taking the germs of this disease, which was called cow-pox, and putting
them into the blood of human beings, he could produce a mild form of
small-pox, which never assumed a dangerous character, and yet prevented
the person treated from taking the real deadly small-pox.

From this experiment vaccination, as we know it to-day, resulted. The
practice was given this name in France; the word is derived from
_vacca_, the Latin for cow.

Since vaccination became general, the decrease in the rate of deaths
from small-pox has been wonderful, and there has not been one serious
epidemic where the practice has been followed.

Yellow fever is a much worse enemy to all people who live in warm
climates than small-pox. It is a terrible disease, and often kills its
victims in a few hours. All sailors and travellers in southern
countries have to meet with the scourge, the sailors calling it
familiarly "Yellow Jack."

If it is indeed true that by inoculation people can be made proof
against this awful disease, it will be one of the greatest blessings
this wonderful century has given to man.

As we have said, yellow fever visits our southern shores every year,
though happily not often in an epidemic form. The Government has
therefore sent an expert down to the affected districts to discover, if
possible, where this disease comes from, and ascertain the best means of
preventing it.

Dr. John Guiteras was chosen as the best man to send, and he reports