490 THE ARTERIES 



(3) Tlie auricular branch ascends over the mastoid process to the back of the 

 ear, and suppHes the pinna and concha. It sometimes takes the pkiee of the 

 posterior auricular artery (f^,L^ 335). 



(4) The mastoid branch is a small tAvig that passes into the skull through the 

 mastoid foramen, sui)})lying the dura mater, the diploe, the walls of the lateral 

 sinus and the mastoid cells. 



(5) The princeps cervicis (fig. 335), the largest of the branches of the occipital, 

 arises from tliat artery just before it emerges from beneath the sjtlenius, and, 

 descending for a short distance between the splenius and complexus, divides into a 

 supertieial and a deep branch. The superficial branch perforates the splenius, 

 supplies branches to the trapezius, and anastomoses Avith the superficial cervical, a 

 l)ranch of the transverse cervical artery. The deep branch passes downwards 

 between the complexus and semispinalis colli, and anastomoses with the deeji 

 cervical branch of the suj^erior intercostal and with branches of the vertebral 

 (fig. 338). The anastomoses between the above-mentioned arteries form important 

 collateral channels after ligature of the common carotid and sul^clavian arteries 

 (fig. 330). 



(6) The communicating branches run deeph' into the triangle formed Ity the 

 superior oblique, inferior obli(|ue, and rectus capitis posticus major muscles, and 

 there anastomose with brandies of the vertelu'al. 



(7) Muscular branches throughout the course of the occipital artery are dis- 

 tributed to the contiguous muscles — viz. in addition to the sterno-mastoid which 

 receives a named branch, to the digastricus, stylo-hyoid, splenius, trachelo-mastoid, 

 trapezius, the small muscles forming the suboccipital triangle, and the posterior 

 belly of the occipito-frontalis. 



(8) The terminal or superficial branches (fig. 335), usually two in number, 

 named from their position internal and external, ramify over the scalp, and have 

 already been described. The internal branch generally gives off a twig which enters 

 the parietal foramen (parietal artery) and is distri1)uted to the dura mater. The 

 occipital artery may also give off the stylo-mastoid, the posterior auricular, or the 

 ascending pharyngeal arteries. 



6. THE POSTERIOR AURICULAR ARTERY 



The posterior auricular artery (fig. 335) arises from the posterior part of the 

 external carotid artery, usually immediately above the posterior belly of the 

 digastric, about the level of the tip of the styloid process. Occasionally it arises 

 under cover of the digastric, quite close to, or as a common trunk with, or as a 

 l)ranch of, the occipital. It courses upwards and backwards in the parotid gland 

 to the notch between the margin of the external auditory meatus and the mastoid 

 process, where it divides into two branches, an anterior or auricular, and a posterior 

 or mastoid. In this course it rests on the styloid process, crosses the spinal 

 accessory nerve, and is crossed itself by the facial nerve. 



Branches of the Posterior Auricular Artery 



The branches of the posterior auricular artery are: — (1) The parotid; (2) 

 the muscular; (3) the stylo-mastoid; (4) the anterior terminal, or auricular; (5) 

 the posterior terminal, or mastoid (fig. 335). 



(1) The parotid branches are distributed to the lower portion of the parotid 

 gland, and anastomnse with tlie other parotid arteries. 



(2) The muscular branches sup})ly the posterior belly of the digastricus, the 

 stylo-hyoid, and retraliens auvem muscles. 



(3) The stylo-mastoid branch comes off from the posterior auricular artery 

 just before it reaches the notch between the margin of the external auditory meatus 

 and the mastoid process, and, following the facial nerve upwards, enters tlie stylo- 

 mastoid foramen in the temporal bone. In the aqueduct of Fallopius it gives off 

 the following named twigs: — (a) meatal, to the external auditory meatus; (}>) 

 mastoid, to the mastoid cells and mastoid antrum; (r) stapedic, wliieh runs for- 



