date--but for
practical approximate purposes the tables serve very well.

A simple way is to count back three months and add seven days. For
instance, a woman's last menstruation occurred on April 4th; counting
back three months gives you January 4th; add seven days and you get
January 11th, the probable date of delivery. The first day of the last
menstruation was December 30th; counting back three months gives you
September 30th; add seven days and you get October 6th, the probable
date of delivery. The presence of a short month like February may be
disregarded, as the calculation is not absolutely, but only
approximately correct.

The period at which the child's movements begin to be felt by the
mother is termed Quickening. It usually occurs at the middle of the
pregnancy, between the 16th and 18th week.

Pregnancy is a normal physiological process; but every active
physiological process is apt to be accompanied by disturbances, and
there is certainly no process in the animal body in which greater
activity, greater changes, go on than during the process of pregnancy.
Just see what occurs in nine months. The uterus, at first the size of
a small pear, reaches a size larger than that of the head of a big
man; it does not merely stretch, as some think, but it actually grows
enormously in size, the muscular walls of a pregnant uterus being many
times thicker than those of a non-pregnant one. They have to be or
they would not have the strength to expel the child, when the proper
time comes. It is to be borne in mind that the child does not slip out
by itself; it is the powerful muscular contractions of the uterus that
push it out. If the uterus should refuse to work, if its walls were
too thin or too weak, the child could not come out, but would have to
be taken out with forceps. Still greater changes than in the uterus
take place in the child itself. At the moment of conception it is the
size of _the head of a pin_; at the moment of birth it weighs from
seven to ten pounds; at the moment of conception it is a minute,
undifferentiated mass of protoplasm, just a single fertilized cell; at
the moment of birth it consists of millions and millions of cells,
which have become differentiated into numerous harmoniously working
organs, and different tissues, such as brain and nerve tissue,
muscular tissue, connective tissue, bone, cartilage, etc., etc. A
truly wonderful process. And in the meantime this child, which is
biologi