ATROPHY OF THE ORGANS OF THE LARVAL FROG. 155 



2. That phagocytosis contrary to being a primary agent in 

 effecting the dissolution of the tissues of the tail is of secondary 



importance. 



BIOCHEMICAL EVIDENCE. 



During the last few years, a more complete understanding of 

 the softening of tissues in the living and in the dead organism 

 without the participation of microorganisms has been obtained 

 through the work of Bradley (13) and others. There is a more 

 or less definite relation between reaction of medium and the proc- 

 ess known variously as self -digestion, maceration, auto-diges- 

 tion, autolysis, etc., wherein tissue enzymes resembling in a 

 general way the enzymes of the alimentary tract operate in the 

 tissues themselves, causing autolytic processes. This relation 

 of reaction is such that when the average normal alkalinity of the 

 tissues falls below a certain point, autolysis begins. In the ter- 

 minology of physical chemistry, when the number of hydroxyl 

 groups or ions (OH) approach (molecular weight in hydrogen 

 equivalent) /( 1 0,000,000) or 7V/(io) 7 , which is neutrality for the 

 ions involved, then either the proteolytic enzymes of autolysis 

 are activated, or the reaction causes a change in the proteins 

 rendering them digestible by the enzymes (14). A distinctly acid 

 reaction, that is, where the concentration of OH ions is less than 

 1/10,000,000 normal, or, in the terminology of Sorensen which is 

 being universally adopted, where Ph < 7 1 , autolysis proceeds 

 rapidly. 



Up until the present time, the hydrogen ion concentration of 

 the blood of the larval frog has not been accurately determined, 

 a point to which the writer means to direct attention when 

 material is available. 2 It is desirable to determine whether there 



1 The expression Ph is borrowed from the principles of electromotive force, 

 where the "potential" difference is measured on a potentiometer between a known 

 concentration of hydrogen or hydroxyl ions and the unknown solution whose 

 concentration in hydrogen or hydroxyl ions is required. The expression Ph sig- 

 nifies that the potential refers to hydrogen (h). Its numerical value is the same 

 as the expression N/(io) a , where a is a number greater than 7 if the solution in 

 question is alkaline, or less than 7 if the solution is acid. Inasmuch as AT/(io) a 

 is the same as N(io)~ a , the expression Ph means "minus the logarithm of con- 

 centration." 



2 Only the larger species of frogs can be utilized for these determinations. The 

 arva of Rana catesbiana is of sufficient size to give 2 c.c. of blood for experimental 



