\ PHYSICAL ann LITERARY. 437 
heart, fuffer fome change in time of fleep, 
i.e. become then flower, fuller and more e- 
quable, than when we are awake *, it may 
be worth while to enquire a little into the 
reafon of this phaenomenon. 
Ir has been fhewn, that as the dilatation 
_of the ventricles of the heart, is owing to 
the force of the refluent venous blood; fo 
their contraction is produced, by the fame 
blood acting upon them as a fimulus+: and 
that the heart can only be affected by Amul, 
‘in fo far as it is a fentient organ, 7. @. en- 
dued 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. wiz. 1. A diminution of the ftimu- 
lating quality of the blood. 2. Its flower re- 
turn to the heart; or, 3. A lefs degree of 
fenfibility or aptitude for motion in the heart 
itfelf. 
I, 
* BoeRHAAVE Inftitut. Med. § 599. 
+ Vid. Effay on Vital and other Involuntary motions of | 
animals, fect iii. and iv. 
f Ibid. (e@. x. p. 271. &e. 
