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fail to awaken the idea of their sound, or of the movement for pronouncing them. We ought, in short, to have alexia, or inability to read; and this is just what we do have as a complication of aphasic disease in many cases of extensive injury about the fronto-temporal regions.
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 interesting way how numerous are the incoming paths which all end by running out of the brain through the channel of speech.
eye-path be closed.
The hand-path is open, though the 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 disorder can only come from extensive brain-injury.
The centre for hearing is situated in man in the upper convolution of the temporal lobe (see the part marked Wernicke' in Fig. 44). The phenomena of aphasia show this. We studied motor aphasia a few pages back; we must now consider sensory aphasia. Our knowledge of aphasia 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. In the seven cases of pure 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. leftbrained, 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 most of us (as Wernicke said) speech must go on from auditory cues; that is, our visual, tactile, and other ideas probably 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 destruction 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 vision, touch, etc., without leaning on the auditory region. It is the minuter analysis of such individual differences as these which constitutes Charcot's contribution towards clearing up the subject.
Every namable thing has numerous properties, qualities, or aspects. In our minds the properties together with the name form an associated group. If different parts of the brain are severally concerned 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 connection amongst all these brainparts that the activity of any one of them will be likely to
awaken the activity of all the rest. When we are talking whilst we think, the ultimate process is utterance. If the brain-part for that be injured, speech is impossible or disorderly, even though all the other brain-parts be intact: and this is just the condition of things which, on p. 109, we found to be brought about by lesion of the convolution of Broca. 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 is, as aforesaid, 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's mind the look of an object or the look of its name be what habitually precedes articulation, then the loss of the hearing centre will pro tanto not affect that individual's speech or reading. He will be mentally deaf, i.e. his understanding of the human voice will suffer, but he will not be aphasic. In this way it is possible to explain the seven cases of word-deafness without motor aphasia which figure in Dr. Starr's table.
If this order of association be ingrained and habitual in that individual, injury to his visual centres will make him not only word-blind, 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 convolutions under which those fibres pass which connect the visual centres with the rest of the brain (see Fig. 47, p. 116). With this result Dr. Starr's analysis of purely sensory cases agrees.
In the chapter on Imagination we shall return to these differences in the sensory spheres of 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. There is no organ' of Speech in the brain any more than there is a faculty' of Speech in the mind. The entire mind and the entire brain are more or less at work in a
man who uses language. The subjoined diagram, from Ross, shows the four parts most vitally concerned, and, in the light of our text, needs no farther explanation (see Fig. 48, p. 117).
Centres for Smell, Taste, and Touch.-The other sensory centres are less definitely made out. Of smell and taste I will say nothing; and of muscular and cutaneous feeling only this, that it seems most probably seated in the motor zone, and possibly in the convolutions immediately backwards and midwards thereof. The incoming tactile currents must enter the cells of this region by one set of fibres, and the discharges leave them by another, but of these refinements of anatomy we at present know nothing.
Conclusion. We thus see the postulate of Meynert and Jackson, with which we started on p. 105, to be on the whole most satisfactorily corroborated by objective research. The highest centres do probably contain nothing but arrange
FIG. 48.-A is the auditory centre, the visual, W the writing, and E that for speech.
ments for representing impressions and movements, and other arrangements for coupling the activity of these arrangements together. Currents pouring in from the senseorgans first excite some arrangements, which in turn excite others, until at last a discharge downwards of some sort. occurs. When this is once clearly grasped there remains little ground for asking whether the motor zone is exclusively motor, or sensitive as well. The whole cortex, inasmuch as