ANAEROBIC METABOLISM 211 



recovered it exclusively from the carboxyl group of the 

 succinic acid. 



Finally, mixed fermentations were observed in mala- 

 ria parasites, but only when these organisms were kept 

 under aerobic conditions. As was mentioned in a pre- 

 vious section, their metabolism is of the pure glycolysis 

 type when oxygen is completely absent. Wend el (1943) 

 found that Plasmodium knoivlesi, in the course of its 

 aerobic sugar degradation, produced relatively large 

 amounts of lactic acid, sufficient to account for about 

 half the glucose decomposed. Furthermore, the quanti- 

 tative relationships between oxygen consumption and su- 

 gar disappearance proved that the remaining half of the 

 glucose could have been oxidized only partially. One of 

 the end products of this process was probably pyruvic 

 acid, Wendel and Kimball (1942) found that large 

 amounts of this acid were formed during the aerobic incu- 

 bation of blood containing the parasites. The aerobic sugar 

 metabolism of Plasmodium gallinaceum is somewhat sim- 

 ilar to that of Plasmodium knoivlesi (Silverman, Ceithaml, 

 Taliaferro and Evans, 1944). It leads to the production 

 of carbon dioxide and lactic acid, but the carbon contain- 

 ed in these substances corresponded, in various series of 

 experiments, to 58 to 93 per cent of that of the sugar 

 consumed. Small amounts of pyruvic acid and traces 

 of succinic acid were found, but they were not suffi- 

 cient to account for all the missing carbon of the sugar. 

 Whether a fixation of carbon dioxide is involved in these 

 processes remains an open question ; experiments with 

 radio-active carbon in the medium yielded inconclusive 

 results. 



Coelenterates. The nature of the fermentations 

 occurring in this group is not well known. We do pos- 

 sess indications, however, that they are of a mixed type. 

 Kramer (1937) working with isolated tentacles of Anemo- 

 nia sulcata kept under anaerobic conditions, tested for the 



