235 



have seen reason to conclude, that the inspired air 

 is decomposed in the bronchial cells (114.) of the 

 lungs, and that all its oxygenous portion which dis- 

 appears, is converted (123.) into carbonic acid, by 

 carbon emitted from the exhalent surface (157.) of 

 those organs. During this gradual conversion of 

 the oxygen gas, a quantity of specific caloric (166.), 

 much greater than what is necessary to maintain the 

 elasticity of the carbonic acid that is formed, is ne- 

 cessarily set free ; and to this excess of heat, thus 

 constantly liberated in the lungs, by the decompo- 

 sition of the air, do we look as the source of that 

 superiority of temperature, above the surrounding 

 medium, which man and other animals, under every 

 vicissitude of climate, are enabled to exhibit and 

 maintain. 



191. But if a quantity of caloric be thus con- 

 stantly disengaged in the lungs, it may be expected 

 that the blood, in its transmission through those or- 

 gans, should acquire a certain portion of it. To as- 

 certain this point, Dr Crawford, pursuing the dis- 

 cpveries of Drs Black and Irvine, mixed together 

 certain quantities of water, at the temperature of 

 53, with separate portions of arterial and venal 

 blood ; and then measuring the heat of the mixture, 

 at different successive periods, till coagulation took 

 place, he found, that the water containing arterial 

 blood preserved a superiority of temperature over 

 that mixed with venal blood ; and, from the re- 

 sults of several trials, he concluded, that the specific 

 heat of the arterial blood of a dog, was to that of 

 fhe venal as 114 to 100, and that of a sheep as 115 



