( «7J ) 
After having considered the extent of the Cavity of 
the Heart, there remain two things to be examined. 
The hrft is, that in its back-part there are five Holes or 
Orifices, two whereof are on the Left Side : Thele are 
the Orifices of the two Funnels of the Auricles : They 
are covered by a large Valve lying flat upon them, 
fupported in its middle by the Prolongation of the 
Septum, which divides the Auricles, in fucb a manner, 
that half of It covers the Orifice of the Right Auricle , 
and the other half that of the Left 5 fo that this 
Valve refembles two folding Doors of a Porch, which 
have the fame fupporr, and where f one opens or 
(huts to the Right, and the other to the Left. It is 
vifible, that this Valve permits the Entrance of the 
Blood into the Ventricle of the Heart, but oppofes its 
return into the Auricles $ becaufe this Blood being once 
in the Heart, prefles by its own weight upon this dou- 
ble Valve , and keeps it clofe and flat upon thefe 
Orifices r Which confirms perfectly well the Office of 
the Valve ,. which is in the Foramen Ovale in the Heart 
of an Human Fcetur , the Difpofition being entirely the 
fame. The other three Holes lying on the Right fide 
of the Ventricle of the Heart, are the Orifices of the 
four Arteries which come out of the Bajis : Of thefe three 
Holes, that which is the mod Left is the Orifice of the 
Pulmonary Artery 5 that which is the higheft, is the 
Orifice of the Aorta Jinijlra defcendens 5 and that which 
is the mod to the Right fide, is common to the Artcria 
Aorta dextra , and to the fnperior Aorta. Each of thefe 
Orifices is furnifhed with two Semilunary Valves , which 
permit the Blood to pafs without difficulty from th eVen- 
tricle of the Heart into the Arteries, but hinder its 
i return into the Heart. ’Tis a pure Illufion, to place 
thefe Holes in ^different Ventricles 5 they are all in one 
and the fame Cavity j fo that the Blood enters into this 
only Gavity, by the two Holes which are on the Left 
Z 2 Side, 
