PUBLISHED MONTHLY SUBSCRIPTION PRICE $1.75 PER YEAR No. 53 PRICE 15 CENTS MAR., 1884 THE HUMBOLDT LIBRARY6CIENCE ANIMAL AUTOMATISM AND OTHER ESSAYS BY THOMAS H. HUXLEY NEW YORK THE HUMBOLDT PUBLISHING COMPANY' 64 FIFTH -AVENUE __ ■NTKRE» AT THE NEW YORK POST OFFICE AS SECONB CI.AS 6 MATTER ANIMAL AUTOMATISM. AND OTHER ESSAYS, Viz,: Science and Culture; Elementary Instruction in Physiology; The Border Territory between Animals and Plants; Universities, Actual and Ideal. THOMAS HENRY HUXLEY, LED., F.R.S. I. the expressed or implied fundamental proposition of the whole doctrine of sci- entific Physiology. If we ask to whom mankind are indebted for this great service, the general voice will name William Harvey. For, by his discovery of the circulation of the blood in the higher animals, by his explanation of the nature of the mechanism by which that circulation is effected, and by his no less remarkable, though less known, in- vestigations of the process of development, Harvey solidly laid the foundations of all those physical explanations of the functions of sustentation and reproduction which modern physiologists have achieved. But the living body is not only sustained and reproduced : it adjusts itself to exter- nal and internal changes; it moves and feels. The attempt to reduce the endless complexities of animal motion and feeling to law and order is, at least, as important a part of the task of the physiologist as the elucidation of what are sometimes called the vegetative processes. Harvey did not make this attempt himself; but the influence of his work upon the man who did make it is patent and unquestionable. This man was Rene Descartes, who, though by many years Harvey’s junior, died before him; and yet, in his short ON THE HYPOTHESIS THAT ANIMALS ARE AUTOMATA, AND ITS HISTORY.* The first half of the seventeenth century is one of the great epochs of biological science. For though suggestions and in- dications of the conceptions which took definite shape, at that time, are to be met with in works of earlier date, they are lit- tle more than the shadows winch coming truth casts forward; men’s knowledge was neither extensive enough, nor ex- act enough, to show them the solid body of fact which threw these shadows. But, in the seventeenth century, the idea that the physical processes of life are capable of being explained in the same way as other physical phenomena, and, therefore, that the living body is a mech- anism, was proved to be true for certain classes of vital actions ; and, having thus taken firm root in irrefragable fact, this conception has not only successfully re- pelled every assault which has been made upon it, but has steadily grown in force and extent of application, until it is now * An Address delivered at the meeting of the British Association for the Advancement of Science at Belfast, 1874. ANIMAL AUTOMATISM, span of fifty-four years, took an undisput- ed place, not only among the chiefs of philosophy, but amongst the greatest and most original of mathematicians; while, in my belief, he is no less certainly entitled to the rank of a great and original physi- ologist ; inasmuch as he did for the physi- ology of motion and sensation that which Harvey had done for the circulation of the blood, and opened up that road to the mechanical theory of these processes, which has been followed by all his suc- cessors. with their weapons of war,” but who, while they yet lived, won splendid victo- ries over ignorance. It is well, again, to reflect that the fame of Descartes filled all Europe, and his authority overshadowed it for a century; while now, most of those who know his name think of him, either as* a person who had some prepos- terous notions about vortices and was de- servedly annihilated by the great Sir Isaac Newton ; or as the apostle of an essen- tially vicious method of deductive specula- tion ; and that, nevertheless, neither the chatter of shifting opinion, nor the silence of personal oblivion, has in the slightest degree affected the growth of the great ideas of which he was the instrument and the mouthpiece. Descartes was no mere speculator, as some would have us believe: but a man who knew of his own knowledge what was to be known of the facts of anatomy and physiology in his day. He was an unwearied dissector and observer; and it is said, that, on a visitor once asking to see his library, Descartes led him into a room set aside for dissections, and full of specimens under examination. “ There,” said he, “ is my library.” I anticipate a smile of incredulity when I thus champion Descartes’s claim to be considered a physiologist of the first rank. I expect to be told that I have read into his works what I find there, and to be asked, Why is it that we are left to dis- cover Descartes’s deserts at this time of day, more than two centuries after his death ? How is it that Descartes is utterly ignored in some of the latest works which treat expressly of the subject in which he is said to have been so great ? It is much easier to ask such questions than to answer them, especially if one desires to be on good terms with one’s contemporaries; but, if I must give an answer, it is this: The growth of physi- cal science is now so prodigiously rapid, that those who are actively engaged in keeping up with the present, have much ado to find time to look at the past, and even grow into the habit of neglecting it. But, natural as this result may be, it is none the less detrimental. The intellect loses, for there is assuredly no more effec- tual method of clearing up one’s own mind on any subject than by talking it over, so to speak, with men of real power and grasp, who have considered it from a totally different point of view. The par- allax of time helps us to the true position of a conception, as the parallax of space helps us to that of a star. And the moral nature loses no less. It is well to turn aside from the fretful stir of the present and to dwell with gratitude and respect upon the services of those “ mighty men of old who have gone down to the grave It is a matter of fact that the greatest physiologist of the eighteenth century, Haller, in treating of the functions of nerve, does little more than reproduce and enlarge upon the ideas of Descartes. It is a matter of fact that David Hartley, in his remarkable work the “ Essay on Man,” expressly, though still insufficiently, ac- knowledges the resemblance of his funda- mental conceptions to those of Descartes ; and I shall now endeavor to show that a series of propositions, which constitute the foundation and essence of the modern physiology of the nervous system, are fully expressed and illustrated in the works of Descartes. I. The brain is the organ of sensation, thought, and emotion; that is to say, some change in the condition of the matter of this organ is the in- variable antecedent of the state of consciousness to which each of these terms is applied. In the “ Principes de !a Philosophic ” (§ 169), Descartes says :—* “ Although the soul is united to the whole body, its principal functions are, neverthe- less, performed in the brain; it is here that it not only understands and imagines, but also feels; and this is effected by the intermedia- tion of the nerves, which extend in the form of delicate threads from the brain to all parts of the body, to which they are attached in such a manner, that we can hardly touch any part of the body without setting the extrem- ity of some nerve in motion. This motion passes along the nerve to that part of the brain which is the common sensorium, as I have sufficiently explained in my Treatise on Dioptrics: and the movements which thus * I quote, here and always, Cousin’s edition of the works of Descartes, as most convenient for ref- erence. It is entitled “ CEuvres completes de Des- cartes,” publiees par Victor Cousin. 1824. AND OTHER ESSAYS. travel along the nerves, as far as that part of the brain with which the soul is closely joined and united, cause it, by reason of their diverse characters, to have different thoughts. And it is these different thoughts of the soul, which arise immediately from the movements that are excited by the nerves in the brain, which we properly term our feelings, or the perceptions of our senses.” quent of a change in the brain excited by the sensory nerves; and, on the well- known effects of injuries, of stimulants, and of narcotics, it bases the conclusion that thought and emotion are, in like man- ner, the consequents of physical antece- dents. 11. The movements of animals are due to the change of form of muscles, which shorten and become thicker; and this change of form in a mus- cle arises from a motion of the sub- stance contained within the 7iervcs which go to the muscle. Elsewhere,* Descartes, in arguing that the seat of the passions is not (as many suppose) the heart, but the brain, uses the following remarkable language;— “ The opinion of those who think that the soul receives its passions in the heart, is of no weight, for it is based upon the fact that the passions cause a change to be felt in that organ; and it is easy to see that this change is felt, as if it were in the heart, only by the intermediation of a little nerve which de- scends from the brain to it; just as pain is felt, as if it were in the foot, by the interme- diation of the nerves of the foot; and the stars are perceived, as if they were in the heavens, by the intermediation of their light and of the optic nerves. So that it is no more necessary for the soul to exert its functions immediately in the heart, to feel its passions there, than it is necessary that it should be in the heavens to see the stars there.” In the “ Passions de I’Ame,” Art. vu., Descartes writes ; “ Moreover, we know that all the move- ments of the limbs depend on the muscles, and that these muscles are opposed to one another in such a manner, that when one of them shortens, it draws along the part of the body to which it is attached, and so gives rise to a simultaneous elongation of the muscle which is opposed to it. Then, if it happens, afterward, that the latter shortens, it causes the former to elongate, and draws toward itself the part to which it is attached. Lastly, we know that all these movements of the muscles, as all the senses, depend on the nerves, which are like little threads or tubes, which all come from the brain, and, like it, contain a certain very subtle air or wind, termed the animal spirits.” This definite allocation of all the phe- nomena of consciousness to the brain as their organ, was a step the value of which it is difficult for us to appraise, so com- pletely has Descartes’s view incorporated itself with every-day thought and common language. A lunatic is said to be “ crack- brained ” or “ touched in the head,” a con- fused thinker is “ muddle-headed,” while a clever man is said to have “ plenty of brains ; ” but it must be remembered that at the end of the last century a consider- able, though much over-estimated, anat- omist, Bichat, so far from having reached the level of Descartes, could gravely argue that the apparatuses of organic life are the sole seat of the passions, which in no way affect the brain, except so far as it is the agent by which the influence of the passions is transmitted to the muscles.f Modern physiology, aided by pathology, easily demonstrates that the brain is the seat of all forms of consciousness, and fully bears out Descartes’s explanation of the reference of those sensations in the vis- cera which accompany intense emotion, to these organs. It proves, directly, that those states of consciousness which we call sensations are the immediate conse- The property of muscle mentioned by Descartes now goes by the general name of contractility, but his definition of it re- mains untouched. The long-continued controversy whether contractile substance, speaking generally, has an inherent power of contraction, or whether it contracts only in virtue of an influence exerted by nerve, is now settled in Haller’s favor, but Des- cartes’s statement of the dependence of muscular contraction on nerve holds good for the higher forms of muscle, under normal circumstances ; so that, although the structure of the various modifications of contractile matter has been worked out with astonishing minuteness—although the delicate physical and chemical changt s which accompany muscular contraction have been determined to an extent o which Descartes could not have dreamed and have quite upset his hypothesis thai the cause of the shortening and thickening of the muscle is the flow of animal spirits into it from the nerves—the important and fundamental part of his statement remains perfectly true. The like may be affirmed of what he says about nerve. We know now that * “ Les Passions de I’Ame,” Article xxxiii. t “ Recherches physiologiques sur la Vie et la Mort.” Par Xav. Bichat. Art. Sixieme. ANIMAL AUTOMatTISM, nerves are not exactly tubes, and that “ an- imal spirits ” are myths ; but the exquis- itely refined methods of investigation of Dubois-Reymond and of Helmholz have no less clearly proved that the antecedent of ordinary muscular contraction is a mo- tion of the molecules of the nerve going to the muscle ; and that this motion is propagated with a measurable, and by no means great, velocity, through the sub- stance of the nerve toward the muscle. With the progress of research, the term “ animal spirits ” gave way to “ nervous fluid,” and “ nervous fluid ” has now given way to “ molecular motion of nerve-sub- stance.” Our conceptions of what takes place in nerve have altered in the same way as our conceptions of what takes place in a conducting wire have altered, since electricity was shown to be not a fluid, but a mode of molecular motion. The change is of vast importance, but it does not affect Descartes’s fundamental idea, that a change in the substance of a motor nerve propagated toward a muscle is the ordinary cause of muscular contrac- tion. these images except this; seeing that the mind is readily excited by a picture to con- ceive the object which is depicted, they have thought that it must be excited in the same way to conceive those objects which affect our senses by little pictures of them formed in the head; instead of which we ought to recollect that there are many things besides images which may excite the mind, as, for ex- ample, signs and words, which have not the least resemblance to the objects which they signify.” * Modern physiology amends Descartes’s conception of the mode of action of sen- sory nerves in detail, by showing that their structure is the same as that of mo- tor nerves; and that the changes which take place in them, when the sensory or- gans with which they are connected are excited, are of just the same nature as those which occur in motor nerves, when the muscles to which they are distributed are made to contract; there is a molecu- lar change which, in the case of the sen- sory nerve, is propagated toward the brain. But the great fact insisted upon by Descartes, that no likeness of external things is, or can be, transmitted to the mind by the sensory organs; but that, between the external cause of a sensation and the sensation, there is interposed a mode of motion of nervous matter, of which the state of consciousness is no likeness, but a mere symbol, is of the profoundest importance. It is the physi- ological foundation of the doctrine of the relativity of knowledge, and a more or less complete idealism is a necessary con- sequence of it. For of two alternatives one must be 111. The sensations of animals are due to a motion of the substance of the nerves which connect the sensory or- gans with the brain. In La Dioptrique (Discours Quatrieme), Descartes explains, more fully than in the passage cited above, his hypothesis of the mode of action of sensory nerves : “ It is the little threads of which the inner substance of the nerves is composed which subserve sensation. You must conceive that these little threads, being inclosed in tubes, which are always distended and kept open by the animal spirits which they contain, neither press upon nor interfere with one an- other, and are extended from the brain to the extremities of all the members which are sen- sitive—in such a manner that the slightest touch which excites the part of one of the members to which a thread is attached, gives rise to a motion of the part of the brain whence it arises, just as by pulling one of the ends of a stretched cord, the other end is instantane- ously moved. . . . And we must take care not to imagine that, in order to feel, the soul needs to behold certain images sent by the objects of sense to the brain, as our philoso- phers commonly suppose; or, at least, we must conceive these images to be something quite different from what they suppose them to be. For as all they suppose is that these images ought to resemble the objects which they represent, it is impossible for them to show how they can be formed by the objects received by the organs of the external senses and transmitted to the brain. And they have had no reason for supposing the existence of true. Either consciousness is the func- tion of a something distinct from the brain, which we call the soul, and a sen- sation is the mode in which this soul is affected by the motion of a part of the brain; or there is no soul, and a sensa- tion is something generated by the mode of motion of a part of the brain. In the former case, the phenomena of the senses are purely spiritual affections; in the latter, they are something manufact- ured by the mechanism of the body, and as unlike the causes which set that mech- anism in motion, as the sound of a re- peater is unlike the pushing of the spring which gives rise to it. * Locke (“Human Understanding,” Book 11., chap, viii. 37) uses Descartes’s illustration for the same purpose and warns us that “ most of the ideas of sensation are no more the likeness of something ex- isting without us than the names that stand for them are the likeness of our ideas, which yet, upon hear- ing, they are apt to excite in us,” a declaration which paved the way for Berkeley. AND OTHER ESSAYS. The nervous system stands between consciousness and the assumed external world, as an interpreter who can talk with his fingers stands between a hidden speaker and a man who is stone deaf— and Realism is equivalent to a belief on the part of the deaf man, that the speak- er must also be talking with his fingers. “ Les extremes se touchent; ” the shib- boleth of materialists that “ thought is a secretion of the brain,” is the Fichtean doctrine that “ the phenomenal universe is the creation of the Ego,” expressed in other language. intervention of the soul, may take their course toward certain muscles, rather than toward others, and thus move the limbs, as I shall prove by an example. If some one moves his hand rapidly toward our eyes, as if he were going to strike us, although we know that he is a friend, that he does it only in jest, and that he will be very careful to do us no harm, nevertheless it will be hard to keep from winking. And this shows, that it is not by the agency of the soul that the eyes shut, since this action is contrary to that volition which is the only, or at least the chief, func- tion of the soul; but it is because the mech- anism of our body is so disposed, that the motion of the hand toward our eyes excites another movement in our brain, and this sends the animal spirits into those muscles which cause the eyelids to close.” IV, The motion of the matter of a sen- sory nerve may be transmitted through the brain to motor nerves, and thereby give rise to contraction of the muscles to which these motor nerves are distributed; and this re- flection of motion from a sensory in- to a motor nerve may take place without volition, or even contrary to it. Since Descartes’s time, experiment has eminently enlarged our knowledge of the details of reflex action. The discovery of Bell has enabled us to follow the tracks of the sensory and motor impulses, along distinct bundles of nerve fibers; and the spinal cord, apart from the brain, has been proved to be a great center of reflex action; but the fundamental conception remains as Descartes left it, and it is one of the pillars of nerve physiology at the present day. In stating these important truths, Des- cartes defined that which we now term “ reflex action.” Indeed he almost uses the term itself, as he talks of the “animal spirits ” as “ reflechis,” * from the senso- ry into the motor nerves. And that this use of the word “ reflected ” was no mere accident, but that the importance and ap- propriateness of the idea it suggests was fully understood by Descartes's contem- poraries, is apparent from a passage in Willis’s well-known essay, “ De Anima Brutorum,” published in 1672, in which, in giving an account of Descartes’s views, he speaks of the animal spirits being di- verted into motor channels, “ velut undu- latione reflexa.”f V. The motion of any given portion of the matter of the brain excited by the motioji of a sensory nerve, leaves behind a readiness to be moved in the same way, in that part. Any- thing whidh resuscitates the motion gives rise to the appropriate feeling. This is the physical mechanism of memory. Descartes imagined that the pineal body (a curious appendage to the upper side of the brain, the function of which, if it have any, is wholly unknown) was the instru- ment through which the soul received impressions from, and communicated them to, the brain. And he thus endeav- ors to explain what 'happens when one tries to recollect something:— Nothing can be clearer in statement, or in illustration, than the view of reflex ac- tion which Descartes gives in the “ Pas- sions de I’Ame,” Art. xiii. After recapitulating the manner in which sensory impressions transmitted by the sensory nerves to the brain give rise to sensation, he proceeds : “ And in addition to the different feelings excited in the soul by these different motions of the brain, the animal spirits, without the “ Thus when the soul wills to remember anything, this volition, causing the [pineal] gland to incline itself in different directions, drives the [animal] spirits toward different regions of the brain, until they reach that part in which are the traces, which the object which it desires to remember has left. These traces are produced thus: those pores of the brain through which the [animal] spirits have previously been driven, by reason of the pres- ence of the object, have thereby acquired a tendency to be opened by the animal spirits which return toward them, more easily than other pores, so that the animal spirits, im- * “ Passions de I’Ame,” Art. xxxvi. + “ Quamcumque bruti actionem, velut automati mechanici motuin artificialem, in eo consistere quod se primo sensibile aliquod spiritus animales affi- •ciens, eosque introrsum convertens, sensionem ex- chat, a qua mox iidem spiritus, velut undulatione reflexa denuo retrorsum commoti atque pro concin- no ipsius fabric* oreanorum, et partium ordine, in ■certos nervos nmsculosque determinati, respectivos membrorum w^wjperficiunt,”—Willis : “ De An- im2 Brutorum,” p. 5, ed. 1763. 6 ANIMAL AUTOMATISM, pinging on these pores, enter them more readily than others. By this means they ex- cite a particular movement in the pineal gland, which represents the object to the soul, and causes it to know what it is which it desired to recollect.” * the same molecular change may be re- generated by other agencies than the cause which first produced it. Thus far, the propositions respecting the physiology of the nervous system which are stated by Descartes have simply been more clearly defined, more fully illustrated, and, for the most part, demonstrated, by- modern physiological research. But there remains a doctrine to which Descartes at- tached great weight, so that full accep- tance of it became a sort of note of a thorough-going Cartesian, but which, nevertheless, is so opposed to ordinary prepossessions that it attained more gen- eral notoriety, and gave rise to more dis- cussion, than almost any other Cartesian hypothesis. It is the doctrine, that brute animals are mere machines or automata, devoid not only of reason, but of any kind of consciousness, which is stated briefly in the “ Discours de la Methode,” and more fully in the “ Reponses aux Quatriemes Objections,” and in the cor- respondence with Henry More.* The process of reasoning by which Des- cartes arrived at this startling conclusion is well shown in the following passage of the “ Reponses : ” That memory is dependent upon some condition of the brain is a fact established by many considerations—among the most important of which are the remarkable phenomena of aphasia. And that the condition of the brain on which memory depends, is largely determined by the re- peated occurrence of that condition of its molecules, which gives rise to the idea of the thing remembered, is no less certain. Every boy who learns his lesson by re- peating it exemplifies the fact. Descartes, as we have seen, supposes that the pores of a given part of the brain are stretched by the animal spirits, on the occurrence of a sensation, and that the part of the brain thus stretched, being imperfectly elastic, does not return to exactly its pre- vious condition, but remains more disten- sible than it was before. Hartley sup- pose that the vibrations, excited by a sen- sory, or other, impression, do not die away, but are represented by smaller vibrations or “ vibratiuncules,” the permanency and intensity of which are in relation with the frequency of repetition of the primary vi- brations. Haller has substantially the same idea, but contents himself with the general term “ mutationes,” to express the cerebral change which is the cause of a state of consciousness. These “ muta- tiones ” persist for a long time after the cause which gives rise to them has ceased to operate, and are arranged in the brain according to the order of co-existence and succession of their causes. And he gives these persistent “ mutationes ” the picturesque name of vestigia rerum, “ quae non in mente sed in ipso corpore et in medulla quidem cerebri ineffabili modo incredibiliter minutis notis et copia infinita, inscriptas sunt.” f Ido not know that any modern theory of the physical conditions of memory differs essentially from these, which are all children—mu- tatis mutandis—of the Cartesian doctrine. Physiology is, at present, incompetent to say anything positively about the matter, or to go farther than the expression of the high probability, that every molecular change which gives rise to a state of con- sciousness, leaves a more or less persist- ent structural modification, through which “ But as regards the souls of beasts, al- though this is not the place for considering them, and though, without a general exposi- tion of physics, I can say no more on this subject than I have already said in the fifth part of my Treatise on Method ; yet, I will further state, here, that it appears to me to be a very, remarkable circumstance that no movement can take place, either in the bodies of beasts, or even in our own, if these bodies have not in themselves all the organs and in- struments by means of which the very same movements would be accomplished in a ma- chine. So that, even in us, the spirit, or the soul, does not directly move the limbs, but only determines the course of that very sub- tle liquid which is called the animal spirits,, which, running continually from the heart by the brain into the muscles, is the cause of all the movements of our limbs, and often may cause many different motions, one as easily as the other. “And it does not even always exert this determination; for among the movements which take place in us, there are many which do not depend on the mind at all, such as the beating of the heart, the digestion of food, the nutrition, the respiration, of those who sleep; and, even in those who are awake, walking, singing, and other similar actions, when they are performed without the mind *“ de M. Descartes k M. Morus.” 1649. “ CEuvres,’' tome x. p. 204. “ Mats le plus grand de tousles que nous ayons retenus de notre enfance, est celui de croire que les betes pensent ” etc. * “ Les Passions de I’Ame,” xlii. + Haller, “ Primae Lineae, ed. ill. “ Sensus In- tern!,” dlviii. AND OTHER ESSAYS. 7 thinking about them. And, when one who falls from a height throws his hands forwards to save his head, it is in virtue of no ratioci- nation that he performs this action; it does not depend upon his mind, but takes place merely because his senses being affected by the present danger, some change arises in his brain which determines the animal spirits to pass thence into the nerves, in such a man- ner as is required to produce this motion, in the same way as in a machine, and without the mind being able to hinder it. Now since we observe this in ourselves, why should we be so much astonished if the light reflected from the body of a wolf into the eye of a sheep has the same force to excite in it the motion of flight. “ After having observed this, if we wish to learn by reasoning, whether certain move- ments of beasts are comparable to those which are effected in us by the operation of the mind, or, on the contrary, to those which depend only on the animal spirits and the disposition of the organs, it is necessary to consider the difference between the two, which I have explained in the fifth part of the Dis- course on Method (for I do not think that any others are discoverable), and then it will easily be seen, that all the actions of beasts are similar only to those which we perform without the help of our minds. For which reason we shall be forced to conclude, that we know of the existence in them of no other principle of motion than the disposition of their organs and the continual affluence of animal spirits produced by the heat of the heart, which attenuates and subtilizes the blood; and, at the same time, we shall ac- knowledge that we have had no reason for assuming any other principle, except that, not having distinguished these two principles of motion, and seeing that the one, which depends only on the animal spirits and the organs, exists in beasts as well as in us, we have hastily concluded that the other, which depends on mind and on thought, was also possessed by them.” The Port Royalists adopted the hy- pothesis that brutes are machines, and are said to have carried its practical applica- tions so far, as to treat domestic animals with neglect, if not with actual cruelty. As late as the middle of the eighteenth century, the problem was discussed very fully and ably by Bouillier, in his “ Essai philosophique sur I’Ame des Bates,” while Condillac deals with it in his “Traite des Animaux;” but since then it has received little attention. Neverthe- less, modern research has brought to light a great multitude of facts, which not only show that Descartes’s view is defen- sible, but render it far more defensible than it was in his day. It must be premised, that it is wholly impossible absolutely to prove the pres- ence or absence of consciousness in any- thing but one’s own brain, though, by analogy, we are justified in assuming its existence in other men. Now if, by some accident, a man’s spinal cord is divided, his limbs are paralyzed, so far as his voli- tion is concerned, below the point of in- jury ; and he is incapable of experiencing all those states of consciousness, which, in his uninjured state, would be excited by irritation of those nerves which come off below the injury. If the spinal cord is divided in the middle of the back, for example, the skin of the feet may be cut, or pinched, or burned, or wetted with vitriol, without any sensation of touch, or of pain, arising in consciousness. So far as the man is' concerned, therefore, the part of the central nervous system which lies beyond the injury is cut off from consciousness. It must indeed be ad- mitted, that, if any one think fit to main- tain that the spinal cord below the injury is conscious, but that it is cut off from any means of making its consciousness known to the other consciousness in the brain, there is no means of driving him from his position by logic. But assuredly there is no way of proving it, and in the matter of consciousness, if in anything, we may hold by the rule, “ De non ap- parentibus et de non existentibus eadem est ratio.” However near the brain the Descartes’s line of argument is perfectly clear. Fie starts from reflex action in man, from the unquestionable fact that, in ourselves, co-ordinate, purposive, ac- tions may take place, without the inter- vention of consciousness or volition, or even contrary to the latter. As actions of a certain degree of complexity are brought about by mere mechanism, why may not actions of still greater complexity be the result of a more refined mechanism ? What proof is there that brutes are other than a superior race of marionettes, which eat without pleasure, cry without pain, desire nothing, know nothing, and only simulate intelligence as a bee simulates a mathematician ? * chiens, les chats, et les autres animaux, il n’y any intelligence, ny ame spirituelle comme on I’entend ordinairement. Ils mangent sans plaisir ; ils crient sans douleur ; ils croissent sans le Sfavoir; ils ne desirent rien ; ils ne connoissent rien; et s’ils agis- sent avec adresse et d’une manifere qui marque rin- telligence, c’est que Dieu les faisant pour les con- server, il a leurs corps de telle manure, qu’ils evitent organiquement, sans le tout ce qui peut les detruire et qu’ils semblent craindre.” (“ Feuilletde Conches. Meditations Metaphysiques et Correspondance de N. Malebranche. Neuvieme Meditation.” 1841.) * Malebranche states the view taken by orthodox Cartesians in 1689 very forcibly; “ Ainsi dans les ANIMAL AUTOMATISM, 8 spinal cord is injured, consciousness re- mains intact, except that the irritation of parts below the injury is no longer repre- sented by sepsation. On the other hand, pressure upon the anterior division of the brain, or extensive injuries to it, abolish consciousness. Hence, it is a highly probable conclusion, that consciousness in man depends upon the integrity of the anterior division of the brain, while the middle and hinder divisions of the brain, and the rest of the nervous centers, have nothing to do with it. And it is further highly probable, that what is true for man is true for other vertebrated animals. muscular contractions, co-ordinated to- ward a definite end, and serving an ob- vious purpose. If the spinal cord of a frog is cut across, so as to provide us with a segment separated from the brain, we shall have a subject parallel to the injured man, on which experiments can be made without remorse ; as we have a right to conclude that a frog's spinal cord is not likely to be conscious when a man’s is not. Now the frog behaves just as the man did. The legs are utterly paralyzed, so far as voluntary movement is concerned ; but they are vigorously drawn up to the body when any irritant is applied to the foot. But let us study our frog a little farther. Touch the skin of the side of the body with a little acetic acid, which gives rise to all the signs of great pain in an uninjured frog. In this case, there can be no pain, because the application is made to a part of the skin supplied with nerves which come off from the cord below the point of section ; nevertheless, the frog lifts up the limb of the same side, and applies the foot to rub off the acetic acid ; and, what is still more remarkable, if the limb be held so that the frog can- not use it, it will, by and by, move the limb of the other side, turn it across the body, and use it for the same rubbing process. It is impossible that the frog, if it were in its entirety and could reason, should perform actions more purposive than these ; and yet we have most com- plete assurance that, in this case, the frog is not acting from purpose, has no con- sciousness, and is a mere insensible ma- chine. We may assume, then, that in a living vertebrated animal, any segment of the cerebro-spinal axis (or spinal cord and brain) separated from that anterior divi- sion of the brain which is the organ of consciousness, is as completely incapable of giving rise to consciousness, as we know it to be incapable of carrying out volitions. Nevertheless, this separated segment of the spinal cord is not passive and inert. On the contrary, it is the seat of extremely remarkable powers. In our imaginary case of injury, the man would, as we have seen, be devoid of sensation in his legs, and would have not the least power of moving them. But, if the soles of his feet were tickled, the legs would be drawn up, just as vigorously as they would have been before the injury. We know exactly what happens when the soles of the feet are tickled ; a molecular change takes place in the sensory nerves of the skin, and is propagated along them and through the posterior roots of the spinal nerves, which are constituted by them, to the gray matter of the spinal cord. Through that gray matter, the molecular motion is reflected into the anterior roots of the same nerves, con- stituted by the filaments which supply the muscles of the legs, and, traveling along these motor filaments, reaches the muscles, which at once contract, and cause the limbs to be drawn up. But now suppose that, instead of mak- ing a section of the cord in the middle of the body, it had been made in such a manner as to separate the hindermost di- vision of the brain from the rest of the or- gan, and suppose the foremost two-thirds of the brain entirely taken away. The frog is then absolutely devoid of any spon- taneity ; it sits upright in the attitude which a frog habitually assumes; and it will not stir unless it is touched; but it. differs from the frog which I have just described in this, that, if it be thrown into the water, it begins to swim, and swims just as well as the perfect frog does. But swimming requires the combination and successive co-ordination of a great number of muscular actions. And we are forced to conclude, that the impres- sion made upon the sensory nerves of the skin of the frog by the contact with the water into which it is thrown, causes the In order to move the legs in this way. a definite co-ordination of muscular con- tractions is necessary ; the muscles must contract in a certain order and with duly proportioned force ; and moreover, as the feet are drawn away from the source of irritation, it may be said that the action has a final cause, or is purposive. Thus it follows, that the gray matter of the segment of the man’s spinal cord, though it is devoid of consciousness, nevertheless responds to a simple stimu- lus by giving rise to a complex set of AND OTHER ESSAYS. transmission to the central nervous ap- paratus of an impulse, which sets going a. certain machinery by which all the muscles of swimming are brought into play in due co-ordination. If the frog be stimulated by some irritating body, it jumps or walks as well as the complete frog can do. The simple sensory im- pression, acting through the machinery of the cord, gives rise to these complex combined movements. It is obvious, that had Descartes been acquainted with these remarkable results of modern research, they would have furnished him with far more powerful arguments than he possessed in favor of his view of the automatism of brutes. The habits of a frog, leading its natural life, involve such simple adaptations to surrounding conditions, that the ma- chinery which is competent to do so much without the intervention of con- sciousness, might well do all. And this argument is vastly strengthened by what has been learned in recent times of the marvelously complex operations which are performed mechanically, and to all appearance without consciousness, by men, when, in consequence of injury or disease, they are reduced to a condition more or less comparable to that of a frog, in which the anterior part of the brain has been removed. A case has recently been published by an eminent French physician, Dr. Mesnet, which illustrates this condition so remarkably, that I make no apology for dwelling upon it at con- siderable length.* A sergeant of the French army, F , twenty-seven years of age, was wounded during the battle of Bazeilles, by a ball which fractured his left parietal bone. He ran his bayonet through the Prussian soldier who wounded him, but almost immediately his right arm became paral- yzed ; after walking about two hundred yards, his right leg became similarly af- fected, and he lost his senses. When he recovered them, three weeks afterward, in hospital at Mayence, the right half of the body was completely paralyzed, and remained in that condition for a year. At present, the only trace of the paralysis which remains is a slight weakness of the right half of the body. Three or four months after the wound was in- flicted, periodical disturbances of the functions of the brain made their ap- pearance, and have continued ever since. The disturbances last from fifteen to thirty hours ; the intervals at which they occur being from fifteen to thirty days. For four years, therefore, the life of this man has been divided into alternating phases—short abnormal states interven- ing between long normal states. It is possible to go a step farther. Sup- pose that only the anterior division of the brain—so much of it as lies in front of the “ optic lobes ”—is removed. If that operation is performed quickly and skill- fully, the frog may be kept in a state of full bodily vigor for months, or it may be for years ; but it will sit unmoved. It sees nothing; it hears nothing. It will starve sooner than feed itself, although food put into its mouth is swallowed. On irritation, it jumps or walks ; if thrown into the water it swims. If it be put on the hand, it sits there, crouched, per- fectly quiet, and would sit there forever. If the hand be inclined very gently and slowly, so that the frog would naturally tend to slip off, the creature’s fore paws are shifted on to the edge of the hand, until he can just prevent himself from falling. If the turning of the hand be slowly con- tinued, he mounts up with great care and deliberation, putting first one leg forward and then another, until he balances him- self with perfect precision upon the edge; and, if the turning of the hand is con- tinued, over he goes through the needful set of muscular operations, until he comes to be seated in security, upon the back of the hand. The doing of all this requires a delicacy of co-ordination, and a precis- ion of adjustment of the muscular ap- paratus of the body, which are only com- parable to those of a rope-dancer. To the ordinary influences of light, the frog, deprived of its central hemispheres, ap- pears to be blind. Nevertheless, if the animal be put upon a table, with a book at some little distance between it and the light, and the skin of the hinder part of its body is then irritated, it will jump for- ward, avoiding the book by passing to the right or left of it. Although the frog, therefore, appears to have no sensa- tion of light, visible objects act through its brain upon the motor mechanism of its body.* * u De I’Automatisme de la Mcmoire et du Sou- venir, dans le Somnambulisme pathologique.” Par le Dr. E. Mesnet, Mddecin de I’HQpital Saint-An- toine. V Union Medicate, Juillet 21 et 23, 1874. My attention was first called to a summary ot this remarkable case, which appeared in the Journal des Debats for the 7th of August, 1874, by my friend General Strachey. F.R.S. * See the remarkable essay of Goltz, “ Be it rage zur Lehre von den Functionen der Nervencentren des Frosches,” published in 1869. I have repeated Goltz’s experiments, and obtained the same results. 10 ANIMAL AUTOMATISM, In the periods of normal life, the ex- sergeant’s health is perfect; he is intelli- gent and kindly, and performs, satisfacto- rily, the duties of a hospital attendant. The commencement of the abnormal state is ushered in by uneasiness and a sense of weight about the forehead, which the patient compares to the constriction of a circle of iron ; and, after its termina- tion, he complains, for some hours, of dullness and heaviness of the head. But the transition from the normal to the ab- normal state takes place in a few minutes, without convulsions or cries, and without anything to indicate the change to a by- stander. His movements remain free and his expression calm, except for a con- traction of the brow, an incessant move- ment of the eyeballs, and a chewing mo- tion of the jaws. The eyes are wide open, and their pupils dilated. If the man happens to be in a place to which he is accustomed, he walks about as usual; but if he is in a new place, or if obstacles are intentionally placed in his way, he stumbles gently against them, stops, and then, feeling over the objects with his hands, passes on one side of them. He offers no resistance to any change of direction which may be impressed upon him, or to the forcible acceleration or re- tardation of his movements. He eats, drinks, smokes, walks about, dresses and undresses himself, rises and goes to bed at the accustomed hours. Nevertheless, pins may be run into his body, or strong electric shocks sent through it, without causing the least indication of pain; no odorous substance, pleasant or unpleasant, makes the least impression; he eats and drinks with avidity whatever is offered, and takes asafoetida, or vinegar, or quinine, as readily as water; no noise affects him ; and light influences him only under cer- tain conditions. Dr. Mesnet remarks, that the sense of touch alone seems to persist, and indeed to be more acute and delicate than in the normal state; and it is by means of the nerves of touch, almost exclusively, that his organism is brought into relation with the external world. Here a difficulty arises. It is clear, from the facts detailed, that the nervous appa- ratus by which, in the normal state, sen- sations of touch are excited, is that by which external influences determine the movements of the body, in the abnormal state. But does the state of conscious- ness, which we term a tactile sensation, accompany the operation of this nervous apparatus in the abnormal state ? or is consciousness utterly absent, the man being reduced to an insensible median ism ? It is impossible to obtain direct evi- dence in favor of the one conclusion or the other; all that can be said is, that the case of the frog shows that man may be devoid of any kind of consciousness. A further difficult problem is this. The man is insensible to sensory impressions made through the ear, the nose, the tongue, and, to a great extent, the eye; nor is he susceptible of pain from causes operating during his abnormal state. Nevertheless, it is possible so to act upon his tactile apparatus, as to give rise to those molecular changes in his sensorium, which are ordinarily the causes of associ- ated trains of ideas. I give a striking example of this process in Dr. Mesnet’s words:— “ II se promenait dans le jardin, sous un massif d’arbres, on lui remet a la main sa canne qu’il avait laisse tomber quelques minutes avant. II la palpe, promene a plusieurs reprises la main sur la poignee coudee de sa canne—devient attentif—sem- ble preter I’oreille—et, tout-a-coup, appelle ‘ Henri! ’ Puis, ‘ Les voila 1 Ils sont au moins une vingtaine! a nous deux, nous en viendrons k bout! ’ Et alors portant la main derriere son dos comme pour prendre une car- touche, il fait le mouvement de charger son arme, se couche dans I’herbe a plat ventre, la tete cachee par un arbre, dans la position d’un tirailleur, et suit, I’arme epaulee, tous les mouvements de I’ennemi qu’il croit voir it courte distance.” In a subsequent abnormal period, Dr. Mesnet caused the patient to repeat this scene by placing him in the same condi- tions. Now, in this case, the question arises whether the series of actions con- stituting this singular pantomime was ac- companied by the ordinary states of con- sciousness, the appropriate train of ideas, or not ? Did the man dream that he was skirmishing? or was he in the condition of one of Vaucauson’s automata—a sense- less mechanism worked by molecular changes in his nervous system ? The an- alogy of the frog shows that the latter as- sumption is perfectly justifiable. The ex-sergeant has a good voice, and had, at one time, been employed as a singer at a caffi. In one of his abnormal 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 his bed, as if he were trying to find something. Dr. Mesnet, suspecting that he was seeking his music, made up one of these into a roll and put it into his AND OTHER ESSAYS. 11 hand. He appeared satisfied, took up his cane and went down stairs to the door. Here Dr. Mesnet turned him round, and he walked quite contentedly, in the oppo- site direction, toward the room of the concierge. The light of the sun shining through a window now happened to fall upon him, and seemed to suggest the footlights of the stage on which he was accustomed to make his appearance. He stopped, opened his roll of imaginary music, put himself into the attitude of a singer, and sang, with perfect execution, three songs, one after the other. After which he wiped his face with his hand- kerchief and drank, without a grimace, a tumbler of strong vinegar and water which was put into his hand. An experiment which may be perform- ed upon the frog deprived of the fore part of its brain, well known as Goltz’s “ Quak- versuch,” affords a parallel to this per- formance. If the skin of a certain part of the back of such a frog is gently stroked with the finger, it immediately croaks, it never croaks unless it is so stroked, and the croak always follows the stroke, just as the sound of a repeater follows the touching of the spring. In the frog, this ■“ song ” is innate—so to speak a priori— and depends upon a mechanism in the brain governing the vocal apparatus, which is set at work by the molecular change set up in the sensory nerves of the skin of the back by the contact of a for- eign body. In man there is also a vocal mechanism, and the cry of an infant is in the same sense innate and a priori, inasmuch as it depends on an organic relation between its sensory nerves and the nervous mech- anism which governs the vocal apparatus. Learning to speak, and learning to sing, are processes by which the vocal mech- anism is set to new tunes. A song which has been learned has its molecular equiv- alent, which potentially represents it in the brain, just as a musical box wound up potentially represents an overture. Touch the stop and the overture begins ; send a molecular impulse along the proper afferent nerve and the singer begins his song. Ed himself for a medal, on account of his good conduct and courage. It oc- curred to Dr. Mesnet to ascertain experi- mentally how far vision was concerned in this act of writing. He therefore in- terposed a screen between the man’s eyes and his hands ; under these circumstances he went on writing for a short time, but the words became illegible, and he finally stopped, without manifesting any discon- tent. 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 superimposed sheets of paper. After he had written a line or two, this sheet was suddenly drawn away. There was a slight expres- sion 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 signa- ture at the bottom of the page. Never- theless, 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, in that part of the blank page which corresponded with the position of the words which re- quired correction, in the sheets which had been taken away. If the five sheets had been transparent, therefore, they would, when superposed, have formed a properly written and corrected letter. Immediately after he had written his letter, F got up, walked down to the garden, made himself a cigarette, lighted and smoked it. He was about to prepare another, but sought in vain for his tobac- co-pouch, which had been purposely taken away. The pouch was now thrust before his eyes and put under his nose, but he neither saw nor smelt it; but, when it was placed in his hand, he at once seized it, made a fresh cigarette, and ignited a match to light the latter. The match was blown out and another lighted match placed close before his eyes, but he made no attempt to take it; and, if his cigarette was lighted for him, he made no attempt to smoke. All this time the eyes were vacant, and neither winked, nor exhibited any contraction of the pupils. From these and other expe- Again, the manner in which the frog, though apparently insensible to light, is yet, under some circumstances, influenced by visual images, finds a singular parallel in the case of the ex-sergeant. Sitting at a table, in one of his abnor- mal states, he took up a pen, felt for paper and ink, and began to write a let- ter to his general, in which he recommend- 12 ANIMAL AUTOMATISM, riments, Dr. Mesnet draws the conclusion that his patient sees some things and not others ; that the sense of sight is accessi- ble to all things which are brought into relation with him by the sense of touch, and, on the contrary, insensible to things which lie outside this relation. He sees the match he holds, and does not see any other. the external senses; the impression of the ideas of these in the organ of common sen- sation and in the imagination; the retention or the impression of these ideas on the mem- ory ; the internal movements of the appetites and the passions; and lastly, the external movements of all the limbs, which follow so aptly, as well the action of the objects which are presented to the senses, as the impres- sions which meet in the memory, that they imitate as nearly as possible those of a real man; I desire, I say, that you should con- sider that these functions in the machine naturally proceed from the mere arrangement of its organs, neither more nor less than do the movements of a clock, or other automa- ton, from that of its weights and its wheels; so that, so far as these are concerned, it is not necessary to conceive any other vegeta- tive or sensitive soul, nor any other principle of motion or of life, than the blood and the spirits agitated by the fire which burns con- tinually in the heart, and which is no wise essentially different from all the fires which exist in inanimate bodies.” Just so the frog “ sees ” the book which is in the way of his jump, at the same time that isolated visual impressions take no effect upon him* As I have pointed out, it is impossible to prove that F is absolutely uncon- scious in his abnormal state, but it is no less impossible to prove the contrary; and the case of the frog goes a long way to justify the assumption that, in the ab- normal state, the man is a mere insensi- ble machine. If such facts as these had come under the knowledge of Descartes, would they not have formed an apt commentary upon that remarkable passage in the “ Traite de I’Homme,” which I have quoted else- where,! but which is worth repetition ? And would Descartes not have been jus- tified in asking why we need deny that animals are machines, when men, in a state of unconsciousness, perform, me- chanically, actions as complicated and as seemingly rational as those of any ani- mals ? “ All the functions which I have attributed to this machine (the body), as the digestion of food, the pulsation of the heart and of the arteries; the nutrition and the growth of the limbs; respiration, wakefulness, and sleep; the reception of light, sounds, odors, flavors, heat, and such like qualities, in the organs of But though I do not think that Des- cartes’s hypothesis can be positively re- futed, I am not disposed to accept it. The doctrine of continuity is too well es- tablished for it to be permissible to me to suppose that any complex natural phe- nomenon comes into existence suddenly, and without being preceded by simpler modifications; and very strong argu- ments would be needed to prove that such complex phenomena, as those of consciousness, first make their appearance in man. We know, that, in the individ- ual man, consciousness grows from a dim glimmer to its full light, whether we con- sider the infant advancing in years, or the adult emerging from slumber and swoon. We know, further, that the lower animals, possess, though less developed, that part of the brain which we have every reason to believe to be the organ of conscious- ness in man; and as, in other cases, function and organ are proportional, so. we have a right to conclude it is with the brain; and that the brutes, though they may not possess our intensity of con- sciousness, and though, from the absence of language, they can have no trains of thoughts, but only trains of feelings, yet have a consciousness which, more or less distinctly, foreshadows our own. I confess that, in view of the struggle * Those who have had occasion to become ac- quainted with the phenomena of somnambulism and of mesmerism, will be struck with the close parallel which they present to the proceedings of F. in his abnormal state. But the great value of Dr. Mesnet’s observations lies in the fact that the ab- normal condition is traceable to a definite injury to the brain, and that the circumstances are such as to keep us clear of the cloud of voluntary and involun- tary fictions in which the truth is too often smoth- tred in such cases. In the unfortunate subjects of such abnormal conditions of the brain, the disturb- ance of the sensory and intellectual faculties is not unfrequently accompanied by a perturbation of the moral nature, which may manifest itself in a most astonishing love of lying for its own sake. And, in this respect, also, F.’s case is singularly instruc- tive, for though, in his normal state, he is a per- fectly honest man, in his abnormal condition he is an inveterate thief, stealing and hiding away what- ever he can lay hands on, with much dexterity, and with an absurd indifference as to whether the property is his own or not. Hoffman’s terrible conception of the “ Doppeltganger ” is realized by men in this state—who live two lives, in the one of which they maybe guilty of the most criminal acts, while, in the other, they are eminently virtuous and respectable. Neither life knows anything of the other. Dr. Mesnet states that he has watched a man in his abnormal state elaborately prepare to hang himself, and has let him go on until asphyxia set in, when he cut him down. But on passing in- to the normal state the would-be suicide was whol- ly ignorant of what had happened. The problem of responsibility is here as complicated as that of the prince-bishop, who swore as a prince and not as A bishop. “ But, highness, if the prince is damned