EAR 



187 



and complicated form (Fig. 59). It is made up, in the 

 first place, of two somewhat ovoid sacs separated by a 

 constriction : the dorsal one is called the vtriculus (u), the 

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

 the cochlea (/), projects backwards, and a narrow canal, the 

 endolymphatic duct (d. c), upwards. With the utriculus are 



Fjg. 59. — External view of left organ of hearing of a Vertebrate (semi'dlagrammatic). 

 aa. ampulla of anterior canal, ae. of external canal, and ap. of posterior canal ; 

 ass. apex of utriculus ; ca. anterior semicircular canal ; ce. horizontal canal ; r/. 

 posterior canal ; cus. constriction between sacculus and utriculus ; de, se. endo: 

 lymphatic duct ; /. cochlea ; rec, j/, ss, u. utriculus ; s, sacculus. (From 

 VViedersheim's Vertebrata-,^ 



connected three tubes, called, from their form, the semi- 

 circular canals^ each of which opens into the utriculus at 

 either end. One of them, the anterior canal (<:«), is 

 directed forwards ; another, the posterior canal (cp), back- 

 wards ; both these are vertical in position and are united 

 to one another at their adjacent ends. The third, the 



