2$S O F SLEEP, SECT. XVIII, 21, 



ieen the experiment of a rn'an extending himfelf 

 acrofs the large (lone of a corn-mill, and that by 

 gradually letting the (lone whirl, the man fell afleep 

 before the (lone had gained its full velocity, and he 

 fuppofed would have died without pain by the con- 

 tinuance or increafe of the motion. In this cafe the 

 centrifugal motion of the head and feet muft accu- 

 mulate the blood in both thofe extremities of the 

 body, and thus comprefs the brain. 



JLafHy, we (hould mention the application of cold ; 

 which, when in a lefs degree, produces watchfulnefs 

 by the pain it occafious, and the tremulous convul- 

 fions of the fubcutaneous rnufcles ; but when it is 

 applied in great degree, is faid to produce fleep. To 

 explain this effect it has been faid, that as the veffels 

 of the ikin and extremities become firft torpid by 

 the want of the flimulus of heat, and as thence lefs 

 blood is circulated through them, as appears from 

 their palenefs, a greater quantity of biood poured 

 upon the brain produces fleep by its com-preilion of 

 that organ. But I (houl J rather imagine, that the 

 fenforial power becomes exhaufted by the convulfive 

 actions in confequence of the pain of cold, and of 

 the voluntary exercife previoufly ufed to prevent it, 

 and that the fleep is only the beginning to die, as the 

 fufpenfion of voluntary power in lingering deaths 

 precedes for many hours the extinction of the irrita- 

 tive motions. 



21. The following are the characteristic circum- 

 ilances attending perfect fleep. 



j. The power of volition is totally fufpended. 



2. The trains of ideas caufed by fenfation proceed 

 with greater facility and vivacity; but become in- 

 confi (lent with the ufual order of nature. The muf- 

 cular motions caufed by fenfation continue ; as thofe 

 concerned in our evacuations during infancy, and 

 afterwards in digeftion, and in priapifmus. 



3. The 



