Ion-PROTEID COMPOUNDS 551 
This result agrees with our theory. But in order to 
make the proof complete we must be able to show that an 
addition of certain other ions annihilates the poisonous 
effects of a pure NaCl solution. I tried the following solu- 
tions upon Fundulus: 
(1) 96 cc. $n NaCl+4 ec. 342 MgCl, 
(2) es es “ t4ece $7 KCl 
(3) =“ « «+4 ec. 42 CaCl, 
In each of these solutions the fish died in less than or in 
about twenty-four hours. After this experiment two salts 
were tried in combination with NaCl, and the following 
solutions were prepared: 
(1) 96 cc. §n NaCl+2 cc. 42 MgCl, +2 c.c. 4 CaCl. 
() «© © «4 & «4 «£2 KO 
(3) “ “ « 4 © 48nCaCl, + “ $nKCl 
This time the result was very striking. In the first of 
these three solutions the animals lived less than thirty hours, 
in the second a few hours longer; in the third they were 
still alive ten days later when I discontinued the experiment. 
Thus we see that the poisonous effects of the NaCl solution 
really disappear if we add a small amount of K and Ca ions, 
which makes the proof of our theory complete. 
In the pure NaCl solutions we have to deal with two ions, 
Na and Cl ions. Are both equally responsible for the 
poisonous effect? The fact that KCl and CaCl, prevent the 
poisonous effects of the NaCl solution proves that the metal 
ions are of greater importance than the Cl ions. 
I stated above that Fundulus stands the addition of rather 
large quantities of NaCl to sea-water. I tried to determine 
whether K and Ca ions were able to counteract even larger 
doses of NaCl than are contained in a §n NaCl solution. A 
number of young Funduli were put into the following solu- 
tions: 
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