DISEASES OF THE DIGESTIVE ORGANS. 



99 



It was formerly supposed that these eggs were licked off by the horse 

 and carried upon the tongue to the mouth, and thence to the stomacli, 

 wliere they were hatched; but it is easy to see that they are so firmly 

 glued to the hairs that this is impossible, and it is also now Known that 

 the egg comes to maturity while thus fastened. After a lapse of four or 

 five days, the worm is ready for exit, and then the least application of 

 warmth and friction, as the application of the horse's tongue, is suflQ- 

 cient to cause the eggs to burst and permit the worm to be carried off to 

 the mouth of the animal. Many are, however, crushed in the mastication 

 of food, others may drop out, but enough find their way to the stomach 

 to cause, sometimes, quite serious inconvenience, although usually they 

 do not seem to act injuriously to the health of the horse. Once in the 

 stomach, they fasten themselves to its inner coat by two strong hooks, 

 burying their heads in the mucous membrane, upon which they seem 



Fig. 66. 

 Position of bot-fly in depositing its eggs. 



to feed. The maggot remains in the stomach during the autumn, 

 winter, and sj)ring, and in the following June or July, having become 

 full grown, it loosens its hold and is voided with the dung. It then 

 buries itself in the ground, changes into a chrysalis, and after six or seven 

 weeks emerges in its perfect state, ready to continue its round of life. 



Treatment. — No treatment is of any use in driving this parasite out; 

 once in its natural home, it stays there in spite of any effort to dislodge 

 it. Well educated men, as well as those more ignorant, will often insist 

 that certain remedies will drive them out, and the poor animal suspected 

 of having bots is tormented with all sorts of worm expellers, and purga- 

 tive doses. It may be positively asserted, however, that none of them 

 can be of any use, the horse may be killed, and not the bots. Horses 

 which are out at pasture in the summer and fall are chiefly affected by 

 the bot; those kept in stables are rarely troubled by it. 



