PHYSIOLOGY OF SMOOTH AND STRIATED MUSCLE 499 



ence of semi-permeable membranes surrounding the animal cells. 

 These investigators believe that the taking up and loss of water by 

 muscle in various solutions is to be explained by a comparison of 

 the behavior of muscle with that of gelatin and fibrin under simi- 

 lar conditions. 



The osmotic properties of striated muscle 



Overton- has made a thoroughgoing study of this whole ques- 

 tion, using frog's striated muscle^ as the material for his experi- 

 ments. He comes to the conclusion that the muscle fibers are 

 surrounded by semi-permeable membranes of a peculiar nature — 

 membranes permeable to water and to most fat solvents, but 

 impermeable to sugars and inorganic salts. These membranes 

 are, however, easily injured or destroyed; their destruction marks 

 the irretrievable loss of irritability by the muscle; and after their 

 destruction the tissue swells or loses water in various solutions 

 somewhat as do masses of gelatin and fibrin. 



The reasons which have led Overton and other investigators to 

 believe that the striated muscle fibers are surrounded bysemi- 

 permeable'membranes may be briefly summarized as follows : 



The ash of striated muscle is entirely different from that of the 

 blood plasma. It is well known that the blood plasma contains 

 considerable amounts of diffusible NaCl, while the work of Katz' 

 indicates that the striated muscle fibers often contain little or none 

 of this salt and considerable quantities of the phosphates of potas- 

 sium. It is difficult to see how the salts of the blood plasma 

 and of the muscle are prevented from interdiffusing unless there 

 is some resistance to their passage at the surfaces of the muscle 

 fibers. 



The living striated muscle reacts in general to isotonic, hyper- 

 tonic and hypotonic solutions of salts and sugars as if its fibers 

 were surrounded by membranes permeable to water, but not to 

 salt and sugar in solution, and as if they contained a salt solution 

 isotonic with the blood plasma. The muscle maintains its origi- 



2 Overton; Archiv fiir die gesammte Physiologie, 1902, Bd. 92, pp. 115 and 346; 

 1904, Bd. 105, p. 207. 

 ^ Katz; Archiv fiir die gesammte Physiologie, 1896, Bd. 63, p. 1. 



