TRANSPLANTATION OF TUMORS 385 



various stimuli, showing an increase in growth energy, especially in the 

 course of the first transplantations. If the constitutional factors in host or 

 transplant, in particular the relations between organismal differentials of 

 host and transplant, are unfavorable, the various kinds of growth stimuli 

 may not be able to overcome the obstacles to transplantation, but on the 

 other hand, if the inherent specific tumor stimulus (Gi) is very strong, the 

 tumor may be able to overcome a not quite adequate constitutional condition 

 and may dispense with growth hormones or other growth promoting sub- 

 stances (Ge) circulating in the bodyfluids. The less favorable the constitu- 

 tional condition of the organismal differentials, the stronger must be the 

 growth factors, those present in the host as well as those residing in the 

 transplanted tumor cells, if a continuous growth of the tumor shall be 

 accomplished. 



Because of the action of these variables, including the relationship be- 

 tween the individuality differentials of host and transplant, growth energy 

 and transplantability of a tumor do not need to follow a parallel course. The 

 difference between these two sets of conditions was especially marked in the 

 case of a carcinoma originating in a Japanese waltzing mouse studied by us; 

 all the transplants grew, but the growth energy of the developing tumors 

 was, at least in the first generation, not great. Here the constitutional factors, 

 the individuality differentials, in the host and graft were well adapted to 

 each other. The distinction between growth energy and transplantability was 

 subsequently emphasized also by Apolant, and it still is useful at the present 

 time. 



I. Changes in Growth Energy 



Of the two sets of factors, the constitutional factors residing in the host 

 and those determining the growth energy of the tumor cells, the latter were 

 more readily accessible to experimental analysis and the first attempts we're 

 therefore directed towards their modification by exposing the tumor cells 

 to certain physical and chemical conditions. These experiments revealed the 

 degree of what may be termed the elasticity of the tumor cells, their ability 

 to recover from injury and to regain the growth energy which had been 

 diminished by their exposure to injurious factors. Such reactions on the 

 part of the tumor cells also represent adaptive processes ; but they are 

 temporary, not permanent adaptations. In the early period of experimental 

 cancer investigations, the writer determined the intensity of heat required to 

 cause the death of the rat sarcoma cells, and Jensen, independently, made 

 similar determinations in mouse carcinoma. While the methods used in these 

 two cases were different, the results were of the same kind. We found, also, 

 the conditions under which certain chemical substances, such as glycerin 

 and KCN, kill the tumor cells. It could be shown (1903) by the use of inter- 

 mediate intensities in physical and chemical actions that between the full 

 virulence and the death point of the tumor cells there exists an intermediate 

 stage, in which the latter are still alive though growing with a much 

 diminished energy. In certain cases, tumors grew temporarily; then the 



