408 THE MUSCLES AND FASCIA 



between the muscle and the inferior angle of the scapula. This muscle at its 

 insertion gives off an expansion to the deep fascia of the arm. 



A fleshy slip, the axillary arch, varying from 3 to 4 inches in length, and from ^ to f of an 

 inch in breadth, occasionally arises from the upper edge of the Latissimus dorsi about the middle 

 of the posterior fold of the axilla, and crosses the axilla in front of the axillary vessels and nerves, 

 to join the under surface of the tendon of the Pectoralis major, the Coracobrachialis, or the 

 fascia over the Biceps. The position of this abnormal slip is a point of interest in its relation 

 to the axillary artery, as it crosses the vessel just above the spot usually selected for the applica- 

 tion of a ligature, and may mislead the surgeon during the operation. It may be easilv recog- 

 nized by the transverse direction of its fibres. Dr. Struther found it, in 8 out of 105 subjects, 

 occurring seven times on both sides. In most subjects there is a fibrous axillary arch, in only 

 a few is the arch composed of muscle tissue. 



There is usually a fibrous slip which passes from the lower border of the tendon of the Latis- 

 simus dorsi, near its insertion, to the long head of the Triceps. This is occasionally fleshy, 

 and is the representative of the Dorso-epitrochlcaris muscle of apes. 



Relations. The superficial surface of the Latissimus dorsi is subcutaneous, excepting at its 

 upper part, where it is covered by the Trapezius, and at its insertion, where its tendon is crossed 

 by the axillary vessels and the brachial plexus of nerves. By its deep surface it is in relation 

 with the lumbar fascia, the Serratus posticus inferior, the lower External intercostal mus- 

 cles and ribs, the inferior angle of the scapula, Rhomboideus major, Infraspinatus, and Teres 

 major muscles. Its outer margin is separated below from the External oblique by a small 

 triangular interval, the triangle of Petit (trigonum lumbale [Petiti]); and another triangular 

 interval exists between its upper border and the margin of the Trapezius in which the Rhom- 

 boideus major muscle is exposed. 



Nerves. The Trapezius is supplied by the spinal accessory, and by branches from the anterior 

 divisions of the third and fourth cervical nerves: the Latissimus dorsi by the sixth, seventh and 

 eighth cervical nerves through the middle or long subscapular nerve. 



The Second Layer (Fig. 312). 



Levator anguli scapulae. Rhomboideus minor. 



Rhomboideus major. 



Dissection. -The Trapezius must be removed, in order to expose the next layer; to effect 

 this, detach the muscle from its attachment to the clavicle and spine of the scapula, and turn 

 it back toward the vertebral column. 



The Levator anguli scapulae (m. levator scapulae} is situated at the back part 

 and side of the neck. It arises by tendinous slips from the transverse process of 

 the atlas, and from the posterior tubercles of the transverse processes of the second, 

 third, and fourth cervical vertebrae; these, becoming fleshy, are united so as to 

 form a flat muscle, which, passing downward and backward, is inserted into the 

 posterior border of the scapula, between the superior angle and the triangular 

 smooth surface at the root of the spine. 



The Rhomboideus minor (m. rhomboideus minor) arises from the ligamentum 

 nuchae and spinous processes of the seventh cervical and first thoracic vertebra-. 

 Passing downward and outward, it is inserted into the margin of the triangular 

 smooth surface at the _root of the spine of the scapula. This small muscle is 

 usually separated from the Rhomboideus major by a slight cellular interval. 



The Rhomboideus major (m. rhomboideus major) is situated immediately 

 below the preceding, the adjacent margins of the two being occasionally united. 

 It arises by tendinous fibres from the spinous processes of the four or five upper 

 thoracic vertebra' and the supraspinous ligament, and is inserted into a narrow 

 tendinous arch attached above to the lower part of the triangular surface at the 

 root of the spine; below, to the inferior angle, the arch being connected to the 

 border of the scapula by a thin membrane. When the arch extends, as it occa- 

 sionally does, a short distance, the muscle fibres are inserted into the scapula 

 itself. " 



