struation begin?= The usual age at which
menstruation begins in this country is thirteen or fourteen; in some
it may occur as early as twelve, in others as late as fifteen, sixteen
or even seventeen. For menstruation to begin earlier than twelve or
later than seventeen is in this country a rare exception. But in cold
northern climates the age of eighteen is not rare, and in the hot
southern climates menstruation often starts at the ages of ten or
eleven. Change of climate or of country will often have an influence
on the menses. In the early years of his medical practice, the author
had many Finnish girls as patients. It was a very common occurrence
for them to stop menstruating for the first few months or even for the
first year of their residence in this country.

=At what age does menstruation cease?= The age at which menstruation
ceases is called the _menopause_ or _climacteric_. It usually takes
place at the age of forty-eight or fifty. In some cases it does not
take place until the age of fifty-two, in others it takes place as
early as forty-five or forty-four. In general, it may be said that the
woman's menstruating period, during which she is able to have
children, lasts about thirty-five years. And if no restraint be taken,
and if no precautions be taken against conception, a woman could have
twenty or thirty children during her childbearing period.

=How many days does a woman menstruate?= The usual number of days is
from three to five; in some cases menstruation lasts only two days, in
others as long as seven. As a rule, the greatest amount of blood
passed is during the first two days.

=The amount of blood.= It is hard to estimate the exact amount of
blood passed by a woman during her menses, but it reaches about an
ounce and a half to three ounces. In some women the amount may reach
as much as four or five ounces and in exceptional cases as much as
eight ounces. Where it exceeds this amount, it is an abnormal
condition, requiring treatment. The usual statement that a normally
menstruating woman should not have to use more than three napkins
during the twenty-four hours is correct.

_The periodical regularity_ with which menstruation recurs in many
women is remarkable. I know a woman who has not missed her menses in
twenty years; during those twenty years the menses have started every
fourth Friday, almost always at the same hour. I know another one who
has her menses every fourth Wednesday, about seven