One more question remains for consideration in connection with this weekly rhythm.  Is it possible to trace any connection between the weekly and yearly rhythms of such a character that the weekly day of maximum discharge should vary from month to month in the year; in other words, does the greater frequency of a Sunday discharge characterize one part of the year, that of a Tuesday another, and so on?  In order to answer this question I have re-calculated all my data, with results that are graphically represented in Chart 13.  These curves prove that the Sunday maxima discharges occur in March and September, and the minima in June; that the Monday maxima discharges occur in September, Friday in July, and so on.  Thus, there is a regular rhythm, according to which the days of maximum discharge vary from one month of the year to another; and the existence of this final rhythm appears to me very remarkable.  I would especially direct attention to the almost geometric symmetry of the Sunday curve, and to the only less complete symmetry of the Thursday and Friday curves.  Certainly in these rhythms we have an ample field for farther study and speculation.

I have now concluded my study of this fascinating inquiry; a study that is necessarily incomplete, since it is based upon records furnished by one individual only.  The fact, however, that, even with so few observations, and notwithstanding the consequently exaggerated disturbing influence of minor irregularities, such remarkable and unexpected symmetry is evidenced by these curves, only increases one’s desire to have the opportunity of handling a series of observations sufficiently numerous to render the generalizations induced from them absolutely conclusive.  I would again appeal[384] to heads of colleges to assist this inquiry by enlisting in its aid a band of students.  If only one hundred students, living under similar conditions, could be induced to keep such records with scrupulous regularity for only twelve months, the results induced from such a series of observations would be more than ten times as valuable as those which have only been reached after ten years’ observations on my part; and, if other centuries of students in foreign and colonial colleges—­e.g., in Italy, India, Australia, and America—­could be similarly enlisted in this work, we should quickly obtain a series of results exhibiting the sexual needs and sexual peculiarities of the male human animal in various climates.  Obviously, however, the records of any such students would be worse than useless unless their care and accuracy, on the one hand, and their habitual chastity, on the other, could be implicitly guaranteed.

FOOTNOTES: 

[373] First published in the University Magazine and Free Review of February, 1898, and since reprinted as a pamphlet.  A preliminary communication appeared in Nature, May 14, 1891.

[374] [Later study (1906) has convinced me that my attempt to find a lunar-monthly period in the female pulse was vitiated by a hopeless error:  for any monthly rhythm in a woman must be sought by arranging her records according to her own menstrual month; and this menstrual month may vary in different women, from considerably less than a lunar month to thirty days or more.]