STRUCTURE OF PROTOPLASM OF PARAMCECIUM. I/ 



solution whose particles carry a definite electrical charge. The 

 colloidal particles in an artificial colloidal solution are apparently 

 identical, as far as their physical reactions are concerned, with the 

 protoplasmic or proteid particles held in the cell sap of proto- 

 plasm ; at least they both react to thermal and chemical changes 

 in the same way. The reaction to chemicals further demonstrates 

 the fact, that, like the colloidal particles, these protoplasmic ele 

 ments carry a uniform electrical charge under normal conditions; 

 for by no other assumption can we explain the facts that salts, 

 acids and bases modify the structure of protoplasm only by virtue 

 of their electrical properties, and that non-electrolytes have no 

 effect whatever beyond that of the osmotic pressure of the solu- 

 tion. Indeed the action is not, properly speaking, a chemical one 

 at all, but an electrical one. In Paramccciuui the protoplasmic 

 particles are apparently negatively charged, and the mutual repul- 

 sion of these similarly charged particles, keeps them in a state 

 of fine suspension. Under these conditions the protoplasm exists 

 in a " sol " or liquid phase. Predominant cathions neutralize 

 this negative charge ; the repelling force is removed, and the par- 

 ticles fuse, forming a coagulum. A predominant anion further 

 increases the disrupting force, and a state of still greater fluidity 

 or liquefaction results. 



A still closer comparison between artificial colloids and the 

 protoplasm of Paramocciuni is possible. It will be remembered 

 that Hardy succeeded in reversing the charge carried by the 

 colloidal particles by changing the chemical conditions of the 

 solution. Thus the addition to the solution of a small amount 

 of a base gave an alkali-modified colloid whose particles were nega- 

 tively charged. Such a solution was coagulated only by cathions. 

 Likewise the addition of a small amount of acid gave an acid- 

 modified solution, whose particles were positively charged ; this 

 solution was coagulated by anions. How this change is effected 

 by acids and alkalis we cannot say, but certain it is that the 

 electrical nature of the colloid is determined by certain ions 

 present in its fluid matrix. 



The reactions of the protoplasm of paramcecia to electrolytes 

 described above, occurred in organisms which had been reared in 

 a normal, alkaline culture. It was found that when the culture 



