280 DISEASE IN WILD MAMMALS AND BIRDS 
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 excep- 
tions to this statement, since they frequently have 
glomerular lesions and casts in abundance ; this exception 
exemplifies the unwisdom of dra^ving definite conclusions 
in this respect. 
Birds as contrasted with mammals show very promi- 
nent 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 glomer- 
ular 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 ^vill present an opaque condition taking a diffuse 
basic dye. Crystals have not been seen. This form is 
especially common in Columbae, Psittaci and Herodiones. 
General Effects of Nephritis. 
The results of nephritis generally speaking are edema, 
anemia, cardiac hypertrophy, inflammations of the se- 
rous surfaces and uremia. Aside from the cases of chronic 
parenchymatous nephritis cited above, edema has been 
decidedly inconspicuous. It may be found in avian cases 
of acute and subacute nephritis, about the flanks and in 
