PHYSIOLOGICAL OXIDATIONS. 837 



oxidases is oxidized to acetic acid, formic acid, carbon dioxid, and 

 water. From our present standpoint, the production of heat in the 

 body, it is important also to bear in mind the general view advo- 

 cated by Speck and others, namely, that the chemical changes 

 or metabolism of the body may be divided into two general classes : 

 first, the heat-producing metabolism which results finally in the 

 oxidation of the great mass of the food material and which is 

 essential for the production of body heat, and, second, the tissue 

 metabolism proper, that is, the synthesis and disassimilation of 

 the living substance itself. This latter metabolism varies prob- 

 ably in the different tissues; it is concerned with the building up 

 and breaking down of the living machinery and may be attended 

 by the absorption as well as the liberation of heat, and the energy 

 necessary for effecting these reactions is obtained from the heat 

 energy liberated by the oxidation processes. In this last thought 

 there is contained a suggestion which may serve as an explanation 

 of the fundamental value of the physiological oxidations to the body. 

 It may be supposed that these oxidations furnish the energy neces- 

 sary for the nutritive metabolism of living matter. In those or- 

 ganisms or cells that lead an anaerobic existence that is, an exis- 

 tence in the absence of free oxygen the energy necessary for the 

 process is obtained perhaps by hydrolytic changes alone. 



