390 RESPIRATORY METABOLISM 



theory of death. Von Brand (1933) measured the rate of sugar destruc- 

 tion for various trypanosomes, and obtained high values (8.0 mgm. /bil- 

 lion/hour) for the pathogenic trypanosomes T. hrucei, T. gmnbiense, 

 T. rhodesiense, and T. congolense, and very low values for the nonpatho- 

 genic T. letvisi (about 1.4), and still lower values for the pathogenic 

 SchJzotrypanuni cruzi. The results of these investigators indicate that 

 although sugar destruction and formation of acid may be a contributing 

 factor, it will not explain all of the pathological effects of the trypano- 

 somes. This is reviewed by von Brand (1938). 



It is interesting to compare the high aerobic glycolysis rate of trypano- 

 somes with that of malignant tumors. The Warburg quotient (aerobic 

 glycolysis/Qoo ) for normal tissues is usually less than 0.3 (except retina 

 and placenta), while that for benign tumors is about one, and that for 

 malignant tumors is 3.1-3.9 (review, Needham, 1931). The Warburg 

 quotients calculated from the data of von Fenyvessy and Reiner (1928) 

 for T. equiperdum are 0.78 to 2.67. It has been found that KCN may 

 change the Warburg quotient of chick embryos from 0.1 to 3.4, but 

 the quotient for T. equiperdum, in the presence of KCN, showed no 

 significant change (0.78 and 0.80 in two experiments). These compari- 

 sons may be taken to indicate that the relative glycolytic rate of the 

 trypanosomes is different from that of normal tissues and resembles in 

 certain respects that of benign or malignant tumors, but the fact that 

 pyruvic and other acids are formed by trypanosomes instead of lactic 

 acid invalidates this comparison. 



Meyerhof quotients were calculated by A. Lwoff (1933) for Stri- 

 gomonas jasckulatn, S. oncopelti, and heptonionas ctenocephali and 

 were found to be 1.20, 1.38, and 0.125 respectively. The first two are 

 within the normal range of metazoan tissues (Needham, 1931), but 

 that of Leptowonas is very low. Values of the M.Q. calculated from the 

 data of von Fenyvessy and Reiner (1928) on trypanosomes are approxi- 

 mately zero, indicating no reversal of glycolysis, and this conclusion 

 agrees with the chemical equations given above. 



Why Are Anaerobes Anaerobes, and Aerobes Aerobes.^ 



One question which arises in any treatment of anaerobiosis is, "Why 

 does oxygen prevent growth of obligatory anaerobes?" There are several 

 explanatory theories: 



