William Christopher Krauss (1863-1909) graduated medical school from Bellevue Hospital Medical College in 1886. He studied an additional 2 years in Berlin, Germany. He practiced neurology and pathology in Buffalo, New York.
Krauss exhibited his hammer at the 20th annual meeting of the American Neurological Association held in Washington, DC in 1894. He stated:
Having had occasion to make constant use of a percussion hammer in my private and hospital practice, I have devised some improvements and modifications which widen the field of its usefulness, thus making it more serviceable to those engaged in neurological research. The hammer is constructed after the French pattern having a heavy metallic head fixed to a flattened oval handle seventeen centimetres long. As a hammer it may be used to examine the tendon and muscular reflexes, to percuss the head spine, superficial nerves, etc. The handle (a) being of hard rubber becomes warm on friction, while the head being of metal remains cold, thus offering the means of examining the sense of heat and the sense of cold, fulfilling the requirements of a thermo-aesthesiometer. The cap (c) when removed discloses a triangular spear head about one-half centimeter long, while at the other end of the hammer head is the rounded roubber points – the two ends furnishing, therefore, a sharp and a dull point for examining for anesthesia or hyperaesthesia…The spear is divisible into two portions, one securely fixed upon the hammer head, the other moveable upon a metallic slide upon which is engraved the metric and English scales. This arrangement furnishes an excellent aesthesiometer and is as accurate and convenient as any on the market. Replacing the cap (c) and removing the cap (e) a camel’s hair brush is exposed, giving a soft surface, while the metallic cap (c) gives a hard surface. The hammer is conveniently carried in the pocket, and has served me with much satisfaction.
Primary reference: Lanska, DJ; Neurology Nov 1989 p1542-9; The History of Reflex Hammers