Cabanis had already made some observations to much the same effect. Referring to the years of nubility following puberty, he remarks: "I have very often seen the greatest fecundity of ideas, the most brilliant imagination, a singular aptitude for the arts, suddenly develop in girls of this age, only to give place soon afterward to the most absolute mental mediocrity." (Cabanis, "De l'Influence des Sexes," etc., _Rapports du Physique et du Morale de l'Homme_.) This phenomenon seems to be one of the indications of the immense organic significance of the sexual relations. Woman's part in the world is less obtrusively active than man's, but there is a moment when nature cannot dispense with energy and mental vigor in women, and that is during the reproductive period. The languidest woman must needs be alive when her sexual emotions are profoundly stirred. People often marvel at the infatuation which men display for women who, in the eyes of all the world, seem commonplace and dull. This is not, as we usually suppose, always entirely due to the proverbial blindness of love. For the man whom she loves, such a woman is often alive and transformed. He sees a woman who is hidden from all the world. He experiences something of that surprise and awe which Dostoieffsky felt when the seemingly dull and brutish criminals of Siberia suddenly exhibited gleams of exquisite sensibility. In women, it must further be said, the sexual impulse shows a much more marked tendency to periodicity than in men; not only is it less apt to appear spontaneously, but its spontaneous manifestations are in a very pronounced manner correlated with menstruation. A woman who may experience almost overmastering sexual desire just before, during, or after the monthly period may remain perfectly calm and self-possessed during the rest of the month. In men such irregularities of the sexual impulse are far less marked. Thus it is that a woman may often appear capricious, unaccountable, or cold, merely because her moments of strong emotion have been physiologically confined within a limited period. She may be one day capable of audacities of which on another the very memory might seem to have left her.