120 



THE NERVOUS TISSUES 



essential elements of structure are the nerve cells, nerve fibres, 

 and a supporting framework of rather dense connective tissue. 



Many of the nerve cells of the adult mammal are unipolar in 

 the cerebro-spinal ganglia, but are usually multipolar in the sympa- 

 thetic. The spinal ganglia of the lower vertebrates and of the 

 embryo mammal, however, contain bipolar ganglion cells. In mam- 



FlG. 115. A SMALL PORTION OF A HUMAN GASSERIAN GANGLION. 



a, funiculi derived from the nerve trunk ; &, nerve cells. Hematein and eosin. Photo. 



x 60. 



mals the two processes fuse to form a single one which branches 

 in a Y- or T-like manner soon after leaving the parent cell body. 



The nerve cells of all ganglia are surrounded by a peculiar 

 connective tissue capsule. It is composed of flattened endothe- 

 lioid connective tissue cells which form a complete investment for 

 the nerve cell and are continued on to its processes, possibly be- 

 coming continuous with the neurilemma. The capsule is not, as 

 a rule, closely applied to the cell, but leaves a narrow interval 

 which is occupied by lymph or " tissue juice." 



