268 



FASCI.E AND MUSCLES OF THE HORSE 



three inches (ca. 5 to 8 cm.) above the carpus and extends almost to the insertion 

 of the tendon. 



Relations. — Superficially, the skin and fascia, the posterior superficial pectoral 

 and the tensor fasciae antibrachii; deeply, the elbow joint, the radius, the deep 



flexor, the flexor carpi medius, the posterior radial 

 vessels, and the median nerve. At the elbow the artery 

 and nerve lie in front of the muscle, but below they 

 dip beneath it. 



Blood-supply. — Posterior radial artery. 

 Nerve-s upply. — Med i an nerve . 



On removing thedeop fascia on the inner surface of the elbow 

 the student may notice a small muscle lying along the lateral liga- 

 ment. This is the pronator teres, which is usually not present or 

 a mere vestige in the horse. It arises by a small, flat tendon from 

 the flexor epicondyle of the humerus, and is inserted into the in- 

 ternal lateral ligament of the elbow. On account of its small size 

 and the fact that the forearm is fixed in the position of pronation, 

 the muscle can have no appreciable function. It is usually repre- 

 sented by the long portion of the internal lateral hgament. 



2. Flexor carpi medius (M. flexor carpi ulnaris s. 

 ulnaris medialis; oblique or middle flexor of the meta- 

 carpus). — This muscle lies on the inner and posterior 

 aspect of the forearm partly under, partly behind, the 

 preceding muscle. It arises by two heads — humeral 

 and ulnar. 



Origin. — (1) The flexor (internal) epicondyle of 

 the humerus just behind the preceding muscle; 

 (2) the inner surface and posterior border of the 

 olecranon. 



Insertion. — The upper edge of the accessory carpal 

 (pisiform) ])one. 



Action. — To flex the carpal joint, and to extend the 

 elbow. 



Structure. — The humeral head is much the larger, 

 constituting, in fact, the bulk of the muscle. It is 

 flattened, curved, and tapers at both ends. The 

 ulnar head, much smaller and very thin, is covered 

 by an aponeurosis from which many of its fibers 

 arise. It joins the large head a little above the 

 middle of the forearm. The tendon of insertion is 

 short and strong; it blends with the posterior annular 

 ligament of the carpus. 



Relations. — Superficially, the tensor fascise anti- 

 brachii, superficial pectoral, and flexor carpi internus, 

 the skin and fascia, and cutaneous branches of the ulnar 

 nerve; deeply, the superficial and deep flexors of the 

 digit. In the distal half of the forearm the ulnar vessels 

 and nerve lie between the outer edge of this muscle and 

 the external flexor of the carpus. 



Blood-supply. — Ulnar and posterior radial arteries. 



Nerve-supply. — Ulnar and median nerves. 

 3. Flexor carpi extemus (M. extensor carpi ulnaris^ s. ulnaris lateralis; 

 external flexor of the metacarpus). — This muscle lies on the outer face of the 

 forearm, behind the lateral extensor of the digit. 



1 In man the muscle is an extensor of the hand. 



Fig. 193. — Deeper Muscles of 

 FoRE.\.RM OF Horse, In- 

 TERN.\L View. 

 23, Internal head of triceps; 

 SO, flexor carpi mediu.s; 31, flexor 

 carpi internus; 31', tendon of 31; 

 32, superficial digital flexor; 32', 

 radial check ligament; 32" , tendon 

 of superficial flexor; 33a, 33b, 33c, 

 humeral heads of deep flexor; 33' , 

 deep flexor tendon; 33", subcarpal 

 check ligament; 34, ulnar head of 

 deep flexor; 35, radial head of deep 

 flexor; 36, suspensory ligament. 

 (After EUenberger, in Leisering's 

 Atlas.) 



