The very worst complication of laryngitis is oedema of the glottis. It {95} affects both the mucous membrane and the submucous tissue of the larynx. It is met with on the inferior (posterior) surface of the epiglottis, in the ary-epiglottic folds, and on the false (inferior) vocal cords, the submucous tissue of which is of a very loose structure normally. Amongst its causes--which may be various (foreign bodies in the larynx, injuries, mechanical and chemical irritants of any kinds; typhoid, tubercular, variolous, syphilitic ulcerations; erysipelas of the neighborhood, inflammations of the parotids or tonsils, suppuration in the pharynx, thyroid body, and cellular tissue of the neck)--both catarrhal and croupous laryngitis are not at all uncommon. This is particularly so when they are complicated with cardiac and renal anomalies, pulmonary emphysema, and compression of the veins of the neck by glandular swellings; also with changes in the structure of the walls of the blood-vessels. The last-named pathological conditions are alone capable of giving rise to chronic oedema of the larynx, which is by no means so fatal, but still dangerous. In glottic oedema the dyspnoea is both very great and very sudden. First, it is inspiratory only, but soon becomes both inspiratory and expiratory. The swelling is felt distinctly by the examining finger; the laryngoscope is neither required nor advisable. DIAGNOSIS.--It is by no means easy in all cases. When laryngeal diphtheria (membranous croup) happens to be frequent, the most experienced diagnostician will meet with occasional difficulties. The sound of the barking, explosive, tickling cough locates its origin in the larynx, but the affection may be very mild or very severe. Expectoration in small children is not pathognomonic; even when it is copious it is not brought up, but swallowed. Fibrinous expectoration would settle the diagnosis of a croupous process. Depressing the tongue with a spoon or spatula and producing the movements of vomiturition often reveals the presence of a tough, viscid mucus rising from the larynx. It renders the catarrhal nature of the laryngitis positively clear. The frequency or volume of the pulse is of no account in diagnosis; it is too variable. Of more importance is the temperature, at least in children. Uncomplicated sporadic croup has no increase, or very little; catarrhal laryngitis is mostly attended with high fever. In very many cases this symptom has guided me safely, in spite of the statements of the books. The stenosis of catarrhal laryngitis comes on very suddenly, in diphtheritic laryngitis mostly slowly. In the former it is not of long duration; remission sets in soon, and is more complete than in membranous croup. An attack of stenosis occurs mostly in the night, and is apt to return with the same vehemence after a fair remission after twenty-four hours. The frequency of relapses in catarrhal laryngitis in children who have been affected before must,