this effect: thus meat requires more pepsin for satisfactory
digestion than bread, and consequently meat calls forth a larger
quantity of gastric juice.

Fat in all probability is not digested in the stomach; even starch
and protein are not broken down sufficiently by the time gastric
digestion is complete to permit them to be absorbed into the body.
"The value of digestion in the stomach," as Howell says, "is not so
much in its own action as in its combined action with that which
takes place in the intestine." It is even possible for satisfactory
digestion to take place without the assistance of the stomach. This
fact has been substantiated by several cases in which men have lived
for years after the stomach was removed to eradicate a disease. It is
true, nevertheless, that intestinal digestion can be performed more
economically if it begins where gastric digestion normally leaves
off.

Of the changes wrought in the food by the various digestive
processes, those which are the most profound take place in the
intestine. While the food is being moved through this organ--some
thirty feet in length--it is reduced to simple chemical fragments,
which are absorbed by the intestinal wall. Digestion in the intestine
is carried on through the agency of a number of ferments, the more
important of which are supplied in the juice manufactured by the
pancreas. The pancreatic secretion contains three separate and
distinct ferments, which act respectively upon carbohydrate, protein,
and fat. The absorption of fat, however, is materially assisted also
by the action of the bile.

A part of what we eat always escapes digestion; the unused portion,