330 INSECTA. 



nerve, arises (fig. 165, b b) by two roots from the opposite extremities 

 of the brain, close to the origins of the antennal nerves. The nervous 

 cords thus derived soon unite to form a minute central ganglion 

 (fig. 165, i), from which proceeds a single nerve (fig. 165,/fc) that 

 runs with the gullet beneath the brain, and spreads in delicate ramifi- 

 cations upon the oesophagus as far as the muscular stomach (fig. 164, 9 9), 

 or to the gizzard when that organ exists. 



(860.) The sympathetic system properly so called consists of four 

 small ganglia (fig. 165, cc, 1 1), the two anterior of which communicate 

 with the brain and with each other by means of connecting filaments. 

 These ganglia are closely applied to the commencement of the ceso- 

 phagus, and supply it with minute nerves. 



(861.) Various are the conjectures entertained by different authors 

 concerning the senses possessed by the members of the insect world, 

 and the organs subservient thereunto. The possession of certain sources 

 of perception has been alternately granted and denied ; the nature of 

 their sensations has been a fruitful subject of inquiry ; and some physio- 

 logists have even gone so far as to deny the correspondence of the 

 impressions derived by insects through the medium of their senses with 

 those which we ourselves receive. It would lead us far out of our 

 course did we even advert to the multiplicity of opinions and conjec- 

 tures promulgated from various sources relative to these inquiries, and, 

 perhaps, with little addition to our real knowledge. It is true that we 

 cannot deny the possibility of the existence of other modes of sensation 

 than those familiar to us ; but it is likewise evident that, as we can 

 never have the most remote conceptions concerning their nature, specu- 

 lations respecting them are not at all calculated to lead to satisfactory 

 conclusions. We must from necessity take our own senses as the 

 standard of comparison, limiting our inquiries to examining how far 

 insects possess means of intercourse with the external world similar to 

 those which we enjoy, and, when we find certain faculties to exist, 

 investigating the structure of the organs by which they are exercised. 



(862.) The sense of touch is indubitably bestowed upon all insects ; 

 and, to judge from the perfection of the edifices which they build, and 

 the precision of their usual operations, this must be extremely delicate. 

 It is sufficient, however, to look at the external construction of the 

 skeletons of ARTICTTLATA to perceive that the hard and insensible inte- 

 gument spread over the entire surface of their bodies is but little calcu- 

 lated to receive tactile impressions. The antennae, or feelers as they 

 are popularly called, have been very generally regarded as being pecu- 

 liarly instruments of touch ; and whoever watches the proceedings of an 

 insect in which these appendages are largely developed will, we appre- 

 hend, easily convince himself that they are employed to investigate 

 surrounding objects by contact. Straus-Durckheim regards the feet as 

 being specially appropriated to the sense of feeling ; but this opinion 



