4
much enhanced doses of the same serum to combat a more severe form of the
malady.
The animals used at Muktesar for the production of virulent blood are
the small breed of cattle, rarely exceeding 200 lbs. in body weight, indigenous
to the Himalayan or hill regions. These are more susceptible to rinderpest
than any of the animals of the plains of India, as far as is known, for here-
ditary or acquired immunity is seldom observed. The incubation period of
inoculated rinderpest in hill bovines is generally 3½ days, but it has been
found that after passing the virulent strain through a succession of Hill
animals, an uncertain percentage of these exhibit the primary rise in tempera-
ture after a period of 2½ days, and there appeared to be marked indications
that the inoculated disease, after being passed through a long series of animals,
possessed the same or more virulent qualities than the strain of virulent blood
at the time of its first collection.
In this regard, it is of importance to note that Pasteur passed the virus
of rabies through a succession of rabbits for a period of 2 to 3 years, until the
course of the disease, which at first occupied 18 days, was reduced to a fixed
period of ten days only. The material obtained from such animals he termed
his " virus fixe."
On the 14th and 22nd April 1901, two strains of blood were obtained,
one from plains cattle in the Hamirpur District, United Provinces, and a
second from Talli Byarhi, near Ranikhet, from the small Himalayan breed in
the hills.
Both varieties of blood appeared to be equally virulent and produced
the usual train of symptoms of rinderpest when inoculated into hill
cattle, but it was advisable to carry on our researches with but one strain of
the disease, so the hill blood was selected for the purposes of further inocula-
tion. From the time of collection, 22nd April 1901, to the end of 1904, this
strain of blood was used in all instances and there appeared to be no reason
why it should not be as virulent or more so than the blood obtained from
fresh epizootics of rinderpest.* During the winter months a reduction in
the number of inoculations was made, and as the blood on one occasion
failed to reproduce a virulent form of disease this necessitated our obtaining
fresh material from a virulent source. An outbreak was reported, on the 20th
December 1904, from Talli Mirai near Ranikhet and the necessary blood
collected, which on inoculation into hill animals reproduced a severe type of
rinderpest.
No. XXIV serum had been tested with the strain of rinderpest blood
just previous to its failure, and the dose proved to be 3 c. c. for plains
and 54 c. c. for hill cattle, per 600 lbs, respectively. In order to test the
value of the new strain of virulent blood and compare the result with that of
the old sera previously tested, experiments were initiated and these proved
that 3.66 times the dose of serum was necessary as compared with that
previously found experimentally. Consequently, comparative experiments
were conducted with several brews of rinderpest sera with the following
results:—
Number
of
serum.
XXIV
XXV
Dates of preparation.
August 9th and September 27th, 1904 .
September 28th and November 30th, 1904.
First test with old
strain of virulent
blood.
Plains.
c. c.
3
3
Hill.
c. c.
54
54
Second test with new
strain of virulent
blood.
Plains.
c. c.
10
10
Hill.
c. c.
180
180
From the above figures it will be observed that a much enhanced dose
of serum was necessary in the cases of XXIV and XXV sera, when the new
strain of blood was used as compared with the old strain.
* Vide Pasteur's result of experiments as stated above.