carried by these to larger vessels,
and at last reach the heart, thence to be distributed to the tissues.

155. Absorption from the Mouth and Stomach. The lining of the mouth
and oesophagus is not well adapted for absorption. That this does
occur is shown by the fact that certain poisonous chemicals, like cyanide
of potash, if kept in the mouth for a few moments will cause death. While
we are chewing and swallowing our food, no doubt a certain amount of water
and common salt, together with sugar which has been changed from starch by
the action of the saliva, gains entrance to the blood.

In the stomach, however, absorption takes place with great activity. The
semi-liquid food is separated from the enormous supply of blood-vessels in
the mucous membrane only by a thin porous partition. There is, therefore,
nothing to prevent the exchange taking place between the blood and the
food. Water, along with any substances in the food that have become
dissolved, will pass through the partition and enter the blood-current.
Thus it is that a certain amount of starch that has been changed into
sugar, of salts in solution, of proteids converted into peptones, is taken
up directly by the blood-vessels of the stomach.

156. Absorption by the Intestines. Absorption by the intestines is a
most active and complicated process. The stomach is really an organ more
for the digestion than the absorption of food, while the small intestines
are especially constructed for absorption. In fact, the greatest part of
absorption is accomplished by the small intestines. They have not only a
very large area of absorbing surface, but also structures especially
adapted to do this work.

157. The Lacteals. We have learned in Section 144 that the mucous
lining of the small intestines is crowded with millions of little
appendages called villi, meaning "tufts of hair." These are only
about 1/30 of an inch long, and a dime will cover more than five hundred
of them. Each villus contains a loop of blood-vessels, and another vessel,
the lacteal, so called from the Latin word _lac_, milk, because of the
milky appearance of the fluid it contains. The villi are adapted
especially for the absorption of fat. They dip like the tiniest fingers
into the chyle, and the minute particles of fat pass through their
cellular covering and gain entrance to the lacteals. The milky material
sucked up by the lacteals is not in a proper condition to be poured at
once into the bl