conspicuous as the increase in
industrialism. In 1880, twenty-nine and five-tenths per cent of the
population was urban and seventy and five-tenths per cent was rural;
in 1910, forty-six and three-tenths per cent was urban and fifty-three
and seven-tenths was rural, the increase being most marked in cities
of over five hundred thousand inhabitants. Of the total increase in
population between 1900 and 1910, seven-tenths per cent was in the
cities and three-tenths per cent in the country. City life in itself
is not necessarily unhealthy and there are many advantages associated
with it. The conditions which have chiefly fostered it are the
immigration of people who are accustomed to community life, the
increase in factory life and the increased number of people of wealth
who seek the advantages which the city gives them. The city has always
been the favored playground for the social game. The unhealthy
conditions of city life are due to the crowding, the more uncertain
means of livelihood, the greater influence of vice and alcoholism.
Prostitution and the sexual diseases are almost the prerogatives of
the cities.

3. All means of transportation have increased and communication
between peoples has become more extended and more rapid. In the past
isolation was one of the safeguards of the people against disease.
With the increase and greater rapidity of communication there is a
tendency not only to loss of individuality in nations as expressed in
dress, customs, traditions and beliefs, but many diseases are no
longer so strictly local as formerly--pellagra, for example. Only
those diseases which are transmitted by insects which have a strictly
local habitat remain endemic, although the region of endemic
prevalence may become greatly extended, as is seen in the distribution
of sleeping sickness. Diseases of plants and of animals have become
disseminated. Any plants desirable for economic use or for beauty of
foliage and flower become generally distributed, their parasites are
removed from the regions where harmonious parasitic inter-relations
have been established, and in new regions the parasites may not find
the former restrictions to their growth. There have been many examples
of this, such as the ravages of the brown-tail and gypsy moths which
were introduced into New England and of the San Jose scale which was
introduced into California. There have been many other examples of the
almost incredible power of multiplicati