54 ANATOMY OF THE RAT 



middle of the clavicle to form the subclavian. The sub- 

 clavian, coursing caudally, receives the blood from the 

 anterior jugular vein, which enters the subclavian just 

 median to the entrance of the external jugular. 



Trace the external jugular vein anteriorly to its origin 

 near the occipital region of the head. It receives blood, 

 near its middle point, from the superficial muscles and 

 skin of the occipital region through the posterior external 

 Jugular vein. 



Cephalad to its union with the posterior external jugular, 

 the external jugular is joined by the anterior facial vein. 

 Trace this vein and its tributaries along the ventral and 

 lateral regions of the head and identify them from the 

 following description. The supraorhital vein, arising on 

 the dorsal side of the head where it joins the superficial 

 temporal (to be described), courses anteriorly and unites 

 with the nasal vein at the base of the nose to form the 

 angular vein. This runs ventrally, unites with the supe- 

 rior labial, and forms the anterior facial. The latter re- 

 ceives the inferior labial vein, continues ventrally, then 

 caudally a short distance along the ventro-median border 

 of the masseter muscle, and finally to its junction with the 

 external jugular. 



Carefully dissect the remaining tributaries of the external , 

 jugular vein on the lateral side of the face, neck, and lower 

 jaw. Identify these vessels from the following descrip- 

 tion. The superficial temporal vein, arising in the supra- 

 orbital region, passes ventrally posterior to the eye, receiv- 

 ing the transverse facial, which courses caudally near the 

 zygomatic arch. Crossing the posterior root of the zygo- 

 matic arch, the superficial temporal runs posteriorly, is 

 joined by the anterior auricular from the base of the 

 external ear, then unites with the internal maxillary vein 

 (described below) to form the posterior facial. The pos- 



