. The eggs of mammals. Ovum; Embryology -- Mammals; Mammals -- physiology; Ovum. VESICLE GROWTH AND IMPLANTATION 121 minimum daily sterilizing dosage for days 3 and 4 is 150 rat units of oestrone-in-oil. When lesser dosages are injected a partially sterilizing effect is observed. This partially steriUz- ing effect is measured by observing the ratio between the num- ber of corpora lutea and the number of implantations. The re- lation of the implantation ratio to the hormone dosage is given in Figure 32. It will be seen that even relatively low hormone dosages have a lethal effect upon a number
. The eggs of mammals. Ovum; Embryology -- Mammals; Mammals -- physiology; Ovum. VESICLE GROWTH AND IMPLANTATION 121 minimum daily sterilizing dosage for days 3 and 4 is 150 rat units of oestrone-in-oil. When lesser dosages are injected a partially sterilizing effect is observed. This partially steriUz- ing effect is measured by observing the ratio between the num- ber of corpora lutea and the number of implantations. The re- lation of the implantation ratio to the hormone dosage is given in Figure 32. It will be seen that even relatively low hormone dosages have a lethal effect upon a number of the embryos. This effect may be due either to prevention of implantation of vesicles developing normally till implantation time or to a. 120 150 Fig. 32. Abscissa: oestrone dosage in per day. Ordinates: A, per cent of embryos unimplanted; B, number of unimplanted embryos per female. (From the American Journal of Physiology.) degeneration before implantation. The latter alternative seems most likely when one observes the degenerated condi- tion of the preimplantation blastocysts. In addition prac- tically all the embryos that do become implanted are normal in appearance, and, in fact, give rise to normal young at term (rabbit no. 47). W^en eggs in the blastocyst stage are placed in culture they will develop normally for 24 to 36 hours (Brachet, 1913; Pincus, 1930). Cleaving ova will, as we have seen, develop for several days and collapse when the blastocyst stage is reached and presomite stages continue development for 3 to 9 days. This implies that the explanted blastocyst either carries with it from the uterine environment a limited supply of necessary nutrition or that it rapidly exhausts the necessary materials from the ordinary culture 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 Pinc
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