514 STUDIES IN GENERAL PHYSIOLOGY 
interested in testing how isotonic calcium and potassium 
solutions act upon muscle when acids are added to these 
solutions. I usually added 10 cc. of a one-tenth normal 
acid to 100 c.c. of the salt solution, so that the acid was 74, 
normal. HNO, or HCl were the acids generally employed. 
I showed in the article cited above that at this concentration 
we are dealing only with the effects of ions, and that the 
effect is quantitatively the same whether 10 c.c. one-tenth 
normal HCl or 10 ¢.c. one-tenth normal HNO, are added. 
The experiments yielded the result that acids markedly 
increase the amount of water absorbed by muscles in CaCl, 
solutions, but that they have the reverse effect in solutions 
of potassium salts, where they diminish the amount of water 
absorbed. In one experiment the muscle increased 35 per 
cent. in weight in an isotonic KI solution, but only 6.2 per 
cent. in an isotonic KI solution to which had been added 
the amount of acid indicated above! The addition of 10 c.c. 
of one-tenth normal HNO, to 100 c.c. KI solution decreased 
the amount of water absorbed almost 29 per cent. expressed 
in terms of the original weight of the muscle! In another 
experiment the muscle increased 54 per cent. over its origi- 
nal weight in an isotonic KCl solution, but only 39 per cent. 
after the addition of the acid, or 15 per cent. less. In an 
isotonic solution of K,SO, the muscle lost 4 per cent. of its 
original weight in eighteen hours. By the addition of 10c.c. 
of a one-tenth normal acid to 100 c.c. of the isotonic K,SO, 
solution the muscle lost 22 per cent. of its original weight 
in the same time! 
Exactly the opposite is observed when acid is added to 
CaCl, solutions. While a muscle in an isotonic CaCl, solu- 
tion loses about 20 per cent. of its weight in eighteen hours, 
it increases about 30 per cent. when 10 c.c. of a one-tenth 
normal HNO, solution are added to 100 c.c. of the CaCl, 
solution. 
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