Iiitravciitiicular uml Aortic rrcssure Curves. 42!) 



to the pressure-bottle is turned at such a rate tliat tlie pressure in 



i the manometer changes at the rate of 1100 mm of mercury -per 



second ^), the meniscus takes up its final position without vibrations, 



as shown by the photograph Fig. 1. plate XX. (The lower angle is 



the one to be observed.) When tlie rate of cliaiige of pressure exceeds 



this, there are a few rapid vibrations (63 per second), before the 



; meniscus comes to rest. Measurements of the most rapid changes in 

 i 

 the intraventricular curve (the ascending part) show that in the cases 



observed by us, it never exceeded 1000 mm Hg. per second, and this 

 is within the capability of the instrument to respond to without vibra- 

 tions. An important point is that, in the capillary manometer, this 

 aperiodicity is obtained without any additional damping, as in Hiirthle's 



: and von Frey's instruments, although the former instrument can be at 

 any time damped to any degree once found to be adequate by means 

 of the graduated scale to the stopcock, and in practice shows itself 

 to be a very convenient and accurate instrument. 



A final advantage the capillary manometer possesses as an accurate 

 recorder of pressure curves is that the unavoidable friction of the 

 tracing point on the smoked paper is absent; anyone, who has worked 

 with any of the manometers writing on smoked paper, knows how 

 very little friction is sufficient to obliterate all the secondary waves 

 on the curve. 



Our object in describing this capillary manometer is to show that 



I.; it is an instrument giving a truer reproduction of the intraventricular 

 variations of pressure than any other equally simple one, and there- 

 fore curves obtained by it may serve as standards with w^hich to 



' compare those obtained by any other form of manometer, and to accept 

 or reject them accordingly. Our method is not one capable of general 

 use, because of the complications of the photographic recording method, 

 but it seemed to us worth doing on account of the truth of the records 

 so obtained. 



^) Of course this does uot mean that the pressure ever reached this amouut, 

 the pressure actually used (equal to the height of the pressure-bottle above the 

 manometer) was 95 mm Hg. and, in the case mentioned, this was reached in 



0-08 sees 



