menstruation, the diagnosis of pregnancy would be greatly simplified.
But any one can appreciate the fact that diseases of the womb may
interfere with the menstrual process. Menstruation is influenced,
also, by the ovaries. As a result of age, for example, the ovaries
undergo changes which invariably bring about the permanent cessation
of menstruation, called the menopause. This event occurs prematurely
if both the ovaries are removed by operation. In view of these facts
it is not surprising that sometimes ovarian disorders abolish
menstruation. An impoverished state of the blood, or nervous shock
and strain, or constitutional debility may also interrupt the regular
appearance of the menstrual discharge.

The value of menstrual suppression as an evidence of pregnancy is
not, however, to be discounted to the extent that we might expect.
This is true because the ailments which lead to confusion are
relatively infrequent, and also because they exhibit characteristic
symptoms which are foreign to pregnancy. Often these symptoms are
obvious to the patient herself; if not to her, they will be obvious
to her physician. It is about the doubtful cases, naturally, that a
professional opinion is sought, and on that account physicians are
perhaps inclined to overestimate the difficulty women have in
learning for themselves whether or not they are pregnant. As a matter
of fact, it is unusual for a prospective mother to fail to reach a
correct decision--a decision for which she relies chiefly upon the
suppression of her menstrual periods.

It is doubtful whether menstruation ever continues after conception
has taken place. Instances in which the menstrual function is
believed to persist are not uncommon, and yet in all probability the
discharge regarded as menstrual has a different origin. In most cases