The X-Rays (1897)
The X-Rays (AKA: The X-Ray Fiend) is a 1897 British short silent comedy film, directed by George Albert Smith, featuring a courting couple exposed to X-rays. The trick film, according to Michael Brooke of BFI Screenonline, "contains one of the first British examples of special effects created by means of jump-cuts" Smith employs the jump-cut twice; first to transform his courting couple via "X rays," dramatized by means of the actors donning black body-suits decorated with skeletons, and then to return them back to normal. The couple in question are played Smith's wife Laura Bayley and Tom Green (a Brighton comedian).
More at Wikipedia.