students at the time of athletic contests and difficult
examinations.[30] We have seen what an important role the various
internal secretions, such as the adrenal and thyroid secretions play
in fitting the body for flight and combat, and how large a part fear
and anger have in their production. Constant over-production of these
secretions through chronic states of worry is responsible for many a
distressing symptom.

[Footnote 30: Cannon.]

Most graphic evidence of the disturbance of secretions by emotion is
found in the response of the salivary and gastric glands to painful or
pleasurable thinking. As these are the secretions which play the
largest part in the digestive processes, they lead us naturally to our
next heading.

=Digestion.= Everybody knows that appetizing food makes the mouth
water, but not everybody realizes that it makes the stomach water
also. Nor do we often realize the vital place that this watering has
in taking care of our food. "Well begun is half-done," is literally
true of digestion. A good flow of saliva brings the food into contact
with the taste-buds in the tongue. Taste sends messages to the
nerve-centers in the medulla oblongata; these centers in turn flash
signals to the stomach glands, which immediately "get busy" preparing
the all-important gastric juice. It takes about five minutes for this
juice to be made ready, and so it happens that in five minutes after
the first taste, or even in some cases after the first smell, the
stomach is pouring forth its "appetite juice" which determines all the
rest of the digestive process, in intestines as well as in stomach.
Experiments on dogs and cats by Pawlow, Cannon, and others have shown
what fear and anger and even mildly unpleasant emotions do to the
whole digestive process. Cannon tells of a dog who produced 66.7 cubic
centimeters of pure gastric juice in the twenty minutes following five
minutes of sham feeding (feeding in which food is swallowed and then
dropped out of an opening in the esophagus into a bucket instead of
into the stomach). Although there was no food in the stomach, the
juice was produced by the enjoyment of the taste and the thought of
it. On another day, after this dog had been infuriated by a cat, and
then pacified, the sham feeding was given again. This time, although
the dog ate eagerly, he produced only 9 cubic centimeters of gastric
juice, and this rich in mucus. Evidently a good appetite and
attractively served f