The Book of Household Management by Mrs. Beeton

are composed of an earthy substance,--to which they owe their solidity,--of gelatine, and a fatty fluid, something like marrow. _Two ounces_ of them contain as much gelatine as _one pound_ of meat; but in them, this is so incased in the earthy substance, that boiling water can dissolve only the surface of whole bones. By breaking them, however, you can dissolve more, because you multiply their surfaces; and by reducing them to powder or paste, you can dissolve them entirely; but you must not grind them dry. We have said (99) that gelatine forms the basis of stock; but this, though very nourishing, is entirely without taste; and to make the stock savoury, it must contain _osmazome_. Of this, bones do not contain a particle; and that is the reason why stock made entirely of them, is not liked; but when you add meat to the broken or pulverized bones, the osmazome contained in it makes the stock sufficiently savoury.