Double focus x-ray tube, Europe, 1896. This tube worked by using an alternating current, which accelerates electrons towards an aluminium plate. This produced x-rays at both ends of the tube. Wilhelm Roentgen, a German physician, took the first x-ray in 1896 of his wife's left hand. Dense areas of bone show up as white whilst soft tissue allow the x-ray to pass through undeterred. Very quickly x-rays proved their usefulness as a diagnostic and therapeutic tool in medicine. Within six months of Roentgen's announcement, x-rays were being used by battlefield physicians to locate bullets in wounded soldiers. X-rays allowed physicians their first look inside the body without resorting to surgery.