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XX. 



ON THE LOCAL APPLICATION OF RADIUM IN 

 THERAPEUTICS. 



By J. JOLT, ScD., F.R.S. 



[Read March 24 ; Published Mai 8, 1914.] 



Within recent years the application of radioactive substances, such as radium 

 emanation, or mesothorium, to malignant and pathological growths, is often 

 carried out by introducing the substance contained in a closed tube into an 

 incision made in the tissues. The tube is screened with lead folded around 

 it to a thickness which is generally about two or three millimetres. The amount 

 of radioactive substance used is seldom less than the equivalent of fifty 

 millicuries of emanation. It may be as much as 300, or even more. The 

 dosage may amount to the application of such quantities for from six to 

 twelve hours, or longer. According to the statements of medical men having 

 special experience in this branch of therapeutics, too feeble a radiation may do 

 more harm than good, actually stimulating the morbid growth. 



On the other hand, the screening of the tube is necessitated by the 

 observed fact that too concentrated a radiation may give rise to deleterious 

 effects arising from necrosis of the tissues. Now, close to the tube the rays 

 are much concentrated ; and not only is this the ease from the mere geometrical 

 conditions, but because the softer gamma rays, if they are permitted to 

 escape, will here be absorbed. These amount to a large part of the total 

 gamma radiation, and their concentration near the tube would give rise to 

 a very intense illumination of the tissues. There are also the beta rays to be 

 considered. These will be completely cut off by a screen of 3 mms. of lead- 

 It is probable that these rays very materially affect the morbid tissues — 

 they may, in all cases, be the immediate cause of the effects, beneficial or 

 deleterious, observed. It may be recalled here that secondary beta rays are, 

 in any case, powerfully excited by the gamma rays, where these emerge 

 from the lead. 



The arrangement described above is a wasteful one. A large percentage of 

 what should be useful radiation is absorbed in the screen or filter. Moreover, 

 it is tlie worst possible method for securing uniformity of illumination of the 



