230 OUR BODIES AND HOW WE LIVE 



injurious habits, whether in the important or the compara- 

 tively trifling matters of daily living, are drafts drawn on 

 the future, which must be met at no distant day with all 

 the attendant perils of physical or mental bankruptcy. 



310. The Importance of Sleep. The need of sleep is 

 self-evident, and the loss of it is one of the more common 

 causes of ill health. The muscles and the nerves, the 

 brain in particular, are in full activity when we are awake. 

 Repair goes on every moment, whether we are awake or 

 asleep. During the waking hours, however, the waste of 

 the tissues is in excess of the repair, while during sleep the 

 repair exceeds the waste. 



Hence the good mother, nature, at regular intervals, 

 causes all parts of the bodily machinery to be run at their 

 lowest pressure. In other words, we are put to sleep. 



311. Rest of Important Organs during Sleep. During 

 sleep the heart beats, the lungs take in air, and the stomach 

 digests its food ; but these great organic processes are 

 carried on but feebly. The vital organs rest because they 

 are worked at their lowest rate. 



The eye, the ear, the brain, and the nerves are rested by 

 darkness, silence, and unconsciousness. The tired muscles 

 thus regain their vigor and the exhausted brain is refreshed. 



Sleep is more or less sound according to circumstances. 

 Fatigue, if not too great, aids it ; while idleness lessens it. 

 Anxious thought and pain and even anticipated pleasure 

 may prevent it. The sounder the sleep, the more the body 

 and the mind are refreshed. 



312. Hints about Sleep. The best time for sleep is at night. 

 The soundest and best sleep is obtained during silence and 

 darkness. People who are forced to work at night and to 

 sleep during the day usually have a strained and wearied look. 



