-21microns external diameter) in several irradiated organs. The lesion was described as a plaque-like thickening of intima due to collection of foam cells alone or foam cells mixed with various other cells, fluid, fibrin or hyaline material, between endothelium and internal elastic membrane. Although pathological changes were found sometimes also in adjacent internal elastic membrane, media and adventitia, these structures were often normal. of fhumen. The plaque may cause marked narrowing or even occlusion Thrombosis, fibroblastic proliferation of deposition of elastic tissue in the thickened intima seldom result. The foam cell plaques “were found in small arteries in organs subjected to radiation therapy (large doses) by roentgen rays and/or gamma rays from radium sources. The paper states that the plaques probably result from migration of lymphocytes and monocytes into the intima from the blood stream and subsequent transformation (meaning differentiation or metamorphosis) of these cells into foam cells by their ingestion of lipids which have been freed by the dissolution of red cells in the intima or which have accumulated in the intima efter passage across portions of the endothelium that was rendered more permeable than normal by irradiation. The paper contained a casual or incidental statement to the effect that the foam cell plaques in irradiated small arteries closely resemble the early lesion of atherosclerosis. If this were true, it would be indicative of some of the kinds of changes which may occur in vessels before, and presumably responsible for, subsequent deposition of calcium, It is interesting to point out, however, that earlier in this paper, Sheehan indicated that foam cell plaque was an uncommon or at least rarely described lesion,