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"A contrivance for measuring the extreme differential capacity of the human lungs. The instrument most commonly employed consists on an inverted chamber submerged in a water bath. The breath is conducted by a flexible pipe and internal tube so as to collect in the chamber, which rises in the water, and is fitted with an index which marks the cubic inches of air expired after a forced inspiration...a, is a small gas-holder containing an inverted vessel a'; b, index which shows on the scale c the number of cubic inches expired; d, manometer, which, when a' is held down, shows the pressure which the lungs can exert; e, plug-vent for outlet of the expired air; f, cock for outlet of water; g, tube through which the expiration is made." —Whitney, 1889

Spirometer

"A contrivance for measuring the extreme differential capacity of the human lungs. The instrument most…

"A small bronchial tube and the air sacs in which it ends." — Ritchie, 1918

Bronchial tube

"A small bronchial tube and the air sacs in which it ends." — Ritchie, 1918