ANATOMY AND PHYSIOLOGY gl 
innervates the antennz; and (3) the tritocerebrum, which in 
Apterygota bears a pair of rudimentary appendages that are 
regarded as traces of a second pair of antenne. 
Fic. 112, 
Successive stages in the concentration of the central nervous system of Diptera. A, 
Chironomus; B, Empis; C, Tabanus; D, Sarcophaga.—After Branprt. 
Fics i123: 
CTL 
" 
‘ 
d . x28 ii 
Nervous system of the head of a cockroach. a, antennal nerve; ag, anterior lateral 
ganglion of sympathetic system; b, brain; d, salivary duct; f, frontal ganglion; hh, hypo- 
pharynx; /, labrum; /i, labium; m, mandibular nerve; mx, maxillary neive; n/, nerve to 
labrum; uli, nerve to labium; o, optic nerve; ov, esophageal commissure; oe, esophagus; 
pg, posterior lateral ganglion of sympathetic system; r, recurrent nerve of sympa- 
thetic system; s, subcesophageal ganglion.—After HoFerr. 
The subcesophageal ganglion (Fig. 113) is always con- 
nected with the brain by a pair of nerve cords (@sophageal 
