A count of the cardiac contractions heard with the stethoscope and a count of the pulse shows a great discrepancy in number. This has been called the "pulse deficit" (Hart). In order to arrive at the true average systolic pressure the following procedure is done. "The apex and radial are counted for one minute, at the same time by two observers, (if possible) then a blood pressure cuff is applied to the arm, and the pressure raised until the radial pulse is completely obliterated; the pressure is then lowered 10 mm., and a second radial count is made; this count is repeated at intervals of 10 mm. lowered pressure until the cuff-pressure is insufficient to cut off any of the radial waves (between each estimation the pressure on the arm should be lowered to zero). From the figures thus obtained the average systolic blood pressure is calculated by multiplying the number of radial beats by the pressures under which they came through, adding together these products and dividing their sum by the number of apex-beats per minute, the resulting figure is what we have called the 'average systolic blood pressure.'" (Fig. 43.) [Illustration: Fig. 43.--The shaded area represents the pulse deficit; the upper edge is the apex rate, the lower edge the radial rate. The broken line indicates the "average systolic blood pressure." (Compare these values with the figures at the bottom of the chart, which show the systolic blood pressure determined by the usual method.) (After Hart.)] For example: "B. S., April 29, 1910, Apex 131; radial, 101; deficit, 30. BRACHIAL PRESSURE RADIAL COUNT 100 mm. Hg. 0 90 mm. 13 13 x 90 = 1170 80 mm. 47 - 13 = 34 x 80 = 2720 70 mm. 75 - 47 = 28 x 70 = 1960 60 mm. 82 - 75 = 7 x 60 = 420 50 mm. 101 - 82 = 19 x 50 = 950 ---- Apex = 131) 7220 ---- Average systolic blood-pressure 55 plus B. S., May 11, 1910, Apex 79; radial, 72; deficit 7. BRACHIAL PRESSURE RADIAL COUNT 120 mm. Hg. 0 110 mm. 44 44 x 110 = 4840 100 mm. 64 - 44 = 20 x 100 = 2000 90 mm. 72 - 64 = 8 x 90 = 720 ---- Apex = 79) 7560 ---- Average systolic blood-pressure 95 plus"