Role of Salts in Preservation of Life 173 



but they were rendered normal by the addition of a Uttle CaCl.. 

 A mixture of NaCl+CaCl^ also caused abnormal contractions 

 of the heart, but these were rendered normal by the addition 

 of KCl. Ringer drew the conclusion that there existed an 

 antagonism between potassium and calcium, similar to that 

 which Schmiedeberg had found between different heart poisons, 

 e.g., atropin and muscarin. Biedermann had found that alka- 

 line salt solutions cause twitchings in the muscle and Ring<'r 

 found that the addition of Ca inhibited these twitchings. 

 Since these experiments were made many examples of the 

 antagonistic action of salts have become known. 



It had generally been assumed that the antagonistic action 

 of two salts was based on the fact that each salt, when applied 

 singly, acted in the opposite way from that of its antagonist. 

 We shall see that in certain cases of antagonistic salt action at 

 least this view is not supported by fact. 



IV 



What is the mechanism of antagonistic salt action ? I 

 believe that an answer to this question lies in the following 

 observations on the eggs of Fundulns. If these eggs are put 

 immediately after fertilization into a pure sodium chloride 

 solution which is isotonic with sea-water, they usually die 

 without forming an embryo. If, however, only a trace of a 

 calcium salt, or of any other salt with a bivalent metal (with 

 the exception of Hg, Cu, or Ag) is added to the in 2 NaCl 

 solution, the toxicity of the solution is dimmished or even 

 abolished. Even salts which are very poisonous, namely, salts 

 of Ba, Zn, Pb, Ko, Ni, Mn, and other bivalent metals, are able 

 to render the pure solution of sodium chloride harmless, at 

 least to the extent that the eggs can live long enough to form 

 an embryo. The fact that a substance as poisonous as Zn or 

 lead can render harmless a substance as indifferent as sodium 

 chloride seems so paradoxical that it demanded an explanation, 



