8 4 



PHYSIOLOGY FOR BEGINNERS 



CHAP. 



ventricle from the left auricle. This valve is called the 

 bicuspid or mitral valve. 



Pinch up the wall of the right ventricle at its lowest part, 

 close to the apex of the heart, and cut the chamber open with 

 scissors. Go on cutting upwards a short distance, at the front 

 and at the back, keeping on the front of the heart close to the 

 oblique groove, and on the back of the heart close to the 

 middle vertical groove, until the cavity is laid well open. The 

 wall of the right ventricle is thicker than that of the auricles, 



Iva 



FIG. 42. View of the orifices and valves of the heart from above, the auricles and 

 vessels being cut away. 



Aa, aorta; PA, pulmonary artery, each with its closed semilunar valves; RAT, 

 opening between right auricle and right ventricle, closed by the three flaps Ai, 

 h'2, tvi, of the tricuspid valve ; LA V, opening between left auricle and left 

 ventricle closed by the two flaps m.-u.\, m.v.2, of the mitral valve; b, bristle 

 passing into coronary vein. 



and the inner surface is more uneven. The three flaps of the 

 tricuspid valve will be seen hanging down. Each flap is a 

 thin transparent membrane, roughly triangular in shape, fixed 

 to the wall of the ventricle above, and with its tip hanging 

 down below. Attached to the sides and tip of each flap are 

 several thin white cords passing from it to little projections or 



