(3) Degeneration, whether of centrifugal or centripetal nature. (4) Anatomical examination of the calcarine cortex.

But it is not in accordance with the results of physiological experiments on animals.

The accurate limitation of the cortical visual centre is of great moment as determining the importance of the rest of the parietal and occipital cortex.

The next aim will be to solve this problem.

The destruction of the bulbs, or of the external geniculate body will produce changes in the rest of the occipital and parietal cortex but not so great as in the calcarine fissure.

Also Soul-blindness (Seelenblindheit), word-blindness, and the existence of unilateral hallucinations support the supposition of a connexion between the eye and the other occipital and angular cortex and of the necessity of this portion to visual representations.

Professor DAVID FERRIER, F.R.S., of London, remarked:

Professor Henschen's localisation of the visual centre in the calcarine fissure being founded only on an analysis of clinical and pathological record, however elaborate, cannot be regarded as founded on altogether satisfactory data. The facts of human pathology are much too complex to permit of their being made the basis, by themselves, of the exact delimitation of any cortical centre. They are a valuable test of the accuracy of the results of the experimental method, but cannot be safely relied on alone. There is no doubt that most of the cases of enduring hemianopsy from apparently cortical diseases have been found in connection with lesions invading the visual surface of the occipital lobe. But this is in my opinion due to the fact that lesions in this region are specially apt to implicate the whole stem of the optic radiations, and not because this region has, more than the rest of the occipital lobe, a special relation to vision. Unless the brain of man is constructed on a totally different type from that of the monkey, it is certain, both from the result of experimental excitation and destruction, that the visual area of the cortex includes, not only the visual surface of the occipital lobe, but also the convex surface, as well as part (Schäfer), or, according to my own observation, the whole, of the angular gyrus.

Professor HENSCHEN replied:

Mr. Ferrier cannot agree with the conclusions I have reached respecting the localisation and limitation of the visual centre; and he supposes that the result would be different and more in agreement with the results obtained by his experiments upon animals, if only the necessary

consideration were given to the circumstance that in some cases of hemianopsia the lesion is only cortical, wheareas in others it enters into the medulla. I quite agree with Mr. Ferrier that it is necessary by postmortem examination of the cases of hemianopsia to investigate how deep the lesion is; but I maintain that the authors who have localised the visual centre in the angular gyrus or in the outer surface of the occipital lobe have not examined the cases in this respect. In my work just published on the pathology of the brain I endeavoured to make a careful examination of every case from this point of view, and the result was that I was able to limit the visual centre to the cortex of the fissura calcarina. There are many cases of hemianopsia with a lesion of the cortex of the angular gyrus or of the outer occipital surface, but in all these cases the lesion reached the fibres of the visual path which lie in the medulla of the respective lobes. I am convinced that Mr. Ferrier will be persuaded, if he will have the kindness to examine my work, that I have followed the above rule in all cases.

Professor VICTOR HORSLEY, F.R.S., of London, read a paper On some points of Psychological Interest in the Cerebral Localisation of Function.

The first question included the degree to which function of movement is limited by circumscribed boundaries to certain points in the superficies of the cortex. The previous experiments of Paneth and of Marigny in which certain centres in the cortex were circumscribed by an incision and so separated from the neighbouring and closely allied centres seem to show that a certain degree of independence exists. A further point also in harmony with this view is the so-called march of the epileptic spasm, this suggesting not only the spread of nerve impulses from one centre to another, but also that unless successive points in the cerebral cortex were excited definite parts of the body would be omitted from taking part in the fit. This same point has also been discussed by Professor Hitzig. The next class of experiments bearing upon this subject are those by Beevor and myself which show that in certain regions minimal excitation of certain points in the cortex produces movements of only one limited part of the body. Further, the electrical experiments of Gotch and myself seemed to show that so far as the course differentiation of the representation of the movements of the limbs is concerned the demarcation was sharp. Finally, as confirmatory of these

facts, we have those rough data which can be drawn from clinical observation. Against all these facts are the very weighty philosophical arguments of Dr. Jackson who considers that from the evolutionary standpoint each and every part of the body must be represented in any one unit of the cerebral cortex. I think it must be conceded by all psychologists that Dr. Jackson's position has not yet been shaken. I would submit for consideration that the method of excitation is not, with our present means, capable of answering the question, since it is quite possible that a very limited degree of representation at a given point may be completely swamped by movements which happen to be more extensively represented therein.

The importance of this subject makes it, I think, worthy of the attention of investigators so that the devising of some new method of investigation might result in solving the problem; and considering that such solution is necessary for the full comprehension both of the sub-stratum of the voluntary act and of the chief features of an epileptic convulsion it does not require more words from me to impress the matter upon this Congress.

I will therefore turn to the next point upon which I hope to raise profitable discussion: that is the representation of sensation in the so-called motor region. English psychologists are familiar with the view taken by Professor Ferrier, that there is no representation of sensation whatever in the so-called motor cortex. In a few experiments which Professor Schäfer and myself made, and in which certain portions of the psychical surface of the brain were removed, we did not succeed in determining, with the means we employed, that there was any affection of sensibility in the parts which were paralysed. These observations were contested experimentally by Luciani, and I have now no doubt with complete accuracy. I have caused careful investigations to be made in clinical cases where certain portions of the socalled motor cortex have had to be removed for disease, and where there has been no involvement of other parts of the brain constituting so-called sensory centres. I have tested such cases in a very special manner for tactile sensibility, temperature sensation, localisation of touch, sense of position, and sense of movement, and have found that each of these is affected in proportion to the amount of brain substance that is destroyed, and therefore, usually, in proportion to the amount of paralysis of movement. I say usually because the complex conditions which sees clinically often include cases in which the outgoing

one

channels are affected more than the ingoing or the cortical substance. Under these circumstances therefore the paralysis of movement is in greater excess than the anaesthesia. I have stated succinctly these points in a paper in the Nineteenth Century. I wish now to mention that in proof of my contention it will be found that the affection of sensation is limited to the same sections of the body as the paralysis of movement.

To sum up, I wish to take this opportunity of acknowledging that the views I am now enunciating, on which I have collected and published evidence, are but the vindication and confirmation of the wonderful researches made by our chairman in conjunction with Professor Fritsch.

Dr. W. B. RANSOM, M.A., of Nottingham, read a paper on

A Case illustrating Kinesthesis.

In a case of Epilepsy the convulsions of which began by tingling and spasm in the left hand, the following permanent adnormal conditions obtained in that hand:

Operation showed a cyst compressing the Cortical Centre for the left hand: After recovery from the operation this area was faradized by electrodes inserted through the scalp, without an anæsthetic.

The chief results obtained were

(1) Contraction of groups of muscles in arm and hand by a moderate current.

(2) The production of a sensation in those parts when a weaker current was used, contraction being added as the current was strengthened.

(3) Improvement in the muscular sense during and after stimulation.

(4) Weakening of voluntary motor power after a strong induced contraction.

The case is of interest as bearing upon the question whether the so-called "motor centres of the cerebral cortex are limited in their action solely to the initiating of voluntary motor pro

cesses, as Dr. Ferrier has suggested, or whether they are themselves also directly connected with afferent or sensory processes as is maintained by Dr. Bastian.

The facts observed, in the author's opinion, tend rather to support the latter view.

Professor FERRIER, remarked:

I have listened with much attention to the interesting communications which have been made by Mr. Horsley and Dr. Ransom, and desire to make a few remarks on one only of the points which Mr. Horsley has brought up for consideration, viz.-The localisation of the sensations accompanying the act of movement.

Whatever meaning we may attach to the term muscular sense, everyone admits that the act of movement is associated with certain sensations or states of consciousness which constitute the sense of movement. These sensations are, in normal or physiological conditions, an invariable concomitant of the movement, whether this be carried out actively by the individual himself, or passively communicated to his limbs by others. But though the association between movement and the sense of movement is physiologically constant and invariable, yet in pathological conditions the two may be absolutely dissociated from each other, so that on the one hand the volitional movement may be effected without any sense of movement, and on the other hand a correct sense of the range and quality of the movement passively communicated to a limb may be experienced when the individual has entirely lost all power of moving it volitionally. Examples of the first condition are met with in certain forms of spinal disease, and, in hemianæsthesia of organic or functional origin, and the second condition is illustrated daily in motor hemiplegia, due to cerebral disease. These facts prove that the tracts of sensation are functionally and anatomically distinct from those of motion, so that the one may be destroyed while the other remains intact. The question then arises whether the tracts which have remained separate as far as the cerebral cortex become fused together in the cortex itself, or are distributed to separate regions.

It is maintained by some that these actually coalesce, and that the so-called motor centres of the cortex are at the same time the centres of perception of the sensations which accompany the act of movement and of common sensation in general. There are in my opinion insuperable objections to this view on theoretical, experimental and clinical grounds. My own experiments on the hippocampal region, supplemented and extended by those of Horsley and Schäfer on the gyrus fornicatus, have shown that, in monkeys at least, the falciform lobe is the centre of common sensibility apparently in all its forms. For when this is destroyed, the phenomena are such as to indicate entire loss of perception of tactile,