OF THE BACK. 431 



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 Cpraco-brachialis, 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 application of a ligature, 

 and may mislead the surgeon during the operation. It may be easily recognized by the transverse 

 direction of its fibres. Dr. Struther found it, in 8 out of 105 subjects, occurring seven times on 

 both sides. 



Relations. Its superficial surface 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 muscles and ribs, inferior angle of the scapula, Rhom- 

 boideus major, Infraspinatus, and Teres major. Its outer margin is separated 

 below from the External oblique by a small triangular interval ; and another 

 triangular interval exists between its upper border and the margin of the Trapezius, 

 in which the Rhomboideus 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 middle or long subscapular nerve. 



Second Layer. 



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 spine. 



The Levator anguli scapulae is situated at the back part and side of the neck. 

 It arises by tendinous slips from the posterior tubercles of the transverse processes 

 of the four upper 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, betAveen the superior angle and the triangular 

 smooth surface at the root of the spine. 



Relations. By its superficial surface, with the integument, Trapezius, and 

 Sterno-mastoid ; by its deep surface, with the Splenius colli, Transversalis colli, 

 Cervicalis ascendens, and Serratus posticus superior muscles, and with the trans- 

 versalis colli and posterior scapular arteries. 



The Rhomboideus minor arises from the ligamentum nuchae and spinous 

 processes of the seventh cervical and first dorsal vertebrae. 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. 



Relations. By its superficial (posterior) surface, with the Trapezius ; by its 

 deep surface, with the same structures as the Rhomboideus major. 



The 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 dorsal vertebrae and the 

 supraspinous ligament, and is inserted into a narrow tendinous arcb 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 occasionally does, but a short 

 distance, the muscular fibres are inserted into the scapula itself. 



Relations. By its superficial (posterior) surface, witb the Latissimus dorsi ; by 

 its deep (anterior) surface, with the Serratus posticus superior, posterior scapular 

 artery, the vertebral aponeurosis which separates it from the prolongations from 

 the Erector spinae, the Intercostal muscles, and ribs. 



Nerves. The Rhomboid muscles are supplied by branches from the anterior- 



