. The Cambridge natural history. Zoology. TRACHEAL, MUSCULAR AND VASCULAR SYSTEM IS pit are placed between the tracheae, and similar but slightly more elongated nuclei are found along the bundles. The tracheae are minute tubes exhibiting a faint transverse striation which is prob- ably the indication of a spiral fibre. They appear to branch, but. Fig. 10.—Section throiigli a traclieal pit and diverging bundles of traclieal tubes taken transversely to the long axis of the body. (After Balfour.) tr, Tracheae, showing rudimentary spiral fibre ; , cells resembling those lining the trac
. The Cambridge natural history. Zoology. TRACHEAL, MUSCULAR AND VASCULAR SYSTEM IS pit are placed between the tracheae, and similar but slightly more elongated nuclei are found along the bundles. The tracheae are minute tubes exhibiting a faint transverse striation which is prob- ably the indication of a spiral fibre. They appear to branch, but. Fig. 10.—Section throiigli a traclieal pit and diverging bundles of traclieal tubes taken transversely to the long axis of the body. (After Balfour.) tr, Tracheae, showing rudimentary spiral fibre ; , cells resembling those lining the tracheal pits, which occur at intervals along the course of the tracheae ; , tracheal stigma ; tr.;p, tracheal pit. only exceptionally. The tracheal apertures are diffused over the surface of the body, but are especially developed in certain regions. The Muscular System. The general muscular system consists of—(1) the general wall of the body; (2) the muscles connected with the mouth, pharynx, and jaws; (3) the muscles of the feet ; (4) the muscles of the alimentary tract. The muscular wall of the body is formed of—(1) an external layer of circular fibres ; (2) an internal layer of longitudinal muscles. The main muscles of the body are unstriated and divided into fibres, each invested by a delicate membrane. The muscles of the jaws alone are transversely striated. The Vascular System. The vascular system consists of a dorsal tubular heart with paired ostia leading into it from the pericardium, of the pericar- dium, and the various other divisions of the perivisceral cavity (Fig. 14, D). As in all Arthropoda, the perivisceral cavity is a haemocoele ; it contains blood and forms part of the vascular system. The heart extends from close to the hind end of the body to the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly res
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
