XI 



EAR 187 



skull (Fig. 10), and consisting of a kind of bag of 

 very peculiar and complicated form (Fig. 59). It 

 is made up, in the first place, of the vestibule two 

 somewhat ovoid sacs separated by a constriction : 

 the dorsal one is called the vtriculns (ut}, the ventral 

 the sacculus (s), and from the latter a small process, 

 the cochlea (cc), projects backwards. \Yith the 



FIG. 59. The membranous labyrinth of the Frog's ear. A, outer, and B, inner 



view. ( x 6.) 



am', am", am", ampulla? of the semicircular canals ; a. s. c. anterior semicircular 

 canal ; cc. cochlea ; h. s. c. horizontal (external) semicircular canal : p. sc. 

 posterior semicircular canal ; r. ut. recess of the utriculus ; s. sacculus ; ut 

 utriculus ; VIII. branches of auditory nerve. (After Howes.) 



utriculus are connected three tubes, called, from 

 their form, the semicircular canals, each of which opens 

 into the utriculus at either end. One of them, the 

 anterior canal (a.s.c), is directed forwards ; another, the 

 posterior canal (p.s.c), backwards ; both these are 

 vertical in position and are united to one another at 

 their adjacent ends. The third, the external canal (h.s.c), 



