t had cow-pox, scratched the arm of
a little patient of his, and rubbed some of the pus into it. Only a
short time after, the family of this little boy was exposed to
smallpox, and all the other children took it badly, but he escaped.

This was the beginning of what we call _vaccination_; and as soon as
it was found that this scratching of the arm and putting a little of
this _vaccine_ matter into it would cause only a few days of
feverishness, and then after that give complete protection against
smallpox, the Boards of Health all over the civilized world took it up
and insisted upon everybody's being vaccinated when a baby.

As a result, smallpox has become one of the rarest, instead of the
commonest, of our infectious diseases. Only a few dozen people die of
it each year in Europe, instead of several hundred thousands; scarcely
one one-hundredth of the people now in our blind asylums have been
sent there by smallpox, and I dare say that many of you have never
even seen a pock-marked person.

Another disease that used to be very dangerous to little children is
_diphtheria_. It was not only very infectious, but very deadly; and
nearly half of the children who took it died of it, and the doctors
didn't know anything that would cure it. About twenty years ago, two
great scientists, one a Frenchman named Roux--a student of the great
Professor Louis Pasteur, of whom I am sure you have heard--and the
other, a German, named Behring, discovered an _antitoxin_ for
diphtheria; that is, something to defeat the poison of the diphtheria
germ. When this antitoxin is injected into the blood, it will cure
diphtheria.

The doctors and the Boards of Health took this up too, and insisted
upon its being used in all cases; with the result that where the
antitoxin is used early, scarcely one in twenty of the patients dies,
instead of eight or ten out of twenty, as before.

You know how careful we are all trying to be not to let consumption
spread. By insisting that all houses shall be built so as to give
plenty of light and fresh air to everyone; and by forbidding spitting
upon the streets; and by insisting that food to be sold, especially
milk, shall be clean,--by preventing the spread of the disease in
every way, our Boards of Health have cut down the number of deaths
from this disease nearly one half; and people in the United States,
for instance, or in England, where these health laws are enforced,
live now almost exactly twice as