322 



THE MUSCLES OF THE DOG 



The teres major is thick. It arises on the upper part of the posterior bordei 

 of the scapula and on the subscapularis. 



The coraco-brachialis is short and undivided, and is inserted into the upper 

 part of the postero-internal surface of the humerus. 



The capsularis is absent. 



The biceps brachii lies almost entirely on the inner 

 surface of the humerus. It is long and fusiform. The 

 tendon of origin is round, and passes through the cap- 

 sule of the shoulder joint. The tendon of insertion is 

 bifid, one branch being attached to the ulnar, the other 

 to the radial tuberosity. 



The brachialis is very little curved, and is inserted 

 chiefly into the tuberosity and inner border of the ulna. 



The tensor fasciae antibrachii is thin and narrow. 

 It arises on the outer surface of the latissimus dorsi, 

 and ends on the olecranon and the fascia of the forearm. 



The triceps has an additional deep head (Caput 

 accessorium), which arises just below the head of the 

 humerus. 



The brachio-radialis is a long, narrow, delicate 

 muscle, situated superficially on the anterior surface of 

 the forearm. It arises with the extensor carpi on the 

 crest above the extensor epicondyle of the humerus, 

 and is inserted into the distal part of the inner border 

 of the radius. It is often much reduced, and is some- 

 times absent. It rotates the forearm and paw out- 

 ward. 



The extensor carpi divides into two parts. The 

 larger outer part, the extensor carpi radialis brevis, ends 

 on the proximal end of the third metacarpal })one. 

 The inner and more superficial part, the extensor 

 carpi radialis longus, ends on the second metacarpal 

 bone. (A tendon to the fourth metacarpal may occur.) 



The extensor carpi obliquus or abductor pollicis 

 longus arises from the outer border and anterior 

 surface of the ulna, the interosseous ligament, and 

 the outer border of the radius. It is inserted into 

 the first metacarpal bone by a tendon which contains 

 a small (sesamoid?) bone. It abducts the first digit. 



There are three (or four) extensors of the digits. 



1. The common digital extensor (M. extensor digi- 

 talis communis) arises on the extensor epicondyle of 

 the humerus and the lateral ligament of the elbow 

 joint. It has four bellies, each terminating in a tendon. 

 These are inserted into the third phalanges of the 

 second, third, fourth, and fifth digits. 



2. The extensor of the first and second digits 

 M. extensor ])ollicis longus et extensor indicis j)ro- 

 prius) is small, and is covered by the common and 



lateral extensors. It arises on the proximal part of the ulna. Its tendon passes 

 down with that of the common extensor and divides into two branches. The 

 delicate inner branch ends on the first digit, while the other lilends with the tendon 

 of the common extensor for the second digit. 



3. The lateral digital extensor (M. extensor digitalis lateralis) consists of two 



Fig. 233. — Muscles of Antibra- 



CHIUM AND MaNUS OF DoG, 



External View. 



a. Triceps brachii; b, brachi- 

 alis; c, extensor carpi radiaUs; </, 

 common or anterior digital e.xten- 

 sor; d', d" , d'", d"" , tendons of 

 preceding; e, lateral digital exten- 

 sor; e', /, tendons of preceding; g, 

 extensor carpi ulnaris; h, h' , flexor 

 carpi ulnaris; i, extensor carpi ob- 

 liquus (s. abductor pollicis longus) ; 

 k, interossei; /, branches from pre- 

 ceding to extensor tendons; 1 , ole- 

 cranon; 3, radius; 3, extensor epi- 

 condyle of humerus. (After Ellen- 

 berger, in Leisering's Atlas.) 



