INTEEXAL STEUCTURE. 



495 



situated externally, whilst the grey matter is disposed in the 

 interior. 



The white substance of the anterior and posterior columns is pene- 

 trated by the median fissures, and by trabeculte of connective tissue 



Fi- 348. 



Fig. 348. — Trajjsverse Sections of Spinal Cord at different heights. M.\gnifieb 



Two Diameters. 



The letters and numbers indicate the position of each section : C 1, C 2, &c., at level 

 of first cervical nerve, second cervical nerve ; D 1, &c. , first dorsal, &c. ; L 1, &c., first 

 lumbar, &c. ; sac. 2, second sacral ; ca. 2, second coccygeal nerve. The grey substance 

 is shaded dark, and the nerve-cells within it are indicated by dots. 



extending inwards from the surface. Most of these are irregular and 

 indistinct, but in the cervical region a septum extends forwards and 

 inwards from the fissure just described which bounds the posterior 

 median column. This column is thus marked off from the rest of the 

 posterior column as a wedge-shaped area on each side of tlie posterior 

 median fissure. 



