vii MECHANICS OF THE HEAKT 195 



centrifugal vortex and subsequent wave of regurgitation, which 

 drives the valves upward, and tends to close them. So soon as the 



FIG. 60. Apparatus to demonstrate presy-stolic closure of auriculo-ventricular valves. The two 

 figures represent the same normal heart of a young subject. The two arteries, aorta and 

 pulmonary, are divided near the orifices, and ligatured to corks. The walls of the auricle are 

 opened above and stitched to an iron ring clamped to a support. On filling the cavity of the 

 heart with water, the auriculo-ventricular valves are seen to float into the semi-open position 

 (upper figure). After injection of a few c.c. of water in the direction of the axes of both 

 orifices, the valves temporarily assume the position of perfect closure (lower figure). 



injection ceases, the flaps of the valves suddenly come together, 

 closing the ostium completely for the space of a few seconds. 



