1. Inflammation of the urinary passages have to be first mentioned, and especially a. Catarrhal inflammation, both on account of its frequent occurrence, as on account of its consequences and its transition to the substance of the kidneys. As a primary disease, it appears in the shape of inflammation of the renal pelvis and the calices (pyelitis), with inflammation of the kidney, as may be gathered from the description of nephritis and Bright's disease; it may be secondary, owing to irritation exerted by accumulation of urine and urinary concretions on the mucous membrane of these parts (pyelitis calculosa); and it may also be and very often is metastatic, the inflammation of the bladder being transferred to the ureters, the pelves, and calices.

It is either acute, as in the case of complication with acute nephritis, or more commonly chronic, being maintained by lasting and repeated noxious influences, or being the result of a chronic morbid process in the bladder, in which case we meet with temporary acute exacerbations. It is of extreme importance, and renders the following details necessary.

The characters are, in proportion to the degree of intensity and duration, a dusky reddish or brown-red congestive state, similar or ashy dis-colorations in the shape of solitary spots or islands, or of extensive connected patches, tumefaction and villosity of the mucous membrane, and secretion of a yellow puriform mucus, blennorrhcea.

The longer the inflammatory condition lasts, the more the gradual dilatation of the urinary passages, with hypertrophy of the membranes, increases, both in consequence of the paralysis of the external contractile and irritable layer as from the accumulation of the renal and the morbid mucous secretion.

At an advanced degree, as in the temporary exacerbation of chronic inflammation, the mucous membrane, particularly when subject to irritation by gravel and calculi, which chiefly affect the calices and pelves, appears of a saturated red color, considerably swollen, spongy, and friable; a purulent, more or less sanguineous, fluid is secreted (superficial suppuration), the surrounding cellular and adipose tissues are traversed by varicose vessels, and infiltrated. We find that moderate catarrhal inflammation of the ureters gradually extends to the kidney in the shape of chronic inflammation; it equally attacks the kidney with tumultuous symptoms as acute inflammation when it has reached this advanced degree, and thus proves fatal.

The above-mentioned high degree of inflammation is also found to pass into suppuration of the urinary passages, which spreads from the calices to the tissue of the kidneys, and causes in the latter the formation of abscesses or extensive ulcerative destruction, occasionally urinous infiltration of the renal parenchyma, gangrenous ulceration, and gangrene of the calices and pelvis. We thus find it gradually proceeding in the ureters to perforation, slow infiltration of urine in the adjoining tissues, inflammation, suppuration, necrosis, and in fortunate cases, formation of circumscribed abscesses with indurated parietes.

In these various conditions, the urinary passages contain an alkaline urinous fluid of a pungent odor, which is variously discolored; it is mixed up with puriform mucus or true pus, sanies, blood, and portions of broken-up tissue, and it frequently deposits a sedimentary incrustation upon the inflamed mucous membrane.

In rare cases the advanced stages of the disease terminate favorably in obliteration of the urinary passages. After the cessation of the urinary secretion, consequent upon complete atrophy of the renal tissue, from pressure exerted by the dilated renal calices, or more frequently consequent upon the coexisting chronic inflammation of the kidney, the tissues contract, the parietes become thickened, and the calibre of the passages is gradually reduced, till complete obliteration results. The fluid contained in the cavity of the calices, which consists of blennorrhoic mucus, pus, and urine, the latter being strongly impregnated with alkalies, salts of lime, and particularly with phosphates, first causes an incrustation on the parietes of the calices, and then becomes inspissated, so as to form a grayish or yellowish-white, greasy, and chalky pulp, which fills the calices; the kidney thus presents the appearance of a loculated cyst, the compartments of which contain the pulp, and radiate from the hilus to the circumference. This pultaceous substance is in due course converted into a dry mortar-like, gritty, dense, calculous mass, and the tissues contracting at the same time, the sac is reduced, the kidney and the efferent channels are obliterated. Occasionally this metamorphosis is observed to take place in one or more detached calices.

Occasionally laminated, corded, nodulated, and amorphous bony concretions are formed in the membranes of the renal calices and pelves, after these have been previously converted into a fibroid or cartilaginous tissue by the inflammatory process; the same may occur in the ureter, though we have not observed it ourselves.

B. Exudative Inflammation

This is on the whole an unusual occurrence, and as far as we are able to judge, invariably a secondary affection; we have never met with a case of idiopathic croup of the urinary organs. It is found complicated with products of the most various plasticity, following typhus, exanthematic diseases, more especially variola and scarlatina, exudative processes in other tissues, as diphtheritis and acute tuberculosis, and purulent infection of the blood; it is very frequently the consequence of extreme disorganization of the blood (especially the so-called status putridus), and then appears as hemorrhagic exudation with purple or dark-red discoloration, sanguineous infiltration, friability and solution of the mucous tissue, and hemorrhage. It may extend over a large surface, or be confined to isolated spots, and it not unfrequently implies gangrene.