Lowne portable spirometer by Weiss & Son. The instrument and mahogany case are original. The tubing, mouthpiece and glass are replacements. Given that the case has no room for the glass, it was apparently sold separately or  clinicians supplied their own.

“Spirometers were developed in England in the 1840s. They measured the ‘vital capacity’ of the lungs. This means the largest amount of air they can hold, which can indicate the health of the respiratory system. They also indicated improvement or deterioration in conditions such as tuberculosis. 

The patient’s breath bubbled up a water-filled collecting glass and pushed up a sliding weight. A scale on the attached spirometer indicated the capacity of the lungs. Scientific instrument maker, Robert Mann Lowne (1844-1929) patented this portable spirometer in 1865. ” London Science Museum