MUSCLES OF THE THORACIC LIMB 371 



The rhomboideus consists of three parts. The rhomboideus thoracalis is 

 small; it arises from the fourth to the sixth or seventh thoracic spine, and is inserted 

 into the medial surface (chiefly) of the dorsal angle of the scapula. The rhom- 

 boideus cervicalis arises from the ligamentum nuchae as far forward as the second 

 or third cervical vertebra, and is inserted into the medial surface of the cervical 

 angle of the scapula. The rhomboideus capitis is a narrow band which is given off 

 laterally from the preceding; it is inserted into the nuchal crest. 



The latissimus dorsi is extensive ; it has an attachment to the last two ribs and 

 also to the upper part of the spine of the scapula in addition to the origin from the 

 lumbo-dorsal fascia. Its lower edge blends near the shoulder with the cutaneus. 



The brachiocephalicus contains in front of the shoulder a tendinous intersec- 

 tion and a fibrous mass in which the clavicle is embedded. Anterior to this it sepa- 

 rates into two diverging parts. The dorsal part is the cleido-cervicalis, which 

 widens above and is attached to the median raphe of the neck and to the occipital bone. 

 The ventral part is the cleido-mastoideus ; it is narrow and is attached to the mas- 

 toid process. The common mass posterior to the clavicle and the fibrous inter- 

 section, which is attached to the humerus, is homologous with the clavicular part 

 of the deltoid of man. 



The superficial pectoral muscle is small. It arises on the sternum from the 

 manubrium as far back as the third costal cartilage, and is inserted into the humerus 

 at the border between the medial and anterior surfaces. A superficial slip detached 

 from it is inserted into the fascia of the forearm. The deep pectoral has no scapular 

 part. It arises on the sternum and costal cartilages from the second costal to the 

 xiphoid cartilage, and from the aponeurosis of the obliquus abdominis externus. 

 It is inserted chiefly into the medial tuberosity of the humerus, but also bj- small 

 slips into the lateral tuberosity and the fascia of the arm. 



The serratus ventralis shows no clear division into cervical and thoracic parts. 

 It arises from the last five cervical vertebrae and the first eight ribs, and is inserted 

 into the upper part of the costal surface of the scapula. 



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

 part is triangular and arises from almost the entire length of the spine of the scapula; 

 it is inserted largely into the fascia on the lateral surface of the arm. The acromial 

 part is short, thick, and fusiform; it arises from the lower edge of the acromion, 

 and ends on the deltoid tuberositj'. 



The supraspinatus is large; it ends chiefly on the lateral tuberosity of the hu- 

 merus, but has a small attachment to the medial tuberosity also. 



The infraspinatus is bipennate. The tendon of insertion passes in a groove on 

 the lateral tuberosity of the humerus, to end on a well-defined mark on the same; a 

 large bursa lies under the tendon. 



The teres minor is short and fusiform; it arises on a tubercle on the posterior 

 border of the scapula, just above the glenoid cavity, and is inserted into a tubercle 

 on the upper part of the deltoid ridge. 



The subscapularis is wide and is multipennate in structure, being intersected 

 by fibrous septa which are attached to the rough lines on the costal surface of the 

 scapula. It is inserted into the medial tuberosity of the humerus. 



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

 of the scapula and on the subscapularis, and is inserted into an eminence (tuber- 

 ositas teres) on the proximal third of the medial surface of the humerus by a com- 

 mon tendon with the latissimus dorsi. 



The coraco-brachiaUs has a short and undivided belly. It arises from a small 

 depression on the medial surface of the tuber scapulae, and ends on the proximal 

 third of the humerus, just medial to the brachiahs. The tendon of origin has a syno- 

 vial sheath. 



The capsularis is absent. 



