injudicious treatment, it may be supposed that the medicines cured him, though he actually recovered _in spite of them_, because that same blessed _vis medicatrix naturæ_ came to the rescue. If there be so much liability to error in a disease so simple and uniform as small pox is, it is still greater in those complaints which are more complicated, from collateral and accidental influences and affections. Perhaps I cannot adduce a better example for our purpose than is to be found in scarlet fever. There is no disease, the history of whose treatment shows so strikingly the uncertainty of medical knowledge and experience as this does. The most opposite and various remedies and modes of treatment have been lauded as successful, in standard medical works, and in medical journals, and multitudes of _certain_ cures have been proclaimed in the newspapers. What is praised by one is condemned by another; and it is the individual experience of every rational and candid practitioner, that a mode of treatment which at one time is attended with marked success at another is wholly unsuccessful. It cannot be otherwise in a disease which varies so much as this does in its degree of severity, in its real character, and in its attendant circumstances. A respected medical friend, in reviewing his cases of scarlet fever, found that he had treated one hundred cases since he had lost a patient with this complaint. But on the very day on which he made this review, he was called to a case of scarlet fever which ended fatally, and out of thirteen cases in the same neighborhood he lost seven. With such variations in the severity of this disease, it is very difficult to avoid erroneous inferences as to the comparative success of modes of treatment. This difficulty is increased by the fact, which is remarkable in this disease, that the degree of severity, or amount of danger, is by no means always capable of being measured by the symptoms which present themselves. In the experience of every physician, who has seen much of this complaint, many cases have ended fatally, which, up to within a short period before death, appeared to be doing better than some others in which recovery took place. There was much wisdom in the reply that one physician made to another, who asked him what his mode of treatment was in scarlet fever. “I have no treatment,” said he. “I manage each case as an individual case, just as it strikes me at the time.” And to this conclusion will experience lead every judicious practitioner. Let me not be understood to mean that experience, so valuable in the treatment of all other diseases, is nothing worth in this complaint—that it establishes no facts, and no general principles. All that I mean is, that this disease is so variable in its character and tendencies, that extreme caution is necessary in applying these principles, and that the treatment must be at the very antipodes of stereotype—as variable as the disease itself.