i.e.
brothers and sisters; while others include in it breeding from parents
and offspring, and others still employ the term to embrace those of
more distant relationship. For the latter, the term breeding in, or
close breeding, is deemed more fitting.

The prevalent opinion is decidedly against the practice of breeding
from any near relationships; it being usually found that degeneracy
follows, and often to a serious degree; but it is not proved that
this degeneracy, although very common and even usual, is yet a
necessary consequence. That ill effects follow in a majority of cases
is not to be doubted, but this is easily and sufficiently accounted
for upon other grounds. In a state of nature animals of near
affinities interbreed without injurious results, and it is found by
experience that where domesticated animals are of a pure race, or of a
distinct, well defined and pure breed, the coupling of those of near
affinities is not so often followed by injurious effects as when they
are crosses, or of mixed or mongrel origin, like the great majority of
the cattle in the country at large. In the latter case breeding
in-and-in is _usually_ found to result in decided and rapid
deterioration. We should consider also that few animals in a state of
domestication are wholly free from hereditary defects and diseases,
and that these are propagated all the more readily and surely when
possessed by both parents, and that those nearly related are more
likely than others, to possess similar qualities and tendencies.

If such is to be regarded as the true explanation, it follows that the
same method would be also efficacious in perpetuating and confirming
good qualities. Such is the fact; and it is well known that nearly all
who have achieved eminence as breeders, have availed themselves
freely of its benefits. Bakewell, the Messrs. Colling, Mr. Mason, Mr.
Bates and others, all practiced it. Mr. Bates' rule was, "breed
in-and-in from a bad stock and you cause ruin and devastation, they
must always be changing to keep even moderately in caste; but _if a
good stock_ be selected, you may breed in-and-in as much as you
please."[20] Bakewell originated his famous sheep by crossing from the
best he could gather from far or near; but when he had obtained such
as suited him, he bred exclusively from within his own. As in all
breeding from crosses, it was needful to throw out as weeds, a large
proportion of the progeny, but by rigidly doing so