192 Striafcd Mtisclc Contraction [Jan. 



Slippose two adjacent regions, A and B, in a living muscle for 

 example, to differ in the fact that A is pure water and 5 is a 5 per 

 Cent. Solution of butyric acid in water. What is the surface tension 

 between them ? From the curve it is evident that the surface tension 

 of pure water against air is 74 dynes per cm., that of a 5 per cent. 

 butyric acid Solution is 40 dynes per cm. The surface tension be- 



-o 



G 



< 



0. 



I ■ I » ' u_J u-_L»-j L— i_-_L 



I 254 5 6769i0(r 



Mols of butyric acid per kilogram of Solution. T. 25° C. 



The lower curve was obtained by plotting the figures of Drucker (Ztschr. f. 

 physikal. Chem., 1905, lii, p. 641) obtained from Freundlich (Kapillarchemie, p. 

 59; Leipzig, 1909). 



The upper curve, for sodium butyrate, was obtained from Forch {Annalen 

 der Physik und Chemie, 1899, Ixviii, p. 801). 



tween A and B would, therefore, be the difference between the two, 

 or 34 dynes per cm. But suppose that A and B differ in the fact 

 that A contains 25 per cent. and B anywhere up to 100 per cent. of 

 butyric acid. There would be practically no surface tension be- 

 tween the two, altho the difference in concentration is very great. 

 For the present it is immaterial how the difference in concentration 

 is brought about. The blood-lymph might bring equal amounts of 



