104 
MANUAL OF MODERN FARRIER* 
animal body, this organ is so admirably constructed that in 
its healthy condition no artificial aid is necessary to enable 
it to perform its office. If the opinion of Mr. Clark were 
correct, what would supply the place of those parasites 
during that portion of the year when the grub assumed 
its perfect condition ? 
Post-mortem dissection has proved that bots are not so 
inoffensive as Mr. Clark supposed ; as it has been found 
that horses which have been infested with these grubs had 
ulcers of considerable extent in the muscular coat of the 
stomach. 
Symptoms and Habits. —The progress of the disease gene¬ 
rally manifests itself gradually ; the horse becomes hide¬ 
bound, his coat becomes rough and unhealthy, he loses flesh 
and strength, although he feeds with his usual appetite, and 
has frequently a tickling cough. 
Cause. —The bots are a species of gad-fly called oestrus 
equi by naturalists, which may be observed in the month of 
July flying actively about the legs of horses in the fields. 
These flies are represented, (plate x., fig. 1,) which is the 
common gad-fly. They may be seen flying rapidly towards 
the sides and knees of horses. These are the females 
depositing their eggs in the hair, to which they adhere by a 
glutinous fluid by which they are surrounded (fig. 2, 3.) In 
a few days the eggs are hatched, and the minute grubs 
or caterpillars which they contain are set at liberty. This 
operation is performed by the horse, which, in licking him¬ 
self, bursts the eggs, and the caterpillar adheres to his 
tongue, and in the operation of eating the little animal is 
carried into the stomach along with the food. These 
caterpillars are provided with a small hook on each side 
of their mouths and by means of which they cling per- 
tinaceously to the cuticular portion of the lining of the 
