182 The Mechanistic Conception of Life 



of these cells, as it does in the experiments on gelatin or as in 

 the cases of tanning of hides by the combined action of acids 

 and salt solutions. This combined dehydrating or ''tanning" 

 action of acid and salts on the surface of the epithelial cells of the 

 gills diminishes the permeability of this layer for the acids and 

 prevents them from diffusing into the cells and thus destroying 

 the protoplasm. In this way the gills are kept intact and the 

 life of the fish is saved. 



As long as the amount of acid is small the amount absorbed 

 is not essentially diminished by the presence of salts; but while 

 in the presence of salts the acid is consumed in the tanning 

 action of the surface layer of the cells, or is absorbed in this 

 layer; if no salt is present part of the acid diffuses into the 

 epithelial cells and kills the latter. 



VII 



We have thus far considered the cases of antagonism between 

 two electrolytes only. The case of the antagonism between three 

 electrolytes is a little more complicated. 



We choose as an example the antagonism between NaCl, 

 KCl, and CaCl, — the antagonism which is most important in 

 life phenomena. If the mechanism of the antagonism between 

 NaCl, on the one hand, and KCl and CaCl.,, on the other, is of 

 the same nature as that between NaCl and ZnSO^ in the case of 

 the eggs of Fundulus, it must be possible to show that not only 

 is NaCl toxic if it is alone in solution, and that it is rendered 

 harmless by the two other salts, but that the reverse is true 

 also. This can be proved in the case of KCl. To demonstrate 

 it, we have again to experiment on organisms which are, in wide 

 limits, independent of the osmotic pressure of the surrounding 

 solution since the concentration of the KCl in sea-water is very 

 low. The experiments were carried out by Mr. Wasteneys 

 and myself on Fundulus. The method consisted in putting six 

 fish, after washing them twice with distilled water, into 500 c.c. 



