44^ Water Absorption by Protoplasm [Mar. 



Lactic acid is important, though I have never held it to be the 

 only acid involved in the production of edema. It does figure in 

 my summaries, as witness my papers on the swelHng of fibrin.^ 

 That I did not use it more extensively was determined by the fact 

 that it is not absolutely stabile, 



Fischer's experiments involved treatment of colloids and tissues 

 with large and excessive volumes of stagnant acid Solutions. He does 

 not show that sufficient organic acid has ever been produced in a given 

 case of edema to cause directly the water accumulation and the swell- 

 ing observed. (Page 305.) 



I used different acids in such widely varying concentrations 

 that the first Statement does not seem to me to be entirely true. In 

 answer to the second Statement it is sufficient to redirect attention 

 to the analyses of G. Strassburg, A. Ewald and F. Hoppe-Seyler, 

 who found an abnormally high organic acid content in various 

 edema fluids; to H. J. Hamburger's Observation that the red and 

 white blood corpuscles swell when carbonic acid is led into arterial 

 blood in sufficient amount to raise it merely to a venous Standard ; 

 and K. Schorr's finding that a purified protein colloid indicates by 

 an increased swelling (increased viscosity) the difference between 

 the carbonic acid content of conductivity water and of ordinary 

 laboratory water. The protein colloids are probably more sensitive 

 to small changes in acid concentration than some of our finest 

 indicators. 



What is the reaction of juice suitably obtained from a typical 

 edematous tissue? Does such liquid contain lactic acid in the free 

 State? (Page 305.) 



Such fluid is acid to Phenolphthalein always, and I have seen 

 it afifect indicators that turn as high as io"^C-h. Yet this means 

 but little. The protein colloids of the body (which are chiefly re- 

 sponsible for the water held by the tissues) combine chemically 

 with acids added to them. Such acid proteins have an enormously 

 increased hydration capacity and yet indicators hardly serve to 

 show that any acid has been added. So far as the question of the 



' Martin H. Fischer and Gertrude Moore : American Journal of Physiology, 

 20, 332 (1907) ; Martin H. Fischer: Pflüger's Archiv, 125, 102 (1908). 



