io8 



Scientific Proceedings (38). 



comes absorbed. Our experiments consisted in the subcutaneous 

 inoculation into a rat, of the normal skin and spleen tissue of a 

 mouse followed in a few days by a subcutaneous inoculation of 

 Ehrlich's sarcoma of a rat. The aim of this treatment was to 

 accustom the tumor cells to mouse tissue, and then to see whether 

 such a rat tumor, which may have obtained during its growth the 

 food supplied by the inoculated normal mouse tissue, would not 

 grow more readily when inoculated subsequently into a mouse. 

 The results of this investigation were negative, but the extremely 

 interesting fact was observed that a certain number of the rats 

 treated with mouse tissue appeared immune against growth of the 

 rat sarcoma. The following table will illustrate this phenomenon : 





Treated Animals. 



Controls. 



No. of rats inoculated with tumor. 



40 



40 



No. of rats survived at the final examination. 



27 



40 



No. of rats with tumors. 



IO 



36 



Per cent, of takes. 



37% 



90% 



Similar positive results were obtained recently by C. Lewin, 

 who succeeded in immunizing rats with mouse tumor and vice versa. 



It would seem that this discovery of the possibility of immuniz- 

 ing an animal against growth of tumor by treatment with alien 

 tissue not only adds a new fact to the study of artificial immunity, 

 but is also of some theoretical interest. It would appear that 

 Ehrlich's atreptic theory, with which he explains all the phases of 

 tumor growth, while possibly of great importance in the explana- 

 tion of certain facts, probably does not have a universal applica- 

 tion. According to this theory the tumor of a rat grows within 

 that animal because it finds there the necessary specialized food. 

 On the other hand, organ cells of a mouse do not possess, nor do 

 they require the specific food of the rat and this is the reason why 

 a rat tumor fails to grow indefinitely in a mouse. When a rat is 

 immunized against growth of rat tumor by previous treatment 

 with mouse tissue, such a failure to grow cannot be ascribed to 

 the lack of proper nourishment within the host, since the previously 

 inoculated mouse cells could not assimilate such food. The ex- 

 planation must rather be sought in some protective substances 

 within the host created under the influence of the implanted mouse 

 tissue. 



