500 ESSAYS AND OBSERVATIONS 



ilowly than whea we are awake *. But, 

 from what has been faid, it appears, tha^ 

 the fuhiefs of the pulfe in fleep is not 

 owing to the quicker circulation of the 

 blood, but to a leis degree of fenfibility 

 in the heart, whereby its ventricles arq 

 not excited into contradlion, till they have 

 been more fully dilated than ufual, by 

 the returning blood. It is, however, to 

 be obferved, that the fulnefs of the pulfe 

 in fleep, may be owing partly to the fluids 

 pafling, with greater difficulty, through 

 the very fmall lateral arteries, and the ie- 

 cretory tubes of the glands f. For we 

 know that the fulnefs or foftnefs of the 

 pulfe does not depend folely upon the 

 quantity of blood thrown out by the left 

 ventricle of the heart, but alfo upon the 

 more or lefs difficult pafTage of this fluid 

 through the extreme arteries ; fince, in 

 proportion as thefe are obftrudled or open, 

 a greater or lefs refiftance will be oppofed 

 to the blood projected by the heart. 



After 



f Boerhaave infticut, med, § J97. 

 f Exercit. de fosnao ec vigilia, § 4*0 



