DISEASES 01' THE DIGESTIVE ORGANS. 173 



nJii 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 means 

 of two dark brown hooks, between which a longitudinal slit is seen, 

 which is the mouth of the larvae. When removed from the stomach 

 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 present 

 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 

 length 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. 



Tlie (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 titra- 

 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 oestrus 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 

 both sheep and horses, when teased by them, to look into the grass 



