LIPOID-ALTERANT SUBSTANCES 199 



In a considerable number of cases the degree of ])hysio- 

 logical action has been shown to follow a similar rule; 

 the observations of Fiihner on haemolysis (cited below) 

 are a good example. 



If physiological activity is in fact a function of capil- 

 lary activity, solutions of equal surface-tension should 

 exhibit equal narcotic action or otherwise produce equal 

 effects in protoplasm; and Czapek has brought forward 

 evidence that this is very frequently the case.' Using 

 a large number of surface-active organic compounds, he 

 determined the surface-tensions of those solutions which 

 had equal effect in liberating tannin from plant cells 

 (chiefly the leaves of Echeveria) ; this effect depends on 

 a permeability-increasing action analogous to that 

 accompanying cytolysis. In general he finds that solu- 

 tions of a concentration just sufficient to cause exosmosis 

 of tannin have very nearly the same surface-tension 

 against air; viz., about two-thirds that of pure water; 

 according to his hypothesis, the surface-tension of the 

 protoplasm becomes zero in such solutions and an 

 effective surface of separation ceases to exist. Kisch'' 

 also finds that isocapillary solutions of alcohols have equal 

 effects in liberating invertase from yeast and molds 

 and in inhibiting the growth of yeast cells; and II. 

 Zuckerkandl-^ has observed a similar relation in the 

 protoplasmic streaming of plant cells. According to 

 Traube and others, haemolysis follows the same ruk-.-' 



^ Czapek, loc. cil. 



* Kisch, Biochem. Zeitschrijt, XL (1912), 152. 



3H. Nothmann-Zuckerkandl, Biochem. Zeitschrijt, XLV (1912), 412. 



"Traube, loc. cil.; Fuhner and Neubaucr, Zcnlralbl. f. PhysioL^ 

 XX (1906), 117; Arch, cxper. Path. u. Plhirmakol., LVI (1907), 333- 



