effect of the mind upon the body, and especially perhaps upon the
process of digestion, may find it hard to believe that these
distressing symptoms and profound changes in the aspect and nutrition
of the patients were due entirely to mental causes and were symptoms
in accord with the attempted suicide or the theft of the money. In
nervous little children we shall not often find such complex actions
as suicide or theft, although they do occur, but combined with other
evidence of nervousness we shall meet commonly enough with a
persistent setting aside of appetite and refusal of food and with
continuous and habitual vomiting, from nervous causes.

The experiments of Pawlow and others have explained the dependence of
digestion upon mental states. They show that even before the food is
taken into the mouth, while the meal is still in prospect, there has
been instituted a series of changes in the wall of the stomach, which
gives rise to the so-called psychic secretion of gastric juice. These
changes are preceded by the sensation of appetite, which is evoked not
by the presence of food in the stomach--for the food has not yet been
swallowed--but by the anticipation of it, by the sight and smell of
food, as well as by more complex suggestions, such as the time of day,
the habitual hour, the approach of home, and so forth.

Emotional states of all sorts--grief, anger, anxiety, or
excitement--put a stop to the process or interfere with its action, so
that the sense of appetite is absent, and the taking of food is apt to
be followed by discomfort or pain or vomiting. No doubt good digestion
leads to a placid mind, but it is equally true that a placid mind is
necessary for good digestion. Therefore we civilised people, living
lives of mental stress and strain, try to increase the suggestive
force of our surroundings and to provoke appetite by all devices