140 Experiments on Bats dtfrtved of Sight. 



ozier twigs with its Wings, and made the air refound with 

 itrokes which it gave itfelf pn the muzzle. This experiment 

 was repeated on other hats with the like effects. 



The tympanum of a large horfe-fhoe hat was pierced with 

 a pin (tr&is-qitart). The animal appeared to fuffer much from 

 the operation, and fell down in a perpendicular direction 

 when thrown into the air. It died next morning. The fame 

 effe& was produced on piercing the tympanum of a long- 

 -eared hat with a needle. 



The author then made very accurate rcfearches on the dif- 

 ference between the organifation of the hrain of thefe two 

 kinds of hats, and, after a careful difle&ion, found that the 

 eye of the long-cared hat is much larger than that of the 

 horfe-fhoe bat, but that the optic nerve is proportioned & it. 

 The outer part of the car of the former is much larger than 

 that of the latter, but the interior part is fmallef. 



The horfe-fhoe hat is indemnified for this difference by a 

 greater extenfion of the organ of fmeil, as evidently appears 

 when the external elevations and irregularities of its muzzle 

 are examined. When it is about to take flight, it agitates 

 its note much more than the long-eared bat. 



From thefe experiments the author concludes, firft, that 

 the eyes of the bat are not indifpenfibly neceflary to it for 

 finding its way ; fecondly, that the organ of hearing appears 

 to fupply that of fight in the difepvery of bodies, and to fur- 

 nifh thefe animals with different fen Cations to direct their 

 flight, and enable them to avoid thofe obftacles which may 

 prefent themfelves. The author alfo found on thefe animals 

 a particular kind of fleas. 



VII. <fo 



