Abstract
Previous work by the writer 1 showed that the blood proteins, serum albumen and globulin, when fed to normal, thyroidectomized, or hypophysectomized frog larvae, exert no effect upon differentiation; but when properly iodized these same substances greatly accelerated the differentiation changes incident to metamorphosis. It will be recalled that thyroidectomized and hypophysectomized tadpoles do not metamorphose, but permanently retain their larval characters unless fed, injected, or transplanted with thyroid.
Iodofibrin.
Ten grams of pure fibrin from beef blood was pulverized and mixed with five grams of KI and two and a half grams of KIO3. To this mixture was added a solution containing 2 cc. of concentrated H2SO4 and 300 cc. of water. The material was heated in a water bath at 90°—100° C. for 4 hours and stirred frequently. It was then filtered, washed first with water and then with dilute NH4OH, followed by washing with water, alcohol and ether. The resulting product was iodofibrin.
Thirty completely hypophysectomized Rana sylvatica tadpoles averaging 30 mm. total length and showing no indications of metamorphosis were fed iodofibrin. Within 24 days, the entire culture, with the exception of 7 larvae which died at various stages of transformation, had differentiated to the stage where the animals had fore and hind limbs, frog mouth and marked tail resorption. All of the animals died at this stage of transformation.
A control culture of 30 hypophysectornized larvae fed non-iodized fibrin showed no metamorphic change at the end of 30 days feeding. The same experiment was repeated on completely thyroidectomized tadpoles with similar results.
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