HUMAN PHYSIOLOGY 



CHAP. 



FIG. 117. Nerve cells of a rat 

 (Pratt) , 



tion called the axone, and several shorter, treelike 



branches called dendrites. Every nerve cell has a cell 



body, an axone, and den- 

 drites. Some nerve cells with 

 their projections are very 

 long. A cell body located in 

 the spinal cord of the neck, 

 sends its axone out to the fin- 

 gers, and some in the lower 

 part of the cord send their 

 axones to the toes. A single 



nerve fiber may extend the whole length of the arm or 



of the leg. Some of the cell 



bodies of the cord are large 



enough to be seen with the 



naked eye. Others are very 



small and have short axones 



and dendrites. 



The dendrites serve to 



connect one cell with other 



cells and carry messages to 



the cell bodies of which they 



form a part. The cell body 



receives the message over 



the dendrites and directs it 



out over its axone. The 



axone carries the message 



from the cell body to a muscle or to a gland. Some- 

 times the dendrites are very long, bringing messages a 



long distance. 



FlG. 118. Human nerve cell, show- 

 ing dendrites, cell body, and 

 axone. (From Huxley.) 



