362 RALPH S. LILLIE. 



factor of any importance in true anaesthesia. The effective con- 

 centrations are too high and the effect is too variable. 



A probably more significant physical change caused by lipoid- 

 solvent anaesthetics is an increase in the viscosity of lecithin 

 suspensions. Handowsky and Wagner 1 observed such an in- 

 crease of viscosity in the presence of alcohol; and A. Thomas, 

 working in my laboratory, has confirmed and extended these 

 observations. 2 Thomas observed that in the case of ether the 

 increase of viscosity in concentrated emulsions of lecithin might 

 go so far as to cause true gelation. I have found that this 

 effect is very general; it is well shown in lecithin emulsions of 

 10 to 12 per cent, concentration; these are highly viscous, but 

 still fluid in consistency; on the addition of many anaesthetics 

 this consistency changes to that of a soft more or less coherent 

 and elastic gel, in some cases of sufficient firmness to permit the 

 inversion of the test-tube without spilling. Well-marked gelation 

 was observed with the following compounds: alcohols (w-propyl, 

 i-propyl, w-butyl, i-amy\, capryl), esters (ethyl formate, acetate, 

 propionate, butyrate, nitrate), ethyl ether, ethyl chloride, ethyl 

 bromide, chloroform, carbon tetrachloride, benzol, toluol, xylol, 

 chloretone, chloral hydrate, chloralose, paraldehyde. On the 

 other hand, certain very efficient narcotics had no such effect, 

 e. g., methyl, ethyl and phenyl urethanes, ethyl alcohol, nitrome- 

 thane and acetonitrile. Gelation, however, is to be regarded as 

 simply an end-effect of increase in viscosity; the latter change is 

 the essential, and this is perhaps the most general and significant 

 of the purely physical changes produced by lipoid-solvent 

 anaesthetics in colloidal suspensions of lipoids. Such a change 

 will have in general a retarding influence on physical and chemical 

 processes taking place in such a system; it will decrease diffusion- 

 rates and hence reaction-velocities depending on such rates; 

 more energy, mechanical or other, is required to produce any 

 kind of change in a highly viscous system. A general hindrance 

 to diffusion would express itself in a decrease of permeability 

 and of electrical conductivity. The influence of changing viscos- 

 ity on the electrical conductivity of lipoid suspensions remains 



1 Handowsky and Wagner, Biochem. Zeitschr., 1911, Vol. 31, p. 32. 



2 A. Thomas, Journ. Biol. Chem., 1915, Vol. 23, p. 359. 



