Maximilian (Max) Ruppert Franz von Frey (16 November 1852 – 25 January 1932) was an Austrian-German physiologist who was born in Salzburg.
Frey's primary work in Leipzig dealt with the circulatory system, and he is credited with developing an early prototype of a heart-lung machine.
During the 1890s, Frey proposed that pain is an independent tactile quality, alongside touch, heat and cold, and that it is associated with stimulation of high-threshold free nerve endings.
[2] He created a unique type of esthesiometer, now referred to as a von Frey hair, which consisted of various calibrated monofilaments.
These filaments can be used to determine the threshold force required to produce the sensation of touch or pain.