COLUMBIA LIBRARIES OFFSITE HEALTH SCIENCES STANDARD HX00028525 ijmUUMtittJiint.'ii; milium ; !«*.!:Mjiiii:iiiini"i EIOHET! HISTOLOGY AND PHYS. CEREBRAL CONVOLUTIONS. POISONS OE THE IN ! 1 1 1 1 1 1 ISM FOWL iiuiiMni jiiiiltiiii 111111111 |iii>i' nil I i lmiiiinii iiniiuiiHiiiuiill IIIIIKIIIllMllliilllllMllllll llll I tlllll'lllll; ln .UI!fllllliflllUllli:iMI!l!itMI!tlillllIllfllllM>IIIIM HIIIIIIIIHIHll' h illl!il|iliiiii;.iiii:!i.iii!iiiiii'iiii;in lltiiultiijimiWIjlfiHuttlli mm ilifili 11:1 ii'iiinliHiimiinmuim . liiiiiiiiilll'llilini: ■■■•MinhJufijiiiiiiuiiiiiiiitiiMiiiHiii llllltll till 11IIIHI IllltJII •iiiiiliiiilliimmiiMiiiiiiiiitiiiimiiiiiHMiiiii liWitilt tun iimmmitinimittiiiintiiii iiimmimimi ,af!lHlf»iu'iJ:iilliiMiii::iini Hjl|lmwijiimtiti:itiii;ltiii- THE SEGUIN COLLECTION OF BOOKS RELATING TO THE NERVOUS SYSTEM THE BEQUEST OF EDWARD C. SEGUIN, M.D. TO THE DEPARTMENT OF PATHOLOGY OF THE COLLEGE OF PHYSICIANS AND SURGEONS, NEW YORK. D It "b L- This book is not to be removed D00K\ ^ 7-~T\b f r om the Departmentof Pathology. Digitized by the Internet Archive in 2010 with funding from Columbia University Libraries http://www.archive.org/details/physiologyhistolOOrich PHYSIOLOGY AND HISTOLOGY Cerebral Convolutions ALSO, POISONS OF THE INTELLECT, BY CHAS. R1CHET, A.M., M.D., Ph.D., (Former Intern of the Hospital of Paris.) TRANSLATED BY EDWARD P. FOWLER, M.D. NEW YORK : WM. WOOD & CO., 27 GREAT JONES ST. 1879. Ksi Copyright by WILLIAM WOOD & COMPANY STEAM PRESS OF H. O. A. Industrial Schooi , 76TH St., near Third Avf. MM. BROCA and CHARCOT. PROFESSEURS À LA FACULTE' DE MEDECINE DE PARIS, WHO HAVE SO GREATLY HONORED FRENCH SCIENCE BY THEIR MAGNIFICENT WORKS UPON CEREBRAL CONVOLUTIONS. CHARLES RICHET, WV OTHER WORKS BY THE SAME AUTHOR. i. Recherches expérimentales et cliniques sur la sensi- bilité, in 8vo (Masson), 1877. 2. Les poisons de l'intelligence, in i2mo 1 P. Ollendorf), 1877. 3. Le somnambulism provoqué {Jour, de F anatomic et de la physiologie) , 1877. 4. Etude sur la douleur {Revue Philosophique), 1877. 5. Essai sur les causes de degoiit {Revue des Deux Mondes), 1877. 6. Du suc gastrique chez l'homme et les animaux, ses propriétés chimiques et physiologiques, in 8vo (Germer, Baillière et Cie.), 1878. AUTHOR'S PREFACE TO THE TRANSLATION. Should my work appear to its readers in some degree incomplete, as it certainly must, I will solicit indulgence upon the following grounds : i st. That discoveries in cerebral physiology succeed each other with exceptional rapidity, and any work upon this subject, after a few months of existence, of course fails to include an important mass of facts which each new day develops. 2d. To fairly understand this department in medical science, and to be able to explain it intelligently, exacts a familiarity with a greater number of sciences than does almost any other subject. First of all, it is, as a matter of course, requisite to be a physiologist: the most important results are derived from vivisections, but it must be learned (no small task) both how to make and to interpret them. There must also be a knowledge of surgical pathol- ogy in order to discriminate between cerebral commotions resulting from surgical processes (trephining, etc.), and those depending upon other (physiological) causes. Joined with this, proficiency in MEDICAL PATHOLOGY is imperative, in order to recognize those pathological con- ditions (cerebral atrophy, general paralysis, cortical Vlll AUTHOR S PREFACE. paralysis, aphasia, etc.) which are so inseparable from this study. There must be, too, a degree of acquaintance with the science of PHYSICS, as exemplified in understanding electric excitations, their number, frequency, diffusion, polariza- tion, etc. As for anatomy, a thorough knowledge of that which concerns the human subject is but the introduction ; com- parative anatomy, histology, embryology, and physiology are of still vaster importance, and for this purpose we are forced to the study of another science, zoology. Having surveyed the wide field of zoology and returned to the culminating object of our study — man — necessary com- parisons between human beings and races are impossible without the aid of another science, that of anthropology. Again, in cerebral physiology the science of psychology is especially requisite, for no one who has not deeply re- flected upon the processes of intellection is capable of producing a good cerebral physiology ; the very essence of the subject would be to him a closed volume. To be sure, this science, notwithstanding the many admirable works written, and the labors which many profound thinkers have bestowed upon it, is as yet in its rough outline. The laws of human thought, what is more mysterious ! They lie at the very foundation of our subject. The movement of the heart is its physiological function ; thought is the physiological function of the brain. Now the movement of the heart, though relatively easy to see and study, has required centuries of gropings and errors to become under- stood, and is there not much greater reason to anticipate like obstacles to a complete understanding of the action of thought, a subject so difficult to examine and analyze ? AUTHOR S PREFACE. IX The list might be indefinitely multiplied, and in all these sciences, each one of which is a life-long study, who can hope to be so perfected as not to be justly exposed to criticism ? I have been and perhaps will again be charged by my readers with a lack of positiveness, in other words of being skeptical. But the very accusation seems to me eulogis- tic, for in science there is nothing more baneful than to treat hypotheses as certainties. On the contrary, when serious criticism has revealed the defects and feebleness of an experiment, a real service has been rendered, for it may incite to new experiments and unequivocal conclu- sions. Inductions from probabilities or ill-demonstrated experi- ments are unreliable, and intelligent skepticism is more valuable to the advance of science than unbridled enthu- siasm. In connection with our subject, I would refer to one danger which should be guarded against and which has been somewhat overlooked. That is, recent labors have been accepted too much to the exclusion or neglect of those further in the past. It is an unfortunate tendency and one that results in injustice. For example : in the physiological history of the convolutions, some of the finest discoveries were made by Flourens. There are few experiments as interesting as that in which the pigeon, deprived of its cerebral lobes, sits plunged into a profound sleep of everlasting tinconscious- ness. I most fuily recognize that recent investigators, Fritsche and Hitzig, Ferrier, Charcot, and others have made mag- nificent discoveries; still it is Flourens who stands in the AUTHOR S PREFACE. front rank, and it need not be considered that the science of cerebral physiology dates from 1872. I am gratified that Dr. Fowler, who has already so ably translated Charcot's work upon Localization in Dis- eases of the Brain, has deemed my book worthy the same consideration. He has my full appreciation of the compliment and of the conscientious and scholarly manner in which his labor has been performed. Lastly, I do not feel that, in addressing itself to the American profession, my volume is going among strangers, for in science there is but one land and one people. Ch. Richet. Paris, April 29, 1879. TRANSLATOR'S PREFACE. Every student in medicine knows that an intelligent recognition of pathology, and a judicious, rational manage- ment of disease, are in exact ratio to a precise knowledge of normal anatomy and physiology. For this reason, Richet's Physiology and Histology of the Cerebral Convolutions seems a natural com- plement to Charcot's " Localization in Diseases of the Brain." In the anatomical portion, Richet includes the latest researches. As regards physiology, he indicates those points which are settled beyond dispute ; but where the matter is still under discussion, the arguments upon both sides are faith- fully given, and the author conscientiously abstains from lending bias by way of mere personal opinion or theory ; he is preeminently a dealer in facts. The author suggested that an abridged form of a little monograph which he has written upon " POISONS OF THE Intellect " would add somewhat to the interest of the physiological part of the book, and in compliance there- with, I have made the addition, which my friend Dr. John C. Minor has very kindly and ably translated and arranged. It was originally written as a popular article for non-pro- fessional readers, and hence the author has presented the Xll AUTHOR S PREFACE. subject as a study in psychology rather than in the more exact sciences of anatomy and physiology. In order to bring the subject within the required limits, it has been necessary to condense as much as the preser- vation of the original plan of arrangement would permit, and at the same time to eliminate everything that was not essential to the subject. Hence, perhaps the most inter- esting portion of the work, that which dealt particularly with illustrative cases and extended descriptions, was unwillingly sacrificed in order to present the work in its abridged form. New York, June, 1879. INDEX OF ILLUSTRATIONS PAGE Fig. i. — Pyramidal cell of middle occipital lobe (solitary cell of Meynert). (Mierzejewski) 9 Fig. 2. — Giant-cell : — paracentral lobe. (Mierjewski) 9 Fig. 3. — Section of cortical cell of deep layer (mag. 800 diam.). (Luys) 11 Fig. 4. — Section of third convolution. (Meynert) 16 Cornu Ammonis. (Richet.) Plate 1 26 Plate II 27 Fig. 5. — Portion of injected sheep's brain. (Gerlach) 39 Fig. 6. — Arteries of the convolutions. (Duret) 40 Fig. 7. — Lateral convolutions and sulci of human brain. ... 48 Fig. 8. — Inter-hemispheric convolutions of human brain. (Ecker) 49 Fig. 9. — Left hemisphere of dog's brain. (Ferrier) 50 Fig. 10. — Tracings of electric experiments. (Richet) 66 Fig. 11. — Tracings of electric experiments. (Richet) 66 Fig. 12. — Tracings of electric experiments. (Franck and Pitres) 67 Fig. 13. — Dog's brain explanatory of Fritsch and Hitzig's experiments. (Fritsch and Hitzig) 84 Fig. 14. — Dog's brain, left hemisphere. (Ferrier) 84 Fig. 15. — Monkey's brain, left hemisphere. (Ferrier) 86 Fig. 16. — Human brain, left hemisphere 87 Fig. 17. — Tracing of electric experiment. (Franck and Pitres.) 97 Fig. 18. — Tracing of electric experiment. (Franck and Pitres) 97 Fig. 19. — Monkey's brain, left hemisphere : lesion producing blindness. (Ferrier) 124 Fig. 20. — Brain of a Charruas, right hemisphere. (Leuret). 132 Fig. 2i. — Brain of Fieschi, right hemisphere. (Leuret) .... 133 Fig. 22. ) — Large plate at end of work, folded. Tracings Fig. 23- ^ of electric experiments. (Richet.) TABLE OF CONTENTS. First Part: Structure of the Convolutions. Sec. i. Historical, ..... i 2. General arrangement, ... 4 " 3. Organized elements, .... 6 " 4. General structure, .... 13 " 5. Special structure, .... 19 " 6. Structure in mammifera, . . . 32 " 7. White substance, .... 34 " 8. Vessels, ..... 38 " 9. Development, ..... 43 Second Part : Physiology of the Convolutions. Anatomical introduction, .... 47 Historical introduction, . . . . 51 Chapter First : Physiological Properties. Sec. 1. Excitability, ..... 59 " 2. Thermic, electric, and chemical conditions, . 72 " 3. Circulation, ..... 74 Chapter Second : Functions. Sec. 1. Motor Functions, .... 81 A. Methods of investigation, . . . 81 B. Action upon the muscles of animal life, . 83 C. Action upon the muscles of organic life, . 99 D. Aphasia, ..... 107 E. Theories of motor innervation, . . 109 Sec. 2. Sensorial Functions, .... 122 " 3. Intellectual Functions, . . . 130 Bibliography, ...... 141 CEREBRAL CONVOLUTIONS. FIRST PART. STRUCTURE OF THE CONVOLUTIONS. I. HISTORY. Although the arrangement and the morphology of the cerebral convolutions are now tolerably well known, their structure has not been described with corresponding exact- itude, and our latest knowledge upon the subject is still defective. We will first examine the opinions of the an- cient anatomists. Hippocrates' compares the brain to a gland : caput quoque ipsum glandulas habet; nam cerebrum glandulce simile. According to Malpighi 2 and Vieussens 3 also, the cere- bral cortex was a gland. With some reservations, Malpighi compares the cerebral glands to the hepatic lobule, — Non improbabile interim pit- tans iisdem ctiam acinis (of the liven has cerebri glandulas eouglobari posse.* Indeed, Malpighi supposed the brain to be composed of fibres and glands — Corticales glandulce tortuose pocatce exte- riores cerebri gyros componunt, et exorient ibus inde medullaribus fibris, sen vaseulis, appenduntur, ita ut ubicunque per trans- fer sum secantur gyri, détermina ta et fir ma semper glandu la- rum congerie medullœ affuudatur. 'Cited by Longet, Anat. et. physiol. du système nerveux, I., p. 160. '-' De cerebri cortice dissertatio, in Bibl. anat. de Manget, t. ii., p. S2. Ge- nève, 1699. 3 Institut, de méd.,t. iii., p. 109, 2d edition. 4 Loc. cit., p. 323. 2 CEREBRAL CONVOLUTIONS. I do not know that one can be as positive as Luys, 1 and affirm that Malpighi discovered the brain-cells ; yet it seems to me very probable. In another place he says : glandular inn exiguitas acicm microscopii subtcrfugit ; probably signifying that he expected to see the lobules, but has only seen simple, very small, non-agglomerated cells (?). However it may be, the ideas of Malpighi were soon forgotten. In 1698, Ruysch, 8 from the results of his mar- vellous arterial injections, considered the cerebral cortex as a vascular network. That opinion, advanced some time before by Leuwenhoeck, was generally adopted by anato- mists. Boerhave," who at first had admitted the opinion of Malpighi, finally adopted that of Ruysch. The theory of Ruysch rested upon an exact fact : the extreme vascularity of the cerebral cortex. At first no objection was offered. At the time of Haller 4 (1766) the opinion was classic. It was admitted that there were ar- teries which could be injected, and others which were in- visible and which could not be injected — all being plunged into a very fine cellular woof. There were distinguished in the brain a white portion (medulla) and a gray portion (cinereus cortex) made up by a mesh of arteries. The first anatomist who gave a good idea of the cere- bral structure was probably Vicq d'Azyr." He pointed 1 Le cerveau et ses fonctions, p. 15. ■' Thesaurus anatom., vi., n. 73, thés, iv., n. 78, p. 78 ; p. Si (citation of Hal- ler, t. iv., epist. xi., p. 24). 3 Cited by Haller, elementa phys., iv., p. 25. 4 Loc. cit., p. 27. 5 Vicq d'Azyr thus expresses himself : "In preparing the centrum ovale of Vieussens, if the form of the posterior cerebral convolutions which lie upon the tentorium cerebelli be examined, there generally will be noticed several that are remarkable on account of a while line which longitudinally divides the cortex, following all its conlours, and which give to that portion of the cor- tex the appearance of a striped ribbon. I have found that arrangement in no other region of the brain." That remarkable observation of Vicq d'Azyr, though not overlooked, was not utilized, and it is but recently that Broca was the first to make apparent its importance. — Upon the special structure of the inferior convolutions of the occipital lobe ; constant presence of the striped rib- bon of Vicq d'Azyr. — Bull, de la soc. d'anthropologie, 1861, /. ii.,p- 313. STRUCTURE OF THE CONVOLUTIONS. 3 out that the gray cortex was really composed of three layers : a white layer between two gray layers, giving to the gray substance the appearance of a striped ribbon. The fact was generally accepted, being exact and indis- putable. Gennari, 1 however, admits the existence of a peculiar yellow substance between the central white sub- stance and the cortex. Subsequent observations have shown that this yellow layer is in reality the deeper por- tion of the cortex. In 1 840 appeared the standard work of Baillarger a ; that eminent anatomist announced that the gray portion of each convolution was composed of six layers, alternately gray and white. To demonstrate his proposition, Baillarger examined the convolutions both by transmitted and direct light. When rendered transparent, the gray layers appeared clear, the white opaque. Baillarger showed that in voung infants this appearance was very marked, and could be found even in the foetus of four or five months. It was about this time that the microscope was brought into use, and with that the minute structure of the convo- lutions could be investigated. The discovery of nerve- cells by Ehrenberg, Valentin, Purkinje (1835 to 1840) de- monstrated the presence of nerve-cells very variable in form in the cerebral cortex. Whatever may be the interest belonging to the revolu- tions from that time-to the present concerning the subject of nerve-tissue, I cannot stop to consider it. Respecting the convolutions, Mevnert is certainly the first who has given an exact description accompanied with good illustrations. At the same period, Luys, in his grand work upon the nervous system, established the connection of the cortical and ganglionic systems of the brain. After Luys and Mey- 1 Cited by Longet, loc. cit., t. i., p. 608. 2 Recherches sur la structure de la couche corticale des convolutions du cer veau. — Mém. de l'Acad. de méd., t. viii., 1840. 4 CEREBRAL CONVOLUTIONS. nert ought to be cited the work of Betz, who first described certain cells in the motor-centres of the cortex. Also the staff of the Lunatic Assylum of London has recently pub- lished a series of valuable works upon the structure of the convolutions. Reviewing this rapid history we find : i st. That probably Malpighi discovered the cells and nerve-fibres of the cerebral cortex. 2d. That Vicq d'Azyr and Baillarger have well de- scribed the structure of the convolutions as seen by the naked eye. 3d. That Meynert, Luys, and Betz have made known the microscopic structure. Sec. 2. GENERAL ARRANGEMENT OF THE CONVOLUTIONS. If a human brain, divested of its membranes, be examined, it will be observed that the surface is of an ash-gray, cov- ered with a multitude of furrows variable in dimensions, irregular in appearance, and which limit the projections, the elevations of which are the cerebral convolutions. 1 Thus each convolution forms an oblong mass, with blunt and rounded angles so confounded at each end with other convolutions that the precise point of commencement and ending can only be schematically designated. It rests against one or more of the neighboring convolutions, and the intervening furrow, empty when the pia mater and arachnoid are removed, is, when the membranes are in place, filled with vessels. The joining faces of the convolu- 1 Gratiolet proposed to replace this unwieldly and inexact term (as applied to the lower mammifera at least) by the word fold (plis), but usage has not sanctioned the term. Perhaps, as Broca suggests, they might be called volu- tions. STRUCTURE OF THE CONVOLUTIONS. 5 tions are filled out, and they so join each other that the intermediate furrow is divided into two parts, the superior one for the veins, the inferior for the arteries. The entire gray cortex, here rising into a convolution, there sinking into a furrow, may be looked upon as a continuation of a single layer folded upon itself. This was Gall's idea, an ingenious one, and well calculated to express in schematic and easily-to-be-remembered manner the construction of the exterior cerebral covering. The gray and white substance of the convolutions form a cortex sometimes called convolutionary, which should, according to Burdach and Broca, 1 be called palleum or manteau (mantle). The remainder of the cerebral hemisphere forms the body of the brain. The convolutions are separated by furrows of various depths, and according to their depths and their morphol- ogy they are differently named, fissures, furrows, creases." It should be especially observed that none of these fissures or furrows serve to completely separate adjoin- ing convolutions, the continuity of which is never inter- rupted. To employ a common comparison, the cerebral convolutions represent a chain of mountains in which no valley traverses in such manner as to isolate the mountain peaks and plateaux. Nowhere upon the brain do two transverse, parallel furrows intersect two longitudinal parallel furrows. In-short, all the furrows are incomplete — insufficient, as it were — as though they were unable to at- tain to the extremity of the convolution with which they commenced. Perhaps this may be of some importance in a functional point of view. Broca thus defines the term convolution : a — " The word, 1 Revue d'anthropologie, 1878, p. 197. 2 See article, Circonvolutions (Pozzi), Diet, encyclop. des sciences me'd.,p. 342. 3 Anatomie comparée des circonvolutions cérébrales. — Revue d'anthropologie, 1878, p. 391. 2 6 CEREBRAL CONVOLUTIONS. convolution, which has heretofore been employed to designate some portion of the folded surface of the brain, has now come to have an accepted meaning : it is applied to the subdivisions of lobes, and if in some cases a lobe can be composed of a single convolution, on the other hand no convolution can exceed the limits of its lobe, even though it may continue more or less directly with a convolution of a joining lobe." As fissures differ in importance, so also do convolutions. To slightly marked furrows and to creases belong convo- lutions which are barely outlined, and which, according to Pozzi, may be called folds. But however greatly the fur- rows and convolutions may vary in size, the structure is always the same, and consequently a general description applies to the entire mass. In certain parts of the brain the cortex folds upon itself, and by invagination forms an inverted convolution (gyrus Hippocampi), but here, too, the structure and arrangement are the same. A point which should be well observed, but which we cannot properly dwell upon here, is that the convolutions, in most individuals at least, are not symmetrical. Sec. 3. ORGANIZED ELEMENTS OF THE CON- VOLUTIONS. As observed by the anatomists of the last century, each convolution is composed of an external gray layer which exactly fits to the central white part : both receive vessels. We have, therefore, to study : — 1 st. The gray layer, the cortex of the convolution (cor- tex cerebri). 2d. The white layer, which forms the axis. 3d. The vessels distributed to each layer. STRUCTURE OF THE CONVOLUTIONS. 7 The gray cortex probably is not a homogeneous layer ; Baillarger 1 maintains that it is composed of six layers, being arranged from without towards the centre as follows : — i. White layer. 2. Gray layer. 3. White layer. 4. Gray layer. 5. White layer. 6. Gray layer. The four internal layers are often confounded in a single yellowish-red layer, by some authors described as a special layer.'- Meynert holds to five layers. 3 Mathias Duval' admits either five or six layers accord- ing as one counts the fifth and sixth as one or two. Lewis 5 admits, in the human subject, five layers. All these layers of gray substance contain four varie- ties of organized elements : pyramidal, giant and fusiform cells, and granules (myelocytes). 1 st. Pyramidal Cells. — -These are the most numerous and are generally small and more difficult to discover than in the corresponding layers of the cerebellum. They are provided with several slender, pale, ramified prolongations of which three kinds can be distinguished. 7 a. The pointed extremity of the cell, directed towards the periphery, continues by a fine thread which bends backwards 8 (pyramidal prolongation of Meynert). 1 Loc. cit. et Comptes rendus de l'Ac. des sciences. -See Kôlliker, Elém. d'hfstol., French trans., p. 357. 3 Journ. de l'anat., 1874, t. x., p. 100. — Pouchet, Traité d'hist., p. 307. 4 Art. Nerveux (système) du Diet, de méd. et de chirurgie pratiques, p. 480. 5 On the Comparative Structure of the Cortex Cerebri ; Brain. 1878, p. 82. 6 In Henle's Handbuch der Nervenlehre, 1871, p. 277, will be found a com- plete resume of opinions expressed respecting the number of layers contained in the gray cortex. 1 Pouchet and Tourneux : Traité d'histol., p. 307. — Meynert: Strieker's Handbuch, I., p. 708. s This opinion, contrary to that of Biitzke (Archiv. fur Psychiatrie, 1872, t. iii., p. 300, has been admitted by Arndt (Arch, fiir microscop. Anat., 1874). 8 CEREBRAL CONVOLUTIONS. b. Laterally the cell gives from each side prolongations which are either oblique or perpendicular to its axis. c. At the base of the cell is a prolongation analogous to the prolongation of Deiters (basal prolongation of Mey- nert). These cells are generally in form of pyramids or trian- gles, the bases of which face the white substance, the points being directed towards the periphery. These two cellular prolongations have been very well represented in their normal state by Mierzejewski in two figures, which we here reproduce. In the human subject it is difficult to see the basal pro- longation, but that is no reason, as Arndt ' has vainly en- deavored, for putting in question its existence. Naturally it is very difficult to follow to the terminations of the prolongations, and perhaps only a moderate degree of confidence should be given to the investigations of Golgi. 2 Golgi believed to have seen the basal prolonga- tion of the pyramidal cells passing backwards, and, after a short distance, dividing and giving lateral branches, which, bending back again, ran to the periphery of the brain. The other prolongations are in connection with the con- junctive or granular cells. The anastomoses of the various parts were first illustrated by Luys, then by Besser 3 and Arndt. According to Koschewnikoff, the basal prolongation may be followed into the white substance, where it is surrounded by myéline, and becomes the axis-cylinder of a nerve. 4 Boll '" considers the pyramidal form of the cells the result of the preparation : treated with osmic acid, which sur- prises them as it were living, they are circular. 1 Arndt : Studien tiber die Architectonik der Grosshirnrinde, Max Schulze's Archiv, 1874. 2 Sulla struttura della sostansa grigia del cervelle». Communie, preventiva. Gaz. méd. ital. Lomb., ser. 6, t. vi. 3 Eine Anastomose fur die Centralen Ganglien-Zellen. Virchow's Archiv, Bd. 36. 5 Arch, fur Psych., 1873. 4 Koschewnikoff : Arch, de Schultze, 1869, p. 332 et 375. STRUCTURE OF THE CONVOLUTIONS. Fig. i. Fig. 2. Fig. i (After Mierzejewski). — Pyramidal cell of the middle occipital lobe (solitary cell of Meynert). Fig. 2. — Giant cell, common to the paracentral lobe. At the lower part, the basal prolongation ; at the upper part, the pyramidal prolongation. IO CEREBRAL CONVOLUTIONS. They are often supplied with pigmentary granulations. According to Luys, 1 they have, in fresh specimens, an amber-yellow color, and are provided with a brilliant nucleus and a nucleolus. It seems possible to penetrate still further into the inti- mate structure of the cell. Without discussing this ques- tion, histologically so interesting, we would remark that the researches of Harless, Wagner, Flemming, Stark, and others indicate that the nerve-cell is a very complicated structure. The study of the minute structure of the nerve- cells, however, has generally been pursued in the spinal cord of the ox (anterior cornua), few observations having been made of the cells in the reticulum of the cerebral cor- tex. Luys, however, has well described these cells, and below is the plate which he gives (Fig. 3). That learned anatomist considers the cellular body to possess a truly reticulated structure. The reticulum is made up of fibrillar, which, arranged like the trellis of a willow-basket, converge towards the nucleus of the cell. Some of the pyramidal cells are small, 10 mm.; others average 22 mm. According to Luys, who first described them, their number approximates about no to the square millimetre — a considerable number, considering the sur- face of the brain, as compared to the small number of the medullary cells. Thus there are very many more cells in the brain than in the spinal cord. It appears that the protoplasmic prolongations of all the cells anastomose in such way as to form a fine nerve-net- work, analogous to that found in the spinal cord (Gerlach and Boll.) Biitzke 2 considers a distinctive characteristic of the nerve- cells of the cortex cerebri to be the longitudinal striation of the cellular body, as well as of its prolongations ; the same as transverse striations characterize muscular fibre. 1 Le cervau, 1876, p. 14. ■ Loc. cit. p. 589. STRUCTURE OF THE CONVOLUTIONS. II 2d. Giant-cells. — There is another variety of cells found in certain regions, which are remarkable on account of their size. They are faithfully described by Betz, 1 who calls them giant-cells. 2 They attain a diameter of 50 mm. Mier- zejewski says that they always contain a yellowish-brown pigment. 3 It is generally believed that they are very \ Fig. 3. Fig. 3 (after Luys). — A cortical cell of the deep layers — about 800 diameters. The cell is divided in its long axix, and the interior texture can be seen. A represents the superior prolongation, coming from the body of the cell. B, lateral and posterior prolongations. C, spongy, areolar substance, in which is found the cellular stroma. D, the cell seems to have the same thickness as the stroma ; it sometimes has a radiated appearance. E, the brilliant nucleolus is also decomposable into secondary fibres. 1 Anat. Nachw. zweier Gehirn-Centra. Centralblatt, 1S74, Nos. 37 and 38. - Mierzejewski (Arch, de physiol., 1875, p. 226) observed them one year prior to Betz perhaps, but the determining of their topography undoubtedly belongs to Betz. 3 Loc. cit., p. 228. 12 CEREBRAL CONVOLUTIONS. analogous to the pyramidal cells, from which they differ only in size. 3d. Myelocytes. — The myelocytes, or granules, are especially abundant in the lower layers of the cortex. They should not be regarded as cells, but as cellular nuclei, the cellular body which surrounds them being very reduced, and requiring special preparation in order to be seen. There is a lack of accord concerning the nature of these elements, though present opinion seems inclined to view them as embryonic nerve-cells. Biitzke holds that between the granules and the true conjunctive cells there is an entire series of intermediate bodies. Perhaps observation has here been too much adapted to the support of a theory. It is possible that there may be in the gray cortex cere- bri every transition between these cells (of which the nuclei are the granules) and the nerve-cells proper. Per- haps we should consider as the element of transition from the granule to the nerve-cell, these irregular, globular, non- pyramidal cells described by Meynert, and apparently resembling the elements of the granular layer of the retina. All this is still obscure. 4th. Fusiform Cells. — This variety has been described bv Mernert, and prior to him by Berlin ;' they are fusiform (spindelfôrmig), generally bipolar, one prolongation being directed towards the periphery, the other towards the centre. According to Lewis, they are found in every part of the encephalon, and always in the most internal layer of the cortex, which they serve to characterize. They are very abundant in the claustrum (avant-mur), as we will see further on. Between the fusiform, pyramidal, and giant-cells there exists a fine, granular, amorphous substance more or less abundant, a description of which has been given by Robin. 1 Berlin : Beitrage zur Structurlehre der Gross-Gehirnwindungen. Erlan- gen, 1858. J, STRUCTURE OF THE CONVOLUTIONS. 1 3 German authors generally consider this amorphous mat- ter to be conjunctive tissue ; concerning the myelocytes, anatomists are greatly at variance ; but that discussion would carry us too far and outside of our subject. To complete a mention of all the elements to be found in the gray cortex, we should add the very minute fibril prolongations of the nerve-cells, and also the vessels sur- rounded by a lymphatic sheath. A résumé gives as follows : i. Pyramidal cells. 2. Giant-cells. 3. Myelocytes. 4. Fusiform cells. 5. Amorphous substance. 6. Fibrillary nerve-prolongations. 7. The vessels with their lymphatic sheaths. Sec. 4. STRUCTURE OF THE CONVOLUTIONS IN GENERAL. Let us now examine the relations of these diverse ele- ments and the arrangement of the concentric layers. We will cite especially from the works of Meynert 1 and Lewis." We will describe, as Meynert has done, the general type of the convolutions, following this with the special struc- tures of this or that one. A. First Layer (external). — This layer is formed almost exclusively of amorphous substance and contains few if 1 Der Bau der Grosshirnrinde und seine ôrtlichen Verschiedenheiten, Wien. Med. Jahrb., 1869; Jour, de l'anat., t. viii., 1S72, p. 106; t. x., 1874, p. 98. Strieker's Handbuch fiir Geweblehre, t. i„ p. 694 et suiv. An excellent îësumé of the latest microscopic researches is to be found in Charcot's Leçons sur les localisations, 1876, p, 20 et suiv. * On the Comparative Structure of the Cortex Cerebri. Brain, 1878, No. 1, p. 79. 14 CEREBRAL CONVOLUTIONS. any nerve-cells. To the unaided eye it appears white, as Baillarger long since observed. Kolliker described and figured it 1 as being especially composed of very fine, inter- mingling tubes. They are the fibres which Valentin, at the commencement of microscopy, called terminal handles, indeed, according to Kolliker, such would be their appear- ance. This layer contains few vessels ; only the arterioles going from the pia mater to the cortex. This has been observed by Duret; 2 besides, it is a general law in the structure of the nervous system that the parts richest in cells are the ones most abundantly supplied with blood- vessels. The illustration by Luys 3 is very exact. Meynert and Kolliker regard this layer as conjunctive ; that opinion, however, is not general, and Henle, Wagner, Stilling, and Robin think it a true nerve-layer. According to Meynert, its thickness in different animals would correspond to the cortex entire ; one-eighth for man, one-seventh for the monkey, one-sixth for the dog, one- fifth for the cat, one-fourth for the mole, one-third for the calf. According to Lewis, 4 in the sheep its thickness would be about 0.55 mm., the entire thickness of the cortex being about three mill., that is about one-fifth. Lewis gives to the external layer in the human brain a diameter of from .250 to .340 millimetres, about the fifteenth or sixteenth part of the entire thickness of the cortex, a figure notably different from Meynert's. According to the same author, there are immediately under the pia mater, cells analogous to the cells of Deiters, adherent to the vessels and so connected with them and the pia mater that in removing the vascular membrane of the encephalon the first layer of the cortex is taken with it. 1 Elém. d'histol., French transi., 1872, p. 399, fig. 206. 2 Arch, de physiol., t. vi., pi. 6, figs. 2 et 3. 3 Le cerveau, p. 12, fig. 1 ; the cut is a faithful reproduction of the beautiful photographs which M. Luys has kindly shown me. 4 Loc. cit., p. 92. See the excellent plates which he has given of the struc- ture of the human convolutions (plate 1), of the cat's (plate 2), of the sheep's (plate 3). STRUCTURE OF THE CONVOLUTIONS. 1 5 He has seen this both in man and in the sheep ; Major has noticed the like with the baboon. 1 Boll and some other authors (Gerlach, Golgi) hold the outer layer to be mostly composed of Deiters' cells. B. Second Layer (compact pyramidal). — The second layer is almost entirely composed of numerous small pyra- midal cells crowded against each other. Lewis gives to these cells a diameter of from 9 to 13 mm. They are a little larger than the cells of the first layer. There is a little amorphous matter. 2 This layer is generally thin. The schematic tables of Lewis make it the thinnest of all the cortical layers. Its thickness seems to be tolerably constant, not only in the various regions of the encephalon, but also with various animals. Luys considers it the zone of the sensorium commune; the opinion, however, is yet a hypothesis. C. Third Layer [ammonique). — The third layer is also composed of pyramidal cells, but of a larger size than the preceding, some of them reaching a diameter of 51 mm. (Lewis). By some, the layer is divided into two distinct layers and indeed the most' voluminous cells seem to pre- dominate in the inner portion of the layer. Meynert thinks the cells fusiform rather than pyramidal, and pro- poses to name the layer, the Layer of the cornu Ammonis, as the fusiform cells are the only kind found in the cornua Ammonis. In addition to these cells, there are in this layer fasciculi of medullary fibres which rise perpendicu- larly to the surface- of the cortex, forming columns-like between the groups of pyramidal cells ; the arrangement is well depicted in the illustrations of Luys and Meynert. It should be observed that this third layer is thicker than the first two layers combined. Its appearance differs greatly according to the region of the brain examined and 1 Observations on the brain of the Chacma Baboon. Journal of Mental Science, Jan., 1876, p. 49S (see plate 1). - This layer has been well represented by Duval : art. Nerfs, du Diet, de Méd. et chir. prat., p. 480, fig. 74. i6 CEREBRAL CONVOLUTIONS. ►3 / 4, M;U itell this is chiefly dependent upon the presence or not of the giant-cells of Betz which are only found in the motor centres of the cortex cerebri. 1 D. Fourth Layer (gran- ular). — The Fourth Layer is chiefly composed of myelocytes, lying regularly side by side : the general arrangement of this layer allows it to be compared with the granular layer of the retina, an interesting similarity to which we will have occasion to revert. E. Fifth and Sixth Layers (claustral). — This layer seems to be the most important of all those which combine to form the cortex cerebri. It has a reddish-yellow color (Kôlliker) due to pigment- ary cells (which are very abundant in aged subjects), and is made up of cells, and FlG. 4 (after Meynert). — Section of the third frontal convolution of man. (Enlarged 500 times.) 1. Superficial layer, poor in nerve elements. 2. Layer of small pyramidal cells. 3. Layer of great pyramidal cells. 4. Layer of globular cells. 5. Layer of fusiform cells. See Charcot, loc. cit., p. 27. STRUCTURE OF THE CONVOLUTIONS. \J of fasciculi which form isolated loops, the convexities of which are turned towards the surface of the brain. The fibres composing the fasciculi are at first about 2.6 to 6.7 mm. in size, but at the external portion they become ex- tremely fine, 0.9 to 1.8 mm. in size (Kôlliker). Some authors have thought that they have seen these fasciculi ramify and divide, within the cerebral cortex, be- tween the gray and white substance, 1 but that appears yet doubtful. It is important to study also the cells. Their form is so characteristic that Lewis terms this inner layer of the cortex the ganglionic layer. They are sometimes stel- late, sometimes pyramidal, and sometimes fusiform (large cells of volition of Robin). The fusiform cells are espe- cially abundant at the deeper part of the fifth layer, so much so that it may be viewed as a sixth layer (Meynert). These cells generally present a cylinder-axis (prolongation of Deiters ; basal prolongation of Meynert) directed to- wards the white cerebral substance. Meynert thinks they ought not to be called bipolar, that they probably give off other lateral prolongations more difficult to see. The dimensions of the fusiform or pyramidal cells are sometimes comparatively enormous, as has been observed by Betz. Lewis gives to the largest, diameters of 126 mm. The dimensions, however, vary greatly, as we will see fur- ther on, according to the regions examined. The fifth layer has nearly the thickness of the third. In a rough way, allow- ing the entire cortex a thickness of three millimetres, the internal or fifth layer would have one millimetre, the third the same, and the first, second, and fourth combined, one millimetre ; of course this is but approximative, still it is sufficiently close to the observations which I have made upon various preparations, and to the illustrations of the various authors. As to a name for this last layer : As Meynert compares 1 Hessling and Schaffner, cUed by Kôlliker, lue. cit., p. 402. I 8 CEREBRAL CONVOLUTIONS. it to the claustrum {avant-mur), and as Vicq d'Azyr, who first closely studied the avant-mur, called that the claus- trum, 1 would propose to call the last cortical layer the claustral layer, a term which has the advantage of recall- ing- the discovery of Vicq d'Azyr, and which at the same time does not prejudge its function. Thus we would have the following layers : i. External limiting layer. 2. Compact, pyramidal layer. 3. Layer ammonis. 4. Granular layer. 5. Claustral layers, superficial and profound. 1 The entire gray layers of the brain have a certain thick- ness, which the medical superintendents of the insane have frequently studied in order to ascertain if there exists a relation between its dimension and the mental condition of their patients. Their results are not yet definite. It is supposed, however, that the greatest depth of the cortex is to be found in the brains of the most intelligent. H. Major, with the aid of an ingenious instrument (Te- phrylometre) has ascertained : 1 st. That the thickness of the cortex varies considerably in the different convolutions of the same brain. 2d. That the variations in thickness were not homolo- gous in different brains. Unfortunately these researches have been made upon the insane, and cannot serve in any way to elucidate that very interesting question in normal anatomy. 2 The designations given are those which we shall hence- forth employ ; they will avoid fatiguing repetitions and facilitate descriptions. 1 These divisions must not lead to the supposition that the layers are dis- tinctly marked. The limits of the layers are to a considerable degree artificial, and vary somewhat according to the will of the observer, and to the process employed in making the preparation (Luys). 3 H. Major : A new Method of Determining the Gray Matter of Convolutions. Lunatic Asylum Report, 1872, p. 67. STRUCTURE OF THE CONVOLUTIONS. 19 Sec. 5. STRUCTURE OF INDIVIDUAL CONVO- LUTIONS. We will first study the motor and the sensorial zones of the cortex, and then the special convolutions (the lobe of the island of Reil, gyrus hippocampi, olfactive bulb, etc). The anatomical difference in the motor and sensorial zones escaped Meynert, and it was only later, guided by physiology and pathology, that anatomists have been able to discover it. An important point well brought into relief by Lewis is. that these differences between the zones are never abrupt, it is always gradual, giving place to a transitional zone as it were. We will first study the type of the paracentral lobule, as it has been studied by Betz. Morphology, as elsewhere indicated, assimilates that lo- bule, in a functional point of view, with the two convolu- tions bordering the fissures of Rolando (asc. frontal and asc. parietal). The paracentral lobule and the two Rolandic convolu- tions are characterized by the presence of the giant-cells of Betz. These cells, already described, 1 are found in all the parts which are considered motor-centres. Charcot" remarks that this fact is the more interesting for the reason that these cells are found in all the points considered as motor-centres, whatever may be the mor- phological difference in the convolutions. In the dog they surround the crucial furrow. Now it has been for a long time known that the motor- cells of the spine are very voluminous, whilst in the sen- sorial regions they are very small, or medium sized. So anatomy as well as physiology indicates a relation be- 1 See page 9, fig. 1. - Loc. cit., p. 29. 20 CEREBRAL CONVOLUTIONS. tween the size of the cells and their functions. Where there are motor-centres there are large cells ; this is true of the cortex cerebri as well as of the spinal axis. To this knowledge Pierret 1 has added the interesting fact that the dimension of the 'nerve-cell is not only pro- portionate to its function, but that it also holds relation to the distance to which it must transmit the motor incita- tion ; that seems proven in case of the spinal cord, and perhaps an analagous demonstration will be arrived at in case of the brain. The large cells are found more especially in the zone Ammonis (third layer), and in the claustral zone (fifth layer). Lewis, who has studied the details of their distribution, gives the following measurement : In man- Asc. front. Asc. pariet. In the cat — Gyrus sig. In the sheep — Gyrus sig. CLAUSTRAL LAYER. 126 m. 55 m. 2 88 m. 41 m. 106 m. 32 m. 65 m. 23 m. LAYER AMMONIS. 41 m. 23 m. 51m. 32 m. 23 m. 13 m. 18 m. 10 m. For more details upon this question we refer to the memoir of the author. The motor-cells seem to form in groups in very limited zones, with a determined and constant situation in certain points of the cortex cerebri ; each group appears to be di- vided into a series of secondary groups, which are the nests {nids) described by Betz. Except the great cell-layers, the layers in the motor- zones have no special characteristics ; at all events, the details given by certain authors are too accessory or too uncertain to be mentioned. I will say the same respect- ing differences between superior and inferior regions of the same convolution. 3 As for the cells of the transition-space between the motor 1 Comptes rendus de l'Acad. des sciences, 1878, 1, p. 1423. - The two figures indicate the large and the small diameters. 3 See the tables of Lewis. STRUCTURE OF THE CONVOLUTIONS. 21 and sensorial zones, the change is not brusque, and the cells, though larger than in the occipital lobe, are yet smaller than in the convolutions anterior to the fissure of Rolando. To a certain degree the ascending parietal con- volutions may be considered as the transition zone. In man, the cells of that convolution measure : At the top 88 — 41 m. In the centre .... 55 — 32 m. At the bottom .... 41 — 24 m. To Lewis' opinion may be added that of Betz, who held that there were two fundamental regions, separated by the fissure of Rolando. Anteriorly were the great-cell, and posteriorly the small-cell convolutions. Physiology does not confirm this distinction, for the ascending parietal con- volution, back of the fissure of Rolando, manifestly belongs to the motor-region. In accordance with Lewis, however, this convolution can be considered as representing a transi- tional zone. Occipital Type. — The sensorial (?) convolutions em- brace : 1 st, the cuneus ; 2d, the posterior half of the lingual and fusiform lobules ; 3d, the occipital lobe ; 4th, the first two sphenoidal convolutions and the marginal fold. 1 All these convolutions have a structure apparently differ- ent from the anterior parts. Vicq d'Azyr observed a white band {ruban de Vicq d'Azyr) between two gray layers, the whole constituting the gray cortex of the posterior convolutions. The correctness of this observation has been confirmed and perfected by modern researches. The layer Ammonis (third) is seen to be replaced by two layers of myelocytes with fewer cells, though relatively voluminous. The morphological modification of the layer Ammonis can be otherwise described in saying that the original has disappeared and been replaced by the exten- sion of the subjacent granular layer, divided into three secondary layers, so furnishing eight layers. 1 Charcot, loc. cit., p. 29. 22 CEREBRAL CONVOLUTIONS. Clarke ' takes the structure of the occipital convolutions as his starting point in the description of the cortex cere- bri ; he recognizes the two granular zones, but makes no difference between the fusiform and granular cells. Meynert found, in various parts of the granular layers, cells which he called solitary, and which he deemed very voluminous, though they are not so large as the cells of the motor-regions. Probably they belong to the pyramidal type. Let us now compare the structure of the posterior sen- sorial convolutions with that of the retina, a sensitive expansion and in the embryo all but an encephalic convo- lution. Owing to the curve of the retinal layer, and to the atro- phy of the posterior lamina, which forms the pigmentary layer, the anterior lamina becomes the homologue of the superficial encephalic layer, in such way that the most superficial portion of the convolutions are morphologically represented by the most profound layers of the retina, those which are in contact with the vitreous humor. We can establish a sort of parallel between these various parts, and group them thus ; of course, somewhat artificially : OCCIPITAL CONVOLUTIONS. External limiting. Represented by the handle- fibres of Valentin and Kôlliker. Pyramidal layer. External granular layer, which replaces the layer Ammonis. RETINA. Internal limiting. Layer of nerve-fibres. Layer of nerve-cells. Layer of myelocytes. Intermediate layer. Layer of myelocytes. External limiting layer. — Exists in the retina only as a rudiment. Membrana Jacobi. Internal granular layer. Claustral layer. 1 Clarke: Proceedings of the Royal Society, London, 1863. STRUCTURE OF THE CONVOLUTIONS. 23 In brief, from its structure, development and function, the retina can be regarded as an expansion of the sensorial cerebral cortex. Such, then, are the principal differences existing between the posterior and anterior motor parts of the cortex cere- bri, and they may be expressed in two propositions. A. The motor regions possess giant-cells located in the layer Ammonis and throughout the claustral laj^er. B. In the posterior regions the layer Ammonis is replaced by a granulo-glandular layer. We will now examine the arrangement in some special convolutions. Meynert describes three distinct types : — 1, Found in the fissure of Sylvius and the Island of Reil ; 2, in the cornu Ammonis ; 3, in the olfactive bulb. Tvpe of the Fissure of Sylvius. — The convolutions surrounding the fissure of Sylvius are remarkable only for the development of fusiform cells, which form a deep claus- tral layer, better limited here than elsewhere. Notwithstanding its obscurity, and perhaps because of its obscurity, here arises an important morphological question. The layer of gray substance, extended as a little band between the lenticular ganglion of the corpus stri- atum and the gray cortex of the island, that which Mey- nert calls the " avant-mur" has been considered as a part of the cortex cerebri, the claustral layer of the three convo- lutions of the Island. It appears that in the brains of idiots, the white lamina, which separates the insulary con- volutions from the avant-mur, is absent, and the avant-mur really becomes the internal layer of the cortex cerebri (Betz). Now, according to Meynert, the structure of that avant-mur is identical with the claustral layer ; there are to be found fusiform cells, pressed one against another, a structure widely differing from that of the gray ganglion of the corpus striatum and thalamus opticus. To employ Meynert's expression, the formation belongs, not to the central ganglia of the brain, but to the system of associ- 24 CEREBRAL CONVOLUTIONS. ation, which always constitutes the internal claustral layer of the convolutionary cortex. It is here useless to recall the arrangement of the cen- tral ganglia relatively to the avant-mnr. It is known that the external capsule, situated externally to the lenti- cular ganglion, is divided by the gray band (the avant-mur) into two parts, the external one belonging to the cortical system, the internal, or profound, to the central system. Besides, the circulation of the avant-mur is a part of the circulation of the convolutions of the island and not that of the corpus striatum. 1 I will add that this is not admitted by all authors. Luys in particular considers the avant-mur a dependence of the corpus striatum. This interesting point demands new re- searches, but I do not believe the solution belongs to pure anatomy. Physiology and pathological anatomy must solve it. Some English authors have studied the special structure of the insular convolutions; especially Broadbent 2 and Major. 3 The latter concludes that there exists no funda- mental difference between the layers of the island and those of the vertex. He has measured the cells of the island and gives the following figures for the various layers : i. Ext. layer, .... 0.008 to 0.012 mm. 2. Pyramidal layer, 3. Layer Ammonis, . 4. Granular layer, . 5. Sup. claustral layer, 7. Profound claustral layer, The last layer is generally composed of fusiform cells. The layer Ammonis (third) is the only one of the island which differs from the same layer in other convolutions. 1 Duret : Anat. Researches upon Encephalic Circulation. Arch, de physio!., 1874, P- 79- ' 2 Structure of the Cerebral Hemisphere (cited by Major). s The Histology of the Island of Reil. West-Riding Lunatic Asylum Med. Reports, t. vi., 1876, p. 1 et suiv. 0.012 " 0.02 0.020 " 0.028 O.OI2 " 0.024 0.020 " 0.024 0.016 " 0.02 STRUCTURE OF THE CONVOLUTIONS. 2$ The cells contained therein are smaller than in the frontal regions, which perhaps removes the island from being in- cluded as a motor-centre. 1 Type Hippocampi. — The study of the cornu Ammonis and the gyrus hippocampi should be made morphologically as well as microscopically, for it is interesting to show by what modifications Nature has converted a normal convo- lution into an aberrant one, as in the instance of the cornu Ammonis. To render the structure of this region comprehensible, I refer to the accompanying schematic plates. The transverse sections of Luys, best expose the cornu Ammonis. Upon a brain hardened by alcohol, or one quite fresh, let the occipito-sphenoidal lobe be cut in paral-. lei slices commencing at the anterior extremity, and the modifications of the cortex can be observed as it becomes the cornu Ammonis. This is the process long ago recom- mended by Vicq d'Azyr. 2 First is seen a little gray band of the outside cortex which becomes invaginated, folds upon itself, whilst the subjacent white substance,- at first very large, little by little becomes thinner, as though the lateral ventricle (V) pro- longed into the sphenoidal lobe were about to invade it. Gradually this white substance becomes thinner and at last assumes the form of a thin resisting lamina, the wall of the lateral ventricle and the superficial portion of the cornu Ammonis. This is what anatomists term the alveolus (B). Pro- ceeding posteriorly it will be seen that, upon the internal side of the fold, this cerebral lamina lessens in such way that finally, at the most posterior part, it is reduced to sim- ply a thin layer of white substance, which layer, through constant decrease, finishes by becoming in the lateral ven- tricle entirely free from the inner side and becomes the 1 A good plate is annexed to Major's memoir. 2 See Sappey's Anat. desc, t. iii., p. 105 and figs. 457, 458, 459. 26 CEREBRAL CONVOLUTIONS. Plate I. EXPLANATION OF PLATES. (cornu ammonis.) Plate I. — Figs. I and 2, relations of the hippocampus with the lateral ventricle. The letters are the same as for plate II. Plate II. — Figs. 1, 2, 3, 4, 5, 6, 7, 8, 9. (See next page.) V. Cavity of the lateral ventricle. A. Point where the gray substance invaginates to form the hippocampus. B. Lamina of the deep white substance which tapers down to form the ven- tricular wall of the cornu Ammonis (cuneus). S. Subiculum, a white lamina originating in the peripheric gray substance, curving at C so as to form a crosier (bishop's pastoral cross). To render the figures more distinct, the corpus fimbriatum and choroid plexus are suppressed. STRUCTURE OF THE CONVOLUTIONS. Plate II. (Cornu Ammonis). 27 Fig.l. Fia. 5. Fifl. 2 Fig. 6. Fig. 7. B T S A Fig. 3.7T 28 CEREBRAL CONVOLUTIONS. ribbon which anatomists call corps bordant (the taenia hip- pocampi). Thus the lobule hippocampi is first formed by the fold- ing of the gray substance and a more or less voluminous vessel at its base giving off twigs which penetrate between the two gray laminae of the convolutionary axis thus formed. The presence of these twigs in the brains of aged subjects are of great advantage to the observer. Following these two layers, it is seen that upon the peri- pheric surface (now become the central) of one of them appears a very slight layer of white substance arising from the gray substance itself (S). This is described by authors as the subiculum. 1 This white layer is not a dependence of the medullary white substance of the brain, but a dependence of the gray cortex cerebri from which it originates. If this were all, the gyrus hippocampi would be rela- tively simple ; but a new complication renders the descrip- tion somewhat difficult. That gray lamina, surrounded by the alveolus of the internal or ventricular side, and by the subiculum on the external or peripheric side, coils upon it- self like the top of the pastoral staff of a bishop, sometimes completing a circuit similar to the spiral or helix of a snail. The gray blade accompanied by these two white laminas appears like a twisted, elastic lamina, strongly stretched and fastened at one of its edges. In the very body of the gray lamina there is a very attenuated layer of white sub- stance, which can be seen only with a glass and which ap- pears to extend to the extremity of the central lamina. Finally, to complete this difficult description, we would add that the thin gray blade seems at its extremity to con- tinue directly with that little reddish band, covered with projections and called the choroid plexus (corps goudronné) 1 It can be very well seen in the schematic figure given by Mathias Duval, art. Nerfs, du Diet, de méd. et chir. prat., p. 474, fig. 72. — See also in Traité d'anat. of Sappey, fig. 459, 2 — white lamella which separates the fimbriated body from the gyrus hippocampi. STRUCTURE OF THE CONVOLUTIONS. 29 which, with the cornu Ammonis and the taenia hippocampi, jut into the lateral cavity of the fourth ventricle. Lélut. quoted by Sappey, makes the subiculum pass around the choroid plexus and become confounded with the alveolus. 1 All these details are somewhat difficult to understand, and I think that they can be followed only by referring at the same time to the plates. 2 (Cornu Ammonis, pp. 26 and 27.) When the anatomical description is so obscure, it is al- ways difficult to determine the minute structure. We are indebted entirely to Meynert for instructions upon the structure of the gyrus hippocampi, and these instructions are not over-satisfying. In the cornu Ammonis there exist only large pyramidal cells, and the second layer is lacking. Also there is an absence of fusiform cells (claustral layer). In other words, the layer Ammonis is larger- developed, and unaccompanied by other layers. Supposing the cornu Ammonis unfolded, a section would discover: 1st, the subiculum with very small nerve-cells (homologue of the external layer) ; 2d, the lacunal stratum, with a network of pyramidal prolongations (homologue of the pyramidal layer), but where the pyramidal cells are lacking ; 3d, the stratum radiatum (homologue of the upper layer Ammonis ; 4th, the pyramids (homologue of the lower 1 That peculiarity, represented by Sappey (fig. 459, I., 2) has not been figured by Mathias Duval. 2 Among the atlases which I have been able to consult on this subject {Tiedeman, Foville, Hirschfield, Leuret and Gratiolet, Gall and Spurzheim. etc.) none are exact concerning the cornu Ammonis except the works above cited ; Sappey, Anat. descript., t. iii., and Mathias Duval, art. Nerfs, p. 474. I will also add : Wundt, Physiologische Pyschologie, p. 82, fig. 34. The plates of Luys, Recherches sur le système nerveux, 1865, atlas, pi. xxi., figs. 1, 2, 3, 4, 5, 6, are perhaps not very clear. On the other hand, in his photographic- atlas the transverse sections (pis. i. to xi.) show the structure of the gyrus hippo- campi with a remarkable clearness and exactitude. I regret not having been able to consult the work of Kupffer, eulogistically spoken of by Frey : De structure cornu Ammonis, Dorpat, 185g. Microscopically there is a good cut in Meynert (loc. cit., fig. 236). 30 CEREBRAL CONVOLUTIONS. layer Ammonis) ; 5 th, the alveolus (the homologue of the projection of the ependyma ventriculorum). 1 Olfactive Bulb. — To these varieties of convolutions should be added another, of a special form, so special as to be at first confounded with a nerve ; I refer to the olfactive bulb. The olfactive bulb, truly speaking, is as distinct from a convolution as from a nerve ; it is an organ by itself, a kind of aberrant type, which can, however, thanks to comparative studies, through morphology and embry- ology, be classed under the general type of the peripheral gray cortex. 2 Luys rightly compares it to the retina. The olfactive bulb is, in the embryon, a hollow organ, an olfactive vesicle, the same as there is a retinal and auditory vesicle. With some animals this vesicle remains permanent, presenting an olfactive ventricle, lined with vibratory cells, the bases of which are in rapport with the subjacent nuclei (myelocytes). 3 As for the white root of the olfactive nerve, that should be considered as a com- missure of the white substance. In man, however, this ventricle does not exist. The other constituents of the olfactive bulb have not been rightly studied, and seem to be ill-known, though some labors in this direction have been undertaken. 4 The external layer seems to be formed of a white sub- stance containing pale nerve-fibres, without myéline, which intermix like a network. Beneath that layer is a zone of gray substance, which contains voluminous multipolar 1 These details will not be understood, except by following the scheme of Meynert, fig. 237. loc. cit. 2 Broca makes two types of mammifera, according to the volume of the olfac- tive lobe ; the horse and the dog, for example (psmatiques), man and monkey, anosmatique or very atrophied. See Revue d'anthropologie, 1878, p. 392 et suiv., Le Lobe olfactive et le sens de l'odorat. 3 Owjamniskow : Midler's Arch., i860, p. 54. Walter: Virch. Arch., xxii., p. 241. See also illustration of horse by Broca, loc. cit., Fig. 3. 4 L. Clarke: Zeitschrift fiir Wiss. Zoôl., xi., p. 31. Schultze, quoted by Kôlliker, Element, d'histol., p. 961. Golgi : Ricerche sulla fina struttura dei bulbi olfactorii, Reggio, 1875. Meynert : loc. cit., t. x., p. 102. STRUCTURE OF THE CONVOLUTIONS. 3 1 cells and some peculiar bodies, globular in form, first described by Leydig as found in fish, then by Schultze Golgi, and others under the name of glomeruli ; l they seem to be only a mass of ganglionic cells' 2 (Schultze, Kôlliker). Meynert's term of stratum glomerulosum may be accepted. There is then a second layer, which embraces superficially the glomeruli, and, deeper down, the large nerve-cells, analogous to the cells of Purkinje, in the cerebellum. Between these two ranges of cells are found axis-cylinders, serving probably to connect them. Besides this, these cells give out prolongations, which connect equally with each layer, both of which layers are essentially composed of the fasciculi of the olfactive nerve. In the deep layer there are also pyramidal cells with prolongations, which may be traced to the nerve-cells and to the glomeruli of the middle layer. Nothing is less elucidated than the structure of the olfactive bulb (olfactive convolution, or, still better, olfac- tive lobe). New researches are necessary. We will con- tent ourselves with the establishment of two facts — about the only things at present positively known respecting that obscure part of the cerebral structure: 1st, the olfactive nerve-fibrillae divide and anastomose in a network ; 2d, they are in rapport with the nerve-cells and the special cells of the second layer of the olfactive bulb {Glomeruli of Golgi). 3 1 This is what Pouchet and Tourneux call the spheric mass of gray substance (loc. cit., p. 587). 2 See Meynert, fig. 240. The vessels which go to the glomeruli are shown. 3 Among the different works undertaken upon the structure of the gray cor- tex I will cite that of Major, especially interesting in an anatomico-pathologi- cal point of view : " On the minute structure of the cortical substance of the brain." West-Riding Lunatic Asylum Reports, 1872, page 41, and various articles published in these reports and in The Lancet (21st July, 1877). The work of Lubimoff ought also to be noted (Arch, de physiol.) 32 CEREBRAL CONVOLUTIONS. Sec. 6. STRUCTURE OF THE GRAY SUBSTANCE OF THE CONVOLUTIONS OF MAMMIFERA. Here again the details are few, and information can be found only in the writings of Meynert, 1 Major, 2 and Lewis. Among various animals there exists considerable differ- ence ; the layers thus far spoken of, however, always exist and are tolerably well outlined, as shown in Lewis' plates of the cat and sheep, 4 the only specimens perhaps which have been given of the convolutions of mammifera. In one of Luys' unpublished photographs of the convolutions of a pig, the external limiting layer — that which is poor in cells, and perhaps of a conjunctive nature — is very thick, and the layers to which the nerve-cells belong occupy not more than two-thirds of the gray cortex ; the claustral layer is seen to be also very thick. But there is not much interest in stating that this or that layer of cells has greater or less thickness, or differ- ent lengths of prolongations in different animals. Besides, it has been little studied, and it is only known that the differences are nearly always confined to the occipital lobes. On the contrary, the structure of the cerebral cortex of the monkey has a great interest. In comparing it with the human cortex, we may hope in a certain degree to find a reason for the enormous difference of intelligence, or at least without adventurous hypothesis to establish a com- parison between the absence or the increase of volume of 1 Strieker's Handbuch, etc., loc. cit. - Observations upon the brain of the Chacma Baboon (Cynocephalus Porca- rius, Journal of Mental Science, Jan., 1876, p. 502. This memoir is very re- markable and interesting. 3 Loc. cit. 4 Loc. cit., plates 2 and 3. STRUCTURE OF THE CONVOLUTIONS. 33 certain cells, as accompanied by the diminution or increase of intelligence. Major has studied successively the number and the ap- pearance of the layers, the general character of the nerve- cells and their prolongations, and the number of these prolongations. The following are his principal conclu- sions : 1st. In monkey and man, the number and the relative dimensions of the cortical layers are nearly identical. There is no difference as to the intimate nature of the cells, and their reactions are identical. 2d. All the layers of cells are similar, save the second one in the frontal convolutions, 1 where in man there abound large cells, whilst in the monkey they are rare. Major supposes, and not without some likelihood, that there is a relation between the volume and number of these cells in man, and the faculty of language special to man, and localized in the frontal lobes. Moreover, it seems that old age and intellectual enfeeblement in man coincides with degeneration of the large cells, so that their paucity of numbers in the Chacma baboon would be a sign of inferiority. As a rule, the number of the prolongations, and conse- quently the sphere of action of each cell, is considerably greater in man. Major has also studied the senile alterations of the nerve-elements of the convolutions of animals, and he in- sists upon the pigmentary degeneration of the nerve-cells. 'Major says the second layer, p. 510. It seems, however, that the large cells belong rather to the third layer (Ammonis). a On the Morbid Histology of the Brain in the Lower Animals. West-Riding Lunatic Asylum Reports, 1875. 34 CEREBRAL CONVOLUTIONS. Sec 7. WHITE SUBSTANCE OF THE CONVO- LUTIONS. We now pass to the study of the white substance of the convolutions, and, as with the gray portion, we will not give a general description, but of that only which is im- mediately subjacent to the gray cortex, and which forms the axis of the convolutions. It was the ancient idea that the cerebral convolutions were the result of a doubling-up of a peripheric layer, for Sténon strongly protested against that idea and that error of anatomists. " There are those who would even have us take the substance of the brain for a membrane." 1 Long time after that, the same idea was entertained by Gall, who thus expresses himself : — " Each convolution consists of two fibrous layers which are entirely covered by a gray layer of nearly uniform thickness. The laminas of the cerebellum are formed in the same way. The two fibrous layers, formed by the ascending and diverging fasciculi, are accompanied also by fibres which come from the gray substance, so that each convolution is composed of: — 1st, very fine re-entering nerve-fibres; 2d, fibres of the diverging fasciculi ; 3d, the exterior envelope of gray substance. It is this arrangement which renders it pos- sible to separate the two layers of fibres without injury to them, and to stretch out a surface and unfold each convo- lution or duplicature." 2 That idea of Gall's is perhaps exact, but modern re- searches certainly are based upon different processes, and notwithstanding that the microscope has furnished better 1 Anatomical Exposition of the Structure of the Human Brain, Winslow, Amsterdam, 1752, t. iv., p. 210. 2 Anat. et phys. du syst. nerveux, 1810, t. i., p. 299. STRUCTURE OF THE CONVOLUTIONS. 35 grounds for judgment, the question is still environed with uncertainties. The opinion of Meynert, adopted by Charcot, and the correctness of which seems very probable, is known. It holds the periphery of the brain to be a system of projec- tion. As in descriptive geometry, a projection can be made from the surface of a solid, so the cortex cerebri is the projection of the nerve-fibres contained in the ganglionic centres of the encephalon. To this must be added that these centres furnish a system of condensation, since the number of optico-strio-medullary fibres is much less than the optico-strio-cortical fibres. Besides this, Meynert has described a system of association formed by anastomosing fibres which unite the various convolutions and establish between them a complete and harmonious consensus. These ingenious views are but hypothetical ; and it must be said that, to the present, anatomical observations of the cerebral structure have never passed the domain of hypothesis ; we again repeat, that only physiology and pathological anatomy are capable of judging the relations between the convolutions and the nerve-axis. It should be observed that Baillarger has long since described two rows of vertical fibres in the axis of the con- volutions (in the dog and rabbit), crossed by transverse fibres. The schemes constructed by Luys must also rank as hypothetical. That eminent anatomist has dt^/ibed the relations of the various convolutions with each other and with the central ganglia. In the majority of his conclu- sions, Luys has certainly arrived at the same results as have pathologists ; but as it is the result of pathology which alone carries conviction, we will further along return to what we have to say respecting cortical degenerations. The knowledge derived by the microscope is scanty and inconclusive. It is known that the white substance is composed of cylinder-axes surrounded by myéline, and it may be antici- 36 CEREBRAL CONVOLUTIONS. pated that an attempt has been made to establish a relation between these cylinder-axes and the cells of the cortical layers. The first point is still scarcely known. We have before seen the opinion of Koschewnikoff ; that opinion is very clear and probable, though, as yet, undemonstrated. According to Gerlach, 1 these nerve-fibres penetrate the nerve-substance, and there, losing their myéline, form a very fine, richly anastomosing, fibrillous network, which fibres have cellular terminations. The existence of this network was not universally admitted. Rindfleisch denied its existence.' 2 He maintained that after a series of di- chotomous divisions, the nerve-tubes separate into bundles and fibrils ; these fibrillar go, some to the nerve-cells, and others to the myelocytes. 3 He asks if these nuclei may not be of nerve-origin, thus indirectly putting in doubt the teaching of the German school relative to the interstitial conjunctive tissue. Prior to these two authors, Kolliker had given the exact relation between the nerve-filaments and the cells. 4 It must not be supposed that all these observations are easy to repeat, and Vulpian rightly insists, in this question more than in any other, upon a rigid anatomy, which will not be content with approximative results and which will not affirm when there remains a doubt. 5 According to Kolliker the fibres do not all penetrate directly into the gray substance, there are those which course along the cerebral cortex, forming as it were arches. In the white substance of the convolutions, there exist 1 Centralbt. fiir d. med. Wiss., 1873, No. 18, p. 273. 2 Centralbt. fiir d. med. Wiss., 1872, No. 18, p. 277. :i Luys had already described the connection of the myelocytes with the nerve-fibres : Atlas, 1865, pi. xx., fig. 5. 4 See des Elém. d'histol., French trans'., p. 401. 5 Leçons sur la phys. du syst. nerv., 186S. For the inter-relations of nerve- fibres, the excellent, though schematic design of Henle may be consulted. Hand, fiir Nervenlehre, 1871, fig. 203, p. 275. STRUCTURE OF THE CONVOLUTIONS. 37 also nerve-cells which have been described by Mierzejew- ski ■ and previously by Meynert." These ceils are small, from 0.007 mm - to 0.010 mm., and multipolar; their poles are very long ; they probably are cylinder-axes. Of the nature of these elements Mierzejewski is yet uncertain. They are confined to the gray substance with which they perhaps ought to be classed. Their nuclei are very manifest and easily colored by picrocarmate of ammonia. If we now compare the convolutional structure of the cerebrum with that of the cerebellum, it will be seen that they appear to be constructed upon the same plan. There is only this difference, that the deep layers of the cere- brum are more complex and separated with tolerable distinctness ; whilst in the cerebellum, the nuclei, the nerve-cells, and the cylinder-axes are confounded in the formation of the internal or rust-colored layer (Kolliker). Thus we have the following homologue, somewhat sche- matic: CEREBRUM. CEREBELLUM. Ext. limiting layer. ( Ex. limiting layer, Pyramidal layer. Gray layer. 1 Layer of the cells Amnionic layer. ( of Purkinge. Granular layer. i Myelocytes Claustral layer. Rust-colored layer. 1 and nerve- cells. T , v ... , ] Stretched network with quadran- int. limiting la3 7 er. i ,, , , ( gular, parallel meshes. Perhaps the corpora quadrigemina, or at least their super- ficial portions, should be ranked with the gray cerebral cortex, though it has not yet been done. Although with fishes, birds, etc., the corpora quadrigemina are developed to the extent of veritable lobes, still in the human subject, 1 Loc. cit., p. 202. 2 Strieker's Handbuch fur Geweblehre, 1870, p. 709. 4 38 CEREBRAL CONVOLUTIONS. they are very reduced ; in no case presenting folds and convolutions and their structure is very simple. 1 Sec. 9. VESSELS OF THE CONVOLUTIONS. The arrangement of the circulator) 7 apparatus in the surface of the nervous system, apparently so well-known, is really still quite obscure, since upon certain points there is complete discord. For the historical part, we turn to the work of Duret, 2 where the question is treated of in a very complete manner. We first observe that the gray substance of the convolu- tions is much richer in vessels than the white, illustrated by the following cut borrowed from Gerlach. This is a well-known general fact and which applies to the spinal cord as well as to the cortex cerebri. The gray cortex is so vascular that Ruysch considers it a sort of arterial plexus. Upon an injected brain may be seen an infinite number of minute branches which fall like a shower of rain, per- pendicularly, from the pia mater into the cerebral sub- stance. These are the terminal arteries : they may be divided into two groups: one, very long and voluminous, penetrates through the gray layer and into the white substance ; these are the medullary arteries : the other, smaller (cortical arteries) and much more numerous, appear to be distributed in a uniform manner to the gray layer. Between all these branches there is a rich network of anastomoses. According to Duret, from whom we borrow these de- tails, 3 these arborescences of the gray cortex are responded 1 According to Serras, Anat. comparée du cerveau, Paris, t. ii., p. 277, the surface of the optic lobes are formed of alternate gray and while layers. 2 Recherches anatomiques sur la circulation de l'encéphale. Historique, p. 343 et suiv., Arch, de physio!., 1874. 3 Loc. cit., p. 334. STRUCTURE OF THE CONVOLUTIONS. 39 to by similar arborizations from the pia mater, from which it may be inferred that all the vessels ramify before send- ing branches to the brain. Layers. Fig. 5 (After Gerlach). — Portion of injected sheep's brain, showing the dif- ference in the vascularity of the gray (a) and white {b) substance. In a section of vascular-injected convolution, the capil- lary network seems to have four different grades. f Pyramidal ] Very rich, irregular poly- Ammonic' gonal network. This is Granular the vascular region of the [ Claustral superf. encephalon. i Transition network, less rich than Deep claustral layer. \ the preceding and richer than the subjacent. ( Network, with meshes three or four ') times larger. The veins, like the arteries, may be divided into medul- White substance. 40 CEREBRAL CONVOLUTIONS. lary and cortical. The medullary veins do not follow the exact course of the medullary arteries. According to Duret, they communicate with the veins of the base and of the ventricle of the brain, especially with the vena? Galeni. The cortical veins are larger and less numerous than the corresponding arteries. 1 Arteries of the cortex, or grey substance , ..Medullary ' Arteries Arteries of the commissural fissure of Graholet. Fig. 6 — Circulation in the convolutions (after Duret). It seems probable that there are no canals of communi- cation between the arteries and veins of the gray cortex other than the capillaries. 1 See Duret (loc. cit., p. 338), who has studied the question with minute care. Charcot (Leçons sur les Localisations, 1876, p. 54) has shown that Hubner's researches on the subject were absolutely simultaneous and not posterior, hav- ing been communicated upon the same day (7th Dec, 1872), a portion to the Biological Society, and a portion to the Centralblatt fur med. Wissenscli. STRUCTURE OF THE CONVOLUTIONS. 4 1 Regarding- the pia mater the question is still under dis- cussion ; the objections of Duret to the theory of Ecker and Sucquet, which admits derivative canals, seems to me, however, very serious. As with all questions in dispute, the subject requires new researches. 1 An interesting thing, from various points of view, is the relative independence of the different vascular territories of ffrav cortex cerebri. 2 Determined more especially by pathology, Duret and Charcot hold that there are two very distinct regions in the distribution of the cerebral arteries : the cortical region and the central {corps opto-stric's). " These two systems," says Charcot, " although common in origin, are entirely inde- pendent of each other, and at their peripheries they have no point of communication." Not only is there no communication between the corti- cal and medullary systems, but the various divisions of the cortical system do not intercommunicate except by very fine capillaries, so that the independence of the several cortical regions is nearly complete. Duret says 3 " that in man, the dog, and the rabbit, there are three separate regions, each furnished by a special artery ; the anterior cerebral arteries supply the frontal lobes, the sylvian (median) arteries the convolutions about the fissure of Rolando, and the posterior cerebral arteries the occipital lobes." Cadiat opposes various objections to the views of Duret, 1 the most important on.e seems to be that in making even a gentle injection into any branch of the arterial hexagon (circle of Willis), the entire lobe becomes injected, but it must be observed that Duret and Cadiat do not absolutely 1 According to Heubner and Cadiat, there should be anastomoses between the veins and arteries of the pia mater. 2 See fifth and sixth Lessons upon Les Localisations du cerveau, by Charcot. Part I., 1876, p. 53 et seq. 3 Revue des Soc. méd., t. x., 1877, P- 4 2 $. 4 Bull, de la Soc. de Biol., 1S76, p. 342. 42 CEREBRAL CONVOLUTIONS. differ, for Duret does not deny anastomoses of the arteri- oles of either the pia mater or the brain ; he only contends that their diameters do not exceed one-fourth of a milli- metre, whilst Cadiat and Huebner allow them one full mil- limetre. It then is but a difference of degree, and the ques- tion is evidently difficult to settle, for an arterial injection always distends the capillaries. In short, to Duret the anastomoses are not important, to Cadiat they are. The matter is still undecided ; the mode of operation and the kind of injection employed have greatly to do with the affair. I would add, however, that the exact limitation of cerebral infarctus and embolism lends a certain degree of support to Duret's theory. I will say a few words only concerning the structure of the cerebral arterioles. It is known that Robin has pro- ven that the cerebral capillaries are surrounded with a lymphatic sheath. 1 That sheath is studded with ovoid nuclei ; it has a thick- ness of o.ooi mm. to 0.002 mm., and completely surrounds the vessel in such a way that two concentric tubes may be seen, each containing different liquids. The internal tube contains red globules ; the external, leucocytes. As yet it is by no means proven that these canals are lymphatic, inasmuch as they have never been injected or traced immediately to a ganglion. German anatomists have met this proposition with a multitude of conjectures (cellular-perilymphatic spaces, cellular perivascular sheaths, etc.). Some histologists have even thought these canals to be pathological alterations (Kesteven 2 ). But as we have not general anatomy under consideration, it suffices to note the existence of a lympha- tic sheath to the blood-capillaries, as if the cerebral tissue were too delicate to endure the immediate contact of the blood. 1 For the complete bibliography see Riedel : Die Perivasculare Lymph- râume, Arch, filr mik. Anat., t. xi., 1875. 2 Brit. Med. Jour., June, 1874, p. 840. STRUCTURE OF THE CONVOLUTIONS. 43 Sec. 8. DEVELOPMENT OF CONVOLUTIONS. Notwithstanding the considerable number of authors who have written upon the anatomy of the nervous sys- tem, the development of the convolutions, structurally, not morphologically, has received the attention of but few. Until the third month, as Tiedemann * has observed, the surface of the hemispheres is smooth, without fissures or convolutions. According to both Tiedemann and Duret, a the first cerebral folds appear at about the third or fourth month. The first fissure is not that of Rolando or Syl- vius, as the plates of Leuret and Gratiolet 3 would seem to to indicate, but the external perpendicular fissure. 4 Until the fifth or sixth month, there is scarcely any development of true convolutions. Gratiolet has repre- sented the brain of a five-months and a half fœtus, 5 which is entirely analogous to an accompanying illustration of the brain of a stupid monkey. There are incisions, shal- low fissures, outlining of lobules, or groups of lobules ; but there are no true convolutions, intermixed, compli. cated, and with blunt angles as in adult brains. Even with new-born children 6 the convolutions are very simple, so that they continue to form after birth ; the sulci deepen, new marginal gyri appear. In a word, the convolutions seem obstructed, mal- arrêtées, to use Parrot's expression. 7 It is probable that these exterior differences correspond to 1 Anat. du cerveau, trad, de Jourdan, Paris, 1823, p. 36, pi. I. 2 Bull, de la Soc. de Biol., in Gaz. méd., 1877, p. 172. 3 Anat. comp. du syst. nerv., Paris, 1839-57, pi. xxix., figs. 3, 4, 5. 4 See also Duval, in Gaz. Med., 1877, p. 161. 5 Mém. sur les plis cereb. de l'homme et des primates, p. 82. Atlas, pi. xi., fig-. 1. 2, 3- 6 Leuret and Gratiolet, loc. cit., pi. xx., fig. 2. 1 Etude sur le ramollissement, etc., Arch, de Phys., 1S73, p. 63. 44 CEREBRAL CONVOLUTIONS. differences of structure, but this point does not seem to have been studied. The first attempt seems to have been made by Tiede- mann, 1 who wrongly supposed that the cortical substance was secreted by the pia mater upon the surface of the brain after birth. But Baillarger 2 has shown that, in the human foetus of four or five months, there already exists at the periphery a very thin layer of gray substance, showing several concentric zones, alternately opaque and trans- parent. According to Duret, 3 from the seventh to the ninth months, whilst the convolutions are forming, there appear, on the one hand, nerve-tubes which reach the superficial portion of the cerebral hemispheres, and, on the other hand, the nerve-cells in the cortex. It is not until this period also that the arteries develop. Duret considers the coincident development of the nerve- cells, vascularization, the ascent and development of the peduncular expansion and the appearance of the convo- lutions to prove that the cortex does not acquire func- tional properties until towards the end of fcetal life. Phy- siology has arrived at a similar conclusion. Lubimoff (of Moscow) has arrived at analogous results. The nerve-cells of the cerebrum and cerebellum develop last, whilst the cells of the spinal cord, and especially those of the great sympathetic, develop much more rapidly. Mierzejewski 4 holds that, in the white substance of the newly-born, among the axis-cylinder, may be found amoe- boid cells (which are colored black by osmic acid), polygo- nal cells and small, ovoid, flat cells. To explain the rôle which he assigns to these elements, it would be necessary to enter into the history of the development of nerve-tissue. 1 Loc. cit., p. 87. '-' Mémoire sur la formation des centres nerveux. Jour. l'Esculape, 1840, et Mém. de l'Acad. de Méd., 1840, p. 150 et suiv. 3 Bull, de la Soc. de Biol., in Gaz. Méd., 1877, !'• I 7 2 - 4 ^Loc. cit., p. 202. STRUCTURE OF THE CONVOLUTIONS. 45 Respecting the development of the gyrus hippocampi, Duret, who made observations upon a four-months' foetus, says that it is simply a folded convolution, which projects underneath the corpus callosum. Anteriorly this convo- lution disappears, little by little, but posteriorly it remains, as before observed, and folds back upon itself. In the large work of Mihalkowitz ] are to be found details, too long and unimportant to engage our attention, and the plates are also difficult to comprehend. Flechsig, in his great work on the nervous system, does not dwell upon the stratification of the layers ; he describes the relations of the various fasciculi of nerve-fibres, and thinks that the white substance is developed very late in the embryonic convolutions; in other words, that Meynert's "système d'association" becomes established only at birth. 2 This is pretty much Duret's conclusion. There are two other interesting facts to be added to the little which is known upon the development of convolu- tions. First, the existence of "transitory convolutions" found in the embryon of four or five months, and which disappear towards the seventh or eighth months. 3 Second, Major, 4 who examined the cortical nerve-cells of an eight-months' foetus, reports the almost complete absence of cellular prolongations, so that the cells have the appearance of round cells. Perhaps the nerve-cells (motor or sensorial) only develop with the commencement of functional action. It also appears that the nerve-pro- longations become lost in advanced age. It would be an interesting study to ascertain at just what time the large motor-cells first appear. 1 have not had 1 Entwickelungs-Geschichte des Gehirns, Leip., 1877, p. 145 et suiv., pi. xx., xxi. 2 Die Leitungsbahne im Gehirn und Riïckenmarke des Menschen. Leip. . 1S76, in Jahresber. fiir Anat., 1876, p. 275. 3 Milhalkowitz, loc. cit., p. 144. Ecker : Arch, fiir Anthrop., 1868, t. iii. His : Entwickelungs-Geschichte der Grossgehirnhemisphàren. Sitzber. der Nat. Gesellschaft in Leipzig, 1874, p. 1. 4 Loc. cit., Jour, of Mental Science, p. 511. 40 CEREBRAL CONVOLUTIONS. time to undertake it. I would observe, however, that, in a cat one month old, I have, in company with M. Tourneux, noticed that there was, even at that age, a difference between the anterior and posterior cortical cells, the latter being a little smaller. Betz says that giant-cells do not exist in the new-born. PHYSIOLOGY OF THE CONVOLUTIONS. 47 SECOND PART. PHYSIOLOGY OF THE CONVOLUTIONS. ANATOMICAL INTRODUCTION. Although the topography of the cerebral convolutions is known, still a short anatomical review may not be useless and will avoid repetition and confusion. The human brain is composed of four distinct portions. 1 The anterior plane includes the frontal lobe ; the middle plane includes, superiorly the parietal lobe, inferiorly the sphenoidal, the posterior plane the occipital lobe. 2 To these we will add other lobes of secondary importance, at least to man : the olfactive, very reduced ; the gyrus hippocampi, impossible to well determine ; the lobe of the Island of Reil, deeply hidden in the depths of the fissure of Sylvius; the lobe of the corpus callosum, and the gyrus angularis. In the lobes are to be distinguished lobules and convolu- tions. The lobules are but topographic regions, whereas the convolutions have a real anatomical existence. Between the various lobes are fissures. Between the frontal and parietal lobes is the fissure of Rolando; between the parietal lobe and the gyrus angularis is the occipital fissure (or perpendicular) ; between the fronto-parietal lobe and the temporal, is the fissure of Syl- vius. Between the fronto-parietal lobe and the lobe of the cor- pus callosum lies the calloso-marginal fissure. Between the occipital lobe and the gyrus angularis lies the fissure calcarina. 1 The anatomy and morphology of the convolutions belong entirely to French science ; Vicq d'Azyr, Rolando, Foville, Leuret, Gratiolet, Broca. 2 We adopt the terms employed by Broca. Mém. sur la nomenclature céré- brale (Revue d'Anthrop., 1878, p. 193). 4 8 CEREBRAL CONVOLUTIONS. Between the convolutions are furrows (sulci). The frontal lobe is composed of three convolutions : first or superior, second or middle, and third or inferior. 1 The inferior portion of the frontal lobe is known as the orbital lobule ; upon which may be observed three orbital volutions, prolongations of the frontal volutions. Surrounding the fissure of Rolando are two important convolutions ; anteriorly the ascending frontal convolution Sup. pariet'l Jyobule. / / Rolando. ^ -parietal £ .-K fissure. *« S \ pu Fissure of $ylviu< Parallel fissure. Fig. 7. — Convex surface of a hemisphere of the human brain (parietal lobe partly schematic). (Foville.) or better, pre-rolandic, which seems to give three prolonga- tions, that is, the three frontal convolutions. Posteriorly is the ascending parietal, or better, post-rolandic. The union of these two convolutions on the internal face of the hemisphere forms the paracentral lobule. The temporal lobe includes the first, second, and third temporal convolutions, Fig. 7. The fissure separating the 1 As remarked by Charcot, it would be proper to make an exception and call the third frontal convolution the convolution of Broca. PHYSIOLOGY OF THE CONVOLUTIONS. 49 first and second temporal convolutions is the parallel fis- sure, which terminates in the parietal region, called gyrus angularis. The parietal lobe is divided into two parts by the inter- parietal fissure. This gives a superior and an inferior parietal lobule. The occipital lobe embraces the first, second, and third occipital convolutions. Inferiorly, the temporal and occi- pital lobes seem confounded, so as to furnish a first and second temporo-occipital convolution. -ssJ»^- — y -^ * Fiss.of Rolande cent,, conv. |Post.cent.ccav. Fig, S. — Internal face, right hemisphere of human brain (Ecker.) This nomenclature applies equally to man and monkey ; but as one cannot experiment upon man, 1 and as physiolo- gists rarely have monkeys at command, it is of special im- 1 There are exceptions to all rules. Bartholow (Revue des Scien. Méd., t. iv., 1874, p. 65), gives some interesting experiences with one of his patients. He plunged needles into different parts of the brain, passed electric currents through them, and watched the results. The patient died two days after, but l he needles had nothing to do with the death! 5o CEREBRAL CONVOLUTIONS. portance to have a full knowledge of the dog's brain and its comparative parallelism with man's. Thus pathological facts in man and physiological experiments upon the dog can be systematically compared, so that a very good idea can be obtained of the functions of the various convolutions according to their location. The configuration of the dog's brain, as first shown by Gratiolet, has no direct relation with man's, at least the homologies are not at first seen, and the type is different. The fissure of Sylvius exists, but not that of Rolando ; or at least it is replaced by a much more anterior fissure, called the crucial (B, Fig. 9). Fig. 9. — Right hemisphere of dog's brain (after Ferrier). A, Fissure of Sylvius ; B, crucial fissure ; O, olfactive bulb; I., II., III., and IV. represent respectively the first, second, third, and fourth convolutions. The crucial fissure crosses the inter-hemispheric fissure at right angles, giving the appearance of a cross. It is the same with the cat, only that the crucial fissure is still more anterior than in the dog. About the crucial fissure is a convolution which seems to respond to the pre- and post-rolandic convolutions in men. The olfactive lobe is greatly developed, the frontal scarcely at all. HISTORICAL INTRODUCTION. 5 I HISTORICAL INTRODUCTION. The brain of man differing greatly from that of animals, it can be foreseen that experiments upon animals will not give results exactly applicable to man. This fact must be specially emphasized, as it is a very important and com- manding one. Compare the human blood with that of the sheep or fish. As these different kinds of blood have the same functions (absorption of oxygen and nutrition of tissues), have the same general chemical constitution and a very analogous anatomv, it will suffice to examine the function of the sheep's or fish's blood in order to understand the function of human blood. The same for other tissues and organs ; the kidneys for example, or the muscular tissue. The same also for cer- tain nervous functions, innervation of the heart or blood- vessels : that observed in animals can serve in human physiology. But for the encephalon, and especially for the cerebral convolutions, this identity no longer holds. For example, if Cuvier's brain be compared to that of a dog, it will be seen that the anatomical constitution and the physiological function are very different ; and there- fore the conclusions of physiological experiments upon the brain of a dog cannot be applied exactly and abso- lutely to the human brain. A very important reserve, however, should always be made ; that is, that these differences are quantitative, not qualitative. To explain : The reaction of the cortex cere- bri to excitants should be, and really is, identical in man and dog; it would be more or less marked, more or less extensive in one case or the other ; but the functional essence would remain identical, as is the case with the blood, the spinal cord, the nerves, and heart. 52 CEREBRAL CONVOLUTIONS. If we observe that the cortex cerebri is both motor and sensorial in the dog, that would be sufficient to allow us to affirm the same in case of man. The question can be stated still more clearly. In the sigmoid gyrus of the dog, we find a motor-centre for the fore-legs ; that permits us to say that it also exists in man. But can we venture to say that this motor-centre in man is near the fissure of Rolando, and that the ascending frontal convolution corresponds to the sigmoid gyrus of the dog ? Should we dare to say that there exists for the anterior member one motor-centre and not two, or three or four? That would exceed the limits of legitimate deduction. From the fact that there are motor-centres in the dog, we may conclude that there are also motor-centres in man. From the fact that intelligence in the dog de- pends upon the convolutions, we may conclude that it is the same with man ; but we can go no further. Applications to human physiology would very soon be limited were there not another precious source of knowl- edge ; that is, pathological anatomy and physiology. Pathology and physiology do not antagonize ; they are two branches of the same science, biology, and they should afford mutual light. Though physicians are too often ungrateful to physiologists, the latter should not return ingratitude, and disdain the countless contributions which are scattered through medical lore upon the subject of the functions of the cerebral convolutions. Good obser- vations equal good experiments, and we are resolved to profit largely from the valuable gifts which pathological anatomy offers to the study of the cortex cerebri. However, in the study of cerebral convolutions, the two sciences differ in their points of advantage and disadvan- tage. Physiology has these two advantages : i st. The experiment can be repeated as often as desired. 2d. The conditions of the experiment can be determined, a thing necessary to the value of the phenomenon. The advantages of pathology are also considerable. HISTORICAL INTRODUCTION. 53 ist. The lesions are upon the human subject, in whom the encephalon differs much from that of animals. 2d. The lesions are always better limited than in physio- logical experiments. 3d. The symptoms are studied for a much longer time, (and probably with more care). 4th. The subject can describe his sensations. Thus we think that physiologists should profit from the results of pathology, and that in all physiological study we should highly estimate medical observations made upon man. The ancient authors, especially Galen, 1 had very incom- plete ideas. Galen called the gray cortex of the brain epencranis {ènkynpavii), after Erasistratus, and the folds of the brain (eXixsc). Erasistratus thought the human epicranium more complex than animals, for the reason that he has more intelligence. To this, Galen offered a rather worthless argument: " Asses," he said, " have a very complicated encephalon, whereas their imbecile character would exact an encephalon quite simple and free from varia- tions." Whatever the ground of that strange idea respect- ing the imbecility of the ass and the complexity of his convolutions, it may be seen that, even in ancient times, the brain and even the cortex cerebri was considered as the seat of intelligence. To the quotation already given Galen added this curious sentence, showing the admirable sa- gacity and prudence of this genius : " To refrain from speaking of the substance of the soul, when speaking of thcstructure of the body which contains it, is impossible ; but if this is impossible, it is possible to turn promptly away from a subject upon which we should not dwell." This is the programme which we shall attempt to follow. Galen also noticed that the brain is insensible.' 2 This 1 De usu partium, viii., 13 Ed. de Daremberg, t. i., p. 563. i Cité par Longet, loc. cit., p. 640. 5 54 CEREBRAL CONVOLUTIONS. important fact has since been observed by other writers, and seems now well attested. From Galen to the commencement of the present cen- tury, only scattered facts can be produced. Surgeons of the seventeenth and eighteenth centuries thought that lesions of the cortex cerebri might produce paralyses, and to remedy this, they had recourse to trephin- ing ; but their opinions are very confused. Concussion, and above all compression, played the principal part in their theories. It should be remarked also that, in the cases observed, it is rare that the lesions are exactly lo- cated. Concussion, consecutive hemorrhage, and encepha- litis quickly extended to all parts of a hemisphere. Lorry, 1 however, gave some very exact experiences and stated that the cerebral pulp was insensible. Haller, 2 with some important restrictions, expresses very nearly the same opinion. He says that it is necessary to go deeper than the cortex cerebri in order to provoke movements or sensations, and that the medulla of the brain is the sensitive portion. " Non ergo videtur aut sensum in cortice cerebri exerceri, nut plenam perfectamque causant motus musculosi in co Jiabitare, cum prœterea plurima expérimenta demonstrent, prof undo de- mum loco, et a cortice cerebri valde remoto mcdullam lœdi opor- tere, ut convulsio superveniat."* I dwell upon the ancient ideas only because they have not until the present ever been disturbed, the doctrine of Galen, Lorry, and Haller having held sway until 1870. The importance of cerebral convolutions as related to the intellectual faculties, though suspected by physiologists and medical practitioners, 4 was especially brought to light by Gall. Gall's merit was not the invention of an absurd 1 Mém. de l'Acad. des Sciences (Recueil des savants étrangers, 1700, t. iii., P- 352). - Elementa physiologise, t. x., p. 312 et suiv., lib. x., § xx. Num cerebri medulla sentiat. 3 Same, p. 392, § xxiii. 4 Van Swieten, t. iii., p. 264 ; t. ii., p. 604, Boerhave, etc. HISTORICAL INTRODUCTION. 55 theory, but the proving, by comparative anatomy, and by the study of the brains of idiots and the insane, that intelli- gence is a function of the convolutions. He was followed in this direction by Flourens, one of the most vigorous opponents of phrenology. This cele- brated physiologist 1 demonstrated beyond dispute that the encephalic nervous system is the seat of intelligence, the origin of sensation and motion. From this time, that which was previously but a supposition or a feeling, be- came a positive acquisition to science, based upon firm, unshakable proofs. We must turn to the experiences of contemporaneous physiologists for new facts respecting the physiology of the convolutions ; but from Flourens to the present time (evidently guided by his labors), other authors, zoologists, and medical practitioners have furnished a large number of interesting facts well calculated to illuminate physiology. It is somewhat remarkable that the three most important observations occurred in the same period, and are due to three French savants. 1 st. Desmoulins' 2 demonstrated by comparative anatomy that the number and perfection of the intellectual faculties are in direct ratio to the number and depth of the cerebral convolutions. 2d. Calmeil, 3 in an admirable series of observations, proves that with the insane, especially with general paraly- tics, the alterations are in the gray portions of the convo- lutions, and that therefore there is a direct connection between mental disturbances and lesions of the cortex cerebri. 3. Bouillaud, the illustrious dean of French medicine,' demonstrated by a great number of pathological facts that language is located in the anterior lobes of the brain. 1 Mémoires lus a l'Institut, 1822, 1823. Recherches expérimentales sur les propriétés et les fonctions du système nerveux, 1st Ed. 1824, 2d Ed. 1842. "Anatomie du système nerveux des vertébrés, 2d partie, p. 606, Paris, 1825. 3 De la paralysie chez les aliénés, Paris, 1826. 4 Traité de l'encéphalite, Paris, 1825, p. 279. 56 CEREBRAL CONVOLUTIONS. From 1825 to 1861, the physiological history of the cor- tical system remained absolutely stationary. In 1861, Paul Broca, in a remarkable mémoire 1 made it apparent that language was not only located in the anterior lobe, but that it was confined to a special convolution, and to the posterior portion of that convolution (third convolu- tion of left frontal lobe). 2 About this time, the conformation of the human brain began to be looked upon as an orderly development instead of a result of chance. The researches of Foville, and those of Leuret, Gratiolet, and Broca (1 855—1865), es- tablished the constancy of the form of the convolutions. Excepting some isolated instances, the profession did not admit the localization of cerebral functions, beyond that concerning language. 3 The celebrated researches of Fritsch and Hitzig 4 ter- minated these hesitations and established the motor-power of the cortex cerebri. Whatever interest attaches to subsequent labors, it must be recognized that the first work of Fritsch and Hitzig contains all that is essential upon the question. 5 They have shown : 1 st. That there are motor-centres in the brain (excitable by electricity), and again that certain portions are not thus excitable (p. 311). 2d. That the points where excitation affects certain 1 Sur la siège de la faculté du langage articulé, avec deux observations d'aphémie. Bull, de la soc. anat., 2d série, t. iv., 1861. ' 2 It is but just to say that the relation between language and a lesion of the left hemisphere had been noted by Dax in 1836 (See Dax fils, Gaz. hebd., 28th April, 1865. 3 Hughlings Jackson, 1868. — Prévost, a pupil of Vulpian, says in his inau- gural thesis, p. 140, " crossing of the eyes may be observed in cases of super- ficial lesions of a hemisphere." 1868. 4 Ueber die Electrische Erregbarkeit des Grosshirns. Arch, fur Anat., 1870, 28th April, p. 300-332. 5 It may be interesting to read the polemic acerbity of Hitzig respecting Carville and Duret. Gaz. méd., 1875, Feb. 6th, and Arch, fur Anat., etc.- 1875, p. 428 et suiv. But Hitzig defends a cause not attacked. HISTORICAL INTRODUCTION. 57 groups of muscles are very precisely limited to a small area of the cerebral surface (p. 311). 3d. That the results are more regular with the direct than with the induced current (p. 316). 4th. That the removal of a localized cerebral region with the scalpel will produce paralyses (p. 328). ' The question of motor functions of the convolutions has been considered by numerous writers. Among all the newly demonstrated facts there are four of some importance : A. There are no motor-centres in the newborn (Solt- mann). B. Excitation of the white layer below, gives the same results as exciting the gray substance above (Dupuy, Car- ville, and Duret). C. The motor-centres of the limbs are also vaso-motor excito-secretor (Boc he font aine and Lépine), and sensorial cen- tres (Vulpian). D. There are sensorial centres in the occipital convolu- tions (Ferrier). In a medical point of view, the researches of Charcot and his pupils have established upon a firm basis the theory of localization, thus medicine has lent to physiology a proof which was perhaps necessary before admitting the exist- ence of motor-centres. We will now study the physiology of the convolutions under two aspects ; the properties of the gray cortex, and its functions. Indeed, in the physiology of organs there 1 Some remarks, more or less precise, do not establish the title of priority to a discovery. A single observation of Griesinger (see Bernhardt, Arch, fur Psychiatrie, iv., p. 480), or a remark of Eckert (Exper. Phys. des Nervensystems Giessen, 1867, p. 157) are not sufficient. In this way Breca should be cited who says, in 1861 (Bull, de la Soc. d'anthropol., p. 318) : " The posterior con- volutions differ notably from the middle and anterior convolutions. The prin- ciple of cerebral localizations is established both by physiology and pathology, the latter showing the independence of the functions, and also by anatomy, ■which shows the diversity of the organs." Neither should the persevering labors of H ughlings Jackson be forgotten. But these do not take from Fritsch and Hitzig the incontestable right of priority. 58 CEREBRAL CONVOLUTIONS. should always be distinguished a state of repose and one of activity ; they may be termed, respectively, static and dynamic. According to this division, we will first examine the ex- citability of the convolutions, their electric condition, and their nutrition. In the second chapter, we will consider their relations and functions in the organism as regards motion, sensation, and intelligence. PHYSIOLOGICAL PROPERTIES OF THE CONVOLUTIONS. 59 FIRST CHAPTER. PHYSIOLOGICAL PROPERTIES OF THE CON- VOLUTIONS. A. — EXCITABILITY. The apparent inexcitability of the cerebral surface, the inability of chemical, mechanical, or other agents to pro- voke motion is something which has attracted the attention of all observers from Galen to Lorry. The experiment of Fritsch and Hitzig, however, renewed attention to the sub. ject, and to-day the question stands, Is the gray substance inexcitable ? Writers generally hold that mechanical and chemical agents are incapable of exciting motion. 1 Respecting the chemical or mechanical inexcitability of the gray substance, however, authors are not in accord. Brown-Séquard 2 has recently made some interesting experi- ments in this field. According to him, mechanical and especially thermic excitations of the cerebral surface pro- duce, at least temporarily, the same effects as a section of the cervical sympathetic nerve of the side corresponding to the excitation. These phenomena would be as complete as after section of the sympathetic ; moreover, that action would not be produced except after excitation of the right hemisphere. Eulenberg and Landois have noticed analo- gous phenomena. In applying sea-salt to the cerebral sur- face, they found, first, a lowering of temperature (excitation) followed by an elevation of temperature in the fore-limbs, 1 Nothnagel, cited by Dupuy (Lond. Times and Gazette, No. 1410, 1877), found the rabbit's brain mechanically excitable with a needle. Dupuy wittily added that Nothnagel's rabbits differed from those which could be obtained in France and England (see Nothnagel, Virchow's Arch., lviii., p. 420). 2 Arch, de physiol., 1875, P- 854. 6o CEREBRAL CONVOLUTIONS. which they attributed to the destruction of the gray cor- tex. 1 We cannot tell how far these effects are attributable to the action of the cerebral cortex. It is likewise doubtful if movements of the limbs, such as those following galvanic excitation, can be produced by mechanical or chemical excitations to the brain, or if either the gray or white cere- bral substance can be excited by those agents. The question of excitation by galvanism is still more difficult and more undecided. When certain regions of the gray cortex are excited, the sigmoid gyrus in the dog for example, either by a moderate direct, or an induced electrical current, movements of the limbs follow, and it may be concluded that the gray sub- stance has been excited and has produced them. The conclusion, however, would be rather superficial, and we are indebted to Dupuy 2 and Carville and Duret 3 for having shown that the electric current diffuses at the base of the brain, and produces excitement of the white substance. In placing at the base of the brain the nerve of a galva- noscopic frog, Dupuy has seen electrization of the sigmoid gyrus produced a movement of the paws as before men- tioned. Carville and Duret have also studied, with the galvano- meter, electric diffusion upon the brains of both dead and living animals, and they have noticed very feeble induced currents to extend themselves from one to another point of the periphery, extending at the same time also a certain distance down into the white substance. It always seemed to me that experiments with the gal- vanometer were of no special importance, and proved very 1 Berl. Klin. Woch., 1876, Nos. 42 and 43, also Virchow's Arch., t. lxviii., P- 245. - Thèse inaugurale, Paris, 1873. Examen de quelques points de la physi- ologie du cerveau, pp. 23, 26. 3 Bull, de la Soc. de Biol., 20th Dec, 1874, p. 374. PHYSIOLOGICAL PROPERTIES OF THE CONVOLUTIONS. 6 1 little, for the reason that the instrument is so sensitive that it shows currents of diffusion almost everywhere. In electrizing the right arm, there will be produced an electric state of the left arm, and a current which will produce an enormous deviation of the galvanometer. 1 It is preferable to use the sciatic of the frog, which has a very sensitive reaction, and evidently quite sufficient, for when the nerve will not react, the cerebral substance can- not, as it is less easily excited than the galvanoscopic leg. Very moderate electric currents induce movements in the legs of a dog ; but the galvanoscopic leg will not be excited, provided it is placed at a sufficient distance from the cerebral points excited, say one or two centimetres or more ; consequently, the electric current, though diffused physically, is not physiologically so diffused but that the excitation may be limited to certain well-defined portions of the brain. Moreover, a very simple experiment demonstrates that the current may be localized in certain points of the peri- phery, since either negative or positive effects can be obtained at will by exciting two points separated by inter- vals of not more than one or two millimetres 2 (Rouget). I have made analogous experiments with the galvanic limb and with well-defined results. To excite the sciatic nerve it was only necessary to bring it near the electrodes. But if the electrodes were close together, and the current not too strong, there would be at one or two centimetres distance from them no diffusion. It is not simply a, question of peripheric diffusion, for the diffusion from the periphery to the parts underneath cannot be avoided. The gray layer is so thin that it can- not be expected to limit excitation to that part alone, so that the current necessarily extends to and excites the subjacent white layers. 1 Onimus : Bull, de la Soc. de Biol., 1867 and 1874, p. 379. 9 Cited by Bochefontaine, Arch, de Phys., 1876, p. 171, et Bull, de la Soc. de Biol., 1875, p. 131. 62 CEREBRAL CONVOLUTIONS. This suggested another experiment. 1 In place of excit- ing the gray substance, that can be removed, and the white substance underneath excited. Many writers have made experiments, but without ac- cord in results. Putnam, 2 on the one hand, has observed that in removing a bit of the gray cortex and exciting the subjacent white substance a stronger excitant was required to produce a movement. In replacing the bit which had been cut out, the currents were without effect ; he therefore concludes that the gray substance itself is susceptible of excitation. Carville and Duret had a similar experience respecting the necessity of a stronger current, where the gray sub- stance had been removed. Hermann 3 and Braun, 4 on the other hand, have obtained quite different results. Hermann shows that, after de- stroying the gray substance with chemical cauteries, a very feeble current sufficed to produce movements, and that in cutting away slices from the brain the effect was decided in proportion as the central regions were approached. In some cases, however, it was necessary to increase, in others to diminish the force of the current To this, Braun has added the important fact, that if the white fibres beneath the point excited be cut, the exci- tation fails to produce the movement which occurred be- fore the section of the white fibres. The section does not prevent the receiving of currents, though in exciting the surface the corpora striata are not excited, but only the subjacent white substance or the gray substance itself. 1 Upon this subject see Vulpian's lesson, June 29th, 1876 ; in Journal l'Ecole de medicine ; Carville and Duret, Arch, de Phys., 1875 ; Bourdon-Sanderson, Proceed. Roy. Soc, June, 1874, xxii., p. 338 ; Furrier, Functions of the Brain, p. 218. 2 Boston Med. and Surg. Journal, July, 1874. 3 Ueber elektrische Reizversuche an der Grosshirnrinde, Pfluger's Archiv., t. x., p. 77- 4 Eckhard's Beitrâge, etc., 1874, t. vii., p. 127. Beitrâge zur Frage iiber die elektrische Erregbarkeit des Grosshirns. PHYSIOLOGICAL PROPERTIES OF THE CONVOLUTIONS. 63 When the gray substance which has been removed from above the white is replaced and electrized, it will be ob- served to have become inert, resulting from the section. Other well-attested facts prove also that in exciting the cerebral periphery the corpora striata are not affected. Carville and Duret observed, in experimenting with a dog, that very strong electric currents would produce no mus- cular movements ; autopsy brought to light a considerable lesion of the centrum ovale, thus interrupting the physio- logical, though not the physical continuity between the corpora striata and cortex cerebri. The corpora striata were sound. The excitation then was not diffused beyond the border of the corpus striatum. 1 Ferrier remarks that excitation of the corpora striata, or of the peduncles, gives quite different results from excitation of the cortex cerebri. 2 Franck and Pitres, in the remarkable researches which they have undertaken upon the functions of the cerebral hemispheres, have often noticed that electrization of the corpora striata, carefully avoiding the white fibres which penetrate the nuclei of the gray substance, is absolutely without results. 3 The general conclusion then is : in exciting the cortex cerebri, there are currents of diffusion to the periphery and towards the centre ; but these currents are insufficient to excite either the entire periphery or the subjacent cen- tral ganglia. Respecting the greater or less degree of excitability of the white substance, when the gray substance is avoided or destroyed, there are great differences of opinion. Tn closely examining the facts, however, that discord is found to result from a difference of conditions. 1 Carville and Duret : Notice of a pathological Lesion of the Centrum Ovale in a Dog. Arch, de physiol., 1875, p. 136. 2 Functions of the Brain, French trans., 1875, p. 258 et suiv. 3 A portion of the researches of Franck and Pitres has been communicated to the Soc. de Bi >1., Nov. and Dec, 1877. See Gaz. méd. of Jan. 3d, 1877. But many of the facts here given are unpublished, and we are indebted for them to our good friend, Fr. Franck. 64 CEREBRAL CONVOLUTIONS. In one of the experiments which I made with Bochefon- taine, in the laboratory of Vulpian,the following facts were observed : A dog was chloralized and the sigmoid gyrus exposed. In exciting the anterior part by a current of variable inten- sity, it was found that in order to provoke a movement it required an electric current (induced, continuous) corre- ponding in strength to No. 12 upon the indicator of Du- bois-Reymond. 1 After cutting away the gray substance and exciting the white substance immediately underneath (before the occur- rence of congestion caused by the cut), a very feeble cur- rent, scarcely sensible to the tongue — 23, sufficed to provoke motion. After the lapse of an hour, excitability had greatly dim- inished, 1 1 being required to produce motion, and the exci- tability rapidly vanished. This was followed by exposing the right hemisphere to 12, the gray substance did not respond to the excitation, though upon removing the gray substance, the white sub- stance responded to 12. This would allow the conclusion that the white substance is more excitable than the gray. Still, as Franck has, in a large number of experiments, uniformly obtained a great diminution of excitability after removal of the gray cortex, and as my experiment just given is very clear, I see no possible explanation of the dis- agreement except in the difference of experimental condi- tions. The dogs upon which I experimented were chlor- alized, whilst Franck's were neither anaesthetized nor under influence of curare. It seemed as though the chloral had paralyzed the gray cortex, thus interposing an inert tissue between the electric excitation and the white fibres which alone were susceptible. 1 That index, though very imperfect, is perhaps all that is necessary for phy- siological uses. With an ordinary Gremet pile, o indicates very strong, 10 middling, 20 very feeble, 30 perceptible only to the galvanometer. PHYSIOLOGICAL PROPERTIES OF THE CONVOLUTIONS. 65 These various experiments seem to prove that it is the gray substance which is really excited. To these facts are associated other phenomena espe- cially pertaining- to the cortex cerebri ; they show that its reaction to excitation differs from the reaction of nerve- trunks. As I have had occasion to demonstrate elsewhere, 1 it appears that successive excitations do not accumulate in the nerve, whereas it is quite probable that they do in the receiving organs, whether muscular or sentient. It was of interest to ascertain if the cortex cerebri acted in the same manner, and here is the result of experiment. With a chloralized dog, excitation of the antero-superior portion of the sigmoid gyrus induced movements of the eyelids upon the same side and of the fore-legs of the oppo- site side. Currents were frequently repeated at a strength of 10, Dubois-Reymond indicator. At o° (maximum) with a single excitation (closed or open) there followed no effect. A movement could be induced by making with the hand three or four tolerably rapid interruptions. In replacing the indicator at io°, very frequent excitations produced movements both of eyelids and fore-legs, but, as has been noticed by Schiff, the movements were very retarded. That retardation only signifies that the excitations are accumulated, and that they end in producing a result : the first excitations give no result, the last only (which includes the previous ones) does. To explain this phenomenon it will perhaps be well to introduce one of my old tracings. It shows that frequently repeated excitation's end by accumulation and produce no motion except when made with a certain frequency (fig. 10). I have obtained phenomena which can be compared, by exciting the cerebral surface of a dog, and registering his movements. After adapting an instrument to register the muscular 1 Thèse inaug. , Recherches sur la sensibilité. Paris, 1877. 66 CEREBRAL CONVOLUTIONS. PHYSIOLOGICAL PROPERTIES OF THE CONVOLUTIONS. 6j movements of the fore-legs, 1 observed that isolated exci- tations produced no effect, whereas closely succeeding excitations produced a manifest tetanus (fig. n). In a similar experiment, MM. Franck and Pitres have also observed this addition of excitation, even when they were somewhat separated (fig. 12). It cannot be supposed that we are here dealing with latent accumulations either in the gray ganglionic sub- stance or in the subjacent white fasciculi ; in fact, direct excitation of these fasciculi, after removal of the gray cor- tex, gives no accumulation of excitations. Fig. 12. — Addition of excitations in the substance of the gray cortex. From a to b, excitations induced without effect. The line commences to wave at b, and continues to increase. At the bottom, line of vibrations of the diapason. (One hundred vibrations per second.) As a result of all these facts it seems that the gray cortex is directly excitable. A number of other experiments also support this hypo- thesis. Pitres and Franck have shown that the interposi- tion of the gray substance produces a retardation of -^ in a second, a small figure of itself, but enormous consider- ing the trifling distance of only some millimetres. This indicates that the subjacent white fasciculi are not excited, but rather the gray cortex, which responds very slowly to the excitation. It has been objected that abrasion of the gray cortex does not prevent the action of electricity, the subjacent white fasciculi alone being excited. But does that prove 68 CEREBRAL CONVOLUTIONS. that the cortex is not a centre ? Not at all. Let us sup- pose, as Vulpian has said, that the abraded cortex is really a centre, it must have conductors which run to the deep part of the brain. These conductors are precisely the white fibres, and excitation of the conductors should give the same results as excitation of the centres from whence they start. The reason adduced by Dupuy, that there were no centres in the cortex because chemical or mechanical excitation produced no reaction, is evidently insufficient ; indeed, the white substance which does not respond to chemical exci- tants evidently does respond to electricity ; so that, should any part of the nervous system may respond to chemical agents, that would be no proof that it would not respond to electricity. We cannot dwell upon these facts, and will but add a resume : i st. Peripheric diffusion can be avoided, but diffusion from the gray to the white substance cannot be avoided. 2d. The white substance of the brain is certainly excita- ble, as Haller thought, and contrary to Flourens' opinion. 3d. The cortex cerebri is probably excitable by elec- tricity, though it is nearly impossible to furnish direct proof of it. 4th. In the order of electric excitability of the nervous system, there may be admitted (though perhaps as yet some- what hypothetically) : (a), the nerve terminations ; (b), nerve- trunks ; (V), central gray substance; (d), white substance of the nerve-centres. I will also call attention to an important fact hitherto imperfectly studied ; that is, the rapidity with which exci- tation disappears. It seems that the nervous centres are much more delicate than the nerve-trunks, and that ex- haustion there ensues much more promptly. But, on the other hand, after a very short repose, excitability returns. I will not dwell upon the facts which seem to prove that the cortex cerebri may give rise to epileptiform convul- PHYSIOLOGICAL PROPERTIES OF THE CONVOLUTIONS. 69 sions (Hughlings Jackson). Vulpian says that the mani- festations in partial epilepsies always leave a considerable doubt in the mind ; because, although a lesion may be dis- tinctly visible in the cortex, still it is impossible to know if the epilepsies really proceed from it. Partial epilepsies often exist when there is no lesion appreciable either to the naked eye or the microscope. The experimental epi- lepsy observed by Franck fully proves the excitability of the gray substance. It would be interesting to investigate how that excite- ment is modified by sanguiferous tension. The influence of the brain upon sanguiferous tension has heretofore been investigated ; but the influence of arterial pressure upon the excito-motor power of the brain would be a curious study. We are here brought to a consideration of the method in which the cortical region responds to electricity. Hitzig has especially employed direct currents, which afford better results than the induced, interrupted current chosen by Ferrier. Of the two poles, the anode (positive) acts more energetically than the cathode (negative), and this differ- ence is more marked in proportion to the feebleness of the current. Schiff has also made some interesting obser- vations upon the same subject, though they have led to a theory certainly erroneous. 1 The constant current acts better than the induced ; and of the induced currents the open one is best. This is be- cause it lasts longer ; and Schiff says that for the sensa- tions a certain duration of excitement is necessary. Motor responses, he says, are not instantaneous, but require the ■g^-g of a second ; whereas, if a nerve was employed as the conductor, the interval would be but the 3-0V0 of a second. He holds that it consequently involves a reflex action. Now this conclusion is not exact, because the cortical substance is evidently concerned in these phenomena. 1 Lezioni sopra il systemo nervoso encefalico, Firenze, 1S74, et lo Speri. mentale, xxxvii., p. 239, xxxviii., p. 241. 6 JO CEREBRAL CONVOLUTIONS. A very important problem to elucidate, not only on ac- count of the method, but in a general physiological point of view, is the influence of various poisons on the cerebral excitability. Hitzig in his first memoir 1 has shown that, in animals etherized or under the infl uence of morphine, the sigmoid gyrus is excitable. He concludes by saying : " When ani- mals are profoundly etherized, though all traces of reflex action have disappeared, the electric excitability of the brain is partlv retained, partly lost. On the contrary, with morphine, even in large doses, the excitability is not dimin- ished." Carville and Duret 2 in their experiments have employed chloral with good results, it giving an absolute insensibility, though preserving, with some reduction, the cerebral excitability. Bochefontaine, 3 in a remarkable series of experiments, shows that with the use of curare, which completely para- lyzes the voluntary muscles without affecting those of organic life, it can be proved that the brain preserves all its excitability. This is an interesting confirmation of the celebrated experiments of Claude Bernard, and it is seen that curare affects the nervous system only as it is con- nected with the muscles of animal life. Any one may satisfy himself that, as has been shown by Schiff, when an animal is in a profound state of anaesthesia, all motor re- action disappears, the bulb only exercising its functions. Upon this fact, together with those just mentioned, Schiff based his reasons for considering the movements succeed- ing the excitation of the convolutions as movements of reflex origin, a theory to which we shall recur. We only observe that, without further demonstration, it ought not to be said that chloral or ether affects only the reflexes. ■On the contrary, it very probably affects all the nerve- elements. 1 Loc. cit., p. 401 - Bull, de la Soc. de Biol., 1874, p. 377. 3 Arch, de physiol., 1876, p. 140. PHYSIOLOGICAL PROPERTIES OF THE CONVOLUTIONS. J\ When chloralization has been pushed to the extreme, the bulb is the only vestige of nervous life retained by the torpid animal, and by it are maintained the rhythmic movements of respiration ; under these circumstances it can be demonstrated that galvanization of the brain is not without effect. The following experiment affords proof : A small, lean cat was etherized and tied. Into the crural vein I injected forty-seven grains of chloral. The skull was opened and the crucial fissure laid bare. Excitation of that region provoked not the slightest movement of the legs, but it suspended the respiratory rhythm. In differ- ent regions of the cortex cerebri various points were found, the excitation of which immediately arrested respiration. Notwithstanding the enormous dose of chloral, the cat lived and respired with regularity for nearly four hours. At various times we verified that excitation of the brain and of the sciatic would arrest respiration. At the end of three hours sciatic excitation was without effect. A little later the same was true of cerebral excitation, and there- after the strongest electric currents had no apparent effects. We may hold, then, that .the respiratory action is the last to fail ; for when the excito-motor power of the limbs has disappeared, the action of the brain upon the bulb remains intact. It would seem that the excito-motor apparatus of respiration is the last to be paralyzed by poisons, both in the bulb and the cortex cerebri. The effects of asphyxia on cerebral excitability have also been sought, but the results are not very concordant. Hitzig 1 found from asphyxia no action upon the excita- bility. 1 Unters. iiber das Gehirn, Arch, fur Anat., 1873, P- 4°4- J2 CEREBRAL CONVOLUTIONS. Sec. 2. THERMIC, ELECTRIC, AND CHEMICAL CONDITIONS OF THE CONVOLUTIONS. Few experiments have been made upon the electric and thermic state of the convolutions. Schiff l and Caton - only have furnished some information upon the subject. Schiff, by means of thermo-electric apparatus, has proposed to measure the rise of temperature in the nerves and the nervous centres resulting from the influence of various excitations. I regret not being able to go into the details of these remarkable experiments ; I will give the conclu- sions only. Sensible irritation of the peripheric nerves produced an increase of heat in the brain ; excitation of the special senses, hearing, smelling, etc., had same result, so also with vivid impression, unexpected view of an object. In- deed, all mental activity expressed itself by augmented heat in the cerebral hemispheres. Other authors (Broca, Voisin) have observed the tem- perature of the skull a and obtained similar results. All lively impressions or mental labor augmented the exterior heat of the skull, often it was confined to one side, gener- ally the left (Broca). It is probable that this difference in the external tem- perature corresponded to a difference of temperature in the deep parts of the hemispheres. It might be supposed that thermic oscillations belonged 1 Arch, de phys., t. iii., 1870, pp. 1, 198, and 451. 2 Brit. Med. Jour., 28th Aug., 1875, p. 278. It is by an error that in the Revue des Se. méd. the quotation from Caton is translated as though the ex- periments had been made by Ferrier. 3 Lombard, Expériences sur l'influence du travail sur la température de la tête, analyse dans les Arch, de physiol., 1868, t. i., p. 670. Broca, Congrès de 1877. Voisin, Leçons sur les maladies mentales. France médic, 10 juillet, 1878. In course of publication. PHYSIOLOGICAL PROPERTIES OF THE CONVOLUTIONS. 73 to change of cardiac rhythm or to a difference in the local tension of the blood-vessels. Schiff rejects the first propo- sition, but is not so sure concerning the second. Whatever hypothesis may be adopted concerning the cause of these thermic phenomena, the fact of itself is very important and accords with that which we know concern- ing the chemical activity of the encephalon. Experiments of some date back 1 have shown that cerebral activity in- creased the production of carbonic acid, urea, and proba- bly also cholesterine. Consequently the nervous excite- ment which puts into activity the cerebral cells increases also the temperature and the chemical combustion. There is a third phenomenon correlative to the chemical phenomena, that is the variation of the electric condition of the brain. It has been observed by Caton and described in a short note. In the normal state, there is an electric current (positive) which goes from the cortex cerebri to the white substance (cut), or into which a gal vano metric needle (negative) has been plunged. Those points in the cortex cerebri where electrization induces movements of the head and neck, and which in repose are positive, Caton has observed to become negative when connected with the white section, after sensorial ex- citations, especially after excitation of the retina. The current changes direction and develops an absolutely negative variation as in a nerve which is excited and the muscle which contracts. 1 have repeated this experiment upon a chloralized dog with Lippmann's electrometer which gives such precise indications, and I have been but partially able to verify these statements. It is true that if an electrode be placed at the surface of the convolutions and another to the deep parts, there will be found to exist an electro-motor power, less than that in the muscle and considerably more than that in the skin and fibrous tissues. But in exciting the sciatic, I have been able to discover 1 Flint, Journ. de l'Anat., t. i., p. 565. ityasson, thèse inaug., Paris. 74 CEREBRAL CONVOLUTIONS. no variation in the direction of the cerebral electro-motor current. Perhaps the chloral-poisoning has prevented the phenomenon. However it may be, the experiment remains subject to repetition, and it would be interesting to follow the electric, thermic, and chemical variations of the brain, under the influence of sensorial or sensitive excitants. The theory of these phenomena is too complex to be discussed here. To my mind, the theory of Dubois-Rey- mond and Pfliiger is perhaps less satisfactory than that of Hermann, who explains the electric variations by chemical combinations. It is probable that the electric conditions depend upon increased chemical combustions, correspond- ing to increased nervous activity. Sec. 3. CIRCULATION IN THE CONVOLUTIONS. We will not pretend to treat of cerebral circulation in a complete manner ; it is proper, however, to speak of it as connected with the convolutions which are supplied with a rich and highly contractile arterial network. Very precise experiments demonstrate that this abun- dant circulation is necessary to maintain the life of the nerve-substance. By ligating the carotids and vertebral arteries, encephalic circulation is more or less completely arrested 1 and with it the phenomena of encephalic activity cease. Generally the circulation is at first completely abolished ; after a little it becomes re-established, and the lives of rabbits, and especially of dogs, can be preserved after the four arteries supplying the encephalon have been tied. Vulpian has employed a still more certain process for 1 For the history of the question I refer to the work of M. Couty, Influence de l'encéphale sur les muscles de la vie organique. Arch, de phys., 1876, p. 673. PHYSIOLOGICAL PROPERTIES OF THE CONVOLUTIONS. 75 the purpose of suppressing the circulation, not only in the spinal cord, but also in the brain, which is to inject the ar- teries with water containing a pulverized substance, pow- der of lycopodium for example, which serves to obstruct the minute encephalic arteries. 1 From this process, sensibility and voluntary motion dis- appear with surprising rapidity, the animal remains inert, the bulb alone retaining its power of function. Vulpian observed that in the spinal cord the gray sub- stance only was paralyzed, the white preserving its normal conductibility. Resting upon these fundamental facts, Couty has studied the effects of cerebral anaemia from arterial obstruction, and he first observed that this kind of anaemia did not affect the peripheric vessels, though galvanic excitation of the cortex cerebri does ; consequently, galvanic excitation acts some other way than as a simple arterial constrictor. This is worthy of note ; for some authors, especially Brown-Séquard, without clearly defining his opinion upon the effect of electric excitation, maintain the idea of vascu- lar constriction. It is not probable that he still holds that opinion as concerns galvanic excitation of the cortex cere- bri. In carefully examining the cerebral surface when electricity is being applied, no vascular contraction is ob- served ; on the contrary, there is dilatation, and capillaries before invisible, increase and become visible. I am aware, however, that the opposite effects have been seen, but I believe those to be complex effects, which attentive analy- sis can unravel. To the present there is nothing entirely positive and constant. Couty has made another deduction from these experi- ments : that since the gray substance exercises no influence upon the vessels, and electricity does, therefore electricity does not directly influence the gray substance. The de- duction is reasonable, but as it is always necessary in 1 Leçons sur l'appareil vaso-moteur, t. ii., 1S75, p. 11S. y6 CEREBRAL CONVOLUTIONS. physiology to distrust indirect proofs, it would be better to make the direct experiment, and ascertain if the cortex cerebri of the animal whose encephalon is anasmied by the powdered injection is still excitable by electricity. This alone will permit a rigorous and indisputable conclusion. Be this as it may, so far as concerns cerebral function, we see that complete anasmia rapidly suspends sensibility and voluntary motion. We will now see what modifications belong to normal cerebral circulation. Attention is at first called to the difficulties of experi- mentation. If the brain of an animal is exposed, contact with the air will excite or paralyze the vessels, and gener- ally produce intense congestion. If it be shielded with a glass cover, the exuded blood and fluids prevent seeing what goes on ; and besides, what could be concluded, for might not the consecutive encephalitis be a source of error difficult to eliminate ? Moreover, to prevent voluntary movements of the animal, which, if violent, would suddenly change the venous pressure, chloral, morphine, or ether would be necessary, and consequently no conclusion of a certain nature could be arrived at. Thus we have recourse only to indirect proofs or to in- conclusive experiments. Physiological knowledge upon the subject is as yet very vague. Some things, however, are precisely known. Long since, Claude Bernard ' observed that, after section of the great sympathetic, the hemisphere of that side was warmer than the other. In this respect, the arteries of the brain acted in a similar manner to those of the eye, the ear, and the face. Vulpian" repeated these experiments by exciting in- stead of cutting the sympathetic nerve, and in various cases he has seen the vessels contract in a most notable manner. Nothnagel states that excitation of the sciatic nerve 1 Mém. de la Soc. de Biol., 1853, p. 94. 2 Loc. cit., t. i., p. 109 ; t. ii., p. 120 et seq. In that work will be found a complete history of the question ; it is therefore needless to reproduce it here. PHYSIOLOGICAL PROPERTIES OF THE CONVOLUTIONS, yj causes a reflex dilatation of the vessels of the pia mater. But that, reflex in the encephalic capillaries has been thrown in doubt, and it does not appear to me that the matter can be considered as settled, although Regnard, in an interest- ing work, 1 states that he has seen peripheric excitations produce cerebral congestion (Expér. I. et III.). As Vulpian remarks, excitation of the sciatic (after sec- tion of the great sympathetic) often causes contraction of the vessels of the ear, and the same phenomenon is proba- bly produced in the vessels of the encephalon. It is possi- ble, then, that the vaso-motor action upon the periphery of the vessels from the pia mater may induce either dilatation or contraction, according as the great sympathetic is in- tact or not. In its pathological aspect, Brown-Séquard thinks that the reflex contraction of the vessels of the pia mater might produce cerebral excitation and consecutive epilepsy by anaemia. This theory seems controverted by that which we have just remarked, concerning the immediate paraly- sis of the excitability of the brain by anaemia. Besides, Ferrier has observed that, accompanying an epileptic at- tack produced by galvanic excitation of the cortex cerebri of an animal, the surface of the cortex was congested and not anasmied. Vulpian has several times observed the same. Many authors have dwelt upon the relation of sleep to encephalic circulation. It has been supposed that sleep was due to cerebral congestion. This was contested by Durham, who made the first regular experiments upon the subject. 2 Removing a round bit of the skull, he laid bare the dura mater and examined the brain. From his experiments he concluded, that during normal sleep, the brain is anae- mied and that upon waking the brain became congested, so that anasmia was either the cause or the effect of sleep. Durham's experiments are, to be sure, few and open to 1 Thèse de Strasbourg, 1868. ■ Physiology of Sleep. Guy's Hosp. Reps., i860, p. 14g et seq. 78 CEREBRAL CONVOLUTIONS. criticism. I would remark the same respecting observa- tions made upon those ill or wounded. 1 Regnard's experiments upon chloroformed animals prove nothing for the normal state, at least the demonstra- tion is insufficient.' 2 Flemming 3 has made some researches which seem to confirm the theory that sleep results from anaemia. Strong pressure upon the carotids produces a passing hyperesthe- sia, characterized by vertigo, ringing in the ears, hyperi- deation, analogous to that in sleep, finally sleep — sleep and anaesthesia. But what relation is there between these phenomena and real sleep ? Brown-Séquard has also defended the theory of cere- bral anaemia as the cause of sleep, and to a certain degree he assimilates normal sleep to a light attack of epilepsy. He produces an ingenious likeness, but a phenomenon of which the cause is not known cannot, be explained by a phenomenon yet more mysterious. 4 At all events, the theory of anaemia, supported by the facts of Durham and Flemming, carry no more conviction than other facts which would seem to prove the contrary. The direct experiments undertaken for the purpose of judging the condition of the cerebral surface have never given uniform results. Neither Regnard, Langlet, Durham, Hammond nor J. Cappie 5 have ever been able to precisely describe, by these methods, the condition of cerebral circulation during sleep. Gubler 6 thought that observation of the pupils would give useful indications. In fact, it is admitted, and many 1 Krauss, Gaz. hebd., 1854. — Brown, Am. Jour. Med. Se, 1S61, etc. '-' See the excellent thesis of Langlet, Etude critique sur quelques points delà physiologie du sommeil, th. inaug., Paris, 1872. 3 Anœsthesia by Compression of the Carotids, Bull. gén. de thérapeut.), t. xlix., p. 37). 4 For an exposé of these opinions by Brown-Séquard, consult an analysis which he has given of Kussmaul and Tenner. Jour, de Phys., t. i., 1858, p. 201. 5 The Causation of Sleep, Edinb., 1S72. 6 Gaz. des hôp., 1S58. PHYSIOLOGICAL PROPERTIES OF THE CONVOLUTIONS. 79 facts seem to prove it, that the encephalic circulation and that of the iris are allied, congestion of the first always coinciding with irido-choroidian congestion. Now when the iris is congested, the pupil is contracted, consequently contraction of the pupil is a sign of cerebral congestion. In normal sleep there certainly is almost always contrac- tion of the pupil ; but, as I have before said, should we not exercise prudence in accepting indirect proofs, requir- ing a series of reasoning which may be excellent in appear- ance, but perhaps in reality erroneous ? To affirm that a thing exists, it must have been seen, and unfortunately it has not yet been seen in normal sleep, un- complicated by pathology or experiment, whether the brain was congested or angemied. The question, then, is in dispute and the protocol incomplete. Thanks to registering instruments, science has lately been enriched by some valuable knowledge relative to cerebral circulation. Some time since, Magendie, 1 Bourgougnon, 2 and my father 3 studied the movements of the brain and the oscil- lations of the cephalo-rachidian fluid. 4 These labors demonstrated that the encephalon becomes swollen during violent respiratory efforts, and that cere- bral movements depend in part upon the cardiac impulse and partly upon the respiratory rhythm. In the hands of Salathé, Franck, 5 Mosso and Giaccomini, 6 the graphic method has given very remarkable results, which confirm and complete the opinions of previous observers. Although these experiments could not, as was realized 1 Jour, de la phys., t. vi., et t. vii., 1825. 2 Th. inaug., Paris, 1S35. 3 Anat. méd. chir., 1st éd., 1857. 4 For the bibliography see the very complete thesis of our friend Dr. Salathé, Recherches sur les mouvements du cerveau, Paris, 1877. The major part of the experiments there mentioned may be found in the Comptes rendus du labora- toire de M. Marey, for 1876. 5 Researches upon Expansion of the Brain. Jour, de l'Anat., 1877, P- 20 7- 6 Comptes rendus de l'Acad. des Se, 3d Jan., 1877. SO CEREBRAL CONVOLUTIONS. by Franck 1 and Salathé 2 serve to settle the question re- specting - the circulatory cause of sleep, nevertheless it gave positive facts relative to arterial tension in the brain. The following are the principal facts thus brought for- ward : — i st. In repose, in absence of all effort, movements of the brain do not correspond to the respiratory rhythm ; only to the arterial rhythm. 2d. Each systole of the heart increases the volume of the brain, a kind of congestion. This fact respecting the brain is analogous to that which Piégu, Mosso, and especially Franck have observed in various other parts of the body, only on account of the enormous vascularity of the cortex cerebri the phenome- non is there much more emphasized. 3d. Inspiratory and expiratory efforts greatly change the movements and volume of the brain. Expiration and effort augment its volume, inspiration greatly diminishes it. Compression upon the veins of the neck increases it. 4th. The cephalo-rachidian liquid is the moderator or safety-valve which protects the distended cerebral pulp from pressure against the skull-walls (A. Kichet). We reconsider these facts first, because they are the only positive ones which we possess relative to cerebral circulation, and also that cerebral circulation is in reality the circulation of the convolutions. The white matter has little vascularity, and the central gray masses have a vol- ume greatly inferior to the cortex cerebri. It may be said that about half of the blood sent to the encephalon is dis- tributed to the cortex. The convolutions, then, do not always contain the same quantity of blood ; with each action of the heart it varies, but this variation produces no functional disturbance. The knowledge furnished by pathology relative to cere- bral congestion or anaemia is of minor value (heart disease, maladies of the great sympathetic, migraine, disorders of sleep, plethora, etc.), and we will not here discuss it. 1 Loc. cit., p. 285. * Loc. cit., p. 48. FUNCTIONS OF THE CONVOLUTIONS. 8 1 CHAPTER II. FUNCTIONS OF THE CONVOLUTIONS. Unfortunately we cannot treat of this vast question in its entirety. We will attempt, however, to bring out the positive points which the various methods of investigation have given to science. Convolutions can be said to have three principal func- tions : motion, sensation, and intellection ; we will examine them successively. Sec. i. FUNCTION OF MOTION. A. METHODS OF INVESTIGATION. Method by excitation. — We have before spoken of the methods of electrizing certain portions of the cortex cere- bri. Some points only remain to be noticed. a. The current must not be too strong. b. The electrodes should be near together. c. Care should be taken that the surface is not covered with blood. Without all these precautions there is greater liability to diffusion, and therefore the conclusions cannot be so exact. Furthermore, shaking of the brain, loss of blood, pro- longed exposure of the convolutions to the air, should be avoided. The results of different experiments cannot be considered as susceptible of comparison unless the experimental con- ditions have been the same. (Chloroform, chloral, mor- phine, etc.). 82 CEREBRAL CONVOLUTION'S. Electric excitation is an excellent process, but as it is subject to various grave objections it should be corrected by other methods. Method by destruction. — Abrasion was first employed by Fritsch and Hitzig. Upon removing with the bistoury a thin bit of cerebral substance, paralyses follow. These have been especially studied by Carville and Duret. The cerebral bit may be taken away with a scraper in place of a bistoury, or still better, may be cauterized with a hot iron. According to Carville and Duret all these processes give about the same results. These authors have shown that dogs so operated upon present certain paralyses, or rather — the loss of motion being incomplete — pareses. A second method has been employed by Fournie, 1 Noth- nagel, 2 and Beaunis. 3 This consists in the injection of a caustic liquid (chloride of zinc, perchloride of iron, chro- mic acid) serving to destroy the cerebral parts with which it comes in contact. On account of the diffusion of liquids and consecutive inflammation, it is doubtful if this method gives good results, at least for the cortex, though respecting the cor- pora striata and the optici thalami, interstitial injections seem to have rendered Nothnagel some tolerably precise facts. Along with interstitial injections should be placed Goltz's method of injecting compressed water into differ- ent points of the hemisphere. This process, which destroys the cortex upon a somewhat extended scale, does not seem adapted to determining the motor regions of the convo- lutions. The third method we have before spoken of, it is that of Vulpian and Couty. 1 Experimental Researches upon the Functions of the Brain. Paris, 1873. ■ Virchow's Arch., t. lvii. , lviii., lx. , and Ixii. ; Experimentelle Untersuchur gen uber die Functionen des Gehirns. 3 Traité de phys., 1876, note 5, p. 1101. FUNCTIONS OF THE CONVOLUTIONS. 83 It consists in injecting powdered lycopodium and then examining the condition of the arteries in the brain, to ascertain precisely the cerebral regions which have been anaemied. Experimental process, to a certain degree, makes known to us the general influence of the encephalon, but for pre- cisely localizing a phenomenon as originating in a certain convolution or in a specified region, it is doubtful if this method is sufficient ; but it may always serve as a means for correction. In short, the method of superficial destruction, either bv bistoury or red-hot iron, and that of electric excitation are those which have given and will give the greatest services. Thev have their inconveniences, but we know nothing better. B. ACTION OF THE CONVOLUTIONS UPON THE MUSCLES OF ANIMAL LIFE. When, as in the experiments of Fritsch and Hitzig, the superficial part of a dog's encephalon is excited by a moderate electric current that half of the body opposite to the hemisphere excited will exhibit movements, vary- ing according to the points excited and differing somewhat also as the experimental conditions may differ. The general character of movements thus induced differ considerably from those produced by excitation of the nerves or muscles. They are combined movements, limited to a group, or rather to a muscular function. They appear as if destine'd to some use. Besides this, they are much slower and more feeble than movements occasioned by direct nerve or muscular excitation. The exact limitation of the action from motor-centres interests the physiologist less perhaps than the medical practitioner ; much, however, has been written on the question. The following cut gives an idea of the centres found by 8 4 CEREBRAL CONVOLUTIONS. Fritsch and Hitzig, and the explanatory text beneath suf- ficiently conveys their opinion. Fig. 13. — A dog's brain, serving to explain the researches of Fritsch and Hitzig. Triangle, motor-centres of muscles of the neck. Cross and dot, centre of extensors and adductors of fore-leg. Cross, centre of flexion and rotation of fore-leg. Quadruple cross, centre of hind-leg. Circle, centre of facial nerve (?). •uric I Fig. 14. — Right hemisphere of dog's brain (after Ferrier). A, Fissure of Sylvius. B, Crucial furrow. O, Olfactive bulb. I., IL, III., and IV., first, second, third, and fourth convolutions. The first result acquired by Fritsch and Hitzig, and con- firmed by Ferrier, Carville, Duret, and many others, is FUNCTIONS OF THE CONVOLUTIONS. 85 that only the region surrounding the crucial furrow is motor. To this rule, however, there are some exceptions. Ac- cording to Hitzig, movements of the muscles of the neck could be excited at the point indicated by the triangle, though these movements were not produced with con- stancy. Ferrier, in his numerous and interesting experi- ments, differs somewhat from Hitzig. The preceding cut (fig. 14) illustrates the localizations given by Ferrier: 1. The hind leg is advanced as for walking. 3. Undulatory motion of the tail. 4. Retraction and adduction of fore-leg. 5. Elevation and forward movement of shoulders. 7. Movements of the eyes. 8. Retraction of angle of the mouth. 9. Opening of the mouth and barking. 1 1. Retraction of angle of the mouth. 12. Opening of the eyes; head turns to the opposite side. 13. Eyes turn to the opposite side. 14. Ear becomes erect. 15. Twisting of nose to the same side (?). These experiments have been repeated upon jackals and cats, and even upon animals where the convolutions are scarcely developed. They have no great interest though, especially as the exact localization of these excitations, as related to the resulting movements, is in no way certain. Experiment has been made upon the monkey by Hitzig and frequently repeated by Ferrier. In the following cut Ferrier has represented the various excitable points of the cortex cerebri of the monkey : — 1. Leg advances as in walking. 2. Complex movements of thigh, leg, and foot. 3. Movement of tail. 4. Retraction and adduction of arm. 5. Forward extension of arm and hand. 6. Supination and flexion of fore-arm. 7 86 CEREBRAL CONVOLUTIONS. 7. Zygomatic action, drawing the mouth backwards and upwards. 8. Elevation of ala of the nose and upper lip. 9 and 10. Opening of mouth with protrusion (9) and retraction (10) of the tongue. Fig. 15. — Lateral hemisphere of the monkey (after Ferrier). 12. Eyes open and turn to opposite side, pupils dilate. 13. Eyes turned to opposite side, raised (13), lowered (13'). Pupils contracted. 14. Pricking of opposite ear, pupils dilated, head and eyes turned to opposite side. On account of the similarity between the monkey's brain and that of man, experiments made upon the monkey may serve to determine the motor-centres in man, and Ferrier has indicated upon the preceding schematic figure how his experiments may be applied to the human subject. 1 In the monkey, excitations about the fissure of Rolando give the same results as excitations of the sigmoid gyrus in the dog. Elsewhere, at the periphery of the occipital, or even the frontal lobes, no movement follows. The question is less simple, however, than one would at first believe, and is not settled so but that there still re- main uncertainties. 1 Functions of the Brain, French trans, by Duret, 1878, p. 222. English Edition, p. 304. FUNCTIONS OF THE CONVOLUTIONS. 87 Thus Hitzig, 1 in other experiments, seemed inclined to believe that the anterior portion of the sigmoid gyrus (that which in his design responds nearly to the letter N, and the sign A), is not excitable by electricity, and may be removed without producing paralysis. The posterior part of the gyrus (that corresponding to E, and 1, 5, and Fig. 16. — Lateral view of human brain. (Letters same as for preceding cut.) 4 of cut 14), on the contrary, cannot be destroyed without consequent paralysis. With this paralysis there is a series of complex phenomena, difficult to disentangle, and which Schiff calls ataxia, and which Hitzig considers as signifi- cant of the abolition of muscular sensibility ; besides the phenomena of paralysis (absence of energy, will), there are also phenomena of special anaesthesia, particularly muscular ansesthesia. 1 Neue Untersuchungen, Arch, fiir Anat., 1S74, p. 432. 88 CEREBRAL CONVOLUTIONS. Marcacci ' has recently observed that the excitable zone of the sheep's brain is chiefly in front of the crucial fissure, where there are four distinct centres, one for movements of the fore-legs, one for the neck, one for the face and tongue, and one for the movements of the jaw. No dis- tinct centre is found for movements of the hind legs. According to Ferrier, the anterior part of the sigmoid gyrus produces movements either in the head, eyes, or neck. I will add, that in experiments made with Boche- fontaine, we have confirmed this statement, and we have also observed that with quite moderate currents, move- ments were induced either in the eyes or eyelids. We have seen electrization of the anterior part of the sigmoid gyrus of a chloralized dog provoke contraction of the orbicularis palpebrare of the same side, and this where the influence of the dura mater was out of the question, as it was cut to a considerable distance, and upon being ex- cited did not induce the same reflex. Another fact seems to prove that there is not in the manifestation of any given movement the regularity sought for. Indeed, with the same dog, the electric excitation at the same point back of the crucial furrow, without chang- ing position of the electrodes, we have frequently seen were dependent upon the strength of the current, move- ment of the fore-leg, movement of the hind-leg (with very feeble movement of the fore-leg), and a very forcible move- meni of both fore and hind-legs. Consequently, absolute, inflexible localization of the motor-zones is all but impossible. There are zones which encroach upon each other, but none of these zones have limits of determined, rigorous constancy. The best proof of this is the difference existing among authors. If I were to venture an opinion on the subject, I should say that so far as concerns details, the point is of small im- portance. It is of no special importance to know if there 1 Arturio Marcacci, in Rendiconto delle ricerche sperimentali eseguite nel gabinetto di fisiologia délia R. Universita di Siena. Milan, 1S76. FUNCTIONS OF THE CONVOLUTIONS. 89 is a centre for the ear, and exactly how many millimetres it is distant from the centre for the pupil. That which is important is to know if there certainly are centres for certain determined movements. It is already proved (as respects the dog) that the pos- terior part of the crucial furrow is the eminently excitable region ; above for the hind legs, below for the fore-legs. Concerning centres for other muscular movements, I refer to Ferrier's work. Their existence is more question- able and additional investigation is evidently necessary. We need not here consider the excitation of the surface of the cerebellum from which Ferrier observed movements of the eyes, we would only remark that the phenomena of diffusion towards the bulb ought to be more pronounced than that following the excitation of the hemispheres. Electricity not having given entirely indisputable re- sults, 1 the adjunct of another process has naturally been sought ; that of abrasion. According to Carville and Duret, this operation gives the following results : — 1 st. The paralysis is limited to a well-defined group of muscles. 2d. It is intermittent. 3d. It disappears at the end of five or six days. Generally the paralysis is not complete, it is a sort of lameness, so that the dog operated upon cannot bring the foot to place and so walks upon the back of it. Goltz remarked that the dogs could not give the paw, but that in combined movements they contracted the muscles very well, when such movements were induced by the reflexes. Schiff has dwelt upon the exhibition of ataxia and con- secutive movements resulting from ablations of the cortex, which he compares to the phenomena arising from section of the posterior columns of the spinal cord. 2 1 See that before said, p. 65 et seq. ■ Account of similar phenomena will be found in the memoirs of Goltz, Ueber die Verrichtungen des Grosshirns, Pfliiger's Arch., t. xiii., and of Hitzig, Neue Folge, etc., Arch, fur Anat., 1876, p. 692. 90 CEREBRAL CONVOLUTIONS. Albertoni and Michieli ' from their labors have given the following results : A. In rare cases there is no paralysis, though the opera- tion has been exactly at the sigmoid gyrus. B. The effects are more pronounced, defined, and dura- ble with dogs than with rabbits. C. Paresis in dogs diminishes upon the next day after operation, with rabbits it has by that time entirely disap- peared, and at the end of four or five days it disappears in the dog. It seems certain that in some cases there are more or less extensive destructions of the motor region of a cere- bral hemisphere without consequent paralysis. Upon this subject may be recalled an experiment of Renzi's, cited in their remarkable work by Lussana and Lemoigne. 2 It is stated that the power of standing was unimpaired, but the body was inclined to the right side. The instance published by Bochefontaine 3 is still more significant. " Vulpian, in one of his lectures of the course of 1875, repeated upon several dogs the experiments of Hitzig. In one the operation terminated, the wound was stitched up, and there was found complete absence of paralysis. The animal was kept ; some days after he was bitten by a another dog, the sutures were torn out, and a portion of the brain, in appearance like a reddish pulp, protruded through the opening in the skull. The wound healed without trouble, and for two months, during which the dog was kept under observation, there was no paraly- sis." The results, then, of the method by abrasion are : A. With a great majority of dogs, the ablation of the convolutions of the gyrus produces paralysis. B. These paralyses are transitory. C. With a small number of dogs there are no paralyses. 1 Lo Sperimentale, Feb., 1876. 2 Des centres moteurs encéphaliques, 1877, Arch, de phys., p. 121. 3 Bull, de la Soc. de Biol., 1875, p. 387. FUNCTIONS OF THE CONVOLUTIONS. QI Now as to the phenomena resulting from pathological causes. 1 st. There are a certain number of instances (very few, however) in which an entire cerebral hemisphere has been destroyed without effecting paralysis. Several cases may be cited. In a few words T will condense the following one borrowed from Prof. Porta and recounted by Lussana and Lemoigne. 1 "A young woman had an abscess upon the forehead . . . by use of a sound, destruction of the corresponding lobe could be recognized. During the last three days of her life, to the last moments, when convulsions and coma terminated life, the s?d?j'ect retained her mental, sensorial, and motor faculties as entire as though the brain had been uninjured. Post-mortem revealed the right hemisphere entirely suppurated, that is, converted into a yellow- ish-gray puriform substance . . . entirely disorganized and de- stroyed." As it is not my intention to enter pathology, except so far as it will serve physiology, I will not recite other analo- gous cases which may be found (few, to be sure, are well authenticated) in the old archives of surgery or in the bul- letins of the Anatomical Society, 2 etc. As Charcot says, very many of the reports of cases are without value, but it would be difficult to deny the truth of all. Thus, with the human subject, as with the dog, there are exceptions to the general and well-established law, that destruction of certain parts of the cortex results in par- alysis of certain muscles. 2d. The characters of these paralyses are the same as those of experimental paralysis, and 1 can do no better than to repeat the words of Charcot. 3 " There are hemiplc- 1 Loc. cit., p. 122. -See also the memoir by Brown-Séquard in les Arch, de physiol., 1877 P- 655. 3 In the thesis inaug. of M. Landouzy, Paris, 1876, p. 56; Convulsions et paralyses liées aux méningo-encephalites. 92 CEREBRAL CONVOLUTIONS. gias which may be called cortical, in contradistinction to those called central. The cortical paralyses are limited, transient, and variable ; the central paralyses total, embracing the entire one-half of the body, and always presenting the same characters ; cortical paralysis is abnormal, partial, so that it may be a mon- oplegia or may include the surface only y These curious modifications of cortical motor-innervation will be examined further on, in the theory of these phe- nomena. Some questions are yet to be resolved, for which pathol- ogy furnishes valuable knowledge. i st. Can lesion of a convolution or of a very limited re- gion of the cortex cerebri of itself produce paralysis ? We could cite a great number of cases, 1 but we will con- tent ourselves with recalling the following very clear one : Without loss of consciousness, a consumptive was affected wit Ji a sudden weakness of the left arm. The feebleness increased until death, which occurred on the fourth day after. The par. alysis was much more pronounced in the fore-arm than in the arm, and especially in the muscles supplied by the radial nerve. No sensorial disturbance. AUTOPSY. — A tubercle, the size of a millet seed, was found imbedded in the cortex, surrounded by a zone, one centimetre in diameter, of red softening. The lesion was located upon the posterior border of the fissure of Rolando {ascending parietal convolution), five centimetres and a half from the zipper border of the Jiemispliere. The brain was otherwise absolutely sound? 2d. Where are the pathological, alterations of the cortex located which produce paralyses ? 1 See Charcot and Pitres : — Contribution à l'étude des localisations dans l'écorce des hémisphères du cerveau ; in Revue mens, de méd. et chir., 1877, Nos. ii., iii. Bourdon : — Rech. Clin, sur les centres moteurs des membres, in Bull, de l'Acad. de méd., 1875, 2d série, t. vi., No. 43. — Foville : Ann. méd. psych., t. xvi., Jan., 1877. Bull, de la Soc. anat., 1875, 1876, 1877, 1878. Bull, de la Soc. Biol., 1876, 1877, 1878. — Lépine, in Revue mens, de méd. et de chir., mai, 1877. — Ferrier, British Med. Jour., March and April, 187S. — Bull, de l'Acad. méd., 1877, observations of Lucas. — Championnière, Terrillon, et Proust, reported by Gosselin. 8 Maurice Reynaud: — Bull, de la Soc. anat., 25 juillet, 1876. FUNCTIONS OF THE CONVOLUTIONS. 93 Observations of cerebral pathology, to a certain degree confirm the doctrine of cortical localizations. In the last few years, a large number of cases have been adduced and a very exact representation of the present aspect of the question may be found in the formulated conclusions clos- ing the Mémoire by Charcot and Pitres ;' they are deduced from the observations contained in the work: — a. The cortex cerebri is not functionally homogeneous ; only one part is concerned in the regular exercise of vol- untary motion. That part, which may be called the cor- tical motor-zone, includes the paracentral lobule, the frontal and parietal ascending convolutions, and perhaps also the foot of the frontal convolutions. /;. No cortical lesions, whatever their extent, situated outside the motor-zone, affect the power of motion. c. On the other hand, destructive lesions, even very limited, which affect either directly or indirectly the mo- tor-zone, necessarily entail disturbance of voluntary mo- tion. Pitres 2 has shown that lesions involving the centrum ovale are not manifested by motor disturbances unless they affect the fasciculi subjacent to the zone of cortical motor- centres (fronto-parietal fasciculi) ; if, however, they affect the prefrontal, occipital, or sphenoidal fasciculi, they pro- duce no motor trouble. He holds that the fibres composing the fasciculi of the centrum ovale are conductors, a section of which prevents manifestations from the cortical centres, as absolutely as the cutting of a telegraphic wire interrupts the current for telegraphy and renders useless the galvanic battery. Such, in a general way, is the topography of the corti- cal motor-zone. But would it not be possible to determine somewhat more precisely the motor-centre of such or such 1 Loc. cit., p. 456. ■ Recherches sur les lésions du centre ovale et des hémisphères cérébraux étudiées au point de vue des localisations cérébrales. Thèse, Paris, 1877. — See also Ballet, Gaz. méd., 1878, No. 2. 94 CEREBRAL CONVOLUTIONS. a limb or of the various muscular groups? Examination of facts has enabled Charcot and Pitres to say that the cortical motor-centres for the opposite limbs are situated in the paracentral lobule, and in the upper two-thirds of the ascending convolutions ; and that centres for facial movements are situated in the lower third of the ascend- ing convolutions, in the neighborhood of the fissure of Sylvius. Though in fact this only concerns the lower part of the face, inasmuch as cerebral lesions give rise to a hemiplegia which is always limited to the lower portions of the face, the superior parts remaining free (orbicularis palpebra- rum, superciliaris, frontalis), a symptomatic dissociation which gives us a right to seek a correlative anatomical dissociation. It is probable that the centre for isolated movements of the upper extremities is located in the middle third of the ascending frontal convolution. The exact situation of the cortical motor-centres for the nape of the neck, the neck, the eyes, and the eyelids is not at present known. 1 Respecting instances of united deviation of the head and eyes from hemispheric lesion, there is at present no abso- lutely satisfactory solution. Is paralysis a necessary consequence of destruction of the motor-zone ? Charcot, as will be seen, says yes. But such is not the opinion of all physiologists. Vulpian and Brown-Séquard cite some exceptions to the rule, and re- mark that, if there exist cortical centres, their suppression ought invariably to entail a loss of their function. Fur- ther on, this question will be examined as relates to supple- mentation. The three questions which have been proposed may be answered thus : i st. Cortical lesion alone can produce a permanent or a transitory paralysis. 1 Notwithstanding an observation of Grasset's, Progrès méd., 27 mai, 1876, p. 431. See also Landouzy, Arch. gén. de méd., 1877, août. FUNCTIONS OF THE CONVOLUTIONS. 95 2d. Cortical lesion produces paralysis only when it is seated in the motor-zone. 3d. All cortical lesions of the motor-zone produce paral- ysis (there are exceptions to this law). An important discovery confirms these different results ; that is, descending sclerosis from the brain ; it has been shown that in certain lesions of the motor-zone there was sclerosis of the spinal cord, consequently that the cerebral periphery is intimately allied to certain fasciculi of the spinal cord and the bulb. 1 The motor action of the cortex cerebri may manifest itself in many ways ; the action may be normal or convul- sive, and some writers have made interesting remarks upon that subject. Fritsch and Hitzig, 3 in their work of 1870, report having seen electric excitations of the cortex cerebri provoke convulsive contractions. These convulsions at first con- fined themselves to the muscles responding to the cerebral region excited, then became more general and extended so as at length to become truly epileptiform. Ferrier repeated these experiments and found that with animals under the influence of anaesthetics there were no epileptiform convulsions, whilst with those not chloralized they were easily provoked. 3 Other experiments in this field have been made, especially by Albertoni, 4 who describes an epilepto-genetic zone, which appears to be the same as the motor-zone of Hitzig and Ferrier. 1 Bouchard : Secondary, degenerations of the spinal cord, Arch, de méd., 1866, p. 443, t. i. — Cotard : Study upon Partial Atrophy of the Brain, thèse, Paris, 1868, obs. iv. — Charcot: Localizations in Diseases of the Brain, 1875. Lépin : De la Localisation dans les maladies cérébrales, thèse d'agrégation, 1875, p. 53. — Pitres : Soc. de Biol., 21st Oct., 1876.— MacDonnel : Dub. Jour. Med. Se, Nov., 1377, p. 451. — MacDonnel : Brit. Med. Jour., 14th July, 1877, p. 49. — Vulpian : Destruction of the Sigmoid Gyrus of a Dog, Arch, de phys., 1876. s Loc. cit., p. 317. 3 Loc. cit., p. 208. 4 Rendiconto di esperienze fatte nello gabinetto di Sienna, 1876, 2d semes- tre. ç6 CEREBRAL CONVOLUTIONS. Franck and Pitres have made experiments upon cortical epilepsy, and it is through their kindness that I am able to reproduce here some of their tracings (figs. 17, 18). It will be seen that excitation of the intact cortical zone produces phenomena quite different from those resulting from excitation of the subjacent white fasciculi. From the first there is a primary tetanus provoked by the direct excitation, but this is followed by a very remarkable secondary tetanus, which is entirely absent in excitation of the white fasciculi. The physiological interest of that experiment is easy to comprehend. According to Franck and Pitres, the centre of the gray substance which appears to be the point of departure may be removed during the provoked epileptic attack, and nevertheless the paroxysm will continue ; precisely as if, immediately after transmitting a telegraphic dispatch, the first end of the wire were to be cut ; that cutting would not destroy the dispatch which had gone on its way. From the observations of these authors it may be con- cluded that cortical epilepsy results from the accumulation of excitations in the gray substance, which excite in the way of successive discharges. In experiments mutually conducted by Bochefontaine and Viel, and recited in a well-written work by the latter, 1 Viel has succeeded in producing epileptic attacks by another process. Injection of nitrate of silver between the dura mater and the brain produces menigo-encephalitis accompanied by convulsions. "At the onset,'" says Viel, " there are only varied phenomena of ataxia. There is an uncertainty in the movements of the limbs, or of a single limb on the side opposite the lesion . . . when inflammation supervenes, the attacks become clearly epileptiform, with dilated pupils, striking togetlier of the teeth, excessive salivation, a tonic and a clonic period." 1 Symptomatologie de la méningo-encéphalite. — Thèse inaugurale, Paris, 1878. FUNCTIONS OF THE CONVOLUTIONS. 97 Pk .; iljîll . iliïiiuiKiir iiiiii'i (illiimmii" ■'limn ill Hindu; iiiiimiiin. 1 III1II11II1U 1 liliiii 1 (in .'llilll (IlillKllllll ' iniui 111111111. in riKilliKiin.' 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