A watery fluid secreted by the salivary glands in the mouth. Production of saliva is stimulated by the presence of food in the mouth and also by the smell or thought of food. Saliva contains mucin, which lubricates food and eases its passage into the oesophagus, and in some animals salivary amylase (or ptyalin), which begins the digestion of starch. Lysozyme, an antimicrobial enzyme, also occurs in saliva, helping to protect the teeth and oral cavity against the bacteria in food. The saliva of insects is rich in digestive enzymes, and that of bloodsucking animals contains an anticoagulant.