An attempt to discover minute lesions peculiar to the various groups gives results that are far from satisfactory. With reserve it may be said that carnivorous animals show a tendency to greater interstitial and glomerular lesions than do herbivorous ones, and that casts are more often found, in all kinds of nephritis, in the former varieties. Rodents are conspicuous exceptions to this statement, since they frequently have glomerular lesions and casts in abundance; this exception exemplifies the unwisdom of drawing definite conclusions in this respect. Birds as contrasted with mammals show very prominent tubular and inconspicuous glomerular lesions. The principal alterations seen in the avian kidney are round cell infiltrations of the deep cortical and outer medullary zones, and cloudy or hydropic swelling of the convoluted tubules. In chronic cases intertubular fibrosis is clear but not so definite as the perivascular, while the glomerular tufts are occasionally wholly normal. When these are destroyed it seems to have occurred by compression rather than by inflammation. A form of nephritis peculiar to birds might be termed local necrotizing. It seems to be due to local urate deposits and to have its origin like that form already mentioned under acute interstitial nephritis. It has been seen in avian gout, a condition in which the kidneys may or may not have visible masses of hardened urates in them. The gross picture is of a spotty pale organ of a gray-brown color. Minutely studied the medulla, adjacent cortical tubules and perhaps the pelvic tissues will present an opaque condition taking a diffuse basic dye. Crystals have not been seen. This form is especially common in Columbæ, Psittaci and Herodiones. GENERAL EFFECTS OF NEPHRITIS.