on holds some amount of truth is borne out
by the fact that, since a greater attention has been paid to the selection
of our cart animals, side-bone has grown a great deal less common.

Is side-bone hereditary? We can best answer that by saying that, some
several years ago, the Council of the Royal College of Veterinary Surgeons,
at the request of the Royal Commission on Horse Breeding, drew up a list of
those diseases 'which by heredity rendered stallions so affected unfit as
breeding sires,' and that in that list was included side-bone.

Side-bones, therefore, are hereditary. We think, however, the statement
needs qualifying. It is in this way: side-bones occur only at a certain,
usually well-defined, time after birth, and we might say are _never_
congenital. They occur only after the animal has been put to work, and are
more or less plainly due to mechanical causes--namely, the ill effects of
shoeing and concussion. The cause of their appearance, in short, is more
plainly extrinsic than intrinsic, and side-bone in the horse is, as
Professor McCall puts it, about as much due to heredity as is corn on the
human foot.

Between these two opinions--that they are plainly hereditary, and that they
just as plainly are not--it is well to strike a middle course. They are, we
will say, hereditary in this way: So long as a cart animal is bred, to put
it vulgarly, 'top-heavy' (that is, with a body out of reasonable proportion
to the feet that have it to support), so long will the foot be subjected to
a greater concussion, and so long will side-bones in such animals commence
to make their appearance at about middle life.

In addition to the causes we have now mentioned, side-bones are often
the result of other diseases of the foot. They thus occur as a sequel to
sub-horny quittor, to suppurating corn, to complicated quarter sand-crack,
or to the inflammation of the parts occasioned by a prick. They also arise
in many instances from the effect of a prick or injury to the coronet.
Among the latter we may mention treads from other animals, and treads
inflicted by the animal himself with the calkin of an opposite shoe, or the
repeated injury occasioned by the shafts being carelessly allowed to drop
on to the foot. In severe cases of laminitis, too, the cartilages are
nearly always affected. In this instance the inflammatory phenomena in the
os pedis no doubt give rise to an abnormal activity of bone-forming cells.
The cartilage is i