an. Some gestations are more
protracted than others, but the average duration is the time we have
given. A very reasonable way to compute the term, is to reckon three
months back from the day when the menses ceased and then add five days
to that time, which will be the date of the expected time of
confinement. It is customary, also, for women to count from the middle
of the month after the last appearance of the menses, and then allow ten
_lunar_ months for the term. This computation generally proves correct,
except in those instances in which conception takes place immediately
before the fast appearance of the catamenia. A few women can forecast
the time of labor from the occurrence of quickening, by allowing
eighteen weeks for the time which has elapsed since conception, and
twenty-two more for the time yet to elapse before the confinement. With
those in whom quickening occurs regularly in a certain week of
pregnancy, this calculation may prove nearly correct.

The English law fixes no precise limit for the legitimacy of the child.
In France a child is regarded as lawfully begotten if born within three
hundred days after the death or departure of the husband. There are a
sufficient number of cases on record to show that gestation may be
prolonged two, and even three, weeks beyond the ordinary, or average
term. The variation of time may be thus accounted for: after
insemination, a considerable interval elapses before fecundation takes
place, and the passage of the fertilized germ from the ovary to the
uterus is also liable to be retarded. There are many circumstances and
conditions which might serve to diminish its ordinary rate of progress,
and postpone the date of conception. This would materially lengthen the
_apparent_ time of gestation.

It is likewise difficult to determine the shortest period at which
gestation may terminate, and the child be able to survive. A child may
be born and continue to live for some months, after twenty-four or
twenty-five weeks of gestation; it was so decided, at least, in an
ecclesiastical trial.

We have not the space to describe minutely, or at length, the formation
and growth of the foetal structures, and trace them separately from
their origin to their completion at the birth of the child. The student
of medicine must gain information by consulting large works and
exhaustive treatises on this interesting subject.

What trifling contingencies defeat vitality! Conception may be