Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . in insects are called trachece, havingtheir parietes strengthened by an elastic cartilaginous filament, notindeed disposed in a series of distinct rings, but in a continuous closespiral coil. By this structure the most delicate and invisible ramifi-cations of the air-tubes may be easily recognised under the micro-scope. The spiral filament is situated between the external cellularand an internal delicate epithelial lining. The tracheae commence either from lateral apert
Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . in insects are called trachece, havingtheir parietes strengthened by an elastic cartilaginous filament, notindeed disposed in a series of distinct rings, but in a continuous closespiral coil. By this structure the most delicate and invisible ramifi-cations of the air-tubes may be easily recognised under the micro-scope. The spiral filament is situated between the external cellularand an internal delicate epithelial lining. The tracheae commence either from lateral apertures, called spi-racles and stigmata (7?^. 153,/), or from pneumatic tubes (z), gene-rally continued from the anal segment; these latter are peculiar toinsects which live in water, as the Nepa and Ranatra; and usuallyco-exist with stigmata. The air is conducted by the spiracles or the pneumatic tubes, or, as * Vol. ii. p. 31. Mr. Bowerbank (CCXLIX. p. 239), accurately observed thatthe blood was inclosed in distinct parietes, and did not flow in the commonabdominal cavity, as Cams and Wagner believed. t CCL. IXSECTA. 385. U^l^cJ^^^X^ in Nepa, by both, Into a large longitudinal tracheal trunk (g\ whichruns near each side from one end of the body to the other; they areconnected together by transversetubes, which run across the pos- j ^^terior margin of each abdominalsegment, and distribute an in-finitude of smaller tracheal ra-mifications. Some of thesebranches dilate into air recep-tacles (//), the number and sizeof which, like the air-cells inbirds, are in direct relation withthe powers of flight. In theNepa these reservoirs of airare confined to the thorax : inother insects, as the grasshop-per, they are frequently deve-loped also upon the transverseabdominal trachece: they arevery capacious in the abdomenof the bee. The spiracles are narrowtwo-lipped orifices, situated atvarious points on the externalsurface of the body, and differ-ing in number and size in diffe-rent insects.
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Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1850
