Tóm tắt
Before entering upon the description of the skeleton of the Megatherium, it is requisite to premise some remarks on the vertebrae of the Mammalia in general. Hitherto these parts have been described by means of the terms supplied by Human Anatomy. But the skeleton of Man is one which deviates most from the common archetype: some parts are developed in excess; other parts, which are present as a general rule in the Mammalian series, are either rudimental or absent. The latter is more particularly the case with those processes of the vertebrae which are developed in relation to the attachment and force of the muscles ; and which, being connected with particular modes and media of motion, become eminently significative of the habits and affinities of the species. The consideration and comparison of these processes, therefore, most of which have received no names in Human Anatomy, are essential to a right determination of the habits and affinities of the Megatherium; and in order to make intelligible the terms in which the vertebral peculiarities of that great extinct animal will be described, I propose first to illustrate them by giving a comparative survey of the principal modifications of the exogenous processes in the vertebrate series. The ‘exogenous’ processes of a vertebra are those which grow out of the previously ossified parts, and are so classified and named in contradistinction from the ‘autogenous’ parts or elements of a vertebra which are developed from their own proper centres of ossification.
