504 Seifriz.—Observations on the Reaction of 
stant requires a concentration [of but 0-005 mol. per litre to cause the same 
(34 per cent.) retardation in oxidation. This same relationship holds in the 
retardation of oxidation in living cells; thus, a 10 mols. per litre solution 
of methylurethane is necessary to cause a 60 percent, retardation in respira¬ 
tion in red blood corpuscles, while but a 0-05 mol. per litre solution of 
phenylurethane is necessary to lower respiration the same amount. 
The retardation of oxidation is looked upon as a consequent of 
a diminution of the free adsorptive surface of the carbon (or of the living 
solid particles) due to the adsorption of the narcotic. That is, since oxida¬ 
tion is augmented by an increase in adsorptive surface, just as are many 
other chemical reactions (e g. gas reactions are accelerated by the presence 
of quartz, porcelain, carbon, &c.), then a decrease in this surface by the 
adsorption of another substance, the narcotic, would cause a decrease in 
oxidation. 
From the above experimental observations by Warburg, one can con¬ 
clude that narcosis is an adsorption phenomenon ; that the toxic effect of 
a narcotic is proportionate to its adsorption index ; and that the chemical 
nature of the adsorptive substance (e. g. whether lipoid or protein) is not 
a factor in narcosis. 
To consider the newest of these several theories first, it would seem 
clear that while Warburg’s theory of narcosis is a most convincing one, 
and stands as the best explanation which we have of narcosis—in so far as 
narcosis consists in a suppression of respiration—it cannot be accepted as 
a theory which covers all permeability phenomena. It stands as a simple 
and attractive explanation of a very complex vital process, but whether the 
whole story is told is another matter. It is a debatable question whether 
the striking increase in permeability produced by such different substances 
as alcohol and saponin (and strontium and copper 1 ) is in each case the out¬ 
come of the same single simple physical phenomenon. 
The Overton lipoid theory of protoplasmic permeability is well 
supported by the reaction of protoplasm to the saponins, and possibly also 
by the toxic eftect of alcohol. How far lipoids play a part in the toxicity 
of alcohol on protoplasm it is difficult to say. Lecithin is easily soluble in 
concentrated alcohol (12, pp. 153-4), but cholesterin is practically insoluble 
in cold aqueous solutions of alcohol (2, p. 1071). One would, therefore, not 
expect so low a concentration of alcohol as 10 percent., which is highly 
toxic, and still less would one expect a 2 per cent, concentration, which we 
have seen is sufficiently concentrated to produce pronounced changes in 
permeability, to strongly attack the lipoid constituents of the plasma 
membrane. However, it is conceivable that higher concentrations of the 
alcohol could be arrived at as a result of adsorption on the membrane 
surface, a process which probably takes place. The concentration of alcohol 
1 For the results on strontium and copper see ( 21 ). 
