Abstract
Investigation was made of the effects of hypophysectomy on the growth of rats, by using bone, teeth and hair. To measure the rate of growth, the lead acetate method was used for bone and tooth growth and the thallium acetate method for hair growth. The results obtained are as follow. 1) The sham-operation did not affect the bone growth of proximal tibia. But 9 days after hypophysectomy the cartilage became obviously narrow, and metaphyseal bone almost stopped growing. 2) After hypophysectomy the longitudinal growth of incisal dentin was inhibited by about 60%. Calcification was also inhibited, but one month after hypophysectomy, teeth, though extremely inhibited, still continued growing. 3) After hypophysectomy, the longitudinal growth of incisal dentin was much more inhibited than its appositional growth. The ratio, longitudinal growth/appositional growth, was smaller after operation than in control or before operation. 4) Hypophysectomy had almost no effect on the hair growth, although it showed a slight retardation in the hair eruption. The conclusion thus attained was that, under hypophysectomy, tissues differ in the rate of growth according to their embryological origin.
