328 RALPH S. LILLIE. 



cell lipoids, but rather by undergoing surface-condensation or 

 adsorption at the physiologically active surfaces within the 

 living system ; these may be the surfaces of special cell-structures 

 or of colloidal particles, whether lipoid or protein. The catalytic 

 activity of these surfaces is thus decreased, and the reaction- 

 velocities of essential chemical processes, especially oxidations, 

 is lowered. A corresponding depression of cell-functions results. 

 Whether this effect is to be attributed to a displacement of 

 metabolically active water-soluble substances like sugar, whose 

 surface-activity is relatively small, or to a direct alteration in 

 the catalytic properties of the physiologically active surfaces 

 themselves, is uncertain. The essential feature of Traube's 

 view is that it regards the surface-activity of a narcotic com- 

 pound, i. e., its influence in lowering surface-tension rather than 

 its lipoid solubility as the determining factor in its depressant 

 action. This surface-activity determines the degree of adsorp- 

 tion, and hence, indirectly, of anaesthetic action. It is well known 

 that the surface-tension of such a solvent as water, in contact 

 with air or with another liquid or a solid, is greatly influenced 

 by the presence of dissolved substances. This influence is 

 usually in the direction of a decrease. A few substances like 

 inorganic salts and sugars increase the surface-tension of water, 

 although the effect is slight; but the majority, especially of 

 organic substances, cause well-marked and often great decrease. 

 This is especially true of substances whose water-solubility is 

 limited; and in general the more soluble a substance is in oils 

 or other w r ater-insoluble organic solvents, and the less soluble 

 in water, the greater is its influence (for a given molecular concen- 

 tration) on the surface-tension of water. In a capillary tube the 

 level of pure water or of an aqueous solution is raised, by the 

 contractile force or tension of the surface of the water-film lining 

 the walls of the tube, to a certain height above the level of the 

 water outside. This height (h) is proportional to the surface 

 tension of the water (cr), and inversely proportional to the 

 radius of the tube (r} and the specific gravity (g) of the liquid 

 (h -- 2<T/rg). The relative surface-tensions of aqueous solutions 

 may thus be determined by measuring the heights to which the 

 column of solution is raised by capillarity in a given tube. This 



