INSECTS. 



oval form, and fituated upon the lunula that terminates the 

 fifth abdominal ring potleriorly. Befides the nerves intend- 

 ed for tiie mufcles of the fifth ring, which are detached 

 from this ganglion in two diflimfl parts, it produces four 

 other pairs polleriorly. Thefe nerves appear to be diftri- 

 biUed to the parts of generation, and to the niulcles of tiie 

 laft abdominal rings, which, in the female, are elongated 

 like a tail to aflill in laying eggs. 



E. Neuropttra. — The infeSs with naked wings, that is to 

 fay, the hymenopteraj neuroptera, and diptera, which have 

 freq\icnt>y very large eyes, have alfo the optic nerves of a 

 proportional fize. This is particula^rly obfervable in the 

 dragon flics. Their brain is formed of two very fmall lobes ; 

 but their optic nerves are dilated into the form of two large 

 plates, which have the figure of a kidney, and which is fpread 

 upon all the inner fiufac£ of tlic eye next the head. The 

 remainder of their meduUai-y cord is exceedingly flender, 

 and furnithed with twelve or thirteen fmall ganglia, the lall 

 of which is, as ulual, connedled with tlie parts of genera- 

 tion. 



F. Hymawpkra. — The brain of the bee is fmall, and 

 divided into four lobes. It produces immediately the nerves 

 which are diftributed to the different parts of the mouth, and 

 the two large optic nerves which are dilated and applied 

 behind each eye as in the dragon flies. There are afterwards 

 feven ganglia, three of which are in the corfelet, and four 

 in the abdomen. The nerves of the laft chiefly fupply the 

 parts of generation. 



G. Diptera. — Tlie apiform fly (il/;/^a tofl.v, Linn.) has 

 a fmall brain, formed of two lobes, which are lituated very 

 clofe together, but diftinguifhed by a longitudinal furrow ; 

 the anterior part produces a large nerve, which is afterwards 

 diftributed to the antenna and the probofcis. 



The optic nerves are very thick, cylindrical, and equal in 

 diameter to the length of the brain, on the lateral parts of 

 which they reft ; they terminate at their extremities in very 

 large bulbs, which correfpond to the breadth of the eyes. 



The firft ganglion of the medulla is produced by two 

 cords, which come from the pofterior part of the brain, and 

 embrace the oeiophagus as a collar ; it is very flender, and 

 fituated in the breaft ; it furniflies a pair of filaments to the 

 mufcles of the anterior feet. 



The fecond and the following ganglia, in all three in num- 

 ber, are united to each other merely by a fingle cord. The 

 laft ganglion is one-half larger than that which precedes it. 

 Polleriorly it produces eight or nine filaments, which are 

 intended for the parts near the anus ; the firft of the three 

 is fituated in the breaft, where it furnifties nerves for the 

 mufcles of the wings and the feet ; the other two ganglia 

 are in the abdomen ; the laft but one is placed above the 

 union of the third ring with the fourth ; and the laft on the 

 interior and inferior edge of the fifth ring. 



In the hornet-fly {Afdus crabroniformis) we alfo obferve a 

 fingle cord uniting the abdominal ganglia, which are fix in 

 number. 



The brain is fimilar to that of the fyrphus ; but the bulbs, 

 formed by the optic nerves, are ftill broader, in proportion 

 to the extent of the eyes they have tc inveft. 



H. Gnathaptcra. — In the great fcolopendra ( Scolopendra 

 morfttans). the brain has a very Angular form : it is, as ufual, 

 conipofed of two lobes, which are almoft fpherical ; it pro- 

 duces laterally the optic nerves, which are very fliort, and 

 may be obferved to divide long before they roach the eye. 

 The filaments are four in numb>'r; but two nerves arife an- 

 teriorly, which are fo very thick, that they appear a part 

 of the brain, to which they are equal in diameter. Thefe 

 serves are particularly intended for the antennae, into wliich 

 I 



we obferve them enter, and in which they may be followed 

 on account of their magnitude. 



The two cords which embrace the oefophagus proceed 

 direftly downward, and form a large ganglion at the union 

 of the firft ring with the head. The firft ganglion produces 

 two nerves pofteriorly, and feveral towards the fides. A 

 ganglion, precifely of the fame fliape, is placed above each 

 of the articulations : thus there are, in all, twenty -four very 

 diftinft ganglia ; the laft of all is fmalleft, neareft the pre- 

 ceding, aud fcems to float in the abdomen ; each detaches 

 three pairs of nerves ; one which afcends towards the head^ 

 a fecond which runs tranfverfely ; both tliefe are diftributed 

 to the mufcles of the abdomen : the third defcend.=, and then 

 proceeds backwards and upwards ; it furniflies filaments to 

 the lateral mufcles, and to thofe of the back. 



Organs of Sfnfe. — We have very little to obferve on this 

 fiibjeft, in addition to what will be found in the article 

 Entomology, under the divifions. Organs ofTcJSt, Palp't, 

 OlfaSlory Organs, Eyes, Skmtr.ata, Organs of Hearing. 

 ■ Few fubjeft s in comparative anatomy and phyfiology have 

 given rife to more various aad contiadiftory opinions, than 

 the organs of fenfe in fome clafles of animals. Much mif- 

 underftanJing on this point has clearly arifen from the in- 

 confiderate application to animals, of inferences drawn from 

 the human fubjeft. Thus, it has been fuppofed that thofe 

 which pofiefs a tongue, muft have it for the purpofe of 

 tafting ; and that the fenfe of fmeil muft be wanting, where 

 we are unable to afcertain the exiftence of a nofe. Obferva- 

 tion and refleflion will foon convince us, that the tongue, in 

 many cafes (in the ant-eaters among mammaha, and almoft 

 univerfa)ly in birds) cannot, from its fubftance andmechanifm, 

 be confidered as an organ of tafte ; but muft be fubfervient 

 merely to the ingeftion and deglutition of the food. Again, 

 in feveral animals, particularly among infeds, an acute fenfe 

 of fmell fecms to exift, although no part can be pointed out 

 in the head, which analogy would jullify us in defcribing as 

 a nofe. 



However univerfally animals may poflefs that feeling, 

 which makes them fenfible to the impreffions of warmth and 

 cold, very few poffefs, like the hum.an fubjeft, organs ex- 

 clufively appropriated to the fenfe of touch, and exprelsly 

 conftrufted for the purpofe of feeling, examining, and ex- 

 ploring the qualities of external objefts. This fenfe appears, 

 according to the prefent ftate of our knowledge, to exift 

 only in three claffes of the animal kingdom ; -ciz. in moft 

 of the mammalia, in a few birds, and probably in infeils. 

 All the obfervations and inveftigations of the ftrufture of 

 the anteHnx, thofe peculiar organs which exift univerfally 

 in the more perfeCl infefts; and of the ufe vi'hich thefe 

 animals generally apply them to ; lead us inevitably to the 

 conclufion, that they reafy are, what their German name 

 implies (Fiihlhorner ; the hteral tranflation of which is feel- 

 ing horns) proper organs of touch; by which the animal 

 examines and explores furrounding objefts. Such organs 

 are particularly necelfary to infefts, on account of the in- 

 fenfibihty of their external coat, wnich is generally of a 

 horny confiltence ; and alfo from their eyes being deftitute 

 in moll inftances of the piiwer of motion. 



We are not wai-ranitd in confidering the tongue as an 

 organ of tafte in all animals, bccaufe it is fubfervient to that 

 fundion IH the human fubjett, and in fome other inftances. 

 We have already obferved, that this organ, in many cafes, 

 ferves merely for taking in the food ; and it is at leaft very- 

 doubtful whether it pofiefles the fenfe of tafte in many others. 

 Yet, on the contrary, we fliouid not be warranted m deny- 

 ing the exiftence of the fenfe in thefe animals, nor even in fuch 

 as arc entirely dellitutt of a tongue ; for this function may 



