J98 MUSCLES OF THE BACK. 



processes of the five superior cervical vertebrae above, and to the boaies 

 of the last three cervical and first three dorsal below. 



Relations. By its anterior surface, with the pharynx, oesophagus, the 

 sheath of the common carotid, internal jugular vein and pneumogastric 

 nerve, the sympathetic nerve, inferior laryngeal nerve, and inferior thyroid 

 artery. By its posterior surface it rests upon the cervical and upper dor- 

 sal vertebrae. 



Actions. The rectus anticus major and minor preserve the equilibrium 

 of the head upon the atlas ; and, acting conjointly with the longus colli, 

 flex and rotate the head and the cervical portion of the vertebral column. 

 The scaleni muscles, taking their fixed point from below, are flexors of 

 the vertebral column ; and, from above, elevators of the ribs, and there- 

 fore inspiratory muscles. 



Eighth Group. Muscles of the Larynx. 



These muscles are described with the anatomy of the larynx, in Chap- 

 ter XI. 



MUSCLES OF THE TRUNK. 



The muscles of the trunk may be subdivided into four natural groups ; 

 viz. 



1. Muscles of the back. 3. Muscles of the abdomen. 



2. Muscles of the thorax. 4. Muscles of the perineum. 



1. Muscles of the Back. The region of the back, in consequence of its 

 extent, is common to the neck, the upper extremities, and the abdomen. 

 The muscles of which it is composed are numerous, and maybe arranged 

 into six layers. 



First Layer. (Cervical Group.) 



Cervicalis ascendens. 



Irapezius Transversalis colli, ' 



Latissmms dorsi. Trachelo-mastoideus, 



Second Layer. Complexus. 



Fifth Layer. 



Levator anjnih scapulae, /T ^ -, ^ x 



Rhomboideus minor, . (Dorsa Group.) 



Rhomboideus major Semi-spina is dorsi, 



Semi-spinahs colli. 



TIArd Layer. ( Ce f vical Grou P') 



Rectus posticus major, 



Serratus posticus superior, Rectus posticus minor, 



Serratus posticus inferior, Rectus lateralis, 



Splenius capitis, Obliquus inferior, 



Splenius colli. Obliquus superior. 



Sixth Layer. 



Fourth Layer. Multifidus spin*, 



(Dorsal Group.) Levatores costarum, 



Sacro-lumbalis, Supra-spinales, 



Longissimus dorsi, Inter-spinales, 



Spinalis dorsi. Inter-transversales. 



