244 A SYMPOSIUM ON RESPIRATORY ENZYMES 



row erythroid cells. In both these cases the anaerobic glycolysis 

 Q values are of the same order of magnitude (7-10) as that of the 

 embryonic Hvers containing a high percentage of red cells, and the 

 other metabolic values are hkewise comparable. Direct measurement 

 of the metabolism of the red cells in the embryonic livers offers con- 

 siderable diflBculty experimentally; moreover, when they are ob- 

 tained, the measurements might still be somewhat uncertain because 

 of possible secondary effects of the technical methods employed to 

 separate them from the liver. But it is felt that in the light of the 

 two quite comparable cases offered and a considerable background 

 of knowledge regarding the metabolism of blood cells generally, 

 there is no reason to doubt that the rather high glycolytic metabohsm 

 of embryonic hvers is due to the erythropoietic element and not to 

 the true liver cells. In other words, neither the embryonic liver per 

 se, nor the regenerating Hver, nor adult normal liver, nor in fact any 

 healthy liver, growing or otherwise, possesses a noteworthy glycolysis, 

 in contrast with the various malignant hepatomas, where a large 

 glycolytic capacity obtains. The case of Berenblum, Chain, and 

 Heatley ( lb) that "when a tumour is compared with the tissue from 

 which it is derived, there are no metabolic characteristic differences 

 or pecuHarities between the carbohydrate metabolism of the two" is 

 clearly not valid; nor, for lack of evidence, is the more general 

 contention quoted earlier that tumors glycolyze by virtue of their 

 origin from normal tissues which also possess this metabohc charac- 

 ter* (Id, p. 138). 



The question whether the increased formation of lactic acid in 

 the hepatic tumors— or in tumors generally— is necessarily an expres- 

 sion or requirement of the growth involved, as is commonly believed, 

 is thus answered in the negative by the experiments briefly described 

 in Table 1. It may be concluded, more generally, that growth does 

 not necessarily require glycolysis, and may on occasion be main- 

 tained at the highest levels on an essentially aerobic non-fermenta- 

 tive metabolism. 



If it should be asked why malignant tumors possess glycolysis 

 if not because of growth, I would venture the opinion that the 

 glycolysis is better correlated with the more primitive organization 

 or lesser differentiation involved. 



Most of the foregoing discussion has been concerned with com- 



* I do agree with Berenblum et al. — and not with Dickens, as aheady indi- 

 cated — tliat the medium-low respiratory quotient of tumors may well be derived 

 from the tissues of origin, in the sense that it remains by and large unchanged 

 in tumors. 



