236 A SYMPOSIUM ON RESPIRATORY ENZYMES 



both types of comparison, involving non-homologous as well as 

 homologous contrasts and similarities, must be made. 



In furtherance of their position, Berenblum, Chain, and Heatley 

 advance the view that "the tumors which have hitherto been found 

 to have a glycolyzing type of metabolism associated with a low 

 R.Q, possess these properties in virtue of their origin from noiTnal 

 tissues which also possessed these metabolic characters" (Id, p. 138). 

 In experimental support of this view they reported, following Crab- 

 tree's earlier measurements showing that whole skin undergoes little 

 alteration of metabolism when it becomes papillomatous, that noniial 

 skin epithelium and Shope papilloma of the domestic rabbit also 

 possess essentially the same quantitative metabolism in regard to 

 aerobic and anaerobic glycolysis, respiration and respiratory quo- 

 tient. Unfortunately these data, although interesting enough in 

 themselves, have no great bearing on the really pertinent problem 

 as to the difference (or similarity) between a definitely malignant 

 tumor and a closely homologous normal tissue; indeed the support- 

 ing experiments are themselves somewhat unsatisfactory, being diffi- 

 cult to analyze because of the unorthodox technical method em- 

 ployed and the fact that Q values were based on nucleic acid- 

 phosphorus content instead of on dry weight. Certainly there are 

 advantages in the use of the nucleic acid-phosphorus criterion, but 

 it is unfortunate that the dry weight values were not at least reported 

 so that the reader could make Q value comparisons by the standard 

 methods and check, in particular, the bare and doubtful state- 

 ment (lb, le) that the normal skin epithelium and Shope papilloma 

 metabolic values were "very similar to those for many skin carci- 

 nomas quoted in the literature." (By certain inferences, the anaerobic 

 glycolysis of the skin epithelium and papilloma studied would appear 

 to have been at most Q^^a = 1 to 3, or quite low for the usual malig- 

 nant tumor.) The two criticisms of the unorthodox (however correct) 

 procedures employed are admittedly minor as compared with the 

 fact that the Shope papilloma, as such, is not malignant, nor was it 

 so described. 



Table 1, now presented for discussion, provides, in regard to 

 primary rat liver tumors, not merely one but several types of homol- 

 ogous tissue, including adult normal liver and two types of growing 

 liver, regenerating and embryonic. These materials will provide, I 

 believe, as pertinent cases as are yet available for the comparison of 

 a malignant tumor with an homologous, in fact identical, tissue of 

 origin (liver). 



