74 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



In earlier investigations, Schoene compared various types of transplanta- 

 tions of skin into defects in the skin ; he used as criterion of the results the 

 healing' in or the casting off of the transplants, which represents an all or 

 nothing effect and does not allow the recognition of intermediate degrees of 

 reactions. In young rats, autotransplantations of skin succeeded almost invari- 

 ably, while in older rats the pieces were entirely or partly cast off. In trans- 

 plantations between relatives, the most favorable results were obtained be- 

 tween brothers and sisters, provided the animals were young; but only in a 

 small minority of cases did the grafts in relatives behave like autotransplants ; 

 in the large majority, they were cast off like homoiotransplants. However, 

 altogether only eighteen transplantations between relatives were carried out, a 

 number which, considering the method used and the results obtained, was 

 hardly sufficient to differentiate between different types of transplantations. 



If instead of considering merely the averages, also the intensity of the reac- 

 tions in the individual experiments are taken into account, it is found that in 

 the spectrum of relationships the grades of the syngenesiotransplants range 

 between those characteristic of homoiogenous transplants and those approach- 

 ing almost the grades characteristic of autogenous transplants, all transitions 

 in grades being found. These results indicate the presence of multiple factors 

 as the genetic determiners of the individuality differentials in the different 

 animals. We have not to deal with the simple proportions of alternating 

 Mendelian inheritance, such as we find if one or two factors are the hereditary 

 determiners. The results are similar to those noted in the hereditary trans- 

 mission of quantitative differences in the two parents, each quantity being 

 represented by multiple factors and one-half of the multiple factors of each 

 parent being united in the child ; this condition would lead to a series of inter- 

 mediate results in different matings and to the appearance of a blending in- 

 heritance. The combination of the multiple factors of the parents leads in the 

 offspring to the production of a chemical substance, the individuality differ- 

 ential, which is present in all, or almost all, the tissues and organs of the child. 

 The assumption of the presence of multiple factors as determiners of the 

 individuality differential is also in accordance with the gradations in the in- 

 tensity of the reactions against homoiogenous tissues which were found in the 

 numerous experiments carried out. 



The effect of variations in the individuality differentials of host and donor 

 on transplanted organs and their constituent parts in the rat. We may here 

 digress from the consideration of syngenesiotransplantations and discuss the 

 manner in which different organs and tissues can be used in the analysis of the 

 character of the individuality differentials and of the organismal differentials. 

 Not only the reaction of the lymphocytes and of the connective tissue against 

 the transplant, but also the survival and preservation of the constituent parts 

 of the transplanted organs may be used in the standardization of the individual- 

 ity differentials, provided their comparative power of resistance is taken into 

 account, and, conversely, the various degrees of injury inflicted on these con- 

 stituent parts of organs may serve as a test of their sensitiveness. Conditions 

 prevailing in syngenesio-, homoio- and heterotransplantations cause different 



