within the last ten years, illustrating two peculiar kinds of mental alteration often allied with aphasia. One is known as "word blindness," the other as "word deafness." Individuals not blind at all, and perfectly able to see printed or written words, and even sometimes to copy them, may be absolutely unable to understand the meaning of any word placed under their eyes, and, what is still more strange, they can write what is dictated to them. Believers in cluster-localizations have placed the center then affected in the sphenoidal lobe. I will only say, that in many cases of destruction of that lateral part of a cerebral hemisphere there was no loss of the power of understanding words seen, and that in some cases of loss of that faculty there was a lesion in other parts. What I have said of word blindness I can say of word deafness, which consists in a lack of power of understanding words heard. As regards the localization of the power of understanding spoken words, it has been supposed to be nearly the same as that of the faculty of understanding words seen. There are similar reasons for rejecting both these localizations.

IX. I will say only a few words of the power of expressing ideas by writing. The loss of this faculty, which is called agraphia,” very rarely exists without the loss of mental speech, ie., aphasia. All I have said about aphasia and the center for the expression of ideas by speech is true for agraphia and the mental center for writing.

X. No special localization has been assigned to memory. If I were to commit the ordinary fault of cluster-localizers, I should say that the seat of memory is in the cerebellum, as I have found this faculty altered in many cases of disease of that nervous center; but the truth is, that a lesion almost anywhere in the brain can destroy memory, and, on the other hand, a lesion in any part of the encephalon can exist without the loss of that faculty. The conclusion is that, like other cerebral faculties, memory has its localization in cells widely spread in a great many parts of the encephalon.

XI. The localization of centers of sensorial perceptions has been the object of widely different opinions. The center for vision, which has been considered as located in the tubercula quadrigemina or in the optic thalami, is now supposed to be in

the convolutions of the occipital lobes, according to Munk and Schaefer, or in both the parietal and the occipital lobes, according to Ferrier. There are stubborn facts against all the views proposed. I will briefly mention two sets of them. In the first place, there are cases in which amaurosis, i. e., loss of sight, has been produced by disease elsewhere than in the various parts which have been supposed to be the centers of vision. In the second place, there are cases of destruction of either of these parts without loss of vision. Many facts, besides, show that one half of the brain is sufficient for perfect perception of visual impressions coming from the two eyes. No cluster-localization exists for either of the other higher senses.

XII. As regards the sense of touch and the power of perceiving painful impressions, the demonstrations I have given. are quite decisive against the views of cluster-localizers. For a long time the optic thalami had been considered as the seat of perception of the various sensitive impressions. Meynert's opinion, grounded chiefly on anatomical facts, is that the center for touch and pain is in the occipital lobes. Ferrier has tried to show that the cluster-localization for common and tactile impressions is in the falciform lobe, a part of the under surface of the brain. Other physiologists have tried to show that that center is, on the contrary, at the top of the cerebrum, where the centers for volitional movements are located. There are plenty of decisive facts against any cluster-localization as regards the center of common and tactile perceptions.

Some experiments of mine decisively show that the various views concerning the channel of transmission of sensitive impressions in the brain must all be rejected. I will mention only one fact, relating to a part where, exceptionally, almost all physiologists agree that all the conductors for sensitive impressions have to pass; it is called "internal capsule." This part, on the right side, is supposed to convey the impressions coming from the left side of the body, while the left capsule conveys the impressions from the right side of the body. Let us suppose that a complete loss of feeling has been caused in the right limbs of an animal by a section of the left internal capsule. This being ascertained, I divide the right half of the spinal cord in the

dorsal region, and I find that the right posterior limb, which was anæsthetic, becomes more sensitive than in the normal state, while the left posterior limb becomes anæsthetic. It is clear that if anæsthesia, as believed by cluster-localizers, existed in the right posterior limb after the first lesion, on account of the section of all the conductors bringing to the brain the sensitive impressions made on that limb, the second lesion could not have had the least power of reproducing sensibility in that limb. This experiment shows, first, that the localization of conductors for sensibility in the internal capsule is wrong; secondly, that each hemisphere of the brain is endowed with the perception of sensitive impressions coming from the two sides of the body.

A large number of facts show that every part of the encephalon can cause anaesthesia, and that, on the other hand, each part may be destroyed without the appearance of anesthesia. It is clear, therefore, that there is no cluster-localization, and that nerve-cells endowed with the power of perception of sensations are scattered in many parts, each cerebral hemisphere being sufficient for the two sides of the body.

XIII. Since the discovery made by Fritsch and Hitzig, that there are parts of the surface of the brain which, being galvanized, give rise to certain movements of the face, the eye, the neck, the limbs, on the opposite side, many physiologists, and most medical men, have accepted the conclusions of these experimenters, or rather the nearly similar views put forward by David Ferrier. Clinical facts, and especially those published by my former assistant, who has acquired a well-deserved eminence, Dr. J. H. Jackson, and by my illustrious friend, Professor Charcot, have given great weight to the supposition that in a small part of the surface of the brain there are centers for the movements of the face and of the arm. Some other clusterlocalizers-Ferrier, Horoley, Beevor-have tried to show where are the centers for the movements of the various parts of the legs and arms.

Many eminent physiologists-Schiff, Hermann, Goltz, Vulpian, and my pupils, Dr. E. Dupuy and Dr. Couty-have successfully fought against the cluster-localization for volitional movements. I will mention only a few of the arguments I have

employed against the supposed existence of psycho-motor centers in the parts known as ascending frontal and parietal convolutions. The admitted doctrine is, that volition, acting in these parts in the left hemisphere, sends a nervous current which descends to the lowest part of the encephalon, where it passes into the right side, and thence, through the spinal cord and nerves, goes to the muscles of the right side which are to be moved. This is proved absolutely false by experiments I have made a great many times. I will mention only one set of experiments. I divide transversely the whole half of the base of the brain, either at the level of the medulla oblongata, or of the pons varolii, or of the crura cerebri, or of the internal capsule, and I find that galvanization of the so-called psycho-motor centers on the side of the section produces more powerful and extensive movements than before this operation in the limbs on the other side; while, if the views of cluster-localizers were right, no movement at all should occur.

Clinical facts are decisive, also, against these views. They show, first, that a destructive lesion anywhere can exist without paralysis; secondly, that a lesion anywhere can produce paralysis; thirdly, that paralysis may appear only in a limited part of one side of the body from a lesion having destroyed the whole of the so-called psycho-motor centers; fourthly, that a paralysis of every part of the body on one side may appear from a lesion limited to a small part of the psycho-motor zone.

A great many quite as decisive facts could be mentioned if room allowed. It is clear from this criticism that we are not to consider paralysis, in cases of organic brain disease, as being a direct effect of destruction of cerebral tissue. The doctrine held in this essay as regards the production of loss of function of any kind in the brain is perhaps more fully demonstrated for paralysis and anesthesia than for any other cessation of function. The cells endowed with the power of producing volitional movements are of two kinds. One set of them, used in the mental part of such an action, are chiefly, if not exclusively, disseminated through the cerebrum; and the other set, used in putting in play nerves and muscles for a movement, are located in the base of the brain and the spinal cord. Paralysis appears through an

act of inhibition of either one or the other of these sets, or of both. The great function of volitional movements is, therefore, spread about in the encephalon, each half of which is sufficient for the performance of that function in both sides of the body.

XIV. Of all localizations of function in the brain none has ever been so completely and so universally admitted, and none, also, has been so generally abandoned, as that of the power of breathing in the medulla oblongata. The same arguments that I have employed against all other cluster-localizations in the brain, I made use of long ago against the location of the respiratory power in a part of the medulla. On the one hand, irritations in a good part of the encephalon, especially the base and the cerebellum and also in the spinal cord, can inhibit breathing at once. On the other hand, breathing may persist even after the destruction of the whole encephalon and even of a part of the cervical spinal cord. The nervous center for respiratory movements belongs to cells diffused in the base of the brain (including the whole medulla) and in the upper part of the spinal cord.

XV. Most physiologists are now gradually giving up the strict cluster-localizations which have been for many years accepted by them. Being little inclined to recognize that they had been misled or have made mistakes, they try to escape in supposing that if a function does not disappear when its pretended center is destroyed, it is owing to the fact that other parts of the brain are able to perform that function. In the same way they explain that if speech, sensibility, volitional movements, return, after having been lost, owing to a local lesion in one hemisphere, this is due to the fact that the other hemisphere acts in place of the diseased one. That such may be the case, in a measure, I do not deny; but what I consider as true and established is, first, that the various mental and physical functions of the brain are localized in nerve cells so arranged that those employed for the same function, instead of being agglomerated together, are scattered about in many parts; secondly, that each half of the brain contains centers for all the cerebral functions, physical or mental.

C. E. BROWN-SÉQUARD.