IO A. W. GREELEY. 



2. Those that modify the structure of the protoplasm inde- 

 pendently of the osmotic pressure. The first class includes the 

 non-electrolytes used, the second, the electrolytes. 



Non-clectrolytcs. The non-electrolytes used, distilled water, 

 cane sugar and urea, affect the protoplasm of paramcecia only 

 through the osmotic pressure of the solution. There is no chem- 

 ical effect. All those solutions hypotonic to protoplasm produce 

 a liquefaction through the absorption of water, while isotonic 

 solutions have no effect on the structure of the protoplasm, and 

 hypertonic solutions coagulate the protoplasm through a with- 

 drawal of water. These effects are shown in the following table : 



TABLE I. 



7/5 ;/io in 40 ;/i6o 



Cane sugar, Coagulation. Coagulation. No effect. Liquefaction. 



Urea, 



An examination of these structural changes under a high magnifi- 

 cation makes clear the fact that these non-electrolytes modify the 

 structure of the protoplasm solely through a change in the amount 

 of water in the fluid matrix which holds the more viscous elements 

 in suspension. The size of the protoplasmic particles remains 

 unaffected. In hypotonic solutions the protoplasmic particles are 

 more widely separated by an increase in the amount of water in 

 the fluid matrix. In hypertonic solutions they are brought 

 closer together, or may fuse through a withdrawal of the sur- 

 rounding liquid. 



Electrolytes. - - As far as their effect on the physical structure 

 of the protoplasm of Paramcecium is concerned, all the electro- 

 lytes used fall into two classes : first, those that coagulate even 

 in solutions whose osmotic pressure is far less than that of the 

 protoplasm ; second, those that liquefy the protoplasm in any 

 dilution. Moreover, all the members of the first class agree as 

 far as their electrical conditions are concerned. They all have a 

 predominantly powerful cathion, 1 but resemble each other in no 

 other particular. Likewise all the members of the second class 

 agree in possessing a predominantly powerful anion. Thus we 



1 This "predominance" may be a function of the solution tension of the ions. 

 See Mathews, Amer. Jour, of Physiol. , 1904, X., p. 290. 



