Primary croup of the vesical mucous membrane is extremely rare; but secondary exudative processes are by no means as unusual as is commonly thought. The latter occur during the course of exanthematic diseases, especially of scarlatina and variola, during typhus as a symptom of an anomaly and degeneration of the typhous process, in consequence of absorption of pus in the blood, and associated with exudative processes in other mucous membranes.

The affection gives rise to a more or less coagulable fibrinous exudation of varying thickness, or to a viscid, gelatinous, discolored, purulent, or sanious product; it rarely involves the entire bladder, or even a large portion of it, but is generally limited to round spots or striae. The mucous membrane presents the most various degrees of injection and redness, varying from an almost imperceptible change to complete saturation of some portions, with considerable thickening and tumefaction, and an induration proportionate to the coagulability of the deposit. According to the character of the process, the diseased tissue becomes softened and converted into a pale or dark-red, reddish-brown pulp, or a gelatinous, purulent, or sanious mass; the local process not unfrequently assumes a gangrenous character, and the tissues are then resolved into a putrescent sanies, or become detached in the shape of an eschar.

As the exuded matter coagulates, it not unfrequently takes up urinary sediments, or these are subsequently deposited, and give rise to an incrusted appearance of the coagula or of the bladder.

We see the typhous process occurring in the vesical mucous membrane under various forms: a. It is rarely presented in the genuine shape, i. e. characterized by a product resembling that formed in the intestinal follicles and in the mesenteric glands.

B. It is frequently met with as a degenerate exudative process in the shape of scattered, insulated, and soft exudations.

y. It is seen degenerated to an exudative process resembling a gangrenous eschar. Opportunities of observing the complete metamorphosis of the products and their subjacent strata, in the shape of softening, fusion, and separation, are but rarely offered, as the general disease commonly proves fatal prior to these events.