HEARING. 191 



is like that of the strings in a tiny piano, with the short treble ones at the bottom 

 of the cochlea and the bass ones at its top. The difficulty is to see how even the 

 longest of these very small fibres can have a natural period as slow as that of the 

 lowest note which we can hear. Of course the period of them all is increased 

 because of the fluid about them but, even so, the difficulty has not been com- 

 pletely met. 



FUNCTION OF THE SEMICIRCULAR CANALS. 



Experiment 76. Place a frog on a glass plate and cover with a 

 funnel or beaker. Rotate about longitudinal, transverse and 

 vertical axes (referred to frog's body), and notice compensatory 

 movements. 



Expose one of the white otolithic masses in an anesthetized 

 frog by removing the cartilage after slitting the mucous mem- 

 brane of the roof of the mouth medially from the Eustachian 

 tube. Remove one otolithic mass in one 'frog and both masses 

 in a second frog. After recovery from the anesthesic compare 

 the compensatory movements and equilibration with a normal 

 frog when rotated in the different axes, and when swimming. 



COMPENSATORY MOVEMENTS IN MAN. 



Experiment 77. Let the subject sit in a swivel chair in which 

 he is rotated 10 to 20 seconds. Describe his movements after 

 the chair stops. Let the subject describe his sensations during 

 and after the rotation with and without the eyes closed. 



