The mucous membrane here differs from that of the mouth proper, chiefly in respect that in addition to the ordinary mucous glands there are numerous Lymphatic follicles. The distinction between these two is not always correctly appreciated. The mucous glands are racemose glands with proper ducts, opening on the surface of the mucous membrane. The follicular glands, as they are often called in rather a confusing way, are strictly comparable with the closed follicles of the intestine. In the pharynx, soft palate, and root of the tongue they occur in the form of isolated rounded masses of lymphatic tissue, like the solitary follicles of the intestine. In the tonsils we have aggregations of these follicles not unlike Peyer's patches. Their prominence in the tonsils causes the mucous membrane to be thrown into folds, and so we have comparatively deep recesses, which are sometimes called Crypts, and in which secretions may accumulate, especially if their depth is exaggerated by diseased conditions.
From their exposed position these parts are peculiarly prone to irritation from agents coming to them from without. The mucous membrane of the mouth seems peculiarly resistant to external irritations, but here, where there is the transition, as it were, from the mucous membrane exposed to external influences to that protected from them, these inflammatory manifestations occur with peculiar frequency. Almost all the diseases we have to treat of here are forms of inflammation, and it is usual to describe these under the general designation of Angina.
The fistula colli congenita (see p. 53) commonly opens into the pharynx, unless it be a blind external canal. Sometimes there is an internal fistula, which is incomplete externally. Sometimes also there is a cyst having this origin.