HURTIILE'S MANOMETER 



185 



In this instrument (fig. 147) the mass of all moving parts is reduced 

 to a minimum. Among these is also included the column of fluid 

 connecting the manometer to the blood vessel. This is reduced in 

 quantity as far as possible, and, further, by choosing a tambour of very small 

 size the movement of fluid in and out of the tambour is rendered extremely 

 minute. The instrument consists of a tambour, B, of very small capacity 

 whose upper surface is covered with thick rubber. An inlet tube, F, with a 

 tap on it, D, communicates with the tambour, and is for connection to the 

 artery. A second tube, g, allows of a flow of fluid from a pressure bottle. A 

 small vertical metal piece is attached to the centre of the rubber membrane 

 and moves a recording lever, o, pivoted about an axis which can be raised or 

 lowered by the lever c, so that a horizontal position can be given to the 

 writing lever. The lever c can be clamped by the screw h. The manometer 

 is also provided with a second writing point, N, for recording the zero pressure. 

 This can be adjusted to the writing surface by a screw, a, and can be raised or 

 depressed by a second screw, l. Both writing points can be adjusted to the 

 blackened surface by a screw, k. 



A record of the pressure changes is taken by this instrument by first filling 

 it with half-saturated sodium sulphate from a pressure bottle, and connecting 

 it to the cannula, which is also filled, and then closed by the spring clip. The 

 manometer is again connected to the pressure bottle, and this time- the tambour 

 membrane rises. By the handle c the writing lever is brought to the horizontal 

 position, and clamped there by the screw h. The clip on the cannula is again 

 opened and the lever o falls. Its level now records zero pressure, and the 

 writing point N is brought to that level. The cannula is again closed, the 

 pressure in the manometer raised, the tap on G shut, and now the forceps on 

 the artery can be removed, and the manometer lever allowed to record its 

 movements. 



Fig. 148 is such a tracing taken with the recording surface moving 

 at the same rate as that in fig. 135. The tracing i was recorded 



a «.: A A ' A 71 



/v_^v /v_j 



,Mw/r0mn Iwwv f0WMy >»»ww\ y^\ J ^^\/i''^>, i /* 



Fig. 148. — Tracings of Blood Pressure of the Babbit b? Ilnnmi's .M urota rBB : 

 i, during Normal Respiration ; n, during Aktiiuiw, Respiration. I'm 

 Upper Horizontal Line gives Zero Pressi re, 



immediately before that reproduced in fig. L35 from the mercury 

 manometer. A height of 16 mm. in this figure therefore represents 

 a pressure of 150 mm. of mercury. The variations due to respiration 



