222 



THE NERVOUS SYSTEM 



cylinder. Bipolar cells are prolonged in two directions, and may 

 be looked upon as simply protoplasmic enlargements of the nerve 

 fiber. This cell is frequently covered by a connective tissue en- 

 velope which is continuous in both directions with the sheath of 

 Schwann. Multipolar cells have three or more prolongations, 



Nerve proc 

 or axone 



Neurilemma. ......... 



Neurilernma 



Nerve- cell. 



Terminal . 

 branches. 



A B 



FIG. 65. 



A, efferent neuron; B, afferent neuron. 



(Brubaker.) 



one of which always becomes continuous with the axis cylinder 

 and is called the axis-cylinder process, the neuraxon, or the axone. 

 The other poles branch in various irregular directions like the 

 limbs of a tree, and are hence called dendrites. They also go 

 under the name of protoplasmic prolongations. Some of these 

 unite the cells to contiguous cells by interlacing with, but not 



