Abstract
Observations regarding the effects of hypophysectomy during the course of gestation in the rat were reported. 1 ,2 It was shown that the removal of the gland during the second half of pregnancy was followed by a lengthening of the gestation period by 3 to 4 days. In many instances normal young were delivered several days beyond term, and although the mammary glands were well developed, suckling was not observed. Furthermore, hypophysectomy even as early as the twelfth day of gestation had no effect upon the subsequent development of the corpora lutea of pregnancy. Such corpora lutea were in no way distinguishable from the corpora of a normal animal of the same day of pregnancy. Similar experiments have now been extended to the guinea pig and the original observation in the rat that the latter part of pregnancy is not interrupted by hypophysectomy has been confirmed.
Our findings in the rat have since been substantiated by Allen and Wiles 3 in the cat, and Selye, et al. 4 ,5 in the rat and mouse. The latter workers also found that milk secretion may take place for a very brief period but ceases within a few hours postpartum.
In all, 23 guinea pigs were used. Fifteen were hypophysectomized between day 34 and 36 of pregnancy, and 8 between day 40 to 41. Hypophysectomy on day 34 to 36 was invariably followed by resorption of the foetuses within 2 days after the operation. Animals subjected to the same operation day 40 to 41, delivered viable young at term. In contrast to the findings in the rat, the period of gestation was not significantly prolonged (63 to 67 days).
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