SPINAL CORD. 



281 



The dorsal column is marked off plainly in the cervical 

 region into two parts, a median segment, the funiculus gracilis 

 (column of Goll), and a lateral segment, the funiculus cuneaius 

 (column of Burdach) (Fig. 205). 



We may begin the study of the finer structure of the cord 

 by a consideration of the nerve cells, which, as has been noted, 

 are found almost exclusively in the gray matter. Of these, 

 there are three main varieties : 



1. Motor cells (Fig. 210) are situated in the ventral and lat- 

 eral horns, and are arranged usually in groups. Especially in 

 the cervical and lumbar regions are such groups to be observed, 



FIG. 213. 



MeduUated ncrre 

 fibres cut transversely 



MeduUated nerve fibres 

 cut longitudinally 



Nucleus of glia cell 



Transverse section through the white matter of the spinal cord of an ox. X 260. 



the more important being the dorso-lateral, ventro-lateral, and 

 ventro-medial groups. Motor cells are unusually large cells, 

 from each of which an axone extends into the ventral root of 

 the same side to form the axis cylinder of a medullated nerve 

 fibre. The dendrites are numerous, and extend back toward 

 the dorsal horn. 



2. Cells of the columns (Fig. 209) are cells which send out 

 axones into the white substance to form the fibres of the white 

 columns. They may be divided into (a) cells whose axones 

 pass into the white matter of the same side (tautomeric), and 



