They have been attributed to various causes, as caustic alkalies and acids, the smoke of a burning building (Bouley, Rey, Riss), to an infection which operated on dogs and horses (Robertson), to bacteria and other irritants. _Lesions._ The mucous membrane of the mouth, pharynx and even the nares presents active inflammation with branching redness, petechiæ, circumscribed foci of necroses, and false membranes of a grayish, yellowish, reddish, greenish or blackish color. These are formed of a pellicle consisting mainly of fibrine and epithelium, pus globules and numerous cocci, and ovoid bacteria. The false membranes have been found on other parts of the intestinal canal (colon, cæcum); and broncho-pneumonia and pulmonary dropsy have been concomitants. The effect of the toxic products is seen in hæmorrhagic inflammation and infarctions of the kidneys, and in a black color of the somewhat diffluent blood. _Symptoms._ Besides the usual phenomena of pharyngitis, there is intense hyperthermia (105°–106°), hurried breathing threatening suffocation, painful cough roused by the slightest pressure on the swollen throat and often causing the discharge from the nose of shreds of false membrane. Auscultation of the pharynx gives a loud gurgling sound. Deglutition is very difficult and painful, liquids and even solids being rejected through the nose. The face is pinched and anxious and the mouth is often held open and the tongue pendant. Weakness and prostration are marked symptoms from the first, and the walk may be unsteady and swaying. The visible mucous membranes are congested and usually have a more or less deep tinge of yellow. The disease makes rapid progress and may prove fatal under six days. When it takes a favorable turn, recovery and convalescence may be equally prompt. Unless the expectoration of false membrane is detected, such cases are difficult of diagnosis, though a fair inference may be deduced from the extreme severity of the symptoms, and the unusual degree of prostration which is present. When a pharyngeal speculum, passing through the nose, can be availed of, it may become possible to reach a more definite conclusion. _Treatment._ Beside the measures advised for catarrhal pharyngitis (poultice, counter-irritants, laxatives, antithermics, alkalies, etc.), the main reliance must be placed on antiseptics. Persistent inhalations of warm water vapor with carbolic acid, creolin, tar, lysol, camphor or sulphurous acid are in order: also a mixture of one or other of these agents or of boric acid, bisulphite of soda, or salicylic acid in honey or molasses to be frequently smeared on the teeth. One of the best agents is the saturated solution of chlorate of potash in tincture of muriate of iron, of which a drachm may be added to three ounces of water and given every hour or two. Calomel may be injected through the nose during inspiration, by means of an insufflator, care being taken not to exceed the physiological dose.