AAP, aN attin irradiated mice had opacities detectable with the slitelamp. The rate cf propresgion of the opacities varied directly with the dose (Chart 1). Lens damage was nore severe for 2 given dose of neutrons than for camxparable doses of ge-ma rays; thus, in cataract. induction approximately 100 rep of neutrons corresponded to about 650 r of gamma rays (nee = 6.5). Systenetic studies of the eye disclosed a resarkable change of the iris consisting of prorressive loss of iris tissue, as illustrated in Fig. 1. This process appears to be an abloatropry apparmtly hereditary in this strain, as mild atrophy of the iris occurred In aging nonirradiated contrels; like cataract, however, the degree of atrophy was significantly greater following irradiation, in proportion to the dese. Greying of the fur saa noted as early as 3 months! pestirradiati on, progressing with time as a fmetion of the dose (Chart 2). It varied with different anatomical regions bot in certain areas was sufficiently weil correlated with the dose te constituta a simple, though only approximate, biclogical dosimeter. DO ARCHIVES