THE EAR OF MAN. 195 



projects from the bottom of the ampulla into its cavity 

 and bears on its free surface the hair-bearing sensory 

 cells constituting the percipient elements of the nerve 

 end-organs of the ear. 



Each ampulla is connected with the main sac by a 

 shorter or longer tube (Figs, i-6), the length of the 

 tubes varying with the canal, and in greater degree 

 with the animal species under consideration. 



In the Torpedo the ampullar tubes of the anterior and 

 the external canals join before opening into the utriculus 

 (Fig. I, near U'), while the posterior canal has a sep- 

 arate and very large tube which opens into the saccular 

 division of the main sac (Fig. i, near U"). 



So far as the main sac of the Torpedo ear is con- 

 cerned, it appears when viewed from the side (Fig. i) to 

 be composed of three large communicating chambers, — 

 6'7 U,'^ and SC. When, however, it is seen from the 

 inside, the chamber U'^ appears as a median vesicle 

 from which are given off cephalad the utricular recess 

 U,' and caudad the saccular recess SC, and the lagena. 

 This central portion, then, is the connecting chamber of 

 the primitive ear-sac, and is composed in part of the 

 original sacculus and in part of the original utriculus. 

 This chamber, as you see, is produced into a conical 

 body, CO, which is continued outward to the surface of 

 the body by the long and slender canal c.e. Shortly 

 before the slender tube or endolymphatic duct reaches 

 the surface it presents an enlargement in the form of a 

 broad sac which lies just below the skin of the dorsal 

 region of the head. The duct is continued beyond the 

 sac where it pierces the skin, and thereby places the 

 cavity of the ear in communication with the surrounding 



