ACTIONS UPON SURFACES 99 



cotic actions of a given substance are produced by the 

 sanie mechanism. Hence it does not follow that what is 

 established for a narcotic in one connection is necessarily 

 involved in any other action involving the same narcotic. 



Theories of Actions upon Surfaces 



Permeability to narcotics. It is very common to find that 

 the effectiveness of a narcotic increases as the oil-water 

 partition coefficient is increased: the greater the relative 

 concentration in oil, the greater is the narcotic action. 

 The question naturally arises as to whether this is due 

 to differences in cell permeability, for permeability 

 usually also increases as the oil-water partition coefficient 

 increases. This, however, is very unlikely to be the case, 

 for most effective narcotics have a structure which allows 

 them to penetrate quite rapidly into cells. For example, 

 the aliphatic alcohols display an activity which usually 

 increases by between 2.4 and 4.5 fold for each additional 

 CH2 group in the molecule. But all the aliphatic alcohols 

 penetrate very rapidly into cells and the differences be- 

 tween the rates at which they permeate are far too small 

 to allow for the increments in activity for each CHg group 

 added to the molecule. It is probably quite seldom that 

 the differences in narcotic activity in a homologous series 

 can be attributed to the differences in rates at which the 

 different members of the series penetrate into cells. 



Cell Physiology 7 



