Population of the diaphragm by mast cells in growing rats

The mast cell content of the diaphragm of the rat was examined using electron microscopy, and using light microscopy in material stained with Alcian blue. The concentration and diameters of the mast cells were estimated in animals at regular time intervals from 16 days gestation to 14 weeks of age and compared to the mast cell content of muscles of the calf and anterior abdominal wall. The results were discussed in relation to the origin of mast cells. It was proposed that if mast cells develop in haemopoietic sites that they may populate adjacent tissues by migrating within the connective-tissue spaces.