The Principles of Psychology, Vols. 1-2

Within the psychic life due to the cerebrum itself the same general distinction obtains, between considerations of the more immediate and considerations of the more remote. In all ages the man whose determinations are swayed by reference to the most distant ends has been held to possess the highest intelligence. The tramp who lives from hour to hour ; the bohemian whose engagements are from day to day ; the bachelor who builds but for a single life ; the father who acts for another generation ; the patriot who thinks of a whole community and many generations ; and finally, the philosopher and saint whose cares are for humanity and for eternity, — these range themselves in an unbroken hierarchy, wherein each successive grade results from an increased manifestation of the special form of action by which the cerebral centres are distinguished fyorn all below them.

In the ' loop-line ' along which the memories and ideas of the distant are supposed to lie, the action, so far as it is a physical process, must be interpreted after the type of the action in the lower centres. If regarded here as a reflex process, it must be reflex there as well. The current in both places runs out into the muscles only after it has first run in ; but whilst the path by which it runs out is deter mined in the lower centres by reflections few and fixed amongst the cell-arrangements, in the hemispheres the reflections are many and instable. This, it will be seen, is only a difference of degree and not of kind, and does not change the reflex type. The conception of all action as conforming to this type is the fundamental conception of modern nerve-physiology. So much for our general pre liminary conception of the nerve-centres ! Let us define it more distinctly before we see how well physiological ob servation will bear it out in detail.

Nerve-currents run in through sense-organs, and whilst provoking reflex acts in the lower centres, they arouse ideas in the hemispheres, which either permit the reflexes in question, check them, or substitute others for them. All ideas being in the last resort reminiscences, the question to answer is : How can processes become organized in the hemi spheres ivhich correspond to reminiscences in the mind ?* Nothing is easier than to conceive a possible way in which this might be done, provided four assumptions be granted. These assumptions (which after all are inevitable in any event) are :

1) The same cerebral process which, when aroused from without by a sense-organ, gives the perception of an object, will give an idea of the same object when aroused by other cerebral processes from within. 2) If processes 1, 2, 3, 4 have once been aroused to gether or in immediate succession, any subsequent arousal of any one of them (whether from without or within) will tend to arouse the others in the original order. [This is the so-called law of association.]

3) Every sensorial excitement propagated to a lower centre tends to spread upwards and arouse an idea. 4) Every idea tends ultimately either to produce a movement or to check one which otherwise would be pro duced. Suppose now (these assumptions being granted) that we have a baby before us who sees a candle-flame for the first * I hope that the reader will take no umbrage at my so mixing the \ physical and mental, and talking of reflex acts and hemispheres and remi-

' niscences in the same breath, as if they were homogeneous quantities and factors of one causal chain. I have done so deliberately ; for although I admit that from the radically physical point of view it is easy to conceive of the chain of events amongst the cells and fibres as complete in itself, I and that whilst so conceiving it one need make no mention of • ideas,' I yet suspect that point of view of being an unreal abstraction. Reflexes In centres may take place even where accompanying feelings or ideas guide / them. In another chapter I shall try to show reasons for not abandoning this common-sense position ; meanwhile language lends itself so much more easily to the mixed way of describing, that I will continue to employ the latter. The more radical-minded reader can always read ' ideationa] orocess' for 'idea.'

time, and, by virtue of a reflex tendency common in babies of a certain age, extends his hand to grasp it, so that his fingers get burned. So far we have two reflex currents in play : first, from the eye to the extension movement, along the line 1—1—1—1 of Fig. 3 ; and second, from the finger to the movement of drawing back the hand, along the line 2 — 2 — 2 — 2. ^ If this were the baby's whole nervous system, and if the re flexes were once for all organic, we should have no alteration in his behavior, no matter how often the experience recurred. The retinal image of the flame would always make the arm shoot forward, the burning of the finger would always send it back. But we know that ' the burnt child dreads the fire,' and that one experience usually protects the fingers forever. The point is to see how the hemispheres may bring this result to pass. We must complicate our diagram (see Fig. 4). Let the current 1 — 1, from the eye, discharge upward as well as downward when it reaches the lower centre for vision, and arouse the perceptional process sl in the hemispheres ; let

the feeling of the arm's exten sion also send up a current which leaves a trace of itself, in1 ; let tli3 burnt finger leave an analogous trace, sa ; and let the movement of retrac tion leave m2. These four processes will now, by virtue of assumption 2), be associ ated together by the path 6-1 — ra1— s2 — m2 , running from +l,a fivc-f fn fLa Incf GO -fTmf if tne first tO tlie last» SO ttiat " anything touches off s1, ideas of the extension, of the burnt finger, and of the retraction will pass in rapid succession

FIG. 4.— The dotted lines stand for afferent paths, the broken lines for paths through the mind. The effect on the child's conduct when the candle-flame is next presented is easy to imagine. Of course the sight of it arouses the grasping reflex ; but it arouses simultaneously the idea thereof, together with that of the consequent pain, and of the final retraction of the hand ; and if these cerebral processes prevail in strength over the immediate sensation in the centres below, the last idea will be the cue by which the final action is discharged. The grasping will be arrested in mid-career, the hand drawn back, and the child's fingers saved.

In all this we assume that the hemispheres do not natively couple any particular sense-impression with any special motor discharge. They only register, and preserve traces of, such couplings as are already organized in the reflex centres below. But this brings it inevitably about that, when a chain of experiences has been already regis tered and the first link is impressed once again from without, the last link will often be awakened in idea long before it can exist in fact. And if this last link were previously coupled with a motion, that motion may now come from the mere ideal suggestion without waiting for the actual impres sion to arise. Thus an animal with hemispheres acts in an ticipation of future things ; or, to use our previous formula, he acts from considerations of distant good and ill. If we give the name of partners to the original couplings of impressions with motions in a reflex way, then we may say that the func tion of the hemispheres is simply to bring about exchanges among the partners. Movement mn , which natively is sensa tion sn's partner, becomes through the hemispheres the partner of sensation s1 , s2 or s3 . It is like the great cornmutating switch-board at a central telephone station. No new elementary process is involved ; no impression nor any motion peculiar to the hemispheres ; but any number of combinations impossible to the lower machinery taken alone, and an endless consequent increase in the possibilities of behavior on the creature's part.

* I shall call it hereafter for shortness ' the Meynert scheme;' for the child-and-flame example, as well as the whole general notion that the hemi spheres are a supernumerary surface for the projection and association o* with the general look of the facts as almost to impose itself on our belief ; but it is anything but clear in detail. The brain-physiology of late years has with great effort sought to work out the paths by which these couplings of sensa tions with movements take place, both in the hemispheres and in the centres below.

So we must next test our scheme by the facts discovered in this direction. We shall conclude, I think, after taking them all into account, that the scheme probably makes the lower centres too machine-like and the hemispheres not quite machine-like enough, and must consequently be softened down a little. So much I may say in advance. Meanwhile, before plunging into the details which await us, it will somewhat clear our ideas if we contrast the modern way of looking at the matter with the phrenological concep tion which but lately preceded it.

In a certain sense Gall was the first to seek to explain in detail how the brain could subserve our mental opera tions. His way of proceeding was only too simple. He took the faculty-psychology as his ultimatum on the mental side, and he made no farther psychological analysis. Wherever he found an individual with some strongly-marked trait of character he examined his head ; and if he found the latter prominent in a certain region, he said without more ado that that region was the ' organ ' of the trait or faculty in question. The traits were of very diverse con stitution, some being simple sensibilities like ' weight ' or ' color ; ' some being instinctive tendencies like ' alimentiveness ' or ' amativeness ; ' and others, again, being com plex resultants like 'conscientiousness,' 'individuality.' Phrenology fell promptly into disrepute among scientific men because observation seemed to show that large facul-

sensations and movements natively coupled in the centres below, is due to Th. Meynert, the Austrian anatomist. For a popular account of his views, see his pamphlet ' Zur Mechanik des Gehirnbaues,' Vienna, 1874. His most recent development of them is embodied in his ' Psychiatry,' a clinical treatise on diseases of the forebruiu, translated by B. Sachs, New York, 1885. ties and large ' bumps ' might fail to coexist ; because the scheme of Gall was so vast as hardly to admit of accurate determination at all — who of us can say even of his own brothers whether their perceptions of weight and of time are well developed or not ? — because the followers of Gall and Spurzheim were unable to reform these errors in any appre ciable degree ; and, finally, because the whole analysis of faculties was vague and erroneous from a psychologic point of view. Popular professors of the lore have nevertheless continued to command the admiration of popular audiences ; and there seems no doubt that Phrenology, however little it satisfy our scientific curiosity about the functions of dif ferent portions of the brain, may still be, in the hands of intelligent practitioners, a useful help in the art of reading character. A hooked nose and a firm jaw are usually signs of practical energy ; soft, delicate hands are signs of refined sensibility. Even so may a prominent eye be a sign of power over language, and a bull-neck a sign of sensuality. But the brain behind the eye and neck need no more be the organ of the signified faculty than the jaw is the organ of the will or the hand the organ of refinement. These correlations between mind and body are, however, so frequent that the ' characters ' given by phrenologists are often remarkable for knowingness and insight.

Phrenology hardly does more than restate the problem. To answer the question, "Why do I like children?" by saying, " Because you have a large organ of philoprogenitiveness," but renames the phenomenon to be explained. What is my philoprogenitiveness ? Of what mental ele ments does it consist ? And how can a part of the brain be its organ? A science of the mind must reduce such complex manifestations as ' philoprogenitiveness ' to their dements. A science of the brain must point out the func tions of its elements. A science cf the relations of mind and brain must show how the elementary ingredients of the former correspond to the elementary functions of the latter. But phrenology, except by occasional coincidence, takes no account of elements at all. Its « faculties,' as a rule, are fully equipped persons in a particular mental attitude. Take, for example, the ' faculty ' of language. It involves

in reality a host of distinct powers. We must first have images of concrete things and ideas of abstract qualities and relations ; we must next have the memory of words and then the capacity so to associate each idea or image with a particular word that, when the word is heard, the idea shall forthwith enter our mind. We must conversely, as soon as the idea arises in our mind, associate with it a mental image of the word, and by means of this image we must innervate our articulatory apparatus so as to repro duce the word as physical sound. To read or to write a language other elements still must be introduced. But it is plain that the faculty of spoken language alone is so complicated as to call into play almost all the elementary powers which the mind possesses, memory, imagination, association, judgment, and volition. A portion of the brain competent to be the adequate seat of such a faculty would needs be an entire brain in miniature, — just as the faculty itself is really a specification of the entire man, a sort of bomunculus.

Yet just such homunculi are for the most part the phrenological organs. As Lange says : " "We have a parliament of little men together, each one of whom, as happens also in a real parliament, possesses but a single idea which he ceaselessly strives to make prevail " — benevolence, firmness, hope, and the rest. "Instead of one soul, phrenology gives us forty, each alone as enigmatic as the full aggregate psychic life can be. In stead of dividing the latter into effective elements, she divides it into personal beings of peculiar character. . . . ' Herr Pastor, sure there be a horse inside,' called out the peasants to X after their spiritual shepherd had spent hours in explaining to them the construction of the locomotive. With a horse inside truly everything becomes clear, even though it be a queer enough sort of horse— the horse itself calls for no explanation ! Phrenology takes a start to get beyond the point of view of the ghost-like soul entity, but she ends by populating the whole skull with ghosts of the same order." *

Modern Science conceives of the matter in a very differ ent way. Brain and mind alike consist of simple elements, sensory and motor. "All nervous centres," says Dr. Hughlings Jackson,f " from the lowest to the very highest (the substrata of consciousness), are made up of nothing else than nervous arrangements, representing impressions and movements. ... I do not see of what other materials the brain can be made." Meynert represents the matter similarly when he calls the cortex of the hemispheres the surface of projection for every muscle and every sensitive point of the body. The muscles and the sensitive points are represented each by a cortical point, and the brain is nothing but the sum of all these cortical points, to which, on the mental side, as many ideas correspond. Ideas of sensation, ideas of motion are, on the other hand, the ele mentary factors out of which the mind is built up by the associationists in psychology. There is a complete parallel ism between the two analyses, the same diagram of little dots, circles, or triangles joined by lines symbolizes equally well the cerebral and mental processes : the dots stand for cells or ideas, the lines for fibres or associations. We shall have later to criticise this analysis so far as it relates to the mind ; but there is no doubt that it is a most convenient, and has been a most useful, hypothesis, formulating the facts in an extremely natural way.

If, then, we grant that motor and sensory ideas variously associated are the materials of the mind, all we need do to get a complete diagram of the mind's and the brain's relations should be to ascertain which sensory idea corresponds to which sensational surface of projection, and which motor idea to which muscular surface of projection. The associa tions would then correspond to the fibrous connections be tween the various surfaces. This distinct cerebral localization of the various elementary sorts of idea has been treated as a 'postulate' by many physiologists (e.g. Munk) ; and the most stirring controversy in nerve-physiology which the present generation has seen has been the localizationquestion.

Up to 1870, the opinion which prevailed was that which the experiments of Flourens on pigeons' brains had made plausible, namely, that the different functions of the hemispheres were not locally separated, but carried on each by the aid of the whole organ. Hitzig in 1870 showed, how ever, that in a dog's brain highly specialized movements could be produced by electric irritation of determinate regions of the cortex ; and Ferrier and Munk, half a dozen years later, seemed to prove, either by irritations or excis ions or both, that there were equally determinate regions connected with the senses of sight, touch, hearing, and smell. Munk's special sensorial localizations, however, disagreed with Ferrier's ; and Goltz, from his extirpationexperiments, came to a conclusion adverse to strict local ization of any kind. The controversy is not yet over. I will not pretend to say anything more of it historically, but give a brief account of the condition in which matters at present stand.

The one thing which is perfectly well established is this, that the ' central ' convolutions, on either side of the fissure of Kolando, and (at least in the monkey) the calloso-marginal convolution (which is continuous with them on the mesial surface where one hemisphere is applied against the other), form the region by which all the motor incitations which leave the cortex pass out, on their way to those executive centres in the region of the pons, medulla, and spinal cord from which the muscular contractions are discharged in the last resort. The existence of this so-called ' motor zone ' is established by the lines of evidence successively given below :

(1) Cortical Irritations. Electrical currents oi small intensity applied to the surface of the said convolutions in dogs, monkeys, and other animals, produce well-defined movements in face, fore-limb, hind-limb, tail, or trunk, according as one point or another of the surface is irritated. These movements affect almost invariably the side opposite to the brain irritations : If the left hemisphere be excited, the movement i& of the right leg, side of face, etc. All the objec tions at first raised against the validity of these experiments have been overcome. The movements are certainly not due to irritations of the base of the brain by the downward spread of the current, for : a) mechanical irritations will produce them, though less easily than electrical ; 6) shifting the

electrodes to a point close by on the surface changes the movement in ways quite inexplicable by changed physical conduction of the current ; c) if the cortical ' centre' for a certain movement be cut under with a sharp knife but left in situ, although the electric conductivity is physically unaltered by the operation, the physiological conductivity is gone and currents of the same strength no longer pro duce the movements which they did ; d) the time-interval between the application of the electric stimulus to the cor tex and the resultant movement is what it would be if the cortex acted physiologically and not merely physically in transmitting the irritation. It is namely a well-known fact that when a nerve-current has to pass through the spinal cord to excite a muscle by reflex action, the time is longer than if it passes directly down the motor nerve : the cells of the cord take a certain time to discharge. Similarly, when a stimulus is applied directly to the cortex the muscle contracts two or three hundredths of a second later than it does when the place on the cortex is cut away and the elec trodes are applied to the white fibres below.*

(2) Cortical Ablations. "When the cortical spot which is found to produce a movement of the fore-leg, in a dog, is excised (see spot 5 in Fig. 5), the leg in question becomes peculiarly affected. At first it seems paralyzed. Soon, how ever, it is used with the other legs, but badly. The animal does not bear his weight on it, allows it to rest on its dorsal surface, stands with it crossing the other leg, does not remove it if it hangs over the edge of a table, can no longer « give the paw' at word of command if able to do so before the opera tion, does not use it for scratching the ground, or holding a bone as formerly, lets it slip out when running on a smooth

* For a thorough discussion of the various objections, see Ferrier's 'Functions of the Brain,' 2d ed., pp. 227-234, and Fra^ois-Franck's ' Le9ons sur les Fonctions Motrices du Cerveau ' (1887), Le?on 31. The most minutely accurate experiments on irritation of cortical points are those of Paneth, in Pfliiger's Archiv, vol 37, p. 528.— Recently the skull has been fearlessly opened by surgeons, and operations upon the human brain per formed, sometimes with the happiest results. In some of these operations the cortex has been electrically excited for the purpose of more exactly localizing the spot, and the movements first observed in dogs and monkeys have then been verified in men.

surface or when shaking himself, etc., etc. Sensibility of all kinds seems diminished as well as motility, but of this I shall speak later on. Moreover the dog tends in voluntary movements to swerve towards the side of the brain-lesion in stead of going straight forward. All these symptoms gradu ally decrease, so that even with a very severe brain-lesion the dog may be outwardly indistinguishable from a well dog after eight or ten weeks. Still, a slight chloroformization will reproduce the disturbances, even then. There is a cer tain appearance of ataxic in-coordination in the movements — the dog lifts his fore-feet high and brings them down with more strength than usual, and yet the trouble is not ordi-

FIG. 5.— Left Hemisphere of Dog's Brain, after Ferrier. A, the fissure of Sylvius. B, the crucial sulcus. O, the olfactory bulb. J, II, III, IV, indicate the first, second, third, and fourth external convolutions respectively. (1), (4), and (5) are on the sigmoid gyrus. nary lack of co-ordination. Neither is there paralysis. The strength of whatever movements are made is as great as ever — dogs with extensive destruction of the motor zone can jump as high and bite as hard as ever they did, but they seem less easily moved to do anything with the affected parts. Dr0 Loeb, who has studied the motor disturbances of dogs more carefully than any one, conceives of them en masse as effects of an increased inertia in all the processes of innervation towards the side opposed to the lesion. All such movements require an unwonted effort for their exe cution ; and when only the normally usual effort is made they fall behind in effectiveness.*

* J. Loeb : ' Beitriige zur Physiologic des Grosshirns;; Pflliger's Ar- chiv, xxxix. 293. I simplify the author's statement. Even when the entire motor zone of a dog is removed, there is no permanent paralysis of any part, but only this curious sort of relative inertia when the two sides of the body are compared ; and this itself becomes hardly notice able after a number of weeks have elapsed. Prof. Goltz has described a dog whose entire left hemisphere was de stroyed, and who retained only a slight motor inertia on the right half of the body. In particular he could use his right

paw for holding a bone whilst gnawing it, or for reaching after a piece of meat. Had he been taught to give his paw before the operations, it would have been curious to see whether that faculty also came back. His tactile sensi bility was permanently diminished on the right side.* In monkeys a genuine paralysis follows upon ablations of the cortex in the motor region. This paralysis affects parts of the body which vary with the brain-parts removed. The monkey's opposite arm or leg hangs flaccid, or at most takes a small part in associated movements. When the entire region is removed there is a genuine and permanent hemiplegia in which the arm is more affected than the leg; and this is

followed months later by contracture of the muscles, as in man after inveterate hemiplegia.* According to Schaefer and Horsley, the trunk-muscles also become paralyzed after destruction of the marginal convolution on both sides (see Fig. 7). These differences between dogs and monkeys show the danger of drawing general conclusions from experiments done on any one sort of animal. I subjoin the figures given by the last-named authors of the motor regions in the monkey's brain, f