8o 



NORMAL HISTOLOGY. 



the cranial nerves, and especially of the sympathetic system, groups 

 of nerve-cells occur associated with the nerve-fibres in the form of 

 ganglia ; these may be large and conspicuous masses, as the Gasserian 



FIG. 96. 



Spinal ganglion, in longitudinal section, from cat : the groups of nerve-cells lie embedded among the 

 bundles of the nerve-fibres. 



ganglion of the trifacial nerve, or their size may be microscopic, as 

 many of the interstitial ganglia connected with the distribution of 

 the sympathetic fibres. 



The outer covering of the ganglion consists of a fibrous envelope, 

 a condensation of the adjacent epineurium in many cases, from which 



prolongations extend among 



FlG - 97- the nervous elements, where 



they break up into delicate 

 bundles of connective tissue, 

 which serve for the union 

 and the support of the cells 

 and the fibres. Some of the 

 nerve-fibres pass through 

 the ganglion on their way 

 to more distant points with- 

 out joining any of the nerve- 

 cells, while many others end 

 in or take origin from these 

 elements. The presence or 

 absence of the medullary 

 coat depends upon the char- 

 acter of the component 

 fibres of the nerve-trunk ; 

 before joining a nerve-cell, 



however, the medullary substance disappears, while the neuri- 

 lemma of the fibre continues and becomes the nucleated capsule 



9 



Section of spinal ganglion more highly magnified : 

 g; the nerve-cells, cut in various planes, surrounded 

 by the nucleated sheath (c) ; a, the medullated nerve- 

 fibres, on which several nodes of Ranvier are seen ; t, 

 cells of the supporting connective tissue. 



