Cardiac Orifice; _d._ Pylorus; _e._ Small Intestine; _f._ Bile Duct;
_g._ Pancreatic Duct; _h._ Ascending Colon; _i._ Transverse Colon; _j._
Descending Colon; _k._ Rectum.]

THE DIGESTION OF A MOUTHFUL OF BREAD.--A mouthful of bread
represents all, or nearly all, the elements of nutrition. Taking a
mouthful of bread as a representative of food in general, it may be said
that its digestion begins the moment that it enters the mouth, and
continues the entire length of the alimentary canal, or until the
digestible portion of the food has been completely digested and
absorbed. We quote the following brief description of the digestive
process from Dr. J.H. Kellogg's Second Book in Physiology[A]:--

[Footnote A: Good Health Pub. Co., Battle Creek, Mich.]

"_Mastication._--The first act of the digestive process is mastication,
or chewing the food, the purpose of which is to crush the food and
divide it into small particles, so that the various digestive fluids may
easily and promptly come into contact with every part of it.

"_Salivary Digestion._--During the mastication of the food, the salivary
glands are actively pouring out the saliva, which mingles with the food,
and by softening it, aids in its division and prepares it for the action
of the other digestive fluids. It also acts upon the starch, converting
a portion of it into grape-sugar.

"_Stomach Digestion._--After receiving the food, the stomach soon begins
to pour out the gastric juices, which first makes its appearance in
little drops, like beads of sweat upon the face when the perspiration
starts. As the quantity increases, the drops run together, trickle down