ONE OF US (J. W. W.) recently1 recommended a putty composed of 84% bismuth subnitrate and 15% anhydrous wool fat to replace sheet lead for shielding the peripheral normal skin during treatment of a dermatologic lesion with x-rays. Since that article was submitted for publication careful measurements of the efficiency of this material in stopping radiation have been made, and additional experience, enhanced by critical evaluation of the method by several colleagues, has yielded improvements in technic.
EFFICIENCY OF MATERIAL
A sample of putty prepared according to the original formula was examined in the following manner:Small portions were compressed between the plane surfaces of a hinged, two-bladed, wooden paddle so that discs varying from 1 to 5 mm. in thickness were produced. Each disc was prevented from adhering to the wooden surfaces by two sheets of cellophane. When these discs were cooled by being placed upon a metal