CHAPTER XIII

IMMUNITY OF THE SKIN AND MUCOUS MEMBRANES 403 Protective function of the skin.—Exfoliation of the epidermis as a means of ridding the animal of micro-organisms.—Localisation and arrest of micro-organisms in the dermis.—Intervention of phagocytes in the defence of the skin. Elimination of micro-organisms by the conjunctiva.—Microbicidal function of the tears.—Absorption of toxins by the conjunctiva.—Protection of the cornea.—Elimination of micro-organisms by the nasal mucosa.—Protection by the respiratory channels.—Dust cells.—Absorption of poisons by the respiratory channels. Alleged microbicidal property of the saliva.—Part played by microbial products in the protection of the buccal cavity.—Antitoxic function of the saliva. Antiseptic action of the gastric juice.—Antitoxic function of pepsin. Protective function of the alimentary canal.—Absence of microbicidal power from the intestinal ferments.—Protective function of the bile.—Antitoxic rôle of the digestive ferments.—Favouring and retarding functions of the intestinal micro-organisms.—Destruction of toxins by these micro-organisms. Defensive rôle of the liver. Protective function of the lymphoid organs of the alimentary canal. Protective function of the mucous membrane of the genital organs.—Autopurification of the vagina.