212 LECTURE V. 



and worms succeed to insects. I have told 

 you what Mr. Hunter knew and thought 

 about the structure and functions of worms ; 

 first, because it is probable that analogy, as 

 well as his own observations, which may 

 indeed have been biassed by analogy, led 

 him to believe, that the circulating and 

 respiratory organs of insects were similar to 

 those of vermes. Like Swammerdam and 

 others, he considered the dorsal vessel as 

 the heart of the insect, and it is exposed 

 in his Museum in the bee, the preparation 

 being marked, the heart of the bee. We 

 find bees, beetles, and silk-worms injected 

 in the Hunterian Collection, but how, no^ 

 one can tell. I should not have supposed 

 that Mr. Hunter would have injected from 

 the spiracula or orifices of the tracheae, 

 with which he was well acquainted. Yet 

 the injection, wherever impelled, might 

 have been effused, or have got into and per- 

 vaded the air-vessels, which is supposed to 

 be the case, by those who put faith in the 

 modern opinions respecting the anatomy of 

 insects. Mr. Hunter also believed, that 

 the pulmonary organs of insects were simi- 



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