: . .- ows . st CP eaten ee le bel eter fae - . 7 ‘ - In some cases hair shafts in the superficial pars reticularis were narrow or absent; in others the hair shafts appeared normal. showed mild atrophy. Small hair follicles (plate 25) and sweat ducts in sam cases Biopsies of three pigmented lesions were taken fran two of the white Americans of the Rongerik group. Only one of the three gave evidence of damage, which was slight and confined to the epidermis. Third series — 6th month post-exposure. — Sections of skin at this time revealed some changes persisting in the epidermis and to a lesser extent in the dermis (plates 28 and 29). Epidermis. — The following changes were found to varying degrees: focal atrophy of the stratum granulosum; slight focal pigmentary disturbances in cells of the basal layer; slight to moderate hyperkeratinization; and slight disturbances in polarity of epithelial cells in the the still persistent basal papillary projections. Dermis, - In the dermis, telangiectasis superficially persisted from a slight to moderate. degree in most of the sections, and contributed the only abnormality noted. 2. Epilation The incidence and time of appearance of epilation in the various groups is illustrated in tables 1 and 2, and figure 1. Epilation was first observed on the fourteenth post-exposure day in the Rongelap group, and somewhat later in the other groups. It was of a spotty nature and was confined almost entirely to the head region. Epilation was divided arbitrarily into three degrees of severity. “1+” indicated loss of hair without obvious thinning; “2+’’ indicated loss of hair sufficient to cause thin spots; and “3+” indicated an extensive epilation with bald spots. Table 1 illustrates that there was a greater degree of epilation in the children (0 to 15 years), with over 90 percent developing epilation to some degree as compared with only 28 per— cent in the older age group. The preponderance of scalp lesions in the areas of epilation indicated that radiation from the fallout material on the skin was primarily responsible for the epilation. Only three cases of mild epilation developed in Ailingnae children and one case of questionable epilation in one of the Americans. Regrowth of hair in almost all individuals was noted commencing some time during the third month post-exposure. By the 6 months’ examination complete regrowth of hair normal in color, texture, and abundance had taken place. Plates 13-15, 17,18, and 19 show epilation and regrowth of hair. 3. Nail Pigmentation. An unexpected observation was the appearance of a bluish-brown pigmentation of the fingernails which was first well documented on the 23rd post-exposure day. The discoloration began in the senilunar area of the fingernails (to a lesser extent in the toenails), and tended to spread outward sometimes in streaks. As the discolored area grew outwards the semilunar area usually became clear. Plate 20 shows pigmented bands in the nails at 77 days. At six months the pigmentation had grown out with the nails, and was no longer evident except in three cases which still showed pigment at the distal end of the nail. The pigment appeared to be on the under side of the nail plate, between it and the nail bed. Discoloration of the nails was seen in ‘a large proportion of the two higher exposure groups (tables 1 and 2). The phenomenon ap- peared to be a radiation response peculiar to the dark-skinned races since it was seen in all of the exposed American Negroes and in none of the white Americans. This lesion was not observed in the Utirik people or in unexposed Marshallese. Since the nail pigmentation occurred in individuals without skin lesions, it appeared to be the result of a more penetrating ganma component of radiation. SoG1e3% 431