578 



ZOOLOGY 



SECT. 



series of segmentally-arranged fan-shaped bundles of muscles 

 the ala rii muscles (Fig. 484, m.}. 



Respiration takes place through the instrumentality of a 

 system of air-tubes or trachccc (Figs. 459 and 460), opening on the 

 surface at the stigmata, to which reference has already been made. 

 These tracheae form a richly ramifying system extending to all 

 parts of the body. They possess a chitinous internal lining, 

 supported by means of a spirally- wound, fibre-like thickening. 

 By means of this system of air-tubes air is conveyed throughout 



thcr.2 



FIG. 460. Periplaneta. View of 

 the arrangement of the principal 

 trunks of the traeheal system. 

 (After Miall and Denny.) 



FIG. 461. Periplaneta. General view of the 

 uervoxis system, riini. sixth abdominal gang- 

 lion ; ant. antennary nerve ; hi: brain : conn. 

 cesophageal connective ; inf. sub-cesophageal 

 f ganglion ; oj,t. optic nerve ; MO/-.I tltoi-,- thorj 

 first, second, and third thoracic ganglia. 

 (After Miall and Denny.) 



the body to all parts, and there is thus ensured the rapid and 

 complete oxygenation which the functional activity of the Insect 

 requires. 



The nervous system consists of a brain (Fig. 457, brn., and 

 461, br.), a ml-cesophageal pair of ganglia (infr. gang.), three 

 Hi in-uric (Fig. 461, thor. 1, 2, and 3), and six abdominal pairs of a 

 ganglia, a system of connectives uniting the ganglia together, and 

 a series of nerves given off to the various parts of the body. The 

 brain consists of a bilobed mass of nerve-matter situated in the 



