The true Democrat. [volume] (Bayou Sara [La.]) 1892-1928, 1912-08-17

I.
field Thomas, the eminent English
zOolOgist, includes in this family no
less. than Z genera, or almost half the.
total of 10 which he ascribes to he
whole order of Rodentia. He further
subdivides the Muridae into a dozen
subfamilies, of which the Murinae
and the Sigmodontinea are the most
extensive.
The Murinae comprise only Old
World rats and mice, while the
CriCetnae are, in the main, Amerl-
can forms. In the Murinae the cuSpS,
or tubercles, of the unWorn upper
moiars are arranged triserially, or in
three longitudinal rows; in the Crice-
tinae they are arranged biserially olc
row on the outer and one on the in
her margin. The wearing away of
these cusps leaves characteristic
curved lines of hard enamel sur
rounding areas of dentine. When
the cusps are in pairs the worn pat
tern looks somewhat like the Greek
letter sigma co. whence the name
sigmodont, often applied to native
American rats and mice.
The Murinae are the true rats and
mice, typified by the genus Mus,
which contains by far the largest
number of species. TrOuessart, in
his Catalogus Mammalium numerates
$50 species of Mus described before
1905. Since that date number OF
rev forms have been described.
The genus Mus is characterized by
narrow, ungrooved incisors; three
small, rooted molars; soft fur mixed
with hairs, sometimes with spineS; a
rudimentary pollex having a short
nail instead of a claw; "a long tai
bearing rings of overlapping scales
and often naked or nearly so. The
ears are rather large, the eyes
bright and prominent, and the muzz'e
somewhat pointed. The members OF
the genus are natives of the Old
World, throughout which, with the
exception of Madagascar, they are
quite generally distributed. Nearly
seven-eighths of the whole number of
species are commonly called rats.
The distinction between rats and
mice is arbitrary and based on size.
! Exclusive Of the tail, rats may be
said to vary in length from AZ to 10
inches or more, while mice measure
from to 4 inches. With few excep-
tons, rats have six well-defined foot
pads (plantar ;tubercles), the last on
the hind foot being elongated in
shape; the last hind foot pad of mice
is usually circular.
Of the many species of Mus only
three or four have developed the
ability to adapt themselves to such
d variety of conditions as Ito become
cosmopolitan. Four have found lodg-
ment in America: The common house
mouse (Mus musculus); the old Eng
| lish black rat, mus aleXandrinus) !;
and the brown rat Mus nOrvegicusj
lnown also as the gray rat, barn rat,
wharf rat, sewer rat, and Norway rat
| The black rat and the roof rat differ
from each other chiefly in color. In
deed some biologists regard them. as
races of the same species, and the
trDominal Mus rattus alexandrinuS
| for the roof rat is now in use among
biologists.
Distribution of the Genus Mus in
| America.
| The common house mouse on.
nusculus) found it's way to America
soon after the first settlement by
Europeans. 1t now inhabits all set,
tied parts of North and South Amer
Ca, as well as nearly the entire Old
World; but in very cold regions it
does not always survive the winters,
and is therefore comparatively scarce
or local. 1t almost always reaches a
new settlement sooner than the rat
The black rat ON. rattus) has been
known in Europe since the twelfth
century. 1t was carried to, South
and Middle America about three and
a half centuries ago 0554. The
time of its arrival in the English col
Onies of North America is not known
with certainty, but it was we'll estab
ll3hed in the settled parts by the
beginning of the eighteenth century
Soon after the arrival of the browr
rat, the black species began to de
crease in numbers, and has become
extinct in most localities. At pres
ent it is not uncommon in some part
CT the South, and still occurs I
scattered colonies in Canada AM
some of the states east of the Mis-
|