were: (1) That an excitation of certain parts containing the supposed centers produces effects in harmony with the function they are considered as being endowed with. (2) That a destructive alteration or the ablation of a supposed center is followed by loss of the function admitted to belong to it.

Unfortunately for the doctrine I reject, a great many facts show that these two supposed proofs must be put aside as worthless. The first one is annulled by a large number of experiments and clinical cases establishing that most various effects can be produced by an irritation of one and the same part of the encephalon, and, besides, that identical effects can arise from an irritation in widely different parts of the brain. As regards the second of the grounds of the doctrine of cluster-localizations, it would be decisive if, in every instance of complete destruction of a supposed functional center, there was a loss of the action of that part. But there are experimental and clinical facts showing that each part of the brain can be destroyed without any cessation of function. Even the most ardent of the believers in cluster-localizations, Dr. David Ferrier, has been compelled to recognize that I have demonstrated the above points, at least so far as regards clinical cases. *

Nothing is more natural than to conclude that, if a function ceases more or less suddenly, at the time of the destruction or removal of a part of the brain, this is owing to the fact that the power of performing that function existed in that part. But, natural or not, this kind of reasoning loses all value when we know that a function can disappear without any organic alteration of the nervous elements in which it was located, and in consequence of an irritation coming from a more or less distant part of the nervous system. This effect is then due to a mere dynamical change taking place by inhibition. Every cerebral function can vanish in that way, through an act of inhibition, caused by an irritation due to worms in the bowels. A great many facts have led me to the conclusion that it is by a mechanism similar to that which exists when intestinal worms cause paralysis, insanity, loss of sight, deafness, etc., that organic lesions of the brain produce analogous effects. The only difference *The Functions of the Brain," 2d ed. p. 377.

between the encephalon and the intestinal nerves, as regards the production of these losses of function or other effect, is, that the great intracranial center causes them far more frequently than these nerves.

There is no doubt that every destruction or removal of a part, however small, of brain tissue takes away contributors to several or to many functions; but the nervous elements remaining are evidently sufficient for the performance of these functions.

II. The mental and physical functions of the brain I propose to study as regards their localization are the following: 1, Intelligence; 2, Consciousness; 3, The faculties of expressing ideas by speech, writing, and gesture; 4, Memory; 5, Vision, audition, olfaction, taste, touch, and the common kinds of general sensibility; 6, Muscular sense; 7, Voluntary movements; 8, Respiratory movements; 9, Deglutition.

III. Are all those functions exclusively located in the encephalon? This is the admitted view. It would be out of place here to discuss the question at length. I will merely say, that nothing proves that no perception of sensation takes place in the spinal cord, and that voluntary movements cannot arise from that nervous center. When we think that the brain receives the incitations to action from the organs of sense, and that the spinal cord, separated from the encephalon, is deprived of all communications with the senses; when we think, also, that the brain, being the seat of intelligence, consciousness, and memory, requires so much education to perform voluntary movements; is it not natural that the spinal cord, even if endowed with a kind of will power, does not show it when separated from the encephalon? What we know is, simply, that animals deprived of the whole intracranial nervous mass, and anencephalous human monsters, have no spontaneous movement, and only show reflex actions.

IV. It is almost universally admitted that each lateral half of the brain, i. e., each cerebral hemisphere, contains the centers for the opposite side of the body as regards voluntary movements and the perception of the various impressions coming from the organs of sense and all sensitive parts. I have shown

by a large number of facts that this localization is erroneous. In reality we have two full brains, as each hemisphere is endowed with all the powers we believe to exist in the two cerebral halves. It is now recognized that one half of the cerebrum is enough for all intellectual functions; but facts show that this is the case also for the power of speech (notwithstanding what is so often seen in cases of aphasia), and for all the motor, sensorial, and sensitive functions. The fact that a paralysis of movement or the loss of feeling will almost invariably appear in parts of the body on the opposite side to that of a brain lesion, does not prove, as will be shown hereafter, that the generally admitted view is correct. The same mechanism which may make the intelligence or the memory disappear when a lesion exists in one half of the brain, may also produce a loss of voluntary movements or a loss of feeling in cases of a unilateral cerebral lesion. In many animals the extirpation of one half of the brain, after having temporarily produced symptoms of paralysis, shows that all cerebral functions can exist as if nothing were missing. There are cases of destruction of one half of the cerebrum in man showing also the same thing. I will later on revert to the subject of duality of the brain in regard to volition and sensation.

V. It is extremely probable that the mental faculties, and especially the intellect, are chiefly located in the convolutions of the brain. If a high forehead, which implies a rather large development of the frontal cerebral lobes, generally coexists with somewhat more than an average degree of intelligence, we know that great mental powers have existed in men whose forehead and frontal lobes were not large. Still more, some physiol ogists have tried to show that the location of intelligence and of the other mental faculties is chiefly in the posterior parts of the brain. In this, as with the other functions of the encephalon, the powers are located in elements scattered through the gray matter of the various parts of the cerebrum, and chiefly in the convolutions. In this view I am in perfect agreement with many physiologists, and especially with Professor Vulpian.

VI. What is the seat of consciousness? No better proof can be given that we ought not to believe that a certain function belongs to a certain part simply from the fact that a lesion of

that part destroys that function, than the following peculiarities relating to a loss of consciousness: (1) A lesion, and sometimes a very extensive one, can exist in any part of the brain without loss of consciousness; indeed, in that respect the destruction of considerable portions of the two hemispheres can exist without the least diminution of consciousness. (2) On the contrary, any lesion, however small, can produce an immediate loss of consciousness.

A great many facts show that the loss of consciousness in cases of cerebral lesions depends on an act of inhibition caused by an irritation which has started from the neighborhood of the lesion. This we clearly see in one of the most remarkable experiments that can be made on the nervous centers. It consists in pricking with a fine needle a part of the medulla oblongata, called the "nib of the calamus." I have found that sometimes, then, the animal drops down suddenly, having irrevocably lost every power of the brain, i. e., consciousness (and, of course, every mental faculty), instinct, sensibility, the sensorial functions, and the respiratory power. This is the way bulls are sometimes killed by Spanish toreadors. I mention this experiment because it shows, more than any other fact, how immense is the power of inhibition to produce loss of function.

VII. Speech, like all voluntary actions, is a complex of at least two distinct things, one mechanical and the other mental. The center of the mechanical power of speech, according to some physiologists, is located side by side, if not fused with, the seat of the faculty of expressing ideas by speech. This view cannot be accepted, because, even in cases of genuine and complete aphasia (loss of the mental faculty of speech), it is very frequent that some words, or at least one or two, can be perfectly articulated. I have seen aphasic patients who, while trying to speak, uttered pretty well a word or two (always the same, as usual in such cases); but who also could distinctly utter a great many words in dreams, in delirium, or in singing. The power of articulation of words is frequently lost without aphasia, and if we were to decide, from a large number of cases, what is the location of that power, we should say that it occupies different parts in different individuals, and that its seat can be almost

anywhere. On the other hand, as we find cases of destructive disease in any part of the cerebrum, and in most parts of the base of the brain, without alterations in mechanical speech, we should have to conclude that that muscular power has no center in the cerebral lobes, and that such a center exists only in some parts of the base of the brain.

As regards the faculty of expressing ideas by speech, I have shown, especially in 1861 and 1877, that the view that that mental power is located in a small part of the brain is in absolute opposition to a great many facts. The idea that the mental faculty of speech belongs to the left side of the brain in righthanded, and to the right side in left-handed persons, seems to be in harmony with many facts, but there are rebellious cases which protest against these views. I will merely say, that in a pretty large number of cases in which there was, in both sides of the cerebrum, complete destruction of all the parts considered as centers of mental speech, there was no aphasia. As regards the location of that power, there are many facts which are in perfect harmony with Broca's supposition that it is in a part of the third frontal convolution, in the left cerebral hemisphere; but there are also many facts favorable to the view of Meynert and Sanders, who have located that faculty in another part, the insula. If we make use only of cases in which disease was entirely limited either to Broca's supposed center or to the insula, it is clear that one of these two sets of cases positively proves against the conclusion drawn from the other, Meynert's view being disproved by Broca's facts, and Broca's view by Meynert's facts. Besides, according to a number of cases, every part of the left side of the brain might be looked upon as containing the centers of mental speech, as in these cases there was aphasia allied with disease of either of these parts. The truth is, that aphasia is due to the propagation of an irritation arising from the diseased place, or round it, going to the cells endowed with the mental power of speech, and stopping their activity by inhibition. These cells must be scattered in most parts of the two hemispheres, as we find that considerable destruction can exist in either of them or in both without aphasia.

VIII. Very interesting facts have been published, especially