72 INTERNAL ORGANS. 



they might be looked for being the place where the 

 four wings are afterwards jointed, M. Blainville infer* 

 red that the wings, when expanded, in the moth and 

 butterfly, were nothing more than spiracles. In this 

 singular opinion, M. Audouin would have agreed, 

 had it not occurred to him, that if the wings were to 

 be considered spiracles, there would not be both wings 

 and spiracles in the same insect at these four points, 

 which upon examination he actually found, as in the 

 cockroach and the mole cricket; and of course M. 

 Blainville's fancy is thence annihilated. 



The opening of these spiracles is surrounded by a 

 ring, more or less circular, and somewhat elevated, 

 which being contractile, may be considered as similar 

 to the lips of the mouth. 



The composite spiracles ( l ) are never placed in the 

 abdomen, but exclusively in the fore corselet, and are 

 (so far as is at present known) only two in number. 

 These are very obvious in grasshoppers. They are 

 composed of two horny pieces, which move outwards 

 and inwards in the process of breathing, like a pair of 

 folding doors, their movements being produced by two 

 muscles. 



The spiracles convey the air which they inspire 

 from without to a corresponding number of air pipes, 

 to be carried into the body, as the air inspired by 

 man is carried into the windpipe and the lungs. The 

 several air pipes which go from the spiracles end in a 

 common pipe on each side, and these two common 

 pipes may be termed the main air pipes ( 2 ). They run 

 lengthways from the head towards the vent, and send 

 off innumerable small branches to convey the air to 

 the different parts of the body, somewhat like the 

 branches of certain shrubs ; the'branchlets ( 3 ) interlace 



(1) In Latin, Tremaeree or Spiracula composita. 

 (2) In Latin, Tracheae. (3) In Latin, Ramuli* 



