i7« 



THE FARM DOCTOR. 



aid of the hooks around their heads they attach themselves ta 

 the mucous membrane mainly of the left half of the stomach, 

 but often also of other parts, such as the right side of the 

 stomach, the duodenum or small gut leading from the stomach, 

 and the throat. There they steadily grow in the winter. 



Fiof. 20. — Bot-fly, Oistrus Equ.i, 



V\". 21. — Bot. Larva of CEstrus. 



Fig. 22. — Bots hooked on the mucous 

 membrane of the stomach. 



and in spring pass out with the dung, burrow in the soil, 

 and are transformed into the gadfly. The disturbance they 

 cause depends on their numbers and the portions of the canal 

 on which they attach themselves. In the throat tliey produce 

 a chronic sore-throat and discharge from the nose, which con- 

 tinues until the following spring, unless they are previously 

 extracted with the hand. In the left half of the stomach, which 

 is covered with a thick insensible cuticle, they do little harm 

 when in small numbers, hence Bracy Clark supposed them 

 to be rather beneficial in stimulating the secretion of gastric 

 juice. When very numerous, and, above all, when attached to 

 the highly sensitive right half of the stomach or the duodenum, 

 they seriously interfere with digestion, causing the animals to 

 thrive badly, to be weak and easily sweated or fatigued, and 

 even determining sudden and fatal indigestions. This last 

 result is especially liable to occur in spring or early summer, 

 when the bots are passing out in great numbers and hooking 

 themselves at intervals to the coats of the sensitive bowels in 



