268 DISEASE IN WILD MAMMALS AND BIRDS 
was gone, the organ irregular and small, being half or less 
of the size of the other organ which was larger than is 
considered normal for the species. Histologically the 
large organ was practically normal. A common opossum 
(Didelphys virginiana) suffered with a complete suppura- 
tive nephritis of the right side which completely destroyed 
the organ; the origin of this is not clear as no ascending 
disease could be determined and no certain acute infection 
had existed; decomposition precluded satisfactory bac- 
teriology. The left kidney was nearly twice its normal 
size and involved in an early diffuse nephritis, with 
miliary abscesses, in which the glomeruli did not partici- 
pate. There were in these sections evidences of regenera- 
tion, swollen reduplicated epithelial coverings presenting 
a picture similar to those seen in so-called chronic 
nephritis secondary to interstitial change. 
Infiltrations. 
Pathological infiltrations of the renal structures are 
exceedingly uncommon. Early in our experience we were 
often perplexed at the appearance of certain organs, 
notably in carnivores and marsupials to which we were 
inclined to apply the term fat infiltration. However the 
absence of reasons for considering tliis picture pathologi- 
cal seemed sufficient cause to ignore the finding, and later 
Pfeiffer(8) called attention to the apparent inability of 
these kidneys to emulsify fat or at least to combine it in 
an invisible form, an ability possessed by the herbivorous 
organ. A monkey and a passerine bird only showed suffi- 
cient fat \'isible in the renal epithelium to warrant a 
denomination of fatty infiltration ; these were both obese 
specimens. Amyloid infiltration occurred in four mam- 
mals and six birds, being a sequel of its usual causes, 
tuberculosis, chronic suppuration and osseous system 
disease. It is perhaps well to emphasize the fact that 
every organ the seat of amyloid deposit need not be 
(8) Arch. f. Tierheilk., V. 38-99. 
