DURATION.--The course of the disease is slow; it lasts for months and years. The cases vary a good deal in the number and severity of the symptoms. Some cases run their course with nothing but the changes in the urine, loss of appetite, and a moderate degree of anæmia. In other cases the dropsy is the most prominent symptom, and in still others the cerebral symptoms predominate. There may be intervals of weeks and months during which all the symptoms, except the changes in the urine, disappear and then come on again. PROGNOSIS.--The prognosis of chronic parenchymatous nephritis is not good, but still it is not so bad as that of chronic diffuse nephritis: some of the cases recover and never have any further indications of kidney disease. TREATMENT.--The main indications for treatment are to improve the digestion, remove the dropsy, and restore the blood to a natural condition. It is usually necessary for the patient to give up his ordinary business and if possible to pass the winter months in a warmer climate. {82} Acute Diffuse Nephritis. This form of nephritis has been described under a variety of names. It has been called acute Bright's disease, acute desquamative nephritis, acute tubular nephritis, croupous nephritis, acute albuminuria, the first stage of chronic Bright's disease, acute parenchymatous nephritis, glomerulo-nephritis, and acute interstitial nephritis. MORBID ANATOMY.--The kidneys are increased in size, the capsules are not adherent, the surfaces are smooth. There may be an intense congestion of the entire kidney, including its pelvis, or the cortex is of an opaque white color mottled with red spots, and the pyramids are red. The tissue of the kidney is usually moist and succulent. In the tubes the epithelial cells are swollen, granular, and detached. Cast-matter and blood are found in many of the tubes. In the Malpighian bodies the cells which line the capsules are increased in size and number, sometimes to such an extent as to compress the tuft of vessels. The stroma of the kidney is infiltrated with serum, pus-cells, and blood. ETIOLOGY.--Most of the cases of acute diffuse nephritis occur after exposure to cold or as a complication of scarlatina. SYMPTOMS.--(1) The Idiopathic Cases.--Of these we may distinguish two sets of cases. In the first set of cases the invasion of the disease is acute. A person who has previously been usually in good health, after exposure to cold and wet will be suddenly attacked with rigors, a febrile movement, and pain in the back. There will be frequent and painful micturition, the urine being only passed a few drops at a time, or it is completely suppressed. The urine is bloody or of a brownish smoky color. It is of low specific gravity. It contains a very large amount of albumen, numerous hyaline, granular, epithelial, and blood casts and renal epithelium, and sometimes pus-cells. Later in the disease fatty casts are also present.