On the amino-acid content of involuting frog-larvae

Abstract

In order to test the hypothesis that in the metamorphosis of the larvae of the frog autolysis is the principal factor, estimation of the amino-acid content was made by the gasometric method of Van Slyke and by the formol titration method of Sorensen. Beckmann freezing point and conductivity determinations were also made since Bayliss,1 Wells,2 Sjoqvist3 and others have shown that the curve of proteolysis follows that of increase of conductivity and lowering of the freezing point.Individual tadpoles were used at first, the tails being cut from the bodies, dried in an air-blast at 40° C., pulverized in a mortar, dissolved in water to make a one per cent solution, the estimations being made upon the coagulable protein-free filtrates from boiling with basic lead acetate. About 0.40 g. dried material could be obtained from one individual, but this amount became in the neighborhood of 0.10 g. in specimens which were absorbing their tails. The determinations mentioned above gave no characteristic differences betw...