Belonging to the neck, (from cervix, the neck,) the nerves which pass through the vertebrae of the neck.
The first cervical nerve throws out a considerable branch to the occiput; supporting, in some degree, the idea of Gall: it joins the ninth pair from the brain, to form the first cervical ganglion of the intercostal.
The second cervical nerve hath a very remarkable plexus; it sends out a very considerable nerve to the occiput, as well as the first. It sends off three branches behind the sterno mastoideus, where they are entangled with the accessorius Willisii. The first branch, going upward and backward, becomes cutaneous on the posterior parts of the temporal and parietal bones. The second goes upward, and a little forward under the sterno mastoideus, and throws branches to the parotid gland, to the lobe, and to the posterior side of the ear. The third goes horizontally forward to the neck, and there becomes a cutaneous nerve, which is sometimes pricked in opening the external jugular vein.
The third cervical nerve goes downwards by a number of filaments towards the shoulders, and produces the phrenic nerve, which runs towards the thorax, before the anterior portion of the scalenus, between the subclavian artery and vein, contiguous to the trunk of the par vagum; passes down before the root of the lungs, follows the pericardium, and branches out in the diaphragm. That on the right is shorter than that on the left, as the latter goes round the apex of the heart.
The four inferior pairs, since a similar nerve arises on both sides, are larger than those already named. Their main trunk, with the first nerve of the back, passes between the portions of the scalenus over the first rib, into the axilla, where they produce six trunks, which go to the upper extremities. In their way thither:. they detach branches to all the arteries.
The first of these six branches is the humerahs, which follows the course of the artery of that name, round the head of the os humeri.
The second is the cutaneus, which runs down the inside of the arm, and goes into the fore arm, just where we open the basilic vein, and is often wounded.
The third is called the musculo cutaneus, and is larger. It rises pretty high, and throws branches into the coraco brachiaeus, through which the trunk passes obliquely; it is then covered by the biceps, and, passing through between the brachiaeus and biceps, it sends off several branches, and lies on the outside of the tendon of the last mentioned muscle, where we commonly bleed in the median cephalic vein.
The fourth is called cubitalis, or Ulnaris, the ulnar nerve; it follows the course of the artery, but passes gradually backwards, and gets behind the inner condyle of the os humeri, betwixt which and the olecranon it passes to the fore arm. A little above the carpus it divides into an anterior and posterior branch, which goes to the palm, the back of the hand, and fingers. See, under Cubitalis, Cheselden's account.
The fifth branch, called media 'nus, the median nerve, passes down contiguous to the brachial artery, and, accompanying the vessel, goes to the fore arm and to the palm of the hand, thence to the thumb and fingers.
The sixth branch, called the radialis, radial nerve, passes down the inside of the arm, and then backwards between the brachiaeus externus, and the short heads of the biceps externus, attended by the artery. When it hath got round, it runs down; and, at the head of the radius, it gives off a cutaneous branch, which goes to the thumb and fingers on the back of the hand, whilst the main trunk passes round the head of the radius through the supinator radii brevis, and goes betwixt the radius and ulna, to be lost in the extensor digitorum communis, and the muscles of the carpus and thumb.