The author commenced by stating, that “in all the specimens he had examined, two circumstances were at once detected; first, That the balls were enclosed, not in the true ivory, but in an abnormal structure; and secondly, that the holes by which the balls entered were either partially or completely cicatrized in cases of wound of the socket; which led him to suppose that, as the tusk is an organ of double growth, the membrane of the follicle and the pulp both play important parts in the process of enclosure, and that there is no regeneration of true ivory,—an hypothesis which was afterwards verified by observation. From a consideration of the opinions of Camper, Blumenbach, Lawrence, and Cuvier, it appeared that doubts are entertained as to the existence of cicatrices after wounds of the tusk, and opinions held as to the impossibility of the occurrence of such phenomena in a non-vascular substance like ivory.