VI CONTENTS. 



PAGE 



The vent gut .. .. ' *m . 65 



The vent . . . . ? . ib. 



Offensive discharges poison . > % 4. >V.. ib. 



Probable course of the chyle i a.t r . ib. 



The fluid and solid portions .. Ju . 66 



Process of nutrition . . a-.- . ib. 

 ORGANS OF CIRCULATION.. 



The heart or dorsal vessel ,.. . 67 



Its resemblance and difference compared with 



the heart of other animals . . . ib. 



No direct circulation of blood in insects . ib. 



Extent, position, and form of the heart . ib. 



Its structure . ,; x m .t;y . ib. 



Its contents . . ;.;$.>' . ib. 



Opinions of Audouin, Meckel, and Herold . 68 



Description of the heart by M. Straus . ib. 



Circulation of the blood traced }$*'''*' 69 



Its supposed distribution and imbibition . 70 

 ORGANS OF BREATHING. 



Insects have no lungs or nostrils . . ib. 



. The spiracles **>; . 71 



Simple spiracles . . * 7; J . ib. 



Their number and position . ib. 



Wings supposed to be spiracles ! ! ! i to ** . 72 



Lips of the spiracles . . a . ib. 



Composite spiracles . * . !:. ib. 



The air pipes . . *!i. . ib. 



The two windpipes and their branchings . . ib. 



Structure of the air-pipes .. .. . 73 



Structure of the air-cells . , . ib. 



Their ribs . . "! &.< [,j . . 74 



Process of breathing . V 75 



