INTERNAL ORGANS. 77 



ally different ; for the organs run in a longitu- 

 dinal course through the body and disregard in 

 great measure not only the jointed structure but 

 even the regional distinctions of the body. To 

 systematize our examination, therefore, we must 

 treat them differently, and separating them into 

 natural subdivisions according to their functions 

 discuss them in that sequence which promises to 

 give us the clearest conception of their use. 



As the basis of the whole, we have the struc- 

 tural framework of the animal, its outer crust ; 

 and since power of movement is the primal need 

 of a living creature, we shall first consider the 

 muscular system, through which the framework 

 and its appendages are moved ; next we will take 

 up the digestive system, the province of which is 

 to prepare crude nutriment for the insect ; the 

 further preparation of this nutriment by oxygen- 

 ation requires that we should follow with the res- 

 piratory system ; and the distribution of the 

 nutriment over the body by the circulatory sys- 

 tem completes the circuit of the relation of food 

 to the creature ; but whether the natural action 

 of these systems be voluntary, as in the first men- 

 tioned, partly voluntary and partly involuntary, 

 as in the second, or wholly involuntary, as in the 

 last two, they all require to be brought into rela- 

 tion to the will of the animal, or their vital action 

 ceases ; we therefore consider next the nervous 



