TOXICITY OF ACIDS TO INFUSORIA 85 



Euplotes, Ca > Ba > Sr > Mg) , but agrees with that found f or 

 caproic. When NaCl is added to the mixture of alkahne earth 

 chloride and acid, the toxicity of the miture is greatly diminished, 

 except in the case of Sr where it is markedly augmented, and this 

 increase holds for the more dilute as well as foi" the more concen- 

 trated salt solutions. ' The order of efficiency in antitoxic powder 

 for the heavy metal chlorides is : 



Paramecium: Mn > Mg > Co > Cd > Ni > Zn 

 Euplotes: Mn > Mg > Cd > Co > Ni > Zn 



This varies only slightly from the order observed for butyric and 

 acetic. 



To summarize: 



1. The acids tested fall into two groups. The first group in- 

 cludes HCl, formic, acetic, succinic, lactic, tartaric, citric. The 

 second, the more lipoid soluble group, includes butyric, caproic, 

 benzoic, salicylic, phenylacetic. 



2. NaCl diminishes the toxicity of all the acids to Paramecium. 

 For Euplotes it is similarly efficient at all concentrations between 

 0.01 and 0.1 M with acids of the second group, but only at low^ 

 concentrations (0.01 to 0.05 M) with acids of the first group. 



3. The relative antagonistic power of the alkaline earth chlo- 

 rides is : 



Acids of group 1 Acids of group 2 



Paramecium : Ca > Sr > Ba ^ Mg Ca > Sr > Ba > Mg 

 Euplotes: Ca > Ba ^ Sr > Mg Ca > Sr > Ba > Mg 



4. The addition of NaCl, in a ratio of ten to one molecular, to 

 the alkaline earth chlorides increases their antitoxic power toward 

 acids of both groups, with the following exceptions : 



Paramecium: antagonistic power of 0.01 M CaCL and SrClo 

 is diminished with acids of the first group and left unchanged with 

 acids of the second group. 



Euplotes: antagonistic power of SrCl2 0.005 and 0.1 ]M is 

 greatly diminished Vv'ith acids of the first group. \ 



5. The antagonistic power of the heavy metal chlorides is: 



