LIPOID-ALTERANT SUBSTANCES 201 



CNS the least; with ethyl ether and nitrome thane, the 

 chlorides, sulphates, and bromides increased the inter- 

 facial tension, while the iodides and thiocyanates 

 decreased it. Similar conditions were found with 

 CHCI3 and CCI4, but in this case iodide also somewhat 

 increased the surface-tension. 



It would appear that the physical relations (of 

 adhesion, mutual solubility, etc.) between water and 

 the organic compound, as well as between the latter and 

 the non-aqueous protoplasmic phase or structure (e.g., 

 membrane) are of importance in the physiological effect. 

 According to Traube the narcotic action of organic 

 compounds is determined by what he calls their "Haft- 

 druck" (''adhesion- tension"), i.e., special attraction to 

 or affinity for water ;^ the tendency of any compound 

 to pass out of aqueous solution and concentrate in the 

 surface layer between water and the other phase — i.e., to 

 undergo adsorption — is in general the greater the less 

 its affinity for water. This is one manner of interpreting 

 the relation noted by Richet and others between water- 

 insolubility and narcotic action; but since solubility in 

 water and solubiUty in organic solvents — e.g., in the 

 esters of higher fatty acids which form the organic sol- 

 vents of protoplasm — have similarly reciprocal relations, 

 this consideration does not enable us to decide whether a 

 solution-effect or an adsorption-effect is the essential fac- 

 tor in the physiological action. The recent investigations 

 of Langmuir and Harkins on adsorption^ indicate, how- 



^ Cf. Traube, "Theorie des Haftdrucks und Lipoidtheorie," Bio- 

 chem. Zeilschrift, LIV (19 13), 305. 



^ Langmuir, Journal of the American Chemical Society, XXXIX 

 (1917), 1848; XL (1918), 1361; Harkins, Clark, and Roberts, i6JJ.,XLII 

 (1920), 700; Harkins and Cheng, ibid., XLHI (192 1), 35. 



