PHYSICAL AND LITERARY. 495 



the fame circumftances. It remains, 

 therefore, that the flownefs of the heart's 

 motion in time of fleep be owing, either 

 to the flower return of the venous blood 

 to it, or to fpme diminution of its fenfi- 

 t>iUty. 



II. Every one knows, that the afFec-? 

 tions qf the mind difturb the motion of 

 the heart ; that the pulfe is quicker when 

 ■we fit or {land than when we lie ; and 

 that the adion of the mufcles of voluntary 

 piotion, not only promotes the return of 

 the blood to the heart, but determines it 

 thither, with much greater force thaii 

 ufual. In flcep, therefore, where the ho- 

 rizontal pofture of the body, the quief- 

 cenceof the voluntary mufcles, andcom- 

 pofute of the mind, all concur to render 

 the return of the venous blood to the 

 heart more equable and flow, the con- 

 tradlion of this mufcle muft be renewed 

 at greater intervals, and with more regu- 

 larity, than when we are awake, and the 

 circulation is quickened or diflurbed by 

 fome, or all, of the above naentioned cau- 



fes, 



