dy in the production of
motion? What is the special function of each?

PRACTICAL WORK

To obtain clear ideas of the form and functions of the bones, a careful
examination of a prepared and mounted skeleton is necessary. Many of the
bones, however, may be located and their general form made out from the
living body. Bones of the lower animals may also be studied to advantage.

*Experiments to show the Composition of Bone.*--1. Examine a slender bone,
like that in a chicken's leg. Note that it resists bending and is
difficult to break. Note also that it is elastic--that, when slightly bent,
it will spring back.

2. Soak such a bone over night in a mixture of one part hydrochloric acid
and four parts water. Then ascertain by bending, stretching, and twisting
what properties the bone has lost. The acid has dissolved out the mineral
matter.

3. Burn a small piece of bone in a clear gas flame, or on a bed of coals,
until it ceases to blaze and turns a white color. Can the bone now be bent
or twisted? What properties has it lost and what retained? What substance
has been removed from the bone by burning?

*Observation on the Gross Structure of Bone.*--1. Procure a long, dry bone.
(One that has lain out in the field until it has bleached will answer the
purpose excellently.) Test its hardness, strength, and stiffness. Saw it
in two a third of the distance from one end, and saw the shorter piece in
two lengthwise. Compare the structure at different places. Find rough
elevations on the outside for the attachment of muscles, and small
openings into the bone for the entrance of blood vessels and nerves. Make
drawings to represent the sections.

2. Procure a fresh bone from the butcher shop. Note the difference between
it and the dry bone. Examine the materials surrounding the sides and
covering the ends of the bone. Saw through the enlarged portion at the end
and examine the red marrow. Saw through the middle of the bone and observe
the yellow marrow.

*To show the Minute Structure of the Bone.*--Prepare a section of bone for
microscopic study as follows: With a jeweler's saw cut as thin a slice as
possible. Place this upon a good-sized whetstone, not having too much
grit, and keeping it wet rub it under the finger, or a piece of leather,
until it is thin enough to let the light shine through. The section may
then be washed and examined with the microscope. If the specimen is to be
preserved for future study, it may