l&tUnntt Ktbrarg (gtven by ^^, "^^e^^e/^NC^^ \A'tc^^ , MENTAL PHYSIOLOGY MENTAL PHYSIOLOGY ESPECIALLY IN ITS RELATIONS TO MENTAL I) I SO III) E lis THEO. B. HYSLOP, M.D. LECTURER ON MENTAL DLSEASES TO ST. MARV's HOSPITAL MEDIC Vr, SCHOOL, ASSISTANT PHYSICIAN TO BETHLEM ROYAL HOSPITAL, FORMERLY ASSISTANT MEDICAL OFFICER, ROYAL ALBERT ASYLUM FOR IDIOTS AND IMBECILES, LANCASTER, DEPUTY-PATHOLOGIST AND ASSISTANT MEDICAL OFFICER, WEST RIDING ASYLUM, WAKEFIELD ' Non eiiim tarn auctoritatis in disputauilo, quam ratioiiis momenta qiineremla sunt Cicero PHILADELPHIA BLAKISTON, SON & CO ]01i> WALNUT STREET 18 95 GEORGE H. SAVAGE, Esq., M.D.. F.R.C.P., IX GRATEFUL ACKNOWLEDGMENT OF MANY ACTS OF KINDNESS AND ENCOURAGEMENT, AND AS A MARK OF APPRECIATION OF HIS TEACHINGS AND WIDENESS OF VIEW, THIS BOOK Us gciiiratcir BY HIS FRIEND AND PUPIL, THE AUTHOR. P 11 E F A C E. In the following pages an attempt is made to bring together some of the more prominent phenomena of the brain and of the mind, both in their normal and morbid aspects. To the metaphysical and philosophical bearings of the various assump- tions involved in such an attempt, little or no prominence is given. In philosophy we are free to choose between a natural dualism and a h}^Dothetical realism, or we may be materialists or idealists : in empirical psychology or physiology it would, j)resumably, be a work of supererogation to enter at length upon questions of epistemology or metaphysics. In discussing the relations of the outer world as the mind knows it, the assumption that complex mental experience is only an inner representative of a genuine externality has been adhered to, without entering into any philosophical account of the method whereby the existence of the whole outer world is inferred through its representative images. In dealing with many hypotheses which have been given to account for mental events in physical terms, objection has been taken throughout ; and little or no attempt has been made to speculate as to the ultimate nature or quality of nervous or mental events. In an elementary work of this description it is obvious, that an exhaustive account of the anatomy, physiology, and viii PREFACE. pathology of the brain would defeat its own object — viz., conciseness. The author has, therefore, merely sought to bring into apposition, as it were, some of the more important cerebral and mental facts, and no pretence has been made to furnish the student with an elaborate treatise upon any department of the subject-matter. In the preparation of the work the author has much pleasure in acknowledging, with thanks, the valuable assist- ance and advice of his friend, Mr. W. A. Haigh. His thanks are also due to his friends, Mr. H. F. Harding, for revisal of the proof-sheets, and Dr. Maurice Craig, for the preparation of the index. T. B. H. Bethlem Royal Hospital, S.E August, 1895. CONTENTS. INTRODUCTION. PA«E The value of Hypotheses — Boundaries of our Subject — Psycholosfy as a Science — The Relation of Psycho-physiology to the General Study of Mind — Mind Relative or Absolute ? — Defini- tion of Mental Physiology — Mental Pathology — Physiological Pyschology — Relations of Mind to Body — Empirical Psycho- logy — Speculative Psychology — Spiritual Theories — Occa- sionalists — Pre-established Harmony — Theory of Animists — Associationists — Dualism — Monism — Automatism — Material Monadism 1 CHAPTER I. Anatomy of Cortex: Arrangement of Cortical Structures — The Iserve-Cell — Processes of Nerve-Cells — Nerve-Fibres — The Relation between Cells — The Neuroglia, or Connective Tissue Basis — Cell Elements — Caudate Fibre-Cells — Stellate Fibre-Cells — Protoplasmic Glia Cells — Physiology of Nerve- Cell : Nutritive Function — Transmission of Nerve Impulses — Excitability and Conductivity — The Functions of Nerves — Negative Variation 24 CHAPTER 11. Chemical Properties of Nerve-substance: Specific Gravity — Percentage of Water — Albumin — Potash Albumin — Nuclein — Neuro-Keratin — Cholesterin — Cerebrin (Homocerebrin Encephalin) Lecithin — Protagon — Vascular Supply of the CONTENTS, PAGE Brain: Basal Arterial System — Anterior Cerebral Arteries — Middle Cerebral Arteries — Posterior Cerebral Arteries — Arterioles of Cortex — Lymphatic System of the Brain : Regulation of Cerebral Pressure ^ — ^ Lymph-Cisterns — Peri- vascular Channels — Cerebro-Spinal Fluid — Pacchionian Granulations — Subarachnoid Space — Venous Circulation — Quantitative Relations between Blood and Cerebro-Spinal Fluid — Brain-Movements : Pulsatile — Respiratory — Vas- cular — Nutrition of Nerve-elements — Functional Hyperaemias — A^aso-motor Centres — Influence of the Sympathetic . . 56 CHAPTER III. Scheme of the Central Nervous System — Sensory Paths — Cere- bral Localisation for Touch — Course of Sensory Fibres — Special Senses : Sight, Hearing, Smell, Taste — Motor Nerves : Cerebral Localisation — Projection Systems : Association Fibres, Fibrse Proprise — Value of our Knowledge of Cere- bral Localisation : Phrenology, Experimental Research, Com- parative Anatomy, Morbid Anatomy — Sensori-Motor Areas and their Relations to Mental Faculties : Views of Hitzig, Ferrier, Munk, Waller, etc. — Conclusions .... CHAPTER IV. Localisation of the Mental Faculties {continued) : Sensory and Motor Areas subserve Mental Events ^ — Localisation — Diffuse Localisation — Indifferentism — The Frontal Lobe — Intelligence not limited to Local Areas — Ratiocinative Theories : Neural Inference Scheme of Hughlings-Jack son ; Meynert's View of the Forebrain ; Wallers View, based upon Psychological Inference — Value of the Logical Mode of .symbolising Neural Inference — Praefrontal Lobes: Experi- mental Researches ; Pathological Evidences — Consciousness pertaining to Lower Centres— Local Memories — Subjectivity of the Mind — Objective Contents of Consciousness — Specific Functions of Nerve-Cells — \A'allerian Scheme of the Four R's — Specific Quantifications of Motion — Negative Value of Physical Formulae — The Doctrine of " Invariable Con- comitance" '. . . . 123 CONTENTS. CHAPTER Y. PAGE Mind : Scope and Methods of Study — Total Resources at our com- mand for the Study of Mind — Subjective Methods — Subject- Consciousness and Object-Consciousness — The Objective Method — Logical Methods — Inductive Method — Deductive Method — Evolution Theories — Biological — Psychological — Presentationism — Mind-Stuff Theories — Atomistic Hylozoism — Parallelism — Psychological Import of the Theory of Self- Compounding of Mental Facts — Unconscious Cerebration — Arguments for and against the Theory 149 CHAPTER VI. Sensation : Analysis of Sensations and Sense Percepts— Relation of Sensations to Perception — ^ Molar Motions — Atomic and Molecular Motions — Motions of Ether — The Theory of Elec- tricity — Latent Chemical Energy — Power of Selection pos- sessed by Sense Organs— Characters of Sensation — Intensity or Degree — Liminal Intensity — Forms of Excitation — Weber's Law — Discriminative Sensibility — Maximum Intensity — Fechner's Psycho-Physical Interpretation of A\'eber's Law — Wundt's Psychological Interpretation — The Physiological Interpretation — Validity of Weber's Law — The Estimation of Magnitudes by Comparison — Measurement of Absolute Mental Magnitudes Impossible — Quality of Sensations — Generic and Specific Quality — Duration — Local Characters of Sensations — Taste — Smell — Touch — Specific Functions of Tactile Corpuscles or End Bulbs — Pressure Spots — Tempera- ture Sense — Common Sensation — Peripheral Reference of Sensations — Muscular Sense — Hearing — Sight — Pressure Phosphenes — Quality of Sensations of Sight — Simple and Mixed Colours — Colour- Blindness — Young - Ilelmholtz — Hering — Wundt — Yon Kries — Franklin . ... 170 CHAPTER YII. PERCEPnoN : External and Internal Perception — Apperception — Physiological Conditions of Perception — Space Form — Nati- vistic and Empiristic Theories of Perception — Perception of Spatial Order — Theory of Local Signs— Eccentric Projection of Sensations — Spatial Discrimination— Special Channels of xii CONTENTS. PAGK Perception : Perceptions of Smell and Taste : Hearing ; Touch ; Muscular Sensation ; Sight (Pietinal, Monocular, Binocular) 205 CHAPTEE VIII. Sensory Perversioxs : The Origin and Development of Sensory Perversions — Abnormal Conditions of Perception — Definition of Illusion — Sources of Illusion — Classification — Passive Illu- sions — Exoneural — Esoneural — Active Illusions — Voluntary — Involuntary — Secondary Sensations — Sound Photisms — Light Phonisms — Taste Photisms— Odour Photisms — Pain Photisms — Chromatisms — Gustatisms — Olfactisms — Laws concerning Secondary Sensations CHAPTEPt IX. Hallucinations : Distinction between Illusion and Hallucination — The Transition from Illusion to Hallucination — Pielation of Imagination to Hallucination — The Neural Process in Hal- lucinations — -The "Bucket Theory" — Anatomical Regions for Hallucinations and Sensations — Varieties of Hallucina- tions — Classifications — Clinical Considbbations : Statistics of 1,000 Cases — Perversions of Taste — Hypergeusia — Hypo- geusia — Ageusia — Parageusia — Perversions of Smell — Hyper- osmia — Hyposmia — Anosmia — Parosmia — Perversions of Sight — Entoptical Causes — After Images — Perversions of Hearing — Hyperakusis — Hypakusis — Akusis — Parakusis — Perversions of Tactual Perception — Ilypersesthesia — Anaes- thesia — Pselaphesia — Algia — Perversions of the Muscular Sense — Kina^sthesia — Illusions and Hallucinations in Dreams — Hypnagogic Illusions — Dreams in the Insane . . . 248 CHAPTER X. Mental Processes. Attention: Definition — Psycho-Physical Process of Attention — Psychical Theory of Attention — The Neural Processes in Attention — Monoideisra — Polyideism — Reflex Attention — Voluntary Attention — Adjustment of Attention — Attention and Genius — Morbid Conditions — Hyper-attention— Inatten- tion — In Mental Disorders — Conception : Definition — Concept CONTENTS. — Psychological View — Psycho-Physical Theories of Concep- tion — Physiological Theories — Association — Double Nature of Brain — Consciousness the Accompaniment of Nerve Action — The Theories of Dischai'ge and Resistance — Judgment : Definition — Degree of Perfection of Judgments — False Induc- tions — False Deduction — The Perception of Reality — Relief — The Insanity of Doubt — Imagination : Definition — Differ- ences between After-Images and Imagination-Images — The Neural Process of Imagination — Morlnd Conditions — Simple Delusional States — Sensory Types — Emotional or Affective Types — Clinical Considerations . . • . . .291 CHAPTER XL Memory : Elementary Memory — Memory Proper — Secondary Memory — Relation of Memory to Belief — The Process of Recollection — First Impressions — Suggestion — Contiguity, Similarity, and Contrast — Associative Force — Complex, Convergent, Divergent, Obstructive — Methods of Cultivating Memory — Psycho- Physical Theory of Memory — Latent Mental Images — Relation of Primary Image to Revived Image — Disorders of Memory: Forgetfulness — Amnesic States — Congenital Defects — Temporary Loss — Periodic Amnesia in Hypnotic States — Progressive Amnesia — Partial Amnesia — Agraphia, Aphasia, Aphemia, etc.— Hypermnesic States- Congenital — Temporary — Periodic — Partial — Paramnesic States — Simple States— By Association or Suggestion — By Identification 332 CHAPTER XII. Feelings: States of Feeling — Relation of Feeling to Knowing — Instincts and Emotions — Theory of the Emotions — Tempera- ments — Laws of Pleasure and Pain— Tone of Feeling — Physiological Theory of the Feelings — Feeling of Effort — Varieties of Feelings — Classifications — Disorders of the Feelings and Emotions : Sense Feelings — Feelings con- nected with Ideas — Intellectual Feelings — Rational Feelings — Disorders of Childhood, Puberty, Adolescence . . . 373 CONTENTS. CHAPTER XIII. The Will : Definition — Deliberation — Choice — Resolution — Self- determination — Delayed Reflex — Influence of Habit — Desire — Psycho-Physical Processes of Volition — Volition not to be explained Anatomically, Physiologically, Developmentally, or Pathologically — Reflex Acts — Periphero-Motor — Centro- Motor — Automatic Acts — Voluntary Acts — Motor Images— The Will Power in Hypnosis — The Feeling of Effort — Intro- spective Evidences — Physiological Inhibition — Nervous Resistance — Movements — Central — Peripheral — Simulta- neous — Sequential — Speech Movements— Disorders of the Kinsesthetic Word Apparatus — Deaf Mutism — Acquired Defects of Speech — Alliteration — Verbigeration — Akata- phasia — Speech Defects in the Insane — In Sleep and its Associated Conditions — Conduct — Nervous Mechanism of Conduct — Conclusions as to the Existence of a Will — Impairment of Will Power — Irresolution —Defective Impul- sion — Excess of Impulsion — Defective Voluntary Attention — Absence of Will— Conclusions 409 CHAPTER XIV. The Factors of the Insanities : Growth and Development of the Mental Faculties — Developmental Processes in the Infant — Microkinesis — Micropsychosis — Reversion in Adults — Factors of Development. Internal Factors : — Original Capa- cities — Genius — Degeneration and Genius — Balance as the test of Mental Health— Genius a Sociological not a Psycho- logical Concept — Hallucinations not Incompatible with Sanity — Mental Health not to be Estimated Entirely from an objective Standpoint — The Degenerate Advocates — Unre- liability of Statistics — Inherited Dispositions — The Views of Spencer and W'eismann — Hereditary Factors in Insanity- Consanguinity — Phthisis, Scrofula, Gout, Rheumatism, Syphilis — Alcohol — Diabetes — Neurotic Manifestations. External Factors : — Social Environments — Psychopathic Epidemics — Children's Pilgrimages — Lycanthropy — Rapha- nia — Sensory Types — Religious Impostures— Sympathy and Mimicry — Endemic and Epidemic Psycopathies — Folie a (jeu-c — Religion — Physical Environment — Seasons— Climate — Occupation — Town and Country Life 455 CONTENTS. CHAPTER XV. PAGE The Factors of the Insanities {continued) : Physiological Periods of Life — Infanc}^ — Causes of Idiocy and Imbecility — Types of Infantile Mental Defect — Night-Terrors — Dreams — Night- mares — Somnambulism — Infantile Insanity — Causes — Heat — Fevers — Masturbation — Puberty — Adolescence — Puer- perium — Menopause — Senescence — Bodily Affections as Factors —Genital — Urinary — Digestive — Circulatory — PtC- spiratory — Factors — Other Diseases — Neuroses — Spinal — Sympathetic — Cerebral — Intoxicants — Immediate Factors — Vaso-Motor — Vascular — Nutritional — Hughlings-Jackson's Scheme of Factors — Conclusions . . . . . . 49s Appendix A — Hypnotism 529 Appendix B — Psycho-Physics 53.> MENTAL PHYSIOLOGY. INTRODUCTION. The Value of Hypotheses — Boundaries of our Subject — Psychology as a Science — The Relation of Psycho-physiology to the General Study of Mind — Mind Ptclative or Absolute ? — Definition of ^lental Phy- siology, Mental Pathology, Physiological Psychology-^rKelations of Mind to Body — Empirical Psychology — Speculative Psychology — Spiritual Theories— Occasionalists — Theory of Pre-established Harmony — Animists — Associationists — Dualism — Monism — Automatism — Material Monadism. In a system of philosophy every affirmation is liable to have its truth determined by a variety of tests. These tests must not only be in accordance with our manifold conditions of knowledge, but they must also be proportionately varied. The student would do well to proceed according to the admir- able advice of Goethe: — "Let the inquirer consider himself as one summoned to sit on a jury. His part is merely to see ho\\' far the indictment is borne out b}^ the evidence." Truth and distinctness of object are of primaiy importance. The multi- tude of facts at our disposal must be carefully sifted. We must discriminate between the essential and the accessor}-, the important and the insignificant, and when all the arguments in our scientific investigation are exhausted, Ave must not. by the construction of hypothetical fables, falsify many exist- ing truths by fictions of the imagination. In the domain of psychology some inquirers search for novelty rather than truth, " 1 2 INTRODUCTION. and, with the pretence of solving doubts, entertain us with hypotheses which are not only fanciful but absurd.* It is incumbent upon us, therefore, as a duty which we owe to science, to be most scrupulous and cautious in stating our individual opinions. Rather let us remain in a condition of uncertainty than propound doctrines which not only falsify existing truths, but even block the way to further research. If we look at the boundaries of our subject, on the one side we have the domains of metaphysics and ethics, whilst on the other, that of the human organism as viewed by the physiolo- gist. We must endeavour to confine ourselves more particu- larly to our own portion of the study of philosophy, and with regard to the special requirements of the physician, abstract from the study of a rational or empirical psychology, only so much as is essential to our purpose. In speculative psychology little or no account is taken of the relations of the mind and body ; the mind is regarded as a conscious being that perceives, thinks, imagines, remembers, feels, and wills ; and in regard to the infinite variety of relations that exists between the mind and the varied functions of the brain, no attempt is made to reduce them under general laws of cause and effect. The attempt to reduce them under such laws brings us to an empirical psychology, or method of thought resembling the natural sciences, and of which psychology and physiology form, of course, the component parts. The position of our own particular sciences M'ould be as follows : — (1) Physiology. (a) Descriptive. (h) Experimental, (c) Speculative. (2) Psychology. (a) Descriptive. (Ij) Experimental. (c) Specvilative. * Those hypotheses which make the results of physiology involve sub- jective data, and thereby raise metaphysical questions as to the substantive or dynamic nature of mind, must be carefully distinguished from what we can with fairness accept as postulates pertaining to the departments of physiology and psychology. PSYCHO-PHYSIOLOGY AND STUDY OF MIND. 3 The relation of physiological psychology to the general study of mind is shown in the following diagram by Baldwin * : — Psychology Empirical (Inductive) Rational (Deductive) Descriptive (Analytic) Experimental I I Internal External External Internal Cause to effect Cause to effect Hypnotism Dreams Insanity Physiological Mental pathology. I Neuro-psychology Psycho-physics Psychometry. In our account of the relation of psychology to physiology we are absolutely unable to avoid some metaphysical questions ; for, any discussion upon the nature of the mind involves a rational or deductive etement, as much as does also any dis- cussion upon the laltimate nature of the physical elements of the brain. The attempt to analyse physiological data has resulted hitherto in vague conceptions as to inter-atomic motions, and we are taught to imagine oscillatory motion of the atoms of the substances that combine. f kSimilarly, the attempt to analyse psychological data has involved vague conceptions as to inter- psychical motions, and we are taught to imagine that ideas derive their component parts from this or that structural equivalent. How far these hypotheses are supported we shall make it our particular object to inquire, and in our employment of the term " conception " (as applied to such hypotheses) we do not mean thereby that we are able to form a definite picture of what takes place. We use the term in its widest sense, and failure to conceive many of the accepted hypotheses, must be taken as failure to conceive how the requirements of one series of events are met by the events of the other series. In the study of medicine there is a preponderance of * Baldwin, " Handbook of Psychology," p. 31. t Gower, "Dynamics of Life,' p. 10. 4 INTRODUCTION. the somatic element, and little or no regard is paid to the psychical element. According to Hartmann the reason of this neglect is to be found in the fact, that philosophers by profession are not necessarily^ phj^siologists, and, on the other hand, that physiologists are seldom enough of philosophers to handle their subject successfully. In the following pages everything that can tend to effect this union of characters for medical purposes is part of our object. Later we shall see that there are two ways of treating the subject of our investigation — 1st, The analji^ical, A\diich induces the particular from the unity of the scientific idea. 2ndly, The synthetical, which takes particulars as the starting point, and aims at reaching scientific iinity. The question may be asked : Is there a science of psycho- logy ? Our reply must depend upon the meaning in its intension of the word psychology. If it implies a science which deals with mental phenomena as thej^ exist, implying also that the Inental phenomena have physical correlatives, but, at the same time, taking no account of their possible explanation, then our answer would be in the affirmative, and our position would be as secure as that of any other science. Should, however, we restrict our meaning so as to regard the mind as absolute, then we pass from the region of science and implj^ the existence of an entity about which we can only speculate. Unfortunately, the boundaries of mental physiology extend into two spheres. In the one we have conflicting philosophical doctrines, many of ^^'hich, however, may, with advantage, be consigned to oblivion ; whilst, in the other we have that which is empirical, and even more full of conflicting and often superfluous opinions. In the former department the knowledge and examination of some of the philosophical doctrines are, to a great extent, indispensable to us ; whilst in the latter our knowledge is so incomplete that, in order to attain to some degree of precision and clearness, we cannot consider a knowledge of previous opinions super- fluous. If we regard our science, however, as an empirical one. we may with great advantage be allowed to be ignorant of what is useless; and we do not feel bound to transmit all that is believed to have been known. Every system of philosophy is subject to modifications, and, moreover, within limits, will eternally be so. To recognise, IS MIND KELATIVE OR ABSOLUTE? 5 and to be conscious of these limits, is another important part of our task. By the frank recognition of what cannot be known, much time is spared, and much error avoided, and it is only when we are sufficiently clear about the impossibility of ex- plaining many things that we shall be able to avoid vain attempts to estimate or elucidate phenomena, the explanation of which is unknowable for us, and hopelessly beyond our power. In order that we may have a firm foundation and a definite terminology, we must take every step with security, and in so doing we may be able to make some advance in our knowledge of the physiology of mental operations. We shall, therefore, after making an attempt to determine the facts and notions from which we have to proceed, begin with the most simple operations and gradually advance to the more complex. Are we to regard the term " mind " as relative or absolute ? If we are to regard it as relative in meaning, it would denote an object \vhich cannot be thought of without reference to some other object, or as part of a larger whole — i.e., just as the term "father" cannot be thought of but in relation to "child." If this be our position, the terin mind cannot be thought of apart from body, and we are compelled to view " mind " as relative, and "body" as its correlative. Such a distinction is no doubt convenient from a logical point of view, but from a scientific point of view it is somewhat different — i.e., the terms tree, sun, earth may be used as absolute terms in logic (i.e., having no apparent relation to anything else), but in science it would be im- possible to prove their absolute independence. From a scientific standpoint, therefore, we are not justified in regarding mind as absolute, but, as with eveiy other phenomenon of nature, relative. If we accept the term " mind " as relative, however, we do not thereby extend its connotation so far as to imply a causal relation, or even a possible explanation of its correlation. In fact, we must define the term " mind" as relative only so far as we appreciate it in its relation to the body, without in any way implying an explanation of the nature of the relation. As the naturalist knows and applies electro-magnetism in its relations, without comprehending its essence; as the astronomer calculates 6 INTRODUCTION. the movements of the planets, without knowing their absolute relativity: so we can duly appreciate spirit and matter in their relations to each other as body and mind, without being able to explain their actual nature or their deepest relations. Let us now, therefore, understand what is meant by mental physiology. As defined by Hack Tuke,* mental physiology is one division of the great department of physiology. It seeks to discover the bodily organisation with which mental operations are connected. Seeing that the brain is admitted to be the organ of mind, it endeavours to trace their correlations in detail. Unconscious no less than conscious mind falls within its range. The student of mental physiology makes the func- tions of the nervous system his especial object of study, employing for this end all the objects within his reach. He endeavours to discover the laws by which mental operations are governed, and to classify their phenomena ; but he is not con- cerned with speculative metaph^^sics in the usual sense of the term. Mental physiology, however, embraces such modern psy- chological methods of research, as are instituted to determine the relation between the action of external stimuli on the sensory end organs, and the resulting sensation or motion, as well as the reaction time of mental phenomena generally. Ladd defines the expression "physiological psychology" as the science of the phenomena of human consciousness in their relations to the structure and the functions of a nervous system. Carpenter, in his " Mental Phj^siology," has gone a step further, and, b}^ the consideration of mental pathology, has attempted to throw additional light upon the subject. The term "mental pathology" requires some explana- tion. Putting aside for the moment the question of dependence of the mind upon the brain, we are compelled to admit that, just as we are ignorant as to the manner in which physical states cause mental states, so are we absolutely without any knowledge as to the methods hj which morbid physical factors give rise to morbid psj^chical events. By this we mean, that any complete explanation of the ultimate causal connection bet-ween the morbid material factors and the morbid mental manifestations is impossible for us. Therefore, we must of " Dictionary of Psychological Medicine," p. 804. DEFINITION OF MENTAL PATHOLOGY. 7 necessity view the patholog}" of a mental state from a psy- chical, as well as from a physical, standpoint — i.e., until we can associate the simplest mental fact with its corresponding phj^sical fact, we cannot hope to solve in physical terms the most simple morbid train of thought as seen in the insane. Mental pathology must, accordingly, be viewed froili two sides — namelj", its ps^^chological, and its physiological side ; and our hope is that we may bring the two series of phenomena, as it were, "face to face," without in any way rendering our position insecure by unnecessary hypotheses as to ultimate cause and effect. The student will now recognise ho\\' limited must be our explanation of mental and physiological facts, and that no amount of accurac}' in detail, or any mere enumeration of a series of phenomena, will explain the nature of another series. In pursuing these inquiries, much difficulty will be experienced in our efforts to " unlearn the errors of the crowd, and the pre- tended wisdom of the schools." Scientific statements, with the sanction of scholastic authority, will prove more dangerous to us than controversial discussions on points purely speculative, and in this relation we must appreciate that — until the proximal causal connection between the world of immaterial and material things is explained — when we depart from the consideration of the facts contained within each, and attempt to speculate upon their nature and cause, we wander at once from the path of scientific inquiry' into that of conjecture, and find ourselves contemplating problems, the truths of which are far beyond our reach. The psychologist and physiologist, each from his o^^'n point of view, may equally be justified in saying such specula- tions ought to be entirely banished from their practical investiga- tions, as not only useless and improbable, but as beyond the reach of their faculties, and, therefore, contrar}'^ to the first- principles of scientific investigation. Our own object, I appre- hend, should be simply to investigate the facts in regard to both mind and brain, and not so to misconceive the first prin- ciples of scientific inquiry as to attempt to construct a philosophy of cause and effect by unsound reasoning and logical absurdities. Of all the imj)ortant principles which are commonly called 8 INTRODUCTION. first truths, the most important to iis is to be found in the ansM^er to the question — "What is life?" A rigid definition of life is impossible. We can only view it on the physical side as being simply a tendency exhibited by certain forms of matter, under certain conditions, to pass through a series of changes in a more or less definite and determinate sequence. All definitions of the phenomenon of life are objectionable, and really mean nothing, inasmuch as they are merely enumerations of the phenomena observed, which indicate the existence of that called life. Were we in a position to answer this question satisfactorily, we might then ask. What is mind ? and how can we explain it ? Our answer is, and must ever be. We don't know. And we never can know. In the history of psychology many attempts have been made to solve this problem. One source of fallacy has arisen, not infrec|uently in the actual reasonings of so-called materialists and spiritualists, whereby, in disproving a doctrine, they have fallen into the sophism of assuming the opposite doctrine to be true, thus making the truthfulness of that doctrine dependent upon the unsoundness of that which is opposed to it. In the light of existing knowledge, therefoi'e, we are compelled to approach the subject by two roads. Physiologists and psychologists must perforce study their respective sub- jects, to a certain extent, apart and in their entireties. The fundamental disparity of physical and psychical activities renders the explanation of the one impossible from the study of the other ; and, moreover, at the very outset, we must inllj recognise, that in naming the nervous accompaniments, or physical conditions of mental phenomena, we do not fully account for them, no matter how faithfully detailed the description of such accompaniments may be. Such mere enumerations do not in the least degree aid us in the solution of their causal connections. This does not, however, interfere with the pri- mary conception that there is concomitance and co-variation of physical and psychical processes. Hitherto, the attempts to prove causal relations between psychical events and phj'sical processes have proved useless. The two are plainly connected in time, but our recognition that the two conditions have time associations in no way explains their ultimate or causal con- DEFINITION (3F MENTAL PATHOLOGY. 9 nection. Professor James says,* " The ultimate of ultimate problems, in the study of the relations of thought and l:)rain, is, to understand why and how such disparate things are con- nected at all. But before that problem is solved, it must at least be ascertained and reduced to the lo\\'est terms as to which mental fact and which cerebral fact are, so to speak, in immediate juxtaposition. We must find the minimal mental fact whose being reposes directly on a brain fact ; and we must similarly find the minimal brain-event which will have a mental counterpart at all. Between the mental and the physical minima thus found there will be an immediate rela- tion, the expression of which, if we had it, would be the elementary psycho-physic law." A statement of all the relations which exist between mental phenomena and the changes with respect to chemical constitu- tion, structural form, and physiological function, which take place in the molecules of the cerebral areas, would constitute the- foiTndation for an empirical science of the connection of body and mind. lyndallf says, "There is no fusion possible between the two classes of facts." AVe can trace the development of a nervous system, and correlate with it the parallel phenomena of sensation and thought ; we see with undoubting certainty that they go hand in hand, but we cannot comprehend the connection between them." Again. | he says, " The passage from the physics of the brain to the corresponding facts of consciousness is unthinkable. Granted that a definite thought and a definite molecular action in the brain occur simulta- neously, we do not possess the intellectual organ, nor apparently any rudiment of the organ, which would enable us to pass, by a process of reasoning, from one to the other." Spencer § holds that a unit of feeling has nothing in common with a unit of motion, and that this becomes more than ever manifest when we bring the two into juxtaposition. Let us now glance at the so-called science of physio- logical psychology which constitutes a part of our empirical * •' Principles of Psychology,"' p. 177. T " Nature,"' August 20, 1874, p. 318. X " Fragments of Science,"' 5th edit., p. 420. § " Principles of Psychology," p. 62. 10 INTRODUCTION. psychology. (1) There are, without doubt, certam psychical phenomena or processes that do not occur independently of certain material phenomena and processes, and which are not alien to the latter, but stand in obvious correlation to them, and vice versa ; and (2) there are psychical processes for which no corresponding physiological processes in the brain are con- ceivable, and we are not j^et in a position to assert that material processes do accompany all psychical processes. Physiological psychology deals exclusively with those psychical phenomena to which concomitant physiological processes in the brain correspond, and is chiefly concerned M'ith variations ^^dlich occur in the quality, intensity, combination, and time- order of the states of consciousness, as dependent upon the varying amounts and order of different modes of phj^sical energy as applied to the end organs of sense.* According to Ladd, physiological psychology is in a fair way to make out, that all psychical activity has, as its concomitant, some mode of physical action, and that mental life more particularly coin- cides with the central portion of the nervous series ; namely, the cerebral process. " Mental life is thus a chain of events parallel to another chain of phj^sical events." The question as to the mental dependence or causal connections of these two series of phenomena has not been solved by scientific methods. We are not in a position to regard the psychical action as the result of sensory stimulation in the first stage, nor as the result of the muscular action in the final stage. Physiologists look upon the series of nervous processes as complete and satisfactory in themselves, having consciousness as their accompaniment or collateral result. Psychologists, on the other hand, uphold the view that many psychical processes cannot be demonstrated as having any physical correlative. Spencer takes mind in the midst of all its concrete relations, and says that the essence of mental life and bodily life are one — namely, the adjustment of inner to outer relations. "The mind inhabits an environment which acts on it, and on which it in turn reacts." Physiologists say, " No psychosis without neurosis " — and it is to the study of the exact relation between the dispositions of the architecture of the cerebral substance^ * Ladd, " Physiological Psychology," p. 633. DEFINITION OF PHYSIOLOGICAL PSYCHOLOGY. 11 aided hy physiological experiments and pathological anatomy, that they hope to become more closely acquainted with the principles upon which this mechanism operates — infer func- tion from structvire, regarding the former as the natural out- come of the latter. In reply to this, Professor James points out that, no matter how numerous and delicately differentiated the train of ideas may be, the train of brain events that runs alongside of it must, in both respects, be exactly its match, and we must postulate a neural machinery that offers a living counterpart for every shading, however fine, of the history of its owner's mind. Whatever degree of complication the latter may reach, the complication of the machinery must be quite as extreme, otherwise we should have to admit that there may be mental events to which no brain events correspond. In accepting the theory of imiclio-physical parallelism, we limit the parallelism to mental life, and the activities of the nerve structure of the organic world. We stop at conjectures, which make mind co-extensive with matter, or which make the parallelism absolute, and assign a subjective side to every atom of cosmic dust. We accept as fundamental, the psycho-physical parallelism, the conservation of energy, the indispensability of introspection, and the utilit}^ of the experi- mental method. How far Ave are warranted in assuming- that the entire qualitative content of consciousness is explicable by the association of sensational elements in conformity with physical laws, we shall venture to inquire. We shall avoid following the psychology that fails to recognise the limitation on the study of mind through matter. The application of the parallelism beyond consciousness belongs to metaphysics and epistemology. We merely postulate the co-existence in time, between the events, the physical and mental series. The tendency of many authors, who seek to prove a parallelism in the evolution of life and mind, is to start the parallelism somewhere only when the biological evolution has attained a certain degree of comjilexit}- ; others, again, attempt to drop the parallelism AA-hen a further degree of complexity has been attained ; they then assign to the mind or bod}' powers which on analysis are unAA'arrantable. If the paral- lelism is to be complete, the phenomena of human life and 12 INTRODUCTION. mind must be traced as correlatives from the very beginning and to the very end. There is no period in the evolution of the organism when mind can be said to appear. From time to time, v^^e shall have occasion to criticise the principles of physiologists in regard to the complexity of neural action, and we shall see that mere complexity of arrangement in the refined mechanism of the brain may serve to demonstrate the ways and means of physiological activities ; but these principles afford us no solution of any of the sub- jective attributes of the mind. We grant the existence of dynamical functions, and we are forced to accept many of the hypotheses advanced to elucidate the occurrence of activities in a rational and orderly sequence ; but no arguments hitherto addiiced will allow us to grant that consciousness is a mere inert spectator of physiological processes. We shall have occasion to criticise the general law that " no mental modification ever occurs which is not accompanied or followed by a bodily change," and we shall take account, not only of the conditions antecedent to mental states, but also of the resultant consecjuences of such mental states — i.e., a certain amount of brain physiology must be presupposed or included in psychology. Physiological psychology is defined as " the science which investigates the correlations that exist between the structure and functions of the human nervous mechanism and the phenomena of consciousness, and which derives therefrom conclusions as to the laws and nature of the mind."* We do not, however, infer that the science, as such, seeks as its object to form conclusions as to the nature of one series of phenomena from the study of those of the other — i.e., the study of the laws which govern matter and their concomitmice with mental acts, would only form part of the basis of the study of mind. Our task is now one of extreme difficulty. Let us compare the inanimate cerebral mass in all its structural com- plexity, to the earth with its geological strata and substrata, and for illustration let us surround them with the mind and the atmosphere respectively. Putting aside the cjuestion of their several causal connections and mutual dependence, we * Ladd, " Physiological Psycliology," p. 4. DEFINITION OF PHYSIOLOGICAL PSYCHOLOGY. 13 propose to elucidate the phenomena of the one by the study of the other. Geologists divide the globe into a certain number of geographical regions or " zoological provinces," each of which is characterised by the occurrence in it of certain asso- ciated forms of animal life. In the vertical or bathymetrical distribution of animals we find that, as a rule, each species has its own definite bathymetrical zone, and it is by generalising from a large number of such facts that we are able to lay do\\'n and name certain definite zones. In addition, geologists and zoologists have to investigate the conditions and nature of animal life during past epochs in the history of the world. They are enabled to estimate, with a certain degree of accuracy, how one animal differs from another, morphologically in the fundamental points of its structure, and thereby infer a physiological specialisation of function ■ from the grade of its organisation, or they are able to formulate doctrines of evolu- tion. Similarly the physiologist maj^ stud}^ the complex surface of the brain, differentiating it into functional provinces, each having its own definite zone, and he may infer a special- isation of function from the distributive development of its component parts. Further, on the one hand, the geologist may estimate ■\^'ith accuracy the correlation of certain types of structure with certain climatic or atmospheric phenomena ; whilst the physiologist attributes functions to certain nervous elements having mental phenomena as their correlatives. Is it possible, however, for the former to fully estimate the laws which govern the atmosphere, solely from the studj^ of the earth's crust, and the mere estimation of concomitant atmo- spheric conditions ? or, is it possible for the latter to estimate the nature of mind, and the laws which govern it, solel}^ from the study of the structure of the nervous mechanism, and the enumeration of collateral series of mental activities ? Until we are able to formulate one general law as to cause and effect between material and immaterial phenomena we must of necessity approach the subject from its two totally different aspects, and the closest attention to psjxhical lairs (con- sidered as such) is as indispensable to our success as the minutest investigation of structural detail. Any real advance is to be made only b}" the study of the laws of both series- 14 INTRODUCTION. of events. Physical analysis has taught tis nothing as yet about subjective states ; whilst subjective analysis has been just as futile with regard to objective states. Physiological psychology has as its ultimate task the apposition, and com- parison of objective and subjective states. It seeks to discover the laws which bind together processes, which in their essence have no knowable commiTnity with each other. A material bond may be conceived in connection with matter, a non-material in connection with mind, but the bridge between the two must be constructed of one or the other, or, perchance, as suggested by one eminent writer, a substance intermediate between mind and matter, which partakes of the nature of both without being exclusively either. To this Mercier aptly remarks, " Imagine a thing which is partly an iron bar and partly a smell of paint without being exclusively either ! " The connection is no less real, however, because it is inexplicable, and no one doubts that causal connections do exist although they cannot be explained. If we look at the position, as viewed by Ziehen, all psychical processes for which there is no conceivable corresponding physiological process in the brain are to be ignored. He admits, however, that as a consequence, we do not obtain sufficient knowledge unless, in addition, we investigate certain psychical phenomena as purely psychical, but nevertheless being always aware of the possibility of some concomitant cerebral process. Empirical psychology is, therefore, to be studied under two heads. (1) Psychical processes not contingent, or demonstrably dependent, upon cerebral processes, termed by some trans- cendental psychology. (2) Psychical processes concomitant Avith, or apparently dependent upon, cerebral processes, termed the science of physiological psychology, metrical physiological psychology, or psycho-physics. Later, when we discuss mind and nervous conditions in their several relationships to one another, attention will be given to the various psychological methods of research, and the psychical effects of varying con- ditions of nerve organs will be dealt with in detail. Account will also be taken of the question, as to whether the activity of all parts of the brain is directly concerned with conscious life, or only that of certain of its structures ; or whether the organ SPECULATIVE PSYCHOLOGY. 15 of mind includes other centres as well as brain centres ; and we shall have recourse to the i*esnlts obtained by artificial experi- mentation, by which definite external stimuli have been employed, the subjective effects of which have been objective!}' noted and registered ; and to the pathological aspects of cerebral diseases having mental correlations. Before entering, however, upon the cpiestions as to the interaction of mind and brain, let us review, briefly, some of the hypotheses Avhich have been derived from speculation upon the philosophical, ethical, and religious aspects of their causal connections. The spiritual theor^^ holds, that the mind is a soul distinct in its nature and mode of activity from material things, and, in accordance with the Cartesian philosophy, the body and soul cannot act upon each other because of the essential difference between the two. By the Occasionalists, body and mind are regarded as having no causal relations — i.e., neither really acts on the other. An event of a definite kind happens in the bodily realm, a corresponding event of its own definite kind happens in the domain of consciousness, and vice versa. They are connected causally through a common ground by God. A further development is to be found in the theory of p'e-estahlished harmony, by which God has eternally pre- destined the entire succession of events in the world, down to every minutest detail. * Animists (animo, I give life to) adopt the Stahlian theory of the soul, and regard it as the vital principle. The term " animism " is now, however, ordinarily used to express the general doctrine of spiritual agency in the operations of nature, f Mercier ^ regards the whole doctrine of so-called spiritualism as a survival, in slightly altered form, of the old superstition of demoniacal possession. Commenting upon such terms and phrases as " psychomotor-centres," " ideo- motor processes," " sensation changing into movement," he says, " Commonest and worst of all is the prevalent opinion, expressed or implied, that above the material part of the brain, somewhere in the skull cavity, there sits a little deity who * Ladd, " Physiological Psychology," p. 650. t Tuke, "Dictionary of Psych. Med.,"' p. 94. X " Sanity and Insanity,'' p. 48. 16 INTRODUCTION. sends liis orders out this waj^ and that, and by some niysterions but easy process produces all the movements of the body. He plays on the centres of the brain as a performer plays on the keji'-board of the piano, and produces just such combinations and successions of movements as he pleases, imtrammelled by natural laws. This being is variously named, according to the predilections of the writer, some calling him the Will, others the Ego, others again Conscious Personality, others the Soul ; while yet others split him up into several beings, and with the natural tendenc}^ of anthropomorphism, not only let them make common cause against their unfortunate servant — the bod}' — but set them fighting among themselves." The effort to evade the question of the freedom of the will arises, in most instances, from the absence of any definite concept of the nature of the subject under debate. The dilemma is, to a certain extent, extra-psj^chological.* Psycho- logy, however, can deal with the problem through analysis of the activity and selective character of choice. Were we able to eliminate motivation from our consideration, then, also, might we regard determination as external and not internal. The assumption that mechanical law or determination b}" extraneous influences is the onl}^ conceivable type of orderlj'- activity is natural ; the fact that, as yet, we fail to conceive of any universal law of choice, is no argument that the former ass^imp- tion is the only solution. We find ourselves at issue with the psychologists, who regard ideo-motor action as the type of all volition, and we fail to reduce all choice to immediacy Mathout deliberation. Those psychologists who deny their own agencies in volition are fatalists, and base their conclusions upon false ideas of the relation between mechanical causation and self- determined activity. The purpose of modern phj^siological psychology is to try to demonstrate the relation of the mind to the brain, and, at the hands of some inquirers, the problem is solved as physiological fatalism. Others conceive themselves as mere spectators of effects determined by whatever their absolute may chance to be. The logical import of the controversies would lead us to conclude that self-determination cannot be * Prof. A.T. Ormoncl; "Freedom and Psycho-Genesis" — "Psycli. Review," May, 1894. ASSOCIATIONISTS. 17 reduced to mechanical laws. The various laws which prede- termine (through heredit}' and environment) the physiological and psychological individuality give no solution of the self- determination of choice.* The association school, of Herbart in Gernian}^ and of Hume, Mills, and Bain, in England, has constructed a psj^choiogy in which the soul or e(jo of the individual is no longer viewed as the pre-existing source of the representations, but rather as their last and most complicated result. Its disciples endeavour to show how such things as perceptions, emotions, volitions, etc., may be engendered in an individual by the cohesions, repulsions, and forms of succession of discrete " ideas " and without the aid of a soul. Materialists seek to reduce organic life to the effect of mechanical arrangements, and they regard mind as an effluence from, or product of, the activitj^ of this material substratum. They regard the constitu- tion and activities of molecules, as determined by the inter- action of the ultimate atoms which comprise them, under the law of the conservation and correlation of physical energy. Whenever a certain constitution and consequent modes of activity are brought about in the molecules, under this general law, then it is of their own comprehensible nature to exhibit, in addition to the various forms of motion known as nerve commotion, another class of co-existing phenomena, called mental phenomena. f Later, we shall see that the arguments of even the most advanced materialists, who regard thought as the effect, or result of cerebral movement, are insufficient to afford the slightest explanation of any subjective mental state. " The whole circle of consciousness is," says Baldwin, " an added fact to that of movement." Manj^ of the materialists ridicule the idea of an immaterial mind acting upon a material bod}- ; but t\\Qy do not hesitate to affirm that a material body can act on an immaterial mind. If we look more closely at the physical laws of " correlation of energy " we at once see that they afford us no help in the * See Baldwin, " Handbook of Psycliologj"-," vol. ii. pp. 352—376 ; Hodgson, "Free Will : an Analysis " — " Mind," April, 1891. t Ladd, "Physiological Psychology," p. 654. . 2 18 INTRODUCTION. solution of the causal relations of mind and matter ; for we must classify all forms of physical energy according to their quality, nature, degree, and amount of their motion; and we are imable to demonstrate or define states of consciousness in the same manner as modes or amounts of motion, and, in conse- quence, we cannot attempt a strict mathematical correlation between physical motion and such states of consciousness. In the endeavour to bridge the gap between the molecitlar energy of organic material and that of the mode of activity of mind, the various mathematical formulge, under the laws of conserva- tion and correlation of energy, have been unwarrantably extended in their application. Further, as Ladd puts it, " Psychology teaches that the world of mental objects — ^the only world of immediate experiences — is built up by the synthetic activity of mind ; it calls upon the physicist to remember that he has no other way of reaching these atoms and of discovering the laws of their relations except by the path of mental activity ; and it reminds him that this activity cannot escape the control of mental law." In addition to the spiritualistic theory that so-called inani- mate objects are vitalised by a principle which involves purpose or end, and the materialistic view of mind as the result of an activity of complex physical forces, we have combinations which aim at giving equal substantive reality and power, both to the spiritual and to the material. In the theory of dualism we find a combination of the two substances, which are viewed as existing side by side, but as exerting no influence the one on the other, the appearance of interaction being due to Divine arrangement. The molecules of the brain act, dynamically, according to their own constitution and modes of arrangement. The mind, on the other hand, as a real entity of another order, has the various states of con- sciousness as its acts ; and, according to the more recent doctrines of dualism, the two series of phenomena are cor- related. The nature of the correlation is unknown, but it is assumed that the mind and brain act in view of each other: the action of the one accounting for the action of the other in some unexplainable and unknowable way. There are three forms of dualism — viz., (1) The metaphysical, which takes account of MONISM. 19 mind and matter ; (2) The philosophical, which takes accoiTnt of the body and the soul ; and (3) The ethical, which concerns itself with good and evil. The desire to connect the two metaphysically has given rise to the doctrine of monism, according to wdiich, one reality has two aspects — i.e., material phenomena and mental phe- nomena are related as two attributes of the same substance. This implies the existence of a substance composed of two utterly incomparable series of phenomena, and to regard this substance in the terms of either series must result necessarily in arguments from the point of view of the spiritualist or the materialist. Wundt recognises three types of theory : Material- ism, Spiritualism, and Animism, the former two each having a dualistic as well as a monistic form. Bain, on the other hand, forms two main groups — viz., Those which adopt two substances, and those which assume but one. Let us now ventiire to look at the subject for oui-selves and ask ourselves, Is there any test whereby we can distinguish between a physical or physiological and an intelligent act? Many hold the view that the pursuance of future ends and the choice of means for their attainment are the mark and criterion of the presence of mentality, and that no actions but such as are done for an end and show a choice of means can be called intelligent. Professor James says : " If Ave find ourselves unable to banish the impression that there is a realm of final piirposes, that we exist for something, we place intelli- gence at the heart of it and have a religion. If, on the contrary, in surveying its irremediable flux,* we can think of the present only as so much mere mechanical sprouting from the past, occurring with no reference to the future, Ave are atheists and materialists." The same author regards con- sciousness as having a causal efficacy, and as being at all times primarily a selecting agency. " Every actually existing con- sciousness seems to be a Jighter for ends, of Avhich many, but for its presence, Avould not be ends at all." In fact, consciousness directs its OAvn machinery. " The spiritualist may believe in the soul if he Avill, the pessimist may say that Nature, in her unfathomable designs, has mixed us of clay and flame, of * " Irremediable flux " is essentially ijessimistic. 20 INTRODUCTION. brain and mind, that the two things hang indubitably together and determine each other's being, but how or why, no mortal Tonaj ever know." Undoubtedly, the nutrition of the tissues, the circulation of the blood, and the secretion of different kinds of fluids are dependent, to a great extent, upon the states of the mind ; and, later, when we come to study the infl.uence of the mind upon the body, we shall find that, if, with sluggish and abnormal digestion, we have mental depression, it is equally true that an attack of melancholia will retard and pervert th& processes of digestion; and, similarl}^, emotional conditions, stress or strain, may impair the cerebral mechanism and its functions. In opposition to these more or less spiritualistic views we have the authority of Professor Huxley, who ^ says that in animals, their volition, if the}^ have any, is an emotion indica- tive of phj^sical changes, and not a cause of such changes. We are, therefore, regarded as conscious automcda. " Our mental conditions are simply the symbols in consciousness of the changes which take place automatically in the organism. In men, as in brutes, there is no proof that any state of conscious- ness is the cause of change in the motion of the matter of the organism." We can also add, it is not possible to form any conception as to how any state of consciousness can affect the cerebral molecules, and, moreover, we never shall be able to surmount or explain this difficulty ; but our inability to explain such action does not negative its possibility. The view, hoM'- ever, that the feeling we call volition is not the cause of a voluntary act, but the symbol of that state of the brain which is the immediate cause of that act, is open to any number of arguments. Professor Clifford states, dogmatically, that the only thing which influences matter is the position or motion of surrounding matter, and " if anyone says the will influences matter, the statement is nonsense." " Were this the case," remarks Professor James, " the mind's history would run along- side the body history of each man, and each point in the one would correspond to, but not react upon, a point in the other," and we agree with hin; that, " in the present state of psy- chology^ to urge the automaton theory upon us on purely d iriiori or (/wafi-metaphj^sical grounds is an unwarrantable MATERIAL MONADISM. 21 impertinence." Spiritualists and materialists are free to argne from their respective standpoints ; while we, as unbiased specta- tors, are also free to state that we can as readily imagine an immaterial psychical state influencing a material bodily state, as we can a bodily state affecting a mental state ; and this although the two series of activities have no communit}^ with f^ach other. The material monad theory, or the theory of '' poly- zoism'' or "'multiple monadism," as upheld by Leibnitz, Herbart, and Lotze, is as follows : — " Every brain-cell has its own individual consciousness, which no other cell knows anything about, all individual consciousness being ' ejective ' to each other. There is, however, among the cells one central or pontifical one to which our consciousness is attached. But the events of all the other cells physically influence this arch- cell; and through producing their joint effects on it, these other cells may be said to ' combine.' The arch-cell is, in fact, one of those 'external media,' without which we saw that no fusion or integration of a number of things can occur. The physical modifications of the arch-cell thus form a sequence of results, in the production whereof every other cell has a share, so that, as one might say, every other cell is represented therein. And, similarly, the conscious correlates to these phj'sical modifica- tions form a sequence of thoughts or feelings, each one of which is, as to its substantive being, an integral and uncompounded psychic thing, but each one of which ma}" (in the exercise of the cognitive function) be aware of things — many and compli- cated — in proportion to the number of other cells that have helped to modify the central cell." * We shall have occasion to discuss such theories from the point of view of localisation of mental function, and we shall see that we have no anatomical or physiological data for their support. We have not, as yet, been able to attach such anatomical or functional pre-eminence to any one cell or group of cells in the brain. We do not know the brain laws which determine an immediate correspondence between matter and mind ; nor do we know the psychic laws which determine a correspondence between mind and matter : we can only seek to * James, " Principles of Psychology,'' p. 179. 22 INTEODUCTION. determine the laws wliicii mutually or individuall}' regulate the two totally different series of phenomena, and thus, by bringing them into apposition, endeavour to establish a psycho-phj^sical law which shall embrace the requirements of both series of events. Manjr of the existing psycho-physical formulae are the results of unsafe hypotheses within the domains of ps}^- chology and physiology respectively. The student will find that the blind ends of physiology and psj^chology are covered respectively by anverifiable hypotheses, and that it is with the comparison of these blind ends that he has to do in estimating the ultimate nature and correlation of bodily and menta events. Our ideas of the brain, and of its relation to the mind, are derived mainly from some showy results of modern science ; but the modern scientist too often forgets that processes are no explanation of results. The theorists wdio evolve man from an ape see no likelihood that he will ever become an angel. Under the dogma of their one great law they settle the histor}' of the past, and negative the possibilities of the future. Mate- rialists sa}^ that the mind is derived from, or correlated to, atomic movement, and in order to prove a causal nexus they bring the analogy of the cosmical mechanism to bear upon the cerebral atoms. They seek to prove the existence of a mind correlated to the infinitesimally- minute counterpart of the cosmos ; but there they end. They do not coun- tenance any speculation as to the existence of a universal mind correlated to the infinite system from which the}^ draw their analogy. That our minds have a physical basis, without which their phenomena w^ould not exist for us, is as tr^ie as the statement that life itself has a physical basis, without \\'hich it would not exist for us. Beyond this we cannot go, and the state- ment that mind depends upon the body in no "s^'ay implies an explanation of the causal connection between the two states — i.e., to state that one condition depends upon another is not to explain hoiv it depends. The doctrines of concomitance, i:iaral- lelism, and siinultaneity furnish us with an explicandum and not an explica,tio. Since an expliccdio is impossible, we must devote ourselves with an equal amount of attention to the stud}^ of MATERIAL MON.UJISM. 23 the heterogeneous states of mind and matter ; and, in our endeavour to bring them into apposition, Ave must not venture upon any such explicoAio. Finally, it is happily obvious that our knowledge of the brain and its structures is gradually becoming more extensive. The anatomico-physiological school is striving to provide us with data, vsiih. the aid of which it is hoped we may be able to correlate mental facts. The explanation of the absolute reality of physical and psychical acts must remain outside physiological and psychological theories. The phj^siologist seeks to demonstrate the paths of conduction and dissemination of phj^sical forces.* The psychologist seeks to demonstrate the method by which we think ; whilst, lastlj^, the physiological psychologist seeks to establish some relationship between the two processes, without in any way attempting to throw light upon their ultimate nature or causal origin. * See Batty Take, " On the Insanity of Over-exertion. ' 24 CHAPTER I. Anatomy of Cobtex. Arrangement of Cortical Structures — The Xerve-Cell — Processes of Nerve-Cells — Nerve-Fibres — The Relation between Cells — The Neuroglia, or Connective Tissue Basis Cell Elements — Caudate Fibre-Cells — Stellate Fibre-Cells — Protoplasmic Glia Cells. Physiology of Neeve-celi/. Nutritive Function — Transmission of Nerve Impulses — Excitability and Conductivity — The Functions of Nerves — Negative Variation. ANATOMY OF CORTEX. Before examining w^liether the areas of the cerebral cortex are allied Avith particular functions of the mind, it may be well for us to examine, somewhat carefully, the physical side, so that we may build o^ir conceptions upon the basis of facts known to us. If we are to regard the mind as having its seat in the brain, we must study the material elements of which that seat is composed. Starting with the assumption, justified by scientific observa- tion, that the mind, as perceptive, has its seat within the nervous system, and that of this system the structural elements of the cerebral cortex have the greatest claims to being con- sidered as immediately concerned with the occurrence of mental phenomena, it will be advisable to give some account of what is known as to the microscopic and chemical nature of these brain-elements. To enter into a description of the entire encephalon, with its membranes, vessels, tracts, and subordinate regions, would obviously be out of place here. Neither can we deal thoroughly with the anatomy of the convolutions, our knowledge of which has been so much ARRANGEMENT OF CORTICAL STRUCTURES. 25 advanced by the labours of Gratiolet, Ecker, Turner, Broca, Bevan Lewis, Ramon y Cajal, de Vaillet, de Mosso, Golgi, and others. Comparative investigations, in reference to the struc- tural differences of the various regions of the cortex, have proved of great importance. The progression in complexity of structure, as we ascend the scale of animal organism, is significant, and the comparison of the structure and functions of the brain in different animals leads us to fairly definite conclusions concerning the human brain. We are almost compelled to believe that differentiation of cerebral function implies likewise a structiiral differentiation ; but, as we shall see later, we do not yet understand the design of structural differentiation, as allied with psychical events. With the evolution of certain mental manifestations, we look for a corresponding advance in complexity of arrangement of the material elements, " Thus it is," says Bevan Lewis, " we expect the physiological areas ascertained by Ferrier to exist in the brain of the monkey and other animals to exhibit a structural differentiation characteristic of those parts, and hence helpful in the recognition of analogous regions in other orders. If it can be established that areas whose functional endowments are familiar to us present uniformly specialisecl anatomical features, we may reasonably conclude that other structurally differentiated areas, whose functions are unknown to us at present, nevertheless have each and all of them diverse endowments." In urging the importance of making ourselves acc[uainted with the intimate structure of the cortex, he pays this tribute to physiological experimentation that it alone can lead to conclusive results. "An attempt to delineate the homologous areas of the cortex in the different orders of mammalia by simple inspection Avould (on a priori grounds) only lead to failure ; indeed, errors have already been fre- quently committed with respect thereto. Arrangement of Cortical Structures. — To Eamon y Cajal, Retzius, Golgi, and Dejerine, we are indebted for the latest descriptions of the arrangement of cortical cells. Cajal describes four layers of cells in a typical Rolandic convolution — viz. : (Ij A superficial zone, containing a few small fusiform cells, surrounded by numeroiis neuroglia nuclei ; their long 26 ANATOMY OF CORTEX. axis lies parallel to the plane of the surface, and they give off an apical and a basal process, which arises from the proto- plasmic expansions, and not directly from the body of the cell. These processes never descend into the other layers, but run horizontally or slightly diagonallv for a considerable distance, and in their course give off collateral branches, which form a rich terminal plexus. Collaterals are also sometimes given off hj the axis-cylinder, which breaks up into two or three branches. Cajal also describes numerous polygonal, triangular, and unipolar cells belonging to this layer. (2) The second zone contains a number of small pyramidal cells, with apical processes, which end in tufts in the super- ficial layer. Collaterals are given off from these apical processes, and also from the axis-cylinder process, just as in the superficial layer. The lateral expansions end without anastomosing with similar expansions of other cells. The " broad stripe " of Baillarger corresponds to this plexus. (3) The third zone, or the zone of large pyramidal cells, resembles the second zone, except in the size of the pyramids, which are known as " giant-cells." These giant cells are found chiefly near the vertex, and the plexus formed by the collaterals of their axis-cylinder processes corresponds to the " thin stripe " of Baillarger. (4) The fourth zone, or the zone of poltiyonal cells, con- tains cells which are egg-shaped, spindle-shaped, triangular, or polygonal. The apical processes of these cells do not reach the superficial zone, and the collaterals of the axis-cjdinder process either end in terminal ramifications, or form a plexus round some of the nerve-fibres of the Mdiite medullary sub- stance. In the last three zones, according to Golgi, there are also cells with a short axis-cylinder, and spindle-shajDed cells, which send processes to the superficial (Marinotti) and second zone (Cajal). Bevan Lcm^s has devoted much attention to the study of cortical lamination, and also to the local deviations in the general arrangements of cortical structures. He found that the distinctness of lamination not only varies -with the local peculiarities of structure, but also with morbid states of the cortex, and with the full or empty state of its vessels. The ARRANGEMENT OF CORTICAL STRUCTURES. 27 h a ---5 G— 2'?.^L y.^\.. 4th L Fig. 1. Diagrammatic View of Cekkbral Cortex. a, caudate neuroglia fibre-cell ; b, tangential fibre-system ; c, protoplasmic glia cell ; D, bloo.l- \-essel and perivascular space ; e, cells of ambiguous layer ; /, plexus of nerve-fibres and collaterals; G, terminal arborisation of dendron of pyramidal cell; H, long nerve-hbre ascending from white substance to branch and end freely in lacunar and molecu.ar layers; J, pyramidal cell with neuron and dendrons; K, fusiform nerve-cell of poly- morphic layer, with ascending axis-cylinder ; L. neuron from pyramidal cell givmg oft collaterals: M, neuron from cell of ambiguous layer; o. transitional form between caudate and stellate fibre-cell. 28 ANATOMY OF COllTEX. eight laminar types of cortex, described hj Bevan Lewis as occurring in mammals, are characterised by abrupt transitions from one type to the other ; whereas, in higher mammals, and especially in man, there are no abrupt transitional regions. In the latter, the passage from one form to another is gradual, and, according to Bevan Lewis, this gradual pas- sage is a distinctive element in the evolution of the higher brains. The Nerve-Cell. — Much of our knowledge of the nerve- cell — its structure, functions, and relation to other nerve-cells — has been obtained by Marchi's application of the Wallerian methods, and the method of staining i7itra vitam by methyl blue (Ehrlich). Golgi's method of staining with nitrate of silver, after treatment with chromic acid and its salts, has also yielded most important results. Our knowledge of the paths taken by action currents is mainly attributed to the Gotch and Horsley's physiological methods of investigation by the galvanometer and electrometer. The term " nerve-cell " is now commonly used to denote not only the body of the cell, or the part immediately inclosing the nucleus, but all the processes of the cell. The adoption of the term •'' neuron," in Waldeyer's sense, as denoting the whole nerve-cell and its processes, is liable to cause confusion, and is acknowledged to be undesirable. The significance of the relative variations in size of dif- ferent nerve-cells has given rise to a considerable amount of discussion, more especially by Meynert, Bevan Lewis, Ramon y Cajal, and Hughlings-Jackson. Meynert believes that the relative size of the so-called " giant-cells " may be attributed to the greater depth of the convolutions where they are to be found ; " the apex processes of these cells, therefore, having to traverse a greater distance in their low-lying groups ere they reach the outer layer of the cortex." To this assertion, and to the explanation that the grouping of these cells is due to their being pressed together by the bundles of nerve-fibres passing upwards from the medulla of the gyrus, Bevan Lewis takes exception, and finds a more probable explanation in the age and multiplicity of the surrounding connections of the nerve-cell. THE XEPtVE-CELL. 29 " If we carefully note a section of fresh brain, we find that although the majority of the pyramidal cells steadily enlarge at greater depths,, the ganglionic cell clusters, but a very short remove from the largest pyramidal cells, represent an enormous leap in dimensions." . . . "This we believe to be the case ; we find as a constant accompaniment of increas- ing bulk, much complex relationships with surrounding cell-districts — in other words, the larger the cell the greater the nwinher of its branches. But the older the nerve-cell, the longer time has it had for the estab- lishment of organised relationships around ; and hence it follows that the older cell is also the larger element:'* To another factor — -namely the medullciAed fibre (axis-cylinder process) — considerable importance is also attached : — "The medullated fibre, which arises from the basal extremity of the- great motor cells, traverses uninterruptedly an enormous distance to reach the respective cell groups, which represent in the spinal cord the musculature of the limbs. The distance traversed is very unequal between the lumbar and cervical groups : the cortical centres represent- ing the lower extremities having not only a greater distance through which to discharge their energy, but a far more massive musculature to call into activity, than is the case with the arm centres of the cortex. Again, the cortical centres for the upper extremities not only act through a greater I'ange, but they innervate larger groups of muscles than do the centres for the head and neck — the muscles of ai'ticulation, deglutition, etc. It would, therefore, be natural to presume that the cortical cell groups representing these respective regions would differ considerably in the size of their individual elements. The histology of the motor area fully warrants us in stating this to be the case ; the smallest cells being found at the lower end of the central gyri, and Broca's convolution, and thence increasing rapidly in size upwards towards the centres for the musculature of the limbs." * The stndy of the comparative size of the nerve- cells would, therefore, seem to yield the law that " tJbe [ireater musculature is ■presided over hij the groups oflartjest cells," and this conclusion is in accordance with the suggestions of Hughlings-Jackson and others. Bevan Lewis believes that the relative dimensions of the cells are dependent on (1) range of discharging distance ; (2) size of musculature innervated ; (3) age of nerve- cell ; (4) resulting multiplicity of cell connections. Undoubtedly the size of the nerve-cell often bears a distinct relation to the length of the processes which leave it, and an examination of the bulbar-spinal cells groups, and the larger * Bevan Lewis, " Mental Diseases," p. 107. 30 ANATOMY OF COETEX. projection-cells associated with the part of the cerebral cortex, from which the fibres of the pyramidal tract originate, leads to the same conclusion. The same law also holds good for the ganglion-cells of the retina. Professor Schafer, however, believes that this is not an invariable rule, and he doubts whether it will apply to the visceral and vascular nerves. If we look at the dorso-mesial group of cells (Clarke's column) in the spinal cord and compare the individual cells with those of the anterior horn, we see that there is a great resemblance in form but not in size : the diameters of the former varying from 40 to 90 fjb, whilst in the latter the motor cells measure from 67 to 135 /i. In the lower part of the dorsal region, Clarke's column is best developed, and the cells have a relatively larger size than elsewhere. This region is also characterised by a comparatively smaller development of the cells of the anterior cornu. If we accept Gaskell's view, that the number and size of cells in Clarke's column in any particular region appear to vary as the number of leucenteric fibres derived from that region, and if, as the result of Gaskell's researches, we believe that this column is connected with the visceral nerves, are we not also free to assume that the relative size of the cells falls under the general law? In a similar way, in the medulla oblongata the cells of Clarke's column, which retain the same characters as in the cord, swell out into the nucleus of the vagus, the great leucenteric nerve of the thoracic viscera. The relative size of the nucleus of the nerve-cell is regarded as being of peculiar significance, and here, again, we cannot do better than quote from Bevan Lewis, "who says : — " When, however, we consider the assumed sensory element of the cortex — the minute angular and granule cells — we must not lose sight of a remarkable distinction between them and the assumed motor unit, and that is, the great proportionate preponderance of the nucleus to the cell in the former. That the nucleus does exert some mysterious influence over the nutritive and functional activity of the cell has been long surmised ; and the results of our histological inquiry indicate that nuclear degeneration within the nerve-cell is peculiarly associated with certain states of mental and motorial instability. We have long been accustomed to regard it as related more definitely to the fi;nctional activity of the cell, and less directly related to the nutritive activity of the cell. In other woi'ds, the cell is subject to a constant supply of nutritive plasma, it gradually assumes a state of nutritive instability, PROCESSES OF NERVE-CELLS. 31 and will necessarily discharge its accumulated energy in accordance with the simple law of nutritive rhythm, the resulting stable equili- brium is succeeded by a measurable period ere the potential energising of the cell has once more brought it up to its former state of instability. Were this all that "occurs, the process of storage and liberation of energy would be a simpler rhythmic process than the more compounded rhythm which actually pertains to mental operations. If, hoAvever, we regard the nucleus as affecting the functional activity of the cell, as, in fact, restraining or inhibiting its discharge, as a kind of iynperium in imperio exercising a controlling influence upon the perturbations which reach the cell from sensory surfaces ; then the presence of a healthy nucleus would become an all-important feature in the cell life — a feature of the utmost significance to us in our patho- logical inquiries. The view we have here taken of the significance of the nucleus would lead to the conclusion that when, from its degenera- tion or morbid state, it fails to inhibit the cell, these nerve-elements would be subject to a rapid running down on trivial excitation, and in servile obedience to the law of nutritional rhythm ; in fact, we should here find an explanation of morbid instability, such as, e.g., in motor realms results in convulsive states, and in the substrata of mental operations in varied psychical states and reductions of consciousness. It is these considerations which induce us to regard the dispropor- tionately larger nucleus of these smaller angular elements of the second layer of the cortex as being of some significance. Subject, as such minute cells are, to a rapid accumulation of energy, we might presume that some restraint might be established to prevent their reckless liberation of energy, and hence we believe such restraining capacity to be afforded by the vei'y large nucleus. In the next place, we have every reason for believing that this superficial belt of angular cells is in direct organic connection with the subjacent cells of large size, and that their morbid instability would, therefore, affect these larger units, which, from the small size of their nucleus, would be more subject to the law of nutritional rhythm in their discharge of energy. As indicated by Dr. Ross, and also in the preceding note by Dr. IIughlings-.Jackson, the large cell would present a far smaller area in contact with the nutrient material than the same amount of protoplasm broken up into numerous minute elements ; and hence, such large cells would labour under nutritive disadvantages, would be reservoirs for the slow accumulation and storage of energy, which, when liberated, would again resvilt in a tardy reinstatement of nutritive instability." Processes of Nerve-Cells. — Every nerve-cell lias one or more processes. These processes are of two kinds, termed ''neurons'^ and " dendrons ." '"" '"Neuron" is used to signify those processes which first show themselves in the course of * Schafer, "Brain," 1893, p. 136. 32 ANATOMY OF CORTEX. development of the nerve-cell, and whicli hitherto have usualh^ been styled as the axis-cjdinder or nerve-fibre processes. The term " dendron " is applied to the protoplasmic processes of Deiters, which are regarded as not being so essential, since many cells are entirel)^ destitute of them. The term " neuro- dendron " is used for combined processes, snch as occur in the motor nerve-cells of arthropods. The classification of nerve- cells, according to the number of their processes, is regarded as unsatisfactory ; the terms uni-polar, bi-polar, and multi- polar not distinguishing between the kinds of processes. All processes of nerve-cells are ultimately dendritic, and, almost without exception, the neuron, or nerve-fibre process, although it may have a course of several feet without giving off a branch, finally ends in a terminal arborisation. Schafer gives examples of this fact in the arborisation of the nerve ending in muscles, and in the arborisation of nerve-fibrils in sensory structures, su.ch as the cornea of the eye, and the epidermis of the skin. He also adds that even where a nerve-fibre apparently ends in a simple extremity it can generally be noticed, as in the corpuscles of Pacini, and in the tactile corpuscles of Meissner, that the actual ending of the essential part of the nerve-fibre is really arborescent. There are some nerve-cells which have no dendrons, and others which have many dendrons ; all, however, possess at least one neuron. A primar}^ distinction is therefore made between dendric and adend^ric cells ; and, according to the number of neurons, the cells are classified into those which are mononeuric and those which are i?olyneuric (dineuric, trineuric, etc.), according as we find one, two, or more neurons or axis-cylinder processes emanating from the cell-body or from any of the dendrons. As examples of the mononeuric class, Schafer takes the cells of the anterior horn of the spinal cord, many of the cells of the cerebral cortex, and the large cells of Purkinje of the cerebellum; whilst, as instances of the polyneuric class, he quotes, on the authority of Eamon y Cajal, the superficial cells of the cerebral cortex, and he also refers to his own observations on the nerve-cells of the neuro- muscular sheet of the Aurelia. This classification of nerve- cells, therefore, is based upon the kinds of processes which they possess, and, according to the number of neurons, the number NERVE-FIBRES. 33 of dendrons being considered as of minor importance. For the cell with a long axis-cylinder process the term projection-cell (Fig. 2) is used, to distinguish it from the intermedAanj cell with its relatively short axis-cylinder process. Fig. % PKOJECTION-CliLL OF CEREBRAL CORTEX (DIAGRAMMATIC). dr, dendrons ; n, neuron ; coll., collaterals. (Slightli/ hiodified froin Sclilifer.) Golgi, Avho was the first to describe the relative size of the neurons, regarded those cells with comparatively long neurons as being concerned with the giving out of efferent impressions ; those with relatively short and soon-branching processes as being- sensor}^ or receptive in function. Schiifer employs the term " intermediary cell " to imply that, the cell in question offers an intermediary link between centripetal impressions, which may be brought to a nerve-centre by the neuron of a sensory pro- jection-cell, and centrifugal impressions u'hich pass awa}' from the nerve-centre by the neurons of motor projection-cells. 34 ANATOMY OF COKTEX. Ramon y Cajal lias given the term " collaterals " to the fine branches which are now demonstrated as coming from the neuron. The difference in appearance between the two kinds of processes, when prepared by the Golgi method of staining, is readily detected by an experienced observer. The dendrons Fig. 3. Cell of Ieregulab Pyramidal Type. d, dendrons terminating in feathery arborisations ; n, neuron ; coll., collateral. (After Berkley.) usually have a rough outline, while the neurons are generally smooth. The neurons remain comparatively unchanged in diameter along their course, whereas the dendrons branch repeatedly, and hence gradually diminish in size (Fig. 3). Nerve-Fibres. — Nerve-fibres represent to us a conducting apparatus, and they form a means of connection between the central nervous organs and the peripheral end organs. Of nerve-fibres we have two kinds : (1) non-^nedullated nerve-fibres, and (2) onedullated. Of the non-medullated form, the simplest is that of the 'primitive nerve-fibril, which is very delicate, and is often found exhibiting small varicose swellings in its course. These fibrils form by the splitting up of the axis-cylinder of the nerve-fibre near its termination, as seen in the terminations of the olfactory fibres, in the optic nerve-layer in the retina, in the corneal nerves, and in the terminations in non-striped muscle. Similar fibres are also to be found in the finely divided processes of nerve-cells in the grey matter of the brain and NERVE-FIBEES. 35 spinal cord. A second variety is to be seen in the axial- cylinder process of nerve-cells, in which primitive fibrils are held together in bundles by a slightly granular cement, which gives them a very delicate longitudinal striation and finely granular appearance. These are termed nalied, or simple axial cylinders. Remak has described a third variety in the pale non-medullated fibres which are found in abundance in the sympathetic nervous system. They consist of an axial cylinder which is inclosed by a delicate, structureless, and elastic sheath, corresponding to the sheath of Schwann. Ranvier, however, denies the presence of this sheath, and believes that the nuclei are merely applied to the surface, or slightly embedded in the superficial parts of the fibre, and that they belong in reality to the fibre itself. These differ from medullated fibres, inasmuch as they branch and form an anastomosing network. When acted upon by silver nitrate they never show any crosses. Medullated fibres occur, also, in several forms. In the white and the grey matter of the brain and spinal cord we meet with axis-cylinders, or nerve-fibrils, covered only by a medullary sheath or white substance of tSchwann. These are also called varicose fibres, from the fact that after death they often present varicose swellings due to the accumulation of fluid between the medulla of myelin and the axis-cylinder. They are medullated nerve-fibres without any neurilemma, and they have nodes of Ranvier. The great mass of the cerebro-spinal nerves, how- ever, is largely constituted of medullated fibres having the sheath of Schwann. These fibres are highly refractive, homogeneous, and exhibit a double contour, their margins being dark and well defined if acted upon by reagents. Each fibre consists of (1) Schwann's sheath (neurilemma or primitive sheath), which is thin, clear, and has nuclei in it ; (2) inedullary sheath, or white substance of Schwann, Avhich siTrrounds the axis-cylinder and has been compared to an insulating medium round an electric wire. This substance is cpiite homogeneous, glistening, and refractive. It is of fluid consistence, and this fluid can be squeezed out of the cu-t ends of the fibres in spherical drops. After death this substance shrinks slightly from the sheath and breaks up into droplets, not due to coagiilation, but, according to Toldt, to a process like emulsiflcation, the drops pressing 36 ANATOMY OF CORTEX. against each other. It contains a large amount of lecithin and ^ cerebrin, which swell up to form myelin-like forms in warm water.* It also contains fatty matter, is blackened by osmic acid, ^ and rendered transparent by chloroform, ether, and benzine. The axis-cylioider, which lies in the centre of the nerve and is essential to it, is usnally cylindrical and composed of fibrils united by a cement of semi-fluid consistence. KupjBer de- scribes a fluid — " neuro-plasma " — which lies between the fibres. According to other observers, however, the whole cylinder is inclosed in an elastic sheath, peculiar to itself and composed of neuro-keratin. f To this sheath Klihne has given the term axi-lemma. There are, in addition, certain structural modifi- cations which require notice. The nodes or constrictions of Ranvier occur at regular intervals along a nerve-fibre. At these points of consti"iction the white substance of Schwann is interrupted, so that the sheath lies upon the axis-cylinder. The presence of one or more nuclei in each inter-annular or inter-nodal segment has led to the belief that the whole ' segment is equivalent to one cell. These nodes are regarded ■ as being concerned with the diffusion of plasma through the outer sheath into the axis-cylinder, and the giving off of the decomposition products. Each segment is looked upon as being built up of a series of conical sections, each of which is bevelled at its ends. These bevels are arranged one over the other in an imbricate manner, showing slight intervals between. The oblique lines running across the white substance are termed the incisures of Schmidt or Lantermann. In addition to the nucleated nerve-corpuscles, which are found at intervals under the neurilemma, other nerve-corpuscles or " demilunes " have been described as quite distinct. These latter are stained yellow by safronin, while the ordinary nerve-corpuscles are stained by methj^anilin.^ Ewald and Klihne state that the axis- cylinder, as well as the white substance of Schwann, are covered with an excessively delicate sheath of neuro-heratin, and the two sheaths are connected by numerous transverse and oblique fibrils which permeate the white substance. The nature of the fibrillated appearance of the axis-cylinder, * Landois and Stirling, 3rd edit., p. 528. t Ibid., p. 527. t Ibid., p. 518. NERVE-FIBRES. 37 as seen both in nenrons and clenclrons, is still a matter of conjecture. Max Schultze regards the axis-cylinder as con- sisting of two substances — viz., a bundle of fine fibrils (ultimate fibrillte) which serve as conductors, embedded in a clear sub- stance like protoplasm ; and his observations upon the structure of the non-medullated fibres of the olfactor}^ nerve, and of the axis-cylinder of the ordinary medullated fibres, go to prove an anatomical discontinuity of the fibrils. Schiifer argues that this is further borne out when we trace the ramification of the nerve- fibre at its peripheral extremity; as, for example, in the cornea, and even in the nerve-endings of the motor nerves upon the so- called end plates, where there is to be seen a complete separa- tion of the fibrils which have composed the axis-cylinder, and which end here in the ultimate branchings of the axis-cylinder. The occurrence of varicosities upon the nerve-fibrils is regarded as an additional proof that they are excessively fine-walled tubules filled with fluid. The opposing views of Heitzmann, Leydig, Fromann, and Nansen, are, that the nerve-fibrillse of the axis-cylinder are nothing but a repetition of the reticulum of fibrils, as seen in the protoplasm of all nerve- cells; the reticulum haviiag, in this case, been drawn out to such an extent that its meshes have become extremely elongated, and its fibrils, to all appearance, parallel and dis- tinct.* Nansen believes that the apparent fibrils are really the optical longitudinal sections of sheaths or septa of spongio- plasm, which subdivide the fibre into tubes filled with hyalo- plasm, which forms the true conducting material of the nerve- fibre. Engelmann f agrees that the fibrils appear to be distinct, and are never seen to anastomose or form a plexus of fibrils. He does not see, however, how these subdivisions of the axis- cylinder can fulfil any separate function as the conductors of nervous impulses, on account of the closeness of their contact, and the smallness of their number, as compared Avith that of the fibrils into which the fibre breaks up at its peripheral termination. ^ From the experiments of Engelmann, by treat- ing the axis-cylinders with nitrate of silver, the question as to * Schafer, op. cit., p. 144. t " Pfliiger's Archiv.," xxii. p. 26. :j: Ladd, "Physiolog. Psych.," p. 40. 38 AXATOMY OF CORTEX. the continuit}' of the axis-cylinder through the annular con- strictions is by no means settled. The fact that the axis- cylinders, as a rule, when treated in this Avay, were broken off at the annular constrictions does not disprove their discon- tinuity, and possibly there may be exceedingly minute hour- glass constrictions at these nodes. These fibres are regarded as composed of a number of annular segments cemented together — each separate fibril placed exactly end to end with its fellow in the adjoining segments — and possibly such an arrangement Avould accord with the theor}^ which regards the segments as elongated and developed nerve-cells. Bevan Lewis regards the question of the homogeneity or, so to speak, of the fibrillated constitution of the axis-cylinder as of fundamental importance, and if we are to look upon such fibrils as isolated tracts of conduction throughout their length, the nerve-fibre n/ and the cell itself have a far different significance.* He points out that visible continuity of the fibrillse is not essential. More or less fusion may occur throughout the length of the fibre ; and the splitting up into fibrillse may only be observed at the centric and peripheric terminations as an indication of the fibrillar constitution of the axis-cylinder and its lines of molecular disturbances. The significance of Fromami's lines is unknown. These lines are to be seen as transverse markings when the axis-cylinder is treated with nitrate of silver. The silver solution seems to penetrate at the nodes, where it stains the cement substance and also part of the axis-cylinder, giving the characteristic striation. The Relation between Cells. — The relation which nerve-cells bear to one another is important though still some- A^'hat doubtful. Of late, however, much valuable work has been done in this direction, and much evidence has been accumu- lated to show that — (1) there never is direct union of nerve-cells b}^ distinct and comparatively coarse fibres ; (2) there is no union of nerve-cells by means of the ramifications of the fine dendrons, which formerl}^ were supposed to pervade the whole grey matter of the nervous system as a fine fibrillar net-A^'^ork ; (3) every nerve-cell, with all its processes, is a distinct and isolated anatomical unit.f Schafer ^believes that, with great * Op. cit., p. 92. t Schafer, op. cit., p. 147. THE RELATION BETWEEN CELLS. 39 probability, the only connection of one nerve-cell with another is a physiological one, and that it takes place by the adjunction of the arborised process or processes of one nerve-cell, either with the cell-body of another cell, as in the cerebellar cortex, or by the adjunction and interlacement of the arborised processes of one nerve-cell with similar arborised processes of other cells, as in the olfactory glomeruli. In fact, ^ve may regard the basis of the grey matter of the nervous system — the granular-looking substance in which the nerve-cells are embedded — as an ex- \ tremely fine interlacement of ramified processes, not only of the ^ nerve-cells which actually lie in that particular grey matter, but also of nerve-cells Avhich lie in other parts of the nerve- centres, or even in the peripheral parts of the nervous system, and which, on arriving at the grey matter, break up into a fine arborescence of nerve-fibrils. * The iieuroglia or connective basis is, according to Bevan Lewis, composed of a structureless or finely molecular hasis-suhstance, and connective cell and fibre nettcorhs, which act as a supporting and protective material, and differ in special qualities in different regions. In the spinal cord the binding material is in the form of large-sized nucleated cells, with numerous lengthened ramifying processes, together with a plexus of fine fibrils ; whilst a structureless or very finely granular material is found here but sparingly. Nearer the periphery of the cord this connective sheath becomes more fibrillar. In the grey matter of the cord, and in the grey matter of the cortex, the molecular basis preponderates over the fibrillar elements of the neuroglia ; whilst in the medulla of the brain the amount of connective-fibre element exceeds that of the molecular element. In affirming that this basis- substance (Punhtsubsianz, of Leydig), is finely molecular and structureless, Bevan Lewis hardly, perhaps, pays sufficient triljute to the numerous observations which have accumulated since the employment of the methods of Ehrlich and Golgi. By these methods the so-called PuuJdsubstanz is shown to be made up of the ramifications of fibres derived from the neuro- dendrons of the large motor nerve-cells. The Punktsubstanz is now generally regarded as being made up of the ramified processes and their somewhat varicose ends. These processes * Op. cit., p. 148 40 ANATOMY OF CORTEX. / are part of the nerve-cells of tlie central ganglia, and also of the nerve-cells at the periphery. The observations of Retzius, \ liohde,* and Biedermannt also support this view. The cell-elements of the neuroglia are of two kinds, and these differ from one another in regard to size and connections. The smaller of the two kinds of cell vary from ^\jb to 9/^ in diameter. Their nucleus is spheroidal and relatively large, and it is surrounded by an extremely delicate protoplasmic invest- ment. According to Bevan Lewis, these cells are to be found in three situations : (1) irregularly in the neuroglia framework ; (2) in regular series round the nerve-cells • and (3) in more or less regular succession along the course of the blood-vessels (capillary and arteriole). The larger cells are usually XZfx in diameter, and have a relatively larger amount of protoplasm as compared with the size of the nucleus. These cells are also fre- cpently flask-like in appearance, and may contain several nuclei. Their processes are numerous, extremely fine and radiating. The want of affinity of these elements for the staining agent (anilin) has led to the conclusion that they are non-nervous in character. By the employment of a modification of Golgi's method of staining, Andriezen has demonstrated two great morphological groups of neuroglia elements, which he has termed (a) neuroglia fibre-cells, and (6) protoplasmic neurogiia-cells. Of the neu- roglia fibre-cell he describes two species. One species is situated in the first layer of the cortex, and sends its streaming fibres down into the third layer : these are the caudate fibre- cells (Fig. 4). The other species is situated in the medullary substance or white matter, and has radiating fibres passing in all directions : these are the stellate fibre-cells. The caudate fihre-ceUs form a distinct feature in the first laj^er of the grey matter. The bodies of the cells are embedded in the grey substance, and their apices are rounded and pointing downwards, thus giving rise to " tail-like tufts " of smooth fibres, which pass into the deeper layers of the cortex. From the wider ends of the bodies there arises a system of radiating tangential fibres. Andriezen describes the individual fibres * " Histologische Untersuchungen iiber das Nervensystem der Poly- chaten," Breslau, 1887. t "Jenaische Zeitschr. f. Naturwissensch.," 1891. THE RELATION BETWEEN CELLS. 41 as extremely long, smooth contoiTi'ed, and of uniform calibre throughout; as being of remarkably iTuiform thickness one with another, nnbranched, slightly Avavy in their course (which is, on the whole, almost rectilinear J, and as exhibiting here and there small sharp curves and small angular bends, while sharp trans- verse fractures are not infrequent. These fibres formed a line cortical fretwork, and none of them could be demonstrated as forming an anastomosis, nor did they appear to have any special vascular connections. The stellate jil/re-cells have small and indistinct bodies, mainly constituted by the enormous number of fibres which i^n. 2''^L Fig. 4. Thkee Neurowlia Fibre-Cells. fl, caudate cell ; h and c, transitional forms between caudate and stellate fibre-t'ells ; \st I., first layer ; 2nd I., second layer of cortex. (After Amlrie-en.) meet and intercross them. Many of the neuroglia fibres pass through the cell-body. According to Andriezen these are remarkably like the fibres of the caudate fibre-cells in calibre and contour, and exhibit the same peculiar sharp curves and angular bends in a course otherwise straight, and also the same transverse fractures. They stain of the same colour, never branch or anastomose, are of considerable length, and do not exhibit the special vascular attachments which the protoplasmic glia-cell exhibits. 42 ANATOMY OF CORTEX. The protoplasmic cell (Fig. 5) is said b}^ Andriezen to occur abundantly throughout the grey matter of the cortex, and but rarely in the medullary substance. It is of mesoblastic origin, and exercises a lymphatic function. Its processes are stellate or dendritic in arrangement, and the Ijniiph-spaces which surround its coarse, shaggy processes, are in direct communication with the perivascular lymphatics. Bevan Lewis regards these large protoplasmic cells as forming the actual extremities of the lymphatic system, and he maintains that their thick processes end in the perivascular or hyaline sheath, whilst the finer reti- culated processes extend through the neuroglia network. .Fig. 5. Pkotoplasmic Glia-cell from the Human Brain (1st Layer of Cortkx], showing One Expanded Disc-like Attachment to a Vessel. {After Andriezen.) These protoplasmic giia-elements are regarded by Andriezen as being the elements which exhibit a morbid hypertrophy in pathological conditions (alcoholism, general paralysis). The}' also show further morbid activities, in the last stage of which their protoplasm deposits numerous organised fibrillge, in the act of doing which the protoplasm proper is used up. A scanty remnant may persist, ghost-like, to mark the position of what was once a protoplasmic cell-body.* These protoplasmic cells are now regarded as lymph-secreting cells. Andriezen believes that the cell absorbs or takes up lymph from the brain-tissue which it permeates, and that it discharges it, through its peri- dendritic canaliculi, into the perivascular lymph spaces. * Andriezen, " British Medical Journal," July, 1893. PHYSIOLOGY OF THE NERVE-CELL. 43 Other small glia-cells, sometimes mistaken for leucocytes, with sharply-defined nuclei and a small quantity of protoplasm, have been described as surrounding the larger nerve-cells as they lie in their pericellular sacs. Their function, however, is unknown.* Bevan Lewis regards the protoplasmic cells as comprising the distal extension of a lymphatic system, and he has clear h^ pointed out that arrest to the escape of perivascular lymph from the cortex is immediately followed by a morbid development and by a hypertrophic condition of these " spider cells," The question of the significance and nature of these cells in morbid conditions has been freel}^ discussed of late. Bevan Lewis attributes to them an active and aggressive pai't in the pro- duction of disease, and thereby somewhat enlarges the notion of their function as " scavengers " to remove waste products. The more generally accepted opinion, however, is that their role is probably a secondary one, and that they remove rubbish instead of producing it.f PHYSIOLOGY OF THE NERVE-CELL. Nutritive Function. — The nerve-cell's most important function is that of nutrition, and the presence of a nucleus seems to be essential to this. When a nerve-fibre — i.e., a process of a nerve-cell — is cut — no matter whether, in its normal state, it conducts impulses to or from the cell — the part which is cut off" from the parent cell must die. This nutritive function of the nerve-cell has been insisted upon by Nansen4 who believes that the cell-body has no other function than that of effecting the nutrition of the whole cell, and more particularly that of the axis-cylinder process. Schiifer points out that although the nutritive function may be the one essential function of the nucleated body of the nerve- cell, there are many cases in which the body of the cell also serves for the transmission of nevve-imiyulses. As examples, he gives the bi-polar cells, through which impulses must of neces- * Andriezen, "Brain," 1894, p. 664. t Carter, "Brain," 1893, p. 399. % " Histological Elements of the Central Nervous System," Bergen, 1887. 44 PHYSIOLOGY OF THE NERVE-CELL. sity pass; and the motor projection-cells of the spinal cord and bulb, in which instances nerve-impulses are probably communi- cated to the body of the cell from the interlacement of nerve- fibres, derived from other cells, which enfold the body of the motor cell. Whether nerve-impulses reall}^ traverse the cell body is still open to discussion. Schafer believes that in some instances nerve-impulses can be transmitted along nerve-fibres without traversing a nerve-cell at all, and he even goes a step further, with the conception that sensory-impulses may become con- verted into motor-impulses within the PmiMsuhstanz without necessarily traversing the motor nerve-cells at all; the latter being only connected with the Punktsubstanz by dendritic collaterals, which pass ofi" from their large neuro-dendritic processes. Our knowledge of the modes of neural motion — i.e., the methods of propagation of nerve-impulses — is absolutely untrustworthy, and we have yet to solve this problem. Hence we readily see that before an attempt is made to find the solution of psy- chical phenomena in terms of neural molecular motion, we must arrive at some more definite conclusions as to the nature and workings of the material structure. Excitability and Conductivity.— The two forms of molecular motion which characterise both nerve-fibres and nerve-cells may be called excitability and conductivity. The former is looked upon as the motion originally set up in the nervous elements, and corresponds to the excitation of a stimulus ; the latter represents the propagation or conduction of this initial excitation along tracts to other regions. The external and internal stimuli, and their relation to excitation, will be dealt with later. Here, however, Ave must ask the question. Do nerve-cells act as generators of nerve-impulses r It is almost universally held that they do, in which case such commotions are regarded as being essentially automatic. Let us take, as an example of automatic action, the action of the respiratory centre, and let its endeavour to eliminate from it all sources of stimulation from without. In order to do this we must exclude the chemical stimulation which results from varying conditions of the blood : we must also cut off the possibility of stimuli reaching the centre from EXCITABILITY AND CONDUCTIVITY. 45 the peripheiy, or from any other regions whatever. AVhen we have direct proof that nerve-impulses are generated in the nerve-cell under such circumstances, then only shall Ave be able to say that such impulses arise automaticall}^ The end organs of sense are excited specifically by their appropriate stimuli ; the afferent nerves have their specific function of conduction from these end organs of sense; the efferent nerves have their "specific function of conduction from the central organs, and we are not in a position to say that nerve-cells ever do give rise, without some mode of stimulation, to automatic action. We have already seen that nerve-impulses ma}' be transmitted Avithout passing through the nerve-cell at all ; and, further, the power possessed by the bod}^ of the cell of transmitting impulses, when stimulated, is not unique in it, but is equally shared by its processes under preciselj^ the same conditions. " It is," says Schafer, " a function which is not special either to the cell body, or to the processes, but is common to both."* When a stimulus is transmitted by a ganglion-cell, so as to impart motion, such action is termed reflex, and the ganglion-- cell is said to possess reflex function. This form of action is the simplest nervous process with which Ave shall have to deal. Stimulation and reaction are the main conditions of nerve life, and they are essentials of nervous function. Throughout the AA'hole of animal life Ave see this function exhibited in its innumerable modes and degrees. The mere recognition, hoAA'- ever, of this fundamental property, as pertaining to all life, does not iniplj- any explanation of the phenomena in terms either physical or psychical. The phenomenon is essentialh' the same in its rudimentary form in the amoeb£e as in its more complex developments through the paths of conduction in man ; and Ave must ncA^er lose sight of this fact, that no matter hoAv clear our knoAvledge may become of the excitations of stimuli, of the methods and directions of their conduction, and of their numerous expressions as forms of motion, Ave are in realit}^ no nearer the solution of the all-important problem — the ultimate * Eckliard made a distinction between the automatic-tonic and automatic- rhythmic functions of the ganglion-cells, according as the movements over which the cells exercised control occurred at irregular or regular intervals. 46 PHYSIOLOGY OF THE NERVE-CELL. conditions of vital reaction. On the physical side we imagine that within the nerve-cell afferent impulses become modified as to niimber and character by profotind molecular changes, so that they become transformed into efferent impulses of another kind. In reality, however, we do not know how the effects of stimuli are conveyed to the ganglion-cell ; we do not know what becomes of the excitations within the ganglion-cell ; nor do we know how the modified afferent impulses are propagated to their destinations. When we come to consider the phe- nomena of mind, and discuss the various physiological theories which have been advanced to explain those phenomena, we shall see that the endeavour to find a complete expression for all mental acts in physical terms is, to say the least, premature, and scarcely warrantable in our present state of knowledge. This leads us to the question, Has the nervous process of a simple reflex action a concomitant psychical process which corresponds' to it? When we consider the plantar reflex, which is manifested even thoxigh psychical life is supposed to be non- existent, we are able to answer in the negative. The essential anatomical elements involved by the processes of reflex action are known to us, but the nature of the psychical process, or the extent of its concomitance with the physical process, is un- known. Ziehen says our consciousness, which is alone able to decide the question, negatives the idea of such a correspondence. If our foot is but pricked unawares, it is only after the move- ment has been executed that we become aware of what has taken place by a resultant sensation — the sensation of motion. The fitness of reflex action has been given as an argument to support the theory that there is a psychical concomitance with the physical process. In every reflex act we are forced to believe that the physical process is not confined to a single afferent or efferent nerve or ganglion-cell. On the contrary, many are affected ; and if we are to explain the correspondence of a psychical event, we must establish a corre- spondence not of one psj'^chical event with one physical process, but with many physical processes. These physical processes may lead to one result — namely, the motor effect — and in the lower forms of reflex action the result tends to remain the same, no matter how the sensible stimulus may change ; but the con- REFLEX ACTION. 47 sdousness of the excitation, or of its resulting effect (motion), mvist of necessity be, not the correspondence with one physical process, but with many. The lower forms of motor reaction do not seem to depend entirely upon the character of the stimuli. There is, however, a general fitness in their reaction, and it is upon this fitness or unfitness of our reflex mechanism that our survival, as physical organisms, in great part, depends. The argument that this fitness implies a psychical correlate — i.e., that lower reflex acts which are fitting demonstrate their psychical nature — is of great importance as bearing upon the evolution of the mind in animals and man. Nerve-cells are believed to have the power of diminishing or intensifying the nerve-energy entering them. Thus the sensory stimulus may become more complicated in its course of transmission. In the higher form of reflex action — in which co-ordination is evidenced — the concomitance of a psychical process has been assumed. The nature of this complicated motor reaction has given rise to much discussion and difference of opinion. Ziehen believes we have no ground whatever for assuming that these higher or more complicated reflex acts are accompanied by psychical processes. Those motor reactions, hoAvever, which are not the invariable result of a definite stimulus, but are the modified result of new intercurrent stimuli, may be called (lutomatic acts or reactions, using the term automatic in its more restricted sense, and not including the so-called automatic rhythmical movements which are the result of internal stimuli. The instance given us of the pianist who executes an often- practised piece of music while his thoughts are wandering elsewhere, is of great significance, and the explanation is, that the visual image of the notes and the sensations of toiTch, imparted by contact with the keys, act without interrup- tion upon the execution of the movements of the fingers. In an example of this kind the transmissions of the excitations may be explained as occurring along the lines of least resist- ance — along fixed paths, or so-called paths of conduction. Further, we may conceive the occurrence of structural modifi- cations in these paths of conduction with the constant execution of definite functions ; but how are we to explain a still higher form of reaction, in which an individual is able to extemporise 48 PHYSIOLOGY OF THE NERVE-CELL. and construct new combinations whilst liis mind is engaged elsewhere, or, at the most, is only dimly conscious of the working of his reflex mechanism ? Such instances are not uncommon, and the musician may possess a reflex mechanism of such exquisite sensibility that its constructive effects ma}^ be wrought without any obvious psychical correlate. An analysis of this phenomenon, however, is permissible, and we shall see that, in realitj", this constructive power is an advanced develop- ment of the general fitness of reflex action j^^^is intercurrent stimuli. As in the former instance, the pianist's fingers, in spite of his absence of mind, glide over the notes in proper succession, and his movements tend to act in lines of least resistance. No effort of memory is involved in a psychical sense. Oo-ordinative actions, which have been acqiiired for- merly, now succeed each other in a relatively new order or sequence. Experience has taught the fingers how to avoid consecutive fifths and octaves. Relative progressions and in- tervals are treated with an equal amount of accuracy. The hands approximate to, and diverge from, each other, and so accurate is their judgment of distance, that, taking their clue from one another, the fingers fall upon their proper notes without arousing the consciousness. To the 5"0ung musician, such a mechanism is almost incom- prehensible, and were he to attempt to illustrate this by his own efforts, he would find, firstly, a failure in his co-ordinative move- ments — his fingers would be slow to adapt themselves to the necessary intervals, through insufficient practice or ineptitude ; secondly, sensations of resistance would be experienced, with an immediate stimulation or arousal of consciousness ; and, thirdly, the results of long training in resolving discords, in weaving suc- cessions of notes or chords into rhythmical form would be want- ing. Such considerations as these lead us to agree with Ziehen, that intercurrent stimuli may so modify and, so to speak, im- prove upon the fitness of our reflex acts, that some of the highest and most complicated of our actions may be termed automatic, inasmuch as they may be performed ^^ithout the concomitance of conscious phenomena. The " response movements" of Goltz also bear out the same view, in that they are adapted to a definite purpose, and are able to overcome opposing obstacles. Ziehen FUNCTIONS OF NERVES. 49 claims that the first automatic movements to be met with in the animal series have been developed from reflex action through the agency of "natural selection." He believes that originally the amphibians which regularly avoided an obstacle suddenly placed in their way, thereby modifying their locomotor course, were just as numerous as those which did not. In the struggle for existence, however, the former had a decided advantage, for mechanisms situated below the cortex relieved the cerebrum of work, and other deeper nervous centres fittingly performed its functions. This fitting pecu- liarity was inherited, and constantly bred bj^ transmission, while those animals which were less favourably constituted gradually died out. The Functions of Nerves.— Our knowledge of the functions of nerves is no more advanced than that of nerve- cells. The various functions of nerve-fibres have been classified more or less according to the different effects produced by the conduction of nervous impulses along them. Thus we have the follo^^'ing classes : — (a) nerves of motion controlling the muscular apparatus, whether of smooth or of striated muscular fibres ; (/>) nerves of inhibition ; (c) nerves of secretion ; (c/) trophic nerves, or nerves which have a direct influeaice upon nutrition ; (e) centripetal nerves that have no sensory functions ; and (/) sensory nerves, or those the excitation of which may result in conscious sensation.* With results so different as those seen in the above classes, we natiirally ask ourselves whether those differences are due to variations in the modes of transmission of the impulse, or is the cause to be sought in the origin of the nerve-commotion ? For the present we are quite unable to satisfy ourselves in this respect, since our knowledge of the nature of the impulse transmitted has been shown to be so extremely limited. Ladd says, " Just as the same electric current may pass along the same kind of wire, and write a message, or ring a bell, or move the legs of a frog ; just so, the irritation of certain fibres of the pneumogastric nerve results in controlling the motion of the heart ; the irritation of other nerves seems to have no immediate metabolic effect in directing the secretory * Hermann, '• Hanb. d. Physiol." II., i., p, 200 ff. 50 PHYSIOLOGY OF THE NEEVE-CELL. processes ; that of still others profoundly modifies the nutrition of the portions of the body to which they are distributed." A more convenient classification of the nerve function of conduction is that of afferent and efferent, according as the nerves in question serve as conductors of nerve-impulses inv^^ard toward, or outward from the nerve-centres. Some writers have supported the view that afferent and efferent nerves have the same specific mode of neural action ; whilst others believe that their respective molecular processes are essentially different. Our knowledge as yet, however, will not warrant us in giving credence to either of these views. We assume that impulses are propagated somehow along a nerve-fibre : we assume that such impulses may undergo variations, or even in the case of sensory nerves be transmitted backwards ; and we deem it possible that the transmission of impulses is attended with chemical change : but beyond this we ■ must confess to being in a state of complete ignorance. The nature of a nerve-hnpulse is assumed to be that of waves of molecular vibration or of chemical action, or of the two in combination. Schafer holds, that there is absolutely no evi- dence of the first supposition, although the fact still remains that there is some evidence of chemical action. Upon the views of d'Arsonval — that the electrical phenomena of active muscle and nerve are produced by variations of surface-tension passing in a wave-like manner along the fibres — Schafer con- jectures that such waves of pressure, or surface-tension change, might possibly originate in consequence of the rhj^thmical contraction of the nerve-cell, or of any of its processes. In illustration of this view Schafer says, "When a fibre of the pyramidal tract is excited, the nerve- impulses which are generated in that fibre, and which are pro- bably of the same rate as the excitation, pass down to the grey matter of the spinal cord, and are there converted into nerve- impulses, which may have a very much less frequent rhythm. This can only, so far as appears, take place at the adjunction of the terminations of the pyramidal-tract fibres with the motor nerve-cells : and it would appear that the motor nerve-cell is stimulated by the nerve-impulses which are conveyed along the fibre of the pyramidal tract, but that it resj)onds to that action with a very much slower rhythm than that of the assumed excitation : for the excitation may be as rapid as 100 per second, or more ; but provided it is not too FUNCTIONS OF NERVES. 51 intense, the impulses which pass along the motor fibres are only at the rate, as shown by the response of the muscle, of about 10 per second. The same thing is seen when the muscles are made to contract by a reflex excitation of the skin. Such an excitation may be very rapid or it may even be continuous. This rapid or continuous excitation of the skin produces in the sensory fibre nerve-impulses, which may be assumed to be at least as rapid as the excitation itself, and these are ■conveyed to the grey matter of the lower nerve-centres, and are converted into nerve-impulses of a relatively slow rhythm, as shown by the rhythm of the reflex muscular response. This transformation may be assumed to occur either in the motor projection-cell, or in an inter- mediary cell, if any such intervene between the afferent fibre and the motor-cell, and the slow rhythm of the epileptiform convulsions which follow strong electrical excitation of the cerebral cortex, and which certainly originate in the cells of the cortex, furnishes another well- marked instance of rhythmic production of nerve-impulses by nerve- <3ells." When we considered the anatomy of the nerve-cell and the ramification of its processes we said, that there was no direct continuity between the nerve-cells, except through the con- tiguity of those ramified processes. Schiifer has shown that, as a consequence, there is always a partial block to the passage of nerve-impulses at the conjunction of one cell with another, and he regards the period of time lost at this junction as representing the period of latent excitation of the nerve-cell. For an account of what probably happens at this point we cannot do better than again quote his own words : — " The nerve-fibre to which the excitation is applied carries nerve- impulses, which become spread out in the fine arborescence, which forms the termination of that fibre and which enwraps the motor-cell. From this cell nerve-impulses start which are not necessarily of the same rate as those which have reached the terminal arborescence just mentioned, and these new nervous impulses pass down towards the muscle and cause its contraction. It is clear that a change occurs at the adjimction of the arborescence within the cell-body. A change in rhythm certainly occm-s,* and this renders it extremely probable that the nerve-impulses which are passing off from the spinal cord are entu-ely new impulses. If so, we may look upon this cell as having been freshly stimulated by the impulses which have passed along the fibre of the pyramidal tract. We may briefly consider in what manner it can be thus stimulated. Since there is no evidence that the fibrils of the arborescence anywhere touch the cell-body or its processes, we must assume that a space intervenes everywhere between the two, * '•Journal of Physiology," 1886, vol. vii. 52 PHYSIOLOGY OF THE NEKVE-CELL. very narrow indeed, but still a space which cannot readily, if at all, be traversed by nerve-impulses. It is possible to suppose that the nerve- impulses reach the pericellular arborescence, and produce by mere induction new nervous impulses within the cell around which they play. But we have no evidence that such nerve-induction is possible. It is also open to us to suppose that the electrical change (action current), which accompanies the passage of the nerve-impulses to the arbores- cence, may itself be the excitant of the nerve-cell, and that the nerve- cell may respond to this excitation by a rhythmic chemical action, possibly molecular vibration, or perhaps a combination of two of these. At all events, it is probable that a new process is started within the nerve-cell. This does not necessarily follow from the fact that there is time lost at the adjunction, for a partial block to the passage of nerve- impulses and a resultant loss of time may be produced merely by mechanical means; but the change of rhythm renders it extremely probable." The function of conductivity of nervous iinindses varies con- siderably under certain modifying conditions. The velocity of transmission of an impulse along a human motor-nerve is estimated by Helmholtz and Baxt to be 100 to 120 feet per second. In visceral nerves it is somewhat less (26 feet, Chauveau). Both elevation and lowering of the temperature lessen it. Anelectrotonus also diminishes, while cathelectro- tonus increases it. (Rutherford and Wundt). Negative variation in nerve is readily observed if a nerve be placed with its transverse section on one non-polarisable elec- trode, and its longitudinal surface on the other ; then, b}^ stimu- lating it electrically, chemically, or mechanically, the nerve- current is found to be diminished (du Bois-Reymond). Accord- ing to Bernstein, this negative variation is propagated towards both ends of a nerve, and is composed of very rapid, successive, periodic interruptions of the original current. The amount of the negative variation depends upon the extent of the primary deflection, the degree of nervous excitability, and on the strength of the stimulus employed.* Head found that it increased with the duration and strength of the stimulation, and with the drying of the nerve. The velocity with which negative varia- tion is propagated, as estimated by means of the differential rheotome, is a subject of great interest, but its further con- sideration must be for the present deferred. * Landois and Stirling, j). 559. INTERCELLULAR CONNECTIONS. 53 Do nerve-impulses pass backwards? It has been demon- strated by Gotcli and Horsley* that impulses do pass down afferent or sensory paths, but no matter how strong the stimulus emplo3^ed, they do not pass up the efferent or motor- paths. Schafer offers an explanation of this in the anatomical arrangement of the terminations of the pyramidal tract fibres around the motor-cells, as compared with the mode of central termination of the sensory fibres within the grey matter. Such an arrangement, he conceives, may allow of the excitation of new nerve-impulses within the body of the motor-cell by an electrical discharge from the fine brush of pericellular fibrils which envelopes the body of the motor-cell; whilst the electrical change which accompanies nerve-impulses up the motor-fibre, when this is artificially stimulated, may be so diffused throughout the cell-body of the motor-cell, as to fail to stimulate and set up nerve-impiilses in the pericellular ramification of fibrils, Avhich represents the ending of the fibre of the pyramidal tract. The most important fact which has been pointed out of late, is that cells and fibres may functionate by contact only. The observations of Golgi, Ramon y Cajal, and Kolliker seem to demonstrate that direct continuity of structure is not essential for the propagation of motor, sensory, and reflex excitations. Kolliker t has demonstrated the truth of this in the cases of sensory root-fibres, which end free in the grey matter of the cord and medulla, the terminations of lateral branches of the nerve-processes of many of the cells of the grey matter, and also the terminations of the longitudinal fibres and collaterals of the anterior and lateral pyramidal tracts in the grey matter of the anterior horns. Intercellular Connections. — Ramon y Cajal | holds the view, that not only may the protoplasmic prolongations of the nerve-cells possess nutritive functions, but, also, they may, as well as the body of the cell itself, serve as conductors of nervous currents between neighbouring cells and elements at a distance. From the minute study of the histological appear- ances of the connections of the olfactory nerve-fibres, and those * "Phil. Trans.,"' 1891, vol. 182, B. t " Anat. Anzeiger," 1891. t "Crooniaii Lecture," Roy. Soc, March 8, 1894. 54 PHYSIOLOGY OF THE NERVE-CELL. of the visual fibres and of the retinal cells, he drew the conclu- sion, that not only do the protoplasmic expansions act as con- ductors, but also that the nervous current is inward toward the cell in these expansions, and outwards from the cell in the axis-cjdinder. The nerve-cell has, in the dendritic expansion and the cell-body, an apparatus for the reception of cvirrents, an apparatus for transmission in the prolongation of the axis- cylinder, and an apparatus for repartition or distribution in the terminal nervous ramifications. From an analysis of the quantitative and qualitative difference which cerebral action presents among different animals and in the same animal species, Cajal regards the morphology of the pja-amidal cell as but one of the anatomical conditions of thought. But he does not believe that this special morphology will ever siiffice to explain the enormous differences which exist, from a functional point of view, between the pyramidal cell of a rabbit and that of a man, any more than between the pyramidal cell of the cerebral cortex and the stellate-cells of the cord or the great sympathetic. From the fact that the nerve-elements lose their power of proliferating after the embr^^onic period, an increase in the number of cells is not to be looked for as an essential feature in the improvement of organisation of the brain. On the other hand, it is probable that, in those regions which are most exercised, mental activity involves a greater develop- ment of the protoplasmic apparatus, and of the system of collateral nervous paths. It is in this way, says Ramon y Cajal, that associations already in existence between certain groups of cells would be notably reinforced by means of the multiplication of the minute terminal branches of the proto- plasmic expansions, and of the collateral nervous paths. Further, absolutelj^ new intercellulai' connections might be established by the formation of new collateral connections and protoplasmic expansions. The anatomico-physiological hypo- thesis, which bases intellect upon the richness of the cellular association, is open to an objection, which, however, this author fully recognises. How can the volume of the brain be maintained unaltered if there be a multiplication, and even a new formation of the terminal branches of the protoplasmic appendices, and of the collateral nervous connection ? In reply INTERCELLULAK CONXECTIOXS. 55 to this objection, he states there is nothing- to prevent our sup- posing either a correlative diminution of the cell bodies, or a proportional shrinking of those parts of the brain \\diose functions are not directly related to the exercise of the intelligence. We may thus explain family talent by supposing an hereditary transmission to the immediate or, by atavism, to the more dis- tant descendants of this superior organisation of the connections of the pj'ramidal cells. In the case of those men in whom talent is coincident with a brain of small size, the nerve-cells \\'ould be less numerous, or, perhaps, simply smaller; whereas, on the other hand, they would present a very complicated system of protoplasmic nervous associations. The excessively large brain, on the other hand, so often associated with defective intelligence, or even with imbecility, would contain a greater number of cells, but the connections between them would be verj* imperfect. As compared ^^•ith the theory of networks, Cajal believes that the theory of the free branching of cellular expan- sions, capable of growth, is not only more probable but also more encouraging. "A continuous network," he says, "pre- established — a sort of fixed telegraphic grillwork into which it Avould not be possible to introduce either new stations or new lines — it is a thing so rigid, so immutable, so unmodifiable, that it does violence to the feeling which we all have, that the orgfan of thought is, within certain limits, plastic and susceptible of being improved, especially during the period of its development, by well-directed ' mental gymnastics.' " His comparison of the cerebral cortex to a garden containing innumerable trees (the pyramidal cells), ^\hich.in response to intelligent cultivation, can increase the number of their branches, strike their roots over a Avider area, and produce ever more varied and more exquisite flowers and fruits, is open to criticism ; and we shall see that mere quantitative variations in cerebral structures are not, in reality, sufficient to explain cpialitative variations in mental events. 56 CHAPTEE II. Chemical Pkopeeties of Nerve-substance. Specific Gravity — Percentage of Water — Albumin — Potash Albumin^ — Nuclein — Neuro-Keratin — Cholesterin — Cerebrin (Homocerebrin Encephalin) — Lecithin — Protagon. Vascular Supply of the Brain. Basal Arterial System — Anterior Cerebral Arteries — Middle Cerebral Arteries — Posterior Cerebral Arteries — Arterioles of the Cortex. Lymphatic System of the Brain. Ptegulation of Cerebral Pressure — Lymph-Cisterns — Perivascular Channels — Cerebro-Spinal Fluid — Pacchionian Granulations — Subarachnoid Space — Venous Circulation — Quantitative Rela- tions between Blood and Cerebro-Spinal Fluid. Brain-Movements. Pulsatile — Respiratory — Vascular — Nutrition of Nerve-elements — Functional Hypersemias — Vaso-motor Centres — Influence of the Sympathetic. CIIExMICAL PROPERTIES OF NERVE-SUBSTANCE. When we begin to study the chemical and mechanical pro- perties of nervous substance we find that the facts with which we have to deal are comparatively few in number, and their import uncertain. This is not to be wondered at when we remember that the nervous tissues are formed by highly complex and unstable compounds. Attempts have been made to estimate the chemical nature of the white and the grey nervous matter respectively, and they have been found to SPECIFIC GRAVITY. 57 differ not only in chemical constitution but also in specific gravity. It must be remembered, however, that it is difficiilt to make an absolute distinction between the white and the grey substance, and more especially is this the case in investigations where facts can be obtained only by an examination of the entire masses of the brain. Meynert recommends his method of dissecting out the brain-trunk and cerebellum from the hemispheres as peculiarly adapted to such investigations, but no one seems to have adopted his suggestions, and our knowledge on this head is exceedingly fragmentar}^. Danilewski attempted to estimate the elements of the grey and the ^vhite substance by means of a comparison of the differences in their specific r/ravity. He found that the sp. gr. of the grey substance varied between 1"029 and 1*038, and that of the white substance between 1'039 and 1"043. In man, he fovmd the relative proportions of both substances to be 37 '7 to 39 per cent, of grey substance, and 61 to 62*3 per cent, of white substance ; while in the dog, the grey and the white substance were present in equal proportions. Bastian, W. Krause, and L. Fischer estimated the mean sp. gr. of the grey matter at about 1-031, of the white at 1-036— 1-040. * The explanation of this difference in weight is attributed to the relative amount of water and of solids which they contain. Gamgee f has given a tabular statement of Weisbach's investigations as to the amount of water entering into the composition of the different parts of the central nervous system. From this table the largest percentage of water is found in the grey substance of the brain (83 per cent, approximately). The cerebellum comes next with about 78-5 per cent. ; then the medulla oblongata, 74-5 ; pons Varolii, 73-5 ; and the white substance of the brain about 70 per cent. The cortex contains 86 per cent. ; the medullary substance of the hemisphere 70 per cent. ; the oblongata 74 per cent. ; sympathetic 64 per cent. Bernhardt found a smaller proportion of water in the cervical region of the cord (73-05 per cent.) than in the lumbar (7604). Another fact ascer- tained from the results of Weisbach's observations is, that in man between the age of twenty and thirty there is a relatively * Lacld, " Physiol. Psych.," p. -22. t "Physiological Chemistry of the Animal Body," i. p. 445, London, 1880. 58 CHEMICAL PEOPERTIES OF NERVE-SUBSTANCE. higher percentage of Avater than between the age of thirty to fifty ; and, further, that between the age of seventy and ninety- fonr there is a higher percentage than at either of the former ages. Observations are niucli wanted npon these points, and it is of importance to us to know under what conditions we are to expect an increase in the watery constituents, both in tlie normal and the morbid brain. At the present time our know- ledge of the relative proportions of such an increase in general paralysis of the insane, and other progressive brain diseases, is, so far as I am aware, absolutely nil. Meynert regards the preponderance of grey substance in animals compared with the grey substance in man, as dependent upon the excess of amorphous connective tissue in the former. In man this sub- stance is regarded as albuminous in character ; hence Boll considers it allied to connective tissue, which, he claims, con- tains remnants of albumin derived from formative cells, and only differing from other connective tissue in the possession of a greater quantity of albumin. Albumin is found both in the axis-cylinder and in the substance of the ganglionic cells. Some of this proteid substance was formerly regarded as mj'osin, and presented characters not unlike those of this compound. We now know, however, from the experiments of Petrowsky, that this substance is insoluble in a 10 per cent, solution of sodium chloride. The dilute solution of this salt extracts a proteid from nervous matter, which is, however, precipitated by the addition of much water, and by a concentrated solution of the salt. Potash albumin and a r/lobidin-lihe substance are also present.* Both Klihne and Ewald found, that if grey nervous matter was subjected to ai'tificial digestion, by trypsin — the pan- creas ferment — two substances remained midigested, nuclein and neuro-heratin. The latter being obtained b}" treating the residue with caustic potash. The occurrence of nuclein in the grey matter is said to imply the presence of phosphorus in the ganglion-cells and axis-cylinders. But whether this substance (nuclein) is actually present in the brain at all is a matter of doubt. Von Jaksch and Drechsel believe that it does occur, but its existence has * Landois and Stirling, p. 531. NUCLEIN AND NEURO-KERATIN. 59 been denied hj Worm-Miiller and Gamgee. The formula of this substance is given as OggH^gN^PgOgo- Jaksch found an excess of nuclein in the grey substance as compared with the white. He did not, however, thoroughl)' isolate the grey sub- stance. Geoghegan also found it in the proportion of 1'4 to every 1,000 parts of the entire cerebral mass. From the experiments of Meyer and Cornwinder — who proved that in plants the quantity of phosphorus increased in direct pro- portion to the quantity of nitrogen ; and the researches of Bischoff, who found phosphoric acid in a definite proportion to the quantit}^ of nitrogen in the urine of starving animals, whereas, the quantity of phosphorus taken in was greater than that in the excretions if the animal was properly fed — A^oigt infers that the albuminates and phosphates unite, so that the fundamental connective tissue, as well as the nerve-cells in the grey substance of the brain, must be classified with those substances which contain phosphorus. In the chemical com- position of the brain the element of phosphorus of the gre}' substance constitutes an important factor. Meynert, relying upon the observations of Schlossberger, Bibra, Pollak, and Jaksch, estimates that a fresh brain contains 0'49 per cent, of phosphoric acid in its grey substance, and 0'89 per cent, in its white substance. He says ^^'e are not warranted, however, in concluding that the nervous sj^stem contains an absolutely larger quantitj^ of phosphorus. The quantity of phosphorus in the nervous system cannot be gauged hj the amount of phos- phorus in the excretions ; for, as Voigt has determined, the entire nervous system of man contains but 12 grains of phos- phoric acid as compared with 130 grains in the muscles, and 1"800 grains in the bones; and, besides, we know, ever since Chossat's starvation experiments were published, that during starvation the nervous system sho^^'s no appreciable loss of weight. Neuro-heratin occurs in the corneous sheath of nerve-fibres. It is also found in the grey matter of the nerve-centres, and in the retinal epithelial cells and pigment cells of the choroid ; but not in the non-medullated nerve-fibres. It is a bodj^ containing much sulphur, and is closely allied to keratin. It is soluble onlv in a hot concentrated solution of caustic 60 CHEMICAL PEOPEHTIES OF NERVE-SUBSTANCE. potash and sulphuric acid, and amounts to but 15 or 20 per cent, of the dried residue of the alcohohc or ethereal extract of the brain. If the fatty matters of the medullary sheath are extracted with boiling alcohol and ether, this highly refractile substance is left as an irregular network. Cholesterin (CggH^^O + H2O) is regarded as a monad alcohol which occurs in a free state, especially in white nervous sub- stance. It is non-nitrogenous, taking the form of fine needles or rhombic tables when separated from its solution in ether or alcohol. Hoppe-Seyler says that this body is probably merely suspended, and not dissolved, in protoplasm ; that it is common to all living vegetable and animal cells, taking no important part, however, in the development of the cells. It is uncertain whether it is, as maintained by Hoppe-Seyler, a prodvict of decomposition resulting from the organic changes during cell life. Petrowski states that lecithin and cholesterin originate from the cells of the grey substance and not from the white substance mixed with it. According to Drechsel, the terms lecithin, cholesterin, and cerehrin designate mixtures only; of which lecithin applies to the phosphorised substance which has been dissolved by ether and alcohol ; cholesterin to the ethereal extract which remains after removing the lecithin; and cerebrin to the substances which form crystals in hot alcohol, but are insoluble in cold alcohol (y. Meynert). Cerehrin (CggogH^^^yNg^g. Parous) is a white powder com- posed of spherical granules soluble in hot alcohol and ether, but insoluble in cold water. It is prepared by rubbing vip the brain into a thin fluid with baryta water. The separated coagulum is then separated with boiling alcohol (Miiller). Parous gave the name of homocerehrin to a substance which he separated from cerebrin, this substance being slightly more soluble in alcohol than cerebrin. He also found a " clyster-like" body, soluble in hot water, which he named encephalin. Lecithin (C^^Hg^NPOg. Diakanow) occurs as a phosphorised organic compound in the matter of the brain, and from its decomposition products we obtain glycero-phosphoric acid PROTAGOX. 61 and oleophosphoric acid. Lecithin is a salt of the base neurin* Gamgee believes that lecithin is only one of a group of bodies which possess a higher percentage of phosphorus than protagon. It is soluble in water and alcohol, and has been formed synthetically from glycol and trimethylamin. ProtoAion (CijgH.,^^X^Oo,P) is regarded liy its discoverer, Liebreich, to be the chief constituent of the brain. It con- tains N and P, and resembles cerebrin. This substance is considered by some observers to be the only well-established phosphorised proximate principle of the brain. Ladd believes it to be the best representative that chemistry can as yet present, of a scientific result upon which to base any attempt to point out definite relations between psychical activities and the chemical constitution of those complex phosphorised bodies which exist in the central nervous mechanism, and he regards it as highly probable that protagon is not a com- pound or mixture of cerebrin and lecithin. The contro- versy as to whether protagon is a definite ultimate chemical principle, or a mixture of lecithin and cerebrin, has attracted a considerable amount of attention. The former view has been upheld by Kiihne. Blankendorf, and Gamgee, vrhilst Diakanow, Hoppe-Seyler. and Thudicum have advocated the latter. From a physiological and psychological point of view con- siderable importance is attached to the discovery of the com- position of these highly complex phosphorised substances. More recently Drechsel has discredited the view that pro- tagon is merely a mixture, by pointing out that the atomic weights of lecithin and cerebrin do not suffice to make a mixture of the nature of protagon, and that a third substance would have to be shown to exist containing more nitrogen and less carbon. The power the medullary substance of the brain possesses of reducing osmic acid, and turning a black colour, is regarded by Meynert as an additional reason for the exist- ence of a body like protagon. He recognises, however, that these peculiar c[ualities are common, also, to the myelin forms of protagon resulting from prolonged contact of protagon with * Landois and Stirling, p. 331. 62 CHEMICAL PROPERTIES OF NERVE-SUBSTAJS"CE. water. Diakanow contended, althongh apparently withovit proof, that protagon contained no phosphorus at all. Blank en- dorf, Gamgee, and Drechsel found that the percentage of phosphorus was constant in protagon, although it had been re-crystallised four or five times. The hygroscopical characters of lecithin and cerebrin have led Meynert to believe, that though lecithin and cerebrin (the latter a substance without phos- phorus) exhibit the starch-like properties and myelin-like forms, there is not sufficient ground to doubt the formation of these substances from the protagon of the brain, but that their marked hygroscopical properties stand in broad contrast to the lack of such qualities in protagon. " If protagon were .a mixture of cerebrin and lecithin it would be difficult to con- ceive how a non-hygroscopical body could result froin the union of two hygroscopical bodies. It would be more natural to suppose that the hygroscopical properties were the result of the more elaborate methods by which cerebrin and lecithin are recognised as secondary brain constituents, while protagon, a primary brain substance, is obtained in advance of these." From these brief considerations the student must not for one moment imagine that he possesses anything like an adeqtiate knowledge of the chemical constitution of nervous ■substance. Thudicum* states, that a quantitative analysis of the brain involves at least three hundred quantitative deter- minations of definite bodies or compounds. Each of the four divisions of the brain, and each of the two varieties of tissue— the white and the grey — would thus require at least about fifty quantations for chemical characterisation. Our account must necessarily be limited, and we are compelled to refer the student to the comprehensive article by Thudicum, in " Tuke's Dictionary," for details of the group of inorganic principles which have been isolated from the brain ; and Ave hope, with this author, that more attention may be given to this subject by those who make psychological medicine their especial ,stndy. * " Tuke's Diet. Psych. Med.," vol. i. p. 152. VASCULAE SUPPLY OF THE BRAIN. 63 VASCULAR SUPPLY OF THE BRAIN. Our knowledge in reference to the vascular supply of the brain has been rendered more accurate owing to the inde- pendent laboiTrs of Heubner and Duret. The entire arterial supply of the brain has been divided into two systenis^ — viz., a hasal and a cortical arterial system. Here, we shall have to deal more particularly with the latter, for a full description of the source and mode of arrangement of the basal system would be beyond our object. From the hasal arterial sj/stem, as represented by the circle of Willis, numerous small branches pass off nearly at right angles, and enter the ganglia near the base of the brain. These are called " terminal" or " end " arteries, because they do not anastomose with one another ; nor do they anastomose with the vessels of the cortical arterial system. The anterior cerebral and the middle cerebral are the main arteries of the forebrain. The former supplies the superior frontal and anterior two-thirds of the middle frontal convolutions, and the upper extremity of the ascending frontal. It has four cortical branches. The first supplies the two internal orbital convolutions ; the second is distributed, to the anterior extremity of the marginal convolu- tions, to the superior, and to the anterior portion of the middle frontal convolutions on the outer surface ; the third passes to the inner surface of the hemisphere as far as the calloso- marginal fissure ; whilst the foui'th goes to the quadrate lobule, and also gives off a branch to the corpus callosum. On the median surface, the corpus callosum, and the entire region from the frontal apex to the sulcus occipitalis, receive their blood-supply from the anterior, median, and posterior internal branches of the anterior cerebral arteries. The oniddle cerebral. in addition to the numerous small vessels which pass through the foramina of the anterior perforated sjoace to the corpus striatum, the two grey nuclei and lenticular nucleus, and to the posterior part of the nucleus caudatus, gives off from its main trunk, as it reaches the island of Reil, several branches. These branches, as given by Charcot, are as follows : — (1) the 64 VASCULAR SUPPLY OF THE BRAIN. external frontal, supplying the inferior frontal convolution ; (2) the ascending frontal to the region of the anterior cerebral convolution ; (3) the ascending parietal to the posterior central convolution and the superior parietal lobule ; (4) the parietal to the parietal convolutions ; and (5) temporal arteries, which ramifjr over the first and second temporal convolutions. The 2^osterior cerehral artery gives off numerous branches in the posterior perforated spot, and others as it passes round the crus, both of which sets pass into the thalami optici, crura cerebri, and corpora quadrigemina. It has three cortical branches, one to the anterior part of the imcinate gyrus and its immediate vicinity ; one to the posterior part of the uncinate gyrus, and the lower part of the temporo- sphenoidal lobe ; and a third to the occipital lobe on its outer and inner surfaces.* From the distribution of the anterior, middle, and posterior cerebral arteries, we see that they determine the blood-supply to certain regions. Each main artery gives off secondary and tertiar}^ branches. These tertiary branches, in their turn, give off numerous fine fila- ments, which, according to Duret, do not anastomose with one another, although a communication may take place, to a certain extent, between the branches of contigiTOus areas. Opinions differ considerably upon this question of anastomosis between the vessels of the cortical system. Heubner, basing his opinion upon the result of his injections, believes that there is a free anastomosis between the main vessels and also between the secondary branches of the vessels of the cortex, the anas- tomosis being effected through vessels not less than a millimetre in diameter. He does not believe that col- lateral compensation is effected solely through the circle of Willis. In consequence of this view, objection is taken to the statement that an artery supplies any definite region or convolution. In support of Heubner's view, we have the fact, admitted by Charcot, that in certain cases of arterial obstruction by embolism or thrombosis, there is an exemption from softening, * H. Diiret, " Archives de Physiol.," 1874, and Heubner, " Centralblatt fiir die Med. Wissensch.," 1872. ARTERIOLES OF THE CORTEX. 65 which would point to the establishment of a collateral circulation. Duret contends that such anastomoses are absent or extremely rare, and he maintains that it is only through the terminal filaments of the branchlets that communications occur. Such communications, however, he believes, may vary in number in different individuals. Cohnheim also maintains that there are no anastomoses between the larger branches of trunk arteries, but that all the cerebral arteries more or less resemble true terminal or end arteries, in that the^^ onlj- communicate with other vessels through their ultimate capil- lary loops. Meynert believes that the arteries supply definite nutritive areas, and that the influence of the derivative net- work is not as powerful as Heubner would have it ; further, he regards, as of great importance in cerebral pathology, the fact that, as there is no derivative network beyond the circle of Willis, these arteries, because of their shortness, are under the more immediate influence of cardiac action, and are therefore more liable to rupture than the cortical arteries. Arterioles of the Cortex. — In his monograph on the structure of the cerebral cortex (1868) Meynert showed that the cortex was supplied with a large number of arterioles from the broad expansion of pia. All these arterioles were about the same size, and entered adjacent portions of brain tissue. Each one. moreover, represented, to a certain degree, an independent circulatory area. His observations led him to the belief that in a mass of tissues, supplied by a smaller number of larger arterial branches, it would be quite impossible for differences of arterial blood-supply to exist simultaneously in adjacent portions of that tissue. From this he inferred that \ partial functional hyperemia of separate cortical areas was > readily permissible, and that the so-called cortical centres could be functionally hyperasmic at a time when the other cortical centres wei'e functionally at rest. The blood-supply to^ie brain^jvould in this way be determined by the functional hypersemia of the areas which A^-^ere in a state of activity. In the pia mater we have, then, main arteries with their branches, branchlets, and fine filaments. From the branchlets and filaments a great number of minute arterial twigs pass at right 66 VASCULAE SUPPLY OF THE BEAIN. angles into the cortex. These are commonly known as nutrient arteries : they are very slender, and vary in length. The longer twigs pass through the grey matter into the white substance, where they approach the terminal twigs of the basal arterial system, but with which, however, they are said to have no communication. In their course they give ofi numerous fine offsets, which communicate with the capillary network of the shorter ultimate arterial twigs. These latter usually terminate in a capillary network within the grey matter itself. In cases of embolism or thrombosis, therefore, Fig. 6. Injected Cerebellum of Cat, showing Cortical Arrangement of Blood-Vessels. A, inner granule layer ; B, layer of corpuscles of Purkinje ; C, external layer ; D, vessels of pia mater. not only does the grey matter of the cortex suffer, but also the subjacent white matter, the amount of destruction, of course, depending upon the size of the vessel obstructed, and the amount of communication existing between it and its neighbours. Meynert states that the larger branches of the arteries, on the surface of the brain, do not lie within the pia, but in the subarachnoidal spaces ; the smaller branches only entering the pia. The general relations between the blood-vessels of the brain and the membranes is, as we shall see, a question of importance, as bearing upon the mechanism of nutrition. Before entering, however, upon this question, we must con- STRUCTURE OF THE CEREBRAL ARTERIES. 67 sider some other anatomical and physiological conditions, which have a direct bearing upon the quantity and quality of the cerebral blood-siipply. ^.... _.- -..A Fig. 7. Short Nutriejjt Artery of Cortex Cerebri, showing Capillary Network. A, pia mater; B, white matter. Structure of the Cerebral Arteries.— The cerebral arteries have less muscular element than those of the body generally. In the larger arteries the tunica adventitia is directly continuous with the pia mater ; whilst, in the smaller vessels, this sheath becomes an extremely fine membranous investment, either structureless or faintly striated, and with nucleated connective-tissue corpuscles upon it. The nuclei of these corpuscles proliferate readily. In some conditions ampullar dilatations are prone to occur. These dilatations are regarded by Bevan Lewis as being due to separation of the adventitial sheath from the tunica media, and a space between the two coats is to be seen at all times in the angle formed by the bifurcation of the vessel. The vessels of the cortex lie in channels — the perivascular channels of His — which are continuous with the epicerebral space. Numerous delicate fibrillar processes, w^hich arise from the stellate cells of the cortex, traverse this perivascular space, 68 VASCULAE SUPPLY OF THE BRAIN. and form connections with the arterial sheath (Be\''an Lewis). The capillaries of the cortex are of extremelj'^ fine calibre (not over 4yu, in diameter, and of less calibre than the red blood- corpuscles). Be van Lewis says, however, that we must allow for possible shrinking of the vessel by emptying its channel, as well as for the constricting effects of reagents, and that we can scarcely conclude that even these minute ramifications do not permit the passage of the red corpuscle. The same author makes the following observations tipon the structure of the capillaries : — " The only constituents of the arterial tunics, which enter into the structure of the capillary, are the endothelial layer or intima and the adventitial investment. In fact, the transition from the smallest artery Fig. 8. Blood-Vkssel of the Human Brain, showin« seveeal Neuroglia Fibre-Cells SURROUNDING IT AND FORMING A FeLT-WOEK (PERIVASCULAR SYSTEM). a. An encircling cell ; p, perpendicular neuroglia fibre entering the sheath at right angles from a distant (extrinsic) cell (Golgi's method). — [Andriezen.) into the larger capillary is indicated by the disappearance of the muscular fibre-cell, and the continuation of the channel as an apparently homogeneous tubular membrane, with oval nuclei along its course, and here and there nucleated connective cells as the sole representative of the adventitial sheath. The intima, which is a direct continuation of the endothelial lining of the arteries, and by many believed to be the only constituent of the capillary, resembles that lining in every STRUCTURE OF THE CEREBRAL ARTERIES. 69 particular, save the number and form of its squamous cells. These are not only fewer, being often reduced to two in a transverse view of the vessel or its lumen ; but instead of being polygonal, are more often elongated into fusiform plates. " In the smaller capillaries the delicacy of the structure is such that it is at first often overlooked until its course is noticed, mapped out by short, narrow, spindle-shaped nuclei, arranged alternately at regular distances on the opposite sides of the vessel. In the same direction also will be found rounded nuclei, staining readily with aniline blue- FiG. 9. Structure of Large Vessel, showing Perivascular Felt-avork of Neuroglia Fibres. Dense on the right side, less dense on the left side o, where it is distinctly separated from the blood-vessel by a space; (S, extrinsic cells (Human Brain, Golgi's Method). — [Andriezen, " Internat. Monatsch. fiir Auat. u. Phys.," 1893, Bd. x.. Heft, ii.) black, sometimes aggregated into groups or arranged in linear series at very ii-regular intervals along the vessel. These are the derivatives of the adventitial sheath, and are, therefore, always external to, and placed upon, the fusiform nuclei. They are often the best guide to the direction of the capillary loops around the nerve-cell." 70 THE LYMPHATIC SYSTEM OF THE BRAIN. THE LYMPHATIC SYSTEM. To the study of the Ijmiphatic system of the brain consider- able importance is attached, and our knowledge upon this difficult subject may be attributed chiefly to the labours of Obersteiner, Key, Retzius, Schwalbe, Meynert, and Bevan Lewis. Obersteiner was the first to define the nature and con- nections of the lymph-channels in the brain; whilst Bevan Lewis is to be credited with having given us the latest and most advanced details as to the relationship of the cortical nerve- cells to these lymph-channels, both in health and disease. It will simplif}^ the subject, if we diverge for a moment to consider the relationship of the cranium, with its rigid Avails, to the brain. Regulation of Pressure of Cerebral Fluid. — Meynert believes that the skull regulates the pressure of the fluid within its cavity, and hence becomes an important factor in the nutri- tion of the brain. He states that if the brain were surrounded merely by rigid cranial walls, a partial change in the distribution of arterial blood would be conceivable. A functional increase, however, would be possible only upon one of two conditions — viz., a corresponding collateral arterial diminution, or a transfer of venous blood in the direction of the sinuses. For the first condition, he thought it would be difficult to explain an appropriate mechanism. A venous transfer would be altogether too slow, and there could not be any continuous action, for the repulsion of the venous current, dependent upon the respiratory movements, would give rise to a frequently interrupted flow of venous blood in the brain. The cranial cavity is not entirely filled by the brain ; it includes, in addi- tion, a number of spaces filled with lymphatic fluid. The dura mater is separated from the arachnoid b}^ a comparatively small space, which is lined b}^ endothelium. This space communi- cates with the lymphatic glands of the neck, and with the sub- dural spaces which do not immediately surround the nerve- roots, but do so in common with the arachnoid, and are con- nected with the hanphatic spaces of peripheral nerves.* As an example, we have the communication between the auditory labyrinth and the subdural space through the spaces which * Meynert, " Psj'chiatry,'" p. 218. LYMPH-CISTERNS. 71 surround the auditory nerve. In the tissue of the dura itself thei*e are also lymph-spaces which are connected with the subdural space. Lymph-Cisterns. — The explanation of the formation of the so-called " cisterns '" is to be found in the relationship of the arachnoid membrane to the pia. They are connected by means of a network of threads and trabeculee of connective tissue, and at the base of the brain by means of perforated membranes. At the summit of the convolutions the threads of this network are narrower than over the sulci ; whilst, at the base of the brain where the subarachnoidal spaces are dilated, there may be no trabeculas. Meynert enumerates the following- cisterns which belong to the surface of the cortex : — " The space of the fossa Sylvii, wliich is merely spanned by the arachnoid, and a space which separates it from the dorsal surface of the corpus callosum, which space extends on the basilar surface as far as the linea terminalis (of the central grey substance) situated beneath the corpus callosum. Farther back on the basilar surface we come upon the cy sterna chiasmatis and the cy sterna interci-uralis, the latter dividing again into a superficial and a deep reservoir. From the cysterna intercruralis and to the outer side wide subarachnoidal spaces extend across the crus cerebri to the corpora quadrigemina — i.e., from the basilar surface to the dorsal surface of the trunk, the cysterna ambietis. Short trabeculse unite the subarachnoidal space just over the corpora quadrigemina to the surface of the latter. The most extensive sub- arachnoidal space on the dorsal side is the cysterna magna cerebello- medularis, extending from the dorsal surface of the oblongata to the cerebellum, on the superior surface of which exactly the same relations obtain as over the convolutions of the cerebrum. " Behind the corpora quadrigemina, the arachnoid of the cystenia ambiens ascends to the upper wall of the cysterna corporis callosi. The flexion of the cerebellum over the oblongata produces, furthermore, a fold in the pia on its way from the cerebellum to the oblongata, the two laminae of this fold giving rise to the tela choroidea of the fourth ventricle. The foramen Magendie leads through the pia from this ventricle into the subarachnoidal space of the spinal canal. In regard to the third ventricle, it is to be remarked that its membranous tela does not correspond to the superior wall of the primary cerebral vesicle, but that the only vestiges of this which remain are the epithelial cells of the plexus choroideus, at the lateral margin, and on the inferior surface of the velum." In the brain-cortex all the vessels are inclosed within channels, known as the iierivascular channels of His. These 72 THE LYMPHATIC SYSTEM OF THE BKAIN. channels are noticeable in hardened sections, and most markedly so in cases of atrophy of the cortex. Bevan Lewis differs from several authors in that he believes they are not the lymph- channels proper, but simply channels in the brain-substance, without an endothelial lining, and having free communication with the epicerebral space. He says these channels appear to be equivalent to an involution of the naJced surface of the brain, and yet the epithelial elements of the epicerebral surface are not continuous along this tubular canal. Their appearance of being lined by endothelial cells is said to be due to the adventitial sheath of the blood-vessels, which becomes " closely appressed " to its limiting channel. The nerve-cell has around it a somewhat similar space, which Bevan Lewis has termed the pericellular sac, and he regards these as genuine sacs, and not mere artificial gaps in the brain-substance.* The peri- vascular channels and pericellular sacs communicate with the perivascular lymph-spaces of the adventitia. The study of the lymph connective system is of great importance in cerebral pathology; but it is yet to be shown how the individual elements of this system undergo morbid changes and cause alterations in the movements of the lymph. Bevan Lewis has summarised his account as follows : — "The lymphatic system of the brain consists of — " (1) A distensible lymphatic sheath, loosely applied around the arterioles and venules, containing numerous nucleated cells in its texture — the adventitial lymph-sheath — the whole being included within a non-distensible channel of the brain-substance, devoid of endothelial lining — \hQ perivascular channel of His. " (2) A continuation of the cellular elements of this sheath, loosely applied to the arterio-capillary plexuses, still contained Avithin a peri- vascular channel, which now exhibit along the capillary loop sac-like dilatations — the pericellular sacs, within which the nerve-cell lies, surrounded by plasma. " (3) A system of plasmatic cells with numerous prolongations, which are always in intimate connection with the adventitial lymph-sheath, and which drain the areas between the vascular branches — termed the lymph connective elements. "Finally, if we take a comprehensive view of the whole system, the channelled vascular tracts, the saccular arapullse along the capillary tube, the canaliculai'-like formation of the lymph-connective elements, all * Bevan Lewis, " Mental Diseases," p. 823. PACCHIONIAN GRANULATIONS. 73 embedded in a homogeneous matrix of neuroglia, we cannot but be struck by the sponge-like arrangement of the cortex, and the facilities so offered for the free circulation of plasma throughout its most intimate regions." Cerebro-Spinal Fluid. — The cerebro-spinal fluid in the brain is secreted by the epithelium of the choroid plexuses in the lateral, the third, and the fourth ventricles, and, possibly, from the general epithelial linings of these cavities. The fluid is transparent, and has a specific gravity of about 1010. The view that the lymph-cisterns act as a water cushion to minimise the shock to the brain and to compensate variations in blood- pressure, is supported by the fact that, in cases of spina bifida, the cerebro-spinal fluid can be readily driven from the spinal canal into the cranial cavity by pressure on the tumour, so that it may be assumed that a passage may be as readily effected in the reverse direction (Bruce).* Before entering upon a descrip- tion of the various brain-movements, it would, perhaps, be well to consider briefly some points in regard to the Pacchionian granulations. Pacchionian Granulations. — Meynert looks upon these bodies as prolongations of the subarachnoidal spaces. They occur in the course of all sinuses, but more particularly along- side of the sinus longitudinalis. The cerebro-spinal fluid is removed from the subarachnoidal space by several channels. Much of it passes into the corresponding space round the spinal cord, and escapes outwards along the subarachnoidal sheath of the spinal nerves. The remainder passes along the corresponding sheaths of the cranial nerves, or is excreted by the Pacchionian bodies into the superior longitudinal sinus in the dura mater (Bruce). The suharacJmoidal space is to be regarded as a true serous cavity, or lymph-space. Langer describes the sinuses, and the veins adjacent to them, as situated in the substance of the dura, and arranged in such a manner that the veins of the antei'ior portions of the hemispheres meet with the veins of the posterior lobes in the walls of the sinus longitudinalis, as though the former (veins) stood in the relation of vasa vasorwn to the latter. * " Tuke's Diet. Psych. Med.,"' p. 172. y 74 THE LYMPHATIC SYSTEM OF THE BRAIN. Meynert lias shown that a definite brain-pressure forces the serous fluid from the subarachnoidal space into the subdural spaces, whence, by a process of filtration, it empties into the veins and sinuses. "The posterior cerebral veins take a similar longitudinal course forward, between the layers of the dura, so that the cerebral veins empty into the sinus for a distance of only 2 cm., and about below the middle of the parietal vertex. The Pacchionian formations push forward into the cerebral veins as diverticula of the subarachnoidal spaces. The veins lie intradural, and the subarachnoidal spaces are shut off from the subdural space. "The subarachnoidal spaces communicate, moreover, with the lymph- channels of the peripheral nerves, which encircle the roots, as does the dura also. From these subarachnoidal spaces we can throw injecting iiuid into the lymph-space surrounding the optic nerve, into the peri- lymphatic space of the labyrinth, and the lymphatic vessels of the nasal mucous membranes." The venous circulation within the cranium presents several peculiar features. The blood flows along the longi- tudinal sinus towards the occiput, and hence its course is opposed in direction to the blood issuing from the cortical veins, which open into the sinus in a forward direction. Hence the fact, that the blood which enters the brain by ascending arteries reaches the sinuses by ascending veins, is made use of to explain the occurrence of thrombosis in these vessels — the explanation being, that here gravitatioi; is opposed to the flow of blood. In this way, morbid processes affecting the scalp — such as erysipelas, caries, or carbuncle — may readily affect intra- cranial structures by means of the communication with intra- cranial veins — e.f/., those of the nose, the facial through the ophthalmic, the mastoid veins, and the veins of the diplooe. Cerebral anaemia is sometimes produced, owing to hydrostatic causes — e.r/., if a person who has been in bed for a long time and whose blood is small in amount, be suddenly raised into the erect position. Such a condition is also not infrequently at- tended by loss of consciousness. Liebermeister regards the thy- roid gland as a collateral blood-reservoir, which empties its blood towards the head during such changes of the position of the body. Quantitative Relation between Blood and Cerebro- spinal Fluid. — There is an intimate relation bet^^•een the BRAIN-MOVEMENTS. 75 amounts of cerebro-spinal fluid and blood within the cranial cavit}-. When more blood passes in, some cerebro-spinal fluid passes out, and rice versa. Formerly it was taught that, as the skull is a rigid box, and as the brain-substance and its fluids are practically incompressible, no variation in the amount of blood in the brain could be possible. This, however, is now proved to be erroneous. The average quantity of cerebro-spinal fluid within the cranium is about two ounces, and if it be suddenly with- drawn, epilepsy or convulsions may be produced ; or, if it be rapidly increased in amount, coma may result. This fluid has also important mechanical functions, protecting delicate parts of the brain from injury, and by distributing vibratory impulses it insulates the nerve-roots. The presence of the cerebro-spinal fluid is, as pointed out b}' Donders, of great importance in regulating the pressure uniformly when brain- movements occur, so that every s3'stolic and expiratory dilata- tion of the blood-vessels is concentrated upon those parts of the cerebral membrane which do not offer any resistance. These movements almost disappear when the fluid is abstracted. The forece (jlandulares, according to Langer and Trollard, are venous, cavernous spaces produced by the wearing away of the vitrea, and are to be found in drunkards, in the senile, and in the subjects of heart disease. They are not, says Meynert, direct impressions of the Pacchionian dilatations of the sub- arachnoidal spaces. Meyer regarded their life as compensatory, inasmuch as they dilate with ana?mia and collapse when there is a full current of blood within the brain. The increase and diminution of the amount of blood and cerebro-spinal fluid within the cranial cavity, is a question of gi'eat importance as bearing upon the nutrition of the brain ; and it is b}^ means of the orderly working of this mechanism that waste products are transferred from the circulation to the lymph-vessels. BRAIN-MOVEMENTS. The movements of the brain are of three different kinds : — (a) iiiulsaiile movements communicated from the pulsations of the large basal cerebral vessels ; (Jj) respiratory move- 76 BRAIN-MOVEMENTS. ments, so that the brain rises during respiration and falls during inspiration ; and (c) vascular elevation and depres- sions which alternate, and are due to periodic dilatation and contraction of the blood-vessels. This last is a peri- staltic arterial movement, regulated by the vaso-motor centre, and occurring from two to six times per minute (Meynert). These movements have been investigated chiefly over the fontanelles of children, and where the membranes have been exposed by trephining. Burckhardt's observations were made upon four patients with defective skulls. The peristaltic move- ments of the arteries dependent upon the vaso-motor centre are believed by Hering and others to be the result of the respira- tion of the vaso-motor centre itself. These movements are common to blood-vessels everywhere throughout the body, but, according to Hering, the stimuli causing such contractions do not always accumulate sufficiently to exert an influence with every respiratory act ; in which case the rhythm of the move- ment is altered by other influences acting upon the vaso-motor centre by stimulation of the sensory nerves. In the case of the brain, which is surrounded by rigid cranial walls, and by the arachnoidal spaces, and from the fact that it is placed under considerable pressure, Meynert believes a modification of this general vascular movement is effected. The vascular wave, according to Mosso, is independent of the pulse and respiratory waves; but it may exert an influence upon the respiratory and pulse waves. The advance of the peristaltic wave within the rigid cranial walls aids in the establishment of currents of brain fluid, whereby metabolic waste products are carried off" through the lymphatic fluids. The brain and the fluid surrounding it are subjected to a certain mean pressure, which depends upon the blood-pressure within the vascular system. Naunyn and Schreiber showed that cerebral pressure must be slightly less than the pressure within the carotid before the symptoms proper to pressure on the brain occur. The vascular wave causes a hemispherical protrusion of the cerebral mass, followed by a bowl-shaped contraction. The height and length of this wave are not equal. The wave flattens in a cool bath, and it is raised in a warm bath. It is most distinct and regular during sleep ; during the hours of waking its regularity is interfered PULSATORY MOVEMENTS. 77 with. Moderatel}' waniT baths of 77-79° Fahr. lessen the number of waves, but make each wave longer ; warm baths increase the number and shorten the single waves (Meynert). In one of Burckhardt's patients a sudden fright, followed b}" an unexpected noise, caused a rapid rise in the curve, followed by a fall. Whilst another patient was plaj'ing at chess low but long extended waves. Avith a few larger perturbations, were noted. He also found that while doing arithmetical work elevations were noticeable at the beginning and at the end, whilst in between depressions were more frequent. Meynert concludes, that all stimuli acting upon the sensorium create vascular movements, and disturb the periodic changes in the condition of the vessels ; and that, of the psychical influences which may cause elevation, the emotions act more readil}-, and bring about a greater change than purely intellectual processes. Great variations of brain-pressure are almost constantly attended by sj'-mptoms of disturbances of the nutrition of the brain. If the pressure is moderate the symptoms may remain latent, or only show themselves as headaclie, vertigo^ weakness, or disturbance of the sensor}- functions. During sleep the\<^ circulation of the lymphatic fluid in the brain effects the removal of the waste products, and this, to a great extent, is dependent upon the vascular movements of the brain. Burckhardt regards the influence of this vascular wave as far more powerful than that of the respiratory wave : the irregularities of vascular wave-movements, which occur when the individual is awake, indicate that in certain parts of the brain there is an independence of action, just as we know to be the case in reflex ^ arterial constrictions on the surface of the body. Let us now consider the so-called ^^ indm,tor[i movements " of the brain. From the circle of Willis the arteries ascend and their currents are directed upwards, as is also the case with the venous currents. The arteries at the base are the first to en- large with the blood-flow ; then the wave passes into all the branches of the vessels. The brain, however, is only able to enlarge concentrically toward the ventricles, on account of the resistance offered by the roof of the skull to the swelling of the convolutions. This concentric swelling of the brain is almost constant, and the pressure is neutralised in the ventricles in 78 BRAIN-MOVEMENTS. part by the circumstance, that, with the increased pressure arising from the flow of blood through the shorter arteries of supply to the basal portion of the ventricles, there is first an equivalent displacement of the cerebro-spinal fluid within the ventricles ; then, when the engorgement of the walls of the ventricles diminishes, the blood-supply through the longer arteries to the cortex is forced by the cranial walls downwards toward the dorsal aspect of the ventricles. In this way less active movement of the cerebro-spinal fluid is brought about than if the basal and dorsal aspects of the ventricles were engorged simultaneously. The cerebro-spinal fluid finds its way through the foramen of Magendie, and to all the cisterns in general, so that the concentric pressure influences not only the contents of the ventricles, but also all the lymph-spaces. Meynert also points out that the engorged parenchymatous arteries effect the exudation of lymphatic fluid from those perivascular spaces which lie between the blood-vessels and the adventitia, so that the systolic pressure is still further neutralised. Coincidental with the basilar constriction the upper parts of the brain are pressed against the cranial roof, and with the increased pressure within these parts resistance is offered to the advance of basilar cerebral fluid. In addition to the escape of fluid through the foramen of Magendie, during the first phase of the vascular systole, a certain amount flows into the veins of the choroid plexus. With the systole of the superior cerebral arteries, we have the simultaneous occurrence of the basal diastole ; but the displaced cerebral fluid does not now return to the ventricle. In consequence of the swelling of the basal portion, the diastole pushes the fluid past the upper cerebral parts (which have been removed to a distance from the skull by the arterial systole) into the Pacchionian bodies and the sinuses, and then into the basilar nerve-sheaths and into the cervical glands. The return of the ventricular fluid is still further prevented by the increase of ventricular fluid secreted by the choroid arteries during their diastolic dilatation. Quinke injected cinnabar into the spinal subarachnoidal spaces, and found that the greater portion penetrated as far as the Pacchionian glands, the dura, the sheaths of the cerebral nerves, and to the cervical glands, but not to the ventricles, or perivascular spaces between the pia and NUTEITION OF NERVE-ELEMENTS. 79 media of the arteries. The explanation of this, as offered by Burckhardt is, that, if an artery, lying in the midst of a peri- vascular space which communicates with the subarachnoidal spaces, contracts, lymphatic fluid will pass from the parenchyma into the perivascular space (in a direction opposed to the course of the injection from the cerebral surface into the perivascular space), because the passage to the subarachnoidal spaces on the convexity of the brain is now unobstructed ; but if this artery in the perivascular space be dilated, it obstructs this passage by filling out the above space, and no cinnabar will be allowed to enter the subarachnoidal spaces. During this stage the lymph- current is impelled toward the veins, as by the pulse wave, which, with less success during cardiac systole, enables parenchyma- tous lymph-fluid to be absorbed by the veins, and, during cardiac diastole, opens up the passage into the subarachnoidal spaces. The act of inspiration causes a fall, whilst that of expiration causes an elevation of the pulse-wave. This influence is most noticeable during forced efforts of expiration, and depends upon variations in the venous pressure. This venous pressure acts retrogressively upon the cerebral venous sinuses. Starting from the torcular, the stasis occurs first in the longitudinal sinus, and the comparatively short sinus rectus ; hence the veins of the cortex are sooner affected than the longer veins of the choroidal plexus. As the result of this venous pressure, con- centric swelling of the hemispheres occurs, although less frequently than was the case with the pulse-wave ; the venous pressure also acts from the vertex downward, instead of from the base upward, as does the pulse-wave. From these brief considerations of the arterial supply, the movements of the brain during systole and diastole, and the movements of the cerebro-spinal fluid, we can gain some idea as to the mechanism of nutrition of the brain ; but as yet we know little or nothing of the modes of nutrition of the individual nervous elements, and it is to this part of our subject that we must now pay attention. Nutrition of Nerve-Elements.— The fact that, when motor or sensory nerves are cut, they begin to die at their central or peripheral ends respectively, suggests to us the presence of some mode of nutrition other than that dependent upon the plasma of the blood. This other condition is found in )C 80 BRAIN-MOVEMENTS. tlie influence of stimulation and conduction. The non-medul- lated tissue of the axis-cylinder exercises a strong attraction for nutritive plasma, but this is rendered more eflective by the mediation of stimulation. During the processes of stimulation and conduction the axis-cylinder is better able to attract nutri- tion from the plasma, and to increase the chemical changes involved b}' the intensity of the nerve-current. The sheath of the axis-cylinder, consisting, as it does, of horny and glutinous substances, has been compared by Meynert to a sieve, which allows the nutritive plasma, as much of it at least as is attracted from the white substance, to fall upon the axis-cylinder, not with the intensity of a full current, but with the more delicate force of rain ; and we must regard the partial endosmotic permeability of the neuro-keratin sheath as an apparatus regulating the physiological needs of the axis-cylinder. Rumpf has shown that the nutrition of the axis-cylinder depends in part upon stimuli, and therefore upon the axis-cylinder's connec- tions with a peripheral sense organ and a central organ. In the brain there is a larger proportion of water than in nerve-fibres generally, and possibl}^ this fact has some relation to the lessened tension (through absence of the sheath of Schwann), and conse- quent greater exudation of plasma. Owing to the denser supply of blood-vessels to the cortex there is also a relatively larger supplj^ of plasma to the axis-cylinder. In the grey substance generall}^, there is a larger percentage of water than in the white, and the nutrition of the former is almost entirely dependent upon its blood-supply ; thus, in this way, it differs somewhat from the indirect and independent mode of nutrition of the axis-cylinder. The nerve-cell is also surrounded by a perforated keratin- sheath which regulates its supply of nutritive plasma. In the grey substance of the cortex there is less danger of suffering from anaemia than elsewhere. This is to be accounted for by the independence of the ganglion-cells and the axis-cylinder, which, under the influence of attraction, stimulation, and con- duction, are rendered, to a certain extent, safe from vascular disturbances. The nutritive function of the nucleus over the albuminoid substance, is insisted upon by Meynert, who also infers a direct relation between albuminoid substances and the percentage of phosphorus. The influence of the nucleus upon YASO-MOTOR CENTRE. 81 the nutrition of the cell has already been alluded to ; and as nuclein contains a relatively large proportion of phosphorus, its influence by some is regarded as of importance, especially in the regeneration of tissues in pathological processes. In order that we may be better able to understand the mechanism of the so-called '•functional hypenemias " of the brain, we must return to the consideration of some "^ anatomical and physiological condition of the cerebral mechanism, upon the efficiency of which the nutritive processes of the brain in great part depend. The vaso-motor centre is looked upon as the chief y centre which supplies all the non-striped muscles of the arterial system with motor nerves, termed " vaso-motor," " vaso-con- strictor," and " vaso-hj^ertonic " nerves. Under ordinary con- ditions this vaso-motor centre is in a condition of moderate rhythmical tonic activity. When this area is stimulated there occurs a general increase of arterial blood-pressure through contraction of all the arteries. Paralysis, on the other hand, causes a fall of blood-pressure through relaxation and dilatation of all the blood-vessels. This centre can be excited directl}' or >^ reflexh*. It shares also, with some other centres in the medulla oblongata, the functions of dominating or controlling similar centres placed elsewhere. The assumption that there is a continuous, regulating, and inhibitor}^ action of this centre upon the heart through the fibres of the vagus, is, according to Bernstein, not, in reality, sufficient, for there is a reflex condition effected through the abdominal and cervical sjanpathetic. All the three cervical sympathetic ganglia, in some degree, supply C vaso-motor power to the spinal cord and brain. The superior cervical ganglion, by its connection with the lenticular ganglion, has power over the movements of the iris ; by its association with other cranial nerves it takes part in the secretion of saliva, tears, nasal, and pharyngeal mucus ; it supplies vaso-motor fibres to the external carotid and its branches ; it also sends branches to the internal carotid which it follows within the skull, innervating the dura mater, the vessels of the anterior and middle brain, both basal ganglia and cortex, the latter through the vessels of the pia mater. It is not yet definitely known whether this superior cervical ganglion is the only vaso- ' 6 82 BEAIN-MOVEMENTS. motor centre for these portions of the brain, or only the chief one. When there is ablation of this ganglion, vaso- motor influence may gradually be supplied by nerves from the cervical plexus, by fibres from the pons, medulla oblongata, and upper part of the cord. The middle cervical ganglion supplies vaso-motors to the thyroid gland, and to the larynx and part of the trachea. The inferior ganglion supplies vaso-motors to the vertebral and basilar arteries and their branches.* It has not yet been proved how far we may regard the cortex as possessing vaso-motor centres. With arterial systole we have vaso-constrictor influence, and with the arterial diastole we have vaso-dilator influence at work ; but, as pointed out by Meynert, mental processes are not interrupted by arterial systole ; therefore they must, to a certain degree, be independent of functional hyperaemia. Meynert thinks that this independence of mental acts may possibly be due to the fact that the cortex itself acts as a vaso-motor centre in its relations to subcortical centres; and, arguing from the evidence of the influence of cerebral activity over the vaso-motor centre, he concludes that the vaso-motor nerves of the cortex do not reach the blood-vessels at once, but that they are interrupted in the subcortical vaso-motor centre ; and that these sub- cortical centres must be constantly in a state of activity for the vascular innervation of the cortex. Every sympathetic ganglion is a vaso-motor centre, possess- ing some independence of action, biit more or less controlled by a higher ganglion of this extensive system. The vaso- motor nerves of the cranium come from the cervical sympa- thetic ganglia, and are arranged in two plexuses in the vessels of the brain — one in the external tunic, and one in the middle tunic of the artery. The veins, possessing less muscular tissue, receive fewer nerve-filaments. Whether the nerve-filaments terminate outside the muscular elements, as maintained by Krause, or penetrate into the interior of the smooth fibres, as believed by Henocque and Arnold, is a problem which we are not prepared to solve. The terminal fibres of these small plexuses of the arteries end by punctiform swellings in the * 'Long Fox, " Influence of the Sympathetic on Disease," p. 13. VASO-MOTOR CENTRE. 83 nucleus, or in the fibre ; or extend along the interstices of the fibre cells. In the veins their terminations are similar ; and in the capillaries the fibrils probably end in the nuclei of their walls. 8ome ganglion-cells are interposed in a bundle of sympathetic nerve-fibres ; others have prolongations of their siibstance on the axis-cylinder of the nerve-fibre. A partial .independence of these sympathetic ganglia is manifested in various phenomena — viz., (a) nutrition may be carried on in spite of destruction of the cerebro-spinal centres, supporting the view of Goltz, that local centres are able to maintain the tone of arteries within their own immediate vicinity ; Qi) reflex irritation of vaso-motor nerves may be limited to the par- ticular tissue supplied, as seen in the continuance of the heart's action after its separation from the body ; . (c) vaso- motor neuroses of the extremities ; automatic and reflex co-ordinate movements and secretions are known to occur apart from the influence of the cerebro-spinal centi"es ; (d) the stimulus of the blood itself acts reflexly upon vascular tone, and the phenomena of blushing, and local hypersemias further indicate the partial independence. When we consider the partial independence in the action of this complicated sym- pathetic system, and the dependence of action brought about by association with the cerebro-spinal system, we readily appreciate the dictum that. "The use of the central cord of the sympathetic is to make the animal and the vegetative worlds known to each other, so that revictualling should be dispro- portionate to waste."* The independence of the vaso-motor portion of the sympathetic is also shown in many conditions of shock or injury to this system. Woakes has pointed out the \\ relation betw^een injury of the nerves of the brachial plexus and loss of consciousness, the resulting shock of the former j being propagated to the inferior cervical ganglioii, and thence to the vertebral artery, and all its branches. We can state, y therefore, that, under certain conditions, sympathetic ganglia may act as independent centres for reflex acts. The import- ance of this fact, in the production of variations in the vaso-motor conditions in the brain, cannot be over-estimated, * Fox, op. cit. p. 43. 84 BRAIN-MOVEMENTS. especially when we seek to understand the etiology of brain disorders.* It is not part of our object, however, to enter upon the numerous questions of innervation of the vessels, and space will not permit us to consider all the conditions under which contractions, dilatations, and reflex vaso-motor effects occur. The statement, that the mutual interaction of vaso-dilator and vaso-constrictor nerv-es, j:>Z'm.s the factor of cerebral inhibition, are the main elements in the regailation vaso-motor tone in the brain, must suffice for the present. At the same time, bearing in mind that the local circulation is regulated mainly by the motor nerves, which issue from the ganglia of the sympathetic, and extend along the arteries throughout their entire course. This vascular tone is altered by pathological changes in the vessels themselves, as in atheroma, fatty, calcareous, and amyloid degenerations, senility, syphilis, alcoholism, etc., and it is of importance that we should take accoimt of the action of the sympathetic system as a causal factor of pathological conditions, which are known to exist with various morbid mental states. Althann,t more than twenty years ago, pointed out that fulness of cerebral vessels was no measure of the good or bad blood-supply of the nervous elements ; but that oxygen was more readily brought to, and carbonic acid more readil}^ removed from, these elements under such conditions. He regarded this as depending upon (a) the chemical constitution of the blood, and (Ji) the quantity of blood that passes through the capillaries in a given time. For an even and satisfactor}- * Long Fox believes that in those forms of hysteria that depend upon definite uterine or ovarian lesion, the deep-seated sense of pelvic uneasiness, nearly similar in position and sometimes equalling in intensity the sacro- coccygeal pain attending piles, the paresis of intestine evinced by meteor- ismus, the increased flow of limi^id urine, the vomiting, the hiccough, the frequent diarrhoia, the palpitation, the faintness, the sighing respiration, the globus, the difficulty in deglutition, the blushing, the dilated pupil, the tears, the tinnitus, the excitation of the emotional area, the occasional epilepsy, melancholia, mania, to which such patients are liable, are all examples of afferent irritation carried to the solar plexus, and thence, from ganglion to ganglion of the sympathetic chain, to the three cervical ganglia ; thence to the eye, the cerebral vessels, and the medulla oblongata. t Geigel, " Virchow's Archiv,," vol. cxix., p. 93. VASO-MOTOll CENTRE. 85 flow of arterial blood through the capillaries Geigel employed the term ''eudia3morrhysis," whilst too little blood (true anaemia cerebri) and too much blood (true hypersemia cerebri) were termed " adiaemorrhysis " and ''hyperdisemorrhysis" respec- tively. The same author stated that the velocity of the circu- lation of the blood in the capillaries of the brain is directly proportional to the arterial pi'essure, and inversely proportional to the resistance ; and that the resistance depends directly upon the amount of intra-cranial pressure ; therefore (as Fick has shown that the intra-cranial pressure is equal to the intra- arterial pressure, less the resistance which the tension of the arterial walls oppose to it), (1) if the contraction force of the arterial wall gets less, intra-cranial pressure will increase and the velocity will become less — i.e., dilatation of an artery causes \/^ anaemia, and not hypersemia ; (2) contraction of the arteries of the b)rain will increase the velocity of the blood-flow through its capillaries. Again, suppose the heart acts more powerfully, raising intra-arterial pressure, while, at the same time, the arterial walls increase their contraction, intra-cranial pressure will be the same, or e'l'eater or less, according as the arterial contraction ecjuals, or is less or greater than the rise of, intra- arterial pressure. Hence, with increased contraction of ai'torial walls, intra-cranial pressure decreases and capillaries widen. On the other hand, with diminished contraction of arterial walls intra-cranial pressure is raised, the capillaries are com- pressed, and the amount of blood circulating through them is diminished.* Geigel believes that the symptoms of cerebral pressure are really due to the interference with the circulation which the pressure produces, and are not the direct result of the pressure on the cerebral substance ; and in support of this he points out that, provided the cerebral circulation is not interfered with, the brain-sxibstance Avill withstand a pressure of two atmospheres and more without harm. The symptoms of high intra-arterial pressure and of ana3mia are very similar, because the supply of oxygen and the removal of carbonic acid are equally interfered with in the two conditions. Geigel regards the effects of embolism or rupture of a vessel as somewhat * Haig, " Brain,"' ]). 315. 86 BRAIN-MOVEMENTS. similar ; embolism or rupture of one intra-cranial artery pro- ducing temporary diminution of circulation in all the other intra-cranial vessels, and the apoplectic shock of embolism is thus due to diminution of blood-supply. . Lewy* believes that this argument holds good only under certain pathological conditions, but denies that it does so for physiological conditions. His views are : (1) that an intra- cranial artery cannot expand M^ithout taking space from other vessels, the space thus taken being so small, that in physiolo- gical conditions it affects the cerebro-spinal fluid, but not the capillary circulation at all ; (2) that when an artery enlarges, the blood meets with less resistance in passing through it ; and possibly the lessened resistance in the artery more than compensates for an}^ slight increase of resistance in the capil- laries due to the expansion of the artery ; (3) that, conversely, contraction of an artery may inci"ease the resistance more than the corresponding relaxation of capillaries diminishes it ; (4) that, when the arteries all enlarge together, the lymph gets out of the way, and the capillaries are so numerous that they will bear a large amount of compression before they are so far closed as to hinder the circulation ; and under these conditions narrowing an artery diminishes the blood-stream, and widen- ing an artery increases it, so that arterial hypersemia is possible. But beyond a certain point this does not hold, for if we imagine the arteries to enlarge so much that the veins are pressed flat, absolute stasis will result ; if the arteries now begin to contract, passage of blood will begin again and increase, and thus a narrowing of the arteries produces hypergemia ; (5) if, however, part of the intra-cranial space is taken up by a tumour, or, again, if a large number of capillaries have been destroyed by injury or inflammation, then a smaller amount of arterial eii- largement may seriousl}^ interfere with the capillary circulation. Grasheyt has shown that stasis in the veins maybe due not only to the enlargement of the arteries, but also to a rise of inti-a-arterial pressure. When this pressure rises beyond a certain height the central veins begin to vibrate, and then the * " Virchow's Archiv.," vol. cxxii. p. 146. t " Experimentelle Beitrage zur Lehre vou der Blut-Circulation in der Schadel undRuckgratshohle." J. F. Lehmann, Miinchen, 1892. VASO-MOTOR CENTRE. 87 amount of blood streaming through is decidedly reduced. At this point it is possible that the symptoms of pathological brain- pressure begin. Grashey believes that true hypereemia cerebri is not pro- portional to arterial contraction, for, if the spastic contraction of arteries is very great, the blood-stream may be stopped alto- gether, and contraction or dilatation of arteries must influence intra-arterial pressure. Contraction of an artery diminishes, whilst dilatation increases, the pressure in it; therefore, dilata- tion of an intra-cranial artery increases the pressure on the veins and does harm. For the proper nutrition of the brain, a diminution of the amount of blood passing through the cerebral veins is unfavourable. When the veins and capillaries become overfilled with blood, the blood, as a result, is only able to move slowly. Grashey also believes that stasis in the veins adds to the intra-cranial pressure by causing an increase in the amount of cerebro-spinal fluid. These effects of a dilatation of a cerebral artery are observed in the case of local dilatations only. The points of importance in the observations of these authors are : — (1) That proper nutrition of the nervous tissues depends more upon freedom of circulation than upon the quantity of lilood ; and (2) that nutrition is carried on imperfectly if there \ is venous or capillary stasis through high intra-cranial pressure. / Burckhardt's experiments go to prove, that the activity of the hemispheres modify the influence of the vaso-motor centre upon peristaltic vascular movements ; and that in sleep, when this activity is lowest, the vascular movements are most regular. Meynert refers the vaso-motor centres, which govern cortical influence, to the grey substance of the anterior division of the l)rain-trunk. in which are situated, also, the other motor tracts, subject to centrifugally transmitted cortical innervation. Further, if the cortex be excited in its capacity as a vaso-motor centre, the influence of the arterial systole upon the vaso-motor centre will be augmented, thus causing active anaemia of the brain, which, as a rule, remains entirely independent of the ansemia of the rest of the body. But since a functionally active cortex cannot impede the development of functional hypergemia, we must assume that the physiological excitation 88 BEAIN-MOVEMENTS. of the cortex increases, in a centrifugal direction, the arterial diastole which forms part of a peristaltic movement. Meynert also believes, that deficient or diminished cortical activity, as seen in various psychical conditions, is attended by an increase of excitation of the vaso-motor nerves connected with this part of the cortex, and thereby affects the blood-supply as well as the chemical changes in the brain, and that increase in functional activity of the cortex is attended by diminution of cortical vaso-motor influences. Whence, he says, it follows that a cortical process of association by inhibiting vascular innervation will result in immediate functional hypersemia. He seeks to explain, that the cortex in a state of func- tional activity imparts an impulse inwards (centrifugally) to the vaso-motor centre, and, that in some way or another, this impulse is transmitted in a centripetal direction from the subcortical centre reacting upon the vascular system. The view, that hypereemia of the superior surface of the brain occurs in direct relation to psychical activity, is supported by the observations of Mosso, Batty Tuke* and Gibson, who have each made observations upon this point. Batty Tuke, however, regards it still as an open question, as to whether this functional hypergemia is produced by reflex inhibition of the vaso-con- strictor centre by direct action of vaso-dilator fibres, or by a combination of the action of the two systems. From these considerations, as to the complex conditions of nutritive supply, we are now in a position to appreciate how essential to mental life is the proper working of the mechanism whereby nutrition of the nervous elements is effected. It need, therefore, scarcely be urged that, if our object be to understand how morbid psychical manifestations may arise through defect of, or interference with, the effective working of the cerebral mechanism, the study of the varying conditions of nutrition of the brain is of primary importance to us, and the importance of it to us can scarcely be over estimated. * " On the Insanity of Over-exertion of the Brain," p. 18. 89 CHAPTEE III. Scheme of the Central Nervous System. Sensory Paths — Cerebral Localisation for Touch — Course of Sensory Fibres — Special Senses: Sight, Hearing, Smell, Taste — Motor Nerves : Cerebral Localisation — Projection Systems : Association Fibres, Fimbriae Proprise — Value of our Knowledge of Cerebral Localisation : Phrenology, Experimental Research, Compara- tive Anatomy, Morbid Anatomy — Sensori-Motor Areas and their Relations to Mental Faculties : Views of Hitzig, Ferrier, Munk, Waller, etc. — Conclusions. SCHEME OF THE CENTRAL NERVOUS SYSTEM. Hitherto we have considered certain nervous elements, as far as possible, according to their individual anatomical and physiological peculiarities. It is now our task to obtain a general view of the chief arrangements of these individual parts in the complicated structure of the brain. A description of the manner in which the elements are combined is obviously indis- pensable to us. For convenience we shall consider the general scheme of the central nervous system in its triple form, both anatomically and physiologically. We shall, therefore, so far as may be essential to our pur- pose, attempt to comprehend the coinplicated system of afferent, associative, and eiferent nerve-tracts as a systematic whole, and it is obvious that the consideration of every psychical process deemed to have a demonstrable physiological correlative involves, at least, the study of some part or other of this system. It is known to every student that the grey matter of the cerebrum is placed external to, and spread as a thin coating over, the white matter of the centrum ovale. The folding of this grey matter into gyri or convolutions, and their anatomical 90 SCHEME OF THE CENTRAL NERVOUS SYSTEM. lines of demarcation, by means of fissures or sulci, are facts also equally M^ell known. JSTor do we need to enter upon a descrip- tion of the arrangement of the masses of grey matter at the base of the brain, which form the corpus striatum (the caudate and lenticular nuclei), the optic thalamus, the corpora quadri- gemina, and the red nucleus and locus niger within the tegmentum of the crura cerebri. The formation of the central grey tube as a continuation of the grey matter of the cord through the medulla, pons, round the iter, and ending at the tuber cinereum, is a stiidy of great complexity; and the variety of ways in which these various parts are connected with each other, by transverse fibres stretching between the two sides of the brain, or by longitudinal fibres extending from the hinder and lower to the fore parts of the brain, is worthy of careful consideration. The cortex cerebri, as we have already seen, contains in its structures the elements which are regarded as being most closety associated with psychical action. To it, all the fibres coming from sensory organs, proceed, and the}" convey the effects of peripheral or external stimulation to the region, or regions, where psychical perception of external agents is supposed to take place. Our knowledge of these sensory paths is, as yet, unsatis- factory and wanting in precision. Sensory impulses enter the spinal cord by the posterior nerve-roots, and may pass, if to the cerebellum, through the cerebellar tract and pos- terior column to the restiform body, and thence to the cere- bellum ; or, if to the cerebrum (after decussating in their course in the cord), through the, posterior half of the pons, into the tegmentum of the crus under the corpora quadrigeminav to enter part of the posterior third of the posterior segment of the internal capsule. The subsequent course of these fibres, however, is somewhat doubtful ; some fibres enter the optic thalamus (Meynert) ; others pass into the white matter of the cerebrum. According to Meynert, the sensory columns of the cord turn suddenly back from the posterior third of the internal capsule, and are distributed to the occipital and temporo- sphenoidal lobes. From the occurrence of impairment of tactile sensibility, associated with disease of the motor regions CEREBRAL LOCALISATION FOR TOUCH. 91 of the cortex, Gowers asserts that some of these fibres go to the parietal and central regions. Whether some of the fibres pass into the optic thalamus, or whether they have no connec- tion with it, but pass, as stated by Bevan Lewis, uninterrup- tedly" between the lenticular nucleus, thalamus, and caudate nucleus, to their cortical termini, is not 3'et clearly decided. Ferrier found that, when parts of the gyrus hippocampi were removed, loss of sensation occurred on the other side of the body. Horsley and Schafer found similar results from destruction of parts of the gyrus fornicatus. Horsley has also found that when parts of these gyri were removed in man, there was slight loss of sensation ; the patient being- unable to feel very slight touches of the limb, and the point localised as touched was usually a segment higher up than the actual point touched. The observations of Flechsig. Monakow, and Dejeriue seem to demonstrate that the course of the sensory paths (kingesthetic) is up the posterior columns of the cord, through the posterior colunni nuclei, the internal arciform fibres ; thence, after decus- sation, by the inter-olivary tract and fillet of the opposite side to the posterior part of the internal capsule, and eventually to terminate in the central convolutions. Mott* has demon- "^ strated that the so-called motor cortex is concerned with the reception of afferent sensory impulses. This view is supported b}- the experiments of Hitzig, Munk, Luciani and Seppili, Tripier and Moelli. Horsley found undoubted sensory defects <^ following the removal of lai'ge portions of the Rolandic area in man. Allen Starr has endeavoured to demonstrate that the tactile sense-centres are situated in the Rolandic area, especially- behind the fissure of Rolando. Wundt, Bastian, and James agree that the central convolutions possess sensory functions. Mott considers that this view is fully supported by the facts of anatomy, embrj^ology, experimental i^hysiologj^, pathology, and clinical observation. To account for tiie fact that the motor paralysis is greater and more permanent than the loss of sen- sory functions, Mott compares the expansion of the centrifugal and centripetal fibres of the internal capsule to two funnels ; the fibres as they lie in the capsule forming the tubes, and expanding * "British Medical Journal," Sept. 1893, p. 685. 92 SCHEME OF THE CENTRAL NEEVOUS SYSTEM. above like cones, the bases of each of which are nearly coinci- dent although the tubes are not. He says there is one important difference, however ; the base of the efferent cone is made up of axis-cylinder processes just after leaving the cells from which thej grow ; that is (comparing a nerve-fibre to a tree), the base of the efferent cone consists of the trunks, from which all the branches and collaterals spring. The base of the sensory cone in the cortex consists only of the terminal twigs of the afferent nerve trunks. As the afferent fibres to the cortex form an arborisation before terminating in the grey matter, it is con- ceivable that a small portion of grey matter of the area con- nected with tactile perceptions will suffice to restore function, but removal of the base of the efferent cone prevents a,ny volun- tary motor impulse starting. So far, however, it has been found impossible to localise accu- rately the areas which represent the different parts of the body. On the grounds that definite localisation of the centres of sight, hearing, smell, and, probably, taste, as well as the respective motor centres, is possible. Terrier assumes there must be a definite region for the various forms of sensibility included generally under the sense of touch, contact, pressure, tempera- ture, etc. He says,* that up to the point of radiation into the cerebral cortex, the sensory paths have been proved to be entirely differentiated from the motor; and that the two should X^become jumbled together indiscriminately in the cortical centres is a hjrpothesis which, j^rimci f tide, is extremely unlikely. In the spinal cord the sensory and motor nerves are distinct from one another. In the pons and crura cerebri they still remain apart. The observations of Veyssiere, Charcot, Reymond, Rendu and others, go to prove that in the internal capsule the sensory tracts are quite distinct from the motor, and may be injured or diseased separately, causing hemianaesthesia on the opposite side of the body as the result.f When the region of the sensory paths in the internal capsule is divided, volitional movements can be effected, but there is no corresponding consciousness by means of the muscular sense. Ferrier asserts, that the same condition which abolishes cutaneous sensibility also entirely annihilates * " Functions of the Brain," 2nd edit., p. 323. t FeiTier, ibid., p. 323. COURSE OF SENSORY FIBRES. 93 the so-called muscular sense ; and that there is no necessary relation between the power of effecting movement and the sense of movement effected — i.e., the paths of muscular sense are quite distinct from the paths of volitional impulse. Flechsig maintains, that the tracts forming the outer third of the foot of the crus radiate from the internal capsule out- wards and downwards towards the hippocampal region. Ferrier found, that destructive lesions of the hijDpocampal region caused profound impairment or total abolition of cutaneous, muco-cutaneous, and muscular sensibility ; and that the degree of duration of the anaesthesia varied with the completeness of destruction of the region in question. Since, however, recovery sometimes takes place after the removal of the hippocampal region only, Horsley and Schafer made additional experiments, and found that destruction of the gyrus fornicatus alone could produce analgesia and anaesthesia of the opposite side of the body. The falciform lobe is now regarded as the cortical centre of those fibres of the internal capsule, destruction of which is the cause of hemianassthesia of organic origin.* The sense of movement (kinaesthetic sense) will be con- sidered with more convenience when we come to study the motor centres; so we leave this subject for the present and take up briefly that of the special senses. Sight. — -The most important of the special senses is that of sight. Gratiolet believed the optic tract to be directl}- con- nected with every part of the cerebral hemisphere, from the frontal to the occipital lobe in man. Hamilton has demon- strated that its connections are A^ery numerous ; but the obser- vations of Gratiolet have not been confirmed. Certain fibres are connected with the basal ganglia, whilst others are con- nected with the cortex. The former probably arise from the * Ferrier says : — " The symptoms observed in the animals operated on prove that the centres of mere touch proper are precisely the same as those of painful sensation— whether from pressure, heat, or otherwise — the latter being merely an intense degree of the former." " All the facts receive the most satisfactory- explanation, if we regard the falciform lobe as a whole, and in each and every part the centre of tactile sensation for the whole of the opposite side of the body ; though probably the various motor centres are each anatomically related by associating fibres with corresponding- regions of the falciform lobe. The association would form the basis of a musculo-sensory localisation."—" Functions of the Brain," p. -344. '94 SCHEME OF THE CENTEAL NERVOUS SYSTEM. corpora geniculata, pulvinar, and anterior quadrigemina, and from the substance of the thalamus ; whilst the latter (cor- tical fibres) join the former to form the optic tract. In the frontal region, the connection with the cortex is ■effected through " Meynert's commissure " (Hamilton).* To attempt to elaborate or explain the relation of the fields of vision of the retina, tracts, and the cerebral optic centre, is obviously outside our object ; nor can we undertake to explain some of the eye-symptoms which occasionally occur in cerebral disease. Gowers states that affections, (a) of the optic nerve (between the eyeball and the chiasma) — i.e., in the orbit, optic foramen, or within the skull — affect one eye only ; (b) of the middle of the chiasma, cause temporal hemiopia; (c) of the optic tract (between the chiasma and the occipital cortex), cause hemiopia, which is always symmetrical. / The centre for sight has been localised in the angular gyrus, around the posterior end of the parallel sulcus, and in the occi- Vpital lobe. Ferrier, Horsley, and ■ Schafer have found that complete permanent hemiopia for the opposite field of vision is only produced when both these parts are removed. If one occipital lobe be ablated, there is hemiopia for the opposite field of vision, but this is of a temporary natiire. Ferrier has also found, that when the angular gyrus of one side alone is removed, complete blindness of the opposite eye is caused, from which, however, the animal soon recovers. Gowers regards * According to Hamilton, other cortical connections join the tract as it winds round the cerebral peduncle. These other connections comprise — (1) a large mass of fibres coming from the motor areas of the opposite cere- bral hemispheres, crossing in the corpus callosum, entering the outer cap- sule, and joining the tract directly ; (2) fibres uniting it to the temporo- sphenoidal lobe of the same side, especially the first and second temporo- sphenoidal convolutions ; (3) fibres to the gyrus hippocampi of the same side ; (4) a large leash of fibres forming the " optic radiation " of G-ratiolet, which connect it directly with the tip of the occipital lobe. There are pro- bably also indirect connections with the occipital region through some of the basal ganglia. These connections with the frontal and sphenoidal lobes are not admitted by some investigators, but all are agreed as to its connec- tion with the occipital by means of the " optic radiation." The optic radiation gives fibres to the optic tract, to the corpus geniculatum internum and extemiim, to the pulvinar and thalamus, to the posterior third of the poste- rior limb of the inner capsule (" sensitive band " of Meynert) and fibres which run betw-een the island of Keil and the tip of the occipital lobe. SIGHT. 95 the angular gyrus as containing a higher visual centre, in which the half fields are combined, and the whole opposite field is represented. Terrier believes, that each hemisphere is in relation with the corresponding half of both retinae, and that the semi-decussation of the optic tracts is maintained in the cortical centres ; and in addition to the representation of the correlated halves of both retinae in the corresponding occipito-angular region, the angular gyrus is the region of clear or central vision of the opposite eye, and, perhaps, to some extent, also of the eye on the same side. Ferrier says — " Each occipital lobe is in relation with the half of each retina on its own side, while each angular gyrus is in relation with the centre of the opposite eye, partly by fibres which are sup- posed to cross in the chiasma, and partly by fibres which reach it after decussation in the low^er visual centres — possibly the corpora quadrigemina. At the same time, also, a partial inter- mingling in the chiasma of the fibres from the centre of each eye brings each angular gyrus, to some extent, also in relation with the eye on the same side."* There are some small fibres at the posterior part of the chiasma which run along the mesial side of the optic tracts to join the internal geniculate bodies of the two sides. These fibres form the inferior commiss^ire of Gudden ; but they are not supposed to have any visual function. Darkschewitsch states that this commissure unites each mesial geniculate body with the lenticular nucleus of the opposite side.f The intercentral connections of the nervous visual apparatus are probably as follows : A set of fibres passes from the higher visual centre in the occipital lobe through the corona radiata and caudal end of the internal capsule, to the grey matter of the lower optic centres, where they end in arborisations. Another set arises in the lower optic centres, and terminates by arbori- sation in the occipital cortex. There appears to be some con- nection between the grey matter of the bulb and cord and the lower optic centres. There is some direct connection (through the tract of the upper fillet) between the cerebellum and the fibres of the optic tract. * " Functions of the Brain," p. 292. t ■' Quain's Anatomy,'' vol. iii. pt. I. p. 118. 96 SCHEME or THE CENTRAL NERVOUS SUSTEM. Munk * maintains that the identical points of both retinae do not correspond to the same points of the cerebral cortex, but that the external half of each retina is associated with the outer half of the visual area of the same side, and the inner half qorj>us genie, lat. nmleits oculomotorlm. cortex cerehrl. Fig. 10. Diagram of the Probable Course and Relations of some of the Optic Fibres. {A^ter Sehafer and Thane. ) of each retina with the inner half of the corresponding visual area of the opposite side. The relation of the visual area of the cerebral cortex to eye-movements is not yet definitely settled ; nor do we know the exact connection between the optic centres * "The Visual Area of the Cerebral Cortex."— " Brain," 1890, p. 45. SCHEME OF THE CENTRAL NERVOUS SYSTEM. 97 and the nuclei of the nerve to the muscles of the globe of the eye. It is thought possible that this connection may be partly effected through the posterior commissure and posterior longi- tudinal bundle, and that it is probablj^ both crossed and uncrossed. Munk found that stimulation of the cortex (in dogs) somewhat beyond the anterior border of the visual area, or beyond the lateral border of the visual area in the auditory centre caused cessation of eye-movements. When these movements do occur they are supposed to be the results of locally-restricted stimulations of portions of the visual area. When there is total extirpation of both visual areas, perfect blindness results, but eye-movements may remain intact, except those which are entirely dependent upon vision. Munk regards the visual area as having nothing to do with those eye-move- ments which are independent of sight ; neither do these move- ments result from excitation of the visual areas, nor does the path of conduction from the place of their excitation to the periphery lead through the visual centres ; consequently the eye-movements which the electrical irritation of the visual area induces, only correspond to particular eye-movements which are the results of visual perception. He further believes that, out- side the visual area, and in his "tactile sphere," there are two spots on the cortex, the electrical stimulation of which causes eye-movements ; and as one or the other spot is excited, so will the eye-muscles which are set in motion give rise to particular movements, just as arm or leg muscles will be brought into action by stimulation of neighbouring spots on the motor areas.* * " Therefore," he says, '• if an animal makes a movement in consequence of having seen anything, it must be concluded that the excitation conducted through the optic nerve-fibres to the visual area is transferred by associated fibres which connect these same areas with the tactile areas, at one time by this set of associated fibres, at another time by that — according to the kind of movement produced ; and so through certain association fibres the excita- tion reaches the spots C or D if arm or leg-movements occur, through other associated fibres the spots i^'' or H if eye-movements take place. In analo- gous fashion the eye-movements are obtained in our case by excitation of the visual area with induction currents, since the excitation produced by the electrical current spreads to the centres F and H by associated fibres, which run from the visual areas to those centres, whether excitation is originated by the current in the central elements of the visual area, or in the fibres themselves where they terminate in the visual area." 7 98 SCHEME OF THE CENTRAL NERVOUS SYSTEM. Munk attaches no significance to the commissural fibres which pass out of the visual areas into the corpus callosum. He concludes that eye-movements are caused by the electrical stimulation extending to the radiating fibres of the corona radiata which go to the subcortical parts of the brain, and that the excitation starts in the central elements of the visual area — i.e., in the radiating fibres where they proceed from the visual areas. These movements correspond more especially to those eye-movements which produce " wandering vision " and fixation of the eyes upon an object previously indistinctly seen. Further, the portions of both retinae of the corresponding side, which are on the same side of the maculae lutae, belong to each visual area ; while the upper, middle, and lower quadrants of those portions of the retina, belong to the anterior, middle, and posterior zones of the visual area respectively. Munk also upholds the view, that the visual nerve-fibres, after their entry into the visual area, are connected directly and immediately with the central elements which serve for the perception of light.* Sherrington,! however, has found that, in the monkey, after a deep frontal section across the hemisphere and into the * The projection of the retinee upon the visual areas, according to Munk, presents itself now in its full significance as the substratum for the localisa- tion of the visual perceptions, since the involuntary eye-movements, which are brought about through the radiating fibres, supply the necessary com- plement. Successive and opposite positions of the objects in Helmholtz's visual fields are yielded by projections, the judgment being assisted by the sensations which bring about these involuntary eye-movements, upwards, downwards, right or left ; thus projection and eye-movements together, permit such rapid and certain cognisance of the visual field, as we observe in animals, and which would be quite impossible if it were necessary to deliberate regarding every detail in the visual field. The discovery of the new radial fibres of the visual area will prevent the anatomical investigator from being able, without further consideration, to refer all descending degenerations which result from removal of that area to the tracts which conduct visual impressions ; but there is, on the other hand, now opened up to him the prospect of being able to distinguish the two kinds of central elements, and of being able to demonstrate their morphological differences — a prospect which is attractive by reason of the proved connection of the radiating fibres with the light-perceiving central elements, and of the associated fibres with the representative elements (Vorstellungselementen). "Brain," 1890, p. 65. I "Royal Society Proceedings," vol. xxxv. p. 407. "Journal of Physiology," vol. xvii.. No. 1, 1894. HEARING. 99 lateral v^entricle (partly entering the internal capsnle) so as to sever occipital from frontal cortex, he could still evoke move- ments by appropriate excitation of all that portion of the cortex which, on excitation, gives conjugate lateral deviation of the eyes — i.e., from the area discovered by Ferrier in the frontal region, and from that discovered by Schafer in the occipital region. The reaction could also be obtained by excitation of (1) the corona radiata underlying the frontal cortex after complete ablation of the cortex itself; (2) the corona radiata running downwards and forwards from the occipital cortex after free removal of the latter ; (o) the internal capsule itself at two distinct places, one in front of, the other behind, the genu ; (4) the cross-section of the corpus callosum about 3 — 5 millimetres behind the genu ; also at the splenium. Sherring- ton concludes that the inhibition, which can be elicited by experimental excitation of the grey cortex and of the under- lying white matter, is fully and habitually exercised in volitional eye-movements. He also concludes that the action may take place, and probably does so usually, in centres which are subcortical ; and that the grey matter of the cortex is not essential to the phenomenon. Hearing. — The auditory nerve is regarded not only as the nerve of hearing, but also as participating in another function — viz., that of helping to maintain the equilibrium of the body through its connection with the semicircular canals. The nerve arises by two roots : a larger anterior root, from which proceeds the vestibular nerve ; and a smaller posterior root, from which the cochlear nerve comes. Each root springs from a median and a lateral nucleus. The fibres from the cerebellum are regarded as being concerned with equilibration. The chief mass of the posterior ganglion fibres of the cochlear nerve cross and pass to the corpora quadrigemina, the internal geniculate body, and to the temporo-sphenoidal lobe. The striae acusticas form a second decussating projection system, and according to Flechsig, the origins of both acoustic nerves are connected by commissures in the brain. The physiological significance of the exchange of fibres between the auditory and the portio intermedia of the facial nerve is not known. The centre for hearing has been localised by Ferrier in the 100 SCHEME OF THE CENTRAL NERVOUS SYSTEM. first temporo-sphenoidal convolution. According to Munk, destruction of the entire region causes deafness of the opposite ear, while destruction of the middle shaded part alone causes "psychical deafness '^ (Seelentaubheit). Bilateral lesions of the first and second temporo-sphenoidal convolutions in man cause complete deafness. Disease of these convolutions is attended with ivord-deafness. The auditory paths are from the auditor}^ nuclei in the medulla oblongata through the pons, where they perhaps cross into the tegmentum, thence into the sensory crossway, and onwards to the auditory centre.* Gowers records two cases of tumour of the first temporo-sphenoidal convolution, in which there were fits beginning with an auditory aura referred to the opposite ear.f Equally important with these effects of disease are the sensory impressions, or '' cmrce," as seen in epilepsy; and just as a discharging lesion of the occipital lobes may cause flashes of light or coloured visual aurse, so sounds or noises may arise through affection of the first temporo-sphenoidal con- volution, and usher in an attack of epilepsy. Mills ij: has recorded a case of word-deafness following an apoplectic seizure, and more complete deafness and partial left-sided paralysis following a second apoplexj^ In this case there were lesions of the first and second temporal convolutions of both hemispheres. The auditory centres are best developed in the left hemi- spheres, but in order to produce complete brain-deafness destruction of both centres is essential. When the posterior thirds of the first and second temporal convolutions of the left hemisphere are destroyed, an almost complete word-deafness is produced. When a lesion is limited to the centre for word- hearing, and causes word-deafness, it will also cause paraphasia and paralexia. In time, such a lesion will lead to secondarj- atrophy of the speech and oro-lingual centres, and also to affec- tions of the association tracts between the sensory and motor- hearing speech centres. The field for all auditory memories * Landois and Stirling, p. 704. t "Take's Dictionary," p. 156. + "Brain,'" 1891, p. 468. SMELL. 101 seems to include the posterior two thirds of the first and second temporal convolutions. When there is word-deafness there is not necessarily, therefore, inability to recall words through other channels ; as, for instance, through their visual signs, in which case the meaning of the word may be understood, although the name cannot be properly verified in consciousness.* Smell. — The olfactory centre, as inferred from anatomical considerations and direct experimentation, is probably localised in the anterior extremity of the temporo-sphenoidal lobe. Ferrier has found, that destruction of this part produced loss of smell on the same side in monkeys. Hughlings-Jackson, and Beevorf have published a case in which there was a growth in the right hippocampal lobule, associated with epi- leptic fits, which were preceded by the sensation of an un- pleasant smell. I The olfactory bulb and tract, in respect of strxTcture and connections, are regarded rather as constituent parts of the cerebrxim than as a true nerve. The tract is a triangular band of white matter, inclosing a central grey neuroglia substance. It lies in the olfactory sulcus parallel to the longitudinal median fissure. Anteriorly, it is continuous with the olfactory bulb, which rests on the cribriform plate of the ethmoid bone, and receives the fibres of the olfactory nerves, which come from the cells of the olfactory mucous membrane. Posteriorly, it bifurcates into two roots — mesial and lateral — which diverge as they pass backwards, and in- close (1) a space (the trirjonmn olfadoriuni), which is known as the middle or grey root of the tract ; and (2) a portion of grey matter lying between the mesial root and the peduncle of the corpus callosum, and continuous with the commencement of the callosal gyrus. § The mesial root, in passing over the trifjonurth olfactoriwn, subdivides it into two parts. Fibres pass from this root to the area of Broca, and others pass directly from the posterior end of the tract into the trigonum, to join the anterior commissure, and thence to the posterior part of the temporal lobe ; or, according to Meynert, they may cross in this commissure to the temporal lobe and hippocampal region of the opposite side. Fibres from the posterior end of the * Mills, "Brain,"' 1891, p. 468. t "Brain," part XLVII. X "Tuke's Dictionary," p. 156. § Quain, vol. iii. pt. L p. 159. 102 SCHEME OF THE CENTEAL NERVOUS SYSTEM. olfactory tract also pass directly into the white matter of the frontal lobe.* The outer root consists of a band of medullary fibres, which passes along the outer part of the anterior perforated space, to disappear about the posterior border of the Sjdvian fissure. It has been traced by some to the island of Keil, the optic thalamus, and to a nucleus in the substance of the temporo-sphenoidal lobe, in front of the anterior extremity of the hippocampus. Taste. — The sense of taste is supposed to have its centre in close relation to that of smell, and, according to Ferrier, it is probably situated somewhere about the lower extremities of the temporo-sphenoidal lobes. The gustatory path crosses in the posterior part of the posterior segment of the internal capsule- Gowers thinks that taste-impressions reach the brain solely by the roots of the fifth nerve, and not through the giosso-pharyn- geal nerve. He admits, however, that the nerves of taste to the back part of the tongue may be distributed with the glosso- pharyngeal, reaching them through the otic ganglion by the small superficial petrosal and tympanic plexus. The centres which we have considered occup}^ parts of the non-excitable cortex. This non-excitable area has been divided into (1) the parts behind and below the excitable cortex, as well as the convolutions on the median surface of the brain, except the marginal gyrus ; and (2) the frontal region anterior to the excitable area. We shall return, however, to the considera- tion of these later ; and for convenience' sake we shall now look at the construction of the apparatus by means of the working of which mechanical movements are effected. Motor Nerves. — The course of the fibres which convey impulses for motion is as follows : — The pyramidal tracts pass from the motor areas of the cortex through the "v'^diite matter of the cerebrum to the internal capsule, where the fibres for the face and tongue occupj^ the knee of the capsule, those for the arm the anterior third of the posterior segment or limb, whilst those for the leg occupy the middle third. They then pass beneath the optic thalamus to the cnxsta of the cerebral peduncle, which they enter and occupy its middle third ; the fibres for the face lying next to the middle line, then the fibres * Quain, op. cit., p. 160. MOTOR NERVES. 103 for the arm, and external to these the fibres for the leg. Their subsequent course is to the pons on the same side, where the fibres for the face and tongue cross to the nuclei of the facial and hypo-glossal nerves of the opposite side. The fibres for the arm and leg go to the medulla oblongata, where they form the anterior pyramids. Subsequently, the greater number cross at the decussation of the pyramids to form the crossed pyramidal tracts, or lateral columns of the opposite side ; whilst a lesser number continue on the same side as the direct pyramidal tracts.* The question as to whether there is ultimate crossing of the latter set of fibres need not detain us here. According to Melius t and Sherrington,^ some fibres pass to the crossed pyramidal tract of same side. The pyramidal fibres are con- nected with multipolar nerve-cells of the gre}^ matter of the spinal cord at successively lower levels, and it is from these multipolar nerve-cells that the anterior roots of the spinal nerves arise. A somewhat similar course is known to exist for some of the motor cranial nerves. After leaving the internal capsule and the crusta they pass across the middle line to their respective nuclei, from which fibres proceed to the muscles supplied by these nuclei. The excitable part of the cortex is, in the monkey, around the fissure of Rolando, and includes the ascending frontal and parietal convolutions with the parietal lobule, and the posterior parts of the three frontal convolutions, as well as the corres- ponding part of the marginal convolution on the median surface of the hemisphere. The exact localisation of the excitable areas of the cortex is of importance not only in determining the seat of discharging lesions, causing local epileptiform fits, but also in determining the possible rela- tions which exist between various psychic functions and their expression in motion. In brief, stimulation of certain parts of the excitable cortex is supposed to give rise to movements in their corresponding muscular areas. These relations may be tabulated as follows : — * Muratoff, " Neiu-ologisches Centralblatt," March, 1892; also "Arcliiv. f lir Anatomie und Physiologie," 1893, Heft iii. t "Proc. Roy. Soc," 1894. X "Lancet," 1894. 104 SCHEME OF THE CENTEAL NEEVOUS SYSTEM. In Monkey. A)-ea stimulated. Part of marginal gyrus opposite to the ascending frontal convolution. Next to the preceding area, on the outer surface, the upper ends of the ascending frontal and parietal con- volutions as far out and down as the horizontal level of the superior frontal sulcus, and as far forwards as the ver- tical limit of the prse-central sulcus. Results of stimulation. Movements in limbs and trunk- muscles of the opposide side of the body (Horsley and Schafer). Movements in lower limb opposite side (Ferrier). Below this latter area, the ascending frontal and parietal convolutions down to the genu or bend in the fissure of Rolando ; bounded below by a line drawn from the upper end of the pras-central sulcus backwards through the genu of the Eolandic fissure to the anterior end of the intra-parietal sulcus, and in front by a line drawn from the prae-central sulcus upwards to the middle line. Below this latter area, a narrow strip of cortex. Below this area, and between the Rolandic lissui-e and the prse-central sulcus. Round the lower end of the Rolandic fissure. Between the inferior end of the Rolandic fissure and the fissure of Sylvius. In front of the latter area, and bounded below by the fissure of Sylvius, three small areas from behind forwards. Posterior part of third frontal convolu- tion (left side). Posterior part of three frontal convolu- tions in front of vertical limb of prae- central sulcus, and a line drawn between this and the middle line, (a) in the angle formed by the two limbs of this sulcus ; {b) between the horizontal limb of this sulcus and the middle line ; (c) below the latter area. Movements in upper limb. Closure of opposite eye-lids, and if the current is stronger, closure of eye-lids on same side (Horsley and Beevor). Elevation of the opposite angle of the mouth. Retraction of the angle of the op- posite side of the mouth. Bilateral movements the mouth. of opening Rhythmical movements of mastica- tion, SAvallowing, and adduction of vocal cords. Aphasia. («) Synchronous movements of turning head and eyes to op- posite side ; {b) head tends to move without or before the eyes ; (c) synchronous movements of the eyes occur before or without the head. MOTOR NERVES. 105 Reference to Fig. 11 will show, that as we pass from the marginal gyrus along the fissure of Rolando, we meet with areas which represent a gradual increase in complexity of function. No sharp line of demarcation is possible, however, between these areas of representation. Horsley and Beevor have given the name of "border centres" to those places, stimulation of which causes combinations of movements. The same authors have found that the different segments of the limb have areas of representation ; those for the lower limb being (in the monkey) in the following order from before backwards — viz., hip, knee, ankle, and hallux ; whilst in the upper limb area they occur in the order from above downwards I S\0'- p" ELBOW 7 JO^o^imhz ; 7 INDEX ^ - J~L\Z 'f^'" OPENING OF.. Fig. 11. Diagram of Motor Areas. {After ITorfiley and Beevor.) — viz., shoiilder, elbow, wrist, fingers, index finger, and thumb, the three first being most represented in front of the fissure of Rolando, while the^ three last are behind it (Beevor). We have, therefore, in the cortex cerebri some fairly definite areas which are apparently directly concerned with the reception of incoming stimuli, and others which are apparently concei'ned with outgoing impulses or motor stimuli. In addition to these areas, however, there are others, which, so far as we know at present, are non-excitable. Ferrier, Horsley, and Schafer have removed that part of the cortex of the frontal lobe situated anterior to the areas which we have seen to be excitable, with 106 SCHEME OF THE CENTRAL NERVOUS SYSTEM. the result, that there were no observable sensory or motor symptoms ; moreover, there was little or no change observable in the mental condition. Ferrier noted a marked mental change when the cortex was stripped from this area on both sides of the brain, but Horsley and Schafer found no mental change whatsoever. We shall have occasion later to return to the question of the functions of this part of the brain, and of the possible relations it may hold to the rest of the cortex, so we now pass to the consideration of the arrangement of fibres, in the so-called " projection systems." Projection Systems. — Meynert has described three such systems. The first ijrojection system consists of fibres which lead to and from the cortex cerebri ; they pass in a radiate direction through the corona radiata, some traversing the basal ganglia, others forming connections with the cells of the central grey matter. In addition, there are cominis sural fibres of the corpus callosum and the anterior commissure, which are supposed to connect the two hemispheres ; and connecting or associatimj fibres, which connect different areas of the same side with one another. Meynert regards the corona radiata as containing fibres from the corpus striatum, lenticular nucleus, optic thalamus, and corpora quadrigemina. The second projection system consists of fibres of great variation in length, which run in a longitudinal direction downwards to the central grey tube. Some of the fibres end in this central grey matter, while others pass to the level of the lowest spinal nerves. The fibres which descend from the caudate and lenticular nuclei pass through the crusta of the cerebral peduncle, and enter the medulla or pons (Flechsig). Those from the thalamus and corpora quadrigemina pass through the tegmentum to join others from the crusta in the spinal cord. Wernicke believes that the caudate and lenticular nuclei are independent, and that the radiate fibres from the corona radiatoj do not enter them. Fibres, however, may proceed from them to the crusta, to join those fibres coming from the thalamus and corpora quadrigemina. Meynert regards the latter set of fibres as being reflex channels, and he looks upon these regions of the brain as centres for certain extensive co-ordinated reflexes. PROJECTIOX SYSTEMS. 107 The third jjrojedion system consists of the sensoiy, and motoi', peripheral nerves. In the meduliary centre we have, there- fore, three systems of fibres — viz., Projection-fibre, Commis- sural-fibre, and Association-fibre systems. The projection fibres are regarded as being direct pro- longations of the axis-cylinder processes of cells of the cortex. The commissural fibres, which connect the hemispheres, include, as before mentioned, the transverse fibres of the corpus callosum, and the fibres of the anterior commissure. The fibres of the corpus callosum come from the cells of the cortex direct, or they are collaterals derived from the projection system. Sherrington has demonstrated that not only does the anterior portion of the corpus callosum contain fibres from the frontal lobes, the middle from the middle lobes, and the pos- terior from the occipital lobes, but that there is also a tendency to scattering of fibres, so that not only similar but also dissimilar parts of the two hemispheres are connected through this commissure.* Hamilton states that some projection fibres also cross the callosum, and then turn downwards in the internal capsule. The anterior commissure is made up of fibres, which chiefly connect the temporal lobes of the two hemispheres. These fibres spread out into a fan-like arrangement in the temporal lobes. There are also some fibres which are thought to connect the olfactory tract of one side with the opposite hippocampal gyrus.f The association fibres vary considerably in length. The fihriw i?rop'ia (Meynert) are short filjres which pass below the grey matter at the bottom of the fissures, and serve to connect adjacent convolutions ; while the long fibres run free or are grouped into bundles in one of the following directions : — (1) a superior bundle runs below the grey matter of the cortex, serving to connect the frontal and occipital lobes, and the frontal and external part of the temporal lolje : (2) an inferior bundle runs a course near the outer wall of the posterior and inferior cornua of the lateral ventricle, and serves to con- nect the temporal and occipital lobes : (3) an a.nterior bundle * "Journal of Physiology," 1890. t " Archiv. fiir Psychatrie," 1878, vol. ix. 108 SCHEME OF THE CENTRAL NERVOUS SYSTEM. passes across the bottom of the fissure of kSylvius, and connects the frontal, especially the third, with the temporal lobe and the anterior part of the limbic lobe : (4) the cingulum forms the chief bundle of the gyrus fornicatus, its fibres pass from the anterior perforated space in front, above the transverse fibres of the corpus callosum, to curve round the splenium of the callosum behind, and to reach as far as the anterior extremity of the gyrus hippocampi. Some of the fibres diverge into the white matter of the hemispheres, and, according to Beevor,* they probably connect the hippocampal and callosal gyri with the cortex of the outer surface of the Fig. 12. X, Short association fibres connecting adjacent gyri ; f.l.s. , fasciculus longitudinalis superior ; cL, cingulum; c.c, corpus eallosum; f.p., fasciculus perpendicularis; /.i.^., fasciculus longitudinalis inferior; fo., fornix ; f.i., fimbria; v.d'A., bundle of Vicq d'Azyr. (After Meynert.) hemispheres : (5) a perpendicular bundle runs in front of the occipital lobe, and connects the inferior parietal lobule with the fusiform lobule : f (6) the fibres of the fimbria of the fornix connect the hippocampal region of the limbic lobe with the corpus albicans ; and, through the bundle of Vicq d'Azyr, with the thalamus opticus. • " Phil. Trans.," 1891. t Wernicke, " Lehrbuch tier Geliirnkrankheiten," 1881, vol. i. CEREBRAL LOCALISATION. 109 Value of our knowledge of Cerebral Localisation, — Hitherto, the attempt to proceed beyond the objective evi- dences of the localisation of the motor and sensor}^ functions, to the localisation of the parts of the brain subserving the sub- jective side of mental phenomena has been attended with very great difficulty, and these subjective conditions still remain upon a most unsatisfactor)' basis — e.'/., in various morbid mental conditions, where the state of consciousness is more or less altered, it is difficult to explain or localise the seat of the lesion when there is no evidence of paralysis of the motor or sensory functions, and vice versa. The nearest approach to the connecting-link between the seat of intellect and the sensorv and motor functions has been made by the minute study of such conditions as aphasia, and of this relationship Bastian has formulated (provisional!}-) a general law as a working hypo- thesis — viz., " The tendency to mental impairment with aphasia, and the degree of such impairment will, other things being equal, increase as the lesions of the left hemi- sphere, which produce aphasia, recede in site from the third frontal convolution, and approach the occipital lobe." The exact localisation of the excitable cortex is of the highest value in determining accurately the seat of discharging lesions, causing epileptiform fits, etc., but no matter how exact the study, or how accurate the inferences drawn therefrom may be, such data still leave us far from the localisation of mental phenomena. Let us now look more carefull}^ at some of the facts before us, and let us endeavour to arrive at some conclusion as to how far we are really able to localise even the simplest mental state. (1) Phrenolor/ical mc^jpintj out has proved of no value hitherto, and we are forced to acknowledge that phrenologists have not shown us anything that is verifiable. (2) ExjJerimental research has done much to determine certain phj^sical relationships between cortical areas and afferent and efferent impulses. (3) Coinparative anatomy has also done much by demonstrat- ing that differences of brain structure coexist with differences of mental faculty in races and species of animals. Meynert gives three anatomical facts which render a functional differentiation of the various cortical regions highly probable : («) the develop- 110 SCHEME OF THE CENTRAL NERVOUS SYSTEM. ment of the olfactory lobe in different animals associated with the amount of use of the olfactory sense ; (&) the difference in the relation between the median and the convex surfaces of the cortex in animals with strongly-developed olfactory lobes, and in man ■ (c) in the human brain the walls of the Sylvian fissure, are most highly developed. Man excels in the develop- ment of the regions associated with speech, and in the number of convolutions belonging to these regions, as animals with highly-developed olfactory lobes excel in regard to the size of these lobes. Therefore, he believes that the evolution of certain psychical functions goes hand in hand with a proportionate development of certain regions of the cortex. Other morpho- logical points would apparently lead to the same view — e.g., the quantitative differences in the brain trunks both in man and in animals dependent upon quantitative variations in the different parts of the forebrain, giving the idea of a harmonious dependence between the form of the brain-trunk structure and the quantitative development of the forebrain. (4) Morbid anatomy, or the noting of the effects of lesions in different parts of the brain. Kirchhoff* asks the question, " To what extent have focal diseases aided in our knowledge of the location of mental disturbances ? " If we take into account only the lesions which interrupt the various conduction systems, we do not gain much knowledge as to the centres which are probably affected. Of the basal ganglia, the optic thalamus would appear to be more closely connected with the mental functions than the corpus striatum ; inasmuch as the former alone undergoes atrophy in congenital absence of the cerebral hemispheres. Kirchhoff believes that the disturbance in the intellectual development of individuals, in whom the corpus .callosum is absent, or only very small, indicates that the higher mental processes are not dependent upon the frontal brain alone, for in these cases the occipital lobes are mainly atrophied. In some idiots, also, who have imperfect development of the brain as a whole, it is impossible to localise satisfactorily. Nor does he admit of any further conclusion being drawn from the study of irregular development in the cortical layers, unless the area so affected is circumscribed. " For example," he says, " in a * " Handbook of Insanity," p. 9. LOCALISATION OF THE MENTAL FACULTIES. Ill few idiots the frontal lobes contained only very few pyramidal cells, which were distributed irregularly, so that it was almost impossible to distingiTish the layers." In these cases the im- perfect mental development may be attributed to the imperfect development of the frontal cortex. Localisation of the Mental Faculties. — In the "^ attempt to localise activities of the mind, some assert, that each of the ultimate microscopic elements of the grey substance (ganglion-cell) represents a distinct psychical element (sensa- tion) ; others regard the brain as acting in its entirety, or at least through large areas. Before granting that the mind has its seat in the brain at all, let us look at some of the reasons which have led to this conclusion. (1) The brain («) is an indispensable medium between certain changes in. the peripheral parts of the body and corresponding changes in the states of consciousness ; (b) it serves as a basis for the execution of the ideas and volitions of the mind. If nothing takes place here, nothing at the periphery of the body will come from the volitions ; if anything wrong takes place here, all that goes on at the periphery will be wrong, and the mind will not get its volition executed, (c) The brain seems to serve as the special physical basis of the ideas and volitions of motion themselves. After experience in moving a particular member of the body has once been gained, that member may be lost ; and yet, if the proper areas of the brain remain unimpaired, the ideas, feelings, and volitions connected with the movement of the lost member will still arise in the mind. The man whose leg or arm has been amputated can still feel it, can form the image of how it should be moved to be in this position or in that, and even will to have it moved. The leg is not, then, the organ of these ideas, feelings, and volitions (Ladd). (2) If the cerebral hemispheres of animals are removed various effects are produced. Ferrier says there is little difference from the normal mental condition. Vulpian* found, that not only may a fish be urged to move by bringing an object before its eyes, but it would also avoid obstacles as if still possessed of a sense of vision. Steinerf said ^y that the only difference was a greater tendency to impulsiveness, and V less caution in those which had been operated upon ; further, not only do they see their food, but discriminate between the different kinds of food. * '' Systeme Nerveux," p. 669. t "Die Functionen des Centralnervensystems, Zweite Abtheilung," Die tHsche, 1888. y 112 SCHEME OF THE CENTEAL NERVOUS SYSTEM. It is often difficult, so far as their movements and response to peri- pheral stimuU are concerned, to distinguish between a normal and a brainless frog. Terrier believes that, if the observations of Goltz and Steiner are correct, the principal points of distinction between the brainless and the normal frog— namely, the absence of spontaneity and the power to feed itself, which are said especially to characterise the former — are no longer capable of being upheld, and that the brainless frog behaves precisely like the brainless fish. Longet believed that the removal of the cerebral hemispheres anni- hilated only perception proper, as distinct from crude or brute sensation, which had its centre in the mesencephahc ganglia.* Ferrier says that, if the results obtained by Schrader are correct, we must clas^ birds with fishes and frogs, which retain their sense of sight and guide their movements accordingly, even when the cerebral hemispheres are removed. In animals generally, there are great variations, according to their lowness in the scale. Adaptive reactions appear to be better organised in the mesencephalic and spinal centres in fishes, frogs, and pigeons than in the lower mammals, and least of all in monkeys and man. Can we infer, from the adaptive actions of the lower centres, that there is intelligence at the root of those actions ? Ferrier believes that facts lead to the conclusion that between the simplest reflex action and the highest act of intelligence there is no essential difference, the one passes by insensible gradations into the other. He says we can infer only ; we can prove nothing. We can say that the activity of the lower centres does not affect the consciousness — as in lesion of the internal capsule, when the sensory tracts are cut off from their cortical connec- tions. The individual has absolutely no consciousness of impressions made upon his organs of sense, so that we may conclude that, in man at least, states of consciousness are indissolubly connected with the activity of the cerebral hemispheres. Further, says Ferrier, " one may remove, anteriorly or posteriorly, from above, or from the side, a considerable portion of the cerebral lobes without destroying their functions. Even a small portion of these lobes, therefore, suffices for the exercise of their functions. In proportion to the extent of the removal, all the functions become impaired and gradually fail; and beyond certain limits they are altogether annihilated. The cerebral lobes, therefore, co-operate as a whole in the full and complete exercise of their functions. Finally, when one form of perception is lost, all are lost; when one faculty disappears, all disappear. There are, therefore, no special seats, either of special faculties or special perceptions. The faculty of perceiving, judging, and wihing one thing resides in the same region as that of perceiving, judging, and willing another; consequently, this faculty, essentially one, resides essentially in one organ." * Flourens, " Systeme Nerveux," 1842. LOCALISATION OF THE MENTAL FACULTIES. 113 Certain areas of the cerebral cortex do appear to be con- cerned with the execution of certain functions of the mind. We cannot regard the mind, in its special relation to the brain, as limited to any point or small area of the cerebral cortex. Nearly all observers are agreed that considerable parts of the cortex can be destroyed Avithout impairment of any of the special functions or faculties of mind. In fact, there is nothing to indicate that the mind depends upon cerebral activities concentrated in any one minute circumscribed spot. Goltz,* jMunk. and Flourens agree in thinking that the most important cerebral functions, from which we conclude mental functions, cannot depend on definite sections of the cerebrum. If we accept the doctrines of the more recent English school — that individual sensations or ideas exist only as mem- bers of a connected, conscious series, and that consciousness, therefore, can never be conceived as a mere sum or mere product ; t and if we believe with Hume that consciousness is a mere succession of ideas without inner bond or connection, or that it is the series of our actual sensations (John Stuart Mill), it may be thought possible that there are individual nervous elements which possess isolated and distinct forms of con- sciousness. From pathological conditions we do not appear to obtain evidences which may be termed conclusive ; nor do such evi devices prove to \is that consciousness is confined to an)^ supreme part of the cerebral cortex. Glowers i: says. " With the much disputed c{uestion of the relation of mind to brain, the physician has nothing to do. It is enough for him to recognise that mental manifestations and cerebral activity invariably coincide, and that the character of cerebral pro- cesses in some way determines mental states. In the study of diseases of the brain we are concerned only with cerebral processes. Unfortiniately, however, the chief terms available are those of psychology, and we are obliged, therefore, to speak of mental processes when all that we need speak of, and are, indeed, justified in speaking of, are cerebral processes. How- * " Pfliiger's Archh'.," xxvi. p. 35. t Hoffding, "Den engelske Filosofi i vor Tid," Copenhagen, 1874. X " Diseases of the Nervous System," p. 98. Ill- SCHEME OF THE CENTRAL NERVOUS SYSTEM. ever undesirable sucli a confusion may be, it is practically unavoidable.* What are the cerebral processes which in- variably coincide with mental manifestations ? Can we imagine any one cerebral jDrocess, or set of processes, which coincide with any one mental state or group of mental states ? Until we are in a position to answer these questions, it is obvious that we are, in reality, not in a position to speak of mental processes solely as cerebral processes. Nor do we know where to look for the junction of these cerebral processes with their " coinci- dental " mental processes. The pathological data with which we are furnished, are, however, by no means to be ignored. Cases in which there has been complete destruction of one cerebral hemisphere, without mental disturbance, have suggested the possibility of vicarious activity of the other half of the brain, provided that both halves possess originally the capacity for exercis- ing the same function. KirchhofF regards this question of the co-ordinate value of the hemisphere as of the highest importance in the examination of the site of individual func- tions. Similai-ly, in aphasic conditions, the consideration of the physiological variations in the course of speech conception, is of manifest importance. Further, although (as we shall see presently) we are not in a position to say that conscious movements originate in the motor centres ; these centres, nevertheless, constitute stations, or connecting- links, for the transmission of such processes ; hence, with disease or destruction of these areas, there is a tendency to restriction of the objective manifestations of consciousness. In the same way, affections of the so-called sensory areas may restrict or modify the amount or quality of sensory representa- tions in consciousness. In fact, although we cannot bring pathological processes into direct apposition to morbid mental processes, we can conceive, on a lower platform, various con- ditions of disease which lead, in an unknown way, to restric- tions and variations in the phenomena contained in that highest of all platforms — the seat of human consciousness. Speaking of the difficulties of nerve-conduction through the * The facts with which the alienist has to deal are in the main psychic facts. LOCALISATION OF THE MENTAL FACULTIES. 115 network of fibres in the grey substances, Meynert points out, that we may infer that this enlarged surface will be able to per- form a number of totally independent functions ; that a sensory perception, for instance, need not give rise immediately to a motor act. Everj^ spinal <^.ord segment embraces the whole of V the grey siibstance, whereas sections through the cortex contain but a small portion of the cortical grey. This distribution of grey substance will naturally prevent the entire cortex from acting to one single end, while it favours the isolated action of various cortical regions. Irradiation of functions is facilitated / in the grey substance of the spinal cord, and rendered difficult in that of the cortex. Further, purely morphological data and a single pathological anatomical fact will enable us to determine which regions of the cortex, in the probable division of labour, take upon themselves centrifugal functions in the sense applied in Bell's law. The expression " irradiation of functions'^ at once suggests a clue to our actual pathological posi- tion, and we are forced to confess, that pathology, so far, has truly served to demonstrate the implication by disease of the sites concerned with the irradiation of functions, and not of the actual ultimate site of consciousness. Our position, therefore, is only a step higher in the confirmation of Bell's law, of the conduction of nerve-force in a centripetal direction through the posterior, and in a centrifugal direction through the anterior spinal roots. In our attempt to find the site Avhich is concerned directly with consciousness, we have explored various sensory and motor regions from an objective and phj^siological point of view. Before leaving these regions, however, let us really make sure that we are justified in concluding that conscious- ness is not ultimately determined in this sensory or motor platform — i.e.. can we find any reason which would justify the belief that any subjective condition or state of conscious- ness may arise directly from the objective functioning of the so-called areas of sensation and motion without the aid or collaboration of other still higher centres? First of all, let us try to answer the question. Are the so-called " motor centres " and "' sensory centres " really the centres for pure motor and .sensory events ? or, as put by Waller, " Have we reached 116 SCHEME OF THE CENTRAL NERVOUS SYSTEM. any true dead end to knowledge in the conclusion that the cerebral cortex contains ' sensorj^ centres ' and ' motor centres,' and, if so, what signification do we attach to these final terms?"* On the question as to whether excitation-effects are caused by direct actioii upon particular centres in which the voluntary motor impulse arises, or whether they are attributable to an excitation of subjacent fibres, or whether any third possibility exists? Hitzigt says, v/ " Even if we assume as proved that the movements in question are hberated by the ganglionic substance — and it is not proved — this would not be enough to prove that with these movements which are Hberated by the internal event, that precise portion of the cortex furnishes the substratum of the first outward step in the series beginning with the origination of a sense-impression, and finding a temporary end in the expression of will evidenced as muscular movement. " It is, on the other hand, far from inconceivable — and the notion is favoured by our knowledge of the anastomotic structure of these parts — that that portion of the brain which includes the birthplace of a will to move is of another, or perhaps of a more com]3lex nature, and that the parts which we have called centres only constitute agencies, ex- changes, in which an arrangement of muscular movements occurs, similar to that effected through the grey matter of the spinal cord and basal ganglia, but more purposeful." From experiments made upon two dogs, from wdiich por- tions of the motor areas were removed, Hitzig concluded that the animals in question, after the operation, had only an im- perfect knowledge of the state of the affected limb, and that they had lost the power of forming complete representations of it. " Still," he says, " it is clear that very exact representations of the state of muscle must be produced — as we learn from these very images of movement — and it is equally clear that these images are attributable chiefly to the perception of the muscular stage and only in minor degree to joints, skin, etc., this we learn from the well-known illusions of movements occurring in the paralysis of the ocular muscles. "If, nevertheless, our representations of the muscular state of our own body do not overstep the threshold of distinct consciousness, and thus enable us to see into the true nature of the process, we must attribute this failure to a very general law. We are able to distinguish * "Brain," 1892, p. .333. t "Brain," 1892, p. 135. > LOCALISATION OF THE MENTAL FACULTIES. 117 the state of particular organs only in so far as is necessary and suflficient for their use in the uninterrupted maintenance of their functions. " But within such limits the apprehension of these mainly uncon- scious representations of each particular phase of movement, constitutes one of the necessary conditions of a normal progress of its succeeding phase ; subsequently (considering apparent muscular repose as a phase of movement), one must recognise that muscular states in general are among the various causes that guide the organism in its voluntary movements, and that regulate these movements. Let us assume an entire absence of all other sensory stimuli and perceptions, so that we have to do with a simple motor machine of such a kind, set in motion by the muscular impulse, we may then very well imagine it as sufficient for the execution of purposive movements. " AVe have recognised in the above-described portions of the cortex an organ, the function of which coincides with that aspect of the psychical phenomenon that we have been considering, and I do not see the necessity for admitting that will, as such, involves a specific and motor organ." Munk * says, "Just as the cortex of the occipital lobes stands in relation to vision, and that of the temporal lobes to hearing, so the cortex of the parietal area stands in relation to common sensation (Gefiihlsinn) ; in this, as in the other cases, we have the locus where perception is consummated, and where representations — the inemory ^^ images of perceptions — have their seat. Let it be clearly understood, however, that it is not sensation of the skin only that is here in (juestion, but sensation in its broadest sense — the sensation of the Avhole body." Further, he asks, " What are the organs, of M'hich the modifications can reach consciousness as neural sensations ? These organs are : the subcortical ganglia or centres in brain and cord, that invoke movements. As in the infancy of the animal, the representations of movement are developed from its first purely reflex movenients ; as in the adult animal, the representations of movements of a part of the body can still arise in its sensory area, even if {e.ff., in locomotion) this sensory area is not actually participating in the accomplishment of such movt^- ments ; as, finally, the representations of movement lost in consequence of cortical extirpation in a given part of the sensory area, may be formed out of the reflex and automatic movements of the affected part, it cannot but be that fibres ascend to the cerebral cortex from sub- cortical motor centres or ganglia, as well as from the skin and from the muscles — the fibres that subserve cortical perception of these sub- cortical centres. " Our neural sensations are indeed, for the present, to be distinguished from what has hitherto very generally received the name of neural sensation (Innervationsgefiihl) — from the 'perception of the intensity of voluntary effort in connection Avith voluntary movement,' 'will,' * Du Bois-Reymond, " Arcliiv., ' 1878, p. 162. 118 SCHEME OF THE CENTEAL NERVOUS SYSTEM. ' voluntary movement/ with seat and origin in the cerebral cortex, are indeed very convenient, and may, therefore, also be, valid expres- sions, but they are destitute of a phenomenal physiological substratum. All we know of the cerebral cortex is, that it is the place of perceptions and the seat of representations. Beyond this, it is merely admissible to assume, as has been assumed by Meynert on somewhat different data, and by Wernicke, that representations of movement are the causes of so-called voluntary movements ; that with the production of such a representation to a given degree (and, indeed, with a production via sensation, not via its ordinary constituent sensations) eo ipso the corresponding movement is elicited ; and that the greater its forma- tive representation the greater the resultant movement. The * percep- tion of voluntary effort, in connection with voluntary movement,' might, indeed, be the attribute of a representation of movement ; a true perception might still obtain only indirectly, quite independently of the ' will,' and the percept Avould then be nothing but the neural sensation in the sense just set forth." Waller adopts the view that every centre must be sensori- motor, and in the two difTerent components of the double term he does not recognise any phenomenal division of the central process into sensory and motor. He says, "Between centripetal and centrifugal impulses I see a single psychical process, one and indivisible ; to call it sensory or to call it motor, or even to call it sensori-motor, are, to my thinking, imperfectly and improperly to designate it by more or less subjective terms, with more or less obstructive connotations. All that I can recognise in the notion of a centre is an organ of elaboration receiving and giving out impulses. By the term motor I denote that it emits but fail to denote that it receives ; by the term sensory I denote that it receives (and imply that it feels) and fail to denote that it emits impulses ; by the term sensori-motor I denote reception, ' feeling,' and emission. All these meanings when closely analysed are illegitimate, and convey too little or too much. Experimentally I may not predicate 'feeling 'of any centre, biit only of the hypothetical ego, I may only infer from visible movements that other animals ' feel,' and that sensations similar to my own are associated with the activity of certain centres. " I picture a wave of change passing through a cell, but do not know at what transverse section of the wave to label it 'motor' or 'sensory.' The property of cortical grey matter is senso-motivity ; the most typica so-called motor cortex is senso-motor ; the most typical so-called sensory cortex is senso-motor. " A central process is not sensory or motor, but senso-motor (in a guarded sense), and a centre is an ' organ of return of action.' " By those who make a distinction and contrast between a motor and sensory process, the motor idea is a mental picture of movements about COXCLUSIONS. 119 to be made, the kinaesthetic idea is a mental picture of movements just made. The motor idea is considered as an antecedent to motion, the sensory idea as its consequent. " It is not possible to distinguish a ' kinsesthetic ' image of past movements from a ' motor ' image of impending movements. The two words denote one thing. Nevertheless, we can and do recogTiise in the use of the word senso-motor, which connotes the notion that the centripetal generates the centrifugal phenomenon, the principle that phenomena have generators and consequent antecedents; we are reminded by the word that a centre is an organ of return of action and that the type of all motor action is a reflex act. This principle is recognised by all leading workers and thinkers — by Hitzig, in his con- ception that the motor area of the cortex is a ' muscular sense ' area : by Munk, in his conception that it is the motor ' Fiihlsphare ' ; by Bastian, in his conceiJtion that it is the centre of ' kinsesthetic ' impres- sions. These three concex)tions are but one and the same conception^ which I most explicitly and unreservedly accept as a fundamental article of thought." Waller points out that his remarks do not directly involve any question of actual localisation. Its main arguments are equally applicable, whether senso-motility be the property of the entire cortex or of only its Rolandic area, whether we admit motor and sensory centres as taught by Hitzig and by Ferrier, or the cortical map of Munk, or indifference of function in the unrestricted sense of Flourens, or in the restricted sense of Goltz. In whatever light Waller looks upon this question, his remarks — " Thought of movement is memory of movement, or, more generally, the thought is the remembered. An impulse, an intention, a resolu- tion ; a prayer is a more and more concentrated act of attention, of memory, of thought. An identical neural process is the essential phenomenon wrapped up and presented in these very different words : will, attention, memory, belief, thought '' — would appear to infer such functional attributes to the Eolandic area of the cerebral cortex— z.e., to a region essentially sensori-motor in function. He also disagrees with the exclusion of the motor zone from the sphere of consciousness, as enunciated by James, Bastian, Ferrier, Gotch, and Horsley. To James's comparison of the motor area to the mouth of a funnel (through which pour outgoing impulses, caused by incoming impulses) he also takes exception, at least, in so far as the theory holds that the functions of the structures at the mouth of this funnel may be only those of consciousness of the kinsesthetic ideas and sensations, and that this consciousness accompanies the rise in activity of them rather than its discharge. To James's hypothesis that these paths all run one Avay — that is, from " sensory " cells into " motor " cells, and from 120 SCHEME OF THE CENTRAL NERVOUS SYSTEM. motor cells into muscles, without ever taking the reverse direction — he agrees ; whilst with the statement, " All cells are ' motor ; ' we simply call those of the Rolandic region — those nearest the mouth of the funnel — the motor cells par excellence,''' he agrees, "most unre- servedly." Further, he says, " Any motor or discharging centre must also be a ' sensory ' or receiving centre ; it must be excited as well as excite. Any ' sensory ' centre must also be motor, directl}'- or indirectly ; else we could have no objective tokens of sensation ; every centre, whether called motor or sensory, is terminus ad quern as well as terminus a quo." Let us add to these views those of Meynert — ^viz., " Actual sensation is developed by the evolution of equally unknown external forces, which we must suppose differ very materially from one another. Nerves and nerve-cells possess no motor power. Indeed, there is nothing more certain about the functions of the cerebral organism, than that the centripetal sensory nerves are the keys which wind up the mechanism connected with the muscles, and excite the latter to action. "A varying functional energy of brain-cells, according to the special organ of sense with which they may be connected, is quite indemon- strable, since we are acquainted with the physiological conditions favourable to the action of external forces, and can prove easily enough that it devolves upon the terminal organs of the nerves to meet these conditions. " Specific energies, therefore, depend altogether upon the peculiari- ties of the end organs, and sensitiveness is the only specific property of brain-cells^ Conclusions. — What are v\'e to iearn from these con- troversies ? Are we, after all, any the better able to come to any conclusion as to whether consciousnes;:; exists, as such, in the areas we have considered? or is some higher area essential to the psychical events ? If we look upon the so-called sensory and motor areas as containing the structures which have sensitive- ness (by this we do not imply any psychical correlate or state of consciousness) and the power of furthering, or even adapting, forces in a determinate direction ; and, if we regard this physical apparatus more as a further advancement in com- plexity of the fundamental reflex power, it is obvious that the areas of such activities are only in a degree more closely approximated to the actual site of consciousness than other centres on a lower level in the cerebro-spinal system. I^rom experimental investigations upon animals, it may be gathered that extirpation of a certain region, or regions, is followed by total loss of sensori-motor functions, as viewed objectively, but CONCLUSIONS. 121 this is no guarantee that subjective psychical conditions are not still present. On the other hand, just as we may have compli- cated adaptive movements of exceeding fitness performed by the animal whose cerebrum has been destroyed, so we may have complicated mechanical, and even, apparentl}^ intellectual per- formances brought about on a higher level without the slight- est evidence of any conscious psychical correlate. By this is meant, that fitness of reaction is no sure evidence of immediate conscious guidance. The functions of the so-called sensori-motor areas, therefore, can furnish us with no more proofs of their being ultimately concerned with consciousness, than can the activities of lower centres \\diicli possess the same fundamental properties, although developed in a lesser degree. The theory of reflex action, as first applied to explain cere- bral processes by Laycock, has been very generally accepted. He did not, however, attempt to explain why some of the most complicated cortical processes were attended by consciousness and others not. He viewed the objective and subjective phenomena as correlated in some, but he did not seek to establish a direct or local correlation of the phenomena in a definite area, nor did he seek to explain either phenomenon in the terms of the other. The well-known views of Hughlings- Jackson, that the sensori-motor apparatus of the cortex is re-represented in other centres higher in the scale than the physiological sensory and motor areas in the cortex, find the most favour with those who have obtained an intelligent grasp of this subject ; and, if we accept his view, that mental opera- tions are simply the subjective accompaniments of sensori-motor processes, we do not, at the same time, in any way bind our- selves to the possibly erroneous conception that such subjective accompaniments are in immediate local juxtaposition to the physical sensori-motor processes. We have an abundance of examples of complex reactions with ^\•hich no psychical correlate is apparent ; and it is readily conceivable, that just as the nervous apparatus of lower centres is characterised by its sensitiveness and tendency to propagate its functions in a fit and appropriate direction, so the mechanism of the sensori-motor regions is characterised by its still more highly- developed sensitiveness and tendency to react to special stimuli 122 SCHEME OF THE CEXTRAL NERVOUS SYSTEM. conveyed through the medium of the special senses. On this assumption, and on this only, can we seek an explanation of many morbid objective manifestations as seen in the insane. In the early stages of the general paralytic, the occurrence of paralysis of his sensori-motor apparatus, as viewed by us objectively, without implication of the consciousness or totality of his mental being, as viewed by him subjectively; or in the acute maniac, whose sensori-motor apparatiis furnishes ns with objective manifestations of its abnormal activit}^ ; or, again, in the active physical phenomena of sleep, epilepsy, and hypnotism : all these may be explained from a sensory-motor point of view, and without any obvious psj^chical concomitance. It is characteristic of the himian consciousness, that it exists as such over and above all physical processes ; and, as yet, we ai'e far from the possession of one fact, nay even one valid argument, in support of the conception, that the mind has its ultimate dwelling place in any one definite structure contained within the so-called sensori-motor regions of the cerebral cortex. "When we discuss the questions as to whether revived images are gathered together into a special ideational centre, or whether they are merely taken cognizance of by the intelligence while remaining in their own situations, we shall see that the evidence stands in favour of the latter view. Some observers advocate that the intelligence is more especially con- nected with the superficial layers of the cortex ; but even this supposition is not supported by evidence which can be regarded as conclusive. 123 CHAPTEE lY. Localisation of the Mental Faculties — {continued). Sensory and Motoi* Areas subserve Mental Events — Localisation — Diffuse Localisation — Indifferentism — The Frontal Lobe — Intelligence not limited to Local Areas— Ratiocinative Theories : Xeural Inference Scheme of Hughlings-Jackson ; Meynert's View of the Forebrain ; Wallers View, based upon Psychological Inference — Value of the Logical Mode of symbolising Neural Inference — Prse frontal Lobes : Experimental Researches; Patho- logical Evidences — Consciousness pertaining to Lower Centres — Local Memories — Subjectivity of the Mind — Objective Contents ^ of Consciousness — Specific Functions of Xerve-Cells — Wallerian Scheme of the Four R's — Specific Quantifications of Motion — Negative Value of Physical Formulae — The Doctrine of "Invari- able Concomitance." At the close of the preceding chapter ^^■e stated that the per- ception of different sensations was not proved to be consummated within definite pai'ts of the so-called sensori-motor areas. We mentioned, for the pur^DOses of the student, the hypothesis of Hiighlings-Jackson, and others, that in addition to the regions which have been defined as sensory and motor, there may be other and higher motor as well as sensory centres, within which all the motor and sensory functions are again repre- sented, and which form the substrata of the higher mental functions. This hypothesis, according to Ferrier, receives no confirmation from the facts of experiment ; nor does he regard it as at all necessary to explain the facts of normal or abnormal mentation. "We have in the sensory and motor centres of the cortex the substrata of the respective forms of sensory per- ception and ideation, and of the individual acts of volition, simple and compoimd, as well as of the feelings associated with. 124 LOCALISATION OF THE MENTAL FACULTIES. their activity. It seems more reasonable to suppose that there may be higher and lower degrees of complexity or evolution in the same centres, than to assume the separate existence of more highly evolved centres, for which no evidence is obtained by the results of experimental research."* Of this latter view no criticism is necessary, for it has not // yet been proved that a centre for sensation and another for onotion exists in the cortex ; and even though such centres did exist, we are very far from forming any conception as to the actual substrata of the respective forms of sensory perception a/iid ideation, and of the individual acts of volition. We are, to a limited extent, cognisant of the physical conformation of the brain structures ; we know that there are paths of conduction for stimuli of various kinds, and we know that stimuli do pass along those paths and may be reflected in their course by structural realities, but beyond this we can conceive no inti- mate or ultimate substratum which directly serves conscious- ness. In fact, when we speak of the substrata of perception, ideation, and volition, as applied to the cerebral cortex, we can only realise, that we have advanced one step onward in our search for the structures' which are immediatel}^ concerned with modes of consciousness, and that we are still on a level which offers little or no clue to the whereabouts of what we seek. The words of Herbert Spencerf — viz., "Whoever calmly considers the question cannot long resist the conviction that different parts of the cerebrum must, in some ujay or other, subserve different kinds of mental action " — contain the pith of our knowledge of the whole question. The different j)arts of the cerebrum, as M^ell as the whole physical organism, do subserve different kinds of mental action, but they only sub- serve, and we cannot as yet determine A^daere or how the different kinds of mental action are ultimately served. Our position, in regard to the areas sve have already investigated, therefore, is this, they, vii some way or other, subserve the different hinds of mental action. Further, Herbert Spencer says, " Local- isation of function is the law of all organisation whatever; and it would be marvellous were there here an exception. * Ferrier, " Cerebral Localisation," 2nd edit. -p. 460. t " Princii)les of Psychology," 1870. CONSCIOUSNESS SUBSERVED. 125 Either there is . some arrangement, some organisation in tlie cerebrum, or there is none. If there is no organisation the cerebrum is a chaotic mass of fibres, incapable of performing any orderly action. If there is some organisation it must con- sist in that same ' physiological division of labour,' in which all organisation consists ; and there is no division of labour, physiological or other, but what involves the concentration of special kinds of activity in special places." An analysis of this statement in no way invalidates, or tends to check, the coiirse of our thoughts. It involves both physical and mental activities. Of the attempts to localise physiological activities we have only to mention those of Ferrier, Schafer, Horsley. Beevor, Charcot, Dejerine, Goltz, Wundt, Munk, Hitzig, Schiff, Bastian, Hubnoff, Heidenheim, and others ; and from the results of their laboiirs we cannot but recognise the law of the tendency to local differentiation of physical activities. When, however, Ave pass from the objective manifestations of these activities, and en- deavour to sujDerimpose upon them various psychical states, AA'e almost immediately get beyond our depth, and flounder amidst all sorts of conjectures and hypotheses. These hypotheses may be ranged under two classes — viz., (1) those which favour the view of localisation ; and (2) those which support the idea of diffusion of function ("diffuse localisation," or " indifferentism"). But, the student will ask, Ai"e we not still upon too low a plat- form of our organisation to entertain, for the present, such questions ? We are on the platform of the so-called sensory and motor centres; we are dealing with the physical substratum (so far as we know it) of the special senses ; and we are sur- veying the site which we have already granted, '' in some way or other, subserves " consciousness. What we have now to decide is, do the elements of these physical substrata directly and within their oaa'u domain serve consciousness AA'ith the phenomena of sensation ? or do they sul)- serve it by a furtherance or propagation of their physical con- ditions to other regions where their activities are ultimately correlated with consciousness ? Herbert Spencer advocates, that a perception can have, in a nerve-centre, no definite local- isation, but only a diffuse localisation. No one excited fibre or cell produces consciousness of an external object: the conscious- 126 LOCALISATION OF THE MENTAL FACULTIES. ness of such external object implies excitement of a plexus of fibres and cells.* Wundt objects to the view that sensations take place in the separate areas which are now regarded as sensory centres, inasmuch as such a belief would countenance the old phrenological faculty scheme. His doctrine of a frontal organ of apperception might appear to receive ample confirma- tion from the experiments of Terrier, and from the reasonings of Hughlings-Jackson. Let us, therefore, go elsewhere in our search for some more highly evolved substratum, than that of the chaotic mass of tracts and junctions contained within, what we term, the sensory and motor areas. The exclusion of the motor zone from the sphere of con- sciousness — enunciated by James, and approved of by Bastian, Ferrier, Gotch, and Horsley — has been objected to by Waller. The supposition that consciousness accompanies the rise rather than the discharge of activity in these regions in no way implies that the sphere of consciousness exists actually in them. The consciousness accompanying their activities is to be regarded as a collateral manifestation of the activities pro- pagated in some unknown way from these regions to other regions which are more directly concerned with the phenomena of consciousness. That is to say, we have not, as yet, arrived at the conclusion that there exists a more highly evolved centre, with the activities of which the respective forms of sensory perception and ideation, the individual acts of volition, simple and compound, and the feelings, are more directly associated. It does, indeed, seem reasonable to assume that there may be higher and lower degrees of complexity of evolution in the nervous structures ; but we have, as yet, no conclusive proofs, either that the various degrees of evolution occur in the same centres, or that there exist separate or more highly-evolved centres for the phj^sical correlates of mentation. The frontal lobe contains a non-excitable area of cortex, which is situated in front of the area for the representation of the head and eyes, and, in the monkey, is bounded posteriorly by a vertical line drawn through the anterior end of the horizontal limb of the praecentral sulcus, from the median line down to a point a few millimetres in front of the anterior end * "Principles of Psych.,"' 2nd edit. 1870, p. 562. THE FRONTAL LOBE. 127 of the fissure of Sylvius.* This part of the brain is considered by most investigators to be the seat of the highest mental pro- cesses. Meynert believes that within the forehrain sensitiveness is converted into actual sensation. "The relation of the forebrain to the other parts of oereliral mechanism is easily understood. To this end we may recah the structure of the retina, which constitutes a hollow into which the visual rays from the external world are, as it were, entrapped. And, in the same way, we may look upon each half of the cortex of the forebrain as a concave organ, duplicated in parts, enveloping all the nerve-tracts, which conduct to it the impressions from the outer world. In this organ these impressions are converted into the phenomena of sensation. In assimilating totally unknown j)hysical impulses, the cerebral cortex — a complicated protoplasmic structure — resembles the protoplasm of the primitive amoeba, which can transform itself into a hollow mass, and can thus encircle any body which it wishes to assimilate. Just as the mollusea possess tentacles, which they pro- trude toward the outer world, and claws, by means of which they take possession of their booty, so this complicated protoplasmic organism — the prosencephalic cortex — possesses centripetally-conducting pi'ocesses — the sensory fibres of the nervous system — which we may consider its tentacles, and motor fibres, which are its claws. The remainder of the body, with its sensitive surfaces, its muscles, and the skeleton to which these muscles are attached, serves to sustain these tentacles and claws, which enable the forebrain to receive the images of the external world, and to react upon the latter." Mnnk regards the entire frontal lobe as a sensory sphere ; and others have pronounced the frontal region to be the exclusive seat of intelligence. Meynert corroborates the view of Munk, and adds, that consciousness, and intelligence also, which are evolved in the forebrain, depend upon a mechanism, the minute details of \\'hich, if understood, would enable us to restrict intelligence to the forebrain. From the experimental investigations of physiologists, we are led to believe that when the forebrain is extirpated, there is serious impairment of the intelligence of the animal. Goltz, in particular, has demonstrated that the loss of only a fe^' grammes of substance of the frontal lobes of dogs was suffi- cient to produce what he regarded as a state of idiocy. Meynert holds, that the conclusions of experimental physiology strengthen the opinion that intelligence is not limited to defi- * Beevor, "Tuke's Diet.," p. 156. 128 LOCALISATION OF TPIE MENTAL FACULTIES. iiite cortical areas, but that, being based upon perceptions, including the sensations of innervation, it results from the activity of the entire forehrain. The belief that the exercise of intellectual activity by every part of the cortex depends upon the uniform structure of all parts of the forebrain, which makes of each part a centre for inductive processes, and supplies to each part nerve-elements capable of perceiving and receiving images, is unsupported by experimentation and pathology. All parts of the forebrain are joined to each other by anatomical association tracts, and the connections of these tracts with other functionally-perfect association tracts in other regions of the cortex, furnished some investigators with the idea of the presence in the brain of an induction apparatus ; and, according to Meynert, the so-called logical sequence in the evolution of association, which yields the factors of intelligence, is effected in various wa3's, and to a varying degree of perfection, in different brains. Let us here, however, briefly consider the arguments of those who have attempted to give a rational view of psycho- physiology.* To Hughlings-Jacksonf we are indebted for the neural- inference scheme, as given in his well-known "three level." " (1) Evolution is a passage from the most to the least organised — that is to say, from the lowest well-organised centres up to the highest least-organised centres. Putting this otherwise, the process is from centres comparatively well organised at birth up to those, the highest centres, which are continually organising through life. (2) Evolution is a passage from the most simple to the most complex ; again, from the lowest to the highest centres. There is no inconsistency whatever in speaking of centres being at the same time most complex and least organised. Suppose a centre to consist of but two sensory and two motor elements ; if the sensory and motor elements be well joined, so that ' currents flow ' easily from the sensory into the motor elements, * The ratiocinationists (who deduce consequences or form inferences from tlie comparison of premises) follow more or less in the lines of Herbert Sjjencer, who says, " Every ratiocinative act is the indirect estab- lishment of a definite relation between two things, by the process of estab- lishing a definite relation between two definite relations." — " Psychology," vol. ii. p. 16. i' " Evolution and Dissolution." — " Lancet," 1884, HIERARCHY OF NERVOUS CENTRES. 129 then that centre, although a very simple one, is highly organised. On the other hand, we can conceive a centre consisting of four sensory and four motor elements, in which, however, the junctions between the sensory and the motor elements are so imperfect that the nerve-currents meet with much resistance. Here is a centre twice as complex as the one previously spoken of, but of which we may say that it is only half so well organised. (3) Evolution is a passage from the most automatic to the most voluntary. The triple conclusion come to is, that the highest centres, which are the climax of nervous evolution, and which make up the ' organ of mind,' or physical basis of consciousness, are the least organised, the most complex, and the most voluntary. So much for the positive process, by which the nervous system is ' put together ' — evolution." His scheme of the hierarchij of nervous centres is arranged on an anatomico-physiological basis — that is, especially as to degree of indii'ectness -with which each represents the body, or part of it. "(1) The lowest motor centres are the anterior horns of the spinal cord, and also the homologous nuclei for motor cranial nerves higher up. They extend from the lowest spinal anterior horns up to the nuclei for the ocular muscles. They are at once lowest cerebral and lowest cerebellar centres ; hence lesion of them cuts off the parts they repre- sent from the whole central nervous system. "The lowest centres are the most simple and most organised centres : each represents some limited region of the body indirectly, but yet most nearly directly they are representative. The middle motor centres are the convolutions making up FeiTier's motor region and the ganglia of the corpus striatum. These are more complex and less organised, and represent wider regions of the body doubly indirectly ; they are representative. The highest motor centres are convolutions in front of the so-called motor region. I say so-called, as I believe, and have urged for many years, that the whole anterior part of the brain is motor, or chiefly motor.* The highest motor centres are the most complex and least organised centres : and represent widest regions (movements of all parts of the body), triply indirectly; they are re-re-representative. That the middle motor centres represent over again what all the lowest motor centres have represented will be disputed by few. I go further, and say that the highest motor centres (frontal lobes) represent over again, in more complex combinations,, what the middle motor centres represent. In recapitulation there is increasing complexity, or greater intricacy of representation, so that ultimately the highest motor centres represent, or, in other word?,, co-ordinate, movements of all parts of the body in the most special and complex combinations." In regard to the scheme of the sensory centres his conclusions are— * "Brit. Med. Journ.," March 6, 1869. 9 130 LOCALISATION OF THE MENTAL FACULTIES. (1) That the highest (chiefly) sensory centres, parts behind Ferrier's sensory region, and also the highest (chiefly) motor centres, parts in front of the so-called motor region, make up the physical basis of con- sciousness ; and (2) that just as consciousness represents, or is, the whole person psychical, so its anatomical basis (highest centres) repre- sents the whole person physical, represents impressions and movements of all parts of his body ; in old-fashioned language, the highest centres are potentially the whole organism. States of consciousness attend survivals of the fittest states of centres representing the whole organism Meynert has endeavoured to prove a logical sequence in the evolution of association. He follows most authors in regarding the intensity of established associations, as dependent upon their conscious and frequent re-excitation. An accidental suc- cession of impressions is seldom repeated, and relations thus established vanish quickly from the brain. As soon, however, as the " subjective bond of causality " represents an actual union of things, the re-occurrence of external stimuli will estab- lish a permanent association within the brain. The relation of one mind to another, and the effects of the transmission of approved impressions, is of great interest. Individual intelligence may grow from copjang the psychical associations in the minds of others, but any real development ■of intelligence is only to be gained by the individual's own association of ideas. According to Meynert, projection and association are the two forebrain principles of concei'ted action, and such action constitutes an induction. In this way he seeks to demonstrate, that the widespread activity of the fore- brain serves not only as the recipient, but also as the creator of sensations. Wundt* called an induction the fundamental logical func- tion; but Meynert t first tried to demonstrate the association and induction mechanism of the forebrain. He believed that both ends of the association fibres were connected centrally with cortical cells. The projection bundles, consisting chiefly of fibres of the corona-radiata, spreading into the medullary substance of the forebrain, conduct to the cortex the excita- tions from the external world, and distribute them over its different sensory spheres. All objects which, as soon as per- * " Ueber Menschen imd Thierseele." t " Leidesdorf s Manual," 1865. PSYCHOLOGICAL INFERENCE SCIIEiME. 181 ceived, engage two different sensory spheres, niay appear to prove the existence of an induction mechanism, present every- where in the brain, and anatomically dependent upon the asso- ciation and projection-systems ; but, as we shall see later, the physical compounding of sensations is an unwarrantable assiimp- tion. Psychologically, the mind may receive an impression and then refer to the attributes of that impression, thus draw- ing upon the resources of different sensory spheres ; it does not draw from two sources at once. Waller* has endeavoured to demonstrate the essential similarity of neural processes concomitant -with the whole range of subjective phenomena from the simplest sensation to the most complex judgment ; but, as his starting point is -with the ultimate fact " sensation," we do not in reality gain any further insight from his conception of the pliysiolofiical mechanism of ratiocination. In analysing the factors of the simplest sensation, as well as of the most complicated judgment, he adopts the logical expressions, major premise, minor premise, and conclusion.^ In this scheme it is essential to avoid confusion, b}' distin- guishing between subjective sensation and activity within the objective substratum of sensitivity. Viewing the subject from the centripetal aspect of neural processes, he appropriates to the three-level scheme the three terms, impression, sensation, per- ception, using " impression " as the lowest level term, and taking " impression " to denote an effect that does not reach consciousness ; " sensation '' to denote a felt impression ; " per ception " to denote a sensation in its felt consequence. The scheme is based on the type of the psychological process of inference, and is as follows : — The simplest present sensation o- is not the concomitant of any isolate present state of organ S, but the resultant of a comparison based S upon state now and state before now — i.e., of a ratio -,,. The organic state now is the sum of many previous alterations of state ; many sensations o- the concomitants of many previous ratios S ^^-, may be conceived as summed up in the state of sensibility 2. * " Brain," 1892, p. 35.5. t Waller does not imply that the syllogistic terms of logicians correspond to any physiological factors in a neural process. The mental and physiologi- cal states are symholised hy Greek and Roman letters respectively. 132 LOCALISATION OF THE MENTAL FACULTIES. This state of sensibility 2 has as its organic basis a material state, which (having regard to the total 2 by many elementary a, each con- S S comitant with a ratio ^) is properly represented as the ideal symbol ^ . b S' Thus 2 the specific sensibility, the subjective resultant of past S experience, is the concomitant of ~ , the imaginary organic sum of the antecedent series of organic ratios '— . S To this resultant state (subjectively 2, objectively -) he applies the term " personal ratio," meaning to connote in this expression, that the personal state now is composed of compared objective phenomena and not of absolute objective phenomena. This personal ratio he takes to be the subjective attribute of the organic major premise, each new sensificatory change of state he regards as a minor pre?nise, and considers that a conclusion is formed by the com- pounding of these two premises ; this compounding or neural inference may, he thinks, properly be represented symbolically in the form of a multiplication, in which the product represents the conclusion, and at the same time the new major premise in relation to subsequent minor premises. I X 1=11 or subjectively.. But here it is necessary to justify the transition from the use of the word " ratio " to that of the word " premise," and the use of a fractional symbol for both words. The terms of any premise or proposition are the subject and the predicate (joined by the copula) ; in a major premise the subject enumerates and the predicate denominates. The major premise " all oil vj") ATI men are mortal " may be written -— , in which we enumerate all mortals " all men " as forming part of " all beings denominated mortals." The minor premise " Socrates is a man " may be written similarly ' , by which we enumerate Socrates as belonging to the denomi- men ' -^ "^ ^ nation men just enumerated in the subject of the major premise. And the syllogism may be written : — men Socrates Socrates mortals men mortals major minor conclusion. It would be absurd to say that this or any other mode of symbolisa- tion " explains " judgment, attention, sensation; but it is not too much to say that it clearly exhibits the possible factors of neural inference ; each act of observation, each determination of conduct, is the resultant of two factors : (1) the major premise or central state, more or less attended to ; (2) a particular minor premise or group of sensificatory VALUE or THE EATIOCINATIVE METHOD. 133 stimuli, also more or less attended to (within the remaining sensifica- tory field, less or more attended to). Value of the Ratiocinative Method.— The logical mode of symbolising neural processes ma.j serve a purpose ; but, inasmuch as the particular premises — major and minor — are manifestly mental, and only (at least so far as we can imagine them to be) correlates of ultimate physiological factors, the whole scheme resolves itself into a disquisition upon the ordinary rules of the syllogism, with, in addition, the concep- tion that the physical organism in some way or other subserves the phenomenon of sensation. We shall have occasion to dis- cuss at some length the various theories given to explain the correlation, or, as materialists would say, the "evolution" of a major or minor premise as a sensation in consciousness, and we shall see that the objects of consciousness, as viewed objectively by the subject, are the data, or premises, upon which our conclusions are formed. Here we anticipate b}^ assu.ming, that the various presentations and representations in consciousness are correlative states to physiological activities. Every presentation and representation is an objective content of consciousness, and each content in itself forms a major or minor premise. For an explanation of the formation of that major or minor premise, we must have recourse to metaphysics or philosophy. On the psychical side we have the contents of consciousness, which furnish us with data from which we infer our conclusions. On the physiological side we have various activities which resolve themselves into reflex acts, the results of transmitted excitations. It must suffice for the present to recognise that the sum total of the complex phj^siological activities becomes manifested as an objective content of con- sciousness, and that the e^ In'oad sense, it means that eunscioiisness has only to do with conscious events. The narrow sense, that all the elements of psychical life an- primarily and ultimately cognitive elements, is, to us, incon- ceivable : ^\■llereas. the broad sense, that all the elements of psychical life are facts of conscious experience, and that j)sychology has to do solely with conscious processes and events, admits of feelings and attention, and also of the existence of a self which has these feelings and exerts this attention as distinct from sensations and ideas ; i.e., it holds that the feelings, the attention, and the self, are facts of conscious experience. The veiy existence of such conditions as feelings, ideas, and self, consists in their being facts of conscious experience ; if there were not such facts, we should never know anything about them.* A^'ard siimmarises the whole account of the subject in an introspective observation, and three inferences. The facts of mind cannot be properly expressed by saying, there are feelings, ideas, volitions, biit only by saying. I have feelings ; I have ideas ; I have volitions ; or. I feel. I know. I will — i.e.. every luental state in^•olves a subject by whom it is known, felt, or Avilled. lufereucet:. — (1) A subject must be conceived as distinct froni the state which it knows, or feels, or wills ; (2) it nuist be con- ceived as different in kind from all ideas or feelings, or possibilities of such ; and. (3) since all knowledge implies a subject which knoA\'s, all feeling a subject -which feels, it follows that this subject, just because it is the subject, cannot itself be directly known or felt. That sensations are essential to consciousness is evident, but to argue that they are essential to the development of consciousness, and are tluis the primary factors in the evolution of intelligence, is as forcible as to argue, that naitriment. which is essential to us. and to our physical development, is the primary factor through which we are to trace the biological evohition of our organism. And no\\' let us see what the theory of evolution, as it no^v stands, has to say upon such a (juestion as memory. AYe may grant that the sensitive organism transmits, in some^ * Miinsterberg. '•Psycli. Review," vol. i. 158 MIND. way or another, a series of activities wliicli ultimately manifest themselves as the phj^siological equivalents or correlates of sensations; but we have still to explain how these different sensations could form an aggregate which would correspond to intelligence. Does the one sensation, b}^ a force of attrac- tion, cohesion, or gravitation, appose itself to a like sensation ? or does the one compare itself ■\^'ith the other, and, b}^ an inherent power, relegate itself to its proper spheres ? Could we conceive the millions of letters received into St. Martin's le Grand daily sorting themselves into their respective depart- ments without the intervention of an intellectual guidance. Or, again, do the numbers of facts and observations at our disposal arrange themselves as data in a logical sequence, the result of which is our conception of their arrangement and import ? A sensational theory would have to prove, that succession, relation, and difference are not matters of knowledge ; and those who uphold the view must show \\ov>- observation, comparison, and memory can be originated. Were we to grant that one sensation possessed the power of com- paring itself with another, it is evident that, in order to do so. one sensation would possess at least the power of distinction between subject and object ; and here would be acknowledged an intelligence pertaining to the sensation itself. " According to evolution," says Professor Calderwood, " they are all to be created by advance from lower to higher, yet without these higher we cannot have experience. Without observation, involving at least the distinction of subject and object, there can be no such memory as we rely upon in building up our knowledge ; without memoi'y there can be no thought ; without thought no rational life. Neither from organism nor from sensation can help be found here. ' No series of sensory impressions will produce thought ; no series of sensations can result in anything higher than its own content." Cyples says, "Very earlj' we learn that these diversifications of experience, as well as the startings and stoppings of consciousness generally, are determined not by ourselves — at least, not in their natural, unartificially-produced happenings. They are somehow im- posed and prescribed. Moreover, the intellect, by its own proper function, comes to apprehend that a certain oi'der discloses itself in these occurrences, one event following upon or grouping with another. The intellect's complete task is, from these data, to formulate working- rules which will explicate the arising and the ceasing of our conscious- EV(3LUT10N OF MIND. 159 ness, with the occurring of the diversifications of experience into kinds while it subsists." The failure to appreciate liow iiniutelligible is the sensa- tional theory of evolution may be attributed to the fact, that some writers direct their effi )rts more in the direction of giving an explanation of the fundamental nature of the manifestations, than of trying to observe the manifestations as they occur. To us it is all-important to accept no assumptions as valid unless they are quite intelligible. Otherwise, we raise for ourselves barriers which arrest our progress and involve us in endless difficulties. From all points of view the evidence in favour of the theory of sensationalism is in direct opposition to our common sense, and we say of it. as it now stands, the evolution of a cognitive state from a sensation without the existence of an intellectual guiding factor or personality as a pre-rec|uisite, is as readily conceivable as the evolution of a sporran from the classical fig-leaf without the intervention of a tailor. The assumption that our mental states are composite — i.e., made up of smaller states conjoined — has been termed the "mind-stuff" theor}^, and its consideration has engaged the attention of many psj'chologists. If we are to be thorough in our scheme of the evolution of mind, we must either account for the introduction of mental factors, at some period in the history of the organisation of the original cosmical chaos, or we m\ist surrender that position, and grant the existence of mind from the beginning. That is to say, we must either be materialists, or accept as a fundamental truth the t\\in evolution of mind and matter. To enter into the meta- physical cpiestions involved in any attempt to introduce mental factors among the chaotically-dispersed atoms of the universe, is obvious!}' beyond our scope of inquiry. We have merely to note the undeniable discontinuity of the data, and the failure of evolutionists to provide us with explanations upon these points. The advocates of true parallelism must, of necessity, be the enemies of evolutionists ; and, to use a paradox, the strength of the chain of evidence of the former is made up of the missing- links of the latter. It is pathetic to note the positive affirma- 160 MIND. tions of some writers, that there is no possible or conceivable causal connection between mind and matter; and yet they are foremost in giving the body priority as a cansal factor in the introduction of mind. "When the evolutionary afflatus is upon them," says Professor -James. " these very same writers leap over the breach, whose flagranc}' they are the foremost to announce, and they talk as if the mind grew out of the body in a con- tinuous way." Spencer* attempts to demonstrate how we pass " tvithout hreali, from the phenomena of bodily life to the phenomena of mental life." His conception, that the truth of life is the " continuous adjustment of internal to external relations," is manifest to every one; but Ave fail to observe, either liouj we pass from plwsical to psychical actions, or the moment iflien we rise above the correspondences that are few, simple, and immediate. " On ascending from the lowest tj'^pes of life,'" says Spencer, " one marked manifestation of the heightening correspondence is the increasing distance at AA'hich co-existences and sequences in the environment produce adapted changes in the organism. This progress accompanies the development of the senses of smell, sight, hearing, etc., and the subsequent development of the intellect."! His assumption — that all forms of sensibility to external stimuli, are, in their nascent shapes, nothing but the modifications which those stimuli produce in that "' duplex j^rocess of integration and disintegration, Avhich constitutes the primordial life, plwsiologicallj'-considered" — is, to sa}^ the least, vague and confusing.:!: To speak of forms of sensibility as modifications produced by stimuli AN-ould appear to be warrantable ; but no argument would warrant the con- clusion that the external stimuli determined the sensibility itself. It is manifestly true, that various stimuli determine modifications of the organism upon which they act ; but they * "Psychology,^' § 131. t Op. cit., § 139. X To the theory' that forms of sensibility to external stimuli are in their '•nascent" state, James takes serious objection. He points out, that merely to call the consciousness nascent will not serve our turn. He says, " It is true that the word signifies not yet (juite born, and so seems to form a sort of bridge between existence and nonentity. The fact is that discontinuity comes in if a new nature comes in at all. ' EVOLUTION OF MIND. 161 do not determine the existence of that organism. "Were such arguments possible, our difficulties in accepting the evolution theories ^^•o^lld be smoothed over. The theory of atomistic hi/lozoism seems to be the most philosophical view of evolution, and. according to its advocates, there must have been an infinite number of degrees of con- sciousness following the degrees of complication and aggre- gation of the primordial mind-dust. Here, however. Ave are treading upon metaphysical ground, so we return to the psychological significance of the mind-dust theories. SjDencer concludes, that the progress of the correspondence between the organism and its environment necessitates a gradual reduction of the sensorial changes to a succession ; and by so doing evolves a distinct consciousness — a consciousness that becomes higher as the succession becomes more rapid and the correspondence more complete.* The question naturally arises. At what period of the succession of sensorial changes is a distinct consciousness evolved ? Spencer f denies that he means by this passage to tell us an^-thing about the origin of consciousness at all.:^ In a succession of sensorial changes (psychologically-con- sidered), did consciousness evolve with the first, second, or hundredth sensation in that series ? If with the second, the first would have no place in it ; if with the hundredth, the previoiTS ninety-nine would ha\'e no place, because they could only exist so far as they were manifested in consciousness. To say that the factors in the succession become more complex as they advance, does not simplify matters. The question becomes (1) did the primordial bioplasm answer to its first stimulus from without, or did it wait for a period when the stimuli had so modified it that it was then able to respond and manifest itself as life ? (2) did the first stimulus entail even the most rudimentary form of sensation appreciable by the bioplasm ? or. (3) did the organism appreciate the stimulation only when * "Psychology," § 179. t "Fortnightly Review,"' vol. xiv. p. 716. J " This resembles," says Professor James, " too many other passages in his 'Psychology-' not to be taken as a serious attempt to explain how consciousness must at a certain point be evolved." 11 162 MIXD. previous stimuli had advanced the evolution of its complex adaptive apparatus ? If the human mind is to he evolved from mere complexity of physiological arrangements, then why not also evolve vitality from mere complexity of mechanical forces y The conclusion of the sensationists is, obviously, that our knowledge arises from the evolution of data unknown to us. Can we arrive at an idea, conclusion, inference, or what- soever it may be called, only at some period in the evolution of a succession of data, taking no account of data which occurred earlier in that series ? Consciousness must start somewhere within that series, and its evolution must depend upon initial sensor\^ change lyJus subsecjuent sensory changes. The contents of consciousness at any period in that succession must involve the pre-existence of antecedent states right to the very origin of that consciousness. Hence, we again find our- selves compelled to beat consciousness back to the beginning of sentient existence. In fact, the theor}' that holds conscious- ness to be dependent upon the arrival at a period, when the correspondence of the mechanism to its environment is more elaborate and complete. conve3"s as nuTch meaning, concerning the origin of intelligence, as do the activities of a lamp-lighter concerning the origin of light. Spencer says that the doctrine of evolution, under its purely scientific form, does not involve materialism, though its opponents persistenth' present it as doing so. He also speaks of the materialistic hypothesis as being '' utterly futile." Hughlings-Jackson says, that to describe Spencer. Huxley, and Tyndall as materialists is as absurd as to speak of Sir Joseph Lister as an opponent of antiseptic surgery. The words of Spencer — " No effort enables us to assimilate mind and motion ; I am merely showing a [jaralUlum between a certain physical evolution and the correlative psychical evolu- tion " — would apparently place him above any effort to assimilate mind and matter, or any attempt to show that material actions thus become mental actions. But. again, we ask. If a parallelism between a certain physical evohition. and the correlative psj"- chical evolution has taken place, was that parallelism complete? or was a certain degree of physical evolutionary complexitj' essential before the psychical parallel could be started at all ? THE MIND-STUFF TIIEOKY. IGo The •* liappenino" of consciousness thus becomes a problem of the ••first cause." and the psychical functions must hav^" existed coincidentally to the beginnings of life. Any attempt to posit the dawn of consciousness coincidentally to a more complexly- developed state of the physical organism is neither true evolu- tion nor parallelism, it is materialism, and seeks to account for the origin of one series of events bj' taking account of the total complex of the other series. If the two series of events are to correspond they must go hand in hand from the beginning. They must be twins — the one must not be born, and the other happen later on. If there is to be a period of nascence with the one. so there must also be with the other. As far as we can see. the nascence of the one must evolve into perceptible life ; that of the other into conscious experience. The one is not born from a rib of the fully developed other. One contention of the spiritualists against the association- ists in psychology — that individual minds do not agglomerate into a higher compound mind — has never been ans^\'ered by the latter. With this contention we have little to do. Our object, however, includes some discussion of the theory that mind-diist exists, and that mental objects can be com- pounded.* The self-compoimding of mental facts is quite inadmissible. In favoiir of this view Professor James lias pointed out in very clear language, that at most A\'e can compare together objects previously presented to us ; but then Ave find each object stid^bornly maintaining its separate identity liefore consciousness, whatever the verdict of the comparison may be. " All the cctmbinations which we actually know are effects, wrought by the units said to be ' combined,' ujion some entifij other tlian ourselves.'' "' In other words, no possible number of entities (call them as you like, whether forces, material particles, or mental elements) can sum tJieraselres together ; each remains, in the sum, what it always A\as : and. the* sum itself exists only for a hi/staiuler who happens to overlook the units, and to apprehend the sum as such ; or else * See Royce, " Mind," vi. p. 376; Lotze, " Microcosmus," Bk. ii.. Ch. I., ,^ 5 ; Mivart, " Nature and Thought," p. 98 ; Fechner, " Psychophysik,' Bd. ii.. Cap. XLY. ; Brentano, " Psychologie," p. '209 ; Tyndall, " Fragments of Science," p. 420 ; Hughlings-Jackson, "Croonian Lecture?," 1884, 164 MIND. it exists in the shape of some other efed on an entity external to the sum itself." The contention of the spiritualists holds good; says James, against any talk about self-compounding amongst feelings, against any " iDlending," or "complication," or " mental chemistry," or "' psychic sjaithesis," which supposes a resultant consciousness to float off from the constituents pe?* se. in the absence of a supernumeraiy principle of consciousness which they may effect. " The mind-stuff theor}^, in short, is iinintelligible." The contentions of Ward* and James agree in their main points, and they rightly take objection to the views of " mind-stufiists," and associationists, that the "series of states" is the awareness of "itself"; that if the states be posited severally, their collective consciousness is eo ipso given; and that we need no further explanation or " evidence of the fact."" If we try to imagine the ideas of the various con- stituents of a haggis positing themselves in our mind, side by side, so as to form a combination or resultant idea of the haggis in its entirety, that resultant idea would really consist of a reference to a haggis previously compounded and presented to us in its entirety, while the ideas of the constituents Avould remain more or less intact and separate. The super-position of many photographs upon one another gives ITS a composite product more or less blurred or in- distinct, and the mind becomes aware of the properties ot that product as presented to it ; but the mind cannot look at a series of pictures, and by placing their mental images side by side form a composite mental representation of them. The mind can only review the component parts of the series, and it can only view an external resultant com- bination.! Thus, it deals with the haggis. The taste of * ■' Eiicyclopiedia Britannica." t •■ I find in my students," says James, " an almost invincible tendency to think that we can immediately perceive that feelings do combine. ' "What ! ' they say, 'is not the taste of lemonade composed of that of lemon /;^M.s that of sugar?' This is taking the combining of objects for that of feelings. The physical lemonade contains both the lemon and the sugar, but its taste does not contain their tastes, for if there are any two things whicli are certainly not present in the taste of lemonade, those are the lemon-sour on the one hand and the sugar-sweet on the other. These tastes are absent utterly. The entiiely new taste which is present i-esembles, it is. true, botli those tastes." UXCOXSCIOUS CEIIEURATIOX. 10^ the compound may be recognised in its combination, or the (jourmet may even succeed in the detection of elements A\'hich wonld baffle the majority. Let the nninitiated. hciwever. separately imagine the taste of linety-chopped sheep"s heart, liver, etc. etc., suet, and oatmeal ; then let him conjure up a high seasoning of onions and pepper, and then let him sum up the sensation that wo\ild correspond to such a compound after it has been '• boiled i' the maw." Even a Scot woiild confess to failure, and refer to the taste of the compound as formerly presented to him. Of the views of the associationists we shall have much to say in subsequent chapters, so that we now proceed to consider a question implied by the mind- stuff theory — viz., that states of mind may be unconscious. Unconscious Cerebration. The arguments for and against the theory are as follows* : — Ayainst. ]iecause three men are just able to lift a ton weight one foot, it does not follow that two men are able to lift it 8 inches. For. 1. Below the point of liminal in- tensity of stimulation there must be a certain degree of cerebration, because only a small addition is necessary to produce an appreci- able sensation. 2. The intelligence displayed in so- called automatic acts. 3. Thinking of A, we presently find ourselves thinking of C. Now V> is the natural logical link between A and C, but we have no conscious- ness of having thought of B. It must have been in our mind " un- consciously," and in that state affected the sequence of our ideas. 4. Solving problems during sleep, somnambulism, awakening at a predetermined hour, unconscious thinking, volition, time registra- tion, etc. Consciousness must have presided over these acts. There may have been conscious- ness,but the memory of it absent. Either memory at fault, or B"s brain tract alone was adequate to do the whole coupling of A with C, without arousing B. There may have been conscious- ness, but it is forgotten, as in the hypnotic trance. * James, " Principles of Psychology " ; Carpenter, " Mental Physiology,"' Chap. XIII.; Laycock, " Edin. Med. Journ.," July, 1838; Baldwin. "Handbook of Psychology,'' Chap. lY, ; Wundt, " Ueber den Einfluss der Philosophie,'" Antrittsrede (1876), p. 10 ; Hack Tuke, " Unconscious Cerebration "" — " Dictionary," p. 1336. 166 3I1ND. For. . The complicated processes per- formed in epileptiform uncon- sciousness (larvated epilepsy). , Our conclusions often arrive quite unexpectedly without any attempt to analyse their premises. This pre-supposes a mass of ideas in an unconscious state. 7. The general fitness of instinctive actions indicates unconscious in- telligence, as the ends ai'e not foreseen. 8. Eapid judgments of size, distance, shape, and the like, are ready-made conscious percepts derived by un- conscious inference. 9. We constantly discover new ele- ments in accustomed sensations. These elements must have existed in an unconscious state, otherwise we could not single out the sensa- tions containing them from others nearly allied. Against. Eapid oblivescence, as in dreams, occurs. Xo such mass of ideas is suppos- able. The predisposition to bring forth a conscious idea is no evidence that the idea existed unconsciously. Brain processes form the predisposi- tion to call forth the idea, just as external physical processes form the predisposition to call forth the brain processes. The actions may be explained physiologically as occurring along the lines of least resist- ance. Results like those of reasoning may accrue without any actual reasoning process unconsciously taking place. We may have an idea and subse- quently know all sorts of things about it. That we now become aware of the attributes of an object formerly presented is no proof that the awareness of these attributes must have existed unconsciously. That unconscious cerebration can go on, and does go on, without any obvious mental accompaniment is readily con- ceivable ; but when it refers, not to cerebral activities, but more particularly to mental modifications, without the consciousness of the subject, we find ourselves in difficulties. Undoubtedly, many of the phenomena described as evidences of unconscious cerebration may be compared to the automatic unconscious movements of the limbs from habit, as, for instance, in playing the piano. Griesinger has termed it psychical reflex action. According to the associationists, the development of a single thought is effected by the functional activity of association bundles, which unite in a very complicated way the component elements of a so-called residual image of the cortex. These groups rxc'oxscious ceijebilvtiox. 167 of associated cells, which harbour residual imaues. are the startino- point for the excitation of more comprehensive associations, con- stituting simple processes of induction. In this way every process of thought originating- from residual images would be connected with a large number of distinct cerebral elements, and it would have, as its physical counterpart, many separate and A\ell-defined areas of excitation, which areas are united for common action b}' the process of association. Each area is regarded as a separate and fairly-well-defined group of ganglion- cells, standing in relation to one another through the compli- cated system of association fibres, and every cortical image or inference depends iipon the union of these groups of cells. This view, as Me have already seen, precludes the possibility of localising the excitation in the forebrain, and, according to Meynert, the projection system alone stands under the influence of the centres of excitation. For illustration, let us compare the centres of excitation and the projection system to numerous stations on a complicated Ijranching railway. Some associationists hold that the ideas gain their component parts from the separate stations. They imagine that the physical equivalents of these component parts travel either directly or indirectly from their several localities to the central terminus (consciousness) and emerge, not as separate events, biit as one event — i.e., the results of the separate events compounded en route. Consciousness, viewed as the central terminus, is not supposed to Avitness the arrival of individuals, it only witnesses a conglomerate mass of fused passengers. Such is the line of thought advocated by the mind-stuffists, associationists, and unconsciovis cerebrationists. They postulate that psychological data self-compound into con- clusions. Let us continue the analogy a little further. The official recorder of arrivals (ticket collector) at the terminus, on entering upon his duties, notes the individual arrivals with more or less interest. With the daily repetition of the numerous arrivals, however, his acts of checking become more and more auto- matic, and the individuality of each passenger less distinct, until finally he comes to view, not the individuality of any passenger, biit the sum total or mass of individuals, with, 168 MIND. perhaps, some faint qualifying attribute, sncli as " pnshing," etc. In the course of his duties he one day experiences the feeling, that a certain face is familiar to him, but he cannot recall where or when he has seen it before. Or a particularly vigorous push b}' a passenger may make him become aware of the fact, that that same passenger had done the same thing on a former occasion. We might continue the simile, but we should find that every contingency would fit in with the possi- bility of the occurrences tvithin the realms of diffuse conscious- ness, and tvithoitt the direct concentration of attention. In other words, the realms of diffuse consciousness are so wide, that they include most of the phenomena regarded as evidences of un- conscious cerebration. The mere fact, that there is inability to recall former conscious events, is insufficient proof that those former events never existed, or that \h.ej existed unconsciously. The theory of unconscious cerebration we, therefore, hold to be superfluous and unproved. In his lectures on metaphysics* Sir William Hamilton states, that the greater the number of objects among which the attention of the mind is distributed the feebler and less distinct will be its cognisance of each — 2Jluribus intentus, oninor est adj sinr/ida sensus. As we shall have occasion to speak more fully of these things when con- sidering the phenomena of trance, somnambulism, hypno- tism, and epilepsy, we will now sum up in general terms our present position with regard to the evolution of mental states. From the affirmation of a universal law of evolution more information is derived than from the affirmation of particulars ; it logicall}^ follows, that more information can be derived from the denial of particulars than from the denial of universals — i.e., there are cases left doubtful. That there are cases left doubtful requiring the proof or denial of jDarticulars is manifest in current literature upon mental evolution. By the employment of terms such as " unconscious inference," " cortical trace," " subsidiary image," " nascent consciousness," as terms of propositions, we beg questions, and imply the existence of knowledge which we really have not got ; and in * A-'ol. i., p. 254. rXCONSCIOUS CEREBEATIDX. 169 the attempt to define that of which we know nothing we enter upon the fallacy of a circuhis in depniendo. Thus, if the student will sift the terms employed in the various propositions put forward by the mind-stuffists and cerebralists he will readily detect the abuse and equivocation, brought about, no doubt. by their attempts to substitute terms, the definitions of which they neither restrict nor explain. 170 CHAPTER YI. Sensation. Sensation — Analysis of Sensations and Sense Percepts — Relation of Sensations to Perception — Molar Motions — Atomic and Molecular Motions — Motions of Ether — The Theory of Electricity — Latent Chemical Energy — Power of Selection possessed by Sense Organs — Characters of Sensation — Intensity or Degree — Liminal In- tensity — Forms of Excitation — Weber's Law — Discriminative Sensibility — Maximum Intensity — Fechner's Psycho-Physical Interpretation of Weber's Law — Wundt's Psychological Interpre- tation — The Physiological Interpretation — Validity of Weber's Law — The Estimation of Magnitudes by Comparison — Measure- ment of Absolute Mental Magnitudes Impossible — Quality of Sensations — Creneric and Specific Quality — Duration — Local Characters of Sensations — Taste — Smell — Touch — Specific Func- tions of Tactile Corpuscles or End Bulbs — Pressure Spots. — Temperature Sense — Common Sensation — Peripheral Reference of Sensations — Muscular Sense — Hearing — Sight — Pressure Phos- phenes — Quality of Sensations of Sight — Simple and Mixed Colours — Colour - Blindness — Young — Ilelmholtz — Hering — Wundt — Von Ivries — Franklin. In the analysis of sensation and sense-percepts it is necessary (1) to distinguish simple sensations from those derivative and more complex psychic manifestations, to which our educated consciousness becomes so familiar, that it loses sight of their origin and integration ; (2) to demonstrate the quantitative and qualitative variations of sensations and their relations to the various stimtili ; (3) to investigate the psychical methods whereby our perceptions of time-form and space-form are arrived at ; (4) to estimate the part played by the various senses, and to see how far the higher mental activities are involved in the processes of perception. The term " sensation " is used to express the most elementary form of conscious experience. It is a mental state resulting ANALYSIS OF SENSATIONS. 171 from the stinmlation of the pei'ipheral extremity of a sensory nerve, through which the excitation reaches the sensorium. The senses provide our minds with supply. They fill up our con- sciousness Avith data from Avhich A\e gain our ideas. All sensations appear to liave some physical occasion. They do not necessarily involve the action of an external stimulus. When a sensory '• incarrying" nerve is divided there is no sensation arising from external stimuli, but subjective sensa- tions may still arise through the activity of a central process, the nature of which is unknown to \;s. In mental diseases such modes of activity within the sensorium are remarkably freqi^ent. Coupland* regards the term sensation as connoting a sub- jective condition which has no mental but only a physical occa- sion. He claims that a truly original mental phenomenon passes the limits of imagination, because it passes the boiandaries of our knowledge. The phenomenon of sensibility niay pertain to the organism, but the phenomenon of sensation pertains to the mind. All sensations are modes of behaviour of the mind. Sensations only exist in so far as they form contents of con- sciousness. They are not copies of outside molecular activities : they are modes of conscious activity of the mind. If we take an ordinary psA^chical activity, and seek to appose it to its material basis, we have to consider (1) the external stimulus, which is physical; (2) the excitation and transmission of the stimulus; and (3) the psychical process itself. All our knowledge is obtained from objects presented in con- sciousness, and we cannot properly speak of knowledge where no object is presented. Sensations are the mental objects pre- sented to the subject ; they only exist when presented. This presentation of objects is the first clear act of consciousness. Sensations do not exist except in so far as they are perceived by the subject. Sensations are particularised when perceived, and this perception is the first mental fact. The first psychical element perceived by the mind is sensation ; the first act of viewing that sensation is perception. Thus sensation is the first presentation to the consciousness ; perception is the first recognition of that presentation. Sensa- tion is the stimulus AA'ithin consciousness ; perception is the * "Tukes Diet, of Psych. Med.," p. 32. 17.2 SENSATION. appreciation of that stimulus by the mind. What happens within the cerebral hemispheres immediately antecedent toAvhat happens within consciousness is bej^ond our powers to determine. Ward* thinks a presentation (as presented to a subject) might, with advantage, be called an object, or perhaps a psj^chical object. to dis- tinguish it from what are called objects apart from presentation. In the meantime we shall treat of presentations in their literal sense, as presentations to the subject or ef/o. Each presentation has a twofold relation : (1) Its relation to the subject; and (2) its relation to other presentations. Ward states, that the mental facts Mdiich we speak of as sensations, perceptions, images, intentions, concepts, notions, etc., have two characteristics in common : (1) They admit of being more or less attended to ; and (2) they can be reproduced and associated together. Thus the term sensihility -would possess a psychical significance. and would denote the mind's capability of having sensations. General sensibility is that sensibility which represents all the sensitive parts of the organism other than the special sensory organs. Sensations of this character, involving no characteristic nervous structures, are vague and ill-defined. Special sensihility is the term employed to indicate the mind's sensibility to special sensations, brought about in most cases by external agents through the special senses, and from which we gain a know- ledge of our environment. * One simple sensation rarely acts alone. All our senses are open to imjDressions from AA'ithout, and our minds are constantly open to impressions from within the body ; so that, just as the external environment is constantly taking efiect upon our physical organism, so the physical organism is constantly taking- effect upon our consciousness. The various Jdnds of motion ■\\diich can act upon the peripheral organs of sense are as follows : — (1) Molar 'motions : the projection or impact of elastic or inelastic bodies. Definite motion is executed in a definite direction by a material body. To this class belong all the stimuli of touch and pressure. (2) Atoinic and molecular motions : Motions resulting in chemical changes within and among the molecules. Besides * Encyclop;eclia Britannica, " Psychology." ATOAIIC AND MOLECULAR MOTIONS. 173 the stimuli of taste and smell, many visceral stimuli also ])ro- bably belong to this class. (3) Tlte motions of ether : The vibrations of ether, pervading the space between the molecules of matter, according to their velocity, produce the phenomena designated as " light " and '' radiant heat," and probably, also, those of " magnetism " and " electricity."* The forms of energy may exist as energies of motion or of position, and the actual constitiition of the universe is due, in a great measure, to the alternation of these two energies. The various forms of active energ}- show themselves as (1) the energy of visible motion, which may be transformed into an equivalent amount of energy of position; (2) molecular energy, which causes the cohesive attraction, repulsion, and other jorojDer motions of the minute and invisible particles of matter; (3) energy of heat and light, which are transmitted by Avaves of the assumed imponderable mediiim called ether ; (4) energy of chemical action, by which the small ultimate particles of ponderable matter, called atoms, separate and combine into the various combinations of molecules constituting visible matter, in obedience to cei'tain affinities or inherent attractions and repul- sions ; (5) electrical energy, which includes magnetism as a special instance. We cannot enter into an account of the mutual attractions and repulsions of atoms or molecules ; nor can we discuss the nature of the laws by which these energies manifest themselves. The most subtle and the least understandable of all these indestructible energies is that of electricity. The theory of electricity assumes the existence of two opposite electric fluids, which, in the ordinary or unexcited body, are combined and neutralise one another, biit are separated by friction, and flow^ in opposite directions, accumulating at opposite poles; or, it may be, that one is accumulated at one pole, whilst the other is diffused through some conducting medium and lost sight of. The active electricity, be it positive or negative, thus accumu- lated at one pole, and retained there by the substance in contact with it being a non-conductor, disturbs by its influence the electrical equilibrium of any body brought near to it, separates. * Ziehen, " Physiolog. Psycliol." p. 37. 174 SENSATION. its two fluids, and attracts the one opposite to itself". This attraction dra^vs the light body towards it nntil contact ensues, when the electric fluid of the excited body flows into the smaller one, so that its opposite electricity is expelled, and it is in the same condition as its exciter, and, therefore, liable to be repelled by a similar exciter, or attracted by the opposite one, which formerly repelled it. The ultimate elements of the material universe are generally taken to be ether, energy, and matter. Of ether, the universal all-pervading medium whose tremors or vibrations, propagated as Avaves, transport the different forms of energy, light, heat, and electricity, across space, we know nothing. Neither can we here discuss the dynamical and statical aspects of energy as it manifests itself in gravity, mechanical work, molecular or atomic force, light, heat, electricity, or magnetism.. We are unable even to speculate as to the actual nature of energy itself. Some would hold that energy is the one reality of nature, while others would regard the seventy elementary atoms as ultimate facts. In any case, both matter and energy are indestructible, and their present co-existence is not to be explained by. evolution. We must, however, at any rate, take some account of the activities of the ultimate elements of Avhich the human organism is built. Tt is impossible to conceive how the human organism can manufacture molecules of living protoplasm like its own out of foreign molecules — i.e. .how life manufactures life out of non- living materials. A similar problem awaits us in the analysis of sensation. The molecular motion external to the body becomes transformed into another form of energy — the energy of living matter — whilst that, in turn, becomes the physical counterpart of consciousness. Dr. Gowers* has recently drawn attention to the source of energy manifested in the animal body and in the processes of human life, and he believes that every form of energy •• from a sigh to a convulsion," is derived from " latent chemical energy." He discards the old term " transformation of energy." and sub- stitutes that of the '•'transition of motion." "We can, I Think, perceive all stimuli to be forms of motion. In the case of many physiological stimuli the fact is too obvious to need * " The DvE.amics of Life." NERVE EXEKGY. 175 consideration, and I believe that, Avliere it is not obvions. the conception ^^•ill be found to be one from which there is no escape. If that which is added is motion, it is probable that the energy which this increases is also motion."' It is commonly assumed that nerve-force is of the nature of molecular or atomic motion ; it remains, however, for us to ask the question. AVhat is the form of that motion ? Dr. Gowers advances the hypothesis that its source is latent chemical energy, conceived as minute motion, liberated and released by added motion. The nerve-endings receive the different vibra- tions, by A\'hich vibrations outward energy presents itself, and Mhich propagate a current or succession of vibrations of nerve- energ}' along the nerve-fibre. The mechanism by which corre- spondence is kept up between the living individiial and the surrounding universe may appear to be simple ; but the notion of its simplicity vanishes when we attempt to comprehend the transformation of the vibrations of outward energy into vibra- tions of nerve energy, and more especiall}' do we realise our difficulties ■\\hen Ave attempt to give an account of a specific motion, of which sensation would be the mental counterpart. The two chief groups of stimuli are chemical and mechanical. Hermann * believes that magnetism does not act as a nerve-irritant. Ziehen advocates, that the non- nervoiis elements of the sense-organ, which first receives the external stimuhis, act like a sieve, arresting certain qualities of the irritating motions, and permitting certain other qualities to pass on and irritate the nerve-ends. In this way the organs of sense are regarded as possessing the power of selection. In the new-born brain only can pure sensations be experienced. AVitli every sulisequent act of mental stimulation the resultant action is made up in part of antecedent eifects. In adults the immense number of acquisitions and brain modifications render it almost impossible to realise simple sensations. From an analytic point of view, sensations are thought to differ from perceptions only in the extreme simplicity of the object or content of the former. Sensation's function is that of mere acquaintance with a fact. Pei'ception's function, on the other hand, is knowledge about a fact (James). Sensations involve * -'Pfliiger Archiv.,"" Bd. 43. 176 SENSATION. nerve-currents coming in from the periphery. In perception it is thought that these nerve-currents arouse associative or reproductive processes in the cortex. Perception would imply the existence of an efjo ; but, inasmuch as the e) re- versing movements, (c) repetition of movements. (4) The size and form of objects through movement. Tactual percep- tion proper is acquired by movement, and there is interpreta- tion of the local characters of sensations by movement. (5) The simultaneous perception of points. The tactual perception of space is a product of two factors, movement and muscular sensation, and a plurality of sensations of contact. (6) The solidity of an object. (7) The discrimination of single things, and of a number. (8) The perception of moving objects (under this must be distinguished the difference between objective and subjective movement). (9) The sensations of temperature. (Our sensations of temperature vary according to the tempera- ture of the subject.) Our space, however, will not permit us to enter into the numerous details of these relations. We must content ourselves with a few remarks upon the discrimi- nation of the amount and direction of motion in contact with the body. The discriminative sensibility of the skin is much greater for motion than for touch, and this power of discrimination varies with different parts of the skin. Stanley Hall found that these differences do not completeh' correspond to the differences met with in the sensation-circles. The fact that our sensibility to motion is so much greater in each area of the skin than our susceptibility to the distance of stationary 220 PERCEPTIOX. points, is held to accord with the theory of local signs, and it is thought that onr ability to localise the dermal sensations is dependent npon the degree and rate of the clian^jes in the colour-tone of these sensations. Other facts of importance. derived from the experiments of Stanley Hall, may be briefly mentioned. AVe are more likely, when in doubt, to judge motion on the surface of the limbs to be up rather than do^n their axis; on the breast, the shoulder-blades, and the back, the tendency is to jtidge motion to be toward the head. The rate of movement causes variations : thus, a very rapid move- ment may appear to be shortened, or a very slow movement may not be discriminated at all. Heavy weights seem to move faster than light ones going on at the same rate: but here other sensations are called out by the deep pressure, com- bined with those of contact.* 4. The perceiAion of muscular sensations. — The chief theo- ries to account for the so-called muscular sensations have already been given. The theory that these sensations are- specific sensations, dependent on a specific nerve-apparatus of sense, which has its end-organs in the muscle-fibre, finds the most favour. It is doubtful, however, whether the muscular sensations do differ qualitatively. They may have a different colour-tone, and act like local signs ; but the muscular sensations alone do not afford us sufficient data to account for our perceptions of spatial qualities and relations. In addition to the muscular sensations the tactual discrimina- tive element is essential for the perception of spatial relations. Several writers uphold the view, that all spatial measurement arises primarily from the perception of muscular movement. Professor James believes that no evidence of muscular- measurements exists: but that all the facts may be explained by surface-sensibility, provided we take the joint surfaces also into account. Goldschneider goes further, and believes that the joint-surfaces alone are the starting points of sensations by which the movements of our limbs are perceived. From an analysis of the experiments of Goldschneider and Lewinski, it would appear, however, that the joint-feeling is not the sole source of spatial perception of movement. The absolute space- * Ladd, " Phys. Psych.r P- 411. ^TSUAL SPACE. 221 value is derived from secondary suggestive influences brought about by associated tactual and visual perceptions. Professor James says. "The joint-feeling can excellently serve as a map on a reduced scale, of a reality which the imagination can identify at its pleasui'e A\*ith this or that sensible extension simultaneously known in some other way.*" The muscular sensations in themselves give us knowledge of spatial relations only in an indirect way by the efiects of muscular contraction upon the surfaces of the skin and joints. Spatial discrimina- tion would, therefore, appear to be related to the efiects of move- ments upon these surfaces, and the secondary suggestions of visual imagination. James accounts for the phenomenon of eccentric projection by the localisation of the joint-feeling in a space simultaneously I'ecognised from other sources — i.e.. thi'ough the skin or the eye. 5. The percepiion of visual space. — In the perception of smell, taste, touch, and hearing, we have seen that there is usually a corresponding visual presentation. According to the Berkeleian theory the visual sense derives much of its knowledge of external things from touch. The local discrimi- native sensibility of the retina is insufficient by itself to determine spatial relations. Volkmann* gives eight difierent data which are used in monocular vision for perceiving the third dimension of space and of visual objects in space — viz.. monocular vision. (1) Extent ; (2) clearness, of the complex of the sensations of colour and light, as dependent on distance : (3) the perspective elevation of the bottom of distant objects above the horizon ; (4) the covering of known distant objects by those placed nearer ; (5) the alterations of light and shadow on the curved surfaces of the object, according as they are nearer or more remote : (6) the perspective contraction of the retinal image ; (7) the change of the A"isor angle in proportion to the distance of the object ; (S) the muscular sensations of the accommodation of the eye. To these data Laddt adds two othei-s for binocular vision — viz., (9) the stereoscopic double images : (10) the sensations arising from convergence of the axes. The question has been * "Lehrb. d. Psyehologie," ii. p. S-l. t " Phys, Psyeh.," p. 421. 222 PERCEPTION. raised whether tactiial sensations which accompany the move- ments of the eyeballs in their sockets do not possess some spatial value. The local ([uale of the retinal signs has already been referred to. In an act of visual perception certain data are essential. There must be sensations of light and colour simultaneously present in consciousness. The subsequent perception of their spatial relations only becomes possible with the help of retinal signs, and the series of sensations derived from the movements of accommodation. Lipps, Wundt, Mlinsterberg, and others, share this view of the importance of eye-movements, and the sense of their position in determining a spatial series. Volk- mann, Hering, Helmholtz, Goldschneider, James, and others, on the other hand, believe that eye-muscle contractions have only a feeble share in determining sensations of the third dimension. For our part, we believe, that the purel}^ muscular sensory element plays quite a subordinate part to that of the tactual and retinal elements in the estimation of space. Wundt* saj'-s, there are three things to be determined in explaining perceptions of sight : (1) the retinal image of the eye at rest, and the motifs which it furnishes ; (2) the single eye as moved, and the influence of these movements ; (3) the conditions furnished by the existence and relations of the two eyes exercising their function in common. We have, there- fore, to consider the retinal field of vision, and the fields of monocular and binocular vision. The problem of the physiological process, which underlies the perception of distance, has occupied the attention of many psychologists. Helmholtz and Wundt affirm, that the organic eye-process pure and simple, without the aid of other sense data, cannot give us any sensation of a spatial kind at all. That it does not depend upon the combination of images through binocular vision, is proved b}^ the fact that one-eyed people have it. Nor can it be explained by convergence or accommodation feelings. Lipps concludes that our knowledge of the third dimension must needs be conceptual, and not sensa- tional or visually intuitive. Stumpf thinks that the primitive sensation of distance must have an immediate phj^sical ante- * " Physiolog. Psychologie," ii. p. 62. VISUAL SPACE. 22o cedent, either in the shape of an organic alteration accom- panying the process of accommodation, or else given directly in the specific energy of the optic nerve. He also thinks that it is the absolute distance of the spot fixated which is thus primitively, immediately, and physiologically given, and not the relative distances of other things about this spot. James believes the neui-al process is to be found in the number of retinal elements affected by the light ; but that in the case of " pretension " or mere farness, it is more complicated, and is still to seek. He says, " The two sensible qualities unite in the primitive visual bigness. The measurement of their various amounts against each other obeys the general laws of all such measurements. We discover their equivalencies by means of objects, apply the same units to both, and translate them into each other so habitually, that at last they get to seem to us even quite similar in kind. This final appearance of homo- geneity may perhaps be facilitated by the fact that in binocular vision two points situated on the prolongation of the optical axis of one of the eyes, so that the near one hides the far one, are by the other eye seen laterally apart." When we come to consider the various illusions of the senses, we shall return to the view of James, that every spatial determination of things is originally given in the shape of a sensation of the eyes. He sums up his theory in the state- ment that " measurement implies a stuff to measure ; retinal sensations give the stuff; objective things form the yard-stick ; motion does the measuring operation.'' The numberless inves- tigations and discussions which have been brought to bear upon the question of binocular vision, and to explain how it is that a double retinal image is only perceived as one, cannot occupy our attention here; nor can we afford space to elaborate the theories as to how vision receives its stereometric character by association with ideas of motion and touch. The law of Weber is only valid in the case of sight for medium distances in the estimate of magnitudes of extension. It remains for us now to recognise the relationship of the data presented to us in the attempt we have made to explain perception. We have seen that these data depend upon external stimuli, and we have assumed the existence of specific and 224 PERCEPTION. qualitatively-different functional nerve-elements, by the instru- mentality of which, either separately or in combination with each other, these data are presented to the psychical subject. Our efforts, however, have ended in a mere enumeration of data and their possible laws of analysis and synthesis. The influence of the retinal field of vision in determining spatial perception has already occupied our attention. We do not hold, that the retinal field, when its mosaic of nervous elements is stimulated, alone can determine a spatial series ; nor do we believe that sensations of light and colour would have space-form if they only came from an excited but motionless retina without being combined with other sensations of a spatial series ; we merely assume, that spatial perception, at least in a germinal form, is native to the mind by reason of the q^uale of the retinal elements, and that the fully-developed per- ception of spatial quality cannot be entirely explained by tactual or so-called muscular sensations of movement — i.e, we assmne that there is a native content of vastness, and that the spatial relations of the integral parts of the vastness are per- ceived by a process of analysis effected partly through the sensations of movement. We cannot enter into the question of the law which governs all the movements of the eye. We must, however, note the general law, as given by Ladd, that " the construction of the field of monocular or binocular vision is a synthetic mental achievement, dependent upon the varying sensations, which results from the wandering of the point of regard over the outline of an object." This view, as we have just seen, is open to criticism, and we hold that the field of vision in its entire content is one primarily of vastness, and that the perception of the component parts of that field is an analytical mental achievement, depending upon the varying sensations which result from the wandering of the point of regard over the contents of the field of vision. That is to say, oin^ perception of objective space, in its vaster extents, is originally constituted ; the subsequent perception of its spatial contents is secondarily analysed. 225 . CHAPTEE VIII. Sensory Pebveesions. The Origin and Development of Sensoi'y Perversions — Abnormal Con- ditions of Perception — Definition of Illusion — Sources of Illusion — Classification — Passive Illusions — Exoneural — Esoneural — Active Illusions — Voluntary — Involuntary. Secondary Sensations — Sound Photisms — Light Phonisms — Taste Photisms — ■ Odour Photisms — Pain Photisms — Chromatisms — Gustatisms — Olfactisms — Laws concerning Secondary Sensations. The Origin and Development of Sensory Per- versions. — In the consideration of illusory phenomena it is necessary to remember that the perception of" sense-data derived from the finer senses is more readily revivable under abnormal conditions than the perception of those sense-data derived from the less refined senses. The development of perceptual power involves an increasing power of sense-dis- crimination, and also an increasing power of identifying impressions through the " cumulation of traces." That is to say, our senses become more acute in distinguishing impres- sions by means of their local signs, and the mind becomes qviicker and keener in identifying them. The sense-capacity varies in different individuals in its absolute sensibility and in its discriminative power. A general discriminative power probably implies, from the first, a fine organisation or nativistic power of the brain as a whole ; whereas, a special discriminate sensibility implies rather an original structural excellence of the particular sense-organ concerned. The prominent part taken by the visual sense in 16 226 SENSOEY PERVERSIONS. the development of perception as a whole lias been already mentioned. Complete development of the perceptual power involves (a) sense-perceptions in their various degrees of perfection ; (h) daily-renewed conjunctions of simple sense- experiences — e.g., between touch and sight ; (c) noting nature of objects as such and recognising them ; (d) after this the growth of perception is mainly due to an improvement of visual capacity, or increase in visual discrimination • and (e) develop- ment of the power of attention, which, however, is, to a certain extent, pre-supposed. Our knowledge of external things depends upon the training of our perceptual power. Unless we have cultivated the practice of accurately discriminating the forms of things all our after knowledge will be inaccurate. We must not only treat the forms of concrete objects from an analytical, but also from a synthetical point of view — i.e., the analytic and synthetic treatment of the forms of objects should be equally cultivated. The blind man is able to construct perceptions of space quite independently of a visual sense. He is conscious of a horizon, and can appreciate arrangement and dimensions. By a synthetical process he can summarise in his imagination a fairly accurate estimate of the spatial relations of objects. The absence of this sense need in no way interfere with the develop- ment of a full and powerful intellect. What the psychology of a blind man's spatial perceptive power is can only be explained by the assumption that there is a nativistic power within the mind itself, which can assert itself with freedom apart from the direct influence of the visual sense. Abnormal Conditions of Perception may, for con- venience, be described as they occur : (1) In the sane. (2) In intermediate states between sanity and insanity. (3) In the insane. A false perception is technically called an illusion, and it must be borne in mind that the process is often largely the same in a false perception as in a true one. Some authors would seek the explanation of the fallacy in an illusion, by taking into account the action of the senses only, and they would assume ABNOEMAL PERCEPTION. 227 the mental interpretation of the false sensoiy impression to be the abstract result of a fallac}^ of the senses. We have alreadj^ discussed the law of the specific energy of nerves, and we have spoken of adequate (or homologous) stimuli. We have also briefly referred to stimuli (heterologous) which act upon the nervous elements of the sensory apparatus along the entire course from the end-organ to the cortex cerebri. These latter stimuli, when of internal somatic origin, give rise to subjective mental phenomena of varying degrees of quality and intensity. In the s(ine person there is a constant liability to errors of perception. Illusions are common to us all. Our discrimina- tive power is necessarily limited and defective. Thus the study of sensory perversions belongs both to the psj^chologist and to the mental pathologist. There is no sudden break between the illusions of the sane and those of the insane, and there is often great difficulty in distinguishing between them. Our judgments are liable to be distorted at a,nj time, and our sensory discriminations may be at variance. Any emotional disturbance, any state of exhaustion, inattention, expectancy, or mental preparedness, may favour the development of some false sensory perception. The transition from sane to insane perceptions is often difficult to demonstrate. In the intermediate conditions, half-^^'ay conditions between sanity and insanity, we have many examples of sensory dis- tiTrbances. Thiis in some dream-states, night-mare, religious fanaticism, and manj- excessive emotional states, we have perversions which are suggestive of a neurosis rather than true nerve health. In hysterical temperaments, especially, do we find illusory morbid conditions. In the sane, the illusory percepts may be due to defective knowledge ; or the illusory nature of the percepts may be recognised by the individuals in whom they occur as the results of defective energisation. In the intermediate states there is often failure to recognise the true natu.re of the illusory phenomena at the time of their occurrence, but this knowledge may be gained at some subsequent period. In the insane there is not only a failure to recognise the true nature of the phenomena, but also a belief in their objective 228 SENSORY PERVERSIONS. reality, and, as a consequence, there is a tendency on the part of the individual in whom they occur to act upon the false evidence presented to the mind by wa.j of the senses. Definitions of Illusion. — In order that we may fully comprehend the meaning of an illusion, we must take account of its factors from several points of view To define it as a false sensory perception is insuflacient. There is a standard of falseness, and one must remember that human experience is fairly consistent. Our perceptions and beliefs fall into a con- sensus. Some metaphysicians hold the idealistic view, that perception itself is an illusion, inasmuch as it involves the fiction of a real thing independent of the mind, yet somehow present to it in the act of sense-perception. With this question, however, we have nothing to do. An illusion is further defined as a " mistaken identity" — i.e., a partial displacement of an external fact by a fiction of the imagination. Another definition is, that an illusion is a false percept which arises in the mind of an individual iinder circumstances which would not give rise to similar percepts in the case of other people. This is still, however, inadequate. There are special circumstances which are fitted to excite a momentary illusion in all minds — e.r/., optical illusions may be due to refraction of light, reflection, etc., and these may arise in all minds under precisely similar circumstances. Any definition mast be relative. The false percept must be one that can be contradicted by a more acciirate percept ; or, as Sully puts it, it is a deviation from the common or collective ex- perience. This deviation, as met with in the insane, is a species of perceptual error, which is peculiar to the individual, and, as we shall see later, it involves not only present sense-data but also other psychical factors. The sources of illusions of perception are : (1) Suitable soil ; a neurotic type, or physical preparedness, due to inherit- ance or disease. (2) Expectancy ; a mental preparedness is the most prominent factor in the causation of so-called " active " illusions. (3) Inattention or incomplete attention to the sense presentation. Closely allied to this is (4) confusion of sense- impression. In the regions of hazy impression, or of diffuse consciousness, illusions are most apt to occur, and play the ILLUSIONS. 229 greatest pranks. Every cricketer appreciates the difficulty, or confusion of sense-impression, that is apt to arise when tliere is any movement in the fiekl behind the bowk-'r's arm. In the same wa}', the presence of a swallow on the cricket field, as viewed by the retinal points outside the field of central focus, is apt to give a confused impression of a ball moving in space. Organic sensations, occurring in the regions of sub-conscious- ness in both sleeping and waking moments or between them, give rise to illusions. (5) In mental states, which are the result of habits of inaccurate discrimination — i.e., in mental states built upon data which have not been analj^sed — the interpretation of the present sense-impression is apt to follow the law of habit, and the habit of loose inference, or misinterpretation of sense- impressions, may result in the acquisition of so-called uncon- scious fallacious inferences, and fallacious conclusions from present determining sense-data. Varieties of Illusions of Perception. — These have been arranged according as they arise from irithottt, by suggestion of external or physical factors ; or, as they arise from ivithin, due to the development of preperception, or the element of expectancy. The former have been termed passive illusions, the latter adire. The factors of causation may be grouped in the following order : — * PASSIVE ILLUSIONS. 1. Exoneural, determined by — (a) Exceptional external arrangements. (/>) Exceptional relation of stimulus to organ. (c) Illusions of art. (d) The particular forms of objects. (e) The points of similarity of objects. (/) The reverse illusions of orientation. 2. Esoneural, determined by — (ft) The limits of sensihiliti/ : Degree of stimulus. After sensations. Number of stimuli. Specific energy of nerves. Fusion of stimuli. Eccentric projection. * See Sully's " Illusions." 230 SENSORY PER^'ERSIONS. (/j) By the variations in sensibility ; (1) Momentary, or transient, caused by fatigue, malnutrition, or toxic agents. (2) Permanent, caused by variations in excita- bility of sensory organs, hereditary or acquired. In conditions of liypergesthesia, angestliesia, and parEesthesia. ACTIVE ILLUSIONS, which involve the element of expectanc}" : — 1. Voluntar}^ selection of interpretation. 2. Involuntary mental pre-adjustment. (a) Temporary exijectation or preparedness : Snh-expedation. Vivid expjectation. both of which \\iq.j arise from — Present objective facts. Verbal suggestion. Imagination. (6) Compjaratively permanent disposition, as seen in the evolution of conceit, hypochon- driasis, etc. In the account of all these states, it must be remembered, that every function is rendered more facile by exercise, and that illusions become more real by repetition. Passive Illusions determined by environment — 1. JSxceptional external arrangements. — The ordinary physical phenomena of the refraction of light and the reflection of sound. A stick half-immersed in water appears to be bent. The optical illusions of magniitude, due to external conditions, are numerous and well known. The atmosphere has to account for various illusions as to distance. Thus, the person unused to the clear atmosphere of Switzerland is unable to realise distances. At times, great difficulty is experienced in deter- EXONEUKAL CAUSES. 231 mining whether our train or the one alongside it is moving. When we move forward all objects appear to glide backwards. The faster we go, the nearer do the objects seem, and the nearer they seem, the smaller do they look. This fact is explained by the greater rapidity of their apparent translocation (Helmholtz). 2. Exceptional relationship of stimahis to onjan. — Aristotle's experiment, of crossing two fingers of the same hand and rolling a pea between them, is attended by the illusion of there being two peas instead of one. Each of the two points of contact has its local sign ; but, from their inexperience of working in unison under certain particular conditions, there is distortion of the inference. In a similar way the experience of having " sea- legs " on land is to be explained by the absence of the accus- tomed undulations of the structure on which we walk, and the want of the customary tactual and surface sensation experi- ences. The examples given by Sully afford further illustration. AVhen a man crunches a biscuit, the sound is intensified owing to the propagation of the stimulus by other channels than the usual one of the ear. If the two hands are bent into a sort of auricle, and placed in front of the ears, the back of the hand being in front, the sense of direction, as well as of distance, is confused. Thus, sounds really travelling from a point in front of the head will appear to come from behind it. Objects appear smaller and at a greater distance when one eye is used than when both are used. Illusions of movement occur owing to our eyes moving without our knowing it. Perception of an object's movement depends upon the sense of movement in our own eyes. James regards the original visual feeling of move- ment as produced by an image passing over the retina. He says, '"This sensation is definitely referred neither to the object nor to the eyes. Such definite reference grows up later, and obeys certain simple laws. We believe objects to move (1) whenever we get the retinal movement feeling, but think our eyes are still ; and (2) whenever we think that our eyes move, but fail to o-et the retinal movement feelino-. We believe objects to be still, on the contrary, (1) whenever we get the retinal movement feeling, but think our eyes are moving ; and (2) whenever we neither think our eyes are moving, nor get the retinal movement feeling." 232 SENSORY PERVERSIONS. 3. Illusions of art. — Pictorial art aims at stereoscopic effects, and seeks to give to flat surfaces the illusory effect of depth, relief, and solidity. By means of colour in various qualitative and quantitative degrees, an imitation of natiiral objects is sought. This imitation suggests to the mind the habitual interpretation of natural sense-impressions, and hence the imitative art is a source of complete illusory effects. The illusion that the eye in a portrait seems to follow the spectator is due to the fact that the surface of the portrait is flat, so that the profile of the object is never seen. 4. Misinterpretation of form and local a^rrancjement. — This is clearly allied to the foregoing illusions of art. An object appears smaller on the lateral portions of the retina than it does on the fovea. The intensity of the nerve-excitation sometimes increases the volume of the sensation as well as its vividness. Professor James* gives the following instances of these illusions : "If we raise and lower the gas alternately, the whole room, and all the objects in it, seem alternately to enlarge and contract. If we cover half a page of small print with grey glass, the print seen through the glass appears decidedl}^ smaller than that seen outside of it, and the darker the glass the greater the difference. When a circumscribed opacity in front of the retina keeps off part of the light from the portion which it covers, objects projected on that portion may seem but half as large as when their image falls outside of it (Classen). The inverse effect seems produced by certain drugs and anaesthetics — morphine, atropine, daturine, and cold, blunt the sensibility of the skin, so that distances upon it seem less. Haschish produces strange perversions of the general sensibility. Under its influence one's body maj^ seem either enormously enlarged or strangely contracted. Some- times a single member will alter its proportion to the rest ; or one's back, for instance, will appear entirely absent, as if one were hollow behind. Objects comparatively near will recede to a vast distance ; a short street assumes to the eye an immeasur- able perspective. Ether and chloroform occasion all}:- produce not M^holly dissimilar results." To attempt to give an account of all the ambiguities of * " Principles of Psycliology," vol. ii. p. 142. EXONEURAL CAUSES. 233 retinal impressions, and the part they play in misinterpreta- tions of the form and arrangement of external objects, would involve too much time and space. Xor can "vve enter upon the question of the ambiguous import of eye-movements, "and the interpretations of the feelings of convergence and accommodation. For an account of the ambiguities which result from the perception of lines meeting and crossing each other on a plane, the student must refer to the various text-books on physiological psychology. Here we can onlj^ present a brief summary of the phenomena. The law of habit has most to do with the illusions in connection with diagrams on planes. We are apt to view the object in its habitual form — i.e., when we look at a portrait our imagination suggests that the object occupies space in its three dimensions. The actual retinal image suggests the memory of the image in its stereo- typed form. The vividness of the reproductive processes is regarded as greatest when the visual sense is involved. The movements of the eye aid in the education of our perceptual power; but every spatial determination is primarily given in the shape of a sensation of the retinal elements of the eye. The remarks which apply to space-perception apply equally well to colour-perception. Professor James believes, that present excitements and after effects of former excitements may alter the result of processes occurring simultaneously at a distance from them in the retina or other portions of the appa- ratus for optical sensation, and that the spurious account of these ilhisions is that they are intellectual, not sensational ; that they are secondary, not primarj^, mental facts. That is to say, the various illusions as to form and arrangement are mental facts suggested by present objective facts ; but, in their fully developed states, they are due to an imaginary repro- duction of habitual and real forms, suggested by the present objective facts. 5. Illusions arising throtir/h simikmfi/ in objects. — Every one is familiar with the fact that he is apt to make mistakes in identifying persons and things. The process is similar to that just described. The suggestion of a familiar object, made from withoxit, involves the reproduction of an old and habitual perceptual process. The familiar interpretation acquired by 234 SENSOKY PERVERSIONS. practice becomes superimposed, iipoii the present percept, with a vividness which tends to obliterate or submerge the subject- ive perception of the actual object as it exists. In dream- states, and in the insane, one finds innumerable examples. Some insane persons perceive objects or persons so imperfectly that the actual presentation at the time is immediately sub- merged by the vividness of the image of recalled familiar objects or friends, and they are immediately imagined to be those familiar objects or friends. The process is a mental one. From a physiological point of view it may be urged that the actual and immediate perception is distorted by a disordered nerve-tract, and that the misinterpretation is the primary result of such distoi-tion. The answer to this is simple. We have already seen that the element of association is involved in every percept, and that the interpretation of a sense-presenta- tion is to a large extent dependent upon comparison with former presentations. A typical illusion is a secondary product; the initial stimulation by a sense-presentation sug- gests to the mind a representation of more definite organisa- tion, which takes the place of the initial presentation. 6. Reverse illusions of orientation have been fully described by Binet.* These illusions may arise spontaneously, either when we awaken in the darkness of night, or during the day when awake. They consist in any illusory experience that a wrong direction is being taken; that objects are reversed from side to side ; or that the individual is turned round. Beaunis, Passy, Henri, Philippe, Courtier, Thelohan, and others, have described these illusions as part of their own experiences. The author of this work invariably fails to orientate himself on arrival at a certain railway station, and this although he has visited the station weekly for more than six years. Binet dis- tinguishes three kinds of cases : (1) Normal orientation, in which the points of reference recognised confirm the former sense of direction ; (2) disorientation, in which there is no sense of direction at all, and if a familiar point of reference is met with, it is accepted, and the individual orientates himself pro- perly; (3) inexact orientation, in which an individual meets a point of reference, but finds it in contradiction with his * " Le Renversement de I'Orientatior." LIMITS or SENSIBILITY. 235 earlier system ; the false system persists, even though it is known to be false, just as an illusion persists. Binet suggests that possibly the illusion may be produced by a particular derangement of the semicircular' canal of the inner ear.* This, however, is a possibility A\'e are un\\'illing to admit. Passive Illusions determined by the Organism — 1 . i>// the limits of sensihilitii : (ct) Beijree of stimulus. — We have already discussed the various limitations in discriminative power of the different senses, and we have seen, that below the point of liminal intensity, and bej'ond the point of maximum intensity, our perception of stimuli is imperfect or non-existent. This per- ception of degree also is altered considerably in mental diseases. Thus, there niay be defect of discriminative power when the attention of the individual is focussed upon some mental idea or hallucination ; or, as in some cases of stupor, the senses are abnormally slow m their action. In some maniacal conditions, on the other hand, there may be an unusually line degree and rapidity of discrimination. Again, among stimuli arising from without there is alwaj'S a struggle for supremacy within. There is a survival of the fittest and most interesting within the focus of attention ; the remainder lie within the field of diffuse consciousness or outside it altogether. (h) Number of stimuli. — The difficulties met with in the interpretation of local signs have already been considered. The case of two points recognised as one only, owing to character and amount of the interval between them, has also been alluded to. (c) Fusion of stimuli. — The retinas are acted upon sepa- rately, and the resulting impressions become fused into one. How the mind perceives but one object, or how the coalescence occurs, we do not know. Illusions may result from imperfect coalescence of images. When double images are seen, although there may be sets of retinal fibres so organised as to give an impression of two separate spots, yet the excitement of other retinal fibres may inhibit the effect of the first excitement, and * M. Vignier, " The Sense of Orientation and its Organ in Animals and Men," Kev. Phil., July, 1882. Binet, "Vertigo of Direction," Mind, 1884. M. i'lournoy, " Les Synopsies," p. 188. 236 SENSORY PERVERSIONS. prevent tis from actiially making the discrimination (Volk- mann). Still further, retinal processes may bring the doubleness to the eye of attention; and, once there, it is as genuine a sensa- tion as any that our life affords- (James). (d) After sensations. — When a clock strikes we sometimes experience the illusion that a stroke has occurred after the sounds have actually ceased. Discontinuous stimulations rapidly fol- lowing one another appear to be continuous. After a bandage has been removed from the head the sensation is still continued. The tasting of sherry and port alternately, results in inability to distinguish between them. The sensations of the rolling of a ship may remain for days. The sensations of movement after a bicycle ride may continue to assert themselves even during sleep. (e) Specific energy of nerves. ■ — The perception of light (phosphenes) , when the eyeball is pressed, is illusory, inasmuch as we refer the presentation to light. In the insane we occa- sionally see morbid instances of this nature. Thus, stimulation of the various nerves, having their characteristic local colour- ings, is followed by misinterpretations of the actual phj^sical agencies at work which cause the presentations ; the direction of the attention being determined hj the character of the stimulus and the local specific and suggestive energy of the nerves. The interpretation afforded by the mind, when the attention is focussed upon the presentation, is determined by reference to former presentations, and by the mental complexion of the moment — that is to say, the imagination is an important factor. The actual presentation, as determined hj the imme- diate stimulus, is vague and ill-defined ; whereas, the secondary product, derived thi'ough association or expectancy, is often vivid and apparently real. A patient now in Bethlem Hospital has only to press his eyeball with the "stone of life" in order to open up to him a vision of " green fields and objects of wondrous beauty." In this case the primary presentation derived from pressure was that of light only ; imagination did the rest. He now expects the vision, and associates its origin with mechanical means. The interpretation is fallacious, and he locates the apparent reality within the " stone of life " itself. In order to test the accuracy of this view, the stone LIMITS OF SENSIBILITY. 237 was applied to the ear, \\'itli the result that simple " sea-shell " sounds were first experienced ; then followed the element of expectanc}^ and imagination supplied in turn, sounds of whisperings, voices, hummings, -music, etc. No^^' the " stone of life " provides him with the enjoyments of other associative phenomena.* The patient himself gives the following account of the phenomenon : — " When the stone is placed over the eye and kept there for some considerable time, the first impression of sparks of light gradually resolves itself, by a shimmering process, into a more definite representation of a luminous field with a more or less definite coast line, or sometimes a mountain line. Sometimes 1 see distinct trees, and figures of fantastic shapes moving about. The stone possesses this propei'ty within itself, because, without it, I see nothing. On placing it over the ear, the impressions previously produced by the eye become more clearly defined, and even when I press it on my forehead I see all the scenes just as vividly. I have at other times seen flowers and fruit trees, and on applying the stone to the nostrils, I have smelt the odours of the flowers ; and, when the tongue was touched, the taste of the different kinds of fruit. In the case of my sight, I apply the stone first, and all the scenes appear to me ; with the other senses, how- ever, I see what the things are first, and the stone supplies me with the knowledge of their various qualities." (/) Eccentric inrojectioit. — Bj- the " law of eccentricity " physiologists affirm that we refer our sensations to the peri- pheral endings of the nerves concerned. In the case of the senses of smell, hearing, and sight, we are apt to overlook the bodily seat of the sensation and project the cause to some external object. In abnormal conditions of nerve-activity, stimulation of any other point than the peripheral termina- tions is followed by subjective sensations, which are referred to the peripheral end-organs associated with the nerve-point stimulated. Similarly, disorders of the cerebral structures may give rise to sensations which closelj^ resemble hallucinations in' their after effects. As an example, we may give the instance of ilkisions of feeling apparently arising from sensations in toes after the limb has been amputated. The exact seat of the * The case is of long duration, and incurable. 238 SENSOKY PERVERSIONS. stimulus or morbid process is difficult to determine. In the insane, ordinary presentations may be wrongly interpreted. Thus, gustatorj^ sensations assume, with the mental complexion of the individual, the objective significance of poisons ; sub- jective tactual sensations of electricity, numbness, feeling of wool, shrinking, expansion, dragging, tingling, pain, etc., are all projected externally in accordance with the customary interpretations of local signs ; but, in addition, the mental com- plexion determines wrongly the relative import of the causal stimuli, and hence sometimes gives rise to the wildest illusions of torture and persecution. 2. Determined hy variations in sensibility : (1.) Momentary or transient. — Every one is subject to momentary illusions, due to exhaustion of the various organs of sense. The condition may arise from direct strain, or through malnutrition, or, more commonly still, through the administration of toxic agents. Variations in the organic state cause alterations in the strength and quality of the sense presentations. (2.) Comixiratively permanent conditions. — The sense-organ may be unusually sensitive, so that the sense-impressions gain in intensity of effect. There n\Q.j be variations in the excita- bility of the retina, so that colours are raised from violet to red, etc., or vice-versa as in the colour blind. In conditions of hypergesthesia ordinary stimuli become intensified. In anaes- thesia they become less intense. In parsesthesia there is a qualitative change in the effects of stimuli. In the insane every variety of these quantitative and qualitative changes in the presentations of sense may be observed. Sully points out, that all these groups of illusions have one feature in common; they depend on the general mental laAv, that when we have to do with the infrequent, the unimportant, and therefore unattended to, and the unexceptional, we employ the ordinary, the familiar, and the well-known, as our standard. " Thus, whether we are dealing with sensations that fall below the ordinary limits of our mental experience, or with those which arise in some exceptional state of the organism, we carry the habits formed in the much wider region of average every- day perception with us. In a word, illusion in these cases ACTIVE ILLUSIONS. 239 always arises through what may, figuratively at least, he desci'ibed as the application of a rule, valid for the majority of cases, to an exceptional case." In the next group which we have to consider, the mental element is predisposed to the for- mation of sense-illusions ; imagination and expectant attention play an important part. ACTIVE ILLUSIONS. In active illusions there is a mental preparedness or antici- pation for presentations. The mind acts independently of immediate external sense-impressions, and by a process of imagination conjures up various combinations of representa- tions ; the preponderance of the mental element thus tends to colour, modify, or submerge the actual determining presen- tation when it arrives in consciousness. Expectant attention may even lead to the illusory belief that an event takes place before it actually does. In the sane, the independent activity of the imagination may conjure up the image of a friend, and this very mental preparedness may result in illusions of identity. Iia other words, a vivid representation may favour a partial dis- tortion of a presentation ; or rather, a vivid representation, super-imposed upon an imperfectly discriminated presentation, may result in an illusory perception. Wundt found by experi- m.ent, that the exact moment at which a sense-impression is perceived depends on the amount of preparatory self-accommo- dation of attention. Romanes * says, " If a sportsman, while shooting woodcock in cover, sees a bird about the size and colour of a woodcock get up and fly through the foliage, not having time to see more than that it is a bird of such a size and colour, he immediately supplies by inference the other qualities of a woodcock, and is afterwards disgusted to find that he has shot a thrush. I have done so myself, and could hardly believe that the thrush was the bird I had fired at, so complete was my mental supple- ment to my visual perception." " As with game," says James, " so with enemies, ghosts, and the like. Anyone waiting in a dark place and expecting or fearing strongly a certain object will interpret any abrupt sensation to mean that object's * " Mental Evolution in Animals." 240 SENSOKY PERVERSIONS. presence. The boy playing 'I spy,' the criminal skulking from his pursuers, the superstitious person hurrying through the woods or past the churchyard at midnight, the man lost in the woods, the girl who tremulously has made an evening appointment with her swain, all are subject to illusions of sight and sound which make their hearts beat till they are dispelled. Twenty times a day the lover, perambulating the streets with his pre-occupied fancy, will think he perceives his idol's bonnet before him." At seances, full scope is given to the imagination ; the mind is prepared and expectant. In states of hypnotism and trance, suggestion plays a most important part. " This suggestibility is greater in the lower senses than in the higher" (Meyer). Helmholtz doubts this power of imagination to falsify present impressions of sense. In some cases among the insane, the pre- occiipation of the mind by dominant beliefs, fears, persecutions, and morbid anticipations, gives such a powerful mental com- plexion or colouring to all immediate impressions of sense, that the process may be compared to the addition of one drop of clear fluid to the blackest of inks, the one drop of clear fluid representing the present impression, and the blackest of inks the mental saturation by morbid thought. The writer experienced the effects of anticipation some years ago. Having to give a hypodermic injection of morphia every three hours during the night for nearly a fortnight, the expectancy and mental pre- paredness to hear the night-bell, even during sleep, became so powerful, that after the patient had recovered and there was no occasion to administer the drug regularly, at the appointed intervals the illusion became so vivid that several journeys were made under the belief that the bell had actually sounded. Every one is familiar with what Dr. Savage calls the " lost button " condition of thought. The absence of a button is sufficient to occupy our attention so completely, that sooner or later we imagine all eyes are upon the defective spot. The individual who imagines he is suffering the tortures of Hell and is eternally damned, may see a devil in every one who enters his room. Similarly, the exalted general paralytic, whose horizon is bounded by untold wealth and beauty, sees in every object around him some marvellous charm or property. In the maniac who is persecuted, every trivial occurrence, insignificant in itself, is distorted into some sign bearing the stamp of the mental com ACTIVE ILLUSIONS. 241 plexion of the moment. The h}-pochondriac colours every sensory impression with his mental fear of dissolution. The maniac and the melancholiac alike view all incoming impres- sions through their mentally-coloured glasses. To the former all is bright and fanciful ; whilst to the latter all is dark and dismal. 1. Voluntary Selection of Interpretation. — It is possible, by a purely mental act of creative imagination, to f \ \ A h \ \ Fig. 14. superimpose at will the image of the object imagined, upon some other actual objective image present. Thus, we can picture forms and images in clouds, etc. In the diagram, either of the two large surfaces (a, b. c, d, or e,f,g,h,) may appear to be nearer than the other; or one surface may appear to face a point to our left and upwards, or to our right and downwards. Thus the two surfaces, far and near, may be transposed at will ; or each may be regarded as facing two directions. 2. Involuntary Mental Pre -adjustment. — In the percipient mind, which is pre-adjusted to act in certain definite directions, this predisposition may evidence itself as a temporary state of expectation, or as a comparatively permanent condition, (a) Temporary expectation or preparedness. — Action of sub- expectation. — Every one has experienced various illusory beliefs about objects and things. A certain amount of pre- paredness is necessary before witnessing a play. The imagina- tion supplies the preliminar}- data or predisposition to accept the events of the stage as more or less real. Without such pre- paration the mind is apt to construe the performance as either utterh' stupid and void of sense, or as an actual reality. The artist copies the results of his imagination or mental perception 242 SENSORY PERVERSIONS. upon a plane surface. A similar mental preparedness or imagination is essential to those who view the picture. A cow, having no imagination or mental process, preceding the actual presentation of a picture, would view it rightly as a plane surface. A dog, unaccustomed to seeing himself, barks at his reflection in a looking-glass. Vivid expectation may arise or be brought about (1) by means of present objective facts — e.g., the illusions of the conjuror; (2) by verbal suggestion — e.g., at seances, and in the h57"pnotic state ; and (3) imagination, internal and spontaneous — e.g., the picturing of the various diseases described in text books, is apt in many students to be followed by feelings that the diseases are present as they are considered in turn. Comparatively permanent disposition. — In the various tem- peraments there is a tendency to reflect the characteristics of the mental life upon all sense impressions. That is to say, every presentation is toned by the pre-adjustments of the individual's mind. The evolution of conceit in the adolescent is attended by self-exaltation and an illusory interpretation, or deviation from the common or collective estimation of the indivi- dual's own powers or attributes. The bilious person perceives his presentations with an accompanying tone of melancholj^, and interprets from his mental standard. The sanguine and full-bodied muscular individual interprets everything with a halo of hope and well-being. Such a type provides us with the characteristic euphoria of general paralysis. A general paralytic of the nervous type exhibits acute maniacal ravings, whilst one of the bilious type is apt to be melancholic with the onset of the disease. Instances must occur to every mental pathologist where the disease has been attended by the illusory belief by the patient that at last the former dreams and castles in the air are realised. Such instances are common. Poverty suggests dreams of wealth. Inability to help our friends suggests dreams of benevolent gifts and magnificent schemes for the welfare of mankind in general. The onset of a process of degeneration, such as general paralysis, is often characterised by such mental colouring, which is to be explained' only by the comparatively permanent disposition of the mind to imagine the unreal. Present subjective realities SECONDARY SENSATIONS. 243 receive their tone or colouring from a mind more or less saturated with probabilities and imaginary possibilities. Secondary Sensations. — Let us now briefly consider some of those conditions of perception which have been termed " secondari/.'' Some individuals never have a presentation of a certain sense without the occurrence of a presentation of another sense. Thus, some experience a sensation of light with every sensation of sound. Others observe colours with every sound. When the two presentations occur together the condition may be termed one of a dual presentation to dis- tinguish it from a secondari/ presentation, in which case the primary suggestion of one presentation is follo^^'ed by or associated with a secondary and different sensation. Bleuler* has divided these secondary sensations into : — 1. So2md pJiotisms. — Sensations of colour acompanying sensations of sound. 2. Lkiht j^hoiiisms. — Sensations of sound from perception through light. 3. Taste pJiotisms. — Sensations of colour from perception through taste. 4. Odour photisms. — Sensations of colour from perception through smell. 5. Pain photisms .■ — Sensations of colour from perception of pain, temperature, and touch. Blettler and Lehmann found that secondary sensations occurred in seventy-six persons out of 59G (12^ per cent.). According to the former, secondary sensations are transmis- sible by heredity. Entire families of colour-hearers are known. Their connection with nervous and mental disease is unproved. Lepsius, the Egyptologist, connected colour with sounds, and used those colours as a guide in his philological inquiries. Galton relates the case of a lady, in which the tendency was hereditary, but not the details : thus one member of the family might say that a word was blue, and another strongly dissent and say it was green, and some little domestic friction occasionally arose in consequence. GrtilDert has tabulated * "Tuke's Dictionarj' of Psych. Med.,'' p. 1125. t "L'audition coloree et les phenomenes similaires." International Con- gress of E.xperimental Psychology. London. 1S92. 244 SENSORY PERVERSIONS. the various follows * : — f chromatisms and photisms of the senses as Chromatisms Superior Senses ^ Sight.. Photisms f Forms I Movements ^ Elements of I writing I Numbers / Musical sounds Instruments and voice Vowels Diphthongs Consonants Syllables Common names Proper names Hearing { p^ys of the week Seasons Months of the year Elements, geogra- phical Homonyms Abstract names , i^ Numbers ...fT™'}Heari„g...Xoises... ■ Coloured vision. ^ Chromatisms, Phonetic ^ Coloured hearing. Chromatisms, Psychic .Audition illumin^e. Chromatisms (Photisms) ( Inferior senses Taste ...■{ Smell ■ Touch . )■ Coloured taste. { Bitter Sweet Acid Salt Coloured smell. (^ Touch proper Coloured touch. ( Very hot \ I Warm I Coloured Temperature \ Tepid ;. tempera- l I ture. Cool \ Very cold Muscular \ Movements . . . Coloured movement, sensation J Eesistances ... Coloured resistance. * He reserves the term j^hot ism, introduced by Bleuler and Lehmann, for " rauditio7i illumineer and includes under the term chroviatism " les taches subjectives color^e, qui sont evoquees par I'excitation des divers autres sens." SECONDARY SENSATIONS. 245 In addition to these chromatisms and photisms we have various phonisms, which may be tabulated as follows : — Taste Smell Phonisms \ Tactual f Sight . . . . . . . . sight hearing. . . taste hearing. . . smell hearing, . . touch hearing. movement hearing. . . temperature hearing, resistance hearing. Movement Temperature Resistance For the inferior senses we have gustatisms — viz., sight, sound, and smell-tasting; also olfadisms — viz., sight-smelling, sound- smelling, etc. Tactual and temperature sensations may be provoked by the other senses. Thus, we have sight hearing, and taste, giving rise to tactual sensations ; also sight or hear- ing giving rise to temperature sensations. We cannot, however, enter into the details of all these secondary sen- sations. Many theories have been offered to explain their occurrence. Bleuler believes the explanation commonly offered — that colour- hearing is due to a simple association of ideas which constantly occur together — to be false. The regularity \\'ith which light colours predominate for high notes, etc., does certainly, on this theory, appear to be unexplainable. Bleuler has pointed out that the colours appearing in photisms differ but slightly from the ordinary colours perceived by the eye. The photism colours usually appear as pure colour sensations, separated from all ideas of matter which are associated with every colour surface. They can best be compared with coloured flames, or with evening red in a coloured sky. Photism colours have been observed, although very rarely, which, optically, have never been per- ceived, and which are, indeed, optically inconceivable. Bleuler himself experienced a photism for the German modified u (li) as a mixture of light-red and yellow, and a little blue without a trace of green. This observer found that the surroundings of photisms — ^that is, the field on which they appear — are not black, but a neutral ground free from eveiy colour. The transitions from one photism to another frequently correspond to similar changes in common colours ; thus, for a colour-hearer, a (in ''father'") may be blue, o (in "bone") yellow, and the 246 SEXSORY PERVERSIONS. sound between these two, oa (a in "water"), green. Mixtures of colours frequently occur, and follow the ordinarj^ laws which govern the mixing of pigments ; for example, the simple photism of a word of two sj^lables may be orange, because the vowel of the first syllable appears red, and that of the second yellow. The same author gives the folloA\'ing laws concerning secondary sensations * : — 1. Photisms light in colour are produced by sounds of high qualitj^, intense pain, sharply-defined sensations of touch, small forms, pointed forms ; dark photisms from opposite conditions. 2. High phonisms are produced by bright light, well- defined outlines, small forms, pointed forms ; low phonisms from opposite conditions. 3. Photisms with well-defined forms, small photisms. and pointed photisms, are produced by sounds of high pitch. 4. Ked, yellow, and brown are frequent photism colours, violet and green are rare, while blue stands between these extremes. The observations of Lussana, the brothers Nussbaumer, Bleuler and Lehmann, Lauret and Duchaussoy, Ferdinand Saurez de Mendoza, etc., have demonstrated the influence of heredity in the production of secondary sensations ; but, as pointed out by Griiber, all these observations have been made on intellectual and cultivated individuals. It would, therefore, be interesting to ascertain whether these phenomena occur among the illiterate. We do not know how much is hereditarj^ and how much is acquired through cultivation. A second question to ask would be, Do these phenomena fall within the domain of cerebral pathology, or within that of normal phy- siology? Neiglick and Steinbriigge believe that the phenomena * Griiber says : — " Mais auparavant il faut ranger les individus qui posse- dent des sensations doubles (le terme n'est pas assez correct) en deux grandes classes : (1) les individus qui presentent des chromatismes, qui chromatisent leur audition, qui associent une sensation secondaire de couleur a Fetat hallucinatoire ; nous appellerons cet etat ''letat sensationel ;' (2) les indi- vidus qui associent constamment et fatalement les memes idees de coleur aux memes sons, etc., qui presentent cette liaison a Tetat purement intellec- tuel 6tat 2Jsychirjue. Entre ces deux classes, entre le type le mieux done et ceux qui n'ont ces plienomenes qu'a un degre tres faible et tres partiel il y a toutes les transitions possibles." SECONDARY SENSATIONS. 247 are abnormal and symptomatic of a degenerative process. Fere and others regard them as the outcome of " une tonallte jjarticuUere de Vor. 610. PERVERSIONS OF THE MUSCULAR SENSE. 283 would be disposed to think that the starting point was irrita- tion of the aiiditory nerves or auditory centres. He believes, however, that it may be admitted, that in the acute form of paranoia the whole nervous system is in a state of extreme excitement, and that there may be hallucinations both of the muscular sense and of other sensory nerves, as well as motor incitations to the muscles of the voice. Klinke * agrees with Cramers explanation, and believes that abnormal sensations in the tongue and throat may arouse delusive fancies leading to derangements of speech. Sometimes these take the form of babbling and childish sounds, or the patient complains of distress and difficulty in speaking, accom- panied by a feeling of constriction in the tongue or throat. The muscular sense is said to be increased in somnambulistic and hypnotic states. The condition known as anxietas Hhiarum. in which there is a painful condition of uni-est leading to continued change in position of the limbs, is considered to be due to abnormal increase of the muscular sense. Dlmimdion occurs in some choreic and ataxic persons. The serine of moireinent (h-iiuesthesis) has received so mixch attention, and there are so many differences of opinion with regard to it. that we must, before concluding this chapter, review in brief some of the leading discussions. Bastian be- lieves, that impressions of various kinds combine for the per- fection of this sense of movement, and that in part its cerebral seat coincides with that of the sense of touch. He includes under this " sense of movement.'" as its several components, (a) a set of conscioiTS impressions of various degrees of definiteness — ■ viz., cutaneous impressions, impressions from muscles and other deep textures of the limbs (such as fasciae, tendons, and articular surfaces) ; and. in addition. (J)) a set of '•unfelt"' impressions, which guide the motor activity of the brain by the information (unconscious) which they afford as to the different degrees of contraction of all the muscles concerned in the production of any given movement. " The occurrence of movement is for the kinjesthetic sense what the j^resentation of an external object is to the visual sense ; and the inability to cognise the impressions occasioned by movement (either those that are conscious, or * " AUgemeine Zeitsclirift f iir Psychiatrie, " xlviii. Band, 1 and 2 Heft. 284 HALLUCINATIONS. those that are unconscious, or both), which is sometimes produced by certain morbid conditions of the spinal cord or of the brain, is a defect of the kinaesthetic sense altogether analogous to amblyopia or blindness in relation to the visual sense." * The relation of the kinassthetic sense to volition will be discussed later. Here we have to consider only those elements which go to make up the so-called kinsesthetic sensations, and the first question we have to ask is, Do cutaneous impressions — impressions from muscles and other deep textiires of the limb (fasciee, tendons, etc.) — actually exist; and, if so, are they all essential to the formation of a kingesthetic per- cept ? That cutaneous impressions and impressions from articu- lar surfaces do exist there can be no doubt. Duchennef has pointed out, that in patients with cutaneous aneesthesia of a limb, the muscles of which are not sensitive to faradic stimu- lation, there may still be preserved a very accurate sense of the way in which the limb may be flexed or extended by the hand of another. Eulenberg | assumes that the articular surfaces are the seat of the perception of movement. The sense of move- ment maj be impaired when the tactile sensibility is preserved. James points out, that the pretended feeling of outgoing inner- vation obviously plays no part in these cases, from the fact that the movements by which the limb changes its position are passive ones, imprinted on it by the experimenting physician. That the joint surfaces are sensitive appears evident, according to James, from the fact, that in inflammation they become the seat of excruciating pains, and from the perception by everyone who lifts weights or presses against resistance, that every in- crease of force opposing him betrays itself to his consciousness principally hy the starting-Out of new feelings or the increase of old ones in or about the joint. § Lewinski || records the instance of a patient, the inner half of whose leg was ansesthetic. On standing up the patient had a curious illusion that he was knock-kneed, which disappeai'ed the moment he lay down * " Paralyses : Cerebral, Bulbar, and Spinal," p. 108. t "Electrisation Localisee," pp.727, 770, Ley den ; Virchow's " ArchiT," 1869, Bd. xlvii. X "Lehrb. d. Nervenkrankheiten "' (Berlin), 1878, 1, 3. § " Principles of Psychology," vol. ii. p. 191. II " Ueber den Kraftsinn."' — " Virchow's Archiv," Bd. Ixxvii. 134. PERVERSIONS OF THE JklUSCULAR SENSE. 285 again. In this case the inner lialf of the joint probably shared the insensibility of the corresponding pai^t of the skin, and the feeling was just what he would get were his legs forced into a knock-kneed attitude — i.e.Ahe outer-joint surfaces would be more strongly pressed together than the inner. Lewinski also found in every instance that, when the toes of certain ataxic patients with imperfect sense of position Avere flexed and drmcn ujjon simultaneously with the separation of the joint surfaces, all sense of the amount of flexion disappeared. On the contrary, when he pressed a toe in whilst flexing it, the patient's appreci- ation of the amount of flexion was much improved, evidently because the artificial increase of articiilar pressure made up for the pathological insensibility of the parts.* Goldscheider f has proved by a series of experiments, that the joint surfaces, and these alone, are the starting point of the impressions by which the movements of our members are immediately perceived. Goldscheider caused his fingers, arms, and legs to be pas- sively rotated upon their various joints in a mechanical apparatus which registered both the velocity of movement impressed and the amount of angular rotation. • No active muscular contrac- tion took place. The minimal amounts of rotation felt were in all cases surprisingly small, being much less than a single angular degree in all the joints, except those of the fingers. The point of application of the force which rotated the limb made no difierence in the result. Rotations round the hip- joint, for example, were as delicately felt when the leg was hung by the heel as when it ^^-as hung by the thigh whilst the movements were performed. Anaesthesia of the skin, produced by induction-currents, also had no disturbing effect on the per- ception ; nor did the various degrees of pressure of the moving- force upon the skin affect it. It became, in fact, all the more distinct in proportion as the concomitant pressure-feelings were eliminated by artificial ansesthesia. When the joints them- selves, however, v/ere made artificially anaesthetic, the perception of the movement grew obtuse, and the angular I'otations had to be much increased before they were perceptible. X * Quoted from .James, "Principles of Psychology," p. 192. t " Archiv. f. Anat. u. Physiologie," 1889, pp. 369, 540. X James, "Principles of Psychology," p. 192. 286 HALLUCINATIONS. The disorders of" the sense of movement, as met with in the insane, are possibly to be explained as originating from the con- ditions of the general sensibility, and more particularly of the articular surfaces. Thus, general paralytics who say they have walked millions of miles (hyperkingesthesia), or w^ho feel that they are treading on air, have probably some change in the sensi- bility of the articular surfaces, which act in reality as predispos- ing factors of illusory states. The sensations of flying through the air, of extreme buoyancy, or of having leaden limbs, difiicult movements, etc., may all be explained from this point of view. Those abnormal subjective sensations, however, in which the body or limbs appear to shrink or expand, would be better ex- plained as modifications of the cutaneous and general sensibility. The considerations of the " unfelt " impressions, which are said to guide the motor activity of the brain, we leave to a subse- ■quent chapter. It only remains for us now to add that, in accepting the term kinsesthesis, we simply accept it as designating the sense of movement, and we do not attribute to the muscular elements themselves any part in the production of that kinsesthesis, except in so far as they by their action aflect the articular surfaces. Illusions and Hallucinations in Dreams. — The con- dition known as the HyionagogiG state occurs when an individual is neither awake nor fully asleep. During this period the senses become more or less inactive, except the sense of hearing, which is the most persistent. The reflex activity of the spinal ■cord is at first somewhat exalted, owing to its being released in considerable measure from the control of the brain. As sleep becom.es more profound the reflex functions of the cord are also weakened.* It is thought that, as the sensory organs retire from action, the intellectual faculties lose their equilibrium. First the power of volition ceases, then the logical association of ideas comes to an end, the reasoning faculty disappears, and judgment is suspended. We become, therefore, no longer capable of surprise or astonishment at the vagaries of memory and of imagination — the only faculties that remain in action. To their more or less unfettered activity we owe the presence in consciousness of those disorderly pictures which, occurring in * Rosenbach, " Zeitschr. f. Klin. Med.,"' 1881. " Brain,"' vol. iv. p. 138. IIYPXA({(HtIC illusions and HALLICINATIONS. 287 this stage of imperfect sleep, liave been termed liypnagugic hallncinatiuus.* The following diagram, borrowed by L^mian from the " Dietionnaire Encyclopedique des Sciences Medicales," gives some idea of the successive phases during sleep : — £ 3 o 1 O S 'S 3 o .2 t S a 6 o .§1 — C « s 1 ^^-,111 lllj^ Normal life. ^^^^^ 1 1 First stafce of sleep— Hypnagogic hallucina- tions. 1 1 1 Second stage of sleep— Dreaming. 1 Tliird stage of sleep. ^■^^1 ^H ■ Profound sleep. First stage of waking. ^^^^H ^H Second stage of waking — Dreams. 1 ^^^^^^ 1 Third stage of waking — Hypnagogic hal- lucinations. 1 1 1 1 Complet« awakening. 1 1 Fig. 16. Hypnagogic Illusions and Hallucinations. — During sleep, when the subject matter supplied for the exercise of the facilities of perception and judgment, and the operations of the will, are withdrawn, the ideas that still arise are chiefly dependent for their origin and association upon the automatic and endogenous activities of the brain. Undisturbed by im- pulses from the external world, the brain seems then to become more sensitive to impressions having their origin within the body. An overloaded stomach, an enfeebled heart, a turgid sexual apparatus, or an irritable nervous ganglion, may be- * Alfred Maurj', " Le Sommeil et les Reves," chap. IV. Quoted from Lyman, " Insomnia," p. 3. 288 HALLUCINATIONS. come the source of irregular and uncompensated impulses which, without disturbing the organs of special sense, may invade the cerebral cortex, and may there set in motion a whole battery of mechanisms, whose influence upon con- sciousness would remain quite unnoticed were the external senses in full operation.* The same author defines a dream as " the occupation of the field of consciousness during sleep by a succession of ideas more or less completely withdrawn from the guidance of the senses and from the control of the will." The possibility of suggesting to an individual who is in the hypnagogic state the nature of a dream has been often demon- strated. Thus, through the rustling of a newspaper an in- dividual has dreamt of the sounds of waves on the sea shore, and conjured up with vivid intensity the visual picture and accompaniments. Sometimes the impression produced b}^ the dream is so vivid that a belief in its reality exists even some time after waking. Baillarger dreamed one night, that a certain person had been appointed editor of a newspaper ; in the morning he believed it to be true, and mentioned it to several persons, who were interested to hear it ; the effect of the dream persisted all the forenoon, as strongly as that of a real sensation ; at last, about three o'clock, as he was stepping into his carriage, the illusion passed off"; he comprehended that he had been dreaming.! The step between the phenomena of dreams and those of insanity is but a very short one ; in fact, many of these pheno- mena are identical in every respect. There is in both a partial displacement of the ego ; by which the " I " which perceives the abnormal is not the " I " which was wont to perceive the normal. In artificially induced states of unconsciousness {e.g., by chloroform) the writer has seen an insane patient who, whilst under the ansesthetic, gave vent by speech to the same delu- sions and the same train of ideas as when in his ordinary state of insanity. This fact alone was significant that the ego bore a corresponding relationship to the actual cerebral activi- ties in both states. According to Lyman, most dreams are composed of visual images. The dreamer looks upon a picture * Lyman, op. cit., p. 118. t Taine, " On Intelligence," p. 61. Quoted from Lyman, op. cit., p. 126. HYPXAGOGIC ILLUSIONS AND HALLUCINATIONS. 280 which changes silently before his eyes, without appealing to any other sense than that of sight. But in certain cases any other sense may become excited, producing illusions or hallucinations as perfect as the images of health}' vision. They may be suggested by external impressions, or they may, at least apparently, find their starting point in accidental states of the bodily organisation. All unusual modes of dreaming, and all extraordinary vividness of dream-impressions can be con- nected with some departure from the physiological conditions of quiet sleep. Either disease, or exhaustion, or emotional dis- turbance, or narcotic intoxication of the brain may be noted as the immediate cause of such derangement of the cerebral functions.* Maury f states that the ease with Avhich dreams are recollected varies inversely with the depth of the sleep in which they occur. That the mind can solve problems, and perform various intellectual operations in its dream-states is a matter of common observation. The writer has on several occasions drawn upon his hypnagogic hallucinations for melo- dies and other musical ideas. The question of foresight, or actual clairvoyance, cannot be discussed here. The physiological basis of sleep is still a matter of uncer- tainty. It is assumed by most observers that there is at least a partial anaemia, of the cerebral cortex. Ziehen believes that in sleep the initial element of the psychical process — the sensa- tion — is produced by "ideational stimulation;" and that the final element — the motor idea or the action — is almost entirely omitted. " The muscular system seems to be lamed ; even in the deepest sleep the phenomena accompanying the activity of the tendons, otherwise so accurate an index of the existing muscular tone, have disappeared." That motor ideas do occur in our dreams must be manifest to every one. In the fulh^-awake person the judgment percei\'es the nature of the events which are manifested to the mind ; in sleep, and in insanity, on the other hand, the judgment is weak, and there is inability to perceive the absurdity and impossibility of the events which appear to happen. One point in which the dream-state differs from the insane state is to be found in the fact that, in the former a large part of the * Lyman, op. cit., p. 131. t Op. cit., p. 219, d seq. 19 290 HALLUCINATIONS. memory is blotted out, and the mind is nnable to compare present facts with the experiences of the past ; whilst in the insane the memory for remote events is often unimpaired. Hack Tuke* points out a striking characteristic of the dreamer's mental attitude — he is usually free from the nervousness, or lack of courage, or dread of the opinion of others from which he maj suffer during the waking-state. " There is an extra- ordinary change in the personality of the dreamer, to whom the loss of personal identity ceases to be strange, and he passes into the mind and body of the most opposite and improbable characters, without anj sense of surprise or embarrassment." In the insane the dreams are often morbid exaggerations of the waking-thoughts. The writer has observed many instances in which insane persons have dreamt that they had the usual forms of sensory persecution during sleep as during the wide-awake state. Hack Tuke records the case of a lady, the subject of melancholia, who was entirely free from her troubles during the night. It is not uncommon to meet with cases of insanity which have been an actual continuation of the hypnagogic state. Thus, in puerperal insanity we sometimes find that the attack has commenced with a particularly vivid dream occurring in the early morning. In a similar manner an insane hallucinatory condition may be detei'mined by the administration of an anaesthetic, such as ether or chloroform. * " Dictionary of Psychological Medicine," p. 413. 291 CHAPTER X. MENTAL PROCESSES. Attention. Definition — Psycho-Physical Process of Attention — Psychical Theory of Attention — The Neural Processes in Attention — Monoideism — Polyideism — Retiex Attention — Volutitary Attention — Adjust- ment of Attention — Attention and Genius — Morbid Conditions — Hyper-attention — Inattention — la Mental Disorders. Conception. Definition— Concept — Psychological View — Psycho-Physical Theories of Conception — Physiological Theories — Association — Double Nature of Brain — Consciousness the Accompaniment of Nerve Action — The Theories of Discharge and Resistance. Judgment. Definition — -Degree of Perfection of Judgments — False Inductions — False Deduction — The Perception of Reality — Belief — The In- sanity of Doubt. Imagination. Definition — Differences between After-images and Imagination-Images — The Neural Process of Imagination — Morbid Conditions — Simple Delusional States — Sensory Types — Emotional or Affec- tive Types— Clinical Considerations. ATTENTION. Before taking up the stibjects of " conception " and " asso- ciation " it is advisable that we should understand a little more clearly what is meant by attention. Attention is one of the most important of our mental activities, since a mental fact only exists for us in so far as we attend to it. Sully defines it as '■ the active self-direction of the mind to any object which presents itself to it at the moment." In accepting this defini- tion it is necessary, however, that the student should recognise 292 MENTAL PROCESSES. that the mind's consciousness of what is presented to it is not always the result of active self-direction. When we attend to a thing we intensify our consciousness by narrowing or con- centrating it on some definite and restricted area ; but were all our impressions determined only by the active self-direction of attention the mind would no longer be the passive recipient of impressions from without, and all our mental states would be determined by the primary and voluntary activity of the mind. When we force our minds in a particular direction, so as to make the objects as distinct as possible, the action involves a sense of effort self-determined ; but an unusual or novel stimulus may affect our consciousness quite apart from any voluntary effort of attention. In the latter condition the attention is termed reflex, and it may even necessitate a strong effort of will on our part to disengage it from the object which holds it. In the struggle for existence among stimuli the attention (or the result) is determined by the intensity or the distinctness of the sensations derived from the stimuli. It is assumed that the more intense material processes accom- panying the stronger sensations possess a far greater capability for awakening the images of memory, and determining the course of ideation, than those which are indistinct, confused, and wanting in intensity. Ziehen believes that this also explains why only the object situated in the centre of the field of vision generally determines the association of ideas, and it is just this object that produces the most intense and distinct sensation. " No apperception exercises any arbitrary control over the process whatever." Outside the regions of central focus of the attention there is alwaj^s a realm of obscure or sub-conscious ' mental phenomena. How far this region extends in relation to the organism and its processes we are not prepared to say ; nor do we know to what extent it is modified by j)ast psj^chical activities. With every mental act there is a zone or halo of obscure and transitory phe- nomena surrounding the object which calls forth that act. Wundt says the whole mental region (conscious or sub- conscious) answers to the total field of view present to the eye in varying degrees of distinctness at any moment when the organ is fixed in a certain direction; the latter region — ATTENTION. 293 that of attention or clear consciousness — corresponds to that narrow area of "perfect vision" on which the glance is fixed. Every sense-impression (external or internal), and every content of consciousness, when viewed by the " mental eye," is an object of attention. Thus all the phenomena of cognition, emotion, or volition may become the objects of attention. The Psycho-Physical Process in Attention.— The majority of neurologists believe that our sensations are deter- mined, not only by peripheral processes of stimulation, but also by a reflex central reaction, which in turn becomes a deter- mining cause of peripheral ingoing currents. That is to say, not only is every psycho-physical process sensory, but also motor. The ego is regarded as entirely dependent on the sensations which are presented to it, primarily through the senses, or secondarily through the sensations of movement or reaction. To Fechner, Bain, Wundt, Ferrier, Sully, Bastian, and others, we are indebted for many observations upon this subject. The psychical theories of attention are, that (1) the sensory pi'esentation, or its ideational equivalent, is followed and rein- forced by a distinctively active element of attention, a third element of feeling being commonly, if not in all cases, inter- posed between them — i.e., the factors are, sensation and reaction mid feeling. The reaction is regarded by psychologists as being essentially active, and involving a certain degree of voluntary attention.* (2) Attention involves detention in consciousness and a corresponding rise in vividness, distinctness, or intensity.f (3) Attention is the pure reflex of some sensory presentative process. (4) The direction of the attention involves the residua of previous experience and habitual forms of mental activity (Sully). (5) Attention involves a voluntary or consciously- selective process, which is attended by feelings of mental effort, and the sense of resistance. Wundt has tried to determine the duration of the discrimination time and the volition time in attention (" apperception "). Miinsterberg, on the other hand, contends that the whole process is mostly unconscious or sub- * Sully, "Brain," 1890, p. 148. t Ribot, " La Psychologie de I'Attention." 294 MENTAL PliOCESSES. conscious, and that there is no room for the discriminative and volitional period.* Sully regards the result of the experiments made in Germany as being the effects of pre-adjustment, and the quasi-unconscious nature of the phenomena as due to the circumstance that the M^ork of attention had been done in advance. Fouilleef also objects to Miinsterberg's explanation as inadequate, inasmuch as it is not enough that a representa- tion pre-exists in this obscure form to its clear apprehension to generate in us the feeling of activity. He points out, that just as a very distant and feeble light can approach and increase in intensity without producing that feeling, so a reminiscence, confused at first, can suddenly grow clear without any seeking or effort on our part. " Whenever attention is present we have a feeling of mental ivorlc ; of expenditure of energy." With this latter statement we do not agree. That attention to the contents of consciousness always involves a sense of effort implies the invariable presence of a volitionary force in- dependent of the intrinsic attractiveness or intensity of the sensations. Were we to assume that the imperative ideas of the insane, which thrust themselves upon the individual's atten- tion, involve a distinct feeling of expenditure of energy, we should make an assumption which would be in direct opposition to our experience. Foiiillee also believes that attention is always called foi'th hj an emotion or an interest, by pleasure or pain — i.e., the feeling is the first stage, or, rather, "the very ground of attention." The Neural Process Theories of Attention. — Fechner, Bain, Lewes, and others, support the hypothesis that the motor apparatus would account for the whole process of thought- control. Bain believes that every idea is composed of an element of passive and of muscular sensation. Wundt and Ward both recognise the affinity between muscular and mental exertion. Ferrier believes that attention specially involves the frontal lobes which contain some of the centres for movements of the head and eyes. Wundt postulates, that a centrifugal impulse from the centre of attention, or apperception, passes to the sensorium, and that this impulse is simultaneous and * " Beitrage zur Experimentellen Psychologie." t "Brain," 1890, p. 351. ATTENTION. 295 organically conjoined with another centrifugal process of motor innervation issuing from the same region. According to Ziehen * the feeling of attention is merely a concomitant phenomenon. The essential objective characteristic of atten- tive or active sensation, in distinction from the merely passive sensation, is the infliTence which the former exerts in deter- mining the choice and order of ideas by which it is followed. In order to simplify this complicated subject w^e may iise a simple diagram. I may be held to represent the subjective aspect of attention as viewed by the ego within consciousness ; P is the sensory surface of the cortex which presents sensations to I ; M is the motor area, from which efferent nerves pass to the motor apparatus. Fig. 17. (1) Some psychologists hold, that all the phenomena of attention may be determined by the activity of I ; (2) others say that P and I are all-sufficient ; (3) others that P,I,M, is the order of events ; (4) others that M,P,I, occurs; (5) others, again, that M,I,P, is the only sokition; while (6) yet others maintain that P.M, or M.P, precede and determine I; lastly (7) others find the solution of the difficulty in the accom- panying tone of feeling, or motive which manifests itself at I, and in turn regulates P or M. There wall be found room, no doubt, for other modifications and combinations of these theories. When there is temporary predominance of an intellectual state, or of a group of states, the condition is said to be one of intellectual mono'ideism. This condition may arise in a spon- * Op. cit., p. 209. 296 MENTAL PROCESSES. taneotis, natairal, inv^oliTiitaiy, reflex, or instinctive manner; or it nia}^ be volnntar}^, active, and artificial. From a popular standpoint, the normal state of the mind is one of polyideism. Attention is the momentary inhibition (to the exclusive benefit of a simple state) of this perpetual progression: it is monoi'deism. The sub-conscious states lying- outside the limit of attention are regarded as the contents of a diffuse conscious- ness ; and, just as too great a bulk of mere retentions will often impair the process of abstract thought, so diffuse consciousness will tend to impair the process of concentration. We might formulate the law, that the intensity of a state of concentration varies inversely with the diflfuseness of consciousness. An over active mind in acute states of mental disorder fails to concentrate its attention in any one given direction, owing to the rapid seriality and the diflfuseness of its consciousness. Concentration presupposes an abstraction from other and external objects of consciousness, as is evidenced by intel- lectual monoi'deism. We are unable to attend to more than one thing at a time, otherwise the two objects tend to pass into the region of diffuse consciousness. " When an ecjual effort is made, the effective force of an act of attention varies inversely as the extent of object attended to." " The more we comprehend or embrace in the act of attention the less penetrating will it be " (SuUj^). The degree of attention depends on the quantity of active energy disposable at the time, and the strength of the stimulus, or force which excites the attention or rouses it to action. Stimuli which arouse the attention are divided into external and internal. The external relates ,to the striking characteristic or attribute of the object which engages the attention; whilst the internal means the motive v^hich prompts the mind to exert its power of attention. In the insane, the preoccupation of the attention by morbid stimuli often renders the eflfects of the ordinary internal and external stimuli weak and inefficient. Thus, in the attempt to induce hypnotism where attention is an important factor, failure may be due to one of three causes — viz. : (a) In states of diffuse consciousness (acute mania, etc.) great difficulty is experienced in the attempt to reduce the mental states from their considera- EEFLEX ATTEXTIOX. 297 tion of the general to the particular : (7>) in states of limited consciousness, or nionoideism, the consciousness is already so far reduced from the general to the particular, that the reduc- tion itself acts as a deterrent to the alteration of the nature of that particular ; (c) in states of anergia or defective energisa- tion (stupor, exhaustion, etc.) the active or volitional aspect is impaired, and there is failure in the transmission of outward motor and inward sensory currents. Keflex Attention. — The mere force of the characteristics of the object presented to consciousness is enough to determine the direction of the attention. In the struggle for existence among stimuli, the greatest, the most interesting, and the most novel tend to survive. As a rule, each survival is momentary, and it is characteristic of reflex attention that new stimuli can easily divert it. In conditions of morbid excitability the im- pressions are often of morbid intensity; while, in exhaustive states, there may be lessened activity of the will in determining the direction of the attention. The lau's of reflex attention are. according to Sully, determined by :— 1. The quantity of stimulus. The attractive force of a stimulus will vary as its quantity, and more particularly as its degree. 2. The qualiti/ of stimulus. The attractive force of a stimulus depends also upon its quality — i.e., as it is agreeable, disagree- able, or indifferent. 3. The i/«./e?'es/ taken in the object, determined by particular sensibilities, tastes, habits, etc. 4. The absolute and relative impressiveness. The absolute impressiveness is determined by the quantity or quality of the object ; whilst the relative impressiveness is the force which the object owes to its relation to other objects which have preceded it, and to the pre-existing condition of the attention. 5. The change of stimulus. All changes, contrasts, or tran- sitions act as exciting agents to the attention. We are only conscious of an impression when we pass to it from an unlike impression. A certain frequency of transition is, therefore, essential to a state of mental wakefulness. 6. The eflects of novelty. Those objects which are familiar 298 MENTAL PROCESSES. to us, and often recur to consciousness, do not succeed in rous- ing the attention with the same degree of force as objects which are novel. 7. Familiarity or interest often succeeds in arresting the attention. Thus, for example, in visiting a foreign country, familiarity with the events of its history, or knowledge, pre- viously acquired, of its politics or customs, will render every object of more interest. The interest displayed is often ail indication of the character of the knowledge of an individual. Volkmann says the absolutely new does not chain the attention. The amount of expectancy or pre-adjustnient of the attention often causes a shortening of the process of reception and recognition. Voluntary Attention. — Voluntary attention has been compared to the process of artificial selection, and reflex atten- tion to that of natural selection. The will is regarded as supplying the internal motives, which may counteract the effects of external stimuli. In this way it supplements the forces of reflex attention. According to Sully, the mind, through an exertion of will, is able to choose the quarter to which to direct its glance, and is no longer at the mercy of the most powerful external forces. Just as we can lead a horse to the water, but cannot make it drink, so we may force the mind to look at an object, but we cannot compel its fixation upon that object unless there be something of prevailing interest about it, which, by its intrinsic attractiveness, succeeds in furthering our efforts. It is utterly impossible to continue to concentrate attention upon any object for more than a few seconds at a time. We can focus our thought for a moment, and adjust our apparatus to further or facilitate the process of concentration ; but, in order to keep the object within the field of distinct con- sciousness, we have to perform a succession of distinct efforts of recall. Let the student focus his attention upon some object near at hand. He will find, that when he first looks intently at the object he notes its character and dimensions ; then almost immediately he becomes conscious of objects which occupy the zone of diffuse consciousness outside the field of distinct vision ; next he reflects upon the character of the act he is performing, and realises that he himself is subjectively contemplating an VOLUNTARY ATTENTION. 299 external object; and, finally, he discovers that his mind has wandered from its original object, and to correct this he again, by voluntary eifort, re-adjusts his attention. James points out that it is not an identical object in the psychological sense, but a succession of mutually-related objects forming an identical topic only, upon whicli the attention is fixed. " No one can possibly attend continuously to an object that does not change." Helmholtz agrees with this view, and believes that we cannot keep our attention steadily fixed upon a certain object when our interest in the object is exhausted ; but that we can set our- selves new questions about the object, so that a new interest in it arises, and then the attention will remain riveted. That this is true of sensory states is apparently evident, and we shall find it to be equally true of intellectual states. Thus, we see that with every voluntary act of attention there is involved a distinct sense of effort, and this more especially in its early stages before the habit has been acquired. When there is any falling-oflf in vigour, through fatigue or disease, the effort is greater, and attended by a greater expenditure of energy. The available quantity of energy determines the extent to which mental exertions may be carried. Beyond this point, protraction of effort involves tension, and, later, strain. Several wi'iters have stated that there is no such thing as over-strain, but very little experience justifies the conclusion that the over-use of the faculty of voluntary direction of effort is productive of certain forms of insanity, and that the mind, just as the body, may be iiupaired b}^ excessive use of its functions. The adjustment of attention depends upon (1) the characters of the object itself. Impressions of moderate intensity are, in general, more easily attended to than those of very great or very little intensity. Very powerful impressions in general require a greater effort of adjustment than moderate ones. Very feeble ones require a greater effort also, but for a different reason — namely, in order to raise them above the limit of distinct con- sciousness (Sully); (2) it depends upon the preceding state and direction of activity of the attention — e.g., in preoccupied states ; and (3) upon the ability to arouse the attention by an internal or volitional act — e.g., in conditions of somnolescence, where there is lethargy or inattentiveness, there is also impaired 300 MENTAL PROCESSES. power, or complete inactivity. Exercise strengtliens the power of attention, and the gTo^^'th of volnntary attention is to be acquired by practice. Often we can gain an insight into the will-power of an individual by observing the effects of the solicitations of powerful stimuli as opposed to his power of attention. Thus, one has only to observe the respective attitudes of students who are attending a clinical lecture on insanity to satisfy oneself as to which individuals are possessed with a desire to learn, and have the power of resisting the solicitations of unusual stimuli emanating from the patients near at hand. In general, the junior student pays less attention to the lecturer than to the extraneous influences around him; whilst the adult, or post-graduate, is all-attention, and concentrates his thoughts upon the subject-matter of the lecture. This power, however, has its limits, and it is often impossible to resist the solicitations of powerful stimuli. In maniacal states there is little or no resistance to the various stimuli, and it is dif&cult to gain the attention. The growth of voluntary attention means a continual reduction of the difficulty of attending to objects. According to Sully, when an intellectual impulse of curiosity is ^^'ide and impartial, embracing all kinds of subject-matter, we have the versatile mind, ever ready to turn its attention in a new and unexplored quarter. Attention and Genius. — Genius, according to Sully, is| nothing but a continued attention, and great intellectual power turns on the ability to concentrate the attention. James * says it is genius which makes men attentive, and not their attention which makes geniuses of them. Helvetius regarded genius as nothing but a continued attention ; Bufibn as onl}^ a protracted patience ; Cuvier as the patience of a sound intellect ; Chesterfield as the power of applying an attention, steady and undissipated, to a single object. Macaulay regarded genius as subject to the same laws which regulate the production of cotton and molasses ; whilst Hogarth said he knew no such thing as genius — " Genius is nothing but labour and diligence." These views contain something of novelty, but continued attention more often enables genius to manifest itself than to create itself. Moreover, it is just this power of continued attention * "Principles of Psychology,'" vol. i. p. 423. MORBID ATTENTION. 301 Avhicli genius often lacks. Subsequent!}^ we sliall see that attention is a most important factor in the formation of all our conceptions, and in the assimilation of impressions which can be recalled by memory-. We can conceive, that forms of attention which involve no voluntary effort, but are apparently derived from the initiative of the object, may be results rather than causes ; but when we attempt to reduce voluntary efforts to the same platform, we get beyond our depth, and enter upon the discussion of matters which are not to be decided arbitrarily by us, either as physiologists or psychologists. Whichever way we look at this subject we cannot but realise the fact that, until we are able to determine what the agent is which sustains the phenomena of consciousness, we are groping in pitchy darlv- ness. We offer no theories, nor abstruse philosophical doc- trines of the existence of an immaterial agent which determines the order of events by its own inherent laws. In fact, we cannot conceive the existence of such a substantive factor independent of its neural agency. All that we can conceive is, that the vera causa of mind is to us unknowable. Morbid Conditions of Attention. — From the preceding considerations upon the conditions of attention, it will be readily understood how variations may arise in the sane. In the insane we see the more stronglj^ marked or diminished forms of attention. The term " hypertrophy " (Ribot) has been em- ployed to signify an exaggerated form, but we prefer to use the term " hj^erattention." Hyperattentioii. — By this is meant morbid exaggeration or excessive concentration of the attention ; or, in other words, reduction of the general with exaltation of the particular. Nor- mal mind is polyideational. When there is a predominance of an intellectual state, or group of states, to the exclusion or defection of other states, the individual is in the condition generally known as being " mad on a subject." Hyperattentive states are thus meant to signify states of monoi'deism, or states in which the reduction has lapsed from general intellectual activity to concentration upon a fixed idea. As an intensifica- tion or combination of such a condition, we have delusional states, as seen in the insane. Hyperattention may be regarded as invariably tending 302 MENTAL PROCESSES. towards the insane state. Clinically, we may classify the results of hyperattention as follows : — 1. Simple fixed ideas — purely intellectual. (tt) Ideas of greatness. (&) Unfounded suspicions, (c) Unseen agencies. 2. Fixed ideas accompanied by emotion. (a) States of depression. (b) States of exaltation. (c) States of ecstasy. 3. Fixed ideas, with motor activity. (a) Irresistible tendencies which manifest themselves in violence or criminal acts. 4. Fixed ideas, or oft-recurring imperative ideas. We shall speak more particularly of all these forms later, so we now pass to the condition known as " inattention." Inattention. — In the sum total of our conscious existence there are numberless dim, ill-defined, sub-conscious impressions, which have never been illuminated by the mind's attention. Helmholtz has formulated the law, that we leave all impressions unnoticed which are valueless to us as signs by which to discriminate things. Were this otherwise, no continuity of thought woiild be possible* the mind would act like a weather-cock, which turns with every breath of wind. Some- times the determined effort to concentrate the attention upon an object only results in fixation of the apparatus ; the mind itself pays more attention to the adjiistment than the object itself. Some individuals, on the other hand, can only resist extraneous stimuli by keeping the motor apparatus in action — e.g., as in pacing the room. This fact has suggested to James, that the activity drains away nerve-currents, which, if pent up within the thought-centres, would very likely make the confusion there worse. He offers the suggestion that it may also be a means of drafting off" all the irrelevant sensations of the moment, and so keeping the attention more exclusively concentrated upon its inner task. Every individual has some characteristic and habitual activity of this sort. One INATTENTION. 303 writer is unable to work without the presence of a pipe in his mouth ; that there is no tobacco in it is immaterial. James also suggests, that a downward nerve-path is thus kept constantly open during concentrated thought ; that incidental stimuli tend to discharge through paths that are already discharging, rather than through others ; and that the whole arrangement might protect the thought-centres from interference from without. In the insane, inattention is frequently seen in the indi- vidual who has abnormal rapidity and exuberance of ideas, so that no particular state of consciousness lasts even for a moment, as in the case of delirium or of acute maniacal states. In another class of cases there is absence or diminution of the power of inhibiting the solicitations of other stimuli — e.(j., in hysteria, irritable weakness, convalescence, intoxication, ex- treme states of bodily and mental fatigue, and in apathetic and insensible individuals. From what we have already said about conditions of hyper- attention the student will be able to appreciate the general law, that when the attention is engaged with the contemplation of the mind's owii contents or ideas there is a corresponding diminution in its reactionary power to extraneous influences — i.e., present-mindedness varies inversely with so-called absent- mindedness. Thus, in the melancholiac, the hypochondriac, the " faddist," or the deluded maniac, the presence of a dominant idea is sufficient to give rise to various degrees of inattention to stimuli from without. To those who work among idiots or imbeciles the element of attention is one of the most difficult questions with which to grapple, and it is to such workers that the importance of attention in the development of mind becomes most clearly evident. In insanity, we may say, that in states of depression there is a tendency to subjective hj^perattention, with a corresponding ratio of inattention to objective stimuli. In states of mental exaltation there is subjective inattention and a corresponding- variation in objective attention, or hyperattention ; in states of mental enfeeblement there may be absence of the power of attention to events both within and without ; whilst in delu- 304 MENTAL PROCESSES. sional states there may be hyperattention to events within or without, with or without a corresponding amount of inattention to events without or within respectively. The power of transition of the attention is a feature worthy of careful observation in the melancholiac and the maniac. In the former, it is held by some dominant idea, and before we can divert it to external events we may have to resort to other stimuli. Thus, in some cases it is impossible to gain even a reply to ia simple question without the aid of an additional stimulus — e.g., a pull on the hand or arm ; whereas, in the maniac, the transition from one external object to another is so rapid that the speech is incoherent in its inability to follow and give expression to what the mind attends to, and the very rapidity of the reaction to external stimuli prevents the forma- tion of any subjective idea other than what is merely transitory. In other words, we may say that in maniacal states the con- sciousness is diffuse ; in melancholia, there is a tendency to internal concentration, or to reduction from the general to the particular; in delusional states the reduction is still greater ; while in degenerative states the consciousness is confused. In maniacal states the attention is essentiall}?- reflex and fleeting ; while in melancholic and delusional states it is more concentrated and of longer duration, and in the latter more liable to be fixed. COXCEPTION. The possession of a conscious intellect, and the power of reasoning by general notions raises man above every other creature on the earth. Everything great in science, art, or literature is the work of intellect. Of the threefold division of mental operations adopted by mental science — knowing, feeling, and willing — that of knowing includes, the operations by which we recognise what is present to the senses, the act of recalling former cognitions, and the processes of reasoning. The psy- chologist differs from the logician, in that the former has to do with the usual modes of thought, whilst the latter has to do with the rirjM modes of thoiight. CONCEPTION. 305 A concept, notion, or general idea, is the representation in our minds answering to a general name — e.(j., soldier, man, animal. All thinking implies comparison of one object with another. We recall, group, and arrange the cognitions gained by former perceptive processes, and retained by memory. The stages of thinking are : (1) The formation of general concepts, which constitute the elements of thought — e.g., the recognition of a body as material ; (2) the combination of two concepts in the form of a statement = judgment — e.g.. material bodies have weight ; (3) the process of drawing an inference or conclusion = reasoning — e.g., gases are material substances, therefore gases have ^\'eig•ht.* Concepts are formed (1) by comparuon of the objects presented, or of those called up by the representative imagination ; (2) by abstraction, ^^'hieh implies the action of attention (a passive reception of impressions with a compara- tivel}^ feeble action of abstraction results in a want of clearness, or an imperfection in the concept) ; (3) by generalising the objects compared. Concepts may be wanting in distinctness when their elements are not distinctly represented. The concept must also be distinct from a somewhat similar concept. other\A'ise it tends to become indistinct. Thus, there is a vast difference between the conception of a "form of epilepsy " and an " epileptiform " condition. A lish may perform whaliform movements without being a kind of a A\'hale. Our notions can only be clear when we recognise the things which correspond to them ; when we do not do this they are necessarily obscui-e and ill-defined. A notion is distinct when its several parts are distinctly represented ; otherwise it is indistinct or confused. f The tendency in mental disease is for notions to become indistinct from the lapse of memory ; and the organic unity of a concept is thus apt to be weakened. Its associations are dissolved or disintegrated. The common characters of the representation become hazy and indistinct. In this manner, says Sully, the concept tends b}^ lapse of time to return to its early crude state of a string of images, or an imperfectly combined mass of images. Inaccurac}^ of concep- * " Sully, " Outlines of Psychology," p. 339. t Hamilton, " Lectures on Logic.'' 20 306 MENTAL PROCESSES. tions may arise in the same way as mere indistinctness. When we take too narrow, or too wide a view of things, the result is imperfect abstraction and a resulting inaccuracy of the notions. Defective conception, at the outset, often leads to greater inaccuracy through imperfect revision. In this way crude or imperfect concepts frequently evolve into false notions b}^ revision. In many individuals there is a constant tendency to widening of the notions, so that ultimately they embrace too much ; whilst in others there is a tendency to specialise, or reduce too much to the special — e.r/., as seen in the growth of monoideistic states. Frequentl}^, as the result of specialisation, there is developed a tendency to individualise or to appl}^ notions to the personality — e.g., in the various writers who have " fads " and endeavour to assert their individuality synony- mously with the fad. We all vary in our conceptual power and in the power of abstraction. Some individuals are facile in the detection of similarity and diversity, others gather and retain a great bulk of conceptions but are unable to abstract from them. In the uneducated classes, generally, the power of retaining concrete conceptions is often greater than in the educated, who deal largelj' Avith the abstract. Some individuals can only form abstract notions in connection with their special line of thought. The mental physiologist may be deficient in framing wide concepts as to phj^sical formulge, or ideal notions of the mathematics of mind; or, on the other hand, he may lack the philosophic power of abstracting and thinking about the subjective side of mental phenomena. It is not uncommon to meet with a logician m^Iio has at his finger tips, as it were, all the foi'mulee of how we ought to think, but who professes utter ignorance and incredulity about the ways we do think. In the true economic management of brain-power a certain amount of attention to the concrete must always precede abstraction — i.e., we must proceed from the consideration of the particular to the general. The abstract notion must be fed, so to speak, by the concrete perceptions, by memory, and by the reproductive imagination. From a psychological point of view, therefore, we see that morbid conditions may arise as individuals vary (1) in their sensory discrimination, perceptual power, and in their con- CONCEPTION. 307 ceptual power and assimilation : (2) in their power of attention and abstraction (some individuals possess very high theological views derived from tradition, who, nevertheless, have defective power of introspection, or of forming abstract notions for them- selves) ; (3) in the amount of attention given to the concrete (in the uneducated and in the weakminded attention to the trivial events of life gives the sum total of their mental being ; similarly, some plodders ^^'ho devote all their energies to the contemplation of the concrete neither see nor think beyond their microscopic region of central focus). In acute mental disorders the rapidity of formation of notions, the defective conditions of the memory, and the pranks played by the imagination are predominant factors. In subjective and intr-o- spective states the slowness of the processes, and the persistence of the direction of the attention to the false conceptual series, aid, in great measure, in the formation of the narrow egoistic states, or the delusional series. The arguments of some psychologists, that conceptions develop themselves, and that a "judgment" is due to the self- massing of present and previously acquired notions, are incom- prehensible. The original conception remains what it always was. The mind can form a new conception which it can com- pare with the old, but it cannot modify the old so as at the same time to obliterate it. Every conceptiial act is either a new combination formed by the mind itself, or rather a new com- bination viewed b}^ the mind as such ; or it is a reproduction of a former conception in its perfect form, or in its somewhat indistinct state owing to the lapse of memory. Conceptions are unchangeable. The new cannot displace the old — i.e., every conception must always remain in the sum what it was originally. They wdll ever remain as distinct, and as definitely apart from each other, as the first and the sub- secjuent enlarged or revised editions of a book. To the student who thinks of hoiu we think and what our thought comprises, the conviction must force itself upon him that the pou'er of abstraction is a function of the mind which w^ill never come within the province of logical or physical explanation. The fact that we do think about and abstract from ^^•llat our organism presents to us, requires no proof. James has proved 308 MENTAL PROCESSES. that nothing can be conceived twice over without being con- ceived in entirely different states of mind. When we look upon a familiar face the present view is not an exact copy of the former views. When we read a book several times, each time we read it the mind sees something new^ No idea which is conjured up by the context is the exact counterpart of the former ideas. To continue alonp' one line of thouoiit. or to make the mind dwell upon one conception is impossible ; we can revert to it, possibly at will, but each time we do so the thought is in itself a neAv conception bearing a resemblance to the old. The Psycho-Physical Theories of Conception. — It is supposed that, with the first transmission of the physiological force, whereby the impression of an extei'nal object is presented to consciousness, a trace of the cortical excitation that has taken place is left in the cerebral cortex. This conclusion is arrived at from the fact that former presentations can be repro- duced by memory. These images of memory or mental images which are deposited by each sensation are designated as ideas.* The images of memory or ideas are held to be quite different qualitatively from the actual sensations themselves. The process which takes place when a sensation disappears and its image is deposited in memory, is supposed to be some sort of material change which remains as a trace or sign, the cerebral cortex never fully returning to its previous condition. With the deposition of the imiage there is no concomitant psychical process whatever. According to Ziehen this is accomplished latently, without our being conscious of it. " Tliere is no psychical element left of the sensory excitation corresponding to the sensation, but only a permanent material change .... the remanent material trace has no psychical correlate what- ever." He further conceives that this material trace is a definite arrangement and constitution of the molecules com- posing the ganglion-cells, and that it only becomes psychically active as an image of memory or an idea when the object of the primary presentation again asserts itself, or when, by means of the association of ideas or the play of fantasy, some related idea occurs. " In order that the dormant image of memory, which * " Yorstelluiig," Hegel, Lotze, Ziehen, etc. CONCEPTION. 309 is as vet only potential, may be aroused, therefore, the ganglion- cell having the disposition El (latent excitation), must first receive a new impulse from a new and similar sensation, or from some related idea with which it is associated — that is, the El must be still further changed in some definite way, becoming an ideational excitation. Hence the ganglion-cell is trained to a certain extent for a definite idea." Let us now assume with Ziehen, that the ganglion-cell has this greatness thrust upon it. We do not know for certain whether the cells or only their processes are concerned with conscious events, nor do we know which groups of cells are the seats of mnemonic images. This, however, need not detain us. What we have to understand is the power or property of each cell which would correspond to all emergencies. Let us imagine the " seat of memory " to be the library of the British Museum. Every new work or idea is relegated to its proper department and deposited on a shelf, where it remains inert. It is, so far as itself is concerned, a material object only, but contains a large amount of latent thought. In order to set free this latent thought, so that it may be perceived by, say the librarian, the deposit of another somewhat similar book by its side is supposed to be all-sufficient. But, the student will say, in the first instance a knowledge of the contents of the first book is pre-supposed to the librarian, and the addition of another somewhat like it recalls all the contents of the former. Precisely; the librarian represents the mind, he reads the book ; the one book does not jostle its contents into the vacuum of an inert mind. The activity rests in the librarian. The one inert mass of latent thought (the book) does not combine with another inert mass so that the t\\'o hy their own inherent properties evolve a ' mind in the librarian. The mental activity of the man who shelves the books is all-important; and so is the activity of the mind which reads the sensations and forms associations between the gleanings derived from physiological factors of which we know nothing. How the books arrive at their shelves, and how they are classified, is known to the librarian; but the mind cannot, as yet, grasp how the so-called cortical traces are determined, nor can it form any conception as to their mode of classification. 310 MENTAL PEOCESSES. When I look at the book-shelves of my study, and see in each closed volume the idea of their contents, their action is merely by suggestion, my mind does the rest. So it is with the mind and oiir cortical structures. Each book may represent a cortical trace, or latent excitation, but it is the mind which realises that excitation, and which turns and contemplates the appeal from each individual book. As with minds, so with librarians. Some appeal incessantly to their cortical traces or books for knowledge, while others are appealed to by those traces or books for the independent siimmations of an intellect which transcends their contents. To enter upon the question of how far the mind is dependent upon molecular changes for its knowledge of ethical and philosophical systems is not part of our object. All we desire to point out is, that the psycho- physiological theor}^, as depending upon a purely cellular basis of memory, is insiifficient. The physiological theory fares no better than the psycho-physical one. The supposition, that in the case of the visual sense the relations of the retina are to a certain extent reproduced in the visual centre, so that the superior margin of the former corresponds to the anterior margin of the latter, is absolutely withoiit vei-ification. Ziehen states : "To this excitation of numerous ganglion-cells corresponds the visual sensation." We have already discussed the question as to whether sensations and ideas involve the same cortical elements, and we have seen that, from our present knowledge of physiology and pathology, we are justified in the assumption that different cortical elements are involved. It is commonly assumed that the ganglion-cells of the sensory areas transmit their excitation to another ganglion-cell (the "memory-cell") where the molecular counterpart of the visual idea, or proper image of memory, is stored. In order to explain the storing of sensations derived through the different senses whose centres are situated in different parts of the cerebral cortex the following theory is advanced. From the fact, that disease, injury, or extirpation of certain areas of the cortex is followed by partial defects in the memory, it is assumed that the "images" of memory are deposited in immediate association with these regions. An CONCEPTION. 311 idea is regarded as a complex psychical state, deriving its com- ponent parts from the images deposited in different areas of the brain. Thus, assuming that visual, auditory, olfactory, and motor images are stored in their respective regions, and that they have often been called into activity simultaneously, an idea is supposed to be due to the summation of activities Avithin these regions. That is to say, the component sensory elements are deposited in different parts of the brain, and are connected with each other by associative fibres, so that when one of these areas is excited the others are called into action by association. The idea, therefore, would appear to depend upon the functional integrity of the structures from which the. physiological equivalents of its component parts are derived. In favour of this view we have the facts derived mainly from the study of the various forms of amnesic aphasia. With the absence of certain areas, through injury or disease, the corresponding representative element is also absent in the idea. Moreover, the other physiological elements, which are assumed to be functionally competent, are nevertheless unable to com- pensate for the loss by their own activity. That is to say, they are unable to supply the mental deficiency. Experimental evidences are abundant to prove that certain sensory areas may be eliminated (so far as we know them anatomically) ; and with their removal, there is also interference with the material dis- positions through which their representations in consciousness would appear to depend. The seat of transition between sensory stimuli and their mental ecjuivalents, and the seat of the material dispositions which are immediately concerned with the reproduction of these mental equivalents would appear to lie somewhere within the so- called sensory areas. There is scarcely any need for a physical explanation of the summation of the material dispositions which would correspond to the elements derived from the regions of the different senses. Nor do we deem it necessary to surmise that a combination of these material processes occurs in one supreme centre. When once we have grasped the notion that any one percept is the result of a serial analysis of the presen- tative and representative processes derived from the anatomi- call}' distinct sensory areas, and that this psychical associative 312 MENTAL PROCESSES. or serial process is correlated to the plij^sical associative process, the greater part of our difficulties will be surmounted. When Ave discuss language with its ideas of articulation, and the pathological evidences brought to bear upon the question of the acoustic mernor}' cells, and their relation to the acoustic sensory cells, in those mentallj^ deaf to words, the full signifi- cance of this view will become more evident. Double Brain. — Let us now consider the significance of the double nature of the brain, and the relation Avhich each hemisphere has to the formation of an idea. It is supposed, upon the evidence of pathology, that every component of an idea exists twice in the brain. If there is entitjr of mental action, how are we to combine the simultaneous processes which go on within the two hemispheres ? An explanation has been sought from the analogy of what happens in the case of the eye when there is hemianopia. In this case we know that destruction of both the visual regions is necessary to produce complete blindness. The prevailing theory is, that the impressions of the two objects are combined by the mind into one image, which is a compound of both. Brown-Sequard believes that one hemisphere of the brain is enough for all the processes which initiate mental functions. Most observers, however, believe that the representations on each side of the brain are unequal. Goltz removed one hemisphere in the dog and found that the ordinar}^ actions and habits of the animal ^^'ere little affected ; but A^'hen, on the other hand, parts of both hemispheres were removed, the intelligence was markedl}^ affected. Ireland assumes from this, that both halves of the brain have functions closely corresponding ; but in man the specialisa- tion of function in one hemisphere has begun. Hughlings- Jackson believes that the right half of the brain is the auto- matic half, and the left is the half in which automatic action passes into what we call voluntarj^ action. He also believes that when an aphasic patient utters a few words or exclama- tions it is owing to the action of the uninjured right side of the brain. The estimation of the difference in temperature of the two sides of the head associated with use of one side of the body, has, in the hands of Broca and Fasola, proved that frequentl}'- there is a rise in temperature which corresponds CONCEPTION. 313 with the half of the brain affected. The phenomena of sensa- tions referred from one side to the other, and of bilateral reflexes, are suggestive, but they are so rare, and so many other possibilities enter into their explanation, that for the present they cannot help us. The explanation of the phenomenon of mirror writing is that, in the cases of paralysis of the right arm, the image, or impression, or change in the brain tissue, from which the letters are produced b}^ the hand, was destroyed, and that in trjdng to write with the left hand the patient wrote from an image on the right side of the brain in every way corresponding, save that it was reversed. Thus, the motions in each case would be centrifugal and corresponding; in the one case the characters would be formed from an image on the left side ; in the other from the right side of the brain.* Ireland believes that one side of the brain is sufiicient for all the usvial functions of the mind and body in daily life. From an examination of a considerable number of instances, in which there was disease or destruction of one or other hemisphere, he concludes that both sides of the brain are functionally active, and, as far as we know, save in a few instances, both sides have the same work to do. Ireland's remarks upon this subject are so comprehensive that we quote them in his own words : — " We may hold from analogy that, as long as corresponding, or com- plementary, or congruous impressions are produced in each hemisphere, no disparity of thought or affection will be noticed, just as the same or complementary impressions from both retinae are fused into one mental image. Double action of the brain is only displayed in health by the capacity of attending to several mental processes at once. It is in diseased action where one side of the brain is affected, and not the other, that we may expect to find a derangement of the harmonious action of both hemispheres. In cases of wounds or injuries of one side of the brain, the following symptoms have been observed : The patient is quite sensible, though perhaps exhibiting signs of distress or restless- ness, or twitching of the muscles. When spoken to he will answer for a time composedly ; but conversation soon fatigues him, he begins to be anxious, then distressed, and further conversation becomes painful au'l exhausting. Nevertheless, to outward appearance he is composed and reasonable. The explanation of this is, that one side of the brain being still healthy, it acts in a normal manner, but in the exertion to carry on * Ireland, "Tuke's Dictionary," p. 399. 314 MENTAL PEOCESSES. a conversation the diseased hemisphere has to carry on parallel actions. The result is the feelings of distress which oblige him to shun or arrest any unusual mental exertion. In such cases it sometimes hapi^ens that lying on the diseased side causes a painful feeling, and when the patient during sleep turns upon the affected side he awakes in a fearful dream. Inflammatory processes, implicating the surface of the hemispheres, are liable to spread by means of the Inembranes which are united at the middle line. We may also suppose that irritation of particular parts of the brain has an effect upon the opposite side, in the same way as inflammations of one eye have an irritating effect upon the sight of the other eye." The same author believes that the disparity between the weights of the hemispheres in the insane (especially in epilep- tics and general paralytics) is a proof of the existence of un- equal disease of the brain. He endeavours to furnish an explanation of many symptoms in insanity by the assumption that there is one-sided or uneqiial disease of the hemispheres. Such symptoms he describes as (1) la folie lucide, in which, though struggling with delusions and hallucinations, the patient still retains a considerable measure of intellectual clearness and self-control ; (2) cases of melancholia, with dis- like to being disturbed and intense feelings of misery, but it is found afterwards that he has noted and understood everything round about him ; (3) cases in which the patient has struggled with some dominant idea with more or less success ; (4) cases in which the patient asserts, that he has become a new person, that spirits or some other beings introduce new thoughts into his mind and incite him to perform motions which he never willed, and of which he disapproved ; (5) cases of conflicting volition where the person is at a loss whether to commence a motion on one or other side, or in which he alternately uses tne one or the other hand ; (6) cases in which the hallucinations differ on the two sides ; (7) cases in which the patient feels the intrusive force of a second personality ; (8) cases in which the patient seems to obey or receive a delusion, but at the same time disbelieves it, as in those dreams where a person retaining the belief in his own identity witnesses his own death and burial; (9) cases of double-thinking; the subject hears his thoughts repeated into his ear by some strange voices im- mediately after conception (supposed by some to be due to CONCEPTION. 315 retardation of one hemisphere) ; (10) cases of double-conscious- ness, double-memory, in somnambulism or induced hypnotism (supposed to be due to alternate activity of the hemispheres). The comprehension of the relative functional activities of the two hemispheres is as yet, however, in its infancy, and we hope that time and research will do much to throw light upon this intricate subject. Before returning to the psychological side of thought, let us look briefly at another theory as to its material side. Consciousness the Accompaniment of Nerve- Action. — With constant repetitions of a material process the corresponding currents which accompany it are believed to establish, as it were, a right-of-way, or clear line, on which little resistance is experienced. With the establishment of new currents, however, new channels are opened up, and the nerve-elements become iinited by new bonds. It is held by Mercier, that the newer the nerve-action, the more vivid the conscious accompaniments ; hence, he says, it is to this new formation of channels that we have to look for the_physical condition of the occurrence of consciousness. He further states, that in a region which has not yet completed its organi- sation, we find that the cells are less definitely constituted, and that the fibres are far less sharply demarcated from the matter in Avhich they are embedded. So little, indeed, are they differentiated from this substance, that it is often a work of difficulty, of delicacy, and of much laboiir to establish the difference between them ; and the difficulty becomes greater the further the fibres are pursued. This anatomico-physio- logical hypothesis, that the richness of the cellular association furnishes the explanation of the characteristics of intellect, is very general, and has lately been urged chiefly by Eamon y Cajal. If we accept this hypothesis, however, we are really no nearer the solution of the main cjuestion, What is the relation of s^ consciousness to these anatomical tubes or structures? ^ Whichever way we look at the subject, a thoroughgoing- materialistic formula must provide a material accompaniment for every apparent activity of the mind. If one region, above all others, is to be the ultimate substratum of conscious life, then the elements of this substratum must, by their exquisite 316 MENTAL PROCESSES. refinement of structure and incomprehensible versatility of function, provide the mind with all its states, and hold within its material disposition the power of formulating for the mind the infinitesimal number of variations which have been acquired by the experience of a life time. It is held that where a nerve- current passes easily, there is no conscious accompaniment. When the channel is narrowed, however, and the current is unable to pass freely, consciousness appears. Mercier has therefore formulated the law that, " the intensity of consciousness varies as the difficulty which the nerve-current experiences in passing the narrow portion of its channel." Further, he says, " consciousness is an epiphenomenon, and has no community of nature with the nerve-current, whose passage it accompanies." According to this, consciousness would appear to be determined by conditions of mechanical resistance to the flow of currents. If we assume that this is the explanation of consciousness, then we must also assume that consciousness ought to accompany nervous current everywhere ; and, unless we can prove that the cerebral cortical currents differ from the peripheral currents, we must locate consciousness everywhere where there is nervous resistance to be overcome and tubes to have their calibre enlarged. We know of no specific mode of cerebral 'action which would correspond more particularly to states of con- sciousness than the ordinary peripheral currents. To speak of "waves offeree that pass through the grey matter of the cerebrum," "the constitution of the molecules," "their discharge and resistance," " the directions of the poles of the molecules," "the shifting of molecules so as to bring their poles nearer to parallelism," " the permeabilitjr of tracts," and the " accession or decompounding of the molecules," conveys in reality no more meaning to us in regard to the cerebrum than it does in regard to any nerve of the body. Moreover, were these hypotheses verified in the department of phj^sics, they would remain as facts belonging to that department, and would have no community with the facts of mind. If the "epipheno- menon " of mind is in intimate relation to the actual area of obstruction, then mind must needs be everywhere ; if, however, the mind only becomes aware of these sensations of discharge and resistance from a distance, then its ultimate substratum JUDGMENT. 317 must either be a mechanical force, which is central!}^ sensitive to every distant oscillation of molecules directly through its wave of force, or it miist become cognisant of the interhappenings of the molecules at a distance through some other channel, in which case another substratum would have to be devised, whereby the knowledge could be transmitted. If we are told to believe that the mind in some mysterious way perceives the internal current, and witnesses its dilating effects upon the small nervous tubes of the cerebrum, in much the same manner as our fingers feel a pulse, then we have to construct a material counterpart of mind which shall correspond to our fingers. " Of what avail are all these objections?" the student will say; '■ the theories of discharge and resistance are plausible, and serve our imagination better than any others." So long as they serve the imagination only, and do not incorporate themselves as truths known to science ; and so long as they do not form traditions which lead to beliefs, no harm is done. Whether the completely differentiated physiological disposition of molecules will ever become a matter of knowledge is a question which we leave to be answered by science. That the acquisition of such knowledge will ever lead to any explanation of the phenomenon of mind itself in its subjective aspects, we do not deem possible. On the subject of abstract conceptions, physiological psychology has little to say. We cannot reduce them either to sensations or to their mental images. When we speak of imagination, we shall take into account the nature of the so-called reflective ideas, and we shall see how far they may be designated as abstract. JUDGMENT. Judgment is the act of connecting two representations under the form of a statement. We keep the two repre- sentations apart from one another, but at the same time we connect them. Without the element of belief, however, the mere connecting of two representations does not constitute an act of judgment. Bec&pts are spoken of as the first and simplest inferences following continuously upon a concept — e.g., one dog scents another dog.* Eomanes termed these generic * James, " Principles of Psychology," vol. ii. p. 327. 318 MENTAL PEOOESSES. ideas, to distinguish tliem from concepts and general ideas. When we reason, we select the essential qualities and sub- stitute them and their implications for wholes. Thus, in reasoning, the character or quality which has been extracted is taken as equivalent to the entire data from which it comes ; hence the extracted character is more general than that of any individual datum, and its connections are more suggestive and familiar to iis. Reasoning, therefore, implies the ability to extract characters from given data. It is held hj some, that the most elementary simple difference between the human mind and that of brutes lies in the deficiency on the brutes' part to associate ideas by similarity, and to abstract or reason there- from. In a genius this power is often manifested in an extreme degree. The degree of perfection of judgments depends on 1. Its demoness, and this is interfered with b}" (a) Imperfect observation. (h) Defective conditions of memory. (c) Imperfect use and conception of words. (d) The presence of emotional disturbances. (e) Traditions — attending to the notions of others. 2, Its accuracy — interfered with b}^ (a) Imperfect understanding of propositions. (h) Imperfect observation. (c) Imperfect recall. (d) Emotional states — strong feelings. (e) Instability of mental action. (/) Rapidity of formation of judgments. Judgments may be correct or otherwise in respect of their mode of formation, but, if when formed they are persistent, they may become advantageous or the reverse. Thus, in every branch of science and literature, we note the obstinacy with which erroneous judgments are adhered to, and the obstacles which they thus present to the advance of knowledge. A distinction has been made between instinctive and reasoned judgments. " A savage," says James, " is often as tactful and astute socially as a trained, diplomatist. Women's intuitions, so fine in the sphere of social or personal relations, are seldom good in mechanics. Most boys teach themselves how a clock BELIEF. 319 goes ; few girls. Whately says woman is the unreasoning- animal, and pokes the fire from on top." In diseased states, the delusions of women, arrived at b}- intuitional processes, are seldom capable of correction by logical reasoning. The evolution of the mind in man differs essentially from that in ^^'oman. The \\'oman at twenty has often formed her mental character in nearly all its essentials, and this re- mains through life, or, perchance, begins to develop from the reasoning side at the close of the reproductive period ; whereas, in the youth of twenty the reasoning faculty is undergoing active evolution, the mind is developing and endeavouring to assume a shape, is easily moulded, and deals little with intuitions as compared with reasoning. Morbid developments of the reasoning process may arise by (1) inductive processes, as seen in the ideas of self-importance which have arisen gradually from the false interpretations of concrete signs, or the morbid intensification and distortion of concrete facts from imperfect or diseased abstraction ; or, by (2) deductive processes, whereby an invalid conclusion has become evident in consciousness, and through confusion, want of discriminative power, haste, or emotion, the data cannot be analysed correctl}^ The Perception of Reality, Belief. — It is unnecessary for us to point out the difference between imagination and belief in the objective reality of an image. Belief, or the sense of reality, is regarded in its subjective aspects as a sort of feeling or emotion. The condition of doubt is the true opposite of belief; disbelief is as positive a state as belief. Both con- ditions of belief and doubt may be pathologically exalted. James has it that one of the charms of drunkenness lies in the deepening of the sense of reality, and that this goes to an extreme in nitrous oxide intoxication, in which " a man's soul will sweat with conviction." In various pathological states there is inability to rest in any belief without having it con- firmed or explained constantly. This condition ma}^ be par- oxysmal or chronic. Among the insane we meet with every variety of belief and doubt. We are all apt to believe things real until they have been contradicted. Our beliefs and doubts depend on the fact that different minds vary in their way of 320 MENTAL PEOCESSES. looking at things, and that olDJects do not appear the same to all. To attempt to explain belief from a physiological point of view is a task which we cannot undertake ; nor can we describe the apparatus which determines the direction of onr thoughts and enables us to adhere to, or disregard the objects of, belief or doubt. The insanity of doubt has received considerable attention at the hands of Falret, Esquirol, Baillarger, Legrand du Saulle, Oscar Berger, Griesinger, Ball, and others. Professor Ball compares the condition to a sort of incorrigible " cerebral pruritus." The cause of the disease is uncertain. Some ^Titers believe that it is one of the forms of an hereditaiy neurosis. Undoubtedly stress and strain, as in those who are guilty of sexual excesses, or in those who are overworked or worried, may be sufficient to determine the condition. It occurs most frequently among the educated classes, and is commoner in women than in men. Professor Ball believes that it often declares itself at the age of puberty. The disease is not un- common as a sequel to febrile states, and has been met with in the puerperal state. Moral shocks, sudden frights, and strong emotions are also said to cause it. The varieties of doubt met with in the insane may be tabulated as follows : — * f Insanity of < doubt. Intellectual Subjective J Emotional Yolitional r I Objective of the centre and of its etter- '- ^ alphabet, days of / ^ „, -, ^ . I ent fibres, week, etc.). I (c) Spontaneous. / Visual Perceptive Centre, with its afferent and efferent fibres — 1. Sight — good or bad? ^ 2. Comprehension of printed or written words. 3. Recognition of numerals or letters To test the functional activity (as judged by ability to point >• of afferent fibres and of the them out). centre itself. 4. Recognition of common objects. 5. Recognition of pictures of common objects. ■ ' /{a) Imitative (copying of \ numerals or letters, j or " transfer copy- / To test the functional activity 6. Writing Bernhardt, rill Bernstein, 62, 81 Bibra, 59 Billod, 449 Binet, 234 Blandford, 275, 276 Bleuler, 243, 245 Bloch, 217 Blood, in insanity, 513 Bodily diseases as causes of in- sanity, 508 Boll, 58 Bolton, 185 Boulimia, 399 'Bradyphasia, 365 Braid, 327 Brain, double, 312 movements, 76 vascular supply, 63 Bratmoell, 361, 352, 424, 440 Brierre de Boismont, 263 Broca, 26, 101, 312, 364 Browne, Crichton, 426 Brown-Sequard, 312 Bruce, 73 "Bucket, theory" of hallucina- tions, 256 Burckhardt, 76, 77, 78, 87 Buret, 209 C. Caja,l, Ramon y, 26, 26, 28, 32, 63, 64, 65, 315 Calderwood, 155, 158 Campbell, 438 Carpenter, 6, 420, 449 Carter, 43 Catalepsy during hypnosis, 630 Caudate neuroglia fibre-cells, 40 Cells, relation between, 38 Cerebral affection and insanity, 520 arteries, structure of, 67 cortex, 27 fluid, regulation of pressure of, 70 localisation, 92, 104 value of, 109 Cerebration, unconscious, 165 Cerebrin, 60 Cerebro-spinal fluid, 73 Chabalier, on secondary sensa- tions, 247 Charcot, 63, 64, 92, 126 Chemical properties of nerve-sub- stance, 56 Choice, 410 Cholesterin, 60 Chorea, 518 demonomania, 489 Chossat, 59 Christian, on hallucinations, 269 Cingulum, 108 Climate, influence of, 496 Clouston, 445, 452, 476 Coccitas verbahs, 434 Cohnheim, 65 Collective hallucinations, 268 Colour bhndness, 200 sensation, 201 Colours, simple and mixed, 199 Common sensation, 189 INDEX. 543 Comte, loU Conception, 304 phj^siologieal, 310 psycho-physical theories of, 308 Conduct, 440 in the sane, 443 insane, 443 Conductivity of nerve-cell, 44 nervous impulse, o2 Congenital idiocy, oOO syphilis, 476 Consanguinity, laws of, 474, 477 Consciousness, 12o in lower centres, 141 the accompaniment of nerve- action, 315 Control of feelings, 444 thought, 444 loss of, 445 self, 444 Cornu'inder, 59 Cortex, anatomj'^ of, 24 arteries of, 65 Cortical structures, arrangement of, 25 Coupland, 149, 154, 171, 176, 392, 409 Courtier, 234 Cramer, -I^i Cranioschisis, 500 Cretineux, 407 Cretinism, 407 semi, 407 Cyclops, 499 Cyples, 146, 158 Cysterna ambiens, 71 chiasmatis, 71 coi-poris callosi, 71 intercruralis, 71 magna cerebello-medullaris, 71 D. Dancing mania, 489 Danileu'ski, 57 Darkscheiritsch, 95 Darivin, 155, 388, 462 Deaf-mutism, 436 Deafness, psychical, 100 De Crozant, 278 Degeneration and genius, 465 instances of, 466 theory of, 468 objections to, 469 Deiters, 32 Dejerine, 25, 91, 125 Deliberation, 410 Delusional insanity, 329 Delusions, 329 origin of, 330 Dendi'ons, 31 Descartes, 153 Desire, nature of, 412 Diabetes, 479 Diakanoic, 60 Biemerbrock, 138 Digestion, disorders of, 510 Disgust, feelings of, 401 Dispositions, inherited, 471 Bonders, 75, 203 Double-brain, 312 Doubt, insanity of, 320 Doini, Langdon, 476 Dreams, 286, 290 Drechsel, 58, 60 Drohisch, 335 Dualism theory, 18 Duchenne, 284 Buret, 63, 64, 65. Ecker, 25 Eckhard, 45 Eclampsic imbecility, 501 Effort, feeling of, 388, 425 Emotions, 375 disorders of, 393 theory of, 375 Empirical psychology, 14 Encephalocele, 500 544 INDEX. Endemic cretinism, 502 insanity, 491 Engelmann, 37 Entoptical pulse, 267 Epidemic insanity, 481, 491 Epilepsy, impulses in, 453 Jacksonian, 517 masked, 517 Epileptic idiocy, 501 Esquirol, 263, 449 Eulenherg, 284 Eivalcl, 36, 58 Exner, 139, 152. Exophthalmic goitre, 519 Expression, movements in, 389 physical, 389 External factors in development, 480 Eye-movements, 96 r. F(aret, 342 Fear, morbid states of, 403 Febrile affections and insanity, 515 Fechner, 153, 293, 294, 396 Fechner's law, 179, 180 Feeling, 373 eesthetic, 404 connected with hope and fear, 403 disorders of, 393 inner sense, 400 intellectual, 404 in the insane, 402 of shame, reproach, etc., 404 physiological theory of, 387 rational, 405 relation to knowing, 374 tone of, 383 varieties of, 390 Ferrier, 25, 92, 99, 102, 105, 111, 123, 125, 136, 239, 388, 425, 427 Fibrse proprise, 107 Fibre-cells, 40 Fick, 200 First impressions, 333 Fischer, 57 Flechsig, 91, 93, 99, 106 Flourens, 112, 113, 463 Fluid, cerebro-spinal, 73 Folie a deux, 491 Fore-brain, 130 Forgetfulness, 340 Fossa Sylvii, 71 Fouilee, 294 Fournie, 260 Foveas glandulares, 75 Fox, Long, 82, 83, 84 Franklin, theory of colour-vision, 202 Frohlich, 266 Fromann, 37, 38 Frontal lobe, 126 Fulminating psychoses, 447 Functional hypersemias, 81, 525,. 526 Functions of nerves, 49 G. Galton, 243, 271 Gamgee, 57, 59, 60 Gasquet, 493 Geigel, 85 Generic ideas, 317 Genius and attention, 300 and degeneration, 465 nature of, 462 Geoghegan, 59 Gibson, 88 Globus hystericus, 511 Goldschneider, 186, 218, 220, 222, 285 Golgi, 25, 26, 33, 34, 53 Goller, 203 Goltz, 83, 113, 125, 126, 134, 312 Gotch, 53, 126 Gout and insanity, 476 Go^vers, 3, 100, 113, 135, 174, 175, 278 Grand mal. 342 INDEX. 545 Gh-ashey, 86, 87 Gratiolef, 2o, 93 Griesinger, 166, 260, 276, 449 Growth and develoi^ment, 455 Gruher, 243 Gudden, inferior commissure of, 95 Guislain, 278, 449, 475 Gustatory jpath, 102 H. Hagen, 504 Haig, 85 Hall, Stanley, 219, 220 Hallucinations, 248 by physical suggestion, 268 collective, 268 in dreams, 286 in sane persons, 276 neural process in, 254 pathology of, 274 psycho-motor, 277 varieties of, 260 Hamilton, 93, 94, 107 Hamilton, Sir W., 168, 392 Happiness, feeling of, 397 Harris, 420 Hartmann, 4, 209 Haslam, 273 Head, 52, 281 Plearing, 99 centre for, 99 perversions of, 270 sensation of, 191 Heart, diseases of, 512 Heidenheim, 125 Heitzmann, 37 Helmholtz, o'2, 194, 209, 222, 231, 240 Henoch, 504 Henri, 234 Henschen, 134 Herbart, 17, 21, 392 Hereditary neuroses, 473 Hering, 76, 201 Hermann, 49, 175 Heuhner, 63, 64, 65 Hirsch, 469 Hitsig, 91, 116, 125, 134 Hodgson, 17, 392 Hoffding, 113, 182 HopiJe-Seyler, 60 Horsley, 28, 53, 91, 93, 94, 105, 106, 125, 126. Horu'icz, 374, 384 Houdin, 198 Hubnoff, 125 Hughlings- Jackson, 28, 101, 121, 123, 126, 128, 142, 162, 342, 354, 425, 502, 518, 526 Hume, 17 Hunter, 490 Huxley, 20, 162, 465 llydrencephalocele, 500 Hydrocephalus, 500 Hypakusis, 273 Hjrpalgia, 279 Hypersesthesia, 279 Hyperakusis, 272 Hyperalgia, 279 Hyperattention, 301 results of, 302 Hypergeusia, 265 Hypermnesia, 366 Hyperosmia, 266 Hyperpselaphesia, 279 Iljrpertrophic idiocy, 501 Hypnagogic illusions and halluci- nations, 287 Hypnosis, 629 - amnesia and aphasia in, 440 history of, 529 memory in, 349 mental state in, 531 methods of, 529. symptoms of, 530 volition in, 424 Hypogeusia, 265 Hypopselaphesia, 279 Hyposmia, 266 35 546 INDEX. Idiocy, 449 Illusions, active, 230, 239 definitions of, 228 in dreams, 286 of perception, 229 passive, 229, 230 Images, latent mental, 337 primary and revived, 338 Imagination, 323 a constructive process, 324 images, 326 morbid conditions of, 329 neural process of, 326. Imbecility, 499 Impulses, epileptiform, 452 excessive, 451 general, 452 homicidal, 453 morbid, 450 nerve, 50 sexual, 452 suicidal, 453 Inattention, 302 Incisures of Schmidt, 36 Infancy, disorders of, 499 Inflammatory idiocy, 501 Inherited dispositions, 473 Inhibition, 427 theories of, 428, 429, 431 Insanity of doubt, 320 delusional, 329 Instincts, 375 Intemperance, 477 Intercellular connections, 53 Internal factors of development, 460 Intoxicants, 521 Invariable concomitance theory, 148 Ireland, 282, 312, 406, 436, 475, 514. Irradiation of functions, 115 Irresolution, 448 J. James, 9, 11, 19, 21, 91, 126, 140, 160, 163, 175, 210, 214, 220, 231, 236, 239, 250, 254, 258, 284, 307, 318, 356, 375, 423, 426, 462, 533 Jastrow, 539 Joly, 463 Judgment, 317 degree of perfection of, 318 K. Kammler, 189 Kant, 392 Kiesoiv, 184, 186 Kincesthesia, 283, 442 Kirchhoff, 110, 114, 141 Klinke, 283 Kolliker, 53 Koppe, 271 Krxpelin, 368, 369 Krause, 67, 82 Krolin, 186 Kuhne, 36, 68 Kupffer, 36 Kussmaul, 364 L. Ladd, 10, 12, 18, 49, 111, 147, 187, 199, 207, 213, 221, 224, 384, 442, 633 Laihlin, 198 Landois, 279 Lange, 376 Langendorff, 186 Langer, 73 Latent mental images, 337 Laycock, 121 Lead poisoning, 523 Lecithin, 60 Legrain, 438, 478 Lehmann, 243 Leibnitz, 21, 378 INDEX. 547 Lejjsms, 243 Lethargic state in hypnosis, 530 Leubuscher, 449 Leuhossek, 192 Lewinski, 220, 284 Lewis, Bevan, 25, 26, 28, 29, 30, 38, 39, 40, 42, 43, 68, 70, 72, 91, 344, 359, 400, 453, 521, 539 Lewy, 86 Ley'dig, 37 Lichtenfels, 266 Lichtheim, 434 Liebernieister, 74 Liebreich, 61 Linea terminalis, 71 Lipj)s, 222 Local memories, 142 Locahsation, cerebral, 104 of mental faculties. 111, 211 Logorrhoea, 437 Lotze, 21, 212, 384, 385 Lower centres, consciousness in. 141 Luciani, 91, 139 Ludwig, 425 Lussana, 246 Luys, 368 Lycanthropy, 482 Lyman, 288, 289 Lymph-cisterns, 71 Lymphatic system, 70, 72 M. Magnan, 342 Majendie, foramen of, 78 Marinotti, 26 Masturbation, 506 ^Materialistic theory, 17 Material monad theory, 121 Maudsley, 355, 368, 453, 463 Maury, 289, 483 McDowall, 267 Mechanical restraint, 394, 451 Medullated fibres, 34 Meissner, 32 3Iellus, 103 Memory, 332 active, 333 in general paralysis, 358 in hypnotic states, 349 in organic brain disease, 358 in stupor, 344 local, 142 methods of cultivating, 334 passive, 333 projier, 332 psycho-physical theory of, 335 secondary, 332 Mendoza, 247 Meniere's disease, 272 Meningocele, 500 Menopause, 607 Menstruation, 507 Mental automatism, 342 faculties, 111 pathology, 6 physiology, 6 Mercier, 15, 147, 315, 386, 392, 429, 441, 446 Merkel, 187 Meschede, 408 3Ieyer, 59, 75, 240 Meynert, 57, 65, 70, 80, 82, 87, 91, 101, 106, 109, 115, 120, 127, 130, 144, 389, 419 Michelson, 185 Blickle, 270, 278, 438, 512 Microcephalus, 500 Microkinesis, 456 Micropsychosis, 459 Mill, J. S., 113, 152, 155, 156 Mills, 17, 100, 500 Mimicry of disease, 490 Mind, 149 evolution of, 154 methods of study of, 149 stuff theory, 159, 163 subjectivity of, 143 Misery, 394, 397 Moelli, 91 Moizard, 504 548 INDEX Monakoiv, 91 Money, 504 Monism, 19 Monoideism, 290 Monomania, 380 Moon, influence of, 495 Moral defects, 406 insanity, 405 Morel, 453 Morphinomania, 524 Mosso, 76, 88 Motions and sensation, 172 Motor nerves, 102 3Iott, 91, 92 Movements, 432 in the insane, 432 of eye, 96 of speech, 436 Milller, 60, 258, 388, 425 Multiple monadism, 21 3Iunk, 91, 96, 100, 113, 117, 125, 127, 144 Munsterherg, 156, 217, 222, 293, 419, 427 Muscular sense, 190 perversions of, 282 sensation, perception of, 220 Mutism, 436 Myelocele, 500 Myxoedema, 519 N. Nansen, 37 Nasse, 271 Nativistic theory of perception, 208 Natural selection, adequacy of, 472 Naunyn, 76 Negative after-images, 327 variation, 52 Neigliclc, 246 Nerve-cell, 28 conductivity of, 44 physiology of, 43, 144 processes, 31 sizes, 29 Nerve-elements, energy, 175 impulse, 50 nutrition of, 79 substance, chemical properties of, 56 sp. gr. of, 57 Nerve-fibres, classes of, 49 functions of, 49 non-medullated, 34 structure of, 34 Nerves, motor, 102 sensory, 90 Nervous discharge, 430 resistance, 430 Neuralgia, 279 Neural infei^ence scheme, 128 Neiu'oglia cell elements, 40 Neuro-keratin, 58, 59 Neurons, 31 Neuroses inherited, 475 Newbold, 323 Newington, 344 Msbet, 464, 465 Nordau, 140 Nothnagel, 139 Nuclein in nerve-substance, 68 Nutrition of nerve-elements, 79 0. Object, consciousness, 151, 380 Occasionalists theory, 15 Occupation, influence of, 495 Olfactory centre, 101 Optic fibres, 96 Original capacities, 461 Ormond, 16 Pacchionian granulations, 73 Pain, laws of, 378 Panic, 450 Parageusia, 265 INDEX. 549 Paragraphia, 365 Parakusis, 273 Paralgia, '279 Paralytic idiocy, oOl Paramnesia, 368, 369 Parapliasia, 365 Parens, 60 Parosmia, 266 Passu, 234 Pauihan, 388 Perception, 205 abnormal conditions of, 226 illusions of, 229 of nmscular sensation, 220 of spatial order, 210 of A'isual space, 221 physiological conditions of, 206 theories of, 208 special channels of, 215 Pericellular sac, 72 Perivascular channel of His, 67, 71 system, 68 Perroud; 247 Petit mal, 342 Petroirsky, 58, 60 Pettingen, 195 Philippe , 234 Phonisms, 243 Photisms, 243 Phrenology, 109 Phthisis, 475, 514 Physical environment, 495 Physiological psychology, 9, 12 Pierce, 217 Pinel, 453 Pleasure, laws of, 378 Pollak, 59 Polyideism, 296 Polyzoism, 21 Porencei)halus, 500 Post-hypnotic suggestion, 534 Praefrontal lobes, 134 Pre-established harmony, theory of, 15 Presentationism, 156 Presentative feelings, 391 representative feelings, 391 Pressure phosphenes, 267 spots, 189 Preyer, 217 Projection cell, 33 system, 106 Prosencephalon, absence of, 499 Protagon, 61 Protoplasmic cell, 42 Psychical deafness, 100 Psychological process of inference, 131 Psychology, 3 empirical, 14 Psychopathic epidemics, 481 Psycho-physical parallelism, 11 Psycho-physics, 535 , instruments employed in, 537 lines of investigation, 536 methods, 535 reaction time, 537, 539 Puberty, 506 Puerperium, 507 Pulsatory movements of brain, 77 Pulse in insanity, 513 Purkinje, 198 Q. Quantitative relation between blood and cerebro-spinal fluid, 74 Quinke, on Pacchionian glands. R. Ranvier, nodes of, 35 Ratiocinative method, value of, 133 Recepts, 317 Recollection, 333 Reflex action, 45, 419 attention, 297. Pegis, 279, 523 Regression, law of, 353 Reid, 392 550 INDEX. Keligion as a cause of insanity, 493 Religious impostors, 487 pilgrimages, 487 Remalc, 35 Rendu, 92 Representative feelings, 391 Reproach, feelings of, 404 Re-representative feelings, 391 Resolution, 410 Retinal shadows, 267 Retsius, 25, 40, 192 Revington, 475 Reymond, 92 Rheumatism, 476 Ribot, 293, 301, 335, 342, 343, 345, 353, 369, 449 Ritti, 269 Robertson, 530 Romanes, 239 S. Sachs, 500 Salivation, 510 Sandford, 203 Savage, 240, 265, 267, 273, 276, 279, 343, 344, 476, 516 Schafer, 30, 37, 43, 50, 53, 91, 93, 96, 99, 106, 125, 134, 187, 192 Schiff, 125, 385 Schlossberger, 59 Schneider, 374 Schopenhauer, 209, 374 Schrader, 112 Schreiber, 76 Schidtze, 37 Schwann, 35 Scrofula, 475 Seasons, influence of, 495 Seglas, 277 Senile amnesia, 359 Sensation, 170 analysis of, 170 and i)erception, 171 characters of, 177 excentric projection of, 212 Sensation, function of, 183 local characters of, 183 maximum intensity of, 179 motions affecting, 172 of special senses, 184 quality of, 182 secondary, 243 Sense feelings, 391,393 Sensory paths, 90 perversions, 225 origin of, 225 Sentiments, aesthetic, 393 intellectual, 393 moral, 393 Seppili, 91 Shame, feelings of, 404 Shaiv, 269, 277 Sherrington, 98, 99, 103, 107 Shuttleivorth, 476, 477 Sight, 93, 196 perversions of, 267 Silbermann, 503 Simon, 497 Skae, 453 Smell, 101, 185 centre for, 101 perversions of, 334 Smith, R. Percy, 630 Social environment, 480 Sollier, 378 Soltmann, 503 Somnambulism, 530 Spatial order, perception of, 210 Specific gravity of nerve-sub- stance, 57 Spectral illusions, 483 Si^eculative manias, 489 Speech, after sunstroke, 439 defects of, 437 during fatigue, 438 in general paralysis, 439 in the insane, 437 mechanism of, 433 movements, 436 Spencer, Herbert, 9, 124, 155, 160, 206, 209, 334, 374, 382, 385, 391, 406, 462 INDF.X. 551 Spina bifida, oOO Spinal affections, ol9 Spiritual tlieory, 15 Spitska, 1>{)9, 500, 506 Stammering, 437 Starr, 91 Steinbach, 198 Steinbriigge, 246 Steiner, 111, 113 Stellate fibre-cells, 41 Stewart, 335 Stumpf, 217, 222 Stuttering, 437 Subarachnoidal space, 73 Subject-consciousness, 151, 380 Suggestion, 334, 533 Sully, 151, 205, 229, 238, 293, 300, 305, 375, 411, 412, 4:6 Sunstroke, 504, 505 Surditas verbalis, 434 Sympathy, 393, 401 , 490 Syphilis, 476, 516 congenital, 476 T. Tactile corpuscles, 187 Tactual i)erception, 277 Tamhurini, 491 Tarantism, 489 Taste, 102, 184 centre, 102 perversions of, 265 Taylor, 453 Teeth in insanity, 510 Telepathic hallucinations, 268 Temperaments, 378, 394 Temperature sense, 189 spots, 189 Thane, 96 Thelohan, 234 Thovipson, 475 Thudicum, 61 Tigretier, 489 Time relationshix^s of sensations, 380 Tinnitus aurium, 272 Tone of feeling, 379, 380 Tonnini, 491 Touch, centre for, 92 sensations of, 185 Traumatic idiocy, 502 Trigonum olfactorium, 101 Tripier, 91 Trollard, 75 Tuke, Baity, 23, 88, 268 Tuke, Hack, 6, 248, 269, 277, 290, 405, 490, 495, 532 Tumultus sermonis, 365 Turner, 25 Tyndall, 9 U. Unconscious cerebration, 165 Urbantachitsch, on secondary sen- sations, 247 Urinary system, diseases of, 509 Uterus, diseases of, 508 V. Van der Kolk, 475 Vascular supply of brain, 63 Vaso-motor centre, 81 Velocity of blood circulation, 85 Venous circulation, 74 Verbigeration, 437 Veyssiere, 92 Vicq d'Azyr, 108 Vierordt, 198 . Vignier, 235 Visual ai)paratus, 95 centre, 95 space, perception of, 221 Voigt, 59 Volition, 409 a delayed reflex, 411 during hypnosis, 424 nature of, 412 psycho-physical j)rocess of, 417 Volkmann, 221, 222, 236, 373, 395 552 INDEX. Voluntary action, 421, 442 Von.Jaksch, 58, 69 Von Kries, 200, 217 Vulpian, 111 W. Wallace, 15o Waller, 115, 118, 119, 126, 131, 145, 156, 425, 538 Ward, 156, 157, 164, 172, 176, 257, 294, 374 Warner, 456 Water in nerve-substance, 67 Weber, 170, 179, 182, 184, 185, 219 Weisbach, 57 Weismann, 472 Wernicke, 106, 364, 433 Westphal, 439 Wiglesworth, 477 Will, 409 as a delayed reflex, 411 definition of, 409 freedom of, 413 impairment of, 448 'A Will, nature of, 412 psycho-physical processes of, 417 Willis, circle of, 77 Winslow, 367 Witchcraft, 484 Woakes, 83 Word-blindness, 365 deafness, 100, 366 Worm-Muller, 59 Wundt, 19, 91, 125, 130, 156, 180, 184, 201, 205, 209, 219, 222, 292, 294, 374, 377, 386, 392, 425 Wyllie, 363 Young-Helmholts theory of colour vision, 201 Z. Ziehen, 14, 46, 173, 175, 179, 182, 261, 289, 292, 295, 308, 331, 379, 415, 421, 433 Pardon & Sons Printers, Wine Office Court, Fleet Street, London, E.G. /? Z' ^ Cl^lXQ, n SOOTH PROPER QN p$hsonai^i^e;sepvp! m^jj