COORDINATION 73 



Furthermore, recent investigations have led to the gener- 

 ally accepted conclusion that each axon is a part of only one 

 nerve cell; a single cell may give off more than one axon, 

 but the axon is never connected with more than one nerve 

 cell. Of these cells and of their connections with nerve 



FIG. 41. Four nerve cells 



A and C, from the cerebellum ; B, from the gray matter of the spinal cord ; 



D, from the cerebrum ; a, the axon. The cells A and D are stained so that the 



main body and the dendrites (p. 75) are a uniform hlack ; B and C are stained so 



as to show the nucleus and the cytoplasm 



fibers we can get a more definite picture by an examination 

 of the structure of the spinal cord. 



4. Structure of the spinal cord. When the vertebral canal 

 is opened a whitish cord is found within it, the spinal 

 cord, from each side of which arise thirty-one pairs of 

 nerves, or, in general, one pair for each vertebra. One 

 nerve of each pair arises on the ventral side of the cord, the 

 other on the dorsal side. These nerves are known as the 



