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a drop of the clear, slightly opalescent fluid secreted by the lacrimal glands. Tears are slightly alkaline. They contain as much as 99 percent water and 0.9 percent inorganic matter, chiefly sodium chloride and small quantities of sodium carbonate, magnesium carbonate, calcium sulfate, and calcium phosphate, as well as the antibacterial enzyme lysozyme; other proteins constitute 0.1 percent. Tears moisten the anterior surface of the eye and prevent it from drying, wash foreign bodies out of the conjunctival sac, and participate in the nutrition of the cornea.