58 PHILOSOPHY OF ZOOLOGY. 
abundant in animal fluids. It is much more common in 
the vegetable kingdom, especially in land plants. 
11. Soda.—This alkali is present in all the fluids in va- 
rious states of combination, and is more abundant than the 
preceding. It gives to many of the secretions the alkaline 
property of changing vegetable blues into green. It is 
found in union with the carbonic, phosphoric, sulphuric, 
and muriatic acids. 
12. Ammonia.—As the elements of this alkali exist in all 
the fluids, and many of the solids of animals, itis frequently 
produced during putrefaction, and the decompositions of 
analysis. These elements are likewise found united in the 
system, and the alkali then appears in union with the va- 
rious acids, as the phosphoric, muriatic, and lactic. 
13. Lime.—This earth, of which the hard parts of ani- 
mals, such as bones and shells, are chiefly composed, is of 
universal oceurrence. It is always in a state of combina- 
tion, and chiefly with the carbonic or phosphoric acids. 
14. Magnesia.—In the animal system, this earth occurs 
sparingly. It has been detected in the bones, blood, and 
some other substances, but always in small quantity, and 
chiefly in union with phosphoric acid. 
15. Silica.—This earth occurs still more sparingly than 
the preceding. It is found in the hair, urine, and urinary 
calculi. 
16. Iron.—The existence of iron has hitherto only been 
detected in the colouring matter of the blood, in bile, and 
in milk. Its peculiar state of combination in the blood, has 
given rise to various conjectures ; but a satisfactory solution 
of the question has not as yet been obtained. In milk, it 
appears to be in the state of phosphate. 
17. Manganese—The oxide of this metal has been ob- 
served, along with iron, in the ashes of hair, by Vauaur- 
LIN. 
ae. 
