CHAPTER III 



THE SOURCES OF ENERGY IN ANAEROBIOSIS 



Vertebrates can derive energy from the aerobic oxida- 

 tion of carbohydrates, fats and proteins, substances which 

 can usually be used interchangeably. In invertebrates 

 the situation is the same in principle, although under aero- 

 bic conditions one of these substances is often used pre- 

 dominantly. A few examples will illustrate the various 

 possibilities. 



A starving earthworm consumes chiefly protein and 

 glycogen, during the first days of starvation, while later 

 more fat is used (Lesser, 1908). The snail Helix, during 

 hibernation, oxidizes chiefly carbohydrate and some pro- 

 tein; its fat content remains entirely unchanged (von 

 Brand, 1931). The actinians metabolize chiefly protein 

 (Putter, 1911), Hydra, protein and some fat (Kolod- 

 ziejski, 1923; Beutler, 1924). A predominance of protein 

 metabolism occurs also in leeches (Piitter, 1907, 1908; 

 Bialasczewicz, 1919; Laf argue and Fayemendy, 1932). A 

 relatively high rate of fat utilization has been found in 

 developing sea-urchin eggs (Hayes, 1938), in flies during 

 their metamorphosis, (Evans, 1932) and in starving in- 

 sects (Mellanby, 1932). 



The metabolized substances are not so diverse when 

 oxygen is lacking. It is quite generally observed that 

 under such conditions the carbohydrate metabolism be- 

 comes predominant, protein utilization decreases consid- 

 erably and fats are used only in exceptional cases, if at 

 all. The same is observed in organisms that live in nature 

 under anaerobic or nearly anaerobic conditions. 



We shall now consider in detail the evidence for the 

 utilization of these substances as sources of energy in 

 anaerobic metabolism. 



