Abstract
The considerable enlargement and structural changes of the pituitary during pregnancy and lactation seem to indicate that the internal secretion of this organ plays a very important rôle during this period. Therefore repeated attempts have been made to determine whether pregnancy can be maintained after hypophysectomy, but the results of such experiments are contradictory.
Whereas Aschner 1 found that abortion takes place in hypophysec-tomized pregnant dogs, Allan and Wiles 2 observed that pregnancy and parturition are not interfered with in the hypophysectomized cat, although lactation is impossible. Pencharz and Long, 3 working with rats, stated that pregnancy is not interrupted by removal of the hypophysis, but the process of parturition becomes impossible and the foetuses die in utero after a somewhat prolonged gestation period.
Repeating these experiments on rats we were able to confirm the statement that pregnancy is usually prolonged (up to 26 days). If the pituitary is removed between the tenth and fourteenth day of gestation, death and resorption of the foetuses may occur; but when the pregnancy proceeded normally until term, in 22 out of 24 cases the mechanism of parturition was not interfered with, and the litters were born alive; in the 2 exceptional cases hemorrhage occurred at term and the foetuses died in utero. We further established that the milk secretion always sets in normally at birth, but stops after a few hours, so that the hypophysectomized mother is unable to nurse her young.
As has been pointed out previously, 4 milk secretion will also stop immediately if the pituitary is removed in various stages of lactation.
These experiments indicate that the endocrine functions of the pituitary are not indispensable during the second part of pregnancy and parturition in the rat.
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