ION-PKOTEID COMPOUNDS 557 



\n NaCl solution is certainly not so poisonous as af n solu- 

 tion of the same salt. A Fundulus that would be killed by a 

 |n NaCl solution in twelve hours is able to live in a ^n 

 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 KC1 and CaCl 3 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 2 and KC1. 



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. 



