THE LIVING BIRD 



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Fig. 6. Diagram of the Human Ear 



A, outer ear; B, middle ear; C, inner ear. 1, the ear-trumpet 

 (pinna). 2, external ear-passage (meatus) running to 3, the ear- 

 drum (tympanum). On the inner side of this is the middle ear, 

 containing air, and communicating with the cavity of the mouth 

 by the Eustachian tube, 7. It contains the three auditory ossicles, 

 4, 5, and 6, which transmit the vibrations of the drum to the mem- 

 branous window, to the right of 6, in the wall of the inner ear. 

 The inner ear is entirely embedded in bone. It contains a fluid, 

 the perilymph; this surrounds the "membranous labyrinth," 8, 9, 

 10, a series of membranous organs containing another fluid, the 

 endolymph. 8, the utricle with the three semicircular canals 

 arising from it; the organ of balance. P, the sacculus, leading to 

 10, the spiral cochlea, the organ of hearing. Above 11 is a second 

 membranous window which is pushed outwards when the first 

 window is pushed inwards, and vice versa. (Haldane and Huxley, 

 Animal Biology, Oxford University Press.) 



