96
REPORT OF THE IMPERIAL BACTERIOLOGICAL LABORATORY,
immunity, and, in the practice of active immunization of cattle against
the disease in the field this is the consummation to be desired, for not
only are the treated animals in this way placed beyond risk of direct ill-
effects from the rinderpest infection but there is also prevented within
them, by the inhibition of specific tissue depression, a resuscitation of
dormant internal parasites, notably coccidia, which might otherwise
set up a fatal complication. On the other hand, in the production of
a potent anti-serum, the duration of anti-body " secretion " (if we accept
Madsen's conception of the formation of these specific immune subs-
tances or properties) appears to be a function of the intensity of the
morbid reaction which the animal organism is able to deal with effectively.
With the " blocked-out," or nearly " blocked-out" reaction a potent
anti-serum is obtained only for about four weeks after the injection of
the virus, whereas after a " mild, but decided " reaction (with not more
than five per cent. mortality in the serum producing buffaloes) a potent
serum is obtained about a week after the commencement of apyrexia
and then for a period of eight weeks, and perhaps longer, without further
treatment of the animals. Experiments were also undertaken somewhat
extensively in order to ascertain whether the injection of the salts of
certain metals would have a stimulating effect upon the secretion of
anti-bodies, as has been demonstrated recently by Madsen and his
colleagues in the production of anti-diphtheria serum from horses at
the Serum Institute at Copenhagen. The effects of the injections when
undertaken during a limited period following upon the initial infection
seem to be encouraging. The Indian plains buffalo was found to be
a much better serum producer, in the sense that it would furnish a good
serum for a long period, than the local hill bull.
Following upon the accidents that occurred in the Government Mili-
tary Dairies during the cold weather season 1922-23 in the active immu-
nization of the cattle there against rinderpest, a number of observations
relevant to the subject were made at the laboratory and the fatalities
were traceable mainly to the injection of a toxic serum. The serum was
one which had been prepared from buffaloes by repeated " hyperimmuni-
zation " with hill bull blood, and hence it had developed haemolytic
properties for ox blood. In the small doses required for preventive
inoculation the toxic action was without appreciable serious effect, as had
been proved by the tests carried out on it prior to issue at the laboratory,
but when inoculated in the large quantities required for active immu-
nization, notably of cattle with an admixture of European blood, the
toxicity of the serum became a factor of serious importance.
In the early stages of the laboratory investigations upon the cheap
production of a good anti-rinderpest serum many lengthy tests were
made upon the relative efficacy of " hyperimmunization " by various
routes—subcutaneous, intra-peritoneal, and intravenous. The last-
named method produced excessively high mortality, for it is now known
that cattle contain a large number of " blood-groups," in the sense that
the serum of one animal may agglutinate the red corpuscles of another
animal (Panisset and Verge, 1922). The intra-peritoneal method appeared