I will even take a case in which one would suppose that a knowledge of the mechanical structure of the body would be of essential service, as an antidote to quackery. I refer to a belief in the skill of the natural bone-setter. How often does the knowledge referred to entirely fail to dislodge this error. You may show the believer in it the structure of the joints, and demonstrate to him by a clearness of proof which would satisfy him on any other subject, that it is as necessary to understand this structure, as it is any other piece of mechanism, in order to be skilful in detecting the nature of the injuries which it receives, and in repairing them. And yet, he will reply, ‘all this looks right, to be sure; but still here is the fact that the bone-setter does set bones some how or other.’ You will have to do something more, to convince him that his confidence is misplaced. You must show him, how it is that the ignorant bone-setter acquires a reputation, in spite of his ignorance, and his consequent blunders. And this can be done by facts. In commenting on these facts you can make use of the knowledge, which your friend may have of anatomy, as an auxiliary in pressing your point; and it may thus prove of great service, though it is wholly unavailing when appealed to alone. For a full view of this subject I refer the reader to the chapter on Natural Bone-Setters. While a popular knowledge of anatomy and physiology has but little influence in restraining quackery, it sometimes evidently increases it, by giving its possessor an exalted idea of his medical acumen. He upon whom it has had this effect is much disposed to adopt opinions and theories on slight and plausible grounds, and in this way is constantly led into error. The physician meets persons of this character every day. They are always ready to talk with him, and they seem to feel quite at home on medical subjects, and some of them have really acquired considerable information on these subjects; but they have built upon it a superstructure of untenable theories and notions, and they are commonly carried about by every wind of doctrine in medicine.