\ 



THK HEART 



from the right auricle. Hold up the heart by the right auricle 

 with both hands and get some one to pour water through it into 

 the right ventricle till it runs over, and then to press gently the 

 w.illof the right ventricle with the finger; three flaps of membrane 

 at once spring out from the sides, and meeting one another in 

 the middle, completely shut off the ventricle from the auricle. 

 These three flaps of membrane form a valve called the tri- 



< * 



m.r.a 



Fit;. 41. View of the orifices and valves of the heart from below, the whole of the 

 two ventricles being cut away. 



Ao, aorta; f.-l, pulmonary artery, each with its three cups of the closed scmilunar 

 valves seen convex from below. RAl', opening between the right auricle and 

 right ventricle, surrounded by the three flaps, t.v.i, t.v.i, t.r-.T,, of the tricuspid 

 valve with < hordx tendinea: between them, to which three cords are tied, taking 

 the place of the papillary muscles. I.A V, opening between the left auricle and 

 left ventricle, with the two flaps nt.-:\, ;//.:.., of the mitral valves and chorda: 

 tendinea:, to which cords arc tied. 



cuspid valve. The valve bulges up when you press the 

 ventricle because it will not allow fluid to pass from the 

 ventricle to tin- auricle. Do the same thing on the left side, 

 and you will find two flaps of membrane separating the left 



