476 EESPIKATION. 



to the word combustion; 1 but this must simply be for the 

 purpose of retaining the name applied by Lavoisier to the 

 respiratory process, while its signification is altered to suit 

 the facts which have since taken their place in science. There 

 is no doubt that combustion is generally regarded as signify- 

 ing the direct and active union of oxygen with certain prin- 

 ciples, which commonly contain carbon and hydrogen ; and 

 the immediate products of this union are carbonic acid, water, 

 and incidentally heat and light. It is certain that oxygen 

 does not unite in the body directly with carbon and hydrogen, 

 though it is consumed, and carbonic acid and water are pro- 

 duced, in respiration. Important intermediate phenomena 

 take place, and we do not therefore fully express the respiratory 

 process by the term combustion. The researches of Spallan- 

 zani, "W. F. Edwards, Collard de Martigny, 2 and others, who 

 have demonstrated the abundant exhalation of carbonic acid 

 by animals and by tissues deprived of oxygen, show that it 

 is not a product of combustion of any of the principles of the 

 organism. 3 



Rejecting this hypothesis as insufficient to explain the 

 intimate nature of the respiratory process, it remains to be 

 seen how satisfactorily, in the present state of the science, it 

 is possible to answer the several questions proposed at the 

 beginning of this chapter. 



1. In what way is the oxygen consumed in the system f 

 Oxygen, first taken from the air by the plasma of the blood, 

 is immediately absorbed by, and enters into the composition 

 of, the red corpuscles. Part of the oxygen disappears in the 

 red corpuscles themselves, and carbonic acid is given off. 



1 LONGET, Traite de Physiologic, Paris, 1861, tome i., p. 392, note. 



3 COLLARD DE MARTIGNY, Recherches Experimentales et Critiques sur I 1 Ab- 

 sorption et sur V Exhalation Respiratoires. Journal de Physiologic, 1830, tome 

 x., p. 111. 



3 Various other considerations concerning the combustion theory of respira- 

 tion, such as the so-called "respiratory, or calorific food," will be discussed in 

 connection with the subject of animal heat. 



