Saliva, one of the digestive fluids, mainly the product of the SALIVARY GLANDS, of which there are three pairs—the parotid, the submaxillary, and the sublingual, with efferent ducts which convey the glandular secretions into the mouth. These, when mixed with the mucus secreted by the follicles of the mucous membrane lining the mouth, constitute the ordinary or mixed saliva. The Parotid Gland, so called from the Greek
It has a number of excretory ducts, which open separately into the mouth. The salivary glands are racemose, or of the compound acinous type (see GLANDS). The recesses which open into the fine terminal branches of the ducts are 'lined and almost filled' by the epithelial cells which secrete the saliva. True salivary glands exist in all mammals, except the cetacea, in birds, and reptiles (including amphibians), but not in fishes; and glands discharging a similar function occur in insects, many molluscs, &c. Saliva contains about one-half per cent. of solids, chiefly salts and mucus. The proportion of its active constituent, ptyalin, is extremely small; and it has never been satisfactorily isolated (see DIGESTION).
The most common disease of the parotid gland is a specific inflammation, which has been already described in the article MUMPS. Tumours of various kinds sometimes occur in front of the ear and over the parotid gland. Their removal is often difficult. Calculi are occasionally formed in connection with the ducts of the salivary glands. Deficient Secretion is indicated by clamminess or dryness of the mouth, and is common in low forms of fever. It is important as indicating the condition of the system, and seldom requires treatment. If it should occur as an original affection it must be treated by local Sialogogues (q.v.), such as liquorice, horse-radish, pellitory, &c. Alteration of the Saliva is not unfrequent in disease. For example, it sometimes loses its alkaline character, and becomes acid, as in acute rheumatism, diabetes, &c.; whilst in other cases it becomes so fetid as to be a source of annoyance both to the patient and his friends, as, for example, in scurvy, various forms of dyspepsia, salivation, &c. The undue acidity may be corrected by the administration of carbonate or bicarbonate of soda, while the factor may be relieved by attention to diet, by antiseptic mouth-washes, and by the use, both local and general, of creasote, nitromuriatic acid, charcoal, chlorate of potash, &c. Ordinary Inflammation of these glands (distinct from mumps) may proceed from cold or local injury, but it is often produced by decayed teeth.