THE THEORY OF AN/ESTHESIA. 



329 



height is decreased by surface-active substances, and the degree 

 of capillary activity or tension-lowering action of different sub- 

 stances can thus be determined. Now in any homologous series 

 this action (for equimolecular solutions) is found to decrease as 

 the molecular weight increases. The surface-tension in milli- 

 grams per linear centimeter (i. e., the pull exerted by a strip of 

 surface one centimeter wide) of ml\ solutions for the first five 

 aliphatic alcohols at 15 is given by Traube as follows: the 

 surface-tension of the m/q. solution of dextrose, a physiologically 

 important surface-inactive compound, is given for comparison. 



TABLE II. 



The second column gives the concentrations required to effect 

 a definite lowering of surface-tension. It will be observed that 

 the surface-activity of each member (as measured by the recip- 

 rocals of the isocapillary concentrations) is approximately a 

 third of that of its immediate successor. The third column 

 shows that the narcotic activity increases from each member to 

 the next following in a closely similar proportion. Results of 

 this kind are on the whole typical for homologous series. The 

 question arises as to their general physiological significance. 



According to Traube the essential physico-chemical factor in 

 these physiological effects is the characteristic influence which 

 surface-tension has upon the distribution of dissolved substances 

 in any polyphasic system. The general principle of Willard 

 Gibbs and J. J. Thomson states that substances which lower the 

 surface-tension of any solvent attain, when equilibrium is reached, 

 a higher concentration in the surface-layer than in the interior 

 of the solvent; a surface-condensation or adsorption thus results, 

 which is the greater the greater the surface-activity of the dis- 



