1918] CURRENT LITERATURE 389 
As to the mechanism of absorption, a few experiments furnish evidence favoring 
the idea that the plasmatic proteins rather than the lipoids are active in the 
acid absorption. ; 
very important paper by STILES and JorGENSEN™ challenges not only the 
theory of permeability proposed by CzAPEK some years ago, the surface tension 
theory, but also all the facts and assumptions upon which that theory was 
founded. . Because of its greater exactness and more general applicability 
to a study of all kinds of plant tissue, the Kohlrausch electrical conductivity 
method of estimating osmosis of electrolytes was used as a means of measuring 
changed permeability. Disks of potato were placed in non-electrolytic reagents 
of such strength as to produce irreversible changes in the protoplasm. Exos- 
mosis of electrolytes was measured in the presence of a number of homologous 
monohydric alcohols, chloroform, chloral hydrate, ether, urethane, acetone, 
aniline, and pyridine. In all cases corrections for the depression of con- 
ductivity caused by the presence of the non-electrolyte in the external solution 
were made. In every case the rate of exosmosis was found to depend upon the 
concentration of the substance in solution in contact with the disks. The 
higher the concentration the more rapid the exosmosis, and CzAPEK’s observa- 
tion that any member of the homologous series of primary alcohols has a greater 
effect on osmosis than a lower member of the series, if of equimolecular concen- 
tration, is confirmed. No such thing as a critical concentration, however, 
below which exosmosis did not occur and above which it did occur, could be 
found. Exosmose of electrolytes occurred in all concentrations used, down to 
mere fractions of the critical concentrations for exosmosis found by CzaPEK’s 
crude methods. The rate of diffusion of electrolytes was found not to be a 
function of surface tension alone. If the critical concentration of isobutyl 
alcohol were to be taken as 0.3 M. and the other alcohols compared with it 
as to equal exosmosis in a given time, the surface tensions of the alcohols 
do not agree at 0.68 of the surface tension of water, as CZAPEK stated, but vary 
from 0.79 in methyl alcohol to 0.59 in isoamyl. The higher the alcohol the 
greater the lowering of the surface tension required to produce a given amount 
of exosmosis in a given time. Each item of evidence and the whole tissue of 
assumptions upon which CzaPek built his theory of the plasmatic membrane 
is considered in detailed fashion and without gloves. The authors reject each 
int and assumption as untenable. In their own words, ‘‘from this review 
of the details of Czapek’s work on the plasma membrane, it is clear that neither 
the experimental evidence nor any part of the theory based upon it can be 
accepted.” They have sought to apply the law of mass action to the rate of 
osmosis in cases of permeability involving irreversible changes in the proto- 
plasm, and a mathematical expression has been deduced connecting the time 
4 Stices, WALTER, and JéRGENSEN, INGvaR, Studies in permeability. IV. The 
action of various organic substances on the permeability of the plant cell, and its 
bearing on CzapeEx’s theory of the plasma membrane. Ann. Botany 31:47-76. 1917. 
