Abstract
Observations on rats indicate that treatment with large doses of an ACTH-preparation, to which carboxymethylcellulose was added as a retarding agent, results in the development of mast-cell-like elements within the adrenal medulla. At the same time, in some cortical cells and in adrenal-vein blood, occasional granules appear, which give the characteristic staining reactions of mast-cell granules. Carboxymethylcellulose-solutions containing no ACTH produce similar changes.