There are many published studies of the development of malignant tumor after the topical application or injection of anthracene derivatives.1 Only a few of these investigations, however, have dealt with attempts to produce such a tumor in or near a bone or a joint.2 The present study is devoted to this point and specifically to the effects of such a tumor on skeletal tissue, as noted roentgenographically and histologically. In the course of the experiments several noteworthy complications appeared in addition to the tumors. Routine histologic examination of the latter with the aid of hematoxylin and eosin staining was supplemented by comparative studies made with the Laidlaw silver method3 and with the so-called fluorescent technic.4 METHOD The activating agent used was 1,2,5,6-dibenzanthracene. Three milligrams of dibenzanthracene was dissolved in 1 cc. of benzene or suspended in 1 cc. of melted lard.5 Injections were made into