ARTICULATIONS Ot THX ANTWKOE HMB8. 153 



fasciculi, is interposed between the synorthrodial surfaces, and binds them 

 tinnly together. Its ossification is not rare. The diarthrodial facets are 

 maintained in contact by the preceding ligament, and by the carpal ligaments 

 inserted into the head of the lateral mctacarpal bones. The intermetacarpal 

 articulations only allow a very obscure, vertical, gliding movement. 



In the Ox, there is only one intermetacarpal articulation, which is ranch simpler 

 tli in those in the Horse. 



In the Pig, the four metacarpal bones correspond, at tin ir ujip r extremity, by means 



"f small diarthrodial facets on their sides. Fibrous fasciculi, derived from the great 



anterior and posterior ligaments of the carpus, protect these intermetacarpnl articula- 



Ix-fore and behind. Other fibres, situuted between the adjacent faces of the 



i rpal Ixraes, are real interosseous ligaments. 



In the Dog and Cut, the four great metacarpal bones articulate with each other in 

 almost the same manner as in the Pig, but their mobility is greater. 



6. Metacarpo-phalangeal Articulation. 



(Preparation. Turn down the anterior and lateral extensor tendons of the phalanges, 

 after carefully cutting through their attachment with the capsular ligament. Lay open 

 the metacarpo-phalangeal sheath from above to below, and turn down the flexor 

 tendons.) 



This is a perfect hinge-joint, formed by the inferior extremity of the 

 median metacarpal bone on the one part, and the superior extremity of the 

 upper phalanx and sesamoids on the other. 



Articular surfaces. For the metacarpal bone, there are two lateral 

 condyles and a median antero-posterior eminence ; for the first phalanx, two 

 glenoid cavities and an intermediate groove prolonged posteriorly on tho 

 anterior face of the two sesamoids. Divided in this manner into three por- 

 tions, the digital surface is well constituted for solidity, because the pressure 

 transmitted to this region is diminished and diffused by the natural elasticity 

 of the bands which unite these three pieces to each other. 



Mode of union. The means of union may be divided into two categories : 



1, Those which join together the several bones of the inferior surface ; 



2, Those which maintain in contact the two opposed articular surfaces. 



A. Tho first have received the generic name of sesamoid ligaments, and 

 are six in number : an intersesamoid ligament, which keeps together the two 

 nunjilementary bones of the digital surface; three inferior and tico lateral 

 sesamoid ligaments, which unite these bones to the first phalanx. 



a. The intersesamoid ligament is composed of fibro-cartilaginous substance 

 which appears to bo the matrix in which the two sesamoids were developed, 

 as it is spread around these bones, after being solidly fixed on their internal 

 face. Behind, this ligament, in common with the posterior face of the sesa- 

 moids, forms the channel (Fig. 89, 5) in which tho flexor tendons glido. 

 In front, it occupies tho bottom of tho intersesamoid articular groove. 



b. The inferior sesamoid ligaments, situated at tho posterior face of tho 

 first phalanx, are distinguished as superficial, middle, and deep. 



The superficial ligament (Fig. 89, 8), tho longest of the three, is a narrow 

 band flattened before and behind. It arises from the middle of tho fibro- 

 cartilaginous mass which completes, posteriorly, tho superior articular 

 surface of the second phalanx, and slightly widening, ascends to tho base of 

 the sesamoids, into which it is inserted by becoming confounded with the 

 i 1 1 1 1 r scsamoi d li gamcn t. Its posterior face, lined by tho sy novial membrane of 

 the so-called sesamoid sheath, is covered by tho flexor tendons; it partly 

 covers the middle ligament. 



Tin- ////</<//. ligament, triangular and radiating, is composed of three 



