Very great difficulties, to be sure, confront the efforts made in war times to prevent the outbreak of infectious diseases. If the struggle is carried on in an infected region, the troops are often compelled to seek shelter in infected houses; thus during the battles of Orléans and Le Mans in the Franco-German War the troops, in order to protect themselves against the severe winter cold, had to live in houses which small-pox patients had shortly before occupied or were actually occupying at the time. Circumstances frequently arise which render impossible the adoption of the most effective measure calculated to prevent the dissemination of a pestilence, that is, the isolation of infected divisions of troops; one can readily imagine how difficult this would be in the case of an army re-forming after a lost battle. Furthermore, even if one of the belligerent armies is doing all it can to prevent diseases from spreading, its efforts must be seriously handicapped if the enemy’s army does not include an equally diligent sanitary corps and does not devote the same amount of energy to the prevention of the outbreak and dissemination of infectious diseases. For even if a sanitary corps is successful in warding off a reaction upon its own troops, nevertheless this reaction is sure to take place with respect to the civil inhabitants of the country in which the war is waged. During a war, the civil authorities must also do their part in preventing diseases from spreading to the civil population. The local administrations of a region in which fighting is going on are powerless. The generals care very little whether or not a city or village in the enemy’s country is infected by their troops, whom they quarter in whatever house or place best suits their purpose. On the other hand, the communities in which military prisons are located are confronted with a very difficult problem, since these prisons, if infected men are confined in them, easily develop into centres of infection; this fact was observed a hundred times in the year 1870. If a disease breaks out in a community in consequence of the fact that a military prison has been established there, in my opinion it is incumbent on the central government of the country to support the local authorities in their efforts to check the disease, and to give them financial help as well as scientific advice. Unfortunately, it is not to be denied that, in many small cities and in almost all rural communities, absolutely no provision is made for the isolation of persons suffering from infectious diseases; the authorities justify themselves with the reflection that in case of emergency barracks can quickly be erected for the purpose, but at the same time they fail to remember that working-men are not always available in the storm and stress of war times, that building materials in the general scarcity of supplies cannot always be procured with sufficient promptitude, and that pestilences, if the isolation of the