192 The Mechanistic Conception of Life 



not impossible that some of them belong also to the type of 

 those mentioned in this paper. The fact that the addition of 

 calcium to an NaCl solution prevents the twitchings of the 

 muscle, which occur in the pure NaCl solution, suggests the 

 possibility that the CaClj merely prevents or retards the diffu- 

 sion of NaCl through the sarcolemma. But other effects of 

 salts, e.g., the apparent dependence of contractility of the 

 muscle upon the presence of NaCl, or the r61e of PO^, do not 

 find their explanation in the facts discussed here. 



