regularity in the occurrence of these sexual
discharges, and, therefore, gives us reason for expecting to find this
regularity rhythmical. Moreover, since it seemed reasonable to expect
that there might be more than one rhythm, I have examined my data with a
view to discovering (1) an annual, (2) a lunar-monthly, and (3) a weekly
rhythm, and I now proceed to show that all three such rhythms exist.

THE ANNUAL RHYTHM.

It is obvious that, in searching for an annual rhythm, we must ignore the
records of the three incomplete years; but those of the remaining eight
are graphically depicted upon Chart 8. The curves speak so plainly for
themselves that any comment were almost superfluous, and the concord
between the various curves, although, of course, not perfect, is far
greater than the scantiness of the data would have justified us in
expecting. The curves all agree in pointing to the existence of three
well-defined maxima,--viz., in March, June, and September,--these being,
therefore, the months in which the sexual instinct is most active; and the
later curves show that there is also often a fourth maximum in January. In
the earlier years the March and June maxima are more strikingly marked
than the September one; but the uppermost curve shows that on the average
of all eight years the September maximum is the highest, the June and
January maxima occupying the second place, and the March maximum being the
least strongly marked of all.

Now, remembering that, in calculating the curves of the annual rhythm of
the pulse, I had found it necessary to average two months' records
together, in order to bring out the full significance of the rhythm, I
thought it well to try the effect upon these curves also of similarly
averaging two months together. At first my results were fairly
satisfactory; but, as my data increased year by year, I found that these
curves were contradicting one another, and therefore concluded that I had
selected unnatural periods for my averaging. My first attempted remedy was
to arrange the months in the pairs December-January, February-March, etc.,
instead of in January-February, March-April, etc.; but with these pairs I
fared no better than with the former. I then arranged the months in the
triplets, January-February-March, etc.; and the results are graphically
recorded on Chart 7. Here, again, comment would be quite futile, but I
need only point out that, _on the whole_, the sexual activity rises
ste