6 



Scientific Proceedings (69). 



4 (1068) 



The movements of the mitral valve flaps studied by a new method. 



By A. L. Dean, Jr. (by invitation). 



[From the Physiological Laboratory, Cornell University Medical 



College.] 



The desirability of a more accurate knowledge of the move- 

 ments of the auriculo-ventricular valves led to the adoption of 

 the following method of study in the perfused cat's heart: The 

 margins of an opening in the left auricle are stitched to the 

 bottom tube of a small cylindrical reservoir in which the height 

 of pressure is regulated and varied by a set of lateral overflow- 

 tubes. To one of the mitral valve flaps is attached a human hair 

 communicating with a short and delicate lever of straw, held up- 

 ward by slight spring tension. Whenever the valves move up 

 the lever is elevated and a small mirror attached to the axis of 

 the lever system is depressed. Upon this mirror is projected a 

 beam of light and through its reflection the movements of the 

 mirror are recorded upon a moving bromide surface. In this 

 way the oscillations of the valve flaps may be optically recorded 

 and compared with simultaneous optical tracings of auricular and 

 ventricular activity. To prevent the transfer of ventricular 

 movements to the threads connecting with the valves, the heart 

 is fastened by stitches, carefully placed around the auriculo- 

 ventricular ring to a neatly fitted ring of metal. 



A study of the records thus far obtained indicates that the 

 following movements of the auriculo-ventricular valves occur in 

 every cardiac cycle: A very short interval after the onset of 

 auricular systole, the cusps are slightly depressed toward the 

 ventricle, but before the end of auricular systole they quickly 

 ascend toward the auricle. With the onset of auricular diastole 

 (which in these experiments began a distinct interval before sub- 

 sequent ventricular systole) the valves move ventricle-ward to 

 their former position. With the onset of ventricular systole the 

 cusps immediately move upward and close completely. So they 

 remain until ventricular relaxation begins. During ventricular 

 diastole the valves move ventricle-ward to a position that is lower 



