It is in the domain of disease that the most strenuous and, on the whole, the most successful efforts have been made to discover a menstrual cycle in men. Such a field seems promising at the outset, for many morbid exaggerations or defects of the nervous system might be expected to emphasize, or to free from inhibition, fundamental rhythmical processes of the organism which in health, and under the varying conditions of social existence, are overlaid by the higher mental activities and the pressure of external stimuli. In the eighteenth century Erasmus Darwin wrote a remarkable and interesting chapter on "The Periods of Disease," dealing with solar and lunar influence on biological processes.[121] Since then, many writers have brought forward evidence, especially in the domain of nervous and mental disease, which seems to justify a belief that, under pathological conditions, a tendency to a male menstrual rhythm may be clearly laid bare. We should expect an organ so primitive in character as the heart, and with so powerful a rhythm already stamped upon its nervous organization, to be peculiarly apt to display a menstrual rhythm under the stress of abnormal conditions. This expectation might be strengthened by the menstrual rhythm which Mr. Perry-Coste has found reason to suspect in pulse-frequency during health. I am able to present a case in which such a periodicity seems to be indicated. It is that of a gentleman who suffered severely for some years before his death from valvular disease of the heart, with a tendency to pulmonary congestion, and attacks of "cardiac asthma." His wife, a lady of great intelligence, kept notes of her husband's condition,[122] and at last observed that there was a certain periodicity in the occurrence of the exacerbations. The periods were not quite regular, but show a curious tendency to recur at about thirty days' interval, a few days before the end of every month; it was during one of these attacks that he finally died. There was also a tendency to minor attacks about ten days after the major attacks. It is noteworthy that the subject showed a tendency to periodicity when in health, and once remarked laughingly before his illness: "I am just like a woman, always most excitable at a particular time of the month." Periodicity has been noted in various disorders of nervous character. Periodic insanity has long been known and studied (see, e.g., Pilcz, _Die periodischen Geistesstörungen_, 1901); it is much commoner in women than in men. Periodicity has been observed in stammering (a six-weekly period in one case), and notably in hemicrania or migraine, by Harry Campbell, Osler, etc. (The periodicity of a case of hemicrania has been studied in detail by D. Fraser Harris, _Edinburgh Medical Journal_, July, 1902.) But the cycle in these cases is not always, or even usually, of a menstrual type.