eriment 94.

Experiment 96. To fifteen or twenty drops of defibrinated blood in
a test tube (labeled _D_) add five volumes of a 10-per-cent solution of
common salt. It changes to a very bright, florid, brick-red color.
Compare its color with _A, B_, and _C_. It is opaque.

Experiment 97. Wash away the coloring matter from the twigs (see
Experiment 89) with a stream of water until the fibrin becomes quite
white. It is white, fibrous, and elastic. Stretch some of the fibers to
show their extensibility; on freeing them, they regain their elasticity.

Experiment 98. Take some of the serum saved from Experiment 88 and
note that it does not coagulate spontaneously. Boil a little in a test
tube over a spirit lamp, and the albumen will coagulate.

Experiment 99. _To illustrate in a general way that blood is
really a mass of red bodies which give the red color to the fluid in
which they float._ Fill a clean white glass bottle two-thirds full of
little red beads, and then fill the bottle full of water. At a short
distance the bottle appears to be rilled with a uniformly red liquid.

Experiment 100. _To show how blood holds a mineral substance in
solution_. Put an egg-shell crushed fine, into a glass of water made
acid by a teaspoonful of muriatic acid. After an hour or so the
egg-shell will disappear, having been dissolved in the acid water. In
like manner the blood holds various minerals in solution.

Experiment 101. _To hear the sounds of the heart_. Locate the heart
exactly. Note its beat. Borrow a stethoscope from some physician. Listen
to the heart-beat of some friend. Note the sounds of your own heart in
the same way.

Experiment 102. _To show how the pulse may be studied_. "The
movements of the artery in the human body as the pulse-wave passes
through it may be shown to consist in a sudden dilatation, followed by a
slow contraction, interrupted by one or more secondary dilatations. This
demonstration may be made by pressing a small piece of looking-glass
about one centimeter square (2/3 of an inch) upon the wrist over the
radial artery, in such a way that with each pulse beat the mirror may be
slightly tilted. If the wrist be now held in such a position that
sunlight will fall upon the mirror, a spot of light will be reflected on
the opposite side of the room, and its motion upon the wall will show
that the expansion of the artery is a sudden mov