Role of Salts in Preservation of Life 177 



or find an analogue for them in colloid chemistry. But if we 

 realize that NaCl alone is toxic because it is not able to render 

 the egg membrane impermeable; and that ZnSO, if alone in 

 solution is toxic for the same reason; while both combined are 

 harmless (since for the ''tanning" of the membrane the action 

 of the two salts is required) these experiments become clear. 



We may, for the sake of completeness, still mention that 

 salts alone have such antagonistic effects; glycerin, urea, and 

 alcohol have no such action. On the other hand, ZnSO^ was 

 not only able to render NaCl harmless, but also LiCl, NH^Cl, 

 CaCl,, and others; and vice versa. 



These experiments on the egg of Fundulus are theoretically 

 of importance, since they leave no doubt that in this case at 

 least the ''antagonistic" action of salts consists in a modification 

 of the egg membrane by a combined action of two salts, whereby 

 the membrane becomes less permeable for both salts. 



V 



It is not easy to find examples of experiments in the litera- 

 ture which are equally unequivocal in regard to the character 

 of antagonistic salt action; but I think that some recent experi- 

 ments by Osterhout satisfy this demand. 



It has long been a question whether or not cells are at all 

 permeable for salts. Nobody denies that salts diffuse much 

 more slowly into the cells than water; but some authors, 

 especially Overton and Hoeber, deny categorically that they 

 can diffuse at all into the cells. Overton's view is based partl\' 

 on experiments on plasmolysis in the cells of plants. If the 

 cells of plants, for example, those of Spirogyra, are put into a 

 solution of NaCl or some other salt of sufficiently high osmotic 

 pressure, the volume of the contents of the cell decreases 

 through loss of water and the protoplasm retracts, especially 

 from corners of the rigid cellulose w^alls. Overton maintains 

 that this plasmolysis is permanent, and concludes from this 



