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SCIENCE 



[N. S. Vol. XXXIV. No. 881 



this question lies in the following observa- 

 tions on the eggs of Fundulus. 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 m./2 NaCl solution, the toxicity of the 

 solution is diminished 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 ren- 

 der the pure solution of sodium chloride 

 harmless, at least to the extent that the 

 eggs can live long enough to form an em- 

 bryo. The fact that a substance as poison- 

 ous as Zn or lead can render harmless a 

 substance as indifferent as sodium chloride 

 seemed so paradoxical that it demanded an 

 explanation, and this explanation casts light 

 on the nature of the protective or antagon- 

 istic action of salts. For the antagonistic 

 action of a salt of lead or zinc against the 

 toxic action of sodium chloride can only 

 consists in the lead salt protecting the em- 

 bryo against the toxic action of the NaCl. 

 But how is this protective action possible ? 

 We have mentioned that if we put the 

 young fish, immediately after hatching, into 

 a pure m./2 solution of sodium chloride 

 the animals die very quickly, but that they 

 live indefinitely in the sodium chloride solu- 

 tion if we add both CaCL and KCl. How 

 does it happen that for the embryo, as long 

 as it is in the egg shell, the addition of 

 CaCU to the NaCl solution suffices, while 

 if the fish is out of the shell the addition 

 of CaCU alone is no longer sufficient and 

 the addition of KCl also becomes neces- 

 sary ? Moreover, if we try to preserve the 

 life of the fish after it is taken out of the 

 egg in an m./2 sodium chloride solution by 

 adding ZnSO^, or lead acetate, to the solu- 



tion we find that the fish die even much 

 more quickly than without the addition. 



If we look for the cause of this difference 

 our attention is called to the fact that the 

 fish, as long as it is in the egg, is separated 

 from the surrounding solution by the egg 

 membrane. This egg membrane possesses 

 a small opening, the so-called micropyle, 

 through which the spermatozoon enters into 

 the egg. I have gained the impression that 

 this micropyle is not closed as tightly im- 

 mediately after fertilization as later on, 

 since the newly fertilized egg is killed more 

 rapidly by an m./2 solution of NaCl than 

 it is killed by the same solution one or two 

 days after fertilization. One can imagine 

 that the micropyle contains a wad of a col- 

 loidal substance which is hardened gradu- 

 ally to a leathery consistency if the egg 

 remains in the sea-water. With the proc- 

 ess of hardening, or tanning, it becomes 

 more impermeable for the NaCl solution. 

 This process of hardening is brought about 

 apparently very rapidly if we add to the 

 m./2 NaCl solution a trace of a salt of a 

 bivalent metal like Ca, Sr, Ba, Zn, Pb, Mn, 

 Ko and Ni, etc. It is also possible that 

 similar changes take place in the whole 

 membrane. The process of rendering the 

 m./2 Na solution harmless for the embryo 

 of the fish, therefore, depends apparently 

 upon the fact that the addition of the bi- 

 valent metals render the micropyle or per- 

 haps the whole membrane of the egg more 

 impermeable to NaCl than was the case 

 before. 



But these are only one part of the facts 

 which throw a light upon the protective or 

 antagonistic action of salts. Further data 

 are furnished by experiments which I made 

 together with Professor Gies, also on the 

 eggs of Fundulus. Gies and I were able to 

 show that not only are the bivalent metals 

 able to render the sodium chloride solution 

 harmless, but that the reverse is also the 



