ANTAGONISM 173 



tion. This is perhaps explained by the fall of tempera- 

 ture which occurred during the night and retarded the 

 speed of the process. It should bd noted that all the experi- 

 ments in any set were begun at the same time, so that all 

 shared equally in the variations of temperature; in 

 consequence the form of the antagonism curve is not 

 greatly affected by such variations. 



In order to determine whether these alkaloids pro- 

 duce a decrease in permeability they were added to sea 

 water. The experiment was not successful in the case of 

 nicotine, owing to the formation of a visible precipitate, 

 which was apparently due to the presence of calcium and 

 magnesium in the sea water. In the case of caffeine (0.01 

 to 0.04 M) and of cevadine sulfate 42 (0.0006 to 0.0025 M) 

 a distinct decrease in permeability was found (as shown 

 by the rise in resistance) ; this was followed by an 

 increase. In this respect they resemble CaCl 2 which also 

 produces a decrease in permeability when added to 

 sea water. 



The idea that substances which have opposite effects 

 on permeability can antagonize each other seems to apply 

 to alkaloids as well as to salts. 



The question arises whether the decrease of conduc- 

 tivity and the antagonistic action produced by organic 

 substances are of the same nature as those produced by 

 salts. Are they, in terms of the theory outlined above, 

 due to an increase in the thickness of the layer of M at the 

 surface of the cell? The writer is not prepared to answer 

 this question at present, but there is no reason to suppose 

 that their effects may not differ from those produced by 



43 This is regarded as two molecules of cevadine united to one molecule 

 of H 2 S0 4 . It was purchased from Merck under the name of veratrine 

 sulfate ( C 32 H 40 N0 9 ) 2 .H 2 S0 4 . Cf. Osterhout ( 1919.Z) ) . 



