IX 



THE ROLE OF SALTS IN THE PRESERVATION OF LIFE' 



I 



Less is known of the role of the salts in the animal body 

 than of the rdle of the three other main food-stuffs, namely, 

 carbohydrates, fats, and proteins. As far as the latter are con- 

 cerned, we know at least that through oxidation they are 

 capable of furnishing heat and other forms of energy. The 

 neutral salts, however, are not oxidizable. Yet it seems to be a 

 fact that no animal can live on an ash-free diet indefinitely, 

 although no one can say why this should be so. We have a 

 point of attack for the investigation of the r61e of the salts in 

 the fact that the cells of our body live longest in a liquid which 

 contains the three salts, NaCl, KCl, and CaClj in a definite 

 proportion, namely, 100 molecules NaCl, 2.2 molecules KCl, 

 and 1 . 5 molecules of CaClj. This proportion is identical with 

 the proportion in which these salts are contained in sea- water; 

 but the concentration of the three salts is not the same in both 

 cases. It is about three times as high in the sea-water as in our 

 blood serum. 



Biologists have long been aware of the fact that the ocean 

 has an incomparably richer fauna than fresh-water lakes or 

 streams and it is often assumed that life on our planet originated 

 in the ocean. The fact that the salts of Na, Ca, and K exist in 

 about the same proportion in our blood serum as in the ocean 

 has led some authors to the conclusion that our ancestors were 

 marine animals, and that, as a kind of inheritance, we still carry 

 diluted sea-water in our blood. Statements of this kind have 



1 Carpenter lecture delivered at the Academy of Medicine of New York, 

 October 19, 1911. Eeprinted from Science, N.S., XXXIV, No. 881, 653-65, 

 November 17, 1911, by courtesy of Professor James McKeen CatteU. 



169 



