Geographical Distribution of Diseases

Formerly diseases were a umed to be distributed in accordance with climatic, geological, etc., conditions, but now it is believed the principal limit to their extension is the absence of the conditions suitable for the growth of their specific micro-organisms. Asiatic Cholera, long thought to be peculiar to the tropics, has extended almost to the polar circles. Tropical diseases such as yellow fever may flourish to the lines of killing frosts and even beyond. Malaria is found wherever the soil and temperature are of a certain nature. Lock-jaw is universally distributed. but is more prevalent in certain localities, such as portions of Long Island, N. Y. Mountain sickne occurs only at certain altitudes, and many affections such as Delhi boil are found in certain places only; but there is every reason to believe that they may become universally distributed. Calculous affections are rather more common in limestone regions. Cretinism is limited almost exclusively to the mountain regions of Europe. Geographical Mile. Distance on the earth's surface cor responding to one minute of latitude. On a sphere whose sur face is the same as that of the earth this distance is 6,080 ft., the value adopted by the U. S. Coast and Geodetic Survey.