PROCEEDINGS iUN 2 4 1921 * 
OF THE 
NATIONAL ACADEMY of SCIENCES 
Volume 2 SEPTEMBER 15. 1916 Number 9 
THE MECHANISM OF DIFFUSION OF ELECTROLYTES 
THROUGH ANIMAL MEMBRANES 
By Jacques Loeb 
ROCKEFELLER INSTITUTE FOR MEDICAL RESEARCH. NEW YORK 
Received by the Academy. August 7, 1916 
1. In a former paper Loeb and Cattell^ have shown that embryos of 
the marme fish Fundulus poisoned in a KCl solution until all the hearts 
stop beating, cannot recover their heart beat when put into H2O or 
into a solution of cane sugar, although they will live in such a medium 
indefinitely; but that they recover in less than a day when put into a 
salt solution. Eggs which after being poisoned with KCl were kept in 
H2O for twelve days without recovering, recovered when put into the 
solution of an electrolyte. 
Conversely it could be shown that when eggs of Fundulus are kept 
for twent>^-four hours or longer in distilled water they are poisoned by a 
solution of potassium salts much more slowly than when the eggs are 
put into KCl solutions of the same concentration directly from sea water. 
The washing in distilled water frees the surface layer of the egg mem- 
brane from salts and this retards the diffusion of KCl into the egg. 
These facts suggested to me the idea that it was impossible for KCl 
to diffuse through a membrane free from salts and that for such a diffu- 
sion two conditions are required: first, a sufficiently high osmotic 
pressure of the KCl solution, and second, a certain modification of the 
membrane by an electrolyte, which we will call the 'salt effect.' When 
the concentration of the KCl solution was sufficiently high, e.g., 3/8m 
or m/2, the KCl itself might be able to supply this 'salt effect' upon the 
membranes of washed eggs; but when the solution of KCl was m/8 or 
below, the solution might not be sufficiently concentrated to supply 
the 'salt effect' required to allow the diffusion of KCl. This idea was 
found to be correct. 
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