HEARING IN INSECTS. 103 



as readily perceived as before. After the ear is 

 brought into this state it will remain so for some 

 time, without continuing the painful effort to take 

 breath, for, by suddenly discontinuing the effort, the 

 end of the tube will close like a valve, and prevent 

 the air from getting into the drum. The act of 

 swallowing, however, will open the closed tube, and 

 restore the ear to its wonted feeling. 



While the ear is exhausted of its internal air, if 

 we attempt to listen to the sound of a carriage 

 passing in the street, the rumbhng noise cannot be 

 heard, though the rattle of a chain or a loose screw 

 remains as easily heard as before. At a concert 

 the experiment has a singular effect. As none of 

 the sharper sounds are lost, and the great mass of the 

 louder sounds are suppressed, the shriller ones are 

 consequently so much the more distinctly heard, 

 even to the rattling of the keys of a bad instrument, 

 or the scraping of cat-gut unskilfully touched. In 

 the natural healthy state of the ear, there does not 

 seem to be any strict limit to our power of perceiving 

 grave sounds ; but if, on the contrary, we turn our 

 attention to the other extremity of the scale, and 

 with a series of pipes, exceeding each other in sharp- 

 ness, we examine the effects of them in succession, 

 upon the ears of any considerable number of per- 

 sons, we shall find a very distinct and striking dif- 

 ference between the hearing of different individuals, 

 whose ears are in other respects perfect. The sud- 

 denness of the transition from perfect hearing to to- 

 tal want of perception, occasions a degree of sur- 

 prise, which renders an experiment, with a series of 

 small pipes, among several persons, rather amusing. 

 Those who enjoy a temporary triumph, from hearing 

 notes inaudible to others, are often compelled, in 

 their turn, to acknowledge to how short a distance 

 their superiority extends, Dr Wollaston accord- 



