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but chiefly the medulla oblongata and the neighbouring parts of the encephalon, their connexion with which explains the readiness with which they are affected by emotional states. In other parts of the body, the nerves of the blood vessels seem to come partly from the cervical sympathetic, but chiefly from the cerebro-spinal axis; so that if the spinal cord be transversely divided on one side in the dorsal region, we find in the lower limbs of that side the dilatation of bloodvessels, the elevation of temperature, the hyperesthesia, and the increased muscular contractility, which in the head follow the section of the cervical sympathetic.
These vaso-motor nerves are not only called into activity by direct excitation, but are susceptible of being made to call forth contractions in blood vessels by reflex action. This conclusion, the value of which we estimate very highly, was first decisively evidenced several years since by experiments performed by M. Brown-Séquard in conjunction with Dr. Tholozan, on the effect of the application of cold to one hand in producing a marked reduction in the temperature of the other.* They found that when one hand was held in water cooled down nearly to the freezing point, the other gave all the evidence of contraction of its vessels, both in its general aspect, and in its rapid loss of heat, which in some instances was such as to reduce the thermometer held in it as much as 32° Fahr. That this reduction was not due to a loss of heat from the body and members generally, was made clear by the fact that the thermometer placed in either axilla showed scarcely any depression; so that no doubt can be reasonably felt that the stimulus of cold, which produced direct contraction in the vessels of one hand, also operated to call forth reflex contraction in those of the other. If any confirmation were wanting, it is afforded by experiments more recently made; which show that after section of the cervical sympathetic, the distended vessels of the ear may be made to contract by irritation of the cutaneous branches of some of the spinal nerves. This reflex contraction of the muscular walls of the blood vessels may proceed to the extent of spasm, so complete as scarcely to admit of the passage of blood through their tubes; and it is not a little remarkable that transverse section of a lateral half of the spinal cord near the medulla oblongata, whilst it produces paralysis and dilatation of the blood vessels of one side of the body, should call forth such a spasm in those of the other, that scarcely a drop of blood follows the division of the skin upon that side, and the temperature falls rapidly, often to that of the atmosphere. It might of course be suggested that this diminished circulation on one side might be fairly laid to the account of the increased circulation on the other; and this explanation receives due consideration from M. Brown-Séquard, who put its value to the test by the ingenious experiment of forcing the blood into the vessels of the opposite side by putting a ligature round the dilated trunk on the side on which the section has been made, the result of which was that the temperature rose so slowly as to make it obvious that the circulation was obstructed; and he further states that injec* Journal de la Physiologie, Juillet, 1858, p. 497.
tions of blood through the femoral artery in the limbs thus affected are made with far more difficulty than in the limbs of healthy dogs.
The facts thus experimentally ascertained give the fullest confirmation to the doctrine which had been previously taught by various physiologists, ourselves among the rest, that the sudden stoppage of the heart's action, in many cases of shock, is due to a reflex influence transmitted through sympathetic. It is well known that persons have fallen dead on the spot from drinking cold water on a warm day, or from blows on the epigastrium, especially when the stomach is distended with food; whilst a rapid prostration, if not immediate syncope, is an almost pathognomonic sign of the perforation or rupture of any of the principal abdominal or pelvic viscera, quite irrespective of the haemorrhage which may result from such an accident. The same result, moreover, is well known to follow extensive lesions of the peripheral expansions of the cerebro-spinal nerves, as by burns, crushing of joints, and the like; the syncope induced by them being exactly like that which is produced by concussion or other sudden and extensive injury of the cerebro-spinal centres themselves. The like result has been obtained by the sudden application of severe cold to an extensive surface peculiarly susceptible of it; thus when shaved rabbits are plunged into ice-chilled water, they die immediately with spasm of the heart. In all these cases, the par vagum has probably a considerable share in the transmission of the reflex influence to the heart. It is well known that a sudden stoppage of the heart's action may be produced by the application of the magneto-electric current either to the par vagum, or to the medulla oblongata near its origin; and that this effect cannot be produced if the par vagum or its cardiac branches have been previously divided. So it is shown to be probable by M. Brown-Séquard, that in those rare cases in which death from the inhalation of chloroform takes place by the stoppage of the heart's action before the suspension of respiration, the effect is due to the impression made by the chloroform upon the pulmonic branches of the par vagum, and transmitted by reflexion to the cardiac; for he has found that in dogs, which seem to be more frequently affected in this way than are other animals, life may sometimes be restored by mechanically exciting the heart to renewed contraction by pressure on the chest; whilst this mode of death has not occurred in any dog in which the par vagum had been divided previously to the administration of chloroform. Still, it cannot be reasonably doubted that the Sympathetic, not the par vagum, is the channel of this influence to the vascular system generally; and the existence of such a condition as "spasm of the extreme vessels," to use the phrase of the sagacious Cullen, may henceforth be considered a capital fact in biological science, its insecure foundation of vague hypothesis having now been strengthened by the solid supports of experimental proof.
One of the first-fruits of the establishment of this position is a new theory of Epilepsy; which is propounded by M. BrownSéquard as a legitimate inference from facts experimentally ascertained by himself as to the artificial production of this disorder in animals;
and which is applied by him not only with great ingenuity, but, as it appears to us, with great success, to the explanation of the varied phenomena of this disease as it presents itself in Man. In the course of his experiments upon the effects of various injuries of the spinal cord, he observed that after certain lesions of that organ in its dorsal or its lumbar region, especially in guinea-pigs, fits of epilepsy appear spontaneously at intervals of a few hours or of a day or two. These fits consist in clonic convulsions of almost all the muscles of the head, trunk, and limbs (except such as are paralysed by the lesion of the spinal cord), together with laryngismus and loss of consciousness; and when the fit has lasted long, it leaves behind it a state of drowsiness or unwillingness to move. By trying various kinds of irritation, M. Brown-Séquard found that fits could be artificially induced in these animals by simply pinching a particular part of the skin; that, namely, 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 receiving the irritation which excites the fit; as the nerves which supply this part may be irritated without. the occurrence of convulsions. When the spinal cord has been injured on one side only, it is only on that side that the irritation of the skin will induce the fit; if both sides have been injured, then the fit may be induced by irritation of the skin on either side. That the cause of the fit does not lie in the mere pain produced by the irritation, would appear from the circumstance that the degree of sensibility of that part of the face and neck is not greater than that of the neighbouring skin, and is far less than that of some parts of the skin in one of the hind limbs; and it must be attributed to some peculiar kind of irritation, which only the cutaneous ramifications of the nerves that convey it have the power of receiving, and which may not even be felt as a sensation. From a careful examination of the sequence of the phenomena presented by the animals thus affected, M. Brown-Séquard has come to the conclusion that the immediate result of the excitation is to produce, through the Cerebro-spinal centres and their nerves, a more or less powerful convulsion of the muscles of the face, whilst through the vaso-motor fibres of the Sympathetic, it induces a spasmodic contraction of the blood vessels of the Cerebrum and of the face, indicated by the pallor which marks the commencement of the seizure; and it is not a little remarkable that the very same inference has been contemporaneously drawn by two able German experimenters, Kussmaul and Tenner, from researches in many respects different. The following is given by M. Brown-Séquard as the ordinary filiation of the other phenomena of the ordinary epileptic paroxysm:
The asphyxia, to which so great a share is due in the phenomena of epilepsy and in its most serious consequences, depends, according to M. Brown-Séquard, not only on the state of the larynx (as Dr. Marshall Hall maintained), but on that of the chest; for not only cannot the blood return easily from the head on account of the trachelismus, but also it cannot enter the chest from either the spinal canal or the head on account of the fixed state of expiration.* Besides, he continues, the bronchial tubes are themselves frequently obstructed; and all these changes co-exist with an increased production of carbonic acid, and with the change in the circulation of the encephalon, during which the blood accumulates in the base of this organ and also in the spinal cord.
Thus, then, epilepsy appears to consist essentially in an increased reflex excitability of certain parts of the cerebro-spinal axis, and in a loss of that control which, in the normal condition, the will possesses over the reflex faculty. As the base of the encephalon, and especially the medulla oblongata, is the most frequent seat of the augmented excitability, that part of the nervous system must be considered as the centre (so to speak) of the disorder; but for the production of
* We have seen a case of one of the strange varieties of hysteric convulsion, in which there was spasmodic closure of the glottis during expiration, with repeated and most violent expiratory efforts, but without any loss of consciousness; and this was repeated, time after time, in the course of an hour, the obstruction to the return of the blood from the head, as indicated by lividity of the face and the turgescence of the veins of the neck, being such as to occasion the gravest alarm, until it was relieved by the free expiration permitted by the yielding of the glottis.
the convulsive paroxysm some excitation is necessary; and this may spring (as all who have studied the disease are well aware) from a great variety of agencies, some affecting the peripheral portion of the system, some more directly operating upon the central organs. In common with every physician who has treated of this disease with a right appreciation of its nature, he lays great stress on the importance of searching out and removing every kind of peripheral irritation that can be discovered; and the chief novelty in his suggestions as to this point consists in his mode of determining the point whence the first impression proceeds.
"If,” he says, "the unfelt aura starts from some part of the skin or from some organ not deep-seated, as the testicle, or some part of the mucous membrane near the skin, either the first contractions in a fit, or the most violent or the most prolonged, are found in the neighbourhood of the point of starting of the aura. If no indication of this kind can be furnished by the persons who have seen the fits, it will be well to try the application of a very powerful galvanic current, with dry conductors, on the various parts of the skin, when the patient expects to have a fit. I have in this way twice ascertained the point of starting of an unfelt aura: a fit has been produced by the galvanization of certain parts of the skin. Of course there are many cases where such a means of diagnosis ought not to be employed; every one will understand what are those cases. Another and the best means (so far as the limbs alone are concerned) to detect the existence of an unfelt aura, consists in applications of ligatures on each limb alternately. Suppose a case of epilepsy in which the fits are frequent and come at nearly fixed times, or after warnings of any kind, so that it may be known that it is to take place in a given time or nearly so: a very tight ligature is put on one limb; and if the it does not come, it is extremely probable that it depends on the irritation of an unfelt aura; if it comes, the ligature is applied on the other limbs at other times. I am sorry not to be able to give more details in this respect; but I think it will be easy to understand how, by such a means, it may be ascertained if an aura comes from the upper part of a limb, or from a toe or a finger, and from which one.
"Even in cases of epilepsy due to a disease of the encephalon, the cause of the fits may originate from some points of the skin; and the prevention of the passage of the aura, in such cases, can prevent the fits. There are four cases of this kind that I know, in three of which the disease consisted in a tumour in the brain. In my animals the same thing exists: although the alteration of the spinal cord which is the cause of epilepsy-persists, the aura being interrupted by the section of the nerves which go to the skin of the neck and face, epilepsy, so far as I have been able to ascertain, ceases. The aura may originate from any part of any centripetal nerve, and there is no doubt that its place varies according to the location of disease in the nervous centres when it is due to such a disease."
The increased excitability of the central organs, the coexistence of which is necessary for the production of the paroxysm, is best combated, in M. Brown-Sèquard's opinion, by the 'cauterization of the back of the neck by moxas or by the actual cautery; a powerful modification of nutrition, the neglect of which by regular practitioners he much regrets. We presume that want of time prevented him from speaking of those general constitutional means, the efficacy of which, in certain classes of cases, has been placed beyond doubt.