[Electron microscopic changes in the endocrine structures of the ovaries of sheep in anestrous and estrous periods].

Sheep were studied in the periods of anestrum and estrum, giving a description in a comparative aspect of the endocrine structures of the ovary. During estrus a strongly developed theca interna was found. Contrary to other mammals the interstitial gland in sheep was less developed during estrus than during anestrum. This was due to the season, the duration of the phases, and the types of follicle atresia.