philanthropic labors, conferred such signal benefits on the insane, did some disservice to medical jurisprudence when he lent the weight of his authority to this doctrine, and maintained that "persons of common sense, conversant with the world, and having a practical knowledge of mankind, brought into the presence of a lunatic, would in a short time find out whether he was or was not capable of managing his own affairs"; and the late Sir Benjamin Brodie erred, I think, still more grievously when he said: "It is a great mistake to suppose that this is a question (unsoundness of mind) which can be determined only by medical practitioners. Any one of common sense, and having a fair knowledge of human nature, who will give it due consideration, is competent to form an opinion on it; and it belongs fully as much to those whose office it is to administer the law as it does to the medical profession."
Now, it may be admitted that there was a time when medical science was in its infancy, when the functions of the brain were unknown, and when only metaphysical explanations of insanity were attempted, at which the existence of insanity in any given case might have been as correctly determined by plain, unsophisticated men as by pretentious empirics. Further, it may be granted that there are an immense number of cases of insanity in which the symptoms of the disease are so obvious and external, that special skill, although requisite to interpret these symptoms, explain their causes, predict their results, and prescribe treatment, is not necessary to their identification. But, beyond all this, there are, it must be maintained, cases of insanity of so obscure and subtle a nature that they can only be properly identified by those who have made themselves intimately acquainted with the functions of the nervous system in health and disease, and who have by experience come to appreciate the significance of combinations of mental phenomena and of concomitant bodily variations, which would appear meaningless to the uninitiated.
The fact is, that practically the utility of expert testimony in insanity is acknowledged, and it is difficult to understand how it could be otherwise, for all who have made only a superficial study of mental diseases must perceive that there are in them little signs and symptoms, perversions of thought and derangements of bodily functions, which would altogether escape the notice of common sense, but warrant an expert, founding on his experience, in proclaiming that the will is reduced to impotency, and that the lunatic can not control himself. There is something in the appearance, manner, and mode of expression of lunatics of various classes which would pass unnoticed by common sense, but be characteristic to those who had been accustomed to watch them narrowly. There are styles of morbid thought which can not be
