Abstract
The material is the ovaries of a jenny ass assumed to be in the pro-oestrus. One ovary had two follicles before and after the ovulation, while another one was in the resting period. They were investigated anatomically and histologically. The ovarian changes, traced by rectal palpation in the previous report. could be ascertained.
1. The sexual organs of the jenny are much larger than the mare's in the proportion with the body: the ovary is remarkably large, but the relative position between the genital tracts and the ovary is the same as the mare's.
2. Two follicles in one ovary can develop in the same time and they ovulate successively with short interval.
3. The ovulation groove is situated in about the center of the inner curve of the ovary and except the groove surface, is covered with the tough peritoneum. The ovulation takes place at the ovulation groove only.
4. The relation between granulosa cells or theca interna and the maturation of the follicle is almost the same as that of mares.
5. Anatomical and histological observations of the follicle immediately after ovulation are almost the same as that of the mare, that is, thin whitish-yellow layers are seen in its rims and the inner cavity is filled with bloody materials. It is ascertained that the formers develop to the corpus luteum rapidly.
6. It seems that the origin of the luteal cells is the theca interna. In the large follicle just before the ovulation, theca interna cells are rem. arkably enlarged and develop to the so-called "theca luteal cells". After the ovulation, theca interna sends forth rapidly luteal cells into the cavity of the ruptured follicle. The appearance in which granulosa cells develop into the corpus luteum could not be obtained from this material.
