Text-book of Human Physiology, Including Histology and Microscopical Anatomy: With Especial Reference to the Practice of Medicine, By Leonard Landois, Published by P. Blakiston’s son & Company, 1904, page 209. Despite being invented by Gad, this type of spirometer has become known as a Krogh spirometer.
From A Text Book of Physiology by Isaac Ott, published by F.A. Davis Co., 1909, page 356.
Described in a Physiology Textbook from 1899 as being used to measure the respiration in a rabbit. From Jacobsen, Pfluger’s Archive, 1888, page 236.
The diverse, quirky and mostly forgotten history of Pulmonary Function testing