subsequent infection of smallpox. The fact of smallpox
protecting from smallpox is by no means without analogy in
other diseases. Thus in Switzerland, in Africa, in Senegambia,
it has been the custom for a long time, in order to protect the
cattle from pleuro-pneumonia, to inoculate them with the fluid
from the lung of an animal recently dead of pleuro-pneumonia.
Of course since the time of Pasteur we have been quite familiar
with the inoculation of attenuated virus to protect from the
natural diseases in their fully virulent form, for instance,
anthrax, rabies, plague and typhoid fever.

As it was, then, known to mankind from a very early period that
a person could be protected from smallpox by being inoculated
with it, inoculation grew up as a practice in widely distant
parts of the globe. The purpose of intentional inoculation was
to go through a mild attack of the disease in order to acquire
protection from the much more serious natural form of the
disease--to have had it so as not to have it. A very high
antiquity is claimed for this smallpox inoculation, some even
asserting that the earliest known Hindu physician (Dhanwantari)
supposed to have lived about 1500 B.C., was the first to
practice it. Bruce in his "Voyages to the Sources of the Nile"
(1790) tells us that he found Nubian and Arabian women
inoculating their children against smallpox, and that the
custom had been observed from time immemorial. Records of it
indeed are found all over the world; in Ashantee, amongst the
Arabs of North Africa, in Tripoli, Tunis and Algeria, in
Senegal, in China, in Persia, in Thibet, in Bengal, in Siam, in
Tartary and in Turkey. In Siam the method of inoculation is
very curious; material from a dried pustule is blown up into