sentences:  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.He described the skin as a mosaic of discrete spots, each sensitive to one or another of these stimuli.He created a unique type of esthesiometer, now referred to as a von Frey hair, which consisted of various calibrated monofilaments.