340 THE MUSCLES AND FASCIAE 



separated below from the External oblique by a small triangular interval, the 

 triangle of Petit ; 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 transverse process of the atlas, and from the 

 posterior tubercles of the transverse process 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. 



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

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

 cervicis, Cervicalis ascendens, and Serratus posticus superior muscles, and with 

 the posterior scapular artery and the nerve to the Rhomboids. 



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 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 occasionally does, but a short 

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



Relations. By its superficial (posterior) surface, with 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 spinse, the Intercostal muscles, and ribs. 



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

 division of the fifth cervical nerve ; the Levator anguli scapulae, by the anterior 

 division of the third and fourth cervical nerves, and frequently by a branch from 

 the nerve to the Rhomboids. 



Actions. The movements effected by the preceding muscles are numerous, as 

 may be conceived from their extensive attachment. The whole of the Trapezius 

 when in action retracts the scapula and braces back the shoulder; if the head is 

 fixed, the upper part of the Trapezius will elevate the point of the shoulder, as in 

 supporting weights ; when the lower fibres are brought into action, they assist in 

 depressing the bone. The middle and lower fibres of the muscle rotate the scap- 

 ula, causing elevation of the acromion process. If the shoulders are fixed, both 



