in character or even slightly alkaline, according to Howell, while
that in the middle region is highly acid. The pyloric end of the
stomach exhibits strong peptonizing powers and much of the hydrolysis
of protein takes place here. As the food is pushed out of the fundus
it is caught by the waves of peristaltic action and swept toward the
pylorus. This movement of the food mass to and from the pylorus under
the influence of the muscular constriction in the stomach tends to mix
it thoroughly with the juices in all parts of the stomach, and in a
measure to liquefy it to the "souplike" mixture known as chyme.

~Rate of Carbohydrates, Proteins, and Fats.~--Carbohydrates, for
example, do not require any acid for their digestion, hence all of the
acid with which they come in contact can go toward acidifying them,
while the proteins require hydrochloric acid before the enzymes can
begin to exert their activities. Consequently they leave the stomach
much more slowly than the carbohydrates. The fats leave more slowly
than any of the other food combinations. If carbohydrates and proteins
are taken together they leave the stomach more slowly than if the
carbohydrates were fed alone, but more quickly than they would if the
meal consisted of protein alone. When the meal consists of fats and
proteins, the stomach is emptied more slowly than is the case when
either is fed alone.

~Intestinal Digestion.~--Digestion proceeds in an orderly manner
throughout the intestinal canal. The pancreatic juice, bile, and
intestinal juice are poured upon the food mass on its entrance into
the duodenum. The enzymes work simultaneously. _Trypsin_ in the
pancreatic juice takes up the hydrolysis of the proteoses and peptones
and those proteins which have escaped gastric digestion. The
_amylopsin_ likewise in the pancreatic secretion acts upon the starch
and dextrin, changing them to maltose. The lipases split the fats to
fatty acids and glycerol.

The _erepsin_ in the intestinal juice, "succus entericus," brings
about further change in the proteins, with the production of amino
acids. The bulk of the carbohydrates are converted into monosaccharids
in the small intestines. The lactose, maltose, and sucrose are changed
through the activity of the lactase, maltase, and invertase into
glucose. Sherman states that "it is possible that the splitting of the
lactose (milk sugar) may occur in the intestinal wall rather than in
the food mass."[55]

~Bile.~-