. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates. 12 COMPARATIVE ANATOMY skeletal axis ; it is usually replaced by a vertebral column consisting of rcrtebrce, at a later stage of development (Fig. 10). All these structures are median in position, and the body is thus bilaterally symmetrical. The neural tube, or cerebro-sp'uml cavity, enclosed by the skull and arches of the vertebra:, contains the central nervous system (brain and spinal cord]; the visceral tube (co:lome) encloses the viscera (alimentary canal, heart, urinogenital organs, &c.), and its muscular walls
. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates. 12 COMPARATIVE ANATOMY skeletal axis ; it is usually replaced by a vertebral column consisting of rcrtebrce, at a later stage of development (Fig. 10). All these structures are median in position, and the body is thus bilaterally symmetrical. The neural tube, or cerebro-sp'uml cavity, enclosed by the skull and arches of the vertebra:, contains the central nervous system (brain and spinal cord]; the visceral tube (co:lome) encloses the viscera (alimentary canal, heart, urinogenital organs, &c.), and its muscular walls may be strengthened by a series of ribs, articulating dorsally with the vertebral column. Mtd KW. FIG. 10.—DIAGRAMMATIC TRANSVERSE SECTION THROUGH THE BODY OF AN ADULT VERTEBRATE. Ao, aorta ; Co, derm ; DH, lumen of intestine ; Ep, endodermic epithelium of intestine; KW, body-wall ; Med, spinal cord; A/"*, mesentery; Msc, mus- cular coat of intestine ; JV7?, neural tube ; Per, parietal layer of the peri- toneum ; Per1, visceral layer of the peritoneum ; Stil»n, connective-tissue coat of intestine ; VR, visceral tube ; d', vertebra. Certain of the ribs may reach the mid-ventral line and come into connection with a breast-bone or sternum, and thus form complete rings or hoops around the visceral tube. The anterior end of the central nervous system (brain) and of the alimentary tract enter into close relations with the outer world, the former being connected with the higher sense-organs, while from the latter are developed the mechanisms for taking in nutriment and for respiration. The anterior portion of the body, or head, passes behind into the trunk, either with or without the intermediation of a neck. The coelome is practically restricted to the trunk, in the hinder part of. 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 resem
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