LATISSIMUS DORSI MUSCLE. 7 



with the suprascapular nerve and vessels, the transverse cervical 

 vessels from which the superficial cervical already referred to will 

 be seen to spring, and the small nerves to the levator anguli 

 scapulae and rhomboid muscles. 



The dissector of the upper limb will find three muscles pro- muscles 

 ceeding from the vertebral column to the vertebral border of the Jj*^ 6 * 1 

 scapula, viz., the levator anguli scapulae, the rhomboideus minor scapula, 

 and major, from above downwards, and these should be cleaned in 

 the direction of their fibres. The rhomboideus minor and major 

 muscles are often blended together. 



Beneath the lowest part of the reflected trapezius a thin fibrous 

 lamina (aponeurosis), from which the upper part of the latissimus 

 dorsi muscle takes origin from the lower dorsal spines, will be 

 revealed, and care should be taken that it is not cut away. 



The LATISSIMUS DORSI (fig. 3, B) is the widest muscle of the Latissimus 

 back, and is thin and aponeurotic at its attachment to the spine JSgin from 

 and pelvis. It arises along the middle line from the spinous s P ine > 

 processes of the six lower dorsal, all the lumbar, and the upper 

 sacral vertebrae, as well as from the supraspinous ligaments. On 

 the outer side it arises from the posterior third of the outer edge of pelvis, 

 the iliac crest by its aponeurosis, and from the lowest three or four 

 ribs by as many fleshy processes, which interdigitate with slips of ribs ; 

 the external oblique muscle of the abdomen. And in many bodies 

 it receives another fleshy slip from the inferior angle of the 

 scapula. The fibres are directed outwards and upwards, con- 

 verging rapidly ; and the muscle, much reduced in breadth, turns 

 round the lower border of the teres major, to be inserted by tendon 

 into the bottom of the bicipital groove of the humerus (fig. 17, insertion 

 p. 44), where it will be subsequently seen. humerus 



The muscle is superficial, except at the upper and inner part, 

 where it is covered to a small extent by the trapezius. Farther 

 out there is a space between the two, in which the rhomboid and relations ; 

 infraspinatus muscles appear. The outer border overlaps the 

 edge of the external oblique muscle of the abdomen in the interval 

 between the last rib and the iliac crest. The aponeurosis of the 

 latissimus is in its lower part incorporated in the posterior layer 

 of the fascia lumborum, of which it forms the chief constituent. 



Action. If the arm is hanging loose, the muscle can move it use 

 behind the back, rotating it inwards at the same time. If the limb 

 is raised, the latissimus, combining with the large pectoral and teres 

 muscles, will depress the humerus. 



Supposing the arm fixed, the latissimus assists the pectoralis and fixed, 

 major in drawing the movable trunk towards the humerus, as in 

 the act of climbing. 



Dissection. The latissimus is to be divided about midway Dissection 

 between the spines of the vertebrae and the angle of the scapula, 

 and the pieces are to be reflected inwards and outwards. In 

 raising the inner half of the muscle, care must be taken not to 

 destroy either the thin lower serratus muscle, with which it is 

 united, or the aponeurosis continued downwards from the serratus. 



