FATTY DEGENERATION OF THE KIDNEY: STEATOSIS OF THE KIDNEY. Causes: age, overfeeding, idleness, atony, retention of urine. Lesions: kidney enlarged, pale yellow, capsule loose, cut surface glistening unctuous, oil globules in scrapings, granules soluble in ether. Symptoms: in idle, overfed, obese, improved meat producing breeds, closely confined, starchy or saccharine food, fatty granules in urine, finally dropsies, anæmia, debility, sluggishness. Prognosis unfavorable in advanced stage. Treatment: butcher, restricted regimen, open air exercise, nitrogenous diet, crossing, diuretic food or drugs, oil of turpentine, balsam copiaba. Palliation only. Fatty degeneration of the kidneys is by no means unknown in the domestic animals. It has been observed in dogs and cats (Rogers, Goubaux, Vulpain, Trasbot). In dogs it has been erroneously set down as a characteristic lesion of rabies. Like fatty degeneration of other organs, it is also met with in old and overfed individuals of meat producing breeds of animals, in which the tendency to early maturity and rapid and excessive fattening has been fostered from generation to generation. In man small, granular, fatty kidney is a common result of chronic parenchymatous nephritis, and often coincides with fatty liver. Chronic poisoning by arsenic or phosphorus is another cause, as it is of fatty degeneration in other organs. Vulpain has attributed it to a lack of active exertion and of general tone, associated with excessive amylaceous feeding, sluggish, shallow breathing and tardy elimination. Goubaux and Trasbot attach great importance to the compulsory retention of urine in house dogs, cats and horses. The damming back of the urine in the convoluted tubes and glomeruli, temporarily arrests secretion, and the inactive and compressed cells tend at once to granular and fatty degeneration. _Lesions._ The gland is sensibly increased in size, and pale, yellowish or straw yellow. The capsule is easily detached from the cortical substance, contrary to what is the case in chronic productive inflammation. The cortical substance is increased in thickness, and pale, the pallor being largely in ratio with the duration or extent of the fatty degeneration. The cut surface may be glistening and unctuous to the touch. It is softer than usual, rather friable, and if scraped, furnishes a serous or grayish pulp in which oil globules are prominent features, together with granular epithelium and free granules that dissolve readily in ether. Tubules are varicose and unequal at different parts. The medullary portion has undergone little change. It may be paler at certain points, with some shrinking of its substance and increase of firmness.