BLACK LEG 245 
Morbid anatomy. After death the carcass soon becomes distended 
with gas. This is due in part to the fermentation in the digestive 
tract and in part to the formation of gas in the subcutaneous tissues 
due to the presence of the specific bacillus. The subcutaneous dis- 
tension is especially marked in the region of the swellings but it extends 
for a considerable distance from these foci in the direction of least 
resistance. The tympanitic condition often causes the two legs on the 
upper side of the carcass to extend out straight without touching the 
ground. A dark, blood-colored, frothy discharge flows from the 
nostrils and anus. Decomposition takes place very rapidly except in 
the affected muscles, which retain a sweetish-sour odor for a consider- 
able time after other parts of the carcass have become putrid. 
The skin covering the swelling is often affected with dry gangrene. 
The subcutaneous connective tissue is yellow, gelatinous, infiltrated 
with blood and bubbles of gas which escape if the tumor is incised. 
The muscles underneath the tumors are of a dirty brown or of a black- 
ish color. At other places they are dark red or dark yellow and, when 
exposed for some time to the air, they may have a golden lustre. 
They are brittle, putrid and very rich in fluids. They crackle on pal- 
pation. When incisions are made into them, blood of a frothy, greasy, 
tarry appearance and of a sickish, fetid odor issues from them when 
they are squeezed. The fibres of the muscles show extremely varied 
degenerative changes. The gases that are present in the muscles are 
inflammable and burn with a bluish flame on being ignited. They 
are said to have but little odor, on which account it is assumed that 
they consist of carburetted hydrogen. A complete chemical analysis 
of these gases seems not to have been made. The lymph glands near 
the tumors are enlarged and full of blood. They contain hemorrhages 
and are infiltrated with a serous fluid. The afferent lymph vessels 
are sometimes distended with gases, giving them the appearance of 
strings of beads. Changes similar to those of the external muscles 
appear in the muscles of the tongue and pharynx when the disease, as 
may happen in rare cases, is localized on the oral and pharyngeal 
mucous membranes. 
A large amount of blood-red exudate is frequently found in the 
abdominal cavity. In other cases only a small quantity of a serous 
fluid is present. In still others no changes at all appear. The 
abdominal changes seem to be determined by the swelling of the 
muscles, that is, whether it has or has not spread to the peritoneum. 
Yellow gelatinous and hemorrhagic infiltrations are often met with on 
