=Congestion.= This, and its consequences, are the main features of hyperæmia of the kidneys, which is of frequent occurrence. This condition is almost always the result of some prior general affection, such as the scarlatinal poison, the suppression of perspiration, or obstructive diseases of the heart. In a simple congestion, with perfect integrity of the renal tissue, we find the kidney enlarged, and its weight often doubled; of a dark, red color, and dripping with blood when cut into. The cortical substance is somewhat softened, of a dark, red color, presenting in many cases small dark, red spots, the result of hæmorrhagic effusion into and between the tubercles. The Malpighian tufts are distinctly visible on the cut surface, as minute, reddish, semi-transparent grains. In the medullary cones, the congested vessels form long dark red streaks. If the congestions have occurred in an otherwise healthy kidney, the capsule can be readily peeled off. A microscopic examination shows the Malpighian and other capillaries loaded with blood, extravasation sometimes taking place into the capsule of the latter, and often into the channel of the fibres. In extreme cases of hyperæmia and congestion, a fibrinous exudation takes place, which will be found coagulated in the tubes, forming casts of their interior, and consisting of a granular or homogeneous material, entangling blood-globules, and often some particles of detached epithelium. =Hæmorrhage.= As a result of acute congestion, or from injury from falls, blows, or wounds of the kidneys, blood may be effused, either beneath its capsule, or within the sinus, constituting hæmorrhage of the kidney. =Nephritis.= This differs in no material respect from common inflammation of other parts, and like it, often passes into suppuration. Its most common causes are:—Excess in the use of irritating and alcoholic drinks; abuse of diuretics; blows or falls on the loins; the presence of renal calculi; and, according to some authors, a peculiar morbid state of the blood, such as gives rise to carbuncles. This disease can be distinguished from the inflammatory form of Bright’s Disease, during life, by its generally affecting only one kidney, by the much greater pain and tenderness in the lumbar region, by the retracting of the testicles, and the higher degrees of febrile excitement. Then, too, the deeply-colored urine which is voided, contains little or no albumen. In a case of nephritis, unattended with the formation of pus, a _post-mortem_ would probably fail to distinguish it from the condition of congestion just considered. Where suppuration was about taking place, the microscope shows the cortical tubes so distended and crowded together by infarcted epithelium, as to be scarcely distinguishable; in some parts the basement membrane gone, and their contents a uniform mass of nuclei and granular matter. The medullary tubes are also infarcted and opaque.