TOXICITY. OF ACIDS TO INFUSORIA 89 



some extent of CaCU and MgCL is reduced by traces of HCl, 

 apparently because of approach to a balance between the coagu- 

 lative action of the acid and the liquefying action of the salt. 

 BaCl2 and SrCl2 are not susceptible of antagonism by the acid, 

 perhaps because they coagulate the protoplasm readily at the 

 concentration selected. In Lillie's experiments the concentra- 

 tion of salt (usually M/2) was much higher than in my experi- 

 ments, which may account for the dissimilarity in the results, 

 especially with Sr. 



In some of the experiments cited the antagonism appears to 

 be chiefly between the swelling action of dilute acid and the dehy- 

 drating effect of salts, while in others the antagonism is between 

 the coagulative action of the concentrated acid (or salts with 

 bivalent cation) and the liquefying or stabilizing action of a salt. 

 That is to say, the type of antagonism varies with the concentra- 

 tion as well as with the nature of the antagonists. 



This view is borne out not only by the occurrence of visible 

 changes in the cell such as those already described, but also by 

 experiments with non-living systems. With lecithin (Fein- 

 schmidt;^! Handowsky and Wagneri^) and also with globulin 

 (Hardyi*) the pH at which acid precipitation occurs is increased 

 and the completeness of the precipitation is considerably limited 

 by the presence of neutral salts. The acid swelling of gelatin 

 (Fenn,i2 Fisher, ^^ Loeb,i« Proctor^^' ^«), fibrin (Tolman and Stern^") 

 and gluten (Wood and Hardy"^) is diminished by salts, and a 

 similar balanced is to be observed in the setting of gelatin (Traube 

 and Kohler^i) . It is noteworthy that these substances are chemi- 

 cally unlike and agree only in being hydrophilous colloids. 



That the acid acts largely at the surface of the cell is indicated 

 by the experiments already cited (Collett, Loeb, Osterhout) on 

 salt-acid mixtures and by many experiments on salt-salt and salt- 

 anaesthetic mixtures. For example, the adsorption of CI by 

 tissue is less from a bath of NaCl plus CaClo in physiological pro- 

 portions than from a bath of either alone (van Oijen^'O; the 

 electrical resistance of Laminaria is decreased less by a balanced 

 salt solution than by pure salts, and is increased less by a 

 mixture of anaesthetic and NaCl than by anaesthetic alone 



