6i 68 



SCIENCE PRIMERS. 



[§v. 



' the right ventricle ; and you will have no difficulty in 



\ putting your fingers from the auricle into the ventricle 



\ and bringing them out again. 



J But hold the heart in one hand with the auricle 



^ upwards, and try to pour some water into the ventricle. 



f The first few spoonfuls will go in all right, and then 



f you will see some thin white skin or membrane come 



1 floating up into the opening and quite block up the 



] entrance from the auricle into the ventricle; the 



JM 



l'V2 



'•\ 



HAV 



Fig. ^.—The Orifices of the Heart seen from above, the Auricles and 



Great Vessels being cut away. 



P. A. pulmonary artery, with its semilunar valves ; Ao. aorta, do. 



R.A.V. right auriculo-ventricular orifice with the three flaps {Iv. i, 2, 3) of 

 tricuspid valve. 



L.A.V. left auriculo-ventricular orifice, with m.v. 1 and 2, flaps of mitral 

 valve ; b, piece of whalebone passed into coronary vein. On the left part of 

 L.A.V. the section of the auricle is carried through the auricular appendage ; 

 hence the toothed appearance due to the portions in relief cut across,. 



