middle of the clavicle to form the subclavian. The subclavian, 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 supraorbital 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 superior labial, and forms the anterior facial. The latter receives 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 description. The superficial temporal vein, arising in the supraorbital region, passes ventrally posterior to the eye, receiving the transverse facial, which courses caudally near the zygomatic arch. Crossing the posterior root of the zygomatic 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-
