432 NUTRITION. 



nutrition and disassimilation, involving changes in the nitro- 

 genized constituents of the blood and the tissues, are not 

 disconnected with calorification, the production of heat by 

 animals is most closely related to the appropriation of oxygen 

 and the formation of carbonic acid. 



Intimate Nature of the Calorific Processes. A compre- 

 hension of the intimate nature of the calorific processes 

 involves simply an answer to the question, how far we can 

 follow the material transformations in the organism, which 

 involve the consumption of certain principles, the production 

 of new compounds, and the evolution of heat. As regards 

 the nature of the intermediate processes connecting the dis- 

 appearance of oxygen with the production of carbonic acid, 

 we can only explain it by reciting the simple facts. Oxygen 

 disappears, carbonic acid is formed, and the carbon is fur- 

 nished, perhaps by the tissues, perhaps by the blood, probably 

 by both. It is probable that the intermediate changes are 

 more simple and rapid than those which intervene between the 

 appropriation of nitrogenized nutritive matter and the forma- 

 tion of the nitrogenized excretions ; but we have never been 

 able to follow either of these processes through all of their 

 different phases. We must be content, in the present con- 

 dition of our positive knowledge, to regard calorification as 

 one of the attendant phenomena of nutrition ; and we have 

 only to study as closely as possible the facts with regard to 

 the disappearance of certain principles and the formation of 

 effete matters, that are always and of necessity associated 

 with the development of heat. 



Equalization of the Animal Temperature. A study of 

 the phenomena of calorification in the human subject has 

 shown that under all conditions of climate the general heat 

 of the body is equalized. Nearly always, the surrounding 

 temperature is below the standard of the body, and there is, 

 of necessity, an active production of caloric. Under all con- 



