AND OTHER ANIMALS. 117 



the greatest number of bot-holes in them : for although the skin heals 

 up on the exit of the larva, it is not with the same matter as the ori- 

 ginal skin. In the leather, when dry, those holes which were made in 

 the skin the year preceding the death of the beast, cannot be distin- 

 guished from the others which were made at any former period, not 

 being in any perceptible degree less filled up. In the dried hide, it 

 does not appear a round hole as in the living skin, but only as a crack. 

 This arises from tlie spongy substance which had filled the aperture, 

 contracting in drying, and bursting, and also from the artificial mode of 

 hammering and preparing the hide. 



The female fly is very quick in performing the operation of deposit- 

 ing her egg : she does not appear to remain on the back of the animal 

 more than a few seconds. 



The grub is very conspicuous and may easily be detected in the 

 backs of the cattle, and destroyed. The injection of any corrosive 

 liquor into the sack would kill it : or by puncturing the larvae with a 

 hot needle introduced through the aperture of the skin, or even by 

 simple pressure they may be destroyed, afterwards extracting them or 

 leaving them to slough away. A man employed for this purpose, 

 might, in half a day, in this manner, desti'oy every bot in a large drove 

 of cattle. 



Notwithstanding the apparently unnecessary existence and cruel ef- 

 fects of the Oesiri^ they are probably not altogether without some use. 

 I do not believe that any thing was made in vain. May not the remark 

 be ventured, that their effect in keeping up a considerable degree of irri- 

 tation in the membranes in which they are situated, acts like a perpetual 

 issue or blister ? There is abundant proof of the utility of local irrita- 

 tions in preventing the access, as well as in curing diseases. We often 

 see a formidable disease removed by blistering the skin, and may not 

 the bots perform this part in relation to animals ? But, however useful 

 a {ew of these natural slimuli may be, the increase of their numbers , 

 producing bad consequences, should at all times be prevented. 



The bots of sheep (O. ovis,) are not so large as those of oxen. 

 They are mostly found in the horns and frontal sinuses of sheep, but it 

 is probable that during the life of the sheep they inhabit the maxillary 

 sinus, and crawl into the other situations on its death. 



When full grown they fall through the nostrils, and change to the 

 pupa state, lying in the earth, or adhering to a blade of grass. 



The fly bursts the shell in about two months. The manner in 

 which this species deposits its egg, is not so easily observed, owing to 

 the obscure color and rapid motion of the fly and the extreme agitation 



