552 STUDIES IN GENERAL PHYSIOLOGY 
(1) 100 cc. 4°n NaCl 
(2) 96 “ “ +4 cc. $n KCl 
(3) 96 « “ +4 * 427 CaCl, 
(4) 96 “ “« 42 “ 127 CaCl, +2 cc.$n2 KCl 
(5) 93 “ “ 45 “ 1297CaCl, +2 cc. $n KCl 
In solutions 1 and 2 the animals died in less than two hours. 
In solution 3 the animals were found dead the next morning. 
In solution 4 the animals died within three days; and in 
solution 5 one animal was still alive at the end of the third 
day when the experiment was discontinued. The presence 
of small amounts of K and Ca ions prevents or weakens the 
poisonous effects of even large quantities of NaCl. 
I will now consider some possible objections to our theory. 
One might think that with the CaCl, a small amount of HO 
ions might possibly be introduced in cases in which the 
CaCl, was heated before it was dissolved. One might think 
that these HO ions were the essential constituent that 
prolonged the life of these fish. The K ions were only 
needed to overcome certain effects of the Ca ions. There is 
indeed an antagonism between K and Ca ions, as shown by 
Ringer’s experiments. But the fact that Fundulus lives 
indefinitely in distilled water proves that HO ions are not 
necessary to maintain its life. The second objection might 
be that NaCl used contained impurities. But this objection 
may be discarded at once. The NaCl was obtained from 
several leading factories and was chemically pure. The only 
impurity possible could have been a trace of K. Butasa 
further addition of K made the NaCl more harmless, it is out 
of the question that the trace of KCl which the NaCl might 
have contained could have had anything to do with the 
poisonous effects. A third possible objection might be that 
these experiments only prove the necessity of K and Ca ions 
for Fundulus. But this idea is refuted by the fact that 
Fundulus can live indefinitely in distilled water, it is, per- 
haps, worthy of mention that the positive proof for the 
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