GANGLIA 



107 



The function of the astrocytes is associated with sup])ort and 

 heahng in the case of injury and possibly assist with the formation 

 of myehn. The microghocytes may he considered as analogous 

 with phagocytic cells in other regions of the body, and form ]jart 

 of the reticulo-endothelial system of the nervous system. 



GANGLIA. 



A ganglion may be defined as a small aggregation of neurons 

 (cj'tons and processes) outside the central nervous system. (Fig. 02.) 

 Each dorsal root of a spinal nerve possesses a spinal ganglion. The 

 dorsal root of such a nerve is sheathed in external perineurium. 



I. ^ < ■ • ,. . ^r. ■■% ,, . _,ijy 



Fig. 62. — Photograph of spinal ganglion of the cat. Longitudinal section showing 

 groups of ganglion cells separated by fiber tracts. The loose fibroelastic connective- 

 tissue sheath is partly torn away from the ganglion. 



This connective tissue covers the ganglion and extensions from it 

 continue internally, partly separating masses of cytons and fibers. 

 The cytons are large spherical cells of different diameters. Within 

 each is a large nucleus which usually contains a nucleolus. Around 

 each cyton may be seen a row of nuclei, indicati\'e of a sheath of 

 indifferent cells— the so-called satellite cells, which are homologous 

 with neurolemma cells. P^lsewhere are clumps of fibers, usually 

 with myelin and neurolemma. The single process from the cyton is 

 rarely visible in a section. A short distance away from the cyton 

 it divides into a peripheral and central process. The peripheral 



