THE FOOD OF ANIMALS. 4% 
Food is derived from the mineral, vegetable, and animal 
kingdoms. Water and salt, for example, are inorganic. 
The former is the most abundant, and a very essential ar- 
ticle of food. Most of the lower forms of aquatic life seem 
to live by drinking: their real nourishment, however, is 
present in the water in the state of solution. The Earth- 
worm, some Beetles, and certain savage tribes of Men 
swallow earth; but this, likewise, is for the organic matter 
which the earth contains. As no animal, so far as we now 
know, is produced immediately from inorganice matter, so 
no animal can be sustained by it. 
Nutritious or tissue-forming food comes from the or- 
ganic world, and is either albwminous, as the lean meat 
of animals and the gluten of wheat; oleaginous, as animal 
fat and vegetable @b; or saccharine, as starch and sugar. 
The first is the essential food-stuff; no substance can serve 
permanently for food—that is, can prevent loss of weight 
and change in the body—vunless it contains albuminous 
matter. The other two are not absolutely vital. Albumen 
contains nitrogen, which is necessary to the formation of 
tissue; fats and sugars are rich in carbon, and therefore 
serve to maintain the heat of the body. Warm-blooded 
- animals feed largely on farinaceous or starchy substances, 
which in digestion are converted into sugar. But any ani- 
mal, of the higher orders certainly, whether herbivorous or 
carnivorous, would starve, if fed on pure albumen, oil, or 
sugar. Nature insists upon a mixed diet, and so we find 
in all the staple articles of food, as milk, meat, and bread, 
at least two of these principles present. As a rule, the 
nutritive principles in vegetables are less abundant than 
in animal food, and the indigestible residue is consequent- 
ly greater. The nutriment in flesh increases as we ascend 
the animal scale; thus, Oysters are less nourishing than 
Fish; Fish, less than Fowl; and Fowl, less than the flesh 
of Quadrupeds. 
