OVULATION IN THE RABBIT: THE TIME OF FOLLICULAR RUPTURE AND EXPULSION OF THE EGGS, IN RELATION TO INJECTION OF LUTEINIZING HORMONE

Abstract

SUMMARY Fifty-five mature oestrous does were injected intravenously with luteinizing hormone (LH) and subsequently killed between 9 hr. 52 min. and 14 hr. 30 min. after injection. At autopsy the number of freshly ruptured follicles was counted and was expressed as a percentage of the total number of follicles (ruptured and unruptured) counted, that had undergone pre-ovulatory swelling. This method of calculating 'percentage ovulation' gave results which agreed very closely with previously reported data. The calculation showed no ovulation by 10 hr., 50% ovulation between 10½ and 10¾ hr., and 100% ovulation by 14 hr. after the injection of LH. In thirty-nine out of these fifty-five does a special study was carried out to determine in what position (in the ruptured follicle, on the surface of the ovary or in the Fallopian tube) the eggs from the ruptured follicles were recovered in relation to the time elapsing after LH injection. Between 10½ and 11½ hr. after injection about 17% of the eggs were found either still inside the ruptured follicle, or within the cumulus oophorus protruding from the follicle or adhering to the ovarian surface. However, at 11½–13 hr. after injection only 3·6–5·9% were still in the follicle or on the ovarian surface. From 13 hr. after LH injection all the eggs recovered were found in the Fallopian tube. These results suggest that not all the eggs are ejected from the follicle at the time of rupture, and that some appreciable time may elapse between follicular rupture and entry of eggs into the tube.