The limits of this article permit of but a brief reference to the progress in preventive medicine during the century. The studies made in England of the results of the cholera epidemic of 1849, and the experience gained in the English army during the Crimean war, led to some of the most important advances in sanitary science, more especially to the demonstration of the importance of pure water supplies, and of proper drainage and sewerage. During our Revolutionary War, and the Napoleonic wars, the losses to the armies from disease greatly exceeded those from wounds; and hospital fever--in other words, typhus--was dreaded by a general almost more than the opposing forces. During the wars of the last twenty-five years, typhus and hospital gangrene have been unknown, but some extensive outbreaks of typhoid fever have occurred, showing that our knowledge of the causes and mode of transmission of this disease has not been practically applied to the extent to which it should have been; this remark applies also to some of the most fatal diseases in civil life. In the United States diphtheria and typhoid fever each causes from twenty to thirty thousand deaths a year, while more than one hundred thousand deaths are annually due to consumption. Yet for each of these diseases we know the specific germ, the channels through which it is usually conveyed, and the means by which this conveyance can be to a great extent prevented. The ravages of these diseases are, therefore, largely due to the fact that the great mass of the people are still ignorant of these subjects. Antitoxin is not yet used for either prevention or treatment in diphtheria to anything like the extent which our knowledge of its powers demands. Our better knowledge of the causes of certain infectious and contagious diseases, and of the mode of their spread, has been of great importance to the world from a purely commercial point of view, since it has led to the doing away with many unnecessary obstructions to traffic and travel which were connected with the old systems of quarantine, while the security which has been gained from the modern method of cleansing and disinfection is decidedly greater than that secured by the old methods. A striking illustration of the effect of these improvements is seen in the manner in which the news of the recent outbreak of plague in Glasgow was received in England and throughout Europe. One hundred years ago the city would have been almost deserted, and terror would have reigned in all England. To-day it is well understood that the disease spreads by a bacillus which is not conveyed through the air. No one fears a repetition of the ghastly scenes of the Black Death in the fourteenth century. In like manner, and for the same reasons, Asiatic cholera has lost most of its terrors.