connect one vessel with the other. It is best to
precipitate the mucin by acetic acid before making experiments; and to
dilute the clear liquid with a little distilled water.

Experiment 78. _Test for bile pigments_. Place a few drops of bile on a
white porcelain slab. With a glass rod place a drop or two of strong
nitric acid containing nitrous acid near the drop of bile; bring the
acid and bile into contact. Notice the succession of colors, beginning
with green and passing into blue, red, and yellow.

Experiment 79. _To show the action of bile on fats_. Mix three
teaspoonfuls of bile with one-half a teaspoonful of almond oil, to which
some oleic acid is added. Shake well, and keep the tube in a water-bath
at about 100 degrees F. A very good emulsion is obtained.

Experiment 80. _To show that bile favors filtration and the absorption
of fats_. Place two small funnels of exactly the same size in a filter
stand, and under each a beaker. Into each funnel put a filter paper;
moisten the one with water (_A_) and the other with bile (_B_). Pour
into each an equal volume of almond oil; cover with a slip of glass to
prevent evaporation. Set aside for twelve hours, and note that the oil
passes through _B_, but scarcely any through _A_. The oil filters much
more readily through the one moistened with bile, than through the one
moistened with water.

Experiments with the Fats.

Experiment 81. Use olive oil or lard. Show by experiment that they
are soluble in ether, chloroform and hot water, but insoluble in water
alone.

Experiment 82. Dissolve a few drops of oil or fat in a teaspoonful
of ether. Let a drop of the solution fall on a piece of tissue or rice
paper. Note the greasy stain, which does not disappear with the heat.

Experiment 83. Pour a little cod-liver oil into a test tube; add a
few drops of a dilute solution of sodium carbonate. The whole mass
becomes white, making an emulsion.

Experiment 84. Shake up olive oil with a solution of albumen in a
test tube. Note that an emulsion is formed.

Chapter VII.

The Blood and Its Circulation.

177. The Circulation. All the tissues of the body are traversed by
exceedingly minute tubes called capillaries, which receive the blood from
the arteries, and convey it to the veins. These capillaries form a great
system of networks, the meshes of which are filled with the elements of
the various tiss