THE SHEEP EOT. 635 



the mode of defence it takes to avoid it, there is little doubt that the 

 egg is deposited on the margin of the nostril. The moment the fly 

 touches this part of the sheep, they shake their heads, and strike the 

 ground violently with their fore-feet, at the same time running away, 

 and holding their noses close to the ground, and looking about them 

 on every side to see if the fly pursues, and as they go along they often 

 smell also to the grass, and look anxiously into it, lest one should be 

 lying in wait for them ; if they observe one, they gallop back again, or 

 take some other direction. As they cannot, like the horses, take 

 refuge in the water, they have recourse to a rut, dry dusty road, or 

 gravel-pit, as a defence, as we have before remarked. 



" Observations on these flies are best made in dry weather, and dur- 

 ing the heat of the day, when by driving the sheep from the retreats, 

 the attack of the fly and the emotions of the sheep are easily observed 



" I imagine the nostril becomes highly inflamed and sore, from their 

 repeated attacks, and the consequent rubbing of the nose against the 

 ground, which, together with certain instinctive apprehensions of these 

 flies, occasion their touch to be so much dreaded. 



" From the difficult and precarious modes these CEstri pursue in 

 depositing their eggs, they cannot succeed in depositing but a few in 

 each sheep ; whereas, if, on the contrary, they actually entered those 

 cavities of the face to effect it, they must deposit them all, and in one 

 subject, the improbability of which in respect to the other species is 

 already stated. 



" Of the Larva. From one to seven or eight are generally found in 

 the cavities of the face, what are called by anatomists of the human, 

 the maxillary and frontal sinuses, but which in quadrupeds are cavities 

 of considerable extent and magnitude, and the thin flexible bones 

 which constitute them are covered with a dense white membrane, upon 

 the secretions of which they feed, and these membranes are found more 

 or less inflamed by their presence. 



" Vallisneri has remarked, that Alexander Trallien, a famous Greek 

 physician of the sixth century, relates the following anecdote, which 

 has an undoubted reference to these larvae, that * Democrites, an 

 Athenian, being subject to fits of epilepsy, determined to consult the 

 oracle at Delphos for a remedy, and received for answer, 



' Quos madidis cerebri latebris procreare capella 

 Dicitur humores, vermera de vertice longum.' 



