OH. XUI.] CELLS IN THE GREY MATTER. 607 



columnar ciliated epithelium, the cells of which at their outer end 

 terminate in fine processes, which join the neuroglia network 

 surrounding the canal, and form the substantia gelatinosa centralis. 

 It is also developed at the tip of the posterior cornu of grey 

 matter, forming what is known as the substantia gelatinosa 

 lateralis of Rolando, which is much enlarged in the upper cervical 

 region. 



Groups of cells in grey matter. The multipolar cells are either 

 scattered singly or arranged in groups, of which the following are 

 to be distinguished on either side certain of the groups being 



Fig. 451. Section of grey matter of anterior cornu of a calf's spinal cord; d, nerve- 

 fibres of white matter in transverse flection, showing axis-cylinder in centre of each ; 

 a, large stellate nerve-cells with their nuclei and prolongations. (Cadiat.) 



more or less marked in all of the regions of the cord, viz., 

 those (a) in the anterior cornu and (/) those in the posterior 

 cornu. 



(a) The cells in the anterior cornu are large and branching, 

 and each gives rise to an axis-cylinder process which passes out 

 in the anterior nerve-root. These cells are everywhere con- 

 spicuous, but are particularly numerous in the cervical and lumbar 

 enlargements. In these districts they may be divided into several 

 groups (i.) a group of large cells close to the tip of the inner 

 part of the anterior cornu most of the cells of the anterior 

 cornu in the dorsal or thoracic region are said to belong to this 

 group ; (ii.) several lateral groups (2a, 26, and 2c, fig. 452) on the 

 outer side of the grey matter, and (iii.) a certain number of cells 

 at the base of the inner part of the anterior cornu particularly 

 well marked in the thoracic region. 



