of arsenic-eating, which it is stated is carried on extensively in Styria? Indeed we are given to understand that in Styrian Arsenic Works the workman take arsenic with a view of escaping the poisonous effects of its fumes.

He (Dr. Marcet) observed finally that men and animals were not equally affected by poisons, a fact which it was important to bear in mind when experimenting with poisons on animals with the view of applying the results to mankind.-Lancet, No. 1,995, p. 499. [See also Langley, No. 45; Harley, No. 97; Yco, No. 172; Reynolds, No. 175; and Moore, 183.]

(127.)-1st. If I divide the posterior column and almost the whole of the lateral column of the spinal cord, with the posterior and central parts of the grey matter in the dorsal region in a guinea-pig, I find, when the animal has become epileptic, that the irritation of the part of the face and neck which I have called epileptogenous determines reflex convulsive movements everywhere, except in the posterior limb on the side of the injury. This lack of reflex movements is not due to a paralysis of the nerves serving to voluntary movements, as, if that limb is at first a little paralysed after the operation, it soon recovers power, and has no trace of weakness by the time epileptic fits can be provoked.

2nd. If only the posterior column and a very slight part of the grey matter, with a still slighter part of the lateral column of the apinal cord, is divided in a guinea-pig in the dorsal region, the four limbs are attacked with reflective convulsive movements when

the epileptogenous zone is irritated. In this case the encephalon communicates with the posterior limb on the side of the injury for both voluntary and reflected convulsive movements.

3rd. If in another animal the lesions mentioned in the preceding experiments have been made at the same level of the cord, one on the right side the other on the left side, I find that the two sides of the face and neck acquire the epileptogenous power, and that fits can therefore be produced by the irritation of either side, but whether the right or left side be irritated, there are reflected convulsive movements only in three limbs, the posterior one on the side where the lateral column of the cord is divided remaining without the least convulsion, while the three other limbs are violently convulsed. Both lower limbs, however, remain endowed with strong voluntary movements.

4th. In animals having had a complete section of a lateral half of the spinal cord at the level of the vertebra, and having become epileptic, I have ascertained that the voluntary movements after a period of very great diminution in the posterior limb on the side of the lesion, return gradually almost to the normal condition in a variable

LANE LIBRARY. STANFORD

number of months. In many guinea-pigs having recovered voluntary movements, even for a year or eighteen months, I have seen but very slight convulsions in the posterior limb on the side of the injury. Re-union of nerve-fibres serving to voluntary motor fibres can therefore take place to a very great extent in the spinal cord after having been divided, but there is hardly any re-union for the nerve-fibres which in attacks of epilepsy give rise to reflected convulsive movements.-C. E. Brown-Séquard, Lancet, No. 2,418, p. 2.

(128.)-Fortunately animals may not have any apparent diminution of either voluntary movements or sensibility after the exposure of the spinal cord to the air.-Idem, Lancet, No. 1,819, p. 28.

(129.) Before the operation in rabbits the most energetic pinching of the skin produces agitation but no shrieking; after the operation, on the contrary, the least pinching produces shrieking, and a much greater agitation. Sometimes the hyperesthesia is so considerable that the least pressure upon the skin makes the animal shriek. Whether the operation is performed on the lumbar, the dorsal, or the cervical region the phenomena are always the same; that is there is a manifest hyperesthesia in the various parts of the body which receive their nerves from the part of the spinal cord which is behind the section. It has been so in all the animals I have operated upon, and I have already made this experiment upon animals belonging to more than twenty species.

As long as the animals live after the section of the posterior columns, hyperesthesia continues to exist, except in the cases where re-union takes place between the two surfaces of the section; but hyperesthesia is greater during the first week after the operation than it is after a month or many months.-Idem, Iancet, No. 1,819, p. 29.

(130.)-In a mammal the spinal cord is laid bare at the level of the two or three last dorsal vertebræ, and a lateral half of this organ (including the posterior, the lateral, and the anterior columns, and all the grey matter, on one side) is divided transversely. The animal is left at rest for a little while, and then it is ascertained that sensibility seems to be much increased in the posterior limb on the side of the section.-Idem, Lancet, No. 1,820, p. 53.

(131.)To obtain a very striking result from the experiment which consists in only one section of the lateral half of the spinal cord; it is better to make it after the posterior columns have been divided.

We know that after this division there is hyperesthesia in the parts of the body which are behind the section; if, after having ascertained this fact, the section of a lateral half is completed where the posterior columns have been divided, we find that the hyperesthesia seems to increase in the side of the second operation, while in the opposite side, not only the hyperesthesia, but sensibility entirely disappears.

A longitudinal section is made on the cervico-brachial enlargement of the spinal cord, so as to separate it in two lateral halves---I ascertain then that sensibility is lost in the two anterior limbs, while it remains, and even seems to be increased, in the two posterior limbs. Idem, Lancet, No. 1,820, p. 54.

(132.) If the longitudinal section is more than two inches long, it is not sensitive in all its length. When there are three pairs of nerves attached to it, the one nearest to the transversal section is hardly able to give slight sensations; the next is a little more sensitive, but much less than in a normal condition; and the third is very sensitive, though not so much as the others, on the same side and behind it.Idem, Lancet, No. 1,820, p. 55.

(133.)—If the section be made two inches higher in the dorsal region, there is, as in mammals, though less marked, an increased sensibility in the posterior limb on the side of the section, and a diminution of sensibility in the opposite limb. The loss of sensibility is never complete, showing that the decussation is not complete. The same results are obtained in reptiles.—Idem, Lancet, No. 1,820, p. 56.

(134.) The laying bare of the spinal cord, and its free exposition to the action of the atmosphere, instead of being a cause of loss or diminution of sensibility, as it had been said, seems to be followed by a marked increase of sensibility in the parts of the body which are behind the place where the cord is exposed.

The laying bare of the spinal cord even in mammals is very rarely followed, after a number of days, by any kind of accidents (meningitis, myelites, &c.) producing a diminution of sensibility.

Deep injuries to the posterior columns of the spinal cord are always followed by a degree of hypercesthesia greater than after the laying bare of the nervous centres, hyperæsthesia which appears in all parts of the body behind the place injured.

All the parts of the encephalon which are situated in its posterior or superior side are like the posterior columns of the spinal cord in

this respect that a marked degree of hyperæsthesia always follows a transverse section upon any of them. If a complete transverse section is made upon any part of the rectiform bodies, sensibility becomes very much increased in every part of the trunk and limbs. Hyperæsthesia is also but at a less degree, one of the results of a transversal incision in the cerebellum, in the processus cerebelli ad testes, and in the tubercula quadrigemina. Every small por

tion of a transverse section of the conducting zone, in a lateral half of the spinal cord, contains conductors-of sensitive impressions coming from all the points of the body, on the opposite side, which are behind the place of this small portion.-Idem, Lancet, No. 1,823, p. 137.

(135.)—I have found that a convulsive affection very much resembling epilepsy may be produced in animals. A few weeks after certain injuries to the spinal cord, in the dorsal or lumbar region, especially in guinea-pigs, fits appear spontaneously several times a day, or, at least, once every two or three days. But the most interesting point is, that it is possible to produce a fit when we choose, by simply pinching a part of the skin. These fits consist in clonic convulsions of almost all the muscles of the head, the trunk, and the limbs, except those muscles which are paralysed.

I have ascertained that one part only, of the skin has the pow of producing the fit, and this part is that which covers the angle of the lower jaw, and extends from thence to the eye, the ear, and nearly to the shoulder. It is only the skin that has the power of generating the fit, as even the three nerves that send filaments to this part of the skin can be irritated without the occurrence of convulsions. When the spinal cord has been injured only on the right side, it is only on that side that the skin of a part of the face and neck has the power of inducing fits, et vice versa when the injury exists on the left side. If the two sides of the cord are injured, the two sides of the face can produce fits. Idem, Lancet, No. 1,840, p. 571.

(136.)-If we take two living animals of the same species and decapitate them by a section passing in one of them on the nib of the calamus scriptorius and in the other on the fourth or fifth cervical vertebra and cutting also in both the principal nerves of the neck and avoiding the section of the carotids, we often find that the first one has no convulsions, or in other words no agony, while the second almost always has very violent convulsions in the four limbs and in the trunk.

More than ten years ago I found that certain animals may live for many weeks, and in more recent researches for eight months, after the extirpation of the whole medulla oblongata,

In these animals all the functions of organic life except pulmonary respiration continue without any apparent alteration, showing that these functions do not depend upon the medulla oblongata as some physiologists have thought. The persistence of life in these animals was possible on account of the cutaneous respiration, but in animals in which the skin absorbs but a small amount of oxygen, such as birds and mammals, death is said to be always rapid after the extirpation of the medulla oblongata, even when care is taken to avoid the influence of the operation upon the heart. It seems, therefore, that the medulla oblongata is an organ absolutely necessary to respiratory movements.

It is known that the only two appearances of proof that the medulla oblongate is the only centre of respiratory movements, or, in other words, the only source (direct or reflex) of these movements in the cerebro-spinal axis, are, 1st, that a transversal section of the lower part of medulla oblongata causes a sudden cessation of respiration; 2nd, that when transversal sections are made on the encephalon, from its front to its back, taking away layer after layer, it is said that it is only after the greater part of the medulla oblongata has been taken away that respiration is destroyed. Ás regards the first of these two assertions, we have already shown the objections against it, objections which are also very good against the second assertion. But we must say a few words more of this second assertion. When, after a series of transversal sections of the encephalon, we have reached the medulla oblongata, just above the upper roots of the par vagum, we find that respiration continues almost normal. If now we cut away the part of the medulla giving origin to this pair of nerves, we find in most cases that respiration is suddenly stopped.

In weak animals after many parts of the eucephalon have been taken away, the whole of the medulla oblong a and of the pons Varolii remaining, respiration sometimes continues normal, but it suddenly stops after a small part of the pons is removed.

The stronger an animal is the more parts of its encephalon can be taken away before we can destroy respiration.

In the strongest animals death occurs in a few hours and from insufficiency of respiration after the ablation of the encephalon except the whole of the medulla oblongata, and so it often is with anencephalia monsters.

A series of experiments on pigeons has given me the following results; with the spinal cord alone respiration continues a few minutes, with the spinal cord and the part of the oblong medulla giving origin to the principal excitors of respiration, the vagi, this function continues many hours (the longest duration we have seen is thirteen hours), if there is also a great part of the base of the ence