CIRCULATORY SVSTEAJ. 211 



of the cerebrum, and from the cerebellum, as well as veins fiom 

 the dura mater j and also several muscular branches in the course 

 of its descent. 



7. The submaxillary vein, the most considerable branch 

 of the jugular, so large, indeed, compared to the continued trunk, 

 that some regard the two together as a bifurcation of the common 

 jugular. It is formed upon the side of the face by the coalition 

 oi the Jacial, labia/, and varicose veins; whence it turns round 

 the branch of the jaw, between the artery of the same name and 

 the parotid duct, and joins the trunk by the side of the trachea, 

 just below the parotid gland. In its course it receives other 

 veins which likewise contribute to its volume, of which the prin- 

 cipal are — the submental, sublingual, Wigual, pharyngeal, and 

 superior lari/ngeal veins. The Jacial vein results from a ramous 

 expansion of small veins upon the side of the face, and in its 

 course receives one or two branches, one of which is commonly 

 varicose, from the masseter. The labial vein is formed by the 

 union of a plexus of venous branches coming principally from the 

 angle of the mouth, in conjunction with others from the upper 

 and lower lips. I'he varicose vein is a vessel deeply buried under 

 the substance of the masseter, descending obliquely along the 

 furrow made by the approximation of the jaws (wlien the mouth 

 is shut), and is very remarkable from having naturally a large 

 varix or reservoir for blood at its origin : not, however, that this 

 is the only varicose vein, for the temporal conunonly bulges more 

 or less, as well as a vem from this muscle already noticed ; but 

 this is the largest specimen of so extraordinary a formation. I 

 believe that these varices serve to guard against stagnation or 

 congestion in the brain and its membranes, and from consequent 

 rupture of their sinuses and delicate veins, by continuing to ad- 

 mit of the influx of blood at a time that the circulation is inter- 

 rupted or impeded by the motions of the jaw. 



The jugular trunk having received the submaxillary vein, which 

 it does in the space between the larynx and vertebra dentata, 

 proceeds down the side of the neck, covered by the cervical por- 

 tion of the panniculus carnosus, along a channel formed for it by 

 the lower border of the levator humeri and the upper one of the 

 mylo-hyoideus: by a layer of oblique fibres coming from the 

 former of which muscles it is separated from the carotid artery 

 and trachea, they being situated to its inner side, and rather be- 

 low it: in its course down the lower half of the neck, however, 

 the vein gets deeper-seated, approaches the windpipe, and after- 

 wards runs in company with the carotid artery. It terminates in 

 the anterior vena cava within the space between the two first ribs. 

 At or near the junction of the submaxillary, the jugular vein re- 



