48 DYNAMICS. OF LIVING MATTER 



While a small quantity of a salt with a bivalent metal thus suffices 

 to render a solution of a salt with a univalent cation harmless, it was 

 found that it was not possible to produce similar antitoxic effects through 

 the addition of a salt with an anion of higher valency. If sodium sulphate, 



sodium citrate, etc., was added to a — NaCl solution, the latter continued 



2 



to remain toxic for the Fundulus egg. 



It is remarkable that not only the solutions of a salt with a univalent 

 cation, like NaCl, can be rendered harmless by a salt with a bivalent 

 cation, e.g. ZnSO^, but that also the reverse is true; namely, that a 

 toxic solution of ZnSO^ can be rendered harmless by a solution of 

 NaCl, provided the concentration of the ZnS04 ^^ °°t too high. In 

 loo c.c. of a f w NaCl solution no Fundulus egg forms an embryo. 



441 



When from 2 to 8 c.c. -^r- solution of ZnSO. are added to this NaCI 

 64 " 



solution, just as many eggs form embryos as in sea water or distilled 



water. If, however, from 4 to 8 c.c. of a — ZnS04 solution are added 



to 100 c.c. distilled water, not a single egg is able to form an embryo, 

 although in pure distilled water these eggs hve and develop as well as 

 in sea water. The Zn-ions are therefore not only able to prevent the 

 toxic effects of a pure NaCl solution, but the NaCl of this solution also 

 prevents, in this case, the toxic effects of the Zn-ions. 



The quantitative relations are of some interest. About 4 c.c. — 



solution of a salt with a bivalent metal are required to render 100 c.c. 

 of a f w NaCl solution harmless. We may therefore say that for this 

 concentration of NaCl one ion of the bivalent metal sufhces to render 

 1000 molecules of the salt with the univalent metal harmless. When a 



NaCl solution of a lower concentration, namely, f w or — is used, 



less salt with a bivalent metal is required for the antitoxic effect than in 

 the case of a | w solution. If we use a NaCl solution with a concen- 



tration of or below — , it is no longer harmful for the eggs of Fundulus. 



4 

 If we use stronger solutions than f m, we soon reach a limit where the 

 addition of a salt with a bivalent metal no longer renders the solution 

 harmless. It is possible that, at this Hmit, the loss of water on the 

 part of the egg acts harmfully, and this effect, of course, cannot be 

 antagonized by the addition of another salt. If we try to determine 

 how much NaCl is needed in order to render a solution of ZnSO^ harm- 

 less, we find that a comparatively large amount of NaCl is required for 



