DIFFERENTIALS IN CLOSELY INBRED MICE 109 



enter, are in accordance with expectations, considering the fact that, in con- 

 trast to the homogeneous genetic constitution in the F x generation, in the F 2 

 hybrids, different individuals may differ in their genetic constitution. 



Transplantation of ovaries in inbred mice and interaction between endocrine 

 factors and individuality differentials. We have carried out a larger series 

 of transplantations of the ovary in inbred mice for two reasons : 1 ) the ovary 

 in the mouse offers certain advantages over other organs for the study of the 

 relations between transplantation-reactions and the character of the individu- 

 ality differentials, since this organ contains a variety of structures which differ 

 greatly in sensitiveness and thus in their ability to survive ; it presents a grada- 

 tion in the degree of reactions between the individuality differentials of host 

 and donor, without regard to the cellular response of the host against the 

 transplant. The corpora lutea and large follicles are the most sensitive struc- 

 tures ; they are followed in order of decreasing sensitivity, or of increasing 

 resistance, by the medium, small and primordial follicles, by germinal epi- 

 thelium and ducts derived from it, by medullary ducts, by cortical spindle cell 

 connective tissue, and by interstitial gland. The Fallopian tubes, situated near 

 the ovaries, are also rather resistant structures. By noting the survival or lack 

 of survival of these different constituents of the ovary, we can grade the 

 degree of similarity between the individuality differentials of host and donor ; 

 (2) the ovary, also on account of its structure, is a good test organ for the 

 evaluation of the importance of endocrine factors, of age of donor and host, 

 as well as of the sex of the host in the results of transplantation. We are espe- 

 cially concerned with the question as to how far the endocrine influences, 

 which originate in the host ovaries, may affect the fate of the transplants. The 

 associated structures of the ovary, such as germinal epithelial cysts and ducts, 

 medullary ducts and interstitial gland, together with the Fallopian tubes, are 

 comparable in their power of resistance to thyroid gland, striated muscle 

 tissue and some other organs, since they are at least partially preserved under 

 conditions in which the various types of follicles are in a graded manner 

 destroyed. Because the transplantation of the ovary of the mouse has thus 

 many advantages over that of many other organs in the analysis of the in- 

 dividuality differentials, we have carried out a large number of ovarian trans- 

 plantations in various inbred strains of mice, but this account will be limited 

 to a brief statement of some of the principal conclusions at which we have 

 arrived. 



In grafting the ovaries in strains AKA, Old Buffalo, and to some extent 

 also in strain New Buffalo, the follicles are much more injured than are the 

 associated structures of the ovary and the constituents of other organs usually 

 used in our transplantations, indicating a difference in the constitution of the 

 individuality differentials in the animals composing each of these strains. In 

 the other strains, A, C3H, CBA, C57 and D, the disharmony between the in- 

 dividuality differentials is not so great that it affects the state of the follicles 

 very considerably, although it may affect especially the formation of large- 

 sized follicles and corpora lutea under conditions in which the preservation of 

 small-sized follicles is not yet interfered with. In these latter strains, in 



