Scientists working on a problem do not know and sometimes can’t even guess what the final result will be. Professor Rontgen was a physicist at the University of Wurzburg in Germany. Late on Friday, 8 November, 1895, he was doing an experiment in his laboratory when he noticed something extraordinary. He had covered an electric bulb with black cardboard, and when he switched on the current(电流) he saw little dancing lights on his table. Now the bulb was completely covered; how then could any ray penetrate? On the table there were some pieces of paper which had been covered with metal salts. It was on this paper that the lights were shining. Professor Rontgen took a piece of this paper and held it at a distance from the lamp. Between it and the lamp he placed a variety of objects, a book, a pack of card, a piece of wood and a door-key. The ray penetrated every one of them except the key. This mysterious ray could shine through everything except the metal. He called his wife into the laboratory and asked her to hold her hand between the lamp and a photographic plate. She was very surprised by this request, but she obediently helped up her hand for a quarter of an hour, and when the plate was developed there was a picture of the bones of her hand and of the ring on the finger. The ray could pass through the flesh(肌肉)and not through the bone or the ring. At a scientific meeting where he described what happened, Professor Rontgen called this new ray “the Unknown”, the X-ray. Doctors quickly told how this could be used, and soon there was X-ray machines in all the big hospital. At first the doctors did not understand how powerful the rays were and many of them were injured, losing a finger or an arm through exposure to X-rays when they were using the machines. The most obvious use for this discovery was to enable doctors and surgeons to see exactly how a bone was fractured. Other uses came later. It was found that these rays could be used to destroy cancer cells, just as they destroyed the healthy cells of the doctors who first used the machines. Methods were found later by which ulcers in the stomach could be located, and the lungs could be X-rayed to show if there was any tuberculosis present. “Mass X-ray” units are sent to factories and detect early signs of trouble in the lungs. Unfortunately Professor Rontgen, whose discovery did so much for medical science, did not die an honored man. Malicious people spread the story that he had stolen his discovery from a laboratory assistant who worked for him. He died, poor and neglected in 1923.