MUSCLES OF THE FOREARM AND DIGITS 



315 



The brachialis is well developed, and also ends on the radius and ulna. 



The tensor fasciae antibrachii resembles that of the horse. 



The long head of the triceps is divided into two parts, except at its distal end, 

 under which there i.s a synovial bursa. The external head is inserted into a crest 

 on the outer surface of the olecranon by a thin tendon, under which there is a 

 bursa. The internal head arises near the head of the 

 humerus, beneath the coracobrachialis. 



There are two anconei. 



MUSCLES OF THE FOREARM AND DIGITS 



The extensor carpi radialis is a strong, fleshy muscle, 

 the tendon of which is inserted into the proximal end of 

 the third metacarpal bone. It may be divided into two 

 parts (M. extensor carpi radialis longus, brevis). 



The extensor carpi obliquus is well developed; it ends 

 on the second metacarpal ])one. 



There are three (or four) digital extensors. 



1. The common or anterior digital extensor (M. ex- 

 tensor digitalis communis) arises on the extensor epicon- 

 dyle of the humerus and the lateral ligament of the elbow, 

 and divides into three parts. The tendon of the inner 

 part divides into two branches which end on the second 

 and third digits ; the tendon to the second digit is small 

 and often absent. The tendon of the middle part divides 

 lower down into two branches for the third and fourth 

 (chief ) digits ; above tiiis iDifurcation it detaches a small 

 branch to the second digit, which usually unites with the 

 tendon of the extensor indicis. The tendon of the deep 

 head divides into two branches, the inner one joining the 

 tendon of the middle head, while the outer one ends on 

 the fifth digit. 



2. The extensor of the second digit (]M. extensor 

 indicis proprius) is covered by the preceding muscle, 

 with which it is partially fused. It arises on the ulna. 

 Its delicate tendon usually unites Avith the tendon of the 

 middle head of the common extensor which goes to the 

 second digit. 



3. The lateral digital extensor (M. extensor digitalis 

 lateralis) consists of two distinct parts: (1) The large 

 dorsal (anterior) muscle (iM. extensor digiti quarti jiro- 

 prius) has a long tendon which ends on the fourth digit, 

 and often sends a slij:) to the fifth digit. (2) The small 

 volar (posterior) muscle (M. extensor digiti quinti pro- 

 prius) ends by a long tendon on the lateral aspect of the 

 fifth digit. 



The supinator has been found by Arloing and Lesljre, 

 but is usually absent in the pig. 



The pronator teres is a small muscle which lies on the 

 internal lateral ligament of the elbow. It arises from the internal epicondyle of 

 the humerus, and reaches about to the middle of the inner l^order of the radius. 



The flexor carpi internus is well developed. It arises on the flexor epicondyle 

 of the humerus, and is inserted into the third metacarpal bone. 



The flexor carpi medius is narrow and has no ulnar head. 



Fig. 227. — Muscles of Anti- 



BRACHIUM AXD ilAXUS 



OF Pig, Axtero-Ex- 



TERNAL View. 



a, a', Extensor carpi 

 radialis; b, extensor carpi 

 obliquus (s. ahiluctor poUicis 

 longus); c, d, e, common or 

 anterior digital extensor; c', 

 c", tendons of insertion of c; 

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

 tendons of e; /, tendon of 

 extensor indicis; (i, extensor 

 digiti quarti; li, extensor 

 digiti quinti; //, tendon of 

 h; i, tendinous, and k, fleshy 

 part of flexor carjji externus; 

 A', tendon of k; I, ulnar head of 

 deep fligital flexor; in, superfi- 

 cial digital flexor; n , brachialis. 

 (After F211enberger, in Leis- 

 ering's Atlas.) 



