The etiology and pathology of the menopause lie in the sympathetic nervous system. And it is by the breaking up of the harmony of previous processes that nervous disturbances are produced. After the cessation of the flow, over 8% of women suffer from "flashes"; this symptom is caused by irritation of the heart and vasomotor centers. The blood-vessels of the head and neck seem to be most affected, yet the skin of the whole body shares in the disturbance. Besides the vasomotor and heat center being disturbed, the sweat center is irritated. The flushes and flashes are followed by various degrees of sweating, which varies from a slight moisture to great drops. Nervous irritability is a prominent symptom in 8% of women at the time of the menopause. Most of the pain arises around the stomach; that is, the solar plexus. Digestive disturbances are very common at this time; they may be in the shape of fermentation, diarrhea, or constipation, accompanied by congestion of the liver. Tilt holds the very plausible view that the too strong reaction of the sexual organs on the central ganglia of the sympathetic nervous system is their principal cause of disease. Puberty, menstruation, pregnancy, lactation, or the menopause almost always entail some derangement of this system which is sometimes sufficiently severe to lead to insanity and suicide. Debility underlies all affections of the sympathetic nervous system, in the same way as nervous irritability underlies all cerebral diseases. Sometimes there is an overpowering sense of exhaustion pervading the whole system. Forms of climacteric insanity are delirium, mania, hypochondriasis, melancholia, irresponsible impulses, and the perversion of moral instincts. "If the reproductive apparatus does not act on the brain by the instrumentality of the circulating organs of the blood, it must do so by means of the nerves. The genital apparatus is richly endowed with nerves from the sympathetic system, and I have shown how frequently evident signs of disturbance in these centers coincided or alternated with headaches, nervousness, hysteria, and epilepsy. What wonder, then, if the same powerful influence of the sexual organs, through the instrumentality of the sympathetic system, should at times produce a permanent derangement of the mental and moral faculties. I am thus led to look on the sympathetic nervous center as a source of vital power producing reflex morbid phenomena, in accordance with variable cerebral predisposition" (Tilt).