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THE MUSCLES OF THE OX 



IV. MUSCLES OF THE FOREARM 

 A. Extensor Division 

 • The extensor carpi radialis is like that of the horse. There is sometimes a 

 small muscle lying along its inner border, which may represent the extensores 

 pollicis. 



There are three digital extensors : 1. The common or anterior digital extensor 

 (M. extensor digitalis communis) arises by two heads from the extensor epicondyle 

 and the ulna. The heads fuse about the middle of the forearm, and terminate 

 soon on a tendon which passes over the carpus and metacarpus, gradually inclining 



Fig. 21.5. — Right Carpus of Ox with Burs.e and Fig. 216. — Right Carpus of Ox with Burs.e and 

 Synovial Sheaths Injected, External View. Synovial Sheaths Injected, Internal View. 



1, Extensor carpi radialis, with synovial sheath (!') and bursa (/"); S, extensor carpi obliquus, with synovial 

 sheath (2') and bursa {2") ; 3, extensor digiti tertii proprius; 4, extensor digitalis communis; S' , common synovial 

 sheath of 3 and 4, o, extensor digiti quarti proprius, with synovial sheath (5'); 6, 6' , flexor carpi externus, with 

 bursa (6f"); 7, flexor carpi internus, with synovial sheath; S, deep digital flexor, with synovial sheath (8'); 9, 

 flexor carpi medius; 10, superficial digital flexor, with synovial sheath 10'\ a, radius; b, carpus; c, metacarpus; 

 d, cut edge of annular ligament, (.\fter Schmidtchen.) 



forward. At the fetlock joint it divides into two l)ranches, which are inserted 

 into the third phalanges. 2. The internal digital extensor (M. extensor digiti 

 tertii proprius) arises on the extensor epicondyle, and is inserted by two branches 

 into the second and third phalanges of the inner digit. The tendon receives two 

 reinforcing slips from the suspensory ligament. 3. The lateral digital extensor 

 (M. extensor digitalis lateralis s. digiti quarti proprius) arises from the external 

 lateral ligament of the elbow joint, the external tuberosity of the radius, and the 

 ulna. The tendon terminates like that of the preceding nuiscle. 



The extensor carpi obliquus resembles that of the horse. 



The extensor tendons are bound down at the carpus by an annular ligament, 

 and are furnished with synovial sheaths (Figs. 215, 216). 



