DISEASES Of THE DIGESTIVE ORGANS. 173 
mh. At the first hatching, as we observe, it is a small, active 
worm, long in proportion to its thickness; but as its growth ad- 
vances, it becomes proportionably thicker and broader, and beset 
with bristles. 
Bots are very frequent in horses that have been at grass, and 
are, in general, found adhering to the white insensible tissue or coat 
of the stomach. They usually hang in dense clusters to the white 
cuticular lining of the stomach, and maintain their hold by meaas 
of two dark brown hooks, between which a longitudinal slit is seen, 
which is the mouth of the larve. When removed from the stoxrach 
by tne fingers, by a sudden jerk, so as not to injure them, they 
will, if fresh and healthy, attach themselves to any loose mem: 
brane, and even to the skin of the hand. For this purpose they 
sheath or draw back the hooks almost entirely within the skin, 
until the two points come close to each other. They then presem 
them to the membrane, and, keeping them parallel till it is pierced 
through, they expand them in a lateral direction, and afterward, by 
bringing the points downward toward themselves, they include a 
sufficient piece of the membrane, to remain firmly fixed for any 
lencth of time, as if at anchor. These bots pass the autumn, 
winter, and spring months in the stomach, and arrive, about the 
commencement or middle of the summer, at their full growth, 
requiring a year to fully complete their structure. 
The (estrus Hemorrhoidalis, or Fundament Bot.—The parts 
chosen by this insect for this purpose is the lips of the horse, 
which is very distressing to the animal, from the excessive titi‘ta- 
tion it occasions; for he immediately rubs his mouth against the 
ground, his fore-legs, or sometimes against a tree, with great 
emotion, till the animal, at length, finding this mode of defense 
insufficient, quits the spot enraged, and endeavors to avoid it 
by galloping away to a distant part of the field; and if the fly 
still continues to follow and tease him, his last resource is in the 
water, where the estrus never is observed to pursue him. These 
flies appear sometimes to hide themselves in the grass, and, as the 
horse stoops to graze, they dart on the mouth or lips, and are 
always observed to poise themselves, during a few seconds, in the 
air, while the egg is preparing on the extended point of the abdo- 
men. When several! of these flies are confined in a close place, 
they have a particularly strong, musty smell ; and I have observed 
poth sheep and horses, when teased by them, to look into the grass 
