HEAD AND NECK OF THE HORSE 45 



(4) Rami parotidei. — Numerous small veins drain the parotid 

 gland. 



(5) V. occijntalis. — The origin of the occipital vein cannot be 

 determined as yet. In a later dissection it will be found that two main 

 radicles form the vein in the fossa atlantis. One of these is generally 

 the result of the union of the inferior cerebral and condyloid veins ; the 

 other is produced by the confluence of cerebro-spinal and muscular 

 branches. Occasionally the inferior cerebral vein joins the internal 

 maxillary directly. 



The point at which the occipital vein unites with the internal 

 maxillary is variable, but usually it is close to the mergence of this 

 vessel into the jugular. It may happen that the occipital joins the 

 jugular itself. 



A. CAROTis EXTERNA. — The external carotid artery is the largest of 

 the three terminal branches of the common carotid. At the present 

 stage of the dissection not more than the terminal part of the artery is 

 visible. This runs upwards nearly parallel to the border of the ramus 

 of the mandible, and terminates about 5 or 6 cm. below the mandibular 

 articulation by dividing into the superficial temporal and internal 

 maxillary arteries. The following branches may be examined at this 

 stage : — 



(1) A. masseterica. — The greater part of the masseteric artery has 

 been dissected in connection with the face, where it was found pursuing 

 a curved course along the line of insertion of the masseter muscle. The 

 origin of the artery is now disclosed, and it will be observed that one or 

 possibly two branches pass within the mandible to supply the internal 

 pterygoid muscle. It also furnishes branches to the jugulo-mandibular 

 muscle and the parotid gland. 



(2) A. auricidaris jposterior {magna). — The posterior auricular 

 artery is of some size. It arises from the posterior border of the 

 external carotid artery a little beyond the point of origin of the 

 masseteric, passes upwards underneath the parotid gland to the base of 

 the ear, and divides into four rami, the distribution of v/hich has already 

 been noted (page 30). 



(3) A. temporalis superficialis. — The superficial temporal artery 

 is much the smaller of the two terminal branches of the external 

 carotid. After a short course underneath the parotid gland and close to 

 the margin of the mandible, it divides into two branches, (a) The 

 transverse facial artery has been examined in connection with the face. 

 (b) The anterior auricular artery continues the direction of the super- 

 ficial temporal. This carries it behind the mandibular joint, where it is 



