154 THE ARTICULATIONS. 



particular fasciculi : two lateral (seen on each side of the superficial liga- 

 ment in Fig. 89, 8), and a median which has been generally confounded 

 with the superficial ligament, although it is clearly distinguished from it 

 by its inferior insertion. Fixed in common to the posterior imprints of the 

 first phalanx, these three fasciculi diverge in ascending to the base of the 

 sesamoids, where they have their upper insertion. 



The deep ligament is constituted by two small bands concealed beneath 

 the middle ligament. Thin, short, flattened before and behind, and inter- 

 crossed, these bands are fixed to the base of the sesamoids in one direction, 

 and in the other to the superior extremity of the first phalanx, near the 

 margin of its articular surface. This ligament is lined on its anterior face 

 by the synovial membrane of the articulation. 1 



c. The lateral sesamoid ligaments are two thin layers extending from the 

 external face of each sesamoid to the tubercle of insertion on the side of 

 the superior extremity of the first phalanx. They are covered by the digital 

 vessels and nerves, by the fibrous stay detached from the suspensory liga- 

 ment to the anterior extensor tendon of the phalanges, and by the superficial 

 fasciculus of the lateral metacarpo-phalangeal ligament ; they are covered by 

 synovial membrane on their internal face. 



B. The ligaments destined to unite the two articular surfaces of the meta- 

 carpo-phalangeal joint are four : two lateral, one anterior, and one posterior. 



a. Each lateral ligament comprises two fasciculi, a superficial and a 

 deep, firmly united by their adjacent faces. The superficial fasciculus 

 commences on the button of the lateral metacarpal bone, attaches itself to 

 the median metacarpal, and descends vertically to terminate at the superior 

 extremity of the first phalanx. It covers the phalangeal insertion of the 

 lateral sesamoid ligament and the deep fasciculus. The latter, attached 

 superiorly in the lateral excavation of the inferior extremity of the principal 

 metacarpal, radiates as it reaches the sesamoid and the superior extremity 

 of the first phalanx, where it is fixed by mixing its fibres with those of the 

 lateral sesamoid ligament. The inner face of this fasciculus is lined by the 

 articular synovial membrane. 



b. The anterior ligament belongs to the class of capsular ligaments. It 

 is a very resisting membraniform expansion which envelops the anterior face 

 of the articulation. Attached by its upper border to the anterior margin of 

 the metacarpal surface, and by its inferior border to the first phalanx, this 

 expansion is confounded at its sides with the lateral ligaments. It is covered 

 by the extensor tendons of the phalanges, which glide on its surface by means 

 of small serous sacs. Its internal face adheres throughout its whole extent 

 to the synovial capsule. 



c. The posterior ligament, 2 very appropiately named the suspensory ligament 

 of the fetlock (Figs. 88 , 89, 4), is a long and powerful brace, composed of white 

 fibrous tissue, and often containing fasciculi of fleshy fibres in its texture. 

 Lodged behind the median metacarpal, and between the two lateral meta- 

 carpal bones, this brace is quite thin at its origin, but it soon becomes 

 enlarged, and preserves its great thickness to the extent of its upper fourth. 

 Examined in section, it appears to be formed of two superposed portions which 

 are closely adherent to each other. The superficial portion, the thinnest, 

 commences by three small branches, which are fixed to the first and second 



1 The two bands described by Rigot as forming part of this ligament, belong to the 

 lateral fasciculi of the middle ligament. 



2 It corresponds to the two muscles which, in MAN, lie alongside the interosseous 

 metacarpal muscles. See the Muscles of the foot. 



