C 47 I 
ricles. But there being fo much Difparity between 
the contractile Strength of the Ventricles and that of 
the Auricles, there muft neceflarily be fome other 
Caufe, which, when the Heart is fully contracted, 
makes it unbend again, or ceafe to contract ; by 
which means the Auricles, though fo very weak in 
companion of the Ventricles, have Power enough to 
throw in Blood, and thereby to diftend the Ventri- 
cles to a certain Degree, before they are capable of 
acting again* 
CIIL 
. If we might be allowed to make an Eft i mate of 
the Difference between the contractile Strength of 
the Heart and its Auricles,, from the Difference of 
their Bulk, or Quantity of Fibres/ \ve fhould find it 
to Jbe about nine to one; as 1 have obfervea, by 
weighing the Hearts- of feveral- Animals, and their 
Auricles ffparately.- 
Hcnce it does not feem reafonabPe to' think, that 
the weak Efforts of the Auricles would be fufficient 
to caufe the ^Diajiole of the Heart, without fome 
other Affiftant. 
CV. 
One great Ufe of the Auricles is, to receive a 
Quantity of Blood, during the Syftole of the Heart, 
fufficient to fill the Ventricles again at their 
Jlole* 
