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Salivary glands. Historical illustration of the dissected mouth of a human head, showing the left- hand set of the three pairs of salivary glands (pale yellow). To the left of the ear is the large parotid gland. The smaller submandibular gland (below the lower jawbone) has a duct leading to the sublingual gland (beneath the tongue). These glands secrete saliva when stimulated by reflex reactions to the sight, smell, taste or thought of food. Saliva is an alkaline fluid that aids the swallowing of food. It contains enzymes that begin the breakdown of the starch in food. Colour lithograph by Fairland from The Viscera of the Human Body, 1840. Based on drawings by Bagg. (KEYSTONE/SCIENCE PHOTO LIBRARY/SHEILA TERRY)