The Nervous System 



227 



Various emotions also have a reflex 

 action upon the sympathetic system. 

 Thus terror dilates the pupils of the 

 eyes, fear acts upon the nerves of the 

 small blood vessels of the face to pro- 

 duce pallor, and the sight of an acci- 

 dent, or even the emotions produced by 

 hearing of one, may excite nausea and 

 vomiting. 



The maintenance of the tone of the 

 arteries all over the body, as we have 

 learned, is one of the special functions 

 of the sympathetic system (sec. 232). 

 * 345, Need of Rest. The tissues of 

 the body, as has been emphasized in 

 the preceding chapters, are subject to 

 constant waste, which goes on every 

 moment, from the first breath of 

 infancy to the last moment of old age. 

 We should speedily exhaust our vitality 

 from this continual loss, but for its 

 constant renewal. This exhaustion of 

 life is increased by exertion, and the 

 process of repair is vastly promoted by 

 rest. Thus, while exercise is a duty, 

 rest is equally imperative. 



The eye, when exact ingly used in 

 fine work, should have frequent inter- 

 vals of rest in a few moments of dark- 

 ness, by closing the lids. The brain 

 should have occasional seasons of rest 

 and refreshment by a dash of cold 

 water upon the forehead, and a brief 



FIG. 124. Nerve Trunks 

 of the Right Arm. 



