STRUCTURE OF THE WHITE AND GREY MATTER. 



627 



(A) ; the white matter lying laterally between the origin of the anterior and posterior roots of the 

 spinal nerves is the lateral column (L), while the white matter lying between the line of origin 

 of the posterior roots and the so-called posterior median fissure, is the posterior column (P). 

 [The posterior median fissure is not a real fissure, but is filled up with the inner layer of the pia 

 mater, which dips down from the under surface of this membrane quite to the grey matter of 

 the posterior commissure.] Each posterior c , _ ^*//hi{{\\\ \\ O 



column, in certain regions of the cord, may 

 be subdivided into an inner part lying next 

 the fissure, the postero-median or GolVs 

 column, or the inner root-zone {Charcot, fig. 

 454, c) ; and an outer larger part next the 

 posterior root, known as the postero-exter- 

 nal or Bicrdach's column, or the outer root- 

 zone {Charcot, fig.. 454, d). 



Fig. 441. Fig. 442. 



Fig. 441. Transverse section of the white matter of the cord; x 150. a, peripheral layer. 

 Besides the transverse sections of the nerve-fibres, large and fine, there are three branched 

 connective-tissue corpuscles (c). Fig. 442. Multipolar nerve-cells from the grey matter of 

 the anterior horn of the spinal cord (ox), a, nerve-cell ; b, axis-cylinder ; c, grey matter ; 

 d, white matter of column ; e, e, branches of cells. 



The white matter consists chiefly of medullated fibres without the sheath of Schwann and 

 Ranvier's nodes, but provided with the neuro-keratin sheaths of Kiihne and Ewald ( 321), the 

 fibres themselves being chiefly arranged longitudinally. [The incisures of Schmidt exist in these 

 fibres, and can be demonstrated by the interstitial injection of osmic acid (Ranvier).] The 

 nerve-fibres of the nerve-roots, as well as those that pass from the grey matter into the columns, 

 have a transverse or oblique course. There are also decussating fibres in the anterior or white 

 commissure. [In a transverse section of the white matter of the spinal cord, the nerve-fibres 

 are of different sizes, and appear like small circles with a rounded dot in their centre the axis- 

 cylinder the latter may be stained with carmine or other dye (fig. 441). They are smallest in 

 the postero-median or Goll's column, and largest in the crossed and direct pyramidal tracts, 

 which are motor. The white substance of Schwann, especially in preparations hardened in 

 salts of chromium, often presents the appearance of concentric lines. Fine septa of connective- 

 tissue carrying blood-vessels lie between groups of the nerve-fibres, while here and there between 

 the nerve-fibres may be seen branched neuroglia corpuscles. Immediately underneath the pia 

 mater there is a 

 pretty thick lay- 

 er of neuroglia, 

 which invests the 

 prolongations of 

 the pia into the 

 cord. ] 



[The grey mat- 

 ter differs in 

 shape in the dif- 

 ferent regions of 

 the cord, and so 

 does the grey 

 commissure (fig. *ig. 443. 



444). The latter Diagram of the absolute and relative extenc of the grey matter, and of the 

 is thicker and white columns in successive sectional areas of the spinal cord, as well as the 

 shorter in the sectional areas of the several entering nerve-roots. NR, nerve-roots ; AC 

 cervical than in LC, PC, anterior, lateral, and posterior columns ; Gr, grey matter, 

 the dorsal re- 

 gion, while it is very narrow in the lumbar region. The amount of grey matter undergoes a 

 great increase opposite the origins of the large nerves, the increase being most marked opposite 



