Scale
bar = 100 Am. (D) Pyloric caeca at 22 days after hatching. The arrowhead indicates the brush border of the
enterocytes. Hematoxilin and eosin staining. Scale bar = 20 Am; ai = anterior intestine; es = esophagus;
et = stomach; gg = gastric glands; li = liver; lu = lumen; p = pancreas; pc = pyloric caeca; s = spleen.