603 THE VEINS. 



median sinus, channeled near the free border of the face of the brain, passes 

 behind into the torcuhir Herophili. 



The Spinal Sinuses in PARTicnLAii. — We thus designate in Veterinary 

 Anatomy, and with good reason, two series of venous reservoirs which are 

 found throughout the whole extent of the vertebral column, on the sides of 

 the roof of the spinal canal. Lodged in the lateral depressions of the 

 superior face of the vertebral bodies, at the side of the common superior 

 vertebral ligament, and covered by the dura mater, these reservoirs, 

 continued from one vertebra to the other, are like two large, irregular, 

 parallel veins, which commence at the atlo-axoid articulation, terminate 

 on the first coccygeal vertebrte, where their presence is yet well defined, 

 and communicate with one another during their course by transversal 

 anastomoses. 



Affluent Veins that open into the Sinuses op the Dura Matek. — 

 These are the vessels which carry blood either from the dura mater itself, 

 or from the substance of the nervous centres : those of the first category are 

 lure, but the second are numerous. Although we are unwilling to make a 

 detailed study of the latter, we must nevertheless notice what is most 

 remarkable in their disposition. 



a. On the encephalon, the veins form a much richer and closer network 

 than that of the arterial ramifications; from this network proceed a 

 certain number of principal branches, which throw themselves into the 

 sinuses of the cranial dura mater. The veins of the cerebrum, for the most 

 part, gain the median and transverse sinuses ; a few only pass into the 

 cavernous sinuses. Those of the isthmus and cerebellum go to the petrosal 

 and occipito-atloid sinuses. 



With regard to the internal veins of the brain — those which, by their 

 interlacing, constitute the choroid plexus — we see them unite into a large 

 trunk — the great vein of the brain, or vena Galeni, which bends round the 

 superior extremity of the corpus callosum, reaches the interlobular fissure, 

 and throws itself into the falciform or middle sinus, near its posterior 

 extremity, after receiving the superficial veins from the inner face of the 

 hemispheres. 



h. The venules arising from the spinal cord are also very remarkable for 

 the fine network they form on the surface of the organ. They collect into a 

 common trunk — the median spinal vein, which runs from before to behind, 

 throughout the whole extent of the superior groove in the spinal cord ; thus 

 occupying an analogous, though opposite, position to that of the artery of 

 the same name. Prom this vein escape, at intervals, emergent branches which 

 open into the spinal reservoirs. 



Effluent Canals of the Duea Matei? Sinuses.— We have to notice, 

 under this designation, the veins which transport the blood from the sinuses, 

 and wewiU consider m succession those which commence at the encephalic 

 reservoirs, as well as those that emerge from the interspinal canals. 



. «• To be carried from the encephalic sinuses, the blood flows' into two 

 kinds of double gulfs, known as the parieto-temporal and suhsphenoidal 

 confluents. ^ 



The ),arief.o-teraporal confluents are lodged in the canals of the same name, 

 along with the mastoid artery. Each commences at the base of the internal 

 parietal protuberance, and terminates behind the supercondyloid eminence, 

 ihe median and transverse sinuses are confounded with the superior 

 extremity of these reservoirs, and empty into them the blood coming from 

 the encephalic mass. This fluid is subsequently taken away by the super- 



