HEAD AND NECK OF THE HORSE 61 



The internal maxillary artery is the direct continuation of the 

 external carotid. 



Lymph glands (lymph oglandulpe pharyngeales) will be found on the 

 wall of the pharynx along the course of the external and internal 

 carotid arteries, and possibly in the angle of divergence of these vessels. 



A. MAXILLARIS INTERNA. — The internal maxillary artery is divisible 

 into three parts: — (1) From its origin to its entrance into the alar 

 canal ; (2) the part traversing the alar canal ; and (3) after its exit from 

 the canal. The first part only is visible at the present stage of the 

 dissection. 



In its course to the alar canal, the internal maxillary artery forms a 

 double curve. The first bend has a convexity that looks forwards and 

 downwards ; the second convexity looks backwards and upwards. The 

 second curve also carries the vessel nearer to the median plane of the 

 head. 



The lateral relations of the artery are the external pterygoid muscle, 

 the buccinator nerve, and the common trunk of the inferior alveolar and 

 lingual nerves. Its medial surfcice is at first in contact with the 

 diverticulum of the auditory (Eustachian) tube, and afterwards with the 

 tensor muscle of the soft palate, and is crossed by the chorda tympani 

 nerve. 



The following branches leave the first part of the internal maxillary 

 artery : — 



(1) A. alveolaris inferior. — The inferior alveolar artery arises close 

 to the upper border of the great cornu of the hyoid bone and passes at 

 first between the pterygoid muscles and then between the internal 

 muscle and the ramus of the mandible, to reach the mandibular foramen 

 where it has been cut through in the process of removal of the 

 mandible. 



Before entering the mandibular canal, the artery furnishes branches 

 to the pterygoid and mylo-hyoid muscles ; and when within the canal it 

 o-ives off collaterals to the cheek-teeth and gums, the bone and the 

 periosteum. At the mental foramen it terminates by dividing into 

 mental (a. mentalis) and incisive branches. The former leaves the 

 mental foramen and anastomoses with the inferior labial arter3^ The 

 incisive branch continues onwards within the bone and supplies the 

 canine and incisor teeth. 



(2) Rami pterijgoidei. — Small branches, two or three in number, 

 supply the pterygoid muscles and the tensor and levator of the soft 

 palate. 



(3) A. tympanica {anterior). — The tympanic artery is a very small 



