64 



ANATOMY OF THE CENTBAL NERVOUS SYSTEM. 



but from a branch of the Vagus. The spinal sensory nerves are, therefore, 

 relatively small, and in consequence, also, the dorsal column of gray matter, 

 as shown in Pig. 29. 



But if, as in the ease of Trigla (Fig. 29, B), many sensory nerves enter 

 the spinal cord at any particular place, the dorsal column is much increased 

 at that level. Pig. 29, A, shows a section of the spinal cord of the white- 

 fish {Leuciscus rutilus). Xote here the small dorsal columns which receive 



Pig. 28. — The diagram of the spinal cord as seen from behind. Showing the 

 dorsal and ventral columns of the gray matter and the dorsal and ventral nerve- 

 roots, illustrating also what was said about the posterior traoia. 



relatively small roots. Note, also, that between the dorsal columns the 

 posterior tracts contain only a few fibers. 



The ventral columns from which the motor nerves arise are relatively 

 small in Trigla in the cervical region, in the white-fish they are very mucli 

 more strongly developed, btit in the spinal cord of the electric eel (Gymno- 

 tus, Pig. 29, C) they reach a very unusual development. In the last case the 



