_Bos moschatus_, the musk ox.
_Bos frontalis_, the gayal.
_Bos grunniens_, the grunting ox.
_Bos caffer_, the South African buffalo.
_Bos bubalus_, the common buffalo.
_Bos taurus_, the common domestic ox.

GESTATION.

The usual period of pregnancy in a cow is nine calendar months, and
something over: at times as much as three weeks. With one thousand and
thirty one cows, whose gestations were carefully observed in France, the
average period was about two hundred and eighty-five days.

FORMATION OF TEETH.

It is of the utmost importance to be able to judge of the age of a cow.
Few farmers wish to purchase a cow for the dairy after she has passed
her prime, which will ordinarily be at the age of nine or ten years,
varying, of course, according to care, feeding, &c., in the earlier part
of her life.

The common method of forming an estimate of the age of cattle is by an
examination of the horn. At three years old, as a general rule, the
horns are perfectly smooth; after this, a ring appears near the nob, and
annually afterward a new one is formed, so that, by adding two years to
the first ring, the age is calculated. This is a very uncertain mode of
judging. The rings are distinct only in the cow; and it is well known
that if a heifer goes to bull when she is two years old, or a little
before or after that time, a change takes place in the horn and the
first ring appears; so that a real three-year-old would carry the mark
of a four-year-old.

[Illustration: TEETH AT BIRTH.]

The rings on the horns of a bull are either not seen until five, or they
cannot be traced at all; while in the ox they do not appear till he is
five years old, and then are often very indistinct. In addition to this,
it is by no means an uncommon practice to file the horns, so as to make
them smooth, and to give the animal the appearance of being much younger
than it really is. This is, therefore, an exceedingly fallacious guide,
and cannot be relied upon by any one with the degree of confidence
desired.

[Illustration: SECOND WEEK.]

The surest indication of the age in cattle, as in the horse, is given by
the teeth.

The calf, at birth, will usually have two incisor or front teeth--in
some cases just appearing through the gums; in others, fully set,
varying as the cow falls short of, or exceeds, her regular time of
calving. If she overruns several days, the teeth will have set and
attained considera