THE THEORY OF ANESTHESIA. 335 



In each instance equal physiological effects are produced by 

 solutions of approximately equal surface-tension. Czapek finds 

 that the same rule of equal action for isocapillary solutions 

 holds good for ketones, esters, urethanes, and other compounds. 

 Lately, however, Vernon, 1 Hober, 2 and others have pointed out 

 various exceptions to this rule; thus chloroform, chloral hydrate, 

 nitromethane, and ethylene glycol begin to set free tannin in 

 solutions of much higher surface-tensions than the above. And 

 with the higher alcohols the surface-tensions of the effective 

 solutions are lower than the theory requires. These deviations 

 from the rule of isocapillarity are referred by Traube partly to 

 chemical influences (e. g., acid in chloral hydrate solutions), 

 partly to incorrect determination of surface-tension in solutions 

 of volatile substances like chloroform and ether, partly to the 

 influence of viscosity. In general it appears that the more 

 viscous compounds, e. g., the higher alcohols, show equal physio- 

 logical action, e. g., haemolysis, in solutions of lower surface- 

 tension than Traube's theory demands; Traube, however, be- 

 lieves that this difference is due simply to slowness of penetration, 

 incident to the high viscosity of the adsorbed layer of the narcotic 

 at the surfaces (e. g., of red corpuscles) where the essential action 

 takes place. For solutions of approximately equal viscosity the 

 rule of equal action with equal capillarity appears to hold true. 

 In general isocapillary solutions of surface-active substances have 

 less hsemolytic or other physiological action the greater their 

 viscosity; hence equal action for isocapillary solutions is to be 

 expected only when the viscosities are similar. 3 Even this, 

 however, is not always the case. For instance, Loeb 4 has found 

 that weak solutions of fatty acids, as well as weak solutions of 

 narcotics, produce positive heliotropism in daphnids; the least 

 effective concentrations for the first six members of the acid 

 series were: .oo6 formic, .oo6w acetic, .00572 propionic, .004^ 

 butyric, .004^ valerianic, .OO2 caproic. The increase in effec- 

 tiveness with increasing molecular weight is much more gradual 



1 Vernon, Biochem. Zeitschr., 1913. Vol. 51, p. i. 



2 Rudolf Hober. " Physikalische Chemie der Zelle und der Gewebe," 4th edition. 

 1914, pp. 415 seq. 



3 Cf. Traube, " Influence of Viscosity and Surface-tension in Biological Proc- 

 esses," Internal. Zeitschr. f. physik-chem. Biol., 1914, Vol. i, p. 275. 



4 J. Loeb, Biochem. Zeitschr., 1909, Vol. 23, p. 95. 



