It frequently happens that the meibomian glands are the seat of morbid action, along with the lachrymal passages; their secretion is changed, becoming in some cases thick and caseous, in others puriform. By some, affection of the meibomian glands has been considered as the cause of inflammation and abscess of the lachrymal sac. This opinion, however, cannot be agreed to, for the diseases are not always coexistent; and besides, the affection of the surface of the lachrymal sac and ductus ad narem is as likely to be the consequence of morbid action, extending upwards from the nostrils, as of morbid secretion from the eyelids blocking up and irritating the puncta and the lachrymal passages. Disease of the meibomian glands in the under eyelid often exists along with disease of the lachrymal passages, but the latter is generally the primary affection; the conjunctival covering of the eyelid is at the same time inflamed, swollen, and often granulated. In some cases of abscess in the lachrymal sac, before the integuments give way, the subjacent bone becomes diseased in consequence of the pressure of the confined matter; portions are affected by necrosis, and after their separation considerable deformity is produced. The exfoliation is often very tedious, and is attended with discharge of fetid thin fluid from the nostril, and from the ill-conditioned lachrymal fistula. Fistula lachrymalis is often merely one of the symptoms of disease in the bones of the nose, with obstruction of the nasal duct,—as in patients who have suffered from mercury.