i6z OF SLEEP. SECT. XVIII. i j. 



fenfes are alfo alive and excitable In our fleep , but as the ftimuli 

 of external objecls are either excluded from them by the dark- 

 nefs and filence of the night, or their accefs to them is prevented 

 by the fufpenfion of volition, thefe nerves of fenfe fall more 

 readily into their connexion with fenfation and with aflbciation j 

 becaufe much fenforial power, which during the day was ex- 

 pended in moving the external organs of fenfe in confequence 

 of irritation from external ftimuli, or in confequence of volition, 

 becomes now in fome degree accumulated, and renders the in- 

 ternal or immediate organs of fenfe more eafily excitable by the 

 other fenforial powers. Thus in refpecT: to the eye, the irritation 

 from external ilimuii, and the power of volition during our 

 waking hours, elevate the eyelids, adapt the aperture of the iris 

 to the quantity of light, the focus of the cryftalline humour, and 

 the angle of the optic axifes to the diftance of the objeft, all 

 which perpetual activity during the day expends much feniorial 

 power, which is faved during our fleep. 



Hence it appears, that not only thofe parts of the fyftem, 

 which are always excited by internal ftimuli, as the ftomach, 

 inteftinal canal, bile-duels, and the various glands, but the or- 

 gans of fenfe alfo may be more violently excited into aclion by 

 the irritation from internal ftimuli, or by fenfation, during our 

 fleep than in our waking hours ; becaufe during the fufpenfion 

 of volition, there is a greater quantity of the fpirit of animation 

 to be expended by the other fenforial powers. On this account 

 our irritability to internal ftimuli, and our fenfibility to pain or 

 pleafure, is not only greater in fleep, but increafes as our fleep 

 is prolonged. Whence digeftion and fecretion are performed 

 better in fleep, than in our waking hours, and our dreams in the 

 morning have greater variety and vivacity, as our fenfibility in- 

 creafes, than at night when we firft lie down. And hence epi- 

 leptic fits, which are always occafioned by fome difagreeable fen- 

 fation, fo frequently attack thofe, who are fubjecl; to them, in 

 their fleep \ becaufe at this time the fyilem is more excitable by 

 painful fenfation in confequence of internal ftimuii ; and the 

 power of volition is then fuddenly exerted to relieve this pain, 

 as explained Sed. XXXIV. i. 4. 



There is a difeafe, which frequently afFe6ts children in the 

 cradle, which is termed ecftafy, and feems to con (i ft in certain 

 exertions to relieve painful fenfation, in which the voluntary 

 power is not fo far excited as totally to awaken them, and yet is 

 fufficient to remove the difagreeable fenfation, which excites 

 it ; in this cafe changing the pofture of the child frequently 

 relieves it. 



I have at this time under my care an elegant young man 



about 



