ANAEROBIC METABOLISM 227 



In the case of the Qgg^ of Arbacia, Chaetopterus, Mac- 

 tra and street (Ballentine, 1940), all of which probably 

 ferment sugar to lactic acid, negligible amounts of car- 

 bon dioxide were derived directly from metabolic proc- 

 esses. 



Besides lactic acid fermentation, there are also other 

 fermentations which, theoretically, should not furnish 

 any carbon dioxide directly, for example, the previously 

 mentioned metabolic processes occurring in Trypano- 

 soma equiperdum. Actually, however, small amounts of 

 carbon dioxide do appear. Reiner, Smythe and Pedlow 

 (1936) found, as mentioned above, a respiratory quotient 

 of 0.062 instead of zero. This, we said, might well be 

 due to secondary reactions on substances other than sugar 

 or to the presence of leucocytes. Another well-establish- 

 ed case of mixed fermentation, in which no carbon diox- 

 ide is derived from sugar degradation, is that of Tctrahy- 

 mena (Thomas, 1942). 



In many other types of anaerobic fermentation, how- 

 ever {cf. the preceding sections of this chapter), the pro- 

 duction of carbon dioxide is definitely in direct depend- 

 ence on the degradation of carbohydrate. The amount of 

 gas produced (for example, by parasitic worms) is much 

 too large to be explained by its liberation from inorganic 

 substances or by its derivation from protein alone. A 

 calculation from von Brand's (1934a) figures for the car- 

 bon dioxide and the organic acids produced by Ascaris, 

 leads to the conclusion that at least 80 to 90 per cent of 

 the carbon dioxide must have been derived directly from 

 metabolic processes. Since the protein metabolism of 

 these worms is not pronounced and since they consume 

 no fat, there can be no doubt that most of the gas came 

 from the breakdown of carbohydrate. 



An especially clear-cut case is that of the Trichinella 

 larvae. Stannard, McCoy and Latchford (1938) showed 

 that the total bound carbon dioxide of the larvae and of 



