Abstract
Mast cells with metachromatic granules are not detectable in rats after polymyxin-B sulfate treatment. The morphologic and staining characteristics of the cells that repopulate the peritoneal cavity resemble those of mast cells of fetal rats in their maturation sequence, except that, in the adult, the sequence requires at least 56 days. During this time changes occur in the competitive staining of mast cells with acridine orange-sodium chloride, indicating that polyanion synthesis and storage in the granules is a multiphasic phenomenon.