172 WHAT DOES MAN LIVE UPON? 



become the foundation and support of the whole body ; we 

 know that when this bone-earth is not present in sufficient 

 quantity, a dreadful disease, the rickets, ensues. Whence 

 does man obtain this no less essential constituent of his 

 frame ? We know, moreover, that all the fluids of the body 

 contain definite amounts of certain salts, that without 

 these they cannot execute the functions to which they 

 are appointed. Of these substances also must we render 

 an account, if we would explain the nutrition of the animal 

 body. Of the inorganic, as of the nitrogenous portions 

 of the frame, a certain quantity undergoes continual decom- 

 position through the activity of the body, is excreted, and 

 therefore must be renewed. We here involuntarily think 

 of the earth-eating Ottomacs, of the Negroes swallowing 

 clay, of the countless instances of men who have eaten, in 

 the pangs of hunger or from fancy, the Mountain-meal, a 

 fine siliceous or calcareous earth. But we at once turn 

 from these ideas when we observe they do not refer to any 

 universal food, but merely to some few abnormal pheno- 

 mena, proceeding from diseased conditions of the gastric 

 nerves, or from necessity. The source from whence the 

 animal body draws the inorganic constituents, must be 

 universal, and we find ourselves thus directed back to 

 plants. If then bone-earth and nitrogenous constituents 

 build up the animal body, if we know that alkaline salts 

 always accompany the bile, which, according to Liebig's 

 view, plays an important part in the process of respiration 

 and combustion, through which the animal heat is main- 

 tained, it must naturally astonish us to find, in plants, the 

 nitrogenous materials for nutrition constantly accompanied 

 by phosphate of lime, the materials for respiration,, devoid 

 of nitrogen, constantly associated with alkalies. Thus has 



