. Zoology : for students and general readers . Zoology. 340 ZOOLOGY. maxillfe, and labium. The mandibular nerves project for- ward and arise from the anterior part of the ganglion, near the origin of the supra-cesophageal commissures, while the maxillary and labial nerves are directed downward into those organs. The sympathetic ganglia are three in number ; one situ- ated just behind the supra-cesophageal ganglion (Pig. 278, as), resting on the cesophagus, and two others situated each side of the crop, low down. Each of the two posterior ganglia is supplied by a nerve from the anterior ganglio
. Zoology : for students and general readers . Zoology. 340 ZOOLOGY. maxillfe, and labium. The mandibular nerves project for- ward and arise from the anterior part of the ganglion, near the origin of the supra-cesophageal commissures, while the maxillary and labial nerves are directed downward into those organs. The sympathetic ganglia are three in number ; one situ- ated just behind the supra-cesophageal ganglion (Pig. 278, as), resting on the cesophagus, and two others situated each side of the crop, low down. Each of the two posterior ganglia is supplied by a nerve from the anterior ganglion. Two nerves pass under the crop con- necting the posterior ganglia, and from each jDosterior ganglion a nerve is sent backward to the end of the proventriculus. A pair of nerves pass under the oesophagus from each side of the anterior sympathetic ganglion, and another pair pass downward to a round white body, whose nature is unknown (Fig. 278, u). Pig. 280 represents an enlarged view of the brain and sympathetic nerve of a moth. The heart is a long tube lying in the abdomen, dilating at six places along its course, and ending in a conical point near the end of the abdomen ; it is held in place by fine muscular bands. All insects breathe by means of a complicated system of air-tubes rami- fying throughout the body, the air entering through a row of spiracles, or air-holes, or breath- ing-holes {stigmata), in the sides of the body. There are in locusts two pairs of thoracic and eight pairs of abdominal spiracles. The first thoracic pair (Pig. 281) is situated on the membrane connecting the prothorax and mesothorax, and is covered by the hinder edge of the protergum (usually called prothorax). The second spiracle is situated on the. Fig. 880. — Supra-( geal ganglion and visceral (or sympathetic) nervous system of tlie silk-worm moth (Bom- hyx man), gs, Supra-ceso- phageal ganglion (" brain") ; a, antennary nerve ; o, optic nerve; r, azygos trunk of the viscer
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
