358 DISSECTION OF THE BACK. 



the outer border of the erector spinas it blends with the aponeurosis of the 

 latissimus dorsi and inferior serratus. 



The deeper or anterior prolongation passes on the abdominal surface of 

 the quadratus lumborum, and is fixed to the tips and borders of the trans- 

 verse processes. 



In like manner the erector spinae lies in another sheath, which is formed 

 by the vertebral aponeurosis and the tendons of the latissimus and serratus 

 on the one side, and by the superficial of the two prolongations of the fascia 

 lumborum on the other. 



* SECOND LAYER OF MUSCLES (fig. 116). This stratum contains the 

 elevator of the angle of the scapula, and the large and small rhomboid 

 muscles; besides these, the posterior belly of the omo-hyoid muscle, and 

 some vessels and nerves turning backwards towards the scapula are 

 included. 



Dissection. By the reflection of the trapezius and latissimus, and by 

 the dissection made subsequently (p. 355), the several parts in this layer 

 will have been sufficiently prepared for learning. 



* The LEVATOR ANGULI SCAPULAE (fig. 116, c ) arises by tendinous 

 slips from the posterior transverse processes of the upper three or four 

 cervical vertebra?. The fibres form rather a roundish muscle, and are 

 inserted into the base of the scapula between the spine and the superior 

 angle. 



At its origin the muscle lies beneath the sterno-mastoideus, and at its 

 insertion beneath the trapezius, where it touches the serratus magnus mus- 

 cle ; the rest of the muscle appears in the posterior triangular space of the 

 neck. Beneath it are some of the other cervical muscles, viz., splenius 

 colli and cervicalis ascendens. 



Action. The muscle raises the angle and hinder part of the scapula, 

 and depresses the acromion; but united with the upper part of the trape- 

 zius, which prevents the rotation down of the acromion, it shrugs the 

 shoulder. 



When the shoulder is fixed, the neck can be bent laterally to the same 

 side. 



* RHOMBOIDEI MUSCLES. The thin muscular layer of the rhotnboidei 

 is attached to the base of the scapula, and consists of two pieces, large and 

 small, which are separated by a slight interval. 



* The rhomboideus minor (fig. 116, D ) is a thin narrow band, which 

 arises from the spines of the seventh cervical and first dorsal vertebrae, and 

 the ligamentum nuchae; it is inserted into the base of the scapula, opposite 

 the smooth surface at the root of the spine. 



* The rhomboideus major (fig. 116, E ) is larger than the preceding by 

 the width of three or more spinous processes. It arises from the spines of 

 four or five dorsal vertebra? below the rhomboideus minor, and from the 

 supraspinous ligament ; and its fibres are directed outwards and downwards 

 to be fixed to the base of the scapula between the spine and the lower 

 angle. Sometimes all the fibres do not reach the scapula directly, some 

 ending on a tendinous arch near the bone. 



The rhomboidei muscles are covered chiefly by the trapezius and latis- 

 simus; but a portion of the larger rhomboid is subcutaneous near the 

 angle of the scapula. 



Action. From the direction of their fibres both rhomboidei will draw 

 the base of the scapula upwards and backwards, so as to depress the acro- 

 mion. In combination with the trapezius they will carry the scapula 



