METHODS OF MEASURING ARTERIAL BLOOD PRESSURE 2OQ 



certain height. In the case of the rabbit's carotid it is equal to 90 to 120 cm. 

 of blood, or rather more than the same height of water. In the case of the 

 vein, if a similar experiment be performed, blood will rise in the tube only 

 for 8 or 10 cm. or less. 



The usual method of estimating the amount of blood pressure differs 

 somewhat from the foregoing simple experiment. Instead of a simple 

 straight tube of glass inserted into the vessel, a U-shaped tube containing 

 mercury, the mercurial manometer, is employed. The artery is connected 



FIG. 183. Diagram of Ludwig's Kymograph and Mercurial Manometer. A, 

 Revolving cylinder, worked by a clock-work arrangement contained in the box (5), the 

 speed being regulated by a fan above the box; cylinder supported by an upright (6), and 

 capable of being raised or lowered by a screw (a), by a handle attached to it; D, C, E, 

 represent a mercurial manometer, a somewhat different form of which is shown in the next 

 figure. 



with the manometer by means of a small cannula which is inserted into the 

 vessel, an arrangement being made whereby the cannula, tubes, etc., are 

 filled with a saturated saline solution to prevent the clotting of blood when 

 it is allowed to pass from the artery into the apparatus. The loss of blood 

 is prevented during the preparation of the details of the experiment by a 

 clamp or bull-dog forceps. The free end of the U-tube of mercury contains 

 a very fine glass or metal rod with a bulb which floats upon the surface of the 

 mercury and oscillates with the oscillations of the mercury. As soon as 

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