386 MAUEY ON SLEEP AND DEEAMS. 



nature ; and explains many of those anomalous condi- 

 tions which seem to violate this unity, and have fur- 

 nished food for credulity in all ages. 



Pursuing this analysis of the functions affected in 

 sleep, the external senses sight, hearing, and touch 

 are most obvious to familiar observation. Their sen- 

 sibility is suspended to all ordinary impressions coming 

 from without ; and there are degrees, even of natural 

 sleep, so profound Oavdra) ayyivTa eoi/cwg that it is 

 difficult to arouse them from it. We cannot affirm 

 that all the senses are equally affected at the same time; 

 though under the conditions of sound and healthy 

 sleep it is probable that they are so. In the passage 

 from drowsiness and somnolence into actual sleep, it is 

 interesting to note (and to a certain point the sleeper 

 can do this for himself) the dimness gradually over- 

 shadowing those subtle organisations which connect us 

 with the outer world. The condition is one so familiar 

 that we are wont to regard these changes if regarding 

 them at all rather as matter of amusement than curi- 

 osity. To the physiologist, looking on them with more 

 watchful eye, they become the interpreter of much that 

 is of deep interest to his science. 



These natural and simpler conditions of sleep may 

 be studied in various ways, but in no manner so effec- 

 tually as by watching the moments of passaged to sleep 

 and the passage out of it. Each by circumstances may 

 be rendered so sudden as to leave little scope for ob- 

 servation. But, under ordinary conditions, the passage 

 is gradual enough to allow those successive changes to 

 be marked which occur both in bodily and sensorial 



