Introduction 31 



The pole micists pointed to the possibility that in the case of biological dehydrc- 

 genation by DPN, as opposed to chemical dehydrogenation, the 3-phosphogly- 

 ceraldehyde bound to the enzyme protein, be dehydrogenated by DPN; and that 

 the phosphoric acid reacts only afterwards, displacing the protein from the glyceric 

 acid by means of a process that was called "phosphorolysis". 



In the meantime, a decisive experiment was made. If the theory of phosphoroly- 

 sis was correct, the initial velocity of dehydrogenation had to be independent of 

 the phosphate concentration; according to our equations, however, the phosphate 

 had to exert its influence from the beginning. The experiment showed that the 

 initial velocity depends on the phosphate concentration, as required by our 

 equations. 



This is how the last problem of the chemical mechanism of fermentations was 

 solved in 1957 {23, 24). 



IX. Cancer cells 



The transition from tumors to single Cancer cells constituted the most essential 

 improvement in this field since 1945. 



1. Ascites Carcinoma cells (17, 22, 35, 58) 



Our first unicellular material consisted of the cells of the Ehrlich ascitic Carcinoma 

 of mice. These Cancer cells were available in large amounts in the form of stable, 

 easily centrifuged, and almost pure suspensions. Thus, tissue from the original 

 organ, connective tissue, and necrotic tissue no longer constituted sources of error 

 in measurements of metabolic rate, and fermentation rates rose to values two- to 

 three-times higher than those found earlier in the case of even the purest tumors. 

 The two-vessel method, which requires the use of equal amounts of identical 

 cell material in both vessels, only then became truly applicable to Cancer cells; 

 quantitative experimentation with Cancer cells only then became possible, a 

 progress comparable to the transition from mixtures to chemically pure sub- 

 stances in chemistry. 



2. Earle cells 



Cancer cells as suspensions of single cells may be obtained by the method of 

 W. Earle who uses a shaking machine to agitate Cancer cells (contained in large 

 bottles) over a period of years. Like Goldblatt and Cameron in experiments with 

 the Carrel method, Earle succeeded with his new method to transform normal 

 cells to Cancer cells. 



Two lines of Cancer cells were of special interest for use in metabolism tests : 

 These two lines, one of high virulence and the other one of low virulence, had 

 separated spontaneously from a culture Earle had prepared from a single normal 

 cell. Dean Burk and his collaborators, Wood, Hunter and Hobby, have measured 



