MECHANISM OF THE FRAME. 189 



bones are passive levers ; the muscles are the 

 active parts of the frame. 



With all the seeming intricacy in the running 

 and crossing of these tendons, they are adjusted 

 accurately on mechanical principles. Where it is 

 necessary, they run in sheaths, or they receive 

 new directions by lateral ligamentous attach- 

 ments, or there are placed under them smooth 

 and lubricated pulUes, over which they run ; and 

 where there is much friction, there is a provision 

 equal in effect to the friction-wheel of machinery. 



Thus the bones are levers, with their heads 

 most curiously carved and articulated ; and, joined 

 to the intricate relations of the muscles and ten- 

 dons, they present on the whole a piece of perfect 

 mechanism. 



It is with this texture — the coarsest, roughest 

 portion of the animal frame — that our author is 

 running a parallel when he compares it with the 

 common mechanical contrivances of machinery. 

 Whilst these grosser parts of the animal body 

 exhibit a perfection in mechanical adaptation far 

 greater than the utmost ingenuity of man can 

 exhibit in his machinery, let the reader remember 

 that they bear no comparison with the finer parts 

 of the animal body : such, for example, as the 

 structure of those nerves which convey the man- 

 date of the will to the moving parts, or of the 

 vessels which are conveying the blood in the 

 circulation, and where the laws of hydrauhcs may 

 be finely illustrated ; or of those secreting glands 



