SECT. XVIII. 21. OF SLEEP, 



through them, as appears from their palenefs, a greater quantity 

 of blood poured upon the brain produces fleep by its compref- 

 fion of that organ. But I fhould rather imagine, that the fenfo- 

 rial power becomes exhaufted by the convulfive a.clions in con- 

 fequence of the pain of cold, and of the voluntary exercife pre- 

 vioufly ufed to prevent it, and that the ileep is only the beginning 

 to die, as the fufpenfion of voluntary power in lingering deaths 

 precedes for many hours the extinction of the irritative motions. 

 21. The following are the characteriftic circumftances at- 

 tending perfect fleep. 



1. The power of volition is totally fufpended. 



2. The trains of ideas caufed by fenfation proceed with great- 

 er facility and vivacity ; but become inconfifterit with the ufual 

 order of nature. The mufcular motions caufed by fenfation 

 continue ; as thofe concerned in our evacuations during infan- 

 cy, and afterwards in digeftion, and in priapifmus. 



3. The irritative mufcular motions continue, as thofe con- 

 cerned in the circulation, in fecietion, in refpiration. But the 

 irritative fenfual motions, or ideas, are not excited ; as the im- 

 mediate organs of fenfe are not ftimulated into adion by exter- 

 nal objects, which are excluded by the external organs of fenfe j 

 which are not in fleep adapted to their reception by the power 

 of volition, as in our waking hours. 



4. The aflbciate motions continue , but their firft link is not 

 excited into action by volition, or by external ftimuli. In all 

 refpecls, except thofe above mentioned, the three laft fenforial 

 powers are fomewhat increafed in energy during the fufpenfion 

 of volition, owing to the confequent accumulation of the fpirit 

 of animation. 



VOL, I. Y ,SECI\ 



