The Principles of Psychology, Vols. 1-2

but such mere outward teleology as this might still be the blind result of vis a tergo. The growth and movements of plants, the processes of development, digestion, secretion, etc., in animals, supply innumerable instances of per formances useful to the individual which may nevertheless be, and by most of us are supposed to be, produced by automatic mechanism. The physiologist does not con fidently assert conscious intelligence in the frog's spinal cord until he has shown that the useful result which the nervous machinery brings forth under a given irritation remains the same when the machinery is altered. If, to take the stock instance, the right knee of a headless frog be irri tated with acid, the right foot will wipe it off. "When, how ever, this foot is amputated, the animal will often raise the j / left foot to the spot and wipe the offending material away.

Pfliiger and Lewes reason from such facts in the follow ing way : If the first reaction were the result of mere machin ery, they say ; if that irritated portion of the skin discharged the right leg as a trigger discharges its own barrel of a shot gun ; then amputating the right foot would indeed frustrate the wiping, but would not make the left leg move. It would simply result in the right stump moving through the empty air (which is in fact the phenomenon sometimes observed). The right trigger makes no effort to discharge the left barrel if the right one be unloaded ; nor does an electrical ma chine ever get restless because it can only emit sparks, and not hem pillow-cases like a sewing-machine.

If, on the contrary, the right leg originally moved for the purpose of wiping the acid, then nothing is more natural than that, when the easiest means of effecting that purpose prove fruitless, other means should be tried. Every failure must keep the animal in a state of disappointment which will lead to all sorts of new trials and devices ; and tran quillity will not ensue till one of these, by a happy stroke, achieves the wished-for end. In a similar way Goltz ascribes intelligence to the frog's optic lobes and cerebellum. We alluded above to the manner in which a sound frog imprisoned in water will dis cover an outlet to the atmosphere. Goltz found that frogs deprived of their cerebral hemispheres would often exhibit

a like ingenuity. Such a frog, after rising from the bottom and finding his farther upward progress checked by the glass bell which has been inverted over him, will not per sist in butting his nose against the obstacle until dead of suffocation, but will often re-descend and emerge from under its rim as if, not a definite mechanical propulsion upwards, but rather a conscious desire to reach the air by hook or crook were the main-spring of his activity. Goltz con cluded from this that the hemispheres are not the sole seat of intellect in frogs. He made the same inference from observing that a brainless frog will turn over from his back to his belly when one of his legs is sewed up, although the movements required are then very different from those excited under normal circumstances by the same annoying position. They seem determined, consequently, not merely by the antecedent irritant, but by the final end, — though the irritant of course is what makes the end desired.

Another brilliant German author, Liebmann,* argues against the brain's mechanism accounting for mental action, by very similar considerations. A machine as such, he says, will bring forth right results when it is in good order, and wrong results if out of repair. But both kinds of result flow with equally fatal necessity from their conditions. We cannot suppose the clock-work whose structure fatally determines it to a certain rate of speed, noticing that this speed is too slow or too fast and vainly trying to correct it. Its conscience, if it have any, should be as good as that of the best chronometer, for both alike obey equally well the y same eternal mechanical laws — laws from behind. But if the brain be out of order and the man says " Twice four are two," instead of " Twice four are eight," or else " I must go to the coal to buy the wharf," instead of " I must go to the wharf to buy the coal," instantly there arises a conscious- I ness of error. The wrong performance, though it obey the same mechanical law as the right, is nevertheless con demned,— condemned as contradicting the inner law—the law from in front, the purpose or ideal for which the brain should act, whether it do so or not.

We need not discuss here whether these writers in draw ing their conclusion have done justice to all the premises involved in the cases they treat of. We quote their argu ments only to show how they appeal to the principle that / no actions but such as are done for an end, and shoiv a choice of /y means, can be called indubitable expressions of Mind. I shall then adopt this as the criterion by which to cir cumscribe the subject-matter of this work so far as action \ enters into it. Many nervous performances will therefore be unmentioned, as being purely physiological. Nor will the anatomy of the nervous system and organs of sense be described anew. The reader will find in H. N. Martin's * Human Body,' in G. T. Ladd's ' Physiological Psychol ogy,' and in all the other standard Anatomies and Physi ologies, a mass of information which we must regard as pre liminary and take for granted in the present work.* Of the functions of the cerebral hemispheres, however, since i they directly subserve consciousness, it will be well to j give some little account.

* Nothing is easier than to familiarize one's self with the mammalian brain. Get a sheep's head, a small saw, chisel, scalpel and forceps (all three can best be had from a surgical-instrument maker), and unravel its parts either by the aid of a human dissecting book, such as Holden's 'Manual of Anatomy,' or by the specific directions ad Iwc given in such books as Foster and Langley's 'Practical Physiology' (Macmillan) or Morrell's 'Comparative Anatomy and Dissection of Mammalia' (Longmans).

IF I begin chopping the foot of a tree, its branches are unmoved by my act, and its leaves murmur as peacefully as ever in the wind. If, on the contrary, I do violence to the foot of a fellow-man, the rest of his body instantly responds to the aggression by movements of alarm or defence. The reason of this difference is that the man has a nervous system whilst the tree has none ; and the function of the nervous system is to bring each part into harmonious co-operation with every other. The afferent nerves, when excited by some physical irritant, be this as gross in its mode of oper ation as a chopping axe or as subtle as the waves of light, conveys the excitement to the nervous centres. The com motion set up in the centres does not stop there, but dis charges itself, if at all strong, through the efferent nerves into muscles and glands, exciting movements of the limbs and viscera, or acts of secretion, which vary with the animal, and with the irritant applied. These acts of response have usually the common character of being of service. They ward off the noxious stimulus and support the beneficial one ; whilst if, in itself indifferent, the stimulus be a sign of some distant circumstance of practical importance, the animal's acts are addressed to this circumstance so as to avoid its perils or secure its benefits, as the case may be. To take a common example, if I hear the conductor calling ' All aboard ! ' as I enter the depot, my heart first stops, then palpitates, and my legs respond to the air-waves falling on my tympanum by quickening their movements. If I stumble as I run, the sensation of falling provokes a movement of the hands towards the direction of the fall, the effect of which is to shield the body from too sudden a shock. If a cinder enter my eye, its lids close forcibly and a copious flow of tears tends to wash it out.

These three responses to a sensational stimulus differ, however, in many respects. The closure of the eye and the lachrymation are quite involuntary, and so is the disturbance of the heart. Such involuntary responses we know as ' reflex ' acts. The motion of the arms to break the shock of falling may also be called reflex, since it occurs too quickly to be deliberately intended. Whether it be instinc tive or whether it result from the pedestrian education of childhood may be doubtful ; it is, at any rate, less automatic than the previous acts, for a man might by conscious effort learn to perform it more skilfully, or even to suppress it alto gether. Actions of this kind, into which instinct and volition enter upon equal terms, have been called ' semi-reflex.' The act of running towards the train, on the other hand, has no instinctive element about it. It is purely the result of edu cation, and is preceded by a consciousness of the purpose to be attained and a distinct mandate of the will. It is a ' vol untary act.' Thus the animal's reflex and voluntary per formances shade into each other gradually, being connected by acts which may often occur automatically, but may also be modified by conscious intelligence.

An outside observer, unable to perceive the accompany ing consciousness, might be wholly at a loss to discriminate between the automatic acts and those which volition es corted. But if the criterion of mind's existence be the choice of the proper means for the attainment of a supposed end, all the acts seem to be inspired by intelligence, for appropriateness characterizes them all alike. This fact, now, has led to two quite opposite theories about the relation to consciousness of the nervous functions. Some authors, finding that the higher voluntary ones seem to require the guidance of feeling, conclude that over the lowest reflexes some such feeling also presides, though it may be a feeling of which tve remain unconscious. Others, finding that reflex and semi-automatic acts may, notwithstanding their appro priateness, take place with an unconsciousness apparently complete, fly to the opposite extreme and maintain that the appropriateness even of voluntary actions owes nothing to the fact that consciousness attends them. They are, accord ing to these writers, results oi' physiological mechanism pure

and simple. In a near chapter we shall return to this controversy again. Let us now look a little more closely at the brain and at the ways in which its states may be sup posed to condition those of the mind. Both the minute anatomy and the detailed physiology of the brain are achievements of the present generation, or rather we may say (beginning with Meynert) of the past twenty years. Many points are still obscure and subject to controversy ; but a general way of conceiving the organ has been reached on all hands which in its main feature seems not unlikely to stand, and which even gives a most plausible scheme of the way in which cerebral and mental operations go hand in hand.

The best way to enter the subject will be to take a lower creature, like a frog, and study by the vivisectional method the functions of his different nerve-centres. The frog's nerve-centres are figured in the accompany ing diagram, which needs no further ex planation. I will first proceed to state what happens when various amounts of the anterior parts are removed, in different frogs, in the way in which an ordinary ~ * student removes them ; that is, with no ex treme precautions as to the purity of the operation. We shall in this way reach a very simple conception of the functions of the various centres, involving the strongest possible contrast between the cerebral FIO. \.—c H, cerebral hemispheres and the lower lobes. This

Optic fhaiaini; o L, sharp conception will have didactic ad- Cerebellum ; M o, vantages, lor it is olten very instructive s c, spinal Cord, to start with too simple a iormula and correct it later on. Our first formula, as we shall later see, will have to be softened down somewhat by the results of more careful experimentation both on frogs and birds, and by those of the most recent observations on dogs, monkeys, and man. But it will put us, from the outset, in clear possession of some fundamental notions and distinc tions which we could otherwise not gain so well, and none of which the later more completed view will overturn.

If, then, we reduce the frog's nervous system to the spinal cord alone, by making a section behind the base of the skull, between the spinal cord and the medulla oblongata, thereby cutting off the brain from all connection with the rest of the body, the frog will still continue to live, but with a very peculiarly modified activity. It ceases to breathe or swallow ; it lies flat on its belly, and does not, like a normal frog, sit up on its fore paws, though its hind legs are kept, as usual, folded against its body and immediately re sume this position if drawn out. If thrown on its back, it lies there quietly, without turning over like a normal frog. Locomotion and voice seem entirely abolished. If we sus pend it by the nose, and irritate different portions of its skin by acid, it performs a set of remarkable ' defensive ' movements calculated to wipe away the irritant. Thus, if the breast be touched, both fore paws will rub it vigorously; if we touch the outer side of the elbow, the hind foot of the same side will rise directly to the spot and wipe it. The back of the foot will rub the knee if that be attacked, whilst if the foot be cut away, the stump will make ineffectual movements, and then, in many frogs, a pause will come, as if for deliberation, succeeded by a rapid passage of the opposite unmutilated foot to the acidulated spot.

The most striking character of all these movements, after their teleological appropriateness, is their precision. They vary, in sensitive frogs and with a proper amount of irritation, so little as almost to resemble in their machinelike regularity the performances of a jumping-jack, whose legs must twitch whenever you pull the string. The spinal cord of the frog thus contains arrangements of cells and fibres fitted to convert skin irritations into movements of defence. We may call it the centre for defensive movements in this animal. We may indeed go farther than this, and by cutting the spinal cord in various places find that its separate segments are independent mechanisms, for appro priate activities of the head and of the arms and legs respec-

tively. The segment governing the arms is especially active, in male frogs, in the breeding season; and these mem bers alone with the breast and back appertaining to them, everything else being cut away, will then actively grasp a finger placed between them and remain hanging to it for a considerable time. The spinal cord in other animals has analogous powers. Even in man it makes movements of defence. Paraplegics draw up their legs when tickled ; and Eobin, on tickling the breast of a criminal an hour after decapitation, saw the arm and hand move towards the spot. Of the lower func tions of the mammalian cord, studied so ably by Goltz and others, this is not the place to speak.

If, in a second animal, the cut be made just behind the optic lobes so that the cerebellum and medulla oblongata remain attached to the cord, then swallowing, breathing, crawling, and a rather enfeebled jumping and swimming are added to the movements previously observed.* There are other reflexes too. The animal, thrown on his back, immediately turns over to his belly. Placed in a shallow bowl, which is floated on water and made to rotate, he re sponds to the rotation by first turning his head and then waltzing around with his entire body, in the opposite direc tion to the whirling of the bowl. If his support be tilted so that his head points downwards, he points it up ; he points it down if it be pointed upwards, to the right if it be pointed to the left, etc. But his reactions do not go iarther than these movements of the head. He will not like frogs whose thalami are preserved, climb up a board if the latter be tilted, but will slide off it to the ground

be said that this particular cut commonlv proves fatal The he rare cases which survive. board. As his optic nerves are destroyed by the usual operation, it is impossible to say whether he will avoid obstacles placed in his path. When, finally, a frog's cerebral hemispheres alone are cut off by a section between them and the thalami which pre serves the latter, an unpractised observer would not at first suspect anything abnormal about the animal. Not only is he capable, on proper instigation, of all the acts already described, but he guides himself by sight, so that if an obstacle be set up between him and the light, and he be forced to move forward, he either jumps over it or swerves to one side. He manifests sexual passion at the proper season, and, unlike an altogether brainless frog, which em braces anything placed between his arms, postpones this reflex act until a female of his own species is provided. Thus far, as aforesaid, a person unfamiliar with frogs might not suspect a mutilation ; but even such a person would soon remark the almost entire absence of spontane ous motion — that is, motion unprovoked by any present incitation of sense. The continued movements of swimming, performed by the creature in the water, seem to be the fatal result of the contact of that fluid with its skin. They cease when a stick, for example, touches his hands. This is a sensible irritant towards which the feet are automatic ally drawn by reflex action, and on which the animal re mains sitting. He manifests no hunger, and will suffer a fly to crawl over his nose unsnapped at. Fear, too, seems to have deserted him. In a word, he is an extremely com plex machine whose actions, so far as they go, tend to self-preservation ; but still a machine, in this sense — that it seems to contain no incalculable element. By applying the right sensory stimulus to him we are almost as certain of getting a fixed response as an organist is of hearing a certain tone when he pulls out a certain stop.

But now if to the lower centres we add the cerebral hemispheres, or if, in other words, we make an intact ani mal the subject of our observations, all this is changed. In addition to the previous responses to present incitements of sense, our frog now goes through long and complex acts of locomotion spontaneously, or as if moved by what in ourselves we should call an idea. His reactions to outward stimuli vary their form, too. Instead of making simple defensive movements with his hind legs like a headless frog if touched, or of giving one or two leaps and then sit ting still like a hemisphereless one, he makes persistent and varied efforts at escape, as if, not the mere contact of the physiologist's hand, but the notion of danger suggested by it were now his spur. Led by the feeling of hunger, too, he goes in search of insects, fish, or smaller frogs, and varies his procedure with each species of victim. The physiologist cannot by manipulating him elicit croaking, crawling up a board, swimming or stopping, at will. His conduct has become incalculable. We can no longer foretell it exactly. Effort to escape is his dominant reaction, but he may do anything else, even swell up and become per fectly passive in our hands.

Such are the phenomena commonly observed, and such the impressions which one naturally receives. Certain general conclusions follow irresistibly. First of all the following : The acts of all the centres involve the use of the same muscles. When a headless frog's hind leg wipes the acid, he calls into play all the leg-muscles which a frog with his full medulla oblongata and cerebellum uses when he turns from his back to his belly. Their contractions are, how ever, combined differently in the two cases, so that the re sults vary widely. We must consequently conclude that specific arrangements of cells and fibres exist in the cord for wiping, in the medulla for turning over, etc. Similarly they exist in the thalami for jumping over seen obstacles and for balancing the moved body ; in the optic lobes for creeping backwards, or what not. But in the hemispheres, since the presence of these organs brings no new elementary form of movement with it, but only deter mines differently the occasions on which the movements shall occur, making the usual stimuli less fatal and machine-like ; we need suppose no such machinery directly co-ordinative of muscular contractions to exist. We may rather assume, when the mandate for a wiping-movement is sent forth by

the hemispheres, that a current goes straight to the wipingarrangernent in the spinal cord, exciting this arrangement as a whole. Similarly, if an intact frog wishes to jump over a stone which he sees, all he need do is to excite from the hemispheres the jumping-centre in the thalami or wherever it may be, and the latter will provide for the de tails of the execution. It is like a general ordering a colonel to make a certain movement, but not telling him how it shall be done.*

The same muscle, then, is repeatedly represented at different heights; and at each it enters into a different combination with other muscles to co-operate in some special form of concerted movement. At each height the movement is dis charged by some particular form of sensorial stimulus. Thus in the cord, the skin alone occasions movements ; in the upper part of the optic lobes, the eyes are added ; in the thalami, the semi-circular canals would seem to play a part ; whilst the stimuli which discharge the hemispheres would seem not so much to be elementary sorts of sensation, as groups ot sensations forming determinate objects or things. Prey is not pursued nor are enemies shunned by ordinary hemisphereless frogs. Those reactions upon complex cir cumstances which we call instinctive rather than reflex, are already in this animal dependent on the brain's highest lobes, and still more is this the case with animals higher in the zoological scale.

The results are just the same if, instead of a frog, we take a pigeon, and cut out his hemispheres as they are ordi narily cut out for a lecture-room demonstration. There is not a movement natural to him which this brainless bird cannot perform if expressly excited thereto ; only the inner promptings seem deficient, and when left to himself he spends most of his time crouched on the ground with his head sunk between his shoulders as if asleep. * I confine myself to the frog for simplicity's sake. In higher animals, especially the ape and man, it would seem as if not only determinate com binations of muscles, but limited groups or even single muscles could be innervated from the hemispheres.

All these facts lead us, when we think about them, to some such explanatory conception as this : The lower centres 'act from present sensational stimuli alone; the hemispheres act from perceptions and considerations, the sensations which they may receive serving only as suggesters of these. But what are perceptions but sensations grouped together ? and what are considerations but expectations, in the fancy, of sensa tions which will be felt one way or another according as action takes this course or that ? If I step aside on seeing a rattlesnake, from considering how dangerous an animal he is, the mental materials which constitute my prudential reflection are images more or less vivid of the movement of his head, of a sudden pain in my leg, of a state of terror, a swelling of the limb, a chill, delirium, unconsciousness, etc., etc., and the ruin of my hopes. But all these images are constructed out of my past experiences. They are repro ductions of what I have felt or witnessed. They are, in short, remote sensations ; and the difference between the hemisphereless animal and the whole one may be concisely ex pressed by saying that the one obeys absent, the other only present, objects.

The hemispheres would then seem to be the seat of mem ory. Vestiges of past experience must in some way be stored up in them, and must, when aroused by present stimuli, first appear as representations of distant goods and evils; and then must discharge into the appropriate motor channels for warding off the evil and securing the benefits of the good. If we liken the nervous currents to electric currents, we can compare the nervous system, (7, below the hemispheres to a direct circuit from senseorgan to muscle along the line S...C...Moi Fig. 2 (p. 21). The hemisphere, H, adds the long circuit or loop-line through which the current may pass when for any reason the direct line is not used.

the damp eartli beneath a maple-tree. The sensations of delicious rest and coolness pour ing themselves through the direct line would naturally discharge into the muscles of complete exten sion: he would abandon himself to the dangerous repose. But the loop-line being open, part of the current is drafted along it, and awakens rheumatic or catarrlial reminiscences, which prevail over the instigations of sense, and make FlQ* the man arise and pursue his way to where he may enjoy his rest more safely. Presently we shall examine the manner in which the hemispheric loop-line may be supposed to serve as a reservoir for such reminiscences as these. Mean while I will ask the reader to notice some corollaries of its being such a reservoir.

First, no animal without it can deliberate, pause, post pone, nicely weigh one motive against another, or compare. Prudence, in a word, is for such a creature an impossible virtue. Accordingly we see that nature removes those func tions in the exercise of which prudence is a virtue from the lower centres and hands them over to the cerebrum. Wher ever a creature has to deal with complex features of the en vironment, prudence is a virtue. The higheJ animals have so to deal ; and the more complex the features, the higher we call the animals. The fewer of his acts, i/ien, can such an animal perform without the help of the organs in question. In the frog many acts devolve wholly on the lower centres; in the bird fewer; in the rodent fewer still ; in the dog very few indeed ; and in apes and men hardly any at all.

The advantages of this are obvious. Take the prehen-- sion of food as an example and suppose it to be a reflex performance of the lower centres. The animal will be con demned fatally and irresistibly to snap at it whenever presented, no matter what the circumstances may be ; he can no more disobey this prompting than water can refuse to boil when a fire is kindled under the poi His life will again and again pay the forfeit of his gluttony. Exposure to retaliation, to other enemies, to traps, to poisons, to the dangers of repletion, must be regular parts of his existence. His lack of all thought by which to weigh the danger against the attractive-ness of the bait, and of all volition to remain hungry a little while longer, is the direct measure of his lowness in the mental scale. And those fishes which, like our cunners and sculpins, are no sooner thrown back from the hook into the water, than they automatically seize the hook again, would soon expiate the degradation of their intelligence by the extinc tion of their type, did not their exaggerated fecundity atone for their imprudence. Appetite and the acts it prompts have consequently become in all higher vertebrates func tions of the cerebrum. They disappear when the physiol ogist's knife nas left the subordinate centres alone in "place. The brainless pigeon will starve though left on a cornheap.

Take again the sexual function. In birds this devolves exclusively upon the hemispheres. When these are shorn away the pigeon pays no attention to the billings and cooings of its mate. And Goltz found that a bitch in heat would excite no emotion in male dogs who had suffered large loss of cerebral tissue. Those who have read Dar win's ' Descent of Man' know what immense importance in the amelioration of the breed in birds this author ascribes to the mere fact of sexual selection. The sexual act is not performed until every condition of circumstance and senti ment is fulfilled, until time, place, and partner all are fit. But in frogs and toads this passion devolves on the lower centres. They show consequently a machine-like obe dience to the present incitement of sense, and an almost total exclusion of the power of choice. Copulation occurs per fas aut nefas, occasionally between males, often with dead females, in puddles exposed on the highway, and the male may be cut in two without letting go his hold. Every spring an immense sacrifice of batrachian life takes place from these causes alone.

No one need be told how dependent all human social elevation is upon the prevalence of chastity. Hardly any factor measures more than this the difference between civili* zation and barbarism. Physiologically interpreted, chastity means nothing more than the fact that present solicitations of sense are overpowered by suggestions of aesthetic and moral fitness which the circumstances awaken in the cerebrum ; and that upon the inhibitory or permissive in fluence of these alone action directly depends.