Tubercle exists in the kidneys under two distinct conditions; in both, however, the cortical substance is the chief seat of the deposit.

a. In one case, it is the result of a very high degree of tubercular dyscrasia; a partial symptom of the development of tubercular disease in many or the majority of organs, and, in that case, frequently the product of a very tumultuous process of deposition. The tubercles are found to exist in great numbers, and occur in the shape of grayish-white, delicate vesicular, or larger, i. e. miliary granulations, surrounded by congested and ecchymosed parenchyma. The entire viscus is swollen, gorged, and softened; it is hyperaemic, and either darker than ordinary, or paler and infiltrated, and the mucous membrane of the urinary passages is reddened and injected. If the morbid process takes place with less intensity and has a more chronic duration, the tubercular matter is found in less quantity, of the size of millet- or hemp-seeds, and surrounded by pale tissue, which presents no trace of reaction either in the vicinity of or at a distance from the tubercular deposit.

This form of renal tubercle occurs as a complication of tubercular deposit in most parenchymatous organs and membranous expansions; and especially in conjunction with tuberculosis of the abdominal viscera, and more particularly of the spleen, the liver, and the peritoneum. Even when occurring under violent symptoms, it is rarely fatal by itself by paralysis of the renal functions, but it becomes so by the universal affection and by the coexistent disease of other organs. This variety of renal tubercle, even when its progress is less rapid, rarely proceeds further than to a yellow discoloration, and never advances to actual fusion. Both kidneys are commonly attacked uniformly.

/3. In the other case, renal tubercle is a partial appearance of tubercular disease that is limited to the male urinary and sexual organs. It then generally attacks the testes and the allied lymphatic and prostate glands primarily, and extends from these to the urinary apparatus, i. e. the mucous membrane of the entire tract, to the kidneys, and, lastly, to the supra-renal capsules. It is commonly viewed as possessing a blennor-rhoic character or as gonorrhoea! tubercle; but post-mortem examinations have not established the fact by demonstrating any peculiarity in the tubercular deposit. It very often supervenes upon a previous tubercular condition of the lungs, or the latter, as well as tubercle in other organs, allies itself to the advanced stage of renal tubercle. This variety of renal tubercle frequently reaches a high degree as regards the number of the tubercles, and their gradual accumulation into extensive groups and coalition into large masses. The viscus is found to have increased in size and is nodulated, and the tissues in the vicinity of the tubercle, or throughout the organ, are in a state of chronic reaction, and appear pale and dense, and infiltrated with lardaceous matter, and the tunica albuginea is thickened. This form of renal tubercle frequently passes more or less rapidly into the stage of softening, giving rise to tubercular ulceration (vomica renis tuberculosa), tubercular suppuration, and tubercular phthisis of the kidneys.

The disease generally attacks one kidney only in a very extensive degree.