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BY J. LUYS, PHYSICIAN TO THE HOSPICE DE LA SALPETRIEBE. ?^^\versity of ^^^^-jrfff ILLUSTBATIONS. "^ LIBRARY ^5/^/NGT0^iL5i NEW YORK: D. APPLETON AND COMPANY, 1, 8, AND 5 BOND STREET. 1893. \\Q ^c AUTHOR'S PREFACE. The present work, on the structure and functions of the brain, is an abstract of my personal experience as regards this subject, and of most of the ideas I have for many years been endeavouring to popularize in m.y public lectures at the asylum of La Salpetriere. It is divided into two very distinct parts. The first, anatomical, serves as the foundation of the work. It is followed by a second, purely physio- logical, which is its complement and necessary sequence. In the first part I have explained all the technical processes employed in arriving at the results indicated ; insisting at the same time upon the value of the method which I have found it necessary to adopt, which consists in making regularly stratified sections of the cerebral tissue, in the faithful reproduction of these by means of photography, and in the employment of successively graduated powers for the representation of certain details. I have been able, by means of these new methods of in- vestigation, to penetrate further into the still unexplored regions of the nervous centres, and, like a traveller returned from distant lands, to bring back correct views and faithful representations of certain territories of which our predecessors caught scarcely a glimpse. VI AUTHOR^S PREFACE. Thus, in fact, by making this photo-microscopic analysis of the nervous elements, I have been able to throw fresh light upon the intimate structure of the nerve-cell, and on the organization of its protoplasm, and to study it in situ, in its connections with the nerve- fibres and the surrounding network of neuroglia. In my explanation of the grouping of the various portions of the cerebral mechanism, I have endeavoured as much as possible to simplify their description, and above all, to avoid employing that strange vocabulary now-a-days so improperly imported into the nomencla- ture of the different central regions of the brain. I have therefore sketched synthetically the general economy of the structure of the brain, pointing out the intimate relations which exist between the cere- bral cortex, the true sphere of psycho-intellectual activity, and the central ganglions (those of the optic thalami and corpora striata) which are in a manner the intermediate regions interposed between this and the excitations which proceed from the external world. I have insisted on the fact, which ten years ago I was the first in France to bring to light, namely, that the optic thalamus, with the isolated grey ganglions of which it is composed, represents a place of passage and reinforcement for excitations radiated from the sensorial periphery, while the corpus striatum, with its different compartments, and arches one within another, is on the contrary directly related to the passage of voluntary- motor excitations. In this anatomical part I have particularly emphasized those details of the essential structure of the cerebral cortex, to the existence of which sufficient attention has AUTHOR S PREFACE. Vll not as yet been paid, and have utilized them from the stand-point of physiological interpretation. Thus, having- established the presence in the cerebral cortex of special zones of small cells subjacent to the pia-mater, and quite different in configuration from the zones of large cells occupying the deeper regions, I was led to see in this anatomical arrangement a clear relationship to a similar disposition existing m the constitution of the grey axis of the spinal cord. As a consequence, I was led to think that if, as is experimentally demonstrated, the small elements in the spinal cord be affected by the phenomena of sensibility, it was natural to admit physiological analogies where jnorpJiological analogies exist ; and consequently to consider the sub-meningeal regions of the cerebral cortex as being the histological territory specially reserved for the dissemination of sensible impressions ; while the deeper zones of large cells (analogous to the ant-^rior m.otor columns of the cord) might be considered as the regions of emis- sion (psycho-mptor centres) for exciting voluntary motion. Thus, I arrived at the demonstration that, in the very structure of the cerebral cortex, among the thousands of elements of which it is composed, there is an entire series of special nerve cells, intimately connected one with another, constituting perfectly defined zones, anatomically appreciable, and serving as a common reservoir for all the diffuse sensibilities of the organism, which, as they are successiv^ely absorbed in these tissues, produce in this region of the sensoriiiin co7nniiine that series of impressions which brings with it movement and life. viil AUTHOR S PREFACE. In the second part, which comprises an explanation of the uses of the different cerebral apparatuses of which the anatomical details have been previously analyzed, I have in the first place given a physiological explanation of the different fundamental properties of the nervous elements, considered as .living histological units. I have in this manner shewn that these properties, which are the ultimate generating elements of all the forms of activity of cerebral life, may be finally reduced to three principal forms : — sensibility, by virtue of which the cerebral cell enters into relation with the surrounding medium ; organic phosphorescence, which confers upon it the property of storing up in itself and retaining the sensorial vibrations which have previously excited it (as we see in the inorganic world phospho- rescent bodies preserve for a longer or shorter period traces of the luminous vibrations which have impinged upon them) ; automatism, which is merely the aptitude which the nerve-cell possesses, for reacting in presence of the surrounding medium, when once it has been impressed by this. Having thus surveyed each of these elementary pro- perties of the nervous elements in their origin, in their evolution throughout the organism, in their normal mani- festation and pathological deviation, I arrive at the demonstration that it is by means of their combination, and by the harmonious co-ordniation of all their truly specific energies, that the brain feels, remembers, and reacts ; and that, in fact, being the properties in which all the others originate, they are the only living forces that are always present, always underlying the infinite series author's preface. ix of operations which it every moment accomphshes ; and that without them that admirable and complex appa- ratus, at once so delicate and so simple, would be as absolutely without life and without movement, as the earth would be without the sun. Having thus examined the elementary properties of the nervous elements, I have shewn how their co- operation may be used to explain the principal phenomena of cerebral physiology. I have in this manner made it clear that by group- ing among themselves the foregoing data, we may perceive that all manifestations of cerebral activity — even though we have to deal with the phenomena of psychical life proper, or the operations of intellectual life,— like their fellows which have the spinal cord for a theatre (reflex phenomena) are always susceptible of being decomposed into three elementary phases ; that they are always originally determined by the arrival of an incident sensorial impression, recent or former (phase of incidence) ; accelerated by the particular reaction of the interposed medium, reacting by virtue of its specific energy (intermediate phase) ; and completed by the secondary reaction of the intermediate medium, reacting and carrying outwards the primordial vibration which has been communicated to it (phase of re- flexion). It results, then, from this manner of looking at the phenomena of cerebral activity, that 'it is always a fact of the vital order which is at the origin of every process in evolution. Sensibility is always the primary motor agent ; it originates all movement. Propagated through the sensori-motor machinery of the cortex, it becomes X AUTHOR S PREFACE. insensibly transformed, like a force in evolution, and ends by disengaging itself from the organism in the form of a motor act In short, in these researches, in which my sole object has been to carry the data of contemporary physiology into the hitherto uninvaded domain of speculative psy- chology, I have endeavoured to show that the most complex acts of psycho-intellectual activity are all defi- nitely resolvable, by the analysis of nervous activity, into regular processes ; that they obey regular laws of evolu- tion; that, like all their organic fellows, they are capable of being interrupted or disturbed in their manifestations by dislocations occurring in the essential structure of the organic substratum which supports them ; and that, in a word, there is from this time forth a true physiology of the brain, as legitimately established, as legitimately con- stituted, as that of the heart, lungs, or muscular system. As a consequence of what has just been said, it neces- sarily follows that this range of studies, so new and so attractive, should properly belong to the physiological physician and to him alone. Henceforward he may claim as his peculiar patrimony that special domain of the nature of man concerning which speculative phi- losophy has for so many centuries so long and learnedly harangued. It will be his task to fertilize it by his incessant labour, and to make it yield what all labour intelligently directed should afford, legitimate fruits — practical consequences which may be utilized for the benefit of suffering humanity. The history of medical science is present with its daily lessons, to shew us that the useful acquisitions which it has made have always been inevitably subordinated to clearer and more author's preface. xi precise notions concerning the anatomy of the organs whose care is its mission ; and when we transfer the same aspirations to the subject which now occupies us, this fact surely authorizes us to hope that in the future we shall see new methods in the treatment of mental maladies, and modes of action more efficacious than those now at our disposal, arise from a better compre- hended cerebral anatomy, and a more rationally directed cerebral physiology. J. LUYS. CONTENT S. pAca Preface ••••••••••••v PART L ANATOMY OF THE BRAIN. CHAPTER I. Methods of Study • • • • i CHAPTER II. Cortex of the ERArN— The Grey Cortical Substance • , ix CHAPTER HI. The White Substanxe of the Brain ...... 26 CHAPTER IV. The Optic Thalamus 34 CHAPTER V. The Corpus Striatum . 46 CH.IPTER VI. Physiological Deductions 59 2 XIV CONTENTS. CHAPTER VII. PAGB Physico-ChExMical Phenomena of Cerebral Activity . . 68 PART IL GENERAL PROPERTIES OF THE NERVOUS ELEMENTS. BOOK I. SENSIBILITY OF THE NERVOUS ELEMENTS. CHAPTER I. Graduation and Genealogy of thf. Phenomena of Sensi- bility 83 CHAPTER II. Evolution of the Process of Sensibility through the Me- chanism OF THE Nervous System — Unconscious Sensibility — Conscious Sensibility (Sensation) 91 CHAPTER III. Intra-Cerebral Propagation of the Processes of Sensibility 102 CHAPTER IV. r»ERTURBATIONS OF SENSIBILITY ..«••••• II4 CHAPTER V. Dlvelopment of Sensibility ....•«.■ ta6 CONTENTS. XV BOOK 11. ORGANIC PHOSPHORESCENCE OF THE NERVOUS ELEMENTS. CHAPTER I. PAGB INTRODUCTORY ,,,. 133 CHAPTER II. Genesis and Evolution of Memory 142 CHAPTER HI. The Memory in Exercise • • . 150 CHAPTER IV. Development of the Phenomena of Memory . • • . 159 CHAPTER V. Functional Disturbances of the Phenomena of Memory . 165 BOOK TIT. AUTOMATIC ACTIVITY OF THE NERVOUS ELEMENTS. CHAPTER I. Inteoductory ••••.••••••171 xvi CONTENTS. CHAPTER II. Genesis and Evolution of Automatic Activity . . • .176 CHAPTER HI. Automatism in Psycho-Intellectual Activity . • • . 180 CHAPTER IV. Dreams 195 CHAPTER V. Development of Automatic Activity . • • . . •. 200 CHAPTER VI. Functional Perturbations of Automatic Activity . . . ^05 PART III, EVOLUTION OF THi: PROCESSES OF CEREBRAL ACTIVITY. BOOK I. PHASE OF INCIDENCE OF THE PROCESSES OF CEREBRAL ACTIVITY. CHAPTER I. Attention ,. .••• 215 CONTENTS. XVIJ CHAPTER II. PAGE Constitution ok the Sphere of Psycho-Intellectual Activity 226 CHAPTER III. Genesis of the Notion of Personality ..... 233 CHAPTER IV. Development of the Notion of Personality .... 238 CHAPTER V. Functional Disturbance of the Notion of Personality . 244 BOOK II. PHASE OF PROPAGATION OF THE PROCESSES OF CEREBRAL ACTIVITY. CHAPTER I. Dissemination of Sensorial Impressions in the Plexuses of the Psycho-Intellectual Sphere — Glnesis of Ideas . . 250 CHAPTER 11. Evolution and Transformation of Sensorial Impressions . 256 CHAPTER III. The Judgment • »•, 2S9 xviii CONTENTS. BOOK III. PHASE OF REFLEXION OR EMISSION OF THE PROCESSES OF CEREBRAL ACIIVITY. CHAPTER I. PAGE Reflexion of Motor Processes upon the Phenomena of Vege- tative Life 313 CHAPTER n. True Period of Emission of the Processes which produce Voluntary Motion — Spontaneous Reaction of the Sensorjum-— Motived Resolution •••«».* 315 LIST OF ILLUSTRATIONS. PAGE Fig. I. — Diagram of a Section of the Cerebral Cortex . . 15 Fig. 2. — Cortical Cell of the Deeper Zones . . . .19 Fig. 3. — Diagram of Commissural Fibres of the Anterior Regions of the Brain 27 Fig. 4.. — Diagram of Commissural Fibres on the level of the Corpus Striatum .29 Fig. 5. — Diagram of Converging Fibres, and their Relations with the Central Grey Ganglions . . . .31 Fig. 6. — Diagram of the Sensori-Motor Processes of Cerebral Activity •••••••• ..di THE BRAIN. PART I. ANATOMY OF THE BRAIN. CHAPTER I. METHODS OF STUDY. The study of the nervous centres has always strongly attracted the anatomist as a field of labour ; and the reason of this is not far to seek. In the face of such a subject, not only does the very natural desire to pene- trate the inmost secrets of the organization of the anato- mical details under consideration come into play, but, further, there is that unconscious attraction which draws the human mind towards the unexplored regions of the unknown — towards those mysterious realms where the living forces of all our mental activities are silently elaborated, and where the solution of those eternal problems, regarding the relations of the physical organi- zation of the living being to the acts of its psychic and intellectual life, evades us as we pursue it. 2 THE BRAIN AND ITS FUNCTIONS. Hence it is that from century to century most of the great anatomists have, each in his turn, laboured in this direction. Hence Galen, Varolius, Willis, Malpighi, Vieussens, Vicq d'Azyr, Sommering, Reil, etc., have successively, in their immortal works, either described the organization of the nervous centres as they conceived of it at their own epoch, or expressed in their icono- graphies (with a more or less distinct glimpse of the truth) the objective fashion in which they saw the anatomical details they have successively represented. In dealing with a subject so vast and so delicate, and a material so fragile and easily alterable as the nervous matter, the student is necessarily forced to depend on the different methods placed at his disposal by the arts and sciences of his own epoch. Hence the smallest technical discoveries frequently become of inestimable value ; and it may be said, without exaggeration, that the utilization of chromic acid,* which, by hardening the nerve-substance, fixes it, with all its natural relations, without altering it, has been one of those new methods in laboratory work which have most essentially contributed to the success of those great achievements in this particular domain of anatomical science which our own century has witnessed. On the other hand, the perfecting of the magni- (ylng power of microscopes has been of immense service, and has permitted the spirit of man to advance with vast strides into regions as yet unexplored, where it stands face to face with those ultimate anatomical units, the nerve-cells, of which our predecessors scarcely * Hannovor, in 1840, was the first to point out the hardening properties of chromic acid. (Robin, Traite du microscope, p. 297. J. B. Bailliere, 1871.) METHODS iDF STUDY. 3 caught a glimpse. Thus it is now possible to give exact descriptions of their configuration, whether we study their connections, their minute structure, or the different pathological deviations they may undergo. The introduction of the microscope into the study of histology has been in our century for the world of the infinitely Httle, what at another period of human development the intervention of the telescope was for the exploration of the sidereal world. It has rendered distinctly visible all those myriads of elements which, from their extreme smallness, were concealed from the eyes of our predecessors. It has brought them to light, revealed the secrets of their minute organization, and opened to the investigations of anatomists an entire new world of unexpected ideas. Following upon this discovery, as a natural conse- quence, came the revelation of the art — previously un- known in our laboratories — of makinsf thin slices of nervous tissue, colouring them, rendering them trans- parent, and preserving them. The employment of reagents of all kinds, which, testing in some degree the special sensibility of each histological element, colours it in a particular manner, and sets in relief the pecu- liarities of its structure, has opened a new road for progress ; so that all over the civilized world, labourers, aided by physics and chemistry, have united their efforts, until we can say that the limits of the unknown recede, and that new conquests are perpetually being registered in our scientific reports. But this is not all. In this kind of research it is not sufficient to see for ourselves the new facts met with on our road ; it is necessary to make others see them, 4 THE BRAIN AND ITS FUNCTIONS. to represent in faithful statements the details of nature we have examined, and to place the newly-registered facts beyond dispute. Up to the present time it was the observer himself who pourtrayed, by means of his pencil, the objects which passed through the focus of his microscope. And, accordingly, we all know how widely these nominal drawings — even those made by masters of their pro- fession — usually diverge from the truth ; simply because they can never express more than those details which the artist has perceived and recognized, and a species oi unconscious selection from the objects which are passing before his eyes. It is, then, in presence of these deside- rata, as regards graphic representation, in drawings made by hand that we feel the necessity of applying the marvellous resources now oftered us by photography to the reproduction of microscopic objects. The sensitized plate henceforward plays its part in the world of scientific investigation, in the study of the phenomena that occur in the world of the infinitely little, as well as in the study of those that occur in the world of the infinitely great — registering histological facts as well as astronomical phenomena, and thus becoming the impersonal and automatic pourtrayer of the most minute details that have impressed themselves upon it. Thus, wonderful to relate, photography, very much superior to drawing, not only reveals the objects which the eye perceives, but brings to light in addition a whole series of latent details, which await but the intervention of a simple lens to be successively recog- nized upon the prints when obtained. These new means of investigation, which the scien- METHODS OF STUDY. 5 tific methods of the nineteenth century have placed within the reach of our generation, will, therefore, explain the progress accomplished, and show us once more that, in the long process of evolution which extends through ages, man only arrives step by step at the fragments of truth which he snatches, and that even his most persevering efforts only serve to cause the unknown to recede a few paces backwards. It is strange to find that, as fast as any progress is accomplished and new discoveries registered, new problems incessantly start up ; and that just when we thought we had arrived at the utmost limits of the known world, at the demon- stration of elements, simple, fixed, definite, our perfected methods of study enable us to see new complexities and unexpected horizons. Thus, for instance, by means of high powers, the histological elements of the nerve-cell, hitherto con- sidered as the primordial and irreducible units of the system, become themselves divisible into secondary elements. Photo-chemical histology, indeed, shows us that the protoplasm of the cell, formerly described as a homo- geneous substance, is arranged in a fibrillary trellis-work ; that its nucleus presents an arrangement of radiated fibres ; and that what was thought to be the nucleolus is itself a complex element. The nerve-cell thus becomes in its turn a little nervous organ sui generis, {See Fig. 2.) The same analytic processes enable us, moreover, to demonstrate that the network, so dense and compact, which unites all the nerve-cells of the cerebral cortex, for instance, one with another, is so delicate that, when enlarged to 2S5 diameters, the fibres of which it is 6 THE BRAIN AND ITS FUNCTIONS. composed become visible, like single hairs in appearance and magnitude, etc. Wliat will be the end of these unforeseen details which present themselves in the train of each adap- tation of a new method of study, to our researches into the nervous system ? No one knows as yet. It seems as though the secrets of nervous organization escape from our eyes as fast as we press further into the regions where they conceal themselves, and while anticipating the new methods of analysis which the future holds in reserve, we cannot help thinking that there is still much to do, and that now, more than ever, we should remenrber that true saying of Serres : ** We have been dissecting the brain since Galen's time, yet there is not an anatomist who has not left his successors something to do." The labours of which I am about to give a restnn^y are, then, but one of the phases of this long discussion concerning the structure of the nervous centres which has been going on for centuries. If they do not establish the truth absolutely and finally, they will at least have the merit of being the result of contemporary science, and a sort of synthesis of the methods of work at our disposal. The method I have employed for studying the organization of the cerebro-spinal centre in man, I have already explained in my first work.* It essentially consists in the preparation of a series of sections made methodically, millimetre hy millimetre, vertically, hori- * J. Luys, " Recherches sur ranatomie. la physiologic et la pathologie du systenie nerveux." Paris, 1865, J. B. Bailliere. METHODS OF STUDY. 7 zontally, and antero-posterlorly ; and — these sections being thus made according to the three dimensions of the soHd mass which was to be studied — in reproducing them all photographically. I set myself, then, to make a series of successive horizontal sections of the brain, previously hardened in a chromic acid solution, from apex to base, at intervals of about one millimetre, and as perfect as possible ; each being in its turn reproduced by photography. I made similar sections of the brain in a vertical and antero-posterior direction, and at regular intervals from behind forwards. These operations having been thus regularly con- ducted, this method enabled me to have representations of the reality as exact as possible ; to keep the natural relations of the most delicate portions of the nervous centres each by each, according to their normal connec- tions, and, in fact, without deranging anything. Thus by comparing the sections, horizontal or vertical, one with another, I could follow a given order of nerve- fibres in its progress, see its point of origin, and its point of termination ; study the natural increase in com- plexity of the different kinds of nerve fibrils, millimetre by millimetre, changing nothing, lacerating nothing, and leaving everything pretty much in its normal position.* * The plan of this work does not permit me to insist upon the innumerable difificulties I have surmounted, in arriving at the clear result already recorded in my photographic iconography. (Luys, " Iconographie des centres nerveux," J. B. Bailli^re, Paris, 1872.) In the first place I had to invent cutting instruments sufBciently delicate to make complete sections of the brain, of the thickness of about one millimetre. But these pieces, when sufficiently hardened to undergo the action of the cutting instrument, had acquired, on coming out of the bath of chromic acid, 8 THE BRAIN AND ITS FUNCTIONS. By means of these new photographic methods o{ reproduction, which are all the more precise because impersonal, I had only, then, to register the details the sun himself had printed, to place the prints in juxta- position, to compare them one with another, and thus to make a single synthesis of the multiple elements of analysis I had thus obtained by the automatic co-opera- tion of the light. The general view of cerebral topography having thus been fixed by these processes, the regions of more delicate texture, the special points which it was necessary to study in their minute elements, were further suffi- ciently magnified and reproduced, with successively in- creasing powers. I could thus render visible to the naked eye, and exhibit on a plan, details of structure which, up to that time, had only been seen in isolation under the tube of the microscope. By this means the mind of the observer, penetrating successively from the known to the unknown, from well-defined regions to those which are not so as yet, can easily make itself familiar with the details of the minute structure of the final nerve elements. The cerebro-spinal system in man and the vertebrates consists of three departments, independent one of another, and yet very intimately connected. These are: — I. The cerebrum proper. that peculiar uniform greenish colouring which renders them completely unfit for photogenic action. It was therefore necessary to discover a perfectly novel series of processes, in order to purify the >e sections from the chromic acid, and, without altering them, to impart to them photogenic properties. (See Journal d'Anatojme de Robin, Paris, 1872, for the whole series of the pro- cesses emploved to bleach the sections tinted with chromic acid.) METHODS OF STUDY. 9 2. The cerebellum and the apparatuses of cerebellar innervation annexed thereto. 3. The medidla spinalis and its encephalic expansions. In this study we shall occupy ourselves with the cerebrum proper only. The cerebrum consists of two lobes or hemispheres united to one another by a series of white transverse fibres, which form an anastomosis between the homo- ^ logons regions of each lobe, so as to constitute a twin system, of which all the molecules are consonant one with another. Each cerebral lobe, taken alone, presents for considera- tion in its turn : — 1. Masses of grey matter. 2. Agglomerations of white fibres. The masses of grey matter, which are composed of many myriads of cells, and are the essentially active regions of the system, are arranged at the periphery in the form of a thin, undulating, continuous layer, which constitutes the cerebral cortex ; and in the central regions in the form of two grey ganglions, coupled together, which are simply the grey substance of the optic thalami and corpora striata (opto-striate ganglions). The white substance, essentially composed of nerve- tubules in juxtaposition, occupies the spaces comprised between the cortical periphery and the central ganglions. The fibres of which it consists, and which merely represent lines of union between such and such resfions of the cortical periphery and such and such regions of the central ganglions, run, like a series of electric wires stretched between two stations, in two principal direc- tions. lO THE BRAIN AND ITS FUNCTIONS. 1. Some directly unite the different points of the cortical periphery with the central ganglions, and are lost in their mass. These are like the spokes of a wheel which unite its circumference to the central nave, which serves as their point of support. We may therefore describe them under the name of converging fibres. 2. The others, on the contrary, have a transverse direc- r\ tion. They proceed from one hemisphere to the other, thus uniting the homologous regions of the brain, right 1 and left. It may therefore be said that they serve as an anas- tamosis and commissure between these homologous regions, and that they are thus the agents which pro- duce unity of action between the two cerebral hemi- spheres. This order of fibres, by reason of its origin and connections, may legitimately be designated by the name of commissural fibres. These data bsing admitted, it may be said that the anatomic formula bj means of which we may define the structure of the cerebrum, of man as of the other verte- brates, is this : " The cerebrum is the sum total of the cerebral convolutions, united one with another, with those on the same side and with those on the other, and simultaneously with the central opto-striate ganglions." We shall now pass in review the different agglome- rations of the grey matter, and at the same time give a sketch of the principal details of the organization of the white matter. \»> ^oV^ '^ ^^ '^ LIBRARY CHAPTER IT. CORTEX OF THE BRAIN — THE GREY CORTICAL SUBSTANCE. Every one knows the external appearance of the cortical substance of the brain. It is sufficient to recall that of the brains of sheep, as served at table, to see at a glance that the grey cortical substance presents the appearance of a grey undulating layer, folded a great number of times upon itself, and thus forming a series of multiple sinuosities of which the sole object is the obtaining of increased surface. These foldings and refoldings, which attain their maximum of development in the human species, appa- rently obey some fixed laws as regards their distribution.* Some, in fact, have permanent characters which render them easily discoverable in all human brains ; others, and these form the greater number, present all possible varieties of external configuration, not only in different individuals, but even in the same individual, according as we inspect homologous regions in the right or ieic hemisphere. Take, for instance, a sheet of tracing paper, apply * See the interesting description of the topography of the cerebral convolu- fions given by Prof. Charcot in his lectures to the Faculty. — Progris Medical, X875, p. 283, 353, &c. 12 THE BRAIN AND ITS FUNCTIONS. it to a fresh vertical section of the brain, mark with a brushful of water-colour the contour of the cortical substance of one hemisphere, and fold the paper over ; you will thus see very clearly that the outline of the convolutions of one side does not adapt itself to those of the other. I have made such tracings repeatedly, and have never yet found a human brain completely symmetrical, completely balanced in its peripheral regions, and with the left regions of the cortical substance exactly corresponding to the homo- logous regions of the opposite side. There is another peculiarity, which it is important to notice, in the external examination of the cortical substance. In the adult, in vertical or horizontal sections of the brain, it is evident that the line of the summits of the convolutions is continuous, that their culminating points are all on the same level ; there is some uniformity in the distribution of the activity of nutrition over the whole mass. As old age advances different appearances begin to show themselves, and in studying the different effects of senescence in all the organs, it is curious to observe its characteristics in the human brain. We observe, then, that the grey substance becomes diminished in thickness ; that its colour changes to yellowish white in consequence of the passing of the nerve-cells into the granulo-fatty state; and that besides, the convolutions settle down in isolated groups, like mountains, undermined at their bases, which insensibly subside. Thus, in many old men in their dotage, we may note that the line joining the summits of certain CORTEX OF THE BRAIN. 13 groups of convolutions becomes interrupted ; that a cer- tain number of them are retracted and have sunk below the level of the surrounding convolutions ; and that thus, from the effect of time, there exists a slow and progressive absorption of the nervous substance. In individuals who fall prematurely into dotage from alterations of the cerebral substance, under the action of mental diseases, we find the same atrophy of the cortical layer. Thus I have very frequently ob- served atrophy of the convolutions in young subjects attacked by paralytic dementia, persons affected by hallucinations, and patients who have suffered from melancholic delirium. The thickness of the cortical substance in the adult IS on the average about two to three millimetres. Generally it is more abundant in the anterior than the posterior regions. Its mass varies according to age, and especially according to race, Gratiolet remarking that in races of low stature the mass of the cortical substance is but small.* Its colour presents some varieties. It is uniformly greyish, and as it were gelatinous, in the new-born infant ; in the child during its first years it is of a rosy grey ; in the old man it acquires somewhat of a yellowish-white colour, its vascularity being less distinct than in the adult. In the negro this substance is of a darker colour than in the white man. In the adult in whom development is regularly accomplished, the cortical substance presents itself very clearly to the naked eye, m the form of stratified zones, differing slightly in colour. We observe, in fact, that * "Gratiolet, Bulletin de la Societe d Anthropologie," 1859, p. ^% 14 THE BRAIN AND ITS FUNCTIONS. there exists a superficial sub-meningeal zone of a greyish colour, and transparent ; and a deeper zone, underlying the preceding, of a more distinctly reddish colour. When we take a thin section of this cortical sub- stance, compress it between two pieces of glass, and examine it by holding it up to the light, as Bail- larger first pointed out,* we see that it divides into secondary zones of unequal transparency, and that these zones cleave with a regular and fixed striation. We shall see that these appearances are merely the result of the minute structure of the cortical substance. Such are the characters which the cerebral cortex presents to the naked eye, and which every one may observe in fresh brains. Let us now penetrate, by means of magnifying glasses, into the interior of this soft substance, amorph- ous in appearance, of which the homogeneous aspect is far from revealing to us its marvellous details. Let us push our researches still further by means of thin sections rendered transparent and methodically coloured ; let us employ gradually increasing powers to pass from a known to an unknown region ; and avail ourselves of the magnifying processes that photo- graphy places at our disposal. We shall then be able to penetrate into these almost unknown regions of the world of the infinitely little, and, like travellers re- turned from distant lands, to bring back various pho- tographic images — indisputably faithful reproductions of the details which have struck us in the course of our voyage of discovery. We now find in the cortical substance a fixed ♦ " Memoires de I'Academie de Medecine de Paris," 1840. - .> 3 ^ 3 ^ .y ^ a ■" cj > o S JJ rt u S -5 bfi < S i„ = SO rs, givi region ipping 1) 5 ii u ii; t3 « f -^ '5. D x: E r-i 5 -c ■" •^ , ^ s U-i O 1> ^12 5 3 i2 4-1 3 O '^ ■*-• D cS « 3 1) .r. »- -G O 42 hoto- graphique," pi. xi. and xxxi., fig. x. THE CORPUS STRIATUM. 57 silently await the arrival of the stimulating spark destined to call them into activity. Thus it follows, from what we have just explained, that the corpus striatum, like the optic thalamus, is a nervous apparatus with multiform activities. It is a common territory into which the cerebral, cere- bellar, and spinal activities come in succession, to be combined, and I might almost say, to anastomose. It thus represents, from a dynamic point of view, a synthesis of multiple elements. It is in the midst of its tissues that the influence of volition is first received at the moment when it emerges from the depths of the psycho-motor centres of the cerebral cortex. There it makes its first halt in its descending evolution, and enters into a more intimate relation with the organic substratum destined to produce its external manifestations — in one word, materializes itself. (Fig. 6. — 12 and 17.) From this moment it comes into intimate contact with the innervation radiating from the cerebellum, and it is now no longer itself, no longer the simple purely psycho-motor stinlulus it was at its origin. It is asso- ciated with this new influence, which gives it somatic force and continuity of action. It then passes out of the brain by means of the peduncular fibres, combined with a new element, and pursuing its centrifugal course, it is finally extinguished here and there by setting in motion the difl"erent groups of cells of the spinal axis, whose dynamic properties it thus evokes. (Fig. 6. — 18 and 19.) Thus also, proceeding like an electric current into the different departments it animates, it now tends to 6 58 THE BRAIN AND ITS FUNCTIONS. produce phono-motor movements designed to express outwardly the emotions of our sentient personality, and now to determine in the different muscular groups, general or partial movements of flexion, extension, or progression, according as it is distributed to such or such groups of satellite cells, the habitual servants of its excito-motor demands. We see then, to sum up, by means of this simple physiological sketch, what an all-important part these two central ganglions play in the phenomena of cere- bral activity, and how completely different is the mode of action of each. The elements of the optic thalami purify and trans- form by their peculiar metabolic action impressions radiating from without, w^hich they launch in an intel- lectualized form towards the different regions of the cortical substance. The elements of the corpus striatum, on the contrary, have an inverse influence upon the stimuli starting from these same regions ot the cortical substance. They absorb, condense, materialize them by their intervention ; and, having amplified and incorporated them more and more with the organism, they project them in a new form in the direction of the different motor ganglions of the spinal axis, where they thus become one of the multiple stimulations destined to bring the muscular fibre into play. CHAPTER VI. PHYSIOLOGICAL DEDUCTIONS. Now, if we group synthetically the anatomical pro- positions we have tried to establish in the course of this work, we see that the brain is a geminate organ, formed of two hemispheres, of which the elements are strictly associated with one another, by means of a series of commissural fibres which unite them in- timately, and produce a certain tendency in their mole- cules to vibrate in unison. (Figs. 3. and 4.) Each of these two lobes, or hemispheres, is funda- mentally formed of masses of grey matter irregularly distributed — the grey matter of the central ganglions (the optic thalami and corpora striata) and that of the cerebral cortex. These two regions of cerebral activity are united to one another by a series of white fibres, which serve as a bond of union between them, and as a channel of pro- pagation for nervous currents passing from one to the other, either centrifugally or centripetally. The opto-striate central ganglions of each lobe may be ideally conceived as occupying the centre of a hollow sphere, of which the circumference is represented by the undulations of the cerebral cortex ; and the white fibres v/ould thus represent an infinite number of radii 60 THE BRAIN AND ITS FUNCTIONS. uniting the central with the peripheral regions of the sphere. (Fig. 5.) The anatomical study which we have just made, of the grey matter of the optic thalamus and that of the corpus striatum, has enabled us to observe distinct differences between them, and consequently to formu- late the unlike dynamic aptitudes with which each of these two ganglions is gifted. We have thus seen that the function of the optic thalamus in particular seems to be that of receiving, con- densing, and transforming, like a true nervous ganglion, impressions radiating from the sensorial periphery, before launching them into the different regions of the coriical substance ; and that, inversely (Fig. 6. — 14, 9. 4.), the corpus striatum, in connection with exclusively motor regions, appears to be a place of passage and rein- forcement for stimuli radiating from the different psycho-motor zones of the cortical periphery. These anatomical connections being admitted as fun- damental datUy as regards the structure and mode of agency of the nervous elements ; let us now see what use we may make of this, from the standpoint of the particular interpretation of certain phenomena ot cerebral activity. Let us take things as they normally occur, following the natural channels by which excitations from the external world penetrate into the organism. Let us take, for example, the impression upon a sensitive nerve — a vibratory phenomenon which calls into activity the cells of the retina or those of the acoustic nerves ; what then takes place in the secret recesses of the nervous conductors } PHYSIOLOGICAL DEDUCTIONS, 6i Fig. 6. Diagram of the sensor'-motor processes of cerebral activity.— i. Opti<: thaiavius with its centres and ganglionic cells — 2. Co>-piis striatum— j,- Course of the propagation of acoustic impressions. These arrive in the corresponding centre (4), are radiated towards the seusoriion (5), and reflected at 6 and 6', to the large cells of the corpus striatum, and thence at 7 and 7', towards the motor regions of the spmal axis — S. Course of sensitive impressions. These are concentrated (at 9) in the corres- ponding centre — radiated thence into the plexuses of the sensorium (10), reflected to the large cortical cells (11). and thence propagated to the large cells of the corpus striatum, and finally to the different segments of the spinal axis.— 13. Course of optic impressions. These are concentrated I at 14) in their corresponding centre, then radiated towards the sensorium (at 15). They are reflected towards the large cells of the corpus striatum and afterwards propagated to the different segments of the spinal axis ; 18, 19', 19", the antero-lateral fibres from their point of origin in the corpus striatum, are invested by the elements of cerebellar innervation which begin to appear in the peduncles (19), to become considerably thicker at lo', on a level with the region called the pons and to diminish insensibly on a level with the medullary regions, 19'.— 20. Peripheral expansion of the olfactory nerves. 62 THE BRAIN AND ITS FUNCTIONS. Immediately following the direction of their natural channels, these vibrations applied to each par- ticular sensorial nerve, bring into play the specific activities of the different cells of the centres of the optic thalami. (Fig. 6. — 3, 13.) These immediately take up the vibration, and by means of the radiating fibres which unite them to the different regions of the cortical periphery, transmit to their sensitive partner-cells, the new dynamic conditions in which they have just been placed by the fact of the ex- ternal excitation. — (See Fig. 6. — 5 and 15.) External sensorial impressions do not therefore propagate them- selves through and through from the plexuses of the sensorial to those of the cortical periphery, until they have awakened various intermediate cell-territories which give them a new form, cause them to undergo a peculiar metabolic action, and only launch them into the different plexuses of the cortical zones, after they have animalized them, and rendered them somehow more assimilable. (Fig. 6. — 4. 9. 14.) Each special kind of sensorial excitation is thus dispersed, and quartered upon a special area of the periphery of the brain. (Fig. 6 — 15 and 5.) Anatomy shows, then, that there are definite localiza- tions of limited regions, organically designed to receive, to condense, and to transform such or such particular kinds of sensorial impressions. Experimental physiology has proved on its side, that in living animals, as the beautiful experiments of Flou- rens long ago showed, it is possible, by methodically removing successive slices of the cerebral substance, to cause these animals reciprocally to lose either the faculty PHYSIOLOGICAL DEDUCTIONS. 63 of perceiving visual, or that of perceiving auditory impressions.* More than this, Schiff, in his recent experiments, as ingeniously contrived as delicately executed, succeeded in demonstrating in a precise manner, that in the animal under experiment, the cerebral substance was subject to local increase in temperature, according as it was suc- cessively excited by such or such kinds of sensorial impressions ; and that thus, in the brain of a dog, which was made to hear unexpected sounds, such or such a region of the cortical substance was heated, and that in another, in which tactile, olfactory, or gustative sensation was excited, other regions of the brain were reciprocally erethised and heated in an isolated manner.-f- Following up the process of the migration of sensorial excitement from the peripheral to the central regions of the system, we see that all sensorial impressions arrive, in the last stage of their transit, at the plexuses of the cortical substance ; that they arrive transformed by the action of the intermediate media through which they have passed in transitu ; and finally that they there die away and are extinguished, to revive under a new form, by bringing into play the regions of psychic activity where they are at last received. As soon as the sensorial excitation is dispersed in the midst of the plexuses of the cerebral cortex, new phenomena unfold themselves. Here mere analogy leads us to think that the scn- * Flourens " Recherches experimentales sur le systeme nerveux," second edition, 1842. t Schiff, "Archives de physiologic," 1870. 64 THE BRAIN AND ITS FUNCTIONS. sitive cells of the brain may behave like those of the spinal cord, and that in the presence of the physiological excitations proper to them, they will react in a similar fashion. We may, therefore, suppose that at the moment when the cerebral cell receives the impregnation of the external impression, it becomes erect, as it were, develops its peculiar sensibility, and disengages the specific ener- gies which it contains. Thus it is that the impression which is communicated and which manifests itself by a development of heat in certain regions of the cortex (as in the experiments of Schiff ), is propagated through the circumjacent plexuses, and, according to the laws of undulatory movement, develops by degrees the latent activities of new groups of satellite cells, which in their turn become new foci of activity for the neighbouring cells, with which they are intimately anastomosed. In this manner we can conceive how, in consequence of a simple sensorial impression, all the agglomerations of nervous elements of which the cerebral cortex is com- posed, may isolatedly become successively engaged ; how the movement is communicated from point to point (Pig, 6 — ^. 10. 15.) ; how the individual sensibility of the nervous elements begins to take part in the phenomenon ; how life is awakened in regions at first silent ; and how. In a similar manner, the incident excitation, after having thrown into agitation different zones of the cortical substance, is finally transformed into a centrifugal excitation, reflected, and externally discharged in the form of a motor act. (Fig. 6 — 6. II. 16.) Having followed step by step, the phenomena of PHYSIOLOGICAL DEDUCTIONS. 6$ cerebral activity just explained, and interpreted them in ordinary language, we may conclude that sensorial excitations radiated from the periphery reach the regions of psychic activity, and that there, coming under the influence of the elements of which it is composed, they become transformed into persistent impressions — ideas corresponding to their origin ; that they bring into play the sensibility and emotivity proper to these regions ; that they become associated, anastomose one with another in a thousand ways, by means of the organic tissue through which they are evolved ; that they are amplified and transformed by the different zones of cells through which they are sifted ; and that finally, they are exported and reflected outwards in the form of voluntary motor manifestations, expressions more or less indirect of a primordial phenomenon of sensibility. Now, from the premisses of the structure of the cortical substance, comprehended as already indicated, it may be possible to deduce data which will enable us to appreciate the dynamic functions of the diflerent zones of cells contained in it. We have already established, that the elements which compose it have very distinct morphological characters ; that the zones of small cells occupy the sub-menin- geal regions, and that the zones of large cells occupy the deep regions. In the minute constitution of the spinal cord we find similar appearances as regards the distribution of the nervous elements ; and we further know that the regions of small cells are the seat of sensitive, those of large cells the point of departure of motor, phenomena. The laws of analogy therefore lead us to suppose that morphological imply physio- 66 THE BRAIN AND ITS FUNCTIONS. logical analogies, and that in the succession of the multiple activities of the cortical substance, we may pro- bably suppose that the sub-meningeal regions, occupied by small cells, are more particularly the regions fitted for the reception of sensitive impressions, while the deeper layers, occupied by the large cells, appear to be more particularly centres of emission appropriated to motor phenomena. This granted, we arrived at the following conclusion : That in the plexuses of the cortical substance, there is in those formed by the small cells a special sphere for the dissemination and reception of sensitive impressions, which all impinge here and bring into play the peculiar sensibility of the cells ; and that these zones, which are anatomically demonstrable, and which represent the posterior sensitive regions of the spinal cord, receive in their essential structure all the particular sensibilities of the organism, and produce a union between them. They thus form that matrix, that regio princeps of the cerebral cortex, which constitutes the true sensoriiLiii comimLue, the common reservoir into which all the im- pressions that have thrown our sensitive fibres into agitation, flow, and in which they subside. (Fig. i — B, and Fig. 6—5, 10, 15.) Thus, then, is constituted this region which receives into its sensitive tissue the resultant of all sensitive excitations, from the external world as well as from the vegetative life of the organism, and which, when thrown into agitation, sensitized in its turn, reacts in a thousand ways, dispersing in all directions the vibratory excitations which have developed the energies of its elements. It is its task gradually to transform the PHYSIOLOGICAL DEDUCTIONS. 6/ phenomena of sensibility, and finally to cause sensitive excitations, radiated from cell-plexus to cell-plexus, like a force in evolution which is incessantly transformed, to produce insensibly a motor phenomenon. Thus we arrive at the conclusion that, from a phy- siological point of view, the voluntary motor act which emanates from the brain is in all cases nothing more than the repercussion, more or less distant, of a pri- mordial sensitive impression. (Fig. 6 — 6, ii, i6.) It should, however, be added, that although the act of voluntary motion is, as a general rule, only the indirect expression of the agitation of the sensorium, never- theless, from the very fact that it is evolved throughout the plexuses of the cortical substance, laying its various zones under contribution, it is not a simple, purely reflex phenomenon, like those which occur in the similar plexuses of the spinal axis ; it is a complex synthetic phenomenon that resumes in itself the dif- ferent elements which, taken together, constitute human personality. We may also say that if an act of the will be merely a phenomenon of transformed sensibility, it is, nevertheless, sensibility doubled, multi- plied by all the cerebral activities in agitation, in a word, by the feeling and vibrating human personality, which comes into play in a somatic form, and reveals itself externally by a series of rcjicctcd and co-ordinated manifestations. CHAPTER VII. PHYSICO-CHEMICAL PHENOMENA OF CEREBRAL ACTIVITY. The nerve-cells, considered as to their intrinsic proper- ties, individually participate in all the general phe- nomena of the life of cells. Like all their fellows they have their history, their genealogy, their periods of growth and decay. They are subject to alternate phases of repose and labour, and, like them, are all gifted with a specific histological sensibility which gives them special dynamic characters. It is the blood alone that makes them live and feel ; it is it alone which, as sole agent of their incessant activity, percolates everywhere through the nervous tissue, and carries with it the elements of all life and all movement. This is so true, that if we succeed in momentarily suspending the circulation in the encephalon, the whole vital machinery stops at once, and every phenomenon of nervous activity is at the same instant interrupted. Decapitated animals are by this very fact deprived of all cerebral functionment, and, it is a very remarkable fact, that if we succeed in artificially restoring to the cerebral tissue the nutritive materials of which it was deprived ; if, by means of injections of defibrinated blood, such as Brown-Sequard has experimented with, PHENOMENA OF CEREBRAL ACTIVITY. 69 we succeed in giving their habitual stimulation to the nerve-cells, the signs of life come back as if by en- chantment, and the head of a dog, thus momentarily- revived, will still afford ephemeral manifestations of a conscious perception of external things * In man the more or less complete arrest of the blood in the brain, produces accidents which are sometimes overwhelming, faintings, and loss of consciousness with stupor ; and it is now recognized, thanks to the labours of modern physiology, that the greater number of those apoplectiform seizures, which were formerly attributed to a sanguineous plethora in the plexuses of the brain, should on the contrary be ascribed to a more or less complete arrest of the course of the blood in the capillary plexus. The attacks observed in these circumstances may be legitimately attributed to a sort of asphyxia of certain regions of nerve-cells (princi- pally those of the sensormm, when we have to do with losses of consciousness, vertigos, and fainting-fits) ; the nervous elements being stupefied for an instant, in con- sequence of the more or less complete suspension of the arrival of their nutritive materials.t The continuity of the sanguine irrigation is, then, the sine qua non of the regular working of the cerebral ceils. It is at the expense of the juices exhaled from the walls * Brown-Sequard once injected the head of a dog when separated from the trunk with defibrinated and oxygenated blood, and at the moment when the injection of this blood had recalled the manifestations of life, he called the dog by his name. The eyes of the head thus separated from the trunk turned towards him, as if the voice of the master had still been heard and tecognized. (Annales " Medico-physiol.," 1870, p. 350.) t Every one knows that in fainting fits, and syncope, the most rapid method of bringing them to an end is to place the patient horizontally, so as to favour die mechanical afflux. of blood to the brain. yO THE BRAIN AND ITS FUNCTIONS. of the capillaries, that they feed themselves and con- tinually repair the losses sustained by their integral constitution.* Plunged into the midst of this humid atmosphere surcharged with phosphates, of which the materials are incessantly renewed, they extract from this vivifying medium the elements of their reconstitution ; like living beings plunged into the terrestrial atmosphere, borrow- ing from the surrounding air the pabidum vitce which enables them to live, and sustains them. Thus it is that they successfully endure their expenditure of the phos- phorated element during the period of their diurnal activity, and that they can maintain themselves in equilibrium as regards their receipts and expenditure. This truth was very clearly brought to light by the ingenious researches of Byasson, who has pertinently shown that every cerebral cell in functioning expends its phosphorized materials, and that this waste resulting from cerebral activity, like the natural physiological excretions, is drained away from the organism by passing out in the urine, in the form of sulphates and phosphates, which serve as a chemical measure of the intensity of cerebral work done in a given time.f * The blood which comes to the brain red and oxygenated, returns by the capillaries black and charged with carbonic acid. (Gavarret, " Phenomenes physiques de la vie." Annales medico- psychol. 1870, p. 347.) t To arrive at these results, Byasson for several days submitted to a special physical and moral regimen. He estimated exactly the quantity of phosphates and sulphates which entered into his diet, and also the quantity excreted. At the end of a certain time, these fundamental data having been ascertained, he began to work his brain, and in proportion to the amount of his work, the diet remaining constant, the quantity of sulphates and phosphates excreted by the urine had increased in a notable manner. (Byasson, " Essai sur la relation qui existe a. I'etat physiologique entre I'activite cerebral et la composi- tion des urines." Journ. danat., de Robin, 1869, p. 560.) PHENOMENA OF CEREBRAL ACTIVITY. 7 1 These facts show, then, the enormous influence which the blood exercises upon the vegetative phenomena of the Hfe of the nerve-cells, and to what an extent their individual dynamic activity, and consequently the life of the whole system, depends upon it. It is the blood that carries everywhere with its un- interrupted currents the vivifying stimulation which causes the cells to feel, to become erect, and to associate for co-ordinated actions. In the purely sensitive regions, where the phenomena of conscious personality are inces- santly in process of evolution, it keeps them constantly awake, and thus sustains in us the conscious idea which we possess of the external world. In the motor regions it enables the nervous elements to accumulate, as in con- densers, a store of nervous influence destined to pass into the dynamic condition as soon as a call is made upon them. It is everywhere present, flowing every- where, and evoking the specific innervation of each of the cell-territories which it animates and bedews, thus enabling them to renew their latent energies. When once provided with the necessary elements of nutrition, the cerebral cell becomes capable of entering into action, and performing the dynamic function for which it is designed. This new phase under which it reveals itself is characterized : — 1. By an acceleration of the blood-currents in the functioning regions. 2. By a local development of heat in these regions. I. — If it be incontestably demonstrated what an itji- portant influence the regularity of circulatory pheno- mena has in evoking the activity of nerve-cells, it is on the other hand very curious to note what an influence ^2 THE BRAIN AND ITS FUNCTIONS. the activity of these same cells may have in return on the vascular irrigation designed to provide for their nutrition as well as their expenditure. It is not, indeed, without a certain astonishment that we observe that if, on the one hand, the nerve-cells play a passive part with regard to the circulation which feeds them — if they are in subjection to it, and are veritably its tributaries ; by an inverse phenomenon, from the moment they become active their position changes, and, ceasing to be subject as they were, they in turn become dominant. From the very fact that they are working — that there in certain isolated spaces they develop a state of nervous erethism — they at the same time deter- mine hie et nunc a concomitant influx — they make an appeal to the blood, and even turn to their own profit the irrigation of certain neighbouring regions.* Thus the brain, as regards the phenomena of circu- lation, is at the same time active and passive ; it is of necessity subject to their influence, and cannot, on pain of cessation from all work, refuse their aid ; and yet, at a given moment, it reacts, solicits them, makes appeals to them, and thus unconsciously directs the vaso- motor actions designed to maintain the integrity of its vital energy. Thus from this double influence of the phenomena of the circulation on those of cerebral activity, and those of cerebral activity on the acceleration of the * We may perhaps attribute to an accidental derivation of blood towards a circumscribed portion of the brain that is in a state of erethism, and the con- sequent draining of the circumjacent regions, certain phenomena of cerebral lite in which, under the impress of a strong preoccupation, a concentration ol the mind upon a single point, we momentarily lose the notion of the surround- ing mediuiu, aud cease to perceive what is passing around us. phetnOmena of cerebral activity. 73 flow of blood, a vicious physiological circle results, calculated to have an inevitable influence upon the infinite series of regular cerebral operations, as well as upon the progressive evolution of pathological pheno- mena, which mostly are but exaggerations of the normal actions of the organism. Every one knows how fatal chronic lesions of the capillary plexuses are to the delicate substance of the cerebral cells — how the plastic exudations which pro- ceed from the vessels, the fibro-albuminous deposits which become infiltrated into the tissue and interstices of the cells, become like so many foreign bodies hostile to life, and injurious to the physiological medium whence they draw the elements of their normal constitution. Every one knows, further, how moral causes — too energetic work, which exceeds the amount of the reserved nerve-force — prolonged vigils, which do not permit the recuperation of lost materials — pre- occupations concerning a single subject, which induce a condition of chronic congestion within certain circum- scribed limits — are so many morbid modes of excite- ment which maintain a permanent condition of local erethism, and thus indirectly become the causes of those repeated affluxes of blood which are so inevitably followed by exudations of all kinds and persistent new- formations (the lesions of general paralysis). Hence that preponderant influence which the whole series of moral afl*ections exercises upon the genesis of mental maladies. Whether they be derived from an intellectual excitement prolonged beyond physio- logical limits, or result from profound disturbances occurring in the emotional sphere of the sensorium, in 7 74 THE BRAIN AND ITS FUNCTIONS. consequence of trouble, disappointment, misfortunes of all kinds, the minute mechanism of their advent is always fundamentally the same. It is by the physio- logical channel they introduce themselves into the organism ; it is under the form of regular excitations — shocks propagated along the normal processes of cere- bral life — that they implant, develop, and perpetuate themselves ; and the incurable disorders they leave behind them are but the indirect effects of disturbances of nutrition in the nervous plexuses, proceeding from this single source, the afflux of blood too frequently provoked.* Sleep. — By an inverse phenomenon, if the cerebral cell, from the very fact that it is in its period of erethism, its working period, becomes the occasion of a call upon the blood destined for its activity, this curious fact occurs, that so soon as this activity begins to slacken, so soon as fatigue announces itself, and its histological sensibility is exhausted by the action of external impressions, the vascular irrigation is modified simultaneously. It fol- lows step by step the decreasing phase of the dynamic activity of the cells that depend upon it, and at the same time that the brain becomes weary, and that the sum of its functional energies diminishes, the mass of blood which flows to it becomes less, the capillaries * Calmeil thus expressed the same thougJit. "All the so called moral influences, whether they betray themselves by the persistence of annoyances or rei^rets, or take the forms of jealousy, hatred, or ambitious disappointments, may concur to produce a morbid accumulation of blood in the encephaUc capillaries, ^Calmeil, " Maladies inflammatoires du cerveau," vol. i, p. 5.) See also Forbes Winslow, on softening of the brain occurring from anxiety and forced exercise of the organ, and consisting in feebleness of mind (•• Annales naedico-psychol," 1850, vol. ii. p. 711.) PHENOMENA OF CEREBRAL ACTIVITY. 75 are less gorged with blood, and the cerebral tissue insensibly becomes exsanguine. This is that new state of cerebral ischsemia, opposed to the phase of congestive activity, which as an alter- native fact of the general order that exists in the brain of all living beings, inevitably reveals itself whenever their cerebral cells, having exhausted their accumulated nervous forces, become fatigued by exercise and fall into the physiological collapse of sleep.* Where the life of the nervous elements is stilled, a stillness also takes place in the most minute currents of the circulation, and these two phenomena, which act and react on one another in the ascending phases of activity, similarly affect each other in its descending phases. When the vital movement becomes slack, and histological sensibility dull, the demand upon the blood is less imperious. 2. — If, from a chemical point of view, the phenomena of cerebral activity are characterized and gauged in a precise manner by the real loss of brain-substance, and the passage of a certain quantity of phosphorized * The condition of comparative anaemia in the brain during sleep has been directly proved by different observers; thus Ca'dweil, in the case of a wound in the head, with loss of substance in the bones of the cranium, observed that when the patient was plunged in deep and peaceful sleep, the brain remained almost immovable in its envelope, but that when he was dreaming it increased in volume, and when the dream was vivid it protruded through the opening. Blumenbach in an analogous case, similarly remarked that the brain sub- sided during sleep and that waking was accompanied by a more or less con- siderable afflux of blood, and an augmentation of volume. ("Archives generales de Medicine," vol. i. 637.) Durham also has instituted direct e periments to prove that during sleep the brain becomes anaemic. ("Guy's Hospital Reports," i860, vol. vi. p. 149.) See confirmatory experiments by Claude Bernard. " Lecons sur les anesthetiques," p. X17. Paris, J. B. BaiUere, 1875. j6 THE BRAIN AND ITS FUNCTIONS. matters in the urine, from a physical point of view they present characters which are no less significant, and no less important to recognize. The authors who have already occupied themselves with the question, as to what appreciable physical modifications are presented by the brain-substance while in activity, have noted in a precise manner that this inward labour reveals itself by sensible signs, in the form of a more intense disengagement of heat ; and that the brain, like a muscle in action, manifests its dynamic power by a local increase of heat, appreciable by the instruments of the physical laboratory. Thus, Lombard (of Boston), who was the first to institute experiments in this direction, arrived at the following results, by means of very exact thermo-electric apparatuses : — " In the condition of cerebral repose," he says, " during wakefulness, the temperature of the head varies very rapidly. The variations are very slight, not attaining Y-^gth of a degree centigrade, but they are not the less worthy of attention, for this reason — that they are confined to the head. "The variations of temperature appear to be con- nected with different degrees of cerebral activity. During active brain-work it never exceeds -J^th of a degree centigrade. " Every cause that attracts the attention — a noise, or the sight of an object or a person — produces elevation of temperature. *' An elevation of temperature also occurs under the influence of an emotion, or during an interesting reading aloud. PHENOMENA OF CEREBRAL ACTIVITY. J*] " This elevation of temperature is especially well- marked in the region of the occiput." These experiments, as we see, apply only to the appreciation of temperature externally estimated, on the skin of the cranium. The brain was not directly investigated. Schiff has supplied this omission, he has entered the cranium, and by means of thermoscopic instruments of extreme sensibility has succeeded in directly exam- ining the cerebral substance at the moment when it came in contact with external excitations, and thus determining what degree of elevation of temperature the brain is susceptible of attaining in its operations. This ingenious physiologist has therefore succeeded in defining not only what regions of the cerebral cortex are isolatedly called into play by such or such kinds of sensorial impressions, and demonstrating experimentally that there are isolated circumscribed spots reserved for such or such kinds of sensorial impressions (as has already been described on the authority of anatomy) ; but also that the arrival of these impressions resolves itself into a local development of heat in the special area where it disseminates itself ; and that the heat thus developed is a dynamic phenomenon independent of the circulatory activity, a true vital reaction of the sensorium — that, in a word, it is the direct result of the participation of the psychic element on the arrival of the sensorial excitation. " Thus," he says, " the psychical activity, independently of the sensorial impressions which call it into play, is con- nected with a production of heat in the nervous centres, a greater amount of heat than that which simple sen- yS THE BRAIN AND ITS FUNCTIONS. sorial impressions engender. This conclusion is justified by the decrease of the calorific effect of a strong and always identical sensorial impression, which animals have been made to experience many times in succession. Let us take a pullet," he adds, "whose sight or hearing we assail by appropriate means. The first impression which the unprepared animal receives will excite in it more intense psychical reflex actions than the succeed- ing excitations of the same nature, since it insensibly becomes habituated to them." Thus, by eliminating gradually the part played by psychical action in sen- sorial absorption, he arrives at an estimate of the heat evoked by the arrival of simple sensorial impres§ions, and that which proceeds from the direct participation of the psychical activity at the beginning of the experi- ment.* We thus understand, after this series of experiments, how prolonged efforts of the mind, and moral emotions of all sorts, from the very fact of their awaking the activity of the sensorm7n, are calculated to have an immediate effect upon the essential phenomena of the nutrition of the brain. They show us, indeed, on the one hand, that sustained intellectual work is accompanied by a loss of phos- phorized substance on the part of the cerebral cell in vibration ; that it uses it up like an ignited pile which is burning away its own essential constituents j*!" and that, * Schiff, I.e., " Archives de Physiologie," 1870, p. 451. t Louyer-Villermay cites the example of a celebrated lawyer who lost hiji memory in consequence of too long-continued intellectual work; and Moreau de la Sarthe reports a similar case which occurred in a German savant, after an in- tense concentration of mind. We also know of a great number of musicians wtio have become deaf by the immoderate exercise of the organ of hearing. "Joitrnal d'hygifene," 1875. (De la surdite chez les Musiciens, par Dr. Piat.) PHENOMENA OF CEREBRAL ACTIVITY. 79 on the other hand, all moral emotion perceived through the sensorium^ all effective participation of this same saisorium in an excitation from the external world, becomes at the same time the occasion of a local develop- ment of heat. These facts are destined to have a direct effect upon our knowledge of the essential conditions of the in- tegrity of the cerebral functions, and to formulate absolute hygienic principles with regard to them. It stands to reason, indeed, that if the cerebral cell expend its reserve material during its diurnal activity, it is absolutely necessary, to enable it to continue alive and in health, that it shall repose and sleep regularly. Sleep is to the brain, what needful repose is to our fatigued limbs, the necessary condition of its health. Every one knows, indeed, how great is the number of individuals who have sown the seeds of a cerebral disease by a prolonged infraction of these simple laws of hygiene, and who through reiterated vigils and exag- gerated expenditures of activity, have thus passed the physiological limit of the resources at their disposal, and incurred expenditure above their receipts. On the other hand this development of heat, which is produced in certain circumscribed localities of the brain when an emotion or sensorial impression is reverberating through the plexuses of the sensorhnn, further shows us with what circumspection we should manage this kind of excitation in individuals whose brain is in a painful condition, either from a recent congestion, or from for- mer congestions grafted one upon another. We all know from more or less personal experience, that when we have a headache, and our sensoriuui is 8o THE BRAIN AND ITS FUNCTIONS. in a state of hyperaesthesia, the smallest noises, the sb"ghtest external incidents, produce in us painful shocks, and that the absolute incapacity for work is most painful. All doctors know how often, in persons excited by the occurrence of repeated cerebral congestions, paraly- tics, maniacs, and even patients wiin certain forms of melancholia, the unexpected calling up of an old emo- tion, the sight of a relative, may have a sad effect upon their cerebral condition. We see, indeed, their faces redden and grow pale, and very often the effect of an emotion inopportunely provoked, is but the prelude to the return of more and more serious congestive acci- dents. PART II, GENERAL PROPERTIES OF THE NERVOUS ELEMENTS. The phenomena of the life of the nervous centres, spite of their apparent complexity, are nevertheless regulated by laws which are in general simple — common principles, which indisputably give them an air of near relationship. These common principles are, moreover, themselves reducible to elementary vital pro- perties, which form the basis of each of them in par- ticular, and constitute, in a manner, the simple prim- ordial principles which we constantly find underlying every combination of nervous activity, however com- plicated it may be. These fundamental properties, which thus serve as elementary materials for every dynamic action of the system, may at the present day be thus epitomized, under three principal heads : — 1. Sensibility^ by which the nerve-cells feel excitation from without, and react in consequence, by virtue of the excitement of their natural affinities. 2. Organic PJiosphorescence, by which the nervous elements, like bodies which have received the vibrations of light, preserve for a prolonged period traces of the 82 THE BRAIN AND ITS FUNCTIONS. excitations which have in the first place set them in action, thus storing up within themselves phosphorescent traces, which are records of the received impressions. 3. AutoinatisiUy which expresses the spontaneous reactions of the living cell, which sets itself in motion of its own accord {inotit propria), and in an unconscious and automatic manner expresses the different states of its sensibility thrown into agitation. It is the history of these various general properties of the nervous elements that we are now about to study in due course, in the physiological part of this work. These properties once defined and known, we shall attack the study of the different combinations to which they adapt themselves by combining one with another ; and thus, proceeding from the known to the unknown, from the simple to the composite, we shall advance with better ascertained points of support into that domain, so com- plex, and at the same time so rich in interesting pros- pects — that of cerebral activity proper. BOOK I. SENSIBILITY OF THE NERVOUS ELEMENTS. CHAPTER I. GRADUATION AND GENEALOGY OF THE PHENOMENA OF SENSIBILITY. Sensibility is that fundamental property which characterizes the Hfe of cells. It is by means of it that the living cells come into contact with the medium that surrounds them, and that they react motii propria, by virtue of their natural affinities which are thrown into agitation, and exhibit a desire for the excitations which gratify them, and a repulsion for those that are unpleasant to them. Attraction for agreeable and re- pulsion for disagreeable things are the indispensable corollaries of every organism fitted for life, and appa- rently the elementary manifestation of all sensibility. Sensibility, which is, perhaps, itself, in the organic world, only the transformation of those blind forces, which attract among themselves the crystalline mole- cules of the inorganic world, and group them according to their proper affinities ; this phenomenon, sensibility, 84 THE BRAIN AND ITS FUNCTIONS. begins to appear, in its most simple forms, with the first rudiments of life. It is in the unicellular organisms of the vegetable kingdom that it first embodies itself and reveals itself in its own shape ; and here it shows itself as a property of tissue, very distinctly connected with the very sub- stance of the amorphous protoplasm of which it is the endowment, under the form of vague diffuse contractility, no special element being reserved for it, and no nerve- cells being as yet extant* Little by little, as the living cells group together and form more dense agglomerations, the phenomena of sen- sibility become more distinctly evident, and soon^we find them provided with special apparatuses designed to serve them as a support, and to condense and perfect their modes of activity ; while in the superior animals they become more and more highly endowed, to arrive at man as the last term of their long evolution, and produce those phenomena so rich, so varied, so delicate, defined in conci-eto under the name of the moral sense. In this chapter we shall follow the process of the evolution of sensibility, from the most elementary phases under which it shows itself at its point of origin, to the moment of its most complete expansion in man. Sensibility, we may say, in its most simple revelations in unicellular organisms, at first appears in a vague and undetermined form. It reveals itself by that essential tendency which these protorganisms have, to seize upon substances which gratify their natural affini- * Naturalists have made known to us beings of an organization so simple that their entire body is formed of but one cell. Their whole development, their whole existence, is shut up within limits thus strict. We may mention theg7'e£ar/nes in particular. (Frey, " Histologic et Histoc.hemie," p. 74.) THE PHENOMENA OF SENSIBILITY. 85 ties and avoid such as are inimical to them. It regu- lates and governs the continuity of the purely trophic phenomena of the life of cells.* In vegetables the phenomena of sensibility have already taken more distinctly marked forms. Their cycle is no longer restricted to the local operations of rough and ready assimilation and disassimilation. Vegetable cells, even when agglomerated in but small groups, have become sensitive and impressionable by external agents. Calorific and luminous impres- sions produce a certain effect upon them, and if this effect be grateful to certain natural affinities, we may see them gradually inclining in the direction from whence these excitations come. They turn automatically towards the sun, awake with him when he appears, sleep when he has disappeared, and, in a word, present that series of unconscious and graduated movements by virtue of which they tend towards the realization of their latent satisfactions.f Botanists have already described those curious phe- nomena of vegetable sensibility by virtue of which we see the petals of certain flowers fold up at night and unfold in the day time ; the stamens of the barberry, * The gregarines, which are met with in troops as living- parasites in the alimentary canal of insects and other animals, are not only destitute of a mouth, but even of vibratile cilia. They are simple cells with apparent nuclei. (Hartmann, "Conscience des plantes." "Revue Scientifique," July 1S73, p. 623.) f Plants which catch insects are sensitive to the touch ; climbing plants discern points of support. Tlie leaf of the vine feels the hght, towards which it strives to turn the right side, and every flower feels it, and strives to bend its head towards it. The mimosa feels and reacts. It is the essence of every motion that it shall be preceded by sensibility. (Hartmann, loc. at,, p. 625.) 86 THE BRAIN AND ITS FUNCTIONS. under the excitement of a light touch apply themselves to the pistil ; the flowers of the water-lily hide them- selves at the bottom of the water while they wait for the day. It is even more astonishing to see what hap- pens with sensitive plants, and to observe how that curious vegetable, mimosa pudica, presents in itself all the most delicate manifestations of the impressionabiUty of living beings.* Like an animal, it feels and reacts on the contact of the lightest touch ; feels inequalities of temperature ;-|- is influenced and struck with anaesthesia by the in- halation of chloroform ; like an animal, moreover, its sensitive unity forms a complete whole ; its leaflets and rootlets are united in such an intimate conseitstts that if its rootlets be subjected to the action of any irritant, its leaflets are affected at the same time, and sympathize painfully with their sister cells of the lower regions which have been thrown into agitation ; just as we see that sensibility when developed in any region of an animal whatever, has a generalized reaction all over the organism. * Marked movements are performed every evening by vegetables with composite leaves, like the cytisus or robinia pseud-acacia. We see these plants make their preparations for night every evening — some simply fold their leaves, others, with more foresight, prudently enclose their flowers. The great lotuses of the Nile, and the water-lilies of our own lakes, draw down their carefully closed corollas to the bottom of tlieir waters ; and the sun must have come next day to illumine the earth before the chilly and sleeping plant consents to open its petals. The sleep of plants is related to the greater or lesser intensity of the light with which they are surrounded; and, what is more conclusive, plants which have been strongly illuminated at night, while they are in obscurity during the day, have changed their habits so as to sleep in the day and wake at night. Edmond Grimard, " De la sensibilite veg^tale." " Revue w'es Deux Mondes," 868, p. 379.) t Griipard, loc. cit., p. 385. THE PHENOMENA OF SENSIBILITY. ^J In the animal kingdom sensibility reveals itself in its origin by phenomena exactly comparable with those which we have just sketched. There', in the form of amoeboid movements of the white corpuscles and ciliated cells, and contractility of the protoplasmic cells,* it shows itself to us under the appearance of purely histological sensibility, and not as yet in the shape of sensibility belonging to a living autonomous individuality. In the protozoa, rhizopods, and certain polyps, it becomes more and more distinct, and by the very complex operations through which it manifests itself, we perceive how well these protorganisms of the animal kingdom are provided with active and vital energy, and how distinctly general sensibility is inherent in them and combined with their substance. In these elementary forms of animal life, the phe- nomena of sensibility are first united with an organized tissue. They are divided among as many cells as the individual contains ; and they exist in a vague and diffuse manner, without there being as yet a special system of anatomical elements, designed to serve them as an appropriate receptacle. Soon, as we ascend in the series of beings, new factors are added to the preceding ; the phenomena become complicated as they grow more perfect, and we then see that in proportion as animal organisms develop them- selves, and their agglomerations of cells become more numerous, there takes place among them, as it were, a natural selection of the physiological work to be per- formed. Some are gifted with such or such specifi^c * Wund, " Physioloi^ie," p. 83. S8 THE BRAIN AND ITS FUNCTIONS. aptitudes, and appropriate such or such a function, while others, gifted with such or such a different aptitude, reserve themselves for such or such another. For its better performance there is a division of labour. This natural division of the living forces of the living individual, which are thus distributed among the different departments of its substance, constitutes the first outline of the nervous system. It soon appears, like an organ of perfectionment im- planted in the organism. It is henceforward the grand dispenser of sensibility in general, and is designed to collect, to drain all the scattered forms of sensibility, to regulate their course, to condense them in its own reservoirs, to purify them by the participation of its substance, to make them leap forth in the form of motor excitations, or to transform them, like the perfected products of its own industry, into subtle and quintes- sential materials, destined to co-operate in the most subtle phenomena of psycho-intellectual life. Humble in its origin, the nervous system, as F. Leydig has pointed out, makes its first appearance in the midst of the living tissues in the form of three or four cells, independent one of another.* One step further, and the cells are united within a common envelope, a first nervous ganglion being thus constituted. Little by little the work of evolution completes itself; ganglion is united to ganglion ; these soon dispose themselves in the form of two lateral rows, which emit, right and left, radicles which plunge into the surrounding tissues, and soon these two lateral chains, approaching, become fused together, and thus constitute a central unity, * Claude Bernard, "Systeme nerveux,"' vol. i. p. 506. THE PPIENOMENA OF SENSIBILITY. 89 or axis, around which all the nervous radii emerging from the peripheral regions converge. At the same time, a superior ganglion, destined to be the brain, is developed, and uniting itself to the axis, becomes in a manner the crowning of the edifice thus successfully perfected. From this moment the nervous system is constituted as a central force destined to condense in its plexuses sensitive excitations, in order to transform them by its own metabolic action into co-ordinated motor reactions. From this moment the living forces of the organism are duly subordinated and distributed in a methodic fashion ; the physiological task is regularly divided ; one group of elements is connected with sensibility, one centre with motor-power, and another with the functions of organic life. Sensation is henceforward neatly isolated in special regions of the system, neatly collected in particular organs, and from the very fact that it is attracted, like an electric fluid, by means of nervous conductors, from the peripheral regions towards the central, it be- comes a disposable mobile force, transmissible to a distance like dynamic electricity. Once concentrated in the central regions of the system, it thus represents, with all the diverse ele- ments of which it is composed, a true synthesis of all the partial sensibilities of the living being, and the true generating element of its living and feeling unity. , The phenomena of sensation in the superior animals are not, then, simple phenomena, constituted by the mere reaction of a tissue in the presence of external 8 go THE BRAIN AND ITS FUNCTIONS. excitations ; they are the complex subordinated opera- tions of the nervous activity which require the partici- pation of a great many organs successively brought into play, in order to arrive at their complete evolu- tion. We shall now study these different conditions in F accession. CHAPTER XL EVOLUTION OF THE PROCESS OF SENSIBILITY, THROUGH THE MECHANISM OF THE NERVOUS SYSTEM — UN- CONSCIOUS SENSIBILITY — CONSCIOUS SENSIBILITY (SENSATION). The nervous system being constituted, as we have just explained, by a central axis, plunging by its lateral roots into the surrounding tissues, and crowned at its superior extremity by a central ganglion, the brain, gifted with its special activity, we shall now see how the phenomena of sensibility, existing per se as funda- mental histological properties, behave in presence of the machinery which the nervous system places at their disposal ; how they become incorporated with it ; how, arriving in the form of centripetal excitation, they be- come refracted in the plexuses, reappearing as a centrifugal reaction, through the peculiar influence of the new media they have put in requisition ; and how at last, in the most elevated regions of their journey, they come to play a primary part in the evolution of the essential phenomena of psycho-intellectual activity. In taking their departure from the peripheral regions of the nervous system, which physiologically represent the frontiers of the organism, sensitive impressions, wherever they may have originated, once implanted in 92 THE BRAIN AND ITS FUNCTIONS. their tissues in the form of vibratory agitations, follow their natural channels towards the central regions. Some are extinguished in certain interposed gang- lionic masses ; others advance further, become dis- persed in the grey regions of the cord and transformed, either instantaneously or in a more or less gradual manner, into excito-motor reactions — these being the phenomena of unconscious sensibility. Others, finally, endowed with an altogether special vitality, pursue tlieir course, converge, mount up to the sensoriiim and come into contact with the psycho-intel- lectual operations for which they provide the indispens- able food — these being the phenomena of conscious sensibility, or sensation, to which they give birth. We shall successively pass in review the mode of genesis and distribution of these two special groups of sensitive contingents. UnconscioiLs Seiisibility. — Unconscious sensitive exci- tations are derived from two orders of peripheral plexuses : — 1. From the plexus of vegetative life of the sym- pathetic. 2. From the plexus of general and special sensibility. These latter originate in common with the excita- tions destined to ascend to the sensoritiin ; but they are extinguished on the way, and are destined to produce reflex actions (automatic actions) in the interior of the plexuses of the spinal cord. I. Sensitive excitations radiating from the plexus of vegetative life, if we take them from their origin, only expand within a limited radius. They follow the threads of the sympathetic, which are distributed ad EVOLUTION OF SENSIBILITY. 93 infiniUiDi throughout the organism, and only manifest their presence by vaso-motor phenomena, capable of modifying, in a more or less direct manner, certain branches of local circulation. This special order of sensitive impressions is con- densed in special ganglionic masses, which represent small local centres, and are the primitive types of the first traces of a nervous system in the lower species. Sometimes they are capable of radiating to a dis- tance, and thus traversing several ganglionic masses and vibrating even as far as the grey plexus of the spinal cord, of which they thus provoke the secondary activit}'. Thus it is that the sensibility of the intestinal mucous membrane excites the secretion of the juices' destined to co-operate in digestion ; that the sensi- bility of the uterus laden with the product of concep- tion leads to development of the breasts ; that in abnormal conditions certain abnormal sympathies are developed, so that we see, for instance, the irritation of the urethral mucous membrane exercise an influence upon certain articular surfaces ; and that the irritation of certain peripheral nerves leads to the sudden occur- rence of tetanic phenomena and of certain, so called, reflex convulsions. Sometimes also, when certain peripheral regions in which they originate are intensely affected, and have risen to the pitch of pain, the excitations of sensi- bility become capable of an action more penetrating still, and even of reaching the sensorinm, where they are perceived, and whither they carry, as it were, the cry of some organ of vegetative life shaken in its essential constitution. 94 THE BRAIN AND ITS FUNCTIONS. In general we may say, that in the normal sta^e the impressions of vegetative life are quite silent and un- perceived by the seiisoriiim. The wheels of the inner life of the human machine move without noise. Few persons except medical men, are aware that they possess a heart provided with auricles and ventricles, which contract alternately a great number of times a minute ; a stomach which secretes a juice destined to dissolve the azotised elements of the food ; a pancreas designed to act by means of its secretion upon the fatty elements ; intestinal fibres which contract alternately and force along the alimentary bolus, &c. All these phenomena take place without our knowledge, without our having the slightest notion of them, and, strange to say, those facts in which we are most vitally interested we know least about ! But is this really the case, and are we authorized to think that the different forms of sensibility, which are in activity in the inmost recesses of our tissues, really exist without having a sort of obscure influence upon our sensoritLin, analogous in this respect to those obscure rays of the spectrum which our eyes do not behold, and which yet have so real and indubitable an existence ? This does not seem probable to me; for if we think how instantaneously a visceral pain is developed, with what clearness this pain appears when a calculus is fixed in the ductus choledocJms, or when a foreign body is introduced into the stomach or intestines, where it instantly produces painful contraction, we cannot help thinking that there are always open roads between the sensoriinn and the regions of vegetative life ; that there is, in some manner, an incessant relation between these two EVOLUTION OF SENSIBILITY. 95 poles of sensibility ; and we must recognize the fact that there is, in the normal state, a constant though uncon- scious afflux of the partial sensibilities of the organism which converge towards the centres, and that they die away there in silence without making any impression, yet bringing an unconscious notion of all that passes in the periphery of the nervous system. We see every day substances with which we are constantly in contact, from habit pass us by unperceived, leaving in the sensoriinn only an unseized impression, like that pro- duced by the atmospheric air on the respiratory tract. Water and bread, which are so frequently in contact with our digestive mucous membranes, furnish us with but obtuse impressions, which yet are consciously per- ceived. It is then probable that If the sympathetic nerves of vegetative life, starting from the peripheral regions, form a continuous network, of which the converging meshes more and more nearly approach the central regions, the histological sensibility which they abstract from the different cell-territories, amidst which they originate, follows the same natural channels ; and that this is led up to reverberate within th^ sensoriinn, in a disconnected obscure manner it is true, yet, nevertheless, really and permanently. We cannot fail to recognize in this afflux of all the diffuse sensibilities of the organism, each coming to bring to the sensoriuni its sensitive note, that series of generating elements which are designed to implant themselves there and develop in us that essential notion of our vital being, which makes us feel ourselves live in all our organic molecules. It is in itself nothing but g6 THE BRAIN AND ITS FUNCTIONS. the unconscious notion of all the partial sensibilities of the organism, concentrated in this grand common reservoir. 2. Unconscious excito-motor impressions arise, with their sister conscious impressions, in the terminal ex- pansions of all the sensorial and sensitive nerves. Mingled with their fellows they enter the converging channels which are open to them, and advance together with them towards the central regions of the spinal axis, having, however, first traversed the chain of the rachi- dian ganglions. Arrived at the grey plexuses of the spinal axis, they become diffused in their meshes, excite the activity of the posterior grey regions (which represent, as it were, a great common sensor'iuin of unconscious life, for this order of radiations), and pass out in centri- fugal currents, in the form of co-ordinated motor reactions, which thus represent the last phase of a process originating in the purely sensitive regions. The unconscious excito-motor sensibility, transformed by the action of the cells belonging to the automatic sensoriiLin, by this very circumstance acquires new properties. It is stored up, seized upon, and condensed on the spot in the tissue of the organs that receive it, thus becoming in this new form, like a projectile rammed home in a fire-arm, capable of being transmitted to a distance along the centrifugal conductors radiating from the spinal cord, veritable reophores designed to favour its dissemination and transport it to a long distance, even into the most distant and eccentric cell-territories. Thus it directs, in the form of unconscious optic EVOLUTION OF SENSIBILITY. 97 excitations, the different movements of rotation of the ocular globes, the play of the pupil, the accom- modation of the sight to different distances ; excites in the sphere of auditory phenomena the unconscious movements of the chain of little bones, to graduate the alternate tension and relaxation of the tympanic mem- brane ; co-operates so powerfully in the complex and varied movements of mastication and deglutition ; presides over the succession of the acts of erection and ejaculation ; and, in a word, in different forms, without the intervention of the sensorimn, always present, always active, assists in the perfecting of the sense to which it is attached, favours its direction towards an object, governs the play of its mechanism, so as to obtain the maximum of sensorial impression, and thus becomes the indispensable adjunct of conscious impressions. It is still this unconscious excito-motor sensibility that underlies the different processes of the respiratory phenomena during the whole term of our lives, from our first inspiration to our last sigh. It maintains the play of the motor ganglions of the medulla oblongata, those central foci of innervation, whence the inspiratory and cardiac muscles draw their unceasing principle of activity. It expends itself at every instant, day and night, in the continual activity of the mysterious laboratories of organic life. It moreover plays an all-important part in the varied series of our movements of progression, in all those of bodily exer- cise, in the methodical motor actions that we insensibly bnng to perfection by practice and sustained atten- tion — such as those of the hand in drawing or writ- ing — actions which though at hrst conducted with tliC 98 THE BRAIN AND ITS FUNCTIONS. conscious participation of the sensoriiim, insensibly come to be executed under the sole direction of the excita- tions of unconscious sensibility. Thus, then, the phenomena of automatic life, under whatever form they present themselves, occur of them- selves and by virtue of the intraspinal transformation of an incident excitation of reflex sensibility into motor reaction ; and this without the sensorium coming into play, without the intervention of conscious sensibility, simply as a return effect of the calling into activity of process of unconscious sensibility. But although the phenomena apparently take place thus, being evolved without the effective participation of the sensorium, it must not be concluded that no frac- tion whatever of these excitations is radiated towards it and extinguished in it, somewhat in the manner of obscure rays. It is very probable that what we have seen to occur as regards the impressions of purely vegetative life may occur as regards this special order of excitations, there being probably an obscure radiation of these latter impressions which extends to the sensormm, and thus transmits to it the vague and unconscious notion of the activity of such or such a portion of our muscular system. If the sensormm indeed be not directly active in the infinite series of motor acts that we accomplish auto- matically, it nevertheless does not remain a complete stranger to the operations which take place within the organism. If it does not interfere directly to regulate the play of such or such an organ, to move, for instance, the crico-arytenoid muscle in a methodic manner for EVOLUTION OF SENSIBILITY. 99 the production of such or such a laryngeal sound, or the accomplishment of such or such an act of digital dex- terity ; if the conscious personality cannot discern who are the workmen at work, it has at all events an exact notion of the operation in evolution, knows if the work be accomplished, and the requisite muscular exertion made. We do not feel our muscles in a clear and precise manner when they are in a state of repose ; but when they are in activity, this new condition into which they are thrown develops in the sensorium a new mode of existence, so that the unconscious excito-motor sensibility in the dynamic state indirectly strikes upon the styisoriuin, and thus becomes a new element destined to become absorbed in its plexuses. Co?tscious Sensibility l^Sensatioii). — The sensitive exci- tations destined to become conscious and enter into rela- tion with the phenomena of psycho-intellectual activity, are collected, with their excito-motor fellows in the peripheral plexuses, which serve as a region of emission for both. Starting from this, and taken up by means of the converging fibres, they pass on towards the central regions of the axis, are concentrated in the isolated ganglions of the optic thalamus, and are afterwards radiated, as we have already seen, into the different regions of the cortical periphery. (Fig. 6. — 9. 4. 14.) The phenomena of conscious sensibility (or sensa- /; tion) have then as their point of origin, and first halting- , place, the peripheral regions of the nervous system.. \^ It is by the terminal nervous expansions spread out into a network, open, in a manner, to all that comes to impress it, that the external world penetrates and be- comes incarnate in us. And for this a special faculty for 100 THE BRAIN AND ITS FUNCTIONS. receptivity and impressionability in the nervous element thus impressed is in the first place necessary, as a funda- mental and indispensable condition of the phenomenon. In a word, it is necessary that at the moment the sensorial network receives the vibratory excitation, it shall directly participate in the act which takes place within it. It must become active, acquiesce — become in a manner erect ; and must, by a species of vital assimi- lation, convert the purely physical into a physiological excitation, the luminous vibration, for instance, into a nervous one. This is the fundamental act of which we shall speak again subsequently, and which is the first link of that chain of sensitive phenomena which is evolved through- out the nervous system.* It is, in fact, a vulgar truth which reveals itself to simple observation. Every one knows that the simple presence of a physical excitation of a sensorial organ is insufficient to produce a conscious impression, and that an active participation of the sensorial cell in the vibratory movement communicated to it is necessary. Open the eye of a sleeping man — the luminous rays fall in vain upon the retina. It requires a certain time before the nervous cells are wakened up and enter into harmony with the luminous vibrations which * This phenomenon has been perfectly described by Mathias Duval. "When the retina is excited," he says, " perception is not immediate, it is retarded for a very short period ; this retardation is due to the fact that it requires a certain time for the transformation of the luminous into a nervous movement to take place. Then this latter movement requires an interval, exceedingly short indeed, to be propagated along the optic nerve to the cerebral centres ; and finally, the centres of perception themselves are not immediately thrown into agitation. This retardation occupies one-fiftieth to one-thirtieth of a second." (Maihias Duval, " These dagregation," 1873, p. 132.) EVOLUTION OF SENSIBILITY, 10 1 excite them. Pinch the skin of a man in profound sleep, cry into his ear under the same conditions. There is the same apathy, the same default of reaction. The purely physical excitation will gradually become deadened if t Hereco me not m its train a purely vital phenomenon of sensation, which is developed, by a sort of active prehension of the physical food which is oifTered to the impressed cell.* We see, then, judging by what takes place here in this first phase of nervous activity, that the sensitive plexuses of our whole organism are all either isolatedly or simultaneously thrown into vibration, according to their various tonalities. They thus become like vast vibratory surfaces, of which the oscillations, registered as they arrive, are incessantly transmitted to the other parts of the system, and felt in the sensoriiim in a correspond- ing manner. It is a continuous, regular, imperative work, which is accomplished every moment, from the peripheral to the central regions of the system, and this uninterrupted appeal from the external world is so neces- sary, so much the obligatory condition of all cerebral activity, that the latter ceases at once when its means of alimentation from without are cut off (loss of conscious- ness, sleep, lethargy), just as we see the phenomena of haematosis cease, when the atmospheric air suddenly ceases to enter the recesses of the respiratory channels. * The participation of the sensorial element in the external perturbation is itself only a species of fugitive phenomenon, having a transient duration. When the duration of the impression is too prolonged, transgressing physio- logical limits, it brings on a period of fatigue of the receptive element, and ceases to produce any effect. Thus the sensibility of the retina is rapidly blunted. When, for instance, we look for a long time at a white spot on a black surface, and afterwards look at a white surface, we imagine that wa see a black spot upon this, the retma having become insensible to white. CHAPTER III. INTRA-CEREBRAL PROPAGATION OF THE PROCESSES OF SENSIBILITY. Sensitive impressions pursuing their course are, as we have already seen, condensed in the masses of grey matter in the optic thalami. These masses of grey matter represent, then, in the general economy of the nervous system, a species of point of convergence, or cross-roads, and the penulti- mate halting-place where impressions from the external world are united before being radiated towards the peripheral cortical regions. But as regards these different kinds of sensitive ele- ments which come flowing towards the grey ganglions of the optic thalami, these latter, which receive them into their mass, give them each an isolated territory — so that that division of labour of which we have already seen an example in the progressive evolution of the nervous system, here seems to receive a new confirmation, since we see the phenomena of sensibility divided, like white light, into isolated fascicles, each fascicle having a special receptive apparatus reserved for itself exclusively. Thus purely sensitive impressions have a central gang- lion where they are isolatedly condensed (Fig. 6 — 9.); it is the same for the optic, olfactory, and acoustic im- PROCESSES OF SENSIBILITY. IO3 pressions and finally the excitations of vegetative life also find a cell-territory specially appropriated to their reception, — so that as the processes of sensibility become perfected, as they penetrate more deeply into the interior of the nervous system we find them splitting up, divid- ing into elementary fascicles, each gifted with dissimilar specific properties, and yet united among themselves by the common bonds of their origin and evolution. After radiating through the cerebral white fibres, into the difi"erent departments of the cortical substance, the same phenomena of division of labour again occur, and we may directly observe that the regions in which the dissemination of auditory impressions takes place are different from those where that of the olfactory, visual, etc., takes place. So that each isolated region of the brain has also to work and develop its specific energies in isolation. {See Fig. 6 — 4. 9. 14. and Fig. 5 — 7. 8. 10.) When the sensitive excitations, whatever they may be, have been launched into the midst of the plexuses of the cortical layer, they find there also sensitive nervous apparatuses prepared to receive and absorb them, and thus co-operate in the various processes in evolution. We have indeed already studied the remarkable dis- position of the cells of the cortex {see Fig. i .), which are arranged in isolated zones, stratified like the layers of the crust of the earth, and thus constitute a continuous network of which all the organically connected molecules are arranged so as to vibrate in unison, and to propagate the nervous undulations, either vertically or laterally On the other hand, those myriads of nerve-cells, ag- glomerated into a continuous whole in the sub-meningeal regions of the cortical substance, are themselves essen- I04 THE BRAIN AND ITS FUNCTIONS. tially sensitive. They are living, impressionable, and gifted in the highest degree with that vitality which characterizes the nervous elements : and accordingly, when the perturbation from the external world, trans- formed by the metabolic action of the optic thalami, comes to reverberate within them, they are perturbed in their turn, and are in a manner thrown into a condition of erethism, just as the peripheral plexuses were when first agitated by the external excitation.* Thus it is that the sensitive excitations awaken the activity proper to the elements of the cortical substance ; that these are brought into play ; and that the sensitive process, like a force which is incessantly transformed, loses by degrees its primordial character as it advances and enters a new territory. We see then how gradually the processes of sensibility are transformed by incorporating themselves more and more with the organism; how, starting as simple physical elements, they end by becoming, in the last term of their long course, a living excitation, more and more animalized and intellectua ized by the special activities of the different media which they have successively called into action. In this respect they are quite comparable to those physical phenomena by virtue of which we see the luminous rays which pass through our optical instru- ments become subject to the modifying influence of the media they traverse — become concentrated, refracted, unequally diffused ia secondary elements, to present themselves finally to our visual sensibility, perfected, purified, separated, and with their maximum of effect. Genesis of the Notion of Personality and of Moral • Account of the experiments of Scliiff, p. '^'j. PROCESSES OF SENSIBILITY. IC5 Sensibility. — The processes of sensibility have not for f;heir sole object the transformation of external excita- tions ; they contribute in a much more effectual manner to operations of great delicacy, which are designed to co-operate in the genesis of the notion of our individual personality. It is, indeed, throjgh the awakening of the activity of the sensibility diffused throughout the different regions of the organism — vegetative as well as excito- motor sensibility — that this notion is engendered, developed, and maintained constantly active and alive in us. It follows, indeed, as a natural ccnsequence of what we have already indicated, that everything in us which is sensitive — every fibre which vibrates, every sensorial plexus which becomes erethised — produces a vibration which is concentrated in the plexuses of the cortical substance, and finds in their essential structure a vast common reservoir, the veritable scnsorinni commime into which all the excitations collected in the periphery separately flow, and in which they remain latent. The result, as regards the secondary reactions of this scnsorinni, of the general concentration in these plexuses of all the diffuse sensibilities of the organism, is naturally that all the sensibilities of the peripheral regions of the nervous system, drained from the essential structure of our tissues, of our flesh, mucous membranes, viscera — in a word, of our whole organism— and conducted along the converging nervous filaments, as the electric fluid is along the wires which transport it to a distance, inevita- bly travel towards the central regions of the system, towards the sensoriuui conininnc, where they are simul- 9 106 THE BRAIN AND ITS FUNCTIONS. taneously distributed ; and that these conceptive regions of the sensorimn represent, as it were, at the other pole, the sensitive foci correlated to the peripheral regions in agitation. AW these modes of sensibility, whatever be their origin, are, then, physiologically transported into the sensoriiim, and there find a symmetrical region which vibrates in unison with their peripheral tonality ; so that from fibre to fibre, from sensitive element to sensitive element, our whole organism is sensitive, our whole sentient personality, in fact, is conducted, transported just as it exists, as a series of isolated currents, into the plexuses of the sensoriuin commune.'^ • There we are represented in detail, there all our sensitive elements are condensed, fused, and anasto- mosed into an inextricable unity — a unity which is itself only an expression of the organic connection of the underlying nervous plexuses. There, in a word, the synthesis of all our dispersed sensibilities, which are united in a limited space and yet faithfully reproduced, takes place. There our personality lives and feels. Here, by means of the conductility of sensitive ex- citations and the intervention of the nervous system, which represents in the truest sense an organ of per- * Tlie conductility and disperoion of sensibility in the j^wjct/wot, by means of the nerve-fibres, is so real, that in persons who have suffered amputation, when any irritation attacks the stump and engages the sensitive nerves, it immediately awakes and develops in the sensorium the old impressions in a posthumous form. It is not simply the painful state of the sensitive nerves that the patient feels, it is also the resurrection in the serjsorium of a portion of himself, in consequence of the persistence of the conductors which formerly supported it and in which this sensitive portion of his personality was incar- nate. {See MuUe", " Physiologie," vol. i. p. 598 ; Sensations experienced by persons after amputation.) PROCESSES OF SENSIBILITY. I07 fectionment implanted in the organism — something takes place quite like what we see in a camera obscura, when we see images of the external world projected upon a screen which presents only a limited plane surface. The magnifying lenses of the object-glass, the interposed media, have conducted and directed the luminous rays in such a manner that they are pre- sented to the eyes spread out over a limited surface, with all their gradations of tint and colour, and with the relations they have in nature. The external world is thus projected to a distance and conducted into another region than that whence it is derived, just as the sensitive excitations of the organism are dra.'ned off, condensed, and transported to a distance by the nervous apparatuses which project them into the scmsoriiiniy and thus permit of their being grouped according to their natural affinities. Moral Sensibility. — When the peripheral impressions are dispersed in the plexuses of the sensoriiun, and the cerebral cell is called into play, a new series of pheno- mena is developed. This depends on the spontaneous reactions of the elements of the sensoriiim which are in agitation, and which vibrate in unison, and become erethised in consequence of the arrival of an external impression. At this moment a phenomenon, quite similar to that which occurred in the peripheral regions, takes place when the sensorial plexuses are unexpectedly agitated. This process, which leads to the transformation of the incident sensorial im.pression into a physical excitation, is not accomplished coldly and passively. The thou- sands of cerebral cells of the sensorium commune that I08 THE BRAIN AND ITS FUNCTIONS. have been unexpectedly awakened acquiesce in it in their own manner. They react in a specific manner, and, like their partner-cells situated at the antipodes in the sen- sorial plexuses, they react according to the manner in which their natural affinities have been excited. According as the excitation has gratified or wounded their profound sympathies they are agreeably or dis- agreeably impressed. A new phase, therefore, at this moment appears in the evolution of sensibility, a new element comes into play, which speaks, and is excited. This is the specific sensibility of the elements of the sazsoriuin, the emo- tivity which is disengaged from the cortical substance ; and it comes into play in a necessary, involuntary, automatic manner, by the simple awakening of the elementary properties of the regions, engaged. We all know how passively we receive the excitations which agitate us, and how little free we are to feel or not to feel impressions from without. This form of sensibility which runs riot in spite of us, these plexuses of the sensoriiim commwie which com- prehend in themselves all the diffuse sensibilities of the organism, represent, then, a sphere of nervous activity in erethism, always living, always feeling, in the bosom of which our total personality lives and vibrates. There, in this mysterious dwelling, it is in perpetual intercourse with the perpetual movement of the operations of cerebral life. There, according to the nature of the excitations that agitate it, it finds its keenest pleasures and deepest pains — the passionate enthusiasm which exalts it, the anguish which depresses it There vibrate the sensitive chords of our human PROCESSES OF SENSIBILITY. I09 nature, which, alternately tightened and relaxed, express the different pitches of the emotions that set them vibrating.* The phenomena of moral sensibility, conceived, as we have just done, as a purely physiological synthesis of all the nervous activities, consist then in a series of regular processes, executed hy the organism at its own expense, and resulting from the harmonic consensus of all its parts. They present these two very significant peculiarities, which give them a supreme importance in the sum of the acts of cerebral life : I.. On the one hand, they are sustained and vitalized by means of former excitations ; they live upon accu- mulated memories incessantly reviving. 2. On the other hand, they are stirred up and kept awake by the intervention of the intellectual regions, with which they are in perpetual intercourse. I. Thus while the peripheral plexuses are only gifted with a limited power of retaining the external vibra- tions which have called them into action ; the cerebral elements, on the contrary, have this power in a very high degree. As we shall see further on, they can store up the impressions which affect them, as phos- phorescent bodies or collodion plates store up solar rays, and retain, for a greater or less period, a record of the elements which have more or less strongly affected them. * The pages which Guislain has devoted to this subject will be read with interest; and it will be seen that he had a presentiment of the physiological evolution of the phenomena we are now describing. (Guislain, vol. ii. " Lemons sur les Phr(^nopathies," p. 12.) no THE BRAIN AND ITS FUNCTIONS. The result of the awaking of this new property, as regards the evolution of moral sensibiHty, is that, once an excitation has been produced in the sensorium, once it has been incarnated with a special coefficient of pleasure or pain, it remains there like a phosphorescent gleam, and survives itself as a posthumous record. Suppose an object or a person has induced in us a movement of expansion or joy, the memory of the joy perceived will survive in our sensorium^ and will be re- awakened by the memory of the object or person who has provoked this pleasant emotion. In the same way, conversely, the memory of an insult, an injustice, a moral pain, persists in us, and remains attached to the person or the object that has been the cause of it. The emotion is united to this memory to such an extent that it is enough to think of it to cause an unpleasant emotion in us. We know that when we voluntarily recall the image of touching scenes at which we have been present, their reminiscences evoke in us emotions similar to those we experienced at the period when they actually occurred. We knovv also how profoundly the anniversaries of private griefs or public calamities affect our natural sensibility. We may say, then, that moral sensibility is engen- dered by the fact of the arrival and persistence of impressions in the sensoriinn. It is a phenomenon of memory, the memory of the heart, as has been said, which lives and develops itself in us, and is only sus- tained by means of old emotions, which, always more or less lively, are always alive and always ready to cause a sympathetic thrill throughout the sensitive PROCESSES OF SENSIBILITY. m plexuses of our inmost personality. Moral sensibilit)^, then, becomes the resultant of all our joys and sorrows, and the sympathetic link which unites our present to our former emotions. 2. Moral sensibility finds also in the intervention of intellectual activity a new power, which excites it, makes it active, and maintains it in a perpetual state of erethism. It is, in fact, most interesting to observe the important part that the intellect plays in the evolution and main- tenance of the freshness of our natural sensibility. If our sensibility finds an individual existence in the plexuses of the sensorium, we may say that it is enlight- ened, directed, educated only by the direct participa- tion of the intellect and its manifestations. Without the intervention of the intelligence, our sensibility, with all its riches, would be nothing but an inert brute force, diffuse and completely undisciplined. It is, in fact, the forces of the intellect, always active in the form of discernment, which make us reflect upon the choice of things or persons which have more or less affected our sensorhim. It is because we have an acquired experience of certain persons or things that we can give them our confidence. To choose our rela- tionships and friendships, and thus to make repeated rapid diagnoses of men and things, is an entirely intel- lectual operation, which illumines with the light of our reason the too often involuntary impulses of our natural sensibility. Again, it is by virtue of the same intimate participa- tion of the intelligence in the acts of our sensitive life, that a written page, a word, a sound, an appearance, 112 THE BRAIN AND ITS FUNCTIONS. can suddenly thrill all the emotional regions of our being in an agreeable or disagreeable manner. When I receive a telegram or a sudden piece of news \\hich throws me into trouble and consternation — when the reading of a comic author develops hilarity in me, it is still the direct intervention of the intellect, and the intellect alone, which excites and develops these sad or joyful impulses of my moral sensibility. It is because I comprehend — because my intellect works and im.mediately interprets the value of the written charac- ters—that I remember that each word expresses a thought, and determines a sentiment of a certain pitch. It is, then, always the intellect, active and present, that in the presence of a sudden excitation, ab externo, awakes, and causes emotions appropriate to the external phenomena which they symbolize, to arise in the sensoriiivi.^ In the same series of facts, when, for instance, in a foreign country I salute with emotion the appearance of the national flag, which is displayed before me as a symbol of my distant country, I surely do not see in it merely a piece of many-coloured bunting. No — at that moment a series of associated memories is awakened in me. I involuntarily think of a long past of glory, honour, and devotion, which is unrolled with its folds, and of the patriotic solidarity which unites me with those who defend it ; and thus, from idea to idea, from Tiemcry to memory, all the elements of my moral sen- * This connection between tlie intellectual and emotional regions is so inti- mate, that in dreams, when the intellectual regions, abandoned to their free lutomatic activity, engender the strangest conceptions, we are sometimes seized m\\\ impressions of sudden terror and overwhelmed in consequence of certain errific apparitions. PROCESSES OF SENSIBILITY. II 3 sibilli-y, awakened by a single physical impression of an external symbol, are thrilled, one after another, because this external symbol has awakened, in the regions of intelligence, old ideas, and national memories. Thus, then, the activity of the intellectual regions excites, and incessantly keeps our moral sensibility permanently awake within us ; while at every instant of the day, in this incessant working of all our mental activities, the intellect, present everywhere, watches over all, co-ordinates memories, regulates and stimulates the impulses of sensibility, and thus becomes the natural bridle which restrains them, as far as this can be done, within the limits of right and reason.* This is so true, indeed the energy of moral sensibility is so closely connected with the energy of the intellectual faculties, that when the latter are attacked, moral sen- sibility inevitably falls into decay. We often observe, indeed, that in demented old men whose intellectual faculties are considerably impaired, the impulses of moral sensibility simultaneously decay, or are more or less profoundly injured. * It is this direct participation of intellectual activity in the phenomena of sensibility proper, that produces the different modes of feeling in men according to their different degrees of intellectual culture, their mode of life, and the hereditary conditions of organization they may present. 'I he cultivated ni.in will be moved by spectacles different from those which please uncultivated and gross men. The refined in intellect have tueit special delicacies of senti- ment and modes of enjoyment which are uiiknown to the vulgar. CHAPTER IV. PERTURBATIONS OF SENSIBILITY. Physical Pain. — The phenomena of sensibility, like al! phenomena of vital activity, are susceptible of alternate lowering and exaltation, and of presenting maxima and 7ninima of oscillation, in the interval between which their average periods are comprised. Thus, when sensibility is locally annihilated, when the histological tissues are affected with a species of local torpor, anaesthetic phenomena present themselves. When, on the other hand, the contrary phenomena occur, when histological vitality rises several degrees to a state of cellular excitement, and the nervous elements reach a condition of continuous erethism — then manifestations of hyperaesthesia or pain occur. In these two cases phenomena connected with the natural sensibility of the nervous elements are always present, and, as it were, rise from zero to one hundred degrees. The processes of anaesthesia and pain appear to develop like those of normal sensibility, independently of any nervous plexus which underlies them, from the simple fact of the existence of a cell capable of living and feeling. It is certain, indeed, that in sensitive cells sensibility becomes obtuse and grows feeble under the influence PERTURBATIONS OF SENSIBILIIY. II5 of certain special conditions : chloroform makes their reaction impossible. Certain narcotic substances also appear to have a stupefying action on the sensibility of certain plants. It is certain again, that the sensibility of vegetables is perverted when they are thwarted as regards their natural evolution, and do not fmd in the soil with which they are furnished conditions favourable to their physiological nutrition. It is certain that they suffer also, as it is popularly said, and that their sensitive tissues, which are impressionable by external agencies, have to contend against wounds or with enemies of all kinds belonging to the animal and vegetable kingdoms, which under the form of parasites, oidium, phylloxera, etc., fasten upon them and attack them even in their roots, in the very sources of life, thus inflicting upon them the same calamities we may see raging among individuals of the animal kingdom. Pain, from the very fact that It expresses a purely vital action inherent in every living cell, vegetable as well as animal, is therefore the physiological equivalent of the individual sensibility of that same cell in conflict with the surrounding medium which impresses it painfully. It exists wherever there is a cell capable of living and feeling, and independent of the existence of any nervous element. Between the simple histological Irrit- ability of any anatomical element whatever, which is the rudimentary form under which it presents itself at first, and the most exquisite expressions of sensibility in superior beings, there are merely infinite degrees of sensitive vibrations which mark Its difl"erent modes. Just as we see a metal rod placed In a blazing furnace grow hot by degrees, and in proportion as the undula- Il6 THE BRAIN AND ITS FUNCTIONS. tions of the caloric become more and more frequent, pass in succession through the shades of bright red, dark red, and white heat, and develop as it grows hot both heat and hght ; so the Hving sensitive ceils, in presence of the excitations which affect them, undergo progressive exaltation as regards their natural sensibility, arrive at a period of erethism, and with a certain number of vibrations disengage pain, as the phy- siological expression of this sensibility super-heated to a white heat. This is so true — the phenomena of pain are so really an act of vital reaction, that not merely the awakening of sensibility but a certain ten- sion of it, is its necessary condition. When the nervous plexus is torpid, anaesthetic, pain cannot be developed. Suffering is not a thing of the will — to suffer we must feel. All physicians know what curious phenomena the skin of hysteric patients often presents in this respect. You may pinch them, prick them, apply bi/rning sub- stances to the surface of the body ; the patients feel nothing save the simple contact of the substances applied ; their sensitive plexuses, stricken with a species of torpor, are incapable of erection, becoming excited and disengaging pain. In producing local anaesthesia we obtain a similar condition of the sensitive plexuses, and prevent the evolution of pain. When the anaesthetic agent is applied it acts locally upon the iadividual sensibility of the nerves of the region. It chills them in a man- ner, hinders them from becoming heated, as regards the excessive production of painful vibrations, and main- tains them at the low pitch of general sensibility. The PERTURBATIONS OF SENSIBILITY. II7 anaestheticlzed regions, in fact, cease to disengage pain, while they are still conductors of sensitive impressions. Pain being only the expression of the histological sensibility of the nervous elements risen to an extra- physiological pitch, we can understand how, being always identical with itself as regards its genesis, it may reveal itself in a different manner according to the different nature of the nervous plexus thrown into ao^itation. Thus pain presents itself in various modes according as it affects such and such a sensorial plexus. If it be the retina which is affected, we know that when light is too intense its sensibility is developed to excess, and leads to a reverberation excessively painful for the sen- sorimn. It is the same with the acoustic nerves, when violent and s'rident sounds produce contusions of their natural sensibility. The olfactory and gustatory plex uses have also their own forms of suffering, and every- one knows how painfully the contact of bitter and acrid substances, or that of foetid emanations, affects the sensorial plexuses thus brought into play. Finally, when our viscera are attacked in their sensitive ele- ments, we all know that they complain in their own fashion to the scnsorhim, that they reveal their suffer- ing in a peculiar manner, and that the manifestations of pain vary with the tissues engaged, the regions invaded ; that, in a word, the semeiology of pain, as regards its different characters and modes, has a special physiognomy wliich all physicians can appreciate. If we now pass to the examination of the processes of pain in the central leg'.ons of the nervous system, we shall see that they are developed in a manner similar to V Il3 THE BRAIN AND ITS FUNCTIONS. that we have just explained, and that the morbid re- actions of the sensorium have a method similar to that of the morbid processes of the peripheral regions. The plexuses of the sensormm, in the substance of which sensitive impressions are diffused, are normally insensible, like our nerves, which, when in activity, silently transmit and elaborate sensorial impressions, without our having a notion of all their minute opera- tions. It is not always so. Just as the peripheral plexuses are susceptible of exaltation in presence of too-energetic vibratory excitations, or by the occurrence of a local dis- turbance of their habitual state of existence — so the plexuses of the sensorimn are susceptible of excessive heating,* and of exaltation when a too-vivid peripheral impression, or a too-prolonged excitation comes to rever- berate through their meshes, and thus cause them to rise to the vibratory pitch of pain. We know that the absence of repose for the brain, prolonged vigils, uninterrupted intellectual work, moral emotions, engender a local heating of the cerebral sub- stance, cephalalgia, and aching of the brain. The calling into activity of the cerebral cell, in an extra-physiological manner, at the same time abnormally develops its histo- logical sensibility, and induces, as a necessary conse- quence, prolonged erethism and pain, in the manner we have just pointed out. We all know by experience, how painfully a piece of taskwork which does not provoke an intellectual appetite, is done — it is an effort which the brain makes against the grain ; and how, on the contrary, when the • Sec p. 'j'j, " Experiments of Schiff.' PERTURBATIONS OF SENSIBILITY. II9 task is a pleasant one, there is a fascination in setting to work, and a rapidity in the execution. The natural spontaneity of the brain thus supplies the place of effort. All those who have suffered from headache know how exquisite is the sensibility of all regions of the sensoriitm ; how painful a thrill is produced by the least noise from without, the slightest shock of the thoughts which tra- verse the brain. They know also that silence, and sleep — that is to say the cessation of every source of cerebral excitement — are the only efficacious means for charming away these painful crises through which the sensibility of the sensorium has to pass.* More than this, a comparative examination of the manner in which the central and peripheral regions of the nervous system behave in presence of anaesthetic agents, shows us a new connection between the modes in which sensibility is developed in these two opposite regions. Thus, when hyperaesthesia appears in the sensorium, when the pain reveals itself either as the effect of too intense peripheral excitement (a wound, or any injury of the surface of the body), or as the effect of a per- sistent irritation (moral emotion, prolonged intellectual labour, etc.), we may artificially cause the level of pain- ful over-excitement to fall several degrees, just as if we had to deal with a peripheral plexus in a condition of • Just as we have seen before, with regrird to the peripheral regions, that pain was only the e pression of the sensibihty of Hvini( tissues in exercise ; so for the central regions pain is only possible in proportion to their soundness. The slow destruction of the sensorium by chronic disorganizations, progressively leads to the cessation of certain forms of cephalalgia. Thus we find paralytics who at the beginning of their disease have had very severe headaches, end by no longer suffering from any painful symptom. 120 THE BRAIN AND ITS FUNCTIONS. painful erethism, and may thus to a certain extent dull the painful vibrations. It is thus that anaesthetics and stupefying drugs act when introduced as inhalations. In operations on patients under chloroform, this agent spreading through the plexuses of the scnsorimn freezes its nervous elements, which it steeps in the same anaesthesia in which the sensitive plexuses of the skin of a hysterical patient remain.* Painful excitations are in vain launched from the peripheral regions in the form of keen incisive thrills, when the tissues are cut ; they meet in the sensoriinn only zones of cells physically modified^ stricken with anaesthesia, and incapable of erection, of feelings or of being raised to the pitch of pain. To complete the resemblance, just as we see anal- resic patients whose skin is pinched, and into whose tissues needles are thrust with impunity, witness with indifference and without painful reaction what takes place in their bodies ; so we meet with a certain num- ber of operation patients who, being capable of analy- zing their sensations at the moment of operation, tell us that during the period of anaesthesia into which they were plunged, they have felt the cold of the knife penetrating into their flesh — that they have felt the * To understand the mere mechanism of aocesthesia, it should be known that chloroform does not act simply upon the nervous elements. If we place a muscle in the vapours of ether and chloroform, or inject into a limb a weak solution of chloroform or ether, we induce rigidity of the muscle ; and when we e amine the change produced, we perceive that the contents of the muscuiar libre are no longer transparent, but have undergone coagulation. It is to be supposed that something analogous takes place in the nerve cell, but this is much more delicate, much more sensitive to the action of chloroform, it being first to undergo coagulation. As the chloroform is carried off by the blood, the cell recovers from its aniesthesia and returns to its normal condition, as the muscle cx:overs from its rigidity. PERTURBATIONS OF SENSIBILITY. 121 keen instrument cutting through their tissues, but that to their surprise they perceived that they did not suffer, and that the usual pain was not naturally disengaged as they would have expected. One of them told me that he experienced a surprise simi- lar to that of a person who should plunge his hand into a burning brazier, and should naturally be aston- ished at not feeling the burn. Moral Pain. — Moral pain is only the expression of the moral sensibility carried to its maximum of inten- sity, as physical pain is but the most exquisite form of the physical sensibility thrown into agitation. The conditions of evolution are the same in. both cases, except that moral pain presents itself to us under special aspects of amplitude and intensity, which give it an expression of a persistence quite characteristic. Thus in studying the etiological conditions of moral sensibility, we have seen how this sensibility was but a long synthesis and the resultant of a combination of the sensibility of the sensorium thrown into agitation with the involuntary revival of memories, and the incessant participation of intellectual activity, which always under- lies its manifestations. External excitations, as we have already remarked, once deposited in the sensormiHj do not become extinct all at once. They survive, and like phospho- rescent gleams, leave persistent traces of their passage in the nervous plexuses. On the other hand, the ex- citations of intellectual activity are also concerned in the process. They are always alert, always active, and by virtue of their automatic energies they reveal them- selves in the shape of ideas associated with contem- lO 122 THE BRAIN AND ITS FUNCTIONS. porary reminiscences and connected reflections ; so that they also constitute, as it were, so many foci of activity capable of incessantly intensifying the move- ment in the plexuses of the sensorium. The result, as regards the genealogy of moral pain, of the double participation of these two physiolo- gical factors — the persistence of impressions, and the incessant participation of the intellect in the phenomena of sensibility, is this, that when the plexuses of our sensoriurn have been thus thrilled vividly to their depths, the impression so produced does not immediately die away. It becomes persistent — lives upon memo- ries, and vibrates like the dolorous echo of a former agitation of our sensibility, to be effaced only as this sensibility becomes dulled in the region where it was primarily engendered. The shock once produced, it becomes incarnate, and perpetuates itself in us by pro- ducing the phenomena of moral grief We cannot avoid feeling it, and suffering — each in his own manner it is true, each in a different degree, according to the delicacy or richness of the nervous elements which constitute his sensoriurn. It is no more possible to escape from a painful emotion which comes to inflict a sort of contusion upon our natural sensibility, than to escape an ecchymosis when a heavy body crushes our integuments. On the other hand, this participation of the intellect in all that concerns us, and all that moves us, naturally becomes a species of incessant morbid excitement of our moral erethism, and perpetuates the griefs of the sensitive regions of our being. The physiological excit- ations which stir up and vivify our moral sensibility PERTURBATIONS OF SENSIBILITY. 1 23 are, then, also those which vivify and perpetuate our moral pains. It is because man can judge of the loss which he undergoes in consequence of the sudden ruin of his affections and dearest hopes ; because he can estimate the happy memories which are fleeting; the bygone joys, the sorrows of the future, and the griefs of the present ; because he finds before his mind's eye a multitude of elements furnished by his intellectual activity working automatically — that he suffers morally in his sentient being, and that the w-ounds of his heart, incessantly revived by a crowd of memories which assail it like so many morbid stimulations automatically arising, remain always open ; that pain lives within him and preys upon him perpetually. Vuinus alit venis et coeco carpitur igni. Thus it is that when trouble attacks him he passes through that series of dolorous stages which lead him to slow despair, to that phase of profound despondency so often the road to mental maladies. The m.oral life of an individual, his stock of natural sensibility and emotivity, is therefore kept in a con- dition of freshness and integrity only by the incessant activity of his memory, and intelligence, and the con- scious perception of the things of the external world. When the memor}^ and intelligence begin to fail, and the energy of the mind to grow weak, the decadence of the moral sensibility follows that of the intelligence step by step. In a man intellectually degraded w^e can only count upon a low morality. And this is so true, that a perLon w^hose intellectual powers have been 124 THE BRAIN AND ITS FUNCTIONS. already impaired, either by the occurrence of diffuse cerebral congestions or by alcoholic excesses which have impaired the very substance of his sensorium, no longer feels moral pain according to the regular pro- cesses by which it is developed in his fellow men. The student of mental maladies frequently meets with indi- viduals apparently reasoning with inflexible logic, and preserving a certain energy of the intellectual faculties, yet no longer having any exact notion of what is pass- ing around them, or capable of comprehending, like every one else, the emotions of moral sensibility. If we try to convey to them a family trouble, or the loss of one formerly loved ; if we seek to set some chord of emotion vibrating within them, nothing moves them. They remain impassive, and this defect of moral* reac- tion indicates at once their dullness of comprehension, and the silence of the intellectual activity which has not normally interpreted the sense of the words and their range of significance. In this defect of sensitive reac- tion, we have a criterion which indicates to the observer the secret dilapidations which have occurred in the sphere of mental activity. To sum up, it is in this special mode of evolution of the moral sensibility, in its dependence upon both ancient memories and intellectual activity, that we must look for the secret of the strong action of moral influences upon the development of diseases of the brain. It is because man is sensitive that he suffers, and because he is, as an individual, sensitive in a certain manner, and in certain favourite directions — because he is more or less interested in the acts of his life, and conscious of what passes around him, that he suffers PERTURBATIONS OF SENSIBILITY. 12$ morally. The moral wound which is established in him, once produced, does not heal up all at once, it extends its influence, festers like a serpiginous ulcer, and being incessantly irritated by automatic impressions radiating from the sphere of the intellect, perpetuates itself, always poignant, in the sensormm^ reviving in a thousand forms on the smallest provocation. It thus becomes, by reason of the special conditions of the medium into which it has eaten, a cause of ruin, of progressive wear- ing out of the mental energies, unless a profound diver- sion be immediately created, or a salutary method of treatment intervene to arrest disorders which tend to become incurable. CHAPTER V. DEVELOPMENT OF SENSIBILITY. Sensibility in living beings awakens with life. As regards histological sensibility proper, it is inherent in the primordial phenomena of the evolution of the embry- onic cells ; it is a hereditary legacy which accumulates incessantly, by the addition of new elements, and new tissues, in proportion as the organism completes and perfects itself. It is by virtue of the individual sensibility of the em- bryonic cells that these borrow from the surrounding medium, the fluid atmosphere which bathes them, the elements suitable for their special nutrition, and that the nervous system itself appears as an apparatus of centralization and organic perfectionment. In the first phases of foetal life it is very difficult to fix definitely at what epoch sensibility manifests itself as a motor force ; nevertheless, from the fourth month we can observe that the nervous system begins to react and to reveal the vitality of the diff'erent apparatuses of which it is made up. We know, indeed, that from this period the foetjs is sensitive to the action of cold, and that we can develop its spontaneous movements by applying a cold hand to the abdomen of the mother. We know also that it executes DEVELOPMENT OF SENSIBILITY. 12/ spontaneous movements to withdraw from pressure that constrains it and brings its sensibihty into play. We may then legitimately conclude that here we have the first gleams of awakening sensibility, which from this period is transmitted through its natural channels by the nervous system, and already regulated in the manner in which it will subsequently manifest itself throughout the organism. At birth it is the entire cutaneous sensibility, suddenly awakened by the irruption of the young being into a cold atmosphere, which determines its first startled cries, and its first inspirations. It is, then, in the sensitive peripheral regions that the first sparks which are to develop the play of the organic machinery, and those excitations of the vital knot which once set in motion will only cease at the end of life, have their origin. From this time forth the child takes the breast of the nurse automatically, and by virtue of hereditary vital forces which already exist in a latent state in his nervous system. His organic appetites are gratified by the milk he sucks, and he feeds himself organically, like an organic cell, which borrows from the surrounding medium the materials which suit it. But at the same time he ex- presses the satisfaction he feels in his own manner ; he smiles on seeing the breast which yields him his nourish- ment and life, and from that time his natural sensibility is thrown into agitation, his sensorium is affected. He rejoices because he remembers, because he has retained a memory of the satisfaction of his physical appetites. Here, in these first phases of the manifestations of human sensibility, is the rudimentary formula according to which the moral sensibility of the human being shall 128 THE BRAIN AND ITS FUNCTIONS. henceforth be evolved In the course of his Hfe, and already such as we have found it in the adult — that is to say, reducible to a purely sensitive phenomenon multiplied by the intervention of memory and intelligence. From these first moments onwards sensibility develops rapidly. The different sensorial foci by the aid of which it comes to life, light up, multiply, and successively attain to perfection. The child successively learns to see, hear, feel, smell, and taste. He remembers satisfactions re- ceived. He recognizes the persons who immediately surround him and load him with caresses. It was the sight of the bosom of his nurse which in the first instance excited his first smiles, and as his field of vision extends, it is the entire person of his nurse to which these same smiles appeal ; then, as it extends still further, he re- cognizes those whom he frequently sees, and who present a pleasant physiognomy to him. Soon, by the progressive unfolding of all the latent activities of the organic elements which come into exist- ence, the general life of the child develops in ample luxuriance. Moral sensibility undergoes the same developmental movement ; intelligence and memory enrich these first manifestations every instant. Henceforward the first links of family affection bind themselves round his heart, and thus become the origin of his first sentiments and emotions. He loves those who approach him, for the sake of the good things they have already done for him. He can recognize those who wish him well or ill, or who are simply indifferent to him ; and thus DEVELOPMENT OF SENSIBILITY.- 1 29 ft is that to every one who comes in contact with him, and excites his sensibility in one way or another, he devotes an appropriate memory and a gratitude propor- tioned to the good or evil influence he has received. He loves his parents, in the first place, because they contribute more or less to his well-being and his plea- sures, and because he is in the habit of seeing them every day ; and this incessant renewal of physical im- pressions keeps the sentiment of gratitude in a condition of permanence and freshness in his sensormm. Those who are always present before his eyes are similarly present in his heart. At another period of human existence, the most violent of the sentiments which are calculated to set all the sensitive chords of the living being vibrating — love — develops itself merely by virtue of the same physio- logical laws. It is at its outset, as in the young child, the satisfac- tion of physical sensibility which forms the necessary prelude to it, its first stage and indispensable condition. It is because he has been thrilled in all the elements of his physical sensibility that the living creature, at the period of love, is inevitably hurried forward, by invin- cible hereditary impulses, towards the being destined to be his complement and to become the physiological receptacle of his deepest joys. It is because he has been charmed at once, in all the sensitive elements of his being, by the sight of the plastic beauties of the object of his desires, by the seductions of her speech, her voluptuous contact, and all her intellectual and moral wealth, that he is cap- tivated and subdued. It is because all his physical 130 THE BRAIN AND ITS FUNCTIONS. sensibilities have been simultaneously awakened, and that a period of generalized erethism is developed in his seitsorium, that he loves the object who has been for him the origin of all his happiness — that he attaches himself to her, becomes her slave, and surrenders him- self altogether ; just as, when he was a child, he loved, according to the measure of affection of which he was capable, the nurse who gratified his first sensuous appetites. Thus it is that love, the concrete expression of all the sensibilities thrown into agitation, develops itself in the living being as a recognition of physical pleasures satisfied, and as a hope of their repetition ; and that this sentiment, so simple in rudimentary organisms, in which sensibility is little developed, becomes compli- cated in the animal series in proportion as the sum of the sensitive elements multiplies, and the phenomena of moral sensibility come more into play. In fact, in proportion as we pursue the study of this sentiment through the series of living creatures, we see that, by slow gradations, it undergoes a progressive transformation, and that in proportion as the moral influences of civilization become paramount, the purely animal physical love of savage peoples loses its primi- tive character, to become clothed in new forms, appro- priate to the new medium in which it is developed. Thus it is that polygamy, which is the social expres- sion of the satisfaction of all physical pleasures, insen- sibly gives place to monogamy, the most perfect expression of the union of the man and woman, and a more serious guarantee for the maintenance of the family. This regular form of love, which is an epitome DEVELOPMENT OF SENSIBILITY. I3I of the most delicate perfections of human sensibility, concentrates upon a single head the sorrows and joys of the past and the hopes of the future, and thus cements the permanent ties consecrated by the customs of common life. It inevitably engenders, in every degree of the social scale, spite of the numerous short- comings by which it is dishonoured, those natural acts of devotion and self-abnegation for the common work of progeniture, and that whole series of respectable senti- ments of which the domestic morality of monogamous peoples offers most striking examples. As a man advances in life, his sensibility becomes gradually lessened — the senses become dull, the sight loses its sharpness, the skin its impressionability by ex- ternal agents.* A sort of general slackening of all his functions impends over the livmg creature thus arrived at the retrogade phases of his evolution. This condition of diminution of the peripheral sensi- bility is reflected in a similar manner upon the sensibility of the central regions. Moral impressionability and emoti\ ity lose their energy as a man grows old. He is less and less interested in external things capable of exciting his mental activity. He is less sensitive, less impressionable, less curious as to knowledge and feeling, and at the same time his intellectual faculties are simultaneously impaired. Memories of the past, like enfeebled phosphoric gleams, persist for a certain time, to the exclusion of more recent remembrances, but, in * In old persons the skin atrophies very remarkably, and in a great number the skin of the derma is so attenuated, that by pinchmg up a fold in the dorsal region of the hands I have often been able to observe that it has become so thin and translucent that the circulation in the subcutaneous capillary plexuses alight be seen, as in the foot of a frog. 132 THE BRAIN AND ITS FUNCTIONS. the end. even they too are extinguished, so that, the circle of bygone things narrowing by degrees, the indi- vidual feeds his sensorhim only with the current opera- tions of life. Material life with all its necessities — eating, drinking, and sleeping, becomes, little by little, the favourite occupation of organisms in the period of decadence ; and as to moral sensibility, the old man, an egotist with few exceptions, is reduced to vegetative life, and becomes once more a child, caring no longer for those who care for him day after day. He forgets his old friends, and the most natural family affections, for the sake of the newest comer, and succumbing more and more to the interested demands of his personality, he arrives, as regards moral sensibility, at a true anaes- thesia which reflects the languishing condition of the elements of his nervous activity. BOOK II. ORGANIC PHOSFHORESCENCE OF THE NERVOUS ELEMENTS. CHAPTER I. INTRODUCTORY. I HAVE proposed to apply the term phospJiorescencc to that curious property the nervous elements possess, of remaining for a longer or shorter time in the state of vibration into which they have been thrown by the arrival of external excitations — as we see phosphore- scent substances illuminated by solar rays continue to shine after the source of light which has illuminated them has disappeared. We know, indeed, now, thanks to the works of modern physicists, that the vibrations of the ether, in the form of luminous undulations, are capable of being prolonged by phosphorescent bodies for a longer or shorter time, and thus surviving the cause which has produced them. Niepce de Saint-Victor, in his researches on the dy- namic properties of light, has arrived at results much more precise and unexpected ; since, in a series of 134 THE BRAIN AND ITS FUNCTIONS. reports,* he has shown that luminous vibrations may be to some extent garnered up in a sheet of paper, and remain as silent vibrations for a longer or shorter period, ready to appear at the call of a revealing sub- stance. Tnus, having kept in darkness some prints pre- viously exposed to the solar rays, he, several months after this insulation, succeeded in demonstrating, by means of special reagents, persistent traces of the photographic action of the sun upon their surface. On the other hand, the daily practice of photo- graphic reproduction by means of dry collodion, is an irrefragable demonstration of the aptitude which certain substances gifted with special elective sensibility have for preserving persistent traces of the luminous vibra- tions that have for a certain time affected them.* In fact, when we expose a plate of dry collodion to the luminous rays, and several weeks after such exposure develop the latent image it contains, we produce a resur- rection of the persistent vibrations and obtain a record of the absent sun ; and this is so true, in this case of persistence of a vibratory movement which has but a limited duration within which it must be seized, that if we pass the prescribed limits and wait too long, the movement gradually becomes enfeebled, like a source of heat which cools and ceases to be able to reveal its existence. This curious property, which inorganic substances possess, of preserving for a longer or shorter period a species of prolongation of the impressions which have first set them in motion, is found once more under new * "Comptes rendus de I'Academie des Sciences," Nov. i6th 1857, vol. xlv. p. 811, and Mc»rch ist, 1858, vol. xlvi. p. 448. PHOSPHORESCENCE OF THE NERVOUS ELEMENTS. 1 35 forms, with special phenomena, it is true, but essentially the same, when we come to study the dynamic pheno- mena of the life of the nervous elements. These also are gifted with a sort of organic phospho- rescence, and are capable of vibrating and storing up external impressions, of remaining for a certain time in a sort of transient catalepsy, in the vibratory state into which they have been incidentally thrown, and of causing the first impressions to revive after the lapse of time. We all, indeed, know that the cells of the retina con- tinue in a state of vibration after an excitation has ceased. It has been calculated by Platau that this per- sistence of impressions may be estimated at from thirty- two to thirty-five seconds.* To this persistence of vibrations, and that special retentive force which the nervous elements possess, is due the fact that two suc- cessive and rapid impressions become confounded, and thus give a continuous impression : that a live coal whirled round at the end of a string gives the impres- sion of a circle of fire : that a disc, painted with the colours of the spectrum, when in rotation gives only the sensation of white light, because all its colours are confounded and form for us an unique resultant, which is the idea of white. All those who occupy themselves with histology know that after prolonged work the images seen in the focus of the microscope live in the fundus of the eye, and that sometimes, after several * The duration of impressions upon the retina is much longer than that of the action of Uglit. According to Platau, the duration of the consecutive impression increases in the direct ratio of that of the primary impression (Pin the direct ratio of its intensity). Thus the consecutive image of a strongly illu- minated body may be kept in the eye for a very long time. (MuUer, " Piiysio- ogie,' vol. ii. p. 355.) 136 THE BRAIN AND ITS FUNCTIONS. hours' work, shutting one's eyes is sufficient to cause them to reappear with great distinctness. It is the same with auditory impressions. The audi- tory nerves preserve for a long time the trace of im- pressions which have set them vibrating. After a rail- way journey, we hear, for several hours after arrival, the noise of the rattling of the carriage. A musical air, and certain favourite refrains, involuntarily resound in one's ears, and that often in a most disagreeable manner. After long musical seances^ says Dr. Moos (of Heidel- berg), the sounds persisted for fifteen days in one patient, and in another, a professor of music, for several hours after each lesson.* The gustatory plexuses also seem capable of thus preserving the trace of agreeable or disagreeable im- pressions which have affected them, and the intensity of the impression is sometimes lively enough to pro- duce, retrospectively, either a secretion of saliva when the mouth waters at the thought of something nice, or, in other circumstances, a sensation of nausea when the substance has produced an unpleasant sensation. The impressions of general sensibility, olfactory sen- sibility, etc., appear to present analogous phenomena. This species of histological catalepsy, which to some extent polarises the nerve-cells in the situations in which they have been immediately placed at the time of their first impression, is not merely a unique phenomenon, which is met with in the peripheral regions of the nervous system ; it is also met with still more fully developed in the central regions of the system, where it appears with such pronounced and fixed characters * *' Annales Mcdico-psychol.," vol. ii. p. 121, 1869. PilOSPIIORESCENCE OF THE NERVOUS ELEMENTS. I37 that we might say that it governs the manifestations of automatic hfe in the spinal cord, and directs those of psycho-intellectual activity in the brain. In the different segments of the spinal cord the per- sistence of impressions reveals itself very evidently in the accomplishment of all those co-ordinated move- ments which, not being a part of the hereditary patri- mony of the motor apparatuses of the organism, are therefore acquired by habit, being the direct product of education. We know that the greater number of the rhythmic movements we execute in most bodily exercises — dancing, fencing, playing on musical instruments — are methodical movements which we never accomplish (except the first time) by the intervention of the will ; that they are the effect of long apprenticeship ; that they are only acquired by exercise, the force of habit, and the imitative tendency we have, to reproduce patterns presented to us. Now, our muscles can move in such marvellous union according to given indications — our movements can be harmoniously combined in accordance with the operations to be accomplished, only by virtue of' the latent aptitude of the excito- motor cells of the spinal cord for preserving records of the impressions that have first thrown them into agita- tion — for remaining for a longer or shorter time in the primordial condition first imposed upon them. It is, then, our first impressions that vibrate in us like distant echoes of the past, and serve as a stimulus to the excitations of automatic life. It is they that, always alive, always faithful to themselves, are incessantly dis- engaged in the form of imconscions reminiscences, regu- II 138 THE BRAIN AND ITS FUNCTIONS. larly rhythmic motor manifestations, which faithfully reproduce the impression of the primordial excitation. It is the same persistent excitations, condensed in the sphere of automatic activity, that in certain morbid cases, when the regions of the sensormm and conscious perception are temporarily closed to impressions from without, excite those very curious harmonic movements accomplished by certain somnambulists, which take place inotu propria, by the simple calling into activity of the automatic regions which act of themselves, and exhibit externally a series of tniconscioiLs reminiscences. In connection with this subject, Mesnet has lately re- ported a most interesting case — that of a soldier, who, having received a shot in the head, afterwards suffered from very strange symptoms. • This man was subject to a species of somnambulistic crises, in consequence of which his sensoriimt was to a great extent cut off from all external impressions. He ceased, more or less suddenly, to enter into contact with the surrounding medium, and then, while in this condition, would walk about, go and come, and if any- one endeavoured to direct his movements in any definite manner, the impulse was inevitably developed in the direction of former excitations preserved in the state of unconscious reminiscences in the plexuses of his automatic activity. Thus, for instance, on putting his walking stick into his hand, the touch of it reminded him of his gun, and he would then place himself in a position as though he were present at a battle. If a pen were put into his hand, the precise movements necessary for tracing written characters were unconsciously produced in him. riiOSPHORESCENCE OF THE NERVOUS ELEMENTS. 1 39 These motor excitations were automatically developed in the store of latent reminiscences grouped according to a primordial arrangement, and producing, as it were, phosphorescent gleams of the past ; as we see in decapi- tated animals similar movements excited through the preservation of the automatic activity of the spinal cord.* Legrand du Saulle has reported a case which is some- what analogous to the preceding. It is that of a young somnambulist, a ropemaker by trade, who, if seized with a fit of somnambulism when twisting his rope, would continue the operation he had begun, even while asleep.i- In my own wards I had a patient, still young, who had been for a long time attached to the Salpetriere, as an assistant in the linen-room, being employed to fold the clothes and roll bandages. In the last years of her life this woman, completely blind and paraplegic, presented the following phenomena. While lying on her back, if any one put into her hands an unrolled bandage, or even the end of a cord, the touch imme- diately awoke in her reminiscences of her former work, and she began autpmatically to make a rolling motion with her hands, without knowing what she was doing, as though she had been a piece of machinery. We may then assert that the nervous plexuses of the spinal cord preserve in their minute structure (like the peripheral nervous plexuses, the retina among others) records of the impressions which have previously excited * Mesnet, "Sur I'automatisme de la memoire et des souvenirs." (Union Medicale, 1874, number 87,) f " Annales Mddico-psychol.," 1863, tome I. p. 89. (Legrand du SauDe, •* Le somnambulisme natuiel.") 140 THE BRAIN AND ITS FUNCTIONS. them, and that these persistent records thus become like a scries of fixed autogenic excitations, designed to act at a long range, to radiate to a distance, and thus to produce a series of reactions quite similar to those to which they at first gave rise. These phenomena of motor reaction, which take place merely through the calling into play of the organs of automatic life, are capable of spontaneous evolution, and of producing a repetition of certain habitual movements without any participation on the part of the conscious personality, which is absent for the moment.* In entering upon the study of the cerebral activity proper, we shall see what an important part this pro- perty which the nervous elements possess of retaining a record of former impressions, plays in the operations of the life of the brain, and in what varied forms this organic phosphorescence, always identical with itself, always present and distributed throughout the nervous elements which compose the tissue of the brain, per- forms its functions. It is diffused throughout all the agglomerations of cells, which are like so m^any active foci of phospho- rescence, but unites into a single resultant which concen- trates all the sparse activities of the cerebral cells. It thus becomes, under the denomination of the general faculty of memory, a true synthesis of one of the primordial properties of the nervous elements. The elements of the cerebral substance, the uncon- * See an account of experiments made on the body of a decapitated animal, hi connexion w'nh the development of manifestations of automatic hfe, in a direction determined by previous habit, and of the persistence of certain move* nients directed to a certain end. (Ch. Robin, "Journal dePhysiologie," Paris, 1869, p. 90.) PHOSPHORESCENCE OF THE NERVOUS ELEMENTS. I4I scious agents of the manifestations of our psyciio-intel- Icctual life, work in silence at the operations which they accomplish in common. They associate together, with their manifold properties, in one harmonious effort, corresponding with one another by the mysterious channels of their anastomoses, and without our know- ledge preserve in their minute organism posthumous prolongations of past impressions. They act simulta- neously to produce the phenomena of memory, and separately give oft' reminiscences, as illuminated bodies give off the luminous waves they have stored up in their substance ; this marvellous power of the cerebral cells, which depends on the favourable conditions in the midst of which they live, being maintained in a con- dition of perpetual vigour so long as the physical con- ditions of its material constitution are observed, and so long as it is associated with the vital phenomena of the organism. The phenomena of memory, thus looked at as a neces- sary consequence of a fundamental property of the nervous elements, enter directly into the mechanism of the different regular processes of cerebral activity. They may consequently be looked upon from the succes- sive points of view of their genesis, their evolution, their mechanism, the diverse phases they pass through during the life of the individual, and the functional disturbances from which they are liable to suffer. CHAPTER II. GENESIS AND EVOLUTION OF MEMORY. , In order that the processes of cerebral activity which constitute memory shall be evolved according to their natural laws, it is necessary that the peripheral regions of the system which collect and transport sen- sorial impressions, on the one hand, and the central regions which transform and absorb them, on the other hand, shall be reciprocally in suitable conditions of physiological conductility and receptivity. I. It is indeed in the peripheral regions, in the midst of the ultimate nervous expansions, that the activity of the central regions finds its regular food. Thence it is that all the stimulations destined to set them in motion proceed. When an external excitation is reverberated to any point whatever of their essential structure — whether it be a sonorous wave thrilling through the acoustic expansions, or a luminous wave becoming extinguished in the regions of the retina, or any direct stimulus which sets in vibration the sensitive nerves of the skin and mucous membranes — immediately this purely physical excitation is trans- formed on the spot by the peculiar action of the nervous plexus in erethism. It absorbs it, transforms it into nervous vibrations, and to some extent animalizes it by incorporating it with the organism. GENESIS AND EVOLUTION OF MEMORY. J43 Now, since the peripheral nerve-cells, as we have said, retain in themselves, like phosphorescent gleams, the record of those stimulations which have first set them vibrating, the result is that these persistent impressions become, without our knowledge, like a store of latent peripheral reminiscences, which hold the partner cells of the central regions in a sort of persistent vibratory sympathy. They in their turn assist the action of the central memory, and thus become a means of physio- logical reinforcement designed to vivify and maintain its activity. This solidarity between the peripheral and central regions of the system is so real, that when the former fail, the functionment of the central regions is at the same time interrupted. When the sensitive peripheral regions are in a state of anaesthesia central perception ceases. There is no persistent reminiscence in the sejisormnty because the trace of the persistent peripheral impression has not been registered. Touch, pinch, excite the skin of a hysterical patient in any way you please, if the eyes be closed, she will retain no remembrance whatever of the cutaneous excitations, because her peripheral nervous plexuses being stupefied, will not have been able to transmit to the sensorium anything that has taken place in their internal structure. I have often seen general paralytics, attacked with transient anaesthesia of the gustatory and pharyngeal nerves, bitterly complain to me that they had not been given a particular dish at their meal, I having been present when they had partaken of the food which they declared they had not received. Then again, the absence of sensibility in the peripheral 144 THE BRAIN AND ITS FUNCTIONS. region causes the sensorial impression not to be absorbed on the spot, nor directly transmitted to the central regions by its habitual channels. In order that the sensorial impression shall produce the desired effects in the plexuses of the seiisoriiim, and shall be clearly perceived, it is necessary then that the peripheral plexuses, which are its true gates of admission into the organism, shall be in a condition of receptivity and peculiar erethism, that their natural sensibiHty shall be directly awakened, and that there shall be on their part an active and prolonged participation when the stimulation from without arrives. Every one knows, indeed, that a slight and fugitive impression leaves but insignificant traces of its passage ; that an incessant repetition of the same impressions is necessary, in order that they shall be retained in a stable manner ; and that it is only by dint of forgetting, that we come to have certain details present in our minds which escape us and which it has been necessary to learn again and again. The repetition of the same peripheral impressions, the repeated view of the same objects, the hearing of the same sounds, become there- fore indispensable fundamental conditions of the pre- servation of reminiscences ; and from this point of view the rcnn'niscences emanating from the s^wsoxi-aX plexuses^ the memory of the senses, as they are pedantically called, are the most energetic stimulations of mental memory.* On the other hand, in order that the impression per- * All those who have pratically studied anatomy know how necessary it is Ijequently to review certain regions of the human body to know them well ; and that it is only after having seen, touched, and dissected, that we succeed in fixing in our memories the different details we have studied. GENESIS AND EVOLUTION OF MEMORY. I45 sistent in the peripheral plexuses shall produce a durable impression in the central regions, the preceding condi- tions of centrifugal impression are not the only ones necessary. It is necessary that there shall be some- thing more on the part of these same central plexuses of the seiisoriiim — an eftective participation or intimate association of their sensibility with the peripheral exci- tations which thus throw it into agitation. At the moment, indeed, when the external impres- sion sets the peripheral sensorial cells vibrating, these are affected, according to the different modes of their natural sensibility. They are sensitized in a different manner, according as the excitation is agreeable or disagreeable to them. In the first case a sensation of pleasure accompanies the external impressions, in the second case a sensation of discomfort ; so that the nervous element coming into play with its latent activity, transports to the sensoriimty not only the an- nouncement of the arrival of the external excitation, but at the same time the special notion of pleasure or pain related to each excitation. Every former impression, every reminiscence that slumbers within us, remains there from the moment it has been perceived, stored up with a specific coefficient which recalls to us the joy, the pain — or even the indif- ference of these same peripheral plexuses at the moment when it was incorporated with them and when it began to live in their own life. We all know that the reminiscence of physical pain, and corporeal chastisement, so lively in animals that are in training, is for man one of the surest guides of his conduct, and a most faithful warning to 146 THE BRAIN AND ITS FUNCTIONS. avoid faults which will inevitably provoke their recur- rence. We know, conversely, that reminiscences of agreeable impressions, and those which have given us most joy, are also those which have the deepest roots in us, and that in fact different states of emotivity, associated with the arrival in the sensoriiun of such and such a group of external impressions, are what perpetuate themselves with the greatest tenacity. They thus become, as regards the desires they excite or the aversions they beget, the natural pivots around which all human activities gravitate. 2. We have just seen the mode of genesis and trans- mission of persistent sensorial impressions, at the mo- ment when they are begotten in the peripheral regions of the system — let us now see how they are received in the plexuses of the sejisorium, and what reactions they provoke as their consequences. The connections between the peripheral plexuses and those of the sensorium are so intimate that, so soon as an impression has been produced in the former, their partner central regions immediately enter into unison with them. There is a nervous condition of similar pitch which harmonizes one part with another, and whenever the primordial impression has been sufficiently intense, and sufficiently prolonged, whenever there has been an effective participation of the nervous plexuses laid under contribution, the partner plexuses of the se7isormm sympathetically associate in their excitations and enter upon a concordant period of erethism. The incident excitation arrives then in the plexuses of the cortical substance, purified and animalized by the GENESIS AND EVOLUTION OF MEMORY. I47 peculiar metabolic action of the nervous plexuses in the womb of which it is incarnated, and then, transforming?- itself into a psychic excitation, it develops the latent energies proper to the cerebral cells, imprints itself upon them, and perpetuates itself in them in the form of per- sistent vibrations, like a phosphoric gleam of the ex- ternal world. Thus it is, that this mysterious property which the nervous elements possess — that of persisting in the vibratory condition in which they have been placed — is here again found consistent with itself throughout the different stages traversed by the sensorial excitations ; from the peripheral regions where it reveals itself in so indubitable a manner (as in the persistence of impres- sions on the retina), to the central regions, where it acquires characters entirely dependent upon the multi- tude of elements which serve to maintain it. Thus it is then, that external impressions of all kinds, the diverse emotions we have felt, become finally attenu- ated in the plexuses of the sensorium, and in the form of persistent vibratory thrills become the posthumous expressions of impressions and past emotions which remain alive in us when the primordial excitations have long ago disappeared. Sensorial excitations, when they are diffused in the plexuses of the sensormm and fix themselves there in a persistent manner, do not usually remain there in the state of vague, uncertain impressions. They go further, penetrate more deeply into the recesses of cerebral life, and when they are sufficiently lively and often enough repeated, they penetrate even into those inmost regions where the notion of conscious personality 148 THE BRAIN AND ITS FUNCTIONS. is elaborated, and thus become conscious reminiscences of ancient emotions that have thrilled us. Thus it is that, as regards the phenomena of memory, our inner personality is seized upon by the same process by which it was seized upon on the arrival of sensorial impressions ; only that these impressions which call it into activity prolong their action, implant themselves in the organism, and become, as it were, a vibratory echo of the past. It is thus then, that the reminiscence of anterior excitations perpetuates itself in the sensorium with the particular coefficients of joy or sorrow that have presided over their genesis in the peripheral regions, and thus a series of emotions related to each of them becomes developed, and perpetuates itself in the central sensitive regions of our organism. The phenomena of psychical and moral activity, understood as we have previously explained, perpetuate themselves in a similar manner, and develop incessantly, by the mere calling into activity of the two fundamental processes of the nerve-cells — sensibility, and that pecu- liar retentive power, organic phosphorescence, by means of which they prolong the vibratory excitations which have first set them in motion. In the domain of intellectual activity it is still the same force that underlies most of the dynamic opera- tions to which this activity gives birth. It is, indeed, because he remembers, because his sensi- bility has been impressed in a special manner, and this impression is persistent in him, that the young child, from the first instant of his life, expresses his inner sentiments. It is because he remembers, that he recognizes external objects and names them with an GENESIS AND EVOLUTION OF MEMORY. 1 49 appropriate word, which he has retained in his memory from having heard it. It is by means of the persist- ence of acoustic impressions, preserved in the state of sonorous reminiscences, that he speaks, and that his phonetic expressions are applied to each surrounding object. It is also by the same means that he learns to trace written characters, which he recognizes as the symbolic expression of absent objects, and that he reads aloud, transforming each written character into sonorous concordant expressions which he knows to be their equivalents. There are always at the bottom of these different operations of the intelligence, persistent sensorial im- pressions which direct the processes in evolution, and vibrate like a faithful echo of the first impression. It is the same with that admirable faculty which fhe human being possesses, the power of translating into verbal ex- pression his emotions and the thoughts which pass throughhis mind. It is because man has learned that each word expresses an external object, a thought, a sentiment, and because this acquired notion, preserved by daily use, is maintained in liim in a state of permanent freshness, that he speaks, addresses his kind, and is understood by them. It is memory — the accumulated reminis- cences always present to the mind — that forms the basis of his language, and thus becomes the inex- haustible store in which he finds the means of express- ing what he feels and what he thinks. CHAPTER II!. THE MEMORY IN EXERCISE. Besides those phenomena of memory into which the liuman personality more or less enters, there exist a whole series of similar acts which represent processes of memory to some extent incompletely developed. These are those phenomena in which sensorial excitations, not having carried their action as far as the plexuses of conscious personality, remain in the condition of sterile materials, not perceived by the seiisorium. Like those dark ultra-violet rays of the spectrum, which though not perceptible to our eyes, have nevertheless a real existence, they remain silently accumulated in the plexuses of the cerebral cortex, and only await the presence of an exciting cause capable of causing them to start from their obscurity. Thus, we all know that during the period of our diurnal activity, there are a host of various impres- sions which assail us on all sides, and even strike redoubled blows upon our sensitive plexuses, yet to which we pay no attention. The multifarious noises of carriages rolling around us all day, finally come to be un perceived by us and indifferent to us. We know also that when we give ourselves up to an absorbing intel- lectual work, the ticking of the clock beside us strikes THE MEMORY IN EXERCISE. I51 in vain upon our ears, and yet our acoustic nerves have been again and again set vibrating without our having a notion of it. Onimus has made a very curious observation in con- nection with this class of ideas. A man who was walking began automatically humming an air, being very much surprised by its having come into his head. It was only accidentally that he perceived that the air had been suggested to him by a wandering musician who was playing it on his instrument as he passed by, and whom he had not perceived.* This man in humming the air echoed an auditory impression, an unconscious reminiscence. We all know that in examining a picture, or land- scape, or a histological preparation, we first passively see the whole, and that certain details when we are not prepared for them at first escape us ; and if a per- son, after we have gone to a distance from the object we have examined, retrospectively calls to our notice certain peculiarities of the object, we are quite astonished that we have remarked them, and that we recognize in ourselves the existence of certain impressions which have remained silent. It is by means of unconscious impressions which persist in the brain that the activity of our spirit, in the automatic work which takes place in the act of reflection and meditation, is maintained. It is thus that the unexplored sides of certain ques- tions in suspense are made clear by the juxta-position of old impressions which have arisen. A sort of auto- matic appeal is made to revived impressions which have * Onimus, "Journal d'Anat. et Thysiol.," de Robin, p. 551, 1873. 152 THE BRAIN AND ITS FUNCTIONS. some connection, and which come, as new factors, to enlighten our judgments with a number of new ideas. The symptomatic study of mental maladies presents, as regards the subject, phenomena which are often very curious. We sometimes meet persons who have received an excellent education — ladies, young girls, living in the best society, above all taint of impurity, w^ho, when seized with an attack of cerebral excitement, utter the grossest words, quite strange to their ordinary voca- bulary. Evidently, in these cases, the phenomena can only be explained thus : — That in walking in the streets or in public places, these gross phrases have unconsciously impressed them, and have remained in the state of latent memories buried in the cerebral tissue ; an Sliai'un, in the form of persistent sensorial impressions. l62 rilE BRAIN AND ITS FUNCTIONS. In the adult the elements of cerebral activity in a condition of complete development are endowed with all the energies they are capable of assuming. They do not now behave as they did in the young child during the period of his evolution, as far as regards the preser- vation and storing up of external excitations. The period of saturation begins for the cerebral cell. The power of retention of external excitations is already on the brink of decay. New acquisitions of heteroge- neous elements which do not form a portion of the circle of youthful knowledge become very difficult, if not impossible. We know how painful the labour of learning a foreign language, so easy for the young child, becomes for the adult ; how rebellious the memory is as regards the registering of new words ; and with what an expenditure of intellectual force we retain the vocabulary of languages with which we were not familiar in childhood. We also know how blunt, even in the domain of common things, the retentive power of our memory, and consequently our powers of appHcation in general, become, if we have to learn things that are quite new to us ; and how, for instance, we with reason look upon it as impracticable to acquire a special technical education, and con^mence a new career after forty years of age. At this period of life first impressions still faithfully persist in the memory, but nevertheless they have a tendency to diminish in intensity, and it us necessary to vivify them by incessant labour, to stimulate them anew by placing the cerebral regions where they are stored up in identical conditions, by similar impressions of equal intensity, so as to prevent their becoming extinct ; just DEVELOPMENT OF THE PHENOMENA OF MEMORY. 163 as we keep up a fire by continually supplying it with fresh material. As the entire human frame begins to suffer from the effects of senescence, which occurs in different individuals at very different periods, the cerebral cells, like the other elements of the organism, suffer a premature decay. They grow old histologically ; they become more or less infiltrated with fatty granular matter ; they cease to be transparent, shrivel up, and from a dynamic point of view insensibly loce a portion of their sensibility and their special retentive power ; so that, as foci of organic phosphorescence, it may be said that they are extin- guished within certain circumscribed localities of the cere- bral cortex, and consequently cease to preserve a record of their first impressions. Thus it is that the general phenomena of mental activity undergo a perceptible decay proportional to the sum of the cerebral elements superannuated. In the a;;ed, memories sometimes dis- appear in an isolated manner ; sometimes those which are not maintained by regular exercise become extinct; sometimes the general faculty of memory fails altogether, and in its decay involves the progressive blunting of the most lively sentiments. A strange phenomenon now occurs — we perceive, contrary to what a priori would seem most probable, that in old persons, as in patients with dementia, old memories remain the freshest and most vivid, while recent facts, impressions which occur at the very moment, are unperceived and treated as if they did not exist. It is probable that at this period of life, the cells of the sensoriuin, altered in their essential constitution, have become lazy, and incapable of erecting themselves 1 64 THE BRAIN AND ITS FUNCTIONS. in the presence of recent external impressions ; and that this state of torpidity of the elements of the sensorium for new excitations, leaves the field free to the older ones which, not being obscured by more lively impres- sions, continue to vibrate without opposition, and thus perpetuate the last phosphorescent gleams of a far-off past which is dying.* * Thus, in some old persons in dementia, from the mere fact of the non- absorption of recent impressions into the sensorium, the notion of the passage of time is completely annihilated. From the fact that the daily work of the absorption of new impressions has ceased, the individual remains fixed in one spot, as it were, in a cataleptic state, with the ideas and preoccupations that he had at a given moment of his existence. Thus, we see a great number of patients who, having been some ten or twelve years in an asylum, still keep the ideas they had at the moment of their entrance, without having an idea of the passage of time; and who, ii asked how long they have been there, will spe.ik of two or three years. CHAPTER V. FUNCTIONAL DISTURBANCES OF THE PHENOMENA OF MEMORY. The manifestations of memory, looked at as we have just done, do not then present themselves merely as a collection of simple phenomena, nor as the direct resultant of the impression made upon the plexuses of the cortical substance by an external excitation. They consist in true physiological processes, which have an origin and a regular evolution throughout the nervous system. They demand the active participation of the cerebral cell ; and to be regularly executed they must obey certain organic necessities, and the inevitable con- ditions of integrity and co-operation of the organs through which they effect their complete development. When, therefofe, any disturbance whatever occurs either in the essential vitality or in the constitution of the organic elements which they lay under contribution, the processes of memory are ipso facto disjointed, and that faculty is thus maimed in one or other of the operations that constitute it. Tlius there are circumstances in which that property which the nervous elements possess, of retaining a record of external excitations which have formerly impressed them, attains a condition of extreme and permanent 1 66 THE BRAIN AND ITS FUNCTIONS. exaltation. This vibratory phase of their existence perpetuates itself and becomes a species of unsubduable erethism. All phyiologists, indeed, have recognized the impor- tant part a sudden emotion, such as terror or the sight of an epileptic attack,* plays in the production of convul- sive seizures ; and I have further pointed out that violent impressions may remain stereotyped in certain indi- viduals attacked with general paralysis, and that the shock caused in the sensorium may be very vivid, since it is capable of manifesting itself for several consecutive months in a species of cataleptic condition, imprinted upon the countenance, and upon the attitudes of the body.f The symptoms presented by the automaton whose in- teresting case has been reported by Mesnet, come under this class of facts. There are in such cases persistent impressions, which have been formerly accumulated in the automatic sensorium, which continues to direct the excito-motor processes without participation of the con- scious personality. Van Swieten, who was seized with vomiting on coming upon the dead body of a dog which exhaled an insup- portable stench, chanced upon the same spot some years afterwards. The memory of what he had ex- perienced produced the same disgust and the same consequences % This class of morbid phenomena is always developed by virtue of the same physiological processes as those * See Luys, "Actions reflexes cerebrales," p. 83. Morbid phenomena resulting from a persistenl impression. (Paris, 1854.) t Luys, loc. cit., pp. 73 and 87. 5 "Annales. Medico pb}cliol." 1851, p. 242. Fact cited by Parchappe, FUNCTIONAL DISTURBANCES OF THE MEMORV. 16/ ivliich regulate the manifestations of normal activity. There are latent and si'ent stimulations which, by reason of certain conditions which have presided over their impression upon the organism, remain more vivid than others, and which, by virtually becoming incessantly- active stirntili, produce a discharge of nervous force, either in the form of interrupted convulsive currents, in that of continuous motor currents (cataleptic con- dition of the muscles), or in that of sympathetic reactions from the side of vegetative life (vomiting, etc.). In other circumstances, we have no longer to deal with an isolated phenomenon, revealing itself by definite manifestations, and reflecting as before the deviations of a normal process regularly accomplished. We ob- serve, in fact, manifestations of quite a different kind, which reveal themselves by a species of exaltation of the psycho-intellectual regions, which preserve and store up external impressions in a very vivid manner, and when the cerebral elements have risen above their usual pitch, manifest their new condition by an unexpected super- activity quite contrary to the habits of cerebral life of the individual. We see patients, indeed, gifted with very ordinary hi • telligence, who, when in this phase of cerebral erethism, will improvise, make quotations, associate new ideas with extreme rapidity, say witty things and make puns — things they are quite incapable of doing when in their ordinary vital condition. Michea cites the case of a young butcher whom he ob- served in the Bicetre, and who, under the influence of an attack of mania, recited whole speeches from the PJiedrc of Racine. During an interval of calm, he said he had 1 63 THE BRAIN AND ITS FUNCTIONS. but once heard the tragedy in question, and that, spite of all his efforts, he could not recite a single verse. Van Swieten cites from the same author the case of a young workman, who, never having dreamed of making v^erses, during an attack of fever became a poet and inspired. Perfect speaks of a lunatic, who, during his delirium, expressed himself in very harmonious English verse, although previously he had never shown any dis- position for poetry. Tasso is said to have worked better during an attack of mania, than in his lucid intervals.* Finally, in other circumstances we observe phenomena of an entirely inverse character. Far from being pheno- mena of over-excitement of the memory, they are those of dislocation and clouding over. Persons thus affected, more or less completely lo§e the faculty of retaining certain memories ; either through the destruction of certain circumscribed regions in the cortical substance,-]- or through the progressive destruc- tion of its elements. Similarly there are certain persons with dementia who, being affected with partial amnesia, forget the date of the day and year in which they live ; they do not know their way, lose themselves in the streets, and yet they are still able to sustain a certain amount of current con- versation. Others, on rising from table forget they have had their dinner, and order it to be served up. Others, after receiving a visit from their relations or friends, and * Michia, " Aiinales Me(iico-p?;ycliol.," i860, p. 302. f Voisin has pointed out a case of amnesia with softening of the cerebral luijatance. The patient had io t the memory of objects, and had for^jo en names and substantives. If a spoon were presented to him he could not teU the name of it, but showed by his gestures that it was for eating soup with. ("Societie Anatomique," 1867, p. 342.) FUNCTIONAL DISTURBANCES OF THE MEMORY. 169 conversing with them, when the visit is fairly over — an hour afterwards — retain no definite impression about it, or else make mistakes ; when, for instance, they have received a visit from their daughter, they will say they have had one from their grandfather, etc. There are others again who, although enjoying a cer- tain portion of their faculties and the capacity for speaking regularly, lose little by little the memory of proper names, then that of substantives, then of verbs, and make mistakes in orthography. Cuvier, in his lectures, mentions the case of a man who had lost the memory of substantives, and who could form sentences very well, with the exception of names, which he left blank* It is curious to remark, as J. Falret has done, that in this process of decay which takes place, the human mind in despoiling itself of its wealth, loses it chrono- logically in the order in which it has accumulated it. Thus it is the remembrance of proper names which is first extinguished ; these, as we have previously remarked, p. 161, representing the first periods of the work of the intelligence in ascending evolution. Then come com- mon names, adjectives and verbs, which represent a more advanced degree of the perfectionment of the faculties, when the child has begun to express his will by means of appropriate verbs. Thus in these periods of progressive decadence the processes of memory being gradually deprived of the materials by means of which they effect their manifes- tations, cease to be regularly evolved ; amnesia advances further and further, and we see individuals thus affected • "Annales Mcdico-psychol.," 1852, p. 30^. 13 I/O THE BRAIN AND ITS FUNCTIONS. quite incapable of registering present Impressions, pre- serving no remembrance of what passes around them, forgetting the past, and becoming more and more incapable of expressing their sentiments and wishes, in consequence of the progressive wearing out of the organic apparatuses that serve for the evolution of the processes of memory. BOOK III. AUTOMATIC ACTIVITY OF THE NERVOUS ELEMENTS. CHAPTER L INTRODUCTORY. The automatic activity of the nervous elements, like their histological sensibility, is merely one of the special forms of their peculiar vitality. Diffused, in a similar manner, in its most simple forms, through the most elementary organisms, this automatic activity is perfected, and amplified, in proportion as it is distributed through more abundant and more dense agglomerations of cells, which are at the same time endowed with a more intense vital energy. It reveals itself in its most simple forms, as a histologic property of the free cells, the white corpuscles of the blood ; of that series of cells with mobile pro- longations (vibratile cilia, spermatozoids), whose auto- matic energy is manifested in such characteristic amoeboid movements ; and finally of isolated masses of protoplasm. As we ascend in the zoological series, we perceive that the manifestations of automatic life consist not merely in purely local phenomena, in which the histologic ele- 1/2 THE BRAIN AND ITS FUNCTIONS. ments accomplish the natural phases of their evolution mottc proprio, but in the exhibition of new dynamic properties. The histological elements, then, secrete, as it were, at the expense of their substance, peculiar autogenic excitations, and project them to a distance in the form of a continuous or interrupted current, thus acquiring a species of power of radiating to a distance the vital forces they have locally evolved. Thus we see electric fishes accumulate, in special tissues of their organism, the electric force which they emit, for the purpose of defence, in the form of dis- charges regulated by a voluntary excitement* Thus also we see the superior animals condense in the nervous plexuses of their organism stores of motor influence, to be distributed through the peripheral regions in the form of complex manifestations of voluntary motor-power, or of the motor-power of vegetative life. The operations of automatic activity are, then, generally characterized by a series of processes inverse to those of sensibility. In fact while the phenomena of sensibility are usually characterized by centripetal currents which pass from the peripheral regions where they are conceived towards the nervous centres, the phenomena of automatic activity, on the contrary, are marked by currents with a centrifugal direction. With the former they complete the cycle, and reflect outwards the excitations which arrive from the external world through the sensitive regions. Now if we consider the phenomena of automatic activit}^, from the point of view of their relations, and * " De la substance ^lectriciue ou Element anatomique cnracteristique Ju tissue electrogcne." Ch, Robin, "Journal de rAnatomie," 1.865, p. 510. AUTOMATIC ACTIVITY OF NERVOUS ELEMENTS. 1 73 their connections with the nervous system, we see that for them also, for the organic force which excites them, the nervous system similarly plays a perfecting part, that it amplifies them, gives them its own energy, places at their disposal its conducting filaments, and thus enables them to reach their highest point of perfec- tion. They follow indeed, step by step, the progressive stages of development of the nervous apparatuses with which they are connected. Thus, in the peripheral regions of the system, where the phenomena of vege- tative life take place by means of automatic forces alone, the nervous elements — represented by the unicel- lular sympathetic ganglions, which are like so many little outposts in the web of the tissues — interfere only occasionally to regulate the different rhythms of the local circulations. In these distant regions the automatic life of the individual elements reigns without contest. It is local activity that rules here ; and a sort of complete decen- tralization characterizes the life of these regions.* Little by little as we approach the centres a progress towards complete subordination takes place in the distribution of the living forces of nervous activity. Thus, if we pass from the ganglions to the medulla, we observe that sensitive phenomena are distributed in certain regions, and motor phenomena in others. Sensibility and automatic activity, which were vaguely fused together in the peripheral ganglionic masses, are * Unicellular ganglions, or ganglions composed of a few cells, have long been observed in the intestinal coats, in the bladder, and in the walls of the vessels. (Legros, " Th^se d'agr^gation sur les nerfs vaso-moteurs," Paris, 1873, P- i4') 174 THE BRAIN AND ITS FUNCTIONS. here distinctly separated, and exercise their functions regularly by means of nervous cell-territories specially adapted for a determined end. This is still not all ; — in the brain this principle of the progressive perfection- ment of physiological work by the complexity of the apparatuses by which it is accomplished, becomes more and more evident ; so that automatic activity is re- vealed not only in the phenomena of motor-power, but also in the manifestations of psycho-intellectual activity. Wherever, in fact, the phenomena of nervous life are developed, they appear not only with those general characters of individual sensibility and organic phospho- rescence which we have hitherto recognized as being the essential attributes of every living nerve-cell, but with a new co-efficient in addition — that property, so charac- teristic of automatic activity, the capacity for spon- taneous vibration, if their natural sensibility, previously aroused, be thrown into agitation, and for radiating and projecting to a distance the expression of that histologic sensibility thrown into agitation — at first in the form of an automatic reaction completely independent of the existence of the nervous system, and subsequently in the form of nervous discharges. The automatic activity of every living cell is, then, nothing but the spontaneous reaction of its individual histological sensibility, evoked in some manner or another. This special form of the vitality of the nervous elements we are now about to consider. We shall thus see that these automatic activities, together with sensibility and organic phosphorescence, become the fundamental AUTOMATIC ACTIVITY OF NERVOUS ELEMENTS. 1 75 elements of cerebral activity ; that they associate one with another in a thousand ways, and combine to pro- duce the most complex operations of cerebral dynamics; and that they always underlie most of the operations of cerebral life. CHAPTER II. GENESIS AND EVOLUTION OF AUTOMATIC ACTIVITY, Spinal Phenomena. — The phenomena of automatic nervous Hfe reveal themselves, as we have said, in their simplest elementary form in the mysterious operations of vegetative life, while the sympathetic ganglions, scattered through the web of the tissues, and connected with the central regions by their connective threads, locally govern the phenomena of the local life of the different cell-territories, and act as little eccentric centres which hold in subjection the purely vegetative phenomena. In the centres, in the purely spinal regions, the mani- festations of automatic life again reveal themselves in an independent manner, as though they had a special autonomic character in each of the particular regions of the spinal axis. This automatic activity is so vivacious in the minute structure of the grey plexuses of the spinal cord, that it persists of itself, exercises itself motu propriOy apart from all participation of the superior regions of the encephalon ; and each segment of the cord, considered as an independent ganglionic centre, may also, even when distinctly isolated, function regularly and give rise to co-ordinated reactions. EVOLUTION OF AUTOMATIC ACTIVITY. 1 77 In fact, if we cut the spinal cord of living animals into separate segments, as Landry has done,* we shall find that each segment will isolatedly give rise to a series of independent motor phenomena ; and as long as the blood-currents continue to feed the cells, and these can store up new force after each discharge, and continue to live their morphological life as before, they will continue to produce nerve-force, and inevitably give rise to regularly co-ordinated phenomena, according to previously established habits. Moreover, the experiments of Ch. Robin, made upon the corpse of a decapitated criminal,-f have shown that the automatic activities of the spinal cord in man may in similar circumstances continue to exhibit undiminished energy and power of co-ordination, in the form of regu- larly associated movements with a definite object (such as movements of defence made by the hand after a cutaneous excitation), performing these with as much regularity as though the brain had directed them. We have also true types of automatic reactions in that series of excito-motor processes which succeed each other without a break throughout the medtdla oblongata, the region of the vital knot, and in which the cells of this region, like the indefatigable workmen of our great manufactories, work incessantly night and day for the regular maintenance of the foci of inner- vation of the heart and the respiratory muscles — and this without break or halt, our whole life long, without the intervention of the conscious personality, and merely through the permanence of the automatic forces. * Landry, " Trait^ de paralysies," Paris, 1859, p. 48. f Ch. Robin, "Journal de TAnatomie," I'aris, 1869, p. 90. 1/8 THE BRAIN AND ITS FUNCTIONS. It is, moreover, a remarkable fact that this automatic power of the spinal organs is so great ; its participa- tion in all acts that we primarily accomplish with the concurrence of our conscious will is so effective and regular, that little by little it succeeds in gaining ground in the domain of our conscious dynamic operatiojis, obtaining a greater and greater importance by means of prolonged exercise, and finally ruling over them more or less. We all know that those partial movements we accom- plish in tracing written characters, and in playing musical instruments, are at first executed and followed out, with the participation of the conscious will, and that little by little, as exercise, as it were, oils the auto- matic machinery, this comes into play on the smallest excitement, like a well-constructed mechanical contri- vance, automatically reproducing the movements learnt, with a neatness, co-ordination, and correctness, all the more perfect because the conscious personality plays a less distinct part in the process. We all know, more or less, that the action of writing certain phrases, and above all that operation which is the somatic expression of the conscious person- ality /^r ^;r<;^//^;^^^ — that of affixing our signature to a sheet of paper (which indicates the passage of the conscious will through the hand that expresses it) insensibly becomes an operation which escapes our attention, and which, like certain common phrases that we unconsciously pronounce, takes place of its own accord, simply through the apposition of the pen to the paper, and by reason of the coming into play of mere excito-motor activity. EVOLUTION OF AUTOMATIC ACTIVITY. 1 79 We therefore see what an enormous part the phe- nomena of automatism are called on to play in the manifestations of nervous life, since we already know that these not only regulate the essential phenomena of vegetative life, but in addition play a most important part in calling into activity the great mechanism for the maintenance of the human machine, such as the motor-power of the heart and respiratory apparatus — in a word, the phenomena of visceral life ; and that, more than this, they enter into the processes of purely psycho- intellectual life, which have need of their intervention to project outwards their extrinsic manifestations, and escape from the mysterious regions where they have been primitively conceived. CHAPTER III. AUTOMATISM IN PSYCHO-INTELLECTUAL ACTIVITY* If, now, we enter upon the physiological study of cerebral activity proper, we shall see in what complex forms this curious property of the nerve-cell reveals itself, and in what an infinite number of combinations it is capable of taking part. It is principally in the perceptive regions of the sensoriuMy and those that are the seat of purely intellectual phenomena, that the manifestations of intense automatic lite are most distinct. In fact, what takes place within us when an external impression suddenly thrills us, when we find ourselves touched in the sensitive regions of our being, by the sight of an affecting scene, or a spectacle that charms us, or by the hearing of music which pleases our ears, is this : immediately, by reason of the elementary properties of the sejisorium, which are at once called * These cerebral phenomena of automatic activity have been for the first time described and very explicitly demonstrated by Baillarger, both in com- munications made to the Academy of Medicine, and in a series of articles in the " Annales Medico-psychologiques, " under the title of " Tkeoriede I'AutO' matisme et de I' exercice involo7ttaire de la m^moire et de V imagination." "The more I observe lunatics," he says in this remarkable work, "the more I am convinced that it is in the involuntary exercise of the faculties, that we must seek the point of departure of all form'? of delirium." ("Annales Mcdico-psychol.," vol. vi. p. i8S. Idem, 1856, p. 54.) PSYCHO-INTELLECTUAL ACTIVITY. l8l into play, sensibility is awakened, and develops itself into the sense of satisfaction, and this external impres- sion, stored up in the vibratory condition, persists in us, and becomes a durable memory. But this is not all ; these persistent impressions, transformed into durable memories, do not remain there as mere barren stores ; the automatic activities of the nervous elements which have come into play are now evoked. It is, in fact, as we have seen, sufficient that a certain series of cerebral cells shall have simultaneously under- gone a series of sensorial impressions, in order that they shall form among themselves a species of mysterious association, united by the ties of contemporaneous im- pression. If, then, we happen to experience any excita- tion whatever, visual, auditory, or olfactory, the appeal of the first in the series, by virtue of these mysterious associations immediately causes the others to spring up ; former memories reappear, and so blind and inevitable is the communicated movement, that this is effected without any conscious participation of the will. It does not depend upon us to incite or direct it ; it follows its route by virtue of its peculiar affinities and regular anastomoses, as automatically as the sympathetic and excito-motor actions that are propagated through the plexuses of the spinal cord. These phenomena, of the association of former memories following upon a recent impression, repeat themselves at every instant of cerebral activity. It is sufficient for us to come fortuitously upon one external object to think of another, which has either direct, or indirect and artificially maintained relations with the former. 1 82 THE BRAIN AND ITS FUNCTIONS. Reading has no other rational basis. It is the memory of the thing signified, incessantly evoked by the graphic sign, that causes us to adopt automatically, with each graphic sign perceived by the understanding, ideas of which such signs are but the conventional expres- sion. In conversation ideas follow upon, and evoke one another in quite an automatic fashion. We think, without wishing it, of a thing outside of the subject in question, and, automatically, we are drawn away from the principal thought. In assemblies we frequently see certain orators de- viate by degrees from the subject under discussion, through the action of the automatic forces of their minds, which always lead them in the direction towards which they are biassed — that is to say, towards the regions of predilection, where their favourite thoughts have developed a species of persistent erethism. These automatic forces, which guide human thoughts in a certain direction, are so inevitable, and so apt to pass through a certain regular orbit, that, the character and oratorical habits of such and such a person being given, we may infer, a priori^ that at a given moment he will express such and such a thought, or pronounce such and such a phrase. In public lectures there are professors who, speaking volubly, repeat annually the same phrases, and the same words, at the same periods, and this without its being done voluntarily. More than this ; it is notorious that at certain examinations, the examiners in any given subject repeat again and again the same ques- tions ; and this logic of the automatic cerebral activity PSYCIIO-INTELLECTUAL ACTIVITY. 1 83 IS so real, that those interested have instituted a course of questions designed to calculate in advance the auto- matic direction that the mind of their examiner will follow, and to anticipate the questions he will put to them. Every one knows in fine, that it is enough to set certain loquacious individuals going at a favourite sub- ject, to make them immediately unfold all their ideas upon the theme, repeat the same things and recite the same adventures, and this in a manner as monotonous as automatic. Of this class, old soldiers, huntsmen, and travellers, are accomplished specimens, and each of us may recall similar examples in the circle of his acquaintances. The automatic activity of the cerebral elements, when it has been too strongly over-excited, may reveal itself in certain circumstances in a more intense manner, with more vivid colours ; thus assuming a special character without there being, properly speaking, delirium, since the conscious personality still looks on at its morbid condition, like an involuntary spectator. Thus I may here cite a few fragments of a letter written by a young man, who after too prolonged work, gives a frank account of his impressions and the auto- matic determination of his mind to work, in spite of him. This young man had been for several days engaged in making calculations of compound interest, which had caused a great tension of his mind. One evening, after dinner, he was about to go to sleep, when, as he says, " Without the slightest encouragement on my part, in a state between sleeping and waking, waking £84 THE BRAIN AND ITS FUNCTIONS. I may well say, for my mind having worked beyond its powers all day, struggled obstinately against the corporeal fatigue which strongly incited me to sleep. On which side was the victory ? On that of the mind. For without intending it, and having need of the greatest calm and repose to which I could attain, / began ^ without the smallest volitioit on my part, to calculate and go over again exactly the same problems as when in my office. The cerebral machine had been set in motion too violently to be stopped, and this involun- tary work went on in spite of me, and in spite of and against all the means I endeavoured to employ to cause its cessatio7i — that is to say, from about three-quarters of an hour to an hour and a quarter." Commo7t Sense.* — These phenomena of automatic activity are not only developed in the living being, con- sidered as an individual, in a completely unconscious manner, but besides, by a species of diffuse generalization, they are repeated in similar individuals in an identical manner, and throughout space and time provoke in all human brains associations of ideas, and acts connected according to a general and common rule, as similar as though they emerged from a central region which gave them a single impulse. It is, in fact, very curious to observe that there are among all human beings, modes of feeling, of judging of things, and of reacting in consequence, which are everywhere the same. Moral phenomena, in fact, occur in a manner as necessary as if we had to do with purely physical acts. * See the complementary details of the question in the Chapter on the Judg- ment (pp. 291, 292). PSYCHO-INTELLECTUAL ACTIVITY. 1 85 Thus, just as over all the surface of the globe, since men have existed, they move their forearm in the direction of the articular surfaces, in pronation and supination, and bend the articulations of the knee and tlie leg, and the head, in an unchangable manner, and in a predestined direction — so in the circle of ideas, in the gamut of sentiment, in the mode of reacting of the human seiisoriiim, there are universal consonances, which throughout time and space present characters of eternal immutabiJt}'. The history of ancient literature shows us that in the same situations human beings have always felt, and always acted in an identical manner. In every page of their tragic or comic vv^orks, we find that common fund of immortal truth and judicious reflexion, which will be eternally current and applicable at every epoch. Simi- larly, if we consider humanity throughout space, we find that the civilized nations of the extreme East, the Chinese and Japanese, have of themselves in their long social evolution automatically invented the same processes of government and administration which have been for centuries contemporaneously employed in our old Europe. Human brains, therefore, everywhere and always react in a common and identical manner in presence of the external excitations which impress their seji- sormm. Each, more or less, represents a prism of the same composition, exposed at the same angle to the same incident rays of light which traverse them. Each undergoes the action of the same rays, receives them through its substance in an identical manner, according to a common proces , refracts them in a similar manner, 14 1 86 THE BRAIN AND ITS FUNCTIONS. and disperses them, after they have produced in each identical phenomena of elementary decomposition. We thus arrive at the opinion that there is in humanity a sort of general arrangement of ideas and sentiments, by virtue of which all men automatically take the same direction in the same definite circum- stances, and judge of surrounding things in an identical manner. It is this natural aptitude that we all possess for vibrating in unison with others, in presence of an external situation, for refracting external impressions in a fashion identical with that of our fellows, that causes us to have within us that notion of right, accord- ing to which our judgments and actions should be un- consciously directed. There is, then, a common right- line, a regular high-road which is, in a measure, the common meridian line along which the emotions, judgments, and actions of human beings are directed ; and it is this inner notion, that we carry within us, which constitutes the rule of good sense and common sense. The complete man regularly constituted should, then, in presence of fixed determinate emotional situations, react in an appropriate manner, make the same re- flexions, experience the same attractions, and the same repulsions that his fellows experience. This is the happy point of contact v/hich unites all humanity in the same joys and the same sorrows, associates it, under whatever latitude and at whatever epoch we consider it, in the same enthusiasms, the same sympathies and the same aversions. Every theatre-goer has felt himself moved by the pathetic situations, and has associated his bravos and his tears v/ith those of his neighbours. Every one of PSYCHO-INTELLECTUAL ACTIVITY. 187 US in solemn moments of the national life, has felt himself thrilled by the general excitement caused by those poignant patriotic emotions that the men of our generation have experienced in sorrowful alternation. Every one who stood upon the Boulevards of Paris in 1S59, when the French army marched past, returning from the campaign of Italy, must have participated with all his heart in the general intoxication of victory ; and every one who stood on those same Boulevards a few years after, among anxious and over-excited crowds, when all our disasters were announced, must have felt all hearts beat in unison with his own, and his secret borrows reflected in all faces. Comumnication of Automatic Activity to others. — Automatic activity works in human brains according to laws so inevitable and energies so involuntary, that we may count upon it at a given moment, consider it as a livinsf force in the static condition, and excite it without the agency of volition, as we see, for instance, bodies electrified in a certain manner act at a distance upon neighbouring bodies, and modify the dynamic conditions of the electric forces latent in them. The cerebral automatic activity develops itselt also at a distance, passing from one individuality to another by the intervention either of speech, writing, or gestures, which excite the sensor imn of the individual addressed ; and the excitement, once communicated, is propagated from point to point, through the plexuses of the cortex in a continuous manner, by the mere automatic forces of the nervous elements, which disengage their latent energies. Thus it is that human speech provokes in the soi^ l88 THE BRAIN AND ITS FUNCTIONS. soriiun of any one who hears it involuntary reflexions, which traverse the brain, and finally produce a unison between him who hears and him who speaks. The art of persuasion has no other physiological raison d'etre than the setting in vibration of the sensitive cords of the emotional regions of the scnsoviuni, and the direct or indirect neutralization of previous prejudices. It is by this process that the act of causing laughter at the proper time, and of turning aside the attention by exciting unexpected sentiments is often a means of disarming one's judges. It is by setting in motion the automatic forces latent in human brains, that great orators get possession of an attentive audience, subjugate it, and excite in it involuntary ecstasies of emotion and enthusiasm ; that great writers develop a whole series of unconscious emotions through which their moving recitals hold us spell-bound ; that a word or a phrase evokes a whole series of involuntary ideas, which give rise to a crowd of reflexions and emotions, corresponding to those they wish to inspire in us. It is by virtue of the same general laws of communicated emotion that the perio- dical publications of the press, by daily percolating through the minds of their readers, give an automatic direction to their ideas (human laziness being so fond of ready-made phrases;, and produce in those who enjoy them that fixed mental direction they unconsciously acquire. The same automatic tendencies of the human mind to provoke co-ordinated associations of ideas, thoughts and emotions, connected with other thoughts and emo- tions by the mysterious links of former relationship, are PSVCIIO-INTELLECTUAL ACTIVITY. 1 89 visible in every-day life, and, by means of words of double meaning — transparent allusions, which, in connec- tion with one word, make us think of other words — produce the most unexpected effects, and the most unforeseen mental suggestions. People, in fact, who in their conversation handle double meanings with art, know very well that, by underlining a word, by an inflexion of the voice, a look, a gesture, they will awake in the minds of their audience a series of ideas and emotions of a nature different from that indicated by their words. The simple phrase of allusion, when perceiv^ed in the brain in the form of a phonetic impression, follows, as it were, two parallel routes — one natural, apparent, traced by the word itself; the other roundabout, divergent, traced by the intonation and gesture. There result thus from these simultaneous processes, which are propa- gated through the cerebral tissue, various series of unconscious reactions, which, in the form of memories, associated ideas, and different sentiments, are succes- sively awakened. Hence the unexpected, vivid, and piquant relations between certain ideas that provoke hilarity, and certain distant thoughts which may cause the fibres of our inner emotivity to vibrate in a more or less indirect manner. What more simple, apparently, than to speak of a cradle to a young girl, and yet what more cutting, since one is sure to see her sensibility in agitation betray itself by the blush of modesty .? A vulgar proverb, in the same circle of ideas, says that " We must not speak of a rope in the house of one who has been hung." 190 THE BRAIN AND ITS FUNCTIONS. The ancients, at the door of the hipanars, used to inscribe these words : ** Cave canem," etc., etc. It is in these processes, which plunge as it were by multiple roots into the fruitful stores of our memories and emotions, present and past, that dra- matic literature finds its most powerful machinery. How many pathetic, and, more often still, how many comic, scenes are produced by nothing but the apparent contrast between the visible situation of the personages on the stage and the gestures and intona- tions of the actors, which appeal to quite another genus of ideas, thus automatically provoking, by this very fact, bursts of laughter or movements of terror — even in situations which are apparently far from inspiring gaiety or terror. It is always the automatic activity of the cerebral elements that comes into play in those different con- ditions, provoked in the sensoriuin by means of plays on words and certain well-made puns. It is, in fact, in consequence of the unexpected asso- ciation of two opposite ideas that the hilarious paroxysm is produced in us.* Reflexion of Automatic Activity. — One of the most interesting facts as regards the phenomena of auto- matic activity is this : that they are not only maintained * In certain morbid forms of cerebral activity this automatic tendency no longer reveals itself (as regards opposite ideas suddenly associated) by similar words. It is by smiple assonances which appeal one to another and group themselves together automatically. Thus a patient, described by Parehappe, with great mental volubility, often in her speech formed associations of ideas after this fashion. "On dit que la Vierge estfoUe, on parle de la Her, ce qui ne fait pas les affaires du departement de I' Allier.^' On being told to make charpieshe said that she did not know how. ^ his was insisted on, the physician adding ; '* ]t \oViS pleasiLve. This word pleasure characterizes a special state of our seiisoriiiin, a peculiar pitch of the sensibility, which is desired by every one, and which thus becomes a specific mode of existence of the sensorhmi^ which fixes and perpetuates itself in us as a memory and a hope. It is a kind of specific sentiment, a species of standard sentiment with which we compare the greater number of the impressions that come to be reflected in us ; so that, by extension, the notion of the pleasure of our gratified sensitive nerves insensibly becomes subjective, to be transformed into the notion of happiness. It results from this mental evolution that when any act whatever of the human activity is judged of by us, we say that it is good, because it has produced in the sphere of our moral sensibility an impression equivalent to that produced in the domain of physical sensibility by a sensorial impression which has given us pleasure. And, inversely, whatever wounds or offends our physical sensibility — whatever gives us pain — places our senso- riiLin in very different conditions from the foregoing, and thus becomes the subjective notion of unhappiness, to which we refer all the miseries of our moral sensibility. In the domain of intellectual activity proper, sensitive impressions also come to be of the utmost importance. United with the correlated impressions that emanate from the minute structure of our muscles when in action, they make part and parcel of a number of complex notions, by which the understanding profits, and which are incessantly laid under contribution without our having any clear consciousness of the fact. EVOLUTION OF SENSORIAL IMPRESSIONS. 259 It is chiefly tactile impressions that form the special contingent destined to provoke the reactions of the intellectual sphere. Radiated from the extremities of the peripheral plexuses, gifted with a special organization (sensitive papillae, tactile corpuscles of Pacini), these impressions furnish the intellect with a number of notions, not very- numerous, it is true, but very precise, respecting the different qualities of bodies in contact with them. It is by means of them that we form our judgments respect- ing the dimensions and surface-condition of external bodies, and respecting their motion, temperature, and de- gree of dryness or moisture. It is by means of them and their fellows of muscular sensibility that we are informed of the expenditure of nerve-power necessary to gauge the weight of heavy bodies, to lift them, and indirectly acquire a precise notion of their volume and solidity. This special contingent of sensitive elements, by means of which the notion of human personality is developed and maintained, and by means of which also we are constantly in contact with the things of the external world — this contingent, I say, is still destined to vibrate in harmony with all the mental faculties, and to give specific bent to the character of the individual, as well as to the creations of his mind. We may say, then, that a greater or less degree of perfectionment, and a greater or less degree of sensitive power in the sensitive regions, find their counterpart in the central regions, and that the greater the degree of physical, the greater will be the degree of moral sensibility. We all know how fine, delicate, and sensitive is 260 THE BRA.IN AND ITS FUNCTIONS. the skin of women in general, and particularly of those who live in idleness and do no manual work — - how their sensitive nervous plexuses are in a manner exposed naked to exciting agencies of all sorts, and how, from this very fact, this tactile sensibility, inces- santly awake, and incessantly in vibration, keeps their mind continually informed of a thousand sensations that escape us men, and of tactile subtleties of which we have no notion. Thus in idle women of society, and men with a fine skin, mental aptitudes are developed and maintained in the direct ratio of the perfection- ment and delicacy of sensibility of the skin. The perfection of touch becomes in a manner a second sight, which enables the mind to feel and see fine details which escape the generality of men, and constitutes a quality of the first order, moral tact, that touch of the soul (toucher de I'ame), as it has been called, which is the characteristic of organizations with a delicate and impressionable skin, whose sensor mm, like a tense cord, is always ready to vibrate at the contact of the slightest impressions. Inversely, compare the thick skin of the man of toil, accustomed to handle coarse tools and lift heavy bur- dens, and in whom the sensitive plexuses are removed from the bodies they touch by a thick layer of epithelial callosities, and see if, after an examination of his intel- lectual and moral sensibility, you are understood when you endeavour to evoke in him some sparks of those delicacies of sentiment that so clearly characterize the mental condition of individuals with a fine skin. On this point experience has long ago pronounced judg- ment, and we all know that we must speak to every one EVOLUTION OF SENSORIAL IMPRESSIONS. 261 in the language he can comprehend, and that to en- deavour to awaken in the mind of a man of coarse skin a notion of the delicacies of a refined sentiment is to speak to a deaf man of the deHciousness of harmony EJid to a blind man of the beauties of colours."^ Evolution of Optic Impressions. — The luminous vibra- tions, directly transformed into nervous vibrations by the peculiar action of the retina, are all at first con- centrated in the grey centres of the optic thalamus devoted to them, and radiated thence, chiefly into the antero-lateral regions of the cerebral cortex. They arrive in the sensorium, as we have already described, with different degrees of rapidity in different indi- viduals,t and from the time when they come in the morning to illuminate the nervous plexuses of the scn- soriiim they are continuous, and by their incessant stimulation during the period of waking maintain the activity of the cerebral cells in continued erethism. The luminous undulations which thus radiate through the brain are not homogeneous as regards their ex- * To the facts we have already cited respecting the pathogenic influence exercised by certain anaesthesias upon the genealogy of certain forms of deli- rium, we should add as a complement the following observations reported by Dr. Auzouy, which clearly show what a curious influence sensitive impressions may have upon psycho-intellectual phenomena in general. The case was that of a young man, clever and rational, who suddenly became undisciplined and rebellious to the utmost extent, and gave himself up to the worst tendencies, even to the compromising of the peace and honour of his family. Examina- tion showed that he was completely anaesthetic. During his stay in the asylum he successively experienced several intermittent phases of anaesthesia, of which the appearance manifestly coincided with the return of his worst instincts. When sensibility reappeared in the skin, moral dispositions contrary to the pre- ceding were observed to return in him, together with a very clear conscious- ness of his situation. (Auzouy, "Annales Medico-psychol.," 1859, P- 535) Des troubles /onctionnels de la peau et de V action de niectricite chez les alienes. f See p. 255 (note). 262 THE BRAIN AND ITS FUNCTION^. trinsic characters, and do not equally affect the different regions of the cortex in which they are distributed. Thus, not only do they transmit to the sensoriiLin per- ceptions of the different gradations of intensity of light, but furnish as well the most specific notions of the colour of surrounding objects. There are thus, in fact, two different modes in which the elements of the sen- soriiLin may be affected ; and in most men one or other of these modes usually predominates. We meet with certain organizations which from this point of view are very unequally endowed. Every one knows that if all persons with the gift of sight have the faculty of being impressed by light, all have not the faculty of perceiv- ing colours in an equal degree, and that there are persons who suffer from a peculiar form of blindness which makes certain hues virtually non-existent for them.* We all know that certain painters, who are gifted in the highest degree with that natural aptitude for perceiving in a complete manner the different grada- tions of the colour of objects, can give to their works a quite unique intensity of colour, a richness of tone which they draw from their own personality, and which their less gifted rivals can neither comprehend nor imitate. Optic impressions, as well as sensitive, are divided into two contingents which are separately distributed, * Mr. Black saw a man of fifty years of age in Glasgow who had lost his sight when two months old, and yet learnt by dt^grees to distinguish colours so clearly that he could exercise his profession as a dyer, without any help, for more than forty years. He could not only perfectly appreciate colours and shades, but had learnt by practice to give the stuff a lighter or darker tint without making any mistake. ("Annales Midico-psychol.," 1848, p. 414.) See also the memoir of Earle on the incapacity for distinguishing colours. 'Annales Medico-psychoL," 1846, p. 217.) EVOLUTION OF SENSORIAL IMPRESSIONS. 263 either in the sphere of psychical or the sphere of intel- lectual activity. I. Genesis of the Notion of Beauty and Ugliness. The particular contingent of optic impressions des- tined to be distributed in the sphere of psychical activity appears to be the origin of that faculty by which we pronounce as to the beaitty or ugliness of the thing that impresses us, and in this it resembles those sensitive im- pressions that furnish us with the notion of happiness, by means of a regularly accomplished physiological process. These optic impressions are similarly the fun- damental impressions that engender in us the notion of the beantifnl. These optic impressions, indeed, originating as they do, like those of general sensibility, in the peripheral regions, do not ascend into the sensoriiun in the condi- tion of atonic, indifferent, slightly-stimulating impres- sions. They carry with them the special condition into which the peripheral plexuses have been thrown at the moment of their genesis, and the simultaneous notions of concomitant pleasure or pain. When an agreeable spectacle presents itself to our eyes, our retinas, being impressionable nervous plexuses, are more or less directly gratified as regards their natural sensibility, just as when an agreeable sensation affects our sensitive nerves ; and this special satisfaction is transmitted to the sensorinni, thereby producing in it also a special vital condition, a new state which we express under the denomination of a sensation of beanty.'^ * Thus there are intrinsic satisfactions for the eves as well as the ears. It is with infinite pleasure that we all salute the light on emerging from obscurity ; that our eyes are pleased to receive the primitive rays of the spec- 264 THE BRAIN AND ITS FUNCTIONS. Th*^ subjective notion that we have of the beauty of tfiings is thus, in the primitive man, who knows nothing of either the subtleties of art, or the casuistries 01 the different schools, or the code of amateurs, fundamen- tally connected with the memory of an agreeable impression, a purely visual satisfaction felt by the retina when agreeably affected. Children love all that is brilliant and that glitters in the sun ; the inhabitants of northern countries and cer- tain savage tribes, are attracted by the sight of objects of a vivid colour, and tints which violently affect the sight. These are the rudimentary forms of the idea of the beautiful, which is really derived from a primitive physical impression. It is only by degrees, by means of the participation of the intellect, the culture of the judgment, and comparison, that this first notion comes to perfection in us, and becomes a rational well-digested appreciation, though having its origin in a physical impression which is at first addressed to our optic sensibility. Conversely we can comprehend that those things which produce on the retina a painful impression, which are unpleasant to see, are also those which produce a pain- ful im.pression on the sensoidiim, and which bring with them a notion the reverse of the former, that is to say that of ugliness. 2. Optic impressions, when carried up to the scnso- rium, not only excite in it special conditions by means of which the notion of beauty or ugliness is naturally trum, that they rejoice in the magnificent stained-glass of our old cathedrals when the sun shines through them, in the folds of rich satin stuffs, the multi- coiouied reflexes of brilliant flowers, fireworks or coloursd flames. EVOLUTION OF SENSORIAL IMPRESSIONS. 265 developed in us, but they are further gifted with a more intense penetrative power, and while taking upon them a thousand forms they touch and set vibrating all. the chords of our emotivity. Thus the sight of a landscape in full sunshine, enamelled with flowers of a thousand hues, and covered with green meadows w^ith distant horizons, develops in us sentiments of satisfaction which gratify our sensibility and cause it to expand ; while a gloomy place, shut in by high walls, and without verdure, sad- dens the saisoriitin, and develops in us a very legitimate sentiment of repulsion, in which all share. Thus these sentiments of attraction and repulsion are directly imposed upon us in consequence of the perceived impression, without the intervention of memory or of old reminiscences. By reason of those mysterious affinities which unite the present with the past, as regards our ideas and emotions, a simple appearance, a simple optic impres- sion, is capable of reviving old memories, and according to circumstances, of setting in vibration all the different emotional chords that it touches within us. Thus the sight of an external symbol, a banner, a standard, a flag, is capable of suddenly exciting in those who behold and salute it, the most diverse sentiments, from the fact that its appearance awakes in them a series of individual reminiscences. It is by the sight of the external pomp that surrounds them, the display of gold and silver embroideries, of brilliant uniforms, that the possessors of authority at all times and in all places have sought to inspire respect in the crowds before which they have passed. It is by ^9 266 THE BRAIN AND ITS FUNCTIONS. securing the passive admiration of the eyes of their dazzled contemporaries that they have always main- tained their prestige. It is for the gratification of the eye that human beings over the whole surface of the globe seek, according to their means, to ornament their persons and appear to the utmost advantage externally. It is by the lust of the eye that we are all, small or great, young or old, rustics or citizens, captivated and allured ; for it is always our eyes that are first charmed by the contemplation of physical beauty; and the most powerful of sentiments, love, destined to set the heart of man beating, has, as a general rule, its sole origin in the seduction of the sight, the pleasure of the eyes, which ardently desire the object which has charmed them, and excited the spontaneous awaking of all latent delights. It is, moreover, by means of those mysterious links which associate optic impressions with our sentiments, that our former emotions, our secret affections are awakened and maintained by the sight of certain keepsakes. Every one knows what a sweet consola- tion for the absent are the features of a beloved person reproduced by painting ; how certain institutions, cer- tain public or private ceremonies recurring in a periodic manner, certain anniversaries, are similarly calculated to revive in us former emotions, and again bring us into the presence of the persons and circumstances that have first inspired them, recalling the periods at which our emotions have been set in movement. 3. Again, in the sphere of purely intellectual pheno- mena, optic impressions play a very important part which deserves attention. EVOLUTION OF SENSORIAL IMPRESSIONS. 26/ Tlijs, either alone or associated with their excito- motor fellows, which regulate without our know- led^re the different movements of accommodation of the eye, they permit us to judge of the distance, the dimensions, and the forms of different surrounding objects. Thus, as when we have to do with the impres- sions of sensibility proper, former impressions are associated with recent, to form the elements of com- parison. When we say that a body is at such or such a distance from us, there is a reflex action of the intelligence which, from our knowledge of the object, and the manner in which it is illuminated, associates a series of notions previously acquired with a recent impression. When, as regards a body that moves trans- versely before us, we judge of the direction of this movement, it is still the evocation of an impression formerly received that comes to be annexed to a recent impression. Thus by degrees a crowd of complex notions is created in the mind by the arrival of optic impressions, and their preservation in the state of persistent memories. The sense of sight consequently becomes one of the most fertile sources from which all our cere- bral activity is incessantly fed. It is optic impressions again that with their acoustic fellows are called on to play such an important part in the artificial culture of the mind, both in the mental interpretation of graphic signs in the action of writing from dictation, and in the regular tracing of such characters in the action of writing spontaneously. They are also the introducers of the thoughts of others into our minds, when, with cur eyes fixed on the written characters, we attach to 268 THE BRAIN AND ITS FUNCTIONS. each of these characters correlative ideas and co-ordi.. nated emotions. They thus animate these silent cha- racters, giving them Hfe and fixing them in us as mate- rials designed to excite in the mind new associations of ideas, and the most varied impressions. They are therefore, in fact, the most powerful agents that stimulate the culture of the psycho-intellectual sphere, and fertilize its activity. They permit us at once to receive impressions from the thoughts of others, by means of written words, transmitted to a distance, and reciprocally to manifest our emotions and ideas in a manuscript, form, which thus becomes the manifest expression of the different states that they pass through. 4. The important part that optic impressions play in the functionmentof mental activity leads to the con- clusion that when they are wanting there will be a certain disturbance of the general equilibrium, which will have as its consequence special disturbances of cerebral functionment. Up to the present time, the mental condition of the blind has not been studied in a sufficiently precise manner to permit of our clearly appreciating the modi- fications which occur in the character or fashion of their ideas, under the influence of the arrest of development of their optic impressions. Nevertheless, we may say with Dumont, who has already occupied himself with this question, that the influence that optic impressions exercise upon the play of the cerebral functions is most important, and that a certain number of indi- viduals, whom he had an opportunity of observing, presented, from a psychical point of view, changes of temper and symptoms of melancholy, all the more EVOLUTION OF SENSORIAL IMPRESSIONS. 269 marked because the patients were incapable of dis- cerning day from night.* As regards such phenomena, Bouisson has observed a most remarkable case.f The patient was a young man who had become insane in consequence of a double cataract, with incoherence of ideas, complete failure of spontaneity. Bouisson, from the antecedents of the patient, hit on the happy idea of performing an opera- tion. It was simultaneously performed in both eyes, by couching, and a few days afterwards, when optic im- pressions reappeared to stimulate regularly the scnsorimn of the patient, and vision was restored to him, he began to utter a few sensible words, his mental state became progressively better, and, at the end of a i(t\N weeks, he left the hospital capable of attending to his own wants. Baillarger has also reported analogous facts. Thus, he cites from Whytt the case of a patient who, if his eyes were closed by another person, even without sleeping, fell into a great disorder of mind. It seemed to him that he was transported through the air, and that his limbs were falling off. In a patient of twenty-seven, whom he observed him- self, he noticed that as soon as she shut her eyes, she saw animals, fields, and houses. " I several times closed her lids myself," he says, "and immediately she men- tioned to me a number of objects that appeared to her."J * According to Dumont, among 120 blind persons, excluding those who are affected with appreciable brain lesions, there are thirty-seven with intellectual disorders varying from hypochondria to mania, hallucination and dementia, (influence of blindness on the intellectual functions.) "Moniteur des Hopi- tiiux," 1857, pp. 245 and 265. t " Bulletin de I'Academie de Medicine," 8th Oct., i860. X Baillarger, " Annales Medico-psychol.," 1845, pp. 22, 23. (On the influ- ence of the state intermediate between sleep and waking.) 2/0 THE BRAIN AND ITS FUNCTIONS. Evolution of Acoustic Impressions. — Acoustic impres- sions, like optic impressions, play a most important part in the sum-total of the manifestations of mental activity. Like them, they are incessant during the whole diurnal period, and by their uninterrupted stimu- lation maintain cerebral functionment in a perpetual condition of erethism. They are, for us, the natural vehicles of the notion of sound and harmony, while, at the same time, they are the generating elements of articulate language. Through them the ears are charmed, the understanding perceives and interprets, according to conventional methods, articulate vocal sounds, and the human personality thrown into emotion vibrates externally, and expresses itself in regularly co-ordinated vocal sounds. They are collected at the periphery of the acoustic sensorial plexuses, and, like their fellows, are condensed in special ganglia of the grey substance of the posterior regions of the optic thalamus, and thence radiated, prin- cipally into the posterior regions of the cortical sub- stance, which, in the human species, present such a characteristic development. According to Wundt, they are the impressions most rapidly transmitted to the perceptive centre. Like their fellows, they have a double range; they enter into relation successively with the psychic sphere and the intellectual sphere proper, and in these tv\o regions of nervous activity they excite specific reactions of the same nature as their fellows do. I. When dispersed in the plexuses of the sensorinm they at first develop there the same reactions of plea- .sure and pain that we have seen succeed each other in EVOLUTION OF SENSORIAL IMPRESSIONS. 27 1 cunsequence of the arrival of sensitive and optic im- pressions, according to the same physiological processes. The variable condition of impressionability of the peri- pheral regions is always transmitted into the central regions, and there excites concordant emotional states. When the ears are charmed, the sensorhim is similarly delighted, and inversely when the ears are impressed with a certain rhythm and with certain modulations into flat or sharp keys, the same states are impressed upon the sensorium. Thus it is that grave musical sounds, repeated very slowly and in a chanting manner — musical phrases in flat keys, and andante — dispose the sensormm to reminis- cence, and produce in us a special condition which constitutes sorrow ; and that, inversely, loud music, consisting of rapid notes, and allegro in tempo, or airs in ■|-time and tricked out with sharps, awakes emotions of an entirely different nature, predisposing the heart to gaiety and mirth, and inviting us to dance spontaneously and move our limbs to its cadence. Between these two limits of profound sorrow and expansive joy, between which acoustic impressions cause our natural sensibility to oscillate, there is a whole series of intermediate notes which may be successively set in vibration. Music, indeed, v;ith its infinite number of tones, is capable of impressing us in various manners, and deve- loping sensitive conditions very distinctly graduated. It is, like spoken language, of which it is but an amplifica- tion, designed to form a sort of synthetic language, and to join the train of the cardinal sentiments which are capable of causing the plexuses of the human sensorium 272 THE BRAIN AND ITS FUNCTIONS. to vibrate. Thus musical sounds now express tender sentiments, flowing forth in sweet harmonious notes, and in slow time ; while in other circumstances, with that richness of expression the great masters have given to their works, we see a melodious phrase augmented by g^-aduated accompaniments become infinitely complicated, and with the aid of powerful orchestration symbolise the most complex sentiments, not merely of man considered as a sentient unit, but even of man considered as a social unit. Thus it is that the great masters have succeeded in expressing in music the different shades of human sensibility, just as the masters of painting have done with their palette,* and in indelibly imprinting their inmost thoughts, and the sentiments with which they were animated, upon the sensoriiim of those who comprehend them. Acoustic excitations, associated with ail the special emotions of the period at which they are implanted in the sensoriiim, thus perpetuate themselves in the form of memories and as a persistent echo of the past. They are thus capable of reviving, with the qualities with which they were previously gifted. Every one knows, indeed, that a musical phrase is sufficient to recall the circumstances in which we heard it for the first time ; that that instantaneous recollection of certain airs heard during childhood, which is often so vivid, is capable of awakening in us the memory of the places and circumstances in which they were first heard ; and that national airs, among peoples who have imbibed * Tlius Meyerbeer has succeeded in giving a musical expression to the enthusiasms of politics and the fanaticism of religious strife, in his grandiua*! scores of Les Huguenots and Le Prophete. EVOLUTION OF SENSORIAL IMPRESSIONS. 273 the national sentiment in a precise formula, become very aear to those who hear them when far from their coun- try, and are Hke a perfume from their distant home. 2. Besides this special category of acoustic impressions which directly address the smsoriiun, there is another contingent destined to play a most important part in the phenomena of cerebral life — that which directly serves for the manifestations of verbal expression. In the first phases of the development of the young child, it is indeed acoustic impressions that first awaken his mind, and lead him to reproduce the sounds that strike his ears. They are stored up in his sen- soriiLin as persistent memories, represent the absent objects that have been named verbally in his presence, and when reproduced by a reflex action of his brain, become the natural excitants of the different phonetic expressions by the aid of which he designates the same objects, as well as the different conditions affecting his sensibility. It is by means of this series of acts that human speech, the natural daughter of auditory ex- citations, becomes developed in us, expresses itself out- wardly, and manifests through precise and appropriate sounds the emotions of the sentient personality which is in action. It amplifies and develops little by little, and becomes in course of time a true vital force, capable of acting at a distance like a charged electric machine, and of discharging upon the sensoriinn of another person, and modifying by its seductive influence his sensibility as well as his intelligence. By virtue of the energy with which it is projected, and the heat with which it is expressed, it is capable of provoking difierent emotion^ 274 "iW^ BRAIN AND ITS FUNCTIONS. at a distance from the spot where it was engendered, and of exciting sympathetic and persuasive effluences which induce a tacit acquiescence on the part of who- ever perceives it. It thus creates a sort of automatic consonance between the orator and those who hear him, and becomes the bond of union which Hnks us to our fellows. It is always due to it that men speaking the same language have among them common points of contact, by which their sensor ia, the sensitive regions of their whole personality, converse, touch each other, and vibrate in unison. 3. The special contingent of acoustic excitations which reverberates in the purely intellectual regions, becomes the origin of a series of appropriate judgments which we form respecting the timbre and intensity of sounds emanating from the different sonorous bodies around us. Thus we judge of the specific pitch of a given sound, by dint of a phenomenon of the memory, by juxtaposing in our mind the reminiscence of a past sound of the same nature as the sound that now strikes our ear. We judge of the intensity of a sound-producing agency by the manner in which it impresses our auditory nerves, of which the sensibility is called into play ; and perhaps the notion of muscular activity — the work ac- complished by the tensor muscles of the tympanum — may play a certain part in this operation. It is, further, by a reflex effect of the mind and the memory that we arrive at a judgment respecting the distance of a sounding body. We know that when a known sound gradually decreases in intensity, it is be- cause the sonorous body is receding, and when, on the EVOLUTION OF SENSORIAL IMPRESSIONS. 275 contrary it gradually increases, it is because the sonor- ous body is approaching. These two acquired notions afford materials for our judgment in a given case.* Evolution of Olfactory hnprcssions. — Olfactory im- pressions, collected from the peripheral plexuses of tlie corresponding nerves, are directly transmitted, as we have already explained, to a special department of the optic thalamus, the anterior centre. We have already insisted upon the comparatively large volume of this sensorial ganglion in those vertebrates that present a great development of the olfactory nerves ; upon the multiple connections it effects with the grey substance of \\\Q septum lucidum and mamillary tubercles ; and, finally, upon the indirect relations which unite it to the regions of the sphenoidal lobe, and in particular to those of the grey substance of the hippocampus.f The olfactory nerves transmit to the sensoruini the specific and unanalysable notion of odours. They communicate to it at the same time a special coefficient * When the^e relations are interrupted, the conscious personality easily accepts the change and allows itself to be hurried into strange illusions. It is by muffling the sounds that he produces, in the act of production, that a ven- triloquist makes his audience believe that the sounds so produced come from a distance. It is by means of the same mechanism that phantasmagoric illusions in the domain of visual impressions make us think that an image which grows larger f.nd larger on a flat surface is approachmg us. f The multiplicity of the paths traver^ed by the olfactory impressions in pass- ing through the brain, the irregularities and individual varieties of each of the stages through which they are propagated, must exercise an influence upon their central mode of elaboration. It is perhaps only in these quite special con- ditions of irregularity in the transmission of olfactory impressions to the sensorhim, that we must look for the secret of those individual varieties which we so frequently observe among individuals questioned respecting their apprecia- tion of odours. Nothing indeed is more variable than the testimony of each person on this point. Certain odours pleasant to some people oftend the nostrils of their fellows. 2/6 THE BRAIN AND ITS FUNCTIONS, of pleasantness or unpleasantness, according as the Inci- dent excitation has gratified or runcounter to their natural sensibility. For this special group of nerves the impres- sion agreeably felt is expressed by the word perfinne; the impression disagreeably felt by the word stink. These are the two extreme terms between which all the shades of their peculiar sensibility are developed. They aie incapable of penetrating profoundly into the recesses of our inner sensibility, to excite those grand movements of expansion or depression which are epitomised in the sentiments of joy or sorrow. From this point of view they are very inferior to optic and acoustic impressions, which monopolize the power of exciting the vibrations of the sensitive chords of our human nature. They only excite, then, a limited action of the sensoriiim on their arrival. On the other h^nd, if their diffusive power does not extend to the emotional sphere, it is reverberated in a very direct manner throughout both the vegetative sphere and that of the natural sensibility of certain points of the sensoriiLin, and, when examined from this point of view, olfactory impressirjns have reflex effects which are quite unexpected. Thus, we all know that certain odorous substances particularly predispose us to nausea ; that certain ap- petising substances, and the odour of preparations made with vinegar, gum-dragon, etc., act upon the salivary secretion, and, as we say, make our mouths water ; that perfumes and certain specific odours have an aphrodisiac action ; that with certain impressionable pen/ons the presence of certain odours produces profound disturb- ances, sometimes even syncope ; that finally, in certain persons subject to headaches, it is no longer the sensoriuux EVOLUTION OF SENSORIAL IMPRESSIONS. 277 as a centre of reception for the moral sensibility that is affected by them, but the sensitive sensoriiim, the brain itself, that is impressed in a painful manner, in certain of its histological elements. Many persons are aware that the odour of certain flowers that make an agreeable impression on their sensorium produces a painful after- effect, as though they had to do with a physical ache. Olfactory excitations are, like their fellows, capable of being stored up in the sensormm in the form of per- sistent reminiscences, and of being associated either with visual impressions or with those sensitive impres- sions which have been simultaneously imprinted upon us. They are similarly linked with our ideas, and the sentiments that have accompanied their genesis, so that the chance arrival of a perfume in the nostrils, is suffi- cient to awake a whole series of contemporary memories, and of emotions which arise in consequence, and recall to us the moment and the place in which the perfume was first inhaled. Olfactory impressions, again, furnish the intellect with precise and specific data, which, when preserved in the form of reminiscences and compared together, become materials by means of which we fortify certain judg- ments. Thus when associated with their fellows, gustatory excitations, which they perfect and complete in the act of deglutition, they furnish us with precise notions respecting the flavour and sapid qualities of the sub- stances we are eating. They also warn us, by an act of memory and experience, of the presence of foetid emanations float- ing in the air or in the liquids we absorb. They are 278 THE BRAIN AND ITS FUNCTIONS. thus like advanced guards that watch incessantly over the security of the operations of the vegetative life of the human being. Evolution of Gustatory Impressions. — Collected on the surface of the buccal and lingual mucous membranes, in the terminal expansions of the glosso-pharyngeal and lingual nerves, gustatory impressions are thence pro- bably distributed within a definite region of the optic thalamus; but up to the present time, we are not in a position to demonstrate the precise place of their con- densation. From this point they are, like all other im- pressions, distributed in the cerebral cortex, their area of distribution here also not being yet determined. I. Intimately connected with their companion olfac- tory impressions, in their method of impressing the sen- sorium^ and being constantly associated with them, they owe to this union a notable portion of their energy, and the various forms in which they reveal themselves in us. Thus it is that the capacity we have for tasting the flav- our of certain sapid substances, such as the bouquet of some wines, is only the combined effect of olfactory and gustative impressions, these latter being quite incapable of producing such a result, as we may assure ourselves by stopping our nostrils and allowing our gustatory im- pressions to act alone. We then perceive how restrained is their field of activity. They give us the unanalysable and specific notion of sweet, saccharine, salt, acid, acrid, and bitter savours. The diapason of tones that they set vibrating in the sensorium is, as we can see, by no means rich in varied shades. 2. Genesis of the Notion of Good and Evil. — On the EVOLUTION OF SENSORIAL IMrRESSIONS. 279 Other hand, they present this very characteristic quahty, that the mode in which their extreme notes affect the Stusoriiim is so significant and so typical that they con- stitute for it two quite pecuHar and original conditions, which assist us in judging and comparing certain pheno- mena of the moral order. Thus, when the natural sensibility of our gustatory nerves has been gratified, when a sapid substance has brought them into a pleasant condition, this peculiar state of satisfaction is transmitted to the se?isori?mt, is there propagated, and produces an analogous condition ; and this analogous condition, initiated by the peripheral nerves, becomes a subjective notion, the notion of good- iic'ss — equivalent to the notion of beaicty excited in the saisoriiirn by the optic nerves when agreeably impressed. We say then that a thing is good when it has fully satisfied our gustatory nerves ; so that this peculiar w^ord, primarily applied to the agreeable perception of a sapid substance, is generalized in the sensoriiim, and becomes a moral appreciation which we unconsciously apply to a whole series of acts of the human activity. We declare them ^^^^, and consider them 2,^ good actions, merely because they have produced in us, in the emo- tional regions of our moral sensibility, an impression equivalent tp that which a gustatory impression agree- ably perceived determines in the sensorium. Inversely, bitter substances, which cause the nerves of taste to shrink, produce in the sensormm a disagreeable reverberation, and inevitably become, under the designa- tion of bad substances, the expression of a painful im- pression in opposition to the last, and equivalent to that of pain in the purely sensitive order of phenomena. 280 THE BRAIN AND ITS FUNCTIONS. This specific notion is thus susceptible of being gene- rahzed, of becoming subjective, and of being appHed to the appreciation of purely moral actions, which we declare evily tainted with wickedness, because they have, without our knowledge, developed in the sensorium a painful im- pression, equivalent to that produced by a disagreeable gustatory impression. 3. Gustatory impressions, though incapable of causing great shocks in the emotional regions of our personality, are, like their companions, olfactory impressions, capable of radiating into the different regions of the vegetative sphere; they are both of them fundamental excitations of this special division of cerebral life. Thus it is they which directly regulate the functions of the stomach, and through these the life of the organism. Every one knows what a state of erethism is produced in the gastric mucous membrane by sapid, appetizing substances, and what dulness of appetite is produced by insipid ones ; the good appetite produced by the former having a direct influence upon the harmony of the psychic and intellectual activity. Former gustatory excitations, preserved in the sensormm in the form of persistent reminiscences, are on this account easily evoked, and may be compared with recent ones. They are likewise capable of awaking old memories, contemporaneous with the moments in which they have been deposited in the sensormm^ and of reviving past emotions and the old associations of ideas that have accompanied their genesis. Thus the taste of food, wine, or a liqueur, recalls to us such or such a period of our youth, such or such an episode of our life, such or such an incident in our EVOLUTION OF SENSORIAL IMPRESSIONS. 28 1 travels. Thus gustative impressions, like all theh fellows, live with the same life that these do, and participate in the same processes of cerebral activity. United to their partners, olfactory impressions, they have a truly specific and penetrating radiation, which extends at once into the domain of intellectual activity and that of purely vegetative life. They thus become the occasion of a series of memories and comparisons, and of the different gastronomic judgments that we form respecting the degree of sapidness of food, the pre-eminence of certain vintages, and the rules respect- ing alimentary hygiene. They become, when intel- ligently directed, the occasion of a series of particular satisfactions which are associated with all others, and, as Brillat-Savarin has so well expressed it, outlive all the rest to console us for their loss. Evolution of Genital Impressions. — Genital excitations, as regards their genesis, their passage through the nerv^ous system, and their diffusion in the sensoriimiy present the most remarkable analogies to gustatory impressions, of which they are to some extent a copy. Like these, they have no nerves of special sensation ; like these they are conducted into the central regions by means of radicle-filaments which are there dispersed according to the special mode of distribution of the posterior roots of general sensibility ; * and like these they are distributed to the substance of the central grey matter of the optic thalamus, and then to the plexuses * We know also, that in their centripetal course they are extended, with (he conductors which carry them, over the floor of the fourth ventricle, and that lesions of this locality are apt to produce erection, as in those who are l)ung. cSee Luys " Recherches sur le systeme nerveux," pp. 340, 342. 20 282 THE BRAIN AND ITS FUNCTIONS. of the sensoriiim. It is, however, as yet impossible to determine precisely either the special nucleus reserved for them in the optic thalamus, or the territory where their dissemination amc ng the plexuses of the sensoritim is effected. Finally, like gustatory impressions, they are inter- mittent and subordinated to the chance arrival of the causes that determine them ; and, as the last point of analogy, if they are as fugitive they compensate for this by their vividness, their intensity, their suddenness ; by the profound manner in which they affect the senso- riunts and by the ephemeral character of their mani- festations. Collected principally on the surface of the plexuses of the genital organs which are so rich in erectile papillae, genital excitations present at the moment of their genesis (in much ampler proportions) that special phase of erethism common to all their fellow excita- tions, when the sensorial impression radiating from the external world is reverberated in the sensitive plexuses and becomes incarnate in the organism. For this special order of excitations the primordial period of erethism which incarnates them in the organism, instead of being a local and instantaneous phenomenon like those of general sensibility, or vision, for instance, is divided into successive moments. It is effected by means of special erectile apparatuses, which develop, and complete it, and insensibly lead up to a condition of supreme exaltation. Once the external impression is incarnated in the sensitive plexuses, once the notion of physical pleasure is developed with all its conse-^uences, it ceases to be itself, through dynamic EVOLUTION OF SENSORIAL IMPRESSIONS. 283 exhaustion, sheer fatigue of the nerves, as we have seen the retina when fatigued becomes insensible to the contemplation of certain luminous rays. The process of physical pleasure undergoes, then, a series of phases through which it only gradually arrives at its complete expansion. It begins locally, in the peripheral plexuses, with a period of extreme erethism, from the intimate connection of the sexes, through the mysterious conjunctions of the apparatuses of organic life ; it is at the same time enriched by the action and sympathetic participation of all the diffuse sensibilities of the organism which are thrown into agitation, those of the tactile surfaces, the hands, the lips, which all combine to enhance its pri- mitive energy ; it advances towards the central regions, as a true synthesis of all the impressionable ele- ments of our nature in vibration, is propagated through the whole length of the spinal axis by means of the conducting fibres which convey it, and, after passing through its final stages in the intermediate grey regions of the optic thalamus, it is dispersed in the different zones of the sensorium, carrying with it the shock of joy and satisfaction which intrinsically charac- terizes it. Like all the other sensorial impressions, the excita- tions of physical pleasure affect both the sphere of psychical activity and that of intellectual activity proper. I. The excitations of physical pleasure, which, as regards the living being, represent the fundamental elements of the prime function which has for its end the reproduction of the species, arrive in the sensoriunt 284 THE BRAIN AND ITS FUNCTIONS accompanied by an enormous contingent of sensations emanating from different regions simultaneously in a condition of erethism. They essentially carry with them impressions of joy and happiness, and produce like conditions in the elements of the seiisorhnn ; becoming during the period of puberty a dominant note which vibrates above all the rest, which gives its tone to all our actions, all our discourses ; and which, when it happens to be set vibrating with special intensity, extinguishes all the rest by its intensity and splendour. Psychic, ideal love, and physical love are, then, the ultimate links of one and the same chain of which the elements are uninterruptedly connected. It is a regular physiological process, which has its roots in the intimate connection of the sexes, and its expansion in the most elevated regions of psycho-intellectual activity. In evolving itself throughout the organism, it thus involves the incidental calling into play of all the apparatuses of the essential life of the livhig creature, and their harmonious co-operation. It has, then, its raison d'etre in a purely physical plea- surable excitation, which presides over its origin and marks its first stage. It is a fleeting and transient desire, which is born, passes, and fades away as soon as the physical demands for pleasure which gave it birth are appeased ; but as the same physical needs arise again, through the necessary laws of the movement of life in living beings, the same voluptuous desires simul- taneously arising in the sensoriinn, it follows that the reiteration of the same physical satisfactions finally leaves upon the sensorium itself a persistent and con- tinuous impression, vibrnting like an echo of the past, and EVOLUTION OF SENSORIAL IMPRESSIO::S. 28$ thus maintaining a durable and uninterrupted sentiment. Thus it is that love, a sentiment transient and ephemeral as the pleasure which gave it birth, fixes itself perma- nently, and lives with a life of its own. The reiteration of the satisfaction of physical pleasure, obtained from the same sources as formerly, and new desires resuscitate and reinvigorate it, and become the elements of its continuity and its persistence. Conjugal love, thus made an abiding sentiment in the sensoritnny becomes in its turn the physiological pivot around which a new generation of consecutive senti- ments gravitates. Thus, by the natural fact of the evolution of the living organism, physical love, which was at first all concentrated upon a single head, upon the being which gave it birth — its end being the propagation of the species — when once this end is attained is insensibly extended to the offspring, which is the flesh of the flesh of this being, and the veritable proliferation of her substance. The sentiments of the family which are then developed, lead man's emotional nature into the inevitable cycle of the affection of parents for their children, that inevitable cycle in which we have been preceded by all the generations of our ancestors, and in which all the representatives of the human race are destined perpetually to move. Here the process of physical love finds its last stage, dying out of itself after it has accomplished its work, by developing in the living creature, during the period of his maturity, all the energies of his organization, animating his heart with the most intense emotions, inspiring the liveliest sallies of his intellect and imagi- 2S6 THE CRAIN AND ITS FUNCTIONS. nation, and contributing necessarily to the perpetuation of his race and the preservation of his species. 2. In the domain of intellectual activity proper, the excitations of physical pleasure have an action as powerful as that they exercise in the sphere of purely psychical phenomena. In proportion as the human being who has passed through the transitory phases of puberty accomplishes his physiological evolution, new ideas arise, unappeased desires are awakened ; he feels himself incomplete in his solitude, and comprehends that another being is designed to fill the void of his sentiments and desires. Henceforth, urged on by his latent desires, he employs all the resources of his intelligence to seek out his future companion and to prepare for her the necessary material provision. He thinks of his social establishment; he struggles ardently in the battle of life : the woman, and union with her in marriage, are the secret motives of his actions. It is the hope of attaining this end that sus- tains his strength and maintains his courage ; and, later on, when hie has attained this end, he still struggles (and puts forth all his intellectual activity in the struggle) to save his offspring from the troubles of the road along which they must follow him. He thinks of the future, and prepares the inheritance he will leave behind. He thus harmonizes all the intellectual activities, all the social forces he can command, with the different phases of the physiological process which is being inevitably vv'crked out in him ; and under the most diverse forms, in the most dissimilar circumstances, he always obeys the same necessary laws of evolution th^t press upon him and metamorphose him insensibly, from the moment EVOLUTION OF SENSORIAL IMPRESSIONS. 2S7 in which he becomes a candidate for marriage to that in which, after having been a husband and father, he becomes a grandfather, and sees in the second genera- tion that springs up around him the secondary ramifica- tions of the branches of which he is the parent stem. So that, whatever be the position of a man (I mean of a complete and regularly constituted man), on whatever rung of the social ladder we may imagine him placed, v/e are always sure to find at the bottom of his actions, open or secret, as the first cause of their motives, the craving for physical pleasure, and as a consequence, psychic pleasure, with all the sentiments to which it gives birth. It is this which, always present, always active, becomes in every act of his life the natural stimulus of the briskness of his mind, the resources of his imagination, and the vigour with which he enters upon the struggle for existence. It tinges his whole personality, animates him incessantly, and produces such concordant action of all his powers that we may say, without fear of mistake, that the measure of his physical is also that of his moral virility. 3. Genital excitations play such an important part in the sum total of the operations of psycho-intellectual life, that when they 'are arrested in their development, in consequence of certain operations that nip them in the bud in the regions where they have their point of origin, a very remarkable effect is produced upon the intellect and character. Every one knows how mild and easy castrated animals are to manage, and how this fits them for the rule of man, through the modification of their natural impetuosity. In man, the same practice pro- 2u8 THE BRAIN AND ITS FUNCTIONS. duces similar effects. According- to Godard,* castration performed on the adult singularly weakens the moral energy, as the following fact, reported by d'Escayrac, de Lauture, proves. " I have seen," he says, " six slaves belonging to the kachef of Abouharas, in Kor- dofan, who, in consequence of a conspiracy against the life of their master, were emasculated by him. All were adults at the time of this mutilation, and none of them died. Their characters changed completely, and the submission they now show differs remarkably from the spirit of rebellion that animated them previously." Godard afterwards addsf that, according to Dionis, castrated persons are unsociable, liars, and rascals, and that they never seem to practise any human virtue ; and that, according to Benoit Mojou, eunuchs are the vilest class of the human race, cowards and rascals because they are weak, envious and spiteful because they are unhappy. Finally, he has noticed that even where no mutilation has been practised, individuals with congenital absence of the two testicles are effeminate, unenergetic, timid ; they blush easily, everything frightens them, and it is difficult even to examine t'lem without a great deal of trouble. * Godard, " Recherches teratologiquesj iur I'appareii s-^minal dc I'homrne,'' p. 68. Paris, i860. f Loro citifo, p. 73. CHAPTER III. THE JUDGMENT. Judgment is the principal operation of cerebral activity, by means of which the human personahty, in presence of an excitation from the external world, either physical or moral, expresses its condition. Among the diverse operations of the brain in action, that of judging is a regular physiological process, which is developed according to fixed laws and inevitable organic conditions, and which, like the different phe- nomena of muscular activity (the progression of the human body in space, for instance), expresses life in exercise and the nervous power in a dynamic state. The action of judging, so far as it is a physiological process accomplished by means of the cerebral activities in movement, is decomposable into three phases, which are as follows: — 1. A phase of incidence, during which the external excitation impresses the sciisoriiivi and rouses the con- scious personality to action. 2. An intermediate phase during which the person- ality, seized upon and impressed, develops its latent capacities, and reacts in a specific manner. 3. A final phase of reflexion, during which the pro- cess, continuing its progress through the cerebral tissue, 290 THE BRAIN AND ITS FUNCTIONS. is projected outwards in phonetic or written co-ordinated manifestations. The impressed human personality, in fact, expresses itself, exhales itself in its entirety, in either articulate or written language. I. It isvalways a recent or former sensorial impression that naturally excites an operation of the judgment and determines its action. The sensoidiim is impressed, the human personality takes part in the phenomenon ; it is strongly affected, and reacts immediately. This work of absorption of the sensorial excitation and oi conscious reaction, on the part of the personality, implies then a series of connected operations which follow and com- plete one another, like the different phases of a simple somatic process. It even requires a certain appreciable time, to be effected in the cerebral tissue, and, according to the nature of the individual, will act wuth greater or less facility, and perfect itself with exercise, as Bonders has demonstrated.* * Bonders, by means of very ingenious registering instruments, has suc- ceeded in introducing a precise notation in studying the evolution of certain phenomena of the cerebral activity. The method consists in making an impres- sion upon a person and noting the precise instant at which he responds to it. 'I he person who makes the experiment must, as soon as the impression is felt, press with his finger a spring which sets a revolving cyUnder in motion. The number of revolutions indicates the time that has elapsed, that is to say the time necessary to permit the complete process of the judgment, the impregna- tion of the sensorium and its expressed reaction, to manifest themselves externally. The precise duration of voluntary transmission is known, smce it is always pretty much the same, and thus we arrive at the knowledge that a luminous sensation is more quickly perceived than an acoustic or a tactic. In this case it is a simple thought that is transmitted. Donders again applied himself to ascertain by the same process the time n(?cessary to solve a dilemma. A person is in darkness, a green or red light is flashed upon him, and he is to make a certain signal with the right or left han 1 according to the colour exhibited. The sum of these operations is more com- plex and requires much more time; but, as the elements of the previous experi- ment are here ag.iiu found, we have only to deduct the time necessary for this, THE JUDGMENT. 29 1 It is in this first phase of the operation that the whole secret of its final rectitude resides ; for to see well and to judge ivcll are synonymous, and to acquire the power of pronouncing with certainty, respecting such or such a circumstance, we cannot surround ourselves with too many precautions. Nothing, in fact, is more difficult than to have a clear and precise appreciation of real things. The minute care taken by physicists and chemists, and the infinite precautions with which they surround themselves, in order to appreciate simple physical phenomena, show us how frequent are the causes of error, and how liable to deception is all observation ; since we so often find two observers, in the presence of the same physical and palpable phenomenon, each describing it in his own fashion, and each giving a very different report respect- ing it. A fortiori we can understand that when we have to do with the interpretation of complex things, to form judgments respecting history, contemporaneous or past ; respecting the facts of our current life, in which all human passions are openly or secretly at work ; respect- ing political matters ; the ascertainment of the real facts may become very difficult, the very notion of truth obscure. We see how those judgments, which we succeed in formulating, always fail at some point or another, from the intervention, more or less eager, of c ur own personality. (o ascertain the time required by the brain to discern whether the light was green or red, and which hand was to be used. Donders, " Archives need in- daises," 1867, vol. ii. Instrument for measuring the time necessary for psychi- cal acts. 292 THE BRAIN AND ITS FUNCTIONS. 2. The second phase of the process is no less delicate than the first ; for here the human personality, on the advent of more or less clearly distinguishable stimuli from the external world, comes into play with all its sensibilities awake, reacting, like a trustworthy reagent, when the excitable regions of its inmost core have been more or less aftected. It is the human personality that feels, that is moved, that speaks in our judgments, and that reacts in an appropriate manner, according as it is restless, impres- sionable, indifferent, or atonic ; reflecting externally in words or deeds, the infinite varieties of feeling that lie maturing in its recesses. Like a true leading-note, it vibrates every instant in every act of our lives, and gives our judgments an original character accord- ing to the key in which it is pitched, a something racy of the soil, which (when once our ainoitr propre comes into play, and our own personality is concerned) always expresses the different phases through which our senso- rium passes when in a state of agitation. Hence, the difficulty of forming impartial judgments in questions of the moral kind, the judges being biassed ; hence, that series of minute precautions taken by legislators at every step, to eliminate interested persons from juries, and to form these of independent indi- viduals free from all prejudices. Hence, that practical observation, verified by every day's experience, that young and ardent natures in whom the effervescence of the sensorium is still unabated, are apt to judge of men and things with all the rapidity and prejudice of their characters ; and that the judgment is exercised in a more enlightened manner when maturity has arrived, THE JUDGMENT. 293 aiid the wear and tear of life have exhausted the first ardours of the natural sensibility. Cold contemplation of the real facts is more easily attained, and permits the human personality to expand in a calmer and more reflecting manner. It is therefore in this intermediate phase of its evolu- tion, when it enters into contact wath the human persond -a'ity, that the process which is destined to be converted into judgment comes to its crisis, according to the variable emotivity of tlie substratum that receives it. When the phenomenon is produced, two circumstances may occur : either the process may achieve its evolution, and appear externally in a verbal or manuscript formula which epitomizes it ; or it may die out on the spot, re- main silent, and, like a living force which undergoes transformation, may proceed to excite secondary impres- sions throughout ihe cerebral regions it traverses. New territories of affected cells will then come into play, and according to their automatic activity wnll associate themselves with the excitations and ideas in question. Thus it is that a process of judgment, suspended in its course, becomes the local origin of a vibratory move- ment which radiates to a distance and produces secon- dary impressions. It is because of this physiological radiation that related ideas are automatically excited ; that new views arise, manners of looking at the matter not at first dreamed of; and that, from this work of internal digestion of the process in evolution, a whole series of new considerations springs up and gives to the first judgment a weight it had not before, and the natural complements of its real value. The process of juigment has then for its special 294 THE BRAIN AND ITS FUNCTIONS. characteristic, according as it advances, the privilefre of extending itself ; of determining the reaction of the sur- rounding cerebral elements ; of searching, to some ex- tent, into the archives of the past ; of associating former notions with those of the present ; of creating partial local judgments, established d priori as results of the inner experience of the individual ; and of permitting us, at a given moment, to juxtapose and agglomerate partial judgments — to agghUinate them, in the form of arguments, into a complete judgment, which resumes them all in a true synthesis. Thus, for instance, when I auscultate the chest of a patient, and perceiving the existence of tubular respira- tion, declare that the patient is in the second stage of pneumonia, I give utterance to a judgment that has many ramifications in my mind, and is made up of a great number of different materials. Starting from this blowing noise that has struck my ear, I represent to myself what, under similar circumstances, I have per- ceived on previous occasions. I have observed, for instance, that this blowing noise corresponds to a hyperaimia of the pulmonary tissue, with concomitant induration, that it depends upon an induration of tissue, not upon the presence of effused fluid. At the same time I perceive with my eyes the general condition of the patient, I note his countenance, his external habit, the state of his tongue, etc., and a new series of notions acquired by the exercise of optic impressions is awakened in my mind and becomes associated with the process already begun by the auditory impressions. I percuss, moreover; I feel the pulse; I palpate; and once more, starting from a new series of sensorial impres- THE JUDGMENT. 295 sions that come into play, new regions of the scnsorium are associated, set in vibration, and take their part in the complex operation that is taking place. The dif- ferent regions of my brain are successively affected. Notions formerly acquired are laid under contribution ; they come forward of their own accord on the occur- rence of the excitation with which they are methodi- cally connected as contemporary memories ; and thus the personality, reminded of the primordial impression, and enlightened by the total product of the related njtions that spring up automatically, pronounces its judgment with a sufficient number of materials, and expresses the manner in which it is effected in a verbal form which is the index of its present condition. Thus it is that in pronouncing the words "pneumonia — second stage," I epitomize a whole series of former notions, methodically grouped, which have made their appear- ance in my mind viotu propria. Natural Predispositions. — In this second phase of the cerebral process, which is being accomplished, the human personality is seized on, as we have said, and inevitably associated in its evolution. Here a new peculiarity, which occupies an important place in the phenomena of cerebral life, comes in ; viz., the manner in which that personality is brought into play and the particular mode in which the sensorial excitation has affected it. We have already insisted (p. 43) upon the curious re- lations that exist between the different provinces of the cortical substance and certain centres of the optic thalami with which they are more particularly con- nected. We have thus shown that such or such a group of sensorial impressions was more especially distributed 295 THE BRAIN AND ITS FUNCTIONS, to such or such a region of the cerebral cortex ; and we have at the same time made it clear to what an extent the greater or less richness in cells of such or such a cerebral region, and the briskness and impressionabilit)' of these cells themselves, may induce certain functional predominances, and become the natural cause of certain dispositions and special aptitudes of the mind. in applying these data to the evolution of the pro- cess of the judgment, we recognize the fact that if the human personality, at the moment it begins to take part in this, finds in one of the regions of excitation a greater num^ber of nervous elements than in such or such another ; if the elements are more impressionable, more vivacious, better co-ordinated in their internal mechanism, it will be on this account more strongly impressed, and provided with means of expression more rich and more abundant. Thus, served by the best instruments, it will react in a more complete manner ; will do what others, less richly endowed, could not do ; will see better, hear better, taste better, smell better, etc. It is by means of these natural conditions of organization that certain individuals show themselves superior to others as re- gards the operations of the judgment, in the direct ratio of the superiority of their cerebral constitution. On the other hand it is notorious that, just as all the sensorial organs are not gifted with the same energies in all individuals, and that one is marvellously gifted for music, another for drawing, another for painting, etc., so by reason of that pre-eminence of certain impres- sions in the sejisoriuni, which constitutes in a manner the cerebral temperament of the individual, it results THE JUDGMENT. 297 that in the total of mental faculties whatever cerebral region is best furnished, will be the privileged region in whatever operations of the judgment are the best and most rapidly accomplished. Hence will also arise partially competent judgments, the individual being better fitted to judge pertinently respecting some one particular subject. Hence, according to our individu- alities, those striking contrasts of which we daily see so many examples, where we meet with persons who judge soundly respecting some subject they have thoroughly studied, or which is their "hobby," who are yet com- pletely incapable of forming an ordinary judgment re- specting a simple question of everyday life. The human mind, limited in its resources, and the tributary of the nervous elements through whose instrumentality it manifests itself, is only capable of isolated and restrained efforts ; and thus it is that in the infinite variety of its manifestations we see what a division of labour man must adopt to concentrate his energies upon a point so as to bring them to bear with regularity, and, in a word, how truly judgment is said to be a most difhcult operation — -judicmin difficile.^- 3. The process of judgment, when once it has called • It is strange to observe how often, within pathological limits, we meet with individuals who partially preserve their capacity for judging of certain things. We see in fact lunatics who can sustain a connected conversation, provided that those points which bring their personality into play be avoided. If we accidentally touch the sensitive chord the dissonance suddenly bursts out and the delirious conception becomes clear. There are others who are com- pletely incapable of judging of things around them, of acting with discern- ment where their own interests are concerned, and who notwithstanding pre- serve an aptitude for certain games, which require that the attention shall be sustained over a Umited field, the game of draughts, for instance, which demands the contemplation of the draughtboard, witliout necessitating efforts Ot memory, as games of cards do. 21 298 THE BRAIN AND ITS FUNCTIONS. forth, as it passes, the participation of the different regions of the cerebral cortex, and has associated itself with the human personality, tends more and more to effect its extrinsic manifestation, and to express itself outwardly either in suitable articulate sounds, by which custom has taught us to express the different shades of our sensibility, or in the form of graphic characters which similarly signify our ideas and inmost thoughts. Henceforth it assumes in the sensofium the form of a conscious resolution, and, from this moment, the spon- taneous voluntary act is similarly completed in its essen- tial elements ; since the cerebral operation in which it is essentially embodied, the awakening of the human personality, conscious of what is taking place^ has occurred, and is about to reveal itself externally under the most diverse forms. From this moment the process of judgm.ent, in its third phase, belongs to the series of the phenomena of voluntary activity, of which it marks the first stage. It then embodies itself in the somatic translation of a voluntary excitation ra- diating from the psycho-intellectual regions. We shall now follow it in this last phase, by explaining the action of voluntary motor-power. Community and Points of Contact of Human Judg- ments. — Common Sense. — Once, now, the process of the judgment has been externally manifested, and by this has become capable of implanting itself in the brain of another and determining in him similar reactions, — once, I say, this operation has been accomplished, how is it possible to appreciate exactly the value of the physiological act that has been effected } How can we discern the justice of the opinions arrived at, and know THE JUDGMENT. 299 whether the judgment formulated be true or false, and, as we say, reasonable or unreasonable ? When dealing with the discernment of things which fall immediately within the domain of intellectual activity, it is comparatively easy for each of us to know that a judgment pronounced is conformable with truth and reason. Every one knows that in the domain of science, all the fundamental truths which are the common patrimony of the human mind, in evolution from century to century, be they mathematical, chemical, physical or biological, are universally accepted ; that what is true in Paris in astronomy is similarly true in Pekin or New York ; and that in all places in the world, wherever they meet with a sensible and well-informed man, they are well-received and comprehended. Now this universal concord, this acquiescence of all in their acceptance as legitimate and truthful judgments, exists because they only express evident and precise ideas, verifiable by experience ; because every one can directly or indirectly put them to the test ; and because the human personality that observed and expressed them for the first time had nothing to do with their genesis, except the expressing of them in correct and appropriate terms, the emotional regions of the sensibility not having been laid under contribution in the smallest degree. The real only, and nothing but the real, is revealed in the exposition of each of them ; and the indi- vidual who has expressed them, having perceived the external world in an incident form, has but reflected them externally without adding anything of his own. 3C0 THE BRAIN AND ITS FUNCTIONS, Thus, when Copernicus or Kepler formulated his laws of the system of the world and the move- ments of the planets ; when Newton made evident the decomposition of light into its elementary rays; when Lavoisier demonstrated the part played by oxygen in the phenomena of combustion and respira- tion ; when Laennec furnished his contemporaries with a new means of penetrating with the ear the ma- chinery of the living human frame, and following step by step the respiratory movements and those of the heart,— these were new truths, unexpected judgments that were thrown into the intellectual domain, and which, as a correct expression of reality, and certified as conformable to this by every one interested, were addressed to but one region of the living organism, the intellectual, without being addressed to the emotional regions, and without exciting the slightest passion. These are palpable, tangible, verifiable judgments, which, being addressed to all, true for the future as for the present, present those general characters proper to grand truths, permanence and universality. If it be generally possible to appreciate the regularity of a process of the judgment in the sphere of purely intellectual phenomena, by mediate or immediate veri- fication, it, on the contrary, becomes very difficult when we have to judge of a question which belongs to the class of moral phenomena. Here all becomes complicated and obscure ; for the criterion of verification, experience, which we had before, is here wanting. There is no standard by which to measure the things of the moral order ; this incident, fact, or particular document which has to be judged of, THE JUDGMENT. 3OI from the mere fact of being" a direct emanation from some one else's personality, his private opinion which is externally revealed, borrows from the emotional regions whence it proceeds a specific colouring ; his private personality is more or less at work, with its emotions and passions. On the other hand, we ourselves, who have to judge of this incident, this document, these words, are similarly unconsciously affected by latent sympathies or anti- pathies, which make us see and judge of the thing under colours which are not always those of reality. We see, then, of what multiple elements the action of judging of a phenomenon of the moral class is com- posed, and how many unforeseen factors, variable at every instant according to the state of our natural sensibility, come in at cross purposes to drive us away from the desired goal. Thus, in the special domain in which moral sensibility reigns alone, we may say that the experimental methods of valuation are entirely at fault. We must, therefore, have recourse to entirely new methods, considerations of a moral kind which shall serve as a common measure, and which, when applied to the valuation of phenomena of the same nature, may be capable of leading us to a solution of the problem, and the formation of a judgment respecting its nature. If it be true, indeed, that in human practice and the ordinary affairs of everyday life, there is nothing that differs so much from one man as another man (since we each carry in us the weight of hereditary influences, in- fluences of race and education accumulated throug[h loner periods of time, and the shades of .^sensibility of each of 302 THE BRAIN AND ITS FUNCTIONS. US are as different as the details of our persons), there is, nevertheless, in that sum total of data which constitute the elements of the moral life of man, a common stock of fundamental truths which form, as it were, a series of moral axioms and a veritable patrimony, proper to all sentient humanity. In all times, and everywhere, indeed, it has always been a fine thing for a man to serve his country, to sacrifice himself for his kind, to honour his parents, to bring up his family well, or, to make use of a formula which contains an epitome of universal morality, to do or not to do to others as we should like others to do or not to do to us, etc. Within a more re- strained circle of ideas, we know that in unions of men ao-glomerated into isolated societies, though they be in- dependent or even enemies, there is a common fund of ideas and sentiments. Among soldiers, under whatever flag they serve, the sentiment of military honour is always the same. The esprit de corps, which we see de- veloped in certain associations, is nothing but the result- ant of a community of ideas and sentiments among all the individuals living in society, and united by the bonds of a vast confraternity. In all times and places, then, this collection of com- mon ideas and sentiments which serves as a basis for phenomena of the moral order, has been, as it were, a sort of directing clue for humanity, a magnetic meridian of common sympathy, by which men have unconsciously regulated their conduct ; and this is so true, this common fund of moral sensibility is so inherent in our natural sensibility, in our very personality ; it is so vivid in us, and so organically constituted, that wherever we find one of our fellow-creatures we judge, d prioriy that he must THE JUDGMENT. 303 vibrate in the same keys, and thrill to the same impressions. In a word, we believe in the existence of this moral sensibility in others, with the same certainty that we feel regarding the existence of his heart that beats, his lungs that breathe, and his limbs that move according to flexions and extensions previously deter- mined. This common basis of moral sensibility which lives within us and extends to all our fellow-creatures, forming a bond of universal sympathy between all members of the human family, thus becomes the veritable criterion and touchstone that ser\^es us to appreciate and judge of the value of a phenomenon of the moral kind. To a particular phenomenon we logi- cally apply a particular method of diagnosis. It is by taking ourselves as a term of comparison, by bringing our conscious personality into the presence of the actions of another, by placing ourselves in imagination in his place, that we arrive at a notion of their scope, and a judgment as to whether they are conformable to the common average-line of human sentiments and universal sensibilit}'. We thus arrive at the conclusion that there are among mankind fundamental truths of the moral kind, common modes of feeling, which we all uncon- sciously obey, and which constitute the common line of average^ the cojnmon sense, according to which the great human family advances along the path of life. Each of us takes the bearing of his acts more or less from this, and, if these deviate from it, this deviation is then felt by those who are following it, and they accordingly judge of it and condemn it, as a deviation from the 304 THE BRAIN AND ITS FUNCTIONS. common law, and as the patent expression of a perturba- tion which has occurred in the faculties of him who has thus got out of the comm.on rut. We accordingly consider every word, and every piece of writing that is understood and accepted by all, reason- able, according to common sense ; while on the other hand, we characterize as unreasonable every action that shocks the notion of right sense and rectitude of judgment, as they exist in others. Thus, that conception of things in their totality, which we designate under the term reason, is gener- ally, from a physiological point of view, nothing but an abstract synthetic expression which serves to express that unconscious tendency we have to follow, in our lives, our ideas, and our actions, the common course followed by our kind, and not to deviate from the meridian line followed by the majority. Functional Perturbations of Operations of the Jndg- ment. — A study of the morbid forms of the operations of the judgment, shows us how closely united one with another are the different phenomena of which it is con- stituted, and to what an extent the whole becomes perturbed and disordered, when one of these comes to be disturbed in its mode of action, (especially the first, which is the most important, and the point of departure of the operation which takes place) ; and how far the external expression which results, is in more or less complete discord with the reality of things. The first phase corresponds, as we have said, to the moment in which the external impression penetrates the sensorinm, and seizes upon the personality, which immediately participates in the communicated impres- THE JUDGMENT. 305 sion. This is the delicate moment of the process, when the terms of the problem pre stated. Now, what hap- pens when this primordial sensation which should arrive at the sensorunn with the maximum of precision, and reflect, in as exact a manner as possible, the surrounding phenomena, is incompletely transmitted and falsified ; when, from some accidental disturbance in the different centripetal apparatuses charged with its collection and transmission to the sensorimn^ it arrives there deprived of its essential character and incompletely expressed (sensorial illusions) ? What happens when, on the other hand, the intermediate regions, whose mission it is to transmit to the sensoriuut peripheral excitations (centres of the optic thalamus), assume a condition of automatic erethism, and proceed, motit proprio^ to launch towards the scnsor'ULin subjective excitations engendered on the spot (hallucinations) ? The human personality, then without any means of direct control, seized upon by fictitious autogenous excita- tions, according to natural processes, accepts the change; receives them, absorbs them, works them up, submits them to the same, subtle operations as though they were the regular and legitimate aliments of its activity ; and henceforward the abnormal process, by means of the working of the energies proper to the cerebral elements, and by virtue of habits formerly acquired, goes on of itself, as logically and inevitably as though it were a pure emanation from the real world ; of course, to the great stupefaction of persons who are not initiated into the knowledge of mental diseases, and cannot bring themselves to admit that a false conclusion may be deduced with perfect logic, and that logic does not imply 306 THE BRAIN AND ITS FUNCTION^. either the justice or the precision of any judgment v/hat soever. Whether the protopathic excitation, then, be regularly or irregularly engendered, all goes on in the brain auto- matically and, to some extent, unconsciously, by the individual force of the organs traversed by the process in evolution ; as though we had to do with a simple reflex operation in process of development in the grey tissue of the medulla ; as though we had to do with a foreign body, or a poisonous substance accidentally introduced into the stomach, and inevitably passing on its way througn the successive regions of the intestinal canal. We can thus comprehend how the third phase of the process (which is but the ultimate expression of the period of apparition and exteriorization of the human personality, which manifests its peculiar emotivity) ex- presses, in a corresponding manner, the different vices of organization that have accompanied the first moments of its genesis. In fact, if we study the concatenation of ideas and arguments in the case of the most rational lunatics, in those who, with persuasive logic, express, in correct terms, and often in a winning and convincing manner, all their emotions and all their extravagant conceptions ; if we follow out with care the natural sequence of Yheir wanderings, we shall always find that the first origin of their arguments and recriminations, their ideas of those persecutions of which they accuse those who surround them, their family, society in general, or persons un- defined, have for their primary point of departure, an init'al disturbance occurring in the method of .sen- THE JUDGMENT. 307 serial perception, and in the initiatory pliase of a pro- cess of judgment. It is always a sensorial illusion, an hallucination, that is at the bottom of the morbid act, and directs its inevitable course. Thus, we sometimes find an energetic and intelligent patient affected with reasoning mania, who bitterly complains of the soiled linen that is given him. He violently attacks those in his service, and complains 0/ the tricks of which he is the victim ; then shows the linen objected to, and, lo ! it is perfectly clean. We have caught the sensorial illusion causing the extrava- gant judgment in the moment of its genesis. The patient imagined that he saw a spot of dirt, where there was none ; his senses used him badly ; and hence a series of extravagances constantly renewed in the same mind abused by its senses, and recurring by means oi the same mechanism. Or again, we may find another who, also suffering from peripheral disturbances in his nervous system — a special condition of his gustatory sensibility — con- cludes that the food he is given is bad, that powders are put into it, that they wish to poison him, and that such and such a person is guilty. Another has scarcely risen from table, when he makes a great outcr}^, be- cause, as he complains, they have given him no dinner. He is examined, and it is found that he suffers from a temporary anaesthesia of the pharyngeal mucous mem- brane. A laundress, whose case is reported by Charbeyron, and v/ho had given up her business and become a sempstress on account of rheumatic pains, used to 308 THE BRAIN AND ITS FUNCTIONS. work late at night, and got ophthalmia. She, however, continued to work, and saw at the same time four hands, four needles, four seams. She had, in fact, double diplopia. She at first treated this as an halluci- nation ; but, at the end of some days, in consequence of weakness and prolonged mental anxiety, she imagined that she was really sewing four seams at once, and that God, touched by her misfortunes, had worked a miracle in her favour.* As we see here, also, there was a primary disturbance occurring in the first stage of the process (a sensorial illusion, diplopia) determining as its consequence the extravagance and error of judg- ment. In other circumstances, there are true hallucina- tions, phenomena engendered on the spot by a species of erethism of the sensorial channels, which interpose and produce changes in the conscious personality. There are, in fact, almost always hallucinations of hearing, sight, and smell, which, either isolatedly or simultaneously, impinge upon the sensormm^ and which are almost always found at the bottom of all forms of delirium. Sometimes there are voices heard subjectively, which incite the person under hallucination to avoid such or such a person, or to commit such or such an action ; that speak to him in a tone of menace and trouble him in his nightly rest. Sometimes there are various visions which keep him awake, painful per- ceptions, either of taste or smell, which cause him to refuse food, etc. Hence an indefinite series of consecutive judgments * See analogous cases cited by Parchappe, "v^nnales Medico- psychcl.," 1861, p. 271. THE JUDGMENT. 3O9 and reflections, varying infinitely according to the nature of the soil in which they are evolved ; hence all those forms of delirium by which the emotions of the per- sonality reveal themselves, and which all have this common basis which unites thern one with another, that the morbid conception implanted in the mind as a homogeneous element, and to some extent as a con- ception contrary to nature, only reveals itself outwardly in a vague and cloudy manner, yet logically, notwith- standing. The person under hallucination, who has vaguely conceived a suspicion in consequence of a low auditory impression which has affected his sensoriujji, outwardly expresses this state of indecision and vague information in the same vague manner ; and in this we still find the ordinary methods according to which the processes of the judgment manifest themselves in us. The person under hallucination is vague in his expres- sions, because the impression which excites his per- sonality is similarly vague and confused. He does not clearly express what he does not clearly understand. He uses only indistinct formulae to express the con- ceptions that pass through his mind, always impersonal phrases ; — someojie has told him so and so ; some one has warned him of so and so ; his expressions never being descriptive nor vivid, nor possessed of those distinct outlines that characterize impressions really seen and really heard. Thus, in fine, we see to what an extent the morbid processes of divagation, however wide apart be the diiferent forms they assume, obey the same c;-eneral laws as the regular processes of the judgment. They pass through the same phases in their operatioui 310 THE BRAIN AND ITS FUNCTIONS. by means of the same automatic machinery ; they follow logically the same routes ; and when they are at dis- cord with reality, when, in a word, their operation has failed, it is because it was badly prepared as regards the arrival of the sensorial impression, and because the phenomena of perception have been disturbed in their essential connections. The human personality, carried away into this fatal cycle, obeys automatically, and inevitably becomes involved in the pathological dis- orders that occur in the sensorium. It is incapable of resisting the strain ; and when it comes to its senses, and the disease is cured, it is rather owing to a calming down of the regions primarily affected, than to any action of the conscious volition. The mental condition improves with the physical, and if the divagation dis- appears, and the individual ceases to be delirious, it is less by a spontaneous effort of his will, by virtue ot which he abjures his false convictions and yields to the judgment of others, than because his brain becomes permeable by the surrounding reality, and because he absorbs sensorial impressions, and elaborates them as the generality of mankind do. We know, indeed, how refractory to all sane reason are men with false ideas, and what a 'waste of labour it is to endeavour to treat a partially delirious individual by means of logical reasoning. BOOK III. PHASE OF REFLECTION OR EMISSION OF THE PROCESSES OF CEREBRAL ACTIVITY. Preparatory Period. Motor Processes, — In the state- ment we have just made, we have seen that the processes of cerebral activity, which consist first of all in an impression upon the seiisoriitm of external origin, resolve themselves into various reactions on the part of the cerebral apparatuses which are roused into activity, and into a sort of intra-cerebral radiation of the exci- ting movement. Now this impression, which has arrived in the form of an incident excitation, is a living force in act of trans- formation ; this force is implanted in the scnsormm ; it becomes reinforced and concentrated according as it is evolved ; it is necessary that it shall still continue in motion, and that, under one form or another, it shall pass out of the organism, by discharging itself upon other organs designed to serve it as gates of exit. From this new stand-point we shall henceforward consider the phenomena of cerebral activity, at the moment in which, in their third phase of evolution, they finish their last stage and reveal themselves in 312 THE BRAIN AND ITS FUNCTIONS. various reactions. These, however varied their appear- ances, nevertheless represent in the external world the reverberation of a former sensorial impression emanating from this external world. Once upon their outward course, the processes of cere- bral activity take two different routes, according to the variable conditions of receptivity of the cerebral medium in which they are developed, the nature of the individual, and his manner of feeling. Thus they are sometimes reflected towards the different departments of vegetative life. They do not make their exit from the organism, and in that special sphere they produce secondary commotions of a more or less apparent kind ; their reflection takes place.in an entirely automatic manner, and in spite of voluntary action (return shock of mental emotions upon the physical constitution). Sometimes, on the contrary, they appear externally, and reveal themselves by the help of various means of expression — phonetic sounds, graphic signs, appropriate gestures. The external sensorial excitation, radiating from the external world that gave it birth, is in this case directly returned to this external world. CHAPTER I. REFLEXION OF MOTOR PROCESSES UPON THE PHENOMENA OF VEGETATIVE LIFE. In the first series of facts, when the excitations derived from the external world are not directly reflected out- wards — when, under the influence of one cause or another, the primary impression remains confined within our own organism, it dies away there, and the reverberation which results extends to a greater or lesser distance. The nervous discharge of the process, arrested in its course, reacts upon one region or another of vegetative life, and this depends upon the closeness of the sympathetic links uniting each of these with the sensorhim. We have shown, on the other hand, that by reason of these connections, there exist, as it were, incessantly permeable natural channels, by vVhich the impressions of the sensormin may at any moment become associated with the phenomena of vegetative life, and reverberate throughout the whole extent of the life of the viscera. The result of this arrangement is that every external excitation arriving in the sensoriiim is sympathetically felt in the different centres of visceral life, and that the slightest excitations that wrinkle the surface of its plexuses, as well as the shocks that overwhelm it, are sympathetically propagated into such or such a depart- 22 314 THE BRAIN ANC [TS FUNCTIONS. ment of organic life ; now here and now there, centri- fugal currents arise instantaneously, and carry to a distance without our knowledge or voluntary participa- tion, prolonged reverberations of the oscillations of the psycho-intellectual sphere. We all know what an effect painful emotions have upon the phenomena of the circulation ; how the heart palpitates without our knowledge when our emotions are at work ; how apt this latent over-excitement is to fatigue the vital energy, and what a serious, and long ago recognized influence mental causes have as regards the genesis of its organic lesions ; how susceptible the vaso- motor innervation is of becoming associated with our emotions in a similar manner ; since instantaneous paralysis of the capillaries, on the one hand, is apt to determine those sudden blushes which by showing them- selves upon our faces reveal so well, in spite of us, the secrets of our agitated sensibility ; while, on the other hand, their spasmodic contraction excites those instantaneous pallors which as directly reflect the per- turbations that traverse our sensorium. We all know, moreover, how directly the digestive organs are associated with the impressions of this same sensorhnn. The stomach in particular is intimately connected with the phenomena of cerebral activity. Like the heart, it every instant experiences the return shock of our emotions, and like it, becomes the bearer of the sins of our general sensibility. Every one knows that digestion is disturbed by mental emotions ; that vomiting frequently accompanies cerebral disease ; and that in certain localized pains of the sensoriziin (hemicrania), when too strong ^ external excitation REFLEXION OF MOTOR PROCESSES. 315 evokes its sensibility, the discharge of the sensoriiim in erethism takes effect upon the stomach, which to some extent serves as a gate of exit for the nervous over- excitement reflected towards the organs of vegetative Ufe. We all know, further, how intimate is the association between the respiratory organs and our natural emotions. Sighs, spasms, anxieties, the involuntary laugh which sometimes bursts out in so unexpected a manner at the sight of a person who laughs, and the frown which shows itself under similar circumstances, are also co-ordinated external revelations that follow upon an incident exci- tation carried into the sensormm, and reverberated to- wards the organs whose business it is to carry it off externally. More than this — and this also is a phenomenon known to us all — in certain circumstances our muscles, which are usually such faithful interpreters of our wills, escape from the regular stimulation of the conscious personality, and then, under the influence of powerful emotions, become subject to invincible excitations radiated from the sensorium^ apd act like treacherous servants, only in obedience to the instructions of an irregular power, and manifest, without our consent, the different states through which our inner sensibility is passing. It is by reason of this substitution that our gestures, our movements, our attitudes, our physiognomy become, without our knowledge, living expressions of the different states of our sensibility, and in a manner apparent phenomena by which the phase of erethism of certain regions of the sensoriiim is externally dis- charged. In these cases our muscles of expression are 316 THE BRAIN AND ITS FUNCTIONS. grouped ai.'.d harmonized in a co-ordinated manner, so automatically and so unconsciously that we see, for instance, those of the iris dilate and contract alternately, and express by their play, as automatic as unconscious, the different modes of sensibility of the retina which it is their business to protect. We may say, then, in a general manner, that none of the peripheral excitations that arrive at the sensorium in the form of a vibratoiy impression, of a living force in activity, remain there stationary, stored up in one place. They develop there a series of secondary reac- tions, of energies regularly co-ordinated, which are inces- santly distributed in the direction of the apparatuses of organic life, and represent the continuity of the primary movement, and, as it were, the modes of excretion ot the living forces implanted in the organism, which here and there effect their physiological discharge. Extrinsic Manifestations of Cerebral Processes. Genesis of the Will. — The processes of cerebral activity which reveal themselves externally, and make their exit from the organism in the form of voluntary conscious manifes- tations, must be considered successively in the two prin- cipal phases of their evolution : 1. In their period of incubation, when the process of the will is still only constituted by a purely physical impression ; 2. In their second period of extrinsic manifestation, when they take form, reveal themselves in an apparent manner, and lay the purely motor regions of the nervous system under contribution. I. In its preparatory phase of incubation, the process of the will is nothing but the riper and more advanced REFLEXION OF MOTOR PROCESSES. 317 ultimate period of an anterior operation of the judg- ment, constituted as we have already explained. The human personality is seized upon by the arrival of the excitation emanating from the external v/orld. It enters into participation and becomes associated with this ; and from this intricate connection results a true intra-cerebral automatic radiation, which produces the apparition of a series of agglomerated secondary ideas. Rut the matter does not stop here ; this inner personality having been thus seized upon, its sensibility having been touched in any manner whatever, has reacted by virtue of the vital forces that vibrate in it in a latent condition — it has been affected in the direction of its most profound affinities, and necessarily this reactionary period betrays itself by an unconscious desire for such or such a definite object, and by a repulsion from such or such another. Desire, attraction, aversion, repulsion, are therefore new conditions of the sensorium which necessarily result in the natural course of things, and which thus become the primordial elements destined to constitute a process of voluntary activity. 2. The psychic operation which is to be resolved into an act of will is, then, in itself only the second bar of a movement already begun. It is only the regular expres- sion of the human personality, seized on, and impressed by an old or recent excitation from the external world, and carr>qng back to the external world the different states of its sensibility in emotion, in the form of motor manifestations. Hence, as a natural consequence, we come to the conclusion that the act of voluntary motion which is developed in the psychic regions, is nothing but a 3l8 THE BRAIN AND ITS FUNCTIONS. subordinate fact, a secondary phenomenon, the direct resultant of the shock of the sensibiHty in emotion and the spontaneous reaction of the sensorium. Motor power is then, physiologically, nothing but sensibility trans- formed. The voluntary excitation comes to life in that subtle process in which the impressed human per- sonality is aroused. From this reaction of the sen- sibility it emerges as a natural consequence, like a vital force in evolution ; it is like an excito-motor process radiating from the sensitive regions of the spinal axis towards the anterior regions, which progresses motic pro- prio, develops, amplifies, perfects itself infallibly through the whole length of its journey, and expands in its last period into co-ordinated motor manifestations, the faith- ful dependents of the sensitive excitations that have given it birth. CHAPTER n. TRUE PERIOD OF EMISSION OF THE PROCESSES WHICH PRODUCE VOLUNTARY MOTION. SPONTANEOUS REACTION OF THE SENSORIUM. MOTIVED RESO- LUTION. Let us now see how the different periods of voluntary activity are connected one with another, and how the physiological operation pursues its course. The process of external emission of the emotivity of the sensorium manifests itself externally, sometimes in a rapid and instantaneous manner, sometimes slowly, pro- gressively, and after a greater or less period of time ; this extrinsic revelation taking place either in the oral or graphic form, or in the shape of gestures more or less expressive, and varied attitudes. In the first case, when the voluntary motor phenome- non is an immediate translation of external impres- sions, the human personality, aroused and vibrating, rapidly responds to the impressions that affect it. It outwardly expresses itself directly, now in the form of connected articulate sounds, which are appropriate answers to the interrogations that excite it, now in current conversations, in injunctions of all kinds, prolonged discourses, in writings, expressive movements, etc., etc. It expends the stores of emotivity that are 320 THE BRAIN AND ITS FUNCIIONS. vibrating within it, and thus reflects the various sen- sitive currents that have set it vibrating. Sensibility, therefore, underlies every motor act of the organism ; and when we immediately answer to demands, when we let ourselves act upon the natural impulses of our sensibility, and, as it is called, do things on the spur of the moment, it is our person- ality that expands spontaneously, without artifice or premeditation. It reacts with its native and even frank characteristics, as though we had to do with physio- logical phenomena in natural evolution ; for in these circumstances our words express our sentiments in an off-hand manner, and the compromises of meditation, and diplomatic reflection have not yet crossed our path to mask our natural spontaneity. In a number of other cases the discharge does not take place in a rapid and immediate manner ; there is, as it were, a cold maceration of the incident impression in the tissue of the sensoriitm, by which this impression is matured and modified by the mere action of the medium in which it remains. When, in fact, we have to reflect, to mature a project, before coming to a resolution, the primitive idea, the first excitation, in arriving in the sensorium awakens a crowd of related reactions. It has been perceived in the form of sensorial vibrations, and these vibrations radiate to a distance into the dinerent cell-territories. These latter, on being impressed, excite ^the automatic activity of those of the neighbourhood, and at the same time arouse related ideas and associated memories formerly registered ; so that at the end of a period of sojourn in the sensorium, variable according to individual PROCESSES WHICH PRODUCE VOLUNTARY MOTION. 32 I temperament, this primitive impression has proliferated and slowly produced effects that reverberate to a distance. More than this, the ideas of others, In the form of oral counsels, written advice, and auditory and optic impressions interpreted by the intellect, have come to join in, to group themselves around the primary excita- tion, and add a new weight to the operation in process of development. Those reflections which either proceed from ourselves, or are inspired by the surrounding medium, are then converted into agglomerated motives or thoughts, des- tined to influence the direction of the voluntary process and direct its route. Things being thus disposed, a delicate phase occurs in the cerebral operation that is being accomplished. The motives being all confronted with one another, with their intrinsic and extrinsic characters, the shades which characterise them, their relative value, what route will the process take ? Under what form will it reveal itself ; and in what manner will the conscious personality pronounce itself?* * This delicate moment of the operation, by virtue of which the sensorium, when seized upon, reacts spontaneously and carries outwards the different con- ditions of its impressed sensibility, does not occur in some individuals without certain difficulties. There are a great many persons, indeed, whose hesitation is the dominant note of their character. At the moment of making a resolution they dare not decide, but turn about in a persistent indecision, and remain in suspense whea action is necessary. In more pronounced cases, where this psychological con- dition is still more distinctly marked, we find individuals thus affected recount- ing all the anxieties that besiege them when they are on the point of coming to a decision. They hesitate, tormented by a series of uncertainties, and if they have to speak or take up their pen to affix a signature, or perform any spou- 322 THE BRAIN AND ITS FUNCTIONS. On this point, the controversies of philosophers and metaphysicians, which have been taking place from time immemorial, have succeeded in arriving at but one thing — the expression in sonorous language of their ignorance, more or less complete, of the fundamental characters of psychical life. We must, indeed, pene- trate into the inmost essence of the activity of cerebral life, into the complex phenomena in which it reveals itself, to arrive at a comprehension of the evolution of any voluntary act whatsoever, and the natural manner in which it expresses itself through the organism. Little, indeed, as we may reflect upon the concatena- tion of the processes of cerebral activity, considered as we have here just done, we cannot help arriving at the conclusion, that the voluntary act is in itself nothing but the reaction of the sensibility thrown into agitation ; that it is this that is latent in all voluntary manifesta- tions ; and that it is always the sensorium that, under forms the most dissimilar in appearance, reacts and outwardly betrays the inner impressions by which it is excited. The sensibility is, therefore, always in agitation at the commencement of every voluntary act deve- loped. It becomes erect, and excites the opera- tions of judgment and reflexion. It is always present, always in vibration, and inspires our words, our acts, our taneous action, they remain fixed, immovable, in a species of invincible apathy. These different states, from the most simple to the most pronounced forms, are evidently only the effect of a partial or permanent weakening of the mental energies, through which the elements of the sensorium, in a torpid condition, are incapable of rising to the phase of erethism, of reacting, and of leading by their own vitality the process in evolution in the regular direction it should follow. PROCESSES WHICH PRODUCE VOLUNTARY MOTION. 323 writings ; and whatever be the power of the motives calculated to attract it away from its inner inclina- tions, it follows its preordained desires for what is suitable to it, what pleases it, and shrinks from what is repugnant to it. Every one, as we say, gives Jiis opinion, every one judges according to the manner in which he is impressed, in which he fais ; and sensibility, the seeking after what is pleasant to each of us, is, under the name of self-interest, to such an extent the true motive force of all human actions, that we may con- stantly declare that it is always this that directs them, like a powerful magnet, and inclines them in this way or that. All this takes place in so unconscious and certain a manner, that in dealing with a crime, or any guilty action, justice, a priori, ascribes responsibility to those who may have had an interest in committing it, by obtaining some profit from its perpetration. On the other hand, since human sensibility is in itself one of the most mobile of things, and as regards this every one takes his pleasure as he finds it, it results that the manifestations of sensibility will vary infinitely according to individuals, and will sometimes assume paradoxical foi-ms outside of the usual modes of common sensibility. But at bottom, although the sen- timents of egotism and personal satisfaction may apparently be masked, the manifestations of the will will always demonstrate their derivation from the same origin. Everyone, as we have said, has his mode of feeling, and just as we see individuals experience satis- faction in certain enjoyments which they alone are capable of perceiving, so we find them manifesting these different states of their sensorium in eccentric and 524 THE BRAIN AND ITS FUNCTIONS. extravagant forms. Thus it is that the enthusiasms of generosity, self-abnegation, even self-sacrifice, are but too often only a disguised manifestation of egotism, a mode of feeling, sid generis, in which we exchange a physical advantage for an emotion of the moral kind. From the moment, then, in which the personalily becomes interested in the realization of such or such a desire, the moment in which, as we say, a resolution has been taken by it, this physiological condition expresses itself in a co-ordinated manner, according to processes which have been acquired by habit and commenced in infancy, and by which we have learnt to make our fellow- creatures comprehend by means of a special vocabulary the ideas which germinate in us, the desires that demand satisfaction, and our private aversions. Henceforward the mental process has made one more step in the intricacies of the cortical substance. It opens up a new path, that of the motor regions proper. A living automatic pianoforte from this moment comes into play, and in various forms ex- presses the sensitive keys it is bound to interpret faithfully. It is the instrumental part of our organism that vibrates, and the process, tending more and more to emerge from the plexuses of the cortical substance, becomes concentrated within certain circumscribed limits, in certain psycho-motor regions, and hence, in the form of rapid intermittent stimulations, effects its discharge directly upon the dinerent territories of the corpora striata. Coficatenation of Vohtntary Motor Acts. — We have Just seen how the voluntary stimulus, conceived in its primary phase of elaboration, in the substance of the plexuses CONCATENATION OF VOLUNTARY MOTOR ACTS. 325 of the sensoriuni, as a condition of purely psychical vibration, was constituted by a series of multiple elements, all concurring in its genesis ; how it became inevitably united with a previous phenomenon of sensi- bility in agitation ; and how, like a living force in evolution, it tended more and more to emerge from the regions where it was conceived. From this precise moment it leaves the purely psycho- motor regions of the cortex, in the form of transient and rapid stimulations destined to be converted into articulate sounds, digital movements, or expressive ges- tures ; and it proceeds, by help of the special white fibres (cortico-striate fibres), to different territories of the corpus-striatum, of which it thus excites the imme- diate activity. (See 5, ii, 16, Fig. 6, p. 61.) Here, in this first stage of its outward course, it insensibly loses its original character of a purely psychical excitation, to incorporate itself more and more with the organism, to materialize itself, in a man- ner, and increase its dynamic power by the addition of a new nervous element, the cerebellar innervation, which, in the condition of a static force in permanent tension, is incessantly distributed in the plexuses of the corpus striatum. Thus reinforced by this adventitious contingent of innervation which is engrafted into it, it continues its centrifugal course (see 7, 12, 19, Fig. 6, p. 61), and by means of the antero-lateral fibres of the axis (cerebral peduncles) it descends, in the form of an interrupted current, to excite the dynamic activity of the diff"erent motor nuclei of the spinal axis, which, like a series of a^^paratuses always ready to enter into action, only 326 THE BRAIN AND ITS FUNCTIONS. wait its arrival to develop their latent activity. From this moment, mixed up with the proper activity of the different spinal regions, it projects itself along the anterior roots and thus becomes, in its final phases of transformation, one of the multiple exciting causes of muscular contractility. We see then, to sum up, from what precedes, that the processes which produce voluntary motion pass, in their evolution, through phases inverse to those of the processes of sensibility. While these latter, as they approach the central regions of the sensormni, are puri- fied and made perfect, becoming more and more intcl- lectualized by the metabolic action of the different nervous media through which they are propagated ; the former, on the contrary, conceived as psychical vibra- tions at the moment of their genesis, amplify and are fnaterialized more and more, as they descend from the superior regions. They become complicated by the addition of adventitious elements, which reinforce them as they progress (cerebellar and spinal innervation), and thus become, in the last term of their evolution, a true synthesis of agglomerated dynamic elements, which resume in themselves the vital forces of the system through which they have been developed — cerebral, cerebellar, and spinal activities.* Conceived under this simple formula, the processes which produce voluntary motion begin by being a purely psychical excitation, and insensibly become, by the natu- ral play of the organic machinery, a physical excitation. In thus becoming transformed in their successive evolu- * See Luys, " F.echerches sur le systeme nerveux cerebro-spinal," p. 434. (Icoiiographie photographique, p. 71.) CONCATENATION OF VOLUNTARY MOTOR ACTS. 327 tion, they present the fascinating picture we constantly see presented to us in the working of steam-engines. We see, in fact, in this case, how a force, shght at its commencement, is capable of being transformed, and becoming by means of the series of apparatuses it sets at work, the occasion of a gigantic development of mechanical power. In fact, at the moment when the engine begins to work, a very slight force, the mere intervention of the hand of the engine-driver who turns a handle and lets the steam rush against the upper surface of the piston, would suffice for this. This active force, once at liberty, immediately develops its strength, which is proportional to the surface over which it extends ; the piston falls, its rod draws down the beam ; the power is developed as the fly-wheel revolves, and the initial movement, so weak at its commencement, amplifies and increases continually, in proportion as the volume and power of the mechanical appliances placed at its disposal become more considerable and more powerful. We see then, in conclusion, after an examination of all the details of cerebral physiology that we have suc- cessively passed in review, that the different processes of cerebral activity finally resolve themselves into a circular movement of absorption and restitution of forces. The external world, with all its incitements, enters into us by the channel of the senses, in the form of sensorial excitations ; and the same external world, modified, and refracted by its intimate contact with the living tissues it has traversed, emerges from the organism, and is reflected outwards in the various manifestations of voluntary motor-power. .■:---f . ^-^-w ^j. ''■^s'--.mm RARIES H 3W, or at the ^H borrowing, as mM cial arrange- Qn COLUMBIA UNIVERSITY LIB This book is due on the date indicated bel( expiration of a definite period after the date of provided by the rules of the Library or by spe ment with the Librarian in charge. DATE BORROWED DATE DUE DATE BORROWED DATE DUE ^^^ P m ^l¥ Pi ^^ ^DK''>U| C28(i14i)m100 ■mnKMRHm atMgaMaaajegBwawaaBegBWBawaBMBWiiwiiwMtiMW m iwif