INTERNAL GROUP 



257 



spinous fossa; (2) a small part of the posterior border of the scapula, about its 

 middle; (3) a tubercle near the rim of the glenoid artery. 



Insertion. — The deltoid tuberosity and a small area just above it. 



Action. — To flex the 

 shoulder joint and to ab- 'rfjfliitMii 



duct the arm ; also to assist ^Kwff^fcfc^-^- 



in outward rotation. 



Structure. — The muscle 

 is not rounded in the horse 

 and ox, but flat and triangu- 

 lar. Its origin from the pos- 

 terior border of the scapula 

 is by means of an aponeu- 

 rosis which also gives origin 

 to fibers of the infraspinatus 

 and triceps. A bursa is 

 commonly found between 

 the terminal part of the 

 muscle and the capsule of 

 the shoulder joint, and is 

 often continuous with that 

 of the infraspinatus. 



Relations. — Superfici- 

 ally, the deltoid and infra- 

 spinatus muscles ; deeply, 

 the scapula, the shoulder 

 joint, and the triceps mus- 

 cle. 



Blood-supply. — Sub- 

 scapular artery (circumflex 

 branches) . 



Nerve-supply. — Axil- 

 lary nerve. 



Coraco-bracfuali 

 Biceps brae III I 



BuidtKilis 



Extensor (<n pi mil ml 



Tendon of extensor carpi 

 obliquus 



Suspensory It 



Anterior extensor 



Branch of suspensory liga 



Tendon of tensor 

 fascia; antibrachii 



Flexor carpi me- 

 'dius 



..Flexor carpi in- 

 ternus 



Deep flexor tendon 

 Check ligament 



Superficial flexor 

 tendon 



B. Internal Group 

 1. Subscapularis. — 



This muscle occupies the 

 sul)scapular fossa, beyond 

 which, however, it extends 

 both before and behind. 



Origin. — The subscap- 

 ular fossa. 



Insertion. — The poste- 

 rior eminence of the internal 

 tuberosity of the humerus. 



Action. — To adduct the 

 humerus. 



Structure. — The muscle 

 is flat and triangular, with 



the base upward. The latter is thin and interdigitates with the scapular attach- 

 ments of the serratus. Below this the belly thickens and becomes narrower. It 

 is covered by an aponeurosis, and contains a considerable amount of tendinous 

 tissue. The tendon of insertion is crossed by the tendon of origin of the coraco- 

 brachialis; it is intimately adherent to the capsule of the shoulder joint, and 

 17 



Fig. 187. — Muscles of Thor.a.cic Limb of Horse, Internal View. 

 3, 4, Rhomboideu.s; 5, latissimua dorsi; S, posterior deep pecto- 

 ral; 9, anterior deep pectoral; 11, supraspinatu.s; 15, sub.scapularis; 16, 

 teres major; 20, long head of triceps; i23a, 22b, tensor fasciae antibrachii; 

 23, internal head of triceps. (After Ellenberger, in Leisering's Atlas.) 



