196 



MUSCLES OF THE BACK. 



abdomen. The muscles of which it is composed are numerous, and 

 may be arranged into six layers. 



First Layer. 

 Trapezius, 

 Latissimus dorsi. 



Second Layer. 



Levator anguli scapula?, 

 Rhomboideus minor, 

 Rhomboideus major. 



Third Layer. 



Serratus posticus superior, 

 Serratus posticus inferior, 

 Splenius capitis, 

 Splenius colli. 



Fourth Layer. 



(Dorsal Group.) 

 iSacro-lumbali s, 

 Longissimus dorsi, 

 Spinalis dorsi. 



(Cervical Group.) 

 Cervicalis ascendens, 



Transversalis colli, 



Trachelo-mastoideus, 



Complexus. 



Fifth Layer. 



(Dorsal Group.) 

 Semi-spinalis dorsi, 

 Semi-spinalis colli. 



(Cervical Group.) 

 Rectus anticus major, 

 Rectus anticus minor, 

 Rectus lateralis, 

 Obliquus inferior, 

 Obliquus superior. 



Sixth Layer. 



Multifidus spina?, 

 Levatores costarum, 

 Supra-spinalis, 

 Inter-spinales, 

 Inter-transversales. 



First Layer. 



Dissection. The muscles of this layer are to be dissected by making 

 an incision along the middle line of the back, from the tubercle on the 

 occipital bone to the coccyx. From the upper point of this incision 

 cam- a second along the side of the neck, to the middle of the clavicle. 

 Inferiorly, an incision must be made from the extremity of the sacrum, 

 along the crest of the ilium, to about its middle. For convenience of 

 dissection, a fourth may be carried from the middle of the spine to 

 the acromion process. The integument and superficial fascia, together, 

 are to be dissected off the muscles, in the course of their fibres, over 

 the whole of this region. 



The TRAPEZIUS muscle (trapezium, a quadrangle with unequal sides) 

 arises from the superior curved line of the occipital bone, from the 

 ligamentum nuchae, supra-spinous ligament, and spinous processes of 

 the last cervical and all the dorsal vertebrae. The fibres converge 

 from these various points, and are inserted into the scapular third of 

 the clavicle, the acromion process, and the whole length of the upper 

 border of the spine of the scapula. The inferior fibres become tendin- 

 ous near the scapula, and glide over the triangular surface at the 

 posterior extremity of its spine, upon a bursa mucosa. When the 

 trapezius is dissected on both sides, the two muscles resemble a tra- 



