INSECTS. 



• nU'. It Is tru*, that thofe which arife from the right fide fevcral nervous fil.iments arc detached to the fnufcles that 



are parallel to the cord, while thofe of tiie left fide remove move the mandibles, and thofe that ad on the head. This 



farther from it. The ganglia, thus approximated, are eleven ganglion terminates poftcriorly in two parallel nerves, which 



in number, and in a ftraight direftion ; they produce long proceed to the middle of the thorax, above the origin of the 



n;rica, which are lo!l in the mufcles. two pair of feet, and there form a fecond ganglion of an 



The nerves of the cheefe-worm (Mufcapntns,'L.\nn.) are hexagonal figure ; this ganglion furnifhcs filaments to the 



. ibutcd in a very curious manner. The brain is fituatcd mufcles of the feet, and likewife terminates poftcriorly in 



diately above the origin of the ocfophagus, behind the "two nen-es, which extend above the union of the corfelct, 



1 ; it is very large in proportion to the rell of the body ; with the peftns ; they there unite and form a th.ird gan- 



it IS rounded poftcriorly, and notched anteriorly, as if it were glion, which is crefcent-flKiped, with the convexity pollerior : 



formed of two lobes. two other nerves proceed from this convexity, which almoft 



\ pair of nerves arife from the anterior part of the brain, immediately produce another ganglion of the fame form, 



proceed forward, and are dillribtited to the mouth, and even hut fmaller. This ganglion gives origin to five nerves .- 



to the parietes of that cavity. It fliould be remarked, that two lateral, deftined to the mufcles of the intermediate feet, 



thele nerves experience a very coufpicuous enlargement pre- '"to the coxa: of which we oblerve thera enter : poftcriorly 



vioiifly to their diftribution. two, which are {lender, and diilributed to the mufcles of the 



Poftcriorly the brain prtfcnts an aperture, which affords a hind feet and the wings. The fifth is fituated in the mid- 



pafTage for the oefophagus : the nervous part, fituated on its die line ; it is alfo thicker, it fwells almoft immediately into 



fides, may be regarded as the cords which produce the ••n Oval-lhaped ganglion, which is divided pofteriorly into 



.medulla, and all below the oefophagus as the medulla it- two exceedingly flender filaments. Thefe filaments, which 



felf. pafs into the abdomen, form a kind of bridge in the breaft, 



Two pairs of nerves arife from the origin of the nervous in which they occupy the middle line, and leave between 



medulla ; thefe arc directed forward, and principally diftri- them the mufcles of the feet and wings of cither fide. 



buted to the vilcera, and to fome of the mufcles of the 2. In theScarabxus Naficomis. — With refpeft to the nerves, 



anterior rings. The third pair of nerves which this me- this infett differs in the perfeift ftate from the defcription 



dulla produces is the moll remarkable ; it comes from the we have given of its larva. The optic nerves, which are 



part which nearly correfponds to the third ganglion ; we very diftincl and large, proceed to the eye, into which we 



fay nearly, becaufe in this infecl the ganglia are fo clofe obferve them enter by a multitude of filaments when we 



make a horizontal feClion of that organ. 



The nervous cord prefents a very confpicuous difference. 

 In the larva there is only a fingle ganglion ; but the perfecl 

 infed has feveral, which arc very dillind. The firft is 



arife, and are diilributed to the mufcles. Its poft -rior 

 angle detaches two parallel nerves, which proceed into the 

 breaft, where they form a third and a fourth ganglion, 

 fituated very near each other, and apparently divided into 

 two lobes by a longitudinal furrow. All the other nerves 

 of the body depart from thofe two ganglia by an irra- 



•to one another, that the medulla feems to form only 

 piece on the furface of which we merely perceive twelve 

 tranfrerfe wrinkles, which indicate the number of gangha. 

 This third pair extends almoft tranfvcrfely. At a certain 



diftance from its feparation it fwells into a ganghon, and fituated above the condyle ; it proceeds from the two pof- 



then divides into feveral filaments ; thefe are the ganglia terior filaments of the brain, and is diftributed to the mufcles 



which Swammerdam fuppofes are intended for the mufcles vvhich move the head on th- corfelet. Its pofterior part 



of the wings, when they fliall exift in the perfect infed. produces two filaments, which pafs into the breaft, where 



Another pair of nerves, which go to the mufcles of the ''^^7 ^"''^ towards the middle part, and form a triangular 



body, arife from each of the other contradions ; but they ganghon ; from the fides of which three pairs of nerves 

 require no particular remark. 



Brain and Nerves of PerfeS InfeSs. 

 A. Cokoptera. 



I. In the Stas-lectle {Lncamts C^rv!js).—We find in this 



infed, ao in its larva, a brain compofed of two approximated diation, prccifely in the fame manner as In the lar._. 



fpherical lobes, fituated above the cefophagus ; its anterior 5. /« f/je Water Beetles (Dytifcus) arJ the Ground Beethf 



part produces two pair of nerves, which terminate in the {Carabus). — The nervous fyftem is entirely fimilar in thefe 



palpi and other parts of the mouth. There is probably a infeds. The brain is formed of two large hemifpheres, 



recurrent nerve, but our refearches have not yet difcovercd feparatcd from each other by a longitudinal furrow. The 



it- anterior part produces the nerves of the mouth, and the 



There are two ganglia on the lateral parts of the brain, lateral part.<; thofe of the eyes and antcnns. The nerves of 



which are almoft as large as each of the lobes. In their the eyes are (hurt, and differ greatly from thofe of the 



form they refemble a pear, and reft upon the brain by their flag beetles ; they are of a pyramidal form : their bafe 



bafe ; they are prolonged tranfvcrfely into a large nerve correfponds to the eye, and their apex to the brain. We 



on each, chiefly intended for the eye. Before the nerve have not obfervcd any recurrent nerves, 



arrives at that part, we obferve it detach a flender filament. The two filaments which produce the nervous cord de- 



which enters into the great mandible ; then, more exter- part from the brain, not pofteriorly, buf inferioriy, on the 



Jially, another filament which enters into the cavity of the fide of the optic nerves : they are very fhort, as they paf» 



antennas ; laftly, the nerve itfelf, having reached the eye, immediately under the ocfophagus. They furnifli fome 



fwells agaiii into a bulb, and produces a number of nerves, filaments to the mufcles and tlie ocfophagus. The firft 



which we fliall defcribe when we treat of the organ of ganglion they form lies under a kind of bridge, formed of 



^'"'on. homy fubftance, which is fituated in the middle of the 



Pofteriorly the brain produces two very long and flender head, and v.hich affords a point of attachment to the mufcles 



nerves which accompany the cefophagus to the point where of the jaws ; it is of an elongated and quadrangular figure, 



the head unites to the thorax, immediately above the articular and occupies almoft tlu- whole fpace that corrclponds to 



condyle. The two nerves fituated above the cefophagus, the condyle above which it is placed. It is terminated 



then, produce a ganglion of a long oval form, from which pofteriorly by two filaments which proceed in a panillcr 



Vol. ilX. Y direction, 



