Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget (1834) (14592328198)

Identifier: animalandvegetab01roge (find matches)

Title: Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget ..

Year: 1834 (1830s)

Authors: Roget, Peter Mark, 1779-1869

Subjects: Biology Physiology Plant physiology Natural theology

Publisher: London : W. Pickering

Contributing Library: University of California Libraries

Digitizing Sponsor: MSN

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e Clio borealis,of which Fig. 120 is a repre-sentation, is the most perfectspecimen of this form of con-struction. It swarms in theArctic seas, and constitutes the principal food ofthe whale. The position of its gills, which per-form the office of oars or feet, at the same timethat they resemble in their shape and action thewings of an insect, are characters which havesuggested the title of Pteropoda, given byCuvier to this order of MolUisca. ^ 6. Cephalopoda. Following the progress of organic develope-ment, we now arrive at a highly interestingfamily of MoUusca, denominated the Cephalopoda,and distinguished above all the preceding ordersby being endowed with a much more elaborateorganization, and a far wider range of faculties. MOLLUSCA CEPHALOPODA. 259 The Cephalopoda have been so named from theposition of certain organs of progressive motion,which are situated on the head, and like the ten-tacula of the Polypus, surround the opening ofthe mouth. (See Fig. 121). These feet, or arms,

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or tentacnla, if we choose so to call them, are long,slender, and flexible processes, exceedingly irri-table, and contractile in every part, and providedwith numerous muscles, which are capable ofmoving and twisting them in all directions withextraordinary quickness and precision. Theyare thus capable of being employed as instru-ments; not only of progressive motion, but alsoof prehension. For this latter purpose they arein many species peculiarly well adapted, because,being perfectly flexible as well as highly muscu-lar, they twine with ease round an object of anyshape, and grasp it ^vith prodigious force. Inaddition to these properties they derive a re-markable power of adhesion to the surfaces ofbodies from their being furnished with nume- 2G0 THE MECHANICAL FUNCTIONS. roiis suckers all along their inner sides. Eachof these suckers, as shown separately in Fig.122, is usually supported on a narrow neck, orpedicle, and strengthened at its circumferenceby a ring of cartilage. Their in

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1834

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