Now the brain feels, and thinks, and wills; but the blood is also essential to these faculties. If part of the brain is changed, or its circulation deranged, in that instant an _effect unlike health_ is produced: and such is the illusion of the ghost-seer. Or if the substance of the organ of sense, as the eye, be altered, its function is deranged, and an illusive spectrum appears to float before it. Nay, we are assured by Tiedeman and Gall, (opinions of high value,) that they have known patients who (smile as you please) were mad only on _one side_ of the brain, and perceived their madness with _the other_; and _I_ may assure you, too, that there have been persons who really thought with half the brain only. I will again claim the courtesy of these fair dames, while I offer another glimpse of the dull cold region of physiology. Recollect the illustrations I have adduced in allusion to those classes, on whose privacy the ghost has the privilege of intrusion. I will now offer illustrations of those _remote influences_ which work these seeming mysteries in the sensitive or diseased brain. A patient of Dr. Gregory, at the hour of six, _one hour after dinner_, was daily visited by a hag, or incubus, which confronted him, and appeared to strike him with a crutch. Immediately on this he would fall from his chair in a swoon. This gentleman was relieved by bleeding and abstinence. The Abbé Pilori, in Florence, invariably saw the phantom of scorpions around him, after he had partaken of luncheon. There was a gentleman in Edinburgh, learned in fourteen languages, of the age of seventy-six. In 1819, he began to see strange faces, in old dresses, like paintings, and his own face changing from young to old; and these phantoms came at his call. Wine drinking increased especially these spectres, during the twelve years that the illusion continued; yet his mental faculties were not much impaired. When eighty years old, he came to London to dine with the Knights of the Bath, and went back at the rate of a hundred miles a-day. His language latterly was a _patois_ of fourteen. One night he saw his dead wife’s shadow, and jumped after her out of the window, and ran after her through the conservatory; yet he remembered, when told that his wife was dead, and was then quiet. Disordered digestion aggravated his case extremely. Mr. Gragg’s opinion was, that “his thinking was correct, but the _expression_ of thought wrong.” On examination, the _dura mater_ was found adherent to the skull: in parts there was a thick effusion and vascularity over the brain, and the _carotids_ were partially ossified.