yo HEAD AND NECK 



its large size. It receives the special name of greater 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. 56). 



The medial division of the third nerve also sends an offset 

 to the occipital portion of the scalp (p. 55). 



The medial divisions of the lower three posterior rami 

 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. 



Thoracic Region. The posriteor rami 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 

 the ilio-costalis on the other. The upper six or seven of the 

 nerves are exhausted in the supply of the intermediate and 

 lateral columns of the sacrospinalis ; the lower Jive or six, 

 however, are considerably larger, and contain both motor and 

 sensory fibres. After giving up their motor fibres to the muscles, 

 they become superficial, by piercing the serratus posterior in- 

 ferior and the latissimus dorsi, in line with the angles of the 

 ribs. Their cutaneous distribution has already been examined 

 by the dissector of the upper limb. 



The medial divisions also are distributed differently in the 

 upper and lower portions of the thoracic region. The lower 

 five or six are very small, and end in the multifidus 

 muscle. The upper six or seven pass medially between the 

 multifidus and semispinalis, and, after supplying the muscles 

 between which they are situated, they become superficial. In 

 passing towards the surface they pierce the splenius, rhom- 

 boids, and trapezius muscles, and thus gain the superficial 

 fascia, where they have been dissected already. 



Lumbar Region. The medial divisions of the posterior 

 rami of the five lumbar nerves are small, and, like the 

 corresponding twigs in the lower thoracic region, they have 

 a purely muscular distribution. They end in the multifidus. 



