DORSAL SCAPULAR MUSCLES. 245 



The TERES .MINOR (fig. 74, c) is a narrow fleshy slip, which is often 

 united inseparably with the preceding muscle, along whose lower border 

 it lies. It arises on the dorsum of the scapula from a special surface along 

 the upper two-thirds of the interior costa of the bone, and from the invest- 

 ing fascia ; and it is inserted by a tendon into the lowest of the three marks 

 on the great tuberosity of the humerus, as well as by fleshy fibres into the 

 humerus below that spot about an inch together. 



This muscle is partly covered by the deltoid ; it rests on the long head 

 of the triceps and the shoulder joint. Underneath it the dorsal branch of 

 the subscapular artery turns. 



Action. The arm hanging the muscle rotates it out and moves it back ; 

 the arm being raised the teres depresses the humerus. 



In climbing it supports the joint like the preceding scapular muscles. 



The TERES MAJOR muscle (fig. 74, i>) is extended from the inferior 

 angle of the scapula to the humerus. Its origin is from the rough surface 

 on the dorsum of the bone at the inferior angle ; from the inferior costa 

 as far forwards as an inch from the long head of the triceps ; and from 

 the fascia covering the teres minor. The fibres end in a tendon which is 

 inserted partly into, and partly behind the inner edge of the bicipital groove 

 of the humerus. 



This muscle assists in forming the posterior fold of the axilla; and is 

 situate beneath the axillary vessels and nerves near the humerus (fig. 70). 

 At its origin it is covered by the latissimus dorsi. The upper border is 

 contiguous to the subscapularis muscle, and the lower is received into a 

 hollow formed by the fibres of the latissimus dorsi At the humerus the 

 tendon of the muscle is one inch and a half to two inches wide, and is 

 placed behind that of the latissimus : the two are separated above by a 

 bursa ; but they are united below, and an expansion is sent from them to 

 the fascia of the arm. A second bursa lies between the tendon and the bone. 



Action. If the limb hangs it is carried back behind the trunk and is 

 rotated inwards by the muscle. The humerus being raised, the muscle 

 depresses and adducts it. 



With the limb fixed by the hand the teres will cause the lower angle of 

 the scapula to move forwards. 



Below the scapula (inferior costa), where the teres muscles separate 

 from one another, is a triangular interval, which is bounded in front by 

 the shaft of the humerus, and above and below by the teres muscles. This 

 space is divided into two by the long head of the triceps. Through the 

 anterior part, which is of a quadrilateral shape, the posterior circumflex 

 vessels and the circumflex nerve pass : and opposite the posterior trian- 

 gular space, the dorsal branch (c) of the subscapular artery bends back- 

 wards. 



Dissection (fig. 75). In order that the acromion process may be sawn 

 through to expose the supraspinatus muscle, the ligaments of the scapula 

 and clavicle, which would be injured by such a proceeding, should next be 

 dissected. 



A ligament (coraco-clavicular) ascends from the coracoid process to the 

 under part of the clavicle : on removing the areolar tissue it will be seen 

 to consist of two parts, anterior and posterior, differing in size, and in the 

 direction of the fibres. 



A capsular ligament, connecting the outer end of the clavicle with the 

 acromion, will be recognized by taking away the fibres of the trapezius 

 iind deltoid muscles. 



