Effect of Chemicals on Growth 497 



A ^ NaCl solution in pure distilled water had no effect on 

 growing Paramecia at 5 or 15 minutes of age (see Table V). At 

 30 minutes, those in the salt were slightly smaller than the con- 

 trols; while at 60 minutes, of 13 specimens in the salt, 1 1 were dead 

 and 2 were smaller than the controls. 



To sum up the results with distilled water, we find that pure 

 distilled water killed Paramecia that have been living in hay 

 infusion by the great change from the high to the low salt content. 

 When the Paramecia are put into distilled water with enough 

 NaCl present to make it a ^^-^ solution, the mjurious effect is not 

 so marked and becomes very noticeable only at 5 to 24 hours. 

 A ^ NaCl solution in distilled water seems to have the necessary 

 salt content to keep the Paramecia in normal condition. The i^ 

 and -^ NaCl solutions in distilled water have a much higher salt 

 content than is beneficial, and so cause a certain amount of 

 inhibition of growth. More light upon this matter is given bv the 

 further work upon NaCl which is to be reported next. 



GROWTH IN SODIUM CHLORIDE 



Perhaps the chief purpose of the present paper was to study 

 the effects on cellular grow^th of certain well-known poisons, 

 particularly nicotine, alcohol and strychnine. In order that there 

 should be no danger of mistaking for specific effects of these 

 poisons symptoms that are likewise produced by other and un- 

 related chemicals, I first made a careful study of the effects of ordi- 

 nary sodiumchloridewhen added to theinfusion in which theanimals 

 live. This substance, though not commonly accounted a poison, 

 has of course most deleterious effects when present in too great 

 amounts. These effects, particularly on growth, we shall now 

 examine. 



A -^^ NaCl solution was made by dissolving 0.146 grams of 

 soldium choride in 25 cc. of hay infusion. This being the most 

 concentrated solution of the salt that was used, any strength 

 desired was made by dilution of this with hay infusion. The 

 same hay infusion without the sodium chloride was used for the 

 control experiments. 



