ARTERIAL PRESSURE IN MAN 97 



The venous pulse. In a recumbent subject fix a small receiving 

 tambour (a small thistle funnel will do) at the place in the lower part 

 of the neck where the venous pulse in the jugular is most distinct. 

 The receiving tambour is connected by rubber tubing to a recording 

 tambour, and the curve is written on paper moved slowly by clock- 

 work. A tracing of the carotid pulse can be obtained on the same 

 paper, another tambour being fixed over the artery. A convenient 

 apparatus for taking such tracings is the polygraph of Mackenzie. In 



a 



FIG. 78. Diagram to show the lever-mechanism of the Dudgeon sphygmograph. 

 a, Spring ; 6, button to be applied to the radial artery ; c, writing point 

 of jointed lever attached to spring ; d, glass plate or paper on which the 

 tracing is recorded. 



his instrument there is a continuous roll of white paper on which the 

 tracings are recorded with ink. 



Arterial pressure in man. The pressure of the blood within the 

 human arteries is determined by the sphygmometer, of which many 

 forms are in use. All have a circular rubber bag (Fig. 79, a] which is 

 enclosed by leather and is placed round the upper arm. The bag is 

 distended with air by a pump (c), the amount of pressure used being 

 recorded either by a mercury manometer (Riva-Rocci) (6) or an aneroid 

 (Hill and Barnard) or by compression of air in a closed tube, using a 

 coloured fluid (Hill) or a mercury index (G. Oliver). As the distension 

 progresses the manometer shows not only the gradual increase of 

 pressure, but also oscillations due to the pulse. These oscillations 

 increase in magnitude up to a certain point. The point around which 



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