DISCUSSION ON TUMOR RESPIRATION 231 



ently respired at the expense of carbohydrate, and in the absence 

 of oxygen the carbohydrate metaboHsm led to lactate accumulation. 

 A third group, including spleen, testis, and submaxillary gland, 

 formed an intennediate group. But cancer tissue seemed to consti- 

 tute a separate class, having a high glycolysis and a low respiratory 

 quotient. It was concluded that in cancer tissue the mechanism for 

 starting carbohydrate metabolism is present, even over-developed, 

 but the mechanism for oxidizing the split products of carbohydrate 

 is lacking. 



However, Dr. Baker and I (7) found specimens of tumors which 

 respired with respiratory quotient values ranging up to unity and 

 pointed out that other workers, including Dickens himself, had 

 found similar high values. On the other hand, we found values 

 of somewhat less than unity for retina and brain. We concluded 

 therefore, that Dickens' generalization was not valid.* Dickens 

 himself, with Weil-Malherbe (4), has now found that normal 

 jejunal mucosa, a rapidly respiring tissue, has a low respiratory 

 quotient with high aerobic and anaerobic glycolysis. A similar type 

 of metabolism was found with synovial membrane by Bywaters 

 (8). Dickens has therefore abandoned his generahzation, since these 

 are normal tissues showing the behavior that was believed to be 

 specific for tumors. 



It thus appears that no characteristic of metabolism is truly spe- 

 cific for cancer tissue. Nevertheless, most cancer tissues show only 

 a moderately high respiration rate, a moderately low respiratory 

 quotient, and a definitely high sustained aerobic and anaerobic 

 glycolysis, whereas few normal tissues show all these characteristics 

 together. Orr and Stickland (9) very recently found that tumors oc- 

 curring in the livers of rats fed butter yellow possess the power, 

 as do most cancer tissues, to form lactate from glucose, anaerobi- 

 cally and aerobically, and differ distinctly in this respect from non- 

 cancerous liver tissue. Dr. Dean Burk [see below, page 242] has 



* Dickens at first defended his tlieory by attacking our value for the respiratory 

 quotient of brain sUces, while ignoring the rest and ridicuhng "a complicated 

 theory of salt eflFects" which did not appear in our paper. Our values for the 

 respiratory quotient of brain slices were supposed to disagree with otliers in the 

 literature, but careful study showed that objections could be raised to all the 

 results cited, except perhaps Dickens' own. Varying results could be due to the 

 fact that early aerobic glycolysis by brain liberates carbon dioxide from the 

 medium, and this must be carefully controlled if incorrectly high or low respira- 

 tory quotient values are to be avoided. Observing this precaution, we ourselves 

 later obtained slightly higher values ( 18 ) . Our figure for retina has been con- 

 firmed by Dixon (19). 



