176 THE HOUSE I LIVE IN. 



chambers of the nose ; and in the same region 

 begin the passages which lead to the middle 

 cavity of the ear which has been already men- 

 tioned, called the tympanum. I have said 

 enough about these various apartments in an- 

 other place. 



A little behind the roof of the tongue, is an 

 opening, whose structure has a strong resem- 

 blance to what is usually called a trap door. It 

 leads to the lungs or breathing apparatus, occu- 

 pying a very large upper apartment of the body. 

 This is one of the most curious parts of the hu- 

 man system. No real gate or door, set on hinges, 

 and guarded by an active and intelligent porter, 

 would better answer its intended purpose. 



I have said that there is a strong resemblance 

 here to a trap door. The passage to the lungs, 

 where it commences, is a mere slit ; though it 

 is true it very soon becomes larger. Over this 

 slit is placed a lid or flap, not unlike the tongue 

 in shape, but of course much smaller, which fits 

 to the opening as exactly as ever a trap door 

 was fitted to its door-way. 



It is not usually shut, however, except when 

 we attempt to swallow something. Then the 



