The present invention is intended to provide a reducing agent effective for color development of meat and uses therefor. When any motion is detected in the distal portion of the endoscope included in the image, a motion direction and a motion amount of the distal portion of the endoscope attributed to the motion are detected, and the distal portion of the endoscope is curved to return the scalpel to an original treatment position. By selecting a pair of the n-type regions 8 and the surface electrodes 7 and thereby making electron emitted from the crossing points due to combination of the surface electrode 7 to be electrically applied and the n-type region 8 to be electrically applied, electrons can be discharged from desired regions of the surface electrodes 7.