PHYSICAL AND LITERARY. 50? 



After whsit has been faid of the 

 ilownefs of the heart's motion in fleep, it 

 will be ealy to fhew why refpiration 

 fliould be performed then at greater inr 

 tervals. 



The caufe exciting the alternate con- 

 |:ra<5lion of the infpiratory mufcles, is an 

 uneafy fenfation in the lungs, occafioned 

 by the blood pufhed into their vefFels by 

 the right ventricle of the heart f. If then 

 lefs blood is fent, in a given time, into 

 the lungs, in fleep, than when we arc a- 

 yrake, the neceflity of new fupplies of 

 frefli air will be lefTened, and confequent- 

 ly infpij-ation will be performed at greater 

 intervals. 



Further, as in tipae of fleep the fen- 

 iibility of the lungs, like that of the heart 

 and guts, mud be fomewhat impaired, 

 fefpiration muft alfo, on this account, be 

 performed more flowly ; for the infpira- 

 tory mufcles will not be excited into ac- 

 tion till a greater degree of irritation than 

 ufual be occafioned by the bipod accu- 

 mulated 



• Eflay on vital and involuntary motions, &c. p. 176. 



kc. 



IL 



