in amount and quality to enable
animals to develop all the excellencies inherent in them, and to
obtain all the profit to be derived from them, is something very
distinct from undue forcing or pampering. This process may produce
wonderful animals to look at, but neither useful nor profitable ones,
and there is danger of thus producing a most undesirable variation,
for, as in plants, we find that forcing, pampering, high culture or
whatever else it may be called, may be carried so far as to result in
the production of double flowers, (an unnatural development,) and
these accompanied with greater or less inability to perfect seed, so
in animals, the same process may be carried far enough to produce
sterility. Instances are not wanting, and particularly among the more
recent improved Short-horns, of impotency among the males and of
barrenness in the females, and in some cases where they have borne
calves they have failed to secrete milk for their nourishment.[3]
Impotency in bulls of various breeds has not unfrequently occurred
from too high feeding, and especially if connected _with lack of
sufficient exercise_.[4]

_Habit_ has a decided influence towards inducing variation. As the
blacksmith's right arm becomes more muscular from the habit of
exercise induced by his vocation, so we find in domestic animals that
use, or the demand created by habit, is met by a development or change
in the organization adapted to the requirement. For instance, with
cows in a state of nature or where required only to suckle their
young, the supply of milk is barely fitted to the requirement. If more
is desired, and if the milk be drawn completely and regularly, the
yield is increased and continued longer. By keeping up the demand
there is induced in the next generation a greater development of the
secreting organs, and more milk is given. By continuing the practice,
by furnishing the needful conditions of suitable food, &c., and by
selecting in each generation those animals showing the greatest
tendency towards milk, a breed specially adapted for the dairy may be
established. It is just by this mode that the Ayrshires have, in the
past eighty or a hundred years, been brought to be what they are, a
breed giving more good milk upon a given quantity of food than any
other.

It is because the English breeders of modern Short-horns altogether
prefer beef-making to milk-giving properties that they have
constantly fostered variation in favor of