extent or
location. It is a misnomer, in a sense, and the veterinarian is
frequently obliged to spend considerable time with his clients in order
to convince them that a spherodial exostosis of the proximal phalanx, in
certain cases, is in reality "ringbone," even though there exists no
exostosis which completely encircles the affected bone.

Etiology and Occurrence.--Exostosis of the first and second phalanges
is usually due to some form of injury, whether it be a contusion, a
lacerated wound which damages the periosteum, or periostititis and
osteitis incited by concussions of locomotion, or ligamentous strain.
Practically the only exception is in the rachitic form of ringbone which
affects young animals.

There are predisposing causes that merit consideration, chief among
which is the normal conformation of the coronet joint. This proclivity
is constant; the normal interphalangeal articulation is an incomplete
ginglymoid joint and while its dorso-volar diameter is great, this in no
wise compensates for its disproportionately narrow transverse diameter.
The pivotal strain which is sometimes thrown upon this articulation when
an animal turns on one foot, as well as the tension which is put on the
collateral ligaments when the inner or the outer quarter of the foot
rests in a depression of the road surface, tends to detach the insertion
of these ligaments or to cause fibrillary fractures of their substance.

Short, upright, pasterns receive greater concussion during fast travel
on hard roads than do the longer more sloping and well formed
extremities. Those who are advocates of the theory that this type of
osteitis with its complications has its origin in the articular portion
of the joint, claim that the upright pastern constitutes an important
tendency toward ringbone. Howbeit, ringbone is an active, serious and
frequent cause of lameness and it affects animals of all ages and occurs
under various conditions. Horses having good conformation and kept at
work wherein no great amount of strain is put upon these parts, are
occasionally victims of this affection.

Classification.--The arrangement employed by Moller[21] is intensely
practical and logical. He considers ringbone as _articular_,
_periarticular_, _rachitic_ and _traumatic_. A mode of classification
that is common and in a practical way, good, is, high and low ringbone.
When prognosis is considered, for instance, it is very convenient to
state that the chanc