720 



THE VASCULAR SYSTEMS 



the vertebral canal; the anterior and posterior vertebral veins; and close to its 

 termination it is sometimes joined by the first intercostal vein. 



The anterior vertebral vein commences in a plexus around the transverse pro- 

 cesses of the upper cervical vertebrae, descends in company with the ascending 

 cervical artery between the Scalenus anticus and Rectus capitis anticus major 

 muscles, and opens into the vertebral vein just before its termination. 



VERTEBRAL 



POSTERIOR 



EXTERNAL 



JUGULAR 



POSTERIOR 



DEEP 



CERVICAL 



VERTEBRAL 



ASCENDING 

 CERVICAL 



FIG. 500. The vertebral vein. (Poirier and Charpy.) 



The posterior vertebral or posterior deep cervical vein (v. cervicalis profunda 

 (Fig. 500) accompanies the deep cervical artery, lying between the Complexuj 

 and Semispinalis colli. It commences in the suboccipital region by communicating 

 branches from the occipital vein and tributaries from the deep muscles at the baq 

 of the neck. It receives tributaries from the plexuses around the spinous processe; 

 of the cervical vertebrae; and terminates in the lower end of the vertebral vein. 



The Veins of the Diploe (Venae Diploicae) (Fig. 501). 



The diploic spaces of the cranial bones in the adult contain a number o: 

 tortuous canals, the diploic canals (can ales diploici [Brescheti]), which are boundec 

 bv a more or less complete layer of compact osseous tissue. The veins the) 

 contain are large and capacious, their walls being thin, and formed only o: 

 endothelium resting upon a layer of elastic tissue; they present at irregulai 

 intervals pouch-like dilatations, or culs-de-sac, which serve as reservoirs for the 

 blood. 



In adult life, so long as the cranial bones are distinct and separable, these 

 veins are confined to the particular bones; but in old age, when the sutures aw 

 united, they communicate with one another and increase in size. They communi- 

 cate, in the interior of the cranium, with the veins and the sinuses of the dura 

 and on the exterior of the skull with the veins of the pericranium. They consist) 



