and winter,[154] to the severely observed fasts of spring, and
to the exhausting harvest-work of summer.

It is instructive to compare the conception-rate of Europe with that of a
non-European country. Such a comparison has been made by S.A. Hill for the
Northwest Provinces of India. Here the Holi and other erotic festivals
take place in spring; but spring is not the period when conceptions
chiefly take place; indeed, the prevalence of erotic festivals in spring
appears to Hill an argument in favor of those festivals having originated
in a colder climate. The conceptions show a rise through October and
November to a maximum in December and January, followed by a steady and
prolonged fall to a minimum in September. This curve can be accounted for
by climatic and economic conditions. September is near the end of the long
and depressing hot season, when malarial influences are rapidly
increasing to a maximum, the food-supply is nearly exhausted, and there is
the greatest tendency to suicide. With October it forms the period of
greatest mortality. December, on the other hand, is the month when food is
most abundant, and it is also a very healthy month.[155]

For a summary of the chief researches into this question, see
Ploss and Bartels, _Das Weib_; also, Rosenstadt, "Zur Frage nach
den Ursachen welche die Zahl der Conceptionen, etc,"
_Mittheilungen aus den embryologischen Institute Universitaet
Wien_, second series, fasc. 4, 1890. Rosenstadt concludes that
man has inherited from animal ancestors a "physiological custom"
which has probably been further favored by climatic and social
conditions. "Primitive man," he proceeds, "had inherited from his
ancestors the faculty of only reproducing himself at determined
epochs. On the arrival of this period of rut, fecundation took
place on a large scale, this being very easy, thanks to the
promiscuity in which primitive man lived. With the development of
civilization, men give themselves up to sexual relations all the
year around, but the 'physiological custom' of procreating at a
certain epoch has not completely disappeared; it remains as a
survival of the animal condition, and manifests itself in the
recrudescence of the number of conceptions during certain months
of the year." O. Rosenbach ("Bemerkungen ueber das Problem einer
Brunstzeit beim Menschen," _Archiv fuer Rassen und
Gesellschafts-Biologie_