sleep, by inducing some idea of great horror. Amongst all the subjects of terror which infest the human mind, there is none so powerful as the idea, which is generally imbibed at a very early period of life, respecting ghosts and supernatural appearances; and there are comparatively few persons who, when alone and in the dark, are perfectly free from them. In sleep, however, we are all much more timid than when awake. I believe every person’s experience coincides in this opinion: hence it arises, that the idea of ghosts and spectres being the idea which inspires us with the greatest terror, is that which most readily and frequently presents itself to the mind, when the nervous system is suddenly agitated during sleep; a state when all objects of fear act with increased force. Whatever may be the cause which induces this kind of shivering during sleep, the shivering itself appears to me evidently to be the immediate cause of the terror, and the accompanying terrific dream; and this I conceive to happen from association; for as this shivering is the kind of involuntary sensation we feel when suddenly alarmed, or even when we hear or read a tale of terror, the feeling itself becomes so associated with terror, as always to recal to the mind, even in sleep, the idea of it; the sensation being the same as if the nerves had actually received some terrific impression; and as the imagination has full play when asleep, it is seldom long in furnishing the terrific object. I have known these dreams to be succeeded by an hysterical affection, of involuntary laughing and crying; and they are, I believe, in all cases attended with a great degree of nervous irritability. It will sometimes happen in this case, as in the preceding, that the patient does not awake from his dream, notwithstanding that his vociferations have been loud enough to wake all those who may sleep near him. When this happens he seldom or never has any recollection of his terror, and feels greatly surprised when told of the alarm he had given to others. The moment the shivering which produced the terror has ceased, this likewise ceases; and seldom leaves in the mind, any trace of its having existed: in this respect it differs greatly from the Night-Mare, in some others it appears to have some considerable affinity to that affection. It is not uncommon for persons affected with these terrific dreams to leap out of bed, and attempt to escape from some imaginary danger by flight. Many instances have occurred of persons jumping immediately out of a high window under these circumstances: the same accident very lately occurred to a youth in this metropolis. There are several other accidents to which our sleep is liable, but as they differ in their nature considerably from Night-Mare, we shall not here take any notice of them. I shall now speak of the persons who are subject to Night-Mare, before entering into an investigation of its causes.