STEUCTUEE OF NEEVE-CENTEES. 



473 



The vesicular nervous substance contains, as its name 

 implies, vesicles or corpuscles, in addition to fibres ; and a 

 structure, thus composed of corpuscles and inter-communi- 

 cating fibres, usually constitutes a nerve-centre : the chief 

 nerve-centres being the grey matter of the brain and 

 spinal cord, and the various so-called ganglia. In the 

 brain and spinal cord a fine stroma of retiform tissue 

 called the neuroglia extends throughout both the fibrous 

 Fig. 138.* Fig. 139^ 





IV\ 



and vesicular nervous substance, 

 and forms a supporting and 

 investing frame-work for the 

 whole. 



The nerve-corpuscles, which 

 give to the ganglia and to 

 certain parts of the brain 

 and spinal cord the peculiar 

 greyish or reddish-grey aspect by which these parts are 

 characterized, are large, nucleated cells, filled with a finely 

 granular material, some of which is often dark like pig- 



* Fig. 138. Nerve-corpuscles form a ganglion (after Valentin). In 

 one a second nucleus is visible. In several the nucleus contains one 

 or two nucleoli. 



t Fig. 139. Stellate or caudate nerve-corpuscles, with tubular pro- 

 cesses issuing from them. Besides being filled with granular material 

 continuous with the contents of the processes, the corpuscles contain 

 black pigment- matter (after Hannover). 



