THE ANTERIOR VENA CAVA. . 689 



which emerge from the bony orifices traversed by the arteries of the same name 

 — that is, the inaxillo-dental canal and the nasal foramen. It also receives the 

 confluent of the palatine veins, which pass by the palatine groove, instead of 

 coursing along the palatine canal with the corresponding artery. In general, 

 these three branches do not join the alveolar vein separately, but rather by a 

 common trunk. 



The alveolar vein does not present a uniform volume. It increases until 

 it reaches the alveolar tuberosity, where it forms a kind of large reservoir ; but 

 in traversing the ocular sheath it suddenly becomes constricted, and maintains a 

 small diameter until its entrance into the cavernous sinus. (The reservoir is 

 supposed to prevent congestion of the cavernous sinus.) 



This vein may be considered as an affluent of the sinuses of the dura mater, 

 as well as of the external maxillary vein. 



b. Labial or coronary veins. — Satellites of the labial arteries. The superior 

 is often rudimentary. The inferior, always voluminous, is constituted by the 

 union of several anastomotic branches lying against the external face of the 

 mucous membrane of the cheek. 



c. Buccal vein. — Among the affluents of the external maxillary vein, we cite 

 this, because it opens into the latter by its anterior extremity, opposite the inferior 

 coronary vein, with which it sometimes conrnaunicates by a particular branch. 

 But the buccal vein, properly speaking, constitutes the root of the internal 

 maxillary, and we will describe it as such. 



d. Sublingual vein. — A large vessel, formed of two branches, which arise in 

 the substance of the tongue, and pass sometimes separately into the internal 

 maxillary vein. This sublingual vein passes through the mylo-hyoideus muscle, 

 from within to without, and joins the principal vessel at the lymphatic glands 

 lodged in the submaxillary space. 



E. Thyroid Vein. — This is a voluminous trunk, resulting from the union 

 of the venous divisions which accompany the laryngeal and thyroid branches 

 of the thyroid or thyro-laryngeal artery. It joins the jugular beside the sub- 

 maxillary vein, and most frequently above it. 



F. Cephalic or Plate Vein. — A superficial vessel, which represents one of 

 the terminal branches of the principal subcutaneous vein of the forearm. It is 

 lodged in the interspace of the mastoido-humeralis and anterior superficial 

 pectoral muscles, and enters the inferior extremity of the jugular vein (Fig. 389). 



G. Innominate Veins. — A certain number come from the parotid gland, 

 but the principal arise in the muscles of the neck and withers. One of the latter 

 accompanies the superior branch of the cervico muscular-artery. 



Roots of the Jugular Vein. 



These are constituted by the superficial temporal and internal maxillary veins, 

 which are chiefly supplied by the stiluses of the cranial dura mater. 



1. Superficial Temporal Vein. 



Corresponding in the most exact manner to the temporal vein, this vessel is 

 lodged behind the posterior border of the maxilla, near the articulation of the 

 jaw. beneath the parotid gland, and is embedded in its tissue. 



From the union of these two roots, there results : 



1. The anterior auricular vein — a very large, often multiple, and reticulated 



