SECTION VI. 
CHEMICAL COMPOSITION AND SECRE- 
TIONS OF VEGETABLES. 
576. Vecrranues consist chiefly of three elementary bo- 
dies, Carbon, Oxygen, and Hydrogen. Nitrogen is found in 
Some, and minute portions of sulphur, phosphorus, potassa, 
soda, lime, magnesia, alumina (argillaceous earth), silica 
(sandy or flinty earth), and iron, may be found in most of 
them. These, however, bear a small proportion to the three 
first, which make up the greater part of all vegetables. 
577. These simple materials, by their combination in dif- 
ferent proportions, compose the different solid parts and fluid 
secretions which we find in plants. Ee See 
_ 578. From animals, in respect to their chemical composi- 
tion, vegetables differ in being frequently destitute of nitro- 
gen, an element which enters largely inte the composition of 
animal compounds. Owing to the presence of nitrogen, and 
the greater variety and more complex nature of animal pro- 
ducts, these are much more readily decomposed than those 
of the vegetable kingdom. The decomposition of the former 
'S generally accompanied with the production of ammonia, 
from the union of their hydrogen and nitrogen, which does 
not so often occur in the decomposition of vegetables. ES: 
579. Between vegetable or animal and inorganic ‘sub- 
Stances, there is a marked difference in chemical composition. 
The latter generally contain some leading element which 
