12 
Attention was drawn to the folding over of the edge of the human 
ear, carrying with it the “tubercle of Darwin ’—a small point 
which still persists with most persons as a vestige of the apex of 
the erect ear of the ape. The middle and internal ear are deeply 
embedded in the temporal bone of the skull, being thus protected 
from external violence. The passage from the outside leads directly 
to the tympanum or drum, which is caused to vibrate by the impact 
of the sound waves. The vibrations are conveyed from the drum 
by a chain of small bones or ossicles to a membrane covering an 
opening (fenestra ovalis) of the internal ear. The fluid in the 
bony labyrinth of the internal ear is thus in continual vibration 
in unison with the sounds of the external air. The Eustachian 
tube, leading from the throat to the middle ear, serves to keep 
the atmospheric pressure equal on the two sides of the drum. The 
sound one hears when one swallows is due to the opening of this 
tube. The most important organ of the internal ear is the cachlea, 
a spiral canal containing a watery fluid. Along this canal is 
stretched a membrane—the Basilar membrane—containing fibres, 
whose length increases from the base of the cochlea to the apex. 
In close association with these fibres are nerve fibrils, which convey 
the impulses to the brain. 
Having described the anatomy of the ear, the lecturer pro- 
ceeded to discuss the theories that have been advanced to explain 
the extraordinary power of the auditory sense of analyzing a sound 
into its component vibrations. Tones can be perceived varying 
trom sixteen vibrations to 40,000 or 60,000 vibrations per second, 
and of these very small differences can be detected. Physiologists 
have been divided into two opposing camps, those who hold that 
this analysis takes place in the brain (the telephone theory), and 
those who maintain that it takes place in the cochlea (the piano 
theory). The former theory does not account for the complicated 
anatomy of the cochlea, nor for the gradually increasing lengths 
of the fibres of the basilar membrane. It seems to remove the 
question from scientific investigation rather than to offer an ex- 
planation. The brothers Charles and John Bell in 1816 first 
suggested, when the microscopic structure of the cochlea was 
unknown, that an organ capable of sympathetic resonance would 
be found, consisting perhaps of a series of strings like those of a 
piano, which could respond to tones of the same pitch as their own. 
Helmholtz, with whose name the piano theory is associated, con- 
sidered that the fibres of the basilar membrane fulfil this function ; 
that the longer fibres of the upper portion detect and respond to 
the low notes, and the shorter fibres below to the high notes. The 
