ARTICULATIONS Of THE ANTERIOR LIMBS. 153 



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

 firmly 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 metacarpal bones. The intermetacarpal 

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



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

 than those in the Horse. 



In the Pig, the four metacarpal bones correspond, at their upper extremity, by means 

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

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

 tions before and behind. Other fibres, situated between the adjacent faces of the 

 metacarpal bones, are real interosseous ligaments. 



In the Dog and Cat, 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. Turndown the anterior and lateral extensor tendons of the phalanges, 

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

 the metacarpo-phalangeal shtath 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 the 

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

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

 complementary bones of the digital surface ; three inferior and two lateral 

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



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

 which appears to be 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 the flexor tendons glide. 

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



6. The inferior sesamoid ligaments, situated at the posterior face of the 

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



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

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

 cartilaginous mass which completes, posteriorly, the superior articular 

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

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

 intersesamoid ligament. Its posterior face, lined by the synovial membrane of 

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

 covers the middle ligament. 



The middle ligament, triangular and radiating, is composed of three 



