HEARING. 551 



by its pressure. The hammer is provided with three muscles 

 the stirrup only with one, and the anvil has none. 1 



There can be no doubt that the use of this apparatus is to 

 enable us to hear more perfectly : but there are instances in which 

 the hearing has remained after the destruction of these organs. Sir 

 A. Cooper has recorded such cases ra ; and deafness has even been 

 suspended, for a short time, by perforating themembrana tympani- 

 In these cases the sound appears to be transmitted to the laby- 



a a a, first turn or gyration of the cochlea. 

 bb b, second turn. 



c, third turn. 



d, very short canals for the entrance of nerves. 



e e, other holes for the passage of nerves and blood-vessels to the internal ears. 



f, canal in the base of the cochlea for the passage of a nervous twig to the 

 infundibulum. 



g, portion of the aqueduct of the cochlea. 



h, canal for the passage of the nerves of the elliptic vesicles of the superior 

 vertical and horizontal semicircular canal. 



i, opening for the passage of the nerves of the inferior semicircular canal, and 

 the nervous flabelliform expansion. 



k, aqueduct of the vestibule. 



I, superior vertical semicircular canal. 



n, inferior vertical semicircular canal. 



u, canal produced by the junction of the two vertical semicircular canals. 



o, horizontal semicircular canal. 



i " B. S. Albinus, Tabulee Muscul. tab. xi. fig. 29. " 

 01 Phil. Trans. 1800. 



