158 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



may explain, as well, the occasional lack of success in autogenous trans- 

 plantations, while we held that the controlling factors are identical in hosts 

 and in autogenous grafts. 



It was at this point in the history of transplantations that the viewpoints 

 developed in immunology and serology began to be applied. It was believed, 

 with some justification, that these differences in the chemical constitution of 

 host and transplant might be due to differences in the structure of proteins or 

 of a certain protein in host and transplant, and that after transplantation of a 

 tissue into a different host, such a protein might give rise to antibodies, com- 

 parable to hemolysins or agglutinins. Furthermore, anaphylactic phenomena 

 were used in explaining the destruction of the transplants in unfavorable 

 hosts. While we stressed the concept that the primary incompatibility between 

 bodyfluids and tissues of host and transplant, as such, may lead to toxic in- 

 jury of the transplant, the large majority of investigators thought at that time 

 that immune processes, taking place in the host against the graft, were the 

 principal factors that produced the injury and destruction of the graft after 

 homoiogenous and heterogenous transplantation, although it was considered 

 possible that a primary toxicity of the bodyfluids might play a minor role. 

 This point of view was presented especially by Schoene, a collaborator of 

 Ehrlich, and there was some direct experimental evidence in favor of this 

 interpretation. In the case of tumor transplantation it had been possible to 

 demonstrate an active immunization of the host as the result of the growth 

 and regression of a primary tumor and of various other conditions, and 

 Russell went so far as to maintain that in every case the lack of success in 

 transplantation of tumors as well as the regression of transplanted tumors 

 was due to the development of an active immunity against the tumors. The 

 reaction of the host towards the transplanted tumor was assumed to be the 

 consequence of the development of immunity in the host and the period 

 necessary for the appearance of a reaction should accordingly correspond to 

 the time required for the production of an immune state. This view was 

 accepted also by Tyzzer and Burgess, and by various other investigators, and 

 Tyzzer applied this conception to the reaction on the part of the lymphocytes. 



In the case of normal tissues, Schoene found it possible to immunize a rat 

 actively against mouse organs ; such an immunized rat reacted more rapidly 

 against a subsequently transplanted piece of mouse skin. It was more difficult 

 to elicit immunity against homoiogenous skin. But Schoene succeeded, by pre- 

 liminary treatments with embryo skin, kidney or liver of rabbit, in immuniz- 

 ing another rabbit against homoiogenous tissues, so that, 24 days after graft- 

 ing, a homoiogenous skin transplant was more rapidly destroyed while autog- 

 enous skin was not affected. The more closely donor and host were related, 

 the more difficult it was to produce such an immunity. Accordingly, skin 

 grafts between brothers and sisters were more successful than those between 

 distant members of the species ; yet Schoene did not recognize the significance 

 of genetic factors in transplantation. Also, the observation that skin grafts 

 could apparently heal in for two or three weeks and that only then were they 

 cast off, was interpreted as indicating that a certain time had to elapse before 



