he utilization of this knowledge is largely due to the
greater forces which we have become possessed of.

Disease plays such a large part in the life of man and is so closely
related to all of his activities that the changes in this period must
have exerted an influence on disease. We have already seen that within
the period we have obtained knowledge of the causes of disease and the
conditions under which these causes became operative. The mystery
which formerly enveloped disease is gone; disease is recognized as due
to conditions which for the most part are within the control of man,
and like gravity and chemical attraction it follows the operation of
definite laws. There has been developed within the period what is
known as preventive medicine, which aims rather at prevention than
cure, and the resources of prevention are capable of much greater
extension.

Have there been new conditions developed within the period, or an
increase of existing conditions which can be regarded as disease
factors and which counterbalance the results which have come from the
knowledge of prevention and cure? There has been an increase of
certain factors of immense importance in the extension of disease.
These are:

1. The increase in industrialism, involving as this does an increase
in factory life. In many ways this is a factor in disease. (_a_) By
favoring the extension of infection, particularly in such diseases as
tuberculosis. (_b_) The life indoors, and frequently with the
combination of insufficient air and space, produces a condition of
malnutrition and deficient general resistance. (_c_) The family life
is interfered with by the mothers, whose primary duty is the care of
home and children, working in factories, and the too frequent
conversion of the house into a factory. (_d_) The influence of factory
life is towards a loss of moral stamina rendering more easy of
operation the conditions of alcoholism and general immorality. How
great has been this increase in industrialism, fostered as it has been
by conditions both natural and artificially created by unwise
legislation, is shown in the figures from the last census. The number
of factory operatives increased forty per cent between 1899 and 1909
and the total population of the country in the period between 1900 and
1910 increased twenty per cent. It is probable that the future will
see an extension rather than a diminution of mass labor.

2. The increase in urban life is as