The fluff structure of pigeon intestine (HE staining: 400×). A, duodenum-fluff; B, jejunum-fluff; C, ileum-fluff; D, rectum-fluff. Note: a, mucosal epithelium; b, mucous muscle layer; c, muscular layer; d, serosa; e, gland; f, nerve fiber; g, lamina propria; h, lymph nodule; i, goblet cells; j, striatum; k, columnar cells; l, central chyle tube; m, isolated lymph nodule; n, lymphocyte.