506 A .H. Estabrook 



further light upon the part played by osmotic pressure, a .079 N 

 solution of cane sugar was made by dissolving 2.681 grams of 

 sugar, which had been rendered free from all impurities, especially 

 sodium chloride, in 100 grams of pure water. This solution has 

 an osmotic pressure of 2.087 atmospheres and is isotonic with a i^ 

 solution of NaCl in distilled water. •^ Halves of Paramecia just 

 divided were used, one-half put in the sugar, the other half in 

 the NaCl solution, both being carefully washed free of any hay 

 infusion. Now if the injurious action upon Paramecia which we 

 have observed is due to osmotic pressure alone, we would expect 

 the two solutions to have the same effect upon the animals m 

 this experiment. The results are shown in Table XV. 



Up to the age of 90 minutes, the specimens in the sugar did not 

 grow as large as normal, but did grow faster than those in the 

 salt. At 5 hours, those in the sugar were slightly larger than at 

 90 minutes, but still smaller than normal, while those in the NaCl 

 were dead. At 24 hours those in the sugar were not as large as at 

 5 hours, but it must be noted that there was no food in the sugar 

 solution. The animals in the sugar were alive, but small, however, 

 at 48 hours. This experiment then shows that osmotic pres- 

 sure has an effect upon growing Paramecia, but that the injury 

 caused by the sodium chloride is not due entirely to the osmotic 

 pressure of the solution, but is also due to some other factor. 

 The effects caused by the action of the sodium chloride then, are 

 due to the osmotic pressure exerted b}' the sodium chloride plus the 

 direct action of the salt upon the protoplasm of the Paramecium. 

 So far as is known the action of the sugar is due entirely to its 

 osmotic pressure. 



To see the effect of even higher osmotic pressures upon Para- 

 mecium, growth in a ^^ NaCl in hay infusion was compared with 

 the growth in an isotonic solution of sugar, i.e., 2l .16 N solution 

 in hay infusion. Growing Paramecia were used, and it was found 

 that the Paramecia died in both of these solutions at about the 

 same time, 10 to 15 minutes. The inability of the Paramecia 



'The measurements for the osmotic pressure of sugar solutions arc taken from some unpublished 

 work of Prof. H. N. Morse of the Johns Hopkins Chemical Laboratory. 



