In the case of a warm-blooded animal (ex cluding the cetacea, and animals that habitually dive) in the full possession of its vital powers, exposed to complete and sudden obstruction of the access of air to the lungs, it may be stated, that the two first of these stages are very generally over within three minutes, seldom extending to five, and that the circulation through the heart has very generally ceased within less than ten minutes from the commencement of the ob struction. The time during which the priva tion of air can be borne may be somewhat ex tended by habit ; and there are instances of men trained to diving in India who have re mained under water three, four, or even five minutes without loss of sensibility or subse quent injury.
In cases of disease, terminating in death by asphyxia, all these stages may often be observed to be distinctly gone through, although in a very gradual and somewhat irregular manner ; the dyspnom and lividity being succeeded by delirium, often by spasms, and ultimately by coma, and the respiration coming to a stand in general a little before the action of the heart.
The most characteristic appearance which is seen after death by asphyxia, is simply the great accumulation of blood in the vessels of the lungs, in the pulmonary artery, right side of the heart, and great veins, and the compara tively empty state of the left side of the heart, the larger pulmonary veins, and the aorta. The left ventricle is not found empty after death, but seldom contains half as much blood as the right; and it is in this part of the heart that the contractions are soonest observed to cease. The accumulation of blood in the lungs and right side of the heart is greatest in cases where the asphyxia has been gradual, the access of air to the blood not having been absolutely obstructed.* Besides this appearance of congestion of blood in the thorax, the liver, the spleen, and the whole venous, system in the abdomen, are generally observed to be unusually congested in such cases, especially those parts which are depending after death; and even ecchymosis on the mucous membrane of the stomach, after strangulation, has been observed by;Dr. Yelloly and others. This congestion of blood in the liver, and in the veins of the abdo men, is remarkably observed, and leads to important consequences, in various chronic diseases of the thorax, threatening death by asphyxia.
The blood after this, as after other kinds of sudden or violent death, is usually found fluid, and very imperfectly coagulated ; and in connection with this state of the blood there are frequently livid marks resembling ecchy mosis, (though not depending on extravasation of blood,) in various parts of the surface of the body, and not exclusively in depending parts. This appearance is, of course, most remarkable in the face and neck after strangulation, and is much less observed on any part of the surface after drowning.
After strangulation, if the body is soon ex amined, congestion of blood in the vessels of the brain and pia mater may often be remarked, but there is seldom any morbid effusion. After drowning, a frothy fluid, in consequence of the introduction of a small quantity of water, and of efforts at respiration, is generally found in the trachea and bronchi.
The successive steps by which physiolo gists have been led to what we may regard as a satisfactory account of the phenomena now described, and of the'death by asphyxia, may be recapitulated, as curious in themselves, and as affording the clearest view of the evidence on which the doctrine, which now appears to be well founded, is supported.
1. The first opinion on this subject, which need be noticed here, is that which was sup ported by the great Haller, viz. that the circu lation, and with it all other functions of the body are brought to a stand, because when the movements of respiration cease, and the lungs are no longer dilated and contracted, there is a mechanical difficulty to the propulsion of the blood through the pulmonary capillaries, by which the fatal stagnation in these vessels, ob vious on •dissection, is produced.
This doctrine was satisfactorily refuted by Goodwyn, in his treatise on the Connection of Life with Respiration, who sheaved that the air-cells of the lungs are not necessarily con tracted at the time of asphyxia, and that after having once admitted air, these cells never are so much emptied of it again, or contracted on themselves, as to offer any considerable impe diment to the free motion of blood in their parietes. Besides, we know that the same stagnation in the lungs takes place in the case of an animal confined in a gas which does not contain free oxygen, as in the case of drowning or strangulation, although in the former case, any impediment to the mechanical acts of re spiration that can occur, must be the conse quence, not the cause, of the fatal changes within the chest.* 2. The well-known theory of Goodwyn him self on this subject was, that the venous blood is not an adequate stimulus to the left side of the heart, which in the natural state circulates arterial blood only, and which fails to contract upon or propel blood which has passed un changed through the lungs.f This doctrine was, in its turn, refuted by Bichat, who showed by experiment that in the case of strangulation the venous blood does penetrate the lungs and left side of the heart, and is delivered from the carotid arteries if these are punctured ; that the appearance of venous blood in these arteries is contemporane ous with what was described as the second stage of asphyxia, viz. the insensibility and spasms ; and further, his experiments have been generally admitted as affording satisfac tory evidence, that the circulation of venous blood through the brain is a sufficient cause for these symptoms, and produces them when the venous blood from the heart of one dog is sent to the brain of another. He also found by experiment, that venous blood could be in jected artificially into the left cavities of the heart, with the effect of exciting, not suppress ing their action.§ 3. Bichat ascribed the cessation of the circu lation in asphyxia, however, not to the penetra tion of the brain by venous blood, and the consequent insensibility (which is now well known to be compatible with the maintenance of circulation for many hours, provided the blood can be arterialized,) but to the penetra tion of the muscular substance of the heart by venous blood, sent to it by the coronary arte ries, and which he held to be equally (although less rapidly) fatal to the vital action of this organ, as of the brain or nerves.