The rapid sale of the first edition of this work has induced the publisher
to reprint it with considerable additions in a less expensive, and more
concise form--and the author embraces this opportunity, gratefully to
acknowledge the liberality with which it has been received, and the
indulgence shown to its many imperfections. At the same time he cannot but
regret, that in some quarters it has been surmised that he yielded
credence to the many strange relations which he has recorded from various
medical works, but which he merely narrated, to show the fallacy even of
experience, and the many dangers that may arise from the most ingenious
theories and doctrines, in the very ratio of their apparent plausibility.
Although these sketches were not intended for the profession, yet they may
prove of some utility to the pupil who commences the arduous study of
medicine. They may convince him, that great names, however justly
respected and renowned, do not constitute a sufficient basis, on which to
rest a satisfactory and conclusive judgment; and, as Locke has justly
observed, that "_reverence or prejudice must not be suffered to give
beauty or deformity to any of their opinions_." He will find that of which
further experience will subsequently convince him, that medical
investigation is too often founded upon analogy and hypothesis--but let
not this painful and disheartening impression arrest his progress, or
deter him from seeking to assist his judgment by collecting "the scattered
parts of truth," for in speaking of hypothesis, Dr. Crichton has thus
expressed himself: "There is a period in knowledge, when it must be
indulged in if we mean to make any progress; it is that period when the
facts are too numerous to be recollected without general principles, and
yet, where the facts are too few to constitute a valid theory. If the
exterior form of an edifice is often the principal motive with men for
examining its internal structure; so it is in science, that the splendour
of an hypothesis, and the desire of proving its solidity, are more
frequent motives for research than a mere love of knowledge."
Notwithstanding our boasted progress in scientific pursuits, and our
supposed approach to perfection, there never perhaps was a period, since
the fanciful days of Paracelsus, Agrippa, and Van Helmont, when more
deceitful and fascinating reveries were indulged in than at the present
_enlightened_ moment, nor more ingenuity and disingenuousness displayed in
seeking to give substance to a vision or overthrowing its baseless fabric.
It is painful to be obliged to admonish the would be legislators of our
belief, in the words of the sceptical Bolingbroke:
"Folly and knavery have prevailed most where they should be tolerated the
least, and presumption has been excused most where diffidence and candour
are on many accounts the most necessary.
"Quale per incertam lunam sub luce maligna
Est iter in Silvis."
_Hanwell Lunatic Asylum,
Dec. 1838._