Many instances of the vomiting of pregnancy cannot be explained by
errors in diet, for the attacks come on repeatedly whether the
stomach contains food or not. Under these circumstances mental
influences frequently have to be reckoned with. Indeed, in most cases
of vomiting of pregnancy dietetic and other hygienic measures are of
no avail unless the patient learns to divert her attention from
troublesome thoughts.

That the brain can exert an influence over the stomach is a fact well
substantiated both by physiological experiment and by medical
observation. In all probability there is a definite spot in the
brain, called the "vomiting center," the irritation of which causes
retching and the upheaval of the contents of the stomach. As this
nervous mechanism is possessed by everyone, it is not called into
existence by the advent of pregnancy. Nevertheless, it seems likely
that pregnancy renders it more sensitive, and it is certain that
pregnancy establishes new means by which the center may be
stimulated. This admission does not imply, however, that the
prospective mother must submit to inevitable discomfort, for she can
and should muster the strength to resist it.

Time and again an unhappy frame of mind exaggerates or prolongs the
vomiting of pregnancy. Thus, disappointment, anxiety, grief, fright,
and other types of mental uneasiness not only magnify the discomfort
but sometimes are its sole cause. The curious cases in which the
husband suffers from nausea while his wife is pregnant are explained
by mental influences. As a result of the same kind of influence,
women who imagine themselves to be pregnant often suffer from violent
vomiting, which ceases as soon as they discover their error. On the