ed, both mastication and insalivation having been
imperfectly performed.

The time usually occupied in the process of chymification, when food has
been properly masticated, varies from _three to four hours_. Digestion
is sometimes effected in less time, as in the case of rice, and pigs'
feet soused; but it more commonly requires a longer period, as in the
case of salt pork and beef, and many other articles of food, both animal
and vegetable.

By the alternate contraction and relaxation of the muscular coat of the
stomach, which is excited to action by the presence of food, a kind of
churning motion is communicated to its contents that greatly promotes
digestion; for by this means every portion of food in turn is brought in
contact with the gastric juice as it is discharged from the internal
surface of the stomach. This motion continues until the contents of the
stomach are converted into chyme, and conveyed into the first intestine,
where they undergo another important change.

3. CHYLIFICATION.--As fast as chyme is formed, it is expelled by the
contractile power of the stomach into the _duodenum_, or first
intestine. It there meets with the _bile_ from the liver, and with the
pancreatic juice. By the action of these agents, the chyme is converted
into two distinct portions: a milky white fluid, called _chyle_, and a
thick yellow residue. This process is called _chylification_, or
_chyle-making_. The chyle is then taken up by the absorbent vessels,
which are extensively ramified over the inner membrane or lining of the
bowels. From the white color of the contents of these vessels, they have
been named _lacteals_ or _milk-bearers_, from _lac_, which signifies
milk. These lacteals ultimately converge into one trunk, called the
_thoracic duct_, which terminates in the great vein under the clavicle
or collar bone, hence called the _subclavian_ vein, just before that
vein reaches the right side of the heart. Here the chyle is poured into
the general current of the venous blood, and, mingling with it, is
exposed to the action of the air in the lungs during respiration. By
this process, both the chyle and the venous blood are converted into
red, arterial, or nutritive blood, which is afterward distributed by the
heart through the arteries, to supply nourishment and support to every
part of the body. The change which takes place in the lungs is called
_sanguification_, or _blood-making_. The chyle is not prepared to impart
n