300 THE MECHANICAL FUNCTIONS. 



exercise of all those faculties of active enjoyment 

 which are characteristic of animal life. She has 

 provided for the first of these objects by en- 

 closing the softer organs in dense and horny 

 coverings, which perform the office of an ex- 

 ternal skeleton, sustaining and protecting the 

 viscera, and furnishing extensive surfaces of 

 attachment to the muscles, from the action of 

 which all the varied movements of the system 

 are derived. 



The muscular system of perfect insects is ex- 

 ceedingly complex. Lyonet has described and 

 delineated an immense number of muscular 

 bands in the caterpillar of the Cossus, and the 

 plates he has given have been copied in a va- 

 riety of books in illustration of this part of the 

 structure of insects. The recent work of Straus 

 Durckheim affords an equally striking example 

 of admirable arrangement in the muscles of the 



144 



Melolontlia vulgaris, or cockchaffer, the ana- 

 tomy of which has been minutely investigated by 



