308 APPLIED PHYSIOLOGY 



for rising is desirable. If a student would go to bed when 

 he feels sleepy, and would sleep an hour or two longer 

 each night, he would feel able to do more and better work 

 during his working hours. 



557. Sleeplessness. Like other organs while resting, the brain 

 contains but a small quantity of blood during sleep. If a large amount 

 of blood continues to flow through it, sleep will be impossible. Often 

 when a person cannot sleep he can feel the pulse in his temples throb 

 and hear it as his head lies upon the pillow. 



A common cause of sleeplessness is an empty stomach. A light 

 lunch will often cause the arteries of the abdomen to dilate and take up 

 the blood which circulates in the brain and so relieve the cause of sleep- 

 lessness. 



Lack of work during the day may be a cause of sleeplessness. Many 

 a man finds himself suddenly unable to sleep when he retires from active 

 business. It seems to be a law of nature that he who does not work 

 cannot sleep, for he is not tired enough to need a rest. Occupation for 

 the mind and body will give such persons a good night's sleep. 



Worry will also cause sleeplessness, for it keeps the cells of the brain 

 in action just sufficiently to attract the blood to the head. The brain 

 can endure extremely hard work if it only gets fest between times. 



Narcotics, like opium and chloral, will always produce sleep if taken 

 in sufficient doses. But they injure the cells to a greater degree than 

 they do good. In times of anxiety the temptation to resort to them is 

 great, but their use at such times invariably leads to a habit of using 

 them, with all its accompanying evils and dangers. 



558. Dreams. Sometimes during sleep the sensory and 

 motor regions recall their memories with the vividness of 

 real life. This is a dream. The thought regions rarely 

 take part in a dream. Disordered memories of the sensory 

 and motor regions seem to be realities, but in the absence of 

 judgment they seem harmonious and natural, and we recog- 

 nize their fantastic nature only when reason returns with 

 the waking hours. Formerly dreams were supposed to be 

 heralds of events to come; but now it is known that they 

 are but the shadows of previous experiences. 



