104 MANUAL OF MODERN FARRIERr. 



animal body, this organ is so admirably constructed that in 

 its healthy condition no artificial aid is necessary to enable 

 it to perform its olffice. If the opinion of Mr. Clark were 

 correct, what would supply the place of those parasites 

 during that portion of the year when the gi^ub assumed 

 its perfect condition 1 



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 



