472 



NEUROLOGY. 



The terminal filament of the cord, which is constructed 'of white 

 fibrous tissue externally, and nervous matter internally, passes 

 through the centre of the cauda equina backwards to the second 

 coccygeal bone. 



When denuded of its coverings, the spinal cord is found to be 

 divided into two lateral symmetrical columns by longitudinal 

 fissures, one on the upper surface, narrower but deeper, the 

 superior median fissure; the other, on the under surface, 

 broader, but shallower, the inferior median fissure. A layer of 

 white matter at the bottom of the latter fissure unites the lateral 

 columns, constituting the inferior white commissure, above 

 which a band of grey matter, the grey commissure^ extends the 

 whole length of the cord. 



Fio. 17e, , ' 



Transverse Section through Spinal Cord, showing roots of nerve. 

 o, Inferior median fissure ; 6, Superior median fissure ; c, Central 

 canal ; d. Inferior, and e, Superior cornu of grey matter ; g. Inferior 

 fc, middle, i, superior columns (?) ; k, White commissure ; I, Grey com- 

 missure ; m, Motor root, and n. Sensory root of spinal nerve ; n'. 

 Ganglion on sensory root. (This cut is lettered upside-dovm.) 



Each lateral column is again divided conventionally into three 

 parts by lateral fissures, a superior (best marked), corresponding 

 with the sensory, and an inferior, corresponding with the motor 

 roots of the spinal nerves. 



A transverse section of the cord shows the white matter exter- 

 nally, in the form of two semi-cylinders , and the grey matter in 

 the centre of each. The grey substance varies in size in different 

 parts of the cord, but always presents the same general appear- 

 ance of two crescentic-shaped masses united in the middle by the 

 grey commissure. Each crescent presents two cornua or horns ; 

 the superior, long and thin, traversing the whole thickness of the 

 cord, and prolonged outwards and upwards to the superior lateral 

 fissure ; the inferior^ thicker and more irreo-idar, is directed towards. 



