File:A text-book of physiology, for medical students and physicians (1907) (14591648967).jpg

Identifier: textbookofphysio1907howe (find matches)
Title: A text-book of physiology, for medical students and physicians
Year: 1907 (1900s)
Authors: Howell, William H. (William Henry), 1860-1945
Subjects: Physiology Physiology
Publisher: Philadelphia, London, W.B. Saunders Co.
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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ame, 2, which serves to keep the rubber membrane in place. When placed in position Uponthe arm the rubber dam lies upon the vein and presses upon il as the pressure i rai ed in the box. The vein is observed through the glass top and the hole in the rubber, and the pressure at which it is just obliterated is read from the manometer. Wiib instruments of ibis kind the degree of pressure neces-sity to obliterate a given vein in the arm, band, or foot can * Von Recklinghausen, Archiv f. exper. Pathol, u. Pharmakol, 55, 470, l!ll)li. • rand Hooker, The Johns Hopkins Hospital Bulletin, 274, L908. VELOCITY AND PRESSURE OF BLOOD-FLOW. 493 be determined readily in terms of a column of water, but itis obvious that for any given vein this pressure will vary withthe position of the vein. When the hand hangs pendent atthe side the pressure within its veins will be greater than whenthe hand is raised to the heart-level. The pressure actuallymeasured for any given position of the hand or foot must,
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Fig. 204.—Apparatus for determining venous blood-pressure in man: B, The boxwith glass top for putting pressure on the vein; the details are shown in the small figure(Fig. 2), in which 1 show- the alumimum box; 2, the brass collar which fits over 1 andholds in place the perforated sheet of rubber dam; 3, which forms the bottom of the boxand is forced down on the vein. E, pressure bulb for increasing pressure in the box untilthe vein is obliterated. G, water manometer to measure the pressure. (Eyster andHooker.) therefore, be corrected for the heart-level by determining thevertical distance between the vein and the heart (costal angle),and subtracting this distance, expressed in centimeters, fromthe pressure, also expressed in centimeters, which was foundnecessary to obliterate the vein. Measurements made by thismethod and corrected for the heart-level show that in the normal 494 CIRCULATION OF BLOOD AND LYMPH. person the pressure within the small veins of the hand or armmay vary bet

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