12 TOPOGRAPHICAL ANATOMY OF THE 



Dissection. — Tlie lyinpli glands must be removed so that the external 

 maxillary vessels and the duct of the parotid gland may be adequately 

 exposed. 



V. MAXiLLARis EXTERNA. — The external maxillary vein is a con- 

 tinuation of the facial and begins at the margin of the mandible on a 

 level with the anterior border of the masseter muscle. It runs back- 

 wards in the groove between the digastric and internal pterygoid 

 muscles, then along the lower border of the submaxillary and parotid 

 glands, and finally forms one of the two radicles of the jugular vein at 

 the posterior ventral angle of the parotid. 



The tributary veins that join the external maxillary are : — 



(1) V. sublingualis. — The sublingual vein, a satellite of the artery 

 of the same name, may join the lingual vein instead of uniting with the 

 external maxillary directly. 



(2) V. lingualis. — The lingual vein joins the external maxillary 

 about the point where this vessel first comes into contact with the 

 submaxillary gland. 



(3) Vv. glandulce suhmaxillaris. — From the submaxillary gland. 



(4) Rami 7inLSCulares. — From the omo-hyoid and sterno-hyoid 

 muscles. 



A. MAXILLARIS EXTERNA. — The external maxillary artery appears 

 in the present dissection from the cleft between the omo-hyoid and 

 internal pterygoid muscles at the anterior end of the submaxillary 

 gland. In the region now being examined the artery follows the dorsal 

 border of the vein of the same name, and curves over the edge of the 

 mandible to gain the face, where it becomes the facial artery. 



The onh^ named branch from this part of the external maxillar}' is 

 the sublingual artery (a. sublingualis), which is detached about the end 

 of the submaxillary gland. It follows the dorsal border of the digastric 

 muscle and disappears by piercing the mylo-hyoid muscle on a level 

 with the third or fourth cheek-tooth, to end in tlie mucous membrane 

 of the floor of the mouth. At or about the point at which, the artery 

 passes through the muscle, it gives off a very small submental^ artery 

 (a. submentalis) that supplies the mylo-glossal muscle and the skin 

 about the symphysis of the mandible. 



The parotid duct (Ductus parotideus).'- — The duct of the parotid 

 is formed by the union of radicles at the anterior ventral angle of the 

 gland and enters the present dissection by crossing the flattened tendon 

 of insertion of the sterno-cephalic muscle. It then runs for a short 



^ Sub [L.], beneath. Mentum [L.], the chin. 

 2 Often designated Stensen's or Steno's duct. 



