istance. Their progeny should show a greater immunity than the
original colony, and, after repeated attacks of the same malady, a
race tolerance would become a characteristic."

"That is certainly a plausible theory."

"It is probably correct. But acquired immunity, possessed by an
individual residing among a people who are susceptible, is the problem
of greatest interest. The difference between a susceptible and an
immune animal depends upon one fact. In the former, when the
disease-breeding germ is introduced, it finds conditions favoring its
multiplication, so that it makes increasing invasions into the
tissues. The immune animal resists such multiplication, and possesses
inherent powers of resistance which finally exterminates the invader.
But how can this immunity be acquired by a given individual?"

"Upon the solution of that question, I would say depends the future
extermination of disease," said the Judge.

"You are right," assented the Doctor. "Ogata and Jashuhara have
recorded some interesting experiments. They cultivated the bacillus of
anthrax in the blood of an animal immune to that disease, and when
they injected these cultures into a susceptible animal, they found
that only a mild attack of the disease ensued, and that subsequently
the animal was immune to further inoculation."

"Why, if that is so, it would seem that we have only to use the blood
of immune animals, as an injection, to insure a person against a
disease!"

"Behring and Kitasato experimenting in that direction, found that the
blood of immune animals, injected into susceptible individuals, after
twenty-four hours rendered them immune, but this would not follow with
all diseases. In many maladies common to man, a single attack, from
which the person recovers, renders him safe from future epidemics. The
most commonly known example of this is the discovery by Jenner, who
gave the world that safeguard against small-pox, known as vaccination.
But the most important discovery in this direction yet made is one
which is not fully appreciated even by the discoverer himself.
Chauveau, in 1880, ascertained that, if he protected ewes by
inoculating them with an attenuated virus, their lambs, when born,
would show an acquired immunity."

"This is incredible!"

"I have now related all that the modern scientists have recorded up to
the present date, and when I tell you that all of this, and very much
more than is at present recognized, was known