204 



THE NERVOUS SYSTEM. 



Nerve-cells are strongly characterized by the possession of 

 processes, often greatly prolonged and very complex, ranging 

 in number from one to many ; at least one process is always 

 present. The processes consist largely of prolongations of 

 the spongioplastic fibrils of the cytoplasm. 



Nerve-cells are classed as unipolar, bipolar, and multipolar 

 according as they possess one, two, or several processes re- 

 spectively. Another variety of ganglion-cell, which may 



FIG. 77. 



Nerve-cells from cerebral cortex (Ramon y Cajal). A, small pyramidal nerve-cell ; 

 B, large pyramidal nerve-cells; C, D, polymorphous nerve-cells; G, neurite; E 

 and F, fibres in white matter. The arrows indicate directions of nerve-impulses. 



be called pseudo-unipolar, is apparently unipolar, but prac- 

 tically bipolar; it possesses a single process which soon 

 divides like a T into two processes ; embryonically this cell is 

 bipolar. 



