198 PROTOPLASMIC ACTION AND NERVOUS ACTION 



the surface- tensions (against air) of 0.25 m aqueous solu- 

 tions of alcohols decrease in regular order as follows: 



Aio^T^^i Surface-Tension 



^'''"^^^ (Mgms. per mm.) 



CH3OH 7.05 



CaHsOH 6.73 



CjHvOH 2.89 



C4H9OH 4-49 



CsH,,OH 3.05 



(H.0) (7.3) 



The order of relative adsorption by charcoal and other 

 adsorbents is similar; if the degree of adsorption runs 

 parallel with the lowering effect on surface-tension, and if 

 equal adsorption corresponds to equal physiological 

 action, we should expect that solutions of the same 

 surface-tension (isocapillary solutions) would have the 

 same physiological effect. Czapek and Traube have in 

 fact demonstrated a close parallehsm between the influ- 

 ence of a large number of compounds on air- water surface- 

 tension and their physiological action. Traube has 

 called attention to the fact that in a homologous series 

 of compounds the degree of activity, both physical and 

 physiological, increases very generally about three times 

 with each increase in molecular weight. According to 

 this rule the isocapillary concentrations of the successive 

 compounds of the series should diminish in geometrical 

 progression, with one-third as exponent, as the molecular 

 weight increases. He gives the following determinations 

 for the series of alkyl acetates: 



Ester and Concentration Capillary Height 



CH3COOCH3.. (m) 58.1m 



C,Hs (m/3) 58.0 



C3H7 (m/9) 57.7 



i-C4H9 (m/27) 58.8 



i-CsHxx (m/8i) 59.9 



(H,0) (91. S) 



