These appearances were entirely confirmed by microscopical examination, inasmuch as only in a few places, especially on the anterior surface of the tooth, were traces of the periosteum to be demonstrated; where this was absent the tooth was eaten away, and its absorption had proceeded in such a manner, that a multitude of globular elements appeared on the section, resembling the fragments which we find in ivory pegs which have been bored into bones, and retained in them a considerable time; in the two above-mentioned cavities the absorption had proceeded farther and farther, and had at last attained its above-mentioned great extent. The cementum could still be demonstrated in certain places, it was, however, absorbed in the greatest part of its extent. In the cavities of the tooth substance, masses of bone were embedded, they were applied to the walls of the cavities without any kind of intermediate substance, and so held the tooth with such extraordinary firmness. This osseous deposit, which was directly connected with the alveolar processes, was freely traversed with blood vessels, which sometimes extended themselves close up to the tooth substance. It was also so fully developed, that the process had to be looked upon as fully accomplished, and therefore, a later exfoliation of the tooth was not to be expected. The dentine itself showed nothing abnormal.” Footnote 2: “Archives of Dentistry,” Edited by Edwin Truman, vol. i., p. 169. We have quoted the author of the foregoing at some length, as some of his conclusions upon this interesting experiment might seem antagonistic to our own. Thus, whilst we agree with him in concluding that a dead tooth becomes united to a living jaw by a certain amount of absorption of its fangs by osteoblasts, and a subsequent calcification of such tissue, we do not believe such process as fully accomplished or permanent. The valuable researches of Tomes and De Morgan show that during life a continual process of formation and absorption is taking place in bone, whilst the former has also pointed out that the process of absorption in the fangs of temporary teeth is one alternating between absorption and deposition, though in the end in favour of the former, _i.e._, that the osteoblasts which effect the absorption of the dentine often become calcified, but are again eventually decalcified and become active osteoclasts. What determines these bodies to act, so to speak, in a positive or a negative capacity would be most interesting to discover, and, in considering the subject, we can hardly overlook the views of Mr. Bridgman, who compares the process of bone formation and decalcification to what occurs in an electrolytic cell, where, by changing the direction of the current, the electrodes assume precisely opposite functions.