492 



THE SnXAL VEINS. 



behind the bodies of the vertebra3 in tlie whole length of the canal : 

 d. The posterior longitndinal veins, situated within the canal on the 

 fore part of the arches of the vertebra : e. The veins of the spinal 

 cord. There are likewise branches of communication, some of which 

 connect all the other sets together, and some which bring them into 

 connection with the general venous system. (Breschet, "Essai sur les 

 Veines dn Rachis," 4to; "Traite Anatomiquc sur le Systeme Veineux," 

 fol., 1829 ; Cloquet, " Traite d' Anatomic descriptive," &c.) 



a. — The dorsal veins. The blood from the muscles and integument 

 along the back of the spine is returned by a series of short veins, which 

 ramify upon tlie arches and spinous processes of the vertebrte. They 

 run forwards close to the spinous processes, and on reaching the in- 

 terval between the arches of the vertebrfe, pierce the ligamenta sub- 

 flava, and terminate in a venous plexus within the canal. Towards the 

 outer part of the intervertebral grooves other veins arise, which pass 

 obliquely forwards, through the intertransverse spaces, in company 

 with the posterior branches of the lumbar and intercostal arteries, and 

 open into the veins which accompany those vessels. 



Fig. 3U. 



Fig. 314, A and B. — HorazoNTAi, and Vertical 

 Sections op the Lower Dorsal Vertebra, 



SHOWING THE EXTERNAL AND INTERNAL VeINS 



OP THE Spine (after Breschet). | 



a, spinous process ; h, transverse process ; c, 

 l)Ocly ; d, sjjinal canal ; 1, anterior external veins 

 of the bodj' ; 2, posterior external veins of the 

 vertebral column communicating witli the internal 

 and foi-ming a plexus over the lamin;o and pro- 

 cesses; 3, the posterior, and 4, the antci-ior in- 

 ternal plexus of veins of the vertebral canal ; 5, 

 the internal veins of the body joining tlie intei'nal 

 spinal veins ; 6, the lateral veins, which ai-e joined 

 by the internal and external spinal veins, and 

 themselves unite with the intercostal. 



//. — The veins of the bodies of the 

 vertebrae (venie basis vertebrarum, 

 — Dupuytren) are comparatively large 

 vessels contained in the canals within 

 the bodies of the vertebra3 ; the arteries 

 which accompany them being very small. 

 They anastomose on the front of the 

 bones with some of the superficial veins ; 

 and the trunk of each, having reached 

 the spinal canal through the foramen 

 in the posterior surface of the body of 

 the vertebra, divides into two branches, which diverge and terminate 

 in the large sjiinal veins l)ehind the bodies of the vertebrae. 



f. — The anterior longittidinal spinal veins. — The blood collected 

 by the different vessels here described is poured into two large veins, or 

 rather tortuous venous canals, which extend, one on each side, along 

 the whole length of the spinal canal behind the bodies of the vertebra}. 

 These vessels (the great spinal veins of Breschet) are alternately con- 

 stricted and enlarged, the constricted points corresponding witli the 

 intervertebral foramina, where they are drawn forwards, and bound 



