HEARING. 



427 



The more internal parts of the ear compose 

 what is designated, from the intricacy of its wind- 

 ing passages, the labyrinth. It is seen at s v k 



in Fig. 390, in connex- 

 x,^^^^ ^^s^^y iqh ^ith the tympanum ; 



but in Fig. 394, it is repre- 

 sented, on a very large 

 scale, detached from every 

 other part, and separated 

 from the solid bone in 

 which it lies embedded. 

 It consists of a middle por- 

 tion, termed the vestibule 

 (v), from which, on its 

 upper and posterior side, proceed the three 

 tubes (x, Y, z), called, from their shape, the 

 semicircular canals; while to the lower anterior 

 side of the vestibule there is attached a spiral 

 canal, resembling in appearance the shell of a 

 snail, and on that account denominated the 

 Cochlea (k). All these bony cavities are lined 

 with a very delicate membrane, or periosteum, 

 and are filled with a transparent watery, or thin 

 gelatinous fluid, which is termed by Breschet 

 the perilymph * 



Within the cavity of the osseous labyrinth now 

 described, are contained membranes having 

 nearly the shape of the vestibule and semicir- 



* Annales des Sciences Naturelles, xxix, 97. It has also 

 been called the Aqua labyrinthi, and the fluid of Cotunnius, 

 from the name of the Anatomist who first distinctly described it» 



