524 STUDIES IN GENERAL PHYSIOLOGY 



solution; that is, of an osmotic pressure of 4.91 atmospheres. 

 In none of these solutions did rhythmical contractions 

 occur. I cannot as yet, however, say that this is true for all 

 non-electrolytes. The circumstance that contractions occur 

 immediately in a NaCl solution of a high concentration 

 suggests the possibility that loss of water by the muscle 

 favors the contractions. I therefore introduced the muscle 

 into glycerin and sugar solutions having two, three, four, 

 and five times as high an osmotic pressure as a 0.7 per cent. 

 NaCl solution. In none of them did rhythmical contractions 

 occur, even though the muscle lost water markedly. What 

 has been said applies, however, only to rhythmical contrac- 

 tions. Single twitches that is, single separate contractions 

 were occasionally observed during the first minutes in 

 glycerin solutions having an osmotic pressure of 4.91 atmos- 

 pheres or more. Such contractions can also be observed, 

 however, at times when fresh muscles are laid upon a glass 

 plate. The glycerin solution is therefore probably only 

 of a secondary importance. 



7. I have above quoted the remark of Biedermann accord- 

 ing to which the stimulating effect of NaOH, as well as that of 

 Na 2 CO 3 , is attributed to the "sodium salts." I have, how- 

 ever, shown that in the specific effects of very dilute alkalies 

 we are really dealing with the effects of hydroxyl ions. 1 I 

 have since then corroborated this statement in that I have 

 convinced myself of the fact that NH 4 HO, which is much 

 less dissociated than NaOH, also acts physiologically as a 

 much weaker alkali solution. Hydroxyl ions are also present 

 in a Na 2 CO solution which bring about the specific alkali 

 effects of this solution. The idea, therefore, suggested 

 itself that the hydroxyl ions are capable of calling forth 

 rhythmical contractions in a similar way to Na and other 

 ions. This seems to be true for the HO ions in even a 



1 Part II, p. 450. 



