I have often made observations on that extraordinary disease, hypochondria; and chiefly on the cases where it presents the phasis of a false conception of the existing condition of external circumstances affecting the patient, accompanied by a terror of their operation on his fortunes and prosperity. These are common. I conceive that they argue a lesser derangement of the cerebral functions, than where there occurs a total overturn of the conception of personal identity; and the conviction of _self_ passes into a belief that the patient is actually something else than himself--nay, something else than a man at all, and even something else than an organised being. In both cases, there is, of course, a false conviction, and so far they range under the same head; yet, as the conception of identity is among the first, and strongest, and steadiest of all the states or acts of the mind, it may be presumed to require a stronger deranging impulse to effect the overthrow of an idea that often remains unimpaired amidst the very wrecks of the intellect, than to produce those conditions of ordinary partial derangement of the rational or perceptive powers which daily come under our observation. Yet--and it is a curious feature of these pitiful states of the diseased mind, and one that argues ill for the superiority of man over the passing humours of a fluctuating temperament--wherever there is a false conception of identity, passing into an idea that the patient is something different from himself, he becomes an involuntary humorist; and, while the ordinary maniac brings tears to the eyes of the shuddering beholders, he, in his character of an animal or piece of inert matter, produces nothing but a tickling sensation of exquisite ludicrousness, passing often into broad laughter, certainly the greatest enemy of pity. Now, I approach a case of this kind with feelings entirely different; and, while I thus confess that I can contemplate no state of derangement but with pity, I shall leave a grave narrative of an extraordinary instance of false conviction--true in all its details[23]--to be read and relished according to the fancies and humours of the public. [Footnote 23: We understand that another case of human incubation occurred, somewhere about the Crosscauseway or Simon Square, of Edinburgh, in Dr Gregory's time.--ED.]