10
Indian Hill cattle, but it will have to be tested on the less susceptible Plains
ones in whom it may possibly give better results. As, however, in point of
susceptibility to the disease the Indian Hill cattle are more on a par with the
South Africa animals than are the Indian Plains cattle, the results so far
obtained are disappointing, and it appears to be an example of the differences
among various breeds of cattle with regard to the ease or difficulty of affording
them protection from the disease by various methods.
21. Liver extracts.-—As the protective substance in rinderpest bile, what-
ever it may be, must be secreted by the liver, it seemed possible that it might
also be present in the liver substance after death in perhaps still larger quan¬
tities, and in that case, if it could be made use of for protective inoculation,
the number of cattle that might be protected from material obtained from
one rinderpest animal might be materially increased. It was recognised that the
liver would also contain a large amount of the infective material, but it was
hoped that this might be eliminated either by keeping it for some time or
by filtering the liver extract through a Pasteur filter.
An animal was first inoculated with a dose of the extract from the liver
of an animal which had died of rinderpest, and which had been kept for three
days in ice, and, as was expected, rinderpest ensued and proved fatal. Another
animal was inoculated with a dose of the same liver extract which had been
kept in ice for eleven days. Rinderpest again ensued and caused death. Two
other animals were inoculated with different doses of liver extract which had
been passed through a Pasteur filter. No reaction ensued, and on inoculating
one with virulent blood subsequently, and exposing the other to natural infec-
tion, both took the disease severely, and one of them died. The unfiltered
extract, then, produced the disease after being kept for eleven days, while the
filtered extract produced little or no protection. The results of the use of
filtered bile mentioned above explains the failure to obtain protection in this
latter way.
22. Bile from a salted animal.—An animal which had been protected
by the simultaneous method of inoculation and had subsequently received
increasing doses of virulent blood, the last being 500 c.c., unfortunately died
of acute Bright's disease, so the opportunity was taken to test if his bile con-
tained any antitoxic properties.
An animal was therefore inoculated with 50 c.c. of the bile on one side
of the body and 1 c.c. of virulent blood on the other side, after the method
of simultaneous inoculation. The animal contracted a virulent attack of the
disease and died. As, however, the beast was a Hill one, which it was subse-
quently found required a very much larger dose of the serum weight for
weight then do Plains cattle, the quantity of bile used was not as great as
would have been required of the serum of the same animal at this stage of
salting to have certainly protected a Hill animal from the disease; so this
experiment cannot be taken to prove that the bile of a salted animal does not
contain the protective material.
Another animal was injected with 20 c.c. of the same bile as that used
in the last experiment, but no protection was afforded by it. It appears from
this that, although the animal from which the bile was taken had a very fair
temperature reaction after he was injected with 500 c.c. of virulent blood,
but showed no symptoms, nevertheless no very active protective material was
being secreted by his liver as occurs during an actual attack of the disease.
As it had been found that during the course of these injections of virulent
blood into immune animals, their blood contains the active infective material,
as shown in experiments mentioned in paragraph 24 by its injection into a
healthy animal producing the disease, it might have been thought that the bile
would have contained the protective material, but this appears not to be the
case. The point is, however, only of theoretical importance, as such animals are
far too valuable as serum producers to be available for furnishing bile.
23. Preservation of the infection in blood.—These experiments were
undertaken partly to see if any attenuation of the virus could be obtained and
partly to see how long the virus could be preserved in blood from an infected
animal kept under different conditions.
A small quantity of blood was placed in a glass bulb, and hydrogen gas
having been passed through the tube to expel all the air, it was sealed up