From: The early detection of Pthisis, including the author’s contributions to diagnostic means, with after considerations of a possible pre-tubercular stage, by Charles Denison, MD. Transactions of the First Pan-American Medical Congress, Part 2, U.S. Government Printing Office, 1895, page 2001.
Invented by Charles Denison. From: The Sanitarian. Volume 25, 1890, page 408. “The spirometer I here show you is of my own experimenting, and I will trust it will commend itself to you as a faithful measurer of vital capacity. When full it is a hollow cylinder, 11.28 inches in diameter, standing on end, the two ends being closed, and the sides made of one piece of light, impervious cloth. The structure is so light as to give little or no resistance to the expired breath. That resistance when desired, however, is intended to be used and measured by weights placed on top of the cylinder, or by a manometer attached, so as to determine the expelling force, in pounds pressure, that each individual may have.”