Continued
The body segments are basically cylindrical, as mentioned above, and each is covered by a tough cuticle which is usually impregnated with calcium (Ca). The animals are therefore much more common in lime-rich soils. The cuticle of each segment is composed of a markedly domed upper shield or tergite, together with two smaller side plates and a sternite on the lower surface. These four plates are often fused together to make a rigid cylinder. The cylindrical nature of each segment is obscured in the flat backed millipedes, for here the upper regions of each tergite are drawn out sideways to form prominent 'wings'. Each millipeed tergite slightly overlaps the one behind it, and there is a simple ball and socket joint between neighbouring rings. These features give the body considerable flexibility and allow many of the millipedes to coil up. The number of body segments between and within the various species, but the British species rarely have more than 60 segments.
Each sternite carries a two pairs of tiny breathing pores which open into the animals breathing tubes or tracheae. Many millipedes also possess stink glands which open on to the lower surfaces of most of the body segments. The stink glands release pungent fluids containing substances such as Chlorine (Cl), Iodine (I), and Hydrogen Cyanide (HCn). These fluids repel many of the millipedes enemies, and they may also exert a disinfectant effect to keep the body free of infection, bacteria and fungi.

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