SOURCES CF AXMAL HEAT. 4:19 



blooded animals generally, the maintenance of the tem- 

 perature of the organism at a nearly fixed standard is a 

 necessity of life and of the physiological action of the dif- 

 ferent parts ; and that while heat is generated in the 

 organism with an activity that is constantly varying, it is as 

 constantly counterbalanced by physiological loss of heat 

 from the cutaneous and respiratory surfaces. Variations in 

 the activity of calorification are not to be measured by cor- 

 responding changes in the temperature of the body, but are 

 to be estimated by calculating the amount of heat lost. The 

 ability of the human race to live in all climates is explained 

 by the adaptability of man to different conditions of diet 

 and exercise, and to the power of regulating loss of heat 

 from the surface by appropriate clothing. 



Our proposition regarding the production of animal heat 

 is in no wise opposed to the so-called combustion-theory, as 

 it is received by most physiologists of the present day ; but 

 it must be admitted that it is an unfortunate use of terms to 

 apply the name combustion to the general process of nutri- 

 tion, as is done by those who attempt to preserve, not only the 

 ideas of the great author of this theory, but certain modes of 

 expression, which were in accordance only with his limited 

 knowledge of the phenomena of nutrition. If we speak of 

 animal heat as the result of combustion of certain elements, 

 it will be necessary constantly to refer to the difference 

 between combustion as it occurs in the organism, and mere 

 oxidation out of the body ; or to start with a full definition 

 of what is to be understood by the term physiological 

 combustion, which reduces itself simply to a definition of 

 nutrition. 



Regarding calorification, then, as connected with all of 

 the varied processes of nutrition, it remains for us to deter- 

 mine the following questions : 



1. In what part or parts of the organism is heat gen- 

 erated ? 



2. What is the relative importance in calorification, as 



