INSECTS. 



-fids of a ftries of thirteen principal ganglia, which furnifh 

 filaments to all other parts of the body. The firft of thefe 

 tliirteen ganglia is fituated in thecavity of the head ; it lies 

 abeve the ccfophacjus, and fupplics th.- place of the brain : 

 it appears formed fuperiorly by the union of two round tuber- 

 cles, inferiorly it is concave, and correfponds to the con- 

 vexity of the ocfophagus. This ganglion communicates 

 with the rell of the nervous cord by two thick filaments, 

 which embrace the afophagus, and which are united below 

 it to the anterior and lateral part of the next ganglion ; it 

 befides produces eight pairs of nerves. 



The firll partly unites with other filaments ; produce* 

 fomc for the cefophagus, and forms feveral remarkable gan- 

 glia below the upper lip. The liirgelt and moft poflerior, 

 which Lyonet has named the JiiJ! frontal ganglion, is pro- 

 longed pofteriorly into a thick recurrent nerve, which is 

 continued tlie whole length of the body, near the back ; 

 this recurrent nerve furnilhes filaments to the cefophagus 

 and its mnfcles ; it penetrates into the dorfal veflel, and it 

 afterwards re-appears, and glides along the cefophagus as 

 far as the ftomach. This nerve produces, at certain dif- 

 tances, very folid filaments, which keep the cefophagus at- 

 tached to the Ikin of the back. 



Befides the recurrent nerve we have juft noticed, feveral 

 -filaments are furniihed by the pofterior frontal ganglion to 

 the mufcles of the oefophagus, and two to the /rMr/ frontal 

 gangUon ; the latter aifo detaches feveral filaments to the 

 cefophagus, and, in particular, a very remarkable one, 

 which, by a fudden ejiglargement, conllitutes the t/jlrd frontal 

 ganglion. This ganglion likewife affords feveral filaments to 

 the oe'ophagus. 



The fecond pair of the brain appears chiefly intended for 

 the aiitennx, though it furnilhes feveral filaments to the 

 neighbouring parts. The third pair terminates particularly 

 in the antennae, and the mufcles which move them. The 

 fourth pair is proper to the eye of each fide ; it accompa- 

 nies the air-tube which goes to that pai-t, and is divided 

 into fix branches, that penetrate into tlie fix eyes, which, by 

 their union, form that of the caterpillar. The fifth is di- 

 rected a little backwa;-d, where it divides into two branches ; 

 one pollerior for the adduftor mufcles of the jaw ; the other 

 anterior, which is loft in the membranes that cover the fron- 

 tal fcales. The fixth and feventh pair unite to form a gan- 

 glion from which feveral filaments are detached, to the 

 n-fophagus and its mufcles. Finally, the lail pair of the 

 brain is entirely loll on an air-tube. 



But befides thefe nerves produced by the firft nervous gan- 

 glion, feveral others are detached from it, which we Ihall 

 briefly notice. In the firft place, we obferve, that it fur- 

 niihes feveral filaments to the dorfal canal : it afterwards gives 

 origin to a pretty long filament, which terminates on the air- 

 veiiels, between the fecond and third ganglion. Laftly, it 

 produces a uervous ring, which embraces the cefophagus in- 

 teriorly like a girth, and fupplies it with feveral filaments. 

 The fecond ganglion is intimately united with the third, and 

 is diftinguiflied from it only by a contraftion. The nerves 

 which proceed from the anterior part appear to be produced 

 by the fecond ganglion, and thofe which arife from the pof- 

 terior part, feem to belong to the third. 



Befides the two filaments which form the collar round the 

 cefophagus, and which unite the firft to the fecond ganglion, 

 the latter has four pair of very diftinft nerves. The moft 

 anterior pair is lent forward to the mouth, but in its courfe it 

 <3ividcs into two branches ; one terminates in tlie tongue and 

 the adjacent parts ; the other branch proceeds to the late- 

 ral parts, where it fub-divides, to fupply the mandible, 

 the jaw, and upper lip, communicating, at the fame 



time, with the firft ganglion, and with the fecond frontal. 

 The fecond pair proceeds to the jaw, but detaches a number 

 of filaments to the mufcles of the neighboivring parts. The 

 tltird pair is deftined for the fpinning apparatus ; in its co-irfe 

 it gives filaments to the filk veftels and mufcles of the head. 

 The fourlli pair arifes near the conti aflion, which indicates 

 tlie union of the t'vo ganglia, between the head and the firft: 

 i-!ng ; it is loft in the fat, in the fkin of the neck, and in the 

 mufcles infcrted into the head. 



The third ganglion, which, as we have obferved, is united 

 to the fecond, produces only three pairs of nerves : the pof- 

 terior is merely the continuation of the nervous trunk of the 

 other two pairs ; the anterior is entirely loft in the mufcles 

 and tlie fliiii ; the intermediate pair fupplies that part alfo ; 

 but it is diftnbuted chiefly to the mufcles, which move tlie 

 articulations of the leg 



We have .ilready ftated, that each ganglion communicates 

 with that which precedes, and that which follows it by two 

 filaments l!iat are diftinft from their origin, and are the bifur- 

 cation of a lingle crunk. The middle of this bifurcation, 

 from the third to the eleventh ganglion, produces a fmall 

 nerve, which Lyouet has named t he fphial frtcnum : this 

 fingle nerve is fituated in the middle line ; it prefently di- 

 vides in'o two branches, which follow the divifions of tlje 

 air-tubes, und penetrate with fome of them into the longitu- 

 dinal velTel. 



The fourth and fifth ganglia produoe the fame number of 

 ncrvis, tlie diftrihution of which i.= alfo nearly fimilar ; their 

 anterior pair proceeds to the muHles, and to the fliin of the 

 rings to which it correfponds ; the intermediate pair fur- 

 nilhes, more particularly, filaments to the mufcles of the 

 leg. 



The fixth ganglion, which correfponds to the fourth ring 

 of the body, alfo furniflics two pair of nerves, which are loft 

 in the mufcles and the llcin. 



The nerves of the five following ganglia are diftributed 

 nearly in the fame manner. 



The twelfth ganglion, and the thirteenth, which is the 

 termination of the nervous cord, are very clofetoeach other, 

 though dillindf. The diftrihution of the nerves, produced 

 by the firft, prcfents nothing remarkable. Thofe furniflied 

 by tlie fecond are very long, being feiit to the laft rings, in 

 the flcin and mufcles of which the firft pair is partly loft. 

 The fecond pair is only fubdivided when it has reached the 

 firft ring ; it there produces a plexus, from which a number 

 of filaments are detached to the great hiteftine. The trunk 

 appears to end on the parietes of the reftum towards the 



F. D'lptera. — The nerves of the larva of the ftratyomis 

 have fome refemblance to thofe of the larva of the fcarabaeuV 

 naficornis. 



The brain is formed of two lobes, placed clofe together, 

 and almoft fpherical ; it is fituated above the cefophagus, 

 on a level with the fecond ring of the body. A number 

 of fmall nervous filaments arife from its jvnleriorpart, and 

 are diftributed to the parietes of the mouth, to the mandibles, 

 and to all the adjacent parts. Thefe nerves are very diftinft, 

 particularly thofe which are removed from the middle line. 

 The pofterior part of thefe two lobes fends off two thick 

 branches which fmbrace the cefophagus, and form the origin 

 of the nervous medulla. This nervous cord is very fliorf, 

 audjts diameter is one-half lefs than that of the brain ; it 

 confifts of eleven ganglia placed very near each other, each 

 of which produces one pair of nerves. 



Thefe nerves proceed directly backward. Swammerdam 

 has erroneoufly reprefented this cord as twifted, hke the 

 tail of a fcorpion, and producing nerves on the left fide 



•nly. 



