788 SALT ANTAGONISM IN STARFISH EGGS 



THEORY. 



In the present case of salt antagonism the effect, removal of the 

 jelly, is a direct result of the incorporation of water in pure NaCl 

 solution with consequent swelling until coherence is lost; in the same 

 solution containing a little calcium the jelly retains its normal hydra- 

 tion and remains coherent and water-insoluble. The chemical com- 

 position of the jelly is unknown, but the presence of a certain pro- 

 portion of protein is probable; this is suggested by its acid-combining 

 properties,^ also by its mode of formation as a cellular secretion, 

 its physical consistency and its variation in properties from species 

 to species. At least it seems clear that some substance is present 

 forming compounds (salts) with sodium and calcium, which differ 

 in their solubilities and in their affinities for water. 



Apparently, in the presence of an excess of NaCl, a Na salt with 

 a marked affinity for water is formed ; hence the swelling and eventual 

 solution. When CaCl2 is present in the solution a water-insoluble 

 Ca salt is formed ; in the presence of a certain proportion of this the 

 jelly as a whole remains insoluble. In other words, the normal 

 coherence and water-insolubility of the jelly depend on the presence 

 of a water-insoluble compound which pervades the system and ren- 

 ders it coherent and water-insoluble. Hence the removal of this 

 by replacement of Ca with Na renders the whole structure soluble. 



Antagonisms depending on differences in the solubilities of Na 

 salts (or in general of alkali metal) and Ca salts (or all<:ali earth and 

 heavy metal) are well known in purely physical systems. In many 

 organic acids the Na salts are highly soluble in water, while the Ca 

 salts are insoluble. The case of soaps is probably the most relevant 

 to the conditions in biological systems. The physicochemical antag- 

 onisms recently investigated by Clowes,^ using salt solutions which 

 were allowed to drop from a stalagmometer through oil containing 

 some fatty acid, depend on the difi'erences between the solubilities 

 of Na soaps and Ca soaps in the oil and the water phases respectively. 

 The antagonisms between the influence of Na and Ca salts on the 

 precipitation of lecithin^ and heat-denatured egg white^ are prob- 



^ Clowes, G. H. A., /. Physical Chem., 1916, xx, 407. 



5 Koch, W., Z. physiol. Chem., 1909, Ixiii, 432. 



6 Mathews, A. P., Am. J. Physiol., 1905, xiv, 203. 



