THE PHYSIOLOGICAL EFFECTS OF IONS 457 



than 5 per cent, of the acids exist in the molecular form. It 

 is therefore only logical to attribute the action of the acids 

 on the absorption of water by the muscle to the dissociated 

 molecules. Furthermore, since HC1 and HNO 3 show the 

 same degree of dissociation, and the acid effects upon the 

 muscle are the same, we may further conclude that at the 

 dilution employed only the hydrogen ions are active, while 

 the anions Cl and NO 3 have no physiological action. 



The same probably holds also for sulphuric acid, even 

 though the degree of dissociation is somewhat less here. We 

 therefore come to the conclusion that the effect of the acid 

 upon the absorption of water by the muscle is determined 

 by the H ions and is independent of the anions SO 4 , NO 3 , 

 Cl, and, further, of the undissociated molecules H 2 SO 4 , 

 HNO 3 , HC1. 



The rest of the experiments in this paper are all made 

 with a 0.7 per cent. NaCl solution, instead of the 0.585 per 

 cent. NaCl solution used in the foregoing experiments. An 

 experiment with 0.7 per cent. NaCl solution when F 210 

 gave the following results: 



For HXO 3 , 5.7 per cent. 

 For HC1, 6.1 per cent. 

 For iH 2 SO 4 , 6.5 per cent. 



I should like to emphasize again how nearly the values 

 are identical. The difference between these values and those 

 obtained with the 0.585 per cent. NaCl solution is determined 

 by the difference in the osmotic pressures, as we shall see 

 later. 



4. The next problem was to determine how the acid 

 effects increase with an increase in the concentration of the 

 acids. In the two experiments of Table II, 10 c.c. of the 

 one-tenth normal solution of the acid was added to each 100 

 c.c. of the 0.7 per cent. NaCl solution. F therefore =110. 



