248 COMPARATIVE ARTHROLOGY 



langes. The other collateral ligaments are arranged lilve 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 (Ligg. phalango-sesamoideae) 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 hgaments 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 end on the proximal sesamoid bones and the distal end, of the large meta- 

 carpal 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 j oin the tendons of the projjer extensors of the 

 digits ; it sends fibers also to the interdigital collateral 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 blends 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 metacariDo-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 



