460 STUDIES IN GENERAL PHYSIOLOGY 



The relative number of dissociated molecules varies con- 

 siderably. In the case of oxalic acid it reaches a value 

 which approximates almost that for hydrochloric acid. We 

 find, also, that the acid effect of oxalic acid approximates 

 that of inorganic acids. For iH 3 SO 4 , KHSO 4 , and NaHSO 4 , 

 when V - 210, we obtain increases in weight which average 

 8.6, 7.9, and 8.2 per cent, (see Tables II and III). For 

 oxalic acid we find an average of 6.9 per cent. The action 

 is somewhat weaker than that of the inorganic acids. We 

 may in this, perhaps, already see the effects of the anion. 

 In the main, however, we may yet attribute the absorption 

 of water under the influence of oxalic acid to the hydrogen 

 ions. 



In the case of lactic acid, however, this is out of the ques- 

 tion. Only one-tenth of all the molecules were dissociated, 

 yet the absorption of water was at least as great as in the 

 case of oxalic acid. It is impossible that we are dealing here 

 with the mere effects of the H ions of the lactic acid. The 

 lactic-acid molecules bring about secondary effects in this 

 case which add themselves to the effects of the H ions. 



Acetic acid acts more than half as strongly as oxalic acid, 

 and yet only 4 per cent, of all the molecules present are 

 dissociated, while 92 per cent, of the oxalic-acid molecules 

 are dissociated. The molecules of the acetic acid must there- 

 fore have secondary effects, and these in even greater degree 

 than in the case of lactic acid, which add themselves to the 

 effects of the few H ions which are already present. 1 



Malic acid, finally, is six times as strongly dissociated as 

 acetic acid ; its activity is, however, only a little greater than 

 that of the latter. 



I am not inclined to admit that these apparent irregulari- 



1 It is also possible that acetic acid migrates comparatively more rapidly into 

 the muscle fiber than oxalic acid. But it is also possible that these acids undergo 

 or cause chemical changes in the muscle substance which increase their efficiency. 

 [1903] 



