Paper - The Comparative Behavior of Mammalian Eggs in Vivo and in Vitro

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Pincus G. and Enzmann EV. The Comparative Behavior of Mammalian Eggs in Vivo and in Vitro. (1935) J Exp Med. 62(5):665-75. PMID 19870440

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The Comparative Behavior of Mammalian Eggs In Vivo And In Vitro

I. The Activation of Ovarian Eggs

By Gregory Pincus, S.D., And E. V. Enzmann, Ph.D.

(From the Biological Laboratories, Harvard University, Cambridge)

This investigation has been aided by a grant from the National Research Council Committee for Problems of Sex.


(Received for publication, July 17, 1935)

The eggs of most mammals are shed from the ovary with the first polar body formed. The mechanism controlling this stage of maturation has never been investigated in detail. Furthermore, under normal conditions only shed ova are fertilized. Does this indicate that the first maturation division is an essential prelude to fertilization? Or may ovarian eggs in fact be activated before the first meiotic division?

This investigation concerns itself with these problems, and falls into two parts dealing with: (1) the mechanism controlling the first meiotic division; (2) the capacity for fertilization of ovarian eggs. Superficially unrelated, these two studies are aspects of the broad problem of the fundamental nature of the activation process.


The rabbit is especially favorable material for this study since it ovulates only after copulation. It has been established that copulation results in a stimulation of pituitary secretion, and that the amount of anterior pituitary secretion necessary to induce ovulation occurs during the 1st hour after copulation (Deansley, Fee, and Parkes, 1930). The injection of pituitary extracts or of prolan induces ovulation (Friedman, 1929); and furthermore, ovulation induced by stimulating hormones occurs at 10 hours after injection (Bellerby, 1929). Ova are normally shed with the first polar body at 10 hours after copulation. According to Heape (1905) both polar bodies are formed at 9 hours after copulation.

Heape’s statement is but partially correct. Only one polar body is formed. We have investigated this situation in detail, and our data are summarized in Table I. Before copulation occurs the ovum contains a single large vesicular nucleus about 30 microns in diameter (Fig. 1). At 2 hours after copulation some

Cite this page: Hill, M.A. (2019, July 21) Embryology Paper - The Comparative Behavior of Mammalian Eggs in Vivo and in Vitro. Retrieved from

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