292 



THE INTERNAL ENVIRONMENT OF THE BODY 



Part III 



Fig. 16.13. The underside of the human brain and the roots of the cranial 

 nerves. Lines are extended from the roots to show the structures with which each 

 nerve is associated. See also Table 16.1. (Courtesy, Ciba Collection of Medical 

 Illustrations. Drawings by Frank H. Netter, 1953.) 



and divide into small branches supplying the muscles, skin, and other struc- 

 tures. They contain the sensory processes over which all impressions of the 

 environment are brought into the spinal cord and brain. They bring to us 

 the raw materials of mind, everything we know of the world. Axons of motor 

 neurons in the brain and cord carry the impulses that direct movements of 

 muscle which largely comprise behavior. Facial expression is muscular ex- 

 ercise; so is a large part of personality. 



