PHYSIOLOGY: J. LOEB 
475 
found that a great number of salts could replace sea water in the two 
above mentioned experiments. Thus m/2 NaCl or m/2 LiCl or NaNOs 
or many other salts retarded the poisoning effect of KCl upon the heart 
of the embryo and accelerated the recovery about as much as did sea 
water. We are, therefore, dealing here with a general salt action which 
increases in certain limits with the concentration of the salt and which 
varies for different salts. Thus it was found that for equal concentra- 
tions the citrates are much more efficient than the sulphates or tar- 
trates and these are more efficient than the chlorides or nitrates; which 
indicates a valency effect of the anion. 
A trace of acid when added to distilled water may also accelerate the 
recovery of the hearts poisoned with KCl. Bases have no such effect. 
Sugar solutions act like distilled water. 
4. The question arises: How is it possible for salts (or acids) to re- 
tard the entrance of KCl into the egg or to facilitate the diffusion of KCl 
out of an egg which has been poisoned with this salt? All previous 
theories of antagonistic salt action (with the exception of the one pro- 
posed by Loeb and Wasteneys for the case of KCl and NaCl) have only 
considered three quantities : the concentration Ci of the poisonous salt 
(in our case KCl) in the outside solution, the concentration Ch of the 
injurious salt inside the membrane, and the '^permeability" of the 
membrane. I am of the opinion that it is necessary to introduce another 
quantity, namely the concentration C„i of the poisonous salt at the 
boundary between the membrane and the outside solution. I assume, 
therefore, that there are forces at work (chemical or kindred) between 
the membrane and the poisonous salt in the surrounding solution (e.g., 
KCl) whereby this salt adheres or is attached to the external surface of 
the membrane in a concentration C„i which is different from Ci; and 
that Cin and not Cj determines the rate at which the salt diffuses into 
the egg. It is further assumed that the presence of other salts influences 
the (chemical or kindred) forces acting on the surface of the membrane 
whereby the concentration Cm at the surface of the egg is different 
from what it would be if the injurious salt (e.g., KCl) were alone in solu- 
tion. Whenever the influence of another salt is such as to diminish Cm 
we are dealing with a case of antagonistic salt action. 
5. In order to test this idea the writer made experiments in which 
he substituted a dye, namely neutral red, for KCl. He found that in 
the same concentration of neutral red the eggs of Fundulus are stained 
red more rapidly if the dye is contained in distilled water than in a salt 
solution or in a solution containing acid. He foimd, moreover, that the 
more dilute the solution of a given salt the less its antagonistic effect to 
