THE ANATOMY OF THE HEART AND BLOOD-VESSELS 329 



elevations, the papillary muscles, Mpm and Mpl, on the interior 

 of the ventricle. The cords are long enough to let the valve flaps 

 rise into a horizontal position and so close the opening between 

 auricle and ventricle which lies between them, and passes up be- 



Sd 



Mpm 



Fio. 104. The left ventricle and the commencement of the aorta laid open. 

 Mpm, Mpl, the papillary muscles. From their upper ends are seen the cordoe 

 tendinece proceeding to the edges of the flaps of the mitral valve. The opening 

 into the auricle lies between these flaps. At the beginning of the aorta are seen its 

 three pouch-like semilunar valves. 



hind the opened aorta, Sp, represented in the figure. The tricus- 

 pid valve is like the mitral, but with three flaps instead of two. 



Semilunar Valves. These are six in number : three at the mouth 

 of the aorta, Fig. 104, and three, quite like them, at the mouth 

 of the pulmonary artery. Each is a strong crescentic pouch fixed 



