158 P. L. Krohn 



trans])lantation and the oldest tissue recovered was forty-one 

 months old, Avhich is ])robably outside the ordinary lifespan 

 of the strain of mice used. Loeb (1945) mentions that similar 

 experiments with grafts of ovary failed entirely. Some 

 comments by Dunham, Watts and Adair (1941) that are 

 incidental to their main work, also suggest that the ovary 

 does not tolerate being transplanted more than twice. 



In our own experiments ovaries have been autotrans- 

 planted from one side of the body to the other at intervals of 

 two or six weeks. Control autografts readily survived a 

 period of up to twelve weeks and gave rise to normal vaginal 

 oestrous cycles. In the first group of animals the period 

 between successive transplantations was two weeks. After 

 the second transplantation two out of eight animals continued 

 to show definite oestrous cycles and four of the eight showed 

 occasional and irregular periods of oestrus. After the third 

 transplantation four out of five animals showed no cestrous 

 cycles at all and only one gave a doubtful positive result. 

 The same results were obtained in another group which were 

 continued to a fourth transplantation. In the final experiment 

 six weeks were allowed to elapse before the second trans- 

 plantation. (Estrous cycles did not recur during the succeed- 

 ing six weeks in any of the four animals used. The experiments 

 have, therefore, failed in their purpose. They are being 

 repeated using orthotopic grafts and allowing a longer interval 

 to elapse between successive graftings. 



The behaviour of old and young ovaries in environ- 

 ments of different ages 



Combinations of orthotopic grafts have ' been employed, 

 either young ovaries into old hosts, old into young, young 

 and old into young, and young and old into old. Only Strong A 

 strain mice have been used. It is too early to say what the 

 effects on the numbers of oocytes and on reproduction 

 will be, but it would appear that old ovaries grafted into young 

 animals behave more satisfactorily, as far as the data on the 

 oestrous cycles go, than young ovaries grafted into old animals. 



