370 



BACK. 



conceals the one above it, and TSO on. The 

 muscle on its way to the humerus glides over 

 the inferior angle of the scapula, from which it 

 receives a small fasciculus of fleshy fibres; then 

 it bends under the teres major, forms a tendon 

 about an inch broad and an inch long, which 

 is connected at first by cellular tissue, and after- 

 wards by a bursa mucosa to the front of the 

 teres major; and is inserted into the inner or 

 posterior edge of the bicipital groove. Some 

 fibres of this tendon line the groove, a few pass 

 up along its edge to the lesser tuberosity. The 

 axillary vessels and nerves, the biceps and the 

 coraco-brachialis, are in contact with its tendon. 



The upper edge of the kiUssimus is nearly 

 horizontal, slightly curved its concavity up- 

 wards and free. The anterior edge is nearly 

 vertical, and for the most part free also. The 

 posterior or inner edge is connected throughout, 

 and takes an extensive irregular sweep. On 

 raising the muscle, we shall find that it was in 

 contact with the serratus posticus inferior, the 

 sacro-lumbalis and longissimus dorsi, the inter- 

 nal oblique and transversalis of the abdomen, 

 the inferior rhomboid, the serratus magnus, the 

 inferior angle of the scapula, the infra-spinatus 

 and teres major, also with some of the ribs and 

 intercostal muscles. 



We sometimes meet a fasciculus of muscular 

 fibres passing from the latissimus dorsi to the 

 pectoralis major across the axillary vessels and 

 nerves. In the Edinburgh Medical and Sur- 

 gical Journal, vol. viii. Dr. Ramsay states 

 that it is found in one subject out of every 

 thirty, and may prove inconvenient to the axil- 

 lary artery, vein, and nerves. 



The latissimus dorsi depresses the arm, draws 

 it backwards and inwards, rotates the humerus 

 so as to turn the palm of the hand first in- 

 wards, then backwards. It serves to keep the 

 lower angle of the scapula in its place. When 

 the arm is raised and fixed, it draws the body 

 up, as in climbing, or elevates the ribs, as in 

 difficult respiration. In using crutches the 

 arm is fixed by grasping the handle of the 

 crutch, then the pectoralis major and latis- 

 simus pull up the body on the cross-bar to- 

 wards their insertions ; and when the body is 

 so raised, it is impelled forwards by the action 

 of this muscle, aided by the feet and by the 

 body's own gravity. 



In quadrupeds it is a muscle of progression, 

 pulling the trunk forwards to the fore-leg, which 

 was previously fixed. The panniculus carno- 

 sus, which is inserted close to it into the hu- 

 merus, assists in this action. In birds it is 

 small, and consists of two portions. 



Second layer. This layer consists of the 

 rhomboidei and levator an gull scapula;. They 

 are seen on raising the trapezius. 



The rhomboidei form a broad thin plane, 

 separated only by a line of cellular tissue into 

 the minor and* major, extending from the spine 

 to the scapula, and nearly concealed by the 

 trapezius. 



The rhomboideus minor arises from about 

 half an inch of the ligamentum nuchse and 

 from the spine of the seventh cervical vertebra; 

 its fibres run downwards and outwards to be 



inserted into the base of the scapula at and a 

 little above the commencement of the spinous 

 process of that bone. The rhomboideu* major, 

 three or four times as broad, arises from the 

 four or five uppermost dorsal spines, runs 

 downwards and outwards, and is inserted 

 below the last into the base of the scapula 

 from its spinous process to its inferior angle. 

 These two muscles are of the same length, 

 thickness, and appearance in every respect, 

 differing only in breadth. Their fibres are 

 parallel to each other, being tendinous at their 

 origin, where they are blended with those of 

 the trapezius, and are inserted between the 

 serratus magnus and the supra- and infra- 

 spinati. The insertion of the major is peculiar; 

 a tendinous band runs along the base of the 

 scapula from its spine to its inferior angle, and 

 it is into this, not into the bone, that the mus- 

 cular fibres are inserted, nearly at right angles. 

 This band is attached only at its two extremi- 

 ties ; it is not seen till we cut a few of the 

 posterior fleshy fibres which do reach the bone. 

 This arrangement is supposed to allow of 

 greater freedom of anastomosis between the 

 scapular vessels. The minor is overlapped at 

 its insertion by the levator anguli scapulae, 

 in the rest of its extent by the trapezius. The 

 major is covered by the trapezius principally ; 

 a very small part of its inferior Angle is covered 

 by the latissimus, and between these it is 

 separated from the integuments only by the 

 superficial fascia. The rhomboids get their 

 name from their shape. Their opposite, but 

 not their adjacent sides and angles are nearly 

 equal. Their internal and external edges 

 are attached; their superior and inferior are 

 free. The inferior edge of the major is a little 

 longer than any other. The deeper surface of 

 these muscles touches the splenii, the serratus 

 posticus superior, sacro-lumbalis and longis- 

 simus dorsi, some ribs and intercostal muscles. 



These muscles draw the base of the scapula 

 towards the spine, acting with most effect on 

 the inferior angle, and thereby depressing the 

 point of the shoulder. With the trapezius they 

 draw the shoulders upwards and backwards. 



In the simiae the rhomboids extend to the oc- 

 ciput. In carnivora the levator major scapula 

 seems to be their occipital portion. In the 

 horse the levator proprius scapula is the ante- 

 rior part of the rhomboid, arising from the 

 ligamentum nuchae. 



The levator anguli scapulae is a long strap- 

 shaped muscle, situated on the side of the 

 neck, and extending from the superior cervical 

 vertebrae to the upper angle of the scapula. 

 Its origin is by four (sometimes three) ten- 

 dinous bundles from the posterior tubercles 

 of the transverse processes of the four superior 

 cervical vertebrae ; Unit which arises from the 

 atlas is the largest ; they are intimately con- 

 nected with the splenius colli behind, and 

 with the scaleni before. The fleshy fibres pro- 

 ceeding from them unite, and passing down- 

 wards, outwards, and backwards, are inserted 

 into the inner surface and posterior margin of 

 the scapula, from its superior angle to near its 

 spine. Here it overlaps a little of the lesser 



