NERVOUS SYSTEM. 295 



Moulting, which involves a casting of the cuticle, of the 

 internal lining of the tracheae, &c., occurs some seven times 

 before the cockroach attains in its fifth year to maturity. 



i:\i& muscles, which move the appendages, and produce 

 abdominal movements essential to respiration, are markedly 

 cross striped. 



Nervous System. — ^A pair of supra-oesophageal or cerebral 

 ganglia lie united in the head. As a brain, they receive 



Fig. 95. — Mouth appendages of Cockroach. (After 

 DUFOUR.) 



I. Mn, Mandibles; II. First Maxillae; c, cardo ; j/, stipes ; Z, 

 lacinia ; G, galea; iiix.fi, maxillary palp; III. Second Maxillae or 

 Labium ; s.jn, submentum ; ?;z, mentuni ; L, lacinias ; pg, para- 

 glossa ; /./, labial palp. 



impressions by antennary and optic nerves. By means of a 

 paired commissure surrounding the gullet, they are connected 

 with a double ventral chain of ten ganglia. Of these, the 

 first or sub-oesophageal pair are large, and give off nerves to 

 the mouth parts, &c. ; from each of the ganglia of the 

 thorax and the abdomen nerves are given off to adjacent 

 parts. There are three pairs of ganglia in the thorax, and six 



