. Dental electro-therapeutics. er number of secondary rays. These diagrams will show that in Fig. 74 only the middlepart of the object will appear on both exposures, whereas inFig. 75 the whole object appears in stereoscopic projectionby either of the two methods employed. In the case of the whole object nevertheless appears in the stereoscope;only the middle part, however, is really plastic. For stereoscopic radiography with plates, sliding plateholders have been put on the market enabling the inter- 1 Archives dElectricite medicale, July 15, 1899. 2 Die Rontgenteehnik. 3 Dental Cosmos
. Dental electro-therapeutics. er number of secondary rays. These diagrams will show that in Fig. 74 only the middlepart of the object will appear on both exposures, whereas inFig. 75 the whole object appears in stereoscopic projectionby either of the two methods employed. In the case of the whole object nevertheless appears in the stereoscope;only the middle part, however, is really plastic. For stereoscopic radiography with plates, sliding plateholders have been put on the market enabling the inter- 1 Archives dElectricite medicale, July 15, 1899. 2 Die Rontgenteehnik. 3 Dental Cosmos, July, 1912. 4 Kelly-Koett stand used by Ivy, of Milwaukee, see Cosmos, July, 1917. 164 THE X-RAYS UR RONTGEN RAYS change of plates without disturbing the position of thepatient. Both plates are placed in the holder simultane-ously, the one being covered by a sheet of heavy metalduring the exposure of the other. Both plates should bedeveloped together for the same length of time in order toproduce the most uniform 1 \ I 1\ \ \\ \ 11\\\ \ Fig. 74.—Lateral move-ment of tube (cylinders par-allel) . b, body to be i-rayed;p, photographic plate; ( (,target; c c, cylinder; cr, cr,central rays. Fig. 75.—1, rotary movement of tube(cylinders converging); 2, lateral move-ment of tube (cylinders converging). The distance from target to film or plate should not be lessthan 35 cm.; for the whole head it should be at least 50 cm. The plates can be viewed in the Wheatstone Stereoscope,in their natural size, or after reducing, in any hand stereo-scope. Various ingenious devices for localizing foreign bodiesin the head and body have been invented in connectionwith stereoradiography, which have proved of inestimable DENTAL RADIOGRAPHY 165 value during this war, in cases of gunshot wounds, for deter-mining the position of bullets and fragments of shells, etc. A few years ago there was considerable discussion about thefeasibility of examining the teeth with a fluorescent screenor
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