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. 
NaClsolution. 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, CO,, isattributed 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.’ I 
have since then corroborated this statement in that I have 
convinced myself of the fact that NH,HO, which is much 
less dissociated than NaOH, also acts physiologically as a 
much weaker alkali solution. Hydroxylions are also present 
in a Na,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. 
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