124 NATURAL THEOLOGr. 



easily yielding to the distentions of that organ occasioned by 

 the descent of solid food. The same rings are also bevelled 

 off at the upper and lower edges, the better to close upon 

 one another when the trachea is compressed or shortened. 



The constitution of the trachea may suggest likewise 

 another reflection. The membrane v/hich lines its inside is 

 perhaps the most sensible, irritable membrane of the body. 

 It rejects the touch of a crumb of bread, or a drop of water, 

 with a spasm which convulses the whole frame ; yet, left to 

 itself and its proper office, the intromission of air alone, 

 nothing can be so quiet. It does not even make itself felt ; 

 a man does not know that he has a trachea. This capacity 

 of perceiving with such acuteness, this impatience of offence, 

 yet perfect rest and ease when let alone, are properties, one 

 would have thought, not likely to reside in the same sub- 

 ject. It is to the junction, however, of these almost incon 

 sistent qualities, in this, as well as in some other delicate 

 parts of the body, that we owe our safety and our comfort — 

 our safety to their sensibility, our comfort to their repose. 



The larynx, or rather the whole windpipe taken togeth- 

 er — for the larynx is only the upper part of the windpipe — 

 besides its other uses, is also a musical instrument, that is 

 to say, it is mechmiism expressly adapted to the modulation 

 of sound ; for it has been found upon trial, that by relaxing 

 or tightening the tendinous bands at the extremity of the 

 windpipe, and blowing in at the other end, all the cries 

 and notes might be produced of which the living animal 

 was capable. It can be sounded just as a pipe or flute is 

 sounded. 



Birds, says Bonnet, have at the lower end of the wind- 

 pipe a conformation like the reed of a hautboy, for the mod- 

 ulation of their notes. A tuneful bird is a ventriloquist 

 The seat of the song is in the breast. 



The use of the lungs in the system has been said to be 

 obscure ; one use, however, is plain, though in some sense 

 external to the system, and that is, the formation, in con 



