40 PHYSICAL CHEMISTRY IN MEDICINE. 



proportional to the amount of change in the osmotic 

 pressure within or without the cell. 



It was soon learned to attribute the exceptions to the 

 first sentence to the relative permeability of the cells for 

 certain substances. But this explanation does not suffice 

 for a large and important number of cases in which the 

 substance that has entered a cell exists here in a greater 

 concentration than in the solution surrounding it. These 

 cases have been explained in part through the distribution 

 law. 



Strange to say, not a single example investigated thus 

 far has ever brought a confirmation of the second con- 

 clusion stated above a change in volume proportional 

 to the change in osmotic pressure. KOPPE, for example, 

 found that it was the rule to discover very considerable 

 variations from this law in the red blood-corpuscles. 

 When the osmotic pressure of the surrounding liquid is 

 increased, the decrease in the volume of the red blood- 

 corpuscles is less than calculated, as is true also of the 

 amount of their swelling when the osmotic pressure in 

 the surrounding fluid is decreased. In the experiments 

 carried out by DURIG on the swelling and shrinkage of 

 frogs great exceptions to the simple laws of osmotic 

 pressure were found to exist. We seem to have every 

 reason for believing that freedom of movement and 

 homogeneousness of solvent, which are demanded for an 

 immediate application of VAN'T HOFF'S theory to the 

 interchange between the fluids within and without the 

 cell, do not exist in our tissues. A chief role in this 

 modification of the solvent will no doubt fall to the part 

 of the colloidal constituents of living matter.* The 



* It does not seem impossible that the relations found to exist here 



