THE OCCIPITAL ARTERY. 



743 



In correspondence with this history, a persistence of the stapedial artery is occasionally 

 found ; but the majority of the usual \ariations of the internal maxillary are due to the second- 

 ary anastomoses which its branches make with other vessels. Thus, by an enlargement of 

 the anastomoses between the middle meningeal and the branches of the ophthalmic artery, that 

 vessel or some of its branches, notably 



the lachrymal, may come to arise from P , 



the middle meningeal (page 749). And, iG. 094. 



similarly, by the anastomoses with the ^ ^ 



facial or transverse facial arteries, the 

 terminal branches of the infraorbital 

 may be transferred to those vessels, the 

 infraorbital itself stopping in the middle 

 of the infraorbital groove. "^^ -% ^Ast 



5. The Ascending Pharyn- 

 geal Artery. — The ascending 

 pharyngeal artery (a. pharyngea 

 ascendens) (Fig. 695) differs from 

 all the other branches of the external 

 carotid by its vertical course. It 

 is a comparatively small stem which 

 arises close to or immediately at the 

 origin of the external carotid and 

 passes upward, at first between that 

 vessel and the internal carotid, and 

 later between the internal carotid 

 and the internal jugular vein. 



^ 



J. 



Diagrams illustrating development of internal max- 

 illary artery ; y4, early stage ; 5, later stage; C, common 

 carotid; Ce, Ci, external and internal carotid. For ex- 

 planation of other letters, see text. ( Tandler.) 



Branches. — {a) A prevertebral branch which supplies the prevertebral muscles of the neck 

 and anastomoses with the ascending cervical branch of the inferior thyroid artery. 



{b) Pharyngeal branches (rami pharyngei), two or three in number, which supply the con- 

 strictor muscles and the mucous membrane of the pharynx. 



{c) Meningeal Branches. — A number of small twigs, into which the artery breaks up as it 

 approaches the base of the skull, pass through the jugular and anterior condyloid foramina to 

 supply the dura mater of the posterior fossa of the skull, and through the cartilage of the middle 

 lacerated foramen to supply the dura of the middle fossa. 



Variations. — The ascending pharyngeal frequently gives origin to the ascending palatine 

 and more rarely to the superior laryngeal artery. It is very variable in its origin, not infre- 

 quently being given off from one or other of the neighboring branches of the external carotid. 



6. The Sterno- Mastoid Artery. — The sterno-mastoid artery (a. sterno- 

 cleidomastoidea) arises from the posterior surface of the external carotid, near its origin, 

 and passes downward and backward to enter the sterno-cleido-mastoid muscle along 

 with the spinal accessory nerve. It is a comparatively small vessel and is not infre- 

 quently absent, being replaced by branches passing to the muscle from other arteries. 

 When it is present, the hypoglossal nerve bends around to it to pass forward to the 

 lingual muscles. 



7. The Occipital Artery. — The occipital artery (a. occipitalis) (Figs. 691. 

 692) arises from the posterior surface of the carotid, opposite or a little below the 

 facial. It passes upward and backward, and is at first partly covered by the posterior 

 belly of the digastric and the stylo-hyoid muscles, the parotid gland, and the temporo- 

 maxillary vein. It crosses in succession, from before backward, the hypoglossal 

 nerve, which, when the sterno-mastoid artery is wanting, winds around it to pass for- 

 ward to the tongue, the pneumogastric nerve, the internal jugular vein, and the spinal 

 accessory nerve. It then passes more deeply, lying in a groove on the posterior sur- 

 face of the mastoid process and beneath the origin of the posterior belly of the 

 digastric, the sterno-cleido-mastoid, and the splenius capitis. Emerging from beneath 

 these muscles, it reappears in the upper part of the occipital triangle, and then ascends 

 in a tortuous course over the back of the skull, sometimes perforating the trapezius 

 near its origin, and breaks up into numerous branches which anastomose with 

 branches from the artery of the opposite side and with those of the posterior auricular 

 and superficial temporal. In this last part of its course it is superficial, lying beneath 



