The great boon that medical science will confer upon humanity, in the future, will not be so much in improved methods of treatment, as in the means and methods which medical science will devise for preventing disease. One ounce of prevention will always be worth a pound of cure. When we look back fifteen or twenty years, we must even now acknowledge that preventive medicine has accomplished greater results than curative measures, because the former can be made in the very nature of things _absolute_, while curative agents are only relative. Puerperal, or childbed fever, which is an _infectious disease_, was at times a pestilence, which destroyed women by the score, in maternity hospitals, or in certain neighborhoods, by the infection being carried by midwives or accoucheurs from house to house, yet no one had the least suspicion that it was possible to carry the germs of this disease under the fingernails of the attendant, or on the clothing or a syringe, or on some other little instrument, from one patient to another, and, indeed, there are a great many to-day who are practicing midwifery who are still ignorant of the importance of refined cleanliness. But for this ignorance, there is no longer an excuse, because the infectiousness of this and other diseases is so positively established, and even the physical characteristics of the micro-organisms have become familiar to the microscopists. This knowledge of the causation of puerperal fever has been applied to the employment of preventive measures, so that this dreadful malady is becoming a rarity, particularly in countries where scrupulous care and cleanliness are enforced by governmental rules and regulations. I refer to this particular _fever_, because it is, to my mind, one of the most brilliant illustrations of the efficacy of preventive or antiseptic medicine.