VELOCITY AND PRESSURE OF BLOOD-FLOW. 



497 



Fig. 196. Diagram showing construction of Hurthle's manometer. (After Curtis.) 

 The interior of the heart or 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 by 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. 



will then record mean pressure and show no variations 

 with the heart-beat. A general idea of the variations in 

 systolic, diastolic, and mean pressures, throughout the 

 arterial system, may be obtained from the schema given 

 in Fig. 195. 



Method of Measuring Systolic and Diastolic Pres- 

 sure in Animals. In animals a manometer may be con- 

 nected directly with the artery and systolic and diastolic 

 pressures may be obtained in one of two general ways: 

 (1) By using some form of pressure recorder or manom- 

 eter sufficiently mobile to follow very quick changes of 



To the artery. 



Fig. 197. 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 6 alone is open. 



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