It must never be forgotten that typhoid fever is a filth disease, and that its most frequent cause is the pollution of drinking water by infiltration from drains or cesspools containing the specific poison of typhoid. To ensure protection against typhoid it is first of all necessary to make sure of a perfectly pure drinking water; but as this is difficult, if not impossible, under all circumstances, the drinking water should be always boiled, where there is reason to believe that the source is or may be polluted. This is a precaution which should be invariably taken in all those countries where the laws of sanitation are not observed, as in Italy, Spain, and the East. A necessary part of the traveller's luggage is a small Etna, by which he can boil in his bedroom all the water he intends to drink. Milk, of the source of which we are not sure, should always be boiled before being given to children to drink. If these simple precautions were observed the cases of typhoid fever which not infrequently occur after a visit to the Continent would often be prevented.