398 HEALTH AND DISEASE 



vical ganglion of the sympathetic. It also supplies the skin of the ear 

 on the inner and lower part. 



The second cervical nerve leaves the spinal canal through an opening 

 at the anterior part of the dentata, under cover of the obliquus capitis 

 inferior. The inferior branches of this nerve are distributed to the 

 mastoido-humeralis and skin of the ears; the superior branches go to the 

 superior and inferior oblique muscles of the neck. The sixth and seventh, 

 and sometimes the fifth, together with a branch from the brachial plexus, 

 form the diaphragmatic nerve. 



From the second to the sixth they communicate with each other, and 

 then divide into three sets of branches; one set joins the vertebral nerve, 

 and goes to the sympathetic or middle cervical ganglion, another is distri- 

 buted to the mastoido-humeralis, longus colli, rectus capitis anticus major, 

 the scalenus, and to the phrenic nerve, and a third to the skin. The sixth 

 nerve also furnishes branches to the levator anguli scapulae and rhom- 

 boideus muscles, and the brachial plexus receives a twig from its phrenic 

 branch. The superior branches of the last six cervical nerves supply the 

 splenius, trachelo-mastoideus, semi-spinalis colli, and complexus muscles, 

 and the skin in the region of the mane. 



The seventh and eighth cervical nerves are expended in the formation 

 of the brachial plexus. Each nerve supplies a branch to the middle cer- 

 vical ganglion, the former joins the vertebral nerve, the latter passes 

 directly to the ganglion. 



BRACHIAL PLEXUS 



The mixing or joining together of nerves to form plexuses is one of 

 the methods which nature adopts in order to establish a material relation of 

 distant parts, and to some extent a dependency of one part upon another, 

 so that the whole shall be capable of co-ordinating and acting simul- 

 taneously and together. The brachial plexus is a large fasciculus or bundle 

 of nerves resulting from the combination of the inferior divisions of the 

 last three cervical and first two dorsal roots. It is chiefly intended for 

 the supply of the fore-limb with the nerves which animate it. 



The branches going to make up the brachial plexus converge together 

 after leaving the spine, the dorsal division winding round the front of the 

 first rib and joining the cervical portion to form a broad flat band which 

 passes between the superior and inferior heads of the scalenus- muscle, and 

 subsequently breaks up into the following branches: — 



\. The Diaphragmatic. 



2. The Suprascapular Nerve. 



3. Nerves to the Pectoral Muscles. 



