LECTURE V. 2 la 



lar to those of the vermes, and he says, 

 they not only serve to ventilate the blood, 

 but to give levity to the body of the ani- 

 mal in those insects which fly. He says, 

 the vesicles are larger in beetles, whose 

 bodies are heavy, than in the lighter kinds 

 of flying insects. He further mentions, that 

 the vesicles or lungs of the flying insects 

 are different from those of others ; as they 

 extend throughout the whole length of the 

 body. 



You probably know. Gentlemen, that 

 the present belief with respect to the nutri- 

 tion of insects is, that the digestive aliment 

 absorbed from the bowels passes on by the 

 same tubes to all parts of the body, and 

 that trachesE, or air-vessels, are equally dis- 

 tributed, so as to produce a general and com- 

 plete aeration of the nutritive fluid. It is 

 further believed that the glands of insects 

 are merely composed of contorted tubes. 

 Yet the crustaceous animals, (formerly ac- 

 counted insects,) spiders, some phalangia, 

 and scorpions, are admitted to be of a dif- 

 ferent structure, and to possess both circu- 



p 3 



