Chap, xxxix.] ANIMAL HEAT. 481 



L is taken by a delicate thermometer before the ex- 

 periment is begun. Again, at the close of the ex- 

 periment, the temperature of the water is taken. 

 The increase affords the basis for estimating the 

 quantity of heat given off. 



The calorimetric method, as applied to animal 

 heat, will be referred to in the next chapter. 



CHAPTER XXXIX. 



ANIMAL HEAT. 



Sources of animal heat. The energy of the 

 human body is derived from the food consumed and 

 the air breathed by means of oxidation processes. 

 Part of that energy is converted into mechanical 

 work, and part is transformed into heat. Chemical 

 actions going on in the body are thus the main 

 sources of heat. Oxidation processes being the chief 

 sources of heat in the body, and oxygen being neces- 

 sary for them, it is evident that the quantity of O 

 consumed, and of C0 2 produced, would give an esti- 

 mate of the amount of heat produced. For example, 

 the oxidation of 1 grm. of carbon to C0 2 gives 8,088 

 units of heat, and the oxidation of 1 grm. of hydro- 

 gen to H 2 O yields 34,460 heat units. The amount of 

 heat capable of being produced may also be estimated 

 by noting the amount of albumen, fats, sugars, etc., 

 taken as food, and calculating how much heat units 

 they are capable of producing by complete oxidation 

 (page 456). They do not, however, undergo com- 

 plete oxidation in the body. Thus, albumen is 

 oxidised to urea, and urea is capable of further 

 combustion. 



F F 7 



