On December 4, 1895, Professor Roentgen, of Wurzburg, Prussia, published a description of a remarkable new ray of light he had discovered, which he called the "X-ray." This light flows from a Crookes tube, which is a glass tube exhausted of air, and traversed by an electric current. From the interior glow in this tube there flows a ray differing from ordinary light, since it fails to pass through some transparent substances and readily penetrates many opaque substances. It passes easily through human flesh, and less easily through bone, so that the bones of the body may be photographed as dark shadows. An important fact is that any foreign substance in the body, as a bullet, a needle, etc., is revealed by the ray, and its exact location fixed. This renders the Roentgen Ray of the greatest value in many surgical operations.