ANIMALS. 13 



very great obscurity by somewhat more obscure : 

 leaving, therefore, those spirits to open and shut 

 the entrances to the brain, let us be contented 

 with simply enumerating the effects of sleep up- 

 on the human constitution. 



In sleep, the whole nervous frame is relaxed, 

 while the heart and the lungs seem more forcibly 

 exerted. This fuller circulation produces also a 

 swelling of the muscles, as they always find who 

 sleep with ligatures on any part of their body. 

 This increased circulation also may be considered 

 as a kind of exercise, which is continued through 

 the frame ; and by this the perspiration becomes 

 more copious, although the appetite for food is 

 entirely taken away. Too much sleep dulls the 

 apprehension, weakens the memory, and unfits 

 the body for labour. On the contrary, sleep too 

 much abridged emaciates the frame, produces 

 melancholy, and consumes the constitution. It 

 requires some care, therefore, to regulate the 

 quantity of sleep, and just to take as much as will 

 completely restore nature, without oppressing it. 

 The poor, as Otway says, sleep little ; forced, 

 by their situation, to lengthen out their labour to 

 their necessities, they have but a short interval 

 for this pleasing refreshment ; and I have ever 

 been of opinion, that bodily labour demands a 

 less quantity of sleep than mental. Labourers 

 and artisans are generally satisfied with about 

 seven hours ; but I have known some scholars 

 who usually slept nine, and perceived their facul- 

 ties no way impaired by over-sleeping. 



