Abstract
The investigation was carried out on 30 immature rats, weighing about 80 g. at the beginning of the expt. Ten rats were treated with 2 mg. of ACTH per day, 10 rats received 2 mg. of albumin per day, and 10 rats served as untreated controls. The animals were killed on the 16th day of the expt., and the right femur was examined histo-logically. The width of the epiphyseal cartilage was decreased in the ACTH-treated animals, the osteoblasts showed signs of inactivation, but the appearance of the osteoblasts was unchanged. Body wt. was not affected by the treatment, but body length was decreased. The expts. seem to indicate that ACTH exerts an anti-anabolic rather than a catabolic effect.