364 



THE MUSCLES OF THE PIG 



digit. (2) The small volar muscle is the extensor digiti quinti proprius; it ends by 

 a long tendon on the lateral aspect of the fifth digit. 



The supinator, when present, is a pale, thin muscular slip which arises on the 



lateral border of the radius just- above the interosseous space, extends medially and 



' doAvnward across the dorsal surface of the bone to its medial 



border, where it blends with the radial head of the deep 



flexor. ■ . ■ - , 



The pronator teres is a delicate, fusiform muscle wbioh 

 lies along the medial surface of the elbow and proximal part 

 of the forearm. It arises from the medial epicondyle and 

 collateral ligament of the elbow and is inserted by a thin 

 tendon to the medial border of the radius about its middle. 

 The flexor carpi radialis is well developed. It arises 

 on the medial epicondyle of the humerus, and is inserted 

 into the third metacarpal bone. 



The flexor carpi ulnaris is narrow and has no ulnar 

 head. It runs obliquely down the back of the forearm in 

 the furrow between the superficial and deep flexors of the 

 digit. It arises from the medial epicx)ndyle of the hmnerus 

 and ends on the accessory carpal bone. 



The ulnaris lateralis (jM. extensor carpi' ulnaris) is 

 covered by a tendinous band, which is a thickened part 

 of the fascia of tlie forearm and extends from the lateral 

 epicondyle to the accessory carpal bone and lateral aspect 

 of the carpus. The belly of the muscle is round: its ten- 

 don of insertion perforates this band in the distal part of 

 the forearm and ends on the proximal end of the fifth 

 metacarpal bone. 



The superficial digital flexor arises from the medial 

 epicondyle of the humerus and, consists of two parts. The 

 tendon of the superficial head passes clown behind the pos- 

 terior annular ligament of the carpus (bound down by a 

 special annular ligament), forms a ring at the fetlock for a 

 tendon of the deep flexor, and ends by two branches on the 

 second phalanx of the fourth digit. It receives a small 

 band from the accessory carpal bone. The tendon of the 

 deep head, after detaching a strong branch to the tendon 

 of the tloop flexor, passes clown with the latter (for which 

 it forms a ring), and ends on the third digit. 



The deep digital flexor has three heads — humeral, 

 ulnar, and radial. The humeral head is very large and 

 forms the greater part of the contour of the volar face of 

 the forearm. It consists of two parts — a large superficial 

 part, and a much smaller deep part which arises with the 

 superficial flexor. Each ends at the distal part of the fore- 

 arm on a short tendon. These unite and receive the ten- 

 dons of the radial and ulnar heads and a branch from the 

 superficial flexor tendon. The ulnar head has a short, 

 thick, prismatic belly which arises from the medial surface of the proximal 

 part of the ulna. Its long, thin tendon passes down on the humeral head and 

 joins the tendon of the latter at the level of the accessory carpal bone. The 

 radial head is small. It arises from the upper part of the medial border of the 

 radius and from the deep fascia, and its tendon joins that of the humeral head at 

 the distal end of the forearm. The common tendon divides into four branches. 



Fig. 317. — Muscles of Axti- 



BRACHIU.\I AND MaXUS 



OF Pig; Dorso-lateral 



a, a', Extensor carpi 

 radialis: b, extensor carpi 

 obliquus (s. abductor pollicis 

 longns) ; r, '/, r, common dig- 

 ital extensor; c', c", tendons of 

 insertion of c; d' , d", tendons 

 of d; c', e", tendons of e; f, 

 tendon of extensor digiti se- 

 cundi; p, extensor digiti quarti; 

 h, extensor digiti quinti; h', 

 tendon of h; i, tendinous, and 

 h, fleshy, part of ulnaris later- 

 alis; k', tendon of k; J, ulnar 

 head of deep digital flexor; m, 

 superficial digital flexor; n, 

 brachialis. (After Ellenberger, 

 in Leisering's Atlas.) 



