134 THE STRUCTURE AND LIFE OF BIRDS cap. 
A few more points must be mentioned. The bony 
labyrinth has a second window of membrane, and this, 
yielding, allows greater vibrations to be imparted to 
the fluid. In the cochlea, are very peculiar cells, 
called the rods or pillars of Corti, forming two rows all 
along the spiral, in all from four to six thousand of 
them. They lie upon the inside of the membranous bag, 
following the line along which it comes into contact with 
the wall of bone. They stand leaning on one another, 
and rather remind one of the keys ofa piano. There are 
delicate hairs at their ends. It is possible that each 
of these rods vibrates to a certain note and no other. 
If you put on a table several tuning forks which have 
different pitches, and if you set vibrating another, 
then if one of those on the table is of the same pitch, 
it also will vibrate. The rest will be motionless and 
silent. So these rods of Corti have been thought to 
respond each to a certain note. In the labyrinth 
there are no similar cells, and it has been suggested 
that the membrane there is sensitive only to noise as 
distinguished from music. 
It is not known exactly to what part of the brain 
the nerve of hearing leads—ze. where we have con- 
sciousness of sound. 
The ear has two openings, the external one with 
which every one is familiar, and another through what is 
called the Eustachian tube to the mouth (E). The 
two tubes from either ear unite and open into the 
roof of the mouth just behind the two openings from 
the nasal passages. 
I must now describe the main differences between 
the human ear and the bird’s, 
