207 
Mr. Carlisle on the Physiology of the Stapes. 
known that persons who hear imperfectly are more sensible 
to sounds in a noisy place, as if the muscles were by that 
means awakened to action. 
The office which the basis of the stapes holds, and which 
the stapedeus muscle is especially destined to perform, seems 
to throw considerable light on the use of the cochlea. It cannot 
be allowed that the pressure of the watery fluid in the labyrinth 
is a requisite condition to produce the sensation of hearing, 
since all birds hear without any mechanism for that purpose, 
but as such pressure must ultimately give increased tension to 
the fenestra cochleae, it follows that we inquire at this part 
for the principal use of the stapes. 
As the membrane of the fenestra cochleae is exposed to 
the air contained within the cavity of the tympanum, it appears 
adapted to receive such sounds as pass through the membrana 
tympani, without exciting consonant motions in the series of 
ossicula auditus. 
Experiment. 
My head being laid on a table, with the meatus auditorius 
externus perpendicular to the horizon, my friend, Mr. William 
Nicholson, pulled the tragus toward the cheek, and dropped 
from a small vial, water, at the temperature of my body, into 
the meatus. The first drop produced a sensation like the report 
of distant cannon, and the same effect succeeded each follow- 
ing drop, until the cavity was filled. 
In this experiment the vibrations of the membrana tympani 
must have been impaired, if not wholly destroyed, by the 
contact and pressure of the water ; yet the motions of the 
whole membrane, from the blow of each drop of water, affected 
