MAMMALS. 595 



ern Europe is far more celebrated. It lives in the far north, but at inter- 

 vals immense hordes, almost as innumerable as the sands of the sea, press 

 southward and westward from the mountains to the plains. These armies 

 follow a straight course: nothing can stop them; they swim the rivers and 

 lakes, and rush through the towns in their way, until at last they are 

 swallowed up in the sea. While on these migrations they suffer from foes 

 of every sort ; carnivorous quadrupeds of all sorts grow fat on the bounte- 

 ous supply, while hawks and owls, swooping down upon them, carry off 

 thousands. Still they press on, utterly oblivious of danger, and apparently 

 of the fate that awaits them. What is the cause of these migrations, 

 seemingly of so little advantage to the race, has not been satisfactorily 

 settled. The best explanation is that they have increased so in numbers 

 in their mountain strongholds that the region is overstocked, and the 

 surplus are forced by circumstances to emigrate, and to try to find a new 

 home elsewhere, an attempt which ends disastrously for the emigrants, but 

 relieves the over-crowded mountains. 



The rats and mice proper — those domestic pests which have followed 

 man all over the world — are too well known to call for extensive descrip- 

 tion, and yet there are some facts connected with them that may bear 

 repetition. First as to the rats. The original house-rat of Europe was 

 the black rat, and from time immemorial until a century ago it swarmed 

 everywhere. It was introduced into America about the middle of the 

 sixteenth century, and multiplied so rapidly that soon this country was 

 as well supplied as the Old World. A change was to occur. As central 

 Asia has been the starting-point for successive waves of man, one after 

 another overrunning Europe, so was it with the rats. From this region 

 the brown rat started. In 1737 it crossed the Volga in immense numbers, 

 overran all Russia, and rapidly spread over Europe. At about the begin- 

 ning of the Revolution it was brought by ships to our continent. This 

 newcomer was from the standpoint of rats a far better animal than the 

 black rat, and the result was that soon the latter had to give way before 

 his stronger rival. To-day the black rat is extremely rare, but everywhere 

 one finds the brown, or wharf rat, which also bears another name, — 

 Norway rat, — given under some misapprehension as to its origin. The 

 whole of this history presents a curious parallel with that of the human 

 population of Europe and America, not only in the place of origin, but in 

 the pre-eminence taken by the later invaders. The Teutonic has largely 

 supplanted the Hellenic-Latin wave. 



This brown rat is a formidable animal. It stands an easy first among 

 all the rodents from its courage, its voracity, and its ferocity. It will eat 

 almost anything, and it attacks and kills animals even larger than itself. 



