Elementary entomology ([c1912]) Elementary entomology elementaryentomo00sand Year: [c1912] ANATOMY OF INSECTS- -INTERNAL 33 extends the length of the body along the median line just beneath the notum. In the abdomen of adult insects this tube is divided into several chambers, each of which has a valve at either side, allowing the blood to flow into it but preventing its escape. The chambers are also separated by valves which allow the blood to flow forward but prevent its backward passage. The abdominal part of the tube, the heart proper, pulsates and drives the blood toward the head, while t
Elementary entomology ([c1912]) Elementary entomology elementaryentomo00sand Year: [c1912] ANATOMY OF INSECTS- -INTERNAL 33 extends the length of the body along the median line just beneath the notum. In the abdomen of adult insects this tube is divided into several chambers, each of which has a valve at either side, allowing the blood to flow into it but preventing its escape. The chambers are also separated by valves which allow the blood to flow forward but prevent its backward passage. The abdominal part of the tube, the heart proper, pulsates and drives the blood toward the head, while the forward part is a simple blood vessel, called the aorta, which usually divides in the head, where it ends abruptly, allowing the blood to flow into the body cavity. Thus the blood is admitted to the heart by the lateral valves, is forced forward to the head, and thence flows in more or less defined currents FIG. 38. Portion of a trachea of a caterpillar, with its branches (After Leydig, from Gegenbauer) throughout the body, bathing all the organs. The pulsation of the heart and the flow of the blood may be observed in many thin- skinned larvas and nymphs. The blood consists of a watery fluid, - - the plasma, or serum, - and the white corpuscles, or leucocytes. Usually colorless, it is often yellowish or greenish. The blood has almost nothing to do with the aeration of the tissues, that being done by the respiratory system, as described below7, its chief function being to nourish the tissues with the food materials that it carries. Respiratory system. Insects have no lungs, but breathe through a system of tubes, called trachea, which extend to all parts of the body, bringing fresh air to the tissues and carrying off the carbon dioxide. On either side of two thoracic segments, and on all the
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