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 THE SEGUIN COLLECTION 
 
 OF BOOKS RELATING TO THE^ — f ' 
 NERVOUS SYSTEM 
 THE BEQUEST OF 
 
 EDWARD C. SEGUIN, M.D. 
 
 TO THE DEPARTMENT OF PATHOLOGY OF THE 
 
 COLLEGE OF PHYSICIANS AND SURGEONS, 
 
 NEW YORK. 
 
 Q t A I — This book is not to be removed 
 
 DOOKi^"" \~ "5 from the Department of Pathology. 
 
 COLUMBIA UNIVERSITY 
 THE LIBRARIES 
 
 HEALTH SCIENCES 
 LIBRARY 
 
THE CROONIAN LECTURES 
 
 ON 
 
 CEREBRAL LOCALISATION 
 
THE CROONIAN LECTURES 
 
 ON 
 
 CEREBRAL LOCALISATION. 
 
 DeLIVEEED BEFOIIE THE ROYAL COLLEGE OF PHYSICIANS, 
 
 June. 1890. 
 
 By DAVID FERRIER, MB., LL.D., F.R.8., F.R.C.P., 
 
 Pro/eaaor of Keuropathology , Kimj's College, London ; Physician to King's College Hospital 
 and to the National Hos]>Ual for the Paralysed and Epileptic. 
 
 WITH ILLiSTHATlOMi. 
 
 LONDON : 
 SMITH, ELDER A ^M) CO 
 
 1.'., WATERLOO PL.\CK, 
 1HJ)(). 
 

 Beprinted from the Bkitish Medical Jouenal. 
 
CONTENTS. 
 
 Lecture I. 
 Introductory Remarks— Effects of Ablation of the Cerebral Hemis- 
 pheres: (1) in Osseous Fishes— Vision in Brainless Fishes— 
 Vulpian's Experiments— Steiner's Experiments— (2) in Frogs — 
 Experiments of Goltz and Steiner- Schrader's Experiments: 
 (3) in Birds — Flourens' Experiments — Longet's Experiments — 
 Vision in Brainless Birds — Experiments of McKendrick, etc. — 
 Munk's Experiments — Schrader's Experiments: (4) in Mam- 
 mals — Experiments on Rabbits — Longet's Experiments — 
 Vision inBrain'ess Rabbits— Christiani's Experiments ; Munk's 
 Experiments — Goltz's Experiments on Dog- — General Con- 
 clusions—Intelligence of the Lower Centres— Spontaneity — 
 Conditions of Consciousness — Relations of the Hemispheres 
 to the Lower Centres— The Question of Localisation of 
 Function — Gall's Opinions — Flourens' Doctrines — Bouillaud's 
 Experiments and Observations — Dax's Observations; Broca's 
 Observations — Hughlings Jackson's Views — Brown-S^quard's 
 Views — Exner's Views on Localisation — Fritsch and Hitzig's 
 Experiments— The Author's Experiments— Excitability of the 
 Cerebral Cortex— Mechanical Excitability— Chemical Excit- 
 ability—Electrical Excitability— Diffusion of Currents — Excit- 
 nbility of the Medullary Fibres— Motor Fibres of the Internal 
 Cipsule— Relative Exjitability of the Cortex and Medullary 
 Fibres — Laws of Excitability of the Cortex — Experiments of 
 
 Franck and Pitres PP- 1 — 24 
 
 Lecture II. 
 Electrical Reactions — Prefrontal Area — Oculo-motor Area — Leg 
 Area^Arm Area — ^Area of Face. Tongue, Larynx, etc — Mar- 
 ginal Convolution — Angular Gyrus and Occipital Lobe — 
 Superior Temporal Gyrus — Hippocampal Lobule and Gyrus 
 Hippocampi — Electrical Reactions in Man — Character and 
 Differentiation of the Electrical Reactions — Signification of 
 the Electrical Reactions — Sensory and Motor Centres — The 
 Sensory C^-ntres: (1) The Visual Centres — Electrical Reactions 
 of the Occipito-Angular Region— The Author's Experiments — 
 Experiments of Luciani and Tamburini, Scbafer; Significa- 
 tion of the Oculomotor Reactions — Experiments of Danillo, 
 Bechterew, Munk — The Author's Earlier Experiments on the 
 Angular Gyrus and Occipital Lobe — Later Experiments of the 
 Author and Yeo — Munk's Experiments — Experiments of 
 Horsley and Schafer pp. 27 — 48 
 
 Lecture III. 
 Visual Centre*' Continued — Experiments of Schafer and Sanger- 
 Brown — Effects of Lesions of the Occipito-Temporal Region — 
 Experiments of Sanger-Brown and Gilman-I'hompson — Ex- 
 periments of Lannegrace — Lesions of the Angular Gyrus — 
 Experiments of Munk, Schafer, and the Author — Relations of 
 the Angular Gyrus — Hemiopic Pupillary Reaction — Lanne- 
 grace's Theory of Cerebral Amblyopia — Pathology of Hemiopia 
 ia Man — Lesions of the Cuneus — Word Blindness — Visual 
 Centres in Lower Vertebrates — F]xperiments of Ilitzig, Goltz, 
 Dalton, Munk, Loeb, Luciani, Bechterew, Gilman-Thompson 
 and Sanger-Brown — Munk's Scheme of the Visual Centres in 
 Dogs — Loeb's Experiments — Visual Centres in Rabbits — Visual 
 Centres in Pigeons — Visual Centres in Owls — General 
 Conclusions pp. 51 — 72 
 
 0^^ 
 
VI CONTENTS. 
 
 Lecttjbe IV. 
 The Auditory Centre — Methods of Investigation— Electrical Re- 
 actions — Earlier Experiments of the Author — Experiments of 
 the Author and Yeo — Schafer's Experiments — Recent Experi- 
 ments of the Author — The Auditory Centre according to Munk 
 — Luciani and Tamburini's Experiments — Comparative Ana- 
 tomy of the Auditory Centre — Deafness from Cerebral Disease 
 in Man ; observations of Shaw, Wernicke and Fried! ander — 
 Word-deafness ; its Pathology — Irritative Lesions of Auditory 
 Centre — Atrophy of Auditory Centre — Central Relations of 
 the Auditory Nerve ; observations of Baginsky Flechsig, and 
 Bechterew. Centre of Tactile and Common Sensation — The 
 Sensory Paths in the Spinal Cord — Experiments of Ludwig 
 and Woroschiloff — Ascending Degeneration in Spinal Cord — 
 The Author's Experiments on the Spinal Cord of Monkeys — 
 Hemisection of the Spinal Cord — Paths of the Muscular 
 Sense — Analysis of Recorded Cases — Observations by the 
 Author .■ pp. 75-99 
 
 Lectuee V. 
 Tactile Centre continued — Course of Sensory Tracts towards Brain 
 — Position of Sensory Tracts in eras cerebri — Position of 
 Sensory Tracts in Internal Capsule — Central Relations of 
 Sensory Tracts — Earlier Experiments of the Author on Hip- 
 pocampal Region — Experiments of the Author and Yeo — 
 Experiments of Horsley and Schafer on Hippocampal Region 
 and Gyrus Fornicatus — Relations of the Falciform Lobe — 
 France's observations on Descending Degeneration from 
 Lesions of gyrus fornicatus. Olfactory and Gustatory Centres 
 — Anatomical Relations of Olfactory Tract — Broca's Views — 
 Zuckerkandl on the Anatomy of the Olfactory Centre — Com- 
 parative Anatomy of the Hippocampus ; Sir William Turner's 
 observations — Relations of the Anterior Commissure — Obser- 
 tions of Flower, Meynert, Ganser, etc. — Relations of the 
 Fornix — Electrical Irritation of Hippocampal Lobule — Inves- 
 tigation of the Sense of Smell in Monkeys — Earlier Experi- 
 ments of the Author — Experiments of Schafer and Sanger- 
 Brown — Recent Experiments of the Author — Munk's observa- 
 tions on Dogs — Luciani's Views — Conclusions from Clinical 
 Observations pp. 103-126 
 
 Lectube VI. 
 Motor Centres — Rolandic Area — Effects of Destruction of the 
 Motor Centres in Monkeys — Experiments of the Author, 
 Horsley and Scha^^er — Effects of Lesions of the Marginal 
 Gyrus — The Laryngeal Centres — Bilateral Relations of the 
 Cerebral Hemispheres — Lesions of the Motor Area in Man — 
 Characters of Cortical Paralysis — Goltz's Observations on Dogs 
 — Lesions of the Motor Area and Affections of Sensation — 
 Observations of the Author, Horsley and Schafer, Goltz and 
 Bechterew — Analysis of Clinical Cases — Motor Paralysis and the 
 Muscular Sense — Muscular Sense in Hemiansesthesia — Bastian's 
 Views — Experiments of Marique, Exner and Paneth — Relations 
 of the Spinal and Cerebral Motor Centres. The Frontal 
 Centres — Anatomical Relations of the Frontal Centres — Effects 
 of Electrical Irritation — Destruction of the Post-frontal and 
 Pre-frontal Centres — I'sychical Effects of Lesions of Frontal 
 Lobes— Conclusion pp. 129—152 
 
LECTURE I, 
 
 
 
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ox 
 CEREBRAL LOCALISATION. 
 
 LECTURE I. 
 Introdttotoky. 
 
 Mr. President and Gentlemen,— While highly appreciating 
 the distinguished honour of being appointed Croonian Lecturer of 
 the College of Physicians, I must confess to having undertaken 
 the onerous duties of the oflSce with considerable hesitation and 
 trepidation, for, though the subject which I have chosen is one to 
 which I have devoted a good deal of attention, and which, in one 
 of its aspects, namely, The Localisation of Cerebral Disease, I 
 have already had the honour of discussing before you as Gulston- 
 ian Lecturer, yet, considering the enormous amount of work that 
 has been done in this department in recent years, and the nume- 
 rous problems which still remain unsolved, I have felt that, with 
 my other duties, time and strength would scarcely permit me to 
 do justice to my subject. I could not feel satisfied with merely 
 repeating the views which I have elsewhere, and at various times, 
 expressed on this subject, and which, to many of you at least, are 
 sufficiently well known ; therefore, it seemed necessary that I 
 should, for the purpose of these lectures, undertake new investiga- 
 tions, in order to throw light, if possible, upon some of the points 
 which are still in dispute. But to compress into practically a 
 few months of otherwise fully occupied time what might well be 
 the undivided labour of a long period has proved a difficult task, 
 and I have fallen far short of what I had hoped to accomplish, 
 though I trust that some of the results at which I have been able 
 to arrive may contribute towards a solution of some of the vexed 
 questions. I purpose in these lectures to sketch the evolution oi 
 the doctrine of cerebral localisation, to indicate the principal data 
 on which it is ba^ed, and to discuss, in the light of the most re- 
 
 B 
 
 M 
 
2 CEREBRAL LOCALISATION. 
 
 cent investigations, the evidence for and against the existence of 
 specific centres, and their exact position in the cerebral cortex. 
 
 Before considering the facts bearing directly upon the specific 
 localisation of f anction in the cerebral cortex, I think it advisable 
 — nay, even necessary — to consider the effects of ablation of the 
 cerebral hemispheres in different classes of animals. A due con- 
 sideration of these phenomena affords, I think, a satisfactory ex- 
 planation of the chief objections which have been urged against 
 localisation in general, and, at the same time, also renders un- 
 necessary certain hypotheses as to the functional substitution of 
 one part of the cortex by another, which have been — and, in my 
 opinion, rightly — regarded by the opponents of localisation as 
 altogether subversive of its fundamental principles. 
 
 Recent researches on the effects of the removal of the cerebral 
 hemispheres, by improved methods, have necessitated some im- 
 portant modifications of the doctrines which, up to quite a recent 
 date, have been generally entertained on the subject. 
 
 Let us begin with fishes. When in osseous fishes the ganglia 
 (which correspond morphologically to the cerebral hemispheres of 
 the vertebrates) are entirely removed, there is little, if anything, 
 to distinguish them from perfectly normal animals. They main- 
 tain their natural attitude, and use their tails and fins in swim- 
 ming with the same vigour and precision as before. It has 
 generally been said that brainless fishes possess no spontaneity, 
 but seem as if impelled by some irresistible impulse (occasioned 
 by the impressions communicated to the surface of their bodies 
 by the water in which they are sustained) to swim until they are 
 exhausted by pure neuro-mu?cular fatigue. In their course, how- 
 ever, as was shown by Vulpian, they do not blindly rush against 
 obstacles, but turn to the right or left, according to circumstances, 
 as if still possessed of some sense of vision. Vulpian says ^ " In 
 fact, when the cerebral hemispheres have been removed from a 
 fish which does not readily succumb tc this kind of operation (a 
 roach, for example), not only may it be urged to move by bringing 
 an object before its eyes, but I have proved that it avoids obstacles; 
 for, by placing a stick to the right or left, a few centimetres from 
 its eye, I have frequently caused the fish to turn in the opposite 
 direction." 
 
 Steiner ^ does not admit the absence of spontaneity in fishes so 
 operated upon, for he has seen that they occasionally remain at 
 
 1 Systime Nerveux, p. 669. 
 2 Die Functionen des C entralnervmsy stems ; Zweite Abtheilung : Die Fische, 1888. 
 
ABLATION OF CEREBRAL REMLSPHERES. 3 
 
 the bottom, at other times balance themselves at various heights 
 in the water, and now and then swim about freely, without any 
 obvious alterations in the conditions by which they are surrounded. 
 He has also shown, and in this he has been conflrmed by Vulpian,^ 
 that they not only see, but are able to find, their food. If worms 
 be thrown into the water in which they are swimming, they im- 
 mediately pounce upon them. If a piece of string similar in size 
 to a worm be thrown in, they are able to detect the difference, and 
 either dii^regard it entirely, or drop it after having seized it. Not 
 only do they seize their food, but they discriminate between 
 different kinds, selecting some, and rejecting others. They even 
 to some extent distinguish colours, for when one red and a few 
 white wafers are thrown into the water, the fish almost invariably 
 selects the red in preference to the white. 
 
 From these facts it would appear that the fish without cerebral 
 hemispheres can see, distinguish colours to some extent, catch its 
 prey, discriminate between different kinds of food, direct its 
 movements with precision, and, in fact, behave to all appearance 
 like a normal animal. The only difference observed by Steiner 
 was that brainless fishes appeared more impulsive and less cautious 
 than those which had not been operated upon. 
 
 What has been said above applies, however, only to Teleosteous 
 fifches. Quite different results appear to follow removal of the 
 cerebral hemispheres in Elasmobranchs. Thus the dog-fish, ac- 
 cording to Steiner,^ after this operation is entirely deprived of 
 spontaneity, and is quite unable to find the food (sardines) by 
 which it is surrounded. The difference between the two orders 
 of fishes is, however, more apparent than real, for the dog-fish is 
 guided mainly by its sense of smell, while the activity of the 
 osseous fish is conditioned more especially by vision; hence, in 
 the dog-fish, removal of the cerebral hemispheres, which are 
 almost exclusively related to the sense of smell (Fig. 1.— a), 
 abolishes all the reactions conditioned by this sense ; while in the 
 osseous fish, the primary visual centres (optic lobes), being intact, 
 the ordinary modes of activity, which are conditioned mainly by 
 the eyes, continue to all appearance unmodified. 
 
 Frogs. — According to the researches, more particularly of Goltz* 
 and Steiner,** frogs deprived of their cerebral hemispheres behave, 
 
 » Comptes liendus. Tome 102 and 103, 1886. 
 
 ♦ Op. cit. 
 
 * Functionen der Nervencentren des Frosches, 1869. 
 
 * Pki/siologie den Froxchhirns, 188.'>. 
 
 b2 
 
4 CEREBRAL LOCALISATION. 
 
 cceteris paribus, essentially like fishes similarly treated; they 
 maintain their normal attitude, and resist all attempts to over- 
 throw their equilibrium. If laid on their backs they will turn 
 over and attempt to regain their ordinary position. If the basis 
 of support on which they rest is tilted in any direction, they will 
 clamber up, forwards, or backwards until they gain a position of 
 stability. Their powers of locomotion are retained, and their 
 limbs are co-ordinated with precision. If a foot be pinched, or 
 any irritation applied to the posterior part of the body, they will 
 hop away ; thrown into the water they will swim, and continue 
 swimming until they have reached the side of the vessel, up 
 which, if possible, they will clamber and rest in peace. It would, 
 in fact, be difficult, so far as their movements and response to 
 
 A 
 
 Fig. 1.— Brain of dog-fish (after Steiner). A, cerebral hemisphere; B, optic 
 lobe ; c, cerebellr.m ; o, olfactory lobe. 
 
 peripheral stimuli are concerned, to distinguish between a normal 
 and a brainless frog. If the back be gently stroked the frog will 
 answer uniformly with a croak, as if of pleasure or enjoyment. 
 If the animal be put in a vessel containing water, the temperature 
 of which is gradually raised, it will jump out as soon as the bath 
 becomes uncomfortably hot. If placed at the bottom of a pail of 
 water, it will ascend to the surface to breathe. If the vessel be 
 inverted over a pneumatic trough and filled with water, sustained 
 by barometric pressure, the frog will ascend to the top as before, 
 but not finding there the oxygen necessary to satisfy its respira- 
 tory craving, it will work its way downwards, and ultimately 
 succeed in making its escape out of the vessel on to the free sur- 
 face of the trough. Like the fish, the brainless frog undoubtedly 
 possesses some form of vision ; it does not, when urged to move, 
 rush blindly against an obstacle, but will leap over it, or turn to 
 
ABLATION OF CEREBRAL HEMISPHERES. 5 
 
 the right or left, or otherwise avoid it. In all these respects a 
 brainless frog behaves like a normal one, but one noteworthy 
 difference has been signalised by most observers — namely, that 
 the brainless frog, unless disturbed by some form of peripheral 
 stimulus, will remain for ever quiet on the same spot, until, in 
 fact, it becomes dried up and converted into a mummy. All 
 spontaneity — that is, varied activity under apparently the same 
 external conditions — appears to be annihilated ; its past expe- 
 rience has been blotted out, and it views with indifference signs 
 and threats which would formerly have made it flee. It is also 
 generally stated that the brainless frog has lost its instincts of 
 self-preservation, and either feels no hunger or possesses no power 
 to satisfy its physical necessities, so that it dies in the midst of 
 plenty. The more recent experiments, however, of Schrader'^ 
 would seem to show that removal of the hemispheres deprives the 
 frog neither of spontaneity, nor of special instincts, nor of the 
 ability to feed itself ; for he has observed brainless frogs which 
 have been kept alive for long periods, apparently " sponta- 
 neously " jump from the pier of a galvanometer, absolutely free 
 from all tendency to vibration, alternate between land and water 
 in the aquarium, crawl under stones, or bury themselves in the 
 earth at the beginning of winter, and, when cautiously submerged 
 under water, begin to swim exactly like normal frogs under the 
 same conditions. These frogs also, after the period of hyberna- 
 tion, or in the summer, when their wounds were entirely healed, 
 diligently caught the flies that were buzzing about in the vessels 
 in which they were kept. It would appear, therefore, if these 
 observations are correct, that the principal points of distinction 
 between the brainless and the normal frog — namely, the absence 
 of spontaneity and the power to feed itself, which are said to 
 especially characterise the former— are no longer capable of being 
 upheld, and that the brainless frog behaves precisely like the 
 brainless fish above described. 
 
 Birds.— Let us now proceed to consider the effects of the re- 
 moval of the cerebral hemispheres in birds, the next higher class 
 of vertebrates, and more especially in pigeons. These have been 
 rendered familiar to all by the classical researches of Flourens ;* 
 but though the picture he has drawn has been accepted as in the 
 main correct, there have been, and there still are, some differences 
 of opinion as to the facts, and more particularly as to their mode 
 
 ' Physlologie des Froschgehirns, PJldger's Archiv fur Physiologie, 1887, Band 41 
 * iSysteme Nerveux, 1842. 
 
6 CEREBBAL LOCALISATION. 
 
 of interpretation. There is, however, no doubt that after this 
 operation pigeons show no disturbance of station or locomotion. 
 They maintain their normal attitude, and resist all attempts to 
 overthrow their balance. Left to themselves they appear, at first 
 at least, to be plunged in profound sleep. From this condition 
 they are easily aroused by a gentle push or pinch. When so 
 urged they march forwards, and should they happen to step over 
 the edge of the table, on which they are placed, they will flap 
 their wings and regain their base of support. Thrown into the 
 air they fly with all due precision and co-ordination. After each 
 manifestation of activity so induced they subside into their 
 original state of repose. Occasionally, and apparently without 
 any external stimulus, they may look up and yawn, shake them- 
 selves, dress their feathers with their beaks, move a few steps 
 forwards or backwards, especially after defaecation, and then settle 
 down quietly, standing sometimes on one leg, sometimes on the 
 other. They are altogether unable to feed themselves ; but, if fed 
 artificially, deglutition, digestion, and nutrition go on in a normal 
 manner, and the animals may be kept alive for an indefinite 
 period. Flourens was of opinion that the removal of the cerebral 
 hemispheres annihilated all the senses, and rendered the animals 
 blind, deaf, and devoid of smell, taste, and tactile sensibility. 
 These conclusions were, however, disputed by Magendie, Bouillaud, 
 Cuvier, and, in particular, by Longet^ and Vulpian." Longet found 
 that the animals appeared to see, inasmuch as they would follow 
 the movements of a flame held in front of their eyes at a sufli- 
 cient distance to prevent all sensation of heat, and also when 
 urged to move, occasionally at least, avoided obstacles in their 
 path. Also they started at loud sounds, such as a pistol shot, 
 made in their immediate vicinity ; and from their movements and 
 gestures appeared to feel impressions made upon the nerves of 
 common sensation. As regards the senses of taste and smell, he 
 found it impossible to arrive at any definite conclusions in animals 
 of this order, and looked upon the statements of Flourens as not 
 supported by convincing evidence. Longet believed that the re- 
 moval of the cerebral hemispheres annihilated only perception 
 proper, as distinct from crude or brute sensation, which had its 
 centre in the mesencephalic ganglia. 
 
 The question as to the sense of sight in brainless pigeons has 
 been much discussed, that is, whether not mere impressionability 
 
 9 Anatomie et Physiologie du Systeme Nerveux, 1842. 
 10 Op. cit. 
 
ABLATION OF CEREBRAL HEMISPHERES. 7 
 
 to light exists, but as to whether the animals see, in the sense of 
 being able to guide their movements in accordance -with their 
 retinal impressions. McKendrick^^ was of opinion that removal 
 of the one cerebral hemisphere caused blindness in the opposite 
 eye; and J astro wit z,^- from his own experiments, arrived at the 
 same conclusion (on this see further below). The experiments of 
 Blaschko," under the direction of Munk, led to no very definite 
 conclusions on this point, though it seemed as if the removal of 
 the one hemisphere did not cause total blindness in the opposite 
 eye. But Munk himself^* has made it the subject of a consider- 
 able number of experiments. He found that in a certain number 
 of pigeons, from which he had attempted to remove the cerebral 
 hemispheres, vision was not entirely abolished, and the animals 
 were able to avoid obstacles placed in their path. Careful investi- 
 gations, however (post mortem) revealed the fact that in such 
 cases the hemispheres had not been entirely destroyed, vision 
 continuing to some extent in the eye opposite the hemisphere, the 
 extirpation of which had not been absolutely complete. In those 
 cases, however, in which not a trace of either hemisphere was 
 allowed to remain, blindness was complete and absolute. These 
 animals, in their attitude and reaction to peripheral stimuli, 
 etc., exhibited the symptoms already described. The brightest 
 light, however, caused no result beyond contraction of the pupil. 
 The animals, when urged to move, ran against every obstacle 
 which came in their way. When thrown into the air, they flew 
 with retracted head and half-raised trunk, outstretched legs, and 
 dashed against obstacles, or fell bump on the ground and slid a 
 considerable distance before coming to a standstill. 
 
 The phenomena described by Munk certainly indicate total 
 blindness on the part of his pigeons, and he is of opinion that all 
 those who have held that ablation of the cerebral hemispheres 
 does not cause total blindness are in error, owing to the fact of 
 the extirpation of the hemispheres not having been complete. 
 Schrader, however,^^ describes the phenomena which he observed 
 in two pigeons, from which, according to the post-mortem exami- 
 nation of von Recklinghausen, he had entirely removed every por- 
 
 U Observations and Bxperiments on the Corpora Striata and Cerebral Hemi- 
 spheres of Pigeons, Royal Society, Edinburgh, 1873. 
 12 Ueberdie Bedeutung des Grosshirns, Archiv.Jilr Psychiatric, 1876. 
 13 Das fiehcentrvm be.i Froschen, Berlin, 1880. 
 »« '* Uber die centralen Organe fiir das Sehen und das H()ren bei den Wirbe- 
 tbleren ; SUzungs/jerichte d. Berlin Akademie d. Wissenschajten, July, 1883. 
 1* Physiologic des Vogelgehirns, Pfliiger's Arehiv, Bd. 44. 
 
8 CEREBRAL LOCALISATION. 
 
 tion of the cerebral hemispheres. None of the cortex remained, 
 but only minute remnants of the cut cerebral peduncles, which 
 ■were, moreover, in a state of softening. These pigeons, within a 
 few days after the operation, behaved in such a manner as can 
 only be explained by their still retaining some form of vision. 
 For they not only avoided obstacles in their path, or in their 
 flight, but appeared able to fly from one place and alight securely 
 on another. These flights were mostly, if not entirely, caused by 
 conditions calculated to induce a change of position, such, for in- 
 stance, as mounting them on a narrow basis of support, or putting 
 them through balancing experiments. They never on any occa- 
 sion spontaneously flew upwards from the ground. 
 
 With respect to the sense of hearing, Schrader verified in some 
 of his animals the observations of Longet, that loud sounds, like 
 the explosion of a percussion cap, caused a sudden start, but be- 
 yond this there were no signs of impressionability to auditory 
 stimuli. If the results described by Schrader are correct, and of 
 this the description given by himself and von Eecklinghausen 
 seems to leave little room for doubt, we shall then be obliged to 
 class birds with fishes and frogs, which without doubt retain their 
 sense of sight, and guide their movements accordingly, notwith- 
 standing the complete removal of their cerebral hemispheres. 
 
 Mammals. — While removal of the cerebral hemispheres (includ- 
 ing corpora striata) in the lower vertebrates is compatible with 
 survival for a considerable length of time, the case is different 
 with mammals. In these the operation causes fatal shock, or is 
 followed by secondary effects which result in speedy death. For 
 this reason it has not beem found possible to determine, as in the 
 lower vertebrates, what functions, after considerable lapse of 
 time, might still be exhibited by the lower centres in the entire 
 absence of the higher. The mammals on which the operation 
 has succeeded best have been chiefly of the lower orders, such as 
 rabbits, guinea-pigs, and rats. When the hemispheres have been 
 removed from a rabbit or a guinea-pig, the animal, at first utterly 
 prostrate, begins after a varying interval, say from half an hour 
 or more, to exhibit a capacity for the performance of actions of a 
 considerable degree of complexity. The muscular power of the 
 limbs has, however, become enfeebled to a noteworthy extent, and, 
 relatively, much more so in the fore than in the hind limbs. It 
 is, nevertheless, .able to maintain its equilibrium, but sits huddled 
 up, while the legs tend to sprawl, or are planted in unnatural 
 positions. It resists attempts to overthrow its balance, and if 
 
ABLATION OF CEREBRAL HEMISPHERES. 9 
 
 disturbed regains its former attitude. If the foot or tail be 
 pinched, the animal will bound forward in its characteristic mode 
 of progression, and again settle down when the efffcct of the sti- 
 mulus has worn off. It may shake its ears, slightly change its 
 position, rub its snout with its paws, or scratch its body, and 
 again subside into a condition of perfect quiescence. The pupils 
 contract when a light is thrown into the eya.and the eyelids wink 
 when the conjunctiva is touched. Loud sounds will cause the 
 ears to twitcb, or provoke a sudden start. According to Longet, 
 colocynth placed in the mouth will cause movements of the 
 tongue and organs of m'l&tication, in all respects resembling 
 those of disgust, and efforts to get rid of the nauseous taste. 
 Ammonia held before the nostrils will cause a sudden retraction 
 of the head, or induce the animal to rub its nostrils with its 
 paws. Not merely does it respond by movements to a pinch or 
 prick of its foot or tail, but, if the stimulation be more severe, it 
 will utter repeated and prolonged cries of a plaintive character. 
 All spontaneity seems to be abolished ; but it is usual for the ani- 
 mals, after the period of quiescence has passed, to make appa- 
 rently spontaneous running movements, which, however, are 
 found to depend upon irritation caused by the secondary changes 
 set up in the wound. 
 
 "Whether after removal of the cerebral hemispheres rabbits and 
 other rodents can see, is a question which has been the subject of 
 lively controversy between Christiani and Munk." Christiani, after 
 careful severance of the hemispheres and corpora striata immediately 
 anterior to the optic thalami, states that he has seen rabbits pass 
 and repass obstacles, such as legs of ch airs and tables, and is of opinion 
 that, though they do not see like normal rabbits, they are still 
 able to guide their movements in accordance with retinal impres- 
 sions. Munk, on the other hand, denies the accuracy of 
 Christiani's experiments, and holds that rabbits, after removal of 
 the cerebral hemispheres, are absolutely blind, and show no indica- 
 tions whatever that they are influenced by light, except as regards 
 the contraction and dilatation of the pupils. He believes that the 
 apparent avoidance of obstacles by Christiani's rabbits was a pure 
 accident, as the obstacles did not happen to lie in their path. 
 
 The question is one which cannot be said to be definitely settled 
 though the facts mentioned in respect to fishes, frogs, and birds 
 would incline one to believe that Christiani's results and conclu- 
 sionfl may have a solid foundation. On this point, however, and 
 
 18 Physiologic des Gehimes, 1885. 
 
10 CEREBRAL LOCALISATION. 
 
 on others relating to the sensory and motor faculties of brainless 
 mammals it is diflacult to arrive at altogether satisfactory con- 
 clusions, as they, unlike the lower vertebrates, have as a rule so 
 speedily succumbed to the operation. Hence, the lower animals' 
 centres have no time to recover from the shock which must neces- 
 sarily ensue from such a violent rupture of the solidarity pre- 
 viously existing between them and the highest centres. As the 
 cause of death in mammals seems largely dependent upon 
 secondary (inflammatory and other) consequences, and not on the 
 mere fact of removal of the hemispheres themselves, it is much to 
 be desired that some method may be discovered whereby the ani- 
 mals may be maintained alive longer than has hitherto been found 
 possible. The nearest approach to this has been attained by 
 Goltz,^'^ who has made a series of careful observations on dogs for 
 prolonged periods, after very extensive destruction of both cere- 
 bral hemispheres. Though the destruction has been far from 
 complete in any case, yet the phenomena described by him teach 
 lessons of the utmost importance in the comparative physiology of 
 the brain. Goltz himself has utilised these experiments as the 
 bases of his polemic against cerebral localisation, but we may, for 
 the time, abstract from their bearing in this direction, and con- 
 sider the facts themselves which he has recorded. 
 
 Goltz ^^ thus describes a dog in which he had by repeated opera- 
 tions destroyed a large extent of both hemispheres. The amount 
 of primary destruction, together with the secondary atrophy so 
 induced, was so great that the whole brain weighed only 
 13 drachms instead of 90, which should have been the weight of a 
 normal brain in an animal of the same size. This dog had a pro- 
 foundly demented, expressionless face. Left to itself it wandered 
 about restlessly, paying no attention to what was going on around 
 it. All its movements were awkward and unsteady, but it ex- 
 hibited no complete paralysis. It slipped, however, on a smooth 
 surface, and its legs tended to sprawl from under it, so that it 
 would fall upon its abdomen. From this position it would re- 
 cover itself and again begin its walk. It had the utmost difficulty 
 in feeding itself, though it could find its food when placed in the 
 customary corner of its cage, yet it seemed unable to find it when 
 placed in an unusual position, and even when the food was 
 brought directly under its nose it would snap aimlessly as often 
 outside the dish as in it. It was utterly unable to use its paws 
 
 1^ Verrichtungen des GroBshirns, Pfluger's Archiv, 1876-1888. 
 18 Op. cit., p. 134. 
 
GOLTZ'S EXPERIMENTS. 11 
 
 for holding and gnawing a bone. It paid no attention to strangers, 
 men or animals ; did not wince at the brightest light suddenly 
 thrown in its eyes, and exhibited no fear at any kind of threat. 
 Though it appeared absolutely blind, yet numerous and varied 
 experiments demonstrated that it was able to guide its movements 
 by sight. It did not run against obstacles as it invariably did 
 when its eyes were blindfolded. It was not deaf, for it could be 
 waked out of sleep by a loud sound, but the character of the sound 
 made no further impression upon it. It did not heed tobacco 
 smoke or chloroform vapour, and would eat a piece of wood as 
 readily as a bone. It did not appear to be influenced by the 
 proximity of another dog. It exhibited no emotion of anger when 
 another stole its food, nor did it express pleasure in the us-ual way 
 by wagging its tail. Its cutaneous sensibility was everywhere 
 diminished, but no part was absolutely without feeling. If its foot 
 was severely pinched it would draw its leg back and bite angrily. 
 The symptoms exhibited by this dog and another similarly 
 operated upon are thus summed up by Goltz : " Both animals were 
 essentially only wandering, eating, and drinking reflex machines. 
 Both were utterly indifferent to man and beast. Both had obtuse- 
 ness of all their senses. Each had sensation in every part of its 
 skin, and effected movements with all its muscles. Neither ex- 
 hibited any expression of pleasure ; on the other hand, both were 
 easily roused to wrath. Both were profoundly demented." 
 
 The impairment of all the sensory and motor faculties in these 
 and other dogs operated upon by Goltz— in which it is certain that 
 not one of the specific centres was entirely destroyed— would 
 without doubt have been more profound than in rabbits and 
 guinea-pigs had it been possible to extirpate the hemispheres 
 entirely. And when we come to consider the effects of partial 
 cerebral lesions in man, we shall see reason for believing that if 
 in him the whole of the hemispheres were removed, providing 
 this were compatible with life, there would be such complete and 
 enduring paralysis of motion, and annihilation of all the forms of 
 sense, that scarcely a trace would remain to those responsive and 
 adaptive reactions which 8ur\ave the removal of the cerebral hemi- 
 spheres in animals lower in the scale. 
 
 It thus appears that, notwithstanding the complete extirpation 
 of the cerebral hemispheres, animals, in proportion to their low- 
 ness in the scale, besides duly maintaining and regulating all their 
 organic functions, remain possessed of varied powers which may 
 be classed generally under the heads of equilibration, co-ordina- 
 
12 CEREBRAL LOCALISATION. 
 
 tion of locomotion, emotional expression, and adaptive reactions 
 in accordance with impressions made upon their organs of sense. 
 These are organised in the mesencephalic and spinal centres in 
 the highest degree in fishes, frogs, and pigeons ; to a less degree 
 in the lower mammals, and least of all in monkeys and man. 
 
 I do not intend on the present occasion to enter on a considera- 
 tion of the respective roles of the spinal, cerebellar, and mesen- 
 cephalic centres in the regulation of these different forms of 
 activity. We may — practically in some and theoretically in all 
 — separate the mesencephalon and spinal cord into a congeries of 
 individual centres, each with its own afferent and efferent nerves, 
 co-ordinating synergic movements, each in its own province, and 
 all co-operating together harmoniously by means of commissural 
 or intracentral fibres. The individual metameres form units in a 
 complex whole, acted on by the nerves of special sense, and sub- 
 ordinate to the supreme nerve centres, through which the 
 adaptation of the organism to its environment is effected. Nor 
 will I enter on a discussion of the vexed question as to whether 
 the actions of the lower centres are indicative or not of intelli- 
 gence. Most of the differences on this point turn mainly on the 
 meaning of terms. If, with Mr. Romanes, we regard fluctuating 
 adaptation to external conditions as the criterion of intelligence, 
 we shall certainly not be able to deny that the actions of the 
 lower centres are indicative of intelligence in this sense. For 
 the observations of Steiner, Schrader, and others on the lower 
 vertebrates, show that forms of activity, which we are accustomed 
 to regard in man as exclusively cerebral, and indicative of con- 
 scious discrimination, are capable of being manifested by these 
 animals in the entire absence of their cerebral hemispheres. Nor 
 can we say that spontaneity, which we have also been accustomed 
 to regard as conditioned by the cerebral hemispheres, is entirely 
 abolished in brainless animals ; for we see that, without any 
 apparent change in external conditions, they move spontaneously, 
 and comport themselves not unlike normal animals. We can, 
 however, in most cases, if not in all, refer these so-called 
 spontaneous movements to immediate ento- or epi-peripheral 
 impressions ; whereas, in normal animals, though their so-called 
 spontaneity is primarily derived from a similar source, the con- 
 nections are more remote and far more difficult to trace. 
 
 These and other similar facts lead to the conclusion that be- 
 tween the simplest reflex action and the highest act of intelli- 
 gence there is no essential difference— each passing by insensible 
 
ADVERSE VIEWS. 13 
 
 gradations into the other. We can infer only, we can prove nothing 
 conclusively, regarding the existence of states of consciousness in 
 others than ourselves, and less easily in the case of the lower ani- 
 mals than in man. But we are entitled to say that the activity 
 of the lower centres does not affect the consciousness of the indi- 
 vidual; for, when by lesion of the internal capsule the sensory 
 tracts are cut off from their cortical connections, the individual 
 has absolutely no consciousness of impressions made upon his 
 organs of sense, so that we may conclude that, in man at leant, 
 states of consciousness are indissolubly connected with the activity 
 of the cerebral hemispheres. 
 
 The results of ablation of the cerebral hemispheres indicate 
 nothing for or against the doctrine of functional localisation, nor 
 do the experiments of Goltz in the least degree militate against 
 the existence of specific centres; for if, even after complete 
 bilateral extirpation of these centres, the functions which survive 
 do not transcend those capable of being manifested in the entire 
 absence of the cerebral hemispheres, there still remains the ques- 
 tion whether the lesions have not caused a loss or paralysis of 
 something of a higher order. That this is so is capable of ample 
 demonstration, of which not the least part has been contributed 
 by the very facts which Goltz himself has ascertained through the 
 numerous and varied devices which he has so ingeniously con- 
 trived. It is no explanation of the defects which admittedly re- 
 sult from removal of the cerebral hemispheres to say that they 
 are caused by a loss of intelligence. This is merely restating the 
 facts in a more metaphysical but less intelligible form. We are 
 not, however, dealing with metaphysical terms when we are 
 studying the effects of lesions of the cerebral cortex. We are 
 dealing with material entities connected with sensory and motor 
 tracts, and it is our object to determine, if possible, what are the 
 anatomical and physiological factors which are co-related with the 
 functions which we generalise under the head of intelligence ; and 
 there appears to be nothing which can, a priori, be urged against 
 the notion that the various factors of intelligence have their sub- 
 strata in definite regions specifically related to certain motor and 
 sensory functions. Flourens, as is well known, denied every spe- 
 cies of localisation in the cerebral hemispheres. To this conclu- 
 sion he appears to have been led not more by his own experi- 
 ments than by the prevalent conceptions as to the unity and in- 
 divisibility of the mind, and as a reaction against the organology 
 of Gall and his followers. To Gall, however, let us in passing pay 
 
14 CEREBRAL LOCALISATION. 
 
 the tribute that in his analysis he followed strictly inductive 
 methods, and made many observations of enduring value ; though 
 his synthesis of the brain as a congeries of separate organs, each 
 autonomous in its own sphere, and all mysteriously inherent in 
 some unifying, immaterial substratum, has failed to commend 
 itself to the scientific world. Flourens thus sums up his conclu- 
 sions ; — 
 
 " Thus one may remove, anteriorly, or posteriorly, from above, or 
 from the side, a considerable portion of the cerebral lobes without 
 destroying their functions. Even a small portion of these lobes, 
 therefore, suffices for the exercise of their functions. In propor- 
 tion to the extent of the removal, all the functions become im- 
 paired, and gradually fail ; and beyond certain limits they are 
 altogether annihilated. The cerebral lobes, therefore, co-operate 
 as a whole in the full and complete exercise of their functions. 
 Finally, when one form of perception is lost, ail are lost ; when 
 one faculty disappears, all disappear. There are, therefore, no 
 special seats either of special faculties or special perceptions. The 
 faculty of perceiving, judging, and willing one thing resides in the 
 same region as that of perceiving, judging, and willing another ; 
 consequently, this faculty, essentially one, resides essentially in 
 one organ."^^ 
 
 Though the doctrines of Flourens met with general acceptation, 
 they were contested on experimental grounds by some physiolo- 
 gists, more particularly by Bouillaud.^" The experiments of 
 Bouillaud on pigeons, dog^, and rabbits led him to conclude that 
 destruction of the anterior lobes alone caused symptoms of pro- 
 found dementia. Though the animals were able to feel, see, hear, 
 smell, and to execute a number of spontaneous and instinctive 
 movements, they were unable to recognise their relations to the 
 objects by which they were surrounded. They were unable to 
 feed themselves, and had in general lost all reasoning powers. An 
 animal, said he, in which the anterior lobes have been destroyed, 
 " though deprived of the exercise of a more or less considerable 
 number of intellectual acts, continues to enjoy its sensory facul- 
 ties; a proof that 'sensation' and ' intellection ' are not one and 
 the same function, and that they have separate localities." Bouil- 
 laud's results have, I think, received confirmation and elucidation 
 from my own experiments on monkeys, as well as those of Goltz 
 
 19 Op. cit., p. 99. 
 
 ^ "Rech. Slxperim. sur les Fonctions du Cerveau, et sur celles de sa portion 
 
 anterieure en particulier." Journ. de Physiol. Expirim., 1830, T. x, p. 91. 
 
BOUILLA rD—BROCA—HUGRLINGS-JACKSON. 15 
 
 and Schrader on dogs and pigeons. Bouillaud, however, did not 
 consider that his own experiments had done more than merely 
 raise the question of localisation, and it was generally believed 
 that, so far at least as experimental data were concerned, the doc- 
 trine of specific localisation had no secure basis of support. From 
 the clinical standpoint, however, facts were continually being pre- 
 sented which seemed altogether unintelligible except on some 
 theory of localisation; and clinical observers, such as Bouillaud 
 himself, Andral, and others, wisely suspended their judgment 
 until further facts should be brought to light, which might serve 
 to explain the apparent irreconcilable discrepancy between human 
 pathology and experimental physiology. 
 
 Bouillaud '^ recorded certain clinical facts which seemed to indi- 
 cate a connection between lesions of the anterior lobes and loss of 
 speech, thus affording some confirmation of the theories of Gall 
 on the subject. Dax (1836) established the special relation of 
 aphasia to right hemiplegia and lesions of the left hemisphere ; 
 but the connection between aphemia, or aphasia, and lesion more 
 particularly of a definite region of the left hemisphere, namely, 
 the base of the third frontal convolution, was first pointed out by 
 Broca (1861). Broca's observations have since been amply con- 
 firmed by clinical and pathological research, and further eluci- 
 dated by physiological experiment. 
 
 The next great advance in cerebral localisation was made by 
 Hughlings-Jackson (1861),-^ who, from a study of the forms of 
 epilepsy, now appropriately known by his name, furnished cogent 
 reasons for believing that certain convolutions near, and function- 
 ally related to, the corpus striatum had a direct motor significa- 
 tion. By irritation or " discharging lesions " of these convolu- 
 tions, localised, or general unilateral convulsions of the opposite 
 side of the body were induced. Omng, however, to the fact, as 
 Hughlings-Jackson has remarked, that " the damage by disease is 
 often coarse, ill-defined, and widespread," the determination of 
 the functions of the brain by the clinico-pathological method had 
 made comparatively little progress, there being apparently no 
 constant uniformity between the seat of the disease and the sym- 
 ptoms manifested. The difficulty of discriminating between the 
 direct and indirect effects of cerebral lesions has furnished Brown- 
 S6quard^^ with arguments in favour of his peculiar views, that all 
 
 *i Archives de Medecine, 1825. 
 22 Clinical and Pathological liesearches on the Nervous System. 
 ** Physiological Pathology of the Brain, Lanzet, 1876, and Archives de Physi- 
 ologic, 1877-1890. 
 
16 
 
 CEREB RAL LOCALISA TION. 
 
 the symptoms of cerebral disease are due to some dynamic in- 
 fluence exercised by the lesion on parts situated at a distance 
 (and always apparently out of reach), which are credited with the 
 functions lost or otherwise disturbed. 
 
 A glance at the accompanying diagram (Fig. 2) founded by 
 Exner^^ on the examination of a number of cases of lesion of the 
 left hemisphere, will show you the extraordinary diversity in posi- 
 
 OPPeR' £KTBI£mTY» O ^^V^^^ EXTBBMITY. m 
 
 FAGIAL MUSCLl^S, ® HYPDGLOSSUS MUSCLES.® 
 
 SPEECH^ © SlCHr. S 
 
 Fig. 2. — After Bxner's Tafel xxv. The diagram is marked with larger and smaller circles of the same 
 order. The larger circles indicate the absolute centres, the smaller the relative centres. The in- 
 tensity of the latter is indicated by the closeness of the circles to each other. 
 
 tion of those accompanied by practically the same symptom. It 
 will be seen, for instance, that though the lesions which cause 
 affection of the upper extremity are mostly grouped in a certain 
 region, yet there is scarcely a point on the convexity of the hemi- 
 sphere lesion of which has not caused a similar result. These and 
 
 2* Localisation der Functionen, in der Grosshirnrinde des Menschen, 1881. 
 
FBITSCn AND HITZIG'S EXPERIMENrS. 17 
 
 such like are the data on which Exner has founded his theory of 
 absolute and relative centres ; absolute centres being those de- 
 struction of which invariably, relative centres being those de- 
 struction of which only frequently, induces the same symptom. 
 The distinction appears to me to have no valid foundation. Mere 
 frequency is not a sufficient basis on which to found causal rela- 
 tionship. For, if the so-called relative centres can be, and have 
 been times out of number, destroyed without any disturbance of the 
 function with which they are supposed to be related, and if the said 
 f auction can be annihilated while the relative centres are intact, 
 it is obvious that the relationship is nothing more than mere 
 coincidence or juxtaposition. 
 
 Fig. 3.— Centres of the brain of the dog according to Fritsch and Hitzig. 
 
 The whole aspect of cerebral physiology and pathology was re- 
 volutionised by the discovery, first made by Fritsch and Hiizig in 
 1870,-' that certain definite movements could be excited by the 
 direct application of electrical stimulation to definite regions of the 
 cortex cerebri in dogs. As these experiments are now of historic 
 interest, I extract the accompanying figure (Fig. 3) and the de- 
 scription, in their own words, of the facts which they had at 
 that time ascertained. 
 
 " The centre for the neck-muscles (Fig .3 a) lies in the lateral 
 part of the prefrontal gyrus at the point where the surface of this 
 convolution abruptly descends. The outermost extremity of the 
 
 2' Reichert, u. l>u Boix-Reymmid'n Archiv, 1870, Ueft 3. 
 
18 CEREBRAL LOCALISATION. 
 
 postfrontal gyrus contains, in the neighbourhood of the lateral 
 end of the frontal fissure (Fig. 3 b) the centre for the ex- 
 tensors and abductors of the fore limb." Somewhat behind 
 the same, and nearer the coronal fissure (Fig. 3 c) lie 
 the ruling centres for the flexion and rotation of the limb. 
 The centre for the hind leg (Fig. 3 d) is also found in the 
 postfrontal gyrus, but nearer the middle line than that of the 
 fore leg, and somewhat further back. The facial (Fig. 3 e) 
 is innervated from the middle part of the super-Sylvian gyrus. 
 This region generally has an extension of over 0.5 centimetre, 
 and stretches before and behind the bend over the Sylvian fissure. 
 We must add that we did not always succeed in getting the neck- 
 muscles in action from the first mentioned point. The muscles of 
 the back, tail, and abdomen we have often enough excited to con- 
 traction from points lying between those marked, but no circum- 
 scribed point from which they could be individually stimulated 
 could be satisfactorily determined. The whole of the convexity 
 lying behind the facial centre we found absolutely unexcitable, 
 even with altogether disproportionate intensity of current." 
 
 The subject of the electrical excitability of the cortex and its 
 signification was next taken up by myself in 1873,^'' more particu- 
 larly with the object of putting to experimental proof the views 
 of Hughlings Jackson in reference to the causation of unilateral 
 epileptiform convulsions. While amply confirming these doctrines 
 in all essential particulars, my attention became specially directed 
 to the question of definite localisation, and I was led minutely to 
 explore, not only the hemispheres of dogs, but also those of mon- 
 keys and various other orders of vertebrates. Similar researches 
 have been undertaken and published in almost every country, and 
 by experimenters too numerous to mention, but nowhere with 
 greater care and detail than by Beevor, Horsley, and Schafer ^' 
 in our own. The facts revealed by electrical exploration of the 
 hemispheres have been, and still are, the subject of considerable 
 diversity of opinion, and by some, as Brown-Sequard,-^ are re- 
 garded as of no greater significance than the contortions which 
 may be induced by tickling the sole of the foot. There cannot, 
 however, be a doubt that from them, and the further experiments 
 to which they have pointed the way, has sprung the whole modern 
 doctrine of exact cerebral localisation. 
 
 26 Experimental Researches in Cerebral Physiology and Pathology, West 
 
 Hiding Lunatic Asylum Reports, vol. iii, 1873. 
 
 27 Phil. Trans., 1888. 
 
 28 Archives de Physiologie, January, 1890. 
 
EXCITABILITY OF BRAIN. 19 
 
 Before discussing the different specific reactions and their func- 
 tional significance, it will be desirable to enter on a brief considera- 
 tion of the characters and conditions of the excitability of the 
 cerebral cortex. 
 
 In normal states the grey matter of the cortex is entirely or 
 almost entirely, insensible to mechanical stimulation. Luciani, 
 however, states that though the convexity of the hemisphere 
 does not react to this form of stimulation, yet he has been able to 
 produce movements of the opposite limbs by irritation of the walls 
 of the crucial sulcus. Gouty-'' also states that he has found the 
 convolutions mechanically excitable after ligature of the cerebral 
 arteries. Whether we accept these statements as being strictly 
 accurate or not, it is certain, as was shown by Franck and Pitres,^" 
 that when the cortex has become inflamed and congested by ex- 
 posure or traumatic lesion, it becomes irritable to mechanical 
 stimulation, and may respond not merely by partial movements 
 of the opposite limbs, but also by a unilateral epileptic fit. This 
 is, in fact, the experimental induction of the discharging lesions 
 described by Hughlings Jackson. It is also held by some— for 
 example, Landois"— that the cortex is chemically excitable: a 
 fact, however, which may be due to the inflammatory condition 
 of the tissues thereby induced. The most effective excitant is the 
 application, by closely approximated electrodes, of a galvanic or 
 faradic current of moderate intensity. Fritsch and Hitzig, in 
 their researches, employed the former, but preference has gene- 
 rally been given by other experimenters to the faradic current as 
 being the best calculated to elicit the characteristic reactions of 
 the cortical centres. When an animal is sufficiently narcotised 
 to abolish all restless or spontaneous movements— and the ana3s- 
 thesia must not be too profound, otherwise all reactions cease— 
 the application of the electrodes to different regions calls forth 
 definite motor reactions with such uniformity that, when once 
 the limits of the said region have been accurately defined, one 
 may confidently predict the exact movement which will occur in 
 animals of the same species. This is a fact which is beyond all 
 dispute, and has been frequently demonstrated by myself, 
 Ilorsley, and others, and, indeed, may be regarded as an ordinary 
 lecture experiment. 
 Couty^^ is perhaps the only physiologist whose results appear 
 
 28 Comptes liendus, March, 1879. 
 
 3" Archives de Physioloijie, 1883. 
 
 '1 Abstract in Nmi,rolo(j. Centralblatt, IS'PO. p. Hf,. 
 
 '2 Le Cerveau Moteur, Archives de I hysioloyie, 1883. 
 
 c2 
 
20 CEREBRAL LOCALISATION. 
 
 to contradict the above statement ; but as his experiments were 
 performed on animals not narcotised, it is probable that any ir- 
 regularity in the effects of excitation was due to spontaneous 
 movements on the part of the animal. Some variations from ab- 
 solute uniformity may, however, occur from want of symmetry in 
 the convolutions, and still more from changes in the excitability 
 of the cortex. These are particularly apt to occur after repeated 
 exploration, so that a mixture of effects may be produced by dif- 
 fusion of the current from the one centre into others which have 
 been rendered hyperexcitable by previous stimulation. The lateral 
 diffusion of the current, which always occurs more or less, is the 
 chief obstacle to the precise delimitation of the cortical centres by 
 the method of excitation. Hence the limits of a region may be 
 somewhat differently given by different experimenters ; but, 
 making due allowance for all these sources of error, it has been 
 found possible to arrive at a remarkable degree of harmony as to 
 the locality and extent of the respective areas. The extrapolar 
 diffusion of current which can be demonstrated in the brain, as in 
 other animal tissues, has been regarded by Dupuy^^ as an in- 
 superable objection to the theory that the results of application 
 of the electrodes to the cortex are due to stimulation of the cortex 
 itself ; and attempts are made to explain them away by mere 
 physical conduction of the currents to centres and tracts at the 
 base of the brain. But no satisfactory explanation can thus be 
 afforded of the manifest differences in reaction which follow the 
 application of the electrodes to regions in close proximity to each 
 other, nor of the total absence of reaction when the electrodes 
 are placed on the island of Reil, which is nearer the base of 
 the brain than other regions which act uniformly and without 
 fail. 
 
 The chief objection to the direct excitability of the cottex itself 
 is found in the fact that, even after removal of the cortex, similar 
 reactions are still obtainable when the electrodes are placed on 
 the subjacent medullary fibres, This was first pointed out by 
 Burdon-Sanderson,^* and has been confirmed by all subsequent 
 experimenters. After removal of the cortex, however, the medul- 
 lary fibres lose their excitability, like motor nerves separated 
 from the anterior cornua of the spinal cord, so that, after a lapse 
 of four days, no reactions can be produced by the strongest 
 stimulation. This fact completely disposes of the physical- 
 
 ss Examen de quelques Points de la Physiologie du Cerveaw, 1873. 
 34 Proceedings Royal Society, June, 1874'. 
 
EXCITABILITY OF BRAIX. 
 
 21 
 
 conduction-to-the-base-of-the-brain hypothesis. It has thus been 
 satisfactorily established that the cones of medullary fibres, cor- 
 responding to the respective cortical centres, are functionally 
 differentiated like the cortical centres themselves, and, as has 
 
 EYES OP: 
 EYES T: 
 MOUTH OP: 
 
 HEAD T; 
 
 TONGUE 
 
 MOUTH REti 
 
 SHOULDER 
 
 ELBOW 
 
 WRIST 
 
 FINGERS 
 THUMB 
 
 TRUNK 
 
 HIP 
 
 ANKLE 
 
 KNEE 
 
 HALLUX 
 
 roEs 
 
 Fig. 4.— Arrangement of the motor fibres of the internal capsule, according 
 to Beevor and Horsley. 
 
 been shown by Franck and Pitres,^' and more recently, with 
 greater detail, by Beevor and Horsley,^* maintain their individu- 
 
 »* Complex fiendus de la Society Bioloff., 1877. 
 3« Proceedings Royal SocieUj, No. 286, 1890. 
 
22 CEREBRAL LOCALISATION. 
 
 ality, and are echeloned in definite and regular order in the internal 
 capsule. 
 
 On the accompanying figure (Fig. 4), kindly supplied me by 
 Dr. Beevor, are marked the points on the internal capsule 
 from which, according to their recent researches, minimal 
 stimulation excites the respective movements which are indi- 
 cated on the margin. But it does not follow, because the medul- 
 lary fibres are excitable, that the corresponding cortical regions are 
 unexcitable, and that the current merely passes through them. It 
 is a priori more likely that there is also functional differentiation 
 of the cortical centres to which they are distributed, and that the 
 grey matter is, under normal conditions, the natural excitant of 
 the reactions which we are able to produce by artificial stimula- 
 tion with the electric current. And a comparison of the respec- 
 tive reactions of the cortex and medullary fibres indicates such 
 differences as can only be explained on the supposition that the 
 cortical centres are themselves excitable. 
 
 First, as regards the relative excitability of the grey matter and 
 subjacent medullary fibres. This is a point on which there are 
 some differences of opinion, but Putnam found ^'^ the medullary 
 fibres less excitable than the cortex, so that in order to produce 
 the customary reaction, it was necessary to use a much stronger 
 current than before. This has been confirmed by Franck and 
 Pitres, who have further shown that the diminished excitability 
 cannot be accounted for by mere shock or haemorrhage, inasmuch 
 as the neighbouring grey matter acted as readily as before. They 
 have further given reasons for believing that the contrary results 
 obtained by Eichet,^^ and Bubnoff and Heidenhain ^^ are due to 
 the action on the cortex of the chloral and morphine 
 under which their experiments were performed. These agents, 
 without doubt, paralyse the excitability of the grey matter. 
 It was noted by Fritsch and Hitzig, in their experiments, 
 that the anodal closure was a more effective stimulus than 
 the cathodal — a fact which might be interpreted as signifying 
 that the real stimulus proceeded from the virtual cathode in the 
 deeper layers of the cortex, or termination of the medullary fibres. 
 This, however, has been ebown by Gerber,*° not to be uniformly 
 
 3T Soston Med. and Surg. Journal, 1874. 
 
 38 Sur les Circonvolutions Cerebrales, 1879. 
 
 39 Pfliiger's Archiv.f. Physiologic, 1881. 
 
 " Beitrage zur Lehre von der electrisctien Eeizung des G-rosshirns," Pflugers' 
 
 Archivfur Physiologie, Band 39, 1888. 
 
EXCITABILITY OF BRAIN. 23 
 
 the case. Gerber finds that when the cortex is in a normal state 
 the cathode is the more effective stimulant, but that when changes 
 have occurred from long exposure the anode predominates. These 
 experiments would, therefore, indicate that in the normal condi- 
 tion of the brain the laws of galvanic excitability are the same as 
 for motor nerves. 
 
 Another important difference between the reactions of the cor- 
 tex and the subjacent medullary fibres, which was first pointed 
 out by Franck and Pitres, is that the time lost between the ap- 
 plication of the stimulus and the occurrence of muscular contrac- 
 tion is much greater in the case of the former than the latter. 
 This interval, after deducting the time necessary for the trans- 
 mission of the impulse through the spinal cord and motor nerves, 
 indicates a retardation in the cortex of 0.045 second. After re- 
 moval of the grey matter and application of the electrodes to the 
 medullary fibres, the period of retardation diminishes to 0.030 
 second, that is, about one-third less, and this difference is put at a 
 considerably higher figure by Bubnoff and Heidenhain. 
 
 The signification of this fact is that the grey matter of the cor- 
 tex does not behave like an inert layer, which merely allows trans- 
 mission of the electric current to the medullary fibres, but, like 
 other nerve centres, stores up and transforms the stimuli which it 
 has received into its own energy. 
 
 There is also a characteristic difference between the muscular 
 curves registered on stimulation of the cortex and medullary 
 fibres respectively. In the latter case the curve rises abruptly, 
 and is of short duration ; while in the former it rises more gradu- 
 ally, is more prolonged, and frequently marked by the occurrence 
 of a secondary tetanus, which latter is altogether peculiar to the 
 cortex, and is never seen when the medullary fibres alone are 
 stimulated. The cortex is apt, after repeated stimulation, or after 
 the receipt of a succession of stimuli each insufficient to produce 
 reaction, to respond by tonic, followed by clonic, spasms of the 
 correlated muscles of a truly epileptic type. These convulsions 
 tend to spread and become generalised in the order and sequence 
 originally described by Hughlings Jackson. They never occur on 
 stimulation of the medullary fibres alone, apart from the inter- 
 vention of the grey matter of the cortex on the one side or the 
 other, and cannot be produced if the cortical centres are entirely 
 destroyed on both sides. The duration of the effects of stimula- 
 tion of the medullary fibres is strictly proportional to that of the 
 stimulus which is applied to them. We shall also see as we pro- 
 
24 CEREBRAL LOCALISATION. 
 
 ceed that the effects of localised destruction of the cortex are the 
 counterpart of those of irritation, however induced, and we may 
 from this conclude that there is the same functional differentia- 
 tion in the cortex as in the medullary fibres, even if the facts 
 which I have just mentioned should not be regarded as of them- 
 selves completely establishing this proposition. 
 
LECTUKE II 
 
LECTURE II. 
 
 Mb. Pbesident and Gentlemen, — I will now invite your at- 
 tention to a brief consideration of the phenomena of electrical 
 irritation of the brain of the monkey, more especially as deter- 
 mined by my own experiments, and those of Horsley, Schafer and 
 Beevor, which, though in all essentials confirming mine, have been 
 worked out with more elaborate detail and minuteness.^ 
 
 Beginning anteriorly we find that what is generally termed the 
 prefrontal lobe— that is, all in advance of a line drawn at right 
 angles to the anterior extremity of the precentral sulcus— gives 
 no, or very doubtful, response to electrical stimulation. 
 
 Between this line and that of the precentral sulcus continued 
 upwards to the longitudinal fissure, there is a region or area (1, 2, 
 Fig. 5 ; Figs. 6 and 7, head), stimulation of which causes open- 
 ing of the eyes, dilatation of the pupils, and movements of the 
 head and eyes to the opposite side. This area has been further 
 differentiated by Beevor and Horsley, according to the primary 
 movements which result from minimal stimulation of the points 
 indicated on their diagram (Fig. 8). The corresponding region in 
 the brain of the dog is (12, Fig. 9). No similarly differentiated 
 centre is seen in the cat (Fig. 10) or rabbit (Fig. 11). 
 
 At the upper extremity of the central convolutions (ascending 
 frontal, ascending parietal, and postero- parietal lobule) (1, 2, Fig. 5; 
 leg, Figs. 6 and 7), and extending over the margin of the hemi- 
 sphere into the posterior part of the marginal convolution, or 
 paracentral lobule, electrical stimulation causes movements of the 
 lower e:ctremity. The movements vary according to the position 
 of the electrodes on this area. Behind the fissure of Rolando the 
 movements are chiefly, or exclusively, of the foot or toes. Anterior 
 to the fissure of Rolando they are combined with flexion of the 
 
 1 Horsley and Schafer, PAii. Tram., B. 20, 1888; Beevor and Horsley, Phil. 
 Tram., B. 1890. 
 
28 
 
 CEREBRAL L CALLS A TION. 
 
 leg and thigh. With minimal stimulation the movements may be 
 still further differentiated (Fig. 8), and, in particular, the great 
 toe can be excited to movement separately by stimulation at the 
 upper extremity of the fissure of Rolando. The corresponding 
 region in the brain of the dog, cat, and rabbit, is indicated by 1, 
 Figs. 9, 10, 11. 
 
 Fig. 5. — The left hemisphere of the monkey. 1. The opposite hind limb is 
 advanced as in walking ; 2, flexion with outward rotation of the thigh, 
 rotation inwards of the leg. with flexion of the toes ; 3, the tail ; 4, the 
 opposite arm is adducted, extended, and retracted, the hand pronated ; 
 5, extension forwards of the opposite arm ; a, b, c, d, movements of 
 fingers and wrist ; 6, flexion and supination of the forearm ; 7, retrac- 
 tion and elevation of the angle of the mouth ; 8, elevation of the ala of 
 the nose and upper lip ; 9 and 10, opening of the mouth, with protru- 
 sion (9) and retraction (10) of the tongue ; 11, retraction of the angle of 
 the mouth ; 12, the eyes open widely, the pupils dilate, and head and 
 eyes turn to the opposite side ; 13 and 13', the eyes move to the opposite 
 side ; 14, pricking of the opposite ear, head and eyes turn to the opposite 
 side, pupils dilate widely. 
 
 Below the leg area, and partly in front of it, and occupying the 
 middle third, or rather two-fourths of the central convolutions, 
 there is a region stimulation of which causes movements of the 
 upper extremity (3, 4, 5, 6, a, b, c, d, Fig. 5, and arm, Fig. 6), In 
 this area it is possible to differentiate, more or less completely, 
 movements of the upper arm (protraction and retraction) ; move- 
 ments of the forearm (flexion, supination, etc.) ; and of the wrist, 
 fingers and thumb. The proximal movements are represented 
 most in the upper part of this region ; the distal movements, that 
 is, those of the fingers and thumb, most at the lower part. 
 
 By minimal stimulation at the lower extremity of the intra- 
 parietal sulcus the thumb may be individually thrown into the 
 action (Fig. 8). The corresponding region in the brain of the dog 
 is that indicated by the numerals 4 and 5 situated on the post- 
 
ELECTRICAL REACTIONS. 29 
 
 crucial division of the sigmoid gyrus (Fig. 9), and by the same 
 numerals on the brain of the cat (Fig. 10), together with a situ- 
 ated on the anterior extremity of the second external convolution. 
 Stimulation of this latter point causes protrusion of the claws ; 
 an action comparable to the movements of the wrist and fingers 
 excited from the lower part of the ascending parietal convolution 
 in the monkey. The corresponding region in the brain of the 
 rabbit is indicated by the same numerals (4, 5, Fig. 11). 
 
 Below the arm area, and occupying the lower third of the 
 central convolutions, there is a region stimulation of which causes 
 movements of the face, mouth and tongue. In the upper part of 
 this area can be differentiated centres for movements of the upper 
 facial muscles (7, 8, Fig. 5) in front of, and platysma (11) behind 
 the fissure of Rolando. The corresponding region in the brain of 
 the dog, relatively much larger than in the monkey, is indicated 
 by the numerals (7, 8, Fig. 9), and the same indicate the homolo- 
 gous regions in the brain of the cat (Fig. 10), and rabbit (Fig. 11). 
 In the lower portion excitation causes movements of the mouth 
 and tongue ; protrusion of the tongue being generally caused by 
 stimulation anteriorly (9, Fig. 5), and retraction by stimulation 
 posteriorly (10, Fig 5). 
 
 It has further been demonstrated by Semon and Horsley ^ that 
 excitation of the lower extremity of the ascending frontal con- 
 volution causes phonatory closure of the vocal cords. The phona- 
 tory closure of the vocal cords was first demonstrated ocularly in 
 the dog, on irritation of the pre-sigmoid region, by Krause,^ though I 
 had many years previously,* given audible demonstration of the 
 same fact by showing that stimulation in this neighbourhood not 
 infrequently caused barking ; and similar effects (spitting, mew- 
 ing) by stimulation of the homologous region in the brain of the 
 cat. I also pointed out that the movements occurring on stimu- 
 lation of this part were distinctly bilateral, an effect which 
 Krause, Horsley and Semon, have found to be true also of move- 
 ments of the vocal cords. 
 
 The areas for the head and eyes, arm and leg, extend over the 
 margin of the hemisphere into the mesial aspect or marginal 
 convolution. These I had to some extent noted in my first ex- 
 periments, but a more thorough exploration of the reactions of this 
 
 * On the Central Motor Innervation of the Larynx, Brittsh Mkdical 
 
 Journal, December 2l8t, 1889. 
 
 » Plluger'i Arctiiv., 1883. 
 
 * Wtit Hiding Asylum. Reports, 1873. 
 
30 
 
 CEREBRAL LOCALISATION. 
 
 region was first made by Horsley and Schafer.® Excitation of 
 this convolution from before backwards (see Fig. 7), causes 
 movements of the spine, tail, and pelvis ; behind these, extension 
 of the hip, flexion of the leg, and lastly,^ movements of the foot 
 and toes. These movements are not, however, always clearly 
 differentiated, as they are apt to run into each other, and to be 
 complicated by secondary movements of the various segments of 
 the limb. 
 
 Fig. 6. 
 
 Stimulation of the angular gyms, pit courbe (13' 13, Fig. 5), causes 
 movements of the eyeballs, and occasionally of the head, to the 
 opposite side, generally combined with an upward or downward 
 direction, according as the electrodes are on the anterior or 
 posterior limb of this gyrus. The condition of the pupils is not 
 constant, occasionally they are contracted. The corresponding 
 region in the brain of the dog is indicated by 13 (Fig. 9), 
 situated on the second external convolution, and the homologous 
 region in the brain of the cat (Fig. 10), and the rabbit (Fig. 11), is 
 indicated by the same numerals. 
 
 5 Phil. Trans., vol. 179, 
 
ELECTRICAL BE A CTIONS. 
 
 31 
 
 Excitation of the occipital lobe appeared in my earlier experiment s 
 to yield negative results. But Luciani and Tamburini * occasionally 
 obtained movements of the eyeballs similar to those occur- 
 ring on excitation of the angular gyrus, though less marked 
 And Schafer ^ describes similar movements as occurring from 
 stimulation of different parts of the occipital lobe and neigh- 
 bouring regions. My own experiments on several monkeys, 
 though not opposed to those of Schafer, are more in harmony 
 
 Fig. 7. — The motor areas according to Horsley and Schafer, 
 
 with those of Luciani and Tamburini, and show that, though 
 movements of the eyeballs may be obtained by excitation of the 
 occipital lobe, they are, as a rule, less constant and less easily 
 excited than from stimulation of the angular gyrus. 
 
 Stimulation of the superior temporal gj'rus (14, Fig. 5) causes 
 pricking of the opposite ear, opening of the eyes, dilatation of the 
 pupils, and direction of the head and eyes to the opposite side. 
 Precisely the same reaction occurs after stimulation of the poste- 
 rior limb of the third external convolution of the brain of the dog 
 
 ' Sui Centri Paico-Senfori Corticali, 1879. 
 1 Proc. Roy. Hoc, 1888. 
 
32 
 
 CEREBRAL LOCALISATION. 
 
ELECTRICAL HE ACTIO XS. 
 
 33 
 
 (14, Fig. 9), and so also in the brain of the cat (Fig. 10), and 
 homologous region of the brain ofthe rabbit (Fig. 11), Sometimes 
 only moTements of the ear are caused, and sometimes the animal 
 attempts to bound off the table as if suddenly startled. 
 
 Stimulation of the hippocampal lobule or anterior extremity 
 of the hippocampal gyrus in monkeys, dogs, cats, and rabbits 
 causes precisely the same results — namely, torsion of the nostril 
 on the same side — as if from irritation applied directly to the 
 nostril itself. Irritation of the gyrus hippocampi occasionally 
 caused movements such as might be conditioned by direct irrita- 
 tion of the opposite limbs ; but beyond this I have not been able 
 
 Pig. 9. — Left hemisphere of the brain of dog. 1. The opposite limb is 
 advanced ; 3, lateral or wagging motion of the tail ; 4, retraction with 
 adduction of the opposite fore limb ; b, elevation of shoulder, and exten- 
 sion forwards of the opposite fore limb ; +, flexion of the paw ; 7, action 
 of the orbicularis oculi and zygomatics ; 8, retraction and elevation of 
 the opposite angle of the mouth ; 9, opening of the mouth and move- 
 ments of the tongue ; 11, retraction of the angle of the mouth ; 12, the 
 eyes widely opened with dilatation of the pupils, with movement of the 
 eyeballs and head to the opposite side ; 1.3, movement of the eyeballs to 
 the opposite side ; 14, pricking, or sudden retraction, of the opposite 
 ear ; 15, torsion of the nostril on the same side. 
 
 to obtain any constant reaction from stimulation of the rest of 
 the temporal lobe or other portions of the cortex. 
 
 Such is briefly a summary of the phenomena of electrical irrita- 
 tion of the different regions of the cerebral cortex. These results, 
 apart from the interpretation which we put upon them, indicate 
 some form of functional differentiation ; and it is obvious, on com- 
 paring the corresponding areas in the brain of the monkey, dog, 
 cat, and rabbit, that there are great differences as regards their 
 relative extent, and the character of* the movements with 
 which they are in relation. Whether complete parallelism obtains 
 
 D 
 
34 
 
 CEREBRAL LOCALISATION. 
 
 between the brain of the monkey and the brain of man is a 
 question which, until recently, could only be answered by reference 
 to the facts of localised lesions. Bartholow * and Sciamanna ^ 
 had observed movements of the opposite side of the body on 
 stimulation of the cortex through the dura mater— the former in 
 a case of cancerous ulceration and the latter in a case of tre- 
 phining. But their results, though so far in accordance with 
 those of experimentation on monkeys, were lacking in precision. 
 Recently, however, surgeons have on several occasions resorted to 
 gentle faradisation of the cortex, in order to define accurately the 
 regions which they have desired to extirpate for the cure of focal 
 jam 
 
 Fig. 10. — Left hemisphere of the brain of the cat. 1. Advance of the oppo- 
 site hind limb ; 4, retraction and adduction of the opposite foreleg ; 5, 
 elevation of the shoulder, with flexion of the forearm end paw ; A, 
 clutching or grasping action of the paw, with protrusion of the claws ; 
 7, elevation of the angle of the mouth and cheek, with closure of the 
 eye ; 8, retraction, with some degree of elevation of the angle of the 
 mouth, and drawing downward and forward of the ear ; 9, opening of 
 the mouth and movements of the tongue ; 13, the eyeballs move to the 
 opposite side ; 14, pricking of the ear, and head and eyes turn to the 
 opposite side ; 15, elevation of the lip and torsion of the nostril on the 
 same side ; divergence of the lips. 
 
 epilepsy. One of these has been reported by Horsley, and several 
 others have been quoted by Mills in his valuable memoir on 
 Cerebral Localisation in its Practical Eelations.^" In one case the 
 lower halves of the two central convolutions — the posterior 
 extremity of the second frontal and the posterior superior corner 
 of the third frontal convolution — were exposed in the left hemi- 
 sphere. "Careful examinations were made with the faradic 
 current applied to the cortex with the view of locating the proper 
 centres for excision. Four distinct responses in the shape of 
 
 8 Amer. Journ. Med. Sciences, April, 1874. 
 9 Arch, di Psichiatria, 1882. 
 10 Read before the Washington Congress, September 19tb, : 
 JBrain, 1889. 
 
 !; reprinted in 
 
ELECTRICAL REACTIONS. .35 
 
 definite movements were obtained after several trials ; these were 
 
 (1) in the most anterior position at which movements resulted, 
 distinct conjugate deviation of the head to the opposite side; 
 
 (2) a little below and behind this point, drawing of the mouth 
 outwards and upwards ; (3) above this spot for movements of the 
 angle of the mouth, about half an inch, extension of the wrist and 
 fingers was produced ; (4) behind and above the latter point, 
 distinct flexion of the fingers and wrist. Continuing and increas- 
 ing the faradic application at this last determined point, the 
 fingers, thumb, wrist, and forearm were successively flexed, and 
 the whole extremity assumed the ' wing-like ' position. The 
 order of events, according to three persons who were present, and 
 who observed the patient's spasms, being exactly that which had 
 been noticed at the beginning of his convulsive seizures." 
 
 Fig. 11. — Left hemisphere of the brain of rabbit. 1. Advance of the oppo- 
 site hind leg; 4, retraction with adduction of the opposite fore limb ; 5, ele- 
 vation of the shoulder and extension forward of the fore limb ; 7, retrac- 
 tion and elevation of the angle of the mouth ; 8, closure of the opposite 
 eye; 9, opening of the mouth, with movements of the tongue ; 1.3, for- 
 ward movement of the opposite eye, occasionally turning of the head 
 to the opposite side ; 14, sudden retraction and elevation or pricking of 
 the opposite ear ; 1.5, torsion or closure of the nostril. 
 
 In a second case reported by Keen:" " On touching the cortex 
 with the electrodes at a position which apparently corresponded 
 to the anterior portion of the pre-Rolandic convolution, just be- 
 hind the precentral fissure, movements of the wrist and fingers 
 were produced. The hand moved in extension in the mid-line and 
 to the ulnar side at different touches, the fingers being extended 
 and separated. Above the region in which these movements were 
 obtained application of the current caused movement of the left 
 elbow, both flexion and extension, and of the shoulder, which was 
 raised and abducted. Below the region, where the hand move- 
 ments were excited, the application of the current produced an 
 upward movement of the whole of the left face." These results 
 correspond very closely with the position of the various centres 
 as already defined. 
 
 " Amer. Jaum. Med. Scitnces, November, 1888. 
 
 d2 
 
36 CEREBRAL LOCALISATION. 
 
 In another case, reported by Lloyd and Deaver,^^ an area was 
 exposed in the right hemisphere corresponding to the junction of 
 the middle and lower thirds of the central convolutions. When the 
 electrodes were applied to a point just posterior to the fissure of 
 Eolando the movements which occurred were in order — flexion of 
 the thumb on the palm, flexion of the flngers, flexion of the wrist, 
 extending to flexion of the elbow. At a point in front and below 
 stimulation caused contraction of the facial muscles of the oppo- 
 site side. 
 
 In a fourth case, reported by Nancrede,^^ movements of the 
 thumb were induced by stimulation of a region corresponding to 
 the second lower fourth of the ascending parietal convolution. 
 All these results are in close harmony with those obtained on 
 stimulation of the cortex of the brain of the monkey, and we have 
 therefore every reason to believe that, cceteris paribus, the func- 
 tional relations of the human cortex are identical with those of 
 the lower animals. 
 
 So far as the excitation method is concerned, we are entitled to 
 say that, whether the individual segments of a limb are separately 
 localised, or are represented, more or less, throughout a common 
 area, the areas as a whole are completely differentiated from each 
 other. No movements of the leg result from irritation of the 
 facial centres, nor of the face from the leg centres. The face area 
 and leg area are thus entirely differentiated from each other, and 
 from the oculo-motor area. What is true of centres widely apart 
 is doubtless true of centres which are in close proximity to each 
 other. The fact that stimulation of the margin of a given area 
 is apt to produce joint movements of this and the adjoining area 
 must not be taken to imply that this portion subserves conjoint 
 functions — say of the arm and leg, or arm and face. 
 
 The true explanation appears to me to be that the excitation 
 method is unable completely to differentiate the boundaries of the 
 respective centres. Eegions which are in the closest proximity to 
 each other, anatomically and functionally, are apt to be discharged 
 together by diffusion of the stimulus. Nor, even if we are unable 
 to entirely dissociate the centres from each other by the destruc- 
 tive method, are we on this ground entitled to conclude that there 
 is any functional fusion between the two ; for a destructive lesion, 
 however small, situated on the margin of any given centre, is cal- 
 culated to affect the functions of more than one. Facts will be 
 
 12 Amer. Journ. Med. Sciences, November, 1888. 
 13 Medical News, November 24th, 1888. 
 
ELECTRICAL REACTIONS. 37 
 
 adduced as we proceed which to my mind justify the conclusion 
 that the areas as a whole are as completely differentiated from 
 each other as the limbs themselves, or one organ of sense from 
 another. 
 
 We have seen, however, in respect to the individual movements 
 of a limb, that though one particular movement can frequently 
 be isolated by minimal stimulation of a definite point within the 
 general area, yet the same movement may occur along with others 
 when another part of the area is uuder stimulation. This may be 
 interpreted either on the supposition that the particular move- 
 ment, say of the thumb, is represented throughout the whole of 
 the arm area, or that it is only a case of diffusion of the stimulus 
 from one part to another. It is difficult to decide which of these 
 views is the correct one, and it may be that neither accurately 
 represents the whole truth. For the reactions of the limbs which 
 result from stimulation of the cortex are not mere muscular con- 
 tractions, but synergic movements co-ordinated into acts; and 
 inasmuch as has been shown by Professor Yeo and myself," the 
 same muscles or muscular groups enter into the composition of 
 the different movements innervated by the respective motor 
 roots of the brachial and crural plexuses, so the same muscular 
 groups may have a multiple representation in the various sub- 
 diTisions of the general area. And it would appear that in the 
 cortical areas there is a much greater differentiation than in the 
 respective segments of the brachial and crural enlargements of 
 the spinal cord. But in my opinion any further multiple repre- 
 sentation outside the general area of a limb is altogether opposed 
 to the facts of localisation as determined either by the methods 
 of excitation, or destruction, or both. 
 
 We have next to inquire into the important and much disputed 
 question as to the signification of the motor reactions which result 
 from electrical stimulation of the different cortical regions. 
 Though many of the movements are evidently such as may be 
 termed purposive, it does not follow that they are indicative of 
 direct stimulation of motor regions in the strict sense of the term, 
 for the movements may be the result of some psychical condition 
 incapable of being expressed in physiological terms ; or they may 
 be reflex, and thereby not differing essentially from those result- 
 ing from peripheral stimulation ; or they may be motor in the 
 sense of being due to irritation of parts in direct connection with 
 
 i* pToe. Hoy. Soc, 1881, The Functional Relations of the Motor Bpote of tlj^ 
 Brachial and Lumbo saural Plexuses. 
 
38 CEREBRAL LOCALISATION. 
 
 the motor tracts and motor nerves, or they may be partly one and 
 partly the other. The method of excitation itself is not compe- 
 tent to solve these questions, and requires as a complement the 
 strictly localised destruction of those areas, stimulation of which 
 gives rise to definite motor reactions. 
 
 A careful consideration of the reactions in different orders of 
 animals, and the fact that similar movements are in some cases 
 excitable from different cortical regions, led me to believe that 
 they might have various significations, and I formed the hypothe- 
 sis that some might be due to stimulation of motor regions proper, 
 while others might be looked upon as the associated expression 
 of subjective sensation. On this hypothesis I instituted localised 
 destructive experiments, and thus determined the existence of 
 sensory or perceptive centres respectively related to the different 
 forms of sensibility, as well as of centres more especially, if 
 not exclusively, motor in character. The existence of distinct 
 sensory centres has been confirmed by succeeding physiological 
 and clinical research, and I have the satisfaction of thinking that 
 such errors as I have committed in the delimitation of the various 
 sensory regions have been errors more of omission than of com- 
 mission, and that the localities in which I originally fixed the 
 respective sensory areas correspond in part at least with the posi- 
 tion assigned to them by the most reliable experimental and 
 clinical methods. 
 
 The Visual Centres. — I will first call your attention to the re- 
 actions occurring on stimulation of the occipito-angular region in 
 monkeys, and its homologue in the lower orders of animals. The 
 reactions, as we have already seen, are movements of the eyeballs, 
 and occasionally of the head to the opposite side ; and frequently 
 also of the pupils, not always uniform in character, being some- 
 times contraction, at other times dilatation. These movements I 
 have found to be most easily and most uniformly excited from the 
 anterior and posterior limbs of the angular gyrus. As a rule, 
 along with the lateral movements there is upward direction when 
 the anterior limb, and downward when the posterior limb of this 
 gyrus is excited. Movements of the eyeballs are also obtainable, 
 as Luciani and Tamburini first pointed out, from irritation of the 
 occipital lobe. Schafer, who omits the anterior limb of the angular 
 gyrus, though I have found this as excitable as the rest, obtains 
 downward movements of the eyes on stimulation, not only of the 
 posterior limb of the angular gyrus, but also of the upper end of 
 the middle temporal gyrus, that part oi the occipital lobe imme^ 
 
THE VISUAL CENTRES. 39 
 
 diately behind the external parieto-occipital fissure, and on each 
 side of the internal parieto-occipital fissure. He obtains upward 
 movements on stimulation of the under surface of the occipital 
 lobe, the lower part of the mesial aspect of this lobe, and of the 
 lower margin of the convex surface. He obtains a simple lateral 
 movement of the eyes on excitation of the rest of the convex 
 aspect of the occipital lobe and a narrow strip of the mesial sur- 
 face along the margin of the great longitudinal fissure. The 
 middle portion of the mesial surface does not appear to be in- 
 cluded in this scheme. 
 
 My hypothesis that these movements of the head and eyes are 
 the signs of the arousal of subjective visual sensation, and due to 
 associated action of the frontal or subcortical oculo-motor centres, 
 has received confirmation from the experiments of Schafer on the 
 latency periods of the ocular movements following excitation of 
 the frontal and occipito-temporal regions respectively.^' The 
 result of this comparison made in a number of monkeys was to 
 show that the latent period is longer by some hundredths of a 
 second in the case of stimulation of the occipital lobe than of the 
 oculo-motor centre of the frontal area; thus indicating that in 
 the former case the nervous impulses must be transmitted through 
 at least one more nerve centre than in the latter. This would 
 agree with the hypothesis that in the one case the movements 
 were reflex, and in the other direct. The fact that the ocular 
 movements are still obtainable on stimulation of the occipito- 
 angular region, after complete removal of the frontal regions, 
 shows that they are not necessarily indicative of the associated 
 action of these cortical centres, but may be due, if they are not 
 always so, to excitation of the oculo-motor centres of the corpora 
 quadrigemina. 
 
 Danillo^* has found that severance cf the fibres of association 
 between the occipital lobe and the frontal region does not prevent 
 the occurrence of the ocular movements ; while Bechterew^'' and 
 Munk^* have found that the movements are entirely annihilated 
 by severance of the subjacent medullary fibres. It is contended 
 by Danillo and Bechterew that the movements cannot, therefore, 
 be regarded as indicative of subjective visual sensation ; but this 
 would not be disproved even if the movements still continued 
 
 IS Proc. Boy. Soc, February 1.3th, 1888. 
 1* Archives de Neurologie, vol. xviii, 1889, p. 145. 
 1' Neurolog. Centralblatt., September 15th, 1889. 
 ** Sitzungsberichte der Akad. d, Wiss. zu, Berlin vol. xvi, January, 1890. 
 
40 CEREBRAL LOCALISATION. 
 
 after removal of the grey matter, for the excitation of the medul- 
 lary fibres would be equivalent to excitation of the cortex itself. 
 We may assume with Munk that there are radial or centrifugal 
 fibres between the occipital cortex and the oculo-motor centres ; 
 and that excitation of the central expansion of these tracts would 
 produce practically the same effect as stimulation of the centres 
 with which they are in relation. 
 
 The occipito-angular region is the visual area of the cortex. 
 Complete destruction of this area in the one hemisphere causes 
 permanent hemianopia to the opposite side by paralysis of the 
 corresponding halves of both retinae ; while bilateral destruction 
 causes complete and enduring blindness of both eyes. Apart from 
 the loss of vision, there are no other sensory or motor defects. The 
 sensibility of the eyeball is intact, and the ocular movements are 
 absolutely unimpaired. There is no impairment of the sensibility 
 or motor power of the limbs. The other special senses are un- 
 affected. If the destruction of the occipito-angular region is in- 
 complete, unilaterally or bilaterally, the resulting hemianopia in 
 the one case is not enduring, nor is the blindness permanent in 
 the other. 
 
 There is, however, scarcely a particular of the above general 
 statement which has not been controverted ; but I am of opinion 
 that every one of them is in accordance with the evidence fur- 
 nished by strictly localised and carefully observed lesions of this 
 region. 
 
 In my earlier investigation, I was led to believe that the angular 
 gyri alone constituted the visual centres, a conclusion which I 
 founded on the positive effects of lesions of the angular gyri and 
 the uniformly negative results of destruction of both occipital 
 lobes, except when the lesions trenched on the parieto-occipital 
 fissure. In the latter case it appeared to me that the imperfec- 
 tions of vision or occasional total blindness were due to inter- 
 ference with the functions or the connections of the angular gyri 
 themselves. I show you here a photograph of the brain of 
 one of my earlier experimental animals." Both occipital lobes 
 were removed at the same time. Some encephalitis ensued, 
 which caused extension of the primary lesions. Tou will see 
 that on the right side, not only the occipital lobe, but also 
 part of the posterior limb of the angular gyrus has been removed. 
 On the left side the angular gyrus is intact, superficially, but the 
 
 " Experiment XXIV, Phil. Trans., vol. clxv, part 2, 1875. 
 
TKE VISUAL CEXTRES. 41 
 
 medullary fibres of the cut surface bulge considerably, owing to 
 inflammatory hernia. Notwithstanding this extensive bilateral 
 lesion, the animal, within an hour of the operation, gave clear 
 evidence of the retention of vision ; for it made grimaces, and ran 
 away when threatened. Subsequent examination revealed the 
 fact that vision, though good, was impaired, as indicated by some 
 want of precision in laying hold of objects offered it. But, be- 
 yond this slight defect in vision, there was no impairment of the 
 animal's faculties in other respects, and it continued well until its 
 death after a second operation three weeks subsequently, in which 
 the greater part of both frontal lobes were removed. This second 
 operation caused no further impairment of the animal's vision — 
 a fact of great importance in reference to the question of the rela- 
 tion of the frontal lobes to the sense of sight. 
 
 Inasmuch as in this animal, as well as in others, in which 
 similar symptoms occurred, the lesions implicated the region of 
 the parieto-occipital fissure and angular gyrus, I attributed the 
 impairment of vision to this cause ; for, when the line of section 
 of the occipital lobes was well separated from this fissure, no 
 impairment of vision was perceptible. Thus the occipital lobes 
 were exposed on both sides in a monkey, and the surface destroyed 
 by the cautery, which was also passed deeply into the interior of 
 the lobes so as to break up the medullary fibres. The operation 
 was completed at 3 30 p.m. The following are the notes of the 
 animal's condition : — 
 
 " 4.10 P.M. The animal, after lying in a state of stupor till now, 
 begins to move, but staggers a good deal. The eyes are open and 
 the pupils dilated. It indicated consciousness by turning its 
 head when called to. 
 
 " 5.45 P.M. Gives emphatic evidence of sight. Ran away when 
 I approached it, carefully avoiding obstacles. Seeing its cage 
 door open, it entered and mounted on its perch, carefully avoiding 
 the cat which had taken up its quarters there. Tried to escape 
 my hand when I offered to lay hold of it, but picked up a raisin 
 which I had left on the perch."^" 
 
 Notwithstanding the extensive destruction of both occipital 
 lobes in this case, the animal, in a little more than two hours 
 after the operation, gave the most emphatic evidence of precise 
 vision. 
 
 In another case in which the occipital lobes were severed by a 
 
 *« Bzperlment XXII, Ph.il. Tram., vol. clxv, part 2, p. 25. 
 
42 CEREBRAL LOCALISATION. 
 
 perpendicular section a quarter of an inch posterior to the 
 parieto-occipital fissure,^^ the animal, notwithstanding the re- 
 moval of at least two-thirds of both occipital lobes, gave clear 
 evidence of vision within half an hour after the operation. In 
 another monkey in which my colleague. Professor G, Y. Yeo, 
 removed about two-thirds of both occipital lobes, the animal 
 within two hours after the operation was able to pick up minute 
 objects lying on the floor.^^ 
 
 I show you here also a photograph of the brain of a monkey in 
 which the left occipital lobe was removed by an incision immedi- 
 ately posterior to the parieto-occipital fissure. In this case, owing to 
 the dressings having been torn off, the wound became septic and 
 the animal died on the fifth day. On the day after the operation, 
 however, no imperfection of vision could be discovered ; for the 
 animal took things offered it on the right or left front, and was 
 able to run about the laboratory in every direction, passing among 
 chairs and other articles of furniture without ever once knocking 
 its head on one side or the other — actions which were altogether 
 inconsistent with the existence of hemianopia. 
 
 You will see that the margin of the plane of section, which 
 bulges considerably from hernial protrusion, corresponds nearly 
 with the external parieto-occipital fissure.^^ These experiments 
 illustrate the negative effects of unilateral and bilateral lesions 
 of the occipital lobe. I had found, however, in my earlier experi- 
 ments that destructive lesions of the cortex of the angular gyrus 
 on the one side caused temporary complete loss of vision in the 
 opposite eye, so that the animal responded to no test of vision, 
 and, when urged to move, ran blindly against every obstacle in 
 its path,^* and that, when both angular gyri were similarly 
 destroyed, complete blindness ensued in both eyes.'^^ 
 
 The following observations were made on a monkey whose 
 angular gyri were destroyed on both sides with the galvano- cau- 
 tery. It was at once let loose, but appeared scared, and would 
 not stir from its place. It was therefore for some hours impossi- 
 ble to obtain any satisfactory information as to its powers of 
 vision. The pupils were contractile to light, and a light flashed 
 in the eyes caused some wincing. When a piece of apple was 
 
 21 Experiment XXIII, Phil. Trans., sup. cit. 
 
 22 Experiment IX, Phil. Trans., 1884. 
 
 *3 See Fig. 1, Plate 20, Phil. Trans., part 11, 1884. 
 
 »* See Experiments VII, VIII, IX, Phil. Trans., vol. clxv, 1875. 
 
 25 Experiment X, op. cit. 
 
THE VISUAL CENTRES. 43 
 
 dropped near it, so as to come in contact with its hand, it took it 
 up, smelt it, and ate it with signs of satisfaction. Hearing was 
 acute, and it turned its head and replied when called to by name. 
 With the exception of reluctance to move from its position, aris- 
 ing evidently from a sense of insecurity, there was nothing to in- 
 dicate decisively that the animal was blind. But I had found that 
 this animal was very fond of sweet tea, and would run anywhere 
 after it. I therefore brought a cup of sweet tea, and placed it to 
 its lips, when it drank eagerly. The cup was then withdrawn and 
 placed in front of it, a little distance, but the animal, though from 
 its gestures intensely eager to drink further, was unable to find 
 the cup, though its eyes were looking straight into it. This test 
 was repeated several times, and with exactly the same result. At 
 last, on the cup being placed to its lips, it plunged its head in, 
 and continued to drink till every drop was exhausted, while the 
 cup was lowered and drawn half way across the room. Next day 
 the animal still continued blind, and paid no attention to threats, 
 grimaces, or other means of appeal to its sense of vision. It was 
 then killed, in order that the position and extent of the lesions 
 might be accurately determined before secondary inflammatory 
 processes could have advanced. These had already begun, but 
 were confined to the angular gyri, which were somewhat swollen 
 and raised, and to the adjoining anterior margin of the occipital 
 lobes, and with slight implication of the posterior margin of the 
 left ascending parietal convolution. The destruction was purely 
 cortical, the grey matter alone being disorganised, and on the 
 angular gyri exclusively. 
 
 These facts seemed to me to justify the opinion that the angular 
 gyri were the visual centres, each being in relation with the 
 whole of the opposite eye, since the effect of unilateral extirpa- 
 tion was for the time total blindness of the opposite eye, and not 
 hemiopia. And it further seemed as if the rapid recovery from 
 unilateral lesion were due to the compensatory action of the other 
 gyrus •, inasmuch as bilateral destruction caused total blindness in 
 both eyes of a more enduring, and, as I ventured to suppose, prob- 
 ably permanent, nature. But further investigation on animals 
 kept alive for much longer periods than were compatible with the 
 exact limitation of the lesion under old surgical methods showed 
 that this conclusion was erroneous. My later investigations, in 
 conjunction with Professor Yeo, under strictly antiseptic precau- 
 tions, proved that the results of unilateral and bilateral extirpa- 
 tion of the angular gyrus, though entirely in harmony with my 
 
44 CEREBRAL LOCALISATION. 
 
 previous researches, were more temporary than I had previously 
 thought, and that bilateral destruction did not cause permanent 
 total loss of vision.^® In illustration I would quote the details of 
 the following experiments. 
 
 In one animal the left angular gyrus was cauterised with the 
 galvano-cautery. " The left eye was secured, and the animal 
 allowed to recover from stupor. At the end of half an hour it 
 was evidently wide awake, but would not move unless touched. 
 At this time it was removed from its cage and placed on the floor, 
 whereupon it began to grope about in a sprawling manner, knock- 
 ing its head against every obstacle. After some minutes of this 
 behaviour it subsided, and refused to move. It made no sign of 
 fear at threatening gestures, and did not wink at a thrust of the 
 finger at its eye until the finger almost touched the conjunctiva, 
 when the usual reflex closure occurred. Half an hour later the 
 same tests were employed, with precisely the same indications of 
 total loss of vision. At the end of still another half hour, while 
 it was lying quietly in its cage, it was gently laid hold of without 
 noise to attract its attention, whereupon it bounded away with an 
 expression of fear and surprise, and ran full tilt against the leg of 
 the table, where it remained groping and sprawling for a few 
 minutes. It then started off, and this time ran against the wall, 
 against which it sprawled helplessly. Similar things were re- 
 peated. It gave no sign of perception when it was cautiously 
 approached without noise ; but when a slight noise was made 
 with the lips quite close to it, it darted off and came against the 
 wall as before, where it lay down. Half an hour later, while 
 it was resting quietly in a corner with its eyes open, the light of a 
 lantern was flashed in its eyes, but it gave no sign. Creeping up 
 to it cautiously without exciting its attention the observer made 
 a slight whisper close to its face, whereupon it peered eagerly, 
 but evidently remembering the results of running away it crouched 
 down and would not move. Half an hour later, when it was 
 quiet in its cage, it started suddenly on being touched, and 
 ran its head into a corner, where it crouched. 
 
 " Next day, its left eye being still closed, it showed unmistak- 
 ably the possession of vision with the right eye. It laid hold of 
 things as usual, and ran about the laboratory in every direction, 
 passing obstacles right and left with perfect precision, and duck- 
 ing its head to pass underneath bars as it ran along the top of 
 
 2fi See Experiments 3, 4, 5, 6, Phil. Trans., vol. ii, 1884. 
 
THE VISUAL CENTRES. 45 
 
 the waterpipes of the laboratory. No defect of vision, amblyopic 
 or hemiopic, could be detected."*^ 
 
 In another animal, the left angular gyrus was cauterised up to 
 the parieto-«occipital fissure, the posterior part of the corpus cal- 
 losum being also divided at the same time.^** 
 
 " The left eye was securely closed, and the animals allowed to 
 recover from its narcotic stupor. In half an hour it began to move 
 about spontaneously, although rather unsteadily. An hour and a 
 half after the operation it walked about the laboratory, knocking 
 its head against legs of chairs and other obstacles in its path. 
 When a piece of apple was held under its nose it grabbed it and 
 ate. It continued to walk about here and there, every now and 
 then coming to a dead halt full tilt against the wall. Three hours 
 after the operation it again, in running about the laboratory, came 
 full tilt with its snout against the wall, where it rested. While it 
 was resting quietly we crept up to it ; but the animal, though 
 with eyes wide open and looking towards us, made no sign of per- 
 ception. Threatening grimaces were likewise without effect ; 
 but on making a noise with our lips the animal seemed alarmed, 
 peered forwards, and yet, though it came close to our faces, seemed 
 to see nothing. It was tried to right and left in the same way, 
 but there was no sign of vision to one side or the other. Next 
 day, the left eye being still closed, the animal ran about in every 
 direction, ducking under bars, passing objects right and left with 
 the utmost precision, and never once knocking against anything 
 one side or the other. Not the slightest impairment of vision 
 could be detected, and it was able to pick up the minutest objects 
 lying about its cage or thrown down near it." 
 
 It was iirst shown by Munk^" that the permanent effect of com- 
 plete unilateral extirpation of the visual sphere was not complete 
 blindness of the opposite eye, but homonymous hemianopia, from 
 paralysis of the corresponding sides of both retinse. This effect 
 he obtained by section in the line of the parieto- occipital fissure, 
 and he localised the visual sphere exclusively in the occipital 
 lobe, regarding the angular gyrus as the " sensory sphere " of the 
 eye. Owing, however, to the fact, as he himself admits, that 
 secondary inflammation and extension of the primary lesion gene- 
 rally, if not universally, followed his operative procedure, Munk's 
 experiments cannot be relied upon when it is a question of the 
 
 *' Experiment 5, Phil. Trans., vol. ii, 1884. 
 
 *8 Experiment 7, op. cit. 
 
 ** Ueber die Fuuctioneu der Qrosshiruriude, 1881. 
 
46 CEREBRAL LOCALISATION. 
 
 exact delimitation of any given area. It is a reasonable supposi- 
 tion that Munk's operations for removal of the occipital lobe 
 would be the cause of secondary implication of the angular gyrus 
 or its connections. The question as to the exact delimitation of 
 the visual sphere, whether it is confined only to the occipital lobe, 
 according to Munk, or embraces also the angular gyrus, according 
 to my view, and the respective relations of the angular gyrus 
 and occipital lobe to the eyes has been the subject of investiga- 
 tion ty numerous physiologists : Luciani and Tamburini,^° 
 Luciani,^^ Horsley and Schafer,^^ Sanger-Brown and Schafer,''^ 
 Lannegraee,^* Gilman Thompson and Sanger-Brown ^' and is still 
 a matter on which opinions are far from being in accordance. 
 
 Luciani and Tamburini, and Luciani have arrived at the con- 
 clusion that the visual centres are not confined to the occipital 
 lobes, but embrace also the angular gyri, though the former be- 
 lieved that the effects of unilateral destruction of the angular gyrus 
 were hemiopic rather than amblyopic. The experiments of Horsley 
 and Schafer and of Sanger-Brown and Schafer are of great value, 
 as, owing to the use of antiseptic precautions, and the full details 
 and figures which illustrate the experiments, their facts are avail- 
 able for all inquirers. Horsley and Schafer record several experi- 
 ments on the occipital lobe on one or both sides. The follow- 
 ing experiment (24), which I give in their own words, is 
 especially worthy of note. " The whole of the left occipital lobe 
 was removed by an oblique incision along the parieto-occipital 
 fissure. The piece removed included the extremity of the posterior 
 cornu of the lateral ventricle, which was thus freely opened. No 
 ill consequences resulted from this, however, and when on the 
 fifth day the dressings were removed the wound was found to be 
 completely healed. Eesult, no muscular paresis. The animal 
 seems to have some disturbance of visual consciousness of the 
 images of objects which fall upon the left side of the retinae; for 
 an object, such as a raisin, presented to it on the right side of the 
 visual line, is either not noticed or its nature is not readily recog- 
 
 30 Su,i Centri Psico-Sensori Corticali, 1879. 
 31 On the Sensorial Localisations in the Cortex Cerebri, Brain, July, 1884. 
 
 32 A Record of Experiments upon the Functions of the Cerebral Cortex, Phil, 
 
 Trans., vol. clxxix, 1888, B. 20. 
 
 33 Functions of the Occipital and Temporal Lobes of the Monkey's Brain, Phil. 
 
 Trans., vol. clxxix, 1888, B. 30. 
 3* Influence des Lesions Corticales sur la Vue, Archives de MMecine Experi- 
 
 mentale, 1889. 
 
 35 The Centre for Vision. Researches of the Loomis Laboratory of the Medical 
 
 Department of the Univenity of the City of New York, No. 1, 1890. 
 
THE VISUAL CENTRES. 47 
 
 nised. This condition, which was very marked at first, gradually 
 improved, until three months after the operation it could no 
 longer be determined." Other portions of the hemisphere, as 
 shown in the figure, were removed, but into the results of these 
 it is not necessary for me here to enter. The appearance of the 
 brain is given in their iigures (24a and 24b), of which one 
 represents the under surface, and, as the authors themselves 
 say, " the representations are mainly of interest as showing 
 the completeness of removal of the frontal and occipital lobes, 
 and the limits of the lesion upon the under surface of the hemi- 
 sphere."^^ 
 
 Several others are recorded in which the lesions, unilateral or 
 bilateral, trenched on the parieto- occipital fissure and region 
 of the angular gyrus, and in none of these was hemiopia or 
 blindness absolute or permanent. In one case (Experiment 
 26), in which both occipital lobes (external and posterior surfaces 
 and a part of the under surface) were removed, with an interval 
 of fourteen days between the two operations, there seemed to re- 
 main a general impairment of visual perception, without, so far 
 as could be made out, absolute blindness in any part of the field 
 of vision, but of this they cannot speak with certainty. On the 
 removal of the right angular gyrus complete left hemianopia was 
 the result, which lasted, without any sign of improvement, until 
 the animal's death, three months afterwards. Horsley and 
 Schafer's experiments, therefore, in which the lesions of the occi- 
 pital lobes were perhaps more extensive than any of those de- 
 scribed by Yeo and myself — my earlier experiments excepted — 
 show that at most the hemiopic disturbances are transient, while, 
 in the first case referred to, there appears to have been complete 
 removal of the occipital lobe, and yet the hemiopia was not of 
 permanent duration. Destruction of the angular gyrus, in com- 
 bination with the occipital lobe, was the only lesion which caused 
 a permanent result. Their conclusions, as stated in their own 
 words, are as follows : — 
 
 " Our experiments upon the occipital region, although few in 
 number, seem to link together the conclusions arrived at by Munk, 
 and by Ferrier and Yeo as the results of their experiments. They 
 indicate that both the occipital lobes and angular gyri are con- 
 cerned with visual perceptions in such a manner that each oc- 
 cipital region is connected with the corresponding lateral half of 
 
 p. 35. 
 
48 CEREBEAL LOCALISATION. 
 
 each retina, and that a part only of the cortex of the region in 
 question is able to take on in great measure — how completely 
 cannot be determined in animals — the functions of the whole. 
 This is in conformity, also, with the results of Luciani. So far as 
 the occipital lobe alone is concerned, our observations confirm the 
 statement of Munk that the effect of this lesion is to produce a 
 hemiopic disturbance of visual consciousness. But the imperfect 
 ■vision which remains after removal of both occipital lobes (see 
 Cases 25 and 26) suggests that the area which is concerned 
 with visual consciousness is not confined to those lobes, as was 
 inferred by Munk, but extends over into the angular gyrus, per- 
 manent hemiopia being produced by the subsequent removal of 
 that convolution. It will, however, be necessary that further ex- 
 periments should be undertaken, in order to determine more pre- 
 cisely, not only the extent, but also the relative importance of 
 the anterior, posterior, and mesial portion of the visual area of the 
 cortex."^''' 
 
 »T Op. cit., p. 19. 
 
LECTURE III, 
 
LECTURE III. 
 
 Schafeb's further investigations, in conjunction -with Sanger- 
 Brown, led him to agree with Munk that complete unilateral ex- 
 tirpation of the occipital lobe alone caused persistent hemiopia, 
 while bilateral extirpation caused total and enduring blindness. 
 Admitting, however, that the lesions described by them were the 
 cause of hemiopia or total blindness, it does not follow that these 
 results are due to removal of the occipital lobe as such. Schafer 
 himself ^ admits that the visual area embraces not only the occipi- 
 tal lobe, but, perhaps also part, or the whole, of the angular gyrus. 
 The relations of the different portions of the visual centres to the 
 retina3, founded on the phenomena of electrical irritation, as well 
 as other facts, necessitate that the angular gyrus (its posterior 
 limb at least, according to Schafer) should be included in the 
 visual area ; more, therefore, than the occipital lobe proper. If 
 total blindness, therefore, is caused by removal of the occipital 
 lobes in the line of the parieto-occipital fissure, it is necessary to 
 suppose that by this operation the medullary connections of the 
 whole of the visual area become implicated. Scbiifer- has him- 
 self suggested that fibres connected with the cortex of the 
 adjoining parts of the brain, and especially of the angular gyrus, 
 may be cut off along with the occipital lobe, and than this is the 
 real explanation is supported by many considerations.^ 
 
 1 Electrical Excitation of the Visual Area, Brain, April, 1888. 
 2 Brain, vol. x, p. 372. 
 3 This, however, does not fit conveniently into Schiifer's scheme, which is as 
 follows : — 1. The whole of the visual area of one hemisphere is connected with 
 the corresponding lateral half of both retina. 2. The upper zone of the visual 
 area of one hemispliere is connected with tlie upper })aU of both retina;. 3. Th« 
 lower zone of the visual area is connected witli tiie lower part of the correspond- 
 ing lateral half of both retinic. 4. The intermediate zone of tlie visual area is 
 connected with the middli- part of the corresponding lateral half of botli retiuiB 
 (loc. cit., p. 5). The rfaictions wouM.liowever, be fully explained on the assump- 
 tion that the angular gyrus has relations with the whole of the opposite eye. 
 
 E 2 
 
52 
 
 CEREBRAL LOCALISATION. 
 
 Lesions of the occipito -temporal region alone are competent to 
 produce hemiopiaor complete blindness, according as the lesion is 
 unilateral or bilateral, altogether apart from affection of the 
 angular gyrus, or any other portion of the occipital lobe. I have 
 myself recorded instances* in which lesions of the occipito- 
 temporal region were followed by temporary hemiopia, and prob- 
 ably similar facts have led Luciani to extend the visual area into 
 the temporal lobe. But, not only may temporary hemiopia occur, 
 but the hemiopia so produced may be persistent. 
 
 Fig. 12. — Horizontal section of left hemisphere of monkey — on a level with 
 the anterior commissure (nat. size) ; a.c, anterior commissure; c.A., 
 cornu Ammonia; cZ., claustrum; e.g., corpora quadrigemina; ex., ex- 
 ternal capsule; i.e., internal capsule; t.i?., island of Reil ;/., anterior 
 or descending (Meynert) pillar of fornix; /^'., ascending fibres or Vicq 
 d'Azyr's bundle; /'.df., Meynert's fasciculus; /.iS., fissure of Sylvius ; 
 n.c, nucleus caudatus; n.l., nucleus lenticularis ; o.r., optic radiations 
 (Gratiolet; ; P., pulvinar ; p., posterior commissure. 
 
 Here is an illustration * of the brain in one of Brown and 
 Schafer's experiments. The operation consisted in removal of the 
 right temporal lobe. Posteriorly, the lesion extended partly over 
 the under surface of the occipital lobe. With the exception of 
 this lesion of the occipital lobe, all the rest of the visual sphere was 
 intact, yet this animal was completely hemiopic. The inference 
 is that the lesion severed the whole of the optic radiations, for, 
 
 * Phil. Trans., vol. ii, 1884, Experiments 27 and 28 
 £ Figs. 4a, 4b, Phil. Trans., 1888, B. 30, plate 49. 
 
THE VISUAL CENTRES. 53 
 
 otherwise, it should, on Schafer's hypothesis, have caused blind- 
 ness only of the lower portions of the retinfe. 
 
 It appears, therefore, that the incision for the removal of the 
 occipital lobe carried along the line of the external parieto- 
 occipital fissure is calculated to sever the whole of the optic 
 radiations of the occipito-angular region, which emerge from the 
 primary optic nuclei about this level. (See Fig. 12). In support 
 of this I quote the following experiment : I exposed the lower 
 extremity of the left external parieto-occipital fissure, and, in- 
 
 Flg. 13. 
 
 eerting a director at this spot between the lower surface of the 
 occipital lobe and and the tentorium, passed a stylet bent at an 
 oblique angle along the groove in such a manner as to make a 
 transverse incision a few millimetres in depth across the occipito- 
 temporal region. The result of this was right hemiopia, which, 
 however, speedily passed off, so that it was no longer clearly per- 
 ceptible on the third day. A fortnight afterwards the right 
 occipito-temporal region was similarly operated upon, the in- 
 cision this time being made just anterior to the lower extremity 
 of the parieto-occipital fissure. The animal died a month after 
 the first operation. During the whole time it survived it re- 
 mained absolutely hemiopic towards the left in every part of the 
 viirual field. It was found after death (see Fig. 13) that the in- 
 cision on the left side was shallow and not continuous, being in- 
 terrupted in the region of the lingual lobule. On the right side 
 
£4 CEREBRAL LOCALISATION. 
 
 the incision extended across the whole occipito-temporal region, 
 and penetrated several millimetres into the substance of the brain, 
 dividing the medullary fibres emerging from the region of the 
 primary optic centres. 
 
 Brown and Thompson ^ believe that removal of the occipital 
 lobe on one side causes hemiopia to the opposite side, altogether 
 apart from lesion of the angular gyrus, which they entirely ex- 
 clude from the visual sphere. They give particulars of a monkey, 
 in which, after removal of the left occipital lobe, right hemiopia 
 resulted, together with right hemiansesthesia, which was still ob- 
 servable on the twenty-sixth day after the operation. One hun- 
 dred days after the first operation the right occipital lobe was 
 similarly removed. This was followed by complete blindness, but 
 they state that after three weeks the animal recovered vision to 
 some extent towards the left. They assume — but furnish no evi- 
 dence of the fact — that probably a few occipital fibres had escaped 
 injury during the second operation. The animal died of phthisis 
 on the 23,1st day. On examination it was found that the entire 
 occipital lobe behind the angular gyrus upon each side had been 
 removed, leaving a clean-cut surface. For some distance around 
 this surface the pia mater was firmly adherent to the convolutions 
 beneath, but it was stated not to have been thickened. It is cer- 
 tain, however, that their first lesion must have extended beyond 
 the occipital lobe, owing to the hemianaesthesia, which does not 
 occur when the lesions are restricted to the occipital lobe itself ; 
 and that the removal of the occipital lobes, as such, which they 
 appear to have found equally complete on both sides, did not 
 cause total loss of vision, is shown by the fact, which they them- 
 selves record, that the animal was still able to see, even if imper- 
 fectly, towards one side. In a second experiment they found that 
 destruction of the left angular gyrus caused no result beyond 
 hemianeesthesia on the right side, together with some paralysis of 
 the right arm (!). On the ninetieth day a second operation was 
 performed, consisting in excision of the whole of the right 
 occipital lobe. This was followed by left hemiopia, which still 
 persisted when the paper was written, seventeen months after the 
 operation. These are the only experiments on monkeys which 
 these authors have recorded. Lannegrace,'' on the other hand, 
 who has performed numerous experiments on the occipital lobes 
 and angular gyri of monkeys, states, in accordance with my o wn 
 and Yeo's results, that destruction of the occipital lobe causes no 
 
 6 Op. cit. T Op. cit. 
 
THE VISUAL CENTRES. W 
 
 appreciable impairment of vision, whereas destruction of the 
 angular gyrus produces crossed amblyopia of a temporary 
 character. He reports two cases of successive lesion of the angular 
 gyri. In the one the first lesion induced crossed amblyopia, which 
 lasted four days. The second lesion, however, produced no ap- 
 preciable alteration. In the other the first lesion again caused 
 crossed amblyopia, which disappeared in two days, while the 
 second gave rise to lasting amblyopia. These results, which are 
 similar to those obtained by Yeo and myself, depend, no doubt, on 
 the degree of completeness of extirpation of the gyri. 
 
 I have already mentioned that my earlier experiments, as well 
 as those made by Professor Yeo, show that unilateral destructive 
 lesion of this gyrus caused temporary blindness of the opposite 
 eye, and that bilateral destruction caused for the time complete 
 blindness in both eyes. Though these results have been much 
 questioned, I must insist on their accuracy. I have corroborated 
 the occurrence of apparently complete blindness of the opposite 
 eye, on destruction of the left angular gyrus in an animal which- 
 I lately made the subject of experiment. In this animal I had 
 previously enucleated the left eye, so as to exclude all complica- 
 tions from this side. After removal of the left angular gyrus, 
 however, the animal, though otherwise well and in complete 
 possession of all its senses and motor powers, was evidently ab- 
 solutely blind. It responded to no test of vision ; would not 
 budge from the spot, but when urged to move sprawled blindly 
 and helplessly. This condition lasted for several hours, during 
 which it was under observation. Next day there were indications 
 of vision, but the animal had become so prostrated, the weather 
 being intensely cold, that it died before any further exact obser- 
 vations were possible. That lesions of the angular gyrus may 
 cause implication of the optic radiations is possible, but this re- 
 sult is neither necessary, nor would it account for complete loss 
 of vision in the opposite eye. The bilateral relations of the 
 angular gyrus account for the transient nature of the amblyopia 
 which results from unilateral extirpation, and, as in few of my 
 experiments was the destruction of this gyrus complete on one 
 side or the other, it occasionally happened that removal of the 
 other gyrus some time subsequently did not seem to impair vision 
 either on one side or the other. When, however, the angular gyri 
 are completely destroyed on both sides, the animal, though for 
 the first three or four days absolutely blind, does not remain so 
 permanently, but it never regains normal vision, This also has 
 
56 CEREBRAL LOCALISATION. 
 
 been confirmed by the researches of Lannegrace. Apart from the 
 afiection of vision, destruction of the angular gyrus causes no 
 other symptoms, either motor or sensory ; there is no ptosis or 
 paralysis of the ocular muscles, and the sensibility of the con- 
 junctiva is absolutely unimpaired. 
 
 These results, confirmed by the researches of Horsley and 
 Scl afer, contradict the statement of Munk that the angular gyrus 
 is the sensory sphere of the eyeball ; and it will be found, on exa- 
 mination of Munk's own data, that the phenomena on which he 
 relies as indicating loss of the sensibility of the eye are in reality 
 due to loss of vision. Thus he says that after destruction of the 
 left angular gyrus approximation of the finger to the left eye in- 
 variably caused winking, whereas the same threat against the 
 right eye caused winking only when the eyelids were actually 
 touched. This appears to be a proof of the sensibility of the eye, 
 and the non-perception of threatened danger at a distance. The 
 absence of winking at threatened danger he admits to be charac- 
 teristic also of blindness, but he argues that, inasmuch as the 
 animal could not be blind, presumably because the occipital lobe 
 was intact, therefore, the non- occurrence of winking could only 
 be due to the inability of the cortex to act on the sphincter pal- 
 pebrarum ! Again, he says, that when the angular gyrus has been 
 destroyed on one side, and the eye on that side closed, the ani- 
 mal often fails to seize things offered it, or thrown down before 
 it, especially when the objects are small. This I consider a clear 
 indication of amblyopia. And he also states that after bilateral 
 extirpation of the angular gyrus of monkeys, " after incomplete 
 restitution " — a phrase, however, which is not very intelligible — 
 are unable like normal monkeys to take things offered them deli- 
 cately with the fingers, but make grabs at them with the whole 
 hand. This is only a further illustration of the same imperfec- 
 tion of vision which I have described — namely, want of precision 
 in prehension, and a continual tendency to place the hand over 
 or short of the object aimed at, instead of on it at once. 
 
 Schafer also* records the symptoms in a monkey in which he 
 destroyed both angular gyri. For the first few days the animal 
 appeared totally blind, but vision gradually returned, and before 
 long was quite good for distant objects. The animal could ap-- 
 parently see small objects, such as a raisin, at a distance, but on 
 running up to it seemed to have some difficulty in finding it, 
 
 8 Brain, July, 1888, p. 159. 
 
THE VISUAL CENTRES. 57 
 
 Scbafer is of opinion that this latter fact is due to absence of 
 vision in the antero-superior and lateral portions of the retinae. 
 I have lately carefully investigated the condition of vision in a 
 monkey in which I had completely destroyed both angular gyri. 
 There was no ptosis, the ocular movements were normal, the con- 
 junctival reflexes unimpaired, sensibility was intact everywhere, 
 and the motor powers were perfect, but, for four days at least, the 
 animal was evidently absolutely blind. When urged to move it 
 ran against every obstacle in its path, paid no attention to threats, 
 could not find its food, except by groping, and appeared insensible 
 to light flashed in its eyes. On the fifth day there were evidences 
 of returning vision. It did not now knock its head against ob- 
 stacles; would not walk over the edge of the table; showed signs 
 of perception of light flashed in its eyes, and occasionally seemed 
 to wince when threatened. Vision gradually improved, but con- 
 tinued very imperfect, especially for minute objects, which it 
 rarely, if ever, seized quite precisely ; groping at them with the 
 whole hand, and reaching short, or over, or to the side. It ap- 
 peared to see objects held above, below, and to either side much 
 better than those held in front of its eyes. Six weeks after the 
 operation my colleague, Professor McHardy, examined the ani- 
 mal, which was very docile, with me, testing every portion of the 
 visual field by pieces of apple suspended by a delicate thread. It 
 was concluded that vision was better in everj' part of the peri- 
 phery than in the centre. Objects held directly before the eyes 
 and at a little distance were apparently not clearly seen, and 
 never laid hold of with precision. The condition remained un- 
 changed for three months after the operation, similar tests being 
 from time to time applied, and with the same result. I noted 
 also that the animal, when examining any object, always held it 
 at full arm's length from its eyes. The phenomena observable in 
 this animal were such as would be best explained by impairment 
 or loss of central vision ; for it is well known that when central 
 vision is lost or impaired in man, objects are better seen at a dis- 
 tance than close at hand, and less distinctly when the ej'es are 
 immediately converged on them. This is practically the condition 
 seen in this animal. The loss of central vision would thus ac- 
 count for the fact, noted by Schafer in his animal, that objects 
 were better seen at a distance than near at hand ; and that Munk's 
 animal could never place its fingers precisely on any small object 
 held directly in front of its eyes. There was certainly no indica- 
 tion, but the reverse, that the upper portions of the retinae were 
 
58 CEREBRAL LOCALISATION. 
 
 less sensitive than the lateral and lower portions. It appears to 
 me, therefore, that the symptoms resulting from bilateral destruc- 
 tion of the angular gyrus, described by myself, Munk, and Schafer, 
 are best explained on the supposition that the angular gyri are 
 more particularly related to the area of distinct vision, and, ac- 
 cordingly, with the maculae lutese. The facts of disease in man 
 render it necessary to assume that the region of the yellow spot 
 is represented in each hemisphere, though more in that on the 
 opposite than on the same side, and the probability is that the 
 area of clear vision is represented mainly in the angular gyrus 
 of the opposite hemisphere. 
 
 The retinal relations of the visual centres are not capable of 
 being explained by a simple division of the retinal fields into co- 
 related halves projected on the corresponding side of each hemi- 
 sphere. For unilateral lesion of the angular gyrus produces a 
 temporary blindness or amblyopia of the opposite eye ; while bi- 
 lateral destruction induces an enduring impairment of visual 
 acuity in both eyes." The results of my experiments seem to show 
 that the angular gyrus has relations with both eyes. The crossed 
 action, however, is the only one which is clearly demonstrable in 
 the lower animals, but this does not exclude the possibility of 
 some impairment of vision on the same side, not perceptible by 
 tests applicable to them. It is certain that in man affections of 
 the visual centres occasionally produce crossed amblyopia, and 
 not homonymous hemiopia. Not only is this characteristic of the 
 visual disturbances seen in hysterical hemianaesthesia, the path- 
 ology of which is obscure, but it has been noticed also in cases of 
 organic disease. Usually, along with the blindness, or great im- 
 pairment of vision in the opposite eye, there has been some degree 
 of contraction of the visual field of the eye on the same side. I 
 have myself reported several such cases,^° and Qowers" has also 
 seen similar instances. A well-observed case of this nature has 
 been recorded by Sharkey.^^ Post-mortem examination revealed 
 softening and absorption of a considerable area of the opposite 
 hemisphere, including the angular gyrus. The occipital lobe was 
 intact, and in nowise reduced in size as compared with the other. 
 
 9 This accords with Gowers's hypothesis that " on the outer surface, in front of 
 the occipital lobe, there is a higher visual centre in which the half fields are 
 combined, and the whole opposite field is represented." (^Diseases of Nervous 
 lii^stem, vol. ii, p. 19.) 
 
 10 Cerebral Amblyopia and Hemiopia, Brain, vol. iii, p. 456. 
 
 11 Diseases of the Nervous System, p. 19. 
 
 13 Medico- Ckirurgical Transactions, vol. Ixvii, 1884. 
 
THE VISUAL CENTRES. 59 
 
 A distinguishing test between tract and central hemiopia has 
 been suggested by Wil brand," and advocated by Wernicke and 
 Seguin, which consists in determining whether a pencil of light 
 thrown on the blind side of the retinae induces contraction of the. 
 pupil or not. As the optic tract is the path of the fibres which 
 excite pupillary contraction through the oculo-motor centres, as well 
 as those which excite visual sensations in the cortex, lesion of the 
 optic tract will cause not only hemiopia, but also paralysis of the 
 reflex reaction of the pupils to light ; whereas, lesion of the cor- 
 tical centres will cause hemiopia, but leave intact the pupillary 
 reaction. This test, however, requires great care in its applica- 
 tion, as it is difficult to restrict the rays of light entirely to the 
 blind side. In a case recently under my care at King's College 
 Hospital,^* in which the dividing line passed through the fixation 
 point, and which was carefully investigated in this relation by 
 Professor McHardy and myself, the pupillary reaction was not ob- 
 tained, as a rule, when the pencil of light was thrown on the right 
 side of the retinte ; whereas it occurred readily when the light was. 
 thrown on the left half of each retina. These facts, therefore, 
 would corroborate the hypothesis that this was a case of tract 
 hemiopia. 
 
 I have recently verified the hemiopic pupillary reaction in two 
 monkeys in which I accidentally severed the optic tract in estab- 
 lishing lesions of the temporal lobe. The result in both cases wa» 
 absolute hemiopia to the opposite side. In both cases the left 
 optic tract was divided, and in both, along with right hemiopia, 
 there was absence of reaction of the pupil when a fine pencil of 
 electric light was thrown on the left half of each retina ; whereas, 
 active reaction took place when the light was thrown on the right 
 half. Both in the monkey, and in several cases of hemiopia in 
 man depending on lesions of the hemisphere, I have found that 
 the pupillary reaction is equally well marked whichever side of 
 the retina is illuminated. There can be no question that in man 
 and monkeys there is decussation of the optic tracts in the 
 
 13 Op. cit. 
 1* Tlie patient was a man, aged 39. Two years before he had contracted 
 syphilis, and at the time of his admission was suffering from a large tertiary 
 ulcer on the soft palate. He bad twitching of the right side of the face, 
 together with weakness and numbness of the left side. The left hand grasp 
 was weak, and there was loss of dorsal flexion of the left foot. The tongue 
 deviatefl to the right on protrusion. He was found to be absolutely hemiopic 
 towards the left side, and a careful perimetric examination by Professor 
 McHardy demonstrated that the dividing line passed exactly through the fixa- 
 tion point. 
 
60 CEREBRAL LOCALISATION. 
 
 chiasma. Michel, in his comparatively recent monograph,^' still 
 maintains the contrary, on the basis of microseop'.cal investiga- 
 tion ; but his results have been attributed by Singer and Miinzer^^ 
 to imperfect methods of examination. 
 
 In reference to the pathology of crossed amblyopia from lesion 
 of the angular gyrus in the monkey, as well as of similar cases of 
 disease in man, I may here allude to the hypothesis advanced by 
 Lannegrace. Lannegrace regards the eyeball as innervated by 
 two sets of fibres — sensorial, or optical proper, and sensory, on 
 which the proper nutrition of the eyeball depends. The sensorial, 
 or optical, decussate in the chiasma, and are distributed to the 
 occipital lobe ; while the sensory decussate in the pons, and, apply- 
 ing themselves to the posterior fibres of the internal capsule, are 
 distributed mainly to the angular gyrus. Lesions of the sensory 
 fibres produce amblyopia and sensory disturbances in the eyeball. 
 A similar result follows lesion of the angular gyrus, and is essen- 
 tially dependent upon changes which are induced in the nutrition 
 of the eye. This hypothesis would require that in all cases of 
 amblyopia from cerebral lesion there should be impairment of 
 sensation in the eyeball. But this is certainly not the case, for, 
 though in hysterical amblyopia there is affection of common sen- 
 sation as well as of vision, it is not so in the amblyopia following 
 destruction of the angular gyrus. Though affections of the fifth 
 nerve, which cause loss or impairment of sensation of the eyeball, 
 frequently also lead to trophic disorders of the eye, yet this is not 
 necessarily so ; and, even when the eyeball is absolutely anaesthetic, 
 provided that no trophic disturbances have occurred, vision is not 
 in the least impaired. In proof of this I would refer to cases 
 (Cases I and iii) reported by Hutchinson in the Ophthalmic Hos- 
 pital Reports, vol. iv, 1863-65. Nor does complete anaesthesia of 
 the eyeball induced by cocaine impair the visual acuteness of the 
 eye. 
 
 These appear to me to be fatal objections to the hypothesis ad- 
 vanced by Lannegrace, and I contend that the only hypothesis 
 which seems to harmonise with all the facts is, that the angular 
 gyri are more particularly the centres for clear vision, each mainly 
 for the eye of the opposite side. Whether the other portions of 
 the retinae, upper, lower, outer, and inner, are specially repre- 
 sented in corresponding regions of the occipital lobe, according to 
 the hypotheses of Munk and Schafer, cannot be said to have 
 
 15 Veber Sehnerven-Degeneration und Kreuzung, 1887. 
 16 Beitriige zur Kenniniss Sehnervenkreuzung, 1889. 
 
THE VISUAL CENTRES. 61 
 
 as yet been established; for, even after the most extensive 
 destruction of the occipital lobes, no portions of the retinae appear 
 to be absolutely blind ; hence, even if we admit that the effects 
 of irritation probably indicate a special relation of the different 
 portions of the visual field to certain portions of the occipital 
 cortex, the relation, so far as we may judge by the facts of dis- 
 ease or experimental lesion, does not seem to be an exclusive 
 one. 
 
 It is true that in man we sometimes find, besides general hemi- 
 opic deficiency, partial, quadrant or sector-like, defects in the 
 upper or lower halves of the visual field. These appear, how- 
 ever, to be merely incomplete hemiopia, and occasionally, as in 
 the case which I show you, an islet of subnormal visual acuity 
 may be seen in the defective half. The pathology of these sector- 
 like defects is a matter of conjecture. They have not been con- 
 clusively brought in relation with lesions of any particular por- 
 tion of the cortex, and the probability is that they are dependent 
 rather upon partial lesions of the optic radiations than of the cor- 
 tical centres themselves. This was without doubt the pathology 
 in the case which I have alluded to, for the defect occurred in a 
 patient who had a sudden attack of hemiplegia accompanied by 
 hemiansesthesia and some affection of speech. 
 
 It is doubtful whether there are on record any cases of strictly 
 cortical lesions of the occipital lobe proper, accompanied by 
 hemiopia, apart from direct or indirect implication of the optic 
 radiations. In most of the cases of hemiopia which have been 
 examined after death, in which the optic tracts, optic thalami, or 
 corpora geniculata have not been obviously diseased, the lesions 
 have been found in the medullary fibres of the posterior region, 
 vaguely or inaccurately called the occipital lobe ; or, if the cortex 
 has been mainly affected, the lesions have been multiple and dif- 
 fuse, and not confined to the occipital region. And in addition 
 to hemiopia, there have been hemiplegia, hemiansesthesia, aphasia, 
 or other symptoms of implication of the cerebral tracts and centres 
 beyond those of the occipital region. 
 
 Under my direction, my friend and pupil. Dr. Ewens, has col- 
 lected and analysed the majority, if not all, of the recorded cases 
 of hemiopia (with necropsies) depending on cerebral lesions which 
 have not obviously been of such a character as to cause indirect 
 and indefinite implication of other regions. Of 41 cases of hemi- 
 opia, 15 were from disease of thp occipito-angular region, 2 were 
 cases of disease of the angular and supramarginal gyri only, 15 
 
62 CEREBRAL LOCALISATION. 
 
 were described as being from disease of the occipital lobe alone. 
 Of these 15, there were only 2 (Hun's case" and Doyne's case^*) in 
 which there was not either a tumour, cyst, abscess, or softening 
 of the medullary substance of the occipital region, or another 
 lesion affecting the optic thalamus; and in 1 of these cases 
 (Doyne's)i the position of the lesion was not accurately described. 
 In the other cases the lesions were of a diffuse character, 6 
 being from lesion of the occipito-temporal region, and 3 from 
 lesion of the occipital, temporal, and parietal lobes simultaneously, 
 the angular gyrus being implicated in all. 
 
 From the comparative frequency with which hemiopia has been 
 found associated with lesions of the cuneus and its neighbour- 
 hood Seguin " and Nothnagel ^^ are of opinion that this portion 
 of the occipital lobe has a special relation to visual perception ; 
 while Wilbrand believes that the visual centre is more especially 
 in the apex of the occipital lobe. These hypotheses are not sup- 
 • ported by experimental research. The probability is that any 
 apparent relation between lesions of the cuneus and the occur- 
 rence of hemiopia, is due to the special proclivity of this region to 
 affection by morbid vascular conditions, and to coincident impli- 
 cation of the optic radiations of the occipito-temporal region. In 
 Seguin's own case,^^ on which he relies in support of his hypo- 
 thesis, not only was the cuneus implicated, but also the fourth 
 and fifth temporal gyri and a part of the gyrus hippocampi.-* 
 Cases have also been recorded in which, not only unilateral, but 
 bilateral lesions have been found in the occipital lobes without 
 any affection of vision whatever. 
 
 Irritative lesions of the angular gyrus occasionally give rise to 
 optical illusions, or flashes of light, followed by temporary 
 amblyopia, as recoMed by Hughes Bennett ^^ ; while destructive 
 lesions of the angular gyrus, more particularly in the left hemi- 
 
 iT Amer. Journ. Med. Sci., 1887, Case i. 
 w Ophthal. Soc, Lond., November 14th, 1889. 
 19 The Journal of Nervous and Mental Diseases, vol. xiii, January, 1886. 
 2U Neurolog. Centr-alblatt, 1387, p. 213. 
 21 Op. cit. 
 22 Since this was written a case has been put on record by Delepine {Trans. 
 Path. Soc. Lond., May 20th, 1890) in which right hemiopia was apparently asso- 
 ciated with softening of the left cuneus. In this case, however, there was 
 general arterial degeneration, and there were many circumscribed patches of 
 softening in various parts of the brain. In particular there was a small area 
 which had destroyed the greater part of the middle occipital convolution. This 
 case is, therefore, too complex to allow of exact conclusions as to the connec- 
 tion between the hemiopia and the lesion of the cuneus in particular. 
 S3 Excessive Sensory Cortical Discharges and their Effects, Lancet, March 30th 
 and April 6th, 1889. 
 
th:e visual centres. 63 
 
 sphere, are generally associated with the special form of sensory 
 aphasia termed " word- blindness " (Kussmaul). Word-blindness 
 i3 not necessarily accompanied by any noteworthy affection of 
 visual sensation, though in some cases, where the lesion of the 
 occipito-angular region is more extensive, there may be a greater 
 or less degree of right hemiopia. 
 
 On the other hand, right hemiopia, pure and simple, is not 
 necessarily associated with any defects in visual ideation. This 
 would be an argument against its cortical nature. The fact that 
 visual ideation, more particularly in reference to the association 
 of written symbols with their meanings, is apt to suffer more 
 readily than simple perception, appears to me to illustrate the 
 laws of the evolution and dissolution of the nerve centres, which 
 have been so ably expounded by Hughlings Jackson in his 
 Croonian Lectures delivered here a few years ago (1884). As 
 evolution is from the most simple and most stable up to the most 
 complex and least stable, so destructive processes annihilate fii'st 
 of all the higher, and last of all the lower functional manifesta- 
 tions. The functions of the visual centres in respect to mere 
 visual sensation, or simple presentation, are much more stably 
 organised than those which imply visual ideation or re-presenta- 
 tion, and in particular such highly specialised and complex pro- 
 cesses as are involved in the association between visual symbols 
 and things signified. Hence, a lesion of the area of clearest 
 vision may paralyse visual re-presentation, while the simpler 
 function of visual presentation may not be appreciably impaired. 
 In order that this also should be entirely abolished it is necessary 
 that every trace of the given centre should be extirpated. In 
 other words, re-presentative blindness will occur sooner than 
 presentative blindness, and the former more readily in its most 
 specialised modes of manifestation. 
 
 In regard to the visual centres of the lower vertebrates, I can-» 
 not quote many observations or experiments of my own. The 
 visual centres of dogs have been the chief subject of physiological 
 investigation. Hitzig^^ first noted the occurrence of blindness m 
 the opposite eye from destruction of the occipital region 
 in dogs- and in 1881 Goltz described an affection of vision 
 resulting from destructive lesions of the opposite cerebral 
 hemisphere, which, however, he did not specially associate 
 with lesions of the occipital lobe, though he has more re- 
 cently admitted this relationship. The affection in question 
 24 Centralblattf. d. med, Wimenschaften, 1874. 
 
64 
 
 CEREBRAL L CALISA TION. 
 
 was, in his opinion, not complete blindness, but an ina- 
 bility on the part of the animal to understand or interpret what 
 it saw. To this condition he gave the name Hirnsehschwiiche, or 
 cerebral amblyopia. It was entirely crossed, and affected only the 
 eye on the side opposite the lesion. Munk, in his first experi- 
 ments, arrived at essentially the same conclusion ; namely, that 
 the affection of vision resulting from lesion at the point A, Fig. 14, 
 occurred only in the opposite eye. Dalton ^' also found that the 
 opposite eye was rendered blind, and to all appearance perma- 
 nently so, when the cortex was destroyed in the region of the 
 
 Fig. 14. — Cortical centres of tlie dog, after Munk. A, Visual area ; B, audi- 
 tory area; C to J , tactile sensory area (Fiihlsphare) ; D, fore-limb 
 region ; C, hind-limb region ; E, head region ; F, eye region ; G, ear 
 region ; H, neck region ; J, trunk region. 
 
 posterior division of the second external convolution, which he 
 terms the angular convolution. Luciani and Tamburini, on the 
 other hand, found that destruction of the second external convo- 
 lution, more particularly of its median or parietal portion, caused 
 blindness of the opposite eye, and also some degree of amblyopia 
 of the eye on the same side. The further experiments of Munk, 
 however, as well as those of Loeb ^* and of Goltz,^'' and also the 
 later experiments of Luciani,^* appeared to show that though in 
 
 25 Centres of Vision in the Cerebral Hemispheres, Med. Rec, 1881. 
 26 Pfiuger's Archiv, Bd. 4., 1884. 
 27 Ibid., p. 450. 
 28 Sensorial Localisations in the Cortex Cerebri, Brain, vol. 7, 1885, p. 145. 
 
THE VISUAL CENTRES. 65 
 
 dogs the visual area is mainly in relation with the opposite eye, 
 it is also in relation with the outer quadrant of the eye on the 
 same side. Hence, destruction of the visual centre in the one 
 hemisphere paralyses the inner three-fourths of the oppoaite 
 retina, and the outer fourth of the retina on the same side. The 
 condition, therefore— at least the enduring one— is that of homo- 
 nymous hemiopia towards the opposite side : the defect in the eye 
 opposite greatly exceeding that in the eye on the same side. But 
 the facts recorded by Luciani and Tamburini indicate that, for a 
 short time at least, after the destruction of the middle portion of the 
 second extf rnal convolution there is blindness in the opposite eye. 
 And Goltz -^ remarks that he does not think that his former con- 
 clusions were due to defective observation, but that there was 
 probably some variation in his operative procedure. It is, how- 
 ever, likely that we have here the same relations as exist in 
 monkeys, and that, for the time at least, after complete extirpa- 
 tion of the visual sphere, there is total blindness in the opposite 
 eye. This is confirmed by the experiments of Bechterew, 
 recently published.'" Bechterew finds that in dogs and cats there 
 are two regions in the cortex related to vision ; the one in the 
 occipito-parietal region, in relation with the corresponding halves 
 of both retinse ; the other, more especially in the parietal region, 
 in relation with the opposite eye alone. Lesion of the former 
 causes homonymous hemiopia; lesion of the latter, generally, 
 possible only in association with the former, causes, along with 
 hemiopia, amblyopia of the opposite eye by paralysing the centre 
 of clear vision. This combined affection usually after a time gives 
 place to homonymous hemiopia ; or, on the contrary, the hemiopia 
 disappears and the cross- ed amblyopia remains. Bechterew's con- 
 clusions may serve to explain, among others, the results arrived 
 at by Gilman-Thompson and Sanger- Brown,'^ which appear to 
 be entirely at variance with those of Munk, Goltz, and most other 
 physiologists. For they find that lesions, of sufficient size and 
 depth, in the posterior part of the occipital region in cats and 
 dogs, invariably cause blindness of the opposite eye, with no im- 
 pairment of vision in the eye of the same side. These authors, 
 however, seem to think that the extent of the visual sphere is a 
 matter more of cubical capacity than accurate anatomical Ipcali- 
 sation ; for they say that in order that the blindness should be 
 
 2» Op. cit., p. 48. 
 
 »u Atistract in Neurolog. Ctrntrnlhlatt, April. 1R90. 
 
 31 Uesearches of the Loomis Labouitory, 1890. 
 
-66 CEREBRAL LOCALISATION. 
 
 permanent, between 2.5 and 3 cubic centimetres of brain tissue 
 should be removed in cats ; and between 4.5 and 6 cubic centi- 
 metres in dogs. To render the blindness permanent, the incision 
 must be at least 0.5 centimetre deep, and 2 centimetres in dia- 
 meter, in cats ; and 1 centimetre deep, and 3 centimetres in dia- 
 metre, in dogs ; and it must involve at least two convolutions. 
 Smaller lesions produce complete blindness of the opposite eye, 
 lasting from a day or two to six weeks. They conclude from their 
 experiments that in cats and dogs there is complete decussation 
 of the optic nerves in the chiasma. This is, however, opposed by 
 the researches of von Gudden,^^ which show that in dogs and cats 
 there is partial decussation of the optic tracts ; and Nicati ^^ 
 found, experimentally, that division of the chiasma in the an- 
 tero-posterior, or sagittal diameter, did not cause complete loss of 
 vision in either eye. The recent researches of Singer and Miinzer, 
 previously alluded to, indicate that there is only partial decussa- 
 tion in the chiasma of the cat, dog, and also in the rabbit. 
 
 The exact limits of the visual sphere in dogs are still the sub- 
 ject of some differences of opinion, but all the experiments agree 
 in including in this area the posterior half of the second external 
 convolution. This is the convolution which in its electrical reac- 
 tions corresponds with the angular gyrus and occipital lobe in 
 monkeys. The visual area, as defined by Munk, is represented in 
 the accompanying figure (Fig. 15). Point A, situated chiefly in 
 the posterior division of the second external convolution, he re- 
 gards as the centre of clear vision (macula lutea) of the opposite 
 eye. The mesial portion of the visual sphere adjoining the falx 
 he regards as the centre for the inner half, the anterior portion for 
 the upper half and the posterior portion for the lower half of the 
 opposite retina. The lateral portion he regards as the centre for 
 the outer quadrant of the eye on the same side. Destruction of 
 each portion he states induces blindness in the respective region 
 of the eye on the opposite or same side accordingly, and it is only 
 by abnormal fixation of the eyes, or by practice, that the animal 
 is able to overcome the defects so induced. 
 
 Munk describes, as the effects of extirpation of a circular area of 
 the cortex in region A, measuring about 15 millimetres in diameter 
 and 2 millimetres in thickness, a condition of vision, or visual per- 
 ception, similar to that already defined by Goltz. The animal is 
 not blind, inasmuch as it is able to avoid obstacles, but it appears 
 
 32 Arch'ves f. Ophthahnologie, 1874, Band 20. 
 33 Archives de Physiologie, 2iid Series, Tome 5, 1878. 
 
TEE VISUAL CENTRES. 
 
 67 
 
 to have lost all visual ideation. To this affection 1 e gives the 
 name Seelenblindheit or " psychical blindness," in contradistinc- 
 tion to Rindenblindheit or "cortical blindness," which implies 
 total loss of vision presentative, as well asre-presentative. In ex- 
 
 Fig. 1.5.— Relations of the eyes to tlie visual area in tlie dog (after Miinlc). 
 
 planation of this condition he propounds what appears to me a 
 somewhat crude hypothesis, viz., that extirpation of the region in 
 question has removed all the visual pictures which are stored up 
 in and around the spot, and that it is only by a process of educa- 
 K 2 
 
m CEREBRAL LOCALISATION. 
 
 tion that the animal again acquires a new stock of pictures which 
 are deposited in the undestroyed portion of the visual sphere. 
 Some pictures, however, apparently less fragile than the rest, may 
 escape the general destruction occasioned by this iconoclastic 
 lesion. In one case it is the picture of the dish out of which the 
 animal has been accustomed to drink ; in another it is the sign 
 to " give the paw," which the animal has been accustomed to obey. 
 Goltz has criticised this hypothesis in the following amusing 
 terms : — 
 
 " A considerable portion of the cortex of the occipital lobe is de- 
 scribed a3 the visual area by Munk. By far the larger portion of 
 this area, however, is, according to him, pure luxus. The me- 
 morial pictures {Er inner ungsbilder) of the visual perceptions are 
 huddled together like sheep in a storm, in a narrow spot which 
 occupies only about two-sevenths of the whole visual area. When 
 this small spot, which corresponds to the macula lutea of the 
 human retina, is destroyed on both sides the animal is at first 
 blind, and only gradually learns to see, like a puppy, with the aid 
 of the rest of its visual sphere. Five-sevenths of the visual sphere 
 — a large portion of the cortex — appears retained in order that a dog 
 which falls into the hands of the physiologist should again learn 
 to see, when its accumulated visual pictures are cut out. All 
 dogs which escape this fate — and these, since the creation of the 
 dog, must be very many — carry during their life five-sevenths of 
 their visual sphere as an uncultivated fallow field. A wonderful 
 thing in hypotheses !" ^* 
 
 Even if it were the case that the different portions of the retina 
 are represented in the indicated regions of the visual area, it is 
 improbable that these could be determined with any degree of 
 certainty except by exact perimetric investigation, which is natu- 
 rally impossible in the lower animals. The difficulties of deciding 
 questions of this kind in the lower animals are illustrated by 
 Munk's account of his experiences with rabbits.^' "I had at least 
 believed that I could determine with which eye the rabbit saw 
 better, and with which it saw worse. In this, however, I have 
 been mistaken, because it occasionally happened to me that where 
 from tests I had thought I had made out that the greater imper- 
 fection of vision existed in the left eye, post-mortem examination 
 revealed the fact that the left tract and the right optic nerve were 
 more atrophied than the right tract and the left optic nerve." 
 
 3* Op. cit., p. 175. 
 35 Sitzungsberichte Akad. d. Wissensch.. zii Berlin, vol. xxxi, June 20th, lf89, 
 
 p. 631. 
 
THE VISUAL CENTRES. 69 
 
 Loeb, after a series of carefully devised experiments, concludes 
 that there is no foundation for the views of Munk that particular 
 segments of the retinre are in special relation to definite regions 
 of the visual area. When defect of vision occurs from lesion of 
 the posterior lobe, it is always of the same hemiopic or hemiam- 
 blyopic character, whatever portion of the visual sphere be in- 
 jured. The lateral portion of this sphere is not in special relation 
 with the outer quadrant of the eye on the same side, nor is any 
 portion more in relation with one part of the opposite retina than 
 another. In particular, central vision is precisely that which is 
 lefist affected in all cases, whether of unilateral or bilateral lesion 
 of the visual zone. There is never any eccentric or abnormal fixa- 
 tion of the eyeballs when the special regions indicated by Munk 
 are destroyed, such as would necessarily result if the correspond- 
 ing portions were paralysed, nor is the recovery of vision, after 
 partial lesions of the visual area due to practice, or to the 
 acquisition of new visual experience, inasmuch as recovery 
 takes place when the animal is kept absolutely in the dark, and 
 thus prevented from exercising its visual faculties. 
 
 In rabbits the visual centre would, according to the homology 
 of the electrical reactions, occupy the parieto-occipital region of 
 the hemisphere. The exact limits of the visual zone of these ani- 
 mals do not appear to have been accurately determined by any 
 observer, though certain experiments of Moeli^' point to lesions 
 of the region indicated as causing, at least, temporary blindness of 
 the opposite eye. It has been supposed that in this animal tliere 
 is complete decussation of the optic tracts in the chiasma, inas- 
 much as the experiments of Brown-S^quard have shown that sagit- 
 tal division of the chiasma causes complete loss of vision of both 
 eyes. The total decussation in the chiasma of the rabbit was also 
 supported by the earlier researches of von Gudden, who found 
 that after enucleation of one eyeball the opposite optic tract only 
 became atrophied." But, in his later researches, he concluded 
 that a small fascicle of uncrossed, or direct, fibres exist also in the 
 optic tract of this animal, similar to that seen in higher verte- 
 brates. Singer and Miinzer are also of opinion that there is only 
 partial decussation in the chiasma of the rabbit, but the uncrossed 
 tract does not run as a separate bundle, but as fibres more or less 
 diffused throughout the optic tract. In the mouse and guinea- 
 's Archives de Pht/siohgie, 1871-72 : Sur les Communications de la Retine avec 
 rBncriilialc". 
 3' Archiv f. Oplithalmologie, Dd. 20, 1874. 
 
70 CEREBRAL LOCALISATION. 
 
 pig, howerer, the decussation is a complete one. The partial de- 
 cussation of the optic tracts in the chiasma would favour the 
 opinion that, in the rabbit also, both eyes are more or less in rela- 
 tion with each visual zone; and certain experiments of Munk 
 would seem to favour this notion. The point, however, is one 
 which requires further investigation. 
 
 In pigeons, and in birds in general, the region which in its elec- 
 trical reactions is homologous with the visual centre of the higher 
 animals occupies the parieto-posterior aspect of the hemisphere, 
 where it forms a thin lamina over the corpus striatum. McKen- 
 drick^^ found that destruction of this region caused blindness in 
 the opposite eye; whereas removal of the anterior part of the 
 hemisphere had no effect on vision, nor removal of the posterior 
 extremity of the hemisphere. Similar results have been obtained 
 by Jastrowitz ^^ and Musehold.*" Blaschko, however, found that 
 vision did not seem entirely abolished in the opposite eye by de- 
 struction of the cortex in the region indicated; and Munk came 
 to the conclusion that though vision at first seems entirely abol- 
 ished in the opposite eye, yet, after a time, it is regained in the 
 extreme outer or lateral portion of the retina. 
 
 It is usually stated that in pigeons a complete decussation of 
 the optic tracts occur in the chiasma, but von Gudden expresses 
 some doubts on this point. Singer and MUnzer, however, believe 
 that in the pigeon a total decussation occurs. Munk quotes, in 
 favour of his conclusions, certain observations by Miiller to the 
 effect that in the retina of the pigeon there is, besides the usual 
 fovea centralis, another fovea, situated nearer the temporal region 
 of the retina. The outer fovese would subserve binocular, and the 
 central fovese monocular vision. These statements have been sup- 
 ported by the ophthalmoscopic investigations of Hirschberg. 
 
 It has seemed to me that if any bird can possess binocular 
 vision it should be the owl, whose eyes are placed almost in the 
 same plane. To decide this question I recently completely extir- 
 pated the right hemisphere of an owl. The right eye was then 
 securely closed. The owl reacts very readily to visual tests, and 
 is keenly alive to every movement coming within its field of 
 vision. This bird, however, for ten days at least, remained per- 
 fectly indifferent to the electric light flashed in its eye, to all 
 kinds of threats, and when urged to move flew blindly against 
 
 38 Trans. Roy. Soc. of Edinburgh, January, 1873. 
 39 Archiv f. Psychiatrie, Bd. vi, 1876. 
 *o Experimentelle Untersuchungen uher das Sehcentrum bei Tauben. Diss inaug. 
 Berlin, 1878. 
 
THE VISUAL CENTRES. 71 
 
 every obstacle in its course. At the end of this time there were 
 indications of vision, which were found, however, to depend on 
 the partial unclosure of the right eye. In order to ascertain if 
 the visual centre of the left hemisphere was undamaged, the right 
 eye was completely freed from its closure. This had the effect of 
 restoring the animal's sight, so far as the right eye was concerned, 
 though no indications of vision could be made out in the left eye. 
 The bird was able to pursue and ultimately catch a mouse intro- 
 duced into its cage, though the mouse frequently escaped for the 
 time by getting to the owl's left. The right eye was then re- 
 moved. It then speedily became apparent that the animal was 
 not entirely blind, but could see towards the right with the outer 
 portion of its left eye. It noticed and winced at threats made 
 towards the right, came forward and pecked at pieces of meat 
 held in this position, though its aim was not very accurate, and 
 one day pursued about the cage and ultimately, after considerable 
 difficulty, captured a mouse, which it devoured whole. No doubt 
 can therefore be entertained as to the binocular relations of each 
 cerebral hemisphere in the owl. It is stated, however, by Michel, 
 as well as by Singer and Miinzer, that there is total decussation 
 of the optic tracts in this bird. If this be correct, it follows that 
 total decussation of the optic tracts is not inconsistent with 
 binocular representation in each cerebral hemisphere. 
 
 My own experiments, as well as those of Munk, Horsley, and 
 Schafer, show that when the lesions are strictly limited to the visual 
 sphere, vision alone is affected or abolished, without any implica- 
 tion of the other forms of sensibility, general or special, and ab- 
 solutely without any motor paralysis. The contrary results ob- 
 tained by some authors are without doubt dependent on primary 
 or secondary injury to other sensory or motor tracts or centres. 
 In Goltz's experiments the affections of vision from injury of the 
 occipital regions appear to have been almost invariably associated 
 with other forms of sensory disturbance ; but the manner in 
 which he established his lesions has not been sufficiently definite 
 as to exclude implication of the sensory tracts of the internal 
 capsule, or other sensory regions of the cortex. Whether after 
 destruction of the whole visual sphere in the higher animals, man 
 and monkey, any form of reaction to retinal impressions, beyond 
 that of the pupil, may continue— as has been contended for by 
 Goltz in the case of dogs, and by Luciani and Tamburini, and 
 Lannegrace even in the case of monkeys— is not supported by 
 clinical investigation, or by my own experiments, or those of 
 
72 CEF.EBBAL LOCALISATION. 
 
 Munk on monkeys. Thotigh the monkey, rendered blind by total 
 extirpation of its yisnal centres, acqaires tbe power of aToiding 
 obstacles when left amidst its usual saseoQiidii^s,yet tiiis appears 
 to be due rather to a sharpening of its other f acaiHeB, cr Bsata 
 attentive appreciation of the impfessuHos saade go. t^ese \rf the 
 objects -with which it is siirroimded, fbaa to 'vienal sensafiaB. 
 The question is, howeTer, cms -miaeh. Biay well bear fiaxliier int- 
 vestigatioiL ; for, if retinal xsa^psessSsBss are eo-<HdiD8ted witb 
 apparently pitrposiTe actions in the STibordinate c^yzea o£ tiie 
 lower Tertebrates, such as fishes, reptiles, and birds, fteie fe at 
 least the possibility that similar reactions may be discoTerable in 
 the higher animals, even though in a much less degree. It is e»- 
 tain, however, that the visual area of the cortex is not a merely 
 functionally differentiated region capable of re^ada^arofbeiBg 
 replaced by, other cortical regions, inasmuch as destraetiois of the 
 visual centres leads to atrophy in the primary optic centres, optic 
 tracts, and optic nerves ; and, conversely, desttaedoa of the offde 
 radiations leads to atrophy strictly confined to the regiDBS in- 
 cluded within the visual zone. The differentiation of an azea ex- 
 clusively — so far at least as can be judged from rfinMJi*! and 
 experimental results — would strongly favour the hypoyiesia thaifc 
 the other sensory faculties are also separately localised in definite 
 cortical regions. 
 
LECTURE IV. 
 
LECTURE IV. 
 
 The Auditory Centre. 
 
 Me. President and Gentlemen, — Among the reactions conse- 
 quent upon electrical stimulation of the cortex there is one, or 
 rather an assemblage of reactions, which might almost be con- 
 sidered of itself indicative of the existence of subjective auditory 
 sensation — a reaction which guided me in my first attempts to de- 
 fine the auditory sphere by the destructive method. The reaction 
 in question is that which occurs on irritation of the superior tem- 
 poral convolution and its homologues in the lower vertebrates : 
 namelj', quick retraction or pricking of the opposite ear, associ- 
 ated frequently with opening of the eyes, dilatation of the pupils, 
 and turning of the head and eyes to the opposite side. These are 
 just the phenomena which occur when a shrill sound is suddenly 
 made in a monkey's ear, as I have found by actual experiment. 
 The reaction, however, varies somewhat in its completeness. 
 After the first surprise is over, the repetition of the experiment 
 always induces the pricking or retraction of the ear, but generally 
 fails to induce the other parts of the reaction, namely, the intense 
 look of surprise, and direction of the head and eyes to the sup- 
 posed source of the sound. The results are still more characteristic 
 on stimulation of the homologous region (14, Figs. 9 — 11) in those 
 animals whose habits are such as to make their safety largely de- 
 pendent on the acuteness of their hearing. The region in question 
 is the posterior division of the third external or supra-Sylvian con- 
 volution. The reaction common to all these is pricking of the op- 
 posite ear, but the other factors vary in intensity. In the lop- 
 eared rabbit, irritation of this region causes sudden elevation of 
 the ear, as well as retraction and exposure of the mouth of the 
 auricle towards the referred region of the sound. Occasionally 
 the animal makes a sudden start and movement, as if to bound 
 off the table. In the wild jackal, also, I observed on one or two 
 occasions that the application of the electrodes to this region 
 
76 CEREBRAL LOCALISATION. 
 
 caused the animal to make a sudden spring or bound forward, 
 pricking up both ears as if suddenly startled. If the movements 
 of the eyeball on stimulation of the occipito-angular region are 
 to be regarded as signs of arousal of subjective visual sensation, 
 we have, I think, in the reactions under consideration, ttill more 
 characteristic indications of the arousal of subjective auditory 
 sensation. The determination, however, of affections of hearing 
 is not so easy as that of sight in the lower animals. It is difficult 
 to discriminate between mere reflex starting to sounds, and hear- 
 ing proper. Nor is it easy to avoid mere coincidences, or to en- 
 tirely avoid attracting the animal's attention by other channels of 
 perception, such as sight, or smell, or sense of proximity condi- 
 tioned by vibration, warmth, agitation of the air, and such like. 
 The animal's present behaviour should be compared with its past, 
 and with that of normal animals under conditions of variation of 
 sound, all other things remaining the same. And even when all 
 these precautions are taken, it is extremely difficult to avoid every 
 source of fallacy. Hence it may happen, as it has actually hap- 
 pened, that different observers may arrive at different conclusions, 
 and animals may be taken to be deaf which are not in reality 
 so, simply because they do not respond to the test employed, or 
 vice versd. 
 
 In one of my earlier experiments, in which the upper two-thirds 
 of the superior temporal convolution were destroyed on both sides, 
 the following note was made as to the condition of the monkey 
 the day after the operation.^ " Sight was good and tactile sensa- 
 tion unimpaired. Various experiments were made to ascertain 
 the existence or not of hearing, but it was not easy to devise a 
 test, as the animal was continually on the alert, and it was not 
 easy to make a sound without in any way attracting its attention 
 by sight. The following method was tried : while the animal 
 was sitting quietly by the fire I retired to the other room, and, 
 whUe watching through the chink of the half-shut door, called 
 loudly, whistled, knocked on the door, tinkled glass, etc., without 
 ever causing it to look around or give any sign of having heard. 
 I then cautiously approached the animal, and not till it saw me 
 did it give any sign of consciousness of my presence. When the 
 same experiment was repeated while the monkey and its com- 
 panion were quietly seated at the fire enjoying the heat, it gave 
 no sign of hearing, while its companion started with alarm, and 
 came with curiosity to ascertain the cause of the sound. Ten 
 
 1 Experiment XV, Phil. Trans., vol. 265, Part II, 1873, 
 
THE A UDITORY CENTRE, 77 
 
 hours afterwards, in the presence of Dr. Burden Sanderson, I re- 
 peated the various tests with the view of eliciting signs of hear- 
 ing. To all it remained without response. It seemed unconscious 
 of my presence when speaking close to its ear, and only started 
 when it caught sight of me." 
 
 I recorded also four other experiments,^ in which, along with 
 destruction of other portions of the temporal lobe, the superior 
 temporal convolution was invaded, unilaterally or bilaterally. In 
 two of the cases (XI and XII), in which the temporal lobe was de- 
 stroyed only on one side, there was impairment or total abolition 
 of reaction to sound when the ear on the same side was plugged ; 
 and in the two other cases, in which the destruction was bilateral, 
 no signs of heating could be elicited during the short period which 
 the animals were allowed to survive, though, in other respects, 
 they were fully on the alert. In these experiments, however, the 
 time that elapsed between the infliction of the lesion and the 
 death of the animals was not sufficient to establish any very re- 
 liable data as to the permanency of the impairment of the sense 
 of hearing, which was undoubtedly, however, affected in all for 
 the time being. In my subsequent investigations, in conjunction 
 with Piofessor Yeo, however, it was established in the first place 
 by an extensive series of experiments on the temporal lobe^ that 
 no signs of impairment of hearing could be detected when every 
 part of the temporal lobe was destroyed, except the superior tem- 
 poral convolution. What appeared to us, and most of those who 
 saw it, conclusive evidence of the relation of the superior tem- 
 poral convolution to the sense of hearing, was the behaviour of a 
 monkey in which both superior convolutions were actually or 
 potentially destroyed by means of the cautery. Where the cortex 
 was not absolutely removed, the grey matter was undermined, 
 and the medullary fibres destroyed by the action of the radiant 
 heat. 
 
 This monkey was exhibited before the assembled physiologists 
 at the International Medical Congress in London ,in Augubt, 1881, 
 and was admitted by all to be deaf, so far at least as that could 
 be determined by comparing its behaviour with that of a normal 
 animal, to the explosion of a percussion cap in the room. 
 
 As questions were raised in regard to the actual condition of 
 this animal before and after the operation by the experiments of 
 Professor Schafer, to which I am about to allude, I have published 
 
 2 Experiments XI, XII, XIII, XIV, op. cit., p. 462. 
 8 PkiloxopkicaL Transactions, Part II, 1884. 
 
78 CEREBRAL LOCALISATION. 
 
 a full account of my notes and observations on this animal.* 
 Briefly, these were as follows : in all other respects, except as to 
 hearing, it was in a perfectly normal condition. During the first 
 four days after the operation, no signs of hearing could te elicited 
 by any sounds made in its vicinity, and which invariably attracted 
 the attention of normal monkeys. While the other animals were 
 observed eagerly listening to approaching footsteps, this animal 
 made no sign of attention until the person came within range of 
 vision. It was observed also that, at first at least, the ears of the 
 animal did not twitch as they do in monkeys which undoubtedly 
 possess the sense of hearing, but it was doubtful whether the 
 absence of reaction in the ears continued during the whole time 
 that the animal survived. Almost daily examination was made 
 during the thirteen months that it was allowed to live. To 
 sounds of various kinds, such as calling by name, to which it used 
 always to respond, tapping, whistling, ringing of bells, shufiiing 
 of feet on the floor (a sound which normal monkeys are particu- 
 larly quick to notice), this animal paid no attention. Occasion- 
 ally, however, it seemed to start coincidently with loud sounds 
 made in its vicinity, so that doubts were constantly being raised 
 as to whether it was absolutely deaf or no. These reactions were 
 considered to be probably mere coincidences, for in general it did 
 not even start when a percussion cap was exploded near it. Six 
 weeks after the operation, while the animal was disporting itself 
 before the assembled physiologists at the Medical Congress, it paid 
 no heed to the explosion of a percussion cap, while another 
 monkey, exhibited at the same time, started visibly, as, in fact, 
 did the whole audience. From this time onward the tests were 
 constantly repeated and varied in every conceivable manner, but 
 the results were essentially the same, and the conclusion seemed 
 to be justified that the animal was essentially deaf, and that the 
 occasional start which it made to loud sounds was either coin- 
 cidence or merely of the character of the reflex start, which may 
 occur in animals after removal even of the whole cerebral hemi- 
 spheres. 
 
 Schaf er, in his earlier experiments, in conjunction with Horsley, 
 did not arrive at any very definite conclusions with regard to the 
 sense of hearing, though in one of their experiments^ in which 
 they had removed the right temporo-sphenoidal lobe, the animal 
 did not seem to hear slight soxmds when the ear on the same side 
 
 4 Brain, April, 1888, p. 13. 
 5 Experiment 30, Phil. Trans., 1880. 
 
THE AUDITORY CENTRE. 79 
 
 as the lesion was stopped. But, working with Sanger-Brown, he 
 succeeded in removing all doubts which he might have entertained 
 on the question, and in convincing himself that hearing was not 
 in the slightest degree affected after complete removal, not only 
 of the superior temporal gyri but of the whole temporal lobe itself 
 on both sides. He thus describes the result of their experi- 
 ments^ : — 
 
 " In six monkeys we have more or less completely destroyed 
 the supsrior temporal gyrus upon both sides. I say more or less 
 completely because in one or two a small shred of grey matter be- 
 longing to this convolution was {oxxnApost mortem, but practically 
 the lesion was complete in all six, some of the grey matter 
 within the fissures bounding the gyrus being all that could be 
 taken to represent the convolution, and even this being deprived 
 of its medullary centre. But in order to make assurance doubly 
 sure we, in one monkey, a large female Rhcesus, separated up the 
 fissures bounding the gyrus and scooped it out entirely from the 
 very bottom of the fissures, so that not a trace of the convolution 
 in question should remain. In all six cases the result was the 
 same. Hearing was not only not permanently abolished : it was 
 not perceptibly affected. The animals, even immediately after re- 
 covery from the anaesthetic, reacted to slight sounds of an un- 
 usual character such as smacking of the lips or the rustle of a 
 crumpled newspaper. Some of them were under observation for 
 several months, and there never was any doubt in our minds as 
 to the full possession of their auditory faculties. Nor could the 
 reactions they exhibited to sounds be explained by supposing that 
 they only responded in a reflex manner, for they gave every evi- 
 dence of understanding the nature of different sounds, such as that 
 caused by turning a door-handle or the differences between the 
 footsteps of different people, varying emotion being exhibited 
 according to the anticipations (of food, etc.) which the sounds 
 called forth." 
 
 Two of these animals, in which the destruction of the superior 
 temporal convolution seems to have been most complete, were 
 examined by several members of the Neurological Society. Two, 
 who, however, did not record the tests they employed, were of 
 opinion that the animal heard ; while another thought on one 
 occasion that one of the animals could hear, at another time that 
 it seemed deaf on the left side, and, on still another occasion, that 
 
 6 iJrain, Vol. 10, p. 373. 
 
80 CEREBRAL LOCALISATION. 
 
 it did not seem to react to sound eo readily and completely as a 
 normal animal.'' 
 
 As illustrating the difficulty of arriving at definite conclusions 
 on this matter, one member of the Society thought that a per- 
 fectly normal monkey was quite deaf, and another that an animal 
 in which both superior temporal gyri had been removed was 
 also deaf. Schafer** believes that I also was satisfied as to 
 the existence of auditory perception in his animals. Such 
 examination as I made of them did not, I think, furnish any un- 
 equivocal evidence on the point. An unaccountable discrepancy 
 between Schafer's results and Yeo's and mine thus appeared to 
 exist. If in his animals hearing was not perceptibly affected by 
 the double lesion, this certainly was not the case in ours ; for 
 there was no question as to the profound difference between it 
 and a normal monkey, and the only doubt was whether it had any 
 real sense of hearing at all. 
 
 In order, if possible, to clear this matter up I have lately re- 
 investigated the question. In one monkey I removed, first, the 
 whole of the convex aspect of the left temporal lobe, including 
 the superior temporal gj'^rus. The animal speedily recovered from 
 the unilateral operation, and, for the first few days, though un- 
 doubtedly it heard, it seemed to hear less distinctly towards the 
 right than towards the left. A fortnight afterwards a similar 
 operation was performed on the right side, but though the animal 
 lived five days it remained in a state of great apathy. It took no 
 notice of what was going on around it, and was altogether in- 
 different to the loudest sounds made in its vicinity. The experi- 
 ment, therefore, on account of the short period of survival, was 
 not quite a satisfactory one. Another monkey in which I per- 
 formed the operation of bUateral extirpation of the superior tem- 
 poral gyrus, with an interval of one month between the two 
 operations, was specially well adapted for experimentation in 
 regard to the sense of hearing. It was a remarkably tame dog- 
 faced monkey, and its character and modes of behaviour under 
 different circumstances were made the subject of careful study 
 before it was operated upon. It was a noisy, talking monkey. 
 It invariably responded when called to by name, and came 
 immediately when called. It imitated smacking of the lips and 
 other sounds of endearment. It always shouted vigorously and 
 loudly when anyone approached or opened the door leading down 
 
 7 See Brain, July, 1889, p. 164. 
 8 Ph-'.l. Trans., 1888, B. 30, p. 325. 
 
THE AUDITORY CENTRE. 
 
 81 
 
 to the laboratory in which it was kept. The rustling of a paper 
 bag, from which it was accustomed to receive sweetmeats and 
 nuts, was the signal for vociferous cries ; as also any movement 
 of the handle of a drawer in which apples and fruits were kept. 
 It had an insatiable appetite, and was always clamouring for food, 
 of which it never seemed to have enough. It had also an insati- 
 able thirst, and the sound of plashing of water, made by turning 
 
 Fig. 17. 
 
 on the water-tap, caused it to shriek to be let out and put its 
 mouth under the tap. Not a sound could be made in its vicinity, 
 or a movement of its companion monkeys in the other cages, with- 
 out exciting its active attention. It was full of fun and mischief, 
 and in every respect an animal unusually adapted for determina- 
 tion of any alterations that might occur in respect of its auditory 
 u 
 
82 CEREBRAL LOCALISATION. 
 
 or other facilities. The left temporal superior convolution was 
 scooped out on October 8th. (As will be seen in the photograph 
 a small portion also of the middle temporal gyrus was destroyed, 
 Fig. 16). 
 
 The next day, owing to the occurrence, as afterwards proved, of 
 some recurrent haemorrhage and tension in the wound, there were 
 one or two slight epileptic seizures affecting the right side. 
 Theae, however, ceased entirely when the wound was redressed, 
 and the animal was speedily quite bright and active. 
 
 On the second day it turned its head to the dangling of keys 
 close to its left ear, but it did not do so, or very doubtfully, to the 
 same test applied to the right. Next day, and from that time 
 onwards, it appeared, as regards its hearing, in every respect as it 
 had been before the operation. It was noted, however, that it had 
 become completely hemiopic to the right— a condition which lasted 
 more or less completely until its death Ave months subsequently. 
 This hemiopia proved after death to be due, in all probability, 
 to the recurrent haemorrhage, which occurred on the day after the 
 operation, ploughing up the optic radiations in the occipito- 
 angular region. 
 
 On November 5 th, the superior temporal gyrus of the right side 
 was similarly exposed and scooped out. This time the lower 
 extremity of the gyrus almost entirely escaped (Fig. 17). On the 
 following day the animal made no response to any sounds made in 
 its vicinity, nor when the door leading to the laboratory was 
 slammed, nor to the noise of footsteps on the stairs which for- 
 merly used to excite lively demonstrations. 
 
 On the third day, though otherwise alert and bright, it made no 
 reaction to sounds of any kind, did not reply to calls, did not 
 notice the noise of footsteps on the stairs, exhibited no sign of per- 
 ception when the water-tap was turned on, though it was evi- 
 dently intensely thirsty, as it drank eagerly when water was pre- 
 sented to it ; paid no attention to the cries of two animals which 
 were placed in the adjoining cage, and, in general, responded to 
 none of the tests of hearing which formerly aroused its active 
 interest. 
 
 On the seventh day the condition was essentially the same. It paid 
 no heed when called to, or when the door leading to the laboratory 
 was slammed. The rattling of the drawer in which the food was kept 
 or the rustling of the paper bag containing the sweetmeats were alto- 
 gether unnoticed ; the plashing of water was unheeded ; and it 
 went on quietly with its occupation, eating or searching for food 
 
TEE A VDITOR Y CENTRE. 83 
 
 on the floor of its cage, while various sounds, such as springing a 
 rattle, loud barking, whistling, etc., were being made, which 
 startled the other animals in adjoining cages. On the tenth day 
 the condition was essentially the same. There was no reaction 
 to calls, shuffling of feet, etc., which caused other two normal 
 E-.onkeys in the adjoining cage to peer curiously. On this day a 
 test was employed to which it formerly invariably responded. It 
 was late in the evening. I put out the light in the laboratory 
 and ascended the stairs and shut the door. Several times I 
 opened the door and called the animal by name. One of the 
 other monkeys called back in reply, but no response was made 
 by this animal. On former occasions this was the signal for 
 shrill and loud outcries. On the following day the same tests 
 were repeated, and vrith the same results. It was very fond of 
 the laboratory attendant, and would invariably go to him if he 
 called it. On this day, while it was on the table and watching 
 my movements, the laboratory attendant came down the stairs 
 and, standing behind it, called it repeatedly. The animal paid 
 no attention whatever, and never once turned its head in his 
 direction. 
 
 On November 20th (fifteen days after the operation) the fol- 
 lowing notes were made : — 
 
 " The animal well and active, occasionally uttering grunts of 
 satisfaction while sitting quietly by the fire. It also cries loudly 
 when it wants food, but it never responds when called to ; pays 
 no attention to the familiar sounds, such as opening the drawer 
 containing the apples or turning on the water tap, which for- 
 meriy excited in it lively demonstrations. To-day a box con- 
 taining a whistle, capable of being blown by a long india-rubber 
 tube in such a manner as to avoid attracting the animal's sight, 
 was placed in its cage and the whistle repeatedly blown, but it 
 was absolutely unmoved. The same experiment with three other 
 monkeys caused signs of alarm and perturbation." 
 
 About this time the question began to be raised whether the 
 animal did not seem to be aware, by a sense of vibration or other- 
 wise, of the approach of footsteps descending the spiral staircase 
 leading into the laboratory. It was quite certain, however, that 
 while it was being watchtd, and its attention thus occupied, it 
 seemed quite uncontcious of any sound made to divert it. On 
 November .30th, that is, three weeks after the operation, these ob- 
 servations were confirmed after careful study by myself and as- 
 sistant for several hours. But when all was still it seemed to be 
 G 2 
 
84 CEREBRAL LOCALISATION. 
 
 aware, as evidenced by its cries, of the proximity of anyone walk- 
 ing on the floor overhead, or opening the door leading down into 
 the laboratory. TMs was noticed more particularly in the early 
 morning, when this and the other monkeys were eagerly looking 
 towards the stairs expecting their breakfast. Eepeated observa- 
 tions during the course of the following week succeeded in clear- 
 ing up the apparent irregularities in its reactions. It became 
 evident that when the animal was left to itself it was aware of 
 being called to, or of the sound of opening or slamming the door 
 leading to the place in which it was kept, but when anyone was 
 present in the laboratory, and the animal occupied in observing 
 him, it showed no signs of hearing, and did not look round like the 
 other monkeys when called to or when sounds of various kinds were 
 made. If I waited in the laboratory within the range of the 
 animal's vision, and my assistant went to the top of the stairs and 
 called, it paid no heed whatever to anything he might do to attract 
 its attention. Though it occasionally started when a percussion 
 cap was exploded in its vicinity, it did not do so or look around if 
 it happened to be engaged on anything else at the moment ; 
 whereas other monkeys would invariably start and look around 
 towards the cause of the sound, and this condition remained prac- 
 tically unchanged until the death of the animal. In the direction 
 of the laboratory door alone, towards which it was almost con- 
 stantly looking, with expectation, did it seem able to refer sounds, 
 but otherwise, especially when its attention was diverted in any 
 way, it seemed entirely unaware of their origin, and did not turn 
 its head in their direction. It either did not hear or wholly dis- 
 regarded such sounds as scratching, tapping, rattling of keys, and 
 so forth, which caused the other animals to peer eagerly through 
 the bars of their cages. The plashing of water, rustling of paper, 
 opening of the drawer from which it was accustomed to receive 
 choice morsels never excited any notice, and caused none of the 
 lively signs of interest which formerly were so characteristic. I 
 did not observe in this animal, at least during the latter periods 
 of observation, that absence of the twitching of the ears which I 
 had noted in a previous experiment. 
 
 The condition of this animal may, therefore, be stated briefly as 
 follows. At first it failed absolutely to respond to any of the 
 tests which formerly excited active reaction, and which invari- 
 ably attracted the attention of normal monkeys. To the last, 
 with the single exception perhaps of the door of the laboratory 
 from which it was alv/^ays expecting something, it never realised 
 
THE AUDITORY CESTRE. 85 
 
 the origin of sounds ; it was altogether indifferent to sounds 
 which formerly were full of significance to it, and all that could 
 be said was that it was not, when otherwise occupied, insensible 
 to sonorous vibrations. And it would have been difficult to make 
 this out with any degree of certainty, had it nob been that the 
 animal was one qualified to give oral testimony of the fact. 
 Whether this form of auditory sensibility is to be attributed to 
 portions of the cortical auditory centres undestroyed by the 
 lesions described, or to subcortical or mesencephalic centres, I am 
 not yet in a position to decide. I have not yet been able success- 
 fully to carry out observations on animals in which the temporal 
 lobes have been destroyed on both sides; but if, as Schafer's ex- 
 periments seem to indicate, the whole of the temporal lobes, like 
 the other cerebral lobes, may be removed without entirely abolish- 
 ing reaction to sounds, we should have reason for believing, with 
 Longet, GoltE, etc., that in monkeys, as well as lower mammals, a 
 crude and simple form of auditory sensation is still possible 
 through the agency of the lower centres. 
 
 Munk, from his experiments on dogs, states that destructive 
 lesion of the point B (Fig. 14), situated towards the lower extre- 
 mity of the supra-Sylvian and adjacent extremity of the second 
 external convolution, causes a condition as regards hearing similar 
 to that resulting from destruction of A (Fig. 14) in the sphere of 
 vision ; a condition which he terms " psychical deafness " (Seelen- 
 taubheit). The dog seems to hear, but is unable to interpret 
 the sound that it hears. This condition, however, lasts only for a 
 few weeks at most. The animal again learns the meaning of 
 sounds, and becomes restored to its normal state. In this region 
 are stored up, according to him, the auditory pictures, similar to 
 the visual pictures in the region A, (Fig. 14). Frequently, how- 
 ever, before the secondary disturbances created by the primary 
 lesion have subsided, the animal appears to be totally deaf, so that 
 it exhibits no reaction to any kind of sound, however loud. Occa- 
 sionally when the whole of the cortex of both temporal lobes had 
 been destroyed, he has observed persistent " cortical deafness " 
 {Rindentaubheit), as he terms it, but as none of the animals on 
 which he has performed this operation seem to have lived be- 
 yond a few days, his experiments do not afford data for the de- 
 termination of the duration of this complete deafness. lie, how- 
 ever, assumes that the auditory area of the cortex embraces a 
 much larger extent than B, and includes, according to his figures, 
 the whole of the posterior half of the third, and also of the pos- 
 
86 
 
 CEREBRAL LOCALISATION. 
 
 terior or lower divisions of the first and second external convolu- 
 tions. With respect to the auditory sphere in the brain of the 
 monkey, he assumes — for he does not appear to have performed 
 any experiments bearing on this point — that it is situated at the 
 lower extremity of the middle temporal gyrus (B., Fig. 18), a region 
 which I have completely extirpated without causing the slightest 
 affection of auditory sensation. And he considers that the upper 
 portion of the superior or temporal gyrus (G, Fig. 18) is the sen- 
 sory sphere of the ear ; of this I can obtain no evidence, for 
 neither after unilateral nor bilateral extirpation of this region 
 have I been able to verify any affection of the sensibility of the 
 auricle. 
 
 Fig. 18.— Cortical centres of the monkey, according to Munk. A, Visual area; 
 C to J, tactile sensory areas (Fiihlsphaere) of Munk ; psychomotor areas of 
 other authors ; D, fore-limb region ; C, hind-limb region ; E, head region ; 
 r, eye region ; G, ear region ; H, neck region ; J, trunk region. B is 
 placed upon that portion of the cortex which, from experiments on dogs, 
 is assumed to be the auditory area. 
 
 Luciani and Tamburini^ found that unilateral destruction of 
 the upper and posterior part of the third external convolution in 
 dogs caused deafness in both ears, but to a greater extent in 
 the ear of the opposite side. The difference in auditory sensi- 
 bility on the two sides greatly diminishes, and after a few days 
 disappears altogether, though it cannot be asserted that perfect 
 recovery ever takes place. After comparative equalisation of the 
 power of hearing on the two sides, removal of the corresponding 
 region of the other hemisphere is followed by almost total deaf- 
 ness, approximately equal on both sides. This bilateral deafness 
 passes off gradually, but data do not yet exist, according to them, 
 
 9 Sui Centri Psico-Sensori Corticali, 1879. 
 
THE A UDITOR 1 ' CENTRE. 87 
 
 for determining whether perfect recovery takes place. When the 
 destructive lesions are confined to the posterior part of the second 
 external convolution, and do not implicate any part of the third, 
 there does not occur the slightest impairment of hearing, which, 
 indeed, sometimes appears to be unusually keen. These authors 
 beUeve that semi-decussation of the auditory nerves exists similar 
 to that of the optic nerves, and that both ears are represented in 
 each cerebral hemisphere. This latter is undoubtedly the case ; 
 for unilateral extirpation never gives rise to permanent deafness 
 of the one ear ; but, though I have on many occasions, after extir- 
 pation of the auditory area in one hemisphere, observed loss or 
 impairment of hearing in the opposite ear, I have never been able 
 to detect the slightest impairment of hearing on the ear of the 
 same side. Lueianii" states: "The effects of extirpations in the 
 province of the parietal lobe confirm what was recognised by 
 Ferrier, and afterwards by Tamburini and myself, that the bend of 
 the third external convolution certainly makes part of the audi- 
 tory sphere in the dog, but demonstrate also that this sphere 
 irradiates from its central point in the temporal lobe, upwards to- 
 wards the parietal region, forwards towards the frontal, back- 
 wards toward the hippocampal, inward towards the cornu 
 ammonis." He thus includes in his auditory sphere a large portion 
 of the cortex which is concerned with other functions. In refer- 
 ence, however, to this and other sensory centres, Luciani appears 
 to contend for a form of localisation which is no localisation at 
 all, as every centre seems to perform to some extent the functions 
 of every other centre ; results which I regard as absolutely op- 
 posed by the facts of strictly localised lesions. 
 
 It will be observed, in reference to the position of the auditory 
 area in the dog, that it does not occupy the same relation to the 
 fissure of Sylvius that the superior temporal gyrus does in the 
 monkey, but is separated from it by the posterior limb of the 
 Sylvian convolution. It has been assumed by Meynert that 
 the posterior division of the Sylvian convolution is the homologue 
 of the superior temporo-sphenoidal gyrus-^^ I, however, have 
 ventured to suggest that the resemblance between the posterior 
 division of the Sylvian convolution and the superior temporal 
 gyrus is only superficial, and is conditioned by the shallowness 
 of the fissure of Sylvius. The investigations of Sir William 
 
 .0 On the Sensorial Localisations in the Cortex Cerebri i?ra^« 1885. p. 154 
 
 u Die WinduQKen der convexen Oberflaohe des Vorder-«lrna, Avcluv f. P^y 
 
 cMatrie, Bd. vii, 1871. 
 
88 
 
 CEREBRAL LOCALISATION. 
 
 Turner '^ have led him to the conclusion that the Sylvian con- 
 volution in the dog is in reality the homologue of the island of 
 Eeil, visible on the surface owing to the shallowness of the 
 Sylvian fissure. In this case the posterior division of the supra- 
 
 Fig. 20. 
 
 Sylvian convolution would correspond accurately with that of 
 the superior temporal gyrus. 
 
 12 Eeport on the Seals, Challenger Expedition, Part LXVIII, p. 124. 
 
THE AUDITORY CENTRE. 89 
 
 The occurrence of deafness from cerebral disease in man is 
 unusual, owing to the extreme rarity of bilateral lesions affect- 
 ing simultaneously both superior temporal gj^ri. There are, 
 however, on record two important cases in which this double 
 lesion occurred. 
 
 Shaw " has recorded the case of a woman, aged 34, who, two 
 months before her admission into his asylum, lost power in the 
 right arm, and soon after had a sudden apoplectic seizure, 
 resulting in loss of speech and deafness. The loss of power in 
 the right hand speedily passed off. She became excited, inco- 
 herent, and subject to delusions. On admission, she was found, 
 after repeated testing, to be perfectly deaf and blind. Tactile 
 sensibility and smell were unimpaired. She had occasional fits, 
 and ultimately died of pneumonia a year after her admission. 
 
 Post-mortem examination showed complete atrophy of the 
 angular gyri and superior temporo-sphenoidal convolutions of 
 both hemispheres. (See Figs. 19 and 20). The grey matter of the 
 atrophied regions had entirely disappeared, leaving the outer layer 
 attached to the pia mater, with a cavity underneath formed at the 
 expense of the grey matter. The other cranial nerves were normal 
 in appearance, but the optic nerves showed increase of the con- 
 nective tissue septa, atrophy of the nerve fibres, and spaces filled 
 with a colloid-like material. "Whether the blindness was due to 
 the lesion of the angular gyri alone or to degenerative changes in 
 the optic nerves is a question, but the sudden onset of deafness in 
 this case, coincidently with symptoms of cerebral lesion and the 
 condition of the brain post mortem, point to the destruction of the 
 superior temporal convolutions as its cause. A similar case has 
 been reported by Wernicke and Friedlander : ^* "A woman, aged 
 43, who had never suffered from deafness or affection of vision, 
 was attacked on June 22nd, 1880, with right hemiplegia and 
 aphasia. She remained in the hospital until August 4th, when 
 she was discharged. At this time the patient could speak, but she 
 spoke unintelligibly, and was sometimes believed to be intoxi- 
 cated. She not only could not make herself understood, but she 
 could not understand what was said to her. She was received into 
 the hospital again on September 10th, with slight paresis of the 
 left arm. The right hemiplegia had entirely disappeared. The 
 patient was looked upon as insane. She was absolutely deaf, so 
 
 i» Archives of Medicine, February 1882. 
 u ForUchritU der Meditin, Bd. 1, No. 6, March 15tb, 1883; Brain, April, 1888. 
 
 p. 19. 
 
90 
 
 CEREBRAL LOCALISATION. 
 
 that she could not be communicated with. She died of an attack 
 of heematemesis on October 2l8t. An extensive lesion was found 
 in each temporal lobe, invading the superior temporal convolution 
 on both sides. (See Figs. 21 and 22). The rest of the brain ex- 
 
 Fig. 22. 
 
 hibited no abnormality, nor were there any conditions leading to 
 increase of the intracranial pressure or 'secondary affection of the 
 cranial nerves. 
 
THE AUDITORY CENTRE. 91 
 
 It was proved that the patient had previously enjoyed excel- 
 lent hearing. Her total deafness occurred suddenly in connection 
 with the other indications of cerebral disease. In order to ex- 
 clude possible local affection of the ears these organs were sub- 
 mitted to examination by Professor Lucae. The result of this ex- 
 amination was practically entirely negative, only a slight dry 
 catarrh being found, and nothing locally to account for deafness. 
 These authors conclude " that the auditory nerves ultimately end 
 in the temporal lobe, and that double or bilateral lesion in these 
 lobes causes complete deafness. It may therefore be stated with 
 all certainty that the temporal lobes are the cerebral centres of 
 hearing." 
 
 Though the lesions were not confined to the superior temporal 
 gyri, yet these were involved both as to the grey matter and me- 
 dullary fibres. The case, therefore, confirms, if it does not of it- 
 self suffice to indicate, the position I have assigned to the audi- 
 tory centre in these gyri. 
 
 The affections of hearing with which we are most familiar in 
 connection with cerebral disease are the various forms of what is 
 termed " word- deafness "—a condition in which auditory ideation 
 is impaired, more particularly as regards the association of articu- 
 late sounds with acts of articulation and things signified. The 
 word-deaf is not devoid of auditory sensation, for he can hear the 
 ticking of a watch, and can recognise and hum an air, but articu- 
 late sounds, except, perhaps, his own name or some simple combi- 
 aation of words, have no meaning, and cannot be repeated. Word- 
 deafness has been found associated with affection of the superior 
 temporal gyrus in the left hemisphere. Seppili^' finds that of 
 seventeen cases, in which a post-mortem examination was made, in 
 every one there was lesion of the superior temporo-sphenoidal 
 convolution, and twelve in which also the second or middle con- 
 volution was involved. 
 
 Of twenty-five cases of word-deafness of which I have notes, 
 collected by Dr. Ewens, ten were from lesions of the temporal 
 lobe alone. In seven of these the first temporal gyrus was par- 
 ticularly affected ; in the remaining three, the exact limits of the 
 lesion were not stated. Eight were from lesions implicating the 
 angular as well as the upper temporal gyrus ; six were from 
 lesions invading the superior temporal gyrus and adjoining por- 
 tions of the occipital or parietal lobes, and one was stated to have 
 
 15 Remit. Speriment. di Freniat, vol. x, 1884. 
 
92 CEREBRAL LOCALISATION. 
 
 been due to lesion of the angular gyrus alone. In this case there 
 appears to have been both word-blindness and word-deafness. In 
 all, therefore, except one, there was obvious lesion of the superior 
 temporal convolution. 
 
 Further confirmation of the localisation of the auditory centre 
 in this convolution is afforded by cases of auditory discharges or 
 subjective auditory sensations in connection with irritative 
 lesions implicating this gyrus. Gowers has reported two cases 
 of this nature.^® In the one a tumour, of which the oldest part 
 was beneath the superior temporal convolution, caused convul- 
 sions commencing with an auditory aura referred to the opposite 
 ear. In the other, a tumour affecting the superior temporal 
 gyrus caused unilateral convulsions, preceded by a loud noise as 
 of machinery. And Hughes Bennett ^^ has reported several cases 
 of auditory sensory discharges followed by temporary loss of 
 hearing in the opposite ear, or in both. Thus a woman subject to 
 epileptic attacks preceded by a loud noise like the ringing of a 
 bell in the left ear, became temporarily deaf in each ear after 
 each attack. Both ears were deficient in hearing, but the left un- 
 doubtedly the more so. The superior gyrus has also been found 
 atrophied in cases of long-standing deafness or congenital deaf- 
 mutism. Mills ^* records the case of a man deaf for thirty years ; 
 the brain, otherwise normal, showed extensive atrophy of both 
 superior temporal gyri, more particularly on the left side. 
 Broadbent^^ describes the brain of a deaf and dumb woman in 
 which, in addition to some defect of the annectent convolutions 
 and supramarginal lobule, there was atrophy of both superior 
 temporal gyri more marked on the left side. The facts of human 
 pathology, therefore, undoubtedly support the view that the sense 
 of hearing is localised in the temporal lobe, and more especially 
 in the superior temporal gyrus of this lobe. 
 
 The experiments of Baginsky,^" as well as the microscopical in- 
 vestigation of Flechsig and Bechterew,^^ indicate that the auditory 
 nerve is in relation with the auditory centre of the cortex through 
 the lower fillet of the opposite side, and thence by means of the 
 posterior tubercle of the corpora quadrigemina and corpus genicu- 
 latum internum with the medullary fibres of the cortex. Ba- 
 
 '^^. Diseases of the Nervous Sys'em, vol. ii, p. 21. 
 
 1^ Sensory Cortical Discharges, Lancet, 1889. 
 
 18 University Medical Magazine, November, 1889. 
 
 19 Journal of Anatomy. 1870 
 
 20 Sitzungsb. Akad. d. Wissenschafien zu Berlin, 1886, 12. 
 
 21 Neurolog, Centralblatt, December, 1886. 
 
THE AUDITORY CENTRE. 93 
 
 ginsky's experiments consisted in destroying the labyrinth in rab- 
 bits, and then tracing the course of the paths of degeneration 
 thereby caused. He found a marked disappearance of the fibres of 
 the lower fillet in the opposite side, and some degree of atrophy 
 also in the posterior tubercle and brachium and corpus genicula- 
 tum internum. Von Monakow also states that, after extirpation 
 of the temporal lobe in newborn rabbits, atrophy occurs in the 
 corresponding medullary fibres of the internal capsule and in the 
 corpus geniculatum internum of the same side ; thus furnishing 
 confirmation of the views of Baginsky and Flechsig. 
 
 We have thus grounds for believing that the central fibres of 
 the auditory nerves do not, as Meynert has stated, all pass through 
 the cerebellum on their way to the cerebral hemispheres— a hypo- 
 thesis which is otherwise inconsistent with the results of destruc- 
 tion of the cerebellum itself. Some of the fibres of the eighth 
 nerve undoubtedly pass into the cerebellum, but these appear to 
 be the vestibular fibres from the semicircular canals, and not the 
 cochlear or true nerve of hearing. 
 
 Centre of Tactile and Common Sensibility. 
 
 I will now proceed to consider the locality of the centres of 
 common and tactile sensibility. 
 
 Many uncertainties still exist as to the paths and centres of the 
 various forms of common sensation. It is universally admitted, 
 since the classical experiments of Brown-S^quard, that, with the 
 exception, perhaps, of the so-called muscular sense, the paths of 
 all the other forms of sensibility are conveyed upwards on the 
 opposite side of the spinal cord. But neither experimental, nor 
 pathological, nor microscopical investigation has accurately de- 
 termined in which particular part of the opposite side of the 
 spinal cord the sensory tracts ascend to the brain. The experi- 
 ments of Ludwig and Woroschilofif -^ appear to show that sensory 
 impressions may be conveyed upwards, without any appa- 
 rent disturbance of the normal relations, when the whole 
 of the anterior and posterior columns, as well as the grey 
 matter, has been severed ; when, therefore, only the lateral 
 columns of the cord remain intact. They found that, when 
 only one lateral column remained, movements of the arms and 
 
 ** Der VerlauJ iMtorUcKen und sensiblen Bahnen dutch das Lendenmark des 
 Kaninchens, 1874. 
 
94 CEREBRAL LOCALISATION. 
 
 anterior part of the body could be readily excited by irritation of 
 the opposite leg behind the section, but only with diffi(?ulty by 
 irritation of the leg on the same side. In order that impressions 
 on the opposite leg should readily excite movements in the 
 anterior part of the body, they found that that portion of the 
 lateral column must remain intact which lies in the area bounded 
 by the prolongation outwards of the anterior and posterior com- 
 missures, that is, the middle third. Ludwig and Woroschiliff were 
 not able to differentiate the sensory from the motor tracts of the 
 lateral columns, and concluded that both were more or less mingled 
 together ; but the facts of human and experimental pathology 
 indicate that they are, to a large extent at least, distinctly separ- 
 able from each other, and doubt may be entertained as to how far 
 their experiments indicate the paths of true sensation as distinct 
 from those of mere reflex reaction, more or less general. It does 
 not appear that the paths of sensation proper degenerate upwards 
 to any great extent after complete severance of the cord at any 
 part. Of the paths which degenerate upwards the principal are 
 the posterior median columns, or columns of GoU, which 
 degenerate upwards, in some measure at least, as far as the nuclei 
 graciles or post-pyramidal nuclei of the medulla oblongata. The 
 posterior external columns, or columns of Burdach, degenerate 
 upwards at most for a distance of only a few roots. In addition, 
 upward degeneration occurs in the direct cerebellar tracts, which 
 can be traced continuously to the restiform bodies, and thence 
 into the superior vermiform process of the cerebellum. Anterior 
 to the direct cerebellar tract, but more or less distinct from it, 
 there is another tract in which ascending degeneration is fre- 
 quently observed, as was first pointed out by Gowers, a tract 
 which, as Bechterew has shown,^^ differs in its period of develop- 
 ment from the other tracts of the cord. This constitutes the 
 antero-lateral column. None of these tracts, however, have been 
 conclusively shown to be the path of any form of sensation proper, 
 using this term to distinguish the paths of conscious from those of 
 mere afferent or centripetal impressions. 
 
 As the direct cerebellar tract undoubtedly ends in the cerebel- 
 lum, and, as the observations of Tooth^* would seem to show, is 
 mainly derived from the posterior roots of the upper dorsal and 
 cervical regions, and not from those of the lower extremities, we 
 may eliminate these from the paths of sensation proper. The 
 
 23 Nmrolog. Centralblatt, 1885. 
 2* Secondary Degeneration of the Spinal Cord, 1889, 
 
THE TACTILE CENTRE. 95 
 
 antero-lateral tract in which Gowers is disposed to place the path 
 of painful impressions, appears, from the researches of Tooth, to 
 consist largely of very fine fibres, and to arise from the cells of 
 Clarke's column. It ascends to the nucleus lateralis, which is (he 
 upward continuation of the lateral horn of the cervical cord, also 
 called the visceral horn. The further course of this tract is un- 
 certain though its larger fibres are supposed by Tooth to ulti- 
 mately reach the cerebellum. Gowers reports a case of unilateral 
 lesion of the spinal cord^' which would appear to support his 
 hypothesis, and Bechterew states that analgesia follows transverse 
 section of the anterior half of the cord. In neither of these obser- 
 vations, however, as Tooth remarks, can we eliminate affection of 
 the grey matter itself. 
 
 I have lately performed an experiment on a monkey in which I 
 divided the convex or outer half of the lateral column in the 
 middle of the dorsal region. (Fig. 23.) Though a slight amount 
 of paralysis occurred on the limb of the same side there was no 
 
 A A A 
 
 impairment of tactile or painful sensibility on the opposite leg the 
 day after the lesion. The slightest touch on either limb imme- 
 diately attracted the animal's attention. In another, in which I 
 divided the greater portion of one half of the cord, excluding the 
 posterior column, part of the anterior column, and that portion of 
 the lateral column lying in the angle formed by the anterior and 
 posterior cornua (Fig. 24), there was almost complete motor para- 
 lysis in the leg of the same side, but sensibility was not abolished 
 on the opposite side. Whether sensation was at all impaired 
 could not be determined with certainty, but the sense of pain was 
 undoubtedly retained. These experiments are, therefore, opposed 
 to the hypothesis that the antero-lateral tract is the path either 
 of tactile or painful sensation. 
 
 In another experiment which I performed on a monkey, the 
 particulars of which I have elsewhere recorded,^* I divided the 
 
 2'' Clinical Society's Trannactions, vol.xl, 1877. 
 2« HemiBectioii of the Spinal Cord, Jirain, vol. vii, p. 1. 
 
96 CEREBRAL LOCALISATION. 
 
 whole of the left side of the cord with the exception of the an- 
 terior and posterior median column. Though the greater portion 
 of the left posterior median column and the whole of the right 
 posterior median column, as well as the grey matter on the right 
 side, and that surrounding the central canal on the left side were 
 intact, there was complete anaesthesia and analgesia on the op- 
 posite side of the body. This experiment, therefore, negatives 
 the hypothesis that the posterior columns are the paths of tactile 
 sensibility. It also is opposed to the hypothesis that the pos- 
 terior median column is the path of the so-called muscular sense 
 on the same side. For the behaviour of this animal indicated, 
 so far at least as can be judged from the observation of the lower 
 animals, that it had entirely lost muscular sense on the opposite 
 limb ; for while it was able to move its right leg volitionally in 
 all directions, and for all purposes, without any appearance of 
 uncertainty or ataxy, and could grip strongly with its foot, this 
 was only when vision was free. When, however, the eyes were 
 blindfolded the animal was utterly unable to extricate its leg 
 from any opposition to its intended movements. 
 
 In another experiment I endeavoured accurately to divide the 
 posterior median columns in the mid-dorsal region. The lesion 
 was effected by plunging a triangular keratome into the posterior 
 median fissure to such a depth — as I had calculated by repeated 
 experiments on the dead spinal cord — as would divide the posterior 
 median columns down to the posterior commissure. Though it 
 seemed as if the whole of the columns should have been severed, 
 I could not after death verify greater destruction than of the 
 portions immediately adjoining the median fissure. (Fig. 25.) 
 Though the animal was for a few hours somewhat weak or awk- 
 ward in its hinder extremities, next day not the slightest impair- 
 ment of tactile or muscular sense could be discovered. It ran 
 about without any sign of ataxy, climbed with its customary 
 freedom, clambered down the bars of its cage, planted its feet 
 with precision and without the aid of vision, and was at once 
 aware when its feet reached the ground. The slightest touch on 
 either foot, or on any portion of the lower part of its body, at 
 once attracted its attention. 
 
 Bechterew has also found^^ that section of the posterior columns 
 in the cervical region in dogs causes no loss of tactile or muscular 
 sensibility, though the operations appear to be followed by dis- 
 orders of equilibration. These, however, tended to disappear with 
 
 27 Neurolog, Centralblatt, February 1st, 1890. 
 
THE TACTILE CENTRE. 97 
 
 the lapse of time. Bechterew's experiments, therefore, are op- 
 posed to the view that the posterior columns are the paths of any 
 of the forms of sensation proper. 
 
 It has been stated by Brown- Sdquard, and generally accepted 
 by physiologists and pathologists, that the paths of the muscular 
 sense do not cross with the other sensory tracts, but ascend in the 
 cord on the same side ; so that in hemisection or unilateral disease 
 of the spinal cord, the muscular sense is impaired or lost on the 
 side of the lesion and retained on the opposite and otherwise 
 anaesthetic limb. The facts of hemisection of the spinal cord in 
 the monkey are, in my opinion, opposed to this hypothesis, but I 
 am ready to admit that experiments on the lower animals, in 
 which we can only infer as to the conditions of consciousness, are 
 not so satisfactory in this relation as accurate observations on 
 human beings. On investigation, however, of the cases which 
 have been adduced in support of Brown- S^quard's contention, I 
 find that the evidence of the retention of muscular sense on the 
 otherwise anaesthetic limb, and its impairment or loss on the side 
 of lesion, is far from satisfactory. 
 
 Out of 43 cases ^^ of apparently unilateral disease of the spinal 
 cord in which, however, there were only two post-mortem exami- 
 nations, in only 24 was there any mention of the condition of the 
 muscular sense in the original papers. In 6 the only evidence 
 given of the muscular sense being retained was the abUity to 
 perceive strong pressure, or the power of directing movements 
 with precision : — a condition, however, which has been proved to 
 be possible in the entire absence of any sense of movement. In 
 4 the method of testing the muscular sense is not stated. In 
 1 muscular sense appeared to be normal on both sides, no further 
 details being given. In another the only note was that the paralysed 
 limb did not judge as exactly as the other side difference in weights. 
 In 3 the muscular sense ^^ was present on the otherwise anaesthetic 
 side, but in these three tactile sensibility was not lost. In one case '" 
 muscular sense appeared to be lost on the paralysed leg ; but in 
 this case there was some anaesthesia of the arm on the same side, 
 and probably, therefore, also on the leg. In one no investigation 
 seems to have been made of the muscular sense while the limb 
 was paralysed. Afterwards it was said to have a certain degree 
 
 28 Most of these cases have been quoted by Brown-Sequard in the Archives de 
 
 Phyiiologie, vol. 1 and 2. 
 
 *• Perroud, Journ. de Med. de Lyon, vol.ix, 1868 ; Gilbert, Archives de Neurologie, 
 
 tome 3, p. 275 ; Bayne, Lancet ii, 1865, p. 117. 
 
 30 Brown-Sequard, Lancet, vol. ii, 1868, p. 689, Case 2. 
 
 11 
 
93 CEREBRAL LOCALISATION. 
 
 of inco- ordination and loss of notion of position. In another ^ 
 the only note was that the patient retained the power of esti- 
 mating weights and the consistency of bodies on the anaesthetic 
 limb. The state of the other was not mentioned, and no exact 
 details are given as to the condition of the various forms of sensi- 
 bility. Of the remaining cases, in one muscular sense was lost on 
 the anaesthetic side.'^ The condition of the other is not recorded. 
 In another^' the conditions varied according to the progress of 
 the disease, but the muscular sense was always retained on the 
 anaesthetic limb, so long as tactile sensibility and the power of 
 localisation were unaffected. In the third ^* muscular sense was 
 retained on the paralysed limb, though its condition on the other- 
 wise anaesthetic limb was not mentioned. This was the only case 
 which was followed by a^osi-TWor^ew examination. In another, Kob- 
 ner's case,^' it was found, on applying proper tests to the paralysed 
 limb, that the patient had a perfect knowledge of any movement 
 passively communicated to it ; and a similar case has been re- 
 corded by Jaccoud.^^ Though, therefore, there appear to be some 
 facts in lavour of Brown-S^quard's theory, others are absolutely 
 opposed to it. So that clinical observation hitherto cannot be 
 said to give unqualified support to the theory that the muscular 
 sense remains unaffected when all the other forms of sensibility 
 have been lost. Such being the state of the question, the particu- 
 lars of the following case, which I have recently had under my 
 observation, are of some importance. 
 
 W. S.,aged 25, admitted as an out-patient at the National Hospital 
 for the Paralysed and the Epileptic on March 21st, 1890. Previous 
 health had been good until three years ago, when he contracted 
 syphilis. At Christmas, 1888, he observed that he had difficulty in 
 emptying his bladder. Soon after this he had temporary para- 
 lysis of the sphincters, both of the bladder and rectum. In April, 
 1889, he complained of weakness of the left leg, which passed off 
 after a few months, at the end of which time the right leg became 
 affected and has continued so, becoming more and more rigid up 
 to the present date. On examination, there is tenderness to per- 
 cussion from the tenth to the twelfth dorsal vertebra, and to a 
 lesser extent for some distance above this point. The patient corn- 
 s'- Dundas, Edin. Med. Jaum., 1825, p. 304. 
 32 Sir Charles Bell's case, Nervous System, p. 245. 
 83 McKenzie's case, Lancet, 1883, vol. i, p. 995. 
 3* Charcot and Gombault, Archives de Physiol., vol. v, p. 144. 
 
 35 Archivf. klin. Med., 1877. p. 208. 
 
 3« Lemons de Clin. Med., 1867, p. 451. 
 
THE TACTILE CENTEE. 99 
 
 plains of constriction round the abdomen, just above the umbili- 
 cus. There are no abdominal or cremasteric reflexes on tne left 
 side, bu*; both are present and well marked on the right. Condi- 
 tion of the limbs : The right leg is paretic and rigid. The iinee- 
 jerk is greatly exaggerated, and there is well marked ankle clonus. 
 In this leg all varieties of sensation are normal. When his eyes 
 are closed, he can indicate with perfect accuracy every movement 
 that is communicated to his limb. There is weakness of the left 
 leg, and the knee-terk is increased. There is no complete anal- 
 gesia, but there is absolute tactile antesthesia from the foot up to 
 the knee, and dulled from this to the level of the umbilicus. 
 Sensibility to heat and cold is very much impaired. With his eyes 
 closed he is absolutely unable to say in what position his limb or 
 any part of his limb is placed, but he is able to direct its move- 
 ments with fair precision. 
 
 In another case, the patient suddenly became paralysed on the 
 Jeft leg, and anaBsthetic on the right. This fact he discovered by 
 the insensibility of the leg to hot water which he could not bear 
 with the right. At the date of my examination, a month after 
 the attack, he had recovered from the motor paralysis of the left 
 leg, but he was still absolutely insensible to thermal and painful 
 stimuli on the right leg. Tactile sensibility was, however, equally 
 good on both sides, and with it the muscular sense was also 
 perfect ia both. 
 
 To my mind the evidence, from the various facts mentioned, is 
 in favour of the view that the whole of the sensory paths pai=s up 
 the opposite side of the spinal cord, and that they are not contained 
 either in the posterior median column, or in the direct cerebellar 
 tract, or in the antero-lateral tract; and, as the pyramidal tract 
 may be entirely sclerosed without any affection of sensation, we 
 are led by a process of exclusion to suppose that the sensory tracts 
 ascend in immediate relation with the central grey matter. If the 
 sensory tracts retain constant relation with the grey matter, this 
 would account for their non-degeneration upwards like the other 
 continuous afferent tracts of the cord. 
 
 h2 
 
LECTURE V. 
 
LECTURE V. "" \ ^ 
 
 Mb. Pbesident and Gentlemen, — Followed upwards in their 
 course to the brain, clinical and pathological investigation 
 would appear to show that in the medulla and pons the 
 sensory tracts run in the fillet, or formatio reticularis. 
 Those tracts — namely, the posterior external and posterior 
 median — which do not decussate in the cord, decussate through 
 the nuclei graciles and cuneati into the inter-olivary layer, 
 and thence into the fillet and reticular formation (Edinger). 
 Higher up, the evidence ia in favour of the continuation of these 
 tracts in the tegmentum of the crus cerebri, and thence into the 
 posterior part of the internal capsule, whence they radiate out- 
 wards, according to Flechsig, and distribute themselves to the 
 cortex in the region lying between the fissure of Rolando and the 
 occipital lobe. It has been supposed by Meynert that the outer 
 third of the foot of the crus is the path by which the sensory 
 tracts of the spinal cord pass into the internal capsule ; and in 
 favour of this view is the fact that descending degeneration, while 
 frequently found in the other fibres of the foot of the crus, has not 
 usually been found here. Bechterew and Rossolymo,^ however, 
 have reported cases of degeneration of this part of the crus appa- 
 rently in relation with lesion of the temporal and occipital lobes, 
 and it is held by Flechsig that these fibres do not enter the in- 
 ternal capsule, but bend downwards and outwards to radiate in 
 the cortex of the occipital and temporal regions. They are sup- 
 posed to connect these regions with the cerebellum through the 
 intermediation of the grey matter of the pons, but this is a point 
 which, I think, stands in need of further investigation. In order, 
 if possible, to throw light on the functions and connections of 
 this part of the crus, I have recently divided it in three monkeys. 
 The operation is a somewhat severe one, but the crus can be com- 
 
 J Newolng. Centralhlatt, No. 7, 1883. 
 
104 CEREBRAL LOCALISATION. 
 
 paratively easily exposed to view after removal of the lower por- 
 tion of the temporal region. In all three animals the lesion was 
 satisfactorily established, but none of them recovered sufficiently 
 from the operation to enable me to make altogether reliable ob- 
 servations. But in none of them was there total loss of reaction 
 to sensory stimulation, or greater impairment than could be ac- 
 counted for by the cerebral lesion. So far as they go, therefore, 
 the experiments are opposed to the view that the outer third of 
 the foot of the crus is the path of the sensory fibres from below. 
 
 That the sensory tracts lie distinct from the motor in the pos- 
 terior division (or rather posterior third of the posterior segment) 
 of the internal capsule has been amply proved by the experiments 
 of Veyssiere^ and by the researches of Charcot, etc., on cerebral 
 hemiansesthesia occurring in man. The sensory tracts being ad- 
 mittedly distinct from the motor in the internal capsule, the ques- 
 tion then arises whether these, which up to this point have main- 
 tained their separate position, fuse in the cortex with the motor, 
 — as some believe — or are distributed to a special region. 
 
 In my earlier researches I had observed that tactile and com- 
 mon sensibility appeared to be entirely unaffected, notwithstand- 
 ing the most extensive lesions of every portion of the convex 
 aspect of the hemisphere, but I noted in several instances in 
 which the destructive lesions extended deeply into the temporal 
 lobe that sensibility became impaired or abolished on the oppo- 
 site side of the body. Careful post-mort6m examination showed 
 that in all these cases the hippocampal region (including cornu 
 ammonis and gyrus hippocampi) was more or less extensively in- 
 vaded. These facts pointed to the hippocampal region as being 
 the centre of common sensibility, and I therefore devised experi- 
 ments by which I might reach and destroy this region by itself. 
 On account of its deep-seated and concealed position this is, 
 however, practically impossible, and it therefore can only be 
 reached by methods which involve a greater or less extent of in- 
 jury to the occipital lobe, or the lower temporal region. The 
 effects of lesions of these regions can, however, be allowed for and 
 eliminated, and any further symptoms than can be ascribed to 
 them can be connected with those inflicted on the hippocampal 
 region. The method which I followed in my earlier experiments 
 was to break up and destroy the hippocampal region by means of 
 
 2 Becherches Cliniques et Experimental es sur V Hemianesthesie de Cause Ciribrale, 
 
 1874. 
 
THE TACTILE CENTRE. 105 
 
 a wire cautery thrust through the occipital lobe, and directed 
 downwards and forwards in the course of the descending cornu of 
 the lateral ventricle. In this manner I succeeded primarily or 
 secondarily in entirely destroying the hippocampal region and its 
 medullary connections without inflicting injury on the crus 
 cerebri or neighbouring structures. The diagram before you^ is 
 an accurate representation of the superficial appearance of the 
 lesion in one of these cases, and the track of the sinus made by 
 the cautery. The result of this operation was anaesthesia and 
 analgesia of the opposite side of the body, there being total or 
 almost total absence of response to any kind of sensory stimula- 
 tion. The limbs were not paralysed as to motion, but they ap- 
 peared to be used with dilBculty and awkwardness, and the feet 
 tended constantly to slip ofE the perch when the animal shut its 
 eyes and went to sleep. In none of my earlier experiments were 
 the animals allowed to live for any length of time, as I considered 
 it necessary to kill them as soon as the symptoms were clearly 
 defined in order to avoid complication by secondary extension of 
 the lesion, antiseptic surgery not being at this time in vogue. 
 The lesion in this case was shown* to be strictly limited to the 
 hippocampal and occipito-temporal region, and without any im- 
 plication whatever of the internal capsule or crus cerebri. These 
 experiments did not furnish any data towards the determination 
 of the permanency of the symptoms, but they were sufficient to 
 indicate a region, if not the whole region, related to the tactile, 
 common, and apparently the so-called muscular, sensibility of the 
 opposite side of the body. 
 
 I renewed my investigations on this subject at a later date' 
 in conjunction with Professor G. F. Yeo. The method of perform- 
 ing the experiments was partly the one I had previously followed, 
 namely, the destruction of the cautery, and partly that of cut- 
 ting in towards the hippocampal region from the convex aspect 
 of the temporo-sphenoidal lobe. Ten experiments in all were per- 
 formed, and in five of these in both hemispheres. The result of 
 this series of experiments confirmed in every particular those I 
 had already arrived at, and showed that tactile sensibility was in 
 every case impaired or abolished, in proportion to the destruction 
 of the hippocampal and inferior temporal region. Unfortunately, 
 none of the animals in which the destruction was complete, and 
 
 « See Fig. 105, function! of the Brain, p. 329, 
 
 * See Figs. 107 and 108. Funrtion$ of the Brain, p. 331. 
 
 » Phil. Trans., Part ii, 1884, Experiments 21 to 33, Figs. 103 to 181. 
 
106 CEREBRAL LOCALISATION. 
 
 the anaesthesia absolute, survived many days, so that the question 
 of duration still remained unsolved. But it was established that 
 a very extensive lesion might be made in one or both hippocampal 
 regions vrithout producing permanent anaesthesia. I need not 
 enter into the details of all these experiments. The two following 
 will suffice. 
 
 In one experiment * the left hemisphere was exposed and the 
 whole of the inferior temporal convolution and hippocampal 
 region were severed and scooped out, the lesion being such as to 
 leave only the internal margin of the gyrus hippocampi with the 
 taenia semicircularis and the fimbria of the fornix intact. Only a 
 portion of the hippocampal gyrus included between the calcarine 
 and collateral iissure (lingual lobule) remained. The result of this, 
 experiment was most marked. There was on the right side com- 
 plete insensibility to thermal stimulation of such intensity as ta 
 cause the most lively signs of sensation on the left side, and total 
 insensibility to every form of mere tactile stimulation, such as 
 toaching, gentle pricking, rubbing etc. The limbs were capable 
 of being freely moved volitionally, but they were planted with 
 great awkwardness and uncertainty as to position. While the 
 animal was resting quietly with its eyes shut, I drew the right 
 arm away from its side, of which fact it seemed unaware until it 
 tumbled over. It was keenly sensitive to every form of stimulus, 
 however slight, on the left side. Hearing was unimpaired in both 
 ears; vision, however, seemed somewhat indistinct, though not 
 abolished, towards the right. (This is an important fact in rela- 
 tion to the occurrence of hemiopia from lesion of the occipito- 
 temporal region discussed above.) There was anaesthesia of the 
 right nostril. The symptoms remained unchanged on the second 
 day after the operation, the animal being otherwise in apparent 
 good health, but on the third day it died suddenly of secondary 
 haemorrhage. A series of microscopic sections of the brain 
 showed that, with the exception of the injuries, above described, 
 in the inferior temporal and hippocampal region, the basal 
 ganglia, crura cerebri, and other structures were perfectly 
 intact. 
 
 In another animal a similar lesion was established, involving 
 almost complete detachment of the hippocampal and lower tem- 
 poral region from the rest of the hemisphere. In this animal 
 there was at first almost, if not total, analgesia, and absolute antes- 
 
 6 Experiment 27, Figs. 125, 132, op. eit. 
 
THE TACTILE CEXTRE. 107 
 
 thesia to all gentle forms of tactile stimulation over the whole of 
 the right side of the body. Hearing was unimpaired, but vision 
 was somewhat defective towards this side, the animal appearing 
 to have some degree of uncertainty as to the position of things 
 offered it on the right front. The condition remained practically 
 unchanged on the third day, when the animal had a slight right- 
 sided fit, indicative of some irritation, found after death to be 
 slight recurrent hosmorrhage. After this the analgesia became 
 absolute, and no sign of perception could be obtained to any form 
 of tactile stimulation. There was also total insensibility to tickling 
 of the right nostril. A similar stimulation of the lef d caused 
 active grimaces and signs of uneasiness. The animal could move 
 its limbs freely and lay hold of objects firmly with the right hand, 
 but it continually fell over on the right side, owing to the awkward 
 and uncertain manner in which it planted its limbs. Death oc- 
 curred on the fourth day. The lesion was found accurately 
 limited to the lower temporal and hippocampal region of the left 
 hemisphere without the slightest implication of the cms or basal 
 ganglia. These experiments proved that the various forms of sen- 
 sation embraced under the term common or tactile sensibility, 
 including cutaneous, muco-cutaneous, and muscular, are capable of 
 being profoundly impaired, or altogether abolished, for the time 
 at least, by destructive lesions of the hippocampal region, and that 
 the degree and duration of the anaesthesia varied with the com- 
 pleteness of destruction of the region in question. 
 
 The subject was next taken up by Horsley and Schafer,'' who, 
 80 far as 1 am aware, are the only physiologists who have repeated 
 my experiments in this direction. 
 
 Horsley and Schafer were at first unable to corroborate my 
 observations, but I was able to demonstrate to them that this 
 depended on the incompleteness of their excisions of the hippo- 
 campal region, and I assisted them in some of the experiments 
 which they further prosecuted with excellent effect. In one ani- 
 mal in which the hippocampal region was removed there was on 
 the following day partial analgesia, and complete insensibility 
 to mere contact on the opposite side. Death, however, occurred 
 on the second day, so that no conclusions as to duration were 
 possible in this case. 
 
 In a second experiment, the hippocampal region was again re- 
 moved, and the incisions made so as to detach also the margin of 
 
 T Functions of the Cerebml Cortex, D. 20, Phil. Trans., 1888. 
 
108 CEREBRAL LOCALISATION. 
 
 the calcarine fissure and hippocampus minor. This animal was 
 profoundly anaesthetic on the opposite side, but there did not ap- 
 pear to be absolute analgesia. All mere tactile stimuli, however, 
 like touch, scratching, rubbing, gentle pricking, were absolutely 
 unperceived, while similar stimulation on the other side at once 
 attracted attention. Tactile ansesthesia continued for several 
 weeks without appreciable alteration, but a gradual improvement 
 occurred, so that examination at the end of six weeks revealed 
 only some degree of impairment, as evidenced by less easily ex- 
 cited attention by gentle pricking, rubbiisg, etc., of the side oppo- 
 site the lesion, as compared with the other. Severe pricking, 
 pinching, or pungent heat, however, appeared to be well perceived. 
 The gradual diminution of the angesthesia, at first induced by ex- 
 tensive, if not complete, removal of the hippocampal reeion, led 
 me to suggest similar experiments on the gyrus fornicatus, on the 
 ground that the tactile centre might extend into the rest of the 
 falciform lobe, of which the hippocampal region was only a part. 
 This originated their experiments on the gyrus fornicatus, which 
 proved the accuracy of Broca's anatomical views as to the unity 
 of the falciform lobe, and demonstrated that lesions of the gyrus 
 fornieatus caused similar symptoms to those produced by destruc- 
 tion of the hippocampal region, of, perhaps, even greater intensity 
 and longer duration. In one of the experiments at which I assisted 
 the animal in which, some weeks previously, the hippocampus 
 had been removed, and which had completely recovered from any 
 anaesthesia which might have existed immediately after the opera- 
 tion, the same hemisphere was again exposed and the region of the 
 longitudinal fissure and the gyrus fornicatus excised along the 
 whole length of the corpus callosum. The effect of this operation 
 was to caus3 absolute analgesia on the opposite side, continuing 
 several days after the operation, as well as complete insensibility 
 to all milder forms of tactile stimulation. The analgesia dimin- 
 ished somewhat as time went on, but six weeks after the opera- 
 tion it was still manifest in some degree. The tactile aEsesthesia 
 was, however, apparently in no wise improved, all gentle forms 
 of tactile stimulation being absolutely unperceived. The animal 
 was in perfect health, and exhibited no indications of motor 
 disorder; though, directly after the operation, there was slight 
 weakness of the opposite leg, owing to the injury to the postero- 
 parietal lobule and neighbourhood during the operations necessary 
 to expose the gyrus fornicatus. 
 Many other experiments were made by Horsley and Schafer, 
 
THE TACTILE CENTRE. 109 
 
 and recorded in their memoir in the Phil. Trans., sup. cit., and 
 they sought also to determine whether there were any parts of 
 the limbic or falciform lobe especially related to particular 
 regions of the opposite side. They conclude from their experi- 
 ments: " We have found that any extensive lesion of the gyrus 
 fornicatus is followed by hemiansesthesia more or less marked and 
 persistent. In some cases the anaesthetic condition has involved 
 almost the whole of the opposite side of the body, in others it 
 has been localised to either the upper or the lower limb and to 
 particular parts of the trunk, but we have not yet succeeded in 
 establishing a relationship between special regions of the body 
 and the parts of the convolution which have been destroyed. 
 Moreover, the anaesthesia was frequently very pronounced and 
 general during the first three or four days after the operation, and, 
 indeed, in several instances took the form of complete insensi- 
 bility to both tactile and painful impressions, so that even a sharp 
 prick or the contact of a hot iron would produce no indication of 
 sensation, but after that time this general condition would become 
 gradually in great part recovered from, or more localised in 
 definite regions. In all cases, however, in which the diminution 
 of sensibility was well marked during the first few days, it has 
 persisted, although with lessened intensity, for many weeks in 
 those instances in which the animals have been preserved for so 
 long. In other cases, in which apparently the lesion was slight, 
 the diminution of sensibility, although at first well marked, sub- 
 sequently disappeared entirely. In some instances the hemi- 
 ansesthesia took the form of inability (or diminution of ability) to 
 localise the seat of irritation, whilst in one case, in which diminu- 
 tion of sensibility was exhibited in a very striking manner, the 
 irritation, when rendered suflBciently intense for the monkey to 
 become conscious of it, was responded to by the animal scratch- 
 ing a different part of its body from that to which the stimulus was 
 applied." 
 
 Fig. 40 A * represents the condition of the right hemisphere of 
 an animal in which the lesion indicated produced at first com- 
 plete analgesia, followed by partial anaesthesia, lasting for ten 
 weeks, at which time the animal died from an operation on the 
 left. Fig. 42 ' represents the brain of an animal in which the 
 anterior two-thirds of the left gyrus fornicatus were removed, 
 For a few days there was complete analgesia. A week after the 
 
 * Op. cit. 
 » Op. cit. 
 
110 CEJREBRAL LOCALISATION. 
 
 operation the condition was much improved, and at this time 
 there was reaction over the whole of the right side to painful 
 impressions, but often want of localisation of the seat of thesff 
 impressions, a totally different part being scratched from tbat 
 which was stimulated. Recovery gradually proceeded, so that 
 after a time the difference of sensibility of the two sides was 
 hardly perceptible, except about the arm and shoulder and in the 
 foot. Eleven weeks after the first operation the right gjrus 
 fornicatus was exposed and injured by scratching its surface 
 with a needle. This, however, produced no perceptible result, 
 and after a fortnight the animal was killed. 
 
 Fig. 43^° represents the brain of a monkey in which the 
 posterior part of the left hippocampal gyrus was destroyed. 
 The result was great diminution of reaction to tactile and painful 
 stimuli over the posterior part of the right side of the body, with 
 slight diminution over the whole side. 
 
 It is not unlikely that, besides representing sensibility of the 
 opposite side of the body generally, certain parts of the falciform 
 loba may represent more particularly the sensibility of special 
 regions. But, though I occasionally noted in my experiments on 
 the hippocampal region — like Horsley and Schafer in their experi- 
 ments in the gyrus fornicatus — that it seemed as if one region 
 had been more affected than another, yet this was at times not 
 apparent, and in general the anaesthesia has affected the whole of 
 the opposite side, face, arm, leg, and trunk. Evidence is, there- 
 fore, so far, not conclusive of the existence of any altogether 
 specialised centres in this general area. It is probable, however, 
 that a certain degree of localisation may be established through 
 the associating fibres, which undoubtedly connect this region with 
 the motor centres of the cortex. 
 
 It has not yet been found possible to produce total persistent 
 loss of all forms of tactile and common sensation on the opposite 
 side after destructive lesions of the falcitorm lobe, but this may 
 be due to the fact that this lobe has never been absolutely de- 
 stroyed throughout its whole extent. It is probable, however, 
 that common sensibility may, to some extent at least, be bilate- 
 rally represented, so that a certain amount of compensation may 
 be effected by the falciform lobe of the other hemisphere. The 
 paths of connection between the falciform lobe and the sensory 
 division of the internal capsule have not yet been traced by any 
 
 30 Op. cit. 
 
THE TACTILE CEXTIIE. Ill 
 
 anatomist, but in view of the proofs which have been above given 
 of the relation between the falciform lobe and tactile and common 
 sensibility, it is obvious that the hypothesis of Flechsig as to the 
 distribution of the sensory tracts in the parietal lobe, requires 
 amendment. No scheme of the cortical distribution of the sen- 
 sory tracts can be admitted as correct which does not connect 
 them with the cortex of the callosal and hippocampal convolu- 
 tions. Though thj gyrus fornicatus appears to be a purely sen- 
 sory region, and, therefore, one destruction of which should not 
 give rise to centrifugal degeneration in the spinal cord, France'^ 
 has found, apparently in relation with destruction of the gyrus 
 fornicatus, secondary degeneration of the pyramidal tracts of the 
 crus cerebri and spinal cord. It is, however, to be noted that in 
 most, if not all, of the cases in which the gyrus fornicatus was 
 destroyed, either the marginal gyrus or neighbouring motor 
 centres and tracts were also more or less implicated, and the sus- 
 picion arises that the descending degeneration is in reality due to 
 this cause. France, however, believes that the degeneration occu- 
 pies a different region of the pyramidal tract from that resulting 
 from lesion of the marginal gyrus alone, being in the latter case 
 towards the posterior and outer part of the crossed pyramidal 
 tract, in the former occupying the whole sectional area of the 
 same. 
 
 These considerations are not, however, sufficient to remove all 
 doubts ; and these are emphasised by the fact that lesions of the 
 hippocampal division of the falciform lobe, suificiently far re- 
 moved from the motor centres and tracts as to ensure their free- 
 dom from injury, lead to no degeneration of the pyramidal 
 tracts. The question is one which requires further investigation. 
 
 Olfactory and Gustatory Centres. 
 
 The position of the olfactory centre, or at least its principal 
 portion, may with great probability be inferred from the cortical 
 connections of the olfactory tract, altogether apart from physio- 
 logical experiment. The chief and, in man, the only constant 
 connection of the olfactory tract with the hemisphere is the so- 
 called external root, which passes outward across the anterior per- 
 forated space to the cortex of the hippocampal lobule, or anterior 
 
 •' Detcendinf; Degenerations which follow Lesions of tlie Gyrus Marginalia and 
 Gyrus FornicatUB in Monkeys, /'hil. Trans , B. 4**, 1889. 
 
112 CEREBRAL LOCALISATION. 
 
 and lower extremity of the hippocampal gyrus (see Fig. 26, Trol.). 
 Owing to the original formation of the olfactory bulb and tract as 
 a diverticulum from the anterior cerebral vesicle, the cavity of 
 which has become almost entirely obliterated, the remnants of 
 its original connection with the mesial, external, upper, and lower 
 aspects of the cerebral hemisphere are still spoken of as roots of 
 the olfactory tract. Though in man and the monkey all the said 
 
 1 F 
 
 A f - 
 
 *'f-^ --Bol 
 
 .Trol 
 
 Vspl-- 
 
 Sim \ 
 
 Co L _ 
 
 Fig. 20 (after Obersteiner).— Pp, pes pedunculi ; Cm, corpus mammillare ; 
 71)c, tuber cinereum ; Til, tractus opticus ; ch, chiasma ; JJ, nervus 
 opticus ; T, temporal lobe ; U, uncus ; Am, nucleus amygdalse ; Spa, sub- 
 stantia perforata anterior ; Lt, lamina terminalis ; Coa, anterior commis- 
 Bure ; PsjoZ, pedunculus septi pellucidi ; Sim, Sulcus medius subst. perf. 
 ant.; Hcc, rostrum corporis callosi ; Gcc, genu corporis callosi ; Nl, nervus 
 Lancisii ; M, longitudinal fissure ; F, frontal lobe ; Bol, bulbus olfactorius ; 
 Irol, tractus olfactorius. 
 
 roots, except the external one, are practically obliterated, yet in 
 other animals, in whom the sense of smell is largely developed, 
 four roots are usually described, namely, an external root passing 
 to the hippocampal lobule ; a superior and middle root, connect- 
 
OLFACTORY AND GUSTATORY CENTRES. 113 
 
 ing the tract respectively with the grey matter of the base of the 
 frontal lobe and the trigonum olfactorium, or grey matter of the 
 anterior perforated space ; and an inner root, which appears to 
 fuse with the anterior extremity of the callosal gyrus. The con- 
 nections of the olfactory tract, by means of its inner and outer 
 root, with the anterior and posterior extremities of the falciform 
 lobe, have been compared by Broca to a tennis racquet, of which 
 the circumference is formed by the falciform lobe and the handle 
 by the olfactory tract and bulb (see Fig. 27). 
 
 According to the development of the sense of smell in different 
 animals, the structures above described, or parts of them, undergo 
 great variations. Broca divides all animals into two classes— first, 
 
 Hr. 27.-Inner surface of the right hemiBphere of the Otter (Broca) O 
 olfactory lobe ; H, hippocampal lobe ; C, commencement of the lobe of 
 the corpus callosum ; C, C, C", lobe of the corpus callosum ; F. frontal 
 lobe; P.P. parietal lobe; 8. limbic fissure; 9, pli de passage r^tro- 
 limblque ; 10, subfrontal sulcus ; 11, pli de passage fronto-limbique ■ 13 
 inferior fronto-limbic annectent gj'rue ; 13, subparietal fissure. 
 
 the " osmatics," a class which includes the great majority of mam- 
 mals, and, secondly, " anosmatics," in which the sense of smell is 
 relatively feebly developed, including (primates, amphibious car- 
 nivora). rudimentary (balaenidae), or altogether wanting (delphi- 
 nidae). In the osmatics, as you may see in the specimens before 
 you, the olfactory bulb and tract are large, and the hippocampal 
 lobule in particular attains extraordinary proportions, and. in 
 some animals, constitutes the greater portion of the cerebral hemi- 
 sphere. In the anosmatics the hippocampal lobule is relatively 
 small in those-euch as in man and monkey-in which the sense 
 of smell, though good, is subordinate to other sensory faculties; 
 while in the balaenidse it is greatly reduced, and in the delphinidae' 
 is almost entirely wanting. The posterior boundary of the hippo- 
 
114 
 
 CEREBRAL LOCALISATION. 
 
 campal lobule is in the osmatics clearly indicated by an annectent 
 gyrus, which interrupts the continuity of the limbic fissure and 
 unites the lobule with the parieto-temporal part of the hemi- 
 sphere. It is termed hj 'QtocSit'ke pit- de passage retro- limbique 
 (see Fig. 27, 9), 
 
 In man and the monkey the homologue of this gyrus is usually 
 considered to be the pedunculus cunei, or cuneo-limbic annectent 
 gyrus (see Fig. 28, PCu), connecting the cuneus with the hippo- 
 campal gyrus. Beauregard,^^ however, places it in the brain of the 
 
 Fig. 28 (after Obersteiner). — Cell, corpus callosum ; Geo, genu of corpus cal- 
 losum ; Coa, anterior commissure ; Fcl, columns of fornix ; Far, crus of 
 fornix; CAm, cornu ammonis ; 3y, tuberculum fascia dentatse ; BW, 
 Balkenwindung (splenial convolution) ; /, isthmus gyri fornicati ; U, 
 uncus ; PCu, pedunculus cunei ; Sbp, sulcus subparietalis ; clc, fissura 
 calcarina ; Rcc, rostrum of corpus callosum ; Spec, splenium of corpus 
 callosum ; Splc, septum lucidum ; Fcp, body of fornix ; Fi, fimbria ; 
 Fd, fascia dentata ; Stlm, stria longitudinalis medialis ; g, gyrus cin- 
 guli ; H, gyrus hippocampi ; Cu, cuneus ; cell, sulcus corporis cal- 
 losi ; poc, fissura parieto-occipitalis ; oti, sulcus ocoipito-temporalis in- 
 ferior. 
 
 whale at the extremity of the temporal lobe, immediately poste- 
 rior to the uncus, and Zuckerkandl" assigns it a similar position 
 in the brain of the dolphin. 
 
 I am inclined to think, on physiological grounds, that in man 
 also and the monkey the posterior boundary of the hippocampal 
 lobule is to be found in the annectent gyrus which connects 
 the uncus with the anterior extremity of the temporo- 
 sphenoidal lobe (+ Fig. 28). This is well seen in the brain of the 
 chimpanzee which I show you. This would make the hippo- 
 
 12 Sur I'Bncephale des Baljenides. 
 
 13 Veher das Riechcentrum, 1887. 
 
OLFA CTOR Y AND G USTA TOR Y CENTRES. 115 
 
 campal or pyriform lobule correspond with the gyrus uncinatus, 
 and not with the gyrus hippocampi as a whole, which, as we 
 have seen, is a portion of the tactile centre. 
 
 The relatively large size of the internal root in some animals, 
 and its apparent connection with the anterior extremity of the 
 gyrus fomicatus, led Brosa to believe that there was a connection 
 between the development of this region and the sense of smell ; 
 but the fact, which he himself admits, that the anterior portion 
 of the callosal gyrus is particularly well developed in the brain of 
 the Cetaceans, in which the sense of smell is merely rudimentary, 
 is decidedly opposed to this hypothesis. Zuckerkandl, however, 
 claims that the anterior extremity of the callosal gyrus in the 
 dolphin is in some degree atrophied as compared with that of 
 osmatic animals. The connection of the inner root with the cal- 
 losal gyrus appears to me to be only superficial, and the proba- 
 bility is that this root really joins with the anterior extremity of 
 what Zuckerkandl terms the marginal gyrus (Randwindung), 
 which forms the callosal margin of the falciform lobe, and is con- 
 tinuous posteriorly with the fascia dentata (see Fig. 28, Fd). The 
 dorsal or supracallosal portion of this gyrus is in anosmatic ani- 
 mals almost entirely obliterated, the atrophied remnants consti- 
 tuting the nerves of Lancisi (Stlm, Fig. 2R), which are visible in 
 man on the superior surface of the corpus callo&um. He also de- 
 scribes, as peculiar to osmatic animals, a process of the falciform 
 lobe which projects below the splenium of the corpus callosum, 
 and which he terms the " Balkenuiindung " (f^plenial gyrus.) 
 Schwalbe, however, regards this merely as a portion of the gyrus 
 dentatus. It is often seen in man {B W, Fig. 28). Zuckerkandl 
 endeavours also to establish a relation between the development of 
 the sense of smell and the s'ze of the hippocampus or the cornu 
 ammonis. He contends that in the dolphin the cornu ammonis is 
 reduced to an insignificant remnant, and maintain!", in opposition 
 to other anatomists, that what has been regarded as the hippo- 
 campus, and which, topographically, and in its other relations, 
 corresponds with this structure, is no hippocampus at all, but 
 merely a prominence in the descending cornu of the lateral v^n- 
 tricle, corresponding to the eminentia collateralis of Meckel. Not 
 having facilities for a proper investigation of this point, I re- 
 quested the opinion of Sir W. Turner. He wrote me as follows : 
 
 " I will describe a dissection I have made of the descending 
 horn of the lateral ventricle in the brain of a porpoise. This 
 horn was continuous with the posterior end of the body of the 
 i2 
 
116 CEREBRAL LOCALISATION. 
 
 lateral ventricle, and passed forwards and downwards into that 
 lobe of the hemisphere which, from its position, may be called tem- 
 poro-sphenoidal. It contained a well-defined eminence along its floor 
 which was undoubtedly the hippocampus major. This eminence, 
 23 millimetres long, swelled out as a club-shaped end anteriorly, 
 which was from 4 millim etres to 5 millimetres in transverse diameter. 
 
 Along the inner border of the hippocampus, the posterior pillar 
 of the fornix was attached as the taenia hippocampi. The choroid 
 plexus projected towards the descending horn immediately in- 
 ternal to the taenia hippocampi. The gyrus hippocampi lay in re- 
 lation to the inner concave border of the taenia hippocampi ; it was 
 between 5 and 6 millimetres in breadth, and terminated anteriorly 
 in a lobus hippocampi, the greatest breadth of which was 8 milli- 
 metres." 
 
 Sir W. Turner's dissection is, therefore, opposed to Zuckerkandl's 
 view as to the absence of the hippocampus in the porpoise. 
 Though the hippocampus is well developed in osmatic animals, it 
 cannot be said to be atrophied in man and in the monkey, or to 
 undergo variations in size with the other parts admittedly in re- 
 lation with the olfactory tracts. It is questionable whether the 
 hippocampus in man is relatively smaller than that of the lower 
 animals; but, as to its absolute size. Sir W. Turner says: "Pos- 
 sibly the elephant, and it may be the largest whales, possess a hip- 
 pocampus absolutely as large as that of the human brain, but I 
 am inclined to think that the human hippocampus is absolutely 
 larger than in mammals generally." 
 
 The hippocampal lobule, however, is relatively much smaller in 
 man than in the osmatic animals, and perhaps is absolutely 
 smaller than in many of them. What are the conditions which 
 lead to variations in size of the hippocampus'^ cannot be said to 
 be clear, but there appears to be an inverse ratio between the 
 size of the gyrus fornicatus and gyrus hippocampi. This is so in 
 the Cetaceans and Delphinidse, in which the gyrus fornicatus is 
 unusually large and more richly convoluted than in the higher 
 animals. So, also, in the osmatic animals generally, the gyrus 
 fornicatus is relatively larger than the gyrus hippocampi (apart 
 from the hippocampal lobule). In the kangaroo the gyrus hippo- 
 campi and hippocampus merge with the gyrus fornicatus, and 
 the hippocampus appears as the inroUed edge of this gyrus (see 
 
 ■** In my experiments on the hippocampal region, it was not possible to distin- 
 guish between lesions of the hippocampus apart from those o£the gyrus hippo- 
 eampi. 
 
OLFACTORY AND GUSTATORY CENTRES. 117 
 
 Fig. 29). This indicates a functional community between the 
 hippocampus and the rest of the falciform lobe, which we have 
 seen is related to the general sensibility of the body. 
 
 By means of the anterior commissure (olfactory division) the 
 olfactory bulbs and tracts are connected with each other. This 
 connection is best seen in those animals which have large olfactory 
 bulbs (see Fig. 30, po), but a similar connection can also be traced 
 in the brain of the monkey and the man (see Fig. 31, ac). The 
 anterior corimissure also connects the hippocampal lobules 
 together (Fig. 30, pt). This division of the anterior commissure 
 (temporal division) does not altogether vary in size with that of 
 
 Fig. 29. — Frontal section of brain of kangaroo (Macropus major) (after 
 Flower). B, body of corpus callosum (connecting the hippocampi, ; P, 
 anterior commissure ; G, septal area ; R, corpus striatum. 
 
 the hippocampal lobule. It varies probably inversely with the 
 corpus callosum, as Flower has pointed out.^" Thus, in the dog, 
 whose hippocampal lobule is seven times as large as that of the 
 rabbit, the temporal division of the anterior commissure is a third 
 smaller. The relative size of the olfactory and temporal divisions 
 is opposed to the theory of Meynert that the anterior commissure 
 forms a chiasma similar to the optic, where the olfactory tracts 
 decussate with each other. And, further, it has been shown by 
 the investigations of Ganger and von Gudden^' that when one 
 olfactory bulb is removed the whole of the olfactory division of 
 the anterior commissure becomes atrophied on both sides, while 
 the temporal division remains unaltered. We may, therefore, 
 
 IS Phil, Trans., 1866, On the Cerebral Commisaure* of the Marsuplalia and 
 
 Monotremata. 
 
 w Archivf. Psychiatrie, Band 9. 
 
118 
 
 CEREBRAL LOCALISATION. 
 
 assume that if the olfactory tract is related to the opposite hemi- 
 sphere the path is not through the anterior commissure. Ana- 
 tomically the olfactory tract appears to be in relation only with 
 the hemisphere on the same side, but there are clinical facts which 
 are diificuld to explain otherwise than on the supposition that 
 some at least of the fibres connecting the olfactory tract with the 
 hemisphere pass into the internal capsule of the opposite side. By 
 
 ■r.cT 
 
 rig. so. — Horizontal section of thie brain of the mole on a level with the 
 anterior commissure (X 4) (after Gauser;. ac, anterior commissure, 
 dividing into po, pars olfactoria, and pt, pars temporalis ; ci, internal 
 capsule ; /, fimbria ; fa, anterior pillar of fornix ; fd, fascia dentata;/illf, 
 Meynert's fasciculus ; gl. ol. glomeruli olfactorii ; hi, posterior longi- 
 tudinal fasciculus ; k, granular layer of olfactory bulb ; mp, middle 
 peduncle of cerebellum ; na, nucleus amygdalae ; nc, nucleus caudatus ; 
 nl, nucleus lentioularis ; P, pyramidal tract ; rn, red nucleus ; r. ol, 
 roots of the olfactory nerve ; rs, regio subthalamica ; s, septum lucidum; 
 sa, substantia alba ; sp, superior cerebellar peduncles ; st, stria term.in- 
 alis ; t. ol, tractus olfactorius. 
 
 means of the fornix the olfactory tract is brought indirectly in 
 relation with the anterior tubercle of the optic thalamus, but 
 there is no correspondence in size between the olfactory tract and 
 the anterior pillar of the fornix. For, in the rabbit, the anterior 
 pillars of the fornix are not more than one-third of the sectional 
 area of the olfactory tract; and in man, while the olfactory tract 
 is a mere thread, the anterior pillar of the fornix is 3 millimetres 
 in diameter.' 
 
OLFACTORY AND GUSTATORY CENTRES. 119 
 
 A certain portion of the fibres constituting the fornix are accord- 
 ing to Owen ^^ commissural fibres connecting the hippocampi with 
 each other. This is seen very clearly in the brain of the kangaroo, 
 in which, as above described, the hippocampus is an induplication of 
 the gyrus fornicatus, the commissural fibres between the two con- 
 stituting what is commonly called the corpus callosum in these 
 animals. {B, Fig. 29). In man also the posterior part of the 
 fornix consists of transverse fibres constituting the psalterium or 
 lyra Davidis. The fact that the hippocampi are connected to- 
 gether by a distinct system of commissural fibres pleads also in 
 favour of a functional differentiation of these structures from the 
 
 Pig. 31. — Frontal section of brain of monkey at right angles to the crura 
 cerebri in the region of the anterior commissure (nat. size), ac, anterior 
 eommissure ; cc, corpus callosum; cl, claustrum ; ec, external capsule; 
 f, pillars of fornix ; ic, internal capsule ; iR, island of Eeil ; nc, nucleus 
 caudatus ; nl, nucleus lenticularis. 
 
 hippocampal lobules, which are connected together by the pos- 
 terior or temporal division of the anterior commissure. 
 
 The effects of electrical irritation of the hippocampal lobule in 
 the monkey and other animals are such as may be most reason- 
 ably interpreted as being indicative of subjective olfactory sensa- 
 tion, namely, a peculiar torsion of the lip and nostril on the same 
 side. Occasionally, however, the reaction is bilateral, and 
 especially so in the rabbit. The reaction is that actually induced 
 in these animals by the application of an irritant, such as a pungent 
 odour, directly to the nostril. I have not observed any similar re- 
 action on stimulation of the exposed hippocampus. But while 
 we can be more or less certain, from the outward reactions, that 
 subjective olfaction is aroused by stimulation, it is an exceed- 
 ingly difficult problem to determine whether smell is lost by 
 
 1' Comparative Anatomy of tke Vertebratet. 
 
120 CEREBRAL LOCALISATION. 
 
 destruction of the same region. In some animals this is more 
 easy than in others, and dogs, whose nose forms the chief organ of 
 intellectual perception, would seem better adapted for experiments 
 of this kind than monkeys. I have found it very difficult to 
 determine the appreciation of odours by monkeys from any out- 
 word signs of like or dislike. To most, what we should consider 
 yery disagreeable odours mixed with their food they seem per- 
 fectly indifferent. I have tested them with sulphuretted hydrogen, 
 bisulphide of carbon, valerian, assafoetida, iodoform, croton- 
 chloral, and various other substances, but they have rarely re- 
 fused their food on that account. The only odour which they 
 seem uniformly to dislike — and that, perhaps, more from the 
 associated taste than the smell itself — is aloes. I have rarely, if 
 ever, found any monkey willing to eat fruits or other articles of 
 food sprinkled with this drug. I have, therefore, almost ex- 
 clusively used aloes to test both the smell and taste of these 
 animals. 
 
 In my earlier experiments I found that in several instances in 
 which I had primarily, or by secondary inflammation, cut off or 
 disorganised the lower temporal regions on one or both sides, 
 there were, for the time at least, indications of impairment or 
 abolition of the reactions usually excited by pungent odours or 
 disagreeable tastes. My experiments in this direction were, I 
 admit, not very exact. 
 
 Schafer and Sanger-Brown ^* have been unable to detect any 
 indications of impairment or loss of the senses of smell and taste 
 from destructive lesions of the lower extremity of the temporal 
 lobes on both sides. They say, page 324, " Animals with the an- 
 tero-inferior portion of the lobe, including the subiculum, com- 
 pletely cut away, smell their food, immediately detect a malo- 
 dorous substance, such as aloes or assafoetida, with which it (that 
 is, the raisin) may have been smeared, and cast it aside without 
 tasting. A raisin into which quinine has been inserted is smelt, 
 eagerly bitten, and immediately rejected with expressions of dis- 
 gust." On looking at the figures which accompany their paper, 
 however, I can see only one (No. 2, Plate 4) in which the anterior 
 extremity appears to have been completely removed. In all the 
 other portions of the hippocampal lobule are still to be seen on 
 both sides.^^ In the notes referring to the experiment No. 2, 1 do 
 not see any reference to tests of the animal's sense of smell, but it 
 
 '8 Ph.il. Trans. B. 30. 1888. 
 ^ FigB. lb, 3a, 6c., op. cit. 
 
OLFACTORY AND GUSTATORY CENTRES. 121 
 
 is stated that on the second day it gave clear indications of re- 
 taining its sense of taste unimpaired. But as to the others, suffi- 
 cient I think is left of the hippocampal region on both sides to 
 permit of the sense of smell being retained, even if not so acutely 
 as before. I have, therefore, thought it desirable to make some 
 new experiments in reference to this point. 
 
 I have in three mnnkeys removed the anterior portion of the 
 temporal lobes by successive operations, but only one of the 
 animals survived the double operation sufficiently long to allow 
 of any satisfactory observations being made. In this case the 
 anterior part of the left temporal lobe was practically entirely 
 
 Fig. .32. 
 
 removed, with the exception of a small fragment of the hippo- 
 campal lobule entirely detached from the rest (Fig, 32). In 
 effecting the lesion the left optic tract was disorganised, and 
 slight damage was also inflicted on the crus cerebri, so that 
 the animal became completely hemiopic towards the right, which 
 condition continued till death. There was also slight hemiplegia 
 with hemiansesthesia on the right side, which, however, com- 
 pletely passed off in the course of a fortnight. The second lesion 
 was established a month after the first. The removal, however, 
 was not 80 complete, and it will be seen that the surface of the 
 hippocampal lobule immediately adjoining the crus is still intact, 
 though it is almost entirely undermined. The olfactory tracts 
 
122 CEREBRAL LOCALISATION: 
 
 were absolutely normal, as well as all the other cranial nerves and 
 the rest of the brain. The animal was allowed to survive for 
 three months, at the end of which time it was killed with chlo- 
 roform. The cut surfaces of the temporal lobes were found 
 firmly adherent to the middle fossse of the skull, and the meshes 
 of the adhesions were infiltrated with fluid ; otherwise all had a 
 normal appearance. The symptoms observable in this animal are 
 of considerable interest. 
 
 Within a week after the establishment of the first lesion 
 numerous observations were made in regard to the sense of smell 
 and taste, which resulted in demonstrating that these were at 
 least good. It was impossible to ascertain definitely whether 
 there was any unilateral impairment, but they were as a whole 
 keen enough to enable the animal to avoid and discard substances 
 formerly distasteful to it. Thus, it refused to eat pieces of apple 
 smeared with aloes, smelling them and at once throwing them 
 down. A piece of apple sprinkled with sulphate of magnesia it 
 examined carefully by smell, and, after tasting a mouthful, threw 
 it away. It, however, eagerly devoured a piece which had not 
 been in any way drugged. Similarly it refused to eat apple 
 sprinkled with sulphate of zinc, and would not touch a piece 
 smeared with colocynth. Such and similar observations were 
 frequently made and confirmed, and there was no doubt 
 whatever that it enjoyed excellent olfactory and gustatory 
 sensibility. 
 
 On the day after the second operation, and for two days subse- 
 quently, the animal was in good physical health and strength, 
 though somewhat dull, appeared to have lost all inclination to eat 
 spontaneously, but it devoured greedily whatever was offered it, 
 and showed no signs of disgust when pieces of food were given it 
 copiously sprinkled with aloes ; nor did it make any grimace when 
 a pinch of aloes was placed in its mouth, but continued eating un- 
 concernedly. On the fifth day after the operation the condition 
 was still the same. On this day, while picking up its food from 
 the floor of the cage, it not infrequently filled its mouth with saw- 
 dust, of the nature of which it did not seem to be aware. On the 
 sixth, seventh, and eighth days similar tests were repeated with 
 precisely the same results. There was no expression of disgust 
 when the food offered it was copiously sprinkled with aloes, colo- 
 cynth, or quinine. On the eleventh day a pinch of colocynth 
 placed in its mouth caused no sign of distaste ; the same placed in 
 the mouth of its companion monkey caused violent nausea. On 
 
OLFACTORY AND GUSTATORY CENTRES. 123 
 
 the eighteenth day the animal, which was very tame, would lick 
 one's fingers which had been dipped in powdered aloes, and it 
 drank up a dish of milk mixed with the same substance which 
 its companions would not touch. A third animal which was 
 offered the dish took a sip, and then, after a doubtful look, 
 smacked its lips suspiciously, and would not take any more. 
 In order to associate the disagreeable taste of aloes with 
 a very definite and strong smell, I had some powdered aloes 
 mixed with musk, so that th^re should be no doubt what- 
 ever as to the odoriferous character of the objectionable sub- 
 stance. This, however, made no difference. Pieces of food 
 smeared with musk- aloes were eaten quite as readily as others ; it 
 seemed to have no suspicion of tricks played upon it, for it would 
 come and lick musk- aloes off the blade of a knife as if it had been 
 something nice. Its companion, however, looked askance and 
 kept at a safe distance after having once experienced the result. 
 At the end of a month the animal, which was in perfect health 
 and full of fun and romps, continued unconcernedly to eat raisins 
 smeared with musk- aloes, which its companion threw down at 
 once as soon as it smelt them. Six weeks after the operation, a 
 pinch of aloes was placed in its mouth. It seemed quite indif- 
 ferent, and exhibited no signs of disgust. The same placed in the 
 mouth of its companion caused retching, salivation, and comic 
 attempts to rub the offending substance from its lips and tongue. 
 Another animal which had not been tested in this way before 
 vomited profusely several times, but our experimental animal 
 within a few minutes afterwards did not refuse to lick some of 
 the same powder off the blade of a knife. Two months after the 
 operation it still did not refuse to lick a finger smeared with 
 musk-aloes, and ate several pieces of apple smeared with the 
 same, which none of the other animals, three in number, would 
 have anything to do with. It also licked up a quantity of sugar, 
 which was copiously mixed with aloes. The quantity of the 
 drug it ate not unfrequently produced the usual medicinal effect. 
 For nearly three months after the operation, the monkey con- 
 tinued almost entirely indifferent to substances, the smell and 
 taste of which were such as to cause the other monkeys to avoid 
 them, and made no grimaces when they were placed in its mouth. 
 But it began at this time to show indications that it did not 
 relish them, as it not unfrequently dropped pieces of apple and 
 other morsels of food which were sprinkled as before. It occa- 
 sionally sniffed at what was offered it before proceeding to eat> 
 
124 CEREBSAL LOCALISATION. 
 
 and would throw it down without tasting. But whether this was 
 due to any sense of smell or merely an habitual action was not 
 quite clear, for it would throw down shells of nuts, crusts 
 of bread, and husks, which are practically without smell, after 
 examining them. It also exhibited likes and dislikes in 
 the matter of food, as, for instance, preferring apples to 
 boiled potatoes, and it seemed to like sugar and boiled rice ; but 
 whether these likes and dislikes depended upon purely sapid 
 characters I could not positively determine. The general results, 
 however, of my observations incline me to believe that the ani- 
 mal's faculties of smell and taste, though obviously impaired, were 
 not entirely abolished. It, however, for a considerable time after 
 bilateral destruction of the lower extremity of the temporal lobe, 
 did not refuse to eat substances the smell and taste of which are 
 in the highest degree objectionable to normal animals, and I do 
 not think it is possible to explain this otherwise than on the hypo- 
 thesis that the centres of olfactory and gustatory perception were, 
 if not completely, at least extensively disorganised. It would 
 have been well to have carried out further observations on this 
 point, but — owing to the rather excessive mortality among my 
 monkeys occurring at the time of the influenza epidemic — I 
 have not been able as yet to extend my researches in this 
 direction. 
 
 An interesting accidental experiment on a dog has been recorded 
 by Munk which is of importance in reference to the question before 
 us. Munk observed that a dog which he had rendered blind by 
 bilateral destruction of its visual centres seemed unable to dis- 
 cover by the sense of smell pieces of meat which were scattered 
 before it. A slight sniflBlng which it occasionally made was the 
 only indication that it might possess some traces of olfactory 
 sensibility. The animal continued in this condition for several 
 months, at the end of which time it was killed. It was found after 
 death that the whole of the hippocampal gyrus on each side was 
 converted into a thin walled transparent cyst, full of flaid. Ex- 
 cept for the cicatrices caused by the removal of the occipital lobes, 
 the brain was otherwise normal, as well as the olfactory tracts and 
 bulbs. Though Munk is of opinion that this case shows that the 
 hippocampal gyrus is the centre of smell, yet inasmuch as the 
 hippocampal lobules were implicated as well as the rest of the 
 hippocampal gyri, we may regard it as merely a confirmation of 
 the facts which indicate that the sense of smell is localised more 
 particularly in the hippocampal lobule. 
 
OLFACTORY AyD GUSTATORY CENTRES. 125 
 
 Luciani,^" as the result of his experiments on dogs, concludes 
 that: " No evident deficiency of smell follows extirpation of the 
 temporal lobe ; but if the lesion extend to the neighbourirg con- 
 volution above the fissure of Sylvius, one observes a notable 
 diminution of that sense. Finally, a number of experiments show 
 that an extensive decortication of the gyrus hippocampi, as well 
 as partial ablation of the cornu ammonis, produces olfactory dis- 
 orders, at first an almost complete loss of smell — a fact which 
 seems to indicate to us that this portion of the brain is the central 
 point of the olfactory sphere." 
 
 Luciani is also of opinion that each centre is in relation with 
 both nostrils, but more particularly with the nostril on the same 
 side. In the diagram, however, which he gives of the limits of 
 the olfactory sphere, he extends it upwards into the parietal region 
 as far as the longitudinal fissure, and partly, also, towards the 
 frontal lobe. In regard to the sense of taste, he states that on 
 one occasion, in a dog, he found that, after unilateral extirpation 
 of the fourth external convolution, and of a portion of the gyrus 
 hippocampi, the animal seemed to be less sensitive to bitters 
 (digitaline) on the opposite side of the tongue. (This is mis- 
 stated in Brain. A reference to the original experiments^ shows 
 that the lesion was in the left hemisphere ; smell was lost in the 
 left nostril, and taste on the right side of the tongue.) 
 
 Clinical and pathological evidence in favour of the localisation 
 of the senses of smell and taste is as yet comparatively scanty. 
 We have seen that, from anatomical considerations at least, the 
 olfactory centre is in direc' relationship with the nostril, but I 
 have already mentioned that the symptoms of hysterical hemian- 
 aesthesia wou'd appear to indicate that the olfactory, like the 
 other centres of special sense, are in relation with the opposite 
 side. It is questionable whether the coincident general anaes- 
 thesia of the nostril met with in this condition altogether ex- 
 plains the anosmia ; for I have found that smell is not abolished 
 when the general sensibility of the nostril is lost inconsequence of 
 disease of the fifth nerve. It is, however, diflBcult, with our present 
 knowledge, to trace an anatomical connection between the nostril 
 and the opposite side of the brain. The matter is, therefore, one 
 which requires further investigation. There are clinical casea 
 which plead in favour of the direct relationship of the olfactory 
 eentrfs. It may be objpcted against those reported by Ogle, 
 
 a« "Seneorial Localisations in the Cortex Cerebri," Brain, 1886. 
 *' Dig Function)- Localuattun auf der Crotihir-jtrrnds, p. 117. 
 
126 CEREBRAL LOCALISATION. 
 
 Fletcher and Ransome,^^ in which anosmia was found associated 
 with aphasia and right hemiplegia, that there may have been 
 direct implication of the olfactory tract or bulb. But a case has 
 been reported by Churton and Griffith,^^ in which smell was im- 
 paired on the same side as the lesion, namely, a tumour which 
 caused erosion of the uncinate convolution, and which did not 
 appear to have, directly at least, affected the olfactory tract. 
 
 Several cases have been recorded of olfactory aurse or crude 
 sensations of smell, in association with lesions implicating the 
 region of the uncinate gyrus. One has been reported by McLane 
 Hamilton,-^ without any implication of the olfactory nerves. 
 Another has been recorded by Worcester,^" and a third by Hugh- 
 lings Jackson and Beevor,^*^ in which the whole of the anterior 
 end of the right temporo-sphenoidal lobe was the seat of a tumour 
 involving the nucleus amygdalae and the medullary fibres. Smell, 
 however, was not lost in this case, either on the one side or on 
 the other, which can be accounted for by the fact that the whole 
 of the centre was not destroyed by the tumour. 
 
 This case as well as the others noted are, as Dr. Jackson re- 
 marks, of considerable value in determining sensory localisation, 
 though naturally they do not afford such precise indications as to 
 the position and limits of the centre as are afforded by destructive 
 lesions causing entire abolition ©r considerable impairment. So 
 far as they go, however, they harmonise with the results both of 
 anatomical and physiological investigation. The smacking of the 
 lips and tasting movements which are sometimes observed along 
 with crude sensations of smell — " the dreamy states " of epilep- 
 tic attacks — are probably discharges of the gustatory centres ; but 
 we have still fewer pathological facts bearing upon this point 
 than on the situation of the olfactory centres. A case has been re- 
 lated by Dr. James Anderson^'^ of a peculiar smell and taste sensa- 
 tion and dreamy state associated with tumour affecting the left 
 temporo-sphenoidal lobe; but the lesion was too extensive, and 
 too indefinite to allow of any precise conclusions being founded 
 on it as to the position of the gustatory centre. 
 
 2* See Functions of the Brain, 2nd Edition, p. 321. 
 
 «3 Brit. Med. Journal, May 28th, 1887. 
 
 "^New York Med. Journ., vol. xxxiv. 
 
 's Amer. Journ. of Insanity, July, 1887. 
 
 26 Brain, October, 1889. 
 
 27 Brain, vol. Ix, 1887, p. 385. 
 
LECTURE VI. 
 
LECTURE Vr. 
 
 Mr. Pbesidsnt and Gentlemen, — I now come to the considera- 
 tion of the physiological signification of the Rolandic area of the 
 monkey and man, and its homologues in the brain of the lower 
 mammals. I have already described with some detail the move- 
 ments which are capable of being excited by electrical stimula- 
 tion of the different regions included within this area. How 
 these movements are to be interpreted is a subject on which 
 there are great differences of opinion. The definite purposive 
 character of the movements, however, their correspondence with 
 the ordinary volitional activities of the animals, and, above all 
 their uniformity and predictability, harmonise best, in my 
 opinion, with the hypothesis that they are indications of the 
 functional excitation of centres directly concerned in effecting 
 volitional movements, and anatomically a part of the motor 
 apparatus. 
 
 It has been established by experiments on monkeys — and now 
 80 generally admitted that it is almost unnecessary to enter into 
 detailed proof — that destruction of the centres, excitation of 
 which produces definite movements causes paralysis {qud voli- 
 tion) of the same movements on the opposite side of the body, 
 varying in degree, completeness, and duration with the extent c f 
 the destruction of the respective centres. When the destruction 
 is complete the paralysis is permanent, and is followed in due 
 course by descending degeneration of the pyramidal tracts of the 
 spinal cord, and secondary contracture in the paralysed limbs. As 
 an illustration I quote the following experiment on a monkey 
 which was exhibited at the International Medical Congress in 
 London, 1881, eight months after the operation. 
 
 The cortex was destroyed as shown in the figure (Fig. 33), in 
 the left hemisphere over an area embracing the ascending frontal 
 and ascending parietal convolutions, except at their upper and 
 lower extremities. The lesion also invaded the base of the 
 superior frontal convolution, and the anterior limb of the an- 
 K 
 
130 
 
 CEREBRAL LOCALISATION. 
 
 gular gyrus. There was thus destroyed nearly the whole of the 
 motor area on the convex aspect of the hemisphere, the centres 
 for the leg, foot, and trunk being only partially destroyed ; those 
 for the angle of the mouth and tongue almost entirely escaping. 
 The result of this lesion was almost complete right hemiplegia 
 with conjugate deviation of the head and eyes to the left side. 
 As in similar cases in man, the deviation of the head and eyes 
 was only of comparatively short duration, and the partial facial 
 paralysis, at first perceptible, also disappeared within a fortnight ; 
 but the paralysed condition of the limbs continued very marked, 
 "With the exception of slight power of flexion of the thigh and 
 leg, the right lower extremity was helpless, and the right arm 
 
 FiK. 3.3. 
 
 was incapable of independent volitional movements. Occasion- 
 ally, when the animal struggled, associated movements were 
 observed in the right hand, similar to those initiated by the left, 
 but only under such circumstances. The power of prehension 
 was entirely annihilated. Cutaneous sensibility was unimpaired 
 throughout. The slightest touch excited attention ; and a pinch, 
 or other painful stimulus, caused signs of sensation quite as 
 vigorous as on the other side. This was the condition in which 
 the animal was when exhibited at the International Medical 
 Congress, and at this time well-marked contracture had become 
 established in the paralysed limbs, with exaggeration of the 
 tendon reactions, as in cases of incurable cerebral hemiplegia in 
 man. 
 
THE MOTOR CENTRES. 
 
 131 
 
 The investigation of the brain of this animal was carried out by 
 a committee appointed by the Physiological Section, and the 
 position of the lesion in the motor zone, and its limitation to the 
 cortex and subjacent fibres, were definitely proved by them. 
 Microscopical investigation also demonstrated the existence of 
 secondary degeneration in the pyramidal tracts of the right side 
 of the spinal cord as far as the lumbar region. 
 
 In the case represented in Fig. 34 the lesion, which was estab- 
 lished at the upper extremity of the fissure of Rolando in the left 
 hemisphere, caused paralysis of the right leg, without affection of 
 sensation, followed in due course by contracture of the paralysed 
 
 Fig. 34. 
 
 muscles. This condition remained unchanged for eight months, 
 at the end of which time the animal was killed. In this case also 
 secondary degeneration was demonstrated in the medullary fibres 
 of the corona radiata, and in the pyramidal tracts of the opposite 
 side of the spinal cord as far as the lumbar region, whence emerge 
 the motor nerves of the lower extremity. 
 
 In another experiment the cortex was destroyed in the middle 
 of the ascending parietal convolution and adjacent margin of the 
 ascending frontal convolution of the right hemisphere. The result 
 of this was almost complete paralysis of the left hand, and great 
 weakness of the flexor power of the forearm. The shoulder 
 movements, however, were unimpaired ; the animal could stretch 
 K 2 
 
132 CEREBRAL LOCALISATION. 
 
 its arm forward, bat could not grip with its hand what it wished 
 to lay hold of. Tactile sensibility was absolutely unimpaired in 
 the paralysed limb, the slightest touch on it at once exciting th© 
 animal's attention, and a painful stimulus, such as a pinch or touch 
 with a heated wire, caused as lively signs of sensation as on the 
 other side. This condition remained essentially unchanged for the 
 two months which the animal survived the operation. 
 
 Many similar experiments have been recorded by Horsley and 
 Schafer,^ and their observations on the functions of the marginal 
 gyrus deserve special note. Extirpation of the marginal convo- 
 lution causes paralysis of those movements which remain more or 
 less unaffected after the destruction of the centres on the convex 
 aspect of the hemisphere ; namely, movements of the trunk, those 
 of the hip muscles, as well as some of those of the leg. In order, 
 however, that these movements should be entirely paralysed, it is 
 necessary that the marginal convolution should be destroyed in 
 both hemispheres ; as it would seem that the trunk movements 
 are so bilaterally co-ordinated in the marginal convolution, that 
 the removal of one only is not sufBcient to cause any very marked 
 effect. When both are removed, however, the most absolute para- 
 lysis of the trunk muscles is induced. " The attitude and general 
 appearance of a monkey in which this double lesion has been 
 produced are very striking. Instead of sitting up with back 
 somewhat curved, in the manner normal to monkeys, an animal 
 which has been submitted to this operation lies prone, with legs 
 and feet outstretched (or, at most, with flexed hips), back flat, 
 tail straight and motionless, and arms put forward to clutch at 
 any neighbouring object. The head retains its power of rotation, 
 as well as flexion and extension, and the movements of the eyes 
 and facial muscles appear normal. The animal frequently props 
 itself upon its elbows, but never assumes the normal sitting atti- 
 tude. If the monkey desires to sit up, it can only do so by drag- 
 ging itself into the sitting posture by its arms and hands, and 
 holding on by these to the wires of the cage, or to any neighbour- 
 ing object. If the hold should be detached the animal imme- 
 diately tends to fall over. Progression is effected almost entirely 
 by the arms, the monkey dragging itself along with the aid of 
 these, assisted by the flexion which occurs at the hips ; the legs 
 are quite limp and draggled, the dorsal surface of the toes being 
 drawn over the ground."* 
 
 1 Phil. Trans., B. 20, 1888. 
 » See illustration, Fig. 20, op. cit.. 
 
THE MOTOR CENTRES. 133 
 
 Besides the movementa of the trunk, there are others which are 
 also bilaterally represented in each cerebral hemisphere. This 
 holds in respect to the upper facial region, as well as those of the 
 larynx. Hence, unilateral extirpation of the centres of these 
 movements causes no, or scarcely any, perceptible impairment ; and 
 it is necessary that the centres should be destroyed on both sides in 
 order that paralysis should result. It has been shown by Krause 
 in dogs, and by Horsiey and Semon in monkeys, that unilateral 
 extirpation of the laryngeal centres does not appreciably impair 
 the adduction of the vocal cords, whereas phonation becomes 
 volitionally impossible when the centres are destroyed in both 
 hemispheres. 
 
 It would appear from the researches of Franck and Pitres,^ 
 Exner,* Lewaschew,' Sherrington,* that such movements as are 
 not primarily bilaterally represented in each cerebral hemisphere 
 are secondarily associated, in accordance with a hypothesis 
 originally advanced by Broadbent, by commissural fibres con- 
 necting the bulbar and spinal nuclei with each other. Though 
 moderate stimulation of the cortical centres of the limbs gives rise to 
 movements as a rule only on the opposite side, yet it not infre- 
 quently happens, if the stimulation be increased, that movements 
 occur in the limbs on both sides. These are, however, more pro- 
 nounced on the opposite than on the same side. In the monkey 
 as well as in man, it i3 not unusual to find descending degenera- 
 tion in both lateral columns as the result of unilateral cortical 
 lesions. 
 
 According to the recent researches of Sherrington, if the cortical 
 lesions affect only the centres for the limbs, bilateral degeneration 
 does not occur, to any extent at least ; but this is very pronounced 
 if the lesions affect the marginal convolution. The degeneration 
 is confined to the pyramidal tracts on the same side as far as the 
 decussation of the pyramids, but becomes bilateral in the spinal 
 cord. In the case, however, of the more obviously bilateral laryn- 
 geal centre, degeneration is well marked in the pyramids of both 
 sides. These facts, as well as clinical observations in man, show 
 that, even in the case of the limbs, each hemisphere represents 
 both sides of the body, mainly the opposite, but to some extent 
 also the same side. 
 
 » LeQorui sur leu Fonctions Matrices du Cerveau, 1887. 
 
 * Sitzungsh. d. Wiener Ahad, .3 Abth., pp. 185-190, 1881. 
 
 •'' Arrhtvf. Phyn^olngie. D<i. .38. 
 
 *Journ. ')f rkynology, Nob. 4. .5, and 6 ; and Brit. Mep. Jottrnai,. January 
 
 4th, 18f»0. 
 
134 CEREBRAL LOCALISATION. 
 
 It was first pointed out by Brown-S^quard, and his observations 
 have been confirmed by Pitres^ and Friedlander,^ that lesions 
 which induce hemiplegia of the opposite side also cause some 
 diminution in the energy of the movements of the limbs on the 
 same side. This is a result which we should expect if each hemi- 
 sphere were in relations with both sides of the body. 
 
 The bilateral relations of each hemisphere, which exist to some 
 extent in monkeys and man, are, as we shall see, still more pro- 
 nounced in the case of dogs and the lower animals ; and, in dogs, 
 as Sherrington has shown, bilateral degeneration from unilateral 
 cortical lesion is more commonly met with. This bilateral repre- 
 sentation accounts for a certain amount of recovery, even when 
 the motor centres of one hemisphere have been entirely destroyed ; 
 and this recovery extends more particularly to those movements 
 of the limbs which are more or less habitually associated with 
 those of the other side, and least of all to those which are more 
 independent and more volitional. Hence, in cortical paralysis, 
 the arm is more paralysed than the leg, and the distal movements 
 of the arm more than the proximal. These facts are of great im- 
 portance in reference to the hypothesis of the functional compen- 
 sation for the centres which have been destroyed by neighbouring, 
 or other, portions of the same cerebral hemisphere. It has now 
 been established beyond all question that cortical lesions of the 
 motor zone in man, if they are such as actually to destroy and not 
 merely push aside the grey matter of the respective centres, in- 
 variably cause paralysis of volitional motion in the related parts. 
 Such results have invariably followed, not only the destructive 
 lesions of disease but also surgical excisions of the cortical centres. 
 Not only does general hemiplegia result from lesions of the whole 
 of the Eolandic area, but limited lesions cause limited paralyses, or 
 monoplegias, of the face, arm, and leg, in precise correspondence 
 with the results of experiments on monkeys. 
 
 In the Gulstonian lectures on Localisation of Cerebral Disease, 
 which I had the honour of delivering in this College twelve years 
 ago, I brought before you a number of cases, collected from various 
 sources, in support of [these statements. Since then many others 
 have been recorded, all confirming the same; and the point has 
 now been considered so completely proved, that clinical observers 
 have practically ceased to record their observations. 
 
 Of 483 cases of cortical (including subcortical) disease collected 
 
 ^ Archives de Neurologic, No. 10, 1882. 
 \ Nsurologisches Centralblatt, No. 11, 1883. 
 
THE MOTOR CENTRES. 135 
 
 under my direction by Dr. Ewens (excluding as a rule tumours 
 and other lesions likely to cause indirect affection of other parts), 
 I have the records of 110 cases of hemiplegia of the opposite side 
 from general lesion of the Rolandic zone ; and 90 cases of mono- 
 plegia from limited lesions of this zone. Of these, 11 are cases 
 of crural monoplegia, from disease of the paracentral lobule ; 15, 
 cases of paralysis of the arm and leg from disease of the para- 
 central lobide and upper third of the ascending convolutions ; 33, 
 cases of brachial monoplegia, including three cases of surgical ex- 
 cision, from lesion of the middle of the ascending convolutions ; 
 19, cases of paralysis of the arm and face from lesions of the lower 
 half of the Rolandic zone ; and 10, cases of facial paralysis from 
 disease of the lower third of this region. In addition to these, I 
 have notes of 20 cases of atrophy of the cortex of the Rolandic 
 zone in connection with congenital or infantile hemiplegia, or as 
 the result of congenital absence, or long-standing amputation, of a 
 limb. 
 
 In the monkey and man, therefore, there is no evidence of func- 
 tional compensation for the paralysing lesions, except in so far as 
 these may be accounted for by the bilateral relations of each cere- 
 bral hemisphere. The theory of compensation by other portions 
 of the same hemisphere has been adduced more particularly in 
 order to account for the apparent recovery in dogs and lower ani- 
 mals after complete unilateral destruction of the cortical motor 
 centres. This is a hypothesis, however, which is inconsistent 
 with the principles of localisation otherwise maintained by those 
 who advance it ; and for which, moreover, there is no necessity. 
 Though dogs appear to recover from the disorders of movement, 
 which are at first obvious enough after unilateral extirpation of 
 their motor centres, yet, in reality, the recovery is never com- 
 plete. Only those movements are permanently affected which are 
 the least automatic and most volitional ; while those which are 
 most automatic and least volitional, such as those concerned in 
 station and co-ordinated locomotion, and which, as we have seen 
 in the first lecture, may continue in some animals even after com- 
 plete extirpation of both hemispheres, are comparatively little 
 impaired. The movements which are most paralysed are those of 
 the limb, as a hand, or organ of prehension. 
 
 It appeared from Goltz's earlier experiments on dogs that the 
 use of the forelimb as a hand, such as in giving a paw, holding a 
 bone when gnawing it, etc., was permanently paralysed by de- 
 struction of the motor centres of the opposite hemisphere. But in 
 
136 CEREBRAL LOCALISATION. 
 
 his last interesting communication^ he has shown that this is not 
 strictly correct. He gives the particulars of a dog in which prac- 
 tically the whole of the left hemisphere was destroyed, and which 
 lived fifteen months afterwards. In this animal, the movemenla 
 of the right limbs, so far aa station and locomotion were con- 
 cerned, were so little affected, though not really normal, that the 
 defect might readily escape superficial observation altogether. It 
 had not entirely lost the use of the right paw as a hand in holding 
 a bone, at least in association vrith the left, though in this respect 
 it was very imperfect. This animal had not been taught to " give- 
 a paw," so that it could not be determined whether this acquired 
 trick could still be exhibited, though Goltz is of opinion that, in 
 rare cases, a dog may perform this act after deep and extensive 
 (but probably not complete) destruction of the motor zone of the 
 opposite hemisphere. The possibility of a certain degree of inde- 
 pendent, or rather associated, volitional use of the opposite limbs 
 is, as Goltz's experiments clearly demonstrate, dependent on the 
 integrity of the motor centres of the uninjured hemisphere ; for 
 when these are destroyed on both sides, all strictly volitional 
 movements are permanently paralysed. Thus he says ; " A dog 
 whose motor centres of both hemispheres have been destroyed 
 cannot feed itself ; the movements of the tongue are greatly im- 
 paired, while the tongue, in a case of unilateral extirpation, can be 
 moved normally. The animal can, as already mentioned, still 
 walk, but in a very awkward and unsteady manner. All move- 
 ments of the paws as hands appear to be utterly impossible." ^"^' 
 This powerlessness depends on the symmetrical destruction of the 
 motor centres in both hemispheres ; for, if the motor centres on 
 the one side, and the occipital regions on the other, are destroyed, 
 the dog can eat and drink and move its tongue, walk and run 
 about fairly well, and use both its forepaws, to some extent, in 
 fixing a bone which it is gnawing. What is true of the bilateral 
 representation of the motor faculties in each cerebral hemisphere 
 appears also to hold in respect to the faculties of general and 
 special sense. 
 
 Apart from motor paralysis, I have never been able to detect 
 the slightest impairment of special, or tactile and general sensi- 
 bility after destruction of the motor centres. One may observe 
 absence or defective reaction of, the paralysed limbs to sen- 
 sory stimulation ; but that this is not dependent on defective sen- 
 
 'i Archivf. Pkysiologie, vol. xlii, 1888. 
 '"' Op. cit., p. 448. 
 
THE MOTOR CENTRES. 137 
 
 Bation is shown by the fact that the animal's attention is at once 
 attracted by the slightest touch on the paralysed side, and by 
 general signs of discomfort if any part is subjected to painful 
 stimulation, such as the prick of a pin. The contrast between the 
 reactions to sensory stimulation in monkeys, in which the falci- 
 form lobe, and those in which the motor centres have been removed, 
 is so striking that no doubt can be entertained that, in the latter 
 case, sensibility is retained, while, in the other, it is abolished or 
 profoundly impaired. Horsley and Schafer have also been unable 
 to obtain any evidence of loss of general sensibility after destruc- 
 tion of the motor centres. 
 
 "We have seen," say they, "sufficient, however, to convince 
 ourselves that a lesion of the cortex which produces paralysis of 
 volitional motion in a part, is not necessarily accompanied, also, by 
 loss of general sensibility of the paralysed part."" In order to test 
 the hypothesis which has been advanced by some— that the super- 
 ficial cells of the motor cortex are sensory in function— they, in 
 one instance, destroyed the superficial layers of the grey matter 
 by means of the actual cautery. " In spite, however, of the com- 
 plete blocking of the superficial vessels so produced,'' they go on 
 to say, " we obtained only an incomplete muscular paralysis as 
 the immediate result of the operation ; but although the super- 
 ficial layers of the cortex must have been destroyed, there was no 
 diminution of sensibility in the parts affected by paresis. The 
 subsequent softening and disintegration which occurred in conse- 
 quence of the thromboses caused by the cautery was accompanied 
 by a much more complete condition of muscular paralysis ; but the 
 general sensibility of the opposite side was still apparently un- 
 affected, and continued so until the death of the animal." ^'^ One 
 of Goltz's experiments on dogs " also showed very clearly that de- 
 struction of the cortical motor zone does not impair sensibility on 
 the opposite side. Taking advantage of the well-known fact that 
 dogs snarl when touched while engaged in eating, he touched the 
 right side of a dog so occupied, which had had its motor centres 
 in the left hemisphere destroyed some time previously. The 
 animal responded invariably with the characteristic signs of dis- 
 pleasure on the slightest touch. Similar facts have been demon- 
 strated in the case of cats by Bechterew.'' " It is a familiar obser- 
 
 " Op. eit., p. 1.5. 
 
 ^^Op.cit , p. 17. 
 ■» Pjliiger's Arckiv, Bd. .34, 1884, p. 46.'5. 
 ' • P/lager's Arc/iio, Bfl. 3.% 188.5, p. 137. 
 
138 CEREBRAL LOCALISATION. 
 
 vation that a cat dislikes having its feet wet, so that, if it should 
 accidentally step on a wet place, it will stop and shake its paw dry 
 before proceeding further ; or if, while indolently slumbering, a 
 drop of water falls on it, it will start up and make off hastily ; or 
 it will close its eyes and contract its ears if its paw is gently 
 touched unobserved." After verifying these facts in a cat about 
 to be operated upon, Bechterew removed the cortex in the region 
 of the sigmoid gyrus. On recovery from the chloroform narcosis 
 the animal exhibited the characteristic motor disorders of the 
 right limbs, and was unable to use the right paw for any inde- 
 pendent volitional act, but touching the ear, or the sole of the 
 right as well as iihe left foot, induced the same closure of the eyes, 
 and drawing in of the ears as before ; and the spriukling of a few 
 drops of water on its paralysed side caused the animal to start up 
 and make off as before. 
 
 It has, however, been maintained by various experimenters, 
 Hitzig, Nothnagel, Schiff, Munk, Tripier, Goltz, Luciani, etc., that 
 the affection caused by destruction of the so-called motor centres 
 is accompanied by, or dependent on, affections of tactile, muscu- 
 lar, or general sensibility, or all three combined, in the paralysed 
 limbs. 
 
 My own experiments, as well as those of Horsley and Schafer, 
 have shown that there is no discoverable impairment or loss of 
 tactile or general sensibility after lesions of the motor zone, and 
 I will not therefore stay to examine in detail the data, so far as 
 they have been given, on which the various authors whom I have 
 mentioned found their conclusions. They appear to me to be 
 based merely on defective reaction to sensory stimulation, which 
 can be equally well explained on the theory of motor inability as 
 sensory deficiency; or they are due to the destruction of other 
 regions than the motor cortex. This applies more particularly to 
 the experiments of Goltz, in which the lesions of the hemisphere, 
 or hemispheres, have been vague and indeterminate. It is un- 
 questionable also that in man paralysis from lesion of the motor 
 area is, in the majority of instances, an essentially motor affec- 
 tion, and is unaccompanied by any discoverable defect of tactile, 
 muscular, or general sensibility. I have myself recorded several, 
 and have collected many other cases of lesion of the cortical motor 
 zone accompanied by paralysis, in which every variety of sensi- 
 bility has been carefully tested and found normal. But it is true 
 also that in a good many instances of lesion of the motor area 
 some degree of impairment of tactile and muscular sensibility 
 
THE MOTOR CENTRES. 139 
 
 general or limited, has been observed. And several authors, 
 Petrina,'' Exner," Luciani and SeppUi,^'' Starr,** Dana,'^ 
 Lisso,^° have endeavoured to show, from examination of 
 the clinical records of cerebral disease, that the motor centres 
 and the centres of tactile and general sensibility coincide so 
 that sensory disturbances, frequently at least, if not always 
 accompany the motor paralysis. The data on which these con- 
 clusions have been based appear to me in the highest degree un- 
 satisfactory. The lesions have been microscopical specks of 
 themselves insufficient to cause anything ; or, and for themost part, 
 tumours which may cause everything ; or multiple foci of disease 
 not limited to the cortex itself. Causation is not established un- 
 less invariable and unconditional relationship has been shown to 
 exist between a particular lesion and a particular symptom. In 
 the case of the motor area it has been satisfactorily demonstrated 
 that destructive lesions invariably give rise to motor paralysis, 
 local or general, according to the position and extent of the lesion. 
 A single case, therefore, of paralysis from lesion of the cortical 
 motor area, unaccompanied by any defect of sensibility, is suffi- 
 cient to overthrow a host of positive instances in which the two 
 symptoms have apparently been caused by the same lesion. Apart, 
 however, from all other considerations, an examination of the 
 clinical records taken indiscriminately from all sources, excluding 
 tumours and such lesions as are obviously calculated to cause 
 widespread and indeterminate disturbances of other parts, is cer- 
 tainly not in favour of the conclusions which the above-mentioned 
 authors have founded on this kind of evidence. For, of 110 cases of 
 general lesion of the Rolandic zone causing hemiplegia, in 52 cases 
 sensibility was unimpaired (in one of these a large portion of the 
 motor cortex was excised).** In 37 the condition as to sensibility 
 is not mentioned, while in 21 it is said to have been to some ex- 
 tent affected. But of these last, in one sensibility is stated to 
 have been blunted over the little finger.*^ In "another there was 
 general hypersesthesia, more marked on the paralysed side. In 
 
 >• Sengibilitatsstorungen bei Hirnrindenliisionen, Zeitsch. f. Heilkunde, Bd. il, 
 
 p. 375, 1881. 
 
 1* Localisation der Functionen in der Grosshirnrinde des Menschen, 1881. 
 
 " Die Functions- Localisation auf der Grosshirnrinde, 1886. 
 
 •• Localised Cerebral Disease, Amer. Jour. Med. Sc, 1884. 
 
 ^'Cortical Localisation of Cutaneous Sensations, 1888. 
 
 *•* Zur Lehre von der Localisation des Ge/i'Ms in der Grosskirnrinde, 1883. 
 
 " Case of J. H., Brain, vol. x, p. 95. 
 
 " Trlpier, Rev. Mens., 1880, Case 4. 
 
140 CEREBRAL LOCALISATION. 
 
 one all varieties of sensibility were retained, but the localisation 
 of touch was somewhat defective.^^ In this case, however, 
 the inner table of the skull had been driven into the brain 
 substance, causing general hemiplegia. 
 
 In two the lesion extended deeply into the white substance. In 
 one case the cortical lesion was complicated by the presence of a 
 large tumour in the centrum ovale.^* In one sensibility is said to 
 have been blunted on both sides of the body. In another ^' the 
 lesion was a large hgemorrhagic cyst in both central convolutions 
 In this, and in five others, the island of Reil or external capsule was 
 involved. In one hemiplegia was accompanied by anaesthetic 
 formication of the paralysed foot. In this case there was tuber- 
 cular deposit implicating the gyrus fornicatus as well as the cen- 
 tral convolutions. In seven others there was diffuse meningo- 
 encephalitis or tubercular meningitis. 
 
 In ten cases of crural monoplegia, from disease of the para- 
 central lobule, cutaneous sensibility was unaffected in six, its 
 condition not mentioned in two, and affected in two. In the 
 one^^ sensibility to pain was a little diminished in the paralysed 
 limb, but this disappeared the next day. In the other^'' the leg 
 became gangrenous, a condition which was preceded by anaesthesia. 
 
 Of fifteen cases of paralysis of the arm and leg from disease of 
 the paracentral lobule and upper third of the ascending convolu- 
 tions, sensation was intact in six, not mentioned in five, and 
 affected in four others. In three of these the paracentral lobule 
 was deeply involved, one of them being a tubercular mass : and 
 in only one was the anaesthesia marked or permanent. In all four 
 the lesion was in immediate proximity to, or actually involved, 
 the gyrus fornicatus. In one case, under my own care,^^ of 
 traumatic cicatrix at the upper third of the ascending frontal 
 convolution, excision of the lesion was followed by loss of tactile 
 sensibility on the dorsum of the two distal phalanges, and ina- 
 bility to indicate the position of the fingers of this hand. This 
 impairment of sensibility ultimately disappeared, while the motor 
 paralysis continued as at first. In this case the lesion was such 
 as to actually implicate the gyrus fornicatus. 
 
 Of 35 instances of brachial monoplegia, 5 were cases of excision 
 
 =•= Bramwell's CaBe, Bbit. Med. Jouenai,, August 28th, 1875. 
 
 2* Seguin's case, Trans. Amer. Neurol. Assoc, 1877, p. 115. 
 
 25 Starr's case, 75. Amer. Journ. Med. Sciences, July, 1884. 
 
 26 Gouguenheim, Soc. Med. des Hopitaux, 1878, p. 48. 
 
 2' Ballet, Archives de Neurologie, Tome v, p. 281. 
 
 28 Case of J.B., Brain, vol. x,, p. 26. 
 
THE MOTOR CEXTRES. u\ 
 
 of portions of the cortex for the cure of focal epilepsy. In two, 
 cases by von Bergmann"" and Keen,3o sensation was intact. In another 
 case reported by Keen," of hemiplegia and epilepsy, resulting 
 from depressed fracture, there was, after the operation, slight im- 
 pairment of sensation in the middle of the forearm and two inner 
 fingers. But this condition of sensibility was similar to what had 
 existed before the operation. In another ^^ there was no obvious 
 impaiiment in tactile (?) or muscular sensibility. The patient 
 could not distinguish the form of objects owing to the inability to 
 mov« his fingers. In a fifth case '^ the removal of a tumour from 
 the right lower parietal region, which was the cause of epilepsy 
 beginning in the thumb, was followed by tactile anesthesia of 
 the whole of the left side, together with loss of so-called muscular 
 sense in the left arm. In this case the sensory tracts for the 
 whole of the opposite side of the body were obviously implicated. 
 Of the 30 others, sensibility was unimpaired in 12, not mentioned 
 in 15, and affected in 3. In one of these the lesion was a gumma.^* 
 In the second ^' there was a clot compressing the island of Keil ; 
 in the third sensibility was said to have been extinguished over 
 the entire surface of the body.^*^ 
 
 Of 19 cases of lesion of the lower half of the Rolandic zone, 
 causing paralysis of the face and arm, sensation was unaffected in 
 11, not mentioned in 5, and affected in 3. In one of these," how- 
 ever, a blood clot in the island of Reil compressed the subjacent 
 convolutions. In another reported by the same author^'* a small 
 tubercle the size of a hemp seed, situated in Broca's convolution, 
 is described as having caused (!) paralysis of the right side of the 
 face and arm, and anaesthesia of the right side of the trunk. The 
 third, also reported by Petrina, was similar to the second. In 10 
 cases of disease of the lower third of the Rolandic zone, causing 
 simple facial paralysis, sensation was intact in 4, not mentioned in 
 5, and affected in 1. In this case =» there wa. said to have been 
 anaesthesia, not only of the face, but of half the trunk. 
 
 29 Archiv. f. Klin. Chirurg., p. 864, 1887. 
 
 30 Amer. Joum. Med. Sc, 1888, Case 3. 
 
 »i Ibid, Case 2. 
 
 32 Lloyd and Deaver'e case, Amer. Joum. Med. Sc, 1888, p. 477. 
 
 33 Jackson and Horsley, Brain, vol. x, p. 93. 
 
 3* Martin, Chicago Med. Jour., vol. 46, p. 21. 
 
 35 Wood, Phil. Med. Times, vol. v, p. 470. 
 
 '• Bingrose Atkins, Bbit. Med. Journal, 1878. 
 
 3' Petrina, Zejf.nrh.f. Hnlkunde, vol. x\, 1S8I, Case 1, 
 
 •'8 Ibid. Case 6. 
 
 3* Petrina, fup. cit., Case 3. 
 
142 CEREBRAL LOCALISATION. 
 
 It thus appears that, of 284 cases of lesion affecting the Rolandic 
 zone, general or in part, in 100 the condition of sensibility was 
 not mentioned ; in 121 it was stated, and by many of the most 
 reliable clinical observers, to have been intact ; and in many of 
 these *" all varieties of sensibility are expressly stated to have 
 been carefully investigated. In the remaining cases no detailed 
 notes are given as to the different modes of sensibility, and the 
 methods applied for testing them. In 68, some impairment of 
 sensibility was noted. In 28 of these, the lesion was not confined 
 to the Rolandic zone, but implicated adjacent lobes, especially the 
 parietal. The remaining 35 have already been analysed, and it 
 has been shown that, in the majority at least, conditions existed 
 which were calculated to implicate either the sensory centres in 
 the gyrus fornicatus, or the sensory tracts of the internal capsule. 
 Even where these cannot have been demonstrated to exist — and I 
 freely admit that there are such cases— it is more logical to assume 
 that they may have existed than that in some individuals the tac- 
 tile and motor centres should coincide, while in other this should 
 not be the case. I do not consider that the sensory aura which 
 occasionally precedes or accompanies a localised epileptiform 
 spasm can be taken as a proof that the motor and sensory areas 
 coincide. It may prove contiguity, functional or anatomical, but 
 not coincidence. For the most careful investigation in a large 
 number of cases has failed to detect the slightest impairment of 
 any of the forms of general sensibility, while the motor affection 
 has been of the most pronounced character. There is also no re- 
 lation between the degree of affection of sensibility and that of 
 the motor paralysis. The motor paralysis has been absolute 
 
 *<> Mills {Trans Amer. Cong, of Phys., etc., 1888, p. 269), (digest in Brain, Oc- 
 tober, 1889); Delepine {Trans. Path. Sac, 1889); Ferrier (.Brain, April, 1883, p. 
 67); Moutard-Martin (Bull. Soc. Anat., 1876, p. 706); Laquer (Inaug. Dissert. 
 Breslau, p. 91, Case 10) ; Mills (University/ Med. Mag., November, 1889) ; Ferrier 
 (Brain, vol. x, p. 95) ; Raymond et Derignac (Gaz. MM., 1882, p. 665) ; Von 
 Bergmann (Archiv. fiir klin. Chir., 1887, p. 864); Davy and Bennett (Brain, 
 vol. ix, p. 74) ; Ballet (Archives de Neurol., vol. v, p. 275, Case 1) ; Lloyd and 
 Deaver, Amer. Jour. Med. Sciences, vol. 96, p. 477); Keen (Cerebral Surgery, 
 Amer. Jour. Med. Sciences, 1888, Case 3). One might add to these cases not a 
 few of hemiplegia with aphasia (not followed by post-mortem examination) in 
 which the symptoms pointed to cortical lesion. In one, recently under my 
 care at King's College Hospital, of absolute paralysis of the right arm asso- 
 ciated with word-blindness and word-deafness, the patient was aware of the 
 slightest touch on the paralysed hand, or of a drop of warm or cold water 
 falling on it, and with eyes blindfolded could put her left hand on the spot, in 
 whichever position her paralysed arm was placed. This is a method of testing 
 the sense of position in those who are unable to understand or speak, and is also 
 applicable to the lower animals. 
 
THE MOTOR CENTRES. 143 
 
 while the affection of sensibility has been slight, and confined to 
 one, or at most two or three, fingers ; or the motor paralysis has 
 been limited, while the impairment of tactile sensibility has been 
 general. And in others the affection of tactile sensibility, at first 
 observed, has disappeared, while the motor paralysis has re- 
 mained. And when, moreover, we take into consideration the 
 fact that tactile and muscular sensibility may be abolished in the 
 absence of motor paralysis, a condition which can be experiment- 
 ally produced in monkeys by lesions of the falciform lobe, we 
 have a further proof that the motor and sensory centres of the 
 cortex are anatomically distinct from each other, and that we 
 cannot attribute the motor paralysis to any defect in tactile or 
 muscular sense. The occurrence of slight defects in tactile and 
 muscular sensibility, more particularly in the fingers, which have 
 been noted by several as a special characteristic of lesions of the 
 cortical motor zone, are, in my opinion, to be looked upon as the 
 beginning or remnants of a general hemiansesthesia, rather than 
 as indicative of special centres for the tactile and muscular sensi- 
 bility of the digits in the motor cortex. 
 
 In illustration of this, I would mention the details of the fol- 
 lowing case. The patient was a lady, aged 50, suffering from 
 word-blindness and a slight degree of right hemiopia, which, from 
 these and other symptoms, I diagnosed to be due to a tumour in 
 the region of the angular gyrus. There was no paralysis of motion, 
 but there was slight impairment of the localisation of touch and 
 the sense of position in the fingers of the right hand, the face and 
 leg being normal in this respect. An operation was undertaken 
 by Mr. Horsley for the removal of the tumour, but it was found, 
 on trephining to be situated beneath the angular gyrus, and could 
 not safely be removed. This was a case in which, without doubt, 
 the sensory tracts of the internal capsule were implicated, but 
 only to a slight extent ; hence the limitation of the anaesthesia to 
 the fingers. Had the implication of the internal capsule been 
 more extensive, there would undoubtedly have been loss of tactile 
 and muscular sensibility on the whole of the opposite side of the 
 body. 
 
 This case has an important bearing on the hypothesis advanced, 
 among others, by Nothnagel " that the centres of the muscular 
 sense are situated in the parietal lobe. Defects of tactile sensi- 
 bility, and of the sense of position of the limbs, have not infre- 
 
 *i VI ConxresB fiir Innere Meclicin, Neurolog. CentralUatt, 1887, vol. 0, p. 2I.'i. 
 
144 cehebral localisation. 
 
 quently been observed in connection with lesions of this regioB, 
 sometimes complicated with hemiopia when the lesions have in- 
 vaded also the occipito-angular region, as in the above case, and in 
 one reported by Westphal." But the real cause of these symptoms 
 I believe to be implication of tne sensory tracts of the internal 
 capsule which lie underneath this region, and not affection of the 
 cortex itself ; for lesions of the inferior parietal lobe do not, in my 
 experience, produce the slightest affection of general sensibility 
 on the opposite side of the body. 
 
 Cortical lesions of the motor zone causing complete paralysis 
 may occur without any impairment whatever of the muscular 
 sense ; and loss of the muscular sense may occur without motor 
 paralysis. I agree with Bastian, James,*^ and others — and have 
 furnished experimental proof thereof — who hold, in opposition to 
 the views maintained by Bain, Wundt, and Hughlings Jackson, 
 that the sense of movement, its range and direction, are dependent 
 upon in-going, or centripetal, impressions conditioned by the 
 movement itself, and not on the out-going current or energising 
 of the motor centres. 
 
 We have, I believe, no sense of innervation independently of 
 the sensory impressions arising from the parts which are moved. 
 The energising of the motor centres and motor apparatus is re- 
 vealed in consciousness only through the functioning of the cor- 
 related sensory tracts and centres. The idea or conception of a 
 movement is, therefore, a revival in the respective sensory centres 
 of the various impressions which have been associated with this 
 particular movement. Of these the most important are the visual 
 factors and those which are included generally under the so- 
 called muscular sense. In learning a movement our chief guide 
 is vision, which enables us to place our limbs in the position re- 
 quisite to produce any desired effect, and we associate also with 
 the particular movement a distinct set of muscular sense impres- 
 sions. The revival of these, singly or conjointly, is the idea of 
 the movement, and this allowed to excite the appropriate muscu- 
 lar combination is the volitional act itself. 
 
 I hold that the centres of the sensations which accompany 
 muscular action, and which form in part the basis of our ideas 
 of movement, are distinct from the cortical centres, through and 
 by which the particular movements are effected. The destruc- 
 
 *2 Zur Localisation der Hemianopsie und des MuskelgefUbls beim Mensohen, 
 
 ChariU-Annalm, 1882. 
 43 The Feeling of Ejfort, 1880. 
 
THE MOTOR CENTRES. 145 
 
 tion of the cortical motor centres paralyses the power of execu- 
 tion, bat not the ideal conception of the movement itself. A dog 
 with its cortical centres destroyed has a distinct notion of the 
 movements desired when asked to give a paw, but it makes only 
 inefftctual struggles and fails to comply. So, too, it not infre- 
 quently happens that a patient rendered hemiplegic by embolism 
 of hii Sylvian artery only discovers his infirmity by his in- 
 ability to extcute the movements which he has distinctly con- 
 ceived. 
 
 Voluntary movements are capable of being carried out in the 
 entire absence of all sense of movement. In the well-known 
 case described by Schiippel,*^ the patient, anaesthetic from spinal 
 disease, was able to co-ordinate his limbs perftctly, and, move 
 them freely and forcibly with the aid of vision ; and even without 
 the aid of vision to employ them with a fair degree of precision 
 and steadiness. A similar condition is met with in hemian- 
 sesthesia from organic lesion of the sensory tracts of the internal 
 capsule, and in the functional forms described under the name of 
 hysterical hemiansesthesia. 
 
 Though the patient is able to move the anaesthetic limb volun- 
 tarily, he has no knowledge of its position or of the resistance 
 which may be offered to its intended movement. Bastian,*' how- 
 ever, maintains that "the rule has been with the hemiansesthetic 
 patients which have been so thoroughly investigated by Charcot 
 at the Salpetriere that, although there has been complete loss of 
 tactile sensibility, and usually absolute insensibility to pain in 
 the skin and all other sensitive structures on the affected side, 
 together with paresis of the affected limbs, the so-called 'muscular 
 sense ' has been nearly always preserved." 
 
 On this question I have appealed to M. Charcot himself. He 
 has favoured me with a reply, from which I quote the following : 
 " Cases of hysterical hemianaesthesia may be seen both in men and 
 women affecting only the superficial integument, and without im- 
 plication of the muscular sense, but the obnubilation, or complete 
 disappearance of the muscular sense — in particular the loss of 
 the sense of position of the limbs — is each very frequent, one 
 might almost say habitual, in hysterical hemiansesthesia, 
 
 especially when it is accompanied by paresis or hemiplegia 
 
 Up to the present I have not met with serious impairment, strictly 
 limited to the muscular sense in hysteria, unaccompanied by cuta- 
 neous hemiansesthesia. It appears from all this that the aboli- 
 
 ♦* Archio d. Heilkundf, 1874, Bd. xv, p. 44. 
 ■*'• The Muscular Sense, Hrain, vol. x, 1889. 
 
148 CEREBRAL LOCALISATION. 
 
 bilities are most varied and most perfect, should be developed far 
 beyond those of other animals, but precisely the opposite holds 
 For relatively as compared with the brain, and relatively as com- 
 pared with the size of the animal, the spinal motor centres of 
 man are less developed than those of the lower animals; and they 
 are absolutely less than those of many animals whose capabilities 
 are of the simplest order. The development of the spinal motor 
 centres corresponds with that of the purely reflex synergic mus- 
 cular combinations of the related metameres or body segments; 
 while that of the cortical motor centres corresponds with the 
 multiplicity and complexity of the motor faculties, volitional and 
 cognitive. 
 
 From the various considerations above advanced I conclude that 
 the motor centres of the cortex are not the centres of tactile or 
 general sensibility, nor are they the centres of the muscular sense, 
 whether we regard this to depend on centripetal impressions, 
 conscious or unconscious, or on a sense of innervation; but that 
 they are motor in precisely the same sense as other motor centres, 
 and, though functionally and organically connected, are anatomi- 
 cally differentiated from the centres of sensation general, as well 
 as special. 
 
 Fbontal Centbes. 
 
 The region of the brain which lies in advance of the Kolandic 
 area and marked off by the precentral sulcus is one respecting the 
 functions of which there is still considerable doubt. Anatomi- 
 cally it is r-lated to the motor tracts of the internal capsule. 
 These tracts, according to the investigations of Flechsig, lie in the 
 inner portion of the foot of the crus, and connect the frontal lobe 
 with the opposite cerebellar hemisphere indirectly through the 
 grey matter of the pons. Destructive lesions of the frontal centres, 
 both of the postfrontal and prefrontal regions, as I have shown 
 experimentally, cause descending degeneration of these tracts ^^ 
 not capable of being followed beyond the upper part of the pons. 
 The direction of the degeneration may be taken as a proof of the 
 motor signiftcancation of the regions in question. Similar degenera- 
 tions have been described by Brissaud^" as the result of lesions of 
 the frontal lobe in man. He has not been able to trace the dege- 
 neration into the pyramid, and concludes that the internal tracts 
 of the foot of the crus connect the frontal regions with the motor 
 nuclei of the medulla. Degenerations in this part of the crus 
 havo, according to his observations, been always associated with 
 
 *9 See Fig. 122, Functions of the Brain. 
 50 Contraction Permanente des Hemiplegiqiies, 1880. 
 
THE FRONTAL CENTRES. 149 
 
 psychical defects, apart from paralysis of the face or limbs. The 
 effects of electrical irritation, combined with those of destruction, 
 more particularly of the postfrontal region, indicate that this part 
 is related to the lateral movements of the head and eyes. Irrita- 
 tion, as wa have seen, causes opening of the eyes, dilatation of the 
 pupils, and conjugate deviation of the head and eyes to the oppo- 
 site side. At the moment of destruction of this region in the one 
 hemisphere there always occurs a temporary deviation of the 
 head and eyes to the side of lesion. This, however, is only transient 
 even when the destruction has been almost if not absolutely com- 
 plete. In two experimespts which I have described," after bilateral 
 destruction of the postfrontal area the animals were unable to 
 turn the head or eyes to either side for a day after the operation. 
 At first they were unable to look round when sounds were made 
 in proximity to the ear ; or, if they did, they moved the trunk and 
 head en masse. The removal of the prefrontal regions alone caused 
 no discoverable physiological symptoms, either sensory or motor. 
 But I found in several instances that after the symptoms which 
 followed destruction of the postfrontal area had entirely disap- 
 peared, the subsequent destruction of the prefrontal area induced 
 paralysis of the head and eyes of exactly the same nature as before. 
 I have confirmed these observations in a recent experiment. After 
 apparently the most thorough cauterisation of the whole of the 
 excitable frontal area, convex as well as mesial aspect, the animal, 
 which at first exhibited marked distortion of the head and eyes to 
 the side of lesion and inability to turn them to the opposite side, 
 recovered within three days to such an extent that the defects 
 were no longer perceptible. 
 
 A month later, extirpation of the prefrontal region, in advance 
 of the former lesion, induced the same condition as before, namely, 
 deivation of the head and eyes to the side of lesion, and total 
 inability to turn them to the opposite side. The conjugate devia- 
 tion of the eyes continued for some time after the movements of 
 the head had been recovered, but within three days no defect was 
 any longer capable of being made out in this respect. These facts 
 indicate that the prefrontal regions have the same functional re- 
 lations as the postfrontal. The transitory duration of the sym- 
 ptoms would be explained by the fact that the postfrontal centres 
 were not entirely destroyed. It is difficult to remove the whole 
 frontal area without inflicting injury on the head of the corpus 
 striatum. 
 In one case in which I removed the frontal lobe on both sides 
 
 »> Kxperiments li) and 20, /'At7. Trans., Part ii., 1884. 
 
146 CEREBRAL LOCALISATION. 
 
 tion of the muscular sense represents the highest degree of the 
 hemiacgesthetic scale." He refers me also to cases of ansesthesia*® 
 in which the sense of position or the limbs was entirely abolished 
 and " yet the patients were able to move the affected members 
 freely even when the eyes were closed. Under such conditions, 
 however, the movements of the limbs deprived of the muscular 
 sense are uncertain and hesitating." 
 
 These and similar facts show that the sense of movement is not 
 essential either to the due co-ordination or power of carrying a 
 movement into effect. Vision may entirely replace the muscular 
 sense, though, as one would naturally expect, volitional move- 
 ments effected only through the aid of vision are, when the eyes 
 are closed, less certain and precise that those which are accom- 
 panied also by a sense of movement. Tet these defects are 
 capable of being overcome in large msasure by practice; so 
 that, even when the eyes are closed, the visual conception of the 
 movement is capable of compensating entirely, or almost entirely, 
 for the loss of the muscular sense. That this does not occur in all 
 cases may be admitted, but the essential point is that it may in 
 some, and one case of thie kind is sufflcient to demonstrate that 
 volitional action is not necessarily bound up with sensations con- 
 ditioned by the muscular action itself. 
 
 It is conceivable that ideas of movements might be formed, and 
 volitional movements effected by a brain consisting only of visual 
 and motor centres. Under these circumstances, however, vision 
 would be largely occupied in directing movements, and the range 
 of muscular action and muscular adaptation would be infinitely 
 less than if these were guided, also, by sensations generated by 
 the movements themselves. By the so-called muscular sense, we 
 are able to conceive and execute movements which we have never 
 seen, but we are unable to conceive or volitionally execute move- 
 ments which we have neither seen nor felt. But though, under 
 ordinary conditions, the sensations of movement are the invari- 
 able accompaniment of muscular action, and are repeated as 
 often as the muscular action itself, this constant association does 
 not imply that the one is dependent on the other, or that the 
 musculo-sensory ideas of movement are the necessary or imme- 
 diate excitants of the movement itself. 
 
 Bastian holds that in addition to the conscious impressions 
 which accompany muscular action, and which he admits may be, 
 chiefly at least, localised in the falciform lobe, there are a set of 
 unfelt impressions which guide the motor activity of the brain by 
 
 *6 Diseases of Nervous System (Sydenham Society), vol. iii, pp. 304, 445, 463. 
 
TRE MOTOR CENTRES. 147 
 
 automatically bringing it into relation with the different degrees 
 of contraction of all the muscles which may be in a state of 
 action. To these unfelt impressions he gives the name " kin- 
 sesthesis," and he considers that the motor centres are the seat of 
 the "kin9B3thesis" or sense of movement. The so-called motor 
 centres are, therefore, according to him, in reality sensory centres 
 which excite the true motor centres of the spinal cord through 
 the pyramidal tracts which connect them therewith. I cannot 
 agree with Bastian in including in the muscular sense, which is 
 so essentially an act of conscious discrimination, the mere afferent 
 or unconscious impressions, through the agency of which the 
 harmonious co-ordination of the different segments of the spinal 
 cord and lower centres is secured, apart from the cerebral hemi- 
 spheres ; nor do I think that impressions, which practically do 
 not rise into consciousness, can be ideally revived or enter into 
 the composition of ideas or conceptions of movement. But if it 
 were the case, as Bastian assumes, that the ideal revival of kin- 
 aesthetic impressions is the immediate excitant of the true motor 
 centres in the spinal cord, it would follow that the so-called 
 motor centres would be independent centres of activity, irre- 
 spective of the stimuli from the sensory centres of the cortex. 
 Experiments show, however, that the motor centres are not inde- 
 pendent centres of action, for it has been found by Marique,*^ 
 whose experiments have been confirmed by Exner and Paneth, ** 
 that when the motor centres have been completely isolated, by 
 section of the fibres which associate them with the sensorj' centres 
 of the cortex, paralysis results of precisely the same character as 
 that which occurs when they are actually extirpated. Marique 
 proved that the same contractions were obtainable on electrical 
 irritation of the respective centres after, as before, isolation, 
 showing that they still retained their excitability and connection 
 with the pyramidal tracts. These experiments indicate, there- 
 fore, that the motor centres of the cortex are not independent 
 centres of action, but act only in response to the stimuli which 
 proceed from the sensory centres by way of the associating fibres 
 which connect them together. 
 
 If the true motor centres were situated only in the spinal cord, 
 one would expect to find the spinal motor centres developed in 
 correspondence with the motor capacities of the animal. In such 
 case the spinal motor centres of man, in whom the motor capa- 
 
 <' Centres Pxycho-moieum du Cerveau, 18S5. 
 ** " VerBuche iiber die Fo1>{en der Durchschneidung von AssociationB-fasera 
 • am Hundehlrn, Archivf. d. gex. Plujx., Ud. xliv, 1889. 
 
148 CEREBRAL LOCALISATION. 
 
 bilities are most varied and most perfect, should be developed far 
 beyond those of other animals, but precisely the opposite holds 
 For relatively as compared with the brain, and relatively as com- 
 pared with the size of the animal, the spinal motor centres of 
 man are less developed than those of the lower animals; and they 
 are absolutely lees than those of many animals whose capabilities 
 are of the simplest order. The development of the spinal motor 
 centres corresponds with that of the purely reflex synergic mus- 
 cular combinations of the related metameres or body segments; 
 while that of the cortical motor centres corresponds with the 
 multiplicity and complexity of the motor faculties, volitional and 
 cognitive. 
 
 From the various considerations above advanced I conclude that 
 the motor centres of the cortex are not the centres of tactile or 
 general sensibility, nor are they the centres of the muscular sense, 
 whether we regard this to depend on centripetal impressions, 
 conscious or unconscious, or on a sense of innervation; but that 
 they are motor in precisely the same sense as other motor centres, 
 and, though functionally and organically connected, are anatomi- 
 cally differentiated from the centres of sensation general, as well 
 as special. 
 
 Fhontax Centbes. 
 
 The region of the brain which lies in advance of the Rolandic 
 area and marked off by the precentral sulcus is one respecting the 
 functions of which there is still considerable doubt. Anatomi- 
 cally it is r.-lated to the motor tracts of the internal capaule. 
 These tracts, according to the investigations of Flechsig, lie in the 
 inner portion of the foot of the crus, and connect the frontal lobe 
 with the opposite cerebellar hemisphere indirectly through the 
 grey matter of the pons. Destructive lesions of the frontal centres, 
 both of the postfrontal and prefrontal regions, as I have shown 
 experimentally, cause descending degeneration of these tracts ^^ 
 not capable of being followed beyond the upper part of the pons. 
 The direction of the degeneration may be taken as a proof of the 
 motor significancation of the regions in question. Similar degenera- 
 tions have been described by Brissaud^" as the result of lesions of 
 the frontal lobe in man. He has not been able to trace the dege- 
 neration into the pyramid, and concludes that the internal tracts 
 of the foot of the crus connect the frontal regions with the motor 
 nuclei of the medulla. Degenerations in this part of the crus 
 havo, according to his observations, been always associated with 
 
 *9 See Fig. 122. Functions of the Brain. 
 50 Contraction Per manente des Hemiplegiques, 1880. 
 
THE FRONTAL CEXTRES. 149 
 
 psychical defects, apart from paralysis of the face or limbs. The 
 effects of electrical irritation, combined with those of destruction, 
 more particularly of the postfrontal region, indicate that this part 
 is related to the lateral movements of the head and eyes. Irrita- 
 tion, as wa have seen, causes opening of the eyes, dilatation of the 
 pupils, and conjugate deviation of the head and eyes to the oppo- 
 site side. At the moment of destruction of this region in the one 
 hemisphere there always occurs a temporary deviation of the 
 head and eyes to the side of lesion. This, however, is only transient 
 even when the destruction has been almost if not absolutely com- 
 plete. In two experim^qts which I havedescribed,'! after bilateral 
 destruction of the postfrontal area the animals were unable to 
 turn the head or eyes to either side for a day after the operation. 
 At first they were unable to look round when sounds were made 
 in proximity to the ear ; or, if they did, they moved the trunk and 
 head en masse. The removal of the prefrontal regions alone caused 
 no discoverable physiological symptoms, either sensory or motor. 
 But I found in several instances that after the symptoms which 
 followed destruction of the postfrontal area had entirely disap- 
 peared, the subsequent destruction of the prefrontal area induced 
 paralysis of the head and eyes of exactly the same nature as before. 
 I have confirmed these observations in a recent experiment. After 
 apparently the most thorough cauterisation of the whole of the 
 excitable frontal area, convex as well as mesial aspect, the animal, 
 which at first exhibited marked distortion of the head and eyes to 
 the side of lesion and inability to turn them to the opposite side, 
 recovered within three days to such an extent that the defects 
 were no longer perceptible. 
 
 A month later, extirpation of the prefrontal region, in advance 
 of the former lesion, induced the same condition as before, namely, 
 deivation of the head and eyes to the side of lesion, and total 
 inability to turn them to the opposite side. The conjugate devia- 
 tion of the eyes continued for some time after the movements of 
 the head had been recovered, but within three days no defect was 
 any longer capable of being made out in this respect. These facts 
 indicate that the prefrontal regions have the same functional re- 
 lations as the postfrontal. The transitory duration of the sym- 
 ptoms would be explained by the fact that the postfrontal centres 
 were not entirely destroyed. It is difficult to remove the whole 
 frontal area without inflicting injury on the head of the corpus 
 striatum. 
 In one case in which I removed the frontal lobe on both sides 
 
 »» Kxperiments Ifl and 20, I'hil. Trans., Part ii., 1884. 
 
152 CEREBRAL LOCALISATION. 
 
 character of experimental lesions, unilateral or bilateral, so far as 
 relates to the sensory and motor faculties in general ; and in 
 several a certain intellectual deficiency and instability of charac- 
 ter have been observed, not unlike those occurring in monkeys 
 and in dogs. Of fifty-seven cases of lesion of the frontal region, 
 collected from various sources, in two there was conjugate 
 deviation of the head and eyes ; twelve in which intelligence 
 was specially impaired ; and in all a total absence of paralysis of 
 the limbs. 
 
 Though I have occupied so much of your time, I have only 
 been able to treat of — and that in many respects very imperfectly 
 — the functions of the cortical centres so far as concerns sensation 
 and motion. There is another question which I have not con- 
 sidered at all, namely, the relations of the cerebral hemispheres 
 to the functions of organic life. This, however, is a subject 
 which is still involved in so much obscurity, and in reference to 
 which there are at present so few facts which are not suscep- 
 tible of different modes of interpretation, that I think it well 
 to wait for further light before hazarding any definite views of 
 my own. And I feel it all the less necessary to do so, seeing 
 that the subject in one of its principal aspects, namely, the rela- 
 tion of the hemispheres to the thermic functions of the body, has 
 been recently so ably placed before you by my predecessor, Dr. 
 MacAlister. 
 
 On the psychical aspects of cerebral localisation I have touched 
 only incidentally. This of itself would require a volume, and 
 that mainly of speculation. As to the questions vphich I have 
 treated more fully, and on which so many differences of opinion 
 at present exist, and will probably still continue, I shall be con- 
 tent if the facts and considerations which I have broaght before 
 you contribute to their solution, if only by stimulating work on 
 the part of others, with a view to arriving at conclusions which 
 shall be acceptable alike to physiologists and physicians. For 
 the true conception of the functions and relations of the cerebral 
 hemispheres, and their constituent centres is not only of the 
 highest scientific and philosophical interest, but of direct and 
 important practical bearing on the diagnosis and treatment of 
 cerebral disease. 
 
 London : Printed at the Office of the British Medical Assodation, 1,39, ,Strand. 
 
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