156 WITHRQW MORSE. 



is any change in alkalinity coordinate with atrophy. In the 

 case of atrophy of the kidney tissue of the mammal where autol- 

 ysis can be demonstrated, the writer and colaborator (15) have 

 found that there is a rapid loss of alkalinity when autolysis sets 

 in, while a true acidity develops later. If, in the larval frog, 

 autolysis is vera causa for the process of atrophy, we should expect 

 to find a low alkalinity or actual acidity of the body fluids of the 

 tail during atrophy. 



If autolysis actually produces atrophy of the larval frog's 

 organs, we should expect to find a difference in the quantities of 

 end products of protein digestion between the normal, non-meta- 

 morphosing tail and that which is atrophying. However, the 

 practical demonstration could not be considered especially easy 

 since the work of Van Slyke and others upon mammals has shown 

 that these end products, the lower polypeptids and amino-acids, 

 are rapidly withdrawn from the blood by the various tissues. 

 Even after a full meal, until the micro-methods of Folin, Van 

 Slyke and others were brought into play, amino-acids in the 

 blood could not be satisfactorily demonstrated. A fortiori, in 

 the atrophying frog, large differences in amino-nitrogen in the 

 two cases in question are not to be expected. Another point 

 should be recalled in this connection: Muscle, of the various 

 tissues, undergoes autolysis slowest, with the exception of nervous 

 tissue. 



The following experiment was designed to show whether, 

 qualitatively, a difference in concentration of amino-acids could 

 be observed between normal and atrophying tissues. 1 



Experiment. The tail of a larva of the common frog, Rana 

 areolata, was used. The larva selected had small posterior legs, 

 anterior ones still beneath the integument and histological sections 

 of similar stages of Rana catesbianalarvx failed to show evidenceof 

 metamorphosis. The tissue was weighed too. 5 gram wet weight, 

 chipped fine and transferred to a Schleicher and Schiill No. 579 



purposes, which is practically the lower limit for work such as the determination 

 of acidity where at least a half cubic centimeter of serum is desirable. 



1 The writer reported, earlier (16) upon the concentration of amino-acids in the 

 tissues of the larval frog, where direct determination by the method of Van Slyke 

 was attempted; from further work it is evident that this evidence is of little value 

 since the calculated amounts of amino-acid would be extremely small. 



