498 



THE SPINAL COED. 



taining nuclei and pigment ; secondly, there are smaller cells, ranging 

 from 7oVo to ^^o of an inch, the majority being from -^^^-^^ to gi^ of 

 an inch in size. 



The smaller cells occur scattered throughout the whole of the grey 

 matter, and are aggregated also in the si/hsfnnfia gelatmosa at the ex- 

 tremity of the caput cornu posterioris, where they are scattered in a 

 finely granular basis, and among them pass many fine nerve-fibres 

 derived from the posterior roots. 



The larger cells are collected into groups. In the anterior horn they 

 are placed chiefly in its anterior and in its outer portions, although 

 scattered cells occur throughout the cornu. The two groups (with 



Fis. 350. 



Fig. 350. — Transverse 

 Section of half the 

 Spinal Marrow in 

 THE Lumbar En- 

 largement. (Allen 

 Thomson.) f 



This is a semidia- 

 gi-ammatic repi-esenta- 

 tion taken from a pre- 

 pared specimen, and 

 founded in 25art on the 

 statements of Lockhart 

 Clarke and of Kolliker. 



1, anterior median 

 fissure ; 2, posterior 

 median fissure ; 3, cen- 

 tral canal lined with 



epithelium ; 

 commissure 

 commissure 

 column ; 7, 

 lumn : 8, 



4, posterior 

 ; 5, anterior 

 ; 6, posterior 



lateral co- 

 anterior co- 



lumn ; (at each of these 

 places and throughout 

 the "white substance the 

 trabecular prolongations 

 of the pia mater are 

 shown ; ) 9, fasciculus of 

 posterior nerve root en- 

 tering in one bundle ; 

 10, fasciculi of anterior 

 roots entering in four 

 spreading bundles of 

 fibres ; a, a, caput cornu 

 posterioris with large and small cells, and above them the gelatinous substance ; h, in the 

 •cervix cornu, decussating fibres from the nerve roots and fiosterior commissure ; c, posterior 

 nresicular columns (of Clarke) ; d, fibres running transversely from the posterior commissure 

 into the lateral columns ; near d, the lateral group of cells, intermedio -lateral tract ; e, c, 

 ifibres of the anterior roots, entering the anterior cornu, and passing through among the 

 Tadiating cells, but not joining their processes ; c', fibres from the anterior roots which 

 decussate in the anterior commissure ; c", external fibres from the roots running round 

 the outside of the anterior grey cornu towards the lateral columns ; /, fibres from the 

 posterior commissure and from the posterior cornu running towards the anterior. Tkree 

 groups of cells are seen in the anterior cornu ; of these the anterior are external and 

 internal, the posterior are chiefly external or lateral. 



which the anterior nerve-roots are connected) are well defined, espe- 

 ■cially in the cervical and lumbar enlargements. The outer group is 

 ■usually cylindrical, the anterior prismatic in form, and the latter is 

 >often broken up into two or three smaller groups. 



