From Palmer, C. F. 1934. Palmer Research and Students’ Apparatus for Physiology, Pharmacology, Psychology, Bacteriology, Phonetics, Botany, etc.: Manufactured by C. F. Palmer (London) Ltd., Myographic Works, 63a, Effra Road, Brixton, London, S.W. 2. England, page 87.

“With this instrument working on the principle used by Prof. Knipping, it is possible to show on the same record, in addition to the volume of oxygen consumed, the volume of C.O2 produced.

“Also by using a rotary air pump to ventilate the apparatus, no valves are necessary.

“Dimensions and features of the spirometer itself and the recording cylinder are identical to those given for No. E150.

“The air circulating pump is substantially made and fitted with a water jacket for cooling; this should be connected to the nearest water supply. Lubricating points in the pump are conveniently placed, and should receive occasional attention.

“The electric motor is quiet running, and has ample power. Two model of this spirometer are made. In one, No. E165, the recording cylinder is driven by a clockwork movement making one revolution in 20 minutes.  In the other, No. E166, the recording cylinder is driven from the motor, this enables a two-speed gear to be used, so the the cylinder can be run at a faster rate (1 revolution in 2 minutes) in addition to the normal speed of one revolution in 20 minutes.”