(The
dates named are those of the entry to classes, and not of actual
occurrence of birth.) A very definite and well-marked curve is
shown, and the average number of births (not conceptions) per
day, for the whole period, is as follows:--
Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
10.5 11.4 11 8.3 10.2 10.5 11.5 12.6 12.3 11.6 12 11.7
There is thus a well-marked minimum of conceptions (a depression
appearing here in each of the three periods, separately) about
the month of July. (In the second period, however, which contains
the smallest number of births, the minimum occurs in September.)
From that low minimum there is steady and unbroken rise up to the
chief maximum in November. (In the first period, however, the
maximum is delayed till January, and in the second period it is
somewhat diffused.) There is a tendency to a minor maximum in
February, specially well marked in the third and most important
period, and in the first period delayed until March.
A very curious and perhaps not accidental coincidence might be briefly
pointed out before we leave this part of the subject. It is found[157] by
taking 3000 cases of children dying under one year that, among the general
population, children born in February and September (and therefore
conceived in May and December) appear to possess the greatest vitality,
and those born in June, and, therefore, conceived in September, the least
vitality.
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