1897] MICROSCOPICAL JOURNAL. 351 



such as wood, leather, tiesh, etc., which hitherto had been 

 classed as opaque, was received with iucredulity, but the 

 circumstantial description of the methods employed ena- 

 bled persons possessing the requisite instruments to 

 repeat the experiments and to confirm the report. Not 

 the least important aspect of the discovery was, that it 

 was likely to prove a valuable means of contributing to 

 the relief of some of the ills to which flesh is heir, by 

 exhibiting details of bony structure of the living subject, 

 bone being opaque to these rays, while flesh is practi- 

 cally transparent. 



Two special features are associated with these X-rays, 

 (a) that the emulsion on an ordinary photographic dry 

 plate is sensitive to them, and (b) that certain chemical 

 salts become fluorescent, that is, appear aglow with 

 light under their influence. 



Let us examine these features in detail. Prof. Roent- 

 gen found that if a photographic dry plate were enclosed 

 in a wooden box, and a coin were placed on the outside 

 of the box with the vacuum tube above, on the tube being 

 excited by means of an electric current the X-rays pene- 

 trated the wood, (which is practically transparent to 

 them) but not the coin, with the result that the image 

 of the coin appeared on the plate inside the box on its 

 being developed. In like manner, if the hand were 

 placed on the box, the bones being opaque to the rays 

 were shadowed on the dry plate. 



The title of photography as ordinarily understood was 

 not applicable to these efi"ects, and the name of radio- 

 graphy was, after considerable discussion, given to the 

 process. It at once became apparent that a large field 

 for investigation and ex})erimeut had been opened, and 

 it was not long ere the London liospitals were employing 

 the X-rays for the investigation of bone diseases and 

 fractures, and for ascertaining the exact position of for- 

 eign bodies, such as bullets, shots, needles, etc., iu the 



