GREAT VESSELS AND NERVES OF NECK 207 



upwards and backwards, under cover of the sterno-mastoid 

 muscle, and, generally, under cover of the lower border of the 

 posterior belly of the digastric, to reach the interval between 

 the mastoid portion of the base of the skull and the transverse 

 process of the atlas. Thence onwards, it has been studied in 

 the dissection of the scalp and the back of the neck (pp. 47, 

 56). The first part of the vessel crosses the internal carotid 

 artery, the vagus nerve, the accessory nerve, the internal 

 jugular vein, and the hypoglossal nerve, which hooks round it. 



The only branches which spring from the occipital artery 

 in the region under consideration are: (i) muscular twigs; 

 and (2) a meningeal branch. 



The muscular twigs are given to the neighbouring muscles. 

 One of them, the sterno-mastoid branch^ is larger than the 

 others and very constant, runs parallel with the accessory 

 nerve, and sinks, with it, into the substance of the sterno- 

 mastoid muscle. 



A meningeal branch associates itself with the internal 

 jugular vein, and can be followed upwards upon it to 

 the jugular foramen, through which it passes into the 

 cranium. 



Arteria Auricularis Posterior. The posterior auricular 

 artery will be found above the level of the posterior belly of 

 the digastric, and, like the occipital, it takes origin from the 

 posterior aspect of the external carotid artery. In the first 

 part of its course it is placed deeply, and runs upwards and 

 backwards, between the styloid process of the temporal bone 

 and the postero-medial surface of the parotid gland, to reach 

 the interval between the mastoid process and the back of 

 the auricle. Then it accompanies the posterior auricular nerve 

 in the superficial fascia of the scalp, where its course has already 

 been studied, in the dissection of the scalp (p. 47). 



As it runs upwards and backwards the posterior auricular 

 artery gives off (i) muscular twigs ; (2) a few branches to the 

 parotid gland ; and (3) the stylo-mastoid artery. 



Arteria Stylomastoidca. The stylo-mastoid artery is a 

 slender vessel which enters the stylo-mastoid foramen. In 

 the interior of the temporal bone it has an extensive dis- 

 tribution. It supplies twigs to the mastoid cells and to the 

 tympanic cavity, and is carried onwards, in the canalis facialis 

 (O.T. Fallopian), to anastomose with the petrosal branch of 

 the middle meningeal. 



