File:A text-book of physiology - for medical students and physicians (1916) (14583666368).jpg

Identifier: textbookofphysio1916howe (find matches)
Title: A text-book of physiology : for medical students and physicians
Year: 1916 (1910s)
Authors: Howell, William H. (William Henry), 1860-1945
Subjects: Physiology Medicine
Publisher: Philadelphia and London : W. B. Saunders Company
Contributing Library: Yale University, Cushing/Whitney Medical Library
Digitizing Sponsor: Open Knowledge Commons and Yale University, Cushing/Whitney Medical Library

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lbox or tambour of very limited capacity; the top of the tambour is coveredwith thin rubber dam and the cavity is filled with liquid and connected byrigid tubing, also filled with liquid, with the interior of the artery or heart.Variations in pressure in the artery are transmitted through the column ofliquid to the rubber membrane of the tambour, and the movements of thislatter are greatly magnified by a sensitive lever attached to it. The liquidconduction and the small size of the tambour, which prevents any notice-able outflow of liquid, combine to make a sensitive and very prompt recorderof pressure changes. It is necessary to calibrate this instrument wheneverused in order to give absolute values to the records obtained. A specimenof a blood-pressure record obtained with this instrument is shown in Fig. 198.It will be noticed that the size of the heart-beat, relative to the distance fromthe base line, is much greater than in the record obtained with the mercurymanometer, Fig. 193.
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Fig. 198.—Blood-pressure record from a dog with a Hiirthle manometer. The sizeof the heart beats is relatively much greater than with a mercury manometer. In this casethe systolic pressure is about 150 mms. Hg; the diastolic, 100 mms.; and the heart beat orpulse pressure, 50 mms. The method that depends upon the use of maximum and minimum valvesmay be understood by reference to Fig. 197. On the path between the arteryand the manometer one may place a maximum and a minimum valve so ar-ranged that the blood-pressure and heart beat may be transmitted througheither valve. As is shown by the figure, if the connection is maintainedthrough the maximum valve for a certain time the highest pressure reachedduring that period will be recorded, while, when the minimum valve is usedthe lowest pressure reached will be indicated. Such valves, of course, act slowly and can not be used to determine themaximum and minimum pressure in the artery during a single heart beat;they record the highest and l

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