i88 Striated Muscle Contraction [Jan. 



be considered with reference to their bearing on the problem of the 

 sources of surface tension in living matter in general and in striated 

 muscle in particular. ) The first class of Solutions to be considered 

 are those which are obtained when two partly miscible liquids, such 

 as ether and water, for example, are thoroly shaken, and then 

 allowed to separate into two layers, forming in this case, a Solution 

 of water in ether and a Solution of ether in water. The surface 

 tension between two such layers is of interest for several reasons, 

 principally because such binary mixtures probably exist in living 

 tissue, which is supposed to consist of a comparatively dilute aque- 

 ous Solution or Suspension of the biological constituents that bathes 

 the more viscous protoplasmic structures. These structures, what- 

 ever their shape and size may be, are commonly regarded as Solu- 

 tions of water in the biological constituents. 



The surface tension between two liquids was studied by Quincke 

 in 1870.^ He found that the surface tension between two liquids, 

 immediately after they have come in contact, is very nearly equal to 

 the difference between their surface tensions when measured sepa- 

 rately against air. For example, the surface tension of Chloroform 

 against air is 30.6 dynes per cm., that of water against air is 80.9; 

 the surface tension between Chloroform and water is approximately 

 the difference between these two figures, or 29.5 dynes per cm. If 

 the two liquids were mutually soluble, the surface tension between 

 the two decreast to an extent which depended upon their mutual 

 solubility and other factors. The following typical data, from 

 Quincke's paper, are of interest because the general principle de- 

 duced from them by Quincke is directly applicable to the conditions 

 existing in a working muscle (on the assumption that the chemical 

 and physical changes underlying muscle contraction take place be- 

 tween Solutions or other liquids and not between Solutions and 

 gases). 



Quincke, loc. cit., p. 27. Table X. Results at 20° C. in dynes per 

 cm. In the first column of figures is given the surface tension of the 

 first liquid against air ; in the second column, the surface tension of the 



1 Quincke: Annalen der Physik und Chemie, 1870, cxxxix, pp. 1-89. (Pog- 

 gendorf's Annalen.) 



