the bones. Triple phosphates may be found as a consequence of obstruction of the urinary passages and stagnation of urine.

Concretions composed of bilirubin may be formed in extreme jaundice, and particularly in the jaundice of the new-born. Infarcts composed of hemoglobin may be seen in cases of hemoglobinuria due to infectious and toxic causes.

INFECTIOUS DISEASES.

Tuberculosis.-Tuberculosis may occur in the kidney in the form of minute, grayish-white miliary tubercles as part of a general hematogeneous tuberculosis. A second form, which is also hematogenic, is known as chronic local tuberculosis. In this form the substance of the kidney near the cortex, or sometimes that adjacent to the pelvis, is occupied by masses of cheesy tuberculous tissue, and there may be secondary miliary tuberculosis near by. Softening is prone to occur, and the tuberculous focus may discharge into the pelvis of the kidney, leaving a necrotie cavity. The entire organ may be transformed in this manner. Tuberculosis of the kidney may also result from ascending infec tion, being secondary to tuberculosis of the seminal vesicles of the bladder, of the ureters, and of the pelvis of the kidney. The pro cess first involves the discharging tubules at the apices of the pyramids and spreads outward toward the cortex. Cheesy foci are formed, which may soften and discharge into the pelvis, as in the case of chronic local tuberculosis of the kidney. It is difficult to determine whether tuberculosis of the kidneys is more frequently the result of urogenital tuberculosis primarily affecting the parts below, or the cause of the latter. Primary affection of the kidney is certainly more common than many have been disposed to admit.

Syphilis. In the earlier stages of syphilis there may possibly be acute nephritis similar to that of other infectious diseases. Syphilis of long duration may lead to amyloid degeneration of the kidney, or to chronic interstitial nephritis. In the latter case contractions of fibrous tissue leading to marked lobulation are rather characteristic. Syphilitic gummata are rare, but have been met with, and in their healing lead to marked scar-formation.

TUMORS.

Fibromata and lipomata may occasionally be met with in the kidney in the form of small rounded nodules. In association with calculous pyelitis and other conditions of the kidney leading to atrophy, the fatty tissue surrounding the kidney may be increased to such an extent as to constitute practically a fatty tumor. Leiomyoma is an occasional growth of the kidney.

Congenital Adenoma.-Under the name of struma aberrata suprarenalis has been described a form of tumor of the kidney which results from splitting off of a remnant of the suprarenal capsule and its incorporation in the kidney, where it subsequently grows. The tumor presents the appearance of a small lipomatous growth beneath the capsule of the kidney, or, more rarely, it may attain considerable size. Histologically it consists of epithelial cells arranged in tubules similar to those of the cortical portion of the suprarenal capsule. These undergo considerable fatty infiltration, and almost the entire tumor may be fatty. Occasionally active proliferative changes occur in the epithelium, and a malignant character is assumed.

Sarcoma of the kidney is the most frequent malignant tumor. It may occur congenitally, or in later life. The size and general appearance vary considerably, but for the most part the structure is soft and grayish or sometimes quite red. Extravasations of blood or hemorrhages into the tumor are not uncommon. There may be a distinct capsule, or the growth may be an infiltrating one. Cystic softening is not infrequent.

Microscopically the appearance varies considerably, and the growth may be composed of round cells, spindle cells, or cells of various shapes. Not rarely a certain number of striped musclefibers are found, and to such growths the term rhabdomyosarcoma has been applied. In other cases there may be embedded in the sarcomatous tissue glandular acini composed of cylindrical or irregular epithelium, and to such the name adenosarcoma is applicable

FIG. 283.-Adenosarcoma of the kidney (modified from Kast and Rumpel).

(Fig. 283). Occasionally myxomatous tissue, smooth muscle-fibers, or even islets of cartilage are found. The multiform character of sarcoma of the kidney suggests an embryonal origin, and it is not unlikely that inclusions of the primitive Wolffian body are the starting-point of the disease.

Adenoma of the kidney is rare. It originates in the convoluted tubules, and presents itself in the form of more or less

nodular masses. Microscopically the appearance is that of a tubular adenoma. Proliferative changes occasionally affect the uriniferous tubules in interstitial nephritis, and give rise to small areas of adenomatous appearance. In such cases, however, the appearances are not those of a tumor in the strict sense.

Papilliferous cystic adenoma is sometimes observed. It occasions tumors of small or large size with fibrous capsules and cystic excavations in which the lining epithelium is elevated in a papillomatous manner.

Carcinoma is a rare primary tumor of the kidney, and occurs in persons of advanced years. The growth begins in the cortical substance or in the medulla, and presents itself as a soft white or, in case of hemorrhage into it, red tumor.

Microscopically it is found to be a glandular carcinoma presenting acini composed of epithelial cells of various shapes. Metastasis is rare.

Secondary Tumors.-Among the secondary tumors of the kidney are both sarcoma and carcinoma.

In the same group may be included the lymphomatous infiltra

tions of leukemia (Fig. 284). In this disease the kidney is often enlarged, and on section is found to be uniformly white or mottled in color, the light-colored areas representing masses of lymphoid cells. Most of these have doubtless been deposited from the circulation, but there is also evidence of local multiplication.

Cysts of the kidney are of various forms. In the course of chronic nephritis, especially the interstitial form, cystic dilatations of the convoluted tubules and Malpighian bodies are observed. These appear as small or large rounded bodies lying immediately beneath the capsule, and on section are found to contain serous liquid,

or colloid material, the result of degeneration of the epithelial lining of the cyst. Sometimes very large cysts of this character are met with in cases of nephritis, or even in otherwise healthy kidneys (Fig. 285). Cysts observed in kidneys which show no other disease

delphia Hospital).

are probably due to undiscovered obstructions of the uriniferous tubules.

Congenital cystic kidneys are of striking appearance. Usually both kidneys are affected, and are transformed into masses composed of innumerable cysts varying in size from microscopic points to cavities as large as a walnut (Fig. 286). On section the cysts are found to be filled with clear urinous liquid, or with colloid material, and between them is a stroma of more or less firm

fibrous tissue. The pelvis of the kidney is usually preserved. These cysts are formed by dilatation of the uriniferous tubules and Malpighian bodies, probably as the result of some fetal disease

FIG. 286.-Congenital cystic kidney (Specimen 2816, Museum N. Y. Hosp.).

which causes obstruction of the tubules at their outlet at the apex of the pyramids, or in consequence of faulty union between the upper and the lower segments of the uriniferous tubules in the development of the organ. Similar cystic degeneration, with enlargement of one or both kidneys, may occur in later life. Finally, cystic adenoma may again be alluded to.

PARASITES.