PHYSICAL AND LITERARY. 493 



main at reft *• But, as refpiration and 

 the motion of the heart, fufFer fome 

 change in time of lleep, i. e. become then 

 flower, fuller, and more equable, than 

 when we are awake f , it may be worth 

 while to inquire a little into the reafon 

 of this phaenomenon. 



It has been fliewn, that as the dilatation 

 of the ventricles of the heart is owing to 

 the force of the refluent venous blood ; 

 fo their contra(5lion is produced by the 

 fame blood acling upon them as a ftimu' 

 lus X : And that the heart can only be af- 

 feifled by ftimuli, in fo far as it is a fen- 

 tient organ, i. e, endued with feeling §. 

 Whence it muft follow, that the flownefs 

 of the pulfe in fleep, and indeed in every 

 other cafe, can only arife from one or 

 more of the following general caufes, viz. 

 X . A diminution of the ftimulacing quality 



of 



* Eflay on the Vital and other Involuntary motions 

 •f animals, Seel. xii. 



-J- Boerhaave Inftitut. Med. § 599, 



% Vid. Eflay on Vital and other Involuntary motioat 

 •f animals, SeQ.. iii. and iv. 



§ Ibid* Sedi. X. p. 271. &c. 



