VERTEBRAL AND OCCIPITAL MUSCULATURE 341 



in size backward to the sacrum, where it is continuous with 

 the abductor caudae posterior. 



An almost separate muscle, covering the neck as a 

 broad sheet immediately beneath the splenius and longis- 

 simus capitis, is the semispinalis capitis. It arises from the 

 transverse processes of the five posterior cervical and the 

 transverse processes of the first four thoracic vertebrae. It 

 is lightly attached on a line from the transverse process 

 of the atlas to the external occipital protuberance, but is 

 inserted on the lateral surface of the latter. The more 

 posterior and medial portion of the muscle is composed of 

 separate slips arising in common with the longissimus 

 capitis, two closely applied slips, however, at the free 

 margin of the muscle, arising from the semispinalis dorsi 

 and the longissimus. The principal, lateral portion is 

 crossed by a tendinous inscription. 



A second muscle, the semispinalis cervicis, is covered 

 by the foregoing one. It arises from the articular processes 

 of the posterior cervical and first thoracic vertebrae, and is 

 inserted on the spinous processes of the cervical vertebrae, 

 chiefly on that of the epistropheus. 

 (c) The intertransversarii are short muscles connecting the 

 lateral portions of the vertebrae. They are distinguishable 

 in part by their darker coloration. They increase in size" 

 backwards, being most conspicuous in the lumbar region, 

 where they form thick muscular pads interposed between 

 the mamillary and accessory processes. The last slip is 

 attached to the crest of the ilium. 



2. The following muscles constitute an occipital group, composed 

 of short muscles arising from the atlas and axis and inserted on 

 the atlas and the occipital portion of the skull. 



(a) The rectus capitis posterior superficialis. Origin: Spinous 

 process of the epistropheus. Insertion: External occipital 

 protuberance. 



(b) The obliquus capitis superior. Origin: Transverse process 

 of the atlas. Insertion: Lateral surface of the occipital 

 protuberance. 



