576 
THE NERVOUS SYSTEM. 
from the second only). It extends backwards beneath the sterno-mastoid, and then 
upwards along its posterior border. Piereing the deep fascia near the apex of the 
posterior triangle, it divides into auricular, mastoid, and occipital branches, and 
/ supphes small cervical branches to the 
upper part of the neck. The auricular 
branch supplies the skin of the deep 
surface of the pinna; the mastoid and 
occipital branches supply the scalp. 
The nerve communicates on the scalp 
with the great occipital and great 
auricular nerves, and with the posterior 
auricular branch of the facial nerve. 
The great auricular nerve (n. auri- 
cularis magnus) is the largest of the 
cutaneous branches. It arises from 
the second and third cervical nerves 
(or, more rarely, from the third alone), 
Winding round the posterior border of 
the sterno-mastoid muscle, it courses 
vertically upwards towards the ear. 
In this course it crosses the sterno- 
mastoid muscle obliquely and is covered 
by the platysma myoides. Before 
arriving at the ear it subdivides into 
mastoid, auricular, and facial branches. 
The mastoid branches ascend over the 
mastoid process and supply the skin of 
the scalp behind the ear, communicat- 
ing with the small occipital and pos- 
terior auricular nerves. The auricular 
branches ascend to the ear and supply 
the lower part of the pinna on both 
aspects; they communicate with the 
Fic. 426.—DuistRIBUTION OF CUTANEOUS NERVES TO 
THE HEAD AND NECK. 
Ophth, Ophthalmic division of the fifth nerve ; ST, Supra- 
trochlear branch; 8.0, Supra-orbital branch ; LT, 
Infra-trochlear branch; L, Lachrymal branch; N, 
External nasal branch ; Sup.Max, Superior maxillary 
division ; T, Temporal branch ; M, Malar branch ; 
1.0, Infra-orbital branch ; Inf.Max, Inferior maxillary 
division ; A.T, Auriculo-temporal branch ; B, Buccal 
branch ; M, Mental branch ; C.2, 3, Branches of the 
second and third cervical nerves ; G.O, Great occipital 
nerve; 8.0, Small occipital nerve; G.A, Great 
auricular nerve ; 8.C, Superficial cervical nerve ; C.3, 
Least occipital nerve; 4, 5, 6, Posterior primary 
same nerves. The facial branches, pass- 
ing over the angle of the jaw and 
through the substance of the parotid 
gland, supply the skin of the cheek 
over the lower part of the masseter 
muscle and the parotid gland. - They 
communicate with branches of the 
facial nerve in the parotid gland. 
The superficial cervical nerve (n. cu- 
taneus colli) arises from the second and 
third cervical nerves. It winds round the posterior border of the sterno-mastoid 
muscle, and crosses the muscle to reach the anterior triangle, under cover of the 
platysma myoides muscle and the external jugular vein. It divides near the 
anterior edge of the sterno-mastoid muscle into upper and lower branches, which are 
distributed through the platysma myoides to the skin covering the anterior triangle 
of the neck. The upper branches communicate freely beneath the platysma myoides 
with the infra-mandibular branch of the facial nerve. 
Descending (supra-clavicular) Branches.—By the union of two roots derived 
from the third and fourth cervical nerves a considerable trunk is formed, which 
extends obliquely downwards from under cover of the sterno-mastoid muscle through 
the lower part of the posterior triangle of the neck. It subdivides into radiating 
branches—sternal, clavicular, and acromial—which pierce the deep fascia of the neck 
above the clavicle, and are distributed to the skin of the lower part of the side of 
the neck, the front of the chest, and the shoulder. The sternal branches (rami supra- 
sternales) are the smallest. Passing over the inner end of the clavicle, they supply 
the skin of the neck and chest as far down as the lower border of the manubrium, 
divisions of 4th, 5th, and 6th cervical nerves. 
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