It is a fact in Psychiatry which has by no means been sufficiently recognised, that attacks of mental disease have early symptoms that are often not mental in character; and it is equally true that in Neurology the fact has not attracted sufficient attention, that all sorts of sensory, vasomotor and motor symptoms may be the mere preludes to an attack of insanity and not of themselves the real disease. Such prodromata of so serious an event as an attack of insanity are exceedingly well worthy of careful study for many reasons, most notably because the recognition of their true character and their explanation might enable us in many cases to anticipate and possibly to ward off the mental attack. The neurologist who is called in to see a woman suffering from an unusual form of headache, with anorexia, insomnia, and obscure paræsthetic sensations, often misses the real point of the case because he does not realise that such symptoms are, in this particular patient, higher-cortical in origin, and may mean an attack of acute mania in a week if nothing can be done to arrest their course. The psychiatrist often considers a mental attack as being sudden in origin, and puts it down as an unled-up-to mental explosion, when in reality there had been sensory and motor symptoms, sleeplessness, and other indications which would have pointed to the existence of previous auto-intoxication, nerve exhaustion, or other disturbance.