"Bone," or plate.
The "bone" of the Cuttle-fish now claims attention. This is a complicated calcareous plate, lodged in a peculiar cavity of the back, which it materially strengthens. This plate has long been known in the shop of the apothecary under the name of Cuttle-fish bone: an observant reader may have noticed scores of these plates in glasses labelled Os Sepiae. Reduced to powder, they were formerly used as an absorbent, but they are now chiefly sought after for the purpose of polishing the softer metals. It is however improper to call this plate bone, since, in composition, "it is exactly similar to shell, and consists of various membranes, hardened by carbonate of lime, (the principal material of shell,) without the smallest mixture of phosphate of lime,[13] (or the chief material of bone.)
