290 THE MUSCLES 



with the spinal accessory, enter witli it the deep surface of the muscle a short 

 distance above the clavicle. 



Action. — Its upper fibres draw upwards the outer end of the clavicle and the 

 point of the shoulder; and acting from below, they extend the head, flex the neck 

 towards the same side, and turn the face to the opposite side. Its middle fibres draw 

 the scapula inwards towards the spine; at the same time they produce a rotation 

 of the scapula on the thorax, by which the point of the shoulder is raised. The 

 lower filjres draw the scapula downwards and inwards, and at the same time rotate 

 it so as to raise the point of the shoulder. 



Acting as a whole, the muscle draws the scapula towards the middle line of the 

 back, and elevates the shoulder by the rotation it impresses upon the shoulder 

 blade. By drawing the scapula backwards, it gives some help to the pectoralis 

 minor ancl other muscles which elevate the ribs in forced inspiration. When it 

 takes its fixed point from the shoulder blade and clavicle, as when the hand grasi)S 

 firmly some immovable ol)ject, the muscle will draw the spines of the verteljrae 

 towards the scapula. 



The presence of the oval aponeurotic patch may be explained by the fact that 

 the range of movement of the scapula in a horizontal direction l^ackwards and 

 inwards is more limited than when the inward movement is coml)ined with an 

 upward or downward direction. This limitation is due to the ligamentous attach- 

 ments of the clavicle and shoulder Ijlade. 



Relations. — Superficially, the integuments and subcutaneous nerves; deeply, 

 the complexus, splenii, serratus posticus superior, rhomboidei, the vertebral apo- 

 neurosis covering the continuations upwards of the erector spinas, the external 

 intercostals, latissimus dorsi, levator anguli scapulae, omo-hyoid, scalenus medius 

 and posticus, the supraspinatus, and a small portion of the infrasj^inatus. 



Variations, — Occasionally the upper or the lower part of its origin may ftiil. The clavicular 

 part of its insertion sometimes extends far forwards upon the clavicle. Frequently fibres pass 

 from its anterior border to the inner end of the clavicle either in front of or behind the sterno- 

 mastoid, forming an arch under which run some of the superficial cervical nerves. This arch 

 may even extend to the sternum. A similar transverse band is occasionally found in the upper 

 part of the posterior triangle, the transversus michce. Sometimes a longitudinal band of fibres 

 covers the spinal origin of the trapezius. 



Second Layer 



Consists of four muscles — the levator anguli scapulae, rhomboideus minor and 

 major; and the latissimus dorsi. 



1. LEVATOR ANGULI SCAPULA 



The levator anguli scapulae (figs. 263 and 266), named from its action in 

 raising the posterior superior angle of the scapula, is a ribbon-shaped muscle. 



Origin. — By four short tendons from the posterior tubercles of the transverse 

 processes of the four upper cervical vertebra?. 



Insertion. — The vertebral border of the scapula opposite the supraspinous 

 fossa. 



Structure. — The tendons of origin, which are closely connected with the inser- 

 tion of the splenius colli, after a short course are succeeded by muscular fasciculi, 

 and these unite to form a thick band of parallel fibres which remain fleshy to their 

 insertion. The plane of the muscle changes as it descends. Aliove, while lying in 

 the posterior triangle of the neck, its surfaces look outwards and inwards; below, 

 they are directed backwards and forwards. 



Nerve-supply. — From the cervical plexus by branches from the third and 

 fourth cervical nerve which enter the front of the outer surface near the origin of 

 the muscle. 



Action. — It raises the posterior superior angle of the scapula; but, by causing 



