The following are extracts from Kitasato, Nakagawa, Yersin, Wyman, Manson.
CAUSES EXTERNAL.
The plague affects all countries.It affects all climates, but it has become practically a disease of warm climates.It affects all altitudes.It affects all seasons, but is worse in moderate temperatures.Moderate temperatures combined with a certain degree of dampness are the most favorable conditions.It affects all races, but the yellow race is the most liable. The white race is much less so. In the epidemic of Hongkong in 1898, the death among the Chinese was 98 per cent., and among the Europeans 18 per cent.It is endemic in many countries of Asia.It exists over such a large area there that the disease may be said to be pandemic.The worse the hygienic conditions, constitutional and general, the worse the disease.Filth and overcrowding are the most potent conditions for the starting and