98 HISTOLOGY. 



A. Nerve Cells. 



The nerve cells (also called ganglion cells) vary in size from 

 4 to 135 (i in diameter in mammals, and are as large as 200 ^ 

 in fishes. Their form is variable round, spindle-shaped, 

 polygonal, or irregularly stellate. The processes of the cells 

 may be divided into two main groups : 



(a) The axis-cylinder process (axone, neuraxone, Deiter's 

 process) develops more quickly than the other processes, and 



FIG. 68. 



Multipolar nerve cell from the medulla of a rabbit. The axone is broken off. X 150. 



has always a smooth, even margin. It leaves the cell at an ele- 

 vation known as the axone hillock, and may proceed out of the 

 central nervous system to form an axis cylinder of one of the 

 fibres of a peripheral nerve. On the other hand, it may end 

 in the central nervous system by brandling. It almost always 

 sends off lateral branches, the so-called collaterals, which cause 

 a communication to be established between the cells to which 

 the axone belongs and other cells. 



