I9I2] Lorande Loss Woodruff 405 



quite well established that the rate of acceleration decreases as one 

 proceeds upward from 0° toward the Optimum temperature. 



The average of the coefficients of the four experiments is 2.84. 

 If, however, the coefficients are weighted on the basis of the rate of 

 division of one cell for five days, the most fair coefficient for the 

 entire series of experiments is obtained, QiQ = 2.yo. The obvious 

 conclusion is that the rate of division of Paramcecium is influenced 

 by temperature at a velocity similar to that for a chemical reaction. 



V 



The recent developments of the ionic theory have lent renewed 

 interest to the problem of the physiological action of salts upon 

 protoplasm and have brought forward strong evidence to support 

 the idea that the pharmacological action of a salt Solution is to a 

 considerable extent due to the ions into which the salt dissociates. 

 Mathews has elaborated and emphasized the idea that atoms act by 

 means of their electrical condition, and that positively and nega- 

 tively charged ions have opposite action. Ions of the same sign act 

 alike, but the degree of their action, i. e., their specific toxicity, 

 differs because the ease with which they change their electrical con- 

 dition varies. The poisonous action of an dement, then, depends 

 to a considerable extent upon the affinity of the atom for its elec- 

 trical Charge. Mathews has suggested the term " ionic potential " 

 to indicate the tendency of any ion or atom to change its electrical 

 State, i. e., the inherent tendency of any ion in any concentration to 

 change into an atom of its metal. 



Comparatively few experiments have been performed on animal 

 organisms to determine if toxicity bears any direct relation to 

 ionic Potential and therefore it seemed worth while to determine 

 the relative toxicity of a number of cations toward the protoplasm 

 of Param(2cium}^ 



The experiments were planned to determine the concentration 

 of any particular salt necessary to kill within two seconds one half 



" Woodruff and Bunzel : The relative toxicity of various salts and acids 

 toward Paratncecium. Amer. Journ, Physiology, vol. 25, no. 4 1909. 



