i6 4 



Scientific Proceedings (120). 



of experiments which have dealt with the transplantation of 

 normal and of neoplastic tissues in vertebrates. 



Following a number of experiments in this field, covering a 

 wide range of material, it has become generally recognized by 

 biological investigators that the closer the genetic relationship 

 between the host and the donor of the graft tissue, the greater is 

 the likelihood of persistent and progressive growth of an implant 

 of tissue from one to the other. 



Similarly it has been found that in the ordinary "laboratory" 

 races of mammals, inbreeding has not been intensive enough to 

 have produced a close degree of genetic resemblance between 

 individuals within the race. Without this resemblance the con- 

 tinued growth of tissue transplants made from one animal to 

 another is impossible. When close relatives such as parent and 

 offspring or litter mates are picked for this interchange of implants, 

 there is, as Loeb and others have pointed out, more chance of 

 persistence of the implants than when unrelated animals are used. 

 Loeb 1 has proposed the term "syngenesio-plastic transplantation " 

 for experiments involving the close relatives referred to. 



When, however, closely inbred races of known genetic constitu- 

 tion are used, results are obtained which show that the distinctions 

 between "homio," " syngenesio," and "auto" transplantations are 

 only relative and may be deliberately broken down by picking 

 animals of certain definite genetic constitutions for experimenta- 

 tion. 



Thus in animals of a closely inbred and genetically homoge- 

 neous strain of Japanese waltzing mice [already described in con- 

 nection with experiments on the inheritance of susceptibility to 

 transplanted tumors*], the general reactions of an individual to 

 subcutaneous transplants of bits of its own spleen (autotrans- 

 plants), or to bits of the spleen of another Japanese waltzing 

 mouse of the same inbred race (homiotransplants) were the same. 

 Both implants "auto" and "homio" persisted successfully, estab- 

 lished a blood supply, and remained healthy. 



1 Loeb, LeO, Journ. Med. Research, I0l8, xxxix, 39 57. 



2 Little, C. C, and Tyzzcr, E. E., Journ. Med. Reseaich. 1916. xxxiii, 393-453. 



