To the Editor:—
It was most interesting to read Dr. Leon Horowitz's letter to the Editor (JAMA192: 919 [June 7] 1965). The type of stethoscope illustrated had been described by Alison in 1859 and Nicolai in 1936. This type of instrument cannot lateralize sound since lateralization requires a difference in the time of arrival of the sound waves that reach the tympanic membranes of the two ears. For this reason, Dr. William J. Kerr devised the Symballophone (Amer Heart J14:594, 1937). It was my privilege to have worked with Dr. Kerr on this project and I have routinely used the Symballophone for the past 28 years.