Where one on trial for murder claimed that he shot deceased in a hand-to-hand combat, and in self-defense, the result of experiments in shooting with defendant's revolver, at blotting-pads, is admissible in evidence for the purpose of ascertaining the distance at which the shot would burn or powder-mark the deceased's scalp, it having been shown that the cartridges used in the experiment were such as were used by the defendant at the time of the homicide.