THE PROPERTIES OF EACH PART OF THE REFLEX ARC 799 



THE NERVE CELL 



Aside from being a meeting place of fibers coming from various 

 sources, the nerve cell may have other functions, such as that of rein- 

 forcing impulses, just as a relay may reinforce an electric current. It 

 is also responsible for maintaining the nutrition of the axon with which 

 it is connected. In the case of the posterior root fibers of higher ani- 



Fig. 208. Normal cell from the anterior horn, stained to show Nissl's granules, a, the axon. 



(From Howell.) 



mals, this function is probably the most important which the cell per- 

 forms, for it has been found by separating the ganglia from their blood 

 supply in the frog that, although the cells degenerate in about two 

 weeks, sensory impulses continue to be transmitted through the gan- 

 glia. Similar observations have been made in the case of the crab, in 

 which the cell bodies of the neurons lie on the surface of the ganglion 



