Rinderpest.                                                  83

The following animals received a single dose of serum and
after 14 days were exposed to natural infection by placing
them in a shed with infected cattle.

Two healthy bulls were exposed to the same infection.
They contracted the disease which ran a similar course as in
the case of controls inoculated with virulent blood, with the
exception that the symptoms of disease appeared three days
later than in inoculated cases. They died on the tenth day.

Out of four bulls exposed to natural infection 14 days after
receiving a single dose of serum, two had severe attacks, and two
had slight temperature reaction only. One died.

                                SUMMARY.

The general conclusions arrived at from the results of these
experiments are that—

(1)  A single dose of anti-Rinderpest serum confers immu-
nity against the inoculated virus for about two weeks only.

A double dose protects for about three weeks, a treble dose
for five weeks and four times the single dose for about six
weeks.

(2)  The serum protects against natural infection for the
same period as against the inoculated disease.

(3)  The. immunity following a simultaneous injection of
serum and virus even when no reaction occurs, is of an active
nature and lasts for several months and that to produce this
result it is not necessary to determine a balance between serum
and virus nor to give rise to any clinical symptoms of the dis-
ease.

(4)  When animals are injected with serum and immediate-
ly exposed to infection, they acquire an active immunity of
several months' duration, without evincing any clinical symp-
toms of the disease.