190 THE DISCOVERY OF RONTGEN. 



The plate was developed with metol and hydroquinone, and 

 showed an exact photograph copy of the skeleton of the hand, on 

 the middle finger of which we clearly saw a ring, which the rays 

 (though passing through the flesh of the hand and the pasteboard) 

 had not pierced. The ring was a band of lead, the ends of which 

 were not quite joined. A mouse was photographed in the same 

 way without removing the hair or the skin. The invisible X rays 

 produced an admirable image, showing all the small bones of the 

 body, as well as the vertebrae of the tail. In order to see in what 

 degree different materials were penetrable, we fastened a piece of 

 metal, a piece of glass, and a lead pencil on the surface of the 

 dark-slide, and were astonished to find that the glass absorbed the 

 rays as much as the metal and the graphite in the pencil, the wood 

 of the latter being pierced without difficulty. We also placed a 

 book of ICO and more pages in the way of the invisible beams, 

 but it was no hindrance. Finally, photographs were taken of a 

 hen's leg and a pigeon, requiring exposures of an hour or more. 



The experiments were not without danger, because of the 

 strong electric currents, but were successful, not only in the labor- 

 atory of the Polytechnic, but also in that of the Urania (popular 

 physical institute in Berlin) and of the Physical States Laboratory 

 at Hamburg. In the laboratory of the Polytechnic we were suc- 

 cessful in modifying the proceedings so that the exposures were 

 shorter and the images more distinct. 



By this new discovery science in general, but especially medi- 

 cine, will benefit. If, for instance, a ball has entered into a 

 soldier's leg, its place and the injury to the bone will be easily 

 found by the X rays. We need only place the closed dark-slide 

 (with the gelatine plate) under the injured leg, and send the X 

 rays from the glass globe through it ; the bone and the ball will 

 then appear as silhouettes on the photographic plate. Practical 

 results have recently been obtained in some hospitals. A young 

 lady had been unable, from some unknown cause, to use her right 

 hand for a long time. A photograph of her hand was made, and 

 the negative showed a white spot caused by a piece of glass through 

 which the X rays had not passed, and which was removed by a 

 simple operation. When the invention is perfected we shall be 



