974 NUTRITION AND HEAT REGULATION. 



as indirect, meaning thereby that the material is not acted upon 

 directly by the molecular oxygen. Chemists are not agreed as to 

 the exact nature of simple combustion, and it is therefore increas- 

 ingly difficult to compare these processes with the oxidations in the 

 body. Leaving aside the details of the process, it may still be be- 

 lieved that the metabolism of material in the body by means of 

 which its heat energy is produced is at bottom comparable to ordi- 

 nary combustions. Oxygen is absolutely necessary to the process in 

 eacn case; the same end-products are formed and the same amount 

 of heat is liberated in the one case as in the other. The fundamental 

 point that the physiologist is attempting to solve is the means by 

 which the body accomplishes these oxidations at such a low temper- 

 ature. The theories suggested to explain this fact have changed 

 naturally with the advance of chemical knowledge. After the dis- 

 covery of ozone (Schonbein, 1840) and its great power of oxidation as 

 compared with oxygen it was suggested that in some way the oxy- 

 gen in the body is ozonized and is thus able to burn the food mate- 

 rial. Gorup-Besanez showed that some of the oxidations that take 

 place in the body can be successfully accomplished outside the body 

 with the aid of ozone, especially in the presence of alkalies or alka- 

 line carbonates. Others suggested that the oxygen in the body be- 

 comes converted to atomic oxygen and is thus enabled to attack the 

 tissue materials. Hoppe-Seyler formulated a theory according to 

 which the living molecule is first split into smaller molecules by the 

 hydrolytic action of ferments. In this process, as in fermentation, to 

 which he compared it, hydrogen is liberated in the nascent or atomic 

 state, and this hydrogen acting upon the oxygen forms water with 

 the liberation of some atomic oxygen, which in turn oxidizes the 

 split products of the fermentation. Others still (Traube) laid stress 

 upon the possibility of the formation of hydrogen peroxid or 

 similar organic peroxids which are then capable of effecting the 

 oxidation of the body material. This last theory, in modified form, 

 still prevails.* 



The great amount of experimental and theoretical work upon 

 the nature and cause of physiological oxidations has established 

 pretty clearly two general beliefs which it is important to keep 

 in mind. It has been shown, in the first place, that the amount of 

 the oxidation is governed by the tissue itself and not by the quantity 

 of oxygen present. The view that by increasing the amount of 

 oxygen offered to the tissue the intensity of the oxidations can 

 likewise be increased was formerly held and is still met with. It 

 is often supposed, for example, that by breathing pure oxygen the 

 oxidations of the body may be augmented. On the contrary, the 



* See Engler and Weissberg, " Kritische Studien iiber die Vorgange der 

 A-utoxydation," 1904. 



