Hallucinations often begin as persistent images, and only gradually acquire that influence over belief that makes the patient regard them as sensations.
And in all cases where images, originally recognized as such, gradually pass into hallucinations, there must be just that "force or liveliness" which is supposed to be always absent from images.
Yet that shout had been so clear and distinct, but such shouts (not only about wolves) I had imagined once or twice before, and I was aware of that. (These hallucinations passed away later as I grew older.)