Valentin knife, circa 1880. A Valentin knife was used to cut fine slices of soft tissues for microscopic examination. The double-bladed knife was used with wet blades, or submerged in water. The blades were nickel-plated steel, and kept in protective leather covers when not in use. The knife was originally designed by Gabriel Valentin (1810-1883), a German-Swiss physiologist. This instrument is of English origin.