476 
PHYSIOLOGY: I LOEB 
neutral red; and that sulphates inhibit the staining of the egg more pow- 
erfully than equal concentrations of chlorides. The same agencies which 
prevent or retard the entrance of KCl into the egg of Fundulus pre- 
vent or retard the staining of the membrane with neutral red. 
If we stain eggs of Fundulus in neutral red and put them afterwards 
into distilled water or salt solutions free from stain, the eggs will be 
decolorized rapidly in salt solutions or in acid solutions, while they will 
be decolorized very slowly in distilled water. The decoloration occurs 
the more rapidly the higher the concentration of the salt, and more 
rapidly in sulphates than in chlorides. 
The antagonism between the staining effect of neutral red upon the 
eggs of Fundulus and salts or acids is, therefore, parallel to that between 
the injurious effect of KCl upon the same eggs and salts or acids. In 
the case of neutral red we can see directly that the salt or acid diminishes 
the concentration Cm of the neutral red on the surface of the egg. When 
an egg stained in neutral red is put into am/2 solution of NaCl or of 
NaCl -f CaCl2 or a m/8 solution of Na2S04 streaks of the dye are seen 
to stream from the surface of the egg into the surrounding solution, 
while nothing of this kind occurs if the eggs are put into H2O. Here 
we can ascertain by direct observation that the antagonistic action of 
the salt on the dye consists in diminishing the concentration Cm of the 
dye on the external surface of the membrane. The diminution of Cm 
on the external surface of the membrane diminishes the rate with v/hich 
the dye diffuses into the egg and accelerates the rate with which the 
dye can diffuse out of the egg. 
If it is legitimate to apply this reasoning to the explanation of the 
second group of cases of antagonistic salt action, the observed facts 
on the antagonism between KCl and other salts or acids could be ex- 
pressed as follows: In distilled water the attractive forces acting be- 
tween the outer surface of the membrane of the egg and KCl are very 
strong and hence the concentration C„i of this salt at the outer surface 
of the membrane reaches a high value; while these forces of attraction 
between KCl and the outer membrane are diminished when salts or 
acids are added to the outer medium in the proper concentration. This 
explains why the recovery of the embryo poisoned in KCl is very slow 
when the egg is put into distilled water, since in this case the concentra- 
tion of the KCl (or other K salts) at the outer surface of the membrane 
remains very high and thus prevents the diffusion of KCl from the 
interior of the egg into the distilled water; while if a salt in a sufficiently 
high concentration is added to the distilled water the value Cm of KCl 
on the outside surface of the membrane is diminished and the barrier to 
