a t Los Aageles
SIX FIGURES
Twelve years ago Allen ('20) showed that addition of the pars anterior of the adult hypophysis to hypophysectomized tadpoles enables the thyroid gland to function. It had been previously shown that the thyroid gland mould not function in the absence of the hypophysis and this experiment demonstrated first that the pars anterior is the portion involved, and secondly that the activity of the hypophysis can begin after a long initial period of arrest. These experiments also demonstrated (Allen, '21) that persistent transplants of large pieces of healthy adult hypophysis substance fail to induce the slightest tendency to metamorphosis in thyroidectomized tadpoles even when the transplants remain in healthy and presumably active condition f o r periods of four or five months.
Allen ('21 and '27) made a more detailed analysis of the function of pars anterior, pars intermedia, and pars nervosa by the same method of transplantation, showing that the addition of the pars anterior causes decided growth of the follicles of thyroidectomized tadpoles.
Ingram ('28) induced metamorphosis of the slowly metamorphosing tadpoles of Rana catesbiana by transplanting