. The eggs of mammals. Ovum; Embryology -- Mammals; Mammals -- physiology; Ovum. OVARIAN ATRESIA AND PARTHENOGENESIS 49 strated similarly that the critical period of secretion increase in the ferret occurs during the first hour of coitus. It seems evident, therefore, that pituitary secretions are responsible for the activation of the egg resulting in the formation of the first polar body and the second polar spindle. Further- more, certain observations of Hinsey and Markee (1933) indicate that the threshold for activation is lower than the. ^ '" ™ i Fig. 18. Ovarian ovum of rabbit doe mat
. The eggs of mammals. Ovum; Embryology -- Mammals; Mammals -- physiology; Ovum. OVARIAN ATRESIA AND PARTHENOGENESIS 49 strated similarly that the critical period of secretion increase in the ferret occurs during the first hour of coitus. It seems evident, therefore, that pituitary secretions are responsible for the activation of the egg resulting in the formation of the first polar body and the second polar spindle. Further- more, certain observations of Hinsey and Markee (1933) indicate that the threshold for activation is lower than the. ^ '" ™ i Fig. 18. Ovarian ovum of rabbit doe mated 9 hours previously. First polar body and second polar spindle. (From the Journal of Experimental Medi- cine.) threshold for ovulation. They observed that ovulation does not occur in large sized ( kilograms and over) hypophy- sectomized rabbit does if prolan injection is made more than four hours after hypophysectomy. And in small sized hy- pophysectomized does (less than kilograms) prolan ovula- tion never occurs. Nonetheless in all non-ovulating does polar body formation took place. Friedgood and Pincus (1935) found that stimulation of the cervical sympathetic of the rabbit resulted in maturation phenomena in those preovulatory follicles which failed to liberate ova. The sympathetic nerves presumably stimulated in these cases. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Pincus, Gregory, 1903-1967. New York, The Macmillan Company
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