LECTURE II. - 69 



marks, it is curious, that insects, having an 

 external articulated skeleton, possess such 

 a combination of motive powers, that some 

 of them walk, run, leap, swim, and fly with 

 as much facility, as beasts, birds, and fish, 

 exercise one or more of these faculties. 

 Professor Cuvier thinks that they are indebt- 

 ed for these advantages, to the numerous 

 articulations which their case or skeleton 

 possesses. It might strike a person who had 

 not considered the subject, that there were 

 animals possessing both an internal and ex- 

 ternal skeleton, as those of the reptile tribe. 

 The muscles of insects, however, act upon 

 the external case, which is therefore similar 

 to the skeleton. The shells of tortoises 

 are to be considered merely as armour, as 

 defences against injuries, which the animals 

 have neither the power to oppose, nor agi- 

 lity to avoid. Even amongst the higher 

 order of quadrupeds, some wear this kind 

 of armour as the rhinoceros ; and many 

 have such thick hides, as protect their pos- 

 sessors from trivial injuries; hides like the 

 leathern doublet of Hudibras, which 



" Thougli not ball was cudgel proof." 

 F 3 



