Golberg, Martin & Batchelor (1960) showed that treatment of mice and rats with heavy doses of iron-dextran complex increased the activity of acid phosphatase and other lysosomal enzymes, not only in liver but also in organs such as spleen and kidney which display low activity in the untreated animal. Some of the largest increases were found at the sites of repeated injections given into the thigh muscles or in the subcutaneous tissues of the abdominal wall, changes clearly reflecting the morphological and cytological alterations which are induced locally under these circumstances