CIRCULATION OF THE BLOOD. 



511 



the degree of occlusion, and to prevent the valves being everted into the 

 auricles. According to the other view, which seems to be supported by 

 the largest amount of proof, the papillary muscles play an active role 

 in the occlusion of the auriculo-ventricular orifices. This view has been 

 strongly supported by Ku'ss, who describes their operation as follows : 

 " If the finger be introduced into the auriculo-ventricular region at the 

 moment of the systole of the ventricle, we find that the kind of funnel 



FIG. 207. HEART OF A Cow, WITH THE RIGHT VENTRICLE LAID OPEN, 

 ONE-FOURTH THE NATURAL SIZE. (Miillei:) 



a, posterior aorta; at, anterior aorta; b b, spaces in the lateral wall of the right ventricle ; p pt pH, 

 papillary muscles ; q q>, columns; carnae ; L, pulmonary artery laid open ; O, opening into right auricle; 

 S, ventricular septum; W, lateral wall of ventricle; 1, 2, and 3, leaflets of the tricuspid valve; 4, chorda 

 tendinse ; 5, 6, 7, cusps of semi-lunar valve ; 8, sinus of Valsalva. 



which hangs from the auricle to the ventricle is continued ; it even 

 appears to lengthen itself out, and the finger, as it were, is drawn into 

 the interior of the ventricle. In fact, the first result of the contraction 

 of the papillary muscle is the lengthening of the auricular cone, the 

 edges of which are afterward brought near each other. While this 

 hollow cone descends into the ventricle, the sides of the latter contract 

 and approach the cone in such a manner that the auriculo-ventricular 



