Alison differential stethocopes
Scott Alison 'Differential Stethoscope' that consisted of two independent chest pieces, was designed to allow the listener to compare the sounds of two areas of the chest. It was first illustrated in the John Weiss & Son catalog in 1863. The Alison's Differential Stethoscope displayed dates to the 1850s. The close up shows the ebony bell chest pieces and is marked "Ferguson" on the connecting mechanism. Mr. Daniel Ferguson of Giltspur Street, London was the well known instrument maker for the Bartholomew's Hospital in London and introduced many of the new instruments that were used in the hospital.
Early differential stehoscope c. 1880
Differential Stethoscope with plastic bell chest pieces, c. 1930.
Modern differential stethoscope with metal diaphragm chest pieces, c. 2000
Leyton Differential Stethoscope, c. 1918. Dr. O. Leyton based its design on the differential stethoscopes developed by H. Bock and M. Y. Oertel. The differential stethoscope was used to determine the relative intensities of heart sounds. The screw mechanism could be adjusted to allow for greater or lesser transmission of sound through the chamber and therefore record the intensity of sound. The stethoscope head was sold either separately or with binaural earpieces. TAlso shown is the original box that contained the stethoscope head and article with a description of the construction of the stethoscope and instructions on how to use the differential stethoscope.