" SLEEP AND DRKAMS." 69 



brain is palor during sleep than when awake, and Dr. 

 Hughlinga Jaclvson examined the arteries of the retina 

 of a man, and found them contracted after he had been 

 asleep some time. The large arteries in the nock are called 

 tlie carotid, from the verb Xapoo), to sleep, because when 

 they are firmly pressed, and the brain thereby deprived of 

 blood, the subject becomes unconscious. Miuiy of us know 

 that one way of getting to sloop is to oat a good dinner, 

 and then sit in an arm chair with our feet to the fire. The 

 explanation usually given is that the dinner draws blood 

 to one part, the lire to tlie other, and tho amount of blood 

 in tho brain is thereby diminished. 



There are, howevcsr. Treasons for thiidcing that this con- 

 dition is not tho cause of sleep, but tho eonsoquenco or 

 concomitant. We sleep, and then our circulations become 

 more languid, and the brain, where the flow of blood meets 

 with mauy imp(!dinients, suffers with tho rest of the body. 

 Tiuire is no good ground fin' supposing that our brains 

 become anaaniic towards niglit, and there are, moreover, 

 obstiM^es to the diminution of bh)od in the luiad which do 

 not exist elsewhere in tlie body. Tliore is, n(!vo7'thoh;ss, 

 a period, ranging from about 12 p.m. to 4 or 5 a.m., during 

 which the tomporattire, and probably the circulation of tho 

 body, are lowered, independently of surroundings. This is 

 the feeblest time of the twenty- four hours, and the time when 

 death is probably busiest. It may bo compared with the 

 other rhythmical phenomena of our bodily functions. But we 

 do not find the depth of sloop coincident with this decrease 

 of temperatnro and languid flow of blood. Direct experi- 

 ment (according to Hermann) shows that it increases in 

 intensity from the commencement : first quickly, then more 

 slowly, till the end of the first hour, and then it gradually 

 diminishes towards morning. 



