A detailed description is given of a surgical technique for selectively removing the pituitary anlage from the intrauterine fetal rat as an alternative to the more generally applied fetal hypophysectomy by decapitation. Fetuses on the 17th day of gestation were approached through a narrow opening in the uterine wall and fetal membranes. The pituitary gland was sucked out with a fine glass tube introduced from the side of the head into the space between the pons and the ventral hypothalamus, where the gland is situated. The female rat was sacrificed on the 22nd day of gestation (the day before delivery) and the surviving fetuses were preserved. On average, 20% of the operated fetuses survived until that day, 20% of which were completely hypophysectomized (microscopical examination). Operated fetuses with intact pituitaries served as surgical controls for the evaluation of selected effects of the total hypophysectomy. Initial comparisons were made with published results based on hypophysectomy by decapitation, evaluated without access to surgical controls. The two methods of fetal pituitary removal provide consistent results as regards the weight increase of adrenal and thyroid glands (retardation), thymus gland (stimulation) and testicles (no effect). On the other hand, body weight increase was not affected by selective hypophysectomy but instead slowed down after decapitation, whereas the growth in length of the humerus bone was stimulated and retarded, respectively.
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