286 A MANUAL OF ANATOMY 



Ligamentum Nuchae. — This is a fibrous band, or intermuscular 

 septum, which occupies the median line of the neck. Its superficial 

 fibres are attached above to the external occipital protuberance, 

 and below to the spine of the seventh cervical vertebra. Its deep 

 fibres are attached to the external occipital crest, and to the spines 

 of cervical vertebrae from the second to the sixth inclusive. They 

 also extend into the interspinous intervals between the inter- 

 spinales muscles, where they represent interspinous ligaments. 



Latissimus Dorsi — Origin. — (i) The spinous processes and supra- 

 spinous ligaments of the lower six thoracic vertebrae; (2) the posterior 

 lamina of the lumbar aponeurosis, through means of which it is 

 attached to the lumbar and sacral spines, and the posterior fourth of 

 the outer lip of the iliac crest ; (3) the outer lip of the iliac crest a 

 little behind the centre for about 2 inches ; (4) the outer surfaces 

 of the last three or four ribs external to their angles by fleshy slips, 

 which interdigitate with slips of the obliquus externus abdominis ; 

 and (5) the back of the inferior angle of the scapula, the last origin 

 being inconstant. 



Insertion. — The floor of the bicipital groove of the humerus about 

 its middle third for about i^ inches. 



Nerve-supply. — The middle or long subscapular nerve from the 

 posterior cord of the brachial plexus, its fibres being derived chiefly 

 from the seventh cervical nerve. The nerve is only seen during 

 the dissection of the axillary space, and it enters the muscle on 

 its deep aspect. 



Blood-supply. — Branches of the subscapular artery. 



The upper fibres of the muscle pass horizontally outwards, and 

 cross the inferior angle of the scapula, which they bind to the chest 

 wall ; the succeeding fibres pass obliquely upwards and outwards ; 

 and those from the iliac crest and lower ribs pass almost vertically 

 upwards. 



Action. — The arm being raised, the muscle draws it downwards 

 and backwards, producing at the same time internal rotation, as 

 when the hands are crossed behind the back. When the muscle 

 acts from its insertion, it raises the pelvis and trunk after the out- 

 stretched arms, as in the act of climbing a pole. It also elevates 

 the last three or four ribs, as in forced inspiration. 



At the inferior angle of the scapula the muscle is behind the 

 teres major ; it then winds round the lower border of that muscle; 

 and eventually it is placed in front of it. The lower borders of 

 the tendons of these muscles near their insertions are closely con- 

 nected, but ultimately they become separated, a synovial bursa 

 intervening between the two. Between the upper border of the 

 latissimus dorsi, the lower border of the trapezius, and the base of 

 the scapula, there is a triangular area in which are exposed a portion 

 of the rhomboideus major, the sixth rib, and the sixth intercostal 

 space. 



Triangle of Petit. — The anterior border of the latissimus dorsi, 

 between the iliac crest and last rib, may or may not overlap the 



