KIESTEVEN ON THE ANATOMY OF THE SPINAL COED, 389 



extending in different directions ; many of the finest pass out with 

 the posterior nerve roots into the posterior columns. The small 

 cells, many of which are nearly as small as blood discs, abound in 

 every part — they are round or oval, somewhat pyrifonn and give off 

 two or more processes. The intermediate cells are found chiefly 

 near the verge of the posterior columns ; some, although they are 

 still true cells, are so fusiform as to appear like gradual dilatations 

 of the fibres. 



2. The anterior, or more opaque, portion of the caput cornu posteri- 

 oris is continuous with the grey substance of the cervix, and is sur- 

 rounded by the arched lamina of the gelatinous substance. In some 

 parts of the cord, as seen in a transverse section, it has the form of a 

 cone, in other regions it is more or less angular or rounded. It con-, 

 sists of longitudinal, transverse, or oblique fibres and ceUs. The 

 longitudinal fibres are collected into bimdles and are the principal 

 cause of the opacity of this portion of the caput. The transverse 

 fibres are continuous with the posterior roots of the nerves and the 

 longitudinal cells, and cross each other in a great variety of ways. 

 The oblique fibres are continuations of the transverse and longitu- 

 dinal at different angles and in different planes. 



The cells are mostly of the smallest and intermediate size — the 

 majority are oval and fusiform and have their long axes chiefly in the 

 direction of the oblique and horizontal nerve roots, and of the longi- 

 tudinal fibres with which they appear to be continuous. A few 

 larger cells are scattered at unequal intervals. 



The cervix cornu posterioris (fig. 4) is described by Mr. Lockhart 

 Clarke in considerable detail, " not only on accoiuit of its great in- 

 terest and apparent importance, but in order that we may recognize 

 its parts as the same during the changes which they undergo in pass- 

 ing through other regions." 



The cervix is thus defined by the author : — 



" The caput cornu posterioris on each side, would be marked off 

 by an imaginary line extending across from the antero-lateral ex- 

 tremity of the gelatinous substance to the bottom of the posterior 

 median fissure ; while the cervix is included between this line and 

 another drawn nearly horizontally across from the anterior border 

 of the transverse commissure which arches over the pellucid space 

 surrounding the central canal." 



On the inner or median half is found the remarkable longitudinal 

 columns, the columnw vesiculoscs posteriores (figs. 3 and 4). Each 

 consists of a somewhat dark cylinder of fibres interspersed and sur- 

 rounded by cells and their processes. The fibres are in great part 

 derived from the posterior roots of the nerves, and are much finer 

 than those of the white columns. These fibres interlace each other in 

 bundles in the most intricate manner. The cells are oval, fusiform, 

 and stellate, diftering in size, some being as large as those of the 

 anterior cornu. The processes of the cells intersect the cylinder in 

 various directions, sometimes suddenly changing their course to become 



