SALT AND WATER IN LIFE AND GROWTH 107 



is not chemically pure sodium chloride, and many of the 

 minor salts mentioned, particularly the lime salts, are con- 

 tained in most food. Thus both milk and cheese are rich 

 in lime salts; most vegetables contain potassium salts, and 

 bread contains both. 



Further investigations have revealed the cause of the 

 deleterious action of pure salt. It can be proved that the 

 outer skin of sea animals, if placed in pure salt solution, 

 loses its natural density. It rapidly swells and begins to 

 disintegrate; if this occurs in the gills of a fish, the fish must 

 suffocate because water cannot pass through the engorged 

 and occluded gills. In a similar manner, men suffocate 

 after inhalation of large amounts of acid vapors or other 

 irritating gases that disintegrate and swell up the tender 

 membranes surrounding the air cells of the lungs; the air 

 cells are engorged by the vapors. Lime salts are naturally- 

 occurring salts which keep cells dense. But some salts, 

 which never occur in the ocean, also act in this way. 



(It has also been possible to make artificial membranes 

 from a fat-and-water mixture. These membranes become 

 permeable in pure salt solution just as does the skin of ani- 

 mals. In these artificial skins, the cause of the increased 

 permeability can be studied and determined. It is due to 

 a separation of the oil and water constituents of the artificial 

 membranes, (according to experiments of G. H. A. Clowes). 



Thus we see that life depends on all the salts contained 

 in the ocean, including those which are present only in small 

 amounts. If it is true that our blood has developed from 

 the ocean, we should expect to find in it, also, all the salts 

 of the sea. An analysis of the blood salts shows that this 

 is the case. We find among them all those minor constit- 

 uents which ocean water contains. Yet there are some 

 discrepancies as follows : 



