The ascending branch almost immediately divides into numerous filaments, some of which supply the platysma royoides ; one or two ascending along the external jugular vein. The greater number are directed upwards and forwards to the upper part or the platysma and digastric muscle, communicate with the deeper seated filaments given off from the portio dura, and becoming cutaneous, supply the skin over the region of the sub-niaxillary gland, the chin (communicating with the sub mental nerve), and the lower part of the cheek ; some filaments being directed to the median line to communicate with the corresponding nerve of the opposite side.
The descending branch forms a loop, the concavity of which looks upwards and inwards, perforates the anterior part of the platysma, a little above the middle of the neck, gives off one or two twigs to accompany the anterior jugular vein, and terminates in the skin about the hyoid bone.
The auricularis magnus (the auricular nerve) arises in common with the trunk of the super ficial cervical from the anastomosing branches between the second and third cervical. It emerges from behind the posterior border of the sterno-mastoid, above the superficial cer vical, and in front of the occipitalis minor. It winds round the edge of the sterno-mastoid, and is directed along it obliquely upwards and inwards to the lower part of the parotid gland on a level with the angle of the jaw, reaches to the anterior border of this muscle, and divides into a superficial and deep ternzinal branch. It gives off before dividing several filaments between the parotid gland and the skin, and others which pass through the sub stance of the former to terminate in the skin in the malar region, where it communicates with the facial nerve.
The superficial branch courses upwards in the parotid fascia, and on a level with the antitragus divides into several filaments, which are distributed on the one hand to the concave surface of the auricle, particularly the concha ; and on the other, to the anterior border of the helix, and the vertical groove in front of it.
The deep branch (anterior mastoid), having perforated the parotid gland, and crossed the auricular branch of the facial, with which it communicates, becomes placed behind the auricle of the ear, ascends along the anterior part of the mastoid process, communicates with the occipitalis minor, and terminates by supplying the skin at the back of the ear, some filaments passing on to its upper border.
The occipitabs nzinor (mastoid, external oc cipital) conics froun the posterior part of the cervical plexus, taking its origin from the second cervical. It appears at the posterior edge of the sterno-mastoid, behind and above the great auricular. It passes upwards parallel with the great occipital nerve directed by the border of the splenius, which it occasionally perforates, to the occipital region behind the mastoid process ; communicates with the great auricular externally, and with the great occipital nerve internally, and ends by terminating in the skin over the parietal bone. There occa sionally occurs a small accessory nerve, be tween the auricularis magnus and occipitalis minor. This is directed along the posterior border of the sterno-mastoid, and is distributed to the skin over the mastoid process.
The supra-clavicular and acromial nerves, form the termination of the cervical plexus, and exist as two primary trunks, which usu ally about the level of the posterior belly of the omo-hyoid, divide and subdivide into numerous branches, which traverse super ficially the posterior inferior triangle of the neck, first passing behind the platysma, then between it and the skin, The internal series (sternal) are directed forwards and inwards, over the lower part of the sterno-mastoid, the inner third of the clavicle, and end in the skin over the upper part of the sternum, and upper and inner part of the pec toralis inajor. The middle filaments (nzanz 'nary) pass over the centre of the clavicle, and are distributed to the skin of the pectoralis major and the mammary gland, and commu nicate with branches of the intercostal nerves. The posterior (clavicular) pass downwards and outwards over the outer third of the cla vicle,and ramify in this skin over the anterior and outer part of the deltoid.
The acronzial nerves are larger than the cla vicular, and are, ordinarily, two in number. They pass obliquely outwards, downwards, and backwards, over the lower part of the superficial aspect of the trapezius, give some filaments to this rnuscle, which communicate with the spinal accessory nerve, and having reached the acromion, divide into numerous cutaneous branches, which are lost in the skin covering th.e spine of the scapula, and the outer and back part of the deltoid.