254 FAMILY MURID^; BLACK AND BROWN RATS. 



time the most numerous, of the Mammalia. As already men- 

 tioned, the animals composing it are distinguished by their long 

 round scaly tails, and by the presence of only three molars in 

 each jaw ; these are originally furnished with rounded tubercles, 

 but wear down into roughened disks. No undomesticated 

 animals are better known than mice and rats. Of the common 

 Mouse, Cuvier thus concisely speaks, " known in all times and 

 in all places." Of the Rats, two species are known in this 

 country, in which they have become completely naturalized, 

 though there is reason to believe that neither is an original inha- 

 bitant of it. The Black Rat is commonly termed the old English 

 Rat, having been known before the introduction of the other ; 

 but it appears not to have been known in England before the 

 middle of the 16th century, when it was introduced from France. 

 This is now becoming rather a rare animal in this country ; 

 having been nearly extirpated by the other species, for which, 

 on account of its inferior size and strength, it is an unequal 

 match. It is now chiefly found in the old houses of large cities, 

 such as London and Edinburgh ; and especially in the cellars and 

 stables of the former. The Brown species is commonly known 

 as the Norway rat ; but to this title it has no claim whatever, 

 since probably not a single individual had existed in that country 

 at the time it received the appellation. It is believed to have 

 originally come from Persia, where it lives in immense burrows ; 

 and is said to have first arrived on the European side of the 

 Volga after an earthquake in 1727- From that time it gradually 

 spread through Europe, and was introduced into England about 

 the middle of the last century. Its astonishing fecundity, its 

 omnivorous habits, the secrecy of its retreats, and the ingenious 

 devices to which it has recourse, either to retain its existing place 

 of abode, or to migrate to a more favourable situation, all con- 

 duce to keep up its overwhelming numbers. By its power of 

 adapting itself to a great variety of circumstances, in regard to 

 food, temperature, and habits, it has been enabled to spread 

 itself, by means of British vessels, to America, New Holland, 

 and almost every other part of the globe; and has already 

 become a source of inconvenience in many of these localities. 



