THE GAD-FLY OR SOT DISEASE. 



303 



" little brain " (B), or the olfactory lobes (c). The spinal column is composed of seven cervical, twenty, 

 four dorsal, five sacral, and about seventeen caudal vertebrae. 



Of the various diseases the stomach of the Horse is liable to, perhaps the most peculiar is that 

 caused by an insect known as the Gad-fly. With regard to this creature and its mode of attack, Youatt 

 gives the following information : " In the spring and early part of the summer, Horses are much 

 troubled by a gnat or caterpillar, which causes a great deal of itching and uneasiness. Grooms are 

 sometimes alarmed at the appearance of these insects. Their history is peculiar, and will dispel every 

 fear with regard to them. We are indebted to Mr. 

 Bracy Clark for almost all we know about them. A 

 species of Gad-fly (CEstrus equi) is, in the latter part 

 of the summer, exceedingly busy about the Horse. It 

 is observed to be darting with great rapidity towards 

 the knees and sides of the animal. The females are 

 depositing their eggs on the hair, which adhere to it 

 by means of a glutinous fluid with which they are 

 surrounded. In a few days the eggs are ready to be 

 hatched, and the slightest application of warmth and 

 moisture will liberate the little animals which they 

 contain. The Horse, in licking himself, touches the 

 egg; it bursts, and a small worm escapes, which 

 adheres to the tongue, and is conveyed with the food 

 into the stomach. There it clings to the cuticular 

 portion of the stomach by means of a hook on either 

 side of its mouth ; and its hold is so firm and so 

 obstinate, that it must be broken before it can be 

 detached. It remains there feeding on the mucus of 

 the stomach during the whole of the winter, and until 

 the end of the ensuing spring ; when, having attained 

 a considerable size, and being destined to undergo a 

 certain transformation, it disengages itself from the 

 cuticular coat, is carried into the villous portion of the 

 stomach with the food, passes out of it with the 

 chyme, and is evacuated with the excrement. The 

 larva, or maggot, seeks shelter in the ground, and 

 buries itself there ; it contracts in size, and becomes a 

 chrysalis or grub, in which state it lies inactive for a 



few weeks, and then, bursting from its confinement, assumes the form of a fly. The female, becoming 

 impregnated, quickly deposits her eggs on those parts of the Horse which he is most accustomed to lick, 

 and thus the species is perpetuated. 



" There are several plain conclusions to be drawn from this history. The bots cannot, while they 

 inhabit the stomach of the Horse, give the animal any pain, for they have fastened on the cuticular and 

 insensible coat. They cannot stimulate the stomach and increase its digestive power, for they are not 

 on the digestive portion of the stomach. They cannot, by their roughness, assist the trituration 

 or rubbing down of the food, for no such office is performed in that part of the stomach ; the food is 

 softened, not rubbed down. They cannot be injurious to the Horse, for he enjoys the most perfect 

 health when the cuticular part of his stomach is filled with them ; and their presence is not even 

 suspected until they appear at the anus. They cannot be removed by medicine, because they are 

 not in that part of the stomach to which medicine is usually conveyed : and if they were, their 

 mouths are too deeply buried in the mucus for any medicine, that can safely be administered, to 

 affect them ; and last of all, in due course of time they detach themselves, and come away. Therefore 

 the wise man will leave them to themselves." 



THE RACE-HORSE. The breed of Horses for which England is chiefly remarkable is the Race- 

 Horse, resulting from a cross of the English stock with the Arabian ; and this was chiefly brought 



J3KAIX OF HOUSE. 



