BRANCHES OF THE EXTERNAL CAROTID. 557 



and the hypoglossal nerve winds around it from behind forward ; higher up, it 

 passes across the internal carotid artery, the internal jugular vein, and the pneumo- 

 gastric and spinal accessory nerves ; it then ascends to the interval between the 

 transverse process of the atlas and the inastoid process of the temporal bone, and 

 |ia-<es horizontally backward, grooving the surface of the latter bone, being covered 

 bv the Sterno-mastoid, Splenius, Trachelo-mastoid, and Digastric muscles, and 

 resting upon the Rectus lateralis, the Superior oblique, and Complexus muscles; 

 it then changes its course and passes vertically upward, pierces the fascia which 

 connects the cranial attachment of the Trapezius with the Sterno-mastoid, and 

 asct-nds in a tortuous course over the occiput, as high as the vertex, where it 

 divides into numerous branches. It is accompanied in the latter part of its course 

 by the great occipital and a cutaneous filament from the suboccipital nerve. 

 The branches given oft' from this vessel are 



Muscular. Auricular. 



Sterno-mastoid. Meningeal. 



Arteria Princeps Cervicis. 



The Muscular branches supply the Digastric, Stylo-hyoid, Splenius, and 

 Trachelo-mastoid muscles. 



The sterno-mastoid is a large and constant branch, generally arising from the 

 artery close to its commencement. It first passes upward and backward, and 

 then turns downward over the hypoglossal nerve, and enters the substance of the 

 muscle, frequently in company with the spinal accessory nerve. 



The auricular branch 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 mater. 



The meningeal branch ascends with the internal jugular vein, and enters the 

 skull through the foramen lacerum posterius, to supply the dura mater in the 

 posterior fossa. 



The arteria princeps cervicis (Fig. 352) is a large branch which descends 

 along the back part of the neck and divides into a superficial and deep branch. 

 The former runs beneath the Splenius, giving off branches which perforate that 

 muscle to supply the Trapezius which anastomose with the superficial cervical 

 artery, a branch of the transversalis colli : the latter passes beneath the Corn- 

 plexus between it and the Semispinalis colli and anastomoses with branches from 

 the vertebral and \\ith the deep cervical artery, a branch of the superior inter- 

 c.-D-tal. The anastomosis between these vessels serves mainly to establish the col- 

 lateral circulation after ligature of the carotid or subclavian artery. 



The cranial branches 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 Occipito-frontalis muscle, 

 the integument, and pericranium. 



The Posterior Auricular Artery (Fig. 349) is a small vessel which arises from 

 the external carotid, above the Digastric and Stylo-hyoid muscles, opposite the 

 apex of the styloid process. It ascends, under cover of the parotid gland, to the 

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

 above which it divides into two branches : an anterior, auricular, passing forward 

 to supply the back of the auricle and anastomose with the posterior division of the 

 temporal : and a posterior, mastoid, to the scalp above and behind the ear, 

 communicating with the occipital. Just before arriving at the mastoid process this 

 artery is crossed by the facial nerve, and has beneath it the spinal accessory nerve. 



Besides several small branches to the Digastric, Stylo-hyoid, and Sterno-mastoid 

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



Stylo-mastoid. . Auricular. Mastoid. 



The stylo-mastoid branch enters the stylo-mastoid foramen, and supplies the 



