RHYTHMICAL CONTRACTIONS IN MUSCLE 519 



In his well-known and thorough work on electro-physiology 

 the same author adds the following: 



Strong solutions of Na 2 SO 4 , as also very dilute solutions of 

 NaOH (in 5 per cent. NaCl solution), act in the same way as 

 Na 2 CO 3 , but not so strongly. In view of the similarity in the 

 effects of those substances upon the heart muscle one is justified in 

 speaking of a specific action of sodium salts, mentioned above, in 

 consequence of which the contractile substance of striated muscle 

 is so altered through the presence of even small amounts of these 

 substances that it is stimulated to contraction more easily and by 

 weaker stimuli than is ordinarily the case. 1 



We also know that Ringer has called attention to the 

 importance of calcium and potassium salts for the activity of 

 the heart, so that one might be inclined to believe that cer- 

 tain salts bring about the activity of the heart directly. In 

 this connection Howell considers particularly the calciiim 

 salts. 2 



2. It therefore seemed of interest to me to determine 

 whether the power to bring about rhythmical contractions in 

 skeletal muscle was not the property of certain ions. My 

 experiments consisted in observing the behavior of the gas- 

 trocnemius muscles of frogs in a series of solutions. The 

 muscle was entirely unweighted and unstretched and freed 

 from all bone. This fact is to be observed in repeating the 

 experiments. Carefully prepared equimolecular or isosmotic 

 solutions were used. The chemicals used were chemically 

 pure, and the water was twice distilled in glass. As we 

 often deal with only very weak contractions, or, more cor- 

 rectly, only with a tremor of individual muscle fibers, the 

 contractions could not be registered graphically, but could 

 only be observed. 



Biedermann has already pointed out that the rhythmical 

 contractions of muscles in the solution used by him are not 

 entirely similar to the activity of the heart. 



1 W. BIEDEEMANN, Electrophysiologie (Jena, 1895), p. 92. 



2 W. H. HOWELL, American Journal of Physiology, Vol. II 



