VELOCITY AND PRESSURE OF BLOOD-FLOW. 



449 



Fig. 183. Diagram showing construction of Hurthle's manometer. (After Curtis.) 

 The interior 9f the heart of the artery is connected by rigid tubing to a very small tambour, 

 T. The tubing and the tambour are filled with liquid. The movements of the rubber dam 

 covering the tambour are greatly magnified by a compound lever, S. t The tendency of this 

 lever to "fling" may be prevented oy an arrangement not shown in the diagram. The 

 essential principles of the recorder are, first, liquid conduction from heart to tambour; 

 second, a very small tambour and membrane so that a minimal volume of liquid escapes 

 from the heart into the tambour. 



To the artery- 



Fig. 184. Schema to illustrate the use of valves in determining maximum (systolic) 

 and minimum (diastolic) blood-pressure. When stopcock a is open the heart beats are 

 transmitted through the maximum valve and the mercury in the manometer is prevented 

 from falling between beats. The manometer will record the highest pressure reached during 

 the period of observation. The reverse occurs when valve b alone is open. 

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