ASPHYXIA. 



259 



breathe by gills, where several of the methods 

 above enumerated are inapplicable, asphyxia is 

 produced, either by confinement in air, or in 

 distilled water, or water impregnated with any 

 gas that does not contain oxygen ; for no ani- 

 mal has the power of decomposing water by 

 its organs of respiration, to obtain oxygen, 

 and all aquatic animals are dependent, either 

 on the occasional respiration of atmospheric 

 air by lungs, or on the more constant respira- 

 tion of the air contained in water by gills or 

 analogous organs. 



In the case of fishes breathing by gills, as 

 the motion of these organs is dependent on 

 nerves arising as high as the medulla oblongata, 

 injury of the nervous system must be as high 

 as that part, in order to produce asphyxia ; 

 and on the other hand, in the case of birds, 

 where the expansion of the thorax in inspira- 

 tion is effected almost entirely by the motion 

 of the ribs, asphyxia may be produced by 

 section of the spinal cord in any part of the 

 neck.* 



We exclude here entirely the cases, often 

 described under the name of asphyxia, in which 

 gases positively noxious (such as carbonic acid, 

 carburetted hydrogen, &c.) have been breathed, 

 because accurate observation shows that these 

 are in fact cases of poisoning, where the poison 

 has been introduced by the lungs, and not 

 simply cases of asphyxia. 



The phenomena of asphyxia, in all the cases 

 above-mentioned, (as occurring especially in 

 the warm-blooded animals,) may be divided 

 into three stages. The first is characterized by 

 the intensity of the sensation which prompts to 

 acts of inspiration, and the consequently violent 

 and laborious, though ineffectual attempts to 

 appease that sensation by the action of all 

 the muscles of inspiration; and in some in- 

 stances by other actions, voluntary or instinc- 

 tive, but still under the guidance of sensibility. 

 Lividity of the surface takes place before the 

 end even of this stage. The next is distinguished 

 by insensibility, rapidly increasing, and attend- 

 ed with irregular spasms or convulsions ; and 

 the last by cessation of all effort, and of all 

 outward signs of life, while the heart's action 

 and circulation are known still to go on for a 

 short time. 



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 dyspnosa 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 we.l founded, is supported. 



* Flourens 

 t. 13. 



in Annales d'Histoire Naturelle. 



* Bichat, Recherches Physiologiques, &c. 

 edit.) p. 338. 



S 2 



(4th 



