Among the great advances made in the last few decades of the nineteenth century must be included the successful battle of modern hygiene against infectious diseases. This struggle was introduced by the development of practical hygiene in England and by the perfection of scientific hygiene through the work of Pettenkofer. But a firm basis on which to combat pestilence was not secured until the brilliant discoveries of Koch and his successors pointed out to us the cause of these pestilences, and methods were found to demonstrate in a short time the presence of disease-germs, even among persons who become ill but slightly, or not at all, and who for that reason are very dangerous to those about them.

Since even in time of peace the close quarters in which soldiers live in barracks greatly favour the outbreak of epidemics, the military authorities constantly watched and profited by these advances in the field of disease-prevention; and with the success of efforts to decrease the prevalence of infectious diseases among the soldiers in time of peace, so also in war-times it became possible to check more thoroughly than ever before the dissemination of these diseases. Hence the number of men carried away by epidemics is much smaller in modern wars than used to be the case.