454 HAYATO ARAI 
days the degenerated follicles were first found and these probably 
originated from enlarged primitive follicles. 
vi Loeb (11), while studying the cyclic changes in the ovaries of 
guinea-pigs, found that at eighteen days of age the degenerative 
process in some follicles had been entirely completed, and con- 
nective tissue had begun to grow into the cavity. Thus the de- 
generative processes occur at about the same phase both in the 
rat and in the more precocious guinea-pig. 
Moreover, Loeb states that, associated with ovulation, all the 
follicles, with the exception of very small ones, degenerate. The 
general degeneration of the follicular granulosa cannot be seen be- 
fore ovulation. This sudden degenerative process, as well as 
typical follicular degeneration, is quite independent of coitus. 
He further found that in newly ruptured follicles the degeneration 
of the granulosa is shown, except in the very small follicles, while 
in a large majority of the follicles almost the whole granulosa is 
found in the process of degeneration, and this degeneration is es- 
sentially independent of copulation and of pregnancy, but di- 
rectly connected with ovulation. Furthermore, from the age of 
the corpora lutea, the ultimate fate of the follicles, i.e., whether 
these will disappear or not may be inferred. At a given time, 
approximately ten days after ovulation, a certain equilibrium is 
reached between the follicles which undergo degeneration and 
those which grow further. Among those which were growing, 
the degenerative process may also take place. 
Though in my study the exact age of the corpora lutea cannot 
be determined, we can assume for the two pregnant rats, whose 
ages are eighty and ninety-five days, respectively, that the cor- 
pora lutea (from the estimated age of the fetus) were formed 
within the ten preceding days. In these cases the number of 
the degenerated follicles of middle and large sizes is far greater 
than in the other rats at about the same age. Although in these 
cases the corpora lutea may have been present within ten days 
after ovulation, as was inferred, yet it is premature to conclude 
from my study that all of the follicles of large and medium size 
undergo degeneration after the appearance of relatively new 
corpora lutea, as Loeb stated. The number of middle-sized 
