ANIMAL HEAT. 2t)l 



in dogs fed on vegetable substances it amounted to over 90 per 

 cent. In some instances, 1 where the animals (rabbits and fowls) 

 were fed on bread and grain exclusively, the proportion of expired 

 oxygen amounted to 101 or even 102 per cent; that is, more oxygen 

 was actually contained in the carbonic acid exhakd, than had been ab- 

 sorbed in a free state from the atmosphere. A portion, at least, of the 

 carbonic acid must therefore have been produced by other means 

 than direct oxidation. 



IY. It has already been shown, in a previous chapter, that the 

 carbonic acid which is exhaled from the lungs is not primarily 

 formed in the blood, but makes its appearance in the substance of 

 the tissues themselves ; and furthermore, that even here it does not 

 originate by a direct oxidation, but rather by a process of decom- 

 position, similar to that by which sugar, in fermentation, is resolved 

 into alcohol and carbonic acid. We understand from this how to 

 explain the singular fact alluded to in the last paragraph, viz., the 

 abundant production of carbonic acid, under some circumstances, 

 with a comparatively small supply of free oxygen. The statement 

 made by Liebig, therefore, that starchy and oily matters taken with 

 the food are immediately oxidized in the circulation without ever 

 being assimilated by the tissues, is without foundation. It never, 

 in fact, rested on any other ground than a supposed probability ; 

 and as we see that carbonic acid is abundantly produced in the 

 body by other means, we have no longer any reason for assuming, 

 without direct evidence, the existence of a combustive process in 

 the blood. 



Y. The evolution of heat in the animal body is not general, as it 

 would be if it resulted from a combustion of the blood ; but local, 

 since it takes place primarily in the substance of the tissues them- 

 selves. Yarious causes will therefore produce a local elevation or 

 depression of temperature, by modifying the nutritive changes 

 which take place in the tissues. Thus, in the celebrated experiment 

 of Bernard, which we have often verified, division of the sympa- 

 thetic nerve in the middle of the neck produces very soon a marked 

 elevation of temperature in the corresponding side of the head and 

 face. Local inflammations, also, increase very sensibly the tempera- 

 ture of the part in which they are seated, while that of the general 



1 Annales de Chimie et de Physique, 3d series, xxvi. pp. 4C9 451. 



