Kidney oncometer, 1877-1879.
© Science Museum / Science & Society Picture Library
This instrument designed by C S Roy (later Profesor of Pathology at Cambridge) was used for measuring blood flow through the kidney. A kidney is placed inside the chamber, surrounded by a delicate membrane made from animal tisue, which in turn is surrounded by oil. As blood flows through the kidney, it swells, and changes the presure of the oil which is recorded.