294 Scientific Proceedings, Royal Dublin Socieiij. 



It is obvious that many advantages attend the use of several centres of 

 radiation. We may omit wasteful screening. The illumination becomes more 

 uniform. Cross-raying is favoured. The distribution of the illumination is 

 under control. In short, the method possesses all the advantages which a 

 number of small lights possess over one central lamp when a large space has 

 to be illuminated. In the case of the radioactive bodies it is to be remembered 

 that subdivision involves no loss of intrinsic efficiency. 



In order to carry out the suggested conditions, I have, in conjunction witli 

 Dr. Walter 0. Stevenson, worked out in some detail a system of applying 

 radium, or its emanation, contained in ordinary exploring needles. The 

 needles may be about 5 to 1 mm. in internal diameter. They may be made 

 of steel, gilt ; or of platinum or gold. The stopping power of such needles 

 and contained glass capillary would not fall short of that of a screen of 

 aluminium 1 mm. in thickness. Their length may be determined according 

 to tlie requirements of the case. They may be used in surface tumours or, in 

 certain cases, inserted from without into more deeply seated growtlis, and 

 withdrawn again from outside when the exposure is completed ; or a eanula 

 may be used in such eases, permitting a repetition of the dose. 



The radium bromide, sulphate, or chloride may be directly packed into 

 the needle ; or the salt, when fusible, may be sucked into an inner tube while 

 melted. The inner tube may in this case be of refractory combustion tubing 

 drawn down to a thick-walled capillary. But the simplest procedure is the 

 use of radium emanation sealed in drawn-out capillary glass tubes. These 

 glass tubes may, for ordinary purposes, be about 2 or 3 cms. in length. They 

 are placed in the needle and retained in position by a little paraffin wax or 

 sealing-wax closing the tube. 



In the case of large growths, a relatively minute subdivision of the charge 

 would probably be advantageous. Thus in place of a central tube containing 

 200 millicuries of emanation, there might be twenty needles each of 10 milli- 

 curies. From what has already been said above it will be evident that there 

 is no reason to anticipate that such a charge contained within an ordinary 

 needle would give rise to injurious effects around it. The intensity near the 

 tube has, in fact, been reduced in the quantities involved from 200 to 10 

 or 20 to 1. On the other hand, there is increased intensity around the 

 needle, owing to absence of a lead screen, and to the increased convergence 

 of the rays. The increase due to convergence may stand as 1 to 10, or 

 thereabouts. 



The charo-iug of the glass capillary tube with emanation presents no 

 special difficulties. I would suggest a method allowing of rapid and accurate 

 work. 



