HEAD AND NECK OF THE HORSE 39 



of the artery. In additioa, the transverse facial, reflex and buccinator 

 veins communicate with the facial. At the present moment, however, 

 no attempt should be made to follow these three vessels, but their 

 connection with the facial may be determined by slightly raising the 

 border of the masseter muscle. 



At the border of the mandible the facial vein becomes the external 

 maxillary. 



The parotid duct (Ductus parotideus). — The formation of the 

 parotid duct by the union of radicles at the anterior ventral angle 

 of the gland has already been noted, as has also its course across 

 the tendon of the sterno-cephalic muscle into the space between the 

 two halves of the mandible. The association of the duct with the 

 external maxillary vein and arter}^ — the duct being the most ventral 

 of the three structures — has been observed. The duct leaves the 

 space by following the margin of the mandible for a short distance, 

 and then turns upwards on to the face. Its course up the face is 

 at first between the edge of the masseter muscle and the facial 

 vein ; but it soon bends forwards between the buccinator muscle 

 and the facial vessels, and disappears by piercing the muscle 

 obliquely. Later, the opening of the duct will be found within 

 the cheek at the summit of a low papilla (papilla salivalis) on a 

 level with the anterior part of the third upper cheek tooth (fourth 

 maxillary premolar). 



A TRANSVERSA FACIEI. — The transverse facial artery arises from 

 the superficial temporal underneath the parotid gland, and, in the 

 present dissection, appears between the gland and the border of the 

 ramus of the mandible just below the condyloid process of the bone. 

 The vessel runs at first on the surface of the masseter muscle close 

 to the facial crest, but before the level of the orbit has been reached 

 it sinks into the substance of the muscle. Terminal twigs anasto- 

 mose with small branches of the facial artery. 



V. TRANSVERSA FACIEI. — The transverse facial vein follows the 

 upper border of the artery of the same name. The anterior part 

 of the vein pierces the masseter muscle very obliquely and joins 

 the facial vein. This union will be revealed when the masseter 

 comes to be examined. 



A. MASSETERICA. — The masseteric artery will be found at the 

 anterior border of the parotid gland, running along the posterior border 

 of the masseter muscle, into which it disappears. It is a branch of the 

 external carotid artery, and reaches the face by bending round the 

 margin of the mandible, just above the insertion of the sterno-cephalic 



