512 
PHYSIOLOGY: J. LOEB 
An m/2 KCl solution caused cessation of the heartbeat of unwashed 
eggs in less than two hours, and of the washed eggs in about nine hours. 
An m/8 KCl solution required six days to cause the cessation of the 
heartbeat in 70% of the eggs previously washed for twenty- 
four hours in distilled water, while the same solution had the same 
effect upon unwashed eggs in less than five hours. This difference 
was due, according to the theory mentioned above, to the presence 
of the salts of the sea water in the superficial layers of the membrane 
of the egg. On this assumption it was to be expected that by adding 
enough sea water to an m/8 KCl solution to bring this solution to a 
total salt concentration of 3/8m or m/2 the washed eggs should be 
poisoned much more rapidly. This was found to be the case. While 
70% of 'washed' eggs were poisoned by m/8 KCl in H2O in about 
six days, the same effect was usually produced in less than one day 
when the m/8 KCl solution was prepared in m/4 sea water. The same 
effect was produced by the addition of any salt of Li, Na, or NH4, and 
others, to the m/8 KCl solution instead of sea water. Since it might 
be argued that the addition of a single salt like NaCl might act by merely 
injuring the membrane and thus increasing its permeability, emphasis 
should be laid on the fact that these experiments succeeded as well when 
the 'salt effect' was supplied by balanced solutions like sea water or NaCl 
•4- CaCl2 as by non-balanced solutions. 
When any of these salts were added to the m/8 KCl solution in a 
slightly higher concentration than the moderate concentration required 
to produce the *salt effect' upon the membrane, the opposite result was 
noticed : the diffusion of KCl into the egg was again retarded or rendered 
impossible (antagonistic salt action). Thus the hearts of Fundulus 
embryos were still practically all beating in m/8 KCl made up in m/1 
(NaCl + CaCl2 + MgCl2) after eighteen days (when the experiment 
was discontinued), while they had all stopped beating in less than three 
days and more than 50% in less than one day in m/8 KCl made up in 
m/8 (NaCl -f CaCl2 + MgCl2). This disposes of the possibility that 
the general 'salt effect' consists in an increase of the 'permeability' of 
the membrane through injury by the salt. 
The most important fact is that only salts act in this way, namely to 
accelerate the diffusion of KCl through the membrane when added in 
moderate concentrations and to retard it again when added in higher 
concentration. Non-electrolytes, like sugars, glycerin, ethyl or methyl 
alcohol, and urea, do not show this behavior. 
2. The difference in the behavior of electrolytes and non-electrolytes, 
and the influence of the' chemical nature of the salt in this general 'salt 
