Purulent collections in the frontal sinus may result from continued irritation, like that due to a badly fitting yoke. They also occur as an accidental complication of general diseases like gangrenous coryza. =Symptoms.= The catarrh or purulent collection in the sinus may be unilateral or bilateral, and the symptoms vary, according to the form which it assumes. _Unilateral collections._—Nasal hæmorrhage is often the first symptom, but this is often regarded as of little importance, because the formation of pus does not occur until very much later. The animal shows ill-defined pain, loses appetite, remains dull and somnolent, and carries its head on one side. The horn on the injured side is hot and sensitive, and at a later stage the eye becomes affected by contiguity of tissue. It is then swollen, closed, and watery; the conjunctiva is infiltrated, and somewhat inflamed. Sensibility and partial or complete dulness of the affected side may be detected by palpation and percussion. On the animal being made to cough, a yellowish or greyish-white discharge of very fœtid and sometimes putrid character escapes. _Bilateral collections._—Catarrh is rarely bilateral at first; but if the unilateral lesion is not treated, it affects the median septum dividing the two cavities, and the inflammation extends to the second sinus. The animal then shows dull pain, and exhibits marked depression; sometimes it appears quite prostrate. The head is carried low and inclined towards the ground, while the above-mentioned ocular symptoms and the indications furnished by palpation and percussion extend to both sides. Coughing produces momentarily a double discharge, which the animal disposes of after the fashion of horned cattle. =Diagnosis.= The diagnosis only presents difficulty in the early stages. Later the warmth and sensitiveness of the horns, the partial dulness, offensive character of the discharge, etc., render diagnosis easy. The disease is not likely to be mistaken for gangrenous coryza, despite the condition of the eyes, because it develops slowly, progressively, and without marked fever. =Prognosis.= If treated early, unilateral or bilateral collections of pus in the sinuses are capable of cure, but later when bodily health is impaired and the local lesions of the mucous membrane very pronounced, there is less chance of success. =Lesions.= The initial lesions consist in cracks, fissures, or fractures of the bones of the face or exostoses of traumatic origin. In other cases the mucous membrane alone is affected. As a result of chronic irritation it becomes thickened, inflamed, and ulcerated, and granulates freely. The depressions in the sinuses contain grumous, fœtid pus, which irritates the surrounding tissues and produces pain and general symptoms of cerebral irritation, which are sometimes very disquieting.