570 THE NERVOUS SYSTEM. 
The main trunk, after piercing the complexus and trapezius, accompanies the 
occipital artery to the scalp as the great occipital nerve (n. occipitalis major). 
This is the chief cutaneous nerve for the back part of the scalp. It enters the 
superficial fascia at the level of the superior curved line of the occipital bone and 
about an inch from the external occipital protuberance. Ramifying over the 
surface, it supplies the skin of the scalp as far as the vertex. It communicates on 
' Occipital attachment of 
I) trapezius 
Insertion of complexus 
“GREAT OCCIPITAL NERVE 
Obliquus superior 
Insertion of sterno- | LG f Y FLY ILE. Rectus capitis posticus major 
mastoid 1 FZ : i i ote ge lectus capitis posticus minor 
wa a 1a ce Ug 
——Vertebral artery 
Splenius capitis \ “~SUBOCCIPITAL NERVE 
i j NERVE 
me . 
Posterior arch of altas 
_ 
Trachelo-mastoid 
“SObliquus inferior 
POSTERIOR DIVISION OF SECOND CERVICAL 
NERVE 
Complexus - 
__ POSTERIOR DIVISION OF THIRD CERVICAL 
LEAST OCCIPITAL NERVE — NERVE 
Deep cervical artery 
~ POSTERIOR DIVISION OF FOURTH CERVICAL 
NERVE 
Semispinalis colli 
Splenius capitis 
Trachelo-mastoid— 
Fic. 423.—THE SUB-OCCIPITAL TRIANGLE. 
the scalp with the following nerves: great auricular, small occipital, posterior 
auricular, and least occipital. — 
The muscular branches of the second cervical nerve are destined for the com- 
plexus, obliquus inferior, semispinalis colli, and multifidus spine. 
Its communicating branches form the posterior cervical plexus. Descending over 
the posterior arch of the atlas is a branch from the suboccipital nerve which forms a loop 
or network with a corresponding branch of the second nerve. From this loop twigs are 
supplied to the surrounding muscles. A similar loop is formed by a communication 
between branches of the second and third nerves from which muscles are also supplied. 
Occasionally a similar loop is formed between branches of the third and fourth nerves. 
Third Cervical Nerve.—This is much smaller than the second cervical nerve. 
Near its origin it forms a loop of communication with the second nerve, and it may 
give off'a similar communicating branch to the fourth nerve. The main trunk divides 
into internal cutaneous and external muscular branches. The external muscular 
branch enters contiguous muscles; the internal cutaneous branch passes backwards 
and inwards, and becomes superficial as the third or least occipital nerve (n. occipi- 
talis minimus), close to the middle line of the neck. It supplies fine branches to 
the neck and scalp, and communicates with the great occipital nerve. 
The fourth, fifth, and sixth cervical nerves are still smaller. Beneath 
the complexus each divides into external muscular and internal cutaneous branches. 
The muscular branches supply neighbouring muscles; the cutaneous branches are 
small nerves, which, passing backwards, become superficial close to the middle line. 
They supply the skin of the back of the neck. The sixth is the smallest, and its 
