DISEASES OF THE SALIVARY GLANDS 139 mouth of the parotid duct is red and pouting, and pus may be seen exuding, or may be produced by gentle pressure on the duct. Pus rarely points externally because of the dense fibrous capsule of the gland. Most cases respond to a broad-spectrum antibiotic, the common organisms being Staphylococcus aureus, haemolytic streptococcus and pneumococcus, and a swab should be taken from the duct mouth for sensitivity tests. Tranquillizers and anti- histamines should be discontinued. Chronic inflammatory diseases may involve the submandibular or parotid glands. Recurring infections of the submandibular gland usually lead to the formation of a calculus in the duct. This is caused by the mixed mucous and serous constitution of the secretion of this gland. The gland becomes swollen and painful while eating. The sight and taste of food stimulates salivary secretion which is held up in the gland because the duct is partially blocked by the calculus. As a rule the swelling subsides gradually afterwards but in long- standing cases there is always some palpable enlargement of the gland. Fig. 56. Sialogram to show sialectasis. Fig. 57. Parotid tumour. While the history is typical the presence of a calculus may be demonstrated by a straight radiograph. Treatment is surgical, and consists either in incising the duct in the floor of the mouth and removing the calculus or, if this is impossible arid in the event of a recurrence, the whole gland may be removed. Chronic recurring parotitis results in chronic inflammatory changes in the parenchyma of the gland with some suppression of salivary secretion. There may be acute exacerbations accompanied by pain and swelling. Between these the gland remains swollen. There is redness and oedema of the duct mouth with occasionally a purulent discharge appearing at the orifice either spontaneously or after gentle pressure. Sialography will demonstrate a typical sialectasis (Fig. 56). If doubt exists regarding the cause of the parotid swelling a needle biopsy may be taken from the gland without danger of producing a salivary fistula. Treatment consists in paying attention to oral hygiene and eradicating any septic foci such as infected tonsils or carious teeth. Should these measures fail surgery may be required for the gland itself. Resolution of symptoms may be achieved by dividing the secretory-motor fibres in the anterior part of the tympanic plexus in the middle ear. Ligation of the parotid duct may result in atrophy of the gland. If neither of these lesser methods succeeds a parotidectomy may be necessary.