From: The Medical Gazette: A Weekly Review of the Medical Sciences, Volume 5, edited by H.W. Turner, 1870, page 134.
Drawings from his patent (#73229) for the spirometer dated 1868. From this It is apparent that it is a rectangular water-seal spirometer. It was made of tin plate and its dimensions are listed as 8-1/2 inches wide, 4-1/2 inches deep and 13-1/2 inches tall. The wire “handle” that projects over the top was a guide for the inner spirometer reservoir (bell). The index (ruler) was attached to the inner reservoir and had a cover that protected it from wear. A 1/4″ of vertical movement was equivalent to 8 cubic inches. He specifically claimed that the guide rods and shield for the index were unique to his invention.
From: The Science and practice of medicine, Volume 2, by William Aitken, 1866, page 553. “Mr. A. Gardiner Brown’s spiroscope is a new and efficient instrument for ascertaining the breathing capacity. It is a wet meter, 6-1/2 inches square, having a dial with two registers, revolving from left to right, marking in a complete revolution 100 and 1000 cubic inches respectively, and a few feet of vulcanized India-rubber tubing to breathe through. Its advantages are facility of management, compactness, portability, security of contained fluid and it may be used several times by the same person without readjustment. The air is measured at its initial temperature. The patient should be taught to practice a powerful inhalation, and as complete an expiration as possible, before noting the mean numbers registered in several trials. It should be placed at a convenient height for a person sitting or standing.”