434 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



in our early analysis of tumor transplantation we admitted the possibility that 

 extraneous agents might be concerned in the growth of tumors, and this sug- 

 gested a possible difference in the behavior of normal tissues and of tumors. 

 Our findings regarding the difference between the results of auto- and 

 homoiotransplantation of tumors, the observations of Schoene and Bashford 

 that an immunity against tumors could be produced by inoculation of normal 

 tissues, but that it was impossible to immunize with autogenous tissues 

 (Apolant, Woglom), as well as the behavior of heterotransplanted tumors, 

 suggested also to Ehrlich and Bashford that in tumor immunity there may be 

 a component directed against the tumor as a tissue and not as a tumor. Ehrlich 

 even went so far as to state that tumors showed in this respect a greater 

 specificity than normal tissues, inasmuch as he assumed that the latter could 

 be successfully transplanted between individuals belonging to different but 

 hybridizable varieties, while it was difficult to transplant tumors even to dif- 

 ferent strains within the same species ; and Bashford, Murray and Cramer in- 

 terpreted the condition following retrogression of a tumor, which was desig- 

 nated as panimmunity by Ehrlich, not as due to a specific tumor immunity but 

 as directed against the tissues of which the tumor was composed. In a similar 

 manner Bashford and Russell (1910) explained the immunity produced 

 against a second heterogenous tumor through a first inoculation with the same 

 heterogenous tumor; in this case, too, they assumed that the immunity was' 

 directed not against the tumor but against the tissues. Some years later 

 Murphy transplanted not only heterogenous tumors, but also heterogenous 

 embryonal tissue, into the chick allantois and found that both tumor and 

 embryonal cells behaved similarly under these conditions, although he stressed 

 the results obtained with tumors rather than those obtained with embryonal 

 tissues. Little also, in 1922, using more closely inbred strains of mice, com- 

 pared the genetic factors underlying the transplantation of tumor tissues 

 with those effective in the transplantation of normal spleen from points of 

 view similar to our own. 



Yet notwithstanding these analogies between the growth of tumors and 

 normal tissues, which began to accumulate more and more, the large majority 

 of authors still conceived tumor growth and tumor immunity as essentially 

 distinct from the growth and immunity of normal tissues. This was true, as 

 mentioned, of Ehrlich as well as of Bashford and his associates. The latter 

 saw one of the characteristic features of tumor immunity in the lack of stroma 

 reaction, as first defined by Russell. Moreover, they attributed all the reac- 

 tions of the host against tumors to an induced active immunity against tumors 

 (Russell), in contradistinction to the writer's subsequently defined concept of 

 preformed individuality differentials, to which the primary reaction against the 

 homoiogenous transplant, in the case of normal as well as of tumor tissues, was 

 attributed ; also, the active immunity against tumors was considered by us as 

 resulting from differences in organismal differentials between host and tumor. 

 Tyzzer, who recognized the importance of hereditary constitutional factors in 

 the immunity against tumors, likewise accepted Russell's interpretation; in 

 estimating the factors which determine the transplantability of tumors and 



