536 
M. FRANCIS. 
My opinion is that the calf licked the sores on his legs, and in 
doing so took in some eggs that hatched and developed in the 
stomach. 
Horses and mules are not so often attacked. In them they 
are usually found in barbed wire injuries, and occasionally in 
the sheaths of horses, the vaginae of mares, and the navels of 
colts. 
Hogs are more liable to become affected than horses. They 
are frequently wounded by dogs and by fighting, or there may 
be barbed wire injuries, wounds from castration, etc. 
Sheep are comparatively free from attacks unless injured 
by dogs. 
In all animals alike, the eggs, after being laid by the fly, 
hatch into larvae or so-called “ worms.” The exact length of 
time this requires seems to vary with circumstances. My 
present opinion is that, if the eggs are laid in a moist place 
and on a warm day, it requires less than one hour; whereas, 
if laid in a dry place they seem to dry up and lose their vital¬ 
ity. The young larvae when first hatched are small and easily 
overlooked. If they are hatched on the surface in a drop of 
blood from a ruptured tick, for instance, they attempt to per¬ 
forate the skin, and if hatched in wounds they at once become 
buried out of sight. They seem to attach themselves by their 
heads, and burrow their way under the skin, completely de¬ 
vouring the soft flesh. Occasionally a few are seen moving 
from one place to another, but usually they remain fixed at 
one point. The worms grow steadily in size, and the hole in 
the flesh becomes larger every day. Sometimes the worms 
make tunnels, but not to an)" depth ; they usually stay on the 
surface. They evidently produce considerable irritation, for 
the part is always swollen and constantly bleeding. This 
swollen, gaping appearance of the wounds, together with the 
constant discharge of blood, are characteristic of the presence 
of worms. It seems to require about a week for the worms 
to become fully grown. At that time they are about five- 
eighths to six-eighths of an inch long. They then leave the 
sore and go into the ground, where they pass their pupa state 
and hatch out as flies in from nine to twelve days. Of several 
