d from Stomach.~--The material prepared in the stomach,
known as ~chyme~, is passed into the duodenum through the pylorus. The
opening of this sphincter is controlled, according to Cannon, to a
certain extent by the liquefication of the chyme, but more especially
by the presence of free acid in the stomach side of the pyloric
orifice.

~Behavior of Food in the Intestines.~--The food does not pass at once
along the canal, but waits in the duodenum until several portions have
passed through. As the food mass is made alkaline in the presence of
the intestinal juices, the pyloric valve closes, opening again as the
contents nearest it on the stomach side are acidified.

~Intestinal Movements.~--The peristaltic waves in the small intestines
begin in the upper part and start a course ever downward. These waves
in the intestines are two-fold in character; the quick shallow wave
which forces the food string forward, breaking it up into segments,
and backward joining the segments together again, and the strong deep
wave which carries the entire mass forward after each segmentation.
This method of movement in the small intestines is the best one
possible under the conditions which prevail in this region of the
digestional apparatus, since it not only mixes the food material with
the juices necessary for its digestion, but likewise spreads it out
over a wide space, insuring a greater contact with the absorbing walls
of the small intestines.

~The Effect of Muscular Constrictions.~--The muscular constrictions
occurring in the intestines producing segmentation of the food string
have, according to Sherman, the effect of "(1) further mixing of the
food and digestive juices, (2) bringing the digested food into contact
with the absorbing membrane, (3) emptying the venous and lymphatic
radicles in the membrane, the material which they have absorbed being
forced into the veins and lymph vessels by the compression of the
intestinal walls."[53]

~Movements in the Large Intestine.~--The movements in the large
intestine or colon are much like those in other parts of the digestive
tract. The small and large intestine are divided by a valve known as
the ileocecal valve, and any food which passes through it cannot
return, since the valve is a competent one. The cells in the walls of
the larger intestine secrete fluids of a lubricating character,
containing no enzymes of digestion but aiding in moving the fecal
matter toward the rectum.

~