BRANCHES OF THE EXTERNAL CAROTID ARTERY. 763 
behind the mastoid process. They enter the posterior fossa of the skull through the anterior 
condyloid foramen, or through the foramen lacerum posterius ; they supply the upper part 
of the internal jugular vein, the lateral sinus, and the dura mater in the posterior fossa 
of the skull, and they anastomose with the middle meningeal and with meningeal branches 
of the ascending pharyngeal artery. ; 
(c) The mastoid, a small and irregular branch (ramus mastoideus) given off from the 
occipital behind the mastoid process. It enters the posterior fossa of the skull through 
the mastoid foramen, supplies the dura mater, and anastomoses with branches of the 
middle meningeal artery. 
(d) The princeps cervicis (ramus descendens) is a large branch given off from the 
occipital upon the surface of the superior oblique. It passes inwards to the outer border 
of the complexus, where it divides into superficial and deep branches. The superficial 
branch runs over the complexus, between it and the trapezius, and anastomoses with the 
superficial cervical artery. The deep branch dips beneath the complexus into the sub- 
occipital triangle, where it anastomoses with branches of the vertebral and profunda 
cervicis arteries. 
(ec) The auricular (ramus auricularis) is an inconstant branch which, as a rule, is 
only given off from the occipital when the posterior auricular artery is absent. It 
ramifies over the mastoid process, and supplies the inner surface of the pinna. 
(7) The terminal branches (rami occipitales) are internal and external. They ramify 
in the superficial fascia of the posterior part of the scalp, anastomosing with the posterior 
auricular and superficial temporal arteries. They are both accompanied by branches of 
the great occipital nerve, and the internal branch gives off a parietal twig, which passes 
into the skull through the parietal foramen to supply the walls of the superior longitudinal 
sinus, and to anastomose with the middle meningeal artery. 
(5) Posterior Auricular Artery (a. auricularis posterior, Figs. 554, 555).—The 
posterior auricular artery springs from the back of the external carotid, 1 
mediately above the posterior belly of the digastric muscle, and terminates between 
the mastoid process and the back of the pinna by dividing into mastoid and 
auricular branches. 
Course and relations.—Commencing in the posterior part of the submaxil- 
lary triangle, it runs upwards and backwards, under cover of the posterior part of 
the parotid gland, to the interval between the mastoid process and the external 
auditory meatus. It is accompanied in the terminal part of its course by the 
posterior auricular branch of the facial nerve. 
Branches.—(a) Muscular branches are given to the sterno-mastoid, the digastric, 
and the styloid group of muscles. 
(6) Parotid branches pass to the lower and posterior part of the parotid gland. 
(c) A stylo-mastoid branch (a. stylomastoidea) is given off at the lower border of the 
external auditory meatus. It runs upwards by the side of the facial nerve, enters the 
stylo-mastoid foramen, and ascends, in the aqueduct of Fallopius, to the upper part of the 
inner wall of the tympanum where it terminates by anastomosing with the petrosal 
branch of the middle meningeal artery. It supplies branches to the external auditory 
meatus, the mastoid cells, the vestibule, and semicircular canals, the stapedius muscle, and 
the tympanic cavity (a. tympanica posterior). One of the latter branches, anastomosing 
with the tympanic branch of the internal maxillary, forms, in young subjects, a vascular 
circle round the membrana tympani; other branches anastomose with tympanic branches 
from the internal carotid and the ascending pharyngeal arteries, and with the auditory 
branch of the basilar. 
(d) The auricular, or anterior terminal branch (ramus auricularis), ascends beneath 
the retrahens aurem muscle. It gives branches to the scalp in the posterior part of the 
temporal region, which Manastomade with the superficial temporal and occipital arteries, 
and to the pinna. The latter branches supply both surfaces of the pinna, piercing or 
turning round the margins of the cartilage to gain the outer surface, and they anasto- 
mose with the auricular branches of the superficial temporal artery. 
The mastoid, or posterior terminal branch (ramus occipitalis), runs upwards and 
ee along the insertion of the sterno-mastoid muscle. It supplies the sterno- 
mastoid, the occipito - frontalis, and the skin, and it anastomoses with the occipital 
artery. 
(6) Ascending Pharyngeal Artery (a. pharyngea ascendens, Fig. 556).—This 
