SLEEP 141 



will produce unconsciousness. The theory supposes that 

 the vasomotor center in the medulla becomes fatigued 

 during the day's work, allows the vessels in other parts 

 of the body to dilate and hold more blood and auto- 

 matically decreases the amount flowing through the 

 brain. No theory has met all the objections. We can, 

 in effect, say nothing confidently save that sleep is nec- 

 essary, that it follows bodily more than mental activity 

 and that some conditions, notably mental worry, may 

 produce a condition (insomnia) most trying to patient, 

 physician, and nurse, and sometimes beyond the power 

 of drugs. 



Dreams are attendants of sleeping hours which have 

 not been satisfactorily explained. They at least serve 

 to show that all of the brain is not asleep, or not pro- 

 foundly asleep ; but whether we dream during the en- 

 tire sleeping period and remember only those dreams 

 which immediately precede waking, or whether we 

 dream only when in the light, or disappearing, sleep 

 which precedes returning consciousness, is a matter 

 entirely unsettled. 



Hypnotic sleep should be mentioned, but not dis- 

 cussed. Many observers doubt its occurrence while 

 those who believe in its existence can furnish no satis- 

 factory explanation of the phenomenon. 



The sleep induced by drugs should be alluded to. It 

 is neither so restful nor so recuperative as normal sleep, 

 though it may be much more profound. The type of 

 drug-induced sleep will vary with the hypnotic em- 

 ployed and with the dose, as well as with the suscepti- 

 bility of the patient and his drug habits and ante- 

 cedents. 



