. Beginners' Zoology . Fig. 131. — Position of Insects Heart,food tube, aTid nerve chain. The heartThe blood comes into each of the heart compartments through a pairof openings. The heart contracts from the rear toward 78 BEGINNERS ZOOLOGY. the front, driving the blood forward. The blood containsbodies corresponding to the w/iite corpuscles of humanblood, but lacks the red corpuscles and the red colour. Theblood is sent even to the wings. The veins in the wingsconsist of horny tubes inclosing air tubes surroundedby blood spaces, and the purification of the bloodtakes place throughout the cours
. Beginners' Zoology . Fig. 131. — Position of Insects Heart,food tube, aTid nerve chain. The heartThe blood comes into each of the heart compartments through a pairof openings. The heart contracts from the rear toward 78 BEGINNERS ZOOLOGY. the front, driving the blood forward. The blood containsbodies corresponding to the w/iite corpuscles of humanblood, but lacks the red corpuscles and the red colour. Theblood is sent even to the wings. The veins in the wingsconsist of horny tubes inclosing air tubes surroundedby blood spaces, and the purification of the bloodtakes place throughout the courseof the circulation. Hence the im-perfect circulation is no disadvan-tage. The perfect provision forsupplying oxygen explains theremarkable activity of which in-sects are capable and their greatstrength, which, considering theirsize, is unequalled by any otheranimals. The Nervous System. — Theheart in backboned animals, , is ventral and the chief nerve trunk is dorsal. Asalready stated, the heart of an insect is dorsal; its chiefnerve chain, consisting of a double row of ganglia, is nearthe ventral surface (Fig. 131). All the ganglia are belowthe food tube except the first pair in the head, which areabove the gullet. This p
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