1910.] 



Coyitributions to tJie Biochemistry of Growth. 



313 



represents the condition where the absolute amount of tumour growth was 

 small, and where therefore practically all the nitrogen retained must have 

 gone to the host. During this period new stroma is formed and the tumour 

 establishes itself. During the third period, starting from the tenth day to 

 the sixteenth after trans])lantation, the absolute amount of tumour growth 

 was large, and practically all the nitrogen found in the tumour when the 

 animals were killed was retained during this period. If this amount is 

 subtracted from the total amount of nitrogen retained during the third period, 

 one arrives at the amount of nitrogen retained by the host during that period. 



Any changes in the metabolism appearing in the first period after trans- 

 plantation can be attributed mainly to the processes following upon inoculation 

 (stroma-formation, etc.), while in the second period after transplantation 

 those changes which are due to the growth of the tumour cells should come 

 out most clearly. We find from Table IV that during the second period after 

 transplantation the nitrogen retention by the host remains as high as it was 

 before transplantation. Table I shows that the nitrogen excretion in the 

 urine gradually diminishes as the tumour grows. In a former paper by one of 

 us* it has been shown that the slow growth of a tumour may have a favourable 

 influence on the growth of the host, and certainly does not retard it. From 

 what has been said above, it is clear that in our experiments the tumour cells 

 derived their supply of nitrogenous material by absorbing a part of that 

 fraction of the nitrogen which otherwise would have served as a source of 

 energy. They do not compete with the growing cells of the host, but they 

 add their demands to those of the growing somatic cells. 



It is obvious that as tlie tumour increases in size the amount of nitrogen 

 necessary to replace the wear and tear of the cells of the tumour- bearing 

 animal increases. At the same time a much larger amount of nitrogen will 

 be necessary to cover the demands of the growing tumour cells, which rapidly 

 increase in number. The result will be that the ergogenic fraction gets 

 smaller and smaller and eventually a condition will arise when the host is 

 incapable of absorbing sufficient nutritive material to cover the metabolic 

 expenses of the host; The animal will then be in a state of under-feeding. 

 The study of this condition will no doubt yield interesting results, but their 

 correct interpretation will present great difficulties, since the essential 

 features of the growth of cancer will be either masked or complicated 

 by secondary factors. This condition will be discussed in another paper. 

 We have referred to it here only in order to emphasise the fact that in our 

 present investigation we have avoided these conditions, and that our present 



* Cramer, " The Gaseous Metabolism of Rats inoculated with Malignant New Growths," 

 ' Phird Scientific Report of the Imperial Cancer Research Fund,' 1908, p. 427. 



