File:Animal and vegetable physiology, considered with reference to natural theology (1836) (14761583441).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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is constituted by the anterior half of the sphe-noid bone, which is its body, and the frontal bones, whichare its leaves. This theory, which originated with Oken,has been farther extended to the bones of the face, by Geof-froy St. Hilaire, who conceives them to be likewise deve-lopments of several other supposed cranial vertebrae;* butthe analogies by which the hypothesis is supported becomemore feeble and confused, as we recede from the middle ofthe spinal column. All the other parts of the skeleton may be regarded as ac-cessory to the spine: and they are far from exhibiting thesame constancy either in form or number, as the vertebralcolumn. In some instances, as in serpents, these accessoryparts are altogether wanting; in others, they exist only inrudimental states; and it is but in a few that they can beconsidered as having reached their full development. In or-der to obtain a standard of comparison by which to estimateall their gradations of evolution, it will be best to consider
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* In this theory of G. St. lliluire, the number of cranial vci-tebra; is seven,each composed of nine elementary pieces. 280 THE MECHANICAL FUNCTIONS. them first in their more perfectly developed forms, as theyare presented in the higher classes of quadrupeds. In thefollowing descriptions, the skeleton of the Hog (Fig. 181) willbe taken for the purpose of reference. The ribs consist of arches of bone affixed at their upperends to the bodies of the vertebrae, and also, by a separatearticulation, to their transverse processes; where, in general,they are allowed a slight degree of motion. Their primaryuse is to defend the vital organs situated in the region of thechest, or thorax, (namely, the heart and the lungs;) but theyare subservient also to the function of respiration, by the al-ternate movements that are given to them by their mus-cles. The two parts, of which they are composed, often forman angle by their junction, and at this angle a process occa-sionally extends, for the purpose

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