SLEEP. 695 



diurnal revolution in my intellect and feelings : in the morning 

 my intellect is stronger, as is that of all persons necessarily after 

 repose ; but in the evening all my social feelings are strikingly 

 more acute. I often am deeply distressed in the evening, when 

 reflecting on the loss or absence of those dear to me, arid at the 

 misfortunes of others not connected with me, till the very mo- 

 ment I go to bed and fall asleep ; and in the morning can reflect 

 upon the very same things with coolness, and perhaps am 

 indisposed to reflect upon them at all. 



Again, brutes have their seasons, periods in which certain 

 propensities become ungovernable, for travelling, for singing, 

 building, for the joys of love. 



Morbid phenomena frequently have periodical recurrences 

 fever, pain, epilepsy, &c., and the intermission may be hours, 

 days, weeks, months, years. 



All brutes, probably, except those whose life is of very short duration, sleep. 

 They sleep, however, at different periods of the twenty-four hours ; so that 

 according to their waking period they have been divided into diurnal, crepus- 

 cular, and nocturnal. Though darkness is not the cause of sleep, its effect 

 upon diurnal birds is strikingly shown, if darkness supervenes in the day : I 

 have been amused to see my birds go to sleep in the morning during a solar 

 eclipse, and awake again when it was over. Those which prey by night, like 

 the cat, see better in darkness from the structure of their eyes, and pass the 

 greater part of their time in sleep ; while those which do not, are awake the 

 greater portion of the twenty-four hours. The former are said to reverse their 

 natural habits if in captivity, and to sleep at night. Carnivorous brutes sleep more 

 than herbivorous. Most brutes, we are informed, sleep longer in winter than in 

 summer. Brutes generally have a certain character of sleep ; all hares, cats, 

 birds (a goose is a far better night watch than a dog), &c. being light sleepers : 

 bears, badgers, turtles, &c. heavy sleepers. Some, as the hare, always sleep 

 with their eyes open (Dr. Macnish, p. 25. sqq.): some sleep well standing, 

 and horses have been known to stand for thirty days. Those which eat at long 

 intervals, as ^some reptiles, have been observed to sleep for days after their 

 enormous meal. 



Plants have been said to sleep, from periodic changes in the position of an 

 entire leaf or of the several leaflets of which a compound leaf is formed. The 

 leaf stalks bend upwards or downwards, so that the flattened surface of the leaf 

 is elevated or depressed : the upper surface of some leaflets and the under of 

 others is brought together. These changes are influenced by light and heat, 

 but not primarily induced. For, in a darkened room, the leaflets of sensitive 



