Effects of Complete and Incomplete Hypophysectomy on Basal Metabolism of Pigeons.

Abstract

Summary Within 10-20 days after complete hypophysectomy the B.M.R. of the adult pigeon undergoes a pronounced decrease, but the extent of the indicated decrease is much influenced by the environmental temperature at which measurement is made. At the critical temperature (30°C.) the B.M.R. of 9 pigeons was decreased by 33% in 7 pigeons measured at 20°C. the decrease was only half as much, or 17%. Seven incompletely hypophysectomized birds (less than 4% of pituitary present) measured at 30° provide data which confirm the important rôle of temperature and further indicate that the B.M.R. of such birds is practically the same as that of the completely hypophysectomized pigeon. Pituitary fragments representing 10-25% of the total gland usually only partially sustain the normal rate of heat production. B.M.R. measurements made at 20° did not distinguish partial from complete hypophysec-tomies, and this provides a further indication that a truer measure of effect of hypophysectomy is obtained from tests made at the animal's critical temperature.