2 28 PROTOPLASMIC ACTION AND NERVOUS ACTION 



imperfectly reversible and may be regarded as destructive 

 rather than simply anti-catalytic. Narcotics also check 

 heterogeneous catalysis in purely inorganic systems; 

 e.g., the oxidation of oxaHc acid by charcoal (Warburg)^ 

 and the decomposition of H2O2 by colloidal platinum 

 (Meyerhof),'' and the same order of relative action is 

 again seen. 



The foregoing association of a precipitating action 

 with an anticatalytic action indicates an alteration of 

 surface-conditions, but precipitation as such is not a 

 necessary accompaniment of this action. Many organic 

 compounds (alcohols) precipitate solutions of proteins 

 and other colloidal compounds, but usually the con- 

 centrations required for precipitation far exceed the 

 anticatalytic concentrations. 



Other effects, also dependent on surface-action, 

 have an intimate bearing on the present problem. Of 

 special interest is the action of narcotic compounds on 

 suspensions of lecithin. Changes in the viscosity, gel- 

 forming properties, and precipitabiUty of lecithin emul- 

 sions are characteristic. Many lipoid-solvents (alcohols, 

 etc.) increase the viscosity of these emulsions to a greater 

 degree than can be accounted for by the increase in the 

 viscosity of the aqueous phase.^ In somewhat concen- 

 trated emulsions (10-12 per cent) the addition of ether 

 even causes gelation, so that the test tube can be inverted 

 without spilling; this effect is also caused by alcohols 

 (n-propyl up to capryl), esters (ethyl formate, acetate, 



^ Warburg, Arch. ges. Physiol., CLV (1914), 547. 



'Meyerhof, Arch. ges. Physiol., CLVII (1914), 280. 



3 Handowsky and Wagner, Biochem. Zeitschrift, XXXI (1911), 32; 

 A. Thomas, Journal of Biological Chemistry^ XXIII (1915), 259. 



