172 



HEAD AND NECK 



is inserted into a somewhat oval area on the occipital bone, between the 

 superior and inferior nuchal lines close to the external occipital crest. It is 

 separated from its fellow muscle of the opposite side by the ligamentum 

 nucha^ ; and its most medial part, which is to a certain extent distinct from 

 the general mass, is divided into two bellies by an intermediate tendon and 

 is frequently spoken of as the biventer cervicis. Occasionally the remainder 

 of the muscle is also intersected by a tendinous septum. 



Dissection. The semispinalis capitis must now be reflected by detaching 

 it from the occiput and throwing it laterally. This dissection requires 



Posterior atlanto- 



occipital membrane 



Posterior branch of 



sub-occipital nerve 



Great occipital nerve 



Vertebral artery 



Anterior branches 

 of spinal nerves- 



Posterior arch of atlas 

 ;amentum nuchae 



Posterior branches of spinal 

 nerves 



Seventh cervical vertebra 



FIG. 72. Dissection of the Ligamentum Nuchoe and of the 

 Vertebral Artery in the Neck. 



care, not only on account of the nerves which have been seen to perforate 

 the muscle to reach the surface, but also on account of the structures 

 which it covers. In its upper part it lies over the sub-occipital triangle 

 and the muscles bounding it, whilst below it covers the semispinalis 

 cervicis. A thick dense fascia is placed over these subjacent parts, and in 

 this lie certain of the cervical nerves and the anastomosis between the 

 descending branch of the occipital artery and the arteria profunda cervicis. 

 The dissector must specially look for a small twig from the posterior 

 branch of the sub-occipital nerve which enters the deep surface of the upper 

 part of the semispinalis capitis, and for a larger branch to the same muscle 

 from the great occipital nerve. 



Ligamentum Nuchae (Fig. 72). This is a strong fibrous 

 partition placed in the median plane between the muscles on 



