From: Lehrbuch der medizinischen Physik: Für Studierende und Ärzte zur Ergänzung jedes Lehrbuchs der Experimentalphysik by Heinrich Johannes Boruttau, published by Barth, 1908, page 131.
From: Kurzes Lehrbuch der Physiologie für Mediciner, by Heinrich Johannes Boruttau, published 1898, page 108.
Described as a modified Hutchinson Spirometer. From: A Text-book of Human Physiology: Including a Section on Physiologic Apparatus, By Albert Philson Brubaker, 1919. Page 410.
The diverse, quirky and mostly forgotten history of Pulmonary Function testing