528 STUDIES IN GENERAL PHYSIOLOGY 



of an alkali. If 2 or 3 c.c. of a ^ normal LiOH solution is 

 added to 100 c.c. of a KC1 solution isosmotic with a 0.7 per 

 cent. Nad solution, no rhythmical contractions occur. 



One might think that acids and alkalies increase the 

 irritability, and that for this reason their addition would 

 accelerate the contractions. We find, however, that in cer- 

 tain solutions periodical contractions occur when the irrita- 

 bility has been decreased, while in other solutions these 

 contractions do not occur at all even when the irritability is 

 normal or above normal. In 100 c.c. KCl solution to which 

 had been added 2 c.c. of a y 1 ^ normal LiOH solution the 

 muscle was still irritable after half an hour when the 

 secondary coil was 420 mm. away from the primary, without 

 a single contraction occurring, while another muscle the irri- 

 tability of which had dropped to 300 mm. in a LiCl solution 

 still gave strong rhythmical beats at the same time. It can 

 further be easily shown that the addition of an acid which 

 accelerates the beginning of contractions soon decreases 

 markedly the irritability of the muscle. 



I am much more inclined to go back to the first explana- 

 tion given, that certain ions for example, Na ions bring 

 about rhythmical contractions in that they enter the muscle 

 and here form definite compounds. H and OH ions have a 

 catalytic action; that is, they accelerate the formation of 

 these compounds. It might also be that they owe their 

 activity to their power of splitting off the material necessary 

 for the formation of the compounds with the Na ions. 1 



10. We have thus far become acquainted, first, with a 

 group of ions which are able to bring about rhythmical con- 

 tractions in skeletal muscle (Li, Na, Rb, Os, F, Cl, Br, I); 

 secondly, we have seen that H and OH ions accelerate the 

 appearance of the effect of the ions just named. There is a 

 third class of ions which inhibit rhythmical contractions. 



1 It is also possible that through their effect on the lipoids they increase the 

 permeability of the muscle for Na and other ions or salts. [1903] 



