INSECTS. 



- direftion, and form a fccond ganglion in the middle part 

 of the corfelet. This ganglion furnilhes nerves to the 

 mufcles of the anterior feet. We obferve them enter 

 into the cavity of the coxs. The third ganglion appears 

 bilobed, or formed of two oval bulbs, the union of which 

 is nKuked by a longitudinal furrow. This ganglion is 

 filuated longitudinally above the anterior inferior edge of 

 the breail. It fends filaments to the mufcles of the inter- 

 mediate feet. The fourth ganglion is very near the pre- 

 ceding ; it is of a roundifli form, and is dillributcd to the 

 mufcles of the pollerior feet and the wings. The fpace 

 between the fifth and fixth ganglion is very fmall : their 

 form is round ; and tliey furnidi filaments to the mufcles 



that move the abdomen on the breail. The remainder of rated by 



the brealt, a fevMth appears. Thefe two ganglia pr"'- 

 duce only one pair of nerves, which are diftributed to tho 

 mufcles. 



There are only two ganglia in the abdomen ; one cor- 

 refponds to the middle part of the fccond ring ; the other, 

 which is the laft and ninth, is fituatcd above the union of 

 the fecond fegment with the third. The laft ganglitu 

 but one h in every refpedl fimilar to the two precediiij; ; 

 but the ninth is one-half-larger, and produces pollerioily 

 four pair of nerves, which are diftributed on both fides to 

 the parts of generation. 



B. Orlhoptera. — In the Cockroach (Blatta Americana.) — 

 The brain of this infedl is compofed of two lobes, fepa- 



the medullary cord is formed by a feries of five ganglia, 

 fitnated fo clofe to one another, that they appear to the 

 naked eye to form only one ; but with a glafs they may 

 be oblerved very diftinctly. We even perceive the two 

 filaments produced by each to form the fucceeding ganglion. 

 The fifth prefents a tranfverfe furrow, which feems to in- 

 dicate the Union of two ganglia. The end of the medulla 

 appears to float in the abdominal cavity, but above the in- 

 teftincs. 



4. In the Great Di-ver (HyJrophilus Piceus, Linn.) — Tlie 

 brain of this infeft, which is fituated in the head, and above 

 the origin of the oefophagus, confifts of two fpherical bulbs 

 clofely uflited. The lateral parts give origin to the optic 

 nerves which proceed towards the eyes without changing 

 their diameter, but which terminate there by a triangular 

 bulb that produces a vaft number of filaments externally. 



The anterior part of the brain detaches fome filaments 

 intended for the parietes of the mouth. We alfo remark, 

 at the fame place, a fmall fpherical ganglion, which ap- 

 pears to belong to the recurrent nerve that accompanies 

 the oefophagus. 



Two filaments, which (honld produce the medullary cord, 

 arile inferiorly: they embrace the oefophagus at tlieir fe- 

 paration, unite immediately belew it, and again, in the ca- 

 vity of the head, to form a fmall ganglion, which furnilhes 

 nerves for the mufcles of the mandibles and the palpi. Two 

 nervous cords are detached from the pofterior part of this 

 .firll ganghon. Almoft immediately after their origin, they 

 pafs under a horny arch, which is produced by the internal 

 furface of the ganache. We obferve that they re-appear 

 pofteriorly, and proceed into the corfelet. They form a 

 fecond ganglion exaftly in the middle of the corfelet ; its 

 figure is quadrangular. The anterior and pofterior angles 

 produce the nerves of the medulla, and the lateral thofe 

 intended for the mufcles of the anterior feet. The inter- 

 val included between the fecond and third ganglion of the 

 medulla is very great. The third ganglion correfponds 

 to the infertion of the intermediate feet : it is large, and 

 of a round form ; it furnifties nerves to the wings, and to 

 the intermediate pair of feet. Pofteriorly it produces two 

 cords, which, at the diftance of about half a fine, fwell and 

 form a fuurtli ganglion, almoft a.s large as the preceding. 

 ■J-Jiis ganglion detaches, from its inferior part, a number 

 of filaments for the mufcles of the pofterior feet, which 

 are fpccially appropriated to fwimming. Two other very 

 thort cords produced by the pofterior part of this ganglion 

 fwell into a fifth, which i.-, one-half lefs than the former, 

 and which furnifties a fin^^ie cord pofteriorly. This cord 

 patTes into a kind of longitudinal groove, formed above the 

 horny appendix, that furnilhes at'tachments to the mufcles 

 of the COXE. A fixth ganglion is fituated at the pofterior 

 and wide part of this appendix : at a certain diftancc, 

 and exattly above tl»e union of the abdomen with 



very 



diftinft notch 



ly. The optic nerves 



arile on the fides, and its anterior part detaches fome ill 

 ments to the parietes of the mouth, and to the inftrumenls 

 of manducation. 



The nervous cords which form the medulla arife from 

 its inferior furface. They proceed direftly downward, and 

 clofely embrace the oefophagus. They afterwards proceed 

 in a parallel direction, but very diftinCi from each otiior, 

 towards the corfelet. When they reach its middle, thev 

 form a very large ganglion, which produces three pairs of 

 nerves laterally, and one pofteriorly. The tirft lateral nerves 

 afcend obliquely towards the head, and furnifti filaments to 

 the mufcles that move it on the thorax, and which acl on 

 the antennse and the parts of the mouth. The others are 

 diftributed to the mufcles of the firft pair of feet. 



The pofterior nerves proceed in a parallel direction back- 

 ward. At the middle of the pectus they produce a ftill 

 more conliderable ganglion than the fecond, which furnifties 

 laterally nerves to the intermediate and pofterior feet, as 

 well as to themufcles of the wings. It alfo fends off two 

 cords pofteriorly, which, by then- union at the junftion of 

 the abdomen and the breaft, form a fourth ganglion, fituated 

 on a projcifting horny fubftance to which the mufcles of the 

 coxae are attached. 



After this fourth ganglion there is only a fingle nerve, 

 which has, at certain fpaces, fmall enlargements. Five of 

 thefe fvvcllings may be counted. Each produces a pair of 

 nerves for the mufcles of the rings of the abdomen : the 

 firft is the largeft, and furnifties befides two nerves which 

 ramify in the parts near the anus. 



In the Great Green Grafshopper ( GryUus Virhnftmui, Linn.) 

 — The brain is fituated in the head above the oefophagus : 

 it confifts of two hibes, which have the form of pears, united 

 at their bafe, and prolonged at the other extremity into an 

 optic nerve for the eye of each fide. The anterior part alfo 

 produces two nerves of a pyramidal form, the bafe of which 

 refts upon the brain. Some filaments arife from the apex of 

 the pyramid, wliicli are loft in tl>e mandible, the jaw and its 

 galea, as welt as in the upper lip. 



Between thefe two anterior nerves we obferve a fmall gaJ5« 

 glion, which is produced by the union of the two filaments 

 of the inferior furface of the brain. This is the recurrent 

 nerve which follows the inteftinal canal. Pofteriorly, and a 

 hi tie inferiorly, we obferve the origin of the two cords which 

 form the nervous medulla. They embrace the oefophagus, 

 below whicli they are immediately directed, and form a 

 ganglion. This firft ganglion if protected and covered by 

 a kind of horny bridge of a reddifli colour. It furnifties 

 nerves to the mufcles of the mouth, and to thofe of the 

 head within wliich it is inclofed. Pofteriorly it produces 

 two long nervous cords, which penetrate into the corfelet. 

 Thefe two cords unite about the middle of the thorax before 

 the appendix, which gives attachment to the mufcles of the 

 coxw and the anterior pair of feet. At this union they form 



a large 



