It is not always after the first menstruation that the subsequent discharges follow at the regular intervals of four weeks. In delicate, anæmic girls the second menstruation may not occur till several months have elapsed after the first; less often the second menstruation ensues a fortnight after the first, or even earlier.
At the time of the menarche the sexual impulse, which has hitherto been dormant, becomes strongly developed. It is evoked at this time of life by the anatomico-physiological changes undergone by the reproductive glands; the stimulus aroused by these processes in the ovary, being conducted to the brain, awakens passion. At the same time the observation of the growth of the hairy covering on the genital organs, the development of the breasts, and the appearance of menstruation, tend to arouse erotic presentiments. The reading of romances, conversations with female friends, and observation of the conduct of full-grown persons, convert these presentiments into clear ideas, and excite the impulse to the production of passionate sexual sensations, the sexual impulse. How far these stimuli arising from the reproductive apparatus are encouraged and accentuated, on the one hand, or repressed and diminished, on the other, depends on external impressions of various kinds. The environment is the determinant for the further transformation of the as yet undifferentiated sexual impulse into the fully-developed copulative and reproductive impulses.
In his work on the _Physiology of Love_, _Mantegazza_ describes the yearning and stress of the awakening sexual life, arising out of the presentiments, hazy sensations, and impulses, which are felt in the very earliest period of the developmental phase known as puberty.
In general, in a young girl during the menarche, the sexual impulse manifests itself rather in the form of semi-conscious reverie, of platonic love. The adolescent girl exercises her imagination with the circumstances of her chaste love, her mind turns to this subject when in solitude, her mood is apt to become melancholy, and it is the perusal of equivocal novels, or the educational assistance of sexually experienced female friends, that transforms the sexual impulse to a vivid flame.