52 NATURAL THEOLOGY, 



this mode of adapting the ear to different sounds, 

 is one of the most beautiful applications of muscles 

 in the body ; the mechanism is so simple, and the 

 variety of effects so great, " 



In another volume of the Transactions above re- 

 ferred to, and of the same year, tw^o most curious 

 cases are related, of persons who retained the 

 sense of hearing, not in a perfect but in a very 

 considerable degree, notwitstanding the almost 

 total loss of the membrane we have been de- 

 scribing. In one of these cases, the use here as- 

 signed to that membrane, of modifying the impres- 

 sions of sound by change of tension, was attempted 

 to be supplied by straining the muscles of the out- 

 ward ear. " The external ear, " we are told, " had 

 acquired a distinct motion upward and backward, 

 which w^as observable whenever the patient lis- 

 tened to any thing which he did not distinctly 

 hear ; when he was addressed in a whisper, the 

 ear was seen immediately to move ; when the tone 

 of voice was louder, it then remained altogether 

 motionless. " 



It appears probable, from both these cases, that 

 a collateral if not principal use of the membrane 

 is to cover and protect the barrel of the ear which 

 lies behind it. Both the patients suffered from 

 cold : one, " a great increase of deafness from catch- 

 ing cold ; " the other, " very considerable pain from 

 exposure to a stream of cold air. " Bad effects 

 therefore followed from this cavity being left open 

 to the external air; yet, had the Author of Nature 



