GANGLIA 



149 



distinguished from the cerebrospinal type. The essential elements of 

 structure are the nerve cells, nerve fibers, and a supporting framework 

 of rather dense fibre-elastic connective tissue. 



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

 oerebrospinal ganglia, but are usually multipolar in the sympathetic. 

 The spinal ganglia of the lower vertebrates and of the embryo mammal, 



FIG. 164. BIPOLAR 

 CELL FROM A 

 SPINAL GAN- 

 GLION OF A FISH. 



(Barker, after 

 Corti.) 



FIG. 165. TRANSFORMATION OF 

 BIPOLAR CELLS INTO UNIPOLAR 

 CELLS IN THE GASSERIAN GAN- 

 GLION OF THE PIG. 



(Barker, after van Gehuch- 

 ten.) 



however, contain bipolar ganglion cells. In mammals the two processes 

 of the embryonal neuron fuse to form a single one which branches in 

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



In the ganglia of the acoustic nerve the primitive bipolar condition 

 of the neuron is retained; and the cell body is not surrounded by a 

 capsule. 



The nerve cells of all other ganglia are surrounded by a capsule of 

 flat epithelioid cells which form a complete investment for the nerve 



