TOXICITY OF ACIDS TO CILIATE INFUSORIA 453 



C. Temperature 



In order to find out something of the nature of the toxic action, 

 acids were tried at several temperatures between 10° and 30° as 

 is indicated in table 1 . The conditions are more readily seen in 

 the curves shown below. In almost every case an increase 

 above room temperature produces an. increase in toxicity both 

 to Paramoecium and to Euplotes and a decrease below room 

 temperature generally produces a decrease in toxicity. If the 

 length of life at, let us say, 10° is divided by the length of life 

 at 20°, the figure so obtained (the temperature coefficient for 

 10°) can be used as a measure of the degree of influence exerted 

 by these temperatures upon the toxicity of the acid. Table 2 

 gives the coefficients found for Paramoecium and Euplotes. 



It will be observed that the coefficient for any one acid is not 

 the same at all temperatures nor at all dilutions. For example, 

 benzoic for the range 20° to 30° has coefficients of 2 at 0.0002 N 

 and 3.88 at 0.0001 N, and for the range 10° to 20°, coefficients 

 of 3 and 2.1, respectively. Often the more dilute solutions have 

 higher coefficients than the more concentrated. It is also remark- 

 able that the temperature coefficient for any given range is 

 not the same for different acids even at equinormal concentra- 

 tions. Thus at 0.0002 N the coefficients for the range 10° to 

 20° are salicylic 1.5, hydrochloric 2.2, benzoic 3, malonic 2.5, 

 etc. All this would indicate that the mode of action of dif- 

 ferent acids is by no means the same and that the action of any 

 one is markedly influenced by concentration and by temperature. 

 Neither do the various acids affect Paramoecium and Euplotes 

 in precisely the same way; if the coefficients for the two organ- 

 isms be compared at corresponding temperatures and concen- 

 trations of the same acids, one finds that they are almost never 

 the same. 



It is impossible at present to interpret these results fully, but 

 some few conclusions suggest themselves. As is well known, a 

 coefficient of from 2 to 3 for every increase of 10° generally 

 indicates a chemical reaction, while a coefficient of less than 2 or 

 over 4 is frequently associated with physical processes. Most 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 29, NO. 3 



