258 



ASPHYXIA. 



excretion of carbon, which immediately on its 

 being evolved from the nourishing fluid, en- 

 tered into combination with the oxygen of the 

 air, and was carried off; and the chief reason 

 for this opinion was, that the volume of oxy- 

 gen which disappeared in the process, was 

 believed to be just equal, in all cases, to that of 

 the carbonic acid that appeared. As it is 

 known that the volume of any quantity of 

 carbonic acid is just the same as that of the 

 oxygen contained in that quantity of acid, if 

 the fact had been as above stated, the coinci- 

 dence could hardly have been accidental, and 

 the inference would have been nearly inevitable, 

 that the oxygen of the atmosphere did not enter 

 the nourishing fluids, but merely dissolved and 

 carried off the excreted carbon. 



But the numerous experiments of Dr. Ed- 

 wards* and of M. Du Long,-f- seem to have 

 nearly established the proposition, that in the 

 respiration of by far the greater number of 

 animals, the volume of oxygen that disappears 

 from, is somewhat greater than that of the 

 carbonic acid that appears in, the air employed : 

 the same result was obtained in experiments 

 by Allen and Pepys on birds ;J and if this be 

 so, it is certain that the respiration of these 

 animals is attended with an actual absorption 

 of oxygen, at least to a certain extent. 



This conclusion authorizes us to inquire far- 

 ther, whether it is not more probable, that the 

 whole of the oxygen which disappears from air 

 in contact with the nourishing fluid of living 

 beings, is absorbed into that fluid, and that the 

 carbonic acid which appears is exhaled, ready 

 formed, in its place. And several facts shew 

 that this is by far the more probable suppo- 

 sition; and that oxygen is essential to vital 

 action, not merely as a means of carrying off 

 superfluous carbon, which has become noxious; 

 but as itself an ingredient in the nourishing 

 fluids, necessary for the maintenance of their 

 motion and vivifying power. 



But without entering at length into this 

 question, which will be more fully discussed 

 under the head of Respiration, it is obvious 

 from what has been said, that provision must 

 be made, in the ceconomy of all living beings, 

 for the exposure of their fluids to the air of the 

 atmosphere, in circumstances admitting of ex- 

 halation and absorption ; and it may be farther 

 stated, that, in the different classes of animals, 

 the amount of this mutual action for which 

 provision has to be made, must be proportioned 

 to the energy and activity of vital action 

 which each animal is destined to exhibit, these 

 qualities being very generally found to be 

 greater, as the consumption and vitiation of the 

 air are more rapid. 



These principles explain the intention of 

 many different contrivances and arrangements, 

 afterwards to be described, which are em- 



* De 1'Influence des Agens Physiques sur la Vie, 

 p. 410, et seq. 



t Journal de Physiologic, t. iv. 



\ See Hodgkin's Translation of Edwards, p. 486. 



$ See Cuvier, La Regne Animale, t. i. p. 56 ; 

 also Marshall Hall, Philosophical Transactions, 

 1832, p. 339. 



ployed in different classes of animals for the 

 performance of the function of respiration ; and 

 the variations of which may be said, in a gene- 

 ral view, to be determined by two conditions, 

 first by the medium in which each animal is 

 destined to exist, and secondly, by the inten- 

 sity and variety of vital actions which it is to 

 be capable of performing. 



The importance, to all living beings, of the 

 action of oxygen on their fluids is most un- 

 equivocally shewn by the nature of the fatal 

 changes which ensue, when that action is in 

 any way obstructed ; i. e. by the nature of the 

 changes which take place in death by asphyxia. 

 The study of these has long been held to be 

 of the highest importance, not only as a car- 

 dinal point in physiology, but as affording the 

 only precise information in regard to the fatal 

 tendency of many and various diseases. 



It is chiefly in animals of the highest orders, 

 i. e. in warm-blooded animals, that these phe- 

 nomena have been studied ; and it is to be 

 remembered, that in them the subject is ren- 

 dered more complex by the higher endow- 

 ments and greater power over all functions of the 

 body,which the nervous system there possesses. 

 When we trace the connection, in these animals, 

 of the different changes that precede the fatal 

 event, it is right to bear in mind, that the in- 

 terruption of the process by which their fluids 

 are exposed to the air is equally fatal, not only 

 to those animals in which no action of the ner- 

 vous system is concerned in that process, but 

 also in vegetables, where no nervous system 

 exists. 



The phenomena of asphyxia in the higher 

 animals are very nearly the 'same, in whatever 

 manner the access of air to the organs of respi- 

 ration is prevented. This may be done, in the 

 case of animals that breathe by lungs, in a 

 great variety of ways ; by strangulation or suf- 

 focation, i. e. by any mechanical means pro- 

 hibiting the ingress of air by the trachea and 

 bronchi ; by submersion in water or any other 

 fluid ; by confinement in vacuo or in such 

 gases as contain no oxygen, but are not them- 

 selves poisonous, such as azote and hydrogen ; 

 by forcible compression of the thorax, prevent- 

 ing its dilatation ; or by the admission of air 

 into free contact with the surface of the lungs 

 on both sides of the chest, so as to prevent 

 their distension, as in the celebrated experiment 

 of Dr. Hooke ; or by the section, either of all 

 the separate nerves which move the muscles 

 concerned in the dilatation of the thorax in 

 inspiration, or of the spinal cord in the upper 

 part of the neck, above the origin of the 

 phrenics, by which the whole of these nerves 

 are simultaneously palsied, as in many ex- 

 periments of Galen, Cruikshank, Le Gallois, 

 and others.* 



In the case of fishes or other animals that 



* These last are the lesions of the nervous sys- 

 tem which cause sudden death by asphyxia. Sec- 

 tion of the par vagum, the sentient nerve of the 

 lungs, produces death by asphyxia also, but 

 slowly, and through the intervention of disease and 

 disorganization of the lungs, to be afterwards no- 

 ticed. 



