Colitis. Light micrograph of a section through colon (large intestine) tissue affected by bacterial infection, causing injury to the mucosal lining, which has resulted in inflammation (colitis). This is characterised here as an excessive production of mucin, fibrin protein and leucocytes (white blood cells). This condition is called pseudomembranous colitis and it arises from infection by Clostridium difficile, which produces toxins that destroy the surface epithelium. It causes diarrhoea, dehydration due to loss of fluid absorption, and may be fatal. Magnification: x13 when printed 10 centimetres wide.