Stiles and j0rgensen. — Studies in Permeability . IV. 69 
impossible to draw general conclusions from such measurements. To this 
criticism Czapek has made no satisfactory reply. 
4 . Czapek shows that seven substances out of twenty-nine examined by 
him have a surface tension far greater than 068. This has also been pointed 
out by Vernon. To this criticism Czapek ( 4 ) replies that he has already 
explained the deviation of these substances from the o*68 rule as being due to 
their ‘ specific toxic action although this is absolutely nothing more than 
stating the same fact in different words. Vernon suggests that in the cases of 
these exceptions, the substances probably dissolved the lipoid substances in 
the membrane, and that it is to be explained on the Meyer- Overton law of 
partition coefficients. Vernon points out that the same order of concentra- 
tions is obtained for tannin exosmosis as for narcosis, in which the results are 
explicable as due to lipoid substances. 
But Schryver (8) suggests that there is no need to assume the results 
for narcotics as due to lipoids. This author shows that if substances 
are arranged in the order of their power of disintegrating a cholate gel, 
that order is exactly the same as found by Czapek in regard to tannin 
exosmosis, and as Schryver says, the cholate gel ‘ cannot, by any extension 
of the meaning of the term, be described as a lipoid ’, and in any case 
Czapek’s ‘ purely mechanical conception of cytolysis is clearly no longer 
tenable \ l 
In any case Czapek’s assumption of specific toxic action is really most 
destructive of his whole case, for it is an admission that factors other than 
surface tension may in some cases be the predominating ones in regard 
to exosmosis. 
Again, it cannot even be conceded that solutions which produce equal 
exosmotic effects have the same surface tension in contact with air. The 
following table is compiled from the results recorded in this paper. The 
values are only approximate, but they are at any rate considerably more 
trustworthy than those of Czapek. 
Strength required 
Surface tension againt 
Substance. 
to produce same 
air ( from the data of 
exosmotic effect. 
Czapek and Traube ). 
Methyl alcohol 
3-2 m. 
0-76 
Ethyl „ 
1.6 m. 
0-70 
Normal propyl alcohol 
0.7 m. 
0^64 
Isobutyl ,, 
0.33 m. 
0,58 
Isoamyl „ 
0-095 m. 
0-58 
Secondary octyl „ 
0.0048 m. 
no data 
Chloral hydrate 
0*17 m. 
°*94 
Urethane 
0.5 m. 
0.77 
Acetone 
1.3 m. 
0.69 
Aniline 
o-o8 m. 
no data 
Pyridine 
0.45 m. 
>9 
1 On the other hand, we do not regard Schryver’s experiments as having any direct bearing on 
cell problems. The comparison of the cholate gel with the cell rests on the similarity of the power 
of certain substances to disintegrate the gel, and their power of producing exosmosis from the cell. 
