162 INJURY, RECOVERY, AND DEATH 



of his investigations on the conductivity of protoplasm. 



Substances which alter the conductivity of protoplasm 

 may be divided into (1) those which cause an increase, 

 but not a decrease, of conductivity and (2) those which 

 can produce a decrease of conductivity (followed by 

 an increase). 26 



The hypothesis states that substances belonging to 

 the first class will antagonize those belonging to the 

 second, and vice versa. In order to predict which sub- 

 stances will antagonize each other it is only necessary 

 to determine to which of these classes the substances 

 belong. The amount of antagonism may also be pre- 

 dicted ; at least to a considerable extent, since the greater 

 effect of the substances on permeability, the greater 

 will be their antagonistic action. This relation may be 

 obscured by secondary causes, so that the predictions 

 which it allows will not be of equal value in all cases. 27 



As we have seen above, NaCl belongs to the first class, 

 being able to increase conductivity but not to decrease 

 it, while CaCl 2 belongs to the second class, as it is able to 

 decrease conductivity. 28 It was found that the antagon- 

 ism between NaCl and CaCl 2 in the case of Laminaria is 

 well marked. These facts led the writer to formulate the 

 hypothesis as stated above. The next step was to test the 

 hypothesis by the investigation of other salts. Magnes- 

 ium seemed of especial interest for this purpose, as in 

 most of the writer's previous experiments (on other 

 plants) it had shown no antagonism to sodium, though it 

 might be expected on chemical grounds that magnesium 

 and calcium would behave alike. To the surprise of the 



28 See page 40. 



27 Cf. Osterhout (1915, A). 



28 



The decrease is followed by an increase if the exposure is suffi- 

 ciently prolonged. 



