The Principles of Breeding | Page 8

generally of a chronic
character.
Scrofula is not uncommon among sheep, and it presents itself in
various forms. Sometimes it is connected with consumption; sometimes
it affects the viscera of the abdomen, and particularly the mesenteric
glands in a manner similar to consumption in the lungs. The scrofulous
taint has been known to be so strong as to affect the foetus, and lambs
have occasionally been born with it, but much oftener they show it at
an early age, and any affected in this way are liable to fall an easy prey
to any ordinary or prevailing disease which develops in such with
unusual severity. Sheep are also liable to several diseases of the brain
and of the respiratory and digestive organs. Epilepsy, or "fits," and
rheumatism sometimes occur.
Swine are subject to nearly the same hereditary diseases as sheep.
Epilepsy is more common with them than with the latter, and they are

more liable to scrofula than any other domestic animals.
When properly and carefully managed, swine are not ordinarily very
liable to disease, but when, as too often kept in small, damp, filthy
styes, and obliged constantly to inhale noxious effluvia, and to eat
unsuitable food, we cannot wonder either that they become victims of
disease or transmit to their progeny a weak and sickly organization.
Swine are not naturally the dirty beasts which many suppose.
"Wallowing in the mire," so proverbial of them, is rather from a wish
for protection from insects and for coolness, than from any inherent
love of filth, and if well cared for they will be comparatively cleanly.
The practice of close breeding, which is probably carried to greater
extent with swine than with any other domestic animal, undoubtedly
contributes to their liability to hereditary diseases, and when those
possessing any such diseases are coupled, the ruin of the stock is easily
and quickly effected, for as already stated, they are propagated by
either parent, and always most certainly and in most aggravated form,
when occurring in both.
With regard to hereditary diseases, it is eminently true that "an ounce of
prevention is worth a pound of cure." As a general and almost
invariable rule, animals possessing either defects or a tendency to
disease should not be employed for breeding. If, however, for special
reasons it seems desirable to breed from one which has some slight
defect of symmetry, or a faint tendency to disease, although for the
latter it is doubtful if the possession of any good qualities can fully
compensate, it should be mated with one which excels in every respect
in which the other is deficient, and on no account with one which is
near of kin to it.
Notwithstanding the importance due to the subject of hereditary
diseases, it is also true that few diseases invariably owe their
development to hereditary causes. Even such as are usually hereditary
are sometimes produced accidentally, (as of course there must be a
beginning to everything,) and in such case, they may, or may not be,
transmitted to their progeny. As before shown, it is certain that they
sometimes are, which is sufficient reason to avoid such for breeding

purposes. It is also well known that, in the horse, for instance, certain
forms of limbs predispose to certain diseases, as bone spavin is most
commonly seen where there is a disproportion in the size of the limb
above and below the hock, and others might be named of similar
character; in all such cases the disease may be caused by an agency
which would be wholly inadequate in one of more perfect form, but
once existing, it is liable to be reproduced in the offspring--all tending
to show the great importance of giving due heed in selecting breeding
animals to all qualities, both external and internal, so long as "like
produces like."
FOOTNOTES:
[2] Finlay Dun, V.S., in Journal of the Royal Agricultural Society.
CHAPTER III.
THE LAW OF VARIATION.
We come now to consider another law, by which that of similarity is
greatly modified, to wit, the law of variation or divergence. All organic
beings, whether plants or animals, possess a certain flexibility or
pliancy of organization, rendering them capable of change to a greater
or less extent. When in a state of nature variations are comparatively
slow and infrequent, but when in a state of domestication they occur
much oftener and to a much greater extent. The greater variability in
the latter case is doubtless owing, in some measure, to our domestic
productions being reared under conditions of life not so uniform, and
different from, those to which the parent species was exposed in a state
of nature.
Flexibility of organization in connexion with climate, is seen in a
remarkable degree in Indian corn. The small Canada variety, growing
only three feet high