THE EAR, HEARING, TASTE AND SMELL 237 



tinuity with any of them. The cells of the epithelium are of two 

 varieties. The columnar cells or hair-cells, c, do not reach the 

 basement membrane, are nucleated or slightly granular : from the 

 free end of each projects a rigid hair process, d. The remaining 

 cells, rod-cells, b, are in several rows: each has a slender inner 

 process extending to the basement membrane and an outer 

 which reaches to the bases of the columnar cells and appears 

 there to end in a rigid membrane, e, which is perforated for the 

 passage of the hairs. They probably are- mere supporting 

 structures. 



In some parts of the utricle and saccule are regions of epithelium 

 very similar to that above described, and also supplied with nerve- 

 fibers. In connection with them are found minute calcareous 

 particles, otoliths or ear-stones. 



The Equilibrium Sense. An important group of afferent im- 

 pulses concerned with the maintenance of bodily equilibrium is 

 derived through the semicircular canals and vestibule of the ear, 

 which are supplied by the vestibular portion of the auditory 

 nerve. 



Experiment shows that cutting a semicircular canal is followed 

 by violent movements of the head in the plane of the canal di- 

 vided; the animal staggers, also, if made to walk; and, if a pigeon 

 and thrown into the air, cannot fly. All its muscles can contract 

 as before, but they are no longer so co-ordinated as to enable the 

 animal to maintain or regain a position of equilibrium. It is like 

 a creature suffering from giddiness; and similar phenomena fol- 

 low, in man, electrical stimulation of the regions of the skull in 

 which the semicircular canals lie. 



If, moreover, a person lie perfectly quiet with closed eyes OR 

 a table which can be rotated, he is able to tell when the table is 

 turned and in which direction, and often with considerable ac- 

 curacy through what angle. If the rotation be continued for a 

 time the feeling of it is lost, and then when the movement ceases 

 there is a sense of rotation in the opposite direction. In such 

 case neither tactile, muscular, nor visual sensations can help, and 

 in the semicircular canals we seem to have a mechanism through 

 which rotation of the head could give origin to afferent impulses, 

 whether the head be passively moved with the rest of the Body 

 or independently by its own muscles. Movements of endolymph 



