ftened as well as
thoroughly mixed. The effect of the gastric juice is to act upon that
portion of food known as proteids. Examples of almost pure proteids are
found in the fiber of beef and other meat, in the yolk of eggs, and in
cheese. Some vegetables, such as peas, also contain large quantities,
and coarse flour and oatmeal contain considerable percentages. The
effect of the gastric juice on this proteid matter is to break up the
complex molecules into small molecules which then pass into solution,
making the mass leaving the stomach a uniformly mixed semiliquid
substance of about the consistency of thick pea soup. The food then
enters the smaller intestine, at the beginning of which the juices from
the pancreas are added. The pancreas is a gland which furnishes a
strongly alkaline liquid neutralizing the acid of the gastric juice, so
that the gastric agent, pepsin, loses its power. From this gland comes a
material which can act on all kinds of food and which is by far the most
important of the digestive juices.

When thoroughly mixed with the bile and pancreatic juice, the contents
of the intestine are gradually absorbed, in so far as their condition
allows, by the surface of that organ and are carried away by the ducts
designed for that purpose to the various organs, while that part not
suited for absorption is eliminated.

_Teachings of the digestive operations._

The matter of hygienic eating, therefore, consists in supplying the
various organs, the mouth, the stomach, and the smaller intestine with
proper food in proper quantity, so that the body itself may be properly
nourished from the food supplied. A great deal of scientific
investigation in this connection has been made to ascertain any relation
which may exist between the different kinds of food and their
availability for the body. Scientists have divided all food into four
classes, namely, proteids, carbohydrates, fats, and inorganic salts, and
they have agreed on the following general statements with reference to
these four classes. Examples of almost pure proteids have already been
given, and it may here be added that carbohydrates are typically shown
by the starchy particles found in potatoes or wheat. Chemically, the
difference consists in the fact that proteids contain nitrogen whereas
carbohydrates do not. Fats are self-explanatory, and the group of
inorganic salts includes such material as salt, lime, phosphates, and
other minerals needed by th