46 MAMMALIA—MAN. 
tion, it is true, are less distinctly understood than those of light: all we 
know is, that sound is principally reflected by hard bodies, and that their 
being hollow also sometimes increases the reverberation. The internal 
cavity of the ear, which is fashioned out in the temporal bone, like a cavern 
cut into a rock, seems to be fitted for the purposes of echoing sound with 
the greatest precision. 
One of the most common complaints in old age is deafness ; which proba- 
bly proceeds from the failure of the nerves, in the labyrinth of the ear. 
This disorder also proceeds sometimes from a stoppage by the wax, which 
art may easily remedy. In order to know whether the defect be an internal 
or an external one, let the deaf person put a repeating watch into his mouth, 
and if he hears it strike, he may be assured that his disorder proceeds from 
an external cause, and may be in some measure cured. 
It often happens that people hear better with one ear than the other ; and 
these, it is observed, have what musicians call a bad ear. Buffon made 
many trials on persons thus circumstanced; and he always found that 
their defect in judging properly of sounds, proceeded from the inequality of 
their ears, and their receiving, by both at the same time, unequal sensations. 
In like manner, as such persons hear false, they also, without knowing it, 
sing false. They also frequently deceive themselves with regard to the side 
whence the sound comes, generally supposing the noise to come on the part 
of the best ear. 
Hearing is a much more necessary sense to a man than to animals. In 
these it is only a warning against danger, or an encouragement to mutual 
assistance. In man, it is the source of most of his pleasures; and with- 
out it the rest of his senses would be of little benefit. A man born deaf, 
must necessarily be dumb; and his whole sphere of knowledge must be 
bounded by sensual objects. We have a singular, and perhaps an unex- 
ampled instance of a young man, who, being born deat, was restored, 
at the age of twenty-four, to perfect hearing. The account, which is given 
in the memoirs of the Academy of Sciences, 1703, page 18, is in substance 
as follows: 
“A young man of the town of Chartres, between the age of twenty-three 
and twenty-four, the son of a tradesman, and deaf and dumb from his birth, 
began to speak all of a sudden, to the utter astonishment of the whole town. 
{le gave them to understand that, about three or four months before, he had 
heard the sound of the bells, and was greatly surprised at this new and un- 
known sensation. After some time, a kind of water issued from his left 
ear and he then beard perfectly well with both. During these three months 
he was sedulously employed in listening, without saying a word, and accus- 
toming himself to speak softly, so as not to be heard, the words pronouncea 
by others. He labored hard also, in perfecting himself in the pronunciation, 
and in the ideas attached to every sound. At length, having supposed him- 
self qualified to break silence, he declared that he could now speak, though 
