Sect. XVIII. 21. OF SLEEP. 169 



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- 

 riai pov/er becomes exhaufted by the convulfive actions in con- 

 ■fcquence of the pain of cold, and of the voluntary exercife pre^ 

 vioufly 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 irritative motions. 

 21. The following are the chara&eriftic 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 inconfiftent 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 fecretion, in refpiration. But the 

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

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

 nal objecls, which are excluded by the external organs of fenfe ; 

 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 fir ft link is not 

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

 refpects, except thofe above mentioned, the three laft fenforiaJ. 

 powers are fomewhat increafed in energy during the fufpenfion 

 of volition, owing to the confequent accumulation of the fbiris 

 of animation. 



* W 



Vol. I* ,• *Y SEC I 



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