Tracheal ulcers are just as multiform as laryngeal ulcers, but far more rare. Like inflammation, they may occur by extension from above or below, {137} and only those following localized morbid conditions are certain to have arisen in the trachea. Under the head of Inflammation it has been stated that simple catarrhal ulceration does occasionally occur; of this there is really no doubt, but some writers have denied it and thrown the whole subject into great confusion. It is true, however, that a tracheal ulcer has usually a so-called dyscratic base, and either is diphtherial or phthisical (tuberculous) or syphilitic or lupoid or leprous or carcinomatous, or else comes from extraneous causes; as, for instance, from traumatic ulceration or extension or perforation from neighboring abscess, etc. There are two kinds of ulcers--viz. one in which the molecular death of tissue proceeds from the surface inward, and another in which it proceeds from within to the surface. Catarrhal ulcers, as well as ulcers from decubitus after tracheotomy, from pressure of the canula, belong to the first kind; when involving only the epithelium or the epithelium and the layer immediately underneath it the name erosions is given them; and if it were true that catarrhal erosions never penetrate to the deeper structures, it would be justifiable to say that there are no catarrhal ulcers, but only erosions: they do, however, penetrate, and sometimes to great depths. In the second kind of ulcers the epithelium is at first normal or intact, and the loss of substance of underlying tissue in consequence of inflammatory processes in the mucosa, submucosa, or perichondrium affects the epithelium secondarily. This occurs whenever, from any cause, there is primarily caries of cartilage or suppuration of submucous tissue, especially in typhoid conditions, in phthisis, and in syphilis. [Illustration: FIG. 27. Tuberculous Ulceration of the Trachea, as seen during life.] [Illustration: FIG. 28. Same case as Fig. 27: post-mortem appearance.] [Illustration: FIG. 29. Syphilitic Ulceration of Trachea, as seen during life.] {138} [Illustration: FIG. 30. Same case as Fig. 29: post-mortem appearance.]