That the teeth are not a part of the osseous system, but are appendages of the skin supported, in man, by a special development of bone forming the alveolar ridges of the maxillary bones, is as well established as any fact concerning human dentition. The work of Oscar Hertwig, "Ueber Bau und Entwickelung der Placoidschuppen," published in Jenaische Zeitschrift, 1874, established very clearly the homology existing between the teeth and the dermal or placoid scales of the ganoid, silurioid and dipnoan fishes, both as to similarity of structure and development.
Much has been written descriptive of the teeth of various animals, their modifications of form and attachment to adapt them to modifications of function, and various classifications of the means of attachment have been made. Of these perhaps the best and most logical is given by Charles Tomes in his "Dental Anatomy," describing four forms of attachment: 1. By fibrous