MUSCLES OF THE SHOULDER MUSCLES OF THE ARM 351 



The omo-transversarius arises on the wing of the atlas, and, inconstantly, 

 the transverse process of the axis, and is inserted into the scapular spine and fascia. 



The rhomboideus is clearly divided into cervical and thoracic parts, the latter 

 extending further than in the horse. 



The latissimus dorsi has a broad tendon of origin, which blends with the 

 lumbo-dorsal fascia; it is also attached to the eleventh and twelfth ribs and the 

 fascia over the external intercostal and oblique abdominal muscles. The anterior 

 fibers end on the tendon of the teres major, the middle part on an aponeurosis on 

 the medial surface of the caput longum, and the posterior part on a tendon which is 

 common to this muscle and the deep pectoral. 



The brachiocephalicus has two distinct parts. The dorsal division, the cleido- 

 occipitalis, arises on the occipital bone and the ligamentum nuchae. The ventral 

 part, the cleido-mastoideus, is smaller and arises by a round tendon on the mastoid 

 process and the rectus capitis ventralis major, and by a thin tendon on the mandible. 



The superficial pectoral muscle is thinner than in the horse and its two parts 

 are not so clearly separable. 



The deep pectoral muscle arises as far forward as the second rib and is un- 

 divided. However, the scapular portion may be considered to be represented by a 

 small branch which arises from the anterior part of the sternum and the first rib 

 and passes upward to end on the deep face of the brachiocephalicus in front of the 

 shoulder joint.'^ A tendon detached from the dorsal edge blends with the latissimus 

 dorsi and coraco-brachialis. 



The serratus ventralis is clearly divided into cervical and thoracic parts. 

 The former is large and extends from the third (or second) cervical vertebra to 

 the fifth rib, being overlapped behind by the thoracic part. It is inserted on a 

 large triangular area on the antero-superior part of the costal surface of the scapula. 

 The thoracic part is relatively thin and is covered by a very strong aponeurosis; 

 it is attached to the fourth to the ninth ribs by six digitations, and is inserted by a 

 flat tendon which insinuates itself between the middle and posterior parts of the 

 subscapularis to end on a rough line — equivalent to the posterior serratus area of 

 the horse — and also on the cartilage of the scapula in continuity with this line. 



n. MUSCLES OF THE SHOULDER 



The deltoid is clearly divided into acromial and scapular parts. The former 

 (Pars acromialis) arises on the acromion, the latter (Pars scapularis) on the posterior 

 border of the scapula and the aponeurotic covering of the infraspinatus. The 

 scapular part of the muscle is largely inserted into the fascia covering the triceps. 



The supraspinatus, infraspinatus, and teres minor do not differ materially 

 from those of the horse. 



The subscapularis consists of three parts with a common tendon of insertion. 



The teres major and coraco-brachialis resemble those of the horse. 



The capsularis is absent. 



m. MUSCLES OF THE ARM 

 The biceps is smaller and less tendinous, and is situated more medially than 

 in the horse. The tendon of origin is flat, and is bound down in the intertuberal or 

 bicipital groove by a flbrous band. The tendon to the extensor carpi radialis is 

 less distinct than in the horse. (In the sheep the tendon of origin is round and is 

 invested by the synovial membrane of the shoulder joint. The tendon of inser- 

 tion bifurcates; one branch ends on the tuberosity of the radius, the other on the 



ulna.) 



1 According to Meckel and Lesbre, this is the homologue of the subclavius of man. 



