332 THE MUSCLES. 



attached to the epitrochlea — the external and oblique flexors of the metacarpus. 

 It responds, anteriorly, with the radius and radial portion of the muscle ; pos- 

 teriorly, with the perforatus ; externally, with the external flexor of the meta- 

 carpus ; inwardly, with the internal and oblique flexors of the same ray. 



The ulnar portion, covered by the antibrachial aponeurosis, covers the epi- 

 trochlean portion. 



The radial division is comprised between the latter and the posterior face of 

 the radius. 



The tendon is in contact, posteriorly, with that of the perforatus ; anteriorly, 

 with the posterior ligament of the carpus, the suspensory ligament of the fetlock, 

 and the sesamoid groove ; by its sides, with the vessels and nerves of the digit. 

 Its terminal expansion is covered by the plantar cushion, which adheres to it, in 

 front, in the most intimate manner ; it covers the navicular bone. 



Actions. — This muscle flexes the phalanges on one another and on the meta- 

 carpus. It also concurs in the flexion of the entire foot on the forearm. The 

 band which attaches its tendon behind the carpus, as well as its phalangeal rein- 

 forcing sheath, gives it the mechanical power necessary to support the angle of 

 the metacarpo-phalangeal articulation and the digital region, while the animal is 

 in a standing posture. 



(In the " Deep Flexor," of Chauveau's description, we find included two 

 portions which are separately named and described by Percivall and Gurlt. 

 These are the ulnaris accessorius and radialis accessorius of the former, and the 

 cubito-ulnar and radial branches of the latter. These, in reality, are portions 

 of the perforans, and have been so designated in this treatise. Though arising 

 independently, they terminate in the perforans tendon before it leaves the carpal 

 sheath, and join with it in flexing the metacarpus and phalanges.) 



Differential Characters in the Muscles of the Forearm in the other Animals. 



A. Ruminants. — In the Ox, Sheep, and Camel, the anterior extensor of the. metacarpus 

 comports itself as in Solipeds. 



The oblique extensor of the same region, terminates inside the upper extremity of the prin- 

 cipal metacarpus. 



The anterior extensor of the phalanges offers a remarkable arrangement. It is divided 

 throughout its length into two parallel portions: an external, which forms the common extensor 

 of the digits; and an internal, the proper extensor of the internal digit. 



a. The fleshy body of the common extensor (Fig- 185, 3) is a little more voluminous than 

 that of the second muscle. Its tendon (8') commences near the inferior third of the radius, 

 passes over the knee, the metacarpal bone, and the metacarpo-phalangeal articulation. On 

 arriving at the origin of the digits it bifurcates, and each of its branches goes to be inserted 

 into the pyramidal process of tlie third phalanx (3"). This muscle, in extending the digits, brings 

 them together, as Lecoq has judiciously remarked. 



h. The proper extensor of the internal digit (Fig. 185, 4) much resembles the common 

 extensor in volume, form, and direction. Its tendon (4') passes, with that terminating the 

 latter muscle, into one of the inferior grooves of the radius and over the capsular ligament of 

 the carpus, where the two cords are enveloped by a common synovial slieatli. Arrived at the 

 metacarpo-phalaJigeal articulation, this tendon is placed at the eccentric side of the internal 

 digit, and descends, graduilly expanding, until it reaches the inferior extremity of this bone; 

 towards the middle of the first phalanx, it receives from the suspensory ligament of the fetlock 

 two oonstraiiiing bands similar to those which, in Solipeds, bind the anterior extensor of the 

 phalanges on the same bone. This tendon bifurcates inferiorly ; one of its branches is attached 

 to the anterior face of the second plialanx ; tiie otiier. much wider than the first, covers the 

 common external lateral ligament of the two inter-phalangeal articulations, and terminates on 

 the whole external side of the third plialanx. In the Sheep, this second branch is slender, and 

 is directed towards the heel, which it envelops by uniting its fibres with the perforans tendon 

 and the plantar cushion. 



