Wargentin, in Sweden, first called attention to the periodicity of the
birthrate in 1767.[151] The matter seems to have attracted little further
attention until Quetelet, who instinctively scented unreclaimed fields of
statistical investigation, showed that in Belgium and Holland there is a
maximum of births in February, and, consequently, of conceptions in May,
and a minimum of births about July, with consequent minimum of conceptions
in October. Quetelet considered that the spring maximum of conceptions
corresponded to an increase of vitality after the winter cold. He pointed
out that this sexual climax was better marked in the country than in
towns, and accounted for this by the consideration that in the country
the winter cold is more keenly felt. Later, Wappaeus investigated the
matter in various parts of northern and southern Europe as well as in
Chile, and found that there was a maximum of conceptions in May and June
attributable to season, and in Catholic countries strengthened by customs
connected with ecclesiastical seasons. This maximum was, he found,
followed by a minimum in September, October, and November, due to
gradually increasing exhaustion, and the influence of epidemic diseases,
as well as the strain of harvest-work. The minimum is reached in the south
earlier than in the north. About November conceptions again become more
frequent, and reach the second maximum at about Christmas and New Year.
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