Aside from their use in the formation of fat, proximates of the first class are employed in the lungs, as fuel to keep up animal heat, which is produced (as in fire and decay) by the decomposition of these substances.
When the food is insufficient for the purposes of heat, the animal's own fat is decomposed, and carried to the lungs as fuel.
The stems, roots, branches, etc., of most plants consist principally of woody fibre.
Their seeds, and sometimes their roots, contain considerable quantities of starch.
Name the parts of the plant in which the different proximates exist.
State what you know about flour.
Do we know that different plants have ashes of different composition?
The protein and the oils of most plants exist most largely in the seeds.
The location of the proximates, as well as of the inorganic parts of the plant, show a remarkable reference to the purposes of growth, and to the wants of the animal world, as is noticed in the difference between the construction of the straw and that of the kernel of wheat.
The reason why the fine flour now made is not so healthfully nutritious as that which contained more of the coarse portions, is that it is robbed of a large proportion of protein and phosphate of lime, while it contains an undue amount of starch, which is available only to form fat, and to supply fuel to the lungs.