526 STUDIES IN GENERAL PHYSIOLOGY 
I now made a series of experiments with a glycerin solu- 
tion the osmotic pressure of which was 4.91 atmospheres; 
which was, therefore, isosmotic with a 0.7 per cent. NaCl 
solution. I added to 100 c.c. of this solution one-tenth 
normal LiOH in different quantities from 1 to 4.¢.c. -In no 
ease did I obtain rhythmical contractions. Similar experi- 
ments with sugar solutions having an osmotic pressure of 
4.91 atmospheres yielded the same results. These experi- 
ments with sugar solutions are, of course, less conclusive, 
since a portion of the hydroxyl ions are in this case rendered 
inactive. The addition of 5 cc. of a one-tenth normal 
LiOH to 100 c.c. dextrose or cane sugar caused no contrac- 
tions. Upon the addition of 10 ¢.c., however, of a one-tenth 
normal LiOH solution a few weak contractions appeared 
during the first minute. Beside the experiments with the 
glycerin solutions the experiments with distilled water 
adduce proof. In no case did hydroxyl ions in distilled 
water bring about rhythmical contractions. One might 
think perhaps that distilled water reduces the irritability so 
rapidly that contractions are no longer possible.’ That is, 
however, not the case. In one case in distilled water the 
muscle was still irritable after an hour to an induction cur- 
rent from the induction coil used in all these experiments 
when the distance of the coils was 310 mm., while the normal 
irritability lay at about 390mm. Rhythmical contractions 
occur in solutions of sodium salts at a still lower irritability. 
The addition of 10 ¢.c. one-tenth normal LiOH to 100 cc. 
of distilled water gave no rhythmical contractions. Even 
in a one-fortieth normal or one-tenth normal LiOH solu- 
tion no rhythmical contractions occur. Very weak, one- 
thousandth to one-hundredth normal LiOH or NaOH solu- 
1It was found in these experiments that a dextrose solution isosmotie with a 
0.7 per cent. NaCl solution reduced the irritability of the muscle more rapidly than 
the NaCl solution; sugar, therefore, is no indifferent substance. That NaCl is not 
has been proved by Locke. 
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