In making the foregoing sketch, I have attempted to put together some ideas on a subject, which has for the last few years been a theme for meditation in leisure hours, viz. What are the causes of Epidemic, Endemic, and Infectious Diseases? The occurrence of Epidemic Cholera last year in this country, awakened a spirit of enquiry. Where there is unrest, whatever may be the cause, there also is disquiet and discontent. When the oracles of the age were consulted in the emergency, the discordant answers perplexed and confused the anxious searcher after truth. In the spring of last year, when the enemy was approaching, unseen and unheard, and the thousands of unconscious victims, who are now lying in their graves, were faithfully trusting and fully relying on the heads of our profession, and the resources of our art, what was the state of our defences, and what the nature or character of our resistance? One considerable body of men would discharge from a little tube of glass, a host of almost invisible globular atoms of sugar, said to be as potent and inscrutably operative as the unseen enemy. These infinitesimal practitioners assured the people that they "_had powerful means of subduing the disease_," {190} but even they differed among themselves, though they carried out to the fullest extent the doctrine of their leader, _similia similibus_, which we may suppose to refer in this case to the minuteness of the opposing armamenta. Without, however, agreeing with this school, I may quote a passage from Dr. Curie, which is, alas! too true: "We have shewn, as they must (allopathists), and many of them do acknowledge, that they have no fixed basis, no natural law upon which their treatment rests." Who can deny the force of this observation? Sheltered by a principle, it matters not how fallacious, a man is placed as behind a barrier. If with any reason it could be shewn that the infinitesimal doses, could by no possibility effect a cure in Cholera; if it could be demonstrated by any line of argument, that a poison, a living poison, circulates with the blood, or lodges in the tissues, the homaeopathist must fall; his "electricity and mineral magnetism," and "_powerful concentration of life power towards the digestive canal_," will stand for what they are worth. That minute doses of medicine can exert an active influence over the body is not to be denied, but these must consist of powerful drugs, as arnica, aconite, and nux vomica, with others, and it is more than probable, that of such medicines, an inconceivably small amount may produce a specific effect upon some portion of the organic nervous system. How is it that a dose of nitre or digitalis, "can {191} convert cheerfulness into low spirits," or a grain of red sulphuret of antimony, "excite warmth and lively spirits?"[74]