132 ROYAL SOCIETY OF CANADA 



vliicJi chemical compoamcU dilïuse into living cells has forniulated cou- 

 clusions which associalte tliis dift'usiou with tlie so-called distribution co- 

 efficient. By this tenu is meant the constant relation in which a sub- 

 stance^ independent of its quantity at a definite temi>erature distributes 

 itself between two differen/t solvents. An example of such a substance is 

 succinic acid^ which lias a distribution coefficient between ether and water 

 ()f 5.2, that is, 5.2 times as much of the acid dissolves in the ether as is 

 taken up by the water. 



Overton found that in general various compounds pass througb 

 membranes tlie more soluble they are in such substances as fats, 

 cholesterin, lecithin, ate, and he holds in consequence that these lipoid 

 bodies in cells are the cause of tlie diffusion into the lattxîr of various 

 lipoid-soluble substances and, further, that the magnitude of the distri- 

 bution coefficient between fat, lecithin and cholesterin on the one hand 

 and water on the other determines the velocity of osmosis. The lipoid 

 material in a membrane takes up a solute from a fluid bathing it at a 

 velocity proportionate to the distribution coefficient and at the same time 

 tlie substance is passed on from the membrane to the interior of the cell. 



In illustration of Overton's theorv it would follow that a substance 

 soluble in water, but not, or scarcely, in oil would not pass through cell 

 membranes readily. For example, glycerine presents this feature and it 

 penetrates cell protoplasm slowly. The monochlor compound of it, mono- 

 chlorhydrin, is soluble in fat and diffuses into the cell quickly, but 

 the dichlor compound, diohlorhydrin, which is extremely soluble in fat, 

 almost instantaneously penetrates cellular elements. One may parallel 

 these results with those obtained with the use of urea, monomethyl urea, 

 dinuethyl urm and trimethyl urea, all of which have solubilities ini fat 

 increasing in the order named and with correspondihg power to penetrate 

 cell protoplasm. On the other hand many very active electrolytes are 

 insoluble in fats, and it is found that they penetrate slowly the cell' 

 protoplasm. 



That lipoid material does obtain in cell membranes seems to be in- 

 dicated by the results of intra vitam sitaining. Overton found that the 

 dyes which stain the living cell are those as a rule which are soluble in 

 fat«?. cholesterin and lecithin, in which the dyes incapable of producing 

 a vital stain do not dissolve. 



One of the most noteworthy points in Overton's generalizations is 

 the remarkable fact that all the principal narcotics, anaesthetics and anti- 

 pyretics are rapidly diffusing substances. This fact was also pointed out 

 independently by Hans Meyer, and both he and Overion hold that the 

 efïïcacy of a narcotic depends on ite solubility in lipoids. 



