PROPERTIES OF PROTOPLASMIC MEMBRANES 143 



dissection;^ the surface of the unfertilized egg is less 

 easily cut or torn with a needle, but exhibits less power 

 of repair than that of the fertilized egg. This latter 

 difference is probably to be correlated with the increased 

 rate of metabolism following fertilization; oxygen- 

 consumption, COz-evolution and heat-production are 

 then greater,^ also the susceptibility to KCN poison- 

 ing and other forms of chemical injury. Facts of this 

 kind illustrate the close correlation existing between the 

 physical state of the plasma membrane and the physi- 

 ological properties and metabolic activity of the cell. 

 Other examples of this correlation will be described 

 later, especially in relation to stimulation-processes, 

 which are intimately associated with changes in the 

 membranes. 



PERMEABILITY AND SOLVENT PROPERTIES OE 

 MEMBRANE CONSTITUENTS 



It was first pointed out by Nernst in 1890 that the 

 solvent properties of the substances composing a mem- 

 brane may determine the latter's permeability to dis- 

 solved substances, and hence the production of osmotic 

 effects. Thus when benzol is separated from ether by a 

 partition consisting of bladder membrane soaked in water 

 (in effect a layer of water), the ether, because of its greater 

 solubility in water, passes the partition more rapidly than 

 the benzol, and a pressure is set up on the benzol side 

 of the partition.^ The membrane is impermeable to 



^ Chambers, Proceedings of the Society of Experimental Biology and 

 Medicine, XVII (i9i9),4i. 



2 Cf. Shearer, Proceedings of the Royal Society, B, XCIII (1921), 

 213,410. 



3 Nernst, Z. physik. Chem., VI (1890), 37. 



