Some cases of catarrh have a more acute character, and assume the characters of suppurative or phlegmonous inflammation, the conditions approximating to those in severe dysentery (see further on). Such conditions are due to peculiar virulence in the intestinal contents, and may be brought about by irritant poisons such as corrosive sublimate. There may also be an acute inflammation in diphtheria. The relation of these conditions to the intestinal contents is shown by the fact that they occur chiefly in the large intestine and in the parts where the contents are especially prone to lie, namely, caecum, flexures, and rectum.