Both species are extremely prolific, breeding at a very early age, several times in a year, and producing from 10 to 14 at a birth. excessive increase of their numbers, where abundant food is to be found, and there are few enemies to interfere with them, is thus easily accounted for. They sometimes multiply amazingly in ships; and perhaps nowhere more than in the sewers of towns. But in the latter situation, they really ren der good service to the promotion of public health, acting as scavengers, and devouring animal and vegetable substances, the putrefaction of which would otherwise be produc tive of pestilence. Such, indeed, seems to be the great use of the rat in the economy of nature; and it is perhaps worthy of notice, that the visits of the plague to western Europe and to Britain have ceased from the very time when rats became plentiful. The brown rat, inhabiting sewers, is generally larger, fiercer, and of coarser appearance than the same species in houses or barns. Rats are also often found inhabiting burrows in dry banks, near rivers, etc. They feed indiscriminately on almost any kind of animal or vegetable food; they make depredations in fields of grain and pulse, from which they often curry off large quantities to be stored in their holes; they devour eggs; they kill poultry, partridges, etc. ; they make most unwelcome visits to dairies and store-closets;
and they multiply enormously in the vicinity of slaughter-houses and knackers' yards, which afford them great supplies of food. Their strong rodent teeth enable them to gnaw very hard substances, such as wood and ivory, either for food, or in order to make their way to more tempting, viands.
They are creatures of no little intelligence. Many curious stories are told of the arts which they employ to attain desire.' objects, of the readiness with which they detect the approach of danger, and the skill with which they avoid it. Their sense of smell is very acute, and the professional rat-catcher is very careful that the smell of his hands shall not be perceived on the trap. They are very capable of being tamed, and have m some instances proved interesting pets.
The flesh of rats is eaten, but only by rude tribes, or when food is scarce. The skin is used for making a fine kind of glove-leather.
The name rat is often popularly given, not only to species nearly allied to these, but to other species of muridcr, now ranked in different genera, some of which are noticed in other articles.