I 



THE ARRANGEMENT OF THE MUSCULATURE OF THE HEART 269 



addition, this firmness and greater prominence of the wall of the orifice 

 must tend to lessen the size of the passage. The arrangement of the 

 chordce tendinece must seem very perplexing to the casual observer. 

 On closer examination, however, it will be seen that they arise from 

 the papillary muscles which are situated at some distance below the 

 basal portions of the different valvei flaps. A very clear picture of 

 the course pursued by them may be obtained in the left ventricle, in 

 which only two papillary prominences are present. In the right cavity, 



on the other hand, the condi- 

 tions are less simple, because we 

 find here three papillary projec- 

 tions and, in addition, also a 

 number of chordae which origi- 



FiQ. 132. Fig. 133. 



Fig. 132. — Heart of the Cow, With Left Auricle and Ventricle Laid Open. 

 {MiiLler.) 



a, Root of the aorta; h, spaces in the wall of the auricle; c, c, orifices of the pulmonary 

 veins; Z, Z, pulmonary veins; p, p, papillary muscles; q, q, columnse carnese. A, orifice 

 of the aorta; K, left ventricle; S, septum; V, left auricle; W, lateral wall of left ventricle; 

 1, 1, 2, leaflets of mitral valve. 



Fig. 133. — Schema to Show Fan-like Distribution op Chordae Tendinece (C) from 

 A Single Papillary Muscle (P), Situated Underneath (V), Two Adjoining Valve 

 Flaps. 



nate from the septum itself. Very soon after they leave their places 

 of origin, the individual chordae divide into smaller strings which ex- 

 tend fan-like through the cavity to be inserted eventually upon the 

 free margins and more centrally located areas of the flaps above them. 

 Moreover, as the papillary muscles are placed as a rule almost ver- 

 tically below the points of union between two neighboring flaps, each 

 colony of chordae concerns itself chiefly with the two margins nearest 

 to them. In reaching their points of insertion they frequently cross 

 one another, but without impairing their movement. 



The structure and general arrangement of the chordae prove very 



