306 



THE HEART. 



and are retained in position within the ventricle by the chordae tendinese, 

 which are attached to their ventricular aui faces and free margins. 



Fig. 230. VIEWS OP PARTS OP 

 THE SEMILUNAR AND MITRAL 

 VALVES, AS SEEN FROM WITHIN 

 THE VENTRICLE. 



A, portion of the pulmonary 

 artery and wall of the right ven- 

 tricle with one entire segment and 

 two half segments of the semi- 

 lunar valves ; a, half the sinus of 

 Valsalva of the anterior segment ; 

 6, the same of the left posterior seg- 

 ment ; c, the entire right posterior 

 segment (See Fig. 231, A, in which 

 the lettering is the same as in the 

 present figure); d, d', inner sur- 

 face of the ventricle ; 1, the 

 attachment of the extremities of 

 the segments to the inner wall of 

 the artery ; 2, the middle of the 

 attached border of the segments ; 

 3, the middle of the free border 

 marked in two of the segments ; 

 upon the middle segment especially 

 the direction of the bands of fibres 

 strengthening the valve, as repre- 

 sented by Pettigrew, is shown. 



B, portion of the aorta and wall 

 of the left ventricle with one entire 

 segment and two half segments of 

 the semiluuar valve, and the right 

 or anterior segment of the mitral 

 valve ; a, half the right anterior 

 sinus of Valsalva and segment 

 (marked b in B, fig. 231); b, 

 the same of the left side ; c, the 

 posterior sinus of Valsalva and 

 segment entire ; in a, and b, the 

 apertures of the coronary arteries 

 are seen ; d, d', the inner surface 

 of the wall of the ventricle to the 

 right of the auriculo-ventricular 

 orifice ; 1, 1, the attachments of 

 the extremities of the segments ; 2, 

 the middle of the attached borders ; 

 3, the middle of the free border 

 with the corpus Arantii shown in 

 the middle segment ; e, e', the 

 base of the right or anterior seg- 

 ment of the mitral valve ; /, its 

 apex ; between e, and e', and /, 



the attachment of the branched chordae tendineas to the margin and outer surface of the 

 valve segment ; g, the posterior principal musculus papillaris ; h t the anterior principal 

 musculus papillaris : the cut chorJae tendinese are those which belong to the left or pos- 

 terior segment and the small or intermediate segments. 



During the contraction of the ventricles, the segments of the valves are 

 applied to the openings leading from the auricles, and prevent the blood from 

 rushing back into those cavities. Being retained by the chordae tendinese, 

 the expanded flaps of the valve resist the pressure of the blood, which 



