344 PHYSIOLOGY AND HEALTH. 



brain, and the nerves of sensation, and those that convey 

 volition, sleep ; but the motory nerves of the heart and arte- 

 ries, and the lungs, never sleep. When a man dreams, his 

 brain is not in complete rest; and, in the cases of sleep- 

 walking, the sleep of the brain and of the nervous system is 

 still less perfect, and of course the system is less refreshed 

 by it. That sleep is most refreshing, and the best recruits 

 the frame, in which there is neither dream nor motion, but 

 absolute inaction of all the voluntary powers. 



CHAPTER VI. 



Night is the proper Season for Rest of the Brain. Brain gains 

 Power, by Exercise. Weakened by Over-Action. Connected 

 with other Organs; with Lungs, Stomach, Muscles. Effect of 

 Alcohol on Brain and Muscle^ ; on Mechanical Skill ; on Use of 

 Tools. 



790. There is a natural connection of the action and in- 

 action of the brain with the alternation of day and night. 

 The brain, as well as the muscles, has more vigor and a 

 greater power of action in the light of day, and is more prone 

 to rest and to recruit itself in the darkness of night. The 

 day is, then, the appropriate time for mental, as well as bodily 

 labor, and the night the proper season for sleep of the mind 

 and the brain. 



791. The stillness of the night, when the busy world is 

 quieted, and we are secure from interruption, seems to in- 

 vite the student to his books. Then the mind is not dis- 

 turbed with other claims upon its attention, and there is 

 then better opportunity for concentration of thought upon 

 any subject. Therefore some attend to external matters 

 during the day, or even sleep during some portion of it, and 

 reserve their mental labor the toil of the brain for the 

 night. It is an unprofitable habit of some clergymen to write 

 their sermons in the evening or night before they must be 

 delivered, and then, by concentrating the whole energy of 



