An interesting group of phenomena connected with the sensory influences discussed in this chapter is furnished by the premonitions of physical disorders and diseases sometimes experienced in dreams. A physical disturbance may reach sleeping consciousness many hours, or even days, before it is perceived by waking consciousness, and become translated into a more or less fantastic dream. This has been recognised from of old, and Aristotle, for instance, observed that dreams magnify sensory excitations, and pointed out that they were thus useful to the physician in diagnosing symptoms not yet perceptible in the waking state. Thus Hammond knew a gentleman who, before an attack of hemiplegic paralysis, repeatedly dreamed that he had been cut in two down the middle line, and could only move on one side, while a young lady who dreamed she had swallowed molten lead, though quite well on awaking, was attacked by severe tonsilitis toward midday. Erythematous conditions of the skin, as has been pointed out to me by Dr. Kiernan, who has met with numerous cases in point, play an especial part in generating these dreams. Jewell, again, mentions a girl who dreamed, three days before being laid up with typhoid fever, that some one threw oil over her and set light to it. Macario, who was, perhaps, the first to record and study scientifically the dreams of this class, termed them prodromic.[73] 'Prophetic' dreams, in which the dreamer foresees, not a physical condition which is already latent, but an external occurrence, belong to an entirely different class, and need not be discussed in detail here, since they are usually fallacious. A fairly common experience of this kind is the dream of an unknown person who is afterwards met in real life. These dreams fall into two groups: in the first the 'prophecy' is based on a failure of memory, the dreamer having really seen the person before; in the second, the subsequent 'recognition' of the person is due to the emotional preparation of the dream, and the concentrated expectation. Sante de Sanctis, who points this out, gives an experience of the kind which happened to the distinguished novelist, Capuana, who had a vivid dream of a dark lady, with expressive eyes, and three days after met the lady of his dream in the street.[74] Women, in a state of emotional expectation, have often mistaken dead (or even living) persons for missing husbands or children, and any one who has observed how, when a noted criminal flies from justice, he is soon 'recognised,' from his portrait, in the most various parts of the world, will have no difficulty in believing that it is easily possible to 'recognise' people from dream portraits, which are much vaguer than photographs. That there are other prophetic dreams, less easy to account for, I am ready to admit, though they have not come under my own immediate observation. FOOTNOTES: