DIFFERENTIALS IN CLOSELY INBRED MICE 107 



between the reactions against the different tissues transplanted from one single 

 donor into the same host. It was also of interest that in cases in which an 

 infection had taken place in a transplant between near relatives within an 

 inbred strain, this infection and the reaction against the transplant usually 

 remained localized and did not interfere with a good preservation of the tissue 

 at some distance from the place of infection. 



In strain D, a number of transplantations were carried out in which tissues 

 were transplanted from parents to children, or from children to parents. In 

 these experiments, also, autogenous or almost autogenous results were ob- 

 tained, but the number of syngenesio-reactions, with marked lymphocytic in- 

 filtration, was distinctly greater than when tissues were exchanged between 

 brothers and sisters. In some instances, even homoiogenous reactions were 

 noted. On the whole, the reactions in transplantations from children to parents 

 were somewhat less favorable than the reciprocal ones. Also, in strain C57, 

 transplantations from parents to children and from children to parents gave, 

 in the majority of cases, autogenous reactions, but there were several marked 

 syngenesio-reactions. In seven transplantations from C57 children to C57 

 parents the average grade was 2.59. In strain A, autogenous reactions were 

 obtained in transplantations from parents to children. In a general way, it 

 seems that in these transplantations between mice in which the individuality 

 differentials were very similar but not yet identical, lymphocytic reactions were 

 more frequent than in transplantations between more distantly related mice. 

 This corresponds to the fact that a lymphocytic reaction is especially prone to 

 develop when the thyroid transplants are well developed, while in a stunted 

 thyroid, such as we find especially after transplantations between more dis- 

 tantly related mice, the lymphocytic reaction is either lacking entirely or at 

 least it is weaker. 



Exchange of tissues between hybrids composed of two different inbred 

 strains and between hybrids and parents as a test for their individuality 

 differentials. In the beginning of this chapter experiments have already been 

 reported in which we transplanted tissue of hybrids (C57xD)F 1 to mice be- 

 longing to different litters as well as to the same litter of the same kind of 

 hybrid, and other experiments in which we exchanged tissues between hybrids 

 and parents, and vice versa. A few experiments were also considered in which 

 we transplanted tissues from hybrids, not to their direct parents but to other 

 members of their parent strains. 



In earlier investigations we had carried out, on a somewhat larger scale, 

 similar transplantations in which we used hybrid strains (C57xA)F 1 , (tan 

 C57xA)F x and F 2 , and (C57xC)F x , as well as the reciprocal hybrids. It will 

 not be necessary to describe these experiments in detail, because they gave 

 essentially the same results as the transplantations already discussed. We shall, 

 therefore, merely state the main results obtained. 



In the following table, the results of transplantations discussed in the be- 

 ginning of this chapter (Group I) and of this group (Group II) are shown. 

 There may be added to the data contained in this table the fact that in control 

 experiments, in which transplantations of tissues (thyroid, cartilage and fat 



