IonN-PROTEID Compounps 557 
sn” NaCl solution is certainly not so poisonous as an solu- 
tion of the same salt. A Fundulus that would be killed by a 
g” NaCl solution in twelve hours is able to live in a dn 
NaCl solution two or three days, which is as long as or a little 
longer than, the frog’s muscle lives at the same (summer) 
temperature in a solution of the same concentration. That 
the effects of a pure NaCl solution upon a frog’s muscle are 
in no way different from those on Fundulus is proved, more- 
over, by the fact that the muscle lives longer in a NaCl solu- 
tion if small amounts of KCl and CaCl, are added. This 
explains the superiority of Ringer’s solution over a physio- 
logical salt solution. Ringer’s solution prevents the Na 
ions of the physiological salt solution from taking the place 
of the Ca and K ions in the tissues. Contractility is pos- 
sible only if the Na, Ca, and K ions exist in definite propor- 
tions in the ion proteids. Hence there is no reason for sup- 
posing that what we have proved for marine animals does 
not hold good for other animals. 
VI. SUMMARY 
The main results of this paper are as follows: 
1. A pure solution of NaCl of the same concentration as 
sea-water is a strong poison for many (if not all) marine 
animals. The poisonous effects of this solution are due to 
the Na ions. The same is true for pure equimolecular solu- 
tions of CaCl, and KCl. 
2. The poisonous effects of the Na ions are antagonized by 
the addition of a small amount of Ca and K ions. Through 
the presence of these two ions the Na ions in the ocean lose 
their poisonous effect. 
3. The Na ions of the blood would not allow the tissues 
to live. The presence of Ca, K, and possibly other ions 
counteracts the poisonous effects of Na ions in the blood. 
This is the reason why tissues live longer in Ringer’s solu- 
tion than in a physiological salt solution, 
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