The Principles of Psychology, Vols. 1-2

^ * Die Seelenblindheit, etc., p. 51 ff. The mental blindness was in this woman's case moderate in degree. t Archiv f. Psychiatric, vol. 21, p. 222. sight altogether.* Kecent pathological annals seem to offer a few such cases. t Meanwhile there are a number of cases of mental blindness, especially for written language, coupled with hemianopsia, usually of the rightward field of view. These are all explicable by the breaking down, through disease, of the connecting tracts between the occipital lobes and other parts of the brain, especially those which go to the centres for speech in the frontal and temporal regions of the left hemisphere. They are to be classed among distur bances of conduction or of association ; and nowhere can I find any fact which should force us to believe that optical images needj be lost in mental blindness, or that the cerebral centres for such images are locally distinct from those for direct sensations from the eyes. §

Where an object fails to be recognized by sight, it often happens that the patient will recognize and name it as soon as he touches it with his hand. This shows in an interest- * Nothnagel (loc. cit. p. 22) says : " Dies trifft aber niclitzu." He gives, however, no case in support of his opinion that double-sided cortical lesion may make one stone-blind and yet not destroy one's visual images ; so that I do not know whether it is an observation of fact or an a priori as sumption.

f In a case published by C. S. Freund : Archiv f. Psychiatric, vol. xx, the occipital lobes were injured, but their cortex was not destroyed, on both sides. There was still vision. Of. pp. 291-5. \ I say ' need, ' for I do not of course deny the possible coexistence of the two symptoms. Many a brain-lesion might block optical associations and at the same time impair optical imagination, without entirely stopping vision. Such a case seems to have been the remarkable one from Charcot which I shall give rather fully in the chapter on Imagination.

§ Freund (in the article cited above ' Ueber optZsche Aphasie und Seelenblindheit ') and Bruns (' Ein Fall von Alexie,' etc., in the Neurologisches Centralblatt for 1888, pp. 581, 509) explain their cases by brokendown conduction. Wilbraud, whose painstaking monograph on mental blindness was referred to a moment ago, gives none but a priori reasons for his belief that the optical 'Erinnerungsfeld ' must be locally distinct from the Wahrnehmungsfeld (cf. pp. 84, 93). The a priori reasons are really the other way. Mauthner (' Gehirn u. Auge ' (1881), p. 487 ff.) tries to show that the ' mental blindness' of Muuk's dogs and apes after occipital mutila tion was not such, but real dimness of sight. The best case of mental blindness yet reported is that by Lissauer, as above. The reader will also do well to read Bernard : De 1'Aphasie (1885) chap, v; Ballet : Le Laugage Interieur (1886), chap, vin ; and Jas. Koss's little book on Aphasia (1887). p. 74

ing way how numerous the associative paths are which all end by running out of the brain through the channel of speech. The hand-path is open, though the eye-path be closed. When mental blindness is most complete, neither sight, touch, nor sound avails to steer the patient, and a sort of dementia which has been called asymbolia or apraxia is the result. The commonest articles are not understood. The patient will put his breeches on one shoulder and his hat upon the other, will bite into the soap and lay his shoes on the table, or take his food into his hand and throw it down again, not knowing what to do with it, etc. Such dis order can only come from extensive brain-injury.*

The method of degeneration corroborates the other evi dence localizing the tracts of vision. In young animals one gets secondary degeneration of the occipital regions from destroying an eyeball, and, vice versa, degeneration of the optic nerves from destroying the occipital regions. The corpora geniculata, thalami, and subcortical fibres leading to the occipital lobes are also found atrophied in these cases. The phenomena are not uniform, but are indispu table ; f so that, taking all lines of evidence together, the special connection of vision with the occipital lobes is per fectly made out. It should be added that the occipital lobes have frequently been found shrunken in cases of in veterate blindness in man.

Hearing is hardly as definitely localized as sight. In the dog, Luciani's diagram will show the regions which directly or indirectly affect it for the worse when injured. As with sight, one-sided lesions produce symptoms on both sides. The mixture of black dots and gray dots in the diagram is meant to represent this mixture of ' crossed ' and ' uncrossed ' con nections, though of course no topographical exactitude is aimed at. Of all the region, the temporal lobe is the most important part ; yet permanent absolute deafness did not

* For a case see Wernicke's Lelirb. d. Gehirnkrankhciten vol n p f The latest account of them is the paper ' Uber die optischen Cenlren Bahnen' by von Monakow in the Archiv fur Psychiatric, vol. xx. p. 714. result in a dog of Luciani's, even from bilateral destruction of both temporal lobes in their entirety. * In the monkey, Ferrier and Yeo once found permanent deafness to follow destruction of the upper temporal con volution (the one just below the fissure of Sylvius in Fig.

6) on both sides. Brown and Schaefer found, on the con trary, that in several monkeys this operation failed to notice ably affect the hearing. In one animal, indeed, both entire temporal lobes were destroyed. After a week or two of depression of the mental faculties this beast recovered and became one of the brightest monkeys possible, domineering over all his mates, and admitted by all who saw him to have all his senses, including hearing, 'perfectly acute.' f Terrible recriminations have, as usual, ensued between the investigators, Ferrier denying that Brown and Schaefer's ablations were complete, J Schaefer that Ferrier's monkey was really deaf.§ In this unsatisfactory condition the sub ject must be left, although there seems no reason to doubt that Brown and Schaefer's observation is the more important of the two.

In man the temporal lobe is unquestionably the seat of the hearing function, and the superior convolution adjacent to the sylvian fissure is its most important part. The phe nomena of aphasia show this. We studied motor aphasia a few pages back ; we must now consider sensory aphasia. Our knowledge of this disease has had three stages : we may talk of the period of Broca, the period of Wernicke, and the period of Charcot. What Broca's discovery was we have seen. Wernicke was the first to discriminate those cases in which the patient can not even understand speech from those in which he can understand, only not talk ; and to ascribe the former condition to lesion of the temporal lobe.* The condition in question is word-deafness, and the disease is auditory aphasia. The latest statistical survey of the subject is that by Dr. Allen Starr, f In the seven cases oipure word-deafness which he has collected, cases in which the patient could read, talk, and write, but not understand what was said to him, the lesion was limited to the first and second temporal convolutions in their posterior two thirds. The lesion (in right-handed, i.e. left-brained, persons) is always on the left side, like the lesion in motor aphasia. Crude hearing would not be abolished, even were the left centre for it utterly destroyed ; the right centre would still provide for that. But the linguistic use of hearing appears bound up with the integrity of the left centre more or less exclusively. Here it must be that words heard enter into association with the things which they represent, on the one hand, and with the movements necessary for pronouncing them, on the other. In a large majority of Dr. Starr's fifty cases, the power either to name objects or to talk coherently was impaired. This shows that in most of us (as Wernicke said) speech must go on from auditory cues ; that is, it must be that our ideas do not innervate our motor centres directly, but only after first arousing the mental sound of the words.

This is the immediate stimulus to articulation ; and where the possibility of this is abolished by the de struction of its usual channel in the left temporal lobe, the articulation must suffer. In the few cases in which the channel is abolished with no bad effect on speech we must suppose an idiosyncrasy. The patient must innervate his speech-organs either from the corresponding portion of the other hemisphere or directly from the centres of ideation,

* Der aphasische Symptomencomplex (1874). See in Fig. 11 the con volution marked WERNICKE. those, namely, of vision, touch, etc., without leaning on the auditory region. It is the minuter analysis of the facts in the light of such individual differences as these which con stitutes Charcot's contribution towards clearing up the subject. Every namable thing, act, or relation has numerous properties, qualities, or aspects. In our minds the proper ties of each thing, together with its name, form an associated group. If different parts of the brain are severally con cerned with the several properties, and a farther part with the hearing, and still another with the uttering, of the name, there must inevitably be brought about (through the law of association which we shall later study) such a dynamic connec tion amongst all these brain-parts that the activity of any one of them wiJl be likely to awaken the activity of all the rest. When we are talking as we think, the ultimate process is that of utterance. If the brain-part for that be injured, speech is impossible or disorderly, even though all the other brainparts be intact : and this is just the condition of things which, on page 37, we found to be brought about by limited lesion of the left inferior frontal convolution. But back of that last act various orders of succession are possible in the associations of a talking man's ideas. The more usual order seems to be from the tactile, visual, or other properties of the things thought-about to the sound of their names, and then to the latter's utterance. But if in a certain individual the thought of the look of an object or of the look of its printed name be the process which habitually precedes articulation, then the loss of the hearing centre will pro tanto not affect that individual's speech. He will be mentally deaf, i.e. his understanding of speech will suffer, but he will not be aphasic. In this way it is possible to explain the seven cases of pure word-deaf ness which figure in Dr. Starr's table.

If this order of association be ingrained and habitual in that individual, injury to his visucd centres will make him not only wordblind, but aphasic as well. His speech will become confused in consequence of an occipital lesion. Naunyn, consequently, plotting out on a diagram of the hemisphere the 71 irreproachably reported cases of aphasia which he was able to collect, finds that the lesions concentrate themselves in three places : first, on Broca's centre ; second, on Wernicke's ; third, on the supra-marginal and angular gyri under which those fibres pass which con nect the visual centres with the rest of the brain* (see Fig. 17). With this result Dr. Starr's analysis of purely sensory cases agrees.

In a later chapter we shall again return to these differences in the effectiveness of the sensory spheres in different individuals. Meanwhile few things show more beautifully than the history of our knowledge of aphasia how the sagacity and patience of many banded workers are in time certain to analyze the darkest confusion into an orderly display. f There is no ' centre of Speech' in the brain any more than there is a faculty of Speech in the mind. The entire brain, more or less, is at work in a man who uses language. The subjoined diagram, from Koss, shows the four parts most critically concerned, and, in the light of our text, needs no farther explanation (see Fig. 18).

f Ballet's and Bernard's works cited on p. 51 are the most accessible documents of Charcot's school. Bastian's book on the Brain as an Organ of Mind (last three chapters) is also good. Everything conspires to point to the median descending part of the temporal lobes as being the organs of smell. Even Terrier and Munk agree on the hippocampal gyrus, though Ferrier restricts olfaction, as Munk does not, to the lobule or uncinate process of the convolution, reserving the rest of it for touch. Anatomy and pathology also point to the hippocampal gyrus ; but as the matter is less interest ing from the point of view of human psychology than were sight and hearing, I will say no more, but simply add LucianiandSeppili's diagram of the dog's smell-centre.* Of

*For details, see Ferrier's 'Functions,' chap, ix. pt. m, and Chas. K. Mills : Transactions of Congress of American Physicians and Sur geons, 1888, vol. i. p. 278. we know little that is definite. What little there is points to the lower temporal regions again. Consult Terrier as below. Interesting problems arise with regard to the seat of tactile and muscular sensibility. Hitzig, whose experiments on dogs' brains fifteen years ago opened the entire subject

which we are discussing, ascribed the disorders of motility observed after ablations of the motor region to a loss of what he called muscular consciousness. The animals do not notice eccentric positions of their limbs, will stand with their legs crossed, with the affected paw resting on its back or hanging over a table's edge, etc.; and do not resist our bending and stretching of it as they resist with the un affected paw. Goltz, Munk, Schiff, Herzen, and others promptly ascertained an equal defect of cutaneous sensi bility to pain, touch, and cold. The paw is not withdrawn when pinched, remains standing in cold water, etc. Ferrier meanwhile denied that there was any true anaesthesia produced by ablations in the motor zone, and explains the appearance of it as an effect of the sluggish motor responses of the affected side.* Munkf and Schiff J, on the

contrary, conceive of the ' motor zone ' as essentially sen sory, and in different ways explain the motor disorders as secondary results of the anaesthesia which is always there, Munk calls the motor zone the Fiihlsphare of the animal's limbs, etc., and makes it coordinate with the Sehsphiire, the Horsphiire, etc., the entire cortex being, according to him, nothing but a projection-surface for sensations, with no exclusively or essentially motor part. Such a view would be important if true, through its bearings on the psychology of volition. What is the truth? As regards the fact of cutaneous anaesthesia from motor-zone ablationsv all other observers are against Ferrier, so that he is proba bly wrong in denying it. On the other hand, Munk and Schiff are wrong in making the motor symptoms depend on the anaesthesia, for in certain rare cases they have been observed to exist not only without insensibility, but with actual hypersesthesia of the parts.* The motor and sensory symptoms seem, therefore, to be independent variables.

In monkeys the latest experiments are those of Horsley and Schaefer,f whose results Ferrier accepts. They find that excision of the hippocampal convolution produces tran sient insensibility of the opposite side of the body, and that permanent insensibility is produced by destruction of its continuation upwards above the corpus callosum, the socalled gyrus fornicatus (the part just below the ' callosomarginal fissure ' in Fig. 7). The insensibility is at its maxi mum when the entire tract comprising both convolutions is destroyed. Ferrier says that the sensibility of monkeys is 'entirely unaffected' by ablations of the motor zone,J and Horsley and Schaefer consider it by no means necessarily

*Bechterew (Pfluger's Archiv., vol. 35, p. 137) found no anaesthesia in a cat with motor symptoms from ablation of sigmoid gyrus. Luciani got hypersesthesia coexistent with cortical motor defect in a dog, by simulta neously hemisecting the spinal cord (Luciani u. Seppili, op. cit. p. 234). Goltz frequently found hyperaesthesia of the whole body to accompany motor defect after ablation of both frontal lobes, and he once found it after ablating the motor zone (Pfliiger's Archiv, vol. 34, p. 471).

abolished.* Luciani found it diminished in his three ex periments on apes.f In man we have the fact that one-sided paralysis from disease of the opposite motor zone may or may not be accompanied with anaesthesia of the parts. Luciani, who believes that the motor zone is also sensory, tries to minim ize the value of this evidence by pointing to the insufficiency with which patients are examined. He himself believes that in dogs the tactile sphere extends backwards and forwards of the directly excitable region, into the frontal and parietal lobes (see Fig. 20). Nothnagel considers that pathological evidence points in the same direction ; ;£ and Dr. Mills, care fully reviewing the evidence, adds the gyri fornicatus and hippocampi to the cutaneo-muscular region in man.§ If one compare Luciani's diagrams together (Figs. 14, 16, 19, 20) one will see that the entire parietal region of the dog's skull is common to the four senses of sight, hearing, smell, and touch, including muscular feeling. The corresponding re gion in the human brain (upper parietal and supra-marginal gyri — see Fig. 17, p. 56) seems to be a somewhat similar place of conflux. Optical aphasias and motor and tactile disturbances all result from its injury, especially when that is on the left side.ll The lower we go in the animal scale the

less differentiated the functions of the several brain-parts seem to be.* It may be that the region in question still represents in ourselves something like this primitive condi tion, and that the surrounding parts, in adapting themselves more and more to specialized and narrow functions, have left it as a sort of carrefour through which they send cur rents and converse. That it should be connected with musculo-cutaneous feeling is, however, no reason why the motor zone proper should not be so connected too. And the cases of paralysis from the motor zone with no accom panying anaesthesia may be explicable without denying all sensory function to that region. For, as my colleague Dr. James Putnam informs me, sensibility is always harder to kill than motility, even where we know for a certainty that the lesion affects tracts that are both sensory and motor. Persons whose hand is paralyzed in its movements from compression of arm-nerves during sleep, still feel with their fingers ; and they may still feel in their feet when their legs are paralyzed by bruising of the spinal cord. In a simi lar way, the motor cortex might be sensitive as well as motor, and yet by this greater subtlety (or whatever the peculiarity may be) in the sensory currents, the sensibility might survive an amount of injury there by which the motility was destroyed. Nothnagel considers that there are grounds for supposing the muscular sense to be exclusively connected with the parietal lobe and not with the motor zone. " Disease of this lobe gives pure ataxy without palsy, and of the motor zone pure palsy without loss of muscular sense." f He fails, however, to convince more competent critics than the present writer,:]: so I conclude with them that as yet we have no decisive grounds for locating muscular and cutaneous feeling apart.

Much still remains to be learned about the relations between musculo-cutaneous sensibility and the cortex, but one thing is certain: that neither the occipital, the forward frontal, nor the temporal lobes seem to have anything essential to do with it in man. It is knit up with the performances of the motor zone and of the convolutions backwards and midtvards of them. The reader must remember this conclusion when we come tc the chapter on the Will.

I must add a word about the connection of aphasia with the tactile sense. On p. 40 I spoke of those cases in which the patient can write but not read his own writ ing. He cannot read by his eyes ; but he can read by the feeling in his fingers, if he retrace the letters in the air. It is convenient for such a patient to have a pen in hand whilst reading in this way, in order to make the usual feel ing of writing more complete.* In such a case we must suppose that the path between the optical and the graphic centres remains open, whilst that between the optical and the auditory and articulatory centres is closed. Only thus can we understand how the look of the writing should fail to suggest the sound of the words to the patient's mind, whilst it still suggests the proper movements of graphic imitation. These movements in their turn must of course be felt, and the feeling of them must be associated with the centres for hearing and pronouncing the words. The injury in cases like this where very special combinations fail, whilst others go on as usual, must always be supposed to be of the nature of increased resistance to the passage of certain currents of association. If any of the elements of mental function were destroyed the incapacity would necessarily be much more formidable. A patient who can both read and write with his fingers most likely uses an identical ' graphic ' centre, at once sensory and motor, for both operations.

I have now given, as far as the nature of this book will allow, a complete account of the present state of the locali zation-question. In its main outlines it stands firm, though much has still to be discovered. The anterior frontal lobes, for example, so far as is yet known, have no definite functions. G-oltz finds that dogs bereft of them both are incessantly in motion, and excitable by every small stimulus. They are kascible and amative in an extraordinary degree, and their sides grow bare with perpetual reflex scratching ; but they show no local troubles of either motion or sensibility. In monkeys not even this lack of inhibitory ability is shown, and neither stimulation nor excision of the prefrontal lobes produces any symptoms whatever. One monkey of Horsley and Schaefer's was as tame, and did certain tricks as well after as before the operation.* It is probable that we have about reached the limits of what can be learned about brainfunctions from vivisecting inferior animals, and that we must hereafter look more exclusively to human pathology for light. The existence of separate speech and writing centres in the left hemisphere in man ; the fact that palsy from cortical injury is so much more complete and endur ing in man and the monkey than in dogs ; and the farther fact that it seems more difficult to get complete sensorial blindness from cortical ablations in the lower animals than in man, all show that functions get more specially local ized as evolution goes on. In birds localization seems hardly to exist, and in rodents it is much less conspicuous than in carnivora. Even for man, however, Munk's way of mapping out the cortex into absolute areas within which only one movement or sensation is represented is surely false. The truth seems to be rather that, although there is a correspondence of certain regions of the brain to certain regions of the body, yet the several parts within each bodily region are represented throughout the whole of the corre sponding brain-region like pepper and salt sprinkled from the same caster. This, however, does not prevent each ' part ' from having its focus at one spot within the brainregion. The various brain-regions merge into each other in the same mixed way. As Mr.

Horsley says : " There are border centres, and the area of representation of the face merges into that for the representation of the upper limb. If there was a focal lesion at that point, you would have the movements of these two parts starting together." f f Trans, of Congress of Am. Phys. and Surg. 1888, vol. i. p. 343. Beevor and Horsley's paper on electric stimulation of the monkey's bruin is the most beautiful work yet done for precision. See Phil. Trans., vol. 179, p. 205, especially the plates.

I am speaking now of localiza tions breadthwise over the brainsurface. It is conceivable that there might be also localizations depthwise through the cortex. The more superficial cells are smaller, the deepest layer of them is large ; and it has been suggested that the superficial cells are sensorial, the deeper ones motor ;f or that the superficial ones in the motor region are correlated with the extremities of the organs to be moved (fingers, etc.), the deeper ones with the more central segments (wrist, elbow, etc.). J It need hardly be said that all such theories are as yet but guesses.

We thus see that the postulate of Meynert and Jackson which we started with en p. 30 is on the whole most satisfactorily corroborated by subsequent objective research. The highest centres do probably FIG. 21. -Dog's motor centres, right contain nothing but arrangements —The points of the motor region for representing impressions and mnscies: the loops with the orbimovements, and other arrangements crosses twith the flexor, the crosses for coupling the activity O/ these

tensor, digitorum communis of arrangements together. § Currents the extensor communis of the first excite some arrangements, f By Lays in his generally preposterous book ' The Brain' ; also by Horsley. § The frontal lobes as yet remain a puzzle. Wundt tries to explain them as an organ of 'apperception' (Grundzuge d. Pbysiologischen Psychologic, 3d ed.. vol. i. p. 233 If.), but 1 confess myself unable to appre hend clearly the Wundtian philosophy so far as this word enters into it. se must be contented with this bare reference.— Until quite recently it wae

which in turn excite others, until at last a motor discharge downwards of some sort occurs. When this is once clearly grasped there remains little ground for keeping up that old controversy about the motor zone, as to whether it is in reality motor or sensitive. The whole cortex, inasmuch as currents run through it, is both. All the currents probably have feelings going with them, and sooner or later bring movements about. In one aspect, then, every centre is afferent, in another efferent, even the motor cells of the spinal cord having these two aspects insepara bly conjoined. Marique,* and Exner and Panethf have shown that by cutting round a ' motor ' centre and so sepa rating it from the influence of the rest of the cortex, the same disorders are produced as by cutting it out, so that really it is only the mouth of the funnel, as it were, through which the stream of innervation, starting from else where, pours ; J consciousness accompanying the stream, and being mainly of things seen if the stream is strongest occipitally, of things heard if it is strongest temporally, of things felt, etc., if the stream occupies most intensely the 'motor zone.' It seems to me that some broad and vague formulation like this is as much as we can safely venture on in the present state of science ; and in subsequent chapters I expect to give confirmatory reasons for my view.