y greater in the
open country surrounded by hygienic conditions than in a city in crowded
quarters, confined for long hours each day at some unhealthy occupation.

As a general warning, it may be stated that a factory containing a
dust-laden atmosphere is most undesirable, and this is particularly so
when the dust is mineral dust. In the country, the only comparison of
conditions possible is between that of the outdoor worker and that of
the indoor worker; enough has already been said upon the value of fresh
air and its improving effect on the vital resistance to make further
repetition unnecessary. Unfortunately, in the past the occupation known
under the general term of farming has not made itself conspicuous in
statistics for healthfulness; but this has been undoubtedly due not to
the lack of the value of the outdoor part of the farmer's life, but to
the monotony of the work and to the very bad conditions found indoors,
particularly in the winter. When this indoor life has been modified so
that plenty of fresh air is supplied day and night, and when reasonable
attention is paid to the demands of the body in the matter of food and
drink, then the duration of life of farmers will rank high in comparison
with other occupations.

_Direct causes of disease._

The direct causes of disease may be due to the introduction into the
human body of a specific microoerganism which, if not met by the
antagonistic agencies, finally pervades the whole system with its
progeny or its virus. The microoerganisms thus responsible for disease
are commonly divided into two classes, namely, parasites and bacteria.
In the first group are included those parasites that cause tapeworm,
malaria, trichinosis, and hookworm; in the second group those bacteria
that cause typhoid fever, cholera, erysipelas, diphtheria, and probably
smallpox, measles, scarlet fever, chicken pox, and a number of others
presumably similar.

_Parasites as causes of disease._

The introduction of worms into the body must come either from impure
drinking water, from impure food, or from the bites or stings of
insects. When introduced into the body, those parasites that are
inimical to man and produce abnormal conditions interfering with usual
physiological functions may or may not develop further. In some cases,
as in malaria, the very act of hatching the malarial brood is sufficient
to throw the host on whom the brood will feed into a violent chill.

In other cases,