Identifier: animalvegetable01roge (find matches)
Title: Animal and vegetable physiology, considered with reference to natural theology
Year: 1836 (1830s)
Authors: Roget, Peter Mark, 1779-1869
Subjects: Biology Physiology Plant physiology Natural theology
Publisher: Philadelphia, Carey, Lea & Blanchard
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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While in the Star-fish, and Ecliinus, nothing; in point of si-tuation was delinite, excepting tlie upper and the lower sur-face, and there was no side which could be exclusively de-nominated either the right or the left side, and no end thatcould be properly said to be the front or the back, in Ar-ticulated as well as in Vertebrated animals, all these distinc-tions are clearly marked and easily defined. In all the Jlnnelida the firmest parts of the body, or thosewhich give mechanical support to the rest, are external, andmay be regarded either as appendages to the integuments,or as modifications of the integuments themselves. Theyconsist of a frame-work, composed of a series of horny bandsor rings: their assemblage having more orless of a lengthenedcylindric shape, and constituting a kind of external skeleton,which encloses all the other organs. This is exemplified inthe earth-worm; in the Pont-obdella, (Fig. 128,) which is aspecies of leech; and in the Nereis, (Fig. 120.) These rings
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give rise to the division of the body into as many difierentsegments. In some cases, however, we find all these ringscompressed into the form of a flat oval disk. This is thecase in the Erpohdella, of which Fig. 130 is an enlargedrepresentation. In general, the first of the segments into which the bodyis divided, contains the principal organs of sense, and is suf-ficiently distinct from those which follow to entitle it to theappellation of the head; while the Icngtiicned prolongationof the opposite extremity, when such a form is present, maybe denominated the tail. 196 THE MECHANICAL FUNCTIONS. The rings which encircle the body are connected lateral-ly by a looser and more flexible portion of integument, andalso by layers of muscular fibres, curiously collected intobands. The muscular flesh of insects, and other animals ofthis class, differs much from that of the larger animals, beingsoft and gelatinous in its texture, though endowed with ahigh degree of irritability, and contracting

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