OF HEARING. 165 



tain very delicate membranous bags, lately discovered 

 by the celebrated Scarpa. Two of these lie in the 

 vestibule, and three in the semicircular canals.* 



251. They, as well as the cavity of the cochlea, con- 

 tain a very limpid fluid, bearing the name of Cotunni, 

 who shewed it to be absorbed by two canals, by him 

 denominated aqueductsf and by the no less illustrious 

 Meckel diverticula ; % the one arises from the vestibule, 

 the other from the inferior scala of the cochlea. 



252. The portio mollis of the seventh pair, together 

 with the portio dura (which afterwards runs along the 

 Fallopian aqueduct), § having entered the internal 

 acoustic opening, transmits its medullary filaments 

 into the lower and cribriform part of it. || These fila- 

 ments run to the vestibule and semicircular canals, but 

 especially to the base of the cochlea, where they form 

 a medullary zonula, marked by beautiful plexiform 

 striae, which pass between the two laminae of the sep- 

 tum cochleae.** 



253. The oscillatory tremor, which we formerly fol- 

 lowed as far as the fenestra ovalis (248), is propagated 

 to the vestibule, where, by means of the water of 

 Cotunni (251), it strikes the auditory nerves distributed 

 among the windings of the labyrinth. 



* Scarpa, Disquisitioncs Anatomicee de Auditu et Ol/aclu. Tab. iv. fig. 5. 

 tab. vii. fig. 3. 



f Cotunni, De Aqueductibus auris Humana. Neap. 1/60. 4to. 



X Ph. Fr. Meckel, De Labyrinthi auris contentis. Argen. 1777. 4to. 



§ Fallopius, Observ.Anat. p. 27 sq. Venet. 1561. 8vo. 



|| Rrendcl, Analecta de Concha aur is Humanee. Gotting. 1747. 4tO. 



The same, De Auditu in apice conchee. IB. EOD. 4to. 



** Consult Zinn, Observ. Botan. Gotting. 1753. 4tO. p. 31 sq. 



Scarpa, 1. c. tab. viii. fig. 1, 2. 



