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- •^jam.j ^ 



duct the arm; also to assist ^■W^Mfct..-<' 



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 scajiula 

 is by means of an apon(^u- 

 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 Coraco-brachiaUs--'^^''^W^.^i 



the shoulder joint, and is 

 often continuous with that 

 of the infraspinatus. 



Relations. — Superfici- 

 ally, the deltoid and infra- 

 spinatus muscles; dee])ly, 

 the scapula, the shoulder 

 joint, and the triceps mus- 

 cle. 



Blood-supply. — Sub- 

 scapular artery (circumflex 

 branches) . 



Nerve-supply. — Axil- 

 lary nerve. 



Coraco-brachialis- 

 Biceps brack ii 



Brachialis 

 Extensor carpi radinli 



..Tendon of tensor 

 fascice antibrachii 



Flexor carpi me- 

 "dius 



..Flexor carpi in' 

 ternus 



Tendon of extensor carpi- 

 obliqiius 



^V 



Deep flexor tendon 

 Check ligament 



Suspensory ligament-... 



Anterior extensor tendon 



Branch of suspensory ligament- 



Superficial flexor 

 tendon 



B. Internal Group 

 1. Subscapularis. — 



This muscle occupies the 

 subscapular 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.vcic Limb of Horse, Internal View. 

 3, 4, Rhomboideus; 5, latissimus dorsi; 8, posterior deep pecto- 

 ral; 9, anterior deep pectoral; 11, supraspinatus; 15, subscapularis; 16, 

 teres major; 20, long head of triceps; 23a, 22h, tensor fasciae antibrachii; 

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



