APPENDIX.

THE following is an abstract of Professor Ferrier's recent experiments upon the functions of the brain, by means of electricity, abbreviated from a report published by him in the "Journal for Anatomy and Physiology."

The first experiments recorded have special reference to the production of epileptic convulsions; and the mode in which the attacks begin and the march of the convulsive spasms are accurately recorded. All the animals were under the influence of chloroform.

It is found that in rabbits, cats, and dogs, the application of the electrodes for a few seconds induced almost immediately, or, on some occasions, after the lapse of a distinct interval, violent epileptic convulsions of one side. When the electrodes were applied, one at the anterior and the other at the posterior part of the hemisphere, the convulsions were complete and violent in the whole of the opposite side of the body. As a rule, they commenced in the face, spread to the neck and upper extremity, and then invaded the hind-leg and tail. Dilation of the pupil, spasms of the jaws, foaming at the mouth, and loss of consciousness, were induced when the fits were at their greatest intensity.

Occasionally the spasmodic convulsions remained localised in one or other limb, or in some one muscle or group of muscles, and frequently, instead of an epileptic attack, a series of twitches alone were manifested.

The paper contains the chief results of a research commenced with a view to test the accuracy of the views entertained by Dr. Hughlings Jackson on epilepsy and St. Vitus' dance. Dr. Jackson regards convulsions affecting one side only as dependent on lesions of the convolutions of a certain part of the brain. In order to put this theory to the proof, the author determined to expose the brain in various animals, and apply irritation to the surface.

The method of irritation was suggested by the experiments of Tritsch and Hitzig, who had shown that contractions of definite groups of muscles could be caused in dogs by passing galvanic currents through certain portions of the anterior regions of the brain.

The progress of the research ultimately led to the endeavour to establish the localisation of cerebral function, not merely as regards motion, but also as regards sensation and the other faculties of the mind.

The method of experimentation which the author has adopted is to place the animal under chloroform, and gradually expose the surface of the brain, by removal of the skull. In this way he has been able to expose the

whole hemisphere.

After removal of the membranous

coat, the points of blunted electrodes in connection with a Du Bois Raymond's coil are applied to the surface of the brain, without injury to the outer grey substance.

The march of the spasms is shown to be quite in accordance with the bedside observations of Dr. Hughlings Jackson in cases of epilepsy of one side in man. Peculiar variations in the mode in which the attacks commenced, depending apparently on the position of the electrodes on the surface of the brain, led the author to approximate the electrodes, and to apply very limited irritation, in order to discover whether the convulsive spasms were not due to over-violent irritation of localized centres in the brain, whose special function is to govern and direct the action of these muscles for definite purposes, possibly such as might indicate volition and intelligence.

The results were such as to indicate, with a beautiful degree of exactness, the localization in certain definite and easily-defined regions, the cerebral centres for various apparently purposive combined movements of the muscles of the limbs, as well as of the tail, the facial muscles, and the muscles of the jaws and tongue. These are all situated in the anterior parts of the brain, and the individual centres are marked off in the various external convolutions.

The general plan is, that in the superior external con

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volutions, the various movements of the paws, legs, and tail, are centralized; and it is shown that the distinctness of these centres is, to a great extent, characteristic of the animal's habits; the centre for the fore-paw in cats being much more highly differentiated than in dogs and rabbits. The middle external convolutions direct movements of the eye-lids, face, and eyes; while the inferior govern various movements of the whiskers, angles of the mouth, depressors of the lower jaw, and tongue.

From other convolutions, when irritated, certain movements are described as resulting, viz., of the ears, eyes, etc. In the paper as yet published, no attempt is made to explain the signification of these; but the author stated at the meeting of the British Association, that, from his later experiments, he had been able to obtain indications of the situation in these regions of the centres of special sense, sight, hearing, and smell. These results and conclusions are, however, not as yet detailed fully. The author indicates, in a note in the paper published in the West Riding Reports, that he had at that time explored the brain of the monkey, and satisfactorily localized the regions and centres corresponding to those already discovered in the brain of the cat, rabbit, and dog.

One of the more important conclusions drawn from the experiments is, that the region which governs the move

ments of the mouth and tongue in cats and dogs corresponds to that which is known as Broca's convolution in man, and which governs the power of speech: viz., the posterior part of the inferior frontal. This, it may be stated, is further borne out by experiments on monkeys.

The pathology of aphasia, or speechlessness, is thus rendered comparatively simple. The memory of words is situated in that part of the brain which governs the movements of articulation. It is shown, however, by the experiments, that the brain is symmetrical, and that the corresponding part of each hemisphere produces exactly the same effects on opposite sides of the body. Generally the action is on one side only, and that the opposite one; but as regards the mouth, the action is almost bilateral, and hence disease of one or other side alone does not cause paralysis of the articulating muscles, because the other side is able to govern as before. The occurrence of loss of speech with lesion of the left side, is attributed to the fact that most people are left brained; and that, therefore, a lesion of the left side causes such an interference with the voluntary recalling of words, that the person is speechless, not because memory of words is utterly lost, as this exists in the undamaged side, but because he is unable to lay hold of the word he wishes to express. With the education of the other side, however, the individual recovers the power of speech. During the interval