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SCIENCE 



[N. S. Vol. XLIII. No. 1105 



to homoiotoxins, the cells of certain tumors 

 can overcome the injurious conditions 

 existing in other individuals of the same 

 species and be propagated indefinitely. 

 Tumor cells and ordinary tissue cells do 

 not differ in potential immortality (as 

 Bashford and others assumed), but in the 

 intensity with which they proliferate and in 

 their destructive power. 



Of equally great biological interest are 

 the defensive reactions called forth in the 

 host through the growth of the tumor cells. 

 As one of the most important results, we 

 may here state that no immunity seems to 

 be produced through tumor growth in the 

 animals in which the tumor originated. 

 "We found that in the case of rat and dog 

 tumors, cells remained alive and grew after 

 transplantation into the animal in whicli 

 they originated, while they died in other 

 individuals of the same species. Tyzzer 

 found the same to be true in the chicken, 

 and Haaland and Fleisher and ourselves in 

 the mouse. Haaland 's experiments sug- 

 gested, furthermore, that the autochthonous 

 tumor could not act as antigen and by prov- 

 ing in addition that this tumor does not neu- 

 tralize immune substances, our experiments 

 prove the correctness of Haaland 's sugges- 

 tion that against an autochthonous tumor 

 no immunity can be produced. The greater 

 significance again attached to the study of 

 animals in which tumors originated in con- 

 tradistinction to bearers of experimental 

 tumors, is one of the characteristic tenden- 

 cies of recent cancer investigation, and it 

 is of interest in this connection to note that 

 our experiments indicate that animals with 

 autochthonous tumors are a better soil for 

 the growth of other spontaneous tumors 

 than normal animals. 



While therefore in the organism in which 

 the tumor originated usually no reaction 

 takes place against tumor cells, reactions 

 do take place after transplantation of 



tumor cells into other individuals. These 

 reactions are essentially of a similar char- 

 acter in the case of tumors and of normal 

 tissues. Again correlation between the be- 

 havior of normal and of cancerous tissues 

 has proven fruitful of results in this case. 

 After autotransplantation of a piece of 

 normal tissue, it may in the same way as a 

 piece of tumor, at least in the case of cer- 

 tain tissues, apparently live indefinitely, 

 while after homoiotransplantation, as we ob- 

 served, the tissues die as a result of the at- 

 tack by lymphocytes and through the in- 

 fluence of fibroblasts of the host which 

 produce dense fibrous tissue which in turn 

 strangulates the foreign cells. There is a 

 possibility that the strange body fluids may 

 also directly interfere with the metabolism 

 of certain transplanted tissues to such an 

 extent as to severely injure them. After 

 heterotransplantation the indirect injuri- 

 ous action of the body fluids, which are un- 

 suitable for the metabolism of the trans- 

 planted cells, is more pronounced and 

 leads to the early death of the transplanted 

 cells. We found in the case of skin under 

 these conditions no noticeable activity on 

 the part of the lymphocytes and fibro- 

 blasts. J. B. Murphy, however, recently 

 showed through very ingenious experi- 

 ments that in the case of heterotransplanta- 

 tion also lymphocytes, under certain condi- 

 tions, may be of importance as a defensive 

 mechanism of the host. 



It has likewise been shown by such inves- 

 tigators as Burgess, DaFano, Baeslack, Rous 

 and J. B. Murphy, that in the case of tumors 

 against which an immunity becomes estab- 

 lished, lymphocytes sometimes, in conjunc- 

 tion with other leucocytes, play a distinct 

 role in the destruction of the tumor tissue. 

 This holds good in the case of tumors al- 

 ready established. If immunity is pro- 

 duced before the transplanted tumor has 

 united with the host tissues, the ingrowth 



