momentary needs, are partly converted into fat and stored as such. A
reserve supply of nourishment is thus provided, and is drawn upon
only when the food that we consume does not contain as much energy as
we expend.

WHAT WE DO TO OUR FOOD.--With the exception of water and mineral
substances, the food-stuffs must undergo chemical alterations before
they are capable of being absorbed into the body; this is the work of
digestion. The digestive processes, the main purpose of which is to
break up the carbohydrates, proteins, and fats into substances of
much simpler chemical structure, begin in the mouth and are not
completed until some time after the food has entered the intestine.
As the food moves through the alimentary canal, it is mixed with the
various digestive juices containing ferments, such as pepsin, which
are the active agents of digestion. Although digestive processes go
on automatically, they are, in a degree that is far from negligible,
influenced by the mind. Thus, cheerfulness promotes digestion, and
not infrequently mental depression may be the direct cause of
indigestion. Indeed, it is chiefly in regard to the state of the mind
of the prospective mother that the existence of pregnancy may be said
to have a bearing, whether favorable or unfavorable, upon her
digestion.

The digestive juices are prepared in glands which lie either within
the lining of the alimentary canal or adjacent to it. In the latter
event the glands are connected with the canal by means of tubes.
These glands must be warned when to pour out their secretion, and
their very first warning usually comes from the agreeable sensations
experienced when we see, smell, or taste inviting food. If we are
hungry, our viands attractive, and our surroundings congenial, the