Abstract
Twenty-four specimens of Rana sylvatica and Rana pipiens hypophysectomized at the tail-bud stage, and kept in the laboratory for 525 days, whose normal mates had metamorphosed at 65–70 days, were divided into 3 groups. Seven animals were kept as controls, 7 were treated with Collip's adrenotropic 1 hormone, batch AI, and the remaining 10 with his thyreotropic 2 hormone, batch TG. As a result of his own bio-assays (on rats) Collip stated that the thyreotropic hormone was not free from adrenotropic material but that the adrenotropic hormone was ‘fairly pure’. The hormones were administered by intraperitoneal injection, using special fine needles, in 0.05 cc. doses, given once daily, 6 days a week. For the injection an animal was removed from its aquarium and placed on a pad of absorbent cotton wet with ice water. It was then immobilized, ventral side uppermost, by a smaller sheet of wet cotton having a slit cut in it through which the injection could be made. Following the injection the animal was quickly returned to its aquarium.
In 4 days both of the treated groups were dark in color. The adrenotropic group was decidedly darker than the thyreotropic. The only other change noted in the first 5 days was a slight reduction of the tail fin in a few cases.
On the 6th day the hind legs of one animal in the thyreotropic group appeared to be lengthening and by the 10th day all but 2 of this group showed definite growth of the hind legs. From then on the changes normally seen at metamorphosis appeared rapidly. Forelegs emerged from the 11th day on, the tail shortened, the mouth became a transverse slit, characteristic frog spots (R. pipiens) appeared and from the 14th day animals were living out of the water.
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