File:Animal and vegetable physiology, considered with reference to natural theology (1836) (14762403674).jpg

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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are very long andmuscular, and of which the toes are furnished with a broadweb, derived from a thin extension of the integuments. No less curious are the changes which take place in all theother organs for the purpose of effecting the transformationsrendered necessary by this entire alteration in all the ex-ternal circumstances of that animal,—this total reversal of Vol. I. ,39 306 THE MECHANICAL FUNCTIONS. its wants, of its habits, of its functions, and of its very con-stitution. I shall have occasion to notice several of thesetransitions when reviewing the other functions of the animaleconomy: but at present our concern is chiefly with thestructure of the frame in its mechanical relations to progres-sive motion. In order to form a correct idea of these re-lations, it will be necessary to notice the leading peculiari-ties of the skeletons of this tribe of animals. The skeleton of the adult frog is shown in Fig. 200; fromwhich it will be seen that the spinal column is comparatively
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much shorter than that of fishes, or, indeed, of any otherclass of animals; for it consists of only eight vertebrae, ex-clusive of those which have united to form the os coccygis.It was evidently the intention of nature to consolidate theframe-work of the trunk, in which flexibility was not re-quired for progressive motion: the performance of that func-tion being transferred to the hind extremities, which are ex-ceedingly large in proportion to the rest of the body. Thereis a tendency in every part of the skeleton to develope itselfin a transverse direction, while the trunk is shortened asmuch as possible. The mode in which the vertebras are articulated together, SKELETON OF THE BATRACHIA. 307 differs widely from what we have seen in fishes, and ap-proaches to the structure of tlie higher chisses of vertel)rata.The body of each vertebra, instead of having at its posteriorsurface a cup-like cavity, terminates by a projecting ball,which is received into the cavity in the anterior surfac

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