The local cause is to be found in the extensive transformation of the ovaries and the uterus, by means of which a peculiar and powerful stimulus, the menstrual stimulus, is elaborated, which has a reflex influence upon heart and brain, vascular and nervous systems, and secretory and nutritive processes. Since we know that in every premenstrual period by the growth of the follicles hyperæmia is excited in the ovary, by means of which the liquor folliculi is increased in amount, we can well understand that at the time of the menarche the ripening of the graafian follicles is accompanied by a considerable degree of hyperæmia of the ovaries and of the whole of the genital organs, now undergoing their fullest development, and we can easily see how this hyperæmia may result in manifold reflex disturbances. But in addition to these reflex disturbances, we have once more to take into consideration the as yet imperfectly known chemical processes which are associated with the ripening and development of the graafian follicles, and an abnormal course of which may give rise to a disordered constitution of the blood, manifesting itself as chlorosis or in other ways. In connection with the growth and ripening of the ova, extensive and novel demands are made on the organism, and these may well endanger metabolic processes which are not established on a very secure foundation. The other cause is to be found in the intellectual processes which occur at this time in the youthfully receptive, highly sensitive organ of mind, the brain. The girl growing into womanhood, who with astonishment and stress has witnessed the visible changes in her body, the outward signs of puberty, as they gradually make their appearance, receives powerful psychical stimulation which cannot fail to exercise an influence upon the entire nervous system and its complex interlacements, alike in the sensory and in the motor sphere. The degree to which these influences radiating from the genital organs make themselves manifest is chiefly dependent upon the resisting power of the nervous system as a whole, upon the temperament, the inherited constitution, and the mode of education of the young girl. In children belonging to families noted for sensibility and irritability, in dwellers in large cities who have attended high schools for girls and have at an early age lifted the veil that covers the sexual processes, the reflex disturbances of the menarche will be more manifold and will manifest themselves with greater intensity than in children brought up in country districts, whose sensibilities are chiefly physical and whose mind is less susceptible to the influence of external stimuli.