174 HEAD AND NECK 



occipital triangle, and will be examined when this space is 

 dissected. 



The posterior branch of the second cervical nerve is very 

 large. It appears between the vertebral arches of the atlas 

 and epistropheus vertebrae. The posterior branches of the 

 succeeding six cenncal nerves arise from the corresponding 

 spinal nerve-trunks in the intervertebral foramina. They turn 

 dorsally on the medial sides of the posterior intertransverse 

 muscles, and appear in the intervals between the transverse 

 processes. 



The lateral divisions are of small size, and are entirely 

 devoted to the supply of adjacent muscles. 



The medial divisions are not all distributed alike, nor 

 indeed do they present the same relations. Those from the 

 second, third, fourth, and fifth nerves run medially towards the 

 spinous processes, superficial to the semispinalis cervicis 

 muscle, and under cover of the semispinalis capitis. When 

 close to the median plane they turn posteriorly, pierce the 

 semispinalis capitis, splenius, and trapezius muscles, and 

 become superficial. In their course to the surface they give 

 numerous twigs to the neighbouring muscles. 



The medial division of the second nerve is remarkable for 

 its large size. It receives the special name of great occipital. 

 It will be noticed turning round the lower border of the 

 inferior oblique muscle, to which it supplies some twigs. In 

 passing to the surface it pierces the semispinalis capitis (O.T. 

 complexus) and trapezius. To the former it gives several 

 twigs. The distribution of this nerve on the occiput has 

 been noticed already (p. 156). 



The medial division of the third nerve also sends an offset 

 to the occipital portion of the scalp (p. 156). 



The medial divisions of the lower three posterior branches 

 of the cervical nerves resemble the preceding, in so far that 

 they take a course medially towards the spinous processes. 

 They differ from them, however, in running deep to the semi- 

 spinalis cervicis, and in being, as a rule, entirely expended 

 in the supply of muscles. 



Dorsal Region. The posterior branches of the thoracic 

 nerves make their appearance in the intervals between the 

 transverse processes. The lateral divisions proceed laterally, 

 under cover of the longissimus muscle, and appear in the 

 interval between the longissimus dorsi on the one hand and 



