There is no subject in the whole range of Physiology more beset with difficulties than the inquiry into the causation of sympathy. Vas cular connection has been thought by some to explain the secret sufficiently, by others the contiguity or continuity of tissues. Some have seen the media of communication in the ganglionic nerves, others in the nerves called respiratory. We cannot enter into the discus sion, and therefore refer to the article SYM PATHY. But we beg to state that we have no where seen the subject treated with more eru dition and acuteness, than in Dr. Fletcher's Rudiments of Physiology.* But while there can be no question that all the organs are more or less related in the man ner above indicated, it is not less evident that the connection between some is of a far more intimate nature than between others. It is almost needless to instance the brain and the stomach, the brain, spinal marrow, and the heart, the heart and every part of the system, &c. &c. By overlooking the sympathetic re lation between the brain and the heart, Bichat fancied that when he had proved the functional independence of the latter organ, he was cotn pelled to search in some third part for the link between the death of the one and that of the other.4- It cannot be denied that in a large proportion of cases, the syncope which follows lesions of the cerebro-spinal system, is not a direct consequence, and that there is an in termediate suppression of the function of the lungs,—that in other words the syncope is the effect of asphyxial (See ASPHYXIA.) It 1S somewhat remarkable that the illustrious phy siologist just mentioned should have forgotten certain pathological facts which afford con vincing evidence that cerebral injury may pro duce death without developing the phenomena of asphyxia; the " apoplexie foudroyante," for example, and the concussion of a blow or a fall. Nor is it less surprising that in his numerous experiments upon animals he should not have noticed what was afterwards fully demonstrated by Legallois and W. Philip, that both the heart and the capillaries may be imme diately paralysed by violence done to the brain and spinal marrow. It must be remembered, however, that this result is much affected both by the extent and by the nature of the injury. Thus the brain may be sliced and the spinal cord divided, with no other influence upon the circulation than that which depends upon the interference with the respiratory actions ; but laceration or crushing of the cerebral matter is immediately felt by the heart and capil laries. In these cases the circulation ceases, not because the cerebro-spinal axis takes any part in that function, but because it is con nected with the heart in the same manner as we have stated that all the parts of the body are more or less connected,— in bonds of alliance though not of dependence. We have reason, however, to believe that the intimacy of the alliance between the brain and the heart is scarcely equalled by that of any other organs in the system.
The anatomical characters of syncope by nervous lesion are determined by the modus operandi of the injury. If the latter arrests the action of the heart only by obstructing the iespiratory movements, the appearances are those of asphyxia, (see AsPnYxIA.) But if the operation be immediately upon the heart, there will be a difference in the appear ances, — a difference which likewise be longs to all cases in which the circulation ceases without previous obstruction of respi ration. The blood, instead of being accumu lated in the right cavities of the heart, and in the pulmonary arteries, is more equally dis tributed between these and the left cavities, and the pulmonary veins. There is generally a perceptible difference in the colour of the blood in the two sides of the heart, but some what less than might at first be expected. The defect of arterial tint in the coagula of the left side may be fairly attributed to the drain ing away of the serum, and consequently with it of the saline particles upon the pre sence of which the red colour depends. Blood is found in the aorta and in many of the ar teries. The signs produced by venous con gestion, such as engorgement of the liver and spleen, turgescence of the cerebral veins and of those of the mucous membranes, are want ing, as well as the tumefaction of the face, the puffing of the lips, the projection of the eyes, and the deep lividities characteristic of that condition. We must remember that the
appearances are considerably modified if syn cope has taken place gradually. In such in stances the heart is generally found empty. The cause of this condition is obvious. In the first place, as the degree of the diastole must be proportionate to the systole, it is obvious that when the latter is enfeebled, less blood will be received into the cavities; and, secondly, as less blood is driven into the pul monary artery and the aorta, there will be less to return in a given space of time, and con sequently there will be less impetus in the returning currents. It is easy to perceive that before the final and feeblest contraction, which must be succeeded by a correspondently slight dilatation, the current of blood pressing for admission must be very trifling.
3. Syncope by injuries of the heart itself.— This is of too obvious a nature to require comment.
4. Syncope by injuries of other organs and tissues.—When death follows quickly upon a lesion which does not necessarily implicate the vital organs, properly so called, we say in ge neral terms that a shock has been given to the nervous system, in consequence of the strong probability that some portion of this system is the agent of sympathy. If violent pain at tends the injury, and to this succeeds loss of consciousness, and then cessation of the heart's action, it is fair to infer that the brain was first operated upon through the nerves of sensation and that the derangement of this organ affected the circulation. But there arc cases of injury in which syncope occurs with out any antecedence of pain or of lcipothymia, and in which there is no reason for supposing any cerebral affection in the chain of events. Of this kind are extensive mechanical injuries of the extremities, burns, rupture or over-dis tention of the stomach, &c. Whether the nerves which convey the morbid impression belong to the ganglionic or to the respiratory class, we do not profess to decide. The im mediately fatal effect of a blow upon the epi gastrium or of a draught of cold water when the body is heated, has been attributed by some to a shock given to the semilunar ganglion, and the communication of the impression to the heart; while others are of opinion that the injury is fatal by " paralysing the whole res piratory set of nerves from the violent shock com municated to the phrenic, -and thus shut ting up as it were the fountain of all the sympathetic actions of the body." " A blow on the pit of the stomach," says Sir Charles Bell, " doubles up the bruiser and occasions the gasping and crowing, which sufficiently indicate the course of the injury—a little more severe, and the blow is fatal. A man broken on the wheel suffers dreadful blows, and his bones are broken, but life endures—the coup cle-grace is a blow on the stomach." 5. Syncope by mental emotion.—Instances of this occurrence must be familiar to every one both by reading and by observation. In some of them .the cause in question has' operated either by aggravating some pre-exist ing malady, or by calling into action some strong predisposition to disease ; as in struc tural lesions of the heart on the one hand, and in the apoplectic diathesis on the other. But in Other instances the mere violence of a pas sion has at once extinguished its subject with out the intervention of morbid tendency or of actual disease. Such cases belong to the Nervous Apoplexy of some authors; and cer tain it is that they present a complete annihi lation of sense and motion, but this condition is only simultaneous with, or immediately suc ceeded by the failure of the circulation. We have no doubt that the change in the organ of the mind, corresponding to the emotion, ope rates upon other parts of the cerebro-spinal axis, which in their turn affect the heart in the same manner as other preternatural states of that system. We are not acquainted with any example in which either high intellectual ex citement unaccompanied by vehemence of pas sion, or mere intensity of external sensation, has been the cause of sudden death ; nor could it be expected a priori, since in the normal condition of the economy there is by no means the sarrie degree of connection between the action of the heart and intellectual and sen sific conditions, as between the former and the emotions and affections.