When a longitudinal section of one of these teeth is made, two substances present themselves, viz. a central and a cortical; these differ from each other both in appearance and in structure. The central substance resembles, and is no doubt analogous to the ivory of other teeth, but the cortical exhibits not the slightest analogy to enamel. In texture it is softer even than the ivory portion, and probably continues to grow or be deposited during the greater part of the life of the Cachalot, until it in fact at last completely encloses the central part, which can be nothing but an ossified pulp: it encloses the central portion in the manner that the ivory of the human tooth encloses the soft dentar pulp.