304 PHYSIOLOGY AT THE FARM. 



in moderate proportion, in certain rocks ; thus albite or natron 

 felspar is a rock in which soda supplies the place of the potass 

 in common felspar. Moreover, the vast store of soda, under 

 the form of chloride of sodium, in sea-water, clearly gives it a 

 good title to the name of mineral alkali. Soda is more parti- 

 cularly the alkali of the animal kingdom. It is soda which 

 gives the alkaline character to the blood. The chloride of 

 sodium, the sulphate of soda, the phosphate of soda, and vari- 

 ous combinations of soda with the organic acids, are met with 

 in the animal fluids. 



Calcium. Lime, or the oxide of calcium, is spread abund- 

 antly throughout organic nature. In the vegetable kingdom 

 the salts of lime exist everywhere in minute proportion. In 

 the animal kingdom lime is collected into masses in combina- 

 tion, in particular, with phosphoric acid. 



Magnesium. Magnesia, or the oxide of magnesium, is far 

 more sparingly found than lime in the vegetable and animal 

 kingdoms. Phosphate of magnesia is often met with in the 

 analysis of vegetable products. Thus in the ashes of wheat, 

 rye, beans, and pease, the phosphate of magnesia exists in con- 

 siderable proportion. The same salt occurs in the blood and 

 in human bones. 



Iron. Iron is possessed of important offices in organic 

 nature. Combined with phosphoric acid in the fruit of wheat, 

 rye, and pease, the oxide exists. The oxide is met with in the 

 ashes of various kinds of wood. In the ashes of fir-wood the 

 oxide has been found to the extent of 22.3 per cent. In 

 the animal kingdom iron is a universal constituent of the 

 blood. 



Manganese. Manganese appears in the analysis of some 

 woods, and it has been found also in the animal kingdom, as 

 in the human hair. 



