The eggs of mammals (1936) The eggs of mammals eggsofmammals00pinc Year: 1936 46 THE EGGS OF MAMMALS ovaries lacking ova (Parkes, 1926-27). This evidence, how- ever, does not prove that normally oestrin-production may not be under the control of the action of pituitary hormones upon the ovum itself. In fact, aside from the presumable atresia-inhibiting in- fluence, there seems to be only one other clearly evident influence of pituitary hormones upon the activities of the »^sfr'*-T^''' ?^ Fig. 15. Ovum removed from a preovulatory follicle of an unmated rabbit showing the vesicular nucleus. (
The eggs of mammals (1936) The eggs of mammals eggsofmammals00pinc Year: 1936 46 THE EGGS OF MAMMALS ovaries lacking ova (Parkes, 1926-27). This evidence, how- ever, does not prove that normally oestrin-production may not be under the control of the action of pituitary hormones upon the ovum itself. In fact, aside from the presumable atresia-inhibiting in- fluence, there seems to be only one other clearly evident influence of pituitary hormones upon the activities of the »^sfr'*-T^''' ?^ Fig. 15. Ovum removed from a preovulatory follicle of an unmated rabbit showing the vesicular nucleus. (From the Journal of Experimental Medicine.) ovum. That is that the production of the first polar body is dependent upon stimulation by pituitary hormones. Since this phenomenon is of some consequence to any discussion of the activation of mammalian eggs the writer, in collaboration with Dr. E. V. Enzmann (Pincus and Enz- mann, 1935), has undertaken an examination of the mecha- nism of polar body formation in the rabbit ovary. The rabbit was chosen for these experiments because it ovulates only after copulation and the ova are liberated regularly between 93^ and 103^ hours after copulation (see Heape, 1905; Walton and Hammond, 1932; Pincus, 1930; Pincus and Enzmann, 1932). Furthermore, the mature ova form polar bodies only after copulation. According to Heape (1905)
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