THE LIFE OF MAMMALS 
bellied variety of it, native to Egypt and the Mediterranean shores, known 
as the Alexandrine rat, or ‘‘roof rat,’ which has never appeared north of 
the Carolinas. Baird thought it probable that the early Spanish discov- 
erers and conquerors carried this variety to America in their vessels, and 
thus introduced it on the continent long before the brown or even the black 
rat. An odd result of this ancient importation was that an idea got abroad, 
and into early books, that these black rats were indigenous American ani- 
mals which had emigrated to Europe. In America, as elsewhere, the big 
brown rat has beaten its earlier but weaker brethren in the competition for 
livelihood, and the latter has become scarce or has taken to the woods. 
This strong brown-coated invader succeeds by its adaptabil- 
ity to all climates and foods, its enormous fecundity, its quick- 
witted intelligence, and its willingness and ability to fight for 
whatever it wants to get or to keep. Its usefulness as a scaven- 
ger is a small offset to the vast evil it does as an agent of infec- 
tious diseases. To the rats of the East is largely due, for 
example, the epidemic spread of the bubonic plague, whose 
germs are carried in the filth frequently attached to their 
feet and fur. When this pest began to appear in Korea and 
Japan in 1903-1904, the Japanese authorities, who were about 
to put great armies into the field, and were preparing to pre- 
vent their decimation by camp diseases, caused the collection 
of all the rats the people could be hired to kill. Each corpse 
was examined for bubonic microbes, and when these were 
found it was destroyed. The result, aided by other means, 
was the extirpation of the plague in that part of the world; 
and the clean skins furnished ear tippets for every soldier 
campaigning in Manchuria. 
The true mice of this group are numerous throughout the 
world, and show many local peculiarities. One of the small- 
est and prettiest is the diminutive harvest mouse, 
weighing only a sixth of an ounce, and familiar in 
English grainfields, where its ball-like nest of woven grass 
blades is suspended near the tops of the stalks. It is often 
carried home with the harvest and remains in the barn or stacks 
430 
Mice. 
