Pi^rf T Transplantation of Tissues in Higher Vertebrates 



as a Method for the Analysis of the Organismal 

 Differentials 



Chapter I 

 General Considerations 



Our analysis of individuality and organismal differentials is based 

 primarily on investigations into the fate of transplants of normal 

 tissues, and also of tumors, and their genetic relationship to the host 

 in which they live. In such an analysis it will therefore be necessary to discuss 

 in more detail the results we have obtained in these experiments, especially 

 in the ones on which a full report has not as yet been published. However, 

 before entering into a discussion of these results, the following questions, 

 which relate to these investigations in general, will be considered: (1) the aim 

 of these investigations; (2) the factors which have to be taken into account 

 in evaluating the conclusions, namely, a) the mode of interaction between host 

 and transplant and the various reactions of the host which are induced by the 

 transplant, b) the differences existing between different species, c) the differ- 

 ences existing between different strains and individuals, d) the differences 

 existing between different tissues serving as transplants; (3) the methods 

 which best serve our purposes and the variable factors which may complicate 

 the application of these methods, and (4) the possible errors which have to be 

 considered in these experiments. 



1. The aim of these investigations is the analysis of the organismal differ- 

 entials of individuals, families, strains and species. We are not primarily con- 

 cerned with various other problems, as, for instance, the. conditions under 

 which tissues survive and the establishment of the methods most suitable to 

 accomplish their survival ; the analysis of polarity in the structure of various 

 organisms and tissues, and the question of the factors which determine the 

 growth of the grafts or the fate of pigmented tissues. Only in so far as such 

 problems aid in the analysis of the organismal differentials and, in particular, 

 of the individuality differentials, are they to be considered. But these investi- 

 gations, in addition to their primary objective, contribute also secondarily to 

 our knowledge of tissue reactions in general, of factors which are active in 

 pigment formation, and to our understanding of the potential immortality of 

 tissues. In a wider sense, our interest centers in the phylogenetic and onto- 

 genetic evolution of the organismal differentials, in the relation of these 

 differentials to organ and tissue differentials, and to the psychical differen- 

 tiation and the social life of individuals. 



2. (a) As to the mode of interaction between host and transplant, the fol- 

 lowing factors have to be considered : ( 1 ) The effect which the bodyfluids of 

 the host exert on the transplanted tissues ; (2) the effect which the connective 

 tissue and blood vessels of the host have on the state of the graft; (3) the 



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