THE NERVOUS SYSTEM 



339 



afferent or sensory cell; 3, an efferent or motor nerve cell, which is con- 

 nected with 4, an effector cell by a neurite. Further complications arise 



CEREBRUM 



CEREBELLUM- 

 CERVICAL PLEXUS 



BRACHIAL PLEXUS 



Fig. 300. — A general view of the nervous system of man as seen from behind. 



by the chaining together of additional nervous units within a central 

 nervous system until, in vertebrates, so few cells are devoid of nervous 



