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To the Editor:
—Recently I thought of a means of making a more sensitive instrument out of a Ford or similar bell stethoscope by fitting a rubber diaphragm (such as the rubber cap from a packing strip test tube) over the bell of the stethoscope. These are inexpensive and serve the purpose very well. A more durable diaphragm might be made of vulcanized rubber, celluloid or metal with a retaining coiled spring of wire situated above the diaphragm on the bell, holding the diaphragm firmly in place against the bell.
Donaldson JB. A STETHOSCOPE OF INCREASED SENSITIVENESS. JAMA. 1919;73(17):1303. doi:10.1001/jama.1919.02610430051027