Chapter $ 



The Relations Between Hybridization 

 and Transplantation 



In the preceding two chapters we have analyzed the relationship which 

 connects fertilization and hybridization with the organismal differen- 

 tials of the organisms which play a part in these processes, the term 

 "organismal differentials" being used in the wider sense. We have stated that 

 in fertilization and hybridization the interaction between the male germ cells 

 and certain somatic tissues in the female, the interaction between the chromo- 

 somes of spermatozoon and egg, and between the genes they contain, and 

 also the interaction between the cytoplasm of the ovum and the male and 

 female nuclear substances, as well as the action of certain substances which 

 develop during embryonal development, have to be taken into account. It 

 was considered at least possible that some of the substances involved in these 

 processes are the precursors of the individuality differentials of the adult 

 organisms. In transplantation of adult tissues we are concerned with the 

 relations to each other of fully developed organismal and organ differentials 

 in host and transplant. It is certain that the results in both transplantation and 

 hybridization depend upon the genetic relationship between the two inter- 

 acting organisms. While, thus, transplantation and fertilization, and in par- 

 ticular hybridization, have certain important factors in common, they differ 

 in other features, and we should therefore expect, in addition to certain paral- 

 lelisms between the feasibility of hybridization and transplantation, the oc- 

 currence of definite differences between these two processes. These have 

 been discussed from general points of view in the preceding chapters, when 

 we analyzed and compared transplantation in higher adult and in phyloge- 

 netically and ontogenetically more primitive organisms and the relations which 

 exist between transplantation and fertilization. 



There still remains the question as to whether actual experiments in trans- 

 plantation support the assumption that a parallelism exists between the 

 ability to make successful transplantations between different species and the 

 ability to hybridize these species. Schoene suggested, in 1912, that hetero- 

 transplantation might be possible between hybridizable species, but he also 

 pointed out that while hybridization can take place between rat and mouse, 

 transplantation of skin from rat to mouse, and vice versa, does not succeed ; 

 however, it is doubtful whether hybridization between rat and mouse can 

 actually be accomplished either. 



As stated previously, the most extensive experiments in which the existence 

 of a parallelism between transplantability and hybridization was tested were 

 carried out by W. Schultz. He attempted to prove that these two conditions 

 follow a parallel course and that a wide cleft exists between hybridizable and 

 non-hybridizable animals as far as the mutual transplantability of their tissues 



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