The ear is appropriately called the vestibulocochlear organ because it not only enables the animal to hear but also provides it with a sense of balance.

The mechanical stimuli produced by sound waves are transformed into nerve impulses in the cochlea, and the action of small amounts of fluid and microscopic crystals on neurore­ceptors within the vestibule provides the animal with a perception of the attitude and movement of its head with respect to gravity. Both functions are performed in the internal ear, the most medial of the three subdivi­sions of the ear as a whole. The other subdivisions are the middle ear and the external ear. Only the external ear is visible in the intact animal; the other two are housed in the temporal bone (Figure 9-24/24).