262 SIR CHARLES BELL ON THE NERVES OF MOTION, ETC. 



c, c. The lateral columns of the spinal marrow (figg. 2. & 3. b, b.), displayed on 

 their posterior surface. They are discovered on raising the cineritious 

 matter b. Into these columns the posterior root of the spinal nerves are 

 traced : they are the columns of sensation. 

 D. The short column formed by the union of the columns c, c. On dissecting 

 this portion, the decussation of the columns will be seen. 



E, E. The same columns which were lateral in the spinal marrow, now continued 

 upwards, and visible in the fourth ventricle without dissection. They 

 ascend under the valvula cerebri and under the corpora quadrigemina, 

 and fall into the crura cerebri. So that, tracing them from above, each 

 of these columns descends from that part of the crus cerebri which is 

 posterior to the corpus nigrum. 



F. The origin of the sensitive root of the fifth nerve of the encephalon. 



G. The processus cerebelli ad medullam oblongatam. 



Fig. 6. This figure represents the further dissection of the parts seen in fig. 5. 

 A, A. The columns marked e in the former plate. They are divided transversely, 

 and the lower portion folded down, being separated from the parts below 

 by a delicate dissection. 

 B. These columns folded down. 

 c, c. The lateral columns of the spinal marrow continued up into b. 



D. The union of the anterior columns seen in their posterior aspect. The late- 

 ral or sensitive columns, and the anterior or motor columns, are held 

 together at this point. But it appears more for security than reunion. 

 A fine dissection exhibits them quite distinct ; and the parts above con- 

 tinuous into the columns of the spinal marrow ; each separately. 

 E, E. The sensitive roots of the fifth pair of nerves. 



