It has been proved in reference to friends and attendants, who are often in consequence in a state of apprehension, favouring the invasion of disease; and in relation to the first, who are made to regard one of the most delightful offices as a duty of imminent peril. It is hurtful both to patient and friend, by forbidding that intercourse which, but for the danger in question, would be so delightful and consoling to both. It tends to the commission of crimes of no trifling character, the desertion of kindred and of friends, the hardening and debasing of the heart, and the general corruption of the finest sentiments that bind and ornament society. It has led to deeds not the least dark in the page of human history. It takes much from the efficiency of medicine, and has been the frequent cause of much evil to its professors. For all those reasons, it is an important subject, and demands patient investigation. Surely a case has been made out to shew how important are its effects, and how much evil might be avoided were it proven, as is proposed to be done, that Atmospheric Contagion has no existence. That is all, that is desired to be shewn from what precedes, and we would on no account wish the amount of mischief it inflicts to be thought as put forward as an argument against its entity, which would be absurd. CHAPTER II. MEDICINE RETARDED—FORMS OF CONTAGION. The progress of medical science has been much impeded by the operation of the doctrine of atmospheric contagion. From the earliest periods the practitioners of medicine have been in the habit of attributing a very great proportion of the worst forms of disease to that agent; and the consequence has been that little attention has been paid to the investigation of the most difficult, and not the least important department, that of the efficient and ordinary causes of disease. It was almost a necessary consequence of the possession of such an instrument, ready on all occasions, to solve the problems offered by the occurrences of disease, that no inquiry would be made into those circumstances by which might be detected those influences that conduce to its production. There was ever at hand an agent whose existence all were alike ready to concede, which was amply sufficient to explain the origin and propagation of pestilence. That being the case, medical men had no inducement to make investigations, and from one generation to another they have gone on in the old way, attributing much to that agency, and leaving uninquired into, with few exceptions, the actual springs of diseased action. Until very lately little was known of the relation between disease and such important matters as these,—the state of the atmosphere, the severities of the weather, and its other contingent circumstances, the quality of the food and drink, clothing, habits, climate, and the like.