Outlines of human osteology / by F.O. Ward.

  • Frederick Oldfield Ward
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of human osteology / by F.O. Ward. Source: Wellcome Collection.

    376/392 page 356
    CRANIAL VERTEBRA. only with reference to the two theories in question, that each appears to possess a philosophical value peculiar to itseit, and adapted to corresponding necessities of the science ; while, on the other hand, their essential prin- ciples are m fact less contradictory than they at first sight appear. ^ 434. In order to conceive the cranium as a prolonga- tion ot the spine, and to trace in its bones the essential elements of vertebras, it must be borne in mind that each vertebra consists of a body and an arch, the former being part of a column of support, the latter of a canal or tube tor the reception of a nervous cord. The relative development of these two parts varies in particular ver- tebrre, according as the column is required to he strono-er, or the cavity more capacious. In the sacrum, wfich serves as a foundation for the spine, the supportmcr column IS required to be massive and strong ; but, as the contained parts are here at a low point of development, the protecting cavity becomes a featui-e of less im- portance. Here accordingly the hodies of the vertebras form a large consolidated mass, while the arches are sniall, and, in the lower sacral vertebras, even altogether deficient. In the cranium a contrary development°talces place. The contained nervous column, sweUiiig out at its upper extremity to form the cerebrum and cere- bellum, requires, for its reception, that the arches of the containing vertebras should here be remarkably broad and capacious ; while, on the other hand, theu- bodies ;ire reduced to mere vestiges, either in accordance with the law of antagonism (as the transcendental i^hi- losophers would say), or simply because a column of sup- port is here not wanted (as the opposite school would affirm). 435. Bearing these facts in mind, we may trace in the cranium_ three separate zones, each presenting, more or less distinctly, the jirincipal elements of a vertebra. The first of these cranial vertebras is the occipital bone; the second is formed above by the parietal bones, below by the greater wings of the sphenoid bone, and by the larger portion of its body; the third is composed of the eth- moid and frontal bones, together with the lesser wiuo-s of tlie sphenoid and that part of its body by which they are supported. The temjjoral bones are said, by some anatomists, to belong to the second or middle cranial ver- tebra : by others they are regarded as parts of a separate,
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