THE EXTERNAL CAROTID ARTERY 599 



The auricular branch (ramus auricular is) supplies the back part of the concha. 

 It frequently gives off a branch, which enters the skull through the mastoid foramen 

 and supplies the dura, the diploe, and the mastoid cells. 



The meningeal or dural branch (ramus meningeus) ascends with the internal 

 jup'iilar vein, and enters the skull through the foramen lacerum posterius. or 

 through the anterior condylar foramen, to supply the dura in the posterior fossa. 



The mastoid branch (ramus mastoideus) is a small vessel, by no means constant. 

 It passes into the skull through the mastoid foramen and is distributed upon the 

 dura of the posterior fossa. 



The arteria princeps cervicis (ramus descendens), the largest branch of the 

 occipital, descends along the back part of the neck and divides into a superficial 

 and a deep branch. The superficial branch runs beneath the Splenius, giving off 

 branches which perforate that muscle to supply the Trapezius, and then anasto- 

 mose with the superficial cervical artery, a branch of the transversalis colli; the 

 deep branch passes beneath the Complexus between it and the Semispinalis colli, 

 and anastomoses with branches from the vertebral and with the deep cervical 

 artery, a branch of either the superior intercostal 'or the subclavian. The 

 anastomosis between these vessels helps to establish the collateral circulatioTi 

 Titter libation of the carotid or subclavian artery. 



The cranial branches (rami occipitales) of the occipital artery are distributed upon 

 the occiput; they are very tortuous, and lie between the integument and Occipito- 

 frontalis, anastomosing with the artery of the opposite side, the posterior auricular 

 and temporal arteries. They supply the back part of the Occipitofrontalis muscle, 

 the integument, and pericranium. 



5. The posterior auricular artery (a. auricularis posterior) (Figs. 439 and 441) 

 is a small vessel w r hich arises from the external carotid, above the Digastric and 

 Stylohyoid muscles, opposite the apex of the styloid process. It ascends, under 

 cover of the parotid gland, on the styloid process of the temporal bone, to the 

 groove between the cartilage of the ear and the mastoid process, immediately 

 above which it divides into its two terminal branches, the auricular and mastoid. 

 Just before arriving at the mastoid process, this artery is crossed by the facial 

 nerve, and has beneath it the spinal accessory nerve. 



Branches. Besides several small branches to the Digastric, Stylohyoid, and 

 Sternomastoid muscles and to the parotid gland, this vessel gives off three branches : 



Stylomastoid. Auricular. Mastoid. 



The Stylomastoid branch (a. stylomastoidea) enters the Stylomastoid foramen, 

 and supplies the tympanum, mastoid cells, and semicircular canals. In the young 

 subject a branch from this vessel forms, with the tympanic branch from the in- 

 ternal maxillary, a vascular circle, which surrounds the tympanic membrane, 

 and from which delicate vessels ramify on that membrane. It anastomoses with 

 the petrosal branch of the middle meningeal artery by a twig, which enters the 

 hiatus Fallopii. 



The auricular branch (ramus auricularis), one of the terminal branches, ascends 

 behind the ear, beneath the Retrahens aurem muscle, and is distributed to the back 

 part of the cartilage of the ear, upon which it ramifies minutely, some branches 

 curving around the margin of the fibrocartilage, others perforating it, to supply 

 its anterior surface. It anastomoses with the posterior branch and also with the 

 anterior auricular branches of the superficial temporal. 



The mastoid branch (ramus mastoideus) passes backward, over the Sternomastoid 

 muscle, to the scalp above and behind the ear. It supplies the posterior belly of 

 the Occipitofrontalis muscles and the scalp in this situation. It anastomoses 

 with the occipital artery. 



