METACARPAL MUSCLES 



305 



B. Flexor Division 



The three flexors of the carpus are hke those of the horse. 



The superficial digital flexor is somewhat blended at its origin with the middle 

 flexor of the carpus. It divides into two bellies, superficial and deep, terminating 

 on tendons at the distal part of the forearm. The superficial tendon passes over 

 the posterior annular ligament (Ligamentum carpi transversum), perforates the 

 metacarpal fascia, and joins the deep tendon about the middle of the metacarpus. 

 The deep belly is connected with the deep flexor by a strong fibrous band. Its 

 tendon passes under the annular ligament in a groove on the deep flexor, from which 

 it receives fibers. The conjoined tendon soon bifurcates, each branch receiving a 

 reinforcing band from the suspensory ligament, and forming near the fetlock a 

 ring for the corresponding branch of the deep flexor tendon. Passing under two 

 digital annular ligaments, they are inserted into the volar surfaces of the second 

 phalanges by three slips. 



The deep digital flexor has the same heads as in the horse, the humeral head, 

 as before mentioned, being connected with the deep portion of the superficial flexor. 

 The tendon divides near the distal end of the metacarpus into 

 two branches which arc inserted into the volar surfaces of the c s 



third phalanges. 



The synovial sheaths at the carpus present the follow- 

 ing special features: One is found in connection with the 

 tendon of the superficial part of the superficial flexor of the 

 digits. There is a common sheath for the tendons of the 

 common extensor and the inner extensor. 



Bursse may occur under the tendons of the proper exten- 

 sors of the digits at the fetlock; they are constant only in old 

 animals (Schmidtchen). The branches of the tendon of the 

 common extensor are provided with synovial sheaths from 

 their origin to the middle of the second phalanx. There are 

 two digital synovial sheaths for the flexor tendons; they may 

 communicate at their upper part, and extend from the distal 

 third of the metacarpus nearly to the distal sesamoids. 

 Bursas occur l^etween the latter and the branches of the 

 deep flexor tendon. 



Fig. 217. — Cross-section 

 OF Distal Third 

 OF Metacarpus of 

 Ox. 



h. Tendon of exten- 

 sor digiti tertii; c, tendon 

 of common extensor; d, 

 tendon of extensor digiti 

 quarti; /t, interosseus medi- 

 us or suspensory ligament; 

 I, tendons of digital flexors; 

 i' , branch of h; 12, meta- 

 carpal bone. (After EUen- 

 berger-Baum, Anat. fiir 

 Kunstler.) 



METACARPAL MUSCLES 



The lumbricales are absent, unless we regard as such 

 the muscular bundles which arise on the deep flexor and are 

 inserted into the superficial flexor tendon at the carpus. 



The interosseus medius or suspensory ligament is somewhat more muscular 

 than in the horse; indeed, in the young subject it may be almost entirely fleshy. 

 Its arrangement is somewhat complex. Single at its origin, it detaches about the 

 middle of the metacarpus a band which joins the tendon of the superficial flexor 

 and concurs near the fetlock in the formation of the ring for the deep flexor tendon. 

 A little lower down it divides into three and then into five branches. The lateral 

 branches (two pairs) are attached to the corresponding sesamoids and tendons of 

 the proper extensors, while the middle branch passes through the sulcus at the distal 

 end of the metacarpus and bifurcates, each division fusing with the tendon of the 

 corresponding proper extensor. 



It is to be noted that the fascia on the posterior face of the metacarpus and 



digit is very thick. It is continuous above with the ligamentum carpi transversum, 



and is attached on either side to the metacarpal bone. At the fetlock it forms the 



fibrous basis for the small claws, and below this it detaches two strong bands which 



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