APPARATUS OF BESPIBATION. 



75 



occupying the upper part of the trunk (Fig. 5, p. 20). These 

 organs are, as it were, suspended in this cavity, and are en- 



Fig. 57. Respiratory Apparatus of the Insect Nepa; 

 Water Scorpion.* 



veloped by a membrane or membranes (one for each lung in 

 most mammals) called the pleurae ; and these membranes, like 



* a, the Mlad ; &, base of the feet of the first pair; c, first ring of the 

 thorax ; d, base of the wings ; e, base of the feet of the second pair ; f t stig- 

 mata; g, tracheae ; h, aerial vesicles. 



