UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN BOOKSTACKS The person charging this material is re- sponsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. To renew call Telephone Center, 333-8400 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN e Qn 1 eas |e) m * 4 S 2A 7 8 i i st, ) & 3 alt 1993 MA L161—O-1096 Digitized by the Internet Archive in 2021 with funding from University of Illinois Urbana-Champaign https://archive.org/details/sensesintellectOObain_0O THE SENSES THE INTELLECT. 1 BY ALEXANDER BAIN, M.A., PROFESSOR OF LOGIC IN THE UNIVERSITY OF ABERDEEN, I : : THIRD EDITION. LONDON: LONGMANS, GREEN, AND CO. 1868. ea Cm eh 85. 7 STEREOTYPED AND PRINTED BY ARTHUR KING AND COMPANY, ABERDLEN, Nee he { ie PREFACE. ue object of this treatise is to give a full and systematic account of two principal divisions of the science of mind,—the Senses and the Intellect. The remaining two divisions, comprising the Emotions and the Will, will be the subject of a future treatise. While endeavouring to present in a methodical form all the important facts and doctrines bearing upon mind, considered as a branch of science, I have seen reason to adopt some new views, and to depart, in a few instances, from the most usual arrangement of the topics. | Conceiving that the time has now come when many of the striking discoveries of Physiologists * relative to the nervous system should find a recog- -nized place in the Science of Mind, I have devoted \. a separate chapter to the Physiology of the Brain “* and Nerves. . In treating of the Senses, besides recognizing the ~. so-called muscular sense as distinct from the five ~ senses, I have thought proper to assign to Movement and the feelings of Movement a position preceding 2 the Sensations of the senses; and have endeavoured yto prove that the exercise of active energy, origi- “nating in purely internal impulses, independent of os y $2 %Z ne Pd lv PREFACE. the stimulus produced by outward impressions, is a primary fact of our constitution. Among the Senses have been here enroiled and described with some degree of minuteness, the feelings connected with the various processes of organic life,— Digestion, Respiration, &c.—which make up so large a part of individual happiness and misery. A systematic plan has been introduced into the description of the conscious states in general, so as to enable them to be compared and classified with more precision than heretofore. However imperfect may be the first attempt to construct a Natural History of the Feelings, upon the basis of a uniform descriptive method, the subject of Mind cannot attain a high scientific character until some progress has been made towards the accomplishment of this object. In the department of the Senses, the Instincts, or primitive endowments of our mental constitution, are fully considered; and in endeavouring to arrive at the original foundation, or first rudiments, of Volition, a theory of this portion of the mind has been sug- gested. In treating of the Intellect, the subdivision into faculties is abandoned. The exposition proceeds entirely on the Laws of Association, which are ex- exemplified with minute detail, and followed out into a variety of applications. | —_—— ae, Lonpon, June, 1855. PREFACE TO THE SECOND EDITION. d Nie edition has been thoroughly revised, and in many places re-written. Although I have not seen reason to change any of my leading views on the subject of mind, I hope I may have succeeded in improving the statement and exposition of them. It is in the first part of the work where most alteration has been made. The explanations of the Nervous system and the Senses have been amended according to the best recent authorities on Physi- ology. The Definition of Mind has been somewhat differently expressed.. The systematic plan of de- scribing the Feelings has been modified, and all the detailed descriptions re-cast. An attempt has been made to generalize the Physical accompaniments of Pleasure and Pain. The Instinctive foundations of Volition are stated more explicitly. In the second part, the Introduction to the Intel- lect has been revised, with a view to rendering as precise as possible the natural subdivisions of this portion of the mind. The doctrine referring to the physical seat of revived impressions has been discussed anew, and applied to clear up the difficulties attending the explanation of Sympathy. The associating prin- ciple of Contrast has, on farther consideration, been V1 PREFACE. treated as the reproductive aspect of Discrimination, or Relativity. The origin of our notions of Space and Time has been more minutely traced; and some additions have been made to the handling of the great Metaphysical problem, relating to the External World. ABERDEEN, February, 1864. PREFACE TO THE THIRD EDITION. N this third edition, the work has again been sub- jected to a thorough revision, involving numerous amendments both in matter and in style. The sketch of the Nervous System, and the Physio- logical references generally, have been compared with the statements given in the newest works. The Reflex Actions, illustrating the Will, by contrast and by re- semblance, are more fully and systematically discussed. In the Intellect, the fundamental conditions, both of Retentiveness and of Similarity, have been set forth with greater precision; whereby clearness is gained in following out the details of those great leading functions. | The value of the work is greatly enhanced by an account of the Psychology of Aristotle, which has been contributed by Mr. Grote. The chief significance of Aristotle’s views, at the present day, lies in his recog- nizing, in an almost unqualified manner, the double- sidedness of the mental states. ABERDEEN, September, 1868. . TABLE OF CONTENTS. INTRODUCTION. CHAPTER I. DEFINITION AND DIVISIONS OF MIND. 1. Mind opposed to the Extended 2. Mind has three properties,—Feeling, Wolnion: Thought 3. Elucidation of these properties ‘ : 4, Classifications of Mind.—Understanding a ‘Will; Thteilotnal Powers and Active Powers; Brown’s division ; Hamilton’s; Dr. Sharpey’s ea : 5. Plan of the present volume we ae aA 6. Statement of the fundamental law of Relativity re os GHA RPE Re IT. THE NERVOUS SYSTEM. 1. Connexion of mental processes with bodily organs .. ae 2. Proofs that the Brain is the principal organ of Mind i. Connexion of size of brain with mental energy a oe 3. Parts of the NERVOUS SYSTEM Ye we ar se THE NERVOUS SUBSTANCE. 4, Nervous substance of two kinds, white and grey Nerve jidres and nerve vesicles THE NERVOUS CENTRES. . Enumeration of parts of the Cerebro-spinal eentre . Detailed description ‘rc (1.) The Medulla Oblongata ie re oe a (2.) The Pons Varolt ss ‘F “e ve Pace. ab. oO 10 4b, 1b. 13 tb. 1b. 17 19 tb. 20 Vill CONTENTS, — eo se (3.) The Cerebrum “ Ay os ve Cerebral Hemispheres fe ae ws Smaller masses of the cerebrum he + (4.) The Cerebellum ee oe ve ve 7. Internal Structure of the Brain .. ne “5 White part of the Brain ° es te Three systems of fibres “eA we we Grey matter of the brain ? re oe 8. Plan of Structure indicated by the arrangement of white and grey substance : Ay AL Note on the Bympatnies Siem oe 6 THE CEREBRO-SPINAL NERVES. 9. Nature of the ramifying nerve cords 4 oe FUNCTIONS OF THE NERVOUS SYSTEM. Functions of the Nerves 10. Division into Spinal and Cerebral Nerves .v ap Anterior and posterior roots of Spinal Nerves ra il. The Function of a nerve isto transmit influence fe 12. Sentient and Motor roots of spinal nerves .. a 13. Cerebral Nerves 56 hy 3 Functions of the Spinal Cord and Meduila Oblongata. 14. Spinal Cord nt : ie a Necessary to sensation nnd moverant | in the trunk and extremi- ties of the body ae Ae 43 A centre of Movements not i os oe Tonicity of the Muscles .. e oe “s 15. Medulla Oblongata we ar oe a Functions of the lesser grey centres of the Brain. 16. Pons Varolit KS 4: Ye ws ud Rotatory movements caused by injuries of parts of the brain 17. Corpora Quadrigemina we ae oe os 18. Optict Thalami .. = ae ae Ae 19. Corpora Striata .. 5. A os “ Functions of the Cerebral Hemispheres. 20. Experiments on the convolutions .. Bs os Functions of the Cerebellum. 21. Harmonizing and co-ordinating the locomotive movements Pace. 20 21 22 24 26 ib. tb. y+ | 29 30 32 ib. 33 ab. 35 37 38 40 41 42 43 44 ib. ab. 45 46 22. 23. Or me © bO CONTENTS. Of the Nerve Force and the Course of Power in the Brain. Nerve force is of the nature of a current Experiments showing the community of nature igen it si electricity : Waste of nerve fibre by ine act of radnetion Rate of propagation of the nerve-force . Nerve-force derived from the common source of patra power, the Sun . Impropriety of looking on ave Bran as a Sereormnn A current action is involved in every exertion of the ei Immediate source of nerve force, the blood .. ae $s MOVEMENT, SENSE, AND INSTINCT. Reasons for including Appetites and Instincts in the same department with the Senses as cies “a: me CHAPTER I. SPONTANEOUS ACTIVITY AND THE FEELINGS OF MOVEMENT. . Feelings connected with Movement, a distinct class .. ee Their consideration to precede the Senses OF THE MUSCULAR SYSTEM. . Muscular Tissue 7 cp 4s ss as . Sensibility of Muscle en =p ae a . Irritability or Contractility of Muscle ns ‘ oe . Tonicity, or Tonic Contraction of muscle .. tie oe PROOFS OF SPONTANEOUS ACTIVITY. . Movements anterior to, and independent of, Sensation 2 Proofs that there are such movements (1.) Tonicity of the muscles .. : es (2.) Permanent closure of the sphincter es oe (3.) Activity maintained by involuntary muscles Ae (4.) Act of wakening from sleep (5.) Early movements of infancy ts ose o. (6.) Activity under excitement (7.) The active temperament .. os Ae (8.) Growth of Volition a Ay py" PAGE. 48 49 50 ab. 52 ab. 53 57 59 ab. 62 ab. 63 64 ab. ab, ab. 65 ab. 67 69 ab. 70 ~I 10. 4 12. 13. 14, 15. 16. 17. 18. 19. 20. 21. 24. CONTENTS, Legions of Spontaneous Activity. - The muscles act in groups, or systems “it As es Locomotive apparatus os Bh te ee Vocal organs oe ‘ eo oe ee Movements of the face, areats and jaw < ee Special aptitudes of animals .. 395 ve ee OF THE MUSCULAR FEELINGS. . The Natural History of the Feelings, a part of the Science of Mind. Method and order of description - os . Classification of Feelings of Movement 5: oe ‘e I. Feelings of Muscular Exercise. Feeling of Muscular Exercise generally .. ss se . Physical side .. oe a8 oe oe oe Mental side es ° a oe a Examples of the Dead Strain igs os ar es Muscular tension with Movement .. os oe ar Slow Movements re. : ss as Movements gradually increasing or idimtneanine Ary oe Quick Movements nes as LG ‘ ae Feeling of loss of support a 5 is es Passive movements a a ye ris oe II. Perceptions grounded in the Muscular Feelings. Discrimination of degrees and modes of muscular exertion .. Consciousness of Exertion or expended force—sense of Resist- ance, force, inertia .. ay s se . Examples of the feeling of verteneel Momentum. Weight... 23. Consciousness of the Continuance of a muscular exertion. KEsti- mate of Time. Means of estimating Extension os Consciousness of the degree of Velocity of movements oe Consciousness of the state of contraction of a muscle. Note ,. Sir W. Hamilton’s distinction between the locomotive faculty and the muscular sense. Note 40 ae ee OTA Palen Bae 1. OF SENSATION. Sensations of the five Senses on & me os Common or general sensibility Propriety of constituting the feelings of Or gAate Life kirtot a class of sensations .. ; . ee . Emotional and Intellectual Bone a. as ve PAGE. 70 71 ab. 72 ab, 76 ib. 80 84 85 ab. 86 87 88 89 90 91 92 94 97 98 99 101 102 103 16, Co 10. 1%} 12. 13, 14. 15. 16. If. 18. 19. 20. 21. 22. 23. 24. 25. CONTENTS. SENSATIONS OF ORGANIC LIFE. . Classification according to locality, or seat .. Of Organie Muscular Feelings. . Organic pains of muscle,—cuts, lacerations, injuries of the tissue; Bodily origin and manifestations oe . Mental characters:—Acute pains in general typified, Avs described .. ae ; oa oP . Cramp or spasm, its physical Nate: at mental character- istics ee ee se ne ve . Over-fatigue, and ittiee: tune Py, ae He . Sensibility of the Bones and Ligaments __., se oe Organic Sensations of Nerve. . Nervous pains, Their consideration complicated _., °. . Nervous fatigue; Ennui .. oe ar . Feeling of the healthy and fresh cunditinn of the nerve tissue. Stimulants .. o x be 7s Organic Feelings of the Circulation and Nutrition. Thirst ; Starvation ; pleasures of pure animal existence as Feelings of Respiration. Respiratory process os i ee we Feelings of pure air; Freshness ; feelings of ‘Relief an Feelings of nendioent and impure air; Suffocation e- Feelings of Heat and Cold Physical effects of heat and cold. The sensation of Cold ee Sensation of Heat a oe oe oe ee Sensations of the Alimentary Canal. Objects of the Sense :—Materials of food .. or o General view of the Organs of digestion .. Summary of the Physiology of digestion .. Alimentary Feelings: taking of food and healthy dieeetion Hunger oe an ee és oe ve Nausea and Disgust ce os oe os we Feelings of deranged digestive organs ae ce ee Feelings of Electrical States. Electric and Voltaic shocks oe i. He ee Electrical state of the Atmosphere MY we Baron Reichenbach’s experiments 20 ee aD PAGE. 104 106 109 110 8 112 113 114 116 117 118 119 120 122 128 125 126 128 129 130 132 134 135 X11 CONTENTS. SENSE OF TASTE. 1. Bodies acting on the sense of Taste sie se 2. Organ of Taste ;—description of the Tongue a ’ 3. Local distribution of the sensibility of the tongue .. . 4, Mode of action in taste .. “e ° oe ee 5. Sensations of Taste ; complex sensibility of ie tongue as 6. Order of Giasetesaen iS ~ ee sy" r 7. Relishes a * ts rs os 8. Disgusts “(s ae oe *> 9. Sweet tastes pel aeemiian of feeling of Sy dations Ws oe 10. Bitter tastes Arg A As mi AP . 11. Saline tastes oe o* AS ee ve e 12. Alkaline tastes .. se Ss a : 13. Sour, or acid tastes we ae iy oe e 14. Astringent tastes oe a He oe oe 15. Fiery tastes “A a 8 ve ve 16. Intellectual aspect of beatae as nt oe SENSE OF SMELL. 1. Objects of Smell a ee oP oe en 2. Production of odours is he a3 Ss . 3, Diffusion of odours ne : * 4, Organ of Smell :—description of the Nose ‘ . 5. Action of odours—the presence of oxygen necessary to athe, ve 6. Sensations of smell :—their classification .. oe ee 7. Fresh odours... 2 _ sis +a as 8. Close or suffocating sone ea an ce oe 9. Nauseous odours se o° 10. Sweet or fragrant odours: a ention of awouens > 11. Bad odours ie ae ee iis ee oe 12. Pungent odours i 2a o. or ee 13. Ethereal odours Be xe oe ee oe 14. Appetizing odours Gs “ se os oe 15. Flavour 4 na ae oe ee ee 16. Uses of Smell .. ma pte x ne ee SENSE OF TOUCH. 1. Position assigned to Touch ah Saar aa Touch an intel- lectual sense ; es ; oe ee 2. Objects of Touch 4 ar ve ee 3. Organ of Touch :—the Skin .> oe : ys 4. Functions and vital properties of the skin .. mt . 5. Mode of action in touch .. is . 6. Sensations :—(I.) Emotional Sensttionsecsiar Touch a . Pungent and painful sensations of touch .. as PAGE: 136 138 140 141 ab. 142 143 144 145 ib. ab, 146 ab. 147 1b. 149 150 ab. 152 153 154 156 ab. ab. 156 157 158 ab. 159 1b, 161 162 165 166 167 168 CONTENTS. . Other painful sensations of the skin—Tickling . (II.) Sensations of Temperature (Intellectual) 10, (III.) The Intellectual Sensations of Touch proper :—(1.) jae pressions of distinguishable Points—Weber’s observations 11. (2.) Sensations of Pressure me Ae Pe 12. (IV.) Sensations of Touch involving neers perceptions :— Weight, Pressure, Resistance ; Elasticity ; Roughness, and Smoothness; increase of sensibility by movement 13. Extension ;—movement by itself inadequate to give the Motion of Extended Matter, or of Space. How the sense of Touch contributes to this perception. Elements of the contrast between the Successive and the Co-existing. Lineal ex- tent ; superficial extent; solid extent .. %- * 14. Distance, Direction, Situation, Form a ae ai 15. Accompaniment of activity in the senses generally .. ae 16. Touch concerned in handicraft operations .. ve fi 17. How far Touch can be a substitute for sight ee eo 18. Subjective feelings of Touch oe Sis ee se SENSE OF HEARING. 1. Objects of Hearing pay bs te as Or 2. The Ear os as 3. Action of the parts of the 6 ear in ae Ute time of spit 4 4, Sensations of Sound ; their classification .., oe a 5. Sweetness se .e ye os ee os 6. Intensity or Loudness: Suddenness a °° ee 7. Volume or Quantity “e ce o- oe i 8. Pitch, or Tune .. . oe . ye ee 9. Waxing and waning of A ite as ne ee or 10. Complexity: Discord and Harmony Be oe Ge 11. Timbre ws 0 ae As 12. Articulate sounds. Helmholtz’ 8 Pepe engin of the vowel sounds 13. Distance re oc 00 oe ae ee 14. Direction oe of oe a oe 15. Duration of an impression of anti “ 3 ii 16. Subjective sensations of sound Ge aS os Wy SENSE OF SIGHT. 1. Objects of Sight “5 ne eh a 2. The Eye oe a Ws + 3. Conditions of perfect vision ie ys 4. Adaptation of the eye to vision at different Benes oe 5. Of single vision with two eyes. Binocular Vision SW heations s co experiments . Erect vision from inverted images .. 5.3 a ne xlil Pace. 169 170 172 176 177 181 186 188 189 ab. ab, 199 ib. 194 196 197 198 199 200 wb. 201 202 203 204 205 206 XiV CONTENTS. 7. Sensations of Sight os re a 8. Sensation of mere Light .. v " ae 9. Colour . oe ea es oe ‘e a 10. iAtificial lights .. oe : oe 11. Lustre.—Explanation of the cause of Pees a 12. Complex sensations of sight. Optical and Muscular Setotis combined .. As ae * ws 13. Visible Movements :—pleasures of eae movement; per- manent imagery of the intellect A : os 14. Visible Form :—the distinction between pace! and the simultaneous, or Co-existence in Space at 15. Apparent size ;—exceeding delicacy of our discrimination of retinal magnitude a oe oe 16. Distance, or varying remoteness .. oY . 17. Visible Movements and Visible Forms in three diinenaonees Volume 5 oe 18. Extent of the intellectual i ini steve bieden fii eye CHAPTER IIL OF THE APPETITES. 1. Appetite, a species of Volition. Enumeration of Appetites .. 2. Sleep .. ve .s 4 i os 3. Exercise and Repose z ¥t as < an 4, Thirst and Hunger ey = ve oe nH 5. Appetite of the Sexes _ es ee we oy 6. Accustomed Routine of life * ae e- es 7. Appetite liable to give false indications og : vs CHAPTER IV. OF THE INSTINCTS. 1. Definition of Instinct 463 1 ae ie 2. Enumeration of instinctive or Pitre arrangements +8 THE REFLEX ACTIONS. 3. The Reflex, Automatic or Involuntary Actions defined; their nervous centres s eo I. The Reflex Actions governing the eae siooheees through the involuntary muscles :— Rhythm of the heart. Vaso-motor action—its influence on the secretions and the excretions. Movements of the intestines; Deglutition—its three stages ; Colic and Diarrheea ; Sonate iy re ae PAGE. 226 ab. 229 ab. 230 ab. 231 234 236 237 238 ib. 240 241 242 244 vb. 246 ab. 247 CONTENTS. II. Reflex Actions affecting organic processes through the volun- tary muscles ;—Respiration; coughing; sneezing ; sucking ITI. Reflex Actions affecting the organic functions by the medium of the cerebro-spinal centres and the involuntary muscles; —Salivation ; flow of tears ; winking of the eye ; movements of the iris .. oe ee ve oe IV. Reflex Actions scivalvitie voluntary muscles stimulated by the cerebro-spinal centres ;—movements of the ciliary muscle ; movements in the ear ; reflex movements of the senses generally : Actions improperly maid ada the denuiecon Y Reflex’ Most general laws at present attainable regarding Reflex Action Resemblances between Reflex Action and Voluntary Action THE PRIMITIVE COMBINED MOVEMENTS. 4. The locomotive rhythm. Proofs of the instinctive eee of this combination : we as 5. It implies an arrangement for reciprocating each ay a 6. Also an alternate movement of corresponding limbs .. cs 7. Lastly, a vermicular propagation of movement 8. Associated or consensual movements.—Associated actions of the two eyes on 9. Law of harmony of state of the Loti sppieinn ne ¢ 10. One sense instinctively acting for another THE INSTINCTIVE PLAY OF FEELING. 11. Movements and effects diffused under Feeling. Miller on ‘Movements due to the passions of the mind’ 12. Sir Charles Bell on the Movements of the face oe 13. Muscles of the face concerned in expression.—Muscles of the Eye-brow .. is e de ae 14. Muscles of the Nose ay “ 15. Muscles connected with the Ae eT of the Mouth 16. The Voice, Diaphragm, and the muscles generally, as affected under Feeling . 17. Organic effects of Feeling.—The Tecievinan Gland, the Saciial Organs, the Digestive Organs, the Skin, the Heart, the Lungs, and the Lacteal Gland in women ma 18. Pleasure connected with an increase, and Pain with an apAtentint of the vital functions. Examples from the agents of pleasure and pain 19. The manifestations of foating coneieeeed wih reatanee to the foregoing principle. The existence of specific muscles of pain accounted for. The lively manifestations of acute pain 20. Laughter and Sobbing .. es a “ rs XV Pace, 256 257 259 261 262 263 265 266 ab, 268 270 271 273 275 276 277 279 280 282 286 290 Xv1 CONTENTS. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. él. 32. 33. 34. 30. . Statement of the law ee ie e a Exceptions to the principle that connects Pleasure with increased vitality “s A principle of Ri@ulaGon must an be adeaeedn pe ature stimulants of the Senses; Narcotics .. ¥e Stimulation might be considered the sole tenis me it is better to allow both principles. Country and city life THE INSTINCTIVE GERM OF VOLITION. Spontaneous actions at the foundation of the will. Miiller on the first commencement of voluntary acts Spontaneity by itself insufficient. Voluntary command of the organs not instinctive oe ee Primordial connexion between feelings and cat phi: Pern, law that connects pleasure with increased energy Examples from the effects of pain .. Ae ys oe Sucking in the infant. Relief from pain .. ros oe Instinct of self-preservation a mode of volition = 2. THE VOICE. Anatomy of the organ of voice os 45 2 Muscles of the larynx .. oe 4 oe *° The larynx as an instrument of sound aS ee oe The articulate voice. Vowel utterance. Consonants—their formation and classification Mental phenomena of voice os a Sensibility to degrees of vocal tension ee ne Pa INTELLECT. Fundamental attributes of Thought or Intelligence es Consciousness of Difference—Law of Relativity es Retentiveness 5 oe oe Consciousness of A preomten te! or ? Siintlarity os As Uses of the scicntific discussion of the intellectual powers... CHAPTER L RETENTIVENESS—LAW OF CONTIGUITY. MOVEMENTS. . Effects of repetition on the spontaneous and the instinctive actions ee ee oe ee ee ° Paar. 292 293 295 298 300 301 302 305 306 309 310 313 316 wb. 321 td. 323 324 325, 327 328 10. Li. 12. 13. 14. 15. 16. ifs 18. 19, 20. 21. 22. 24. 26. 26. 27. 28. CONTENTS. . Acquisition of aggregates and trains of movements .. sie . Conditions regulating the pace of acquisition :—General condi- tions, I, Continuance or Repetition; II. Mental Concentra- tion; IJJ. Adhesiveness of the individual constitution on the Ss oe . Conditions special to Msvementa (1) Bodily Strenatne @) Spontaneity ; (3) Muscular Discrimination ve : IDEAL FEELINGS OF MOVEMENT. . Transition from the actual to the ideal Pe 7. What is the seat of muscular and other feelings foanistinis after the fact ? ae . Seat of revived i pereesione the same as that of the Seuirnia! — Examples from Movement... on be ee . Examples from the Senses nS tea * aa Emotions and Passions .. The tendency of an idea to erste the shite is an te power of the mind, and interferes with the will The tendency exemplified in Fear, and in other instances Sympathy is our acting out the idea of other men’s pains and pleasures .. ee ae Ambition is often of the eeters ay a sien idea ae a Bearings of the foregoing doctrine ny a oe Association of Feelings of Movement Rie as oe Examples from the acquirements of Speech Circumstances favouring the cohesion of feelings of recat SENSATIONS OF THE SAME SENSE. Association of sensations of the same sense with one another Effect of repetition on individual sensations ae we Sensations of Touch oe Sensations of Hearing.—The ear Tas to be ime te indiviiiadl sounds; Successions of sounds :—music, articulation, elo- cution oe . Sensations of Sight : ee Gieblind Bei eade—scienitatiel abbiitaig and artistic 28 oe oe or ve Coloured Surfaces a és es oe Conditions of the retention of veal appearances In the early operations of Intellect, all its three functions are blended ve The cumulative operation of Contiguity infeinuptod ne divetsity of combination ie ve oe The vastness and complicacy of th? sense acquisitions could nel be overcome without the system of patching Xvll Pace, 330 3383 300 336 337 338 340 341 1b. 343 344 ab. 345 046 ab, 347 348 349 350 352 354 358 359 ab, 360 XV CONTENTS. 29. 30. 31. 32. 30. 34, 35. 36. 37. 38, 39. 40, 41. 42. 43. 44, 45. SENSATIONS OF DIFFERENT SENSES. Movements with Sensations :—language of command Muscular ideas with Sensations :—Architectural associations Sensations with Sensations / ss is Rate of adhesiveness in heteropanegn association .. ve OF EXTERNAL PERCEPTION.—THE MATERIAL WORLD. Metaphysical problems connected with Perception Perception of the Distances and Magnitudes of External pone: —Perceptions resulting from the eye alone oe Distance and Magnitude imply other organs than the eye. Berkeley’s theory of vision; criticism of objections urged against it .. : 45 one 35 ar Meaning or import of Bstertion ve Extension the result of an association of iedted atiocka: The opposing views: Hamilton .. Xe -. ee Perception and Belief of the Material World. Questions as to the independent existence of matter .. (1.) No knowledge possible except in reference to our BREA, (2.) The sense of the external implies our own energies (3.) Our experience connects certain changes of sensation with the consciousness of certain movements (4.) Experience furnishes the materials of our belief in what actually takes place s a ee (5.) Suggestions of a plurality of senses : ie (6.) Externality means what is common to us th others. The external world. The meaning of the sentiens and the senswm Process of perceiving the true Magnitude aa Distance nee an object from the ocular adjustment and extent of image on the retina :—Wheatstone’s experiments; the increased in- clination of the eyes suggests diminished size The appreciation of Distance follows the estimate of Mnaenitarde. Reid on the signs of distance furnished by degrees of colour and distinctness, and by intervening objects. Note Perception of Solidity through the presentation of dissimilar pictures to the two eyes. Binocular Vision ar Perception of Solidity implied in the perception of dictunon Question as to the line of visible direction of objects Localization of bodily feelings:—Our own body is to us an external object ; the localizing of feelings is acquired Associated differences in sensations. Hypothesis to account for the localizing of our feelings of Touch and Sight. Note Associated differences in the muscular feelings. Hamilton’s theory of the inverse relation between Sensation and Per- ception. Note % an fs se = Pace. 360 361 362 363 ob. 366 371 376 tb. 376 378 379 382 384 386 388 392 394 396 sor 46, 47, 48. 49, 58. 59. CONTENTS. ASSOCIATIONS WITH FEELING. The element of Feeling may be allied with objects .. - Association of special emotions with objects:—Objects of affec- tion; associates with irascible passion; overflowings of egotistic emotion as Love of money ; passion for pacing) adeeb oe Alisonian theory of Beauty :—Distinction between “ents: and associated effects; Sublimity and Beauty of sounds; associated effects of Forms; Fitness and Ease in machinery . Reading of Emotional expression :—The meaning of a smile or a frown acquired. Pleasure from the sight of the hap- piness of others. Feelings of Moral Approbation and Disapprobation Pe: e ie aE a3 ASSOCIATES OF VOLITION, . Acquired nature of voluntary power. Things implied in the voluntary command of the moving organs. Observations on the early movements of two lambs. Note . Voluntary acquisition exemplified by the case of Imitation (1.) Imitation wanting in early infancy sf (2. ) The power is progressive (3.) Efforts of imitation are at the bata nnn (4.) Imitation of the child’s own acts by others .. (5.) Imitation follows spontaneity ‘f (6.) It progresses with the acquired habits es He (7.) Depends on the delicacy of the senses. Importance of gaining the attention fe NATURAL OBJECTS—AGGREGATES OF NATURAL QUALITIES, . External objects affect us through a plurality of senses. Im- portance of sensuous adhesiveness—the Naturalist . Objects having uses, or related properties NATURAL AND HABITUAL CONJUNCTIONS—STILL LIFE. 55. Variegated imagery of the world. Importance of a retentive- ness for Colour . Aggregates constituted by aPetoal fe pt eentkitormme ane Dia- grams, Pictorial Sketches . Conjunction of objects with their scientific neitios SUCCESSIONS. Successions and changes in nature :—Cycles ; Evolutions es Natural persistence of mental movements once begun. Influ- ence on the recovery of successions ce bi es tix Pace. 400 402 404 ab. 407 409 413 414 ab, 416 1b, 1b. 1b. 417 419 420 421 424 426 XX CONTENTS. PAGE. 60. Successions of cause and effect. Case of human actions as causes 427 61. Action and reaction of man on man ? ie ee 428 62. Our knowledge of living beings made up in aca of those suc- cessions. Susceptibility to the human presence “a 429 MECHANICAL ACQUISITIONS. 63. Conditions of mechanical acquirement :—(1) the active organ,— the Muscles : (2) the Senses concerned ; (3) Taste, or liking, as a motive to concentrated attention .. 480 64. Method of mechanical training :—Recruits in the ery ; the apprentice in handicraft employment .. oe ve 432 VOCAL OR LINGUAL ACQUISITIONS. 65. Acquisition of Vocal music be we XG . 434 66. Speech .. s te ay! ah a ae ab. 67. The mother tongue <¥ sy ie hi oy 436 68. Foreign languages Aye A: - ie ne 457 69. Oratorical acquisition .. de hs bs As 10. RETENTIVENESS IN SCIENCE. 70. The Oxssxcr Sciences. The abstract and the concrete Sciences 439 71. The Sussecr Sciences, or Mind. Inquiry into the nature of the aptitude for the study of mind. Anti-subjective ten- dencies to be overcome Fe uN ae 442 BUSINESS, OR PRACTICAL LIFE. 72. The higher branches of industry .. a ' AP 445 73. Management of human beings a a Ss ‘ ib. ACQUISITIONS IN THE FINE ARTS. 74. Nature of Fine Art ;—qualities of the artist O ae 446 '(1.) Adhesiveness for the material of the art .. + 447 (2.) Special sensibility for the effects called artistic ‘- ib. (3.) An artist a mechanical workman’ .. as ak ab. HISTORY AND NARRATIVE. 75. Transactions witnessed :—their mode of adhesion .. as 448 76. Transactions givenin language na se np 449 OUR PAST LIFE. 77. The train of each one’s existence .. A: +. is 450 78. Our own actions ia 79, 80. — ok W b CONTENTS. Composite stream of our past life .. us i General observations on the force of contiguous adhesion :—I. Proofs of the fact of General adhesiveness; II. Superior plasticity of early years; III. Temporary adhesiveness ; cramming CHAPTER IL AGREEMENT—LAW OF SIMILARITY. . Statement of the law. Knowledge involves the consciousness of Agreement as well as the consciousness of Difference . Mutual relation of Contiguity and Similarity . Under Similarity there is supposed a defect of likeness . The defectiveness is either Faintness or Diversity A . The power of reviving like in the midst of unlike an ett point of intellectual character, varying in individuals FEEBLENESS OF IMPRESSION. . In the case where one person identifies a faint sensible impres- sion, and another does not, the difference may be accounted for (1) by a greater natural delicacy in the Sense ; (2) greater previous familiarity with the particular impression; (3) by the habit of concentrating the attention on the subiect, in other words, the acquired delicacy of the Sense. To these local circumstances, may be added General power Z Similarity 7. Feelings of Organic Life saaitifiod D Aeateneas't in Hae Peepect 8. Identification of Smells ; ‘ we : 9. Hearing. Influence of familiarity ; oa 10. Identification of objects of Sight under dimness a va 11. Acuteness of sense in the Indians a vs vs 12. The scent of the dog “E ak a ve 16. Tastes .. oe Pr “8 2 v3 nb Cc XX1 PAGE. 453 ab, 457 458 460 461 wb. 462 463 464 465 ab. 466 467 468 471 472 XXil CONTENTS. Lis 18. 19. 20. . Sensations of Sight 23. 24, 20. 26. 24 28. 30. ol. 32. 34. Identity of a common effect from different causes; Classifica- tion, and its consequences Touches : Hearing. Musical and artianlate identihesona s in tis midst of diversity .. ‘ The ear as concerned in language .. Identification of Colours ; gree os Generalization of Forms—Mathematical pats ss Arbitrary Forms—written Language an oe Peculiarities of the verbal mind in general Artistic Forms ae a ss ae ss Scenes of Nature, &c. SS Visible Movements “i 5 yar . Properties common to sensations of fterent senses .. e. CONTIGUOUS AGGREGATES,— CONJUNCTIONS. Popular classification of natural objects. Re-classifying of things already classified Things affecting a plurality of Senses Compounds of Sense and Association :—Objects leas Pei their wses ; mechanical invention ; the steam engine Natural objects identified on their EClntiA properties. Chemical discoveries .. Sn a 5: ees Classifications of the TaCeealiate Linneus. Analogies struck by Goethe and Oken The Animal Kingdom :—Improved BEAT L fomeroniee of the skeleton; mental peculiarities of Oken ; enlargement of our Paowiedge through the discovery of real identities PHENOMENA OF SUCCESSION. . Various modes of Succession. Of identities, some are real, others illustrative .. oe Identification among the different Sistene of successions: oie Evolutions .. ee > Successions of Human istueye : harioal comparisons Institutional comparisons—the science of Society Scientific causation : Newton’s discovery of universal ari tion ; intellectual character of Newton a Si REASONING AND SCIENCE IN GENERAL. The different processes of Science :—AssTRACTION ; Controversy of Nominalism and Realism .. we . Inpuction: the inductive process demands he power of Simis larity ; Inductions fitted into previously established for- mulas; Laws of Kepler e a ade we PaGr. 472 475 476 478 479 ab. 481 482 ab. 483 a. 484 486 488 490 491 494 496 497 500 ab, 503 506 506 36. 37. 38. 39. 40. 41. 42. 43. 44, 45. 46. 47. 48, 49, 50. 51. CONTENTS. Depvcrion :—transfer or extension of properties to new cases; Newton on the diamond; given an obscure case to find a principle to illuminate it; Franklin’s identification of lightning and electricity os ye oe Reasoning by Analogy .. ve ye a4 The explanation of the Reasoning Faculty BUSINESS AND PRACTICE. Inventions in the arts:—James Watt; Administration of public and private business; Extension to new cases of devices already in use 3 ce be % ar Persuasion a ay ILLUSTRATIVE COMPARISONS AND LITERARY ART. Comparison an aid to intellectual comprehension:—Bacon ,. Comparisons for ornament and effect :—the Orator and the Poet Figures of speech implying comparison rf we es THE FINE ARTS IN GENERAL. Some of the Fine Arts mvolve the intellect largely .. we The less intellectual Arts; Intellect in the Fine Arts generally SIMILARITY IN ACQUISITION AND MEMORY. Similarity, by tracing repetitions, shortens the labour of acquir- ing new subjects we Ae ae oe Examples from Science .. oa Business acquisitions re oe Case of the Artistic mind . Contiguity tested only by eye and abeclae novel, The Historical Memory Ae ey Corea ET HR. + Di COMPOUND ASSOCIATION. . There may exist in any one case a plurality of associations. Statement of the law COMPOSITION OF CONTIGUITIES. . Contiguous conjunctions :—complex wholes and concrete objects . Connexion with locality and with persons. Searching for things lost .. XX1l Pace, 518 522 528 529 532 535 534 535 537 538 540 541 542 644 545 546 XXIV CONTENTS. 4, Connexion of things with uses E 2c oe os 5. Successions :—the succession of Order in Time ee ve 6. Language ole a ye ee oo es COMPOSITION OF SIMILARITIES. 7. Increase of points of resemblance .. oe * Se 8. Mixture of language and subject-matter .. Ps 4 MIXED CONTIGUITY AND SIMILARITY. 9. The identities struck by pure Similarity are afterwards recovered by Similarity and Contiguity mixed .. : oe 10. Influence of proximity in bringing en a difficult sdennaceion THE ELEMENT OF EMOTION. 11. An emotional state gives its character to the trains of recollection 12. The purely intellectual bonds are made subordinate in emotional natures a On “i as ve INFLUENCE OF VOLITION. 13. Modes whereby volition may operate in resuscitating the past (1.) By the stimulus of excitement (2.) By controlling the intellectual attention THE SINGLING OUT OF ONE AMONG MANY TRAINS. 14. Concurrence of other suggesting circumstances with an object before the view on os 15. Selection of one out of many meer of the same objéct OBSTRUCTIVE ASSOCIATION. 16. Recollection obstructed by the mind’s being Sane with something different é 17. Conflict of the Artistic and the Biientitic nodes of viewing the world. Guessing of conundrums ss ee ASSOCIATION OF CONTRAST. 18. Contrast is the reproductive phase of Discrimination or the Law of Relativity 19. Contiguity and Similarity concur in Peraietie cpakraats os 20. Contrasts are often accompanied with Emotion 21. The power of Similarity, under the guise of Contrast, okt the mind of contradictions ee PAGE. 548 549 651 652 558 554 555 556 ab. 557 658 ab. 560 562 563 564 wb. 566 567 568 bo JI oO oOo © 10. Tis 12. 13. 14. 15. 16, CONTENTS. CHAPTER LV. CONSTRUCTIVE ASSOCIATION. . There is in the mind a power of original construction .. oe MECHANICAL CONSTRUCTIVENESS. . Complex acts acquired by taking the simple acts separately. The three conditions of constructiveness generally VERBAL CONSTRUCTIVENESS. . Constructiveness in Speech. Illustration of Volition as an element in constructiveness . Fulfilment of the conditions of grammar, &e. Necessity of a large stock of vocables FEELINGS OF MOVEMENT. . Construction of non-experienced ideas of Weight, Range, &c. The Associations of Architecture CONSTRUCTIVENESS IN THE SENSATIONS. . Forming by combination new states of Organic Feeling . Tactual constructions. Disassociation y ‘y . States of Hearing the result of a combining effort . Constructiveness in Sight CONSTRUCTION OF NEW EMOTIONS. Elementary emotions of human nature must be experienced. Changing the degree of a known feeling Combining of two emotions so as to bring out a third. Wrnnipiie CONCRETING THE ABSTRACT. Given the abstract properties of an Rarer to conceive the object itself ee xe The farther abstraction is eat the more difficult it is to remount to the concrete a3 Py. sr ‘3 REALIZING OF REPRESENTATION OR DESCRIPTION. The methods of representation Verbal description ‘ Maxim of the describing art in prey pata cbeabine a tone with an enumeration .. XXV PAGE. 570 571 572 574 576 578 579 581 ib. 583 585 588 ab. 589 XXV1 CONTENTS. CONSTRUCTIVENESS IN SCIENCE. 17. Constructiveness in Abstract ideas .. ie ae as 18. Induction .. a 19. Processes of Deduction ; eet ans of eaeiertine 5 < 20. Experimental science vs ve as ee -> PRACTICAL CONSTRUCTIONS. 21. Region of practical inventions. The turn for experimenting, an attribute of inventors: Kepler, Herschel, Daguerre 22. The mental quality termed soundness of Judgment. The power of adaptation to complicated conditions .. os FINE ART CONSTRUCTIONS.—IMAGINATION. 23. The presence of an emotional element in intellectual combina- tions. Distinction between the constructions of Imagina- tion and the constructions of science and of practice. Note 24. Combinations ruled by emotions:—Terror, Anger .. are 25. Superstructures reared on Egotistic feeling .. 49 es 26. Constructions to satisfy the emotions of Fine Art properly so called oe are 27. The artist’s standard is in ‘feeling of the effect Ppetinced a 28. Reconciliation of Art with Nature; the regard due to truth by an artist 3 se we > ae APPENDIX. PSYCHOLOGY OF ARISTOTLE. The Pyschology of Plato was based on his Kosmology .. oe Plato’s location of the divisions of the soul in different bodily organs Theories of the Soul according to other philosophers before Aristotle Aristotle’s criticism of the current theories of his time .. me Aristotle’s definition of Life, or the animating principle, which he makes co-extensive with the Soul us a The Aristotelian distinction of Form and Matter - ae Farther distinction of Potentiality and Actuality “e Matter is not necessarily Body The Soul ranks with Form, not with Matter ; with the nerege ani not with the Potential Soul and Body are mutually correlated si a ‘ Every action and passion has a Formal side as regards the Soul, a Material side as regards the Body: for example, anger .. Soul comprises several varieties:—Nutritive; Sentient; Movent, Appetitive, Imaginative, and Noétic .. a os ee PaGE. 591 593 594 ab. 599 600 603 605 606 608 611 612 614 616 619 620 622 623 624 626 626 628 CONTENTS. The lowest or Nutritive Soui the basis of all the rest .,. The Sentient Soul:—Sense Perception; the Common Darcervapics —Motion, Rest, Number, es Magnitude The Five Senses:—Vision .. : =F ss ee Hearing :—Sound ; Voice Smell and the Olfacients = bie of fs Taste “ ay sf! $e se ve ee Touch , What is the meaning Soe our perceiving “that we see or hele P es The act of comparing sensations ee rr ve We cannot perceive two distinct sensations at one Rone oe ee The Noétic Soul :—Phantasy os He “s we Memory a Reminiscence ee 3 ee we ve oe Association of Ideas Ze +e re Highest form of the Noétic Bacalty, or N ous Opinions of previous philosophers on Nous or Intellect According to Aristotle, the grand region of Form is che Cameras Bopy, the source of all varieties of Soul It is the distinction of the Nous to be unrelated to our Cornet agency, although not separable from all body. It exists in perfection in the divine beings By means of Nous, the Soul acquires an oven pputude for coe nizing the Universal . Nous occurs to a certain erent in the animals Nous supervenes upon sensible perception; and is dependent ae sensible images The Nous is the place of Forms z The Intellectus Agens and Intellectus Patiens .. The Intellectus Patiens perishes with the body; the binteniaaties Agens, or theorizing Nous, i is eternal Nous apprehends the principia of Demonstration ; ascent of the nied to general principles as we oe The Emotions, Appetites and Desires .. oa a oe Summary of the doctrine of the Soul oF oe ee A.—Definition and Divisions of Mind ae Ee ue B.—Physical Accompaniments of Pleasure and Pain ee a C.—The Germs and the Development of Volition Ae by D.—Seat of revived impressions ae a ee ed E.—Perception of the Material World ee A F.—Contiguous Association in the ideas of Natural Gbyeate ne G.—Subjective studies and regards... *e we ee H.—The Abstractions—Number, Time, and Space ia as I.—Classifications of the Intellectual Powers .. Py me XXVIII PAGE. 629 631 634 635 637 639 640 642 ab. 643 644 645 647 649 ab. 650 651 664 666 667 668 671 675 676 678 682 685 689 692 ie 9 Hod elit : iriabcey hana ‘ey et Pepi 2it at 0 . . 4 at b FORE ON. j ai Nd 5, nbs INTRODUCTION, Cre aot res Berens DEFINITION AND DIVISIONS OF MIND. i (ree operations and appearances that constitute Minp are indicated by such terms as Feeling, Thought, Memory, Reason, Conscience, Imagination, Will, Passions, Affections, Taste. But the Definition of Mind aspires : comprehend in few words, by some apt generalization, the whole kindred of mental facts, and to exclude everything of a foreign character. Mind is commonly opposed to Matter, but more correctly to the so-called External World. These two opposites define each other. ‘To know one is to know both. The External, or, in more philosophical language, the Object, World is dis- tinguished by the property called Extension, pertaining both to resisting Matter, and to unresisting, or empty Space. The Internal, or the Subject, World is our experience of every- thing not extended; it is neither Matter nor Space. A- tree, which possesses extension, is a part of the object world; a pleasure, a volition, a thought, are facts of the subject world, or of mind proper. / { | Thus Mind is definable, in the first instance, by the method of contrast, or as a remainder arising from subtracting the Object World from the totality of conscious experience. It happens that the Object World is easily defined or circum- scribed ; the one well-understood property, Extension, serves l 2 DEFINITION AND DIVISICNS OF MIND. for this purpose. Hence the alternative, or the correlative Mind, can be circumscribed with equal exactness. But this negative definition, although precise, so far as it goes, fails to indicate the full scope of the enquiry. Even after the sub- stitution of the correcter phraseology,—Subject and Object: for Internal and External,—we have to admit that Object Experience is still conscious experience, that is, Mind ; and, although the development of the object properties belongs to other sciences, yet the foundations or beginnings of them must be traced in mental science. Now, it has been found possible to sum up all the properly mental phases in a small number of general properties, whose enumeration (which is strictly speaking a Division) is all that can be offered as a positive Definition of Mind,_/ 2. The phenomena of the Unextended, or Subject Mind, are usually comprehended under three heads :-— J. FEELING, which includes, but is not exhausted by, our pleasures and pains. Emotion, passion, affection, sentiment —are names of Feeling. IT. VouTIon, or the Will, embracing the whole of our activity as directed by our feelings. Ill. Tuovucur, Intellect, or Cognition. Our SENSATIONS, as will be afterwards seen, come partly under Feeling, and partly under Thought. ‘The three classes of phenomena have each certain distinc- tive characteristics, and the sum of all these is a definition of mind, by a positive enumeration of its most comprehensive qualities. There is no one fact or property that embraces all the three. We may have a single name for the whole, as Mind, the Subject, the Unextended, Self-Consciousness ; but it does not follow that one general property shall exhaust the whole. Volition is a distinct fact from Feeling, although pre- supposing it ; and Thought is not necessarily implied in either of the two other properties. | 3. A few remarks may here be offered, by way of elucid- ating this threefold definition and division. 0 ee : é (First. For a notion of what FEELING is, we must refer each FEELING. 3 person to their own experience. The warmth felt in sunshine, the sweetness of honey, the fragrance of flowers, the beauty of a landscape, are so.many | known states of feeling. Our pleasures and pains are all included under this head ; but many other states, both simple and complex, that are neutral as regards pleasure and pain, must also be re- ferred to it. The entire compass of our Feelings could be known only by an exhaustive enumeration ; from which also we might expect to obtain a general definition of Feeling. It is not requisite at this stage that we should either classify the feelings, or arrive at their common or defining properties. It so happens, that we can readily circumscribe this part of our mental being, by that negative method already exemplified in the definition of mind as a whole: for the characters both of thought and of volition are remarkably intelligible and pre- cise, and therefore give us a ready means of laying down the boundary of the remaining department. We may, however, remark, before passing to the consider- ation of the other divisions, that the presence of. Feeling is the foremost.and most unmistakable mark of mind. ‘The members of the human race agree in manifesting it. The different orders of the brute creation show symptoms of the same endowment. ‘The vegetable and mineral worlds are de- void of it. True, it is each in ourselves that we have the direct evidence of the state; no one person’s consciousness being open to another person. But finding all the outward appearances that accompany feeling in ourselves to be pre- sent in other human beings, and, under some variety of de- gree, in the lower animals, we naturally conclude their mental state to be similar to our own. The gambols of a child, the smile of joy, a cry on account of pain, and the corre- sponding expressions for mental states common to all lan- guages, prove that men in every age and nation have been similarly affected. The terms for expressing pleasure and pain in their various forms and degrees, are names of feel- ings; joy, happiness, bliss, comfort, sorrow, misery, agony— are a few examples out of this part of the vocabulary. 4 DEFINITION AND DIVISIONS OF MIND. Secondly) All beings recognized as possessing mind can not only feel, but also act. The putting forth of force to at- tain some end marks a mental nature. Eating, running, fly- ing, sowing, building, speaking—are operations rising above the play of feeling. They all originate in some feelings to be satisfied, which gives them the character of proper mental actions. When an animal tears, masticates, and swallows its food, hunts its prey, or flees from danger, the stimulus or support of the activity is furnished by its sensations or feel- ings. To this feeling- prompted activity we give the name Volition. ~The characteristic of being stimulated by the feelings of sentient beings makes a wide contrast between volition and the energies familiar to us in nature,—the powers of wind, water, gravity, steam, gunpowder, electricity, vegetation, &c. For although the strong personifying tendency of mankind has often compared these powers to a human will, yet in reasoning about them scientifically no such comparison is ad-- mitted ; while, in the explanation of voluntary actions, the reference to feeling and to thought is indispensable. Volition is farther contrasted with such animal functions as breathing, the circulation of the blood, and the movements of the intestines. ‘These are actions, and serve a purpose, but they are not mental actions. We could imagine ourselves so constituted, that these processes would have had to be prompted and controlled by sensations, emotions, and desires ; they would then have been mental actions. As it is, they form a class apart, denominated Reflex Actions. When nar- rowly examined, they appear to shade by insensible degrees into voluntary actions; but we are not on that account to confound the broad and fundamental distinction between the unconscious and the conscious, involved in the opposition of the reflex and the voluntary. It is impossible, in a brief preliminary sketch, to indicate and discriminate all the varieties of animal activity. There is a complication to be unravelled in this department of the mind, such as to test severely the resources of mental science. THOUGHT. 5 It is sufficient to remark, as the most general law of volition, that pleasure prompts to action for its continuance, increase, or renewal ; and that pain prompts to action for its cessation, abatement, or prevention. — Soni is “TuoudHt, Tnteliiderice, or Cognition. This mathe such functions as Memory, Reason, Judgment, and -Imagina- tion. The first fact implied in it is Deer eanan or sense of difference, shown by our being conscious of one sensation as more intense than another, or when we are aware of two feelings as differing in kind,—for example, taste and smell, pain and pleasure, fear and anger. Another fact is Semilarcty, or sense of agreement, which is interwoven with the preceding in all the processes of thought. When we identify any sen- sation or present mental impression with one that occurred previously, there being an interval between, we exemplify the power of similarity ; the sun seen to-day recalls our previous impressions of his appearance. A third fact or property of the Intellect is Retentiveness, commonly understood by the familiar names ‘memory’ and ‘recollection.’ This power is essential to the operation of the two former powers ; we could not discriminate two successive impressions, if the first did not persist mentally to be contrasted with the second; and we could not identify a present feeling with one that had left no trace in our framework. ) Retentiveness, which sums up all that we designate by memory, acquisition, education, habit, learning by experience, is not wanting in the lower orders of sentient life. For an animal to have a home, a cer- tain degree of memory is requisite. We have seen that Volition is separated from Feeling, by superadding the characteristic of action, or the putting forth of energy to serve an end. And % now, after the foregoing ‘enumeration of Intellectual attributes, we can draw the line between Thought and Feeling, which is to complete the defi- nition of ene so far as is nme at the outset. In proportion as a mental experience contains the facts named discrimination, comparison, and_retentiveness, it is 6 DEFINITION AND DIVISIONS OF MIND. ‘an Intellectual experience ; and in proportion as it 1s want- ing in these, and shows itself in pleasure or pain, it is of the nature of Feeling. The very same state of mind may have both an intellectual side and an emotional side; indeed, this is a usual occurrence.) And, like many things that are radi- cally contrasted, as day and night, these two distinct facts of our nature pass into one another by a gradual transition, so that an absolute line of separation is not always possible; a circumstance that does not invalidate the genuineness of their mutual contrast. | The exercise of Thought is greatly mixed up with Volition also, but there is rarely any difficulty in distinguishing the two functions. Indeed, it is hardly possible for us to exist in one exclusive state. Still, in our explanations of things, we often require to separate in statement what is not separated in fact. 4, If we advert to the various classifications of the mental phenomena that have hitherto passed current, we shall find that the three attributes above specified have been more or less distinctly recognized. In the old division of mind into Understanding and Will, the element of Feeling would appear to be left out entirely. We shall find in fact, however, that the feelings are implied in, or placed under, both heads. The same remark applies to Reid’s classification, also twofold and substantially identical with the foregoing, namely, into Intellectual Powers and Active Powers. The submerged department of Feeling will be found partly mixed up with the Intellectual Powers, wherein are included the Senses and the Emotions of Taste, and partly treated of among the Active Powers, which comprise the ex- position of the benevolent and the malevolent Affections. Dr. Thomas Brown, displeased with the mode of applying the term ‘ Active’ in the above division, went into the other extreme, and brought forward a classification where Feeling seems entirely to overlie the region of Volition. He divides mental states into Haternal affections and Internal affections, By external affections he means the feelings we have by the Senses, in other words, Sensation. The internal affections he CLASSIFICATIONS OF MIND. vi subdivides into Intellectual states of mind and Emotions. His division therefore is tantamount to Sensation, Emotion, and Intellect. All the phenomena commonly recognized as of an active or volitional character, he classes as. a part of Emotion. Sir William Hamilton, in remarking on the arrangement followed in the writings of Dugald Stewart, states his own view as follows :—‘If we take the Mental to the exclusion of Material phenomena, that is, the phenomena manifested through the medium of Self-consciousness or Reflection, they naturally divide themselves into three categories or primary genera ;—the phenomena of Knowledge or Cognition,—the phenomena of Peeling or of Pleasure and Pain,—and the phenomena of Conation or of Will and Desire.* Intelligence, Feeling, and Will, are thus distinctively set forth. I may farther notice the mode of laying out the subject that has eccurred to an able physiologist. I quote a passage intended as introductory to the Anatomy of the Nervous System. ‘Of the functions performed through the agency of the nervous system, some are entirely corporeal, whilst others involve pheno- mena of a mental or psychical nature. In the latter and higher class of such functions are first to be reckoned those purely intel- lectual operations, carried on through the instrumentality of the brain, which do not immediately arise from an external stimulus, and do not manifest themselves in outward acts. To the same class also belong sensation and volition. In the exercise of sensa- tion, the mind becomes conscious, through the medium of the brain, of impressions conducted or propagated to that organ along the nerves from distant parts; and in voluntary motion, a stimulus to action arises in the brain, and is carried outwards by the nerves from the central organ to the voluntary muscles. Lastly, emotion, which gives rise to gestures and movements, varying with the different mental affections which they express, is an involuntary state of the mind, connected with some part of the brain, and influencing the muscles through the medium of the nerves.’+ * Collected Works of Dugald Stewart, Vol. II.: Advertisement by the Editor, + Dr. Sharpey, in Quatn’s Anatomy, 6th edition, p. clxviii. 8 \ DEFINITION AND DIVISIONS OF MIND. In this passage a quadruple partition is indicated,—Sen- sation, Intellect, Emotion, and Volition. Sensation is raised to the rank of a primary division. Except, however, as regards one important point to be afterwards adverted to, there is nothing in Sensation that does not come either under Feeling, as above defined, or under Intellect. 5. In the plan of the present volume, Part first, entitled ‘Movement, Sense, and Instinct,’ will include the discussion of both Feeling and Volition in their lower forms, that 1s, apart from Intellect, or so as to involve Intellect in the least possible degree; the Sensations of the different Senses will form a leading portion of the contents. This division will comprise all that is primitive or instinctive in the suscepti- bilities and impulses of the mental organization. The second Part will aim at a full exposition of the Intellectual pro- perties. Thus, while Feeling, Volition, and Intellect are regarded as the ultimate properties and the fundamental classification of mind, it is not proposed that the exposition should proceed strictly in the order thus stated. Although Feeling and Volition, in their elementary aspect, can be explained before entering on the consideration of the Intellect, while one large important department of Feeling, namely, Sensation, is always considered as introductory to the Intellectual powers, yet the full exposition of the Emotions and the Active impulses of our nature properly comes last in the systematic arrangement of the mind. 6. It is requisite at the outset to give some intima- tion of a great mental law involved in the fundamental property of Discrimination above noticed, namely, the law of RELATIVITY. By this is meant that, as change of impression is an indispensable condition of our being conscious, or of being mentally alive either to feeling or to thought, every mental experience is necessarily twofold. We can neither feel nor know heat, except in the transition from cold. In every feeling there are two contrasting states ; in every act of know- ing, two things are known together. | oe | LAW OF RELATIVITY. ) “eens With reference to many of our feelings, mankind have always to some extent recognized the working of this prin- *- ciple. It is seen that the first shock of the transition from one state to another—from sickness to health, poverty to abundance, ignorance to knowledge—is the most intense, and that as the memory of the previous condition fades away, so does the liveliness of the emotion caused by the change. Leisure, retirement, rest, are enjoyed only by contrast to pre- vious toils. The incessant demands for novelty and change, for constant advances in wealth, in knowledge, in the arrange- ments of society, farther show the principle of Relativity as applied to pleasure. / ig { Language contains many names avowedly relative, as parent, child ; ruler, subject; up, down ; north, south ; light, dark ; virtue, vice. Ji is obvious that either name in those couples: implies the other; there can be no ruler without a subject. But, in reality, the principle of Relativity applies to _ everything that we are capable of knowing. Whatever we can conceive implies some other thing or things also conceiv- able, the contrast, co-relative, or negative of that. Red means the exclusion of all the other colours. If we had never been affected by any colour except red, colour would never have been recognized by us. ‘When we speak of a fixed star, we mean to exclude certain other things—the sun, planets, comets, &. When we make an affirmation, ‘ the stars shine by their own light, we also by implication make a denial, ‘the stars do not borrow their light.’) The applications of this principle are numerous and im- portant. It bears directly on the arts of human happiness ; it is essentially involved in Fine Art; it must be attended to in the communication of knowledge; in Metaphysics it con- flicts with the doctrine of the Absolute. ‘(For farther remarks on the Definition and Divisions of Mind, see APPENDIX A.) | | CHAPTER II. THE NERVOUS SYSTEM. 1 Fee teen Subject and Object (Mind and Matter) are the most diametrically opposite facts of our experi- ence, yet there is a concomitance or connexion between mind and a material organism. This position is best supported by the subsequent details. (See also APPENDIX B.) The parts of the human frame that chiefly concern the student of mental science are the Nerves and Nerve Centres (principally collected in the Brain), the Organs of Sense, and the Muscular System. The organs of sense and of movement will be described afterwards; a brief description of the Nerves and Nerve Centres will occupy this preliminary chapter, in which we shall confine ourselves as far as possible to the facts bearing directly or indirectly upon Mind. 2. That the Brain is the principal organ of Mind is proved by such observations as the following :— (1.) From the local feelings that we experience during mental excitement. In most cases of bodily irritation, we can assign the place or seat of the disturbance. We localize in- digestion in the stomach, irritation of the lungs in the chest, toothache in the gums or jaws; and when the mental workings vive rise to pain, we point to the head. In ordinary circum- stances we have no local consciousness of mental action, but in a time of great mental agitation, or after any unusual exertion of thought, the aching or oppression in the head tells where the seat of action is, precisely as aching limbs prove what muscles have been exercised during a long day’s march. The observation can occasionally be carried much farther; for it is found that a series of intense mental emotions, or an exces- sive strain on the powers of thinking, will end in a diseased alteration of the substance of the brain. THE BRAIN THE ORGAN OF MIND. 11 (2.) Injury or disease of the brain impairs in some way or other the powers of the mind. A blow on the head will destroy consciousness for the time ; a severe hurt will cause a loss of memory. ‘The various disorders of the brain, as inflammation, softening, &c., are known to affect the mental energies. Insanity is often accompanied by evident cerebral disease. (3.) The products of nervous waste are increased when the mind is more than ordinarily exerted. The alkaline phosphates (triple phosphate of ammonia and magnesia) removed by the kidneys are derived principally from the waste of nervous substance ; and they are sensibly increased after great mental exertion or excitement. Phosphorus abounds more in the brain than in any other tissue. (4.) There is an indisputable connexion between size of brain and the mental energy displayed by the individual man or animal. It cannot be maintained that size is the sole cir- cumstance that determines the amount of mental force. But just as largeness of muscle gives greater strength of body, as a general rule, so largeness of brain gives greater vigour of mental impulse. The measurements of the heads of remark- able men have often been quoted. ‘All other circumstances being alike, says Dr. Sharpey, ‘the size of the brain appears to bear a general relation to the mental power of the individual,—although instances occur in which this rule is not applicable. The brain of Cuvier weighed upwards of 64 oz, and that of the late Dr. Abercrombie about 63 oz. avoirdupois. On the other hand, the brain in idiots is remarkably small. In three idiots, whose ages were sixteen, forty, and fifty years, Tiedemann found the weight of their respective brains to be 19 0z., 25} oz, and 223 oz.; and Dr. Sims records the case of a female idiot twelve years old, whose brain weighed 27 oz. The weight of the human brain is taken at about 3 lbs. (48 02.).—Quain’s Anatomy, Vol. IL, p-. 432.* * In a paper by Mr. John Marshall, of University College, read be- fore the Royal Society (June, 1863), the author gives a minute account of 12 THE NERVOUS SYSTEM. '(5.) The specific experiments on the nerve cords and nerve centres, to be afterwards quoted, have proved the im- mediate dependence of sensation, intelligence, and volition on those parts. No fact in our constitution can be considered more certain than this, that the brain is the chief organ of mind, and has mind for its principal function. As we descend in the animal scale, through Quadrupeds, Birds, Reptiles, Fishes, &c., the nervous system dwindles according to the decreasing measure of mental endowment. three brains, one the brain of a Bushwoman, the others the brains of two idiots of European descent. The Bushwoman’s brain was computed to have weighed in the fresh state 315 oz. One of the idiots was a woman aged forty-two years; she was able to walk, though badly, to nurse a doll, and to say a few words; the weight of her brain was 10 oz. 5 grs. The other was a boy of twelve; he could neither walk nor handle anything, nor articulate a single word; the weight of his brain was 83 oz. These are the two smallest idiot brains whose weight has been recorded. Mr. Marshall enters into a very minute description of the structure of all the three brains, and his remarks are valuable as showing what other defici- encies, besides weight, attach to the brains of human beings of low mental power. Not merely is the cerebrum in idiots a small organ, having all the proper parts on a smaller scale, but these parts are fewer in number, less complex, and different in relative proportion and position. And in particular, the convolutions of the brain are much less developed, much simpler, than in an average brain. On comparing the two idiots in question, the convolutions of the woman were more developed than those of the boy. The circumstance of inequality in the richness of the convolutions has been alluded to by physiologists as explaining the cases of great mental power allied with brains not above the average weight. Such differences have actually been observed in the’examination of brains. The brain of Cuvier was said to be distinguished in this respect, as well as in weight. But the connexion of force of mind with richness of convolutions is also liable to various qualifications. It does not hold in the comparison of different species, —the sheep’s brain is more highly convoluted than the dog’s; and there are well authenticated cases of men of superior powers, whose brains, both as to weight and as to convolutions, were below the average. Still, there can be no doubt that generally, though not universally, an increase in one or both of these peculiarities is the concomitant of a higher mental endowment. Both the statistics of the Races of men, and Comparative Anatomy, are decisive to this extent. We may readily suppose that, with a view to intellectual power, an abundance of nervous elements—fibres and corpuscles—must be accompanied with a felicitous distribution or arrangement of them. | DIVISIONS OF THE NERVOUS SYSTEM. 13 3. ‘The Nervous SystTEM consists of a central part, or rather a series of connected central organs named the cerebro- spinal axis, or cerebro-spinal centre; and of the nerves, which have the form of cords connected at one extremity with the cerebro-spinal centre, and extending from thence through the body to the muscles, sensible parts, and other organs placed under their control. The nerves form the medium of communication between these distant parts and the centre ; one class of nervous fibres, termed afferent (incarrying) or centripetal, conducting impressions towards the centre,— another, the efferent (outcarrying) or centrifugal, carrying material stimuli from the centre to the moving organs. The nerves are, therefore, said to be internuncial in their office, whilst the central organ receives the impressions conducted to it by the one class of nerves, and imparts stimuli to the other, rendering certain of these impressions cognizable to the mind, and combining in due association, and towards a definite end, movements, whether voluntary or involuntary, of different and often of distant parts. —QUAIN, Introduction. The foregoing division of the nervous system into nerve- centres and nerve-cords determines the order and method of description both as regards their Anatomy, or structure, and their Physiology, or function. THE NERVOUS SUBSTANCE. 4. ‘The nervous system is made up of a substance proper and peculiar to it, with inclosing membranes, cellular tissue, and blood vessels. The nervous substance has long been distinguished into two kinds, obviously differing from each other in colour, and therefore named the white, and the grey, or cineritious (ash- coloured). ‘When subjected to the microscope, the nervous substance is seen to consist of two different structural elements, viz., fibres, and cells or vesicles. The fibres are found universally in the nervous cords, and they also constitute the greater part of the nervous centres; the cells or vesicles, on the other hand, are confined in a great measure to the latter, and do not exist in the nerves pro- perly so called, unless it be at their peripheral expansions in some 14 THE NERVOUS SYSTEM. of the organs of special sense; they are contained in the grey portion of the brain, spinal cord, and ganglia, which grey sub- stance is, in fact, made up of these vesicles intermixed in many parts with fibres, and with a variable quantity of granular or amorphous matter.’ The nerve fibres are principally of the class termed white, or tubular nerve-fibres. They are of microscopic minute- ness. In thickness, they range from the ;55 to the zzho0 of an inch; the medium or average being gop of an inch. When in the fresh condition, they are homogeneous and transparent, but after separation from the body they acquire a double outline or contour, and are apt also to assume a varicose or beaded appearance. The inference as to their ultimate structure, from these changes, is that each tube con- sists of (1) an outer structureless membrane, (2) an interior surrounding layer of transparent fatty matter, and (38) a central core or cylinder, which is not fatty, but albuminous in composition. ‘The central band or axis appears alone, or di- vested of the two envelopes, both in the central connexions of the fibres, and in the ultimate ramifications in the extremities of the body ; being, therefore, the essential part of the struc- ture. In thickness, it does not exceed the 757599 of an inch. These tubular nerve-fibres are finest on the superficial layers of the brain, and in the nerves of special sense ; they are largest in the motor nerves. From the foregoing state- ments of their size, we may judge of the immense multipli- cation of the nervous elements. Estimates have been made of the number of fibres in individual nerves, The third cere- bral nerve (the common motor of the eyes) is supposed to have as many as fifteen thousand fibres ; the small root of the fifth (governing mastication) nine or ten thousand ; the nerve of the tongue five thousand; these being all motor nerves, which have the largest fibres. It would be interesting to estimate the probable number of fibres of the nerve of sight, which, besides being a sensitive nerve, is much thicker than any of those just quoted ; there cannot probably be less than one hundred thousand fibres, and there may be many more. THE NERVE CELLS. 15 The number of nerve fibres forming the white substance of the brain must be counted by hundreds of millions. In the grey substance of the nerve centres, the nerve fibres are supposed to be continuous with the cells or vesicles. At their other extremity in the organs of sense, in the muscles, and in the body generally, their mode of termination appears to be varied. Sometimes they end in loops, some- times in meshes of network ; not unfrequently sub-dividing into minuter nerves (besides dropping their two investing sheaths). In other cases, they seem, according to the ma- jority of Anatomists, to end free in fine points, or else in little swellings of various structure. It is important to note that each fibre is continued un- broken and independent from the central nervous masses to the peripheral extremity; there are no loose ends; and although the nervous cords frequently unite, as well as sub- divide, in their course, the ultimate fibres are never fused with one another. The nerve cells, vesicles, or ganglionic corpuscles, are little bodies, of a variety of forms ; being round, oval,» pear-shaped, tailed, and star-like or radiated. They consist of pulpy mat- ter, with an eccentric roundish body or nucleus, enclosing one or more still smaller nuclei, surrounded by coloured granules. They vary in size from 345 to 3995 Of an inch in diameter. * Nucleated nerve-corpuscles magnified 170 diameters. a and 4 from the cortical grey matter of the cerebellum ; ¢ and d from the spongy grey matter 16 THE NERVOUS SYSTEM. When we take into account the amount of grey matter in the brain and spinal cord, which grey matter is made up of these bodies, mingled with fibres, the total number of cor- puscles occurring in the nervous substance would have to be reckoned by millions. With regard to the corpuscles existing in the grey matter of the convolutions of the brain, Dr. Lionel Beale gives the following conclusions as the result of his observations of the brain in man, in the sheep, the cat, and the dog :— ‘1. The numerous nerve cells of the grey matter are all con- nected with, or give origin to, at least two fibres. ‘2. These fibres, wide near their origin, gradually diminish in thickness till they are not more than zg¢¢555 of an inch in diameter. ‘3. It is probable that the cells of the grey matter of the con- volutions are connected together ; but, in the adult, the cells are not often connected with those cells situated nearest them. ‘4, There is no reason for supposing that the nerve cells, here or elsewhere, influence any nerve fibres save those that are struc- turally continuous with them.’ (Proceedings of the Royal Society, Vol. AIL, p.075.) Both the nerve fibres and the nerve cells or corpuscles are largely supplhed with blood, a circumstance indicating great activity. The grey matter, which is constituted by the pre- sence of the corpuscles, is usually spoken of as the seat of central nervous energy, and hence the grey masses are called the nervous centres. The supposition is, that these masses originate or re-inforce nervous power, which is then trans- mitted through the nerve fibres from one part of the system to the other. It is, however, shown by experinents that the nerve fibres themselves generate force; for the currents passing through them are augmented in their progress. A second function of the corpuscles throws light on the plan and workings of the brain. They are the Grand Junc- tions, or Crossings, where the fibres communicate with one of the medulla oblongata; » the nucleus of a cell,— (a, c, and ¢, after Hann- over). From Quain’s Anatomy, THE SPINAL CORD. div another, and establish a vast system of lateral and forward connexions, necessary to the co-ordinating and concatenating of movements and sensations, in the bodily mechanism associated with mind. The fibres ascending through the spinal cord to the brain, pass into cells, some lower and others higher; new fibres proceed from these cells both laterally and onwards, and communicate with other cells and fibres in an exceedingly complicated arrangement. The spread and expansion of the white nervous substance, in the hemispheres of the brain, supposes, of necessity, that the fibres rising from below enter cells in the ganglia at the base of the brain, and that these cells send out in the upward direction a much greater number than what is received from beneath; and so on, till the multiplication attained in the hemispheres is reached. THE NERVOUS CENTRES. 5. In the collective mass made up of the brain and spinal cord, and denominated the cerebro- spinal axis or centre, the following parts stand distinct from each other, although mutually connected by bundles of nerve fibres. I. The Sprnau Corp, contained in the back bone, and sending out two pairs of nerves from between every two vertebre, one pair to each side of the body. The Cord consists of a column of white fibrous matter with a grey portion enclosed. In a cross section, the grey matter is seen to form two crescents, with the horns turned outwards, and connected in the middle of their convexities by a cross band. * ¢Plans in outline, showing the front, A, and the sides, B, of the spinal cord with the fissures upon it; also sections of the grey and white matter, and the roots of the spinal nerves. a, a, Anterior fissure. p, », Posterior 2 18 THE NERVOUS SYSTEM. II. The ENCEPHALON or Bran. This includes the entire contents of the cavity of the skull, or cranium. The spinal cord is continued up into it. The brain is itself an aggregate of distinguishable masses of mixed grey and white matter. Each of these masses is looked upon either as a distinct centre, or as communicating between the centres. In pro- portion as the grey vesicular matter prevails, the mass has the characters of a centre and a grand junction ; according as the white fibrous substance prevails, the part serves as a medium of conduction or communication solely. Of these various masses, some have a preponderance of grey, others of white matter. None are purely of one kind. The roere mechanical arrangement of the brain is ex- tremely complex, and there are different modes of classifying and grouping the various portions. The division adopted by human Anatomists is into four parts (a different arrangement has been proposed, founded on Comparative Anatomy). Those four parts are the Cerebrum, the Cerebellum, the Pons Varolii, Fire.. 3.* fissure. 4, Posterior, and c, Anterior horn of grey matter. e, Grey commis- sure. 1, Anterior, and s, Posterior roots of a spinal nerve.’—Quatn, Vol. II. p. 438. * «A plan in outline, showing, in a lateral view, the parts of the encepha- lon separated somewhat from each other. A, Cerebrum. e, Fissure of THE MEDULLA OBLONGATA. 19 and the Medulla Oblongata. ‘The cerebrum, which is the highest and by far the largest part of the human encephalon, occupies the upper and larger portion of the cranial cavity.’ ‘The cerebellum is placed beneath the hinder part of the cerebrum, by which it is completely overlapped.’ The pons Varolii is in the base of the brain near the entrance of the spinal cord, and connects together the three other parts,— the cerebrum, the cerebellum, and the medulla oblongata. The medulla oblongata connects the spinal cord with the brain. 6. In giving a more detailed description of those four parts, it will be convenient to take them in an inverse order, beginning from below, or where the brain joins the spinal cord. i (1.) The Medulla Oblongata—tThis portion is continuous below with the spinal cord, of which it seems an expansion ; lying wholly within the cranial cavity, its upper end passes into the pons Varolii. See Figs. 3 and 4, D. ‘It is of a pyramidal form, having its broad extremity turned upwards, from which it tapers to its point of con- nexion with the spinal cord; it is expanded laterally at its upper part. Its length from the pons to the lower extremity of the pyramids is about an inch and a quarter; its greatest breadth is about three quarters of an inch ; and its thickness from before backwards about half an inch. In form and general anatomical characters, the medulla oblongata very much resembles the cord, of which it is a prolongation upwards to the brain. It is not our purpose here to enter into the minute anatomy of the part, or to set forth the points of difference between it and the cord; we need only observe that in it the white and grey constituents of the cord are both increased in size and altered in arrangement. The grey matter especially becomes more abundant, and additional deposits occur. The medulla oblongata has thus more of the character of an independent centre of nervous Sylvius, which separates the anterior and middle lobes. 8B, Cerebellum. C, Pons Varolii. D, Medulla oblongata. a, Peduncles of cerebrum; 6, Superior ; c, Middle; and d, Inferior peduncles of cerebellum.’—Quatn. 20 THE NERVOUS SYSTEM. action, as well as of a grand junction, than belongs to the cord. It gives origin to nerves of a very special and im- portant nature. | (2.) The Pons Varolit, or annular protuberance (tuber annulare). (See Figs. 3and 4c.) This ‘is a comparatively small portion of the encephalon, which occupies a central position on its under surface, above and in front of the medulla oblongata, below and behind the crura cerebri a, and between the middle crura of the cerebellum c¢, with all which parts it is connected” By the term ‘crura cerebri, introduced in this description, is meant the ‘legs’ or roots of the cerebrum, or the two bundles of nerves that unite it with the parts below. The crura of the cerebellum express in like manner the several connexions of that centre with the other centres. On account of the intermediate and con- necting position of the pons, it has also been called the middle-brain (meso-cephalon). From its embracing, as in a ring, the medulla oblongata and stems of the cerebrum, it has derived the name of annular protuberance; the other name, ‘pons,’ or bridge, expresses the same circumstance. ‘The substance of the pons Varolii consists of transverse and longitudinal white fibres, interspersed with a quantity of diffused grey matter. The transverse fibres, with a few exceptions, enter the cerebellum under the name of the middle crura or peduncles, and form a commissural (or con- necting) system for its two hemispheres. The longitudinal fibres are those which ascend from the medulla oblongata into the crura cerebri, augmented, it would seem, by others which arise within the pons from the grey matter scattered through it. The pons is thus mainly a grand junction between the medulla oblongata and spinal cord below, the cerebrum above, and the cerebellum behind. The existence of a considerable amount of the grey or vesicular matter proves that simple conduction or communication is not the sole function of this part of the brain. (3.) ‘The cerebrum or brain proper (Figs. 3 and 4, A), as already mentioned, is the highest, and by far the largest THE CEREBRAL HEMISPHERES. pa portion of the encephalon. It is of an ovoid (or egg) shape, but is regularly flattened on its under side. It is placed in the cranium with its small end forwards, its greatest width being opposite to the parietal eminences. ‘The cerebrum consists of two lateral halves, or hemi- spheres, as they are called, which, though connected by a median portion of nervous substance, are separated in a great Fig. 4.* TTT part of their extent by a fissure, named the great longitudinal fissure, which is seen on the upper surface of the brain, and partly also on its base. ‘The cerebral hemispheres are not plain or uniform upon * Shows the under surface or base of the encephalon freed from its membranes. A, Cerebrum. ff, g, h, Its anterior, middle, and posterior lobes. B, Cerebellum. C, Pons Varolii. D, Medulla Oblongata. d, Peduncle of cerebrum. 1 to 9, indicate the several pairs of cerebral nerves, numbered according to the usual notation, viz.:—1, Olfactory nerve. 2, Optic. 3, Motor nerve of eye. 4, Pathetic. 5, Trifacial. 6, Abducent nerve of eye. 7, Auditory; and 7’, Facial. 8, Glosso-pharyngeal. 8’, Vagus. 8”, Spinal accessory nerve. 9, Lingual or hypoglossal nerve. 22 THE NERVOUS SYSTEM. the surface, but are moulded into numerous smooth and tortuous eminences, named convolutions, or gyri, which are marked off from each other by deep furrows, called sulci, or anfractuosities. These convolutions are coloured externally ; for the surface of the cerebral hemispheres, unlike the parts hitherto described, is composed of grey matter,’ The complete description of the cerebrum includes an account of the external surface with its convolutions, and of the various masses that make up the interior, and in part appear at the base of the brain. Although in the highest degree interesting as a study, no important application to our present subject arises out of such minute knowledge. There are, however, a few particulars that it is of use for us to add, selected out of the elaborate detail of cerebral Anatomy. A distinction exists between the convoluted mass of the hemispheres and certain enclosed smaller masses of the cere- brum. Of these, there are two that are usually named together, partly on account of their proximity, and partly because it has not been practicable to distinguish completely their functions. They are the optict thalami and corpora striata, being double and symmetrical on the two sides. They both lie imbedded in the heart of the hemispheres. The peduncles or stems of the cerebrum pass into them before spreading out into the mass of the hemispheres. The third important mass is termed the corpora quadrigemina (quadruple bodies),* from consisting of four rounded masses put together in a square. This portion is more detached than the two others, and finds a place between the cerebrum and cerebellum. In some of the inferior animals it is very large, and takes a prominent position in the general structure of the brain; whereas the two other masses above mentioned for the most part rise and fall according to the degree of development of the convoluted hemispheres. Hence the comparative Anatomist assigns to the quadruple bodies a * See in Fig. 3, the two rounded eminences behind 4, the superior peduncle of the cerebellum. These represent the corpora quadrigemina in section. THE GANGLIA OF THE BRAIN. a character and function apart from the rest of the cerebrum. I quote a short description of each of the three centres. The corpora striata ‘are two large ovoid masses of grey matter, the greater part of which is imbedded in the middle of the white substance of the hemisphere of the brain.’ ‘The surface of the corpus striatum is composed of grey matter. At some depth from the surface white fibres may be seen cutting into it, which are prolonged from the corresponding cerebral peduncle, and give it the streaked appearance from which it has received its name.’ ‘The thalami optici (posterior ganglia of the brain) are of an oval shape, and rest on the corresponding cerebral crura, which they in a manner embrace. On the outer side each thalamus is bounded by the corpus striatum, and is then continuous with the white substance of the hemisphere.’ ‘ The inner side of the two thalami are turned to each other.’ ‘The optic thalami are white on the surface, and consist of several layers of white fibres inter- mixed with grey matter.’ ‘In front of the cerebeilum are certain eminences, which may be reached from the surface of the brain. ‘These are the corpora quadrigemina, and above them is the pineal gland.’ (‘The pineal gland (conarium) so named from its shape (pinus conus, the fruit of the fir), is a small reddish body, which rests upon the anterior pair of the corpora quadrigemina.’ ‘It is about three lines (a quarter of an inch) in length, and its broad part, or base, is turned forwards, and is connected with the rest of the cerebrum by white substance.’) ‘The corpora or tubercula quadrigemina are four rounded eminences, separated by a crucial depression, placed two on each side of the middle line, one before the other. They are connected with the back of the optici thalami, and with the cerebral peduncles at either side.’ ‘The upper or anterior tubercles are somewhat larger and darker in colour than the posterior. In the adult, both pairs are solid, and are composed of white substance outside, containing grey matter within. ‘They receive bands of white fibres from below.’—‘ A white cord also passes up on each side from the cerebellum to the corpora quadrigemina, and is continued onwards to the thalami: 24. THE NERVOUS SYSTEM. these two white cords are the superior peduncles of the cere- bellum. At each side, the corpora quadrigemina send off two white tracts, which pass to the thalami and to the commence- ments of the optic nerves.’ ‘In the human brain these quadrigeminal bodies are small in comparison with their size in the series of animals. In ruminant, soliped, and rodent animals, the anterior tubercles are much larger than the posterior, as may be seen in the sheep, horse, and rabbit. In the brains of carnivora, the posterior tubercles are rather the larger.’ ‘In the foetus this part of the brain appears very early, and then forms a large proportion of the cerebral mass. The eminences are at first single on each side, and hollow. They are constant in the brains of all vertebrate animals, but in fishes, reptiles, and birds, they are only two in number, and hollow. In marsupialia and monotremata, they are also two in number, but solid.’ In this brief allusion to the different parts composing the cerebrum, we have had to exclude the mention of many smaller portions. We have also avoided all allusion to the ventricles of the brain. ‘These are enclosed spades extending in various directions, and serving as boundaries to the other parts.* (4.) ‘ The cerebellum, little brain, or after brain (Figs. 3 and 4, B), consists of a body and three pairs of erwra or peduncles, by which it is connected with the rest of the encephalon. They are named superior, middle, and inferior peduncles. * The following passage may assist in giving a connected view of the cere- brum, and also of the nature of the ventricular cavities or space, ‘The hemispheres are connected together in the middle by the corpus callosum, and it is obvious that the structures filling up the interpeduncular space, serve also as connecting media. Between the corpus callosum above and the peduncles below, the two hemispheres are partially separated from each other, so as to leave an interval, the general ventricular space, across which some slighter connecting portions of nervous substance pass from one hemisphere to another. ‘Again, as seen in a transverse vertical section of the cerebrum, the peduncles diverge as they ascend towards the hemispheres, and pass on each side through two large masses of grey matter, sometimes called ganglia of the brain, —at first through the thalamus opticus, and afterwards through a much larger mass named corpus striatum. These two masses of grey matter project THE CEREBELLUM. 25 ‘The superior peduncles (Fig. 3, b) connect the cerebellum with the cerebrum through the corpora quadrigemina, as already stated. The inferior peduncles d, pass downward to the back part of the medulla oblongata. The middle peduncles, c, pass from the middle of the cerebellum around the outer side of the crura of the cerebrum, and meet in front of the pons Varolii, constituting its transverse fibres. They connect the two halves of the cerebellum below. All these peduncles consist of white fibres only ; and they pass into the interior of the cerebellum at its fore part.’ “The body of the cerebellum B, being covered with cortical substance, is of a grey colour externally, but is rather darker on the surface than the cerebrum. Its greatest diameter is trans- verse: 1t is about three and a half or four inches wide, about two or two and a half from before backwards, and about two inches deep in the thickest part, but is much thinner all round its outer border.’ ‘It consists of two lateral hemispheres, joined together by a median portion called the worm, or vermiform process, which in birds, and in some animals still lower in the scale, is the only part existing.’ ‘The body of the cerebellum at the surface, and for some depth, consists of numerous nearly parallel lamine or folia, which are composed of grey and white matter, and might be compared with the gyri or convolutions of the cerebrum, but are smaller and not convoluted. These are separated by sulci of different depths.’—QuaIn. somewhat, as smooth convex eminences, on the upper and inner surface of the diverging fibres of the peduncles. Immediately above the thalami and corpora striata, the hemispheres are connected together across the median plane by the corpus callosum; and it is between the under surface of the latter, and the upper surface of the eminences mentioned and the interpeduncular struc- tures, that the general ventricular space is situated in the interior of the cerebrum. The upper part of this space is again divided by a median vertical partition, so as to form the two Jateral ventricles : below this, it formsa single cavity named the third or middle ventricle, which communicates with both the lateral ventricles above, and, below, with the ventricle of the cerebellum or fourth ventricle. The median vertical partition, which separates the lateral ventricles from each other, consists at one part (septum lucidum) of two layers, between which is contained the jifth and remaining ventricle of the brain.’ — QUAIN. 26 THE NERVOUS SYSTEM. 7. We must next attend to the internal structure of the brain, considered as made up of the two kinds of matter, the grey and the white. The distribution and arrangement of those two kinds of matter throw light upon the mode of action, or the peculiar kind of activity that distinguishes the brain. ‘White Part of the Encephalon.—The white matter of the encephalon consists of tubular fibres. The general direction which they follow is best seen in a brain that has been hardened by immersion in spirits, although it is true that we do not then trace the single fibres, but only the fine bundles and fibrous lamellee which they form by their aggregation.’ ‘The fibres of the cerebrum, though exceedingly compli- cated in their arrangement, and forming many different col- lections, may be referred to three principal systems, according to the general course which they take, viz—1l. Ascending or peduncular fibres, which pass up from the medulla oblongata to the hemispheres, and constitute the two crura or peduncles of the cerebrum. They increase in number as they ascend through the pons, and still further in passing through the optic thalami and striated bodies, beyond which they spread in all directions into the hemispheres. These were named by Gall the diverging fibres. 2. Transverse or commissural jibres, which connect the two hemispheres together. 3. Lon- gitudinal or collateral fibres, which, keeping on the same side of the middle line, connect more or less distant parts of the same hemisphere together.’ ‘Grey Matter of the Encephalon.—Considering the imputed physiological importance of the grey nervous substance, it may be well to mention connectedly the different positions in which it is found in the several parts of the encephalon.’ ‘ By far the larger amount is situated upon the convoluted surface of the cerebrum and the laminated surface of the cerebellum, forming, in each case, the external cortical layer of cineritious maiter.’ I omit a portion of the connected account of the spread of the grey matter in the parts in the interior and base of the DISTRIBUTION OF GREY MATTER. 27 brain, as including a number of terms that the reader has not been prepared for in the present sketch of the nervous system. We must rest satisfied with perusing, in addition to the above, the account of the distribution of grey substance in the larger portions, and in the parts already in some degree known to us. ‘In the crura cerebri, the grey matter is collected into a dark mass ; below this it is continuous with that of the pons and medulla oblongata, and through them with the spinal cord. Thus, though the crura cerebri are, in the main, con- nexions of white matter between the hemispheres and the parts below, yet, like the medulla oblongata and spinal cord, they contain in the interior a portion of the grey matter, and are to that extent centres and junctions, as well as conductors. ‘In the centre of each of the corpora quadrigemina, grey matter is also found, and it occurs in the pineal gland (and in the corpora geniculata). These last bodies appear to be appendages of the large masses of grey matter, situated in the interior of the cerebrum, named the optic thalami; which again are succeeded by the still larger collections of this substance, and indeed the largest situated within the brain,— viz., the corpora striata.’ 8. Plan of Structure indicated by the above arrangement of white and grey substance—It would appear, thus, that the cerebro-spinal centre, or the brain and spinal cord taken together, is an aggregate of distinct nervous masses or parts, each made up of a mixture of white and grey matter. The grey matter is the vesicular substance, consisting of cells or corpuscles ; the white matter is the fibrous substance, being made up of fibres bundled together. The grey matter is a terminus; to it the fibrous collections tend, or from it com- mence. The fibrous matter contained within any of the cerebral masses is’‘placed there as a means of communicating with some portion or other of the layers, or other collections, of grey substance. Assuming that one class of nerve fibres (the sensory or incarrying)—those distributed to senses, viscera, &c.—are 28 THE NEkKVOUS SYSTEM. employed in conveying influence from without inwards ; and the other class (motory or outcarrying)—distributed to muscles, in conveying influence from within outwards,—we find that both classes are usually mixed together in the same rami- fying branches, and in the common stem of white matter in the spinal cord. Let us imagine, however, the two kinds separated; the sensory nerves all emerging from the centres on oue hand, and the motory nerves emerging apart on the other. We can then express the plan of the brain thus :— The sensory or incarrying fibres arising from the ex- tremities enter the cord, proceed a certain way there, and begin to drop into corpuscles; from these corpuscles fresh fibres arise and proceed, some onwards and some laterally, to other cells; and so on. Thus, in the spinal cord, medulla oblongata, pons Varolii, &c.—up to the cerebral hemispheres, there is a repeated system of fibres passing into cells, and new fibres emerging, and going on to other cells; giving birth to an endless system of cross communications, like the railway network of England. Adverting now to the enormous connecting mass of fibres—ascending, diverging, and trans- verse—that make up the white substance of the brain, we must consider how the multiplication has been effected. There is only one conceivable process, when we consider that the entire mass is in communication, through cells, with the diminutive mass of the spinal cord. The process is this. For one fibre coming up from the sense organs and dropping into a cell, two, three, four, or more must emerge; each of these again, proceeding onwards to a new cell, and there replaced by three, four, &c., new fibres; and so on, until the expansion or multiplication is completed. Within the spinal.cord, where there is no increase of bulk, the mul- tiplying process is not begun; but in the upper course of the cord, where it enters the brain, there is an arithmetical necessity for the multiplication. We can hardly avoid the supposition that the corpora striata and the thalamz optict, through which the great stem of the brain diffuses itself (by the ascending fibres) in the white matter of the hemi- PLAN OF THE BRAIN. 29 spheres, are the principal seats of the multiplying corpuscles. For every fibre carrying impressions up from the senses, and every fibre carrying out stimulus to the moving organs, there must be perhaps ten thousand, perhaps a hundred thousand, traversing the brain, involving a great and rapid multiplica- tion in the corpuscles of the grey substance.* * It will be necessary, in speaking of certain functions closely allied to the mind, that some allusion be made to the portion of the nervous organization called the Sympathetic System, consisting of numerous ganglia, or little knots, together with nerve cords, and united by numerous nerve cords or branches to the cerebro-spinal system. The sympathetic system consists of two knotted or ganglionated cords or strings, running, inside the trunk, from the neck to the pelvis, one on each side of the spine. The upper end is connected with groups of ganglia in the head and face; and, in the trunk, there are detached interlacements of ganglia, or plexuses having connexion with the great viscera in the chest and abdomen. The knots, or Ganglia, are the centres or grey masses of the system, being made up of nerve corpuscles of a particular kind (having usually a single projection or tail). They exercise the usual functions of the corpuscles, in forwarding, diverting, reflecting, and concatenating nervous currents. The Cords are, as in the cerebro-spinal system, made up of nerve fibres, but these are of a peculiar sort, described as soft, granular, flattish (as opposed to tubular) fibres, without any surrounding sheaths or investments, and containing many dark nuclei; they are called the gelatinous, and the non-medullated fibres. United with fibres from the cerebro-spinal system, these branches of the sympathetic are distributed over the whole body. Thus, as regards the head, they are found in the iris and the blood-vessels of the eye, in a muscle of the tympanum, in the nose, the palate, and the salivary glands. The great plexus of the chest (the cardiac) sends fibres to the heart, the great . blood-vessels, and the lungs; from the aorta, nerves are continued to the arteries throughout the body. The abdominal plexus (called the solar plexus) supplies the stomach, intestines, liver, kidneys, and other abdominal viscera ; each organ having a small plexus of itsown. A still lower plexus contributes fibres to the parts contained in the pelvis. As all the ramifications contain a certain number of cerebro-spinal fibres, so it is believed that the cranial and spinal nerves contain everywhere some sympathetic fibres. It is presumed from analogy, and from the functions exerted by the sympathetic system, that the fibres are of the two classes—incarrying and outcarrying. The incarrying nerves would receive stimulation from the peripheral surfaces ; the outcarrying would convey motor stimuli to muscular fibres. This last function is the one most clearly manifested. The muscular fibres stimulated by the sympathetic nerves are almost all involuntary muscles, as the iris, the heart, the muscular coat of the blood-vessels, the 30 THE NERVOUS SYSTEM. OF THE CEREBRO-SPINAL NERVES. 9. By the cerebro-spinal nerves are meant the connexions of the cerebro-spinal centre with the different parts of the body. These connexions consist of ramifications of nerve cords, threads, or bundles, arising in the central masses, and distributed like the blood-vessels, by subdividing and spread - ing themselves over the various organs and tissues, thereby establishing a connexion between the brain and the remotest extremities. ‘These nerves are formed of the nerve fibres already Ce- scribed, collected together and bound up in membranous sheaths. A larger or smaller number of fibres inclosed in a tubular sheath form a small round cord, usually named a funiculus ; if a nerve be very small, it may consist of but one such cord, but in larger nerves several funiculi are united together into one or more larger bundles, which, being wrapped up in a common membranous covering, constitute the nerve (Fig. 5). Accordingly, in dissecting a nerve, we first come to an outward covering, formed of cellular tissue, intestines, &c. All these parts are primarily governed by the sympathetic system, with more or less interference from the cerebro-spinal centres, through the fibres intermingling with sympathetic fibres. The sympathetic system presides over the viscera, which are the organs of the nutritive or vegetative life. It sustains the rhythmical action of the heart, and of the intestines. The fibres distributed to the small arteries everywhere maintain these vessels in a state of permanent contraction, the release from which, by extraneous influence, produces local congestion and the allied results. These fibres and their function, receive the designation vasi-motor. The fibres of the sympathetic are not the medium of sensation. When pain arises in parts mainly supplied by them, as the intestines, it must be attributed to the irritation of the intermingled fibres of the cerebro-spinal class. Many of the so-called reflex functions are due to the operation of the sympathetic nerves and ganglia. The extreme contrast to the proper volun- tary actions is presented by the movements due to this system—witness the heart, the intestines, and the vasi-motor compression of the blood-vessels. Indeed, the absence of sensation and the absence of voluntary control are essentially the same fact. THE NERVES. oe but often so strong and dense, that it might well be called fibrous. From this common sheath we trace lamin passing inwards, between the larger and smaller bundles of funiculi, and finally between the funiculi themselves, connecting them together as well as conducting and supporting the fine blood vessels which are distributed to the nerve.’ ‘The funiculi of a nerve are not all of one size, but all are sufficiently large to be readily seen with the naked eye, and easily dissected out from each other. In a nerve so dissected into its component fasciculi, it is seen that these do not run along the nerve as parallel insulated cords, but join together obliquely at short distances as they proceed in their course, the cords resulting from such union dividing in their further progress to form junctions again with collateral cords ; so that, in fact, the funiculi composing a single nervous trunk have an arrangement with respect to each other similar to what we find to hold in a plexus formed by the branches of different nerves. It must be distinctly understood, however, that in these communications the proper nerve fibres do not join together or coalesce. They pass off from one nervous cord to enter another, with whose fibres they become intermixed, and part of them thus intermixed may again pass off to a third funiculus, or go through a series of funiculi and undergo still further intermixture. But through all these successive associations, the nerve fibres remain, as far as known, indi- vidually distinct, like interlaced threads in a rope.’ * ‘Represents a nerve consisting of many smaller cords or funiculi, wrapped up ina common cellularsheath. A,thenerve. B, a single funiculus drawn out from the rest (after Sir C. Bell). —Quary. oa THE NERVOUS SYSTEM. FUNCTIONS OF THE NERVOUS SYSTEM. The Nerves. 10. The Nerves are divided into two classes, according as they proceed from the Spinal Cord, or issue direct from the brain. The first class, called the Spinal Nerves, is the most numerous. It is not implied that these nerves have no con- nexion with the brain, but merely that their place of emer- gence or ‘superficial origin’ is in the Spinal. Cord. The arrangement is to be looked upon as a matter of local con- venience. The nerves destined for the lower limbs do not leave the general trunk until they approach the neighbour- hood that they are to supply; that is, they are prolonged within the spine to its lower extremity ; whilst those branch- ing towards the arms emerge in the neck and between the shoulders. On the other hand, the nerves that supply the face and head leave the brain at once by openings in the skull; these are the Cerebral Nerves. There is no difference of nature between the two classes. In the mode of junction of the Spinal Nerves with the Spinal Cord, a peculiarity is observed of great importance in ~ the present subject. I have already adverted to the fact that they issue from the spine in pairs, one pair between every two vertebrae; there are in all thirty-one couples. Each couple contains a right and a left member, for distribution to the right and left sides of the body. This part of the arrange- ment is likewise a matter of local convenience. But, further, when one individual:of these emerging couples is examined, say aright branch, we find that this branch does not arise from the cord single; it springs from two roots, and these, after proceeding apart for a short way, unite in the one single nerve that is seen to issue from between the vertebree on the right side. The same holds of any left branch that may be fixed upon; the connexion with the cord is not single, but double. The smaller of the two roots, in each case, proceeds from the fore part of the cord, and is called the anterior root ; FUNCTION OF THE NERVES. he the other or larger proceeds from the hinder portion of the cord, and is called the posterior root. This last root, the posterior, is distinguished in another point, besides its greater size. Just after leaving the cord, there is a ganglion or little swelling formed upon it, composed in part of grey matter, and being to appearance of the nature of a nerve centre. Beyond the ganglion, the two roots mingle and constitute the one nerve seen to emerge from the spine.* 11. Having thus noticed two classifications of the Nerves, the one—into Spinal and Cerebral—unimportant as respects function, the other—into Anterior and Posterior roots—highly important, as will be seen ; we now proceed to illustrate the precise function’ of a nerve. The function of a nerve is to transmit impressions, influences, or stimuli, from one part of the system to another. The experimental proofs of this position are numerous, and they are now reckoned conclusive. If a main trunk nerve supplying a limb be cut through, all sensation in the jimb ceases, and also all power of movement. The blood circulates and the parts are nourished, but, for the purposes of feeling or action, the member is excommunicated, dead. The telegraph wire is cut. If, instead of cutting the nerve through, we prick or irritate it, we cause both feeling and movement, Whether the irritation is applied high or low, near the nervous centres or near the extremities of the body, the effect is the same. The pricking originates an impression or stimulus, which the nerve conveys through its whole length ; wherever that nerve ramifies, there is feeling or movement, or both, It appears, however that the influence increases as it passes along the nerve, presenting a marked contrast to the conduction of electricity by a wire, for the electric current diminishes by transmission. ‘The nerve is not a passive, but an active conductor. 12. We have remarked of the nerves that they convey influence for the two distinct ends of causing action and of * See Fig. 2, p. 17. 34 THE NERVOUS SYSTEM. — causing feeling. For Action, the influence must proceed owt- ‘wards from the centres to the active organs; a stimulus from the brain or spinal cord has to be transmitted to the limbs, trunk, head, eyes, mouth, voice, or other parts that are to be set in motion. For Feeling, the influence must pass inwards. In a sensation of hearing, for example, an impression made on the sensitive surface of the ear is conveyed by the nerve of hearing towards the cerebral centres. Now, it is found that different sets of nerves are employed for these two pur- poses; one class being exclusively devoted to the outward transmission of stimulants to action or movement, while the other class is equally confined to the office of conveying influence centrewards, for the ends of sensation or feeling. The first of these two classes is that named efferent (out- carrying) nerves, the second comprises the afferent (in- carrying) nerves. In the individual fibres, it would appear that the influence always follows one direction. No single nerve combines both functions. It is further known, since the discoveries of Bell and others, that one of the two roots of the spinal nerves is entirely composed of nerves conveying the outward stimulus ; these are, therefore, purely nerves of motion, motor nerves. The other root consists of fibres transmitting influence from the various parts of the body inwards to the centres; these are called the sentient nerves. (They are not all sentient in the full sense of the word, as will be afterwards explained.) The anterior roots are the motor nerves; the posterior roots are the incarrying or sentient nerves. On these last roots, the posterior, the ganglionic swellings occur; and, both in the spinal nerves and in those emerging at once from the brain by openings in the cranium, the occurrence of such a bead is a proof that the nerve is of the incarrying or sentient class. In the experiments above described, as made upon trunk- nerves of an arm or leg, effects both of movement and of sen- sation were seen to follow; the limb was thrown into con- vulsive movements, and the animal showed all the symptoms of being in bodily pain. If, now, instead of a main trunk, TWO CLASSES OF NERVES. 35 the trial is made upon one of the roots of a spinal nerve, only a single effect will be produced,—motion without sensation, ar sensation without motion of the part. If an anterior root is pricked or irritated, movements of some part of the body will follow, showing that an active stimulus has been dis- charged upon a certain number of muscles. If a posterior or ganglionic root is pricked, the animal will show symptoms of pain, and the pain will be mentally referred to the part where the filaments of the nerve are distributed. If the nerve is one proceeding to the leg, there will be a feeling of pain in the leg; but there will be no instantaneous con- vulsions and contractions of the limb, such as are produced by irritating an anterior root. All the movements that an animal makes under the stimulus of a sentient root, are consequent on the sensation of pain; they are not the direct result of the irritating application. In one of the trunk nerves of an arm or a leg, both motor and sentient fibres are mixed up, which is the reason of the mixed effect in the first experiment above mentioned.* 13. Experiments with pure nerves, that is, with motor fibres alone, or sentient fibres alone, are best made upon the nerves of the head,—the Cerebral Nerves. A certain number of these are exclusively motor, certain others are exclusively sentient, while a third kind are mixed, like the spinal nerves beyond the point of junction of the two roots. The Cerebral Nerves are divided into nine pairs, some of these being considered as admitting of farther subdivision. Four are enumerated as nerves of pure sensation :—the nerve * When an anterior root is cut through, irritation of the farther seg- ment produces movements; irritation of the upper segment (nearest the brain) has no effect. Ifa posterior root is cut, irritation of the farther seg- ment gives rise to no signs of sensation or of motion ; irritation of the nearer segment causes signs of pain. The irritation of the farther segment of an anterior or motor root (whose result is movement) may, however, be accom- panied with slight indications of pain; the explanation of which is, that the cramping or violent contraction of the muscles stimulates the sensory muscular fibres, which proceed to the brain by the undivided posterior, or proper sensory roots. 36 THE NERVOUS SYSTEM. of Smell (olfactory nerve, 1st pair); the nerve of Sight (optic nerve, 2nd pair) ; the nerve of sensation of the Tongue and Face generally (5th pair)—(this nerve contains also a motor portion distributed to the muscles of mastication); the nerve of Hearing (auditory nerve, part of the 7th pair). These nerves, therefore, are engaged in transmitting influence from the surfaces of special sense, the nose, eyes, ears, tongue, and face, towards the cerebral mass. Jive nerves are enumerated as purely motor or outcarrying :—the nerve supplying three of the four recti (or rectangularly arranged) and one of the oblique muscles of the eye, and sustaining its ordinary movements (motor communis oculorum, 3rd pair); the nerve supplying the superior oblique muscle of the eye (trochlearis, 4th pair) ; the nerve distributed to the external rectus muscle of the eye, and serving to abduct the two eyes by an inde- pendent stimulus requisite in adjusting the eyes to different distances (abducent, 6th pair); the trunk nerve for setting on the movements of the face and features (2nd part of 7th pair) ; the nerve for moving the tongue (9th pair). The pair reckoned the 8th has three divisions :—(1) the glosso- pharyngeal or sensory nerve of the tongue and throat; (2) the vagus or pneumo-gastric, the sensory nerve concerned in respiration, circulation, deglutition, and digestion; (3) the spinal accessory or motor nerve for regulating the movements of the parts supplied by the vagus—as the throat, larynx, and lungs. If any one of the four sensitive nerves issuing from the cranium be cut through, sensation in the connected organ is lost; disease will produce the same effect. Injury in the optic nerve causes blindness, in the auditory nerve deafness. If any one of them is irritated by pricking, corrosion, or electricity, a sensation is produced of the kind proper to the nerve; if the olfactory nerve, there is a smell; the optic, a flash of light; the auditory, a sound; but no movement is generated. If any one of the five motor pairs is cut, the corresponding muscles cease to act; they are said to be paralyzed, an effect also produced by nervous disease. If the FUNCTIONS OF THE SPINAL CORD. 37 third pair were cut, the motion of the eyeballs would cease, there would no longer be any power of directing the gaze at pleasure ; the most brilliant spectacle would fail to command the sweeping glances of the eye. If the moving portion of the 7th pair were cut on one side, all the muscles of the face on that side would lose their tension, and the equipoise of the two sides being thus destroyed, the face would be set awry, by the action of the unparalyzed muscles. By experiments of this nature, the functions of the several cerebral nerves have been successively ascertained. In like manner, the discovery of the compound nature of the spinal nerves has been fully contirmed. It has been shown beyond the possibility of doubt, that the nerve fibres are of two distinct classes, with different functions, and that the same fibre never serves both functions. Functions of the Spinal Cord and Medulla Obdlongata. 14. With regard to the Spinal Cord, we find, in the first place, that it is necessary to sensation and to voluntary movement (movement from feeling) throughout the entire trunk and extremities of the body. If the cord is cut across at; any part, all feeling is lost, and all power of movement by the will, everywhere below that place, or in every portion of the body where the nerves arising beyond the cut are distri- buted. If the division is made far down in the back, the lower limbs are the parts principally paralyzed ; from them feeling comes no more, nor is it possible to move them by any mental effort. If the cut is in the neck, the paralysis over- takes the arms, trunk, and legs. It becomes evident, that the continuity of the cord with the brain is necessary in order to connect the mental system with the bodily members. The cord by itself will not give the power either of sensation or of voluntary movement. We must regard this portion of the cerebro-spinal axis as a main channel of nervous conveyance for sensation and for voluntary action, between the brain, and the trunk and the extremities of the body. The nerve ramifi- 38 THE NERVOUS SYSTEM. cations are here, as it were, gathered together into one rope or bundle, for convenient transmission to and from the masses of the encephalon. To this extent the cord is the assemblage of the general mass of ramifying or communicating fibres ; we may look upon it as the trunk of the tree, the final stream of the river system.* If now we make experiments upon the cord when dis- severed from the brain, we discover that a power of producing movements, though not voluntary, still remains. On irritat- ing any portion of the substance, movements of the limbs are observed. This effect might, no doubt, arise from the continuity of the part with some of the motor nerves ; for we have seen that movements in a limb are caused by pinching one of the nerves that supply the limb. \ But there is a mode of trying the experiment so as to prove decidedly that the spinal cord is itself a source of movement; that is, to prick the skin of the toes. When this is done, a convulsive stimulus instantly returns upon the limb and throws it into action. Hence we infer that an impression arising on the surface of the body and conveyed to the spinal cord, but not to the brain, causes the cord to send forth a motor stimulus to the moveable organs; a phenomenon, moreover, that ceases on the destruction of the cord. ‘In most instances where the spinal cord has been divided, whether by design or accident, it has been found that al- * Dr. Brown-Séquard has determined by decisive experiments that the transmission of sensitive impressions, in the spinal cord, takes place chiefly through the grey matter, and partly through the anterior columns; the im- pressions being conveyed to the grey matter by fibres passing obliquely across the posterior columns. The novel part of this doctrine is the attributing of a conducting function to the grey matter; although the grey substance of the cord contains white fibres, these are comparatively few in number, and the conclusion seems inevitable that a line of nervous communication is maintained by the corpuscles of the cord and their connecting fibres. The communication with the brain is maintained after cutting through the white columns, provided the grey substance remains intact; or if, although cut into at different places, it is nowhere completely severed. In the point of special function, there is much uncertainty as between the anterior and the posterior columns. CXPERIMENTS ON THE SPINAL CORD. 39 though the will cannot move the paralyzed parts, movements do occur in them of which the individual is unconscious, and which he is wholly unable to prevent. These take place sometimes as if spontaneously, at other times as the effect of the application of a stimulus to some surface supplied by spinal nerves. The apparently spontaneous movements frequently resemble voluntary actions so closely, that it is almost impossible to distinguish them.’ 7 ‘The following experiments serve to illustrate these actions : — ‘If a frog be pithed by dividing the spinal cord between the occipital hole and the first vertebra, an universal convul- sion takes place while the knife is passing through the nervous centre. This, however, quickly subsides ; and, if the animal be placed on the table, he will assume his ordinary position of rest. In some exceptional cases, however, frequent combined movements of the lower extremities will take place for a longer or shorter time after the operation ; when all such disturbance has ceased, the animal remains perfectly quiet, and as if in repose, nor does there appear to be the slightest expression of pain or suffering. He is quite unable to move by any voluntary effort. However one may try to frighten him, he remains in the same place and posture. If now a toe be pinched, instantly the limb is drawn up, or he seems to push away the irritating agent, and then draws up the leg again into its old position. Sometimes a stimulus of this kind causes both limbs to be moved violently backwards. A similar movement follows stimulation of the anus. If the skin be pinched at any part, some neighbouring muscle or muscles will be thrown into action. Irritation of the anterior extremities will occasion movements in them: but it is worthy of note that these movements are seldom so energetic as those of the lower extremities. —Topp and Bowmay, L, 308-9. These and other experiments prove, that to the cord belongs a power of originating movements, at the instance of stimulation applied to the surface or extremities of the body. 40 THE NERVOUS SYSTEM. This function must be attributed to the grey matter, or to the mass of corpuscles enclosed in its substance. It is by the corpuscles that a stimulation can be reflected, diverted, or radiated into new channels. ‘The movements prompted through the cord, by itself, may even be complex and rhythmical, as standing and walking, and locomotion gene- rally ; all which are possible to a certain extent, in many animals, after loss of communication with the brain. The independent action of the spinal cord, in man, is shown in occasional acts of the reflex kind (to be afterwards fully enumerated). When the foot of any one asleep, or under chloroform, is tickled, the limb is withdrawn. In rupture of the spinal cord, irritation of the legs will induce movements, the patient being insensible to the effect. There is one instance of muscular action by most physio- logists ascribed to the spinal cord, and believed to have a peculiar interest in this point of view; that is, the censzon, tone, or tonicity of the muscles. By this is meant the fact that a muscle is never wholly relaxed while the animal is alive. Even in the perfect repose of sleep, there is yet a certain vigour of contraction inhering in all the muscles of the body. ‘The force of contraction is increased at the moment of wakening, and still more when an effort is to be made; but at no time is the relaxation total; the limbs never dangle like a loosely constructed doll, until after the animal is dead. The experiments relied upon for showing that the perma- nent tension of the muscle is in part due to spinal influence, are very striking and not easily explained away. I quote from Dr, Carpenter: ‘It has been proved by Dr. Marshall Hall that the muscular Tension is not dependent on the influence of the Brain but upon that of the Spinal Cord, as the following experiments demonstrate: T'wo Rabbits were taken: from one the head was removed ; from the other also the head was removed, and the spinal marrow was cautiously destroyed with a sharp instrument: the limbs of the former retained a certain degree of firmness and elasticity ; those of FUNCTIONS OF THE MEDULLA OBLONGATA. 41 the second were perfectly lax. Again: ‘The limbs and tail of a decapitated turtle possessed a certain degree of firmness and tone, recoiled on being drawn from their position, and moved with energy on the application of a stimulus. On withdrawing the spinal marrow gently out of its canal, all these phenomena ceased. The limbs were no longer obedient to stimuli, and became perfectly flaccid, having lost all their resilience. The sphincter lost its circular form and contracted state, becoming lax, flaccid, and shapeless. The tail was flaccid.’—(Carpenter, p. 700.) Here we see that the discon- necting of the muscles from the brain still leaves them in a tense condition; whereas that tension gives way the instant the spinal cord is removed; whence we infer that there is an internal source of nervous energy, independent of stimulation from without, although greatly enhanced by the application of the stimulants of the senses. The importance of this fact will be afterwards seen. 15. The Medulla Oblongata, being a continuation of the spinal cord, with additional deposits of grey substance, has the same importance as respects the communication of impressions to and from the brain, but operates more widely in the way of diffusing, transferring, diverting, radiating, and reflecting nervous stimuli. Many of its corpuscles must have for their function the upward spread and ramification of fibres ; while some serve for lateral communication, and others for the reflex function, which probably attains its highest develop- ment in this portion of-the cerebro-spinal axis. Most of the cerebral. nerves arise from the medulla oblongata. It is the proximate centre of hearing and taste ; of the sensibility of the face, the pharynx, larynx, windpipe, and bronchial tubes ; and of the heart, lungs, and stomach. Among reflex movements operated by means of it are— the contraction of the Pupil, and the closure of the Eye-lid, under the stimulus of light; the act of Deglutition ; Sucking in the infant; and, lastly, the capital function of ordinary Respiration. 42 : THE NERVOUS SYSTEM. Functions of the lesser grey centres of the Brain. 16. These various masses lying between the medulla oblongata and the convoluted. hemispheres, must be con- sidered still as the continuation upward of the main stem of the brain, with multiplying, ramifying, and collateral com- munications through the aggregates of corpuscles in the grey portions of each. The paths of sensory impressions upwards, and of motor impressions downwards, must lie in these bodies, although the two lines are not always exhibited in marked local separation. There are also certain instances of the reflex function embodied in these centres. . The Pons Varolit, with the crura cerebri, is to be viewed in great part as a continuation of the spinal cord towards the brain, in which capacity it is essential to sensation and to volition. _The paths of sensation are supposed to be through the fibres and grey substance of the central and posterior portions ; the paths of voluntary motion, through the fibres of the anterior and under portions. By. means .of the grey centres of the pons, there are manifested reflex acts of a marked and powerful kind. It shares’ in the regulation of: the pupil of the eye. More remarkable is its mediation in the prominent movements of expression, as, gesticulation and cries.. It has also, in an eminent degree, ' the function of grouping or. associating the movements; so. long as it:remains, the locomotive rhythm can be maintained, although, after the destruction of the hemispheres, there is no longer a spontaneous commencement of movements. While the pons, and all the centres beneath it, are intact, an animal will: retain and secure the erect posture. Lastly, the removal of the parts above the pons does not take away the promptings to remedy uneasiness, and to remove irritating agents.’ This is the continuation of that exceptional: function of the spinal cord, whereby, in the inferior animals, it can give birth to actions apparently of a voluntary character (see Note, p. 45). It is in connexion with the pons that we have the most FUNCTIONS OF THE PONS VAROLII. 43 conspicuous manifestations of the curious fact of rotatory movement in animals, arising on injuries of parts of the brain. Thus, when the transverse fibres leading to the cere- bellum are cut on one side, the animal revolves, as if on a spit, towards the injured side. Accompanying the rotation, there is a downward movement of the eye-ball on the injured side, and also rolling movements inthe other eye. The effects are arrested. by cutting the. corresponding fibres leading to the other half of the cerebellum. In. reality, the cerebellum may be considered the seat of the disturbance in the case now supposed ; ‘still the movements may also arise by a partial section of one of the cerebral crura or peduncles (in the heart of the pons), but they are’in the opposite direction, that is, away from the injured side.. A complete section of one peduncle. causes.the animal to fall on the opposite side,.on which ‘side the stimulus to the muscles survives, | These rotatory movements: likewise follow from uni- lateral incisions; injuries, and diseases,. in the corpora striata, thalami optici, corpora quadrigemina,. cerebellum, medulla oblongata, and lastly,: the auditory nerve, and the semi- circular canals of the ear.» The: sensation of giddiness or vertigo corresponds to the same: class of effects ; a sensation known to be caused by whirling movements, even although voluntary, and: by rapid visual: movements, as. well as by alcoholic stimulation and other cerebral derangements. | The hypothesis suggested: by this: singular manifestation is, that there exists, in’. permanence,.a powerful nervous stimulation to the muscles of the two sides of the body, such as would cause an’ energetic propulsion of each. In the ordinary condition, the two sets of stimuli are balanced, and produce an equilibrium, disturbed only by the slight remis- sions necessary for locomotion and other voluntary exertions. The destruction of the nervous tracks or centres, on one half of the body, leaves a preponderance on the other; and the one-sided movements, that are seen in consequence, testify how energetic the persistent current must be. If this be the AA THE NERVOUS SYSTEM. true interpretation of the phenomenon, we obtain from it a striking confirmation of the doctrine (to be afterwards ad- verted to) of internal or self-originated movements, as con- trasted with the movements from outward stimulation. 17. The cerebral ganglion named the Corpora Quadrt- gemina is associated with the power of sight. Its destruction produces blindness, and also a permanent dilatation and immobility of the pupil of the eye. The destruction of one side causes loss of vision on the opposite side; but the irri- tation of one side will produce contraction of both pupils. The partial removal of the ganglion is attended with partial and temporary blindness, debility of the muscles on the opposite side of the body, and sometimes giddiness and slight rotatory movements. The anatomical connexions with the optic nerve also point to the conclusion, that the principal track of visual impressions to the brain is by the corpora quadrigemina. 18. Notwithstanding its name, the large ganglion called » Optic Thalami has but little relationship to the sense of vision. Being in immediate connexion with the hemispheres, it is the final organ of multiplication or diffusion of fibres coming from below; and is supposed to consist chiefly of the sensory tracts. Like the other ganglia, it is inferred to contain fibres reflected downwards, as well as those diffused into the hemispheres. Experiments appear to show that it contributes to the function of co-ordinating movements, such as those of locomotion and emotional expression. Section on one side causes rotatory movements, usually towards the opposite side. 19. The other great ganglionic mass at the entrance to the hemispheres, the Corpora Striata, is believed to contain principally the motor fibres. We are to presume that the large amount of grey matter 1s chiefly concerned in mul- tiplying the fibres entering into the hemispheres, but partly also in reflecting them downwards, so as to constitute circuits of reflex movements. The collective reflected fibres of all the ganglia at the base of the brain, together with the cerebellum, FUNCTIONS OF THE CEREBRAL HEMISPHERES. 45 are considered as making up a department or region, which is the seat of reflex acts, and of a large number of grouped or associated movements, involved alike in voluntary action and in emotional expression. It is not unlikely that conscious- ness accompanies the reflected, as well as the transmitted, currents of this whole region. Funetions of the Cerebral Hemispheres. 20. The Convoluted Hemispheres of the brain, in man and in the higher animals, are by far the largest mass of nervous substance, white and grey, and may be considered as associated with the most complicated of the mental functions, namely, those related to Intelligence. Cutting or pricking the hemispheres is not attended with either sensation or movement. Pressure from above down- wards, or concussion, produces stupor. When the hemi- spheres are removed, the following results are observed :— First, the two higher senses, Sight and Hearing, are lost. Secondly, Memory, and all the powers characteristic of in- tellect or thought, are abolished. Thirdly, Volition, in the shape of purpose and forethought, is extinguished.* This is involved in the loss of intelligence. An animal cannot proceed in the search for food, without ideas of what it wants, and a recollection of the means or instrumentality of pro- cedure. Fourthly, there is still a power of accomplishing mary connected movements. An animal may walk, swim, or fly, but there is no tendency to begin these actions. Fifthly, * A lower kind of volition is possible in the absence of the hemispheres, as is shown by the experiments of Pfliiger and others. A beheaded frog, whose hind foot is touched with an acid, makes efforts with the other hind foot to wipe away the acid. If a drop is placed on the back, on one side, the animal uses the leg on that side to relieve itself of the sting; but, if by cutting the nerve that legis rendered powerless, the other leg is stimulated to remove the acid. These actions have the essential character of voluntary actions, and yet they proceed from no higher a centre than the spinal cord. They represent volition in one of its initial or undeveloped forms, the putting forth of action, to alleviate a present pain. The appearances would betoken that the pain is felt, or that the animal is conscious. 46 THE NERVOUS SYSTEM. there remains an inferior form of the sensibility of the three lower senses—Touch, Taste, and Smell. By stimuli applied to these senses, reflex movements may be excited. Thus, the hemispheres are not the exclusive seat of con- sciousness, but they are doubtless the seat both of Intelligence and of nearly all the innumerable shades and varieties of Sensation and Emotion. The attempt to localize the mental functions in special portions of the cerebral mass, has been thwarted by observa- tions of a remarkable kind. The phrenologists noticed cases where the destruction or disease of one hemisphere was un- accompanied with the entire loss of any function; the in- ference being that the hemispheres were duplicate bodies performing the same office, like the two eyes, or the two halves of the nostrils. But cases have been recorded of disease of large portions of the brain in both hemispheres at once, without apparent loss of function ; which would require us to extend still farther the supposition of a plurality of nervous tracks for a single mental aptitude. Functions of the Cerebellum. 21. The experiments made upon the Cerebellum, and the inferences founded upon its comparative size in different animals, have led some physiologists to assign to it the function of harmonizing and co-ordinating the locomotive and other movements. ‘Flourens removed the cerebellum from pigeons by suc- cessive slices. During the removal of the superficial layers there appeared only a slight feebleness and want of harmony in the movements, without any expression of pain. On reaching the middle layers, an almost universal agitation was manifested, without any sign of convulsion; the animal performed rapid and ill-regulated movements; it could hear and see. After the removal of the deepest layers, the animal lost completely the power of standing, walking, leaping, or flying. ‘The power had been injured by the previous mutila- FUNCTIONS OF THE CEREBELLUM. 47 tions, but now it was completely gone. When placed. upon his back, he was unable to rise. . He did not, however, remain quiet and motionless, as pigeons deprived of the cerebral hemispheres do; but evinced an incessant rest- lessness, and an inability to accomplish any regular or definite movement. He could see the instrument raised to threaten him with a blow, and would make a thousand contortions to avoid it, but did not escape. Volition and sensation remained—the power of executing movements remained ; but that of co-ordinating these movements into regular and combined actions was lost. ‘Animals deprived of the cerebellum are in a condition very similar to that of a drunken man, so far as relates to their power of locomotion. They are unable to produce that combination of action in different sets of muscles which is necessary to enable them to assume or maintain any atti- tudes. They cannot stand still for a moment, and in attempting to walk, their gait is unsteady, they totter from side to side, and their progress is interrupted by frequent falls. The fruitless attempts which they make to stand or walk are sufficient proof that a certain degree of intelligence remains, and that voluntary power continues to be enjoyed.’ (Topp and Bowmay, L., p. 359.) When the cerebellum is cut away at the top, the aninal moves backward. When one side is cut away, the animal rolls over to the other side; the eye of the sound side is turned outwards and downwards, the other eye inwards and upwards. Sometimes a vertiginous action ensues, as if the body were revolved on a spit. The inference drawn from these experiments—that the cere- bellum is the exclusive seat of combined movements—is denied by Dr. Brown-Séquard. He says—‘I have ascertained that it is by the irritation they produce on the various parts of the base of the brain that the diseases of the cerebellum, or its extirpation in animals, cause the disorder of movements which has been con- sidered as depending upon the absence of a guiding power. In fact, the least irritation of several parts of the brain with only the 48 THE NERVOUS SYSTEM. point of a needle, may generate very nearly the same disorder of movement that follows the extirpation of the cerebellum. I have thus been led to conclude that, after this extirpation, or after the destruction by disease of a large or small part of this nervous centre, it is not its absence, but some irritative influence upon the parts of the encephalon that remain unaltered which causes the irregularity of movements (Lectures, p. 79). This line of criticism has the defect of proving too much; it would lead to the conclusion that the cerebellum has no function. The views of Flourens have been recently supported by M. Vulpian; who, after comparing numerous facts, has shown that, although disease or deficiency of the cerebellum is not uniformly attended with utter incapability of locomotion, yet there is a want of steadiness, and a great liability to stumble, in such instances. The safest inference at present seems to be, that the cerebellum is not the sole organ concerned in rhythmical or combined movements, but concurs with some of the other ganglia in upholding this function. The remark above made, regarding the plurality of nervous tracks for the higher cerebral aptitudes, may be extended to the inferior department of the com- bined or associated movements. Of the Nerve Force, and the course of Power in the Brain. 22. The structure of the nervous substance, and the ex- periments made upon the nerves and nerve centres, establish beyond doubt certain peculiarities as belonging to the force that is exercised by the brain. This force is of a current nature; that is to say, a power generated at one part of the structure is conveyed along an intervening substance, and discharged at some other part. The different forms of Elec- tricity and Magnetism have made us familiar with this sort of action. In a voltaic cell, energy is generated and trans- mitted along a wire with inconceivable rapidity to any place where the conductor reaches. This portable, or current, character of the nerve force is what enables movements, distant from one another in the body, to be associated together under a common stimulus. THE NERVE FORCE. 49° An impression of sound—a musical note, for example, is carried to the brain; the result is a responsive action and excitement extending to the voice, mouth, eyes, head, &c. This multiplex and various manifestation implies a system of connexion among the centres of action, whereby many strings can be touched from one point; a connexion due to the conducting nerves that pass and repass from centre to centre, and from the centres to the muscular apparatus over the body. Supposing the corpora quadrigemina to be a centre for the sense of vision, an impression passing to this centre propagates a movement towards many other centres,— to the convoluted hemispheres upwards, to the cerebellum behind, and to the medulla oblongata and spinal cord beneath ; and through these various connexions an extensive wave of effects may be produced, ending in a complicated chain of movements all over the framework of the body. Such a system of intercommunication and transmission of power is therefore an essential part of the bodily and mental structure. 23. The experiments of Du Bois Reymond, show that there is a community of nature between the nerve force and common electricity. Electric currents are constantly maintained in the nerves and muscles, their character being changed during sensation and muscular contraction. The direction of these currents has been minutely examined by Du Bois Reymond, aud he lays down a number of general principles regarding them. ‘The following are some of his conclusions :— ‘The muscles and nerves, including the brain and spinal cord, are endowed during life with an electro-motive power.’ ‘This electro-motive power acts according to a definite law, which is the same in the nerves and in the muscles, the law of the antagonism of the longitudinal and the transverse sections. The longitudinal surface is positive, and the transverse section negative.’ ‘Every minute particle of the nerves and the muscles must be supposed to act according to the same law as the whole nerve or muscle.’ The total currents are, in fact, the combined effect of these currents circulating round the ultimate particles. 4 50 THE NERVOUS SYSTEM. ‘The current in muscles when in the act of contraction, and in nerves when conveying motion, or sensation, undergoes a sudden and great negative variation of its intensity.’ ‘It has not been ascertained whether, in the act of contraction, the mus- cular current is only diminished, or wholly vanishes, or whether it changes its direction.’ Thus the proper nerve force—that is to say, the currents in the nerves during sensation and movement—is so far in unison with electricity, that it neutralizes and reverses genuine electrical currents proved to exist in the nerves and muscles in their condition of rest. This is the utmost that can be said in the present state of our knowledge. Even granting that the force conveyed along the nerves during the mental processes were identical with voltaic electricity, the character of the nerve substance would create some points of contrast between the phenomena of vital action and a common voltaic battery. The conducting power of nerve fibre is at- tended with nervous waste, and the substance has to be con- stantly renewed from the blood, which is largely supplied to the nerves, although perhaps not so largely as to the vesicles. If now we compare this liability to waste and exhaustion with the undying endurance of an electric wire, we shall be struck with a very great contrast. The wire is doubtless a more compact, resisting, and sluggish mass; the conduction requires a. certain energy of electric action to set it agoing, and in the course of a great distance becomes faint and dies away. ‘The nerve, on the other hand, is stimulated by a slighter influence, and propagates that influence, with in- crease, by the consumption of its own material. The wire must be acted on at both ends, by the closure of the circuit, before acting as a conductor in any degree; the nerve takes fire from a slight stimulus like a train of gunpowder, and is wasted by the current that it propagates. If this view be correct, the influence conveyed is much more beholden to the conducting fibres, than electricity is to the copper wire. The fibres are made to sustain or increase the force at the cost of their own substance. SOURCE OF THE NERVE FORCE. 51 The nerve force is propagated more slowly than an electric current through a wire. ‘The rate has been estimated at about 200 feet a second on an average. (It is to be remarked that a nerve is not a simple conductor, but is supposed to consist of a countless number of molecules, each of which has, playing round it, an electrical current, or currents, which are an obstacle to the simple or direct propagation.) There is always a certain delay in passing through the nerve centres; a reflex movement occupies from z/5 to 75 of a second under favourable circumstances, which is more time than would be required for transmitting an influence through the same length of nerve without interruption. When the stimulus is weak, a proportionally longer time is required to produce the corresponding movement. We may suppose that what is called nervous excitement is a quicker rate of the nervous current. 24, It is now an admitted doctrine that the nervous power is generated from the action of the nutriment supphed to the body, and is therefore of the class of forces having a common origin, and capable of being mutually converted—including mechanical momentum, heat, electricity, magnetism, and chemical decomposition. The power that animates the human frame and keeps alive the currents of the brain, has its origin in the grand primal source of reviving power, the Sun; his influence exerted on vegetation builds up the structures whose destruction and decay within the animal system give forth all the energy concerned in maintaining the animal processes. What is called vitality is not a peculiar force, but a collocation of the forces of inorganic matter in such a way as to keep up a living structure. If our means of observation and measurement were perfect, we might render an account of all the nutriment consumed in any animal or human being ; we might calculate the entire amount of energy evolved in the changes that make up this consumption, and allow one portion for animal heat, another for the processes of secretion, a third for the action of the heart, lungs, and intestines, a fourth for the muscular exertion made within the period, a $e LIBRARY an ag igs UNIVE eRSITY OF Hs Ne 52 THE NERVOUS SYSTEM. fifth for the activity of the brain, and so on till we had a strict balancing of receipt and expenditure. The nerve force that is derived from the waste of a given amount of food, is capable of being transmuted into any other form of animal life. Poured into the muscles during violent conscious effort, it increases their activity ; passing to the alimentary canal, it aids in the force of digestion ; at other points it is converted into sensible heat ; while the same power is found capable of yielding true electrical currents. The evidence that estab- lishes the common basis of mechanical and chemical force, heat, and electricity—namely, their mutual convertibility and common origin—establishes the nerve force as a member of the same group. | 25. The current character of the nerve force, leads to a considerable departure from the ancient mode of viewing the position of the brain as the organ of mind. We have seen that the cerebrum is a mixed mass of grey and white matter, —the matter of centres and the matter of conduction. Both are required in any act of the brain known to us. The smallest cerebral operation includes the transmission of an influence from one centre to another centre, from a centre to an extremity, or the reverse. Hence we cannot separate the centres from their communicating branches; and if so, we cannot separate the centres from the other organs of the body that originate or receive the nerve stimulation. The organ of mind is not the brain by itself: it is the brain, nerves, muscles, organs of sense and viscera. When the brain is in action, there is some transmission of nerve power, and the organ that receives, or that originated, the power, is an essential part of the circle of mechanism. The notion that the brain is a sensoriwm, or inner chamber, where impressions are accumulated, like pictures put away in a store, requires to be modified and corrected. The brain is highly retentive of the impressions made upon it; they are embodied in its structure, and are a part of its srowth. They may be reproduced on after occasions, and then what we find is a series of currents and counter currents, SUPPLY OF BLOOD TO THE NERVES. 53 much the same as what existed when the impression was first made. When the mind is in the exercise of its functions, the physical accompaniment is the passing and re-passing of innumerable streams of nervous influence. Whether under a sensation of something actual, or under an emotion or an idea, or a train of ideas, the general operation is still the same. It seems as if we might say, no currents, no mind. The transmission of ivfluence along the nerve fibres from place to place, seems the very essence of cerebral action. This trans- mission, moreover, must not be confined within the limits of the brain : not only could no movements be kept up and no sensation received by the brain alone, but it is uncertain how far even thought, reminiscence, or the emotions of the past and absent, could be sustained without the more distant communications between the brain and the rest of the body —the organs of sense and of movement. The more immediate source of nervous power is an abundant supply of blood. The arrest of the circulation in the brain, by stoppage of the heart, or by pressure on the head, is followed by loss of consciousness. On the other hand, excessive rapidity of the circulation quickens the thoughts and feelings, in other words, is productive of excitement, which may amount even to delirium. Again, as regards the quality of the blood, excess of carbonic acid, of urea, or of the other impurities removed by the excreting organs, depresses or destroys the mental function; the same effect arising from deficiency of nutritive material. And, obversely, abundance of nourishment, the full exercise of the purifying organs, and the presence of the agents known as stimulants, by affecting the quality of the blood, impart exhilaration and vigour to the mental functions. ae ‘Ay pam ti ath Feta f i 7% ri “ii: habive) eis + ay 1 ae iy x thee my she j UF rot rh ‘ er a <4 Z 7 bee f v é PO A ree LH bi Pal } - © ail. (CRs f ; iy ato fp ih ee ot Silas aety | ad at bi arte} 1Wacd ity « + if ory ' lier inf aserys qe re} eine $elvivert ' + ve MT S Anlet Ott Holt a, six hh EA ei éhigire ey Ot BRE Pe vin! ‘ae ‘ct 9, re aa vA at fas ry: (aera nse the i ahi aie s ptis9 ms oar | aro * sy. it ih !4 Garces Mh Het ese mits ey Ge rye be nay BULGER | " 47ru mie, Wi icin pe eee eee mit, , id natn ei | 3 ‘ * ai nhab dy. ¢* ee "y q i a as " Paki ed ye ink (a th ina 1) su i of ; MOVEMENT, SENSE, AND INSTINCT. , vo ei; . (aa MAT ied My WE now commence the subject of MIND proper, or the enumeration and explanation of the states and varieties of Feeling, the modes of Action, and the powers of Intelligence, comprised in the mental nature of man. In the First Book, which is to comprehend the Movs- MENTS, SENSATIONS, APPETITES, and Instincts, I propose to deal with what may be termed the inferior region of mind, the inferiority being marked by the absence, in any great degree, of Intellect and cultivation. This is the region wherein man may be most extensively compared with the brute creation, whose intelligence and education are comparatively small. When the powers of a superior intellect, and the example and acquirements of former generations, are superadded to the primitive Sensations and Instincts, there results a higher class of combinations, more difficult to analyze and describe, and belonging therefore more properly to a later stage of the exposition. / Tt will, however, be remarked as a novelty in the plan thus announced, that the Appetites and Instincts have been included in the same department as the Sensations. In the works of former writers on Mental Science, as, for example, Reid, Stewart, Brown, and Mill, those portions of our nature have been included among the general group of ACTIVE Powers, including Desire, Habit, and the Will. My reasons for departing from the example of these eminent writers are the following. | In the first place, the Appetites and Instincts are scarcely at all connected with the higher operations of intelligence, and therefore they do not require to be preceded by the exposition of the Intellect ; everything necessary to be said respecting them may be given as soon as the Sensations 58 MOVEMENT, SENSE, AND INSTINCT. .are discussed. In the second place, I hope to make it appear, that the illustration of the Intellectual processes will gain by the circumstance that Appetite and Instinct have been previously gone into. Thirdly, the connexion of Appetite with Sensation is of the closest kind. Fourthly, as regards Instinct, I conceive it to be proper to render an account of all that is primitive in our nature—all our un- taught activities—before entering upon the process of acquisi- tior as treated of under the Intellect.’ In addition to these reasons stated in advance, I trust to the impression produced by the effect of the arrangement itself, for the complete justification of my departure from the plan of my prede- CeSsors. The division of the present Book will be into four chapters. The subject of Chapter first 1s ACTION and MOVEMENT considered as spontaneous, together with the Feelings and Perceptions resulting from muscular activity. Chapter second comprehends the SENSES and SENSATIONS. Chapter third treats of the APPETITES. Chapter fourth includes the INSTINCTS, or the untaught Movements, and also the primitive rudiments of Emotion and of Volition. These last subjects are necessary in order to complete the plan of the present Book, which professes to exhaust all the primitive germs, whether of Action or Feeling, belonging to our nature, before proceeding to the consideration of intelligence and acquisition. In the complete system of the mind, the Intellect is thus placed midway between the instinctive and the cultivated emotions and activities, being itself the instrument for converting the one class into the other, Sete ete bs OF SPONTANEOUS ACTIVITY AND THE FEELINGS OF MOVEMENT. ik le: feelings connected with the movements of the body or the action of the muscles, are now recognized as a distinct class, differing materially from the sensations of the five senses. They are often regarded as proceeding from a Sense apart, a sixth, or Muscular Sense, and have accordingly been enrolled under the general head of sensations. That they are to be dealt with asa class by themselves, no less than sounds or sights, love, irascibility, or the emotion of the ludicrous, is generally admitted. With regard, however, to the position of this class of feel- ings in the plan or arrangement of our subject, there is still room for differences of opinion. In my judgment they ought not to be classed with the Sensations of the five Senses ; and I believe further that the consideration of them should pre- cede the exposition of the Senses. The reasons for this opinion are the two following :—namely, that movement precedes sensation, and is at the outset independent of any stimulus from without ; and that action is a more intimate and insepar- able property of our constitution than any of our sensations, and in fact enters as a component part into every one of the senses, giving them the character of compounds while itself is a simple and elementary property. These assertions re- quire to be proved in detail, but before doing so, it is advisable to notice briefly the mechanism or anatomy of movement in the animal frame. OF THE MUSCULAR SYSTEM. 2. Muscular Tissue.—‘ The muscular tissue is that by means of which the active movements of the body are produced. It con- 60 THE MUSCULAR SYSTEM. sists of fine fibres, which are for the most part collected into distinct organs, called muscles, and in this form it is familiarly known as the flesh of animals; these fibres are also disposed round the sides of cavities and between the coats of hollow viscera, forming strata of greater or less thickness. The muscular fibres are endowed with contractility—a remarkable and characteristic property, by virtue of which they shrink or contract more or less rapidly under the influence of certain causes which are capable of exciting or calling into play the property in question, and which are therefore named stimuli. A large class of muscles, comprehending those of locomotion, respiration, ex- pression, and some others, are excited by the stimulus of the will, or volition, acting on them through the nerves; these are therefore named ‘voluntary muscles,’ although some of them habitually, and all occasionally, act also in obedience to other stimuli, There are other muscles or muscular fibres which are entirely withdrawn from the control of the will, such as those of the heart and intestinal canal, and these are accordingly named ‘involuntary.’ These two classes of muscles differ not only in the mode in which they are excited to act, but also to a certain extent in their anatomical characters.’—SHARPEY ; QUAIN’S Anatomy. Structure of Voluntary Muscles.—‘The voluntary muscular fibres are for the most part gathered together into distinct masses, or muscles of various sizes and shapes, but most generally of an oblong form, and furnished with tendons at either extremity, by which they are fixed to the bones. The two attached extremities of a muscle are named, in anatomical descriptions, its origin and insertion,—the former term being usually applied to the attach- ment which is considered to be most fixed, although the rule cannot always be applied strictly. The fleshy part is named the belly. ‘The muscular fibres are collected into packets or bundles of greater or less thickness, named fasciculi, or lacerti, and the fibres themselves consist of much finer threads visible by the aid of the microscope, which are termed muscular filaments, or fibrillee. ‘ The fibres, although they differ somewhat in size individually, have the same average diameter in all the voluntary muscles, namely, about z>> of an inch; and this holds good whether the THE MUSCLES. 61 muscles be coarse or fine in their obvious texture. According to _ Mr. Bowman their average size is somewhat greater in the male than in the female, being in the former 34, and in the later 74, or more than a fourth smaller.’—Jb. ‘As to the structure of fibres, it has been ascertained that each is made up of a larger number of extremely fine filaments or fibrils, inclosed in a tubular sheath.’ ‘It would seem that the elementary particles of which the fibril is made up, are little masses of pellucid substance presenting a rectangular outline, and appearing dark in the centre.’ ‘The length of the elementary particles is estimated by Mr. Bowman at 5755 of an inch. He finds that their size is remarkably uniform in mammalia, birds, reptiles, fishes, and insects.’—JD. . Nerves of Voluntary Muscles.—‘ The nerves of a voluntary muscle are of considerable size. Their branches pass between the fasciculi, and repeatedly unite with each other in form of a plexus, which is for the most part confined to a small part of the muscle, or muscular division in which it lies. From one or more of such primary plexuses nervous twigs proceed and end by finer or terminal plexuses, formed by slender bundles consisting of two or three primitive tubules each, some of them separating into single tubules.— Ib. ‘By means of the microscope these fine nervous bundles and single tubules may be observed to pass between the muscular fibres, and after a longer or shorter course, to return to the plexus. They cross the direction of the muscular fibres directly or obliquely, forming wide arches; and on their return they either rejoin the larger nervous bundles from which they set out, or enter into other divisions of the plexts. The nervous filaments, therefore, do not come to an end in the muscle, but form loops or strings amung its fibres.’—Ib.* I refrain from entering into the description given of the involuntary muscles,—those of the heart, intestines, bronchial tubes, iris, middle coat of the arteries, &c.—as being less important for the object of the present work. It will, how- * The active connexion between the nerves and the muscles would seem to consist in an electrical current passing from the one to the other. The numerous experiments of Du Bois Reymond and others in this subject, scarcely permit any other conclusion. 62 THE MUSCULAR SYSTEM. ever, be interesting to hear what the same authority has said on the Sensibility of muscle, and also on the Contractility, or the source of its power as a mechanical prime mover. 3. Sensibility.—‘ This property is manifested by the pain which is felt when a muscle is cut or lacerated, or otherwise violently injured, or when it is seized with spasm. Here, as in other instances, the sensibility, properly speaking, belongs to the nerves which are distributed through the tissue, and accordingly, when the nerves going to a muscle are cut, it forthwith becomes insen- sible. It is by means of this property, which is sometimes called the ‘muscular sense,’ that we become conscious of the existing state of the muscles which are subject to the will, or rather of the condition of the limbs and other parts which are moved through means of the voluntary muscles, and we are thereby guided in directing our voluntary movements towards the end in view. Accordingly, when the muscular sense is lost, while the power of motion remains,—a case which, though rare, sometimes occurs,—the person cannot direct the movements of the affected limbs without the guidance of the eye.’ On this passage I would remark that the two sensibilities described differ very much in their character. The sensibility to injuries is a fact distinct from those feelings of the state of voluntary muscles that serve to guide the movements in working for ends. The one is the passive, and the other the active, sensibility of muscle. 4. Irritability or Contractility.—‘ In order to cause contraction, the muscle must be excited by a stimulus. The stimulus may be applied immediately to the muscular tissue, as when the fibres are irritated by a sharp point; or it may be applied to the nerve or nerves which belong to the muscle; in the former case the stimulus is said to be ‘immediate,’ in the latter ‘‘ remote.” The nerve does not contract, but it has the property, when stimulated, of exciting contractions in the muscular fibres to which it is distributed, and this property, named the “vis nervosa’ (true nervous force), is distinguished from contractility, which is confined tothe muscle. Again, a stimulus may be either directly applied to the nerve of the muscle, as when that nerve is itself mechanically irritated or galvanized ; or it may be first made to THE STIMULI TO MUSCLES. 63 act on certain other nerves, by which its influence is, so to speak, conducted in the first instance to the brain or spinal cord (or perhaps even to some subordinate nervous centre) and thence transferred or reflected to the muscular nerve. ‘The stimuli to which muscles are obedient are of various kinds; those best ascertained are the following, viz. :—1. Me- chanical irritation of almost any sort, under which head is to be included sudden extension of the muscular fibres. 2. Chemical stimuli, as by the application of salt or acrid substances. 38. Electrical ; usually by means of a galvanic current made to pass through the muscular fibres, or along the nerve. 4. Sudden heat or cold. / These four may be classed together as physical stimuli. Next, mental stimuli, viz.—1. The operation of the will, or voli- tion. 2. Emotions, and some other involuntary states of the mind. Lastly, there still remain exciting causes of muscular motions in the economy which, although they may probably turn out to be physical, are as yet of doubtful nature, and these, until better known, may perhaps, without impropriety, be called organic stimuli; to this head may be also referred, at least pro- visionally, some of the stimuli which excite convulsions and other involuntary motions which occur in disease.’—p. clxxvil. Of the stimuli thus enumerated the most interesting to us are the mental stimuli. These are described as of two kinds ; the Emotions —or the influence of the ’eelings—and the Will. A third kind is the Spontaneous force to be presently dis- cussed. _/There is one other property of muscle, alluded to in the previous chapter, which is described as follows :— 5. Tonicity or Tonic Contraction‘ Although in muscles generally, contraction is succeeded by complete relaxation, there are various muscles which, after apparently ceasing to contract, remain in a state of tension, and have still a certain tendency to approximate their points of attachment, altbough this tendency is counterbalanced by antagonistic muscles, which are in the same condition, and the limb or other moveable part is thus maintained at rest. This condition of muscle is named “tonicity,” or the “tonic state.’ It is no doubt a species of contraction, as well as the more conspicuous and powerful action with which it alternates ; but it is employed merely to maintain equilibrium, not to cause motion, and it is not temporary but enduring— con- 64 SPONTANEOUS ACTIVITY. tinuing during sleep when volition is in abeyance, and occasioning no fatigue. It appears to be excited through the medium of the nerves, though independently of the will, for when the nerves are cut it ceases, and then the muscles nearly become flaccid : the stimulus which acts on the nerves is not known.’ PROOFS OF SPONTANEOUS ACTIVITY. 6. We have now to consider the evidence that there is for the existence of a class of movements and actions, anterior to, and independent of, the sensations of the senses. This question, brought on here to settle a point of preced- ence or arrangement, has a far wider.import, and will re-appear on various occasions in the course of the subse- quent exposition. | The proofs principally relied on are the following :— (1.) The already mentioned fact of the Tonicity of muscles. This fact I regard as proving the existence of a central stimulus in the nervous system. The tonicity does not, indeed, amount to actual movement ; still, it is only a lower degree of the same thing: and what one centre does in a low degree, another may do in a higher; the peculiar mode of operation is established as a fact of the nervous mechanism.* (2.) The permanent closure of certain of the muscles— those named sphincters—is an effect of the same nature as the tonicity, but displaying a more energetic stimulus still, * Some physiologists would ascribe the tonicity, not to the exclusive influence of the centres, but to the existence of a constant stimulation pro- ceeding from the extremities by the incarrying nerves. They allege in support of this view, that when all the sensory roots of the spine are cut, the tonicity disappears. This, however, would not affect the general doctrine in question. Granting that the muscular stimulus is in one sense reflex, and arises from a perennial irritation of the incarrying fibres, this constant irritation is not what we usually understand by stimulation from without. It isa current arising out of some constant condition of the sensitive tissues, and not out of visible and remitted applications to the parts. A constant stimulus is no stimulus at all. The real point is—given a certain intensity of outward stimulation, the resulting movements will vary according to the condition of the nerves and nerve centres; the same stimulus finding at one time a feeble, and at another time an energetic, response. PROOFS OF SPONTANEOUS ACTIVITY. 65 such as we can refer only to central influence. It cannot be referred to any impression from without. Neither can it be wholly ascribed to the muscle’s own contractility, seeing that the destruction, or paralysis, of certain of the centres leads to the total relaxation of those muscles. The singular rotatory movements, arising from uni-lateral section of the pons ‘varolii and other ganglia, suggest, in a particularly marked manner, the existence of a high per- manent charge of nervous power, ordinarily disguised by being in a state of equilibrium. (3.) It is not altogether irrelevant, to cite the activity maintained by involuntary muscles, as showing the existence of a mode of power originating with the nerve centres. Nervous influence is required for maintaining the circulation of the blood, the movement of the food along the alimentary canal, &c., all which points to an inward evolution of force, although modified by stimulation in the several organs. It may be said that, when the movements are once commenced, the completion of one may be a stimulus to the succeeding ; still the question would recur—by what force does the heart begin to beat? Thus the notion of an initiative existing in the nerve centres is borne out by the tonicity, by the action of the sphincters, by the still more energetic movements of rotation, and by the analogy of the involuntary muscles. Seeing that the spinal cord and the other inferior ganglia are found capable of originating muscular contractions, we are entitled to suppose that the larger masses of the brain may be the sources of a much more abundant and conspicuous activity than these examples afford. The proofs that follow are intended to put in evidence the existence of such movements. (4.) In wakening from sleep, movement precedes sen- sation, If light were essential to the movements concerned in vision, it would be impossible to open the eyes. The act of wakening from sleep can hardly be considered in any other view, than as the reviving of the activity by a rush of nervous power to the muscles, followed by the exposure 5 66 SPONTANEOUS ACTIVITY. of the senses to the influences of the outer world. The first symptom of awakening that presents itself is a general com- motion of the frame, a number of spontaneous movements— the stretching of the limbs, the opening of the eyes, the expansion of the features—to all which succeeds the revival of the sensibility to outward things. Mysterious as the nature of sleep is in the present state of our knowledge, we are not precluded from remarking so notable a circumstance, as the priority of action to sensibility, at the moment of wakening.* But if this be a fact, we seem to prove, beyond a doubt, that the renewed action must originate with the nerve centres themselves. ‘The first gestures must be stimulated from within; afterwards, they are linked with the gestures and movements suggested by sense and revived by intel- ligence and will. The higher degree of permanent tension in the muscles when we are awake, is partly owing to the increased central force of the waking states, and partly to the stimulus of sensation. But in all cases, the share due to the centres must be considerable, although rendered difficult to estimate when mixed up with sensational stimulus. Thus the force that keeps the eye open throughout the day, is in a certain measure due to the spontaneous energy that opened it at the waking moment, for that force does not necessarily cease when the other force, the stimulus of light, commences. We are at liberty to suppose that the nourished condition of the nerves and nerve centres, consequent on the night’s repose, is the cause of that burst of spontaneous exertion at the moment of awakening. The antecedent of the activity is physical rather than mental; and this must be the case with spontaneous energy in general. When coupled with sen- * This is maintained by Aristotle (Physica VIII. 2). He says that these wakening movements come, not from sense, but from an internal source. Some writers have taken the opposite view, but they have not, so far as I am aware, adduced any decided facts in support of that view. If we cannot establish an absolute priority of movement in the act of awakening, we may, at least, maintain that movement concurs with, and does not follow, the re-animation of the senses. EXUBERANT ACTIVITY OF THE YOUNG. 67 sation, the character of the activity is modified so as to render the spontaneity much less discernible. (5.) The next proof is derived from the early movements of Infancy. These I look upon as in great part due to the spontaneous action of the centres. The mobility displayed in the first stage of infant existence is known to be very great ; and it continues to be shown in an exuberant degree all through childhood and early youth. This mobility can be attributed only to one of three causes. It may arise from the stimulus of Sensation, that is, from the sights, sounds, contacts, temperature, &c., of outward things. It may, in the second place, be owing to Emotions, as love, fear, anger. Or, lastly, the cause may be Spontaneous energy. The two first-named influences, external sensation and inward emction, are undoubted causes of active gesticulation and movement. But the question is, Do they explain the whole activity of early infancy and childhood? I think not, and on evidence such as the following. We can easily observe when any one is under the influence of vivid sen- sation ; we can tell whether a child is acted on by sights, or sounds, or tastes. And if the observation is carefully made, I believe it will be found, that although the gesticulations of infants are frequently excited by surrounding objects, there are times when such influence is very little felt, and when, nevertheless, the mobility of the frame is strongly manifested. With regard to inward feelings, or emotions, the proof is not so easy ; but here, too, there is a certain character belonging to emotional movements, that serves to discriminate them when they occur. The movements, gestures, and cries of internal pain are well marked; so pleasurable feeling is distinguished by the equally characteristic flow of smiles and ecstatic utterance. If there be times of active gesticulation and exercise that show no connexion with the sights and sounds, or other influence of the outer world, and that have no peculiar emotional character of the pleasurable or painful kind, we can ascribe them to nothing but the mere abund- ance and exuberance of self-acting muscular and cerebral 68 SPONTANEOUS ACTIVITY. energy, which rises and falls with the vigour and nourish- ment of the general system. The activity of young animals in general, and of animals remarkable for their active endowments (as the insect tribe), may be cited as strongly favouring the hypothesis of spon- taneity. When the kitten plays with a worsted ball, we always attribute the overflowing fulness of moving energy to the creature’s own inward stimulus, to which the ball merely serves for a pretext. So an active young hound, refreshed by sleep or kept in confinement, pants for being let loose, not because of anything that attracts his view or kindles up his ear, but because a rush of activity courses through. his members, rendering him uneasy till the confined energy has found vent ina chase or arun. We are at no loss to dis- tinguish this kind of activity from that awakened by sen- sation or emotion; and the distinction is recognized in the modes of interpreting the movements and feelings of animals. When a rider speaks of his horse as ‘fresh,’ he imples that the natural activity is undischarged, and pressing for vent ; the excitement caused by mixing in a chase or in a battle, is a totally different thing from the spontaneous vehemence of a full-fed and underworked animal. It is customary in like manner to attribute much of the activity of early human life, neither to sensation nor to emotion, but to ‘freshness,’ or the current of undischarged activity. There are moments when high health, natural vigour, and spontaneous outpouring, are the obvious ante- cedents of ebullient activity. The very necessity of bodily exercise felt by every one, and most of all by the young, is a proof of the existence of a fund of energy that comes round with the day and presses to be discharged. Doubtless, it may be said that this necessity may proceed from a state of the muscles, and not from the centres; that an uneasy craving rises periodically in the muscular tissue, and is transmitted as a stimulus to the centres, awakening a nervous current of activity in return. Even if this were true, it would not materially alter the case we are labouring to EXCITEMENT ILLUSTRATES SPONTANEITY. 69 establish—namely, a tendency in the moving system to go into action, without any antecedent sensation from without or emotion from within, or without any stimulus extraneous to the moving apparatus itself. But we do not see any ground for excluding the agency of the centres, in the com- mencing stimulus of periodical active exercise. The same central energy that keeps up the muscular tonicity, must be allowed to share in the self-originating muscular activity. If so, the demand for exercise that comes round upon every actively constituted nature, is a strong confirmation of the view we are now engaged in maintaining. Coupling together, therefore, the initial movements of infancy, the mobility of early years generally, the obser- vations on young and active members of the brute creation, and the craving for exercise universally manifested, we have a large body of evidence in favour of the doctrine of spon- taneous action. (6.) The operation of what is termed Excitement likewise corroborates the position we are now maintaining. The physical fact of the excited condition is an increase in the quantity, or a change in the quality, of the blood in the brain. The mental fact is the increase of mental energy in all its modes. A stimulus applied, in such a condition, pro- duces a more than usual response; and there is manifested an incontinent activity, irrespective of all stimulation. The outward movements are hurried and uncontrollable, the feelings are more intense, the thoughts are rapid; every mental exertion is heightened. When the excitement rises to the morbid pitch, as in disease, or under the influence of drugs, such as strychnine, there is an enormous expenditure of force, apart from any stimulation whatsoever: the altered nutrition of the brain is the sole influence concerned. (7.) As a farther confirmation, it may be remarked that sensibility and activity do not rise and fall together; on the contrary, they often stand in an inverse proportion to each other. By comparing different characters, or the different states of the same individual, we may test the truth of this 70 SPONTANEOUS ACTIVITY. observation. The strong, restless, active temperament is not always marked as the most sensitive and emotional, but is very frequently seen to be the least affected by these influ- ences. The activity that seems to sustain itself, costing the individual almost no effort, being his delight rather than his drudgery, and very little altered by the presence or the absence of stimulus or ends, is manifestly a constitutional self- prompting force ; and such activity is a well known fact. It is one of the fundamental distinctions of character, both in individuals and in races ; being seen in the restless adven- turer, the indefatigable traveller, the devotee of business, the incessant meddler in affairs; in the man that hates repose and despises passive enjoyments. It is the pushing energy - of Philip of Macedon and William the Conqueror. On the other hand, sensitive and emotional natures, which are to be found abundantly among men, and still more abundantly among women, are not active in a corresponding degree, while the kind of activity displayed by them, is plainly seen to result more from some stimulus or object, than from an innate exuberance of action. ‘The activity prompted by ends, by something to be gained or avoided, is easily distinguished from the other by its being closely adapted to those ends, and by its ceasing when they have been accomplished. He that labours merely on the stimulus of reward, rests when he has acquired a competency, and is never confounded with the man whose life consists in giving vent to a naturally active temperament, or a superabundance of muscular and central energy. (8.) Lastly, it will be afterwards shown, that without spontaneity, the growth of the Will is inexplicable. Regions of Spontaneous Activity. 7. The muscles for the most part act in groups, being associated together by the organization of the nervous cen- tres, for the performance of actions requiring concurrent movements. SPONTANEITY OF THE LOCOMOTIVE ORGANS. 71 The Locomotive Apparatus is perhaps the most conspicuous of the voluntary groups. This involves (taking vertebrate animals in general) the /imbs—or the anterior and posterior extremities with their numerous muscles, and the trunk of the body, which in all animals chimes in more or less with the movements of the extremities. In the outbursts of spontaneous action, locomotive effort (walking, running, flying, swimming, &c.) is one of the foremost tendencies ; having the advantage of occupying a large portion of the muscular system, and thus giving vent to a copious stream of accumulated power. No observant person can have failed to notice instances, where locomotion resulted from purely spontaneous effort. In the human subject, the locomotive members are long in being adapted to their proper use, and in the meantime they expend their activity in the dancing gestures and kicking movements, manifested by the infant in the arms of the nurse. The locomotive action agitates the whole length of the spine up to the articulations of the neck and head. The members concerned, however, have many movements besides, especially in man; and these are found to arise no less readily. Thus the movements of the arms are extremely various, and all of them may burst out in the spontaneous way. The grasp of the hand is the result of an extensive muscular endowment, and at an early stage manifests itself in the round of the innate and chance movements, The erections and bendings of the body are outlets for spontaneous activity, and especially erection, which implies the greater effort. When superfluous power cannot run into the more abundant opening of locomotive movement, it ex- pends itself in stretching and erecting the body and limbs to the extreme point of tension. The erection extends to the . carriage of the head and the distension of the eyes, mouth, and features. The vocal organs are a distinct and notable group of the active members. The utterance of the voice is unequivocally owing on many occasions to mere profusion of central energy, (ee: SPONTANEOUS ACTIVITY. although more liable than almost any other mode of action to be stimulated from without. In man the flow of words and song, in animals the outbursts of barking, braying, howling, are often manifestly owing to no other cause than the ‘fresh’ condition of the vocal organs. The eyes have their independent centre of energy, whence results a spontaneously sustained gaze upon the outer world. When no object specially arrests the attention, the activity of the visual movements must be considered as mainly due to central power. In a person deprived of the sight of one eye, we find that eye still kept open, but not so wide as the other. The mouth is also subject to various movements which may often be the result of mere internal power, as is seen in the contortions indulged in after a period of immobility and re- straint. The jaws find their use in masticating the food, but failing this, they may put forth their force in biting things put into the mouth, as in children not yet arrived at the age of chewing. The tongue is an organ of great natural activity, being endowed with many muscles, and having a wide scope of action. In the spontaneous action of the voice, which is at first an inarticulate howl, the play of the tongue, com- mencing of its own accord, gives the articulate character to utterance, and lays a foundation for the acquirement of speech. Among the special aptitudes manifested among the lower animals we find marked examples of the spontaneity of action. The destructive weapons belonging to so many tribes, are fre- quently brought into play without any stimulus or provocation, and when no other reason can be rendered than the necessity for discharging an accumulation of inward energy. As the battery of the Torpedo becomes charged by the mere course of nutrition, and requires to be periodically relieved by being poured upon some object or other, so we may suppose that the jaws of the tiger, the fangs of the serpent, the spinning apparatus of the © spider, require at intervals to have some objects to spend them- selves upon. It is said that the constructiveness of the bee and the beaver incontinently manifests itself even when there is no end to be gained; a circumstance not at all singular, if we admit NATURAL HISTORY OF THE FEELINGS, 73 the spontaneous nature of many of the active endowments of men and animals. The spontaneous activity is always observed to rise and fall with the vigour and state of nutrition of the general system, being abundant in states of high health, and deficient during sickness, hunger, and fatigue. Energetic movements, moreover, arise under the influence of drugs and stimulants acting on the nerves and nerve centres; also from fever and other ailments. Convulsions, spasms, and unnatural excite- ment, are diseased forms of the spontaneous discharge of the active energy of the nerve centres.* OF THE MUSCULAR FEELINGS. 8. We are now brought to the express consideration of the first class of phenomena proper and peculiar to mind, namely, States of Feeling; these we have from the outset recognized as one of the three distinct manifestations of our mental nature. To give a systematic and precise account of the states of human consciousness,—a Natural History of the Feelings,—is one of the aims of the science of mind.t * A critic of this work in the Nationa! Review, while admitting that the doctrine here contended for serves to explain phenomena that are left unexplained, on the assumption, most generally prevailing in the systems or the human mind, that our activity is called forth solely by the stimulus ot our sensations—takes exception to the purely physical origin above assigned to the spontaneous movements. It is with the writer a serious ground of complaint that these movements are made to proceed from a “ psychological nothing,” or apart from any antecedent mental state. The question thus raised turns upon matter of fact, and if any observations can be produced to show that mind does manifest itself anterior to the spontaneous outburst, my statement is incorrect. But so far as I have been able to judge of what really happens, consciousness rapidly follows or else accompanies the spon- taneous discharge, but does not precede it. We have unequivocal instances of movements arising without consciousness, as under chloroform and in delirium; and it is not contended that mind accompanies the movements of the foetus in the womb. A disputed point substantially identical with this is handled at length in “‘ The Emotions and the Will.” (Emotions, chap. vii., sec. 12). + It may facilitate the comprehension of the method herein adopted for the systematic delineation of the feelings, if I offer a few explanatory 74 THE MUSCULAR FEELINGS. 9. There are three classes of Feelings connected with the moving organs :— (1.) Feelings dependent on the organic condition of the muscles ; as those arising from hurts, wounds, diseases, fatigue, rest, nutriment. Most of these affections the muscles have in common with the other tissues of the body ; and they will be considered under a subsequent head. Our plan requires that we should here exhibit the marked antithesis, or contrast, exist- ing between Muscular Feeling proper (the Consciousnesss of movement, howsoever caused) and Sensation proper. The one is associated with energy passing outwards, the other with stim- ulation passing inwards ; the two facts mingle together in the stream of mental life, but are yet of a widely different nature. remarks as to the scope of it. | The reader is sufficiently acquainted with the threefold partition of mind into Feeling, Volition, and Intellect. If this partition be complete and exhaustive, every mental fact and phenomenon whatsoever falls under one or other of these heads; nothing mental can be stated but what is either a feeling, a volition, or a thought. It must, never- theless, be observed, that. mental states need not belong to one of these classes exclusively. A feeling may have a certain volitional aspect, together with its own proper characters: thus the mental! state caused by intense cold is of the nature of a feeling in the proper acceptation of the term; we recognize it as a mode of consciousness of the painful kind, but inasmuch as it stimulates us to performing actions for abating, or freeing ourselves from, the pain, there attaches to it a volitional character also. In like manner, every state that can be reproduced afterwards as a recollection, or retained as an idea, has by that circumstance a certain intelectual character. | Now, in describing states that come properly under the general head of feeling, we are called upon to bring forward, in the first instance, the pecu- liarities, or descriptive marks, that characterize them as feelings. This done, we may carry on the delineation by adverting to their influence on activity, or volition; and, lastly, we may specify anything that is distinctive in the hold that they take of the intellect. It is clear that if a Natural History of the human feelings is at all possible, we must endeavour to attain an orderly style of procedure, such as naturalists in other departments have had recourse to. If the fundamental divisions of mind have any validity in them, they ought to serve as the basis of a proper descriptive method; in fact, the description should accord with them. [ The plan, in its completeness, may be represented thus :— PuysicaL Sipe. Bodily Origin. (For Sensations chiefly.) Bodily Diffusion, expression, or embodiment. CLASSIFICATION OF THE MUSCULAR FEELINGS. 19 (2.) Feelings connected with muscular action, including all the pleasures and pains of ewercise. These are the states just alluded to as peculiar to the muscular system. (3.) The Feelings that indicate the various modes of tension of the moving organs. According as a muscle is tense or re- laxed, according as much or little energy is thrown into it, and according to the quickness or slowness of the contraction, we are differently affected, and this difference of sensibility enables us to judge of the positions of our active members, and of many important relations of external things. These are the feelings of muscle that enter most directly into our intelligence ; having little of the character of mere Feeling, and a very large refer- ence to Thought, they deserve a separate treatment. MENTAL SIDE. Characters as Feeling. Quality, z.e., Pleasure, Pain, Indifference. Degree. As regards Intensity or acuteness. As regards Quantity, mass, or volume. Special characteristics. Volitional characters. Mode of influencing the Will, or Motives to Action. Intellectual characters. Susceptibility to Discrimination and to Agreement. Degree of Retainability, that is, Ideal Persistence and Recoverability. / It is to be remarked that, asa general rule, pleasures agree in their physical expression, or embodiment, and also in their mode of operating on the will, namely, for their continuance, increase, or renewal. In like manner, pains have a common expression, and a common influence in pro- moting action for their removal, abatement, or avoidance. Hence the fact that a state is pleasurable or painful carries with it these two other facts as a matter of course. Again, as regards the Intellect; Discrimination, Agreement, and Retain- ability are to a certain extent proportional to the degree of the feeling, or the strength of the impression. This being the case, the statement of the degree involves the probable nature of the properties connected with the Intellect. Hence it is unnecessary in most cases to carry the delineation through all the particulars of the table. It is only when a feeling possesses any peculiarities rendering it an exception to the general laws of coincidence now mentioned, that the full description is called for. Two or three examples of the com- plete detail will be given. / Fete cr 76 THE MUSCULAR FEELINGS. All through the present chapter, and through the fol- lowing chapter on sensations, we shall require to keep in view this distinction between feelings that yield a large measure of the distinctive character of feeling, and others whose emotional character is feeble, and whose function it is to supply the materials of the intelligence. In the eye, for example, the effect of a blaze of sunshine is very different from the sight of a watch. The one serves for the pur- pose of immediate enjoyment, the other is nothing in itself, and derives its value from being remotely instrumental to our happiness. Among effects on the ear, the contrast between music and speech expresses the same distinction. I. Feelings of Muscular kxercise. These are feelings proper to the muscles. The mode of consciousness arising under muscular exertion cannot be pro- duced in connexion with any other part of the system. _ 10. Feeling of Muscular Exercise generally. According to the manner of the exertion, the feelings differ considerably ; a dead strain is different from movement; and distinct modes of consciousness attend quick and slow movements respect- ively. The most general and characteristic form of mus- cular exercise is exemplified in a dead strain, or else in great exertion with a moderate pace of movement. 11. To begin with the PuysIcat side. The physical state of a muscle under contraction may be inferred from the details already given. The particles making up the muscular threads are approximated by an energetic attraction developed in the muscle, under the stimulus supplied by the nerves. An intense physical force is produced by a peculiar expenditure of the substance of the muscular mass; and in the production of this force the tissue is affected, as it were, with a strong internal agitation. As the nerves supplied to the muscles are principally motor nerves, by which the muscular movements are stimulated from the brain and nerve centres, our safest assumption is, that the PHYSICAL SIDE OF MUSCULAR FEELING. ree sensibility accompanying muscular movement coincides with the outgoing stream of nervous energy, and does not, as in the case of pure sensation, result from any influence passing inwards, by incarrying or sensitive nerves. It is known that sensitive filaments are distributed to the muscular tissue, along with the motor filaments; and it is reasonable to suppose that by means of them the organic states of the muscle affect the mind. It does not follow that the charac- teristic feeling of exerted force should arise by an inward transmission through the sensitive filaments; on the con- trary, we are bound to presume that this is the concomitant of the outgoing current by which the muscles are stimulated to act. No other hypothesis so well represents the total opposition of nature between states of energy exerted, and states of passive stimulation.* * I shall here present the views of some of the most distinguished physiologists upon this interesting question, I must premise, however, that none of them advert to the presumption arising from the great antithesis of movement and sensation, throughout the whole mental system. To them it would be a small matter, that the feelings of movement were ranked as merely another class of sensations, or as impressions passing to the brain by sensitive nerves. In my view, on the contrary, the most vital distinction within the sphere of mind, is bereft of all physiological support by such an hypothesis. I quote first from Dr. Brown-Séquard: ‘J. W. Arnold has tried to show that the anterior roots of nerves contain the nerve fibres which convey to the sen- sorium the impressions that give the knowledge of the state of muscles,’ as to degree of contraction or amount of movement. ‘The chief fact on which he grounds his opinion is, that after section of the posterior roots of the posterior extremities of a frog, it can make use of its hind legs almost as well as if nothing had been done to the posterior roots.” It would appear, then, that not only the power of movement, but also the sense that guides the movements, is unconnected with the sensory nerves. ‘This experiment is certainly of some value, and we must acknowledge that it is difficult to explain it otherwise than Arnold has done. Moreover, we have found that, after the section of a// the posterior roots of the spinal nerves in frogs, the voluntary movements seem to be very nearly as perfect as if no operation had been performed, and that if the skin of the head is pinched on one side, the posterior limb on the same side tries to repel the cause of the pain, as well as if no injury had been made. I have also ascertained that in frogs rendered blind these experiments give the same result.’ But Arnold’s hypothesis is not the only alternative. The supposition that the mind discriminates the degree of energy of the motor current, or the force 78 THE MUSCULAR FEELINGS. But the physical accompaniments of muscular exertion pass beyond the muscles themselves. We know that active exercise indirectly affects all the organs of the body. The circulation of the blood is quickened generally, and is made to flow by preference to the muscular tissue, the brain being poured out from the brain in voluntary movement, is at least an equally ad- missible view. It would seem an unnecessary complication to have sensory nerves mixed up with the pure motor fibres; it would be to deny that the anterior roots are pure motor nerves. Dr. Brown-Séquard proceeds to re- mark :—‘ But although I agree so far with Arnold, I do not admit with him that it is only through the anterior roots that impressions are conveyed by the muscles to the brain. When a galvanic current is applied to the muscles of the limb of a frog, on which the posterior roots of the nerves of this limb have been divided, no trace of pain is produced, and all the other causes of pain are also unable to cause it when applied either to the skin or the muscles.’ —(Lectures, p. 9.) This is in perfect accordance with the view that would assign the feelings of resistance and movements to the outgoing current by the motor nerves, and the sensibility to cramp and other pains, to the ingoing current by the sensory nerves. E. H. Weber remarks :—‘ The discriminative sensibility of muscle seems, in many cases, owing to the presence, in muscle, of branches of the nerves of sensation going to the extremities, as we see in the distribution of twigs of the trigeminal nerves to the various muscles of the eye. This supply of sen- sitive nerves to the eye may be contrasted with the case of the diaphragm, a muscle under the influence of the will, yet less discriminative than the muscles of the eye, and scantily supplied with nerves of sensation. It would seem, nevertheless, that all does not depend on that ; for, in many cases of complete and genuine anesthesia (that is, loss of sensibility to pain), the power of voluntary motion in the senseless parts is still preserved.’ This is a still more decided fact, inasmuch as the existence of insensibility to pain shows, that all the sensitive fibres are paralyzed, and yet the power of muscular guidance remains. This is consistent only with the supposition that the mind appreciates the motor influerce as it proceeds from the brain to the muscles, without depending on a returning sensibility through the proper sensory fibres. I quote next from Ludwig. ‘ Whether the nerves that subserve the muscular sense, and those that induce the muscular motion, are the same, is at present difficult to decide. It is conceivable, and not unlikely, that all knowledge and discrimination arrived at through the exertion of the voluntary muscles, are attained directly through the act of voluntary excitation; so that the effort of the will is at once proceeded on as a means of judgment. This opinion is supported by the fact, that the movements that give us mental judgments, in by far the greater number of cases, do not appear as muscular sensations; in other words, they are not, like the organic sensations of muscle, localized by us in the muscle and looked upon as possessing the EMBODIMENT OF MUSCULAR FEELING. 79 in this way often relieved from a morbid excess of blood. The lungs are stimulated to increased action. The elimi- nation of waste matter from the skin is promoted. There is a great increase of animal heat. Provided the waste of nutritive material caused by these various modes of increased characters of a sensation.’ Ludwig thus appeals to our consciousness as pre- senting the feeling of muscular energy in a characteristic form, and distinct from the feeling of muscular pains. And in this he seems to be right; for if consciousness be a safe guide in the matter, we should say that in the case of a voluntary effort, the feeling is as of power going out of us, and not as of a surface of sense stimulated by an external agent, and transmitting an im- pression inwards to the nerve centres. The view that organic muscular pains are stimulated through the sensory fibres is strongly maintained by Ludwig. His reasons are :—First, Sensory fibres are distributed to the muscles along with the motor nerves. Secondly, the involuntary muscles, no less than the voluntary, are the seat of acute pains. Thirdly, the stimulation of the anterior roots does not produce pain. Fourthly, pains arising from long-continued action of the muscles exist for days after the cessation of the excitement of the motor nerves. This last phenomenon is explained by the chemical destruction of the muscular tissue, which has an irritating effect upon the sensory nerves existing in the muscles. Finally, Wundt expresses himself as follows: ‘Whether the sensations, accompanying the contraction of the muscles, arise in the nerve-fibres that transmit the motor impulse from the brain to the muscles, or whether special sensory fibres exist in the muscles, cannot be decisively settled. Certain facts, however, make the first assumption more probable. If special nerve- fibres existed, they must be connected with special central cells, and thus, in all probability, the central organs for the apprehension of these sensations would be different from those which send out the motor impulse ; there would be two independent nerve-systems, the one centripetal, the other centrifugal. But in the one—the medium of the sensation—nothing else could be regarded as the stimulus than the changes taking place in the muscle, the contraction, or perhaps the electrical process in nerve and muscle accompanying the con- traction. Now, this process is known to keep equal pace with the energy of the muscular contraction; and we must expect that the muscular sensation would constantly increase and decrease with the amount of internal or external work done by the muscle. But this is not the case, for the strength of the sensation is dependent only on the strength of the motive impulse, passing outwards from the centre, which sets on the innervation of the motive nerves.’ This is proved by numerous cases of pathological disturbance of the muscular action in a limb. The patient can make a great muscular exer- tion, and have the corresponding sensation, although the limb be hardly moved. But, naturally, after long-repeated trial, this small movement becomes associated with the increased exertion. 80 THE MUSCULAR FEELINGS. action is duly supplied, the vital force of the system as a whole is raised by muscular exercise. So much for the corporeal seat or Origin of the sensibility in question. ‘There is still another physical aspect, namely, the Expression or Embodiment of the Feeling, which is not only the means of making known the state to others, but also an essential concomitant of its own existence. By the very nature of the case, the feeling arising from great bodily exertion, is liable to be wanting in Expression, properly so called. The organs are so completely employed in the exercise itself, that they are not disposable as instru- ments of the expression of the feeling. The features of the face and the voice, which are by pre-eminence the organs of expression, are exerted chiefly in sympathy with the muscles engaged in the exercise. Hence, as regards outward embodiment, there is nothing to be remarked in connexion with muscular effort generally. It is only when the feeling happens to be pleasurable or the reverse, that any expression is shown, and such expression is merely the attendant of the pleasure or the pain as such. 12. We pass now to the MENTAL side. In reviewing the characteristics of the mental accompaniment of muscular action, viewed as Feeling, we will advert first to its Quality. Observation shows that this is pleasurable, indifferent, or painful, according to the condition of the system. The first outburst of muscular vigour in a healthy frame, after rest and nourishment, is highly pleasurable. The intensity of the pleasure gradually subsides into indifference; and, if the exercise is prolonged beyond a certain time, pain ensues. In ordinary manual labour, there may be, at commencing in the morning and after meals, a certain amount of pleasure caused by the exercise, but it is probable that during the greater part of a workman’s day, the feeling of exertion is in most cases indifferent. If we confine ourselves to the dis- charge of surplus energy in muscular exertion, there can be no doubt that this is a considerable source of pleasure in the average of human beings, and doubtless also in the animal PLEASURE OF MUSCULAR EXERCISE. 81 tribes. The fact is shown in the love of exercise for its own sake, or apart from the ends of productive industry, and the preservation of health. In the case of active sports and amusements, there are additional sources of pleasurable ex- citement, but the delight in the mere bodily exertion would still be reckoned one ingredient in the mixture. A part of the pleasure of exercise must be attributed to the increase of vital power generally; and the question arises, may not the whole be due to the augmented force of the cir- culation, respiration, &c.? It is certain that the rising toa higher condition as regards these important functions, is a source of pleasurable excitement. We may reasonably suppose, however, that the muscular system, which is the seat of so much unquestioned sensibility, should be capable of affording pleasure under favourable conditions. And I think our consciousness attests the same fact. The agree- able feeling in the exercise of the muscular organs, when the body is strong and fresh, can be localized, or referred to the muscles actually engaged. And it will be seen, as we proceed, that there are various facts connected with movement that are inexplicable, unless we suppose that the muscular tissue is of itself a seat of pleasurable, as it certainly is of painful, sensibility. As to the Degree of this pleasure, we must of course pro- nounce it variable according to circumstances. But taking a common case, as that of an average healthy human being, going through each day the amount of bodily exercise that the system can afford, we should have to admit that this is an appreciable constituent of happiness. Doubtless by con- triving such a combination of exercises as to bring all the powerful muscles into full play, the pleasure could be in- creased considerably above the ordinary experience in this respect. The pleasure is not what would be called acute, or of great intensity ; its degree arises from the stimulation of a large mass of tissue. A measure of the degree of our pleasures is found, not merely in comparing one with another in consciousness, but 6 82 THE MUSCULAR FEELINGS. also in observing the pains that they are respectively able to subdue. In this particular case, however, there is a tendency to subdue pain, not through the evolution of pleasure merely, but through some of the direct physical consequences of muscular movement. The derivation of blood from the brain reduces the cerebral excitement, and with that the mental excitement, and so may operate in quenching painful irritation. The third point in the description respects any Speciality in the case, serving still further to describe or characterize the feeling in question. Now, as regards muscular exertion, there is a notable speciality, a radical difference in kind, signified by such phrases as ‘ the sense of power,’ ‘ the feeling of energy put forth,’ ‘the experience of force or resistance.’ This is an ultimate phase of the human consciousness, and the most general and fundamental of all our conscious states. By this experience we body forth to ourselves a notion of resistance, force, or power, together with the great fact de- nominated an external world. In the sense of energy exerted, we are said to go out of self, or to constitute a something in vital contrast to all the rest of our mental experiences, a not- me as opposed to the me of passive sensibility and thought. With regard to the Volztronal peculiarities of the pleasure of muscular exercise there is not much to be remarked. As a pleasure it will work for its own perpetuation, increase, or renewal. According to the doctrine of spontaneous activity, the sense of pleasure would not be necessary for our passing into an active state in the first instance; but would simply operate to maintain the activity, and, by help of intelligent forethought, to keep the system in a high condition of fitness for the periodical effusion of energy. The distinctively Intellectual properties of the muscular feelings will have to be referred to, as the sources of highly important perceptions. But before considering these, we should notice an intellectual aspect or property belonging to these feelings, in their strict character of feelings, or as pleasures and pains,—namely, the fact of their greater or less FEELING OF EXPENDED ENERGY. 83 persistence in the memory, so as to constitute ideal pleasures or pains, and, in that capacity, to stimulate the will in pursuit orin avoidance. A pleasure may be very intense in the actual, —but-feeble in the ideal, or in the memory. Such a pleasure _would not, in absence, prompt the will to energetic efforts for realizing it. Now, the pleasures of muscular exercise do not take a high place among persisting, remembered, or ideal pleasures ; they are perhaps not at the bottom of the scale in this respect, but they are not much higher than the least in- tellectual of the sensations, as, for example, those of Digestion. But individuals differ in regard to this point; and in so far as active amusements and sports, and occupations largely in- volving muscular exercise, are a fixed object of passionate pursuit, for their own sakes, to that extent they must abide in thought, or possess intellectual persistence. But the truly important intellectual aspect of muscular feeling is something quite different from any ideal pleasures and pains of exercise. It regards the discriminating and identifying of degrees and modes of the characteristic con- sciousness of expended energy ; an experience corresponding with the great facts of the object world, named, resistance, force, power, velocity, space, time, &c. In these perceptions there is a neutrality as regards pleasure or pain. We have already seen that, between the pleasure of exer- cise and the pain of fatigue, there is an intermediate state where there is still the characteristic feeling of energy ex- pended. In this state, we usually cease to attend to the feeling, as feeling proper; we are rather occupied with the purely intellectual functions of discrimination and agreement; we think of the present expenditure as greater or less than some other expenditure, or as agreeing with some previously known instances. This is to be intellectually engrossed ; and, under such an engrossment in the case of muscular exercise, we assume the olyect attitude ; we are not self-con- scious, but are engaged in knowing certain purely object facts called force, extension, &c. Even if muscular exertion were attended with the 84 THE MUSCULAR FEELINGS. pleasures of exercise or the pains of fatigue, yet if, from any circumstance, we were led to consider intently the degree or amount of the expenditure, as in aiming a blow at cricket, we should at that moment be entirely unconscious of the pleasure or pain of the situation ; the intellectual attitude (in this case the object attitude) is incompatible for the instant with the subject experience proper, of which pleasure and pain are characteristic modes. ven in the highest zest of muscular enjoyment, the feeling of pleasure is intermittent; it is eclipsed in the act of putting forth energy and of considering and comparing its amount ; and re-appears at the end of the stroke, or during the suspense of our attention to the act itself. In this subtle transition, or contrast, is laid the groundwork of the great distinction of subject and object— mind and matter. 13. Having thus endeavoured to present a delineation of the first and simplest variety of muscular consciousness under exertion, we shall now cite a few examples of this form of the feeling. The supporting of a weight on the back, head, or chest, or by the arms, is a common example of dead tension. The most interesting form of it is the support of the body’s own weight, which yields a perpetual feeling of the muscular kind, varying with the attitudes. The feeling is least when we lie at full length in bed, and greatest in the erect posture. Some- times the weight is oppresive to us, and gives the sensation of fatigue ; in a more fresh condition of the muscles, it makes one item of our pleasurable consciousness. The fatigue of standing erect for a length of time is, perhaps, one of the commonest cases of muscular exhaustion. The pleasure of standing up after a lengthened repose gives an opposite feel- ing. When the bodily strength is great, the laying on of a ' burden is a new pleasure. This case of great muscular tension, without movement, ‘presents itself under a variety of forms, in the routine of mechanical operations, and in many other ways. In holding on as a drag, in offering or encountering resistance of any SLOW MOVEMENTS. 85 sort, in compressing, squeezing, clenching, wrestling, the situation is exemplified. A certain amount of movement may be permitted without essentially departing from the case of dead tension, as in dragging a vehicle, and in efforts of slow traction generally. 14. When muscular tension brings about Movements, there must be a gradually increasing contraction, and not a mere expenditure of power at one fixed attitude. Each muscle has to pass through a course of contraction ; beginning, it may be, at the extreme state of relaxation, and passing on, sometimes slowly, and at other times rapidly, to the most shortened and contracted condition. The sensibility de- veloped during this process, is greater in degree, and even somewhat different in kind, from that now discussed. As a general rule, the feeling is more intense under movement, than under exertion without movement. The successive contrac- tion of the muscle would seem capable of originating a more vivid stimulus than the fixed contraction. We even find that, in different degrees of rapidity, the character of the feeling changes, which requires us to make a division of movements into several kinds. 15. Let us first advert to what we may term, by compari- son, slow movements. By these I understand such as a loitering, sauntering walk, an indolent style of doing things, a solemn gesture, a drawling speech, whatever is set down as leisurely, deliberate, dawdling. The emotion arising from this kind of movement is far greater than an equal effort of dead tension would produce. Indeed, we may say, that this is an extremely voluminous and copious state of feeling: being both abundant and strong, although deficient in the element that we recognize as the sense of energy, or of expended force ; in fact, approaching more to the class of passive feelings. We may derive the greatest amount of pleasurable sensibility, at.the least cost of exertion, through the means of well-con- certed slow movements. In this case, it seems least unlikely that, together with the sense of expended energy, there is also present the proper sensibility of the muscular tissue, awakened 86 THE MUSCULAR FEELINGS. through the medium ot the sensitive nerves. The resemblance of the state to the feeling of muscular repose, (which probably makes) an element in the voluminous sensation of approaching sleep, favours this view. The sense of expended energy is small, in fact almost wanting. But we must not overlook another circumstance, accounting for a copious sensibility under a small expenditure of force. When the energies of the system are strongly directed into the current of muscular activity, they are less available for the support of sensibility or feeling; the putting forth of energy in bodily movements is a diversion of the forces from the seats of passive sensi- bility, and is a well known remedy for too great mental excitement. Hence, obversely, the smallness of the active expenditure permits a larger manifestation of sensibility or feeling. The relationship of the feeling in question to muscular repose and approaching sleep, is seen in the tendency of slow movements to induce those states. They are pre- eminently soothing in their nature, and when the system has contracted a morbid restlessness, they can gradually restore it to the healthy condition. After a bustling day, tranquillity is attained by the mere sympathy of measured movements, as music and the conversation of persons of sedate elocution. There is also a close intimacy between the feelings of slow movement and certain powerful emotions, as awe, solemnity, veneration, and others of the class of mingled tenderness and fear, entering into the religious sentiment. Accordingly, the funeral pace, the slow enunciation of devotional exercises, the solemn tones of organ music, are chosen as appropriate to the feelings that they accompany. All this still farther supports the position, that the feeling under consideration is not one of active energy, but the opposite. For all those sentiments are the response of man’s powerlessness and dependence, and are developed according as the sense of his own energy is low. 16. There is every reason to believe that movements gradually increasing or gradually diminishing, are more pro- QUICK MOVEMENTS. 87 ductive of pleasurable emotion than such as are of a uniform character. Indeed, a uniform movement is altogether of artificial acquirement. The natural swing of the limbs tends to get quicker and quicker up to the full stretch, and to die away again gradually. There would appear to be a special sensibility connected with the acceleration or steady diminu- tion of movement. The gradual dying away of a motion is pleasurable and graceful in every sort of activity—in gesture, in the dance, in speech, in vision. The ‘dying fall’ in sound is an illustration of the same fact. It also goes to make the beauty of curved lines. Possibly the effect may be explained on the great law of Relativity, or the necessity of change to our being mentally affected. A gradual acceleration or diminution of any agent that wakens sensibility is the surest antidote of monotony, in other words, the condition most favourable to consciousness. 17. We pass next to the consideration of quick move- ments, They differ considerably in feeling both from dead exertion and from slow motion. Although there may seem to be a common muscular sensibility at the bottom, the specific nature of it is greatly altered. One accompaniment of the quickness is the increased excitement of the nerves; an increase totally distinct from the addition of energy expended to heighten an effort of dead resistance. Mere rapidity of movement has a specific influence in exciting the nerves and nerve-centres to a greater spontaneous activity ; in short, it belongs to the class of nervous stimulants. The stimulation would appear to be all the greater, when the organs are unresisted, and consequently demand little expen- diture of energy. For mducing an unwonted degree of excitement generally, for inflaming the animal spirits, and bringing on various manifestations and exaggerated efforts, quick movement is an available instrumentality. We may compare it in this respect with acute pains (not severe enough to crush the energies). Rapid motions are a species of mechanical intoxication. Any one organ, however small, made to move quickly, imparts its pace to all the other 88 THE MUSCULAR FEELINGS. moving organs. In a rapid walk, still’ more in a run, the mental tone is excited, the gesticulations and the speech are quickened, the features betray an unusual tension. Examples of this class of motions and feelings are suffi- ciently abundant. They are expressly sought to give hilarity and excitement to human life. The chase, the dance, the vehemence of oratory and gesture, the stirring spectacle, are prized for their stimulating character, as well as for their proper sensations. In the ecstatic worship of antiquity,—in the rites of Bacchus and Demeter,—a peculiar frenzy over- took the worshippers, yielding an enjoyment of the most intense and violent character, and in its expression mad and furious. This state is often brought on among the Orientals of the present day, and in a similar manner, namely, by rapid dancing and music under the infection of a multitude. Movements, when too quick, excite the brain to the state of dizziness and fainting (see p. 43). Thus, then, Dead Resistance is a source of pleasure in a healthy system, a derivative of morbid excitement from the brain, and the origin of our most general and fundamental sensibility, constituting the consciousness of the object, or external, world. Slow Movements are allied to the passive pleasures, and may affect us more through the sensitive, than through the motor nerves of the muscles. Quick Move- ments affect us less as movement, than as stimulating the nerves to increased action, the consequence being a higher mental tone for feeling, for volition, and for thought. 18. A remarkable feeling connected with movements, is that arising from the sudden loss of support, as when the footing, or any prop that we lean upon, suddenly gives way. The contraction of a muscle demands two fixed points of resistance at its extremities; if one of those breaks loose, the force of the contraction has nothing to spend itself upon, and a false position is incurred. The contraction suddenly freed from its resistance does not make a vehement con- vulsive collapse like a spring; it would appear rather that the contractive force ceases almost immediately ; and the PASSIVE MOVEMEN'S. 89 sensation resulting is one of a most disagreeable kind. It would seem to result rather from the jar given to the nervous system than from any influence flowing out of the muscle. The whole frame is agitated with a most revulsive shock, the cold perspiration is felt all over, and a sickening feeling seizes the brain. The breaking down of any prop that we are resting on, the snapping of a rope, or the sinking of a foundation, exemplify the most intense form of the effect. We may probably look upon the peculiar influence whose repetition induces sea-sickness, as of the same nature. The sinking of the ship has exactly the same unhinging action in a milder degree, although when continued for a length of time, this produces a far worse disturbance than any single break-down, however sudden. ‘The precise physiological action in this situation, does not seem agreed upon; the feeling is known to be one of the most distressing that human nature is subject to, being an intense and exaggerated form of stomachic sickness.* 19. We must next advert to what are called passive (but more properly compelled) movements. Riding in a vehicle is the commonest instance. One of the pleasures of human life is to be driven along at a moderate speed, in an easy carriage. Now, it may be supposed at first sight, that there ought to be no feeling of muscular exertion whatsoever in this case, seeing that the individual is moved by other force than his or her own. Under certain circumstances this would be strictly true. We have no feeling of our being moved round with the earth’s rotation, or through space by the movement about the sun. So ina ship, we often lose all sense of being driven or carried along, and feel pretty much as if there were * Sea-sickness is explained by some as the result of the excessive flow of blood to and from the head. When the ship makes a downward motion, the feeling of loss of support is accompanied by a rapid flow of blood to the brain, and, when the ship rises, as rapid a flow ensues in the opposite direction. It is asserted further, that the flow either way may be diminished, if an upward motion of the body be made at the time of the ship’s downward motion, and a downward motion at the time of the ship’s rising; and that sickness can in this way be prevented. 90 THE MUSCULAR FEELINGS. no forward movement at all. The sensibility arising in a carriage movement, is in part imbibed through the eye, which is regaled by the shifting scene, and partly through the irregularities of the movement, which demand a very gentle action of the museles of the body in order to adapt it to those irregularities. By springs and cushions, all violence of shock is done away, while the easy exercise caused by the commencement and stoppages of the motion, by the slight risings and fallings of the road, is somewhat of the nature of that influence already described as arising from slow and gentle movements. Moreover, as has been observed by Dr, Arnott, the effect of the shaking is to quicken the eirculation of the blood. In horse exercise, there is a large amount of the ingredient of activity. The rider is saved a part of the exhaustion caused in walking, and has yet exercise enough for the stimulus of the bodily functions, and for muscular pleasures. The rocking chair, introduced by the Americans, who seem specially attentive to the luxuries of muscular sensibility, is another mode of gaining pleasure from movement. Anciently, furniture was adapted for the pleasures of repose solely, but now the boy’s rocking horse has its representative among the appurtenances of grown men. On the whole, it is apparent that a large fraction of physical enjoyment flows out of the moving apparatus and muscular tissue of the body. By ingeniously varying the modes of it, this enjoyment is increased still farther. The pleasure comes incidentally to manual labour, when moderate in amount and alternated with due sustenance and repose, and is a great element of field sports and active diversions of every kind; it is a part of the pleasures of locomotion ; and contributes the principal ingredient in gymnastic exercises and athletic displays. Il. Of the Perceptions grounded in the Muscular Feelings. 20. In alluding to the strictly Intellectual properties of the feeling of expended muscular energy, we had to advert to DISCRIMINATION OF MUSCULAR ENERGY. 91 that mode, neutral as regards pleasure and pain, whereby we are occupied with the properties of the object world, as resist- ance, force, &e. This function of our muscular sensibility arises, in the first instance, from our being conscious of the different degrees — of it. We have not only a certain feeling when we put forth muscular power, but we have a change of feeling when we raise or lower the amount of the power. If we hold a weight of four pounds in the hand, the consciousness is changed when another pound is added. This change of feeling is completely expressed by the word, Discrimination, and is the basis of our intelligence; as pleasure or pain, it is nothing, but as the commencement of knowledge, it is all-important. The modes of muscular action that affect us by their differences of degree, appear to be three. ‘The first is the amount of exertion, or of expended force, which measures the resistance to be encountered. This is the fundamental ex- perience. The second respects the continuance of the exer- tion, and applies both to dead strain and to movement. The third is a mode of movement solely ; it is'the rapidity of the muscle’s contraction, which corresponds with the velocity of movement in the organ. In distinguishing the qualities of external things, and in attaining permanent notions of the world, all these discriminations are brought into play. 21. First, with respect to degrees of Exertion or of Ex- pended force. This is the sense of Resistance, the basis of our conception of Body, and our measure of Force, Inertia, Momentum, or the Mechanical property of matter. Every feeling involves a consciousness of degree or amount : to be affected more or less in different circumstances is a consequence of being affected at all. Hven when ex- periencing the pleasure of healthy exercise, or the pain of fatigue, we are aware of differences in the various stages of the feeling. Such differences make one part of the fact that we call knowledge (agreements being the other part). To apply this to the case now before us. We have a certain feeling when called to exert our muscular energy in 92 THE MUSCULAR FEELINGS. causing movement, or in encountering resistance. We have a certain degree of consciousness for some one degree of ex- ertion ; when the exertion increases, so does the consciousness. If a porter places on his back a load of one hundredweight, he has a peculiar and distinct muscular feeling associated with it; if thirty pounds were added, he would have a sense of the addition in the increased expenditure of force; if thirty pounds were removed, he would have a feeling of diminished expenditure. In short, there is a perfect discrimination of degrees and difference of muscular energy, which serves us as a means of discriminating the resistances that we encounter. Hence we are able to say that one body resists more than another—possesses in greater degree the quality that, accord- ing to circumstances, we call force, momentum, inertia, weight, or power. When we encounter two forces in succes- sion, as in a wrestling match or a dead push, we distinguish the greater from the less. 22. Among the various occasions where the sense of eraduated resistance comes into play, mention may be made, first, of the momentum or force of moving bodies. Where we have to check or resist something in motion, as in bringing a vehicle to rest, our sensibility to expended exertion leaves. with us an impression corresponding to the momentum of the vehicle. If we were immediately after to repeat the act with another vehicle heavier or swifter than the first, we should have a sense of increased effort, which would mark our estimate of the difference of the two forces. Supposing the impressions thus made to be gifted with a certain kind of permanence, so that they could be revived at an after time, to be compared with some new case of checking a moving body, we should be able to say which of the three was greatest and which least, and we should thus have a scale of sensibilities corresponding to the three different degrees of moving force. Such exercises as digging the ground, rowing a boat, or dragging a heavy vehicle, do not essentially depart from the case of the dead strain ; and in all these instances, there is an estimate of expended force. Every carriage horse knows the WEIGHT. 93 difference of draught between one carriage and another, be- tween rough and smooth ground, and between up hill and down hill. This difference the animal comes to associate with the carriage, or with the sight of the road, and in con- sequence manifests preferences whenever there is an oppor- tunity; choosing a level instead of a rising road, or the smooth side in preference to the rough. The appreciation of weight comes under the dead strain. We remark a difference between half an ounce and an ounce, or between five pounds and six pounds, when we try first the one weight and then the other. The generality of people can appreciate far nicer differences than these. A sensitive hand would feel a small fraction of an ounce added to a pound. In this respect, there would appear to be wide con- stitutional differences, and also differences resulting from practice, among different individuals. We are all sensitive to some extent,. but there is for each person a degree of minuteness of addition or subtraction that ceases to be felt; this is the limit of sensibility, or the measure of delicacy in the individual case. There are two modes of estimating weight, the relative and the so-called absolute. By relative weights we under- stand two. or more present weights compared together; as when among a heap of stones we pick out what we deem the heaviest. Absolute weight implies a permanent standard, and a permanent impression of that standard. When I lift a weight and pronounce it to be seven pounds, [ make a comparison between the present feeling and the impression acquired by handling the standard weight of seven pounds, or things known to be equivalent thereto. This absolute comparison, therefore, implies the enduring and recoverable sensibility to impressions of resistance, which is also a fact of the human constitution. We can acquire a permanent sense of any one given weight or degree of resistance, so as ~ to be able at all times to compare it with whatever weight may be presented. A receiver of posted letters contracts an engrained sensibility to half an ounce, and can say of any 94 THE MUSCULAR FEELINGS. letter put into his hand whether it produces a sensibility equal to or under the standard. This, too, is a result pre- eminently intellectual in its nature; the process of acqui- sition that brings it about, ranks as a fundamental property of our intelligence. The sensibilities that can assume this permanent character, so as to be used in comparison, without the presence of their original cause, are truly intellectual sensibilities. The sensitiveness to relative weight, or to things actually compared together, may not imply great sensitiveness to absolute weight, which involves a greater or less degree of retentiveness or memory. Although the use of the balance supersedes, to a very great extent, the sensibility to weight residing in the mus- cular system, there are occasions where this sensibility can display its acuteness. In many manual operations, weight is often estimated without the aid of the balance. In throwing a missile to reach a mark, an estimate of weight must enter into the computation of the force expended. In appreciating the cohesiveness of tenacious bodies—the thickness of a dough, or the toughness of a clay—the same sense of resistance comes into operation. In like manner, the elasticity of elastic substances—the strength of a spring, the rebound of a cushion—can be discriminated with more or less nicety. 23. The second mode of muscular discrimination respects the Continuance of it. A Dead Strain of unvarying amount being supposed, we are differently affected according to its duration. If we make a push lasting a quarter of a minute, and, after an interval, renew it for half a minute, there is a difference in the consciousness of the two efforts. The endurance implies an increased expenditure of power in a particular mode, and we are distinctly aware of such an increase. We know also that it is not the same as an increase in the intensity of the strain. The two modes of increase are not only discriminated as regards degree, they are also felt to be different modes. The one is our feeling TIME AND SPACE. 95 and measure of Resistance or Force, the other stands for a measure of Time. All impressions made on the mind, whether those of muscular energy, or those of the ordinary senses, are felt differently according as they endure for a longer or a shorter time. This is true of the higher emotions also. The continuance of a mental state must be discriminated by us from the very dawn of consciousness, and hence our estimate of time is one of the earliest of our mental aptitudes. It attaches to every feeling that we possess. The estimate of continuance attaches to dead resist- ances, but not to that alone. When we put forth power to cause Movement, as in lifting a weight off the ground, or in pulling an oar, we are aware of a difference in the con- tinuance of the movement. We also know that we are moving, and not simply resisting. The two modes of exer- cising force are not confounded in our consciousness; we hold them as different, and recognize each when it occurs, Now, the continuance of movement expresses more to us than the continuance of a dead strain. It is the sweep of the organ through space, and connects itself, therefore, with the measure of space or extension. The range of a muscle’s contraction, which is the same as the range or extent of motion of the part moved, is appreciated by us through the fact of continuance. Being conscious of a greater or less continuance of movement, we are prepared for estimating the greater or less extent of the space moved through. This is the first step, the elementary sensibility, in our knowledge of space. And, although we must combine sensations of the senses with sweep of movement, in our perception of the extended, yet the essential part of the cognition is furnished by the feelings of movement. We learn to know, by a pro- cess to be afterwards adverted to, the difference between the co-existing and the successive, between Space and Time; and we can then, by muscular sweep—that is, by the continuance of muscular movement—discriminate the differences of ex- tended matter or space. This sensibility becomes a means of imparting to us in the first place the feeling of linear 96 THE MUSCULAR FEELINGS. extension, as measured by the sweep of a limb, or other organ moved by muscles. The difference between six inches and eighteen inches is represented by the different degrees of contraction of some one group of muscles ; those, for ex- ample, that flex the arm, or, in walking, ions that flex or extend the lower limb. The inward impression corre- sponding to the outward fact of six inches in length, is an impression arising from the continued shortening of a muscle. It is the impression of a muscular movement having a certain continuance ; a greater linear magnitude is a greater continuance. The discrimination of length in any one direction ob- viously includes extension in every direction. Whether it be length, breadth, or height, the perception has precisely the same character. Hence superficial and solid dimensions, the size or magnitude of a solid object, come to be felt through the same fundamental sensibility to expended muscular force. All this will be understood more fully at an after stage, when we shall have to consider muscularity in connexion with the senses of Touch ard Sight. By means of the muscular se walt associated with prolonged contraction, we can thus discriminate different. degrees of the attribute of space, in other words, difference of length, surface, and form. When comparing two different lengths, we can feel which is the greater, just as in comparing two different weights or resistances. We can also, as in the case of weight, acquire some absolute standard of comparison, through the permanency of impressions sufficiently often re- peated. We can engrain the feeling of contraction of the muscles of the lower limb due to a pace of thirty inches, and can say that some one given pace is less or more than this amount. According to the delicacy of the muscular organs, we can, by shorter or longer practice, acquire distinct impres- sions for every standard dimension, and can decide at once as to whether a given length is four inches or four and a half, nine or ten, twenty or twenty-one. A delicate sensibility to size is an acquirement suited to many mechanical opera- RAPIDITY OF MOVEMENT. 97 - tions; as in drawing, painting, and engraving, and in the plastic arts. 24. Under the foregoing head, we supposed the case of steady or uniform movement; and called attention to the power of discriminating the greater or less continuance of it. But movements may vary in their rate of Speed; and it is now to be considered whether or not the mind is affected when the speed is increased or diminished. This is also a mode of expending additional power; and it is not possible for us to increase the expended energy without being conscious of the fact. The only doubt that might arise is as to our being able to distinguish the various modes of increase— increase In the dead strain at any one instant, increase in the duration of the strain, increase in the duration of a movement, increase in the velocity of the movement—so as to be aware which mode we are under forthe time. If we confounded all these modes of increase under a common impression of inten- sified energy, our muscular discrimination would be wholly inadequate to the perception of the external world; and, in particular, our ability to estimate extension would have to be referred to some other part of our constitution. But it is quite certain that we are differently affected under these various situations. Our consciousness is not the same when we augment the energy of a dead resistance, as when we protract the time of that resistance ; nor is it the same when we prolong the duration of a uniform movement, and when we add to its speed. We are’ aware, when we accelerate our pace, not merely that more power is going out of us, but that such power is in one especial mode, which we distinguish from other special modes. This being assumed, we are cogni- zant of degree in the rapidity of our movements, and so possess the power of estimating another great property of moving bodies, the velocity of their motions. This measure is taken first on our own movements, and thence extended to other moving things that we encounter. When we follow a moving object with the hand, or with the eye, or keep pace with it, its velocity is transferred to ourselves, and estimated accordingly. 7 98 THE MUSCULAR FEELINGS. The feeling of the rapidity of muscular contraction has a further office. It is an additional means of measuring Exten- sion. An increase of velocity in the same time corresponds to an increase of range or extension, no less than the same velocity continued for a greater time. Extent of Space thus connects itself with two separate discriminations—Continu- ance, and Velocity, of movement. The distinct feelings from the various forms of muscular exercise, as formerly explained, whereby we are differently affected according as movement is slow or quick, are thus of great intellectual importance, as enabling us to be character- istically impressed by each varying degree of velocity. The soothing tendency of the slow motions, and the exciting effect of the comparatively rapid motions, are instrumental in en- abling us to discriminate degrees of velocity directly, and of space indirectly.* * A fourth variety of muscular discrimination may be pointed out as in constant use, namely, the sense of the amount of contraction of a muscle, and of the position of the limb in consequence. We are ordinarily aware not merely that we are putting forth a force of a certain degree and continuance, but that we are operating either at the beginning of the muscle’s contraction, so to speak, or at some advanced stage of the contraction. This determines, of course, the attitude or position of the part moved. We know, in exerting the arm in the dark, whether it is extended or bent, and whether it is thrown before or behind. We know in grasping anything in the hand, whether the hand is very much stretched, or very much closed; and we can judge of the different degrees of contraction determining intermediate positions. By this sensibility we are able, after experience, to estimate the magni- tudes of bodies without moving the arnr or the hand, or other organ. By the mere stretching of the arms, without attending to the movement implied in that stretch, we measure in our mind the length of an object, or of an interval. By the dead span of ‘the fingers and thumb, we can estimate any length that is within the scope of the parts. It is usual to describe this particular discrimination as a sense of the state of the muscle’s contraction, and to regard it as the primary or typical form of the muscular sense. Now, the discrimination must no doubt be an original fact; one cannot see how it could be acquired ; but the meaning given to it, the interpretation of the position of the limb, and of the magnitudes embraced between two outstretched parts, is wholly acquired. We must learn by ex- perience what movements correspond to the transition from one mode of con- traction to the other; extension must be measured first by movement. A definite fixed position of the two arms, of the two legs, of the jaws, of the STATE OF A MUSCLE’S CONTRACTION. 99 We have thus gone over the two great classes of muscular feelings enumerated at the outset of the chapter.* This lips, or of the fingers and thumb, comes to represent a series of movements, and the corresponding estimate of space passed over by movement. With one hand resting upon the side of a box, and the other resting upon the top, we can tell the inclination of the two sides, without movement; our experi- ence has made the feeling of certain combined dead tensions a symbol of a series of movements in different directions. Besides, if we would have an accurate appreciation of the amount of the contraction, we may still, in many cases, have to repeat the actual movements. The importance of this mode of discrimination is perhaps best seen in the eyes. It enters into the explanation of the binocular feeling of solidity. I have not inserted this feeling in the text among the fundamental dis- criminations of muscle, because it seems bound up with our sensibility to movement as there given. If, on the other hand, I were to assume the sense of the state of contraction as the primary feeling, the sense of movement would follow; since movement implies that the muscle passes through a series of states of contraction, and the conscious sequence of these states would be the mental fact of movement. It is possible that the feeling of movement may consist of the primary feeling of expended energy (given in its purity in dead resistance), modified by a muscular sensibility arising in the change from one stage of contraction to another. But, be this as it may, I think it enough to assume as distinct and fundamental the three modes of muscular discrimination discussed in the text. * Sir William Hamilton, in his Dissertations on Reid, p. 864, has drawn a distinction between what he calls ‘the locomotive faculty,’ and the muscular sense, maintaining that the feeling of resistance, energy, power, is due to the first and not to the second. By this locomotive faculty he means the feeling of volitional effort, or of the ‘amount of force given forth in a voluntary action ; while he reduces the application of the term ‘ muscular sense’ to the passive feeling that he supposes us to have of the state of tension of the muscle. His words are: ‘ It is impossible that the state of muscular feeling can enable us to be immediately cognizant of the existence and degree of a re- sisting force. On the contrary, supposing all muscular feeling abolished, the power of moving the muscles at will remaining, I hold that the consciousness of the mental motive energy, and of the greater or less intensity of such energy requisite, in different circumstances, to accomplish our intention, would of itself enable us always to perceive the fact, and in some degree to measure the amount, of any resistance to our voluntary movement; howbeit the concomitance of certain feelings with the different states of muscular tension, renders this cognition not only easier, but, in fact, obtrudes it on our attention.’ The sense of expended energy I take to be the great characteristic of the muscular consciousness, distinguishing it from every mode of passive sensa- 100 THE MUSCULAR FEELINGS. fundamental sensibility of our nature will come up again in a variety of connexions; and much has still to be said in order fully to explain the growth of the perceptions of Exter- nality, Force, Space, and Time. tion. By the discriminative feeling that we possess of the degree and con- tinuance of this energy, we recognize the difference between a greater and a less stretch of muscular tension, and this appears to be the primary sensibility operating in the case. The other sensibilities of muscle, derived through the sensitive fibres, may aid us in the important discriminations between the different modes of increased energy above specified. } I may here express the obligations we are under to Sir William Hamilton for his historical sketch of the doctrine of the Muscular Sense, contained in the same note; which is not the least valuable and interesting of his many contributions to the history of mental science. CHAPTER ITI. OF SENSATION. ( Y Sensations, in the strict meaning, we understand the > mental impressions, feelings, or states of consciousness, resulting from the action of external things on some part of the body, called on that account sensitive. Such are the feelings caused by tastes, smells, sounds, or sights. ‘These are the influences said to be external to the mental organiza- tion ; they are distinguished from influences originating with- in, as, for example, spontaneous activity (the case we have already considered), the remembrance of the past, or the anticipation of the future. The Sensations are classified according to the bodily organs concerned in their production ; hence the division into five senses. But along with distinctness of organ, we have dis- tinctness in the outward objects, and also in the inward con- sciousness. Thus, objects of sight are different from objects of smell; or rather we should say, that the properties and the agency causing vision are different from the properties causing smell, taste, or hearing. The difference of the mental feeling or consciousness in the various senses is strongly marked, being a more character- istic and generic difference than obtains among the sensations of any one sense. We never confound a feeling of sight with a feeling of sound, a touch witha smell. These effects have the highest degree of distinctness that human feelings can possess. The discrimination of them is sure and perfect, although we sometimes try to assimilate them. We are commonly said to have five Senses : Sight by the eye, Hearing by the ear, Touch by the skin, Smell by the nose, Taste by the mouth. In addition to these, physiologists 102 OF SENSATION. distinguish a sixth sense, of a more vague description, by the title of common or general sensibility, as will be seen in the following extract from Messrs. Todd and Bowman. ‘ Under the name of common or general sensibility may be included a variety of internal sensations, ministering for the most part to the organic functions and to the conservation of the body. Most parts of the frame have their several feelings of comfort and pleasure, of discomfort and pain. In many of the more deeply seated organs, no strong sensation is ever excited, ex- cept in the form of pain, as a warning of an unnatural con- dition. ‘The internal sensations of warmth and chillness, of hunger, thirst, and their opposites, of nausea, of repletion of the alimentary and genito-urinary organs, and of the relief succeeding their evacuation, of the privation of air, &., with the bodily feelings attending strongly excited passions and emotions, may be mentioned among the principal yarieties of common sensations.’ In this enumeration we can see several distinct groups of feelings, and can refer them to distinct bodily organs. Hunger, thirst, their opposites, nausea, repletion, and evacua- tion of the alimentary tube, are all associated with the digestive system. They might therefore be termed the digestive sensations. The privation of air causes a feeling whose seat is the lungs, and is one kind of sensibility associated with respiration. ‘The sensations of warmth and chillness connect themselves with the skin, with the lungs, and with the organic processes in general. ‘The genito-urinary organs have a class of feelings so special and peculiar, that they had better not be included under common sensibility Looking at the important classes of feelings here indicated, important at least as regards human happiness and misery, considering also that they are but a few examples chosen from a very wide field, I consider it expedient to describe them in systematic detail. It is the business of a work like the present to review the entire range of human sensibility, in so far as this can be reduced to general or comprehensive heads; and the question is, where ought these organic feelings to be CLASS OF ORGANIC SENSATIONS. 103 brought in? I know of no better arrangement than to include them among the Sensations. The only objection is the want of outward objects corresponding to them in all cases. The feelings of comfort or discomfort arising from the circulation, healthy or otherwise, are not sensations in the full meaning of the term; they have no distinct external causes like the pleasures of sound, or the revulsion of a bitter taste. But the reply to this objection is, first, that in most cases, if not in all, an external object can be assigned as the stimulus of the feeling; for example, in the digestive feelings, the contact of the food with the surface of the alimentary canal, is the true cause or object of the feeling ;. so the respiratory feelings may be viewed as sensations .having the air for their outward object or antecedent. And: with reference to the cases where feeling cannot be associated with an external contact, as in the acute pains of diseased parts, we may plead the strong analogy in other respects between such feelings and proper sensations. In all else, except the existence of an outward stimulus, the identity is complete. ‘The seat of the feeling is a sensitive mass, which can be affected by irritants external to it, and which yields nearly the same effects in the case of a purely internal stimulus. So much is this the fact, that we are constantly comparing our inward feelings to proper sensa- tions ; we talk of being oppressed, as with a heavy burden, of being cut, or torn, or erushed, or burned, under acute in- ternal sensibility. Moved by such considerations, I class these feelings with sensations, and place them first in the order of the Senses, under the title of Organic feelings, or Sensations of Organie Life. In the Senses as thus made up, it is useful to remark a division into two groups, according to their importance in the operations of the Intellect. If we examine the Sensations of Organic Life, Taste, and Smell, we shall find that as regards pleasure and pain, or in the point of view of Feeling, they are of great consequence, but that they contribute little of the permanent forms and imagery employed in our Intellectual processes. This last function is mainly served by Touch, 104 SENSATIONS OF ORGANIC LIF. Hearing, and Sight, which may therefore be called the Intel- lectual Senses by pre-eminence ; they are not, however, there- by prevented from serving the other function also, or from entering into the pleasures and pains of our emotional life. SENSATIONS OF ORGANIC LIFE. 1. The classification of these is best made to proceed according to the parts where they have their seat. We have already adverted to the organic feelings connected with one tissue, the muscular ; we shall now have to describe them in full. We must also notice the other tissues entering into the moving apparatus, namely, the Bones and Ligaments. The Nerves and Nerve Centres are subject to feelings dependent on their stimulation, growth, and waste, and on the changes that they go through in health and disease. The Circulation of the Blood, with the accompanying processes of secretion, assimi- lation, and absorption, may be presumed to have a distinct range of sensibility. The feelings connected with Respiration are of a less ambiguous character than the foregoing. The sensations of Dzgestvon are numerous and prominent. I. Of Organic Muscular Feelings. 2. In a quotation given from Dr. Sharpey, it is remarked that muscular sensibility ‘is manifested by the pain which is ’ felt when a muscle is cut, lacerated, or otherwise violently injured, or when it is seized with spasm.’ These forms of pain are so many states of consciousness, having their seat or origin in the muscular tissue ; the integrity of the nerves and nerve centres being likewise essential to this, as to every other kind of sensibility. In describing the states of feeling arising through the Senses, named Sensations, we shall have to assign in each case the external agent that causes the Sensation (light, sound, &c.); to follow this up with an account of the action or change affected on the sensitive surface, (as the skin, the tongue, &c.) ; and then to proceed with a delineation of the feeling itself, according to the plan already laid down. ? ORGANIC MUSCULAR FEELINGS. 105 In the case of the proper muscular sensibilities described in the foregoing chapter, an external agent could not be assigned in the same sense as light is to the eye, or hard surfaces to the skin. But with reference to the first class in Dr. Sharpey’s enumeration, ‘cuts, lacerations, and violent in- Juries,’ we discern both an external agent and an assignable change in the substance of the muscle. There is, in those circumstances, a sudden break in the continuity of the fibre, which is an effect productive of pains in almost any tissue of the body. This is manifestly one of the effects calculated to give an intense shock to the nerves, originating an energetic and pungent stimulus, which is transmitted to the centres, and there wakens up both consciousness and activity in violent forrns. Such being the bodily Origin, let us complete the con- sideration of the PHYSICAL side, by attending to the outward effects, or embodiments, constituting the Expression of the feeling. And the remarks on this point, as well as the further delineation of the conscious state, will serve to typify acute physical pains generally. It is well known that a characteristic expression attends Acute Pains. The features are violently contorted, the voice is excited to sharp utterances, the whole body is agitated. Sometimes the ordinary movements are quickened ; at other times contortions and unusual gestures are displayed. It would appear that the agency causing the pain is such as to stimulate to an intense degree the whole moving system. Indeed, the infliction of pain (within limits) is one of the customary modes of rousing an animal or a human being from lethargy to activity. ‘There is also a well known form of the countenance that marks the condition of pain, being produced by certain movements of the mouth, the nostrils, and the eyes, to be afterwards analyzed ; but whatever be the direction given to these movements, they are marked by the characteristic of violence or intensity. The accompaniment of sobbing shows that the involun- tary muscles and glands are also affected. 106 SENSATIONS OF ORGANIC LIFE. But we should give a most inadequate account of the embodiment of pain, if we failed to note the successive stages of the manifestation. While the first shock may have all the characters of violence and exalted energy now mentioned, there follows, after a time, a state of prostration and ex- haustion, showing that these lively manifestations are no proof of an increase of vital energy on the whole. On the contrary, it is demonstrable that of vital energy on the whole there is a great decrease. Violent exercises of any kind soon wear out the strength; but the depression of vital power in all parts of the system—organic functions as well as muscles—after an attack of pain, is much beyond what would follow from the same discharge of muscular energy in the absence of pain. This is a most material consideration, which is not to be disguised by the show of increased energy in the early stages. The director of the medical staff of the British Army in the Crimea was gravely in error when he discouraged the use of chloroform jin surgical operations, on the ground that pain is a stimulant. If the termination is taken into account as well as the beginning, pain in every form, so far from being a stimulant, destroys the vital energies. Not only does muscular exhaustion follow, but the organic processes—the circulation, respiration, and digestion —are greatly enfeebled, an effect that does not usually result from mere violence of bodily movement. These bodily manifestations, which are the natural ac- companiment of acute pain (arising as an effect of the same cause), by being freely indulged in, operate as a diversion and a relief to the mental system. ‘There is probably a physical sequence in this fact also. Great muscular exertion draws off the circulation from the brain to the muscles; and the effusion of tears also in some way reduces the congestion. We are not, however, rashly to conclude that, under great pain, a free vent to all the manifestations is preferable to forced quiescence or suppression ; there is a great expendi- ture of power under both modes. | 0. To pass now to the MENTAL side, or the character of ACUTE PAINS TYPIFIED. 107 the states in question, viewed as Feelings. We know, each one by our own consciousness, what they are; and they are generalized, pointed out, and understood, by such names as pain, suffering, agony, torture. The quality of the feeling is pain. The degree is intense or acute. The measure is obtained in a twofold manner: by comparing the pain with other pains, and by the amount of pleasure that it can neutralize. Taken in both ways, we consider the sufferings of wounds, lacerations, and acute derangements of our sensitive tissues, to rank among our greatest sufferings, our worst miseries. As respects speci- alities of character, we find language employed to discri- minate the nature of different pains. A cut or a scald is different from a fit of rheumatism or gout. Neuralgia is different from the electric shock. We describe the varieties by such epithets as burning, gnawing, shooting, racking; and there is a pathological interest in noting these distinctions. Pain is apt to rouse some special emotion, in accordance with the general temperament of the individual. Grief, terror, or rage, may prevail according to the circumstances, there being a natural connexion between the shock of acute suffering and all these passions. Our plan of description requires us next to advert to the Volitional characteristics of acute pain. ‘The general prin- ciple of volition, as applied to pains, holds in this instance. Such pains, in proportion to their intensity, stimulate us to efforts for mitigating and putting an end to them when pre- sent, and for avoiding them when there is danger of their recurrence. The peculiarity of the case that most deserves notice is, that since, for a time, they are stimulants of activity, the disposition to work for their abatement is very powerful at first, but fails at last with the prostration of the energies. The effective force of our volitions depends upon the active power of the system at the moment; and a state that increases this power, even by a wasteful stimula- tion, reaps the benefit of that increase, while anything that depresses and destroys the vital functions, as severe pain 108 SENSATIONS OF ORGANIC LIFE, does on the whole, to that extent paralyzes the action of the will. Hence, although a passing smart may waken up the activity, an intense and continuing pain will fail in the effect. The movements that constitute the proper emotional manifestations, are apt to be mixed up and complicated with movements directed by the will with a view to relief. It is generally easy to discriminate the two classes, and it is important for understanding our mental structure that they showld be discriminated. The volitional movements are such as are maintained solely because they bring a felt alleviation. If any specific posture is of this character, it is energetically adhered to; and if the mere vehemence of the outburst is found to deaden our sensibility to the pain, we are induced thereby to keep up the gesticulations prompted in the first instance by the emotional wave. Even in the lower animals, when we witness the convulsions that follow a shock to the physical system, we may satisfy ourselves as to the existence of true volitional movements, in company with the demon- strations that are the proper embodiment of the pain. If we wish to measure the volitional urgency of a feeling, we can adopt the same mode of comparison as that suggested for the degree of pleasure or pain. When two feelings prompt in opposite ways, the one that determines the conduct is sald to be volitionally the stronger. There remains now the bearing of the feelings in question on the Intellect. Here, as in the Will, there is a general principle, liable to exceptions and modifications according to the circumstances of each particular case. The principle is, that feelings are discriminated, identified, and remembered according to their degree, whether in intensity or in quantity. This law holds within a moderate range of excitement. A very feeble impression cannot be nicely discriminated, and is little remembered. But the limitation arises when the degree is excessive and overpowering. There isa pitch of physical agony that overpowers the purely intellectual function of discrimination; and although retentiveness is MEMORY FOR ACUTE PAINS. 109 stimulated by intensity, the remembrance becomes more and more inadequate to the fullness of the reality. Not only are we unable to re-instate the acuteness of the suffering, but we are unable to figure to ourselves even the character of the pain, until it kas become familiar by many repetitions. When the same, or nearly the same, pain recurs, we can mark the agreement, which is a true intellectual function, requiring.for its exercise the retentive property also; but we have little power of remembering or imagining the peculiar features, or the characteristic consciousness of an acute misery. A good retentiveness for acute pains has not the intellec- tual importance possessed by the memory for sights and sounds, but it has a twofold practical importance. In the first place, on it depends the exercise of the will in the way of prevention. When a feeling ceases in the actual, it can have no volitional power, except as it is vividly presented in idea ; and on this ground, the more lively the recollection, the more energetically are we moved in our precautionary labours as regards the future. ‘The degree of retentiveness for pain is thus the intellectual foundation of Prudence. It is, in the second place, the foundation of Sympathy, or the power of entering into the feelings of others when suffering under a like infliction. 4, The muscular pains that have been the subject of the above description, are those arising from cuts, lacerations, and violent injuries, being the incidents that every tissue is liable to. We have not included the characteristic pain of muscle— cramp, or spasm. Cramp is well known to be a violent con- traction of a muscle, in whole or in part, due to some irritation of the motor nerves that supply the muscle. It is a contrac- tion probably far beyond what can be induced by a voluntary effort, and does not relate itself in any way to a power con- sciously proceeding from the brain. The state of cramp acts violently upon the sensitive fibres of the muscle; and, according to Dr. Brown-Séquard, the pain is in proportion to the resistance offered to the muscle’s contraction. ‘I suppose,’ he says, ‘a case of painful contraction of the anterior muscles 110 SENSATIONS OF ORGANIC LIFE. of the thigh ; the pain is increased every time the contracted muscles are elongated; 7. ¢, when the resistance to the con- traction is augmented ; on the other hand, it diminishes when the resistance to the contraction is rendered less than it was, and, at last, 7¢ disappears entirely, or almost entirely, when the resistance is completely, or almost completely, destroyed.— (Lectures, p. 7.) The pains in the uterus are of the nature of spasm, and are relieved by the discharge of the contents. An explanation is now afforded of what was at first considered a paradoxical fact, the production of pain by stimulating the anterior, or the motor, roots of the spinal nerves. The effect of such stimulation is to contract the muscles, not in that measured and moderate degree occuring in their contraction by the will, but with the violence of cramp, thereby imparting a shock to the sensitive nerves of the muscle. When the posterior, or sensitive, roots of the nerves are cut, the pain appears no longer. These explanations are interesting, as they remove what appeared objections to the discovery asso- ciated with the name of Bell It is not requisite to repeat the particulars of the syste- matic description for this peculiar case. It ranks with the class of acute pains in all the general characters. But it is, perhaps, in its nature the most acute and violent of any. We can discriminate it from cuts, scalds, inflammations, and sores ; the familiar name ‘racking’ pain describes and classifies it. Wherever we have the experience characterized by this epithet, it is probable that the seat is in the muscles, and that the action 1s cramp or spasm. ‘The involuntary muscles of the uterus, and of the alimentary canal, occasion the most ageravated forms of the pain. 5. Another class of feelings connected with the muscles may be specified under the same general head of Organic Feelings, those arising from over-fatigue. This cause is known to produce acute pains of various degrees of intensity, from the easily endurable up to severe suffering. It is not neces- sary to advert to these more specifically, they being sufficiently comprehended by referring them to the genus of acute pains FEELING OF REPOSE UNDER FATIGUE. 111 of the muscles; they are part of the misery attending manual toil ; they are also used in punishment. The characteristic state of supporting a heavy burden is a form of general depression, to which many modes of suffering are habitually compared. Very different is the state of feeling produced by mere ordinary fatigue, which we may introduce in the present connexion. This isa state not at all painful, but the opposite. It is one of the pleasurable experiences allied with the muscular system. In this case, there is a pleasurable feeling, more massive than acute. If a considerable number of the larger muscles have been in exercise, the sensibility is proportionably great. Various elements may enter into the effect. The circulation of the blood, directed strongly for a time to the muscular tissue, now returns in a more liberal supply to the other organs,—the brain, the stomach, &c., and the general sensi- bility of the system is increased. There is, in the next place, an agreeable reaction from what may have been the com- mencing pains of fatigue. Allowing for those two collateral effects, we are still to suppose that the muscle itself gives rise to a certain pleasurable feeling when in this state. The degree of it may be, on the whole, considerable ; it is one of the pleasures of a life of hard exercise or bodily toil, and taken along with the luxurious slumbers and the general sensation of health following in its train, it must be regarded as an appreciable fraction of human enjoyment. The connexion already remarked on between slow move- ments and approaching sleep, extends also to muscular repose and sleep. The massive sensation experienced as we fall asleep, has its seat, in no inconsiderable degree, in the muscular tissue, especially after hard exercise, when this sensibility is most powerfully manifested. 6. I will pass over with very few remarks the Bones and Iigaments. Their sensibility is exclusively connected with injury or disease, appearing in that case under the form of acute pain, a form of sensibility that it is sufficient to have 112 SENSATIONS OF ORGANIC LIFE. dwelt upon once for all. The minute discrimination of forms of pain is of great service to the physician, and, if suscep- tible of being accomplished with precision, would enter with propriety into a systematic delineation of the Human Mind. At present we require only to remark, that sensibility every- where demands a distribution of nerve fibres, and that the bones and ligaments are supplied with these; and although not in great number, they are yet sufficient to agitate the nerve centres with overpowering intensity on particular occasions. The diseases and lacerations of the periosteum give birth to excessive pains. The ligaments are said to be insensible to the cut of a knife, while the feeling of their being wrenched is most acute and painful. In extreme fatigue, the ligaments and the tendons of the muscles would appear to conspire with the muscular tissue, in giving rise to the disagreeable feeling of the situation. The joints are noted on various occasions as the seat of pain ; for example, in gout. The diminution of atmospheric pressure consequent on ascending a great elevation, causes an intense feeling of weariness in the hip joints. This is shown by experiments to be a muscular pain. The rarefaction of the air diminishes the support of the limb, and it falls down in the joint by its own weight, thereby becoming an additional burden to the muscles. Fracture of the bones and laceration of the liga- ments are among the agonizing incidents of our precarious existence. Organic Sensations of Nerve. ; 7. The nerves and nerve centres, apart from their action as the organs or medium of all human sensibility, have a class of feelings arising from the organic condition of their pwn tissue. Wounds and diseases of the nerves are productive of intense pains ; witness tic-douloureux and the neuralgic affec- tions of the brain and spinal cord. Nervous exhaustion and fatigue produces a well known sensibility, very distressing in its extreme forms; and repose, refreshment, and stimulants ORGANIC SENSATIONS OF THE NERVES. 113 engender an opposite condition through a change wrought on the substance of the nerve tissue. The nervous pains arising from cuts, injuries, and disease of the substance, are characterized by a most vehement intensity. When a muscle is spasmodically contracted, the influence passes from the muscular fibres to the nerve, and the _ affection of the nervous fibres may then be supposed to be secondary ; but, in neuralgic affections, the influence comes at first hand, and not by propagation from some cther tissue. We have here, therefore, a manifest complication to deal with. The nervous substance is necessary to all sensibility ; strictly speaking, every form of pleasure and of pain is physically embodied in a certain condition of the brain and nerves. But we have to note, under the present head, the effects that arise from operating upon the tissue directly, and not through the organs of sense, or by means of the emotions. This direct action is exemplified in injuries and in diseases of the nerves; in the use of stimulating drugs; and in the agencies whereby the cerebral substance is nourished or impaired. 8. Nervous fatigue and exhaustion, when carried beyond a certain pitch, is an extremely trying condition. Itis produced by excessive expenditure, in one or other of the forms of nervous exercise; by intense pains, by excess of pleasure even, by over-much thought, or by too long continued activity of either body or mind. The effect is a deficient nourishment of the nerve substance, or a low order of nervous action, The resulting sensation can be more readily described. The most painful ageravation of the state occurs when a morbid activity is generated beyond the control of the individual, hurrying him for a time into still greater depths of painful exhaustion. This state of mind merits a full and orderly delineation. Commencing as usual with the quality, we must attribute to it an exaggerated form of pain. This pain is marked not by acuteness or intensity, but by massiveness or quantity. It is a wide spread and oppressive sensation. Its peculiar character 8 114 SENSATIONS OF ORGANIC LIFE. or tone cannot be seized by any descriptive phrase. I must appeal to each person’s own experience for the perception of it. ‘The re-action of an intense excitement, the exhaustion of a severe loss or grievous mortification, will bring up an instance of it to most minds. It will also be illustrated by contrast with the opposite state to be next treated of The Expression of the feeling is one of pain, not acute, but deep- seated and engrossing; collapsed features, restlessness, fretting, and melancholy. The Actions prompted are usually some- thing quite extravagant and misplaced. The getting rid of life itself is suggested when the condition assumes its most virulent forms. This is a proof of the total loss of freshness and health through the substance of the nervous system. Hence the final triumph of ennui :— I am aweary, aweary, O God that I were dead! It is too powerful to be adequately remembered when the reality has passed away. The most obvious comparison that the state suggests is with excessive burden or toil in the moving organs. To fix by a precise delineation this condition of organic nervous exhaustion is an extremely important attempt, not- withstanding the difficulties arising both from the imperfection of our language, and from the fluctuating and various nature of the condition itself. The importance lies in the great fact, that this state is the termination or final issue of a great many other forms of pain. The struggle that we maintain against painful inflictions of all kinds, whether bodily or mental, often preys at last on the substance of the nervous system, and produces as its result this new form of evil. 9. The consciousness arising out of the healthy and fresh condition of the nerve tissue, or out of the operations of the various artificial stimulants, is the exact contrast of the state now described. I do not inquire into the use and abuse of those stimulating materials, but merely advert to the effect common to them all, and for which they are had recourse to ; an effect also to be reaped from the natural condition of the THIRST. 115 nervous organs when in their vigour, as may be seen more particularly in early life. Following a parallel course of description, we may say of the state in question, that the outward causes or antecedents are either healthy agents, or stimulants and drugs. The physical change in the tissue presumably contains one or other of these facts :—an abundant supply of arterial blood, or a great activity of nervous assimilation in the tracks or modes governing sensibility. The consciousness itself is pleasurable, and may ascend to very high degrees of pleasure, both in acuteness and in mass. The action and desire that it prompts are naturally for continuance unlimited, and the cast of thought is hopeful for the future. The intellectual persistence is, as in the other case, low; that is to say, the state is one difficult; to be remembered or imagined when once entirely gone, and when either the opposite condition, or some intermediate neutral one, has taken the place of it. Organic Feelings of the Circulation and Nutrition. 10. The circulation of the blood through the arteries and veins by the force of the heart, the secretion of nutritive material and of excrementitious matter in the several tissues and glands, and the various acts of absorption corresponding to those processes—cannot be unattended with feeling. But the sensation arising out of the different degrees of vigour attending this course of operations, is both vague and difficult to isolate. We may surmise with some probability that the depression of a low pulse and languid circulation has its seat in the capillaries situated all over the body, or is a sensation of the circulating machinery. In this connexion, we may allude to the two formidable experiences—Thirst and Ina- nition, or privation of Food. Thirst shows itself in a dryness of the mouth and throat, accompanied by a feeling of roughness and burning in the hinder walls of the gullet or the palate, and in the roots of the tongue. It is connected with a deficiency of water in the 116 SENSATIONS OF ORGANIC LIFE. blood, as compared with the solid constituents. Hence it is brought on by profuse perspiration, by inhaling dry air, by taking solid food, and by partaking of saline or other matters _ that strongly attract water to themselves. It is sometimes present, as a sensation, when the mouth is not parched, and absent in the opposite case; this would imply some deranged state of the nerve centres. Inanition is different from hunger ; still, as regards their physical foundations, the two may be taken together when we come to speak of Digestion. The feelings of Inanition and of Thirst, when carried to the extreme, are states of pervading, massive, deep, and intolerable wretchedness. They are far more intense than mere nervous depression, and therefore stimulate a more vehement expression and a more energetic activity. Even when not accompanied with the terror of death, they excite lively and furious passions. The unsophisticated brute is the best instance of their power. Like other organic states, they are not very easily realized after they are gone; but the fear, and stir, and energy that they produce at the time, leave a much more lasting impression than mere low spirits; we take far greater precautions against them than against nervous depression. The final result of the healthy operation of the nutrient organs, on the one hand, and of the purifying organs, on the other, may be considered as a perfect state of the blood. The consciousness growing out of a vigorous circulation, with all that this implies, may be looked upon as the most characteristic sensation of pure animal existence. There is a thrill of corporeal gratification, not very acute, but of con- siderable volume, a gentle glow felt everywhere, rendering existence enjoyable, and disposing to serene and passive contentment. Let me have men about me that are fat; Sleek-headed men, and such as sleep o’ nights. It seems to be through the circulation that we are sen- RESPIRATION. 1ti sitive to atmospheric changes, more particularly as regards moisture and dryness. It is found that in a dry atmosphere the capillary circulation is quickened, and in a moist atmo- sphere retarded. The influence of heat and cold probably extends to the circulation and the nutritive functions. Feelings of Respiration. 11. ‘Respiration is that function by which an interchange of gases takes place between the interior of an organized being and the external medium ; and, in the animal kingdom, oxygen is the gas received, and carbonic acid the gas given out. The aeration of the animal fluids or juices is an essen- tial of their vitality ; if this is put an end to, death ensues instantaneously ; if insufficiently performed, the vigour of the animal is lowered, and a peculiar painful sensation expe- rienced. In man and in air-breathing animals, there is a wind-apparatus, the lungs, inflated and contracted by muscles, so as to suck in and force out the air by turns. In this action we have all the particulars necessary to constitute a Sense; an external olject-—the air of the atmo- sphere—which operates by physical contact upon the lining membrane of the tubes and cells of the lungs; an organ of sense, and a resulting state of feeling, or consciousness. The peculiarity of the case lies in its being almost entirely an emotional sense; generating feeling rather than yielding knowledge, or providing forms for the intellect; ranking, therefore, among the lower, and not among the higher, senses. As respects the object of this sense, the external air, it need only be remarked, that the air differs considerably in its quality fer breathing purposes, the chief point of differ- ence being expressed by the term ‘purity.’ The purity is affected first by the loss of oxygen, which happens when the same air is repeatedly breathed, or otherwise consumed ; secondly, by the accumulation of carbonic acid, from the same circumstance ; and, thirdly, by the presence of foreign gases and effluvia arising from animal life, vegetation, or _ other causes, Closeness or confinement is the chief aggra- 118 SENSATIONS OF ORGANIC LIFE. vation of all those impurities. Of the three evils—the loss of oxygen, the accumulation of carbonic acid, and the gene- ration of effluvia of animal and other substances—the second is the least injurious; for, although the production of a carbonic acid atmosphere, by burning charcoal in a close room, is fatal to life, yet the quantity ordinarily occurring in rooms is not found to do any harm, if mixed with air other- wise pure. The loss of oxygen, and the diffusion of the gases of decay, are the main influences that deteriorate the atmosphere. Of the organ acted upon, the lungs, a minute description is not necessary for our present purpose. ‘The structure is so arranged by ramifications and doublings as to present a very extensive surface to the air; the surface consisting of a fine membrane, with capillary blood-vessels, thickly distributed on its inner surface. The'exchange of gases takes place through the double medium of membrane and capillary tube. The muscular apparatus for sustaining the bellows-action, is the diaphragm and abdominal muscles, and the muscles of the chest or ribs. The integrity and vigour of these muscles, and of the centres that sustain and time their action, must be reckoned as a condition of healthy respiration. The respiratory nerve centres are stimulated from all parts of the body, but chiefly from those that, like the muscles, are large consumers of oxygen. The portion of the eighth pair of nerves named the nervus vagus, is instru- mental in keeping up the rhythm of the lungs, and is also necessary to the feeling of suffocation. The feelings of Respiration, both pleasurable and painful, are well marked. They include the gratification from pure air, enhanced by the increased action due to muscular exer- cise ; the various shades of oppression from over-crowded rooms and unwholesome gases ; the distressing experience of suffocation, or want of breath; and the pains attendant on disease of the lungs. 12. The influence of pure and stimulating air abundantly inhaled, spreads far and wide over the system, elevating all PURE AIR, 119 the other functions by the improved quality imparted to the blood. ‘The indirect consequences do not altogether hide the grateful sensibility arising from the lungs themselves, and referred by us to the region of the chest; a sensation not very acute or prominent, but possessing that choice and well known quality, expressed by the term ‘ freshness,’ or ‘ refresh- ing.” This quality manifestly implies a contrast; for it is felt only when we pass from a lower to a higher degree of aeration. We may experience it at any time, by holding in the breath for a little, and then allowing it full play. No technical nomenclature can increase the conception possessed by every one of this remarkable sensibility ; but for the sake of comparison with the other parts of our mental constitution, an attempt at verbal description is necessary. As just remarked, the sensation turns upon the contrast of the greater activity of the lungs with an immediately preceding activity of an inferior degree. It may be affirmed that no feeling arises from the lungs, after a given pace has been estab- lished for a length of time; but any acceleration of the rate of exchange of the two gases (by no means depending altogether on the rate of breathing) does for a time yield that delightful freshening sensation, which tells so immediately on the mental system as a contribution to our enjoyment, and as a stimulus to our activity and to our desire for rural recreation and bodily exercise. 13. The feelings of insufficient and impure air are mani- fested in the forms of faintness, sense of exhaustion and weariness, and are doubtless due, not to the lung-sense alone, but to the lowered condition of the body at large. The characteristic sensibility of the lungs is shown in the state termed suffocation, arising from the want of air, as in drown- ing, in an atmosphere deteriorated by poisonous gases—such as chlorine or sulphurous acid, in attacks of asthma, and in voluntarily holding in the breath. ‘After holding the breath for fifteen or twenty seconds during ordinary respiration, or forty seconds after a deep respiration, there arises an insup- portable sensation over the whole chest, concentrated under 120 SENSATIONS OF ORGANIC LIFE. the sternum, and no effort can maintain the interruption of the respiratory acts. This urgent sensation of want of breath, when carried to its full extent by any mechanical impediment to the aeration of the blood, is one of the most painful and oppressive kind, and is referable to the pulmonary plexuses (of nerves) distributed to the bronchia, and perhaps on the walls of the lobular passages and cells. The impression made on these peripheral nerves by the absence of oxygen, and the undue presence of carbonic acid in the air in contact with them, is propagated to the spinal cord and medulla oblongata by the sympathetic and vagus, and there excites those com- bined actions of the muscles of inspiration. which lead to the renewal of the air.—(Topp and Bowman, II., 403.) The sensation is of the class ‘racking pains,’ and may be, in part, muscular. Feelings of Heat and Cold. 14, The description of these important feelings comes pro- perly under Organic Sensations, in so far as change of tem- perature affects all the organs of the body. Warmth, while abating the activity of the organic processes generally, in- duces in the skin a richer circulation, and a greater activity in the sweat, and in the oil glands. The various parts of the cuticle, the nails and the hair, are more abundantly pro- duced. The sensory powers of the organ are greater, and the texture is softer and more polished. Inasmuch as cold (not in excess) increases the activity of the muscles, the nerves, the respiration, and the digestion, the animal powers attain their maximum in cold climates, and in the winter season, allowance being made for constitu- tions unfitted to endure extreme depression of temperature. Sudden changes of temperature derange the functions. A sudden increase will cause a slight feeling of suffocation, beating of the heart, and increased pulsation and respiration. A sudden chill makes breathing difficult, quick, and irregular, and increases the pulsations. The nerves lose their excit- | SENSATION OF COLD. 121 ability both under a great depression, and under a great | increase of temperature. The feelings of heat and cold are very notable. Let us commence with Cold. The outward cause of this feeling is some influence tending to lower the temperature of the body. The natural heat of the blood is about 98°, and any contact below this point feels cold; any contact above it feels warm. There is a certain surplus heat generated in the human system, which enables us to live in a medium below 98’, without feeling cold; and if this heat be husbanded by cloth- ing, a very great depression of external temperature may be endured. A room is warm at 60°. The outer air can be endured at freezing and far below, either by means of exercise, which evolves heat, or of clothing, which retains it. An acute cold acts like a cut or a bruise, injuring the part affected, and causing painful sensations of the class arising from violent local injuries. The temperature of freezing mercury would destroy the skin like boiling water or a sharp cut. The proper sensation of Cold arises from a general cooling of the body, or any considerable part of it, below blood heat. The term ‘ chillness’ expresses the state of feeling, which is of the painful class. The degree is not acute but massive. In the worst forms, it is wretchedness in the extreme. Toa person suffering from excessive chillness, some powerful stimulant, such as the taking of food, alcohol, or tobacco, is necessary to restore equanimity. The volition and the memory are proportionally impressed by the pains of cold, and they take a high rank in the reckonings of forethought and prudence. It is a singular fact in our constitution, that an agency calculated to quicken the vitality of so many leading organs —muscles, nerves, lungs, stomach—should affect us so power- fully, by the depression of one organ. The fact is highly illustrative of the importance of the skin, whether from its organic functions or from its sensibility. Probably both circumstances enter into the case. It may be that the 122 SENSATIONS OF ORGANIC LIFE. quickened vitality of all the other leading organs is unavailing for a perfectly healthy tone while the skin is depressed. But it must be also true, that we are in a peculiar degree sensitive to changes in the condition of the skin, owing no doubt to its great supply of nerves. 15, The consequences of Heat are, in nearly every parti- cular, the opposite of those now stated. Acute or intense heats agree with intense colds in being simply destructive and painful. Within the point of injury to the tissues, heat is a pleasurable sensation. The pleasure of heat, like the pain of cold, is voluminous or massive. There are cases, however, distinguished by intensity rather than by quantity ; indeed, this distinction of quantity and intensity, used as a part of the description of feelings, has its perfect type in the case of temperature, there being a physical reality correspond- ing to the mental facts. Sometimes we have great intensity and small quantity, as in the scorching rays of a fire, or a cup of hot tea: at other times we have large quantity with low intensity, as in a hot bath, a warm room, a warm bed. The hot bath is the extreme instance. By no other contrivance can such a mass of heat be brought to bear upon the human system ; consequently this presents the sensation of warmth in its most luxuriant form. It is the intoxication of animal heat. We are unavoidably led to assume that this warmth must act powerfully on the sensitive nerves; for itis hardly to be supposed, that the organic processes are so greatly furthered by the sustained temperature as to exalt the pleasur- able consciousness in this remarkable degree. Indeed, we may derange the system by excessive heat, without producing the painful feeling arising from cold. | In the case of morbid activity of the nervous system, warmth is a soothing influence, either by its physical effects, or by the nature of the sensation, or from both combined. The feelings of Respiration, and those of Heat and of Cold, illustrate in a marked manner the fundamental doctrine of Relativity, or of change as a condition of consciousness. There is no feeling of respiration, unless by increase or MATERIALS OF FOOD. Ea diminution of the action of the lungs ; and if we lived in an even temperature, heat and cold would be alike unknown. The induction of the principle of Relativity as regards these states is complete. Sensations of the Alimentary Canal. 16. Digestion offers all the conditions of a sense. There is an external object—the Food ; a distinct organ of sense— the Alimentary Canal and its appendages; and a set of Feelings arising from the contact, also distinct and specific. To treat these feelings under Taste, is to confound together two senses totally different in their character, although hap- pening to have one common object or stimulant. The oljects of this sense are the materials taken into the body as food and drink. These materials are extremely various, but there is no corresponding variety in their action on the stomach. They can be reduced to a few general heads, according to their composition, it being found possible to assign a few leading substances that comprehend all the different sorts of material serviceable in nourishing the body. The following is an abstract of this classification :— 1st. Water and the watery liquids, including substances conveyed in solution, or suspension, in water. 2nd. Saccharine substances derived from the vegetable kingdom. ‘These comprehend sugars, starch, gums, vinegar. 3rd. Orly substances. These include the various fats and oils as well as alcohol. Like the former group, they are com- posed of carbon and the elements of water, but in them the carbon is in a much higher proportion. Ath. Albuminous substances, containing nitrogen : fibrine, gelatine, albumen, caseine (matter of cheese), vegetable gluten. ‘All the materials which make up this group are derived generally from the animal kingdom, with the exception of the last, which is contained in great abundance in wheat ; similar if not identical principles exist in other vegetables. Wheat, indeed, consists of two substances—one referable to 124. SENSATIONS OF ORGANIC LIFE. the saccharine group, the other to the albuminous, the former consisting of starch, the latter of gluten.’ Milk is found to contain matter of all the four classes: water, sugar, oily matters (butter), caseine. The three first classes are incapable of nourishing the principal animal tissues, such as nerve, muscle, &. They are fitted rather for supplying fat, bile, and matters used in the production of the carbonic acid that escapes from the lungs. Being supposed to be mainly destined for the supply of animal heat, by being combined with oxygen, or slowly burned, they were formerly termed calorifacient ; but this is now reckoned a too narrow view. Experiments recently made have proved that their combustion is the chief source of muscular power; being an example of chemical com- bination transmuted into mechanical force, of which a parallel is found in the steam-engine. The same combustion may also be the source of the nerve force ; the parallel case being the voltaic circuit, where the electricity is evolved from chemical combination in the cells. The albuminous bodies are undoubtedly the tissue- forming material, having a composition fitted for the purpose. But they are not confined to this function; in their final transformations and decay, they may be at last oxidized and become the source of heat, muscular force, and nerve force, like the others. Certain substances of the saline, earthy, or mineral class, are requisite; most of them being found in the usual articles of food. Salts of soda, potash, and lime, as well as iron and phosphorus, are essential ingredients. The Stimulants are classified into spices, or condiments ; ‘ vegetable alkaloids, as tea, coffee, cocoa; extractives, as ereatin and creatinin, occurring in the juice of meat; and the alcoholic beverages. For the most part, these substances are not directly nutritive ; they act as stimulants to the nervous system, and also retard the waste of tissue. The organic vegetable acids,—vinegar, the acids of fruit, and lactic acid, are in extensive use as an ingredient of food. ORGANS OF DIGESTION, 125 The differences that exist among the infinity of articles used as food are not at bottom so great as they seem. If we take the different species of grain—wheat, barley, rye, oats, rice, maize, millet, we shall find they are all composed of the same ultimate materials, gluten and starch, though not in the same proportions. In like manner, the potato is a starchy vegetable, with a very small share of gluten, hence the defec- tive character of it as an article of nourishment. Another difference among vegetables relates to their texture, as fitting them for being acted on during mastication and digestion,— a circumstance, however, that cooking can modify. Thus the potato is a much looser texture than grain. of an inch in height. In the ridges, the large papille are placed sometimes in single, but — W€ more commonly in double rows, Ul VY, ; Rew DY — with smaller ones between them, that is, also on the ridges, for there are none in the inter- vening grooves. These ridges are marked at short and tolerably equal intervals with notches, or short transverse furrows, in each of which, about its middle, is the minute funnel-shaped orifice of the duct of a sweat gland. Fine blood-vessels enter the papille, forming either simple capil- lary loops in each, or dividing, according to the size of the papille, into two or more capillary branches, which turn round in form of loops, and return to the veins. Filaments of nerves are also to be discovered ascending into the papille, but their mode of termination is doubtful. In other parts of the skin, endowed with less sensibility, the papille are smaller, shorter, fewer in number, and irregularly scattered. In parts where they are naturally small, they often become enlarged by chronic inflammation round the margin of sores and ulcers of long standing, and are then much more con- spicuous. —QUAIN.T Fig. 6.* * ¢Papille of the palm, the cuticle being detached.—Magnified 35 diameters.’—(‘Topp and Bowman.) + Inside the papille are either nerves or blood vessels, seldom both; and at their base, the nerves are disposed in the form of net-work. In great part of the skin, the nerves cannot be traced farther than this net-work ; it is in the hands, feet, lips (red part), and tongue that they are followed into the interior of the papilla. In these parts they end in a peculiar structure, known as the ‘ little bodies of touch,’ discovered by Wagner and Meissner. These are little sacks, covered by a thin skin, and filled with a round little mass. The skin is pierced by one or two nerves, which often wind spirally, but end by dividing and spreading their twigs in the little sack. These bodies lie in the interior of papille destitute of blood vessels, in such a manner as to project far above the upper end of the papillw, and in immediate contact with FUNCTIONS OF THE SKIN.: 165 I have quoted the description of the papille at length because of their connexion with the sensibility of the skin. I shall refrain from quoting the minute account of the nails and hairs, however interesting their structure in other points of view. Respecting the glands, it is only necessary to advert to the totally different nature of the two sorts, as respects the material secreted. The sweat glands are enormously numerous, and exist in all regions of the skin; they are reckoned to vary from 400 to 2,800 in a square inch. ‘The sebaceous or oil glands pour out their secretions at the roots of the hairs, for, with very few isolated exceptions, they open into the hair follicules, and are found wherever there are hairs.’ 4, With respect to the functions and vital properties of the skin in general, I quote part of Dr. Sharpey’s summary. ‘The skin forms a general external tegument to the body, defining the surface, and coming into relation with foreign matters externally, as the mucous membrane, with which it is continuous and in many respects analogous, does internally. It is also a vast emunctory, by which a large amount of fluid is eliminated from the system, in this also resembling certain parts of the mucous membrane. Under certain conditions, moreover, it performs the office of an absorbing surface ; but this function is greatly restricted by the epidermis. Through- out its whole extent the skin is endowed with tactile sensibility, but in very different degrees in different parts. On the skin of the palm and fingers, which is largely supplied with nerves and furnished with numerous prominent papille, the sense the cuticle. They are most numerous on the inside of the finger tips, and decrease towards the palm; the same happens with the foot. Meissner found in a square line (yz of a square inch) on the index finger, 108 on the last joint, 40 on the second, 15 on the first. In the red part of the lips, the papille carrying nerves are not distinguishable from those carrying blood vessels, the same papilla appearing to have both. The little muscles discovered by Koélliker in the skin, and especially in the glands, excite peculiar movements as in shivering, the creeping sensation, &c. These are especially affected by changes of temperature, and may serve to regulate the supply of blood under such changes. 166 SENSE OF TOUCH. attains a high degree of acuteness ; and this endowment, to- gether with other conformable arrangements and adaptations, invests the human hand with the character of a special organ of touch. A certain, though low degree of vital contractility, seems also to belong to the skin. —QUAIN. Of the other parts sensible to Touch, besides the skin, namely, the tongue and mouth, the needful description has been already furnished under the sense of Taste. The nerves of touch are the sensory or posterior roots of the spinal nerves for the limbs and trunk, and certain of the cerebral nerves (the fifth pair) for the head, face, mouth, and tongue.* 5. The action in touch is known to be simple pressure. The contact of an object compresses the skin, and through it the embedded nerve filaments. That the squeezing or pinch- ing of a nerve can produce sensibility is proved in many experiments : in touch, the squeezing is of a more gentle nature, owing to the protection that the covering of skin gives to the nerves. ‘he only point of interest connected with the mode of action is the singular fact, that very light contacts often produce a great sensibility, as the touch of a feather or of a loose hanging piece of dress, which sensibility is diminished by making the contact more intense. Great pressures yield comparatively little. sensation in the skin ; they are felt mainly in the muscles as a feeling of force and resistance. This fact of the disproportion of the feeling to the pressure I can account for in no other way than by supposing, that ereat compression has an effect in deadening the conducting property of the nerve. We know from various observations that the compression of a nerve does tend to arrest its con- ductibility ; the deadening of the sensibility of the hand by leaning the elbow on a table, so as to squeeze the nerve that * It is supposed that the important nerves of touch in the extremities have a different course in the brain from the nerves of the trunk. Tiirk has shown that in the hand and foot the same spot is supplied from different roots in the spinal cord. SENSATIONS OF SOFT TOUCH. 167 passes near the surface on the elbow joint, is a familiar instance. 6. We come now to the sensations, or feelings of touch, which are various in kind, and have many of them a con- siderable degree of interest, from their bearing on the higher operations of mind. In the order of enumeration, I shall commence as usual (I.) with those having reference to pleasure or pain, or that may be called predominantly emotional. Sensations of Soft Touch—lIn this class of feelings, we suppose the gentle contact of some extended surface with the skin. I keep out of view the feeling of temperature. A good example is furnished by the contact of the under clothing with the general surface of the body, which is most perfect under the bed-clothes at night. The glove not too tight on the hand is another instance. The extended hand, resting on a cushion, or other soft body, is a sufficiently good type of the situation. The resulting sensation is of the pleasurable kind, not acute, but massive. It closely resembles agreeable warmth. It is less powerful, but probably more retainable in idea, than the muscular or the digestive sensibilities. Its rela- tionship tc the tender emotion is elsewhere discussed. (THE EMOTIONS AND THE WILL, Tender Emotion.) The habitual inattention to the sensibility of the clothing is a striking example of the law of Relativity. The remis- sion of the contact is felt, on the same principle, as a sensa- tion of blankness. In the feelings of the lachrymal, mammary, and sexual organs, the mode of action appears to be something more than simple contact ; the quality of the touching substance affects the sensation. In the tranquil flow of the lachrymal fluid, under genial tender emotion, there is a certain amount of agreeable sensation in the eye; but when the eyes are flooded in profuse grief, the contact of the liquid with the eye-lids is scarcely pleasurable. There is probably, if not a chemical, at least a dialytical action on the sensitive surfaces, in those instances. 168 SENSE OF TOUCH. The mutual contact of living animal bodies yields a com- plex sensation of softness and warmth, and excites the corresponding emotions. There may be, in addition, magnetic or electric influences of a genial kind, but the reality of such currents is by no means established. The attraction between the mother and offspring is partly grounded upon the pleasure of the soft warm contact. This keeps the new-born animal by the mother’s side, before it has come under the farther gratification of being fed and nourished ; and continues to co-operate with that still more powerful motive to close proximity. Ata later period, the contact of the opposite sexes, stimulated, in the first instance, by the pleasure of mere touch, discloses and inspires in each the sexual urgencies, and the tentatives for gratifying them. Many of the habitual attitudes and modes of outward expression are regulated by the pleasure of soft touch. The child puts its finger or hand to its mouth, either for the mere pleasure of the act, or as a comforting sensation in distress ; and all through life the contact of the hand with the parts of the face is practised from the same motives. Many other attitudes and actions are governed by the pleasures of touch ; some, as scratching the head, are apparently the search for pungency. 7. Pungent and painful Sensations of Touch—When, instead of a diffusive soft contact, we have an intense action on limited spots, mere points, as in the stroke of a whip, a sensation of smartness is produced very different from the above. In moderate degree, this gives a pleasurable pun- gency, beyond which it is acutely painful. The nerves are shocked as by the prick of an instrument, and the over- intensity and suddenness of the stimulus is a cause of pain. The nature of the sensation is not radically different from a cut in the skin; its peculiar smartness excites the whole system. It prompts the most decisive actions for avoiding the pain, and an intense mental aversion to all that relates to it. The intensity gives to it a hold on the memory not possessed by the luxurious feeling of diffused softness. | PAINFUL SENSATIONS OF TOUCH. 169 Hence the efficacy of skin inflictions in the discipline of sensitive beings. Other things being the same, the sensibility of the skin to these two classes of feelings is greatest in parts most richly supplied with nerves, and where the discriminative or tactile sensibility is greatest, as in the tongue, the lips, and the palm of the hand. 8. Other painful Sensations of the Skin—Among these I would first advert to the sensation of tickling. On this Weber remarks, that the lips, the walls of the nasal openings, and the face generally, when touched with a feather, give the peculiar sensation of tickling, which continues till the part is rubbed by the hand. In the nose, the irritation leads at last to sneezing. The excitation extends to the ducts of the glands, which pour out their contents, and increase the irritation. The violent commotion produced by bodies in contact with the eye, is of the nature of tickling, accompanied by a flow from the glands, and readily passing into pain. Why some places are liable to this sensation, and others not, it is difficult to explain. The possession of delicate tactual discrimination is not necessary to the effect. The singularity of tickling is the fact that a very trifling sensation prompts to extraordinary efforts of the will for deliverance. The tickling of the arm-pit, or the soles of a susceptible person, is as violently repudiated as the touch of a scalding surface. | There is one consideration that may help to account for the anomaly. It is the nature of tickling to stimulate intense reflex movements ; these are, on their own account, a source of massive discomfort and repugnance. ‘The same tactile feeling, if unaccompanied with reflex stimulation, might be wholly indifferent. This remark may apply to the tickling that precedes laughing and sneezing. The irritation of the fauces brings about, in the first instance, reflex contractions of the muscles of the throat; these are more or less acutely painful ; thereupon, we give way to the farther impulse to spasmodic expiration. 170 SENSE OF TOUCII. Possibly the same explanation may be extended to the chafing and fretting of the skin, when too slight to be painful as a pungent smart. A reflex stimulus is applied when the nervous system is irritable, and when forced muscular move- ments would be painful and repugnant. It is not the sensa- tion by itself that we dread, but the wakening up of activity when we are courting repose and quiescence. All the parts of the skin are liable to yield painful sensations, especially under injury or distemper. ‘The epidermis is itself insensible, but the true skin is extremely alive to feeling. When lacerated, chafed, or burnt, it causes acute pains. Its capillary vessels and numerous sweat glands and oil glands are, in all probability, the source of pleasurable or painful organic sensations. ‘The long continued compres- sion of the same part of the skin creates uneasiness. The hairs are themselves insensible, but by their attachment to the skin they are the media of sensation. The place of attachment of the nails is the seat of a violent form of acute pain, which has a facility of seizing on the imagination, and of exciting revulsion even in idea. Clanminess is a distinct sensation arising from the ad- hesion of a substance to the skin, and is an uneasy feeling, the uneasiness being due to some anterrupbion of the natural functions of the part. 9. (IL.) Sensations of Temperature—The feelings of heat and cold are most powerfully felt in the skin ; the sensitive- ness also extending to the gullet, the stomach, and the rectum. There is no reason for supposing that any other nerves than those of touch are needed to a rouse a sensation of warmth or of coolness. As to the mode of action, heat being a state of molecular motion will impart molecular disturbance to the nerves, and thus operate as a stimulant, favourably or un- favourably according to the circumstances.* * Sir William Hamilton thinks it probable that the sensation of heat depends on a peculiar set of nerves, for two reasons: ‘1st, Because certain sentient parts of the body are insensible to this feeling ; and, 2nd, Because I have met with cases recorded, in which, while sensibility in general was DISCRIMINATION OF TEMPERATURE. 171 The sensation of wetness seems to be nothing else than a form of cold. As regards the discrimination of degrees of Temperature, it appears that we are equally sensitive at high and at low points of the thermometer. According to Weber, we can discriminate 14° Reaumur from 14.4°, as well as 30° from 30.4° ; and the discrimination is all the better by the change being rapidly made. It is also better when the unequal temperatures are applied at the same time to contiguous parts, than when the parts touched are remote from each other. The sensitiveness of different parts to temperature is not solely dependent on the abundance of nerves supplied to the part ; some other circumstance at present unknown is in operation. Weber’s graduated scale for heat is as follows :— tip of the tongue, eyelids, lips, neck, trunk. In the face, breast, and abdomen, the central parts are less sensitive than the sides. The sensitiveness is increased by extent of surface. In an experiment with dipping the finger into water at 32° R,, and the whole hand in 294°, the latter appeared the warmer of the two. It is remarked that when one part of the body touches another, the temperature being the same, the part endowed with the finer tactile power feels the other. If the tempera- abolished, the sensibility to heat remained apparently undiminished.’—Rerp, p. 875. On the other hand, the experiments of Weber, while leading to the con- clusion that the integrity of the skin is necessary to the discrimination of degrees of temperature by touch, give no ground for supposing that any other nerve fibres than those of common tactile sensation are necessary.— CARPENTER’S Human Physiology, 4th edition, § 866. Brown-Séquard is, however, of opinion that, in the spinal cord, the channel for conducting impressions of temperature is different from that for tactile impressions. It may be remarked that the discriminative sensibility of the skin, shown in the feeling of plurality of impressions, implies an internal or central organization for receiving, independently, the stimuli of the different parts. Now, an internal derangement might vitiate this independent conveyance of impressions without destroying the sensibility of the fibres to the impulses of heat, or cold, or other strong irritation. It has been stated that when the thalami optici are injured, tactile sensation is lost, but not the sensibility to pain. 172 SENSE OF TOUCH. tures are different, the first feels the second tactually, while the second feels the temperature of the first. The hand is not felt tactually by the brow, nor is the coldness of the brow felt by the hand. It is a singular fact, discovered by Weber, in connexion . with the sense of temperature, that when two substances of the same weight, but of different temperatures, are estimated by the sense of touch or of pressure, the colder appears the heavier. ‘The depressing effect of the cold chill upon the mind may be the explanation. This is somewhat analogous to the perversion of our estimate of time by an unusual elation or depression of the general mental tone: in the one case we imagine it to pass rapidly, in the other slowly. The feeling of temperature is an element in many discrim- inations, as in the distinction between stone and wood. We pass now (IIL) to the most intellectual sensations of Touch, and first to cases of Touch simply. 10. (1.) Impressions of distingushable Points ——I have al- ready called attention to the discriminative or articulate charac- ter of the sense of touch, whereby it receives distinguishable impressions from the variously situated parts of an extended surface. Very interesting differences in the degree of this discrimination are observable on different parts of the surface of the body, which have been especially illustrated by the experiments of Weber. ‘These consisted in placing the two points of a pair of compasses, blunted with sealing wax, at different distances asunder, and in various directions, upon different parts of the skin of an individual. It was then found, that the smallest distance at which the contact can be distinguished to be double, varies in different parts between the thirty-sixth of an inch and three inches ; and this seems a happy criterion of the acuteness of the sense. We recognize a double im- pression on very sensible parts of the skin, though the points are very near each other; while, in parts of less acute sensi- bility, the impression is of a single point, although they may be, in reality, far asunder. DISTINGUISHABLE POINTS. 173 ‘In many parts we perceive the distance and situation of two points more distinctly when placed transversely, than when placed longitudinally, and vice versd. For example, in the middle of the arm or fore-arm, points are separately felt at a distance of two inches, if placed crosswise ; but scarcely so at the distance of three, if directed lengthwise to the limb. ‘Two points, at a fixed distance apart, feel as if more widely separated when placed on a very sensitive part, than when touching a surface of blunter sensibility. This may be easily shown by drawing them over regions differently en- dowed ; they will seem to open as they approach the parts acutely sensible, and vice versa. ‘If contact be more forcibly made by one of the points than by the other, the feebler ceases to be distinguished ; the stronger impression having a tendency to obscure the weaker, in proportion to its excess of intensity. ‘Two points, at a fixed distance, are distinguished more clearly when brought into contact with surfaces varying in structure and use, than when applied to the same surface, as, for example, on the internal and external surface of the lips, or the front and back of the finger. ‘Of the extremities, the least sensitive parts are the middle regions of the chief segments, as in the middle of the arm, fore-arm, thigh, and leg. The convexities of the joints are more sensible than the concavities. ‘The hand and foot greatly excel the arm and leg, and the hand the foot. The palms and soles respectively excel the opposite surfaces, which last are even surpassed by the lower parts of the fore-arm and leg. On the palmar aspect of the hand, the acuteness of the sense corresponds very accurately with the development of the rows of papille; and where these papille are almost wanting, as opposite the flexions of the joints, it is feeble. ‘The scalp has a blunter sensibility than any other part of the head, and the neck does not even equal the scalp. The skin of the face is more and more sensible as we 174 SENSE OF TOUCH. approach the middle line; and the tip of the nose and red parts of the lips are acutely so, and only inferior to the tip of the tongue. This last, in a space of a few square lines (a line is +4; of an inch), exceeds the most sensitive parts of the fingers; and points of contact with it may be gene- rally perceived distinctly from one another, when only one- third of a line intervenes between them. [The superior sensibility of the tip of the tongue to the finger, is illus- trated by the familiar observation, that a hole in a tooth seems very much exaggerated when felt by the tip of the tongue.| As we recede from the tip along the back or sides of the tongue, we find the sense of touch much duller. ‘The sensibility of the surface of the trunk is inferior to that of the extremities or head. The flanks and nipples, which are so sensitive to tickling, are comparatively blunt in regard to the appreciation of the distance between points of contact. Points placed on opposite sides of the middle line, either before or behind, are better distinguished than when both are on the same side. ‘The above are the results obtained by making the several parts mere passive and motionless recipients of impressions. They evince the precision of the sense in so far only as it depends on the organization of the tactile surface. The augmented power derived from change of position of the object with regard to the surface, is well illustrated by keeping the hand passive, while the object is made to move rapidly over it. In this case the contact of the two points is separately perceived, when so close that they would, if stationary, seem as one. If, still further, the fingers be made to freely traverse the surface of an object, under the guidance of the mind, the appreciation of contact will be far more exquisite, in proportion to the variety of the movements, and the attention given to them. We are then said to feel, or to examine by the sense of touch. —Topp and Bowman, L., 429-30. These observations of Weber have been deservedly cele- brated by physiologists, as the foundation of an accurate WEBER'S EXPERIMENTS, 175 mode of estimating the tactile sensibility of the skin. They have been extended by other observers, as may be seen in Dr. Carpenter’s article on Touch in the Cyclopedia of Anatomy* It is necessary, however, for us to discuss more closely the matters involved in them, and especially to discriminate the tactile from the muscular element of the sensations. Whenever two points produce a double sensation, we may imagine that one point lies on the area supplied by one dis- tinct nerve, while the other point lies on the area of a second nerve. There is a certain stage of subdivision or branching of the nerves of touch, beyond which the impressions are fused into one on reaching the cerebrum. How many ultimate nerve fibres are contained in each unit nerve, we cannot pretend to guess; but on the skin of the back, the middle of * The following are a selection from Weber’s measurements. The intervals are expressed in lines, a line being the twelfth part of an inch. The range according to Weber is from the twenty-fourth of an inch, in the tip of the tongue, to two and a-half inches. The range stated in the text is somewhat greater, being founded probably on a comparison of the extreme observations of different observers :— Tip of the tongue, .. = be, oe a { Mk e Faia Tip of the forefinger, palmar surface, is 1 a Red surface of under lip, .. ae ‘ a gs 2 4 Second joint of the fingers, palmar murbioe! 2 2. Last joint of the fingers, back or dorsal surface, .. 3 + Tip of the nose, Ae he me de a 3 te Middle of the back of the nse) is rs me Be 4 pe End of the great toe, es ay aie in +< 5 = Palm of the hand, .. oe oe 5) 3 Cheek, over the buccinator, en ve ae ie 5 be Lower part of the forehead,.. Xe as oe ve 10 i Back of the hand, .. ne a - vs .- 14 a Crown of the head, .. as he ate ve emule . Thigh, by the knee, .. i ve ee eyied ae ‘ Upper and lower extremities of the jbee ot ee wep ko o Breast, ve oe - “s oe ee ca et ¢ Back of neck near occiput, .. - 24 ‘ Middle of fore-arm, middle of thigh, mdale of ‘the bok of the neck, middle of the back, be Set If the points are placed within the limit of ‘doubladee and Pedtally separated, the interval that gives doubleness is greater than in the reverse process. 176 SENSE OF TOUCH. the thigh, and the middle of the -fore-arm, an area of three inches diameter, or between six and seven square inches, is supplied by the filaments of a single unit. On the point of the finger, the units are so multiplied, that each supplies no more than a space whose diameter is the tenth of an inch. Such units would correspond to the entire body of the olfac- tory or gustatory nerve, for these nerves gives but one undi- vided impression for the whole area affected; or at most would give two impressions, one for each side. It is important to observe that the primitive suscepti- bility to a plurality of distinct points, does not enable us to judge what the real distance of the points is; nor can we tell previous to experience whereabouts on the body the im- pression is made. Hence in those of the experiments that relate to our sense of the relative interval of the points, as when they pass from a duller to a more sensitive region, there are involved perceptions that we have got at in some other way than through the sense of contact. This other means is the feeling of movement or the muscular sensibility, without which it is impossible to comprehend fully the sen- sations of Touch. 11. (2.) Sensations of Pressure—When a contact passes from the soft touch to a certain amount of energy of com- pression, the character of the sensation is entirely changed. It becomes indifferent as regards pleasure and pain, unless the pressure is on the verge of injuring the parts, when it becomes painful. The nerves of touch are of course affected, but probably not they alone. The compression may extend its influence to the nerves in the deep seated parts, that is, to fibres supplied to muscles, &c. If the compressed limb is unsupported, its muscles re-act and give the feeling of resistance. If it is supported, as when the hand lies on the table, the effect is one of pressure solely, whether the nerves stimulated are those of the skin alone or of the skin and the interior tissues combined. ‘The sense of pressure is found to have a certain power of discrimination, applicable to determine degrees of weight, hardness, elasticity, PRESSURE, LV7 and other properties. The most sensitive parts, as the tips of the fingers, can distinguish 20 oz. from 19:2 oz.; the forearm distinguishes 20 oz. from 18°7 oz. The interval of time affects the discrimination, as we might suppose. The difference between 14, or even 14°5, could be distinguished from 15, within 30 seconds ; 4 and o could be distinguished within 90 seconds. The discrimination of pressure does not increase propor- tionably with the supply of tactile nerves. 12. (IV.) Sensations of Touch involving muscular percep- tcons.—In discussing these, we shall begin with examples that are almost purely muscular, the tactile sensibility being a mere incident of the situation. The feeling of weight is of this description ; depending on the sense of muscular exertion, although capable also of being estimated to some extent by the feeling of compression of the skin. On this last point, I add some further illustrations from Messrs. Todd and Bowman. ‘Weber performed experiments to ascertain how far we are capable of judging of weight by the mere sense of contact [without muscularity]. He found that when two equal weights, every way similar, are placed on corresponding parts of the skin, we may add to, or subtract from one of them a certain quantity without the person being able to appreciate the change; and that when the parts bearing the weights, as the hands, are inactively resting upon a table, a much greater alteration may be made in the relative amount of the weights without his perceiving it, than when the same parts are allowed free motion. For example, 32 ounces may thus be altered by from 8 to 12, when the hand is motionless and supported ; but only by from 14 to 4, when the muscles are in action ; and this difference is in spite of the greater surface affected (by the counter pressure against the support) in the former than in the latter case. Weber infers that the measure of weight by the mere touch of the skin is more than doubled by the play of the muscles. We. believe this estimate to be rather under than over the mark.’—p. 431. That the discriminating sensibility of the skin to degrees 12 178 SENSE OF TOUCH. of compression may operate in appreciating weight is further confirmed by the following statement. ‘The relative power of different parts to estimate weight corresponds very nearly with their relative capacities of touch. Weber discovered that the lips are better estimators of weight than any other part, as we might have anticipated by their delicate sense of touch and their extreme mobility. The fingers and toes are also very delicate instruments of this description. The palms and soles possess this power in a very remarkable degree, especially over the heads of the metacarpal and metatarsal bones ; while the back, occiput, thorax, abdomen, shoulders, arms, and legs, have very little capacity of esti- mating weight.’—2. p. 432. What is said of weight apples to any other form of pres- sure, force, or resistance. The impetus of a push or a squeeze received on the hand is measured by the muscular exertion induced to meet it, and in some small degree, as above described, by the compression of the skin and other parts at the place of contact. It must not be supposed that we could derive our original feeling of RESISTANCE, with its reference to the object world, by mere tactile sensibility through pressure. The sense of resistance is primarily ‘the feeling of expended energy. When the notion is once formed, we can remark that the degrees of resistance coincide with degrees of the tactile sensibility to pressure; and hence the passive feeling can suggest the active, and become a criterion of its amount. The qualities of hardness and softness are appreciated by this combined sensibility ; the one means a greater resistance to compression, and the other a less. From the unyielding stone or metal to the mobility of the liquid state, we have all degrees of this property ; the entire class of soft, viscous, and fibrous substances lying between. It belongs to many of the manual arts to appreciate minute differences of consistence in the class of soft bodies; the pastry-cook, the builder, the sculptor, &c. In this they are assisted by practice, which improves all sensibilities: but there are great varieties of LS ROUGHNESS AND SMOOTHNESS. 179 natural endowment in the case, which varieties must have their seat principally in the muscular tissue, and only secon- darily in the skin and nerves of the hand. The feeling of elasticity is only a case of ‘simple resistance to force, exerted in the particular circumstance of a rebound or increasing reaction from pressure. The elasticity implies a perfect return to the original position ; air is elastic, and so is steel and ivory, meaning that when in any way compressed or distorted, they recover themselves. We may next consider the sensations rising out of the qualities of roughness and smoothness. Simple contact, we have seen, gives the sense of a multiplicity of points. The finger resting on the end of a brush would make us aware of its character; that is, we should have the feeling of a plurality of pricks. In this way, we are sensitive to rough and pointed surfaces. We can distinguish between bluntly- pointed asperities, like a file, and sharp points, like a horse- comb : the sensibility of a blunt point being distinct from a needle-prick. We can also distinguish between thick-set points and such as are more scattered, provided they are not too close for the limits of sensibility of the part, that is to say, one-twelfth of an inch for the finger, and one twenty- fourth to one-thirtieth for the tip of the tongue. On the back, the calf of the leg, and the middle of the fore-arm, where points are confounded up to the distance of two and a half to three inches, roughness would be altogether imperceptible. In these instances, the thing touched is supposed to lie at rest on the finger, or on the part touched. But this does not do full justice to the tactile sensibility ; we should move the finger to and fro over the surface, in order to try to the utmost the power of discrimination. We may thus discriminate far nicer shades of roughness ; we may appreciate minuter in- tervals than in the resting position. Supposing the sensibility of the tip of the finger at rest to be one line, by motion we can extend this sensibility to an unknown limit. The case may be illustrated by the micrometer screw on an astronomical instrument. The divisions on the limb of the instrument 180 SENSE OF TOUCH. extend, we may suppose, to one minute of a degree, and wf the index lie between two divisions, its place can be measured by the number of turns of the screw required to bring it up to one of the divisions. So, if a point is undistinguished on the finger, in consequence of not being a line removed from the neighbouring point, we may estimate ils distance, never- theless, by the amount of motion of the finger needed to bring it into the limit of sensibility. I will take as an example a row of five points, one-fortieth of an inch apart, the extremes being one-tenth, which is the sensibility of the tip of the finger. This row would be felt as two points if the finger were stationary. But by the motion of the finger one point would pass away and another would come up, and there would be a feeling of the interval moved over between the perception of the successive points, which would be a measure of the intervals. The sense of movement would thus be brought in to aid the tactile feeling, and to reveal a degree of closeness in asperities beyond the reach of touch unassisted by motion. It is consistent with all experience, that the roughness of a surface becomes far more apparent by drawing the hand over it. We must, however, farther consider that friction creates a new variety of pressure on the skin and nerves ; and the kind of friction is so different for a smooth and for a rough body, that by it alone we might learn to distinguish between the rough and the smooth contact. If any one will make the experiment of drawing over the finger two points, so close that to the touch they seem one when at rest, it will be found that the motion gives the feeling of doubleness. Whatis the limit of this (for a limit there is) it would take a considerable amount of observation to decide. I venture to affirm that at least half the interval will become sensible by the motion of the points, the motion being by bringing them in train, and not abreast of one another. Whatever may be the explanation of the increase of sensibility due to movement, the fact is an important one. A large amount of discrimination turns upon it. From the variety of trace made by different kinds of surface, we can TACTILE DELICACY. 181 distinguish them or identify them at pleasure, up to a con- siderable limit of delicacy. Hence the power of telling substances by the touch, and of deciding on the qualities and merits of texture and of workmanship. Degrees of polish in stone, metal, or wood, the fineness of cloths, wool, &c., the beat of a pulse, the quality of powdered substances, and many things besides, are matters of judgment and comparison to the touch, and put to the proof its natural or acquired delicacy. These tactile sensations whereby surfaces are discrimi- nated, have a great degree of persistence in the recollection ; something intermediate between tastes or smells, and sights. We do not revel in them as imagery, it is true, but this would be accounted for by the superior hold that we have of the very same objects by means of sight. With the blind, the case is different ; to them the outer world must be represented as outspread matters of contact ; their visions of the surfaces of all things are visions of touch. Our permanent impressions of touch serve us for com- paring present surfaces with remembered ones, and for identifying or distinguishing, the successive objects that come before the view. The cloth dealer sees whether a given specimen corresponds with another piece that passed through his hands a week ago, or with a permanent standard impressed upon his finger sensibility. 13. Qualities of Extension, Size, Form, &e.—I have endea- voured to show in the previous chapter, that these qualities are impressed upon us by the movements they cause, and that the feelings they produce are feelings of movement or muscularity. It is now to be seen how far the sense of Touch proper enters into our notions of the fundamental property of the object world, namely Extension, of which Distance, Direction, Position, and Form are only special modes or applications. When we examine closely the sensibilities obtained by movement alone, as by passing the arm to and fro in empty space, we find that these have various shortcomings as regards the idea of extended matter, or extended space. 182 SENSE OF TOUCH. In the first place, the absence of some definite marks, to indicate the commencement and the termination of a muscular sweep, leaves a certain vagueness in our feeling of mere movement. The feelings of putting forth power, and of this power taking the form of movement as distinct from dead strain, are present in all cases; but the mind is more alive to them when some definite impression marks where we begin and where we cease. Now, the sense of touch supplies this impression, and furnishes, as it were, a call to attention. Let us suppose the hand moving between two fixed obstacles, for example, from one side of a box to another. There is, to commence with, the contact with one side of the box felt more or less as a sense of touch, pressure, and resistance (a feeling partly muscular, but this need not be considered) ; the abrupt departure from this state is a mark in consciousness, a call to attention; and the mind is awakened to the feeling of movement that follows. After a time, the other side is struck, and the mind is again roused, and takes note of the cessation of the movement. The antithesis of resisting matter and unresisted movement is well brought out by such an experience; there is in it something more than the contrast of the swing of a limb with its undisturbed quiescence, which is all that movement in vacuo can give us. In the next place, when the hand is moved over a surface, touching it the while, the feeling of continuance of movement is accompanied by a feeling of continuance of tactile sensa- tion, making the consciousness more marked and acute, and so enabling us to estimate the degree of continuance more nicely. A feeling of the subject (touch proper) is superadded to the great object sensibility (expended energy as movement), and deepens the impress of that sensibility, without being able to take its place, or to constitute the feeling of objectivity. The peculiar tactile sensation that friction causes, is thus a means of suggesting extension and of estimating it, although incompetent to supply the notion itself. In the third place, movement im vacuo seems unable to (O-EXISTENCE AND SUCCESSION. 183 indicate that distinction between Succession and Co-existence —Time and Space—which must be arrived at before we can say that we recognize Extension. The continuance of move- ment is a fact that we are conscious of; in other words, we are conscious of a peculiar mode of the putting forth of energy which varies in degree, and we remark one movement as different from another on this point. But if any property of things is indicated by this, it would seem to be not space, but time. In truth, neither is known, for they are a corre- lative couple, not known at all till they are known together. Now, we are able to show, how the embodying of our movements in sensation enables us to distinguish between the two facts or properties, called the Co-existing and the Successive. When, with the hand, we grasp something moving, and move with it, we have a sensation of one unchanged contact and pressure, and the sensation is imbedded in a movement. This is one experience. When we move the hand over a fixed surface, we have, with the feelings of movement, a succession of feelings of touch ; if the surface is a variable one, the sensations are constantly changing, so that we can be under no mistake as to our passing through a series of tactile impressions. This is another experience, and differs from the first, not in the sense of power, but in the tactile accompaniment. The difference, however, is of vital im- portance. In the one case, we have an object moving, and measuring ¢¢me or continuance ; in the other case, we have co-existence in space. The co-existence is still farther made apparent by our reversing the movement, and thereby en- countering the tactile series in the inverse order. Moreover, the serial order is unchanged by the rapidity of our own movements. A more rapid pass of the hand makes the series come up quicker; a less rapid, brings the same series in more slowly. By these experiences, we gradually become aware of a wide distinction between identical movements conducted under such different circumstances ; and the dis- tinction is expressed in language, as succession and co- 184. SENSE OF TOUCH. existence—time and space. Succession is the simplest fact ; an unvarying contact accompanied with a movement, is enough for that. But co-existence is highly complex. The chief points involved in it are those now mentioned,—a series of contacts, and the inversion of the series by an inverted movement. The repetition of these, with the same mental effects, constitutes that notion of permanence, or of fixity of arrangements, implied in the object world, the universe as co-existing in Space.* By drawing the hand over a surface, as, for example, twelve inches of wire, we have an impression of the quality of the surface, and also of its length. On transferring the hand to another wire thirty-six inches long, the increased sweep necessary to reach the extremity, is the feeling and the measure of the increased extent. By practising the arm upon this last wire, we should at last have a fixed impression of the sweep necessary for a yard of length, so that we could say of any extended thing, whether it was within or beyond this standard. Nay more, whenever anything brought up a yard to our recollection, the material of the recollection would be an arm impression, just as the material of the recollection of greenness is a visual impression. If we pass from length to two dimensions, as, for example, the surface of a pane of glass, we have only a greater com- plexity of movement and of the corresponding impression. Moving in one direction we get the length ; in the cross direc- * Mr. Herbert Spencer has analyzed the relation of co-existence and sequence with great clearness and felicity. He remarks:—‘ It is the peculiarity alike of every tactual and visual series which enters into the genesis of these ideas, that not only does it admit of being transformed into a composite state, in which the successive positions become simultaneous positions, but it admits of being reversed. The chain of states of consciousness, A to Z, produced by the motion of a limb, or of something over the skin, or of the eye along the outline of an object, may with equal facility be gone through from Z to A. Unlike those states of consciousness constituting our perception of sequence, which do not admit of an unresisted change in their order, those which constitute our perception of co-existence admit of their order being inverted—occur as readily in one direction as the other.’—Principles of Psychology, p. 304. SOLID DIMENSIONS. 185 tion, we bring other muscles into play, and get an impression of movement on a different portion of the moving system. In this way we should have the impression of a right angele, or a builder’s square. The full impression of the pane of glass would arise through movements from side to side over its whole length, or from movements round the edge and several times across, such as to leave behind the feeling of a possibility of finding contact anywhere within certain limits of length and breadth. In this embodiment, and in no other that I know of, would an extended surface be conceived by the mind through muscularity and touch. (The action of vision will be afterwards discussed.) A cubical block, exemplifying all the three dimensions of solidity, presents nothing radically new. A new direction is given to the hand, and a new class of muscles are brought to contribute to the feeling. The movement must now be over the length, over the breadth, and over,the thickness, and the resulting impression will be a complication of the three move- ments. To get a hold of the entire solidity, it is necessary to embrace all the surfaces one after another, which makes the operation longer, and the notion more complex and more difficult to retain. But the resulting impression, fixed by being repeated, is of the same essential nature as the notion of a line or a superficies ; it is the possibility, the potentiality, of finding surface in three different directions within given limits. A cubical block of one foot in the side means that, commencing at an angle, and going along one edge, a foot range may be gone over before the material ceases ; that the same may then be done across, and also downwards ; and that, between every two edges, there is an extended resisting surface. The multiplying of points of contact, by our having a plurality of fingers, very much shortens the process of acquiring notions of surface and solidity. In fact, we can, by means of this plurality, come to measure a length without any movement; the degree of separation of the fingers, made sensible by the tension of their muscles, being enough. Sgt gece 186 SENSE OF TOUCH. Thus I can appreciate a distance of six or eight inches by stretching the thumb away from the fingers, as in the span of the hand. By keeping the fingers expanded in this way so as to embrace the breadth of an object, and then drawing the hand along the length, I can appreciate a surface by a single motion combined with this fixed span of the thumb and fingers. J may go even farther; by bringing the flexibility of the thumb into action, I can keep the fingers on one surface and move the thumb over another side, so as to have a single impression corresponding to solidity, or to three dimensions. We are, therefore, not confined to one form of acquiring the notion, or to one way of embodying it in the recollection ; we have many forms, which we come to know are equivalent and convertible, so that where we find one, we can expect another. But the most perfect combination of perceiving organs is the embrace of the two hands. The concurrence of the impressions flowing from the two sides of the body, produces a remarkably strong impression of the solidity of a solid object. The two separate, and yet coincid- ing, images support one another, and fuse together in such a way as make the most vivid notion of solidity that we are able to acquire by means of touch. The parallel case of the two eyes is equally striking. The notion of solidity thus acquired is complex, being obtained through a union of touch and muscularity, and combining perception of surface with perception of extended form. Space, or unoccupied extension, is movement in vacuo, from one fixed point to another; by the inverted operation, and by repetition giving the same contacts, this is considered to mean extension (as opposed to mere sequence in time). Empty space means the power of movement without contact or resistance, except at the extreme terms. Resistance and empty space are correlatives. In passing from the sense of the resisting to unresisted movement, we make the transition that developes the two cognitions of Body and of Space, under the common cbject property of Extension. 14, Distance, direction, and situation, when estimated thy DISTANCE.—DIRECTION.—SITUATION. 187 touch, involve, in the very same manner, the active organs ; the tactile sensations merely furnishing marks and starting- points, like the arrows between the chain-lengths in land- measuring. Dzstance implies two fixed points, which the touch can ascertain and identify ; the actual measurement is by means of the sweep of the hand, arm, or body, from the one to the other. Durection implies a standard of reference ; some given movement must fix a standard direction, and movement, to or from that, will ascertain any other. Our own body is the most natural starting point in counting direction ; from it we measure right and left, back and fore. For the up and down direction we have a very impressive lead, this being the direction of gravity. When we support a weight we are drawn downward ; when not sustaining the arms by voluntary effort, they sink downward ; when our support gives way, the whole body moves downward. Hence we soon gain an impression of the downward movement, and learn to recognize and distinguish this from all others. If a blind man is groping at a pillar, he identifies the direction it gives to his hand, as the falling or the rising direction. Circumstances do not, perhaps, so strongly conspire to impress the standard directions of right and left, but there is an abundant facility in acquiring them too. The right deltoid muscle is the one chiefly concerned in drawing the right arm up and away from the body, and without our knowing anything about this muscle, we yet come to asso- ciate the feeling of its contraction with a movement away from the body to the right. All directions that call forth the play of the same muscles, are similar directions as respects the body ; different muscles mean different directions. ‘The great pectoral bringing the arm forward, the deltoid lifting it away from the side, the trapezius drawing it backward, indicate to our mind so many different positions of the guiding object ; and we do not confound any one with the others. We learn to follow the lead of each of these indications; we make a forward step to succeed the contraction of the pectoral, a step to the right the deltoid, a step backward the trapezius. 188 SENSE OF TOUCH. Situation, or relative position, is known, if distance and direction are known. The idea of position implies three points. Two points might give extension, but relative position implies that we pass from A to B, from B to ©, and from A to C. Such movements often repeated, both in the direct and in the inverse order, impart the idea of permanent co-existence in relative position, which amounts to an expe- rience of Extension. The multiplication of these is the enlargement of our education in the co-existing and extended, from which at last, by an exercise of abstraction, we rise to the notion of Space or Extension in general. Form or shape is determined by position. It depends upon the course given to the movements in following the outline of a material body. Thus we acquire a movement corresponding to a straight line, to a ring, an oval, &c. This is purely muscular. The fixed impressions engrained upon the organs, in correspondence with these forms, have a higher interest than mere discrimination. We are called upon to reproduce them in many operations—in writing, drawing, modelling, &e.; and the facility of doing so will depend, in great part, upon the hold that they have taken upon the muscular and nervous mechanism. The suscepti- bility and the retentiveness of impressions necessary to draw or to engrave skilfully, are principally muscular endowments. 15. So much for the qualities revealed to us by touch, either alone or in conjunction with movement. The accom- paniment of activity belongs to every one of the senses; it serves to bring about, or increase, the contact with the objects of the sense. There is in connexion with each of the senses, a particular verb, or designation, implying action ; to taste implies the movement for bringing the substance upon the tongue; to smell, or to snuff, means an active inhalation of the odorous stream ; to feel signifies the move- ment of the hand or other organ over the surface in search of impressions ; in like manner, to hear and to see are forms of activity. In the cases of taste and smell, the action does not contribute much to the sensation or the knowledge; in the IMPROVEMENT OF TOUCH. 189 three others (two especially) it is a material element, since in all of them, direction and distance are essential parts of the information. Now, since movement is required to bring objects within reach, the value of any of our senses will depend very greatly upon the activity of the organs that carry the sensitive surface, the tentacula, so to speak. This activity grows out of the muscular and nervous energy of the frame, and not out of the particular endowment of the sensitive part. It is a voluntary exertion, at first spon- taneous purely, always spontaneous in some degree, but linked to, and guided by, the sensibility. The flush of activity lodged in the arm and fingers is the first inspiration towards obtaining impressions of touch; the liking or dis- liking for the impressions themselves, come in to modify and control the central energy, and to reduce handling to a system. 16. Touch being concerned in innumerable handicraft operations, the improvement of it, as a sense, enters largely into our useful acquisitions. The graduated application of the force of the hand has to be ruled by touch; as in the potter with his clay, the turner at his lathe, the polisher of stone, wood, or metal, the drawing of the stitch in sewing, baking, taking up measured quantities of material in the hand. In playing on finger instruments—the piano, guitar, organ, &¢c.—the touch must measure the stroke or pressure that will yield a given effect on the ear. 17. The observations made on persons born blind have furnished a means of judging how far touch can substitute sight, both in mechanical and in intellectual operations. These observations have shown, that there is nothing essential to the highest intellectual processes of science and thought, that may not be attained in the absence of sight. The integrity of the moving apparatus of the frame renders it possible to acquire the fundamental notions of space, magni- tude, figure, force, and movement, and through these to com- prehend the great leading facts of creation as taught in mathematical, mechanical, or physical science. 18. The skin is lable to feelings not produced by an 190 SENSE OF HEARING. external contact, but resembling what would arise from particular agencies, and suggesting those agencies to the mind. These are called ‘subjective sensations. The tingling of a limb asleep, formication—or a sensation as of the creeping of insects, heat, chilliness, &c., are examples.—(ToDD and Bow- MAN, I. 433.) SENSE OF HEARING. This sense is more special and local than the foregoing, but agrees with Touch in being a mechanical sense as dis- tinguished from the chemical senses—Taste and Smell. 1. The objects of hearing are material bodies in a state of tremor, or vibration, brought on when they are struck, which vibration is communicated to the air of the atmosphere, and is thereby propagated till it reach the hollow of the ear. All bodies whatever are liable to the state of sonorous vibration ; but they differ very much in the degree and kind of it. The metals are the most powerful sources of sounds, as we see in bells; after these come woods, stones, earthy bodies. A hard and elastic texture is the property needed. Liquids and gases sound very little, unless impinged by solids. The howling and rustling of the wind arise from its playing upon the earth’s surface, like the Atolian harp. The thunder is an example of a pure aerial sound ; the effect, great as it is, being very small in comparison to the mass of air put in agitation. It belongs to the science of Acoustics to explain the pro- duction and propagation of sound, and the forms of sounding instruments of all kinds. Here we are considering the effects, and not the instruments of sound. Even the human voice, whose description cannot be omitted in a treatise on mind, will come in under another head. 2. The organ is the Ear. ‘It is divisible into three parts —the external ear, the tympanum or middle ear, and the labyrinth or internal ear ; and of these, the two first are to be considered as accessories or appendages to the third, which is the sentient portion of the organ.’ THE TYMPANUM. 191 The external ear includes ‘the pinna—the part of the outer ear which projects from the side of the head—and the meatus or passage which leads thence to the tympanum, and is closed at its inner extremity by the membrane interposed between it and the middle ear (membrana tympani).’ ‘The tympanum, or drum, the middle chamber of the ear, is a narrow irregular cavity in the substance of the temporal bone, placed between the inner end of the external auditory canal and the labyrinth. It receives the atmospheric air from the pharynx through the Hustachian tube, and contains a chain of small bones, by means of which the vibrations, communicated at the bottom of the external meatus to the membrana tympani, are conveyed across the cavity to the internal ear, the sentient part of the organ. The tympanum contains likewise minute muscles and ligaments which belong to the bones referred to, as well as some nerves which end within this cavity, or only pass through it to other parts.’ As to the cavity of the tympanum, I shall content myself with quoting the description of the anterior and posterior boundaries, whereby it connects itself with the outer and inner portions of the ear, and which are therefore the main links in the line of communication from without inwards. The outer boundary, formed by a thin semi-transparent mem- brane, the membrana tympani, which may be seen by looking into the ear, ‘is nearly circular, and is slightly concave on the outer surface. It is inserted into a groove at the end of the passage of the outer ear, and so obliquely that the membrane inclines towards the anterior and lower part of the canal at an angle of 45°. The handle of one of the small bones of the tympanum, the malleus, descends between the middle and inner layers of the membrane to a little below its centre, and is firmly fixed to it; and as the direction of the handle of the bone is slightly inwards, the outer surface of the membrane is thereby rendered concave.’ The inner wall of the tympanum, which is formed by the outer surface of the internal ear, is very uneven, presenting several elevations and foramina. The foramina or openings are two in number, the oval foramen (fenestra ovalis) and the round or triangular opening (fenestra rotunda). Both are closed with membranes, which render the inner ear, with its containing liquid, 192 SENSE OF HEARING. perfectly tight. To one of them, the oval foramen, a small bone, is attached, the other, the round foramen, has no attachment. These two openings are the approaches to the internal ear, and through them les the course of the sonorous vibrations in their progress towards the auditory nerve. The small bones of the tympanum are named from their appearance as follows (beginning at the outermost): the malleus, or hammer, attached to the membrane of the tym- panum ; the incus, or anvil; and the stapes, or stirrup, which is fixed to the oval opening in the inner ear, called the fenestra ovalis. ‘The incus is thus intermediate between the other two, and the result of the whole is, ‘a species of angular and jointed connecting rod between the outer and inner walls of the tympanic cavity, which serves to communicate vibrations from the membrana tympani to the fluid contained in the vestibule of the internal ear.’ There are certain small muscles attached to those bones for the regulation of their movements. The internal ear, or labyrinth, ‘ which is the essential or sensory part of the organ of hearing, is contained in the petrous portion of the temporal bone. It is made up of two very different Fia. 7.* * ¢ An enlarged view of the labyrinth from the outer side:—1. Vestibule. 2. Fenestra ovalis. 3. Superior semicircular canal. 4. External semicircular canal. 5. Posterior semicircular canal. 6. First turn of the cochlea. 7. Second turn. 8. Apex of Cochlea. 9. Fenestra rotunda. * Ampulle of semicircular canal.—The smaller figure represents the osseous labyrinth of the natural size.’—(Quatn). LABYRINTH OF THE EAR. 193 structures, known respectively as the osseous and membranous labyrinth.’ ‘(1.) The osseous labyrinth is lodged in the cancellated struc- ture of the temporal bone, and presents, when separated from this,. the appearance shown in the enlarged figure. It is in- completely divided into three parts, named respectively the vestibule, the semicircular canals, and the cochlea. They are lined throughout by a thin serous membrane, which secretes a clear fluid. ‘(2.) The membranous labyrinth is contained within the bony labyrinth, and, being smaller than it, a space intervenes between the two, which is occupied with the clear fluid just referred to. This structure supports the numerous minute ramifications of the auditory nerve, and encloses a liquid secretion.’ The minute anatomy of these parts I must pass over. The vestibule is the central chamber of the mass, and is the portion of the labyrinth turned towards the tympanum, and containing the cavities of communication above described. The semicircular canals are three bony tubes, situated above and behind the vestibule, into which they open by five apertures ; each tube being bent so as to form the greater part of a circle. The cochlea is a blunt cone, having its surface ‘marked by a spiral groove, which gives to this part of the labyrinth somewhat of the appearance of.a spiral shell —whence its name. Its interior is a spiral canal divided into two by a thin partition, deficient at the apex of the cochlea. ‘The canal opens freely into the cavity of the vestibule. ‘Within the osseous labyrinth, and separated from its lining membrane by a liquid secretion, is a membranous structure, which serves to support the ultimate ramifications of the audi- tory nerve. In the vestibule and semicircular canals, this membrane has the form of a rather complex sac, and encloses a fluid called the endolymph ; in the cochlea, the analogous struc- ture merely completes the lamina spiralis (the partition of the cochlea), and is covered by the membrane which lines the general cavity of the osseous labyrinth.’ The labyrinth is thus to be considered as a complicated 13 194 SENSE OF HEARING. chamber full of liquid, and containing also a membranous expansion for the distribution of the nerve of hearing. Let us next advert to the action of these different parts in pro- ducing the sensations of sound. 3. The waves of sound enter the passage of the outer ear, and strike the membrane of the tympanum. The structure of the outer ear is adapted to collect and concentrate the vibrations like an ear-trumpet. The form of the shell gives it a reflecting surface for directing the sound inwards; while the passage is believed to increase their intensity by reson- ance. Reaching the membrane of the tympanum, the beats communicate themselves to its surface and set it vibrating, which is done all the more easily that the membrane is very thin and light in its structure. Experiments have shown, that the only means of receiving with effect the vibrations of the air, is to provide a thin stretched membrane of this nature. ‘The vibrations of the membrane are communicated to the chain of small bones traversing the middle ear, and connected through the oval foramen with the enclosed liquid of the inner ear. By these means a series of beats are imparted to the liquid, which diffuse themselves in waves all through the passages of the labyrinth, and operate by compressing the membranous labyrinth, and through it the imbedded fibres of the auditory nerve, which compres- sions are the immediate antecedent of the sensation of hearing. The character of the sensation will of course vary with the character of the waves, according as they are violent or feeble, quick or slow, simple or complex, and so forth. There is little difference of opinion as to the general course of the action now described. The transitions have all been imitated by experiments, and it has been found that the arrangement is a good one for bringing about the ultimate effect, namely, the gentle compression of the filaments of the nerve of hearing. No other medium could serve the final contact so well as a liquid, but in order to impress the liquid itself, an intermediate apparatus between it and the air is MUSCLES OF THE EAR. 195 requisite. This intermediate apparatus is solid, and com- posed of two parts, the first a light expanded membrane, susceptible to the beats of the air, the second firm and compact (the chain of bones), to produce a sufficiently powerful undulation in the liquid) The membrane once affected is able to communicate vibrations to the bones; and the last of the chain, the stapes, is able to impress the labyrinthine fluid. So far the process has been rendered sutticiently intelligible. The separate functions of the different parts of the inner ear are not understood. In the cochlea (the most important part), the membrane wherein the nerve is spread takes on peculiar tooth-shaped forms, and also contains elastic films or lamine. The length of each lamina is about 7$5 of an inch, and their thickness 73455 of an inch. The lamine lie upon the ends of the tooth-shaped forms, and are arranged like the keys of a piano, and closely packed together. Wundt believes that different tones affect different parts of the nerve of hearing thus disposed, and that as elastic bodies respond each to some particular tone, and remain quiet when other tones are sounded, so these elaastic laminz are divided into sroups for separate notes, and excite the connected nerve fibres accordingly. There are three muscles in the interior of the tympanum attached to the small bones. The largest, called tensor tympani, is inserted in the malleus, and its direction is such as to draw inwards, and tighten the membrane of the tym- panum. The second, laxator tympani, also inserted in the malleus, is supposed to have the action indicated by the name, but its muscular character has been doubted: the membrane of the tympanum would relax by mere elas- ticity, when the action of the tensor muscle is remitted. The third muscle is the stapedius, attached to the stapes, and seeming to govern the contact of that bone with the mem- brane of the oval foramen: the tensor tympani concurring with it to tighten the membrane. It has not been well ascertained on what occasions and 196 SENSE OF HEARING. with what effect the tensor tympani is brought into play. The only distinct observation on the matter is that made by Wollaston, namely, that when the membrane of the tym- panum is stretched, the ear is rendered less sensible to grave sounds, such as the deep notes of the organ, or the sounds of thunder and ¢annon. If, therefore, the ear is exposed to very intense sounds of the deep kind, such as the firing of artillery, the tensor tympani coming into play would in some measure deaden the effect. The action would make little or no difference to the hearing of acute sounds, such as the sharp notes of a call-whistle. Probably these muscles are excited by the reflex action of the sounds; possibly, also, they may be of the voluntary class, that is, they may come into play in the voluntary acts of listening and of preparing the ear to resist loud sounds. The only circumstance assign- able as determining the reflex action of the tensor tympani is simply the intensity of the sound. We may suppose that every sound whatever brings on a reflex action to stretch the membrane, and the stronger the sound the greater the action. When sounds are too loud, and of the grave kind, this tension mitigates them; when too loud and acute, it either has no effect, or makes the evil worse. ‘Dr. Wollaston performed many experiments upon the effects of tension of the membrana tympani, and he found that deafness to grave notes was always induced, which, as most ordinary sounds are of a low pitch, is tantamount to a general deafness. Shrill sounds, however, are best heard when the tympanic membrane is tense. Miiller remarks, and we have frequently made the same observation, that the dull rumbling sound of carriages passing over a bridge, or of the firing of cannon, or of the beating of drums at a distance, ceases to be heard immediately on the membrana tympani becoming tense; while the treading of horses upon stone pavement, the more shrill creaking of carriages, and the rattling of paper, may be distinctly heard’—Topp and Bowman, vol. II., p. 95. 4, Passing now to Sounds considered as sensations, we SWEET SOUNDS. 197 may distinguish these into three classes ; the first comprises the general effects of sound as determined by Quality, Intensity, and Volume or Quantity, to which all ears are sensitive. The second class includes Musical sounds, for which a susceptibility to Pitch is requisite. Lastly, there is the sensibility to the Articulateness, Distance, and Direction of sounds, which are the more intellectual pro- perties. 5. Sweetness—Under the head of Quality, the terms sweet, rich, mellow, are applied to the pleasing effects of simple sounds. Instruments and voices are distinguished by the sweetness of their individual tones; there is something in the material and mechanism of an instrument that gives a sweet and rich effect, apart altogether from the music of the airs performed upon it. Other instruments and sounds have a grating, harsh, unpleasant tone, like bitterness in taste, or a stink in the nostrils. Some substances, by their texture, have a greater sweetness of note than others. Thus silver is dis- tinguished among the metals; and glass is also remarkable for rich, mellow tones. The researches of Helmholtz and others seem to establish the fact that the differences of sounds as regards Sweetness (with its opposites), Timbre, and Vowel Quality, are owing to the combi- nation of the principal tone of each with a number of over-tones; which combinations are susceptible of great variety. So strong is the tendency of sounding bodies to yield these over-tones—a vibrating string nearly always vibrates in fractions as well as in its whole length—that pure tones, although experimentally pro- ducible, are scarcely known to us at all. Tones very nearly pure arise from wide-stopped organ pipes. The effect of these on the ear is mellow, but insipid; they are intermediate between the sweet and the harsh. According to this view, the sweetness, even of an individual sound, is a harmony; the ground tone is combined with over- tones in a pleasing concord. A harsh grating sound is a combi- nation of dissonant tones. Noise, as opposed to the sweet or the melodious, is dissonance. On this theoretical basis, the primary division of sounds would 198 SENSE OF HEARING. be into Simple sounds, Sweet combinations or concords, and Harsh combinations or discords. But as simple sounds are practically non-existent, we may still abide by the three-fold classification in the text, namely, (1.) Sweetness and Harshness, (2.) Intensity, and (3.) Volume. The second and third properties, Intensity and Volume, are important modifications of sound whatever be the degree of sweetness or of harshness; and they give a character to such as belong to neither extreme. The sensation of the sweet in sound I have characterized as the simple, pure, and proper pleasure of hearing ; a pleasure of great acuteness but of little massiveness. The acuteness of it is proportioned to the rank of the ear as a sensitive organ, or to the susceptibility of the mind to be stirred and moved through the channel of hearing. There is a great superiority in the endurableness of sweet sounds over the sweets of the inferior senses. In Touch the distinction exists in the comparison with Taste and Smell; in Hearing there is a farther progress, and we shall have to note the crowning pitch of this important property when we come to the sense of Sight. By virtue of this fact we can obtain from sight and hearing a larger amount of enjoyment within the same degree of fatigue or exhaustion, or before reaching the point of satiety. Hence one reason for terming these the ‘higher senses.’ The persistence in the intellect, which governs the ideal continuance and reproduction of the pleasures and pains of sound, is of the same high order, and probably grows out of the same fundamental superiority of the sense. The opposite of sweetness is described by the epithets harsh and grating, and is the characteristic pain of hearing, But in accounting for the extremely painful sounds, we must not confine ourselves to the fact of dissonance. 6. Intensity, Loudness—Sounds are more or less faint or loud. A gentle or moderate sound, neither sweet nor harsh, is agreeable in stillness, simply as a sensation, and under the conditions wherein stimulation, as such, is pleasurable. According as the loudness of a sound increases, so does the INTENSITY OF SOUNDS. 199 stimulation. The effect, at a given point, takes the character of pungency, like the action of ammonia on the nose, or a smart stroke on the skin. A loud speaker is exciting. The rattle of carriages, the jingle of an iron work, the noise of a cotton mill, the ringing of bells close to the ear, the discharge of musketry and ordnance, are all exciting from their in- tensity ; to fresh and vigorous nerves plunged into them after quietness, these noises give pleasure. ‘They may be described, however, as a coarse excitement; there is a great cost of tear and wear of nerve for the actual satisfaction. The intensity, rising beyond a certain pitch, turns to pain. The screeching of a parrot-house, the shrill barking of the smaller species of dogs, the whistling in the fingers practised by boys in the streets, the screaming of infants, are instances of painful pungency. The sharping of a saw, and the scratch- ing of a piece of glass, yield an intense shrill note. In most of these cases, we must suppose an element of dissonance as well as a great and smarting intensity. The only criterion of marked dissonance, as opposed to mere pungency, is the offence given to the ear under all conditions, and not merely under fatigue or exhaustion. The suddenness of sounds, by the abrupt transition, aggra- vates their intensity on the general principle of Relativity. If unexpected, they produce the discomposure usually attend- ing a breach of expectation. 7. Volume or Quantity—This means the sound coming from a sounding mass of great surface or extent. The waves of the ‘many sounding sea, the thundery discharge, the howling winds, are voluminous sounds. A sound echoed from many sides is voluminous. The shout of a great multi- tude is impressive fromthe volume. Grave sounds, inasmuch as they require a larger instrument, are comparatively volu- minous. Whether sounds be sweet or indifferent, their multipli- cation has an agreeable effect on the ear. The sensation is extended in volume or amount without the waste of nervous power accompanying great pungency. Both physically and 200 SENSE OF HEARING. mentally, these sounds conform to the laws of massive sensa- tion. If a sound is intrinsically harsh or grating, or if painful from intensity, the increase in volume will be an increase of pain; as in machinery. The braying of the ass combines the harsh and the voluminous. 8. Pitch or Tune—By pitch is meant the acuteness or graveness of a sound, as determined by the ear, and resolvable into the rate of vibration of the sounding body, or the number of vibrations in a given time. The gravest sound audible to the human ear is (according to Helmholtz) 16 vibrations a second; the highest audible sound corresponds to 38,000 vibrations a second; being a compass of eleven octaves. One of the deepest tones in use on orchestra instru- ments is the E of the double bass, giving 414 vibrations a second. The highest note of the orchestra (D of the piccolo flute) is 4752 vibrations. (Helmholtz: Tyndall’s Lectures on Sound, p. 72). The practical range is thus about seven octaves. At the upper limit of hearing, persons differ as much as two octaves; the squeak of the bat and the sound of a cricket are unheard by some ears. A sound of uniform pitth is a musical note. In the fact of uniform continuance, there is a pleasure of the nature of harmony. It is only such sounds that can be farther com- bined into musical harmonies. Although, in music, less intervals than a semitone are not admitted, the ear can distinguish still smaller differences. A quarter of a tone makes a marked difference to an ordinary ear. A good musician can distinguish two tones whose vibrations are as 1149 to 1145, sounded after each other, and even a smaller difference if they are sounded together. Two pitchforks whose number of vibrations per second are 1209 and 1210, sounded simultaneously, can be distinguished by a first-rate ear. 9. The waxing and waning of sound. The gradual in- crease or diminution of the loudness of a sound, is one of the effects introduced into musical composition, owing to the HARMONY AND DISCORD. 201 power it has to impart additional pleasure. The howling or moaning of the wind has sometimes this character, and pro- duces a deep impression upon all minds sensitive to sound. The dying away of sound is especially noted as touching: ‘that music hath a dying fall’ It may be, that a muscular feeling enters into this sensation: the gradually increased or relaxed tension of the muscles of the ear being a probable accompaniment of the increase or diminution of loudness. We cannot affirm, however, that it may not be due to the auditory nerves alone. When the pitch is gradually changed, as well as the degree, we have a farther modification intro- duced into musical composition, but apt to degenerate into the ‘whine’ or ‘sing-song. In the notes of birds, we may trace this effect; in the execution of accomplished singers, in the violin and other instruments, and in the cadences of a musical orator, we may likewise observe it; in all cases telling powerfully. 10. Harmony and Dzscord.—The concurrence of two or more sounds may be pleasing or unpleasing, irrespective of their character individually. The pleasurable concurrence is called Harmony. It is dependant upon the numerical relation- ship of the vibrations of the two sounds. Simple ratios, as 1 to 2 (octave), 2 to 3 (fifth), 3 to 4 (fourth), 4 to 5 (major third), 5 to 6 (minor third), are harmonious in the order stated. All these are admissible in musical composition, and are termed chords. The combination 8 to 9 (a single tone) is a dissonant combination ; 15 to 16 (a semi-tone) is a grating discord. It has already been mentioned that an individual sound whose character is sweetness, is already a harmony, or concord of many sounds; the main tone being combined with over- tones. In music, these sounds are still farther combined, according to the general laws of harmony. The pleasure of harmony is a wide-spread fact of the human mind; it extends to sight as well as to hearing, and is not wanting in the inferior senses ; we may have harmonizing or discordant tastes. In the higher emotions, a concurrence 202 SENSE OF HEARING. may be either harmonious or discordant. The foundation of the pleasure is probably the same throughout; it is a general principle whereby mental states are regarded as either co- operating, or conflicting, with each other; in the one case, economizing nervous power and bringing pleasure; in the other, wasting power and causing pain. 11. Timbre.-—This means the difference between sounds, otherwise the same, proceeding from different materials, instruments, or voices. We recognize a qualitative difference between the flute and the violin, or between the trumpet and the clarionet; we can distinguish between one violin and another, and between different voices sounding the same notes with the same intensity. These differences are now explained by the presence of auxiliary upper tones in all instruments ; which tones vary with the material and the instrument. It is supposed that perfectly pure tones identical as regards pitch and intensity, would be undistinguishable, whatever might be their source. 12. Articulate sounds.—Of articulate sounds, some have a character so peculiar that our discrimination of them is no surprise. ‘I'he hissing sound of s, the burring of the 7, the hum of the m, are well marked modes of producing variety of effect. We can understand how each should impart a different kind of shock to the nerve of hearing. So we can see a reason for distinguishing the abrupt sounds yg, ¢, & from the continuous or vocal sounds 0, d, and g, and from the same sounds with the nasal accompaniment m, », ng. It is not quite so easy to explain the distinction of shock between the labials, dentals, and gutturals ; still, if we compare p (labial), with & (guttural), we can suppose that the stroke that gives the & is harder than the other. The vowel sounds are explained by the over-tones (octaves) concurring with each fundamental tone, and varying according to the resonance of the mouth, the form of which is altered for each vowel. When the ground tone is heard nearly alone, the sound has the character of wu (full). Theo has, along with the ground tone, the next octave audibly combined. The a ARTICULATE SOUNDS. 203 (ah) is characterized by the marked presence of the very hich octaves.* The same principle is applied to explain differences in the consonant sounds; but as respects these, there are other palpable distinctions such as we have alluded to above. Some persons are distinguished by their nice discrimina- tion of articulate sounds. If the foregoing theory be correct, a good ear for musical notes should be also a good ear for articulation, seeing that the articulate sounds involve compo- site musical tones. An ear for pitch is thus the basis both of music and of speech. Strictly speaking, however, this applies to the vowels. The discrimination of consonants may depend on other qualities of the ear; a circumstance requiring to be adverted to, seeing that, in point of fact, the good musical ear is not always a good articulate ear. The sense of Time is not confined to any organ or any class of feelings ; but it may attain to great perfection in hearing. 13. The perception of distance can result from nothing but experience. I quote from Longet. ‘As soon as the organ presents a sensibility and a development sufficient for discerning easily the relative intensity of two consecutive sounds, nothing farther is necessary in order to acquire the notions of distance and direction of the body from which the sonorous waves emanate. In fact, if a sound is already known to us, as in the case of the human voice, or an instru- ment, we judge of its distance by the feebleness of its im- pression upon the nerve of hearing ; if the sound is one whose * The following is Helmholtz’s table for the leading vowel sounds :— Ground- Vowel. Tone. 2nd. 8rd. Ath. 5th. Gth. 7th. u (full) strong — weak — — = me o (oh) strong strong (weak) (weak) — — — e(get) strong middling strong (weak) (weak) — — i (bit) weaker strong (very weak) strong (middling) a(ah) strong (weak) weak middling stronger stronger stronger than 3 and 4, The parentheses denote that the tones they inclose are not absolutely neces- sary to the making of the special vowel-sound. 204 SENSE OF HEARING. intensity, at a given distance, is unknown, as, for example, thunder, we suppose it nearer according as it is louder.’ Weare apt to mix inferential processes with our judgment of distance. If we are led to imagine that a sound is farther off than it really is, we seem to hear it stronger than it is. Awaking suddenly in the night, we hear a faint noise, and suppose it much louder, our notion of its real distance being for a few moments vague and confused. It being an effect of distance that sounds fade away into a feeble hum, when we encounter a sound whose natural quality is feeble, like the humming of the bee, we are ready to imagine it more distant than the reality. 14. Direction—This is a purely intellectual sensation, in other words, is of importance as leading us to perceive the situation of the objects of the outer world whence the sound takes its rise. The following extract from Longet indicates the kind of experience that gives us the feeling of direction :— ‘With regard to the direction of the sonorous waves, we can at present only say, that the knowledge of it is owing to a process of reasoning applied to the sensation. Thus, we hear distinctly a sound emanating from a given point, what- ever be the position of the head; but the ear being able to judge of slight differences in the intensity of sounds, we remark that, in certain positions of the head, the sound seems stronger. We are hence led to place our head in one fixed position as regards the sounding body. But our sight tells what is this direction of most perfect hearing ; and we then apply the observation made on bodies that we can see to those that are not seen.’ The combined action of the two ears also favours the perception of direction of sound very materially. A person that has become deaf on one ear, is usually unable to say whether a sound is before or behind. The change of effect produced by a slight rotation of the head, is such as to indicate direction to the mind. For while the sound becomes more perceptible on one ear,—the ear turned to face the DIRECTION OF SOUNDS. 205 object more directly,—the sound in the other ear is to the same degree obscured. When the head is so placed, after various trials, that the greatest force of sensation is felt on the right ear, and the least on the left, we then infer that the sounding body is away to the right ; when the two effects are equal, and when any movement of the head makes them unequal, we judge the sound to be either right in front or behind ; and we can further discriminate so as to determine between these two suppositions.* The sense of direction is by no means very delicate, even after being educated to the full. We can readily judge whether a voice be before or behind, right or left, up or down ; but if we were to stand opposite to a row of persons, at a distance, say, of ten feet, we should not be able, I apprehend, to say which one emitted a sound. This confusion is well known to schoolmasters. So it is next to impossible to find out a skylark in the air from the sound of its song. 15. The duration of the feeling of an individual beat can be appreciated by noting at what intervals a succession of beats seems an uninterrupted stream of sound. This makes, in fact, the inferior limit of the audibility of sounds. From the experiments of Helmholtz, it would appear that a series of beats begins to be felt as continuous when they number * According to Ed. Weber, in determining the direction of sounds, we employ the external ear for those coming from above, below, behind, before ; the tympanum for those coming from left to right. He made the following experiments :—The head was inserted in water, the air-passage being filled with air, so that the tympanum was free to vibrate. In that case, the ear recognized the sounds as external to itself, but could distinguish them only as right or left in direction. When, farther, the ear itself was filled with water, and the free action of the tympanum arrested, the sense of externality alto- gether was lost. The feelings were regarded as subjective. It was observed by E. H. Weber that the uniting of the double sensation from the two ears (analogous to binocular vision) has its limits. If two watches with different rates of ticking are held before one ear, the ear distinguishes the periods when the strokes of the two fall.together, and forms to itself a rhythm out of the two series of strokes. If the watches are applied, one to each ear, the sense of rhythm is lost. The mind can no longer make the combination effected when the two watches are applied separately to the two ears. 206 SENSE OF SIGHT. sixteen in a second; so that the impression of each must continue not less than the sixteenth part of a second. 16. The sudjective sensations of the ear are such as buzzing, ticking, and humming sounds. They arise from disease of the brain, or the auditory nerve, obstructions in the tympanum and Eustachian tube, &c. SENSE OF SIGHT. 1. The objects of sight include nearly all material bodies. Their visibility depends on their being acted on by Light, hitherto the most inscrutable of natural agents. Certain bodies, as the Sun, the Stars, flame, solids at a high tempera- ture, give origin to rays of light, and are called self-luminous. Other bodies, as the Moon, the Planets, and the greater number of terrestrial surfaces, are visible only by reflecting the rays they receive from the self-luminous class. The reflexion of light is of two sorts: mirror reflexion, which merely reveals the body that the light comes from ; and reflexion of visibility, which pictures the reflecting surface. In this last mode of reflexion, the light is broken up and emitted in all directions exactly as from a self-luminous original. Visible surfaces receiving light from the sun have thus the power of absorbing and re-issuing it, while a mirror simply gives a new direction to the rays. When we look at a picture in a bad light, we find that the rays of reflexion overpower the rays arising from the coloured surface of the picture ; consequently the picture is imperfectly seen. As regards vision, bodies are either opaque or transparent, There is a scale of degrees from the most perfect opacity, as in a piece of clay, to the most perfect transparency, as in air. According as bodies become transparent, they cease to be visible. The transparency of Air is not absolutely perfect ; that is to say, light in passing through the atmosphere is to a certain small extent arrested, and a portion reflected, so as to make the mass faintly visible to the eye. When we look up into TRANSPARENT AND OPAQUE BODIES. 207 the sky through a cloudless atmosphere, all the illumination received beyond the sun’s disc is light reflected by the atmos- phere itself. Liquids are still less transparent ; although they transmit light so as to show objects beyond them, they also reflect a sufficient portion to be themselves visible. Light falling upon the surface of water is dealt with in three different ways. One portion passes through, a second is reflected as from a mirror, a third very small portion is absorbed and radiated anew, so as to make the surface visible as asurface. The same threefold action obtains in transparent solids, as glass, crystal, &e. It is to be remarked of solid bodies that they are almost all transparent to a certain small depth, as shown by holding up their plates or lamin to the light. Gold leaf, for example, permits the passage of light ; and any other metal, if similarly attenuated, would show the same effect. There is, however, in this case, an important difference to be noted, inasmuch as objects are not distinctly seen, although light is transmitted ; hence the name ‘ translu- cent’ is applied to the case to distinguish it from proper transparency. There may be something more than a differ- ence of degree between the two actions. Opaque bodies may diffuse much light or little: some substances, such as chalk and sea foam, emit a large body of light; charcoal is remarkable for absorbing without re-emission of the sun’s rays. This is the ordinary, perhaps not the full, explanation of white and black, the one implying a surface that emits a large portion of the rays of visibility, the other few or none. Besides the difference of action making white and black, and the intermediate shades of grey, there is a difference in the texture of surfaces, giving birth to what we recognize as Colour. Upon what peculiarity of surface the difference between, for example, red and blue, depends, we cannot at present explain. But this fact of colour is one among the many distinctions presented by the various materials of the globe. Along with colour, a substance may have more or less of the property that decides between white and black, namely, 208 SENSE OF SIGHT. copiousness of radiation. This makes richness of colour, as in the difference between new and faded colours, between turkey red and dull brick clay of a similar hue. Some bodies are farther said to possess Lustre. Mineral bodies present all varieties of light, colour, and lustre, but the prevailing tint of rocks and soils is some shade of grey. The reddish tint of clays and sandstones is chiefly due to the prevalence of oxide of iron. Vegetation yields the greenness of the leaf, and the variegated tints of the flower. Animal bodies present new and distinct varieties. 2. We come next to consider the organ of sight, the Eye. ‘ Besides the structures which compose the globe of the eye, and constitute it an optical instrument, there are certain external accessory parts, which protect that organ, and are intimately connected with the proper performance of its functions. These are known as the appendages of the eye (they have been named likewise ‘tutamina oculi’); and they include the eyebrows, the eyelids, the organ for secreting the sebaceous (or oily) matter, and the tears, together with the canals by which the latter fluid — is conveyed to the nose.’ ‘The eyebrows are arched ridges, surmounting on each side the upper border of the orbit, and forming a boundary between the forehead and the upper eyelid. They consist of thick integu- ment, studded with stiff, obliquely set hairs, under which lies some fat, with part of the two muscles named respectively the orbicular muscle of the eyelids and the corrugator of the eye- brows.’ By this last-named muscle the eyebrows are drawn together, and at the same time downwards, so as to give the frowning appearance of the eye; the opposite action of lifting and separating the eyebrows is performed by a muscle lying beneath the skin of the head termed the occipito-frontalis. In regulating the admission of light to the eye, and in the expres- sion of the passions, these two muscles are called into play; the one is stimulated in various forms of pain and displeasure, the other in an opposite class of feelings. ‘The eyelids are two thin moveable folds placed in front of each eye, and calculated to conceal it, or leave it exposed, as occasion may require. The upper lid is larger and more move- able than the lower, and has a muscle (levator palpebree superi- THE EYE. 209 oris) exclusively intended for its elevation. Descending below the middle of the eye, the upper lid covers the transparent part of the organ; and the eye is opened, or rather the lids are sepa- rated, by the elevation of the upper one under the influence of the muscle referred to. The eyelids are joined at the outer and inner angles of the eye; the interval between the angles varies in length in different persons, and, according to its extent, (the size of the globe being nearly the same,) gives the appearance of a larger or a smaller eye. At the outer angle, which is more acute than the inner, the lids are in close contact with the eye-ball; but at the inner angle, the caruncula lachrymalis (a small red conical body) intervenes. The free margins of the lids are straight, so that they leave between them, when approxi- mated, merely a transverse chink. The greater part of the edge is flattened, but towards the inner angle it is rounded off for a short space: and where the two differently formed parts join, there exists on each lid a slight conical elevation, the apex of which is pierced by the aperture of the corresponding eee duct.’—QUAIN. The lachrymal apparatus is constituted by the following assemblage of parts—viz., the gland, by which the tears are secreted at the outer side of the orbit; the two canals, into which the fluid is received near the inner angles; and the sac with the duct continued from it, through which the tears pass to the interior of the nose. The description of these parts need not be quoted in detail here. Suffice it to say that the tears are secreted by the lachrymal gland, and poured out from the eyelids upon the eyeball; the washings afterwards running into the lachrymal sac, and thence by the nose. The parts now dwelt upon are less concerned in vision, than in expression and other functions auxiliary to vision, Though not directly bearing on the object of the present section, they will be of importance when we come to consider the emotions and their outward display. From them we turn to the ball or globe of the eye. ‘The globe, or ball of the eye, is placed in the fore part of the orbital cavity, fixed principally by its connexion with the optic nerve behind, and the muscles with the eyelids in front, but capable of changing its position within certain limits. The 14 , 210 | SENSE OF SIGHT. recti and obliqui muscles closely surround the greater part of the eyeball; the lids, with the caruncle and its semilunar membrane, are in contact with it in front; and behind, it is supported by a quantity of loose fat. The form of the eyeball is irregularly spheroidal; and, when viewed in profile, is found to be composed of segments of two spheres, of which the anterior is the smaller and more prominent; hence the diameter taken from before Fig. 8.* * Horizontal section of the right eye, with two of the muscles,—the ex- ternal and internal recti,—and the optic nerve. a. Aqueous humour. 3. Crystalline lens. ¢. Vitreous humour. 1. Conjunctiva. 2. Sclerotica. 3. Cornea. 4. Choroid. 5. Canal of Fontana. 6. Ciliary processes. 7. Iris. 8. Retina. 9. Hyaloid membrane. 10. Zone of Zinn, or ciliary processes of the hyaloid. 11. Membrane of aqueous humour.—(WHARTON JONES 0” the Eye.) COATS OF THE EYE. ZiT backwards exceeds the transverse diameter by about a line. The segment of the larger sphere corresponds to the sclerotic coat, and the portion of the smaller sphere to the cornea.’ ‘Hxcept when certain muscles are in action, the axes of the eyes are nearly parallel; the optic nerves, on the contrary, diverge considerably from one another, and consequently each nerve enters the corresponding eye a little to the inner or nasal side of the axis of the globe. ‘The eyeball is composed of several investing membranes, concentrically arranged, and of certain fluid and solid parts contained within them. The membranes are three in number, an external fibrous covering named sclerotic and cornea, a middle vascular and pigmentary, in part also muscular, mem- brane, the choroid and the iris, and an internal nervous stratum, the retina. The enclosed light-refracting parts, also three in number, are the aqueous humour, the vitreous body, and the lens with its capsule.’ The conjwnctiwa is more an appendage of the eye than a portion of the globe. Itis a thin, transparent membrane covering only the front or visible portion of the ball, and reflected on it from the interior of the eyelids, of which it is the hning mucous membrane. Over the clear and bulging portion of the eye it is perfectly transparent, and adheres closely to the surface ; on the parts surrounding the clear portion it is less transparent, and contains a few straggling blood-vessels, which are seen as red streaks on the white of the eye. ‘The sclerotic, one of the most complete of the tunics of the eye, and that on which the maintenance of the form of the organ chiefly depends, is a strong, opaque, unyielding, fibrous structure, composed of bundles of strong white fibres, which interlace with one another in all directions. The membrane covers about five-sixths of the eyeball, leaving a large opening in front, which is occupied by the transparent cornea, and a smaller aperture behind for the entrance of the optic nerve. The sclerotic is thickest at the back part of the eye, and thinnest about ¢ of an inch from the cornea. At the junction with the cornea it is thickened. ‘The cornea is a transparent structure, occupying the aperture left in the fore part of the sclerotic, and forming about one-fifth of the surface of the globe of the eye.’ The two together com- JR Wy SENSE OF SIGHT. plete the encasement of the eye, and no other portion is employed for the mere purpose of maintaining the form and rigidity of the ball. Spread over the inner surface of the sclerotic, lie two other membranous expansions, likewise termed coats or tunics, but of totally different nature and properties. Next the sclerotic, is the choroid coat, which is a membrane of a black or deep brown colour, lining the whole of the chamber up to the union of the sclerotic with the cornea, and then extending inwards as a ring stretching across the eye. It also is pierced behind by the optic nerve. The choroid coat is an extremely vascular structure—that is to say, it is composed of a dense mass of blood vessels, which lie in two layers, the outermost of the two being the veins, and the other the arteries. Inside of those two vascular expansions, is the layer containing the black pigment that gives to the coat its colour, and which it is the object of the numerous blood vessels to keep supplied. The pigment is enclosed in the cells of a membrane, and these cells are packed very closely together, and are about the thousandth part of an inch in diameter. Hach cell has a transparent point in its centre, surrounded by a dark margin. The retina, or the nervous coat of the eye, is placed next the choroid, but does not reach so far forward. If a strong light is thrown upon it through the pupil of the eye, it appears of a reddish colour, which is owing to its blood vessels. When examined after death, it is pinkish and transparent. In the centre of the retina, and in the line of most perfect vision, is observed an elliptical yellow, or golden yellow, spot, about 31, of an inch long and +, wide, in the middle of which is a dark depression called by the discoverer, Scemmerring, the central hole. It is not a hole, but a thinner portion of the retina. About z; to =), of an inch from the inner or nasal side of the yellow spot, is a flattened circular papilla, corresponding with the place where the optic nerve pierces the choroid coat. The retina consists of several layers. Beginning at the inside, which is in contact with the vitreous humour, we find a transparent membrane called the limiting membrane, whose thickness does not exceed goby, of an inch. Next are the ramifications of the optic nerve, the fibres being arranged in fine THE RETINA, 213 meshes, and wanting the double outline. These fibres are exceedingly minute; the average diameter is not more than the s0.n00 OF aadoo Of an inch; while some are less than the too000 Of an inch in thickness. Within the fibrous layer, is a layer of nerve cells or vesicles resembling the vesicles that make up the grey substance of the brain. ‘These are most abundant in the hinder or central parts of the retina: they vary from the avo to the 755 of an inch in diameter. Then comes a still more complicated layer called the granular and fibrous layer, which constitutes the link of connexion between the retina and the choroid coat. It is made up of two distinguishable layers of little grains or nuclei, and a number of very fine filaments, with a direction perpendicular to the retina; at their outer connexion, these filaments are the gz,579 to the goz5 in diameter; at their inner connexion with the fibres of the optic nerve, they are from the g5455 to the zzg555 Of an inch in diameter. The inner of the two layers, making up the granular and fibrous layer, immediately adjoins the choroid, and is called the columnar or bacillar layer, being made up of closely-packed perpendicular rods transparené and colourless, about =,45, of an inch in length, and 55,359 Of an inch in thickness. Interspersed with these are larger rods called cones, 3355 of an inch in diameter.* Hach pigment cell of the choroid receives as many as six or eight of the cones, with a larger number of the smaller rods grouped round them. They are connected with the other parts of the retina by the fine perpendicular filaments. It is interesting to notice how those several elements are disposed in the yellow spot and its vicinity, where vision is most perfect. From the margin of the spot towards the central hole, the rods of the columnar layer, the nuclei resting upon them, and the fibres of the optic nerve, gradually diminish, and at last fade away. On the central hole, nothing is left but the larger rods, or cones, with the fine perpendicular fibres, and the vesicles, which are here closer than anywhere else, there being one for every cone, and the layer being 7 or 8 cells thick. Those elements that thus disappear in the central hole, are, however, * The above estimates of size are mostly taken from Koiliker, being transformed from millimetres by dividing by 24, (instead of 25 and a fraction), to keep to round numbers. 214 SENSE OF SIGHT. very abundant near the margin of the yellow spot. The smaller rods take the place of the cones, and the fibres of the optic nerve are very abundant and close. Thus, if we take the yellow spot together with its immediate surroundings, we find there the retina most highly developed ; and it is on this part that we can discriminate visible objects with the greatest delicacy. The unequal distribution of the different elements between the outer and inner parts of the yellow spot is remarkable.* Before pointing out the different bodies that make up the bulk of the eye, and enable it to act as an optic lens, I must call attention to several other substances of a membranous or fibrous character lying under the cornea and near the junction with the sclerotic coat. ‘The first of these is the ciliary ligament, a narrow circular band, of a greyish-white colour, close behind the junction above-named. The fore- most margin, the thicker of the two, gives attachment to the circular curtain called the iris. The thinner and posterior margin is blended with the choroid coat, which here prolongs itself inwards in a series of radiated folds called the cilary processes. ‘The ciliary processes lie behind the iris, and make a black, wrinkled, narrow rim, concealed from external view. * Mr. Herbert Spencer (Psychology, new edition, p. 35) indicates a class of structures, at the extremities of the nerves of sense, as multipliers of disturbances, or a8 serving to enhance the efficacy of the peripheral stimu- lation of the nerves. Thus in touch the short hairs render the skin more sensitive to contacts; while the so-called ‘little bodies of touch’ tend greatly to exaggerate the pressure upon the nerve fibres when the skin is compressed. In the ear, the otolites and minute rods and fibres, serve to transform the liquid vibrations into the more energetic vibrations of solids, so as to affect the nerve more powerfully. Finally, in the eye, the lenses concentrate the light upon the retina. The structures at the back of the eye are interpreted on the same prin- ciple of increasing the susceptibility to slight disturbance; the luminous waves being the feeblest of all known agencies. The fibres of the retina are reduced to the naked core; the protecting medullary sheath being absent. The light, passing through the transparent retina, affects the more sus- ceptible pigment cells of the choroid coat, whence the disturbance is con- veyed by the rods and perpendicular filaments to the nervous layer of the retina. Lastly, the nervous layer itself consists not only of fibres, but also of nerve vesicles or corpuscles, which are much more liable than the fibres to take on molecular disturbance, and originate molecular motions. THE IRIS. 215 ‘The wis may rightly be regarded as a process of the choroid; it is continuous with it, although of a modified structure. It forms a vertical curtain, stretched in the aqueous humour before the lens, and perforated for the transmission of light. It is attached all round at the junction of the sclerotic and the cornea, so near indeed to the latter that its anterior surface becomes continuous with the posterior elastic lamina.’ ‘The anterior surface of the iris has a brilliant lustre, and is marked by lines accurately described by Dr. Jacob, taking a more or less direct course towards the pupil. These lines are important as being indicative of a fibrous structure.’ When the pupil is contracted, these converging fibres are stretched ; when it is dilated, they are thrown more or less into zigzags. The pupil is nearly circular, and is situated rather to the inner side of the centre of the iris. By the movements of the iris, it is dilated or contracted, so as to admit more or less light to the interior; and its diameter under these circumstances may vary from about 35 to 3 of an inch.’— Topp and Bowmay, Vol. IL., p. 25. The iris is thus. to be considered as a muscular structure, its fibres being of the unstriped variety, or of the kind that prevails among the involuntary muscles, as the muscular fibres of the intestines. It is abundantly supplied with nerves. While the radiating fibres above described serve to dilate the pupil, a second class of fibres, arranged in circles round the opening, and best seen at the inner margin and behind, operate in contracting it. The action is regulated by the intensity of the light. In the dark, or in a very faint light, the dilating fibres are tense and contracted to the full, making the pupil very wide. The stimulus of light brings the circular or con- tracting fibres into play, and contracts the opening. The changes thus affected are useful in adapting the eye to different lights, admitting a larger quantity with a feeble light, and a smaller quantity with one that is too strong. When this reflex power of adaptation reaches its limit, and the brilliancy is still too great, We then put forth the voluntary efforts of closing the eye, or of turning the head away from the object. Behind the ciliary ligament, and covering the outside of the ciliary processes, is a greyish, semi-transparent structure, 216 SENSE OF SIGHT. known as the ciliary muscle. ‘It belongs to the unstriped variety of muscle, and its fibres appear to radiate backwards from the junction of the sclerotic and cornea, and to lose themselves on the outer surface of the ciliary body.. The muscular nature of this structure is confirmed by its anatomy in birds, where it is largely developed, as noticed by Sir P. Crampton.’—Topp and Bowman, IL, 27. A peculiar interest has come to attach to this muscle, from its supposed operation in adapting the eye to objects at different distances. Passing now from the coats of the eye to the substance, we find three humours, or transparent masses occupying it in the following order: in the front is the aqueous humour ; next, the erystalline lens ; and backmost the vitreous humour. The aqueous or watery humour is a clear, watery liquid lying under the cornea in front, and bounded behind by the crystalline lens and the folds of the ciliary processes. This humour is very nearly pure water, containing in solution a small quantity of common salt and albumen; and is enclosed in a membrane, which is in contact with the inner surface of the cornea, in front, and the ciliary processes and lens behind. The liquid is partly before and partly behind the iris. The vitreous or glassy humour lies behind the crystalline lens, and occupies the entire posterior chamber of the eye, being about two-thirds of the whole. It consists of a clear, thin fluid enclosed in a membrane, which membrane not merely surrounds it, but radiates inwards into its substance like the partitions of an orange, so as to make up a half-solid gelatinous body—the vitreous body, or posterior lens of the eye. These partitions are very numerous, and point to the axis of the eye, but do not reach to it; and consequently there is a central cylinder passing from front to back, composed only of the fluid of the body. The form of the vitreous body is convex behind, while before there is a deep cup- shaped depression for receiving the crystalline lens. The mem- brane that surrounds it on all sides, as well as entering into the interior, has a twofold connexion in front; it doubles so as to receive the crystalline lens between its folds, and it unites with the ciliary processes, which surround the lens without reaching MUSCLES OF THE EYE. 217 its border. Thus the partition, between the aqueous humour in front, and the vitreous humour behind, is made up of three Successive portions enclosing one another :—the wrinkled black ring of the ciliary processes outermost ; within this, a ring of the doubled membrane of the vitreous humour; and inmost of all, the crystalline lens, enclosed between the two folds of the mem- brane. The crystalline lens is a transparent solid lens, double convex in its form, but more rounded behind than before. It is sus- pended between the aqueous and vitreous humours in the manner already described. Its convexity before approaches very near the curtain of the iris stretched in front of it. The lens is enclosed in a capsule; and of this the front portion is thick, firm, and horny, while the portion on the back is thin and membraneous, adhering firmly to the membrane of the vitreous humour. The substance of the lens varies in its character; the outside is soft and gelatinous; beneath is a firmer layer; and in the cen- tre is the hardest part, called the nucleus. It is supplied with blood vessels in the edges, but none appear to penetrate within except in a very early stage of life. It undergoes altogether a great change during the development of the individual. In the foetus, it is nearly spherical, and not perfectly transparent ; in mature life, it is of the form and character described above ; while, in old age, it becomes flattened on both surfaces, loses its transparency, and increases in toughness and density. Of the six muscles of the eye, four are called recta or straight, and two oblique. The four recti muscles arise from the bony socket in which the eye is placed, around the opening where the optic nerve enters from the brain; they are all inserted in the anterior external surface of the eyeball, their attachments being respectively on the upper, under, outer, and inner edges of the sclerotic. The superior oblique or trochlear muscle arises close by the origin of the superior straight muscle, and passes forward to a loop of cartilage ; its tendon passes through the loop, and is reflected back, and inserted on the upper posterior surface of the eyeball. The inferior oblique muscle arises from the internal inferior angle of the fore part of the orbit, and is inserted into the internal “21S SENSE OF SIGHT. inferior surface of the eyeball, behind the middle of the ball. The motions of the eyeball that would be caused by the contractions of any of these muscles are not difficult to trace. The inferior muscle, by its contraction, will make the ball revolve so as to look downwards ; the superior straight muscle will make it look upwards. The internal and external recti will give it their respective directions, the one inward, the other outward. ‘The action of the trochlear muscle is peculiar. Inasmuch as it is reflected backwards to be inserted in the globe of the eye, it will turn the eyeball downwards and out- wards ; that is, the eye would, by its action, look obliquely downwards and outwards. ‘This muscle tends also to draw the ball of the eye a little forward, or to make it protrude. The inferior oblique muscle, having its origin in the fore part of the orbit, and its insertion in the inner side of the eyeball, will, by its contraction, also draw the eye forward, and turn it upwards and inwards, The external rectus is balanced by the internal rectus. The superior rectus is supported by the inferior oblique, in giving the eye its upward movement. ‘The inferior rectus is supported by the superior oblique, in imparting the downward movement of the eye. There is thus a greater expenditure of muscular tension in moving the eye up and down than in the lateral movements. It may be this that gives a greater impressiveness to the vertical dimension ; the upright line of an equal cross appears to the eye longer. All the movements of the eye could be performed by three recti muscles and one oblique; the two others are, strictly speaking, supernumerary, but still operate. This makes it uncertain which muscles actually perform any one movement. The presumption is that we employ such muscles as in each case perform the movement with the least expenditure of force. Very few movements could arise from a single muscle. The movements possible by two muscles are not very numerous. Meissner gives twelve directions from the primary position of the eye, which is assumed as directed in a line CONDITIONS OF VISION. 219 45° below the horizontal line. The eye, in passing from one part of the field to another, might be supposed to take the straight route. Wundt is of opinion that the straight route is preferred only in the horizontal and the vertical sweep. In other directions, the sweep is in a curve, which is greatest when the two points in the field of vision make an angle of 45° with the horizon. 3. Such being the mechanism of the eye, I must now touch briefly upon its mode of acting as the organ of sight. The optical part of the process is well enough understood. When the eye is directed to any object, an image of that object is depicted on the back of the eye, by means of the rays of light entering the pupil, and duly refracted by the different humours. The precise mode of stimulating the nervous filaments of the retina is not known; but the pigment cells of the choroid play an important part, being themselves highly absorbent of light; where they are not found, as at the place of entrance of the optic nerve, there is no power of vision (the blind spot). In order to perfect vision the following farther conditions are necessary :— (1.) A sufficiency of light or illumination in the object viewed. This is an obvious necessity. We judge of the quantity of light present by the power we have of seeing objects distinctly. Some animals can see with much less light than others, and to such the noonday sun must be painful. (2.) The formation of the image exactly on the retina, and not before or behind. The focus of the image must coincide with the retina. If this is not the case the image is indistinct; the rays of light either do not converge, or have begun to disperse, at the back of the eye. The perfect convergence of the image by the lenses constituting the ball of the eye, depends on the distance of the object, and also in some degree on the self-adjustment of the eye. ‘As this power of adaptation of the eye itself for vision, at different distances, has its limits, there is in every individual a distance at which he sees most distinctly, and at which the focus of the image, formed by the refracting media of the eye, corre- 220 SENSE OF SIGHT. sponds most accurately with the situation of the retina. This distance may be stated at from five to ten inches, in the majority of individuals. Objects which are too near the eye throw very indistinct images upon the retina; a slender body, such as a pin, held close to the eye, cannot be seen at all, or produces only an undefined impression on the retina. Few persons, on the other hand, are able to read print at a much greater distance than twenty inches.’ (3.) The third condition of perfect vision is the minute size of the subdivisions of the retina capable of independent sensation. We are sensitive to very minute lines and points ; and there is a limit of minuteness, where a number of distinct lines would seem as one. This is the limit of the optical subdivision of the retina, analogous to the intervals of double sensation in touch. It appears that minuteness of discrimination is aided by the following circumstances. 1. An intense light will enable a smaller object to be seen. 2. A white picture can be seen smaller than a blue. 3. A line can be seen better than a point of the same diameter. The smallest angle for a round body is 20”; a thread-like object is discernible under an angle of 3”; a glancing wire can impress the eye at an angle of #”. According to Weber and Volkmann, two bright lines must be separated at least from g@5q to go4yq Of an inch on the yellow spot to give a double sensation; which is an estimate quite compatible with the observed minuteness of the fibres and vesicles of the retina, supposing each of these capable of conveying an independent impression to the brain. The power of discrimination diminishes rapidly as the im- pression recedes from the yellow spot. Ata point 60° from the centre of the spot, an object must be 150 times larger, in order to be distinguished. Thus, although the eye can take in a wide field at once, the power of minute observation is confined to a very small part in the centre of the retina.* * Another condition of perfect vision has been suggested by the following experiments of Wundt :—If a small piece of red paper is held before the eye, and then moved to one side without the eye following it, so that the impres- MINUTE SENSIBILITY OF THE EYE. 221 The great superiority of the eye, as a medium for perceiv- ing the outer world, lies in this power of independent sensi- bility to minute points. I have already adverted tv the distinction between the lower and the higher senses in this particular. The nerve of vision must needs consist of a number of independent fibres maintaining their distinctness all the way to the brain, and capable of causing distinct waves of diffusion throughout the entire cerebral mass ; every one of these many thousand impressions varying the mental sion is made first in the yellow spot, and then on the lateral parts of the retina, the colour is variously seen. To the yellow spot, the paper is red ; as it moves sideways, it becomes darker; gradually, it assumes a blueish tint, and, at last, it appears perfectly black. Similar variations occur with any other colour, simple or mixed, and also with white, which unites all the colours. The last in the series is in all cases black. Whence it appears that different parts of the retina are differently sensitive to impressions of colour. The variation occurs in the same order in every direction, but with unequal rapidity. The series is passed through quicker, when the object is moved outwards, than when it is moved inwards; and also quicker for the upward than for the downward movement. It does not follow that in looking at a wide expanse of one colour, we see the gradations of tint in concentric rings. This is only one of many cases where the mind overbears the sense. We have contracted our notion of each surface from the way that its parts affect us when brought successively before the yellow spot—the place of minute examination—and what we seem to see is the habitual effect, rather than the effect at the instant. I shall afterwards allude to an important application of this fact, suggested to explain our power of. localizing the different impressions made on the retina. I may advert here also to the phenomena of colour-blindness, and to the suppositions that have been made to account for it. We have already mentioned a speculation, to the effect that the different parts of the ear may respond to different tones or notes. A similar assumption has been extended to the eye. It is considered not unlikely that there are different nerve fibres and endings for the different primary colours, which endings are unequally mixed over the surface of the retina. It may be supposed that at one place violet rods predominate, at another green; and that in the yellow spot the red endings are most abundant. Colour-blindness would then consist in the deficiency or absence of one set of endings. The most frequent form of this defect is obtuseness to the primary sensation of redness; all coloured bodies are then seen as composed of green and violet. The spectrum to such persons is comprehended as of a yellowish and a blueish tinge. What they call white, the ordinary eye sees to be coloured. Colour-blindness has been known to exist with reference to green, but, as yet, not to violet. O22 SENSE OF SIGHT. experience, and originating a distinct volition. We shall probably meet with no fact attesting more conspicuously the complexity, and yet the separateness of action, of the cerebral system. We can easily satisfy ourselves of the reason why the cerebral hemispheres should be necessary to vision, considering what is thus implied in every instance of seeing whatsoever. 4. On the Adaptation of the Eye to Vision at different Distances—If I see an object distinctly six inches distant from the eye, all objects at a greater distance are indistinct. The image of the near object falls correctly on the retina, the images of remote objects are formed in front of the retina. By a voluntary effort, I can adapt the eye to see a far-off object with tolerable clearness, but it then happens that any near body becomes confused. The questions arise—what is the change produced upon the eyeball, in the course of this adaptation from near to far, and from far to near, and what apparatus effects the change ? In seeing close at hand, the crystalline lens becomes thicker and more convex in front ; in seeing at a distance, the surface is flattened. The change of curvature is considerable. The centre-point bulges out zgth of an inch for near vision. A very slight increase takes place in the curvature of the hinder surface. The changes of curvature depend on the action of the ciliary muscle. This muscle contracts for near vision; the effect of the contraction is to draw the choroid membrane forwards, and by that means to compress the vitreous humour, which exerts a pressure on the lens, pushing it forwards. At the same time, the muscular fibres of the iris come into play, contracting the pupil and also the outer circumference. This brings a pressure to bear upon the lens from before, but not an equal pressure ; it is least at the centre and greatest to- wards the edges. Between these two pressures, from behind and before, the lens is bulged out in the middle, and its curvature increased. Thus, for near vision, there is a very considerable muscular action; when looking at anything BINOCULAR VISION. 223 close, we are conscious of a strain in the interior of the ball. For distant vision, this action is relaxed, and the natural elasticity of the parts restores the flattening of the lens. Hence the natural repose of the eye makes the adjustment for a distant prospect.* The eyeball is subject to alteration chiefly for near dis- tances. Between the smallest visible distance, say four inches, and three feet, nearly the whole range of the adjust- ment is gone through. When we compare distant objects of varying remoteness, as, for example, thirty feet with one hundred, or a thousand, very little change is effected on the form of the eyeball, the adjustment then depending on the greater or less convergence of the two eyes. This leads to the subject of double vision. 5. Of single Vision with two eyes. Binocular Vision— Among the questions Jong discussed in connexion with sight, was included the enquiry, why with two eyes do we see objects single? Answers more or less satisfactory were attempted to be given; but since the year 1838, an entirely new turn has been given to the discussion. In that year, Professor Wheatstone gave to the Royal Society his paper on Binocular Vision, wherein he described his ‘ stereoscope,’ or instrument for imitating and illustrating the action of the two eyes in producing single vision. The following quotation is from the opening paragraph :— ‘When an object is viewed at so great a distance that the optic axes of both eyes are sensibly parallel when directed to- wards it, the perspective projections of each, seen by each eye separately, are similar, and the appearance to the two eyes is * The limits of single vision are illustrated by the following experiment. If a thread is moved against a white wall, and we observe it with one eye through a tube, we can feel a difference when it is moved nearer, but not when it is moved farther away. This is consistent with the circumstances, that in changing to near vision, we cause a muscle to contract, while in changing to a more distant view, the natural elasticity of the parts releases an existing contraction. So, under the same circumstances, we may estimate the interval moved over by the thread, when it is brought nearer; but we can form no estimate of the absolute distance.—(Wundt.) 224 SENSE OF SIGHT. precisely the same as when the object is seen by one eye only. There is in such case no difference between the visual appearance of an object in relief, and its perspective projection on a plane surface ; and hence pictorial representations of distant objects, when those circumstances which would prevent or disturb the illusion are carefully excluded, may be rendered such perfect resemblances of the objects they are intended to represent, as to be mistaken for them; the Diorama is an instance of this. But this similarity no longer exists when the object is placed so near the eyes that to view it the optic axes* must converge; and these perspectives are more dissimilar as the convergence of the optic axes becomes greater. This fact may be easily verified by placing any figure of three dimensions—an outline cube, for instance—at a moderate distance before the eyes, and while the head is kept perfectly steady, viewing it with each eye successively while the other is closed. The figure represents the two perspective Fic. 9. projections of a cube; ais seen by the right eye, and d is the view presented to the left eye, the figure being supposed to be placed about seven inches immediately before the spectator.’ ‘Tt will now be obvious why it is impossible for the artist to give a faithful representation of any near solid object, that is to produce a painting which shall not be distinguished in the mind from the object itself. When the painting and the object are seen with both eyes, in the case of the painting, two similar pictures are projected on the retingw, in the case of the solid object, the pictures are dissimilar; there is therefore an essential * The optic axis of the eye is the line of visible direction for distinct vision, or a line proceeding from the central point of the apo and passing through the centres of the lenses of the eye. DISSIMILARITY OF PICTURES TO THE TWO EYES. 225 difference between the impressions on the organs of sensation in the two cases, and consequently between the perceptions formed in the mind; the painting, therefore, cannot be confounded with the solid object.’ This dissimilarity of the pictures is the chief optical sign of solidity or of three dimensions. The greater the dissimi- larity, the more decidedly is a third dimension suggested ; perfect similarity occurs in looking at things very remote, or in examining a surface at right angles to the line of vision, all the parts being equally distant. Thus, when we gaze at a painting close at hand, we are not deluded into the belief of its being a reality. Anything near must have its parts at an equal distance from the eye, in order to present identical pictures, and we draw the inference accordingly. The stereo- scope gives the illusion of solid effect by presenting to the two eyes dissimilar pictures, imitating the natural presenta- tion in the case of an object or a scene unequally removed from the eye. A great difficulty is experienced in explaining double vision, through mistaking the exact nature of the effect pro- duced upon the mind by the impression made on the eye on one single occasion. We are apt to suppose that the entire conscious state at any one moment—the full imagery pictured to our view—is determined by the rays affecting the retina at that moment. The truth is, that what rises to the mind on the sight of an outward thing, is an aggregate of past impres- sions, which the impression of the moment suggests, but does not constitute. The education of the sense of sight makes us aware, that an identical impression upon both eyes concurs either with great distance, or with mere surface, that is, with two dimensions only, there being no inequality of distance from the eye. On the other hand, unlikeness of picture cor- responds with the introduction of the element of unequal distance, and the more this inequality exists, the greater is the dissimilarity; and, accordingly, the mind, instead of being perplexed with double images, at once adopts the notion of a single complex object with varying remoteness, 15 226 | SENSE OF SIGHT. the variation being estimated among other signs by this very unlikeness of the pictures. It is immaterial whether the retinal presentations be two, as in binocular vision, or thousands, as in the vision of insects; these presentations are but the hint to a mental construction, representing the unity of the external scene, in its length, breadth, and depth. 6. Before quitting the consideration of the Eye, I should mention that the seeing of objects erect by means of an wnverted image on the retina, has been conceived as a phenomenon demanding explanation. But to make this a question at all, is to misapprehend entirely the process of visual perception. An object seems to us to be up or down, according as we raise or lower the pupil of the eye in order to see it; the very notion of up and down is derived from our feelings of movement, and not at all from the optical image formed on the back of the eye. Wherever this image was formed, and however it lay, we should consider that to be the top of the object which we had to raise our eyes or our body to reach.* 7. And now as to the sensations, or the proper mental elements of Sight. These are partly optical, resulting from the effect of light on the retina; and partly muscular, arising through the action of the various muscles. Nearly all sen- sations of sight combine both elements. 8. I shall commence with the sensation of mere light, and shall take the diffused solar radiance as the leading example. This is one of the most powerful of the simple influences that affect the human sense. Light is eminently * Still one can say (with Wundt) that, from the construction of the organ of vision, it even necessarily follows that the image should be inverted on the retina. The anterior and posterior convexities of the ball, it is clear, must always move in opposite senses. Take, then, what we call a downward movement of the eye, as when we run the eye down a spire from apex to base. This means, with reference to the retina, that we bring successively upon the yellow spot. the different parts of the whole image, beginning with the image of the apex. But the retina being at the back of the eye, and the back surface mounting with the downward movement of the anterior, clearly what is apex in the real spire must be the lowest point of the retinal image—if the natural relation of front and back in motion is to be preserved. SENSATION OF LIGHT. 227 a source of pleasure, which rises in degree, within certain limits, in proportion to the abundance of the luminous emanation. The degree is massive or acute, according as the effect proceeds from a diffused surface like the sky, or from luminous points as in artificial illumination. In either case it is possible to obtain a considerable amount of pleasure from this source. As a cheering influence, light ranks with warmth, alimentation, and pleasant repose. On the principle of Relativity, the full effect is experienced only after confine- ment in the dark. | The speciality of the pleasures of light is their endurable- ness. The influence, although powerful, is yet gentle; it does not exhaust the nerves so rapidly as sweet tastes, pungent odours, or loud sounds. This is the great distinction of the sense of sight. Hearing also ranks high in the same pro- perty, but we must still assign to it the second place. One of the things understood by the term ‘refinement, as applied to pleasure, is this aptitude for being endured a great lenoth of time without palling and satiety. The pleasures of sight are of a more lasting kind than those of the inferior senses. From this, and from some other circumstances that I do not here advert to, they enter into the feelings of the Beautiful. Light and shade, and the harmonious arrangement of colours, may suffice to constitute a work of Fine Art. The serene and soothing influence of sunshine furnishes a bond of connexion between effects of light and the tender feeling. The expla- nation I believe to be, that pleasure, when voluminous and not acute, generally subdues the active excitement and the ener- getic disposition of the system, and so brings the mind into the state most congenial to the pleasures of tender emotion. As regards Volition, the pleasures of light so far accord with the general rule ; that is, they stimulate the will in pro- portion to their degree. We shun gloomy abodes and seek the cheerful day, or the well-lighted room ; when the sunlight is painfully excessive, we retire to the shade. There is, however, a remarkable exception to this general tule. In the presence of a light too strong to be agreeable, 228 | SENSE OF SIGHT. the eye is worked upon, as by a spell or fascination, and continues gazing upon what gives pain or discomfort. The experimental proof of the fact is, that we find it a pleasing relief to interpose a screen between us and a light that we cannot divert the eye from, so long as it is within reach. Human beings experience, in a small degree, the fascination that in the moth is overpowering, even to self-destruction. This is the first clear indication of the existence of tendencies thwarting the regular course of the will) which is tc pleasure, and from pain); and constituting us, to that extent, irrational beings. Our sensations appear to have, in some cases at least, an efficacy to attract and detain us not only while wanting in pleasure, but also when positively painful. The present is an unequivocal instance. With reference to Intellect, the sensations of sight have a marked superiority in the scale of the senses. The pleasures and pains of sight possess, in the generality of minds, a higher ideal persistence and recoverability than the feelings of any other sense. If there be any exceptions to this rule, they are probably cases of unusual endowment and cultivation of the sense of hearing. The endurability of the sensations without fatigue, and the comparatively easy persistence in memory or idea, may proceed from the same fundamental characteristic—the great delicacy of the shock of light on the nervous substance, as compared with the resulting sensibility. In the most properly intellectual aspect—the bearings upon knowledge—the superiority of sight is still more pro- nounced. The sensations in the highest degree admit of being discriminated and identified ; and also of being retained in memory as images of surrounding things. The enjoyment of light demands alternation, and limita- tion as to amount. In sunny climates, the exposure to it for the entire day is excessive and exhausting; it has to be balanced by artificial darkness and shade. Places unable to afford the full quantity that human beings can enjoy, are styled gloomy and dull. COLOUR. 229 9. Colour introduces a new effect, as compared with white light. By a measured alternation of the different colours, we gain a new pleasure, which has all the distinguishing pecu- liarities of the pleasure of light and shade. The decompo- sition of the solar ray into certain primary colours, in fixed proportions, is an exact key to the harmony of colouring, or to the alternation most agreeable to the mind. We commonly speak of the different colours as having characteristic effects; blue and green are reckoned mild or soft; red is fiery, pungent, or exciting. The eye when fatigued with the glare of sunshine, is said to find repose in the verdure of the fields. But these allegations camnot be maintained in an absolute sense. Colour, like all other things, operates in accordance with the principle of Relati- vity. The effect of any single colour is due to the transition from others felt previously. If red were the one universal tint, we should never have recognized colour at all; we should have spoken only of light and dark. The effects attributed to redness are due to its contrast with the pre- vailing tints about us. Next to white light and shades of dull grey, we are familiarized to blue and green. The balance is usually in favour of the blue end of the spectrum, and hence the occurrence of red is a lively stimulation. If the proportions were reversed in nature; if red and yellow took the place of blue and green, these last would be the exciting colours: they would have the freshness of rarity and novelty. The pleasure of newly-discovered shades of colour, as the mauve and magenta dyes, has no foundation but novelty and contrast. The variegated aspects of the fields and gardens in the bloom of vegetation, have more beauty than the unbalanced verdure of the leaf. The diffu- sion of red and yellow supplies the wanting ingredients of the picture. The colours of sunrise and sunset are the scenic splendours of the sky. 10. Artificial lights usually fail somewhat in the propor- tions of white light, and, therefore, have the pungency of an unbalanced colour. The flame of a fire is an agreeable stimu- 230 SENSE OF SIGHT. lation ; the intensity does not amount to a painful excess. The light of a lamp arrests and detains the eye; the fresh sensibility of childhood is delighted with the effect, and soon learns the voluntary movements for following it when shifted about. 11. There remains to be noticed the sensation of lustre. The lustrous is opposed to the dull. The pleasure of lustre is greater than the pleasure of colour alone. The most characteristic effect of lustrous bodies is the sparkle, or the occurrence of bright spots in the midst of com- parative darkness—a marked case of light and shade. This is a combination highly favourable to the agreeable stimulus of light. Lustrous bodies have a mirror surface, and reflect the sun’s rays in beams; these, starting out at points, are in strong contrast to the remaining surface. The highest beauty of visible objects is obtained by lustre. The precious gems are recommended by it. The finer woods yield it by polish and varnish. ‘The painter’s colours are naturally dead, and he superadds the transparent film. This property redeems the privation of colour, as in the lustrous black. The green leaf is often adorned by it, through the addition of moisture. Possibly much of the refreshing influ- ence of greenness in vegetation is due to lustrous greenness. Animal tissues present the effect in a high degree. Ivory, mother of pearl, bone, silk, and wool are of the class of bril- liant or glittering substances. The human skin is a com- bination of richness of colouring with lustre. The hair is beautiful in a great measure from its brilliancy. The eye is perhaps the finest example; the deep black of the choroid, and the colours of the iris, are liquified by the transparency of the humours. 12. We have next to deal with the complex sensations of sight, those resulting from the combination of optical effect with the feelings of movement arising out of the muscles of the eyeball. As in the case of Touch, this combination is — necessary as a basis of those perceptions of the external world that are associated with sight—Externality, Motion, Form, VISIBLE MOVEMENTS. 208 Distance, Size, Solidity, and relative Position. Mere light and colour will not suffice to found these perceptions upon ; as already maintained, in the exposition of Muscularity and of Touch, it is necessary to refer them to the moving appa- ratus of the eye and of the body generally. 13. Visible Movements. One of the earliest acquired of our voluntary actions is the power of following a moving object by the sight. Supposing our gaze arrested by a strong light, as a candle-flame, the shifting of the candle would draw the eyes after it, partly through their own movement, and partly by the rotation of the head. ‘The consequence is a complex sensation of light and movement, just as the sensation of a weight depressing the hand is a sensation of touch and move- ment. If the flame moves to the right, the right muscles are engaged in following it; if to the left, the left muscles, and so on; and thus we have several distinct combinations of light and muscular impression, marking distinctness of direction, and never confounded with one another. Motion, instead of continuing in one direction, may change its direction, and take a course crooked or curved. This brings into play new muscles and combinations, and leaves behind a different trace of muscular action. The right muscles of the eye may have to act along with the superior muscles, and ata shifting rate. This gives an oblique and slanting direction, which we can ever afterwards identify when the same muscles are similarly brought into operation. We have thus a perfect discrimination of varying directions, through the distinct muscles that they bring into play, We can with the eye, as with other active organs, dis- criminate the greater or less continuance of a movement, and thereby estimate Duration in the first instance, and, in the next place, obtain another instrument applicable eventually to estimating Extended Magnitude. Our muscular sensibility also discriminates rate or velocity of movement. A quick movement excites a different feeling from one that is slow; and we thence acquire graduated sensations, corresponding to degrees of speed, up to a certain Bou SENSE OF SIGHT. limit of nicety. This estimate of the rate of contraction also indirectly serves as a means of judging of Extension, after we have arrived at the notion of visible Space, as opposed to Succession in Time. The muscular sensibility of the dead strain, or of Resist- ance, can scarcely occur in the eye, there being nothing to resist its movements but its own inertia. What is called straining the eye (which happens in close and minute vision) is not the same thing as straining the arms in the support of a heavy weight. Hence of the three primary sensibilities of muscle—Resistance, Continuance, and Speed—two only be- long to the ocular muscles. Accordingly the eye, with all its superiority in giving the mind the pictorial array of the ex- tended world, cannot be said to include the fundamental consciousness of the object universe, the sense of Resistance. There is a certain kindred sensibility in the common fact of muscular tension; but it is by association, and not by intrinsic susceptibility, that the power of vision impresses us so strongly with the feeling of the Object world. While the retina of the eye is receiving one and the same optical impression (in the supposed case of the candle-flame), this may, by movement, be imbedded in a great many different muscular impressions, and may constitute a great variety of pictorial effect. By changing the muscles and by varying their rate of action, we may so change the resulting impres- sions, that any one motion shall be recognized by us as distinct from every other, while each may be identified on a recurrence. Many of the pleasures of Muscular Movement, described in the previous chapter, may be experienced in the spectacle of moving objects. The massive languid feeling of slow movement, the excitement of a rapid pace, the still higher pleasure of a waxing or waning speed, can all be realized through the muscles of the eye and the head. The slow procession, the gallop of a race-horse, the flight of a cannon- ball, exhibit different varieties of the excitement of motion. In the motion of a projectile, where a rapid horizontal sweep — IMAGERY OF VISIBLE MOVEMENT. BOD is accompanied with a gentle rise and fall, we have one set of muscles quickly moved, and another set in slow varying tension, thereby contributing the still more agreeable effect of increasing and dying motion. While the projectile flies across the field of view, the horizontal motion is uniform, but the pace upwards diminishes, and at last dies away at the highest point ; the body then recommences a downward course, slow at first, but accelerating until it reach the ground. Hence the beauty of curves. The pleasures of moving objects and stirring spectacle count for much in the excitement of human life. They are really pleasures of action; but inasmuch as only a very limited portion of muscle is excited by them, they do not constitute bodily exercise, and are therefore, to all practical intents, passive pleasures, like music or sunshine. Whence dramatic display, the ballet, the circus, the horse race, the spectatorship of games and sports, although engaging the activity of the eye, do not belong properly to our active en- joyments. They may, however, be the means of stimulating the general activity of the frame. Among the permanent imagery of the wntellect, recalled, combined, and dwelt upon in many ways, we are to include visible movements. The flight of a bird is a characteristic that distinguishes one species from another; and the impres- sion left by itis part of our knowledge or recollection of each individual kind. The gallop of a horse is a series of moving pictures, which leave a trace behind them, and are revived as such. The motions that constitute the carriage and expression of an animal or a man, demand particular movements of the eye, in order to take them in and store them up among our permanent notions. All the gestures, modes of action, and changes of feature that emotion inspires, are visible to the eye as an assemblage of movements, and we recognize such movements as marking agreement or difference, among individuals, and in different passions. Many of the aspects of the external world impress them- selves upon the moving apparatus of the eye. The surface 234 SENSE OF SIGHT. of the sea, the drifting of clouds, the fall of rain, the waving of trees in the wind, the rushing of water, the darting of meteors, the rising and setting of the sun—are all mixed impressions of spectacle and movement. In like manner, in the various processes of the arts, there are characteristic movements to constitute our means of discrimination, and our permanent notions of those processes. The evolutions of an army have to be remembered as movements, and there- fore need to be embodied among the muscular recollections of the system. 14. Visible Form.—We have taken the case of moving objects as the least complicated experience of vision. We must now enquire by what process we perceive Visible Form and Extension, and acquire the notion of Simultaneous existence in Space. It has to be shown that the eye is active in the observation even of still life; the special mode of activity being such as to make the mind feel the difference between Succession and Co-existence. When we follow a moving object, as a rocket, or a bird, and when we carry the eye along the curve of the rainbow, there is a common fact of movement, with important dif- ferences in the mode. ‘These differences are, to a great degree, parallel to those described under Touch, whereby the know- ledge of objects as co-existing is attained. (1.) In the first place, in following the outline of the rainbow, we are not constrained to any one pace of movement, as with a bird or a projectile. This alone would give a lively sense of difference between the two appearances. (2.) In the next place, the optical impression, in the case of a still form, is not one unchanging sensation, but a series of sensations, which may be of the same nature— as in the rainbow, or may be all different—as in sweeping across the clouds or the landscape. (3.) Thirdly, we can, by an inverted movement, encounter the same series of optical sensations, in the inverted order ; whereas, in the other case, the object passes finally away from the sight. (4.) In the fourth place, we may repeat the movement, at any rate of speed, and in so doing obtain the same series of sensations, in the same CO-EXISTENCE IN SPACE. 235 order. Both in touch and in sight, this circumstance is pro- bably what, more than anything else, gives us that vivid sense of the difference between objects moving and passing away—thereby typifying Succession—and objects that are simultaneous or co-exist, which is the meaning of Space. The more frequently we experience this fixed recurrence of optical sensations, in company with a definite movement, the broader is the line between that mode of existence and the objects that give us only one chance of observing them. The constant reception of a definite series of sensations by one definite movement, and the equally constant occurrence of the series inverted under an inverted movement, go far to make up our notion, meaning, and expectation, of objects extended in Visible Space. But, (5.) in the fifth place, as regards Sight, the peculiar power of the eye to embrace at one glance a wide prospect, although minutely perceiving only a small portion, is avail- able to confirm the same distinction. When the glance is carried along the field of view, the portions that cease to occupy the centre of the eye, still impress the retina, and have a place in the consciousness, though much less dis- tinctly perceived. This constitutes an additional distinction between the transitory flight of a meteor and the picture of the starry sphere. Touch possesses this means of discrimina- tion only in a very limited degree. The extended surface of the hand, the plurality of fingers, the united touch of the two hands, and such extent of the surface of the body as can make a simultaneous contact,—are all that there is to correspond to this great prerogative of sight, in giving a plurality of simul- taneous impressions, so as to mark the difference between the co-existing in Space and the successive in Time. When a definite series of successive sensations are svmultaneously felt, they suggest all the separate facts of movement, together with the whole fact of movement, involved in a perception of the Extended. 7 Thus, then, the observation of the forms of still life is a combination of the movements of the eye, with the optical 236 SENSE OF SIGHT. impressions corresponding to the different parts of the field of - view. Exactly as in the case of moving things—by a hori- zontal sweep, we take in a horizontal line ; by a circular sweep, we derive the muscular impression of a circle; by a sudden change of direction, we are cognizant of an angle; there being, in all these instances, the persistence on the retina of the whole figure, while the eye scans the successive parts. The transition is easy from Jines to Surfaces. A more numerous and complex series of movements is requisite to give the impression of a visible area or superficies. But the same constant series of optical effects, imbedded in the same movements, inverted and repeated as oft as we please, enters into the cognition of space in ¢wo dimensions, as well as into the perception of linear magnitude, or space viewed in one dimension. 15. Apparent Size.—The apparent size or visible magni- tude is made up of the two discriminations—optical and muscular. ‘The Optical discrimination takes place through the extent of the image on the retina; hence the apparent size is spoken of by Wheatstone as the retinal magnitude. ‘The Muscular discrimination depends upon the sweep of the eye under the action of its muscles; and is, therefore, a fact or experience of our muscular energy or activity. The two estimates co-operate to a joint result. They are both equivalent to an angular estimate, or the proportion of the visible surface to a whole sphere. The apparent diameter of the sun or moon is half a degree, or 7$z of the circle of the sky. The combined estimate of Retinal Magnitude, by our two most sensitive organs—the retina and the ocular group of muscles—renders our measurement of apparent size singularly delicate. In fact, this is the finest discrimination within the compass of our senses; and whenever we desire to measure any property with nicety, we endeavour to resolve the case into a comparison of visible magnitudes. Of this description are the standards of weight (the balance), of heat (the ther- mometer), and many others. DISTANCE FROM THE EYE. 237 The fluctuations of visible magnitude in consequence of changes of Distance are appreciated with similar delicacy ; and after we are aware that these fluctuations correspond to alteration of veal distance, we use them as the most delicate test of remoteness. The celestial bodies and the clouds are conceived by us solely under their apparent or visible size. ‘Terrestrial objects, being seen by us at different distances, vary in apparent size, and we conceive most of them under a more or or less perfect estimate of their real size, as ascertained by handling and locomotion. Failing this estimate, we adopt some one point of view, which we have been most accustomed to, and conceive the object, as seen from thence. In regard to very familiar things, as a chair, or a man, we uniformly translate the apparent estimate into a real estimate. A building, a distant mountain, a landscape, are visually con- ceived as they appear from our most usual position with reference to them. 16. Distance, or varying remoteness——The apparent size, as above considered, includes only two dimensions. In order to appreciate apparent volume or solidity, as an advance upon mere extension, or surface, we must estimate varying remoteness also. Leaving out, at the present stage, the consideration of real distance, as well as real magnitude, we may advert to the various ocular sensibilities affected by alteration of distance. We have already remarked on the two muscular adapta- tions of the eye to distance,—the change in the eye-ball by the operation of the ciliary muscle, for near distances, and the convergence or divergence of the two eyes, for distances both near and far. To preserve a distinct image when an object is brought nearer, we need, by a muscular effort, to change the curvature of the crystalline lens in each eye, and to make the lines of sight of the two eyes converge. Both these efforts are attended with consciousness, and this con- sciousness mingles with the feelings of altered retinal mag. 238 SENSE OF SIGHT. nitude, and with dissimilarity of binocular images, when objects retreat from the eye, or advance toward it; while, in addition, the optical fact of varying clearness may also tell, together with the presence or absence of intervening objects. 17. Visible Movements and Visible Forms in three dimen- sions ; Volume.—By combining the visible movements across the field of view with the movements of adjustment—monoc- ular and binocular—we attain the experience of visible movements, visible forms, and visible magnitudes, in all the three dimensions of space; in other words, volume and solidity, in so far as these are understood by the eye alone. An object moving aslant requires changes of adjustment along with the movements of the eyeball, right or left, up or down ; and its image remains embodied in this more compli- cated series of movements and optical changes. A row of houses seen obliquely, needs the same combination. With the lateral movements of the eye, we must unite adjusting move- ments, in order to maintain the same distinctness of picture throughout. These changes of adjustment are repeated and inverted, along with the other movements, and conspire with these to give the sense of the co-existing in space, as opposed to the passing or successive in time. 18. The intellectual imagery derived through the eye from the forms of still life is co-extensive with the visible crea- tion. or the purposes of discriminating and of identifying natural things, and also for the storing of the mind with knowledge and thought, the sensations of objects of sight are available beyond any other class. The eye is kept constantly at work upon the surrounding scene, following the outlines and windings of form, as these extend in every direction ; and, by the movements thus stimulated, each sparate object is distinguished from those that differ in shape, size, or distance, and identified with itself and those that coincide with it in these peculiarities. The train of movements for a square are recognized as distinct from the train that describes an oval: the outline of a pillar brings on a cycle of motions wholly INTELLECTUAL COMPASS OF THE EYE. 239 different from those dictated by the figure of a tree. The property belonging to the mental system of causing to cohere movements that have been described in succession, fixes the series for each different view, and gives a permanent hold of all the distinct forms presented to the eye. This adhesive process belongs to the intellect, and will be fully treated of in the proper place. GH A.P TE Real GT. OF THE APPETITES. "i taking up, at this stage, the consideration of the Appetites, I do not mean to assert that these entirely bane to our primitive impulses, or that m them the opera- tion of intellect and experience is excluded. On the contrary, I am of opinion that Appetite, being a species or form of Volition, is like all our other effective forms of volition, a combination of instinct and education. But the process of acquisition is in this case simple and short; while, on the other hand, the stimulus to action, or the source of the crav- ing, is usually one of the sensations or feelings discussed in the two previous chapters. Indeed, if we look at the craving alone, without reference to the action for appeasing it, that craving is merely what we have all along styled the volitional property of the sensation. If a spur to action were to prenitie Appetite, all our pains and pleasures would come under this designation. But the Appetites commonly considered are a select class of feel- ings; and are circumscribed by the following property— namely, that they are the cravings produced by the recurring wants and necessities of our bodily, or organic life. ‘The avoiding of a scald, a cut, or a fall, is an energetic impulse of volition, and yet not a case of appetite; there being no | periodic or recurring want of the system in these cases. Sleep, Exercise, Repose, Thirst, Hunger, Sex, are the appetites most universally present throughout the Animal tribes. The state termed Desire so far agrees with Appetite, in being a volitional impulse growing out of some uneasy and unsatisfied condition. But in Desire, there is a prior expe- rience of pleasure, the memory of which is the spur to seek a SLEEP.—EXERCISE AND REPOSE, 24k renewal ; we desire to return to a tasted delight. This is not necessary to a mere Appetite; although obviously, after expe- rience of gratification, all our appetites have also the naa of Desires. / 2. The fact of periodic recurrence is in no case more strik- ingly exemplified than in Sleep. After a certain period of waking activity, there supervenes a powerful sensation of re- pose. If we give way to it at once, the state of sleep creeps over us, and we pass through a few moments of agreeable repose into unconsciousness. If we are prevented from yielding to the sleepy orgasm, its character as an appetite is brought out into strong relief. The voluminous uneasiness that possesses all the muscles and organs of sense, stimulates a strong resistance to the power that keeps us awake; the uneasiness and the resistance increasing with the continued refusal of the permission to sleep, until the condition becomes intolerable, or until a reaction ensues, which drives off the drowsiness for some time longer. The overpowering influ- ence of drowsiness is well seen in infants. 3. The necessity of alternating Lxercise with Repose, through the entire range of our active organs, brings on the like periodic cravings and deep-seated uneasiness. The fresh ‘condition of the muscles is of itself a sufficient stimulus to action ; without any conscious end, in other words, without our willing it, action commences when the body is refreshed and invigorated. If this spontaneous outburst is checked, an intense uneasiness is felt, being one of the conscious states incident to the muscular system. ‘This state is of the nature of all the other appetites, and increases with privation, unless, by some organic change, the fit passes over for the time. The dog chained up to his couch, the exuberaney of childhood restrained from bursting out, the bird in its cage, the prisoner in his cell—experience all the pains and desire of the active organs for exercise. On the other hand, after exercise, comes an equally powerful craving and impulse to rest, which, if - resisted, produces the same intense uneasiness. Under this head of Exercise and Repose I might include 16 242 THE APPETITES. the more active of our senses, that is, Touch, Hearing, and Sight. These senses all embody muscular activity along with the sensation peculiar to each; and the muscular activity, together with the tactile, auditory, and visual sen- sations, lead to weariness of the parts, with a craving for rest ; while, after due repose, they resume the fresh condition, and crave for the renewal of their excitement. The alternate exercise and rest of the senses is in a great measure involved in the rotation of sleeping and waking; indeed, the invo- luntary torpor of the nervous system, is almost the only means of giving repose to such constantly solicited senses as Sight, Touch, and Hearing. A similar train of remarks might be extended to the activity of the thinking organs. But in these, the periodic cravings are less distinctly marked, and more frequently erroneous, than in the case of muscular exercise. There is often a reluctance to engage in thought, when the brain is perfectly vigorous and able to sustain it; and, on the other hand, there is, in nervous temperaments, a tendency to excess of mental action, uncorrected by any regular promptings to take repose. The sense of fatigue, arising soon after beginning a laborious operation, and then disappearing, is connected with inaction of the brain. A little time is requisite to determine the flow of blood to the parts exerted. 4, Thirst and Hunger I have already touched upon. ‘What is called thirst is sometimes rather a call for the cooling influence of cold drinks, as for instance, in the dry, hot state of the air-passages, mouth, and skin, produced in fevers by the increased temperature and diminished tur- gescence of the parts. Exhalation is in such cases often rather diminished, and the dryness of the surface arises from the circumstance that although blood still flows through the capillary vessels, the reciprocal action between the blood and the living tissues, which is denominated turgescence, or tur- gor vitalis, is depressed.’—(Miiller, by Baly, p. 530.) Hunger, unlike Thirst, is a state of the stomach, as yet HUNGER. 243 not exactly understood; while the feeling of inanition, which also grows out of long fasting, must be considered as a general feeling of the system. The urgency of hunger ought to be in accordance with the actual deficiency of nutritive material, but very frequently the case is otherwise. ‘It is heightened by cold baths, by friction of the skin, by friction of the abdomen, and by the agitation to which the abdomen is subjected in horse exercise, as well as by mus- cular exertion.’ It is diminished by all nauseating influ- ences, which probably at the same time weaken the digestion. ‘The local sensations of hunger,’ says Miiller, ‘which are limited to the digestive organs, and appear to have their seat in the nervus vagus, are feelings of pressure, of motion, con- traction, qualmishness, with borborygmi (gripings), and finally pain.’ In the case of Hunger, as in most of the appetites, there is a double spur to the taking of food ; first, the stimulus of uneasiness, and next the impulse arising out of the pleasure of eating. It is well understood that these two things are quite different, and on their difference hangs the whole art of refined cookery. Very plain food would satisfy the craving for nutrition, but there is a superadded pleasure that we have to cater for. The one is the appetite in its strictest signifi- cation, and as found in the lower animals ; the other we may call a desire, because it supposes the remembrance and anti- cipation of a positive pleasure, like the desire for music, or for knowledge. It is in the process of taking food and drink, that we best see exemplified the activity springing out of the sensations of hunger and thirst. The actual assuaging of the uneasiness produces an intense pleasurable sensation that sets on the most vigorous movements for being continued and increased ; while the moving organs themselves, beginning to be invigor- ated, display a spontaneous and lively energy in the cause. To bring together, and make to unite, the sensation of the appeasing of hunger with the acts of sucking, prehension, masticating, and swallowing, is perhaps the earliest link of ° 24-4 THE APPETITES. volition established in the animal system. This is the first case of action for an end, or under the prompting and guid- ance of a feeling, that the newly-born infant is capable of. Besides the natural craving for the elements of nutrition required by the tissues, we may acquire artificial cravings by the habitual use of certain forms of food, and certain accom- paniments, as peppers, flavours, &. Thus we have the alcoholic craving, the craving for animal food, for tea, coffee, snuff, tobacco, &e. 5. The Appetite that brings the Sexes together is founded on peculiar secretions which periodically accumulate within the system, producing a feeling of oppression until they are either discharged or absorbed; there being a certain intense pleasure in discharging them for the ends of reproduction. If we were to place these feelings among Sensations, they would either form a class apart, or they would fall under the first class above described, namely, the Sensations of Organic Life. If the subject were open to full discussion, like the other feelings of human nature, it might be best to treat them as an organic sensibility giving birth to a special Emotion. We have in this case, as in Hunger, both Appetite and Desire ; but we have also, what does not occur toa like degree in hunger, a many-sided susceptibility to inflammation,—through all the senses, through the trains of thought, and through varlous emotions. 6. The accustomed Routine of life leads to a craving almost of the nature of Appetite. As the time comes round for each stated occupation, there is a tendency or bent to proceed with that occupation, and an uneasiness at being restrained. So, our appetites properly so called may have their times of recurrence determined by our customary periods of gratifying them. 7. All the appetites are liable to be diseased or perverted, and to give false indications as to what the system needs. They are likewise liable to artificial and unseasonable inflam- mation, through the presence of the things that stimulate and gratify them. In the lower animals, it is assumed, I. know CORRECTION OF APPETITE, 245 not with what truth, that appetite rarely errs ; in humanity, error is extremely common. We are apt to crave for warmth when coolness would be more wholesome ; we crave for food and drink, far beyond the limits of sutticiency ; we indulge in the excitement of action when we ought to cultivate rest, or luxuriate in repose to the point of debility. So doubtful is the appetite for sleep, that there is still a dispute as to how much the system requires. Perhaps the complicacy and the conflicting impulses of the human frame, are the cause of all this uncertainty and mistake, rendering it necessary for us to resort to experience and science, and to a higher volition than appetite, for the guidance of our daily life. COE GAP Dali ia Delay: OF THE INSTINCTS. is iB the foregoing chapters have been enumerated all the primary modes of consciousness ; we have now to consider in full the original provision in the human system, for Action. The name ‘Instinct’ is especially reserved for what is primitive or primordial on the active side. More expressly, INSTINCT is defined as the untaught ability to perform actions of all kinds, and more especially such as are necessary or useful to the animal. In it a living being possesses, at the moment of birth, powers of acting of the same nature as those subsequently conferred by experience and education. When a newly dropped calf stands up, walks, and sucks the udder of the cow, we call the actions instinctive. | 2. In all the three regions of mind,—Feeling, Volition, ancs Intellect,—there are certain primitive and fundamental arrangements, which education or acquisition proceeds upon. A full account of all our instinctive endowments may be included under the following heads. 1. The heflec Actions.—These are actions withdrawn from the sphere of mind, and yet having analogies, as well as contrasts, with proper mental actions. 1. The primitive arrangements for combined and harmo- nous actions.—The rhythmical acts of walking, flying, swim- ming, &c., are examples of these. The Will may supply the stimulus to move, but the harmonious grouping of the move- ments is, in many instances, provided for among the natural endowments of the system. ur. The connexions existing at the outset between Peeling and its bodily manifestations. REFLEX ACTIONS. 247 Iv. The instinctive germ of Volition. What we call the power of the will, has to be traced back, if possible, to some inborn or primitive stimulus, connecting together our feelings and our actions, and enabling the one to control the other. This is perhaps the most delicate inquiry that our science presents. The primitive foundations of Intellect, I shall defer till the whole subject is entered on in the Second Part. v. The description of the special mechanism of the Vovce, will receive a place at the conclusion of this chapter, not having been included in the chapter on Movement, THE REFLEX ACTIONS. 3. The Reflex, Automatic, or Involuntary actions, are marked by the absence of the circumstance characterizing voluntary actions, namely, the stimulus and’ guidance of feeling. Many of them are essential to animal life. They all demand a nervous arrangement, consisting of incarrying and outcarrying fibres, connected by grey matter. Some are maintained by the system of sympathetic nerves and ganglia, which are the most detached from the brain or centres of consciousness; others depend on the spinal cord; a third group are related to the medulla oblon- gata ; and some are actuated by still higher centres, as the pons varolit and the corpora quadrigemina. Occasionally the sympa- thetic ganglia and a portion of the cerebro-spinal masses concur to the responsive movement. The Reflex Actions may be distributed under the following heads. First, those concerned in the organic processes, and operated through the involuntary muscles,—being the most widely removed of all from the mental or voluntary sphere. The rhythm of the heart is usually counted among reflex actions, but no precise stimulant can be readily assigned. The power emanates mainly from the sympathetic system of nerves, and especially from the ganglia distributed on the heart itself ; the rhythm continuing for some time, even after removal from the body. The influence is thus of the nature of regulated or rhythmical spontaneity, rather than of reflected action. The 248 THE INSTINCTS. accomplished contraction of one portion of the muscular sub- stance is the signal for commencing the contraction of another portion; and no other antecedent can be specified. The mere contact of the blood with the muscular wall of the organ is not to be considered a stimulant, such as would give rise to a reflex act. By galvanizing certain parts of the sympathetic system, in the neighbourhood of the heart, the beats are accelerated. On the other hand, by the stimulation of the vagi nerves, the action is weakened; this is in accordance with a tendency of the cerebro-spinal nerves to hold in check the influence of the sympathetic centres. Itis found, however, that the complete removal of the cerebro-spinal centres has a weakening effect upon the heart’s action, showing that, on the whole, some contri- bution to the force of its pulsations is derived from beyond the confines of the sympathetic system. So, irritation or excite- ment of the spinal cord of a recently decapitated animal, increases the force of the heart in common with the intes- tines and other viscera. While states of mental excitement, especially of the joyful kind, are accompanied with an improved tone of the circulation, depressing passions lower it; effects depending on the comparative energy of the sympathetic and the cerebro-spinal centres. Connected with the circulation of the blood, there is also, what is called, the vaso-motor action ; whereby the smaller arteries, which possess muscular fibres, are contracted or expanded, so as greatly to modify the local circulation, The contraction of these fibres, due to the influence of the sympathetic nerves, diminishes the bore of the vessels, and lessens the flow of blood to the parts ; their relaxation widens the bore, and gives an increased flow, with rise of temperature and quickened action upon the nutrition of the locality. The permanent contraction, maintained in these fibres through the influence of the sympathetic centres, is one of the examples of the spontaneity of muscular energy, and is not a pure case of reflex stimulation. Through the vaso-motor agency, the secretions and excretions are greatly affected by nervous influence; it being uncertain whether this is the sole instrumentality whereby the processes of organic life are subjected to the nervous centres. More clearly reflex are the movements of the intestines. The whole of the intestinal canal is provided with muscular fibres, DEGLUTITION. 249 circular and longitudinal, of the unstriated or involuntary species. By the successive contraction of the circular fibres, aided by the longitudinal, the food is propelled along the entire course of the tube, through reflex stimulation. The first stage of the process commences with Deglutition, or swallowing, which succeeds to mastication. Of the three steps of deglutition, one is purely voluntary, being the propulsion of the food, by the concurrence of the lower jaw, mouth, and tongue, into the bag of the throat, called the pharynx; from which point the movements are purely reflex and involuntary. In the second stage, the contact of the food with the walls of the pharynx brings on the rapid contraction of the constrictor muscles of the pharynx, together with the auxiliary operation of the muscular fibres for raising the palate, and those (called stylo-pharynget) for drawing the walls of the pharynx upwards. The third stage of deglutition occurs in the cesophagus, or gullet, whose circular fibres successively contract in a wave-like manner from above, downwards; while the longitudinal fibres, drawing up and widening the tube, facilitate the descent. This peculiar action, called the vermicular or peristaltic action of the intestines, is extended through the whole length of the canal. Both the cerebro-spinal and the sympathetic centres are concerned in maintaining the action. The stimulus is the contact of the food and of the various digestive fluids, of which fluids the most effi- cient is the bile. This instance exemplifies reflex action in its simplest and most widely spread form, namely, contact with a surface responded to by the muscles of the locality. At each point, the food stimulates the circular and longitudinal fibres of the part touched and those immediately in the rear, so that the morsel is gradually propelled in the forward direction. In the pharynx, the action is violent -and rapid (being under the powerful control of the medulla oblongata) ; as respiration is intermitted during the act, no time must be lost; while certain adjoining muscles concur with the muscles of the pharynx. In the intestine, the action is compara- tively feeble and slow ; the time of descent of the food along the small intestine is estimated at about three hours. Such is the regular course of reflex action in the alimentary canal. Among occasional and extraordinary stimulations, we may include the production of diarrhoea and colic by irritating 250 THE INSTINCTS. substances; which is the same process ina more violent form. A strong irritation will operate at a distance from the part affected, as when these derangements of the bowels are brought on, in infants, from teething. This shows the influence propagated along the main chain of the sympathetic, instead of being re- flected from a single point; it being the tendency of all powerful stimulation to extend its influence. The same tendency is shown in the other direction, when irritation of the alimentary canal spreads from the sympathetic ganglia to the cerebro-spinal centres, and produces, in infants, squinting and convulsions, and, in adults, epilepsy (through the medulla oblongata). Among reflex acts, connected with digestion, we have to include vomiting. The most usual stimulus is the presence of indigestible, irritating, or poisonous substances in the stomach. The response necessary to vomiting is somewhat complicated. The act is proved to occur in two ways. One is by an anti-peri- staltic movement of the intestine, or by an inversion of the order of contraction of the muscular fibres. It is conceivable that violence of irritation may have this effect, not by any specific nervous connexion, but by mere derangement of the usual rhythm. Colic and diarrhcea would be varieties of the same deranging stimulus. In the other mode, which is the one most frequently observed, the effect arises through the abdominal muscles. This will be adverted to under the next head. In the Second class of Reflex Actions, organic processes are affected, but the instrumentality is the voluntary muscles. The chief example is respiration, depending chiefly on the medulla oblongata. The great muscle of Respiration is the diaphragm, whose contraction performs the heaviest duty, namely, inspiration or drawing in breath; while the natural rebound or elasticity of the chest is the chief cause of expiration. Other muscles aid the diaphragm in the inspiratory act; and certain muscles, as those of the abdomen, the internal intercostals, the infracostals, and the muscles of the back, may co-operate with the elasticity of the chest, in expiration. The action consists of a simple rhythm, or alternate contrac- tion and relaxation of the diaphragm, as the muscle in chief; while the co-operating muscles, so far as brought into play, receive, in like manner, an alternated stimulation. RESPIRATION, 251 Although respiration is adduced as a perfect example of the reflex process, there is some doubt as to the exact stimulant employed. The commencing of respiration at birth is said to be due to the effect of cold—especially in the skin of the face— transmitted to the medulla oblongata by the nerves of the fifth pair. We must suppose, however, what everything confirms, that this nervous centre is itself a very energetic one, waiting only for the slightest touch to discharge itself with the requisite vigour. All through life, cold, especially on the face, stimulates respiration ; even so small an application as the fan, in a heated room, rallies the weakened action of the lungs. When respiration is once established, the stimulus is supposed to emanate from the surface of the lungs, and to be due to the influence of the venous blood, surcharged with carbonic acid and other impurities, and devoid of oxygen; but, in the absence either of decided facts, or of the analogy of a principle, this must be looked on as conjecture. Granting that there is reflex stimulation properly so called, we may assume that there is a considerable spontaneous emanation, modified but not created by stimulants.* The principal circle of nervous action is by the vagus nerve (sensitive or incarrying), a small part of the back of the medulla oblongata, and the spinal accessory nerve (motor) originating near the vagus. The circle is extended by including the fifth pair (sensibility of the face); and by the spinal nerves (tactile * When the sensory nerve distributed to the surface of the lungs is cut through, the breathing action is weakened, showing that a certain amount of stimulus is derived from the action going on throughout the surface. If, farther, the brain is paralyzed by any poison, the respiration is still more enfeebled, leading us to infer that the brain contributes to the breathing activity. Dr. Brown-Séquard has been led, by the examination of a great many cases, to the conclusion that the whole base of the brain is employed in respiration. He says :—‘ All the facts just mentioned, and many others, have led me, first, to abandon the view so generally admitted, that the medulla oblongata is the essential source of the respiratory movements in the nervous centres ; and, secondly, to propose the view that these movements depend upon the incito-motory parts of the cerebro-spinal axis, and on the grey matter which connects those parts with the motor nerves going to respiratory muscles. The chief stimulus to respiration is the action on the surface of the lungs, but ‘ excitations from all parts of the body (as by cold, for instance), and also direct irritations of the base of the brain and of the spinal cord, almost constantly taking place, contribute to the production of respiratory movements.’— Lectures, p. 192. 252 THE INSTINCTS. and motor) all over the body. As above remarked, there is little complication in the process; the great desideratum is energy of impulse, following a very simple rhythm. In so far as the operation can be kept up by the diaphragm alone, it is the simplest of all arrangements; a mere exertion and remission of one definite stimulus. The accessory muscles are two opposed groups, like the flexors and extensors of the body ; and that such muscles should be stimulated by turns is a consequence of their being stimulated at all. By the great law of conservation, to be noticed presently, a process so essentially linked with the vital energies of the system would extend the compass of the actions ministering to it, bringing into play remote accessories, as well as augmenting the power of the principal instrument, the diaphragm. The breathing apparatus is the’ medium of certain acts, of occasional occurrence, more decidedly of the reflex character than the breathing function itself. One noted example is cough- ing. Although this act is accompanied with a painful sensation, giving birth to a voluntary impulse, which counts as part of the case, yet there is a marked concurrence of reflex, in the sense of involuntary, stimulation. The localities whose irritation makes us cough are—the glottis, the larynx with the air tubes of the lungs, and the throat or fauces. The irritants are diseased secre- tions from the lungs, and from the stomach, passing over those parts; also solid and liquid substances entering from without, as when food or drink enters the larynx; irritating gases; and, lastly, cold air. The first and immediate result of the reflex stimulus is, by the contraction of the arytenoid muscle, to close the glottis together with the upper opening of the larynx. The second act is a violent movement of expiration, such as to force open the glottis, and clear the passages of the irritating sub- stances ; the instrumentality being the abdominal and other muscles auxiliary to expiration. The more purely reflex operation is probably seen in the first act, which follows the most general law of reflex stimulation— the contracting of the muscles of the locality affected. In the second act, the influence takes a wider sweep, and, through the medulla oblongata, finds its way, by the respiratory nerves, to the muscles of augmented expiration. The irritation produces that peculiarly unendurable feeling called tickling, which, though not of the ordinary character of acute pain, always prompts to COUGHING.—SNEEZING.—SUCKING. 253 energetic voluntary movements for getting rid of it. The ex- planation probably is, that we are made very uncomfortable by the reflex stimulation engendered through a slight touch of very sensitive parts. This second act, if not entirely voluntary, is so in part, and is prompted in the last resort by the self-conserving tendency, which is the only known source of volition. Coughing may arise from cold air on the skin, from coldness of the feet, and from general chillness. In most of these in- stances, if not in all, there is an intermediate effect of the rise of phlegm from the lungs or the stomach, the consequence of the disturbing agency of the cold; so that the irritation of the glottis or neighbouring parts is still the direct influence. Sneezing closely resembles coughing, and the two illustrate each other. The surface affected is the interior of the nose. The irritants are pungent gases, and foreign substances lodging in the cavities of the nostrils. The immediate response, parallel to the closing of the glottis in coughing, would appear to be the closing of the fauces, so as to divert the breath from the mouth to the nose. The more conspicuous act consists in a deep and sudden inspiration, followed by a clearing explosion through the nostrils by a grand expiratory effort. Some part of the stimulus must be regarded as voluntary, with a view to deliverance from the tickling sensation ; for, although a sleeper may be made to sneeze by ad- ministering snuff or other pungent substance, the consciousness is awakened preparatory to the act. When too much light, or the rays of a fire, on the face or head, make one sneeze, there is probably first a reflex effect, of the vasi-motor kind, producing a flow of mucus in the nose. Sucking is a reflex act, passing into the voluntary. The pre- paratory step is the closing of the lips round the nipple, a purely reflex process, stimulated by the mere contact. There are certain concurring adjustments. The tongue is brought forward to the nipple. In the throat, by means of the palate, uvula, and posterior pillars of the fauces, the entrance of air to the mouth through the nose and pharynx is prevented, while respiration is still possible (by the nose), except at the instant of swallowing. The act then consists in drawing away the tongue (the air-tight contact of the lips remaining), so as to produce a partial vacuum in the mouth, and a consequent in-flow of milk by atmospheric pressure. The mere withdrawing of the tongue, however, does 254 THE INSTINCTS. not of itself suffice; this might be done, as any one can test, without swelling out the closed cavity of the mouth. Hither there must be a bulging action of the cheeks, through the buccal muscles, or a momentary inspiration, with the nostrils closed, which would bring about the needful disturbance of the atmo- spheric equilibrium. We have already alluded to the act of vomiting, as per- formed through the involuntary fibres of the alimentary canal. More usually and obviously, it takes place through the abdominal muscles. When the pyloric muscular ring (at the outlet of the stomach into the duodenum) contracts tightly, while the cardiac orifice (the entrance to the stomach) is open, the abdominal muscles, operating powerfully, expel the contents of the stomach from the mouth. The action is essentially an irregular one; the due concurrence of all the acts not being provided for by a pre- conceived arrangement. Sometimes the cardiac fibres are con- tracted, as well as the pyloric, through the reflex stimulation of the alimentary canal itself; in that case, the attempts at vomiting are ineffectual. In order to procure the aid of the abdominal muscles, the medulla oblongata must be affected. Hence there is required a sufficiently powerful stimulation of the pneumo-gastric nerves. This may be gained by an irritating contact with the surface of the stomach, the most usual cause of vomiting. The effect may also arise by tickling the fauces, whence must proceed a very powerful stimulation to the medulla oblongata, at the point where the nerves issue to the abdominal muscles. Certain tastes are called nauseous, from their tendency to excite the stomach to vomiting ; the nervous agency in this case being the glosso- pharyngeal nerves, also connected with the medulla oblongata. Nauseous odours probably operate through the same nerves; the olfactory track would carry the influence too far about. Certain sensations, in their origin still more remote from the stomach, bring on sickness ; as a severe prostrating blow on the shin, the testicle, or on the eye-ball. The seat of irritation in this case is the brain, in the first instance, from which an influence is diffused. to the medulla oblongata. The same may be said of violent emotion generally, which may lead to sickness. Concussion of the brain is also a cause. These circumstances would indicate the result as due to a great loss of cerebral power, and the dis- STIMULANTS OF THE ORGANIC FUNCTIONS, 255 turbance of some tonic state or balance, permitting a special and local outflow of stimulus, which the healthy condition holds in restraint. The case of sea-sickness would readily accord with the same view. The aid given to defecation by the abdominal and expiratory muscles is probably altogether voluntary. Infants seem incap- able of the effort; in them, accordingly, the reflex peristaltic movements of the intestines are the expelling instrumentality. The expulsion of the male semen.is a reflex act operated through the sensory nerves and the cerebro-spinal centres; the muscles are of the voluntary species. In a Third class of Reflex Actions, the organic functions are affected through the medium of the cerebro-spinal system. Salivation is controlled by the nerve of taste. A sapid body entering the mouth causes an increased flow of saliva. The sali- vary glands are all connected with the sympathetic system of nerves; the small arteries of the blood-vessels being kept at a certain point of contraction through the vaso-motor influence of the sympathetic. To produce an increased flow, the muscular fibres are relaxed by influence from the sensory nerves, apparently suspending or diminishing the action of the sympathetic ganglia. The gastric secretion in the stomach is influenced, probably in the same way, through the sensory nerve of the stomach, the pneumo- gastric. So, the flow of milk in the female breast is augmented by irritating the nipple. The jlow of tears is increased when a foreign body enters the eyelids. The same effect is caused by a strong light; also by irritating the conjunctival, nasal, and lingual branches of the fifth nerve, all which reflect influence on the sympathetic ganglia. When the flow is stimulated by the more remote disturbances of vomiting, violent coughing, laughing, and sobbing, there is pro- bably an intermediate stimulation of the fibres of the fifth pair. The flow of tears under pain is a relief from the congestion of the brain, and may be forced on by that circumstance, and not by the process last described. The effect of pain is to weaken the cerebral centres, and give more play to the sympathetic, so that the regular consequence is exemplified in the arrest of secretion (as, for example, the saliva and the gastric juice). The winking of the eye is a reflex act, following the same stimuli as the flow of tears; namely, the presence of a foreign 256 THE INSTINCTS. body, the accumulation of watery drops in the eye, and a strong light. The nerves of the fifth pair are the instrumentality ; and the centres of influence are partly the sympathetic, partly the cerebro-spinal (in this instance, probably the medulla oblongata). The complete and energetic closure of the eye, involving not only the eyelids, but also the eyebrows, is altogether voluntary. The movements of the iris are due to the sympathetic system, controlled by the sensory nerves of the eye-ball, and the motor nerves of the eye. The iris is contracted under a strong light, and expanded as the light becomes feeble. If the process be conducted on the analogy of the foregoing examples, the sympa- thetic ganglia would.control the radial fibres, which keep the eye open; the abatement of this control by sensory action would allow the circular or contracting fibres to operate. It is possible, besides, that the fibres of the third cerebral nerve proceeding to the iris may be stimulated by a reflex influence of the light through some portion of the brain (as the corpora quadrigemina). In the Fourth, and last, Class of Reflex Actions, muscles, more or less voluntary, are affected through the cerebro-spinal centres. Here we have an approximation to proper voluntary acts; the stimulant in all cases being accompanied with sensa- tion, and the movement being such as the will could execute.. The first case that we shall mention is the contraction of the ciliary muscle, in the adjustment of the eye to near vision. This action, without our consciously willing or wishing it, succeeds to the feeling of indistinctness of the picture when anything is brought nearer to us. Consentaneous with the act, are the nar- rowing of the pupil and the convergence of the eyes; all the three adjustments co-operating to the distinct vision of near objects. The nerve for regulating the ciliary muscle is supposed to be a branch of the third pair; the contraction of the iris may be due to the same nerve, which likewise governs the conver- gence of the eyes, through the internal rectus muscle. The nervous centre more immediately concerned is the anterior pair of the corpora quadrigemina, stimulated through the optic nerve. The muscles of the tympanum are controlled in a manner analogous to the adjusting muscles of the eye. The analogy extends to the mixed supply of nerves; those for the tensor tympani being derived from the sympathetic (like the radial fibres of the iris) ; those for the stapedius, from the fifth cranial REFLEX MOVEMENTS OF THE SENSES. 257 nerve. On the theory of the action of these muscles that accords with the above analogy, the tensor tympani tightens both the membrane of the tympanum and the membranes of the foramina of the inner ear, under the influence of the sympathetic ganglia, and renders the ear susceptible, in the highest degree, to sound, like the radial fibres of the iris widening the pupil to the utmost. The feeling of sound in excess would then operate to relax those parts, by the stapedius muscle, which is stimulated through the facial (motor) nerve. Under the same head we may place the reflex movements of the Senses generally. By these are understood the special move- ments of the organ itself, as distinct from the more diffused wave of influence accompanying lively sensation. Thus, an object placed in the hand specially stimulates the muscles that bend the fingers, besides producing the more distant effects associated with a sensation as a fact of consciousness. The effect may be seen in any one asleep. A bad smell affects specially the muscles of the nose; a bitter taste brings on wry movements of the mouth. The word ‘ Reflex,’ as applied to the actions now considered, needs to be specially guarded and explained. It is employed in cases where its obvious meaning is absent, and withheld in others where that meaning is present.* The notion plainly attached to the word is a circle of influence, wherein there can be distinctly shown an outer or peripheral stimulation, conveyed by incarrying nerves to a ganglionic centre, and bringing on, by way of response, certain movements. The stimulation may be unconscious, as in the intestines, or conscious, as in the adjustment of the eye. The distinction is an important one; it marks out two grades of the effect, a lower and a higher; and distinct names have been employed to express the two—the phrase excito-motor being applied to the first, and sensori-motor to the second. But it has been very properly remarked, that actions of the highest order of combined volition and intelligence may have * The term ‘automatic’ is used as a synonym, or asa substitute, for ‘reflex,’ but with still less aptness for the purpose. It would serve to indi- cate the spontaneous activity, and that alone. With proper cautions and explanations, the name ‘ reflex’ is the most suitable that has yet been pro- posed. ‘Involuntary,’ although applicable to the class (allowance being made for a margin of transition), is too wide in its meaning. 17 258 THE INSTINCTS. this reflected character. Any one promptly answering a ques- tion, exemplifies a reflex operation, so far as the general meaning is concerned. But such cases are not included among the so-called Reflex actions, these being set in marked contrast to voluntary actions of every kind. Again, there are included in the class certain effects that are obviously wanting in the peculiarity implied in the name ‘reflex.’ Thus, we have seen that there are many movements due solely or mainly to central influence,—the so-called spontaneous move- ments; with regard to which, either no peripheral stimulus can be assigned, or the stimulus is insignificant compared with the energy of the response, an energy rising and falling with the physical condition of the central grey masses. The convulsive movements in certain ailments, as hydrophobia, hysteria, chorea, epilepsy, tetanus, &c., must be due to diseased changes in the condition of the nervous centres. These are involuntary move- ments, but they are not, strictly speaking, reflex. We may give a similar account of yawning; which is probably due to the unequal subsidence of the nervous action, disturbing the balance of the muscular tension. It would be a very forced supposition, to bring it under the literal meaning of reflex action. In the enumeration of Reflex Actions, there is often included a group of effects distinct from any of the foregoing, namely, those typified by laughter, cries, sobbing, sighing, starting, fidgets, &c. These have been sometimes styled sensori-motor, because they are at the instance of sensations. This circumstance, however, does not show their real characteristic. They are, in my opinion, more aptly brought under emotional diffusion, expression, or embodiment. very conscious state is accompanied with a diffused wave of effects, muscular and organic, which are stronger according as the feeling is more intense. Pleasing emotions are attended with one class of manifestations,—the smile, for ex- ample ; states of pain with a different class. The leading emotions of the mind—Wonder, Fear, Love, Anger, &c.—have each a characteristic and well known embodiment or display. These movements incorporated in our constitution as a por- tion of the very fact of being conscious (we are often said to be ‘moved,’ when it is only meant that an impression is made on the mind), may be called ‘sensori-motor,’ inasmuch as a sensa- tion, when sufficiently powerful, always visibly stimulates them, GENERAL PRINCIPLE OF REFLEX ACTION. 259 rendering them, as it were, the return or response of the outward impression. ‘They may also be styled ‘reflex,’ for the very same reason. They are, farther, ‘involuntary’ movements, being quite distinct from our volitional acts. But they are far from being unconscious: they are, if I am not mistaken, inseparable from consciousness, being entwined with the conscious condition in the mechanism of our frame. When consciousness is feebly excited, so are they,—so feebly that no visible manifestation results; when a stronger excitement is applied, they are roused in proportion. Inacultivated shape, they make the gesticulation and display that constitutes the usual expression or natural language of feeling, which no man and no people is devoid of, while some nations show it in a remarkable degree. The painter, sculptor, poet, actor, seize hold of these movements as the basis of artistic forms; and the interest of the human pre- sence is greatly dependent on them, and on the attributes that result from them. Confining ourselves to the strictly Reflex Actions, whether excito-motor, or sensori-motor, and omitting central spontaneity, emotional diffusion, and voluntary actions properly so called, we may now endeavour to generalize the facts, or to assign the most comprehensive laws at present attainable with regard to this pro- cess of the animal economy. I. We trace one comprehensive arrangement, of wide preva- lence throughout the animal kingdom, namely, the connexion between a peripheral stimulus and the movement of the part affected. This is the simplest and the most generalized type of the nervous system, demanding a circle made up of incarrying fibres, a central ganglion, and outcarrying fibres to the muscles of the same locality. In the lowest creatures possessing a nervous system, the structure and the function are as now described. The fixed mollusk responds to a contact by a move- ment contracting its body. In the experiments on decapitated animals, irritation of the foot is followed by retracting or else throwing out the limb. Notwithstanding the higher complications super-imposed upon this simple arrangement, it is shown, almost pure, in many of the actions above described. The peristaltic movements of the intestines appear to be governed mainly by the contact with the part of the gut actually in movement. It is the same in the 260 THE INSTINCTS. pharynx and cesophagus, and also in the rectum. In coughing, sneezing, and sucking, the first stage is a reflex stimulation to the muscles of the parts irritated. In the operation of the several senses, there is a reflex stimulus of the same character, although usually disguised and overpowered by the wider and more potent influences, respectively called emotional and volitional. We may readily speculate upon the mode of action in these simple reflex circles. The peripheral stimulation is either simple contact, as in the touch of a solid body, or contact with absorp- tion of material fitted to act on the nerves. In both cases a muscular disturbance of the nerves takes place, which is propa- gated to the ganglia, and there re-inforced by the more active changes occurring in the grey corpuscular matter ; whence arises a molecular movement in the outgoing or motor nerves. . It is not every stimulation, however, that imparts or evolves molecu- lar activity ; some stimulants, as cold, under certain circum- stances, tend to lower, reduce, or destroy activity already existing. The most potent stimuli, as we might expect, are nutritive ma- terials, and substances that, by combining with oxygen, or in other ways, generate force. The rise of temperature, in its direct or immediate consequences, contributes molecular power. II. One step above the simplest reflex movement, is the alternation of two movements, carrying the same part to and fro. Wherever an organ is fitted with an opposing pair of muscles, both these have a connexion with the ganglion related to the part ; both receive outcarrying fibres, and the local stimulus will excite movements in both; which movements, however, being opposed, must alternate with one another. It is an incident of such a situation that the muscles should fall into a reciprocating movement, and establish a nervous track inclining to this recip- rocation; so much so, that the completed contraction of one, without any other stimulus, is an occasion of beginning a con- traction of the other. The alternating contraction of opposing pairs, whether in joint response to a peripheral stimulation, or as a result of mere spontaneity, or, lastly, as a consequence of re- mote nervous instigation, is a fact of very wide generality, and is the least possible remove from the simple reflex circuit supposed in the foregoing paragraph. II]. The next advance in complexity is shown in the con- currence of several distinct movements in one act. Such a con- CONSCIOUSNESS PRESENT IN SOME REFLEX ACTIONS. 261 currence is required in deglutition, in sucking, in coughing, in forcible inspiration, in the adjustment of the eyes, and in loco- motion. The regulating circumstance of the united action is the furtherance of some end in the economy. We know by what means combined movements are acquired, in ordinary education ; namely, by tentatives under the guidance of the desired effect. IV. The self-adjusting power now hinted at (to be afterwards fully elucidated in connexion with the Will) may be traced in the inferior region we have been considering. The supply of nutri- tion or other stimulus gives birth to molecular force, ending in muscular movement; which movement, in many circumstances, furthers the nutritive or other contact, and is thereby still further stimulated; as when the shell-fish in the sea opens its mouth to the water containing its food. In several of the reflex actions above described, consciousness is usually present ; as coughing, sneezing, sucking, the increased respiratory activity from cold, the reflex action of the senses, and the special adjustments of the ear and the eye. In so far as these actions arise during sleep, they may be regarded as inde- pendent of consciousness. But in some, consciousness is a part of the case; the object of them is, not to respond to a physical stimulation, but to remove an uneasiness; such are winking, and the adjustments of the eye to vision, and of the ear to sound. An obscure sense of discomfort is the antecedent circumstance in winking. To all these cases, we must apply the fundamental law of the will; they contain the essential fact of volition. They differ from the more usual forms of voluntary action, only in not engrossing our attention ; we may be occupied with other matters while they are taking place. In this respect, they resemble actions in the stage of consummated habit. Yet it is impossible to overlook the great resemblance to the course of voluntary action in those inferior reflex processes, commonly accounted devoid of consciousness. They are usually, although not always or necessarily, pointed’ to the conservation of the individual, which is the foundation circumstance of con- scious and voluntary action. When several movements are united in one act, as in sucking, it is the better to answer some function of preservation. We may not be able to draw a sharp line between the reflex involuntary and the voluntary: the two may shade into one 262 THE INSTINCTS. another by insensible degrees; and a common fact or tendency of the system may be at the foundation of both. THE PRIMITIVE COMBINED MOVEMENTS. 4, Of the primitive combined movements, in the human subject, the leading example is the locomotive rhythm. The instinctive character of locomotion, so obvious in the inferior animals, is less apparent in ourselves, seeing that the power of walking is not possessed by us until about a year after birth. Nevertheless, there are certain strong presumptions in favour of an original endowment entering into our aptitude for locomotion. (1.) The analogy of the inferior quadrupeds countenances the probability of a locomotive rhythm in the human limbs. The community of structure of the vertebrate type is sufficiently close, to involve such a deep peculiarity of the nervous system as this. What nature has done for the calf, towards one of the essential accomplishments of an animal, is not unlikely to be done in some degree for man. To equip a creature for walking erect would doubtless be far more difficult, and might surpass the utmost limits of the primitive structural arrangements ; but seeing that the very same alternation of limb enters into both kinds, and that nature gives this power of alternation in the one case, we may fairly suppose that the same power is given in the other also. (2.) It is a matter of fact and observation, that the alter- nation of the lower limbs is instinctive in man. I appeal to the spontaneous movements of infancy as the proof. Mark a child jumping in the arms, or lying on its back kicking ; observe the action of the two legs, and you will find that the child shoots them out by turns with great vigour and rapidity. Notice also when it first puts its feet to the ground; long before it can balance itself, you may see it alternating the limbs to a full walking sweep. Only in virtue of this instinc- tive alternation is walking so soon possible to be attained. THE LOCOMOTIVE RHYTHM. 263 No other combination equally complex could be acquired at the end of the first year. Both a vigorous spontaneous im- pulse to move the lower limbs, and a rhythmical or alternating direction given to this impulse, are concerned in this very early acquisition. Let the attempt be made to teach a child to walk sidewaysat the same age, and we should entirely fail for want of a primitive tendency to commence upon. (3.) It has been already seen, that the cerebellum is pro- bably concerned in the maintenance of combined or co-ordi- nated movements. We have proof that these movements can be sustained without the cerebral hemispheres, but hardly without the cerebellum. Now, that the cerebellum should be well developed in man, and yet not be able to effect those harmonized arrangements found in the inferior vertebrata, is altogether improbable. Unless some mode of invalidating these facts can be pointed out, the reasonable conclusion will be, that there is in the human subject a pre-established adaptation for locomotive movements, which adaptation we shall now attempt to analyze. 5. First, it involves the reciprocation or vibration of the limb. Confining ourselves to one leg, we can see that this swings back and fore like a pendulum, implying that there is a nervous arrangement, such that the completed movement forward sets on the commencing movement backward, and conversely. ‘The two antagonist sets of muscles concerned in walking, are chiefly members of the two great general divisions of flexor and extensor muscles. Every moving member must have two opposing muscles or sets of muscles attached to it, and, between these, the limb is moved to and fro at pleasure. There is obviously an organized con- nexion between antagonist muscles generally, so as to give spontaneously a swinging or reciprocating movement to the parts ; in other words, when any member is carried to its full swing in one direction, there is an impulse generated and diffused towards the opposing muscles, to bring it back, or carry it in the other direction. Of course this reaction will be most strongly brought out, on occasions when the commencing 264 THE INSTINCTS. movement takes a wide and energetic sweep. Thus in a swing of the arm carried up so as to point perpendicularly upward, we may discern an impulse in the opposing muscles to come into play in order to bring it down. Every swing- ing motion, whether of arm, leg, trunk, head, jaw, if not entirely due to volition, which it would be difficult to prove, must be supported by an arrangement of the nature now described.* In walking, there is also, of course, a pendulous swing of the leg, arising out of mere mechanical causes. Like any other body hanging loose, the leg is really and truly a pen- * On the antagonism of muscular movements generally, I quote the following statements from Miiller :— ‘There are groups of muscles opposed to each other in their action in almost all parts of the body. The extremities have flexors and extensors, supinators and pronators, abductors and adductors, and rotators inwards and rotators outwards. Frequently the opposed groups of muscles have different nerves. ‘Thus the flexors of the hand and fingers derive their nervous fibrils from the median and ulnar nerves; the extensors theirs from the radial nerve; the flexors of the fore-arm are supplied by the musculo-cutaneous ; the extensors by the radial nerve. The crural nerve supplies the nervous fibres for the extensors of the leg; the ischiadic those for the flexors. The perineal muscles, which raise the outer border of the foot, derive their nervous fibres from the perineal nerve ; the tibialis posticus, which raises the inner border of the foot, is supplied by the tibial nerve. The circumstance of the convulsive motions in affections of the spinal cord being frequently such as to curve the body in a particular direction, shows that there must be something in the disposition of the nervous fibres in the central organs which facilitates the simultaneous excitement to action of particular sets of muscles, as the flexors, or extensors, &c.; although Bellingeri’s opinion, that the anterior columns of the spinal cord serve for the motions of flexion, the posterior for those of extension, is based on no sufficient facts. Too much importance, however, must not be given to the above remark relative to distinct nerves supplying the different groups of muscles; it is not a constant fact. Sometimes the same nerve gives branches to muscles opposed in action ; the ninth, or hypo-glossal nerve, supplies both the muscles which draw the hyoid bone forwards, and one muscle which retracts it; the perineal nerve supplies the perineal muscles, which raise the outer border of the foot, and the tibialis anticus, which opposes this motion. Antagonist muscles can, moreover, be most easily made to combine in action ; thus the perineal muscles and the anterior tibial, acting together, raise the foot. The flexor carpi radialis and the extensor carpi radialis can combine so as to abduct the hand.’—p. 925. ALTERNATING MOVEMENT OF THE LIMBS. 265 dulum, and when thrown back begins to move forward of its own accord. Again, the extensor muscles, which maintain the body in an erect position, are antagonized by the weight of the parts ; hence in dancing up and down, the downward movement may take place by simply relaxing the tension of the supporting muscles. In the same manner, the jaw tends to drop of its own accord. 6. Secondly, there is implied in locomotion, an alternate movement of corresponding limbs, or an alternation of the two sides of the body. After one leg has made its forward sweep, an impulse has to be given to the other leg to commence a movement in the same course. ‘The two sides of the body must be so related, that the full stretch of the muscles of the one side originates a stimulus to those of the other. Nothing less would suffice to enable a new-born calf to walk. The alternation between the right and left legs, both fore and hind, must be firmly established in the animal’s organization by a proper arrangement of the nerves and nerve centres. And if the power of walking in human beings be assisted by primi- tive impulses and arrangements, this specific provision is necessarily implied. The alternation of the two sides in locomotion extends beyond the muscles of the limbs; the whole trunk and head sway in harmony with the members, both in quadrupeds and in man. There are some important exceptions to this alternating arrangement; but these are of a kind to place in a stronger light the examples of it now quoted. The two eyes are made to move together, and never alternate. This arrangement is the most prominent, but not the only, example of assoczated simultaneous movements. It has, doubtless, to do with the unity and singleness of the act of vision. Moreover, if we observe the early movements of the arms in children, we shall find in them more of the tendency to act together than to alternate; showing, as we might otherwise infer, that the impulse of alternation of the limbs is not so deep-seated an instinct in man as in quadrupeds. In like manner, the move- °66 THE INSTINCTS. ments of the features are, for the most part, the same on both sides of the face. 7. Thirdly. The locomotion of animals moving on all fours suggests a further necessity of primitive adjustment. It is requisite that there should be some provision for keep- ing the fore and hind legs in proper relation and rhythm. Something of the nature of the vermicular movement (that is, the locomotion of worms), or the movements of the alimen- tary canal, needs to be assumed in this case. Such a con- nexion must exist between the fore and hind segments, in order that the movements of the one may stimulate in suc- cession the movements of the other, by a nervous propagation along the spinal cord to the cerebellum, or other centre go- verning the primitive rhythmical motions. In the crawling of reptiles, it is obvious that the muscular contraction in one segment or circle, must yield a stimulus to a nerve in con- nexion with the next circle, which is made to contract in consequence, and furnish a stimulus to the third, and so on through the whole line of the body: the action of the intes- tines being almost the same. Ina dog, we see the move- ment of the limbs propagated to the tail. Each species of animal has its particular formula of ordering the legs in walking, determined, it may be, in part by the shape of the body, but duly transmitted in the breed as a property of its structure. ‘lhe shamble of the elephant represents one spe- cies of rhythm; while the horse can pass through all the varieties of walk, gallop, and canter. In climbing, too, the alternation and the propagation both come into play as helps. In swimming, both are likewise apparent. 8. I must now mention more particularly the associated or consensual movements, or those that are so connected as to occur together. The most perfect example of this is in vision. In order to make the two eyes act together, the corresponding muscles of each must be simultaneously excited by the nerves. The following are the facts connected with this interesting case. I quote from Miiller. ‘Some of the most remarkable facts illustrating the association PRIMITIVE SIMULTANEOUS MOVEMENTS. 267 and antagonism of muscular actions, are presented by the muscles which move the eyes. The corresponding branches of the third, or motor oculi, nerve of the two sides have a remarkable innate tendency to consensual action, a tendency which cannot be ascribed to habit. The two eyes, whether moved upwards, downwards, or inwards, must always move together; it is quite impossible to direct one eye upwards and the other downwards at the same time. This tendency to consensual action is evi- denced from the time of birth; it must therefore be owing to some peculiarity of structure at the origins of the two nerves. The association in action of the corresponding branches of the two nervi motores oculi, renders the absence of such tendency to consensual motion in the two external recti muscles and the sixth nerves more striking. We do, it is true, in a certain measure cause the two external recti muscles to act together when we restore the two eyes, of which the axes are converging, to the parallel direction; but there the power of consensual action ends; the two eyes can never be made to diverge, however great the effort exerted todo so. There is an innate tendency and irresistible impulse in the corresponding branches of the third nerve to associate action; while in the sixth nerves not only is this tendency absent, but the strong action of one of these nerves is incompatible with the action of the other. These innate tendencies, in the third and sixth nerves, are extremely important for the functions of vision: for if, in place of the sixth nerves, the external recti muscles had received each a branch of the third nerve, it would have been impossible to make one of these muscles act without the other; one eye, for example, could not have been directed inwards while the other was directed outwards, so as to preserve the parallelism, or con- vergence of their axes; but they would necessarily have diverged when one rectus externus had been made to act voluntarily. To render possible the motion of one eye inwards, while the other is directed outwards, the external straight muscles have received nerves which have no tendency to consensual action. In conse- quence, however, of the tendency in the two internal straight muscles to associate motion, it is necessary when one eye is directed inwards and the other outwards, that the contraction of the rectus externus of the latter should be so strong as to over- come the associate action of the rectus internus of the same eye ; 268 THE INSTINCTS. and in the effort to direct one eye completely outwards, we actually feel this stronger contraction of the external rectus. These considerations enable us to understand perfectly the hitherto enigmatical fact that, in all vertebrata, the external rectus muscle receives a special nerve. —(p. 929.) The author then goes on to show the relation of the corresponding oblique muscles to each other, and the similar reason there is for having a distinct nerve to the superior oblique or trochlear muscle. An association exists between the adjustment of the iris and the other movements of the eye; thus, whenever the eye is voluntarily directed inwards, the iris contracts. Hence the fact already stated, that the iris is contracted during near vision. 3 Miiller also remarks that ‘the motions very prone to be associated involuntarily, are those of the corresponding parts of the two sides of the body. The motions of the irides, of the muscles of the ear, of the eyelids, and of the extremities, in the attempt to effect opposed motions, are examples of such associations.” Ihave already remarked that this coin- cidence of movements on the two sides, co-exists, in the case of the limbs at least, with an organization for an alter- nating motion. The same author further observes, that ‘the less perfect the action of the nervous system, the more frequently do associated members occur. It is only by education, that we acquire the power of confining the influence of volition, in the production of movements, to a certain number of nervous fibres issuing from the brain. An awkward person, in per- forming one voluntary movement, makes many others, which are produced involuntarily by consensual nervous action.’ (p. 928.) ‘This, however, introduces much larger considera- tions, involving the whole mechanism of emotion and volition. 9. There are various appearances that suggest the ex- istence of a law of general harmony of state throughout the muscular system. In stretching the lower limbs, we feel at HARMONY OF STATE OF THE MOVEMENTS GENERALLY. 269 the same time an impulse to stretch the arms, the trunk, the head, and the features, or to put in action the whole class of extensor or erector muscles. The act of yawning propagates a movement over the whole body. I cannot positively affirm that this may not be explained by similarity of state produc- ing everywhere a similar impulse, but the appearances are more in favour of a harmony of condition produced through the nervous system. When the eye is gazing attentively on an object, the whole body is spontaneously arrested, the features are fixed, the mouth is open; and the same har- monizing fixity is observed in the act of listening. So, a movement in one part propagates itself to other parts, un- less a special check is maintained ; the movements of the eye excite the whole body. Vocal utterance brings on gesti- culation. The pace of movement is also rendered harmoni- ous. Rapid movements of the eye from exciting spectacles make all the other movements rapid. Slow speech is accom- panied by languid gestures. In rapid walking (before the exercise has a derivative effect on the brain), the thoughts are quickened. These movements are to be ranked among the primitive impulses that serve the useful ends of the animal; they count among the practical instincts now under discussion. They cause the animal to come into harmony with the circum- stances that surround it,—to be quiet when the scene is still, to start up and join when others are stirring. This property imparts character to individuals. A person is either slow or vivacious, generally ; the cast of movement is the same in all organs, in action and in thought.. From it arises, likewise, a means of rousing and controlling the actions, thoughts, and passions, of men and animals, In the cries of human beings and animals, which is a part of the expression of feeling, there is a primitive combi- nation or concurrence of movements, remarkable for its uni- formity. The tension of the vocal cords, through the laryngeal muscles, the forced expiration, and the adjustment of the mouth, are united in the same act. Possibly these are con- 270 THE INSTINCTS. curring effects of the emotional wave, or the diffused stimulus of strong feeling, to be noticed presently. 10. There are certain cases, where one sense can appa- rently act for another, previous to experience, as when an animal detects wholesome or unwholesome food by the smell, before tasting it. That the sense of taste should inform us of what is good for digestion (which it does to an im- perfect degree in the human subject), is not surprising, seeing that, in the mouth, the alimentary canal is already commenced ;’ we feel more difficulty in discovering how smell should have this power of anticipating digestion and nutrition. The effluvia that bodies emit to the nostrils, may be a specimen or representative of their substance as applied to the stomach, and may have something of a like effect on the nervous system. We know that the smell of putridity causes loathing and disgust, and that an attempt to eat such material would only complete the effect already begun ; while, on the other hand, substances that have a sweet or fresh flavour, would in all probability be free from nausea in the stomach. On the general fact of one sense acting for another by way of warning or invitation, it is to be remarked that a deep harmony appears to exist among the different senses, in con- sequence of which we apply common epithets to the objects of all of them. Thus, the effect we call ‘freshness,’ deter- mined by the stimulus of the lungs, the digestion, or the general nervous tone, arises in several of the senses. The difficulty is to find the same external olyect, acting in the same manner upon two or more of them, as in the case of discerning food by the sight, or by the smell. I am of opin- ion that these coincidences, recognized before experience, are very few in number, and that the great safeguard of animals lies in making the direct experiment of eating what comes in their way, and in deciding according to the feel- ings that result therefrom.* * It is a fact that lambs commence eating, not the short tender grass, but the long and dried tops. TRANSFERENCE OF SENSATIONS, 271 Among concurrences in Sensation, there may also be noticed the facts known as the transference, radiation, and reflexion of sensations. Reference has already been made (Reriex Actions, p. 250) to the tendency of violent nervous stimulation to extend its sphere into collateral tracks. There are certain cases of definite and uniform transference of the seat of a sensation to a distant locality. In disease of the hip, the pain is felt in the knee ; when the kidney is the seat of irritation the feeling of pain may be localized in the heel; certain diseases of the brain are accompanied with pains in the limbs (Marshall’s Physiology, Vol. L., p. 347). THE INSTINCTIVE PLAY OF FEELING. 11. In following out our present object, which is to pass in review all that is primitive among the sensibilities and the activities of the mental system, we shall next consider the instinctive or original mechanism for the expression of Feeling.* It is well known that some of the most con- spicuous among the manifestations of human feeling, as Laughter and Tears, belong to us from our birth. Education here finds work in repressing original impulses, no less than in imparting new and artificial forms of emotional display. It will be instructive to quote the section devoted to this subject in Miiller’s Physiology. The professed title of the section is, Movements due to the Passions of the Mind. * T have already referred (see p. 258), to the general law which I believe connects together emotion, or feeling, and those physical activities of the frame known as the expression or manifestation of feeling. The movements and display caused by mental excitement have been commonly regarded as merely incidental to certain of the stronger feelings, and little attention has been paid to them in the scientific consideration of the mind. For my own part, however, I look upon these active gestures as a constituent part of the complex fact of consciousness, in every form and variety. I do not say but we may have feelings that do not give rise to any visible stir of the active members, either in consequence of voluntary suppression, or because the diffused stimulus is too weak to overcome the inertia of the parts to be moved,—but I mean to affirm that with feeling there always is a freely diffused current of nervous activity, tending to produce movements, gesture, expression, and all the other effects described in the course of the next few pages.—See ‘The Emotions and the Will,’ Emotions, Chap. I., § 2. 272 THE INSTINCTS. ‘It is principally the respiratory portion of the nervous system which is involuntarily excited to the production of mus- cular actions by passions of the mind. Here again we see that any sudden change in the state of the brain, propagated to the medulla oblongata, immediately causes a change of action in the respiratory muscles, through the medium of the respiratory nerves, including the respiratory nerve of the face. There are no data for either proving or refuting the hypothesis, that the passions have their seat of action in a particular part of the brain, whence their effects might emanate. But these effects are observed to be transmitted im all directions* by the motor nervous fibres, which, according to the nature of the passion, are either excited or weakened in action, or completely paralyzed for the time. ‘The exciting passions give rise to spasms, and frequently even to convulsive motions affecting the muscles supplied by the respiratory and facial nerves. Not only are the features dis- torted, but the actions of the respiratory muscles are so changed as to produce the movements of crying, sighing, and sobbing. Any passion of whatever nature, if of sufficient intensity, may give rise to crying and sobbing. Weeping may be produced by joy, pain, anger, or rage. During the sway of depressing pas- sions, such as anxiety, fear, or terror, all the muscles of the body become relaxed, the motor influence of the brain and spinal cord being depressed. The feet will not support the body, the features hang as without life, the eye is fixed, the look is completely vacant and void of expression, the voice feeble or extinct. Fre- quently the state of the feelings under the influence of passion is of a mixed character ; the mind is unable to free itself from the depressing idea, yet the effort to conquer this gives rise to an excited action of the brain. In these mixed passions the expres- sion of relaxation in certain muscles,—in the face, for example,— may be combined with the active state of others, so that the features are distorted, whether in consequence merely of the antagonizing action of the opposite muscles being paralyzed, or by a really convulsive contraction. Frequently also, both in the mixed and the depressing passions, some muscles of the face are affected with tremors. The voluntary motion of a muscle half * Italics mine. NERVES OF EXPRESSION OF THE FEATURES. 273 paralyzed by the influence of passion is frequently of a tremulous character, in consequence of its being no longer completely under the influence of the will. We experience this particularly in the muscles of the face, when, during the sway of a depressing or mixed passion, we endeavour to excite them to voluntary action ; the muscles of the organ of voice also, under such circumstances, tremble in their action, and the words attempted to be uttered are tremulous. ‘ The nerve most prone to indicate the state of the mind during passion is the facial ;* it is the nerve of physiognomic expression, and its sphere of action becomes more and more limited in different animals, in proportion as the features lose their mobility and ex- pressive character. In birds, it has no influence on the expression of the face ; those only of its branches exist which are distributed to the muscles of the hyoid bone and the cutaneous muscle of the neck ; and the erection of the skin of the neck, or, in some birds, of the ear feathers, is in them the only movement by which the facial nerve serves to indicate the passions. Next to the facial, the respiratory nerves,— those of the internal organs of respira- tion, the laryngeal and phrenic nerves,t as well as those of the external thoracic and abdominal muscles—are most susceptible of the influence of the passions. But when the disturbance of the feelings is very intense, all the spinal nerves become affected, to the extent of imperfect paralysis, or the excitement of trembling of the whole body. ‘The completely different expression of the features in different passions shows that, according to the kind of feeling excited, en- tirely different groups of the fibres of the facial nerve are acted on. Of the cause of this we are quite ignorant. ‘The disturbed action of the heart during mental emotions is a remarkable instance of the influence of the passions over the move- ments of organs supplied by the sympathetic nerve.’—p. 932-4. 12. With regard to the Movements of the Face, Sir Charles * ‘The facial nerve is the motor nerve of the face. It is distributed to the muscles of the ear and of the scalp; to those of the mouth, nose, and eyelids ; and to the cutaneous muscles of the neck.’ + The laryngeal nerves are distributed to the different parts of the larynx, and are, therefore, instrumental. in stimulating the voice. The phrenic, or diaphragmatic nerve, is the special nerve of the diaphragm. 18 274 THE INSTINCTS. Bell is of opinion, that many of them are secondary to the movements of respiration, He regards the heart and the lungs as the great primary sources of expression—the organs first affected by the emotional excitement of the brain. He calls attention to ‘the extent of the actions of respiration ; the remoteness of the parts agitated in sympathy with the heart. The act of respiration is not limited to the trunk; the actions of certain muscles of the windpipe, the throat, the lips, the nostrils, are necessary to expand those tubes and openings, so that the air may be admitted through them in respiration with a freedom corresponding to the increased action of the chest. Without this, the sides of these pliant tubes would fall together, and we should be suffocated by exertion or passion. Let us consider how many muscles are combined in the single act of breathing—how many are added in the act of coughing—how these are changed and modified in sneezing ;—let us reflect on the various combinations of muscles of the throat, windpipe, tongue, lips, in speaking and singing,* and we shall be able justly to estimate the extent of the muscles which are associated with the proper or simple act of dilating and compressing the chest. But how much more numerous are the changes wrought upon these muscles when nature employs them in the double capacity of communicating our thoughts and feelings ; not in the language of sounds merely, but in the language of expression of the countenance also; for certainly the one is as much their office as the other.’ ‘Let us see how the machine works. Observe a man threat- ened with suffocation: remark the sudden and wild energy that pervades every feature ; the contractions of the throat, the gasp- ing and the spasmodic twitchings of his face, the heaving of his chest and shoulders, and how he stretches his hand and catches like a drowning man. These are efforts made under the oppres- sive intolerable sensation at his heart; and the means which nature employs, to guard and preserve the animal machine, giving to the vital organ a sensibility that excites to the utmost exertion.’ —Anatomy of Expression, 3rd Edition, p. 91. This last illustration does not decide the point as to the * These, however, are not primitive or instinctive associations, the class that we are most interested in tracing out at present. MOVEMENTS OF EXPRESSION. 275 dependence of the contortion of the features upon the respi- ratory organs, inasmuch as the state of intense pain supposed would excite every part of the body by direct action. The previous remarks on the necessity there is for movements of the respiratory passages,—the throat, mouth, and nostrils,— to accompany the action of the lungs, are very much in favour of the author’s view. But that the action on the face is not wholly a conse- quence of respiratory excitement, 1s decisively proved by the expression of the eyes, for this in no way ministers to the breathing function. We are, therefore, led to conclude that, while a certain amount of the facial expression is due to the sympathy ur association of the parts with the movements of the lungs, there still remains a source of independent ex- citement derived from the brain at first hand, and through the same common impulse that affects the respiratory, the vocal, and other organs. This distinctness of action is recognized in the passage above quoted from Miiller. 13. In tracing out systematically and minutely the physi- cal accompaniments of states of feeling, there is observable a broad and fundamental division into two classes—namely, effects of movement through the muscular system, and organic effects, or the influences exerted upon the viscera and glandu- lar organs. Let us consider first the Movements. We find certain muscles more particularly acted on under feeling, and named, for that reason, muscles of Expression. Of those more susceptible regions, our attention is specially called to the Face. The muscles of the face, whereby all the movements are sustained, are arranged round three distinct centres,—the Eyes, the Nose, and the Mouth. The mouth has the largest number of muscles, and is the most easily affected by states of feeling. The nose is the least endowed with mobility. The muscles of the Eyebrow have been already pointed out. The occipito-frontalis descends over the forehead, and is inserted into the eyebrow ; this it raises or arches. It is opposed by the corrugator supercilu, which corrugates or 276 THE INSTINCTS. wrinkles the forehead, drawing the eyebrows together. These are pre-eminently muscles of expression, although also em- ployed as voluntary muscles for the purposes of vision. They are emotionally moved by opposite states of feeling, the one in the more pleasing emotions, the other in pain, doubt, and embarrassment ; and the appearance that they cause to a spectator suggests, by association, the ccrresponding states of mind. The orbicular muscle of the eyelids, which closes the eye, is of the nature of a sphincter, like the muscle surround- ing the mouth, and constituting the lips. This is opposed by the levator palpebre, or the elevating muscle of the upper eyelid, which opens the eye, both voluntarily and under emo- tion. The tensor tarst ‘is a very thin, small muscle, placed at the inner side of the orbit, resting against the fibrous covering of the lachrymal sac, and behind the tendon of the orbicularis.’ | ‘The corrugator muscle, being fixed at its inner extremity, draws the eyebrow and eyelid inwards, and throws the skin into perpendicular lines or folds, as in frowning. The occipito-frontalis will, on the contrary, elevate the brow, and wrinkle the skin transversely ; which actions are so frequently repeated by most persons, and so constantly by some of a particular temperament, that the skin is marked permanently by lines in the situations just referred to. The orbicular muscle is the sphincter of the eyelids. It closes them firmly, and at the same time draws them to the inner angle of the orbit, which is its fixed point of attach- ment. The levator palpebree is the direct antagonist of the orbicular muscle; for it raises the upper eyelid, and uncovers the globe of the eye. ‘The tensor tarsi draws the eyelid towards the nose, and presses the orifices of the lachrymal ducts close to the surface of the globe of the eye. It may thus facilitate the entrance of the tears into the ducts, and promote their passage towards the nose.’—QUAIN. 14. The muscles of the Nose are, first, the pyramidal, ‘which rests on the nasal bone, and appears like a prolon- gation of the occipito-frontalis, with whose fibres it is inti- mately connected. It extends from the root of the nose to about half-way down, where it becomes tendinous, and unites MUSCLES OF THE FACE. 277 with the compressor naris. Its chief effect seems to be that of giving a fixed point of attachment to the frontal muscle ; it also wrinkles the skin at the root of the nose.’ The common elevator of the lip and nose lies along the side and wing of the nose, extending from the inner margin of the orbit to the upper lip. It raises the wing of the nose and the upper lip together. The compressor naris ‘is a thin, small triangular muscle, which lies close upon the superior maxilla and the side of the nose, being transverse from without inwards and upwards.’ Contrary to its name, the principal action of it must be to expand the nostril by raising the lateral cartilage. This is an action in obvious harmony with respiration, seeing that it opens the nasal passage. The depressor ale nasi ‘is a small flat muscle, lying be- tween the mucous membrane and the muscular structure of the lip, with which its fibres are closely connected.’ Of these and other bundles of muscular fibres, traceable on the small cartilages of the nose, the only considerable or powerful muscle is the Common Elevator of the Lip and Nose, which is thoroughly under the command of the will, and produces a very marked contortion of feature, wrinkling the nose and raising the upper lip. In expressing disgust at a bad smell, this muscle is strongly brought into play, and thence it comes to be employed in expressing disgusts gene- rally. It is, however, employed without any such intention. 15. There are nine muscles connected with the move- ments of the Mouth. One of them, the orbicularis, is single, and surrounds and forms the aperture itself; the other eight are pairs, and radiate from this as from a centre. The proper elevator of the upper lip extends from the lower | border of the orbit to the upper lip, lying close to the border of the common elevator of the lip and nose. When the lip is raised without raising the nose, which is not a very easy act, this muscle is the instrument. The elevator of the angle of the mouth ‘lies beneath the preceding, and partly concealed by it.’ 278 THE INSTINCTS. ‘The zygomatict are two narrow fasciculi of muscular fibres, extending obliquely from the most prominent point of the cheek to the angle of the mouth, one being larger and longer than the other. The elevator of the angle of the mouth, and the zygomatic muscles, serve to retract the angle of the mouth in smiling; they are therefore muscles of ex- pression. The two first of these four muscles are concerned in raising the upper lip, but they do not act very powerfully, or conspicuously. In fact, the upper lip is a feature remarkable for fixity, as compared with the under lip, and is not often elevated in man; and on the occasions when it is raised, this is done by the common elevator rather than by its own pro- per muscles. The region of the lower jaw contains three muscles, the depressor of the angle of the mouth, the depressor of the lower lip, and the elevator of the lower lip. The depressor of the angle of the mouth lies at the side and lower part of the face, being extended from the angle of the mouth to the lower jaw. The depressor of the lower lip is a small square muscle, lying nearer to the middle line of the chin than the preceding, by which it is partly concealed. It arises from the fore part of the lower jaw-bone, and is inserted into the lower lip ; its fibres become blended with those of the orbicular muscle of the mouth, having been previously united with those of its fellow on the opposite side. The elevator of the lower lip arises from a slight pit below the teeth-sockets of the lower jaw, near the middle line of the jaw, and is inserted into the tegument of the chin, which it lifts when in action. The remaining muscles of the mouth are unconnected with either jaw, having a sort of middle position between them. ‘At each side of the face, in the part called the “ cheek,” is a muscle—the buccinator; and, round the margin of the mouth, one—the orbicularis oris.’ . EXPRESSION OF THE MOUTH. 279 ‘The buccinator is a thin, flat plane of muscular fibres, quadrilateral in figure, occupying the interval between the jaws. This muscle is exerted in masticating the food, and receives nerves from the same source as the masseter, which is one of the principal muscles engaged in the act of mas- tication. The orbicularis oris ‘belongs to the class of sphincter muscles, and, like them, is elliptic in form, and composed of concentric fibres, so placed as to surround the aperture of the mouth ; but with this peculiarity, that the fibres are not con- tinued from one lip into the other. The muscle is flat and thin ; its inner surface being in contact with the coronary artery of the lips, labial glands, and the mucous membrane ; the external with the skin and the fibres of the different muscles which converge towards the margin of the mouth.’ ‘The aperture of the mouth is susceptible of considerable dilatation and contraction; the former being affected by the different muscles which converge to it, and which may be com- pared to retractors drawing, with different degrees of obliquity, the lips, or their angles, in the direction of their respective points of attachment. The elevators are necessarily placed at the upper part of the face, the depressors in the opposite situation, and the proper retractors on each side; and these are the zygomatici and the buccinators. The buccinators also contract and compress the cheeks ; this power is brought into play when any substance becomes lodged in the interval between them and the jaws.’ 16. But it would be a mistake to confine the wave of movement to the Face, although this is the region where it is pre-eminent. The Voice acts in concert, giving forth sounds that are characteristically different under joy or woe, affection or rage. (The mechanism of the vocal organs is described in a separate section.) Among muscles specially affected under mental states, we should not omit the Diaphragm. All the muscles of the body may be thrown into agitation under a wave of strong feeling; the movements, gesticulations, and carriage of the frame at any one moment are confidently 280 THE INSTINCTS. referred to as proof of a certain emotional state. In Joyful moods, an abundance of gesticulation is often displayed in company with the play of the features and the voice. In Sorrow, there is sometimes a wild frantic excitement, but more commonly we observe the inaction and collapse of the moving members generally. In Wonder, there is apt to be a liveliness of movement; so in Rage; while a tremulous quaking is the characteristic of Fear. 17. I must next advert to the Organic effects of emotion, which are quite equal in point of importance to the muscular. The viscera and glandular organs that are known to be the most decisively acted on are the following :— (1.) The Lachrymal Gland and Sac. The Anatomy of this part has been adverted to in speaking of its associated organ, the Kye. ‘The effusion of Tears from the gland is constantly going on during waking hours. Certain states of emotion,—tenderness, grief, excessive joy,—cause the liquid to be secreted and poured out in large quantities, so as to moisten the eye, and overflow upon the cheek. By this outpouring, a relief is often experienced under oppressive pain, the physical circumstance being apparently the dis- charging of the congested vessels of the brain. A strong sensibility undoubtedly lodges in the lachrymal organ, the proof of a high cerebral connexion. The ordinary and healthy flow of this secretion, when conscious, is connected with a comfortable and genial feeling ; in the convulsive sob, not only is the quantity profuse, but the quality would appear to be changed to a strong brine. (2.) The Seawal Organs. These organs are both sources of feeling when directly acted on, and the recipients of influence from the brain under many states of feeling other- wise arising. ‘They are a striking illustration of the fact taat our emotions are not governed by the brain alone, but by that in conjunction with the other organs of the body. No cerebral change is known to take place at puberty ; nevertheless, a grand extension of the emotional suscepti- bilities is manifest at that season. Although the organs may OLGANIC EFFECTS OF FEELING. 281 not receive their appropriate stimulation from without, the mere circumstance of their full development, as an additional echo to the nervous waves diffused from the cerebrum, alters the whole tone of the feelings of the mind, like the addition of a new range of pipes to a wind instrument. It is the con- tribution of a resonani, as well as of a sensitive part. (3.) The Digestive Organs. These have been already fully described ; and their influence upon the mental state has also been dwelt upon. In the present connexion, we have to advert more particularly to the reciprocal influence of the mind upon them. It may be doubted whether any consider- able emotion passes over us without telling upon the pro- cesses of digestion, either to quicken or to depress them. All the depressing and perturbing passions are known to take away appetite, to arrest the healthy action of the stomach, liver, bowels, &c. A hilaricus excitement, within limits, stimulates those functions; although joy may be so intense as to produce the perturbing effect ; in which case, however, it may be noted that the genuine charm or fasci- nation is apt to give place to mere tumultuous passion. The influence of the feelings in digestion is seen in a most palpable form in the process of Salivation. In Fear, the mouth is parched by the suppression of the flow of the saliva : a precise analogy to what takes place with the gastric juice in the stomach. An equally signal example in the same connexion is the choking sensation in the throat during a paroxysm of grief. The muscles of the pharynx, which are, as it were, the beginning of the muscular coat of the alimentary canal, are spasmodically contracted. The remarkable sensibility of this part during various emotions, is to be considered as only a higher degree of the sensibility of the intestine generally. The sum of the whole effect is considerable in mass, althougn wanting in acuteness. In pleasurable emotion even, a titilla- tion of the throat is sometimes perceptible. . (4.) The Skin. The cutaneous perspiration is liable to be acted on during strong feelings. The cold sweat from fear or 282 THE INSTINCTS. depressing passion, is a sudden discharge from the sudorific glands of the skin. We know, from the altered odour of the insensible or gaseous perspiration during strong excitement, how amenable the functions of the skin are to this cause. It may be presumed, on the other hand, that pleasurable elation exerts a genial influence on all those functions, A similar line of remark would apply to the Kidneys. (5.) The Heart. The propulsive power of the heart’s action varies with mental states as well with physical health and vigour. Some feelings are stimulants to add to the power, while great pains, fright, and depression reduce the action. Miiller remarks above, that the disturbance of the heart is a proof of the great range of an emotional wave ; or its extending beyond the sphere of the cerebral nerves to parts affected by the sympathetic nerve. (6.) The Lungs. The quotations above given, from Miiller and Bell, sufficiently express the influence of emotional states on the movements of respiration. The immediate effect of in- creasing or diminishing the movements will be to increase or to diminish the rate of exchange of the two gases—oxygen and carbonic acid—at the surface of the lungs. We cannot show that this exchange is influenced, through the nerves, other- wise than by the altered energy of the breathing movements. (7.) The Lacteal Gland in woman. Besides the six organs now enumerated as common to the two sexes, we must reckon the speciality of women, namely, the Secretion of the Milk. Like all the others, this secretion is genial, comfort- able, and healthy, during some states of mind, while depress- ing passions check and poison it. .As an additional seat of sensibility, and an additional resonance to the diffused wave of feeling, the organ might be expected to render the female temperament to a certain degree more emotional than the male, especially after child-bearing has brought it into full play. 18. The question now presents itself : can any general law be pointed out as giving a clue to this blending of physical effects with states of feeling ? A very considerable number of the facts may be brought GENERAL PRINCIPLE OF EMOTIONAL EXPRESSION. 283 under the following principle, namely, that states of pleaswre are connected with an increase, and states of pain with an abatement, of some, or all, of the vital functions, Let us first revert to the known Agents, or stimulants, of pleasurable feeling, and compare them with their opposites. Beginning with the muscular Feelings, it is known that exercise is pleasurable only when we are expending surplus energy, and thereby making the blood to course through the system more rapidly. Both the heart and the lungs are quickened by bodily exercise ; while an accumulation of force, which it would be painful to restrain, finds a vent. Let the stage of fatigue, however, be reached, and let the spur to exertion be still continued, we then witness the concurring circumstances of the sense of pain, and the lowering of vital energy. When exercise is prolonged to the point of painful fatigue, there is an actual diminution in the amount of carbonic acid given off by the lungs, showing an enfeebled respiration. The action of the heart is likewise enfeebled, and thus upon two vital organs has fallen an abatement of energy. It is equally certain that the digestive power is reduced under the same circumstances. Then, as to Muscular Repose, a feeling highly pleasurable, especially if the amount of exercise has been well adjusted to the strength, the generalization is not less applicable. What happens in resting after exertion is evidently this :—The muscles have expended all their surplus energy, and in so doing have stimulated several of the vital functions, such as the Heart, the Lungs, and the Skin. The Digestive function is not directly quickened under exercise, but rather retarded by the concentrating of the nervous currents in the muscles. Still, much good has been effected by the exalted operation of these other organs ; and now, at the stage of repose, the power hitherto compelled into one exclusive direction, being set free, returns to the other parts, and especially to the Digestive functions, whose exaltation through that circum- stance coincides with the pleasant sensibility of the resting posture. Thus, while in Repose we have the cessation of one 284 THE INSTINCTS. vital energy, a corresponding increase takes place in several others: the organic functions generally are heightened, as the mental and the muscular activities subside. Regarding the Sensations of Organic Life, commentary is almost superfluous. There are but few seeming exceptions to the rule, that organic pains are connected with the loss of power in some vital function, and organic pleasures with the opposite. Wounds, hurts, diseases, suffocation, thirst, hunger, nausea, are so many assaults upon our vitality. Taken in the gross, there can be no dispute as to the general tendency. As to the exceptions, the study of them, in some instances at least, serves to elucidate the principle. Cold is a painful agent; yet we know that it increases the functional activity of the muscles, the nerves, the lungs, and the digestion— depressing only one organ, the skin. We may hence infer that the skin is an organ of greater sensibility than any of these others. The stimulation is sometimes obtained without the depression, as in the reaction after a cold bath, whereby the skin recovers its tone; the whole effect is then exhilarating. When this is not so, we may still desire to precure the organic advantage, though at the expense of a skin pain; as in walk- ing out on a cold day in wiuter. Another apparent exception is the eS absence of all pain in the sick bed; also the happy elation sometimes shown in the last moments of life. These cases prove, what we are already prepared for, by the example of muscular repose already cited, that a high condition of ail the vital functions is not necessary to agreeable sensibility ; and open up the important enquiry, which of these functions are most connected with our happiness, and which least? It is clear that great muscular energy, exerted or possessed, is not an immediate essential, although an indirect adjunct of consi- derable value. It is equally clear that the power of digestion, and a certain degree of animal heat, are indispensable. There are states of inanition, of indigestion, and of chillness, that would sink the loftiest spirit into despair. Thus it may he, that the comfort of the bed-ridden patient, and the placidity EXCEPTIONS TO THE LAW OF SELF-CONSERVATION, 285 of the dying moments, are in a measure due to the fact, that disease has overtaken chiefly the functions that least partici- pate in our sensitive life. Painless extinction is in this way contrasted with suffering continued through a long life. There are parts whose derangement is not felt till on the eve of a fatal issue ; there are others that cannot be impaired without making the fact known, and that may work ill for many years before causing death. Even the organs most connected with mind, next to the brain, may undergo morbid changes that do not prevent them from giving their usual genial response to a pleasurable wave. Obstructed bowels will quench more hap- piness than certain kinds of organic disease of the intestines. The lungs are sometimes at the last stage of decay before affecting the enjoyment of the patient; while the healthiest man is distressed by partial suffocation. When we pass from the Organic Feelings to the Sensa- tions of the five senses, we miss the same decided coincidences. In Taste and Smell, for example, the rule might hold with those sensations that involve important vital organs as the Stomach and the Lungs, but scarcely with the proper sensibilities of the senses. A taste merely sweet, without being a relish, gives pleasure; but we cannot, in this instance, assign any marked increase of vital function. A bitter taste can even operate as a tonic. So with odours. We have sweet odours that are sickly, in other words, depressing; and although some of the mal-odours may lower the vital power, this does not always happen, and there is no proportion between the pain and the lowering of the functions. Soft and agreeable touches have an effect on the mind somewhat analogous to agreeable warmth; but we cannot attribute the same physical consequences to the one as to the other. On the other hand, the painful smart, far from diminishing the energies, rather excites them for a time at least ; so that here too the induction would appear to fail. The pleasures of Hearing and Sight are probably accom- panied with increased vital energy to some extent. Whena person is brought from confinement in the dark to the light 286 THE INSTINCTS. of day, there is observed a rise in the pulsation and in the breathing, which is so far in favour of the general doctrine. Still we cannot contend, that the degree of augmented vital energy corresponds always with the degree of the pleasure. In short, the principle that served us so well in summing up most of the organic pleasures and pains, does not apparently hold in the five senses. Some additional mode of action must be sought for, in order to give a complete theory of pleasure and pain. But before enquiring into this supple- mentary law, let us complete the survey of the facts bearing upon the one already announced, by viewing the accompani- ments of feeling under another aspect. 19. Hitherto we have considered the physical agents of pleasure or pain, and have ascertained that in a number of cases, these are agents of bodily exaltation or depression. This does not exhaust the evidence. Another set of proofs is furnished by studying the manifestations under the opposing mental conditions, which will bring under review other plea- sures and pains besides those arising from the Senses. What, then, is the universally observed expression of pleasure, no matter how originating? Can it be better described than in the synonyms of the word pleasure,— such epithets as lively, animated, gay, cheerful, hilarious, applied to the movements and expression,—all tending to suggest that our energies are exalted for the time. In joyful moods, the features are dilated ; the voice is full and strong ; the gesticulation is abundant ; the very thoughts are richer. In the gambols of the young, we see to advantage the coupling of the two facts—mental delight, and bodily energy. Intro- duce some acute misery into the mind at that moment, and all is collapse, as if one had struck a blow at the heart. (I leave out of account at present the one form of uproarious and convulsive grief.) A medical diagnosis would show, beyond question, that the heart and the lungs were lowered in their action just then; and there would be good grounds for inferring an enfeebled condition of the digestive organs. But we can be more particular in our delineation. The EXPRESSION OF THE FACE ANALYZED. 287 expression of the face has been completely analyzed by Sir Charles Bell. In pleasing emotions, the eyebrows are raised and the mouth dilated, the whole effect being to open up the countenance ; in painful emotions, the corrugator of the eye- brow acts according to its name ; the mouth is drawn together, and perhaps depressed at the angles, by the operation of the proper muscle. Now, in the cheerful expression, there is obviously a considerable amount of muscular energy put forth ; a number of comparatively powerful muscles have been prompted to contract through their entire range. Here we have a confirmation of the general principle. It might seem hard to say, why nature selected those muscles for more especial stimulation when the bodily powers respond to a thrill of pleasure. ‘These preferences are obviously a part of our constitution. So far the case accords with our view. But turn now to the painful expression, and what do we find? An apparently mixed effect.* On the one hand, there is a relaxation of those parts that were made tense under a pleasurable wave, which is what we should expect. If this were all, the proof would be complete ; the state of pain would be accompanied with loss of muscular energy in the features of the face. But this is not all. It would appear that new muscles are brought into play, for example, the corrugator of the eyebrows, the orbicular of the mouth, and the depressor of the angle of the mouth. Thus, if energy has been withdrawn from one class, another class has been concurrently stimulated. It is not then loss, but transference, of power that we witness. It was from looking at the matter * ‘Tn sorrow, a general languor pervades the whole countenance. The violence and tension of grief, the lamentations and the tumult, like all strong excitements, gradually exhaust the frame. Sadness and regret, with depres- sion of spirits and fond recollections, succeed ; and lassitude of the whole body, with dejection of the face and heaviness of the eyes, are the most striking characteristics. The lips are relaxed, and the lower jaw drops; the upper eyelid falls and half covers the pupil of the eye. The eye is frequently filled with tears, and the eyebrows take an inclination similar to that which the depressors of the angles of the lips give to the mouth.’— Tie feat i Eiht / ee blag ae Te Chae faite oi aoe, ci cll AN alae Sire a iaiy) Sigs | in ge ae ve bhi Mi) 2 i i hg ee J ates | i” - av ve. atts 7 1 i | ia “5 pees) ae af be. hens ed ae : Mak “ Liter ei, ‘dt pail ) Lo Fr Leaner A? OD Uy, one hay ee ) , . ae of | | 5 rae ty, anahaney? ee at ee ne Hearn hes _ areas: Oui wel NN, ; sent jis "4 4, ‘ t, Sans Hd ult ee AT ie eager Ps Aa : iS " ; YS an) i ‘Arey ee ob« ni ioe A fay 3 RY Abb Py hy iy vi 4 Delian le eae (Yuet Te ilh oe ' ’ ; Me f Pine wi " i us 5 a ‘ ri on U im, we ki ts yi Ras ; ; \ : ha er aay. uy : al \ j ; < 4, : i ; ; aA ye ; ; h rT Teac Pian” Mel bane : a) Salen tay @ a. ; 4° rye y ‘ PQ Al ; + et 5 Tae ae f : ym if , a iT) 4 We! : f t . ». , ‘. | Pan ‘ ° at ms We now proceed to view the Intellect, or the thinking fe function of the mind. The various faculties known as Memory, Judgment, Abstraction, Reason, Imagination,— are modes or varieties of Intellect. Although we can hardly ever exert this portion of cur mental system in separation from the other elements of mind—Feeling and Volition, yet scientific method requires it to be described apart. The primary, or fundamental attributes of Thought, or Intelligence, have been already stated to be, Consciousness of Difference, Consciousness of Agreement, and Retentiveness. The exposition of the Intellect will consist in tracing out the workings of these several attributes; the previous book con- taining the enumeration of all that we at first have to discri- minate, identify, and retain. | (1.) The first and most fundamental property is the Consciousness of Difference, or DISCRIMINATION. To be dis- tinctively affected by two of more successive impressions is the most general fact of consciousness. We are never conscious at all without experiencing transition or change. (This has been called the Law of Relativity.) lw hen the mental outburst is characterized mainly by pleasure or pain, we are said to be under a state of feeling. When the prominent circumstance is discrimination of the two dis- tinct modes of the transition, we are occupied intellectually. There are many transitions that give little or no feeling in the sense of pleasure or pain, and that are attended to as transi- tions, in other words, as Differences. In states of enjoyment or suffering, we cannot be strictly devoid of the consciousness of difference ; but we abstain from the exercise of the dis- ceriminating (and the identifying) function, and follow out the 21 ino ~> 32 / ff ~ B22 THE INTELLECT. consequences of a state of feeling as such, these being to husband the pleasure and abate the pain, by voluntary actions. / In the foregoing detail of the Feelings of Movement and the Sensations, the properties of each, as regards Feeling, and as regards Intellect, have always been kept distinct. In some of the Senses, as the Organic Sensibility, feeling is nearly every thing. In Taste and Smell, both feeling and discrimination are fully manifested. In Touch, and still more in Hearing, and in Sight, there are states of pleasure and of pain, and also a great number of sensations that are indifferent in those respects, and whose character it is to call forth the sensibilities to difference and to agreement. These last are the proper Intellectual Sensations. Thus the degrees of roughness or smoothness, of hardness or softness in Touch, are nothing as feeling, and everything as knowledge. Heat may be in such amount as to give intense pleasure or pain 5 it may also be wanting in either respect, and may occupy the mind purely with the consciousness of degree. The sensa- tions of sound, in the same way, may incline to feeling, as in the pleasure of Music, or to intellect as in articulation. Light, colours, and visible forms have, similarly, a double aspect. The sense of Difference, or Discrimination, has therefore been unavoidably illustrated, almost to exhaustion, in the enumeration of the muscular feelings and the sensations. As ameans of intellectual reproduction—which is a leading function of Intellect, commonly expressed by Memory— the property of Discrimination manifests itself in one form, called the associating principle of Contrast. As identical with the law of the Relativity of all feeling and knowledge, it must emerge at a great many points, and be everywhere tacitly implied. Some notice will have to be taken of acgutred discri- mination, but this is one of the applications of the Retentive power of the mind. The conscious state arising from Agreement in the midst of difference is the natural complement of the foregoing PRIMARY FUNCTIONS OF THE INTELLECT. 323 attribute ; the two together exhaust the primitive forms of intellectual susceptibility. But in the order of exposition, we shall give precedence to the property of Retentiveness, inasmuch as Agreement in its higher applications presupposes the whole range of our acquired knowledge, which depends upon the Retentive function. (2.)[The fundamental property of Intellect, named Re- TENTIVENESS, has two aspects, or degrees. First. The persistence or continuance of mental impres- sions, after the withdrawal of the external agent. | When the ear is struck by a sonorous wave, we have a sensation of sound, but the mental excitement does not die away because the sound ceases ; there is a certain continuing effect, gene- rally much feebler, but varying greatly according to circum- stances, and on some occasions quite equal to the effect of the actual sensation. ‘In consequence of this property, our mental excitement, due to external causes, may greatly outlast the causes themselves ; we are enabled to go on living a life in ideas, in addition to the life in actualities. But this is not all. We have, secondly, the power of recovering, or reviving, under the form of ideas, past or ex- tinct sensations* and feeling of all kinds, without the originals, and by mental agencies alone. / was ms ty latthough we can hardly avoid using such terms as ‘ recover,’ ‘revive, ‘reproduce,’ ‘recollect,’ with reference to Sensations, it is to be borne in mind that there is a radical difference between the Sensation and the recollection of the Sensation, or what is properly termed the Idea. This fundamental and unerasible difference relates to the sense of objective reality which belongs to the sensation, and not to the idea. The sensation caused by the sight of the sun is one thing, and the idea or recollection of the sun is another thing; for although the two resemble each other, they yet differ in this vital parti- cular. For certain purposes (as, for example, in urging the will to pursuit or to avoidance) the idea can stand in the room of the sensation ; the recollection of things answers the same ends as the real presence. But there is one great question connected with our science, in which this distinction is the turning point of the problem, namely, the question as to our perception and belief of an external world. In discussing that subject, we shall have to attend closely to the circumstances that characterize a sensation as distinct from the counter- part idea. | 32-4 THE INTELLECT. After the impression of a sound has ceased entirely, and the mind has been occupied with other things, there is a possibility of recovering from temporary oblivion the idea, or mental effect, without reproducing the actual sound. We remember, or bring back to mind, sights, and sounds, and thoughts, that have not been experienced for months or years. This implies a still higher mode of retentiveness than the previous fact; it supposes that something has been engrained in the mental structure; that an effect has been produced of a kind that succeeding impressions have not been able to blot out. iE Now, one medium of the restoration to consciousness of a eee past state, is the actual presence of some impres- sion that had often occurred im company with that state. Thus we are reminded of a name—as ship, star, tree—by seeing the thang ; the previous concurrence of name and thing has led to a mental companionship between the two. Impres- sions that have frequently accompanied one another in the mind grow together, so as to become at last almost insepar- able: we cannot have one without a disposition or prompting to renew all the rest. This is the highest form of the Reten- tive, or plastic, property of the mind. It will be exemplified at length under the title of Association by Contiguity. } (3.) The remaining property of Intellect is consciousness of AGREEMENT. Besides the consciousness of difference, the mind is also affected by agreement rising out of partial difference. The continuance of the same impression produces no effect, but after experiencing a certain impression and passing away from it to something else, the recurrence of the first causes a certain shock or start,—the shock of recognition ; which is all the greater according as the circumstances of the present and of the past occurrence are different. Change produces one effect, the effect called discrimination ; Similarity in the midst of change produces a new and distinct effect ; and these are the two modes of intellectual stimulation, the two constitu- ents of knowledge. When we see in the child the features of the man, we are struck by agreement in the midst of difference. ‘This power of recognition, identification, or discovery of THE DIVISION INTO FACULTIES. 325 likeness in unlikeness, is another means of bringing to mind past ideas; and is spoken of as the Associating, or Repro- ductive principle of SrMILARITY. We are as often reminded of things by their resemblance to something present, as by their previous proximity to what is now in the view. Con- tiguity and Similarity express two great principles or forces of mental reproduction ; they are distinct powers of the mind, varying in degree among individuals—the one sometimes preponderating, and sometimes the other. The first governs Acquisition, the second Invention. / | The commonly recognized intellectual faculties, enumer- ated by Psychologists with much discrepancy, in so far as they do not involve Feeling and Volition, are resolvable into these three primitive properties of Intellect—Discri- mination, Retention, Similarity. The faculty called Memory is almost exclusively founded in the Retentive power, although sometimes aided by Similarity. The processes of Reason and Abstraction involve Similarity chiefly ; there being in both the identification of resembling things. What is termed Judgment may consist in Discrimination on the one hand, or in the Sense of Agreement on the other: we determine two or more things either to differ or to agree. It is im- possible to find any case of Judging that does not, in the last resort, mean one or other of these two essential activities of the intellect. Lastly, Imagination is a product of all the three fundamentals of our intelligence, with the addition of an element of Emotion. | The exposition of Intellect proper will consist mainly in a full development of the two processes of Retentiveness and Agreement. These will constitute the two first chapters.