Seven areas on the abdomen of each of fourteen rabbits were exposed to soft Roentgen radiation of constant quality in doses varying, in the region of the value critical for the production of persistent alopecia, by regular steps of about 4 per cent. Without exception the critical dose was found to lie between two such values, the upper limit being represented by exposures on eight of the animals and the lower on ten of them. With certain reservations, the critical dose corresponds to the production of 2.04 x 1015 ions of either sign per gm. of tissue.

This content is only available as a PDF.