164 AEROBIC FERMENTATIONS 



have become adapted to this type of metabolism to such 

 a degree that a complete transition to purely aerobic 

 oxidations has become incompatible with their organi- 

 zation (an assumption which, of course, is no real ex- 

 planation). It is of interest to note, in this connection, 

 that at least in intestinal worms the fermentations in 

 the presence of air lead to the same end products as the 

 fermentations under purely anoxic conditions. Experi- 

 ments proving this have been performed with Ascaris 

 by Weinland (1901 and 1904) for anaerobic conditions, 

 and by Oesterlin (1937) for aerobic conditions, with 

 Parascaris by Toryu (1936), with Moniezia by von Brand 

 (1929 and 1933a) for anaerobic conditions and by Alt 

 and Tischer (1931) for aerobic conditions. 



An adaptation to incomplete oxidations due to lack of 

 oxygen in the normal surroundings cannot be assumed 

 for blood parasites like the trypanosomes. It is true 

 that they live in the blood plasma which contains only 

 relatively small amounts of oxygen, but they are able to 

 draw on the vast store of oxygen present in the erythro- 

 cytes of the host. It can easily be shown that blood con- 

 taining trypanosomes rapidly assumes the color of re- 

 duced haemoglobin when removed from the host. This 

 was demonstrated as early as 1911 by Nauss and Yorke. 



The situation in malaria parasites is directly compar- 

 able to that found in trypanosomes. That they are also 

 able to consume the oxygen bound to the haemoglobin 

 of the host has been shown experimentally by Christo- 

 phers and Fulton (1938). The reasons why incomplete 

 oxidations occur in blood parasites are entirely unknown. 



A comparison of two processes which are quite sim- 

 ilar chemically but are of different physiological sig- 

 nificance in two different groups of animals may furnish 

 a tentative explanation of at least one type of incom- 

 plete oxidation. The synthesis of fat from carbohy- 

 drates in animals living aerobically is primarily intend- 



