File:A text-book of physiology for medical students and physicians (1911) (14776814924).jpg

Identifier: textbookofphysio1911howe (find matches)
Title: A text-book of physiology for medical students and physicians
Year: 1911 (1910s)
Authors: Howell, William H. (William Henry), 1860-1945
Subjects: Physiology
Publisher: Philadelphia, London, W.B. Saunders company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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t has been found most conve-nient is represented in Fig. 250. To avoid escape of water at the upper endof the tube and at the same time to prevent compression of the veins of thearm a very thin rubber glove with long gauntlet is used. The gauntletis strengthened by cuffs of dam tubing, as shown in the illustration, and allare reflected over the end of the plethysmograph. The outer cuff (3) maybe omitted. The hand is inserted into the cylinder and is held in place byflexing the fingers through the rings. The plethysmograph being suspendedfreely from the ceiling, any movement of the arm will move the instrument asa whole without disturbing the position of the arm in the instrument. Bymeans of rings of hard rubber (D,E), one fitting around the rim of the plethys-mograph and the other adapted more or less closely to the size of the forearm,the reflected portion of the gauntlet and cuff is held in place and preventedfrom giving way readily to any rise of pressure in the plethysmograph. The
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Fig. 249.—A schematic diagram of Mossos plethysmograph for the arms: a, the glasscylinder for the arm, with rubber sleeve and two tubulatures for filling with warm water;s, the spiral spring swinging the test tube, t. The spring is so calibrated that the level ofthe liquid in the test tube above the arm remains unchanged as the tube is filled andemptied. The movements of the tube are recorded on a drum by the writing point, p. interior of the latter is connected, as shown in Fig. 249, to a test tube swungby a spiral spring (Bowditchs recorder). The spring is so adjusted by trial thatit sinks and rises exactly in proportion to the inflow or outflow of water. Bythis means the level of the water in the tube is kept constant, and since the posi-tion of this level determines the pressure upon the outside of the arm in theplethysmograph this pressure is also kept constant independently of thechanges in volume of the arm. The level should be set in the beginningso as to make a slight posit

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