502 EDWARD B. MEIGS 



with more water, thus rendering the salts more concentrated in 

 the remaining uncombined water. 



The existing evidence, then, justifies the following conclusions 

 in regard to frog's striated muscle: The surfaces of the muscle 

 fibers are highly permeable to water, and offer a marked, though 

 not absolute, resistance to the passage of salts and sugars in solu- 

 tion. The muscle is able to maintain a salt content different from 

 that of the blood plasma by means of chemical processes which are 

 not yet understood. A part of the water within the muscle 

 fibers is held by the colloids as organic water, and does not act 

 as a solvent for the muscle salts; and the taking up or loss of 

 water by muscle immersed in isotonic and non-isotonic solutions 

 is probably influenced by changes in the amount of the organic 

 water within the fibers. 



The osmotic properties of smooth muscle 



In order to determine how far the 'osmotic properties' of 

 smooth muscle resemble those of striated muscle, it will be neces- 

 sary to know the results of subjecting smooth muscle to such 

 experiments as have been carried out on striated muscle. The 

 ash of smooth muscle has been analyzed by several investigators.^^ 

 The results have shown that the smooth muscle fibers probably 

 contain somewhat less potassium and phosphorus and somewhat 

 more sodium and chlorine than the striated fibers of the same 

 animal; but in most of the animals investigated the ash of the 

 smooth muscle resembles that of striated muscle much more 

 nearly than it does that of the blood plasma. In the case of the 

 frog the smooth muscle fibers contain much more potassium and 

 phosphorus and much less sodium and chlorine than does the 

 blood plasma. ^2 



These facts do not, however, show conclusively that the smooth 

 muscle fibers are surrounded by semi-permeable membranes. In 



^^ See Saiki; Jour. Biol. Chemistry, 1908, vol 4, p. 483; Costantino, Biochemische 

 Zeitschrift, 1911, Bd. 37, p. 52; Macallum, Ergebnisse der Physiologie, 1911, p. 642; 

 Meigs and Ryan, Jour. Biol. Chemistry, 1912, vol. 11, p. 401. 



^'^ For an analysis of the ash of frog's blood plasma, see Urano, Zeitschrift fiir 

 Biologie, 1907, Bd. 50, pp. 218, 219, 224 and 225. 



