Abstract
Summary and Conclusion
Progesteronelike activity was determined in the plasma of the ovoviviparous snake by the Hooker-Forbes technic. Snakes with inactive ovaries or preovulatory follicles showed a concentration of 0.3 to 1.0 μg equivalent of progesterone per ml of plasma. This litre rose to 2 μg following ovulation, to 4 μg by mid-pregnancy and to 8 μg per ml of plasma at full term. Minimal amounts of progesterone-like activity were found in the plasma of male snakes. The possible role of this substance in the reptile and its evolutionary significance are discussed.
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