62 HAYATO ARAI 



After recording the body weight and body length, the abdomen 

 was opened and the left surviving ovary was carefully removed 

 from the surrounding tissues. The examination of the uterus 

 showed no abnormality except in some cases in which the stump 

 of the right cornu was adherent to the intestine or peritoneum, 

 though in the majority of cases it was free and mobile. So far 

 as gross appearance was concerned, the right cornu appeared 

 about the same as the left. No sign of atrophy could be found 

 on either side, and when the left was hyperemic, the right was 

 hyperemic also. The surviving left ovary was weighed and the 

 sections of it made in the same way as that just described for 

 the right ovary. The viscera of the control rats were also 

 examined, but no abnormahties were found in them. The left 

 ovary of the control rats was also prepared at the same time. 

 The procedure just described gave for histological study in each 

 group the right ovary of the operated rat at the age of operation 

 — twenty days — and the left, surviving ovary of the operated 

 rat at the time of killing — together with the left ovary of the 

 control rat taken also at the time when the operated rat was 

 killed. 



The method of counting the ova has been fully described in 

 my earher paper ('20). Briefly it is as follows: The number of 

 ova was counted from all sections, but in order to avoid the 

 counting of one ovum more than once only those which possess 

 a distinctly outlined and deeply stained nucleus were recorded. 

 I have divided the larger degenerated folhcles into medium-sized 

 and large degenerated follicles. The medium-sized are repre- 

 sented by those follicles which may in some instances, though 

 not always, show quite a small cavity, and in which the ovum 

 has either degenerated or disappeared, leaving at times the mere 

 contour of the ovum without a nucleus. The large degenerate 

 follicles are represented by those which possess a completely 

 formed cavity, as well as a cumulus ovigerus, and in all cases 

 the ovum has either disappeared or lost its nucleus. 



The Ust of rats used is as follows : 



