The cornea, although non-vascular, is subject to inflammations even of an acute suppurative character. The inflammatory exudation passes into the canals and spaces with which the cornea abounds, and by its presence produces a clouded or opaque condition.

The cornea takes part in the acute inflammations of the conjunctiva, being liable to suppuration, softening and sloughing. In addition, chronic inflammations begin external to, or arise in the cornea itself, some of them being due to direct irritation, and some to the presence of ulcers.

Vascularization of the cornea is a frequent result of chronic inflammation. It frequently occurs in the upper part in cases of granular conjunctivitis, in which case it is ascribed to the irritation of the rough conjunctiva rubbing against the cornea. The superficial layers of the cornea become the seat of new-formation of blood-vessels, which frequently cover the whole surface. This condition is called Pannus. and it is generally recovered from when the primary affection is removed.

A more profound vascularization occurs in some cases in the form of localized crescentic areas at the upper and lower borders of the cornea. This form has been ascribed to nervous lesions. Vaseulariza-tion also not infrequently attends ulcer of the cornea, a fasciculus of vessels running in from the border to the ulcer.

Interstitial keratitis is a name given to eases in which the cornea assumes an opaque appearance. It is met with chiefly, as Hutchinson pointed out, amongst persons the subject of Hereditary syphilis, in whom it is associated with a special condition of the teeth (see under Syphilis). The cornea has in the milder cases an appearance compared to that of ground glass. The actual histological condition of the tissue is various. There may be simply an infiltration of inflammatory products, or there may be more profound changes in the tissue, sometimes even a kind of cicatricial condition.

Herpes sometimes attacks the cornea along with the skin in the course of one of the branches of the fifth nerve (Zona ophthalmca). The eruption may lead to an ulcer or even perforation of the cornea.

Paralysis of the fifth nerve also leads to inflammation and oloera tion of the cornea (Neuropathic ophthalmia). The cornea becomes cloudy and opaque, and ulcers, form which may perforate. These results have been variously ascribed, on the one hand to the anaesthesia, which admits of injuries to the eye and exposes it to the presence of foreign bodies without their being felt. and. on the other, to a special affection of the trophic nerves.

Another form of Keratitis is that which occurs when, in consequence of great weakness in the patient, the eyelids are not closed, and the lower part of the cornea undergoes dessication (Keratitis e lagophthalmia). There may be ulceration in consequence.

Ulcers of the cornea arise, as indicated in the remarks made above, under a large number of different circumstances. Ulcers heal by the new-formation of connective tissue, which fills the gap. As this has not the structure of the corneal tissue it is more or less opaque, and appears in the clear cornea as a white area These areas, being weak, are liable, if large and central, to yield before the pressure within and form a bulging outwards, a condition named Staphyloma of the cornea. The iris is frequently adherent to the cicatrix and is often protruded in a staphyloma.