, some writers have supposed that the doctrine of a creation of new animals, to meet these several secondary changes, is not incompatible with reve- lation, since all the animals that were first created account for this bird being common in the more northern king- doms of Sweden and Germany ? Climate in this case can have no influence ; neither can food, since insects and their larvse, of the same species, are found in all these localities. The thickets of Scotland are as favourable for breeding in as those of Sweden ; and, in regard to foes, no reason can possibly be devised. In what way, also, can the circular range of the nightingale be made out ? Again, we will allow that these causes are sufficient to account for the fire-crested warbler (Sylvia ignkapilld) being found in the Parisian gardens, while it is a stranger to England. Tlie difference of temperature, we will say, is the reason : Eng- land is colder than France. But how are we to account for two species of these gold-crested warblers being common in North America, in precisely the same latitudes, yet totally distinct from those of Europe ? It is by such questions, of which every class of animals will furnish numerous examples, that closet-theories must be tried : at the same time, they will at once point out the very distinct nature of local dispersion from that of geo- graphical distribution, properly so called." — Swatnson's Geo- graphy of Animals, p. 8. 56 LETTER IL were such as the surface of the earth at that time reqmred ; but as that surface was changed, so were the animals that dwelt upon it. That changes in the structure of animals are the result only of secondary causes, in active operation at the pre- sent time, is clear ; and that these are causes grafted, as it were, upon some original cause, which is entirely unknown to us, is equally cer- tain. That some great cause must have formed the type, and given to every kind and every spe- cies those indelible distinctive marks which, in spite of the long-continued operation of numerous external modifying circumstances, have remained unaltered from the earliest period of which we have authentic records, we have abundant evi- dence to prove. " We may indeed," says Swain- son, " build a theory upon every thing in nature ; but the more we investigate, the stronger will be our conviction in the following deduction — that the primary causes which have led to the differ- ent regions of the earth being peopled by differ- ent races of animals, and the laws by which their dispersion is regulated, must be for ever hid from human research. This conclusion is strengthened by the inference which will be drawn from the facts we shall subsequently state, — an inference so well expressed by a very intelligent writer, that we shall give it nearly in his own words : ' It appears that the various tribes of organised beings were originally placed by the Creator in certain LETTER II. 57 regions, for which they are, by their nature, pecu- harly adapted. Each species may have had only one beginning in a single stock ; probably a single pair, as Linnaeus supposed, was first called into being, and their progeny left to disperse them- selves to as great a distance from the original centre of their existence as was compatible with its physical capabilities, and with those unknown laws by which the Creator has regulated the geographic distribution of his creatures.' "* The memorials of one of the most ancient nations in the world have preserved animal remains which furnish the strongest evidence in support of the belief, that the essential characteristics of every race of animals have not varied for many hun- dred years ; and if they have been immutable for so long a period, we are entitled to infer that no variation in them has taken place from the begin- * Geography of Animals, p. 9. It is quite certain that many of " those unknown laws by which the Creator has regulated the geographic distribution of his creatures," must have operated upon other and infinitely less durable parts of the structure of animals besides the skeleton. Those parts have now perished, and have left few traces from which any correct physiological data can be derived ; and therefore the observation of Buckland — that " our knowledge of the osteology of a large number of extinct genera and species now rests on nearly the same founda- tion, and is estabUshed vnth scarcely less certainty than the anatomical details of those creatures that present their living bodies to our examination" {Geology, vol. i. p. 109) — is an assertion not strictly in accordance with sound physiology. 58 LETTER II. ning. The remains to which I refer are the Egyp- tian mummies of many species of animals ; respect- ing which Mr. Lyell says, " By a singular accident, the priests of Egypt have bequeathed to us, in their cemeteries, that information which the mu- seums and works of the Greek philosophers have failed to transmit. Among the Egyptian mummies were not only those of numerous wild quadrupeds, birds, and reptiles, but what was, perhaps, of still higher importance in deciding the great question under discussion, there were the mummies of do- mestic animals : the bull, the dog, and the cat, were frequent. Now, such was the conformity of the whole of these species to those now living, that there was no more difference, says Cuvier, between them than between the human mummies and the embalmed bodies of men of the present day. Yet some of these animals have, since that period, been transported by man to almost every climate, and forced to accommodate their habits to the greatest variety of circumstances. The cat, for example, has been carried over the whole earth, and, within the last three centuries, has been naturahsed in every part of the new world — from the cold regions of Canada to the tropical plains of Guiana ; yet it has scarcely undergone any perceptible mutation, and is still the same animal which was held sacred by the Egyptians."* * Principles of Geology, vol. ii. p. 397. LETTER II. 59 To suppose that temperature, locality, and the like, exercise a primary influence upon the confor- mation and distribution of animals, is attaching an importance to those circumstances which does not belong to them, and is, in fact, quite ridiculous. The extent to which this notion has been carried is well exemplified in BufFon's account of the Bac- trian camel, which he was of opinion had origin- ally but one hunch, and acquired the other in consequence of the servitude to which that race has (as he affirmed) been subjected ; and the value of such conjectures as this may be esti- mated from the fact, that, unfortunately for M. Buifon's hypothesis, the Bactrian camel is the only species which exists in a free and natural state ! The folly of the doctrine which teaches that the characteristics of the various races of animals are attributable to the operation of the circum- stances above mentioned, and not that animals were originally adapted to those circumstances, is clearly shewn by Mr. Lyell in the following passage : " It being assumed as an undoubted fact, that a change of external circumstances may cause one organ to become entirely obsolete, and a new one to be developed, such as never before belonged to the species, the following proposition is announced, which, however staggering and ab- surd ' it may seem, is logically deduced from the assumed premises. It is not the organs, or, in other words, the nature and form of the parts 60 LETTER II. of the body of an animal, which have given rise to its habits and its particular faculties ; but, on the contrary, its habits, its manner of liv- ing, and those of its progenitors, have in the course of time determined the form of its body, the number and condition of its organs — in short, the faculties which it enjoys. Thus, otters, beavers, water-fowl, turtles, and frogs, were not made web-footed in order that they might swim ; but their wants having attracted them to the water in search of prey, they stretched out the toes of their feet to strike the water, and move rapidly along its surface. By the repeated stretching of the toes, the skin which united them at the base acquired a habit of extension, until, in the course of time, the broad membranes which now connect their extremities were formed. In like manner, the antelope and the gazelle were not endowed with light agile forms, in order that they might escape by flight from carnivorous animals ; but having been exposed to the danger of being de- voured by lions, tigers, and other beasts of prey, they were compelled to exert themselves in run- ning with great alacrity; a habit which, in the course of many generations, gave rise to the pe- culiar slenderness of their legs, and the agility and elegance of their forms. The cameleopard was not gifted with a long flexible neck because it was destined to hve in the interior of Africa, where the soil was arid and devoid of herbage ; LETTER 11. 61 but being reduced, by the nature of that country, to support itself on the fohage of lofty trees, it contracted a habit of stretching itself up to the high boughs, until its fore-legs became longer than the hinder, and its back so elongated, that it could raise its head to the height of twenty feet above the ground."* Absurd as this may seem, it is nevertheless true, as Mr. Lyell says, that it is nothing more than a fair deduction from the views entertained by many naturalists. That, in opposition to these views, the in- fluence of external circumstances is very limited, I have already given abundant evidence to prove. I cannot, however, refrain from adding to it by referring to the human species, which fru'nishes a remarkable example of the tendency of animals to diverge from their original type under varieties of situation, and, at the same time, of the extremely limited extent to which such divergence is possible. If we believe that, originally, " God made of one blood all nations of men for to dwell on all the face of the earth" (Acts, xvii. 26), we must admit that, at the deluge, the characters of the five dis- tinct varieties of the human race — the Caucasian, the Malay, the Ethiopian, the Mongolian, and the American — could be traced in the persons of the family of Noah ; whence it follows, that the dis- tinctive characters of each variety are not sus- * Principles of Geology, vol. ii. pp. 370-1. 62 LETTER II. ceptible of change, since, in spite of the most com- plete intermixture of the races, they have never been defaced. For if second causes had any power of affecting the different varieties of man, they would surely have a tendency to change the colour of the negro's skin, after a series of years passed in a temperate clime. Although, however, we maintain that certain unchangeable characteristics were impressed by the Creator upon every distinct species of animal, which serve to distinguish each from every other species, it does not thence follow that we have it in our power to acquire a perfect knowledge of all these characteristics. On the contrary, we assert that there are geographical and other impediments to the acquisition of such knowledge, which may almost be called insurmountable : certainly, in the present state of the world and of science, they must be looked upon as such. Hitherto natu- rahsts have not accomphshed any thing like a complete classification, even of the animals with which they are best acquainted ; and, in perform- ing this task, there are numerous sources of error which have almost entirely escaped observation, and have consequently misled even the most as- siduous and acute observers. As an example I may mention that, according to Cuvier, few of the eagle species assume the adult plumage until they are three or four years old ; and this circumstance has occasioned the same species to receive several LETTER II. 63 very different names. Since this fact has been made known, naturahsts have begmi to suspect that those eagles known formerly by the names of common, royal, golden, black, ring- and white- tailed, are only the same bird under different circumstances of plumage. Errors such as this must continue to be committed, until we under- stand better the laws which regulate the plumage of birds, which are different in every species, and in many respects very obscure. But if these im- pediments were overcome, still greater difficulties present themselves ; for to be able to determine, with any approach to certainty, questions such as those which we are now discussing, we ought to know what is the extent to which each genus or species can diverge from its type, and what is the time required for reaching the limit of that diverg- ence, according to the fixed laws which govern it. In order to this, we must possess an inti- mate acquaintance with the structure, economy, and habits of many animals which hitherto have barely received a name. Without this know- ledge, it is impossible for us to ascertain the precise extent of the influence which the se- condary causes already enumerated exert in regu- lating the numbers, locality, extent of range, &c. of any particular species, and, through these cir- cumstances, in affecting its increase or diminution — its universal diffusion, or its extinction. With these facts before us, with what semblance of rea- 64 LETTER II. son can it be asserted that new creations of animals have taken place, when we have no evidence to disprove that the original types of those very ani- mals whose existence is supposed to render the admission of the assumption inevitable, did not form part of the creation recorded by Moses ? That these animals have but recently been dis- covered, is no proof that they have only recently begun to exist ; and until we know the laws which govern the distribution of each distinct species, it is vain to expect that we shall understand why some animals have taken so conspicuous a station, while others have remained almost, and many quite unknown ; or why some animals have been multiplied in some countries, at the expense of others, to so great an extent as to lead to the extinction of the less-favoured species. It is our ignorance of the fixed laws which govern every genus and species of animals, which gives rise to the idea that food, temperature, and locality, act in the same manner upon all : and the more our knowledge extends in this direction, the less in- clined we shall be to reason, even analogically, respecting the operation of similar causes upon different species. Similar kinds of food do not produce the same effect upon, nor go through the same changes in, all ; but, on the contrary, it is certain that, in every genus and species, the mu- tual influence of food upon organisation, and of organisation upon food, is different. Experience LETTER II. 65 teaches us that one kind of food will not nourish all the animals belonging to a genus, and consequently differing very Httle in external character.* If tem- perature and locality always produce the same re- sults, how do we account for the totally different genera and species of animals found in two coun- tries under the same parallels of latitude, having the same temperature, and furnished with the same means of support and enjoyment ?f * " It has been well observed by Dr. Fleming, that the kind of food which the existing species of elephant prefers will not enable us to determine, or even to offer a probable conjecture concerning, that of the extinct species (mammoth) . No one acquainted with the gramineous character of the food of our fallow-deer, stag, or roe, would have assigned a lichen to the rein-deer." — Lyell's Geology, vol. i. p. 155, quoted from the Edinburgh New Philo- sophical Journal. t " The plains of the New World, no less than those of Australia, are as perfectly adapted for the comfortable existence of the horse or the ox, as are the fields and the pastures of Europe, or the grassy deserts of Asia; yet nature has placed these animals in one hemisphere, and denied them to the other." — Swainson's Geography of Animals, p. 9. In proof of the fact, that local circumstances exercise a primary influence on the rano-e of animals, Swainson says, " The peregrine falcon is found in America, Europe, and Australia ; but it is totally unknown throughout the whole continent of Africa — an immense region thus intervening between two of its habitats. The great bustard of Europe is another familiar example : its distribution is latitu- dinal. . It is found in the centre of England, through the heart of Europe, and to the confines of Asia. Now, according to the idea of animals enjoying a circular range, the first of these birds should be found in Africa, and the latter throughout a circle F G6 LETTER II. But it is said, we have proofs that many ani- mals have become extinct ; and this fact entitles us to infer that a new creation has taken place. It is certainly probable that since the creation many animals have become extinct ; for we have a sort of evidence of it in the fossil skeletons which have been discovered of animals supposed no longer to exist. Cuvier says he has found nearly forty species of the pachydermata alone, belonging to genera now entirely extinct, and presenting forms and proportions to which there is nothing that can be compared in the present animal kingdom, excepting two tapirs and a da- man.* And that some of these animals had ceased which would then comprise the whole of northern and southern Europe and Barbary." — Ibid. p. 7. * Theory of the Earth, p. 273. Buckland seems to think that these extinct animals were necessary to fill up the chain of nature, which, in our most perfect classification, has still many links requiring to be added. But if this is true, it follows (if we admit the geological hypothesis of the existence of these animals previous to the creation of man), that the Adamic creation was not perfect. He says " the study of these remains (of extinct animals) presents to the zoologist a large amount of extinct species and genera, bearing important relations to existing forms of animals and vegetables, and often supplying links that had hitherto ap- peared deficient in the great chain whereby all animated beings are held together in a series of near and gradual connexions. This discovery, amid the relics of past creations, of links that seemed wanting in the present system of organic nature, afibrds to natural theology an important argument in proving the unity and universal agency of a common great First Cause." — Geology, vol. i. p. 114. LETTER II. ()7 to exist before our deluge, is also probable. But there are no grounds for referring the extinction of these races to a period antecedent to the crea- tion of man ; since those changes of the earth which are supposed to have occasioned that ex- tinction may have taken place slowly and gra- dually, in regions unknown to, or unoccupied by man, long after the creation of Adam. One of the most powerful proofs confirmative of this opinion, may be gathered from the recent interpretations which have been given of the " than," " leviathan," and " behemoth" of the Scriptures. These animals have been most satis- factorily proved to be the crocodile, the mega- losaurus (a very large carnivorous lizard), and the iguanadon (a huge herbivorous lizard) — the two last species being found only in a fossil state in the wealden beds. Now, these latter two spe- cies, according to the opinion of geologists, must have become extinct several thousand years be- fore the formation of man. Yet that this is im- possible, will be seen by referring to the fortieth chapter of the book of Job, in which the Almighty is represented as speaking out of the whirlwind to him, and saying (15th verse), " Be- hold now behemoth, which I made with thee;' and again, in the forty-first chapter, speaking of leviathan, " Canst thou draw out leviathan with a hook?" &c. It is evident, from these passages, that, whatever animals were here intended (and 68 LETTER II. that they are extinct species there is considerable evidence to prove), man must have existed at the same time upon the earth.* We have therefore * It would take up too mucli space, and lead us too far away from the main course of our argument, to introduce into the text the evidence in support of the interpretation above referred to ; but as it is a much- disputed point, and possesses considerable interest, I subjoin them in the form of a note. Mr. Thompson of Hull, who has discussed this subject in a paper read before the Philosophical Society of that town in January 1835, and afterwards published in the eighth volume of Loudon's Magazine of Natural History, considers that there is little doubt that the animal designated by the Hebrew word " than," which in our translation is rendered dragon, was in reality the crocodile. (See a Critical Dissertation upon the true meaning of the word Than, by the Rev. James Hurdis.) It is strongly confirmatory of this opinion, that the substitution of the word crocodile for dragon, in all the passages of our version where the latter is used, may be made with jDerfect propriety, and, in fact, adds to the expressiveness of the context. (See Ezek. xxix. 3, 4 ; Is. xiii. 22 ; li. 9 ; Mic. i. 8 ; Jer. li. 34 ; ix. 11.) Mr. Thompson has shewn that the five modes of capturing the crocodile, viz. by the baited hook mentioned by Herodotus {Euterpe, cap. 70) ; by the club used britUe-wise, mentioned by Pliny (lib. viii. cap. 25) ; by the iron net men- tioned by Diodorus ; the upright spike, and the spear fixed to a rope, aUuded to by M. Bosc and Pocock, are all referred to in the forty-first chapter of Job as unavailable in capturing the leviathan. That this animal is identical with the megalosaurus he gives the strongest reasons for believing, based upon a comparison of the descriptions given of the latter by Buckland and Cuvier with that of the leviathan contained in the book of Job ; and between which descriptions there is the closest coincidence. The name being compounded of the word than (a crocodile) and levi (which in the LETTER II. 69 no right to assume that all the anhnals, the fossil bones of which have been discovered, have become extinct. We do not know what animals may still Hebrew signifies joined, lengthened, extended), it would imply an animal a than in form, but equal in size or extension to several thanim. He shews that the leviathan was an animal of the crocodilean family ; that it once existed in this country ; was seventy feet long, with limbs exceeding in size those of the eleijhant. It is easy to see that the modes of destroying the than could have been of but little avail against the leviathan, if this latter animal were of the huge dimensions here mentioned ; and therefore the expressions, " Canst thou draw out leviathan with a hook, or bore his jaw through with a thorn ? canst thou fill his skin with barbed irons ? who can come to him with his double bridle ? and he esteemeth iron as straw," have much force, if we suppose the Almighty to have used them to assure Job that the ordinary mode of capturing the crocodile could not be re- sorted to against the leviathan. By comparing the same descrip- tions of Cuvier and Buckland with the fortieth chapter of the book of Job, Mr. Thompson arrives at the conclusion, that behe- moth is the iguanadon of geologists. This conclusion he founds on the perfect coincidence between the most remarkable charac- teristics of the iguanadon, and the description of behemoth given in Job. First, the teeth of this animal are herbivorous. Of behemoth it is said, " he eateth grass like an ox." No other saurian, whether existing or in a fossil state, is known to have fed on vegetables. The allusion to this circumstance, therefore, in the book of Job, is remarkably striking. Secondly, the tail of the iguanadon resembles, on a very large scale, the tail of the modern iguana in its flexibility and other characters, and, in pro- portion to the size of the body, must have been immense. The contrast between tlais flexible tail of the iguanadon and that of most other saurians, which is fixed and inflexible, is, in the description of behemoth, forcibly alluded to : "he moveth his 70 LETTER II. be living in some parts of the earth, much less those which are contained in the deep. A sounder argument in support of the opinion that animals have become extinct, is, that we know that that is a law operating at the pre- sent time. But our knowledge of this law does not give us any ground for supposing that the extinction of every genus and species is depend- ent on the same causes. On the contrary, we know that the causes which lead to the exten- sion and multiplication of some races, thereby necessarily diminish the number of other races : for example ; by means of the increase of the carnivorous races in any country, the herbivo- rous are displaced. Previous to experience, we could not have inferred that the carnivora would produce such havoc amongst the more numerous and more defenceless species. Neither could we have had, some centuries ago, any idea of the tail like a cedar." Thirdly, the head of the iguanadon has a homy appendage, which resembles the same process in the greater number of existing species of the modern iguana. No other saurians having this appendage, it is made the object of particular distinction. " He that made him can make his sword to ap- proach unto him ;" or, according to Harris's translation, " he that made him has fastened on his weapon ;" "his nose pierceth through snares." These and other circumstances mentioned by Mr. Thompson seem to confirm his idea, that the leviathan and the behemoth were really two animals which are now extinct, and which are known to geologists by the names of megalo- saurus and iguanadon. LETTER II. 71 great revolution which was to take place, and of the mutations which have been brought about by the human species as it extended. The changes caused directly and indirectly by man, in the rela- tive position of animals, and in their propagation and extinction, are of the greatest importance, and may be looked upon as among the most powerful of the causes now in operation to alter the geographical distribution of animals — to spread some races over vast tracts of uncultivated land — and to ex- tinguish other races, which can no longer exist in those countries which have undergone the changes consequent upon drainage and civilisation.* Hum- boldt asserts, that in the Pampas of Buenos Ayres alone there are more than twelve millions of cows, and three millions of horses, exclusive of the cattle * " Many species, most hostile to our persons or property, multiply in spite of our efforts to repress them ; and others, on the contrary, are augmented many hundredfold in number by our exertions. In such instances we must imagine the relative re- sources of man, and of species friendly or inimical to him, to have been prospectively calculated and adjusted. To withhold assent to this supposition would be to refuse what we must grant, in respect to the economy of nature, in every other part of the organic creation ; for the various species of contemporary plants and animals have, obviously, their relative forces nicely balanced, and their respective tastes, passions, and instincts so contrived, that they are all in perfect harmony with each other. In no other- manner could it happen that each species, surrounded as it is by countless dangers, should be enabled to maintain its ground for periods of considerable duration." — Lyell's Geology, vol. ii. p. 413. 72 LETTER IT. which have no acknowledged owners :* and it must be borne in mind, that all the vast herds of wild cattle and horses which now overrun America must have been derived from a very few pairs, which the Spaniards took over with them to that continent.f But man has been hardly less powerful in dis- placing or diminishing some kinds of animals than in multiplying others, and in diffusing them over the earth. In some cases, even, there can be little doubt that his progress has completely extermi- * This stock was first introduced about the year 1548, by Christoval Rodriguez. Humboldt remarks, that when we hear of the prodigious number of oxen, horses, and mules, spread over the plains of America, we forget that in civilised Euroije the ag- gregate amount is not less surprising. According to Peuchet, France feeds 6,000,000 of the large-horned cattle ; and in the Austrian monarchy the oxen, cows, and calves, are estimated by M. Lichtenstein at about 13,400,000. — Humboldt's Travels, by Macgillivray, p. 195. t " The first hogs were carried to America by Columbus, and estabUshed in the island of St. Domingo the year following its discovery, in November 1493. In succeeding years they were introduced into other places where the Spaniards settled ; and in the space of half a century they were estabhshed in the New World from the 25" north to the 40° south latitude. Sheep also and goats have multiplied enormously in the New World, as have also the cat and the rat ; which last, as before stated, has been imported unintentionally in ships. The dogs introduced by man, which have at different periods become wild in America, hunt in packs like the wolf and the jackall, destroying not only hogs, but the calves and the foals of the wild cattle and horses." — Lyell's Geology, vol. iii. p. 115. LETTER II. 73 nated whole species.* The emu, the cassowary, the kangaroo, are all rapidly receding before the incursions of man. The dodo has entirely disap- peared from the Isle of France since the Dutch first landed there. Wolves, which formerly over- ran this and the neighbouring countries, are now not known in England, and rarely to be met with in France. The Irish elk, that gigantic creature, the horns of which measured fourteen feet fr'om one point to the other, following the curvatures,-}* and which stood six feet high, once the inhabitant of these islands, and of France, Germany, and Italy, is now entirely extinct.^ Now, it is well * In the famous cave of Guacharo, in South America, there is a distinct genus of nocturnal birds, wliicli are peculiar to this neighbourhood. Every year, about midsummer, the Indians enter the cave for the purpose of destroying several thousands of the young birds, in order to obtain the fat, which exists abundantly in their bodies. This fat is in great esteem as a culinary article in the kitchen of the monks. Humboldt says, the Guacharo would have been long since destroyed, had not the superstitious dread of the Indians prevented them from penetrating far into the cavern. — Humboldt's Travels, by Macgilhvray, p. 102. t Cuvier, Recherches sur les Ossemens Fossiles, vol. iv. p. 70. X " There are many proofs that this animal was in existence at no very distant period. Mr. Hart, in his report made to the Com- mittee of Natural Philosophy of the Royal Dubhn Society, men- tioned an instance of a pair of these horns having been used as a field-gate near Tipperary. Since then he has learned that a pair had been in use for a similar purpose near Newcastle, county of Wicklow, until they were decomposed by the action of the weather. There is also a specimen in Charlemont House, the town residence of the Earl of Charlemont, which is said to have 74 LETTER II. known, that before man took possession of these countries, and for a long time afterwards, these and other animals, such as the wild ox, the bear, the wild boar, the wild cat, the otter, the beaver, &c., and many reptiles and birds which are not now to be found, were exceedingly numerous. These are a few of the difficulties which stand in the way of those who assert, that the facts disclosed by the study of geology, inas- much as they demonstrate that the osseous struc- tures of some animals that have passed away differ from those of the present day, are sufficient to prove that there has been a succession of creations. Another opinion connected with this theory is, that the creation of man took place at a compa- ratively recent period; that his organisation, his habits, his intellect, were not fitted to treat with that condition of the earth which enabled so many inferior and less highly organised beings to exist. As the different circumstances which have given origin to this conjecture pass under consideration, we shall find that the inference drawn from them is hable to many insuperable objections, and that, granting the facts which are supposed to warrant it, they do not, when rightly understood, lead to any such conclusion. been used for some time as a temporary bridge across a rivulet in the county of Tyrone." — Jameson's note on the fossil elk of Ire- land, in his translation of Cuvier's Theory of the Earth, p. 487. LETTER II. 75 It is urged, that man cannot be of very high antiquity, because his remains are never found in those strata which were formed during the period when the species now his contemporaries began to exist, and which abound with the remains of other animals ; and that therefore it is not probable that our race co-existed with assemblages of animals and plants, of which all, or the greater part of the species, have become extinct. By way of shewing the force of the argument derived from this ab- sence of human remains in the tertiary forma- tions, it has been said, "' No inhabitant of the land exposes himself to so many dangers on the waters as man, whether in a savage or a civilised state ; and there is no animal, therefore, whose skeleton is so liable to become imbedded in lacus- trine or submarine deposits : nor can it be said that his remains are more perishable than those of other animals ; for in ancient fields of battle, as Cuvier has observed, the bones of men have suf- fered as little decomposition as those of horses which were buried in the same grave. But, even if the more solid parts of our species had disap- peared, the impression of their form would have remained engraven on the rocks, as have the traces of the tenderest leaves of plants, and the integuments of many animals. Works of art, moreover, composed of the most indestructible materials, would have outlasted almost all the 76 LETTER II. organic contents of sedimentary rocks. Edifices, and even entire cities, have, within the times of history, been buried under volcanic ejections, sub- merged beneath the sea, or engulfed by earth- quakes ; and had these catastrophes been repeated throughout an indefinite lapse of ages, the high antiquity of man would have been inscribed in far more legible characters on the framework of the globe, than are the forms of the ancient vegetation which once covered the isles of the northern ocean, or of those gigantic reptiles which, at later periods, peopled the seas and rivers of the northern hemi- sphere."* It will be seen, that the only fact alleged in support of the doctrine we are now about to con- sider is — the absence of human remains from cer- tain strata ; the rest of our quotation merely goes to shew the conclusiveness of that supposed fact. And yet, strange to say, it is certain that such remains have been found, mingled not only with * Lyell's Geology, vol. i. p. 231, third edition.— That man has not been found in those beds which formerly composed the bottom of lakes and seas, is obviously to be accounted for by the circumstance, that man, even up to the deluge, was unacquainted with the art of navigation, and cannot be supposed to have per- formed any kind of nautical expedition ; and as the human race was numerically small, cities must have been comparatively few. The remains of the first city (Enoch) may, however, for aught that we know to the contrary, be somewhere buried in the earth to this day. LETTER II. 77 those of man's contemporaries, but also with ani- mals which, according to the successionists, formed part of some bygone creation.* The premises being false, we might be excused from inquiring whether the conclusion they are supposed to establish is logically deducible from them ; but it may be worth while briefly to shew that, even admitting, for the sake of argument, that human remains are never found in the early * In the quarries of Kosritz, described by M. von Schlott- heim, human bones are mixed indiscriminately with extinct and existing species, although Mr. Buckland states that these rocks contain only the bones of the hyaena, mixed with those of the rhinoceros, horse, ox, stag, bear, and extinct tiger (Rel. Diluv., p. 25), omitting altogether human bones. " The limestone for- mations which flank the valley of the Elster, in the neighbourhood of Kosritz, in Upper Saxony, consist of zechstein, or alpine lime- stone, which passes into cavernous limestone. This latter limestone is accompanied with subordinate beds of ancient secondary gypsum, so compact as to require to be blasted with gunpowder. The gypseous mass is perforated with fissures not so broad as in the superincumbent limestone, but fiUed with the same loamy deposit. In the fissures or cavities of the limestone have been found re- mains of the antediluvian rhinoceros, of enormous oxen and stags, of an antediluvian hyaena, and of the leo diluvianus (an extinct lion resembUng the jaguar). These bones are nearly in the same state as those at Gadenreuth, Scharzfeld, &c. In the fissures or cavities of the subordinate gypsum formation, human bones, dis- tinctly recognisable, have been found, together with bones of small quadrupeds and of birds, at the depth of sixteen to thirty feet in every quarry which has been opened — not in caverns, but enveloped in the loam." — Penn's Comparative Estimate, note 5, vol. ii. p. 402, and note to p. 403. 78 LETTER IT. formations, that fact is wholly insufficient to prove the non-existence of man at the period of their deposition. The position of man on the globe is distinguished from that of its other denizens by many great pecu- liarities. His physical conformation, his intellect, his habits, his growth, his duration, and finally his death, are all marked by characteristics which differ, in almost every respect, from the corre- sponding characteristics in other animals. As bearing closely upon the subject now under con- sideration, we may instance the phenomena of re- production. The most highly organised animals are invari- ably the least prolific. They usually bring forth one at a time ; while oviparous animals, and some of the smaller tribes of viviparous, propagate with amazing rapidity,* and apparently in the ratio of their minuteness, and lowness in the scale of exist- ence. Duration of life seems also to bear some proportion to this ratio. Now, man is at the top of the scale ; his or- ganisation is more complex than that of any other animal, and accordingly there is reason to believe that he propagates more slowly than any of the inferior races.f Supposing, then, that man origi- * More than half a million of eggs have been discovered in a single mackarel. t According to Cuvier, " but one child is usually produced at a birth, as in five hundred cases of parturition there is but one of twins." — Rrgne Animal, ord. Bimana. LETTER II. 79 nated from a single pair, and that each indi- vidual of that pair, and of their immediate de- scendants, lived nearly a thousand years, it is by no means wonderful that his fossil remains have never yet been found in the earlier strata, which may, nevertheless, abound in memorials of other races ; for many animals may have begun their existence at the same time as man, and have multiplied thousands of generations, and finally become extinct, while, perhaps, the first generation of mankind had not passed away. No other explanation seems to be necessary to account for the number and variety of fossil shells and molluscae which every where present themselves in the early strata, and for the absence of any traces of man and the higher animals : it also accounts for the frequent occurrence of large oviparous reptiles in the same situations.* Another circumstance of considerable import- ance as regards this question, is, the slow diffusion of the human race over the earth ; a result in part * It is worthy of remark, that some of the very largest rep- tiles often produce many hundred eggs, which are capable of being hatched by the sun's heat. A crocodile, for instance, will lay two hundred eggs ; and this fact readily accounts for the abund- ance of these animals during the early period of the earth's history, before the ichneumon, and other animals destructive to their eggs, had become numerous. The skeleton of the ichneumon is found only in those strata above the chalk which are supposed to be of more recent deposit. 80 LETTER II. attributable to his slow propagation, and partly to various other causes to be hereafter mentioned.* In the early ages of the world man must have been confined to a very small portion of the earth's surface ; while the lower animals, meeting with no obstacles to their rapid extension, quickly spread themselves over the most extensive regions. This fact alone would account for the absence of human remains from strata abounding in other fossils, numerous events causing their deposition having, doubtless, taken place in remote ages in regions * Although, as we shall hereafter see, man, by his physical conformation, is adapted for a wider distribution than perhaps any other animal, yet this supposes that he has not obstacles to contend with which are beyond the reach of that physical conformation. It is on this account we find that " the human population," as Mr. Turner very justly observes, " has always very gradually diffused itself; and that in all the regions whose commencing population we have witnessed or can trace, they have had to clear the soil of its previous occupants, before they could dwell comfortably upon it. We may, therefore, be sure that the primeval state of all the antediluvian dry land was that of copious and successive vegetation long before man could be on every part of it ; that animals must have enjoyed this provided feast long before he could reach it ; and that wherever the waters were resting or flowing, fish, and saurians, and phocse, and the testaceous and crustaceous fishes, and all kinds of aqueous plants, must have been its first inhabitants, and so they have remained as long as man was not there. They were created to be so ; they were formed to be his predecessors. He was the latest made ; he always spreads himself far less rapidly than they do ; they have often preceded him by many ages." — Siiakon Turner's Sacred History of the World, vol. ii. p. 352. LETTER II. 81 occupied by none but the lower races ; and those limited locahties in which the human race then existed may not yet have been examined. The following passage from Turner's Sacred History of the World relates to another question ; but the argument contained in it is so applicable to our subject that I shall quote it here : " It has been inferred by some that there was no ante- diluvian race, because no fossil human bones of that antiquity have yet come to light; but their absence does not disprove the existence of man- kind between the creation and the deluge ; it only indicates that they were not living in those sites where these strata have been examined, as there are now many parts of Asia, Africa, and even America, without them. Human existence began in the east. The rocky beds of Asia have not yet been penetrated or examined like those of Europe, nor is there any evidence that the antediluvian race were either a very numerous or a very dis- persed population." Cuvier's sensible remarks on this subject de- serve citation. ^'^AU these facts tend to confirm the assertion, that the human race did not exist in the countries where fossil bones are found, at the epoch of the revolutions which buried those bones ; but I do not wish to conclude that man did not exist at all previously to this epoch. He might have inhabited some small districts, whence he repeopled the world after those ter- 82 LETTER II. rible events. Perhaps the places in which he dwelt have been entirely swallowed up, and his bones buried at the bottom of the present seas, with the exception of the small number of indi- viduals who have continued the species."* It appears then, that, supposing we had never yet discovered human fossils in the situations in question, we certainly should not be entitled to infer that none existed ; and there are other facts leading to the same conclusion. We are con- stantly obtaining from the earth's crust the fossil bones of animals, each species of which probably far exceeded the human race in number, of which, notwithstanding, we had previously discovered no remains. Of the existence of other species, some of which were more than twenty feet in length, we have, in some cases, been informed by a single joint, the only remnant hitherto discovered of races which once were monarchs of the earth.f It is not much more than a century since the mammoth came to light, J although its existence * Cuvier, Discours sur les Revolutions de la Surface du Globe, p. 137. f What there can be in so small a remnant of an extinct animal, to enable us to draw any just conclusions as to its relative numbers, or mode of propagation, I am, I must confess, at a loss to imagine. X In the year 1728, Sir Hans Sloane gave an account of ele- phants' teeth found under ground, which were proved to be those of the mammoth, an extinct species. — See Phil. Trans, abrid. vol. viii. p. 155. " The entire carcass of a mammoth, or extinct LETTER II. 83 in comparatively quite a recent period, its enor- mous size, and its nmxibers* (it being herbivo- rous), would, a priori, have rendered its early discovery exceedingly probable. These considerations (to which others might, species of elephant, was obtained ia 1803 by Mr. Adams. It fell from a mass of ice in which it had been encased, on the banks of the Lena, in lat. 70° (Siberia) ; and so perfectly had the soft parts of the carcass been preserved, that the flesh, as it lay, was devoured by wolves and bears. This skeleton is still in the museum of St. Petersburg, the head retaining its integuments and many of the ligaments entire. The skin of the animal was covered first with black bristles, thicker than horse-hair, from twelve to sixteen inches in length ; secondly, with hair of a reddish-brown colour, about four inches long ; thirdly, with wool of the same colour as the hair, about an inch in length. Of the fur upwards of thirty pounds' weight were gathered from the wet sand-bank. The individual was nine feet high and sixteen feet long, without reckoning the large curved tusks, — a size rarely surpassed by the largest living male elephants." — Journal du Nord, St. Petersburg, 1807, quoted in LyeU's Geology, vol. i. p. 151. * " So fresh is the ivory throughout northern Russia, that, according to Tdesius, thousands of fossil tusks have been col- lected and used in turning, yet others are stiU procured and sold in great plenty. He declares his belief, that the bones stUl left in northern Russia must greatly exceed in number all the ele- phants now living on the globe." — Lyell's Geology, vol. i. p. 153. It is only within a few years that the fossil teeth of the elephant have been known to exist in the eastern part of Norfolk. They are now found in such abundance, that Mr. "Woodward, in his Outlines of the Geology of Norfolk, says, that " the grinders found on the oyster-ground of Hapsborough warrant us in con- cluding that upwards of 500 elephants were deposited in that limited space." 84 LETTER II. if necessary, be added), we think, shew pretty clearly that there is but little foundation for the theory of the late creation of man in the alleged fact (which, however, be it remembered, we ex- pressly deny), that his remains have never been found in certain strata, which, nevertheless, abound with those of existing animals. From the Mosaic history we learn that man began to multiply upon the earth previous to the deluge, and that " giants were in the earth in those days ;" so that when the deluge came, it must have swept off great numbers of the human race ; yet it is said we do not find great numbers of human bones to mark that event. But, we may ask, is there not every probability that more will be dis- covered? Already, in many caves in England, France, Germany, and other parts of the world, human bones have been found, mixed with those of the rhinoceros, elephant, hippopotamus, deer, hysna, tiger, bear, and other living and extinct species. This was the case in the Kirkdale cave, in the cave Beze situated in the department of Aude, and in caverns on the banks of the Meuse. In the cavern of Durfort, near Alais,* * The cavern is situated in the mountain of La Coste, which forms part of the chain of mountains called Cevennes. It con- sists of two different calcareous formations, as distinct in their positions as in their mineralogical natures. The inferior forma- tion consists of transition limestone and of a blackish saiidstone, in the mass of which no organised bodies are discernible, although the surrounding rock exhibits an astonishing quantity of petrified LETTER II. 85 numerous human bones, both of young and old individuals, and of both sexes, have been found, as M. Marcel de Serres has informed us ; and with these human bones there are no remains of any other animal, excepting a single shell, the helix striata. It is a singular fact, that the shells, siliceous and calcareous. The upper formation appears to belong to the Jura or cavernous limestone, which exhibits throughout the chain a great number of subterraneous cavities of vast extent. The orifice of the cavern presents itself in a vertical fissure or crevice in the ground, about five feet in length, and one foot and a half in width. The descent is per- pendicular for about twenty feet ; at the bottom of this tunnel is the entrance to the cavern of the dead, which is so small as to aiford an opening of only about one (French) square foot. Thence you enter a sort of gallery, which divides to the right and left. The passage to the right leads by a gentle slope to the principal chamber, ten or twelve feet in length, and three feet in height : the sides of this passage, as well as the roof, appear to consist of a single mass of Umestone. The passage to the left extends to an equal distance. No bones are seen in either of these pas- sages. The cave is terminated by a smaU chamber three feet square, in which aU the human bones are found, lying together in quantities so great as to form half of the bed. They are mixed without any order : the bones are partly filled with cal- careous earth, covered with oxide of iron ; and some of them are raised upon a surface half a foot above the true floor, and in- sulated from the rest, or united to the rock by calcareous incrus- tations. The bones evidently have not been moved since they were first deposited : they have not been completely mineralised, but retain a portion of their animal matter (gelatine). — See the account of this cave in Penn's Comparative Estimate, note 5, passim, where it is abridged from M. Marcel de Serres' account, published in the Bibliotheque Universelle . 86 LETTER II. entrances to this cave, as well as to that at Kirk- dale, are too small to have admitted of the entire carcasses of the animals they contain being con- veyed through them ;* so that Buckland thought that both these caverns must have been hyaenas' dens. But hyenas do not live in dens ; and there- fore the difficulty, in the way of those who consider that these bones were not antediluvian, remains. Another objection to the hypothesis, maintained by Cuvier as well as Buckland, that these caves served as retreats to carnivorous animals, is de- rived from the manner hi which the bones in them are frequently placed. " The presence of bones in the clayed mud of the floor of the Adelsberg cave, in Carniola, accords well with this hypothesis," says M. Bertrand Geslin ; " but the case is different with those which I found in the heaps of limestone blocks and clayed mud. The bones are not at the surface of the heap, but rather towards its middle part, buried among the blocks, and crushed by them. From this position, and the height from the floor of the cave at which the skeleton mentioned above (the bear) occurs, it cannot be supposed that it * This was the case also in the celebrated cave of Gaylenreuth, which Esper was of opinion (as we are told by Goldfuss), con- tained, at the lowest estimate, several hundred wagons' load of bones. The fissure in the third grotto, leading to a cave where the greatest quantity of hyaena or lion bones were found, was much too small for these animals io have passed through. LETTER II. 87 formed part of the bones with which the bottom of the cave is strewed, nor that the blocks had fallen upon it. The bones contained in the heap in question must have been brought into their present position at the same time, and by the same cause, as the limestone blocks. They could not, therefore, have belonged to animals which inhabited these caves, and died there peace- ably."* So that while there are difficulties which do not suffer us to believe that these caves were formed subsequently to the deluge, there is strong evidence to shew that the human hones contained in them are of the same antiquity with those of the extinct animal species mingled with them,^ and that * See note by Jameson in Cuvier's Theory of the Earth, p. 540, abridged from Geslin's paper in the Annales des Sciences Naturelles for April 1826. t Geologists too often make assertions for the purpose of supporting their own theories, wholly regardless of truth. How, for example, can we reconcile the facts which we have just ad- duced with the observations that have been made so recently by a great American geologist ? " It is in alluvial deposits (de- posits above those formed by the deluge) of this kind that the remains of man first appear : human skeletons, and the rude in- struments of a half-civilised race, are found associated with the bones of animals which still inhabit this country, and in some instances intermixed with the osseous remains of a few species that appear to have been extirpated by man. "J The reader shall judge of the truth of this assertion ; and although the author, in another part of his work, says, the " subject before us is not one X See Silliman's Consistency of Geology with Sacred History, p. 65. 88 LETTER IT. they were all entombed together at the same time by one and the same event.* The occmTence of bones belongmg to land animals is very rare in those strata which are sup- posed to have been formed previous to the delug 3 ; and, judging from the statements already made this might have been anticipated. " By far the greatest part of the organic remains found in the earth's crust/' says Lyell, " consist of corals and testacea, the bones of vertebrated animals beins: comparatively rare. When these occur, they be- long much more frequently to fish than to reptiles, and but seldom to terrestrial mammaha. This might, perhaps, have been anticipated as the gene- ral result of investigation, since all are now agreed that the greater number of fossiliferous strata were deposited beneath the sea, and that the ocean pro- which can be advantageously discussed by the people at large, "f we do not think this plain perversion of truth can be misunder- stood even by the most unlearned. * Human bones have been found in other caves besides those above referred to : as at Burringdon, in the Mendip hills, com- posed of mountain limestone ; at Wokely hole, in the same hills ; at Paviland, in Glamorgan, &c. The quantity of black " animal dust" w^hich is contained in some of these caves, as in that of KuUoch, where Buckland tells us there were hundreds of cart- loads, comprising not less than 5,000 cubic feet of animal re. mains, is perhaps too great to enable any one to form a conjecture what the cave contained, inasmuch as there was nothing but a uniform black dust to guide the anatomist in determining the animals which were there deposited. t lb. p. 114. LETTER II. 89 bably occupied in ancient times, as now, the greater part of the earth's surface. We must not, how- ever, too hastily infer from the absence of fossil bones of mammaha in the older rocks, that the highest class of vertebrated animals did not exist in the remoter ages. There are regions at present in the Indian and Pacific oceans, co-extensive in area with the continents of Europe and North America, where we might dredge to the bottom, and draw up thousands of shells and corals with- out obtaining one bone of a land quadruped."* It is evident, however, that in order to place beyond a doubt the theory of the successive cre- ation of a gi-aduated scale of beings, beginning with the corals and some of the simpler shell- fish, and terminating in man, it would be neces- sary to prove that in the successive strata, from the oldest to the most recent, there is a progres- sive development of organic life from the simplest to the most complicated forms. The writings of many eminent men in the present day would lead us to suppose that this was really the case, and that there were no difficulties opposed to the theory of a gradual succession of development. " The deeper we descend," says Buckland, " into the strata of the earth, the higher do we ascend into the archaeological history of past ages of crea- tion. We find successive stages marked by vary- ing forms of animal and vegetable life ; and they * Lyell's Geology, vol. i. p. 232, 90 LETTER II. generally differ more and more widely from existing species as we go further downwards into the recep- tacles of the wreck of more ancient creations."* The fact, however, is very different ; for, setting aside the difficulty we have lately alluded to, aris- ing from our utter inability to ascertain all the animal remains, their number, variety, and relative proportions, we are in possession of facts which completely refute all idea of the remains of animals being found in regular order and succession. In one of the early strata remains of the carnivora have been discovered ; a race of animals whose ap- pearance upon the earth, according to the theory of a succession of creations, occurred at a much later period than that of the molluscse, fishes, and * Geology, p. 113. See also Sir H. Davy's Consolations in Travel, dialogue 3 ; Phillips' Outlines of Geology, p. 276 ; as also the works of Man tell, Conybeare, Hitchcock, and others. This error seems to have originated in the fact of so many more extinct animals having been discovered in the lower strata than in the superior ; but which fact is explained in the most satisfactory manner, by supposing that for some time after the creation of Adam a much larger portion of the surface of the earth was covered with water than was the case subsequently to the deluge, and that the laws which regulated the increase of aquatic animals were different (as we know they are) from those which regulated the increase of ten-estrial species. When the vast multitude of the lower animals was destroyed in the sea at the time of the deluge, probably by enclosing them in the strata in which we find them, which might have been produced by sub- marine volcanic action, it is not likely that land animals were here included, their position upon the earth, and their relative numbers, being circumstances against such a supposition. LETTER II. 91 reptiles, " In the oolite of Stonefield, near Ox- ford (one of the secondary rocks, in which it has been asserted that no signs of warm-blooded ani- mals exist), a rock which has been well ascer- tained to hold a somewhat inferior position in the great oolite series, the jaws of at least two species of small manmiiferous quadrupeds have been found. A specimen of one of these, now in the Oxford Museum, was examined by M. Cuvier, and pro- nounced by him to be allied to the didelphis (opossum). According to this naturalist, it was probably a small carnivorous animal not larger than a mole, yet differing from all known car- nivora in having ten teeth in a row."* So * Lyell's Geology, vol. i. p. 237. " Some years ago," says Pennant, " two great grinding teeth and part of the tuslvs of an elephant were given me by some miners, who discovered them at the depth of forty-two yards, in a lead-mine in Flintshire. One of the strata above was limestone, about eight yards thick. The teeth w-ere found in a bed of granite in the same mine. The grinders were almost as perfect as if just taken from the animal ; the tusk much decayed, soft, and exfoliating. A stag's horn was found with them." — History of Quadrupeds, vol. i. p. 172. " We find, likewise, that new facts are occurring, which are likely to introduce new views among our intelligent geologists, and to cause material alterations to be made in many parts of their former theories, and which will bring them into greater coincidfence with the Mosaic intimations. The fossil remains in the limestone of Burdie-house, near Edinburgh, are instances of the new facts and reasonings which the contents of a single rock may suddenly and unexpectedly introduce into geology, and of the alterations in many favourite theories which had been pre- viously asserted. Dr. Hibbert shewed this to differ materially 92 LETTER II. that, without insisting any further upon the i?n- prohahiUty of a succession of creations, we here find a. fact which certainly disproves it ; for if the carnivora came into existence only at a period scarcely less distant than that of man's creation, how comes it that their skeletons are procured from some of the early strata ? We think this is sufficient evidence to shake the very general belief in the order and regu- larity of the deposition of animal remains. On from the common carboniferous limestone of marine origin, and to form a species of deposit of a fluviatile character. Among the organic fossils were more particularly observed the remains of fresh-water fish resembling the Cyprinidee. There also appeared to be in this deposit an immensity of very minute crustaceous and shell animals. Besides these animals, a remarkable variety of fossd plants, embedded in the limestone, were exhibited, indica- tive of the vegetation of a tropical country. A tooth was found in a fi'agment of the rock two inches and a qiiarter in length, like that of a saurian animal." — Turner's Sacred History of the World, vol. ii. p. 349. This saurian tooth, which was found by Dr. Hibbert in the carboniferous strata near Edinburgh, Agassiz has lately attempted to prove belonged to a sauroidal fish, or a fish of the highest rank in structure, approaching in its osteolo- gical characters much nearer than those of any other fishes to the true saurian. But this attempt to prove that no bones of reptiles are to be found in the carboniferous formations, is rendered of little importance by the fact which has just been stated, that individuals of the class mammalia have been found in a rock which has been supposed to hold nothing higher in the organic world than tortoises and lizards. And if this tooth shall here- after be proved to be that of a true saurian, the successionists will not sustain a greater shock than they did when the didelphis was discovered in the Stonefield slate. LETTER II. 93 the assumption of such a deposition, however, the ages of different strata have been determined in a most arbitrary and unsatisfactory manner. If, for example, two different strata, composed of dis- tinct ingredients, and situated thousands of miles apart, happen to contain the same organic remains, their contemporaneous origin is considered no longer a matter of conjecture.* It was this error * " The same formation which in England constitutes the argillaceous deposits of the London clay, presents at Paris the sand and freestone of the calcaire grossier ; whilst the resemblance of their organic remains proves the period of their deposition to have been the same, notwithstanding the character of their mineral ingredients." — Buckland's Geology, vol. i. p. Ill, note. "Placed in circumstances of juxtaposition, one rock might easily have been distinguished from another ; but when seas and ontinents intervened, or even when separated, as they often are, by considerable intervals in the same country, it would have been difficult to pronounce upon the identity of any series of rocks. Besides, there would have been very little interesting in such knowledge, even if attained with any degree of accuracy, as nothing farther could have been intimated than the fact, that dif- ferences did exist among the rocky strata of the earth ; but how these were produced, what was the state and condition of the earth at the period of their formation, could not have been ascer- tained, nor even so much as conjectured. Now, in the organic remains which lie entombed in the interior of the earth, we have a more accurate test to enable us to decide upon these points, by which the contemporary origin of different groups can often be established, even where aU identity of mineralogical character is wanting, and where no light can be derived from the order of superposition." — No. V. on Organic Remains, in the Scottish Christian Herald, by S. Anderson, vol. ii. p. 534. 94 LETTER II. which led the great mind of Cuvier to form his unsomid theory respecting the strata of the Paris basin. " Cuvier and Brogniart," says Parkinson, " had founded their opinion of the fresh-water origin of the upper beds of gi/psiwi chiefly on the presence of a shell found in the gypsum, which appeared to be a Cyclostoma, and was supposed to be a fresh-water shell. Of these shells two only were found in the gypsum ; one of which, in the possession of Brogniart, had its mouth unluckily concealed ; but the other, in the possession of Faujus St. Fond, fortunately had it displayed so as to shew that it agreed with Cyclostoma rnumia of Lamarck, who had only named it so provi- sionally, since from its thickness he had supposed it to be a sea-shell. Mr. Beard hence concludes that the fresh-water origin of gypsum does not derive any support from this shell."* M. Cuvier, however, considered that these were fresh-water shells, and that the gypsum was superimposed upon marine limestone ; and hence he concluded that the soil around Paris had been twice covered by the sea, and three times by fresh water. The more we become acquainted with the true characters of marine and fresh-water shells, the more plainly we shall see the difficulty of arriving at correct general conclusions respecting them. Some of the hardest and coarsest shells are found * Foss. Organ. Remains, pp. 255-9. LETTER II. 95 in fresh water ; and perhaps the most fragile and dehcate are destined for the ocean.* But^ on the other hand, we find many marine shells con- structed upon the plan which insures the greatest resistance, and many fresh-water shells so delicate as to yield to the slightest pressure. Still further, the shells of the same species vary according to the roughness or smoothness of the sea in which they live. This is the case with the whelks, some of which are thick and rough, others thin and smooth. Thus we see that, in pronouncing upon the locality of shells, the same difficulties await us as in determining the locality of animals by their fossil remains. * "It sometimes appears extraordinary, when we observe the violence of the breakers on our coast, and see the strength of the current in removing chfFs and sweeping out new channels, that many tender and fragile shells should inhabit the sea in the im- mediate vicinity of this turmoil. But a great number of the bivalve testacea, and many also of the turbinated univalves, burrow in sand or mud. The solen and the cardium, for example, which are usually found in shallow water near the shore, pierce through a soft bottom without injury to their shells ; and the pholas can drill a cavity through mud of considerable hardness. The species of these and many other tribes can sink when alarmed with con- siderable rapidity, often to the depth of several feet, and can also penetrate upv/ards again to the surface if a mass of matter be heaped upon them. The hurricane, therefore, may expend its fury in vain, and may sweep away even the upper part of banks of sand or mud, or may roll pebbles over them, and yet these testacea may remain below, secure and uninjured." — Lyell's Geology, vol. iii. p. 271. 96^ LETTER II. We see, then, that the number, variety, and even the discrepancy in the forms of fossil re- mains, may be explained to a sufficient extent, and in a perfectly rational manner, without de- parting so far from the sacred narrative as to assume that there has been a series of creations and destructions of our globe, following each other in gradual succession, each creation assuming a more perfect type. For the consecutive order and arrangement which is supposed to exist is by no means proved ; and the appearance of regularity in the disposition of fossils is capable of being explained, as we have above shewn, without any such hypothesis. Admitting that every animal which geology has discovered, and those which are yet unknown to us, were originally created at the same time as Adam, and had their several types fixed at the period of that great event, it is probable that many of the mammalia, and other land animals, propagated very slowly, as few of them could have existed at that early period, when the relative position of land and sea, and conse- quently the temperature of the earth, were very different from what they are now ; which, together with the absence of other causes which appear to have been brought into operation as a contingency entirely dependent upon man's extension, must have rendered their development in great numbers a physical impossibility. An equilibrium of life has doubtless ever been LETTER II. 97 maintained by the great Conservator of all ; yet it is equally certain, not only that the relative numbers of the various races of animals have been constantly varying, but also that whole races have become extinct, as their places have been encroached upon by the development of more powerful animals. Nothing seems to us more natural than to suppose that, at the period when Adam was created, the land upon the surface of the globe was not in a condition to admit of the propagation and extension of terrestrial animals, but afterwards became so when the waters of the deluge had subsided, and the temperature had been changed.* The phenomena presented to our * " When we examine the several classes of organic remains, we discover indications not only of a higher temperature than now any where exists on the earth's surface, but we discover also a gradual diminution of temperature as we descend from the ancient to the more recent strata. The gigantic vegetables which are found in the coal formation are allied to the flora of equa- torial countries, and demonstrate, from their large development and immense abundance, the high temperature as well as great humidity of the atmosphere which prevailed at that period. The reptiles and the great amphibia, with bodies like turtles, but fur- nished with necks longer than their bodies, to enable them to dart upon their prey, or to feed on vegetables growing in the shallows of the primitive ocean, seem to shew a state of things consider- ably different from the present. The temperature, besides being higher, was also more equable and uniform over the globe. The proof of this arises from the universal distribution of the same species of plants and animals, which are found not to have been limited to particular countries, or bounded by geographical lines, but to be coextensi,ve with the strata in which they occur. H 98 LETTER II. notice by the early strata seem to shew that before this last catastrophe the sea occupied more of our torrid and temperate regions than at present ; and if so, the larger number of living creatures must have been adapted to the sea. In other words, aquatic animals were more quickly developed, and were diffused to a greater extent, than others created at the same period, but whose develop- ment and extension over the earth were to be the result of future changes in its condition. The absence of remains of the higher animals from the earlier strata, and the abundance of marine fossils in them, are both satisfactorily accounted for by this hypothesis; which thus shews the absurdity of concluding from these facts, that the warm- blooded animals did not exist at the time those strata were formed. For the purpose of shewing still more clearly the incorrectness of this inference, I shall lay be- fore my readers some details respecting the rela- tive numbers of the various tribes of animals. There are at the present time eight thousand Thus, in a variety of climates, and in very distant parts of the globe, secondary strata of the same order are found, and they contain generally the same kind of organic remains. Similar fossil fish-bones are found in the limestone of the old and new continents ; and the same species of plants w^hich are so abundant in the coal measures of Great Britain, have left proof of their luxuriance and abundance in every quarter of the world." — No. VI. of Organic Remains, in the Scottish Christian Herald, by John Anderson, vol. ii. i>. 574. LETTER II. 99 known living species of fish ; — Cuvier says about six thousand, and he computes the species of birds to amount to the same number ; — whereas the number of known species of mammaha does not exceed twelve hundred, according to the same authority : so that there are far more species of the lower animals than of the more highly organised. But this is not all. The species of the former contain an infinitely greater number of individuals than those of the latter. For every whale there are probably many millions of the cod, the whit- ing, the pilchard, or the herring.* We cannot be surprised, therefore, at the inconceivable multi- tudes of animals in the lowest scale of life, such as sponges, polypi, and medusae, which are capable of existing amid circumstances incompatible with the existence of higher races. In estimating the number of these lower creatures, we are lost in imaginative calculation, — we cannot form even a conjecture of the space which their aggregate would occupy in the bowels of the earth. " What language can we speak, when we consider that the laws which connect matter with animal life * " Their shoals consist of myriads of myriads, and are many leagues in width, many fathoms in thickness, and so dense that the fishes touch each other. Lacq^ede says, that in Norway twenty millions have been taken at a single fishing ; that there are few years that they do not capture 400 millions ; and that at Gottenburg and its vicinity 700 millions were annually taken. Of the pilchard he says 1000 millions have been caught." — See Kirby's Bridgewater Treatise. 100 LETTER II. may be as infinitely varied as those which re- gulate material existence ? The little we know might, perhaps, lead us to infer a far more un- limited field of choice. The chemist has reduced all the materials of the earth with which we are acquainted to about fifty simple bodies ; but the zoologist can make no such reductions in his science. He must claim for one scarcely no- ticed class, that of intestinal parasites, about thirty thousand speeies ; and, not to mention the larger class of animals, who shall number all the species of infusoria in living waters, still less those which are extinct, and whose scarcely visible relics are contained within the earth in almost mountain masses ? Professor Ehrenberg, of Berlin, has dis- covered that the tripoli employed in that city for polishing metals, which is dug up at Bilia, in Bo- hemia, consists almost entirely of the siliceous remains of infusoria, of a species so minute, that about 41,000 millions of them weigh 220 grains, and occupy the space of a cubic inch."* The number of living beings in a coral colony, judging from the unquestionable accounts which have reached us from different navigators, must far exceed our powers of calculation. It has been asserted, with some probability, that all the smaller tropical islands of the South Sea owe their origin to this order of polypi.f Flinders tells us that the * Babbage's Ninth Bridgewater Treatise, p. 61. I Vide Cook's Voyages, passim. LETTER II. 101 quantities of coral-reefs between New Holland, New Caledonia, and New Guinea, were so great, that they extended in a straight line to a distance of 350 miles, uninterrupted by the sea ; and these were connected by others beneath the sea, so as to extend to nearly 1,000 miles, being fifty miles in breadth. But though it is certain that these animals occupy a space not easily to be calculated, we can hardly believe that the great masses of matter which compose many of the coral islands and reefs are all the product of animal secretion. This was the opinion of MM. Quoy and Gaimard, who paid great attention to the coral islands. They were of opinion that they resulted from the inequalities of the mineral masses beneath, the cir- cular form of some being occasioned by the crusts of submarine craters. Admitting, however, that some of the accounts respecting these animals are exaggerated, we yet think the rapidity with which they increase is sufficient to account for the number of coral beds and banks which have been found in such great abundance, and in such curious connexion with volcanic lava. " Mr. Lloyd, while engaged in his survey of the isthmus of Panama, seeing some beautiful polypifer on the coast, detached specimens of them; and it being inconvenient to take them away at the time, he placed them on some rocks, or other corals, in a sheltered and shallow pool of water. Returning to remove them a few days afterwards, it was 102 le;j[ter II. found that they had secreted stony matter, and fixed themselves firmly to the bottom. Now this property must greatly assist in the formation of solid coral banks ; for if pieces of live coral be struck off by the breakers, and throv^n over into calm water or holes, they would affix themselves, and add to the sohdity of the mass."* The durable nature of the coverings of those animals which are encased in shell, such as corals, testacea, &c., is, no doubt, the reason why so many of these creatures have been found entombed in sohd hmestone and other rocks, a large proportion of the entire substance of which is not unfrequently composed of myriads of their shells. Nay, the microscope has disclosed to us the remarkable fact, that they sometimes constitute the entire bulk of rocks. " Besides these more obvious re- mains," says Buckland, " of testacea and of larger animals, minute examination discloses occasionally prodigious accumulations of microscopic shells, that surprise us no less by their abundance than their extreme minuteness. The mode in which they are sometimes crowded together may be estimated from the fact, that Saldani collected from less than an ounce and a half of stone, found in the hills of Casciana, in Tuscany, 10,454 microscopic cham- bered shells. The rest of the stone was composed of fragments of shells of minute species of echini, and of a sparry calcareous matter. Of several * De la Heche's Manual of Geology, p. 151. LETTER II. 103 species of these shells, four or five hundred weighed but a single grain ; of one species he calculated that a thousand individuals would scarcely weigh one grain."* That it is quite impossible, by the examination of the earth's strata, to ascertain what animals existed at the time of their formation, is evident. The fact that none but crustaceous animals are found there, is no proof that more fleshy and gelatinous creatures, such as the medusae, were not in being. " More fleshy creatures," says De la Beche, " may have existed in myriads, without a trace of them having been transmitted to us. In proof of this, if any were requisite, we may inquire what portion of those myriads of fleshy animals which now swarm in some seas could be trans- mitted as organic remains to future ages ? Dr. Turner has suggested to me, that under this sup- position of an abundance of medusae, or of analo- gous creatures, among the early inhabitants of our globe, we may perhaps account for the bituminous nature of some of the earlier limestones, more par- ticularly of the carboniferous series, in which not a trace of solid organic remains can be observed ; for the decomposition of a mass of such creatures would produce much bituminous matter, which may have entered largely into the composition of limestones then forming."f * Geology, p. 117; quoted from Saggio Orittografico, 1780, p. 103. t lb. p. 47G. 104 LETTER II. Thus, though we find rocks without any ap- parent traces of organisation, we have no right to assume that they are not as much the receptacle of animal remains as those which contain corals and shells, and other ossific and durable relics of previously existing animals, some of which have only been discovered by the aid of microscopic instruments. Since, then, it is impossible to ascertain, by the examination of strata, what races existed at the period of their formation, it follows that the plan adopted by geologists, of calculating the relative ages of rocks by the animal remains found in them, cannot lead to correct results, inasmuch as it leaves out of consideration altogether the countless tribes of worms, insects, and soft molluscae ; as though no animals had been created in the primeval ages but such as could stand the test of time. In taking this hasty glance over that part of the animal creation which has ceased to exist, we have felt not a little pleasure in being able to collate these ancient records of creation with those whicli have been revealed to us by the God of the Scriptures, through the mouth of his holy prophet. In a work purporting to shew forth the power and wisdom of God, however feeble may be the at- tempt, it is our distinguished province to adduce such facts in the economy of the animated creation as most strongly corroborate what has been so LETTER II. 105 plainly told us in the book of Moses, namely, that that Great Being brought out of nothing all the materials of the earth, placed them in order, sub- jected them to laws, and bestowed upon some of his beings that incomprehensible power of life which he alone possesses ; and, moreover, that he bestowed this power upon a countless number of bodies, which were all created in the space of six days and nights,* adapted in the most wonderful * In Professor Sllliman's Consistency of Geology with Sacred History, — a work purporting to shew the inconsistency which pre- vails between the theories of geology and the sacred record, — an attempt long since proved to be abortive has been renewed. It is to prove that it is not necessary to interpret the word " day" in the account of the creation as meaning a period of twenty-four hours. In order to shew that the word translated in our version by "day" is used in the Hebrew Scriptures in more senses than onef (a fact with which the world has long been acquainted), he quotes various other passages in which it occurs ; and on this slender ground he proceeds to discard the interpretation given by all the most eminent biblical critics and divines, by whom the word in question is considered to mean twenty-four hours, on account of the words " evening" and " morning" being used in connexion with it. He says, " we may speak, for instance, of the life of a man as his day ; and in the same sense, and in harmony with this rhetorical figure, J we speak of the morning and the evening of life." It is quite obvious that the English word day is in like manner used in very different senses ; but we find no f The most obvious is in Job, xviii. 20: "They that come after him shall be astonished at his day." In the New Testament the sense is equally wide : " Your father Abraham rejoiced to see my day ; . . . and was glad." John, viii. 56. X See Consistency, &c. p. 126. 106 LETTER II. manner to the stations designed for them to oc- cupy, subject to individual laws, which, being under his almighty government, operated in bring- difficulty in determining its meaning according to the context. There is no difficulty, except in the mind of the professor, in dis- criminating those passages wherein the word day is intended to convey the meaning of twenty-four hours, and wherein it signifies the whole period of a man's life. "When we are told that David died " full of days," we do not believe that he hved through thousands of epochs ; when our Saviour told the Jews that Abra- ham "rejoiced to see his day," we clearly vmderstand a longer period than twenty-four hours : but when we are told that Moses reqmred the Israelites to gather on the sixth day a double quantity of manna, to be baked or seethed against the Sabbath, we cannot possibly suppose anything is meant but twenty-four hours. In this same sense we must take the six days of creation, and the day of rest was the seventh twenty-four hours, which, up to the present time, is observed by the remnant of that ancient people the Jews. As to the professor's argument, that the " arrangement by which the sun was to measure time was not completed till the evening of the fourth day," and that " the first three days could not have had the present measure of time applied to them," it must vanish before the known facts, that light existed before the sun, and moreover, that the Hebrew term for " day" is derived from two words meaning " to agitate" and " light." If any reflection is called up in studying the event of creation, it is, that there was purpose designed in the creation of the whole — a purpose imply- ing a mutual dependence and relation of one part with another. Now, we read that vegetables were brought into existence on the third day ; and if we consider this to represent a long epoch of time, it follows that there was vegetable food provided for the subsistence of man and the lower creatxires, and yet there were no creatures to live upon it ; thus destroying the harmony which pervades all the works of God. LETTER 11. 107 ing about, according to the most perfect adjust- ment, as the different conditions of the earth required, the development or the extinction of dif- ferent races. In the following Letters it will be endeavoured to shew how that creative power has been exerted, and how indelibly its effects are stamped upon every creature. LETTER III. " It has been said, that ' an undevout astronomer is mad ;' yet the astronomer only contemplates the immensity and order of the works of nature, and the causes of the varieties of light and seasons, so serviceable to the living beings which inhabit this planet, and, as he infers, to the inhabitants of others. But what shall we say of the anatomist, who observes the structure and functions of these beings, who examines their extreme variety and regular gradation and connexion, with- out any feeling or perception that Intelligence has operated in ordaining the laws of nature ? We judge of others by our- selves ; and assuredly such a character must, by the bulk of mankind, be considered as possessing either a deficient or per- verse intellect," — Abernethy's Physiological Lectures, p. 331, The desire which you have frequently expressed to me, of becoming better acquainted with that part of God's creation which calls forth so much of our praise and admiration — I mean the struc- ture and phenomena of living bodies — has in- duced me to undertake the task of unfolding to you some of the countless wonders which there present themselves to our view. When I reflect that many of the greatest men have been engaged during a long series of years, nay, even during their whole lives, in the investigation of the phenomena to which I shall take occasion to draw your attention ; when I contemplate the labours of Linnaeus, Hunter, Haller, Blumenbach, Cuvier ; when I call to mind the names of Pallas, LETTER ITI, 109 Edwards, Daubenton, Carus, Humboldt, Audubon, and many others equally deserving of mention ; and read the learned Haller's opinion, that twenty years are not sufficient for acquiring a perfect knowledge of the anatomy of man alone, who is but an unit in a numerical scale of many thousand creatures which surround him ; — my mind would shrink from commencing a task of such magnitude, if I thought I should be regarded as aspiring to any higher character than that of a compiler of facts taken from the storehouses of all those naturalists and physiologists whose labours have shed so much light upon this, one of the noblest and most useful of the sciences. It has often been a subject of regi-et to me, that the discoveries of such men as those above mentioned, respecting the structure and uses of the various parts of the animal economy, de- veloped in countless forms and modifications, have been unavoidably expressed in the technical language of science, or published in a form which is an effectual bar to their general dis- persion, and, for the most part, confines a know- ledge of them to professional students. When, in addition to this, I tell you that many of these dis- coveries have from time to time been recorded by those who made them — learned naturalists and physiologists of Germany, Sweden, Italy, France, and other lands — in the periodical journals of their respective countries, and have never yet 110 LETTER III. been translated from the original languages into our own, — you will, I think, perceive that the task I have undertaken is one from the careful perform- ance of which may reasonably be expected to be derived much useful and interesting knowledge, tending to strengthen the proofs, ever increasing in number and force, of design, intelhgence, and beneficence in the works of creation. That you may the better understand what I am about to write, I shall now give you a brief outline of the plan I intend to pursue, and explain, in the simplest language I can employ, the mean- ing of those terms which the subject compels me to use. I shall first speak of the nature of those beings which have been endowed by the Almighty with vitality, and, having alluded to their structure and classification, proceed to make some remarks re- specting the living principle which pervades them, and in so marked a manner distinguishes them from all other existences. I shall then compare the various tribes of animals, in relation to their adap- tation to the duties and stations assigned to them by the Creator, beginning with man. I shall next endeavour to explain the difference between rea- son in man, and instinct in the lower animals ; and shall take occasion to notice how much this instinct is favoured by the development of the external senses; and shew, by a number of ex- amples, how beautifully the structure of every LETTER III. Ill animal is fitted to accomplish the three great objects or ends to which that structure is in- tended to be subservient, viz. the defence, support, and reproduction of hfe. And lastly, by referring to some parts of the framework or skeleton of various animals, I shall call your attention to the harmony which exists throughout the whole animal kingdom — to the fundamental similarity which may be traced in all the endless diversities of organisation; thus furnishing you with one of the most powerful proofs that they are all the work of one Being, whose attributes are infinite. This arrangement will enable you to take the most extended and general view of the subjects of contemplation, and is therefore far preferable to the plan of considering each species of ani- mals by itself; which would, besides other in- conveniences, be attended with much vmavoidable repetition. Before I proceed further, I must observe that the imperfection of our senses precludes us, in many cases, from an accurate and complete know- ledge of the phenomena of life. The microscope has revealed to us infinite tribes of beings, whose extreme minuteness prevented us from becoming acquainted with their existence, so long as only our own unassisted organs of vision were at our com- mand ; and the same may be said of many of the constituents of organic structure — of the blood, for example. But although this instrument has 112 LETTER III. enabled us to pry much more deeply into nature than was possible before its discovery, we have no reason for believing that nothing now remains to be discovered and explored. On the contrary, as every improvement in the microscope has brought within the reach of our vision existences of which we were previously ignorant, we are bound to infer that such will ever be the case.* Nothing is better calculated to teach man humi- lity than such facts as these — than the reflection, that all that he can learn, by the aid of the most perfect instruments, is, when compared with the in- finite creation, so insignificant in amount, that it sinks into absolute nothingness. And when he is informed that the head of a common dragon-fly presents a surface for the display of twenty-five thousand lenses, or eyes; that there are animal- cules many thousand times less than a grain of sand, and which in proportion to the smallest * It is now a generally received opinion, which has been established by numerous experiments, that the luminosity so often observed by navigators over vast tracks of the ocean, is owing to various kinds of animalcules, which have the power of emitting light. Some of these minute creatures are not larger than a grain of sand ; yet their organisation is found to be of the most beautiful, varied, and complicated character. Many of them are set round by a circular collar of smaU transparent bodies, ap- pearing like a rich necklace of the finest pearls. The body of the animal is so dehcate that the fluids may be seen in a constant state of motion. The Medusa pellucens and the Pyrosoma atlan- tica give out so much light as to be painful to the sight. LETTER III. 113 creature visible by the unassisted eye, are what a fly is to an elephant ; that the melt of a cod contains more animalcules than there are people living in the world, and that upwards of two hundred thousand of them could be contained in a globe not exceeding a hair's breadth in diameter ; he may well say, what the great and unassuming mind of Abernethy expressed respect- ing this subject : '^ We confide more in the eye of reason than in that of sense, and would rather form opinions from analogy than from the imper- fect evidence of sight ; for it seems too hasty an inference to conclude, that in the minute animals there are no vessels nor other organisation, be- cause we can discern none. Who has seen the multitudinous, distributive, and absorbing vessels, and all the other organisation, which doubtless exists in the vitreous hurnour of the eye, than which no glass ever appeared more transparent, or more seemingly inorganic ?"* The vitreous humour, however, is not the only part of the eye which is transparent. The functions of the eye could not be performed unless the crystalline lens, the aqueous humour, and the cornea, all which are placed anterior to it, were transparent also ; for otherwise the representations of external objects could not be clearly transmitted to the retina, which is the expansion of the ojjtic nerve over the concave surface of the back part of the eye, and * Abernethy's Physiological Lectures, p. 203. I 114 LETTER III. receives impressions of light. That, notwithstand- ing their transparency, all these parts are endowed with a very high degree of organisation, I need only quote the words of an intelligent writer to convince you. " Let us take, as a specimen, the crystalline lens, or hard centre-part of the eye of a cod-fish, which is a perfectly transparent, and to all appearance homogeneous spherule. No one un- accustomed to explore the wonders of nature would suspect that so simple a body, which he might sup- pose to be formed of a uniform material, cast in a mould, would disclose, when examined under a powerful microscope, and with the skill of a Brewster, the most refined and exquisite conforma- tion. Yet this little spherical body, scarcely larger than a pea, is composed of upwards of five miUions of fibres, which lock into one another by means of more than sixty-two thousand five hun- dred milhon of teeth. If such be the complica- tion of a portion only of the eye of that animal, how intricate must be the structure of the other parts of the same organ, having equally important offices!"* * Roget's Bridgewater Treatise, vol. i. p. 60. " Mere size, indeed," says Roget, " is of all circumstances attendant on orga- nised beings that which least should be assumed as a criterion of complication or refinement of structure. An object is great or small only in relation to the standard of our own limited and imperfect senses ; but with reference to the operations of crea- tive power, all such distinctions must vanish. There is not, as far as we have the means of judging, in the colossal fabric of LETTER III. 115 It appears, then, that we are precluded from investigatmg the structure of many animals which form links in the great living chain of creation.* In the examination, however, of those which are open to our inquiries, we shall find abundant causes for admiration of the infinite wisdom and beneficence displayed in their formation : to this I at once proceed. The organisation of animals is comprehended in the term anatomy ; and it is the only natural foundation on which any systematic arrangement of the animal kingdom can be built. The investi- gation of the structure of the lower animals was at a very early period entered upon by anatomists, in the hope that it might throw some light upon the organisation of the human body ; and the term comparative anatomy was employed to dis- tinguish what related to their structure from hu- man anatomy. The former term is now more generally used to imply the comparison of all living beings one with another. The science of comparative anatomy supplies us with the facts which constitute the basis of physiology — the science which treats of the operation of the living principle upon organised bodies, and inquires how the elephant any structure more comphcated than exists in the minutest insect that crawls unheeded at our feet." — Animal Physiology. * Ehrenberg estimates the smallest visible animalcule at about 1 -24,000th of an inch. 116 LETTER III, its laws are determined, and its phenomena ex- hibited. You will thus see how essential a know- ledge of the sciences of comparative anatomy and physiology are to the comprehension of zoology, or the natural history of animals. The first step in the latter study must be, to examine the struc- ture of those organs or instruments by which the phenomena of life are manifested, in order to ascer- tain what are their functions, or the uses to which they are intended to be applied. To this end, they must be viewed in all their modifications and combinations, from the most simple to the most compHcated animal ; and we shall thus arrive at a satisfactory knowledge of most of the gradations which unite the chain of living beings, from the simply constructed polypus to man, whose organi- sation is more comphcated than that of any other animal. There are many diflEiculties pecuhar to the study of comparative anatomy, the greatest of which is, perhaps, the necessity for studying the mutual connexion and influence of the organs. And on this point the anatomy of the lower animals will disclose facts which we never could have arrived at whilst contemplating the more complex organi- sation of the higher animals alone; for in the various classes of animals we may find every pos- sible combination and adaptation of organs, and there is no organ that is not wanting in some one class. I shall not here enter minutely into the LETTER III. 117 varieties of structure which characterise every spe- cies of animal ; as it is my intention, in a future Letter, to shew you the direct influence which every organ has upon the mode of hfe of the being of which it forms a part, and upon the relation in which it stands to other living creatures ; when it will appear that each addition to the organisation confers some new power, and raises the being on whom it is bestowed a step higher in the scale of creation, fitting it for the accomplishment of more important purposes in the great scheme of Provi- dence. You will then see that man is the noblest work of God, possessing, in addition to a refined and exquisite organisation, the high and distin- guishing faculty of reason. I wish now only to make you acquainted with the chief physical dis- tinctions which have regulated naturalists in form- ing their classifications, and with the meaning of the terms denoting the various branches of those classifications. You will by this means obtain a general and comprehensive view of the animal kingdom, which will enable you the better to arrange and remember the information to be hereafter communicated in detail. That the structure of animals could not be accurately described by those who had not atten- tively examined it, is evident. Little reliance can, therefore, be placed upon the writings of those who, in the infancy of science, taught in the schools of 118 LETTER III. philosophy. They substituted theory for observa- tion, and imagination for the demonstration of facts. Hippocrates, Aristotle, Empedocles, and the fol- lowers of Pythagoras, took but little pains to col- lect materials for the erection of sound and useful theories ; indeed, until the results of the investi- gations of Linnaeus — who, as you know, was a Swedish naturalist, and flourished at the beginning of the eighteenth century — were published, no classification can be said to have been formed. That of Linnaeus was founded upon the difference of structure in the organs of circulation, such as the heart, lungs, and blood-vessels. Our present classifications are those of Cuvier and Blumenbach, both of which are modifications of the systema na- turae of Linnaeus, which comprised three great divi- sions. The^r*^ contained the mammalia and birds, which have red and warm blood ; the second, the amphibia and fishes, whose blood is red, but cold ; the third, insects and worms, whose blood is colourless and cold. These divisions Linnaeus subdivided into six classes, which Blumenbach has adopted, subject, however, to modifications ; but Cuvier recognises only four divisions. Blumenbach's six classes are as follow : — The^r*^ class comprehends all mammiferous or teat-bearing animals, so called because they suckle their young. They are viviparous, and their blood is red and warm. LETTER III. 119 The second class comprises birds, which are oviparous, and clothed with feathers. Their blood is red and warm. The tJw'd class contains the amphibious ani- mals, which, though they live in the water as well as on land, yet breathe by means of lungs like the first two classes. Their blood is red and cold. The fourth class contains the fishes. They breathe, or rather oxydise their blood, not by lungs, but by means of gills, an organ adapted to the element in which they move. Their blood is red and cold. The fifth class consists of insects, having an- tennae or feelers upon the head, and limbs fur- nished with joints. Their blood is white and cold. In the sixth class are worms. They have no feelers, but spiracula, or organs for bringing the air in contact with the blood, arranged on each side of the body. They have no joints, and their blood is white and cold. These six classes are subdivided into orders, genera, and species. Cuvier's four divisions or departments are the following : — • The first he designated vertehrata, which in- cludes the mammalia, birds, amphibia or reptiles, and fishes, because these only have a real internal articulate or jointed skeleton ; the most important part of which is the chain of bones called the mrtebrw, or spine, from the Latin vertere, to turn, 120 LETTER III. because the whole body turns upon it, either di- rectly or indirectly. It is also formed to defend the spinal cord, whicli is the great organ of vitality in this department of animals. The second he called mollusca, from the Latin mollis, soft. In this division are comprised all animals having fleshy bodies clothed with a simple, unarticulated shell — such as the oyster. The third he named articidata, from articiilus, a joint. The Crustacea, worms, and insects, are in this division. They have no skeleton, but their skins or outward coverings are jointed. The fourth he called radiata, or zoophyta, from la^SJov [zo-on], an animal, and pvrov [phuton], a plant, from the beings so denominated having some of the properties of animals and some of plants.* Whichever of these arrangements we follow, (and that of Cuvier is undoubtedly the most com- plete and satisfactory), it is obvious that, as we * The labours of these naturalists, in arranging and classifying the animal creation, cannot receive too great praise, for they serve to direct us through paths which would otherwise have remained obstructed by difficulties scarcely to be overcome by any other means ; and though such classifications are uninteresting to the general reader, yet they are the basis of all those works on natural history, which, being written with less regard to system or arrangement, are better calculated to please the young and unscientific. To use the words of Goldsmith, — without the aid of system, nature must still have lain undistinguishable, like furni- ture in a lumber-room ; every thing we wish for is there indeed, but we know not where to find it. LETTER III. 121 descend in the scale, all the most important organs are gradually withdrawn, until we arrive at the apparently homogeneous and simple structure of the animalcule of infusion, which presents an ap- pearance of mere jelly. The numerous subdivisions of the animal king- dom into orders, genera, and species, enable us, when we speak of an animal, to convey a know- ledge of its structure in one word, which to the naturalist speaks as clearly and comprehensively as if we had entered into a detailed description of its organisation and habits. Thus, if I speak of the cat, I know that it belongs to the genus felis, which is of the order carnivora and class mammalia^ in the department of the vertebrata ; and I know, from the external organisation of the animal, its claws, its teeth, and strong mus- cular appearance, what must be its internal struc- ture. But you must not suppose that we can give such brief yet accurate descriptions of every ani- mal ; for the habits and organisation of many are totally unknown to us. This is one of the diffi- culties which present themselves when we endea- vour to arrange the animate creation in regular and uninterrupted order, which, after what has been said, you might be disposed to think could be done, from the highest to the lowest in the scale : but the links of the living chain are not so easily put together as at first sight you may suppose; and there are causes which must operate so as almost 122 LETTER III. wholly to exclude many animals from om* observa- tion, such as climate, locality, and habits. It has often been said, that by arranging all ani- mals in a line, beginning with man and proceeding downwards to the animalcule of infusion, we have a tolerably distinct gradation from the more com- phcated to the more simple forms of organisation. This assertion is correct only to a limited extent : the complicated and highly organised structure which has been ascertained to be possessed by some of the less pretending or conspicuous orders of animals, shews that it is not to be assented to without quahfication. Thus, in one order there is a certain mode of aerating the blood; in another order there is a different mode. In the one the air circulates all over the body, and the blood is confined to a reservoir, as in worms ; in the other the blood circulates all over the body, and the air is confined to a reservoir, as in warm-blooded ani- mals. But who is to say which is the higher or- ganisation, or which the more complicated ? More- over, certain links of this chain have had their beauty and connexion more clearly developed than others ; and it is probable, that, with the limited instruments we possess, greatly as they have of late years been improved, much additional know- ledge cannot be obtained respecting them ; while, on the other hand, there are links which have received scarcely any attention whatever, and of which we are totally ignorant. LETTER III. 123 That which distinguishes hving beings from one another, is the diversity in the arrangement of those materials which compose their structures ; each kind of animal having a certain definite form by which it may be recognised. The body of all animals is composed of solids and fluids : the former constitute the bulk and determine the form of the body ; the latter are conveyed to every part of the body by a circulatory apparatus, for the purpose of depositing or removing particles either required for its support, or rejected as no longer useful. And it is worthy of remark, that though, for purposes essential to its existence, the materials of the body have been thus divided, nevertheless the fluids suspend all the elements of the organs, which are composed of solids con- tained in and deposited by the fluids.* Thus, if blood be subjected to an analysis, it will be found to contain fibrin, which is the basis of muscle ; albumen, the material out of which are formed many membranes or coverings, such as the skin and the internal coverings of the joints ; fatty matter, which M. Chevi'eul has discovered to be the same as the substance of the brain and nerves ; and phosphate of lime and 7nagnesia, which com- pose the greater portion of the bones ; besides * Miiller says, in nearly all the solids of the body water con- stitutes four-fifths of their weight. — Elements of Physiology, p. 144 (translation). 124 LETTER III. many other substances necessary to the animal economy, such as osmazome, lactic acid, &c. Such is the wonderful property of the blood, that when it is set in motion by the life-giving power of the Creator, through the agency of the atmosphere, conveyed to it by means of the lungs, it is propelled and carried by the heart and blood-vessels to all parts of the living frame in a fluid state. It cannot cease to move onwards in its course without becoming solidified, and so ceasing to be a fluid. Thus, all living bodies ex- hibit a constant internal motion, which is kept up by the circulatory power of the blood, which is capable of being subdivided so minutely, that it can with facility insinuate itself into the finest texture ; in proof of which I may tell you, that the globules which are present in the blood of all the higher animals, and give to it its red appear- ance,* have been found to measure not more * According to the experiments of Englehart, the red colour of the blood appears to be produced by the presence of iron in a metallic state, and not in the state of an oxide. How it is com- bined with the elements of the blood, is unknown. There is, ac- cording to Berzelius, no analogous instance known of a qmnary combination of a metal with nitrogen, carbon, hydrogen, and oxygen. — lb. p. 123. In inorganic substances, the elements are always in a binary combination, that is to say, two of the elements unite together. In organic substances, the elements unite three or four together, but seldom five. LETTER III. 125 than one three-thousandth part of an inch in diameter.* The blood, then, is the most important material of the body, since it develops and sustains all the rest ; and it is necessarily composed of a greater or less number of ingredients, according to the required development of every animal. For in- stance, the brain and spinal cord are organs essential to the existence of the higher animals ; without them they could neither have external nor internal senses, to inform them of the nature of objects which surround them. They would, therefore, be unable to detect their food, nor would they possess the power of motion. So that the blood in those animals which have a brain or spinal cord necessarily contains the fatty matter, of which those organs are composed, in greater abundance than the blood of those desti- tute of them ; and hence the constitution of the blood is by no means the same in all animals. Again ; in birds it is necessary that there should be a particular contrivance for rendering their bodies specifically lighter than the atmo- sphere in which they move. Accordingly, we see that their whole structure is modelled in relation to this end : if they were formed of * Magendie's Physiology. Haller. in speaking of cold-blooded animals, says that the globules of the blood are to an inch as one inch is to five thousand. Leuwenhoeck's conclusions are more minute. 126 LETTER III. a substance as light as the feathers which cover them, they would still be unable to raise them- selves from the ground into the air, had they not some power within them to counteract the weight of their bodies. And whence this power but from their blood ? which, being many degrees higher in temperature than that of man or any of the quad- rupeds, so expands and rarefies the air which is contained in their bones, and other appropriate apparatus with which they are furnished, as at all times to render them specifically hghter than the external air ; so that they may float about, or raise or lower themselves, upon the same principle that we would regulate a balloon, but with a dexterity and precision which will bear no comparison. The blood of birds must, therefore, contain a larger quantity of oxygen and of combustible materials than that of quadrupeds. To give another example : in all those animals that possess an internal, or true skeleton, the depo- sition of fresh bony matter not only requires that the blood should contain phosphate of lime and magnesia, for these exist in the blood of the lower animals, but also that its temperature should be elevated, in order to give it the power of chemically uniting these materials with animal matter to form bone ; which is not necessary for the mere sepa- ration of those materials, as takes place in shell- fish, and other animals lower in organisation. Having shewn you that the blood of every race LETTER III. 127 of animals differs in some respects from that of all other races, I will now give you an account of the apparatus for transmitting that fluid to all parts of the body. The interior of the body of all the warm-blooded animals, called quadrupeds or mam- mals, is divided into two great cavities * by a thick muscular partition, which bears the name of the diaphragm : the lower cavity is the abdomen, and contains all those organs which are employed to separate the nutritious from the innutritions parts of the food, such are the stomach, liver, spleen, pan- creas, &c. ; the upper cavity, called the thorax, or chest, contains the organs for propelling the blood over the body, and for exposing it to the atmo- spheric air, by which process it receives oxygen,f one of its vivifying principles, and gives out car- bonic acid, another principle which has been formed by the chemical combination of a portion of the oxygen with the carbon which is contained in the blood. According to the theory of Lavoisier and * See Plate I. fig. 1. t The length of time during which life can be supported without breathing, or, in other words, without the oxygen of the atmosphere being brought in contact with the blood, varies in different animals. It is shortest in warm-blooded animals and insects. Miiller says, warm-blooded animals, placed in the vacuum of an air-pump, die in less than a minute ; birds even from thirty to forty. seconds. Reptiles will live a considerable time. Caira- dori shewed {Ann. de Chim. et de Phy. tom. v. p. 94) that a tor- toise placed under oil lived from twenty-four to thirty-six hours. — Elements of Physiology, p. 294 (translation). 128 LETTER III. Laplace, the oxygen of the atmosphere combines with the carbon of the blood, and carbonic acid being thus formed is expired. It is still, however, uncertain whether the carbonic acid which the lungs give out is actually formed there, or in other parts of the circulation. Part of the oxygen which enters the lungs unites with the hydrogen of the blood, which is exhaled in the form of water. The oxygen which is absorbed by the blood can- not, by any process, again be separated from it. Unless the blood absorbs oxygen and separates carbon, it has a poisonous action upon the body, and particularly upon the nervous system, pro- ducing insensibility and death. The progress of the blood through the lungs, and thence through the body, takes place in the following manner. In the lower part of the left side of the chest is placed the heart, a hollow mus- cular organ containing four cavities, two auricles and two ventricles. The same quantity of blood enters the right auricle as is afterwards impelled over the body by the left ventricle. When the right auricle contracts, the blood passes into the right ventricle, which immediately contracts, and projects the blood into the lungs. It cannot regurgitate ; as, when the ventricle contracts, the auricle dilates, and the blood is prevented passing back into the auricle by the tricuspid or three- pointed valves, which, being distended by the blood in the auricle, completely obstruct the pas- LETTER III. 129 sage from that cavity to the ventricle.* In hke manner, the blood is prevented returning by the same vessel, the pulmonary artery, which conveys it into the lungs, in consequence of the obstruction which it meets from the semilunar valves that surround the entrance of that vessel.f The lungs are two elastic and membranous organs, fitted up with innumerable small cells, into which the branches of the trachea, or windpipe, open to convey fresh draughts of atmospheric air at every act of inspiration. Upon these cells in- numerable minute blood-vessels are ramified, and the blood is thus brought into contact with the atmosphere ; by which means its impurities are expelled, and it is again rendered fit to support life. The blood passes through the minute vessels of the lungs in a continuous stream while respiration is gentle and slow ; but when it is hurried, the flow of blood is partly interrupted. During full in- spiration or expiration, the blood cannot traverse the lungs with freedom: as in the former case, the air taken into that organ compresses the veins, so in the latter, by the collapsing or falling to- gether of the lungs, the veins are obstructed. It is only between these two extreme states that the blood can pass through the lungs without diflS- culty.J The course of the blood from the right * See Plate I. fig. 1. f See Plate I. figs. 2 and 3. X Dr. Southwood Smith, in the second volume of the Phi- losophy of Health, estates that Dr. Dill and himself instituted, some K 130 LETTER III. ventricle of the heart through the lungs, and its return to the left ventricle, is called the lesser cir- culation. The heart is supposed to contract, and so propel the blood into the lungs, and through the other parts of the body, in consequence of some mutual action, unknown at present, between the blood in its minute vessels and the nerves which are distributed to it. On its return from the lungs, the blood, which had previously almost a black appearance, having exchanged the carbon, the presence of which caused that appearance, for oxygen, is now of a bright vermilion colour, and being received into the left auricle, passes thence to the left ventricle of the heart, whence it is projected by the contracting power of that organ and of the great vessels called arteries,* and is by them conveyed to all parts of the body. A provision of the same kind as that which I have noticed as preventing the return of the blood into the right ventricle, exists for a similar purpose at the entrance of the left ven- tricle, and also at that of the aorta, the great vessel which proceeds from the latter cavity, and conveys the blood to the arteries. time ago, various experiments respecting respiration; and that they ascertained that no degree of collapse or dilatation (with air) is capable of altogether preventing the passage of the blood through the lungs. Vide p. 73, section 407 et seq. * From the Greek a^/j, air, and r^ripeu, to keep; because the ancients thought, from finding these vessels alvi^ays empty of blood, that they contained air in the living animal. LETTER III. 131 The blood is supposed to convey to every organ the heat without which its functions could not be performed ; for when the blood returns by the veins from these organs, it has become of a dark colour, and has lost some of its heat. In this state the blood is collected, on its return, into a large vein, which pours it into the right side of the heart, again to undergo the same changes. Every animal which breathes through lungs must have a double heart, and is warm-blooded : this is the case with man, quadrupeds, and birds.* But as we advance downwards in the scale, we find forms of organisation differing widely from those which we have been considering ; difference of circumstance requiring corresponding changes of structure. Thus, the temperature of the blood of fishes is not raised above that of the surround- ing medium ; and their blood, instead of being ex- posed to the air by means of lungs, as in the higher animals, is carried for that purpose to correspond- ing organs called gills,f which are composed of plaits or folds, in the innumerable vessels ramified * But in birds, although they breathe in the atmosphere like quadrupeds, yet the circumstances of their rapid movement, and the long-continued exercise of their vocal powers, require the pulmonary organs to be constructed in a particular manner to meet these ends. In this class of animals we see, therefore, the same apparatus differently modelled : on the consideration of which I shall enter more fully when I come to speak of the adaptation of birds to the element in which they exist. t See Plate I. fig. 4. 132 LETTER III, upon the surfaces of which, the blood is presented to the water, and extracts from it the vital prin- ciple, oxygen. In reptiles the blood becomes so slow in its movement as to admit of their exist- ence in a very low temperature. The brain also in these animals is a smaller and less important organ than in the higher races. But the diversities of circumstance which modify these organs in various animals I do not now intend to mention : this is a subject on which I shall enlarge when I come to speak of the creative wisdom displayed in their adaptation to the endless varieties of situation. I must in this place mention another system of vessels, called absorbents, which are employed in conveying lymph and chyle to all parts of the body, and in removing old materials which have become impoverished by use. For this purpose they communicate with the large blood-vessels, into which they convey the old and the new mate- rials of the body, to be again mixed with the blood, which thus receives fresh vigour. The worn-out particles are conveyed out of the body altogether, by organs expressly formed for that purpose. The absorbents are much smaller than the blood-vessels. There are two sets, which convey different fluids into the circulation. The one is called lacteal, because the fluid they absorb is white like milk : their function is to extract all the nourishment afforded by the digested food. Converging from all parts of the small intes- LETTER III. 133 tines, they deposit their contents into a vessel about the size of a crow-quill, called the tlioracic duct, from its passing through the thorax or chest in front of the spine, in its course from the ahdom'en to its final termination at the angle formed by the union of the internal jugular vein with the subclavian vein, which returns the blood from the head and upper limbs to the right side of the heart. The chyle, or nutrient part of the food, is taken up from the internal surface of the intestines by means of numerous villi, or short processes, about one-fourth of a line* in length, and composed of arteries, veins, nerves, mucous ducts, and lacteals. The globules of the chyle, accordinar to Prevost and Dumas, do not exceed 1-7 199th part of an inch in diameter, about half the size of the red globules of the blood. Muller says, he has ascertained that the thickness of the membrane which forms the villi in the calf is l-530th 'of an inch, and the diameter of the capillary f (minute) blood-vessels of this membrane may be reckoned at from" l-3700th to 1-1 850th of an inch.;!; The other set of absorbents are called lym- phatics, from their contents having a transparent colourless appearance like lymph {lympha, water). These, arising, it is supposed, from every part of * A line is a French measure : it is the twelfth part of an inch, t From caplllus, a hair. I Elements of Physiology. 134 LETTER III. the body, accompany all the great blood-vessels, and on arriving at the abdomen join the lacteals to form the thoracic duct above named. Miiller discovered small pulsating sacs connected with the lymphatic cavities in frogs, which he styled lym- phatic hearts.* They are seen more plainly in reptiles. Sometimes there are two pairs : they pulsate about sixty times in a minute, and are supposed to aid the heart in pumping the lymph into the veins. I cannot conclude this Letter without making some observations upon the nervous system ; for there is reason to believe that all animals, even of the simplest structure, have some rudiments of this system. The material of which the organs composing it are formed is of a soft tenacious substance, varying in colour from white to yel- lowish brown, gray, or black. I have already told you that this matter is secreted from the blood ; when submitted to a powerful microscope, it is found to consist of an aggregate of globules, varying in size, the largest being considerably smaller than a globule of blood. The nervous system is composed of two parts : a central organ, consisting of two chords, corresponding to each half of the body ; and the nerves, which proceed from it to the diiferent surfaces of the body. The central organ is very simple in the lower animals,f sometimes forming a ring in the in- * See Plate II. fig. 1. f See Plate II. fig. 2. LETTER III. 135 terior of the body ; in other cases, a nodule on each side of the gullet ; and in others, again, tra- versing the whole length of the body. In the vertebral animals there is added to the top of this spinal cord two nodules, which gradually increase in size and become more complicated as we ad- vance upwards in the scale of creation. These nodules are the brain, which is protected by a thick bony case, to prevent injury or concussion of its delicate structure. The nervous system is the source of sensation, and is essential to the production of motion in animals. I shall speak more at length respecting it in another Letter. It is here named only that you may know that such a system forms part of the organisation of the body. A cursory glance may here be taken of the muscular and bony systems. The former com- prises the fleshy parts of animals, the latter being the solid framework which supports the body, and furnishes fixed points for the action of the muscles, by which locomotion is effected. These two sys- tems are constructed and arranged with the strictest relation to the purposes required of them. Thus, as the power of locomotion becomes more or less essential, or more or less extensive, so is the system of muscles modified or enlarged. The same prin- ciple regulates the structure of the bony system, which is formed in relation to three essential purposes in the construction of organised bodies. 136 LETTER III. namely, to support the softer parts, to defend the more vital parts, and to effect locomotion. But, as it will require much space to point out the adaptation of the skeleton in different animals to their circumstances, in this place I simply mention these systems as also forming part of the organi- sation of animals, reserving the further considera- tion of them for a future Letter. LETTER IV. " The Spirit of God hath made me, and the breath of the Almighty hath given me life." — Job, xxxiii. 4. " And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life, and man became a Hving soul." — Gen. ii. 7. " For the life of all flesh is the blood thereof." — Levit. xvii. 14. I NOW come to speak of that principle which pro- duces all those phenomena that distinguish or- ganic fi'om inorganic bodies, and which we call life. Life, then, is a term used to express a set of phenomena characteristic of organisation ; those which are displayed in the bodies of man and of other animals being designated by the term animal life. What that principle is, we know not; our acquaintance with it is limited to its operations or effects ; we are ignorant of its cause. But though we cannot speak of it positively, we may give a negative description of it, which will at least shew that it has no resemblance to any thing material ; that though it is always manifested in a material body, yet being the cause of the existence of that body, it must nevertheless be independent of it (for we know of no substance which is capable of gene- rating' that upon which it is dependent) ; and that the only physical evidence we possess concurs with revelation in declaring that life is a principle 138 LETTER IV. superadded- It is this evidence, consisting of the phenomena denoted by the term hfe, or soul, which I shall endeavour to lay before you in this Letter ; and I think it will convince you that the pheno- mena of organised bodies result from a higher principle than any to which inorganic bodies are subject, and cannot proceed from mere physical structure.* What becomes of this principle after it quits the body of the inferior animals, we cannot presume to say, further than that revelation assures us that " the spirit of the beast goeth downwards to the earth. "f I shall first consider the soul or animal spirit, common to all hving creatures with man ; to which is added in man, as I shall afterwards shew, * " Now, without attempting to define matter or mind, and only taking the evidence of our senses for the existence of the former, it is surely safe to affirm that we find in ourselves, and observe in other animals — in some in an equal, in others in an inferior degree — a power of sensation and reflection, and a power of moving ourselves and other things — that we find in the world other bodies, which are to all appearance entirely without the sensitive and reflecting power, and are certainly incapable of spontaneous motion. It has, therefore, been pretty generally con- cluded, that animals endued with these quahties owe their supe- riority over the other bodies which are without them, and which we term inanimate, to the exclusive possession of an immaterial substance, which philosophers have called spirit ; and that there are, in fact, two sorts of beings in the world, cogitative and in- cogitative, corporeal and spiritual." — Sumner's Records of Crea- tion, vol. i. p. 40. t Eccles. ii. 21. LETTER IV. 139 the rational or responsible soul, or spirit, which is given exclusively to man by inspiration of God.* I have said that the animal soul is known to us only by its effects, or the phenomena which it pro- duces in the body, every part of which is an organ of the soul. Thus, spontaneous motion and sensa- tion are seated in all the muscles and other parts of the body, and are conveyed to them by the nerves. The nerves are in connexion with the brain and spinal cord ; and hence these phe- nomena are said to emanate from those sources. In physiological language, we say, then, that the brain and spinal cord are the immediate instru- ments of animal life ; and according to the nature of every animal, and its place in the scale of exist- ence, these instruments are put together with more or less of complication, both in their structure and in the number of their parts. The operations of the mind are also carried on by the brain ; but we shall, in this place, speak of that organ in reference to the vital principle only. There are, as you doubtless know, agents of an invisible and imponderable nature, which are used by the Creator to effect the many changes that take place in unorganised bodies ; such as heat, hght, electricity, &c. ; of which we know nothing, except the power they exercise in the production of sensible phenomena. * " There is a spirit in man, and the inspiration of the Almighty giveth them understanding." — Job, xxxiii. 8. 140 LETTER IV. Now the first proof we shall adduce of the ex- istence of a vital principle in animals (which exists, though in a less degree, in vegetables also) is, that they are capable of modifying the influence of the agents just enumerated, which act upon all inor- ganic bodies with an irresistible power, separating their component particles, and forming them into other and widely diff'erent combinations. Judging from the sensible properties of substances alone, we should never for a moment imagine that the frail and comphcated structure of organised beings could withstand the force of those agents which crumble into dust the hardest and most compact unorganised substances. That such is the case, however, will admit of no dispute ; and that this remarkable property is derived from the vital prin- ciple, is demonstrated by the fact, that as soon as it is extinct in the body which it had animated and protected, these physical agents, till now defied, at once begin to operate upon it, and work in it the same changes as they produce in inorganic matter.* * No more striking illustration of this fact can be given than the following. The juices formed by the power of the living principle are capable, when that principle is withdrawn, of dis- solving the very organ that secreted them. The stomach has been found after death perforated by the solvent power of the o-astric juice. Mr. Hunter observed (Animal Economy, p. 229), that a particular portion of the stomach is occasionally softened, or even partially or wholly dissolved, after death ; and parts adja- cent to that organ are affected by its contact with them. LETTER IV. 141 The soul, then, is the monarch of the flesh ; and as long as it reigns in that earthly palace, it reigns triumphant over every other agent. Those inferior ministers which it calls in to do it service it keeps in entire subjection, and subdues them to its purposes. But as soon as it is fled, the body becomes the prey of anarchy ; and those distinc- tions which so remarkably characterised the vari- ous organic parts are no longer to be traced in the general ruin and devastation that is brought about by those very agents which, whilst under the direction of their divine governor, were made instruments of its safety and conservation. When we contemplate this wondrous change, feelings of profound astonishment take possession of our minds, and we are irresistibly led to make such inquiries as those so eloquently expressed in the following words : — '' What potent spell has been dissolved, which could retain in combination, for so long a period, the multifarious elements of that exquisite organisation ; and from the control of which, being now released, these elements hasten to resume their wonted attractions, and, entering into new forms of combination, are scattered into dust, or dissipated in air, leaving no trace of their former union ? By what transient power, above all, does this assemblage of material particles first beconie animated by the breath of life ; and from what elevated source did they derive those higher energies, apparently so foreign to their inherent 142 LETTER IV. properties, and invest those once lifeless and inert materials with the exalted attributes of acti- vity, of sensation, of perception, of intelligence ? Shall we ever comprehend the natm'e of this subtle and pervading principle, by the agency of which all those wonderful phenomena of life are pro- duced, and which, combining into one harmonious system so many heterogeneous and jarring ele- ments, have led to the formation of this exquisite frame, this elaborate machine, this marvellous assemblage of faculties ?"* The protective power of the living principle, however, is perhaps the least striking of the pheno- mena which attest its existence. There are others which ever have confounded, and must still con- tinue to confound, the fruitless inquiry of man. The knowledge of some of these phenomena is withheld from him, because it is in nowise con- nected with the preservation of his existence, but, as I shall hereafter notice, would probably in- volve consequences destructive of it. Yet, because some of the laws of the principle of life are above our comprehension, it does not therefore follow that we are unable to observe many of its phe- nomena— to watch, imitate, and admire them — and from them to derive practical inferences highly conducive to our comfort and happiness. That our knowledge on this subject is ex- tremely limited, I shall have no difficulty in prov- * Roget's Animal Physiology, vol. i. p. 21. LETTER IV. 143 ing. The science of anatomy, it is true, discloses to us most accurately the materials of which all organised bodies are composed. We have ascer- tained that they may be separated more or less completely. To the simpler combinations, such as gelatine, fibrin, starch, albumen, &c,, we have given the appellation of proximate principles; which are capable of still further analysis, and may be resolved into oxygen, hydrogen, nitro- gen, and carbon, the primary elements of matter.* Yet, with these fects before us, which, discovered by chemical science, have brought us to the margin of organised structiu-e, how far can we be said to have advanced in the knowledge of the vital principle ? We are assured by the most accurate experi- ments, that all bodies consist of materials chemi- cally combined in certain fixed and invariable pro- portions. These materials we can separate from one another with the greatest precision; but no discovery has yet enabled us to unite them again, as in their original state. This is the case in regard to substances that are without life : we may subtract the different parts which go to form their structure, and each part may be reduced to * There are eighteen simple substances which compose all organised bodies. In man and the higher animals these sub- stances are oxygen, hydrogen, carbon, nitrogen, phosphorus, sulphur, iron, chlorine, fluor, potassium, sodium, calcium, mag- nesium, silicium, and manganese. 144 LETTER IV. its elements, and the phenomena thus resulting are more simple, more certain, and less conjec- tural, than when they can only be viewed in com- bination, as in organised bodies. With this advan- tage, the experiments to which inorganic bodies have been subjected might, with more reason, have been expected to furnish an explanation of the causes which regulate their combination ; but even here the difficulty is impenetrable, and, as if to mock our efforts to discover these mysteries, we see the same simple elementary materials forming, by their admixture in slightly varied proportions, the most opposite substances. Who, for example, would suppose that the brilliant diamond was com- posed of the same material (carbon) as common charcoal, or white cotton ? We are wholly ig- norant of the means employed by the Creator to produce such diversified appearances out of the same materials. Such being the difficulty of ex- plaining the cause of the construction of inorganic bodies, you cannot fail to perceive that the diffi- culty must be much increased when we direct our inquiries to organised beings. The analysis of our bodies into their compo- nent elements, their exact proportions, and their various combinations, which chemistry has accom- plished, has been looked upon as a satisfactory and progressive advancement towards the discovery of the principle of life. Admitting that we have been successful in our analysis of these materials, we LETTER IV. 145 would ask, how far have we advanced in the syn- thesis, or, if I may so term it, in the chemical architecture of the living body ? An idiot can pull to pieces the various materials of a bird's nest, can separate the moss from the hair, and the feathers from the sticks ; but even Sir Christopher Wren, with all his constructive skill, could not put to- gether this unostentatious and apparently simple dwelling. If, even in the inorganic world, all our efforts to discover the laws which combine the elements of matter have been completely baffled, how can we dare to hope that, in a higher and more incomprehensible mode of arrangement, our labours will be successful ? Do we find that, by com- bining hydrogen and carbon, we can produce the inimitable diamond ? Yet such is man's self-confi- dence, that, because he can produce a substance re- sembling one of the elementary parts of living matter, he is vain enough to suppose he has placed his foot upon the first step of the ladder of synthesis.* I shall not, in this Letter, enter upon the con- sideration of the other characteristics of life ; but lay before you some remarkable illustrations of its protective influence over the structures which it animates, and of its modifying power over physical laws and agencies. * Du.trochet thought that he could form muscular fibre from the albumen of the blood, by the aid of galvanism. The appear- ances which he produced were, however, only such as would result from the action of physical, not vital laws. L 146 LETTER IV. Living bodies are subject to chemical and other physical laws to such an extent only as is conducive to their conservation. Beyond this they are freed from their control, and modify or suspend their operation, but for organisation universal and omnipotent. The proofs of this fact are of such a kind, and so strong, that it seems hardly possible for a reasonable being to be acquainted with them, and not to be convinced that the principle which distinguishes organic from inorganic existences is independent of matter, and constitutes a wholly distinct agency. The phenomena of life, as far as we can trace their causes, appear to be generally produced by the same means as are employed in the production of similar phenomena in the inorganic world. Thus, combustion is produced by the union of oxygen, one of the constituents of atmospheric air, with portions of an inflammable principle called carbon, which enters largely into the com- position of most bodies. The same phenomenon takes place in the production of animal heat, the oxygen of the air being united in respiration with a portion of the carbon which is contained in the blood. From this provision, made for its evo- lution, we might, even in the absence of any direct proof, reasonably infer that heat was an agent of great importance in the animal economy : we have, however, decisive and abundant evidence to prove that such is indeed the case. But the LETTER IV. 147 agency of heat in the production of the phenomena of hfe, is widely different from that which it exerts over unorganised bodies ; and the modifications which it undergoes are strikingly illustrative of the power of the living principle in controlling the operation of physical laws. One of the laws of heat is, its tendency to become equally diffused through all adjoining bodies, the higher temperature of some being speedily reduced by the transference of a portion of their heat to the others. From the operation of this law living beings are alone exempted. Whatever be the heat or coldness of the surround- ing media, they preserve that exact degree of tem- perature which is essential to the continuance of their existence ; neither, when enveloped in highly heated air, do they attract to themselves beyond a certain quantity of it ; nor, on the contrary, when in an intensely cold atmosphere, do they lose any portion of their genial warmth. They maintain a fixed temperature in spite of all external circum- stances.* The human body maintains the same * It is essential to the preservation of animals that their heat should reach and be maintained at a certain elevation ; and hence the provisions made in the formation of those animals whose blood-heat is above the standard of the atmosphere, to counteract the natural tendency of heat to become equalised. One of the means resorted to for this purpose is to envelope the body in those materials which transmit heat with difficulty. Accordingly we find those animals which most require the protection of such coverings, as birds and warm-blooded animals, clothed with 148 LETTER IV. heat in the intensely cold climates of Norway, Siberia, and Kamschatka, where the mercury sinks into the bulb of the thermometer and becomes frozen, as in Senegal and on the scorching shores of Africa, where the thermometer has been known to rise to 133 in the shade.* Even under the high temperature of 240, life can be maintained for a short time, as in the instance of Sir C. Blagden ;f in the heated rooms of experimenters it has been encountered at 260 ; and in stoves used for drying grain as high as 290. On one occasion, when it stood at 270, a girl employed in attending these ovens went into one of them, and remained for a quarter of an hour. She could bear 292^ for ten minutes; but when it reached 315, she could not support it longer than five minutes. During these experiments meat and fruit were baking by the side of the experimenter. It was afterwards found that persons could stay for some minutes in a room heated to 260, in which the breath of the experimenter, expelled upon the bulb of the thermometer, reduced it rapidly ; a fact which clearly proved that the heat of his body (as was likewise shewn by placing the bulb of fur or feathers, two of the greatest non-conductors of heat. When man covers himself with materials of this nature, he is merely imitating the means adopted by the Creator for the pre- servation of the lower animals. * Lawrence's Lectures on the Natural History of Man. t Philosophical Transactions, vol. Ixv. p. 489. LETTER IV. 149 the thermometer under the tongue) did not exceed the natural heat, which is about 98.* On the other hand, in the coldest regions of the earth the blood maintains its fixed tempera- ture, while the atmosphere around is far below the freezing-point of water, or even of quicksilver (which is forty degrees lower), and where brandy and ink become frozen in a room where there is a fire. In this intense cold the Greenlander will expose himself in the open air, with his head and neck uncovered, and a very slender covering upon his body.f Wood says, the Greenland dogs live a very hardy life, sleeping constantly abroad, where they make a lodge in the snow, in which they lie completely covered except their noses. | Birds retain the same heat in their blood when perched on the icebergs around Spitzbergen, as when seated upon the branches of a tropical forest. The blood of the whale, in the frozen-bound waters * Lawrence's Introductory Lecture on Comparative Anatomy, p. 135. t lb. p. 133. + Zoography, vol. i. p. 170. The capability of the human body to resist heat and cold to so great an extent, explains why man is able to inhabit countries under every variety of tem- perature, from one extreme to the other. Humboldt has shewn that at Cumana, within the trojjics, there is a difference of only four degrees between the temperature of the warmest and the coldest months. Whereas at Quebec and Pekin, in the tem- perate zones, the annual variation amounts to about 60° (Fahren- heit).— Lyell's Geology, vol. ii. p. 390. 150 LETTER IV. of the northern seas, is warmer than that of the floating turtle of the Indian ocean, or the tardy crocodile of the Nile, where the sun's heat is sufficient to hatch their eggs without incubation. Mr. Hunter shewed that an egg possessed of the principle of life preserves that degree of heat which is essential to its existence, and which, in the case alluded to, was three degrees above the atmosphere in which the egg was placed ; and that this was not the case with those eggs whose vital principle was extinct.* So subservient is the agency of heat made to the wants and the instincts of animals, that while one species of birds is leaving our coasts to win- ter in a warmer climate, we see another species moving still further north in defiance of the cold which they will encounter.f How, I would ask, can such results proceed from physical causes alone, when it is plain those very causes are made to act out of their nature ? Surely we cannot behold these things, and compare them with what has been revealed, without believing that they proceed from the life-giving power of Him who sustains them above the operation of any cause which we see around us. All living bodies have the property, in differ- * Animal Economy. t There cannot be a more satisfactory proof than this, that temperature can have little effect in regulating the geographical distribution of animals, if separately viewed as a cause. LETTER IV. 151 ent degrees, of generating heat, according to the chemical changes required to be effected in each body ; and hereafter we shall see that these de- grees are most beautifully adapted to the habits of the animal, and to the element in which it exists. The temperature of vegetables and cold-blooded animals is very little above the surrounding media. The standard heat of man is about 79 ; in other viviparous animals about 100; while in birds it rises to 107. The tenacity with which the hving fabric maintains this necessary degree of heat has been already sufficiently illustrated. The discoveries made in animal chemistry seem to shew that the wonderful changes effected in the blood of living animals are attributable to the powerful operation of heat. Heat, then, is concerned in the movement of the blood, and therefore it is the prime agent in carrying on the functions of every organ of the body. But this its power is not inherent in itself, but is communicated to it by the agency of another principle, called electricity, which is rendered subservient to the purposes of animal existence by means of a particular set of organs, the brain and nerves, whose function it is to transmit it. Heat and electricity, then, by their conjoint operation, produce the phenomena of secretion. I told you in my last Letter, that the materials which form the brain and nerves exist 152 LETTER IV. in the blood; and it is ascertained that one-fifth part of the blood is sent to the brain alone. We might reasonably infer from this fact, that the brain and nervous system perform some very pro- minent part in the machinery of life; and this inference is established by the discovery of their function, above explained. Electricity, like heat, pervades all bodies ; but when it is employed in the animal economy, we shall see that, like heat, it becomes obedient to the living principle. As this agent, however, is so essential to hfe, it will furnish sufficient materials for another Letter. LETTER V. " The Spirit of God hath made me, and the breath of the Almighty hath given me life." — Job, xxxiii. 4. " And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life, and man became a living soul." — Gen. ii. 7. " For the life of all flesh is the blood thereof." — Levit. xvii. 14. Having shewn the relation which heat bears to the principle of life^ I shall now proceed to point out the connexion between that principle and electricity. ' Electricity (from the Greek word jjXskt^ov [elek- tron], amber, because it was first discovered in this substance, or from zXtcoj [helko], to draw, on account of its magnetic power) is an agent pervading all bodies, and is extensively concerned in all their operations. It is quite imponderable, for the finest balance has never been able to detect the slightest weight accompanying it. Like heat, it exhibits itself to us only by its effects ; the more striking of which is its property of attracting and repelling bodies : it can be insulated in some more readily than in others, and those bodies that do not insulate or retain it, transmit or conduct it. When it is expelled from bodies, it produces sparks and sound ; but its power of producing different phenomena is greatly in- fluenced by its condensation or expansion. It exists in two very different states, which are called positive and negative, or vitreous and resinous. 154 LETTER V. When these two states of electricity are combined, they neutrahse each other, and in that case the body containing them shews no signs of their pre- sence ; but when they are separated from each other, and accmnulated either in different bodies or in different parts of the same body, then the bodies so circumstanced exhibit signs of elec- tricity. When separated, electricity is capable of moving through its conductors with incalculable velocity. Sir William Watson passed a charge of electricity through a metallic wire several miles in length : its velocity was so great, that no per- ceptible time was found to elapse between com- pleting the circuit and receiving the shock. Mr. Cavendish, who was the first to reduce the theory of electricity to mathematical precision, found that iron wire conducts four hundred million times better than pure water. These discoveries excited the attention of Frank- lin and Volta : the former shewed the identity of lightning and electricity ; the latter first made known the fact, that conductors, when brought into con- tact, acquire different electric states ; and this dis- covery led him to construct an instrument, called, after his name, the Voltaic pile, and composed of alternate plates of zinc, copper, and pieces of cloth.* * See the account in the Philosophical Transactions for the year 1800. Since this time Seebeck has discovered that bars of the same metal, heated to different degrees of temperature, and placed one upon the other, will become electric ; and that even a LETTER V. 155 Previous to this time, Galvani, a professor at Bologna, being engaged in making electrical ex- periments, observed on one occasion that some frogs, which had been flayed and were near his machine, became convulsed each time a spark was drawn from the apparatus. He investigated the subject, and found that when a metallic conductor is applied to a nerve and a muscle, the three forming a circuit, each being in contact with the other two, violent contraction is produced in the muscle. His discoveries were called, after his name. Galvanism. The singular effects of elec- tricity on the animal body, disclosed by the re- searches of Galvani and Volta, have given rise to the idea that the brain is an electric pile constantly in action, and discharging itself at regular intervals when a given quantity of the electric fluid has been generated, which, through its conductors the nerves, it communicates to the heart, and thus excites the pulsation of that organ ; to the diaphragm, thereby producing respiration ; to the stomach, which is by this means enabled to carry on the process of digestion ; and to all other organs, for the purpose of setting them in action, simple metal bar heated at one end, the other being of a diiFerent temperature, has the same property. Indeed, a weak galvanic pile has been formed by Buntzen of alternate layers of muscle and nerve ; and Kaemtz has shewn that galvanic piles can be con- structed from organic substances alone. — Consult Muller, Phy- siology, p. 64 et seq. (translation.) 156 LETTER V. and of qualifying them to perform their various functions. That electricity exists in animals, there is no ground for doubting, for it is given out by the torpedo, the electric eel, and other animals ; and that the brain also is an electric machine, I think I shall be able to prove. Electricity, as I have already said, is modified by the living principle ;* and we shall find that its action in animals is arrested by causes which do not appear to operate upon it in inorganic bodies. Animal electricity cannot produce its effects with the same facility as common electricity ; the former appears to be a weaker agent than the latter, not display- ing the phenomena of positive, but those of ne- gative, electricity. Mr. Walsh, in his paperf on the torpedo, has proved that electricity, as it is condensed or rarefied, produces, in the one case, light, heat, attraction, and repulsion ; and in the other the same phenomena as are exhibited by the torpedo ; that is, it does not produce sparks and their attendant sound, nor attract and repel light * It is highly probable that the luminous appearance which the bodies of many marine animals present is produced by elec- tricity, in some way modified by the living principle. Its disap- pearance as soon as life is extinct favours this idea ; and Sir E. Home has proved that it cannot be caused by a phosphorescent substance, for it is found to be strongest and most constant when oxygen is excluded ; now phosphorus burns intensely when exposed to this gas. t Philosophical Transactions abridged, vol. ix. p. 469. LETTER V. 157 bodies, but in effecting its equilibrium (a process identical with the discharge of electricity from the electric organs of that animal), runs through a considerable circuit of different conductors, if perfectly continuous, and makes us sensible of an impulse in its passage. These latter are the phe- nomena which result from the discharge of the electric fluid by the torpedo, so that we cannot be mistaken in referring them in both cases to the same cause.* A stronger proof of the identity of the phe- nomena of the galvanic pile and those of the brain, is supphed by the experiments of Dr. Wilson Philip, which shewed that when the lungs of ani- mals are deprived of the nervous influence, by cutting off their communications with the brain, their function is destroyed ; and that when di- gestion is interrupted, by withdrawing the same influence from the stomach, these two vital func- tions are renewed by exposing the organs which perform them to the influence of the galvanic pile. The following experiment of Dr. W. Philip is adduced to shew that electricity and the ner- vous power are identical, inasmuch as it proves * It is, however, right to observe here, that no one has ever been able to detect electric currents in the nerves ; although PfafF and Ahrens, by the aid of a gold-leaf electrometer, have proved that free electricity is given out by man. It exists in a positive state generally, and is greater in quantity at different times of the day, in different constitutions, and under different degrees of heat. 158 LETTER V. that they have the same influence in promoting the phenomena of secretion. The eighth pair of nerves, which are distributed to the stomach, were divided by incisions in the necks of several hving rabbits. After the operation, the parsley which they ate remained without alteration in their sto- machs ; and the animals, after evincing much difii- culty of breathing, died, apparently of suffocation. But when in other rabbits, similarly treated, the galvanic discharge was transmitted along the nerve below its division to a disc of silver placed in close contact with the skin of the animal, opposite to its stomach, no difficulty of breathing occurred. The voltaic action being kept up for twenty-six hours, the rabbits were then killed, and the parsley was found as perfectly digested as that in healthy rabbits fed at the same time ; and these experi- ments were several times repeated, with similar results.* Numerous experiments and facts shew that destruction, or injury to a certain extent, of the brain produces instant death ; you will therefore not be surprised to hear that, for many ages, the brain was believed to be the focus of nervous power, and the source and seat of the living prin- ciple. Subsequent experiments have, however, clearly proved how dependent the functions of this * See Dr. Philip's Experimental Inquiry into the Laws of the Vital Functions, and also his papers in the Philosophical Transactions. LETTER V. 159 organ are upon other agents, and have demon- strated that any body which can give out elec- tricity is capable of manifesting the same phe- nomena as are brought about by the nervous system of animals ; thereby shewing not only that that system is dependent upon some other agent for the performance of its functions, but also that in its operation it resembles ordinary electricity.* The experiments of Weinhold prove that the principle of hfe is independent of the nervous system, although that system is made use of to prepare and convey electricity to the different organs of the body. For example ; he cut off a cat's head, and when its arterial pulsation and muscular motion had ceased, took out the spinal marrow, and placed in its stead an amalgam of mercury, silver, and zinc ; immediately the pulsa- tion recommenced, and the body made a variety of movements. He removed the brain and spinal cord of another cat, and filled up the skull and spinal canal with the same metaUic mixture. Life * Le Gallois, the great French physiologist, by a series of experiments, in which he decapitated animals and kept them alive by artificial respiration, endeavoured to prove that the mo- tion of the heart depended upon the spinal marrow, and that it immediately ceased when that was removed. Dr. Wilson Philip, however, has clearly shewn that these experiments do not esta- blish Le Gallois' conclusion ; for he removed the brain and spinal cord of a rabbit, having previously rendered it insensible by a blow upon the head, and notwithstanding this, the circulation of the blood was maintained by means of artificial respiration. 160 LETTER V. appeared to be instantaneously restored ; the ani- mal lifted up its head, opened and shut its eyes, and, looking with a fixed stare, endeavoured to walk ; and whenever it fell, tried to raise itself again upon its paws. It continued in this state for twenty minutes, when it fell down and re- mained motionless. During all the time, the cir- culation of the blood appeared to go on regularly ; the secretion of the gastric juice was more than usual, and the animal heat was re-established. (See the account in the Florence Anthology,) Dr. Ure, in company with Dr. JefPray and others, per- formed some exceedingly interesting experiments upon the dead body of a criminal. He applied the rod of one end of the galvanic battery to the spinal marrow, while that at the other end touched the great nerve of the leg. Every muscle of the body was immediately agitated with convulsive move- ments, resembling a violent shuddering from cold ; and the leg, being previously bent, was thrown out with such violence as nearly to overturn one of the assistants. The rods were then removed, and one placed upon the phrenic nerve in the neck (which is the nerve distributed to the diaphragm, the organ mainly concerned in carrying on respira- tion), while the other was applied to the great head of the diaphragm. Full and laborious breath- ing instantly commenced, and the chest heaved and fell. This process was continued without in- terruption as long as the electric discharges were LETTER V. 161 applied. Similar results were obtained by placing the conducting rods upon the nerves of the face and of the arm ; in the one case producing simul- taneous action of all the muscles of the face — in the other, a nimble movement of the fingers, and a convulsive agitation of the arm. Enough has now perhaps been said to convince you that the brain is not the cause of life — a truth which was long since hinted at by Haller, in his experiments on the irritability of the heart ; and Mr. Hunter shewed that the power of produ- cing animal heat — so important, as I have shewn, in the vital economy — did not certainly depend upon the nervous system ; for it is found in animals that have neither brain nor nerves.* I must not omit to mention, however, that Sir B. Brodie's experi- ments have proved that the power of generating heat is as effectually destroyed in animals possessing a brain, by depriving them of sensibility by means of narcotics (the lungs being afterwards artificially inflated), as by decapitation ; and that the power is restored in exact proportion to the return of sensi- bility, when the influence of the poison has ceased to act upon the system.f You have seen that, after decapitation, as in the experiments of Le Gallois, an animal continued to live by means of artificial respiration, during as long a period of * See Hunter on the Animal Economy, p. 103. -j- See his Experiments in the Philosophical Transactions for 1811. M 162 LETTER V. time as is requisite to kill an animal by suffoca- tion. In the one case, the influence of the brain is entirely removed, so that it cannot act upon the blood ; in the other, the influence of the brain is destroyed by depriving that organ of the oxygen which is conveyed to it in the blood. It is quite evident, then, that in the present state of science, our knowledge of the principle of life is limited to the fact, that atmospheric air, by means of the stimulating power of its oxygen, pro- pels the blood through the lungs, and thus gives rise to all the vital phenomena. That the passage of the living current through the pulmonary organs is not determined by any other than an extraneous cause, is rendered certain by the experiments made on asphyxised animals, that is, on animals which have been suffocated. If air be excluded from the lungs, the power and stimulus derived from this source are rapidly withdrawn, and the animal be- comes inanimate, and eventually stiff and cold. The large quantity of air consumed by animals is suffi- cient proof of the great importance of that element in their economy, and may convince you that I have not magnified its influence in producing the phe- nomena of life. " An adult man," says Plenck, " draws into his lungs at each respiration about thirty cubic inches of atmospheric air ; and as in the space of a minute we inspire fifteen times, hence every minute we require four hundred and fifty, every hour twenty-seven thousand, and in twenty- LETTER V. 163 four hours six hundred and forty-eight thousand cubic inches of atmospheric air for respiration."* Thus the electricity of the brain is given out through the influence of the blood, and the mo- tion and influence of the blood are derived from the oxygen of the air. We are therefore satis- fied, that all the researches w^hich have hitherto been made in physiology have brought us to re- sults in perfect harmony with the fact made known by revelation, that " God breathed into his nostrils the breath of life, and man became a living soul :"f a most extraordinary coincidence and confirma- tion, if revelation be, as we are told by some, no more than the mere wisdom of man. Can we, then, persist in the belief that the prin- ciple of life, which I have shewn to be the support of all living bodies, in defiance of the perpetual operation of those agents which, in its absence, so rapidly decompose them, is a principle dependent on matter ? Is it reasonable to believe that a material body should have the wonderful property of producing that immaterial principle within it, which is to bring about all those phenomena by which it distinguishes the matter to which it is united from all other kinds of matter ? ^ If so, * Plenck's Hygrology, translated by Hooper, p. 104. t Gjen. ii. 7, X Cuvier's idea of this principle is far too material : he says, " There is great probability that it is by an imponderable fluid that the nerve acts upon the fibre, and that this nervous fluid is 164 LETTER V. why cannot the body perpetuate that principle ? Why is it that an accident can withdraw it alto- gether, and that no combination of mechanical means that may be employed to produce ijnita- tioiis of its phenomena, however long continued, can cause it to return ? The vital principle, it is true, engages heat and electricity to fulfil the chemical or the mechanical purposes of the body ; but we must not forget, that even these agents it controls and renders subservient to itself ; and that when it is withdrawn, these agents, being unre- strained in their operation, most rapidly bring the body to destruction. And even supposing the body had the power to generate this living principle, it would still remain to be known whence this power was derived : for as yet we can only shew that it is able to generate heat and electricity. But heat and electricity are in subjection to life ; they can- not act upon the living body in the same manner as upon any other body, but work under the direc- tion of a higher principle. Fruitless indeed must be the attempt to prove drawn from the blood and secreted (or separated) by the medullary matter" (substance of the brain.)* I believe that the living prin- ciple has just as much, and no more, to do vi'ith the brain, as light has to do with a piece of glass through which it is trans- mitted ; and as light cannot pass through a body that is not transparent, so the hving principle cannot operate upon the body by any other medium than nervous matter. Bftgne Animal, Introduct. p. 30. LETTER V. 165 that the vital principle, which on such strong evi- dence we beheve to be not only imperishable itself, but able also to preserve from destruction bodies otherwise most perishable, owes its existence to any thing created and perishable. Another fact deserving of consideration is, that there are many more contrivances and apparatus necessary to fit a material body to contain, or be inhabited by, the animating principle, than would be required were that principle a mere modification of caloric or electricity;* which agents, it is, moreover, to be * Mr. Kirby, in his Bridgewater Treatise, accuses Lamarck, the French zoologist, and that very justly, of assimilating too closely the vital principle to certain imponderable fluids, as heat, electricity, and the magnetic fluid ; so that he makes it almost dependent upon them for its existence. " Now," says Mr. Kirby, " though heat, electricity, &c. are necessary to put the principle of life in motion, they evidently do not impart it. The seed of a vegetable, or the egg of a bird, have each of them, if I may so speak, a punctum saliens, a radiating principle, which. Tinder cer- tain circumstances, they can retain in a latent state for a consider- able time ; but if once that principle be extinct, no apphcation of heat or electricity, under any form, can revive it, so as to com- mence any development of the germ it animated. Experiments have been made upon human bodies, and upon those of other animals, which, by the apphcation of galvanism after death, have exhibited various muscular movements, such as lifting the eye- lids, moving the arms and legs, &c. ; but though motions usually produced by the will acting by the nerves upon the muscles have thus bfeen generated by a species of the electric fluid, pro\dng the affinity with the nervous power or fluid, yet the subjects of the experiment, when the action was intermitted, continued still without life, no return of that power or essence, which was fled 166 LETTER V. remembered, are subject to the control of this very principle, which has most absurdly been thought not simply to resemble, but even to be identical with them. But the vital principle not only directs the oper- ation of heat and electricity — not only displays all those phenomena which we might refer to these agents solely — but, by some mysterious conjunction with the materials existing in the blood, produces in one organ the gastric juice, in another bile, in an- other saliva, &c. Now, if electricity governs the motive power, why is it that, although conveyed in the blood under apparently similar circumstances, it in one case produces the phenomenon of touch, in another of smell, in another of regular pulsation ? It is true that appropriate machinery is furnished for the manifestation of each of these phenomena ; yet, supposing that both heat and electricity are necessary agents in their production, what is, and whence comes, the power which selects these agents for ever, being effected by It ; which seems to render it clear, that neither caloric nor electricity, though essential concomitants of life, form its essence."* I cannot refrain from observing, that the definition given by our author of the vital principle, in the above passage, and in page 4 1 of the same work, where he charac- terises it as "a radiant principle, shewing itself by successive developments," affords no elucidation of the subject ; for we might as well say that one animal is not another, as that they are different mechanical contrivances for the display of the living principle. * Kirby's Treatise, Introduction, p. 42. LETTER V. 167 in accurate proportions, without wliich they might produce any other effect than that they actually do ? For we know that, in inorganic bodies, all the varieties of their external conformation are refer- rible to the same combination of principles or atoms differently arranged ; and it is evident that inor- ganic bodies are not results of the operation of mere heat, otherwise why can we not advance in our knowledge of synthesis ; why can we not manu- facture a ruby, an emerald, or a diamond ? The fact is as obvious in inorganic bodies as in those which are organised : in both departments of crea- tion, the principles which determine the structure and properties of bodies are wholly beyond the knowledge and control of man. Electricity, then, is an essential agent in the operations of living bodies : it helps to explain the phenomena of secretion and digestion, as well as those of motion and sensation. The manner in which it is made to produce such remarkable and dissimilar effects, proves that the living principle exerts not less influence over it than over heat. We know that the proximate principles of matter are oxygen, hydrogen, carbon, and azote, and that these principles, combined in different proportions, and under different circumstances, unknown to chemical synthesis, produce all the varieties of external form, colour, weight — in a word, of natu- ral qualities, in every thing existing on this globe ; 168 LETTER V. and though we know the proportions of these prin- ciples which compose many substances, we are, nevertheless, at a loss to account for the plujsical cause of their difference. In the same way, may not electricity, governed and combined in certain fixed proportions with heat by the hving principle, give rise to the phenomena of sensation ? The vital principle is manifested in, and deve- loped by, an infinite variety of bodily structures, upon which it has been bestowed in very different degrees. In all its forms, however, it is calculated to increase our wonder, and enlarge our praise, of that infinite Being who is the " God of the spirits of all flesh." These successive developments are not the vital principle itself, but only the diversity of contrivance which the Creator has made, that we may behold what great resources he has at his disposal. There is a difficulty which meets all inquiries into the hidden mystery of our creation, w^hich is presumptive evidence of its impenetrable nature. I have, however, shewn that there is a phenomenon even in the material world which we cannot comprehend, and whose cause we are unable to discover. We cannot comprehend the nature of the material parts of the machinery of hving beings ; it must necessarily, therefore, be folly to suppose we can define that immaterial agent which sets it in motion. That some essential but incomprehensible agent LETTER V. 1 69 is added to all organised bodies, you have now, I think, all the evidence that can reasonably be required ; and that this agent is held by man under a peculiar tenure, I shall endeavour to make clear when comparing his organisation with that of animals. LETTER VI. " And God said, Let us make man in our image, after our like- ness ; and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth."— Gm. i. 26. " We are not all body, nor mere animal creatures. We find we have a more noble nature than the inanimate, or brutal part of the creation. We cannot only move and act more freely, but we observe in ourselves a capacity of reflection, study, and forecast, and various mental operations, which irrational animals discover no symptoms of. Our souls, therefore, must be of a more excellent nature than theirs ; and, from the power of thought with which they are endowed, they are proved to be immaterial substances, and consequently in their own nature capable of immortality ; and that they are actually immortal, or wiU never die, the sacred Scriptures do abundantly testify." — Mason on Self-Knoioledge, chap. ii. In the two preceding Letters I have endeavoured to shew, as far as our analysis will go, that there is nothing in the nature or constitution of organic bodies to account for that principle of life which they possess. I have glanced at the resemblance which that principle bears to other principles that are manifested in inorganic bodies, such as heat, electricity, &c., with the nature of which also we are wholly unacquainted. The phenomena pro- duced by these agents have been contrasted with those of the living principle ; and I hope I have shewn that they are in many respects widely dif- LETTER VI. 171 ferent. I shall now proceed to contemplate more particularly the arrangement of living bodies, in reference to their adaptation to the circumstances in which they are placed, and the purposes they are destined to fulfil ; in doing which, I am na- turally led first to consider the organisation of man, constituting as he does the highest link in the chain of animal creation. The consideration of the physical conformation of man in relation to the objects which surround him, and the place which he fills in the great family of creation, will, if I mistake not, lead to the conclusion, that his diffusion over the whole earth, resulting principally from his power to en- dure all varieties of temperature, has been brought about by means of peculiarities in his structure bestowed upon him for this express purpose. Thus, while all other animals have been chained down, as it were, to certain localities, by the limited adaptation of their bodies to circumstances and places as variable as the surface of the globe, man knows no limit to his extension, save those of the earth itself. In the deep valley, below the level of the ocean, as well as on the mountain- top reared above the clouds, he has pitched his habitation ; there he exists, multiplies, and exerts his universal dominion. In the burning regions of the south, where the vegetable kingdom displays its utmost luxuriance and splendour ; and in the arctic circle also, where vegetable life is almost 172 LETTER VI. extinct, man is found capable not only of existing, but of enjoying his existence. This fact is strik- ing, even to the superficial observer. It is a phy- sical evidence, as his reason is a moral one, that man was destined to hold a superiority over all the creatures that surround him. If we contemplate the lower animals apart from their defence, support, and reproduction, we can see no end to which their creation is sub- servient ; since all the beautiful contrivances and wonderful machinery of their bodies have no other apparent purpose than the accomplishment of these important objects. It is not so with man ; for in him we find other important ends required to be attained, to aid in the accomplishment of which his organisation is expressly and wisely fitted. The scheme of his creation has a wider scope ; and we behold him possessed of an organisation which, unlike that of the beasts that perish, has reference to other spheres of action besides the world around him. He is enabled to say with the patriarch, " God our Maker teacheth us more than the beasts of the earth, and maketh us wiser than the fowls of heaven :"* and though it cannot be said that man is indebted for his superiority over the creature to his reason alone, yet all his other attributes derive much of their value and power from this presiding and directing attribute. When, for example, we consider his distribution =*= Job, XXXV. 10, 11. LETTER VI, 173 over the entire globe, — a circumstance which, as I have already observed, is peculiar to him, and does not characterise even those animals that, from their close resemblance to him, have been called anthropomorphous (from dv&^omoc, [anthropos], a man, and (Lo^(pyj [morphe],/o/'Wi, — having the form of man), but which nevertheless are confined to a comparatively limited space, — we are almost ready to infer some constitution of parts and general durability of frame which is not given to any other animal. But it is the mind which employs the structure of the body to such useful ends, and lifts it up above the rest of the creation, accom- modating it to circumstances and places in which, without such instrumentality, it would be wholly unable to exist. Some physiologists are disposed to think that the influence of mind over matter is not so great as I have now represented ; and they assure us that man could never become, as he is, the inhabitant of all climates, if he did not possess the most enduring and flexible corporeal frame. Yet that this capability is not referrible to the cause to which they ascribe it, but to man's foresight and ingenuity, is obvious. " The arts of human ingenuity furnish a defence against the dangers that surround our species in every region. Accordingly we see the same nation pass into all the climates of the earth ; reside whole winters near the pole ; plant colonies beneath the equator ; pursue their connnerce, and establish their fac- 174 LETTER VI. tories, in Africa, Asia, and America. They can equally live under a burning sky or an ice-bound soil, and inhabit regions where the hardiest animals cannot exist."* Other animals have no such power of defending themselves against the injurious operations of a new climate ; they are all under the direction of laws, which are modified in their application to every individual species, in order to fit them to exist under the diversified conditions of climate, food, locality, and other circumstances, which naturally surround them. The more we enter into the de- tails of these beautiful combinations and adapta- tions, the more profound will be our conviction that they are manifestations of the infinite wisdom of the omniscient God. The locality of animals, for example, is in a great measure determined by the kind of food adapted to support them, and which an unerring instinct directs them to select ; and the reason why they do not occupy one cli- mate or country as well as any other, as man does, is because they are unable to accommodate themselves to the differences in food, &c. which a change of circumstances occasions. Thus it is that many species of birds (as, for instance, the class trochilus) are physically prevented from existing out of the tropical regions, by the fact that their food consists entirely of insects produced * Lawrence's Lectures on the Natural History of Man, p. 194. LETTER VI. 175 only in those parts of the world. The hum- ming-bird not only feeds upon insects all the year round, but in all probability upon a variety peculiar to the tropical climes they inhabit. Monkeys, again, are found indigenous in a particular region only, having ends to answer by their existence which could not be effected were they removed elsewhere ; their natural food being in perfection and in sufficient abundance in that part of the globe only to which they are attached. This law of locahty, to which the several cir- cumstances of temperature, food, &c. are all made subservient, is indispensable to the keeping up of that balance in the living creation which alone renders possible the simultaneous existence of so many different races and grades of beings ; and to maintain which, we find that all animals are fixed in their respective stations by inherent and im- mutable impulses. Thus, there are fishes ap- pointed to every depth of the sea, birds to take their different elevations in the air, and animals created to endure the greatest degree of tempera- ture which is experienced on the earth's surface. It is not so difficult for animals to exist under great extremes of temperature as it is for them to exist otherwise than under that peculiar ordi- nation of Providence, which, for the fulfilment of the most important ends, demands that each spe- cies of animal should be confined to the region or spot assigned to it by its Creator. 176 LETTER VI. But to say that the organisation of man is superior to that of other animals, because he can endure a " winter's cold," or because he can ac- commodate himself to a heat exceeding by many degrees the temperature to which he has been accustomed, is not true, neither is it borne out by physiological experiment. Other animals could bear the same changes, and accommodate them- selves in a similar manner, if they had the faculty of reason, which teaches man how to discriminate, to compare, and thence to provide for all the varie- ties of his situation, which, but for this, he could no more withstand than can the inferior animals. There are dogs in Kamschatka which live con- stantly in the snow, sleeping and living there as their natural abode. On the other hand, there are animals which live and thrive in climates so hot as to be altogether incompatible with human existence for any long period of time. The only difference, then, between the consti- tution of man and that of other animals, is the possession by man of that high and distinguishing faculty of reason, which is wholly wanting in the inferior races, and to which his superiority over them is solely attributable ; for though his funda- mental distinction involves a difference of organi- sation, it would obviously be incorrect to treat the latter as an original cause. The limited adaptation of the bodies of the lower animals to the different circumstances above LETTER VI. 177 referred to, is no proof that their organisation is inferior. The pecuharities of man's organisation no more constitute it superior to theirs, than the possession by one race of animals of organs and qualities that do not belong to others justify us in considering the latter inferior to the former. If man's ability to extend his race in every climate is the result of his organisation alone, then that circumstance is no proof that he is superior to a monkey, a pig, or a dog ; for, place either of these animals in any part of the globe, and they will exist, and feed on almost every substance. Most writers express themselves very obscurely when attempting to explain in what respect the mere organisation of man is superior to that of the brutes. Sir C. Bell says, " In discussing the sub- ject of the progressive improvement of organised beings, it is affirmed that the last created of all — man — is not superior in organisation to the others, and that if deprived of intellectual power, he is in- ferior to the brutes. I am not arguing to support the theory of the gradual development and im- provement of organisation ; but, however indiffer- ent to the tendency of the argument, I must not admit the statement. Man is superior in organi- sation to the brutes, superior in strength, in that constitutional property which enables him to fulfil his destinies, by extending his race in every cli- mate, and living on every variety of nutriment."* * On the Hand, p. 42. N 178 LETTER VI. We would rather concur in the learned professor's admission which precedes this sentence, that " the creation of a living animal, the bestowing of life on a corporeal frame, however simple that body, is of itself an act of creative power so inconceivably great, that we can have no title to presume that any change in the organisation, such as the provision of bones or muscles, or the production of new organs of sense, is a higher effort of that power." In one place we understand Dr. Kidd to infer, that the organisation of man differs in no respect from that of animals. He says, " Although, when viewed in the aggregate of his faculties, moral as well as physical, man confessedly holds the first rank among animals, yet if we exclude from our consideration those intellectual powers and moral qualities by which he is essentially characterised, and confine our views to his mere animal nature, we find that he scarcely differs in any important point from any of the species of the higher classes. In each there is the same necessity for air, and sleep, and food ; and the nature of the food, and the mode of its digestion, are not materially dif- ferent : the nutrient fluid, extracted by the process of digestion, is converted into blood of the same character, and distributed in the same manner through the system : the constituent parts of the body, and their mode of growth, are almost pre- cisely the same; for the bone, muscle, tendon, skin, hair, and brain of the horse, deer, tiger, or LETTER VI. 179 bccar, scarcely differ in their chemical or physical characters from the correspondent parts in man : similar secretions, as the bile, tears, and saliva, are separated by similarly constructed organs; and similar parts become similarly diseased : the spe- cial senses of sight, hearing, taste, and smell, are exercised through the medium of similar organs, simply modified according to the particular wants of individual species ; the sources of mere bodily pain or pleasure are generally the same ; the in- stinctive affections, passions, and propensities are the same, and are manifested in the same way ; the angry look of a dog, for instance, bespeaking the internal feelings as strongly as that of the man ; and the playful and rapid movements of the young puppy resembling the careless hilarity of childhood, no less than the staid motions and wary eye of the aged hound resemble the sedateness of the aged human being."* But how can we reconcile this with the reasoning which follows ? " And yet, even if we entirely omit the consideration of the soul, that immaterial and immortal principle which is for a time united to his body, and view him only in his merely animal character, man is still the most excellent of animals. How confined are the powers of other animals, considered generally, when com- pared with those of the human species ! The comb' of the bee is, indeed, in its construction * Physical History of Man, p. 9. 180 LETTER VI. wonderful ; and so is even the nest of the bird, or the habitation of the beaver. But these animals could never be taught to fabricate or to use the simplest of those machines or instruments which man, even in a very partially civihsed state, is in the daily habit of making and employing ; much less could they be taught to perform those compli- cated operations which result from their employ- ment."* " Man, then, is in every sense superior in organisation, as well as in intellectual powers, to all other animals."f This is the unavoidable conclu- sion deduced fi'om such reasoning ; but, as I shall presently prove, it is false, originating in the attempt to compare one set of animals with another, in refer- ence to the sphere for which the latter alone were designed, and consequently out of that in which they have been placed by their Creator. The connexion of mind and matter, and the all-important influence which the former exerts over the latter, is a subject the consideration of which would lead us away from that which more particularly demands our attention in this place ; and having stated how far I believe that influ- ence to extend, I shall now proceed to take a view of the several physical distinctions which separate man from animals — in a word, to consider him as an object of zoology ; and having enume- rated and reviewed these distinctions, and pointed * Physical History of Man, p. 18. f lb. p. 20. LETTER VI. 181 out the great assistance which the physical man receives from the intellectual, I shall then shew how wisely he has been formed to be the inhabitant of all parts of the globe. Revelation tells us, that man was to " have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth."* And accordingly we shall find that the configuration of his body, as well as of each subordinate instrument, is such as to qualify him for the exercise of this extensive power, with which he has been exclusively invested. The distinguishing characteristics which sepa- rate man from all other creatures, and which enable him to fulfil the moral as well as the phy- sical duties imposed upon him, may be divided into two classes, the intellectual f and the physical. His numerous and varied intellectual faculties enable him to perceive the relation of cause and effect; from past experience to calculate, with various degi-ees of certainty, the consequences of present or future events ; and thus to provide for his safety and well-being by modifying the ope- ration of the laws of nature, or by accommodating himself to their influence in such a manner as to * Gen. i. 26. t In the term intellectual, as here used, the organ of the mind, as well as the mind itself, is included. 182 LETTER VI. render them harmless or beneficial to him. These faculties (which involve that of speech, so indis- pensable to man's social state) are brought into communication with the world of matter by means of the nervous system, with which the mind is in some mysterious and wholly incomprehensible manner connected. In particular, the brain, the centre of that system, is generally considered to be the direct instrument of the mind, the mani- festiitions of which are hence regarded as in a great measure dependent upon the development of that organ, the greater complexity and propor- tionate size of which in man, compared with the brain of other animals, is thought to be satisfac- torily accounted for by the numerous additional mental faculties which he possesses, and which re- quire a corresponding enlargement of the nervous system for their manifestation, and for bringing them into contact with the material universe. The more important of his physical peculiarities are, first, the upright position of his body, to secure which the whole conformation of the spine, of the upper and lower extremities, and of other organs, is expressly designed ; second, the peculiar structure of the digestive organs (corresponding to which is the particular formation of the jaws, and arrange- ment of the teeth), which enables him to subsist upon all kinds of food, the principal of those cir- cumstances which qualify him to become an in- LETTER VI. 183 habitant of all countries ; third, his slow growth^ long infancy, and late maturity; and fourth, the want of natural external covering. I shall, in this Letter, consider the first and most distinguishing characteristic of man, the fa- culty of comparing or reasoning; from which re- sults his abihty to appreciate all the wondrous design displayed in the great miracle of creation. Before, however, I enter upon this subject, it is right to premise, that in whatever way it may be thought necessary to associate the organisation of the body with the phenomena appearing to result from that organisation, I consider there is no ground on which to rest any hypothesis that denies the separate condition of mind and matter. The body is appointed to be the medium of com- munication between our minds and the external world; but however convincing may be the evi- dences which we discover in it of its divine origin, it must nevertheless be confessed that nothing is there presented to our observation, to lead us to ascribe to the mere materials of which it is com- posed properties which belong to no other species of matter, such as the power of modifying the influence and controUing the operation of those laws which govern the universe with irresistible sway; and we are therefore compelled to regard this power as resulting from a higher and inde- pendent existence. This, I hope, I have already made clear in the preceding Letter. If what I 184 LETTER VI. have there observed is true, it is certain that man is sustained, as there is every assurance he was created, by some supernatural power ; and this assertion holds good with respect also to the other animals, to which in so many respects he is allied. Their great similarity in structure and function leads us to infer that they had the same origin as ourselves ; but a slight investigation into the graded diversity of their structures will readily convince us that the animating principle is conferred on them upon a tenure widely differing from that upon which man enjoys it. And no gi'eater proof of this can be adduced, than the differences ob- servable between the physical structure of man and of animals. In the latter, the contrivance and skill employed in providing for the defence of their bodies, and for aiding their instinctive powers, as well as the formidable size and ferocious habits by which many of them are distinguished, are strongly contrasted with the seeming neglect of man, and his weak and defenceless appearance. But he is amply recompensed for this physical inferiority. It is true that, without the aid of his intellectual powers, he would fall far below many of the creatures which surround him ; but by means of this endowment he is enabled to sub- due every other animal that has been created, and to assert his supreme dominion over the earth. A learned writer has commented upon the re- markable power which mind exercises over matter LETTER VI. 185 in so masterly a manner, that I shall give you his words. " The situation of man on the globe he inhabits, and over which he has obtained the con- trol, is in many respects exceedingly remarkable. Compared with its other denizens, he seems, if we regard only his physical constitution, in almost every respect their inferior, and equally unpro- vided for the supply of his natural wants, and his defence against the innumerable enemies which surround him. No other animal passes so large a portion of his existence in a state of absolute helplessness, or falls in old age into such pro- tracted and lamentable imbecility. To no other warm-blooded animal has nature denied that in- dispensable covering, without which the vicissi- tudes of a temperate, and the rigours of a cold climate, are equally insupportable ; and to scarcely any has she been so sparing in external weapons, whether for attack or defence. Destitute alike of speed to avoid, and of arms to repel, the aggres- sions of his voracious foes; tenderly susceptible of atmospheric influences, and unfitted for the coarse ahments which the earth affords sponta- neously during at least two-thirds of the year, even in temperate climates, — man, if abandoned to mere instinct, would be of all creatures the most destitute and miserable. Distracted by terror and goaded by famine, — diiven to the most abject ex- pedients for concealment from his enemies, and to the most cowardly devices for the seizure and de- 186 LETTER VI. struction of his nobler prey, — his existence would be one continued subterfuge or stratagem ; his dweUing would be in dens of the earth, in clefts of rocks, or in the hollows of trees ; his food, worms and the lower reptiles, or such few and crude pro- ductions of the soil as his organs could be brought to assimilate, varied with occasional relics, mangled by more powerful beasts of prey, or contemned by their more pampered choice. Remarkable only for the absence of those powers and quahties which obtain for other animals a degree of security and respect, he would be disregarded by some, and hunted down by others ; till, after a few genera- tions, his species would become altogether extinct, or at best would be restricted to a few islands in tropical regions, where the warmth of the climate, the paucity of enemies, and the abundance of vege- table food, might permit it to linger. — Yet man is the undisputed lord of the creation. The strongest, the fiercest of his fellow-creatures — the whale, the elephant, the eagle, and the tiger — are slaughtered by him to supply his most capricious wants, or tamed to do him service, or imprisoned to make him sport. The spoils of all nature are in daily requisition for his most common uses ; yielded with more or less readiness, or wrested with re- luctance, from the mine, the forest, the ocean, and the air. Such are the first-fruits of reason."* * Herschel's Preliminary Discourse on the Study of Natural Philosophy, p. 1. LETTER VI. 187 And such are the facts which distinguish man from the creatures that are around him, and force upon our minds the conviction that, how- ever remarkable he may be in the configuration of his body, there is added to that body a distinct, superior, and supernatural principle, which renders it victorious over all other beings. When we be- hold how feeble and defenceless an instrument the corporeal structure of man appears, compared with that of other animals ; and when, on the other hand, we consider the high station which he holds, and the difficulties which he surmounts, we cannot look for a physical explanation of these wonders. We have many striking proofs of what mind can accomplish through its instrument, the body, even when this is imperfectly formed, or has been injured by accident. There exists an artist at Paris who has no trace of arms, fore-arms, or hands ; there is but one toe on each foot, and one of them is smaller than ordinary ; and yet his mind is not inferior to that of most youths of his age. He draws and paints with his feet, and ex- hibits the promise of considerable talents.* In- stances of this kind are frequently presenting themselves, where the hands, either by injury or malformation, have been rendered useless or de- stroyed, and where, in consequence, much of their office has been transferred to the feet or the * Majendie's Physiology. 188 LETTER VI. mouth, or any other prehensile part of the body. We have all seen written specimens (they cannot be called manuscripts) done in this way, which could not have been excelled by any one possess- ing the free use of his hands. The history of all nations will furnish us with the most wonderful accounts of the contrivances which have been in- vented as substitutes for the upper and lower limbs. Thus, then, while it is admitted that the de- velopment of the instincts of animals, and even of the intellectual faculties of man, is favoured by the formation of their bodies, and that, indeed, in many instances the display of instinct and intel- lect would not take place but for the co-operation of nicely adapted organisation ; it is nevertheless evident that the animating and governing power is in both cases wholly distinct from that organisa- tion, all the parts of which are nothing more than the instruments provided for its service ; and, as we have already seen, when any organ is injured, or even wholly wanting, this superior power is capable, to some extent, of accomplishing, by other organs, the purpose for which the lost one was designed. This is peculiarly the case with man ; and the supremacy of his nature, and the existence of a higher principle within him than mere organisation, is distinctly proved by this circumstance, as well as by the fact that, though LETTER VI. 189 physically inferior in many important respects to the lower animals, he has yet established his pre- eminence over them as lord of the creation. Dr. Spurzheim has ably shewn the comparative unimportance of man's organisation, compared with his intellectual faculties, in the following passage : " Even in mankind there is no proportion between the manifestation of the faculties, and the per- fection of the external instruments. If man owe his arts to his hands, why do not idiots invent ? Why do painters drop the pencil, sculptors the chisel, and architects the compass, as soon as their understanding is deranged, while other individuals bring forth stupendous works by the assistance of crippled hands or of stumps? From these con- siderations we consequently see, that the external instruments do not produce the faculties. I do not, however, deny the importance of these ex- ternal instruments. It must even be admitted, that there is some relation between the internal faculties and the external instruments. Without external instruments the internal faculties cannot manifest themselves ; without muscles the will cannot actu- ate any limb ; without hands, or something equi- valent, we cannot seize any object. Carnivorous animals could not destroy without claws and teeth : without these instruments, therefore, they could not subsist. Thus the ancient doctrine of Anax- agoras, that the hand of man is the cause of his understanding, falls to the ground ; and it is evi- 190 LETTER VI. dent that the wisdom of Solomon, Solon, and Plato, and all the master-pieces of Homer, Euclid, and Raphael, are by no means the result of their hands ; and that the surprising instincts of animals are not the eifect of their antennas, or their feet, teeth, probosces, or tails. I repeat, that it must be nevertheless allowed, that the external instru- ments, though not in proportion to the internal faculties, cannot be in contradiction to them ; and that these faculties perform their function with greater facility, and in higher perfection, if the external instruments be more perfect. Therefore the hand of man, which is divided into several movable parts, and capable at every movement of changing its form and closely surrounding the surface of external bodies, is more fit for appre- ciating their tractile qualities than the feet of birds, invested with scales, or than those of quadrupeds, covered with a horny substance."* We must now direct our attention more closely to the intellectual part of man's nature. The mind is so intimately connected with the body, and especially with the nervous system, that it is necessary I should first give you some in- formation respecting that system. The brain is the instrument for the manifesta- tion of varied degrees or shades of nervous or intellectual power, and is modified in different animals according to their nature or mode of life ; * Spurzheim's Outlines of Phrenology, pp. 74, 75. LETTER VI. 191 and in man is more largely developed than in most other animals, in order to render it capable of dis- playing that high and dignified distinction of his nature, the faculty of reason. It has been always asserted, from the earliest times, that the brain of man is larger than that of any other animal ; not larger merely in relation to the size of the whole body, but absolutely larger ; and to this assertion only one exception (which was first mentioned by Aristotle) has been named, and that is the ele- phant. Hence, in man, the size of the cranium, which is the receptacle for the brain, is much greater in proportion to that of the face, which is the receptacle for the senses and the organs of mastication, than in other animals. The brain, in all warm-blooded animals, is a plural and very complicated organ ; but it is most perfect in man in the number and development of its parts, none being found in any animal which man has not, while several of those found in him are either reduced in size or wholly wanting in various other animals. Hence it has been truly said, that by taking away, diminishing, or changing the proportions of its parts, you might form from the human brain that of any other animal ; while, on the contrary, it would be impossible to con- struct the brain of man from those of all other animals together.* Blumenbach says, that in insects and many * Lawrence's Lectures on Zoology, p. 169. 192 LETTER VI. worms a ganglionic system of nerves can be distin- guished, arising in general from what is called the spinal marrow, the superior extremity of which, slightly enlarged, constitutes the brain. In both classes of cold red-blooded animals (reptiles and fishes), and still more so in those which have warm blood (mammalia and birds), the brain has a much more complicated structure, and a far greater relative magnitude. In both these points, how- ever, the brain of man surpasses that of all other animals ; and, according to the ingenious observa- tions of the learned Sommering, he also possesses by far the largest brain in proportion to the size of the nerves which arise from it. The comparison of the brains of different animals with one another, or with that of man, affords no proof of the supe- riority of the latter (beyond its larger size), since their comparative weight and size admit of con- siderable variation, which is not so much a matter of surprise when we consider the brain in its plural office, supplying the five external senses, which, in every species of animal, there is reason to believe are developed in a particular manner, with various degrees of power suitable to their different circum- stances ; furnishing the organic life with the ner- vous fluid, by means of which the processes of secretion, digestion, respiration, nutrition, and cir- culation are carried on, each of which admits of very great modifications ; but more particularly as the material source of those instinctive powers LETTER VI. 193 possessed by the lower animals^ and which often exceed in vigour and extent of application the cor- responding powers of man. All these circumstances shew that the mere size of the brain cannot be relied on as an accurate means of ascertaining the mental capacity of animals. From the brain arise all those nerves which give to the external senses their activity, and to the different organs of animal life their due balance of power and function. The size of these nerves, relatively to that of the brain, differs exceedingly in different animals ; and their function is proportionably either enlarged or contracted. The body of an ox will weigh six times heavier than that of a man, yet the brain of the former is found to be only a fourth part of the size of the latter ; so that man, in proportion to the size of his body, possesses a brain twenty-four times larger than that of the ox. On the other hand, the nerves proceeding out of the brain of the ox are many times larger than those proceed- ing from that of man ; * which latter, indeed, are known to be smaller in proportion to the size of the brain than in any other animal : and it seems to be an established fact, that, throughout the animal kingdom, down to the lowest creature in the scale, as the size of the brain diminishes, the mass of the nerves' relatively to it increases. There is some reason for supposing, though it is not clearly ascer- * Monro on the Nerves. O 194 LETTER VI. tained, that in proportion to the size of the nerves issuing from the brain, a larger or smaller portion of that organ is occupied in supplying them with energy. If this is the case, the brain of those animals whose nerves are so large must be very nearly all occupied in performing this function ; and it is placed beyond a doubt, that the small size of the brain in proportion to the rest of the ner- vous system, has a very considerable influence on the whole animal economy of cold-blooded animals, and gives rise to some of the most striking distinc- tions observable between them and warm-blooded animals. It explains the diminished sympathy between the two parts of their nervous system, and the consequently weak powers of motion in their whole machine. It also enables us to under- stand how the vitality of their bodies is so inde- pendent of the brain, as also the extraordinary power inherent in them, of re-producing any part of their bodies which may be destroyed. It was long thought that the brain of man was the largest in proportio?i to the size of his body ; but subsequent researches have shewn that this opinion is incorrect ; and it is now very generally known, that the brains of many birds, some of the mammalia, especially of the quadrumana, equal, and even exceed, that of man. That of the canary- bird, for example, in proportion to the weight of its body, is as one to fourteen ; that of the saimiri sciurea, an American monkey, as one to twenty- LETTER VI. 195 two ; that of the field-mouse as one to thirty-one ; while that of the adult man is as one to thirty- five. The relative size of the brain to the body varies so much, that to give the proportions in all animals would be tedious. If, as some physi- ologists have shewn, the brain performs two dis- tinct and independent functions, namely, that which is immediately connected with the sensorial extremities of the nerves and receives their impres- sions, being devoted to the purposes of animal life, and that which may be considered as connecting the functions of the nerves with the faculties of the mind ; then it is evident, that the greater the de- velopment of the latter part, the more intelligent and superior must the animal be, and vice versa. Now, compared with the size of the nerves which proceed out of it, the brain of man is much larger than that of the simia) or the seal, and conse- quently of all other animals ; for the proportion of the nerves to the brain increases as we approach the ruminantia, felinse, and particularly the edentata and marsupial animals. From the facts I have already stated, it may be inferred that, as the hand of man in many respects resembles more or less closely the anterior extre- mities of all animals, but surpasses them all in the delicacy of its structure and the perfection of its contrivance, so the brain of man, though built up probably of the same materials as that of other animals, is a more elaborate organ, for the manifes- 196 LETTER VI. tation of higher faculties, and the accomplishment of purposes not contemplated in their formation. It is a larger and more complex organ ; and, as I have already observed, has many parts not found in the lower animals. This circumstance at once affords a physical explanation of the conspicuous place which man occupies in the creation, agreeing with that given in revelation ; for if the station of every animal is determined by its organisation, no part of which is useless or unemployed, it follows that man must have faculties higher than any which other animals possess, and wholly peculiar to him, inasmuch as the superior parts of his nervous system are developed to so much greater an extent than theirs : for no function can be assigned to these additional parts, save the mani- festation of such faculties. We are in possession of many facts which prove that man's intellectual endowments are in proportion to the size and development of his brain. Thus, it is well known that, of the varieties of the human species, some are very inferior to others in their intellectual vigour and perfection ; the smaller development of their brain correspond- ing to this inferiority. Idiots, and those born with a deficiency of intellect, have very small brains, their foreheads forming an acute angle with their nose, and the brain itself weighing as much as a pound less than ordinary. On the other hand, the brain of Sir Isaac Newton is known to have been LETTER VI. 197 heavier and larger than that of any other person whose brain has been examined. Baron Cuvier's also was remarkably large, exceeding by several ounces the usual size ; and it is a singular fact, that the ancient sculptors made all great philoso- phers and statesmen with heads far exceeding in size any observed at the present day : a circum- stance which might occasion some doubt as to the existence of such heads, if we did not know how careful the ancient artists were faithfully to copy nature, and the universal estimation in which their works are now held for this very reason. All this proves that the brain of man, as of all other animals, has to contribute, in different de- grees, to the wants and functions both of the organic and of the animal life, which comprise all those processes by which the body is sustained and protected ; that it is also the instrument by which the mind in man, and that power which we call instinct in other animals, is manifested. Now, if we deduct that portion of the brain of the lower animals which supplies animal life and the five external senses, the remaining part will be found to be very small compared with the corresponding part in that of man. This part, devoted to the use of the mind, is both relatively and positively larger in man than in any other animal. It is the organ, then, of the mind ; the organ by which the mind is brought into contact with the external world, by which it directs 19S LETTER VI. the movements of the body, and through which all its manifestations are made. But to say, therefore, as some have contended, that sensation, perception, memory, judgment, thought — in a word, all the phenomena called mental or intellectual, are the production of the brain, and that the brain thinks, and feels, and wills, as certainly as the liver has the power of producing bile, is as illogical and absurd, as the assertion, that because a piece of glass is capable of transmitting light, or a piece of iron of conducting heat, the one has the power of making or secreting light, and the other, heat. In answer to those who, revolted at the doctrine of materialism,* maintain that thought is not an act of the brain, but an immaterial principle residing in and appearing through it, it has been said, that in that case the brain is " almost without an office." I shall not, however, insult your good sense by taking up much of your time in shewing the ground- lessness and dangerous tendency of this doctrine. The eye is an organ formed with consummate skill, to transmit to the perceptive principle sensa- tions of light, a substance (if so it may rightly * There are two kinds of materialism : one maintains that there is no Creator ; that matter has always existed ; and that all the phenomena of nature are the product of matter. The other admits a Creator, but contends that man is not made up of body and soul ; but that all the phenomena usually attributed to the soul result from combinations of matter under particular circum- stances ; and that the soul is a fluid pervading all things. LETTER VI. 199 be denominated) of the most subtle kind. And although all our acquaintance with light is derived through the medium of the eye — but for which we should have no conception whatever of it — no one has ever imagined that that organ is the source of light ; no one finds any difficulty in understanding the relation between them, and their perfect inde- pendence of each other. In like manner, the brain is, in our present state of existence, the medium through which mind is brought into communication with matter — through which it acts upon matter ; and there can be no more reason in this case than in the other, for confounding the instrument with the agent, the medium with the source. How, then, can it be said, that the brain, any more than the eye, is " almost without an office ?" Are not all the senses mere contrivances for conveying impres- sions made upon them by external agents — mere passive conductors, wholly incapable of originating any sensation whatever ? Yet that they have " offices," and those of the most important kind, no one will deny. These considerations will enable you to under- stand, imperfectly it is true, the functions and nature of the most wonderful of all organs ; and at the same time will guard you against some preva- lent erroneous notions respecting this subject : as, for example, many of those contained in Dr. Elliot- son's work on Human Physiology, a book designed for the instruction of youth ; which, among other 200 LETTER VI. equally startling assertions, contains that to which I have already adverted, viz. that the brain thinks, feels, and wills, as surely as the liver secretes bile. It can hardly be necessary to expose more fully than I have already done the absurdity of this notion ; but in the following passage, from a review of Mr. Lawrence's Lectures on Physiology, it is so ably treated, and rendered so ridiculous, that I think you will be glad to have it laid before you. " It is indeed the philosophy of common sense, that matter can produce nothing but matter ; that whatever is separated, or secreted, from the animal body, must have some of the properties of ani- mal substances. But what are the properties of the secretion of the brain ? Has Sir Humphry Davy analysed a parliamentary harangue, or a lec- ture on physiology ? Have his most delicate tests made any impression upon the Iliad, or the Novum Organum ? Has he ever succeeded in decom- posing Marmion, or the Tales of my Landlord ? Has he detected the slightest affinity betwixt the substance of the brain and these remarkable secre- tions ? There are various other views which might be taken of this important subject, and which, we think, must satisfy every candid inquirer, that the phenomena of mind are utterly inconsistent with any idea we can form of a material function. Let us take a single example, and inquire, in a few words, how, upon the principles of materialism, we LETTER VI. 201 are to account for the phenomena of memory ? We find some difficulty in conceiving how the matter of the brain receives the impressions of history, philosophy, and mathematics ; how various sciences and various languages, with the addition of innumerable affairs of ordinary life, are all received, without confusion, into ' one small head.' But we think there is still a greater difficulty ; and that is, the manner in which they are retained. It is well known to physiologists that all the parts of a healthy body are in a constant state of change ; that there is a constant, though gradual, removal of the old matter, and a corresponding deposition of new matter in its place. We cannot ascertain the precise periods connected with this remarkable process ; but we have every reason to believe that there is a period, and not a very long one, during which every particle of the body is removed. Now, if memory be merely an impression made upon a material organ, in what manner is the impression transmitted ? Does an old man relate the tales of his early days. How has he retained them ? There is not in his body a single particle that was present when the incident occurred upon which he dwells with such complacent garrulity. Has one series of particles, as they departed, related the tale to those who came to occupy their place ; as a sentinel, on quitting his post, repeats his instructions to him who relieves him ? Or is there some provision, to the world a secret yet, by which the newly acquired 202 LETTER VI. matter is instructed in what it is expected to know ? Does the new matter that is added to the body of a Gregory, undergo, from time to time, a course of instruction in physic ? Was the nutriment of Por- son regularly drilled in Greek ? Do the particles of Wilberforce relate to one another the tale of Afric's wrongs ? Did the atoms of Buonaparte urge on the conscript atoms in their wild career of ruth- less ambition ? Is it to this simple and easy course of transmission that we are all indebted for the little learning we have been able to retain ? And have certain neghgent atoms failed in their duty in regard to much useful knowledge that we all have forgotten ? — V/e cannot enlarge upon this curious subject; but it is highly important, in a moral point of view, especially in regard to crimes and punishments. Upon the principle of materialism, it will evidently be necessary that the punishment shall immediately follow the offence ; for if a single day intervene betwixt them, some of the peccant matter will have eluded our grasp, and some in- nocent matter will be punished with the guilty. Upon this obvious principle, what shall we say of a remarkable instance, in which an individual suffered the highest award of British justice on account of a crime committed in a foreign country twenty years before ? Whatever ideas we may entertain of the enormity of the offence, we shall be obliged to acknowledge, that long before the period we have mentioned, every particle of the real offender LETTER VI. 203 had ' absconded from justice.' But why talk we of morals ? Upon the principles of materialism there can be neither morals nor moral responsi- bility. Are ' all the manifestations which we call mental or intellectual, the functions of the brain ; as digestion is of the alimentary canal, motion of the muscles, and the various secretions of the respective glands?' then justice, humanity, bene- volence, and patriotism, are the healthy condition of this important function ; and injustice, robbery, murder, and sedition, are merely the function in a state of disease. But why should diseases of this function be considered as objects of punishment, while hepatitis (inflammation of the liver) and jaundice escape with impunity ? 'Tis strange, 'tis passing strange, that, in this enlightened nation, one function should be left to the care of the phy- sician, while another is consigned to his majesty's advocate for his majesty's interest : that calomel and Cheltenham waters should be considered as remedies adapted to the one, while for the other, nothing will answer but Newgate and Tyburn Tree."* The possession of reason, involving as it does moral responsibihty, inasmuch as it enables man to understand the consequences of his actions, and thus to discriminate between good and evil, is a presumptive proof that his destinies are of a more * Review of La-wTence's Lectures on Physiology, in the Edinburgh Medical and Surgical Journal, vol. xv. p. 606. 204 LETTER VI. dignified and enduring description than those of the inferior creatures. Hence we are naturally led to infer the prolongation of the existence of the human soul after its separation from the body. This opinion has been maintained from the earliest times, and was held by the Chaldees and the ancient Britons ;* among the heathen, by Homer, Pindar, Socrates, and Epictetus ; and by almost all Christian philosophers of more modern times, amongst whom I might mention Bacon, Locke, Newton, Boyle, Shakspeare, and many others. Another argument in support of this behef is admirably expressed in the following words of the writer whom I have just quoted : " From the planets that revolve in their appointed orbit, to the insect on which we tread, each is endowed with properties exactly suited to the situation in which it is placed, and each fulfils, in the most perfect manner, the purpose for which it was cre- ated. In this fair field of harmony and order, the only anomaly is man : he alone is endowed with powers for which there appears no adequate range in the spot of earth on which he is fixed, and the point of time to which his existence is limited. After a long and helpless infancy, and a protracted period of intellectual culture, his powers at length expand in all their glory ; and oft, alas, how oft! when they have just opened in their meri- * See Csesar's Fifth Commentary ; and Burton's Anatomy of Melancholy. LETTER vr. 205 dian splendour, is he cut down as a flower, and withereth ! If this be his end, he is an anomaly, which, in the wide expanse of creation, stands alone — a beacon set to record the fact, that in the mightiest works of Omnipotence something has been made in vain."* Most writers upon the nature of man lean to the opinion, that he is a tripartite being, or a creature made up of three distinct parts : the hodij, or dust of the earth ; the living soul, which is the animal or sensitive part ; and the spirit, or rational mind: and, supported as this opinion is by all the most learned writers,f St. Paul among the number, I am not disposed to dissent from it ; but, for better distinction, I here include the body and the animal or sensitive part under the term animal life; and to that which is commonly under- stood by the word soul I have apphed the term spiritual life. Of that spiritual life it does not form part of my present design to speak. I can only assure you that it exists, and manifests itself through a particular organisation. The author of the book of Genesis, whose knowledge of the circumstances attending the creation of man is so remarkable, and so evidently derived from a supernatural * Review of Lawrence's Lectures on Zoology, in the Edin- burgh Medical and Surgical Journal, vol. xv. p. 610. t Amongst whom I may name Marcus Antoninus, Sallust, Laertius, Nemesius, Lee, Whiston, &c. 206 LETTER VI. source, has thus expressed himself in recording the creation of man : " And God breathed into his nostrils the breath of life, and man became a Hving soul ;" or, the Hebrew being hterally trans- lated, " God breathed into his nostrils the breath of lives, and man became a living soul." Now, the expression, " breath of lives;" appears to convey the meaning, that God breathed into man at his creation a breath, or life, for the use of the body, or animal function ; and a breath, or hfe, for the use of the soul, or spiritual part. It is evident that this explanation of the passage is borne out by what we know respecting the constitution of our nature. The first of these lives is bestowed on all hving creatures, in common with man ; and being fixed and regulated by Him who created it, cannot vary, but with undeviating certainty accom- plishes the purposes to which it was designed to be subservient ; and hence, among the lower crea- tures, animated by no higher principle, we observe but little difference between individuals of the same species ; they all manifest the same powers and propensities, exist a certain number of years, and, having in the most perfect manner fulfilled the objects of their existence, cease to be. The second, or spiritual life, is given exclu- sively to man. Of this superior endowment I have already stated the general characteristics, as fully as the subject of my present undertaking allows me to do. I must just mention, however. LETTER VI. 207 the influence which it exerts over the animal life, modifying and controlling it, and thus preventing it from bringing about that uniformity in the lives and dispositions of men, vi^hich, as I have already observed, prevails to so great an extent among other animals. Whatever arguments can be adduced against the existence of this spiritual life, apply with equal force against that of the animal life. I have al- ready shewn that the latter is distinct from the organisation in which it resides — neither originating in, nor depending upon it ; and that therefore we have no sensible or material evidence of its exist- ence, but infer that from observed phenomena. Now, we have precisely the same proof, equal in strength and clearness, of the existence of the spiritual life, or immortal soul. For in man, in addition to those phenomena which all animals exhibit, there are others of a far higher and refined character, wholly peculiar to him. Are we not, then, irresistibly led to conclude, that a principle distinct from, and superior to, that which produces the phenomena common to man and the beasts, is concerned in the production of those which man alone displays ? This reasoning is strongly supported by St. Paul, who, speaking of the word of God, says, that " it is quick and powerful, and sharper than any two-edged sword, piercing even to the dividing 208 LETTER VI. asunder of soul and spirit:"* and in another epistle he addresses the Thessalonians thus ; '^ I pray God your whole spirit, and soul, and body, be preserved blameless/' f &c. ; in both cases evi- dently making a distinction between the animal and spiritual life. Man in his present state enjoys not indeed an altogether unencumbered, yet certainly a free, use of those intellectual powers which enable him to ascertain, with considerable accuracy, the advan- tages or disadvantages of any given course of con- duct. Of the tendency which the brain may have to direct his actions, we can only speak by analogy. We know that if our hands are used and exercised in a particular manner, they can perform many things of which they would otherwise be inca- pable ; and the brain, if exercised in any particular direction, undoubtedly establishes a facility of action in that direction, whether it be for good or for evil. But respecting the function of the brain, as the in- strument of the mind, I do not intend to say any thing beyond merely mentioning it. Since man, being endowed with reason, is left so much more dependent on himself for his pre- servation than other animals — and, being indivi- dually so much physically inferior to many of them, can only secure his safety by co-operation, — the importance to him of the faculty of speech * Heb. iv. 12. t 1 Thess. v. 23. LETTER vr. 209 must be obvious. It is by means of artificial lan- guage alone that he can communicate his wants, his acquirements, and his feehngs, to his fellow- men ; and this artifice is capable of accomplishing these great objects, in a manner not otherwise approachable, and nearly perfect. That the faculty of speech is a result of the possession of reason, is evident. The lower ani- mals, though possessing a larynx and tongue as perfectly developed as those of man, are yet, with- out exception, incapable of using artificial language otherwise than by mere unintelligent imitation. The voice or cry of animals is a sound pro- duced by the vibration of certain ligaments in the larynx or organ of voice, which is situated in a little box in the front of the throat. The voice of each species of animal has a particular tone, by which it is recognised, and which is susceptible of variation even in the different ages or sexes of individuals. The circumstances upon which these various modifications depend are unknown ; but it is probable that the minute muscles which pro- duce the innumerable movements of the cartilages of the larynx, are in each animal capable of a particular mode of action, which, aided by the varieties in the shape of that organ, will go very far to account for the phenomena of natural voice. All these are peculiar sounds, which admit of no change, are susceptible of no improvement, neces- p 210 LETTER VI. sarily resulting from the particular organisation by which they are produced. It is not so with the acquired artificial voice of man. In earliest youth his reason leads him to observe that his fellow-men communicate their wants and wishes by means of sounds ; and he soon learns the meaning attached to particular vocal combinations, and acquires the faculty of employ- ing them for his own purposes. Children that have been born deaf, and who therefore can have no notion of sound — and idiots, who can establish no connexion between the sounds they hear and the ideas which they represent — though they have a perfect vocal apparatus, are not capable of acquiring the use of language. Though sound proceeds from the larynx in man, as it does in all other animals having voice, and is produced by the friction of air against the sides of the mouth and nose, mocUfied by the position of the tongue, the teeth, or the lips ; yet these parts are only subservient, not absolutely in- dispensable, to the formation of artificial language ; for some of them may be injured or destroyed, and yet the individual continue able to speak.* Several kinds of animals, through their imita- * "We have the case of a woman who, after the loss of the whole of her tongue, was able not only to articulate sounds, but even to speak fluentl)^ Such cases are mentioned by Bartholin, Huxham, Richter, and others. LETTER VI. 211 tive powers, have been taught to pronounce words, and even to repeat sentences, regardless of any particular language, and sometimes combining one language with another. Prince Maurice's parrot, for example, proves beyond a doubt that it is not inability to produce particular sounds which pre- vents the lower animals from making use of arti- culate language, but the want of that reasoning faculty which enables man to form associations between such sounds and ideas. Without the power to do this, man's proud pre-eminence could not have been gained, nor could it be maintained. It is this which unites men for mutual protection and assistance, and enables them to resist their powerful enemies. It is this which secures the constant progression of our race in civilisation and happiness, by diffusing abroad the feelings, knowledge, and discoveries of every individual among his fellow-men. Animals in their natural language of inarticu- late sounds and gestures find a facility of expres- sion amply sufficient to serve the limited purposes of their creation ; but man, whose race is spread over every climate of the globe, and whose pro- gression depends upon the intellectual exertions which he is able to make, finds in artificial lan- guage the only means of communication commen- surate with his wants, and worthy of his exalted nature. Speech, then, loudly proclaims the fact, that 212 LETTER VI. man possesses the superior powers of reason and judgment, which involve the high moral responsi- bility that attaches to his existence here ; and hence, by a chain of reasoning which forces itself upon our minds, we are led to the conviction that he has been placed on the earth by a wise and intelligent Being, for objects and purposes, which, bearing no relation to any thing in the present state of existence, silently, but awfully, remind him that he is on his passage to another, and, as he is taught to believe, a happier and a higher sphere. LETTER VII. " If, now, I should go about to reckon up the several uses of this instrument (the hand), time would sooner faU me than matter. By the help of this we do aU our works ; we build ourselves houses to dwell in — we make ourselves garments to wear — we plough, and sow our grounds with corn, dress and cultivate our vineyards, gardens, and orchards, gather and lay up our grain and fruits — we prepare and make ready our victuals. Spinning, weaving, painting, carding, engraving, and that divinely invented art of writing, whereby we transmit our own thoughts to posterity, and converse with, and parti- cipate the observations and inventions of them that are long ago dead, — all performed by this. This is the only instru- ment for all arts whatsoever ; no improvement to be made of any experimental knowledge without it. Hence, as Aristotle saith well, ' they do amiss that complain man is worse dealt with by nature than other creatures : whereas they have some hair, some shells, some wool, some feathers, some scales, to defend themselves from the injxiries of the weather ; man alone is bom naked, and without all covering.' " — Ray on the Creation. " And hath made of one blood aU nations of men for to dwell on aU the face of the earth." — Acts, xvii. 26. " For every kind of beasts, and of birds, and of serpents, and of things in the sea, is tamed and hath been tamed of man- kind."— James, iii. 7. I HAVE said enough to call your attention to the first great distinguishing characteristic of man — the faculty of reason ; and I think I have shewn that this is an endowment fully adequate to enable him to maintain his elevated position in the scale 214 LETTER VII. of creation, at the head of which it has pleased God to place him. It remains for me to shew how far his physical constitution is calculated to make him the conqueror of every creature, and the inhabitant of every region of the earth. I shall therefore proceed to consider the principal physi- cal distinctions of man, namely, his erect stature and biped progression, the peculiar structure of his digestive apparatus, his teeth, skin, &c. Man is the only animal, with which we are acquainted, distinguished and dignified by the erect position of his body. This attitude, and the biped mode of progression resulting from it, are not natural to any other animal. Man, to all physical as well as moral appearances, the favoured creature of God, forcibly announces his superiority over all other creatures by his majestic attitude and upright stature. To effect this object, the structure of his body is so singularly and admirably adapted, that the comparison of it with that of the brute creation will strongly confirm us in the belief, that the genus to which he belongs is wholly distinct from every other. I make this remark, because it has been asserted, and strenuously maintained, that there is a specific identity between the African and the ourang-outang ; a notion which is not only philosophically false, but must lead to consequences, both political and moral, which cannot be too strongly deprecated. The great inaccuracies con- tained in the writings of Monboddo, White, Rous- LETTER VII. 215 seau, and others, upon this subject, have not only been overlooked by those whose want of correct anatomical knowledge . is their sufficient excuse, but have also passed current with some men of scientific acquirements, because they favour the notion, warmly supported by many, of uniformity and uninterrupted gradation in the animal king- dom. There is certainly little difficulty in tracing the outline of such an arrangement throughout all the departments of the animate creation ; but the interesting question of man's superior and distinct nature is nowise affected by this admission ; nor does it therefore follow, as some contend, that man should only be looked upon as a more perfect kind of monkey. The lower limbs of man, which support his trunk, and the muscles which move them, exhibit characters of form, size, and arrangement not seen in any other animal. The pelvis or basin also, which consists of a set of bones situated at the base of the trunk, and so called from their resemblance to a vessel used by the ancients, is formed to sus- tain the entire weight of the body, head, and upper limbs, and to supply a fixed point for their motion. In connexion with this we notice the comparative lightness of the arms, which serve merely for pre- hension, and not to support weight ; and also the peculiar mode of junction of the head with the spinal column, which insures its safe balance, and the proper direction of the eyes and mouth. If 216 LETTER VII. we except those animals which do not use their limbs merely for walking, such as the kangaroo, jerboa, flea, grasshopper, and locust, no other animal has lower limbs so long in proportion to the body as man ; his legs being equal in length to the trunk and head together. The articu- lation, or joint, of the thigh-bone, connected with the pelvis by a long neck, which stretches out obliquely from the shaft of the bone, is another important distinction in the human organisation. By this contrivance the shaft is so completely dis- engaged from the hip-joint, as to allow a freedom of rotation and progression, which could not be attained were the bone joined to the pelvis in the same manner as it is in other animals. The con- struction of this joint gives the body greater firm- ness, the head of the bone being the centre of motion ; and by means of its great latitude of movement, the entire body can be supported upon one limb — a circumstance peculiar to man. The short and weak thigh-bone of the monkey tribe, though stronger in proportion than that of many other quadrupeds, renders them quite incapable of sustaining their bodies in an upright position ; and the shortness of the bone causes it to be concealed in the muscles of the body, the rest of the limb being comparatively weak and slender; whereas the length of the thigh-bone in man, so necessary to the erect attitude, renders him quite unable to go upon all-fours. In all other animals LETTER VII. 217 the thigh-bone forms an angle with the spine, and sometimes even a right angle, which entirely precludes the possibility of an erect attitude. In monkeys the angle is more obtuse, which favours the perpendicular position of the spinal column, especially in those varieties whose arms are longer and lighter, and so assist them to support this attitude. But the foot being the ultimate support of the whole frame, and the primary agent in locomotion, we find in this part of man's structure an unequalled combination of advantages. The breadth, solidity, and strength of the tarsus, or sole of the human foot, exceeds in proportion that of any other ani- mal ; and its whole surface at once resting upon the ground, a provision pecuhar to man, causes the OS calcis, or heel-bone, to form a right angle with the leg. Whatever animal's foot we examine, we shall find the os calcis more or less elevated from the ground, which proves that the power of resisting force apphed to the front of the body, which its position in man confers upon it, and which renders it so useful to him, is not required in four-footed creatures. Such is the importance of this peculiarity in enabling man to maintain his balance and upright attitude, that Mr. Lawrence considers it the chief cause of man's distinction as an erect animal. Even the simiag and the bear have this bone raised ; and most animals rest the weight of their bodies upon 218 LETTER VII. the toes, as the felinae, or upon the ends of the toes, as the ruminantia and sohpeda.* In these last animals the os calcis forms scarcely any per- ceptible angle, but is perpendicular with regard to the leg. Thus, as we depart from man, the parts serving for support, which enter into the composi- tion of the foot, become more contracted, and less available for the purpose of an erect posture. The solid and almost immoveable structure of the foot of man, the direction and shape of the toes admitting as little motion as is consistent with their office, forms a striking contrast with the very flexible and free movement, but weaker organisa- tion, of the hand. Even the outward character or contour would be sufficient to satisfy us that the upper and lower extremities in man (corresponding to the anterior and posterior in other animals) are formed for purposes quite different and independent. Whereas, such is the close resemblance between the fore and hinder extremities even of the anthro- pomorphous animals already mentioned, that this genus is correctly and characteristically denomi- nated quadrumanous, ox four-handed, inasmuch as the structure of the hinder feet of almost all the monkey tribe is much more like that of the human hand than of the foot : this is particularly the case * Many persons will be much surprised to learn that the horse, for example, rests the whole weight of its body upon one toe in each leg ; and still more so, that the arctic fox rests upon the thick bristles which extend beyond the toes. LETTER VII. 219 with the simia troglodytes (the chimpanse or pigmy) ; for, while all quadrumanous animals have opposible members, or thmiibs, on their hinder as well as anterior extremities, this animal alone has nails upon the thumbs of the hind feet as well as of the fore. But I shall presently have to speak more particularly about the hand, when its con- trast with the corresponding member in different animals, varied according to their locahty or mode of life, will prove with greater force the distinct offices of the fore and hinder extremities in man. The spinal column in man furnishes many proofs that his natural attitude is an erect one. The great difference between the size of the bones which compose the lower part of that chain, and of those in the neck, clearly shews that the former were constructed to support a superincumbent weight ; and the shortness of the processes called spinous, which project down the back in the form of a ridge, compared with those in other animals, indicates that in the former they were not designed to afford the space necessary for the attachment of the numerous and powerful ligaments and muscles requisite to support a pendent position of the head, but which in man is not required, as his head rests upon the spinal column. r have thus briefly noticed the most important of the facts which prove how unfit all animals except man are to maintain a perpendicular posi- 220 LETTER VII. tion, which must be irksome and fatiguing to them in the highest degree, seeing that the mechanical means essential to such an attitude are altogether wanting in them. I shall not mention here all the anatomical differences that distinguish man, as I wish merely to give a general view of the object intended in his creation. But I must call your attention to that limb in man which gives attach- ment to " the instrument of instruments." The most superficial survey of the arm and hand of man will convince you that they are quite unsuited to support the weight of the body. We have already noticed the provision made in the sohd and unyielding construction of the leg for the support of great superincumbent weight : we now behold a limb which is evidently formed for mobility. It has been said, that the hand is not a distinct instrument; but, at all events, it is a complete one, for it combines all the movements requisite for prehension and defence, which, in other animals, are distributed over various parts of the body. To this end the arm has been fixed to the body in such a manner as to admit of the most extensive lateral movement— there being no part upon the surface of the body that the hand cannot reach. If it had been placed in a deep cup, like the hip-joint, its movement must have been restricted to the simple motion of the legs, back- wards and forwards, combining with this only a slight lateral movement. Again, if the upper ex- LETTER VII. 221 tremity had been intended for support, constituted as the shoulder-joint is, it must have been liable to displacement at almost every motion attended with the least exertion. But, viewed exclusively as an instrument of prehension, the hand is per- haps the most perfect and most extensively useful organ of the body. Much of its power, how- ever, is adventitious, concentrated there for faci- lity and ease ; and in other animals we see the same power divided among numerous organs. Thus the ruminantia and the pachydermata per- form many of the duties of the hand by means of their horns and tusks, or some other process upon their heads, as in the ox and boar; the quadru- mana, by means of their tails, as in numerous kinds of monkeys ; and the rodentia, by means of their tails and teeth, as in the beaver and rat.* The hand, therefore, though so beautifully formed to suit an infinite variety of purposes, * " The ribs, which in quadrupeds are usually employed for respiration, are in serpents converted into auxiliary organs of progressive motion ; and in the draco volans, or flying lizard, they are extended outwards from the sides to serve as wings ; the teeth, usually intended for mastication, are in many animals en- larged, in order to serve as weapons of offence, as in the elephant, the boar, the narwhal, and the pristis. In like manner as in the Crustacea, organs of the same general structure are converted, sometimes into jaws, sometimes into feelers or palpi, and some- times into feet ; and the transition from one to the other is so gradual, that it is difficult to draw a proper distinction between them." — RoGET, Bridgewater Treatise, vol. i. p. 56. 222 LETTER VII. has attained its multitudinous capacities as much by civilisation, which is the offspring of reason, and by habit, which is the result of animal in- stinct, as by any inherent property. Compared with the eye or ear, it appears to be much less essential to the well-being of the individual. The functions of these organs cannot be performed by any others, and hence their destruction entails an irremediable loss; whereas many operations performed by the hand are capable of being trans- ferred to other organs, having indeed devolved upon the hand for the sake merely of freedom and convenience. The hand, therefore, is not an instrument sjii generis ; but from circumstances connected with the faculty of reason, its power has been apphed to a number of purposes, now so blended with the instrument as to be inse- parable from it.* Instances occasionally present * " Whereas they (animals) have natural weapons to defend themselves and offend their enemies — some horns, some hoofs, some teeth, some talons, some claws, some spurs and beaks — man hath none of all these, but is weak, and feeble, and unarmed sent into the world. Why, a hand, with reason to use it, supplies the uses of all these ; that is, both a horn, and a hoof, and a talon, and a tusk ; because it enables us to use weapons of these and other fashions, as swords, and spears, and guns. Had we wanted this member in our bodies, we must have led the life of brutes, without house or shelter, but what the woods and rocks would have afforded — without clothes or covering — without corn, or wine, or oil, or any other drink but water — without the warmth and comfort or other uses of fire ; and so without any artificial, baked, boiled, or roast, meats, but must have scrambled with the LETTER vir. 223 themselves, as I have elsewhere remarked, where these organs having, either by injury or malforma- tion, been rendered useless or destroyed, much of their office is transferred to the teeth, mouth, or some other prehensile part of the body. So beautifully constructed is the hand, with so many movable parts, and so fine a sense of touch, that it must be regarded as an instrument which, when applied to such adventitious machinery as man's reason has invented, is admirably calculated to execute the highest conceptions of his mind, and to accomplish his boldest purposes. His reason discovers the properties of inorganic substances and their application to his various wants, and the hand is the chief instiiiment by which these disco- veries are brought into practice. Thus, from being the weakest and most defenceless of creatures, man, by the aid of his hand, under the guidance of reason, has become the monarch over all creatures, whether of the forest, the ocean, the desert, or the plain. By the discovery of gunpowder, for example, and its application to weapons of defence, he sub- dues the fiercest tiger in its own jungle, and the intrepid elephant in its native woods. By his knowledge of the properties of steam, he is enabled to employ that mighty agent so as to diminish, to wild beasts for crabs, and nuts, and acorns, and such other things as the earth puts forth of her own accord. We had lain open and exposed to injuries, and had been unable to defend ourselves arainst almost the weakest creature." — Rat on the Creation. 224 LETTER VII. an incalculable extent, the labour of his body, and to aid his advances towards a more perfect civili- sation ; so that whatever object he desires to gain is accomplished by means of those contrivances, invented by his reason, to which he is indebted for all his power. But animals, though in many in- stances their organisation surpasses, both in strength and particular adaptation, that of man, being denied the power which reason alone can give of super- adding to that organisation, remain ever in their original state, unable either to make the best use of their natural powers, or to improve them ; and thus man, gradually acquiring knowledge and power, subjects them all to his irresistible dominion. Dr. Kidd is inclined to believe that " the human hand gives the power of execution to the mind ;" and he thinks it is " the relative position of one of the lingers to the other four which gives it that complete dominion which it possesses over the various forms of matter."* If so, the simia tro- glodytes ought to be twice as ingenious and dexte- rous as man, because it has the opposible members called thumbs on the fore as well as on the hind feet. But to compare in this manner the organi- sation of man with that of the lower animals, or even the latter with one another, is both useless and unmeaning ; for it can only be done by view- ing animals in relation to spheres of action for which they were not created. When the strict * Phys. Hist, of Man, p. 19. LETTER VII. 225 relation of all the varieties of organisation to the purposes designed to be subserved by them is recollected, it must be admitted that there can be no such thing as superiority of one variety over another, all being equally perfect. It is physi- cally impossible for a bird with claws to construct the simplest instrument ; and it is as physically impossible for a man to fly, or to construct a nest with the skill of a bird. Who can say that animals fitted to move in the rare medium of the air possess either a superior or an inferior organisation to that of man ? But viewing organisation abstractedly, and considering that superior which possesses the greater power, it would not be difficult to shew that parts of the organisation of not a few of the lower animals are actually superior to that of man ; witness the eyes of many birds, or the electric apparatus of the torpedo, which, for delicacy of structure, and complication of parts, is not to be compared with any part of man's organisation. The functions of the hand are another proof of the important influence of reason upon all human concerns. It is reason which has made the hand the most delicate, as well as the most mighty in- strument ; so that while it is calculated to deal with the finest and most subtle materials, it is able also to subdue all animals, and to employ the most powerful agents made use of by the Creator to effect his purposes. I shall now proceed to consider the remaining Q 226 LETTER VII. physical marks of distinction in man, constituting the pecuhar formation which enables him to inhabit all parts of the globe. Since the vegetable productions and animal inhabitants of any one portion of the earth are widely different from those of all other portions, no species of animal capable of subsisting upon only one kind of food could be universally diffused over its surface. Man, therefore, is necessarily omnivorotis. He can either subsist exclusively upon animal food, as in the arctic regions, or upon vegetables alone, as in tropical climates ; and such is the adaptability of his constitution, that the food which in one case would be wholly incapable of supporting life, is in the other the best for main- taining his frame in health and strength.* That, however, this power in man, as well as all bis other physical qualities, is greatly dependent upon, and increased by, his reason, I shall here- * Man, however, is not the only omnivorous animal ; the hog, monkey, dog, guinea-pig, hedge-hog, rat, mouse, and many others are so likewise. And animals naturally confined to one kind of food are, by man's instrumentality, frequently rendered omnivorous. Even herbivorous animals, when deprived for a considerable period of their natural food, readily devour animal substances, and have been known to refuse vegetable food when afterwards offered to them. Gassendus mentions an instance of this kind in a lamb. Monkeys and pigs, which, in their natural state, subsist princi- pally upon vegetables, are, when domesticated by man, capable of living upon animal matter alone. In Paris it is common to fatten hogs upon horse-flesh. LETTER VII. 227 after shew. At present I shall enter into some details, which will prove that express provision is made in his frame to render him omnivorous. All animals have a stomach and intestines, the organs for the assimilation of their food, which are longer or shorter in different animals. In the carnivorous order they are always shorter and less complicated than in the herbivorous — for this reason, that the food of the former, being much more nearly allied to the structure of the body which it goes to support, requires less elaboration to convert it into nutritious chyle ; on the other hand, the nature of vegetable substance is such, that it is impossible to obtain a large supply of nourishment from it unless taken in great quan- tities, which necessitates a much more capacious and complicated apparatus in animals subsisting upon it than is required by those whose food con- sists of animal matter. Accordingly, while there are no carnivorous animals with more than one stomach, we find many of the herbivora with four ; and while the length of the alimentary duct of the former is in some cases, as in one species of bat (vesjjertilio noctuld), only twice the length of the body, that of the ruminants, belonging to the latter class, is more than twenty times as long as their bodies. In reptiles, as in the frog, and in fishes, as in the lamprey and shark, this tube does not equal the length of the body, while in the ram it is twenty-seven times longer. These are the ex- 228 LETTER VII. tremes in the length of the intestines in proportion to that of the body ; and I mention them here in order to shew you, that there is a physical mode of accounting for the particular food upon which each animal subsists. How wisely the apparatus of digestion is fitted to the exigencies of every individual species, I shall hereafter have occasion to point out in detail. Man, having to digest both animal and vegetable substances, resembles in this part of his structure neither of the classes of ani- mals just mentioned ; his alimentary canal being about six or seven times longer than his body. As the food of the carnivora does not require to remain long in the stomach, that organ is con- structed to favour a quick passage through it: the opening by which the food enters (the cardia) being placed at the upper and anterior extremity, while that by which the food passes into the intes- tines (the pylorus) is at the lower and posterior part of that organ. This is remarkably contrasted with the stomachs of some of the herbivora ; in these the food enters almost at right angles, and near the centre of the organ, and passes out by an opening almost in the same position, so that it has to be expelled against its own gravity.* The stomach of man holds a middle place between these two ; for while at one end it is dilated into a sac, in which some portions of food may be retained, at the other there is a free egress for that * See Plate IV. Fiff. 2. LETTER VII. 229 which has been duly prepared. The stomachs of the pigmy and hog are the nearest in shape to that of man, and these animals are alike omnivorous. But there are evidences of another character to the same effect. It is certain that those animals which are strictly carnivorous, as well as those which are strictly herbivorous, have their teeth formed and arranged in a particular manner. In the one they are adapted for tearing their food, in the other for triturating or masticating it. How admirably the latter are formed to withstand the friction which they undergo in grinding down the substances requiring to be comminuted previously to their admission into the stomach, I shall here- after explain. Man has teeth of each kind — tee^h for tearing, and teeth for grinding. Since, then, man is obviously formed to subsist upon all kinds of food, it is absurd to maintain, as some have done, the superiority of any specific diet ; for we find that, in cold climates, the more stimulating and heat-making food is alone provided in sufficient abundance for his support ; while in the equatorial regions, cooling and less exciting food abounds. In those regions of the earth where its surface is encased in an impenetrable covering of snow and ice, how could roots or vegetables grow or be preserved ? Wisely, then, is the natural food of the Esquimaux and the Samoiede made to consist entirely of the raw flesh of animals. It is well known that there is not a more healthy diet 230 LETTER VII. for those people than rein-deer blood and raw flesh. When you consider the excessive cold to which the body is in arctic countries exposed^, you will not fail to perceive the beneficence of this arrangement ; the stimulating properties of animal food being the chief means by which the natural heat of the body is kept up in the midst of the intensest cold. Com- pare with this the diet of the inhabitants of the torrid zone, where the impediments to an animal diet are as great as those which exist in colder regions to a vegetable one. The number and fierceness of the beasts of prey, the long-continued operation of a vertical sun, and the extensive in- undations which frequently occur, are insuperable obstacles to the propagation of such large flocks of cattle as would be required to feed the inhabitants of those parts on animal food. But this is more than compensated for by an abundant supply of the most succulent and nutritious roots, seeds, and fruits. The natives of Hindostan subsist almost entirely upon rice or grain. Humboldt tells us that the Ottomaques, a people inhabiting a country on the banks of the Oronoco, feed on a fat kind of earth, which contains the oxide of iron : this they knead into balls, and preserve it in their houses for food. Man appears in his omnivorous character in those climates only where the temperature is favourable to the production of both animal and vegetable food ; and there the mixed diet is the LETTER VII. 231. most natural as well as the most wholesome. As we pass from the temperate climates towards the poles, we find that his diet is composed more and more largely of animal matter ; while towards the equator vegetables form the chief means of human subsistence. Is it chance that has so wisely ap- portioned to man in every climate that food only which is most healthful and invigorating ? Rather should we regard it as a law ordained by the great Conservator, to enable man to be the inhabitant of all the earth, from the icy shores of Labrador to the scorching deserts of Africa. The slow growth and long infancy of man is a condition imposed upon him, and upon him alone- Man passes through a long period of infancy, of phy- sical immaturity, and of helplessness, while other animals quickly arrive at their full development. The purpose of this great difference cannot be mis- understood. It is a law of our nature, that the con- templation of helplessness invariably calls forth our kindest sympathies; and when on ourselves devolves, for any considerable period, the care of providing for its well-being, our feelings of affection towards it become of the most intense and enduring kind : hence the long infancy of the human being tends powerfully to endear him to his parents ; and thus also feelings of gratitude and affection are excited in the mind of the child towards those to whom it is indebted for support during the time of its dependence, and from wliom it has received so 232 LETTER VII. many other benefits. Here are the foundations of human society. The lower animals, on the contrary, for pur- poses essential to their existence, as well as to the general economy of nature, require the superin- tending care of the mother for a comparatively short period ; are soon able to provide for themselves ; and, forgetting the ties of kindred, live unconscious of any pecuUar relationship. " They go forth, and return not unto them."* And is not this a wise and beneficent law ? Had it been otherwise, the ends for which they were created must necessarily have entailed unspeakable mental suffering upon them ; and therefore the justice and goodness of God are strikingly displayed in depriving them of the power of recognising their offspring, as soon after their birth as support and protection are no longer required. There is yet a wider intention manifested in this arrangement ; for, had the infe- rior animals been as slow as man in arriving at maturity, the great object of the creation of a large portion of them, viz. that they should contribute to the support of man and other carnivorous ani- mals, would have been frustrated. On the other hand, had man been brought to maturity at an earher period, consequences must have ensued destructive of that equilibrium which is so conspi- cuous throughout the whole animal kingdom. I shall now briefly shew, that the nature and * Job, xxxix. 4. LETTER VII. 233 function of the skin in man is adapted to facilitate his extension over all parts of the earth. It has been asserted, that we can have no greater proof of an intelligent First Cause than the coverings which protect the skin of animals. " Animals in cold climates have been provided with a covering of fur : men in such climates cover themselves with that fur. In both cases, whatever may have been the end or intention, no one can deny that the effect at least is precisely the same : the animal and the man are alike protected from the cold. Now, since the animal did not clothe itself, but must have been clothed by another, it follows, that whoever clothed the animal, apparently knew what the man knows, and reasoned like the man ; that is to say, the clother of the animal knew that the climate in which the animal is placed is a cold climate, and that a covering of fur is one of the best means of warding off the cold ; he therefore clothed his creature in this very appropriate mate- rial. The man who clothes himself in fur to keep off the cold performs an act directed to a certain end ; in short, an act of design. So, whoever, directly or indirectly, caused the animal to be clothed with fur to keep off the cold, must likewise have performed an act of design. But, under the circumstances, the clother of the animal must be admitted to have been also the creator of the ani- mal ; and, by extending the argument, the creator of man himself, of the universe. Moreover, the 234 LETTER VII. intelligence which the Creator has displayed in clothing the animal, he has deigned to impart to man, who is thus enabled to recognise his Creator's design." * Some animals, then, being provided with thick coverings of fur to defend them from the cold, and others being comparatively destitute of this protection, both classes are prevented from mul- tiplying beyond certain geographical limits, ex- cept by the assistance of man, inasmuch as they have no power to change their clothing according to the varying temperature. But man is furnished with no such covering — naked he comes into the world ; and this very deficiency is essential to his universal diffusion. For if man were naturally clothed in fur, he would not be so well able, if at all, to accommodate himself to all degi*ees of tem- perature. But without the faculty of reason, he could not avail himself of this peculiarity in his frame, which would then be a source of weakness, and effectually prevent his extension over the earth. Possessing it, however, he is enabled to encounter all climates, since it teaches him how to regulate his clothing so as to retain or part with the natural heat of his body at pleasure. We have here another case where reason converts what is physically an inferiority into an important means of ensuring man's supremacy. * Prout on Chemistry, Meteorology, &c., Introduct, p. 3. LETTER VII. 235 I shall now give you a short account of the functions of the skin. There is every reason to believe that the structure of the skin in the dif- ferent species of animals is exceedingly diversified ; and while it freely transmits in one individual, it as rigidly retains in another, the fluids which it sur- rounds, and which are secreted by the body. In animals, the provision for this arrangement is ob- vious in the oily and viscid secretions which are continually prepared upon its surface, both as an additional protection to it from friction and other injuries to which the skin is liable, and for the purpose of preventing too rapid transpiration. In fresh-water fish, and the mollusca, the skin is thus protected, though it is absent in most animals inhabiting the sea. The skin of eels is supplied with much of this mucus, which is supposed to be necessary to them on account of their exposure to the air during their frequent migrations, which would be attended with excessive perspiration but for this provision. The great extent of surface which the skin is estimated to cover, in man exceeding two thou- sand five hundred square inches, may give you an idea of the importance of the chief function of this organ, the elimination or disengagement of the worn-out particles of the body, which early came under the notice of physiologists. Sanctorius, a physician of Padua, about the beginning of the seventeenth century, invented a statical chair, by 236 LETTER VII. means of which he was enabled to make many accurate phj^siological expenments, during a period of thirty years, the correctness of which made his name a proverb in these matters. He found, that five-eighths of his food, both sohd and hquid, passed off by the skin. This organ, therefore, is of the greatest importance to the sustaining of hfe, as has also been shewn by the experiments of Berzelius, Lavoisier, Seguien, Edwards, and others. It is likewise of great importance in regulating the tem- perature of the body ; but I cannot explain in this place the way in which it exerts this influence. I can merely state the fact, that the skin of man is gifted with the power of retaining or transmitting the fluids of the body which it surrounds according to fixed laws, and thus of keeping up or of lower- ing the natural heat. I have now given you a general view of the physical distinctions by which man is enabled to exercise the high prerogative of his nature, and to reign triumphant over all flesh. That this superiority is the result of his intellectual endowments, I think the statements which have been made fully prove ; while, at the same time, they shew that his phy- sical conformation is sufficiently distinct to con- stitute him, on that account alone, a distinct genus. Many writers, however, have maintained that he is not a distinct genus ; but for this opinion there is no foundation ; and, in answer to it, I shall content myself with quoting the words of the illustrious LETTER VII. 237 Cuvier: " Man forms but one genus, and that genus the only one of its order." * To attempt to explain the primary cause of the variety of the human race, would be as useless as to attempt to prove what was the primary cause of all the mineral productions of the earth. Second causes are always acting, and may help to make the differences between the various races of man appear greater than they really are. But all these differences are no argument against the truth of the declaration of Scripture, that the whole hu- man race originated from one pair; for at what- ever subsequent period those indelible marks which distinguish its varieties were stamped, no causes now in existence have any power to alter them. " Man," says Swainson, " although naturally formed to inhabit but one element, is yet enabled by art to traverse vast oceans, and, by the peculiarity of his constitution, to live in all climates which produce vegetation. In his natural state, he is among the least qualified of hving beings for making rapid transitions from one part of the earth to another ; and yet he has peopled its entire surface. A fair- haired native of Europe migrates with his family, and settles among the woolly-haired and swarthy inhabitants of Africa. Do his descendants, in the lapse of a century, born under a scorching sun, begin to assume any of the characteristics of the * Cuvier's Regne Animal, ord. Bimana. 238 LETTER VII. races that surround him ? Do their hps gradually become thick, their nose flattened, and their com- plexion black ? Assuredly not ; the supposition is refuted by actual experience to the contrary. Again, does an African diet, or a change of cos- tume, create any change in their form or their mental perceptions ? Are their natural character- istics, in short, in any degree lost, so long as their race is preserved pure ? Let the Spaniard, settled for more than two centuries among the copper- coloured Indians of Mexico and New Spain — the Dutch boors of Southern Africa — the descendants of the whites who first settled in the West Indies — above all, the Jews — how scattered among every nation under heaven! — let these, I repeat, tacitly reply to these questions. Such living testimonies, known to all, should at once have dispelled the illusion which many writers, and some of them able ones, have indulged in, that temperature, food, clothing, and other secondary influences, were the chief causes of that extraordinary variation in the aspect of the human species which the different nations of the earth exhibit, and which, so long as each race is preserved pure, is vmchanging and un- changeable. Upon such a subject the modest and ingenious mind may indulge conjecture ; but when we attempt to penetrate the darkness of primitive ages, and pretend to trace the first cause of such things, we wander in regions from which human knowledge is excluded. He alone, that great First LETTER VII. 239 Cause ' by whom all things are made,' is master of this impenetrable secret."* The varieties in the hmiian species are not greater or more diversified than those which exist in many other species of animals ; in confirmation of which assertion I cannot adduce more convincing evidence than the words of the learned Blumen- bach. " Some late writers on natm^al history seem doubtful whether the numerous distinct races of men ought to be considered as mere varieties, which have arisen from degeneration, or as so many species altogether different. The cause of this seems chiefly to be, that they took too narrow a view in their researches ; selected, perhaps, two races the most different from each other possible, and, overlooking the intermediate races that formed the connecting links between them, compared these together ; or they fixed their attention too much on man, without examining other species of ani- mals, and comparing their varieties and degenera- tion with those of the human species. The first fault is, when one, for example, places together a Senegal negro and a European Adonis, and at the same time forgets that there is not one of the bodily differences of these two beings, whether hair, colour, features, &c., which does not gradually run into the same thing of the other, by such a variety of shades that no physiologist or naturahst is able to establish a certain boundary between * Geography of Animals, p. 3. 240 LETTER VII. these gradations, and consequently between the extremes themselves. The second fault is, when people reason as if man were the only organised being in nature ; and consider the variety in his species to be strange and problematical, without reflecting that all these varieties are not more striking or more uncommon than those into which so many thousands of other species of organised beings degenerate, as it were, before our eyes. More reasons than one have induced me to make choice of swine for this comparison ; but, in par- ticular, because they have a great similarity in many respects to man — because both, in regard to the economy of their bodily structure, taken on the whole, shew unexpectedly, on the first view, as well as on closer examination, a very striking simi- litude. Both, for example, are domestic animals, both are omnivorous, both are dispersed through- out all the four quarters of the world, and both, consequently, are exposed in numerous ways to the principal causes of degeneration arising from climate, mode of life, nourishment, &c. ; both, for the same reason, are subject to many diseases, and, what is particularly worthy of remark, to diseases rarely found among other animals than men and swine. Another reason why I have made choice of swine for the present comparison, is, because the degeneration and descent from the original race are far more certain in those animals, and can be better traced, than in the varieties of LETTER VII. 241 other domestic animals. For no natm'alist, I believe, has carried his scepticism so far as to doubt the descent of the domestic swine from the wild boar ; which is so much the more evident, as it is well known that wild pigs, when caught, may easily be rendered as tame and familiar as domestic swine : and the contrary also is the case ; for if the latter by any accident get into the woods, they as readily become wild again ; so that there are in- stances of such animals being shot for wild swine. It is well ascertained, that before the discovery of America by the Spaniards, swine were un- known in that quarter of the world, and that they were afterwards carried thither from Europe. All the varieties, therefore, through which this animal has since degenerated, belong, with the ori- ginal European race, to one and the same species ; and since no bodily difference is found in the human race, as will presently appear, either in regard to stature, colour, the form of the skull, &c., which is not observed in the same proportion among the swine race, while no one on that account ever doubts that all these different kinds are merely varieties that have arisen from degeneration, through the influence of climate, &c., this comparison, it is to be hoped, will silence those sceptics who have thought proper, on account of these varieties in the human race, to admit more than one species. " With regard to stature, the Patagonians have afforded, as is well known, the greatest employ- R 242 LETTER VII. ment to anthropologists.* The romantic tales, however, of the old travellers, who give to these inhabitants of the southern extremity of America a stature of ten feet and more, are scarcely worth notice ; and even the more modest relations of later English navigators, who make their height from six to seven feet, have been doubted by other travellers, who, on the same coast, sought for such children of Enoch in vain. But we shall admit every thing said of the extraordinary size of these Patagonians by Byron, Wallis, and Carteret ; the first of whom assigns to their chief and several of his attendants a height of not less than seven feet, as far as could be determined by the eye ; the second, who asserts that he actually measured them, gives to the greater part of them from five feet ten inches to six feet, to some six feet five inches, but to the tallest six feet seven inches ; and this account is confirmed by the last men- tioned of the above circumnavigators. Now, allow- ing this to be the case, it is not nearly such an excess of stature as that observed in many parts of America among the swine originally carried thither from Europe ; and of these I shall mention in particular those of Cuba, which are more than double the size of the original stock in Europe. " The natives of Guinea, Madagascar, New Hol- land, New Guinea, &c. are black ; many American tribes are reddish brown, and the Europeans are * Writers on the natural history of man. LETTER VII. 243 white. An equal difference is observed among swine in different countries. In Piedmont, for example, they are black. When I passed through that country during the great fair for swine at Salenge, I did not see a single one of any other colour. In Bavaria they are reddish brown ; in Normandy they are all white. " Human hair is indeed somewhat different from swine's bristles ; yet, in the present point of view, they may be compared with each other. Fair hair is soft, and of a silky texture ; black hair is coarser, and among several tribes, such as the Abyssinians, negroes, and the inhabitants of New Holland, it is woolly, and most so among the Hottentots. In like manner, among the white swine in Normandy, as I was assured by an incomparable observer, Sulyer of Ronnenburg, the hair on the whole body is longer and softer than among other swine ; and even the bristles on the back are very little different, but lie flat, and are only longer than the hair on the other parts of the body : they cannot therefore be employed by the brush-makers. The difference between the hair of the wild boar and the domestic swine, particularly in regard to the softer part between the strong bristles, is, as is well known, still greater. " The whole difference between the cranium of a negro and that of an European is not in the least degree greater than the difference that exists between the cranium of the wild boar and 244 LETTER VII. that of the domestic swine. Those who have not observed this in the animals themselves, need only to cast their eye upon the figure which Dau- benton has given of both. I shall pass over less national varieties which may be found among swine as well as among men, and only mention, that I have been assured by M. Sulyer, that the peculiarity of having the bone of the leg remark- ably long, as is the case among the Hindoos, has been remarked with regard to the swine in Nor- mandy. He (Sulyer) says they stand very long on their hind legs ; their back, therefore, is highest at the rump, forming a kind of inclined plane, and the head proceeds in the same direction, so that the snout is not far from the ground. " I shall here add, that the swine in some countries have degenerated into races which, in singularity, far exceed every thing that has been found strange in bodily variety among the human race. Swine with solid hoofs were known to the ancients, and large herds of them are found in Hungary, Sweden, &c. In the like manner, the European swine first carried by the Spaniards in 1509 to the island of Cuba, at that time celebrated for its pearl fishery, degenerated into a monstrous race, with hoofs which were half a span in length." * The truth of those words of revelation, that God " hath made of one blood all nations of men for to dwell on all the face of the earth," f is, I * Phil. Mag. vol. iii. t^ Acts, xvii. 26. LETTER VII. 245 think, here borne out by ample physical evi- dence. Every nation will supply us with sufficient tes- timony to the fulfilment of the decree of the Creator, that man should have dominion over every living creature. The fiercest animals become his prison- ers ; even the mighty elephant is tamed to do him service. That man is able to subdue the greater beasts of the sea — the whale, the crocodile, and the shark, is, however, perhaps still more wonder- ful. The following extract contains a graphic account of a complete victory over the latter vora- cious animal, obtained by a native Indian. " The gallant manner," says Martin, " in which some of the natives in India will, single-handed, and armed only with a long knife, attack the most ferocious tiger for a trifling reward, has been often described, and needs not recapitulation here ; but their agility and bravery in voluntarily encountering a formidable shark in his native element, for the sake of a few shilhngs, is not so well known. An illustration of this fact, as it occurred near Calcutta in 1830, may be here given. The boat was on its progress down the Hoogly, when a huge shark was seen swimming round it ; the combatant, on the offer of a small reward for his dexterity, holding the rope, on which he had made a sort of running knot, in one hand, and stretching out the other arm, as if already in the act of swimming, stood in an atti- 246 LETTER VII. tude truly picturesque, waiting the re-appearance of the shark. At about six or eight yards from the boat the animal rose near the surface, when the native instantly plunged into the water, a short distance from the very jaws of the monster. The shark immediately turned round and swam slowly towards the man, who, in his turn, nothing daunted, struck out the arm that was at liberty, and ap- proached his foe. When within a foot or two of the shark, the native dived beneath him, the animal going down almost at the same instant. The bold assailant in this frightful contest soon reappeared on the opposite side of the shark, swimming fear- lessly with the hand he had at liberty, and holding the rope behind his back with the other. The shark, which had also by this time made his ap- pearance again, immediately swam towards him ; and while the animal was apparently in the act of lifting himself over the lower part of the native's body, that he might seize upon his prey, the man, making a strong effort, threw himself up perpendi- cularly, and went down with his feet foremost, the shark following him so simultaneously, that we were fully impressed with the idea that they had gone down grappling together. As far as could be judged, they remained nearly twenty seconds out of sight, while we stood in breathless anxiety, and, it may be added, horror, waiting the result of this fearful encounter. Suddenly the native made his appearance, holding up both his hands over his LETTER VII. 247 head, and calling out with a voice that proclaimed the victory he had won while underneath the wave, Ian ! Ian ! The people in the boat were all pre- pared, the rope was instantly drawn tight, and the struggUng victim, lashing the water in his wrath, was dragged to the shore and despatched. This truly intrepid man received only a cut on the left arm, apparently from the fin of his formidable enemy." * According to Waterton, it is the custom among many nations to mount on the backs of crocodiles, for the purpose of capturing them. Herodotus and Pliny relate the different ways of catching this animal in its native element ; and their accounts have been confirmed by Pocock and many other modern travellers. The intrepid inhabitants of Tentyra, an island in the Nile, are known to climb the crocodile's back, and, bridling his mouth with a staff, force him out of the river, and despatch him. Pliny says, " There is a race of men hostile to the crocodile, called Tentyretas, from an island in the Nile itself, which they inhabit. Their sta- ture is small, but their courage in this practice is wonderful. This beast is terrible to them that flee from him, but runs away from his pursuers ; and these men alone dare attack him. Moreover, they swim after him in the river, and, mounting on his back like horsemen, as he opens his jaws to bite, with his head turned up, they thrust a club * History of the British Colonies, vol. i. p. 117. 248 LETTER VII. into his mouth, and holding the ends of it, one in the right hand, and the other in the left, they bring him to shore captive as with bridles, and so frightened with their shouts only, that they compel him to disgorge the bodies he had but just swal- lowed, in order that they may be buried." * M. Bosc mentions a way of capturing this animal on land used by the natives of Egypt and Senegal. As soon as the inhabitants perceive a crocodile out of the water, they go boldly up to him; and when he opens his mouth to bite, they thrust in their arm with a piece of iron or strong wood pointed at both ends, in an upright position, which hinders him from shutting his mouth again, and then they despatch him with spears.f Though I have in this Letter endeavoured to shew that man is lord of the creation, it must not be forgotten that he is but one of many thousand species, in the formation of which the great Author of all things has displayed varied and endless wis- dom ; that each animal, in its appointed sphere, is an aggregate of wonder equally surpassing our com- prehension — a distinct construction, which nothing less than almighty power could create : so that, when we compare the mechanism of man's body with that of many of the creatures which surround him, we shall find that the Creator has displayed * Pliny's Nat. Hist. lib. viii. cap. 25. -j- See a more detailed account in Loudon's Magazine of Natural History, vol. ii. p. 14 ; and vol. viii. p. 196. LETTER VII. 249 many magnificent contrivances of an altogether diJfFerent kind in the construction of numerous other animals. But I shall continue this subject in another Letter. LETTER VIII. " But that which is most considerable in this matter, and plainly sheweth the Divine management in the case, is, that those creatures are manifestly designed for the place in which they are, and the use and services they perform therein. If all the animals of our globe had been made by chance, or placed by chance, or without the Divine providence, their organs would have been otherwise than they are, and their place and resi- dence confused and jumbled. Their organs, for instance, of respiration, of vision, and of motion, would have fitted every medium, or have needed none ; their stomachs would have served any food ; and their blood, and the covering of their bodies, been made for any clime, or only one clime. Consequently, all the animal world would have been in a confused, incon- venient, and disorderly commixture. One animal would have wanted food, another habitation, and most of them safety. They would have all flocked to one or a few places, taken up their rest in the temperate zones only, and coveted one food — the easiest to come at and most specious in shew ; and so would have poisoned, starved, and incommoded one another. But, as the matter is now ordered, the globe is equally be- spread, so that no place wanteth proper inhabitants, nor any creature is destitute of a proper place, and all things neces- sary to its life, health, and pleasure." — Derham's Physico- Theology, vol. i. p. 236. Having considered the circumstances which dis- tinguish man from the other denizens of the earth, and thus, I trust, proved that his organisation has been designed to make him the inhabitant of all parts of the earth, and the conqueror of every LETTER VIII. 251 creature which it contains, according to the ex- press command of God, I now proceed to set forth the wisdom displayed in the formation of the other creatures, as exemphfied in their adaptation to the various stations in which they are placed, and in their relations with one another ; producing, by their different powers and propensities, the nicest adjustment and most perfect harmony in the creation. What a scene of wonder is here presented to our minds ! How infinite must be the wisdom which called into being so many diversified exist- ences, placed them in circumstances so widely dif- ferent, or even wholly opposite, and yet preserved such admirable order, connexion, and harmony, throughout the whole extent of the creation ! Who but the Creator of the elements, of the inorganic world, and of the vegetable kingdom, could have so perfectly adapted to them all the innumerable living tribes which people the air, the earth, and the sea ? The relations between all the departments of creation are so intimate, so evidently designed, and the mutual operation of these departments upon one another is so nicely balanced, and produces such uniform and con- sistent results, that no reasonable mind can fail to be convinced that the whole creation, animate and inanimate, material and immaterial, was pro- duced by one and the same infinitely powerful and benevolent Being. 252 LETTER VIII. I shall now proceed to establish and illustrate the propositions — that the organisation and in- stincts of animals are expressly adapted to the sphere in which they live, to the position which they hold in the animal kingdom, and to their mode of life ; including in the latter the localities in which they dwell, and the species of food on which they subsist. To whichever department of the animate crea- tion we direct our attention, this perfect adapta- tion is observable : it is as conspicuous in the smallest insect as in the gigantic whale ; in the most minute and unobserved parts of their orga- nisation, as in its more obvious and striking cha- racteristics. Before I enter into details, I must notice the remarkable fact, that all the forms of animal orga- nisation, which to the common observer appear to differ so essentiaUy from one another, are in reality built up of precisely the same parts, modified in each species to fit it for its appointed mode of existence. These modes of existence, it is true, are so infinitely various, and in many cases so seemingly opposite, that it is at first sight incon- ceivable how the same elementary parts could be put together in so many ways as to be capable of supporting life in such widely different circum- stances. Yet it is indisputable that, for example, the hand, the paw, the wing, the fin, the paddle, the hoof, are essentially one and the same organ. LETTER VIII. 253 all bearing the same relation to the structures of which they form a part.* The distribution of animals over the globe has occupied the thoughts and observations of natu- ralists to a considerable extent. It has given rise to many theories ; but before it can be brought fully within the comprehension of even the most scientific readers, our knowledge of natural history must be greatly augmented and improved. The mind of the most casual observer cannot fail to notice, that there are many parts and circum- stances in the structure of animals, relating to laws and to ends of which, although we do not doubt their existence and fulfilment, we are at present wholly ignorant. It is quite certain that climate, food, locality, and foes, are only a part of the causes to which the existence of animals under the most opposite conditions is attributable. These secondary or instrumental causes must contribute to modify, in some degree, greater or less, the dif- * " We recognise the same parts in the mole, formed into a powerful apparatus for digging, by which the animal soon covers itself, and burrows its way under ground. In the wing of the eagle we shall count every bone, and find that they are adapted to a new element, as powerful to rise in the air as the fin of the salmon is to strike through the water. The solid hoof of the horse — the cleft hoof of the ruminant — the paw, with retractile claws, of the feline tribe — the long folding nails of the sloth, — are among the many changes that are found in the adjustment of the chain of bones, which in man ministers to the compound motion of the hand." — Bell on the Hand, p. 46. 254 LETTER viir. ferences which distinguish the genera and species of the animal kingdom; but that they are sub- ordinate to some other and higher influence, is evident from the fact of their being occasionally made to act in a manner diametrically opposed to the laws which are supposed to guide their opera- tions. This is continually exemplified in regard to temperature. We see some animals existing high up in the northern hemisphere, and dying if re- moved to a more temperate clime ; while others of the same genus, and scarcely differing at all from them in organisation, except, perhaps, in some such part as the horns, which we know has no connexion with the cause in question, are in- capable of living, if removed from a temperate to an arctic climate. As a proof that other than these secondary causes must have operated in the first instance to characterise the various groups of animals, I would draw your attention to the remarkable dissimili- tude which is to be observed in animals occupying different parts of the globe, but, nevertheless, simi- larly circumstanced with respect to locality, tem- perature, food, and other such causes. Compare the quadrupeds which inhabit the European and African continents with animals living in countries of the same temperature in America, — and the greatest differences will be found to exist in their physical configuration. If temperature, food, &c. alone were to be taken into account in this matter. LETTER VIII. 255 might we not have expected to find some of the animals of the former countries amongst those vi^hich are indigenous to the latter ? Yet, v^hen America was first discovered, nearly all the ani- mals it contained were dissimilar from those known in other countries. " The north hemisphere," says Prout, " possesses the horse and the ass, while in the south these species are represented by the zebra and the quagga. In the south hemisphere there also exist many species that are quite pe- culiar, as the giraffe. Cape buffalo, and a variety of animals having the antelope form. So, likewise, the animals of the Old and those of the New World are in general quite distinct, unless, per- haps, towards the north, where the two continents approximate, and where, in consequence, there are some species common to both. Thus the elephant, the rhinoceros, the hippopotamus, the giraffe, camel, dromedary, horse, ass, lion, tiger, and vari- ous species of apes, baboons, and other animals, with which we are familiar in the Old World, were not found in America. On the other hand, the American species, the lama, the peccori, and among carnivorous animals the jaguar or Ame- rican tiger, also the agouti, the paco, the coati, the sloth, and others, were equally unknown in the Old World. Again, the animals of New Hol- land ■ differ, like its vegetation, not only from all those of our continent, but from those of all the world besides. In New Holland there are more 256 LETTER VIII. than forty species of marsupial or pouched ani- mals, of which the kangaroo is that with which we have become best acquainted, while every where else there is hardly a known pouched animal. Nor are these differences confined to the more perfect animals, they are even more striking as we descend in the zoological scale."* The distribution of animals would thus appear to have been originally regulated and fixed by some other cause than those above referred to, and manifestly superior to them. This cause can be no other than the fiat of the Creator, who gave to all the species of animals their varied forms, for purposes many of which are withheld from our view ; whose works we can never, in our present state, " find out unto perfection." " Touching the Almighty, we cannot find him out ; he is excellent in power."f It was essential to the great purposes of the creation that the organisation of animals should be infinitely diversified ; for otherwise but a small part of the earth could be inhabited. Accordingly we see some, by the complexity of their nerves and blood-vessels, and by their outward structure, raised to a station inferior only (infinitely so, how- ever) to that which man occupies ; and, on the other hand, there are many animals whose simple structure, and comparatively feeble vitality, enables * Prout's Bridgewater Treatise, p. 388. f Job, xxxvii. 23. LETTER viir. 257 them to exist in a very low degree of temperature, and to sustain uninjured the violent mechanical shocks to which they are exposed, thus fitting them for a more limited sphere, and one, more- over, in which the higher orders could not exist. Many of these lower animals, having scarcely any power of locomotion, are unable to avoid im- pending danger, and would therefore speedily be destroyed, were their organisation as delicate and complex as that of the higher races. But this is not all : in addition to a structure of the most simple kind, they are endowed with the power of living after the loss of portions of their bodies which in other animals are essential to life ; and in numerous cases, of reproducing the parts entire. This latter power diminishes in proportion as an animal becomes more complex ; a fact which, to use the words of Miiller, " cannot be accounted for otherwise than by supposing, that by the de- velopment of the body the formative principle becomes, as it were, more divided, and, in part, fixed in the separate organs that it has itself cre- ated."* In the higher animals, it would appear, * Elements of Physiology, by J. MiiUer, M.D., translated by Baly, p. 401. This idea is illustrated and enforced by our author in the following passage : — " When, as in very simple animals and plants, a perfect individual consists of a certain sum of similar parts, and grows simply by increase of the number of these similar parts, the perfect being may be divided, and the separate portions will still contain the essential parts of the integral being, though in smaller number ; and each portion will S 258 LETTER VIII. that the essential elements which go to form an individual being are contained in separate portions of the body ; while in the inferior creatm-es they are more concentrated, so that parts of their bodies may be removed without disturbing the essential elements which pervade every part alike. The facility with which the limbs of the Crus- tacea are detached, is remarkable. The lobster, when alarmed by thunder, &c., has the power of separating its limbs from the body by a voluntary action.* The nervous and vascular systems of the lower animals are upon a very simple plan; and hence they suffer httle from the loss of hmbs and other parts of their bodies.f Many of the radiate continue to live, and form itself into a perfect being. Thus it is that cuttings of plants placed in the ground grow, and become new productive individuals. The different parts of a plant are essentially so similar to each other, that branches can transform themselves into roots, and stamens into petals. In the same way, the regeneration of the fresh- water polypes — the hydra, and similar animals — maybe explained; although the polypes, judging from the structure of the infusoria, are certainly much more complex in their organisation than was formerly believed." . . . . " Even if polypes are divided, either transversely or longi- tudinally, each half will become a perfect animal." — lb. p. 402. The earth-worm also gives a familiar example of the power of sustaining injury, in the fact that it is capable of division, each part forming a separate animal. Some animals may be turned inside out ; and if this is done, the internal surface acquires the power of digestion. * See Cams, Compar. Anatomy, by Gore, vol. i. p. 102. t To shew the extent of injury which can be endured by LETTER VIII. 259 animals have the power of existing after the most extensive mutilations, and even of giving indivi- dual life to detached members of their bodies ; so that they are converted into animals as perfect as those to which they were previously attached. These animals, when made prisoners beneath rocks and large stones, by the action of the mechanical agents which surround them, have the power of casting off their limbs by which they may have been entangled, and thus escape. Some lizards can in this way part with their tails. By this benevolent and wise arrangement, conferring a power which is so wonderful as at first sight to appear scarcely possible, a continual, extensive, and otherwise unavoidable sacrifice of life is pre- vented. But this remarkable power has been found to extend beyond rendering harmless the loss of a limb, or even beyond restoring the lost member ; for the eye itself is frequently renewed, after having the chelonian reptiles without extinction of life. Brown says : " A singular circumstance occurred at Ludlow with a tortoise, the property of Mr. Jones, which was put in a convenient place to spend the winter. It was soon attacked by rats, who ate away his eyes, tongue, and all the under part of its throat, to- gether with the windpipe. In that mutilated state it is supposed to have continued three weeks prior to its being discovered. The most remarkable circumstance attending tlais is, that the animal did not exhibit the least signs of decomposition, nor was anima- tion perceptible. It is, however, quite evident it was alive, otherwise putridity would have ensued." — See his edition of White's Natural History of Selborne, p. 125. 2G0 LETTER Vlll. been entirely removed. Nearly the whole of the eye of a water-newt (Jacerta palustris) was extir- pated, all the humours (fluids) escaped, and four- fifths of the membranes were cut away. Within ten months a new eye was formed, with cor- nea, iris, lens, &c. (parts of the perfect eye), all complete. " In the salamander the under jaw is also reproduced ; and in the triton {aquatic salamander), Blumenbach has seen even the eye, with cornea, iris, and lens, reproduced within the space of a year."* Cuvier says of this extraordi- nary animal : " If a limb be amputated, another limb is reproduced in its stead, with all its bones, muscles, &c. ; and this takes place several times in succession."! Redi found, in making experi- * Miiller, p. 405. t Regne Animal. Charles Bonnet proved by numerous expe- riments that extensive reproductions take place in many animals ; a phenomenon first discovered by Spallanzani. The latter phy- siologist shewed that the common snail, having been decapitated, vv^as capable of reproducing an entire and perfect head. In this reproduced head, both the larger and the smaller horns, the eyes, and the mouth, aU attained their original perfection. J Miiller says, that snails possess this power only when the temperature is moderate, and that it fails if the brain, which lies above the oesophagus, is injured by the wound. § Experiments have lately been made by Madame Jeannette Power, to determine whether marine species possess in an equal degree the power of reproduc- tion. She has clearly proved this question in the affirmative; and shewn that the tentacula, the operculum, and even the heads X See Spallanzani's Proo;ramma. § Physiology, p. Wii. LETTER VIII. 261 ments upon vital motion, that the brain of the tortoise might be completely removed, and the animal w^ould walk away as if no injury had been done to it. In this way a tortoise lived six months, walking about as before. He cut off the head of another, and it lived twenty-three days after : the jaws snapped a quarter of an hour after the sepa- ration of the head from the body : the heart's motion also was perceptible for many days. I have seen the heart retain its contractile powers for nearly three hours after its removal from the body, when placed upon a cold iron slab — the blood being coagulated about it ; the interval be- tween the pulsations towards the end of that period was about ten minutes. It appears, then, that ample provision has been made for adapting the organisation of terrestrial animals to the duties and stations assigned to them by their Creator, and thus for peopling every part of the earth. In comparing this organisation, I shall first notice it in relation to locomotion; secondly, to digestion ; and, thirdly, to the circu- lation. It will be recollected that, in speaking of the locomotive power of man, I stated that his organs of motion are much better calculated to enable him to extend his race than those of any other of molluscous animals are capable of reproduction. This was the case with the tritons and murices. — See Magazine of Natural History, new series, vol. ii. p. 63. 262 LETTER VIII. animal ; and that his superiority in this respect was shewn to be mainly owing to the upright position of his body ; for the muscular power of many animals very far exceeds that of man. The quickness, variety, and vigour of their movements frequently excite our surprise and admiration; but it is not perhaps generally known, that while the human body contains only about five hundred muscles, many insects — the insignificant caterpillar, for example — possess as many as four thousand.* Single organs in the bodies of some animals are often composed of a greater number of muscles than are found in the whole human body. " The number of transverse and longitudinal muscles," says Lawrence, " which are supposed to hold an influence over, and to be the cause of all those wonderful varieties of motion which are seen in the trunk of the elephant, have been computed at not less than thirty or forty thousand."f Cams thinks there are as many muscles upon the back of some species of snakes as Lyonet found in the caterpillar. We need not therefore wonder that many ani- mals, even insects, possess a far greater relative * Lyonet reckoned 4061 muscles in the caterpillar found on the willow. — See his work, Sur la Chenille qui ronge le bois de saule. It is, however, doubted by some whether all these little bundles of fibres can be looked upon as constituting distinct muscles. See Carus, Comp. Anat. t See note to Blumenbach's Comparative Anatomy, p. 246. LETTER Vlll. 263 muscular power than man. The hon can with facihty leap twenty feet at a spring ; the kangaroo twelve feet ; and the jerboa, an animal found in Egypt, about the size of a large rat, and supposed to be one of the swiftest animals in the world, can jump six or eight feet at a spring. But if we are surprised at such muscular power as is here ex- hibited, what must we think of that which is dis- played by the grasshopper, the locust, or the flea ? — the two latter being capable of leaping at least two hundred times the length of their own bodies. " Ants," says Roget, " will carry loads which are forty or fifty times heavier than their own bodies ; and the distance to which many species, such as the elata, the locust, the lepisma, and, above all, the pulex, are capable of leaping, compared with the size of the insects themselves, appears still more astonishing. Linnaeus has computed that the meloloritha, or chaffer, is, in proportion to its bulk, more than six times stronger than the horse ; and has asserted that, if the same proportional strength as is possessed by the lucanus, or stag- beetle, had been given to the elephant, that animal would have been capable of tearing up by the roots the largest trees, and of hurling huge rocks against its assailants, like the giants of ancient mythology."* Nevertheless, there are no animals except man that are not confined within certain limits, * Animal Physiology, vol. i. p. 358. 264 LETTER VIII. notwithstanding their vast locomotive and mus- cular powers. For the accomplishment of certain ends, their locomotive powers are made to accord with other parts of their organisation ; and though they may possess the physical power necessary to transport themselves from one region to another, yet this power is rendered unavailable, inasmuch as they are unable to maintain themselves in other districts than those in which they have been placed, either on account of the absence of food, or of other causes. But the range of different animals is very variable in extent. That of some animals extends over vast tracts of country, and cannot be limited by ordinary obstacles ; while that of others is con- fined to a narrow space, and difficulties even of a minor character diminish it still further. The general organisation of each animal constitutes, as we shall presently see, the chief cause in regu- lating its extent of range. The principal diffi- culties which oppose the efforts of land animals to extend their boundaries, — for they are all dis- posed to scatter themselves over as wide an area as possible, — are, first, the sea; secondly, some zone of uncongenial climate ; thirdly, high ranges of mountain chains ; and fourthly, the previous occupation of the contiguous tracts of country by more powerful and inimical races. Many of the larger herbivorous animals herd together in such immense flocks, and consume LETTER VIII. 265 such quantities of food, that the necessity for their moving from place to place is often most pressing.* Accordingly, they put forth their utmost strength to overcome these great obstacles. Rivers and narrow friths can seldom interfere vy^ith the pro- gress of the larger animals ; for the greater part of them swim well, and few are without the power, when urged by danger and pressing want. Thus, the tiger is seen swimming about among the islands and creeks of the Delta of the Ganges ; and the jaguar traverses with ease the largest streams in South America.f " The bear also, and the bison, cross the current of the Mississippi. The popular error, that the common swine cannot escape by swimming when thrown into the water, has been contradicted by several curious and well-authen- ticated instances during the recent floods in Scot- land. One pig, only six months old, after having * " The large herbivorous animals which are gregarious can never remain long in a confined region, as they consume so much vegetable food. The immense herds of bisons which often, in the great valley of the Mississippi, blacken the surface near the banks of that river and its tributaries, are continually shifting their quarters, followed by wolves, which prowl about in their rear. It is no exaggeration, says Mr. James, (Expedition from Pittsburgh to the Rocky Mountains, vol. ii. p. 153) to assert, that in one place, on the banks of the Platte, at least 10,000 bisons burst on our sight in an instant. In the morning we again sought the living picture ; but upon all the plain, which last evening was so teeming with noble animals, not one remained." — Lyell's Geology, vol. iii. p. 35. t Buffon, vol. v. p. 204. 266 LETTER VIII. been carried down from Garmouth to the bar at the mouth of the Spey, a distance of a quarter of a mile, swam four miles eastward to Port Gordon, and landed safe. Three others, of the same age and litter, swam at the same time five miles to the west, and landed at Black-hill."* Many animals can even cross the smaller seas ; and Lyell thinks that this is the most probable way of accounting for the existence of the tapir in some of the islands in the Indian sea. " It is obvious that powerful tides, winds, and currents, may sometimes carry along quadrupeds capable, in like manner, of preserving themselves for hours in the sea, to very considerable distances ; and in this way, perhaps, the tapir {tajnr indtcus) may have become common to Sumatra and the Malayan peninsula."f Even the colossal elephant is not des- titute of this power ; and the manner in which it crosses deep rivers is surprising. We cannot help noticing here the use which this animal makes of its trunk. Lyell says, " the elephant crosses the stream in twd ways. If the bed of the river be hard, and the water not of too great a depth, he fords it ; but when he crosses great rivers, such as the Ganges and the Niger, the elephant swims deep, so deep that the end of his trunk only is out of the water ; for it is a matter of indifference to * See Sir T. D. Lauder, Bart., on Floods in Morayshire, quoted in Lyell's Geology, vol. iii. p. 34. t lb. p. 34. LETTER VIII. 267 him whether his body be completely immersed, provided he can bring the tip of his trmik to the surface, so as to breathe the external air."* In general, however, the sea is an obstacle to general distribution which cannot be overcome ; for when countries are separated by a great ex- panse of ocean, their climate and other character- istics are usually exceedingly different, although they may be situated in the same latitude ; and thus an almost new character is given to the same genus of animals. Accordingly we have three different groups of tropical mammalia, be- longing severally to America, Africa, and conti- nental India. Animals are also limited in their range by zones of uncongenial climate ; and it is on this account that the organisation of the same genus of animals often differs according to the country which they inhabit, so that they are physically prevented from passing beyond certain boundaries. The antelopes of northern and southern Africa are distinctly marked, and not one species has been found common to both. It is well known that the species of monkeys, so numerous within the tropics, are all confined to particular woods, which they are incapable of quitting ; and when brought beyond the thirtieth degree of north latitude, they are subject to a disease not known to affect them in their native climate, and which sooner or later * Lyell's Geology, vol. iii. p. 35. 268 LETTER VIII. terminates their existence ; — they die of consump- tion. Other tropical animals, particularly lions and tigers, are similarly circumstanced. Climate and other causes, then, operate so as to confine animals to particular regions,* to which their organisations have been expressly adapted, and beyond which they are prevented from pass- ing, either by varieties of temperature incapable of supporting the life of all in the same degree of vigour, or by chains of high mountains, which pre- sent an insuperable barrier to their extension. Many races of animals, again, are surrounded by those of a more powerful character, and are in this way confined to certain locahties, which, in return, are defended from the encroachments of such formidable and unequal opponents by the absence of some pecuUarity which is indispensable to their existence. All those circumstances which brino; about the localisation of animals will be found to be associated with the most appropriate forms of organisation. The locomotion of all the higher classes is performed by means of their extremities. When these are wanting, as in snakes, the great increase * " Experience," says Swainson, " has taught us that the productions of every quarter of the globe have a marked and peculiar character. . . As a striking instance of this, we may cite the hons, which naturalists, up to this day, have viewed as con- stituting but one species. The fact, however, wiU turn out to be, that there are no less than five, if not six." — Geography of Animals, p. 284. LETTER VIII. 2G9 in the size and flexibility of the spine, and conse- quently the freer movement of the ribs, w^hich are the locomotive organs in the ophidians, are found to be a sufficient compensation for the want of limbs. Mr. Anderson, in the Transactions of the Royal Society, gives an account of some small eels rising up the flood-gates and posts of the water-works of the city of Norwich, and making their way to the water above, though the boards were smooth-planed, and five or six feet in a per- pendicular position. He says that when they first rose out of the water upon the dry board, they rested a little, apparently until a sufficient quantity of glutinous matter was thrown out upon the skin ; and then they rose up the perpendicular ascent as if they had been moving on a plain surface. Limbs, however, are not only the instruments of locomotion, but are frequently subservient to defence, and to the obtaining of food. And the first thing with which we are impressed, on com- paring the various forms which these organs assume, is their adaptation to these distinct purposes, them- selves so infinitely modified and diversified by the habits and localities of animals. In some animals the limbs are formed of extraordinary strength, to support an unusual weight ; and then they are thick, and possessed of only a limited power of movement, as in the elephant and rhinoceros ; and because of the difficulty which such animals would hence experience, were they compelled to 270 LETTER VIII. seek their food over a large tract of country, or at much expense of motion, they subsist on food which abounds in the places where they dwell. Their great size is a sufficient protection to them ; and accordingly their limbs are seldom available as weapons of defence. Animals which cannot be confined to a narrow range, whether on account of their defenceless conformation, or the extent of surface over which their food is cast, can find safety only in the swiftness with which they move their limbs. In them, therefore, these members are peculiarly fitted for rapid motion ; the muscles and joints are connected in a remarkable manner; every thing that would contribute to augment the bulk of the limb without facilitating its movements is rejected ; and the marvel is, that so many muscles and tendons can play in so small a compass, and that so much fatigue can be endured by so slender an organ. Some of the ruminants are thus pro- vided. The varieties of the stag and the antelope offer examples of the fleetest animals. The timid and defenceless character of many of these species is wisely blended with this method of escape from their enemies. On the other hand, the tardigrade motion of some animals contributes as much to their safety and support, and is equally deserving of our admi- ration, indicating, as it does, the same protective superintendence. " We must not estimate the slow motions of animals by our own sensations. LETTER VIII. 271 The motion of the bill of the swallow or the fly- catcher in catching a fly is so rapid, that we do not see it, but only hear the snap. On the con- trary, how very different are the means given to the chameleon for obtaining his food. He lies more still than the dead leaf; his skin is like the bark of the tree, and takes the hue of surrounding objects. Whilst other animals have excitement conforming to their rapid motions, the shrivelled face of the chameleon hardly indicates life ; the eyelids are scarcely parted ; he protrudes his tongue with a motion so imperceptible tow^ards the insect, that it is touched and caught more certainly than by the most lively action. Thus, various creatures living upon insects reach their prey by different means and instincts : rapidity of motion, which gives no time for escape, is bestowed on some ; while others have a languid and slow movement, that excites no alarm. The loris, a tardigrade animal, might be pitied too for the slowness of its motions, if they were not the very means bestowed upon it as necessary to its existence. It steals on its prey by night, and extends its arm to the bird on the branch, or the great moth, with a motion so imperceptibly slow as to make sure of its object."* The same law which confines the wild goat to the rocks, or the rabbit to its warren and the ground immediately about it, keeps the monkey * Sir C. Bell on the Hand, p. 31. 272 LETTER VITI, tribes prisoners in their native woods ; gives the range of the forest to the hon and the tiger, and of the wilderness to the camel and the ostrich. So that, by a wonderfully diversified application of the same elemental parts, the great Architect has fitted each animal to inhabit some particular spot upon the earth. If we notice the extremities and the tails of the quadrumanous animals, we cannot fail to per- ceive their application to the purposes for which they were formed, viz. to lay hold on the branches of trees, and to transport themselves from one tree to another without touching the ground. " It often happens that she (the female monkey) is unable to leap from one tree to another when thus loaded (with her young) ; and upon such occasions their dexterity is very surprising. The whole family form a kind of chain, locking tail in tail, or hand in hand ; and one of them holding the branch above, the rest swing down, balancing to and fro like a pendulum, until the undermost is enabled to catch hold of the lower branches of some neighbouring tree. When the hold is fixed below, the monkey lets go that which was above, and thus comes undermost in turn ; but, creeping up along the chain, attains the next branches like the rest ; and thus they all take possession of the tree, without ever coming to the ground."* The object of placing these animals in the * Goldsmith's Natural History. LETTER VIII. 273 regions where alone they are found, and of con- fining them there by a pecuhar organisation, is evidently to prevent the too rapid increase of birds, which they do by destroying vast numbers of eggs, that would otherwise be brought into life almost by the sun's heat alone. " The fea- thered inhabitants of the woods, who build their nests upon the trees, are continually disturbed by the monkeys, who are perpetually on the watch to rob them; and such is their mischievous disposi- tion, that we are assured they will fling their eggs upon the ground, when they want appetite or inclination to devour them."* Accordingly, that these ends may be fulfilled, the food of monkeys, consisting chiefly of fruits, and seeds, and roots, is of such a kind, that they are never compelled to wander from their native woods in search of it. Thus, the peculiar organisation of these ani- mals, particularly that of their extremities, limits their range to the tropics, and even confines many species to the branches of trees. Their extremities are wholly unfit for purposes of defence, being formed almost exclusively for prehension ; and thus, enabling them to retreat with surprising agility into the loftiest branches, and to place themselves out of the reach of their enemies, they render any other means of defence unnecessary.f * Wood's Zoography, vol. i. p. 154. t " It is of no avail for the lion or the tiger to dispute the point with these active little wretches, who carry on an offensive T 274 LETTER VIII. Slight varieties of structure, however, will hardly account for the remarkable fact, that the different species of monkeys are confined to particular woods and cantons, and have no communication with one another ; although there can be little doubt that the organisation of each species is especially adapted to the circumstances in which it is placed. " There are not many varieties in the larger tribes of the monkey kind ; but when we come to the smaller class, the differences among them are exceedingly increased. Most of the countries in the tropical climates abound with them, where they take pos- session of the woody parts, and live in separate colonies ; each of which, we are told, is different from that of the next district, in colour, in size, and malicious mischief. It has been remarked, that the monkeys of two cantons are never found to mix with each other, but rigorously to observe a separation ; like the savage nations among whom they are found, they guard their limits against the intrusion of all strangers of a different race from themselves."* There are other animals besides the quadru- manous which live chiefly upon the branches of trees, and whose locomotive organs are adapted to this mode of existence. Among these I may war from the tops of the trees, and springing from branch to branch, bid defiance to their pursuers." — Wood's Zoography, vol. i. p. 154. * lb. vol. i. p. 153. LETTER VIII. 275 mention the sloth, an animal whose habits were until recently almost unknown, and respecting which very erroneous notions were consequently entertained. " Modern travellers express their jiity for these animals. Whilst other quadrupeds, they say, range in boundless wilds, the sloth hangs suspended by his strong arms, a poor, ill-formed creature, deficient as well as deformed ; his hind legs too short, and his hair like withered grass ; his looks, motions, and cries, conspire to excite pity ; and, as if this was not enough, they say that his moaning makes the tiger relent and turn away. This is not a true picture ; the sloth cannot walk like quadrupeds, but he stretches out his arms, and if he can hook on his claws to the inequalities of the ground, he drags himself along. . . . But when he reaches the branch or the rough bark of a tree, his progress is rapid ; he climbs hand over head along the branches till they touch, and thus from bough to bough, and from tree to tree ; he is most alive in the storm ; and when the wind blows and the trees stoop, and the branches wave and meet, he is then upon the march."* Waterton says, " After fully satisfying myself that it only leads the world into error to describe the sloth while he is on the ground, or in any place except in a tree, I carried the one I had in my possession to his native haunts. As soon as he came in con- tact with the branch of a tree, all went right with * Bell on the Hand, p. 30. 276 LETTER VIII. him. I could see, as he cHmhed up mto his own country, that he was on the right road to happi- ness; and felt persuaded more than ever, that the world has hitherto erred in its conjectures concerning the sloth, on account of naturahsts not having given a description of him when he was in the only position in which he ought to have been described, namely, clinging to the branch of a tree."* One of the lizard family, the dragon {draco volans), is formed for the same sphere of action, though in a very different manner. The false ribs, instead of encirchng the abdomen, extend outwards in a straight Hue, and support a pro- duction of the skin forming a kind of wing, which has been compared to that of the bat, but which is not connected with the fore-feet, like the wing of that animal. It acts as a sort of parachute in supporting these animals as they leap from branch to branch : but it has not the power of raising them, like a bird, from the ground. The bats are a family to which I would draw your attention, as having been provided with loco- motive organs fitting them, like the quadrumana, to inhabit trees and other elevations from the ground, and also to fly. For this purpose, the anterior limb differs, in a remarkable manner, from the ordinary formation of these parts. That part which corresponds to the hand is the chief * Wanderings, &c. p. 297. LETTER VIII. 277 thing to be noticed. The thumb is short, and furnished with a hook-hke nail, which the animal uses to suspend its body. The four fingers are extremely long and thin, like fish-bones. A mem- brane, or fold of skin, occupies the intervals be- tween them, and, extending down from the sides of the neck, forms wings, which possess a larger surface than those of birds, and enable them to fly to great heights with considerable rapidity.* In hot climates, where fruit and birds abound, these animals are very common. The roussetts, which are the largest bats known, measuring four feet between the extremities of the wings, are found in great numbers, suspended to the trees, between the straits of Sunda and the Moluccas. But the true bats, which are all insectivorous, have the membrane less developed, and more divided over the body. In the molossi, a species of bat found in America, the membrane extends between the hind legs the whole length of the tail, and even beyond it. Some of these cheiroptera (%s/^, a hand, and irrz^ov, a wing — wing -handed) are ex- tremely numerous in the East, and are wisely placed there to keep under the insects, which in- crease often to a most destructive extent. St. John mentions having seen great numbers of bats * The manner in which this membrane is modified according to the situation of each species, constitutes their chief distin- guishing character. 278 LETTER VIII. in the temple of Faras, in Nubia. " In the third chamber our progress was stopped by a singular obstacle. Ten thousand bats, which had been sleeping quietly on the walls, roused and terrified by our hghts, disengaged themselves in clouds, and, flying about in all directions, struck against our face, breast, head, and hands, threatening to extinguish the tapers. On looking upwards, we saw them clinging by myriads to the roof, all in convulsive motion, with glittering eyes, open mouths, and hideous trembling wings; seeming, in their fear, to be hanging one to the other, tier below tier."* As insects abound within the tropics, so also do birds. Of the family of the humming-bird, for instance, there are nearly four hundred species. These birds, in their turn, are exposed to the attacks of numerous animals, formed expressly for the purpose of limiting their increase. The pre- hensile tail of some of these animals is of great service in enabhng them to traverse the branches of trees, and to surprise their prey. Such is the case with many monkeys, bats, and opossums {(Udelphis). The tail of the latter animal having hooks or spines on the under side, at the articu- lation of each joint, the animal is enabled to hang for hours together by it, without any labour of its muscles. In this position it watches for its prey, * Travels in the Valley of the Nile, p. 487. LETTER VIII. 279 casting itself from one tree to another, and seizing it with the swiftness of thought. On the ground this animal makes but slow progress. Ant-eaters also derive much assistance from the tail, in sustaining themselves upon the trees while in search of ants' nests, which in hot climates are often built off the ground.* In the flying squirrel {jjteromys) the skin of the body extends between the fore and hind legs, giving them the power to support themselves in the air for a few moments, in leaping from one tree to another. On the outer edge of their wrist there is a sharp-pointed bone, connected by two smaller bones to that part, which enables them to spring from tree to tree. " This action is impro- perly called flying, for the animal cannot go in any other direction than forward, and even then cannot keep an even line, but sinks considerably before it can reach the place it aims at : sensible of this, the squirrel mounts the higher in propor- tion to the distance it wishes to reach. When it would leap, it stretches out the fore-legs, and, extending the membranes, becomes specifically lighter than it would otherwise be, and thus is enabled to spring further than other squirrels that have not this apparatus."f Let us now consider the locomotive organs of * See Pennant's History of Quadrupeds, vol. ii. p. 260. t lb. vol. ii. p. 154. 280 LETTER VIII. the ostrich,* the bird of the wilderness, whose defence consists in the fleetness of its movements, whose food is obtained at long intervals, over a barren and waste land. Here we see the legs con- structed with a view to lightness and speed ; and as they are not simply intended for the support of superincumbent weight, they contain no unwieldy bones, but are light and tendinous. And the wings, by giving its body an additional impetus, contribute to render this one of the swiftest ani- mals that traverse the earth. " Professor Thun- berg says, it is impossible to overtake an ostrich with the swiftest horse, when the wind is in its favour; as its expanded wings so much assist its flight, that, unless it receive a wound, so as to dis- able its wings, it will be in vain to pursue the bird. To follow it with success, the weather should be both warm and calm ; and it is then the Arabian hunters mount their fleetest horses, and seek the bird in its native plains." f If we examine the internal mechanism of the ostrich, we notice the lungs and air-cavities of a bird, which have been provided in order that the rapidity of its move- ments should not interfere with the important functions of respiration and the circulation of the blood. One of the most remarkable proofs of the wise * The ostrich, though a bird, is confined to the earth's surface. t Wood's Zoography, vol. i. p. 468. LETTER VIII. 281 adaptation of animals to particular countries, be- yond which they are not permitted to live or to propagate, is seen in the dromedary ; an animal inhabiting the deserts of Arabia, a great part of Southern Africa, Persia, Tartary, and the East Indies, and incapable of existing in more temperate climates or more cultivated districts. Destined to live in the midst of, and to pass over, extensive tracts of dry and yielding sand, the hoof of the dromedary is unusually expanded, and thus sus- tains the weight of the body without sinking in the sand ; and having a toughness and spongy soft- ness, is prevented from cracking through the heat and want of moisture. To this animal the sultry deserts of the torrid zone are more genial and healthy than the rich pastures of Europe and the west; and it is well known that it can neither subsist nor propagate in the variable countries towards the north.* Of all animals, this is the * " An animal thus formed for a sandy and desert region can- not propagate in one of a different nature. Many vain efforts have been tried to propagate the camel in Spain ; they have been transported into America, but have multiplied in neither. It is true, indeed, that they may be brought into these countries, and may perhaps be found to produce there ; but the care of keeping them is so great, and the accidents to which they are exposed from the changeableness of the climate are so many, that they cannot answer the care of keeping. In a few years also they are seen to degenerate ; their strength and their patience forsake them ; and instead of making the riches, they become the burden of their keepers." — Goldsmith's Natural History. 282 LETTER VIII. most temperate ; and the wisdom of this arrange- ment is manifest, for they are often required to perform journeys of a week's duration without a supply of food ; travelhng, according to Leo Afri- canus, at the rate of a hundred miles a-day.* The rein-deer is another animal which exem- plifies most forcibly the wise adaptation of the locomotive organs of animals to the nature of the countries which they inhabit. The locality of the rein-deer forms a remarkable contrast to that of the camel. It inhabits tracts in the frigid zone as extensive as those wherein the latter is found in the torrid. It can exist in the ice-bound regions of the north alone ; and, being the only hoofed animal which inhabits those climes, is of the utmost utility to that portion of the human race which peoples the same dreary regions, and is even essen- tial to their existence. In America it cannot live farther south than Canada, or in Asia than Siberia. In Europe it abounds in Samoidea, Lapland, and Norway. Many attempts to introduce the rein- deer into more southern countries have failed : the animal invariably dies in a few months. In its native country it runs along the snow with great speed ; and its foot is secured from sinking by a particular formation. In all the ruminants the foot is split into two parts, hence the term cloven- * Pennant's History of Quadrupeds, vol. i. p. 131. The Chinese have a swift variety, which they call by the expressive name oifong kyofo, or, camels with feet of the wind. LETTER VITI. 283 footed. Sir C. Bell thinks this must add to its spring and elasticity : it certainly prevents the foot sinking in soft ground, and permits it to be more easily withdrawn.* But in the chamois, and other species of the deer, there is an additional toe, which projects backwards. " The two lateral toes of the hog are short, and do not touch the ground ; yet they must serve to sustain the animal when the foot sinks. In the rein-deer these bones are strong and deep, and the toe, by projecting back- wards, extends the foot horizontally — thus giving the animal a broader base to stand on, and adapt- ing it to the snows of Lapland, on the principle of the snow-shoe.f The systematic naturalist will call these changes in the size, number, and place of the metacarpal bones (bones of the foot), ' gra- dations ;' I see in them only new proofs of the same system of bones being applicable to every circumstance or condition of animals, and furnish- ing us with other instances of adaptation."^ In my next Letter I shall shew, that the internal organisation of animals is equally adapted to localise them. * " We may observe how much more easily the cow with- draws her foot from the yielding margin of a river than the horse. The round and concave form of the horse's foot is attended with a vacuum or suction as it is withdrawn ; while the spHt and conical- shaped hoof expands in sinking, and is easily extricated.'' — Bell on the Hand, p. 99. t See Plate IV. Fig. 4. } Bell on the Hand, p. 100. LETTER IX. " As the surface of the terraqueous globe is covered with dif- ferent soUs ; with hUls and vales ; with seas, rivers, lakes, and ponds ; with divers trees and plants in the several places; — so all these have their animal inhabitants, whose organs of life and action are manifestly adapted to such places and things ; whose food, and physic, and every other convenience of life, is to be met with at that very place appointed it." — Derham's Physico-Theology, vol. i. p. 236. The second great cause which Hmits the sphere of animals, and binds them down to particular spots, is the infinitely diversified nature of their food, — no species being capable of subsisting upon any other kind than that which has been appointed for its sustenance, and which is only to be procured in certain localities. The digestive apparatus (that by which the food is so prepared as to be fitted to become a part of the living body,) is in all animals modified according to the nature of the food upon which it is destined to act ; and as the varieties of food are almost innumerable, so also this apparatus, though fundamentally the same in every animal, is yet constructed with endless diversity. All the varie- ties of food, however, may be divided into the two great divisions, vegetable and animal ; correspond- LETTER IX. 285 ing to which are the digestive apparatus of her- bivorous and carnivorous animals, in which two classes the whole animal creation may, for our present purpose, be considered as included. In order to maintain that equilibrium in the creation which is necessary to the continuance of animal existence, the Creator has ordained that some animals should serve as food to others ; and this ordination, which at first sight may appear to accord ill with the benevolence of the Creator, is nevertheless a striking proof of that attribute, as well as of the endless resources of our Maker, in- asmuch as it admits of a greater number and variety of creatures being brought into the enjoy- ment of life — an enjoyment so great, that the pain which they endure in losing hfe by the vio- lence of their fellow-creatures sinks into insignifi- cance in comparison with it. Were all animals designed to subsist upon vegetables, thousands of creatures, which we now see enjoying the light of heaven, would never have come into existence, and many other species must have rapidly become ex- tinct. The present wise dispensation provides for the wants of innumerable diverse tribes, and main- tains their relative numbers ; thus preventing their too great increase, and consequent misery from want of food. The whole tribe of monkeys and lemurs, and many of the tardigrade animals, are placed in woods, within and about the tropics, for the express purpose, as I have before observed, of 286 LETTER IX. limiting the number of birds, by destroying vast quantities of the eggs, which in those chmates are produced in myriads. The abundance of birds which, notwithstanding this check, exist in the regions in question, is evidently intended to dimi- nish the prodigious numbers of winged and other insects which are found there, and which would otherwise devastate whole countries.* A similar office is performed by the ant-eaters, and by many species of the lizard tribe. Again, in those countries where the crocodile abounds, an animal has been placed for the pur- pose of destroying the eggs of this monstrous and formidable creature, namely, the ichneumon, or Egyptian cat ; an animal of the weasel kind, which in the southern regions of Asia is held in high esteem, on account of the number of noxious vermin it destroys. Rats, mice, birds, serpents, Hzards, and insects, are all equally attacked by * The words of a modern traveller will give you some idea of the swarms of insects which infest warm chmates. " While I was enjoying hy anticipation the luxury of quenching my thirst with pure water, myriads of winged ants, arising from the earth and stagnant pools, settled upon our faces, heads, shoulders, and hands, buzzing and stinging like bees. Their numbers were in- credible. We appeared to each other like moving ant-hiUs ; for thou"-h we swept them oiF by thousands, until they stunk Hke putrid flesh about our hands and clothes, the swarms never seemed to be diminished until we arrived at Beninsouf, where they were killed with a besom in the court of the caravanserai." — St. John's Travels in Egypt, vol. ii. p. 264. LETTER IX. 287 the ichneumon, which appears to disregard the size of its foes. But what is most remarkable is the sagacity with which it discovers the eggs of the crocodile, though hid beneath the sand. The usefulness of this fierce little creature may be esti- mated, when it is known that the crocodile lays two or three hundred eggs at a time, few of which escape its vigilance. If they were suffered to come to maturity, the country would be rendered unin- habitable by man, and by many other animals which now exist there. The ichneumon was formerly embalmed by the Egyptians — a proof of the high veneration in which they held it. They even wor- shipped it, not knowing the God who made them, and by whose kind providence they were supplied with an animal which freed them from the greatest evils. Having made these preliminary observations, I proceed to the consideration of the digestive apparatus. Vegetable food, differing far more widely in its nature from the constituent parts of the animal frame than animal food of any kind, is neither so easily assimilated, or, in other words, converted into the substance of the body, nor does it contain so large a proportion of nutritive particles ; and hence the construction of the digestive apparatus of herbivorous animals is more complicated, and upon a larger scale, than that of the carnivora. Many of the herbivora have four, and some even 288 LETTER IX. five, stomachs, and their alimentary duct is up- wards of twenty times the length of their body. The stomach of horned ruminants, such as the ox, sheep, &c., is a very complicated organ ; but its complexity is exceeded by that of the un- horned ruminants, as the camel, lama, &c. In the horned ruminants it consists of four distinct com- partments; and these animals possess the extra- ordinary power of keeping the food and the fluids confined in the different divisions, in the order required to complete the digestive process. For this power they are indebted to strong muscular fibres, which are continued down from the gullet into the stomach, passing through that organ in the form of a groove, which terminates in the third cavity. The opening of the gullet into these cavi- ties is between the first and second stomachs, the food passing into the first stomach, or paunch, in a perfectly dry state ; in this bag it is macerated in a considerable quantity of fluid. From the paunch the food passes into the second stomach, or honey- comb bag, from which it is returned to the mouth for more perfect mastication ; and this is termed rumination. When the food has been properly prepared by rumination, it is again swallowed. The groove of muscular fibres appears to be sub- ject to the will of the animal, which by this means is enabled to carry the food, in its second descent, past the two first cavities into the third, or many- plies, whence it is conveyed, through a narrow LETTER IX. 289 opening, into the red, or rennet-bag, the fourth and proper stomach.* Digestion does not com- mence mitil the food arrives here. The first three cavities, which are hned with the same covering as the mouth and gullet, appear to subject the food to certain preliminary processes necessary for rendering it capable of animahsa- tion in the true stomach ; and it is worthy of re- mark, in confirmation of this, that in young ani- mals which are still suckled, the paunch is of a very inconsiderable size ; and the milk, which is a simple animal product and easily assimilated, ap- pears to pass direct into the fourth stomach — the sides of the third cavity adhering closely together. Thus, when the animal is fed upon food analogous to the substance of its own body, the vegetable ap- paratus is closed, being unnecessary. Under these circumstances the paunch is found filled with a glutinous matter, which prevents the admission of food. In ruminant animals arrived at maturity the paunch seems to be a sort of store-room for food, and vegetable matter can be retained there for a considerable time without being changed.f In the same manner the monkeys of the old world use their cheek -pouches, which are situated at the sides of the mouth, and receive the food before it * See Plate III. fig. 4 ; and Plate IV. fig. 1. t Sir E. Home found it half full in an ox that had fasted seven days. — Lecture on Comparative Anatomy, p. 174. U 290 LETTER IX. passes into the stomach, which accordingly is not a very comphcated organ. And it is singular that the only known monkey of the old world {se?ti?iopi- thecus entellus) which has no cheek-pouches, is pro- vided with a stomach more intricate than that of other monkeys.* The stomach of the dromedary has two cel- lular appendages to the paunch, and to the honey- comb-bag there is attached a number of cellular cavities, about an inch in diameter, and sur- rounded by numerous muscular fibres, which have the power of contracting and closing the openings which lead to them so completely, as to retain water without allowing it to be intermixed with the other contents of the stomach during the pas- sage of the ruminated food.f Home says these cells will contain nearly eight gallons ; and when the animal drinks, the fluid passes directly into them. A smaller quantity is conveyed into the cellular appendages of the paunch ; and Cams says that it serves to moisten the food contained in it as much as is necessary to fit it for being returned to the mouth for rumination. When the food is swallowed after rumination, it passes through the second cavity directly into the third, which is very small, and from that into the fourth. Now, this fourth stomach is apparently divided into two portions, which Daubenton considered * See Plate IV. fig. 3. t See Plate III. fig. 3. LETTER IX. 291 were similar to the third and fourth stomachs of the horned ruminants. The difference, then, between the stomach of the camel and that of the ox is, that the former possesses an apparatus for the retention of large quantities of fluid, so indispensable to this animal of the desert ; to effect which, the honeycomb- bag, instead of being made to contain fluids for digestion, as in the latter animal, has been con- verted into a cavity containing numerous mus- cular fibres, which, by contracting its sides upon the fluid, keeps it apart from the food in its pas- sage through ;* and the fluid required for diges- tion, instead of being contained in the honeycomb- bag, is conveyed from the cellular appendages attached to the paunch above mentioned. This is the character of the stomach of the true vegetable-feeders, by which they turn their coarse food into proper nourishment. In Africa the plants are of a more solid and fleshy structure, and afford greater nourishment than those in tem- perate climates ; and accordingly, Buffon observes that several animals which with us have four sto- machs, there have only two. In the true carnivorous animals there is no in- stance of more than one stomach ; and the length * In addition to this provision, these animals have a little bag placed behind the palate, containing a lubricating fluid, which serves to moisten their throat. Blumenbach says, this has only been observed in the camels of the old vv^orld. 292 LETTER IX. of the alimentary duct in some of them does not exceed that of the body. Between these ex- tremes there is every variety of length and com- plication, according to the nature and variable proportions of the food. It may be observed, that all the varieties of food have corresponding con- trivances for their digestion and elaboration. The food of carnivorous animals, approaching in its constituent elements more nearly to those of the body than that of the herbivorous tribes, is more easily converted into nourishment in the former than in the latter case. Hence arises the chief distinction between the stomachs of these two orders of animals. The food of some animals is of a mixed kind, consisting more of vegetable than of animal sub- stances. When these animals have only one sto- mach to carry on the process of digestion, it is ne- cessary to retain the food as long as possible within that cavity ; and we accordingly see every means taken to prevent a rapid passage through it. The oesophagus, or passage leading from the mouth into it, opens considerably to the right of its greater end, so as to leave a large cul de sac on the left side ; and the passage leading out of the stomach {pylorus) is upon the same level as, and near to, the entrance (cardid), leaving a similar blind bag on the right. The food must be detained for a long time in such an organ, and in its passage out has to rise against its own gravity. This is the form of the LETTER IX. 293 stomach of animals of the mouse kind. There is a remarkable difference between the two halves of the stomach in these animals. The internal coat of the left half is covered simply with cuticle, like that which lines the mouth ; and it serves as a sort of reservoir, for no digestion takes place in it ; where this cuticular lining terminates, it forms a prominent ridge, which serves to keep the food separate in the two halves. The right half is the true digesting stomach, and is for this purpose lined with a proper mucous secreting membrane. This kind of stomach forms a connecting link between those of the ruminants and those of truly carnivorous animals ; which latter have the whole of the stomach lined with the proper secreting membrane. In the carnivora, the food in general enters at the anterior portion of the stomach, near one end, and the intestine commences at the oppo- site end ;* so that every thing favours a quick pas- sage of the food. This is the form of the stomach of the weasel. Occasionally we see additional con- trivances made use of in those animals whose food consists of the least nutritious substances, such, for instance, as the bark and chips of trees. The beaver and the dormouse furnish instances of this. Blumenbach says, " There is a pecuhar glandular body at the upper orifice of the beaver's stomach, about the size of a shilling, full of cavities that secrete mucus.f It assists in the digestion and * See Plate III. fig. 1. t See Plate III. fig. 2. 294 LETTER IX. animalisation of the dry food which this curious animal takes, consisting chiefly of the barks and chips of trees, &c."* Very few quadrupeds are wholly destitute of teeth ; and the trituration and mastication of their food, performed by these instruments, renders it unnecessary that the stomach should be sur- rounded by such strong muscular bands as are seen in the gizzard or stomach of birds. But the pangolin, or scaly lizard, has no teeth ; and accordingly it is provided with a stomach which compensates for their loss, being almost as thick and muscular as that of the gallinaceous birds, and containing, like it, small stones and gravel ; the probable use of which is, to bruise and kill the insects that form the ordinary food of the animal, and which might otherwise, by means of their vitality, resist the action of the gastric juice.f Apart from the instinct which is so remarkably displayed in almost all animals in obtaining their food, we notice other parts of their organisation^ besides the stomach, expressly devoted to this purpose. Many animals are distinguished by the form of their head and the numerous horny pro- cesses which issue from it, and which are fre- quently of great service in enabling the animal to procure food. This is strikingly the case with the rein-deer (cervus tarandus), which, as I have before told you, is confined to the northern coun- * See Manual of Comparative Anatomy. f lb. LETTER IX. 295 tries, that are almost continually covered with deep snow. In the winter season this animal sub- sists entirely upon rein liver-wort (lichen rangi- ferinus), a lichen very abundant in those parts, but which frequently lies buried several feet be- neath the snow. The rein-deer has large but slender horns, covered with a down like velvet, branching forward over its eyes, and palmated towards the end. By means of these instruments the animal is able to satisfy its wants : it em- ploys them to remove the deep snow from the ground, and thus arrives at the food destined for its subsistence. The down which covers the ant- lers prevents the snow from adhering to them, and so impeding their progress. It is not the least proof of the superintending care of the great Parent of good, which we have seen so fully dis- played in this animal, that it is the only species of stag to the female of which antlers have been given.* Though not strictly belonging to this division of my subject, the peculiar contrivance on the head of the rhinoceros-beetle, for enabling it to * There is perhaps no single animal upon which the exist- ence of man in any part of the globe is so entirely dependent as upon the rein- deer in the glacial countries. It serves him at once with food and raiment, and it transports him from place to place, — three indispensable conditions of his existence. Its flesh, blood, and milk serve for food, its skin for clothing, and its tendons are used to make tackle for sledges and bows ; so that it supplies the place of the horse, the cow, the goat, and the sheep. 296 LETTER IX. obtain its food, may not inappropriately be noticed here. The knife-grinder, or rhinoceros-beetle, re- sembles the common beetle in shape and colour, but is much larger (about six times as large) : it has a long stout horn projecting from the end of the nose, forming a curve backwards, and a smaller one behind and beneath, forming a curve forwards. With these horns the knife-grinder seizes on the young branches of trees ; then, set- ting its body in rapid circular motion, attrition is kept up for some time, until the wood is com- pletely sawn through, the insect making all the while a deafening noise, like that of a knife-grinder holding steel against the stone of his wheel. When the branch drops off, the animal strips it of the bark, upon which it subsists.* In many parts of the western continent, black and red ants are so prolific, as well as destructive, that several animals are placed in those parts for the express purpose of keeping them under. Martin says, " The red ant is a very destructive insect : its march is in dense columns of myriads at a time, destroying and devouring every thing in their way. These vermin, in utter contempt of the safeguard of lock and key, make their way through the smallest crevice, and take up their abode as long as any thing in the shape of food remains : it is said, indeed, that they will cover the whole body of a sleeping person, and there stick with the tena- * Martin's History of the British Colonies, vol. ii. p. 109. LETTER IX. 297 city of leeches until satisfied. They have even been known to cause the death of animals by lodging themselves in the hollow part of the foot, and eating their way clean to the bone."* The creation of an animal adapted to dwell in the regions where these destroying insects abound, and to subsist entirely upon them, is another proof of the wisdom by which the animal kingdom is regulated. Such an animal is the ant-eater, or ant-bear : the organisation of which is admirably suited to the nature of its food. It has two, three, or more claws on the fore feet, one of which is generally much longer than the rest. It com- mences its search for food by scratching the ant- hills with these long claws ; and when, alarmed by this proceeding, the insects flock from all quarters to defend their dwellings, it draws over them its cylindrical tongue, which resembles a worm, and may be protruded about eighteen inches. When the tongue, which is covered with a glutinous substance, is loaded with ants, the bear withdraws it into its mouth ; and so expert is the animal at this operation, that it is asserted to protrude the tongue and draw it back again twice in a second. I have already mentioned, that nearly all qua- drupeds are furnished with teeth,f instruments * Martin's History of the British Colonies, vol. ii. p. 112. t All the mammalia have teeth, except the proper whciles (balcenee) ; the Asiatic and African ant-eaters, called scaly lizards or pangolins (manis) ; and the American (south) ant-eaters (myr- 298 LETTER IX. for preparing the food to undergo digestion, which have been formed with so strict a relation to the food designed for their subsistence, that they indi- cate with great accuracy the mode of hfe pursued by many creatures now extinct. So true is this, that some early systems of classification were entirely based upon the form and structure of the teeth. Linnaeus made his arrangement with refer- ence to this part of the skeleton. But the teeth are not subservient to the purposes of digestion alone. " Considering the teeth generally as belong- ing to man and the brutes, they are for masticating the food ; they are for retaining the prey ; they are for weapons of defence ; in some classes they are for digging and searching for food ; in some ani- mals we can see no other use for them than for defending the eyes, as in the sus cethiopicus* Nor mecophaga). Among the amphibia, frogs and toads have no teeth — the margin of the jaw being denticulated. The whole class of birds are destitute of teeth ; and by way of compensation, many of them have very strong muscular stomachs, which contain stones that act on the principle of a grinding-mill, and thus serve the purpose of teeth. Of fishes, in which the greatest variety in the form, distribution, and structtu-e of the teeth is observed, the sturgeon is toothless. Whales have in place of teeth a peculiar substance known in commerce by the name of whalebone, which covers the whole surface of the upper jaw, and in its composition resembles hair, horn, and suchlike materials. * The use assigned in Paley's Natural Theology (chap, xiii.) to the tusks of the babyroussa (sometimes called the horned hog, or stag-boar,) has been proved not to be the real one. The animal does not, as was supposed, use them to support its head LETTER IX. 299 are we to consider them as exclusively belonging to the jaws, for they are sometimes seated in the back part of the mouth; and in fishes we find them in the beginning of the oesophagus, or at its termination (at the entrance of the stomach), as in the crab and lobster." The structure of the teeth, both as to shape and composition, is admirably adapted to each of the purposes above named. Thus, in animals that live on meat, the digestive power of the stomach is so great as to render mastication unnecessary ; and hence the teeth, being used merely to seize the prey, are sharp-pointed, and only externally covered with enamel.* The teeth of man and those animals whose food consists partly of animal and partly of vegetable substances — of carnivorous ani- mals in general — and of those which live on fruits and seeds, as the quadrumana, — are of this kind. In herbivorous animals, whose food must be ground like corn in a mill, the teeth have a broad irregular upper surface ; and the use to which they were to be applied was considered, not only in their during sleep, by hooking its upper tusks upon the branches of trees. Home says, upon the authority of his friend Mr. Marsden, that, inhabiting the densest thickets of Sumatra, they employ them as a defence to their face and eyes. — Home, vol. i. p. 212. * The substance which covers the crovi^n of the teeth, caUed enamel; is characterised by its peculiar hardness ; sparks of fire may be produced by striking it against steel. No animal matter enters into its composition, and it equals in density the hardest marble. 300 LETTER IX. shape, but in their internal construction also ; for, as scarcely the hardest material could long resist the constant friction to which the teeth of these animals are exposed in preparing their food, the striated cortex or enamel is distributed, not only over the body of the teeth, but extends into the osseous portion, forming convolutions in their structure, evidently intended to resist the friction, v^^hich would otherwise soon wear them down, and render them plane and unfit for the office of grind- ing. For the purpose of preventing rapid detrition, the teeth of all the ruminants, of the elephant, the horse, the Indian hog, and of many of the chisel- toothed animals {edentata), have, in addition to the ivory and enamel, a third substance, still more durable, which forms part of the grinding surface.* These component parts vary in their positions and relative proportions according to the food, the habits, and the locahties of different animals ; and these variations often constitute the only essential distinction between the species of the same genus. The Asiatic and African elephant are distinguished by the arrangement of the ivory and enamel in their teeth. In the Asiatic variety, the teeth are constructed for triturating herbage, which con- stitutes its food. In that of Africa, on the other * This substance was discovered by Blake, who called it the fars petrosa, or stony part. See his work on the teeth of various animals ; also Sir E. Home's paper on the structure of the teeth of graminivorous animals, in Phil. Trans, abrid., vol. xviii. p. 519. LETTER IX. 301 hand, the teeth have less ivory in their internal structure, because it feeds on the more fleshy kinds of shrubs, which grow only in the tropics, and require less mastication. But the difference between the teeth of the Asiatic and those of the African rhinoceros is still more remarkable. The former animal has two sharp, chisel-like, incisor teeth in the front of the lower jaw, and two flat or lobular ones in the upper jaw to receive them. This animal can cut the grass and herbage on which it feeds as with a knife on a block. The African variety has no provision of this kind, as its food is more fleshy, and does not require to be so cut. The teeth of most animals seem to have been formed to last during their lifetime, and hence they are firmly fixed by fangs into the jaw ; but having been once formed, they do not increase ; their surface above the socket in the jaw, but not below it, being covered with a plate of enamel, which, being an inorganic substance, cannot grow. Some animals, however, such as the beaver, squirrel, rat, and hare, have \he\r front teeth so formed that the substance of the tooth, as it is worn down, may be replaced. As they exist upon the hardest vegetable substances — to obtain and masticate which they must have teeth peculiarly fitted for cutting, — the front edge only of their teeth is covered with enamel, which, being harder than the body of the tooth, the latter wears down much 302 LETTER IX. faster, leaving a very sharp edge of enamel, admi- rably calculated for penetrating the hard bark of trees ; yet, as this employment subjects the teeth to great friction, they are rapidly worn away, and would soon be completely destroyed, did they not possess some unusual power of reproduction. Ac- cordingly they are very deeply implanted in a hori- zontal position in the jaw-bone, where the enamel is secreted, in readiness to be projected whenever it may be required for use. In the beaver, the enamel pervades the body of the tooth, as well as surrounds the external surface. The front teeth of the hippopotamus, which have the chisel form, are rather pecuhar. Sir E. Home says : " The two teeth corresponding to the incisors in the upper jaw have an outer crust of enamel, while the cor- responding ones in the lower jaw consist wholly of ivory." * Thus, the deeper we investigate the structure of animals, and consider it in connexion with the offices assigned to it, the less reason shall we have to doubt, that all the minutest shades of difference have some relation to the mode of life allotted to each animal; and the more clear it will appear, that all animals have a boundary assigned to them, beyond which their organisation will not permit them to pass. But to enumerate all the modifica- tions by which different animals of the same genus have been qualified to occupy the various climates * Lectures on Comp. Anat., vol. i. p. 193. LETTER IX. 303 and places in which we find them, is a task, you must be aware, requiring for its performance knowledge far exceeding that which man at pre- sent possesses. I shall now consider the third great cause to which the distribution of animals is attributable ; namely, the nature of the apparatus for respiration and for the circulation of the blood. And here I must lament, that the compass of this work will not admit of my giving you more than a general idea of the Divine wisdom displayed in the adapta- tion of this part of the organisation of animals, which is no less calculated to meet every contin- gency than those parts of their structure to which I have already adverted : I can only point out the more striking examples of this adaptation. Respiration, as before mentioned, is the func- tion by which the atmospheric air is brought into contact with the blood, which absorbs oxygen from the air, and thus maintains its vital power, which is rapidly lost when respiration is inter- rupted. The breathing organs are placed either on the surface of the body, in which case the skin is the sole respiratory organ, as in the lowest orders of animals ; or in the interior of the body, and communicate with the air by means of a tube called the windpipe, which commences in the mouth, and passes down the throat. The latter apparatus is better fitted for animals in the more advanced stages of development, where the unin- 304 LETTER IX. terrupted communication of the air with the blood is necessary. This apparatus is called the lungs, the modifications of which, peculiar to birds, will be hereafter explained. Between these extremes there are many varieties of contrivance for accom- plishing the same end. In fishes the apparatus is called gills, — the breathing organs best fitted for extracting air from the water, with which they are in contact. The amphibia have lungs capable of retaining the atmospheric air within them, and so of obviating the necessity for frequent acts of breathing, which would be incompatible with their long continuance under water. They are for this purpose provided with large air-sacs ; and those of the amphibia which are more water-breathing than air-breathing have air-bladders, or, as they have been called, swim-bladders, communicating with the stomach and intestinal canal ; which organs, as we advance downwards, are themselves made subservient to breathing. Thus, there are also intestinal organs of respiration. In the arach- nida (the spider tribe), and in insects, there are tracheal organs which ramify minutely over all parts of the body, and aerate the blood. Cams discovered a visible circulation in insects. In the fifth Letter I gave you a brief descrip- tion of the nature and use of the circulation, as it is found in the higher vertebrated animals. I there pointed out how essential it is that the blood should be fully exposed in the lungs to the oxygen LETTER IX. 305 of the atmosphere, as it traverses those organs ; in its subsequent circulation receiving from one set of vessels the nutritive parts of the food, to be converted into blood, and giving out in various organs peculiar juices, which are employed for the purposes of the economy. But so complicated a system is not required in all animals, and is indeed dispensed with, to a considerable extent, in most of the lower races. As the duties and wants of animals become more hmited, so is the circulation narrowed and simplified, till we reach the lowest example ; yet even in the most simple structures, vessels for conducting the circulation are observ- able. Ehrenberg has discovered them in the roto- toria; and even microscopic minuteness does not preclude their existence.* The wisdom of God, in giving to all animals peculiar modes of circulation, is such as to call for the highest admiration. The circulatory sys- tem, like all other contrivances in which his hand can be traced, is made to answer a number of important purposes in addition to that which it is specially intended to subserve. Thus, of no animals, except the mammaha and birds, is the heat of the blood suffered to rise more than a few degrees above that of the surrounding media ; in consequence of which law, they are enabled to live in places and circumstances in which the higher animals could not exist ; for instance, in * Miiller's Physiology, p. 155 (translation). X 306 LETTER IX. water at the freezing point. Tiedemann observed, that at night, when water was frozen, a frog placed in it had a temperature of 33" Fahrenheit, and the water immediately surrounding it was not frozen.* But cold-blooded animals, especially fish inha- biting lakes, are frequently placed in circumstances where the cold is so intense as to render this pro- vision insufficient for their protection : this state of things is provided for by the remarkable condition of the animal economy denominated hyhernation, to which warm-blooded animals also are sometimes subject; during the continuance of which animals are in a dormant state, neither eating nor breathing. Thus, fishes can exist while encased in ice, pro- vided their vital powers are in this state of com- plete torpidity. Pallas relates that, on the melt- ing of lakes in Siberia, crucians {cyjmnus crassiits), which have been frozen to the bottom, are restored to life ; and mentions a similar fact observed by Bell, namely, the revival of gold fishes from frozen water.f Insects and mollusks of temperate and cold climates are subject to hybernation. Another important end besides that above mentioned is an- * Physiology (translation), p. 240. -j- In Rudolphi's Grundriss der Physiologic, vol. i. p. 176, quoted inMuller's Physiology, p. 81. Franklin observed, that when the fish were taken out of the nets, near the Copper-mine river, they were frozen, and in a short time became a solid mass ; so that, by a blow with a hatchet, they were easily split open. On being thawed before the fire, they recovered their animation. LETTER IX. 307 swered by hybernation : when food is in abund- ance, these animals are hvely and on the alert ; but as it becomes more scanty, their circulation growing languid causes them to fall into that state, in which they continue during the winter months, without food, and almost without life, till the pe- riod of their usefulness returns, and they are again required to keep under the smaller animals on which they feed. It is remarkable that many animals, which in northern countries pass the winter in a dormant state, are not distinguished by this peculiarity in more temperate climes. The fact, that these animals become quite fat before the period of hybernation commences, and that when the time of their reappearance arrives, they have become thin and even emaciated, proves how wisely the Creator has provided a means, out of the ordinary course of nature, for preserving his creatures in those countries, at a season when no food is to be obtained. A further proof that such is the design of this wonderful provision is, that the bear in its half- tame state, that is, when it is able to accommo- date itself to different circumstances, and is never without a supply of food, loses this habit. But even in a state of nature the bear hybernates but imperfectly. In Norway, Laing says, " it retires to its den, which is generally some sheltered hole in the rocks of the Fjeld, in November, and re- mains in a dormant, or inactive state, without food, OUO LETTER IX. until April. The female brings forth her young, and suckles them, during this period of hyberna- tion ; the animal functions are therefore not en- tirely suspended. It is said there is nothing found in the stomach or bowels of the bear when he is tracked to his winter lair and killed, and that he eats nothing for some days before retiring ; that he is quite fat at that period, but when he reap- pears is very meagre and exhausted. Many of the smaller animals, the field-mice, the lemmings, and perhaps many of the birds, pass the winter in this climate in a state of occasional torpidity. They retire, and are not to be seen, during the continuance of very severe weather in winter."* *' The temperature of animals during hybernation, although it falls proportionately with the tempe- rature of the surrounding air, still is 4^" Fahren- heit higher than it. Respiration is kept up, though slowly and almost imperceptibly. The marmot during hybernation breathes seven or eight times in a minute ; the hedgehog four or five times ; the great dormouse nine or ten times in the same period. During the state of the deepest torpor, * Residence in Norway, p. 327. Otto says, the following genera are subject to a state of more or less complete hybernation ; viz. the bat, hedgehog, shrew, mole, lemming, mouse, hamster, jerboa, marmot, gerbil, and squirrel. Blumenbach says, that, " as far as he knows, no bird hybernates ; but the greater part of the amphibia sleep during all the winter season." — Manuel d' Hist aire Naturelle, vol. i. p. 47. LETTER IX. 309 however, respiration ceases entirely ; and then the animals, if Spallanzani's observation is correct, may- be placed with impunity in an irrespirable gas.* Saissy found that, until this last state ensues, they continue to remove the oxygen from the air, the quantity of oxygen consumed decreasing as their temperature falls ; but it still continues, together with the exhalation of carbonic acid, as long as any oxygen remains in the air ; whereas animals which do not hybernate, such as rabbits, rats, and sparrows, die when they have consumed a small portion only of the oxygen of the air contained in the vessels."f But hybernation is not in all cases the result of a low temperature. Being an arrest of the functions of life, induced when the growth of vegetation is stopped, or the increase of the smaller animals and insects prevented, we find animals in hot climates also, during great drought, brought under the in- fluence of hybernation. Within the tropics, when the heat has dried up those places which would * Dr. M. Hall shewed, that the power which hybernating animals possess of supporting the deprivation of atmospheric air belongs peculiarly to this state. After having found that the dor- mant bat in summer endured immersion in water during eleven minutes uninjured, he was anxious to know whether the active hedgehog possessed the same power. He immersed one of these animals in water ; it expired in three minutes, the period in which immersion proves fatal to all other mammalia. — See his paper in Medical Gazette, vol. xi. p. 211. t Midler's Physiology, p. 78. 310 LETTER IX. otherwise teem with food, the same phenomena occur as in the depth of the arctic winter. Hum- boldt remarks, that the dry season of the torrid zone corresponds to the winter of the temperate regions of the globe ; and that, while the alhgators of North America become torpid through excess of cold, the crocodiles of the Llanos are reduced to the same state through deficiency of moisture.* " In the dry season," says Miiller, " reptiles bury themselves, and fall into a state similar to hyber- nation, from which they recover in the rainy sea- son. In warm-blooded animals there is only one known instance of this summer sleep, that is the tanrec,— the hedgehog of Madagascar." Dr. Edwards's f experiments upon some of the lower animals are extremely interesting, proving how httle vital principle their blood requires to carry on the functions of life. He shewed that frogs and salamanders possess the power of living after the circulation and respiration have been arrested. He cut out the hearts of several frogs and salamanders, leaving some of the animals so treated in the air, while he put others into water deprived of air by boihng. The salaman- ders lived seven or eight hours in the water, and from twenty -four to twenty -nine hours in the air. The frogs lived a similar period. If a frog was kept immersed in water till no sign of life * Travels in North America, by Macgillivray. f See his work on the Influence of Physical Agents on Life. LETTER IX. 311 was left, it speedily revived on exposure to the air. Such facts prove that the air affects these animals by directly influencing the nervous and muscular systems, independent of any power it may possess through the medium of respiration. If a tight hgature were tied round the neck, so as to prevent any access of air to the lungs. Dr. Edwards found they lived in some cases five days. This fact may convince us that many reptiles are capable of existing without so large a supply of oxygen as is required by warm-blooded animals. The lower animals are often placed in such situa- tions as the clefts of rocks, or under the banks of rivers, and in the winter-time they penetrate some depth in the earth ; so that the necessity for breathing frequently, and thus deriving all their vitality through the lungs, would incapacitate them for their sphere of life. Accordingly we find that the air may be transmitted to their blood through the skin. This remarkable power of cutaneous respiration, coupled with the fact, which has been demonstrated by experiments, that rep- tiles grow by absorption,* will serve to shew the groundlessness of the incredulity with which the well-attested accounts of the existence of toads in the hearts of trees, and even in solid rocks, * See Townson's Tracts and Observations on Natural His- tory. 312 LETTER IX. have generally been received.* Many of these accounts are certainly very marvellous, particu- larly as they have been drawn up without regard to scientific exactness. They are, however, quite reconcilable with strict philosophical deductions ; and they present us with a durable monument of the bounty of God, in bestowing life capable of being maintained under such adverse circum- stances. Out of a vast number of well -authenticated statements, I select the following : A correspond- ent in Loudon's Magazine of Natural History says, " I have a toad in my possession, preserved in spirits of turpentine, taken from a cavity of the solid rock upwards of two hundred feet deep. The space was quite sufficient to contain the body of the animal ; and the gentleman who presented the specimen to me saw it alive forty-eight hours after its detachment from the rock."f At Chatsworth there is a print of a toad upon a marble chimney- piece, with an account of the way in which it was discovered. A wet spot had always been observed upon a freestone mantel-piece, which afterwards cracked at that place ; and upon its being taken down, a dead toad was found in it. J It was * Bacon has noticed the fact of toads being found in soUd rocks. See also Plott's History of Staffordshire, t Vol. vi. p. 453. + Jesse's Gleanings in Natural History, vol. i. p. 116. LETTER IX. 3 1 3 conjectured that this animal had died for want of moisture in the stone ; and there is httle reason to doubt that, had the stone been placed in a moist situation, the animal would have existed in spite of the contrivances of art, or the unnatural position in which it was placed.* For the fact of their having been found in the interior of oaks, elms, and other trees, I rely chiefly on the accounts given in the Memoirs of the Academy of Sciences. That these accounts are not inconsistent with reason, we shall have no difficulty in believing, when we consider that the skin is the real organ of respiration and nutrition in frogs and other rep- tiles. Herissant shewed this by his experiments before the Academy of Sciences, in 1777 ; and Dr. Edwards afterwards confirmed it by several experi- ments. He entirely removed the lungs of frogs from the body, and they lived more than a month after- wards— the skin being kept moist. As long as aerated water is supplied in sufficient abundance, the vessels of the web between the toes of a frog may be seen to contain oxygenated blood. The power of absorption which resides in the skin of these animals is very great. Townsonf says, that a frog can absorb its own weight of water in a few hours; and the less moisture a toad is supplied * For further accounts of these discoveries, see Young's Geo- logical Survey of the Yorkshire Coast, — Loudon's Mag. of Nat. Hist. vol. vii. t Tracts. 314 LETTER IX. with, provided that little is capable of sustaining vitality, the more torpid the animal is observed to become.* I particularly mention this, because it is a physiological proof of the indefinite length of time during which the vital principle may be pre- served in many reptiles. The wisdom of Provi- dence, in so constituting the lower animals that they do not require to breathe during their fre- quent submersions under water, or even during a long hybernation, is obvious. That these animals can exist for many years enclosed on all sides by sohd rocks, or sealed up in the hearts of trees, is, in my opinion, most satisfactorily established in the works of the late Dr. Edwards, who has shewn, that as long as air and moisture, however small in quantity, can be conveyed to reptiles thus placed, they may live for an indefinite period of time. One of the most remarkable accounts of the long duration of the vital principle in animals, with which I am acquainted, is mentioned by Dr. SilH- man,f who, on the authority of Professor Eaton of New York, states that the diluvial deposit through * The office of absorption which the skin of these reptiles performs, requires that organ to be kept constantly moist : and for this purpose, Bennett says, they are provided with a cavity which always contains water ; and thus, when the animal is exposed to a dry atmosphere, it has the power of conveying the water from this reservoir to the surface of the body, and so keeping the skin moist. — See note to his edition of White's Selborne, p. 96. t American Journal, No. 15, p. 249. LETTER IX. 315 which the Erie canal was made, contains ridges of hard compact gravel, and that on cutting through one of these near Rome village, sixteen miles west of Utica, the workmen found several hundreds of live molluscous animals. They were chiefly of the mya curiosa and the mya 'purpurea. The workmen fried and ate them. He adds, " I was assured they were taken alive forty-two feet deep in the deposit. Several of the shells are now before me. The deposit is diluvial. These animals must have been there from the time of the deluge ; for the earth in which they were is too compact for them to have been produced by a succession of genera- tions. These fresh-water clans of three thousand years old precisely resemble the same species which now inhabit the fresh water of that district ; there- fore the lives of these animals have been greatly prolonged by their exclusion from light and air for more than three thousand years." A toad was buried in a flower-pot for twenty years, and when taken out was found to be healthy and increased in size.* That snails can exist for a long period by means of the exclusion of air, and the retention of moisture, which they are enabled to accomplish by the eplphragma, a sort of door at the aperture of the shell, has been proved by Mr. Simon,f who mentions the circumstance of having had one in his cabinet for fifteen years; and, for * Jesse's Gleanings in Natural History, t Phil. Trans, abrid., vol. xiii. p. 565. 316 LETTER IX. ought he knew, it might have been in his father's possession many years before, as it was in his col- lection of fossils. Speaking of this snail, he says, it had come out four several times, in the presence of different people, each of whom assured him that they saw it. A day or two after this, he brought the identical shell, as he declared, into the pre- sence of several other persons, that they might try if the snail would again make its appearance. After the shell had lain ten minutes in a glass of warm water, the snail began to appear, and in five mi- nutes more they perceived half the body fairly pushed out from the cavity of the shell. It after- wards crawled about, erected its horns, and seemed in perfect health. According to Gaspard, snails hybernate in winter as well as in summer ; so that this state would seem to be brought on either by want of heat or moisture : and therefore the truth of Mr. Simon's account is not to be doubted. If this snail was the cyclostomum thermale (Ranzani), which lives in the hot springs of Abano, the tem- perature of which is 83|° Fahr., and which has been seen by Rudolphi moving briskly in water at 99i° Fahr.,* this will account for its making its appearance when placed in warm water by, Mr. Simon. Edwards repeated Herissant's experiment, by enclosing toads in boxes of plaster of Paris sealed u}), which, at the end of eighteen montlis, were * See Miiller's Physiology, p. 82 (translation). LETTER IX. 317 taken out alive.* That air in some way or other must have reached them, was proved by immersing the boxes which contained the toads into water, when they very soon perished. After what has been said about cutaneous breathing in the lower animals, you will have no difficulty in believing that a toad can be maintained alive, though immured in the centre of rocks or in the hearts of trees. The difficulty of existing under such circumstances is greater in appearance than in reality ; for if respiration through the lungs were essential to the life of all animals, it is very certain these incarcerations would be incompatible with existence. There is a class of animals called amphibious, because the food on which they live, or the places assigned for their dwelling, or some other circum- stances connected with their economy, render it necessary that they should be capable of existing under water as well as on land. If they were designed to be entirely aquatic animals, or, on the other hand, to live always on the earth, the apparatus of gills in the one case, or the apparatus of lungs in the other, would be found to answer every purpose ; but, as I shall presently shew, these animals would die of suffi)cation, were they furnished only with gills ; and the pulmonary apparatus of the higher animals would be equally certain to produce the same effect. The provision * This was the case with two out of three. 318 LETTER IX. made under their peculiar circumstances, for the support of life, is one of the most remarkable proofs of the wisdom manifested in the creation. In those wonderful animals, the syren lacertinay first dissected by Mr. Hunter, and the i^roteus an- guinus, from the Cirknitz lake of Carniola,* there are not only two bladder-like lungs, but also the regular gill apparatus. By this arrangement, they are rendered capable of living in subterranean and stagnant water, where a fish with gills only would die. In the tadpole, and the young of some hzards which bring forth in the water, there are two organs resembling the gills of fishes, which, as the animal advances towards maturity and becomes less aquatic, dry up, and are replaced by lungs. Three minutes is the utmost length of time that warm-blooded animals can continue under water without breathing.f So short an interval as this between the acts of breathing would be incom- patible with the existence of amphibious animals. Unless some contrivance for retaining the air in their bodies had been made, so as to obviate the necessity for frequent breathing, these animals could not have formed part of the creation. The principle upon which the lungs of amphibious ani- mals are constructed is, that, instead of having a * Phil. Trans, abrid., vol. xii. p. 360. t The exploits of some of the native Indians would seem to shew the possibility of this period being prolonged a minute or two by long practice. LETTER IX. 319 natural power to contract, which is the character of the lungs of warm-blooded animals, they remain expanded, and the air is driven into them, not by the formation of a vacuum, which that contraction in warm-blooded animals creates, but by the action of muscles ; so that the lungs are a mere mem- branous bag, divided into cells or vesicles for the reception of air. When a frog inspires, it first shuts its mouth, and by the action of the muscles in the throat, causes a vacuum there ; the air is then drawn in with great rapidity through the nostrils to fill this vacuum — its return being prevented by the action of the tongue, — and it is then driven down the windpipe, which is the only passage left open. It follows then, that, in order to suffocate a frog, it is only necessary to keep its mouth open. The lungs of these animals extend down into the belly, and the air is expelled from them by the abdomhial muscles. By this means the animal is enabled to retain the air in its lungs for an arbi- trary period. LETTER X. " Doth the hawk fly by thy wisdom, and stretch her wings towards the south ? Doth the eagle mount up at thy com- mand, and make her nest on high ? She dwelleth and abideth on the rock, upon the crag of the rock and the strong place. From thence she seeketh the prey, and her eyes behold afar oiF."— /o6, xxxix. 26-29, Having, in the two preceding Letters, considered the organisation of land animals, and shewn its adaptation to the varieties of climate, locality, and food, which the earth's surface presents, I now pro- ceed to treat in a similar manner the next class of animals, — birds, which inhabit the regions of the air, and differ widely in structure and habits from all other kinds of living beings. You will remember that, in my third Letter, I explained the necessity for warm blood in some of the vertebral animals, and the manner in which that blood is circulated through the body; and that I shewed how the blood of birds, by its ele- vated temperature, rarefies the air in their bodies, and thereby renders them specifically lighter than the atmosphere. I shall now resume that subject, to enable you fully to comprehend which, I must first direct your attention to the nature of that fluid. The best eudiometers, or instruments for mea- suring the purity of the atmosphere, shew that it LETTER X. 321 is composed of one-fifth of oxygen gas and four- fifths of nitrogen (frequently called azote) ; but the solvent power which it possesses being ex- ercised upon innumerable substances, causes it to contain a portion of every thing it is capable of suspending, just as water is found to contain particles of whatever it can dissolve.* Whether the oxygen and nitrogen composing the atmo- sphere are chemically combined, or whether they are in a state of simple mixture merely, without being united, I shall not inquire, as this is a question of no importance in reference to the sub- ject before us ; but, as Dr. Prout very justly says, " were the gaseous principles composing the atmo- sphere in ever so slight a state of union, they could not readily diffuse themselves through each other ; and partial accumulations of one or other of * " The immense mass of permanently elastic fluid that sur- rounds the globe we inhabit must consist of a general assemblage of every kind of air which can be formed by the various bodies that compose its surface. Most of these, however, are absorbed by water ; a number of them are decomposed by combination with each other ; and some of them are seldom disengaged in considerable quantities by the processes of nature. Hence it is that the lower atmosphere consists chiefly of oxygen and nitrogen, together with moisture and occasional vajjours, or exhalations of bodies. The upper atmosphere seems to be composed of a large proportion of hydrogen, — a fluid of so much less specific gravity than any other, that it must naturally ascend to the highest place, where, being occasionally set on fire by electricity, it appears to be the cause of the aurora borealis and fire-balls." — Ure's ChC' mical Dictionary . y 322 LETTER X. them would be constantly taking place; but as the atmosphere is at present constituted, if a little more oxygen be consumed in one spot than in ano- ther, instantly the deficiency is supphed from the neighbourhood by diffusion, and the equilibrium is scarcely affected in a sensible degree."* The fact to which I would here draw your attention, as a proof of the providing care of the Creator, is the wonderful property which the atmosphere pos- sesses of constantly maintaining a fixed standard of its constituent parts, in opposition to the nu- merous causes which are operating to deteriorate and alter them. If it were regulated by a mere chemical law, this equal diffusion of its constitu- ents could not take place, and it would therefore be unable to support either vegetable or animal life. The atmosphere is of so elastic a nature, that it is capable of being expanded or compressed to almost any degree. It is supposed to extend up- wards of forty miles above the earth's surface ; but as, at the level of the sea, it exerts a pressure equal to fifteen pounds upon every square inch, it is necessarily more condensed near the surface of the earth than in the higher regions ; so much so, indeed, that at an elevation of three miles the pressure is found to be diminished one-half. This accounts for the upper air being expanded, or, as it is called, rarefied, to such an extent as to be inca- * Chemistry and Meteorology, p. 202. LETTER X. 323 pable of supporting animal life ; oxygen, which is the heaviest of the constituents of the atmosphere, and which, as I have already shewn, is essential to organised existence, being almost wholly wanting. The specific gravity of air, according to Biot, is 820 times lighter than water ; according to the experiments of Sir George Shuckburg, one hundred cubic inches of it weigh little more than thirty grains troy ; so that this fluid is lighter than almost any other substance with which we are acquainted. Let us now consider the adaptation of the structure of birds to this subtile element. " It is in birds alone," says Roget, " that we find the most perfect adaptation of structure to the purposes of rapid and extensive flight : in them the frame of the skeleton, the figure, position, and structure of the wings ; the size of the muscles, the peculiar nature of their irritability, and even the outward form of the body, have all a direct and beautiful relation to the properties of the element in which nature has intended them to move. As they swallow their food entire, there is no necessity for the bulky apparatus of hard and solid teeth, large muscles, and heavy jaws, which are required by most quadrupeds : hence the head admits of being greatly reduced in its dimensions ; and the form of the beak, which is drawn to a point, and cuts the opposing air, tends to facilitate the pro- gress of the bird in its flight. Great condensation has been given to the osseous substance, in order 324 LETTER X. that the greatest degree of strength might be pro- cured with the same weight of sohd materials ; and the mechanical advantage derived from their being disposed in the circumference rather than in cen- tral masses, has been obtained to the utmost extent. The horny material of which the stems of the feathers are constructed is, in like manner, formed into hollow cylinders, which, compared with their weight, are exceedingly strong. A similar shape has been given to the cylindrical bones, which are fashioned into tubes, with dense but thin sides ; most of the other bones have like- wise been made hollow, and instead of their cavi- ties being filled with marrow, they contain only air."* Still, birds would be unable to raise themselves from the earth's surface, had not some provision been made by which their bodies are capable of being rendered lighter than the specific gravity of the atmosphere. The contrivance by which this is effected, and which is subservient to other important purposes in their economy, as I shall take occasion to shew, is what we have now to consider. The lungs of birds are distinguished by several striking peculiarities from those of quadrupeds : they are almost incapable of motion, being firmly fixed to the back part of the thorax, and are much smaller in proportion to the size of the body ; a * Animal Physiology, vol. i. pp. 555, 6. LETTER X. 325 fact which, considering the mode of their exist- ence, you will be astonished to learn. But this is more than compensated for by the numerous mem- branous air-cells, which occupy a considerable part of the abdomen as well as of the thorax, and are found also between the muscles. All these cells communicate with one another and with the lungs, from which they are supplied with air, which by this apparatus is conveyed to every part of the body ; even, as has been already noticed, into the interior of the bones. These cells are largest and most numerous in those birds which take the high- est and most rapid flight, as the eagle, the hawk, and the lark ; in them they are found even in the integuments of the neck, and under the blade- bones. The advantages derived from this construction in lightening the body of the bird and facilitating its motions, whether in flying, swimming, or run- ning, are obvious, and a brief exposition of them will be sufficient. The great space in the interior of the body by this means filled with air, not only materially diminishes its weight, and thus conduces to the facihty with which it is supported in the atmo- sphere, but at the same time furnishes an ample supply of that fluid for the vital purposes of the economy ; and it is probable that to this extensive diffusion of air over every part of the body is attri- butable the more complete oxydation of the blood 326 LETTER X. of birds, and consequently its higher temperature, which, reacting upon the air contained in the cells, expands it, and renders it specifically lighter than the external air, and thus counteracts the weight of the body, enabling it to float in the atmo- sphere without any exertion on the part of the bird — a fact which I shall presently endeavour to prove.* This large supply of air (which, for an obvious reason, birds are able to retain, by closing the upper part of the windpipe) obviates the ne- cessity for frequent respiration, which would effec- tually destroy the power of long-continued and rapid flight, and enables them to soar, without in- convenience, into those elevated regions of the atmosphere where its rarity is so great that they could not otherwise exist in it.f The small size and immovable position of the lungs are not only highly conducive to the conve- nience of the animal in its quick movements, but also render it unnecessary that the spine and ribs should be yielding and flexible, as in the mammalia, in order to accommodate themselves to the varying capacity of the chest ; accordingly, the dorsal ver- * That these cells serve as auxiliaries to the lungs in the vitalisation and purification of the blood, was demonstrated long ago by John Hunter. He completely stopped the windpipe of various birds, and admitted the air into their bodies by openings in the thigh-bones and cells of the abdomen, after which they continued to live for a considerable time. t For a full discussion of this subject, vide a paper by M. Jacquemin, read a few years ago before the French Academy. LETTER X. 327 tebrae, or that portion of the spine which forms the upper part of the back, are frequently anchylosed, or immovably fixed by a continuation of bony se- cretion ; thus a firm point is furnished for the action of the powerful muscles which move the wings. Several interesting questions arise out of these statements, to which we shall now turn our atten- tion. The alternate expansion and dilation of the lungs of the mammalia is of considerable service in aiding the circulation of the blood ; and as the lungs of birds have no such motion, they, of course, cannot perform this function. How, then, it may be asked, is this loss compensated ? By giving to the right ventricle of the heart, instead of the valve which has been mentioned as serving in the mam- malia simply to prevent the reflux of the blood, a strong, tense, triangular muscle, which by its action materially assists the heart in propelling the blood.* Again, since neither the lungs nor the air-cells of birds have much motion, how is the air expelled from them ? The cells of some of the larger birds are provided with strong muscular fibres, to which no other function can be assigned than that of drawing together the sides of the cells, and thus expelling the air. But whether there is any direct provision in their structure for expelling the whole of the air, or whether this is effected by chemical * See Plate V. fig. 3. 328 LETTER X. changes in the air contained in the body, making it lighter than the external air, and thus liable to be continually displaced by it, are questions which, notwithstanding the many curious experiments set on foot by Albers and others in reference to them, are yet undetermined. It appears highly probable, however, that causes of both kinds concur for accomplishing this object, Roget thinks the air in the cells finds a ready outlet when it becomes rarefied by the ascent of the bird into the higher regions of the atmo- sphere.* That birds and other aerial animals can sustain themselves in the lower regions of the air by some power independent of their wings, is proved by humming-birds, and many wingless insects, as the spider ; and therefore cannot be doubted. Whether the air-cells are not the source of this power in those animals that live and feed constantly on the wing, I must leave to be determined by the rest of the evidence which I shall adduce. It is pleasing to find the observations of na- turalists unintentionally bearing upon this point. Bullock, who has had great opportunities of ob- servation, speaking of that beautiful creature, the trochilus, or humming-bird, says, " They were suspended in the air in a space barely sufficient for them to move their wings ; and the humming noise proceeds entirely from the surprising velocity with * Animal Physiology, vol. i. p. 557. LETTER X. 329 which they perform that motion, by which they will keep their bodies apparently motionless for hours together." It should be premised that hum- ming-birds are insectivorous : they seek their food in the deep cups and tubes which protect the seeds of various plants within the tropics. It would be impossible for them to obtain a supply, which is only to be found in these places, unless they had some power of suspending their bodies, not appa- rently, but really motionless in the air ; for if they attempted to rest on the plant, it would yield to their weight, and the insect would escape ; and it can hardly be doubted, that the rapid motion which their wings are supposed to make when so employed, would be still more likely to disturb their prey. I do not deny that the expanded state of the wings may favour the suspension of their bodies, as it certainly does their direction — for in this position they offer a wider surface for the ex- pansion of the gas contained in the air-cells ; but some additional contrivance must be required to counteract the weight of their bodies. In saying this, I am not to be understood as underrating the importance of the wings as in- struments of transport. That wings almost inva- riably constitute a part of the structure of those animals which support their bodies in the air, clearly shews the utility of these organs in regu- lating their motions : and the difference in the relative size and strength of the pectoral muscles 330 LETTER X. for moving the wing, as seen in the cassowary and swallow — the one a bird living entirely off, the other almost constantly upon the wing,* — is a proof that the wings contribute in some way to- wards the power of flying. As I have already said, however, I do not think that by their aid alone the majestic condor could dart from the lowest valleys up beyond the limits of the clouds ; nor do I believe that birds, however highly their muscles may be endowed with irritability, are capable of performing those long journeys which they undertake, in their migrations over thousands of miles, without resting their wings ; yet we are assured by the most accurate observers, that they journey across the equator without once settling upon the earth. On the approach of winter we see the migratory birds collecting on our shores prepara- tory to their mighty fliglit ; and they appear always to enter upon their arduous undertaking when the wind seems to be adverse to it.f That their wings * No bird excels or even equals the humming-bird, either in the extraordinary length and size of its wings, or in the rapidity of its flight. The immense strength of the pectoral muscles in the humming-bird enables it to use its long-pointed wings with a dexterity truly astonishing. This peculiarity distinguishes, to a greater or less extent, all birds inhabiting the tropics ; where the frequent occurrence of hurricanes would, but for this wise provi- sion, prove exceedingly destructive to them. t Until of late years, naturalists were unable to explain why birds of passage enter upon their journey when the wind is in an opposite direction to that which they are about to take. But tlie LETTER X. 331 do not fail them in these long-continued flights has, from the earliest times, been a source of asto- nishment ; and some writers endeavour to account for it by supposing that a part of their journey lies overland, whereby the difficulty and hazard of migration is lessened,* affording them resting- places in the progress of their route : but how- ever this may be, it is quite certain that they are many days at a time upon the wing, and pass over several thousands of miles without intermission. According to Richardson, about five-sixths of the whole number of birds migrate. This calculation existence of a counter-current in the higher regions of the atmo- sphere is now no longer a matter of doubt. Lyell says, " The heat and cold that surround the globe are in a state of constant and universal flux and reflux. The heated and rarefied air is always rising and flowing from the equator towards the poles in the higher regions of the atmosphere, while in the lower the colder air is flowing back to restore the equilibrium. That this circumstance is continually going on in the aerial currents, is not disputed ; it is often proved by the opposite course of the clouds at different heights ; and the fact was further illustrated, in a striking manner, by an event which happened during the present century. The trade- wind continually blows with great force from the island of Barbadoes to that of St. Vincent ; notwithstanding which, during the eruption of the volcano in the island of St. Vincent in 1812, ashes feU in profusion from a great height in the atmosphere upon Barbadoes. This apparent transportation of matter against the Mind confirmed the opinion of the existence of a counter- current in the higher regions, which had previously rested on theoretical conclusions only." — Geology, quoted from Daniel's Meteorological Essays, p. 103. * See White's Natural History of Selborne, Letter 42. 332 LETTER X. applies to the birds of North America. We may, however, infer from it, that a very large proportion of birds are distinguished by this wonderful habit. Enough has been said to shew, that, connected with the power given to birds of inhabiting the air, many phenomena still remain unexplained. This is not a fit place to enter into a controversy as to the propriety of attaching so much importance to the temperature of their blood (which is six- teen degrees higher than that of other animals), as a means of rarefying the air in the cells, and thus of supporting their bodies upon the principle of a balloon ; although I am certainly disposed to think that this fact is somewhat more important than Dr. Roget will allow. " The air," he says, " being contained in the interior of the body, which pre- serves a very elevated temperature, must be con- stantly in a state of greater rarefaction than the cooler external air; a condition which must con- tribute in some slight degree to render the whole body lighter than it would otherwise have been. It appears to me, however, that considerably greater importance has been attached to this circumstance than it really possesses. Many have gone so far as to represent the condition of a bird as approach- ing to that of a balloon filled with a lighter gas than atmospheric air; and have been lavish in their expressions of admiration at the beauty of a contrivance which thus converted a living struc- ture into an aerostatic machine. A httle sober LETTER X. 333 consideration will suffice to shew, that the amount of the supposed advantage resulting to the bird from the diminution of weight occasioned by the difference of temperature between the air included in its body and the external atmosphere, is per- fectly insignificant. Any one who will take the trouble to calculate the real diminution of weight arising from this cause, under the most favourable circumstances, will find that, even in the case of the largest bird, it can never amount to more than a few grains." * The presence of air-cells in all animals which fly is a sufficient proof of their connexion with the power by which they are distinguished; and though it may be difficult to prove that this power is dependent upon the rarefaction of the air con- tained in those cells by the blood, still the provi- sion made for increasing its temperature affords strong ground for beHeving that that fluid has some share in producing the phenomenon in ques- tion. The provision to which I allude, so far as relates to birds, is the great enlargement of their brain and heart : — organs, as we have seen, of primary import- ance in generating and maintaining the heat of the blood. The weight of the brain of the canary, for exaniple, in proportion to that of its body, is as one to fourteen ; while in man the proportion is as one to thirty or thirty-five : the canary therefore * Animal Physiology, vol. i. p. 557. 334 LETTER X. has, relatively to man, more than double the quan- tity of brain in proportion to the size of their re- spective bodies. The relative size of the heart also, especially of those birds which are remarkable for their rapid flight, as the starling, swift, and swallow, is much greater than in quadrupeds. The cassowary, ostrich, goose, the common fowl, and other birds which are attached to the ground, have very much smaller hearts than those which live on the wing. There can be little doubt that these modifica- tions in the organisation of birds have much to do with their power of suspending their bodies in the atmosphere. The mere expansion by the blood's heat of the atmospheric air received into the air-cells would hardly appear to explain this phenomenon. The 'heat of the blood of birds scarcely ever rises above 108° Fahr. :* a degree of heat which, assuming that the laws which have been discovered with respect to water apply to the blood, would resist a weight of about sixteen ounces only to every square inch ; but this force would obviously be insufiicient to raise birds in the air, inasmuch as the atmosphere, as already stated, exerts a pressure of fifteen pounds upon a square inch.f * Tiedemann says, in the swallow and the great titmouse it rises to 110°. The same author makes the heat of the whale to be 102°, that of the squirrel and the bat 105°. — Phi/siologi/ (trans- lation), p. 234. t It should be understood, that, at common temperatures, LETTER X. 335 Another difficulty is, that we have no positive evidence to prove that the air-cells are unable to resist the force of steam : their structure and appearance, in many instances, would lead us to suppose they were not intended merely to contain common air. " These openings (leading to the air-cells) are in general, as their connexion with the lungs or air-tubes renders necessary, situated in concealed parts and the extremities of bones. This circumstance, coupled with their smallness, makes their discovery difficult. The direction in which the openings penetrate these long parietes (surfaces) is not uniform. Sometimes it is oblique, so that a short oblique canal is formed ; at others there is an oblique groove, with a sieve-like base for the entrance of air. The edgings of the openings are even, smooth, and rounded, which gives them a peculiarly regular appearance. Their shape is either circular, oval, or elliptical ; their breadth water and many other liquids would exist in the form of air, were it not for the pressure of the atmosphere opposing the separation of the particles. But these liquids being raised to different degrees of heat above the ordinary temperature, require a greater pressure than that of the atmosphere to prevent their passing into the aeri- form state. This pressure as regards water has been investigated with great care ; and it has been ascertained, that the pressure of the -steam of water heated to a temperature of 50° is equal to a weight of two ounces and three quarters upon every square inch ; heated to 100°, it is equal to thirteen ounces ; and when heated to 212° Fahrenheit, which is the boiling point of water, it is equal to a weight of fifteen pounds. 336 LETTER X. bears some kind of proportion to the size of the bone, or at least to the extent of the internal cells ; so that large birds and large bones have much larger openings than the small ones. There are, however, very remarkable exceptions. With respect to the internal air-cells, great differences exist. There has been found in the internal periosteum (covering of the bone) which lines the air-cells in the bones of the upper and lower extremities, a fine network of blood-vessels."* All this shews that these cells are formed for some more elaborate use than the reception of common air, and supports the belief that they are constructed to resist pres- sure from without. " The animal body," says Arnott, " is made up of solids and fluids, and is affected by the at- mospheric pressure accordingly. There is a diffi- culty at first in believing that a man's body should be bearing a pressure of fifteen pounds upon every square inch of its surface, while he remains alto- gether insensible to it ; but such is the fact ; and the reason of his not feehng the fluid pressure is its being perfectly uniform all round. If a pres- sure of the same kind be even many times greater, such, for instance, as fishes bear in deep water, or as a man supports in the diving-bell, it equally passes unnoticed. Fishes are at their ease in a depth of water where the pressure around would instantly * See Lawrence's note to Blumenbach's Manual of Com- parative Anatomy, p. 179. LETTER X. 337 break or burst inwards almost the strongest empty vessel that can be sent down ; and men walk on earth without discovering a heavy atmosphere about them, which, however, will instantly crush together the sides of a square glass bottle emptied by the air-pump ; or even of a thick iron boiler, left for a moment by any accident without the counteracting internal support of steam or air."* The internal parts are thus held together by the pressure of the atmosphere, so as to be materially aided in the performance of their function. The joints in par- ticular require this support, to enable them to resist the force applied to them. The pressure of the atmosphere must have con- siderable influence upon the air -cavities in the bodies of birds ; so that, without some counteract- ing force generated within them greater than that exerted by the atmosphere, their sides would yield, and the air contained in them be expelled when- ever a partial vacuum was formed in them, or even if they contained air lighter than the atmosphere. Those cells which are formed in bone may be pro- tected from this pressure by the firm substance which surrounds them ; while those composed of membrane, and situated in the softer parts of the body, may resist it by means of the strong mus- cular bands with which they are furnished. Let us suppose, then, that these cells are pro- vided with the means of resisting the pressure of * Elements of Physics, vol. i. p. 342, Z 338 LETTER X. the atmosphere, and at the same time of creating a vacuum to a certain extent within them, and we shall have no difficulty in understanding how the blood (which is distributed in numerous minute vessels upon their internal surface), at a temperature of 1 08°, may expand the air to such an extent as to generate a force capable of overcoming the resistance of the atmosphere, and of raising the largest bird into the air. For when the pressure of the atmosphere is taken off, many fluids will boil at very low temperatures. Under the exhausted receiver of an air-pump, ether boils at the same temperature at which water freezes ; and water itself boils when twenty degrees less warm than the blood of animals. Without, then, forcing the theory of the rarefaction of the air in the air-cells of birds by the heat of their blood, there is at all events ground for believing, that, in some such manner, the weight of their bodies is counteracted by an internal power de- rived from the blood, acting under a high degi-ee of nervous irritability upon a machinery whose builder and maker is God. And if I could do it justice, I might enlarge upon the skill which is here displayed — the result of a perfect knowledge of the force required — and of how and when that force should be applied ; and which has fitted up every individual according to the most profound calculation. Here we have no fears about explo- sion, nor distrust of the ability of the engineer ; all is security and precision. Have we not in this LETTER X. 339 wonderful mechanism the clearest proofs of mtel- ligent agency — of mfinite wisdom ? " It is pleasing to observe this superb bird (the albatros) sailing in the air in graceful and elegant movements, seemingly excited by some invisible power — for there is rarely any movement of the wing seen after the first and frequent impulses given when the creature elevates itself in the air, — rising and falling as if some concealed power guided its various motions without any muscular exertion of its own, and then descending and sweeping the air close to the stern of the ship with an independence of manner as if it were monarch of all it surveyed. It is from the very little muscular exertion used by these birds that they are capable of sustaining such long flights without repose. How, then, do these birds, it may be asked, execute such move- ments ? The whole surface of the body in this, as well as, I believe, most, if not all, of the Asiatic tribes, is covered by numerous air-cells, capable of voluntary inflation or diminution by means of a beautiful muscular apparatus. By this power the birds can raise or depress themselves at will ; and the tail, and great length of the wing, enable them to steer in any direction. Indeed, without some provision of this kind to save muscular exertion, it would be impossible for these birds to undergo such long flights without repose as they have been known to do ; for the muscles appertaining to the organs of flight, although large in these birds, are 340 LETTER X. evidently inadequate in power to the long dis- tances they have been known to fly, and the im- mense length of time they remain on the wing with scarcely a moment's cessation."* We must admire also the analogous organs in insects, by which they are capacitated to take their stations in the same element with birds. " The fibres or nervures/' says Roget, " as they are called, form a delicate network for the support of the fine membrane, like the frame of the arms of a wind- mill which supports the canvass spread over them. The microscope shews that these fibres are tubu- lar, and contain air — a structure the most effectual for conjoining lightness with strength; and many entomologists are of opinion, that the insect has the power, during the act of flying, of directing air into the nervures, so as to dilate them to the utmost, and render them tense and rigid." f No doubt, I think, can now remain respecting the secondary causes of the power which birds possess of inhabiting the regions of the air. The various degrees of this power, and of that of trans- porting themselves from one climate to another, which are exhibited by the various species, there is good reason for supposing result from differences in the comparative lightness of their bodies, and in the relative size of their wings. Let us now inquire how it is that birds, though * Bennett's Wanderings in New South Wales, vol. i. p. 45. t Animal Physiology, vol. i. p. 345. LETTER X. 341 SO volatile and migratory in their nature, and pos- sessing such extraordinary means of locomotion, are yet, like all other animals (man excepted), confined to particular quarters of the globe ; going from one locality to another only at certain sea- sons, and not capable of being removed to any other than those they naturally inhabit, or at any other time than that which is appointed, without danger to their existence. It is a law in the economy of all living beings, that a certain mutual connexion, or harmonious combination among all, should be kept up, in spite of the operation of causes which would seem to be insurmountable obstacles to that law, but which, under the guidance of the Creator who made all things, actually concur and co-operate with it. No more striking proof of this truth can be fur- nished than the geographical distribution of ani- mals. As we have already seen, the limits to which each species is confined are as impassable as if surrounded by a wall of adamant; and yet, in innumerable cases, there is no physical barrier of any kind to their wider diffusion. Birds are formed for different elevations in the air, fishes for dif- ferent depths in the sea, and beasts for various part§ of the earth's surface ; and the appointed boundaries of their habitations they never, when left to themselves, abandon. This fact, on account of the circumstances already mentioned, is perhaps more striking in 342 LETTER X. birds than in any other class of animals. " It has indeed/' says Swainson, " been objected to this class of animals, that no very certain results can attend the study of their distribution. Possessing the powers of locomotion in a higher degree than any others, and, by their migratory nature, per- petually wandering into distant countries, they would seem of all animals the most widely dis- persed, and consequently the least calculated to assist such an inquiry. Certain, however, it is, that if under such disadvantages any definite no- tions on animal distribution can be derived from such volatile beings, the result will go very far to strengthen our views upon two material points : first, that a division of the earth, characterised by strong peculiarities in its ornithology, must be, to a certain extent, a natural division ; and, secondly, that we shall be fully authorised in sup- posing by analogy that the same results would attend an equally close investigation of other animals ; since it cannot for a moment be supposed that man and birds are distributed according to one plan, and all other animals by another."* That food, temperature, and the physical fea- tures of a locality, exercise great influence in regu- lating the physical distribution of animals, has already been abundantly proved ; but these circum- stances must be taken together — separately they are wholly insufficient to explain any phenomena of * Geography of Animals, p. 19. LETTER X. 343 this kind. The chamois or wild goat, for example, dwells upon the most barren rocks, yielding no food of any kind, and descends into the valleys in order to obtain its food ; eagles and hawks, which seek their food upon the earth, fix their abodes in the higher regions of the atmosphere ; and we cannot but adore that careful Providence which, in such cases, has always appointed means to reconcile all such apparent incompatibilities. This is very striking with regard to the vulture. Tainted carrion is the appointed food of this bird. Now, as the air pro- duced by putrefaction (hydrogen) is lighter than common air (as I have stated in the beginning of this Letter), it ascends into the atmosphere, and is carried to and fro through the expanse of heaven by every gust of wind. The vulture, soaring aloft, comes in contact with this tainted current, and instinctively follows it down to its source, and there finds that which is destined to be its support and nourishment.* The extraordinary fecundity of the insect tribes was doubtless ordained to give food to birds ; for we find that many of the inhabitants of the air are insectivorous. In those countries where the high temperature causes insects to abound, there we find the greater number of those birds which are destined to feed upon them. This, to a certain extent, will account for the migration of birds, but not wholly ; for the propensity to * See Waterton on the Faculty of Scent in the Vulture, in Loudon's Mag. of Nat. Hist. vol. v. p. 234. 344 LETTER X. migrate is manifested in some birds even when confined in a cage and surrounded by abundance of food, and cannot therefore be considered to arise from want of food alone. But many of the accipitres, or birds of prey, in addition to insects, devour reptiles, fish, and flesh ; and these birds are stationary in particular regions, because their food can at all times be obtained there. How wisely, therefore, are vultures placed in those countries where carrion, if suffered to remain upon the earth, might cause infectious dis- eases among the inhabitants ; and the great secre- tary bird (Jalco serpeiitarius) in the regions which abound with venomous reptiles. In all these cases the manner in which the sto- mach is adapted to the food is truly remarkable. The most tainted carrion, or the most venomous reptile, are received into that organ, and go to form the natural nourishment of the body. Waterton says, the true vulture recognises nothing but carrion for its food ; and speaking of the vidtur aura of Guiana, which is the same as is found in European Andalusia, he says, " I am intimately acquainted with all these useful scavengers ; and I have never known any of them to kill the food on which they feed, or, when they are in a complete state of nature, free from the restraints or allurements of man, ever feed upon that which was not putrid."* " The secretary bird is a native of the southern * See his paper in vol. v. of Loudon's Mag. of Nat. Hist. LETTER X. 345 parts of Africa : it is about three feet high, chiefly arrayed in purple, with some long feathers ele- gantly falling from the head. It destroys serpents, rats, and vermin, and is on that account much esteemed, as the Cape abounds with venomous serpents, snakes, scorpions, scolopendrae, and noxious reptiles, also with lizards of many descrip- tions ; the land-tortoise, gryllag or locusts, in va- riety, abundance, and depredation, equalling their destructive hosts in other countries. Barrow re- lates a very curious circumstance respecting living serpents in the stomach of one of these birds after death. An English gentleman, who held an official situation at the Cape, being out on a shooting party, killed a secretary bird, which he carried home with the intention of having an accurate drawing made from it. He threw it on the floor of the balcony near the house, when, after it had remained some time, and been examined and tossed about, one of the company observed a large snake pushino- open the beak, out of which it speedily crawled, in perfect vigour, and free from any injury. On the supposition that others might be in the stomach, the bird was suspended by the legs, and presently a second made its appearance, as large and as hvely as the first. The bird was afterwards opened, when the stomach was found to contain seven dead snakes, with a half-digested mass of lizards, scor- pions, scolopendrae, centipedes, and beetles."* * Forbes's Oriental Memoirs, vol. i. p. 443, 346 LETTER X. In our own country we see the same wisdom evinced in placing birds where their particular food abounds. The pheasant, the cock, the cuckoo, feed upon those insects, worms, or grubs, which would otherwise be destructive of vegetation in our country. It is not generally known that pheasants are beneficial to the farmers ; this fact, however, was fully proved, in 1821, at Witney Court, when Tomkin Day, Esq. shot a hen pheasant that ex- cited the notice of the sportsmen present from the immense size of its craw, which, on being opened, was found to contain more than half-a-pint of that destructive insect the wire-worm.* The true serpent-eaters are never seen in Europe. It was on account of the great service which some of these birds were to the ancient Egyptians, by ridding them of many noxious rep- tiles, that this wicked and idolatrous nation, not knowing the God of the spirits of all flesh, who made them, were led to " worship the creature more than the Creator," and to bestow rehgious homage upon the ibis, punishing all with death who were, even unintentionally, the cause of its destruction. To such a pitch did they carry their reverence for this bird, that it was admitted within their temples, and dignified after death with the honour of embalming ; to use the language of Cuvier, " it was a bird whose form the gods would * See note to White's Natural History of Selborne, by Brown, p. 293. LETTER X. 347 have assumed had they been forced to adopt a mortal figure, and into which Mercury really transformed himself when he had a mind to tra- verse the earth and instruct men in the sciences and arts." Many doubts have existed as to the true nature of this bird ; but that great naturahst has at length proved that the true ibis was a species of curlew. The propensity to seek their food certainly operates in birds to determine their distribution ; but it cannot explain, for example, why the falcon of Iceland, which, though it has been carefully confined and fed, often, the first time it is sent in pursuit of a heron, ascends vertically into the air, and proceeds towards the north. The singular power which birds have of returning to the same spot every year, after they have quitted it in order to migrate into distant countries, cannot indeed be accounted for by the mere propensity to seek food. Naturalists record many interesting proofs of this power : that it results from an innate and irre- sistible impulse, independent of external causes, I shall hereafter prove when I come to speak more particularly of instinct. But its bearing on the distribution of birds renders it necessary that I should notice it in this place. By this faculty, pigeons, though transported to a distance of many hundred miles, confined to a cage, and thus com- pletely prevented from observing the features of the country through which they pass, are enabled 348 LETTER X. to return to the spot whence they were taken. By this power also the various tribes of birds seek different elevations and localities for building their nests — some in rocks, some in the tops of trees, some in their trunks, and some in their roots. I have thus hastily gone over the great physi- cal characteristics of birds, which enable them to dwell in the air over those regions of the earth to which they have been appointed. In my next Letter I shall consider the structure of fishes. LETTER XL " 0 Lord, how manifold are thy works ! in wisdom hast thou made them all : the earth is full of thy riches. So is this great and wide sea, wherein are things creeping innumerahle, both small and great beasts. There is that leviathan, whom thou hast made to play therein. These wait all upon thee, that thou mayest give them their meat in due season." — Psalm civ. 24 et seq. " But of all the countless multitudes of creatures which populate and give life to the liquid element, none so abound — none are so exclusively peculiar — none so remarkable for their number, their varied forms, their beautiful colours, and, above all, the infinite benefits which man derives from them, as those which belong to the class of fishes." — Cuvier's Natural History of Fishes. Having thus exemplified the wisdom manifested in those animals whose structm'e is formed in relation to the atmosphere and to the earth's surface, I shall now pursue the same plan in regard to an- other and widely different class of animals — those which inhabit the waters. " The empire of the waters/' says Cuvier, " which so extensively exceeds the amount of dry land, is far from yielding to the latter in the num- ber and variety of living creatures which inhabit its depths. On the land the matter susceptible of life is, for the most part, appropriated to the formation and support of vegetable species ; the herbivorous 350 LETTER XI. animals are sustained upon these species, which becoming animahsed by this process, constitute the proper food of the carnivorous animals : these latter, however, scarcely form more than half the terrestrial classes of hving beings. But in the waters, and, in an especial manner, in the ocean, where the vegetable kingdom is infinitely more circumscribed, every thing teems with hfe, or is ready for that condition. Here the animals sustain existence only at the expense of each other, or by feeding on the mucus and other remains of animal bodies. Here, too, may be contemplated the ex- tremes of greatness and httleness, from the miUions of monads and other species, which might have been eternally invisible to us without that marvel- lous auxiliary the microscope, up to those cache- lots and other whales, which exceed twenty times the largest terrestrial quadrupeds." * In order that you may more fully appreciate the design which marks this class of beings, I will first say a few words respecting the nature and rela- tive position of the element in which they move. The specific gravity of water is upwards of eight hundred times greater than that of the atmosphere, and hence it takes its station below that fluid. It has been wisely ordained that the specific gravity of water should not exceed that of the solid mate- rials of the globe. Had it been less, it is easy to * Natural History of Fishes, in Cuvier's Regne Animal (trans- lation), vol. ii. p. 260. LETTER XI. 351 see that it must have endangered the safety of man and the other terrestrial animals. It is estimated that about three-fourths of the entire surface of the earth are covered with water. As its mean depth is unknown, its absolute quantity cannot be ascertained. There is, however, a vast space for the display of the unsearchable wisdom of God, in peopling with great multitudes of hving creatures this part of the globe. You are aware that, in order to maintain the life of animals, their blood must be exposed in a greater or less degree to the operation of the air. In this contact the air removes from the blood some of the elements that compose it, and in re- turn the blood acquires some of the elements of the air. It is thought to be one of the indispen- sable conditions of the existence of warm-blooded animals, that a stratum of blood equal in super- ficial extent to the entire surface of the body should be constantly exposed to the action of the air. The extent of surface furnished by the air- cells of the lungs has been differently estimated. If the above-mentioned supposition is correct, it must, in man, be about 2,500 square inches, or fifteen square feet, such being the mean super- ficies of his body. Lieberkuhn is thought to err in making it fall below this. He considers the extent of surface of the air-cells of the lungs in man to be equal to 1,800 square inches. But, as I have already stated, it is not necessary that 352 LETTER XI. the blood of all animals should be so fully oxy- genated as that of man and the other warm- blooded animals : fishes, being cold-blooded, can exist in an element of the bulk of which atmo- spheric air does not compose more than l-28th or l-36th part; their life can be maintained by a smaller supply of oxygen than is necessary for the warm-blooded animals. The changes, therefore, which the blood undergoes in fishes are the same in kind as in the mammalia, but different in degree. Thus, the mammalia give out from the lungs about fifty times more carbonic acid, for every 100 grains of their weight, than fishes. Boyle first discovered that air existed in water. Shiel first observed that this air contains a greater proportion of oxygen than the common atmo- spheric air; which is borne out by the fact, that the air upon the surface of the sea contains more of that principle than elsewhere. Notwithstanding this circumstance, it would be necessary that a quantity of water thirty times greater than that of the air which goes to the lungs of other animals should pass through the gills of fishes, in order to supply the same amount of oxygen to the blood. To obviate the inconvenience that would hence arise, were the gills the only breathing organs in fishes, we find that these animals " absorb oxygen and exhale carbonic acid, not merely with their gills, but with the whole surface of the body, as long as they are surrounded with water impreg- LETTER XI. 353 iiated with atmospheric air, not when they are exposed to the air itself. Humboldt proved this satisfactorily by experiment."* The waters of the sea, which contain the greatest number of living creatures, suspend be- tween three and four per cent of different saline matters, which have the effect of raising the freez- ing point, and diminishing the tendency to give off vapour. They also render the water more buoyant, and thus make it better fitted to support the animals which it contains. The body of the fish is as beautifully adapted for swimming as that of the bird is for flight. It has no necessity for wings to support it, being suspended in a liquid whose specific gravity is nearly equal to its own. But, that the body may rise and sink in obedience to the will of the animal, most fishes are provided with an air-bladder, called also the natatory or swim-bladder, which communicates either directly or indirectly with the stomach or some other part of the alimen- tary canal, and contains gases of different kinds.f This bladder the animal is able to compress or * Miiller's Physiology, p. 314 (translation). t As this bladder in numerous genera has no communication with the outer air, the gases which are contained in it can only be produced by secretion ; for which purpose we see in some a glandular organ placed within the bladder. This is the case in the cod and the haddock ; and Monro says tliis gland is composed of a vast number of leaves, or membranes doubled. The structure of this bladder is of a very peculiar nature, and yields the common isinglass of commerce. A A 354 LETTER XI. dilate at will, as it requires to descend or ascend, its specific gravity being thereby varied. Many fishes possess a single, and some a double swim- bladder, which, Blumenbach* says, in the fresh- water fish of Germany contain nitrogen gas, while in the salt-water fishes they contain chiefly car- bonic acid gas. Biotf observed, that when a fish was suddenly brought from a great depth towards the surface, the air-bladder swelled so much that the fish could not again be made to sink ; and that the bladder often burst, the air forcing its way into the stomach, and upward through the mouth. He afterwards made many experiments upon the air- bladder of fishes, and found in most, if not all of them, a mixture of azotic and oxygen gas, in vari- able quantities. Sometimes the amount of oxygen was very minute, sometimes it constituted nearly the whole of the contents. He ascertained that this variation is by no means arbitrary, but is re- gulated by the station which the fish takes in the water. Thus, the air-bladders of those fish which live near the surface contained least oxygen gas, and the bladders of those which were brought up from a great depth contained the most. He pub- lished a table shewing how accurately these pro- portions are regulated by the depth at which each fish habitually dwells. La Roche confirmed the cor- rectness of these statements. In accordance with * Manual of Comparative Anatomy, by Lawrence, p. 185. t Mem. d'Arcueil, vol. i. p. 252. LETTER XI. 355 this we find that there is very little oxygen in the air-bladders of those fresh-water fish which are taken near the surface. Sea-water brought from a great depth does not contain so much oxygen as that nearer the surface.* Without this wonderful provision, therefore, in the bodies of the fish which live at great depths, their gills and cutaneous sur- face might fail to extract oxygen enough to carry on the functions of life. Some fishes do not possess the swim-bladder, because their position is always at the bottom of the sea ; and it is because this organ is wanting in many fishes that its real use has not been fully understood. Where it is absent, its use is pro- bably compensated for by some other organisation. Most fish are confined to a particular depth, at which they always remain. Thus, flat-fish, lam- preys, and mackarel, live in deep water, and do not possess an air-bladder at all ; while, on the other hand, in fish which are continually near the surface, there are sometimes additional contriv- ances in their bodies for containing air. The tetraodons and the diodons, commonly called bloaters, from the faculty which they possess of * " From the air of the air-bladder of fishes which live in the depth of the ocean, Biot (Gilbert's Annal., vol. xxvi. p. 454) ob- tained from 69 to 87 per cent oxygen ; while the air with which the water of the ocean at a considerable depth was impregnated contained only 29 parts oxygen and 71 parts nitrogen in 100 parts." — Muller's Physiology (translation), p. 315, note. 356 LETTER XI. swelling themselves up like a balloon, have, in addition to the air-bladder, a sort of thin exten- sible crop, which occupies the whole length of the body, and contains air. When this is inflated, they roll over, with the abdomen upwards, on the sur- face of the Avater, unable to direct their course ; but in this state they are much better defended than at other times, for they are thereby enabled to erect a number of spines with which their skin is every where furnished, and are thus rendered secure on all sides from the attacks of their enemies. In the little argonaut, the nautilus, and the pompilus of the ancients [argonauta argo), we find the most beautiful contrivance for bringing the blood into contact with the atmosphere. These mollusca are always found in a very thin shell, symmetrically fluted and spirally convoluted, the last whorl of which is so large that it bears some resemblance to a galley, the spine representing the poop. The animal makes use of its shell for the purpose of supporting its body on the water as in a little ship ; and in calm weather, whole fleets of them may be observed sailing about the surface of the ocean, employing six of their tentacula (limbs) for oars, and elevating the two membranous ones to serve for sails, on which the blood is distributed in numerous vessels, and thus exposed to the air. If the sea becomes rough, or any danger threatens, the argonaut withdraws all its arms, concentrates LETTER XI. 357 itself within its shell, and at once descends to the bottom. Roget says, " The physalia, or Portuguese man-of-war, as it is called, is furnished with a large air-bladder of an oval shape placed on the upper part of the body, and also with a membrane of a beautiful purple colour which, as in the velella, serves as a sail. These zoophites are met with in great numbers in the Atlantic ocean, and more especially in its warmest regions, and at a con- siderable distance from land. In calm weather they float on the surface of the sea, rearing their purple crests, and appearing at first like large air-bubbles, but distinguishable by the vivid hues of the tentacula which hang down beneath them. Nothing can exceed the beauty of the spectacle presented by a numerous fleet of these animals quietly sailing in the tropical seas. Whenever the surface is rufiied by the slightest wind, they suddenly absorb the air from their vesicles, and becoming thus specifically heavier than the water, immediately disappear by diving into the still depth of the ocean. By what process they effect these changes of absorption and reproduction of air, yet remains to be discovered. Other genera, as the physsophora, have several of these air- bladders, but in other respects resemble the ordi- nary medusas in having no membranous crest."* Having been all thus provided with contriv- * Animal Physiology, vol. i. p. 195. 358 LETTER XI. ances for rendering their bodies specifically lighter or heavier than water, according to their various wants, the progression of fishes is further facilitated by means of a very powerful tail,* which, by strik- ing the water alternately from one side to the other, controls the movement of their bodies in the same way as a rudder does that of a ship. Having, for the most part, no occasion for limbs, truef fishes have these members converted into fins or paddles, in which may be traced all the rudiments of the corresponding instruments in terrestrial animals. These fins are placed on all parts of their bodies, and thus contribute to their pro- gression in the same manner as an oar assists in propelling a boat. By extending or retracting these organs, fishes are enabled to turn their bodies in whatever direction they please. As the true fishes are required to breathe through the medium of the water, we find in them * In tlie shark this organ is so powerful, that it seems to supersede the necessity for a swim-bladder, which is accordingly- absent. t This class of fishes is the most remarkable, as well as the most extensive, of all the multitude of creatures which people the sea. Yet it must be remembered, that the whales and other warm-blooded animals, as the seals, morses, and sea-cows, as well as tortoises, crocodiles, and serpents, together with the whole race of moUusca, Crustacea, zoophites, and others, have strictly no claim to this designation, though they are all inhabitants of the water ; some of them have no power to breathe under water, their blood requiring to be vitalised directly by the air. LETTER XI. 359 an organisation expressly adapted to accomplish this purpose. On each side of the neck they have an apparatus called hrancliice, or gills, which are their breathing organs, and consist of a number of plaits, suspended upon arches of bone attached to the central bone of the throat. These arched bones or cartilages are in most fishes four in number in each gill. Monro* says, that on each side of the body of the skate there are four double gills, or gills with two sides each, and one single gill ; that is, in all eighteen sides or surfaces upon which the branchial artery is spread out. Blumenbachf says, the distribution of this vessel in the folds and divisions of the gills constitutes one of the most delicate and elaborate pieces of structure in the animal economy. There arises from the heart a single trunk, which goes straight towards the gills ; and arriving there, it divides and subdivides into numerous rami- fications, and spreads itself over the whole extent of the thin membranous surface of the gills, which if viewed through a microscope, is seen to be covered with a beautiftil network of exceedingly minute vessels. On each of the eighteen surfaces presented by the gills there are, according to Monro, J about fifty divisions or doublings of the membrane ; and each of these divisions has upon * Physiology of Fishes, p. 15. t Manual, by Lawrence, p. 185. X Physiology of Fishes, p. 15. 360 LETTER XI. each side of it 1 60 subdivisions or folds, the length of each of which, in a very large skate, is about one-eighth of an inch, and its breadth about one- sixteenth of an inch, so that in the whole gills there are 144,000 subdivisions:* the two sides of each fold are therefore equal to the sixty-fourth part of a square inch ; the total extent of the sur- face of the gills of such a fish must be 2,250 square inches, or more than fifteen square feet. This great extent of surface, in which the blood comes into contact with the water, is a wise provision, considering that the air contained in water amounts only to one thirty-sixth part of its bulk.f The circulation of the blood through the branchiae is also hastened by a remarkable pecu- liarity of structure. " Many animals," says Miiller, " which respire by means of branchiae in water, produce remarkable currents in the water around the branchiae. These currents are now known to be produced by the vibration of minute cilia; J and the phenomenon is called ciliary motion." There is a communication with the gills from the back part of the mouth ; and the muscles of the throat drive the water, which the fish appears * Or more correctly, 288,000. f Miiller says, " water never contains more than y|-^ of its volume of air, of which 31 per cent is pure oxygen." — Physiology, p. 314 (translation). X From cilium, an eyelash, because they resemble that struc- ture in appearance. LETTER XI. 361 to swallow, through these apertures, which lead to the branchial cavities ; by which process the air contained in the water is brought with con- siderable force into contact with the blood-vessels distributed over the surface of the gills. While the water is passing through the gills, their various surfaces are expanded by that fluid ; but when fishes are removed from the water, the plaits of the gill can be no longer unfolded, but adhere together ; the blood thus ceases to circulate, and the animals are soon suffocated. The water passes out of the back part of the mouth usually through five fissures on each side ; and it is worthy of notice that, in order to prevent the egress of food through them, these fissures are internally guarded by little papillae, or small branchial teeth. They have also peculiar muscles for this purpose, some of which are attached to the ribs, and some to the bone of the tongue. The gills likewise are moved by particular muscles attached to this bone and to the gill-cover, by which means the branchial aperture is alternately opened and closed. In most cases the gills communicate directly with the mouth ; there are, however, some excep- tions, which place in a striking light the intimate connexion between the habits of animals and their organisation. In the lampreys and some of the suckers, as, for example, the myxine, which attack and pierce other fishes, in doing which they bury 362 LETTER XI. their heads and even part of their bodies in the flesh of their adversaries, the respiratory organs are removed to a sufficient distance from the head to prevent any inconvenience to their breathing while employed in procuring food. In these ani- mals the water does not first enter the mouth, but is received at once into the gills, and passes out at the same opening. One object in causing, in most fishes, the water to pass through the mouth in its way to the gills, is, to prevent its passing into the stomach, which it otherwise obviously would do every time the animal opened its mouth for the purpose of swallowing. Now, to obviate this dif- ficulty in the lamprey, the gills of which are, as above mentioned, removed some distance from the head, the water which enters the mouth with the food passes down to the branchiae through a membranous canal which is placed under the oesophagus for that purpose. To protect the dehcate structure of the gills, fishes are furnished with a large gill-cover (oper- culum), which spreads over their whole surface, leaving a wide fissure below for the escape of the water. In some fishes, and other aquatic animals, that occasionally seek their food upon the dry land, as the perca scandens, a species of perch, of which great numbers inhabit the Indian seas, and different varieties of eels and water- serpents, the operculum is thicker than the covering of common gills. It is also furnished with a slimy mucus. LETTER XI. 363 which hinders it from becoming dry for many hom-s^ while the animals are performing locomotion out of the water. Roget says, the perca scandens " has a very remarkable structm-e, adapting it to the maintenance of respiration, and consequently to the support of life, for a considerable time when out of the water. Hence it is said to travel occa- sionally on land to some distance from the coast, and that it is even capable of climbing the trees which grow on the coast. The pharyngeal bones of this fish have a fohated and cellular structure, which gives them a capacity for retaining a suffi- cient quantity of water, not only to keep the gills moist, but also to enable them to perform their proper office, while not a particle of water is suf- fered to escape from them, by the opercula being accurately closed."* Such being the arrangement of the respiratory apparatus in fishes, of which I have attempted to give you a short description, you will not be sur- prised to learn that these animals are endowed with much less vitality than warm-blooded animals, and that consequently their senses are compara- tively but slightly developed. In reference to this subject, Cuvier says, "performing the process of respiration simply through the medium of water, in other words, only avaihng themselves of the small proportion of oxygen which is contained in the air mixed with the water, for the purpose of * Animal Physiology, vol. ii. p. 307. 364 LETTER XI. giving an arterial character to their blood, it fol- lows that this blood must remain cold, and that consequently the vitality of the fishes, and the energy of their senses and of their motions, must be inferior to those of the mammalia and the birds ; and, in point of fact, their brain, though similar in structure, is much smaller than it is in the former classes, and their external organs of sense are not of that nature to enable them to feel any pow^erful sensations. The fishes, therefore, form that divi- sion of the vertebrated animals which possess the least appreciable signs of sensibility. Excluded from the use of elastic air, they are consigned to eternal dumbness, — at least, this is very nearly the case, — and all those feelings which vocal sounds are calculated to excite are to them for ever strangers. Their eyes have no faculty of motion ; their faces are long and fixed ; their limbs are in- capable of flexion, and, always moving in one single mass, afford no opportunity for the play of their physiognomy, and no power for the expres- sion of their emotions. Their ear, enclosed on every side in the bones of the head, destitute of an external concha (ear), as also of a cochlea (part of the internal ear of warm-blooded animals, resem- bling a snail's shell), and composed solely of httle sacs and membranous canals, hardly enables them to hear the loudest sounds.* Of httle use would * To shew that fish are not altogether destitute of hearing, Jesse says, " there is a singular mode of taking trout practised in LETTER XI. 365 be the faculty of hearing to these animals, that are condemned to live in the realms of silence, where all about them is still. Vision would be of little advantage to fishes in the depths to which they are consigned, had not most of these species, in the large proportion of their eyes, a resource against the weakness of the light ; but in these animals the direction of the eye is scarcely ever changed, and still less can they vary its dimen- sions, so as to accommodate the organ to the dis- tance of visible objects. The iris neither contracts nor dilates, and the pupil is never altered, what- ever be the diversity of the quantity of light. No tear bathes that eye ; no eyelid drys or affords it protection ; and in the fishes there is only found a very feeble image indeed of that organ, so remark- able for its beauty and its animation in the higher classes of animals. They procure their food only by swimming in pursuit of their prey, which itself swims with greater or less rapidity. They possess the power not indeed of seizing, but merely of swallowing, so that the delicate faculty of taste would have been thrown away upon them, had nature bestowed it ; but their tongue, almost im- some of the rivers in South Wales. The sides of the rivers are here and there very rocky, and where there is a flat shelving rock trout generally haunt under it. If this rock is struck forcibly with a large sledge-hammer, the trout rise to the surface of the water, appearing as if they were stunned, and are then taken." — Gleanings in Natural History, third series, p. 71. 366 LETTER XI. movable, sometimes completely bony, or like a coat of mail, studded with plates of teeth, and supplied very sparingly with nerves, demonstrate to us that the organ is just as blunt as we should have pre- viously concluded from its very little use. The function of smell, also, cannot be so continually exercised by fishes as it is by animals that breathe the air, and through whose organs of smell odori- ferous vapours are constantly circulating. Lastly, their touch, almost obliterated at the surface of the body by the scales, and also in their limbs in con- sequence of the absence of the power of bending their rays, and further in consequence of the dry- ness of their enveloping membranes, — their touch, I repeat, has been forced, as it were, to take refuge at the extremity of their lips, and these even, in some species, are reduced to a state of bony hard- ness that renders them insensible. Thus, the ex- ternal senses of fishes supply them with a very small share indeed of lively and distinct impres- sions; the natural objects which surround them must affect them only in a confused manner ; but httle variety belongs to their pleasures, and no sufferings are likely to visit them from without, save such as may be the effect of wounds. Their unceasing craving, that which alone influences and acts on them, that predominant passion, must be enough to satiate their internal sense of hunger ; to devour is almost the entire business of their lives ; and it is solely for this great purpose, feed- LETTER XI. 367 ing, that their structure is adjusted, and all their organs of motion arranged.* To pursue their prey, or to escape an enemy, is the double em- ployment of their hves. It is these that determine the various habitations of which they make choice, and the variations of their forms ; they also serve to explain why nature supphed some of the species with so few instincts, and so httle of any faculty of contrivance." f Yet, though these animals have been placed, as * Many kinds of fish are extremely voracious. Jesse mentions that he had a dead pike sent him, weighing about seven pounds, which was killed by endeavouring to swallow another pike of about five pounds. They were both found on the bank of a pond, the head of the smaller pike being in the throat of the other. He speaks also of a pike that was killed, from the mouth of which the tail of a rat was found projecting. — Gleanings in Natural History, third series, p. 83. Though the food of fishes is very variable, yet they may generally be considered either as insectivorous or carnivorous. For catching their prey they have many very beautiful con- trivances; but none, perhaps, exceed that 'of the chsetodon ros- tratus, consisting of an extraordinary prolongation of the snout, having an opening at the extremity, through which this little animal spurts out drops of water upon the insects on which it feeds, and which settle upon aquatic plants ; and so accurately does it take its aim, that the insect invariably falls into the water, and thus becomes its prey. The teeth of the ch^todon are so very delicate and fine, that they resemble the pile on velvet. Another species, the toxotes jaculator, or archer, from Java, is celebrated for the same faculty. Cuvier says, it can force the water to a height of three or four feet, and rarely misses its aim. t Cuvier, Animal Kingdom, p. 262. 368 LETTER XI. it were, in a lower sphere, we do not find the adaptation of their bodies less wonderful, or that they display less of the interminable resources of the Creator. For here, as in all other parts of the living creation, organisation is perfectly adapted to the circumstances in which animals are placed ; so that these comparatively insensible creatures are equally dignified with the stamp of Divine workmanship.* If any one part of their organi- sation displays this more forcibly than another, it is the construction and arrangement of their teeth. In many of the varieties of fishes, a devi- ation from the ordinary laws which regulate the growth and arrangement of these instruments f in * Cuvier says, " these beings, to which enjoyments have been so scantily suppUed, are decorated by nature with every sort of beauty ; variety in their forms, elegance in their proportions, diversity and gaiety in their colours ; nothing, in fact, is wanted in them to fix the attention ; and it really would seem that nature had this end in view in her design. The splendour of the metallic bodies, and of all the precious stones with which they shine forth, the colours of the iris which they exhibit, are reflected in bands or spots in undulating or angular lines, but invariably regular and symmetrical, the shades wonderfully adjusted and contrasted. Wherefore should all these endowments be distributed to creatures like the fishes, which scarcely ever see each other, save only in those depths where the light of the sun hardly penetrates ? and even when they do see each other, what sort of pleasurable sensation can be excited among them by these characters ?" — Histoire Naturelle des Poissons, chap. i. t Occasionally we see, as in the sun-fish (orthagoriscus), in- stead of teeth, two solid sharp bones in the form of gums. LETTER XI. 369 terrestrial animals, is particularly required, on ac- count of the nature of their food, and the diffi- culties they have to encounter in obtaining as well as in securing it. For this cause, in the cartilaginous fishes there are provisions for replacing whole rows of teeth when they are torn away in the act of pre- hension. This is remarkably exemplified in the shark. M. Andre* says, this animal has fifty-two rows of teeth, six being contained in each row, making in all three hundred and twelve teeth. But of all these teeth those only which form the front row are uncovered and have a perpendicular direction ; all the other rows are inclined back- wards towards the throat, and are covered by the gum. These teeth have no fangs, but adhere to a firm cartilaginous substance which covers the jaw : they appear to be in a graduated state of perfec- tion as they advance from the posterior to the anterior rows, so that they may be fitted for the use of the animal when any of the front rows are lost. The lophia piscatorius (sea-devil) derives much advantage from a similar cartilage. Blake f says, " all the teeth are turned towards the oesophagus, and are connected with the internal side of an elastic cartilage, so that the slightest pressure will cause them to yield, and permit the animals * See his paper in the Phil. Trans, ahrid., vol. xv. p. 540. t De Dentibus in variis Animalium Classibus, ch. viii. B B 370 LETTER XI. which this fish entices to enter into its mouth ; but when the external pressure is removed, the elastic cartilages react, and the teeth resume their former situation. As the external part of the jaw acts like a fulcrum, and on that account resists the pressure from the internal part, so I was enabled to remove one of them from its place. The teeth in the stomach of this animal are found to be of a similar structure." Many fish, particularly the skate (^rajci hatis), have their teeth pointed in the direction of the gullet ; and their principal use seems to be to prevent what is taken into the mouth from shpping out again,* for their food is not always deprived of life ; so that this provision has direct reference to the activity and vivacity which some fishes, designed to serve for food to others, display, and which would other- wise frequently enable them to escape after being captured. But the adaptation of the teeth of animals to the nature of their food is no where more mani- festly observable than in those of the sea-wolf {anarrhichasj' lupus). This animal subsists entirely upon crabs, muscles, and other shell-fish, which must be ground down before they can be swal- lowed ; its teeth are accordingly fitted for this pur- * Some of the chsetodons have teeth resembUng the hairs of a brush in length and tenuity, placed in several close rows. f Or sea-cat ; so named by Gesner, because it is said to climb upon rocks, by means of its fins and tail, in search of shell-fish. LETTER XI. 371 pose. The outer row is sharp and pointed, for prehension ; within these are several blunt and rather flat teeth, which serve to break down the hard shells that envelop their food. But to shew more fully the beauty and completeness of this adaptation, it will be proper to notice the manner in which the jaw is put together and made to move. In herbivorous animals, which have to grind down their food by constant trituration, the jaw is fixed to the skull so as to allow it to have a rota- tory movement ; but such a movement would be useless to carnivorous animals. Where a rotatory motion of the jaw is not required, it is locked into the cavity of the skull by ligaments, in the same manner as the two parts of a hinge are fixed together. The cavity is deep and elongated, and the articulating surface of the jaw-bone corre- sponds, so that the joint can have only a hinge- like motion. This is remarkably conspicuous in the condyles of the lower jaw of the sea-otter.* The jaw of the sea-wolf is composed of several pieces, instead of being one entire bone ; and these pieces are connected by loose hgaments, so that a greater freedom of motion is allowed, and the con- cussion to the brain arising from the reduction of * These also live on shell-fish, and their teeth are so shaped that the crowns, instead of being flat and irregular upon the upper surface, are formed into round prominent knobs, fitting them for breaking shells. o 72 LETTER XI. such hard bodies is diminished, the jar being broken by being divided over a number of bones. As most of the inhabitants of the sea are ex- posed to great external violence, they are either protected by a very hard, unyielding skin, as the crocodiles and many kinds of fish ; or else the skeleton, which in the higher animals is placed in- ternally, for the purpose of supporting and defend- ing the softer structures, is made equally available for those purposes by forming an outward cover- ing, as in the tortoises and molluscous animals. So impenetrable is the skin of the crocodile, that St. John says, " the balls fired at them appeared to rebound from their scaly rinds harmless as hail- stones, nor did such as were hit seem to quicken their pace in the least when jumping into the river with the rest." * In some fishes, as, for instance, the sun-fish (orthagoriscus), the skin is perfectly invulnerable. Cuvier says there is a thick layer of a gelatinous substance spread under the skin of these animals, which may contribute to give it this character. But the shells of the testaceous and other ani- mals inhabiting the sea furnish the most striking examples of wise provision against the external forces to which they are so peculiarly exposed by the motion of the waters. Shell is one of those structures which are made up of animal and earthy matter, combined in fixed proportions. The dif- * Travels in the Valley of the Nile, vol. i. p. 304. LETTER XI. 373 ference between shell and bone consists in the relative proportions of these two ingredients : in shell there is a great excess of earthy matter, car- bonate, and, in some instances, phosphate of lime ; in bone the proportion of animal matter is much greater than in shell. The relative proportions of these elements differ in almost every species of animal, the chemical composition of whose bones has been ascertained ; and there is good reason for concluding, that every shade of proportion in the component parts of the bony apparatus of animals is regulated in the most perfect manner by the mode of life destined to be pursued by each animal. This opinion is very strongly supported by an analysis of the bones which compose the skeleton of fishes. That which would add most to their weight, the phosphate of lime, is here found in very small proportion ; which circumstance gives to the bones of fishes the cartilaginous appearance they possess, at the same time rendering them light and easily suspended in the water. Animal matter is most abundant in the bones of fish ; in the am- phibious tribes its quantity is diminished ; it exists to a still smaller amount in quadrupeds and bii'ds ; and is almost lost in the calcareous and inflexible crust of the mollusca and testacea. As already stated, these last-mentioned animals are exposed to extreme violence, from the effects of which their pecuhar covering is in most cases a complete protection. The vital, and even the 374 LETTER XI. muscular parts, are thus defended by a movable fortress, every part being covered by an arch of shell, a substance better adapted than even bone to secure their safety, more capable of resistance, and wholly insensible, so that the shell may be broken without injury to its inhabitant, and sometimes is so for its convenience. The shells of molluscous animals are very variable in their composition and appearance, though they are all composed either of carbonate or phosphate of lime and animal matter ; and as one or other of these ingredients prevails, they are called vitreous, porcelaneous, or membranous, according as they bear a greater re- semblance to glass, porcelain, or membrane. Most shells are composed of three distinct layers, the fibres of each layer being placed at right angles with those of the contiguous layers, so that the greatest strength is obtained for breaking the force of blows, in whatever direction they are applied. "We here find," says Roget, "that a principle which has only of late years been recognised, and applied in the building of ships, namely, that of the diagonal arrangement of the framework, and the oblique position of the timbers, is identical with that which, from the beginning of creation, has been acted upon by nature in the construction of shells."* As the shell of the Crustacea is incapable of yielding after it has been once formed, it is neces- * Animal Physiology, vol. i. p. 235. LETTER XI. 375 sary, in order that the parts which it encloses may grow, that the old shell be cast off, to make way for one of larger dimensions to take its place. Did these animals possess a very high organisation, this process, which is attended with much danger and pain, as well as mutilation, could not take place. Speaking of the lobster. Goldsmith says, " the body still continuing to increase, while its shell remains unalterably the same, the animal becomes too large for its habitation ; and imprisoned within the crust that has naturally gathered around it, there comes on a necessity of getting free. The young of this kind, therefore, that grow faster (as I am assured by the fishermen), change their shell oftener than the old, who have come to their full growth, and who remain in the same shell often for two years together. In general, however, all these animals change their shell once a-year; and this is not only a most painful operation, but also subjects them to every danger. " Their moulting season is generally about the beginning of summer, at which time their food is in plenty, and their strength and vigour in the highest perfection. But soon all their activity ceases ; they are seen forsaking the open parts of the deep, and seeking some retired situation among the rocks, or some outlet, where they may remain in safety from the attacks of their various enemies. For some days before their change the animal discontinues its usual voracious- 376 LETTER XI. ness ; it is no longer seen laboriously harrowing up the sand at the bottom, or fighting with others of its kind, or hunting its prey ; it hes torpid and motionless, as if in anxious expectation of the ap- proaching change. Just before casting its shell, it throws itself upon its back, strikes its claws against each other, and every limb seems to tremble ; its feelers are agitated, and the whole body is in vio- lent motion ; it then swells itself in an unusual manner, and at last the shell is seen beginning to divide at its junctures ; particularly it opens at the junctures of the belly, where, hke a pair of jumps, it was before but seemingly united. It also seems turned inside out, and its stomach comes away with its shell. After this, by the same operation, it disengages itself of the claws, which burst at the joints ; the animal, with a tremulous motion, cast- ing them off as a man would kick off a boot that was too big for him. " Thus in a short time this wonderful creature finds itself at hberty, but in so weak and en- feebled a state, that it continues for several hours motionless ; indeed, so violent and painful is the operation, that many of them die under it ; and those that survive are in such a weakly state for some time, that they neither take food nor venture from their retreats. Immediately after this change they have not only the softness but the timidity of a worm ; every animal of the deep is then a powerful enemy, which they can neither LETTER XI. 377 escape nor oppose; and this, in fact, is the time when the dog-fish, the cod, and the ray devour them by hundreds. But this state of defenceless imbecility continues for a very short time ; the animal in less than two days is seen to have the skin that covers its body grown almost as hard as before. Its appetite is seen to increase, and, strange to behold, the first object that tempts its gluttony is its own stomach, which it so lately was disengaged from. This it devours with great eagerness, and sometimes eats even its own shell. In about forty-eight hours, in proportion to the animal's health and strength, the new shell is per- fectly formed, and as hard as that which was just thrown aside."* We here see the necessity and advantage of the external position of the skeleton in animals that are subject to all the tempestuous motions of the sea ; how their organisation permits them to part with that skeleton when the growth of the body requires it ; and how beautifully the means of defence in these lower animals are adapted to the vitality of the animal, and to the difficulties with which they have to contend. " In this view of the structure of animals forming the different gradations in nature, we are led at every step to look up to their Creator with wonder and admiration, and, in the contem- plation of his works, to learn what constitutes perfection." f * Natural History, book iv. c. ii. f Sir E. Home on Comp. Anat., vol. i, p, 70. 378 LETTER XI. It should be observed, that provision for com- plete security from danger, inasmuch as it is in- compatible with the scheme of Providence, must not be looked for in the mechanical arrangements of organised bodies. Many animals come into life principally for the purpose of furnishing subsist- ence to the creatures that surround them. If, therefore, their instruments of defence were appli- cable to every mode of assault, one of the great ends of creation would be defeated. To assist them in avoiding their enemies, as well as injuries resulting from inorganic bodies, we find them gifted with means of defence in an instinctive power, in addition to the organisation of their bodies; yet, notwithstanding these organic and instinctive contrivances, animals become a prey to their more formidable opponents. Thus, flying fish (exocetus volitans) can raise themselves out of the water high enough to avoid the shark ; but in doing so they are frequently devoured by voracious birds, such as the albatros, which are continually on the look-out for them. Beyond 22° latitude, Humboldt found the surface of the sea covered with these fish, which sprang into the air to the height of twelve, fifteen, and even eighteen feet, and sometimes fell on the deck. The great size of the swimming-bladder in these animals (it being two-thirds the length of their body), as well as of the pectoral fins, enables them to traverse at one time in the air a space of twenty-four feet horizontally. They are incessantly pursued by LETTER XI. 379 dolphins while in the water, and when flying are attacked by frigate-birds and other predatory species. The means of defence possessed by some of the inhabitants of the deep are of a very singular description. Thus, the calmars {loligo) are pro- vided with a bag, containing a kind of ink, which they have the voluntary power of ejecting on the approach of an enemy ; by this means they render the water turbid, and secure their own safety. I would also direct your attention to the circumstance, that the feet of most molluscous animals are provided with little cups, or suckers, at their extremities, by which these animals fix themselves immovably as if at anchor, and so bid defiance to the storm. LETTER XII. " The hearing ear and the seeing eye, the Lord hath made even both of them." — Prov. xx. 12. I COME now to speak of the five external senses, and the organic parts by which these senses act, namely, the eye, the ear, the nose, the tongue, and the skin. I will first, however, make a few remarks respecting ordinary sensation. It is essential to the continued existence of animals, that they have means of knowing when their bodies are exposed to the operation of agents detrimental in themselves to their well-being, or to the too powerful action of those which in a moderate degree are beneficial. Were animals incapable, for example, of discriminating between the various de- grees of temperature, they might be subjected to one which would rapidly disorganise their struc- ture and deprive them of life, without being con- scious of it, and without making any eff'ort to escape the impending danger. But it is not so ordered ; means are provided for the protection of the organisation in which so much Divine skill has been displayed. The power of sensation has been bestowed upon all animals for this among other purposes. When the agents acting upon the body are harmless or beneficial to it, the impressions LETTER XII. 381 which they make upon the sentient principle are agreeable or pleasurable, and are therefore volunta- rily prolonged. If, on the other hand, these agents are injurious, the impressions they produce are pain- ful, and consequently endeavoured to be removed. This power of sensation resides in almost every part of the body. All parts, however, are not equally exposed to injury ; and in proportion to the decrease of danger, the power of sensation becomes less strong. The internal organs, for example, possess little sensation ; that is, have few nerves of sensation distributed to them, compared with the surface of the body.* It might be thought, * In proof of this fact I may mention, that in the year 1828, when I was house-surgeon to St. Bartholomew's Hospital, a boy was admitted who had fallen from a high warehouse, and in the fall was caught by a chain-hook. Nearly half the bowels pro- truded through the wound which was the consequence of this accident. I replaced them ; and during the operation repeatedly asked the boy if I gave him much pain ; he said he was in none. This extraordinary case recovered, through the attention and skill of Mr. Vincent, in whose ward he was placed. The follow- ing passage proves clearly the low degree of sensibility possessed by the heart. " A noble youth of the family of Montgomery, from a fall and consequent abscess on the side of the chest, had the interior marvellously exposed, so that after his cure, on his return from his travels, the heart and lungs were still visible, and could be handled ; which, when it was communicated to Cliarles I., he expressed a desire that Harvey should be permitted to see the youth and examine his heart. ' When,' says Harvey, ' I had paid my respects to this young nobleman, and conveyed to him the king's request, he made no concealment, but exposed the left side of his breast, where I saw a cavity into which I could intro- 382 LETTER XIT. that the more tender and dehcate the structure, the more susceptible it would be of pain : such, however, is not the case. The knife of the oculist penetrates the delicate internal parts of the eye, and the pain experienced is by no means great ; while the outer coverings of that organ are pos- sessed of high sensibility, which, being easily ex- cited by any foreign substance, gives notice to the animal of the presence in the eye of whatever would, if suffered to remain, inflame it, and might destroy vision, — thus leading to its expulsion. Before I proceed to the special senses, I will give one or two illustrations of the utility of ordi- nary sensation. When the muscular power has been overstrained and exhausted by long-continued exercise, a feeling of lassitude and oppression, in the highest degree painful, supervenes ; every joint of the body partakes of this feeling, and it does not cease until the exercise is succeeded by rest and repose, which is, under these circumstances, ex- duce my fingers and thumb. Astonished with the novelty, again and again I explored the wound, and first marvelling at the ex- traordinary nature of the cure, I set about the examination of the heart. Taking it in one hand, placing the finger of the other on the pulse of the wrist, I satisfied myself that it was indeed the heart I grasped. I then brought him to the king, that he might behold and touch so extraordinary a thing ; and that he might perceive, as I did, that unless when we touched the outer skin, or when he saw our fingers in the cavity, this young nobleman knew not that we touched the heart.' " — Quoted in Sir C. Bell on the Hand, p. 186. LETTER XII. 383 ceedingly pleasurable. Again : we have seen that a certain degree of temperature is necessary to keep in motion the different machineries of the animal economy ; and that for this purpose a cer- tain quantity of caloric or heat is generated in the living body. But the application of cold to the skin, if too long continued, would eventually be destructive to life, by reducing this standard heat. Here sensation is the only monitor — it is the mer- cury in the thermometer of life. Immediately the impression of extreme cold is felt, the greatest anguish and pain is produced, until the body, or the part so affected, has again reached its proper standard of temperature. For their greater accommodation, and freer communication with each other and the world around them, animals have been gifted with parti- cular kinds of sensation, which, from the fact of their possessing the power of conveying external impressions to the brain, have been called external senses. Without these faculties we must for ever have been shut out from the enjoyment which the outward world is so capable of affording, and should have been deprived of that evidence of adaptation and design which so strongly confirms the truth of revelation. " The external world," says Sedgewick, " proves to us the being of a God in two ways — by addressing the imagination, and by informing the reason. It speaks to our imaginative and poetic feelings ; and they are as much a part of 384 LETTER XII. ourselves as our limbs and our organs of sense. Music has no charms for the deaf, nor painting for the blind ; and all the touching sentiments and splendid imagery borrowed from the world without by the poet, would lose their magic power, and might as well be presented to a cold statue as to man, were there no pre-ordained harmony between his mind and the material things around him. It is certain that the glories of the external world are so fitted to our imaginative powers as to give them a perception of the Godhead, and a glimpse of his attributes ; and their adaptation is a proof of the existence of God, of the same kind, but of greater or less power according to the constitution of our individual minds, with that we derive from the adaptation of our senses to the constitution of the material world."* In order that these senses may have a wider sphere of action, as well as that any injury done to their instruments may not be altogether destruc- tive of them, the organs of every sense are double. Yet there is so intimate a connexion between the two instruments of a sense, that the consciousness of both impressions is single. There is reason to believe that the senses of every animal have some pecuharities causing them to differ from the corre- sponding senses of all other animals, being modified by external impressions according to fixed laws. By this, in conjunction with other means, animals are * Discourse on the Studies of the University, p. 17. LETTER XII. 385 directed to their proper food, which is thus also preserved from all other animals. Occasionally we find one or more of the exter- nal senses completely lost. Animals are some- times born blind, or become so accidentally. The consequences of this misfortune are worthy of remark. As the other organs of the body are strengthened by exercise, so is it with the organs of sense ; and when one of them has been destroyed, the remaining senses are capable of acquiring a degree of vigour and activity which, if it cannot be called an additional or superadded power, is at least not to be comprehended by those who have never suffered such a loss. How wise and benevolent a compensation is this for the loss of such valuable instruments ! Blind persons have been said to feel the proximity of objects by the impression of air upon their faces. The blind Weissenbourg of Mannheim judged exactly of the distance and size of persons who, in an erect pos- ture, spoke to him. The blind Schonburger of Weide, in the Upper Palatinate, had the sense of hearing so acute, that by striking the place where the nine-pins or the shooting-mark were put up, their situation was so clearly indicated to him as to enable him frequently to hit them.* Blind per- sons often find a pin or piece of money which makes a noise in falling. " Some blind persons have the other four senses * See Spurzheim's Phrenology. C C 386 LETTER XII. in such exquisite perfection, that if they hear any one speak, they directly estimate his height ; will find out the size of an apartment if it contains much furniture ; and at their own houses will dis- cover if any article has been displaced. They know, by the remembrance of sounds, persons whom they have heard speak formerly. They can tell if they are in a street or a blind alley, in a large or a small room ; and they recognise places where they have formerly been introduced. They calculate the proximity of the fire, from the de- gree of heat ; the fulness of vessels, by the noise the liquor makes when poured into another cup ; and the neighbourhood of bodies, by the action of air upon their faces. Their hands are scales for weigh- ing; they judge correctly of the duration of bad weather ; feel accurately the vicissitudes of the at- mosphere ; and remark, by the different action of the rays of the sun on their face, when a cloud obscures its disc. All this is doubtless astonishing ; but to walk alone in Paris is still more difficult. I know several who possess this audacious skill ; amongst others, the intelligent Lere and the bold Maune. I recollect meeting them passing over the most dan- gerous crossings, with only a stick to guide them. At Paris, in a very thick fog, some blind men of the Quinze-Vingts served as guides to those who saw, and even conducted them to their dwellings."* * Medical Gazette, vol. xvii. p. 729. See a paper written by the blind Rodenbach. LETTER xir. 387 In like manner, the eyes acquire a very high degree of activity when any of the other senses are lost. Deaf and dumb persons distinguish what other persons say, from the motion of their lips. Their feeling is also acutely sensible. While they are totally deaf to the sound of a gun or cannon, they are conscious of any one passing by them, although they do not see him. It would appear fi'om a letter written by M. Rodenbach, a member of the Chamber of Deputies at Brussels, who was himself blind, that this in- creased power of the external senses is not peculiar to those who have been deprived of one or more of them, but that all are alike capable of improvement in this respect to an astonishing degree. He thinks that ancient writers have exaggerated the talents and defects of the blind, and that the moderns, without examination or reflection, have repeated their errors. Still, blind men do display much higher tact than others ; and it is pretty certain that, where all the senses are retained, such per- fection in individual senses as that of which I have been speaking, seldom occurs. But I will quote his own words : " An idea which has been gene- rally received is, that the loss of one sense adds to the perfection of the other senses. This assertion is bold : I will say more, it is totally absurd. The perfectibility of the touch among the blind, called, so ingeniously, the geometrical sense, is only ac- quired by the continual exercise of this sense. 388 LETTER XII. Necessity, the powerful mover of all our actions, is the sole cause of the superiority that we have in this respect over those who see. If these last practised more the sense of tact, the pre-eminence would no longer be in favour of the blind. If the prejudice which I have just observed was correct, it would follow that we might establish as a prin- ciple, that the loss of two or three senses would be attended by a moral compensation. It is not so. M. Hauy mentioned to me the case of a young girl, deaf, dumb, and blind, whom he tried to instruct, without being able to succeed. Instead of having a double degree of intelligence, this un- happy creature was in some measure deprived both of intellect and feeling. Many persons believe that the blind can distinguish colours by the touch ; and some well-informed men, at least on other subjects, have often asked me questions on this point. I can assure them that it is absolutely impossible ; but the blind have some other means of distinguishing colours, although imperfectly. I knew a blind man whose sense of smelling was so exquisite, that by rubbing a piece of coarse blue cloth with his hand, he smelt indigo, and thence drew the conclusion that the cloth was of a blue colour. Another blind man had a habit of chewing any article of stuff that was presented to him, and was enabled by this means to guess the colour, particularly when gall- nuts had formed a part of the dye. I met one day a blind Frenchman wandering about the Boule- LETTER XII. 389 vards of Paris ; he was surrounded by a troop of citizens, who were all in ecstasies at perceiving that a man deprived of sight could ascertain colours. This man held in his hand a wooden octagon, whose eight sides were each painted of a different colour. When the curious bystanders placed his finger upon the surfaces, he cried out this side is red, or green, or blue, &c. ; but when he asked for some money, the crowd disappeared, and I requested permission to examine his octagon. I remarked distinctly with my finger, that one of the surfaces was highly polished, whilst others were rough and sharp to the touch. These irregularities were produced either by the particles of the paint, of which some are infinitely coarser than others, or by the labour of the carpenter, who, I am inclined to believe, had contrived, with great art, different marks or signs easily recognised by the touch. Such are the secrets of those blind persons who pretend to find out colours by the touch or smell. To discern the truth, it is necessary to place in their hands articles which they had not previously studied in the company of a person who sees : you will then soon be convinced of their ignorance."* To enable animals to distinguish the various objects by which they are surrounded from one another, and to acquire a knowledge of their several qualities, many — most, indeed — of which cannot be detected by ordinary sensation, they are, as I have * See the above paper. Medical Gazette, vol. xvii. p, 727. 390 LETTER XII. already said, fiirnished with special senses, four or five in number, the organisation subservient to which consists of distinct nerves of sensation, con- nected with appropriate structures, on which they are expanded and exposed in such a manner as to fit them to receive a vast variety of impressions, and thus to convey to the perceptive principle, through the medium of the brain, in which they terminate, a knowledge of external objects sufficient for all the ordinary purposes of life. These senses are known by the names of sight, hearing, touch, taste, and smell ; and their nerves by those of the optic, auditory, cutaneal, gustatory, and olfactory. As the organs of sense are the only instruments by which we can obtain a knowledge of the count- less objects that surround us, they must neces- sarily be highly important as means of defence ; they are also indispensable to the obtaining or selecting of food, and are at the same time sources of never-ending pleasure. Respecting the use of the nerves which belong to the external senses, an opinion has been advanced by M. Ma- gendie, very different from that generally received, but professedly the direct result of experiment. By dividing the different nerves of the living subject, he conceives he has discovered that the senses of sight, hearing, smell, and taste, are not exercised through the media of the optic, auditory, olfactory, and gustatory nerves, as they have been named from their supposed offices, but that the LETTER XII. 391 impressions are, in all these cases, conveyed to the sensorium by certain branches of the Jifth pair of nerves, which are distributed in greater or less quantity over all the organs of sense. With re- spect to the eye in particular, he found that the division of the Jifth pair of nerves always caused blindness, although the optic nerve was untouched ; the division of the optic nerve also produced blindness ; so that this last appears to be essential to sight, although not capable of producing it with- out the co-operation of the fifth pair. Magendie likewise informs us, that all these nerves are insen- sible to chemical stimuh, while the Jifth pair is exquisitely sensible to them.* Many agents are capable of acting only upon the organs that are pecuharly adapted to receive their impressions, and consequently are not re- cognisable by any other means ; so that a know- ledge of their nature could not be imparted to animals through any other channel. In their re- lationship to external bodies the senses are said to differ from one another in this particular, that each is fitted to receive a certain kind of impression, which cannot be made upon any of the others. Thus, the sound of a cannon has no influence upon the optic nerve, nor does the auditory nerve recog- nise the grandeur of the surrounding scenery. If, however, a substance has two or more sensible pro- * See note to Bostock's Physiology, vol. ii. p. 92. 392 LETTER XII. perties, these are capable of being detected through the instrumentahty of one, two, or three senses. Thus, the vivid hght of the sun's rays conveys to the sense of touch a feehng of heat, to that of vision a feehng of hght ; but we can neither hear, taste, nor smell it. Again : many fluids have to the eye the appearance of water ; and it would not be pos- sible to detect their peculiar properties by the sense of touch, though taste and smell might decide. Thus, by the combined operation of all the exter- nal senses, our ideas of the nature of objects are enlarged. The different spheres of existence, the habits, food, and other circumstances characteristic of every distinct race of animals, render necessary some diversity of arrangement in the structure and functions of the organs of sense, and of the nerves which constitute their essential parts. Nerves are distinguished from one another by several circumstances ; their size, shape, colour, consistence, all vary according to the purposes which they subserve ; some of these properties, particularly size and consistence, are of such a nature as to incapacitate us for gaining a know- ledge of them beyond the variations which we can detect by means of our eyes, though doubtless there are many arrangements and modifications of nervous fibres which we shall never be able to detect. There is, nevertheless, not so gi'eat a difference in the outward character as there is in LETTER XII. 393 the functions of these nerves, which must certainly depend upon that part of the brain from which they take their rise. The various degrees of power which are manifested in the senses of different animals may, however, often be explained by the diiferences in the magnitude, as well as in the con- struction, of the sensorial nerves. The wonderfully enlarged powers which the senses of many animals possess are therefore to be considered not merely as the result of instinct, but, in connexion with that, also of peculiar forms of organisation. Nor must it be presumed that the organs of sense are similarly constructed in all animals ; they are all modified so as to be adapted to the respective cases and spheres to which they apply. If, for example, we examine the eye of the amphibia, we shall find that these animals have the power of varying its action according to the situation in which they are placed. The eye of the seal {phoca vituUna) displays a remarkable disposition of structure. This animal can lengthen or shor- ten the axis of vision at pleasure, by which means it is enabled to see at one time through a dense medium, as when it is in the water ; at another through a rarer medium, as when on land. Some of the senses are wanting in those cases where they would not be available. The sense of touch is not supposed to extend to more than four classes of animals — the mammaha, birds in a few instances, serpents, and insects ; but it is not 394 LETTER XII. found in all the individual species even of those classes. The organs by which this sense is mani- fested are very diversified. In serpents the tongue is thought to perform this function, though the skin has many nerves distributed to it. Bats have been supposed to possess a peculiar power, enabling them to avoid coming in contact with bodies in their rapid and uncertain movements through the air during the night, when the organs of sight must be comparatively useless. Spallanzani, and M. Jurieu of Geneva, thought this was a sixth sense ; but it has since been shewn to be a modification of the sense of touch. The nerves in the wing of this animal are numerous and very large; and their greater sensibility, by which they detect the approach of foreign bodies, is perhaps attributable to the extreme delicacy of the cuticle that covers them. The snout of the pig, mole, and tapir, the tongue of some of the ruminants, the whiskers of the cat and seal, are all named by naturalists as instruments of touch. The elephant is said to possess the same power in the extremity of its trunk, and some apes in their tails ; while ducks are said to feel with their bills. In fact, any part of the animal body that is most naturally apphed to any of the purposes which, as I have shewn, have been concentrated in the human hand, may become the organ of the sense of touch ; and this fact is borne out by the plentiful supply of nerves which is given to those parts. LETTER XII. 395 So, likewise, with regard to the organs of taste. In birds and ant-eaters the tongue cannot be looked upon as filling this office, for its me- chanism is by no means adapted for it. To prove that this sense is capable of being transferred to other parts, I need only tell you, that Blumenbach knew a man who had been born without a tongue, and yet could distinguish the taste of salt, sugar, and aloes, when rubbed upon his palate ; and ex- pressed the same in writing.* Some animals have no tongue, as the whale ; in others it is extremely long and narrow, like a worm, and being covered with a glutinous substance, is clearly meant to be an instrument for drawing in their food — it is their hand ; and its prehensile power is increased in some species of the vampire, the cat, and the opossum, by strong papillae or points, which are directed backwards. These papillae are particularly large and prominent in the ruminants. In regard to the sense of smell, which is more widely bestowed than either of the preceding senses, there is a difficulty in determining the organ appropriated to it in many of the cold- blooded animals. But in some animals it is very much developed, and assists them in the choice of their food. Circumstances may render this organ, as well as that of taste, unnecessary, as * Manual of Comparative Anatomy. 396 LETTER XII. where the animal always exists upon the same kind of food, which it may be able to recognise by its touch alone. The organs of hearing are present in most animals, but are often imperfectly developed in fishes; and in some their structure is so simple, and so much modified by circumstances, that they almost assume a different function. But the eye is a more important and more extensively useful organ, and is possessed by all animals that have free communication with light, with which it is formed to treat. It is subject, nevertheless, to very great variety, and sometimes is wanting. But, as I am about to consider each of the senses and its organs in relation to the various stations and habits of animals, it is not necessary for me to make any further general statements. The eye being an organ of the most delicate structure, fitting it to be acted upon by the most subtle of fluids, I shall first direct your attention to it, premising a few observations upon the laws of light. The laws and phenomena of light are of the most interesting character, even when viewed in their simple but grand and intimate arrangement ; but in connexion with the organs of vision, no part of the creation is more calculated to excite our astonishment, or more clearly bespeaks the agency of a God. LETTER XII. 397 Although we may be said to be ignorant of the nature of hght, we can trace its sources with con- siderable certainty; and of late years many facts have been collected in support of the theory of its extreme tenuity, which is supposed to exceed many times that of air. Its effects, however, are more remarkable, more easily to be detected. We know that it moves with almost inconceivable swiftness, being calculated to travel a distance of 195,000 miles in a second, which brings it to us from the sun in about eight minutes and a quarter ; — that it moves in straight lines, if not obstructed by denser bodies than the air ; — that it passes through many bodies, which are thence called transparent; or, if it enters them in an oblique direction, that it passes out in the same manner, and is thus refracted ; — that when it falls upon other bodies, it does not enter them, but is reflected from the surface in their natural colours, which renders it invisible ; — that it is composed of seven primary colours, which are those of the rainbow, a fact which Sir Isaac Newton succeeded in discovering by means of a prism (a triangular cube of glass) : these colours are violet, indigo, blue, green, yellow, orange, red, which are named prismatic colours, because in the spectrum, pro- duced by making a ray of light to pass through a prism, they are seen in the order above mentioned. Each of these colours has a different refractive power — the red being bent the least, and the 398 LETTER XII. violet the most, in passing through the prism. It is the nature of most bodies to attract different prismatic rays ; the rays which some bodies absorb are reflected by others from their surface ; and the colour of bodies depends upon the particular rays which are reflected from them. Having decom- posed white light into seven elementary colours. Sir Isaac Newton shewed that they could be put together again to form white light. It is well known, also, that many bodies on which light falls being rough or irregular, or having other proper- ties, assume all those varied and endless shades of beauty and colour which are produced by the transmission of some of these primary colours, and the reflection of those that are not transmitted. Of the properties of hght, none is more im- portant, in relation to our present subject (for I do not here intend to enter more largely into the science of optics than is just suflicient to explain its connexion with the eye) than that law which regulates the bending or refraction of its rays. As different colours have different refractive powers or degrees of refrangibihty, so also have all bodies which admit light. When a ray of light passes from a rarer to a denser medium, or vice versa, its direction is altered, and the degree of refraction depends upon the nature of the body through which it passes. Salt water refracts it at a greater angle than fresh water ; spirit of wine still more ; oil more than spirit ; and glass more than oil. LETTER XII. 399 The eye contains bodies which have different powers of refraction ; and it is certain that they could not have been formed and placed in their relative positions in that organ by any other than One who knew most intimately all the laws and properties of light ; for it will presently be shewn^ that it is to this law of refraction that many of the phenomena of vision are attributable. The various coats, humours, and lenses, contained in the eye, are all arranged for the express purpose of gathering the scattered rays of light which fall upon that organ as they do upon other transparent bodies. " Does not the optician who designedly places his convex lens at the proper distance in a darkened box, for the purpose of obtaining vivid pictures of the external scene, evince his know- ledge of the laws of hght, of the properties of refracting media, and of the refined combination of those media, by which each pencil is brought to a separate focus, and adjusted to form an image of remote objects ? Does it not, in like manner, argue the most profound knowledge and foresight in the divine Artist, who has so admirably hung the cry- stalline lens of the eye in the axis of a spherical case, in the fore part of which he has made a cir- cular window for the light to enter, and spread out on the opposite side a canvass to receive the pic- ture ? Has no thought been exercised in darken- ing the walls of this camera obscura, and thus preventing all reflection of the scattered rays 400 LETTER XII. that might interfere with the distinctness of the image ?" * The position of the eye deserves to be noticed here as indicative of the wisdom of the Creator. Being in all animals which possess it the most im- portant external sense, it is placed in the most commanding and conspicuous position. In warm- blooded animals there are muscles by which the globe of the eye can be turned in any direction, according to the will of the animal, and thus a greater facility of vision is obtained. In fishes, where the eye is more fixed, many means are taken to compensate for the want of mobility.f I will now enumerate the different parts which compose the eye, in order that when they are spoken of hereafter, the design manifested in their variations, by which they are adapted to the diversified circumstances of animals, may be fully appreciated. The eye is regarded as an optical instrument consisting of three orders of parts. The first con- sists of those parts by which the rays of light are received and so far modified as to be rendered subservient to vision; the second, of the nerves which receive the impressions of light, and convey them to the sensorium or brain ; and the third, of * Roget's Animal Physiology. t Althougli fishes have as many muscles attached to the eye as man, yet these muscles are employed for altering the axis of the organ more than for motion. LETTER XII. 401 a number of accessory parts, which preserve the eye m the proper state for the performance of its functions, and enable it to execute them in the most perfect manner. The globe or ball of the eye is composed of three transparent humours or fluids* of various densities, and encased in membranes or coats of different thicknesses. The vitreous humour con- stitutes the chief bulk of the eye, and is of the consistence of the white of egg. It occupies the back part of the organ. In its anterior part there is a depression which receives another of the hu- mours, called the crystalline lens. This is a body of greater consistence than the vitreous humour, and, having the form of a double convex lens, is placed behind the pupil in a perpendicular direc- tion, so that every ray of light which enters that opening must pass through it. The crystalline lens has a refractive power greater than that of water, and less than that of glass. Chenevix shewed f that the chief cause of the difference between the refractive powers of this and the other humours of the eye is the presence of dif- ferent proportions of albumen.^ Anterior to the crystalline lens is placed the aqueous humour ; a fluid in no respect distinguish- able from water, save that it holds in solution * See Plate V. fig. 1. t Philosophical Transactions for 1803, p. 195. X Monro's Three Treatises. D D 402 LETTER XII. several saline ingredients.* In this fluid the iris, the dark part of the eye which surrounds the pupil, floats like a curtain, dividing it into two chambers — the anterior, or that which is situated between the iris and the cornea, and the posterior, or that which is situated between the iris and the crystalhne lens. There is reason to beheve that the iris consists of two sets of muscular fibres, one set being circular, the other radial ; and it is con- jectured that their function is to contract and expand the aperture of the pupil. Which of these conditions is the state of repose of the iris, is not certain. Fontana thought that when the pupil is contracted, and the iris consequently expanded, the latter is in a state of relaxation, this being the case in sleep. If the iris is muscular, its fibres are not of the same kind as those which compose the muscles. The pupil in man and most animals is perfectly round ; but in animals which climb, it is elliptical, the ellipse being perpendicular to the body : in the frog it forms a rhomboid placed * In fishes the vitreous humour is comparatively small in quantity ; the crystalline lens is dense and hard, and instead of being flattened is nearly round ; and the aqueous humour is almost wanting. All these changes are rendered necessary by the greater density of the medium through which Hght is con- veyed to fishes ; for water, having the same refractive power as the aqueous humour, performs the office which in terrestrial animals is performed by the latter fluid ; and the peculiar struc- ture of the lens is intended to make up in refractive power for the density of the medium in which fishes exist. LETTER XII. 403 transversely, and in the crocodile it is a vertical fissure. The optic nerve is the only part of the eye that is sensible to light, all the other parts being simply the media by which the light is conveyed to it. It enters the eye from behind, and expands in a circular direction over the back part of the organ, being situated behind all the humours, so as to receive and concentrate all the rays of light. In its expanded form the optic nerve is called the retina. In consequence of the outer coat of the eye, called sclerotic (from aySkn^og [skleros], hard, on ac- count of its firm texture), being thick, and incapable of transmitting light, the eye would be dark, were it not for the transparency of the cornea (so named from its horny consistence), which is a continua- tion of the sclerotic, and situated immediately before the pupil. The cornea, being perfectly transparent, serves the purpose of a window ; and it would, from its appearance, seem to be less highly organised than the other parts of the eye. It has, however,, a larger instead of a smaller number of vessels distributed over it, although those vessels are too minute to be visible. The shape of the cornea is of the greatest importance : if it were too convex, the rays of light would be brought to a focus before they reached the retina, and thus objects would not be perceived distinctly ; if, on the other hand, it were too flat, the rays. 404 LETTER XII. instead of meeting before they reached the retina, would not meet even at that point, and thus an equal obstruction to vision would take place. Those who have the former kind of cornea are called short-sighted, those with the latter, long- sighted. The first is a defect very common in youth, and is removed by age ; the last is common only in old age. The external surface of the cornea in fishes is almost flat, but its internal surface is more convex. In birds the cornea is required to be so convex that it is removed away from the globe of the eye by means of a short cylinder, which, becoming narrower as it advances forward, permits the cornea which is attached to it to be made more convex. Within the sclerotic membrane is placed the choroid coat ; a membrane of much thinner and more delicate texture, and of a highly organised and vascular nature. Upon this membrane, which lines almost the whole inner surface of the eye, advancing as far forward as the commencement of the iris, the delicate expansion of the optic nerve called the retina is placed ; and there is no doubt that the very liberal supply of blood-vessels to the choroid membrane is intended to convey the vital principle to the retina through the medium of the blood. The choroid coat secretes a black substance called pigmentum nigrum, which is situated be- tween that membrane and the retina ; and it has LETTER XII. 405 been supposed that it is placed there to absorb any superfluous rays of hght transmitted to the retina, which might confound the sight, and so render objects indistinct. This idea is strength- ened by what is observed in the eyes of animals designed to prowl by night, or to obtain their food in situations where few rays of hght are admitted. In these animals the pigmentum is not provided, or it is of a light colour. Albinos also are unable to bear a strong light. It was left for M. Desmoulins* to shew, that in all animals the colour of the choroid admits of great variation ; and that it is of the darkest colour in those which can see in a strong light : hence he concluded, that in animals in whose eyes the pigment is wanting, this membrane is designed to reflect the rays of light from its surface to the back part of the retina, and not to absorb them, as is the case where there is nothing but black pigment. Parts of the inner surface of the choroid are sometimes, however, altogether destitute of pigment, and pre- sent at the bottom of the eye the most brilliant yellow, green, and sapphire-blue colours, forming what is called the tapetuni lucidum. This appear- ance is particularly remarkable in the nocturnal and carnivorous tribes ; it is sometimes seen even in the ruminants. It exists also in the solipeda, pachydermata, and cetacea ; in the dog, wolf, and * See Magendie's Journal, tome iv. p. 89. 406 LETTER Xll. badger, it is of pure white bordered by blue.* The use of the tapetum cannot be misunderstood ; for when httle hght comes to the eye, less must be required to be absorbed, and more to be reflected. I will now adduce a few facts illustrative of the perfect adaptation of the eye to the situation of every variety of animal, and consequently to the different media through which they receive light ; the direct inference from which will, if I mistake not, be, that the Creator of this elaborate instru- ment of vision must have had the most profound and extensive knowledge, not only of the laws and properties of light, but also of the influence ex- erted upon it by all other bodies; that, in short, none other than an omniscient Being could have formed the eye. Flat-fish inhabit the lowest depths of the sea ; and as this situation removes all danger to them from below, there is no necessity for visual organs upon the under surface of their bodies, the invari- able position of which, moreover, would render an eye so placed almost entirely useless. Hence both eyes are situated upon the upper surface of their bodies, on which the light from above descends. The cornea, or outer coat of the eye of these animals, is also obviously formed to transmit light coming through a great depth of water. The various forms of the pupil, or opening in * Blumenbach's Manual of Comparative Anatomy. LETTER XII. 407 the iris by which light is admitted to the eye, is another provision whereby vision is facihtated, and accommodated to the habits of animals. In animals which climb, such as the felinse and simias, the pupil, particularly in a bright light, is elliptical, the greater length being in the axis of the body. Animals whose habits render it necessary that they should have a considerable extent of lateral vision, such as whales and the cloven-footed and solid- hoofed genera, have oblong and obliquely trans- verse pupils. " The form of the globe (of the eye) varies according to the medium in which the organ is to be exerted. In man and the mammalia it deviates very little from the spherical figure ; in fishes it is flattened on its anterior part ; in birds it is remarkably convex in front, the cornea being sometimes absolutely hemispherical. The con- vexity of the crystalline lens is in an inverse ratio to that of the cornea. Thus, in fishes it is nearly spherical, and projects through the iris, so as to leave little or no room for the aqueous humour. The cetacea, and those quadrupeds and birds which are much under the water, have this part of the same form. The aqueous humour being of the same density with the medium in which the animal lives, w^ould have no power of refracting rays of light which come through that medium ; its place is therefore supplied by an increased sphericity of the lens. In birds these circumstances are re- 408 LETTER XII. versed ; they generally inhabit a somewhat elevated region of the atmosphere, and the rays which pass through this thin medium are refracted by the aqueous humour, which exists in great abundance. Man and the mammalia, which live on the surface of the earth, hold a middle place between these two extremes."* The sclerotic coat is of different degrees of thickness, being much thicker at its posterior part than towards its juncture with the cornea. Its thickness in some animals is so great at the back as to be equal to one-third, or one-fourth, of the diameter of the entire eye. This circumstance very much alters the relative position of the inter- nal parts. By means of it, the length of the axis of vision is diminished, and the lens is brought nearer the back of the eye, or the focus of vision. In amphibious animals, which frequently pass from the thin medium of air to the dense medium of water, and vice versa, Blumenbach noticed a particular provision for enabling them to vary the situation of the lens at will, and so to accommodate the axis of vision according to the density of the medium or the distance of objects ; without which power they would be but imperfectly adapted for their twofold mode of existence. For this purpose, as in the Greenland seal, the cornea is thin and yielding, the anterior part of the sclerotic is thick and firm, its * Lawrence's Note to Blumenbach's Manual of Comparative Anatomy. LETTER XII. 409 middle segment thin and flexible, its posterior part thick and almost cartilaginous. The eye is sur- rounded with very strong muscles, by the action of which the requisite changes in the relative position of the internal parts are accomplished. When the animal is in the air, the axis of vision is shortened by bringing the lens nearer to the back of the globe (which is rendered yielding by the flexibility of the middle segment of the sclerotic), in order to counteract the strong refraction which the rays of light experience in passing from the thin medium of the air into the denser medium of the eye. But perhaps the most singular adaptation of the eye to the two media of air and water is seen in the anableps, an animal which inhabits the rivers of Guiana, so called from ccva^XsToj [anablepo], to look tip, because it can see above the water and in it at the same time. The orbit or socket of the eyeball extends so far above the head, that the eye, as the animal swims near the surface, is partly in and partly out of the water, and all its internal parts correspond with this curious external conformation. The iris being partially divided into an upper and a lower portion, there are consequently two distinct pupils ; the cornea consists of two globes, an upper and a lower one attached together, but divided by a dark band ; the anterior globe, which the animal uses out of the water, is in all respects like the eye of terrestrial animals, adapted to refract rays trans- mitted through the rare medium of air; the inferior 410 LETTER XII. one, which is always under the water, like the eye of aquatic animals, is adapted to refract light trans- mitted through the denser medium of water. So that the refracting power of the upper glohe is less than that of the lower. The size of the eye in some animals is very great in proportion to that of the brain. In many birds it almost equals the brain in weight ; whereas in man the latter organ is more than sixty times heavier. This fact is sufficient to shew, that the power of vision must be very variable. Many birds, living high in the regions of the air, whence they seek their prey, would be incapa- citated for their modes of existence, unless they had eyes capable of " beholding afar off." The unerring aim of the eagle and the kite is attribut- able to the lengthened power of vision which these birds possess. The eye is protected in most animals by an outer covering, called the eyelids.* The number of these varies. Many animals have two. All birds, together with the crocodile, turtle, frog, and toad, have three. The use of the third eyelid, or nicti- tating membrane, is not accurately known. Cuvier says, it is by means of this covering that the eagle is able to look at the sun. It certainly serves to defend the eye, and probably to cleanse its surface. * In the Proteus anguinus the external covering so completely conceals the eye, that it is hardly to be seen. This animal, which dwells in dark caverns, is very sensible to light. LETTER XII. 411 But I wish to call your attention more particularly to this membrane, on account of the very beautiful contrivance by which it is drawn over the eye. The nictitating membrane lies, when not in use, folded up in the inner corner of the eye, over the globe of which it is drawn by two muscles, which are expressly appropriated to that function. One of these muscles is necessarily fixed to the lower and back part of the eye, near where the optic nerve penetrates the sclerotic ; so that, when act- ing, the tendon of this muscle would press upon the nerve, and thus suspend the power of vision,* unless some means were taken to divert its course. This is effected by a muscle named, from its shape, the quadratus, which, arising from, the upper and back part of the eye, and descending in the di- rection of the optic nerve, terminates by forming a groove or cylindrical canal.f The muscle first mentioned, which moves the nictitating membrane, and is called, from its form, pyramidalis, terminates in a long tendinous chord, which passes towards the membrane through the groove of the quadratus, as through a pulley, and is thus kept completely away from the delicate nerve of vision. * Nerves cannot perform their function if pressed upon. A familiar example of this may be given in the ulnar nerve at the elbow', the least pressure of which produces the sensation called pins and needles. t See Plate II. %. 4. 412 LETTER XII. Having considered the eye, and shewn its adaptation to the habits and locahties of different animals, I shall next speak of the ear. We have seen that there is considerable diffi- culty in investigating the subtle nature of light ; but that attending the examination of sound is still greater. The httle command we possess over the various causes of sound, prevents us from acquiring a complete knowledge of the uses of the component parts of the ear ; a difficulty in- creased by the internal situation of its essential parts, which being lodged deep in the head, are totally excluded from our view in the living animal. Sound is produced in various degrees by the vibra- tion of all bodies ; those which yield it most abun- dantly are called sonorous. It may be transmitted through substances of every kind, solid, fluid, or aeriform. It is usually conveyed to the ears of ter- restrial animals through the air, but water is a better conductor; and this is probably the reason why the ears of aquatic animals are not so complicated either in the number or shape of their parts. Sound resembles light in being capable of reflec- tion, and probably of refraction also ; and conse- quently it may either be given off at different angles, or be concentrated in the same manner as light. But w^e are unable to measure the exact amount of reflection, as in the case of the latter fluid. Echoes are results of this property of sound : LETTER XII. 413 they proceed from the surfaces of bodies of parti- cular shapes, such as domes, whispering-galleries, speaking-trumpets, and the like. Following the same plan as I have pursued in regard to the eye, I shall first give you a succinct description of the anatomy of the ear as developed in the mammalia, and then point out the more striking modifications of it in various classes of animals, and their relation to different modes of life. The ear has been divided by anatomists into three parts, denominated the external, middle, and internal ear. I shall, however, treat of the two latter under the common name of the internal ear. The outward ear, which is attached to the sides of the head, is formed for conducting sounds through its cartilaginous folds into a tube that leads to the internal parts. Most of the mammalia have this external organ ; but in many of the cetacea, as well as in all fishes, it is either very small, or altogether wanting. Its use is particularly exemplified in some animals, where it is of considerable size, and furnished with muscles by which, at the will of the animal, it can be turned in any direction — a great advantage to many creatures, whose safety or sup- port depends upon the quickness with which they perceive the approach of their enemies, or of those animals which form their natural food. As it would be destructive to the organ were water permitted to come in contact with those deli- 414 LETTER XII. cate parts which have been constructed to deal with sound coming through the medium of air, there are many wise adaptations of the ear of the higher animals, in order to prevent this serious in- convenience. The first appearance of any part resembling an outward ear in aquatic animals, is seen in the crocodile. And in this case it does not resemble that of the mammalia, which is more or less open and expanded, but merely consists of two fleshy folds, like eyehds, which the animal has the power of opening or closing at will. And it is worthy of remark, that in some warm-blooded ani- mals which are much in the water — such, for example, as the aquatic shrew {sorex fodiens) — the mechanism of the outer ear is so contrived, as that neither water nor any other foreign body can penetrate to the inner ear when the animal is in the act of diving or burrowing. The muscles which open and close the ear are in this case under the complete control of the animal. In man the outer ear is seldom much deve- loped except among savage tribes, whose circum- stances so nearly resemble, in many respects, those of the lower animals, and thus render necessary somewhat similar organisation. Sommering, in his essay on the comparative anatomy of the European and the negro, tells us, that savages can move their ears at pleasure, and possess the sense of hearing in great perfection. The external ear is not indispensable to the LETTER XII. 415 sense of hearing, but merely assists it in those cases where, from natural causes, the impressions of sound would not otherwise be sufficiently power- ful. A case is mentioned by Sir E. Home,* in which the outer membrane of the ear, commonly called the membrane of the drum, and some of the bones, had been destroyed; when whispers were uttered near the ear, it was seen immediately to move, but when the tone of the voice was louder, it then remained altogether motionless. I have mentioned that an outward ear is never found in fishes ;•! and the reason is, because this apparatus is fitted only to receive sounds conveyed through air. In examining the internal ear, which is situated in a cavity of the temporal bone, we find the following order of parts. The entrance of the tympanum or drum of the ear is guarded by a delicate and highly vascular membrane, called the membrane of the tympanum ; and to this membrane is attached, by means of a very minute muscle, one of four small bones which form a link to convey the sound from the surface of that membrane into the inner chambers of the ear. These four bones, from their resemblance to a hammer, an anvil, a globe, and a stirrup, have been called the malleus, incusi OS orhiciilare, and stapes. The bottom of the * Philosophical Transactions Abridged, vol. xviii. p. 630. t There is one exception mentioned by Otto, the lepidoleprus trachyrhynchus. 416 LETTER XII. stirrup-bone, which is the last of the chain, fits into an opening forming the entrance to the cavity- called the vestibulum, so that a chain of communi- cation is formed across the tympanum, connecting its membrane with another membrane hning an oval tube which leads into the vestibulum. The bone of the malleus is united to the membrane of the tympanum by a portion of its handle, and to the second bone or incus by its head. The incus is united to the malleus by a regular joint, the surface of the bones being covered with cartilage ; and it is also attached to the side of the cavity of the tympanum by a ligament which moves back- wards and forwards : at its lower process it joins the orbicularis and the stapes. Connected with these bones are four small muscles, three of which are attached to the malleus, and one to the stapes. Of the first three, one is called the tensor, from its pulling the malleus inwards, and so tightening the membrane of the tympanum ; the other two act in an opposite direction, and relax the membrane. The muscle of the stapes brings that bone nearer to the oval opening over which it is placed, the foramen ovale. The cavity of the tympanum across which these bones are placed communicates with the air by means of a tube, called, after its dis- coverer Eustachius, the eustachian tube, which opens into the back of the mouth, so that there is always air behind the membrane of the tym- panum. LETTER XII. 417 The other parts of the internal ear are the semicircular canals, leading from the vestibule, and the cochlea, so named from its resemblance to the shell of a snail, which has an opening called the fenestra rotunda, covered with a membrane like that of the tympanum, but much smaller, which retains the fluid within the cochlea. The nerve that conveys the sensation of sound to the brain is expanded over the surface of these canals. The four bones have the power of tightening or relax- ing the membrane of the tympanum, and so modu- lating the impressions of sound. It is to the delicate adjustment of the muscles by which these bones are moved that we are indebted for the nicety with w^hich we can distinguish minute differences in those sounds which, from their distinctness, are called articulate. Inarticulate sounds have fewer and less minute variations, and consequently the lower animals do not possess so perfect an appa- ratus for hearing as man. The application of mus- cular power to such infinite varieties of movement as we here see, is one of the most wonderful efi^ects that can be produced by organised structure. In animals that receive sound through the medium of water there is no eustachian tube, because air is not required to come in contact with the tympanum ; the contrivance, therefore, which we notice in the whale is very remarkable. In this animal, though an inhabitant of the water, the internal ear is formed to treat with sound E E 418 LETTER XII. conveyed through the medium of air. For this purpose it has an eustachian tube ; yet if this tube were situated at, and made to communicate with, the back of the mouth (as it usually is in land animals), it is easy to see that its use must be sus- pended, for it would transmit water to the ear, and not air. Instead, therefore, of terminating at the back of the mouth, the eustachian tube in this animal goes out of its usual course, and communi- cates with the air through the blowing-hole, the only part above water. The way in which the water is excluded from this tube is another ad- mirable provision. The tube is furnished with a valve which covers its entrance, and so prevents the admission of water when the animal is in the act of spouting. To compensate for the absence of the eustachian tube, the swim-bladder in many genera of fishes is, as Weber* has shewn, connected with the internal ear in such a manner as to serve the purpose of the membrane of the tympanum in the mammalia. This union is accomplished in some by means of three small bones, while in others these bones are wanting. There is great diversity of contrivance in the construction of the ear, to give illustrations of which would occupy too much space. Where articulate sounds are required to be recognised, the organisation is the most elaborate. For example, * De Aure et Auditu. LETTER XII. 419 the four bones in man and the higher animals are united to one another in such a manner as that the state of the tympanum may be susceptible of the most minute variations, from relaxation to tension, by means of the muscles before named. In the ear of birds these four bones are united into one ; and it is by this means that they are rendered capable of attaining to a minuteness in the scale of notes of which the ear of man is not capable. In birds, the single bone projecting against the membrane of the tympanum keeps it always in a state of tension and convexity. On this account, the scale in birds cannot descend so low as in the human ear ; but the intervals in the scale are more minute, in con- sequence of the slightest tremor communicated by the action of the muscles at one end of the slender bone being conducted to the internal parts of the ear without any interruption, which is not the case in man, where the impulse has to pass from one bone to another. But it is not necessary for me to enter more fully into the various changes by which this organ is adapted to the circumstances of different animals. It is worthy of notice, however, in proof of the compensative power which we sometimes see, that when the membrane of the tympanum has been destroyed, the membrane which covers the opening of the labyrinth, provided it is unin- jured, is known to accommodate itself to the reception of sounds, and to carry on the function 420 LETTER XII. of the former with great correctness, though with an inferior degree of power. The sense of touch is of much value to many animals by assisting the other senses. Individually its province is to detect the temperature or the con- sistence of bodies. In man the principal seat of touch is in the hands ; and the skin which covers those organs has many peculiarities fitting them to perform their office ; which we see also, to a certain extent, bestowed on the extremities of the quadru- mana. I have before shewn that this sense resides in the organ which is most useful as an instrument of prehension, and thus all animals are provided with the sense of touch in the most convenient part. In consequence of the scaly covering of their feet, and the feathered surface of their whole bodies, it would seem difficult to bestow this sense upon birds, yet they possess it in a high degree. In them it resides in the mouth, the bill, or the tongue. For this purpose the bill of many birds is copiously supplied with nerves. Many fishes have the upper lip devoted to this sense. In the elephant it is seated in the small process at the end of the trunk. In the rhinoceros the soft upper hp is used as the organ of touch. Blumen- bach describes in the seal* a long orbital nerve proceeding from below the socket of the eye to be * Comparative Anatomy, p. 260. Carus says, the seal has lonff and stifF mustache?, to which these nerves point. LETTER Xir. 421 distributed to the projecting lips. This nerve is composed of forty branches or more ; and in animals that have large whiskers the roots are abundantly supplied with nerves, the object of which can only be to confer a more acute power of feeling upon those appendages. It is said that these thick bristles extend in a lateral direction beyond the greatest width of the animal's body, so that those animals which prowl by night, as the felinae, are able, by inserting the head into any opening, to ascertain with great exactness whether they can pass through it ; for if the whiskers do not come in contact with the sides of the aperture, it is large enough to admit their bodies. In water-birds, particularly the orni- thorhynchus (duck-billed animal), this sense resides in the integuments which cover the expanded pro- boscis of the jaws, particularly the upper. These parts are accordingly very liberally supplied with nerves. The skill and wisdom thus displayed in the organ of touch of different animals must strike every mind. Animals would be exposed to serious inconvenience, perhaps fatal accidents, without such peculiarities of organisation. The bat, being a nocturnal animal, seeks its food at a period when neither sight, hearing, nor smell, are of much ser- vice' to it ; the benevolence of that arrangement which gives to this animal so high and extensive a sense of feehng or of touch as that it is able to detect, by the vibrations and impulse of the air 422 LETTER XII. against its wings, the situation or near approach of bodies with which it is hkely to come in contact, is therefore obvious. In many birds of the duck kind this sense must be very highly developed to enable them to detect with so much ease and certainty the food for which they have to grope in the mud and water. Many fishes have large branches of the fifth pair of nerves distributed to the lips and fins,* which it is likely possess the sense of touch, and thus be- come the means of obtaining food.f It is highly probable, that it was by this sense, aided by that of sight, that fishes were brought so much under the control and guidance of man in the time of the Romans, as mentioned by Pliny, Petronius, Martial, and others. In the pond at Balise, be- longing to the emperor Domitian, each fish came as its name was called. The same fact is men- tioned by Plutarch of Marcus Crassus' lamprey. M. Arderon considered it quite as probable that fish in ponds, either by their sight or feeling, discovered the approach of their benefactors, whose coming they were accustomed to expect, as that they were sensible of their voices calling them. He had often struck with his thumb-nail against the edge of a * The appendices called cirri, such as may be seen in the cod and the shark, and those filaments called fingers in the mullet, detached from the pectoral fin, seem to possess the sense of touch. t Monro on the Nerves, p. 1G2. See there Plate XXXIII., shewing the nerves distributed to the fin of a haddock. LETTER XII. 423 glass jar in which he kept two ruffs, a stroke not harder than the beat of the pulse, which would cause them in a moment to dart from the bottom of the jar to the top, though he was sure they did not see him. But if he made the same motion without hitting the glass, or if he made a hundred times louder noises than the striking of his nail against the glass at a very small distance from it, he could not perceive they were in the least affected by it; a fact which might be thought to amount to a proof that this kind of fish at least is destitute of the sense of hearing ; and that their delicate sense of feeling supplies them with a know- ledfije of the motion of bodies when their other senses fail.* The senses of taste and smell have received the title of subjective, on account of the proximity of their relation. Taste and smell are so essential to the existence of animals, that few are without one of them at least, and many possess, both. Smell is the more common, because there are many animals that, having been by means of it enabled to select their food, do not afterwards require to taste it. Such is the case with those animals which live chiefly upon one or a few substances. It is now very satisfactorily ascertained, that the existence of a tongue does not absolutely prove the possession of the sense of taste. It is em- * Philosophical Transactions Abridged, vol. ix. p. 466. 424 LETTER XII. ployed in ant-eaters, chameleons, and some kinds of birds, as the woodpecker, for the mere mecha- nical prehension and deglutition of their food,* and as an organ of touch. Serpents feel with their tongue. The organ of smell consists of a number of surfaces or duplicatures of very thin plates of bone, contained in a cavity at the root of the nose. These thin plates project into proper cavi- ties, and are covered by a delicate membrane. The filaments of the nerve of smell penetrate this bone so thoroughly, that it resembles the most delicate network. " The variations in the form of the olfactory bones deserve notice, as connected with the degree and mode of development of the sense of smelling. In herbivorous mammalia their form is turbinated (pointed), in the proper sense of the word. In the hog, though large, they are in structure very similar to those of man. In the horse they are of considerable diameter and great length, reaching nearly from one extremity of the nostrils to the other. Externally they are convoluted in a spiral form, and are pierced by numerous perforations, * In some of the lower animals, instead of a tongue we find tentacula, or organs of touch, placed about the mouth for the pur- pose of examining food passing into the alimentary canal. In the Crustacea and insects, in addition to feelers about the mouth, large antennae are furnished, which are admirably adapted to examine those substances with which the animal comes in contact. LETTER XII. 425 which allow the passage of the membrane, with numerous fine branches of the nerves, from side to side ; the surface for the olfactory membrane is still further increased by several transverse septa contained within the spiral shell. In the sheep, goat, and deer, the lower is larger than the upper olfactory bone, and is furnished with two convolu- tions— one superior, the other inferior. The per- forations are very numerous, and continued through the whole of the convoluted portions, as well as through the septa with which they are furnished, like the bones of the horse. In the deer the number of perforations is so great, and they are so minute, as to resemble the finest lacework. The olfactory membrane is expanded over the whole of this osseous network, and from its internal lamince (plates), every bony fibril is supplied with a distinct nervous covering. The ethmoidal cells (cells con- tained in the ethmoid bone, in which the organ of smell is situated) are ramified in the hog and horse ; whilst in the sheep, goat, and deer, they are convoluted and perforated like the other olfac- tory bones. In the carnivora the olfactory bones are distinguished by their ramified, laminated struc- ture, which is pecuharly developed in the seal. The principal stem of the bone attached to the ascending ramus of the superior maxillary (upper jaw-bone) divides into about eight horizontal la- minae, which are again subdivided in the same direction so minutely, that upwards of a hundred 426 LETTER XII. laminas have been traced to one of the eight stems. These ramifications occupy the cavity of the nares (nose) almost completely, without, however, com- ing into contact with its parietes (sides). The olfactory membrane, with its accompanying nerves, is closely apphed to every one of these laminae, as well as to the main trunk and to the surface of the cavity of the nares. The extent of these surfaces has been estimated at upwards of 120 square inches in each nostril, namely, eight laminae, each subdi\ided into 100 minor laminae with two sur- faces, an inch in length by one-twentieth of an inch broad, which, with the addition of one-half for the rest of the bone and the surface of the cavity of the nares, gives the extent above stated. In the cat, fox, and dog, particularly the latter two, the bones are less extensive than in the seal, and tend to approach to the convoluted form of those of the herbivora." * In many animals, as the elephant, the mole, the dog, and most of the ruminants, the organ of smell is very complicated.f * Harwood's System of Comparative Anatomy, p. 18 et seq. t The aquatic mammalia, when diving, have the power of perfectly closing the slit -like opening of the nose, and so of excluding the water. Some aquatic animals, which have lungs, breathe chiefly through the mouth. Harwood says, " the pos- terior apertures of the nose, where they communicate with the mouth, are each beset with a fringe of long papillce (fleshy pro- jections) stretching quite across it ; which, as the animal respires principally through the mouth, may serve to obstruct the passage LETTER XII. 427 There can be no doubt that the sense of smell is of the highest importance to many animals, by aiding their instincts ; and that it often causes them to act in a manner which might be mistaken for a consequence of reason. Some birds, as the vulture, possess it in so high a degree, as to be able to detect their food though many miles' distant from it. That it is by the faculty of scent, and not of vision, as Audubon and many physiologists affirm, is, I think, proved by many undeniable facts, and especially by the observations of Water- ton,* whose statement is worthy of attention. It of foreign bodies in that way to the nose, the small size of the external orifices being sufficient to defend it from without." — System of Comp. Anat., p. 33. True fishes are supposed to have but httle susceptibility to aeriform odours. The faculty by which these animals are capable of perceiving very minute variations in the state of water, and that by which rapacious fishes recognise a carcass at a distance, appears to be attributable to some peculiar modification of smell and taste. t * "When I had done with the carcass of the large snake, it was conveyed into the forest, as I expected it would attract the king of the vultures as soon as time should have rendered it suffi- ciently savoury. In a few days it sent forth that odour which a carcass should send forth, and about twenty of the common vul- tures came and perched on the neighbouring trees ; the king of the vultures came too ; and I observed that none of the common ones seemed inclined to begin breakfast till his majesty had finished. When he had consumed as much snake as nature f See Carus' Comparative Anatomy, by Gore, vol. i. p. 283 ; Scarpa de Auditu et Olfactu; and Mailer's Elementa Physiologiae. 428 LETTER XII. is well known in Demerara^ that when a person dies, before any exposure for burial takes place, and generally within a very few hours after death, the vultures collect upon the roof of the house, to the painful annoyance of the friends of the de- ceased. It would be absurd to suppose that their eyes could be of any use to them in this case, and very difficult to explain by what other means but by the sense of smell they could ascertain the fact of a dead body being in the house on which they assemble. The fact that the organ of scent in the vulture is very largely developed, is a pre- sumptive proof of the high degree in which it possesses the sense of smell.* The minuteness of the particles of scent which animals are able to detect is most surprising. " Above all things, the scent has been ever my admiration. The bulk, size, figure, and accidents or qualities of these parts or portions of matter that discharge themselves from the bodies of these beasts of game, are subjects much fitter for the experiments and learned descants of a philosopher informed him would do him good, he retired to the top of a high mora-tree, and then all the common vultures fell to and made a hearty meal." — Wanderings in South America. * " When," says Waterton, " the American pliilosophers shall have proved to me that effluvium from putrid substances does not ascend in the air, and that the organisation of the vulture's nose is imperfect, then I will consider myself vanquished — efficaci do manus scientice." — See Loudon's Mag. of Nat. Hist., vol. vii. p. 278. LETTER XII. 429 than a simple huntsman. That these particles are inconceivably small is, I think, manifest from their vast numbers. I have taken hundreds of hares after a chase of two, three, four, or five hours, and could never perceive the least difference in bulk or weight from those I have seized or snapped in their forms ; nor could I ever learn from gentle- men who have hunted basket hares that they could discover any visible waste in their bodies, any fur- ther than may be supposed to be the effect of natural causes. But, supposing an abatement of two or three grains, or even drachms, after so long a fatigue, yet how minute and almost infinite must be the division of so small a quantity of matter, when it affords a share to so many couple of dogs for eight, ten, or twelve miles successively ; de- ducting, at the same time, the much greater number of those particles that are lost in the ground, dissipated in the air, extinguished and ob- scured by the fetid perspirations of the dogs and other animals, or by the airy fumes and exha- lations of the earth itself. It is also to be remem- bered, that there is no small accidental difference in the very particles of scent ; I mean that they are stronger, sweeter, or more distinguishable at one time than at another ; and that this difference is found not only in divers, but often in the same individual creature, according to the changes of the air or the soil, as well as of her own motions or conditions. That there is a different scent in 430 LETTER XII. other animals of the same species, is evident from draught-hounds, which were formerly made use of for tracing and pursuing thieves and deer-stealers ; or rather from any common cur or spaniel, which will hunt out their master, or their master's horse, distinctly ft'om all others."* It will be seen from what I have said of the acuteness of smell in many brutes, that man has this sense much less developed than they. It, however, is possessed in widely different degrees of power by the varieties of the human race. In the negro the nasal cavities are larger and the sense of smell more acute than in the European. In the native American and Ethiopian the scent is sufficiently correct to distinguish a negro from an European. The wise adaptation of this sense to the many purposes accomplished by it in animals, furnishes another instance of the Divine wisdom, which, as we have seen, is so conspicuously displayed in every part of the animal creation. To many animals it is of the greatest utihty, and its absence, there being no reason to direct them, would lead to their destruction. I have thus laid before you a brief, and there- fore imperfect, account of the organs of sense. It has been my object merely to shew that the evi- dences of design which are so clear in other parts of the animal organisation, are pre-eminently mani- * Essays on Hunting, Sagacity, &c. 1733. LETTER XII. 431 fest in this ; and that there is uniformity and consistency in the whole. This, I trust, I have accomphshed, notwithstanding the shortness of my exposition ; for the purpose above mentioned does not require that I should descend to minutiae, or point out every particular instance of wisdom and benevolence, — it is sufficiently answered by making a selection from the innumerable facts which prove the existence of these attributes in the works of creation ; for, from a few examples, a conclusion as to the whole may be logically derived. LETTER XIII. " Shall the work say of him that made it, He made me not? or shall the thing framed say of him that framed it, He hath no understanding?" — Isaiah, xxix. 16. In this Letter I intend to give an account of the more remarkable facts relating to the skeleton. If any one part of the structure of animals bears a more manifest impress of Divine wisdom than another, it is the ossific fabric. This is so inti- mately connected with all other parts of the frame, and exercises so important an influence over them, that its construction affords many striking proofs of the perfect knowledge possessed by the Creator of all that exists, and of the uniformity and harmony which pervade his works. Notwithstanding the innumerable diversities of structure with which the skeleton is connected, and consequently the equally innumerable forms which it assumes, it has been satisfactorily shewn that it is in every instance composed of the same essential parts, and that the corresponding parts in its most dissimilar forms perform similar or analogous func- tions. The two primary objects attended to in the formation of the osseous framework are, protection to those parts which are so delicate as to be peculiarly liable to injury, such as the central parts LETTER XIII. 433 of the nervous system, and the other vital organs of the body ; and support to the fleshy parts, which by this means become organs of locomotion. The form and composition of the skeleton, therefore, are regulated by the development of these parts. I have in a previous chapter had occasion to explain why the lower animals are defended by an external, instead of an internal skeleton, and how beautifully appropriate this mode of defence is to those creatures which are destined to be exposed, in the impetuous ocean, to accidents which, but for this fortification, would crush and destroy them. The nervous system of these animals is of the simplest kind compatible with life, and the means provided for its defence are consequently far from elaborate. But in animals whose nervous system is more highly developed, such as the mammalia, birds, and other red-blooded animals, there is an express contrivance for its protection. Sir E. Home says, " The bony skeleton appears only to be given to animals that possess a regularly formed brain, and therefore one of its essential uses is to defend that organ from injury, a purpose for which shell appears unfit ; since in all those that I have examined there is no provision in the mode of its growth for the enlargement of the original cavity. This leads me to infer that the formation of bone, as it is a more complex operation than that of shell, may exceed the limited powers of these in- ferior animals to perform. As the discoveries F F 434 LETTER XIII. made in animal chemistry render it probable that the secretions depend upon the nerves, so the modelling process, by which a bone retains its shape during the increase of its size, may require some action of the nerves which can only be effected when that system is connected with a brain whose structure and dimensions are enlarged to a certain degree."* I will first give an account of the materials which have been selected by the Divine Architect for the construction of the ossific fabric : the reader will thus be enabled more fully to comprehend the consummate wisdom manifested in this part of the animal frame. Bone, being designed to support and defend the softer and more delicate parts of the body, is ne- cessarily solid ; it must also possess the property of yielding, in order that the injuries arising from severe concussion, to which very hard bodies are exposed when struck, may not be inflicted upon the frame. To combine in one substance the apparently incompatible qualities of yielding and resisting, appears at first sight impossible, and would certainly exceed man's powers. Yet this is effected in bone, and furnishes another proof of God's infinite wisdom and resources, which will endure till the whole creation of living beings has passed away. The composition of bone has distinct reference * Lectures on Comparative Anatomy, p. 70. LETTER XIII. 435 to the uses which it subserves. Hence it is ahnost infinitely diversified. Not only is the composition of the bones of one animal different from that of the bones of other animals, but the bones of any one animal vary widely from one another ; nay, even the parts of the same bone are not all alike — no one bone is perfectly homogeneous. In man, for example, the bones of the ear, the enamel of the teeth, and the inner table of the skull,* are all composed of the same materials, but in different proportions, adapting them for the various purposes to which they are devoted. Bone is composed chiefly of animal or organic matter, which closely resembles cellular tissue, and of phosphate of lime, an inorganic substance. There is also a small proportion of other mineral ingre- dients, such as carbonate and fluate of lime, phos- phate of soda, and magnesia. On the proportion between the animal and the earthy ingredients de- pends the degree of hardness which bones possess. The bones we have just instanced all contain an excess of mineral matter, which gives them their hard and resisting character. The bones of fish, on the other hand, are for the most part composed * That bone in the side of the skull which is fitted up for the purpose of producing vibrations of sound through the auditory- nerves, is, from tlie hardness of its texture, called in anatomical language the. stony bone (oslapidosum). This bone is exceeded in hardness by nothing in the animal composition, except the enamel of the teeth. In the black and white whales these bones are as hard and dense as the most compact marble. 436 LETTER XIII. almost entirely of animal matter, and are accord- ingly soft and pliable. The shells of the Crustacea and mollusca, in which there is a very great excess of earthy or mineral matter, are the hardest forms of bone. Herissant was the first to shew that bone is composed of an animal and an earthy substance. More modern chemists, as Gahn, Hatchett, Four- croy, Vauquelin, and Berzelius, have ascertained the nature and relative proportions of these in- gredients with greater exactness. Gahn shewed that the earth is chiefly phosphate of lime ; and we are indebted to Mr. Hatchett for a knowledge of the nature of the animal matter of bones.* Observations and experiments have proved that phosphate of lime is one of the most imperishable substances : it is insoluble in water, that great solvent of so many substances ; it bears without decomposition a very high degree of heat, as well as the action of those agents which often effect quicker and greater changes in inorganic sub- stances than either water or heat. To the durable * See Bostock's Physiology, vol. i. p. 109, and Phil. Trans, abridged, vol. xviii. p. 554. Mr. Hatchett found the porce- laneous shell to contain more carbonate of lime, and less animal matter, than any other ; and that the mother of pearl shell con- tained a less quantity of carbonate of lime, and was combined with more fibrous and gelatinous (animal) matter. There can be little doubt, that the materials which compose bones are combined in proportions almost as numerous as the species of animals which possess a skeleton. LETTER Xlll. 437 nature of phosphate of hme we owe all the know- ledge we possess of those animals which formed part of the creation recorded by Moses, but which are now extinct — knowledge which, shewing the essential identity between their forms and those of existing animals, proves that they were all moulded by the same Almighty hand. Having shortly adverted to the composition of bone, I will now proceed to shew how wisely those materials are blended, and formed into structures subservient to all the purposes of the animal eco- nomy. And first, I shall draw your attention to the covering of bone which protects the brain. That, in the higher and more perfect animals, the brain is the most important organ in the body, is universally admitted ; it cannot, therefore, be a matter of surprise that a vast accumulation of ingenious contrivance is exhibited in providing for its defence. When we fully comprehend the numerous physical forces which the brain has to resist — the variety in the nature of those forces, some operating from within, others from without, and consider, withal, the peculiar consistence of that substance which forms its perfect protection, a substance characterised by qualities seemingly the most opposite and incompatible — we are irre- sistibly led to the conviction, as we survey it, that some superior being must have formed this master- piece of defence. " An architectural dome is con- structed to resist one kind of force only, always 438 LETTER XIII. acting in one direction, viz. gravity, and therefore its strength increases regularly towards the bottom, vs^here the weight and horizontal thrust of the whole are to be resisted ; but in the skull the tenacity of the substance is many times more than sufficient to resist gravity, and therefore aids the form to resist forces of other kinds, operating in all directions. When we reflect on the strength displayed by the arched film of an egg-shell, we need not wonder at the severity of blows which the cranium can with- stand."* The bones of the skull are united by joinings called sutures, formed according to the nature of the bones they unite, or the object required to be accomplished by their union. The arch of the skull could form no other abutment than that which takes place at the temporal suture, which is situated above the ear, passing across the skull in a circular direction corresponding with the arch of the external ear. The circumstance that the edge of one bone is placed over that of the other, in the same manner as the scales of fish, greatly strengthens the abutment, which is formed by two bones, one of which passes completely across the base of the skull, acting as a sort of tie-beam. The arch of the skull is locked in at this suture ; and a provision is thereby made against any yielding in the abutment. But, it may be asked, why all this elaborate contrivance ? could not some less com- * Arnott's Elements of Physics, vol. i, p. 202. LETTER XIII. 439 plicated means have been devised to protect the brain ? To this I answer, that in arches constructed by man, it is necessary that all the strength should be seated in the abutment : now, in the arch of the skull the abutment would seem to be almost unavoidably the weakest part ; and that it is not so, is owing to the peculiar contrivance I have pointed out. Proud man boasts of the invention of counter-arches, spurs, collar-beams, and tie-beams, which, in truth, are striking proofs of the limited nature of his powers — clumsy inventions, alto- gether wanting in the roof of his own skull, the first and the finest arch that ever was made. No arch of the same dimensions has ever been devised capable of bearing so much weight as the skull. It is not perhaps generally known, that the structure of the brain of all animals is such that that organ is rendered unable to perform its func- tions by any injury which presses on its substance, or causes vibration or percussion in it. To obviate this evil, to which it is more or less exposed upon every movement of the body, the whole of the spinal machinery, and every joint in the body, are constructed so as to aid in breaking the effect of external force. As the brain is more susceptible of injury from severe concussion than from any other species of violence, it was essentially necessary that the substance selected for its protection should pos- sess the property of deadening vibrations — should not conduct, but ward them off from the brain, the 440 LETTER XIII. centre of life ; yet it was equally necessary that the covering of the brain should be hard, and ca- pable of resisting considerable force. Now, as the harder a substance is, the more readily it receives and communicates vibration, it might seem that two conditions perfectly irreconcilable were here required, and that consequently the contrivance, in one respect or the other, would be imperfect. Such, however, is not the case. The two condi- tions are united, and the protection of the brain is complete. The bones of the skull are formed of two tables or plates, of different characters and structure, se- parated by the intervention of a light cellular net- work, having, when magnified, the appearance of an innumerable number of pillars, the crown and base of which rest upon the two tables. This sub- stance is called diploe. The purpose which it answers cannot be mistaken. The outer table of the skull is thicker, more spongy, and therefore more yielding and less easily broken, than the inner table, which is a compact, hard, and comparatively brittle substance. Hence, a blow upon the skull causes a yielding of the outer table, and conse- quently of the diploe, which, being compressible, prevents the blow taking effect upon the inner table, which, but for this admirable arrangement, would necessarily be pressed upon the brain, and thus suspend its functions. Even if the blow be so severe as to affect the inner table, its hard tex- LETTER XIII. 441 ture does not in general yield, but cracks, and thus injures the brain but slightly. In most birds, particularly those which live much on the wing, the diploe is exceedingly deli- cate and hght, and air is admitted between the two tables of the skull through the nose or mouth, which, being probably in some way rarefied, serves to lessen the weight of the cranial bones. Other animals have this structure much enlarged. Such is remarkably the case with the elephant, in the skull of which there are extensive cells, that serve to increase the surface for the attachment of muscles necessary to support so large a head.* By this con- trivance lightness is combined with strength. Being filled with air, these cells serve also, by communi- cating with the internal ear, to give to that sense so high a degree of perfection as to enlarge the instinctive power of the animal. All animals, with the exception of the elephant and duck-billed animal (ormthorhynchus jyaradoxus), have their skulls divided by sutures, or lines of junction ; a circumstance which enables the brain * It is a curious fact, that the reticular osseous texture in the skull of the elephant, where it is about four inches and a half thick, is not perfectly developed until the appearance of the tusks, when, by adding to the extent of surface of the skull, it affords a greater- space for the attachment of the muscles of the neck, the strength of which necessarily requires some addition in order to correspond with the increased weight of the head, res\ilting from the presence of the tusks. — Home's Lecture on Comparative Ana- tomy, p. 76. 442 LETTER XIII. to grow during the early period of life, before it is entirely covered by bone. These sutures do not become wholly obliterated even in old age. The skull of almost all animals is thus divided into the same number of bones. The sutures always take a course furthest removed from the outworks, or most exposed parts ; and as they traverse in all directions, some foresight was surely necessary to determine their course. But I would particu- larly direct your notice to the appearance of these joinings upon the outer and the inner table. " If we see that the outer table is tough like wood, and the inner table brittle hke glass, for sufficient reason we may see also how the joinings of the bone are different. The outer edge of each true suture is dove-tailed, or joined by teeth, while the inner edge of the same suture is merely laid in contact. If you have a fine piece of foreign wood, and desire to have it formed into a box, you give it to the cabinet-maker, and he joins it curiously, by minute carvings of corresponding edges. But if you had slabs of marble or alabaster, you would not give it to the cabinet-maker, but to the marble- cutter, to join it, and form a trough or sarco- phagus; and you would expect him to lay its smooth edges together, and join it with cement ; for if he cut it into dove-tailing, it would chip off, and fail to give security. ■ Would you, then, have a negligence exhibited in the structure of an animal body of that which is so evident to a villain work- LETTER XIII. 443 man ? The outer table of the skull has its suture ; but the mner table is laid in simple contact, by joining called harmonia."^ In the lower animals, before we arrive at those possessing any organ resembling a brain, we find nervous centres or ganglions situated in those parts where protection is most insured. In such animals the nervous system consists of these central bodies, which are composed of several distinct portions extending down the back, each giving off nerves. As the form of the skeleton is determined by the shape which the nervous system assumes, so the first rudiments of a skeleton consist of a series of osseous rings, which, being united together, form a closed canal for the protection of these nervous ganglia. As we advance towards the more perfect animals, the spinal chord is enlarged, and the pro- vision made for its protection is more complex and complete. The chain of bones called the spinal column, in which the central nervous masses are contained, is one of the most beautiful contrivances in the animal kingdom, and is perfectly adapted to all the numerous circumstances to which a highly developed nervous system gives rise. In all animals that have limbs, the spinal column is the only medium of connexion between the upper and lower extremities, and therefore the prime agent in locomotion. In man it supports all the upper part * Bell's Anatomy, vol. i. p. 111. 444 LETTER XIII. of the body, and in the quadrumana it contributes very greatly to its support ; but in animals that are without limbs, it admits of the most extraor- dinary latitude of motion, which, when aided by other parts, endows them with a power of loco- motion little inferior to that of animals possessed of proper hmbs. In this part of the skeleton, strength to support the weight of the body and to resist external pressure, is indispensable ; and great freedom of motion among the bones which com- pose it is equally so. The perfect mechanism of the spine, enabhng it to accomphsh all these widely dissimilar purposes, must strike every ob- server, and impress the reflecting mind with a deep sense of the wisdom and goodness of the Creator. It is on account of their great flexibility and power to turn readily in all directions, that this chain of bones has received the name of vertebras ; and scarcely can any thing be more surprising than the free motion which they enjoy, when contrasted not only with the power of resistance necessary to enable it to support the weight of the body, but with that rigid and inflexible state which they can assume when sustaining a body of several hundred pounds' weight. The difference in the flexibihty of the spine is brought about not merely by muscular power, but also by varying the number of bones which com- pose it, ranging from twenty-four, as in man, to LETTER XIII. 445 three hundred, as in some species of snakes.* In fishes, all the vertebrae have a funnel-shaped cavity on each articulating surface, and the space formed by the juxta-position of two such cavities contains a considerable quantity of albuminous fluid, which gives great elasticity to the motions of the spine, though only in a lateral direction.f In a cavity of this kind in a shark. Home found three pints of fluid, which, when the joint was cut into, sprang up four feet high.;|; It is hardly pos- sible to conceive how great a degree of elastic power such a distended cavity may impart. Ser- pents have more than three hundred vertebrae, to which the facility of their motion is mainly attribut- able. In birds, whose back, on account of the pe- culiar formation of their lungs, as I have elsewhere shewn, is required to be without motion, this is wisely compensated for by increasing the number of verte- brae in the neck. It is remarkable that, in almost all the mammaha, the number of the bones of the neck is seven. § The giraffe, which rears its head to feed * In the carp there are forty-one, in the burbot fifty-seven, in the dolphin and porpoise sixty- six, in the eel one hundred and fifteen, in the shark two hundred and seven. In the ichthyosauri and plesiosauri, two extinct animals, the total number of vertebrcE is between eighty and ninety, of which, in the latter animal, those of the neck alone amount to thirty-five ; hence the specific term, dolichodeiros (long-necked). t See Carus, Comp. Anat. (translation), vol. i. p. 116. + Phil. Trans. 1809, p. 177. § The ant-eater is an exception ; Cuvier having discovered in 446 LETTER XIII. upon the lofty branches of the forest-tree, and the Httle mole, which appears to possess no neck at all, have both an equal number of these bones, because the object to be obtained in the former is merely an extension of the neck. But birds, having no flexibility in the back, the vertebrae being here firmly united,* are provided with a greater number of bones in the neck, the flexibility of which com- pensates for the want of motion in the other parts of the spinal column ; and besides, the length of neck which is thus obtained is beautifully in agree- ment with the instinct of the animals, and perfectly fitted to enable them to procure their food in the water, or other places not easily to be approached ; for it will be remembered that birds have no pre- hensile power in the superior extremities, which are converted into wings; the great latitude of motion which is given to the neck suppUes this want, and enables them to reach every part of their bodies with their bills. But the manner in which these bones are joined together in birds must not be passed over. The bones of the neck, instead of being united by plane, horizontal, or this animal nine. The number of vertebrae in the necks of birds is not so uniform as in the mammalia. In the swallow there are eleven ; in the vulture, dove, and raven, there are twelve ; in the cock, thirteen ; in the ostrich and heron, eighteen ; in the stork, nineteen ; and in the swan, twenty-three. * The ostrich and the cassowary, not being birds of the wing, form the only two exceptions to this rule: their backs are movable. LETTER XIII. 447 oblique surfaces, as in the mammalia, are articu- lated in such a way as to admit of a greater extent of motion, and yet without increasing the risk of dislocation. The several bones fit into each other as an acorn fits into its cup, so that a motion almost rotatory is obtained ;* and this is rendered complete, by the head, instead of being united to the neck, as in mammals, by two surfaces, having only one, so that it turns round as upon a pivot. In the mammalia the number of vertebrae is regulated by the number of the ribs. " The true dorsal vertebrse (those which support ribs) are twelve in mice, rabbits, hares, bats, and several apes, as well as in man. The carnivora have usually thirteen ; as have also the rodentia, ru- minantia, and palmata. In the horse there are eighteen ; in the tapir and elephant, twenty ; in the unau {hradypus didactylus) twenty-three ; in the megatherium, sixteen. The lumbar vertebrae vary in number from two (in the two-toed ant- eater) to nine (in the lori). The number is very generally seven, remarkable from its analogy with the number of cervical vertebrae (those of the neck). This is the case in many apes, carnivora, rodentia^ &c. In some apes, opossums, the vampyre, &c. there is but a single sacral vertebra ; in other instances, as the mole, the number is increased to seven. It is more generally three, by which we are involuntarily reminded of the three cra- * See Plate V. fiff. 2. 448 LETTER XIII. nial vertebrae of the head. The caudal vertebrae, which, in fishes, and many amphibia, compose the sole or most important organ of motion, are also usually found in considerable number in mam- malia. In several apes there are from twenty to thirty ; in the two-toed ant-eater there are forty."* The organs for aerating the blood have, on account of the extreme delicacy of their structure, a particular bony contrivance to insure their de- fence. Animals which have true lungs are provided with a number of ribs, which, joined to the dorsal vertebrae behind, stretch forwards in the form of an arch, and encompass those organs so essential to the purification and circulation of the blood, the uninterrupted carrying on of which processes could not be insured unless the lungs were effectually pro- tected from external injury and pressure. In fi^ont, these ribs are firmly united by means of strong cartilage to the chest -bone, or sternum. The lungs in different animals occupy more or less room. In warm-blooded animals they seldom occupy more than half the length of the cavity of the body, which part is accordingly covered by the ribs.f In the amphibia and many reptiles, the * Carus, Comp. Anat. (translation), vol. i. p. 188. \ Wolves and cats have 1 3 pairs of ribs ; most of the quad- rumana 14 pairs, but some 13 ; the guinea-pig, armadillo, and porpoise, 13; the manati and phocae 15, and in some 16; the ornithorhynchus and rytina, 17 ; the horse, 11 ; the rhinoceros, 19; the elephant, 20; the unau (two-toed sloth) 23. The ribs are in many animals remarkably broad; in the two-toed ant- LETTER XIII. 449 lungs assume more the character of air-bags, and extend nearly through the entire length of the body. In these cases they are sometimes pro- tected by great numbers of ribs, amounting in some to as many as 250 pairs ;* in others, different means are employed for the same purpose. Thus, in the crocodile the sternum is prolonged over the whole length of the abdomen, and this animal has not more ribs than man. In reptiles, however, the chest-bone is generally either a mere rudiment, or at most but very few of the ribs are attached to it. The chelonia have the whole dorsal spine and ribs consolidated into one case, called the carapace, which consists of about fifty pieces of bone united by suture, and the under part of the body is covered by a corresponding plate of bone, called the plastron. It is remarkable that frogs and toads have no ribs ; and the way in which this apparent deficiency is made up to them is worthy of your attention. The dorsal vertebrae are furnished with broad trans- verse processes. The scapula or blade-bone, the clavicula or collar-bone, and the furcula or fork- eater {myrmecophaga didactyla), which has sixteen pairs, they are so broad, that Blumenbach says they resemble a coat of mail. * In the coluber natrix there are 204 pairs of ribs ; in the rat- tlesnake, 1 75 ; in the blind worm, 32 ; in the chameleon and gecko, 17. The number in the plesiosaurus and ichthyosaurus is not certainly known, but they extend the whole lengtJi of the spine, and are therefore very numerous. G G 450 LETTER XIII. bone, are so united to the chest-bone as to render ribs unnecessary. You will bear in mind that the principal use of the ribs is to afford a protective covering to the respiratory organs ; and as these organs (gills) in fishes are placed immediately beneath the basis of the skull, so also are those ribs which correspond to that part which in the mammalia is known by the name of the thorax, or chest. The gill-appa- ratus is supported and protected in the same manner by the branchial arches as the lungs are by the ribs. Their movement is the same ; and they are united in front by a true sternum. This thorax is composed, in most fishes, of four ribs on each side, united by one elastic cartilaginous arch ; or of two or more bones or cartilages connected to- gether by a joint in the shape of a h> ; and accord- ing as they approach or recede from one another, the gills close or open.* In the more highly organised fishes these branchial arches are more connected with the vertebral column than with the head, thus occupying a region nearer to the true thorax of warm-blooded animals than is the case with the sharks and lampreys.f In fishes, the bones which are attached to the spine do not * See Cams, Comp. Anat., vol. i. p. 120 (translation). t Spix lias adduced good reason for believing that the larynx, or organ of voice, in the higher classes of animals is a modification of the branchial apparatus in fishes. — Cephalogenesis, chap. i. LETTER Xlir. 451 converge in front, like true ribs, but are often imbedded in the muscles, the strengthening of which appears to be their chief use. Hence they have been called by Artedi muscular bones (ossicula musculorum). But I hasten to consider that part of the ske- leton which supplies so many animals with the power of locomotion. The adaptation of these organs to the many purposes of life, gives to the superficial observer the appearance of a want of uniformity in this part of the skeleton. But let us look deeper. " We may assert," says Lawrence, as a general observation, that the four component parts of the upper extremity, viz. the shoulder, arm, fore-arm, and hand, can be clearly shewn to exist in the anterior extremities of all mammalia, however dissimilar they may appear to each other on a superficial inspection, and however widely they may seem to deviate from the human struc- ture. Whenever an animal of one class resembles those of a different order in the form and use of any part, we may be assured that this resemblance is only in externals, and that it does not affect the number and arrangement of the bones. Thus, the bat has a kind of wings ; but an attentive exami- nation will prove that these are really hands, with the phalanges (small bones) of the fingers elongated. The dolphin, porpoise, and other cetacea, seem to possess fins consisting of a single piece ; but we 452 LETTER XIII. find under the integuments (skin) of the fin-like members all the bones of an anterior extremity, flattened in their form, and hardly susceptible of any motion on each other. We can recognise very clearly the scapula, humerus, (bones of the fore- arm,) and a hand consisting of five fingers ; the same parts, in short, which form the anterior ex- tremity of other mammalia.* The bones of the wings of birds have a considerable and unexpected resemblance to those of the fore-feet of the mam- malia ; and the fin-like anterior membrane of the penguin contains within the integuments the same bones as the wings of other birds." f How perfectly, by giving to animals such ap- propriate instruments, either for progression or prehension, for flying, digging, or grasping objects, they are enabled to fulfil their destinies, I have already shewn. Many animals use their anterior extremities not only for swimming or walking, but also for obtaining their food, or for defending themselves ; and hence arise the differences in the form of these limbs. In bats, mice, moles, hedgehogs, ar- madillos, sloths, beavers, squirrels, and porcu- pines, a bone crosses the front of the neck, and is fastened to the centre of the sternum ; and thus these animals are provided with a * See Tyson's Anatomy of a Porpoise. t Note to Blumenbach's Manual, p. 48. LETTER Xlll. 453 means of employing their extremities to many additional purposes. Those animals whose feet simply support their bodies do not require the clavicle ; in hoofed and other herbivorous ani- mals it is absent ; so that these latter are un- able to seize any thing with their extremities. LETTER XIV. " Go to the ant, consider her ways, and be wise ; which, having no guide, overseer, or ruler, provideth her meat in the summer, and gathereth her food in the harvest." — Proverbs, vi. 6-8. In the preceding Letters I have endeavoured to shew that the organisation of animals is not only adapted with the utmost precision to the various elements in which they exist, some being fitted for living on the earth and in the air, others in the waters, but also that the structure of each of the innumerable individual species which compose those great divisions of the animal kingdom has been formed with especial reference to the peculiar circumstances in which it is placed ; the organs of digestion, circulation, locomotion, and defence, in every case having a specific relation to the food, habits, locality, and natural enemies, of any given species. But organisation alone would be insufficient to secure the well-being of animals ; there must be some j)ower to direct and employ that organisation, otherwise it could not effect the purposes for which it was created. Thus, all animals have their natural foes, and are supplied with means of defence which, to a certain extent, protect them from those foes. But a power is necessary to enable them to recog- nise their enemies, and to make the proper use of LETTER XIV. 455 the means which they possess for ehiding them. Again ; for the support of animals, it is needful, not only that a supply of food should be at hand, and that an apparatus for its assimilation should be provided, but also that they should have the power of selecting those kinds of food which are fit for them, and of rejecting those which are not. And, in like manner, for the continuation of their species, in addition to a proper organisation for the produc- tion of offspring, there must be in animals a power to provide for the sustenance, defence, and well- being of their weak and otherwise unprotected young, until they arrive at maturity. A survey, then, of the whole economy of ani- mals seems to shew that every part of their orga- nisation is intended to be subservient to, or the instrument of, three inherent and unchangeable principles, viz. the instinct of self-preservation ; the instinct to replace the constantly exhausting energy and substance of the body, so that an equal phy- sical standard may be maintained ; and the instinct of perpetuating their species, and defending their offspring until they reach maturity, and are ca- pable of protecting themselves. In order that these three powers or instincts may never cease to act as long as the animal exists, the all-provident Creator has attached to their exercise, in every animal, the very highest enjoyment of which it is susceptible. Operating through the medium of the brain, and its instruments of perceptive com- 456 LETTER XIV. munication, the nerves, every tendency to call into action either of these three inherent propensities is accompanied by a freedom of motion in most cases pleasurable in the highest degree. That this triple power or instinct is wholly in- dependent of the brain, is evident. It is manifested in all the grades of the sentient creation ; in the most insignificant polypi, possessing no trace of any such organ, as well as in the highest vertebrated animal, in which the brain is found in the most per- fect state of development. This power, like all the other characteristics of animals, has been wisely modified so as to suit their several stations, and to meet the various difficulties to which they are ex- posed. As the sphere of the lower animals is for the most part contracted, and consequently their wants but few, the instinctive powder is in them less developed ; yet it is indisputable that their conduct frequently appears to be as much the result of reason as that of the higher animals. No one, however, would hence infer that the molluscous animals, for example, act by the dic- tates of mind ; for it is clear they have no organ through which the mind, if they had any, could manifest itself Diquemare notices the singular fact, that oysters which are attached to rocks occasionally left dry by the retreat of the tide, always retain within their shells a quantity of water sufficient to serve the purposes of respira- tion, and kce]) their Vcdves closed until the return LETTER XIV. 457 of the tide; whereas oysters taken from the greater depths, where the water never leaves them, when removed to situations where they are exposed to those vicissitudes of which they have had no pre- vious experience, improvidently open their shells after the sea has left them, and, by allowing the water to escape, soon perish.* As we ascend higher in the creation, instinct becomes more fully developed, and its application more extensive. But to say that even the most surprising manifestations of instinct are conse- quences of some reasoning power, would be as- suming more than there is evidence to prove ; for because the course which is taken by animals re- sembles in some cases the conduct which man, guided by the dictates of reason, would pursue in similar circumstances, it does not therefore follow that it is the result of the same faculty. To argue in this manner would be unphilosophical, inasmuch as we have no authority for asserting that similar effects invariably result from similar causes. One great proof that the instinct of animals is closely connected with their organisation, and is given to assist that organisation, without regard to the station which the animal holds, is furnished by the soldier-crab, a species of lobster which does not possess a shell. Organisation alone has given to most animals of this kind the power to reproduce a new shell, when the old one, becoming * Roget's Physiol., quoted from Journtil de Pliys. xxviii. 244, 458 LETTER XIV. too small, is cast off.* But to the soldier-crab the power of secreting a covering has been denied ; yet its habits and locality render it necessary that it should have some such means of defence as are pos- sessed by other cognate species. What the Creator has denied this animal, probably on account of its being incompatible with some part of its organisa- tion, it is permitted to supply by instinct; and " taking possession," says Goldsmith, " of the de- serted shell of some other animal, it resides in it till, by growing too large for its habitation, it is under the necessity of a change. It is a native of the West India islands, and, like the violet crab, it is seen every year descending from the mountains to the sea-shore to deposit its spawn, and to provide itself with a new shell. Its descent is not only to pro- duce an offspring, but to provide itself a covering ; not only to secure a family, but to furnish a house. This is a most bustling time with it, having so many things to do ; and, in fact, very busy it appears. It is very probable that its first care is * From experiments which have been made, it appears that the secreting surface is unable to produce a new shell till the old one, or any artificial covering, has been removed. " Are these new layers (of shell) formed by vessels existing in the shell itself, or are they produced by exudation from the surface of the animal ? Reaumur broke the shell of snails, and found that no reproduction took place when he covered the exposed part of the animal's body ; while the injury was quickly repaired when no artificial obstacle impeded the effusion of fluids from the surface." — Lawrence's Note to Blumenhach' s Manual of Comparative Anatomy, p. 3. LETTER XIV. 459 to provide for its offspring before it attends to its own wants ; and it is thought, from the number of little shells that it is seen examining, that it de- posits its spawn in them, which thus is placed in perfect security till the time of exclusion. How- ever this be, the soldier is in the end by no means unmindful of itself. It is still seen in its old shell, which it appears to have considerably outgrown; for a part of the naked body is seen at the mouth of it, which the habitation is too small to hide. A shell, therefore, is to be found large enough to cover the whole body, and yet not so large as to be unmanageable and unwieldy. To answer both these ends is no easy matter, nor the attainment of a slight inquiry. The little soldier is seen busily parading the shore along that hue of pebbles and shells that is formed by the extremest wave ; still, however, dragging its old incommodious habitation at its tail, unwilling to part with one shell, even though a troublesome appendage, till it can find another more convenient. It is seen stopping at one shell, turning it, and passing it by ; going on to another, contemplating that for a while, and then slipping its tail from its old habitation to try on the new. This also is found to be inconve- nient, and it quickly returns to its old shell again. In this, manner it frequently changes, till at last it finds one hght, roomy, and commodious ; to this it adheres, though the shell be sometimes so large as to hide the body of the animal, claws and 460 LETTER XIV. all.* Yet it is not till after many trials, and many combats also, that the soldier is thus completely equipped ; for there is often a contest between two of them for some well-looking favourite shell for which they are rivals. They both endeavour to take possession ; they strike with their claws, they bite each other, till the weakest is obliged to yield, by giving up the object of dispute. It is then that the victor immediately takes possession, and parades it in his new conquest three or four times backwards and forwards upon the strand before his envious an- tagonist."f An amusing and instructive correspondent in Loudon's Mag. of Nat. Hist. :]: quoting Carreri GemeUi, says, that " the oran-otang {simia satyrus) feeds on a large species of oyster ; and that fearful of inserting its paws between the open valves, lest the oyster should close and crush them, he first places a tolerably large stone within the shell, and then drags out his victim with safety. Now, the oran-otang is one of those animals to which Locke would have allowed a certain degree of reason, from the superiority of their instinct; but what shall we say of the crab {cancer pagurus), which has generally been considered so much lower in the scale of animated beings, but which, from good authority, is said to make use of the very same * Peru du Testre. t Natural History of Fishes, book iv. c. 2. I Vol. ii. p. 149. LETTER XIV. 461 contrivance to accomplish the same end? The oyster-dredgers on this coast (Lynn Regis) will tell you, that one of their greatest enemies is the crab ; and I have been assured by an old dredger, that he has, with his own eyes, more than once seen the crab take a stone in his claw and insert it between the open valves of the oyster (ostrea eclulis) before he ventured to seize upon his prey. Another man asserted, that although he had never detected the crab in the act, he had frequently found a stone placed between the emptied shells of the oyster."* The course pursued by many of the lower animals is perfectly in accordance, then, with the most profound reasoning and calculation, for there is design and purpose in all their labours ; but no one would thence conclude that they are conscious of that design, or that they have the end of their labours in view. For example, the manner in which the coral polypi pursue their labours, shews that there is a design in the work which they have un- dertaken ; and though they are quite unconscious of the gigantic power which collectively they pos- sess, they undoubtedly adopt a course not only consonant with sound reasoning, but agreeable to the profoundest calculations, capable of meeting and overcoming the most stupendous difficulties that oppose their proceedings. The vast coral rocks which they are concerned in erecting, is no * Loudon's Mag. of Nat. Hist. vol. iv. p. 157. 462 LETTER XIV. proof that intelligence is manifested by the little architects, for these rocks are the result of a natu- ral chemical process, over which they can have no control ; and the fact that coral reefs are built in the form of a crescent, and sometimes in that of a circle, as if the polypi were aware of the resisting power of an arch, and knew that it would be more capable of preserving their habitations from the force of an impetuous ocean than a straight line or an irregular projection, is no evidence that these animals are at all conscious of the nature of the operations in which they are engaged ; for it has been proved by MM. Quoy and Gaimard, that the circular character of some of these reefs is caused by their formation taking place on the crests of submarine craters.* But let us turn to the ant, of which Solomon says, " Consider her ways, and be wise." It is impossible to see the order, the industry, the apparent intelligence of these little insects,— to notice the choice which they make from among the many materials for building which surround them, or to watch the seeming ingenuity with which they elude difficulty, or apprehend the cir- cumstances which would contribute to the advan- tage of their commonwealth, without recognising the hand of their Creator in all that they do. To admit that they reflect upon the course they are * Quoy et Gaimard sur I'Accroissement des Polypes litho- phytes considere geologiquement. Ann. des Sci. Nat. torn. vi. LETTER XIV. 463 about to pursue, would be to admit but a scanty means for furnishing them with the power which they so frequently display. In selecting their food, and especially in preserving it when it is gathered into their granaries, they act in the man- ner which the profoundest reasoning would direct ; so that we have some difficulty in persuading our- selves that they are not regulated by some such faculty. Addison,* in a paper on these little crea- tures, relates an act of foresight truly wonderful. " Every body knows that ants come out of their holes in the day-time, and expose to the sun the corn which they keep under ground in the night. Those who have seen ant-hillocks have easily perceived those small heaps of corn about their nests. What surprised me at first was, that my ants never brought out their corn but in the night, when the moon did shine, and kept it under ground in the day-time, which was contrary to what I had seen and saw still practised by those insects in other places. I quickly found out the reason of it ; there was a pigeon-house not far from thence ; pigeons and birds would have eaten their corn if they had brought it out in the day- time. It is highly probable they knew it by expe- rience ; and I frequently found pigeons and birds in that place when I went to it in a morning. I quickly delivered them from these robbers ; I * The Guardian, No. 156. 464 LETTER XIV. frighted the bhds away with some pieces of paper tied to the end of a string over the window. As for the pigeons, I drove them away several times ; and when they perceived that the place was more frequented than before, they never came to it again. What is most admirable, and what I could hardly beheve if I did not know it by experience, is, that those ants knew some days after that they had nothing to fear, and began to lay out their corn in the sun. However, I perceived they were not fully convinced of being out of all danger, for they durst not bring out their provisions all at once, but by degrees, first in a small quantity, and with- out any great order, that they might quickly carry them away in case of any misfortune, watching and looking every way. At last, being persuaded that they had nothing to fear, they brought out all their corn almost every day, and in good order, and carried it in at night. Those insects never go about this work but when the weather is clear and the sun very hot. I observed that those httle animals having one day brought out their corn at eleven o'clock in the forenoon, removed it, against their usual custom, before one in the afternoon. The sun being very hot and sky very clear, I could perceive no reason for it. But half an hour after, the sky began to be overcast, and there fell a small rain, which the ants foresaw ; whereas the Milan almanac had foretold there would be no rain upon that day." LETTER XIV. 465 " We observe/' says an intelligent writer, '' nu- merous bodily actions which, in ourselves, result from mental operations, or are, in other words, manifestations of the mind ; but the question comes to be, do these necessarily imply mental opera- tions ? What do we see in the automaton ? it moves, it writes, it draws figures, it performs music, plays at chess. These actions are in ourselves manifestations of mind ; but there they are the result of mere mechanism, set in motion by an impulse communicated by the exhibitor.* Why may we not suppose, that certain manifestations in animals may result from particular arrangements of matter ordained by the Creator to act in a certain manner, and to be set in motion at certain times by bodily feelings, or by an impulse commu- nicated through the senses ? They resemble the manifestations of mind, but they are clearly distin- guished from them. We call them instinct; and even in the highest degree of it, we see the line * " "Will any one contend," says Fenelon, " that they are perfectly acquainted with mechanics, because they regulate their motions by mechanical laws, because they run, leap, swim, hide themselves double, use shifts to avoid pursuit, and make use of the strongest parts of their body when they defend themselves ? If a rope-dancer, in the midst of his performances, should begin to reason with himself on the laws by which he is kept in equili- brium, he would soon fall to the ground, losing that command of his bodily powers which he so completely enjoys without the aid of reason." — On the Deity, H H 466 LETTER XIV. drawn between it and reason with great precision. The acts of animals that are regulated by instinct, we have every reason to believe are called into action by bodily feelings, or by impressions upon the senses, and regulated by fixed and determinate laws. This uniformity or regularity shews some- thing remarkably different from those actions in man which are governed by reason. These are called into action not by impulse, but by motives addressed to the mind. Here is a power of reason- ing and deliberating ; of acting or abstaining from action; of following a present impulse, or resist- ing it, under the influence of motive, which refers to something future, and consequently can exist only in mind. This power of being influenced by the future, in opposition to present feelings and present impulse, indicates, at first sight, the re- markable difference between reason and instinct, between man and animals. We see its influence in man by the daily occurrences of life ; and it leads us to the high principle of moral responsi- bility, to which animals exhibit nothing in the smallest degree analogous. There may be in animals much appearance of sagacity and contri- vance; but wherever there is this acting upon impulse, and this inability to resist impulse under the influence of something future, there is nothing of the nature of mind or soul, nothing of the nature of moral responsibility, and nothing that we have LETTER XIV. 467 the slightest reason to beheve is either immaterial or immortal." * The instinct of animals furnishes them with an intimate knowledge of all those beings which are hostile to their existence, and gives rise to the propensity to avoid such objects, not only those which are living, but those also that are without hfe. It is this principle also which directs animals to select that which is beneficial, and to avoid that which is hurtful for the nourishment and support of the body; and not without considerable appa- rent intelligence do they select particular herbs, and other substances, when exposed to a great variety of choice. Sheep, oxen, deer, pigs, horses, rabbits, have all their choice herbs, and even sepa- rate parts of the same herb. If the power of dis- tinguishing one substance from another, and of preferring that which is harmless or wholesome to that which is injurious or destructive, is to be assumed as a mark of reflection, we must grant this high intellectual power to all the lower ani- mals, and thereby take from the prerogative of the Creator ; for, we are told that " every living thing waits upon God, that he may give them their meat in due season." f Instinct, moreover, gives to animals a gigantic power to overcome every * Review of Lawrence's Lectures on Physiology, in Edin. Med, Surg. Jour. vol. xv. p. 609. t Psalm civ. 27. 468 LETTER XIV. obstacle that opposes the perpetuation of their species. It draws forth such unbounded courage in animals, as to lead them to expose themselves to dangers, from which, at other times, they would shrink with fear and trembling. The many arts which animals display in the accomplishment of the three ends before mentioned, constitute some of the most interesting subjects connected with the science of natural history. But it is a singular fact, as it is also a proof of the irrational constitution of the lower animals, that though in the exercise of this triple power there is so obvious an appearance of intelligence, it is never found to be overpowered or con- trolled, as it would be if subject to the operation of reason. We do not see animals attempting to destroy themselves, or putting themselves in the way of destruction ; their art is to avoid the snares of men, or of those animals which would endanger their existence. Nor do they choose poison instead of food, but carefully avoid every thing of a deleterious kind. They neither mix out of their own species, nor are careless of their off- spring ; but, undaunted by the greatest difficulties, they display unwearied diligence and ingenuity in all matters relating to their young. The innumerable varieties of habit, and of the conditions of physical life, the necessarily very large development of external sense, and the rapid LETTER XIV. 4G9 advancement to maturity, which characterisesj in a greater or less degree, the whole animate creation, if we except man, are circumstances favourable to the conclusion, that the powers of animals are derived immediately from God in a fixed and de- terminate manner ; for if the conduct of animals were regulated by reflection, their reasoning facul- ties would necessarily be far more powerful and exalted than those of man ; inasmuch as they, without any previous experience or practice, per- form numerous operations which long study and practice would not enable him to accomplish. As, however, this hypothesis is universally admitted to be absurd, it follows, that their actions must be the result of impulse, communicated by the Being who formed their organisation. " There are some," says Mr. Abernethy, " who seem to wish it should be believed that the in- stincts of animals, the curious arts and expedients which they employ to obtain food, and to avoid injury, are the effect of reason ; but they cannot maintain this opinion without granting to the lowest kinds of animals a greater share of intelli- gence than they themselves possess or can have any idea of. We may take some spiders' eggs, and when hatched select a young one who has never had any communication with his species ; and we shall find that, in due season, without any plan or preparatory attempts, it will construct as curious a web as any of its ancestry ; then secrete himself 470 LETTER XIV. till au unwary fly becomes entangled, which he will suddenly seize and destroy."* All attempts to account for the conduct of animals upon a principle of reason are at once overturned by this fact, which proves that there must be a power in them prior to and inde- pendent of all natural reason and experience. Unless this be granted, how can we account for the mathematical skill and precision displayed by the bee in the construction of its house — so perfect, ih^t no human science or art can im- prove upon it? Are we to believe that the bee is conscious, as she pursues her labours, that the hexagon is the only shape which will admit her elaborate workmanship to be constructed at the least expense of time and materials, and in the smallest possible space ? Or, again ; are we to believe that it is from deliberate forethought that bees, in a country where the seasons are always temperate, take no steps to lay up a provision against the winter, and that they are aware it will not be required ? We forbear to enter upon the economy of the hive ; its architecture is sufficiently indicative of the power and wisdom of God to call forth our highest admiration. Were animals permitted to regulate themselves by reason, how powerless would they be when opposed by obstacles which instinct makes them * Abernethy's Reflections on Gall and Spurzheim's Phreno- logy, p. 27. LETTER XIV. 471 disregard, and enables them to overcome : fear- less of danger, they face difficulties which reason would shew to be insurmountable. It is a blind impulse, which is given to animals purposely and solely to aid them in the three great ends which I have before alluded to. And that reason would obstruct rather than assist the accomplishment of those ends, is proved by the very wonderful ac- counts on record of animals which annually under- take journeys from remote regions for the purpose of depositing their spawn, unconscious of the fatal obstacles which often lie in their path, and which, had they reason, they would become acquainted with, and consequently endeavour to avoid. More- over, that animals have no choice in the course they are destined to take, is manifest by their never deviating from their accustomed plan, which they would certainly sometimes do, were they free agents and under the dominion of reason. Again, if these powers were dependent upon reason, why should they cease to act when the ends to which they point are for a time accomplished, and be again called forth when an occasion for their exercise presents itself? a phenomenon of which we have numerous instances. A bird cannot build its nest at any other period of the year than that season when the climate favours the propagation of its young. , Although as Mr. Abernethy's and our own ob- servations would lead us to infer, instinct places 472 LETTER XIV. animals far above rational man in many particu- lars, nevertheless it often falls below the reasoning power ; and these instances serve to shew us, in a forcible and distinguishing manner, the ardour which characterises instinct, and separates it from reason. With what thoughtless perseverance will a turkey, at the period of incubation, sit upon a shapeless stone, or upon an empty nest, regardless alike of food or danger ! '' A certain swallow, for two years together, built upon the handles of a pair of garden-shears that was stuck up against the boards of an outhouse ; so that her nest must have been spoiled whenever that implement was wanted ; and what is still stranger, another species built its nest on the wings and body of an owl that happened to hang dead and dry on a rafter. This owl, with the nest on its wings, and with eggs in the nest, was brought to a distinguished naturahst, as a curiosity worthy of the most elegant museum in Great Britain. The naturalist, struck with the oddity of the sight, furnished the bringer with a large shell, or conch, desiring him to fix it just where the owl hung : the person did as he was directed; and the following year a pair, probably the same pair, built their nest in the conch, and laid their eggs. The owl and the conch make a strange grotesque appearance, and are not the least curious specimens in that wonderful collection of art and nature. Sir Ashton Lever's museum."* * White's Nat. Hist, of Selborne, letter xviii. LETTER XIV. 473 " Some time since a pair of blue titmice (parus ceruleus) built their nest on the upper part of an old pump, fixing it on the pin on which the handle worked. It happened that, during the time of building and laying the eggs, the pump had not been in use. When again set going, the female was sitting, and it was naturally expected the motion of the pump-handle would drive her away. The young brood were hatched safely, however, without any other misfortune than the loss of part of the tail of the sitting bird, which was rubbed off by the friction of the pump-handle ; nor did they appear disturbed by the visitors who were fre- quently looking at her."* '' Birds are wise in general in their choice of station," says White ; '' but in this neighbour- hood every summer is seen a strong proof to the contrary, at a house without eaves, in an exposed district, where some martins build year by year in the corners of the windows. But as the corners of these windows, which face to the south-east and south-west, are too shallow, the nests are washed down every hard rain ; and yet these birds drudge on to no purpose from sum- mer to summer, without changing their aspect or house. It is a piteous sight to see them labour- ing when half their nest is washed away, and bringing dirt generis lapsi sarcire ruinas. Thus is instinct a most wonderfully unequal faculty ; in * Loudon's Mag. of Nat. Hist. vol. ii. p. 64. 474 LETTER XIV. some instances so much above reason, in other respects so far below it."* " What can be more careful of her little one than the ewe! Yet will she suffer it to he and expire in a small pit or gutter before her eyes, without so much reflection as to put a single foot to turn it on its legs. No master of defence can make a shew of more skill or address to strike or pare than a game cock ; but if this was the effect of contrivance or reason, he would not give us the best samples of it in his first battle, nor would he exert or waste his labour against an impenetrable looking-glass. The most skilful architect or mathematician, with all his dexterity, cannot equal the art of a bird in framing her nest ; yet will the sagacious builder herself stave upon eggs that are not her own, or purvey for a young one that is an enemy to her species, and which will ungratefully devour her foster parent. The goose or gander will give you a mark of fortitude and conduct in covering their squadhng family from the approaches of an enemy ; but at the same time they distinguish not an enemy from a friend, but fall with equal fury upon the latter when he comes to feed them, to help or succour them ; nay, will they often stupidly trample them under their feet, or suffer them to sprawl and perish on their backs, without the sense to help them." f * White's Selborne, part 2, letter xvi. t Essays on Hunting, Sagacity, &c. p. GO. LETTER XIV. 475 These are some of the most obvious objections which present themselves to the inquiring natura- hst, who endeavours to trace all the actions of animals which indicate design to a mental process resembling, in an inferior degree, the rational powers of man. In the next Letter we shall in- quire more fully whether the cause of their actions is not distinct from reason, and what is the cause to which they are attributable. There is, however, yet another light in which instinct must be contemplated, and which will shew still more clearly its direct subjection to Divine superintendence. The phenomena which result from organisation are often so intimately connected with instinct, that it would be impos- sible to trace any ingenuity in the latter, unless the design intended in the former were compre- hended. Yet in these cases we do not say that the organisation reasons, but that it exhibits powers conferred upon it by the Creator. No instance can more forcibly shew this than the conduct pur- sued by birds in the hatching of their eggs. The various species of birds are distinguished from one another by many peculiarities in this part of their economy, which result from their habits, the situa- tion in which they build their nests, or the climate in which they live. Witness the variety of nests, and the numerous methods of concealment and contrivance adopted by different birds. All their peculiarities give rise to the display of various kinds 476 LETTER XIV. of instinct ; yet the position of the embryo in the egg during the period of incubation, a circumstance of the highest importance, is, in every case, wholly beyond the control of the parent bird. It has been shewn that the spot which is upon the upper surface of the yolk, and which is the embryo of the future bird, is always nearest the body of the incubating bird; and though the fact has been denied by Haller, and other writers, it has been satisfactorily shewn, that the internal construction of the egg is such, that it would be impossible, by any shifting or displacement of the bird, to alter this disposition of the parts of the egg. This curious fact was accounted for by Derham in the following manner : — "As the shell and skin keep the yolk and two whites together, so each of the parts (the yolk and the inner white at least) are separated by membranes involving them. At each end of the egg is an opaque band called ckalzay which being of a white dead substance, serves to keep the white and the yolk in their proper places. ' But the use of these,' says Dr. Harvey, in Wil- loughby's Ornithology, chap. 3, ' is to be, as it were, the poles of this microcosm, and the con- nexion of all the membranes twisted and knit toge- ther, by which the liquors are not only conserved each in its place, but do also retain their due posi- tion one to another.' This, although in a great measure true, does not come up to what I myself have observed ; for I find that these chalzae, or LETTER XIV. 477 treddles, serve not barely to keep the liquors in their place and position to one another, but also to keep one and the same part of the yolk upper- most, let the egg be turned nearly which way it will ; which is done by this mechanism : the chalzse are specifically lighter than the whites in which they swim, and being braced to the membrane of the yolk, not exactly in the axis of the yolk, but somewhat out of it, causeth one side of the yolk to be heavier than the other, so that the yolk being by the chalzse made buoyant, and kept swimming in the midst of two whites, is, by its own heavy side, kept with the same side always uppermost ; which uppermost side, I have some reason to think, is that on which the cicatricula lies, that being commonly uppermost in the shell, especially in some species of eggs, more than I think in others."* As the learned Blumenbach has now set this matter at rest, and decided that the cicatricula, or living spot, is always near the body of the incu- bating bird, the conjecture of Mr. Derham, that the specific lightness of the chalzse has a tendency to keep that part uppermost to which they are attached, appears highly probable. We see, then, that we cannot so much as infer a perceptive power in those birds which are said, by some writers, to change the position of their eggs with a view to equalising the degree of heat, as though they were aware that nothing short of * Physico-Theology, vol. ii. p. 52. 478 LETTER XIV. thermometrical exactness would enable them to accomplish the task they had undertaken. If it can be proved that birds really do change the posi- tion of their eggs, — a proceeding which is thought to savour so much of rationality, — the necessity for so doing has, as we have just shewn, been antici- pated by the great wisdom of the Creator. Of this fact we are certain, that the life of the future bird could not be preserved by any effort of its parent ; for it has already been shewn, that unless that small vesicle, the cicatricula, be placed next to the body of the incubating bird, no living result can take place ; and it need hardly be observed, that the parent bird would be wholly unable to ascertain the exact position of the cicatricula. The act of turn- ing the eggs over, ascribed to some birds, is too such like an act of supererogation, to induce us to suppose that it was ever dictated by instinct.* I would direct your attention to another in- stance, where both the organisation and the in- stinct seem to point to a rational act. It is not an uncommon thing for birds to build their nests, or to cover them, with materials which, upon the closest inspection, resemble the trees in * Eggs that are hatched by the sun, or by the heat imparted by ovens, come into life in consequence of the warmth being uniform over the whole egg, and therefore sufficient to keep the cicatricula alive. This uniform heat cannot be maintained by incubation ; and the contrivance above explained is therefore abso- lutely necessary. LETTER XIV. 479 the branches of which they are constructed, or the ground on which they are placed. But this act, so much resembhng reason, would fail to secure the concealment which is its object, were the sitting bird decorated with an attractive plumage. It is to this cause that the dull appearance of the plumage of the female bird is to be attributed. It would be futile to affirm that the bird has any more control over the building of its nest, than it has over the plumage which so remarkably con- ceals it. The power which some of the lizard tribe pos- sess of rapidly changing the colour of their skin, so as to resemble the objects on or near which they are placed, and thus to hide themselves from the observation of their enemies, is another proof that organisation and instinct have a mutual de- pendence, of which the animal cannot be conscious. It is said that many species of the chameleon pos- sess the voluntary power of changing the colour of their skin, if in any way excited by fear ; but the American chameleon, called in that country the agama, appears to surpass all the other species in the variety of shades which it is capable of assum- ing. It is distinct from the African species in shape ; the back part of the head not running to a point, and its tongue being short and thick. The principal change of colour observed in it is from green to brown, or vice versa ; which, in the opinion of Baron von Sack, who had several of 480 LETTER XIV. them domesticated, is assumed to deceive an enemy when approaching, and to render itself invisible. For example ; if put upon a green umbrella, says the Baron, it immediately changed to that colour ; and upon being let down upon the floor, which was made of the ballo tree, of a dark brown, it assumed a very dark chocolate colour. This change seems to be effected by the motion or disposition of its scales, as they are either elevated or depressed by its voluntary power ; and when the reptile is fresh caught, this will take place five or six times in a minute, the animal all the time snapping at any thing that approaches it.* We cannot, then, admit that any part of the conduct of the lower animals is regulated by an inherent rational power, without admitting also that they possess a power which is superior to rea- son, namely, that of foreknowledge ; for that ani- mals often anticipate natural events is obvious to every body. For example, the tortoise during the winter buries itself in the earth, that it may be protected from the cold ; and, from the course it pursues, it seems to have a previous knowledge of what sort of winter it will have to contend with ; for the colder the winter is going to be, the deeper the animal buries itself in the ground. A corre- spondent in Loudon's Magazine of Natural His- toryf says, that " in the winter of 1832 the top of * Martin's British Colonies, vol. ii. p. 104, t Vol. vii. p. 157. LETTER XIV. 481 a shell of a tortoise in his garden was only covered two inches. There were only two nights in that winter which could really be called frosty; and now, December 14, 1833, his shell is only just level with the earth, the very top of it being visible through the turf; therefore there was to be no frost at all." On the 17th of January, 1834, the same correspondent writes : *' The tor- toise emerged from his hiding-place, and walked about as in summer." Many of the birds in and about the torrid zone, where the extreme heat encourages the existence and growth of many ferocious and for- midable animals, are found to adopt unusually careful means for the preservation of their young from the dangers peculiar to the climate they in- habit. Their mode of nidification is upon a plan very different from that followed by birds in more northern regions. Now, these contrivances are looked upon as proofs of design and of prescience of the dangers that await them in the birds them- selves. In the same light must be viewed the propensity to lay up a store against the winter season, as we witness in hunsters, bees, ants, and many other animals. Jesse tells us the moor-hen sometimes displays a degree of foresight in her care for her young which is particularly pleasing. " It is well known that she builds her nest amongst sedges and bulrushes, and generally pretty close to the water, as it is there less likely to be observed. I I 482 LETTER XIV. In places, however, where any thing hke a flood is likely to take place, a duphcate nest, more out of the reach of the water, is constructed, which is in- tended to be in readiness in case a removal of the eggs or young ones should be found necessary. This observation was made by a family residing in an old priory in Surrey where moor-hens abound, and where the fact was too often witnessed, by themselves and others, to leave any doubt of its accuracy." * But I shall not accumulate particular instances of foreknowledge in animals, which maybe observed constantly in almost all of them. My object is to shew that they are destitute of the faculty of reason, and that those manifestations of other and higher faculties which they so frequently make, proceed from the immediate direction of their Crea- tor. In my next Letter I shall examine what the faculties of animals consist of, and to what pur- poses they are applied. * Gleanings in Natural History, Second Series, p. 249. LETTER XV. " Instinct is that faculty whicli animals possess of performing by an inward, innate, and involuntary movement, without any instruction and of themselves, actions conformable to an end, and tending to their preservation and to that of their species." — Blumenbach's Nat. Hist. sec. 3. That the organisation of animals exhibits many- marks of Divine wisdom, the facts stated in the previous Letters have, I trust, convinced you. To shew that their instincts furnish proofs of intelHgent design neither less numerous nor less imposing, is the purpose of this Letter. Instinct, as I have already said, is so dependent upon organisation, and their mutual results are so blended, that we are often inclined to refer to some mental operation phenomena which in reality result solely from the very high degree of energy vested in particular nerves, such as those of sight, smell, hearing. The influence which those nerves indis- putably possess in conveying to the lower animals, in which they are so largely developed, knowledge which man obtains by the aid of his reason, I have already considered in a former Letter. The con- duct' of animals being so remarkably in accordance with reason, as to lead many persons to believe that they really do, in some cases, exercise that faculty (though this is undoubtedly a moral impos- 484 LETTER XV. sibility), it becomes a very interesting question to inquire upon what terms they hold the various powers which they display. It is important to bear in mind that the three inherent propensities, or instincts, spoken of in my last Letter, namely, those of defence, support, and reproduction, are necessarily displayed under cir- cumstances, and in degrees of development, differ- ing widely probably in every species of animal, as the locality, the nature of the food, the temperature, and the various kinds of foes, require. Thus, every species possesses some faculties common to all animals, which are more or less developed accord- ing to circumstances; so that the faculty or pro- pensity which is predominant in one species may be both relatively and absolutely feeble in another. Some of these faculties are common to man and the lower animals; others are peculiar to the latter, and even to individual species. The phe- nomena resulting from the faculties common to all sentient beings have many points of resemblance, even when exhibited in species the most dissimilar in other respects. In man, however, these inferior faculties are modified to a considerable extent by reason ; and thus the phenomena they produce in him, though still essentially the same, differ widely from those they produce in other animals. It is to the circumstance that some of the faculties of animals are common to them and man, that we must attribute the original aptitude of LETTER XV. 485 the animals now subject to him for domesticity. Considering the various degrees of development of these faculties in the inferior races, it is easy to see how readily some animals might be made serviceable to man, while others are altogether useless and even injurious. It has been well observed by M. F. Cuvier and M. Bureau de la Malle, that unless some animals had manifested in a wild state an aptitude to second the efforts of man, their domestication would never have been attempted. If they had all resembled the wolf, the fox, and the hyaena, the patience of the expe- rimentalist would have been exhausted by innu- merable failures, before he at last succeeded in obtaining some imperfect results. If all animals had the propensity to destroy in as great a degree as some of the carnivora, their utility to man would in no wise compensate him for his efforts in sub- duing them to his service. On the other hand, those animals in which this propensity is weak, and which defend themselves by the aid of facul- ties apparently given to them in lieu of it, are by means of those faculties brought into sub- jection and rendered serviceable to man, some- times in a manner which would at first siffht induce us to suppose that they are actuated by reason.* It is very justly thought by some writers, that some of the faculties of particular animals have been given with a view to the con- * Lyell's Geol. vol. ii. p. 408. 486 LETTER XV. nexion which it was foreseen would exist between them and man. M. F. Cuvier, in a paper pub- lished in the Mem. du Mus. d'Hist. Nat., has pointed out this as the origin of many faculties which are vulgarly attributed to the influence of education alone. " Such attainments, as well as the habits and dispositions which the shepherd's dog and many others inherit, seem to be of a nature and extent which we can hardly explain by supposing them to be modifications of instincts necessary for the preservation of the species in a wild state. When such remarkable habits appear in races of this species, we may reasonably con- jecture that they were given with no other view than for the use of man and the preservation of the dog, which thus obtains protection."* Guided by the best authority, and by the nu- merous facts of which we are in possession, I shall now proceed to examine the constitution of what is called the animal life ; a collective term by which we denote a variety of faculties, all of which are designed for the use and service of the body, and, so far as we understand them, have no relation to any thing more exalted and enduring. Apart from the highly wrought and magnificent organisation which many animals display, there must be a power in them to receive impressions independent of the instruments by which those impressions are conducted ; they must have a sort * Lyell's Geol. vol. ii. jj. 411. LETTER XV. 487 of audience-chamber into which impressions may be conveyed by their external senses ; for without this, those very senses which we know they pos- sess, and which, as I have abeady shewn, are developed much more fully in them than in man, would be without an end ; an unreasonable hypo- thesis, since, so far as our knowledge of the crea- tion enables us to judge, every thing that exists has some end to which it is subservient, and for which it was created. Whether this audience- chamber exists, or whether it can receive impres- sions after the external senses have taken them up, are questions, therefore, into which I shall not enter, but shall assume them both in the affirmative. It cannot be disputed that the inferior animals, as well as man, are possessed of many innate or internal faculties, which subserve the ends for which they were created. These various secondary powers are all comprehended under the general term i?isti?ict ; yet they are capable of individual definition, as they are of action. I shall revert to them separately under the titles of inigration, imitation, construction, courage, and many others, the manifestation of which in animals must be obvious to every one. But the most interesting inquiry is, whether they act simply by the impulse of these secondary powers, or whether they have understanding also ; that is, whether they can compare their sensations and ideas ? I am not unmindful how stoutly this point has been con- 488 LETTER XV. tested ; and in making my observations,, shall en- deavour to avoid controversy as much as possible, relying rather upon facts for the establishment of what I may assert. Many learned men believe that animals have understanding, yet they do not decidedly say that they have reason ; they call it a sort of reason. I do not go so far as this ; but think that their impulse to act one way or another is regulated by the relative forces of their faculties. Motive, therefore, has no necessary share in the actions of animals ; and if they are modified, it is not a consequence that they must act from motive. It is said that a dog does not act from instinct only, but shews a certain degree of understanding, be- cause, when he is hungry, for example, he does not eat, fearing the blows of his master. But I shall shew that this mode of action is not incom- patible with the possession of merely single ideas, which animals must have to render them capable of avoiding harm. The fear of pain in this in- stance prevails over the anticipation of pleasure, and thus prevents the taking of food. Understanding is a general term expressive of many faculties, which are called by philosophers determinate species of understanding, such as per- ception, memory, judgment, and imagination. I do not think that perception and memory, even when combined with all other innate faculties, except judgment and comparison, though essential to un- LETTER XV. 489 derstanding, are of themselves capable of consti- tuting what is called reason. We cannot deny perception and memory to the lower animals ; but we are assured that they have not the faculty of reason. But the proof of this will chiefly rest upon the facts to be brought forward. That animals have perception is self-evident, for otherwise they could neither perform locomo- tion, nor defend their bodies from ordinary inju- ries to which they are daily exposed, nor discri- minate wholesome food from pernicious. Percep- tion being the first step towards knowledge, as well as the inlet of all the materials of it, the fewer and less perfect the organs by which the animal receives sensations, or perceives, the duller are the impressions conveyed to the sentient principle. In those animals whose locomotive powers are limited, and whose existence is supported with little exertion on their part, the organisation ap- propriated to the service of the perceptive faculty is neither extensive nor highly developed. " The faculty of perception," says Locke, " seems to me to be that which puts the dis- tinction between the animal kingdom and the inferior parts of creation. For, however vege- tables have many of them some degree of motion, and, upon the different application of other bodies to them, do very briskly alter their figures and motion, and so have obtained the name of sensi- tive plants from a motion which has some resem- 490 LETTER XV. blance to that which in animals follows upon sen- sation ; yet I suppose it is all bare mechanism, and no otherwise produced than the turning of a wild oat-beard by the insinuation of the par- ticles of moisture, or the shortening of a rope by the effusion of water. All this is done without any sensation in the subject, or the having or receiving any ideas." " Perception, I believe, is, in some degree, in all sorts of animals ; though in some, possibly, the avenues provided by nature for the reception of sensations are so few, and the perception they are received with so obscure and dull, that it comes extremely short of the quickness and variety of sensation which is in other animals ; but yet it is sufficient for, and wisely adapted to the state and condition of that sort of animals who are thus made, so that the wisdom and goodness of the Maker plainly appear in all the parts of this stupendous fabric, and all the several degrees and ranks of creatures in it. We may, I think, from the make of an oyster or cockle, conclude that it has not so many, nor so quick senses as a man, or several other animals ; nor if it had, could it, in that state and incapacity of transferring itself from one place to another, be bettered by them. What good would sight and hearing do to a creature that cannot move itself to or from the objects wherein, at a distance, it perceives good or evil? And would not quick- LETTER XV. 491 ness of sensation be an inconvenience to an animal that must lie still where chance has once placed it, and there receive the afflux of colder or warmer, clear or foul water, as it happens to come to it ?" * If we cannot but admit that animals have ex- ternal senses, that they can see, hear, smell, taste, and feel, we must further admit that they per- ceive ; for these are the organs of perception ; and no animal possesses an instrument without having also the power to make use of it. And if they perceive, they must have ideas of what they per- ceive, otherwise they could not distinguish one thing from another ; this, therefore, is as essential as that they should have common sensation, without which they could not discriminate between varie- ties of temperature, a knowledge of which is so necessary to their existence, and is obtained by them through the medium of pleasurable or pain- ful feelings. It is not a question, then, whether animals receive ideas ; for unless they did, they could not exist. A dog could not know its master, nor distinguish its food, unless it had an idea of its master and of its food. This is as plain as that it is impossible to see without the organ of vision. Persons born blind derive their ideas of those qua- lities which the eye has the exclusive power to recognise from what other senses they possess. Thus, Cheselden's blind boy could only speak of colours by the touch. After he had been couched, * On the Human Understanding, vol. i. p. 109. 492 LETTER XV. he thought that pictures would feel like the things they represented, and was enraged when he found that those parts which, by their light and shade appeared round and uneven, felt flat like the rest.* Thus it is obvious that animals must have ideas, or their perceptions would avail them no- thing. But we can by no means prove that they are able to associate ideas, or to use them in arbi- trary combination ; their ideas are simple, and can- not be collated. For instance, an animal can dis- tinguish one creature from another by its shape or its size ; it knows whether it is inimical or friendly through the memory which it retains of single ideas, such as its size or hostility. Locke thought that the idea which a dog forms of its master is com- plex, but that it does not compound the simple ideas of which that complex one is formed. They are fixed and compounded for it. " In this also, I suppose, brutes come far short of man ; for though they take in and retain together several combina- tions, or simple ideas, as possibly the shape, smell, and voice of his master, make up the complex idea a dog has of him, or rather are so many distinct marks whereby he knows him ; yet I do not think they do of themselves ever compound them and make complex ideas. And perhaps even where we think they have complex ideas, it is only one simple one that directs them in the knowledge of several things which possibly they distinguish less * Phil. Trans. Ab. vol. vii. j). 238. LETTER XV. 493 by their sight than we imagine ; for I have been credibly informed, that a bitch will nurse, play with, and be fond of young foxes, as much as and in place of her puppies, if you can but get them once to suck her so long that her milk may go through them. And those animals which have a numerous brood of young ones at once appear not to have any knowledge of their number ; for though they are mightily concerned for any of their young that are taken from them whilst they are in sight or hearing, yet if one or two of them be stolen from them in their absence, or without noise, they appear not to miss them, or to have any sense that their number is lessened." * This I believe to be the grand difference be- tween man and the lower creatures ; for if it can be shewn that the latter have any power by which to compare or to select the ideas they receive, they cannot differ from ourselves ; they must have a knowledge of good and evil ; they must be rea- soning and accountable beings. Now this is clearly not the case ; for notwithstanding the remarkable powers which they possess, animals are dull and foolish on all other subjects but those immediately affecting the preservation of themselves and their offspring. Whereas, if the perceptive powers made the difference between man and animals, as they indisputably do between the various grades of animals, man would be second to many of the * On the Human Understanding, vol. i. p. 119. 494 LETTER XV. lower creatures. That one animal displays a greater degree of instinctive power than others, is to be accounted for by the difference of its organi- sation, and its consequent higher position in the creation. As I have before remarked, both the organisation and the instincts of all animals are perfectly adapted to their spheres of action; and viewed in reference to those spheres, there can be neither inferiority nor superiority. There is no generic difference between the instincts of the most highly organised animal and those of the lowest sensitive creature. We in vain seek for any faculties in an oyster, such as many of those possessed by that useful and tractable animal the elephant; yet, as we have elsewhere shewn, an oyster will display as much appearance of reason as an elephant ; for it can protect its life against the operation of causes to which it is commonly, or in the course of ordinary circumstances, exposed : an elephant can do no more. Yet who will say that an oyster can rea- son? Many, however, maintain that an elephant does. Their mistake arises from inattention to the arrangement and degrees of animal organisation and instinctive development. Another faculty common to man and other animals, is memory. Without memory, no idea could be recalled, and a new impression would be necessary upon every occasion ; which would so hamper the perceptive and ideal powers, that LETTER XV. 495 animals, with the few ideas they possess, would be unable to acquire a knowledge of the objects which surround them, and which it is necessary they should be able to distinguish for their preservation and support. If an animal had every day to learn the qualities of its food, or the character of the beings with which it comes into contact, it would never advance beyond a day; it would be totally helpless, and soon perish for want of proper direc- tion. " The faculty of laying up and retaining the ideas that are brought into the mind, several other animals seem to have, to a great degree, as well as man. For, to pass by other instances, birds learning of tunes, and the endeavours one may observe in them to hit the notes right, put it past doubt with me that they have perception, and retain ideas in their memories, and use them for patterns. For it seems to me impossible that they should endeavour to conform their voices to notes, as it is plain they do, of which they had no ideas. For though I should grant sound may mechanically cause a certain motion of the animal spirits in the brains of those birds whilst the tune is actually playing, and that motion may be con- tinued on to the muscles of the wings, and so the bird be mechanically driven away by certain noises, because this may tend to the bird's preservation ; yet that can never be supposed a reason why it should cause mechanically, either whilst the tune was playing, much less after it is ceased, such a 496 LETTER XV. motion in the organs of the bird's voice as should conform it to the notes of a foreign sound, which imitation can be of no use to the bird's preserva- tion ; but, which is more, it cannot, with any appearance of reason, be supposed, much less proved, that birds, without sense and memory, can approach their notes nearer and nearer, by degrees, to a tune played yesterday, which, if they have no idea of in their memory, is now no where, nor can be a pattern for them to imitate, or which any repeated essays can bring them nearer to. Since there is no reason why the sound of a pipe should leave traces in their brains, which not at first, but by their after-endeavours, should produce the like sounds, and why the sounds they make themselves should not make traces which they should follow, as well as those of the pipe, it is impossible to conceive." * And again : " Dogs have at least a certain degree of memory. A dog is first taught by repeated trials to know something by a certain mark, and then to distinguish one ace from ano- ther ; they frequently offer him food on a card he is unacquainted with, after which they send him to find it out from the rest, and he never mistakes. The habit of profiting by that discovery, and re- ceiving caresses, enables him by degrees to grow acquainted with each particular card, and he brings them with an air of gaiety, and without confusion : and, in reality, it is no more surprising to see a * Locke on the Human Understanding, vol. i. p. 115. LETTER XV. 497 dog distinguish one card from thirty others, than it is to see him distinguish his master's door from the rest of the neighbourhood." * But memory is a faculty which operates differ- ently according to the constitution of every indi- vidual animal. It is distributed over every faculty and feeling which the animal possesses ; and ac- cording to the development of these faculties or feelings is the memory more or less acute. Thus, some animals have great caution, others great courage, and others, again, great firmness ; and the memory will be found most retentive of facts connected with whichever of these feelings is pre- dominant. It is in this way that many anecdotes of remarkable conduct in animals may be ex- plained. Witness the cunning and courage which they so frequently exhibit when their food or their safety is at stake. Yet how soon do they become dormant when the danger is removed or their hun- ger appeased. I have already noticed that the instincts of animals, and their various artifices, although in so many cases they assume a character resembling reason, are clearly referrible to, and dependent upon, the three inherent propensities of self-pre- servation or defence, self-support, and reproduc- tion. . On all these points we have clearly shewn that animals display an apparent inteUigence quite inconsistent with other parts of their conduct, * Wood's Zoology, vol. i, p, 166. K K 498 LETTER XV. which frequently bespeaks unconsciousness even of the existence of things. This seeming contra- diction is exphcable by the absence of that faculty which associates two or more ideas. If animals had the power to compare their ideas, and conse- quently to draw conclusions, they would doubtless employ this power to regulate their conduct, which would then differ in many respects from what it actually is. I shall now return to the consideration of the propensities or feelings by which animals are ac- tuated. And, first, of the feehng of attachment to offspring. This feeling exists in almost every degree of intensity : in some animals it overcomes every other feeling, inspiring the most timid with un- daunted courage, and the most dull with surprising sagacity and cunning ; while in others it is scarcely discoverable at all, or is altogether wanting.* Yet we shall find that all its modifications are in per- fect harmony with the habits, the dangers, and the localities peculiar to each animal ; and that the exact degree of strength is given to it in each, which is best fitted, under all the circumstances of its situation, to enable it to provide for its helpless young ; so that the degree possessed by one animal, * Of some kinds of animals, neither the male nor the female takes care of their oifspring, which is consigned to the uncon- trolled influence of external agents. This is the case with reptiles, fishes, and insects. LETTER XV. 499 and essential to the perpetuation of its species, would be destructive both of parent and offspring if given to creatures differently situated. Thus, all the varieties of this propensity display the wisdom and beneficence of God, and his power over the creatures of his hand. In proof of these assertions, I shall refer at considerable length to the ostrich and cuckoo, animals generally considered (though as to the former very erroneously) wholly destitute of the feeling of parental affection, and utterly neglectful of their young ; and shall shew that this propen- sity in them, and the conduct resulting from it, are admirably suited to the nature of their offspring, and to secure their existence and safety. The ostrich dwells in wide-spread wildernesses, where there is neither shelter nor place of conceal- ment ; and being incapable of flying, and of so large of size, she would, if she sat upon her eggs in the day-time, form an easy and conspicuous object of attack; and thus the safety of her offspring, as well as her own, would be endangered.* In her native deserts, moreover, the heat of the sun is amply sufficient to carry on the vivifying process ; and when the sun descends below the horizon, the ostrich returns to its nest, even the male taking a * It appears, however, that ostriches are sometimes observed even in the day-time seated upon their nests. This, it is probable, happens in wholly uninhabited districts. 500 LETTER XV. part in this duty, which is frequently wholly ne- glected by the male of other species. Most authors concur in stating that these birds possess a very strong affection for their young, and watch their eggs with the greatest assiduity ; nei- ther do they forsake their young after they are hatched, but expose themselves to danger for their protection. It is well known that the ancients were accustomed to plant a number of sharp stakes round the ostrich's nest in her absence, upon which she pierced herself on her return. The incorrectness of the popular opinion, that the ostrich entirely abandons its eggs after they are deposited in the sand, which has been sanc- tioned by Shaw and others, who have enjoyed the reputation of faithful naturalists, is conclusively proved by the following extract from the work of a recent traveller, which contains also a striking fact in the economy of this bird, — the use to which some of its eggs are applied. " On approaching the nest," says the Rev. Dr. Broadbent, " we saw the female ostrich sitting upon it ; and though she had been disturbed before by the Hottentot, she remained till we were very near, and then ran off at the report of two guns that were fired. The ground was sandy for several miles around, and covered with thinly scattered bushes. There lay a great number of loose ostrich feathers about the nest, which appeared to have LETTER XV. 501 come off the female while sitting, and she had the marked appearance which domestic fowls have at such periods. The eggs were forty-two in nmnber, including two that had been taken away, and were arranged with great apparent exactness. Sixteen were close together in the middle of the nest, and on these the ostrich was sitting when we arrived ; they were as many as she could cover. The re- maining twenty-six were placed very uniformly in a circle, about two or three feet from those in the middle. The eggs which were in the circle were found to be quite fresh, at which I expressed my surprise. The Hottentots informed me that these had been provided by the ostrich against the hatch- ing of those in the middle, when she would break them one after another, and give them to her young ones for food ;* and that by the time they were all disposed of in this manner, the young ostriches would be able to go abroad with their mother, and provide for themselves such things as the desert afforded." t In the whole range of natural history there is no more remarkable proof than this of the super- intending Wisdom which regulates all the pheno- * If this statement required corroboration, it would be found in the fact, that the embryo of all birds is nourished by the yolk, which gradually diminishes up to the period of hatching, and that the intestines of newly hatched birds contain some of the yolk, which serves to support them till they are able to digest more complicated substances. t Kay's Travels in CafFraria, p. 216. 502 LETTER XV. mena of nature, and adapts with such wonderful precision organisation to circumstances, and in- stinct to both. From this brief review of the feeling of attach- ment to offspring manifested by the ostrich, it is evident that in this bird, which is commonly repre- sented as careless of its young, that propensity exists in full force ; and that all its peculiarities, which so broadly distinguish it from that observed in other birds, are modifications of it essential to the well-being of both parent and offspring.* * The account here given of this bird would, at first sight, appear to be inconsistent with that contained in the book of Job ; but this inconsistency will, I think, disappear upon deeper investi- gation. It is probable that if the ostrich displayed its attachment towards its young in the way that most other animals do, it would not have been selected by the Almighty as a remarkable animal in this particular ; and it is still less probable that if it had been really neglectful of its young, it would have been brought before Job's attention as an instance of Divine wisdom and superintend- ence. If I might offer any opinion upon these passages in the book of Job, I should say that this description is founded upon, as it is certainly in accordance with, the apparent habits of the bird, without any reference to the rules of science or of experi- mental knowledge, in the same way as many other natural phe- nomena are spoken of in Scripture. Judging from mere casual observation, the ostrich is careless of her young ones as though they were not hers ; but this apparent carelessness is the very means by which its young are preserved from destruction. If, instead of forgetting " that the foot may crush them, or that the wild beast may break them," this bird, Hke most others, should express the greatest anxiety about them, she would probably be the means of their detection, and thus of their destruction. LETTER XV. 503 The cuckoo neither builds a nest nor hatches its eggs, but deposits the latter in the nests of other birds, and entirely abandons its young to their care. In the words of Mr. Swainson, cuckoos " fasten themselves, as it were, on the living- animal whose animal heat brings their young into life, whose food they alone live upon, and whose death would cause theirs during the period of in- fancy." Hence this bird has always been regarded as an example of want of affection for, and neglect of offspring, almost unparallelled. Yet I doubt not to be able to prove, that the conduct of the cuckoo is not less wisely adapted for the rearing and pre- servation of its young, than the more watchful and attentive care bestowed by other animals upon their offspring ; that, indeed, it is a more remarkable exemplification of design than is commonly ex- hibited. The young cuckoo is a most voracious animal, and is perhaps the largest insectivorous bird. It has been calculated that many thousands of insects are daily required to appease its hunger and main- tain its life. Being a soft-billed animal, and having therefore a membranous stomach, its food consists chiefly of maggots, spiders, flies, &c. ; but its insa- tiable appetite will tempt it to eat fruit, seeds, and other vegetable substances. The cuckoo in this country lays one, two, or three eggs ; in warmer climates, where insects are 504 LETTER XV. more abundant, the yellow and black-billed cuckoos lay four or five. Now, the cuckoo does not pair ; and it is evident that the female bird alone could not provide a sufficient quantity of food to support even two of its young ones ; and it may be doubted whether its utmost exertions are more than capable of sup- plying its own wants. This difficulty is overcome by the peculiar disposal of its eggs. The cuckoo, as I have already stated, deposits its eggs in the nests of various species of birds, generally placing one egg only in a nest.* It does not select the first nest it meets with, but inva- riably chooses those of birds whose food is of the same kind as its own.f The hedge-sparrow, more frequently than any other, is made the foster- parent. It is to be noticed also, that upon no bird is this office imposed whose young ones are not smaller than the young cuckoo ; the object of which preference will presently be pointed out. The intimate connexion between organisation and instinct is well shewn in the fact, that the size * We have no instance of more than one cuckoo having been reared in the same nest, though several authors have observed two eggs, in all v^^hich cases the stronger bird, when hatched, has succeeded in usurping the whole nest by the expulsion of the weaker. t Its eggs have been found in the nest of the wagtail, hedge- sparrow, titlark, white-throat, red-breast, yellow-hammer, green- linnet, and winchat, all which have membranous stomachs, hke the cuckoo, and consequently live on analogous food. LETTER XV. 505 of the cuckoo's egg is less than that of the hedge- sparrow, so that in proportion to the size of these respective birds, the egg of the former is six times smaller than that of the latter. This wonderful disproportion is probably designed to secure to the embryo cuckoo the services of the hedge-sparrow, or other foster-parent; for though a turkey will sit with the same ardour upon a shapeless piece of chalk as she would on one of her own eggs, we are by no means qualified to say that the propen- sity to incubate is so impetuous in all birds ; and the little birds to which the cuckoo consigns its offspring might be tempted to forsake their nests, were the intruder's egg as large in proportion to the size of the body of the bird which it produces as is usually the case. But it may be said, if the cuckoo is unable to provide for the subsistence of its young, how can smaller birds, which have to support their own, in some cases numerous, offspring, do so ? And but for a most wonderful instinct and appropriate organisation in the newly hatched cuckoo, it would undoubtedly, in the majority of cases, perish. The instinct to which I refer is the propensity to expel from the nest the eggs or young ones of the right- ful owner; and the organisation consists in the shape of the back, which is altogether peculiar to the young cuckoo. From the blade-bone down- wards, the back is very broad, with a considerable depression in the middle, which gives a secure 506 LETTER XV. lodgement to the egg or the young of the foster- bird, and thus facilitates their ejection from the nest. When the bird is about twelve days old, this cavity is quite filled up, and then its back resembles that of nestling-birds in general, — a very remarkable coincidence, that being the day on which the instinct for displacing the other occu- pants of the nest ceases to operate. * The following extract from Dr. Jenner's cele- brated paper gives a most interesting illustration of the propensity in question : — " A hedge-spar- row built her nest in a hawthorn-bush in a timber- yard. After she had laid her two eggs, a cuckoo dropped in a third. The sparrow continued laying as if nothing had happened, till she had laid five, her usual number, and then sat. On inspecting the nest, June 20, 1786, I found that the bird had hatched this morning, and that every thing but the young cuckoo was thrown out. Under the nest I found one of the young hedge-sparrows dead, and one egg by the side of the nest entangled in the coarse woody material that formed its outside covering. On examining the egg, I found one end of the shell a httle cracked, and could see that the sparrow it contained was yet alive. It was then * Jenner says, after the twelfth day it neither disturbs nest- ling or egg that may be placed with it, though before that time it would be restless and uneasy till it had accomplished this end. — (See his paper on the Cuckoo, in Philosophical Transactions, vol. Ixxviii. p. 119.) LETTER XV. 507 restored to the nest, but in a few minutes was thrown out. The egg being again suspended by the outside of the nest, was saved a second time from breaking. To see what would happen if the cuckoo was removed, I took out the cuckoo, and placed the egg containing the hedge-sparrow in the nest in its stead. The old birds during this time flew about the spot shewing signs of great anxiety ; but when I withdrew, they quickly came to the nest again. On looking into it in a quarter of an hour afterwards, I found the young one completely hatched, warm and lively. The hedge-sparrows were suffered to remain undisturbed with their new charge for three hours, during which time they paid every attention to it, when the cuckoo was again put into the nest. The old sparrows had been so much disturbed by these intrusions, that they for some time shewed an unwillingness to come to it; however, at length they came; and upon examining the nest again in a few minutes, I found the young sparrow was tumbled out. It was a second time restored, but experienced the same fate. From these experiments, and supposing, from the feeble appearance of the young cuckoo just disengaged from the shell, that it was utterly incapable of displacing either the egg or the young sparrow, I was induced to beheve that the old sparrows were the only agents in this seemingly unnatural business ; but I afterwards clearly per- 508 LETTER XV. ceived the cause of this strange phenomenon, by- discovering the young cuckoo in the act of dis- placing its fellow-nesthngs, as the following rela- tion will fully evince. June 18th, 1787. I ex- amined the nest of a hedge-sparrow, which then contained a cuckoo's and three hedge-sparrow's eggs. On inspecting it the day following, I found the bird had hatched, but that the nest now con- tained only a young cuckoo and one hedge-spar- row. The nest was placed so near the extremity of the hedge, that I could distinctly see what was going forwards in it ; and, to my astonishment, saw the young cuckoo, though so young, in the act of turning out the young hedge-sparrow. The mode of accomplishing this was very curious ; the little animal, with the assistance of its rump and wings, contrived to get the bird on its back, and making a lodgment for the burden by elevating its elbows, clambered backwards with it up the side of the nest till it reached the top, when, resting for a moment, it threw off its load with a jerk, and quite disengaged it from the nest. It remained in this situation for a short time, feeling about with the extremities of its wings, as if to be convinced that the business was properly executed, and then dropped into the nest again. With these, the extremities of its wings, I have often seen it ex- amine, as it were, an egg and nesthng before it begins its operations; and the nice sensibility which LETTER XV. 509 these parts appeared to possess seemed sufficiently to compensate for the want of sight, which as yet it was destitute of." The conduct of the cuckoo indicates very clearly the direct guidance of the Creator ; and its whole economy, as well as the instincts and struc- ture of its young above described, proves so ne- cessary a connexion between its organisation and propensities, that none but a prejudiced mind can fail to recognise the hand of a Being possessed of attributes infinitely superior to reason. The feeling of attachment to offspring is not often absent in both sexes. Thus, in some kinds of animals the female alone takes care of their pro- geny ; bulls, stallions, dogs, cocks, &c., are indif- ferent about their young ; while the cow, mare, bitch, and hen, are extremely attached to them. In other species the male and female form an attachment for life, and both sexes take care of their offspring; this instinct, however, being more energetic in the female. The fox, which so much resembles the dog, differs from it in this respect ; the male fox is attached to the female for life, par- takes of the same cares with her, and if she be killed, he seeks food for his young ones. Yet this pro- pensity is stronger in the female than in the male ; for if both be pursued, the male leaves the cubs sooner than the female. Many birds also are paired, both males and females taking care of their offspring. 510 LETTER XV. Another propensity, which exercises consider- able influence over many animals, is that of form- ing attachments with individuals of their own or other species. Most domesticated animals possess this propensity in a high degree, and all of them display it towards man. Manifestations of the latter kind are very frequent, and some of them are ex- ceedingly interesting.* The absence of such a feeling would be attended with the greatest evils to many animals, which are by means of it enabled to congregate for the purpose of mutual protec- * Wood mentions a very strong case. " Old Daniel, game- keeper to tlie Rev. Mr. Corsellis, had reared a spaniel, which became so fond of him as to be his constant attendant both by night and day. Whenever the gamekeeper appeared, Dash was never far distant; and in his noctm^nal excursions to detect poachers, this dog was of infinite use to him. At these times, the dog altogether neglected the game ; but if a strange foot had entered any of the coverts. Dash, by a different whine, informed his master that the enemy was abroad. Many poachers were caught and detected from this singular inteUigence. During the last stage of a consumption which carried his master to the grave. Dash unwearily attended the foot of his bed ; and when he died, the dog would not quit the body, but lay upon the bed by its side. It was with difficulty he was tempted to eat any food ; and although after the funeral he was taken to the house of Mr. Corsellis, and caressed with all the tenderness which so fond an attachment naturally excited, he took every opportunity to steal back to the room in the cottage where the gamekeeper breathed his last, and where he would remain for hours. From thence, for fourteen days, he constantly visited the grave ; at the end of which time he died, notwithstanding all the kindness and atten- tion that were shewn him." — Zoography, vol. i. p. 163. LETTER XV. 511 tion. The excessive strength of this feeling in some animals is a sufficient proof that it is a blind impulse wholly independent of reason. I will now speak of cunning, caution, or con- cealment. Some quality answering to this is essential to animals, to enable them to obtain food, or to protect the body. The fox is careful to avoid observation, and in taking its food displays this feeling ; cats, when watching birds and mice, move with the greatest caution. This instinct renders many timid and irresolute animals, as the stag, roe, otter, mole, exceedingly circumspect, and keeps them on the alert to avoid harm. Some animals, directed by it, place sentinels to warn them of approaching danger. The chamois, crane, starling, bustard, goose, and rook, are character- ised by this practice. This power also teaches animals the necessary arts for the protection of their young ; and it is very remarkable, that most birds which build their nests on the ground possess much cunning, which they employ to allure in- truders from their nests. Mr. Salmon does not think that this is the case with birds generally ;* but he mentions that the same cunning is dis- played in the black-headed bunting {emheriza schce- niculus), which shuffles through the rushes, and trails along the ground, as if one of her legs or wings was broken. It is observed also in the ring- plover (charadrius hiaticuld), and the golden plover * See Loudon's Magazine of Nat. Hist., vol. viii. p. 506. 512 LETTER XV. {charadrms pluvialis) ; also in the wild duck {anas hoschas). " A hen-partridge came out of a ditch, and ran along shivering with her wings, and crying out as if wounded and unable to get from us. While the dam acted this distress, the boy who attended me saw her brood, that was small and unable to fly, run for shelter into an old fox-earth under the bank : so wonderful a power is instinct !" * " It is not uncommon to see an old partridge feign itself wounded, and run along on the ground flut- tering and crying before a dog or man, to draw them away from its helpless unfledged young ones. I have seen it often ; and once in particular I wit- nessed a remarkable instance of the old bird's soli- citude to save its brood. As I was hunting with a young pointer, the dog ran on a brood of very small partridges ; the old bird cried, fluttered, and ran trembling along just before the dog's nose till she had drawn him to a considerable distance, when she took wing, and flew still farther off, but not out of the field. On this the dog returned to me, near the place the young ones lay concealed in the grass, which the old bird no sooner perceived than she flew back again to us, settled just before the dog's nose again, and, by rolling and tumbhng about, drew off his attention from her young, and thus preserved her brood a second time."f Many other animals manifest this propensity. * White's Selborne. f Markwick : quoted in Brown's edition of White's Selborne. LETTER XV. 513 A gentleman had a horse which he had often sus- pected of opening the corn-bin ; and to prevent further pilfering, a strong padlock was fastened to the lid. The animal soon found that the hinges presented the least resistance, and these it con- trived to loosen, and thus again got free access to the corn. No halters that had been devised could be kept upon the head of this animal — it always got loose. The propensity to construct is another instinct given to many animals, though it has been denied to others,* as we have lately seen in the cuckoo. It cannot be disputed that some such power as this is essential to the welfare and existence of many creatures. The rabbit, hamster, beaver, marmot, field-mouse, and most varieties of birds, are indebted to it for the protection they derive from their beau- tiful and ingenious dweUings. The fact that these animals exhibit, at certain fixed periods of the year, and only at those periods, a propensity to build houses for their young, is wholly inexplicable on any other supposition than that they are under the guidance of their Creator. When the genial temperature of the season draws forth the leaves, which both serve to defend or conceal the birds which dwell among them, and to support the innu- merable insects which are at this time called into * " The greater number of animals have no necessity nor pro- pensity to build ; so that this very curious instinct is also a very partial one." — Auernetuy's Reflections on Phrenolocjy, p. 15. L L 514 LETTER XV. life, and which supply abundant food for their young, then this wonderful phenomenon takes place. " How very curious it is," says Mr. Abernethy, " that, at certain seasons of the year, animals should be seized with a propensity to build nur- series for their young, and storehouses and habi- tations for themselves, without foreknowledge that they may be wanted for future inhabitants, or at future periods. Some birds begin to build before they procreate ; and the sterile labouring bees, in constructing a storehouse for their community, do not neglect to provide necessaries and accommo- dations for the young of the common parent of the hive. How very curious also are the struc- tures which many animals erect without previous plan or design, and, in some instances, without any communication with one another. How admirably suited also are these structures to exigencies un- foreseen by the artificers. Some hornets build the exterior of their nests with agglutinated leaves, and the interior cells with the same materials re- duced to the state of paste or mortar ; whilst the bees which build in hollow trees, requiring no pro- tecting walls, merely build a comb with plates of wax resembling tiles, which are prepared and formed between layers constructed for this purpose on the surface of their bodies." * It is not in the co?istniction alone of the dwel- lings of animals that a knowledge far beyond the * Reflections on Physiognomy and Phrenology. LETTER XV. 515 reach of their unaided capacities is displayed. The situations in which they are placed, and the innu- merable modifications which adapt them to all varieties of situation, indicate the interference of an Intelligence possessed of an intimate acquaint- ance with atmospheric phenomena, and with all natural agencies, as well as with all the other cir- cumstances, such as the habits of animals, neces- sary to be provided against, in order to render these habitations places of security for their inhabitants. This knowledge which the lower animals appear to possess, independently of experience, far exceeds any thing which reason can boast of. Let a man be taken into a distant country, with the nature of the climate of which he is wholly unacquainted, as well as with the animals which inhabit it ; then let him construct a dwelling ; and there is every chance that, with all the assistance which he can receive from his reasoning powers, this dwelling will be but very imperfectly adapted to these various cir- cumstances, and be far from furnishing complete defence against the dangers which surround him. How, then, can we suppose that the perfect con- trivances of the lower animals are produced by their own inherent and independent faculties ? Who taught the Indian birds to construct their nests in such an intricate manner, or to place them in such situations as will preserve them from harm while surrounded by their most deadly ene- 516 LETTER XV. mies?* Who directs the moor-hen, and other aquatic birds which build in rushes, to erect a second habitation at a higher elevation, that in case the floods or the tide should overtake them in the one, there may be another to resort to ? Who told the little tailor-bird that there is no safety for its offspring but in suspending its nest, not from a twig, as many of the smaller birds in hot climates do, but from a leaf, its usual attach- ment ?f These are cases obviously indicative of design ; but it is only necessary that we investigate the less complicated contrivances, to be assured * " The birds of India are obliged to resort to unusual artifices for placing their little broods out of the reach of invaders. Each aims at the same end, though by different means. Some form their pensile nests in the shape of a purse, deep and open at top ; others with a hole in the side ; others, still more cautious, with an entrance at the very bottom, forming their lodge at the sum- mit."— Pennant's Indian Zoology, p. 46. " The banana bird, so called from its fondness for that fruit, builds its nest nearly a yard in height, of a conical form, com- posed mostly of grass, with an opening half-way down for its entrance. The bottom is semi-globular, with the upper narrowest part fastened to the extremity of a branch that overhangs the water, in order to secure its inmate and brood from lizards and other reptiles." — Martin's British Colonies, vol. ii. p. 96. t " The motacilla sutoria, or tailor-bird, will not trust its nest even to the extremity of a slender twig, but secures its safety still more completely by fixing it to the leaf itself. It picks up a dead leaf and sews it to the side of a living one, its slender beak being its needle, and its thread some fine fibres ; the lining is thread, gossamer, and down." — Pennant's Indian Zoology, p 46. LETTER XV. 517 that these also are equally fitted for their situa- tions, equally proofs of a higher power than even reason. But the manifestations of this propensity in the beaver bear a closer resemblance to reflection than perhaps in any other animal. In order to facilitate the procuring of their food, which consists of fish and the branches and roots of trees growing near the water, these animals build their houses and reside chiefly on rivers or ponds. If on a running stream, they construct a dam to keep off" the force of the cur- rent ; but if the water is still, this is never done. Likewise in felling the trees for constructing these dams, the beaver always chooses those which are nearest the water, and cuts them with its teeth in such a manner that they fall into the stream, which readily floats them to the place where they are wanted. " Admitting that man, like animals, possesses in various degrees a natural propensity and talent for construction, yet no blind impulse regulates his labours ; he constructs what his rea- son directs or his fancy suggests ; he forms previous plans or designs, and alters them till the whole seems to accord with his intentions ; and yet none of his works is so unalterably perfect as are those produced by blind instinct operating according to the ordinances of over-ruling Intelligence."* Imitation is a propensity so powerful in some animals as to urge them to actions highly amusing, * Reflections on Physiognomy and Phrenology. 518 LETTER XV. on account of their resemblance to those of man. In some cases it is so strong, that the memory in this direction becomes very retentive. I do not think, with some, that imitation is essential to enable animals to acquire their different natural languages and habits, although it must assist them very much in their intercourse with one another. Monkeys and dogs possess this power in an emi- nent degree. The conformation of the bodies of the former approaching so closely to that of man, greatly assists its manifestation in them. BufFon relates many interesting accounts of the conduct of monkeys illustrative of their imitative powers. Some birds possess this faculty in so high a degree, as to be able to produce artificial tunes. This is the case with the bulfinch and the parrot. The famous parrot which Colonel O'Kelly pur- chased at Bristol had an accurate ear for music, and would beat time while it whistled a tune ; and if by chance it mistook a note, it would return to the bar where the mistake was made, and, still beating regular time, would finish the tune with wonderful accuracy. But the power of imitation is most developed in a bird which takes its name from this circumstance, and is called the mocking- bird. It is larger than a starling, and of a black and yellow colour. It delights to take up its abode near the habitation of man. Martin says its note is sweet and short; but if a sheep bleats, a dog barks, or a hen cackles in its hearing, it stops its LETTER XV, 519 own note, and instantly commences, with apparent delight, an extraordinarily close imitation of the animal it hears. Imitation is of great use to animals in obtaining food or avoiding harm. No thought is required to put this power in operation. Many animals, con- stantly observing man's actions, would be able, by means of imitation, to do what he does, if they had the same instruments. Who has not seen a favourite dog or cat watching, and even touching, the handle of the door when it wishes to be let out of the room in which it is confined ? The fact that man always touches the handle previous to open- ing the door leads these animals to do the same.* * A remarkable case of this kind is quoted of a dog obtaining food by ringing a bell. At a convent in France, twenty paupers were served with a dinner at a certain hour in the day. A dog belonging to the convent did not fail to be present at this regale, to receive the odds and ends which were now and then thrown down to him. The guests, however, were poor and hungry, and of course not very wasteful ; so that their pensioner did little more than scent the feast, of which he would fain have partaken. The portions were served by a person at the ringing of a bell, and dehvered out by means of what in a rehgious house is called a tour, which is a machine like the section of a cask, that, by turning round upon a pivot, exhibits whatever is placed upon the converse side with- out discovering the person who moves it. One day this dog, which had only received a few scraps, waited till the paupers were all gone, took the rope in his mouth, and rung the bell. This stratagem succeeded. He repeated it the next day with the same good fortune. At length, the cook, finding that twenty-one portions w^ere gone out instead of twenty, was determined to discover the trick ; in doing which he had no great difficulty ; for ly'ia^ perdu, and noticing the 520 LETTER XV. Locality, or the faculty of finding and recog- nising places, is another power inherent in ani- mals, without the assistance afforded them by which they could not even exist. They could neither find their dwellings, their offspring, nor their food, having once quitted them, unless they were able to distinguish the places in which they were left. This would not fail to be the case were the objects quitted within even a short distance; and therefore the possession by animals of some such faculty is sufficiently proved by the well- authenticated accounts, which are so frequent in works on natural history, of the return of many animals from distant countries to the place whence they had been taken, surmounting difficulties which would seem to be insuperable. The readiness with which dogs distinguish their masters' houses from neighbouring ones is merely an inferior manifesta- tion of this power, and may be explained without supposing any exertion of intelligence. This faculty is very active in some animals ; and, hke other powers, it varies in individuals of paupers as they came, in great regularity, for their different por- tions, that there was no intruder except the dog, he began to sus- pect the real truth, which he was confirmed in when he saw him wait, with great deliberation, till the visitors were all gone, and then pull the bell. The matter was related to the community ; and to reward him for his ingenuity, he was permitted to ring every day for his dinner, when a mess of broken victuals was purposely served out to him.— Quoted in Wood's Zoographi/ , from Dibdin's Observations in a Tour throucjh England. LETTER XV. 521 the same species. Some possess it to an extra- ordinary degree^ while others appear completely destitute of it. By it, appropriate organisation being superadded, animals are enabled to live in particular spots. As I have shewn, in my Letter on the adaptation of animals to their various sta- tions, there can be little doubt that particular re- gions have been set apart for their habitations, to which they are attached, not only by the circum- stances of climate, food, &c., but also by the propensity we are at present considering, which in many cases operates so as to impel them, at certain stated periods, to quit one country, and resort to another far distant land, in alternate suc- cession. In proof of the influence of this propen- sity, I may mention, that turtlers affirm that if a turtle be transported many hundred miles from its usual abode, and again liberated in the ocean, it will return to its former place of habitation. Pigeons conveyed to great distances in close cages, so as to be unable to observe the distinguishing features of the country through which they pass, are capable of finding their way back to the spot from which they were taken. By this power animals in the earliest stages of their existence are impelled to seek their natural element. Thus, turtles and ducks, for example, need no monitor to direct them to the water as soon as they are hatched. And it is this power, also, which causes the various tribes of birds to choose 522 LETTER XV. different elevations and localities for building their nests : some in rocks, some in the tops of trees, some in their trunks, some in their roots. It is not generally known that there are several species of rats, each of which hves in a different locahty ; one species Hves always in cellars and ditches, an- other in the higher parts of houses and upon high ground. The operation of this power is further exemphfied in the choice of situation made by the chamois, the ptarmigan,* and many other animals. When this faculty predominates very much, it gives rise to conduct almost surpassing belief A dog was transported in a carriage from Vienna to Petersburg ; six months afterwards it returned to Vienna. Another dog was transported from Vienna to London, and found its way back by attaching itself to a traveller in the packet-boat.f Jesse mentions the circumstance of a dog finding its way from London to Scotland, and another from * •' The habits of this bird are well known ; but they cannot fail to strike every one who observes them as an instance of the adap- tation of animal life to peculiar and unpromising locahties. Closely resembling as they do the grouse, they seem to abhor the heather, in which the latter delights ; and in no instance did I find a single bird of the species within the verge of that vegetation. It is only where the bare grey rock juts out of the earth that they are to be found ; and no painter could imitate more accurately the general hue of the rock than does the summer plumage of its resident, which, as we all know, in winter, Uke the coat of the mountain- hare, becomes as white as the snow it then inhabits."— ^w^r/er'^ Rambles, by Edward Jesse, p. 261. t Spurzheim's Phrenology. LETTER XV. 523 America to England ; also of an ass that found its way from the Point de Gat to Gibraltar, though it had been conveyed thither by ship.* This faculty also explains the wonderful phe- nomenon of migration, which has puzzled so many learned naturalists. At different periods of the year, directly after the summer solstice has passed, we observe a variety of birds beginning to prepare for their departure from this to other countries, many thousand miles distant. It has been well ascertained that, in many instances, they leave our country for a more temperate and uniform climate. It is by no means certain, however, that all birds have this object in migrating from one country to another. The cuckoo visits us first in April, when our climate is cold and unequal, and leaves us the first week in July. Judging from the various pe- riods at which migratory birds arrive and depart, it would seem that certain of them are appointed to change their habitations at fixed seasons, in order to keep up the due equilibrium of life in the differ- ent countries which they frequent. For this pur- pose, they are endowed with the power of trans- porting themselves from one region to another widely distant. When the purpose for the attain- ment of which they were conveyed to one country has been fulfilled, they instinctively seek another, regardless of all opposing difficulties. The chief object accomplished by the migra- * Second and Third Series of Gleanings in Natural History, 524 LETTER XV. tion of birds appears to be the destruction of innu- merable myriads of insects and worms of all sorts, which, but for this check to their multiplication, would increase to so awful an extent, as to threaten the earth with famine and desolation. He who cannot perceive the hand of God in this wise and merciful arrangement must be blind indeed. We need no longer marvel, then, to see the little swal- low or the house-marten return to our land with such faithful exactness : and not only to the same country, but to the same place, the same window, or the same hole ; for we know that the power by which they are guided is given to them by their Creator, and that it is his hand which directs their movements. It is well known that birds kept in a cage, though fed with an abundance of food, become restless at the period at which they would, if at liberty, migrate ; an indication that the propensity to transport their bodies to some other clime is not attributable to external causes alone — such as food, temperature, and the like — but is an innate feeling given to them by their Maker. The power of self-defence, and the propensity to destroy, which is closely connected with it, are possessed by all animals in a greater or less degree. Some animals are defenceless and timid, others courageous and destructive ; and the distribution of the various shades of this, as well as of all the other propensities, being in perfect harmony with LETTER XV. 525 the rest of the economy of animals, furnishes an- other proof of omniscient superintendence in the creation. In the herbivorous animals this instinct is generally but imperfectly developed, while in the carnivorous it is the most energetic. Some ani- mals kill only those creatures which they require for their support ; others, such as the hyagna, pole- cat, tiger, &c., kill every thing around them, without any apparent object. Different individuals of the same species possess this power in various degrees of strength : it is most variable in man. In some of the smaller animals it is developed to an extra- ordinary extent. The hamster is actuated by it so strongly, that it attacks every animal that comes in its way, without any regard to its size. It will suffer itself to be killed rather than yield ; it will fly at a horse that happens to come too near it, and hang by its nose so firmly as not to be dis- engaged without the greatest difficulty. This fe- rocious temper will not allow the hamster to live in peace with any other animal. Two hamsters will attack each other with the utmost fierceness, and generally fight till one of them is killed. Besides those which I have enumerated, there are other powers inherent in animals, all of which act in conjunction, and so produce the various cha- racters which animals display. My object in speak- ing of the most conspicuous has been more to prove their existence independently of the rational faculty, than to give a systematic description of them. 526 LETTER XV. Before I conclude this Letter, I must remark, that the curious and artful plans of animals are rendered nugatory and unnecessary, and their various propensities and feelings are suspended or changed, by domesticity and human intercourse. If we require proof of this, we need only compare the difference between wild and tame individuals of the same species. Even their organisation is changed; and if so, why should the feelings and propensities remain unaltered, especially as there is, as we have seen, so intimate a connexion be- tween organisation and instinct ? It is very certain, that though innate, they do not remain unaltered, but that they are modified by the circumstances under which the animal is placed. The proofs of this operation are decisive. " When man," says Lyell, '' uses force or stratagem against wild ani- mals, the persecuted race soon becomes more cautious, watchful, and cunning — new instincts seem often to be developed, and to become here- ditary in the first two or three generations ; but let the skill and address of man increase, however gradually, no further variation can take place, no new quahties are elicited by the increasing dangers. The alteration of the habits of the species has reached a point beyond which no ulterior modifi- cation is possible, however indefinite the lapse of ao-es during which the new circumstances operate. Extirpation then follows. It is undoubtedly true, that many new habits and qualities have not only LETTER XV. 527 been acquired in recent times in certain races of dogs, but have been transmitted to their offspring. But in these cases, it will be observed that the new peculiarities have an intimate relation to the habits of the animal in a wild state, and therefore do not attest any tendency to departure to an in- definite extent from the original type of the species. A race of dogs employed for hunting deer in the platform of Santa Fe, in Mexico, affords a beau- tiful illustration of a new hereditary instinct. The mode of attack, observes M. Roulen, which they employ, consists in seizing the animal by the belly, and overturning it by a sudden effort, taking ad- vantage of the moment when the body of the deer rests only upon the fore legs. The weight of the animal thus thrown over is often six times that of its antagonist. The dog of pure breed inherits a disposition to this kind of chase, and never attacks a deer from before while running. Even should the deer, not perceiving him, come directly upon him, the dog steps aside and makes his assault on the flank, whereas other hunting-dogs, though of superior strength and general sagacity, which are brought from Europe, are destitute of this instinct. For want of similar precautions, they are often killed by the deer on the spot, the vertebrae of their neck being dislocated by the violence of the shock." * It has been said, that the lower animals can * Lyell's Geology, vol. ii. p. 409. 528 LETTER XV. form some idea of time, and that they have been known to recognise the day of rest from those of work ; but there is no ground whatever for beUev- ing that they have any conception of time resem- bhng that which man forms. The idea expressed by the word time is so complex, that it can hardly be believed that irrational creatures have any con- ception whatever of it. Locke (vol. i. p, 142) says, ** It is to me very clear that men derive their ideas of duration (or time) from their reflection on the train of the ideas they observe to succeed one another in their own understandings, without which observa- tion they can have no notion of duration, whatever may happen in the world." With this statement Mill, in his Analysis, substantially agrees (vide vol. ii. p. 118). The actions which may be thought to indicate a power of measuring time in the lower animals may be more satisfactorily accounted for by referring them to mere sensation — that of hunger, for ex- ample, or of light ; the latter exemplified in the crowing of the cock at dawn of day. The exercise of the powers which are common to man and the lower animals must in both cases produce similar results, modified only by reason and by differences of organisation. CONCLUSION. I HAVE now completed the task which I have un- dertaken, of setting forth the physical evidence furnished by the living creation, of the power and wisdom of the One God. Whether this evidence contradicts or confirms the declarations of revela- tion, I think there can be no difficulty in determining. But let me ask, can such striking manifestations of the Creator's protective superintendence be viewed without any thought that some purpose was de- signed in unfolding to our senses so much that calls up our wonder and admiration ? Could it be the design of that Being by whom we are so fearfully and wonderfully made, to bring before our minds such clear and unquestionable proofs of his exist- ence and power, for no other purpose than that of exciting our natural feelings ? " Has he," to use the words of Sumner, " revealed no commands, and prescribed no worship to the human race ? Then he remains the inactive deity of philoso- phic theism ; the indifferent spectator of the crimes and the virtues, the cares and the sorrows of mankind." By such arguments as I have been enabled to adduce, I trust I have proved the identity and imity of the Being who has manifested such won- derful power with the Being who has revealed to us MM 530 CONCLUSION. his infinite love ; of the Being who has wrought us with his hand with the Being who has redeemed us by his blood. This is the great truth, to the establishment of which the philosopher of nature is bound to direct all his arguments. It is the only rational inference that can be drawn from the science of natural theology, and consequently the only useful purpose to which that science can be applied. The contemplation of the fact, that God begat man " by the word of truth, that we should be a kind of first-fruits of his creatures," should excite us to love and venerate that wonderful Being, who, instead of placing us upon a level with the other creatures which he has formed, hath made us but a little lower than the angels, and dignified us with reasoning faculties, by which we are enabled to comprehend so much of his power in our present state of existence. What, then, must be the rap- tures of the renewed soul contemplating the decla- ration of the same Being, that " eye hath not seen nor ear heard, neither have entered into the heart of man, the things which God hath prepared for them that love him !" FJLAli^ 1. Fiff. 1. PLATE II. Fig. 1. ABC Fig. 4. PLATE III. (A.) Fig. 1. Fig. 2. PLATE III. (B.) Fig. 3. Fij?. 4. PLATE IV. (A.) Fig. 1. Fig. 2. PLATE IV. (B.) Fig. 3. Fig. 2. Fig. 3. Fig. 4. EXPLANATION OF THE PLATES. PLATE I. Fig. 1. view of the interior of the human body in situ (from Cheselden). 1. the trachea or winpdpie. 2 2. external jugular veins. 3 3. subclavian veins. 4. vena cava superior. 5. the right side of the heart. 6. the left side of the heart. 7. the apex of the heart. 8. the artery leading from the left side of the heart, called the ascending aorta. 10. the right lung. 11. the left lung. 12. the diaphragm, which is a muscle dividing the chest from the abdomen. 13. the right lobe of the liver. 14. the small lobe of the liver, 15. the gall-bladder. 16. the stomach. 17. the intestines. 18. the left lobe of the liver. Fig. 2. the tricuspid valves of the right ventricle of the heart (from Mayo's Physiology). A. shews the valves open for the transmission of the blood. B. the same valve closed. Fig. 3. the semilunar valves (from the same). A. the vessel cut open. B. a transverse section of the vessel below the valves, shewing them closed- Fig. 4. (from a Dkawing by Professor Owen.) A. a single plait of the gills of a fish, shewing the way in which the blood penetrates them. B. a number of plaits, forming together a fold. PLATE IL Fig. 1. a lymphatic heart magnified (yrom Baly's Transla- tion o/'Muller's Physiology), a. the vein. b. the cavity of the heart, c. a muscular band, four of which run across the cavity, and communicate with three lymphatic vessels, one of which is seen at d., and with two veins at e. By the dilatation and con- traction of this heart, the lymph is pumped into the vein at a. Fig. 2. ABC. nervous cords of the lower animals (from Carus' Comparative Anatomy). 12 3 4, &c. the nervous centres. Fig. 3. stomach of a hamster (from the same), a. the intes- 546 EXPLANATION OF THE PLATES. tine, b. the lower or pyloric orifice, c. the lower half of the stomach, d. a blind cavity, e. the upper half of the stomach, f. the superior orifice of the stomach, leading from the mouth. Fig. 4. back part of the eye of a bird, shewing the quadratus and pyramidal muscles {from a Drawing by Professor Owen). a a a a. oblique and straight muscles of the eye. b. the quadratus. c. the pyramidalis, the tendon of w^hich passes through a groove in the quadratus. d. the optic nerve. PLATE III. (A.) Fig. 1. the stomach of a lion, shewing the ramification of the blood-vessels upon its surface {from the Original in the Royal College of Surgeons). A. the cardiac orifice. B. the pylorus. Fig. 2. a posterior view of the first cavity of the camel's sto- mach unopened, and an internal view of the second, third, and fourth cavities, in their relative situation to the first {from Sir E. Home's Lectures on Comparative Anatomy). A. the oesophagus. B B. the coats of the first cavity in a distended state. C. the communication between the first and second cavity. D D. the muscle running along the upper part of the latter to terminate in the orifice of the third cavity. This muscle, when it acts with its greatest force, brings forward the orifice of the third cavity nearly close to that of the second, and shuts up the cells, so that no part of the solid food can pass into them. E E. the rows of cells M^hich form a reservoir for water. F. the open- ing leading into the third cavity of the stomach. G. the third cavity. H. the orifi^ce of the fourth cavity. I L the longitudinal plica of the fourth cavity. K K. the rugous structure of the lower parts of the fourth cavity. L. the glandular projection opposed to the orifice of the pylorus. M. the pylorus. N. a dila- tation or membraneous cavity between the pylorus and duodenum. O. the duodenum. PLATE III. (B.) Fig. 3. an internal view of the first cavity of the camel's sto- mach {from Sir E. Home's Lectures on Comparative Ana- tomy). In this cavity there are two compartments, separated from each other by a longitudinal ridge, which is composed of strong muscular fibres. The orifice leading into the second cavity EXPLANyVTION OF THE PLATES. 547 is distinctly seen. There is a strong muscle passing from the orifice of the first cavity through the upper part of the second to the third, where it terminates. This muscle and the longitudinal ridge form two sides of a canal, along which the ruminated food passes into the third, and hence into the fourth cavity, in which digestion, properly so called, commences. A. the oesophagus. B B. the longitudinal ridge dividing the cavity into two compart- ments. C C. the muscle which passes into the third cavity. D. the opening into the second cavity. E E. the muscular cells on the right side of the cavity. F F. the larger cells on the left side, which contain water to moisten the food lying over them, and make it of a fit consistence to be regurgitated into the mouth along the canal formed by the longitudinal ridge and the muscle going to the third cavity. G G. a broad mtiscular band, sepa- rating the cellular structure into two portions. Fig. 4. a longitudinal section of the first cavity of the bul- lock's stomach, which consists of two compartments, separated from each other by two strong transverse ridges, composed of ligamentous and muscular fibres ; also shewing the opening into the second cavity, a part of that cavity, the orifice leading to the third, and the canal through which the food is thrown up from the second cavity into the mouth, to be again masticated before it is conveyed into the third {from Sir E. Home's Comparative Anatomy). A. the oesophagus, terminating in the first cavity of the stomach. B B B B. the cavity itself exposed. C C. the two ridges dividing it into two compartments. D D. the orifice of the second cavity. E. the passage leading to the third cavity. F F. two muscular bands which have their origin in the coats of the first cavity, and terminate in the orifice of the third ; forming a canal along which the food is conveyed from the second cavity to the mouth, and from the mouth to the third cavity. PLATE IV. (A.) Fig. 1. a posterior view of the first and second cavities of the bullock's stomach unopened, and an internal view of the third and fourth, in their natural relative situation to the others {from Home's Comparative Anatomy). A. the rosophagus. B B. coats of the first cavity in a distended state. C. coats of the second cavity. D. orifice leading into the third cavity. E E. the plica of diflferent breadths which are contained in the third cavity. 548 EXPLANATION OF THE PLATES. F. the vascular termination of the third cavity in the fourth. G G G. the longitudinal plica of the fourth cavity. H. the rugae of the fourth cavity near the pylorus. I. the glandular projec- tion opposed to the orifice of the pylorus. K. the pylorus or ter- mination of the fourth cavity. Fig 2. A. the beaver's stomach in an inverted state, to shew its shape, and the appearance of its internal membrane, a. the oesophagus, b b. the cardiac portion, c. the glandular struc- ture peculiar to this stomach, which appears to be a cluster of gastric glands, d. the contraction between the cardiac and pyloric portion, e. the pyloric portion, f. a glandular zone at the pylorus, g. the duodenum. B. the orifices of the glandular structure, shewing how much they admit of being dilated, and the three internal openings leading into the substance of the gland, which become visible when the gland is dilated, a, the oesophagus, b b. the three ridges of glandular structure. C. the processes which belong to two of the three internal openings of the gland. PLATE IV. (B.) Fig. 3. stomach of the semnopithecus entellus, exhibiting its elaborate form {from the Original in the Royal College of SuRGEONs). A. the upper portion of the stomach. B. the pyloric end. Fig. 4. legs of the antelope and rein-deer, shevnngthe lateral toes and their comparative use {from Sir C. Bell on the Hand). A. leg of the antelope. B. leg of the rein-deer. a. lateral toes of antelope, b. lateral toes of rein-deer. PLATE V. Fig. 1. section of the human eye, displaying the relative situa- tion of the internal parts {from a Drawing by Professor Owen). a. the optic nerve, b. the vitreous humour, c. the crystalline lens. d. the aqueous humour, e. the cornea, f. sclerotic coat, g. pigmentum nigrum. Fig. 2. Cervical vertebrae in birds, shewing the manner in which one vertebra fits into another {from a Drawing by Pro- fessor Owen). Fig. 3. a section of the heart of a swan, to shew the strong muscular fold by which great additional impulse is given to the EXPLANATION OF THE PLATES. 549 flow of blood through the lungs, which is a means designed to compensate for the loss of the contractile power of these organs {from the Cyclopedia q/" Anatomy and Physiology). K. the right ventricle. O. the left ventricle. 1. the strong muscular fold, nearly as thick as the walls of the ventricle itself, n n. the pulmonary artery divided into two branches, one for each lung, n. the passage leading into the pulmonary artery. 1 1. two arterise innominatae, to convey the blood to the head and wings, s. the aorta, to convey the blood over the other parts of the body. Fig. 4. the human stomach {from a Preparation in ^AeRoYAL College of Surgeons), shewing its shape, and the position of the upper and lower orifices. A. the cardia. B. the pylorus. THE END. LONDON : PRINTED BY LEVEY, IIOBSON, AND FRANKLYN, 4C St. Martin's Lane. 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