STRUCTURE OF PROTOPLASM OF PARAMCEC1UM. 5 



still further. As a result water is absorbed so that a liquefaction 

 of the whole colloid occurs, as by a slight increase in the tem- 

 perature. Thus cathions liquefy positively charged colloids ; 

 anions, negatively charged colloids. 



C. The same conditions prevail in the reaction of colloids to 

 the electrical current. Negatively charged colloidal particles 

 fuse and form a " gel" around the anode, and tend to liquefy 

 about the cathode during the passage of the current. Positively 

 charged colloids coagulate about the cathode, and liquefy about 

 the anode. 



From the behavior of these colloidal solutions under various 

 chemical and electrical conditions Hardy concluded, that the 

 " sol " phase is maintained under normal conditions because all 

 the colloidal particles carry an electrical charge of the same 

 sign, and are thus mutually repelled, and remain in a state 

 of fine suspension. Whenever there is introduced an elec- 

 trical charge of an opposite sign, either by means of a dissociated 

 electrolyte or by the electrical current, the charge carried by 

 the colloidal particles is neutralized, and fusion or coagulation 

 occurs. 



The reaction to temperature variations is apparently due to 

 the fact that, within certain limits, the kinetic energy of the colloi- 

 dal particles varies directly with the temperature. A reduction 

 of the kinetic energy causes a gradual fusion of the particles ; an 

 increase brings about a still finer state of suspension, and conse- 

 quent liquefaction of the colloid through the absorption of water. 

 The sudden coagulation at the critical point is probably due to 

 a chemical change in the colloid itself. 



The chief points of similarity between these colloidal solu- 

 tions and protoplasm made apparent by Hardy's work are as 

 follows : 



i . The elementary physical structure of the two is the same. 

 Like the colloid, protoplasm is known to be made up of two 

 substances (a) the fluid cell-sap or matrix which holds in 

 suspension ($) the more solid proteid or protoplasmic particles, 

 granules or microsomes of the morphologists. And the physical 

 state of the protoplasm depends on the condition of these proto- 

 plasmic granules, just as the state of the artificial colloid depends 



