(2) More Severe Cases.--The kidneys are increased in size. The cortex is thick and whitish, with white striæ extending in to the bases of the pyramids. The epithelium of both the convoluted and straight tubes and of the Malpighian bodies is swollen and granular. There is cast matter in the tubes. {79} (3) The Most Severe Cases.--The increase in the size of the kidneys is still more marked. The epithelium of most of the tubes is not only swollen and granular, but is also in many tubes detached from their walls. A great deal of cast-matter, and sometimes blood, is found in the tubes. There are no changes in the stroma or in the blood-vessels of the kidneys. ETIOLOGY.--Acute parenchymatous nephritis occurs both as a primary and secondary lesion. The idiopathic cases occur without assignable cause or after exposure to cold, and are not very common. The secondary cases are seen very frequently. They complicate a variety of other diseases. With pneumonia, typhus fever, and typhoid fever the nephritis is usually of mild type. With yellow fever and acute atrophy of the liver the nephritis is very severe. With scarlatina, diphtheria, pyæmia, peritonitis, phosphorus- and arsenic-poisoning the severity of the nephritis varies with the different cases. SYMPTOMS.--(1) The Idiopathic Cases.--The urine is diminished in quantity and may be suppressed; its specific gravity continues nearly normal; it contains albumen, usually in large amounts, sometimes blood: in some cases very few casts are seen, in others there are large numbers of hyaline, granular, and nucleated casts. As regards the other symptoms, it is convenient to divide the idiopathic cases into three classes. In the first class dropsy and anæmia are the most marked symptoms; with these there are loss of appetite and a depreciation in the general condition of the patient. In the second class cerebral symptoms are more prominent. There will be delirium, convulsions, stupor, coma, and with these persistent vomiting, dyspnoea, and great prostration, but no dropsy. The third class suffer from the symptoms of both the other classes. Dropsy, anæmia, loss of appetite, cerebral symptoms, vomiting, dyspnoea, and prostration are all present. (2) The Secondary Cases.--The condition of the urine varies with the intensity of the nephritis. In the mild cases the urine is unchanged. In the more severe cases we find the urine diminished in quantity, containing albumen in varying amount, sometimes blood. Hyaline and granular casts are often present, but are not very numerous. Dropsy does not usually occur except with the parenchymatous nephritis of scarlatina. Nausea and vomiting are not infrequent, but it is often difficult to tell whether they are due to the primary disease or to the nephritis. Cerebral symptoms--convulsions, delirium, stupor, and coma--occur with the more severe cases.