960 NUTRITION AND HEAT REGULATION. 



energy is produced is at bottom comparable to ordinary combus- 

 tions. Oxygen is absolutely necessary to the process in each 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 temperature. 

 The theories suggested to explain this fact have changed naturally 

 with the advance of chemical knowledge. After the discovery of 

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

 pared with oxygen it was suggested that in some way the oxygen 

 in the body is ozonized and is thus able to burn the food material. 

 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 latter 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 

 facts indicate that when a sufficient supply of oxygen is provided 

 any further increase has no immediate effect in aiding or hastening 

 the oxidations. The intensity of the process is conditioned by the 

 tissue itself. The initial stimulus or substance that sets going the 

 whole reaction arises within the tissues. The second generalization 

 that seems to be accepted more and more of recent years is that the 

 oxidations of the body, those reactions that give rise to much heat, 



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

 Autoxydation," 1904. 



