. The Roentgen rays in medicine and surgery as an aid in diagnosis and as a therapeutic agent; designed for the use of practitioners and students . focus tubes is that they have two sources from which the X-rays origi-nate (see Fig. 32); the definition, therefore, is not so good as it may bewith a single focus tube. To obviate this objection to the use of alternat-ing currents. Dr. Rollins has designed the tubes shown in Figs. 33-35 —one the cooled target type, and the other of the rotary target type. Whenthese tubes are used as double focus tubes with high frequency currents,one radiant area
. The Roentgen rays in medicine and surgery as an aid in diagnosis and as a therapeutic agent; designed for the use of practitioners and students . focus tubes is that they have two sources from which the X-rays origi-nate (see Fig. 32); the definition, therefore, is not so good as it may bewith a single focus tube. To obviate this objection to the use of alternat-ing currents. Dr. Rollins has designed the tubes shown in Figs. 33-35 —one the cooled target type, and the other of the rotary target type. Whenthese tubes are used as double focus tubes with high frequency currents,one radiant area is formed on the back of the target, or that side facing -8 THE ROENTGEN RAYS IN MEDICINE AND SURGERY away from the patient. The X-rays from this radiant area are sent outof the field, exerting no injurious action on the definition, if the tube isin a suitable opaque box, as shown in Fig. 33. Dr. Rollins prefers touse these tubes in another way, however, the central piece of metalbeing always one terminal through which the current passes, instead ofsimply a target, having no connection with the generator. There is in LL -^^^ 1 T ;■ - 1 0. Fig. 31. Illustrates the formation of the cathode stream and X-rays. (Rollins.) The cathode stream is represented by dotted lines, the X-rays by unbroken lines. When thecathode stream strikes the target, X-rays are given off in all directions from the point of contact, butonly one-half of the sphere is seen, as the other half is obstructed by the platinum of the target. Inthe figure these rays are represented as passing through the aluminum of the cathode and the glasswalls of the tube until stopped by the white lead lining of the box. A cone of X-rays, large enoughto cover the part of the patient to be examined, is allowed to escape through the hole in the revolvingdiaphragm plate. LL, lead lining composed of white lead and japan; J^P, rubber plugs throughwhich pass the wires .-/ and Cfrom the electric generator. HD, revolving diaphragm p
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