© Science Museum/Science and Society Picture Library
X-rays were discovered in 1895 when Wilhelm Röntgen, a German professor of physics, encountered unknown emissions from a Crookes discharge tube. Experiments revealed that these rays penetrated some substances more easily than others, and also fogged photographic plates. The fact that X-rays could produce images differentiating between the densities of body tissues, produced results which medical enthusiasts for 'the new light' were keen to exploit. X-rays were also used to treat tumours. This early German X-ray tube is of the form originally used by Röntgen in his research.