"I had a turn last night, and for the moment thought I had caught the spook of my predecessor, but, alas! it all ended in smoke instead of spook. It gave me a turn, though, and made cold water run rippling down my back. It happened thus:--I had paid a good-night visit to the room of a dear little friend, a Callithrix monkey, whose lodgings are in a side building which has a door opening into the entrance hall. There was no light in the room of my friend, but a side light shone in through the door from the hall. (I was smoking.) On going out I looked back before shutting the door, and was startled to see just behind me, in the dark shade, the face of a human being--apparently an old man with grey hair. The face was perfectly distinct in every detail for an appreciable interval, and the eyes seemed to look sadly at me, and I looked sadly at him. The face moved, and the appearance, though a bit out of shape, still remained. I, however, saw what it was, and gave a gasp of relief which blew the old man's countenance into the shapelessness of the last remains of an extra strong puff of tobacco smoke I had left behind me." Hallucinations of this kind, whose origin we can trace with more or less probability to some external sensation, may be in some respects compared with the visions seen on blank cards by the subjects of MM. Binet and Féré. But there are other hallucinations which cannot with any plausibility be referred to peripheral excitation. Such, as already said, are many hypnotic hallucinations, and the majority of the fully-developed hallucinations of normal life would appear to fall under the same category. Hallucinations of this class, like what may be called hallucinatory[103] dreams, are no doubt due to the spontaneous activity of the higher cerebral centres; they are simply ideas which take on sensory colouring. And just as the hallucinations of hypnotism, for the most part, are due to external suggestion, so it would seem that amongst the centrally initiated hallucinations of normal life there are some which owe their origin not to the spontaneous activity of the percipient's brain, but to an idea intruded from without--a suggestion not verbal but telepathic.