TRAPEZIUS. LATISSIMUS DORSI. 205 



left side is seen a triangular space bounded by the rhomboid, trapezius, and latisshuus dorsi muscle*, in 

 which parts of the sixth and seventh ribs are exposed ; 9, back part of the external oblique muscle of 

 the abdomen ; between 9 and 2', a small part of the internal oblique ; 10, part of the gluteus medius 

 covered by the fascia lata ; 11, gluteus maximus ; 12, gracilis ; 13, small part of the adductor magnus ; 

 14, semitendinosus ; 15, biceps ; 16, fascia lata covering the vastus externus. 



Relations. The trapezius is superficial in its whole extent : it lies over the splenius, a 

 part of the complexus appearing- above the splenius, the levator anguli scapulae, the rhom- 

 boidei, the supraspinatus, and small portions of the infraspinatus and latissimus dorsi. The 

 spinal accessory nerve and the superficial cervical artery pass into it on its deep surface. 



Varieties. The trapezius is subject to considerable variations in its attachments : it is 

 not unfrequently shorter than above described, and the number of dorsal vertetrrrfi^wlth which 

 it is connected is sometimes diminished to eight or even fewer. Its occipital attachment may 

 be wanting 1 ; and occasionally a separation exists between its cervical and dorsal portions, a 

 condition which is frequent in the lower animals. More extensive deficiencies, and complete 

 absence of the muscle have also been observed. The insertion into the clavicle is sometimes 

 continued forwards to meet the sterno-mastoid muscle. 



A vestige of the panniculus carnosus superficial to the trapezius has been recorded in a few 

 instances. 



The latissimus dorsi muscle arises by tendinous fibres from the spinous pro- 

 cesses of the lower six or seven dorsal vertebrae, and from the posterior layer of the 

 lumbar aponeurosis, through the medium of which it is attached to the lumbar and 

 sacral spines and the back part of the iliac crest ; it also arises by short tendinous 

 fibres for an inch or more from the iliac crest in front of the outer margin of the 

 lumbar aponeurosis, and from the last three or four ribs by narrow fleshy slips which 

 interdigitate with the lower attachments of the external oblique muscle of the 

 abdomen. The fibres at the upper part are the shortest, and pass almost horizontally 

 outwards over the lower angle of the scapula, from which they often receive a small 

 slip of fleshy fibres ; those lower down become longer and pass more obliquely 

 upwards ; finally, those which are attached to the ribs ascend almost vertically. 

 By this convergence the fibres of the muscle come to form a narrow band of some 

 thickness, which, accompanying the teres major towards the axilla, winds round the 

 lower and outer border of that muscle so as finally to be placed in front of it. It 

 terminates in a flat tendon of less than an inch and a half in breadth, which is 

 adherent at its lower border to that of the teres major, but is again detached from 

 it previous to its insertion, a synovial bursa intervening between them. The tendon 

 is attached to the floor of the bicipital groove of the humerus, a little higher than 

 the insertion of the teres major. From this twisting of the muscle upon itself, the 

 anterior surface of the tendon is continuous with the posterior surface of the rest of 

 the muscle. 



Relations. The latissimus dorsi is subcutaneous, except at its origin from the dorsal 

 vertebras, where it is covered by the trapezius, and at its insertion, where it is crossed by the 

 axillary vessels and the nerves of the brachial plexus. It rests on part of the rhomboideus 

 major and infraspinatus, on the teres major, serratus posticus inferior, vertebral aponeurosis. 

 lower ribs and external intercostal muscles, and the posterior borders of the external and 

 internal oblique muscles. 



Between the adjacent borders of the latissimus dorsi, trapezius, and rhomboideus major, 

 there is left, when the scapula is drawn forwards, a triang-ular area in which a portion of one 

 or two ribs and of an intercostal space becomes superficial ; this is taken advantage of for the 

 purpose of auscultation. 



Varieties. The number of dorsal vertebrae to which the latissimus dorsi is attached varies 

 from four to seven or eight, and the number of the costal attachments is also inconstant, 

 being- frequently diminished and more rarely increased : the iliac origin is occasionally want- 

 ing. Muscular bands (axillary arches) are sometimes seen to pass from this muscle near its 

 insertion across the great vessels and nerves to the fore part of the axilla, where they termi- 

 nate variously, in the tendon of the greater pectoral, in the coraco-brachialis muscle, the biceps, 

 or in the fascia : their nerve of supply is usually derived from the internal anterior thoracic, 

 but it has been seen coming from the nerve of Wrisberg, or intercosto-humeral. A slip 

 passing from the costal origin of the latissimus to the coracoid process represents a form of 

 the costo-coracoid muscle (p. 209). From the lower border of the tendon a muscular slip is 



