BONE. An important organ in the higher orders of animals, forming the solid support of their fabric, and pro tecting the vital organs, such as the brain and the heart and lungs, from external pressure and injury. In the human skele ton there are commonly enumerated 200 distinct bones. They, however, admit of classification under three heads : namely, long or cylindrical bones, such as those of the extremities ; broad and flat bones, such as those of the skull ; and short, square, irregular, or solid bmes, such as the vertebrae, and those of the wrist and instep, and the patella or knee-pan : the first bones are generally' filled with mar row, and are admirable specimens of strength of structure with the least possi ble weight. The hones are covered by a membrane called periosteum, by which the ramifications of blood-vessels and nerves pass into the bone. In the growth of a bone, the gelatinous or cartilaginous portion, as it has been sometimes called, is first formed, and the earthy or indur ating part is afterwards deposited. We are indebted to Mr. IIatchett for our principal information respecting the proximate chemical components of bone. The soft parts consist of gelatine and al bumen, and the hard portion is composed of phosphate of lime and carbonate of lime, with small quantities of other salts. The animal matter of bones amounts on an average to about half their weight, or when dried, to between 30 and 40 g)er cent.; so that they contain a large relative
proportion of nutritive matter. The bones, including their animal matter, are the most durable parts of the animal fa bric: hence theproposal of storing them up as occasional sources of nutriment ; for not only is the cartilaginous portion unimpaired, in bones which have been kept dry for many years, but it has even been found perfect in bones of apparently antediluvian origin. The best mode of extracting the nutritious part of bone for human food Consists in grinding it fine, and subjecting it with water to a heat of about 220° in a digester ; or the earthy part may be removed by dilute muriatic acid. When dogs and some other ani mals devour bones, the nutritive part is abstracted by their gastric juice, and the earthy part is voided in their excrement, forming what was formerly called album grcecum.
When bones are submitted to destruc tive distillation, the gelatine and albumen which they contain is abundantly produc tive of ammonia hence a copious source of that alkali and its compounds ; the residue is a mixture of the earthy part of the bone with charcoal, commonly termed ivory or bone black.