RHYTHMICAL CONTRACTIONS IN MuscLE' 527 
tions were also ineffective. Hydroxyl ions, therefore, do not 
belong to those ions which are capable of liberating rhythmi- 
cal contractions. They only accelerate the production of 
rhythmical contractions when added to electrolytes in which 
such rhythmical contractions occur without the addition of 
the hydroxyl ions. 
8. What has been said in the foregoing on the effects of 
hydroxyl ions holds also for hydrogen ions. The addition 
of hydrogen ions accelerates the appearance of the contrac- 
tions in a 0.7 per cent. sodium-chloride solution. If 1, 2, or 
3 c.c. of a 747 normal HNO, solution are added to 100 c.c. 
of a 0.7 per cent. NaCl solution, rhythmical contractions 
begin immediately, or at least earlier than in the pure salt 
solution. It can, however, again be shown that in non- 
electrolytes, such as glycerin and sugar solutions, having an 
osmotic pressure of 4.91 atmospheres acids do not produce 
this effect, nor do they do it in distilled water, no matter 
what the concentration of the acid. That we are indeed 
dealing in this case with the action of hydrogen ions is 
shown by the fact that inorganic acids produce the same 
effects if the same number of hydrogen ions are contained 
in the unit volume. Hydrogen ions, therefore, do not 
belong to the ions which produce rhythmical contractions. 
9. The question now arises how it happens that H and 
OH ions accelerate the rhythmical contractions in electro- 
lytes. It might be thought that these ions have an etching 
effect, and so bring about continually differences in potential 
between different portions of the muscle fibers. In this way 
the muscle would be stimulated continually through its own 
currents and would be kept in a state of rhythmical activity. 
It would be in harmony with this view that these contrac- 
tions do not occur in distilled water and in non-electrolytes. 
Against it, however, stands the fact that not every electro- 
lyte brings about rhythmical contractions upon the addition 
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