Abstract

1 . Groups of male and female rats, 25 each, were maintained on diets containing 0 (control groups), 0.0025, 0.020, 0.16 per cent methoxychlor for a period of two years. No effect on growth was noted in the rats given the 0.0025 and 0.020 per cent diets, respectively. A moderate growth reduction was evident in the rats given the 0.16 per cent diet. No decrease in life span was observed. Normal values were found in urine analyses, in a thorough series of periodic hematologic examinations, and in organ weights at autopsy. No histological changes were found that were attributed to the administration of methoxychlor. Little tendency for accumulation of methoxychlor in the tissues was found.

2. Two dogs were fed each of the following doses of methoxychlor for one year: 0 (control dogs), 20, 100, and 300 mgm./kgm./day. Two dogs died from intercurrent disease; in neither case was the cause of death related to the treatment. Hematological observations, urine analysis and organ weights lay within normal limits. No evidence of tissue damage was found histologically.