NATURAL THEOLOGY. 101 



A. Besides protecting the heart and the lungs, 

 and this use alone, in respect to the heart especially, 

 would have been sufficient evidence of design, they 

 are made to render another service which a hasty ob- 

 server would hardly have suspected. The play of 

 the lungs is referrible to the arrangement, of these 

 bones. As breathing is nothing more than the rising 

 and falling of the lungs, which operate like a pair of 

 bellows, a contrivance was wanted to perform this 

 mechanical operation. We mark in the provision 

 adopted, the admirable simplicity, as a mechanic 

 would say, the happy thought, of the expedient. 

 The contrivance is this. The rib bones are united 

 to the spine in a direction sloping downwards. Being 

 firmly attached at the ends where they are set on, the 

 consequence of their sloping is, that when they come 

 to rise, the muscles which pull them up necessarily 

 draw them out, upon the principle of an umbrella. 

 The cavity of the chest is consequently enlarged, 

 and the lungs are permitted to fill, as the air rushes 

 into the bellows when they are extended. Again, by 

 sinking down into their former position, the cavity is 

 diminished and the breath is forced out. 



B. One cannot but reflect with admiration upon 

 how slight a piece of mechanism our lives are depend- 

 ing ; that is to say, upon the right choice of so sim- 

 ple a circumstance,, as whether the ribs in their nat- 

 ural position, should pass directly around the chest, 

 as most persons, it is likely, have never observed but 

 that they do ; or should have a slight degree of 

 inclination downwards. 



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