secretions; e.g., typhoid fever, cholera,
dysentery, etc.

The first group, which includes practically all the ordinary diseases
like measles, mumps, whooping cough, influenza, colds, pneumonia,
scarlet fever, diphtheria, etc., is conveyed in most cases by one
infected person transmitting directly to another person,--through
coughing, spitting or sneezing,--germs present in the nose and mouth
secretions.

The second group is conveyed by insects biting people or animals
infected with the disease, and subsequently biting people who are
healthy. In this way the disease-producing organism is introduced into
the body of the healthy person, and beginning to multiply, brings
about the symptoms of the disease. Malaria is transmitted in this way
by the anopheles mosquito; typhus fever by lice, and plague by the rat
flea. These are all diseases greatly to be dreaded in the army.

The third group, including typhoid and paratyphoid fevers, cholera,
and dysentery, all of which are intestinal diseases, is largely
conveyed from the sick to the well indirectly through contaminated
water and food. To develop one of these diseases means that the
excreta of somebody who has the disease or who has had it, has been
taken into the mouth and swallowed, and the germs finding a favorable
medium in the intestines have multiplied and produced the typical
symptoms. One of the chief ways in which this type of infection occurs
is through drinking sewage-contaminated water or milk; another is
through contamination of food by the hands of the person excreting
the germs; and the third is through the contamination of the food or
eating utensils by flies and other insects which carry filth germs
from place to place on their feet and bodies.

With these facts in mind and with some knowledge of sanitation and
medicine it is easy to see how most epidemic diseases can be held in
check. Put briefly, it means that the sanitary organization must be
such that the germs from one infected soldier are prevented from
reaching another, or as is sometimes said, some link in the chain of
circumstances whereby disease germs can pass from one to another, must
be broken.

The methods employed to break these links are simple; the carrying out
of the methods is oftentimes very difficult.

It is obviously essential in the first place to remove from the army,
at the earliest possible moment after it has been diagnosed, every
case of communicable disease. This means t