488 MUSCLES ON POSTERIOR NECK AND BACK. 



Eectus capitis lateralis arises from the transverse pro- 

 cess of the atlas, and is inserted into the jugular eminence 

 of the occipital bone on the outside of its condyle. It is 

 a very short muscle, and its function is to bend the head 

 to the one side. It covers the vertebral artery and has the 

 jugular vein resting upon it. 



SECTION II. 



ORGANS OF MOTION, OR MUSCLES ON POSTERIOR NECK AND BACK. 



Dissection. Eaise the chest by placing a block beneath 

 it, and let the arms and head hang, so as to make the mus- 

 cles and integument tense. Commence an incision from 

 the external occipital protuberance, which carry along the 

 Bpinous processes to the coccyx. Make a second from the 

 lower cervical spine, to the acromion process ; and a third 

 from the occipital protuberance, along the superior trans- 

 verse ridge, towards the mastoid process. Commence the 

 dissection at the second incision, and raise the skin upward 

 and downward, dissecting always in the course of the fibres 

 of the muscle, and taking care to take oif the cellular struc- 

 ture, along with the integument, so as to leave the muscles 

 clean and distinct. The muscles of the posterior neck and 

 of the back have been divided into six layers. 



The first layer is superficial, and consists of two muscles, 

 the trapezius and latissimus dorsi. 



The Trapezius, so called from its resemblance to the 

 mathematical figure of that name, is a triangular, broad 

 muscle, having its base at the spine, and apex at the acro- 

 mion process of the scapula. It is situated on the back 

 part of the neck and chest, and arises from the external 

 occipital protuberance and its superior transverse ridge, by 

 a thin aponeurotic tendon ; also from the spinous processes 

 of the five superior cervical vertebras, by the ligamentum 

 jmchre ; and again tendinous from the spinous processes of 

 the two lower cervical, and all the dorsal. The superior 

 fibres descend, the inferior ascend, and the middle rim 

 transversely, all converging towards the shoulder, to bo 



