I mention as another very common cause of inaccurate observation in medicine, an easy credulity, and a consequent fondness for novelty and change. It is a very prevalent opinion that the medical profession is opposed, as a general thing, to anything which is new, and that it really thus stands in the way of the march of improvement. This may have been true once, when the authority of antiquity held an almost undisputed supremacy over all the votaries of learning and science. But it is far from being true now. One of the prominent faults of the medical profession in the nineteenth century is, on the other hand, that it is as a body too fond of new things, and too much disposed to receive them upon doubtful evidence. There is a great disposition to hail every new remedy with enthusiasm. The annals of medicine are therefore burdened with false statements in regard to the effects of remedies. Though the public think that there have been of late many discoveries of new medicines of great value, there really have been but few. There have been many improvements in the _forms_ of medicines. I mention as examples, quinine and morphine, the active principles of bark and opium. But there have been but few absolutely new medicines introduced which are of any importance. Many have been announced with much flourish, and have been extensively used for a time, but the confidence which has been put in them has in most cases been found to be misplaced. And it may be remarked, that physicians, who try all the new remedies recommended from time to time in medical journals, do not add so much to their stock of available experience, as those do who are more cautious, and less ready to adopt everything which is new. The science of medicine, in all its departments, is in a very changeable state. The discoveries, which are made from time to time in anatomy, physiology, and pathology, the theories which are put forth, and the new remedies, and modes of treatment which are continually proposed, keep up a constant excitement in the profession. In this unsettled state of things, with so many novelties to attract the attention, the temptation is so strong to act as a mere gazer, and, setting aside the labor of investigation, to adopt what is asserted upon deficient evidence, that there is the more need of maintaining that cautious observation, which is the only preventive of error.