Treatment using X-rays. 19th-century artwork of a patient in bed being treated by X-rays from the machine at right. At the time (1897), X-rays had been systematically studied since 1895 by Wilhelm Roentgen, but it was not yet realised that excessive exposure is dangerous. This machine was constructed in Paris by French instrument makers Eugene Ducretet (1844-1915) and L. Lejeune. Artwork from the first volume (1897) of 'La Revue Scientifique et Industrielle' by French chemist and inventor Jules-Louis Breton (1872-1940).