92 ENTOMOLOGY 
commissures) between which the cesophagus passes. ‘This 
compound ganglion represents at most four neuromeres: (1) 
mandibular, innervating the mandibles; (2) superlingual, 
found by the author in Collembola, 
but not yet reported in the less gen- 
eralized insects; (3) maxillary, inner- 
vating the manille; (4) labial, which 
sends a pair of nerves to the labium. 
The minute structure of the brain, 
though highly complex, has received 
considerable study, but will not be 
described here for the reason that the 
anatomical facts are of no general 
interest so long as their physiological 
interpretation remains obscure. 
Sympathetic System.—Lying 
along the median dorsal line of the 
cesophagus is a recurrent, or stomato- 
gastric, nerve (Fig. 114), which 
arises anteriorly in a frontal gan- 
glion and terminates posteriorly in 
a stomachic ganglion situated at 
the anterior end of the mid intes- 
tine. Connected with the recurrent 
nerve are two pairs of lateral ganglia, 
Sympathetic nervous system the anterior of which innervate the 
of an insect, diagrammatically 
Poresehicd =. autenwal, “COrsal: vessel, and the jpoctemon sauce 
Derves > Pi Drains ijys tronidls “aches of the: heads | Phet-ventuar 
ganglion; 7, 7, paired lateral : ; 
ganglia; m, nerves to upper nerve cord may include also a median 
mouth parts; o, optic nerve; = . pete Aaa | Sonne 
Pieecuteent netves sc nerve co eT Ve thread (Fic. 01) winiene oie. 
sauvary -glands; 4, stomachic: - off ipaired transverse Nerves muse 
ganglion.—After Kose. . : 
muscles of the spiracles. 
Structure of Ganglia and Nerves.—A ganglion consists 
of (1) a dense cortex, composed of ganglion cells (Fig. 115), 
each of which has a large rounded nucleus and gives off usu- 
ally a single nerve fiber; and (2) a clear. medullary portion 
