It is somewhat remarkable that, so far as I have observed, none of these authors refer to the possibility of any heightening of the sexual appetite at the monthly crisis which they believe to exist in men. This omission indicates that, as is suggested by the absence of definite statements on the matter of increase of sexual desire at menstruation, it was an ignored or unknown fact. Of recent years, however, many writers, especially alienists, have stated their conviction that sexual desire in men tends to be heightened at approximately monthly intervals, though they have not always been able to give definite evidence in support of their statements. Clouston, for instance, has frequently asserted this monthly periodic sexual heightening in men. In the article, "Developmental Insanity," in Tuke's _Psychological Dictionary_, he refers to the periodic physiological heightening of the reproductive _nisus_; and, again, in an article on "Alternation, Periodicity, and Relapse in Mental Diseases" (_Edinburgh Medical Journal_, July, 1882), he records the case of "an insane gentleman, aged 49, who, for the past twenty-six years, has been subject to the most regularly occurring brain-exaltation every four weeks, almost to a day. It sometimes passes off without becoming acutely maniacal, or even showing itself in outward acts; at other times it becomes so, and lasts for periods of from one to four weeks. It is always preceded by an uncomfortable feeling in the head, and pain in the back, mental hebetude, and slight depression. The _nisus generativus_ is greatly increased, and he says that, if in that condition, he has full and free seminal emissions during sleep, the excitement passes off; if not, it goes on. A full dose of bromide or iodide of potassium often, but not always, has the effect of stopping the excitement, and a very long walk sometimes does the same. When the excitement gets to a height, it is always followed by about a week of stupid depression." In the same article Clouston remarks: "I have for a long time been impressed with the relationship of the mental and bodily alternations and periodicities in insanity to the great physiological alternations and periodicities, and I have generally been led to the conclusion that they are the same in all essential respects, and only differ in degree of intensity or duration. By far the majority of the cases in women follow the law of the menstrual and sexual periodicity; the majority of the cases in men follow the law of the more irregular periodicities of the _nisus generativus_ in that sex. Many of the cases in both sexes follow the seasonal periodicity which perhaps in man is merely a reversion to the seasonal generative activities of the majority of the lower animals." He found that among 338 cases of