THE POSTERIOR AURICULAR ARTERY. 401 



ascending 1 on the internal jugular vein, and passing- through the jugular foramen to ramify 

 in the dura mater of the posterior fossa of the base of the skull. The parietal branch is an 

 occasional offset which springs from one of the terminal branches of the occipital artery, and 

 enters the skull by the parietal foramen to be distributed to the surrounding dura mater. 

 The occipital artery sometimes gives origin to the stylo-mastoid branch (normally an offset 

 of the posterior auricular), to the posterior auricular artery, or to the ascending pharyngeal 

 artery. 



5. Posterior auricular artery (v). The posterior auricular artery arises from 

 the external carotid a little higher up than the occipital. It ascends under cover of 

 the parotid gland, resting on the styloid process of the temporal bone and being 

 crossed by the facial nerve, reaches the groove formed by the cartilage of the ear 

 with the mastoid process, and there divides into two terminal branches, auricular 

 and mastoid, which are distributed to the auricle and to the scalp behind and above 

 the ear. 



Branches. (a) Small branches to the parotid gland, and to the digastric and 

 styloid muscles. 



(b) The stylo-mastoid branch, long and slender, enters the foramen of the same 

 name in the temporal bone in company with the facial nerve. It sends small 

 branches backwards to the mastoid cells, and others forwards to the stapedius muscle 

 and the tympanum. One of the latter branches is constantly found in young 

 subjects to form, with the tympanic branch of the internal maxillary artery, a 

 vascular circle around the margin of the tympanic membrane, from which delicate 

 offsets are distributed to that structure. The continuation of the stylo-mastoid 

 branch is a minute twig which runs forwards in the aqueduct of Fallopius and 

 anastomoses with the petrosal branch of the large middle meningeal artery. The 

 stylo-mastoid branch frequently arises from the occipital artery. 



(c) The auricular branch, ascends behind the ear, passing beneath the retrahens 

 auriculam which it supplies, and is expended mainly in offsets to the auricle, a small 

 branch being prolonged to the integument of the hinder part of the temporal region, 

 and anastomosing with the posterior branch of the superficial temporal artery. The 

 offsets to the auricle are two or more in number ; they supply the inner surface of 

 the pinna, and to a great extent also the outer surface by means of branches which 

 perforate the cartilage or turn over its margin. 



(d) The mastoid or occipital branch is directed backwards over the insertion of 

 the sterno-mastoid, supplies the occipitalis muscle and overlying integument, and 

 anastomoses with the occipital artery. 



Varieties. The posterior auricular artery is frequently very small, and has been seen to 

 end in the stylo-mastoid branch. On the other hand it may be larger than usual and com- 

 pensate for a deficiency of the occipital or superficial temporal artery. It is often a branch 

 of the occipital. 



6. Ascending pharyngeal artery (v). This artery, the smallest branch of 

 the external carotid that has received a distinctive designation, is a long straight 

 vessel which arises most commonly from half an inch to an inch above the 

 beginning of the external carotid, and runs upwards to the base of the skull on the 

 mesial side of the internal carotid artery, between that and the wall of the pharynx. 



Branches. These are numerous, but very small and inconstant in their 

 arrangement. They may be divided as follows : 



(a) The pharyngeal branches pass inwards, for the most part to the pharynx. 

 One or two small and variable branches ramify in the middle and inferior constrictor 

 muscles, and anastomose with the superior thyroid artery. Higher up than these is 

 a larger and more regular branch, which runs upon the upper constrictor, and sends 

 small ramifications to the Eustachian tube, to the tensor and levator palati muscles, 

 and to the tonsil. 



