Elementary anatomy and physiology : for colleges, academies, and other schools . elementaryanato00hitc Year: 1869 AND PHYSIOLOGY. 277 of some insects, and the tracheae are very minute, ramifying through the most delicate organs of the body, which plan allows a rapid aeration of the blood, and greatly assists in diminishing the specific gravity of the animal. The openings upon the surface of the body are called Spiracles or Stigmata, and are either oval or made in the shape of a slit, as is seen in the adjoining cut. In the soft-skinned insects they Fig. 273. Spiracle of Common Fly. are sur
Elementary anatomy and physiology : for colleges, academies, and other schools . elementaryanato00hitc Year: 1869 AND PHYSIOLOGY. 277 of some insects, and the tracheae are very minute, ramifying through the most delicate organs of the body, which plan allows a rapid aeration of the blood, and greatly assists in diminishing the specific gravity of the animal. The openings upon the surface of the body are called Spiracles or Stigmata, and are either oval or made in the shape of a slit, as is seen in the adjoining cut. In the soft-skinned insects they Fig. 273. Spiracle of Common Fly. are surrounded by a ring of cartilage, to prevent their closing by ordinary accidents or pressure, and all spiracles are pro- tected by a kind of sieve or grating, made up of hairs ex- tending from either side of the aperture, which keeps out dust, that would otherwise enter with the air and stop the passage. The interchange of air is effected by the enlarge- ment and contraction of the abdomen. The rings, (or skele- ton), which surround the abdomen, are seldom inflexible, but are made up in one part of membrane, and the horn-like ends are brought together by muscular contraction, by which means expiration is effected. The enlargement or inspira- tion is accomplished by the simple elasticity of the encasing rings of the body, as well as of the trachea. Hence, full- ness is the natural or passive state of the respiratory or- What are the spiracles? How are they sometimes protected? Give the mechanism of respiration.
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