unbroken curve, attaining a maximum in June and a minimum in
December, the curve rising steadily through the first six months, sinking
steadily through the last six months, but always reaching a somewhat
greater height in May than in July.[164] Morselli shows that in various
European countries there is always a rise in spring and in autumn (October
or November).[165] Morselli attributes these spring and autumn rises to
the influence of the strain of the early heat and the early cold.[166] In
England, also, if we take a very large number of statistics, for instance,
the figures for London during the twenty years between 1865 and 1884, as
given by Ogle (in a paper read before the Statistical Society in 1886), we
find that, although the general curve has the same maximum and minimum
points, it is interrupted by a break on each side of the maximum, and
these two breaks occur precisely at about March and October.[167] This is
shown in the curve in Chart 6, which presents the daily average for the
different months.

The growth of children follows an annual rhythm. Wahl, the director of an
educational establishment for homeless girls in Denmark, who investigated
this question, found that the increase of weight for all the ages
investigated was constantly about 33 per cent. greater in the summer
half-year than in the winter half-year. It was noteworthy that even the
children who had not reached school-age, and therefore could not be
influenced by school-life, showed a similar, though slighter, difference
in the same direction. It is, however, Malling-Hansen, the director of an
institution for deaf-mutes in Copenhagen, who has most thoroughly
investigated this matter over a great many years. He finds that there are
three periods of growth throughout the year, marked off in a fairly sharp
manner, and that during each of these periods the growth in weight and
height shows constant characteristics. From about the end of November up
to about the end of March is a period when growth, both in height and
weight, proceeds at a medium rate, reaching neither a maximum nor a
minimum; increase in weight is slight, the increase in height, although
trifling, preponderating. After this follows a period during which the
children show a marked increase in height, while increase in weight is
reduced to a minimum. The children constantly lose in weight during this
period of growth in height almost as much as they gain in the preceding
period. This