194 INJURY, RECOVERY, AND DEATH 



conductivity of Laminaria, experiments were made by 

 adding small amounts of nicotine, caffeine and cevadine 

 sulfate to sea water (and then making the solution the 

 same conductivity as sea water). The experiment was 

 not successful in the case of nicotine, owing to the for- 

 mation 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 16 (0.0006 to 0.0025 M) a distinct decrease 

 in permeability was found I (as shown by the rise in 

 resistance) ; this was followed by an increase. 



18 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^H^NO, ) a .H 2 SO 4 . 



