32 BULLETIN 1G1, U. S. DEPARTMENT OF AGRICULTURE. 
The animals are anemic, and pronounced accumulations of serum 
are usually found beneath the skin and in connection with the serous 
surfaces. This in the cases autopsied was especially pronounced in 
the mesentery, which was much thickened and contained a jellylike 
deposit which in some cases forced the serous layers apart. The 
swelling ruptures numerous blood vessels, causing hemorrhagic spots. 
The heart had many petechias or small hemorrhages on its surfaces, 
and there was sometimes a serous accumulation on its surface or on the 
pericardium. 
The abdominal cavity of one animal was distended with a serous 
accumulation. The kidneys may show small hemorrhages. 
One animal autopsied appeared to have passed by the acute stage of 
congestion. The intestines were darkened from an old congestion, 
and the thickened mesentery was adherent in places to the body wall, 
as were the liver and kidneys. In this case no serous deposits were 
found under the skin, but the skin was unusually adherent to the flesh. 
MICROSCOPIC PATHOLOGY. 
The most prominent lesions in cattle killed by oak-brush poisoning 
occur jjlthe alimentary tract and the kidneys. The abomasum and 
the inii|tines show a condition of gastroenteritis, often in a very 
severe'ferm. The part of the alimentary canal where this inflamma- 
tion is exhibited in the greatest intensity varies in different animals. 
The intestines are inflamed or show changes which follow this con- 
dition, such as degeneration of epithelial lining and glandular tissue, 
increase in connective tissue especially in the mucosa, and edema of 
the intestinal walls, which are often thickened. Both small and large 
intestines are involved. 
The abomasum or fourth stomach in most cases shows changes 
similar to those found in the intestines. 
The kidneys are inflamed and show a pronounced edema, which is 
indicated by shrunken glomeruli, enlarged tubules, and numerous 
casts in the tubules. In some cases the epithelial cells lining the 
tubules appear stretched and flattened, but in most cases they are 
more or less degenerated. The epithelium in many tubules is sloughed 
off from the basement membrane. The enlarged tubules give the 
kidney sections a cystic appearance. There is an increase in the 
connective tissue between the tubules. 
Most of the other tissues may be edematous. This condition is 
frequently seen in the heart, liver, pancreas, and various serous tissues. 
In connection with these edematous swellings hemorrhagic spots often 
occur. 
LENGTH OF TIME NECESSARY TO PRODUCE HARM FROM OAK FEEDING. 
Observation on the range and experimental feeding both show that 
some cattle may eat oak brush for a long time with no definitely bad 
effect. Some will even eat oak exclusively with no harm. Generally 
