132 AN AMERICAN TEXT-HOOK OF PHYSIOLOGY. 



curves of the ventricle and the auricle, or of the ventricle and the artery, any 

 \v,t sudden change of pressure, produced in auricle or artery at the opening or 

 shutting of a cardiac valve, will produce a peak or angle in the curve of pres- 

 sure of the auricle or artery. By the rules of the graphic method the point in 

 the pressure-curve of the ventricle can easily be found which was written at 

 the same instant with the peak or angle in the auricular or arterial curve. 

 That point upon the ventricular curve, when marked, will indicate the instant 

 of opening or shutting of the valve in question. In the pressure-curve ob- 

 tained from the aorta close to the heart, there is a sudden angle which clearly 

 marks the instant when the opening of the semilunar valve leads to the sudden 

 rise of pressure which causes the up-stroke of the pulse (see Fig. 23). Again, 

 the fluctuation of aortic pressure which we shall learn to know as the "dicrotic 

 wave" begins at a moment which many believe to follow closely upon the clos- 

 ure of the semilunar valve. That moment may be indicated by a notch in the 

 aortic curve. So, too, the rise of pressure within the auricle produced by its 

 systole may suddenly be succeeded by a fall, the beginning of which must mark 

 the closure of the cuspid valve, which closure thus may correspond with the 

 apex of the auricular curve. 



In Figure 23, ordinate 1 indicates the closing, and ordinate 4 the open- 

 ing, of the mitral valve. These two points were found by help of the dif- 

 ferential manometer. < Ordinate 2 indicates the opening, and ordinate 3 the 

 closing, of the aortic valve. These two points were marked with the help 

 of the curve of aortic pressure, also shown in Figure 23, each ordinate of 

 which has the same number as the corresponding ordinate of the ventricular 

 curve. In the arterial curve, 2 marks the beginning of the systolic rise, 

 and 3 the beginning of the dicrotic wave, which latter point is treated by 

 the observer as closely corresponding to the closure of the aortic valve. In 

 figure 24 each ordinate has the same number, and, as regards the valve- 

 play, the same significance, as in figure 23. Ordinate 1 corresponds to the 

 apex of a peak in the auricular curve (not here given) which represents the 

 end of the auricular systole. Ordinate 2 corresponds to the beginning of the 

 systolic ascent in the aortic curve (not here given). Ordinate 3 was found 

 by comparing, by means of two elastic manometers, the simultaneous pressures 

 in the ventricle and the aorta. Ordinate 4 corresponds, on the auricular 

 pressure-curve, to a point which marks the beginning of a decline of pres- 

 sure believed by the observer to succeed the opening of the cuspid valve.- 

 In both the figures given of the ventricular curve, and in such curves 

 in general, the points which mark the valve-play occur as follows: The 

 .closure of the cuspid valve corresponds to a point, not tar above the line 

 <>f atmospheric pressure, where the moderate upward sweep of the ventric- 

 ular curve takes on the steepness of the systolic ascent. The systole of the 

 auricle is of little force, and the blood injected by it into the distensible ven- 

 tricle rai-e- the pressure there but little; that little, however, is more than 

 the relaxing auricle presents, and the cuspid valve is closed. Somewhere on 

 the steep -ystolie ascent occur- the point corresponding to the rise of the ven- 



