^^Aavjian-^vv> ^ommww '^momow ?Aavaani^ ^^V\tUNIVERS/4 &Aav8ani^ ^(7Aavaan-3^ ^5MEUNIVER% ^ i 3 ^ _ § fe ^•UNIVER% ^ aWEUNIVER% 3. — is <(JT30NVS(n'^ ^/^a3AINfl-3«^ ^iU3NVS0V^" ^/JaJAINniVtt-' ^^^^E•UN1VER% ^lOSMElfj^ ^mmwj^ i^UBRARVO^ ^ THE PHYSICAL BASIS OF MIND. Mill; lllustralioits. 3/ff BEIiXG THE SECOjVD SERIES PEOBLEMS OF LIFE AND M GEOEGE HENEY LEWES. BOSTON AND NEW YORK : HOUGHTON, MIFFLIN AND COMPANY. €f)C JaibCDJiOe tOrc^i, Cambrilrjje. ISOL AUTHOR'S EDITION. From Advance Sheets. The Riverside Press, Cambridge, Mass., U. S. A. Printed by H. O. Houghton & Company. 3 PREFACE The title indicates that this volume is restricted to the group of material conditions which constitute the organ- ism in relation to the physical world — a group which furnishes the data for one half of the psychologist's quest; the other half being furnished by historical and social conditions. The- Human Mind, so far as it is accessible to scientific inquiry, has a twofold root, man being not only an animal organism but an unit in the social organism ; and hence the complete theory of its functions and faculties must be sought in this twofold direction. This conception ( which has been declared " to amount to a revolution in Psychology " ), although slowly prepared by the growing conviction that Man could not be isolated from Humanity, was first expounded in the opening volume of these Problems of Life and Mind; at least, I am not aware that any predecessor had seen lioia the specially human faculties of Intellect and Conscience were products of social factors co-operatihg with the animal factors. In considering the Physical Basis a large place must be assigned to the mechanical and chemical relations which are' involved in organic functions ; yet we have to recognize that this procedure of Analysis is artificial and preparatory, that none of its results are final, none rep- resent the synthetic reality of vital facts. Hence one leading object of the following pages has been every- where to substitute the biological point of view for the VI PREFACE. metaphysical and mechanical points of view which too often obstruct research — the one finding its expression in spiritualist theories, the other in materialist theories ; both disregarding the plain principle that the first req- uisite in a theory of biological phenomena must be to view them in the light of biological conditions : in other words, to fix our gaze upon what passes in the organism, and not on what may pass in the laboratory, where the conditions are different. Analysis is a potent instrument, but is too often relied on in forgetfulness of what consti- tutes its real aid, and thus leads to a disregard of all those conditions which it has artificially set aside. We see this in the tendency of anatomists and physiologists to assign to one element, in a complex cluster of co- operants, the significance whicli properly belongs to that cluster : as when the property of a tissue is placed exclu- sively in a single element of that tissue, the function of an organ assigned to its chief tissue, and a function of the organism to a single organ. Another object has been to furnish the reader unin- structed in physiology with such a general outline of the structure and functions of the organism, and such details respecting the sentient mechanism, as may awaken an interest in the study, and enable him to understand the application of Physiology to Psychology. If he comes upon details whicli can only interest specially educated students, or perhaps only by them be really understood, he can pass over these details, for their omission will not seriously affect tlie bearing of the general principles. I have given the best I had to give ; and must leave each reader to find in it whatever may interest him. The uses of books are first to stimulate inquiry by awakening an interest ; secondly, to clarify and classify the knowledge already gained from direct contemplation of the phe- nomena. They are stimuli and aids to observation and PREFACE, Vll thought. They should never be allowed to see for us, nor to think for us. The volume contains four essays. The first, on the NatiLre of Life, deals with the speciality of organic phe- nomena, as distinguished from the inorganic. It sets forth the physiological principles which Psychology must in- cessantly invoke. In the course of the exposition I have incorporated several passages from four articles on Mr. Darwin's hypotheses, contributed to the Fortnightly Re- view during the year 1868. I have also suggested a modification of the hypothesis of Natural Selection, by extending to the tissues and organs that principle of com- petition which Mr. Darwin has so luminously applied to organisms. Should this generalization of the "struggle for existence" be accepted, it will answer many of the hitherto unanswerable objections. The second essay is on the Nervous Mechanism, setting forth what is known and what is inferred respecting the structure and properties of that all-important system. If the sceptical and revolutionary attitude, in presence of opinions currently held to be established truths, surprises or pains the reader unprepared for such doubts, I can only ask him to submit my statements to a similar scepticism, and confront them with the ascertained evidence. After many years of laborious investigation and meditation, tlie conclusion has slowly forced itself upon me, that on this subject there is a "false persuasion of knowledge" very fatal in its influence, because unhesitatingly adopted as the ground of speculation both in Pathology and Psychol- ogy. This persuasion is sustained because few are aware how mucli of what passes for observation is in reality sheer hypothesis. I have had to point out the great extent to which Imaginary Anatomy has been unsuspect- ingly accepted ; and hope to liave done something towards raising a rational misgiving in the student's mind respect- Vm PREFACE. ing "the superstition of the nerve-cell" — a superstition \vhicli I freely confess to have shared in for many years. The third essay treats of Animal Automatism. Here the constant insistance on the biological point of view, while it causes a rejection of the mechanical theory, ad- mits the fullest recognition of all the mechanical relations involved in animal movements, and tlms endeavors to rec- oncile the contending schools. In this essay I have also attempted a psychological solution of that much-debated question — the relation between Body and Mind. This solution explains why physical and mental phenomena must necessarily present to our apprehension such pro- foundly diverse characters ; and shows that JMaterialism, in attempting to deduce the mental from the physical, puts into the conclusion what the very terms have ex- cluded from the premises ; whereas, on the liypothesis of a physical process being only the objective aspect of a mental process, the attempt to interpret the one by the other is as legitimate as the solution of a geometrical problem by algebra. In the final essay the Ecjlcx Theory is discussed ; and here once more the biological point of view rectifies the error of an analysis which has led to the denial of Sensi- bility in reflex actions, because that analysis has over- looked the necessary presence of the conditions which determine Sensibility. In these chapters are reproduced several passages from the Physiology of Common Life. Accordino- to my orioinal intention, this volume was to have included an exposition of the part I conceive the brain to play in physiological and psychological processes, but that must be postponed until it can be accompanied by a survey of psychological processes which would ren- der the exposition more intelligible. The rKiouv, March, 1877. CONTENTS. PROBLE]M I. THE NATURE OF LIFE. CHAPTER I. PAGE The Problem; stated '^ (The Position of Biology) 4 {Organisms) ....••••• ° {Vital Force) 1* {Vital Force controlling Physical and Chemical Forces) . 16 CHAPTER 11. Definitions of Life • .24; CHAPTER IIL Organism, Organization, and Organic Substance . . 37 {Organism and Medium) ...... 45 {The Hypothesis of Germinal Matter) .... 57 {Organisms and Machines) ...... 67 CHAPTER IV. TuE Properties and Functions 70 {Does the Function determine the Organ ?) ■ . . 78 CHAPTER V. Evolution 89 {Natural Selection and Organic Affinity) . . . 115 {Mecajntulation) . . . . . . . .152 CONTENTS. PROBLEM II. THE NERVOUS MECILVNISM. CHAPTER I. Survey of the System 157 {The Early Forms of Ncrve-Centres) .... 168 {The Peripheral Si/stem) ....... 171 {Ganglia and Centres) 172 CHAPTER II. Tue Functional Relations of the Nervous System . T^G CHAPTER III. Neurility 189 {Origin of Nerve-Force 201 {The Hypothesis of Specific Energies) .... 207 CHAPTER IV. Sensibility 211 CHAPTER V. Action without Nerve-Centres 227 CHAPTER VI. What is taught by Embryology? 237 CHAPTER VII. The Elementary Structure of the Nervous System . 251 {Difficulties of the Investigation) ..... 252 {The Nerve-Cell) 258 {The Nerves) 270 {The Neuroglia) 273 {The Relations of the Organites) 278 {Recapitulation) 299 CONTENTS. XI CHAPTER VIII. TuE Laws of Nervous Activity (The Energy of Neurility) (The Propagation of Excitation) (Stimuli) ...... (Stimulation) ..... (The Late of Discharge) (The Law of Arrest) (The Hypothesis of Inhibitory Centres) . (Anatomical Interpretation of the Laws) 310 311 314 321 324 32G 333 33G 339 PROBLEM in. ANIMAL AUTOJ^IATISM. CHAPTER L The Course of Modern Thought .... 345 CHAPTER IL The Vital Mechanish 363 CHAPTER IIL The Relation of Body and Mind 376 CHAPTER IV. Consciousness and Unconsciousness . 399 CHAPTER V. Voluntary and Involuntary Actions 415 CHAPTER VL The Problem stated 431 CHAPTER VIL Is Feeling an Agent? 440 xn CONTENTS. PROBLEM IV. THE REFLEX THEORY. CHAPTER L The Problem stated 467 CHAPTER IL Deductions from General Laws 490 CHAPTER IIL Inductions from Particular Observations . . . 509 {Cerebral Reflexes) . 511 {Discrimination) . 520 {.Memory) . . ' 522 '{Instinct) 522 {The Mechanism of Instinct) . . . . . . 536 {Acqriisition) . . . 546 CHAPTER IV. Negative Inductions 550 PROBLEM I, THE NATURE OF LIFE. "La Physiologie a pour but d'exposer les phenomenes de la vie luimaine et les conditions d'oii ils dependent. Pour y arriver d'une maniere sure, 11 faut necessairement avant tout determiner quels sont les phenomenes qu'on designe sous le nom de vie en general. C'est pourquoi la premiere chose a faire est d'etudier les proprietes geuerales du corps qu'on appelle organiques ou vi- vans." — TiEDEMANN, Traite de Physiologie de V Homme, I. 2. "Some weak and inexperienced persons vainly seek by dialectics and far- fetched, arguments either to upset or establish things that are only to be founded on anatomical demonstration and believed on the evidence of the senses. He who truly desires to be informed of the question in hand must be lield bound either to look for himself, or to take on trust the conclusions to which they who have looked have come." — Harvey, Second Dissertation to Riolan. THE NATURE OF LIFE. CHAPTER I. THE PROBLEM STATED. 1. Although for convenience we use the terms Life and Mind as representing distinct orders of phenomena, the one objective and the other subjective, and although for centuries they have designated distinct entities, or forces having different substrata, we may now consider it sufficiently acknowledged among scientific thinkers that every problem of Mind is necessarily a problem of Life, referring to one special group of vital activities. It is enough that Mind is never manifested except in a living organism to make us seek in an analysis of organic phe- nomena for the material conditions of every mental fact. Mental phenomena when observed in others, although interpretable by our consciousness of what is passing in ourselves, can only be objective phenomena of the vital organism, 2. On this ground, if on this alone, an acquaintance with the general principles of structure and function is indispensable to the psychologist ; although only of late years has this been fully recognized, so that men pro- foundly ignorant of tlie organism have had no hesitation in theorizing on its highest functions. In sayinjr that such knowledge is indispensable, I do not mean that in the absence of such knowledge a man is debarred from under- standing much of the results reached by investigators. 4 THE niYSICAL BASIS OF MIXD. nor that he may not himself make useful observations and classiiieations of iJsychological facts. It is possible to read books on Natural History with intelligence and profit, and even to make good observations, without a scientific groundwork of biological instruction ; and it is possible to arrive at empirical facts of hygiene and medi- cal treatment without any physiological instruction. But in all three cases the absence of a scientific basis will ren- der the knowledge fragmentary and incomplete ; and this ought to deter every one from offering an opinion on de- batable questions which pass beyond the limit of subjec- tive observations. The psychologist who has not prepared himseK by a study of the organism has no more right to be heard on the genesis of the psychical states, or of the relations between body and mind, than one of the laity has a right to be heard on a question of medical treat- ment. THE rOSITIOX OF BIOLOGY. 3. Science is the systematic classification of Experi- ence. It postulates unity of Existence with great varieties in the Modes of Existence ; assuming that there is one Matter everywhere the same, under great diversities in the complications of its elements. The distinction of Modes is not less indispensable than the identification of the elements. These Modes range themselves under three supreme heads : Force, Life, ]\lind. Under the first, range the general properties exhibited by cdl substances ; under the second, the general properties exhibited by organized substances ; under the third, the general properties ex- hibited by organized animal substances. The first class is subdivided into Physics, celestial and terrestrial, and Chemistry. Physics treats of substances which move as masses, or which vibrate and rotate as molecules, without undergoing any appreciable change of structural integrity ; THE NATURE OF LIFE. 5 they show changes of position and state, without corre- sponding changes in their elements. Chemistry treats of substances which undergo molecular changes of composi- tion destructive of their integrity. Thus the blow which simply moves one body, or makes it vibrate, explodes another. The friction which alters the temperature and electrical state of a bit of glass, ignites a bit of phos- phorus, and so destroys its integrity of structure, convert- ing phosphorus into phosphoric acid. 4. The second class, while exhibiting both physical and chemical properties, is markedly distinguished by the addition of properties called vital. Their peculiarity con- sists in this : they undergo molecular changes of compo- sition and decomposition which are simultaneous, and hy this simultaneity preserve their integrity of structure. They change their state, and their elements, yet preserve their unity, and even when differentiating continue specific. Unlike all other bodies, the organized are born, grow, de- velop, and decay, through a prescribed series of graduated evolutions, each stage being the indispensable condition of its successor, no stage ever appearing except in its serial order. 5, The third class, while exhibiting all the character- istics of tlie two preceding classes, is specialized by the addition of a totally new property, called Sensibility, which subjectively is Feeling. Here organized substance has become animal substance, and Vegetality has been developed into Animality by the addition of new factors, — new complexities of the elementary forces. Many, if not most, philosophers postulate an entirely new Exist- ence, and not simply a new Mode, to account lor the manifestations of Mind ; they refuse to acknowledge it to Ijo a vital manifestation, they demand that to Life be added a separate substratum, the Soul. Tliis is not a point to be discussed here. We may be content with the 6 THE niYSICAL BASIS OF MIND. assertion that liowever great the phenomenal difference between lliunanity and Aniraality (a difference we shall hereafter see to be the expression of a new factor, namely, the social factor), nevertheless the distinctive attribute of Sensibility, out of which rise Emotion and Cognition, marks the inseparable kinship of mental wdth vital jihe- nomena. Thus all the various Modes of Existence may, at least in their objective aspect, be ranged under the two divis- ions of Inorganic and Organic, — Non-living and Living, — and these are respectively the objects of the cosmologi- cal and the biological sciences. 6. The various sciences in their serial development develop the wliole art of Method. Mathematics devel- ops abstraction, deduction, and definition ; Astronomy abstraction, deduction, and observation ; Physics adds ex- periment ; Chemistry adds nomenclature ; Biology adds classification, and for the first time brings into promi- nence the important notion of conditions of existence, and the variation of phenomena under varying conditions : so that the relation of the organism to its medium is one never to be left out of sight. In Biology also clearly emerges for the first time what I regard as the true notion of causality, namely, the procession of causes, — the com- bination of factors in the product, and not an ah extra de- termination of the product. In Vitality and Sensibility we are made aware that the causes are in and not outside the organism ; that the organic effect is the organic cause in operation ; that there is autonomy but no autocracy ; the effect issues as a resultant of the co-operating condi- tions. In Sociology, finally, w^e see brought into promi- nence the historical conditions of existence. From the due appreciation of the conditions of existence, material and historical, we seize the true significance of the principle of Relativity. THE NATURE OF LIFE. ■ 7 7. Having thus indicated the series of the abstract sciences we have now to consider more closely the char- acter of Biology. The term was proposed independently yet simultaneously in Germany and France, in the year 1802, by Treviranus and Lamarck, to express " the study of the forms and phenomena of Life, the conditions and laws by which these exist, and the causes which produce them." Yet only of late years has it gained general ac- ceptance in France and England. The term Cosmology, for what are usually called the Physical Sciences, has not yet come into general use, although its appropriateness must eventually secure its recognition. Biology, — the abstract science of Life, — -embracing, the whole organic world, includes Vegetality, Animality, and Humanity ; the biological sciences are Phytology, Zoology, and Anthropology. Each of the sciences has its cardinal divisions, statical and dynamical, namely. Mor- phology — the science of form, — and Physiology — the science of function. Morphology embraces — 1°, Anatomy, i. e. the descrip- tion of the parts then and there present in the organism ; and these parts, or organs, are further described by the enumeration of their constituent tissues and elements ; and of these again the proximate principles, so far as they can be isolated without chemical decomposition. 2°, Or- (lanogcny, i. e. the history of the evolution of organs and tissues. Pliysiology embraces the properties and functions of the tissues and organs — the primary conditions of Growth and Development out of which rise the higher functions bringing the organi.sm into active relation with the sur- rounding medium. Tlie first group of properties and functions are called those of vegetal, or organic life ; the second those of animal, or relative life. THE rilYSICAL BASIS OF MIND. OKGANISMS. 8. It will be needful to fix M'itli precision the terms, Ori^anism, Life, Property, and Function. An organism, although usually signiiying a more or less complex unity of organs, because the structures which first attracted scientific attention were all thus markedly distinguished from inorganic bodies, has by the gradual extensions of -research been necessarily generalized, till it now stands for any organized substance capable of inde- pendent vitality : in other words, any substance having the specific combination of elements which manifests the serial phenomena of growth, development, and decay. There are organisms that have no differentiated organs. Thus a microscopic formless lump of semifluid jelly-like substance (Protoplasm) is called an organism, because it feeds itself, and reproduces itself. There are advantages and disadvantages in such extensions of terms. These are notable in the parallel extension of the term Life, which originally expressing only the complex activities of com- plex organisms, has come to express the simplest activities of protoplasm. Thus a Monad is an organism ; a Cell is an organism ; a Plant is an organism ; a Man is an organ- ism. And each of these organisms is said to have its Life, because " Through all the mighty commonwealth of things Up from the creeping worm to sovereign man " * there is one fundamental group of conditions, one organized substance, one vitalit3^ Obviously this unity is an abstraction. In reality, the life manifested in the Man is not the life manifested in the Monad : he has Functions and Faculties which the Monad has no trace of; and if the two organisms have certain vital characteristics in common, this unity is only * WORDSWOKTH. THE NATURE OF LIFE. 9 recognized in an ideal construction which lets drop all con- crete differences. The Life is different when the organism is different. Hence any definition of Life would be man- ifestly insufficient which while it expressed the activities of the Monad left unexpressed the conspicuous and im- portant activities of higher organisms. A sundial and a repeater will each record the successive positions of the sun in the heavens ; but although both are instruments for marking time, the sundial will not do the work of the repeater ; the complexity and delicacy of the watch mech- anism are necessary for its more varied and delicate uses. A semifluid bit of protoplasm will feed itself ; but it will not feed and sustain a complex animal ; nor will it feel and think. 9. Neglect of this point has caused frequent confusion in the attempts to give satisfactory definitions. Biologists ouglit to have been warned by the fact that some of the most widely accepted definitions exclude the most con- spicuous phenomena of Life, and are only applicable to the vegetable world, or to the vegetal processes in the animal world. A definition, however abstract, should not exclude essential characters. The general consent of mankind has made Life synonymous with Mode of Existence. By the life of an animal is meant the existence of that animal : when dead the animal no longer exists ; the substances of which the organism was composed exist, but under another mode ; their connexus is altered, and the organ- ism vanishes in the alteration. It is a serious mistake to call the corpse an organism ; for that special combination which constituted the organism is not present in the corpse. Tliis misconception misleads some speculative minds into assigning life to the universe. The universe assuredly exists, l)ut it does not live ; its existence can only bo identified with life, such as we observe in organisms, by a complete obliteration of the speciality which the term 1 * 10 THE niYSICAL BASIS OF MIND. Life is meant to designate. Yet many have not only pleased themselves with such a conception, but have con- ceived the universe to be an organism fashioned, directed, and sustained by a soul like that of man — the anima mundi. This is to violate all scientific canons. The life of a plant-organism is not the same as the life of an animal-organism ; tlie life of an animal-organism is not the same as the life of a human-organism ; nor can the life of a human-organism be the same as the life of the world- organism. The unity of Existences does not obliterate the variety of Modes ; yet it is the speciality of each ]\Iode Avhicli Science investigates ; to some of these Modes the term Life is consistently applied, to others not ; and if we merge them all in a common term, we must then invent a new term to designate the Modes now included under nfe. 10. In resisting this unwarrantable extension of the term I am not only pointing to a speculative error, but also to a serious biological error common in both spirit- ualist and materialist schools, namely that of assigning Life to other than organic agencies. Instead of recogniz- ing the speciality of this Mode of Existence as dependent on a speciality of the organic conditions, the spiritualist assigns Life to some extra-organic Vital Principle, the materialist assigns it to some inorganic agent — physical or chemical. Waiving for the present all discussion of Vitalism, let us consider in what sense we must separate organic from all inorganic phenomena. 11. There is a distinction between inorganic and organic which may fitly be called radical : it lies at the root of the phenomena, and must be accepted as an ultimate fact, although the synthesis on which it depends is analytically reducible to a complication of more primitive conditions. It has been already indicated in § 5. All organisms above the very simplest are syntheses of three terms : Structure, THE NATURE OF LIFE. H Aliment, and Instrument. Crystals, like all other anor- ganisms have structure, and in a certain sense they may be said to grow {Mineralia crescunt), though the growth is by increase and not by modification : * the motherlye, which is the food of the crystal, is never brought to the crystal, nor prepared for it, by any instrumental agency of the crystal. Organisms are exclusively instrumental ; the organ is an instrument. The structural integrity of an organism is thus preserved through an alimentation which is effected through special instruments. Nothing like this is visible in anorganisms. The increase of a crystal is further distinguishable from the growth of an organism, in the fact of its being simple accretion without development : and the structure of the crystal is distinguishable from that of an organism in the fact that its integrity is preserved by the exclusion of all molecular change, and not by the simultaneous changes of molecular decomposition and recomposition. Inor- ganic substances are sometimes as unstable as organic, sometimes even more unstable ; but their instability is the source of their structural destruction — they change into other species ; whereas the instability of organized substances {not of organic) is the source of their structural integrity : the tissue is renovated, and its renovation is a consequence of its waste. 12. But while the distinction is thus radical, when we \iew the organism from the real — that is, from the syn- thetic point of view — we must also urge the validity of * Crystals not only grow by assimilation, but even repair injuries, with a certain superficial resemblance to the repair of animal tissues. Thu.s, according to tlic expiM-iments of JonD.VN cited by Sir .Tames Pagkt {Lectures o-fi Surgical ratkoUxjy, I. 153, and 2d ed. p. 115), an octohe- dral crystal of alum, if fractured and replaced in a motherlye will in a few days exhibit a complete restoration of the original form. The whole crystal increases, but the increase is greatest on the broken edge, and the octohcdral form is completely renewed. (Comji. § 113.) 12 THE PHYSICAL BASIS OF MIND. the analytical point of view, which seizes on the con- ditions here coni})licated in a special group, and declares these conditions to he severally recognizahle equally in anorganisms and in organisms. All the fundamental ])ro])erties of Matter are recognizahle in organized JMatter. Tlie elementary substances and forces familiar to physi- cists and chemists are the materials of the biologist ; nor has there been found a single organic substance, however special, that is not reducible to inorganic elements. We see, then, that organized Matter is only a special combina- tion of that which in other combinations presents chemical and physical phenomena ; and we are prepared to find Chemistry and Physics indispensable aids in our analysis of organic phenomena. Aids, but only aids ; indispensa- ble, but iusufficient. 13. There is therefore an ambiguity in the common statement that organized matter is not ordinary matter. Indisputable in one sense, this is eminently disputable when it is interpreted as evidence of a peculiar Vital Force "wholly unallied with the primary energy of Motion." If by " ordinary matter " be meant earths, crystals, gases, vapors, then assuredly organized matter is not ordinary. " Between the living state of matter and its non-living state," says Dr. Beale," there is an absolute and irreconcil- able difference ; so far from our being able to demonstrate that the non-living passes by gradations into or gradually assumes the scale or condition of the living, the transition is sudden and abrupt, and matter already in the living state may pass into the non-living condition in the same sudden and complete manner." * The ambiguity here is sensible in the parallel case of the difference between crystallizable and coagulable matter, or between one crys- tal and another. If we can decompose the organic into * Cited by Dry.sdale, Life and the Equivalence of Force, Part II. p. 149. THE NATURE OF LIFE. 13 the inorganic, this shows that the elements of the one are elements of the other; and if we are not yet able to recompose the inorganic elements into organic matter (not at least in its more complex forms), may this not be due to the fact that we are ignorant of the proximate synthesis, ignorant of the precise way in which the ele- ments are combined ? I may have every individual part of a machine before me, but unless I know the proper position of each, I cannot with the parts reconstruct the machine. Indeed the very common argument on which so much stress is laid in favor of some mysterious Prin- ciple as the source of organic phenomena, namely, that human skill is hopelessly baffled in the attempt to make organic substances, still more a living cell, is futile. Men can make machines, it is said, but not organisms, ergo organisms must have a spiritual origin. But the fact is that no man can make a machine, unless he take advan- tage of the immense traditions of our race, and apply the skill of millions who have worked and thought before him, slowly and tentatively discovering the necessary means of mechanical effect. The greatest thinker, or the deepest scholar, who did not place himself in the line of the tra- dition, and learn the principles of mechanism, and the properties of the materials, would Ije as incapable of mak- ing a watch, as the physiologist now is of making a cell. But the skill of man has already succeeded in making many organic substances, and will perhaps eventually succeed in making a cell, certainly will, if ever the special synthesis which binds the elements together should be discovered. Not that such a discovery would alter the position of Biology in relation to Chemistry. The making of albumen, nay, the construction of an organism in the laboratory, would not in tlie least affect the foundation of Biology, would not obliterate the radical difference be- tween organisms and anorganisms. It is the speciality of 14 THE niYSICAL BASIS OF MIND, organic phenomena wliicli gives them a special place, although the speciality may only be due to a complication of general agencies. VITAL FORCE. 14. A similar ambiguity to that of the phrase " ordinary matter " lies in the equally common phrase " Vital Force," ■which is used to designate a special group of agencies, and is then made to designate an agent which has no kinship with the general group ; that is to say, instead of being employed in its real signification — that which alone represents our knowledge — as the abstract statical ex- pression of the complex conditions necessary to the mani- festation of vital phenomena, or as the abstract dynamical expression of the phenomena themselves, it is employed as an expression of tlieir unknown Cause, which, because unknown, is dissociated from the known conditions, and erected into a mysterious Principle, having no kinship with ]\Iatter. In the first sense the term is a shorthand symbol of what is known and inferred. The known con- ditions are the relations of an organism and its medium, the organism being the union of various substances all of which have tlieir peculiar properties when isolated ; properties tliat disappear in the union, and are replaced by others, which result from the combination — as the properties of chlorine and sodium all disappear in the sea-salt which results from their union ; or as the proper- ties of oxygen and the properties of hydrogen disappear and are replaced by the pro]3erties of water. When there- fore Vital Force is said to be exalted or depressed, the phrase has rational interpretation in tlie alteration which has taken place in one or more of the conditions, internal and external : a change in the tissues, the plasma, or the environment, exalts or depresses the energy of the vital manifestations ; and to suppose that this is effected THE NATUKE OF LIFE. 15 through the agency of some extra-organic Principle is a purely gratuitous fiction. 15. That we ai'e ignorant of one or more of the indis- pensable conditions symbolized in the abstract term Vi- tality or Vital Force, is no reason for quitting the secure though difficult path of Observation, and rushing into the facile but delusive path of Fiction, which proposes metempirical Agents (in the shape of Vital and Psychical Principles) to solve the problems of Life and Mind. We may employ the term Vital Force to label our observa- tions, togetlier with all that still remains unobserved ; and we are bound to recognize the line which separates observation from inference, what is proved from what is inferred ; but while marking the limits of the known, we are not to displace the known in favor of the un- known. It is said that because of our ignorance we must assume these causes of Life and Mind to be unallied with known material causes, and belonging to a different order of existences. This is to convert ignorance into a proof ; and not only so, but to allow what we do not know to dis- place what we do know. The organicist is ready to admit that much has still to be discovered ; the vitalist, taking his stand upon this unknown, denies that what lias been discovered is really important, and declares that the real agent is wholly unallied to it. How can he know this ? He does not know it ; he assumes it ; and the chief evidence he adduces is that the ordinary laws of inorganic matter are incapable of explaining tlie plienomcna of or- ganized matter; and that pliysicaland clienucal forces are controlled l)y vital force. I accept botli these positions, stripping tlicm, however, of tlieir ainl)iguities. The laws of ordinary matter are clearly incompetent in tlie case of matter which is not ordinary, but specialized in organisms ; and when we come to treat of Materialism we sliall see how unscientific have been the hypotheses which disre- IC THE niYSICAL BASIS OF MIND. gard the distinction. The question of control is too inter- esting and important to be passed over here. VITAL FOHCE CONTROLLING PHYSICAL AND CHEMICAL FOKCES. 16. The facts relied on by the vitalists are facts which every organicist will emphasize, though he will interpret them difiereutly. When, for example, it is said that " Life resists the effect of mechanical friction," and the proof adduced is the fact that the friction which will thin and M-ear away a dead body is actually the cause of the thickening of a living — the skin of a laborer's hand being thickened by his labor ; the explanation is not that Life, an extra-organic agent, " resists mechanical friction " — for the mechanical effect is not resisted (the skin is rubbed off the rower's hand sooner than the w^ood is rubbed off the oar) — but that Life, i. e. organic activity repairs the waste of tissue. 17. Again, although many of the physical and chemical processes which invariably take place under the influences to which the substances are subjected out of the organism, will not take place at all, or will take place in different degrees, when the substances are in the organism, this is important as an argument against the notion of vital phenomena being deducible from physical and chemical lav)s, but is valueless as evidence in favor of an extra- organic agent. Let us glance at one or two striking ex- amples. 18. Xo experimental inquirer can have failed to observe the often contradictory results which seemingly unimpor- tant variations in the conditions bring about ; no one can have failed to observe what are called chemical affinities wholly frustrated by vital conditions. Even the ordinary laws of Diffusion are not always followed in the organism. The Amceba, though semifluid, resists diffusion when alive ; but when it dies it swells and bursts by osmosis. The THE NATURE OF LIFE. 17 exchange of gases does not take place in the tissues, pre- cisely as in our retorts. The living muscle respires, that is, takes up oxygen and gives out carbonic acid, not on the principle of simple diffusion, but by two separable ])hysiological processes. The carbonic acid is given out, even when there is no oxygen whatever present in the atmosphere, and its place may then be supplied by hydro- gen; and this physiological process is so different from the physical proqess which goes on in the dead muscle (the result of putrefaction), that it has been proved by Pianke to go on when the temperature is so low that all putrefaction is arrested. The same experimenter finds * that whereas living nerve will take up, by imbibition, 10 per cent of potash salts, it will not take up 1 per cent of soda salts, presented in equal concentration ; and he points to the general fact that the absorption of inorganic sub- stances does not take place according to the simple laws of diffusion, but tliat living tissues have special laws, the nerve, for instance, having a greater affinity for neutral potash salts than for neutral soda salts. Let me add, by way of anticipating the probable argument that may urge this in favor of Vital Principle which is lightly credited with the prescience of final causes, that so far from this " elective affinity " of the tissues being intelligent and always favorable, Eanke's experiments unequivocally show that it is more active towards destructive, poisonous sub- stances, than towards the reparative, alimentary substances ; which is indeed consistent with the familiar experience that poisons are more readily absorbed than foods, wlien both are brought to the tissues. Thus it is well known that of all the salts the sulphate of copper is that which plants most readily absorb — and it kills them. The spe- cial affinities disappear as the vitality disappears, and dying plants absorb all salts equally. * Ranke, Die Lchensbcdingungcn dcr Nerven, 18G8, p. 80. 18 THE niYSICAL BASIS OF MIND. 19. The more the organism is studied, the more evident it will become that the simple laws of diffusion, as pre- sented in anorganisms rarely if ever take effect in tissues ; in other words, what is called Imbibition in Physics is the somewhat different process of Absorption in Physiol- ogy.* The difference is notable in this capital fact, that whereas the physical diffusion of liquids and gases is determined by differences of density, the physiological absorption of liquids and gases is determined by the mo- lecular organization of the tissue, which is perfectly indif- ferent to, and resists the entrance of, all svibstances incapa- ble of entering into organic combination, either as aliment or poison. A curious example of the indifference of or- ganized substances to some external influences and their reaction upon others, is the impossibility of provoking ciliary movement in an epithelial cell, during repose, by any electrical, mechanical, or chemical stimuli except pot- ash and soda. Virchow discovered that a minute quan- tity of either of these, added to the w^ater in which the cell floated, at once called forth the ciliary movements. 20. The true meaning of the resistance of Vitality to ordinary chemical affinity is, that the conditions involved in the phenomena of Vitality are not the conditions in- volved in the phenomena of Chemistry ; in other words, that in the living organism the substances are placed under conditions different from those in which we observe these substances when their chemical affinities are dis- played in anorganisms. But we need not go beyond the laboratory to see abundant examples of this so-called re- sistance to chemical affinity, when the conditions are altered. The decomposition of carbonates by tartaric acid is a chemical process which is wholly resisted if alcohol * "II n'y a peut etre pas un seul phenomeiie chimique dans rorganisme qui se fasse par les precedes de la chimie de laboratoire ; en particulier i1 n'y a peut etre pas una oxydation qui s'accomplisse par fixation directH d'o.xvffene. " — Claude Bekxard. THE NATURE OF LIFE. 19 instead of water be the solvent employed. The union of sulphur with lead is said to be due to the affinity of the one for the other ; but no one supposes this affinity to be irrespective of conditions, or that the union will take place when any one of these conditions is absent. If we fuse a compound of lead and iron in a crucible containing sulphur, we find it is the iron, and not the lead, whicli unites with the sulphur ; yet we do not conclude that there is a Crucible Principle which frustrates chemical affinity and resists the union of sulphur and lead ; we simply conclude that the presence of the iron is a condi- tion which prevents the combination of the sulphur with the lead : not until all the iron has taken up its definite proportion of sulphur will the affinity of the lead come into play. This is but another illustration of the law that effects arc 2^'>'ocessions of their causes, summations of the conditions of their existence. If the fire burns no hole in the teakettle so long as there is water to conduct the heat away, this is not due to any principle more mysterious than the presence of a readily conducting water.* * Dr. Maddex, in his essay On the Relation of Therapeutics to Medi- cine, 1871, p. 5, gives a remarkaDle illustration of what may be called the frustration of chemical affinity effected by mechanical conditions. " Be- fore calico can be printed, every loose particle of cotton must be removed from the surface in order that the colored inks may not run. This re- moval is effected by passing the calico over and in contact with a red-hot iron cylinder, and by regulating the rapidity with which the cylinder re- volves, the intense heat burns off the loose fibres, yet does no injury to the woven cloth. In other words, the changes in the relation of the liigh temperature and tlie cotton arc too rapid to admit of the fibre combining with the oxygen. Let the rate of revolution bo reduced but very little, and the calico would burst into flames." Any one who has snuffed a candle with his fingers will understand this. Dr. Madden further in- stances certain fulminates which can be detonated in contact with gun- cotton without causing it to explode — the extreme rapidity with which the fulminates exj)and is too great to enable the gun-cotton to adjust its movements to this new motion. Precisely the same kind of thing occurs in organized matter. If the rate of its elianges be reduced below a cer- tain point, the ordinary chemical affinities will assert themselves. 20 THE PHYSICAL BASIS OF MIND. 21. In accordance with the law of Causation just men- tioned, whicli has been expounded in detail in our First Series (Vol. II. p. 335), the special combinations of Matter in organisms must present special phenomena. Therefore since the province of Biology is that of explaining or- ganic phenomena by means of their organic conditions, it must be radically distinguished from the provinces of Pliysics and Chemistry, which treat not of organized but of inorganic matter. It is idle, it is 'vvorse, for it is mis- leading, to personify the organic conditions, known and inferred, in a Vital Principle ; idle, because we might with equal propriety personify the conditions of crystallization in a Crystal Principle ; misleading, because the artifice is quickly dropped out of sight, and the abstract term then becomes accepted as an entity, supposed to create or rule the phenomena it was invented to express. 22. Inquirers are but too apt to misconceive the value of Analysis, which is an artifice of Method indispensable to research, though needing the complementary rectifica- tion by Synthesis before a real explanation can be reached. Analysis decomposes the actual fact into ideal factors, separates the group into its components, and considers each of these, not as it exists in the group, in the reality, but as it exists when theoretically detached from the others. The oxygen and hydrogen into which water is decomposed did not exist as these gases in the water ; the albumen and phosphate we extract from a nerve did not exist as isolated albumen and phosphate in the nerve, they were molecularly combined. In like manner the physical and chemical processes which may analytically be inferred in vital processes do not really take place in the same way as out of the organism. The real process is always a vital process, and must be explained by the synthesis of all the co-operant conditions. The laws of Physics and Chemis- try formulate abstract expressions of phenomena, where- THE NATURE OF LIFE. 21 ever and whenever these appear, without reference to the modes of production ; and in this sense the movement of a limb is no less a case of Dynamics than tlie movement of a pulley — the decomposition of a tissue is a case of Chemistry no less than the decomposition of a carbonate ; the electromotor phenomena observed in muscle are as purely physical as those observed in a telegraph. But when a biologist has to explain the movements of the limbs, or the decompositions of tissues, he has to deal with the phenomena and their modes of production, he has a particular group before him, and must leave out noth- ing that is characteristic of it. The movements of the pulley do not depend on Contractility and Sensibility, which in turn depend on Nutrition. The decomposition of the carbonate does not depend on conditions resem- blino- those of a livinf^ tissue. Vaucanson's duck was sur- prisingly like a living duck in many of its movements ; but in none of its actions was there any real similarity to the actions of a bird, because the machine was unlike an organism in action. The antithesis of mechanism and organism will be treated of in § 78. 23. We conclude, then, that defining physical phenom- ena as the movements which take place without change of structure, and chemical phenomena as the movements with change of structure, although both classes may be said to take place in the organism, and to be the primary conditions on which organic phenomena depend, they ^o not embrace the whole of the conditions, nor are the sci- ences which formulate them capable of formulating either the special phenomena characteristic of organisms or their special modes of production. The biologist will employ chemical and yjliysical analysis as an essential part of his method ; but he will always rectify what is artificial in this procedure, by sul)ordinating the laws of Pliysics and Chemistry to the la\\'s of Biology revealed in the syn- 22 THE niYsicAL basis of mind. thetic observation of the organism as a whole. The recti- fication, here insisted on, will be recognized as peculiarly urgent in Psychology, which has greatly suffered from the misdirection of Analysis. 24. No one will misunderstand this specialization of Biology to mean a separation of Life from tlie series of objective phenomena, and the introduction of a new entity ; the specialization points to a Mode of Existence. All classifications are artifices, but they have their objec- tive grounds ; the ground of difference on which Biology is separated from Chemistry and Pliysics, though all three may be merged in a common identity, is such as to justify the term radical. A vital process is no more to be considered physico-chemical, because physico-chemical conditions are j)resuj)posed in it, than a feeling is to be considered a nutritive process, because Nutrition is pre- supposed in all Feeling. Organic substances have been made by chemists, and inorganic " cells " have also been made ; but these substances were not organized, these " cells " would not live. The germ-cell is the workshop of generation, the secreting-cell the workshop of secre- tion, the muscle-cell the workshop of contraction. What is required over and above organic substances and cell- forms, is that special state called organization. See § 49. Those who contemplate the manifestations without also taking into account their modes of production may see nothing but physico-chemical facts in vital facts. It is by a similar limitation of the point of view that A'itality is often confounded with IMovement, and portions of organic matter are said to live, simply on the evidence of their movements.* * I am often reminded of the sui-prising movements of particles of carbonate of lime in water which mj' friend Professor Peeyek showed me during a visit to Bonn. He had removed one of the concretions, usu- ally found in connection with nerves along the spine of old frogs, and THE NATUKE OF LIFE. 23 crushed it in water ; under the microscope the seeming spontaneity and variety of the movements of the particles was such that had we not known their origin we should certainly have attributed them to vitality : no infusoria could have moved with more seeming spontaneity. It is hardly physiological to conclude that because fragments of tissue mani- fest amcebiform movements therefore they are alive (Stricker, art. Die Zcllc in his Handbuch der Lchre von den Geweben, 1868, p. 7), or that the heart removed from the body is alive because it still beats. Lieber- KUHN, Ueber Bcwegungsersclieinungen der Zellen, 1870, pp. 357-359, cites examples of such movements in undeniably dead substances. For Life, we demand not only Movement, but Functional Activity. 24 THE PHYSICAL BASIS OF MIND. CHAPTEE II. DEFINITIONS OF LIFE. 25. Biology, the science of Life, being thus assigned its place in the hierarchy of objective laws, we now pro- ceed to consider what the term Life symbolizes. By a large preliminary simplification. Life may be de- fined as the mode of existence of an organism in relation to its inedium. To render this of any value, however, a clear conception of the organism is first indispensable ; and this must be preceded by an examination of the vari- ous attempts to define life in anticipation of such a clear conception. 26. Every phenomenon, or group of phenomena, may be viewed under two aspects — the statical, which considers the conditions of existence ; and the dynamical, which con- siders these conditions in their resultant, — in their action. The statical definition of Life will express the connexus of the properties of organized substance, all those con- ditions, of matter, form, and texture, and of relation to external forces, on which the organism depends. These various conditions, condensed into a single symbol, con- stitute Vitality or Vital Force, and are hence taken as the Cause of vital phenomena. Tlie dynamical definition will express the connexus of Functions and Faculties of the organism, which are the statical properties of organ- ized substance in action, under definite relations. It is obvious that the term Life must vary with the varying significates it condenses, — every variation in the complexity of the organism will bring a corresponding THE NATUEE OF LIFE. 25 fulness in the signification of the term. The life of a l)lant is less significant than the life of an animal ; and tlie life of a mollusc less than that of a fish. But not only is the term one of varying significance, it is always an abstract term which drops out of sight particular con- crete differences, registering only the universal resem- blances. 27. It would be a profitless labor to search out, and a wearisome infliction to set down, the various definitions which have been proposed and accepted; but certain characteristic examples may be selected. All that I am acquainted with belong to two classes : 1°, the mcta-Ythj- siological hypothesis of an ea^^ra-organic agent, animating lifeless matter by unknown powers ; 2°, the physiological hypothesis which seeks the cause of the phenomena (i. e. the conditions) icithin the organism itself, — a group of conditions akin to those manifested elsewhere, but differ- ently combined. The first hypotheses are known under the names of Animism and Vitalism, — more commonly the latter. The second are known as Organicism and Materialism, — but the latter term only applies to some of the definitions. 28. Under Vitalism are included all the hypotheses of a soul, a spirit, an archai'us, a vital principle, a vital force, a nisus formativus, a plan or divine idea, which have from time to time represented the metaphysical stage of Biol- ogy. The characteristic of that stage is the personifi- cation of a mystery, accompanied by the persuasion that to name a mystery is to explain it. In all sciences when processes are imperfectly observed, the theory of the pro- cesses (which is a systematic survey of the available evi- dence marshalled in the order of causal dependence) is supplemented by JiypotJiesis, which fills up witli a guess the gap left by observation. The difference between the VOL. ni. 2 26 THE PHYSICAL BASIS OF MIND. metaphysical and the positive stages of a science lies in the kind of guess thus introduced to supplement theory, and the degree of reliance accorded to it. I have more than once insisted on the scientific canon that " to be valid, an explanation must be expressed in terms of phenomena already observed " ; now it is quite clear that most of the extra-organic hypotheses do not fulfil this con- dition ; no one having ever observed a spirit, an archseus, or a vital principle ; but only imagined these agents to explain the facts observed. As an example of the dif- ference, and a proof that the value of an hypothesis does not rest on the facility with which it connects observa- tions, and seems to explain them, take the three hypoth- eses of animal spirits, nervous fluid, and electricity, by which neural processes have been explained. The ani- mal spirits are imaginary ; the nervous fluid is without a basis in observation, no evidence of such a fluid having been detected ; but electricity (or, speaking rigorously, the movements classed as electrical), although not proved to be the agent in nerve-action, is proved to exist in nerves as elsewhere, and its modes of operation are verifiable. It, therefore, and it alone of the three h}^otheses, is in conformity with the scientific canon. It may not, on full investigation, meet all requirements ; it may be rejected as imperfect ; but it is the kind of guess which scientific theory demands. The second difference noticeable between the meta- physical and the positive stages is the degree of reliance accorded to hypothesis ; which is very much the same as that noticeable in the uncritical and critical attitudes of untrained and trained intellects. The one accepts a guess as if it were a proof ; is fascinated by the facility of link- ing together isolated observations, and, relying on the guess as truth, proceeds to deduce conclusions from it ; the other accepts a guess as an aid in research, trying by THE NATUEE OF LIFE. 27 its aid to come upon some observation wliicli will reveal the hidden process ; but careful never to allow the guess to siq^erscde observation, or to form a basis of deductions not immediately verified. 29. A glance at the metaphysiological definitions will detect both the kind of guess and the kind of reliance which prevailed. The mystery was not simply recog- nized, it was personified as an entity : Will and Intelli- gence were liberally accorded to it, for it was supposed to shape matter, and direct force into predestined paths by prescience of a distant end. The observed facts of the egg passing through successive changes into a complex organism were so marvellous, so unlike any facts observ- able in the inorganic world, that they seemed to demand a cause drawn from higher sources. The mystery of life obtruded itself at every turn. It was named, and men fancied it explained. But in truth no mj^stery is got rid of by explanation, however valid ; it is only shifted farther back. Explanation is the resolution of a complex phe- nomenon into its conditions of existence — the product is reduced to its factors ; the explanation is final when this resolution has been so complete that a reconstruction of the product is possible from the factors. The vast ma- jority of explanations — especially in the organic region — are no more than what mathematicians call " a first approximation." It is through successive approximations that science advances ; but even when tlie final stage is reached a mystery remains. We may know that certain elements combine in certain proportions to produce cer- tain substances ; but why they produce these, and not different substances, is no clearer than why muscles con- tract or organisms die. This Why is, however, an idle fpiestion. That alone which truly concerns us is the How, and not the Why. 30. Biology is still a long way off the How. But it 28 Tin-: thysical basis of mind. can boast of many approximations ; and its theories are to be tested by the degree of approximation they effect. In this light the physiological, m/ra-organic, hypotheses manifestly have the advantage. Many of them are in- deed vei-y unacceptable ; they are guided by a mistaken conception of the truths reached by Analysis. For when men first began to discard the extra-organic hypotheses, and to look into the organism itself, they were so much impressed by the mechanical facts observed, that they endeavored to reduce all the phenomena to Mechanics. Tlie circulation became simply a question of hydraulics. Digestion was explained as trituration. The chemists then appeared, and their shibboleths were " affinities " and "oxidations." With Bichat arose the anatomical school, which decomposing the organism into organs, the organs into tissues, and these tissues into their elements, sought the analytical conditions of existence of the or- ganism in the properties of these tissues, and the functions of these organs. The extra-organic agent was thus finally shown to be not only a fiction, but a needless fiction. Every student of the history of the science will note how from the very necessities of the case the metaphysi- ologists, without relinquishing their Vital Principle, have been led more and more to enter on the track of the physiologists, pursuing their researches more and more into the processes going on in the organism, and assigning more and more causal efficiency to these, with a corre- sponding restriction of the province of their extra-organic cause. Hence in the ranks of the vitalists have been found some of the very best observers and theorists ; but they were such in despite of, and not in consequence of, their hypothesis, which was only invoked by them when evidence was at fault. Nor, unscientific as vitalism is, can we deny tliat it has been so far serviceable to the science, that it has corrected the materialist error of THE NATUItE OF LIFE. 29 endeavoring to explain organic phenomena by physico- chemical laws ; and has persistently kept in view the radical difference between organic and inorganic. 31. These remarks may justify a selection of defini- tions, classified under the two heads. Tlie selection is fitly opened by the Aristotelian definition which prevailed for centuries. Aristotle distinguishes Life, which he says means " the faculties of self-nourishment, seK-development, and self- decay," from the Vital Principle. Every natural body manifestiug life may be regarded as an essential existence (over la); but tlicn it is an existence only as a synthesis (<»9 avvOe-rr]) ; and since an organism is such a synthesis, being possessed of Life, it cannot be the Vital Principle {"y^v^fri). Therefore it follows that the Vital Principle must be an essence, as being the Form of a natural body holding life in 'potentiality. The Vital Principle is the primary reality of an organism. " It is therefore as idle to ask whether the Vital Principle and Organism are one, as whether the wax and the impress on it are one Thus if an eye were an animal, Vision would be its Vital Principle : for Vision is, abstractedly considered, the essence of the eye ; but the eye is the body of Vision, and if Vision be want- ing, then, save in name, it is no longer an eye." Apart from certain metaphysical implications, inevitable at that period, there is profound insight in this passage. His adversary Telesio quite misconceives the meaning liere assigned to the Vital Principle.* 32. Let us pass over all tlie intermediate forms of the liypotliesis, and descend to Kant, who defines Life "an internal principle of action " (this does not distinguish it * Telesiu.s, De Natura Rerum, 1586, V. 184. Telf.sio nii^'lit have 1)oon savf'd from the mistake had he attended to what Niphus had .said on the point in liis Exposilio suUilissimn, 1559, p. 245. Conip. also PiiiLELi'iius, Epist. Familiarum, 1502, p. 253, verso. 30 THE riiYsic.a, basis of mind. from fermentation) ; an organism he says is " that in which every part is at once means and end." " Each part of the living body has its cause of existence in the whole organism ; whereas in non-living bodies eacli part has its cause in itself." Johannes ]\Iuller adopts a similar view : " The harmonious action of the essential parts of the indi- vidual subsist only by the influence of a force, the opera- tion of which is extended to all parts of the body, and does not dej^end on any single parts ; this force, must exist before tJie parts, which ai-e in fact formed by it during the development of the embryo The vital force inherent in them generates from the organic matter the essential organs which constitute the whole being. This rational creative force is exerted in every animal strictly in accord- ance with what the nature of each requires." 33. This is decidedly inferior to Aristotle, who did not confound the vegetative with the rational principle. It rests on the old metaphysical error of a vis meclicatrix, an error which cannot sustain itself against the striking facts wdiich constantly point to a vis dcstriictrix, a destructive tendency quite as inexorable as the curative tendency. And the experimental biologist soon becomes impressed with the fact that the tissues have indeed a sclcctim action, by which from out the nutrient material only these sub- stances are assimilated which will enter into combination with them ; but this selective action is fatal, no less than reparative : substances which poison the tissue are taken up as readily as those which nourish it. The idea of prescience, therefore, cannot be sustained ; it is indeed seldom met with now in the M'ritings of any but the Montpellier school, who continue the traditions of Stalil's teaching. It has been so long exploded elsewhere that one is surprised to find an English physiologist clinging to a modification of it — I mean Dr. Lionel Beale, who repeatedly insists on Life as " a peculiar Force, tempera- THE NATURE OF LIFE, 31 rily associated with matter," a "power capable of con- trolling and directing both matter and force," an " undis- covered form of force having no connection ivith primary energy or motion" " The higher phenomena of the ner- vous system are probably due primarily to the movements of the germinal matter due to vital power, which vital power of this the highest form of germinal matter is in fact the living /." 34. Apart from the primary objection to all these definitions, namely, that they seek to express organic phenomena in terms of an extra-organic principle, to formulate the facts observed in terms of a cause inferred, there is the fatal objection that they speak confidently on what is avowedly unknown. If the force be, as Dr. Beale says, "undiscovered," on what grounds can he assert that it has no connection with the forces which are known ? All that the observed facts warrant is the assertion that organic phenomena are special (which no one denies), and must therefore depend on special com- binations of matter and force. But on this ground we might assume a crystallizing Force, and a coagulating Force, having no connection with the molecular forces manifested elsewhere : these also are special phenomena, not to be confounded with each other. 35. Schelling defines Life as " a principle of individua- tion " and a " cycle of successive changes determined and fixed l)y this internal principle." Which is so vague tliat it may be applied in very different senses. Bichat's celebrated definition (which is only a paraphrase of a sentence in Stahl), " the sum of the functions which re- sist Death," altliough an endeavor to express the facts from the Intra-organic point of view, is not only vague, but misrepresents one of the cardinal conditions, by treat- ing the External Medium as antagonistic to Lift!, wliercas Life is only possible in the relation to a Medium. 32 THE PHYSICAL BASIS OF mND. 36. Were it not so vague, the definition proposed by Dugcs and Beclard would be unexceptionable : the former says it is " the special activity of organized beings " ; the latter, " the sum of the phenomena proper to organ- ized bodies." When supplemented by a description of organized bodies, these formuhe are compendious and exact. The same remark applies to the definition of Lamarck: "that state of things which permits organic movements; and these movements, which constitute active life, result from a stimulus which excites them." 37. De Blainville, and after him Comte and Charles Eobin, define it thus : " Life is the twofold internal move- ment of composition and decomposition at once general and continuous." This, excellent as regards what is called vegetal life, is very properly objected to by Mr. Herbert Spencer in that it excludes those nervous and muscular functions which are the most conspicuous and distinctive of vital phenomena. The same objection must be urged against Professor Owen's definition : " Life is a centre of intussusceptive assimilative force capable of reproduction by spontaneous fission." 38. In 1853, after reviewing the various attempts to fexpress in a sentence what a volume could only approxi- /mately expound, I proposed the following : " Life is a se- 'ries of definite and successive changes, both of structure and composition, which take place within an individual without destroying its identity." This has been criticised by Mr. Herbert Spencer and by Dr. Lionel Beale, and if I had not withdrawn it before their criticisms appeared, I should certainly have modified and enlarged it after- wards. I mention it, however, because it is an approach to a more satisfactory formula in so far as it specifies two cardinal characteristics distinguishing organisms from all anorganisms, namely, the incessant evolution through definite stages, and the preservation of specific integrity THE NATURE OF LIFE. 33 throughout the changes ; not only the organism as a whole is preserved amidst incessant molecular change, but each tissue lives only so long as the reciprocal molec- ular composition and decomposition persist. On both of these points I shall have to speak hereafter. The defini- tion, however, is not only defective in its restriction to the molecular changes of Nutrition, taking no account of the Properties and Functions of the organism ; but defec- tive also in giving no expression to equally important relations of the organism to the medium. 39. This last point is distinctly expressed in Mr. Spen- cer's definition: "Life is the continuous adjustment of internal relations to external relations." Considered as a formula of the most general significance, embracing there- fore what is common to all orders of vital phenomena, this is the best yet proposed.* If I propose another it will not be to displace but to run alongside with Mr. Spencer's ; and this only for more ready convenience. Before doing so I must say a few words by way of clear- ing the ground. 40. What does the term Life stand for ? What are the concrete significates of this abstract symbol ? As before stated, it is sometimes a compendious shorthand for the special phenomena distinguishing living from non- living bodies ; and sometimes it expresses not these ob- served phenomena, but their conditions of existence, which are by one school personified in an abstract and extra- organic cause. Thus the life of an animal, a man, or a * The authorities just cited are Aristotle, De Anima., Lib. IL c. L Kant, Krilik dcr Urthcilskraft. Muller, Physiology. Beale, Bioplasm, and Introduction to Todd and Boioman's Anatomy. Sciiem.ing, Erstcr Entvnirf, and Transcendent. Idcalisnius. Bichat, Rcclierchcs siir la Vie et la Mart. Stahl, Tlieoria Vera Medica. DuGi;.s, Physiologic Com- parSc. Bi^xlard, Anatomic G&nirah. Lamarck, Philosophic Zoo- logiquc. Comte, Cours de Philosophic Positive. Owen's Htmterian Lectures, 1854. Herbert Spencer, Principles of Biology. 2* 34 THE PHYSICAL BASIS OF MIND. nation, means — 1°, the special manifestations of these organisms, and groups of organisms ; or 2°, the causes which produce these manifestations. We are often mis- understood by others, and sometimes vague to ourselves, when we do not bear these two different meanings in view. It was probably some sense of this which made Aristotle distinguish Vitality from Life, as that of the one uniform cause separated from its multiple effects ; it was certainly the motive of Fletcher, who thus ex- pressly limits the meanings : " Vitality or Irritability, the property which characterizes organized beings of being acted on by certain powers otherwise than either strictly mechanically or strictly chemically ; Life, the sum of the actions of organized beings resulting directly from their vitality so acted on." * Vitality and Life being thus discriminated as the stat- ical and the dynamical aspects of the organism, we find in relation to the former two radically opposed concep- tions : the metaphysiological or extra-organic, and the physiological or intra-orgauic. The first conceives Vi- tality to be a Vital Principle, or extra-organic agent, sometimes a soul, spirit, archseus, idea, and sometimes a force, which easily becomes translated into a property. The conception of an entity must be rejected, because it is metempirical and unverifiable, § 34. The concep- tion of a force must be rejected, because it is irrecon- cilable wdth any definite idea we have of force. What the term Force signifies in Physics and Chemistry, name- ly, mass animated by velocity, or directed pressure, which is the activity of the agent, — is precisely that w^hich these vitalists pertinaciously exclude. They assume a force which has nothing in common with mass and ve- locity ; which is not a resultant, hut a principle ; which * Fletcher, as quoted by Drtsdale, Life and tlie Equivalence of Force, Part II. p. 120. THE NATURE OF LIFE. 35 instead of being a directed quantity, is itself autonomous and directive, shaping matter into organization, and en- dowing it with powers not assignable to matter. If this vital force has any mass at its back, it is a spiritual mass ; if it is directed, the direction issues from a " ]\iind somewhere." Now this conception is purely metempir- ical. Not only is it inexact to speak of Vitality as a force, it is almost equally inexact to speak of it as a property ; since it is a term which includes a variety of properties ; and when Fletcher assigns the synonym of Irritability, this at once reveals the inexactness ; for beside this property, we must place Assimilation, Evo- lution, Disintegration, Eeproduction, Contractility, and Sensibility, — all characteristic properties included in Vi- tality. 41. Having thus rejected the conceptions of entity, force, and projDerty, we are left in jDresence of — 1°, the organic conditions as the elements, and 2°, of their syn- thesis (in the state called organization) as the personified principle. Vital forces, or the vital force, if we adopt the term for brevity's sake, is a symbol of the conditions of existence of organized matter ; and since organisms are specially distinguishable from anorganisms by this spe- ciality of their synthesis, and not by any difference in the nature of the elements combined, this state of organ- ization is the " force " or " principle " of which we are in quest. To determine what Life means, we must observe and classify the phenomena presented by living beings. To determine what Vitality — or organization — means, we must observe and classify the processes which go on in organized substances. These will occupy us in the succeeding chapters ; here I may so far anticipate as to propose the following definitions : — 42. Life is the functional activity of an organism in relation to its medium, as a synthesis of three terms : 36 THE niYsicAL basis of mind. Structure, Aliment, and Instrument ; it is the sum of functions which are the resultants of Vitality ; Vitality being the sum of the properties of matter in the state of organization. 43. Vital phenomena are the phenomena manifested in organisms when external agencies disturb tlieir molecular equilibrium ; and hy organisms when they react on ex- ternal objects. Thus everything done in an organism, or by an organism, is a vital act, although physical and chemical agencies may form essential components of the act. If I shrink when struck, or if I wliip a horse, the blow is in each case physical, but the shrinking and the striking are vital. Every part of a living organism is therefore vital, as pertaining to Life ; but no part has this Life when iso- lated ; for Life is the synthesis of all the parts : a feder- ation of the organs when the organism is complex, a fed- eration of the organic substances when the organism is a simple cell. 44. All definitions, although didactically placed at the introduction of a treatise, are properly the final expression of the facts which the treatise has established, and they cannot therefore be fully apprehended until the mind is familiarized w'itli the details they express. Much, there- fore, which to the reader may seem unintelligible or questionable in the foregoing definition, must be allowed to pass until he has gone through the chapters which follow. THE NATURE OF LIFE. 37 CHAPTEE III. ORGANISM, ORGANIZATION, AND ORGANIC SUBSTANCE. 45. There is a marked difference between organic and OTg&niscd substances. The organic are non-living, though capable of living when incorporated in organized tissue (albumen is such a substance) ; or they may be incapable of living because they have lived, and are products of waste, e. g. urea. The organized substance is a specific combination of organic substances of various kinds, a combination which is organization. Any organized sub- stance is therefore either an independent organism, or part of a more complex organism. Protoplasm, either as a separate organism or as a constituent of a tissue, is organized substance. Organic substances are numerous and specific. They are various combinations of proximate principles familiar to the chemist, which may conveniently be ranged under three classes : The first class of organic substances com- prises those composed of principles having what is called a mineral origin ; these generally quit the organism un- clianged as they entered it. The second class comprises those which are crystallizablc, and are formed in, the or- ganism, and generally quit it in this state as excretions. The third class comprises the colloids, i. e. substances which are coagulable and not crystal! izal)le, and are formed in and decomposed in the organism, thus fur- nishing the principles of the second class. All the prin- ciples are in a state of solution. Water is the cliief SB THE PHYSICAL BASIS OF MIND. vehicle of the materials which enter and the materials which quit the organism; and bodies in solution are sol- vents of others, so that the water thus acquires new sol- vent properties. 45 «. Two points must be noted respecting organic substances : they are mostly combinations of higher mul- tiples of the elements ; and their combinations are not definite in quantity. Albumen, for example, has (accord- ing to one of the many formulas which have been given) an elementary composition of 21G atoms of Carbon, 169 of Hydrogen, 27 of Nitrogen, 3 of Sulphur, and 68 of Oxygen ; whereas in its final state, in which it quits the organism as Urea, it is composed of 2 atoms of Carbon, 4 of Hydrogen, 2 of Nitrogen, and 2 of Oxygen, all the Sulphur having disappeared in other combinations. In like manner in the organism Stearin falls from Cn4, Hhq, Oi2, to Oxalic Acid, which is C4, H2, Og. It is obvious that the necessary modifiability of organic substance is due to this multiplicity of its elementary parts and the variety of its molecular structure. 455. Nor is the indefiniteness of the quantitative com- position less inq:)ortant, though seldom adequately appre- ciated, or even suspected. Eobin and Verdeil * are the only writers I can remember who have distinctly brought the fact into prominence. That all inorganic substances are definite in composition, every one knows. Quick- lime, for example, may be got from marble, limestone, oyster-shells, or chalk ; but however produced, it always contains exactly 250 ounces of calcium to 100 ounces of oxygen ; just as water is always OH2. Not so the pre- eminently vital substances, those which are coagulable and not crystaUizable : no precise formula will express one of these ; for the same specific substance is found to vary from time to time, and elementary analyses do not * RoBix et Verdeil, TraiU dc Chimic Anatomiquc, 185-3. THE NATURE OF LIFE. 39 give uniform results. Thus, if after causing an acid to combine with one of these substances, we remove the acid, we are not certain of finding the substance as it was before — as we are, for example, after urea is combined with nitric acid and then decomposed. The same want of definiteness is of course even more apparent in the combinations of these proximate principles into organized substance. Protoplasm differs greatly in different places. Epithelial cells differ. Muscular and nervous fibres are never absolutely the same in different regions. A striped and unstriped muscular fibre, the muscular fibre of a sphincter or of a limb, a nerve-fibre in a centre, in a trunk, or in a gland, will present variations of composi- tion. The elastic fibres of the ligaments are larger in the horse than in man ; and in other animals they are smaller. These differences are sometimes due to the constituents, and sometimes to the arrangement of the constituents ; the conversion of Albumen into Fibrine without elementary loss or addition, is a good example of the latter. That the tissues of one man are not absolutely the same as the tissues of another, in the sense in which it is true to say that the chalk of one hill is the same as that of another, or as gold in Australia is the same as gold in ]\Iexico, is apparent in their very different reactions under similar external conditions : the substance which poisons tlie one leaves the other unaffected. The man wlio has once had the small-pox, or scarlet fever, is never the same afterwards, since his organism has now become insusceptible of these poisons. And Sir James Paget has called attention to tlie striking lact revealed in disease, namely, that in the same tissue — say the bone or the skin — a morbid substance fastens only on certain small portions leaving all tlie rest unaltered, but fastens on exactly corresponding spots of the opposite sides of the body ; so that on both arms, or both legs, only the corrc- 40 THE PHYSICAL BASIS OF MIND. sponding bits of tissue will be diseased. " Manifestly wlien two substances display different relations to a third their composition cannot be identical ; so that tliouoh we may speak of all bone or of all skin as if it were all alike, yet there are differences of intimate composition. ISTo power of artificial chemistry can detect the difference; but a morbid material can." * It is to this variability of composition that we must refer individual peculiarities, and those striking forms of variety known as idiosyn- crasies, which cause some organisms to be affected by what seem inexplicable influences — physical and moral. In spite of all these variations, however, there are certain specific resemblances dependent of course on similarity of composition and structure, so that the muscle of a crusta- cean is classed beside the muscle of a vertebrate, althouuli the elementary analysis of the two yields different results. Xerve-tissue, according to my experience, is the most va- riable of all, except the blood ; variable not only from individual to individual, and from genus to genus, but even in the same individual it never contains the same quantities of water, phosphates, etc. Hence it is that dif- ferent nerves manifest different degrees of excitability, and the same nerve differs at different times. Thus the fifth pair, in a poisoned animal, retains its excitability long after the others are paralyzed ; and the patient under chlo- roform feels a prick on the brow or at the temples, when insensible at any other spot. The pneumogastric which is excitable during digestion is — in dogs at least — in ex- citable when the animal is fasting. 46. The organic substances are what analysis discovers in organized substances, but none of them, not even the highest, is living, except as organized. Albumen alone, or Stearin alone, is as incapable of Vitality, as Plumbago, or Soda ; but all organic substances are capable of playing a * Paget, Lectures on Surgical Pathol oriy, p. 14. THE NATURE OF LIFE. 41 part in vital actions ; and this part is the more important in proportion to their greater molecular variety. Organi- zation is a special synthesis of substances belonging to all three classes ; and the organized substance, thus formed, alone merits the epithet living. AVe see how organized substances, being constituted by principles derived from the inorganic world, and principles derived from the or- ganic world, have at once a dependence on the external Medium, and an independence of it, which is peculiar to living beings. An analogous dependence and independ- ence is noticeable with respect to the parts ; and this is a character not found in inorganic compounds. The organ- ism, even in its simplest forms, is a structure of different substances, each of which is complex. While one part of a crystal is atomically and morphologically identical with every otlier, and is the whole crystal " writ small," one part of an organism is unlike another, and no jJcirt is like the whole. Hence the dependence of one organ and one tissue on another, and each on all. Yet, while every part is, so to speak, a condition of existence of every otlier, and the unity of the organism is but the expression of this solidarity, — wherever organized substance has been differentiated into morphological elements (cells, etc.), each of these has its own course of evolution independ- ently of the others, — is born, nourished, developed, and dies. 47. The interdependence of nerve and muscle is seen in this, that the more the muscle is excited the feebler its contractions become ; this decrease in contractility is com- pen.sated by an increased excitability in its nerve ; 8o that while tlie muscle demands a more powerful stimulus, the nerve acquires a more energetic activity. Ranke's curious and careful experiments seem to prove that this depends on the wearied muscle absorliing more water, owing to the acids developed by its activity, and on the nerve losing 4J Tin-: nivsicAL basis of mind. this water — a nerve being always more irritable when its quantity of water diminishes. 48. Herein we see illustrated the great law of organ- ized activity, that it is a simultaneity of opposite tenden- cies, as organized matter is a synthesis of compositions and decompositions, always tending towards equilibrium and disturbance, storing up energy and liberating it. Un- like what is observed in unorganized matter, the condi- tions of waste bring with them conditions of repair, and thus — within certain limits — every loss in one direction is compensated by gain in another. There is a greater flow of nutrient material, or, more properly speaking, a greater assimilation of it by the tissue, where there has been made a greater opening for it by previous disintegra- tion. The alkaline state of the nutrient material, and the acid state of the material that has been used, — the alka- line state which characterizes repose and assimilation, and thfe acid state which characterizes activity and deassirai- lation, are but cases of tliis general law ; on the synthesis of these opposite tendencies depends the restless cliange, together with the continued specific integrity, of organized matter. 49. The state of organization may therefore be defined as the molecular union of the proximate principles of the three classes in reciprocal dissolution. An organism is formed of matter thus organized, which exists in two states — the am.orphous and the fignrcd. The amorphous substances are liquid, semi-liquid, and solid ; the figured are the cells, fibres, and tubes, called "anatomical ele- ments." For these I prefer the term suggested, I believe, by Milne Edwards, namely, organitcs, because they are the individual elements which mainly constitute the organs, and are indeed by many biologists considered as element- ary organisms. These organites, which go to form the tissues, and by the tissues the organs, have their specific THE NATURE OF LIFE. 43 form, volume, structure, and chemical reactions. They exist in textures or tissues, or separately (e. g. blood cor- puscles), and are in many respects like the simplest organ- isms known, such as Monads, Vibrios, Amoebte, etc. 50. The simplest form of life is not — as commonly stated — a cell, but a microscopic lump of jelly-like sub- stance, or protoplasm, which has been named sarcodc by Dujardin, cytodc by Haeckel, and (jcrminal matter by Lionel Beale. This protoplasm, although entirely destitute of texture, and consequently destitute of organs, is never- theless considered to be living, because it manifests the cardinal phenomena of Life: Assimilation, Evolution, Eeproduction, Mobility, and Decay. Examples of this simplest organism are Monads, Protamoebas, and Polytha- lamia.* Few things are more surprising than the vital activity of these organites, which puzzle naturalists as to whether they should be called plants or animals. All microscopists are familiar with the spectacle of a formless lump of albuminous matter (a Ehizopod) putting forth a process of its body as a temporary arm or leg, or else slowly wrapping itself round a microscopic plant, or mor- sel of animal substance, thus converting its whole body into a mouth and a stomach ; but these phenomena are surpassed by those described by Cienkowski,"!- who nar- rates how one Monad fastens on to a plant and sucks the chlorophyll first from one cell and then from another ; another ]\Ionad, unable to make a liole in the cell-wall, thrusts long processes of its body into the opening already made, and drags out the remains of the chloropliyll left there by its predecessor ; while a third JMonad leads a l)redatory life, falling upon other Monads that liave filled themselves with food. Here, as he says, we stand on the * Comp. Haeckei,, in Suhold unci Kollikcr's Zeitschrift, 1865, p. 342, and his GcncrclU Morpholor/ic, 1866, I, 13.5, 336. t In the Archivfiir mikros. Anatomic, 1865, p. 211. •1-i THE niYSICAL BASIS OF MIND. tliresliold of tlmt dark region where Animal "Will begins ; and yet there is here only the simplest form of organi- zation* 51. Now let our glance pass on to the second stage — the Cell. Here we have a recognized differentiation in the appearance of a nucleus amid the protoplasm. The nucleus is chemically different from the substance which surrounds it ; and although perhaps exaggerated impor- tance has been attributed to this nucleus, and myste- rious powers have been ascribed to it, yet as an essential constituent of the cell it commands attention. Indeed, according to the most recent investigations, the defini- tion of a cell is " a nucleus with surrounding proto- plasm." The cell-wall, or delicate ^investing membrane — that which makes the cell a closed sac — is no longer to be regarded as a necessary constituent, but only as an accessory.-f- * Here organization is the simplest form of all — molecular organized structure, which in the higher forms becomes tissue structure, and organ structure. The word structure properly means orderly arrangement of different materials ; and molecular structure refers to the different prox- imate principles which constitute the organized substance. Usuallj', however, the word structureless indicates the absence of visible arrange- ment of the parts ; a cell has structure suice it has nucleus and pro- toplasm. t In the cell-theory established by Scht.eiuen and Sciiwanx, in 1838, and which has formed the basis of modern histology, the cell-wall was endowed with an importance which can no longer be upheld now that the existence of independent organisms, and of cells, without a trace of enveloping membrane has been abundantly observed. Cells without walls were first described by CosTE in the Comptcs Rcndus, 1845, p. 1372. They were also described by Charles Eobix in 1855, Diet, de la Medicine, art. Cellule. But little notice was taken until Max Sciiultze, in his famous essay, Ueher Muskelkorpcrchen imd was man eivc Zelle zu ncnnen habe, which appeared in Rcichert zind Du Bois Rcymond's ArcMv, 1861, — Bruecke, in his memoir. Die Elemcntarorcjanismcn, 1861, — and Lionel Beale, in his Structure of the Simple Tissues, 1861, — all about the same time began the reform in the cell-theory which has effected a decisive change in the classical teaching. Leydig claims, and with justice, to have furnished important data in tliis direction {Vovi Bau des thicrischcn THE NATURE OF LIFE. 45 52. The cell may be either an organism or an organite. It may lead an isolated life as plant or animal, or it may be united with others and lead a more or less corporate existence ; but always, even as an element of a higher organism, it preserves its own individuality. At first we see that the corporate union is very sliglit, merely the contact of one cell with another of its own kind, as in the filament of a Conferva. Eising higher, we see the cell united with others different from it ; plants and ani- mals appear, having structures composed of masses of various cells, liising still higher, we see animal forms of which the web is woven out of myriads upon myr- iads of cells, with various cell-products, processes, fibres, tubes. ORGANISM AND MEDIUM. 53. But we have only one half of the great problem of life, when we have the organism ; and it is to this half that the chief researches have been devoted, the other falling into neglect. What is that other ? The Medium in which the organism lives. Every individual object, organic or inorganic, is the product of two factors: — first, the relation of its constituent molecules to each other; secondly, the relation of its substance to all surrounding objects. Its properties, as an object or an organism, are tlie results of its constituent molecules, and of its relation to external conditions. Organisms are the results of a peculiar group of forces, exhibiting a peculiar group of Korpcrx, 18G4, I. p. 11). The student interestod in this discussion should consult M.\x Sciim/rzK, Das Protoplasma dcr Rhizopnden und dr.r PJlan- zcnzcUcn, 1863; Hakckel, Die Radiol nricn, 18G2; the controversial papers by Riciciiert, in his Arcliiv (beginning with tlie Report of 1863\ and Max Sciiultze, in his Archiv fUr mikros. Amit., with IIenle's judg- ment in his Jahrcshcrichfx, and Koij.iker's summing-up in tlu; last edi- tion of his Gcioehclehrc. For a full yet brief history of tlic cell-theoiy see Drysdale, Tlie Protoplasmic TJieory of Life, 1874, pp. 96-106. 4G THE niYSICAL BASIS OF MIND. phenomena. Viewing these in the abstract, wc may say- that there are three regulative laws of life : — (1) The Lex Formationis — the so-called tiisus formativus, or "organiz- ing force"; (2). the Lex Adaptationis, or adaptive ten- dency ; (3) the Lex Hcrcditatis, or tendency to reproduce both the original form and its acquired modifications. We have always to consider the organizing force in rela- tion to all surrounding forces — a relation succinctly ex- pressed in the word Ada]jtation. Just as water is water only under a certain relation of its constituent molecules to the temperature and atmospheric pressure — just as it passes into other forms (ice or steam) in adapting itself to other conditions; so, likewise, the organism only pre- serves its individuality by the adjustment of its forces with the forces which environ it. 54. This relation of Organism and Medium, the most fundamental of biological data, has had a peculiar for- tune : never wholly unrecognized, for it obtrudes itself incessantly in the facts of daily experience, it was very late in gaining recognition as a principle of supreme im- portance ; and is even now often so imperfectly appre- hended that one school of philosophers indignantly re- jects the idea of the Organism and Medium being the two factors of which Life is the product. Not only is there a school of vitalists maintaining the doctrine of Life as an entity independent both of Organism and Medium, and using these as its instruments ; but tliere is also a majority among other biologists, who betray by their arguments that they fail to keep steadily before them the fundamental nature of the relation. Something of this is doubtless due to the imperfect conception they have formed of what constitutes the Medium ; instead of recognizing in it the sum of external conditions affecting tlie organism — i. e. the sum of the relations wdiich the organism maintains with external agencies, — they re- THE NATUKE OF LIFE. 47 strict, or enlarge it, so as to misapprehend its significance — restrict it to only a few of the conditions, such as climate, soil, temperature, etc., or enlarge it to embrace a vast array of conditions which stand in no directly appreciable relation to the organism. Every one under- stands that an organism is dependent on proper food, on oxygen, etc., and will perish if these are withheld, or be affected by every variation in such conditions. Every one understands that an animal which can devour or be devoured by another, will flourish or perish according to the presence of its prey or its enemy. But it is often forgotten that among external existences, all those which stand in no appreciable relation to the organism are not properly to be included in its Medium. In consequence of this oversight we frequently hear it urged as an ob- jection to the Evolution Hypothesis, that manifold organ- isms exist under the same external conditions, and that organisms persist unchanged amid a great variety of con- ditions. The objection is beside the question. In the general sum of external forces there are certain items which are nearly related to particular organisms, and constitute their Medium ; those items which are so dis- tantly related to these organisms as to cause no reactions in them, are, for them, as if non-existent.* Of the mani- fold vibrations which the ether is supposed to be inces- santly undergoing, only certain vibrations affect the eye * At the time this was written, I had some fish ova in the course of development. Out of the same mass, and in the same vessel, all those which were supported by weed at a depth of lialf an inch from the sur- face, lived and developed ; all those, witliout exception, that were at a depth of two to four inches, i)eri.shed. In ordinary parlance, .surely, nothing would be olyected to in the phrase, "these ova were all in the same iledium " ; the water was the same, tlic weed the same, the ves.sel the .same ; yet some difference of temperature and carbonic acid made all the difference between life and death. Another curious fact was ol)- served ; I removed eight of tliese ova with active embiyns, and placed them in a large watch-glass containing a solution (one half i)er cent) of 48 THE PHYSICAL BASIS OF MIND. as light ; these constitute the Medium of Siglit ; the others are as if they were not. Only certain vibrations of the air afl'ect the ear as Sound ; to all other vibrations we are deaf; though ears of finer sensibility may detect them and be deaf to those which affect us. 55. " The external conditions of existence " is therefore the correct definition of the Medium. An animal may be surrounded with various foods and poisons, but if its organism is not directly affected by them they cannot be food or poison to it. An animal may be surrounded with carnivorous rivals, but if it is not adapted to serve them as food, or is too powerful to be attacked by them, they only indirectly enter into its Medium, by eating the food it would eat. The analogy is similar with anorganisms and their relation to their media. Every physical or chemical phenomenon depends on the concurrence of definite condi- tions : namely, the substance which manifests the change, and the medium in which the change is manifested. Alter the medium, solid, liquid, or gaseous, change its thermal or electrical state, and the phenomenon is altered. But although similar alterations in the medium notoriously influence the organism, yet, because a great many varia- tions in external conditions are unaccompanied by appre- ciable clianges in the organism, there are biologists who regard this as a proof of Life being independent of phys- ical and chemical laws ; an error arising from their not recognizing the precise nature of organic conditions. 56. To give greater precision to the conception of a Medium it will be desirable to adopt the distinction much bichromate of ammonia. In this acid the embryos lived and v.-ere active fifty-seven hours, although other embryos placed in a similar watch-glass containing pond-water, survived only forty hours. The non-effect of the acid was probably due to the non-absorption which nullifies the effect of certain virulent poisons when they are swallowed ; but why the fish should live longer in the acid than in the simple water, I do not at all comprehend. THE NATURE OF LIFE. 49 insisted on by Claude Bernard, namely, 1°, an External or Cosmical Medium, embracing the whole of the circum- stances outside the organism, capable of directly affecting it, and 2°, an Internal or Physiological Medium, embra- cing the conditions inside the organism, and in direct rela- tion with it — that is to say, tlie plasma in which its tis- sues are bathed, by which they are nourished. To these add its temperature and electrical conditions. Bernard only includes the nutritive fluid ; but inasmuch as each organism possesses a temperature and electrical state of its own, and these are only indirectly dependent on the external temperature and electricity, and as it is with these internal conditions that the organism is in direct relation, I include them with the plasma among the constituents of the Pliysiological Medium. Any change in the External Medium, whether of temperature or electricity, of food or light, which does not disturb the Internal Medium, will of course leave the organism undisturbed; and for the most part all the changes in the External Medium which do affect the organism, affect it by first changing the Internal Medium. External heat or cold raises or depresses the internal temperature indirectly by affecting the organic processes on which the internal temperature depends. We see here the rationale of acclimatization. Unless the organism can adapt itself to the new External JMedium by the readjustment of its Internal Medium, it perishes. 57. We are now enabled to furnish an answer to the very common objection respecting the apparent absence of any direct influence of external conditions. Let the objec- tion first Ije stated in the words of a cehibrated naturalist, Agassiz : " It is a fact which seems to be entirely over- looked by those wlio assume an extensive influence of l)hysical causes upon tlie very existence of organized l)eings, that the most diversified ty])es of animals and plants are everywhere found under identical circumstan- 60 THE niYsiCAL basis of mind. ces. The smallest sheet of fresh Avater, every point of the sea-shore, every acre of dry land, teems with a variety of animals and plants. The narrower the boundaries which are assigned as the primitive home of all these beings, the more uniform must be the conditions under which they must be assumed to have originated ; so uniform indeed that in the end the inference would be that the same physical causes can produce the most diversified effects." Obviously there is a complete misstatement of the ar- gument here ; and the excess of the misstatement appears in the following passage : " The action of physical agents upon organized beings presupposes the very existence of those beings." Who ever doulited it ? " The simple fact that there has been a period in the history of our earth when none of these organized beings as yet existed, and when, nevertheless, the material constitution of our globe and the physical forces acting upon it were essentially the same as they are now, shows that these influences are insufficient to call into existence any living being."* Although most readers will demur to the statement that because the material constitution of our globe was " essen- tially the same" before and after animal life appeared, therefore there could have been no special conditions de- termining the appearance of Life, the hypothesis of Evo- lution entirely rejects the notion of organic forms having been diversified by diversities in the few physical condi- tions commonly understood as representing the Medium. Mr. Darwin has the incomparable.merit of having enlarged our conception of the conditions of existence so as to embrace all the factors which conduce to the result. In his luminous principle of the Struggle for Existence, and the Natural Selection which such a struggle determines, we have the key to most of the problems presented by * Agassiz, Essay 011 Classijication, 1859, p. 15. THE NATURE OF LIFE. 51 the diversities of organisms ; and the Law of Adapta- tion, rightly conceived, furnishes the key to all organic change. 58. In consequence of the defective precision with which the phrase " Medium," or its usual equivalent " physical conditions," is employed, several biological errors pass undetected. Haeckel * calls attention to the common mistake of supposing the organism to be passive under the influence of external conditions, whereas every action, be it of light or heat, of water or food, necessarily calls forth a corresponding reaction, which manifests itself in a modification of the nutritive process. He points out the obverse of this error in the current notion that Habit is solely due to the spontaneous action of the organism, in opposition to the influence of external agency, — as if every action were not the response to a stimulus. Corre- sponding with the fluctuations in the Medium there must necessarily be fluctuations of Adaptation, and I think we may safely assume that it is only when these fluctuations cease that the Adaptation becomes Habit. Tliis is the interpretation of the phrase " Hal)it is second Nature," and is very different from the common interpretation which attributes it to the use or disuse of organs ; as if use or disuse were a spontaneous uncaused activity. 59. The organism, simple or complex, is, we have al- ready seen, built up from materials originally derived from the External jVIedium, but proximately from the Internal Medium. This statement, however, requires some quali- fication, especially in view of the hypotliesis that organ- ized substance was originally created such as we now find it, and not evolved from inorganic materials. Whether this hypotliesis be adopted, or rejected, we have the fact that tlic immense majority of organisms noiv existing — if not all — are products of pre-existing organisms; and * Haeckel, GencrcUe Morphologic, II. 211. d2 the physical basis of mind. therefore organized matter is now mainly, if not solely, formed by organized matter. "We take, therefore, as our point of departure, the pro- toplasm ; this is the first of the three terms of the vital synthesis : Structure, Aliment, and Instrument. The eto- lution of this is proximately dependent on the ^jaZ>i<^w?;i afforded it in the Internal Medium, which is the true nutrient material, and to which what is usually called food stands in an external relation : for between the recep- tion of food and its assimilation by the organite, there is an indispensable intermediary stage, through which matter passes from the unorganized to the organized state. This intermediate is now recognized in plants as in animals. The old belief that plants were nourished directhj from the soil and atmosphere can no longer be sustained. The process of Nutrition is alike in both : in botli the mate- rials drawn from the External Medium are formed into proximate principles and organic substances. It is daily becoming more and more probable that the inorganic materials, water and oxygen, so freely entering into the or- ganism, never pass directly from the External JNIedium to the tissues, but have to pass through the Internal Medium where they are changed, so that the water is no longer free, but exists in a fixed state which has no analogue out of the living substance. Only a part of the water can be pressed out mechanically; tlie rest — that which is already incorporated with the other elements — can only be got rid of in a vacuum and at a high temperature. Oxygen, also, comports itself differently in the tissue ; as is proved by the fact that its physiological absorption is markedly diff'erent from any chemical oxidation in a dead or decom- posing tissue.* Be this as it may, we know that organic substances have to be unbuilt and rebuilt in the organ- ism ; that the albumen of our food never passes directly * See on this last point Ranke, Die Lehenshedingungen der Nerven, 1868, p. 34. THE NATUKE OF LIFE, 53 into the albumen of our tissues ; any more than the milk drunk by a nursing mother will pass into her breasts, and increase her supply, except by nourishing her. 60. In the First Series of these Problems the term Bioplasm was employed to designate this organized part of the Internal Medium. I was led to adopt it as a cor- responding term to that of Psychoplasm, by which I wished to designate the sentient material of the psycho- logical medium. There can be little doubt that the term Bioplasm was an unconscious reproduction of the title of Dr. Beale's work, which I must have seen advertised. I withdraw it now that I have read Dr. Beale's work, and see that the signification he attaches to the term is almost identical with Protoplasm. In lieu thereof, the term Plasmode (from iilasma, anything formed, and odos, a pathway) may be substituted : it represents the nutrient material on its way to form Protoplasm, whicli is forma- tive material; while the materials formed may be termed Organites and Products : the organite being the cell or cell-derivative (fibre, tube) ; the products being the gaseous liquid and solid derivatives of vital processes, which are secretions when they form intercellular substance or return into the plasmode and re-enter the vital circle ; excretions when they are rejected, as incapable of further assimila- tion. The liver-cell will furnish an example of each kind of product. The bile, though containing principles service- able in the chemical transformations, is for the most part excreted ; but besides bile, the liver-cell produces starchy and saccharine principles which are true secretions, and le-enter tlie plasmode. 61. The organite is thus composed of sap, sul)stance, and product ; tlie organism, of plasmode, tissue, and prod- uct. A glance at the vegetable-cell shows it to be con- stituted by the primordial utricle, or proto])lasm, the outermost layer of wliich is condensed into a membrane. 54 THE PHYSICAL BASIS OF MIND. or cell-wall, and the cavity thus enclosed is filled with sap. The cell-wall grows as the protoplasm grows, and the pro- toplasm draws its material from the plasmode. A glance at the blood, the great reservoir of the river of life, shows us plasmode in the serum, and organites in the corpus- cles ; the one distinguished by sodic salts, the other by potassic salts. The plasmode, or serum, is in a constant change of composition and decomposition, giving up to the various tissue-organites and iutercellular plasmodes the requisite materials, and receiving from organites and plasmodes the products of their changes. The serum is fed from the food and the tissues ; and it feeds the several plasmodes which bathe the several tissues. Passing into the capillaries, it becomes transformed as it passes through their walls into the intercellular spaces, saturating the acid products of the cell-activities with its alkalies, and furnishing the protoplasms with their needed materials. 62. It will be understood that, althougli in appearance these stages are sharply defined, in reality they are insen- sible. But from the analytical point of view we may re- gard Nutrition as the ofhce of the plasmode, and Evolu- tion as the office of the protoplasm. Although evolution or genesis of form depends on assimilation, it is not a necessary consequence : the plasmode or the protoplasm might preserve such perfect equality in the waste and repair, such complete equilibrium, as not to undergo any development. The ova, for example, which exist in the ovaries at birth are not all subsequently developed ; and if with modern embryologists we conclude that there is no replacement of these by proliferation we shall in them have examples of organites remaining unchanged through a period of fifty years.* But such an equilibrium is per- haps only possible in complete inactivity. * See Walpeyer, art. Eierstoclc, in Stricker's Handbuch der Lchre von den Gewchcn, 1870, p. 570. " I found in a foetus, which, in a case of THE NATURE OF LIFE. 55 63. Again, although the office of the plasmode is pri- marily that of forming protoplasm, I think tliere is evidence to suggest that it not only does this, but that some of it is used in the direct development of energy, especially heat and electricity. The various forms of starch and sugar taken in -with the food or formed in the liver, cer- tainly do not as such enter into protoplasm. The same with alcohol. 64. It is perhaps in forgetfulness of the artificial nature of analytical distinctions that controversies rage respect- ing what are called intercellular substances and cell-walls. Xow that the wall is no longer regarded as an essential constituent of the cell, but as a secondary formation, two opinions are maintained : first, that it is merely a concen- tration of the external layer of protoplasm ; secondly, that it is a product of secretion from the protoplasm. Both positions may be correct. Certainly in some cases there is no other appreciable difference between wall and protoplasm than that of a greater consistence ; whereas in many other cases there exists a decided difference in their chemical reactions, showing a difference of composi- tion. Taking both orders of fact, we may conclude that tlie cell-wall is sometimes part of the organite, and some- times product : a blood-cell and a cartilage-cell may be cited as examples of each. And this argument applies to the intercellular substance also. G5. The terms plasmode and protoplasm are general, and include many species. There are different plasmodes for the different tissues, so tliat we find phosphates of soda in the blood-serum, phosphates of potash in the nerve-plasma, phosphates of magnesia in the rauscle- j)lasma, and phosphates of lime in the bone-plasma ; hav- cxtra-iiterine pregnancy, had lain thirty years in the hody of its motlier, tlio .structure of tlie muscles as intact as if it had been born at its full time." — Viuciiow, Cellular Palholorjie, Lect. XIV. 56 THE PHYSICAL BASIS OF MIND. ing severally to form the specifically different protoplasms of these tissues. Observe, moreover, the gradations of these in respect of their physical state : the blood being the most liquid, the nerve a degree more solid, the muscle still more solid, and the bone almost entirely solid ; and since solubility of material is a necessary condition of the chemical changes, we can understand how the blood, the nerve, the muscle, and the bone represent degrees of vital activity : the greater the instability of organized sub- stance, the more active its molecular renovation. Many serious errors result from overlooking the specific differ- ences of protoplasms ; among them may be mentioned that very common one of asserting that the ovum of a man is not distinguishable from the ovum of any other mammal, nor the ovum of a mammal from tliat of a reptile ; nay, we sometimes see it stated that the protoplasm from which a mammal may be developed is the same as that which is the germ of an oak. So long as this simply asserts tliat we have at present no means of distinguish- ing them by any chemical or physical tests, there can be no objection raised ; but it is a serious misconception, which any embryological investigation ought to rectify, to suppose that the ovum is not specific from the first. 66. Between the organites and their plasmodes tliere is the necessary relation, which corresponds with the rela- tion between organisms and their mediums. Once formed, the organites are arranged side by side, or end on end, into textures or tissues, and these are grouped into organs, every organ being constituted by a collection of tissues, as every apparatus is by a collection of organs, and the organism by the federation of all the parts. We have more than once insisted on the necessity of synthetic in- terpretation to complete the indications of analysis : which means that no account of vital phenomena is real unless THE NATURE OF LIFE. 57 it takes in all the co-operant factors, both those of the or- gauism and the medium. Neglect of this canon vitiates Dr. Beale's otherwise remarkable labors, THE HYPOTHESIS OF GERMINAL MATTER. 67. It may help to elucidate certain important points if I here examine the hypothesis which Dr. Beale has worked out with such patient skill, but with what seem to me such unphysiological results. He deserves, I think, more applause than has been awarded to him, not only for the admirable patience with which lie has pursued the idea, but also for the striking definiteness of the idea it- self — always a great advantage in an hypothesis, since it gives precision to research. If biologists have paid but little attention to it, this is no doubt due to the theoreti- cal, still more than to the observational contradictions it presents. Histologists dispute his facts, or his interpreta- tions ; while other biologists do not see their way in the application of his hypothesis. Eespecting all disputed points of observation I shall be silent, for I have myself made no systematic researches in this direction, such as would entitle me to form an estimate of the evidence. But my dissent from the hypothesis is founded on bio- logical principles so fundamental that I should be willing to take my stand entirely on the facts he himself puts forward.* 08. The hypothesis is that notliing in the organism has any claim to vitality except the minute masses of proto- plasm (by him called bioplasm), which in the egg repre- sent, he thinks, about the one-thousandth part of the whole mass, the rest being lifeless matter, namely, pab- ulum, and formed material. This l)ioplasm is the gcr- * Sec Bkai.K, The Strvdurc of Ihc Simple Tisanes, LSCl ; tlm Iiitrod. to his edition of Todd and Bowman's Pliysiolorjicnl Anatomy, 18CG ; and Uow to Work u-itk the Microscope, 4th ed., 18G8 ; also Bioplasm, 1872. 58 THE PHYSICAL BASIS OF MIND. minal matter out of which, by a process of dying, arise the tissues and humors constituting the formed mate- rial — these, -with the pabulum which feeds the germinal matter, being all dead material. The germinal matter itself, though living, only lives because there is tempo- rarily associated with it that Vital Force of which we have already spoken (§ 14). In virtue of this associa- tion, a particle of matter not exceeding the one hundred- thousandth of an inch in diameter is said to be alive; and, presumably, to contain within it all those manifold powers which the term Life condenses. The pabulum brought under tlie influence of this Vital Force is trans- formed into germinal matter which, escaping from this mysterious influence, dies into tissue. Muscle-fibres and nerve-fibres are thus not living parts, nor are their ac- tions vital. So that, to be consistent, we must not speak of the organism as living, but as a dead structure ^j?'o- duccd by the Vital Force, and set in action by the aid of scattered bits of germinal matter. He has not, 1 think, stated whether each of these bioplasms lias its own Vital Force, so that the organism is the theatre of millions of Vital Forces ; or whether it is one Vital Force which ani- mates the whole organic world of plants and animals. But nothing can be less equivocal than his position re- specting the lifelessness of every jDart of the organism except the germinal matter. 69. The germinal matter may be selected as the pri- mary stage of the formed material, the initial point of growth, and thus stand for the pre-eminently distinctive centre of Nutrition ; but were we to limit all Nutrition to the germinal matter, as defined by Dr. Beale, and deny the co-operation of all the formed material, we should still not be justified in restricting Life to simple Nutri- tion. "We cannot exclude such phenomena as those of Sensation and Motion, nor can we assign these to the THE NATURE OF LIFE. 59 germinal matter* To suppose this, would be equivalent to saying that the steam which issues from a teakettle is capable of tlie actions of a locomotive engine. The steam from tlie kettle is like the steam from the boiler, it has molecular energy, and by this will co-operate in the production of mechanical work, if the mechanism be ad- justed to it. The molecular energy of the protoplasm in muscular fibre may be indispensable to the movements of the muscles, but these, and not the protoplasmic move- ments alone, are muscular contractions. An hypothesis, therefore, which is obliged to declare that muscle-fibre and nerve-fibre are not living, even when active in the organism, seems to me defective at its base. If we view these apart from the organism, they may, like all the other formed materials, be regarded as dead ; and no one doubts that epidermis, nail, horn, hair, and bone are dead in this sense, that they cannot live independently, and do not reproduce themselves. But so long as even these form constituents of the living organism, they also are living (§ 42). f It is only by a misconception of the ana- lytical artifice that so simple a truth could have been missed. 70, But this misconception meets us at many a turn. The Vitalist hypothesis of an extra-organic agent of * "The phy.sical property of the tissue does not depend upon this mat- ter, nor is Us function due to it." — Beale, Introduction to Todd and Bourman, p. 11. That is to say, he regards even contractility and neu- rility as pliysical, not vital facts. t In turning over the pages of a work which was celebrated some half- century ago — WvDOhvni'a Grundriss dcr Physiolo(jic — I was interested to find a clear recognition of this hiological principle : "Alio Thcile aller Organismen," he says, I. 2.33, "sie miigen noch so verscliieden in ihrem liaii, in ihrer Mischung, und in ihrer Thiitigkeit .seyn, sind ohno Aus- nahme als organisch mid niithin nls lehend zu bctrachf.rn." In a note he adds that i)hysiologists have considered certain solid parts — opidcrniis, nail, hair, and hones — to be dead ; " but all these are organically devel- oped, and arc in direct connection with tlie other parts." 60 TUE PHYSICAL BASIS OF MIND. course refuses to regard Life as the exj^ression of all the co-operant conditions; and even opponents of that hy- pothesis often fall into the same error of principle, when they attempt to explain Life by localizing it in the cells ; which is simply a morphological substitution for the once popular doctrine that only the vascular parts were organ- ized, and every part destitute of blood-vessels was dead. This idea seemed supported by the facts of the most higldy vascular parts being the most vital, and of a par- allelism existing between the vital activity of those organs which when injected seemed almost entirely com- posed of blood-vessels, as the liver and brain, and those which showed scarcely a trace of vessels, as cartilage and bone ; it seemed supported also by the appearance of blood-vessels in all new formations, and by the idea of the blood as the nutrient fluid. Tlien came the cell-doc- trine, and the belief that the cell was the really ultimate morphological element — which may be true — and that " here alone there is any manifestation of life to be found, so that we must not transfer the seat of vital action any- where beyond the cell," * — which is very questionable. 71. We have already seen that the cell is an anatomi- cal element, or organite ; the organism is but an aggre- gate of organites and their plasmodes. But Biology, which deals with the organism as a whole, and with func- tions which are the resultants of all the vital properties, must not be restricted to any single factor, how^ever im- portant. It would assuredly be deemed absurd to say that diamond rings and lead-pencils were the same, be- cause the diamond and the plumbago, which are the specific elements of each, are both the same chemical element, — carbon. The substance is really different in diamond and plumbago, is different in properties, and is, in rings and pencils, united with different substances into * ViRCHOW, Die Cellular Pathologic, 1860, Lect. I. THE NATURE OF UFE. 61 objects having very different properties. Whatever anal- ysis may discover as to the identities of organic struc- tures, we cannot explain a single vital phenomenon with- out taking into account the three terms, Structure, Ali- ment, and Instrument ; and whenever a cell is said to be the seat of vital action, these three terms must be im- plied. In Dr. Beale's hypothesis the restriction is carried to its extreme ; not content with the cell, he withdraws vital action from the cell as a whole, assigning it to the protoplasm and nucleus — cell-contents and cell- wall be- ing, in his view, dead. If it be true that the protoplasm is alone concerned in Nutrition, yet Nutrition is not Life. Occupied mainly with formative processes, it leaves other indispensable processes to other parts. He instances the removal of all the tissues during the metamorphoses of insects : — " new organs and textures are laid down afresh and developed ah initio, instead of being built up upon those first formed." But to show how he restricts the idea of Life, he adds : " Such complete change, however, necessitates a state of existence during which action or function remains in complete abeyance." * The muscles and nerves which are instrumental in this functional life are said to be dead. It is true that the ]nuscle-fibre does not develop fresh fibres. But it is equally true that tlie protoplasm of muscle does not alone execute muscular contraction. Each has its special ofiice. Hence I reject the idea that formed material is dead. He further says " formed material may he changed, it can- not change \i^e\t" Tiie antithesis is doubly inexact: 1°, nothing changes itself, but only yields to pressure, or re- acts on being stimulated ; and 2°, all tlie evidence at hand is against tlie notion tliat the formed material is not the seat of incessant molecular change ; it is wasted and re- paired molecule by molecule. Kolliker properly protests * Beale, Bioplasm, 104. 62 THE PHYSICAL BASIS OF MIND. against the growing tendency of histologists to deify protoplasm, and to make it the sole seat of vital changes, the cell-wall and cell-products having also, he says, their physiological importance. It is manifestly erro- neous to deny vital changes to the red blood-corpuscles on the ground of their no longer containing germinal matter.* 72. The analytical view may separate certain parts as active, and other j^arts as passive, and thus regard the cells as the seats of vital activity, the intercellular substance as merely accessory and instrumental ; but the real or synthetical view must recognize both parts as equally indispensable, equally vital. Take cartilage, for instance, with its enormous preponderance of intercellular sub- stance (formed material), and consider how absolutely impossible any of its uses would be were it reduced to the germinal matter of its corpuscles ! And so of all the tissues. 73. If formed material is not to be excluded from the living parts of the organism, neither is the plasmode, out of which the germinal matter arises, since here we have the nutritive changes in their highest activity ; and be- cause the property of Nutrition is here most active, the other property of Development is in abeyance. Dr. Beale holds that pabulum necessarily becomes germinal matter ; but when we come to treat of Nutrition it will appear that this is not more true than that Food necessarily be- comes Tissue : some of it does ; but much of it is used up for heat and other purposes. 74. What is true and important in the distinction be- tween germinal matter and formed material is, that from the former onwards there is a gradual process of devitali- zation, the older parts of every organite and tissue ap- proaching more and more to the state of inorganic matter. * KoLLiKER, Gcwebekkre, 5th ed., 1867, p. 12. THE NATURE OF LIFE. 63 But to show liow vain is the attempt to restrict Vitality to any one out of a complex of co-operant factors, we might set up a chemical hypothesis to the effect that Vitality depends on phosphates, and with it explain the phenomena quite as well as with the hypothesis of ger- minal matter. For not only is it found that the jDroduc- tive quality of a soil dej)ends on its richness in phos- phates, but, as Lehmann has shown, wlierever cells and fibres make their appearance phosphates are found, even in the lowest organisms, which, however, contain but little. Phosphates abound in seeds and ova, in muscles and gan- glia, and are deficient in the woody parts of plants and the elastic fibres of animals. The infant absorbs phos- phates in large quantities and excretes them in small quantities. Nervous activity is accompanied by the con- sumption of a third more phosphorus than accompanies muscular activity. Phosphates are among the most ener- getic of organic stimulants. But who would endow the phosphates with A'itality, on the ground of their indispen- sable presence in all vital processes ? 75. Life, as we saw, is the expression of the whole organism. Many of the parts are incapable of manifest- ing any vital phenomena except in connection with all the rest ; and of those parts which may be separated from the organism and continue to manifest some vital phenomena, none are capable of manifesting all. When the connexus of the parts is destroyed tlie organism is dead. Long after tliat cessation which we call Death, tliere are still evidences of Vitality in some of the parts : tlic heart will continue to beat, the glands will secrete, tlie liair will grow, the temperature will still be above that of the sur- rounding medium, the muscles will be excitable ; these vital properties are the activities of organized substances, and so long as tlie state of organization is preserved they are preserved ; but the Life, which is the synthesis of all 64 THE PHYSICAL BASIS OF JIIND. the vital properties, vanishes with the destruction of that synthesis. 76. May we not generalize this, and say that every special form of e.xistenee, organic or inorganic, is deter- mined by the synthesis of its elements ? Atoms are grouped into molecules, molecules into masses, masses into systems. Out of the textureless germinal membrane and the yolk, with no additions from without except oxygen and heat, are developed all tlie textures and organs of the chick ; and this chick weighs no more than the egg out of which it was evolved. The development has been a succession of syntheses — epigenesis upon epigenesis. We may, if we please, regard each organite, as it appears, living its separate life, and each tissue its separate life ; but we must not confound under the same symbol modes of existence so widely different as the activities of an organite, and the activities of an organism constituted by millions of organites. 77. If therefore we cannot restrict Life to the processes of Nutrition, Dr. Beale's hypothesis, whatever value it may have as explaining histogenesis, is quite unaccepta- ble. Neither Vital Force nor Bioplasm covers the whole ground. For the former there is no better evidence than our ignorance of tlie real synthesis ; for the latter the evi- dence is positive in its nature, but its interpretation is questionable. Dr. Beale selects as the germinal matter those portions of tissue which are susceptible of being deeply stained by the carmine solution, the formed mate- rial being only stained in a faint degree ; the nucleus and nucleolus are the portions of germinal matter which are most deepl)'- stained; and hence he concludes that the older the matter the fainter will be its coloration. There is no dispute as to the value of the staining process, in- vented by Gerlach, for the discrimination of chemically different parts of a tissue ; and Dr. Beale has made excel- THE NATURE OF LIFE. 65 lent use of it in his researches* But I altogether dispute tlie conclusion that the staining process reveals the parts which are exclusively vital ; and for this reason : it de- pends solely on the acid reaction of those parts ; and we cannot divorce the acid from the alkaline agencies, both being indispensable. Nay, it has been proved that in the living animal no organized substance can be stained. Lord Godolphin Osborne first discovered, in 1856, that the protoplasm of growing wheat was susceptible of col- oration ;f but Gerlach, in 1858, found that this never took place in the animal during life. He kept tadpoles and intestinal worms for weeks in colored fluids, without a single spot becoming stained ; although no sooner did these animals die than the staining began. Nor even when he injected the colored fluids under the skin and into the stomach, was the slightest coloration produced.^ To Gerlach's testimony may be added that of Stein, who, in his magnificent work on Infusoria, says that not only has no foreign substance ever been found in the pro- toplasm of the Opalina, but in the Acineta, and all the embryos of the higher Infusoria known to him, he has been unable to color the living substance. § This resist- ance of the living protoplasm is surely a serious objection to the hypothesis tliat only those parts of the dead organ- ism which are stained were the truly vital parts. Ranke * Nevertheless there are some facts dii'ectly contradicting his conclu- sions. For examine, he considers the axis cylinder of the nerve to be loinied material, and agrees with Max Schultze and others as to its lilirillated structure; j'et according to Listku and Turner, Gkrlach and Frey, the axis cylinder is deeply stained by cannine, and in this re- spect resembles the nucleus of protof)lasni. t From the quite recent experiments M. Baillon has submitted to the Acadimin des Sciences {I'Ah February, 1875), it appears that although cut flowers absorh) colored fluids, the roots when intact only absorb the lluid, and reject the coloring matters, by a veritable dialysis. X Gerlach cited by Ranke, op. cit., p. 76. § Stein, Dcr Organismus der Infusionsthicrchcn, 1859, p. 76. G6 THE PHYSICAL BASIS OF MIND. sums up the results of bis experiments thus : " They all show that the living cell resists the imbibition of every substance "which it cannot assimilate. It is precisely the impossibility of staining the cell that proves this conclu- sively, since every particle of carmine absorbed would have revealed its presence." It is not to be supposed that Dr. Beale was unac- quainted with Gerlach's experiments. He lias at any rate so far qualified the statement of his hypothesis as to ad- mit that it is only after death that the germinal matter is stained. " The living matter " (he says, Hoio to Work vjith the Microscope, p. 107) " possesses an acid reaction, or to speak more coiTectly, an acid reaction is always developed immediately after its death." Xow, since this acid reac- tion only presents itself after death, and it is this which is revealed by the carmine, we have no right to conclude that the carmine singles out the vital parts. Every one knows that the living muscle and nerve, when in repose, present an alkaline or faintly neutral reaction, and after excitation this is changed into an acid reaction, which increases Mith the exhaustion of the tissue. In strict logic, therefore — if we could logically apply such a test — it is the unstained parts that ought to be called vital But, in truth, alkalinity and acidity are equally indispen- sable. 78. The main object of my bringing this question for- ward was to illustrate the danger of being misled by analysis : a danger we shall see to be very serious in psy- chological inquiries. The aid derived from analysis need never be undervalued ; all that we have to bear in mind is that it is only a logical artifice, and that our real expla- nation must always be synthetic. Because of the ten- dency to rely on analysis there has been an imperfect dis- crimination of the profound difference between THE NATUKE OF LIFE. 67 ORGANISMS AND MACHINES ; and while on the one hand the legitimate striving of the biologist to display the mechanism of organic actions has been denounced by a certain school as Materialism and a hateful attempt to " rob Life of its mystery," there has been on the other hand a misconception of this mechan- ism, as if its dependent actions were of the nature of machines, that is to say, as if organized mechanisms were strictly comparable with machines constructed of inor- ganic parts. No doubt the laws of Mechanics are the same in both, for these are abstract laws which take no account of concrete differences. But when elaborate parallels are drawn up between steam-engines and ani- mal organisms, the coal consumed in the one likened to the food in the other, and the force evolved in the com- liustion in both being the same, there is a complete oblit- eration of all that specially distinguishes vital activity. 79. Between an organism and a machine there is the superficial resemblance that both have a complex struc- ture, and are constructed of different and dependent parts. But underneath this resemblance there is a radical diver- sity.* The arrangement of parts in the organism is more than Q, jnxtajwdtion, it is a solid ar it y,^x\?,\x\gixom. tlie fact of their being all differentiations from a common sub- stance which is a special combination of the three classes of proximate principles. Tlius they are not parts which have been put together, but which have been evolved, each out of a pre-existing part, and each co-o])erating in the very existence of the otlier. The machine is made of independent and primarily unrelated parts ; its integrity depends on tlie continued preservation of the substance * Staiil had a profound conviction of the radical difference, though lie was not able to point out the conditions involved. See his Disquisi- Ho de mcc/ianismi el onjanismi vera divcrsitate. G8 THE PHYSICAL BASIS OF MIND. of each part; waste is here destruction. The organism is constituted by interdependent and primarily related parts ; its integrity depends on the continued destruction and renovation of their substance ; waste is a condition of vitality. The actions of the machine are s/f&ordinated ; the actions of an organism are co-ordinated. The lever moves a wheel, and the wheel in moving liberates a spring, each transmitting a communicated impulse, but otherwise each acts independently — no slight modifica- tion in the structure or movement of the wheel will modify the structure or the movements of the lever, no alteration in the tension of the spring will affect the structure of the wheel. But in the organism all are parts of one sympathetic whole ; each reacts on each ; each is altered by the other. Not a nerve is stimulated, nor a muscle moved, but the entire organism is affected. A condensation here is the cause of a greater imbibition there. The injection of salt or sugar under the skin of the frog's leg will produce cataract in its eye. The activ- ity of a secreting cell in the ovary, or liver, alters the condition of the byain ; the activity of the brain will check the secretion of a gland, or relax the sphincters of the bladder. When we observe the growth of horns, or the appearance of the beard, concomitant with the secretion of spermatic cells — and especially when we observe with these a surprising cliange in the physical and moral capabilities and tendencies of the organism — we under- stand how the remotest parts of this mechanism are bound together by one subtle yet all-powerful tie. Noth- ing of this is visible in a machine. In a machine the material is so far of secondary importance that it may be replaced by materials of various kinds : a pulley may be worked with a hempen cord, a silken cord, or an iron chain ; a wheel may be wood, iron, copper, brass, or steel ; the actions will in each case be similar. Not so the THE NATURE OF LIFE. 69 organic meclianism : the slightest variation, either in com- position or intimate structure, will affect, and may frus- trate the organic activity. It is only in the skeleton that the specific character of the materials may be changed ; and here only in the substitution of one pliosphate for another in the solid masonry.* 80. Another marked characteristic of the organism is that it has a connexus of actions, the simultaneous effect of a continuous evolution, appearing in stages and ages. And in the animal organism there is a consensus as well as a connexus, through which there is evolution of Mind ; and in the Social Organism an evolution of Civilization. This consensus forms an intermediate stage through which the animal actions are sensitive as well as nutri- tive, and the nutritive are regulated by the sensitive. It is obvious that nothing like this is to be found in a machine ; and we conclude, therefore, that any view of the organism which regards its mechanism without tak- ing in these cardinal characteristics must be radically defective. We no more deny the existence of mechani- cal phenomena in denying that the organism is like a machine, tlian we deny the existence of chemical phe- nomena in denying that Vitality is chemical. * M. Feunaxd Papillon ha.s sliown that animals may bo foci with food deprived of phosphates of lime if its place is supplied with magnesia, strontia, or alumina ; they make their hones out of these as out of lime. Bat no such substitution is possible in muscle, nerve, or gland ; we can- not replace the phosphate of magnesia in muscles by the phosphate of iron, lime, or potash, as we can replace the iron of a wheel by steel, cop- licr, or brass. 70 THE PHYSICAL BASIS OF MIND. CHAPTEE IV. THE PKOPERTIES AND FUNCTIONS. 81. The terms Property and Function are not always used with desirable precision. There is, however, a marked distinction between the property which charac- terizes a tissue in whatever organ the tissue may be found, and the function which is exhibited by an organ composed of several tissues. We ought never to speak of a function unless we imply the existence of a correla- tive organ ; and it is therefore incorrect to speak of the function of Nutrition, since all the tissues nourish them- selves; but we may speak of certain organs as special instruments in facilitating Nutrition. Thus also with respiration, usually, but not accurately, spoken of as the function of the lungs ; the lungs being simply the most effective of the instruments by which the interchange of gases (which also takes place in every tissue) is facili- tated. If by Ptespiration we mean Breathing, then, in- deed, Eespiration is the function of the lungs ; if we mean the absorption of oxygen and the exhalation of carbonic acid, Piespiration is a general property of vital tissue. A fragment of muscle removed from the body respires, so long as its organization is intact ; but it does not hreathe — it has no accessoiy instruments, nor does it need them. The co-operation of nerve centres, dia- phragm, ribs, circulating system, etc., necessary in the complex organism to bring the due amount of oxygen to the tissues, and convey away the carbonic acid, is here THE NATURE OF LIFE. 71 needless. In the ascending animal series we find this necessity growing with the complexity of the organism. The whole skin respires in the amphibia, and to some extent in man also : a frog will live for ten or fourteen days after extirpation of its lungs, the skin respiring- sufficiently to keep up a feeble vitality. But the skin does not suffice; and, very early, certain 'portions are specialized into organs (at first in the shape of external gills, and finally as internal lungs), for the more energetic, because more specialized, performance of this office. In the simpler organisms the blood is easily reached by the air; therefore no instrument is needed. In primitive societies the transport of goods is effected by men and women carrying them ; in civilized societies by the aid of horses and camels, and wagons drawn by oxen ; till finally these are insufficient, and railways are created, whose power of transport transcends the earlier methods, as the breathing of a mammal transcends the respiration of a mollusc. Breathing is the special function of an organ — the lungs (or more strictly, the thoracic appara- tus) — as Eailway Transport is a special social function. Although each of the tissues forming this organ can, and does, exhale carbonic acid and absorb oxygen — and each of the railway servants can, and does, transport objects to and from the locomotive — yet the main work is thrown upon the special apparatus. 82. What is meant by properties of tissue and func- tions of organs may be thus illustrated. Let us suppose ourselves investigating the structure of a sliip. Wc find it composed of various materials — wood, iron, copper, hemp, canvas, etc. ; and these under various configura- tions are formed into particular parts serving particular purposes, such as deck, masts, anchor, windlass, chains, ropes, sails, etc. In all these parts the materials preserve their properties ; and wherever wood or iron may be 72 THE PHYSICAL BASIS OF MIND. placed, whatever purpose the part may serve, the prop- erties of wood and iron are unaffected ; and it is through a combination of these properties that the part is effec- tive ; while through the connection of one part with another the purpose becomes realized. The purposes to which masts, ropes, or sails are subservient may be called their functions ; and these of course only exist, as such, in the ship. It is the same with the organism. We find it composed of various Tissues, and these are com- bined into various Organs or Instruments.* The prop- erties of Tissues remain the same, no matter into what Organs they may be combined ; they preserve and exert their physical, chemical, and vital properties, as wood and iron preserve their properties. Each Tissue has its characteristic quality; and the Organ which is constructed out of a combination of several Tissues, more or less modified, is effective solely in virtue of these properties, -f- while the Function of that organ comes into play through its combination with other organs. For example, mus- cular tissue has a vital property which is characteristic of it. Contractility; and muscles are organs constituted by tliis tissue and several others ; :j: such organs have the * Anatomy resolves the Tissues into Organites (cells, fibres, tubes) ; here its province ends, and that of Chemistiy begins by pointing out the molecular composition of the Organites. t This luminous conception, though vaguely seized by Pixel, was first definitely wrought out by Bichat. See his Eecherches sur la Vie c.tla Mort — and especially his Jnatomie Generale, 1812, I. p. Ixx. It was one of the most germinal conceptions of modern times. X Just as there go other materials besides canvas to make a sail, and others besides iron to make a windlass, so there go other tissues besides the muscular to form a muscle — there is the membranous envelope, the nerve, the blood-vessels, the lymphatics, the tendon, and the fat. Even in Contraction there is another property involved besides the Contrac- tility of the muscular element, namely, the Elasticity of the fibrous wall of the muscular tube ; but Contractility is the dominant property, and determines the speciality of the function. THE NATURE OF LIFE. 73 general function of Contraction, but whether this shall be specially manifested in the beating of the heart, the winking of the eyelid, the movement of the chest, or tlie varied movements of the limbs, will depend on the ana- tomical connections. The reader unfamiliar with Biology is requested to pay very particular attention to this point ; he will find many obscurities dissipated if he once lays hold of the " principal connections." 82«. Although Bichat's conception was of great value, it was not sufficiently disengaged from the metaphysical mode of viewing biological phenomena. Both he and his disciples will be found treating Properties as entities, and invoking them as causes of the phenomena instead of recognizing them simply as abstract expressions of tlie phenomena. Eeaders of my First Series will remember how often I have had occasion to point out this common error: men having baptized observed facts with a com- prehensive name, forget the process of baptism, and sup- pose the name to represent a mysterious agency. The fact that gases combine is expressed in the terra affinity ; and then Affinity is understood to be the cause of the combinations. The fact that bodies tend towards each other is called their gravitation, and Gravitation is then said to cause the tendency. The doctrine of vital prop- erties has been thus misunderstood. While no one im- agines that he can operate on affinity otherwise than by operating on the known conditions under which gases combine, many a biologist and physician speaks as if he could operate on the Irritability of a tissue, or the Co- ordination of muscles, by direct action on these abstrac- tions. Let it be tlierefore once for all expressly stated that by the property of a tissue is simply meant tlie constant mode of reaction of that tissue under definite conditions. Tlie property is not a cause, otherwise than the conditions it 7-i TUH PHYSICAL BASIS OF MIND. expresses are a cause. And these conditions are first those of the organized structure itself, and secondly those of the medium in whicli it lives. Oxygen unites with Hydrogen to form water, but only under certain pressures ; so likewise muscles manifest Contractility on being stim- ulated (that is tlieir mode of reaction), but only under certain degrees of temperature, humidity, and a certain chemical composition of the plasmode. The property is so truly an expression of the co-operant conditions, that it is found to vary with those conditions, and to vanish when they vary beyond a certain limit. An attempt has been made to restrict the notion of a property to an ultimate fact. Whatever is not reducible to known conditions is to be accepted as a property. Combustion, for example, is reducible to the molecular combination of oxygen and some other gas ; but this combination itself is not reducible, and it is therefore chris- tened affinity. I cannot accept this view. Admitting our inability to say ivhy gases combine under certain con- ditions (and in this sense all facts are inexplicable and ultimate, unless we take the lioio as ample explanation of the loliy), I must still say that since affinity itself depends on the co-operation of known conditions, it is not less ex- plicable than combustion. But the point is unimportant : what we have liere to settle is the meaning of a property of tissue, — and that is the mode of reaction which tliat tissue manifests under constant conditions, internal and external 83. The evolution of Life is the evolution of special properties and functions from general properties and func- tions. The organism rises in power as it ramifies into variety. Out of a seemingly structureless germinal mem- brane, by successive differentiations certain portions are set apart for tlie dominant, or exclusive, performance of certain processes; just as in the social organism there is THE NATURE OF LIFE. 75 a setting apart of certain classes of men for the domi- nant or exclusive performance of offices, which by their co-operation constitute Society. The soldier fights, but ceases to build or reap, weave or teach ; the mason builds ; the agriculturist sows and reaps ; the priest and thinker teach ; the statesman governs. In simple societies each does all, or nearly all ; but the social life thus manifested is markedly inferior to the energetic life of a complex society. So with organisms. An amoeba manifests the general properties of Nutrition, Eeproduction, Sensibility, and Movement. But it has no special organs, conse- quently no special functions. The polype has a certain rudimentary specialization of parts : it has a simple ali- mentary cavity, and prehensile tentacles ; and although by these it can seize and digest its prey, it can only do so in a limited w^ay — all the manifold varieties and power of prehension and digestion observed in more complex organisms are impossible with such organs as the polype possesses. 84. Differences of structure and connection necessarily bring .about corresponding differences in Function, since Function is the directed energy of the Properties of tissues. One organ will differ from another in structure, as the liver from the pancreas, or the kidney from the spleen ; or one organ may closely resemble another but differ from it only in co7inections, as a sensory and a motor nerve, or an extensor and a flexor muscle. We must therefore always l)ear both points in mind. Every modification, structural or connectional, is translated by a corresponding modifica- tion in the office. The hand and the foot sliow this well. The tissues are the saYne in both, the properties are the same, and botli have the same general function of Pre- hension ; but their morphological differences carry corre- sponding differences in tlieir uses. Suppose we have a galvanic battery, we know that its 76 THE PHYSICAL BASIS OF MIND. electric force may be variously applied. Two pieces of charcoal lixed to the ends of its conducting wires give us the electric light ; replacing the charcoal by a telegraphic apparatus we can transmit a message from one continent to the other ; the wires dipped in a solution effect a chem- ical decomposition, dipped into a mixture of gases they effect a chemical composition. In these, and many other applications, the property of the battery is constant ; but the functions it subserves have varied with the varying co-operants. So with the properties of tissue.* Not only have we to bear in mind the organic connections of the tissues, but also the relation of the organs to their media. Swimming and Walking, for example, are both functions of the locomotive apparatus, but they are specially differ- enced by the media in which the animal moves. 85. The properties of tissues are their peculiar modes of reaction, and each tissue has its dominant characteris- tic, such as the Contractility of the muscle, and the Neur- ility of the nerve. But there has of late years sprung up a misleading conception, partly a consequence of the cell- theory, and partly of the almost ine\itable tendency of analysis to disregard whatever elements it provisionally sets aside ; this conception is the removal of the property from its tissue, and the localization of it in one of the organites — cell or fibre. This has been conspicuously mischievous in the case of the nerve-cell, which has been endowed with mysterious powers, and may be said to have usurped the place of nerve-tissue. I shall have to speak of this in the next problem. Here I only warn the student against the common error. The properties of a * "L'element musculaire peut etre annexe a une foule de niecanismes (livers ; tantot a nn os, tantot a un intestin, tantot a line vessie, tantSt a un vaisseau, tantot a un conduit excreteur, tantot enfin a dcs appareils tout a fait speciaux acertainesespeces d'animaux." — Claude Bernard, Eapport sur Ics Progrks de la Physiologie g&iierale, 1867, p. 38. THE NATURE OF LIFE. 77 tissue depend on the structure and composition of that tissue, together with its plasmode and products ; they vary as these vary. To select any one element in this complex, and ascribe the reaction of the tissue to that, is only permissible as a shorthand expression. 86. What has just been expounded may be condensed in the following l;)iological law : — Identity of tissue everywhere iinplies identity of property ; and similarity of tissue corresponding similarity of prop- erty. Identity of organic connection everywhere implies identity of function ; and similarity of organic connection sim ilarity of function. 87. This law, first formulated by me in 1859, and then applied to the interpretation of nervous functions, was so little understood that for the most part it met with either decided denial or silent neglect ; no doubt because of the general disinclination to admit that tlie properties and functions of the spinal cord could ha similar to those of the brain, in correspondence with the similarity of their tissues and organic connections. Even Professor Vulpian, who adopted it, as well as my principal interpretations, hesitated, and relapsed into the ortliodox view in assign- ing three different properties to one and the same tissue in cord, medulla oblongata, aud cerebrum.* In the course of our inquiries we shall so frequently liave to invoke this law til at I earnestly beg the reader to meditate upon it, and ask himself upon what other grounds, save those of structure and connection, the properties and functions * Vulpian, Lccons sur la PIn/sio/ogic du Syslhnc Ncrvcux, 18G6, p. .')81 . In a work just published I find M. Luvs hesitating at the consistent application of this law. After pointing out the identity of the tissue in cerebnim and spinal cord, he is only prepared to say that we cannot deny that there is no irnpossibilUy in admitting physiological equivalence where there is morphological equivalence. — LuYS, Actions Reflexes du Ccrveau, 1874, p. 14. 78 THE rnYsicAL basis of mind. can possibly rest ? If on no other, then similarity in structure and connection by logical necessity involves similarity in property and function. DOES THE FUNCTION DETERMINE THE ORGAN ? 88. Closely connected with this law, which simply formulates the self-evident principle that every action is rigorously deter nvmed hy the nature of the aycnt, and the conditions under which the act takes place, is the surpris- ing question whether functions are dependent upon organs, or organs dependent on functions ? — a question which sometimes takes this shape : Is Life the result of organ- ization, or is organization the result of Life ? The vitalist, who holds that Life is an extra-organic agent, is logical in declaring organization to be the conse- quence of Life ; * but there are many organicists who conclude from certain facts that organs are developed by functions, and that organization is a result of Life. There seems, however, to be some equivoque here. I cannot otherwise understand how Mr. Spencer should have writ- ten : " There is one fact implying that Function must be regarded as taking the precedence of Structure. Of the lowest rhizopods which present no distinctions of * It is because men converted the result into a principle, and sup- posed that Life preceded the Organism, that they were led to puzzle themselves over such facts as the continuance of vitality in divided organisms. Aristotle felt the force of the objection : "Plants when divided are seen to live, and so are certain insects, as if still possessing the same Vital Principle (fvxv) considered specifically {tu etdei) though not the same numericallj' (fir) d.pi6fj.u}). Each of these parts has sen- sation and locomotion for a time ; and there is no room for surprise at their not continuing to manifest these properties, seeing that the organs necessary for their preservation are absent." — Dc Anima, Lib. I. Ch. IV. Compare Basso, Pliilos. Naturalis advcrsus Aristotclcm, Amster- dam, 1649, p. 260 ; and Taurellus, Contra Cccsalinnum, 1650, p. 850 ; neither of them grappling with the difficulty so firmly as Aristotle. THE NATURE OF LIFE. 79 parts, and nevertheless feed and grow and move about, Professor Huxley has remarked that they exhibit Life without Organization." * The equivoque here arises from the practice of calling all living bodies " organisms," even those destitute of the differentiations called organs ; but if we substitute the term " living body " in lieu of " organism," the equivoque will disappear, and Function no longer seem to precede Structure. Neither Mr. Spen- cer nor Mr. Huxley would affirm that Life can be man- ifested without a living body; and every living body must have a structure of some sort — unless by structure be meant a special configuration of parts. The proper- ties of a body, whether it be simple or complex in struc- ture, result from the properties of its components ; and the vital phenomena vary with these varying compo- nents. The substance of a Rhizopod is indeed simple as compared with that of higher organisms, but is com- plex as compared with anorganisms ; and corresponding with this simplicity of structure there is simplicity of vital function, -j* 89. The properties of steam are exhibited by the kettle on the fire, no less than by the gigantic engine which animates a manufactory ; but the uses of steam (the functions of the engine) vary with the varying structure, and the applications of that structure to other structures. Precisely analogous is the case of the organ and its func- tion, in relation to the living substance of which it is a peculiar modification. Vital actions are manifested by a lump of protoplasm ; but tliese actions are as sharply demarcated from the actions of more highly organized animals, as the phenomena of a steam-engine are from those of a teakettle. 90. Mr. Spencer has nowhere defined what he means * Si'ENCER, Principles nf Biology, ]864, I. 153. t Coinp. Lamarck, Philos. Zool., IL 114. 80 THE PHYSICAL BASIS OF MIND. by Structure, nor given a definition of Organ, and this neglect makes it dillicult rightly to appreciate his view. But whether we take structure to signify the substance of the living body, or the differentiations of that sub- stance into separate tissues and organs, in either case the actions (functions) of which this structure is the agent must be rigorously determined by it. Mr. Spencer has avowed this in declaring that the "general physiologist may consider functions in their widest sense as the cor- relatives of tissue." Is this true in the widest sense and not true in the narrowest ? I am puzzled to find him insisting that "function from beginning to end is the determining cause of structure. Not only is this mani- festly true where the modification of structure arises by reaction from modification of function ; but it is also true where a modification of structure otherwise produced apparently initiates a modification of function." Such language would be consistent were he a vitalist who believed in a Principle independent of Matter which shapes matter into organic forms ; but as a positive thinker he can scarcely escaj)e the admission that since Function is the activity of the Agent (Function in the widest sense being the action of the whole Organism, and in its narrowest sense the action of the special Organ) there cannot be an aetivity preceding the agent. I sus- pect that he does not always bear in mind the distinction between Property and Function, and consequently is led into statements at variance with the principles he pro- fesses. As far as I understand the course of his thought, it runs somewhat thus : AVitli the increased use of an organ its volume may be increased, its structure altered ; this alteration will, by reaction, cause alterations in other organs, and thus the result of a change in the habitual activities of an animal will be an alteration in the ar- rangement of its parts. THE NATURE OF LIFE. 81 91, We speak loosely of an organ being developed by increased activity ; but this is loose speech, and investi- gation shows that the organ is not developed ly, but accompanies the increased activity, every increment of activity being necessarily preceded by a corresponding increment of structure. This is evident a 'priori: the force manifested is inherent in the structure manifesting it. Thus we ought not to say " the vascular system fur- nishes good instances of the increased growth that follows increased function " ; we ought to say, " that permits in- creased function." The muscle having a contractile power represented by 10, expends, we will suppose, 7 units of force in its normal activity, and these are replaced by its normal nutrition. If from an extra demand upon it 9 units are expended, the muscle becomes fatigued, if 10, exhausted, and it will no longer contract, the whole dis- posable sum of its contractility being dissipated. During all these stages the structure of the muscle — or to pre- vent all equivoque, let us say the substance of the muscle — has been changing, not indeed in any degree apprecia- ble to the eye, but appreciable by the more decisive tests of chemical and pliysiological reactions. Yet inasmuch as in the ordinary course of things the waste is quickly re- paired, the muscle in repose once more regains its origi- nal state, once more represents 10 units of contractility. Now let us consider what takes place wlien extra labor is thrown upon the mu.scle, when exercise causes growth. At the outset of a walking tour we may not be able to com- pass more than twenty miles a day, at its close we manage thirty. Is it the increased activity of the function which has caused tliis increase of structure ? In one sense, yes ; but let us understand it. Had the increase of activity been temporary, there would liave been only a temporary increase of structure. But wlien the ordinary expendi- ture of 7 units rises to 9, on several successive days, tliis 4* F 82 THE PHYSICAL BASIS OF MIND. extra expenditure of tissue has had to be met by an extra nutrition — i. e. more plasmode has been formed and more protoplasm. It is a physiological law, easily ex- plained, that, within due limits, extra waste brings about extra repair : as the channels are widened and raultijjlied, the derived currents become stronger, and the increased flow of nutrition which was temporary becomes perma- nent, because this increase is no longer dependent on an extra stimulus, but on an enlarged channel.* When the channels have not become multiplied or enlarged, which must be the case whenever the extra stimulus is fluctuating and temporary, the extra expenditure is not followed by increased size of the muscle : the currents resume their old directions, no longer being diverted. 92. Let the social organism furnish us with an illus- tration. At the present moment there is a movement against the retail shopkeepers of London in favor of Co- operative Stores. The stimulus of getting better goods and cheaper, attracts tlie flow of custom from its old chan- nels ; and if this continue a certain time the new arrange- ments will be so thoroughly organized, and will work so easily, that Co-operative Stores will to a great extent sup- plant the retail shops. But if from any causes the stim- ulus slackens before this reorganization has passed from the oscillating into the permanent stage — if the goods are not found to be superior, or the cheapness not worth the extra trouble — the old influences (aiding our indo- lence) which have been long and continuously at work, will cause the social organism to resume its old aspect, and the co-operative "varieties" will disappear, or exist beside the ancient " species." In the one case as in the other a glance at the process is enough to detect that the increase in the activity has * Comp. Spexcer, op. cit., II. 362, 363, for good illustrations of this. THE NATURE OF LIFE. 83 been preceded by a corresponding increase in the struc- ture. The muscle has not been enlarged ly extra activ- ity, but with it. The co-operative action has grown Avith each additional co-operator. Looking at the cases from afar we may justly say that development has been due to function ; but looking to the process we see that each increment of activity was necessarily dependent on an increment of substance. When changes of habit or adap- tation are said to produce modifications in structures, this is true in as far as one modification of structure necessa- rily brings with it correlative modifications, the growth of one part affecting the growth of all more or less ; but we must remember that to render the structure capable of new adaptations corresponding modifications must have been going on. The retail shopkeepers might securely laugh at the co-operative movement if the respectable families would not or could not become co-operant. When Mr. Spencer urges that " not only may leaf-stalks assume to a great degree the character of stems when they have to discharge the functions of stems by support- ing many leaves, and very large leaves, but they may assume the characters of leaves when they have to under- take the functions of leaves," I would ask if he is not reversing the actual process ? The stem cannot assume the functions of a leaf until it has first assumed the char- acter of a leaf. The assumptions of both must be grad- ual, and pari passu. 93. The liand is an organ, its function is prehension. Tlic performance of this function in any of its numerous applications is rigorously limited l)y the structure of the liand — the bones, muscles, nerves, circulating and ab- sorbent vessels, connective tissue, fat, etc. Fatigue the nerve, and the function will be feebly performed ; exhaust it, and the function ceases ; diminish tlie action of the heart, tie an artery, or vitiate tlie structure of the blood, S4 THE PHYSICAL BASIS OF MIXD. and the function will be correspondingly affected ; stiffen the tendons, soften the bones, diminish the synovial fluid, or increase the fat — in short, make any alteration what- ever in the structure of the hand, and an alteration is necessarily produced in its function. So rigorously is function dependent upon structure, that the hand of one man will execute actions which are impossible to another. The hand of a baby is said to be the same in structure as the hand of a man ; and since the powers (functions) of the two are notoriously different, we might rashly con- clude that here function was dissociated from structure. The case is illustrative. In baby and man the structure is similar, not the same ; the resemblance is of kind, not of degree ; and the function likewise varies with the de- gree. The penny cannon which delights the child is sim- ilar in structure to the ten-j)ounder which batters down walls ; and though, speaking generally, we may say that the function of both is to fire gunpowder for human ends, no one expects the penny cannon to be employed in war- fare. In physiology, as in mechanics, the effect A^aries with the forces involved. There can be no doubt that an exaggerated activity will produce a modification in the active organ, for this is only the familiar case of increased growth with increased exer- cise, and this is the biological meaning in which Function can be said not, indeed, to create, but to modify an exist- ing Organ. Preceding the activity there must be the agent. Every organ although having its special function has also the properties of all the tissues which constitute it. The function is only the synthesis of these properties to which a dominant tissue gives a sj)ecial character. The eye, for example, though specially characterized by its retinal sensibility to light, is largely endowed with muscles, and its movements are essential to Vision. The intestinal canal, again, though specially characterized by THE NATURE OF LIFE, 85 its secretions for the decomposition of food, has muscles which are essential to Digestion. In many animals, especially vegetable-feeders, there is an exaggeration of the muscular activity in certain parts of the intestinal canal which is only possible through a corresponding de- velopment of the muscular tissue, so that in some birds, crustaceans, and molluscs we find a gizzard, which is wliolly without a nuicous membrane to secrete fluids, and which aids Digestion solely by trituration. 94. IVIr. Spencer, as I have already suggested, seems to have been led into his view by not keeping distinctly present to his mind the differences between Properties of tissue and Function, the activity of an organ. "That function takes precedence of structure," he says, " seems implied in the definition of Life. If Life consist of inner actions so adjusted as to balance outer actions — if the actions are the substance of Life, while the adjustment constitutes its form ; then may we not say that the ac- tions formed must come before that which forms tliem — that the continuous change which is the basis of function must come before the structure which brings tlie function into shape?" The separation of "actions formed" from " that wliich forms them " is inadmissible. An action cannot come lefore the agent : it is the agent in act. The continuous change, which is the basis of Vitality, is a change of molecular arrangements ; and the organ whicli gives a special direction to the vital activity, e. g. whicli shapes the property of Contractility into the function of Prehension, this organ must itself be formed before it can manifest this function. It is true that in one sense the organs are formed by, or are differentiated in, a pre-exist- ent organism ; true that the general activity of living sub- stance must precede the special activity of any organ, as the expansions of steam must precede any steam-engine action ; but the general activity depends on the general 86 THE PHYSICAL BASIS OF MIND. structure ; and the special actions on the special struc- tures. If by Organization we are to understand not sim- ply organized substance, but a more or less complex arrangement of that substance into separate organs, the question is tantamount to asking whether the simplest animals and plants have life ? And to ask the question, whether Life precedes organic substance ? is tantamount to asking whether the convex aspect of a curve precedes the concave ! or whether the motions of a body precede the body ! To disengage ourselves from the complicated suggestions of such a word as Life, let us consider one of the vital phenomena. Contraction. This is a phenomenon manifested by simple protoplasm, and by the highly dif- ferentiated form of protoplasm known as muscle. In one sense it would be correct to say tliat Contractility as a general property of tissue precedes Contraction, which is specialized in muscle. But it would be absurd to say that viaiscular contraction preceded the existence of mus- cle, and formed it. Tlie contractions of the protoplasm are not the same as muscular contractions any more than the hand of a baby is the same as a man's ; the general property which both have in common depends on the substance both have in common ; the special property which belongs to the muscle depends on its special struc- ture. An infinite activity of the contractile protoplasm would be incompetent to form a muscle, unless it were accompanied by that peculiar change in structure which constitutes muscle. The teakettle might boil forever without producing a steam-engine or the actions of a steam-engine. That which is true of one function is true of all functions, and true of Life, which is the sum of vital activities. 95. It is this haziness which made Agassiz " regret to observe that it has almost become an axiom that iden- tical functions presuppose identical organs. There never THE NATURE OF LIFE. 87 was a more incorrect principle leading to more injurious consequences."* And elsewhere he argues that organs can exist without functions. But this is obviously to pervert the fundamental idea of an organ. " The teeth of the whale which never eat through the gums, and the breasts of the males of all classes of mammalia," are cited by him as examples of such organs without functions ; but in the physiological significance of the term these are not organs at all. It is no more to be expected that the breasts of the male should act in lactation, than that the slackened string of a violin should yield nmsical tones ; but the breasts of the male may be easily stimulated into yielding milk, and the slackened string of the violin may be tightened so as to yield tone. Even the breasts of the female do not yield milk except under certain conditions, and in the absence of these are on a par with those of the male. 96. Organized substance lias the general properties of Assimilation, Evolution, Sensibility, and Contractility ; each of the special tissues into which organized substance is differentiated manifests a predominance of one of these properties. Thus although the embryo-cells all manifest contractility, it is only the specialized muscle-cell which continues throughout its existence to manifest this prop- erty, and in a dominant form ; the muscle-cell also assim- ilates and develops, but besides having these properties in common witli all other cells, it has the special property of contracting with an energy not found in the others. All cells respire ; but the blood-cells have this property of absorbing oxygen to a degree so far surpassing that of any other cell that physiologists have been led to speak of their containing a peculiar respiratory substance. In like manner all, or nearly all, the tissues contain mydinr, — w^hich indeed is one of the chief constituents of the * Agassiz, Essay on Cla,ssification, p. 91. 88 THE niYSICAL BASIS OF MIND. yolk of eggs — but only in the wliite sheath of the nerves is it detached and specialized as a tissue. 97. But while Sensibility and Contractility are general properties of organized substance, specialized in special tissues, Sensation and Contraction are functions of the organs formed by such tissues ; and these organs are only found in animal organisms. It is a serious error, which we shall hereafter have to insist on, to suppose that Sen- sation can be the property of ganglionic cells, or, as it is more often stated, the property of the central gray matter. Sensation is the function of the organism ; it varies with the varying organ ; the sensation of Touch not being the same as the sensation of Sight, or of Sound. 98. AVe may consider the organism under two aspects — that of Structure and that of Function. The latter has two broad divisions corresponding with the vegetal and animal lives ; the one is Nutrient, the other Efficient. The one prepares and distributes Food, the other distrib- utes ]\Iotion. Of course this separation is analytical. In reality the two are interblended ; and although the neuro- muscular system is developed out of the nutritive system, it is no sooner developed than it plays its part as Instru- ment in the preparation and distribution of Aliment. This not being a treatise on Physiology, there can be no necessity for our here considering the properties and func- tions in detail. What is necessary to be said on Sensi- bility and Contractility will find its place in the course of future chapters ; for the present we will confine our- selves to Evolution on account of its psychological, no less than its physiological, interest. THE NATURE OF LIFE. 89 CHAPTEE V. EVOLUTION. 99. That organized substance has the property of nourishing itself by assimilating from its internal me- dium substances there present in an unorganized state, and that this is followed by a development or differentia- tion of structure, is familiar to every inquirer. Every one who has pursued embryological researches, and in a lesser degree every one who has merely read about them, must have been impressed by this marvel of marvels : an exceedingly minute portion of living matter, so simple in aspect that a line will define it, passes by successive modifications into an organism so complex that a treatise is needed to describe it ; not only do the cells in which the ovum and the spermatozoon originate, pass into a complex organism, reproducing the forms and fea- tures of the parents, and with these the constitutional peculiarities of the parents (their longevity, their diseases, their mental dispositions, nay, their very tricks and hab- its), but they may reproduce the form and features, the dispositions and diseases, of a grandfather or great-grand- father, wliich had lain dormant in the father or mother. ( 'onsider for an instant what this implies. A microscopic fell of albuminous compounds, wholly witliout trace of organs, not appreciably distinguishable from millions of (ither cells, does nevertheless contain within it tlie "pos- sihilities" of an organism so complex and so special as that of a Newton or a Napoleon. If ever there was a case 90 THE PHYSICAL BASIS OF MIND. when the famous Aristotelian notion of a "potential existence " seemed justified, assuredly it is tliis. And although we can only by a fallacy maintain the oak to be contained in the acorn, or the animal contained in the ovum, the fallacy is so natural, and indeed so difficult of escape, that there is no ground for surprise when physi- ologists, on first learning sometliing of development, were found maintaining that the perfect organism existed already in the ovum, having all its lineaments in minia- ture, and only growing into visible dimensions through the successive stages of evolution.* The preformation of the organism seemed an inevitable deduction from the opinions once universal. It led to many strange, and some absurd conclusions ; among them, to the assertion that the original germ of every species contained within it all the countless individuals which in process of time miglit issue from it ; and this in no metaphysical " poten- tial " guise, but as actual boxed-up existences (emboUes) ; so that Adam and Eve were in tlie most literal sense pro- genitors of the whole human race, and contained their progeny already shaped within them, awaiting the great accoucheur, time. 100. This was the celebrated " emboitement " theory. In spite of obvious objections it gained scientific accept- ance, because physiologists could not bring themselves to believe tliat so marvellous a structure as that of a human organism arose by a series of successive modifications, or because they could not comprehend how it was built up, part by part, into forms so closely resembling the parent- forms. That many and plausible reasons pleaded in favor of this opinion is evident in the fact that illustrious men like Haller, Bonnet, Vallisneri, Swammerdamm, Eeaumur, and Cuvier, were its advocates ; and if there is not a sin- * " Nulla in corpore animali pars ante aliam facta est, et omnes simul creatae existunt." — Haller, Elemcnta Physioloyice, VIII. 148. THE NATURE OF LIFE. 91 gle physiologist of our day who accepts it, or who finds any peculiar difficulty in following the demonstrations of embryologists, how from the common starting-point of a self-multiplying epithelial cell parts so diverse as hairs, nails, hoofs, scales, featliers, crystalline lens, and secreting glands may be evolved, or how from the homogeneous germinal membrane the complex organism will arise, there are very few among the scorners of the dead hypothesis who seem capable of generalizing the principles which have destroyed it, or can conceive that the laws of Evo- lution apply as rigorously to the animal and vegetable kingdo7ns as to the individual organisms. The illustrious names of those who advocated the preformation hypothe- sis may serve to check our servile submission to the authorities so loudly proclaimed as advocates of the fixity of species. The more because the two doctrines have a common parentage. The one falls with the other, and no array of authorities can arrest the fall. That the mani- fold differentiations noticeable in a complex organism should have been evolved from a membrane wholly des- titute of differences is a marvel, but a marvel which Sci- ence has made intelligible. Yet the majority of those to whom this has been made intelligible still find an impos- sibility in admitting that the manifold forms of plant and animal were successively evolved from equally simple origins. They relinquish the hypothesis of preformation in the one case, and cling to it in the other. Evolution, demonstralile in the individual history, seems prepos- terous in the history of the class. And thus is pre- sented the instructive spectacle of pliilosophers laughing at the absurdities of " preformation," and yet exerting all their logic and rhetoric in defence of " creative fiats " — which is simply the preformation liypothesis " writ large." 101. It would not be difficult to show that tlie doc- 92 THE I'HYSICAL BASIS OF MIXD. trine of Epigenesis, with which "Wolff forever displaced the doctrine of Preformation, leads by an inevitable logic to the doctrine of universal Evolution ; and that we can no more undei'stand the appearance of a uew organism which is not the modification of some already existing organism, than we can understand the sudden appearance of a new organ which is not the modification of some existing structure. In the one case as in the other we may disguise the process under such terms as creative fiat and preformation ; but these terms are no explana- tions ; they re-state the results, they do not describe the process ; whereas Epigenesis describes the process as it passes under the eye of science. 102. If any reader of these pages who, from theo- logical or zoological suspicion of the Develoj)ment Hy- pothesis, clings to tlie hyjDothesis of a creative Plan which once for all arranged the organic world in Types that could not change, will ask what rational interpretation can be given to the succession of phases each embryo is forced to pass through, it may help to give him pause. He will observe that none of these phases have any adap- tation to the future state of the animal, but are in positive contradiction to it, or are simply purposeless ; whereas all show stamped on them the unmistakable characters of ancestral adaptations and the progressions of Organic Evolution. What does the fact imply ? There is not a single known example of a complex organism wliicli is not developed out of simpler forms. Before it can attain the complex structure which distinguishes it, there must be an evolution of forms similar to those which distin- guish the structures of organisms lower in the series. On the hypothesis of a Plan which prearranged tlie or- ganic world, nothing could be more unworthy of a su- preme intelligence than this inability to construct an organism at once, witliout previously making several THE NATURE OF LIFE. 93 tentative efforts, undoing to-day what was so carefully done yesterday, and repeating for centuries the same ten- tatixcs, and the same corrections, in the same succession. Do not let us blink this consideration. There is a tra- ditional phrase much in vogue among the anthropomor- phists, which arose naturally enough from the tendency to take human methods as an explanation of the divine — a phrase which becomes a sort of argument — " The Great Architect." But if we are to admit the human point of view, a glance at the facts of embryology must produce very uncomfortable reflections. For what should we say to an architect who was unable, or being able was obstinately unwilling, to erect a palace except by first using his materials in the shape of a hut, then pulling it down and rebuilding them as a cottage, then adding story to story and room to room, not with any reference to the ultimate purposes of the palace, but wholly with reference to the way in which houses were constructed in ancient times ? What should we say to the architect who could not form a museum out of bricks and mortar, but was forced .to begin as if going to build a mansion : and after proceeding some way in this direction, altered his plan into a palace, and that again into a museum ? Yet this is the sort of succession on which organisms are con- structed. The fact has long been familiar; how has it been reconciled with Infinite Wisdom ? Let the follow- ing passage answer for a thousand : — " The embryo is nothing like the miniature of the adult. For a long while the body in its entirety and its details presents the strangest of spectacles. Day by day and hour by hour the aspect of the scene changes, and this instability is exhibited by the most essential parts no less than by the accessory parts. One would say that Nature feels her way, and only reaches the goal after many times missing the path, — on dirait que la nature tatonnc et ne conduit 94 THE PHYSICAL BASIS OF MIND. son ceuvre i\ bon fin qii'apres s'etre souvent trompee." * Writers have no compunction in speaking of Nature feel- ing her Avay and blundering ; but if in lieu of Nature, which may mean anything, the Great Architect be sub- stituted, it is probable that the repugnance to using such language of evasion may cause men to revise their con- ceptions altogether ; they dare not attribute ignorance and incompetence to the Creator. 103. Obviously the architectural hypothesis is incom- petent to explain the phenomena of organic development. Evolution is the universal process ; not creation of a direct kind. Von Baer, who very properly corrected the exaggerations which had been put forth respecting the identity of the embryonic forms with adult forms lower in the scale, who showed that the mammalian embryo never was a bird, a reptile, or a fish, nevertheless empha- sized the fact that the mammalian embryo passes through all the lower typical forms ; so much so that, except by their size, it is impossible to distinguish the embryos of mammal, bird, lizard, or snake. " In my collection," he says, " there are two little embryos which I have omitted to label, so that I am now quite incompetent to say to what class they belong. They may be lizards, they may be small birds, or very young mammals ; so complete is the similarity in the mode of formation of the head and trunk. The extremities have not yet made their appear- ance. But even if they existed in the earliest stage we should learn nothing from them, for the feet of lizards, mammals, and the wings of birds, all arise from the same common form." He sums up with his formula : " The special type is always evolved from a more general type."t * QuATREFAGES, Metamorphoses de V Homme et des Jnimaux, 1862, p. 42. t Von Baer, Ueber Entwickelungsgeschichte, 1828, I. 221. THE NATURE OF LIFE. 95 Such reminiscences of earlier forms are intelligible on the supposition that originally the later form was a modi- fication of the earlier form, and that this modification is repeated ; or on the supposition that there was a similar- ity in the organic conditions, which similarity ceased at the point where the new form emerged. But on no hy- pothesis of creative Plan are they intelligible. They are useless structures, failing even to subserve a temporary purpose. Sometimes, as Mr. Darwin remarks, a trace of the embryonic resemblance lasts till a late age : " Thus birds of the same genus, and of closely allied genera, often resemble each other in their first and second plum- age : as we see in the spotted feathers in the thrush group. In the cat tribe most of the species are striped and spotted in lines ; and stripes or spots can plainly be distinguished in the whelp of the lion and the puma. We occasionally, though rarely, see something of this kind in plants The points of structure in which the embryos of widely different animals of the same class resemble each other often have no direct relation to their conditions of existence. We cannot, for instance, suppose that in the embryos of the vertebrata the peculiar loop- like courses of the arteries near the bronchial slits are re- lated to similar conditions in the young mammal which is nourished in the womb of its mother, in the egg of a bird which is hatched in a nest, and in the spawn of a frog under water." 104. It would be easy to multiply examples, but I wiU content myself with tliree. The tadpole of the Sala- mander has gills, and passes his existence in tlie water ; but the tSnlamandra atra, which lives high up among the mountains, brings forth its young full-formed. This ani- mal never lives in tlie water. Yet if we open a gravid female, we find tadpoles inside her with exquisitely feath- ered gills, and (as I have witnessed) these tadpoles " when 96 THE niYSICAL BASIS OF MIND. from tlio mother's womb untimely ripped," if placed in water, swim about like the tadpoles of water newts. Ob- viously this aquatic organization has no reference to the future life of the animal, nor has it any adaptation to its embryonic condition ; it has solely reference to ancestral forms, it repeats a phase in the development of its pro- genitors. Again, in the embryo of the naked Nudibranch, we always observe a shell, although the animal is without a shell, and there can be no purpose served by the shell in embryonic life.* Finally, the human embryo has a tail, which is of course utterly purposeless, and which, although to be explained as a result of organic laws, is on the creative hypothesis only explained as an ad- herence to the general plan of structure — a specimen of pedantic trifling " worthy of no intellect above the pongo's." t 105. Humanly appreciated, not only is it difficult to justify the successive stages of development, the inces- sant building up of structures immediately to be taken down, but also to explain why development was necessary * Curiously enough, while the Nudibranch, which is without a shell, possesses one during its embryonic life, there is another mollusc, Ncritina fluviatilis, which possessing a shell in its subsequent life is without one during the early periods, and according to CLArAKEDE begins an inde- pendent existence, capable of feeding itself before it acquires one. See his admirable memoir on the Neritina, in Miiller's Archiv, 1857. + Has any advocate of the hypothesis that animals were created as we .see them now, fully formed and wondrously adapted in all their parts to the conditions in which they live, ever considered the hind legs of the seal, which he may have watched in the Zoological Gardens ? Here is an animal which habitually swims like a fish, and cannot use his hind limbs except as a rudder to propel him through the water ; but instead of hav- ing a fi,sh-like tail he has two legs flattened together, and nails on the toes — toes and nails being obvious superfluities. Now which is the more rational interpretation, that these limbs, in spite of their non- adaptation, were retained in rigid adherence to a Plan, or that the limbs were inherited from an ancestor who used them as legs, and that these legs have gradually become modified by the fish-like habits of the seal ? THE NATUEE OF LIFE, 97 at all. Why are not plants and animals formed at once, as Eve was mythically affirmed to be taken from Adam's rib, and Minerva from Jupiter's head ? The theory of Evolution answers this question very simply ; the theory of Creation can only answer it by affirming that such was the ordained plan. But the theory of Evolution not only gives the simpler and more intelligible answer to this question, it gives an answer to the further question which leaves the theory of Creation no loophole except a soph- ism — namely, why the formation of organisms is con- stantly beiug frustrated or perverted ? And, further, it gives an explanation of the law noticed by Milne Ed- wards, that Nature is as economical in her means as she is prodigal in her variation of them : " On dirait qu'avant de recourir a des ressources nouvelles elle a voulu q)uiser, en quelque sorte, chacun des precedes qu'elle avait mis en jeu." * The aj^plause bestowed on Nature for being economical is a curious transference to Nature of human necessities. Why, with a whole universe at her disposal, should Nature be economical ? Why must she always be working in the same groove, and using but a few out of the many substances at her command ? Economy is a virtue only in the poor. If Nature, in organic evolutions, is restricted to a very few substances, and a very few modes of combination, always creating new forms by modification of the old, and apparently incapable of creat- ing an organism at once, this must imply an inherent necessity which is very unlike the free choice that can render economy a merit. lOG. There may indeed be raised an objection to the Development Hypothesis on the ground tliat if the com- plex forms were all developed from the simpler forms, we ought to trace the identities through all their stages. If the fi.sh developed into the reptile, the reptile into the * Milne Edwards, Intro, d la Zoolugie Giniralc, 1851, p. 9. VOL. III. 5 o 98 THE PHYSICAL BASIS OF MIND. bird, and the bird into the mammal (wliich I, for one, think (questionable), we ought to find, it is urged, evidence of this passage. And at one time it was asserted that the evidence existed ; but this has been disproved, and on the disproof the opponents of Evolution take their stand. Although I cannot feel much confidence in the idea of such a passage from Type to Type, and although the pas- sage, if ever it occurred, must have occurred at so remote a period as to leave no evidence more positive than infer- ence, I cannot but think the teaching of Embryology far more favorable to it than to our opponents. Supposing, for the sake of argument, that the passage did take place, ought we to find the embryonic stages accurately repro- ducing the permanent forms of lower types ? Yon Baer thinks we ought ; and lesser men may follow him without reproach. But it seems to me that he starts from an inadmissible assumption, namely, that the development must necessarily be in a straight line rather than in a multiplicity of divergent lines. " When we find the em- bryonic condition," he says, " differing from the adult, we ought to find a corresponding condition somewhere in the lower animals." * Not necessarily. We know that the mental development of a civilized man passes through the stages which the race passed through in the course of its long history, and the psychology of the child repro- duces the psychology of the savage. But as this develop- ment takes place under conditions in many respects dif- ferent, and as certain phases are hurried over, we do not expect to find a complete parallel. It is enough if we can trace general resemblances. Yon Baer adds, " That certain correspondences should occur between the embry- onic states of some animals and the adult states of others seems inevitable and of no significance (?). They could not fail, since the embryos lie within the animal sphere, * Von Baer, o^. ciL, I. 203. THE NATURE OF LIFE. 99 and the variations of wliicli the animal body is capable are determined for each type by the internal connection and mutual reaction of its organs, so that particular repe- titions are inevitable." A profound remark, to which I shall hereafter have occasion to return, but its bearing on the present question is inconclusive. The fact that the embryonic stages of the higher animals resemble in gen- eral cliaracters the jDcrmanent stages of the lower animals, and very closely resemble the embryonic stages of those animals, is all that the Development Hypothesis requires. Nor is its value lessened by the fact that many of tlie details and intermediate stages seem passed over in the development of the higher forms, for the recapitulation can only be of outlines, not of details ; since there are differences in the forms, there must be differences in their histories. 107. In the preceding observations the object has sim- ply been to show that tlie phenomena to be explained can be rationally conceived as resulting from gradual Evolu- tion, whereas they cannot be so rationally interpreted on any other hypothesis. And here it may be needful to say a word respecting Epigenesis. The Preformation hypothesis, which regarded every organism as a simple educt and not tlie product of a germ, was called by its advocates an evolution hypothesis — meaning that the adult form was an outgrowth of the germ, the miniature magnified. Wolff, who replaced that conception by a truer one, called his, by contrast, Epige- nesis, meaning that there was not simply oii^-growth but new growth. " The various parts," he says, " arise one after the other, so that always one is secreted from {exccr- nirt), or deposited (deponirt) on the other ; and then it is either a free and independent part, or is only fixed to that which gave it existence, or else is contained within it. So that every part is the effect of a 2'>Te-existing part, and in 100 THE niYSICAL BASIS OF MIND. turn the cause of a succeeding part." * The last sentence expresses the concei:»tiou of Epigenesis which enibryolo- gists now adopt ; and having said this, we may admit that Wolff, in combating the error of preformation, replacing it witli tlie truer notion of gradual and successive forma- tion, was occasionally open to the criticism made by Von Baer, that he missed the true sense of Evolution, since the new parts are not added on to the old parts as new formations, but evolved from them as transformations. " The word Evolution, therefore, seems to me more de- scriptive of the process than Epigenesis. It is true that the organism is not preformed, but the course of its devel- opment is precisely the course which its parents formerly passed through. Thus it is the Invisible — the course of development — which is p^redetermined." -f- "When the word Epigenesis is used, therefore, the reader will under- stand it to signify that necessary succession which deter- mines the existence of new forms. Just as the formation of chalk is not the indifferent product of any combination of its elements, carbon, oxygen, and calcium, but is the product of only one series of combinations, an evolution through necessary successions, the carbon uniting with oxygen to form carbonic acid, and this combining with the oxide of calcium to form chalk, so likewise the formation of a muscle, a bone, a limb, or a joint has its successive stages, each of which is necessary, none of which can be trans- posed. The formation of bone is peculiarly instructive, because the large proportion of inorganic matter in its substance, and seemingly deposited in the organic tissue, would lead one to suppose that it was almost an acci- dental formation, which might take place anywhere ; yet * Wolff, Theorie der Generation, 1764, § 67. The reader will find abundant and valuable corroboration of this biological principle in Siu James Paoet's LeHures on Surgical Palholof))/. t Von Baer, Selbstbiographie, 1866, p. 319. THE NATURE OF LIFE. 101 although what is called connective tissue will ossify under certain conditions, true bone is the product of a very pe- culiar modification, which almost always needs to be pre- ceded by cartilage. That the formation of bone has its special history may be seen in the fact that it is the last to appear in the animal series, many highly organized iishes being without it, and all the other systems appear- ing before it in the development of the embryo. Thus although the mother's blood furnishes all the requisite material, the fcetus is incapable of assimilating this ma- terial and of forming bone, until its own development has reached a certain stage. Moreover, when ossification does begin, it generally begins in the skull (in man in the clav- icle) ; and the only approach to an internal skeleton in the Invertebrates is the so-called skull of the Cephalo- poda. Not only is bone a late development, but cartilage is also ; and although it is an error to maintain that the Invertebrates are wholly destitute of cartilage, its occa- sional presence having been fully proved by Claparede and Gegenbaur, tlie rarity of its presence is very signifi- cant. The animals which can form shells of chalk and chitine are yet incapable of forming even an approach to bone. 108. Epigenesis depends on tlie laws of succession, which may be likened to the laws of crystallization, if we l)ear in mind the essential differences between a crystal and an organism, the latter retaining its individuality through an incessant molecular change, the former only by the exclusion of all change. When a crystalline solu- tion takes shape, it will always take a definite shape, which represents what may be called tlie directum of its Corccs, jhc polarity of its constituent molecules. In like manner, when an organic plasmode takes shape — crystallizes, so to speak — it always assumes a specific shape dependent on the polarity of its molecules. Crys- 102 THE PHYSICAL BASIS OF MIND. tallographers liave determined the several forms possible to crystals ; histologists have recorded the several forms of Organites, Tissues, and Organs. Owing to the greater variety in elementary composition, there is in organic substance a more various polar distribution than in crys- tals ; nevertheless, there are sharply defined limits never overstepped, and these constitute what may be called the specific forms of Organites, Tissues, Organs, Organisms. An epithelial cell, for example, may be ciliated or colum- nar, a muscle-fibre striated or non-striated, a nerve-fibre naked or enveloped in a sheath, but the kind is always sharply defined. An intestinal tube may be a uniform canal, or a canal differentiated into several unlike com- partments, with several unlike glandular appendages. A spinal column may be a uniform solid axis, or a highly diversified segmented axis. A limb may be an arm, or a leg, a wing, or a paddle. In every case the anatomist recognizes a specific type. He assigns the uniformities to the uniformity of the substance thus variously shaped, under a history which has been similar ; the diversities he assigns to the various conditions under which the pro- cesses of growth have been determined. He never expects a muscular tissue to develop into a skeleton, a nervous tissue into a gland, an osseous tissue into a sen- sory organ. He never expects a tail to become a hand or a foot, though he sees it in monkeys and marsupials serv- ing the offices of prehension and locomotion. He never expects to find fingers growing anywhere except from metacarpal bones, or an arm developed from a skull. The well-known generalization of Geoffroy St. Hilaire that an organ is more easily annihilated than transposed, points to the fundamental law of Epigenesis. In the same direction point all the facts of growth. Out of a formless germinal membrane we see an immense variety of forms evolved ; and out of a common nutritive fluid this variety THE NATURE OF LIFE. 103 of organs is sustained, repaired, replaced ; and tins not indifferently, not casually, but according to rigorous laws of succession ; that which precedes determining that which succeeds as inevitably as youth precedes maturity, and maturity decay. The nourishment of various organs from plasmodes derived from a common fluid, each select- ing from that fluid only those molecules that are like it-s own, rejecting all the rest, is very similar to the forniation of various crystals in a solution of different salts, each salt separating from the solution only those molecules that are like itself Reil long ago called attention to thi-s analogy. He observed that if in a solution of nitre and sulpliate of soda a crystal of nitre be dropped, all the dis- solved nitre crystallizes, the sulphate remaining in solu- tion ; whereas on reversing the experiment, a crystal of sulphate of soda is found to crystallize all the dissolved sulphate, leaving the nitre undisturbed. In like manner muscle selects from the blood its own materials which are there in solution, rejecting those which the nerve will select. 109. Nay, so definite is the course of growth, that when a limb or part of a limb is cut off from a crab or salaman- der, a new limb or new part is reproduced in the old spot, exactly like the one removed. Bonnet startled the world by tlie announcement that the Nals, a worm common in ])onds, spontaneously divided itself into two worms ; and that when he cut it into several j)ieces, each piece repro- duced head and tail, and grew into a perfect worm. Thi« had Itcen accepted by all naturalists without demur, until Dr. "VVilliams, in liis "Iteport on I'ritisli Annelida, 1851," declared it to be a fable. In 1858, under the impulse of Dr. Williams's very emphatic denial, I rc]teateossihle extent, i. e. possi- ble when there are no resistances to be overcome. Not only the increasing tension of antagonist muscles, but the resistance of tendons, bones, and softer parts must be taken into account. Thus, the increase of the black- smith's muscular power would involve a considerable in- crease in all the tissues of tlie arm ; but such an increase would involve a reconstruction of his whole organism. Whenever there is an encroachment of one tissue on another, there is a disturbance of the normal balance, which readily passes into a pathological state. If the brain is overrun with connective tissue, or the heart with fatty tissue, we know the consequences. If connective tissue is deficient, epithelial runs to excess, no longer lim- ited by its normal antagonist, and pus, or cancer, result. 118 c. It is unnecessary here to enlarge on this point, I have adduced it to show tliat we must extend our con- ception of the struggle for existence beyond that of the competition and antagonism of organisms — the external struggle ; and include under it the competition and antag- onism of tissues and organs — the internal struggle. Va- riability is inherent in organic substances, as the result of their indefiniteness of composition (§ 45?>). Tliis vari- ability is indefinite, and is rendered definite by the com- petition and antagonism, so that every particular variation is the resultant of a composition of forces. The forces in operation are the internal and external conditions of ex- istence — i. e. the nature of the organism, and its response to the actions of its mediunj. A cliange may take place 120 THE PHYSICAL BASIS OF MIND. in UiG niedimii witliout a corresponding response from the organism ; or the change may find a response and the organism become modified. Every modification is a selec- tion, determined by laws of growth ; it is the resultant of a struggle between what, for want of a better term, may be called the organic affinities — which rej)resent in organized substances what chemical affinities are in the anorganized. Just as an organism which has been modi- fied and thereby gained a superiority over others, has by this modification been selected for survival — the selection being only another aspeqt of this modification — so one tissue, or one organ, which has surpassed another in the struggle of growth, will thereby have become selected. Natural Selection, or survival of the fittest, therefore, is simply the metaphorical expression of the fact that any balance of the forces which is best adapted for survival wHl survive. Unless we interpret it as a shorthand ex- pression of all the internal and external conditions of existence, it is not acceptable as the origin of species. 118 (i. Mr. Darwin has so patiently and profoundly meditated on the whole subject, that we must be very slow in presuming him to have overlooked any important point. I kuow^ that he has not altogether overlooked this which we are now considering ; but he is so preoccupied with the tracing out of his splendid discovery in all its bearings, that lie has thrown the emphasis mainly on the external struggle, neglecting the internal struggle ; and has thus in many passages employed language which implies a radical distinction where — as I conceive — no such distinction can be recognized. "Natural Selection," he says, " depends on the survival under various and complex circumstances of the best-fitted individuals, but has no relation whatever to the primary cause of any modifica- tion of structure." * On this we may remark, first, that * The Variation of Aniiwds and Plants, 1868, II. p. 272. THE NATURE OF LIFE. 121 selection does not depend on the survival, but is that sur- vival ; secondly, that the best-fitted individual survives because of that modification of its structure which has given it the superiority ; therefore if the primary cause of this modification is not due to selection, then selection cannot be the cause of species. He separates Natural Selection from all the primary causes of variation, either internal or external ■ — either as results of the laws of growth, of the correlations of variation, of use and disuse, etc., and limits it to the slow accumulations of such vari- ations as are profitable in the struggle with competitors. And for his purpose this separation is necessary. But biological philosophy must, I think, regard the distinction as artificial, referring only to one of the great factors in the production of species. And for this reason : Selec- tion only comes into existence in the modifications pro- duced either by' external or internal clianges ; and the selected change cannot be developed further by mere inheritance, unless the successive progeny have such a disposition of the organic affinities as will rej)eat the pri- mary change. Inherited superiority will not by mere transmission become greater. The facts which are relied on in support of the idea of " fixity of species " show at any rate that a given superiority will remain stationary for thousands of years ; and no one supposes that tlie progeny of an organism will vary unless some external or internal cause of variation accompanies the inheritance. Mr. Darwin agrees with Mr. Spencer in admitting the dif- ficulty of distinguishing between the effects of some definite action of external conditions, and the accumula- tion through natural selection of inherited variations serviceaV)lo to the organism. But even in cases where the di.stinction could be clearly established, I think we should only sec an historiral distinction, that is to say, one between effects produced by particular causes now VOL. HI. 6 122 THE PHYSICAL BASIS OF MIND. in operation, and effects produced by very complex and obscure causes in operation during ancestral develop- ment. 118 e. The reader will understand that my criticism does not pretend to invalidate Mr. Darwin's discovery, but rather to enlarge its terms, so as to make it include all the biological conditions, and thus explain many of the variations which Natural Selection — in the restricted acceptation — leaves out of account. Mr. Darwin draws a broad line of distinction between Variation and Selec- tion, regarding only those variations that are favorable as selected. I conceive that all variations which survive are by tliat fact of survival, selections, whether favorable or indifferent. A variety is a species in formation ; now Selection itself is not a cause, or condition, of variation, it is the expression of variation. Mr. Darwin is at times explicit enough on this head : " It may metaphorically be said tliat Natural Selection is daily and hourly scrutiniz- ing throughout the world the slightest variations ; rejecting those tliat are bad, preserving and adding up all that are good ; silently and insensibly working, whenever and wherever opportunity offers, at tlie improvement of each organic being in relation to its organic and inorganic con- ditions of life."* But the metaphorical nature of the term is not always borne in mind, so that elsewhere Natural Selection is said to " act on and modify organic beings," as if it were a positive condition and not the expression of the modifying processes. Because grouse are largely destroyed by birds of prey, any change in their color which would render them less conspicuous would enable more birds to escape ; but it is obvious that this change of color will be due to Organic Affinity ; and only when the change is effected will there have been that selection which exjjresses it. 'Sh: Darwin's language, how- * Origin of SiKcies, 5tli ed. p. 96. THE NATURE OF LIFE. 123 ever, is misleading. He says : " Hence Natural Selection might be most effective in giving the proper color to each kind of grouse, and in keeping that color when once acquired." This is to make Selection an agent, a condi- tion of the development of color ; which may be accepted if we extend the term so as to include the organic changes themselves. Again : " Some writers have imagined that Natural Selection induces variability, whereas it only im- plies the 2)reservation of such variations as are beneficial to the being under its conditions of life." It, however, is made to imply more than this, namely, the accumulation and further modification of such variations. " The mere existence of individual variability and of some well- marked varieties, though necessary as the foundation, helps us but little in understanding how species arise in nature. How have all those exquisite adaptations of one part of the organization to another part, and to the con- ditions of life, and of one organic being to another being, been perfected ? " ]\Iy answer to this question would be : By Organic Affinity, and the resulting struggle of the tis- sues and organs, the consequences of which are tliat very adaptation of the organism to external conditions, which is expressed as the selection of the structures best adapted. The selections are the results of the struggle, according to my proposed extension of the term " struggle." Mr. Darwin defines the struggle : " The dependence of one being on another, and including (what is more important) not only the life of the individual but success in leaving progeny." This definition seems defective, since it omits the primary and more important struggle wliicli takes place between the organic affinities in operation. To suc- ceed in the struggle with competitors, the organism must have first acquired — by selection — a su])eriority in one or more of its organs. 118/. A little reflection will disclose the importance 124 THE PHYSICAL BASIS OF MIND. of keeping our eyes fixed on the internal causes of varia- tion, as well as on the external conditions of the struggle. Mr. Darwin seems to imply that the external conditions which cause a variation are to be distinguished from the conditions which accumulate and perfect such variation, that is to say, he implies a radical difference between the process of variation and the process of selection. This, I have already said, does not seem to me acceptable ; the selection, I conceive, to be simply the variation which has survived.* If it be true that a Variety is an incipient Species and shows us Species in formation, it is in the same sense true that a variation is an incipient organ. A species is the result of a slowly accumulating divergence of struc- ture; an organ is the result of a slowly accumulating differentiation. At each stage of differentiation there has been a selection, but we cannot by any means say that this selection was determined by the fact of its giving the organism a superiority over rivals, inasmuch as during all the early stages, while the organ was still in formation, there could be no advantage accruing from it. One ani- mal having teeth and claws developed will have a decided superiority in the struggle over another animal that has no teeth and claws ; but so long as the teeth and claws are in an undeveloped state of mere preparation they confer no superiority. 118//. Natural Selection is only the expression of the * Mr. Darwin has himself, iu the following passage, stated a somewhat similar view, and rejected it : "In one sense the conditions of life may be said not only to cause variability, but likewise to include Natural Selection, for the ccmditions determine whether this or that variety shall survive. But when man is the selecting agent, we clearly see that the two elements of change are distinct ; the conditions cause the variability, the will of man acting either consciously or unconsciously accumulates the variations in certain directions, and this answers to the survival of the fittest under nature." (p. 168.) THE NATURE OF LIFE. 125 results of obscure physiological processes ; and for a satis- factory theory of such results we must understand the nature of the processes. In other words, to understand Natural Selection we must recognize not only the facts tlius expressed, but the factors of these facts, — we must analyze the " conditions of existence." As a preliminary analysis we find external conditions, among which are in- cluded not only the dependence of the organism on the inorganic medium, but also the dependence of one organ- ism on another, — the competition and antagonism of the whole organic world; and internal conditions, among which are included not only the dependence of the organism on the laws of composition and decomposition whereby each organite and each tissue is formed, but also the depend- ence of one organite and one tissue on all the others — the competition and antagonism of all the elements. The changes wrought in an organism by these two kinds of conditions determine Varieties and Species. Al- though many of the changes are due to the process of natural selection brought about in the struggle witli com- petitors and foes, many other changes have no such rela- tion to the external struggle, but are simply tlie results of the organic affinities. They may or they may not give the organism a greater stability, or a greater advantage over rivals ; it is enougli that they are no disadvantage to the organism, they will then survive V)y virtue of the forces which produced them. 119. Tlie position tlius readied will be important in our examination of tlie Theory of Descent by whicli Mr. Darwin tentatively, and liis followers boldly, explain the oljserved resemblances in structure and function as due to blood-relationship. The doctrine of Kvolution allirins that all (^oiii]il(',x organisms are evolved by differenlialidii I'rora simpler organisms, as we see the complex organ (ivolved from simj)ler form.s. But it does not necessarily allirm 126 THE PHYSICAL BASIS OF MIND. that the vast variety of organisms had one starting-point — one ancestor ; on tlie contrary, I conceive that the principles of Evolution are adverse to such a view, and insist ratlier on the necessity of innumerable starting- points. Let us consider the question. That the Theory of Descent explains many of the facts must be admitted ; but there are many which it leaves obscure ; and J\lr. Darwin, with that noble calmness ■which distinguishes him, admits the numerous difticulties. Whether these will hereafter be cleared away by an im- provement in the Geological Eecord, now confessedly imperfect, or by more exhaustive exploration of distant countries, none can say; but, to my mind, the probability is, that we shall have to seek our explanation by enlarg- ing the idea of Natural Selection, subordinating it to the laws of Organic Affinity. It does not seem to me, at pres- ent, warrantable to assume Descent as the sole principle of morphological uniformities ; there are other grounds of resemblance beyond those of blood-relationship ; and these liave been too much overlooked ; yet a brief con- sideration will disclose that similarity in the physio- logical laws and the conditions of Organic Affinity must produce similarity in organisms, independently of rela- tionship ; just as similarity in the laws and conditions of inorganic affinity will produce identity in chemical species. We do not suppose the carbonates and phos- phates found in various parts of the globe, or the families of alkaloids and salts, to have any nearer kinship than that which consists in the similarity of their elements and the conditions of their combination. Hence, in or- ganisms, as in salts, morphological identity may be due to a community of conditions, rather than community of descent. Mr. Darwin justly holds it to be "incredible that individuals identically the same should have been produced through Natural Selection from parents s])ecijl- THE NATURE OF LIFE. 127 ccdly distinct" but he, since he admits analogous varia- tions, will not deny that identical forms might issue from parents having Mddely different origins, provided that these parent forms and the conditions of their reproduc- tion were identical, as in the case of vegetable and animal resemblances. To deny this would be to deny the law of causation. And that which is true of identical forms under identical conditions is true of similar forms un- der similar conditions. When History and Ethnology reveal a striking uniformity in the progression of social ])hases, we do not thence conclude that the nations are directly related, or that the social forms have a common parentage ; we conclude that the social phases are alike because they have had common causes. A¥hen chemists point out the uniformity of type which exists in com- pounds so diverse in many of their properties as water and sulphuretted or selenetted hydrogen, and M'hen they declare phosphoretted hydrogen to be the congener of ammonia, they do not mean that the one is descended from the other, or that any closer link connects them than that of resemblance in their elements. In the case of vegetal and animal organisms, we ob- serve such a community of elementary sul)stance as of itself to imply a community in their laws of combina- tion ; and under similar conditions the evolved forms must be similar. With this community of elementary substance, there are also diversities of substance and of co-operant conditions ; corresponding witli tliese diversi- ties there must be differences of form. Thus, although observation reveals that the bond of kiusliip does really unite many widely divergent forms, and tlie princijilc of Descent with Natural Selection will account for many of the resemblances and differences, there is at present no warrant for assuming that all resemblances and differ- ences are due to this one cause, but, on the contrary, we 128 THE PHYSICAL BASIS OF MIND. are justified iu assuming a deeper principle which may be thus formulated : All the complex organisms are evolved from organisms less complex, as these were evolved from simpler forms ; the link which unites all organisms is not always the common bond of heritage, but tlie uniformity of organized substance acting under similar conditions. It is therefore consistent with the hypothesis of Evo- lution to admit a variety of origins or starting-points, though not consistent to admit the sudden appearance of complex Types, sucli as is implied in the hypothesis of specific creations. 119 a. The analogies of organic forms and functions demand a more exhaustive scrutiny than has yet been given them. Why is it that vessels, nerves, and bones ramify like branches, and why do these branches take on the aspect of many crystalline forms ? Why is it that cavities are constantly prolonged in ducts, e. g. the mouth succeeded by the oesophagus, the stomach by the intes- tines, the bladder by the urethra, the heart by the aorta, the ovary by the oviduct, and so on ? Wby are there never more than four limbs attached to a vertebral column, and these always attached to particular verte- brae ? Why is there a tendency in certain tissues to form tubes, and in these tubes commonly to assume a muscular coat ? * To some of these queries an answer might be suggested which would bring them under known physical laws. I merely notice them here for the sake of emphasizing the fact that such analogies lie deeply imbedded in the laws of evolution, and tliat what has been metaphorically called organic crystallization will account for many similarities in form, without forcing us to have recourse to kinship. To take a very simple case. No one will maintain that the crystalline forms of snow have any kinship with the plants wliich they often re- * Even in the nerve-sheaths of some Annelids there are muscles. THE NATURE OF LIFE. 129 semble. Mr. Spencer has noticed tlie development of a wing-bearing brancli from a wing of the Ptilota jjlamosa, when its nutrition is in excess. " This form, so strik- ingly like that of the feathery crystallizations of many inorganic substances, proves to us that in such crystalli- zations the simplicity or complexity of structure at any place depends on the quantity of matter that has to be polarized at that place in a given time. How the ele- ment of time modifies the result, is shown by the famil- iar fact that crystals rapidly formed are small, and that they become larger when they are formed more slowly." * It may be objected, and justly, that in the resemblance between crystals and organisms the analogy is purely that of form, and usually confined to one element, where- as between organisms there is resemblance of substance no less than of form, and usually the organisms are alike in several respects. The answer to this objection is, that wherever there is a similarity in the causal condi- tions (substance and history) there must be a correspond- ing similarity in the results ; if this similarity extends to only a few of the conditions, the analogy will be slight ; if to several, deep. But whetlier slight or deep we are not justified, simply on the ground of resemblance, in assuming, short of evidence, that because they are alike, two organisms are related by descent from a com- mon ancestor. 120. Let us glance at a few illustrations. It has been urged as a serious objection to Mr. Darwin's hypothesis, f that it^fails to explain the existence of phosphorescent organs in a few insects ; and certainly, when one con- siders the widely different orders in which tliese organs appear, and tlieir absence in nearly related forms, it is a difficulty. In noctilucae, earthworms, molluscs, scolo- * Spencrb, Principles of JjiciJog!/, II. 72. ■y Fai\'Ri:, Variahilil.r. de I'Esp^cc, p. 15. 6* I 130 THE niYSICAL BASIS OF MIND. pendra, and fireflies, we may easily supi^ose tlie presence ot" similar organic conditions producing tlie luminosity; but it requires a strong faith to assign Descent as the cause.* We may say the same of the electric organs possessed by seven species of fish, belonging to five widely separated genera. Although each species appears to have a limited geographical range, one or the other is found in almost every part of the globe. These organs occupy different positions, being now on each side of the head, now along the body, and now along the tail ; and in different species they are innervated from different sources. Their intimate structure also varies ; as appears from the remarkable investigations of Max Schultze.f They cannot, therefore, be homologous. How could they have arisen ? Xot by the slow accumulations of Natural Selection, because, until the organs were fully formed, they could be of no advantage in the struggle ; hence the slow growth of the organ must have proceeded without the aid of an advantage in the struggle — in each case * These luminous organs would furnish an interesting digression if space permitted it. The student is referred to the chapter in Milne Edwakds's Leqons sur la Physiolorjie ct V Anatomic Comparee, 1863, VIII. 94, sq. Leydig, Histologic, 1857, p. 343. Kolliker, Microscopi- cal Journal, 18§8, VIII. 166, and Max Schultze, Archiv fur viikros. Anat., 1865, p. 124. My friend Schultze vas kind enough to show me some of his preparations of the organs of Lempyris splciididula, fiom which the drawings in his memoir were made. They reminded me of the electric organs in fishes by a certain faint analogy, the trachea in the one holding the position of neiTCs iu the other. I ma}"^ remark, in passing, that it is not every phosphorescent animal that has distinct luminous organs. There is a lizard {Pterodactyl us Gecko) which occa- sionally becomes luminous. "Asingiilar circumstance occurred to the colonial surgeon, who related it to me. He was lying awake in bed when a lizard fell from the ceiling upon the top of his mosquito-curtain ; at the moment of touching it the lizard became brilliantly luminous, illuminating the objects in the neighborhood, much to the astonishment of the doctor." Collingwood, Rambles of a Naturalist, 1868, p. 169. + Max Schultze, Zur Kenntniss der eledrischen Organc der Fische, 1858-9. THE NATUEE OF LIFE. 131 from some analogous conditions which produced a dif- ferentiation in certain muscles. The fundamental resem- blance to muscles was pointed out by Cams long ago. It has been insisted on by Leydig:* and Owen says, " The row of compressed cells constituting the electric prism of the Torpedo offers some analogy to the row of microscopic discs of which the elementary muscle fibre appears to consist." f We must not, however, forget that tliese resemblances are merely such as suggest that the electric organ is a differentiation of the substance which elsewliere becomes muscular, and that Dr. Davy was justified in denying the organ to be muscular. § That it is substituted for muscle cannot be doubted. Now, although we are entirely ignorant of the conditions which cause this differentiation of substance whicli else- where becomes muscular, but here becomes electric organs, we can understand that, when once such a development had taken place, if it in any way profited the fish in its struggle for existence, Natural Selection would tend to its further increase and propagation. So far Mr. Darwin carries us with him ; but we decline proceeding further. The development of these organs in fishes so widely re- moved, does not imply an ancestral community. It is interpretable as mere growth on a basis once laid ; and therefore would occur with or without any advantage in the struggle with rivals. Tlie similarity in concurrent conditions is quite enough to account for the resemblance in structure. This, with his accustomed candor, Mr. Darwin ailuiits. " If the electric organs," he says, " had been inheiited from one ancient progenitor thus provided, we might have expected that all electric fishes would be specially rehited to each other. Nor does Geology at all ♦ LeydiGj Ilislolorjie, 1857, p. 45. t Owen, Anatomy of the Vertebrates, 1866, I. 358. X Davy, llesearches, Physiolo(jical and Anatomical, 139, I. 33. 132 THE niYsiCAL basis of mind. lead to the belief that formerly most fishes had electric organs wliich most of their modified descendants have lost." 121. It may seem strange that he should nrge a diffi- culty against his hypothesis when it could be avoided by the simple admission that even among nearly allied animals great differences in develoj)ment are observable, and the electric organs might be ranged under such diversities. But Mr. Darwin has so thorouohlv wrought out his scheme, that he foresees most objections, and rightly suspects that if this principle of divergent devel- opment be admitted, it will cut the ground from under a a vast array of facts which his hypothesis of Descent requires. The sudden appearance of new organs, not a trace of which is discernible in the embryo or adult form of organ- isms lower in the scale, — for instance, the phosphorescent and electric organs, — is like the sudden appearance of new instruments in the social organism, such as the print- ing-press and the railway, wholly inexplicable on the theory of Descent,* but is explicable on the theory of * " If it could be demonstrated that any complex organ existed which could not possibly have been fonned by numerous successive slight modi- tications, my theory would absolutely break down." — Dakwix, Origin of Species, 5th ed. p. 227. In several passages insistence is made on this. "Natura non facit saltum " may be perfectly true ; but without impugn- ing the Law of Continuity we may urge that the Law of Discontinuity is equally true. The one is an abstract ideal conception ; the other is a concrete ideal conception. According to the one, eveiy change from rest to motion, or from one state to another, must pass through infinites ; ac- cording to the other every change is abrupt. In my First Series, Vol. I. p. 327, I have shown how, on mechanical principles, ever}' change in an organism must be abrupt. A glance at the metamorphoses of the em- bryo, or the stages of insect-development, will show very sudden and abrupt changes. Let me also cite Mr. Darwin against himself : "When we remember .such cases as the formation of the more complex galls, and certain monstrcsities, which cannot be accounted for by reversion, cohe- .sion, etc., and sudden, strmigly marked deviations of structure, such as THE NATURE OF LIFE. 133 Organic Affinity. For observe : if we admit that differ- entiations of structure, and the sudden appearance of organs, can have arisen spontaneously — i. e. not heredi- tarily — as the outcome of certain changed physical con- ditions, we can hardly refuse to extend to the whole organism what we admit of a j)articular organ. If, again, we admit that organs very similar in structure and func- tion spontaneously appear in organisms of widely differ- ent kinds — e. g. the phospliorescent and electric organs — we must also admit that similar resemblances may pre- sent themselves in organisms having a widely difCereut parentage ; and thus the admission of the spontaneous evolution of closely resembling organs carries witli it the admission of the spontaneous evolution of closely resem- bling organisms : that the protoplasm of muscular tissue should, under certain changed conditions, develop into the tissue of electric organs, is but one case of the law that organized substance will develop into organisms closely resembling each other when the conditions have been similar. 122. It is to be remarked that Mr. Darwin fi.xes his attention somewhat too exclusively on the adaptations which arise during the external struggle for existence, and to that extent neglects the laws of organic alfinity ; just as Lamarck too exclusively fixed liis attention on the influence of external conditions and of wants. Not that Mr. Darwin can l)e said to overlook the organic laws ; he simply underestimates the part tliey play. Occasionally he seems arrested by them, as when instancing the " trail- ing ])alm in the JNIalay Archipelago, which cliiul)S the loftiest trees by the aid of exquisitely constructed hooks, the appearance of a moss-rose on a cointnon rcse, we must admit that the organization of tlie individual is cajjable througli if.s own laws of growth, inide.r crrt.ain cmulitions, of unchTgoing great modifications, iiid(![)('ndent of the gradual accumulation of sliglit inherited modifications." — Origin, ji. 151. See also note to § 130, further on, p. 142. 134 THE PHYSICAL basis of mind. clustered arouiul the ends of the branches, and this contriv- ance no doubt is of the highest service to the plant ; but as there are nearly similar hooks on many trees which are not climbers, the hooks on the palm may have arisen from unknown laws of growth, and have been subsequently taken advantage of by the plant undergoing furtlier mod- ification and becoming a climber." 12r). I come round to the position from which I started, that the resemblances traceable among animals are no proof of kinship ; even a resemblance so close as to defy discrimination would not, in itself, be such a proof. The absolute identity of chalk in Australia and in Europe is a proof that tliere was absolute identity in the formative conditions and the constituent elements, but no proof whatever that the two substances were originally con- nected by genesis. In like manner the similarity of a plant or animal in Africa and Europe may be due to a common kinship, but it may also be due to a common his- tory. It is indeed barely conceivable that the history, from first to last, would ever be so rigorously identical in two parts of the globe as to produce complex identical forms in both ; because any diversity, either in structure or external conditions, may be the starting-point of a wide diversity in subsequent development ; and the case of organic combinations is so far unlike the inorganic, that while only one form is possible to the latter (chalk is either formed or not formed), many forms are possible to organic elements owing to the complexity and indefi- niteness of organic composition. But although forms so allied as those of Species are not readily assignable to an identical history in different quarters of the globe, it is not only conceivable, but is eminently probable, that Or- ders and Classes have no nearer link of relationship than is implied in their community of organized substance and their common history. The fact that there is not a single THE NATUllE OF LIFE. 135 mammal common to Europe and Australia is explicable, as Mr. Darwin explains it, on the ground that migration has been impossible to them ; but it is also explicable on tlie laws of Evolution — to have had mammals of the same species and genera would imply a minute coinci- dence in their history, which is against the probabilities. Again, in the Oceanic Islands there are no Batrachians ; but there are Reptiles, and these conform to the reptilian type. ]\Ir. Darwin suggests tliat the absence of Batrachia is due to the impossibility of migration, their ova being destroyed by salt water. But may it not be due to the divergence from the reptilian type, which was effected elsewhere, not having taken place in these regions ? AVlien we find the metal Tin in Prussia and Cornwall, and nowhere else in Europe, must we not conclude that in these two countries, and nowhere else, a peculiar con- junction of conditions caused this peculiar evolution ? 124. The question at issue is. Are the resemblances observable among organic forms due to remote kinship, and tlieir diversities to the divergences caused by adap- tation to new conditions ? or are the resemblances due to similarities, and the diversities to dissimilarities in the suhstance and history of organic beings ? Are we to assume one starting-point and one centre of creation, or many similar starting-points at many centres ? So far from believing that all plants and animals had tlieir origin in one primordial cell, at one yiarticular spot, from which descendants nn'grated and l)ecame diversified under the diverse conditions of tlieir migration, it seems to me more consistent with the princijilc of Evolution to admit a vast variety of origins more or less resembling each other ; and this initial resemblance will account for the similari- ties still traceable under the various forms ; while the carbj differences, becoming intensified by development un- der different conditions, will yield the diversities. The 136 THE niYSICAL BASIS OF MIND. evolution of organisms, like the evolution of crystals, or the evolution of islands and continents, is determined, 1st, by laws inherent in the substances evolved, and, 2d, by relations to the medium in which the evolution takes place. This being so, we may a priori afiirm that the resultant forms will have a community strictly correspond- ing with the resemblance of the substances and their con- ditions of evolution, together with a diversity correspond- ing with their differences in substance and conditions. It is usually supposed that the admission of separate " cen- tres of creation " is tantamount to an admission of " suc- cessive creations " as interjn-eted by the majority of those who invoke " creative fiats." But the doctrine of Evolu- tion, which regards Life as making its appearance conse- quent vpon a coneurrcnce of definite conditions, and regards the specific forms of Life as the necessary consequences of special circumstances, must also accept the probability of similar conditions occurring at different times and in different places. Upon what grounds, cosmical or bio- logical, are we to assume that on only one microscopic spot of this developing planet such a group of conditions was found — on only one spot a particle of protein sub- stance was formed out of the abundant elements, and under conditions which caused it to grow and multiply, till in time its descendants overran the globe ?- The hy- pothesis that all organic forms are the descendants of a single germ, or of even a few germs, and are therefore united by links of kinship more or less remote, is not more acceptable than the hypothesis that all the carbon- ates and phosphates, all the crystals, and all tlie strata found in different parts of the globe, are the descendants of a single nnolecadc, or a few molecules ; or, — since this may seem too extravagant, — than that the various mala- dies which afflict organic beings are, in a literal sense, members of fcimilu's liaving a nearer relationship than THE NATURE OF LIFE. 137 that of being the jjhenomena manifested by similar organs under similar conditions — a conception wliicli might have been accepted by those metaphysical pathologists who regarded Disease as an entity. Few philosophers have any hesitation in supposing that other planets besides our own are peopled with organic forms, though, from the "reat differences in tlie conditions, tliese forms must be extremely unlike those of our own planet. If separate worlds, why not separate centres ? The conclusion seems inevitable that wherever and whenever the state of things permitted that peculiar combination of elements known as organized substance, there and then a centre was estab- lished — Life had a root. From roots closely resembling each other in all essential characters, but all more or less different, there have been developed the various stems of the great tree. Myriads of roots have probably perished witliout issue ; myriads have developed into forms so ill- adapted to sustain the fluctuations of the medium, so ill-fitted for the struggle of existence, that they became extinct before even our organic record begins ; myriads have become extinct since then ; and the descendants of those which now survive are like the shattered regiments and companies after some terrific battle. 125. There seems to me only one alternative logically permissible to the Evolution Hypotliesis, namely, that all organic forms have had either a single origin, or else numerous origins ; in otlier word.s, that a primordial cell was the starting-point from which all organisms liave been successively developed ; or that the development issued from many independent starting-points, more or less varied. This is apparently not the aspect presented by the liypothesis to many of its advocates ; they seem to consider that if all organic forms arc not the lineal descendants of one progenitor, they must at any rate be the descendants of not more than four or five. The com- 138 TIIK niYSICAL BASIS OF MIND. moil belief inclines to one. Mr. Darwin, whose caution is as leiiiai'kable as his courage, and whose candor is delightful, hesitates as to which conclusion should be adopted : " I cannot doubt," he sajs, " that the theory of descent, with modifications, embraces all the members of the same class. I believe that animals have descended from, at most, only four or five progenitors, and plants from an equal or lesser number. Analogy would lead me one step further, namely, to the belief that all animals and plants have descended from some one prototype. But analogy may be a' deceitful guide." 126. I cannot see the evidence which would M-arrant the belief that Life originated solely in one microscopic lump of protoplasm on one single point of our earth's surface ; on the contrary, it is more probable that from innumerable and separate points of this teeming earth, myriads of protoplasts sprang into existence, ivlienever and wherever the conditions of the formation of organized substance were present. It is probable that this has been incessantly going on, and that every day new protoplasts appear, struggle for existence, and serve as food for more highly organized rivals ; but whether an evolution of the lower forms is, or is not, still going on, there can be no reluctance on the part of every believer in Evolution to admit that when organized substance was first evolved, it "was evolved at many points. If this be so, the commu- nity observable in organized substance, wherever found, may as often be due to the fact of a common elementary composition as to the fact of inheritance. If this be so, we have a simple explanation both of the fundamental resemblances which link all organisms together, and of the characteristic diversities which separate them into king- doms, classes, and orders. The resemblances are many, and close, because the forms evolved had a similar ele- mentary composition, and their stages of evolution were THE NATURE OF LIFE. 139 determined by similar conditions. The diversities are many, because the forms evolved had from the first some diversities in elementary composition, and their stages of evolution were determined under conditions which, though similar in general, have varied in particulars. Indeed, there is no other ground for the resemblances and differences among organic beings than the similari- ties and dissimilarities in their Substance and History ; and, whether the similarities are due to blood-relation- ship, or to other causes, the results are the same. There is something seductive in the supposition that Life radi- ated from a single centre in ever-increasing circles, its forms becoming more and more various as tliey came under more various conditions, until at last the whole earth was crowded with diversified existences. " From one cell to myriads of complex organisms, through count- less a^ons of development," is a formula of speculative grandeur, but I cannot bring myself to accept it ; and I think that a lingering influence of the tradition of a " cre- ative fiat " may be traced in its conception. May we not rather assume that the earth at the dawn of Life was a vast germinal membrane, every slightly diversified point ])roducing its own vital form ; and these myriads upon myriads of forms — all alike and all unlike — urged by the indwelling tendencies of development, struggled with each other for existence, many failing, many victorious, the victors carrying their tents into the camping ground of the vanquished ? The point raised is the immense im- ])robability of organized substance having been evolved only in one microscopic spot ; if it were evolved at more than one spot, and under slightly varying conditions, tlierc would necessarily have arisen in these earliest for- mations the initial diversities which afterwards determined the essential independence and difference of organisms. 129. Let us for a moment glance at the resemblances and 140 THE PHYSICAL basis of mind. diversities observable in all organisms. All have a com- mon hasiii, all being constructed out of the same funda- mental elements : carbon, hydrogen, nitrogen, and oxygen ; these (the organogens, as they are named), with var}^- ing additions of some other elements, make up what we know as Organic Substance, vegetal and animal. Another peculiarity all organisms have in common, namely, that their matter is neither solid nor liquid, but viscid. Be- side this community of Substance we must now place a community of History. All organisms grow and mul- tiply by the same process ; all pass through metamorphic stages ending in death ; all, except the very simplest, differentiate parts of their substance for special uses, and these parts (cilia, membranes, tubes, glands, muscles, nerves) have similar characters in whatever organism they appear, and their development is always similar, so that the muscles or nerves of an intestinal worm, a lob- ster, or a man, are in structure and history fundamentally alike. When, therefore, we see that there is no biological character of fundamental importance which is not uni- versal throughout the organic world, wlien we see that in Structure and History all organisms have a community pervading every variety, it is difficult not to draw the conclusion that some hidden link connects all organisms into one ; and wlien, further, it is seen that the most divergent forms may be so arranged by the help of inter- mediate forms only slightly varying one from the other, that the extreme ends — the monad and the man — may be connected, and a genealogical tree constructed, which will group all forms as modified descendants from a single form, the hypothesis that kinship is the hidden link of which we are in search becomes more and more cogent. 130. But now let the other aspect be considered. If there is an unmistakable uniformity, there is also a diver- THE NATURE OF LIFE. 141 sity no less unmistakable. The chemical composition of organic substances is various. Unlike inorganic sub- stances, the composition of which is rigorously definite, organic substances are, within narrow limits, variable in composition (§ 45). I pass over the resemblances and differences observed in the earliest stages of development, marked as they are, and direct attention to the fact, that down at what must be considered the very lowest organic region, we meet with differences not less striking than those met with in the higliest, we find structures (if structures they may be calledj, wliich cannot be affiliated, so widely divergent is their cuniposition. The structureless vibrio, for example, is not only capable of living in a medium destitute of oxygen, but is, according to M. Pasteur, actually killed by oxygen ; whereas the equally simple bacteria can no more dispense with oxygen than other animals can. Consider for a moment the differences implied in the fact that one organism cannot even form an enveloping membrane to contain its protoplasm, whereas another contrives to se- crete an exquisite shell ; yet between the naked liliizopod and the shelled Rhizopod our lenses and reagents fail to detect a difference. One Monad can assimilate food of only one kind, another Monad assimilates various kinds.* What a revelation of chemical differences appears in the observations of M. Pasteur respecting the vibrio and bac- teria, in a fermentescible liquid — the former beginning the ])utrid fermentation which the latter completes ! We cannot doubt that some marked difference must exist be- tween the" single-celled organism which produces alcoholic fermentation, and that which produces acetic fermenta- tion, and that again which produces l)utyric fermentation ; and if we find distinctions tlius established at the lowest * On till! Nutrition of Monads, seo tlie rtiinaikahle memoir by CiEN- KOWSKi, in \\\ii Archiv fur mikros. ylnalomic, I. 221, sq. 142 THE niYsicAL basis of mind. region of the organic series, we need not marvel if the ilistinctions become wider and more numerous as the series becomes more diversified. The structure and devel- opment of an organism are dependent on the affinities of its constituent molecules, and it is a biological principle of great importance which Sir James Paget insists on, wlien he shows how " the existence of certain materials in the blood may determine the formation of structures in which they may be incorporated." * Any initial diver- sity may tlius become the starting-point of a considerable variation in subsequent evolution. *(' Thus, supposing that on a given spot there are a dozen protoplasts closely resembling eacli other, yet each in some one detail slightly varying ; if tliis variation is one which, by its relations to the external medium, admits of a difference in the assim- ilation of materials present in the medium, it may be the origin of some ncio direction in development, and the ulti- mate consequence may be the formation of a shell, an internal skeleton, a muscle, or a nerve. Were this not so, * Paget, Lectures on Surgical Pathologij, edited hy Turner, 1865, p. 19. t It has recently been sliown that certain Crustacea vary not only from species to species, but from genus to genus, when living in water of different degrees of saltness. By continued dilution of the salt water an Artcmia was developed into another .species, and this again into a Brmichijixs — a genus of large dimensions, with an extra abdominal segment, and a different tail ; a genus, moreover, Mhich is propagated sexually, whereas the Artcmia is parthenogenetic, as a rule. See Nature, 1876, June 8, p. 133. The exceeding importance of this fact is, that it proves sjjpcific and even generic differences to originate simply through the gradual changes of the medium and the adaptation of the organism to these new condi- tions. It also disproves the very common notion — adopted even by Mr. Darwin himself — that " organic beings must be exposed during several generations to new conditions to cause any appreciable amount of varia- tion." Again, "Natural Selection, if it be a true principle, will banish the belief of any groat and .sudden modification of structure." — Comp. note to § 121, p. 132. THE NATURE OF LIFE, * 143 it would be impossible to explain such facts as that chit- ine is peculiar to the Articulata, cellulose to Molluscoida, carbonates of lime to Mollusca and Crustacea, and phos- phates to Vertebrata — all assimilated from the same external medium. But we see that from this medium one organism selects the materials which another rejects ; and this selection is determined by the nature of the structure: which assimilates only those materials it is fitted to assimilate. We hear a great deal of Adaptation determining changes of structure and function, and are too apt to regard this process as if it were not intimately dependent on a corresponding structural change. By no amount of external influence which left the elementary composition of the structure unchanged, could an organ- ism with only two tissues be developed into an organism with three or four. By no supply or stimulus, could an animal incapable of assimilating peroxide of iron acquire red blood corpuscles, although it miglit have the iron without the corpuscles ; nor could an oyster form its shell unless capable of assimilating carbonate of lime. For myriads of years, in seas and ponds, nnder endless varie- ties of external conditions, the amcebte have lived and died without forming a solid envelope, althougli the ma- terials were abundant, and other organisms equally sim- ple have formed envelopes of infinite variety. In all the seas, and from the earliest ages, zoophytes have lived, and assumed a marvellous variety of shapes and specialization of functions ; but although some of them have acquired muscles, none liave acquired true nerves, none bone. Ages upon ages rolled on before fishes were capabhi of forming bone ; and thousands are still incapable of form- ing it, though living in the same waters as the osseous fishes. 131. " Ivooking to the dawn of life," says IMr. Darwin (repeating an objection urged against his hypothesis), 144 • THE PHYSICAL BASIS OF MIND. " when all organic beings, as we imagine, presented the simplest structure, how could the first steps in advance- ment, or in the differentiation and specialization of parts have arisen ? I can make no sufficient answer ; and can only say that, as we have no facts to guide us, all specu- lation would be baseless and useless." Where Mr. Darwin hesitates, lesser men need extra caution ; but I must risk the danger of presumption, at least so far as to suggest that while an answer to this question is difiicult on that dynamical view of Evolution which regards Function as determining Structure, it is less difficult on the statico-dynamical view propounded in these pages ; the difficulty which besets the explanation when all the manifold varieties of organic forms are con- ceived as the successive divergences from an original starting-point, is lessened when a variety of different starting-points is assumed, in each of which some initial diversity prepared the way for subsequent differentia- tions ; just as we know that between the ovum of a ver- tebrate and the ovum of an invertebrate, similar as they are, there is a diversity which manifests itself in their subsequent evolution. If Function is determined by Structure, and Evolution is the product of the two, it is clear that the different directions in the lines of develop- ment will have their origin in structural differences, and not in the action of external circumstances, unless these previously bring about a structural change. The action of the medium on the organism is assuredly a potent fac- tor which Biology cannot ignore : but the organism itself is a factor, and according to its nature the influence of the medium is defined. (§ 118.) 132. Quitting for a moment the track of this argu- ment, let us glance at the resemblances and differences observable in Plants and Animals, because most people admit that these have separate origins. The resemblan- THE NATURE OF LIFE. 145 ces are scarcely less significant than those existing among animals. Both have a similar basis of elementary com- position ; not only are both formed out of protoplasts with similar properties, but in both the first step from the protoplasm to definite structure is the Cell. And the life of this Cell is remarkably alike in both, its phases of de- velopment being in many respects identical; nay, even such variations as obtain in the cell-membranes are curi- ously linked together by a community in the formative process.* In both Plants and Animals we find individ- uals constituted — 1st, by single cells ; 2d, by groups of cells undistinguishable among each other ; and 3d, by groups of differentiated cells. In both we find colonies of individuals leading a common life. In both the processes of Nutrition and Eeproduction are essentially similar; both propagate sexually and asexually ; both exhibit the surprising phenomena of parthenogenesis and alternate generations. In both there are examples of a free-roving embryo which in maturity becomes fixed to one spot, los- ing its locomotive organs and developing its reproductive organs. In both the development of the reproductive organs is the climax wlucli carries Death. So close is the analogy between plant-lil'e and animal-life, that it even reaches the properties usually held to be exclusively ani- mal ; I mean that even sliould we hesitate to accept Cohn's discovery of the muscles in certain plants,! ^^'<2 cannot deny * C^onipare Leydig, Vom Bau des Ihierischcn Kurprrs, 1864, ji. 27. t Fekdinand Cohn, Die contractile Gcwcle im Pjlanzenreich, 1862. I>y a scries of numerous well-devised experiments, Colin found tliat in the stamen of the centauria a tissue exists which is excitahh; by the same stimula as muscle is, and which reacts like muscle, descrii)ing a similar ( urve when excited, and, after reaching its maximum, relaxing. Like the nmscle it becomes fatigued by repeated contraction, and recovers its ) lowers by repo.se. Like the muscle it may be rendered tetanic. (The researches of Dr. Buudon Sandeiison and Mr. Dai:win have .since placed beyond a doubt the Contractility and Sensibility of certain plants.) VtiL. III. 7 J 14G THE niYsiCAL basis of mind. that plants exhibit Contractility ; and should we refuse to interpret as Sensibility the phenomena exhibited by the Sensitive Plants, we cannot deny that they present a very striking analogy to the phenomena of Sensibility exhib- ited by animals. 133. It is unnecessary to continue this enumeration, which might easily be carried into minute detail. A chapter of such resemblances would only burden the reader's mind, without adding force to the conclusion that a surprising community in Substance and Life- history must be admitted between Plants and Animals. This granted, we turn to the differences, and find them no less fundamental and detailed. Chemistry tells us nothing of the differences in the protoplasms from which animals and plants arise ; but that initial differences must exist is proved by the divergence of the products. The vegetable cell is not the animal cell ; and although both plants and animals have albumen, fibrine, and case- ine, the derivatives of these are unlike. Horny substance, connective tissue, nerve tissue, chitine, biliverdine, crea- tine, urea, hippuric acid, and a variety of other products of evolution or of waste, never appear in plants ; while the hydrocarbons so abundant in plants are, with two or three exceptions, absent from animals. Such facts imply differences in elementary composition ; and this result is further enforced by the fact that where the two seem to resemble, they are still different: the plant protoplasm forms various cells, but never forms a cartilage-cell or nerve-cell ; fibres, but never a fibre of elastic tissue ; tubes, but never a nerve tube ; vessels, but never a vessel with muscular coatings ; solid " skeletons," but always from an organic substance {cellulose), not from phosphates and carbonates. In no one character can we say that the plant and the animal are identical; we can only point throughout the two kingdoms to a great similarity accompanying a radical diversity. THE NATURE OF LIFE. 147 t 134. Having brought together the manifold resem- blances, and the no less marked diversities, we must ask what is their significance ? Do the resemblances imply a community of origin, an universal kinship ? If so, the diversities will be nothing more than the divergences which have been produced by variations in the Life- history of the several groups. Or — taking the alterna- tive view — do the diversities imply radical differences of origin ? If so, the resemblances will be nothing more than the inevitable analogies resulting from Organized Substance being everywhere somewhat similar in compo- sition, and similar in certain phases of evolution. To state the former position in the simplest way, we may assume that of two masses of protoplasm having a com- mon parentage, one, by the accident of assimilating a certain element not brought within the range of the other, thereby becomes so differentiated as to form the starting-point of a series of evolntions widely divergent from those possible to its congener ; and at each stage of evolution tlie introduction of a new element (made possi- ble by that stage) will form the origin of a new variation. It is thus feasible to reduce all organic forms to a pri- mordial protoplasm, in the evolutions of which successive differentiations have been established. On the other hand, it is equally feasible to assume that the existence of radical differences must be invoked to account for the possibility of the successive differentiations. 135. The hunt after resemblances has led to nnu^li mistaken speculation ; and with reference to the to])ic now before us, it may be urged, that although by attacli- ing ourselves to the points of community, in disregard of the diversities, we may make it appear that all animals have a common parentage, and that plants and animals are merely divergent groups of tlie same prototype, a rigorous logic will force us onwards, and compel us to 148 THE PHYSICAL basis of mind. admit tliat a kinship no less real unites the organic with the inorganic world. Tor upon what principle are we to pause at the cell or protoplasm ? If by a successive elimination of differences we reduce all organisms to the cell, we must go on and reduce the cell itself to the chemical elements out of which it is constructed ; and in- asmuch as these elements are all common to the inorganic world, the only difference being one of synthesis, w'e reach a result which is the stultification of all classification, namely, the assertion of a kinship which is unixersal. We must bear in mind that all things may be reduced to a common root by simply disregarding their differences. All things are alike when we set aside their unlikeness. 136. Suppose, for the sake of illustration, we regard an Orchestra in the light of the Development Hypothesis. The various instruments of which it is composed have general resemblances and particular differences, not unlike those observable in various organisms ; and as Ave proceed in the work of classification we quickly discover that they may be arranged in groups analogous to the Sub- kingdoms, Classes, Orders, Genera, and Species of the organic world. Each group has its cardinal distinction, its initial point of divergence. All musical instruments resemble each other in the fundamental character of pro- ducing Tone by the vibrations of their substance. Tliis may be called their organic basis. The first marked difference which determines the character of two sub- kingdoms (namely, instruments of Percussion and Wind instruments) arises from a difference in the method of im- pressing the vibrations ; and the grand divisions of these sub-kingdoms arise from the nature of the vibrating sub- stances. Each type admits of many modifications, but the primary distinction is ineffaceable. We can conceive the Pipe modified into a Flute, a Flageolet, a Clarionet, a Hautbois, a Bassoon, or a Fife, by simple accessory THE NATUEE OF LIFE. 149 changes ; to modify the Pipe into a Trumpet, and thus produce the peculiar timhre of the trumpet, would be impossible except by the substitution of a new material ; by replacing the wood with metal we may adhere to the old Type, but we have created a new Class. (Attention is requested to this point, because the current views respecting the transmutation of tissues, which seem to lend a decisive support to the hypothesis of the trans- mutation of species are very commonly vitiated by the confusion of transformation with substitution. No ana- tomical element is transformed into another specifically different — an epithelial-cell into a nerve-cell, for instance — but one anatomical element is frequently suhstituted for another.) To convert the Pipe or the Trumpet into a Violin or a Drum would be impossible. We can follow the modifications of a Tambourine into a Drum or Ket- tle-drum, but no modifications of these will yield the Cymbals. That is to say, the vibrating materials — wood, metal, parchment, and the combination of wood and strings — have peculiar properties, and the instru- ments formed of such materials must necessarily from the very first belong to different groups, each subdivision of the groups being dependent on some characteristic difference in methods of impressing the vibrations, or in the materials. Although all musical instruments have a common property and a common purpose, we do not regard them as transformations of one primitive instru- ment ; their kindred nature is a subjective conception ; the analogies are numerous and close, but we know their origin. It is obvious that men being pleased by musical tones, have been led by their deliglit to construct instru- ments whenever they have discovered substances capable of musical vibrations, or methods of impressing sucli vibrations. By substituting the bow for the plectrum or the fingers, they may have changed the Lyre into the 150 THE niYSICAL BASIS OF MIND. Violin, Viola, Violoncello, and Bass. (It seems histori- cally probable that the real origin of the Violin class was an instrument with one string played on by a bow.) ]>y grouping together Pipes of various sizes they got the Pan- pipes ; by substituting metal and enlarging the blowing apparatus they got the Organ. By beating on stretched parchment wdth the finger, they got the Tambourine and Tom-Tom ; by doubling this and using a stick they got the Drum. By beating metal with metal they got the Cymbals ; by beating wood they got the Castanets. 137. The application of this illustration is plain. Just as a wind-instrument is incapable of becoming a stringed instrument, so a Mollusc, with all its muscles unstriped, and its nervous system unsymmetrical, is incapable of becoming a Crustacean, with all its muscles striped and its nervous system symmetrical. Indeed there are proba- bly few biologists of the present day who imagine the transmutation of one kind into the other to be possible ; but many biologists assume that both may have been evolved from a common root. The point is beyond proof; yet I think there is a greater probability in the assump- tion that both were evolved from different roots. At any rate, one thing is certain ; a divergence could only have been effected by a series of siibstitutions ; and the question when and how these substitutions took place is unan- swerable : one school believes them to have been creative fiats, the other school believes them to have been trans- mutations. 138. When we see an annelid and a vertebrate resem- bling each other in some special point which is not com- mon either to their classes or to any intermediate classes — as when we see the wood-louse (Oniscus) and the hedgehog- defend themselves in the same strange way by rolling up into a ball — we caimot interpret this as a trace of distant kinship. When we see a breed of pigeons and a breed THE NATURE OF LIFE. 151 of canaries turning somersaults, and one of the Bear fam- ily (Iiatd) given to the same singular habit, we can hardly suppose that this is in each case inherited from a common progenitor. When we see one savage race tipping arrows with iron, and another, ignorant of iron, using poison, there is a community of object effected by diversity of means ; but the analogy does not necessarily imply any closer connection between the two races than the fact that men with similar faculties and similar wants find out sim- ilar methods of supplying their wants. Even those who admit that the human race is one family, and that the A'arious peoples carried with them a common fund of knowledge wdien they separated from the parent stock, may still point to a variety of new inventions and new social developments which occurred quite independently of each other, yet are strikingly alike. Their resemblance will be due to resemblance in the conditions. The exist- ence, for example, of a religious worship, or a social insti- tution, in two nations widely separated both in time and space, and under great historical diversities, is no absolute ])roof that these two nations are from the same stock, and that tlie ideas have the same parentage. It may be so; it may be otherwise. It may be an analogy no more im- plying kinship than the fact of ants making slaves of other ants (and these the black ants !) implies a kinship with men. Given an organization wliich in tlie two na- tions is alike, and a history which is in certain character- istics analogous, there must inevitably result religious and social institutions liaving a corresponding resemblance. I do not wisli to imply that the researches of philologists and ethnologists are misdirected, or that their conclusions respecting the kinship of mankind are to be rejected ; I only urge the consideration that perhaps too mucli stress is laid on community of l)lood, and not enough on com- munity of conditions. 152 THE PHYSICAL BASIS OF MIND. RECAPITULATION. 139. The various lines of argument may here be reca- pitulated. The organic world presents a spectacle of end- less diversity, accompanied by a pervading uniformity. The general resemblances in forms and functions are more or less masked by particular differences. The resem- blances, it is said, may be all due to kinship, all the living- individuals having descended from a primordial cell ; and at each stage of the descent the adaptations to new con- ditions may have issued in deviations from the ancestral form, while the process of Natural Selection giving sta- bility to those variations which best fitted the organism in the struggle of existence, has made greater and greater gaps, and produced more marked diversities among the descendants. This is the Darwinian Theory : " On my theory unity of Type is explained by unity of Descent." 140. By the general consent of biologists, this theory is held to explain many if not all the observed facts. It is a very luminous suggestion ; but it requires an enlarge- ment so as to include Organic Affinity ; and when once this fundamental principle is admitted, it brings with it very serious doubts as to the theory of Descent. We are then entitled to assume that many of the most striking resemblances, instead of being due to kinship, are due simply to the general principle that similar causes must have similar effects, and that organic substances having a very close resemblance, organized substances must have similar stages of evolution imder similar conditions ; and thus organs will necessarily take on very similar forms in very different organisms (for example, the eye of the cephalopod and the eye of the vertebrate), and organisms having widely different parentage may closely resemble each other. If we are entitled to assume that protoplasm appeared not in one microscopic spot alone, but in many THE NATURE OF LIFE. 153 places and in vast quantities — and this is surely the more justifiable assumption — then we must also admit that these germinal starting-points were from the first, or very shortly afterwards, differentiated by variations in their elementaiy composition. Now we know that a very minute change in composition may lead to immense dif-' ferences in evolution. Thus the descendants of two slightly different progenitors may, by continual differen- tiation, become very markedly unlike ; yet, because of the original resemblance of their substances, they will reveal a pervading similarity. While it is thus conceivable that all organisms may resemble each other, and all differ, owing to the similari- ties and diversities in the " conditions of existence " (and among those conditions that of descent is of wide range), it is not very readily conceivable how advantage in the external struggle could have determined the varieties of form and function, because many differentiations give no superiority in the struggle. As Mr. St. George Mivart urges, " Natural Selection utterly fails to account for the conservation and development of the minute and rudi- mentary beginnings, the slight and infinitesimal com- mencements of structures, however useful those structures may afterwards become."* And this is undeniable on the supposition that Natural Selection is an agency not iden- tical with the variations of growth, but exclusively con- fined to the accumulation of favorable variations. 141. In estimating the two hypotheses — First, of Descent from one primordial germ, and the niodifications due to Natural Selection, or, as I should say, expressed in Selection ; and Secondly, of Descent from innumerable germs having initial differences, whicli differences radiated into the marked modifications, there is this superiority to be claimed for the first, that it is more easily handled as * MiVAKT, The Genesis of Species, 1871, p. 23. 7* 154 THE niYsiCAL basis of mind. an aid to research, and is therefore more decidedly useful. The laws of Organic Affinity are at present too obscure for any successful application. I only wish to point out that the theory of Descent is an imaginary construction of what may have been the process of species-formation, not a transcription of the process observed. It constructs an imaginary Type as progenitor of a long line of widely different descendants. The annelid which is taken as the ancestor of the vertebrates is not any annelid known either to zoologists or geologists, but a generalized and imaginary type. So daringly liberal is the imagination in endowing the ancestor with whatever may be required for the descendants, that Mr. Darwin thinks it probable, from what we know of the embryos of vertebrates, that these animals " are the modified descendants of some an- cient progenitor which was furnished in its adult state with branchiae, a swim-bladder, four simple limbs, and a long tail, all fitted for an organic life," (p. 533) ; and Dr. Dohrn conceives the original type to have contained within itself all that has been subsequently evolved in the highest vertebrate, the other and less elaborate organ- isms being mere degradations from this type.* This use of the imagination, although not without advantages, is also not without dangers. It may direct research, it must not be suffered to replace research. * DoHRX, Der Urs2}rung der Wirhelthicrc und da^ Princip des Func- tionsivcchsds, 1875, p. 74. PROBLEM II. THE NERVOUS MECHANISM. "All the functions of the nervous system are as dependent upon its struc- ture and nature, as tHe accurate indication of time upon the construction of the chronometer." — Prochaska. " Unser Wissen wird nie vollendet, ist und bleibt Stiickwerk ; dessen Erganzungdas Streben und Hoflfen der forschenden Denker bleiben wird fiir alle Zeit." — Radenhausen, Osiris. " Our nimble souls Can spin an insubstantial universe Suiting our mood, and call it possible, Sooner than see one grain with eye exact, And give strict record of it." George Eliot, T/ie Spanish Gypsy, "If we compare the teachings of our books with what Nature is constantly showing, we find there is no agreement between those two sources of learn- ing." — Brown Sequaed. THE NERVOUS MECHANISM. CHAPTEE I. SUEVEY OF THE SYSTEM. 1. OtJK knowledge of mental processes is derived from reflection on our personal experiences, combined with in- ferences from our observation of other men and animals, under similar conditions. The processes are comj)lex and variable ; so complex and variable, that knowledge of their comj)onent factors can only be gained through long tentative study, aided by fortunate circumstances which present these factors separately, or at any rate in such marked predominance as to fix attention. This subjec- tive analysis of the processes has to be supplemented by, and confirmed by an objective analysis of, the conditions, external and internal : the facts of Feeling have to be traced to facts of Physiology, which will exhibit that Physical Basis of Mind so earnestly sought by the inquirer. Both the subjective and the objective analysis are at present in a very imperfect state. Although there is much confident assertion and " false persuasion of knowl- edge " in both regions, there is, unhappily, little that can be seriously accepted as demonstrated. In the present volume we shall concern ourselves almost exclusively with the objective analysis, and do our utmost to mark what is mere inference from what is verified observation. It is only by Observation that facts can be settled ; how- 158 THE PHYSICAL BASIS OF JIIND. ever Analogy and Inference may suggest where the truth may lie, they are finger-posts, not goals. At the best they only tell us what Observation icoidd reveal could the processes be submitted to Sense. In a loose and general way every one knows that the Xervous System is a dominant agent in all sentient pro- cesses ; although not by any means tlie only agent, yet, because of its predominance, it is artificially accepted as the only one. With the greater complexity of this sys- tem, there is observed a corresponding increase in the variety of sentient phenomena. The labors of anatomists have secured a tolerably exact plan of the topographical distribution of this system ; a somewhat chaotic mass of observation and inference passes as a description of its elementary structure. The labors of physiologists have succeeded to a small extent in localizing certain functions in certain organs of this system. But imperfect as our knowledge of the elementary structures is, our knowledge of the functions is still more so. I wish I could say otherwise, and that I could ask my readers to accept with confidence what teachers confidently propound. The atti- tude of scepticism is always repulsive ; the sceptic is sel- dom received without disfavor, because he throws on us the labor of investigation there where we wish for the confidence of knowledge. Yet it is only by facing the facts that we can hope one day to solve the great ques- tions. 2. The nervous system has, in our artificial view of it, tw'o divisions : the Peripheral, which connects the organ- ism with the external world ; and the Central, which con- nects each part of the organism with all the other parts. Although the system is constituted by various tissues — neural, connective, vascular, and elastic — it receives its characteristic designation from nerve-fibrils, nerve-fibres, and nerve-cells ; just as the muscular system receives its THE NEKVOUS MECHANISM. 159 designation from contractile cells and fibres. This neural tissue assumes three well-marked forms : 1°, nerves, whicli are bundles of fibres and fibrils, enclosed in a membra- nous sheath ; 2°, ganglia, which are clusters of cells, fibres, and fibrils, sometimes enclosed in a sheath, sometimes not ; o", centres, which are artificial divisions of the neural axis, serving as points of union for different organs. In the Invertebrata the neural axis is the chain of ganglionic masses running along the ventral side, and giv- ing off the nerves to organs of sense, and to the muscles. It may be seen represented in Fig. 1. In the Vertebrata the axis is dorsal, and is called the cerebro- spinal axis, including brain and spinal cord. When we look at this structure superficially we see various nerves radiating from it to skin, glands, and muscles ; but a closer examination, enlight- ened by knowledge of function, shows that some of these nerves pass into it from the various sur- faces and sense-organs, and are "'^^*«'i ^'^ longitudinal fibres, ^ ' anil from the ganglia issue fibres therefore called afferent or se7i Fig. 1. — Nervous system of a beetle. The small round masses, or ganglia, are seen to be cen- to tlie limbs, organs of sense, and viscera. sory ; whereas another set passes out of it to glands and muscles, and these nerves are therefore called efferent or motory. There are also fibres which, passing from one part of the great centre to an- other, are called commissural. To this brief account of the cerebro-spinal system may 1)C added a word on the connected chain of ganglia and nerves known as the Sympathetic, because it was formerly supposed to be the organ through which the various " sympathies " were effected. It is now held to be the ItJO THE PHYSICAL BASIS OF MIND. system devoted to the viscera and blood-vessels ; but there is still great want of agreement among physiologists as to whether it is an independent system, having a spe- cial structure somewhat ditferent from that of the cerebro- spinal, or whether it is simply a great plexus of nerves and ganglia, only topographically distinguishable from the rest of the nervous system. Into this point it is un- necessary for me to enter here. Enough to say, that I entirely agree with Sigmund Mayer in adopting the sec- ond view.* In no histological character, yet specified, are the sympathetic nerves and ganglia demarcated from the others. There are, indeed, more non-medullary fibres (the gray fibres of Eemak) in the sympathetic ; but the same fibres are also abundant in the cerebro-spinal sys- tem ; and the sympathetic has also its large medullary fibres. 3. The Centres are composed of two substances : the gray and the white. The gray substance is often called the vesicular because of its abundant cells ; but it has even more fibres than cells, and the wliite substance has also a few cells.f The gray substance is distributed over the surface of the brain — in the convolutions ; and in various other parts of tlie encephalon. It surrounds the central canal which forms the ventricles of the brain and is continued as a very small cavity all down the spinal cord. Besides entering into the important and conspic- uous masses known as the cerebral ganglia — (the optic thalami, and corpora striata) — the gray substance is massed in the corpora quadrigemina, crura cerebri pons varolii, and medulla oUongata. We shall have occasion to refer to each of those parts. Until modern times all the masses included in the skull under the familiar term * SiGMUXD Mayer, Die 2>eriplicrische Ncrvcnzellc %ind die sympathische NervcTisystem, 1876. t On these cells see note to § 1 40. THE NERVOUS MECHANISM. 161 Brain (or the technical term Encephalon) were regarded as the only centre, and also as the origin of all the nerves. Nor has this notion even yet entirely disappeared, al- though the spinal cord is known not to be a large nerve trunk, but a centre or connected chain of centres, struc- turally and functionally similar to the cranial centres. The shadow of the ancient error still obscures inter- pretation of the part this spinal cord plays in the sentient mechanism ; and thus although the cord is universally admitted to be a centre for " sensitive impressions," it is usually excluded from Sensation. This widespread and misleading notion will be critically examined in a future problem. 4 Beginning our survey of the cerebro-spinal axis with the Spinal Cord, we observe it to consist : 1°, of cen- tral gray substance surrounding the scarcely visible canal, which is all that remains of the primitive groove in the germinal membrane (§ 9) ; 2°, irregular gray masses, called the anterior and posterior horns* connected with the anterior and posterior roots of the spinal nerves ; and 3°, strands of white fibres enclosing this central substance, and called the anterior lateral and posterior columns. Like the Cerebrum, it is a double organ formed by two symmetrical halves, as the cerebrum is of two hemispheres. Each half innervates the corresponding half of the body. The cord is unlike the cerebrum in external form, though very like it in internal structure. The gray structure is mainly external in the cerebrum, and is internal in the cord. From the anterior side of the cord (that whicli in ani- mals is the under side) the motor nerves issue ; from the posterior (in animals the upper) side, issue the sensory nerves. On each of the sensory nerves there is a ganglion. * These terms designate the surface aspect of a transverse section, of what more correctly should be called the gray columns. See Figs. 3 to 6. 162 THE rUVSlCAL BASIS OF MIND. The roots of each nerve, formed of several rootlets issuing from the anterior and posterior columns, subsequently unite together, and proceed in a single sheath to muscles and skin, separating again, however, before they reach muscles and skin. Fig. 2 represents this arrangement. Fig. 2. — A portion of the spinal cord iviili its nerves (after Bernard). The left-hand figure shows the anterior side ; the right-liand the posterior. A the anterior, and P, the posterior root, they meet at g, the ganglion ; c and d are filaments connecting two posterior roots. 5. There are thirty-one pairs (sometimes thirty-two) of such nerves — namely, eight cervical, twelve thoracic, five lumbar, five sacral, and one (or two) coccygeal. Figs. 3 to 6 represent transverse sections, which display the entrance of the roots of the nerves into the anterior and posterior horns. 6. Similar masses of gray substance in the 3fedulla Oblongata (which is the name given to the cord when it passes into the skull)* are supposed to be the origins of some other nerves (the cranial). * But this only in the higher animals. In reptiles and amphibia the medulla descends into the cer^'ical region, as far as the second and third cerv'ical vervcbrae. This should be remembered in e.xj)erimenting. THE NERVOUS MECHANISM. 16^ Fig. 3. — Transverse section of one half of the spinal cord in the lumbar region (after Kolliker). a, anterior root eutering tlie anterior gi-ay horns, m and I, wliere cells are clustered ; c, central canal ; d and e, the anterior and posterior commissures unit- ing the two halves of the cord ; 6, posterior root entering the posterior gray horn. i4 Fig. 4. — Transverse section of loth halves of the cord, cervical region, a, Fissure sep- arating the anterior columns ; l>, fissure of the posterior. Fig, 5. —Transverse section of the cord in the dorsal region. 164 THE PHYSICAL BASIS OF MIND. Pig. 6. — Transverse section in the lumbar region. Although the Medulla Spinalis is unquestionably con- tinued as the Medulla Oblongata, the arrangement of its tissues here becomes gradually changed, and so compli- cated that it baffles the scalpel. Anatomists are, however, agreed on the one point of fundamental importance to us here — namely, that there is only a rearrangement, not a new tissue. Accepting the artificial division into two organs, we may say that their functions are different, inasmuch as they are different in their anatomical con- nections — they innervate different parts ; but as nerve- centres they have one and the same property. On its posterior surface the Medulla Oblongata opens as the fourth ventricle. It is then no longer a closed canal, but an expansion of the spinal canal, which is covered by the Cerebellum. On its anterior surface pro- jects the pons varolii. Figs. 7 and 8 represent these. While thus on the one hand continuing tlie Medulla Spinalis, the Medulla Oblongata is seen on the otlier hand to be continuous with the Brain — its white columns passing upwards in the crura cerebri, its cavity repeated in the other ventricles. Above it lie the ganglionic masses, the corpora quadrigemina, optic thalami, and corpora striata. Crowning these are the big and little THE NERVOUS MECHANISM. 16^ Fig. 7. — Back, or upper view of the Medulla Oblongata as it continues the Med. Spi- nalis. 1, Sectiou of tlie thalaini ; 2, corpora quadrigeiiiina (the two lower bodies are imperfectly represented in tlie engraving) ; 3, section of tlie crura cerebelli ; 4, the fourth ventricle ; 5, the restiform bodies ; 6, the calamus scriptorius. Pig. 8. — Front, or under view of the Med. Oblong. 1, Optic nerves cut off at the (hiasma ; 2, crura cerebri ; 3, pons varolii ; 4, olivary bodies ; 5, anterior pyramids ; G. spinal columns. brains, Cerebrum and Cerebellum. Figs. 9 and 10 rep- resent this relation of Medulla Spinalis, Medulla Ob- longata, and Brain. Fig. 11 is a purely artificial diagram Fig. 9. — Human Brain in Profile. 1 , Cerebnim ; 2, cerebellum ; 3, pons varolii and medulla oblonjrata. 166 THE PHYSICAL BASIS OF MIND. which will give the reader some idea of the disposition of the white and gray substances. Fig. 10. — One half of thi Brain in Profile, from the inside. 1, Convolutions of the cerebrum ; 2, corpus callosum or great commissure uniting the two hemispheres ; 3, arbor vitae or branching arrangement of gray and white matter in the cerebellum ; 4, pons varolii and medulla. Fig. 11. — Diagram of a vertical section of Vie Brain (after Dalton). 1, Olfactory ganglion ; 2, cerebral hemisphere ; 3, corpus striatum ; 4, thalamus ; 5, corpora quad- rigemina ; 6, cerebellum ; 7, ganglion of the pons varolii ; 8, olivary body. 7. In man the Cerebrum is to the Cerebellum as 9 to 1. In the lower vertebrates the preponderance is stiU THE NERVOUS MECHANISM. 167 greater. The cerebrum is in our artificial systems com- monly divided into three lobes. The frontal lobe is that portion which lies in front of the deep fissure named after Rolando ; between that fissure and the "internal perpen- dicular fissure " lies the parietal lobe ; behind this we have the occipital lobe ; and, below the fissure of Sylvius, the tempero-sphenoidal lobe. Each lobe is again subdi- vided according to its convolutions. The 'disposition of the fibres in the brain is far too complex to be accurately followed. All that we can say is, that there are strands which connect one convolution with another, strands which connect one hemisphere with another, strands which connect cerebrum with cere- bellum, and strands whicli connect the cerebrum with the lower ganglia. It is important to conceive this dis- tinctly ; for we shall hereafter see that the function of the Brain (by brain is here meant both Cerebrum and Cerebellum) is not that of innervation, but of incitation and regulation. To speak metaphorically, it is the coach- man wlio holds in his hands the reins, and guides the team. One cardinal fact should arrest attention, namely, that not a single nerve in the body has its origin or centre of innervation in the cerebrum and cerebellum. The olfactory and optic nerves do indeed seem to issue from the cerebrum ; and are commonly described as cer- ebral nerves. But the facts of Development, minute Anatomy, and Experiment prove this to be inexact. Although I shall continue to speak of the olfactory and optic nerves in accordance with universal usage, not wishing to burden the reader witli unnecessary innova- tions, I must at the outset express my opinion that these nerves cannot be brought under tlie same general type as the other sensory nerves. Embryology and Anatomy suggest that they have no more claim to the title than the crura cerebri. Of tliis Iiereaftcr. Setting these aside, 1G8 THE PHYSICAL BASIS OF MIND. no one now vei'uses to acknowledge that Cerebrum and Cerebellum, although centres of Incitation and Associa- tion, are not the centres of direct Innervation : the or- ganic mechanism in all its ^^Ayszo/o^ica/ processes wdll act independently of them (so far as such artificial dis- tinctions are admissible at all). This does not throw a doubt on their inhysiologiccd functions, nor on their participation in the normal execution of physiological processes. 8. From this rapid survey two important points may be selected for special attention. First, the continuity of the neural axis throughout ; secondly, the fundamental similarity of its structure, underlying great variations in its form and connections. This, which is the anatomical expression of the Unity of the nervous system, will be- come more evident after we have expounded what Em- bryology and Microscopic Anatomy teach. We may therefore digress here awhile to consider THE EARLY FOKMS OF NERVE CENTRES. 9. In the outermost layer of the germinal membrane of the embryo a groove appears, which deepens as its sides grow upwards, and finally close over and form a canal. This canal is composed of cells all alike. Its foremost extremity soon bulges into three w'ell-marked enlargements, which are then called the primitive cerebral vesicles. The cavities of these vesicles are continuous. Except in position and size, there are no discernible dif- ferences in these vesicles, which are known as the Fore- brain, Middle-brain, and Hind-brain. 10. The Fore-brain soon buds off from each side a small vesicle. This is the oj^tic vesicle, the first rudi- ment of what subsequently becomes optic nerve and retina. At thi.-i period it is simply a vesicle with a hollow stem, the cavity being continuous with the cavity THE NERVOUS MECHANISM. 169 of the cerebral vesicle, and the walls continuous with the cerebral wall. It thus appears that the retina and optic " nerve " are primitive portions of the brain — a detached segment of the general centre, identical in structure with the cerebral vesicle, and not unlike in form. A cup-like depression quickly forms the optic vesicle into an inner and an outer fold. The inner or concave fold becomes the retina, and the outer or convex fold (that nearest to the brain) be- comes its choroid membrane. On the fourth day of incubation the retina of the chick is composed of spindle- shaped cells, all alike. On the seventh day there is a differentiation into layers, one of which on the eighth day is granular ; on the tenth two are granular ; and on the thirteenth ganglionic cells appear. Some of the cells have elongated into radial fibres (known as Miiller's fibres) ; and with the appearance of rods and cones the normal retinal elements are complete. 11. The researches of Foster and Balfour* confirm the statement that all the different parts of the retina (whether nervous or connective) are derived from one and the same layer of embryonic cells, which originally formed a portion of the first cerebral vesicle. 12. Meanwhile the hollow stem of this optic vesicle begins to develop fibres amidst the nuclei of its walls. The " optic nerve " arises : it is still hollow ; and in birds remains so through life. The fibres as they are developed [jroiv forivards towards the retina, and spread over its in- ternal surface. They also grow forivards toicards the brain, and spread over its substance ; but it is not, as might be supposed, and is generally believed, with the cerebral hemispheres (or that portion of the Fore-brain from which * Foster and Balfouii, Elcmcntu of Emhnjolorjij, Part 1., 1874. Comp. ScuwALBE, art. Die Retina, in the Handhuch dcr Augenheilkunde of GiiAEFK und Samiscii, 1871, T. 363. VOL. Ill, 8 170 THE PHYSICAL BASIS OF MIND. these are derived), but with the IMiddle-brain (which becomes tlie corpora quadrigemina), that the optic fibres are in connection.* 13. This will be understood when the further develop- ment is traced. The Fore-brain, after budding off the optic vesicles, buds off two larger vesicles — the future cerebral hemispheres. This is noticeable on the second day of incubation, and by the third day each vesicle is as large as the whole of the original Fore-brain. Their develop- ment is essentially like that of the optic vesicles ; both as to the cellular and the fibrous elements. The convolutions, corpus callosum, nucleus lentiforniis, and corpora striata are then indicated. INIean while, that which originally was the Fore-brain has lapsed into the secondary rank as Intermediate-brain {Zunsclievhirn), and becomes the parts surrounding the third ventricle, namely, the thalami, corpora candicantia, infundihuhim, and what is called the " posterior perforated substance." 14. The MidAllc-brain, or Second Vesicle, develops the corpora quadrigemina from the roof of its cavity, and the crura cerebri from its floor. The Hind-brain, or Third Vesicle, divides into two, like the First Vesicle ; it buds off the hemispheres of the cere- bellum ; its cavity forms the fourth ventricle ; its walls the medulla oblongata. 15. It thus appears tlmt the primitive membrane forms into a canal, which enlarges at one part into three vesicles, and from these are developed the encephalic structures. The continuity of the walls and cavities of these vesicles is never obliterated throughout the subsequent changes. It is also traceable throughout the medulla spinalis. And microscopic investigation reveals that underneath all the morphological changes the walls of the whole cerebro- * The development of the olfactory lobe and bulb is similar ; it need not be followed here. THE NERVOUS MECHANISM. 171 spinal axis are composed of similar elements on a similar plan.* 16. Two conclusions directly follow from this exposi- tion : — first, that since the structure of the great axis is everywhere similar, the projjerties must he similar; sec- ondly, that since there is structural continuity, no one jpart can he called into activity without at the same time more or less exciting that of all the rest. THE PERIPHERAL SYSTEM. 17. Following the analytical division, we now come to the Peripheral System of nerves and ganglia. The separa- tion, I must often repeat, is purely artificial ; but the artifice has conveniences. We separate in the same way the heart from veins and arteries, and the capillary cir- culation from the arterial. Each nerve has its direct connection with a particular centre, and indirectly with the whole system. It has its circumscribed territory, and individual office. Except in a few cases of anastomosis, the action of one nerve does not involve that of another : only one muscle or one group of muscles is moved, without exciting motion in a neiglibor. It is through the centres that these individual territories are united ; and a wave of excitation always passes throughout the central substance. Thus the cen- tres are not simply organs of association, consequently of * German anatomists divide this axis into trunk and crown {Hirn- ■stamm and Hirnmantd). There is convenience in this division. If we remove all the gray matter of the cerebrum, with all the white matter radiating from it, until we again come upon gray matter— and if we then cut the cerebellum from its descending strands of white matter — we shall liave removed the crown, and leave the trunk remaining. This tnink is lonstituted by the corpora striata, nucleus lentiforniis, optic thalami, cor- pora quadrigemina, crura cerebri, pons, medulla oblongata, and medulla spinalis. From this trunk all the organs of the body are directly inner- vated (except those innervated fiom th(! sympathetic ?). 172 THE PHYSICAL BASIS OF MIND. legulation, but are the nexus whereby the diversity of the actions is integrated into the unity of consensus. 18. Nothing further need at present be stated respect- ing the nerves ; but it is needful to give precision to the ideas of GANGLIA AND CENTEES, usually spoken of as if they were convertiljle terms. That this is inexact may be readily shown, and that it is mis- leading appears in its causing physiologists to credit every ganglion, wherever found, with central functions ; and, by an almost inevitable extension of the error, has led to the assignment of central functions to a single ganglionic cell ! This is but part of that " superstition of the cell " against which I shall have to protest. I will not here raise the doubt which presses from various sides respecting the central functions oi the ganglia in the heart and intestines, because the reader perhaps shares the general opinion on that point ; but let me simply ask what central function can possibly be assigned to the ganglia on each of the spinal sensory nerves ? above all to those grouped and scattered ganglionic cells w^hich are found at the peripheral termination of some nerves, and in the very trunks of others ? There may, indeed, be imagined a central function for the ganglia in the mesen- tery, and even in tlie choroid coat of the retina, on the hypothesis (quite gratuitous, I think) of their regulating the circulation ; but even this explanation cannot be adopted with respect to the ganglionic cells which appear in the course of the nerve.* * "On s'est preoccupe du role special que pouvaient jouer les gangli- ons peripheriques situes dans le voisinage de certaines organes ; et on a ju'etendu que les nerfs ne jouissaient de leur propriete d'agir sur ces iirganes qu'apres avoir traverse ces ganglions. On avait admis que I'exci- tation portee sur le filet nerveux avant son entre dans le ganglion lestait .sans effet ; que pour obtenir Taction excitatrice des fonctions de Torgam' il fallait exciter le nerf entre lui et le ganglion voisin."- — Claude Ber- THE NEKVOUS jNIECHANISM. 173 The meaning of a physiological centre is, that it is a point to which stimulations proceed, and from which they are reflected. The meaning of a ganglion is, that it is a group of nerve cells dispersed among, or in continuation with, nerve fibres : it may be a centre of reflection, or it may not ; and in the latter case its physiological office is at present undetermined. A ganglion is no more a centre in virtue of its cell-group tlian a muscle is a limb. All function depends on connection, and central function de- mands a connection of afferent and efferent parts. 19. The ganglia found in the ventral cord of the Inver- tebrate (see Fig. 1) are centres, each of which has consid- erable independence, each regulating a single segment of the body, or a group of similar segments. As the scale of animal complexity ascends, these separated centres tend more and more to coalesce, and with this coal^escence comes an increasing comhination of movements.* Ob- serve the caterpillar slowly crawling over a leaf; each segment of its body moves in succession ; but when this caterpillar becomes a butterfly the body moves rapidly, and all at once. Open the caterpillar, and you find its nervous centres are thirteen separate ganglia, each presid- ing over a distinct part of the body, and each capable of NARD, Sijsfemc Nerveux, II. 169. But on proceeding to verify these statements by experiment, Bernard is led to the conchision, "que h- ganglion n'a pas d'influence propre sur lo mode de I'excitatiou transmise a I'organe." I was delighted to find my opposition to the current teaching respect- ing the central functions of ganglionic cells thoroughly borne out by the elaborate researches of Sigmund Maykh {Archiv fiir Psijchiatric, Bd. VI. Heft 2). Having artificially produced such cells, he j'Prtinently asks, How can we attribute central functions to cells which appear in tlie pro- cess of regeneration of a divided nerve ? The error has its origin in tlu; confusion of functions with jiroperties. * It is often, though incorrectly, stated that every segment of an annulose animal has its separate ganglion. Tlic fact is, that while the ganglia are usually fewer than the segments, they are sometimes more numerous. 174 THE rilYSICAL BASIS OF MIND. independent action. Open the butterfly, and you find tlie thirteen ganglia greatly changed: the second and third are fused into one ; the fourth, fifth, and si.xth into another; the eleventh and twelfth into anotlier ; the only trace of the original separation is in a slight constriction of the surface. The movements of tlie caterpillar were few, simple, slow, and those of the butterfly are many, varied, and rapid. 20. In the Vertebrates the coalescence of oanalia is such that the spinal axis is one great centre. "We do indeed anatomically and physiologically subdivide it into several centres, because several portions directly innervate separate organs ; but its importance lies in the intimate blending of all parts, so that Jluduating combinations of its elements may arise, and varied movements result. Eacli centre combines various muscles ; the axis is a com- bination of centres. The brainless frog, for instance, has still the spinal cord, and therefore the power not only of moving either of his limbs, but also of combining their separate movements : if grasped, he struggles and escapes ; if pricked, he hops away. But these actions, although complex, are much less complex and varied than the ac- tions of the normal frog. There is not only a coalescence of ganglia, but a greater and greater concentration of the substance in the upper portions of the axis. In the inferior vertebrates, and in the mammalian embryo, the spinal cord occupies the whole length of the vertebral canal from the head to the tip of the tail ; and here the centres of reflexion corre- spond with the several segments. But as the cranial mass develops there is a withdrawal of neural substance from the lower parts, and the centres of reflexion are then some way removed from the segments they innervate. In the animal development there is even a greater and gi'eater predominance of the upper portions, so that the THE NEKVOUS MECHANISM. 175 brain and medulla oblongata are of infinitely more impor- tance than the spinal cord. 21. Besides the central group of elements which belong to fixed and definite actions, we must conceive these ele- ments capable of variable combinations, like the pieces of colored glass in a kaleidoscope, which fall into new groups, each group having its definite though temporary form. The elements constitute really a continuous net- work of variable forms. It is to such combinations, and not to fixed circumscribed ganglia, that we must refer the subordinate centres of the axis. We speak of a centre for Eespiration, a centre for Laughing, a centre for Cry- ing, a centre for Coughing, and so on, with as much pro- priety as we speak of a centre for Swallowing or for Walking. Not that in these cases there is a circumscribed mass of central substance set apart for the innervation of the several muscles employed in these actions, and for no other purpose. Each action demands a definite group of neural elements, as each geometric form in the kaleido- scope demands a definite group of pieces of glass ; but these same pieces of glass will readily enter into other combinations ; and in like manner the muscles active in Respiration are also active in Laughing, Coughing, etc., though differently innervated and co-ordinated. 22. The physiological rank of a centre is therefore the expression of its power of fluctuating combination. The medulla oblongata is higher than the medulla spinalis, because of its more varied combinations ; the cerebrum is liigher than all, because it has no fixed and limited com- binations. It is the centre of centres, and as such the supreme organ. 176 THE PHYSICAL BASIS OF MIND, CHAPTEE II. THE FUNCTIONAL RELATIONS OF THE NERVOUS SYSTEM. 23. The distinguishable parts of this system are the central axis, the cranial nerves, and the spinal nerves, with the chain of ganglia and nerves composing the Sympa- thetic. Let us briefly set down what is known of their special offices. Men very early discovered that the nerves were in some way ministrant to Sensation and Movement ; a divided nerve always being accompanied by insensibility and im- mobility in the limb. Galen, observing tliat paralysis of movement sometimes occurred without insensibility, sug- gested that there were two kinds of nerve ; but no one Fig. 12. — Tyansverse sections of spinal cord (dorsal region). THE NEEVOUS MECHANISM. 17/ was able to furnish satisfactory evidence in support of this suggestion until early in the present century, when the experiments of Charles Bell, perfected by those of Majendie and Mtiller, placed the suggestion beyond dis- pute. 24. Fig. 12 is a diagram (not a drawing of tlie actual aspect, which would be hardly intelligible to readers un- versed in such matters) representing two transverse sec- tions of the spinal cord just where the nerve-roots issue. The gray substance is somewhat in the form of a rude H, in the dorsal region, and of the expanded wings of a butter- Hy in the lumbar enlargements (Figs. 4 - 6) ; the extrem- ities of this gray substance are the anterior and posterior horns. We have already said that from the anterior horns of each half issue the roots of the motor nerves, which pass to the muscles. From the posterior horns issue the sensory nerves, which, soon after leaving the cord, enter the ganglia before joining the motor nerves, and then pass to the skin, in the same sheath with their companions, separating again as tliey reach the muscles and surfaces where they are to be distributed. When this mixed nerye is cut through, or tied, all sensation and movement disap- pear from the parts innervated. But if only one of the roots be cut through, above the ganglion, there will then be only a loss of movement or a loss of sensation. Thus suppose the section be made at a, h, A : we have then divided a sensory nerve, and no pinching or pricking of the part innervated by that nerve wull be felt ; but move- ment will take place if the under nerve be irritated, or if a sensation elsewhere be excited. Now reverse the experi- ment, as at B, c, r/. Then, pricking of the skin will be felt, but no movement will respond. The nerve wliich enters the cord at the upper (posterior) part is therefore a sensory nerve ; that which enters at the under (anterior) ])art is motor. The direction is in each case indicated by 178 THE PHYSICAL BASIS OF MIND. the arrow. The central end h, if irritated, will produce sensation ; whereas the peripheral end a produces neither sensation nor movement. The central end d produces neither sensation nor movement ; the peripheral end c produces mo\'ement. 25. Two facts are proved by these experiments. First, that the co-oi:)eration of the centre is necessary for Sensa- tion, but not for Movement. Althouj^h normally all the muscles of the trunk are moved only when their centre has been excited, yet any irritation applied directly to the muscle nerve, even when separated from its centre, pro- duces a movement. And to this we may add that a slighter stimulus will move the muscle by direct irrita- tion of the nerve, than by indirect irritation through the centre ; a slighter stimulus also will suffice when applied to the nerve than wlien applied to the muscle itself. 26. The second fact proved is known as BclFs Law, that the sensor}^ and motor channels are respectively the posterior and anterior nerves. The fact is indisputable, but its theoretic interpretation can no longer be accepted in its original form. Bell supposed tlie two nerves to be different in kind, endowed with different specific energies, the one sensitive, the other motor. The majority of writ- ers still express themselves as if they adopted this view. We shall, however, presently see reason for replacing it by the more consistent interpretation which assigns one and the same property to both nerves, marking their dis- tinction by the terms afferent and efferent ; the one set being anatomically so disposed that it conveys stimuli from the surfaces to the centre, and the other set convey- ing stimuli from the centre to the muscles, glands, and other cells.* * It has been proved that the cells of the cornea and the pigment cells of the skin contract under nervous excitation. We cannot suppose that although these are the only cells which have hitherto been brought under THE NERVOUS MECHANISM. 179 27. Bell's discovery was rapidly generalized. The principle of localization was extended to all nerves, and of course to the posterior and anterior columns of the spinal cord, which indeed were assumed to be continua- tions of the nerves. Bell, who was greater as an anato- mist than as a philosopher, always maintained that ana- tomical deduction was superior to experiment. But this was to misunderstand the reach of deduction, which is only valid to the extent of its premises.* In the present case, the premises assumed that the posterior columns were continuations of the posterior roots, and carried impressions to the brain, the anterior columns carrying back from the brain the " mandates of the will." Exper- iment lias, however, decisively shown that it is not through the posterior columns that sensory impressions travel to the brain, but through the central gray substance. 28. The spinal cord with its central gray substance is at each point a centre of reflexion. Connected as it is with different organs, we artificially consider it as a chain of different centres, and try to detect the functional rela- tions of its parts. The inquiry is important, but we must bear in mind the cardinal principle that diversity of Function depends on the organs innervated, and not on a diversity of Property in the nervous tissue. Although all nerves have a common structure and common prop- erty, yet we distinguish them as sensory and motor ; and the sensory we subdivide into tliosc of Special Sensation and those of Systemic Sensation. The motor we divide into muscular, vasomotor, and glandular. The hypothesis of specific energies must be relinquished (§ 63). experimental okservation, they arc the only cells .subject to nerve-influ- ence. We may safely assume tliat wheiever a nerve-fibre terminates, its action will be transformed into an excitation of the part. Habitually, however, motor-nerves are spoken of as muscle-nerves. * On Deduction, see Problems : First Series, Vol. II. p. 159 180 THE PHYSICAL BASIS OF MIND. In like manner all centres have a common structure and a common property, M'ith a great diversity of func- tional relations. Here also the hypothesis of specific energies has been generally adopted, owing to a mistaken conception of the biological principle just mentioned. The cerebral hemispheres are credited with the properties of sensation, thought, and volition ; the cerebellum with the property of muscular co-ordination ; the spinal cord with the property of reflexion. 29. No attempt to assign the true functional relations of the centres will be made at the present stage of our exposition. We must learn more of the processes in Sen- sation, Thought, and Volition, before we can unravel the complex physiological web on which they depend. But here, provisionally, may be set down what observation and experiment have disclosed respecting the part played by certain centres. We know, for example, that when the cerebral hemispheres are carefully removed from a reptile or a bird, all the essentially vital functions go on pretty much as before, but a great disturbance in some of the psychical functions is observed. The brainless bird eats, drinks, sleeps, moves its limbs separately and in combination, manifests sensibility to light, sound, and touch, performs such instinctive actions as preening its feathers, or thrusting the head under the wing while roosting. Throw it into the air and it will fly. In its flight it will avoid obstacles, and will alight upon a ledge, or your shoulder. But it will not fly unless thrown into the air ; it will not escape through the open door or win- dow ; it will avoid objects, but will show no fear of them, — alighting on your head, for example, without hesita- tion. It is sensitive to light, and may in a certain sense be said to see; but it fails to ijerccive what is seen. It will eat and drink, if food and water be administered, but it will starve near a heap of grain and never peck it, not THE NERVOUS MECHANISM. 181 even if the beak be thrust into the heap. A grain, or •strip of meat, may be thrust inside the beak ; there it will remain unswallovved, unless it touches the back of the mouth, then swallowing at once follows the stimulus. The bird u-itli its brain will fly away if you turn the linger, or stick, on which it is perching ; without its l)rain, it makes no attempt to fly, but flutters its wings, and balances itself. If you open the mouth of a cat, or rabbit, and drop in some bitter fluid, the animal closes its mouth firmly, and resists your efforts to repeat the act ; without its brain, the animal shows the same disgust at the taste, but never resists the preliminaries of the repetition. 30. These, and analogous facts, have been noted by various experimenters. They are very far from proving what is usually concluded ; but they prove the important negative position that the cerebrum is not the centre of innervation for any of the organs on which the observed actions depend. Thus, the cerebrum is not necessary to sight: ergo it does not innervate the eye. It is not neces- sary to hearing : ergo it does not innervate the ear.* It is not necessary to breathing, swallowing, flying, etc. : ergo it does not innervate the organs of these functions. What then is lost? We have only to remember that the cerebrum is continuous with the thalami and corpora striata, and, through its crura, with the medulla oblon- gata and medulla spinalis, to foresee that its removal must more or less affect the whole neural axis, and con- sequently disturb the actions of the whole organism ; this disturbance w^ll often have the appearances which would * I do not here touch upon tlie question as to whetliev these actions of the senses are sensations, because that (juestion deuiands that we should lirst settle what is Sensation. I may at once, however, say that what is ordinarily understood as a sensation of color, or a sensation of sound, is, in my opinion, not possible without the cerebrum. But the sensibility of the eye and ear is manifestly preserved. 182 THE PHYSICAL BASIS OF MIND. be due to the removal of a central a}iparatus, so that we shall be apt to attribute the cessation of a lunction to the loss of its organ, when in fact the cessation is due simply to an arrest of the organ by irritation. Thus the cessa- tion of consciousness, or of any particular movements, when the cerebrum is removed, is no decisive proof that the cerebrum is the organ of consciousness, or of the movement in question. This point will be duly con- sidered hereafter. "What we have now to consider is the facts observed after removal of the cerebrum. First, we observe a loss of that power of combining present states with past states, present feelings with feel- ings formerly excited in conjunction with them, the power which enables the animal to adjust its actions to certain sensations 7iou- unfdt but which icill he felt in consequence of the adjustment. Secondly, we observe a loss of Spontaneity : the bird, naturally mobile and alert, now sits moveless for hours in a sort of stupor, occasion- ally preening its feathei"s, but rarely quitting its resting- place. All the most conspicuous phenomena which we assign to Intelligence and "Will seem alisent. The sen- sations are altered and diminished. Many Instincts have disappeared, but some remain. The sexual feeling is preserved, although the bird has lost all power of direct- ing its actions so as to gratify the desire. But these effects are only observ^ed when the whole of both hemi- spheres have been removed. If* a small portion remain the bird retains most of its faculties, though with less energy. In frogs and fishes there is little discernible effect observed when a large portion of the cerebrum is removed. 31. Xow take away from this mutilated bird its cere- bellum : all the functions continue as before except that some combined movements can no longer be effected ; flight is impossible ; walking is a mere stagger. Remove THE NERVOUS MECHANISM. 183 only the lateral lobes, and though flight is still possible great incoherence of the wings is observed, whereas walk- ing is not much affected. If only the cerebellum be removed, the cerebrum being intact, the phenomena are very different. All the perceptions and almost all the emotions, all the spontaneity and vivacity are retained ; but tlie sexual instinct, which was manifested when the cerebrum was removed, is now quite gone. What we call Intelligence seems unaffected. The bird hears, and understands the meaning of the sounds, sees and per- ceives, sees and fears, sees and adjusts its movements with a mental vision of unseen consequences.* 32. Are we from these facts to conclude tliat the cere- brum is the "organ of the mind"; that it is "the seat" of sensation, thought, emotion, volition; and that the cere- bellum is the " seat " of the sexual instinct, and muscular co-ordination ? Such conclusions have found acceptance, even from physiologists who would have been startled had any one ventured to affirm that the medulla oblon- gata was the " organ " of Eespiration, because Eespiration ceases when this centre is destroyed. I shall have to combat this notion at various stages of my exposition. Here let me simply say that it is irreconcilable with any clear conception of organ and function ; and is plainly irreconcilable with any survey of })sychical phenomena in animals in whom the cerebrum does not exist, and in animals from whom it has been removed. What the facts indisputably prove is that the cere- Ijrum has an important part in the mechanism by which the most complex psychical combinations are effected, and that the cerebellum has an important part in the mechanism by which the most complex muscular com- * It has been ob.serve(l that removal of the cerebellum affects the pig- ment cells of the skin. No doubt other parts are also affected, but the changes have hitherto escaped observation. 184 THE PHYSICAL BASIS OF MIND. lunations are effected. Tlic su})renie importance of the cerebrum may be inferred from its dominating all the other centres, and from its preponderance in size. In man it stands to all the other cranial centres together in the relation of 11 to 3. It is about five times as heavy as the spinal cord — that is to say from 1,100 to 1,400 granunes, compared with 27 to 30 grammes. The quan- tity of blood circulating through it is immense. Haller estimated the cranial circulation as one fifth of the whole circulation. If, therefore, the Nervous Centres are agents in the production of Sensation and Intelligence, by far tlie largest share must be allotted to the cranial centres, and of these the largest to the Cerebrum. 33. It is, however, one thing to recognize the Cere- brum as having an important part in the production of psychical phenomena, another thing to localize all the phenomena in it as their organ and seat — a localization which soon beciomes even more absurd, when of all the cerebral structure the multipolar cells alone are admitted as the active agents ! As was said just now, we recognize in the Medulla Oblongata the nervous centre of Eespiration, but we do not suppose that Eespiration has its seat there, nor that this centre is absolutely indispensable for the essential part of the process. We respire by our skin, as well as by our lungs ; many animals respire who have nothing like a medulla oblongata ; as many animals feel, and manifest will, who have nothing like a cerebrum. The destruction of centres is of course a disturbance of the mechanisms which they regulate. But even the observed results of a destruction require very close examination, and are liable to erroneous interpretations. The disap- pearance of a function following the destruction, or disease of a particular part, is not to be accepted as a proof that this part is the organ of the lost function ; because pre- THE NERVOUS MECHANISM. 185 cisely the same phenomena may often be observed follow- ing the destruction of a totally different part.* But one result may always be relied on, and that is the j^rsistcncc of a function after removal of a particular part. Thus there is a certain spot of the cerebral convolutions from which movements of the limbs are excited when the electrodes are applied to it ; removal of the substance is immediately followed by paralysis of the limbs. Are we to conclude that this spot is the organ of the func- tion ? It is true that the function is called into action by a stimulus applied to this spot : true that the func- tion suddenly vanishes when the substance of this spot is destroyed. Nevertheless, what seems a loss of func- tion is only a disturbance. In two or three days the paralysis begins to disappear, and at the end of a week the limbs are moved nearly in the normal manner. And the same is true when tlie spot in question is destroyed on both sides. The recovery of the function shows that the absent part was not its organ. There is a paradoxical experiment recorded by M. Paul Bert which may be cited here. He removed the right cerebral hemisphere from a chameleon, and found that the limbs on the left side were paralyzed ; but on liis then removing the left cerebral hemisphere the limbs of the left side recovered their activity. A similar result was obtained by Lussana and Lemoigne by extirpation of tlie thalami. When we find combined movements persisting after the cerebellum has been destroyed, we may be sure that the cerebellum is * OwsJANNiKOW describes the results of removing carefully the cra- nial ganglia of the crayfish ; and these effects Mfa'ER observes to be iden- tical with those which follow removal of the large claw of the crayfish ! A. B. Meyer, Das Jlcmmungsnerven-si/stem dcs Herzcns, 1869, p. 23. Let me add that the jilienomena described by M. Faivre as following the destruction of one subrjesojjhagcal ganglion in the Dytiscxis, are so little to be referred to the mere absence of the ganglion, that I find them not to occur when the whole head is removed. ISG THE PIIYSIC.U, BASIS OF MIND. not tlie organ by which such combinations take place ; and when we find sensation and volition manifested after the cerebrum has been removed, we may be sure that the cere- brum is not the organ ibr these sensations and volitions. 34. And this we do find. Physiologists, indeed, for the most part, deny it ; or rather, while they admit the observed facts, they refuse to admit the only consistent interpretation, biassed as they are by the traditional con- ception of the brain. After having for many years per- sistently denied Sensibility to any centre except the cere- brum, they are now generally agreed in including the medulla oblongata within the privileged region; but they still exclude the medulla spinalis. 35. If all the cranial centres as far as the medulla oblongata are removed from young rabbits, dogs, or cats, there are unmistakable evidences of Sensibility in their cries when their tails are pinched, their moving jaws (as in mastication) wdien bitters are placed in their mouths, and their raised paivs rubbing their noses, wlien irritating vapors are applied. It is said indeed that the cries are no signs of pai^i ; and this is probable ; but they are assuredly signs of Sensibility. 35. The frog thus mutilated has lost indeed all its spe- cial senses,, except Touch, but it still breathes, struggles when grasped, thrusts aside the pincers which irritate it, or wipes away acid dropped on its skin. If the eye be lightly touched, the eyelid closes ; if the touch be repeated three or four times, the foreleg is raised to push the irri- tant away ; if still repeated, the head is turned aside ; but however prolonged the irritation, the frog neither hops, nor crawls away, as he does wdien the cerebellum remains. Place the brainless frog on his back, and if the medulla oblongata remains he will at once regain the normal posi- tion ; but if that part is absent he will lie helpless on his back. The ]iower of preserving equilibrium in difficult THE NERVOUS MECHANISM. 187 positions — which of course implies a nice co-ordination of muscles — resides in the so-called optic lobes of the frog (what in mammals are called the corpora quadrigemina). 37. With the destruction of each part of the central mass there will necessarily be some disturbance of the mechanism ; but difficult as may be the task of detecting by experiment what is the normal action of any one part, there ought to be no hesitation in recognizing the persist- ence of functions after certain parts are destroyed. The spinal cord is anatomically known to be the centre from which the limbs, trunk, and genito-urinary organs are innervated. So long as the mechanism of the actions in- volving such organs is intact, no removal of other parts will prevent this mechanism from exhibiting its normal action. There may indeed arise, and there has arisen, the doubt whether Sensibility is involved in the action of any nerve centre below the medulla oblongata. But this doubt is founded on the traditional hypothesis respecting the seat of Sensation, and is flagrantly at variance with the logical conclusions of Anatomy and Experiment. 38. Anatomy shows that the structure of the spinal cord is in all essential characters the same as that of the medulla oblongata ; and indeed that the whole central axis has one continuous tissue, somewhat variously ar- ranged, and in relation with various organs. Abundant Experiment has shown that the spinal cord, apart from the encephalon, is capable of acting as a sen- sorial and volitional centre. The striking facts advanced by Pfluger, Auerbach, and myself, have not been im- pugned ; * but their interpretation has been generally * Pflugeu, Z>ie Senso^'ischcii Fuiikf.ioiir.ndes Riic/cenmarks,lS53. AuER- liACH, Gilnzhurg's Zcitschrift. Jahrganf; IV. p. 486. Lewes, Leeda Meet- I'nrj of British Association, 18.58, and Physiolofjy of Common Life, 1860. This recognition of sensation, and even of volition, in spinal actions may be foi;nd in the writings of AViiytt, Unzek, Prochaska, Legal- 188 THE PHYSICAL BASIS OF MIND. rejected. "VVe showed that a brainless frog responded to stimulation in actions which bore so close a resemblance to actions admitted to be sensorial and volitional — showed the frog ada]3ting itself to new conditions, and acquiriny dexterity in executing actions which at first were impos- sible or difficult, devisiyig combinations to effect a purpose which never by any possibility could have formed part of its habits — manifesting, in a word, such signs of Sensi- bility, that no one witnessing the experiments could hesi- tate as to the interpretation, had he not been biassed by the traditions of the schools. 39. Our opponents argued that in spite of all appearan- ces there were profound differences between the actions of the normal and the brainless animal, and that the latter were due simply to Reflex Action. I also insist on profound differences ; but underlying these there are fundamental identities. As to the Tieflex Action, two points will here- after be brought forward: 1°, that «// central action is reflex, the cerebral no less than the spinal ; 2°, that the hypotliesis of Eeflex Action being purely mccJtaniccd, and distinguished from Voluntary Action in not involving Sen- sibility, is an hypothesis which must be relinquished. 40. Postponing, however, all discussion of these points, let me here say that the doctrine maintained in these pages is that the whole cerebro-spinal axis is a centre of Reflexion, its various segments taking part in the per- formance of different kinds of combined action. It has one common property, Sensibility ; and different parts of it minister to different functions — the optic centre being different from the auditory, the cerebral from the spinal ; and so on. To make this intelligible, however, we must first learn Avhat is known respecting the properties of nerve-tissue. LOIS, and Mayo ; but the establishment of the Reflex Theory had dis- placed it, and its revival dates from PflUger. THE NERVOUS MECHANISM. 189 CHAPTEE III. NEURILITY, 41. Observation having found that the activity of a nerve was always followed by a sensation when the nerve ended in a centre, and by a movement when the nerve ended in a muscle, Theory was called upon to disclose the nature of this peculiar property of nerves. That a pecul- iar and mysterious power did act in the nerves no one doubted ; the only doubt was as to its nature. The an- cient hypothesis of Animal Spirits seemed all that was needed. The spirits coursed along the nerves, and obeyed the mandates of the Soul. When this hypothesis fell into discredit, its place was successively taken by the hy- potheses of Nervous Fluid, Electricity, and Nerve Force. The Fluid, though never manifested to Sense, was firmly believed in, even so late as the days of Cuvier ; * but when the so-called electrical currents were detected in nerves, and the nervous phenomena were shown to resem- ble electrical phenomena, there was a general agreement in adopting the electrical hypothesis. The brain tlien took the place of a galvanic battery; the nerves were its electrodes. 42. Closer comparison of the phenomena detected vari- ous irreconcilaljle differences, which, if they proved noth- ing else, proved that nerve-action took place under con- * Friedlandrr {Versuch ilber die innmi Sinnn, 1826, I. 77) declares it to be a rational necessity: " Die Annalime eines Nervcnfluidums ist Notliwendigkeit der Vernunft." 190 THE PHYSICAL basis of mind, ilitions so special as to demand a special designation. Electricity itself is so little understood, that until its nature is more precisely known, we cannot confidently say more than that nerve-action resembles electrical- action ; meanwhile the speciality of neural conditions ren- ders all deduction illusory which is based on electrical- action as observed under other conditions. In presence of these difficulties, cautious physiologists content them- selves with assigning the observed phenomena to the observed and inferred conditions, condensing these in the convenient symbol " nerve-force," without pretending to any specification of the nature of that force. It may be a wave of molecular movement dependent on isometric change or on metamorphic change. It may be the libera- tion of molecular tension resembling electricity ; it may be electricity itself. But whatever the nature of the change, it is an activity of the tissue, and as such comes under the general dynamic conception of Force or Energy. 43. In this sense the term has nothing equivocal or obscure. It is a shorthand expression S3^mbolizing cer- tain well-defined observations. Xevertheless, it is a term whicli ^re shall do well to avoid when possible, and to replace by another having less danger of misinterpreta- tion ; the reason being that Force has become a sort of shibboleth, and a will-o'-wisp to speculative minds. All that we knov- of Force is ]\Iotion. But this is too meagre for metempirical thinkers, who disdain the familiar expe- riences expressed in the term Motion, and demand a tran- scendent cause " to account " for what is observed. They seek an entity to account for the fact. Motion is a very definite conception, expressing precise experiences ; we know what it means, and know that the laws of moving bodies admit of the nicest calculation. A similar pre- cision belongs to Force when understood as "mass ac- celeration," or M V2. But this does not content those THE NERVOUS MECHANISM. 191 metaphysicians who understand by Force " the unknown reality behind the phenomena" — the cause of Motion. This cause they refuse to recognize in some antecedent motion (what I liave termed a "differential pressure")/ but demand for it a physical or metaphysical agent : the physical agent being a subtle fluid of the nature of Ether, or a nerve atmosphere surrounding the molecules ; the metaphysical agent being a Spirit or aggregate of Soul- atoms. The second alternative we may decline here to discuss. The first alternative is not only a pure fiction, but one which is inconsistent with the demonstrable velocity of the neural process, which is not greater than the pace of a greyhound, whereas the velocities of light and electricity are enormously beyond this. It is incon- sistent also with the observation that a much feebler cur- rent of electricity is requisite for the stimulation of a muscle through its nerve than when directly applied to the muscle : a proof that the nerve does not act solely by transmission of electricity — unless we gratuitously as- sume that the nerve is a multiplicator. When it is said that the living nerve is incessantly lib- erating Force which can be communicated to other tissues, the statement is acceptable only if we reject the meta- ])hysical conceptions it will too generally suggest — the conceptions of Force as an entity, and of its being passed from one object to another like an arrow shot from a bow. The physical interpretation simply says that the mole- cules of the nerve are incessantly vibrating, and with varying sweep ; these vibrations, when of a certain en- ergy, will set going vibrations in another substance by disturbing the tension of its molecules, as the vibrations of heat will disturb the tension of the gunpowder mole- cules, and set them sweeping with greater energy : this is the communication of the force. Just as we say that a magnet communicates magnetic force to a bit of iron, 192 THE niYSiCAL basis of mind. though all we ineau is that the magnet has so altered the molecular condition of the iron as to have given it the movements called magnetism — in short, has excited in the iron the dormant property of becoming magnetic — so we say the nerve communicates its force to the muscle, exciting in the muscle its dormant property of contrac- tion. But in truth nothing has passed from magnet to iron, or from nerve to muscle. 44. Do what we will, however, there is always, in the present condition of philosophical chaos, the danger of being misunderstood when we employ the term Nerve- force ; and I have proposed the term Neurility as an escape from the misleading suggestions. It is a symbol expressing the general property of nerve-tissue. For rea- sons presently to be stated, I restrict Xeurility to the peripheral system, employing Sensibility for the central system. The excited muscle manifests its special prop- erty of Contractility ; the excited nerve manifests its special property of Neurility; the excited centre mani- fests its special property of Sensibility.* The terms are * These terms and the conception they embody were proposed by me in 1859 in a paper " On the necessity of a reform in Xerve-physiology," read at the Aberdeen meeting of the British Association, and were repro- duced in the Physiology of Common Life. (Prof. Owen, probably in forgetfulness of my suggestion, proposed "neuricity." Lectures on the Comi). Anat. of Vertebrates, 1866, I. p. 318.; The terms were fortunate enough to meet with acceptance from some physiologists both in England and France ; and the conception has been more widely accepted than the terms. The most distinguished approver was Prof. Vulpian. " Faute d'une meilleure determination on pent, avec M. Lewes, donner a la propriete physiologique des fibres nerveuses le nom de neurilite; c'est la ce qui correspondra a la contractilite des fibres musculaires." Lerfins sur la physiologic dii systeme nerveux, 1866, p. 220. He also adopted my suggestion (since modified) of Sensibility as the property of ganglionic cells. Compare also Gav arret, PMnomenes physiques de la Vie, 1869, pp. 213 and 222. Taule, Notions sur la nature de la matiere organisee, 1866, p. 131. Charles PiOBIX, Anatomie et physiologie ccl- lulaires, 1873, p. 166. By these channels, and by the German, Italian, Russian, Polish, and THE NERVOUS MECHANISM. 193 •simply descriptive, and cany with them no hypothesis as to lohat Neurility is in its hidden process, nor hoio Sensi- bility arises in a nerve-centre, and not elsewhere. We know that a stimulated muscle contracts, and we express the fact by assigning to muscular tissue the property of Contractility. We know that a stimulated nerve trans- lates an impulse from one point to another, and excites the muscle to contract ; and we express the fact by as- signing to nerve-tissue the property of transmitting stim- ulation, which is further specified, as unlike other trans- missions, by the term Neurility. 45. What is the meaning attached to the term Prop- erty, and how it is distingui,shed from Function, has been already expounded in Problem 1, §§81-6. There also was laid down the principle of identity of structure imjjly- ing identity of property. Inasmuch as observation reveals a fundamental similarity in the structure of the nervous tissue throughout the animal kingdom, we must conclude the existence of a fundamental similarity in the property of that tissue : a conclusion confirmed by observation. There is a corresponding agreement in the organs and functions ; so that, within certain limits, the experiments performed on an insect may be verified on a mammal. Everywhere nerve-tissue has certain characters in com- mon, accompanied by variations in the degree and mode of manifestation corresponding with variations in struc- ture and connection. Obvious as the fact is, we must emphasize the great variety which accompanies the un- derlying uniformity, for this is recognizable both in the individual organism and in the animal kingdom at large. Hungarian translations of my woik, the suggostions were carried over Europe, crept into scientific journals, and became known to writers who never heard of me. I only mention thi^se facts lest the reader should suppose that my views had been anticipated by certain continental writers. VOL. III. 9 M 194 THE niYSICAL BASIS OF MIND. Even such seemingly individual terms as nerve-cell and nerve-fibre are in truth generic; and the description which accurately represents one cell or fibre needs modifying for others. Properties are generalized expressions; they result from the comjyodtion, the structure, and the tcj:turc of a sub- stance. Thus one bar of iron may differ from another of equal bulk in being more or less crystalline in structure, though having the same composition and the same tex- ture. This difference will modify the mode of manifes- tation of the iron-properties. Cast-iron pillars, for ex- ample, will support, as a roof, a weight which would break them if suspended ; wrought-iron pillars of similar bulk will bear a weight suspended which would crush them as a roof. Yet both cast and wrought iron pillars have the same properties, because they have the same composition and similar structure ; the variation of struc- ture only producing a difference in the modes. Texture may also vary. The bar of iron may be beaten into a plate, rolled into a cylinder, or split into wire-work, with- out any change in its properties, but with marked dif- ferences in its modes of manifestation, and in the uses to wdiicli it may be applied. These uses are of course dependent on the connections established betw^een the iron and other things. In Physiology, uses are called functions. 46. Nerve-tissue must be understood as having ever}-- where the same general Property. In one animal and in another, in one part and in another, jSTeurility is the same in kind, but not everywhere manifesting the same degree, nor applied to the same Function. The conqjosition of nerve-tissue varies, but not more than the composition of all other organized substances ; the stnicturc is variable, but only within a small range ; the texture also ; while the connections are very various. Hence, whatever the varia- THE NERVOUS MECHANISM. 195 tions in composition or structure, the nerve-fibre has every- where one fundamental property, which in connection with a muscle has the functional activity of exciting contrac- tion ; in connection with a gland of exciting secretion ; and in connection with a centre of exciting reflexion.* 47. Had a clear idea of Function as dependent on con- nexion been present to their minds certain physiologists would hardly have raised the mirage of " Nerve-force," a mysterious entity endowed with " specific energies," and capable of producing vital and psychical phenomena by an occult process ; nor would others have been led to the monstrous hypothesis of particular nerve-cells being en- dowed with thought, instinct, and volition. They would have sought an explanation of functions in the combined properties of the co-operant organs and tissues. They would not have endowed one nerve with Sensibility, and another nerve of identical structure with Motility ; f one nerve with a motor property, and another with the oppo- site property of inhibition. They would have seen that all nerves have the same property, but different uses when in different connexions. 48. Throughout the animal kingdom we see movement following on stimulation. Stimulation may be defined the cliange of molecular equilibrium. The stimulation of a muscle is produced indirectly tln^ougli a change in * " La force nerveuse n'existe pas comme puissance independant des proprietos de tissu. Elle consiste en Taction des parties excites, sur les parties excitables, I'etat de I'excitation des premieres agissant comme impression ou stimulation sur les secondes."— Landuy, Traite des Pa- rahjsics, 1859, I. 142. t " Le systeme nerveux est tout h, la fois I'origine des sensations ct I'origine des mouvements. Mais est-ce par une propriete unique, ou par deux jiroprii'tes divcrses qu'il determine deux phenomenes aussi dis- tincts ?" Floi'I'.kxs, Rccherchcs sur leu proprietis ct les fonct.ions du Sys- Ume Axrveax, 1824, p. 1. He concludes tliat "la puissance nerveuse n'est pas unitiue ; il n'y a pas une seule propriete, il y en a deux," p. 24. In this he has been generally followed. 196 THE niYSICAL BASIS OF MIND. the nerve, ov directly through a change in the muscle itself. In the simplest organisms there is no trace of nerve-tissue ; hut their substance manifests Irritability (or as it is often called Sensibility) ; and a stimulus to one part is propagated throughout — the whole body moves \\'hen touched. Even in Polypes, where there is the beginning of a differentiation, the motion is slowly propagated from one part to the rest. A single tentacle retracts when touched ; but the movement rarely ends there ; it is slowly communicated from one tentacle to the other, and from them to the whole mass. Touching the body, however, will not, if the touch be slight, cause the tentacles to move ; so that we see here a beginning of that principle of specialization which is so manifest in the higher organisms : the tentacles have become the specially sensitive parts. Ascending higher in the scale of organisms we find those which habitually move par- ticular parts without at the same time necessarily moving the rest ; and this independence of parts, accompanying a more perfect consensus, we find to be developed |:)ari passu with a nervous system. An immense variety of part-movements, with varying combinations of such move- ments, is the physiological expression of the more com- plex nervous system. 48 a. Deferring what has to be said of Sensibility till the next chapter, we may here touch on its relation to Irritability, which is often iised as its synonym. Ohjec- tively it cannot be distinguished from Irritability, nor indeed from the most general phenomenon of reaction under stimulation ; in this it is an universal property. But subjectively it is distinguishable as a peculiar mode of reaction, only known in nerve-tissues. While all tis- sues are irritable, and react on being stimulated, each tis- sue has its special mode of reaction. The secreting-cell reacts differently from the muscle-cell. The reaction of THE NERVOUS MECHANISM. 197 the nerve is the innervation of a centre or a muscle ; the reaction of an innervated centre is sensation ; of a muscle, contraction. There are three aspects of neural reaction : excitation, propagation of the disturbance, and innervation. The first is expressed by irritability, the second by conductibility, the third by sensibility ; but these are only artificial distinctions in the general phe- nomenon of transmitted excitation. The nerve substance is specially distinguished by its instability of molecular equilibrium ; it imdergoes chemical change with a readi- ness comparable to that of explosive substances. Hence its facility of propagation of disturbance. There is irri- tability and propagation of disturbance in muscular tis- sue, notably evideiit in the continuous tissue of the heart, intestines, and ureter; but the propagation is slow and diffusive ; whereas in the nerve it is rapid, and restricted along a definite path. By this rapidity and restriction the force of the impact is increased ; and thus a slight stimulus applied to the nerve is capable of disturbing the state of the muscle. 49. Thus while molecular movement is a fundamental condition of Vitality, and is incessant throughout organ- ized substance, the massive movements of the organism, and the movements of particular parts, are the directed quantities of this molecular agitation. They are due to stimulation. AVe distinguish this from mechanical im- pulsion. It is a vital process involving molecular change; it is not simply the communication of motion from with- out, but the excitation of motion within. It is not like the blow which merely displaces an object, but like the blow which disturbs its molecular equilibrium. The ef- fect, therefore, depends on this molecular condition : the l»low which scatters a heap of gunpowder will explode a fulminating salt, and this, in exploding, will excite the gunpowder to explode. Tiic stimulus which is too leoblc 198 THE niYsiCAL basis of mind. to excite contraction in a muscle will be powerful enough to excite the neurility of a nerve, and that will excite the contractility of the muscle. The nerve-force is simply- neural stimulus. It acts upon the other tissues as the nitrogenous salt upon the gunpowder. Although it is now common to speak of nerves as trans- mitting waves of molecular motion, and to regard nerves as the passive medium for the " transference of force," whereby the force is thus made an abstract entity, we must always remember that such phrases are metaphors, and that the truer expression will be not "transference of force," but the " propagation of excitation." I mean that it is not the force, of the impact nor its energy wliich a nerve transmits, it is the vibratory change produced in the nerve by the impact, which excites another change in the organ to which the nerve goes. We know by accurate measurements that the excitation of a nerve lasts nmcli longer than the stimulus, a momentary impact producing an enduring agitation. We know also that tlie excitation of a centre lasts longer than the muscular contraction it has initiated. We know, moreover, that a nerve may be totally incapable of conducting an external stimulus, yet quite capable of conducting a central stimulus ; were it a passive conductor like a wire this would not be so.* 50. The nerve is essentially an exciter of change, and thereby a regulator. A muscle in action does not appre- ciably determine action in any other (except in the com- paratively rare cases of anastomosing muscles) ; a secret- ing cell does not propagate its excitation to others. The nerve, on the contrary, not only propagates its excitation, * "I have raised and stretched the thick orbital nerve of horses on the handle of a scalpel, like a string on the bridge of a violin, without exciting the least sensation ; but as soon as mechani>jal or chemical irri- tation had given rise to inflammation of the nerve a gentle touch caused violent pain." — Romberg, Nervous Diseases (translated for the Syden- ham Society), I. 10. THE NERVOUS MECHANISM. 199 and awakens the activity of the muscle or gland with which it is connected, but through the centre affects the whole organism — "Ein Selling tausend Verbindungen schlagt." Thus it is that stimulation which in the simpler organ- isms was diffused throughout the protoplasm, has in the complex organisms become the specialized property of a particular tissue. 51. Two general facts of supreme importance must now be stated : One is the law of stimulation — every excitation pursues the jxith of least resistance. The second is the condition of stimulation — unlike tnechanical im- indsion, it acts only at insensible distances. 52. This means that although a nerve may be excited by any stimulus external to it which changes its molecu- lar condition, no propagation of that change (i. e. no stinm- lation througli the nerve) is possible except through con- tinuity of substance. Mere physical contact suffices to excite the nerve ; but if there be an interruption of con- tinuity in the nerve itself, no stimulus-wave passes across that line. Cut a nerve, and bring the divided surfaces once more into close contact, there will still be such a solution of continuity as to arrest the stimulus-wave, mere physical contact not sufficing for the propagation. Whereas across the cut ends of a divided nerve, even visibly separated, the electric current easily passes. T]iis necessity for the vital continuity of tissue in the propaga- tion of stimulation must always be borne in mind. The presence of a membrane, liowever delicate, or of any tissue liaving a different molecular constitution, suffices to arrest or divert the wave. I conceive, therefore, that it is abso- lutely indispensable that a nerve should terminate in and hlend with a muscle or a centre, otherwise no stimulation of muscle or centre will take; place through tlic nerve. 200 THE niYSICAL BASIS OF MIND. 53. The difierence between excitation from contact and stimulation from continuity may be thus illustrated. In Fig. 13 we see the legs of a frog attached to the spine by Fig. 13 the lumbar nerves (J), and lying on the muscles (m) of one leg is the nerve (c) of another frog's leg. Applying the electrodes to (l), the muscles (m) are violently con- tracted ; not only so, but their contraction excites the other nerve (c), and the leg attached to this nerve is thereby thrown into contraction. This "secondary con- traction," as Dubois Reymond calls it, might be supposed to be due to a diffusion of the electrical current ; but that it is due to a change in the muscles (m) is proved by deli- cate experiments showing that the movements in tlie detached leg are of precisely the same kind as those in the legs directly stimulated. If there is only a muscular shock in the one case, there is only a muscular shock in the other ; if tliere is tetanus in the one, there is tetanus THE NEEVOUS MECHANISM. 201 in the other ; if the muscles of the first leg are fatigued and respond slowly and feebly, the response of the second is slow and feeble. Moreover, the secondary contraction may be produced by chemical or mechanical stimulus, as well as by the electrical. 54. Although tlie contraction of a muscle is thus seen to be capable of exciting a nerve in contact with it, the reverse is not true : we can produce no contraction in a muscle by exciting a nerve simply in contact with the muscle, and not penetrating its tissue and termi- nating there. Accordingly we always find a nerve when about to enter a muscle or a centre losing its protecting envelopes ; it gradually becomes identified as a proto- plasmic thread witli the protoplasm of the muscle or the centre. 55. Neurility, then, is the propagation of molecular change. Two offices are subserved by the nervous sys- tem, which may respectively be called Excitation — the disturbance of molecular tension in tissues, and conse- quent liberation of their energies ; and Co-ordination — the direction of these several energies into combined actions. Thus, when the muscle is in a given state of molecular tension, the stimulation of its nerve will change that state, causing it to contract if it be in repose. But this stimulation, which will thus cause a contraction, will be arrested, if at the same time a more powerful stimula- tion reaches the antagonist muscle, or some distant cen- tre : then the muscle only tends to contract. ORIGIN OF NERVE-FORCE. 56. After this brief account of Neurility we may pass to the consideration of its origin. Arc we to understand that this property belongs to the nerves themselves in the sense in which Contractility belongs to the muscles ? or are we to accept tlie teaching which assigns the origin of 202 TIIE niYSICAL BASIS OF MIND. "nerve-force" to the ganglia, and regards the nerves sim- ply as passive conductors of a force developed in the cells ? 57. It is now many years since I ventured to criticise the reigning doctrine, and to urge the necessity of consist- ently carrying out the distinction between Property and Function. I called attention to the positive evidence which contradicted the idea of passive conduction ; and pointed out the illusory nature of the favorite analogy, in which ganglia were likened to batteries, and nerves to the conducting wires. But the old image still exerts its empire ; and writers are still found speaking of the brain as a telegraphic bureau, the ganglia as stations, and the nerves as wires. In the cells of the gray substance they place a constantly renewing reservoir of nerve- force. There the force is elaborated, stored up, and from thence directed along the nerves. The sensory nerve " transmits an impression to the brain " — as the wire transmits a message to tlie bureau. The motor nerve, in turn, '•'transmits the mandates of the will" — and all is clear! Clear, until we come to translate metaphors into visible facts, or try to conjure up some mental image of the process. For myself, I can only conceive nerve-force as the activity of the nerve, and not of something else. This becomes still more evident when J find that the activity is equally manifest after its imaginary source has been removed. Transmitting impressions, or messages, implies as a preliminary that there should be an impressible agent, or a message-sender, at the periphery. Xo one sup- poses that simply touching one end of a wire would send an "impression" or a "message" to the battery; or that without the battery this touch would evolve a current. The battery is indispensable ; in it is evolved the current which the wire transmits. Not so the ganglion, or brain. Remove the wire from its connection with the battery, THE NERVOUS MECHANISM. 203 and it is a bit of wire, nothing more. But remove a nerve from its connection witli a ganglion, and it is still active as nerve, still displays its ^Neiirility when excited, still moves the muscle as before. The amputated limb will move when its nerves are stimulated, just as when a reflex from its centre moved it. Every one knew the fact ; it was staring them in the face, yet they disregarded it. Even the old anatomist, Willis, had recorded experi- ments which ought to have opened their eyes. He tied the phrenic nerve, and found that, when he irritated it below the ligature, the diaphragm moved ; but when he irritated it above the ligature, no movement followed. Since his days, thousands of experiments have shown that the presence of a ganglion is not necessary to the action of a nerve.* 58. Of course an explanation was ready. The nerve was said to have been " endowed with force " from its ganglion during their vital connection; and this force, stored up in the nerve, was disj)Osable for some time after separation from the ganglion. We need not pause to criticise this misty conception of one part " endowing " another with force ; the plain facts afford the best answer. There seemed, indeed, a confirmation of the hypothesis in the fact that although the nerve separated from its gan- glion was capable of excitation, yet after a few excitations it was exhausted, and ceased to stimulate the muscle. It seemed like the piece of magnetized iron which would act as a temporary magnet, though quickly losing this bor- rowed power. But the whole fabric fell — or ought to have fallen — when extended observation discovered that * The cxperimeiits of IIaller, Sar la nature sensiUc ct irritable des }>a,rtics, I. 24r); and the remarks of Prochaska, De Functionihus Syste- matis Ncrvosi (translated by Laycock in the volume publislied by the Sydenliam Society, p. 396), ought to have sufficed. See further on, Chap. V. 204 THE niYsic.vL basis of mind. this exhausted nerve would, if left in repose, recover its lost power. A nerve preserves its e.xcitability as long as it preserves its structural integrity, and recovers its power in recovering that integrity. The lengtli of time varies.* Gratiolet found the muscles in the leg of a tortoise, which had been amputated a week before, contract when the nerves were irritated ; and Schiff found the divided nerve of a winter frog excitable at the end of three weeks. Even after all excitability has disappeared, it will reap- pear if arterial blood be injected ; just as muscles whicli have already begun to assume cadaveric rigidity recover their contractility after transfusion. Nor is this all. The separated nerve finally degenerates, and loses all its struc- tural characters and physiological properties ; yet under favorable conditions it will regenerate — recover its struc- tures and properties ; and this even apart from a centre, as Vulpian showed. Very noticeable is the fact that the force said to be produced in the centre, and only " con- veyed " by the nerve, vanishes gradually from the centre to the periphery, and recovers from the periphery to the centre — the part of the nerve whicli is farthest from the centre being excitable when the part nearest the centre is still inexcitable. Again, when a nerve is pinched, con- traction in tlie muscle follows ; but the pinch has for a time so disturbed the structural integrity of the nerve (at that spot) that no irritant applied to the spot, or hetiveen it and the centre, will be followed by contraction, whereas helow the spot an irritation takes effect. This is another form of the experiment of Willis. Even in its normal state, the nerve has different degrees of excitability in different parts of its course, — a fact discovered by rfliiger which is quite irreconcilable with the hypothe- sis of passive conduction. Doubts have been thrown on * In mammals about three days, in birds four da3's, in frogs fourteen to twenty days. THE NERVOUS MECHANISM. 205 Pfliiger's interpretation,* namely, that there is an ava- lanche-like accumulation of energy proportionate to the length of the stimulated portion ; but the fact remains, that one and the same irritant applied successively to two different points of a nerve does not irritate the muscle in the same degree. Llunk also finds the velocity of trans- mission in a motor nerve increases as it approaches its termination in the muscle.*!* 59. Nothing can be more unlike the conduction of an electric current than this excitation of Neurility ; nothing more accordant with the idea of it as a vital property of the tissue. The notion of its being derived from a centre is on a par with the notion first successfully combated by Haller,| that the muscle derived its Contractility from the nerves ; or the analogous notion that the electric organ in fishes derived its property from the brain. In- deed, it was in support of the hypothesis that the brain was a battery, and nerves the conductors, that the phe- nomena observed in electrical fishes were frequently cited. The electric organ was seen to be connected with the brain ; its discharges were under the control of the ani- mal, and were destroyed on one side when the brain on the corresponding side was destroyed. But Charles Eobin long ago suggested, what indeed ought never to have been doubted, that the brain was not the source of the elec- tricity ; but that the tissue of the electric organ itself had this special property, which the nerve merely called into activity. The suggestion has been experimentally veri- fied by M. Moreau, who divided all the nerves supplying the electric organ on one side, and, liaving thus cut off all * Ruth r.i; FORD, in Journal of Anatomy, 1873, No. VIII. p. 331. (Fleischl denies that the nerve in situ lias difTerent degrees of reaction. Sitzunr/sherichle (ler Wiener Akad., December, 1876.) + MuNK, in the Archiv fur AnaL, 1860, p, 798. t Halleii, 3f6moires sur la nature sensible ct irritable des parties. 206 THE niYsiCAL basis of mind. communication -with the brain, produced electrical dis- charges by irritating the nerves ; precisely as the muscles are made to contract when the divided nerves are irri- tated. Had tlie experiment ceased here, it might have been interpreted on the old hypothesis : tlie electric organ might be supposed to liave a certain amount of electric force condensed in it, stored up there, as it is said to be in the nerves, and discharged when tlie organ is irri- tated. But experiment has decided this point also. Elec- tric fishes notoriously exhaust their power by a few dis- charges, and recover it after repose. When ]\L IMoreau had exhausted his mutilated fishes, he replaced them in the water, and allowed them repose. On again irritating the divided nerves, the discharges were again produced.* 60. On all sides the idea of nerves deriving their power from another source than their own substance is seen to be untenable. A j^nori this might have been concluded. Neurility is the vital property of nerve-tissue. " Nerve- force" is nerve-action — molecular changes in the nerve itself, not in some remote substance. That nerve and centre are vitally connected is true ; and what their phys- iological relations are will hereafter be examined ; but we must dismiss the idea of nerves having the relation to centres that electrodes have to batteries. 61. In proposing the term Xeurility, I not only wi.shed to get rid of the ambiguities which hovered round " nerve- force " and " nerve-current," but to recall the physiologi- cal principle that properties are dependent on structures ; and therefore that the special property of nerve-tissue is conditioned by its structure. Neurility is, of course, an abstraction ; but so is the nerve an abstraction. The con- crete manifestations are the several nerve-actions. These we classify and specify. One class we call sensory, another class motor ; not because the nerve-action itself » Com2)tes Rcndus, 1862, LIV. p. 965. THE NERVOUS MECHANISM. 207 is different, but because it is in each class in a different functional relation to other parts. In classing men as governors and governed, employers and employed, we do not suppose antliropological distinctions, but only differ- ences in their social functions. 62. This is the modification of the Law of Bell to which reference was made in § 26. It replaces the idea of two different kinds of nerve, sensory and motor, by that of two different anatoniical connections. I need not reproduce here the argument with which I formerly criti- cised the supposed distinction between sensory and motor nerves ; because the old idea is rapidly falling into dis- credit, and physiologists so eminent as Vulpian and Wundt have explicitly announced their adhesion to the principle of identity, — a principle which, as Vulpian truly remarks, dominates the whole physiology of the nervous system.* THE HYPOTHESIS OF SPECIFIC ENERGIES. 63. One development of the theory of Bell, respecting the different kinds of nerve, has been the still accredited hypothesis that each nerve has a " specific energy," or qual- ity, in virtue of which it acts and reacts only in one way. The optic nerve, no matter how stimulated, only responds by a sensation of color, the auditory nerve only by a sen- sation of sound ; and so on. This hypothesis, which (as I learn from a correspondent) f was originally propounded by Bell himself, was developed and made an European doctrine by Johannes Mliller, first in his remarkable trea- tise, tlhcr die 'plicmtastisclien Gesichtsersclicimtngcn (1826), * " J'espeieVous convaincre que tovis les elements anatomiques dcs nerfs sensitifs, motciirs, vasomoteurs, et autrcs, ont les memes proprietes, et ne sont distincts que par leurs fonctions. Cette question est de la plus haute importance pour la physiologie generale. C'est celle qui domine toute la phj'siologie dcs fibres nerveuses." — VULPIAN, Ler^ons sur la Physiologie dii Systimc Nervciix, p. 1 1 . t Mr. James Andi-.ews. 208 THE niYSICAL BASIS OF MIND. and afterwards in his Physiology. Like all good hypoth- eses, it has been iVuitlul ; and Helmholtz still holds it to be of extraordinary importance i'or the theory of percep- tion. Although combated by a few physiologists, it has kept its place firm in the general acceptance ; no doubt because it I'orms a ready explanation of the facts. But, as I often have to remark, explanation is not dcmonstratio7i* 64. The first criticism to be made on tlie hypothesis is that it commits the error of confounding function with property, assigning as a specific quality of the nerve the reaction of the organ innervated. Thus Mliller speaks of the specific energy as " the essential condition of the nerves in virtue of which they see light and hear sound." But the optic nerve no more sees, than the liver-nerve secretes bile. That the optic nerve is one element in the mechanism on which vision depends, is all that we can say. Midler declares that it is not sufficient to assume each nerve to be so constituted that it has a susceptibility to certain stimuli rather than to others ; but that " with Aristotle we must ascribe to each a peculiar energy as its vital quality. Sensation," he adds, " consists in the sen- sorium receiving through the medium of the nerves a knowledge of certain qualities, — a condition, not of the external bodies, but of the nerves themselves," — and these qualities are different in different nerves. In other words, he assumes a special substance for each special energy. The sensation of color depends on the spe- cial Visual substance {Sehsinnsulstanz) ; the sensation of sound on the Auditory substance {Horsinnsubstanz) ; and so on. 65. We have here an hypothesis analogous to that of Innate Ideas, or a priori Forms of Thought. It is, in fact, only a reproduction of that conception carried into the * In the second number of Za Revue Philosophique, Paris, 1876, I have treated this question of specific energies more at length than I could find space for in the present volume. THE NERVOUS MECHANISM. 209 sphere of Sense. No one thinks of assigning specific energies to the several muscles, yet a movement of pre- hension is as different from a movement of extension, a peristaltic movement is as different from a movement of occlusion, as a sensation of sound is from a sensation of color. If movement is common to both of the one class, feeling is common to both of the other: the forms and mechanism are different and specific. Muscles have the common property of contracting under stimulation ; what- ever be the nature of the stimulus, each muscle has its own particular response, or mode of reaction : the Hexor always bending, never extending the limb ; the sphincter always closing, never opening the orifice. The move- ments of the heart are not the same as those of tlie eye ; both are unlike the movements of the intestine. There are muscles which respond to some stimuli, and not to others. Those of the eye, or of the vocal chords, respond to impulses which would leave the niasseter or biceps unstirred. According to Marey, the liyoglossus of a frog will become tetanic under a stimulus of only ten pulses in a second ; whereas the gastrocnemius of that same frog resists a stimulus of less than twenty in a second. We find the retina responding to ethereal pulses which leave the auditorius unaffected ; we find the muscles of a gnat's wing so exquisitely susceptible that the wing beats eight thousand times in a second, — a delicacy in comparison with wliich even our muscles of the eye are coarse. 66. The facts which the hypothesis of specific energies is called on to explain are more consistently interpreted on the admission of a common property in nerve-tissue, manifesting different degrees of excitability, and entering into different mechanisms, so that the functional results differ. A nerve which may be stimulated from the skin will not respond at all, or not in the same way, if the stimulus be applied under the skin. Are we to suppose 210 THE niYsicAL basis of mind. that the specific energy resides in one part of the nerve, antl not in another ? * Tiiat the optic nerve responds to stimuli whicli will not sensibly excite a motor nerve, depends on the terminal structures through Avhich the stimulation is excited ; for the optic nerve itself, apart from the retinal expansion, is as insensible to light as the motor nerve is. And the specific sensation, or movement, which results from stimulation of a nerve depends not on the nerve, but on the mechanism of which the nerve is one element. Sensations of touch, temperature, and pain are assuredly specific ; they are as unlike each other as a sensation of taste is unlike a sensation of smell. Yet the same nerves, variously stimulated, produce all three sensations. 67. We conclude, therefore, that the phrase "specific energy" is an elliptical expression for the particular office of a nerve. In this meaning there is no obscurity. The optic nerve is not a vasomotor nerve, the skin nerve is not a muscle nerve ; the auditory nerve is a nerve of special sensation, the vagus is a nerve of systemic sen- sation ; and so on. Neither movement nor sensation be- longs to the nerves themselves. * In 1859 I mentioned that if the nerves of a frog's back he exposed by raising the skin, they may be pricked or even cut without sensible effect, although a slight prick on the skin -will excite the nerves, and cause a reflex action. In 1870, Prof. FiCK expressed his astonishment at finding that after he had cut out a piece of the skin, leaving it attached to the body by a single nerve, electrical stimulation of this excised skin caused the frog to make the reflex movement of rubbing the irritated sur- face ; whereas electrical stimulation of the nerve-trunk itself produced no reflex effect, only a twitching of a muscle. PJliigcrs Archiv, 1870, p. 327. Browx S6QUARD tries to establish a distinct species of nerves as conductors of sensitive impressions, from those which are imiyrcssion- ablc. The facts on which he founds these two properties simply show that nerves are so disposed that the stimulus which excites them in one place fails in another. He could hardly maintain that a skin nerve contained impressionable fibres at its periphery, and only con- ducting fibres in its trunk ? See his communication to the Eoyal Society, Proceedings, 1856 ; and Lectures in the Lancet, lOtli July, 1858. THE NERVOUS MECHANISM. 211 CHAPTER IV. SENSIBILITY. 68. The principles laid down in the preceding chapter are equally applicable to the central system. But here greater difficulties await us. We cannot expect tradi- tional views to be easily displaced, when they have taken such hold on the mind, as is the case with regard to Sensibility. To admit that all nerves have a common property, and that their functional relations depend on tlie organs which they innervate, demands small relin- quishment of cherished opinions. But to admit that all nerve-centres have a common property, and that their functional relations depend on their anatomical connec- tions, is to sweep away at once a mass of theoretic in- terpretations which from long familiarity have acquired an almost axiomatic force. That the brain, and the brain only, is the source and seat of Sensibility is the postulate of modern Physiology. 69. The question is one of extreme complexity, but may be greatly simplified, if we can manage to reduce it to purely physiological terms, and consider the phenome- na in their objective aspect. In dealing with nerves and their actions this was comparatively easy ; we had for the most part only physiological processes to unravel. It is otherwise in dealing with nerve-centres — the sub- jective or psychological aspect of the phenomena inevi- tably tln-usts itself on our attention ; and all the mys- teries of Feeling and Thought cloud our vision of the •212 THE niYSICAL BASIS OF MIND. neural process. Do what we will, we cannot altogetlier divest Sensibility of its psychological connotations, can- not help intei'preting it in terms of Consciousness ; so that even when treating of sensitive phenomena ob- served in molluscs and insects, we always imagine these more or less suffused with Feeling, as tliis is known in our own conscious states. 70. Feeling is recognized as in some way or other bound up with neural processes ; but Physiology proper has only to concern itself with the processes ; and the question whether these can, and do, go on unaccompa- nied by Feeling, is, strictly speaking, one which belongs to Psychology. It demands as a preliminary that the term Feeling be defined ; and the answer will depend upon that definition, namely, whether Feeling be inter- preted as synonymous with Consciousness in the re- stricted sense, or synonymous with the more general term Sentience. If the former, then since there are unques- tionably neiu'al processes of which we are not conscious, we must specify the particular groups which subserve Feeling ; as we specify the particular groups which sub- serve the sensations of Sight, Hearing, Taste, etc.; and localize the separate functions in separate organs. If the latter, then, since all neural processes have a common character, we have only to localize the particular varia- tions of its manifestation, and distinguish sensitive phe- nomena as we distinguish motor phenomena. 71. It is absolutely certain that the Feeling we attrib- ute to a mollusc is different from that which we attrib- ute to a man ; if only because the organisms of the two are so widely different, and have been under such differ- ent conditions of excitation. If every feeling is the func- tional result of special organic activities, varying with the co-operant elements, we can ha\e no more warrant for assuming the existence of the same particular forms THE NERVOUS MECHANISM. 213 of Feeling in organisms that are unlike, than for assum- ing the 47th proposition of Euclid to be presented by any three straight lines. The lines are tlie necessary basis for the construction, but they are not the triangle, ex- cept when in a special configuration. This is not deny- ing that animals fed (in the general sense of that term), it is only asserting that their feelings must be very unlike, our own. Even in our own race we see marked differ- ences — some modes of feeling being absolutely denied to individuals only slightly difiering from their fellows. If, however, we admit that different animals must have different modes of Feeling, we must also admit that the neuro-muscular activities are generically alike in all, because of tlie fundamental similarity in the structures. Whether we shall assign Feeling to the mollusc or not will depend on the meaning of the terra ; but, at all events, we require some term general enough to include the phenomena manifested by the mollusc, and those manifested by all other animals. Sensibility is the least objectionable terra. Unless we adopt some such general designation, physiological and psychological interpreta- tions become contradictory and obscure. The current iloctrine which assigns Sensibility to the brain, denying it to all other centres, is seriously defective, inasnmch as it implies tliat tissues similar in kind have utterly diverse properties; in other words, that the same nerve- tissue which manifests Sensibility in the brain has no such property in the spinal cord. 72. How is this tenable ? No one acquainted at first hand with the facts denies that the objective phenomena exhibited Ijy the brainless animal liave the same general character as those of tlie animal possessing a brain : the actions of tlie two are identical in all cases which admit of comparison. That is to say, the objective appearances are the same ; differing only in so far as the mechanisms 214 THE niYSiCAL basis of mind. are made different by the presence or absence of certain parts. The brain not being a necessary part of the me- chanical adjustments in- swimming, or pushing aside an irritating object, the brainless frog swims and defends it- self in the same way as the normal frog. But no sooner do we pass from the objective interpretation, and intro- duce the subjective element of Feeling among the series of factors necessary to the product — no sooner do we ask whether the brainless frog fceh the irritation against which it struggles, or wills the movements by which it swims — than the question has shifted its ground, and has passed from Physiology to Psychology. The appeal is no longer made to Observation, but to Interpretation. Ob- servation tells us here nothing directly of Feeling. What it does tell us, however, is the identity of the objective phenomena; and Physiology demands that a common term be employed to designate the character common to the varied phenomena. Sensibility is such a term. But most modern physiologists, under the bias of tradition, refuse to extend Sensibility to the spinal cord, in spite of the evidences of the spinal cord possessing that prop- erty in common with the brain. They prefer to invoke a new property ; they assign spinal action to a Eeflex Mechanism which has nothing of the character of Sen- sibility, because they have identified Sensibility with Consciousness, and have restricted Consciousness to a special group of sensitive phenomena. 73. Nor is it to be denied that on tliis ground they have a firm basis. Every one could testify to the fact that many processes normally go on without being accom- panied by consciousness, in the special meaning of the term. Eeflex actions, — such as winking, breathing, swal- lowing, — notoriously produced by stimulation of sensi- tive surfaces, take place without our " feeling " them, or being " conscious " of them. Hence it is concluded that THE NERVOUS MECHANISM. 215 the Eeflex mechanism suffices without the intervention of Sensibility. I altogether dispute the conclusion ; and in a future Problem will endeavor to show that Sensibility is necessary to Reflex Action. But without awaiting that exposition we may at once confront the evidence, by ad- ducing the familiar fact that " unconscious " processes go on in the brain as well as in the s]3inal cord ; and this not simply in the sphere of Volition, but also in the sphere of Thought.* We act and think " automatically " at times, and are quite " unconscious " of what we are doing, or of the data we are logically grouping. We often think as unconsciously as we breathe ; although from time to time we become conscious of both processes. Yet who will assert that these unconscious processes were inde- pendent of Sensibility ? Who will maintain that because cerebral processes are sometimes unaccompanied by that peculiar state named Consciousness, therefore all its pro- cesses are unaccompanied by Feeling ? And if here we admit that the Reflex mechanism in the brain is a sensitive mechanism, surely we must equally admit that the similar Reflex mechanism in the spinal cord is sensitive ? 74. Let it be understood that Sensibility is the com- mon property of nerve-centres, and physiological inter- pretations will become clear and consistent. Conscious- ness, as understood by psychologists, is not a property of tissue, it is a function of the organism, dependent indeed on Sensibility, but not convertible with it. There is a greater distinction between the two than between Sensa- tion, the reaction of a sensory organ, and Perception, the * In conseriuenoe of tliis observation some pliysiologists liave main- tained that Feeling or Consciousness never arises in cerebral activity, unless the thalami and the connected tracts are at the same time in action. I go further, and maintain that there is no Consciousness (in the restricted meaning of the term) un/eas the whole onjanism is involved. Cerebral or spinal activity will be activity of Sensibility ; but this is only the basis of Consciousness. 210 TlIK rilYSICAL BASIS OF MIND. combined result of sensory and cerebral reactions ; or than that between Contractility, the property of the mus- cles, and Flying, the function of a particular group of muscles. It is not possible to have Consciousness with- out Sensibility ; but perfectly possible to have Sensations without Consciousness. This will perhaps seem as incon- ceivable to the reader as it seemed to Schroder van der Kolk.* 75. Let us illustrate it by the analogy of Pain. There is a vast amount of sensation normally excited which is totally unaccompanied by the feelings classed as painful. The action of the special senses may be exaggerated to an intolerable degree, but the exaggeration never passes into pain : the retina may be blinded with excess of light, and the ear stunned with sound — the optic nerve may be pricked or cut — but no pain results. The systemic sen- sations also are habitually painless, though they pass into pain in abnormal states. Clearly, then, Pain is not the necessary consequence of Sensibility ; and this is true not only of certain sensitive parts, but of all ; as is proved in the well-known facts of Analgesia, in which complete insensibility of the skin as regards Pain co-exists with vivid sensibility as regards Touch and Temperature. Hence the majority of physiologists refuse to acknowl- edge that the struggles and cries of an animal, after removal of the brain, are evidences of pain ; maintaining that they are " simply reflex actions." This is probable ; the more so as we know the struggles and cries which tickling will produce, yet no pain accompanies tickling. But if the struggles and cries are not evidence of pain, they are surely evidence of Sensibility. 76. Now for the term Pain in the foregoing paragraph * "An unconscious sensation, which Lewes distinguishes from percep- tion, is to me an inconceivable (ist fiir mich ein Unding)." — Schroder VAN DKR Kolk, Die Pathologic dcs Geistcs-Krankhciten, p. 22. THE NERVOUS MECHANISM. 217 substitute the terra Consciousness, and you will perhaps allow that while it may be justifiable to interpret the actions of a brainless animal as due to a mechanism which is unaccompanied by the specially conditioned forms of Sensibility classed under Consciousness — just as it is unaccompanied by the specially conditioned forms of Perception and Emotion — there is no justification for assuming- the mechanism not to have been a sensitive mechanism. The wingless bird cannot manifest any of the phenomena of flight; but we do not therefore deny that its other movements depend on Contractility. 77. Difficult as it must be to keep the physiological question apart from the psychological when treating of Sensibility, we shall never succeed in our analysis unless the two questions are separately treated. The physiolo- gist considers organisms and their actions from their objective side, and tries to detect the mechanism of the observed phenomena. These he has to interpret in terms of Matter and Motion. The psychologist interprets them (in terras of Feeling. The actions which we see in others we cannot feel, except as visual sensations ; the changes which we feel in ourselves we cannot see in others, except as bodily movements. The reaction of a sensory organ is by the physiologist called a sensation, — borrowing the term from the psychologist ; he explains it as due to the stimulus which changes the molecular condition of the organ ; and tliis changed condition, besides being seen to be followed by a muscular movement, is inferred to be accompanied by a change of Feeling. The psychologist has direct knowledge only of the change of Feeling which follows on some other change ; he infers that it is origi- nated by the action of some external cause, and infers that a neural process precedes, or accompanies, the feeling. Obviously there are two distinct questions hero, involving distinct methods. The physiologist is compelled to com- VOL. III. 10 "218 THE PHYSICAL basis of mind. plete his objective observations by subjective suggestions; compelled to add Feeling to the terms of Matter and Motion, iu spite of the radical diversity of their aspects. The psychologist also is compelled to complete his sub- jective observations by objective interpretations, linking the internal changes to the external changes. A complete theory nmst harmonize the two procedures. 78. In a subsequent Problem we shall have to examine the nature of Sensation in its psychological aspect ; here we have first to describe its physiological aspect. To the psychologist, a sensation is simply a fact of Conscious- ness ; he has nothing whatever to do with the neural pro- cess, which the physiologist considers to be the physical basis of this fact ; and he therefore regards the physiolo- gists as talking nonsense when they talk of " unconscious sensations," the phrase being to him equivalent to "unfelt feelings," or "invisible light." It is quite otherwise with the physiologist, who viewing a sensation solely as a neu- ral process, the reaction of a sensory organ, can lawfully speak of unconscious sensations, as the physicist can speak of invisible rays of light, — meaning those rays which are of a different order of undulation from the vis- ible rays, and which may become visible when the sus- ceptibility of the retina is exalted. He knows that there are different modes, and different complexities of neural process ; to one class he assigns consciousness, to the other unconsciousness. If he would be severely precise, he would never speak of sensation at all, but only of sen- sory reaction. But such precision would be pedantic and idle. He wants the connotations of the term sensa- tion, and therefore uses it. 79. The functional activity of a gland is stimulated by a neural process reflected from a centre ; by a similar ])rocess a muscle is called into action. No one supposes that the neural process is in the one case secretory, in the THE NERVOUS MECHANISM. 219 other motory: in both it is the same process in the nerve; and our investigation of it would be greatly hampered if we did not disengage it from all the suggestions hovering around the ideas of secretion and muscular action. In like manner we must disengage the neural process of a sensory reaction from all the suggestions hovering around the idea of Consciousness, when that term designates a complex of many reactions. In Problem III. we shall enter more particularly into the distinction between Sen- sibility and Consciousness; for the present it must suffice to say that great ambiguity exists in the current usage of these terms. Sometimes Consciousness stands as the equivalent of Sensibility ; sometimes as a particular mode of Sensibility known as Eeflection, Attention, and Thought. The former meaning is an extension of the term similar to that given to the word Eose, which origi- nally meaning Red came to be restricted to a particular red flower ; and after other flowers of the same kind were discovered which had yellow and white petals, instead of red, the term rose still adhered even to these. "Yellow Rose " is therefore as great a verbal solecism" as uncon- scious sensation. We have separated the redness from the rose, and can then say that the color is one thing, the flower another. By a similar process of abstraction we separate Consciousness from Sensation, and we can then say that there are sensations without consciousness. In consequence of this, psychologists often maintain that to liave a sensation and be conscious of it are two diflerent states. We are said to. hear a sound, and yet not to be conscious of hearing it. The sound excites a movement, but it does not excite our consciousness. Now although it is true that there are roses wliich are not red, it is not true that there are roses which have no color at all. Al- though it is true that there are sensations which are not of the particular mode of Sensibility whicli psychologists 220 THE niYSICAL BASIS OF MIND. specially designate as Consciousness, it is not true that there are sensations which are not modes of Sensibility. 80. And what is Sensibility which, on its sul)jective side, is Sentience ? In one sense it may be answered that we do not know. In another sense it is that which we know most clearly and positively : Sentience forms the substance of all knowledge. Being the ultimate of knowl- edge, every effort must be vain which attempts to explain it by reduction to simpler elements. The human mind, impatient of ultimates, is always striving to pierce beyond the fundamental mysteries ; and this impatience leads to the attempts so often made to explain Sensibility by re- ducing it to terms of Matter and Motion. But inasmuch as a clear analysis of Matter and Motion displays that our knowledge of these is simply a knowledge of modes of Feeling, the reduction of Sentience or Sensibility to Mat- ter and Motion is simply the reduction of Sensibility to some of its modes. This point gained, a clear conception of the advantages of introducing the ideas of Matter and Motion will result. It will then be the familiar and in- dispensable method of explaining the little known by the better known. The objective asjDect of things is com- monly represented in the visible and palpable; because what we can see we can also generally touch, and what we can touch we can taste and smell ; but we cannot touch an odor nor a sound; we cannot see them; we can only connect the odorous and sonorous objects with vis- ible or palpable conditions. Everywhere we find sensa- tions referred to visible or palpable causes ; and hence the desire to find this objective basis for every change in Sen- sibility. The sensation, or state of consciousness, is the ultimate fact ; we can only explain it by describing its objective conditions. 81. Thus much on the philosophical side. Eeturning to our physiological point, we miist say that a sensation THE NERVOUS MECHANISM. 221 is, objectively, the reaction of a sensory organ, or organ- ism ; subjectively, a change of feeling. Objectively it is a phenomenon of movement, but distinguishable from other phenomena by tlie speciality of its conditions. It is a vital phenomenon, not a purely mechanical phenom- enon. Although the molecular uiovement conforms, of course, to mechanical principles, and may be viewed ab- stractly as a purely mechanical result, yet, because it takes place under conditions never found in machines, it has characters which markedly separate it from the move- ments of machines. Among these differential characters may be cited that of selective adaptation,^' which is most conspicuous in volition. 82. In the early stages of animal evolution there is no differentiation into muscle and nerve. The whole organism is equally sensitive (or irritable) in every part. Muscles appear, and then they are the most sensitive * Bj'' selective adaptation is meant the varying combination of motor impulses to suit the varying requirements of the effect to be produced. Physical mechanisms are limited to the performance of definite actions ; sensitive mechanisms employ fluctuating combinations of elements in response to fluctuations of stimuli. The wheels, levers, springs, and valves of a machine cannot be diff"erently combined according to varying degrees of the motor-force, as the nerves and muscles of an organism are differently combined by varying sensations. An automaton may be con- structed to ])lay on the violin, but it will only play the air to which it is set; it cannot vary tlie performance, — cannot play a fivlse note, or throw in a crescendo here, a largo there, according to a caprice of feeling. We must admit that a violinist has his delicate and changing movements guided by sensations, auditory and muscular ; any interrujition in the .sensations would arrest the movements, which in truth incorporate them. And yet it is well known that the violinist m.iy perform while completely " unconscious." I do not simply refer to the fact that his thouglits and attention may be elsewhere; I refer to such facts as are recorded in Pathology. Thousseau, for example, had an epileptic patient who was occasionally .seized with attacks of complete unconsciousness while he was performing in the orchestra; yet, on reawakening to consciousness, he found tliat Ik; had continued to play, had kept proper time, and played the proper notes. 222 TllH PHYSICAL BASIS OF MIND. parts. Nerves appear, and the seat of Sensibility has been transferred to them ; not that the muscles have lost theirs, but their irritability is now represented by their dominant character of Contractility, and the nerves have taken on the special office of Sensibility. That is to say, while both muscle and nerve form integral elements of the sensitive reaction, the process itself is analytically conceived as a combination of two distinct properties, resident in two distinct tissues. 83. Carrying further this analytical artifice, I propose to distinguish the central organs as the seat of Sensibility, confining Neurility to the peripheral nerves. In physio- logical reality both systems, central and peripheral, are one; the separation is artificial. Strictly speaking, there- fore, Neurility — or nerve-action — is the general prop- erty of nerve-tissue, central and peripheral. But since Neurility may be manifested by nerves apart from cen- tres, whereas Sensibility demands the co-operation of both, and since we have often to consider the central process in itself, without attending to the process in the nerves, it is well to have two characteristic terms. I shall therefore always use the term Sensibility for the reactions of the nervous centres, — Sentience being its psychological equivalent; although the reader will un- derstand that in point of fact there is no break, nor transformation, as the wave of change passes from sen- sory nerve to centre, and from centre to motor nerve : there is one continuous process of change. But just as we analytically distinguish the sensory from the motor element of this indissoluble process, so we may distin- guish the ingoing and outgoing stages from the combining stage. Sensibility, then, represents the property of com- bining and grouping stimulations. 84. Fully aware of the misleading connotations of the term, and of the difficulty which will be felt in disen- THE NEKVOUS MECHANISM. 223 gaging it from these, especially in reference to Conscious- ness, I have long hesitated before adopting it. But the advantages greatly outweigh the disadvantages. Sensi- bility has long been adndtted to express the peculiar modes of reaction in plants and animals low down in the scale. No one hesitates to speak of a sensitive jolant, or a sensitive surface. The tentacles of a polype are said to be sensitive ; though probably no one thereby means that the polype has what psychologists mean by Consciousness. By employing the general- term Sensibility to designate the whole range of reactions peculiar to the nerve-centres, Avhen tliese special organs exist, it will be possible to in- terpret all the physiological and psychological phenomena observed in animals and men on one uniform method. The observed variations will then be referable to varieties in organisms. 85. Suppose, for illustration, an organism like the hu- man except that it is wholly deficient in Sight, Hearing, Taste, and Smell. It has no sense but Touch — or the general reaction under contact with external objects. It will move on being stimulated, and will combine its movements differently under different stimulations. It will feel, and logically combine its feelings. But its mass of feeling will be made of far simpler elements than ours ; its combinations fewer ; and the contents of its Consciousness so very different from ours that we are unable to conceive what it will be like ; we can only be sure that it will not be very like our own. This trun- cated organism will have its Sensibility ; and we must assign this property to its central nerve-tissue, as we as- sign our own. If now we descend lower, and suppose an organism with no centres whatever, but which neverthe- less displays evidence of Sensibility — feelings and com- binations of movements — we must then conclude that tlie property specialized in a particular tissue of the 224 THE PHYSICAL BASIS OF MIND. highly difTerentiated organism is here diffused through- out. It is obvious that the sensations or feelings of these supposed organisms will have a common character with the feelings of mor^ highly differentiated organisms, al- though the modes of manifestation are so various. If we recognize a common character in muscular movements so various as the rhythmic pulsation of the heart, the larger rhythm of inspiration and expiration, the restless movements of the eye and tongue, the complexities of manipulation, the consensus of movements in flying, swimming, walking, speaking, singing, etc., so may we recognize a common character in all the varieties of sen- sation. The special character of a movement depends on the moving organ. The special character of a sen- sation depends on the sensory organ. Contractility is the abstract term which expresses all possible varieties of contraction. Sensibility — or Sentience — is the ab- stract term which expresses all possible varieties of sen- sation. 86. The view here propounded may find a more ready acceptance when its application to all physiological ques- tions has been tested, and it is seen to give coherence to many scattered and hitherto irreconcilable facts. ]\Iean- while let a glance be taken at the inconsistencies of the current doctrine. That doctrine declares one half of the gray substance of the spinal cord to be capable only of receiving a sensitive stimulation, the other half capable only of originating a motor stimulation. AVe might with equal projDriety declare that one half of a muscle is ca- pable only of receiving a contractile stimulation, and the other half of contracting. The ingoing nerve, passing from the surface to the posterior part of the spinal cord, excites the activity of the gray substance into which it penetrates ; with the anterior part of this gray substance THE NERVOUS MECHANISM. 225 an outgoing nerve is connected, and through it the exci- tation is propagated to a muscle : contraction results. Such are the facts. In our analysis we separate the sen- sory from the motor aspect, and we then imagine that this ideal distinction represents a real separation. We suppose a phenomenon of Sensibility independent of a phenomenon of Contractility — suppose the one to be " transformed " into the other — and we then marvel " how during this passage the excitation changes its nature." * 87. Before exerting ingenuity in explaining a fact, it is always well to make sure that the fact itself is cor- rectly stated. Docs the neural excitation change its nature in passing from the posterior to the anterior gray substance ? I can see no evidence of it. Indeed the statement seems to confound a neural process with a muscular process. The neural process is one continuous excitation along the whole line of ingoing nerve, centre, and outfToincj nerve, which nowhere ceases or changes into another process, until the excitation of the muscle introduces a new factor. So long as the excitation keeps within the nerve-tissue, it is one and the same process of change ; its issue in a contraction, a secretion, or a change in the conditions of consciousness, depends on the organs it stimulates. 88. I have already called attention to the artificial nature of all our distinctions, and the necessity of such artifices. They are products of that ' ' Secondary power By which we multiply distinctions, then Deem that our puny boundaries are tilings That we perceive, and not that we have niade." + The distinction of Central and Peripheral systems is not * Claude Bernard, Syddme Nervcux, 1858, I. 349. t WonnswoKTiT, The Prelude. 10* O 226 THE niYSICAL BASIS OF MIND. simply anatomical, it has a physiological justification in this, that the Central System is the organ of connection. Any one part of it directly excited by an ingoing nerve projiagates that excitation throughout the whole central mass, and thus affects every part of the organism. There- fore we place Sensibility in it. But this general Property subserves various Functions, according as the Central System is variously related to different organs. This fact has given rise to the idea that different portions of the cerebro-spinal axis have different properties — which is a serious error. What is certain is that the Cerebrum must have a different function from that of the Thalami, and the Cerebellum one different from the Medulla Oblongata ; while that of the Medulla Spinalis is different from all. Precisely on the same grounds that a muscle-nerve has a different office from a skin-ner\^e, or the pneumogastric from the acoustic. But all nerves have one Neurility in common ; all centres have one Sensibility in common. THE NERVOUS MECHANISM. 227 CHAPTEE V. ACTION WITHOUT NERVE-CENTRES. 89. It has long been one of the unquestioned postu- lates of Physiology that no nerve-action can take place without the intervention of a centre ; and as a corollary, that all movement has its impulse — reflex or volitional — from a centre.* The postulate rests on the assumption that nerves derive their " force " from their centre. This assumption we have seen to be erroneous. Yet, in con- sequence of its acceptance, experimenters have failed to notice the many examples of nerve-action independent of centres. Indeed, except Schiff, Goltz, and Engelmann, I can name no one who has ventured to suggest that movements may be excited through nerves without the co-oi:)eration of centres ; f nor have even they explicitly formidated the conclusion to which their observations point. It is true that the majority of muscular movements are deternnned by a reflex from centres ; and that any break * "On pent dire que tonjours un plicnomene de mouveriKnit leeoniiait l)our point de depart une impression sensitive." — Claude Behnaud, I. 267. t Since this was written Prof. Michael Fo.ster and Mr. Dew Smith liave published their very important researclies on the motions of the lieart, vvhieh e.stablish beyond a doubt that, in the molluscs at least, there is no co-operation of either centre or nerve. — Proceedings of the Royal Society, 18th March, 1875. (See also Studies from the Physiologi- cal Laboratory nf Cambridge, Part II., 1876.) Mr. Foster knows that I had independently, and from a totally diderent line of research, arrived at the same conclusion respecting the heart's movement. 228 THE niYSICAL BASIS OF MIND. in the triple process of the ingoing nerve, centre, and outgoing nerve, prevents such movements. It is true that the more conspicuous and liarmoniously co-ordinated phenomena belong to this class. But it is also demon- strable that many nerve-actions may, and some do, take place by direct stimulation of the nerve, or direct stimu- lation of the muscle, without the intervention of a centre, without even the intervention of a ganglion. This must obviously be the case in animals which have no centres ; and even in some which have well-developed nervous centres, there is every reason to believe that these cen- tres often act rather in the way of co-ordinating than of directly stimulating actions. 90. I was first led to doubt the reigning doctrine by a surprising observation (frequently repeated) after I had removed the whole nervous centres from a garden snail {Helix i^omatia). The muscular mass called "the foot" was thrown into slow but energetic contraction whenever the skin was pricked with the point of a scalpel, or touched with acid ; nay, even when a glass rod dipped in the acid was brought close to, without absolutely touching, the skin, the foot curled up, and then slowly relaxed. The same effect was produced on the "mantle" — where there was of course no centre. But direct irritation of the mus- cles under the skin produced no such contraction ; only through the skin could the stimulation take effect. In one case I observed this strange phenomenon five hours after removal of the centres. It was a great puzzle. At first I concluded that there must be minute ganglia in the skin, serving as reflex-centres. I searched for them in vain ; and although a longer search on better methods might 'possihhj have detected ganglionic cells, I soon re- lin([uished the search, because I had other grounds for believing tliat e\'en the presence of abundant ganglia would not suffice, until some better proof were afforded that such ecansclia were reflex-centres. THE NERVOUS MECHANISM. 229 91/ That direct stimulation of the nerve suffices to move the muscles, is familiar to all experimenters. There is no centre, or ganglion, in the amputated leg of the frog, which nevertheless contracts whenever the sciatic nerve is stimulated. And after the nerve has been exhausted, and refuses to respond to any stimulus, the muscle itself may be directly stimulated. Inasmuch as the movement depends on the contractility of the muscles, a stimulation through centre, through motor-nerve, or through muscle, will be followed by contraction. Let us take a clear case of reflex action. The j)upil of the eye contracts when a beam of light falls on it, and dilates when the beam is shut off. The path of the neural process is normally this : the light stimulates the optic nerve, which in turn stimu- lates the corpora quadrigemina ; (here the nerves which move the eye are experimentally proved to be stimulated;) and it is through these that the pupil is caused to con- tract. If the optic nerve be divided, no such reflex takes place — proving that the contraction does not, at least normally, come from the ciliary ganglion. But now it is matter of observation that the pupil will contract and dilate under the stimuli of light and dark- ness, when there is no such reflex pathway open. Re- moval of the eye from the body obliterates this path, cuts the eye off from all connection with the centre. Brown Sequard removed both eyes from a frog, placed one in a dark box, and left the other exposed to the light : the })upil of the former was found dilated, that of the latter contracted. On reversing the experiment, and placing the eye with contracted pupil in the dark box, he found it there dilate, while the dilated pupil exposed to the light contracted.* In frogs with very irritable tissues, I have * Comptes Rcndus de la SociiU de Biologic, 1847, I. 40. In 1856 he showed that not only were the muscles of the iris directly stimulated by light (and this not by its calorific or chemical rays), but that sixteen days 2o0 THE niYSICAL BASIS OF MIND. found not only llie jjiipil contracting, ;ii'ter the whole cranial cavity has been emptied, but even the eyelid close, on irritating the conjunctiva* — yet this is one of the typical retlex actions ! I am disposed to think that even the action of swallowing may be faintly excited by stimulation of the pharynx of a brainless frog ; but I have not observations sufiiciently precise to enable me to speak confidently. Goltz has, however, shown that after removal of brain and spinal cord and heart, there is spon- taneous and active movement in wsophagus and stom- ach.i* This will no doubt be referred to the agency of the ganglionic plexus ; but similar movements have been observed by Engelmann in the ureter, and in isolated after removal of tlie eye from the orbit, this effect was observable in the eel. Yet a very few days after extirpation of the eye the nerves are dis- integrated. — Proceedings of tlic Loyal Society, 1856, p. 234. DoNDEES has the following observations : " The movements of the iris are of two kinds — reflex and voluntary. Reflex action is exhibited as constriction of the pnpil in con.sequence of the stimulus of incident light upon the retina. Fontana has shown that the light falling upon the iris produces no remarkable contraction. We have confirmed this result by causing the image of a small distant light to fall, by means of a convex lens, upon the iiis, whereby, during slight fierception of light, a doubtful contraction occurred, which gave way to a strong contraction so soon as the light entering the pupil excited a vivid perception. Nevertheless, the experiments of Harless and Budge have shown that even after death, so long as irritability remains, the pupil still contracts upon the continued action of light. Of the con-ectness of this we have satisfied ourselves. In a dog killed by loss of blood the one ej'e was closed, the other opened and turned to the light : after the lap.se of an hour, the pupil of the opened eye was perceptibly smaller than that of the closed eye. The lat- ter now remained also exposed to the light, and on the following day the diameter of both eyes was equal. The upper jaw, alone with the eyes, was taken out of some frogs ; one eye was exposed to the light, while the other was covered with a closely folded piece of black paper : after the lapse of half an hour the pupil turned to the light was narrow, the other wide. But the latter also contracted almost immediately after the removal of the pajx-r." — Dc^xdrhs, On the Ano7nalics of j4 ccommodation end Refraction of the Eye. Trans, of the New Sydenham Society, p. 572. * The experiment often fails, but I have seen it several times succeed. t Pfliigcr's Archil; 1872, p. 618. THE NERVOUS MECHANISM. 231 fragments of the ureter in which not a ganglionic cell was present.* 92. That nerves are stimulated by internal changes has long been recognized with reference to "subjective sensations." The divided nerve, in that portion which remains connected with the centre, will at times cause great pain. Obscure organic conditions, changes of tem- perature, states of the blood, excite the nerves, and the patient feels as if the surface of the amputated limb were irritated. It is all very well to call these "subjective sensations"; that does not alter the fact of the nerve being called into activity by other than the normal stim- uli from the surface ; in like manner muscular move- ments (which are not to be explained as "subjective movements ") will be excited by organic stimuli when motor-nerves are separated from their centres. In each case it has sufficed that the nerve should be excited ; and when excited, no matter by what means, the effect is always similar. 93. Here are a few facts. Stimulation of the nerves which send filaments to the chromatophores of the skin in reptiles causes the skin to become paler, and even colorless : the color-specks disappear under this contrac- tile stimulus. This being known, Goltz deprived a frog of brain, spinal cord, and heart, thus eliminating all possi- Ide influence from them, slit up the skin of the back, and displayed the nerves which pass from each side of the spine to the skin ; these nerves he then divided on the right side, and observed the skin on this side slowly become paler and paler, till finally it was as yellow as wax ; the left side, having its nerves intact, retained its color. Two conclusions seemed to him warranted by this experiment : First, that even in the dead frog the nerves separated from their centre were still active ; secondly, * See his Eesearclies in Pflilr/cr's Archiv, Bdc. II. and IV. , 232 THE PHYSICAL basis of mind. that the irritation of the nerves resulting from tlieir sec- tion Mas the cause of the color-specks disappearing. This second conclusion was strengthened wlien he found that the irritation was increased wlien he cut the nerves bit by bit. It is not at present, I believe, clearly made out that the color-specks of the Cephalopoda are in direct connection with nerves ; but it is tolerably certain tliat they are in some way under the influence of nervous stimulation, directly or indirectly. D'Orbigny, indeed, goes so far as to say they are dependent on the will of the animal.* This seems very lax language ; but restricting ourselves to the fact of nervous influence, the experiments of Goltz receive further illustration in an observation I have else- where recorded.-j- I found that a strip of skin taken from the dead body of a calamary {Lolirjo) showed the color-specks expanding and contracting with vigor. 94. The heart is M'ell known to beat after death, if death be not the result of a gradual decay. Sometimes, indeed, its muscular irritability is so active that the heart will beat for hours. E. Rousseau observed it beating in a woman twenty-seven hours after she had been guillo- tined. \ Xot only will it beat after death, but in many animals even after removal from the body : the heart of a young puppy, or kitten, will beat for three or four hours after its removal ; that of a full-grown dog, or cat, not one hour ; whereas the beating of that of a tortoise, or a frog, will, under proper precautions, be preserved for days — and even after it has stopped, it may be stimulated to fresh pulsations. Physiologists explain this spontaneous movement of the heart as due to the ganglia in its substance. This * D'Orbigxt, Dr^ Mollusques Vivants ct fossils, p. 113. t Seaside Studies, 2d ed., p. 101. :J: Cited by Buowx SIvQUArd, Journal de la Fhi/siologie, 1858, p. 359. THE NERVOUS MECHANISM. 233 explanation, which is founded on what I cannot but re- gard as a purely imaginary view of the functions of gan- glionic cells, must stand or fall with that hypothesis. A long and arduous investigation has led me to doubt whether in any case the heart's movements are primarily due to its ganglia ; at all events, the same spontaneous movements are observed in the hearts of molluscs and crustaceans, which are without even a trace of ganglia ; and in the hearts of mammalian embryos long before ganglia or nerve-fibres make their appearance. Not less certain is it that movements of contraction and dilatation are produced in the blood-vessels independently of all central influence. This has been decisively proved by the Italian physiologist, Mosso, when experimenting on an organ isolated from the organism ; and although the ves- sels have their nerve cells and fibres, he justly doubts whether it is to these that the stimulation is due, because the phenomena are observed after the nervous vitality has disappeared. Goltz severed all the tissues in the leg of a rabbit, so that the only connection of the leg with the rest of the body was through the crural vein and artery, which kept up the circulation ; yet although the nerves of the skin were thus separated from their centre, so that no sensation could be produced by stimulating the skin of the leg, consequently no reflex from the centre on the vessels, Goltz found that a marked reddening of the skin from congestion of the capillaries followed the application of mustard to the skin. Physiologists who believe that the constriction and dilatation of blood-vessels are due to the action of the ganglionic cells distributed over the walls of the vessels will explain Goltz's observation as a case of reflex action ; but those who agree with me that such an hypothesis respecting the part played by the cells is untenable, will class the observation among other cases of direct stimulation. 234 THE PHYSICAL BASIS OF MIND. 95. But piissiug from these perhaps questionable cases, let us glance at other cases. The mobile iris of the bird displays movements after the nerves have been divided. Even the voluntary striped muscles are not altogether motionless. Schiff divided the hypoglossus on one side, and Ibund, of course, the tongue paralyzed on that side ; but lie also found that on the third day after the opera- tion some of the muscles of that side were quivering : the agitation spread to others, till by the end of the fourth (Jay all the fibres were rhythmically contracting. From this time onwards, the contractions were incessant ; though they were never able to move the tongue, be- cause the fibres did not contract simultaneously. Schiff also observed that the hairs over the eyes and the " whiskers " of cats, rabbits, and guinea pigs were for months after section of their nerves in incessant rhyth- mical vibration. This was observed when the animals were asleep as when awake. Valentin records the spon- taneous movements in the diaphragm of animals just killed ; and this even after section of the phrenic nerve. The same movements may be seen in the operculum of fishes. Henle observed the spontaneous contractions of the intercostal muscles ; which Schiff confirms, adding that the movements observed by him in cats and birds were not simply contractions of some fibres, but of all the muscles, so that three or four excised ribs rhythmically contracted and expanded. I have performed a great many experiments with a view of determining this question, but the phenomena were so variable that I refrain from adducing any,* and * Dr. NoRRis has recorded some striking observations in liis paper on "Muscular Irritability " in the Journal of Anatonvi, 1867, No. II. p. 217. Here is the only one I can find room for : " On taking up the dead frog and touching the limb (which during life had been paralyzed by sec- tion of its nerve) with my finger, it was suddenly shot out as if alive. I placed the body down, and one or two apimrcntly spontaneous movements S9 THE NERVOUS MECHANISM. 235 merely state the general result as one in harmony with the foregoing examples. The great variability of the phe- nomena depends upon the variable conditions of muscular irritability and anatomical relations. When the heart of one woman is found beating twenty-seven hours after death, while in most men and women it ceases after a few minutes, we must be prepared to find different, and even contradictory phenomena under varying unkno\^» ^J conditions. There is, however, a general agreement amoi§ Hj experimenters that muscular irritability increases aft^ W separation fi^om nerve-centres, and then quickly decreas^ ^ again. M p^ 96. Although the stimulation of muscles usually comS S||{ throvgh a nerve-centre, yet since the muscles do not d™ ► rive their Contractility from nerve-centres any stimulfV ET tion will suffice. Now since we have abundant procfi c^ that sensory nerves are stimulated by certain organfe ^ changes, by poisons in the blood, excess of carbonic acid, q etc., we are justified in concluding that motor nerves Jp* will be stimulated in like maimer, and thus muscular movement be produced occasionally without the inter- vention of a centre. Pressure on a motor nerve, or the irritation which results from inflammation, will determine contraction, or secretion directly. Eecently, Erb and Wcstphal have disclosed the fact that the leg will be suddenly jerked out if the patella be gently tapped ; and they prove this not to be a reflex action, because it fol- lows with the same certainty after the skin has been made insensible.* There are doubtless many other phenomena which, though commonly assigned to reflex stimulation, are of small extent afterwards occurred. On touching tlie skin gently with the point of a needle, by the .slight pressure upon the muscle beneath, movements of the lirnh were, also induced, hut this high degree of exalta- tion very rapidly disa[ipeared." * See their papers in the Archie fiir PsycJdatrk, 1875, Bd. V. Heft 3. 236 THE PHYSICAL BASIS OF MIND. really due to direct stimulation. Eesearcli might profit- ably be turned towards the elucidation of this point. Since there is demonstrable evidence that a nerve when no longer in connection with its centre, or with ganglionic cells, may be excited by electricity, pressure, thermal and chemical stimuli, we must conclude that even when it is in connection with its centre, any local irritation from pressure, changes in the circulation, etc., will also excite it. But as such local excitations will have only local and isolated effects, they will rarely be conspicuous. THE NEEVOUS MECHANISM. 237 CHAPTER VI. WHAT IS TAUGHT BY EMBRYOLOGY? 97. Subject to the qualification expressed in the last chapter, stimulation of muscles and glands involves a neural process in ingoing nerve, centre, and outgoing nerve. These are the triple elements of the " nervous arc." If muscles were directly exposed to external in- lluences, they would be stimulated without the interven- tion of a centre; but as a matter of fact they never are thus exposed, being always protected by the skin. Did the skin-nerves pass directly to the muscles underneath, they would move those muscles, without the intervention of a centre ; but as a matter of fact the skin-nerves pass directly to a centre, so that it is only through a centre that they can act upon the muscles. Were muscles and glands directly connected with sensitive surfaces, their activity would indeed be awakened by direct stimulation; l)ut unless the muscles were so connected the one with the other, by anastomosis of fibres or continuity of tissue, that the movement of one was the movement of all, there would need to be some other channel by which their sep- arate energies should be combined and co-ordinated. In the higher organisms anastomosis of muscles is rare, and the combination is effected by means of the nerves. 98. Although analysis distinguishes the two elements of the neuro-muscular system, assigning separate prop- erties to the separate tissues, an interpretation of the phe- nomena demands a synthesis, so that a movement is to be 238 THE niYSICAL BASIS OF MIND. conceived as always involving Sensibility, and a sensation as always involving Motility.* In like manner, although analysis distinguishes the various organs of the body, assigning separate functions to each, our interpretation demands their synthesis into an organism ; and we have thus to explain how the vjhole has different j^^o^^s, and how these difierent parts are brought into unity. Embry- ology helps us to complete the fragmentary indications of Anatomy and Physiology. 99. Take a newly laid egg, weigh it carefully, then hatch it, and when the chick emerges, weigh both chick and shell : you will find that there has been no increase of weight. The semifluid contents have become trans- formed into bones, muscles, nerves, tendons, feathers, beak, and claws, all without increase of substance. There has been differentiation of structure, nothing else. Oxygen has passed into it from without ; carbonic acid has passed out of it. The molecular agitation of heat has been re- quired for the rearrangements of the substance. With- out oxygen there would have been no development. Without heat there would have been none. Had the shell been varnished, so as to prevent the due exchange of oxygen and carbonic acid, no chick would have been evolved. Had only one part of the shell been varnished, the embryo would have been deformed. 99 «. The patient labors of many observers (how pa- tient only those can conceive who have made such observations !) have detected something of this wondrous history, and enabled the mind to picture some of the in- cessant separations and reunions, chemical and morpho- logical. Each stage of evolution presents itself as the consequence of a preceding stage, at once an emergence and a continuance ; so that no transposition of stages * This latter statement will be justified when I come to expound the Triple Process, which I have named the Psychological Spedrum. THE NERVOUS MECHANISM. 239 is possible ; each has its appointed place in the series (Problem I. § 107). For in truth each stage is a ^9?'o- cess — the sum of a variety of co-operant conditions. We, lookincr forward, can foresee in each what it will become, as we foresee the man in the lineaments of the infant; but in this prevision we always presuppose that the regular course of development will proceed unchecked through the regular succession of special conditions : the infant becomes a man only when this succession is unin- terrupted. Obvious as this seems, it is often disregarded ; and the old metaphysical conception of potential powers obscures the real significance of Epigenesis. The poten- tiality of the cells of the germinal membrane is simply their capability of reaching successive stages of develop- ment under a definite series of co-operant conditions. We foresee the result, and personify our prevision. But that result wdll not take place unless all the precise changes that are needful serially precede it. A slight pressure in one direction, insufficient to alter the chemi- cal composition of the tissue, may so alter its structure as to disturb the regular succession of forms necessary to the perfect evolution. 100. The egg is at first a microscopic cell, the nucleus of which divides and subdivides as it gro\\s. The egg becomes a hollow sphere, the boundary wall of which is a single layer of cells, all so similar that to any means of appreciation we now possess they are indistinguishable. They are all the progeny of the original nucleus and yolk, or cell contents. Very soon, however, they begin to show distinguishable differences, not perhaps in Jdnd, but in (hrjrce. The wall of this hollow spliore is rapidly converted into tlie germinal membrane, out of which the embryo is i'ormed. Kowalewsky (confirmed l)y ]>alfour) has pointed out how in the Amphioxus the liollow si)here first assumes an oval shape, and then, by an indentation 240 TIIK PHYSICAL BASIS OF MIND. (if the under side, with corresponding curvature of the upper side, presents somewhat the shape of a bowl. The curvature increases, and the curved ends approaching each other, the original cavity is reduced to a thin line separating the upper from the under surface. The cavity of the body is formed by the curving downwards of this double layer of the germinal membrane. 101. This is not precisely the course observable in other vertebrates ; but in all, the germinal membrane, which lies like a watch-glass on the surface of the yolk, is recognizable as two distinct layers of very similar cells. What do these represent ? They are the starting-points of the two great systems : Instrumental and Alimental. The one yields the dermal surface ; the other the mucous membrane. Each follows an independent though analo- gous career. The yolk furnishes nutrient material to the germinal membrane, and so passes more or less directly into the tissues; but unlike the germinal membrane, it is not itself to any great extent, the seat of generation by segmentation. There are two yolks : the yellow and the white (which must not be confounded with what is called the white of egg) ; and their disposition may be seen in the diagram (Fig. 14) copied from Foster and Bal- four's work. The importance of the white yolk is that it passes insensibly into a distinct layer of the germinal membrane, between the two primary layers.* Each of the three layers of the germinal membrane has its specific character assigned to it by embryologists, who, however, are not all in agreement. Some authorities regard the topmost layer as the origin of the nervous system, the epidermis, with hair, feathers, nails, horns, the cornea and lens of the eye, etc. To the middle layer are assigned the * Foster and Balfour, Elements of Embryoloriy, 1874, Part I. p. 52. His, Untersuchungen uber die erste Aiilage dcs Wirbelthierleibes, 1868, p. 197. THE NERVOUS MECHANISM. 241 muscular and osseous systems, the sexual organs, etc. To the innermost layer, the alimentary canal, with liver, pan- creas, gastric and enteric glands. Other authorities are in favor of two primary layers : one for the nervous. e^.i Fig. 14. — Diagrammatic section of an unincubated hen's egg. bl, blastoderm ; w y, white yolk ; y y, yellow yolk ; v t, vitelline membrane ; x and w, layers of albumen ; ch I, chalaza ; a ch, air-chamber ; i s m, internal layer of shell membrane ; s m, ex- ternal layer ; s, shell. muscular, osseous, and dermal systems ; the other for the viscera and unstviped muscles. Between these two layers, a third gradually forms, w^hich is specially characterized as the vascular. 102. INfessrs. Foster and Balfour, avoiding the con- troverted designations of serous, vascular, and mucous layers, or of sensorial, motor germinative, and glandular layers, employ designations whicli are independent of theoretic interpretation, and simply describe the position of the layers, namely, cpiUast for the upper, mcsohlast for the middle, and hypoblast for the under layer. From the VOL. iir. 11 p 242 THE PHYSICAL BASIS OF MIND. epiblust they derive the epidermis and central nervous system (or would even limit the latter to the central gray mutter), together with some parts of the sense-organs. From the mesoblast, the muscles, nerves (and probably white matter of the centres), bones, connective tissue, and blood-vessels. From the hypoblast, the epithelial lining of tlie alimentary canal, trachea, bronchial tubes, as well as the liver, pancreas, etc.* Kollikcr's suggestion is much to the same effect, namely, that the three layers may be viewed as two epithelial layers, between which subsequently arises a third, the origin of nerves, muscles, bones, connective tissue, and vessels.^ 103. The way in which the history may be epitomized is briefly this : There are two germinal membranes, re- spectively representing the Instrumental and Alimental Systems. Each membrane differentiates, by different ap- propriations of the yolk substance, into three primary layers, cjnthdial, neural, and muscular. In the e])iblast, or upper membrane, these layers represent : 1°, the future epidermis with its derivatives — hair, feathers, nails, skin glands, and chromatophores ; 2°, the future nervous tis- sue ; o°, the future muscular tissue. J (Bone, dermis, connective tissue, and blood-corpuscles are subsequent formations.) Tlie hypoblast, or under membrane, in an inverted order presents a similar arrangement : 1°, the unstriped * They state that the cells of the epiblast are the results of direct .segmentation, whereas the cells of the other layers are formed at a sub- sequent period, and are only indirectly results of segmentation. But if the observations of Kowalewsky are exact, this is not the case with the hypoblast of the Amphioxus, which is from the first identical with the epiblast. t KoLLiKER, Entvxicklwngsgeschichte des Menschen und dcr hiiheren Thicrc, 1861, p. 71. t [According to Balfour's recent observations, a large part of the muscular tissue is derived from the layer of the mesoblast belonging to the hypoblast.] THE NERVOUS MECHANISM. 243 muscular tissue of viscera and vessels ; 2°, the nervous tissue of the sympathetic system; 3°, the epithelial lin- ing of the alimentary canal with its glands. Fundamentally alike as these two membranes are, they have specific differences; but in both we may represent to ourselves the cmhryological unit constituted by an epi- thelial cell, a nerve-cell, and a muscle-cell. All the other cells and tissues are adjuncts, necessary, indeed, to the working of the vital mechanism, but subordinated to the higher organites. 104. This conception may be compared with that of ^ His in the division of Archiblast and Parablast assigned by him to the germ and accessory germ.* We can im- agine, he says, the whole of the connective substances removed from the organism, and thus leave behind a scaffolding in which brain and spinal cord would be the axis, surrounded by muscles, glands, and epithelium, and nerves as connecting threads. All these parts stand in more or less direct relation to the nervous system. All are continuous. By a similar abstraction we can imagine this organic system removed, and leave behind the connected scaffolding which is formed from the accessory germ ; but this latter has only mechanical significance ; the truly vital functions belong to the other system. 105. The researches of modern histologists have all converged towards the conclusion that the organs of Sense are modifications of the surface, with epithelial cells which on the one side are connected Avith termi- nal hairs, or other elements adapted to the reception of stimuli, and are connected on the other side through nerve-fibres with the perceptive centres. It has been shown that nerve-filjres often terminate in (or among) epithelial cells — sensory fibres at the surface, and motor- * His, Untersuchungcn, pp. 39, 40. 244 THE PHYSICAL BASIS OF MIND. fibres in the glands.* Whether the fibres actually pene- trate tlie substance of the cell, or not, is still disputed. Enough for our present purpose to understand that there is a i^hysiolofjical connection between the two, and above all tliat sensory nerves are normally stimulated through some epithelial structure or other. 106. And this becomes clear when we go back to the earliest indications of development. Look at Fig. 15, rep- resenting a transverse section of the germinal membranes in a chick after eishteen hours' incubation. Here the Fig. 15. — Transverse section of a Blastoderm Incubated for eighteen hours. The sec- tion passes through the medullary groove, m e. A, epiblast. B, mesoblast. C, hy- poblast, mf, medullary fold ; c h, notochord. three layers, A, B, and C, have the aspect of simple cells very slightly differing among each other. Yet since each layer has ultimately a progeny which is characteristically distinguishable, we may speak of each not as what it now is, but what it will become. Although the most expert * Quite recently Owsjanxikow has pointed out the termination of fibres in the phosphorescent cells of the Lampyris Noctiluca. See his paper in the Memoires de I'Jcad. de St. Petersbourg, 1868, XI. 17. These phosphorescent cells are said to be ganglion-cells by Panceri, Intorao delta, luce che emana. dalle celleule nervosc (Rendiconto della Accad. delle Scienze, April, 1872); and by Eimer, Archiv fur mikros. A'lmtomie, 1872, p. 653. Kolliker also calls the phosphorescent organ a nervous organ. This is not to be intei-preted as meaning that neu- rility is phosphorescence, but simply that in some nerve-cells there is jjhosphorescent matter, which is called into activity by stimidus of the THE NERVOUS MECHANISM. 245 embryologist is often unable to distinguish the embryo of a reptile from that of a bird or of a mammal, at certain stages of evolution, so closely does the one resemble tlie other, yet inasmuch as the embryo of a reptile does not, cannot become a bird, nor that of a bird a mammal, he is justified in looking forward to what each will become, and in calling each embryo by its future name. On the same ground, although we cannot point to any such distinction between the layers of the blastoderm as I have indicated in the separation of Instrumental and Alimental Systems, nor specify any characters by which the cells can be rec- ognized as epithelial, neural, and muscular, yet a forward glance prefigures these divisions. We know that the first result of the segmentation of the yolk is the formation of cells all alike, which in turn grow and subdivide into other cells. We know^ that these cells become variously modified both in composition and structure, and that by such differentiations the simple organism becomes a com- plex of organs. 107. But here it is needful to recall a consideration sometimes disregarded, especially by those who speak of Differentiation as if it were some magical Formative Prin- ciple, quite independent of the state of the organized substance which is formed. There is a luminous concep- tion — first announced by Goethe, and subsequently de- veloped by Milne Edwards — which regards the organism as increasing in power and complexity by a physiological " division of labor," very similar to that division of em- ployments whicli characterizes the developed social organ- ism. But tlie meta])hor has sometimes been misleading; it has been interpreted as indicating that Function cn^ates Organ (see Problem I. § 88), and as if Difrercntiation itself were something more than the expression ol' the changes resulting from the introduction of different ele- ments. In the Social Organism a "division of labor" 2-46 THE PHYSICAL basis of mind. presupposes that laborers with their labor-materials are already existing ; the change is one of rearrangement : instead of each laborer employing his skill in doing many kinds of work, lie restricts it to one kind, which he is then able to do with less loss of time and power. Thus is social power multiplied without increase of population, and the social organism becomes more complex by the differentiation of its organs. It is not precisely thus with the Animal Organism during its evolution. Indeed to suppose that the differentiation of the germinal membrane into special tissues and organs takes place by any such division of employments, is to fall into the ancient error of assuming the organism to exist preformed in the ovum. The unequivocal teaching of Epigenesis is that each part is produced out of the elements furnished by previous parts ; and for every differentiation there must be a differ- ence in composition, structure, or texture — the first con- dition being more important than the second, the second more important than the third. The word protoplasm has almost as wide a generality as the word animal, and is often used in forgetfulness of its specific values : the pro- toplasm of a nerve-cell is not the same as that of a blood- cell, a muscle-cell, or a connective-tissue cell, any more than a bee is a butterfly, or a prawn a lobster. No sooner has the specific character been acquired, no sooner is one organite formed by differentiation, than there is an abso- lute barrier against any transformation of it into any other kind of organite. The nerve-cell, muscle-cell, and epi- thelial cell have a common starting-point, and a commu- nity of substance ; but the one can no more be trans- formed into the other than a mollusc can be transformed into a crustacean. In the homogeneous cellular mass which subsequently becomes the "vertebral plates," a group of cells is very early differentiated : this is the rudimentary spinal ganglion, which becomes enveloped in THE NERVOUS MECHANISM. 247 a membrane, and then pursues a widely different course from that of the other ceils surrounding it, so that " the same cell which was formerly an element of the vertebral plate now becomes a nerve-cell, while its neighbors be- come cartilage-cells." * Indeed all the hypotheses of trans- formation of tissues by means of Differentiation are as unscientific as the hypotheses of the transformation of animals. In the organism, as in the Cosmos, typical forms once attained are retained. There probably was a time in the history of the animal series when masses of proto- plasm by appropriating different materials from the sur- rounding medium were differentiated into organisms more complex and more powerful than any which existed be- fore. But it is obvious that from a common starting-point there could have been no variations in development with- out the introduction of new elements of composition: there might have been many modifications of structure, but unless these facilitated modifications of composition, there could never have resulted the striking differences observed in animal organisms.-f- 108. To return from this digression, we may liken the three primary layers of the germinal membranes to the scattered and slightly different masses of protoplasm out of which the animal kingdom was developed. In this early stage there are no individualized organites — no nerve-cells or muscle-cells. Tliey are cells ready to re- ceive modifications both of composition and structure, appropriating slightly different elements from the yolk, and according to such appropriation acquiring different * Bidder unci Kupffer, Tcxtur dcs RiiclcrMmarks, 1857, p. 108. [What is said in the text ha.s been rendered doubtful by the recent researches of Mr. F. Balfour, On tJie Development of the Spinal Nerves in Elasmo- hranch Fishes (Philos. Trans., Vol. CLXVI. Part I.), whicli show that in these fishes the ganglion has its origin in the spinal cord.] t Comp. PiiORLKM I. § 130, witli tlie remarks of Cii.\rlks Konix, Anatomic et Physiologic Cellulaircs, 1873, p. 20. 248 t;ii: thysical basis of mind. properties. And lliis is necessarily so, since tlio different cells have not exactly the same relation to the yolk, nor are they in exactly the same relation to the incident forces which determine the molecular changes. The uppermost layer (epiblast) under such variations develops into epithe- lium and central nerve-tissue ; the epithelial cell cannot develop into a nerve-cell, the two organites are markedly unlike, yet both spring from a common root. Another modification results in the development of muscle-cells from the inner layer. 109. Hence we can understand how the surface is sen- sitive even in organisms that are without nerve-tissue ; and also how even in the highest organisms there is an intimate blending of epithelial with neural tissues. The same indication explains the existence of neuro-muscular cells in the Hydra, recorded by Kleinenberg, and of neuro- muscular fibres in the Bcroe, by Eimer.* In the simpler organisms the surface is at once protective, sensitive, and absorbent. It shuts off the animal from the external medium, and thus individualizes it ; at the same time it connects this individual with the medium ; for it is the channel through which the medium acts, both as food and stimulus. The first morphological change is one whereby a part of the surface is bent inwards, and forms the lining * Kleinexbeeg, Hydra; Fine Anatomisch-Entwickclungs-Untcrsu- cJmng, 1872, p. 11. Eimer, Zoologische Studien auf Capri, 1873, p. 66. A similar formation is described by Dr. Allman in the Myriothda ; he says, however, that he has never been able to trace a direct continuity of the caudal processes of the cells with muscular fibrils. He believes that the processes make their way to the muscular layer through undifferen- tiated protoplasm. — P/i27os. Transactions, Vol. CLXV. Part II. p. 554. An intermediate stage between this neuro-muscular tissue and the two differentiated tissues seems presented in the Nematoid worms which have muscles that send off processes into which the nerves pass. Gegekbauu declares his inability to decide whether these processes are muscles or nerves. BUtsciili thinks the nerve-process blends with the muscle-pro- cess. — Archiv fiir 'inikros. Analomie, 1873, p. 89. THE NERVOUS MECHANISM. 249 of the body's cavity. Soon there follows such a modifi- cation of structure between the outer and inner surfaces (ectoderm and cndodcrm) that the one is mainly sensitive and protective, the other mainly protective and absorbent. The outer surface continues indeed to absorb, but its part in this function is insignificant compared with that of the inner surface, which not only absorbs but secretes fluids essential to assimilation. The inner surface, although sensitive, is subjected to less various stimulation, and its sensibility is more uniform. 110. The uppermost of the primary layers we have seen to be epithelial ; and we know that the first lines of the central nervous system are laid there. A depression called the medullary groove is the first indication of the future cerebro-spinal axis. Some writers — Kolliker, for instance — regard this medullary groove as continuous with but different from the epithelial layer; others main- tain that it lies underneath the epithelium, just as we see it in later stages, when the differentiation between epi- thelial and nerve cell has taken place. Since no one dis- putes the fact that when the groove becomes a closed canal its lining is epithelial, one of two conclusions is in- evitable : either the cells of the primary layer develop in the two diverse directions, epithelial and neural ; or else epithelial cells can be developed on the surface of neural cells and out of them. The latter conclusion is one which, involving the conception of transformation, would seem to be put out of court. I tliink, then, we must admit that the under side of the primary layer of cells becomes differentiated into nerve-cells ; and this is in accordance with the observations of Messrs. Foster and Balfour.* * "The gray matter of the cord seems undouljtcdly to lie formed by a metamorphosis of the external cells of tlie epihlast of the neural tube, and is directly continuous with the epithelium; there being no strong line of demarcation between them." — Op. cit., p. 185. 11* 250 THE PHYSICAL BASIS OF mND. 111. While there is this intimate morphological and physiological blending of epithelial and neural organites, there is an analogous relation between neural and mus- cular organites. As the neural layer lies under the epi- thelial, the muscular lies under the neural. The surface stimulation passes to the centre, and is reflected on the muscles. Embryology thus teaches why a stimulus from the external medium must be propagated to a nerve-centre before it reaches the muscles ; and why a stimulus on one part of the surface may set all the organism in movement, by passing through a centre which co-ordinates all move- ments. This, of course, only applies to the higher organ- isms. In the simpler structures the sensitive surface is directly continuous with the motor organs. It is unnecessary here to pursue this interesting branch of our subject ; nor need we follow the analogous evolu- tion of the second germinal membrane representing the Alimental System. Our attention must be given to what is known and inferred respecting the elementary structure of the nerves and centres, on which mainly the interest of the psychologist settles, since to him the wdiole of Physiology is merged in nerve actions. THE NERVOUS MECHANISM. 251 CHAPTER VII. THE ELEMENTARY STRUCTURE OF THE NERVOUS SYSTEM. 112. The progress of science involves an ever-increas- ing Analysis. Investigation is more and more directed towards the separated details of the phenomena previously studied as events ; the observed facts are resolved into their component factors, complex wholes into their sim- pler elements, the organism into organs and tissues. But while the analytical process is thus indispensable, it is, as I have often to insist, beset with an attendant danger, namely, that in drawing the attention away from one group of factors to fix it exclusively on another, there is a tendency to forget this artifice, and instead of restoring the factors provisionally left out of account, we attempt a reconstruction in oblivion of these omitted factors. Hence, instead of studying the properties of a tissue in^ all the elements of that tissue, and the functions of an organ in the anatomical connections of that organ, a single element of the tissue is made to replace the whole, and very soon the function of the organ is assigned to this particular clement. The "superstition of the nerve-cell" is a striking illustration. The cell has usurped the place of the tissue, and has come to be credited with central functions ; so that wherever anatomists have detected ganglionic cells, physiologists have not liesitated to place central functions. By such interpretations the heart and intestines, the glands and blood-vessels, have, erroneou.sly, I think, their actions assigned to ganglionic cells. 252 THE PHYSICAL basis of mind. It is unnecessary to point out the radical misconception which thus vitiates a great mass of anatomical exposition and pliysiological speculation. I only call the reader's attention to the point at the outset of the brief survey we have now to make of what is known respecting the ele- mentary structure of the nervous system. DIFFICULTIES OF THE INVESTIGATION. 113. So great and manifold are the difficulties of the search, tliat although hundreds of patient observers have during the last forty years been incessantly occupied with the elementary structure of the nervous system, very little has been finally established. Indeed, we may still repeat Lotze's sarcasm, that " microscopic theories have an aver- age of five years' duration." This need not damp our ardor, though it ought to check a too precipitate confi- dence. Nothing at the present moment needs more rec- ognition by the student than that the statements con- fidently repeated in text-books and monographs are very often for the most part only ingenious guesses, in which Observation is to Imagination what the bread was to the sack in Falstaff's tavern bill. Medical men and psychol- ogists ought to be w^arned against founding theories of disease, or of mental processes, on such very insecure bases ; and physiological students will do well to remem- ber the large admixture of Hypothesis which every de- scription of the nervous system now contains. Not that the potent aid of Hypothesis is to be undervalued ; but its limits must be defined. It may be used as a finger- post, not as a foundation. It may suggest a direction in which truth may be sought ; it cannot take the place of Observation. It may link together scattered facts ; it must not take the place of a fact. We are glad of corks until we have learned to swim. We are glad of a sugges- tion which will for the nonce fill up the gaps left by ob- THE NERVOUS MECHANISM. 253 servation, and hold the facts intelligibly together. And both as suggestion and colligation, Hypothesis is indis- pensable. Indeed, every discovery is a verified hypothe- sis ; and there is no discovery until verification has been gained : up to this point it was a guess, which might have been erroneous — a torchbearer sent out to look for a missing child in one direction, while the child was wan- dering in another ; only when he finds the child can we acknowledge that the torchbearer pursued the right path. Hypothesis satisfies the intellectual need of an explana- tion, but we must be wary lest we accept this fulfilment of a need as equivalent to an enlargement of knowledge ; we must not accept explanation as demonstration, and suppose that because we can form a mental picture of the possible stages of an event, therefore this picture repre- sents the actual stages. Let us be alert, forewarned against the tendency to seek evidence in support of a conclusion, instead of seeking to unfold the conclusion step by step from the evidence. To seek for evidence in support of a guess is very different from seeking it in sup- port of a conehision ; which latter practice is like that of people asking advice, and only following it when it chimes in with their desires. 114. Is not the warning needed, when we find anato- mists guided by certain " pliysiological postulates," and consequently seeing only what these postulates demand ? For example, there is tlie postulate of " isolated conduc- tion," which is said to require that every nerve-fibre should pursue its course singly from centre to periphery. Accordingly the fibres are described as unbranched. Whatever may be the demand of the postulate, or the felt necessity of the deduction, the fact is that nerve- fibres do branch off during their course at various points ; nay, it is doubtful whether any lengthy fibre is un- branched. Other postulates demand what fact plainly 254 THE PHYSICAL BASIS OF MIND. denies. It is said to be "necessary" that every cell sliould have at least two fibres, and that sensory and motor nerves should be directly connected through their respective cells. These things cannot be seen, but they are described with unhesitating precision. Diagrams are published in which the sensory fibres pass into the cells of the posterior horn of the spinal cord, and these cells send off prolongations to the cells of the anterior horn, and thence the motor fibres pass out to the muscles : an absolutely impossible arrangement, according to our pres- ent data! Again, the postulate that nerve-force originates in the cells, and that nerve-functions depend on cells, re- quired that the cells should be most abundant where the function w^as most energetic. Of course they were found most abundant in the required places — no notice what- ever being taken of the facts which directly contradicted the deduction. 115. Among the serious obstacles to research w^e must reckon this tendency to substitute Imaginary Anatomy for Objective Anatomy. I am conscious of the tendency in myself, as I note it in others ; and have constantly to struggle against it, though not perhaps always aware of it. jSIany a time have I had to relinquish plausible ex- planations, which would have supported my speculations could I but have believed that they represented the facts ; but beins unable to believe this, I had to remember that hypotheses and explanations appear and disappear — only the solid fact lives. If there is one lesson emphatically taught by Philosophy, it is the unwisdom of founding our conclusions on our desires rather than on the objec- tive facts. 116. In the following pages a constantly critical atti- tude is preserved : this is simply to keep active the sense of how much is still needed to be done before a satisfac- tory theory of the nervous system can be worked out. THE NERVOUS MECHANISM, 255 The objective difficulties are greater than in any other department of Anatomy. The problem is to form a pre- cise picture of what the organites are, and of how they are arranged in the living tissue ; yet our present means of investigation involve as a preliminary that we should alter that arrangement, removing some elements of the tissue, and cluinfjing the state of others, without knowing what were their precise state and arrangement before the change. Place a piece of nerve-tissue under the micro- scope, without having subjected it to various mechanical and chemical operations, and you can see next to nothing of its structure. You must tear the parts asunder, and remove the fat and nerve-sap (plasraode) before you can see anything; you must coagulate the albumen, and other- wise chemically alter the substances before a thin section can be made ; you must get rid of the tissues in which it is embedded, without knowing what are the connections tlnis destroyed. Living neurine has no greater consist- ence than cream, often no greater than oil. How, then, can thin sections be made until this viscid substance has been hardened by alcohol or acids ? But substances tluis acted on lose their constituent water, which can no more be removed without alteration of their structure, than it can be removed from certain salts witliout de- struction of their special properties. Losing their water alone, they become deformed. They lose much more. Sometimes the loss can l)e estimated, as in the case of the hyaline substance investing the nucleus during the process of segmentation in emljryonic cells, which may be seen to disappear when a weak solution of acid is ap- plied.* At other times we are unable to say wliat has disappeared. Under different modes of preparation very different appearances are observed, and anatomists are accordingly at variance. Yet unless some hardening * Robin, Anat. el Physiol. Cellulaircs, p. 332. 25G TIIK PHYSICAL BASIS OF MIND. method be adopted little can be seen ! Stilling, who has given liib lile to the study, declares that no results are reliable which are obtained from the unprepared tissue, because the mechanical isolation of the elements destroys the textural arrangement* There is one method of hardening, and only one, which we can be certain does not chemically alter the structure, and that is tlie freezing method. The experiments of Dr. Weir Mitchell and Dr. Eichardson prove this, because they prove that the brain of the living animal may be frozen and frozen again and again, yet recover its vital activity when tliawed. Pro- fessor Eutherford has invented an admirable instrument for making sections of the frozen tissue, of any delicacy that may be required; but with the thinnest section there will still be certain difficulties of observation, unless the tissue has undergone a staining process. Whatever is seen, however, in the frozen tissue is to be accepted as normal. 117. Two points must be determined before reliance can be placed on observations of tissues chemically acted on : First, we must prove that the forms now visible ex- isted before the preparation — the chemical action merely unveiling them ; secondly, we must estimate the part played by the elements which have been removed in order to make the rest visible. We know, for example, that the nucleus often exists in the cell, though an acid may be needed to make it visible. We also know that cells which during life are quite free from visible granules are distinctly granulated after death, even without ex- ternal chemical action. Imagine the explanation of a steam-engine to be attempted by first taking it to pieces, and examining these pieces, with no account of the coals and steam which had previously been removed in order to facilitate the examination. When we know the part * Stilling, Bau der Nervenprimitiv-Fasern, 1856, p. 16. THE NEKVOUS MECHANISM. 257 played by coals and steam, we may disregard these items of the active machine. So when we know the part played by water, fat, amorphous substance, and plasmode, we may describe nerve-tissue without taking these into account. 118. "You have convinced me," said Easselas to Imlac, " that it is impossible to be a poet." My readers may, perhaps, infer from this enumeration of the difficulties that a knowledge of the minute anatomy of the nervous system is impossible. Not so ; but a knowledge of these difficulties should impress us with the necessity for a vigilant scepticism, and the search after new methods. If the difficulties are fairly faced, they may be finally over- come. What we must resign ourselves to at present is the conviction that our knowledge is not sufficiently accu- rate to be employed as a basis of deduction in the expla- nation of physiological and psychological processes. * 119. Having said so much, let me add that there are some positive materials, and these yearly receive addi- tions. The organites are described with a general agree- ment as to their composition and structure — although there is much that is hypothetical even here. Neurine is known under two aspects : the amorphous and the figured. The figured, which is the better known, comprises cells of different kinds, fibres and fibrils. The amorphous, more generally called Neuroglia, or nerve-cement, is less under- stood, and is indeed by many authorities excluded alto- gether from the nerve-tissue proper, and relegated to the class of connective tissues. * "There was a time," says Kum.ikep., "wlicn I confidently believed that an hypothetical ex])lanation of the an'angement of elements in the spinal cord could he f^ioiinded on a basis of fact ; hut the deeper my insight into the minute anatomy, the less my confidence became ; and now I am persuaded that the time is not yet come to frame such an hypothesis." — Gewebekhrc, 5te Auf. 18C7. 258 THE PHYSICVL BASIS OF MIND. THE NERVE-CELL. 120. It is unfortunate that the term nerve-cell is ap- plied to organites of very variable structure. Nerve-cell is a generic term of which the species are many ; under it are designated organites in different stages — as infancy, childhood, and manhood are all included under Man. Most commonly by nerve-cell is understood the gan- glionic corpuscle, conspicuous in its size and its prolon- gations, such as it appears in the great centres, and in ganglia. It also designates smaller different organites, sometimes called "nuclei" {Kcrnc), sometimes grains {Korner). There would be advantage in designating the earlier stages as neuroblasts, reserving the word cells for the more developed forms. Such a distinction would facilitate the discussion of whether nerve-fibres had or had not their origin in cells ; because while I, for one, see very coercive evidence against the accepted notion that all the fibres have their origin in the processes of gan- glionic corpuscles, I see no reason to doubt that both fibres and corpuscles have their origin in neuroblasts. Of this anon. The cell is a composite organite, the primary element being a microscopic mass of protoplasm, or what may more conveniently be termed neuroplasm. It appears as finely granulated and striated or fibrillated substance on a hyaline ground, with water, fat, and diffused pigment in varying quantities. The cell contains a nucleus, and nucleolus — sometimes two. Like other animal cells, it sometimes has a -distinct cell-wall, sometimes not. Its size and shape are variable : sometimes distinctly visible to the naked eye, generally visible only under the micro- scope.* It is round, oval, pyramidal, club-shaped, pear- * In the Gasteropoda the cells range from 220 /x to 3 /x (/i = 0,001 millimetre). THE NERVOUS INIECHANISM. 259 shaped, or many-cornered. It has one, two, three, or many outgrowths called " processes," and according to the processes it is known as unipolar, bipolar, and multipolar. Fig. 16.— Ke.rve-cell from anterior horn of spinal cord (man), magnijicd 150 diameters, a, cell process unbranched passing into or joining an axis cylinder, the other pro- cesses are branched ; 6, pigment. The nucleus and nucleolus are visible. When there are no processes the cell is called apolar. Some idea of these processes may be formed if they are likened to the pseudopodia of Amoeba and Foraminifera. ?2^ e is ^ fe - THE NERVOUS MECHANISM. 261 Compare Fig. 16, a nerve-cell, figured by Gerlach, with Fig. 17, one highly magnified, in which Max Schultze's hypothesis is represented. 121. Such is a general description of the nerve-cell as it is seen in various places, and under various modes of preparation. How much is due to preparation we can- not positively say. Wliile we always discover fibrine in the blood after it is withdrawn from the vessels, we know that fibrine as such does not exist in the circulating blood. And if neurine is a semi-liquid substance, we may doubt whether in the living cell it is fibrillated. Doubts have been thrown even on the normal existence of the granular substance, which has been attributed to coagula- tion. Thus we know' that the nucleus of the white blood- corpuscle appears perfectly homogeneous until subjected to heat, yet at a certain temperature (86° F.) it assumes the aspect of a fine network. Haeckel observed the hya- line substance of the neurine in crayfish become troubled and changed directly any fluid except its own blood-serum came in contact with it. Leydig noticed the transparent ganglion of a living Daphnia become darker and darker as tlie animal died ; and I saw something like this, after prolonged struggles of a Daphnia to escape from a thread in which its leg was entangled. Charles Robin, indeed, asserts that the passage from the hyaline to the finely granulated state is a characteristic of the dying cell.* On * Haeckel, Milllcr's Archiv, 1857. Leydig, Voni Bait dcs ihieri- schen Korpcrs, 1864, I. 84. llonix, Anat. ct Physiol. C'eUulaircs, p. 89. Should the observations of Heitzmann be confirmed, tlierc would be ground for believing that neurine is nomially fibrillated. He says that the living ])rotoplasm in tlie Anueba, white blood-corpuscle, etc., is an excessively fine network, which condenses into granules at each contrac- tion. (Cited in the Jahreshcrichte iihcr Anat. und Physiol., 1873, ]5d. II.) Waltheu, who examined frozen brains, describes the cells as ([uite trans- parent at first, with very rare granules, but gradually wliih; under obser- vation the granules became more numerous. Ccntralblatt, 1868, p. 459. 262 THE PHYSICAL BASIS OF MIND. the other hand, it should be noted tliat Max Schultze de- scribes a fibriUated appearance in cells just removed from the living animal, and placed in serum. When, therefore, one observer describes the neuroplasm as being clear as water, another as finely granular, and a third as fibrillated, we must conclude that the observa- tions refer to cells, 1°, under different states of vitalization, or, 2°, under different modes of preparation. On the first head we note that some nerve- cells are so perishable that Trinchese declares he could find no cells in the ganglia of a cuttlefish which had been dead twenty-four hours, although they were abundant in one recently killed.* On the second head we note that the changes wrought by modes of preparation cannot be left out of consideration. Auerbach notices that the cells and fibres apparent in the plexus mycntcricus after an acid has been aj^plied, cannot be detected before that application — nothing is visible but a pale gelatinous network, with here and there knots of a paler hue ; and I remember my surprise on exam- ining the fresh spinal cord of a duck-embryo, and finding no trace of cells such as I had that very morning seen in the cord of a chick of earlier date, but which had been soaked in weak bichromate of potash. Xow w^e have excellent grounds for believing that in both cases these organites were present, and that it was the reagent which disclosed their presence in the chick; and so in other cases we must ask wdiether the forms which appear under a given mode of preparation are simply iinm asked, or are in truth i^'oduced by the reagent ? This question we can rarely answer. According to IIauthnee, Bcitrdge zur Kenntniss dcr morpJiologischen Elemcntc des Kervcasystcrns, 1862, p. 41, neurine has three cardinal forms — transparent, finely granular, and coarsely granular. * TiUNCHESE, Struttura del sistema nervosa dei Cefalopodi, Florence, 1868, p. 7. THE NERVOUS MECHANISAI. 263 If one of the very large cells be taken from the gan- glion of a living mollusc, and be gently pressed till it bursts, the discharged contents will be seen to be of a hyaline viscid substance, with fine granules but no trace of fibres. Yet we must not rashly generalize from this, and declare that in the vertebrate cells the substance is not also fibrillated. As a good deal of speculation rests on the assumption of the fibrillated cell-contents, I have thought it worth while to note the uncertainty which hovers round it. 122. Among the uncertainties must be reckoned the question as to the cell-processes. The existence of apolar and unipolar cells is flatly denied by many writers, who assert that the appearances are due to the fragility of the processes. Fragile the processes are, and evidence of their having been broken off' meet us in every preparation ; but the denial of apolar and unipolar cells seems to me only an example of the tendency to substitute hypothesis for observation (§ 114). The "postulate" which some seem to regard as a " necessity of thought " that every nerve- cell shall have at least two fibres, one ingoing, the other outgoing, is allowed to override the plain evidence.* It originated in the fact first noticed by Wagner and Charles Robin that certain cells in the spinal ganglia of fishes are bipolar. The fact was rapidly generalized, in spite of its not being verified in other places ; the generalization was accepted because (by a strange process of reasoning run- ning counter to all physiological knowledge) it was thought to furnish an elementary illustration of the re- flex process. As the centre liad its ingoing and outgoing nerve, so tlie cell was held to be a centre " writ small," * An eminent friend of mine was one flay insisting to me that tlie phys- iological postulate made it impossible for a nerve-cell to be without its ingoing and outgoing fibres ; and he was not a little astounded when I replied, "Come into my workroom and I will show you a thousand." 264 TIIK PHYSICAL BASIS OF MIND. and required its two fibres. No one paused to ask, how a cell i)luced in the trade of an ingoing nerve could fulfil this otlice of a reflex centre; no one supposed that the portion of the sensory fibre which continued its course, after the interruption of the cell, was a motor fibre. What does Observation teach ? It teaches that at first all nerve-cells are apolar. Even in the cortex of the cere- brum, where (unless we include the nuclei and grain-like corjiuscles under cells) all the cells are finally multipolar, there is not one which has a process, up to the seventh or eighth day of incubation (in the chick) ; from that day, and onwards, cells with one process appear; later on, cells with two, and later still, with three. By this time all the apolar cells have disappeared. They may there- fore be regarded as cells in their infancy. However that may be, we must accept the fact that apolar cells exist ; whether they can co-operate in neural functions, is a question which must be decided after the mode of opera- tion of cells is placed beyond a doubt. 123. If apolar cells are embryonic forms of cells which afterwards become multipolar, this interpretation will not suffice for the unipolar cells. They are not only abun- dant, but are mature forms in some organs, and in some animals ; though in some organs they may truly be re- garded as embryonic. Thus in the human embryo up to the fourth month all the cells of the spinal cord are said to be unipolar,* later on they become multipolar. But in birds, rabbits, dogs, and even man, the cells in the spinal ganglia are mainly (if not wholly) unipolar ;t nor is there * EiCHHOEST in Virchows Jrchiv, 1875, LXIV. p. 432. + AuEUBACH (Ueber einen Plexus My enter icus, 1862) describes the ganglia as filled with apolar cells, among which only a few are unipolar. Stieda {Centralncrvcnsystem der Vbgcl, 1868) finds both apolar and uni- polar cells in the spinal ganglia of birds. Axmann {De Gangliorum Systematis Strudiira penitiori, 1847) says the spinal cells are all unipolar. ScHWALDE {Archiv fiir mikros. Anat., 1868) and Couiia'oisieu {ibid.. THE NERVOUS MECHANISM. 265 any difficulty in observing the same fact in the oesopha- geal ganglia of molluscs (see Fig. 22). Such are the observations. They have indeed been forced into agreement with the bipolar postulate, by the assumption that the single process branches into two, one afferent, the other efferent.* But before making observa- tion thus pliant to suit hypothesis, it would be well to look more closely into the evidence for the hypothesis itself For my own part, I fail to see the justification of the postulate ; wdiereas the existence of unipolar cells is an observation which has been amply verified. 124. Bipolar cells abound ; multipolar cells are still more abundant ; and these are the cells found in the gray substance of the neural axis. Deiters, in his epoch-mak- ing work,f propounded an hypothetic schema which has been widely accepted. Finding that the large cells in the anterior horn of the spinal cord gave off processes of different kinds, one branched, the other unbranched, he held that the latter process was the origin of the axis 1869) say the same. So also Ranvier, Comptes Rcndus, 1875. Kolli- KER {Gcicchehhre) speaks decidedly in favor of both apolar and unipolar cells, but thinks the apolar are embryonic. Pagliani {Saggio sullo Stato attuale ilclle Cognizioni delta Fisiologia intornoal Sisteina nervoso, 1873), who represents the views of Moleschott, admits the existence of apolar and nnii)olar cells. The authors just cited are those I happen to have liefore me during the rewriting of this chapter, and the list might easily be extended if needful. Auerbach, Bidder, and Schwkigger-Seidel descrilje unipolar cells which in some places present the aspect of bipolar cells simply because two cells lie together, their single poles having op- posite directions. I will add that the bipolar cells do not really render the physiological inter2)retation a whit more easy than the unipolar, for they are simply cells which form enlargements in the cour.se of the nerve- fibres. * When Dr. Beai.e .says "that it is probable no nerve-cell exists which has only one single fibre connected with it" (Bioplasm, p. 186), he has no doubt this in his mind ; since he would not, I presume, deny that there are cells each with a single process. t Deiteus, UntcrsucJmngen ilbcr Gchirn und Rilckcnmark, 1866. K. THE NERVOUS MECHANISM. 267 cylinder of a nerve-fibre, whereas the branched process was protoplasm which divided and subdivided, and formed the connection between one cell and another. Gerlach has modified this by supposing that the minute fibrils of the branching process reunite and form an axis cylinder (Fig. 18). There is no doubt that some processes terminate in a fine network ; and there is a probability (not more) that the unbranched process is always continuous with the axis cylinder of a motor nerve, as we know it sometimes is with that of a dark-bordered fibre in the white sub- stances. This, though probable, is, however, very far from having been demonstrated. Once or twice Kolliker, Max Schultze, and Gerlach have followed this unbranched process as far as the root of a motor nerve ; and they infer that although it could not be traced further, yet it did really join an axis cylinder tliere. In support of this in- ference came the observations of Koschennikoff,* that in the cerebrum and cerebellum, processes were twice seen continuous with dark-bordered nerve-fibres. But the ex- treme rarity of such observations amid thousands of cells is itself a ground for hesitation in accepting a generalized interpretation, the more so since we have Henle's obser- vation of the similar entrance of a branched process into the root.f Xow it must be remembered that the branched process is by no anatomist at present regarded as the origin of the axis cylinder; so that if it can enter the root without being the origin of a nerve-fibre, we are not entitled to assume that the entrance of the unbranclied process has any other significance (on this head compare § 145), especially when we reflect that no trustworthy observer now professes to have followed a nerve-fibre of the posterior root i-iglit into a multipolar cell. Figures, * Archiv fiir mikros. Armt., 1869, p. 217. Compare also BuTZKE, Archivfiir Psychiatric, 1872, p. 584. t Henle, Nervenlehrc, 1871, p. 58, Fig. 21. 268 THE PHYSICAL BASIS OF MIND. indeed, have been published which show this, and much else ; but such iigures are diagrams, not coj)ies of what is seen. They belong to Imaginary Anatomy.* The re- lation of the cell-process to the nerve-fibre will be dis- cussed anon. 125. A word in passing on the contradictory assertions respecting the anastomosis of nerve-cells. That the gray Fig. 19. — Anastomosing nerve-cells (after Gratiolet). a, body of the cell ; c, process of uniting two cells ; d, branching process. substance forms a contimiv/in of some kind is certain from the continuity of propagation of a stimulus. But it is by no means certain that one cell is directly united to its neighbor by a cell-process. Eminent authorities assert that such direct union never takes jjlace ; others, that it is a rare and insignificant fact ; others, that it is constant, and " demanded by physiological postulates." I will not, * "When men of such experience and skill as Kolliker, Bidder, GoLL, and Lock hart Clarke declare that they have never seen a cell- process pa.ss directly into a dark-bordered fibre in the anterior root, what are we to say to such figures and descriptions as those given in the works of Schroder van der Kolk, Gratiolet, and Llvs? Even did such arrangements exist, no transverse nor longitudinal section could display them, owing to the different planes at which the fibres enter, and the length and irregularity of their course. THE NERVOUS MECHANISM. 269 in the presence of distinct affirmations, venture to deny that such appearances as are presented in Fig. 19 may occasionally be observed ; the more so as I have myself seen perhaps half a dozen somewhat similar cases ; but it is the opinion of Deiters and Kolliker that all such ap- pearances are illusory.* Granting that such connections occur, we cannot grant this to be the normal mode ; espe- cially now the more probable supposition is that the con- nection is normally established by means of the delicate ramifications of the branching processes. Imaginary Anatomy has not been content with the cells of the anterior horn being thus united together, to admit of united action, but has gone further, and supposed that the cells of the posterior horn, besides being thus united, send off processes which unite them with the cells of the anterior horn — and thus a pathway is formed for the transmission of a sensory impression, and its conversion into a motor impulse. What will the reader say when informed that not only has no eye ever beheld such a pathway, but that the first step — the direct union of the sensory nerve-fil)re with a cell in the posterior horn — is confessedly not visible ? 126. The foregoing criticisms will perhaps disturb the reader who has been accustomed to theorize on the data given in text-books ; but he may henceforward be more cautious in accepting such data as premises for deduction, and will look with su.spicion on the many tlieories wliich have arisen on so unstable a basis. "When we rellect how completely the modern views of the nervous system, and the physiological, pathological, and psychological expla- nations based on tlicse views, are dominated by tlie cur- * Long after tlie text was written, Willkik publishud in Virchow's Archiv, IST.'i, LXIV. p. ]63, observation.s of anastomoses which even KoLLiKEii admitted to be undeniable. Yet out of sixty-four i)re])arations, amid hundreds of cells, he could only reckon seven cases of conjunction. 270 THE niYSICAL BASIS OF MIND, rent notions of the nerve-cell, it is of the last importance that we should fairly face the fact that at present our knowledge even of the structure of the nerve-cell is ex- tremely imperfect ; and our knowledge of the part it plays — its anatomical relations and its functional relations — is little more than guesswork ! THE NEKVES. 127. We now pass to the second order of organites ; and here our exposition will be less troubled by hesita- tions, for although there is still much to be learned about the structure and connections of the nerve-fibres, there is also a solid foundation of accurate knowledge. A nerve is a bundle of fibres within a membranous envelope supplied with blood-vessels. Each fibre has also its separate sheath, having annular constrictions at various intervals. It is more correctly named by many French anatomists a nerve-tiihe rather than a nerve-/6?'c; but if we continue to use the term Jibre, we must reserve it for those organites which have a membranous sheath, and thereby distinguish it from the more delicate Jihnl which has none. The nerve tube or fibre is thus constituted : within the sheath lies a central band of neuroplasm identical with the neuroplasm of nerve-cells, and known as the axis cyl- inder ; surrounding this band is an envelope of whitish substance, variously styled myeline, medullary slicath, and white substance of Schwann : it is closely similar to the chief constituent of the yolk of egg, and to its presence is due the whitish color of the fibres, which in its absence are grayish. The axis cylinder must be understood as the primary and essential element, because not only are there nerve-fibrils destitute both of sheath and myeline yet fulfilling the ofiice of Neurility, but at their termi- THE NERVOUS MECHANISM. 271 X:: . 1. M nations, both in centres and in mus- cles, the nerve - fibres always lose sheatli and myeline, to preserve only the neuroplasmic threads of which the axis cylinder is said to be composed. In the lowest fishes, in the invertebrates, and in the so- called sympatlietic fibres of verte- brates, there is either no myeline, or it is not separated from the neu- roplasm. 128. Nerve-fibres are of two kinds — 1°. The darJc-hordered or medid- lary fibres, which have both sheath and myeline, as in the peripheral system ; or only myeline, ■without the sheath, as in the central sys- tem. 2°. The non-mcdidlary fibres, which have the sheath, without ap- preciable myeline — such are the fibres of the olfactory, and the pale fibres of the sympathetic. Nerve-fibrils are neuroplasmic threads of extreme delicacy, visible only under high magnil'ying powers (700 - 800), which abound in the centres, wliere they Ibrm networks. The fibrils also form the termina- tions of the fibres. Many fibrils are supposed to be condensed in one axis cylinder. This is repre- sented by Max Schultze in Figs. 17 and 20. 129. As may readily be imag- Fig. 20. — o, axis cylinder formed by the (ibrils of the cell contents, and at a' .issuming the medullary sheath ;?;, naked incd, thc SeUli-litplid Uature of the axis cylinder from 8i>inal cord. 272 THE PHYSICAL BASIS OF MIND. neuroplasm throws almost insuperable difficulties in the way of accurately determining whetlier the axis cylin- der in the living nerve is fibrillated or not; whether, indeed, any of the aspects it presents in our prepara- tions are normal. Authorities are not even agreed as to M'hether it is a pre-existent solid band of homogeneous substance, or a bundle of primitive fibrils, or a pro- duct of coagulation.* Eudanowsky's observations on frozen nerves convinced him that the cylinder is a tubule with liquid contents.! My own investigations of the nerves of insects and molluscs incline me to the view of Dr. Schmidt of New Orleans, namely, that the cylinder axis consists of minute granules arranged in rows and united by a homogeneous interfibrillar substance, thus forming a bundle of granular fibrils enclosed in a delicate sheath $ — in other words, a streak of neuroplasm whicli has a fibrillar disposition of its granules. We ought to expect great varieties in such streaks of neuroplasm ; and it is quite conceivable that in the Rays and the Torpedo there are axis cylinders which are single fibrils, and others which are bundles, with finely granulated interfibrillar substance.§ The fibres often present a varicose aspect, as represented in Fig. 21. It is, however, so rarely observed in the fresh tissue, that many writers regard it (as well as the double contour) as the product of preparation. || It is, indeed, always visible after the application of water. * See the history given in Stilling's learned work, Ueber den Bau der Kervenprimitiv-Fascr, p. 34 ; and compare Max Schtjltze, De Eetince Slrudura, p. 8, and Bau der NasensMeimhaut, p. &Q ; Waldeyer, in the Zeitschrift fiir rat. Med., 1863; Li.ster and Turner, Observations on the Structure of Nerve-Fibres, in Quarterly Micros. Journal, 1859 ; Ranvier, in the Archives de Physiologic, 1872. t Virchovfs Archiv, Bd. LXXII. p. 193. X Monthly Journal of Micros. Science, 1874, XI. p. 214. § Babuchin, Centralblatt, 1868, p. 756. II Even so eminent an authority as W. Krause holds this both vitli THE NERVOUS MECHANISM. 273 "We need say no more at present respecting the struc- ture of nerve-fibres, except to point out that we have here an organite not less complex than the cell. Fig. 21. — Nerve-fibres from the ivhite substance of the cerebrum, a, a, a, tlie medul- lar contents pressed out of the tube as irregular drojis. THE NEUROGLIA. 130. Besides cells and fibres, there is the amorphous substance, which constitutes a great part of the central tissue, and also enters largely into the peripheral tissue. It consists of finely granular substance, and a network of excessively delicate fibrils, with nuclei interspersed. Its character is at present sv.h judice. Some writers hold it to be nervous, the majority hold it to be simply one of the many forms of connective tissue : hence its name neuroglia, or nerve-cement. regard to the varicose a.spcct and the double contour : Handhuch dcr mcnschlichcn Anatomic, 1876, I. 367. Hut.sciili, however, describes the ner\'es in a living Nematode as varico.se : Archiv fur Anat., 1873, p. 78 ; iiml I have .somewhere met with an observation of the double contour being vi.sible in the living animal. 12* u 274 THE niYsiCAL basis of mind. In the convolutions of the frozen brain Walther finds the cells and fibres imbedded in a structureless semi-fluid substance ^vholly free from granules ; the granules only appear there ^vhen cells have been crushed. It is to this substance he attributes the fluctuation of the living brain under the touch, like that of a mature abscess ; the solid- ity which is felt after death is due to the coagulation of this substance. Unhappily we have no means of deter- mining whether the network visible under other modes of investigation is present, although invisible, in this sub- stance. The neuroglia, as it appears in hardened tissues, must therefore be described with this doubt in our minds. If we examine a bit of central gray substance where the cells and fibres are sparse, we see, under a low power, a network of fibrils in the meshes of which lie nerve-cells. Under very high powers we see outside these cells an- other network of excessively fine fibrils embedded in a granular ground substance, having somewhat the aspect of hoar-frost, according to Boll. It is supposed that the first network is formed by the ultimate ramifications of the nerve-cell processes, and that the second is formed by ramifications of the processes of connective cells. In this granular, gelatinous, fibrillar substance nuclei ajDpear, to- gether with small multipolar cells not distinguishable from nerve-cells except in being so much smaller. These nuclei are more abundant in the tissue of young animals, and more abundant in the cerebellum than in the cere- brum. The granular aspect predominates the fresher the specimen, though there is always a network of fibrils ; so that some regard the granules as the result of a resolution of the fibrils, others regard the fibrils as the linear crys- tallization (so to speak) of the granules.* * BuTZKE, Archiv fur Psychiatric, 1872, p. 594, states that the granular substance has the chemical composition of myeline. If this be so, we may suppose the "fibrils of crystallization " to represent the THE NERVOUS MECHANISM. 275 131. Such is the aspect of the neuroglia. I dare not venture to formulate an opinion on the histological ques- tion whether this amorphous substance is neural, or partly neural and partly connective (a substance "which is poten- tially both, according to Deiters and Henle), or wholly connective. The question is not at present to be an- swered decisively, because what is known as connective tissue has also the three forms of multipolar cells, fibrils, and amorphous substance ; nor is there any decisive mark by which these elements in the one can be distinguished from elements in the other. The physical and chemical composition of Xeurogiia and Neuroplasm are as closely allied as their morphological structure. And although in the later stages of development the two tissues are mark- edly distinguishable, in the early stages every effort has failed to furnish a decisive indication.* Connective tissue is dissolved by solutions which leave nerve-tissue intact. Can we employ this as a decisive test ? No, for if we soak a section of the spinal cord in one of these solutions, the ^:)w mater and the membranous septa which ramify from it between the cells and fibres disappear, leaving all the rest unaltered. This proves that Neuroglia is at any rate chemically different from ordinary connective tissue, and more allied to the nervous. As to the staining process, so much relied on, nothing requires greater cau- tion in its employment. Stieda found that the same parts were sometimes stained and sometimes not ; and Mauthner observed that in some cells both contents and nucleolus were stained, while the nucleus remained clear, coagulation of the substance which is in solution amid the inyeline gran- ules, and corresponds with the axis cylinder of a fibre. I may remark that in almost every good prejjaration nerve-cells will be found in which, while one process is distinctly granular, another is striated or even fibrillated. * Boll, Die Ilisliologic und Ilisliogcncsc dcr ncrvosen Ccntralorganc, in the Archiv fiir Psychiatric, 1873, p. 47. 276 THE niYSICAL BASIS OF MIND. in other cells the contents remained clear ; and some of the axis cylinders were stained, the others not* Lister found that the connective tissue between the fibres of the sciatic nerve, as well as the 'pia mater, were stained like the axis cylinders ; f and in one of my notes there is the record of both (supposed) connective cells and nerve-cells being stained alike, while the nerve-fibres and the (sup- posed) connective fibres were unstained. Whence I con- clude that the supposition as to the nature of the one group being different from that of the other was unten- able, if the staining test is to be held decisive. 132. The histological question is raised into undue im- portance because it is supposed to carry with it physio- logical consequences which would deprive the neuroglia of active co-operation in neural processes, reducing it to the insignificant position of a mechanical support. I cannot but regard this as due to the mistaken tendency of analytical interpretation, which somewhat arbitrarily fastens on one element in a complex of elements, and assigns that one as the sole agent. Whether we call the neuroglia connective or neural, it plays an essential part in all neural processes, probably a more important part than even the nerve-cells, which usurp exclusive attention ! To overlook it, or to assign it a merely mechanical office, seems to me as unphysiological as to overlook blood-serum, and recognize the corpuscles as the only nutrient elements. The notion of the neuroglia being a mere vehicle of support for the blood-vessels arises from not distinguishing between the alimental and instru- mental offices. In the function of a limb, bone is a co- operant. In the function of a centre, connective tissue is a co-operant ; so that even if we acknowledge neuroglia * Stieda, Sludien iiher das Ccntrahicrvensystem der Vogel, 1868, p. 65. Mauthner, Op. cit., p. 4. t TuiiNEU and Lister, Op. cit., p. 8. THE KERVOUS MECHANISM. 277 to be a special form of connective tissue, it is an agent in neural processes ; ichat its agency is, will be hereafter considered. Following Bidder and Kupffer, the Dorpat school pro- claimed the wliole of the gray substance of the posterior half of the spinal cord to be connective tissue ; and Bles- sig maintained that the whole of the retina, except the optic fibres, was connective tissue.* Even those anato- mists who regarded this as exaggerated, admitted that connective tissue largely enters into the gray substance, especially if the granular ground substance be reckoned as connective, the nerve-cells being very sparse in the posterior region. Be it so. Let us admit tliat the gray matter of the frog's spinal cord is mainly composed of neuroglia, in which a very few multijDolar nerve-cells are embedded. What must our conclusion be ? Why, that since this spinal cord is proved to be a centre of ener- getic and manifold reflex actions — even to the extent of forcing many investigators to attribute sensation and voli- tion to it — this is proof that connective tissue does the work of nerve-tissue, and that the neuroglia is more impor- tant than nerve-cells ! Three hypotheses are maintainable — 1°. The neuroglia is the amorphous ground-substance of undeveloped tissue (neuroplasm) out of which the cells and fibres of nerve- ti.ssue and connective tissue are evolved. 2°. It is the product of dissolved nerve cells and fibres. 3°. It is the undeveloped stage of connective tissue. For physiologi- cal purposes we may adopt any one of these views, pro- vided we keep firm hold of the fact that tlie neuroglia is an essential element, and in the centres a dominant element. To make this clear, however, we must inquire more closely into the relations of the three elements, nerve-cells, fibres, and neuroglia. * Blessig, De RetincB Struclura, 1857. 278 THE niYSICAL BASIS OF MIND. THE RELATIONS OF THE ORGANITES. 133. In eimnierating among the obstacles to research the tendency to substitute hyiDothetic deductions in place of objective facts, I had specially in my mind the wide- reaching influence of the reigning theories of the nerve- cell. Had we a solidly established theory of the cell, eg^uivalent, say, to our theory of gas-pressure, we should still need caution in allowing it to override exact obser- vation ; but insecure as our data are, and hypotlietical as are the inferences respecting the part played by the cell, the reliance placed on deductions from such premises is nothing less than superstition. Science will take a new start when the whole question is reinvestigated on a pre- liminary setting aside of all that has been precipitately accepted respecting the office of the cell. This exercise of the imagination, even should the reigning theories subsequently be confirmed, would not fail to bring many neglected facts into their rightful place. I am old enough to remember when the cell held a very subordinate position in Neurology, and now my meditations have led me to return, if not to the old views of the cell, at least to something like the old estimate of its relative importance. Its existence was first brought prominently forward by Ehrenberg in 1834, who de- scribed its presence in the sympathetic ganglia; and by liemak in 1837, who described it in the spinal ganglia. For some time afterwards the ganglia and centres were said to contain irregular masses of vesicular matter which were looked on as investing the fibres ; what their office was, did not appear. But there rapidly arose the belief that the cells were minute batteries in which "nerve- force " was developed, the fibres serving merely as con- ductors. Once started on this track, Hypothesis had free THE NERVOUS MECHANISM. 279 way, and a sort of fetichistic deification of the cell in- vested it with miraculous powers. In many works of repute we meet with statements which may fitly take their place beside the equally grave statements made by savages respecting the hidden virtues of sticks and stones. We find the ner\e-cells credited with "metabolic powers," which enable them to "spiritualize impressions, and ma- terialize ideas," to transform sensations into movements, and elaborate sensations into thoughts ; not only have they this "remarkable aj)titude of metabolic local action," tliey can also " act at a distance." * The savage believes that one pebble will cure diseases, and another render him victorious in war ; and there are pliysiologists who believe that one nerve-cell has sensibility, another motricity, a third instinct, a fourth emotion, a fifth reflexion : they do not say this in so many words, but they assign to cells which differ only in size and sliape, specific qualities. They describe sensational, emotional, ideational, sympa- thetic, reflex, and motor-cells ; nay, Schroder van der Kolk goes so far as to specify hunger-cells and thirst- * LuYs, HccJierches sur Ic Sijstbne nerveux, 1865, p. 267. In a recent and remarkable treatise the student is informed that "plusune cellule est chargee d'un rule purement mecanique plus elle est voluniinouse ; plus I'acte qu'elle produit tend a revetir un caractere psychique plus olio est petite " ; to move a limb the agitation of the cerebral cells must tnatcricdize itself more and more, " 11 a besoin de passer par des cellules, de moins en moins spirituellcs et de plus en jilus matf'ricUes Do ineme pour les cellules sensitives. L'im])ression exterieure va en se modifiant, en se spiritualisant, de la peripheric au centre Un phenomene de I'ordre spirituel ne saiirait devenir sans transition un jihenomene d'ordre physi([ue." And what is this marvellous transition between spiritual and physical ? It is the action of medium-sized cells which "travaillent la vibration re9ue, la modifient de fa(;on a lui Oter de son spiritualismc et a la rapprocher davantage des ebranlemeiits phy- siques." I will not name tl)e estimable author, because he is simply restating what many others imjAicitly or explicitly teach ; but I will oidy ask the reader to try and realize in thought the process thus described. 280 THE PHYSICAL BASIS OF MIND. cells.* With \vluit grace can these writers laugh at Scholasticism ? 134. The hypothesis of the nerve-cell as the fountain of nerve-force is supported by the gratuitous hypothesis of cell-substance having greater chemical tension and molec- ular instability than nerve-fibre. No evidence has been furnished for this ; indeed the only experimental evidence bearing on this point, if it has any force, seems directly adverse to the hypothesis. I allude to tlie experiments of Wundt, which show that the faint stimulus capable of moving a nmscle when applied directly to its nerve, must be increased if the excitation has to pass through the cells by stimulation of the sensory nerve.f Wundt interprets this as proving that the cells retard every im- pulse, whereby they are enabled to store up latent force. The cells have thus the office of locks in a canal, which cause the shallow stream to deepen at particular places. I do not regard this interpretation as satisfactory; but the fact at any rate seems to prove that so far from the cells manifesting greater instability than the fibres, they manifest less. 135. The hypothesis of nerve-force being developed in the ganglia, gradually assumed a more precise expression when the nerve-cells were regarded as the only important elements of a ganglion. It has become the foundation- stone of Xeurology, therefore very particular care should be taken to make sure that this foundation rests on clear and indisputable evidence. Instead of that, there is ab- solutely no evidence on which it can rest ; and tliere is much evidence decidedly opposed to it. Neither struc- * Schroder van der Kolk, Pathologic der Geisteshrankheiten, 1863, p. 69. t WuxDT, Physiologischc Psyclwlogie, p. 261. In his Meclianik der Nerven, 2 AUh. (published just as this sheet is going to press), he shows that a stimulus is both retarded and weakened in its passage through a ganglion. THE NERVOUS MECHANISM. 281 ture nor experiment points out the cells as the chief agents in neural processes. Let us consider these. Fig. 22 sliows the contents of a molluscan ganglion which has been teased out with needles. Fig. 22. — Cells, fibres, and amnrphous mihstirncf ftam the gnnglion of a mollusc (uftcr Uucholtz). 282 THE PHYSICAL BASIS OF MIND. The cells are seen to vary in size, but in all there is a rim of neuroplasm surroiinding the larire nucleus, and from this neuro- plasm the fibre is seen to be a pro- longation. The dotted substance in the centre is the neuroglia. Except in the possession of a nucleus, there is obviously here no essential differ- ence in the structure of cell and fibre. Now compare this with Fig. 23, rep- resenting three fibres from the audi- tory nerve. Here the cell substance, as Max Schultze remarks, "is a continuation of the axis cylinder, and encloses the nucleus. The medulla commonly ceases g at the point where the axis enters the cell, to reappear at its exit; but it sometimes stretches across the cell to enclose it also : so that such a gan- glion cell is in truth simply the nu- cleated portion of the cylinder axis."* There are many places in which fibres are thus found with cells inserted in their course as swellings : in the spinal ganglia of fishes these are called bi- polar cells ; they are sometimes met with even in the cerebellum ; but oftener in peripheral nerves, where they are mostly small masses of gran- ular neuroplasm from which usually aZtorTZrtl^^^^l a branching of the fibre takes place, cylinder ; &, the ceUniar en- rrii ... 1 • 1 ,, ,• . n 1 larj;ement ; c, the medullary Ine pomt to which attention is called sheath. * Trinchese also says that the fibres "provengono dalle cellule e non son altro che i loro jrrolungamenti o poli." — Op. cit., p. 13. An THE NERVOUS MECHANISM. 283 is that in some cases, if not in all, the nerve-fibre is structurally continuous with the cell contents. The two organites — fibre and cell — differ only as regards the nucleus and pigment. Haeckel, who affirms that in the crayfish [Astacus Jluviatilis) he never saw a cell which did not continue as a fibre, thinks there is al- ways a marked separation of the granular substance from its " hyaline protoplasm," and that only this latter forms the axis cylinder. But although my observations agree with this as a general fact, I have seen even in crayfish the granular substance prolonged into the axis cylinder; and in other animals the granular substance is frequently discernible. Indeed it may be said that anatomists are now tolera- bly unanimous as to the axis cylinder being identical with the protoplasmic cell substance. If this be so, we have only to recall the principle of identity of property accompanying identity of structure, to conclude that ■whatever properties ive assign to the cells (unless we restrict these to the nucleus and pigment) ive must assign to the axis cylinders. We can therefore no longer entertain the hopothesis of the cells being the fountains or reservoirs of Neurility ; the less so when we reflect that cells do not form the hundredth part of nerve-tissue: for even the gi'ay substance Itears but a small proportion to the white; and of the gray substance, Henle estimates that one lialf is fibrous, the rest is partly cellular, partly amor])Iious. Those who derive Neurility irom the cells, forget that although the organism begins as a cell, and for some weeks consists mainly of cells, yet from this time onwards there is an ever-increasing preponderance of cell-deriva- tives — fibres, tubes, and amorphous substance ■ — and cor- unequivocal exanijilc is socn in the Torpedo, where the large cell.s have each their prolongation continuing without interruption into the elec- trical organ. See the figure given hy Ueiciieniieim in the Archiv filr Anat., 1873, Het't VI. 284 THE PHYSICAL BASIS OF MIND. responding with this is the ever-increasing power and complexity of tlie organism. 13G. From another point of view we must reject the hypothesis. Not only does the evidence which points to the essential continuity in structure of nerve cell and fibre discredit the notion of their physiological diversity, but it is further supported by the fact that although the whole nervous system is structurally continuous, an im- mense mass of nerve-fibres have no immediate connection with ganglionic cells : — neither springing from nor ter- minating in such cells, their activity cannot be assigned to them. To many readers this statement will be start- ling. They have been so accustomed to hear that every fibre begins or terminates in a cell, that a doubt thrown on it will sound paradoxical. But there is an equivoque liere which must be got rid of. When it is said that every fibre has its " origin " in a cell, this may be true if origin mean its point of deijcirture in evolution, for " cells " are the early forms of all organites ; but although every organite is at first a cell, and in this sense a nerve- fibre must be said to orioinate in a cell, we must guard against the equivoque which arises from calling the highly differentiated organite, usually designated gangli- onic cell, by the same name as its starting-point. On this ground I suggest the term neuroblast, in lieu of nerve-cell, for the earlier stages in the evolution of cell and fibre. Both Embryology and Anatomy seem to show that cell and fibre are organites differentiated from iden- tical neuroblasts, with a somewhat varying history, so that in their final stages the cell and fibre have con- spicuous differences in form with an underlying identity ; just as a male and female organism starting from identi- cal ova, and having essential characters in common, are yet in other characters conspicuously unlike. The mul- tipolar cell is not necessarily the origin of a nerve-fibre, THE NERVOUS MECHANISM. 285 although it is probable that some short fibres have their origin ill the prolongations of cells. Although the latter point has not, I think, been satisfactorily established, except in the invertebrata, I see no reason whatever to doubt its probability ; what seems the least reconcilable with the evidence is the notion that all fibres arise as prolongations from ganglionic cells, instead of arising independently as differentiations from neuroblasts. The reader will observe that my objection to the current view is purely anatomical ; for the current view would suit my physiological interpretations equally well, and would be equally irreconcilable with the hypothesis of the cell as the source of Neurility, so long as the identity of struc- ture in the axis cylinder and cell contents is undisputed. 137. The evidence at present stands thus : There are numerous multipolar cells which have no traceable con- nection with nerve-fibres ; and fibres which have no direct connection with multipolar cells. By the first I do not mean the disputed apolar cells, I mean cells in the gray substance of tlie centres which send off pro- cesses that subdivide and terminate as fibrils in the net- work of the Neuroglia (Figs. 16, 18). It is indeed gen- erally assumed that tliese have each one process — the axis-cylinder process — which is prolonged as a nerve- fibre ; nor would it be prudent to assert that such is never the case ; though it would be difficult to distin- guish between a fibre wliich had united with a process and a fibre which was a prolongation of a process, in both cases the neuroplasm being identical. I only urge that the assumption is grounded not on anatomical evidence, but on a supposed necessary postulate. All that can be demonstrated is that some processes terminate in exces- sively fine fibrils ; and occasionally in tliousands of speci- mens processes liave been traced into dark-bordered fibres. It is true that they often present appearances which 286 THE PHYSICAL BASIS OF MIND. have led to the inference that they did so terminate — appearances so deceptive that Golgi and Arndt inde- pendently record observations of unbrauched processes having the aspect of axis cylinders being prolonged to a considerable distance (600 fj, in one case), yet these were found to terminate not in a dark-bordered fibre, but in a network of fibrils.* 138. While it is thus doubtful whether dark -bordered fibres are always immediately connected with cells, it is demonstrable that multitudes of fibres have only an indirect connection with cells, being developed as out- growths from other fibres. Dr. Beale considers that in each such outgrowths have their origin in small neuro- plasmic masses (his "germinal matter"). That is an- other question. The fact here to be insisted on is that we often find groups of cells with only two or three fibres, and groups of fibres where very few cells exist. Schro- der van der Kolk says that in a sturgeon {Accipenser stu- rio) weighing 120 pounds he found the spinal cord scarcely thicker than that of a frog ; the muscles of this fish are enormous, and its motor nerves abundant; yet these nerves entered the cord by roots no thicker than a pig's bristle ; and in the very little gray matter of the cord there was only a cell here and there found after long search. Are we to suppose that these rare cells were the origins of all the motor and sensory nerves ? A similar want of correspondence may be noticed elsewhere. Thus in the spinal cord of the Lamprey my preparations show * Golgi, Sulla struttura della sostanza grizia del Cervello. Arndt, Archivfilr mikros. Anat. 1870, p. 176. Rindfleiscii also traces these processes into the neuroglia (lirf?., 1872, p. 453). "Deiters, Boddaert, and other observers have stated that one dark-bordered nerve-fibre enters each cell My own observations lead me to conclude that all the fibres are composed of the same material, but that one fibre does not divide until it has passed some distance from the cell, while others give off branches much closer to it." — Beale, Bioplasm, p. 189. THE NERVOUS MECHANISM. 287 very few cells in any of the sections, and numerous sec- tions show none at all. Stieda counted only eight to ten cells in each horn of some osseous fishes, except at the places where the spinal roots emerged. In the eel and cod he found parts of the cord quite free from cells, and in other parts found two, three, never more than ten. In birds he counted from twenty-five to thirty. Par- ticular attention is called to this fact of the eel's cord being thus deficient, because every one knows the ener- getic reflex action of that cord, each separate segment of which responds to peripheral stimulation. It may indeed be urged that these few cells were the origin of all the fibres, the latter having multiplied by the well-known process of subdivision ; and in support of this view the fact may be cited of the colossal fibres of the electric fishes, each of which divides into five-and- twenty fibres, and in the electric eel each fibre is said by Max Schultze to divide into a million of fibrils. But I interpret this fact otherwise. It seems to me to prove nothing more than that the neuroplasm has differentiated into few cells and many fibres. And my opinion is grounded on the evidence of Development, presently to be adduced. If we find (and this we do find) fibres making their appearance anywhere before multipolar cells appear, tlie question is settled. 139. Dr. Beale regards the large caudate cells of the centres as different organites from the oval and pyriform cells, and thinks they are probably stations through wliich fibres having different origins merely pass, and change their directions ; and Max Schultze says that no single fibril has been found to have a central origin ; every fibril arises at the periphery, and passes through a cell, which is thus crossed by different fibrils.* (Comp. Fig. 17.) * Beale, Bioplasm, p. 177. Max Sciu.'mze, in Strieker's Ilandbueh, p. 134. Com\>.^T:ihi.iS(i, Nervenprimitiv-Faser,\}.\ZZ. Aksbt, Archiv 288 THE niYsiCAL basis of mind. The teaching of Development is on this point of su- preme importance. Unhappily there has not yet been a sullicient collection of systematic observations to enable us to speak very confidently as to the successive stages, but some negative evidence tliere is. The changes take place with great rapidity, and the earliest stages have hardly been observed at all. Although for several succes- sive years I watched the development of tadpoles, the difficulties were so great, and the ajDpearances so perplex- ing, that the only benefit I derived was that of being able the better to understand the more successful investiga- tions of others. Four or five days after fecundation is the earliest period of which I have any recorded observation ; at this period the cerebral substance appeared as a finely granular matter, having numerous lines of segmentation marking it off into somewhat spherical and oval masses, interspersed with large granules and fat globules. Here and there hyaline substance appeared between the seg- ments. Similar observations have since been recorded by Charles Robin in the earliest stages of the Triton.* He says that when the external gills presented their first indications, nuclei appeared, each surrounded by a rim of hyaline substance, from which a pale filament was pro- longed at one end, sometimes one at both ends, and this filament subdivided as it grew in length until it had all the appearance of an axis cylinder. This, however, he says, is a striation, not a fibrillation ; he refuses to admit that the axis cylinder is a bundle of fibrils. He further notices the simultaneous appearance of amorphous sub- fiir mikros. Anat., 1868, p. 512 ; and 1869, p. 237. "Weighty as these authorities are, their view is questionable — firstly, because tlie forms of these cells are too constant and definite in particular places to result from the union of fibrils coming from various origins ; but secondly, and mainly, because the teaching of Development is opposed to it. * KoBiN, A'/iat. et Physiol. Ccllulaires, p. 335. THE NERVOUS MECHANISM. 289 stance ; and as this is several days before there is any trace of a ^jm mater, or proper connective tissue, he urges this among the many considerations which should prevent the identification of neuroglia with connective tissue. In a very young embryo of a mole (I could not deter- mine its age) the cortex of the hemispheres showed granular amorphous substance, in whicli were embedded spherical masses of somewhat paler color, which had no nuclei, and were therefore not cells. Besides these, there were nucleated masses (apolar cells, therefore) and more developed cells, unipolar, bipolar, and tri polar. Not a trace of a nerve-tibre was visible. In agreement with this are the observations of Masius and Van Lair, who cut out a portion of the spinal cord in a frog, and observed the regenerated tissue after the lapse of a month. It con- tained apolar, bipolar, and multipolar cells, together with " corpuscles without processes, for the most part larger than the cells, and appearing to be mere agglomerations of granules," — these latter I suppose to have been what I describe as segmentations of the undeveloped sub- stance. Gray fibres, with a few varicose fibres, also appeared.* 140. Tlie admirable investigations of Franz Boll have given tliese observations a new significance. He finds in the cerebral substance of the chick on the third or fourth day of incubation a well-marked separation between the neuroglia and nerve-tissue joroper. Fig. 24, A, represents three nerve-cells, each with its nucleus and nucleolus, and each surrounded with its layer of neuroplasm. The other four masses he regards as nuclei of connective tissue. Three days later tlie distinction between the two is more marked (Fig. 24, B). Not only liavc tlic nerve-cells ac- quired an increase of neuroplasm, tliey also present indi- cations of their future processes, which at tlie twell'tli day * Archives dc Physiologic, 1872, p. 268. VOL. III. 13 8 290 THE I'lIVSICAL BASIS OF MIND. are varicose (Fig. 24, C). (All this while the connective corpuscles remain unchanged.) Although Boll Mas unable to trace one of these processes into nerve-fibres, he has little doubt that they do ultimately become (unite with ?) axis cylinders. It is difficult to reconcile such observations with the hypothesis of the cells being simply points of reunion of fibrils. We see here multipolar cells before any fibrils appear. Eespecting the development of the white sub- stance, i. e. the nerve-fibres, Boll remarks that in the corpus callosiim of the chick the first differentiation re- sembles that of the gray substance. The polygonal and spindle-shaped cells represented in Fig. 25, A, are respectively starting-points of connective and neural tissues. The spindle-shaped cells elongate, and rapidly become bipolar. This is supposed to result in the whole cell becoming transformed into a fibre, the nucleus and nucleolus vanishing ; but the transformation is so rapid that he confesses that he was unable to trace its stages ; all that can positively be asserted is that one or two days after the appearance presented in Fig. 25, B, the aspect changes to that of fibrils. The columns of polygonal cells between which run these fibrils, he re- gards as the connective corpuscles described by several anatomists in the white substance both of brain and cord, and which are sometimes declared to be multipolar nerve- cells.* 141. Dr. Schmidt's observations on the human embryo were of course on tissue at a very much later stage. * The fact of the existence of cells in the white substance is one which is very difficult of interpretation on the current hypotheses. The cells are found in regular columns and irregularly scattered. Boll thinks that while in the white substance of both cerebrum and cerebellum there are trae nerve-cells as well as connective corpuscles, in the cord there are only the latter. But hitherto there has been no decisive test by which a nerve- cell can be distinguished from a connective corpuscle. THE NERVOUS MECHANISM. 291 According to him, the fibrils of the axis cylinders are formed by the linear disposition and consolidation of elementary granules. The fibrils thus formed are sepa- rated by interfibrillar granules which in time become fibrils. Not earlier than three montlis and a half does the forma- tion of individual axis cylinders begin by the aggregation Fig. 24. — Embryonic nerve-cells. Fig. 25. — Embryonic nerre-fihres. 292 TIIK I'llVslCAL r.ASIS OF MIXD. of these fibrils into minute bundles, whicli are subse- quently surrounded by a delicate slieatb* 142. With resjiect to the transition ol' the spindle- shaped cells into librils, since there is a gap in the obser- vations of Boll, and since those of Schmidt are subsequent to the disappearance of the cells, and in both cases all trace of nucleus has disappeared, I suggest that vre have here an analogy with what Weismann has recorded of the metamorphoses of insects. In the very remarkable me- moir of that investigator t it is shown that the metamor- phoses do not take place by a gradual modification of the existing organs and tissues, but by a resolution of these into their elements, and a reconstruction of their elements into tissues and organs. The muscles, nerves, trachea?, and alimentary canal, undergo what may be called a fatty degeneration, and pass thence into a mere blastema. It is out of these ruins of the old tissues that the neiv tisstics are reconstructed. On the fourth day the body of the pupa is filled with a fluid mass — a plasma composed of blood and dissolved tissues. The subsequent develop- ment is thus in all essential resj)ects a repetition of that which originally took place in the ovum. I * Monthly Journal of Micros. Science, XI. 219. This accords with what KuPFFER saj-s respecting the entire absence of cells in the earliest stages obser^-ed by him in the sheep. The Avhite substance of the spinal cord he describes as soft, transparent, and gelatinous, in which dark points are visible ; these dark points are seen in longitudinal sections to arise from the fibrillation of the substance. — Bidder und Kupffer, Op. cit., p. 111. + AVeismanx, Die nachcrahryonalc Eniivick. ckr Mtcscideji, in the Zcit- schrifl fur JFissen. Zoolorjir, 1864, Bd. XIV. Heft III. + The suggestion in the text has since received a striking confirmation in the observations of Sigmund Mayer on the regeneration of nerves. The nerve when divided rapidly undergoes fatty degeneration, which is succeeded by a transformation of the myeline and axis cylinder into a homogeneous mass ; in this resolved pulp new longitudinal lines of divis- ion appear, which subsefjuently become new fibres, and new nuclei are developed in the remains of the untransformed substance. — Archiv fur Psychiatric, Bd. VI. Heft II. THE NERVOUS MECHANISM. 293 Two points are especially noticeable : First, that in this resolved mass of granules and fat globules there quickly appear large globular masses which develop a fine mem- brane, and subsequently nuclei. A glance at the figure 51 of Weismann's plates reveals the close resemblance to the earliest stages of nerve-cells ; and the whole process recalls the regeneration of nerves and nerve-centres after their fatty degeneration. Secondly, the nerves reappear in their proper places in the new muscles, and this at a time when the nerve-cen- tres are still unformed ; so that the luliole pcriijhcral sys- tem is completely ixhuilt in absolute independence of the central system. The idea, therefore, that nerve-fibres are the products of ganglia must be relinquished. This idea is further discountenanced by Boll's observations, which show that the fibre-cells are from the first different from the ganglionic cells ; and by the observations of Foster and Balfour, that " fibres are present in the white sub- stance on the third day of incubation " ; whereas cell pro- cesses do not appear until the eighth day. Foster and Bal- four are inclined to believe " that even on the seventh day it is not possible to trace any connection between the cells and fibres." In the later stages, the connection is perhaps established.* * Strong confirmation of various statements in the text, since they were written, has been furnished by the researclies of Eiciihoust, pub- lished in Virchow's Archiv, LXIV. Our knowledge of the development of nerve-tissue in human embryos is so scanty that these researches have a great value. Eichuokst describes the striation of the cells in the cord to begin only at the fourth month ; up to this time they are, what I find most invertebrate cells to Ije, gi-anular, not fibrillar. Theie is very slight branching of the cell processes until the ninth or tenth month, when the multipolar aspect first appears ; the cells are unipolar up to the end of tiie fourth month. The connection between the white columns and the gray columns is very loose up to tiie fifth mouth ; and tlie two are easily separated. Subseriucntly the union is closer. The substance of the white columns readily separates into bundles and fibres, but that of the gray 294 THE niYSiCAL basis of mind. 143. "We may, I think, conclude from all this that in the higher vertebrates the white substance of brain and cord is not the direct product of the gray substance ; in other words, that here nerve-fibres, even if subsecjuently in connection with the ganglionic cells, have an inde- pendent origin. They may grow towards and blend with cell processes ; they are not prolongations of those pro- cesses. They may be identical in structure and property, as one muscle is identical with another, but one is not the parent of the other. 14-4. Sigmund Mayer emphatically declares that in no instance has he traced a cell process developed into a dark-bordered nerve-fibre. The process, he says, may often be traced for a certain distance alongside of a fibre ; but it then suddenly ceases, whereas the fibre is seen con- tinuing its course unaltered. Still more conclusive is the evidence afforded by nerves having only very few fibres (2-4 sometimes in the frog), which have, nevertlieless, a liberal supply of cells, visible without preparation. Valentin counted twenty-four cells in a nerve M'hich had but two fibres.* Now although it is possible to columns falls into a gi-annlar detritus if attempted to be teased out with needles. But after the fifth month this is no longet so. Instead of a granular detritus there appears a network of fine fibres and fibrils. Al- though the white posterior columns are developed before the fifth month, not a single cell can be seen in the posterior gray columns until the second half of the ninth month. (Yet the fibres are imagined to arise in the cells !) The passage from the granular to the fibrillar state is the same in the cell substance and the neuroglia. The nerve-fibre, as distin- guished from a naked axis cylinder, does not appear till the fourth montli. It is at first a bipolar prolongation of the nucleus. As it elongates, the nucleus seems to sit on it, and so loosely that it is easily shifted away by pressure on the covering glass. Finally the fibre separates entirely from the nucleus, and tJien begins to clothe itself with the medullary sheatli. Very curious is the observation that so long as the axis cylinder is naked it is never varicose, but with the development of the medulla the primi- tive axis becomes fluid. * Mayer, Op. cit., 393. I cannot, however, agree with Mayer when THE NERVOUS MECHANISM. 295 explain the presence of numerous fibres with rare cells either as due to subdivisions of fibres, or to the fibres having cells elsewhere for their origin, it is not thus that Ave can explain the presence of numerous cells which have no fibres developed from their processes. 145. With regard to this observation of the cell pro- cess running alongside of the fibre, the recent researches of Eanvier may throw some light on it. He describes the cells in the spinal ganglia as all unipolar; each single process pursues a more or less winding course as a fibril, often blending with others, till it reaches one of the fibres from the sensory root. It blends with this fibre at the annular constriction of the fibre, becoming liere incorporated with it, so that a T-shaped fibre is the re- sult.* If this should be confirmed, it would reconcile many observations ; but it would greatly disturb all cur- rent interpretations, llanvier remarks that it is no longer tenable to suppose that the ganglionic cell is a centre, sensory or motor, receiving the excitation or sending forth a motor impulse ; for if the fibril issuing from a cell becomes laterally soldered to a nerve-fibre, there is no possibility of saying in which direction this cell receives the excitation, nor in which it transmits the impulse. lie says that the continuity of a nerve-fibre with a cell has never been distinctly shown (p. 395) ; in the Invertebrata and in the Electric fishes such a continuity is undeniable ; and it has occasionally been seen in Vertebrata. * Kanvier, in the Comptes Rendus, 1875, Vol. LXXXI. p. 1270. This observation throws light on the fact that cell processes iuo soinetiiiics seen entering nerve-roots (§ 124). The very remarkable okservations of Mr. F. Balfour, (hi the Develop- ment of the Spinal Nerves in Elasmohranch Fishes (Philus. Trans., Vol. CLXVI. p. 1), show that the spinal root, ganglion, and nerve-trunk arise from histologi('!il changes in a mass of cells at first all alike ; not that ganglion-cells are formed and from their jiroccsses elongate into fibres. The nerve, he says, forms a continuation of its root rather than of its ganglion (p. ISl) ; which aci^ords with Hanvi Kit's view. 296 THE niYsiCAL basis of mind. 14G. We have seen good reason to conclude that the essential element of tlie nerve — the axis cylinder — is the same substance as the neuroplasm which forms the essential element of the cell. At any rate, we are quite certain that the cell process is neuroplasm. On this ground there is no difficulty in understanding that a cell process may sometimes be drawn out into an axis cylin- der (as indeed we see to be the case in the invertebrata and electric fishes) ; while again in numerous other cases the nerve-fibre has an independent origin, being, in short, a differentiation from the neuroplasm which has become a "fibre instead of a cell. It is clear from the observations of Eouget on Development, and of Sigmund Mayer on Regeneration, that fibres, nuclei, and cells become differ- entiated from the same neuroplasm, those portions which are not converted into fibres remaining first as lumps of neuroplasm, then acquiring a nucleus, and some of these passing into cells. I mean that between fibres, nuclei, and cells there are only morphological differences in an identical neuroplasm.* If this is in any degree true, it will not only explain how fresh fibres may be devel- oped in the course of fibres, branching from them as from trunks, and branchlets from branchlets, twigs from branchlets, the same conditions of growth being present throughout ; it will also completely modify the notion of any physiological distinction between cell and fibre greater than can be assigned to the morphological differ- ences. We shall then no longer suppose that the cell is the fountain whence the fibre draws its nutrition and its " force " ; and this will be equally the case even if we admit that a cell is, so to speak, the germ from which a whole plexus of fibres was evolved, for no one will pretend that the " force " of an organism is directly de- * In the I/andbuch der menschlichen jinatomie of W. Krause, which has just appeared, I am pleased to find a similar view, p. 376. THE NERVOUS MECHANISM. 297 lived from the ovum, or that the ovum nourishes the organism. 147. At this stage of the discussion it is needful to consider a point which will spontaneously occur to every instructed reader, I mean the interesting i'act discovered by Dr. Waller, that wlien a sensory root was divided, the portion which was still in connection with the ganglion remained unaltered, whereas the portion whicli was only in connection with the spinal cord degenerated ; and vice versa, wdien a motor root was divided, the portion con- nected with the cord remained unaltered, tlie portion severed from the cord degenerated. The observation has been frequently confirmed, and the conclusion drawn has been that the cells in the ganglion of the posterior root are the nutritive centres of posterior nerves, the cells in the anterior horn of the cord being the nutritive centres of the anterior nerves. Another interpretation is how- ever needed, the more so because the fact is not constant.* True of some nerves, it is not true of others. Yulpian found that when he cut out a portion of the lingual nerve, and transplanted it by grafting under the skin of the groin, where of course it was entirely removed from all ganglionic influence, it degenerated, but it also regen- erated. Pathological observations convinced Meissner that the ganglia are wholly destitute of an influence on tlie nutrition of the vagus ; and Schiff proved experi- * On this point consult Axel Key and Rktzius, in the Jrchiv fiir nxikros. Anal., 1873, p. 308, where the nutritive disturbance is assigned to tlie fact that the lymph can no longer take its normal course. Wal- LElt's oVjservations on the degeneration of the optic nerves, with preserva- tion of the integrity of the retina, after division of the nerves {Pror.cedimjs of Ilotjfxl Society, 1856, p. 10), cannot he urged in support of his view, because Beulin and Lebeut's observations are directly contradictory of his. Sakmisch und Giiaefe, Handbach dcr Augenlieilkundc, II. 346. It is said by KuENCiiEr, that if the nerves be divided, .so as to prevent disturbances in the circulation, no peripheral degeneration takes place (cit(!d by Engel-MANX in PJliigers Archiv, 1875, p. 477). 23* 298 THE niYSICAL BASIS OF MIND. mentally that other ganglia were e(|ually inoperative, since motor nerves could Ije separated from the Ri)inal cord without degeneration.* Not however to insist on this, nor on the other facts of regeneration, in the ahsence of ganglionic influence, let us remark tliat Dr. Waller's examples would not be conclusive unless the teaching ol" Embryology could be disproved. That nerves degenerate when separated from ganglia is a fact ; but it is also a fact that muscles degenerate when separated from a nerve-centre ; yet we do not suppose the nerve-centre to nourish the muscles. And against the fact that the sensory nerve remains unaltered only in that portion which is connected with the ganglion, we must oppose the observations of Kolliker and Schwalbe,! wlio aftirm that none of the fibres which enter the posterior columns ( of the spinal cord have any direct connection with the cells of the ganglion on the jDosterior root. The cells of this ganglion they declare to be unipolar (in the higher;/ vertebrates), and the fibres in connection with these cellsj are not those which pass to the cord, but all of them pass to the periphery. According to Eanvier, the fibres from the cells join the fibres of the posterior root. Schwalbe found that if the spinal nerve be firmly grasped and steadily drawn, it will often be pulled from its sheath, and the ganglion laid bare ;+ in this ganglion all the cells are found undisturbed, Avhich could not be the case had fibres from those cells entered the cord, since the traction would necessarily have disturbed them. * SCHIFF, Lehrbuch der Physiologic, pp. 120, 121. t Kolliker, Gewehelchrc, 317. Schwalbe, Archivfiir mikros. Anat., 1868, p. 51. X I was first shown this in 1858 by the late Prof. Haeless in Munich, who at the same time showed me that the nerve thus bared of its sheath, if left some hours in gastric juice, split up into regular discs, like the sarcous elements of muscles. THE NERVOUS MECHANISM. 299 RECAPITULATION. 148. At the opening of this chapter mention was made of the besetting sin of the analytical tendency, namely, to disregard the elements which provisionally had been set aside, and not restore them in the reconstruction of a synthetical explanation. Familiar experiences tell us that a stimulus applied to the skin is followed by a mus- cular movement, or a glandular secretion ; sometimes this takes place without any conscious sensation ; sometimes we are distinctly conscious of the stimulus ; and some- times we consciously will the movement. These facts the physiologist tries to unravel, and to trace the complicated processes involved. The neurologist of course confines himself exclusively to the neural processes ; all the other processes are provisionally left out of account. But not only so : the analytical tendency is carried further, and even in the neural process the organs are neglected for the sake of tlie nervous tissue, and the nervous tis- sue for the sake of the ncrvc-cell. The consequence has been that we have an explanation offered us which runs thus : — 149. The nerve-cell is the supreme element, the origin (jf the nerve-fibre, and the fountain of nerve-force. The cells are connected one with another by means of fibres, and with muscles, glands, and centres also by means of fibres, which are merely channels for the nerve-force. A stimulus at tlie surface is carried by a sensory fibre to a cell in the centre ; from that point it is carried l)y another fibre to another cell ; and from that by a third fibre to a muscle : a reflex contraction results. This is the elemen- tary " nervous arc." But this arc has also higher arcs with which it is in connection : the sen.sory cell besides sending a fibre directly to a motor cell, also sends one upwards to the cerebral centres ; and here again there is 300 THE PHYSICAL BASIS OF MIND. a nervous arc, so that the cerebral centre sends down an impulse on the motor cells, and the contraction which results is due to a volitional impulse. The transmission of the stimulation which in the first case was purely physical, becomes in the latter case psychical. The sen- sory impression is in one cell transformed into a sensa- tion, in another cell into an idea, in a third cell into a rolitioji. 150. This course is described with a precision and a confidence which induces the inexperienced reader to sup- pose that it is tlie transcript of actual observation. 1 venture to say that it is imagmary from beginning to end. I do not affirm that no such course is pursued, I only say no such course was ever demonstrated, but that at every stage the requisite facts of observation are either incom- plete or contradictory. First, be it noted that the actions to be explained are never the actions of organs so simple as the description sets forth. It is not by single fibres and cells that the stimulus is effected, but by complex nerves and complex centres. Only by a diagrammatic artifice can the fibre represent the nerve, and the cell the centre. In reality the cells of the centre (supposing them to be the onli/ agents) act in groups, and Anatomy should therefore show them to be mutually united in groups — which is what no Anatomy has succeeded in showing, unless the Neuroglia be called upon. Secondly, be it noted that the current scheme of the relations between cells and fibres is one founded on physiological postulates, not on observation. Thirdly, much of what is actually observed is very doubtful, because we do not know whether the appearances are normal, or due to modes of preparation and post-mortem changes. We cannot at present say, for instance, whether the fibrillated appear- ance of cell contents and axis cylinder represents the liv- ing structure or not. We may either suppose that the THE NERVOUS MECHANISM. 301 neuroplasmic pulp splits longitudinally into fibres, or that neuroplasmic threads resolve themselves into a homo- geneous pulp — the axis cylinder may be a condensation of many fibrils, or the fibrils may be a resolution of the substance. 151. Let us contrast step by step the Imaginary Anat- omy found in the text-books with the Objective Anatomy as at present disclosed by the researches of all the chief workers. Imaginary Anatomy assumes that the sensory fibre passes from a surface into the cells of the posterior horn of the spinal cord. Objective Anatomy sees the fibre pass into the gray substance, but declares that no direct entrance of a fibre into a cell is there visible. Imaginary Anatom.y assumes that from the sensory cells of the gray substance pass fibres in connection with the motor cells of the anterior horn, thus forming a direct channel through which the excitation of a sensory cell is transmitted to a motor cell. Objective Anatomy fails to discover any such direct channel — no such fibres are demonstrable. Imaginary Anatomy assumes that from the motor cells issue fibres which descend to the muscles and glands, and carry there the motor impulses and tlie " mandates of the will." Objective Anatomy fails to find at the utmost more than a probability that these cells are continued as fibres, a probability whicli is founded on the rare facts of cell processes having been seen extending into the roots of the nerves, and of a cell process having occa- sionally been seen elsewhere continuous with a dark- bordered fibre. Granting, liowever, tliat this probability represents the fact, we have tlius only one part of tlie "nervous arc" which can be said to have been verified. Imaginary Anatomy further assumes that this nervous arc is connected with cerebral centres by means of fibres going upwards from the posterior cells, and fibres descend- 302 THE PHYSICAL BASIS OF MIND. ing downwards to the anterior cells. Objective Anatomy- sees nothing of the kind. It sees fibres entering the gray substance, and there lost to view in a mass of granular substance, fibrils, neuroblasts, and cells. There may he uninterrupted fibres passing upwards and downwards ; but it is impossible to see them. And if we are told that physiological interpretations demand such a structure, we may fairly ask if this, and this only, is the struc- ture which is adequate to the propagation of excitation ? Now it seems to me that another kind of structure, and one more closely agreeing with what is observed, better answers the demands of Physiology. This will be more evident after the Laws of Nervous Action have been ex- pounded in the succeeding chapter. Meanwhile we may remark that the arrangement of cells and fibres which is imagined as the mechanism of propagation and reflexion is absolutely irreconcilable with the teaching of Experi- ment : for the spinal cord may be cut through anywherej without destruction of the transmission of sensory and motor excitations, provided only a small portion of gray substance be left to establish the continuity of the axis. Divide all the substance of the posterior half in one place, and all the substance of the anterior half in an- other, yet so long as there is a portion of gray substance left as a bridge between the lower and upper segments, the transmissiou of sensory and motor excitations will take place. 152. In other essential respects we have to note that the anatomical evidence for the current interpretations is absolutely deficient or contradictory. There is no ade- (l^uate warrant for the assumption that all nerves have their origin in ganglia, all fibres in cells. Such evidence as at present exists is against that supposition, and in favor of the supposition that both cell and fibre are dif- ferentiations of a common neuroplasm, sometimes directly, THE NERVOUS MECHANISM. 303 sometimes indirectly continuous. Fibres, and plexuses of fibres, interspersed with cells irregularly distributed — now singly, now in small groups, now in larger and larger groups — constitute the figured elements of nerve- tissue ; and even if we set aside the amorplious substance as indifferent or subordinate, we have still no ground for assigning the supremacy, much less the sole significance, to the cells. The grounds of this denial have been amply furnished in our exposition. For, let it be granted that nerve-cells are the origins of the fibres and the sources of their nutrition — a point which is eminently disputable — this would in no sense help the physiological hypothesis of the cell as the fountain of Neurility. If the fibre is simply the cell-contents drawn out longitudinally, if its essential element is identical with the essential element of the cell, then we can no more ascribe to the cell the exclusive property of Neurility than we can draw a lump of lead out into a wire, and then ascribe different prop- erties to the thin end and the thick end. But on this point it is needless to speculate, since we have experi- mental evidence proving that tlie nerve-fibre has its Neu- rility even when separated from the cell, or even from the ganglion. 153. It is possible — I do not see sufficient evidence for a stronger assertion — tliat the cells are the nutri- tive sources of the fibres. They may represent the ali- mental rather than the instrumental activities of nervous life. (Compare Problem I. § 42.) My contention is that in any case tliey are not the su])reme elements of the active tissue, and in no sense can they be considered as organs. Only confusion of ideas could for a moment permit sucli language, or could assign central functions to cells wliicli are elements of tissue. If the cell be cred- ited witli such powers anywhere, it must be credited with them everywhere. Now I ask wliat conceivable central 304 THE PHYSICAL basis of mind. function can be ascribed to a cell which terminates the fibre in a peripheral ganglion, or which is merely an en- larsement in the course of a fibre in a nerve-bundle ? Besides the facts already adduced, let attention be called to this : If a nerve-bundle from the siihniucusa of the in- testine be examined, there appear among the fibres many nuclei (neuroblasts), and occasionally cells, unipolar and bipolar. These cells — if we may trust the observations of liouget on the earliest development of nerves, and of Sigmund Mayer on regenerated nerves — are simply more advanced stages of evolution of the neuroblasts ; but what- ever their genesis mav be, there can be nothing in the nature of a central function assigned to them. 154. It may be asked, "What part can we assign to cells in neural actions if they are apolar, unipolar, and even when multipolar, isolated from each other, and from fibres ? I confess that I have no answer ready, not even an hypothesis. Until some rational interpretation of the cell be given we must be content to hold an answer in suspense. "What I would urge is that we are precipitate in assuming that the anatomical connection between one element and another must necessarily be that of a fibre. In a semi-fluid substance, such as neurine, continuity may be perfect without solid fibres : the amorphous substance and the plasmode may as well transmit waves of molecu- lar motion from one part of the tissue to another, and therefore from cell to cell, or from cell to fibre, as a figured substance may. When the posterior root enters the gray substance of the cord, there is no more necessity for its fibres passing directly into the cells of that gray sub- stance, in order to excite their activity, than there is for a wire to pass from the bell to the ear of the servant, who hears the vibrations of the bell through the pulsations of the intervening air upon her tympanum. Look at the structure of the retina, or the cerebellum, and you will THE NERVOUS MECHANISM. 305 find that the ganglionic cells which have processes pass- ing in a direction contrary to that whence the stimulus arrives, have none where continuity of fibre and cell would be indispensable on the current hypothesis. Light stimulates the rods and cones, but there are no nerve- fibres, hitherto discovered, passing from these to the gan- glionic cells ; instead of that there is a ground-substance thickly interspersed with granules and nuclei. From the cells we see processes issue ; to the cells none are seen arriving. So with the cerebellum. The large cells send their processes upwards to the surface; but downwards towards the white substance the processes are lost in the granular layer, which most histologists regard as connec- tive tissue. 155. A mere glance at nervous tissue in any part will show that cells are far from forming the principal constit- uents. In the epidermis or a gland the cell is obviously tlie chief element, forming the bulk of the tissue, and being the characteristic agent. In nerve-tissue, as in connective tissue, the reverse is the case. We must therefore cease to regard the cell as having the impor- tance now attached to it, and must rather throw the emphasis on the fibres and neuroglia. 156. Before quitting this subject let a word be said on the amazing classification wliich has attained wide accept- ance (although rejected by the most eminent authorities), founded on the size of the cells — the large nmltipolar cells being specified as motor, the smaller cells as sensory, while those of an intermediate size are sympathetic. I forbear to dwell on the development of this notion which specifies sensational, ideational, and emotional cells, be- cau.se this does not pretend to have a basis in observation ; whereas there are anatomical facts which give a certain superficial plausi))ility to the original classification. The conception is profoundly unphysiological ; yet, if the ana- 306 THE PHYSICAL BASIS OF MIND. tomical evidence were constant, one might give it another interpretation. The evidence is, however, not constant. Large cells are found in regions assigned to sensory nerves, and small cells in motor regions. In the spinal cord of the tortoise Stieda declares that the so-called motor cells are limited to the cervical and lumbar enlargements ; all the rest of the motor region being absolutely destitute of them.* Again look at the cells of the retina — no one will assign motor functions to them — yet they are the same as those of the cerebellum and the anterior horns of the spinal cord. (It is worth a passing mention that the structure of the nervous parts of the retina more closely resembles that of the cerebellum than of the cerebrum.) 157. While our knowledge of the cell is thus far indeed from having the precision which the text-books display, and in no sense warrants the current physiological inter- pretations, our knowledge of fibres and neuroglia is also too incomplete for theoretic purposes. We know that the axis cylinder is the essential element ; but we are stiU at a loss what part is to be assigned to the medullary sheath. There is indeed a popular hypothesis which pro- nounces it to be the means of insulating the fibre, and thus preserving the isolated conduction of nerve-force. Being of a fatty nature, this insulating office was readily suggested in agreement with the assumption that ISTeuril- ity was Electricity. Now, w^ithout discussing whether Neurihty is or is not Electricity, even admitting the former to be satisfactorily proved, I must remark that the admission still leaves the medullary sheath incapable of fulfilling the supposed office, since not only is there no such sheath in most of the invertebrates and in the sym- pathetic ner\'es of vertebrates, but even in those nerves which have the sheath it is precisely in places w^here the * Stieda, Bau des centralen Neroensystem der AmpMbien und Reptilien, 1875, p. 41. THE NERVOUS MECHANISM. 307 insulation would be most needed — namely, just before the terminations of the fibres in muscles and in centres — that the sheath is absent. This is as if we tried to con- duct water through a pipe which fell short at both ends — before it left the cistern, and before it reached the spot to be watered. If there is a tendency in Neurility to spread wherever it is not insulated by a medullary sheath, then before reaching the centres and the muscles, it nmst, on the insulating hypothesis, dribble away ! 158. The facts expressed in the "law of isolated con- duction " are important, and are difhcult of explanation ; but it is obvious that they cannot be referred to the pres- ence of the medullary sheath. Xor indeed will any in- sight into the propagation of stimulation through the central axis be intelligible until we have reformed our anatomical theories, and taken the Neuroglia into account. The theory which connects every fibre directly with a cell, and every cell with another by anastomosis — even Avere it demonstrated — would not explain tlie law of isolated conduction. Butzke cogently remarks * that such a dis- position of tlie elements should render all neural paths invariable ; whereas the fact is that tliey are very varia- ble. We learn to perform actions, and then we unlearn tliem ; the paths are traversed now in one direction, now in another. Fluctuation is the characteristic of central combinations. And for this fluctuating combination of elements a corresponding diversity is required in the pos- sible channels. This seems to be furnished by the net- work of tlie Neuroglia. See the representation copied from Butzke's plate, and note how the cell-process blends with the meshes of the Neuroglia. Is it fanciful to regard tliis network of flbrils as having somewhat the relation of capillaries to blood-vessels ? iJid we not experimentally * Butzke, in Arcldv fur mikroslcojnsclic Anatomic, Bd. III. I left 3, p. 596. 308 THE rilYSICAL BASIS OF MIND. know that the capillaries are terminal hlood-vessels, we sliould not suspect it from mere examination of the structure. 159. Having insisted that our knowledge is insufficient for any explanation of the " law of isolated conduction," I can only suggest a path of research which may lead to some result. What we know is that some stimulations are propagated from one end of the cerebro-spinal axis to the other in definitely restricted paths, while others are Fig. 26. — Nerve-cells with processes terminating in neuroglia. irradiated along many paths. In the succeeding chapter this will be more fully considered ; what we have here to note is that the manifold irradiations of a stimulation have an anatomical substratum in the manifold sub- divisions of the network of fibrils and the amorphous substance in which they penetrate. 160. In conclusion, I would say, let no one place a too great confidence in the reigning doctrines respecting the elementary structure of the nervous system, but accept every statement as a "working hypothesis" which has its value in so far as it links together verified facts, or THE NERVOUS MECHANISM. 309 suggests new researcli, but is wholly without value in so far as it is made a basis of deductions not otherwise verified. Hypotheses are indispensable to research, but they must be accompanied by vigilant scepticism. Imagi- nation is only an enemy to Science when Scepticism is asleep. 310 THE niYsicAL basis of mind. CHAPTEE VIII. THE LAWS OF NERVOUS ACTIVITY. 161. The foregoing remarks have bad tlie object of sbowiDg bow bttle substantial aid Psycbology can at present derive from wbat is known of the elementary structure of the nervous system, indispensable as an ac- curate knowledge of that structure must be to a com- plete analysis of its functions. This caution has been specially addressed to those medical and psychological students whose researches leave them insufficient leisure to pursue microscopical investigations for themselves, and who are therefore forced to rely on second-hand knowl- edge, which is usually defective in the many qualify- ing considerations which keep scepticism vigilant. Eely- ing on positive statements, and delusive diagrams which only display what the observer imagines, not what he actually sees, the}'' construct on such data theories of dis- ease, or of mental processes ; or else they translate ob- served facts into tlie terms of this imaginary anatomy, and offer the translation as a new contribution to Science. 162. But little aid as can at present be derived from the teaching of the microscope, some aid Psychology may even now derive from it. The teaching will often serve, for instance, to correct the precipitate conclusions of subjective analysis, which present artificial distinctions as real distinctions, separating what Nature has united. It will show certain organic connections not previously suspected ; and since whatever is organically connected THE NERVOUS MECHANISM. 311 cannot functionally be separated, such sharply marked analytical distinctions as those of periphery and centre, or of sensation and motion, must be only regarded as artificial aids. The demonstration of the indissoluble union of the tissues is a demonstration of their functional co-operation. So also the anatomical demonstration of the similarity and continuity of all parts of the central system sets aside the analytical separation of one centre from another, except as a convenient artifice ; proving that cerebral substance is one with spinal substance, having the same properties, the same laws of action. For the present. Psychology must seek objective aid from Physiology and Pathology rather than from ele- mentary Anatomy. In the paragraphs which are to fol- low I shall endeavor to select the chief laws of nervous activity which the researches of physiologists and patholo- gists disclose. By these laws we may direct and control psychological research. THE ENERGY OF NEURILITY. 163. Vitality is characterized by incessant molecular movement, both of composition and decomposition, in tlie building up of structure and the liberation of energy. The life of every organism is a complex of changes, each of which directly or indirectly affects the statical and dynamical relations, each being the resultant of many co-operant forces. In the nourishment of every organite there is an accumulation of molecular teiiKion, that is to say, stored-up energy in a latent state, ready to be expended in the activity of that organite ; and this ex- penditure may take place in a steady flow, or in a sud- den gush. The molecular movements under one aspect may be called convergent, or forviativc: they liuild the structure, and tend to the state of equilibrium which :U2 THE PHYSICAL BASIS OF MIND. ■\ve call the statical condition of tlic organite, i. e. the condition in Mliich it is not active, but ready to act. Perfect equilibrium is of course never attained, owing to the incessant molecular change : indeed Life is incon- sistent -with complete repose. Under another aspect the molecular movements may be called di>ic]iar(jinaw of Arrest, in his paper on " Stamnicrinfj with other Organs than those of Speech," IJn'tish Medical Journal, 1808, Vol. II. p. 437, reprinted in his Clinical Lectures and Essaya, 1875, p. 77. 334 THE niYSIGAL BASIS OF MIND. another. If the foreleg of a headless frog be irritated, the hind-leg will also be moved by the stimulation ; or vice versa. Here there has been a propagation of the ex- citation in either direction. But if while the legs are thus irritated, and the centres are ready to discharge, an- other and more powerful irritation reach the centre — say by pinching the skin of the back — there will be no discharge on the legs. If the vagus be irritated, tlie heart is arrested ; but this does not take place if at the same time, or immediately before, the foot has been sharply pinched. A few gentle taps on the abdomen suffice to stop the heart ; but if a drop of acid be previously placed on the skin, we tap in vain, the heart continues to beat. Brown Sequard cites several cases in which convulsions were arrested by irritation of sensitive surfaces ; * and Dr. Crichton Browne records a case of a patient in whom there was abolition of spinal reflex, due to cerebral irrita- tion : tickling the soles of the feet, or pricking the toes, which normally excites reflex movements, in this case excited none whatever. " This seems to prove that nerv^e currents, set in motion by irritation of the brain, or some of its convolutions, transmitted down the cord, may in- hibit reflex action."! Examples might indefinitely be multiplied. Pinch the skin of a rabbit between the eyes, and you will observe that pulse and respiration are slack- ened ; but if the tail, which is very sensitive, be pinched, this slackening is only momentary, and is succeeded by a quickening — unless the pain be great. Even the effect of intense pain may be neutralized by stimulating the vagus — just as the effect of stimulating the vagus may be neutralized by pain. Claude Bernard found that having dropped ammonia on the eyelid of a dog, the pain caused a convulsive closure of the lid ; but * Archwes de Physiol., 1868, p. 157. t TVcst Riding Lunatic Asylum Reports, 1874, p. 200. THE NERVOUS MECHANISM. 335 on galvanizing the vagus, the lid opened again, to be closed when the galvanism ceased* When the heart is beating faintly (as in syncope), any irritating vapor ap- plied to the nostrils will cause a more energetic pulsa- tion ; yet a very irritating vapor lowers the action of the heart beating normally, and will even arrest that of a rabbit. Over-stimulation has almost always the opposite effect of moderate stimulation. 192. "While there seems every reason to believe that an excitation necessarily affects the whole cerebro-spinal axis, there is no doubt that there is a certain restriction of this irradiation to definite paths, i. e. the responsive discharge is confined to definite groups. Some of tliese restrictions are connate pathways : we bring tliem witli us at birtli ; but most of them 8,re pathways acquired after birth. The boy who sheds tears at parting from his mother when he goes to school, will shed no tears when he parts from her to go to college, nay, perhaps will shed none when he parts from her forever : not that his love has lessened, but that the idea of such expression of it as "unmanly" has become an organized tendency and arrests the tears. A youth of southern race, who has not learned to be ashamed of tears, weeps freely under such circum- stances. 193. The pathways organized at birth are not many. Examples are the inspiration which follows expiration ; the movements of coughing when the larynx is tickled ; the movements of swallowing, sneezing, etc. Even these may be arrested for a brief time by what is called "the will"; but when once the discharge begins in any part of the mechanism, the whole group is necessarily involved and the action is then inevitable. Many of the reflex actions which are universal are nevertlieless acquired. "Winking, for instance, when an object approaches the * Claude Bernakd, Syslivic Ncrvcux, I. 383. 33 G THE PHYSICAL BASIS OF MIND. eye, is universal among us, but is never seen in infants, nor in animals. It is even doubtful whether the draw- ing up of the leg when the toes are pinched is not an acquired reflex. Doubtful, I mean, in this sense, that although the fact of non-withdrawal is observable in infants, who cannot localize their sensations, tliis may be due to the imperfect development of their nervous sys- tem. Mr. Spalding has proved that although the callow bird cannot fly, the mechanism of flight is no sooner developed than the action follows at once, without any previous tentative experiences. 194. By experience we learn to restrict the paths of irradiation, so as to wink witli one eye while the other is unmoved, to bend one finger wdiile the rest are extended, to move one limb, or* one group of muscles, while the others are at rest ; in short, to execute any one particular action, and not at the same time agitate superfluously many other organs. The boy when first learning to write is unable to prevent the simultaneous motions of tongue and legs, which are ludicrously irrelevant to the purpose of writing ; but he learns to keep all his organs in sub- jection, and only the eyes and hands active.* An anal- ogous restriction takes place in thinking. A train of thought is kept up by the exclusion of all suggestions which are not pertinent ; and the power of the thinker is precisely this power of concentration. THE HYPOTHESIS OF INHIBITORY CENTRES. 195. The facts and their formulated laws which have just.been adduced furnish a sufficient explanation of all the phenomena of arrest which of late years have been detached * See the excellent remarks of Dr. Lauder Bruxton on this point in his paper on Inhibition in the West Riding Lunatic Asylum Reports, 1874, p. 180. THE NERVOUS MECHANISM. 337 and assigned to a special mechanism of inliibitory nerves and centres. In spite of the eminent authorities counte- nancing the hypothesis of a particuhir set of inhibitory nerves, and particular centres of inhibition, I must con- fess that the hypothesis appears to me inadmissible ; and that I side with those physiologists who hold that each nerve and each centre has its inhibitory action. Indeed, if the action of arrest be, as I maintain, only another aspect of the action of discharge, the result of the conflict of forces, to say that all centres have the property of ex- citation, is to say that all have the properties of discharge and arrest : the discharge is only the resultant of the con- flict along the line of least resistance ; the arrest is the c'ffect of the conflict along the line of greatest resistance. The observed phenomena of arrest are so varied and nu- merous that the npliolders of the inhibitory hypothesis have been forced to invent not only arresting centres, but centres which arrest these arresting centres ! Dr. Lauder Brunton candidly remarks : " At present our notions of nervous action seem to be getting as involved as the Ptolemaic system of astronomy, and just as ei)icyelos became heaped upon cycles, so nerve-centres arc being added to nerve-centres. And yet, clumsy though the sys- tem may be, it serves at present a useful purpose, and may give real aid until a better is discovered." I do not think a Copernicus is needed to discover a better. The Law of Arrest as a general neural law suffices, wlien the right conception of a wntrc as a i)hysiological rather than an anatomical designation is admitted. (See p. 173.) 19G. It would be out of place liere to consider the con- flicting evidence wliich at present renders the question of the movements of the heart one of the most unsatis- factory in the whole range of experimental jiliysiology. After devoting much time to it, and after writing a long chapter on it, I suppress wliat I had written, and content VOL. III. 15 V 338 THE PHYSICAL BASIS OF MIND. myself with tlie statement that no advantage whatever is derived from the hypothesis of a special mechanism of arrest, unless perhaps in giving a temporary precision to the direction of research. I mean that the search for special centres may lead to the discovery of the partic- ular paths to which an impulse is restricted in any one action : as, for instance, the vagus in retarding the pulsa- tion of the heart. If the cerebrum can determine a move- ment, and combine various movements, it is a centre of arrest ; if the cerebellum can determine and regulate movements, it is a centre of arrest ; if the medulla oblon- gata can determine and regulate movements, it is a centre of arrest ; if the medulla spinalis can determine and com- bine movements, it is a centre of arrest ; if a nerve can dilate a constricted blood-vessel, or constrict a dilated one, it is a nerve of arrest. In other words, every centre exerts its action either in discharging, or in arresting the discharge of some other centre. The physiological process of Arrest may be physically interpreted as Interference ;* not that the process in nerve-tissue is to be understood as the same as that ob- served in fluids, or that the metaphor of neural waves is to be taken for more than an intelligible picturing of the process ; the difference in the two agents forbids our admitting the resemblance to be more than analogical. Thus interpreted, however, we see that not only will one centre arrest the action of another, but one nerve may be made to arrest itself! I mean that, under similar condi- tions of interference, the stimulation which normally fol- lows on external stimulus may be inhibited by a previous, or a counter stimulation. Thus the nerve which will be * The interesting question of interference lias been experimentally treated by "VYundt in his recently published Meclianik der Kerven, 1876, and theoretically as wave-movement by Medem, Grundziige ciner exakten Psychologic, 1876. THE NERVOUS MECHANISM. 339 stimulated by a chemical or mechanical stimulus, wholly fails to react if a constant current is passing through it, although this constant current does not itself cause a con- stant contraction. Eemove the electrodes, and then the chemical or mechanical stimulus takes effect. Or the experiment may be reversed : let the nerve be placed in a saline solution, and the muscles will be at once thrown into violent contraction ; if the electrodes are now applied to the nerve, the contractions suddenly cease, to begin again directly the electrodes are removed. ANATOMICAL INTERPRETATION OF THE LAWS. 197. The problem for the anatomist is twofold : First, given the organ, he has to determine its function, or vice versa, given the part of an organ, to determine its func- tional relation ; secondly, given the function, he has to determine its organ. The structural and functional rela- tions of nerves and centres have been ascertained in a general way ; we are quite sure that the posterior nerves carry excitations from sensitive surfaces, that the anterior nerves carry excitations to muscles and glands ; and that the central gray substance not only reflects a sensory exci- tation as a motor excitation, but propagates an excitation along the whole cerebro-spinal axis. But when we come to a more minute analysis of the functional activities, and endeavor to assign their respective values to each part of the organic mechanism, the excessiv'e complexity and deli- cacy of the mechanism baffles research. We are forced to grope our way ; and the light of tlie hypothetic lamps whicli we hold aloft as often misdirects as helps us. The imaginary anatomy which at present gains acceptance, no doubt seems to simplify explanations ; but this seeming turns out to be illusory when closely examined. The imagined arrangement of fibres and cells we have seen to 340 THE PHYSICAL BASIS OF MIND. be not in agreement with observation ; and were it demon- strable, it would not account for the laws of propagation. Suppose sensory fibres to terminate in cells, and fibres from these to pass upivards to other sensory cells and transversely to motor cells, how in such a connected sys- tem could irradiations take jjlace, if the law of isolated conduction were true ? And how could isolated conduc- tion take place, if the excitation of a part were necessa- rily the excitation of the whole? Why, for 'example, is pain not always irradiated ? Why is it even localized in particular spots, determining movements in particular muscles ; and when irradiation takes place, why is it cir- cumscribed, or — and this is very noteworthy — mani- fested in two widely difierent places, the intercostal and trigeminal nerves ? Why does the irritation of intestinal worms manifest itself now by troubles of vision, now by noises in the ear, and now by convulsions ? 198. Answers to such questions must be sought else- where. Our first search should be directed to the ana- tomical data, which have hitherto been so imprudently disregarded. Under the guidance of the laws formulated in this chapter, let us accept the anatomical fact of a vast network forming the ground-substance in which cells and fibres are embedded, and with which they are continuous ; let us accept the physiological principle of similarity of property with similarity of composition and structure ; let us accept the hypothesis that the discharge of neural energy is dependent on the degree of stimulus and the degree of tension at the time being — and we shall have at least a general theory of the process, though there will still remain great obscurities in particular applications. We shall have before us a vast network of pathways, all equally capable of conducting an excitation, but not all equally and at all moments open. It will always be diffi- cult to determine what are the conditions which at any THE NERVOUS MECHANISM. 341 nioment favor or obstruct particular openings. Paths that have been frequently traversed will of course be more readily traversed again ; but this very facility will some- times be an obstacle, since it will have caused that path to be preoccupied, or have fatigued the organ to which it leads. 199. Since the escape of an excitation must always be along the lines of least resistance, an obvious explanation of the restriction to certain paths has been to assume that some fibres and cells have naturally greater resistance than others. But this explanation is simply a restate- ment of the fact in other words. What is this greater resistance ? Why is it present in one fibre rather than in another ? We should first have to settle whether the resistance was in the nervous pathway itself, or in the centre, or in the organ innervated ; an excitation might pass along the nervous tract, yet fail to change the state of the centre, or the organ, sufficiently to produce an ap- preciable response ; and only those parts where an appre- ciable response was produced would then be considered as having had the pathways of propagation open. 200. When we reflect on the innumerable stimulations to which the organism is subjected from so many various l)oints, and remember further that each stimulation leaves behind it a tremor ivhieh does not immediately subside, we shall conceive something of the excessive complexity of the mechanism, and marvel how any order is established in the chaos. What we must firmly establish in our minds is tliat the mechanism is essentially a Jluctuating one, its elements being combined, recombiued, and re- .solved under infinite variations of stimulation. If it were a mechanism of fixed relations, sucli as we find In ma- chines, or in the " mechanism of the heavens," we might accept the notion of certain organites having greater resist- ance as a consequence of their structure, just as one mus- 342 THE niYsicAL basis of mind. cle resists being moved by the impulse which will move another. Nor is it doubtful tliat such differences exist in nervous organites ; but tlie laws of central excitation are not interpretable by any such hypothesis, since we know that tlie paths which were closed against an impulse of considerable energy may be all open to an impulse of feebler energy, and that a slight variation in the stimulus will be followed by a wide irradiation. For example, a grain or two of snuff' will excite the violent and complex act of sneezing, but the nerves of the nasal cavity may be pinched, cut, or rubbed, without producing any such result. One group of nervous organites will fail to in- volve tlie activity of neighboring groups ; and the simple movement of a single organ is then all that appreciably follows the stimulation ; yet by a slight change in the stimulation, the organites are somewhat differently grouped, and the result is a complex movement of many organs. It is this fluctuation of combination in the organ- ites which renders education and progress possible. Those combinations which have very frequently been repeated acquire at last an automatic certainty. "We are now in a position to examine with more precis- ion the extremely important laws of nervous action which are involved in the phenomena designated by the terms Eeflex Action, Automatic Action, and Voluntary Action. PROBLEM III. ANIMAL AUTOMATISM. " L'organisme le plus complexe est vrn vaste mecanisme qui resulte de I'as- semblage de mecanismes secondaires." — Claude Bernard. ' ' Les corps vivants sont machines a rinfini." — Leibnitz. " Noi lamentiamo con Majendie clie nel linguaggio fisiologico siensi intruse le preopinioni psicologiche col trascico inevitabile del vocaboli, ai quali co- deste preopinioni si trovano legate. Probabilmente questa fu una delle princi- pal! cagioni degli errori e degli equivoci anatomofisiologici, da cui non poterono svincolarsi, a loro insaputa, 1 cultori sperimentali della scienza, perche nell' interpretare i fenomeni osservati erano obbligati ad usare il linguaggio di una falsa moneta in corso." — Lussana e Lemoigne, Fisiologia dei Centri Ner- vosi, 1871, 1. 16. ANIMAL AUTOMATISM. CHAPTEE I. THE COUKSE OF MODEEN THOUGHT. 1, MoDEKN Philosophy has moved along two increas- ingly divergent lines. One, traversed by Galileo, Des- cartes, Newton, and Laplace, had for its goal the absolute disengagement of the physical from the mental, i. e. the objective from the subjective aspect of phenomena, so that the physical universe, thus freed from all the com- plexities of Feeling, might be interpreted in mechanical terms. As a preliminary simplification of the problem tliis was indispensable ; only by it could the First Notion of primitive speculation be replaced by the Theoretic Conception of scientific speculation.* The early thinker inevitably invested all external objects with properties and qualities similar to those he assigned to human beings, and their actions he assigned to human motives. Sun, moon, and stars seemed living beings; flames, streams, and winds were supposed to be moved by feelings sucli as those known to move animals and men. Nor was any other conception then possible : men could only in- terpret the unknown by the known, and their standard of all action was necessarily drawn from their own ac- tions. Not having analyzed Volition and Emotion, above * On the distinction between first notions and theoretic conceptions, see Problems of Life and Mind, Vol. II. p. 277. 10* 346 THE niYSICAL BASIS OF MIND. all not having localized these in a nenro-muscular system, men could not suspect that the movements of planets and plants, and of streams and stones, had motors of a different kind from the movements of animals. The sci- entific conception of inert insensible JNIatter was only attained through a long education in abstraction ; and is assuredly never attained by animals, or by savages. But no sooner were vital conditions recognized, than the dif- ference between vital and mechanical movements emerged. When men learned that many of their own actions were unaccompanied either by Love or Hate, by Pleasure or Pain, and that many were unprompted by conscious in- tention, while others were unaccompanied by conscious sensation, they easily concluded that wherever the special conditions of Feeling were absent, the actions must have some other motors. Intelligence, Emotion, Volition, and Sensation being one by one stripped away from all but a particular class of bodies, nothing remained for the other bodies but insensible Matter and Motion. This was the Theoretic Conception which science substituted for the First Notion. It was aided by the observation of the misleading tendency of interpreting physical phenomena by the human standard, substituting our fancies in the place of facts, manipulating the order of the universe ac- cording to our imagination of what it might be, or ought to be. Hence the vigilance of the new school in sup- pressing everything pertaining to the subjective aspect of phenomena, and the insistance on a purely objective classification, so that by this means we might attain to a knowledge of things as they are. By thus withdraw- ing Life and Mind from Nature, and regarding tlie uni- verse solely in the light of Motion and the laws of Motion, two great scientific ends were furthered, namely, a clas- sification of conceptions, and a precision of terms. Ob- jective phenomena made a class apart, and the great ANIMAL AUTOMATISM. ' 347 aim of research was to find a mathematical expression for all varieties under this class. Masses were conceived as aggregates of Atoms, and these were reduced to mathe- matical points. Forces were only different modes of Mo- tion. All the numberless difierences which perception recognized as qualities in things, were reduced to mere variations in quantity. Thus all that was particular and concrete became resolved by analysis into what was gen- eral and abstract. The Cosmos then only presented a problem of Mechanics. 2. During this evolution, the old DuaUsm (which con- ceived a material universe sharply demarcated from the mental universe) kept its ground, and attained even greater precision. The logical distinction between Matter and Mind was accepted as an essential distinction, i. e. representing distinct reals. Tliere was on the one side a group of phenomena, Matter and Force ; on the other side an unallied group, Feeling and Thought : between them an impassable gulf. How the two were brought into relation, each acting and reacting on the other, was (Usmissed as an " insoluble mystery " — or relegated to Metaphysics for such minds as chose to puzzle over ques- tions not amenable to experiment. Physics, confident in the possession of mathematical and experimental methods which yielded definite answers to properly re- stricted questions, peremptorily refused to listen to any suggestion of the kind. And the career of Physics was so triumphant that success seemed to justify its indif- I'erence. 3. In our own day this analytical school has begun to extend its metliods even to the mental group. Having reduced all the objective group to mathematical treat- ment, it now tries to bring the sul)jective group also witliin its range. Not only has there been more than one attempt at a mathematical Psychology ; but also 348 THE PHYSICAL BASIS OF MIND, attempts to reduce Sensibility, in its subjective no less than in its objective aspect, to molecular movement. Here also the facts of Quality are translated into facts of Quantity ; and all diversities of Feeling are inter- preted as simply quantitative differences. 4. Tims far the one school. But while this Theoretic Conception stripped Nature of consciousness, motive, and passion, rendering it a mere aggregate of mathematical relations, a critical process was going on, which, analyz- ing the nature of Perception, was rapidly moving towards another goal. Locke, Berkeley, Hume, and Kant, direct- ing their analysis exclusively to the subjective aspect of phenomena, soon broke down the barriers between the physical and mental, and gradually merged the former in the latter. Matter and its qualities, hitherto accepted as independent realities, existing where no Mind perceived them, were now viewed as the creations of Mind — their existence was limited to a state of the percipient. The old Dualism was replaced by Idealism. The Cosmos, instead of presenting a problem of Mechanics, now pre- sented a problem of Psychology. Beginning with what are called the secondary qualities of Matter, the psycho- logical analysis resolved these into modes of Feeling. " The heat which the vulgar imagine to be in the fire and the color they imagine in the rose are not there at all, but are in us — mere states of our organism." Having gained this standing-place, there was no difficulty in ex- tending the view from the secondary to the primary qual- ities. These also w^ere perceptions, and only existed in the percipient. Nothing then remained of Matter save the hypothetical unknown x — the postulate of specu- lation. Kant seemed forever to have closed the door against the real Cosmos when he transformed it into a group of mental forms — Time, Space, Causality, Quan- tity, etc. He propounded what may be called a theory ANIMAL AUTOMATISM. 349 of mental Dioptrics whereby a pictured universe became possible, as Experience by its own a •priori laws moulded itself into a consistent group of appearances, which pro- duced tlie illusion of being a group of realities. He ad- mitted, indeed, that by the operation of Causality we are compelled to believe in a Real underlying the appear- ances ; but the very fact that this Causality is a subjective law, is proof, he said, of its not being an objective truth. Thus the aim of the mechanical conception was to free research from the misleading complexities of subjective adulterations, and view things as they are apart from their appearances ; but this aim seemed illusory when Psychol- ogy showed that Time, Space, Matter, and Motion were themselves not objective reals except in so far as they represented subjective necessities ; and that, in short, things are just what they appear, since it is only in the relation of external reals to internal feelings that objects exist for us. 5. Idealism has been the outcome of the psychological method. It has been of immense service in rectifying the dualistic conception, and in correcting the mechanical conception. It has restored the subjective factor, winch the mechanical conception had eliminated. It has brought into incomparable clearness the fundamental fact that all our knowledge springs from, and is limited by. Feeling. It lias shown that the universe represented in that knowl- edge, can only be a picture of the system of things as these exist in relation to our Sensibility. But equally with the mechanical conception it has erred by incom- plete analysis. For a complete theory of the \miverse, or of any one phenomenon, those elementary conditions which analysis has provisionally set aside must finally be restored. When Quality ir? replaced by Quantity, this is an artifice of method, which does not really correspond with fact. The quality is the fact given in feeling, which ;'.50 THE riiYsicAL basis of mind. we analytically refer to quantitative differences, but which can never be wholly resolved into them, since it must be presupposed throughout. One color, for example, may be distinguished fi"om another as having more or fewer un- dulations ; and so we may by abstraction, letting drop all qualitative characters, make a scale of undulations to represent the scale of colors. But this is an ideal fig- ment. It is the representation of one series of feelings by another series of different feelings. No variation of imdulations will really correspond with variation in color, unless we reintroduce the suppressed qualiti/ which runs through all color. Attempt to make one born blind feel, or even understand. Color by describing to him the kind of wave-movement which it is said to be, and the vanity of the effort will be manifest. Movement he knows, and varieties of movement as given in tactile and muscular sensatioiis ; but no combination and manipulation of such experiences can give him the specific sensation, of Color. That is a purely subjective state, which he is incapable of experiencing, simply because one of the essential fac- tors is absent. One set of objective conditions is present, but the other set (his sense-organ) is defective. Without the " greeting of the spirit " undulations cannot become colors (nor even undulations, for these also are forms of feeling). Besides the sense-organ there is needed the feeling of Difference, which is itself the product of past and present feeling.s. The reproduction of other colors, or other shades of color, is necessary to this perception of difference ; and this involves the element of Likeness and Unlikeness between what is produced and reproduced. So that a certain mental co-operation is requisite even for the simplest perception of quality. In fact, psycho- logical analysis shows that even Motion and Quantity, the two objective terms to which subjective Quality is reduced, are themselves Fundamental Signatures of Feel- ANIMAL AUTOMATISM. 351 ing ;* so that here, as elsewhere, it is only by analytical artifice that the objective can be divorced from the sub- jective. Matter is for us the Felt ; its Qualities are dif- ferences of Feeling. 6. Not that this result is to be interpreted as freeing our Theoretic Conception from its objective side, and landing us in Idealism, which suppresses the real uni- verse. The denial of all reality apart from our minds, is a twofold mistake: it confounds the conception of general relations with particular relations, declaring that because the External in its relation to the sentient organism can only be what it is felt to be, therefore it can have no other relations to other individual reals. This is the first mistake. The second is the disregard of the constant presence of the objective real in every fact of Feeling : the Not-Self is emphatically present in every conscious- ness of Self The legitimate conclusion is neither that of Dualism nor of Idealism, but what I have named Reasoned Eealism (Prohlems, Vol. I. p. 201), which reconciles Common Sense with Speculative Logic, by showing that although the truth of things (their Wahrheit) is just what we perceive in them (our Wahrnchmnng), yet their reality is this, and much more than this. Things are what they are felt to he ; and what they are thought to be, wlien thoughts are symbols of the perceptions. Idealism declares that they iire nothing hut this. It is against this nothing hat that (.'ommon Sense protests ; and the protest is justified by Keasoned Eealism, which, taking a comprehensive survey of the facts, thus answers the idealist : " Your synthesis is imperfect, since it does not include all the data — nota- bly it excludes the fact of an objective or Not-Self ele- ment in every feeling. You may, conceivably, regard the * Not transcendental and a priori, as Kant teaches ; but immanent in Feeling. 352 THE niYSICAL BASIS OF MIND. whole universe as nothing but a series of changes in your consciousness ; but you cannot hope to convince nie that I myself am simply a change in yourself, or that my body is only a fleeting image in your mind. Hence al- though I conclude that the Not-Self is to you, as to me, undivorceable from Self, inalienable from Feeling, in so far as it is felt, yet there must nevertheless be for both of us an existence not wholly coextensive with our own. My world may be my picture of it ; your world may be your picture of it; but there is something common to both which is more than either — an existent which has different relations to each. Yov, are not me, nor is the pictured Cosmos mc, although I picture it. Looking at you and it, I see a vast whole of which you are a small part ; and such a part I conclude myself to be. It is at once a picture and the pictured ; at once subjective and objective. To me all your modes of existence are objec- tive aspects, which, drawing from my own experience, I believe to have corresponding subjective aspects ; so that your emotions, which to me are purely physical facts, are to you purely mental facts. And psychological analysis assures me that oW physical facts are mental facts exp7xssed in objective terms, and mental facts are physical facts ex- pressed in subjective terms. 7. But while Philosophy thus replaces the conceptions of Dualism and Idealism by the conception of the Two- fold Aspect, the special sciences in their analytical career have disregarded the problem altogether. The mechani- cal theory of the universe not only simplified research by confining itself solely to the objective aspect of phe- nomena, but by a further simplification set aside all vital and chemical relations, to deal exclusively with mechani- cal relations. In ascertaining the mathematical relations of the planetary system, no elucidation could possibly be gained from biological or chemical conceptions ; the ANIMAL AUTOMATISM. 353 planets therefore were provisionally strij^ped of every- thing not mechanical. In systematizing the laws of mo- tion, it was necessary to disengage the abstract relations from everything in any way resembling spontaneity, or extra-mechanical agency : Matter was therefore, by a bold fiction, declared to be inert, and its Motion regarded as something superadded from without. 7«. And this was indispensable for the construction of those ideal laws which are the objects of scientific research. Science, as we often say, is the systematization of Experience under the forms of ideal constructions. Experience implies Eeeling, and certain fundamental Sig- natures, all reducible to the primary discernment of Like- ness and Unlikeness. Hence Science is first a classifica- tion of qualities or discerned likenesses and differences ; next a measurement of quantities of discerned likenesses and differences. Although measurement is itself a species of classification, it is distinguished by the adoption of a standard unit of comparison, which, being precise and unvarying, enables us to express the comparisons in pre- cise and unvarying symbols. Whether the unit of length adopted be an inch, a foot, a yard, a mile, the distance of the earth from the sun, or the distances of the fixed stars, the quantities thus measured are symbols admit- ting of one invariable interpretation. The exactness of the mathematical sciences is just this precision and in- variabiHty of their symbols, and is not, as commonly supposed, the source of any superior certainty as to the facts. The classificatory sciences, which deal with quali- ties rather than with ([uantities, may be equally certain, and represent fuller knoidcdge, because involving more varied feelings, but they cannot pretend to exactness. Even on the quantitative side, certainty is not identical with exactness. I may be quite certain that one block of marble is larger than another — meaning that it affects w 354 THE PHYSICAL BASIS OF MIND. me more voluminously — but I cannot know how mueli larger it is, without interpreting my feelings by the stan- dard of quantity — the how-muchness as represented by that standard. The immense advantages of exact meas- urement need not be insisted on. The Biological Sci- ences, which are predominantly classificatory, can never rival the Cosmological Sciences in exactness ; but they may reach a fuller knowledge ; and their certainty will assume more and more the character of exactness as methods of measurement are applied to their classifi- cations of qualities. The qualitative and quantitative as- pects of phenomena are handled by the two great instru- ments, Logic and Mathematics, the second being only a special form of the first. These determine the general conceptions which are derived from our perceptions, and the whole constitute Experience. 8. What is the conclusion to which these considera- tions lead ? It is that the separation of the quantitative from the qualitative aspect of phenomena — the objective mechanical from the subjective psychological — is a logi- cal artifice indispensable to research ; but it is only an artifice.* In pursuance of this artifice, each special science must be regarded as the search after special analytical results ; and meanwhile this method should be respected, and no confusion of the boundaries between one science and another should be suffered. Mechanical problems must not be confused by the introduction of biological relations. Biological problems must not be restricted to mechanical relations. I do not mean that the mechani- cal relations present in biological phenomena are not to be sought, and, when found, to be expressed in me- chanical terms ; I mean that such an inquiry must be * The reader will understand that although mechanical relations are modes of Feeling, as all other relations are, yet their aspect is exclusively objective, referring to objects ideally detached from subjects. ANIMAL AUTOMATISM. 355 strictly limited to mechanical relations. Subjective rela- tions are not to be denied, because they are provisionally set aside, in an inquiry into objective relations ; but we must carefully distinguish which of the two orders we are treating of, and express each in its appropriate terms. This is constantly neglected. For example, nothing is more common than to meet such a phrase as this : " A sensory imjjrcssion is transmitted as a ivave of motion to the brain, and there being transformed into a state of consciousness, is again reflected as a moto7- impulse." The several sciences having attained certain analytical results, it remains for Philosophy to co-ordinate these into a doctrine which will furnish general conceptions of the AVorld, JMan, and Society. On the analytical side a mechanical theory of the universe might be perfected, but it would still only be a theory of mechanical re- lations, leaving all other relations to be expressed in other terms. We cannot accept the statement of Descartes that Nature is a vast mechanism, and Science the uni- versal application of mathematics. The equation of a sphere, however valuable from a geometrical point of view, is useless as an explanation of the nature and prop- erties of the spherical body in other relations. And so a complete theory of the mechanical relations of the organism, however valuable in itself, would be worthless in the solution of a biological problem, unless supple- mented by all that meclianical terms are incompetent to express. 9. The course of biological speculation has l)een simi- lar to the cosmological. It also began with a First Notion, which compendiously expres.sed the facts of Experience. Nor can any Theoretic Conception be finally adopted wliicli does away with these facts, known with positive certainty, and ])0])ularly expres.sed in the phrase: " I have a body, and a soul." We may alter tlic ])hras(' 356 THE PHYSICAL BASIS OF MIND. either into " I am a body, and I am a soul " ; or into, " My body is only tlie manifestation of my soul " ; or, " ]\Iy soul is only a function of my body*" ; but the fundamental ex- periences which are thus expressed are of absolute au- thority, no matter how they may be interpreted. That 1 have a body, or am a body, is not to be speculatively ar- gued away. That I move my arm to strike the man \\\\o lias offended me, or stretch out my hand to seize the fruit which I see, is unquestionable ; that these movements are determined by these feelings, and are never thus effected unless thus determined, is also unquestionable. Here are two sets of phenomena, having well-marked differences of aspect ; and they are grouped respectively under two general heads. Life and Mind. Life is as- signed to the physical organism, or Body — all its phe- nomena are objective. Mind is assigned to the psychical organism, or Soul — all its phenomena are subjective. Although what is called my Body is shown to be a group of qualities which are feelings — its color, form, solidity, position, motion — all its physical attributes being what is felt by us in consequence of the laws of our organiza- tion ; yet inasmuch as these feelings have the character- istic marks of objectivity, and are thereby referred to some objective existence, we draw a broad line of demar- cation between them and other feelings having the char- acteristic marks of subjectivity, and referring to ourselves as subjects. Psychological analysis shows us that this line of demarcation is artificial, only representing a di- versity of aspect ; but as such it is indispensable to sci- ence. We cannot really separate in a sensation Avhat is objective from what is subjective, and say how much belongs to the Cosmos apart from Sensibility, and how much to the subject pure and simple ; we can only view the sensation alternately in its objective and subjective aspects. What belongs to extra-mental existence in the ANIMAL AUTOMATISM. 357 phenomenon of Color, and what to the " greeting of the spirit," is utterly beyond human knowledge: for the ethe- real undulations which physicists presuppose as the cos- mic condition are themselves subjected to this same greeting of the spirit : they too are ideal forms of sensi- ble experiences. 10. This conclusion, however, was very slowly reached. The distinction of aspects was made the ground of a cor- responding distinction in agencies. Each group was per- sonified and isolated. The one group was personified in Spirit — an existent in every respect opposed to Matter, which was the existent represented in the other group. One was said to be simple, indestructible ; the other com- pound, destructible. One was invisible, impalpable, be- yond the grasp of Sense ; the other was visible, tangible, sensible. One was of heaven, the other of earth. Thus a biological Dualism, analogous to the cosmological, re- placed the First Notion. It was undermined by advances in two directions. Psychology began to disclose that our conception of ]\Iatter was, to say the least, saturated with Mind, its Atoms confessedly being ideal figments ; and that all the terms by which Ave expressed material qualities were terms which expressed modes of Feeling ; so that whatever remained over and above this was the unknown X, which speculation required as a postulate. Idealism, rejecting this postulate, declared that Matter was simply the projection of Mind, and that our Body was the olyec- tivation of our Soul. Pliysiology began to disclose that all tlie mental processes were (mathematically speaking) functions of physical jjrocesses, i. e. varying with the vari- ations of bodily states ; and this was declared enough to banish forever the conception of a Soul, except as a term simply expressing certain functions. 11. Idealism and Materialism are equally destructive of Dualism. The defects of particular idealist and mate- 358 THE PHYSICAL BASIS OF MIND. rialist theories \\e will not here touch upon ; they mainly result iVom defects of Method. Not suthciently recogniz- in. So. ■ 16* X 370 THE PHYSICAL basis of mind. find a portion of a skull with two occipital condyles, that the animal to which this skull belonged had red blood- cori)uscles without nuclei, and (if a lemale) suckled its young. If in that fragment of skull there remain a single tooth, it will prove that the animal was carnivorous or herbivorous, and had, or had not, retractile claws. From such data a general conclusion may be formed as to the instincts and habits of the animal. The data dis- close much of the primary constitution, that is to say, the mechanism which the animal brought with it into the world, ready prepared to react in definite ways on being stimulated. The connate mechanism has correlative ten- dencies of reaction. Some of these tendencies are inevi- tably called into play by external conditions, and they continue unaltered amid great varieties of circumstances, provided none of these variations directly deprive them of their appropriate stimulation. Such tendencies of the connate mechanism are styled automatic (an unfortunate metaplior, which has led to the theory of Automatism), and include, besides the visceral reactions, the more com- plex reactions of winking, breathing, swallowing, cough- ing, flying, walking, etc. It is true that we learn to walk, and learn to wink, whereas the other actions require no tentative efforts directed by experience ; but the mechan- ism of all these actions is already laid down in the pri- mary constitution, and is inevitably called into play. 22. The instincts also belong to the connate mechan- ism, and in the course of the normal experience of the animal inevitably come into play ; but, unlike the auto- matic tendencies of breathing, swallowing, and coughing, they are capable of modification, or even suppression, by alterations in the course of individual experience. The connate mechanism of the cat determines its dread of water, and its enmity to the dog and mouse ; yet a cat will by the modifications of certain experiences become as ANIMAL AUTOMATISM. 371 ready as an otter to take to the water, and become so fond of a dog that she will allow him to tend upon her kittens ; and so indifferent to the mouse that she will let it run over her body. All this implies a new adjustment in the nefvous centres, with new modes of reaction on sensory impressions : the inherited mechanism has been modified. I need not dwell on the profound modifica- tions which the human inherited mechanism undergoes in the course of experience — how social influences and moral and religious teachings redirect, or even suppress, many primary tendencies; so that "moral habits" become organized, and replace the original tendencies of the organ- ism. These, when organized, become the inevitable modes of reaction, and are sometimes called secondarily auto- matic. It is important to recognize this organization of experiences, this acquisition of a secondary or modified constitution, if we would explain psychological processes by physiological processes. Tlius the processes of Logic are automatic, they belong to the connate primary mech- anism, and their action is inevitable, invariable. The elements of a judgment, like tlie elements of a perception, may vary, and we therefore say that one judgment is false, and one perception incomplete ; but the judging process is always the same, and the perceiving process is always the same. We may breathe pure air or impure air, but the breathing process is in each case the same ; and judgment is as automatic as breathing, not to be altered, not to be suppressed. Again, tlie moral terror at wickedness of any recognized kind is as automatic as the instinctive terror at danger. The one lias its roots in the primary disposition called love of approbation and its correlative dread of disapprobation : the social instinct. The other has its root in the primary disposition called "instinct of self-preservation," whicli is really the reflex shrinking from pain : tlie physiological instinct. diJ, THE PHYSICAL BASIS OF MIND. 23. Besides the connate and acquired mechanism, we have now to consider the temjiorary and H actuating ad- justments which represent the statical condition of the organism at each moment. The automatism of the pri- mary constitution is such that previous experience and conscious effort are not needed ; nor will any experience or any effort alter the mode of reaction. If a strong light falls on the eye, the iris contracts ; if the eyeball is dry, the eyelid drops ; if sound-waves beat upon the tympanum, the stapedius muscle contracts ; if the lin- ing of the throat be tickled, the muscles involved in coughing or in vomiting contract. No experience is necessary for these actions, some of which are so com- plicated that if we had to learn them, as we learn far simpler actions, the organism would perish before the power was attained. Yet all of these presuppose a cer- tain normal state of the mechanism, any considerable variation in which will modify or suppress them. 24. Secondarily automatic actions are those which have been acquired through experiences that have modified the organism, and produced a new adjustment of parts. We learn to shield the eyes against a strong glare of light by raising the hand ; by winking we learn to shield the eye against an approaching body ; we also learn to turn the head in tlie direction of a sound, and to thrust away with our hands the object that is irritating our skin. Experience has been necessary for all these actions, and has finally organized the tendencies to perform them, so that the reaction is invariable, inevitable, unless controlled by the will. If you tickle my throat, I may, or may not, push aside your hand ; but if the inside of my throat be tickled, I must cough. Here we see the difference between the automatic and secondarily automatic actions. The second being due to individual experience, are more or less controllable ; and whether they are or are not ANIMAL AUTOMATISM. 37S controlled depends on the condition of the nerve-centres at the moment. You may tickle my throat, or irritate my skin, without causing any movement of my hands to thwart you, either because my nerve-centres are preoccu- pied by other stimulations, and I am not conscious of the irritation, or because I do not choose to tliwart you. 25. It should be added that some secondarily auto- matic actions have become so firmly organized that we can only with great difficulty interfere with them. Others never enter into consciousness, and are therefore often supposed to be purely mechanical. Tlie movement of the eye towards the brightest light, and the convergence of the axes of both eyes, are reflexes which, although involuntary and unconscious, are the products of educa- tion. They do not belong to the connate constitution, although they are so inevitably acquired by experience that they belong to every normal child. At first the infant stares with a blank gaze, and its eyes, though mov- ing under the stimulus of light, move incoherently ; the axes never converge except by accident. Very early, however, the infant's eyes are observed to follow the movements of a bright light ; and at last they acqiiire so certain and rapid a power of adjustment that the eyes .shift from spot to spot, always "fixing" the object by bringing the most sensitive part of the retina to bear on it. The incoherent movements have become precisely regulated movements. It is the same with speech. The vocal organs are exercised in an incoherent babble. By degrees these movements become regulated so as to re- spond definitely to definite stimuli, and words are formed, then sentences, till finally fluent speech becomes in a great degree automatic. The vocal muscles respond to an auditory stimulus, and the cliild repeats the word it li.'is heard, just as the eye-muscles respond to a retinal stimulus. That we acquire tlie power of converging the 0/4 THE PHYSICAL BASIS OF MIND. axes, and accommodating the lens to near objects, is not only proved by observation of infants, but also by cases of disease. After the reliex mechanism has been Ion"; established, so that it acts with inevitable precision, a slight paralysis of one of the muscles has the effect of making all objects appear in a different position ; the patient trying to touch an object, then always moves his hand on one side of it. Von Graefe relates the case of a stonebreaker who always struck his hand with the hammer when he tried to strike the stone. Yet this very man learned to accommodate his movements to the new impressions ; so that if his paralysis had been cured, his modified mechanism would have been ill adapted to the new conditions, and he would once more have struck his hand instead of the stone. 26. This digression on the native and acquired dispo- sitions of the organism, while it has brought into strong light all that can be cited in favor of regarding animal bodies as mechanisms, and their actions as the direct con- sequences of mechanical adjustments, has also made con- spicuous the radical difference between an organism and a machine. We cannot too emphatically insist on this radi- cal difference. Between the group of conditions involved in the structure and action of a machine, and the group of conditions involved in the structure and action of an organism, there are contrasts as broad as any that can be named. To overlook these in taking account solely of the conditions common to both groups is a serious error. On such grounds we might insist that a tiger is a violet, because bolh are organisms. The biologist will admit that an organism is a mechan- ism, and (in so far as its bodily structure is concerned) a material mechanism. All the actions of this structure are therefore mechanical, in the two senses of the term : first, as being the actions of material adjustments ; sec- ANIMAL AUTOMATISM. 375 ondly, as being movements, and thereby included under the general laws of motion represented in JSIechanics ; the abstract laws of movement for an organic body are not different from the abstract laws of movement for an inorganic body. So far we have been considering the abstract relations only. No sooner do we consider the phenomena as concrete wholes, than we find great di- versity in the modes of production of the movements in organisms and machines. Now it is precisely the modes of production which have interest for us. We never understand a phenomenon so as to gain any practical control over it, or any tlieoretical illumination from it, unless we have mastered some of its conditions ; our knowledge of these conditions is the measure of our power. 37G THE niYSICAL BASIS OF MIND. CHAPTEE III. THE RELATION OF BODY AND MIND. 27. The second question proposed was, In what sense can Feeling be correctly spoken of as an Agent in organic processes ? This brings us face to face with a much- debated topic, the relation of Body and Mind; and de- mands a theoretic interpretation of that First Notion which expresses universal experience, namely, that what I know as Myself is a Body, in one aspect, and a Soul, in the other. What I call my Body is a persistent aggre- gate of objective phenomena ; and my Soul is a persistent aggregate of subjective phenomena : the one is an indi- vidualized group of experiences expressible in terms of Matter and Motion, and therefore designsited phi/sical ; the other an individualized group of exj)eriences expressible in terms of Feeling, and therefore designated psT/chical. But, however contrasted, they are both simply embodi- ments of Experience, that is to say, are Modes of Feeling. All Existence — as known to us — is the Felt. The laws of our organism compel us, indeed, to postulate an Exist- ent which is extra meoitem — a Real not Ourselves — but the same laws debar us from any knowledge whatever of what this is, or is liJce. We know Things absolutely in so far as they exist in relation to us ; and that is the only knowledge which can have any possible significance for us. 28. It is impossible for me to doubt that I am a Body, though I may doubt whether what is thus called is any- ANIMAL AUTOMATISM. 377 thing more than a group of feelings. It is impossible for me to doubt that I am a Soul ; though I may doubt whether what is thus called is more than a group of bodily functions. In separating what is unquestionable from what is questionable, we separate the fundamental facts of consciousness from the theoretic interpretations of those facts : no theoretic interpretation can efface or alter the facts. Whatever Philosophy may disco^•e^, it cannot displace the fact that I know I am a Soul, in every sense in which that phrase rep^xscnts Experience : I know the Soul in knowing its concretes (feelings), and in know- ing it as an abstraction which condenses those concretes in a symbol. The secondary question is, Whether this abstraction represents one Existent, and the abstraction Body another and wliolly different Existent, or the two abstractions represent only two different Aspects ? this may be debated, and must be answered according to theo- retic probabilities. 29. What are the probabilities ? We are all agreed that Consciousness is the final arbiter. Its primary de- liverance is simply that of a radical distinction. It is silent on the nature of the distinction — says nothing as to whether the distinction is one of agents or of aspects. It says, " I am a Soul." With equal clearness it says, "I am a Body." It does not say, " I am two things." Nor does the fact of a radical distinction imply more tlian a contrast of aspects, such as that of convex and concave. The curve lias at every point this contrast of convex and concave, and yet is the identical line tliroughout. A mental y^rocess is at every point contrasted with the physical j)rocess assumed to be its correlate ; and this contrast demands equivalent expression in the terms of each. The identity underlying the two aspects of the curve is evident to Sense. The identity underlying the mental and physical process is not evident to Sense, 07S THE PHYSICAL BASIS OF MIND. but may be made eminently 2^'obahlc to Speculation, especially when we have explained the grounds of the ditrerence,, namely, that they are apprehended through different modes. But although I admit that the conclu- sion is only one of probability, it is one which greatly transcends the probability of any counter- hypothesis. Let us see how this can be made out.* 30. "We start from the position that a broad line of demarcation must be drawn between the mental and the physical aspect of a process, supposing them to be iden- tical in reality. Nothing can be more unlike a logical proposition than the physical process which is its cor- relate; so that Philosophy has hitherto been forced to forego every attempt at an explanation of how the two can be causally connected: referring the connection to a mystery, or invoking two different agents, spiritual and material, moving on parallel lines, like two clocks regu- lated to work simultaneously. But having recognized this difference, can we not also discern fundamental re- semblances ? First and foremost, we note that there is common to both the basis in Feeling: they are both modes of Consciousness. The Mind thinking the logical propo- sition is not, indeed, in the same state as the Mind pic- turing the physical process which is the correlate of that logical proposition — no more than I, who see you move on being struck, have the same feelings as you who are struck. But the ]\Iind which pictures the logical proposi- tion as a process, and pictures the physical process as a bodily change, is contemplating one and the same event under its subjective and objective aspects; just as when I * The solution offered in the present chapter was first offered in Prob- lems of Life and Mind, 1875, II. 465, sq. I mention this because .since the publication of that volume other writers have expressed the same ideas, sometimes using my language and illustrations : e. g. M. Taine in the Revue Philosophiquc, January, 1877, art., Les Vibrations cerebralcs ct la Pensee. ANIMAL AUTOMATISM. 379 picture to myself the feelings you experience on being struck I separate the subjective aspect of the blow from its objective aspect. Secondly, between the logical propo- sition and the physical process there is a con!munity of causal dependence, i. e. the mode of grouping of the constituent elements, whereby this proposition, and" not another, is the result of this grouping, and not another. In fact, what in subjective terms is called Logic, in objec- tive terms is Grouping. 31. Let us approach the question on a more accessible side. Sensation avowedly lies at the basis of mental manifestations. Now, rightly or wrongly. Sensation is viewed alternately as a purely subjective fact — a psycho- logical process — and as a purely objective fact — the physiological reaction of a sense-organ. It is so con- spicuously a physiological process that many writers exclude it from the domain of IMind, assign it to the material organism, and believe that it is explicable on purely mechanical principles. This seems to me emi- nently disputable ; but the point is noticed in proof of the well-marked objective character which tlie phenome- non assumes. In this aspect a sensation is simply the reaction of a bodily organ. The physiologist describes how a stimulus excites the organ, and declares its reaction to be the sensation. Thus viewed, and expressed in terms of Matter and IMotion, there is absolutely notliing of that subjective quality which characterizes sensation. Yet without this quality the objective process cannot be a sensation. Exclude Feeling, and tlie excitation of the auditory organ will no more yield the sensation of Sound l)y its reaction, than the strings and sounding-board of a piano when the keys are struck will yield music to a deaf spectator. Hence tlie natural inference has been that inside tlie organism there is a listcmcr : tlie Soul is said to listen, transforming excitation into sensation. This infer- 380 THE PHYSICAL basis of mind. ence only needs a more systematic interpretation and it will represent the biological theory, which demands some- thing more than the reaction of the sensory organ — namely, thf, reaction of the whole organism through the sensory organ. I mean, that no organ isolated from the organism is capable of a physiological reaction — only of a physico-chemical reaction ; and sensation depends on (i.9) the physiological reaction. When a sense-organ is stimulated, this stimulation is a vital process, and is raised out of the class of physico-chemical processes by virtue of its being the indissoluble part of a complex whole. Interfere with any one of the co-operant conditions — withdraw the circulation, check respiration, disturb secre- tion — and the sense-organ sinks from the physiological to the physical state ; it may then be brought into contact with its normal stimuli, but no stimulation (in the vital sense) will take place, there will be no vital reaction. Condensing all vital processes in the symbol Vitality, we may say Vitality is requisite for every physiological process. A parallelism may be noted on the subjective side : all the sentient processes may be condensed in the one symbol Sensibility (Feeling), and we nmst then say, No psychological process is possible as an isolated fact, but demands the co-operation of others — it is a resultant of all the contemporaneous conditions of Sensibility in the organism. In ordinary language this is what is meant by saying that no impression can become a sensation without the intervention of Consciousness — an ambigu- ous phrase, because of the ambiguity of the term Con- sciousness, but the phrase expresses the fact that in Sensation a process in the organism is necessary to the reaction of the organ. 32. Having recognized the distinction between the two processes objective and subjective, physical and mental. ANIMAL AUTOMATISM. 381 we have recognized the vanity of attempting to assign their limits, and to say where Motion ends and Feeling begins, or how Feeling again cliauges into Motion. The one does not begin where the other ends. According to the two-clock theory of Dualism, the two agents move on parallel lines. On the theory of Monism the two aspects are throughout opposed. Both theories explain the facts ; which explanation is the most congruous with experience? Against the first we may object that the hypothesis of two Agents utterly unallied in nature wants the cardinal char- acter of a fertile hypothesis in its unverifiableness : it may be true, we can never know that it is true. By the very terms of its definition, the Spirit — if that mean more than an abstract expression of sentient states — is beyond all sensible experience. This is indeed admitted by the dualists, for they postulate a Spirit merely because they cannot otherwise explain the plienomena of Con- sciousness. Herein they fail to see that even their pos- tulate brings no explanation, it merely restates the old problem in other terms. 33. Up to the present time these same objections might liave been urged with ecpial force against Monism. In- deed, although many philosophers have rejected the two- clock theory of Leibnitz, they have gained a very hesitat- ing acceptance for their own hypothesis of identity. To most minds the difficulty of imagining how a physical process could also be a p.sychical process, a movement also be a feeling, seemed not less than that of imagining how two sucli distinct Agents as Matter and Mind could co- operate, and react on eacla otlier, or move simultaneously on parallel lines. Although for many years I have ac- cepted the hypotliesis of Monism, I have always recog- nized its want of an ade([uate reply to such objections. Unless I greatly deceive myself, I have now found a solu- tion of the main difficulty ; and found it in psychological 382 THE niYsiCAL basis of mind. conditions wliich are perfectly intelligible. But knowing how easily one may deceive one's self in such matters, 1 will only ask the reader to meditate with open-minded- ness the considerations now to be laid before him, and see if he can feel the same confidence in their validity. 34. One of the early stages in the development of Expe- rience is the separation of Self from the Not-Self. I look out on " the vast extern of things," and see a great variety of objects, included in a visible hemisphere. All these objects in various positions, having various forms and col- ors, I believe to be wholly detached from, and in every way unallied to. Myself. And what is that Self '? It is my Body as a visible and tangible object, separated from all other visible and tangible objects by the constant pres- ence of feelings connected with it and its movements, and not connected with the other objects. This constant pres- ence of feelings is referred to a Soul, which I then sepa- rate from my Body, as an Inner Self; and from this time onwards I speak of the Body as mine, and learn to regard it in much the same light as other outer objects. In my naive judgment the external objects are supposed to exist f(s I see and touch them, whether I or any one else see and touch them or not : they in no sense belong to the series of feelings which constitute the Me. And since my Body resembles these objects in visible and tangible qualities, and also in being external to my feelings, it also takes its place in the objective world. Thus arises the hypothesis of Dualism which postulates a Physis, or ob- ject-world, and an yEsthcsis, or subject-world : two inde- pendent existents, one contemplated, the other contem- plating. 35. Philosophy, as we know, leads to a complete reversal of this primitive conclusion, and shows that the contemplated is a syntlusis of contemplations, the Physis be- ing also the ^sthesis. Psychological investigation shows ANIMAL AUTOMATISM. 383 that the objects supposed to have forms, colors, and posi- tions within an external hemisphere, have these only in ■\-irtue of the very feelings from which they are supposed to be separated. The visible universe exists only as seen : the objects are Eeals conditioned by the laws of Sensi- bility. The space in which we see them, their geomet- rical relations, the light and shadows which reveal them, the forms they affect, the lines of their changing direc- tions, the qualities which distinguish tliem, — all these ate but the externally projected signs of feelings. They are signs which we interpret according to organized laws of experience ; each sign being itself a feeling connected with other feelings. We project tliem outside according to the " law of eccentric projection " — which is only the expression of the fact that one feeling is a sign of some other, and is thereby ideally dctaehecl from it. According to this law I say, "my Body"; just as I say, "my House " ; or, " my Property." IMisled by this, Dualism holds that in the very fact of detaching my Body from my Self, calling it mine, is the revelation of a distinct entity within the body. But that this is illusory, appears in the application of this same law of eccentric projection to sensations and thoughts, which are called mine, as my legs and arms are mine. If it is undeniable that I say my Body — and thus ideally detach the Body from the Soul — it is equally undeniable that I say my Soul ; and from what is the Soul detached ? In presence of this difficulty, the metaphysician may argue tliat neither Body nor Soul can be coextensive with its manifestations, but demands a noumenal Real for each — a substratum for the bodily manifestations, and a substratum for the mental manifestations. This, however, is an evasion, not a solu- tion of the difficulty. If we postulate an unknown and unknowable noumenon, we gain no insight : first, because Pliilosopliy deals only with the known functions of un- 384 THE PHYSICAL BASIS OF MIND. known quantities, and therefore leaves the x out of the calculation ; secondly, because, granting the existence of these noumena, we can have no rational grounds for asserting that they are not of one and tlie same nature ; for we have no grounds for any assertion whatever about them. And if it be urged against tliis, that Conscious- ness testifies to a distinction, I answer that on a closer scrutiny it will be found to testify to nothing more than a diversity of manifestation. All therefore that comes within the range of knowledge is, How does this diversity arise \ 36. There are two ways, and there are only two, in which differences arise. These are, 1°, the modes of pro- duction of a product, and, 2°, our modes of appreliension of the product. Things may be very different, and yet to our apprehension indistinguishable, so that we regard them as identical ; and they may be identical, yet appear utterly unlike. A mechanical bird may seem so like a living bird, and their actions so indistinguishable to the spectator, that he will not suspect a difference, or suspect- ing it, will not be able to specify it. Of both objects, so long as his modes of apprehending them are circumscribed, he can only say what these imply : he sees familiar forms, colors, and movements, which he interprets according to the previous experiences of which these are the signs. But by varying the modes of apprehension, and gaining thus a fuller knowledge, he finds that the two products have very different modes of production ; hence he con- cludes the products to be different : the mechanism of the one is not the organism of the other ; the actions of the mechanical bird are not the actions of the living bird. The fuller knowledge has been gained by viewing the ob- jects under different relations, and contemplating them in their modes of production, not as merely visible products. He sees the mechanism performing by steel sjorings. ANIMAL AUTOMATISM. 385 wheels, and wires, the work which the organism performs by bones, muscles, and nerves ; and tlie farther his anal- ysis of the modes of production is carried, the greater are the differences which he apprehends. 37. Xow consider the other side. One and the same object will necessarily present very different aspects under different subjective conditions, since it is tliese which de- termine the aspect. The object cannot be to Sight what it is to Hearing, to Touch what it is to Smell. The vibra- tions of a tuning-fork are seen as movements, heard as sounds. In current language the vibrations are said to cause the sounds. Misled by this, philosophers puzzle themselves as to how a material process (vibration) can be transformed into a mental process (sensation), how such a cause can have so utterly different an effect. But I have formerly* argued at some length that there is no transformation or causation of the kind supposed. The tuning-fork — or that Real which in relation to Sense is the particular object thus named — will, by one of its modes of acting on my Sensibility through my optical apparatus, determine the response known as vibrations ; but it is not this response of the optical organ which is transformed into, or causes the response of the auditory organ, known as sound. The auditory organ knows noth- ing of vibrations, the optical nothing of sounds. The responses are botli modes of Feeling determined by or- ganic conditions, and represent the two different relations in which the Eeal is apprehended. The Real is alter- nately the one and the other. And if the one mode of Feeling has a physical significance, while the otlier has a mental significance, so that we regard tlie vil)rations as objective facts, belonging to the external world, and the sounds as subjective facts, exclusively belonging to the internal world, this is due to certain psychological influ- * Problems of Life and Miiid, Vol. IT. pp. 443 and 482. VOL. III. 17 Y 386 THE PHYSICAL BASIS OF MIND. ences presently to be expounded. Meanwhile let us fix clearly in our minds that both vibrations and sounds are modes of Feeling. My consciousness plainly assures me that it is I who see the one, and hear the other ; not that there are two distinct subjects for the two distinct feel- ings. Add to which, manifold uncontradicted experiences assure me that the occasional cause — the objective factor — of the one feeling, is also the cause of the other, and not that the two feelings have two different occasional causes. From both of these undeniable facts we must conclude that the difference felt is simply a difference of aspect, determined by some difference in the modes of apprehension. 38. Assuming then that a mental process is only an- other aspect of a physical process — and this we shall find the more probable hypothesis — we have to explain by what influences these diametrically opposite aspects are determined. From all that has just been said we must seek these in the modes of apprehension. There can be no doubt that we express the fact in very different terms ; the question is, "What do these terms signify ? Why do we express one aspect in terms of Matter and Motion, assigning the process to the objective world; and the other aspect in terms of Feeling, assigning the process to the subjective w^orld ? Let the example chosen be a logical process as the mental aspect, and a neural process as its physical corre- late. The particular proposition may be viewed logically, as a grouping of experiences, or physiologically, as a group- ing of neural tremors. Here we have the twofold aspect of one and the same reality ; and these different aspects are expressed in different terms. We cannot be too rigorous in our separation of the terms ; for every attentive student must have noted how frequently discussions are made turbid by the unconscious shifting of terms in the course ANIMAL AUTOMATISM. 387 of the argumentation. This is not only the mistake of opponents who are unaware of the shifting which lias occurred in each otlier's minds, so that practically the adversaries do not meet on common ground, but cross and recross each other ; it is also the mistake of the soli- tary thinker losing himself in the maze of interlacing con- ceptions instead of keeping steadily to one path. Only by such shifting of terms can the notion of the physical process causing, or being tranformed into, the mental process for a moment gain credit ; and this also greatly sustains the hypothesis of Dualism, with its formidable objections : How can Matter think ? How can Mind act on Matter causing Motion? 39. Those who recognized that the terms Matter and j\Iind were abstractions mutually exclusive, saw at once that these questions, instead of being formidable, were in truth irrational. To ask if Matter could think, or Mind move Matter, was a confusion of symbols equivalent to speaking of a yard of Hope, and a ton of Terror. Al- though Measure and Weight are symbols of Feeling, and in this respect are on a par with Hope and Terror, yet because tliey are objective symbols they cannot be ap- plied to subjective states, without violation of the very significance they were invented to express. No one ever asks whether a sensation of Sound can be a sensation of Color : nor whether Color can move a machine, althoufrh Heat can, yet the one is no less a sensation than the other. On similar grounds no one should ask whether Matter can think, or Mind move Matter. The only rational question is one i)reserving tlie integrity of the terms, namely, whether tlie living, tliinking organism presents itself to apprehension under the twofold a-spect — now under the modes of Feeling classified as ol)jective or physical ; now under the modes classified as subjective or mental. 388 THE PHYSICAL BASIS OF MIND. 40. We are told that it is " impossible to imagine Matter thinking," which is very true ; only by a gross confusion uf terms can Thought be called a property of cerebral tissue, or of Matter at all. We may, indeed, penetrate beneath the terms which relate to aspects, and recognize in the underlying reality not two existences, but one. Our conceptions of this reality, however, are expressed in symbols representing different classes of feelings, objec- tive and subjective ; and to employ the terms of one class to designate the conceptions of the other is to frustrate the very purposes of language. Matter and Mind, Ob- ject and Subject, are abstractions from sentient experi- ences. We know them as abstractions, and know the concrete experiences from which they are abstracted. Philosophers, indeed, repeatedly assure us that we neither know what Matter is nor what Mind is, we only know the 2^^icnomenal pj^oduds of the action and reaction of these two unknown noumena. Were this so, all dis- cussion would be idle ; we could not say whether Matter was or was not capable of thinking, whether ]\Iind w^as or w'as not the same as Matter, we could only abstain from saying anything whatever on the topic. What should we reply to one who asked us to name the pro- duct of two unknown quantities ? So long as x and ?/ are without values their product must be without value. If the value of x be known, and that of y unknown, then the product still remains unknown : x -{• y ='x -\- o = x. Therefore, unless the Objective aspect were the equivalent of the Subjective aspect, it could never be subjectively present. Feeling is but another aspect of the Felt. 41. It is because we do know wdiat Matter is, that we know it is not Mind : they are symbols of two different modes of Feeling. If we separate the conception of cit- izenship from the conception of fatherhood, although the same man is both citizen and father, how much more ANIMAL AUTOMATISM. 389 decisively must we separate the conception of Matter, which represents one group of feelings, from the concep- tion of ]\Iind, which represents another ? One element in the former is common to the whole group, namely, the reference to a Not-Self, induced by the sensation of Ee- sistance, which always ideally or sensibly accompanies the material class. The axiom, I feel, ergo I exist, has its correlative : — I act, ergo there are other existents on which I act ; and tliese are not wholly Me, for they re- sist, oppose, exclude me ; yet they are also one with Me, since they are felt by me. In my Feeling, that which is not Me is Matter, the objective aspect of the Felt, as Mind is the subjective aspect. But since Hunger and Thirst, Joy and Grief, Pain and Terror, are also felt, yet are never classed under the head of Matter, the grounds of the classification of feelings have to be expressed. Professor Bain makes the distinc- tion between Matter and Mind to rest solely on the pres- ence or absence of Extension : this is the decisive mark : Matter he defines as the Extended. The definition is in- adequate. When I see a dog and its image reflected in a pool, or see a dog and think of another, in the three cases dog, image, and idea have Extension ; but I recognize the dog as a material fact, the idea as a mental fact; and although the image of the dog has material conditions by which I am optically affected, just as the idea has ma- terial cerebral conditions, I recognize a marked difference between them and the dog, due to the different modes of apprehension. The dog is known as a persistent reality, which, when Sight is supplemented by Touch, will yield sensations of liesistance, and thus disclose its materiality. The image vanishes if I attempt to touch it ; I see its outlines waver and become confused with every disturb- ance of the surface of tlie pool ; the idea vanishes when another idea arises ; whence I conclude that neither has 390 THE PHYSICAL BASIS OF MIND. material reality, because neither lias the Eesistance which characterizes the Not-Self. The image and the idea may be referred to material conditions, but so may pains, ter- rors, volitions, yet these are all without Extension, simply because they are not visual feelings. 42. Matter does not represent all feelings, but only the objective sensibles ; and these are not all characterized by Extension, but only those which directly or indirectly involve optico-tactical experiences accompanied by mus- cular experiences. Matter is primarily the Visible and Eesistent ; and secondarily, whatever can be imagined as such ; so that ether, molecules, and atoms, although nei- ther visible nor tangible, are ranged under the head of Matter. Color is a feeling as Sound and Scent are feel- ings, and although material conditions are equally presup- posed in all three, yet Color alone has Extension, and be- cause it can be imaged it has a more objective character than the others, which having no lines and surfaces, want the optical conditions for the formation of images, and are less definitely connected with tactical and muscular expe- riences. Nevertheless, since Sound and Scent are obvi- ously associated with objects seen and touched, they have a degree of materiality never assigned to such feelings as Hunger and Thirst, Pleasure, Terror, and Hope. 43. When we refer feelings to material conditions, we follow the natural tendency to translate the little known in terms of the better known, and employ the symbols Matter and Motion, because these furnish the intellect with images, i. e. definite and exact elements to operate with. In hearing a sound, there is nothing at all like "vibrations," nothing like "aerial waves" and "neural processes," given in that feeling; but on attempting to explain it, we remove it from the sphere of Sensation to carry it into the sphere of Intellect, and we must change our symbols in changing our problem ; here our only re- i ANIMAL AUTOMATISM. 391 source is to translate the subjective state into an imagi- nable objective process, which can only be expressed in terms of Matter and Motion. What we heard as Sound is tlien seen as Vibration. When we are optically or mentally contemplating vibrations and neural processes, we are supplanting one source of feeling by another, translating an event in another set of symbols. But we can no more hear the sound in seeing the vibrations, than a blind man can see the fly in the amber whicli he feels with his fingers, or than we can feel the amber he holds, while we are only looking at it. The j)hrase " ma- terial conditions of Feeling" sometimes designates the objective aspect of the subjective process, and sometimes the agencies in the external medium which co-operate w'itli the organism in the production of the feelings. In each case there is an attempt to explain a feeling by in- telligible symbols. 44. The Animal probably never attempts such expla- nation; satisfied with the facts, it is careless of their factors. Man is never satisfied : is restless in the search after factors ; and having found them, seeks factors of these factors ; so that Lichtenberg felicitously calls him "das rastlose Ursachenthier " — "the animal untiring in the search for causes." And thus sciences arise : we translate experiences into geometrical, physical, chemical, physiological, and p.sychological terms — different sym- bols of the different modes of apprehending phenomena. 45. "I see an elephant." In other words, I am af- fected in a certain way, and interpret my affection by previous similar experiences, expressing these in verbal symbols. - But I want an explanation, and tliis tlio ])hi- losopher vouchsafes to me by translating my afl'ection into his terms. He takes me into another sphere — tells me of an undulating Ether, the waves of which beat upon my retina — of lines of Light refracted by media 302 THE niYsiCAL basis of mind. and converged by lenses according to geometric laws — of the formation thereby of a tiny image of the gigantic elephant on my retina as on the plate of a camera- obscnra — this, and mucli more, is wliat he sees in rmj vis- ual feeling, and he bids me see it also. Grateful for the novel instruction, I am compelled to say that it does not alter my vision of the elephant, does not make the fact a whit clearer, does not indeed correspond with what I feel. It is outside knowledge, valuable, as all knowl- edge is, but supplementary. It is translation into another language. And when I come to examine the translation, I find it very imperfect. I ask my instructor : Is it the tiny image on my retina which I see, and not the big elephant on the grass ? And how do I see this retinal image, which you explain to be upside down ? — how is it carried from my retina to my mind ? I have no con- sciousness of tiny reversed image, none of my retina, only of a fact of feeling, which I call "seeing an ele- phant." The camera-obscura has no such feeling — it reflects the image, it does not see the object. Here my instructor, having reached the limit of his science,* hands me over to the physiologist, who will translate the fact for me in terms not of Geometry, but of Anatomy and Physiology. The laws of Dioptrics cease at this point : the image they help to form on the retina is ruthlessly dispersed, and all its beautiful geometric construction is lost in a neural excitation, wdiich is transmitted through semifluid channels of an optic tract to a semifluid gan- glion, whence a thrill is shot through the whole brain, * "The retinal image is the last effect known of the action of objects on us ; what happens beyond the retina we know not ; our knowledge of the objective process has at present here its limit." — Ewald Hering, Beilrdge zur Physioloriie, 1862, p. 166. That is to say, we have a defi- nite translation of the process in geometric terms as far as the retina, and thence onwards Geometry fails us, and Neurology and Psychology are invoked. ANIMAL AUTOMATISM. 393 and is there transformed into a visual sensation. Again I fancy I have gained novel instruction of a valuable kind ; but it does not affect my original experience that I am enabled to translate it into different terms; the less so because I cannot help the conviction that the translation is imperfect, leaving out the essential points. If a phrase be translated for me into French or German, I gain thereby an addition to my linguistic knowledge, but the experience thus variously expressed remains un- affected. When tlie fact is expressed in geometrical or physiological terms, the inycMcal i^occss finds no ade- quate expression. Neither in tlie details, nor in the totals, do I recognize any of the quahties of my state of feeling in seeing the elephant. I do not see the geomet- rical process, I do not see the anatomical mechanism, I see the elephant, and am conscious only of that feeling. You may consider my organism geometrically or anatomi- cally, and bring it thus within the circle of objective knowledge ; but my subjective experience, my spiritual existence, that of which I am most deeply assured, de- mands another expression. Nay more, on closely scru- tinizing your objective explanations, it is evident that a psychical process is im'pliecl tliroughout — such terms as undulations, refractions, media, lenses, retina, neural ex- citation, overtly refer, indeed, to the material objective aspect of the facts, but they are themselves the modes of Feeling by which the facts are apprehended, and would not exist an such without the " greeting of the spirit." 4G. What, then, is our conclusion ? It is, that to make an adequate explanation of psychical processes by material conditions we must first establisli an equiva- lence between the subjective and objective aspects ; and, having taken this step, we must complete it by showing M'herein the difference exists ; having established this entity and diversity, we have solved the problem. 17* 394 THE niYSICAL BASIS OF MIND. Let us attempt this solution. When I speak to you, the spoken words are the same to you and to me. You hear what I hear, you apprehend what I apprehend. But there were muscular movements of articulation felt by me and not felt by you ; to feel these you also must articulate the words ; but so long as you merely hear the words, there is a difference in our states of feeling. Some of my movements you can see, others you can im- agine ; but this is not my feeling of them, it is your optical equivalent of my muscular feeling. On a similar assumption of equivalence, a neural process is made to stand for a logical process. In thinking a proposition, we are logically grouping verbal symbols representative of sensible experiences ; and this is a quite peculiar state of Consciousness, wholly unlike what would arise in the mental or visual contemplation of the neural grouping, which is its physiological equivalent. But this diversity does not discredit the idea of their identity; and al- though some of my readers will protest against such an idea, and will affirm that the logical process is 'not a process taking place in the organism at all, but in a spirit which uses the organism as its instrument, I must be allowed in this exposition to consider the identity estab- lished, my purpose being to explain the diversity neces- sarily accompanying it. Therefore, I say, that although a logical process is identical with a neural process, it must appear differently when the modes of apprehending it are different. While you are thinking a logical propo- sition, grouping your verbal symbols, I, who mentally see the process, am grouping a totally different set of symbols : to you the proposition is a subjective state, i. e. a state of feeling, not an object of feeling : to become an object, it must be apprehended by objective modes : and this it can become to you as to me, when we see it as a process, or imagine it as a process. But obviously your ANIMAL AUTOMATISM. 395 state in seeing or imagining the process must be different from your state when the process itself is passing, since the modes of apprehension are so different. There may be every ground for concluding that a logical process has its correlative physical process, and that the two processes are merely two aspects of one event ; but because we cannot apprehend the one aspect as we apprehend the other, cannot see the logical sequence as we see the physi- cal sequence, this difference in our modes of apprehension compels us to separate the two, assigning one to the sub- jective, the other to the objective class. Between the sensible perception of an object and the reproduced image of the object there is chiefly a quantitative difference in the physiological and psychological processes : the image is a faint sensation. Yet this quantitative difference brings with it the qualitative distinction which is indi- cated in our calling the one a sensation, the other a thought. The consequence has been that while all phi- losophers have admitted the sensation to be — at least partly — a process in the bodily organism, the majority have maintained that the thought is no such process in the organism, but has its seat in a spirit independent of the organism. 47. The states of Feeling which are associated with other states characterized as objective because overtly referring to a Not-Self, we group under the head of Mat- ter: we assign material conditions as their antecedents. Whereas states of Feeling whicli are not thus associated we group under the head of Mind, and assign internal conditions as their antecedents. Color and Taste are very different states of Feeling, yet both are spontane- ously referred to external causes, because they are asso- ciated with visual and tactical states ; wliereas ITuuger, Nausea, Hope, etc., have no such associations, and their material conditions are only theoretically assigned. 396 THE PHYSICAL BASIS OF MIND. Our intelligible universe is constructed out of the ele- ments of Feeling according to certain classifications, the broadest of which is that into external and internal, ob- ject and subject. The abstractions Matter and Mind once formed and fixed in representative symbols, are easily accredited as two different Eeals. But the sepa- ration is ideal, and is really a distinction of Aspects. We know ourselves as Bbdy-Mind ; we do not know our- selves as Body and ]\Iind, if by that be meant two coex- istent independent Existents ; and the illusion by which the two Aspects appear as two Eeals may be made intel- ligible by the analysis of any ordinary proposition. For example, when we say " this fruit is sweet," wo, express facts of Feeling — actual or anticipated — in abstract terms. The concrete facts are these : a colored feeling, a solid feeling, a sweet feeling, etc., have been associated together, and the colored, solid, sweet group is symbolized in the abstract term " fruit." But the color, solidity, and sweetness are also abstract terms, representing feelings associated in other groups, so that we find " fruit " w^hich has no "sweetness"; and "sweetness" in other things besides " fruits." Having thus separated ideally the "sweetness" from the "fruit" — wdiich in the concrete sweet-fruit is not permissible — we easily come to imagine a real distinction. This is the case with the concrete liv- insr orcranism when we cease to consider it in its concrete reality, and fix our attention on its abstract terms — Body and Mind. We tlien think of Body apart from Mind, and believe in tliem as two Eeals, though neither exists apart. There is no state of consciousness in which object and subject are not indissolubly combined. There is no phys- ical process which is not indissolubly bound up with the psychical modes of apprehending it. Every idea is either an image or a symbol — it has therefore objective ANDIAL AUTOMATISM. 397 reference, a material aspect. Every object is a synthesis of feelings — it has therefore subjective reference, a ma- terial aspect. Thus while all the evidence points to the identity of Object and Subject, there is ample evidence for the logical necessity of their ideal separation as As- pects. This I have explained as a case of the general principle which determines all distinctions — namely, the diversity in the modes of production of the products, which — subjectively — is diversity in the modes of ap- prehending them. The optico-tactical experiences are markedly different from the other experiences, as being more directly referred to the Not-Self wMch resists ; and because these lend themselves to ideal constructions by means of images and symbols, it is these experiences into which we translate all the others when we come to ex- plain them and assign their conditions. For — and this is the central position of ovir argument — all interpre- tation consists in translating one set of feelings in the terms of another set. We condense sets of feelings in abstract symbols ; to understand these we must reduce them to their concrete significates. They are signs ; we must show what they are signs of Now the symbols Object and Subject are the most ab- stract we can employ. Because they are universal, they represent what cannot in reality be divorced. We can, indeed, ideally separate ourselves from the Cosmos ; in the same way we can ideally separate our inner Self or Soul from our outer Self or Body ; and again our Soul from its sentient states, our Body from its physical changes. But not so in reality. The separation is a logical artifice, and a logical necessity for Science. The necessity will be obvious to any one who reflects how the ideal constructions of Science demand precision and integrity of terms. The problem of Automatism brings this very clearly into view. The question is, Can 398 THE niYSicAL basis of mind. we translate all psychological phenomena in mechanical terms ? If we ca7i, we ought ; because these terms have the immense advantage of being exact, dealing as they do with quantitative relations. But my belief is that we cannot — nay, that we cannot even translate them all into physiological terms. The distinction between quan- titative and qualitative knowledge (p. 354) is a barrier against the mechanical interpretation. Physiology is a classificatory science, not a science of measurement. Nor can the laws of Mind be deduced from physiological pro- cesses, unless supplemented by and interpreted by psy- chical conditions individual and social. ANIMAL AUTOMATISM. 399 CHAPTEE IV. CONSCIOUSNESS AND UNCONSCIOUSNESS.* 48. Science demands precision of terms; and in this sense Condillac was justified in defining it, " icne langue Men faiur The sciences of Measurement are exact be- cause of the precision of their terms, and are powerful because of their exactness. The sciences of Classification cannot aspire to this precision, and therefore, although ■ capable of attaining to a fuller knowledge of phenomena than can be reached by their rivals, this advantage of a wider range is accompanied by the disadvantage of a less perfect exposition of residts. While physicists and chem- ists have only to settle the significance of the facts observed, biologists and social theorists have over and above this to settle the significance of the terms they employ in expressing the facts observed. Hence more than half their disputes are at bottom verbal. This is markedly the case in the question of Autom- atism. One man declares that animals are automata ; another that they are conscious automata ; and while it is quite possible to hold these views and not practically be in disagreement with the views of ordinary men, or in- deed with the views of spiritualist and materialist philoso- phers, we can never be sure that the advocates of Autom- atism do not mean wliat they are generally understood to mean. If a man says that by an automaton lie does not here mean a machine, such as a steam-engine or a watch, * Compare Problem II. Cliap. IV. 400 THE PHYSICAL BASIS OF MIND. but a vital mechanism whicli lias its parts so adjusted that its actions resemble those of a machine ; and if he adds that this automaton is also conscious of some of its actions, though unconscious of others, we can only object to his using terms which have misleading connotations. If he mean by " conscious automata," that animals are mechanisms moved on " purely mechanical principles," their consciousness having notliing whatever to do with the production of their actions, then indeed our objection is not only to his use of terms, but to his interpretation of the facts. 49. The questions of fact are two : Are animal mechan- isms rightfully classed beside machines ? and. Is conscious- ness a coefficient in the actions of animal mechanism ? The first has already been answered ; the second demands a preliminary settlement of the terms " conscious," " un- conscious," " voluntary," and " involuntary." The aim of Physiology is to ascertain the particular combinations of the elementary parts involved in each particular func- tion — in a word, the mechanism of organic phenomena ; and the modern Eeflex Theory is an attempt to explain this mechanism on purely mechanical principles, without the co-operation of other principles, especially those of Sensation and Volition. It is greatly aided by the am- biguity of current terms. We are accustomed to speak of certain actions as being performed unconsciously or involuntarily. We are also accustomed to say that Con- sciousness is necessary to transform an impression into a sensation, and that Volition is the equivalent of conscious effort. "Wlien, therefore, unconscious and involuntary actions are recorded, they seem to be actions of an in- sentient mechanism. The Reflex Theory once admitted, a rigorous logic could not fail to extend it to all animal actions. 50. I reject the Eeflex Theory, on grounds hereafter to ANIMAL AUTOMATISM. 401 be urged, but at present call attention to the great ambi- guity in the terms " conscious " and " unconscious." In one sense no definition of Consciousness can be satisfac- tory, since it designates an ultimate fact, which cannot therefore be made more intelligible than it is already. In another sense no definition is needed, since every one knows what is meant by saying, " I am conscious of such a change, or sucli a movement." It is here the equivalent of Feeling. To be conscious of a change, is to feel a change. If we desire to express it in physiological terms, we must define Consciousness — "a function of the organ- ism " ; and tliis definition we shall find eminently useful, because the organism being a vital mechanism, and the integrity of that mechanism being necessary for the in- tegrity of the function, while every variation of the mechan- ism will bring a corresponding variatipn of the function, we shall have an objective guide and standard in our inquiries. Organisms greatly differ in complexity, yet because they also agree in the cardinal conditions of Vitality, among which Sensibility is one, we conclude that they all have Feeling ; but the Feeling of the one will differ from that of another, according to the com- plexity of the sentient mechanism in each. The per- fection of this mechanism lies in the co-ordination of its parts, and the consensus of its sentient activities ; any dis- turbance of that consensus must cause a modification in the total consciousness; and when the disturbance is profound the modification is marked by such terms as " insanity," "loss of consciousness," "insensibility." These terms do not imply that tlie sentient organs liave lost their Sen- sibility, but only that the disturbed meclianism has no longer its normal consensus, no longer jts normal state of Consciousness. Each organ is active in its own way so long as its own mechanism is preserved ; but the united action of the organs having been disturbed, their resultant 402 THE PHYSICAL BASIS OF MIND. function has been altered. Hence in a fit of Epilepsy- there is a complete absence of some normal reactions, with exaggeration of otliers. In a state of Coma there is no spontaneity — none of the manifold adaptations of the organism to fluctuating excitations, external and in- ternal, observable in the normal state. The organism still manifests Sensibility — but this is so unlike the manifestations when its mechanism is undisturbed (and necessarily so since the Sensibility varies with the mechan- ism) that it is no longer called by the same name. In the normal organism Sensibility means Feeling, or Con- sciousness ; but in the abnormal organism there is said to be a "loss of Consciousness." "VVliat the physiologist or the physician means by the phrase "loss of Conscious- ness " is intelligible, and for his purposes unobjectionable. He observes many organic processes going on undisturbed — the unconscious patient breathes, secretes, moves his limbs, etc. These processes are referred to the parts of the mechanism which are not disturbed ; they are obvi- ously independent of that adjustment of the mechanism which by its consensiis has the special resultant named Con- sciousness ; he therefore concludes that these, and many other organic processes, which are neither accompanied nor followed by discriminated feelings, are the direct conse- quences of the stimulated mechanism. He never hesitates to adopt the popular language, and say, ""We sometimes act unconsciously, perceive unconsciously, and even think unconsciously, all by the simple reflex of the mechanism." Xow observe the opening for error in this language. The actions are said to go on unconsciously, and, because unconsciously, as pure reflexes, which are then assigned to an insentient mechanism, and likened to the actions of machines. But, as I hope hereafter to make evident, the reflex mechanism necessarily involves Sensibility; and therefore reflex actions may be unaccompanied by ANIMAL AUTOMATISM. 403 Consciousness — in one meaning of that term — without ceasing to be sentient . the feelings are operative, although not discriminated. On the other hand, there is another and very general meaning of the term Consciousness, which is the equivalent of Sentience. 51. In discussing Automatism, or the Reflex Theory, it is absolutely necessary that we should first settle the meaning we assign to the term Consciousness* The lax- ity with which the term is used may be seen in the enu- meration occupying six pages of Professor Bain's account of the various meanings. Psychology is often said to be "the science of the facts of Consciousness"; and the Brain is often assigned as " the organ of Consciousness." Yet there are many mental processes, and many cerebral processes, which are declared to be unconscious. Obvi- ously if Consciousness is the function of the Brain, there can be no cerebral activity which is unconscious ; just as there can be no activity of the lungs which is not respira- tory. Usage therefore points to a general and a special sense of the term. The general usage identifies it with Sensibility, in its subjective aspect as Sentience, including all psychical states, both those classed under Sensation, and those under Thought. These states are the " facts of consciousness " with which Psychology is occupied. In the special usage it is distinguished from all other psychi- cal states by a peculiar reflected feeling of Attention, whereby we not only have a sensation, but also fed that we have it ; we not only think, but are conscious that we are thinking ; not only act, but are conscious of what we do It is this which Kant indicates when he defines it " the subjective form accompanying all our conceptions (Begriffe) " ; and Jessen Avhen lie defines it " the internal knowing of our knowing, an in itself reilected knowing." * * "Das Bewusstwerden ist nichts Anderes als cin weiter fortgeschrit- tenes Eriimem oder Neuwerden des von aussen aufgenommenen Wissens, 404 THE PHYSICAL BASIS OF MIND. 52. We shall often have to recur to this general and this special meaning, both of which are too hrmly rooted for any successful attempt to displace them. The fact that some organic processes and some mental processes take place now consciously and now unconsciously, i. e. now witli the feeling of reflected attention, and now with no such feeling, assuredly demands a corresponding ex- pression ; ijor, in spite of inevitable ambiguities, is there ground for regretting that the expression chosen should be only an extension of the expression already adopted for all other states of Sentience. A sentient or conscious state can only be a state of the sentient organism, itself the unity of many organs, each having its Sensibility. There is more or less con.sensus, but there is no introduc- tion of a new agent within the organism, converting what was physical impression into mental reaction. From first to last there has been nothing but neural processes, and combinations of such processes — which, viewed subjec- tivel}', are sentient processes. Thus the gradations of sensitive reaction are Sentience, Consentiencc, and Con- sciousness, whieli are represented in the Logic of Feeling and the Lo^ic of Sii^ns. The familiar term Conscience will then represent the Logic of Conduct. Thus under- stood, we may say that a man sometimes acts uncon- sciously, or thinks unconsciously, although his action and thought are ruled by Consentience, as he sometimes acts and thinks unconscientiously, although he is not without obedience to Conscience on other occasions. The feeling which determines an action is operative, although it may not be discriminated from simultaneous feelings. When this is the case, we say the feeling is unconscious; but this no more means that it is a purely physical pro- ein innerliches Wissen dieses Wissens oder ein in sicli reflectirtes Wis- sen. ' ' — Jessf.x, Versuch einer WissensclMftlichcn Begriindung der Psycho- logic, 1855, p. 477. ANIMAL AUTOMATISM. 405 cess taking place outside the sphere of Sentience, than the immoral conduct of a man would be said to be mechani- cal, and not the conduct of a moral agent. There is undoubtedly a marked distinction expressed in the terms Consciousness and Unconsciousness, but it is not that of contrasts such as Mental and Physical, it is that of grades such as Light and Darkness. Just as Darkness is a posi- tive optical sensation very different from mere privation — just as it replaces the sensation of Light, blends with it, struggles with it, and in all respects differs from the absence of all optical sensibility in the skin ; so Unconsciousness struggles with, blends with, and replaces Consciousness in the organism, and is a positive state of the sentient organ- ism, not to be confounded with a mere negation of Sen- tience ; above all, not to be relegated to merely mechanical processes. 52 a. Eemember tliat, strictly speaking. Consciousness is a psycliological not a physiological term, and is only used in Physiology on the assumption that it is the sub- jective equivalent of an objective process. To avoid the equivoque of " unconscious sensation," we may substitute the term " unconscious neural process " ; and as all neural processes imply Sensibility, which in the subjective aspect is Sentience, we say that Sentience has various modes and degrees — such as Perception, Ideation, Emotion, Volition, which may be conscious, sub-conscious, or unconscious. When Leibnitz referred to the fact of "obscure ideas," and modern writers expressed this fact as "unconscious cerebration," the first phrase did not imply a process that was other than mental, the second phrase did not imply a process that was other than physiological : botli indicated a mode of the process known as Consciousness under other modes. There are different neural elements grouped in Ideation and Emotion ; there are different neural elements grouped in Consciousness, Sub-consciousness, and Uncon- 406 THE PHYSICAL BASIS OF MIND. sciousness; but one tissue with one property is active in all. 53. The nervous organism is affected as a whole by every affection of its constituent parts. Every excitation, in- stead of terminating with itself — as is the case in most physical processes — or with the motor impulse it excites, is propagated throughout the continuous tissue, and thus sends a thrill throughout the organism. The wave of excitation in passing onwards beats against variously grouped elements — temporary and permanent centres — disturbing their balance more or less, and liberating the energy of some, increasing the tension of others, neces- sarily affecting all. Those groups which have their energy liberated set up processes that are either discriminated as sensations, or are blended with the general stream, accord- ing to their relative energy in the consensus. Thus the impulse on reaching the centres for the heart, lungs, legs, and tail excites the innervation of these organs ; but as these are only parts of the organism, and as all the parts enter the consensus, and Consciousness is the varying resultant of this ever-varying consensus, the thrill which any particular stimulus excites will be unconscious, sub- conscious, or conscious, in proportion to the extent of the irradiated disturbance, which will depend on the statical conditions of the centres at the moment. A sound sends a thrill which excites emotion, causes the heart to beat faster, the muscles to quiver, the skin-glands to pour forth their secretion ; yet this same sound heard by another man, or the same man under other conditions, physical or historical, merely sends a faint thrill, just vivid enough to detach itself as a sensation from the other simul- taneous excitations ; and the same sound may excite a thrill which is so faint and fugitive as to pass un- consciously. Physiological and psychological inductions assure us that these are only differences of degree. The ANIMAL AUTOMATISM. 407 same kind of physiological effect accompanies the con- scious and unconscious state. Every sensory impres- sion, no matter whether discriminated or not, affects the circulation and develops heat. The blood-vessels of the part impressed expand, vessels elsewhere contract — a change in the blood pressure has been effected, which of course implies that the whole organism has been affected. Delicate instruments show that at the time a sensation is produced the temperature of the brain is raised. The same is true of ideation. Mosso has invented a method of registering the effect of thought on the cir- culation. He finds ideation accompanied by a contrac- tion of the peripheral vessels proportionate to the degree of intellectual effort. A young man translating Greek showed greater contraction than when he was translating Latin. During sound sleep — when we are said to be unconscious — sudden noises always cause contraction of the peripheral vessels. Psychological observation as- sures us that the conscious and unconscious states were both consentient, and were both operative in the same degree. The absorbed thinker threads his way through crowded streets, and is sub-conscious and unconscious of the various sights, sounds, touches, and muscular move- ments which make up so large a portion of his sentient excitation at the time; yet he deftly avoids obstacles, hears the sound of a hurried step behind him, recognizes an in- teresting object directly it presents itself, and can even recall in Memory many of the uninteresting objects wliicli he passed in sub-conscious and unconscious indifference. 54. On all grounds, therefore, we must say that be- tween conscious, sub-conscious, and unconscious states the difference is only of degree of complication in the neural processes, which by relative preponderance in the con- sensus determine a relative discrimination. We can only discriminate one thrill at a time ; but tlie neural excita- 408 THE niYsic.vL basis of mind. tions simultaneously pressing towards a discharge are many; and the conditions which determine now this, and now the other excitation to predominate by its difi'erential pressure, are far beyond any mechanical estimate. I mention this because the advocates of the Eeflex Theory maintain that the neural processes are the same whether a sensation be produced or not ; and that since the same actions follow the external stimulation whether sensation be produced or not, this proves the actions to be purely mechanical. I reply, the neural processes are not the same tin-oughout in the two cases — otherwise the effects would be the same. You might as well say, " Since the explosion of the gun is the same, whether shotted or not, a blank cartridge will kill " ; but if you tell me that your gun killed the bird, I declare that the cartridge was not a blank one. Whether the explosion of the gun also pro- duced terror in one bystander, curiosity in a second, and attracted no notice from a third, will be altogetlier another matter. In like manner the sensory impression which determines a movement may or may not be accompanied or followed by other sentient states ; the fact of such movement is evidence of its sentient antecedent ; and an external stimulus that will produce this neural process, and this consequent movement, must produce a feeling, although not necessarily a discriminated sensation. Now since, for discrimination, other neural processes must co- operate, we cannot say that in the two cases all the neural processes have been the same throughout ; nor because of this difference can we say that the process of the undis- criminated sensation is a mechanical, not a sentient process. In the next problem this point will be argued more fully. 55. The need of recognizing Consciousness and Con- sentience as degrees of energy and complexity in sen- tient states is apparent when we consider animal phenom- ena. Has a bee consciousness ? Has a snail volition ? ANIMAL AUTOMATISM. 409 or are they both insentient mechanisms ? All inductions warrant the assertion that a bee has thrills propagated tln'oughout its organism by the agency of its nerves ; and that some of these thrills are of the kind called sensa- tions — even discriminated sensations. Nevertheless we may reasonably doubt whether the bee has sentient states resembling otherwise than remotely the sensations, emo- tions, and thoughts which constitute human Conscious- ness, either in the general or the special sense of that term. The bee feels and reacts on feelings ; but its feel- ings cannot closely resemble our own, because the condi- tions in the two cases are different. The bee may even be said to think (in so far as Thought means logical com- bination of feelings), for it appears to form Judgments in the sphere of the Logic of Feeling — to potjtikov ; althougli incapable of the Logic of Signs — to SiavorjTtKov. We should therefore say the bee has Consentience, but not Consciousness — unless we accept Consciousness in its general signification as the equivalent of Sentience. The organism of the bee differs from that of a man, as a mud hut from a marble palace. But since underlying these differences there are fundamental resemblances, the functions of the two will be fundamentally alike. Both have the function of Sentience ; as mud hut and palace have both the office of sheltering. 56. The question of Volition will occupy us in the next chapter. Eestricting ourselves here to that of Consciousness, and recalling the distinction of the two meanings of tlie term, we now approach the question of Unconsciousness. Are we to understand this term as designating a purely physical state in contrast to tlie purely mental state of Consciousness ; or only as des- ignating a difference of degree ? This is like asking wliether Light and Darkness are both optical feelings, or one an optical feeling and the other a physical process? VOL. III. 18 410 THE niYsiCAL basis of mind. On the Iveflex Tlieory, no sooner does a vital and mental process pass from the daylight of Consciousness, or twi- light of Sub-consciousness, into the darkness of Uncon- sciousness, than the whole order of phenomena is abruptly changed, they cease to be vital, mental, and lapse into physical, mechanical processes. The grounds of this con- clusion are, first, the unpsychological assumption that the unconscious state is out of the sphere of Sentience ; and secondly, the unphysiological assumption that the Brain is the only portion of the nervous system which has the property of Sensibility. Eestate the conclusion in differ- ent terms and its fallacy emerges : " organic processes suddenly cease to be organic, and become purely physical by a slight change in their relative position in the consen- sus ; the organic process which was a conscious sensation a moment ago, when its energy was not balanced by some other process, suddenly falls from its place in the gi'oup of organic phenomena — sentient phenomena — to sink into the gTOup of inorganic phenomena now that its energy is balanced." Consider the parallel case of ]\Iotion and Eest in the objective sphere. They are two functions of the co-operant forces, one dynamic, the other static ; although markedly distinguishable as functions, M-e know that they are simply tlie co-operant forces now unbalanced and now balanced ; what we call Eest is^ also a product of moving forces, each of which is operant, and will issue in a definite resultant when its counter-force is removed. Motion and Eest are correlatives, and both belong to the sphere of Kinetics. In like manner Consciousness and Unconsciousness are correlatives, both belonging to the sphere of Sentience.* Every one of the unconscious pro- * In commoa'language a stone or a tree is said to be uncouscious ; but this is an anthropomorphic extension of the term. In strictness we should no more speak of unconsciousness outside the sphere of Sentience than of darkness outside the sphere of Vision. AXIMAL AUTOMATISM. 411 cesses is operant, changes the general state of the organ- ism, and is capable of at once issuing in a discriminated sensation when the force which balances it is disturbed. I was unconscious of the scratch of my pen in writing the last sentence, but I am distinctly conscious of every scratch in writing this one. Then, as now, the scratching sound sent a faint thrill through my organism, but its relative intensity was too faint for discrimination ; now that I have redistributed the co-operant forces, by what is called an act of Attention, I hear distinctly every sound the pen produces. 57. The inclusion of Sub-consciousness within the sen- tient sphere is obvious ; the inclusion of Unconsciousness within that sphere may be made so, when we consider its modes of production, and compare it with the extra-sen- sible conception of molecules and atoms. The Matter which is sensible as masses, may be resolved into mole- cules, which lie beyond the discrimination of sense ; and these again into atoms, which are purely ideal concep- tions ; but because molecules are proved, and atoms are supposed, to have material properties, and to conform to sensible canons of the objective world, we never hesitate to class them under the head of Matter ; nor do we im- agine that in passing beyond the discrimination of Sense they lose their objective significance. They are still phys- ical, not mental facts. So with Sentience : we may trace it through infinite gradations from Consciousness to Sub- consciousness, till it lades away in Unconsciousness ; but from first to last the processes have been those of a sen- tient organism ; and by this are broadly distinguished from all processes in anorganisms. The movement of a limb has quite different modes of production from the movement of a wheel ; and among its mut what does not seem per- 448 THE niYSiCAL basis of mind. missible is to deny that their actions exhibit tlie clearest evidence of scnsc-guidancc, and the kind oi' volition which this sense-guidance implies ; and this is quite enough to separate them from actions of automata. AVhen a man ducks his head to avoid a stone which he sees falling towards him, he assuredly has a sensation, i. e. there is a grouping of neural elements, which subjectively is a sen- sation, and this originates a grouping of other neural elements, the outcome of which is a muscular movement, which subjectively is a motor sensation : this grouping would not have been originated unless the particular grouping had preceded it ; nor would the simple retinal stimulus have excited this sensation unless the nerv^e- centres had been attuned to such response by many pre- vious experiences : the ignorant child would not duck its head on seeing the stone approach. In our familiar use of the word Consciousness it would be correct to say that the man ducks his head " unconsciously " ; and yet ex- pressing the fact in psychological language, we also say : He ducks his head because rcmemhering the pain of former similar experiences, he knows that if the stone strikes him he will again be hurt as before, therefore he ivills to avoid it ; expressing it in physiological language we may say : The man acts thus because he is so organ- ized that a particular neural process is the stimulus of a particular central discharge ; and he became thus organ- ized through a long series of anterior adjustments re- sponding to stimuli, each adjustment being the activity of the vital organism. 88. There can be no doubt that the soldier had percep- tions, and that these perceptions guided his movements ; whether these shall be called " states of conscious- ness" or not, is a question of terms. Now since we know that certain actions arc uniformbj consequent on certain perceptions, we are justified in inferring that ivhenever the ANIMAL AUTOMATISM. 449 actions are performed, the 2Jcrceptions preceded them : this inference may be erroneous, but in the absence of positive evidence to the contrary it is that which claims our first assent. Is it evidence to the contrary that the perception may have stimulated the action, yet been unaccompanied by the special mode named consciousness ? Not in the least. We learn to read with conscious effort ; each letter has to be apprehended separately, its form distinguished from all other forms, its value as a sign definitely fixed, yet how very rarely are we " conscious " of the letters when we read a book ? Each letter is perceived ; and yet this process passes so rapidly and smoothly, that unless there be some defect in a letter, or the word be mis- spelled, we are not " conscious " of the perceptions. Are we therefore reading automata ? * We are said to walk unconsciously at times ; and the continuance of the movement is said to be due to reflex action. But it is demonstrable that the cutaneous sensi- bility of the soles of the feet is a primary condition. If the skin be insensible, the walking becomes a stumble. In learning to walk, or dance, the child fixes his eyes on his feet, as he fixes them on his fingers in learning to play the piano. After a while these registered sensations connected with the muscular sense suffice to guide his feet or his fingers ; but not if feet or fingers lose their sensi- bility. 89. Witli these explanations let us follow the further details of this soldier's abnormal actions : — * M. LuYs cites the case of a patient who conversed quitj rationally with a visitor "sans en avoir conscience, et ne se souvenait de ricn" ; and he draws the extraordinary conclusion that the conversation "s'ope- rait en vertu des fprces reflexes." — Etudes dc Physiologic ct dc Pathologic. Cerebralcs, 1874, p. 117. Is it not obvious that the patient must liave been conscious at the time, though the consciousness vanislied like that in a dream ? The persistent consciousness is the continuous linking on of one state with previous states — the aji2)erception of tlie past. c c 450 THE PHYSICAL BxVsis of mind. "The mau is insensible to sensory impressions made through the ear, the nose, the tongue, and, to a great ex- tent, the eye ; nor is he susceptible to pain from causes operating during his abnormal state. Nevertheless it is possible so to act upon his tactile ajjjjaratus as to give rise to those molecular changes in his scnsorium which are ordi- narily tJie causes of associated trains of ideas. I give a striking example of fliis process in Dr. Mesmet's words : ' II se promenait dans le jardin, on lui remet sa canne qu'il avait laisse tomber. II la palpe, promene a plu- sieurs reprises la main sur la poignee coudee de sa canne — devient attentif — semble preter Toreille — et tout a coup appelle, " Henri ! les voila ! " Et alors por- tant la main derriere son dos comme pour prendre une cartouche, il fait le mouvement de charger son arme, se couche dans I'lierbe a plat ventre dans la position d'un tirailleur, et suit avec I'arme epaulee tons les mouve- ments de I'ennemi qu'il croit voir a courte distance.' In a subsequent abnormal period Dr. Mesmet caused the patient to repeat this scene by placing him in the same conditions. Xow in this case the question arises whether the series of actions constituting this singular pantomime was accompanied by the ordinary states of consciousness, the appropriate trains of ideas, or not? Did the man dream that he was skirmishing ? or was he in the con- dition of one of Yaucanson's automata — a rnecJmnism vjorhecl hy molecular changes in the nervous system ? Tlie analogy of the frog shows that the latter assumption is perfectly justifiable." 90. Before criticising this conclusion let me adduce other illustrations of this dreamlike activity. "A gentle- man whom I attended in a state of perfect apoplexy," says Abercrombie, " was frequently observ^ed to adjust his nightcap with the utmost care when it got into an un- comfortable state: first pulling it down over his eyes, and ANIMAL AUTOMATISM. 451 then turning up the front of it in the most exact man- ner." According to the current teaching, these actions, whicli seem like evidence of sensation, are nothing of the kind, because — the patient was " unconscious " ; that is to say, because he did not exhibit one complex kind of Sensibility, it is denied that he exhibited another kind ! he did not feel discomfort, nor feel the movements by which it was rectified — because he could not speak, dis- cuss impersonal questions, nor attend to what was said to him ! Abercrombie cites other cases : " A gentleman who was lying in a state of 'perfect insensibility from disease of the brain " (note the phrase, which really only expresses the fact that external stimuli did not create their normal reactions) " was frequently observed even the day before his death to take down a repeating watch from a little bag at the head of his bed, put it close to his ear and make it strike the hour, and then replace it in the bag with the greatest precision. Another whom I saw in a state of profound apoplexy, from which he recovered, liad a perfect recollection of what took place during the attack, and mentioned many things which had been said in his hearing when he was supposed to be in a state of perfect unconsciousness." Dr. Wigan also tells of a lady A\hom he knew, and who was actually put in a coffin, under the belief that she was dead when in a trance. Her sense of hearing was then preternaturally acute. Tn her second-floor bedroom she heard what the ser- vants said in her kitchen. When lier brotlicr came to see her and he declared slie should not be buried until putrefaction set in, slie felt intense gratitude and a gush of tenderness, but was unable to move even an eyelid as a manifestation of her feeling. Suddenly all her faculties returned. Dr. Wigan adds that he visited tlie Countess Kscalante, one of tlie Spanish refugees, who remained in a similar state for a short period, during wliicli slie saw 45'2 THE niYSICAL BASIS OF MIND. lici" husliaiul and children, and was quite conscious of all they did and said — but did not recognize them as her own. She Mas absolutely without the power of moving a finger or of opening her mouth. Dr. Neil Arnott told me of a similar case in his practice. In these last cases Ave learn that consciousness — in its ordinary accepta- tion — was present, though bystanders could see no trace of it. And very often in cases where Consciousness, or at any rate Sensibility, is clearly manifested, its presence is denied, because the patient on recovering his normal condition is quite unable to remember anything that he felt and did. Under anffisthetics patients manifest sensa- tion, but on awaking they declare that they felt nothing — of what value is their declaration ? M. Despine tells us of a patient who under chloroform struggled, swore, and cried out, " Mon Dieu ! queje sovffrc ! " yet when the operation was over, and he emerged from the effects of the chloroform, he remembered nothing of what he had felt.* 91. Eeturning now to Dr. Mesmet's soldier, and to the conclusion that his dreamlike acts were no more than the actions of one of Vaucanson's automata, surely we are justified in concluding, first, that these actions were not of the same kind as those of an automaton, since they were those of a living organism ; secondly, that they pre- sent all the evidence positive and inferential which Sen- sibility can present in the actions we observe in another, and do not feel in ourselves ; and thirdly, if with physi- ologists we agree that the mechanism of these actions is " worked by molecular changes in the nervous system," there is some difficulty in understanding how Conscious- ness, which is said to be caused by such changes, could * Abercrombie, Inquiries concerning the Intellectual Powers, 1840, p. 151. WiGAX, The Diuility of the Mind, 1844, p. 270. Despine, La Psychologic Naturelle, 1868, I. 54. ANIMAL AUTOMATISM. 453 have been absent — how the cause could operate yet no effect he lirodiiccd. 92. What automata can be made to perform is sur- prishig enough, but they can never be made to display the fluctuations of sense-guided actions, such as we see in the report of Dr. Mesmet's soldier : — "The ex-sergeant has a good voice, and had at one time been employed as a singer at a cafe. In one of his ab- normal states he was observed to begin humming a tune. He then went to his room, dressed himself carefully, and took up some parts of a periodical novel which lay on the bed, as if he were trying to find something. Dr. Mesmet, suspecting that he was seeking his music, made up one of these into a roll and put it into his hand. He ap- 2Jeared satisfied, took up his cane, and went down stairs to the door. Here Dr. Mesmet turned him round, and he walked quite contentedly in the opposite direction. The light of the sun shining through a window happened to fall upon him, and seemed to suggest the footlights of the stage on which he was accustomed to make his appear- ance. He stopped, opened his roll of imaginary music, put himself in the attitude of a singer, and sang with perfect execution three songs one after the other. After which he wiped his face with his handkerchief and drank without a grimace a tumbler of strong vinegar-and-water." 93. Epileptic patients have frequently been observed going through similar dreamlike actions in which only those external stimuli which have a relation to the dream seem to take effect.* We interpret these as phenomena of disordered mental action, the burden of proof lies on liim who says they are phenomena of pure median ism. A mail-coach does not suddenly cease to be a mail-coach * Dr. HucnLiNGS Jackson has quite recently cited some curious examples in his own practice. See West Riding Lunatic Asylum Re- ports for 1875. 454 THE PHYSICAL BASIS OF MIND. and become a wlieelbarrow because the coachman is drunk, or lias fallen from the box. The horses, no longer guided by the reins, may dash off the highroad into gar- dens or ditches ; but it is their muscular exertions which still move the coach. Can any one conceive an automaton acting as the ser- geant is described to be in the following passage ? — " Sitting at a table he took up a pen, felt for paper and ink, and began to write a letter to his general, in which he recommended liimself for a medal on account of his good conduct and courage. It occurred to Dr. Mesmet to ascertain experimentally how far vision was concerned in this act of writing. He therefore interposed a screen be- tween the man's eyes and his hands ; under these circum- stances he ivcnt on tvriting for a short time, hut the words be- came illegible, and he finally stopped. On the withdrawal of the screen, he began to write again where he had left off. The substitution of water for ink in the inkstand had a similar result. He stopped, looked at his pen, wiped it on his coat, dipped it in the water, and began again, with the same effect. On one occasion he began to write upon the topmost of ten superposed sheets of paper. After he had written a line or two, this sheet was suddenly drawn away. Thej^e ivas a slight expression of surprise, but he continued his letter on the second sheet exactly as if it had been the first. This operation was repeated five times, so that the fifth sheet contained nothing but the writer's signature at the bottom of the page. Neverthe- less, when the signature was finished, his eyes turned to the top of the blank sheet, and he went through the form of reading over what he had written, a movement of the lips accompanying each word ; moreover, with his pen he put in such corrections as were needed" 94. Dr. Mesmet concludes that " his patient sees some things and not others ; that the sense of sight is accessible ANIMAL AUTOMATISM. 455 to all things which are brought into relation with him by the sense of touch, and, on the contrary, is insensible to things which lie outside this relation." In other words, the sensitive mechanism acts, but acts abnormally. This is precisely what is observed in somnambulists. Yet Professor Huxley, who makes the comparison, appears to regard both states as those in which the organism is re- duced to a mere mechanism, because on recovering tlieir normal state the patients are unconscious of what has passed ; and because the frog, without its brain, also mani- fests analogous phenomena. Neither premise warrants the conclusion. I have already touched on the uncon- sciousness of past actions ; let me add the case of Faraday, who w^as assuredly not an automaton when he prepared and delivered a course of lectures which were neverthe- less so entirely obliterated from his memory that the next year he prepared and delivered the same course once more, without a suspicion that it was not a new one. As to the frog, I must leave that case till I come to examine the evidence on which the hypothesis of the purely mechani- cal nature of spinal action rests. 95. The point never to be left out of sight is that actions which are known to be preceded and accompanied by sensations do not lose their special character of Sen- tience, as actions of a sentient mechanism, because they are not also preceded and accompanied by that peculiar state which is specially called Consciousness, i. e. attention to the passing changes (comp. p. 403). When we see a man playing the piano, and at the same time talking of some- thing far removed from the music, we say his fingcre move unconsciously; but we do not conclude that he is a musical machine — muscular sensations and musical sen- sations regulate every movement of his fingers ; and if he strikes a false note, or if one of the notes jangles, he is instantly conscious of the fact Either we must admit 456 THE niYSicAL basis of mind. that his brain is an essential part of the mechauisni by which the piano was played, and its function an essential agent in the playing ; or else we must admit that the brain and its function M'ere not essential, and therefore the playing would continue if the brain were removed. In the latter case, we should have a musical automaton. That a particular group of sensations, such as musical tones, will set going a particular group of muscular move- ments, without the intervention of any conscious effort, is not more to be interpreted on purely mechanical prin- ciples, than that a particular phrase will cause a story- teller to repeat a familiar anecdote, or an old soldier " to fight his battles o'er again." 9G. Let us now pass to another consideration, namely, whether Consciousness — however interpreted — is legiti- mately conceived as a factor in the so-called conscious and voluntary actions ; or is merely a collateral result of certain organic activities ? To answer this, we must first remember that Consciousness is a purely subjective pro- cess ; although we may believe it to be objectively a neural process, we are nevertheless passing out of the region of Physiology when we speak of Feeling determining Action. Motion may determine Motion ; but Feeling can only determine Feeling. Yet we do so speak, and are justified. For thereby we implicitly declare, what Psychology ex- plicitly teaches, namely, that these two widely different aspects, objective and subjective, are but the two faces of one and the same reality. It is thus indifferent whether we say a sensation is a neural process, or a mental process : a molecular change in the nervous system, or a change in Feeling. It is either, and it is both, as I have elsewhere explained.* There it was argued that the current hypoth- esis of a neural process causing the mental process — molecular movement being in some mysterious way trans- * Problems, Vol. II. p. 478, sq. ANIMAL AUTOMATISM. 457 formed into sensatioij — is not only inconceivable, but altogether unnecessary ; Avhereas the hypothesis that the two aspects of the one phenomenon are simply two differ- ent expressions, now in terms of Matter and Motion, and now in terms of Consciousness, is in harmony with all the inductive evidence. 97. "It may be assumed," says Professor Huxley, "that molecular changes in the brain are the causes of all the states of consciousness of brutes. Is there any evidence that these states of consciousness may conversely cause those molecular changes which give rise to muscular motion ? I see no such evidence. The frog walks, hops, swims, and goes through his gymnastic performances, quite as well without consciousness, and consequently without volition, as with it ; and if a frog in his natural state possesses anything corresponding with what we call volition, there is no reason to think that it is anytliing hut a concomitant of the molecular changes in the train, which form 2jart of the series involved in the production of motion. The consciousness of brutes would appear to be related to the mechanism of their body simply as a collateral product of its working, and to be as completely ivithout any power of modifying that working as the steam-whistle which accompanies the vjorh of a locomotive engine is without in- Jluence upon its r^iaehinery. Their volition, if they have any, is an emotion indicative of physical changes, not a cause of such changes." Particular attention is called to the passages in italics. In the first is expressed a view which seems not unlike the one I am advocating, but wliich is contradicted by the second. Let us consider what is implied. 93. When Consciousness is regarded solely under its subjective aspect there is obviously no place for it among material agencies, regarded as objective. So long as we have the material mechanism in view we have nothing VOL. III. 20 458 THE PHYSICAL BASIS OF MIND. but material changes. This applies to the frog, with or without its brain ; to man, supposed to be moved by voli- tion, or supposed to move automatically. The introduc- tion of Consciousness is not the introduction of another agent in the series, but of a new aspect ; the neural process drops out of sight, the mental process replaces it. The question whether we have any ground for inferring that in the series there is included the particular neural state which subjectively is a state of Consciousness, must be answered according to the evidence. Well, the evi- dence shows that the actions do involve the co-operation ; and this Professor Huxley expresses when he says that the molecular changes in the brain form part of the series in- volved in the production of motion. Whether we regard the process objectively as a series of molecular changes, or subjectively as a succession of sentient changes, the sum of which is on the one side a motor impulse, on the other a state of consciousness, we must declare Conscious- ness to be an agent, in the same sense that we declare one clmngc in the organism to he an agent in some other change. The facts are the same, whether w^e express them in physiological or in psychological terms. The physiolo- gist, having only the material aspect of the organism in view, says, "A cerebral process initiates a motor process " ; the psychologist says, "A sensation determines an action." Unless the two processes have been linked together by an organic disposition, native or acquired, there will be no such motor process following the cerebral process. A dog standing outside the gate is unable to ring the bell, though having seen anotlier dog ring it, he may wish to do so ; but the cerebral process (his wish) is not linked on to the needful motor process — he has not learned to realize the wish ; whereas the other dog, having by trial hit upon the right mode of directing his muscles, has registered this experience, and can ring the bell. The organized disposi- ANIMAL AUTOMATISM. 459 tion which enables the dog to do this may truly enough he called a modification of the mechanism ; but what we have here to note is that a sensation originally determined the movement, and always determines it. 99. It is the unfortunate ambiguity of the word Con- sciousness, and tlie questionable hypothesis of the brain being the sole seat of Sensibility, which darken this in- vestigation. Because animals, after the brain has been removed, are seen to perform certain actions as deftly as before, they are said to perform these without the inter- vention of Consciousness ; when all that is jDroved by the facts is that these actions are performed without the in- tervention of the brain. In support of this explanation, examples are cited of unconscious actions performed by human beings. But if we assign Sensibility not to one part of the nervous system exclusively, but to the whole, we can readily understand how the loss of a part will be manifested by very marked changes in the reactions of the whole, and yet not altogether prevent the reactions of the parts remaining intact. An animal must respond somewhat differently with and without a brain. One marked difference is the spontaneity of the actions when the brain is intact, and the loss of much spontaneity when the brain is injured or removed. Cerebral processes prompt and regulate actions, as the pressure of the driver on the reins prompts and regulates the movements of the horses ; but the carriage is moved by tlie horses and not by the driver ; and the action is executed by the motor mechanism, whether the incitation arise in a cerebral process or a peripheral stimulation. 100. If we admit that Consciousness is itself an organic process, accompanying the molecular changes as a convex surface accompanies a concave, we must also admit that its fluctuations are adjustments and readjustments of the organic mcclianisin, and that the actions arc tlic (sffects 460 THE PHYSICAL BASIS OF MIND. of these — tlieir resultants. The loss of the brain must obviously cause a great disturbance in these adjustments. We may call that a loss of Consciousness, if we clioose to limit the term to one mode of sentient reaction. But this loss of a mode does not change those reactions which persist so as to convert them into purely mechanical re- actions. A troop of soldiers may have lost its directing officer, but will fight with the old weapons and the old intelligence, though not with the same convergence of individual efforts. A frog or a pigeon no more acts as tvcll without a brain as with a brain, than the troop of soldiers fights as well without an officer. 101. Having thus claimed a place for Consciousness in the series of organic processes, let us now see whether it has a place among the active agencies. According to Professor Huxley it is not itself an agent, but only the " collateral product of the working of the machine." It accompanies actions, it does not direct them. It is an index, not a cause. Surely it seems more accurate to say that it accompa- nies and directs the working ? It accompanies the work- ing in two senses : first, as the subjective aspect of the objective process ; secondly, as the change which pro- duces a subsequent change, that is to say, the movements initiated by a feeling are themselves also felt as they pass ; and this feeling enters into the general stream of simulta- neous excitations out of which new movements and feel- ings arise; or to express it physiologically, the sensory impressions determine muscular movements, which in turn react on the nerve-centres, and these reactions blend with the general excitation of reflected and re-reflected processes.* Since every change in Consciousness is a * "Le sentiment fait naitre le mouvement, et le mouvement donne naissance au sentiment." — Van Deen, Traites et Decouvcrtes sur la Moelle Spinier e, 1841, p. 102, ANIMAL AUTOMATISM. 461 change in the sentient organism, which objectively is a change in the nervous centres, the working of the mechanism being itself a dependent series of such changes, each movement must have a reflected influence on the general state. This reflected influence may be viewed as a collateral product of the working ; but there is no real analogy between it and the whistle of the steam-engine, because this reflected influence demonstrably docs inter- vene in the subsequent movements. The feeling which accompanies or follows a particular movement cannot indeed modify J7ia^ movement, since that is already set going, or has passed ; here there is some analogy to the steam- whistle ; but the analogy fails in the subsequent history : no movements whatever of the steam-engine are modified by the whistle which accompanies the working of that engine ; yet how the reflected influence modifies the working of the organism ! If the hand be passing over a surface, there is, accompanying this movement, a succession of muscular and tactile feelings which may be said to be collateral products. But the feeling which ac- comjoanics one muscular contraction is itself the stimulus of the next contraction ; if anywhere during the passage the hand comes upon a spot on the surface which is wet or rough, the change in feeling thus produced, although a col- lateral product of tlie movement, instantly changes the di- rection of the hand, suspends or alters the course — that is to say, the collateral product of one movement becomes a di- recting factor in the succeeding movement. Now this is pre- cisely what no automaton can effect, unless for changes that are prearranged. A steam-engine drives its locomo- tive over the rails, be they smooth or rough, entire or broken ; it whistles as it goes, but no whistling directs and redirects its path. 102. Volition is said to be an " emotion indicative of physical changes, not a cause of such changes." Here it 462 THE PHYSICAL BASIS OF MIND. is necessary to understand in what sense the term cause is employed. I should prefer stating the proposition thus: a volition is a state of the sentient organism, indic- ative of physical changes which have taken place, and of changes which will take place. Because it is the ex- pression of the first group of changes, it cannot be their origin; but it can be, and is the origin of the second group, which it initiates. The indignation excited by an insult or a blow is not the origin of the emotion or the pain, but it is the origin of the actions which are prompted by this sentient state. In fact no sooner do we admit that the organism is a sentient mechanism, than the con- clusion is irresistible that Sensibility is a factor in the working of that mechanism. 103. " Much ingenious argument," says Professor Hux- ley, " has at various times been bestowed upon the ques- tion : How is it possible to imagine that volition which is a state of consciousness, and as such has not the slight- est community of nature with matter and motion, can act upon the moving matter of which the body is com- posed, as it is assumed to do in voluntary acts ? But if, as is here suggested, the voluntary acts of brutes — or in other words, the acts which they desire to perform — are as purely mechanical as the rest of their actions, and are simply accompanied by the state of consciousness called volition, the inquiry, so far as they are concerned, becomes superfluous. Their volitions do not enter into the chain of causation of their actions at all As consciousness is brought into existence only as the con- sequence of molecular motion in the brain, it follows that it is an indirect product of material changes. The soul stands related to the body as the bell of a clock to the works, and consciousness answers to the sound wdiicli the bell gives out when it is struck." This has been answered in the foregoing pages ; nor do I think the reader who ANIMAL AUTOMATISM. 463 has recognized the ambiguity of the term Consciousness, and the desirability of replacing it in this discussion by the less equivocal term Sentience, will need more to be said. 104. The important question whether reflex actions are insentient, and therefore mechanical, will occupy us in the next problem. The question of Automatism which has been argued in the preceding chapters, may, I think, be summarily disposed of by a reference to the irresistible evidence each man carries in his own consciousness that his actions are frequently — even if not always — deter- mined by feelings. He is quite certain that he is not an automaton, and that his feelings are not simply collateral products of his actions, without the power of modifying and originating them. Now this fundamental fact cannot be displaced by any theoretical explanation of its factors. Nor would this fundamental truth be rendered doubtful, even supposing we were to grant to the full all that is adduced as evidence that some actions were the result of purely mechanical processes without sentience at all. I am a conscious organism, even if it be true that I some- times act unconsciously. I am not a machine, even if it Ije true that I sometimes act mechanically. PROBLEM IV. THE REFLEX THEORY, "Si onmes patres sic, at Ego non sic." - Abelard, Sic et Kon. " Will man bestimmen wo der Mechanismus auflidrt und wo der Wille anfiingt so ist die Frage iiberhaupt falscli gestellt. Dean mau setzt liier Be- griffe einander gegeniiber die gar keine Gegensatze sind. Vorgebildet iu den mechanischen Bedingungen des Nervensystems sind alle Bewegungen." — WuNDT, Physiologische Psychologie. " SoUte die so durchsiclitige Homologie zwischen Him iind Riickenmark, wie solche sich schlagend in Ban und Entwicklung dartbut, wesentlich andere physiologiscbe Qualitaten bedingen?" — Luschinger in Pfluger's Archiv, Bd. XIV. 384. 20* THE REFLEX THEORY. CHAPTEE I. THE PROBLEM STATED. 1. The peculiarity of the Eeflex Theory is its exclusion of Sensibility from the actions classed as reflex ; in conse- quence of which, the actions are considered to be " purely mechanical." No one denies that most of the reflex actions often have conscious sensations preceding and accompanying them, but these are said not to be essential to the per- formance of the actions, because they may be absent and the actions still take place. It is notorious that we breathe, wink, swallow^ etc., whether we are conscious of tliese actions or not. Our conclusion therefore is that these jjeculiar states of Consciousness are accessory, not essential to the performance of these actions. The fact is patent, the conclusion irresistible. But now consider the equivoque : because an action takes place without our being conscious of it, the action is said to have had no sensation determining it. This, which is a truism when we limit Consciousness to one of the special modes of Sensibility, or limit sensation to this limited Conscious- ness, is a falsism when we accept Consciousness as the total of all combined sensibilities, or Sensation as the reaction of tlie sensory mechanism. That a reflex action is determined by the sensory mechanism, no one disputes ; 468 THE PHYSICAL BASIS OF MIND. whether the reaction of a sensory mechanism shall be called a sensation or not, is a question of terms. I have shown why it must be so called if anything like coherence is to be preserved in physiological investigations ; and I have more than once suggested that the fact of intellectual processes taking place at times with no more conscious- ness than reflex actions, is itself sufficient to show that a process does not lapse from the mental to the mechanical sphere simply by passing unconsciously. Inasmuch as an organism is a complex of organs, its total function must be a complex of particular functions, each of which may analytically be treated apart. Vitality is the total of all its physiological functions, and Con- sciousness the total of all its psychological functions. But inasmuch as it is only in its relation to the whole that each part has functional significance, and cannot therefore be isolated in reality, as it is in theory — can- not live by itself, act by itself, independently of the organ- ism of which it is an organ, there is strict accuracy in saying that no particular sensation can exist without in- volving Consciousness ; for this is only saying that no sensory organ can react without at the same time involv- ing a reaction of the general sensorium. But since this general sensorium is simultaneously affected by various excitations each of which is a force, every sensation, perception, emotion, or volition is a resultant of the com- position of these forces ; and as there can be only one resultant at a time, to be replaced by another in swift succession, this one represents the state of Consciousness, and this state may or may not be felt under the peculiar mode named " Consciousness," in its special meaning. In other words, the reaction of a sensory organ is ahvays sen- tient, but not always consentient. 2. Let us illustrate this by the sensation of musical tone. When we hear a tone we are affected not only by THE EEFLEX THEORY. 469 the fundamental tone, representing the vibrations of the sounding body as a whole, but also by the harmonics or overtones, representing the vibrations of the several parts of that whole. It is these latter vibrations which give the tone its timbre, or peculiar quality ; and as the har- monics are variable with the variable structure of the vibrating parts, two bodies which have the same fun- damental tone may have markedly different qualities. There are some tones wliich are almost entirely free from harmonics ; that is to say, their harmonics are too faint for our ear to appreciate them, though we know that the vibrations must be present. Apply this to the excitations of the sensorium. Each excitation will have its funda- mental feeling, and more or less accompanying thrills of other feelings : it is these thrills which are the harmonics, giving to each excitation its specific quality; but they may be so faint that no specific quality is discriminated. A fly settles on your hand while you are writing, the faint thrill which accompanies this excitation of your sensory nerve gives the specific sensation of tickling, and tliis causes you to move your hand with a jerk. If your atten- tion is preoccupied, you are said to be unconscious of the sensation, and the jerk of your hand is called a reflex action ; but if your attention is not preoccupied, or if the thrill is vivid, you are said to be conscious of the sensa- tion, and the action is no longer reflex, but volitional. Obviously here tlie difference depends not on the sentient excitation by an impression on the nerve, but on tlie state of the general sensorium and its consequent reaction. Had not the impression lieen carried to tlie sensorium, no movement would have followed the fly's alighting on your hand, because no sen-sation (sensory reaction) would have been excited; the hypothesis of a purely mechanical re- llcx is quite inadmissiljle. 3. Or take another case. It sometimes happens that 470 THE PHYSICAL basis of mind. we fall asleep while some one is reading to us aloud. The sounds of the reader's voice at first awaken the familiar thrills whicli give the tones their quality, and the words their significance ; but gradually as sleep steals over us, the organism ceases to react thus ; the words lose more and more of their significance, the tones lose more and more of their harmonics ; at last we pass into the state of unconsciousness — we cease to hear what is read. But do we cease to feel ? AVe have not heard, but we have been affected by the sounds. Not by distinguishable sen- sations ; nevertheless a state of the general Sensibility has been induced. To prove that we have been affected is easy. Let the reader suddenly cease, and if our sleep be not too profound, we at once awake. Now, unless the sound of his voice had affected us, it is clear that the ces- sation of that could not have affected us. Or let us sup- pose our sleep to be unbroken by the cessation of the sound ; even this will not prove that we have been unaf- fected by the sounds, it will merely prove that those sounds, or their cessation, did not excite a conscious state. For let the reader, in no louder tone, ask, "Are you asleep?" and we start up, with round eyes, declaring, "Not at all." Nay, should even this question fail to awaken us, the speaker need only utter some phrase likely to excite a thrill — such as, " There 's the postman ! " or, " I smell fire ! " and we start up. I remember once trying the experiment on a wearied waiter, who had fallen asleep in one of the unoccupied boxes of a tavern. His arm rested on the table, and his head rested on his arm : he snored the snore of the weary, in spite of tlie noisy laughter and talk of the guests. I called out " Johnson," in a loud tone. It never moved him. I then called "Wilson," but he snored on. No sooner did I call " waiter," than he raised his head with a sleepy " yessir." Now, to suppose, in this case, that he THE REFLEX THEORY. 471 had no sensation when the words " Johnson " and " Wil- son " reached his ears, but had a sensation when the word " waiter " reached his ears, is to suppose that two similar causes will not produce a similar effect. The dissyllable " Johnson " would excite as potent a reaction of his sen- sory organ as the dissyllable " waiter " ; but the thrills — the reflex feelings — were different, because tlie word " Johnson " was not associated in his mind with any defi- nite actions, whereas the word " waiter " was so associated as to become an automatic impulse.* 4. Two sisters are asleep in the same bed, and a child cries in the next room. The sounds of these cries will give a similar stimulus to the auditory nerve of each sis- ter, and excite a similar sensory reaction in each. Never- theless, the one sister sleeps on undisturbed, and is" said not to hear the cry. The other springs out of bed, and attends to the child, because she being accustomed to attend on tlie cliild and soothe it when crying, the pri- mary sensation has excited secondary sensations, thrills which lead to accustomed actions. Could we look into the mind of the sleeping sister, we should doubtless find that the sensation excited by the child's cry had merged itself in the general stream, and perhaps modified her dreams. Let her become a mother, or take on the tender duties of a mother, and her vigilance will equal that of her sister ; because the cry will then excite a definite reflex feeling, and a definite course of action. But this very sister, who is so sensitive to the cry of a child, will be undisturbed by a much louder noise ; a dog may bark, or a heavy wagon thunder along the street, without caus- ing her to turn in bed.f * Dr. Cakpkntkr tells a similar story of Admiral Codiunoton, who, wliPii a midshipman, could always be awakened from the profoundest slumber if the word "signal" were uttered ; whereas no other word dis- turbed him. t C'ompare an intere.sting personal example given by Joufkuov, ijuoted in Sir W. Hamilton's Lectures, I. 331. 472 THE PHYSICAL BASIS OF MIXD, Although during sleep the nervous centres have l)y no means their full activity, they are always capable of responding to a stimulus, and sensation will always be produced. When the servant taps at your bedroom door in the morning, you are said not to hear the tap, if asleep; you do not perceive it ; but the sound reaches and rouses you nevertheless, since when the second tap comes, al- though no louder, you distinctly recognize it. In ether- ized patients, sensation is constantly observed returning before any consciousness of what is going on returns. " I was called," says ]\Ir. Potter, " to give chloroform to a lady for the extraction of ten teeth. The first five were ex- tracted without the slightest movement, but as the opera- tion proceeded, sensation returned, and I was obliged to use considerable force to keep her in the chair during the extraction of the last tooth. She came to herself very shortly after, and was delighted to find she had got over all her troubles without having felt it the least in the world."* 5. We do not see the stars at noonday, yet they shine. We do not see the sunbeams playing among the leaves on a cloudy day, yet it is by these beams that the leaves and all otlier objects are visible. There is a general illumina- tion from the sun and stars, but of this we are seldom aware, because our attention falls upon the illumined objects, brighter or darker than this general tone. There is a sort of analogy to this ih the general Consciousness, which is composed of the sum of sensations excited by the incessant simultaneous action of internal and external stimuli. This forms, as it were, the daylight of our exist- ence. We do not habitually attend to it, because attention falls on those particular sensations of pleasure or of pain, of greater or of less intensity, which usurp a prominence among the objects of the sensitive panorama. But just * Lancet, 10th July, 1858. THE REFLEX THEORY. 473 as we need the daylight to see tlie brilliant and the sombre forms of things, we need this living Consciousness to feel the pleasures and the pains of life. It is therefore as erroneous to imagine that we have no other sensations than those which we distinctly recognize — as to imagine that we see no other light than what is reflected from the sliops and equipages, the colors and splendors which arrest the eye. The amount of light received from the stars may be small, but it is present. The greater glory of the sun- liglit may render this starlight inappreciable, but it does not render it inoperative. In like manner the amount of sensation received from some of the centres may be in- appreciable in the presence of more massive influences IVom other centres ; but though inappreciable it cannot be inoperative — it must form an integer in the sum. 6. The reader's daily experience will assure him that over and above all the particular sensations capable of being separately recognized, there is a general stream of Sensation which constitutes his feeling of existence — the Consciousness of himself as a sensitive being. The ebullient energy which one day exalts life, and the mourn- ful depression which the next day renders life a burden almost intolerable, are feelings not referable to any of the particular sensations, but arise from the massive yet ob- scure sensibilities of the viscera, wliich form so important a part of the general stream of Sensation. Some of these may emerge into distinct recognition. We may feel tlie lieart beat, the intestines move, tlie glands secrete ; any- thing unusual in their action will force itself on our attention. " What we have been long used to," says Whytt, " we become scarcely sensible of; while things which are new, though much more trifling, and of weaker impression, affect us remarkably. Thus he who is wont to spend his 474 THE PHYSICAL BASIS OF MIND. time in the country is surprisingly affected, upon first coming- into a populous city, with the noise and bustle which prevail there : of this, however, he becomes daily less sensible, till at length he regards it no more than they ■who have been used to it all their lifetime. The same seems to be the case also with what passes within our bodies. Few persons in health feel the beating of their heart, though it strikes against their ribs with considerable force every second ; whereas the motion of a fly upon one's face or hands occasions a very sensible and uneasy titil- lation. The pulsation of the great aorta itself is \vholly unobserved by us ; yet the unusual beating of a small artery in any of the fingers becomes very remarkable." 7. A large amount of sensation is derived from the muscular sense, yet we are not aware of the nice adjust- ments of the muscles, regulated by this sensibility, wheu we sit or walk. Xo sooner are we placed in an exceptional position, as in walking on a narrow ledge, than we become distinctly aware of the effort required to preserve equi- librium. It is not the novelty of the position which has increased our sensibility ; that has only caused us to attend to our sensations. In like manner, the various streams of sensation which make up our general sense of existence, separately escape notice nntil one of them becomes obstructed, or increases in impetuosity. When we are seated at a windov/, and look out at the trees and sky, we are so occupied with the aspects and the voices of external Nature, that no attention whatever is given to the fact of our own existence ; yet all this while there has been a massive and diffusive feeling arising from the organic processes ; and of this we become distinctly aware if we close our eyes, shut off all sounds, and abstract the sensations of touch and temperature — it is then perceived as a vast and powerful stream of sensation, belonging to none of the special Senses, but to the System as a whole. THE EEFLEX THEORY. 475 It is on this general stream that depend those well-known but indescribable states named " feeling well " and '' feel- ing ill " — the hien etre and malaise of every day. Of two men looking from the same window, on the same land- scape, one will be moved to unutterable sadness, yearning for the peace of death ; the other will feel his soul suf- fused with serenity and content : the one has a gloomy background, into which the sensations excited by the landscape are merged ; the other has a happy background, on which the sensations j)lay like ripples on a sunny lake. The tone of each man's feeling is determined by the state of his general consciousness. Except in matters of pure demonstration, we are all determined towards certain conclusions as much by this general consciou.sness as by logic. Our philosophy, when not borrowed, is little more than the expression of our personality. 8. Having thus explained the relation of particular sensations to the general state of Consciousness consid- ered as the function of the whole organism, we may henceforward speak of particular sentient states, as we speak of particular organs and functions, all the while presupposing that the organs and functions necessarily involve the organism, since apart from the organism they have no such significance. The reaction of a sensory organ is therefore always a sentient plienomenon. Apart from the living organism there can be no such vital re- action, but only a physical reaction. It is commonly supposed that sensation is simply the molecular excitation of the cerebrum ; yet no one will maintain that if the cerebrum of a corpse be excited, by a galvanic current sent through the optic nerve, for instance, this excitation will be a sensation. Whence we may conclude that it is not the physical reaction or stimulus which constitutes sensation, but the physiological reaction of the living organism. 476 THE PHYSICAL BASIS OF MIND. 9. Now this is the point which the advocates of the Reflex Tlieory, implicitly or explicitly, always deny. Let us trace the origin of the fallacy, if possible. When we remove the eye from a recently killed animal, and let a beam of light fall on it, the pupil contracts. This is a purely mechanical action ; no one would suggest that a sensation determined it. When we remove the leg, and irritate its nerve, the leg is jerked out. This is also a I)urely mechanical action. When we remove the brain Irom an animal, and pinch its toes, the leg is withdrawn or the pincers are pushed aside. Is this equally a purely mechanical action ? And if not, why not ? The Reflex Theory would have us believe that all three cases were mechanical, at least in so far as they were all destitute of sentient co-operation, the ground for this conclusion being the hypothesis that the braiu is the ex- clusive seat of sensation. The Reflex Theory further con- cludes that since these, and analogous actions, are per- formed when the brain is removed, they, being thus independent of sentience, may be performed when the brain is present without any co-operation of sentience. The grounds for this conclusion being the facts that in the normal state of the organism there are many actions of which we are sometimes conscious, and at other times unconscious ; and some actions — such as the dilatation and contraction of the pupil — of which we are never conscious. This observation of parts detaclied from the organism seems confirmed by observation of actions pass- ing in our own organisms, both converging to the con- clusion that the actions in question are purely mechanical, involving no sentience whatever. We are taught, there- fore, that there is besides the sentient mechanism, to which all conscious actions are referred, a reflex mechan- ism, to which all unconscious actions are referred. The cerebro-spinal axis, acting as a whole, constitutes the first; THE REFLEX THEORY. 477 the spinal axis, acting without the co-operation of the cerebrum, constitutes the second. 10. Before proceeding with our exposition of the theory- it may be Avell to state two considerations which must be constantly in view. If it should appear that there is any reasonable evidence for refusing to limit Sensibility to the cerebrum — and this evidence I shall adduce — the Keflex Tlieory must obviously be remodelled. Nor is this all. We might see overwhelming evidence in favor of the hypothesis that the cerebrum is the exclusive seat of Sensibility, and still reject as a fallacy the con- clusion that because certain actions can be performed in the absence of the cerebrum, therefore those actions in the normal organism are likewise performed without cere- bral co-operation. I mean that it is a fallacy to conclude from the contractions of the pupil, and the jerking of the leg, when eye and leg are detached from the organism, that therefore when eye and leg form integral parts of the organism, such contractions and jerkings are mechani- cal reflexes without sentient conditions. And the fallacy is analogous to that which would conclude from the ob- servations of a mechanical automaton, that similar ap- pearances in a vital organism were equally automatic and mechanical. So long as both sets of phenomena are apprehended simply as they appear to the senfee of sight, they may be indistinguishable ; but no sooner do we appreliend them tlirough other modes, and examine the modes of production of the plienomena, than we come upon cardinal differences. A limb detached from the organism is like a plirase detached from a sentence : it has lo.st its vital significance, its functional value, in los- ing its connection with the other parts. The wliole sen- tence is necessary for the slightest meaning of its con- stituent words, and each word is a language-clement only when ideally or verbally connected with the other words 478 THE niYSICAL BASIS OF MIND. required to form a sentence ; without subject, predicate, rtud copula, no sentence can be formed. So the organic counexus of parts with a living whole is necessary for the simplest function of each orgaji ; and a limb, or any other part, is a physiological element only when (ideally or really) an integral of a vital whole. The organism may be truncated by the removal of certain parts, as the sentence may be abbreviated by the removal of certain phrases; but so long as subject, predicate, and copula remain, there is a meaning in the sentence ; and so long as the organic connexus needful for vitality remains^ there will be vital function. The eye detached from the organism is no longer a part of the living whole, it no longer lives, its phenomena cease to be vital, its move- ments cease to have sentient conditions. The move- ments of the pupil may seem to be the same as those of the living eye ; but when we come to examine their modes of production, we learn that they are not the same. The stimulus of light falling on the eye in the two cases necessarily has a different effect, because the effect is the result of the co-operating causes, and the co-operation in the one case is that of a lifeless organ, in the other that of a living organism. So long as the eye forms an inte- gral part of the organism, every stimulus acting on the eye necessarily acts on the organism, and every reaction of the organ is necessarily conditioned by the state of the organism. Further, every stimulation of a sensory nerve necessarily affects the general sensorium, since the whole nervous system is structurally continuous and func- tionally co-operant. (See Prob. II. § 16.) Therefore, the stimulation of the eye, although too faint to be discrimi- nated as a conscious sensation, must enter as a sentient tremor into the general stream of Sentience ; and although we have no test delicate enough to reveal this operation, we know the obverse, operation of conscious sensation on THE KEFLEX THEORY. 479 the movements of the pupil — in surprise, for example, the pupil is dilated. 11. There are still stronger reasons for asserting that the spinal reflexes are necessarily conditioned by the general state of the sensorium, so that in the normal organism we cannot legitimately exclude them from Sen- tience ; and the Eeflex Theory is therefore unphysiologi- cal, even on the hypothesis that the cerebrum is the exclusive seat of Sensibility. This hypothesis, however, seems to me untenable ; and all the observed facts which it is invented to explain admit of a far more consistent explanation. It is irrational to suppose that a limb, de- tached from the body, felt the stimulus which caused its muscles to contract. The limb is not a living organism, having a sentient mechanism in its nervous mechanism. Not less irrational is it to suppose that when the limb forms an integral part of a living organism, with a sen- tient mechanism of nerves and nerve-centres, this organism does not react on the stimulus which excites the muscles of the limb to contract ; nor, pursuing the same train of reasoning, is it irrational to suppose that when this liv- ing organism has been mutilated, and certain parts de- stroyed, which do not in tlieir destruction prevent the counexus of tlie rest, but leave intact a sentient mechan- ism of nerves and nerve-centres, then also this truncated organism still reacts as a whole, still feels the stimulus wliich causes the muscles of the limb to contract. Hy- pothesis for hypothesis, we may at least say that the one is as reasonable as tlie other. And I shall 1)(; disap- pointed if, when the reader has gone through all the evi- dence hereafter to be adduced, he does not conclude that the hypothesis which a.ssigns Sensibility to the nervous mechanism as a wliolo is not the more acceptable of the two. 12. Let us now pursue our exposition of the licflex 480 THE niYsiCAL basis of mind. Theory. All that ^vc have endeavored to establish re- specting the essential identity of tlie processes in conscious and unconscious states, and voluntary and involuntary actions, — an identity which does not exclude differences of degree corresponding with these different terms, — is ignored or denied in the Eeflex Theory. Whereas I sup- pose all processes to be reflex processes, some of them hav- ing the voluntary, others the involuntary character, phys- iologists generally distinguish the involuntary as reflex, and invent for this class a special mechanism. Accord- ing to Marshall Hall, who originated the modern form of this theory, actions are divisible into four distinct classes : the voluntary, dependent on the brain ; tlie in- voluntary, dependent on the irritability of the muscular fibre ; the respiratory, wherein " the motive influence passes in a direct line from one point of the nervous sys- tem to certain muscles " ; and the reflex, dependent on the " true spinal system " of inciclent-excitor nerves, and of reflex-motor nerves. These last-named actions are pro- duced when an imjjrcssion on the sensitive surface is con- veyed, by an excitor-nerve, to the spinal cord, and is there reflected back on the muscles by a corresponding motor- nerve. In this process no sensation whatever occurs. The action is purely reflex, purely excito-motor — like the action of an ordinary mechanism.* Miiller, who shares with Marshall Hall the glory of having established this classification, thinks that although the absence of sensation is a characteristic of the reflex actions, these actions may be, and are at times, accompa- nied by sensation. "The view I take of the matter is the following : Irritation of sensitive fibres of a spinal nerve excites primarily a centripetal action of the nervous prin- * Marshall Hall in Philos. Trans., 1833. Lectures on the Nervous System and its Diseases, 1836. A^ew Menwir on the Nervous System, 1843. THE REFLEX THEORY. 481 ciple, conveying the impression to the spinal cord ; if the centripetal action can then be continued to the scnsorium commune, a true sensation is the result; if, on account of division of the cord, it cannot be communicated to the sensorium, it still exerts its whole influence upon the cord ; in both cases a reflex motor action may be the result." * 13. It is needless nowadays to point out that tlie ex- istence of a distinct system of excito-motor nerves belongs to Imaginary Anatomy ; but it is not needless to point out that the Imaginary Physiology founded on it still sur- vives. The hypothetical process seems to me not less at variance with observation and induction, than the hypo- thetical structure invented for its basis. We have already seen that w^hat Anatomy positively teaches is totally un- like the reflex mechanism popularly imagined. The sen- sory nerve is not seen to enter the spinal cord at one point, and pass over to a corresponding point of exit ; it is seen to enter the gray substance, which is continuous throughout the spinal cord ; it is there lost to view, its course being untraceable. Nor does the physiological process present the aspect demanded by the theory : it is not that of a direct and uniform reflexion, such as would result from an impression on one spot transmitted across the spinal cord to a corresponding motor-nerve. The impression is sometimes followed by one movement, some- times by another very different movement, each deter- mined by the state of neural tension in the whole central system. p]ven the facts on which the Ileflex Theory is based are differently interpreted by different physiologists. Van Deen, for instance, considers tliat lieflexion takes place without Volition, but not without Sensation ; and Budge, that it takes place without perception ( Vorstellung). And * JliJi.LER, Physiology, I. 721. VOL. III. 21 E E 482 THE PHYSICAL basis of mind. ■when it is remembered that most of the reflex actions will be accompanied by distinct consciousness whenever atten- tion is directed to them, or the vividness of the stimu- lation is slightly increased, it becomes evident that the absence of Consciousness (discrimination) is not the dif- ferentia of Eeflex action. 14. Nor can the absence of spontaneity be accepted as a differentia. All actions are excited by stimulation, internal or external. What are called the spontaneous actions are simply those which are prompted by internal, or by not recognizable stimuli ; and could we see the pro- cess, we should see a neural change initiated by some stimulation, whether the change was conscious and vo- litional, or unconscious and automatic. The dog rising from sleep and restlessly moving about, is acting sponta- neously, whether the stimulation which awakens him be a sensation of hunger, a sensation of sound, the sharp pain of a prick, or a dash of cold water. If he wags his tail at the sight of his master, or w^ags it when dreaming, the stimulation is said to be spontaneous ; but if after his spinal cord has been divided the tail wags when his abdo- men is tickled, the action is called .reflex. In all three cases there has been a process of excitation and reflexion. 15. The advocates of the Reflex Theory insist that spontaneity is always absent in brainless animals; whence the conclusion that the brain is the exclusive organ of sensation. But the fact asserted is contradicted by the evidence. No experimenter can have failed to observe numberless examples of spontaneity in brainless animals. Many examples have already been incidentally noticed in previous pages. Let me add one more from my notes : I decapitated a toad and a triton, and divided the spinal cord of another triton and a frog. At first the movements of the decapitated animals were insignificant ; but on the second day the headless toad was quite as lively as the THE EEFLEX THEORY. 483 froo- • and the headless triton little less so than his com- panion with cord divided hut hrain intact. I have, at the time of writing this, a frog whose cord was divided some weeks ago. He remains almost motionless unless when touched ; he is generally found in the same spot, and in the same attitude to-day as yesterday, unless touched, or unless the table be shaken. He occasionally moves one of the forelegs ; occasionally one of the hind-legs ; but without changing his position. If he M^ere brainless, this quiescence would be cited in proof of the absence of spon- taneity in the absence of the brain ; but this conclusion would be fallacious, and is seen to be so in the sponta- neous movements of his companion who has no brain. 16. With spontaneity is associated the idea of volition, and with volition choice. Now I admit that it is com- plicating the question to ask any one to conceive a head- less animal choosing one action rather than another ; but it is equally difficult to reconcile ourselves to the idea of " choice " in contemplating tlie actions of a mollusc. In what sense we can speak of the volition of a mollusc or an insect has already been considered (p. 408). When a man in a fit of coughing seizes a glass of water to allay the tickling in his throat, we have no hesitation in declaring this to be volitional — and the remedy to be chosen. But when a brainless animal adopts some unusual means, after the failure of the usual means, to allay an irritation, we still hesitate to call the action volitional. I see, however, no objection to calling it the adaptation of a sensitive mechanism which is markedly unlike any inorganic mech- anism. Place a child of two or tlu'ce years old ujjou his back, and tickle his right cheek witli a feather. lie will prob- ably move his head away. Continue tickling, and he will rub the spot with his riglit \\^m\, never iising the left hand for the riglit clieek, so long as the right hand is free ; but 484 THE PHYSICAL BASIS OF MIND. if you hold his right hand, he will use the left. Does any- one dispute the voluntary character of these actions ? Now compare the actions of the sleeping child under similar circumstances, and their sequence will be pre- cisely similar. This contrast is the more illustrative, because physiologists generally assume that in sleep con- sciousness and volition are suspended. They say : " The brain sleeps, the spinal cord never ; volition and sensation may be suspended, but not reflex action." This proposi- tion is extremely questionable ; yet it is indispensable to the reflex theory ; because unless sensation and volition are suspended during sleep, we must admit that they can act, without at the same time calling into activity that degree of sensibility which is supposed to constitute con- sciousness. The child moves in his sleep, defends him- self in his sleep ; but he is not " aware " of it. " Children," says Pflliger, " sleep more soundly than adults, and seem to be more sensitive in sleep. I tickled the right nostril of a three-year-old boy. He at once raised his right hand to push me away, and then rubbed the place. When I tickled the left nostril he raised the left hand. I then softly drew both arms down, and laid them close to the body, embedding the left arm in the clothes, and placing on it a pillow, by gentle pressure on which I could keep the arm down without awakening him. Having done this I tickled his left nostril. He at once began to move the imprisoned arm, but could not reach his face with it, because I held it firmly though gently down. He now drew his head aside, and I con- tinued tickling, whereupon he raised the riffht hand, and with it rubbed the left nostril — an action he never per- formed when the left hand was free." 17. This simple but ingenious experiment establishes one important point, namely, that the so-called reflex actions observed in sleep are determined by sensation and THE EEFLEX THEORY. 485 volition. The sleeping child behaves exactly as the waking child behaved ; the only difference being in the energy and rapidity of the actions. If the waking child felt and willed, surely the sleeping child, wlien it per- formed precisely similar actions, cannot be said to have felt nothing, willed nothing ? It is not at one moment a sentient organism, and at the next an insentient mech- anism. It is possible to meet this case by assuming that the child was nearly awake, and that a dim consciousness was aroused by the tickling, so that the cerebral activity was in fact awakened. But, plausible as this explanation may be (and I am the more ready to admit it because I l)elieve the brain always co-operates when it is present), it altogether fails when we come to experiments on de- capitated animals. If any one will institute a series of such experiments, taking care to compare the actions of the animal before and after decapitation, he will per- ceive that there is no more difference between them than between those of the sleeping and the waking child. 18. Even more striking is the following experiment, devised by Pflliger, which I have verified, and varied, many times : A frog is decapitated, or its brain is re- moved.* When it has recovered from the effect of the ether, and manifests lively sensiljility, we place it on its back, and touch, with acetic acid, the skin of its thigh just above the condt/las intcrnus fcmoris. (Let the reader imagine his own shoulder burnt at the point wliere it can be reached with the thumb of the same arm, and lie will * It is better simply to remove the brain, than to remove the whole head, whieh causes a serious loss of blood. An etherized animal may be ()l)erated on with case and accuracy. For many experiments, mere divis- ion of the spinal cord is better than decapitation. Great variations in the results must be expected, because the condition of the animal, its age and sex — whether fasting or digesting — whether the season lie spring or summer — and a hundred other causes, complicate the ex- pi'iimont. 486 THE PITYSICAL BASIS OF MIXD. realize the operation.) No sooner does the acid begin to burn than the frog stretches out tlie other leg, so that its body is somewluit drawn towards it. The leg that has been burnt is now bent, and the back of the foot is ap- plied to the spot, rubbing the acid away — just as your thumb might rub your shoulder. This is very like the action of tlie tickled child, who always uses the right hand to rub the right cheek, unless it be held ; but when the child's right hand is prevented from rubbing, the left will be employed ; and precisely this do we observe with the brainless frog : prevent it from using its right leg, and it will use its left ! This has been proved by decapitating another frog, and cutting off the foot of the leg which is to be irritated. No soouer is the acid applied, than the leg is bent as be- fore, and the stump is moved to and fro, as if to rub away the acid. But the acid is not rubbed away, and the ani- mal becomes restless, as if trying to hit upon some other plan for freeing himself of the irritation. And it is worthy of remark that he often hits upon plans very similar to those which an intelligent human being adopts under similar circumstances. Thus, the irritation con- tinuing, he will sometimes cease the vain efforts with his stump, and stretching that leg straight out, bends tlie other leg over towards the irritated spot, and rubs the acid away. But, to show how far this action is from one of " mere mechanism," how far it is from being a direct reflex of an impression on a group of muscles, the frog does not always hit even on this plan. Sometimes it bends its irritated leg more energetically, and likewise bends the body towards it, so as to permit the spot to be rubbed against the flank — just as the child, when both his hands are held, will bend his cheek towards his shoulder and rub it there. 19. It is difficult to resist such evidence as is here THE KEFLEX THEORY. 487 manifested. The brainless frog "chooses" a new plan when the old one fails, just as the waking child chooses. And an illustration of how sensations guide and deter- mine movements, may be seen in another observation of the brainless frog, when, as often happens, it does not hit upon either of the plans just mentioned, but remains apparently restless and helpless ; if under these circum- stances we perform a part of the action for it, it will com- plete what we have hegun : if we rub the irritated leg, at some distance from the spot where the acid is, with the foot of the other, the frog suddenly avails itself of this (juiding sensation, and at once directs its foot to the irri- tated spot. In these experiments on the triton and the frog, the evidence of sensation and volition is all the stronger, be- cause the reactions produced by irritations are not uni- form. If when a decapitated animal were stimulated it always reacted in precisely the same way, and never chose new means on the failure of the old, it would be conceiv- able to attribute the results to simple reflex action — i. e. tlie mechanical transference of an impulse along a pre- scribed path. It is possible so to conceive the breathing, or the swallowing mechanism : the impression may be directly reflected on certain groups of muscles. But I cannot conceive a machine suddenly striking out new methods, when the old methods fail. I cannot conceive a machine thrown into disorder when its accustomed actions fail, and in this disorder suddenly lighting upon an action likely to succeed, and continuing that ; but I can conceive this to be done by an organism, for my own experience and observation of animals assures me that this is always the way new lines of action are adopted. And this which is observed of the unmutilated animal, I have just shown to be observed of the brainless animal ; wherefore the conclusion is, that if ever tlie frog is sen- 4S8 THE riivsiCAL basis of mixd. tient, if ever its actions are guided by sensation, they are so when its braiu is removed. 20. Schroder van der Kolk thinks that rfliiger was deceived in attributing sensation and volition to the frog, because the reflex actions are, he says, so nicely adapted to their ends, that they are undistinguishable from volun- tary actions. The mechanism is such that, by means of the communications established between various groups of cells, all these actions adapted to an end may be ex- cited by every stimulus. But I deny the fact. I deny that all the actions are awakened by every stimulus. Only some few are awakened, and those are not always the same, nor do they follow the same order of succession. One decapitated frog does not behave exactly like another under similar circumstances ; does not behave exactly like himself at different seasons ; unlike a machine, he manifests spontaneity in his actions, and volition in the direction of his actions. 21. The reader will notice that my illustrations show these actions of the brainless animal to have the same external characters as those of the unmutilated animals. I am therefore not here concerned to prove the psychical nature of these actions, unless it be granted that the un- mutilated animal has sensation and volition. This of coiirse can only be inferred, not proved. But the infer- ence must not be allowed in the one case and refused in the other. Young rabbits and puppies when taken from their mothers manifest discomfort by restless movement and whining. Do they feel the discomfort they thus ex- press ? If ever rabbits and jDuppies may be said to feel, we must answer. Yes. Well, if the brain be removed from rabbits and puppies, precisely similar phenomena are observed when these young animals are taken from their mothers. " I observed the motions, which seemed the result of discomfort, quickly cease w^hen I warmed the young rabbit by breathing on it. After a while it THE EEFLEX THEOKY. 489 was completely at rest, and seemed sunk in deep sleep ; occasionally, however, it moved one of its legs without any external stimulus having been applied, and this not spasmodically, but in the manner of a sleeping animal."* Is this cessation of the restlessness, when warmth is re- stored, not evidence of sensation ? We see an infant rest- less, struggling, and squalling ; and we believe that it is hungry, or that some other sensations agitate it ; it is put to the breast, and its squalls subside ; or a finger is placed in its mouth, and it sucks that, in a peaceful lull, for a few moments, to recommence squalling when the finger yields no satisfaction. If we accept these as signs of sen- sation, I do not see how we can deny such sensation to the brainless animal which will also cease to cry, and will suck the delusive finger. 22. One of the earliest advocates of tlie Eefiex Theory sums up his observations in these words : " It is clear that brainless animals, although without sensation, be- cause not endowed with mind, nevertheless, by means of external impressions which operate incessantly on them, perform all the acts and manifest all the activity of the sentient animal ; everything that is effected sensationally and volitionally, they effect by means of the organic forces of the impressions." f Call Sensibility one of the organic forces, if you please, but so long as the acts per- formed are not only the same as those of a sentient ani- mal, but are performed by the same mechanism, they have every claim to the character of sensational acts wliich can be urged in the case of these animals wlien the brain is present. And the only reason on which this claim is disputed is the assumed loss of aU sensation with tlie loss of tlie brain. Here, therefore, lies the central point to be determined. * VoLKMA.NX, quoted by PflUger. t UxzER, y/w Principles of Physiology (translated for tlie Sydenham Society), p. 235. 21* 490 THE PHYSICAL BASIS OF MIND. CHAPTER II. DEDUCTIONS FROM GENERAL LAWS. 23. The evidence is of two kinds : deductions from the general laws of nervous action, and inductions from par- ticular manifestations. The former furnish a presump- tion, the latter a proof. The central process which initiates a reflex action may be excited by the external stimulation of a peripheral nerve, by the internal stimulation of a peripheral nerve, or by the irradiation from some other part of the central tissue. The last-named stimulations are the least intel- ligible, because they are so varied and complex, and so remote from observation ; among them may be placed, 1°, the organized impulses of Instinct and Habit, with their fixed modes of manifestation ; 2°, the organized impulses of Emotion, which are more variable in their manifesta- tions, because more fluctuating in their conditions; 3°, the organized impulses of Intellect, the most variable of all. Whether we shrink on the contact of a cold substance or on hearincf a sudden sound, — at the sif^ht of a terrible object, — at the imaginary vision of the object, — or be- cause we feign the terror wliich is thus expressed, — the reflex mechanism of shrinking is in each case the same, and the neural process discharged on the muscles is the same ; but the state of Feeling which originated the change — or, in strictly physiological terms, the inciting neural process which preceded this reflex neural process — was in each case somewhat different, yet in each case was a mode of Sensibility. THE REFLEX THEOKY. 491 24. The property of Sensibility belongs to the whole central tissue ; and we have every reason to believe that unless it is excited no reflex takes place, wliereas when it is exaggerated — as in epilepsy, or under strychnine — the reflex discharges are convulsive. When anaesthetics are given, consciousness first disappears, and then re- llexion. When the sensorium is powerfully excited by other stimuli, the normal stimulus fails to excite either consciousness or reflexion. Hence our conclusion is that for consciousness, on the one hand, and normal reflexion, on the other, the proximate condition is a change in the sensorium; or — to phrase it more familiarly — Feeling is necessary for reflex action. The difficulty in apprehending this lies in the am- biguity of the term Feeling. Many readers who would find no difficulty in admitting Sensibility as a necessary element in reflex action, will resist the idea of identifying Sensibility with Feeling. But this repugnance must be overcome if we are to understand the various modes of Sensibility whicli represent Feeling in animals, and its varieties in ourselves. We understand how the general Sensibility manifests itself in markedly different sensa- tions — how that of the optic centre differs from that of the auditory centre, and both from a spinal centre. The tones of a violin are not the same as the tones of a vio- loncello, botli differ from the tones of a key-bugle : yet they all come under the same general laws of tonality. So, as I often insist, the tissues in brain and cord being the same, their properties must be the same, their laws of excitation, irradiation, and combination the same, through all the varieties in their manifestations due to varieties of innervation. Hence it is that there are reflex cerebral processes no less than reflex spinal processes : the motor impulse from the hemispheres on tlie corpora fitriatu, or from posterior gray substance on anterior gray 492 THE PHYSICAL BASIS OF MIND. substance, is similar to that from the anterior gray sub- stance on the motor nerves. The difference in reflexes arises from the terminal organs ; as the difference in sen- sations arises from the surfaces stimulated. But not only are there reflex processes in the brain, of the same order as those in the cord, there are volitional processes in the cord of the same order as those in the brain. And in both the processes are sometimes conscious, sometimes unconscious. No evidence suggests that in the conscious action there is a sensorial process, and a purely physical process in the unconscious action — only a different rela- tion of one sensorial process to others. 25. Let us contrast a cerebral and a spinal process, in respect to the three stages of stimulation, irradiation, and discharge. A luminous impression stimulates my retina, this excites my sensorium, in which second stage I am conscious of the luminous sensation ; the final discharge is a perception, or a mental articulation of the name of the luminous object. But the irradiation may perhaps not have been such as to cause a conscious sensation, be- cause the requisite neural elements were already grouped in some other way ; in this case there is an unconscious discharge on some motor group, and instead of perceiving and naming the luminous object, I move my head, or my hand, or my whole body, avoiding the object, or grasping at it. A third issue is possible : the irradiation, instead of exciting a definite perception, or a definite movement, may be merged in the stream of simultaneous excitations, and thus form the component of a group, and the dis- charge of this group will be a perception or a movement. It is the same with a spinal process. An impression on the skin is irradiated in the cord, and the response is a movement, of which we are conscious, or unconscious. Here also a third issue is possible : the irradiation may be merged in a stream of simultaneous excitations, modi- THE REFLEX THEORY. 493 fying them and modified by them, thus forming a com- ponent in some ulterior discharge. 26. The obstacle in the way of recognizing that cere- bral processes and spinal processes are of the same order of sensorial phenomena, and have the same physiological significance when considered irrespective of the group of organs they call into activity, is similar to the obstacle which has prevented psychologists from recognizing the identity of the logical process in the combinations of Feeling and the combinations of Thought, i. e. the Logic of Feeling and the Logic of Signs. This obstacle is the fixing attention on the diversity of the effects when the same process operates with different elements. Because the spinal cord manifests the phenomena of sensation and volition, we are not to conclude that it also manifests ideation and imagination ; any more than we are to con- clude that a mollusc is capable of musical feelings be- cause it is affected by sounds. 27. The careless confusion of general properties with special applications of those properties, and of functions with properties, has been a serious hindrance to the right understanding of Sensibility and its operations. Instead of recognizing that the nervous system has one general mode of reaction, which remains the same under every variety of combination with other systems, physiologists commonly lose sight of this general property, and fix on one mode of its manifestation as the sole characteristic of Sensibility. Sometimes the mode fixed on is Pain, at other times Attention. Thus, when an animal manifests no evidence of pain under stimulations which ordinarily excite severe pain, this is often interpreted as a proof that all sensation is absent ; and if with this absence of pain there is — as there often is — clear evidence of the pres- ence of some other mode of sensil)ility, the contradiction is evaded by the assumption that what here looks like evi- 494 THE PHYSICAL BASIS OF MIND. dence of sensation is merely meclianical reflexion. One would think that Physiology and Pathology had been silent on the facts of analgesia witliout anaesthesia, and of so much conscious sensation which is unaccompanied by pain.* Who does not know that a patient will lose one kind of sensibility while retaining others — cease to feel pain, yet feel temperature, or be insensible to touch, yet exquisitely alive to pain ? f Inasmuch as Sensibility depends on the condition of the centres, an abnormal condition will obviously transform the reaction of the centres into one very unlike the normal reaction. For example, Antoine Cros had a patient who was quite una- ble to feel the sensation of cold on her left side — every cold object touching her skin on that side was felt as a very hot one ; whereas a hot object produced " the sort of sensation which followed the application of an intermit- tent voltaic current."! Thus also the experiments of Piose § and others have exhibited the effects of a dose of Santoniue in causing all objects to be seen as yellow in one stage, and violet in another. * Even so eminent an investigator as Goltz has fallen into tins confu- sion. He introduces an experiment to prove that the brainless frog is insensible to pain by the words "when an animal, placed under circum- stances which would be very painful, makes no movement, although quite capable of moving, the least we can say is that it is improbable that the animal has sensation " {Nervenccntrcn cles Frosches, p. 127). I need not iliscuss the proof itself, having already done so in Nature, Vol. IX. p. 84. The point to which I wish to call attention is the confusion of insen- sibility in general with insensibility to pain. t See DucHENXE, De J^lcctrisation localisee, p. 398. Griesinger cites various examples of insane patients who have burned the flesh off" their bones while manifesting a total indifference to these injuries. 3Ia- ladies Mentales, yj. 94. Fai.ret says, "Nous avons vu plusieurs fois des alienes s'inciser, s'amputer eux-memes diverses parties du corps sans pa- raitre ressentir aucune soufi'ranee." Ler^ons cliniques de Midicinc Mcntale, 1854, I. 189. Patients incapable of feeling the contact of a hot iron with their skin have felt subjective burnings in the .skin thus objectively insensible. X Chos, Les Fonct ions super ieiircs du Syst. 'lurveux, 1875, p. 27. § Virchows Archiv, Bd. XXVIII. p. 30. THE KEFLEX THEOEY. 495 28, If, then, certain alterations in the organic condi- tions are accompanied by a suppression or perversion of some modes of Sensibility, without suppressing the rest, it is but rational to suppose that profound disturbances of the organic mechanism, such as must result from the removal of the l^rain, will also suppress or pervert several modes of Sensibility, and yet leave intact those modes which belong to the intact parts of the mechanism. As- suming that the spinal centres with the organs they innervate are capable of reacting under certain modes of sensation, these will not necessarily be suppressed by removal of the brain — all that will thereby be sup- pressed is their co-oj)eration with the brain. I know it will be said that precisely this co-operation is necessary for sensation ; and that the spinal reactions are simple reflexions in which sensation has no part. This, however, is the position I hope to turn. Meanwhile my assump- tion is that sensation necessarily plays a part in the reflex actions of the organism, and when that organism is trun- cated, its actions are proportionately limited, its sensations less complex. The spinal cord, separated from encephalic connections, cannot react in the special forms of Sensation known as colrtr, scent, taste, sound, etc., because it does not innervate the organs of these special senses, nor co- operate with their centres. But it can, and does, react in other modes : it innervates skin and muscles ; and the sensibilities, thus excited, it can also covihine and co-ordi- nate. It has its Memory, and its Logic, just as the brain has : both no longer than they are integral parts of an active living organism : neither wlien the organism is inactive or dead. We do not expect the retina to respond in sounds, nor the ear to respond in colors : we expect each organ to have its special mode of reaction. What is common to both is Sensibility. What is common to brain and cord is Sensibility — and the laws of Grouping. In- 496 THE PHYSICAL BASIS OF MIND. stead of marvelling at the disappearance of so many modes of Sensibility when the brain is removed, our sur- prise should be to find so many evidences of Sensibility remaining after so profound a mutilation of the mech- anism. 29 The current hypothesis, which assumes that the brain is the sole organ of the mind, the sole seat of sensa- tion, is a remnant of the ancient hypothesis respecting tlie Soul and its seat ; and on the whole I think the an- cient hypothesis is the more rational of the two. If the Soul inhabits the organism, using it as an instrument, playing on its organs as a musician plays on his instru- ment, we are not called upon to explain the mode of oper- ation of this mysterious agent ; but if the Soul be the subjective side of the Life, the spiritual aspect of the ma- terial organism, then since it is a synthesis of all the organic forces, the consensus of all the sentient phenom- ena, no one part can usurp the prerogatives of all, but all are requisite for each. And this indeed is what few physiologists would nowadays dispute. In spite of their localizing sensation in the cerebral cells, they would not maintain that the cerebral cells, nor even the whole brain, could produce sensation — if detached from the organism ; the cheek of the guillotined victim may have blushed when struck, but who believes that the brain felt the in- sult, or the blow ? Obviously, therefore, ^^•hen we read "that thought is "a property of the gray substance of the brain, as gravitation is of matter," or that the brain is the exclusive organ of Sensation, the writers cannot consist- ently carry out their hypothesis unless tliey silently rein- troduce other organs as co-operating agents ; for a neural process in the cerebrum is in itself no more a sensation than it is a muscular contraction, or a glandular secretion : the muscles must co-operate for the contraction, the gland for the secretion, the neural process being simply the ex- THE KEFLEX THEORY. 497 citing cause. In like manner the Sensorium is necessary for the sensation, the neural process — in cerebrum, or elsewhere — being simply the exciting cause. 30. And what is the Sensorium ? A long chapter would be required to state the various opinions which have been held respecting its seat, althougli amid all the disputes as to the organ, there has been unanimity as to the function, which is that of converting stimulations into sensations. I cannot pause here to examine the contend- ing arguments, but must content myself with expounding the opinion I hold, namely, that the Sensorium is the vjliole of the sensitive organism, and not any one isolated portion of it. When light falls on the optic organ, or air pulses on the auditory organ, the reaction of each organ determines the s-pccific character of the sensation, 'but no such sensation is iMssihle unless there he a reaction of the organism; and the nature of the product will of course vary with tlie varying factors which co-operate — a sim- ple organism, a truncated organism, an exhausted or oth- erwise occupied organism, will react differently from a complex, a normal, or an unoccupied organism. Detach the optic organ with its centre from the rest of the organ- ism, and no normal sensation of Sight will result from its stimulation ; and in a lesser degree this is equally true of a stinmlation of the optic organ when the sensorium is exhausted, or powerfully affected by other stimuli. Be- cause of the great importance of the cerebrum, and its I)redominance in the nervous system, it has been supposed to constitute the whole of the sensorium, in sj^ite of the evidence of varied Sensibility after the cerebrum has been removed. I do not wish to underrate tlie cerebral impor- tance (see p. 16G), yet I must say that the modern phrase cerebration, when employed as more than a shorthand ex- pression of the complex processes which a cerebral pro- cess initiates, and when taken as the objective equivalent 498 THE PHYSICAL BASIS OF MIND. of Consciousness or of Thought, seems to me not more justifiable than to speak of Combustion as the equivalent of Kailway Transport. The railway wagons will not move unless the fuel which supplies the boiler be ignited ; the organism will not think unless the cerebrum excites this peculiar mode of Sensibility by its action on the organs. It is the ma7i, and not the brain, that thinJcs : it is the organism as a whole, and not one organ, that feels and acts. 31. Consciousness, or Sensation, is a complex product not to be recognized in any one of its factors. Cerebral processes and spinal processes are the elements we analyti- cally separate, as muscular contractions are the elements of limb-movements. The synthetic unity of these ele- ments is a reflex ; this we analytically decompose into a sensation and a movement; and then we speak of sensation as the reaction of the sensory organ, the movement as the reaction of the muscular organ. By a similar procedure we separate the stimulation of a sensory nerve from the reaction of the sensory organ, and that from the reaction of the sensorium ; and in this way we may come to regard Cerebration as Thought. But those who employ this arti- fice should remember that the organism is not an assem- blage of organs, made up of parts put together like a machine. The organs are differentiations of the organism, each evolved from those which preceded it, all sharing in a common activity, all wi^cr-dependent. 32. That co-operation of the Personality which is con- spicuous in conscious actions is also inductively to be inferred in sub-conscious and unconscious actions. We know that a man reacts on an impression according to his physical and mental state at the moment — that through his individuality he feels differently, and thinks differ- ently from other men, and from himself at other epochs, and in other states. Because he resembles other men in THE REFLEX THEORY. 499 many and essential points we conclude that he will resemble them in all; but observation proves this con- clusion to be precipitate. Other men see a blue color in the sky, or feel awe at sight of the setting sun ; but he has perhaps not learned to discriminate this sensation, is not conscious of the blue ; nor has he learned to feel awe at the setting sun. Why — having normally con- structed eyes — does he not see the blue of the sky ? For the same reason that a dog, or an infant, fails to see it. The color has no interest for him (and all cognition isi/ primarily emotion), nor has this want of personal interest been rectified from an impersonal source : he has never been taught to distinguish the color of the sky ; and his eye wanders over it with the indifferent gaze with which a savage would regard a Greek codex. 33. The point here insisted on, namely, that every reaction on an impression is indirectly the reaction of the whole organism, and that no organ detached from the organism has more significance than a word detached from a sentence, is of far-reaching importance, and peculiarly worthy of attention in considering the Eeflex Theory, because almost all the evidence urged in support of that theory presupposes the legitimacy of concluding what takes place in the organism from what is observed in an organ detached from its normal connections. No experi- mental proof is necessary to show that many actions take place unconsciously ; the fact is undisputed. But does unconsciously mean insentiently ? It is certain that the unconscious actions take place in a sentient organism, and involve organic processes of the same order as the actions which are conscious. It is also certain that many sen- tient processes take place unconsciously. For thousands of years men used their eyes, and saw as their descend- ants see, yet were unconscious of the blue sky and green of the grass. Were their visual reactions not of the same 500 THE PHYSICAL BASIS OF MIND. order as our own ? So far as the optic apparatus is con- cerned, there cannot be a doubt on the point ; yet in them the sensorium having a somewhat different disposition — the neural elements being ditferently combined — their reactions correspondingly differed. Tliey too had optical Sensibility, and visual sensations ; but they did not feel precisely what we feel. 34. I have chosen these somewhat remote illustrations for the sake of their psychological interest ; but I might have confined myself to more familiar examples. Thus the contents of the consciousness of a man born blind cannot be the same as the contents of one who has had visual experiences, which wiU enter into the complex of every conscious state, because the visual organs will have affected his sensorium; nevertheless in the organism of the blind man there are conditions so similar to those of other men, and his experiences will have been so simi- lar, that in spite of the modifications due to the absence of visual experiences, his consciousness will in the main resemble theirs. But now let us in imagination pursue this kind of modificatiou, let us take away hearing, taste, and smell, and we shall have proportionately simplified the contents of consciousness — the reactions of the sen- sorium — in thus simplifying the organism. There still will remain Touch, Temperature, Pain, and the Systemic Sensations. There will still remain an organism to react on impressions. So long as there is a living organism, liowever truncated, there is a sentient mechanism. When tlie brain has been removed, the removal causes both a disturbance of function and a loss of function ; the mech- anism has been seriously interfered with ; yet all those parts of the mechanism which still co-operate manifest their physiological aptitudes. The animal can live with- out its brain, ergo it can feel without its brain. Observa- tion proves this, for it discovers the brainless animal THE REFLEX THEORY. 501 manifesting various sensibilities, and combining various movements. Tlie vision of the brainless animal is greatly impaired, but it nevertheless persists. The intelligence is greatly impaired, the spontaneity is reduced to a mini- mum ; but still both intelligence and spontaneity are manifested. 35. The physiologist has only two conclusions open to him. Either he holds Sensation to be a ijropcrtij of nerve- tissue — and in that case he must assign it to the spinal cord as to the brain ; or else he holds Sensation to be a function of an organ — and in that case, although ana- lytically he may decompose the organism into separate organs, assigning special sensations to the reactions of each, he must still admit that in reality these organs only yield sensations as component parts of the organism. The notion of a separate organ, such as the brain, being the exclusive seat of sensation is thus seen to be unten- able. In popular phrase, "it is not the eye which sees, but the mind behind the eye." It is not the stimulus which is the object felt — it is the change in consciousness — the reaction of the sensorium. No one would propound the absurdity that the retinal cells sec, or the auditory cells hear (although by a conventional ellipsis these cells are said to be " percipient " of colors and sounds), yet many writers have no hesitation in asserting that the cerebral cells are the seats of these and all other sensations. In a hundred treatises may be read the most precise descrip- tion of the transformation of molecular changes in the retinal cells into molecular changes in tlie cerebral cells, where, it is said, " we know that the stimulations become sensations." Now who knows this ? How can it be known ? Nay, who, on reflection, fails to see tliat this can- not be so ? If a sensation of sight were not much viorc tlian a molecular change in the cerebrum stimulated by a 502 THE PHYSICAL BASIS OF MIND. molecular change in the optic tract, three conclusions woulil follow, each of which is demonstrably erroneous : — I. The cerebrum in a decapitated animal would respond by a sensation of sight to a retinal stimulation. II. The animal deprived of its cerebrum could not re- spond by a sensation of sight to a retinal stimulation. III. The same retinal stimulation would always pro- duce the same cerebral process and the same sensation ; whereas the sensation depends on the condition of the sensorium at the time. 36. The diflerence between the Eeflex Theor}^ and that here upheld is important in its general relations, and yet turns on a point which may easily appear insignificant. The Eeflex Theory asserts that when a sensory nerve is stimulated, the excitation of the centre may either sub- divide into two waves, one of which passes directly to the brain and there awakens sensation, the other passes over to the motor-roots and causes muscular contractions ; or, in- stead of thus subdividing, the wave may pass at once to the motor-nerves, and then there is movement without sensa- tion. This is obviously a restatement in anatomical terms of the observed fact that some reflexes take place con- sciously and some unconsciously. But what evidence is there for this anatomical statement ? "We have seen that there is none. According to all we actually know, and reasonably infer, the continuity of tissue and the irradia- tion of excitation are such that the stimulus wave must always affect the whole system, so that brain and cord being structurally united, their reactions must co-operate with varying energy dependent on their statical conditions at the time.* * The idea of a fixed anatomical mechanism for reflexion, such as that of an excito-motory system, is completely refuted by the fact that the gray substance may anywhere be cut away, and yet so long as a small bridge of gray substance remains the stimulation will be propagated through it. THE REFLEX THEORY. 503 37. The physiological fact that the irradiation is re- stricted to certain paths, and therefore only certain por- tions of the whole system are excited to discharge — the fact that stimulation takes effect along the lines of least resistance — is that which gives the Keflex Theory its plausible aspect. But this fact of restriction is not de- pendent on an anatomical disposition of structure, it is, as we have already seen (Problem II. § 166), dependent on a fluctuating physiological disposition — a temporary statical condition of the centres. And it enables us to understand wliy the reflex action which is at one moment a distinctly conscious or even a volitional action, is at another sub-conscious or unconscious. When an object is placed in the hand of an infant the fingers close over it by a simple reflex. This having also been observed in the case of an infant born without a brain,* one might inter- pret it as normally taking place without brain co-opera- tion, were there not good grounds for concluding that normally the brain must co-operate. Thus if the object be placed in the hand of a boy, or a man, the fingers will close, or not close — not according to an anatomical mech- anism, but according to a physiological condition : if the attention preoccupy his sensorium elsewhere, his fingers The idea of a fixed pathway is also refuted by the fact of the variations in the reflex responses, and the necessary irradiation even for very simple reflexes. Take, for example, that of breathing. An irritation of the bronchial filaments is transmitted by the pneumogastric to its centre in the medulla oblongata ; from this, however, it is immediately irradiated downwards to the cervical and dorsal regions, which innervate the muscles of chest and diaphragm, and upwards to the brain, whether the stimulation awaken consciousness or not. One may say, indeed, that inasmuch as under normal conditions tlie bronchial irritation always causes a movement of a particular group of muscles, there is to this ex- tent a fixed pathway of discliarge ; but, as I have formerly explained, this is only an expression of the particular tcmsion of particular centres, and is variable with that tension ; the other centres are also aff'ected, even when tlioy are not excited to discharge. * Lallema.nd, llec/ierc/ies sar i Enolphalc, IlL 310. 504 THE PHYSICAL BASIS OF MIND. will probably close, probably not; if his sensorium be directed towards the object, either by the urgency of the sensitive impression, or by some one's pointing to the ob- ject, the fingers will close or not close, just as he chooses — perhaps tlie hand will be suddenly drawn away. The centre of innervation for the fingers is in the cord, and from this comes the final discharge of the sensitive stimu- lation ; but the neural j)rocesses which jjreceded this dis- charge, and were consequent on the stimulation, were in each case somewhat different. In each case the impres- sion on the skin was carried to the cord, and thence irradiated throughout the continuous neural axis, re- stricted to certain paths by the resistance it met with, but blending with waves of simultaneous excitations from other sources, the final discharge being the resultant of these component forces. We may suppose the brain to be the seat of consciousness, and yet not conclude that the brain was unaffected because the fingers closed un- consciously ; any more than we conclude that the retina of the unoccupied eye is unaffected by light when with the other we are looking through a microscope, and only see objects with this eye — though directly we attend to the impressions on the other eye we see the objects which before were unseen. We know that the muscles of the back are all involved in walking, standing, etc., but we are seldom conscious of their co-operation till rheumatism or lumbago makes us painfully alive to it. 38. The two main positions of the Eeflex Theory are, 1°, that reflex actions take place without brain co-opera- tion, — as proved by observation of decapitated animals ; 2°, that they take place without brain co-operation, — as proved by our being unconscious of them. To these the answers are : 1°. The proof drawn from observation of decapitated animals is defective, because the conditions of the organism are then abnormal — there THE REFLEX THEORY. 505 is a disturbance of the mechanism, and a loss of some of its components. The fact that a reflex occurs in the absence of the brain is no proof that reflexes when the brain is present occur without its participation. 2°. The absence of consciousness cannot be accepted as proof of the brain not being in action, because much brain-work is known to pass unconsciously, and there are cerebral re- flexes which have the same characters as spinal reflexes. 39. A prick on the great toe traverses the whole length of the spinal axis with effects manifested in various or- gans — the muscles of the limb, the heart, the chest, the eyes, etc. The leg is withdrawn, the heart momently arrested, the eyes turned towards the source of irritation, the thoughts directed towards relief. These effects can be observed — there are others which lie beyond our ob- servation, and can only be revealed by delicate experi- mental tests. But even the observable effects are very fluctuating, because they depend on fluctuating condi- tions. All we can say is, that so long as there is con- tinuity of structure, there must be continuity of excita- tion; and the brain structurally connected with the centre of a sensory impression, must necessarily co-operate more or less in the reactions of that centre. In other words, the "brain, although not the exclusive seat of sensation, plays a part in every particular sensation, so long as it forms a part of the stimulated organism. 40. This view being so widely opposed to the views current in physiological schools, I was gratified to find Dr. Crichton Browne led by his researches to a conclu- sion not unlike it in essential features. In his essay on the Functions of the Optic Thalami* (well worthy of attention on other grounds) he says : " Allowing the spi- nal cord a power of independent action, it may still be that it generally acts reflexly through, or in association * JFest Riding Lunatic Asylum Reports, 1875, Vol. V. pp. 252, sq. vol,. III. 22 506 THE niYSICAL BASIS OF MIND. with, a superior centre. The sensorial ganglia can un- doubtedly act alone in a reflex manner, but they almost invariably consult the cerebrum before dealing with the impressions which they receive ; so it may be that the spinal cord, though capable of spontaneous reaction, may yet commonly refer to some higher seat of compound co- ordination before sending forth an answer to any message brought to it." What is here stated as a possible and occasional process, I consider to be a necessary and uni- versal process. Dr. Browne acutely remarks that if "what may be termed the encephalic loop were an integral part of every reflex act, then the influence of an intracranial lesion in checking reflex action would not be difficult to understand" — and we may add the notorious influence of the brain in arresting reflex actions, and modifying them by the will, which is only explicable on the suppo- sition that the cerebral and spinal centres are functionally associated. Dr. Browne further remarks : " In experi- menting upon myself I have sometimes thought that when the toe is pricked the sensation of pain actually precedes the movement of withdrawal ; and in experi- menting upon patients with sluggish nervous systems I have certainly noticed that after the pricking of the toe the little cry of pain has anticipated the muscular con- tractions of the leg. Now this cry of pain is a secondary reflex act through the sensorial centre ; it is the result of a discharge from efferent nerves from the summit of what we have spoken of as the encephalic loop line ; and we should certainly not expect that it would be developed earlier than the primary reflexion upon the motor appa- ratus, unless indeed what we have regarded as the primary reflexion really itself took place by way of the loop line." 41. The difference between a voluntary and involun- tary act is not, I conceive, that in the one case the brain co-operates and in the other is inactive, but that while in THE KEFLEX THEORY. 507 both the brain co-operates, the state of the sensorium known as mental prevision or ideal stimulation, is present in the one, and absent or less conspicuovis in the other. So likewise the difterence between a normal reflex action accompanied, and the same action unaccompanied by con- sciousness, is not that the brain co-operates in the one and is inactive in the other, but that the state of the sen- sorium is somewhat different in the two cases. Move- ments Avhicli originally were voluntary and difficult of execution — accompanied therefore by brain co-operation — become by frequent repetition automatic, easy of ex- ecution, and unconscious — they are then said to de- pend on the direct action of the established mechanism. Granted. But what are the components of this mechan- ism ? Are they not just those centres and organs which at first effected the movements ? In becoming easy and automatic, the movements do not change their mechanism — the moving organs and the motor conditions remain what they were ; all that is changed is the degree of con- sciousness, i. e. the state of the sensorium which precedes and succeeds the movement. It is this which constitutes the difficulty of the question. Some readers may con- sider that all is conceded when unconsciousness is admit- ted. But this is not so. My present argument is the physiological one that the brain co-operates in reflex actions whenever the brain is structurally united with the reflex centres ; the psychological question as to whether consciousness is also involved in this brain co-operation must be debated on otlier grounds ; and we have already seen that consciousness operates in gradations of infinite delicacy. Observe a man performing some automatic action, sucli as planing a deal board, or cutting out a pattern, whicli lie has done so often that he is now able to do it " me- chanically." It is certain tliat liis brain co-operates, and 508 THE PHYSICAL BASIS OF MIND. that he could not act thus with an injured brain ; yet he is said to act unconsciously, his brain occupied else- where as he whistles, talks to bystanders, or tliinks of his wife and children. Yet the brain is acting as an over- seer of his work, attentive to every stroke of the plane, every snip of the scissors ; and this becomes evident directly his attention is otherwise absorbed by an inter- esting question addressed to him, or an interesting object meeting his eye: then the work pauses, his hands are arrested, and the automatic action will only be resumed when his attention is released — when he has answered your question, or satisfied himself about the object. 42. This is a step towards understanding the co-opera- tion of the brain even in those connate reflexes which were not originally voluntary acts, but were from the first organized tendencies, and are capable of being real- ized in the absence of the brain. I admit that it is diffi- cult to find proof of brain co-operation here, though I think the anatomical and physiological evidence render it highly probable. But distinct proof to the contrary would not suffice for the Eeflex Theory — would not prove that reflex actions were insentient — unless there had previously been proved that which seems to me con- tradicted by the clearest and most massive evidence, namely, that the brain is the sole seat of sentience. This contradictory evidence we will now furnish. THE KEFLEX THEOKY. 509 CHAPTEE III. INDUCTIONS FROM PARTICULAR OBSERVATIONS. 43. In the last chapter we surveyed the deductive evi- dence, from which the conclusion was that Eeflexion necessarily involves Sensibility, but not necessarily any one particular tnode of Sensibility, such as Consciousness, Pain, Discomfort, Attention, or the reaction of any one of the special Senses. Although each or all of these modes may be involved in the sensorial process which determines a reflex act, each or all may be absent. Such is the fact of observation. This fact is interpreted on the hypothesis that Reflexion is the exclusive property of the spinal cord, as Sensation is of the brain. When we come to examine the evidence for this hypothesis, we find it to move in a circle : the brain is said to be the exclusive seat of sensation, because reflex actions can be effected after its removal ; and reflex actions are said to be insentient because they take j)lace in the absence of the brain. A gentleman was one day stoutly asserting that tliere were no gold-fields except in Mexico and Peru. A nug- get, dug up in California, was presented to him, as evi- dence against his positive assertion. He was not in the least disconcerted. " This metal, sir, is, I own, extremely like gold ; and you tell me that it passes as such in the market, having been declared by the assayers to be un- distinguishable from the precious metal. All this I will not dispute. Nevertheless, the metal is not gold, but 510 THE PHYSICAL BASIS OF MIND. auruminium ; it cannot be gold, because gold comes only from Mexico and Peru." In vain was he informed that the geological formation was similar in California and Peru, and the metals similar ; he had fixed in his mind the conclusion tliat gold existed onli/ in Mexico and Pern : this was a law of nature ; he had no reasons to give why it should be so; but such had been the admitted fact for many years, and from it he would not swerve. He was not fond of new-fangled notions, which, after all, would only lead us back to the exploded errors of the past. To accept the statement that gold was to be found elsewhere than in Mexico and Peru, would be to return to the opinion of the ancients, who thought there was gold in the upper regions of Tartary ! Sensation is not tangible, assayable, like gold. We can understand, therefore, that the very men who would make merry with the auruminuim, would accept easily such a phrase as "reflex action." The decapitated animal de- fends itself against injury, gets out of the way of annoy- ances, cleans itself, performs many of its ordinary actions, but is said to do these things without that Sensibility which, if its head were on, would guide tliem. Even be- fore the Eeflex Theory was invented this line of argu- ment was used. Gall, referring to the experiments of Sue, previously noticed, says that " Sue confounds the effects of Irritability with those of Sensibility."* Not gold, dear sir, but auruminium ! 44. On investigating the phenomena we soon come upon two classes which must cause hesitation. We find that the brain has its reflex processes, of the same order as those of the cord ; we find that these processes may be conscious or unconscious, voluntary or involuntary ; so that we can no longer separate brain from cord on the ground of Reflexion. In this respect, at least, the two * Gall d Spurzheim, Anat. ct Physiol, du Systanc Nerveux, I. 83. THE REFLEX THEOEY. 511 are mechanisms with similar powers. Turning now to the other class of phenomena, M'e find that precisely as the brain is an organ of Eeflexion, the cord is an organ of Sensation. All the evidence we can have, from which to infer the presence of sensation, is furnished by the sensorial processes in the cord, liemove the brain, and the animal still manifests Sensibility, and this in degrees of energy and complexity proportional to the mechanisms still intact : some of these manifestations have the char- acter of volitional actions, some of automatic actions, some of Memory, Judgment, and selective Adaptation. These we observe not indeed with the energy and variety of such manifestations when the brain co-operates, since the disturbance of the organism which is the consequence of the brain's removal — or the meagTeness of the organ- ism which is the correlative of the brain never having been developed — must of course involve a corresponding difference in the observed phenomena ; but the point here brought forward is that phenomena of the same order are manifested by organisms with or without a brain. 45. Let us go seriatim through the evidence of these two classes : — CEREBRAL REFLEXES. While Theory separated the actions of the cord from those of the brain on the ground of their being at times unconscious and involuntary, Observation disclosed that this distinction could not be maintained. This step was taken by Dr. Lay cock in 1840. In a striking paper* read by him at the British Association in 1844, he brought together the evidence on which his view was founded. The idea has been adopted and illustrated in the writings of Dr. Carpenter, who now calls the action " unconscious cerebration," * Piintcd in the British and Foreign Medical Eevieir, Jan. ISl.'j. 512 THE niYSICAL BASIS OF MIND. '' I was led to tliis opinion," Dr. Laycock says in an- nouncing liis view, " by the general principle that the ganglia within the cranium, being a continuation of the spinal cord, must necessarily be regulated as to their re- action on external agencies by laws identical with those governing tlie spinal ganglia and their analogues in the lower animals. If, therefore, the spinal cord is a centre of reflexion, the brain must also be one." It is a matter of regret that Dr. Laycock did not extend this principle, and declare that whatever was true of the properties of the cranial centres must also be true of the spinal cen- tres ; if the brain have Sensibility, the spinal cord must also have it. Dr. Laycock refers to the curious phenomena of Hydro- phobia in proof that reflex actions may be excited by the optic nerves, or by a mere idea of water. When a mirror was presented to a patient, the reflexion of the light act- ing on liis retina, in the manner of a reflexion from the surface of water, produced a convulsive sobbing, as in the attempt to swallow water, and the patient turned aside his head with expressions of terror. Money was given him to induce him to look a second time, but before he had looked a minute the same effect w^as produced. The idea of water excited similar convulsions. Xo sooner was it suggested that the patient should swallow a little water than he seemed frightened, and began to cry out. By kindly encouragements he was brought to express his willingness to drink, but the sound of the Walter, as it was poured out again, brought on convulsions. In another case, " on our proposing to him to drink, he started up, and recovered his breath by a deep convulsive inspiration. On being urged to try, he took a cup of M'ater in one hand and a spoon in the other. With an expression of terror, yet with great resolution, he filled the spoon and proceeded to carry it to his lips ; but be- THE EEFLEX THEORY, 513 fore it reached his mouth his courage forsook hira, and he was forced to desist. He repeatedly renewed the attempt, but with no more success. His arm became rigid and immovable whenever he tried to raise it to his mouth, and he struggled in vain against this spasmodic resist- ance." In 1843 Griesinger — who appears to have known nothing of Dr. Laycock's paper — published his remark- ably suggestive memoir on Psychical Reflexes,* in which he extends the principle of lieflexion to all the cerebro- spinal centres. The whole course of subsequent research has confirmed this view ; so that we may say with Lan- dry, "L'existence du pouvoir reflexe dans I'encephale ou dans quelques unes de ses parties etablit une nouvelle analosie entre le centre nerveux crauien et la moelle epiniere.f Indeed we have only to consider the Laughter which follows a ludicrous idea, or the Terror which fol- lows a suggestion of danger, — the varying and involun- tary expression of Emotion, — and the curious phenomena of Imitation and Contagion, — to see how large a place cerebral reflexion occupies. 46. The existence of cerebral reflexion having been thus made manifest. Dr. Carpenter classed all reflex actions under three heads : 1°, the excito-motor, deter- mined by the spinal cord ; 2°, the sensori-motor, de- termined by the ganglia at the base of the brain ; 3°, ideo-motor, determined by the brain. From all these Consciousness is absent. From the first, he supposes ►Sensation to be absent. As an artifice, such a classifi- cation may have its value, but it is physiologically and * Griesinger, Abhandlungen, 1872. The first volume contains a re- ))rint of this memoir. t Laxdrv, TraiU des Pamlysics, I. 55. Conf. Ziemssen, Chorea in the Ilandbuch dcr specielhn Pathologic, Bd. XII. 2, p. 408. And Luys, Etudes dc physiol. etpalhol. cMbrales, 1874, pp. 89-94. 22* 514 THE PHYSICAL BASIS OF MIND. psychologically misleading. It sustains the hypothesis of an imaginary excito-motor mechanism. It restricts Sensibility to one of its many modes. It fails altogether to connect Sensation with Tliought, the Logic of Feeling M'ith the Logic of Signs. 47. The view of Sensibility as common to the whole cerebro-spinal axis is by no means new. Robert Whytt maintained it. Prochaska held that the spinal cord formed the greater part of the sensorium commvMe; and he adduced, in proof, the familiar facts of sensibility manifested by headless animals. The next writer whom I can discover to have held this opinion is J. J. Sue, — the father of the celebrated French romance-writer, — who, in 1803, conceived tliat his experiments proved the spinal cord to be capable of replacing, to a certain ex- tent, the functions of the brain.* Next came Legallois,t who undertook to show, by a series of experiments, that the principle of sensation and movement, in the trunk and extremities, has its seat in the spinal cord. The mere division of the cord, he said, produces " the aston- ishing result of an animal, in which the head and the body enjoy separate vitality, the head living as if the body did not exist, and the body living as if the head did not exist. Guinea-pigs, after decapitation, seem very sen- sitive to the pain caused by the wound in the neck ; tliey alternately carry first one hind-leg and then the other, to the spot, as if to scratch it. Kittens also do the same." A few years afterwards, 1817, Dr. Wilson Philip con- cluded that "the spinal marrow possesses sensorial power, as appears from very simple experiments " ; but he held * Sue, Rccherches PhilosopMques siir la VitaliU et Ic Galvanisme, p. 9. He was not consistent, however, but adopted Bichat's opinion respecting the sensibility of the viscera, p. 68. t Legallois, Ex2)eriences sur h principe de la vie. Published, I con- clude, in 1811; the edition I use is the one printed in the Enq/dqpedie des Sciences Mcdicales, IV. THE KEFLEX THEORY. 515 the brain to be the chief source of sensorial power.* The following year, Lallemand supported this opinion by the very curious phenomena exhibited by infants born with- out brains : these infants breathed, swallowed, sucked, squalled, and gave very unequivocal signs of sensibility. The value of such observations consists in disproving the objection frequently urged against the evidence of decapi- tated animals, namely, that in these animals the spinal cord preserves the remains of a sensibility endowed by the brain. Longet here places an observation recorded by Beyer. A new-born infant, whose brain, during the birth, had been completely extirpated (to save the mother's life), was wrapped in a towel, and placed in the corner of the room, as a lifeless mass. While the surgeon Was giving all his care to the mother, he heard with horror a kind of murmur proceeding from the spot where the body had been placed. In three minutes a distinct cry was heard. The towel was removed, and, to the surprise of all, this brainless infant was seen struggling with rapid movement of its arms and legs. It cried, and gave other signs of sensibility for several minutes.-j* In 1828 Calmeil arrived at the same conclusion as that reached by Legallois, A¥ilson Philip, and Lallemand. In- deed when, in 1833, the Picflex Theory appeared, this opinion was so Ih-mly rooted, that we find Mr. Grainger combating it as the established eiTor of the day. He takes as much pains to show that physiologists are wrong in attributing sensation to the spinal cord, as I am here taking to show that they were right. :J: "It is, indeed, * WiL-soN Philip, Experimental Inquiry into the Laws of tlic Vital Functions, ]ip. 209, 210. t Longet, Trait6 dc Physiolngic, II. lOo. X He cites Cuvier, Majendie, Desmoulins, aud Mayo as maintaining this error. 516 THE PHYSICAL BASIS OF MIND. apparent," he says, " that the whole question concerning the truth or falsehood of the theory which attributes the reflex power to the spinal cord hinges upon the correct- ness or incorrectness of the received doctrines respecting the seat of sensation and volition ; so that until those doctrines are proved to be false, it is impossible to estab- lish the hypothesis of Dr. Hall." * The reader is requested to take note of this, because when we come to the evidence which proves the spinal cord to be a centre of sensation, we shall find that the only ground for rejecting that evidence is the assumed truth of the Eeflex Theory, coupled with the assumption of the brain being the exclusive seat of sensation. Whereas if the evidence proves that the spinal cord is a sensational centre, then the Eeflex Theory is destroyed, and cannot be urged against such evidence. 48. Thus many of the facts whicli prove the sensa- tional function of the spinal cord were known, and even a vague conception of their real significance was general, until the Eeflex Theory came to explain all such facts as the results of mechanical adjustment, and of a new ner- vous principle called " Eeflexion." For many years this theory has reigned, and met with but little opposition. Yet the true doctrine has not wanted defenders in Ger- many. ISTasse f denied that decapitated animals showed no spontaneity ; he asserted that they exhibited clear signs of mental activity. Carus sarcastically pointed out that the word " reflex " was replacing " irritability," as a key to unlock all puzzles ; and he took up a position which is very similar to the one occupied in these pages, namely, that the spinal cord being formed of gi'ay matter as well as of fibres, it must have sensibility and power of reacting on nervous stimulus, no less than conductibility ; * Graixger, structure and Functions of tlie Sjnnnl Cord, p. 66. + Kasse, Untcrs. zur Physiologic und Pathologic, Vol. II. Part 2. THE REFLEX THEORY. 517 that, in fact, it is a centre, and must act like all other nerve-centres.* J. W. Arnold opposed the Eeflex Theory in a very remarkable little work, in which he vindicates the claim of the spinal cord as a sensory and motor cen- tre, although denying to its actions any volitional char- acter.-f- This was in 1844. Eleven years elapsed without any further opposition, when Edward Pflliger, in 1853, published his work on the Sensorial Functions of the spinal cord.:]: In this work he recurred to the old views of Prochaska and Legallois ; but although he attacked ISIarshall Hall with merciless severity, he did not point out the fundamental error of the Pteflex Theory, which theory he seems to accept. Nor did he give his views that philosophical and anatomical basis which could alone render his interpretations acceptable. Added to this, the tone of asperity in which his work was written, created some prejudice against him ; and thus, while many ad- mitted his facts, they rejected his conclusions.§ In 1858 Professor Owen read a paper of mine at the Leeds meeting of the British Association, on " The spinal cord as a centre of Sensation and Volition," in which a rapid indication of my point of view, and an account" of some experiments to illustrate it, were given — not, I believe, conclusive to any of the audience. Indeed, the subject was too vast to be discussed in such a paper ; and my object was rather to excite new inquiry, than to make converts to a view which could only be embraced after a thorough reinvestigation of the dominant theories. In 1859 appeared Schiff 's work ; || and here we find a ♦ Caru.s, System der Physiolofjie, III. 101. t J. W. Arnold, Die Lehrc von der Eeflex- Function, 86. t Pfl'uger, Die scnsorischen Funclionen des Eilckenmarks der Wir- heUMere. § Except AuERBACH, who repeated and varied the experiments ; and FrsKE, who partially adopted the conclusions in his systematic treatise on rhvsiolog)-. Sc/MT, Lfhrhuch der Pluisiulofjic, 208. 518 THE PHYSICAL BASIS OF MIXD. large space allotted to the discussion of Pfliiger's doctrine. Schiff, Avhose immense experience as an experimentalist, and whose acuteness and caution every one will highly estimate, frankly pronounces in favor of the sensational character of spinal actions ; but he denies that they are volitional, and objects strongly to the introduction of any such idea as that of " psychical activity." He thinks it utterly untenable to suppose that impressions have reac- tions in the brain which they have not in the spinal cord : — if one has sensibility, the other must have it ; and he thinks that, so far from the actions of the cord being distinguishable from those of the brain by the character of " reflexion," and depending on a mechanical arrangement — all actions, cerebral or spinal, are reflex ; all depend on a mechanical arrangement.* Since that time there has been the remarkable work of Goltz, so often cited in these pages,! and his subsequent experiments on dogs, which ( although he does not deci- sively adopt the views of Pfliiger ) furnish ample evidence that sensation and vohtion cannot be exclusively localized in the brain. 49. Heubel's interesting experiments % show that a frog may be thrown into a state of profound sleep by the withdrawal of all external stimulation, and in this state will remain lying on its back for hours. N'ow this posi- tion is one so very imcomfortable that, when awake, the frog will not retain it a moment, if free to turn round ; and * Landry, Traite des Paralysies, 1859, maintains that the cord is a centre of sensation, and that there is in it a faculty analogous to the per- ception and judgment of the brain. Compare pp. 163 et sq. and 305. He also cites an essay by Dr. Paton of Edinburgh ( Edinburgh Medical Journal, 1846 ), iA which the sensational and volitional claims of the spinal cord are advanced. + Goltz, Beitrdge zur Lehre von den Functionen dcr Nervcnccntren des Frosches, 1869. J Pfliiger s Archiv, Bd, XIV. p. 158. THE REFLEX THEORY. 519 Aviien asleep, a prick on the toe, a sudden noise, or a beam of light will awaken it, causing it to turn. That is to say, the withdrawal of the normal stimuli so lowers the sensibility of the frog's nerve-centres, that he does not feel the effects of the unusual position, but feels them directly the centres are stimulated into activity. All this is intelligible enough on the supposition of the state of sleep being dependent on a lowering of the cerebral activity. But what shall we say on learning that pre- cisely the same phenomena are manifested by a brainless frog ? Every one knows tliat the brainless frog is intol- erant of lying on its back, and immediately turns round, if placed on it. Yet the brainless frog may be thrown into deep sleep by the same exclusion of external stimuli ; from which he also will be awakened by a prick, a noise, or a beam of light ; and no sooner is he awakened than he at once turns round. Were the brainless frog inca- pable of sensation, a prick on his toe would cause a simple reflex withdrawal of the leg ; but this is not the effect ; on the contrary, the stimulus excites the whole spinal cord, and whatever sensation of discomfort may be caused by the abnormal position of the limbs in an uninjured awakened frog, is excited in the brainless frog. 50. I need not swell this chapter with examples of Sensibility in animals deprived of the brain ; many have already been given, and any text-book of Physiology will supply more. No one disputes the observations, only the inference that these manifestations were sentient : they are said to have been merely mechanical reflexes. Tf, however, we can detect in them some evidence of what all recognize as peculiarly characteristic of Mind, the mechan- ical interpretation will be less plausible. At the outset the reader must be warned against exaji- gerating and distorting the beanng of my remarks, and must not suppose that I disregard the vast differences 520 THE niYSICAL BASIS OF MIND. between the Logic of Signs which belongs to Thought, and the Logic of Feeling which belongs to Sensation, nor suppose that I look upon the spinal cord as a mental organ having the same functions as the brain. All that I wish to establish is the common character of spinal and cerebral processes, modified as each is by the character of the actions initiated by the process. 51. This premised, let us begin with the evidence of DISCEIMINATION. Although this process is usually regarded as purely psychological, it must obviously have its physiological side ; we find it in Sensation as in Ideation, and may ex- pect to find it in unconscious as in conscious processes — in a word, in all sensorial processes whatever. Place a bit of marble on your tongue, and it will be touched, but not tasted : the sensations of contact and temperature will excite reflexes, but little or no reflexes from parotid and salivary glands. A difference in sensation has a corre- sponding difference in reflex action ; which may be made evident by removing the tasteless marble, and replacing it by a pinch of carbonate of lime, i. e. the marble in an- other state reduced to a powder : this will excite a sen- sation of taste, and a secretion from the glands. In both cases your sentient organism was affected, but it reacted differently because the difference of the stimulation was discriminated : consciously or unconsciously, you felt dif- ferently. Again : touch the back of your mouth with your finger, or a feather, and a convulsive contraction of the gullet responds, followed by vomiting, if the excita- tion be renewed. Yet these same nerves and muscles respond by the totally opposite action of swallowing, if instead of the stimulation coming from your finger, it come from the pressure of food or drink. THE REFLEX THEOKY. 521 Analogous experiments on animals without their brains yield similar results.* The salivary secretion and the ordinary reactions of Taste are provoked by sapid sub- stances. Still more conclusive are the observations made on a dog whose spinal cord has been divided, and who therefore according to the reigning ideas is incapable of feeling any impression made on parts below the section. A pencil inserted in the rectum causes a reaction of the muscles energetically resisting the entrance of this for- eign body ; yet tliis rectum so sensitive in its reaction on the stimulus of the pencil, responds by the totally different reaction — the relaxation of the muscles — on the stimulus of faecal matters. 52. " This is all mechanical," you say ? Mechanical, no doubt, as all actions are ; but the question here is whether among the conditions of the mechanical action Sensibility has a place ? Tlie answer can only be grounded on induction. The actions of the dog are analogous to the actions which you know were sentient in yourself. There was in both a discrimination, in both a correspond- ing reaction. I admit that what is here called "discrim- ination " is the application of a logical term to a mechan- ical process ; I admit that if the spinal mechanism is • insentient, the fact of discrimination may still be mani- fested ; but I conceive that the many and coercive grounds for admitting that the mechanism is sentient gain further support in the evidence of discrimination. Every par- ticular sensation has its corresponding reaction ; and al- tliough this has been acquired during ancestral or indi- vidual experiences, so that in the majority of cases there is no consciousness accompanying tlie operation, this, as we have seen, is not a valid argument against the ex- istence of a sensorial process. We have only to lower the Sensibility of tlie cord l)y ana3Sthetics, or to jpreoccupy * SeeProb. II. §183. 522 THE PHYSICAL BASIS OF MIND. its energies by some other excitation, and the reaction fails. MEMOPwY. 53. " But discrimination, if not a purely physical pro- cess, implies Memory ? " No doubt. And what is Mem- ory — on its physiological side — but an organized ten- dency to react on lines previously traversed ? As Gries- inger truly says : " There is Memory in all the functions of the central organs, including the spinal cord. There is one for reflex actions, no less than for sense-images, words, and ideas." Gratiolet makes a similar assertion.* Indeed if, as we have seen, reflex actions are partly con- nate, and partly acquired, it is obvious that the second class must involve that very reproduction of experiences, which in the sphere of Intellect is called Memory. There is assuredly something paradoxical at first in this application of the terms of the Logic of Signs, yet the psychologist will find it of great service. But if the terms discrimination and memory be objected to, they may be replaced by some such phrase as the " adaptation of the mechanism to varying impulses." On its objective side, Discrimination is Neural Grouping; on its subjec- tive side, it is Association of experiences. INSTINCT. 54. If we can detect evidences of Volition and Instinct in the absence of the brain, our thesis may be considered less questionable. And such evidence there is. Goltz decapitated a male frog (in the pairing season), and ob- served that it not only sought, grasped, and energetically * " II y a (lone une memoire par le cerveau et une memoire par I'au- tomate. Tous les organes ont une memoire propre, c'est h dire une ten- dance a reproduire les series d'actes qu'ils ont plusieurs fois executes." — Gratiolet, Anat. du SysUme Kcrvcux, 1857, p. 464. THE EEFLEX THEORY. 523 embraced a female, but could always discriminate a fe- male from a male. Thus when a male frog closely re- sembling a female in size and shape was presented to this decapitated animal, he clasped it, but rapidly let it go again, whereas even the dead body of a female was held as in a vice. Goltz tried to delude this brainless animal in various ways, always in vain. Only a female would be held in his embrace. Goltz then presented a female in a reversed position, so that the head was grasped by the male. Xow here, had there been simply a reflex machine, incapable of sentient discrimination, the clutched female would have been held in this position, just like any other object which excited the reflex ; there would have been no " sense of incongruity," such as Goltz no- ticed in his frog, who at once began a series of move- ments by whicli he was enabled, without letting the fe- male escape, to bring her into the proper position. To render this observation still more significant, I may add that Goltz did not find all male frogs act thus — many relinquished the female thus improperly presented to them. Such phenomena observed in frogs possessing brains, would be accepted as evidence of sexual instinct and volition. Further : Goltz removed the brain from a frog, which he then held under water, gently pressing the body so as to drive the air out of its lungs ; the body being then heavier than the water sank to the bottom, where it re- mained motionless. He repeated this procedure with an- other frog, not brainless but blinded. This one sank also, but in a few minutes rose to the surface to breathe. This difference naturally suggests that the brainless frog was insensible of the condition which in the otlier caused a movement of relief The one felt impending suffocation, the other felt nothing. Such was the interpretation of a German friend in whose presence I repeated tlie oxpcri- 524 THE PHYSICAL BASIS OF MIND. ment. But I had been instructed by Goltz, and bade my friend wait awhile. He did so, and saw the brainless frog slowly rise to the surface and breathe there like his blinded companion. So that the only difference observ- able w^as in the lessened sensibility of the brainless frog. 55. But Goltz records a still more conclusive case. In a large vessel of water he inverted a glass jar also con- taining water, which could then only be retained in the jar by atmospheric pressure. Through the neck of this inverted jar he tlirust a blinded frog, not having pressed the air out of its lungs. It rose at once in the jar, touch- incr the inverted bottom with its nose, and when the necessity of fresh air was felt, the frog began restlessly feeling about the surface of its prison till an issue was found in the neck of the jar, through which it dashed into the vessel, and at once rose to the surface of the water to breathe. In this observation are plainly mani- fested the stimulation of uneasy sensation, the volition of seeking relief, and the discrimination of it when found. If this frog was a sentient mechanism, what shall we say to the fact that a brainless frog was observed to go through precisely the same series of actions ? Goltz pertinently remarks : " So long as physiologists satisfied themselves that the brain was the sole organ of sensation, it was easy to declare all the actions of the brainless animal to be merely reflex. But now we must ask whether the greater part of these actions are not due to the 'power of adaptation in the central organs, and are therefore to be struck out of the class of simple reflexes ? If I bind one leg of a brainless frog and observe that he not only sees an obstacle, but crawls aside from it, I must regard these movements as regulated by his central power of adaptation ; but now suppose I unbind the leg and re- move the obstacle, then if I prick the frog he hops for- ward. Must I now declare this hop to have been a THE EEFLEX THEORY. 525 simple reflex ? Not at all. In both cases the physio- logical processes have been similar." 56. There are no doubt readers who will dismiss all evidence drawn from experiments on frogs, as irrelevant to mammals and man. Let us therefore see how the evidence stands with respect to animals higher in the scale, endowed with less questional)le mental faculties. In a former chapter (Problem II. § 29) we recorded the marked results of removing the cerebral hemispheres ; and at the same time suggested that these by no means justified the conclusion usually drawn respecting the hemisj)heres as the exclusive seat of sensation. And this on two grounds : First, because the absence of some sen- sitive phenomena does not prevent the presence of others : the mutilated organism is still capable of manifesting Sensibility in those organs which remain intact. Sec- ondly, because were the mutilation followed by total de- struction of Sensibility, this would not prove Sensibility in the normal organism to have its seat in the part in- jured. If the removal of a pin will destroy the chrono- metric action of a watch, we do not thence infer that the chronometric action was the function of this pin. And this objection has the greater force when we remember that one hemisphere may be removed without the conse- quent loss of a single function, and both may be removed without the loss of several functions usually ascribed to cerebral influence.* * To ohviatc misnnflorstandiiiff let mo say that, unless the contrary is specified, I use the term Brain throughout this argument as equivalent to the cerebral hemispheres, because it is in these that .sensation, volition, and consciousness are localized by the generality of writers, many of whom, indeed, regard the cells of the gray matter of the convolutions as the exclusive seat of these phenomena, dividing these cells into sensa- tional, emotional, and intellectual. There are physiologists who extend .sensation to the cerebral ganglia and gray masses of the medulla obloii- 526 THE PHYSICAL BASIS OF MIND. 57. Consider the analogous effects of injuries to or re- moval of the Cerebellum, in causing disturbance of loco- motion, whence the conclusion has been drawn that the Cerebellum is the exclusive organ of muscular co-ordina- tion, in spite of the unquestionable evidence that very many muscular co-ordinations still persist after this organ is removed. What is the part played by tlie Cerebellum I do not pause here to examine.* I only say that the movements of swimming, suckimi, swallowing, breathinir, crying, micturition, defecation, etc., are co-ordinated as well after removal of the Cerebellum as they were before, and that consequently their co-ordination has not its seat in the Cerebellum. The parallelism is obvious. Ee- moval of the Cerebrum causes a disturbance in the com- bination of sensations, and the execution of certain sense- guided actions, but causes little appreciable disturbance in others. Eemoval of the Cerebellum causes a disturb- ance in the combination of certain muscular sensations, and the execution of certain co-ordinated actions, with little appreciable disturbance in others. 58. So little have the facts been surveyed and esti- mated in their entirety that there is perhaps no subject on which physiologists are more agreed than on the func- tion of the Cerebellum being that of co-ordination. Yet consider this decisive experiment. I etherized three healthy frogs, from one I removed the entire cranial cen- tres ; from another I removed only the cerebellum ; and, gata ; but the medulla spinalis is so clearly continuous with the medulla oblongata that there is a glaring inconsistency in excluding sensation from the one if it is accorded to the other ; and the grounds on which sensi- tive phenomena are admitted in the absence of the hemispheres, force us to admit analogous phenomena in the absence of the ganglia and medulla oblongata : in each case the phenomena are less complex and varied as the mechanisms become less complex. * Compare LussANA e Lemoigne, Fisiologia del ccntrL encefalici, 1871, II. 239, 240, 330. THE REFLEX THEORY. 527 leaving the third in possession of an intact encephalon, I made two sections of the posterior columns of the spinal cord. The two first hopped, swam, used their legs in de- fence, and exhibited a variety of muscular co-ordinations, although in both the supposed organ of co-ordination was absent. Whereas the third, which had this organ intact, and was capable of moving each limb separately, and each pair of limbs separately, was utterly incapable of moving all four simultaneously. Why was this ? Obvi- ously because in the first two frogs the motor mechanism remained intact, and only the cerebral and cerebellar in- fiuence was removed ; in the third frog the sensory part of the motor mechanism had been divided, and no com- bination of the limbs was possible. 59. Physiological induction agrees witli anatomical in- duction in assigning to the cerebrum and cerebelhun the office of incitation and regulation rather than of innerva- tion ; for, as we have seen, no nerve issues directly from them (Problem II. § 7). Consequently the effects of in- juries to these centres are losses of spontaneity and of complexity in the manifestations. Inasmuch as in the intact organism all sensory impressions are propagated throughout the nervous centres, the reactions of these highest centres will enter into the complex of every ad- justed movement; so the abolition of these centres will be the dropping of a link in the chain, the abolition of a special element in tlie conii)lex group. The organs which are still intact will react, each in its own way, on being stimulated ; but the reaction will be without the modi- fying influence of the absent centres. For instance, the retinal stimulation from a luminous impression normally calls up a cluster of associated feelings derived originally from other senses, and a perception of the object is asso- ciated with emotions of desire, terror, etc., according to the past history of the organism, and its organized reac- 528 THE PHYSICAL BASIS OF MIND. tions, due to hereditary or acquired experiences. It is these which form tlie comjilex feeling discharged in the particular movement of prehension, or flight, llemove the brain, and there can be no longer this cluster of associated neural groups excited ; there will be therefore no emo- tion, simply the visual sensation, and such a movement as is directly associated with it. The brainless dog moans when hurt, it does not bark at the cat which it neverthe- less sees, and avoids as a mere obstacle in its path ; the cat will cry, it will not mew. The present pain moves the vocal organs, but does not revive associated experi- ences. All those combinations by which a series of dependent actions result from a single stimulation are frustrated when the mechanism is disturbed, so that the mutilated animal can no longer recognize its prey or its enemy, to feed on the one and fly from the other ; no longer builds its habitation, or rears its offspring. It can still live, feed, sleep, move, and defend itself against pres- ent discomfort ; it cannot find its food, or protect itself against prospective discomfort. We must supply the place of its Intelligence. We must give it the food, and protect it from injuries. There is therefore ample evidence to show that what is specially known as Intelligence is very imperfect after the cerebral influence has been abolished ; but this does not prove the Cerebrum to be the exclusive seat of Intel- ligence, it only proves it to be an indispensable factor in a complex of factors. Still less does it prove the Cere- brum to be the exclusive seat of Sensation, Instinct, Voli- tion ; for these may be manifested after its removal, although of course even these will be impaired by the loss of one factor. 60. And here an objection must be anticipated. In spite of the familiar experience that one mode of Sensi- bility may be destroyed without involving the destruction THE KEFLEX THEORY. 529 of other modes, there is a general belief — derived from a mistaken conception of what is really represented by the unity of Consciousness — that Consciousness disappears altogether when it disapjDears at all ; and hence, since Sensation is supposed to imply Consciousness, it also cannot be divisible, but must vanish altogether if it van- ish at all. The first answer is that Sensation as an ab- straction is neither divisible nor indivisible ; but as a generabzed expression of concrete sensorial processes it is reducible to these processes, and divisible as they are- No one doubts that we may lose a whole class of special sensations — sight, hearing, pain, temperature, etc. — yet retain all the others. No one doubts that we may lose a whole class of registered experiences — forget a language, or lose memory of places so familiar as the streets of the small town we inhabit, or of faces so familiar as those of friends and relatives, while the names of these streets and friends are still remembered when the sounds are lieard. Yet sensation and intelligence are not wholly lost. The mind is still erect amid these ruins.* 61. This premised, let ns consider the experimental evidence. Flourens declares that when he removed the whole of the Cerebrum from pigeons and fowls, they lost all sensation, all perception, all instinct, and all volition. They lived perfectly well for months after the operation, if the food were placed in their mouths ; but they never sought their food ; they never took it, even when their l)eaks were plunged into it : they could swallow, and digest the grains ; but they had no instinct to make tlicm seek, no volition to make them pick up the grains. They savj nothing, although the iris remained irritaljle ; they heard * See a veiy interesting case of this special loss of memoiy in a priest who still occui)ie(l himself reading classic authors and pcrfonning his of- ficial duties many months after an injury to the brain. IjUs.sana e Le- .MoKiNE, Fisiologia dei centri cncefalici, I. 201. vfiL. III. 23 H H 530 THE PHYSICAL BASIS OF MIND. nothing ; they could not smell. A state of stupor came on, resembling that of deep sleep. All voluntary action ceased. If they were thrown into the air, they flew ; if irritated, they moved away; but if left to themselves, they remained motionless, with the head under the wing, as in sleep. ISTow, inasmuch as these effects always ensue when the Cerebrum is removed, and Tiever when only the Cere- bellum is removed, he concludes that all instincts, voli- tions, and sensations "belong exclusively to the cerebral lobes." But all experimenters do not agree in other points named by Flourens ; nor in the conclusions he has drawn. On the contrary, it is very certain, and we find evidence even in Flourens himself, that all instincts and all sensa- tions are not destroyed by the removal of the cerebral lobes. 62. Let us hear Bouillaud on this subject.* He re- peated the experiment of Flourens, removing the whole of the Cerebrum from the Brain of a fowl ; and he thus records his observations : " This fowl passes the greater part of her time asleep, but she awakes at intervals, and spontaneously. When she goes to sleep, she turns her head on one side and buries it in the feathers of the wing ; when she awakes, she shakes herself, flaps her wings, and opens her eyes. In this respect there is no difference ob- servable between the mutilated and the perfect bird. She does not seem to be moved at all by the noise made round about her, but a very slight irritation of the skin suffices to awaken her instantaneously. When the irritation ceases, she relapses into sleep. When awake, she is often seen to cast stupid glances here and there, to change her place, and walk spontaneously. If put into a cage, she tries to escape ; but she comes and goes without any pur- * BoTTlLLAtTD, Becherclics Expirimentales sur Ics Fondions du Cerveau en general, 1830, p. 5, sq. THE KEFLEX THEORY. 531 pose, or rational design. "VVlien either foot, wing, or head is pinched, she withdraws it ; when she is laid hold of, she struggles to escape, and screams; but no sooner is she liberated than she rests motionless. If severely irritated, she screams loudly; but it is not only to express pain that she uses her voice, for it is by no means rare to hear her cacJde and cluck a little spontaneously ; that is to say, when no external irritation affects her. Her stupidity is pro- found ; she knows neither objects nor places, nor persons, and is completely divested of memory in this respect : not only does she not know how to seek or take food, she does not even know how to swallow it when placed in her beak — it must be pushed to the throat. Nevertheless her indocility, her movements, her agitation, attest that she feels the presence of a strange body. Inasmuch as external objects excite in her no idea, no desire, she pays no attention to them ; but she is not absolutely deprived of the power of attention, for if much irritated her atten- tion is awakened. She knows not how to escape an enemy, nor how to defend herself All lier actions, in a word, are blind, without reflexion, without knowledge." In this recital, the evidence both of sensation and in- stinct is incontestable, to any unprejudiced mind. Bouil- laud, in commenting on his observations, remarks, that assuredly all sensation was not destroyed, since the sensi- bilities of touch and pain were very manifest. Nor is it certain, he says, that the fowl heard nothing, saw nothing. It is true that she stumbled against olyects, and knew not how to avoid them. She opened lier eyes on awaking, looked about, and showed a sensibility in the pupil to light ; which, he thinks, is incompatible with the absence of all sensation of sight. 63. The experiments of Longet* seem decisive on this latter point. Having removed the whole of the Cere- ♦ Longet, Traiie dc Physiologic, II. 240. 532 THE PHYSICAL BASIS OF MIXD. brum from a pigeon, lie observed that whenever he approached a light brusquely to its eyes, there was con- traction of the pupil, and even winking ; but, what was still more remarkable, " when I gave a rotatory motion to the candle, and at such a distance that there could be no sensation of heat, the pigeon made a similar movement with its head. These observations, renewed several times in the presence of persons who were at my lectures, left no doubt of the persistence of sensibility to light after removal of the cerebral lobes." We have only to think of the baby following with its eyes the light moved before it, to understand the kind of impression produced by the candle on the pigeon. Longet also declares that his ex- periments prove the existence of sensations of sound, after removal of the whole cerebrum. 64. Dr. Dalton, giving the results of numerous experi- ments he performed, says that removal of the Cerebrum plunges the animal in " a profound stupor, in which he is almost entirely inattentive to surrounding objects Occasionally the bird opens its eyes with a vacant stare, stretches his neck, perhaps shakes his bill once or twice, or smoothes down the feathers upon his shoulders, and then relapses into his former apathetic condition. This state of immobility, however, is not accompanied by the loss of sight, of hearing, or of ordinary sensibilit}'". All these functions remain, as vjcll as that of foluntary motion. If a pistol be discharged behind the back of the animal, he at once opens his eyes, moves his head half round, and gives evident signs of having heard the report; but he immediately becomes quiet again, and pays no further attention to it. Sight is also retained, since the bird will .sometimes fix its eye on a particular object, and watch it for several seconds together." * While, therefore, Flourens concludes from his experi- * Daltox, Human Physiolocjij, Philadelpliia, 1859, p. 362. THE REFLEX THEORY. 533 ments that tlie Cerebrum is the seat of all sensation and all volition ; and Bouillaud concludes that it is most prob- abl}'- the seat of none; Dr. Dalton concludes that the functions of the Cerebrum are restricted to those usually classed as intellectual. " The animal," he says, " is still capable, after removal of the hemispheres, of receiving sensations from external objects. But these sensations appear to make upon him no lasting impression. He is incapable of connecting with his perceptions any distinct succession of ideas. He hears, for example, the report of a pistol, but he is not alarmed by it ; for the sound, although distinctly perceived, does not suggest any idea of danger or injury. The memory is altogether destroyed, and the recollection of sensations is not retained from one moment to another. The limbs and muscles are still under the control of the will ; but the will itself is inac- tive, because apparently it lacks its usual mental stim- ulus and direction."* Dr. Dalton reminds us how disturbance of the cerebral functions in human beings recalls these observations on animals. " In cases of impending apoplexy, or of soften- ing of the cerebral substance, among the earliest and most common phenomena is a loss or impairment of the mem- ory. The patient forgets the names of particular objects, or particular persons; or he is unable to calculate num- l)ers with his usual facility. His mental derangement is often shown in the undue estimate which he forms of passing events. He is no longer able to appreciate the true relation between different objects and different phe- nomena. Thus he will show an exaggerated degree of solicitude about a trivial occurrence, and will pay no atten- tion to other matters of importance. As the difficulty increases, he becomes careless of the directions and advice of his attendants, and must be watclied and managed like * Dalton, p. 362. 534 THE PHYSICAL BASIS OF MIND. a child or an imbecile. After a certain period he no longer appreciates the lapse of time, and even loses the distinc- tion between day and night. Finally, when the injury to the hemispheres is complete, the senses may still re- main active and impressible, while the patient is com- pletely deprived of intelligence and judgment."* 65. Having seen how far other experimenters are from confirming the conclusions of Flourens, let us glance at his record of observations, and w^e shall find there evi- dence that all sensation and all volition cannot be local- ized in the Cerebrum. Speaking of a fowl whose Cere- brum was removed the day before, he says : " She shakes her head and feathers, sometimes even she cleans and sharpens them with her beak ; sometimes she changes the leg on which she sleeps, for, like other birds, she sleeps habitually resting upon one leg. In all these cases she seems like a man asleep, who, without quite waking, changes his place, and reposes in another, from the fatigue occasioned by the previous posture : he selects one more comfortable, stretches himself, yawns, shakes himself a little, and falls asleep again On the third day the fowl is no longer so calm ; she comes and goes, but with- out motive and without an aim ; and if she encounters an obstacle on her path, she knows not how to avoid iff In his second work he remarks of a Duck operated on in the same way : " As I mentioned last year a fro'pos of fowls, the duck walks about oftener, and for a longer time together, when it is fasting, than when it is fed." Here he observes the unmistakable evidence of feelings of Hunger, Fatigue, and Discomfort in animals which, according to him, have lost all sensation. He also ob- serves the operation of instinct (cleaning the feathers), and of spontaneous activity (walking about), in animals said to have lost all instinct and all volition. * Dalton, p. 363. t Flourens, p. 89. THE KEFLEX THEORY. 535 66. Still more decisive are the observations recorded by other experimenters. Leyden removed the hemi- spheres and the ganglia at their base from a hen ; yet this hen moved about and clucked. Meissner noticed that a pigeon whose hemispheres had been removed always uttered its coo, and showed restlessness at the usual feed- ing-time.* Voit carefully extirpated the cerebrum from some pigeons, and kept them for many months in health. For the first few weeks they exhibited the well-known stupor. Then they began to shake this off, open their eyes, walk, and fly about spontaneously. They gave un- mistakable signs of seeing and hearing. But the chief defect was in the inability to feed themselves, and the complete insensibility to danger. They also manifested signs of sexual feeling with lively cooings ; though quite unable to gratify their desires, f Vulpian having removed the cerebrum, optic thalami, and corpora striata from a young rabbit, found that on pinching its tail it cried out and struggled to escape ; and a rat thus mutilated not only struggled and cried when pinched, but manifested strong emotion. " II est tres craintif, tres impressionable ; il bondit pour peu qu'on le touche ; le moindre bruit le fait tressaillir. Un certain bruit d'appel fait avec les levres, ou un soufflet brusque imitant celui qu'emettent les chats en colere excitent chez le rat une vive emotion.^ 67. There are several well-authenticated cases on rec- ord of children born without a vestige of brain, and oth- ers with only a vestige, who nevertheless manifested the ordinary signs of sensation. I will cite but one, and it shall Ije one for which an illustrious physiologist, Panizza, is tlic guarantee. A male infant, one of twins, who lived * Leyden in the Berliner klinischc IVochenschrift, 1867, No. 7. Mei.ssseu, Jahreshcricht iibcr Physiol., 1867, p. 410. t Voit in the Sitzungnherichtc dcr Milnchcner Academic, 1868, p. 105. Comj). also Goltz in PJlurjcr's Archiv, IM. XIV. 435. % VuLi'iAN, SysUme Ncrvcux, 542-48. bob THE niYSicAL basis of mind. Init eighteen hours, during that period manifested such un(}ucstionable signs of Sensibility as the following: the pupils contracted under light, sharp sounds caused iiutter- ings, and a bitter solution when placed in the mouth was instantly rejected. This infant had not a vestige of cere- brum, cerebellum, or cerebral ganglia. The medulla ob- longata was normal. There were no olfactory nerves, and the optic nerves terminated in a little mass of mem- brane.* 68. The observations of Lussana and Lemoigne are both extensive and precise, and the conclusion at which they arrive is that the removal of the Cerebrum is the abolition of Intelligence and Instinct, but is not the abo- lition of Sensation. Whereas Rolando, and after him Eenzi, consider that only the Intelligence is abolished, the supposed loss of Instinct being really nothing more than the loss of the directive influence which makes the In- stinct to be executed. 69. Here it becomes needful to understand THE MECHANISM OF INSTINCT. Were we dealing with an ordinary mechanism, and the disturbances produced in its actions by the removal of any part, we should attribute all observed effects to interfer- ence vjith the conditions of dependent sequence : we should infer that the actions were imperfectly performed, or wholly abolished, because their requisite mechanical con- ditions were disturbed. Let us be equally precise in deal- ing with the physiological mechanism. If we have de- prived it of an organ in which certain combinations are effected, we must expect to find all actions which were dependent on such combinations to be now impossible ; * For other e.xamples see Gintrac, Pathologic Interne, 1868, VI. 51-57. THE REFLEX THEORY. 537 but all the actions which are not directly dependent on these combinations may still be possible. The actions of feeding, for example, are determined by certain sensations, when these are present in a particular sequence, but not otherwise ; the sensation of sight does not suffice, because the animal must not only see the food, he must perceive it. The action of defence and flight are also determined by certain sensations, but only when these are connected in a certain sequence : the brainless animal will defend itself, or move out of the Avay, under the stimulus of unpleasant sensation ; but wall not be moved by o, pi'^^ospective injury, because he fails to associate it with the sight of the threat- ening object. In the same way a blind man shrinks at tlie actual contact of the heated poker, but does not shrink at the approach of that poker which he does not see. We do not deny him the possession of the so-called instinct of Self-preservation on this ground ; why deny it to the brainless animal ? The brainless fish or frog swims when placed in the water, because the sensation from the mov- ing water * sets going the swimming mechanism. To call this a " swimming instinct " may seem extravagant ; yet it is as fully entitled to the name as Self-defence is, or the Alimentary Instinct. In all three cases there is a con- nate mechanism set going by appropriate feelings. 70. Since all admit that there is an Alimentary In- stinct, let us see what kind of mechanism it implies. There must be a state of feeling called Hunger, which — combined with other feelings — determines certain mus- cular adjustments in the search, recognition, capture, and finally the swallowing of the food: — a very conqjlex scries of actions, which lead to and sustain one another until the desire is gratified. On the mental side there * If the water is jjerfectly still the fish sinks to the hottorn and re- mains motionless imtil the water he stirred. Mere contact does not suf- fice ; there must be intemiittent pulses from the moving water. 23* 538 THE PHYSICAL BASIS OF MIND. are three constituents, all indispensable : the hunger must be felt, the food must be discriminated, the desire must be gratified ; on the physical side there are also the indispensable arrangements of the motor mechanism. Now it is obvious that the entire mechanism of this in- stinct cannot be localized in the brain, even if its mental elements are localized there ; and there is reason to be- lieve that even the mental elements — the feelings of hunger, discrimination, and gratification — are not exclu- sively localized there. The brainless animal manifests if not the feeling of Hunger, at any rate that feeling of dis- comfort which is the basis of Hunger. The restlessness is that of a hungry animal. Now we know that some of the Systemic Sensibility is preserved, for we see the ani- mal breathing, swallowing, urinating, sleeping, preening its feathers, changing its attitude, resting on one leg after the fatigue of the other, etc. AVe may therefore infer that other systemic sensations, such as Hunger and Thirst, arise under the usual conditions. 71. We have noted an indication of Hunger ; but on further observation we discover that although the food is eaten, if brought within reach of that portion of the feed- ing mechanism which is still intact, yet the second step — the feeling of recognition — is wanting. The animal fails to perceive the food brought under his eyes, or even placed in his mouth ; unless the back part of the mouth be touched, no swallowing takes place. Hence the animal can no longer feed himself, and is therefore said to have lost his instinct. But although the mechanism of the instinct has been disturbed, its action is not wholly abol- ished. The brain is necessary for that combination of adjustments which normally accompany the perception of food through sight and scent; and its absence of course frustrates such combination ; but we shall presently see that although certain sensible marks by which a percep- THE REFLEX THEORY. 539 tion is guided are absent, others may still be present, and suffice. 72. Before adducing examples let me say that we can- not legitimately attribute the abeyance of an instinct solely to the absence of the brain, 1°, because we ob- serve a similar abeyance of the instinct and frustration of perception, even when the brain is present, and the animal is in its normal state. 2°. On the other hand, some instincts are unmistakably manifested, and some perceptions excited, after the brain has been removed. In fact, all that is needful is that some of the mental elements of such perception and such instinct be pre- served; and this is the case so long as the leading element is present. 73. On the first point consider this unequivocal ex-, ample. A healthy, hungry frog may be placed in a ves- sel in which lie a quantity of dead flies. He sees these flies, but sight is not enough ; to him they are only so many black spots, in which he does not recognize his food, because the flies do not move, and the leading dement in his perception of food is not a colored form, but a moving form. Hence this frog, in spite of brain and an intact organism, will starve amidst appropriate food. Whereas the frog that will not snap at motionless flies snaps at any other small moving object, though it be not his food. Goltz ol)served one incessantly snapping at the moving tentacles of a slug which was in the vessel — as if that were possible food ! Not only the stupid frog, but the more intelligent carnivora will starve in the presence of appropriate food which is unrecognized, because the leading element in tlie recognition is absent. The cat will not eat a dead mouse, unless slie has killed it herself. Predatory animals must capture their food — unless the scent of blood excites their alimentary instinct. So inti- mately is this sensation of a moving object connected 540 THE PHYSICAL BASIS OF MIXD. with the predatory impulse, that the cat which is unex- cited by the dead mouse cannot resist springing on a moving ball. We need not suppose the cat to mistake this ball for food ; but we must suppose that, accustomed to pounce upon moving food, it is unable to resist the impulse of this leading sensation. 74. The 2y^'cscncc of the brain not sufficing, in the ab- sence of the leading sensation, we shall now see that the absence of tlie brain will not prevent the execution of the instinctive action, if the leading sensation be present. The brainless bird sees a heap of grain, or a pan of water, but no more recognizes them by sight alone than the frog recognizes the dead flies ; yet if the bird's feet be placed in the water, this sensation will suffice to make him drink ; if placed amid the grain, this sensation will (sometimes) suffice to make him feed. Lussana and Le- moigne state that their brainless pigeons ate and drank with avidity when their feet were placed in grain and water.* M. Krishaber removed the hemispheres from a pigeon, and observed that when his beak was thrust into a heap of hempseed the head was quickly withdrawn, whereas when the beak was plunged into water the bird drank eagerly. Every day he was forced to feed the bird by pouring the seed into its throat, but every day it drank when the beak was thrust into the pan of water.-f- Briicke noticed that his brainless hen, which made no attempt to peck at the grain under her very eyes, began pecking if the grain were thrown on the ground with force, so as to produce a rattling sound. The sensation of hearing was here more perfect than that of vision, and sufficed to awaken the state of feeling necessary to initiate the pecking movement.;): * Lussana e Lf.moigne, Oj). cit., I. 15. + Archives de Physiologic, 1869, p. 539. J Bkucke, Physiologic, II. p. 63. WTiile these sheets are passing THE KEFLEX THEOEY, 541 75. Somewliat analogous phenomena are observed in Aphasia. The patient can see printed or written letters, and even copy them ; but he cannot read, i. e. interpret, these symbols; as the birds see the grain, but cannot con- nect this sensation with others. These letters and words, which the patient cannot interpret when seen, he can in- terpret when heard; he can not only understand them when spoken, but write them if they are dictated to him. The birds recognize the grain and water (or act as if they did) wlien other sensations than those of sight are ex- cited. Sound is the leading element in Language, both spoken and written. "We hear the M^ords even when we see them, but we do not see them when we hear them. The visible symbols are accessory and subordinate. But to the born deaf the visible symbols dominate. How one sensation will determine a particular group of movements which cannot be effected by any other stimulus is abun- dantly illustrated in disease no less than in experiment. Here is a very luminous example: Gratiolet had a patient for six months under his eye incapable of articulating a single word, owing to the incoherence of her incessant ut- tlirough the press, GoLTZ has published his second series of experiments on the brain. Tlie following detail is a good illustration of what is said in the text: A dog deprived of a portion of both hemisjiheres displayed a marked imperfection in the execution of ordinary instincts. Although sight was impaired he could see, and recognize men and certain objects: the sight of a wliip made him cower, but the sight of meat did not suf- fice to set the feeding mechanism in action. When meat was suspended above his head, the scent caused him to sniff about in search, but he failed to find it, and even when he was so placed that he could see the susjjcnded meat, the unusual impression failed to guide him. If the meat were held towards him, or placed before him in a dish, he took it at once — this being the customary stimulation. So also, if the hand were held up, in the usual way when dogs are made to leap for food, this dog sprang vigorously up and caught the food ; but he would spring up in the .same way when the hand was held empty, and continue fruitlessly springing, whereas an uninjured dog ceases to sj)nng wiien he sees the hand is empty. — Pflikjcrs Archiv, lid. XIV. p. 419. 542 THE PHYSICAL BASIS OF MIND. terance — she babbled sounds, but could not group the syllables into a recognizable word. Yet she could sing the words of any song she knew, the musical sensations being sufficient to guide her vocal organs. "Ainsi la meinoire, infidele dans le cas oii les mots etaient des idees, devenait claire et precise quand les mots etaient des chansons." * 76. These illustrations plainly tell how the brainless animal may starve amid his food, failing to perceive it because tlie leading sensation is not excited ; and how the same animal may manifest his feeding instinct if the mechanism be set going by a leading sensation. We are told, indeed, that in the absence of the brain the actions are mechanical reflexes from impressions, and not com- parable with the complex processes determined by per- ception. I think, however, that tlie only difference is in degree of complexity : a combination of touch, tempera- ture, and muscular movement will be simpler than one which also combines sight, smell, and the revived images of associated sensations. The sight of a sheep affects the instinctive mechanism of a wolf only when combined with the leading element of smell. Place a stuffed sheep in a field, and no wolf will approach and spring on it, whereas the blind wolf will find and capture the real sheep ; and I believe that were it practicable to remove the brain without injury to the organ of scent and the powers of locomotion, the wolf would track and capture the living sheep. 77. The outcome of this discussion is that the mechan- ism of each instinct is the adjustment of the organs which effect the instinctive action ; and this adjustment is not simply a cerebral process, but a complex of many sensorial processes ; consequently the instinct cannot be exclusively localized in the brain, altliough the cerebral process may * Gratiolet, Anat. Comparee die SysUme Nerveux, 1857, p- 459. THE KEFLEX THEOKY. 543 be a very important element in the adjustment. This is true even on the supposition that in speaking of Instinct we refer only to the state of feeling which originates the action — separating the psychological from the physiologi- cal aspect of the phenomenon. \^or the brain minus the organism is obviously incapable of feelings ; whereas the organism minus the brain is obviously capable of sensi- bilities adequate to determine the actions. Thus the feel- ing of hunger which prompts the alimentary actions does not arise if tlie animal is satiated, nor does the sexual feeling which prompts generative actions arise when the animal is castrated ; but each arises when the organism is in a particular state. In vain will food be placed before the satiated animal, or a female before the castrated male; food and female are seen and recognized, but no desires are excited, in spite of the brain and its supposed in- stincts. On the contrary, when the brain is removed, the need of tlie organism for food is felt, and this need deter- mines restless movements, which are directed by certain other sensations, and the instinctive action of feeding is finally effected ; although, of course, the removal of the brain has so disturbed the normal mechanism of the in- stinct that the action is imperfect. Renzi says that an animal deprived of its brain has lost the intelligence which enables it to seek and seize its food, but not the instinct, since it still has the desire for food. The fol- lowing experiment may illustrate this. Eenzi wounded superficially one optic thalamus of a frog without in- juring the external margin, or optic tract. Tlie frog showed no appreciable loss of sight, but hopped timidly away whenever approached. Then botli thalami were divided transversely, the optic tract still being spared. This frog remained motionless under every threat. It manifested no alarm, and even when directly irritated, only crawled or hopped away like a brainless frog. Sight 544 THE PHYSICAL BASIS OF JIIND. still SO far remained that obstacles were avoided* Now since this animal's brain was intact, and its organs of movement were capable of responding to stimulation, how are we to explain the loss of its instinct of self- preservation ? The i'rog perceived no danger in a threat- ening approach, yet perceived an obstacle and avoided it, getting under it if there were room enough, crawling be- side it if that was the easier escape. Why did one vision prompt the movements of escape, and another fail ? AVas it not that in the one case the normal pathway was still open, in the other closed? We know that one injury will destroy the perception of color without destroying that of light and shadow ; so one injury may destroy the combination of neural processes necessary for the percep- tion of a danger, without destroying those necessary for the perception of a hindrance. If all actions depend on their mechanical conditions, they must be disturbed according to the disturbance of the conditions. Nothna- gel found that after removing the nucleus Icntiformis on both sides of a rabbit, leaving all the rest of the encepha- lon intact, the rabbit hopped when its tail was pinched ; yet although starting at the sound when hands were loudly clapped, did not hop as a normal rabbit does ; nor although closing his eyes when a light was brought near them, did he ever move aside. No feeling of danger was excited by sound or sight. In striking contrast are the phenomena manifested by a rabbit whose corpora striata have been removed : it is with difficulty made to hop by pinching its skin, whereas noises and sights cause it to make terrified bounds.-f* * Ltjssana e Lemoigne, Op. cit., I. 363. + Virclioiv' s Archiv, Bd. LX. pp. 130-33. Yet there are many physi- ologists who persist in placing the motorium commune in the corpora striata ! And they place the scnsorium commune in the optic thalami, although, not to mention the ambiguous evidence of Pathology, the ex- periments of NoTHNAGEL and VEYSSifeRE show that destniction of the THE REFLEX THEOEY. 545 78. No sooner do we analyze the conditions of an in- stinct than we see the error of recrardins instincts as local- ized in the brain. The cerebral process is only one factor in the product — an important factor, no doubt, since the cerebrum is the supreme centre of incitation and regu- lation ; but its absence does not wholly carry away the activity of the mechanism, sentient and motor, on which the instincts depend, it only carries away one source of stimulation and regulation. 79. An instinct depends on a connate mechanism. Let us glance for a moment at a parallel case of an ordinary reflex action, also dependent on a connate mechanism, say that of sneezing. When the inner surface of the nose is stimulated by snuff, or other irritant, the nasal branch of the trigeminus is excited, and the effects are first a deep inspiration, then a closure of the respiratory orifices by the tongue, which in turn excites a spasmodic expiration. But the same effects are producible from quite different stimulations — namely, that of the ciliary nerves on sud- den exposure to a glare of sunshine — or of the skin nerves on a sudden draught of cold air. Briicke re- marks that there is perhaps no spot on the surface of the body from which this reflex may not be excited in very sensitive people. He knew a gentleman who always sneezed when in winter he laid hold of a cold door-bell ; and the fit of sneezing was only arrested by giving him a crust of bread or something hard to gnaw. Now just as the connate mechanism of sneezing may be set in action l)y a variety of stimulations, so may the connate mechan- ism of an instinct. tlialami does not destroy sensation. See VEYS.sifeRE, Hechcrchcs sur VhemianestJiesie de cause ccribralc, 1874, pp. 83, 84. I may observe, in passin;^, tliat the notion of tlie coiyora striata being tlie necessary cliannel tor volitional impulses, and the optic thalami for rede.v aetions, is utterly dispioved by the experimental evidence recorded in the text, as well as in § 66. 1 1 546 THE PHYSICAL BASIS OF MIND. ACQUISITION. 80. Not only may Discrimination and Instinct be mani- fested in the absence of the brain, but even the acquisi- tion of new modes of reaction, such as are classed under Learning through Experience. The objection is some- times urged that animals without their brains only mani- fest single reactions on stimulation — the pinched foot is withdrawn, and then remains motionless until again pinched. But although the stimulation does not excite a consecutive series of movements, because there is no cerebrum to react in successive stimulation, this does not prove the absence of sensation in the one movement which is excited. If my hand be lying on the table, and something irritates it, my hand is withdrawn, and then remains as motionless as the limb of the brainless animal, until some fresh stimulation, external or internal, moves it. Although removal of the brain causes a manifest re- duction in the variety and succession of the movements, all experimenters are agreed that animals acquire a cer- tain dexterity in executing actions which they had pre- viously failed to carry out after removal of their brains. "There is," says Freusberg, "a decided improvement ac- quired in the reactions of the motor centres after division of the spinal cord, not indeed in vigor, but in delicacy. Eemoved from the regulating influence of the brain, the legs acquired through practice a power of self-regulation." Nor is this wonderful : pathways are made easy by repeti- tion of impulses, and new adaptations form new adjust- ments. It is thus all learning is effected — intelligent, and automatic. Nor is there any force in the objection that the power thus acquired speedily disappears, so that if the stimulations are effected at long intervals the reac- tions do not manifest their acquired dexterity. The spinal centres forget, as the cerebral centres forget; but they also THE REFLEX THEORY. 547 remember, i. e. they learn. Because an animal shows to- day none of the aptitude it acquired three days ago, we are not to deny that it had once acquired the aptitude it lias now lost. Attempt to teach a child to read by giving it spelling lessons of two or three minutes at inter- vals of two or three months, and little will the acqui- sition be ! 81. Hitherto we have been considering phenomena manifested in the absence of the cerebral hemispheres, because it is in these that the majority of writers place the sensorium. There are, indeed, many authoritative writers who regard the ganglionic masses at the base of the cerebrum, and even those of the medulla oblongata, as participating in this sensorial property, which they refuse to the lower ganglia in the spinal cord. I cannot follow their logic. The cerebrum is by its position as a centre of centres, and its detachment from all direct innervation of organs, so different from the rest of the neural axis, that we can understand how it should be assigned a special function ; although being of the same tissue as the other ganglionic masses, it must have the same prop- erty. And Avhat that special function is I shall hereafter endeavor to set forth. But that the upper region of the spinal axis should differ so profoundly from the lower region as to be the seat of psychical processes, while the lower region is simply the seat of mechanical processes, is what I cannot understand, so long as the anatomical structure and physiological properties of the two regions are seen to be identical. The various centres innervate A'arious organs, and have consequently various functions. As each centre is removed, we observe a corresponding loss of function — the organism is truncated, but con- tinues to manifest such functions as have still their mechanisms intact. Let us suppose the brain or upper 548 THE PHYSICAL BASIS OF MIND. regions of the cord detached from the lower regions by a section of the cord ; the animal will still live, and per- form almost all its functions in the normal way, but there will be little or no consensus between the lower and the upper regions. Granting Sensibility to both, we must still see that the sensation excited in one will not be felt in the other. And this is the ground on which physiolo- gists deny that the lower regions have Sensibility. With- out pausing here to examine this point, which will occupy us in the next chapter, I assume that the positive evi- dence of Sensibility suffices to discredit that argument ; and in furtherance of that assumption will cite an ex- ample of sensation and volition manifested by the lower portion of the cord when separated from the brain and upper portion. 82. The function of Urination is one which notori- ously belongs to the voluntary class, in so far as it is initiated or arrested by a voluntary impulse, and it is one which, according to the classic teaching, has its centre in the brain. The grounds on which this cerebral centre is assigned are very similar to those on which other func- tions are assigned to cerebral centres, namely, observation of the suppression of the function when the pathway between certain organs and the brain is interrupted. But the careful experiments of Goltz * have demonstrated that the " centre " of Urination is not in the brain, but in the lower region of the cord. When the cord is com- pletely divided. Urination is performed in the normal way — not passively, not irregularly, but with all the characters of the active regular function. And, what is also noticeable, this function is so intimately dependent on Sensibility that it will be arrested — like any other function — by a sensation excited from the periphery — to be resumed when the irritation ceases. Now this * Pfliigcrs Archil; Bde. VIII. and IX. THE KEFLEX THEORY. 549 arrest from a stimulation of sensory nerves takes place when the brain is cut off from tlie spinal centre, just as when the brain is in connection with it. The same is true of Defecation, and the still more complex functions of Generation and Parturition. I can only refer the reader to the very remarkable case of Goltz's bitch with the spinal cord divided in the lumbar region, if evidence be wanted for the performance of complex functions so long as the spinal centres were intact. It is true that Goltz considers these functions to have been independent of sensation; but that is because he has not entirely emancipated himself from the traditional views ; for my purpose it is enough that he admits the functions to be dependent on sensorial processes. 83. To sum up the evidence, we may say that observa- tion discloses a surprising resemblance in the manifesta- tions of the cord and brain. In both there are reflex pro- cesses, and processes of arrest ; in both there are actions referable to conscious and unconscious processes ; in both depression and exaltation are produced by the same drugs ; in both there are manifestations interpretable, as those of Discrimination, Logic, Instinct, Volition, Acquisition, Memor}^ ; in both there is manifestation of Sensibility — how then can we deny Sensation to the one if we accord ^ it to the other ? 550 THE PHYSICAL BASIS OF MIND. CHAPTER IV. NEGATIVE INDUCTIONS. 84. I FANCY some reader exclaiming -: " All your reason- ing, and all your marshalled facts, are swept away by the irresistible eyidence of human patients with injured spinal cords, whose legs haye manifested reflex actions, and who nevertheless declared they had no sensation whatever in them. We can never be sure of what passes in an animal ; but man can tell us whether he feels an impression, or does not feel it ; and since he tells us that he does not feel it, cannot, however he may try, we conclude that reflex action may take place without sensation." As this is the one solitary fact which is held to nega- tive the mass of evidence, anatomical and physiological, in favor of the Sensibility of the spinal cord, it is neces- sary that we should candidly examine it. No reader will suppose that during the twenty years in which I have advocated the doctrine expounded in this volume, I have not been fully alive to the one fact which prevented the general acceptance of the doctrine. From the first it has seemed to me that the fact has been misinterpreted. 85. Certain injuries to the spinal cord destroy the connection of the parts below tlie injury with the parts above it ; consequently no impression made on the limbs below the injured spot is transmitted to the brain, nor can any cerebral incitation reach those limbs. The patient has lost all consciousness of these limbs, and all THE REFLEX THEORY. 551 control over them. Hunter's patient on being asked if he lelt any pain when the prick caused his leg to kick, answered, " No : but you see my leg does." This answer has been regarded as a drollery ; 1 think it expressed a physiological truth. For on the assumption that the whole of the cerebro-spinal axis had one uniform prop- erty, corresponding with its uniform structure, and vari- ous functions, corresponding with the variety of organs it innervates, a division of this axis would necessarily create two independent seats of Sensibility, and inter- rupt the consensus of their functions. In such a case it would be absurd to expect that, the cerebral segment could be affected by, or co-operate with, what affected the spinal segment. Now, when a man has a diseased spinal cord, the seat of injury causes, for the time at least, a division of the whole group of centres into two independent groups. For all purposes of sensation and volition it is the same as if he were cut in half ; his nervous mechanism is cut in half. How then can any cerebral control be obeyed by his legs ; how can any impression on his legs be felt by his cerebrum ? As well might we expect the man whose arm has been amputated, to feel the incisions of the scalpel, when that limb is conveyed to the dissecting- table, as to feel by his brain impressions made upon parts wholly divorced from organic connection with the brain. 86. But, it may be objected, this is the very point urged. The man himself does not feel the impressions on his legs when his spine has been injured; he is as insensible to them as to the dissection of his amputated arm. Very true. He, does not feel it. But if the amputated arm were to strike the anatomist who began its dissection, if its fingers were to grasp the scalpel, and push it away, or with the thumb to rub off the acid irritating one of the fingers, I do not see how we could 552 THE PHYSICAL BASIS OF MIND. refuse to admit that the arm felt although the man ditl not. And this is the case \vith the extremities of a man whose spine is injured. They manifest every indication of sensibility. In the frog and pigeon the legs manifest the unmistakable control which we ascribe to volition. It is true that the man himself, when interrogated, declares that he feels nothing ; the cerebral segment has attached to it organs of speech and expressive features, by which its sensations can be communicated to others ; whereas the spinal segment has no such means of com- municating its sensations ; but those which it has, it cm^ploys. You can ask the cerebral segment a question, which can be heard, understood, and answered ; this is not the case with the spinal segment : yet if you test its sensibility, the result is unequivocal. You cannot ask an animal whether it feels, but you can test its sensi- bility, and that test suffices. 87. The question we have to decide, therefore, is not whether a patient, with an injured spine, can feel im- pressions on, or convey voluntary impulses to, limbs be- low the seat of injury — for as respects the nervous mechanism these limbs are separated from him, no less than if actual amputation had taken place — the ques- tion is, whether tliese separated limbs have any sensibility ? And the answer seems to me unequivocally affirmative. I assert, therefore, that if there is ample evidence to show that the spinal centres have sensibility, when separated from the cerebral centres, such evidence can in no re- spect be weakened by the fact that a man with an in- jured spine is unconscious of impressions made below the seat of injury ; since such a fact necessarily follows from the establishment of two centres : the parts above are then not sensitive to impressions on the parts below ; nor are the parts below sensitive to impressions on the parts above ; but each segment is sensitive to its own affections. i THE REFLEX THEORY. 553 88. Every one knows that there are animals, low down in the scale, which may be cut in two, each half continu- ing to live, and each capable of reproducing its lost segments. Would any one, seeing these separated halves move and manifest ordinary signs of sensibility, venture to say that the one half was a living, the other an insen- tient, mechanism ? And since the one half had eyes, mouth, tentacles, etc., while the other half had none of these, would the observer be surprised that the functions of the one differed from those of the other in these re- spects ? Why, then, should he not conclude the same of the two halves of the human mechanism, when disease had divided them ? 89. The man, you urge, does not feel the prick on his leg. This is true, because " the man " here designates the seeing, hearing, tasting, smelling, talking, thinking group of organs — to the exclusion of the limb or limbs which are no longer in sensitive connection with this group. When a leg is amputated " the man " remains — a truncated man, indeed, yet still one having all the dis- tinguishing human characters. Yet obviously in strict language we can no longer say that the man is the same as he was. "Man" or "animal" means the complex whole; and eacli anatomically separable part forms one constitu- ent of that whole. The medulla oblongata and spinal cord innervate certain parts ; the mesencephalon inner- vates others ; the cerebrum rises above the whole. If after removing one limb, then another, we continued truncating the organism till we left only the head, should we call that the man ? Clearly not. Should we even suppose that the intact brain — the supposed seat of sen- sation and volition — still felt, and willed ? Clearly not. There is absolutely no evidence, however faint, of the isolated head manifesting any sensational and volitional phenomena ; whereas there is ample evidence of the trun- vou III. 24 554 THE PHYSICAL BASIS OF MIND. cated spinal cord manifesting some of these phenomena. And this is intelligible when we understand that tlie nerve-centres stimulate into action the organs the}^ inner- vate, but do not by themselves play any other part. 90. " The man " then does not feel the prick on his leg, but his leg feels it. The man has no consciousness of what takes place outside the sphere of his sensitive mechanism ; and the leg is now outside that sphere. Consciousness — as distinguished from Sentience in gen- eral — we have seen to be a resultant of the composition of forces co-ojoerating at the moment ; the Sensibility of the spinal cord in the regions below the injury cannot oiovj enter into that composition. It is detached from the upper organs. But inasmuch as the organs it innervates are still living and active, the functions of this detached jjortion are still displayed. We have seen the dog with divided cord capable of Urination, Defecation, Generation, etc. ; its hinder legs, though not moving in a consensus with the forelegs, yet moved independently ; and all the normal reflexes of the parts followed on stimulations. To say that "the dog" showed no signs of Sensibility when its hinder limbs were irritated, is identifying " the doGC " with the anterior half of the oroanism which was not in connection with the posterior half. It is equally true that the posterior half showed no signs of Sensibility when the anterior was irritated. The two halves were united by the circulation, nutrition, etc., but disunited as to sensation and volition. 91. Do I then suppose the separated half of an animal to feel pain and pleasure, hope and terror ? The reader who has "attentively followed the exposition will be at no loss to answer. Pain, pleasure, hope, and terror, are special modes of Sensibility, dependent on particular neural combinations. The organs comprised in the an- terior half of the animal furnish the main conditions for these special modes, whereas the organs comprised in the THE KEFLEX THEORY. -555 posterior half furnish few or none of those — they con- tain none of the special Senses, and they are without the chief combining centre, the brain. But since we know that a large amount of normal Sensation is wholly with- out the special characters of pain, pleasure, hope, or terror, we need not hesitate to assign Sensation to the spinal cord because these characters are absent. 92. All I contend for is that tlie spinal centres have Sensibility of the same order as the cerebral centres ; and that in the normal organism this Sensibility enters as a factor into the general Consciousness — no one portion of the nervous system being really independent of all tlie others, all co-operating in every result. Over and over again I have had to insist that the property of Sensibility is only the general condition of Sensation ; and that each particular sensation receives its character from the organs innervated, ]jIus the reaction of the whole organism. Ob- viously, therefore, the peculiar character of a sensation, or "state of consciousness," must vary with the variations in either of these factors. To say that every segment of the spinal cord has Sensibility, is not saying that an ex- citation of that segment will produce a particular sensa- tion of definite character-; because for this definite char- acter there is needed the co-operation of all those parts of the mechanism which enter into the complex product. 93. And here attention must be called to a double fallacy pervading the arguments on the other side. It is always assumed that the reactions of an organ, or part of tlie organism, when separated from the rest, are typical of their reactions when forming constituents of the nor- mal organism. Nothing of the kind. The movement of a muscle or a limb separated from the body may resemble that movement when normally effected — but only as the movements of a mechanical bird resemble those of a liv- ing Ijird : the modes of production are different. So that 556 THE niYsicAL basis of mind. were we to grant the postulate of the brain being the ex- clusive seat of sensation, we should still deny that an action which was effected after removal of the brain was typical of the action effected when tlie brain ^vas present. The leg of Hunter's patient jerked when the skin was irritated ; but this action could not be altogether the same as the similar action in a leg united with the rest of the sensitive mechanism. Nor is this all. The leg may have been insensible, the spinal segment which in- nervated it may have been wholly without Sensibility, and still we should have to question the logic Mdiich ex- tended such an inference to the very different and far more complex actions of decapitated animals. On this ground : — The leg is, by the hypothesis, insensible be- cause cut off from all connection with the sensiti^'c mechanism. But this is not the case with the decapi- tated animal : there still remain the essential parts of a sensitive mechanism — all the chief organs are still in activity, still manifesting their functions. Decapitation has produced a great disturbance in the mechanism, and has removed an important centre ; but nevertheless every impression excites a connected group of centres, and this group responds. 94. In conclusion, unless we adopt the opinion that Sensation — Consciousness — Sensibility, is something not belonging to the physiological properties of the ner- vous system in a vital organism ( the opinion held by spiritualists ), there seems no alternative but to adopt the opinion advocated in this volume, namely, that the phys- iological properties of the nervous system are inseparable from every segment of that system ; and the functions are the manifestation of those properties as determined by the special organs with the co-operation of all. <^A ''/sfflAiNnav^i ^OFCAUFOR^ ^OfCAllFOI?4^ ^5MEDNIVER% |^^4S^i ^KiC^Vp; ^^.^-^^ ^aan-i^ '%3Dnvso# ^lUBRARYQ^ -5 «^5J\EUNIVER%. ^lOSANCEl^^ ^^EUNIVE!% %a3AINft-3ir ^lOSANCfUr^ %JflMNn-3V{^^ -o\lUBRARYa- ^'^ONVSOl^ ^■UBRARYOc A^UBRARYd?/ UC SOUTHERN REGIONAL LIBRARY FACILITY AA 001 057 118 "^immi^ '"^o-mrn^ ^o-mrn^ K^mimoA, -j^lUBRARYQr. ^5»EINIVER% ^lOSANCnar^ %jnv3jo^ ^^m'm-i^ <^3nvso# %a3AiNiimv' ^OF-CAllF0ff4^ ^OF-WUFOR^ •^^AHvuani^ "^^AHvaan-^ .«^ %U3NVS(n^ '%a3AiNn-3V^^ ^^F'UNIVER% ^U)SANCEl% L^