VENOUS BLOOD PRESSURE AND CAPILLARY PRESSURE 



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with a recording tambour, the entire apparatus being fully supplied with 

 the necessary valves and adjusting devices which make it mechanically very 

 perfect. The instrument is mounted on a stand with a small clock and 

 recording cylinder adapting it to convenient clinical use. 



The brachial arterial pressure of man when taken by this form of appara- 



FIG. 189. Erlanger's Sphygmomanometer, Shown with the Rubber* Bag Attached to 

 the Arm. The picture is taken at the end of an experiment after the pressure in the instru- 

 ment is run up again to above the systolic pressure. The upper part of the cylinder shows 

 a sphygmogram taken with the instrument. (Experiment and photo by Hill and Watkins.) 



tus has been found to vary greatly, but Erlanger gives no mm. of mercury 

 as the average of observations on young adults in the determination of the 

 systolic pressure; i.e., the maximal arterial pressure. He gives for the dias- 

 tolic pressure 40 to 45 mm. of mercury below the systolic pressure. Other 

 observers using the same method find a somewhat higher average pressure, 

 see figure 190, which represents a fair type of observation. 



The Venous Blood Pressure and Capillary Pressure. The blood 

 pressure in the veins is nowhere very great, but is greatest in the small veins, 



