C 49 ] 
But the great Difficulty in accounting for the "Dior 
ftole of the Heart, is from the Difproportion between 
its contractile Power, and that of the Auricles ^ it 
being plain, from what has been Paid above, that 
the Momentum of the Blood in the Veins is ftopt by 
the Contraction of the Auricles, fo that the Ventri- 
' cles of the Heart can receive no other Impulfe from 
the Blood at that time, than what is derived from 
the Contraction of the Auricles. 
CVIIL 
Hence therefore it follows, that if the Syfiole was 
the natural State of the Heart, and to which it al- 
ways tended with its full contractive Power, the 
Impulfe of the Blood, from the Contraction of the 
Auricles, could never be able to dilate it. 
CIX. 
Dr. Lower makes the Syfiole the natural State or 
ACtion of the Heart, and the Diafiole the violent 
one : Boerhaave, on the contrary, makes the Syfiole 
the violent, and the Diafiole the natural State. But 
perhaps neither of thefe Opinions may be right, in 
the ftriCteft Senfe ; for if we look back we (hall 
find, that if the. Fibres were not tenfe they could 
not be elaftic ; and if fome Violence was not put 
upon them, by the Impulfe of the circulating Fluids, 
they would not be tenfe : Hence it appears, that 
Elafticity proceeds from a State of Violence. 
G CX. 
i 
