LIPOID-ALTERANT SUBSTANCES 211 



division cause decrease of viscosity, i.e., facilitate the 

 displacement of granules by the centrifuge. In some 

 cases, however, Heilbrunn found effects of the opposite 

 kind; and he distinguishes two kinds of ana,'sthesia, in 

 which protoplasmic viscosity is respectively increased 

 and decreased. The significance of such changes in 

 relation to the functional activity of the cell is not clear. 

 They show, however, that the structural conditions 

 within the protoplasmic system are modified reversibly 

 by the lipoid-solvent group of compounds and that the 

 concentrations required for this effect correspond to 

 those which produce narcosis. 



Apparently the most general inference to be drawn 

 from the foregoing facts is that one constant accomi)ani- 

 ment of narcosis is a modification, in the direction of 

 greater stability or impermeability, of the physical state of 

 the plasma membrane of the irritable cells; and there is 

 good reason to beheve that the physiological effect of 

 narcotic compounds depends on this effect; this conclusion 

 will receive further support when the subject of stimula- 

 tion is discussed. The chief locus of action of anaesthetics 

 thus appears to be the same as that of salts, which is 

 evidently superficial, as already pointed out. Antago- 

 nisms between salt action and aucTsthctic action are in 

 fact readily demonstrable in many cases. ^ Salts like 

 NaCl in pure solution tend to disintegrate the plasma 

 membranes, and the addition of an aniesthetizing 

 compound to the solution frequently retards or prevents 



^ See my series of papers on antagonisms between salts and anes- 

 thetics, American Journal of Physiology, XXIX (191 2), 372; XXX, i, 

 and XXXI (1913), 255; dlso Journal of Experimental Zoology, XVI (1914), 

 591. Hober's observations (above cited) on the ctTects of anesthetics 

 in retarding the production of injury-currents in muscle by salts furnish 

 other examples of this phenomenon. 



