54 HUMBLE CREATURES. 



LETTEE VII. 



THE ANATOMY OV THE PLY. — ITS ORGANS OF DIGESTION ; OF 

 CrBCUIiATION ; OF BESPmATION, — ■WONDBBFIIL STETTCTDEB 

 OF THE SPIEACLES OB BBEATHING-HOLES, AND TEACHB^ 

 OB BBSPIBATOBY TUBES.— NBBVOITS SYSTEM. — CONStDEEA- 

 TIONS UPON THE NBEVOUS SYSTEM OF THE HOUSE-FLY 

 AS COMPARED -WITH THAT OP ITS LABVA AND OP THE 

 WOEM. 



From the foregoing description of the external mem- 

 bers of the House-fly, you mil have perceived how 

 well adapted they are to its aerial existence ; and if 

 we now investigate its internal structure, we shall see 

 that the vital organs are so disposed and constructed 

 as also to facilitate its movements in the atmosphere. 

 Les us take each function seriatim. First, as regards 

 that of nutrition. We have fiiUy considered the pro- 

 boscis, by which the food is procured; thence it passes 

 into the throat, which is muscular, and forma the 

 entrance into a species of crop (PI. III.) situated at 

 the left side of this throat, and opening into it is a 

 lock-necked food-reservoir, not inaptly termed the 

 paunch, and which is adapted, by its conformation, to 

 facilitate the ruminating process*. 



* L^on Dufoui, Anatomie G^n^rale des Dipteres, Ann. des 

 Sci. Nat. i. p. 244; Vogt, Zoologische Briefe, vol. i. p. 598. 



