Microstructure and mast cells in the hedgehog’s duodenum (A, magnification of 100X; B to I, magnification of 400X). A to C, HE staining; D to I, toluidine blue staining. Black arrows indicating MCs. M, mucosa; LMM, lamina muscularis mucosa; LP, lamina propria; GC, goblet cell; A, adventitia; ICML, inner circular muscle layer; OLML, outer longitudinal muscle layer; S, submucosa; D, duct; V, villi; IG, intestinal glands.