. A text-book of physiology : for medical students and physicians . Fig 202.—Record {Erlanger) to show the maximum size of the recorded pulsewave when the outside or extravascular pressure is equal to the internal diastolic pressureihe artery is compressed first pressure above systolic, sufficient to obliterate thelumen. As this pressure is lowered in steps of 5 mms. the recorded pulse wave increases insize to a maximum and then again becomes smaller. The outside pressure with which themaximum pulse is obtained measures the amount of the internal diastolic pressure (Mareys cording to so
. A text-book of physiology : for medical students and physicians . Fig 202.—Record {Erlanger) to show the maximum size of the recorded pulsewave when the outside or extravascular pressure is equal to the internal diastolic pressureihe artery is compressed first pressure above systolic, sufficient to obliterate thelumen. As this pressure is lowered in steps of 5 mms. the recorded pulse wave increases insize to a maximum and then again becomes smaller. The outside pressure with which themaximum pulse is obtained measures the amount of the internal diastolic pressure (Mareys cording to some observers, the diastolic pressure is indicatedmore accurately by a change in the character of the sound, fromsharp to dull, which takes place just before it disappears.* If,. Fig. 203.—Schema showing the construction of the Erlanger apparatus: a, Rubberbag of the arm piece; c, bulb for blowing up this bag and putting pressure on the arm; b,the manometer for measuring the pressure; _ i, two-way stopcock (when turned so as tocommunicate with the capillary opening, k, it allows the pressure in a to fall slowly); e,a rubber bag in a glass chamber, /; e communicates with a when stopcock d is open andthe pulse waves from a are transmitted to e; the pulsations of e in turn are transmittedto the delicate tambour, h, and are thus recorded. however, for any reason it is desirable to obtain a record of thesystolic and diastolic pressures, some form of sphygmomanometer * Taussig and Cook, The Archives of Internal Medicine, 11, 542, 1913;also Hooker and Southworth, ibid., 13, 384, 1914. VELOCITY AND PRESSURE OF BLOOD-FLOW. 503 must be employed in which the pulse from the artery under thecuff is recorded upon the smoked surface of a instruments of
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