t'ooLK — Notes on the Distribution of Activity in Radium Therapy. 49 



Table 2. 



Four emanation tubes, each 15 mm. long, in coplanar, parallel serum needles equally 

 spaced 4 mm. apart, forming a rectangle 15 mm. x 12 mm. 



a = distance in millimetres from plane containing the four tubes. 

 & = „ „ „ ,, " equatorial plane." 



The plane of the table passes midway between two tubes, so that for « = and 

 h < 7-5 the nearest tubes are at 2 mm. on either side. The maximum activity on 

 the surface of one of the needles (1-2 mm. diameter) would be 1600 on the same 

 scale. 



For values of a greater than 20 the activities are the same as for the corre- 

 sponding points in Table 1, from which they may be taken. 



With the exception of a layer a few millimetres thick next to the plane of the 

 tubes, the distribution in the " equatorial plane " would be nearly the same, I being 

 now measured from the original plane of the table. 



