Cut a sheet of foolscap in two pieces. Roll one half into a compact
cylinder, and fold the other into a close, flat strip; support the ends of
each and hang weights in the middle until they bend. The superior strength
of the roll will astonish one unfamiliar with this mechanical principle.
In a rod, the particles break in succession, first those on the outside,
and later those in the center. In a tube, the particles are all arranged
where they resist the first strain. Iron pillars are therefore cast
hollow. Stalks of grass and grain are so light as to bend before a breath
of wind, yet are stiff enough to sustain their load of seed. Bone has been
found by experiment to possess twice the resisting property of solid oak.]
and also a larger surface for the attachment of the muscles.

The Composition of the Bones at maturity is about one part animal to two
parts mineral matter. The proportion varies with the age. In youth it is
nearly half and half, while in old age the mineral is greatly in excess.
By soaking a bone in weak muriatic acid, and thus dissolving the mineral
matter, its shape will not change, but its stiffness will disappear,
leaving a tough, gristly substance [Footnote: Mix a wineglass of muriatic
acid with a pint of water, and place in it a sheep's rib. In a day or two,
the bone will become so soft that it can be tied into a knot. In the same
way, an egg may be made so pliable that it can be crowded into a narrow-
necked bottle, within which it will expand, and become an object of great
curiosity to the uninitiated. By boiling bones at a high temperature, the
animal matter separates in the form of gelatine. Dogs and cats extract the
animal matter from the bones they eat. Fossil bones deposited in the
ground during the Geologic period, were found by Cuvier to contain
considerable animal matter. Gelatine was actually extracted from the
Cambridge mastodon, and made into glue. A tolerably nutritious food might
thus be manufactured from bones older than man himself.] (cartilage) which
can be bent like rubber.