. Radiotherapy and phototherapy : including radium and high-frequency currents, their medical and surgical applications in diagnosis and treatment ; for students and practitioners . Double-bulb tube. APPARATUS 69 that is given up to the first bulb very slowly as the latterbecomes more and more exhausted. The additional advan-tage is claimed that it will operate no matter in which direc-tion the current flows through it, and can be used with highfrequency or other apparatus of alternating Regulable Tubes. It was recognized almost from theearliest use of tubes that the vacuum increas
. Radiotherapy and phototherapy : including radium and high-frequency currents, their medical and surgical applications in diagnosis and treatment ; for students and practitioners . Double-bulb tube. APPARATUS 69 that is given up to the first bulb very slowly as the latterbecomes more and more exhausted. The additional advan-tage is claimed that it will operate no matter in which direc-tion the current flows through it, and can be used with highfrequency or other apparatus of alternating Regulable Tubes. It was recognized almost from theearliest use of tubes that the vacuum increased very rapidlyas the tube was used, and efforts were made to discovera means of remedymg this fault. Aside from uniformlyheating the tube and thus liberating some of the gases heldin the walls, the first method used was to fuse into the maintube a small tube containing a quantity of caustic potashand sealed at the outer end, while the inner end communi-cated with the interior of the larger bulb. Fig. Gundelach tube with heavy anode for radiographic work. The caustic potash in the small tube was maintained ata red heat by means of a small lamp, while the bulb wasbeing exhausted, so as to cause it to give up the smallamount of vapor it contained. When the exhaustion in thebulb had progressed to a certain point, the smaller tubewas allowed to cool, and in so doing it absorbs the lasttrace of moist vapor in the tube. When the tube becomestoo high, the annex containing the potash is heated byapplying a lamp or by causing the current to enter the tubethrough a platinum wire embedded in the potash and fusedinto the glass, and thereby causing it to give up some of itscontained moist gas, again lowering the vacuum. The most commonly used type of this tube is that devisedby INIuller. It is very much like the preceding, but containsa piece of palladium wire as seen at i? in Fig. 15, fusedthrough the small tube instead of containing caustic potash. 70 GENERAL CONSIDERATIONS UPON RADI
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