CELLS AND TISSUES. 41 



fact that protoplasm behaves in many ways as a mixture 

 of different solvents might also be of importance. 



V. 



A peculiar and important place biologically is occupied 

 by those crystalloids which because of their behavior 

 in the electric current (conductivity and electrolysis) are 

 called electrolytes. These are substances which in aqueous 

 solutions (and in certain other solvents) break up into 

 electrically charged particles, the ions (the electronegative 

 anion and the electropositive cation). This electrolytic 

 dissociation, which may in dilute solutions attain a very 

 high grade, is, however, never complete; beside the ions 

 there exist also non-dissociated, electrically neutral 

 molecules. The investigation of the role of electrolytes 

 in life phenomena must be directed toward an under- 

 standing of the part played by each of these. 



Experiment has taught us that there exist physiological 

 effects which are attributable solely to ions. The vital 

 property of the ions to keep in solution the widely 

 distributed globulins cannot be replaced by any other 



may be expressed mathematically. Support for this is found in the 

 no longer negligible volume of molecules present in colloidal mixtures 

 which bind the solvent. The water found in gels is, moreover, to be 

 regarded as freely movable only in part, and this part decreases rapidly 

 with an increase in the amount of shrinkage. In consequence of the 

 increase in the values of the volume and the attraction cf the gas mole- 

 cules the simple equation pv = R.T. no longer holds, as is well known, 



at higher temperatures, but VAN DER WAAL'S equation f/'+^J (vb} = 



R.T. Much seems to speak in favor of the idea that the relation 

 between osmotic pressure and cell volume may be kindred to the latest 

 modification of the law of Mariotte-Boyle. 



