1897, pp. 113 et seq.) Although Fliess brings forward a number of minutely-observed cases, I cannot say that I am yet convinced of the reality of this 23-day cycle.  It is somewhat curious, however, that at the same time as Fliess, though in apparent independence, and from a different point of view, another worker also suggested that there is a 23-day physiological cycle (John Beard, The Span of Gestation and the Cause of Birth, Jena, 1897).  Beard approaches the question from the embryological standpoint, and argues that there is what he terms an “ovulation unit” of about 231/2 days, in the interval from the end of one menstruation to the beginning of the next.  Two “ovulation units” make up one “critical unit,” and the length of pregnancy, according to Beard, is always a multiple of the “critical unit;” in man, the gestation period amounts to six critical units.  These attempts to prove a new physiological cycle deserve careful study and further investigation.  The possibility of such a cycle should be borne in mind, but at present we are scarcely entitled to accept it.

So far as I am aware, Professor Nelson’s very interesting series of observations, which, for the first time, placed the question of a menstrual rhythm in men on a sound and workable basis, have not directly led to any further observations.  I am, however, in possession of a much more extended series of ecbolic observations completed before Nelson’s paper was published, although the results have only been calculated at a comparatively-recent date.  I now propose to present a summary of these observations, and consider how far they confirm Nelson’s conclusions.  These observations cover no less a period than twelve years, between the ages of 17 and 29, the subject, W.K., being a student, and afterward schoolmaster, leading, on the whole, a chaste life.  The records were faithfully made throughout the whole of this long period.  Here, if anywhere, should be material for the construction of a menstrual rhythm on an ecbolic basis.  While the results are in many respects instructive, it can scarcely, perhaps, be said that they absolutely demonstrate a monthly cycle.  When summated in a somewhat similar manner to that adopted by Nelson in his ecbolic observations, it is not difficult to regard the maximum, which is reached on the 19th to 21st days of the summated physiological month, as a real menstrual ecbolic climax, for no other three consecutive days at all approach these in number of ecboles, while there is a marked depression occurring four days earlier, on the 16th day of the month.  If, however, we split up the curve by dividing the period of twelve years into two nearly equal periods, the earlier of about seven years and the latter of about four years, and summate these separately, the two curves do not present any parallel as regards the menstrual cycle.  It scarcely seems to me, therefore, that these curves present any convincing evidence in this case of a monthly ecbolic cycle (and, therefore, I refrain from reproducing them), although they seem to suggest such a cycle.  Nor is there any reason to suppose that by adopting a different cycle of thirty days, or of twenty-three days, any more conclusive results would be obtained.