248 COMPARATIVE ARTHROLOGY 
langes. The other collateral ligaments are arranged like those of the horse. A strong 
interdigital ligament (Lig. interdigitale), consisting of short intercrossing fibers, 
unites the middles of the interdigital surfaces of the first phalanges of the chief digits. 
It prevents undue divergence of the phalanges. It is not present in the sheep. 
Cruciate ligaments (Lige. phalango-sesamoidez) connect the proximal sesamoids 
with the proximal end of the opposite first phalanx. 
The intersesamoid ligament connects all four sesamoids, and extends upward 
much less than in the horse. 
The laterate and medial sesamoidean ligaments end chiefly on the first phalanges, 
but also detach a small part to the large metacarpal bone. 
The superficial or straight distal sesamoidean ligament is absent. The middle 
distal sesamoidean ligaments of each digit are two short, strong bands which extend 
from the distal margins of the proximal sesamoids to the proximal ends of the first 
phalanges. The deep distal sesamoidean ligaments are strong and distinctly 
cruciate. 
The suspensory ligament or interosseus tendon contains more muscular 
tissue than in the horse—indeed, in the young animal it consists almost entirely of 
muscular tissue. At the distal third of the metacarpus it divides into three branches. 
These give rise to five subdivisions, either by bifurcation of the lateral and medial 
branches or trifurcation of the middle branch. The two lateral and two medial 
bands ena on the proximal sesamoid bones and the distal end of the large meta- 
‘arpal bone, and detach slips to the extensor tendons. The middle band passes 
through the groove between the two divisions of the distal end of the metacarpus, 
and divides into two branches which join the tendons of the proper extensors of the 
digits; it sends fibers also to the interdigital coliateral ligaments and to the central 
sesamoids. About the middle of the metacarpus the suspensory ligament detaches 
a band which unites lower down with the superficial flexor tendon, thus inclosing 
the tendon of the deep flexor of the digit; it also biends with the thick fascia of the 
region. The latter gives off a band on either side to the accessory digits, and a ten- 
dinous band descends from each accessory digit to the third phalanx and distal sesa- 
moid bone, blending with the tendon of the corresponding proper extensor. 
Pig.—There are four metacarpo-phalangeal joints, each of which has a capsule, 
collateral, intersesamoidean, and cruciate sesamoidean ligaments. Since distinct 
interosseous muscles are present, there are, of course, no suspensory ligaments. 
Dog.—There are five metacarpo-phalangeal joints, each having its own capsule 
and indistinct collateral ligaments. A small sesamoid bone occurs in the anterior 
part of each capsule, over which the corresponding extensor tendon plays. The 
intersesamoidean ligaments do not extend above the sesamoids. The cruciate 
ligaments are present, as well as a fibrous layer which attaches the distal margins 
of the sesamoids to the posterior surface of the proximal end of the first phalanx. 
INTERPHALANGEAL JOINTS 
Ox.—The two proximal joints have separate capsules, and broad, but rather 
indistinct, collateral ligaments. Each joint has also central and collateral volar 
ligaments. The central ligaments are largely fused to form a strong band which is 
attached by two branches to the distal end of the first phalanx and to the depression 
on the volar surface of the proximal end of the second phalanx. The collateral ones 
extend from the borders of the first phalanx to the proximal end of the second 
phalanx; those on the interdigital side are weak and indistinct. 
The distal interphalangeal joints have, in addition to the capsules and collateral 
ligaments, bands which reinforce them on either side. ‘The interdigital pair arise 
in the depressions on the distal ends of the first phalanges, receive fibers from the 
second phalanges, and end on the interdigital surfaces of the third phalanges at the 
