Chapter p 



Individuality Differentials in Closely 

 Inbred Strains of Mice 



We have already discussed the transplantations of tissues from one 

 closely inbred strain of mice to another, as well as some trans- 

 plantations in non-inbred mice, and we shall later analyze also 

 heterogenous transplantations between mice and some other species of ani- 

 mals. We shall now consider the transplantations within inbred strains — 

 intra-strain transplantations — the character of the individuality differentials 

 of mice belonging to such strains, and the effects of hybridization between 

 different inbred strains on the character of the individuality differentials of 

 the hybrids. 



From among the large number of these types of transplantation carried 

 out, we shall first select a smaller representative group, in which, to a large 

 extent, some of the complicating factors, as indicated by the presence of 

 polymorphonuclear leucocytes in the transplants, have been avoided. We shall 

 then analyze the results of other groups of intra-strain transplantations, as 

 well as transplantations between hybrids, and some experiments in which 

 the analysis of the complicating factors mentioned, as well as of some addi- 

 tional ones, has been attempted. 



In inter-strain transplantations between strains C57 and D, which we have 

 already discussed, the average grade of ten transplantations was 1.29. This 

 corresponds to a homoiogenous relationship of the individuality differentials. 

 In ten transplantations between not closely related mice belonging to the 

 same inbred strains C57 or D, the average grade was 2.26, which corresponds 

 to syngenesiotransplantation. The grades varied between 2 and 3.12, but 

 in one case the grade was as low as 1.75. In four transplantations within 

 inbred strain A, the average grade was somewhat higher, namely, 2.81. In 

 two New Buffalo mice the average grade was 2. These grades varied between 

 those characteristic of favorable and of average syngenesiotransplantations. In 

 eight transplantations between hybrids (DxC57)F 1( belonging to different 

 litters, the average grade was 1.91, which, in accordance with expectation, 

 is below the grades obtained in grafts between members of inbred strains. 

 In 11 transplantations between hybrids (DxC57)F 1; which were brothers, 

 the average grade was much higher, namely 3.04, a result which approaches 

 that found in autogenous conditions. In 21 transplantations from parents 

 D or C57 to their hybrid children (C57xD)F 1 , the average grade was 

 2.60, which corresponds to a favorable syngenesio-reaction. In case members 

 of the strains to which the parents belonged, but not the parents them- 

 selves were the donors, the average grade in six transplantations was 

 2.35, which is slightly less favorable than the transplantations from the 



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