THE GEXETICS OF TUMOR TRAXSPLAXTATIOX 301 



It will be necessary to wait until far more extensive and carefully con- 

 trolled studies have been made before any conclusions of general applica- 

 tion can be drawn. 



Relation to Indriduality 



Transplantation studies afford one of the most promising methods 

 of investigation of the process of acquisition of complete biological 

 individuality. 



By the growth of heterologous adult tissue in embryonic culture media, 

 such as the allantois of the chick embryo, and by the opposite process of 

 growing embryonic tissue for a considerable period in heterologous adult 

 individuals, evidence is clearly provided that full expression of the bio- 

 chemical characteristics of the species, strain or individual is gradually 

 developed. 



Tumors which represent a source of supply of rapidly growing tissue in 

 which the degree of biochemical specificity may. to some extent, be measured 

 by genetic tests are valuable aids in such research. 



By holding the source of tumor material constant and by varying the 

 degree of biological differentiation of the host that receives the implant, 

 information concerning the process of differentiation both chemical and 

 morphological should be obtained. 



Similarly by the inoculation of several types of tumors in a single host 

 the reaction of that host can be measured in terms of its response to different 

 biological stimuli. 



The REL.A.TION OF Transplant.able Tumors to Spontaneous Tumors 



The bearing of genetic work with transplanted tumors on the genetics 

 of spontaneous tumors in mice is one on w^hich a great deal of difference of 

 opinion exists. One of the commonest points of view is that a clear and 

 distinct line should be drawn between experimental work on (/) transplanted 

 tumors, (2) induced tumors and (j) spontaneous tumors. While there is 

 no doubt that characteristic differences exist between the three groups as 

 regards the t>^e of problem which each is best fitted to cover, it seems likely 

 that an extreme point of view^ such as that cited is incorrect. One of the 

 reasons why a point of view of that sort has developed is that there is proper 

 objection to applying, in toto, the results obtained with either transplanted 

 or induced tumors to the field of the spontaneous tumors. This does not 

 mean, however, that work with spontaneous and induced tumors may not 



