r 308 ] 
If this be denied, let the^ody of an animal be taken 
quickly after death, and let a warm mild fluid of 
any kind be injected gently into the heart, fo as to 
fill it. When this is done, we fhall fee the heart 
quicken and contract, as in the life of the animal. 
This experiment was fird didindly mentioned by 
Peyer a Switzer (fee a fmall treatife of his, printed 
anno 1682, at Amsterdam, and intituled, Miracuhun 
anatomicnm in cordibus fujc it at is) and is now known 
to every anatomid. But if this efled is thus con- 
lbantly produced foon after death, how much more, 
when the animal is alive ? And if, by the introduc- 
tion of any common fluid, with the bare addition of 
a warmth cognizable by our fenfes, how much more 
by the introdudion of the living blood, an inimitable 
and wonderful fluid, and the immediate fubjed of 
the vital warmth ? 
If therefore it is granted, that we ought not to ad- 
mit more caufes of natural things than are real (and 
prefent for the occalion) and fufflcient for explaining 
the appearances (# ), and we muft grant a rule, whofe 
ufe is fo obvious in the Newtonian, which is the phi- 
lofophy of nature ; we fhall, I fay, alfo grant, that the 
contradion of the heart, in its natural date, in a living 
animal body proceeds folely from, or is mechanically 
caufed by, the warm blood, flowing into, and filling, its 
flefhy fubdance in every part. Which was to be proved. 
Corollary . 
The fubfequent relaxation admits no difficulty : 
for if the blood is the immediate mechanical caufe of 
the contradion, when the blood is removed, the ef- 
fed ceafes. 
Lemma (*) 
(*) Newton, R. 1. 
