viz MECHANICS OF THE HEAET 191 



constructed than the tricu spiel, to meet the greater force they have 

 to encounter. 



Kiirschner (1844) was the first to show that not a few of the 

 muscular fibres descend from the auricle to the superior or internal 

 surface of the valvular fibres. Oehl (1861) described small muscle 

 bundles which accompany the larger cords of the mitral valves. 



L I 



r^Vi 



ire 



_M-d 

 -II 



in 



FIG. 58. A, Mitral valve of man, seen from below. The whole valvular ring has been spread out 

 in one plane, by a section through the median line of the great flap. B, Tricuspid valve of 

 man, seen from below. The valvular ring has been cut at the junction of the antero-external 

 and the internal flaps. I'.a, Anterior papillary muscles ; P.p, posterior papillary muscles ; 

 M.d, right flap of mitral valve ; M.g, left flap of mitral ; T.e.a, exterior and anterior flaps of 

 tricuspid ; T.e.p, exterior and posterior flaps of tricuspid ; T. i, interior flap of tricuspid ; L, L, 

 accessory tongue of valves ; A, great arch of free border of valves ; a, a, small arch of free 

 border of valves. I, Tendinous cords of first order ; II, tendinous cords of second order ; III, 

 tendinous cords of third order. (Marc See.) 



Paladino (1876) described muscle fibres that are continued from 

 the base of the ventricle to the lower or internal surface of the 

 valves. 



It is certain that without these valves, with which the auriculo- 

 ventricular orifices are provided, not a single drop of blood could 

 pass from the ventricles to the arteries during systole ; it would 

 all be forced back into the auricles and veins, where the pressure is 

 very low. 



Many theories are current about the function of these valves, . 



