DIFFERENTIALS IN CLOSELY INBRED MICE 111 



a 15 months old host, 2^ months after transplantation, good, large follicles 

 and many well preserved corpora lutea were found and there was only a slight 

 lymphocytic infiltration ; likewise in a 19 months old host, large follicles 

 were noted, but here there was too some lymphocytic infiltration around the 

 ovary. We have found indications also that a lymphocytic infiltration may set 

 in late, and further, that a number of successive transplantations may lead to 

 injury of the transplant. 



Such serial transplantations were carried out in strain A. The transplanted 

 ovaries remained in each host for 4 to 6 months, after which time they were 

 re-transplanted into another host. Altogether, the ovaries were thus kept in 

 successive hosts for periods ranging between 14 and 24 months and the age 

 of these ovarian grafts varied between 24 and 36 months. Only in four of 

 eleven of these serial transplants was living transplanted tissue found at the 

 end of the experiment ; and only associated structures were recovered, such as 

 germinal epithelium lining a cyst, ducts consisting of germinal epithelium, and 

 interstitial gland tissue ; in one instance, also a Fallopian tube with preserved 

 epithelium, connective tissue and muscle tissue was found. Lymphocytic in- 

 filtrations were observed in some cases around or near surrounding parts. 

 These experiments prove that only the most resistant tissues were able to 

 survive, and they also indicate that the ovary is less suitable for such serial 

 transplantations than the thyroid gland. 



Transplantation of anterior pituitary glands as indicators of individuality 

 differentials in inbred strains of mice. We have shown previously that anterior 

 pituitary glands may be transplanted successfully and that such transplants 

 may exert effects on the ovaries, which, under certain conditions, increase the 

 incidence of mammary gland carcinoma in the inbred strain A. Additional ex- 

 periments have now been made, in which we compared the reactions against 

 these transplants in various inbred strains differing in regard to the homozy- 

 gous state which they had attained. In most cases, between two and six pitui- 

 tary glands from sisters and brothers were transplanted subcutaneously. 



In this series of transplantations, the transplants of anterior pituitary glands 

 survived readily for long periods of time in most of the inbred strains, espe- 

 cially if the glands were taken from brothers and sisters. However, in the Old 

 Buffalo strain, the transplants had apparently been destroyed at the time of 

 examination ; whether this was an accidental occurrence or is an indication of 

 a more destructive action of the host against the transplant, perhaps caused by 

 a greater dissimilarity of the individuality differentials, an effect similar to that 

 seen after transplantation of the ovaries in this strain, needs further investiga- 

 tion. The most interesting observation from our point of view is the fact that 

 under the conditions of these experiments, lymphocytic infiltration around or 

 in the transplant was, on the whole, rare, and if it occurred at all it usually 

 remained slight. In this respect the results differ from those obtained after 

 long-term transplantation of thyroid gland, ovaries and adrenal gland, where 

 as a rule the lymphocytic infiltration was more marked. On the basis of these 

 experiments we may also conclude that the transplantation of anterior pitui- 

 tary glands is less suited for the analysis of individuality differentials than that 



