For some centuries, at least, inquisitive observers here and there have thought they found reason to believe that men, as well as women, present various signs of a menstrual physiological cycle.  It would be possible to collect a number of opinions in favor of such a monthly physiological periodicity in men.  Precise evidence, however, is, for the most part, lacking.  Men have expended infinite ingenuity in establishing the remote rhythms of the solar system and the periodicity of comets.  They have disdained to trouble about the simpler task of proving or disproving the cycles of their own organisms.[117] It is over half a century since Laycock wrote that “the scientific observation and treatment of disease are impossible without a knowledge of the mysterious revolutions continually taking place in the system”; yet the task of summarizing the whole of our knowledge regarding these “mysterious revolutions” is even to-day no heavy one.  As to the existence of a monthly cycle in the sexual instincts of men, with a single exception, I am not aware that any attempt has been made to bring forward definite evidence.[118] A certain interest and novelty attaches, therefore, to the evidence I am able to produce, although that evidence will not suffice to settle the question finally.

The great Italian physician, Sanctorius, who was in so many ways the precursor of our modern methods of physiological research by the means of instruments of precision, was the first, so far as I am aware, to suggest a monthly cycle of the organism in men.  He had carefully studied the weight of the body with reference to the amount of excretions, and believed that a monthly increase in weight to the amount of one or two pounds occurred in men, followed by a critical discharge of urine, this crisis being preceded by feelings of heaviness and lassitude.[119] Gall, another great initiator of modern views, likewise asserted a monthly cycle in men.  He insisted that there is a monthly critical period, more marked in nervous people than in others, and that at this time the complexion becomes dull, the breath stronger, digestion more laborious, while there is sometimes disturbance of the urine, together with general malaise, in which the temper takes part; ideas are formed with more difficulty, and there is a tendency to melancholy, with unusual irascibility and mental inertia, lasting a few days.  More recently Stephenson, who established the cyclical wave-theory of menstruation, argued that it exists in men also, and is really “a general law of vital energy."[120]

Sanctorius does not appear to have published the data on which his belief was founded.  Keill, an English, follower of Sanctorius, in his Medicina Statica Britannica (1718), published a series of daily (morning and evening) body-weights for the year, without referring to the question of a monthly cycle.  A period of maximum weight is shown usually, by Keill’s figures, to