434 FOOT AND MOUTH DISEASE 
the tongue. In some cases the back of the tongue may be the seat of 
large blisters. 
The vesicles burst soon after their appearance, sometimes on the 
first day. More rarely they may persist for two or three days. After 
the vesicles rupture the temperature subsides. After they have 
ruptured the grayish-white membrane forming the blister may remain 
for a day or more or disappear speedily and leave deeply reddened 
areas or erosions which 
are very painful. These 
exposed areas may soon 
become covered with 
epithelium or they may 
be converted into ulcers. 
In this stage the saliva 
forms in large quantities 
and hangs in strings 
from the mouth. In 
eight to fourteen days 
the disease may have 
entirely disappeared. 
In addition to the 
changes in the mouth, 
one or more feet may 
become diseased. The 
skin around the coronet 
and in the cleft between 
the toes becomes hot and 
Fic. 93. PHOTOGRAPH OF SICK COW SHOWING tender and may swell. 
DROOLING. 
Blisters appear as in 
the mouth, but they are speedily ruptured and the inflamed, exposed 
areas are covered with a viscid exudate. The animals move in a 
stiff manner. Emaciation progresses rapidly, and in milch cows lac- 
tation is greatly diminished. 
The udder, more particularly the teats, may be the seat of lesions. 
Some authorities regard the udder disease merely as the result of 
infection during milking. The vesicles are broken by the hands of the 
milker and the teats become covered with reddened areas deprived 
of the superficial layer of the skin and are very tender. The healing, 
however, goes on quite rapidly. These are the main symptoms 
