OF SENSATION AND THE SENSES. 483 



vours to free themselves from a disagreeable restraint. In favour of 

 the adoption of this opinion the deficient formation of the blood in 

 insects speaks, in consequence of which no inflammation and suppura- 

 tion can take place. Inflammation, however, or the immediate touch- 

 ing of the nerve laid bare, by the air or other extraneous bodies, occa- 

 sions our feeling pain from a wound, and as long as this irritable con- 

 dition does not occur no pain is felt. This irritable condition, however, 

 can never take place in insects, they having no blood-vessels and cellular 

 membrane, through which the irritable matter may transude, but merely 

 a lymph, circulating freely in the body. This lymph encompasses the 

 extraneous body, the pin, coagulates around it, and thus perfectly pro- 

 tects the nerves from its influence. According to this view the majority 

 of impaled insects die of hunger, and not by mechanical wounding ; if, 

 for instance, the thoracic ganglion or the nervous cord be not separated ; 

 for so serious an injury to the nervous system the preceding experi- 

 ments have shown must speedily produce death ; but yet I would not 

 be understood as approving of that certainly very unnecessary torture 

 to which poor captured insects are exposed by the young and old, as 

 objects of their pleasure. In support of this opinion we may still men- 

 tion that many impaled insects still continue the exercise of their most 

 usual corporeal functions ; for instance, still eat, still evacuate excre- 

 ment, creep about with the pin through them, and sometimes even fly, 

 and lastly, the Lepidoptera even copulate in this state, and, a still more 

 common occurrence, is their continuing to lay eggs. 



277- 



Upon passing from these introductory observations upon the functions 

 of the nervous system in general to the senses themselves, we may 

 maintain, in reference to these, that insects are not deficient in any 

 important one found in the superior animals. At the end of the pre- 

 ceding division we described the organs of the several senses, but we 

 yet found only one certain organ of sense, which, with few exceptions, 

 is discoverable in all insects, and this was the eye. We, nevertheless, 

 endeavoured to discover the other organs of the senses, proceeding from 

 determinate observations which prove that insects have perceptions which 

 can only be received by senses of touch, taste, smell, and hearing, and we 

 then found several organs, each individual one of which admitted of being 

 referred to some one of these senses, cither from analogous situation or 

 structure to that of the same organ of sense in the higher animals, and 



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