BLOOD VESSELS OF THE MEDULLA SP1NALIS. 337 



SECT. III. OF THE BLOOD VESSELS OF THE MEDULLA SPINALIS. 



The Arteries of the Spinal Marrow are derived frorHythe 

 Vertebra], Intercostal, Lumbar, and Sacral Arteries. 



1. The Posterior Spinal Artery (Arteria Spinalis Posterior) 

 is the lowest branch of the vertebral, given off in the cavity of 

 the^ cranium. It reaches, soon after its origin, the posterior 

 face of the Medulla Spinalis, and runs to the lower extremity 

 of the latter, on the side of its posterior fissure. Its course is 

 parallel with its fellow, and very serpentine. In its descent it 

 is continually re-enforced by small branches which get into 

 the spinal cavity through each of the intervertebral foramina, 

 they being twigs from the Vertebral Intercostal, and Lumbar 

 Arteries. 



2. The Anterior Spinal Artery (Jlrteria Spinalis Anterior) 

 arises above the last from the vertebral. Shortly after its ori- 

 gin it unites with its fellow into a common trunk, which de- 

 scends along the anterior fissure of the medulla spinalis, but is 

 subject to interruptions. It also is re-enforced by twigs from 

 the same arteries that pass into the spinal cavity through the in- 

 tervertebral foramina. In its whole course it sends off branches 

 from each side to the medulla spinalis. 



The Cauda Equina is supplied by arteries from the Lumbar 

 and from the Sacral Arteries, which reach it through the fora- 

 mina, between the vertebra and in the sacrum. 



The Veins of the Spinal Marrow are very abundant. A large 

 one on each side of the middle line, called the Sinus Columnar 

 Vertebralis, is situated in the spinal cavity, on the posterior 

 face of the bodies of the vertebrae, between their ligamentous 

 covering and the dura mater. They are the general recipients 

 for the blood of the contiguous structure. They detach a con- 

 siderable number of branches, which run transversely, and 

 anastomose with one another on the body of each vertebra, so 

 that each vertebra has its little system of anastomosing 

 branches. These junctions constitute the Circelli Venosi. 



VOL. II. 30 



