11
and kept at the room temperature, which at that time was only from 4° to 10°
centigrade. Some of the same blood was put up in a similar tube from which
the air was not expelled before it was sealed up. In the first experiment, blood
which had been thus put up four days after it was obtained from the animal
and kept for eleven days more under the same conditions was used, and both
that in hydrogen and the control blood in air produced a severe and fatal
attack of the disease. In a second experiment, with the same blood which had
been kept under the conditions noted for twenty days, the result was negative,
but in a third series, blood which had been put up in hydrogen for nineteen
days caused a severe and fatal attack of rinderpest when injected subcutaneously,
but some of the same blood which had been sealed up without removing
the air gave the same result.
It appears, then, that hydrogen gas had no effect either in preserving or
in attenuating the virus over ordinary air. The length of time which the blood
remained virulent was also uncertain, but might be considerable, and as it has
recently been found that difficulty is sometimes met with in villages in getting
the consent of the people to allow the small quantity of virulent blood that is
required for the simultaneous method of inoculation to be taken from any of
their sick cattle, these experiments will be continued ; for, if a method of pre-
serving the virus for two or three weeks without loss of virulence can be dis-
covered, it may be found possible to keep such a supply of virulent material at
the Bareilly Experimental Station when that place is completed. Dried rinder-
pest blood is also being tested.
24. Inoculation of blood from animals in different stages of salting.—
In the process of making protective serum, large doses of virulent blood in
increasing quantities are injected into animals which have recovered from the
disease, with the result that only a temperature reaction without symptoms is
produced. It appeared to be likely that the virus was modified in some way in
this process, and although it was probable that its intensity would be increased
on account of the resistance that it would meet with from the antitoxine or
other protective substances already produced in the animal's body by its re-
action to the virus, rather than reduced, yet the question seemed to be worth
testing.
A series of animals were therefore inoculated with blood obtained from
animals at different periods after injections of large doses of virulent blood
subcutaneously. It was found that if the blood was taken after the reaction
was over and the temperature had fallen to normal, no effect was produced.
If, on the other hand, it was taken after the reaction had begun and up to the
time it attained its height, the disease was always produced, but if the
temperature was on the decline it was uncertain whether the disease
would be produced or not. The blood of salted animals, then, during
the period of the reaction contains the virus in an active state. With
regard to the question as to whether any modification of the virus was brought
about, it was found that the disease produced was always severe, and never in
any degree modified. On the contrary, an analysis of the figures shows that
the incubation period, and to a less marked degree the duration of the disease
before death ensued, were shorter in the case of the animals which were
injected with blood from salted animals while reacting than in the case
of controls injected with the blood of ordinary inoculated rinderpest animals.
In some of these cases the blood was injected directly into a vein, and in
these the incubation period was a day shorter than when the same blood was
inoculated subcutaneously into another animal, and the duration of the disease
was also shortened by one day. This point is of some practical importance, as
when a quantity of virulent blood is wanted urgently for the serum-producing
inoculations, it can be obtained a day sooner by inoculating the control animal
intravenously instead of subcutaneously.
25. The preparation of the protective serum.—The reports of the suc-
cessful application of the serum method in South Africa having reached the
Laboratory just as preparations were being made for the commencement of the
experiments on rinderpest here, it was at once recognised that this method was
likely to be more suitable to the conditions of the disease in India than the
former bile ones, and arrangements were at once made for the preparation of
the serum in considerable quantities. Fortunately, too, just at this time the