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 c.c. of a one-tenth normal 

 acid to 100 c.c. of the salt solution, so that the acid was -j-j-jy 

 normal. HNO 3 or HC1 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 HC1 or 10 c.c. one-tenth normal HNO 3 are added. 



The experiments yielded the result that acids markedly 

 increase the amount of water absorbed by muscles in CaCl 2 

 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 3 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 KC1 solution, but only 39 per cent, 

 after the addition of the acid, or 15 per cent. less. In an 

 isotonic solution of K 3 SO 4 the muscle lost 4 per cent, of its 

 original weight in eighteen hours. By the addition of 10 c.c. 

 of a one-tenth normal acid to 100 c.c. of the isotonic K 2 SO 4 

 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 

 Ca01 2 solutions. While a muscle in an isotonic CaCl 3 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 3 solution are added to 100 c.c. of the CaCl 2 

 solution. 



