550 DISSECTION OF THE FACE. 



the Lack, and from the lumbar and lateral sacral below. They arc 

 distributed after the following plan : 



toihe^erte 1 ^ eac ^ arterv eilters tne spinal canal by the intervertebral fora- 

 bra' men, it divides into two branches, upper and lower. From the 

 point of division the branches are directed, one (6) upwards and 

 the other (c) downwards, behind the bodies of the two contiguous 

 vertebrae, and join in anastomotic loops with an offset of the intra- 

 by loops : spinal artery above and below. From the loops offsets (f?) are 

 furnished to the periosteum and to the bodies of the vertebrae. 

 Anastomotic twigs connect the arches across the vertebrae. 

 and a cen- The intraspinal vessels produce also a central longitudinal 

 lse1 ' artery (), like that on the front of the spinal cord, which lies on the 

 bodies of the vertebrae, and is reinforced at intervals by offsets from 

 the loops. 



intraspinal The intraspinal veins (fig. 201) consist of two anterior longitu- 

 targe. are dinal vessels, which extend the whole length of the spinal canal ; 

 of veins inside the bodies of the vertebrae ; and of a plexus of veins 

 beneath the neural arches. 



Anterior The anterior longitudinal veins (6) are close to the bodies of the 



areSnlodies vertebrae, one on each side of the posterior common ligament ; and 

 of vertebrae, they are irregular in outline, owing to certain constrictions near the 

 intervertebral foramina. They receive, opposite the body of each 

 vertebra the veins (c) from that bone ; and through the interverte- 

 bral foramina they have branches of communication (a) with the 

 veins outside the spine in the neck, the dorsal region, the loin .1 and 

 the pelvis. 



Veins of the Veins of the bodies of the vertebra?. Within the channels in the 

 bodies of the vertebrae are large veins, which join on the front of 

 the bone with veins in that situation. Towards the back of the 

 vertebra they are united in an arch, from which two trunks issue 

 by the large apertures on the posterior surface. Escaped from the 

 bone, the trunks diverge to the right and left, and open into the 

 longitudinal veins. 



s >0 iimi veins The P os ^ er ^ or spinal veins form a plexus between the dura mater 



are in con- and the arches of the vertebrae. A large vein may be said to lie on 



arches! th eac ^ s ^ e ^ ^ e middle line, which joins freely with its fellow, 



and with the anterior longitudinal vein by lateral branches. Offsets 



from these vessels are directed through the intervertebral foramina, 



to end in the veins (a) at the roots of the transverse processes. 



SECTION V. 



DISSECTION OF THE FACE. 



DIRECTIONS. After the dissections of the perineum and of the 

 back have been completed, the body will be turned on to the back 

 and will remain in that position. 



First dissect The worker on the head and neck will first dissect the face, 

 face. 



