HEARING, 39 



It is well known to musicians, that a violin or 

 common drum will not sound well without a hole 

 in it, to cause the sound produced to come with more 

 force by a communication with the air without. The 

 sound indeed would otherwise be imprisoned in the 

 instrument, and would be heard muffled and confined 

 by the surrounding wood. The same would be the 

 case in the ear. The sound transmitted from the 

 drum to the bony spring's, and by them to the parts 

 of the labyrinth, would be smothered in its passage 

 almost as soon as it had passed the drum. To 

 prevent this, there is a contrivance exactly like the 

 hole in the common drum and in the violin. 



For this purpose, behind the drum of the ear, a 

 tube opens, and runs by the side of the labyrinth, 

 widening as it goes, till it ends in a trumpet-like 

 opening behind the curtain (velum pendulum palati), 

 which separates the nostrils from the mouth. It is 

 named from its describer, Eustachius, the Eustachian 

 tube *. It is so indispensable to perfect hearing, that 

 when it is in any way obstructed there always follows 

 some degree of deafness. When it is opened also by 

 opening the mouth, we hear better than when the 

 mouth is shut, the orifice of the tube being thereby 

 enlarged, an observation which did not escape 

 Shakspeare : 



I saw a smith stand with his hammer thus, 

 The whilst his iron did on the anvil cool, 

 With open mouth swallowing a tailor's newsf. 



Such is the ear of man : but in birds it differs in 

 many particulars. Instead, for instance, of the ex- 

 ternal shell .(concha), with its windings terminating 

 in a funnel, there is only a circular tuft of feathers 

 in some species, which is besides riot found in many 

 others,, " Night birds alone," says Baron Cuvier, 

 * Eustachius de Auditus Organ. f King John. 



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