45 



by a glutinous substance, whereby the drum is guard* 

 ed against the water in the secundine, and against the 

 injuries of the air, as soon as the infant is born. 



It is remarkable, that in the ear of most, if not all 

 animals, where the meatus auditorius is long enough to 

 afford harbour to ear wigs, or other insects, ear-wax 

 is constantly to be found. But in birds, whose ears 

 are covered with feathers, and where the drum lies 

 but a little within the skull, no ear-wax is found, be- 

 cause none is necessary to the ears so well guarded, 

 and so little tunnelled. 



29. In this, besides a little branch of nerves, there 

 are four little bones, two passages, and two windows. 

 Three of those bones, from some imagined resemblance, 

 are stiied the hammer, the anvil, and the staple : the 

 fourth is termed, the orbicular bone. These are 

 fastened by strong ligaments to each other, and to 

 the neighbouring parts. The passages go from the 

 side of the drum : one of which, termed the labyrinth, 

 by a very winding way, carries a part of the auditory 

 nerve to the external muscles of the head. The other 

 passes from the bottom of the drum to the palate ; 

 whereby not only air, if needful, may be received, 

 but the defect of hearing, in some measure supplied 

 by speaking to the mouth. 



The labyrinth contains, besides the entrance, three 

 bony, semicircular cavities, and a bony canal, in the 

 form of a screw, divided into two parts, from the top 

 to the bottom. The labyrinth is lined throughout with 

 a thin membrane, furnished with veins, arteries and 

 nerves. And this membrane may not improbably be 

 the organ of hearing. 



The curious structure of the labyrinth and screw, 

 tend to make the weakest sounds audible. Those 

 canals, by their winding, contain large portions of the 

 auditory nerve, upon every point of which, at once the 

 sound being impressed, becomes audible ; and by their 

 narrowness the sounds are hindered from dilating, 

 which must have weakened them proportionally.' 



