24 PHYSIOLOGY OF FARM ANIMALS [CH. II 



Tf we follow a nerve fibre along its entire length we finally 

 come, either in one direction or the other, to the nerve cell of 

 which the axon of the fibre is in reality a part. For the nerve 

 cells give off prolongations, sometimes a great many and some- 

 times only a iew, and these prolongations become the axons of the 

 nerve fibres. A nerve cell possesses a nncleus like all other cells 

 and external protoplasm which contains characteristic fibrils 

 and grannies. The name neuron is applied to the nerve cell 

 together with all its various prolongations, including the axons 

 of the nerve fibres. (See fig. 46, p. 98.) 



