540 



SCIENCE. 



[N. S. Vol. III. No. 67. 



ity with which the discharge passes through 

 the tube. The fluoroscope tells us that 

 there is then a perfectly definite tempera- 

 ture at which the tube will work most effi- 

 ciently and it is desirable to operate the 

 tube at this temperature. This can be eas- 

 ily done by directing currents of air against 

 those parts of the tube where it heats most, 

 that is, against the parts opposite to the 

 electrodes. By a suitable regulation of the 

 air currents and a careful watching with 

 the fluoroscope the tube can be kept steadily 

 at the temperature of its highest efficiency 

 for hours. A deviation above or below this 

 point will produce a very large diminution 

 in the Rontgen effect. This temperature of 

 highest efficiency is so sharply defined that 

 it looks very much like a critical point in 

 the discharge. Below this temperature the 

 discharge is in straight lines from the ca- 

 thode and the portion of the glass opposite 

 to the cathode fluoresces much more in- 

 tensely than the rest. Above this temper- 

 ature the discharge begins to spread in all 

 directions from the cathode and the whole 

 tube fluoresces strongly. There is then 

 considerable flickering until the tempera- 

 ture is sufficiently above the critical tem- 

 perature. The tube heats then rapidly and 

 a yellowish mist begins to rise from the 

 anode. As soon as the air blast begins to 

 cool the tube this mist begins to clear away 

 and the whole tube regains a clear trans- 

 parency. If the tube is made too cool the 

 discharge becomes too faint ; there is very 

 little heating because the coil fails to force 

 a strong enough current. The Buusen 

 burner will assist the coil then to force a 

 sufficiently powerful discharge again. The 

 blackening of the tube by the disintegration 

 of the electrodes seems to be the only thing 

 that will determine the length of its life. 



The Combination of a Fhioresveiit Screen 

 with a Photographic Plate- Photography at 

 a Long Disstovce from the Tube and through, 

 the Hearier Pnrlii of the Hitman Body. — 



With an arrangement of apparatus as de- 

 scribed above it was found possible to 

 produce very much stronger photographic 

 effects, but not sufficiently strong for pene- 

 tration through the thigh and the trunk of 

 the human body at reasonably short expo- 

 sures and at long enough distances from the 

 tube to obtain the desirable clearness in the 

 pictures of these massive parts. A com^- 

 pletely successful application of Eontgen's 

 beautiful discovery to sui'gery depends for 

 the present on a successful solution of 

 the problem just mentioned. I have ob- 

 tained one satisfactory solution with the 

 method which I first described before the 

 Academy on March 2d. It consists in 

 placing in contact with the photographic 

 plate a fluorescent screen and thus trans- 

 forming most of the Eontgen radiance into 

 visible light before it reaches the sensitive 

 film. Photographs of the hand were thus 

 obtained at a distance of twenty- five feet 

 from the tube with an exposure of half an 

 hour. At the distance of four inches the 

 hand can be photograjihed by an exposure 

 of a few seconds. It was in this manner 

 only that I succeeded in photographing on 

 a single plate the whole chest, shoulders 

 and neck of my assistant, with an exposure 

 of seventy minutes and at a distance of 

 three feet between the plate and the tube. 

 The collar button and the buttons and 

 clasps of the trousers and the vest show 

 very strongly through the ribs and the 

 spinal column. This result seems to prove 

 beyond all reasonable doubt the applica- 

 bilitj' of radiography to a much larger field 

 in sui'gery than was expected a few weeks 

 ago. 



Diffuse Rejlfction of the Ebntgen Radiance. 

 — The question of reflection and refraction 

 of the X-rays is a very important one. It 

 was discussed by Prof. Eontgen in sections 

 7 and 8 of his original essay. Neither by 

 photography nor by the fluorescent screen 

 could he detect an appreciable refraction 



