7
4. THE MEASURE OF IMMUNITY AGAINST RABIES IN' ANIMALS.
BY
•J. W. CORNWALL AND M. KESAVA PAL
Employing the method described in section 3 we found that the blood of normal rabbits
failed to destroy fixed virus emulsions in the proportion of 200 serum to 1 virus. Similarly
normal Goat serum was ineffective in. a proportion of 350 to 1 virus. It may be remarked. by the.
way that all the experiments alluded to were rigidly controlled by simultaneous inoculations with
fixed virus diluted to an equivalent degree with salt solution and kept under exactly the same
conditions.
Preliminary experiments, moreover, had shown that uniformly positive results are obtained
with a filtered through paper fixed virus emulsion in dilutions up to at least 1 in 700, whereas.
in practice one seldom has occasion to use a dilution higher than 1 in 250. Few workers since
Pasteur's time seem to have been as successful as he was in immunising animals against rabies
by subcutaneous inoculations, but exact information is rarely available in the published records.
concerning the quantities of inoculum used, the weights of the animals, the virulence of the
inoculum, the time occupied in the process and, lastly, whether the immunity was finally tested.
by fixed or street virus. .
In a detailed paper just published Prof. Claudio Fermi (33) of Sassari has been at some--
pains to tabulate most of the attempts at immunisation of which accounts have been written
since Pasteur's day, and concludes therefrom, as well as from his own experience, that the
possibility of immunisation against subdural inoculation with either street or fixed virus is not.
yet proved.
As we have elsewhere remarked this is comparatively unimportant, as such conditions cannot
occur in nature. We are concerned with the degree of immunity necessary to protect from the
. small quantity of virus which can be introduced by the bite of a rabid animal, and this unques-
tionably is very much less, though possibly of a different quality, than the quantities frequently
artificially injected to test immunity.
Fermi's own experiments show that rats, weight not given, which have received from 10 to
64 cc, strength not given, of attenuated fixed virus, i.e., cords dried from 12 to 3 days, are not
saved from a subcutaneous inoculation of fresh fixed virus weighing 16 gramme administered
at some later period, whereas from 80 to 90 cc of the same material saved 100 per cent.
Using the same attenuated fixed virus Fermi found that from 60 to 80 cc were required
t o s a v e 1 0 0 p e r c e n t . o f r a t s f r o m s u b s e q u e n t s u b c u t a n e o u s i n o c u l a t i o n w i t h s t r e e t v i r u s . H i s r a t s
must therefore have received from one-thirtieth to one-hundredth of their body weight of cord
substance. To give an. idea of the quantity of virus used to attain a state of serum immunity in
rabbits and goats the following records, may be not without interest and value. The material used
was always fresh rabbit or guinea-pig fixed virus cord or brain, generally the latter, emulsified in
salt solution.
Goat A—Weight about 26 kilos.—Received the intensive treatment administered to the
patients of this institute, 2. 55 grams cord substance preserved in glycerine subcutaneously in 18
days, 1/10000 of its body weight.
1 day after the end of treatment, 100 serum did not destroy 1 virus.
25 days
10
1
25 „
did.
„
1 „
155 days
20 „
Goat B—Weight 27. 4 kilos.—Received the ordinary treatment of patients, 1 . 35 grammes. .
cord substance preserved in glycerine subcutaneously, 1/20290 of its body weight.
16 days after end of treatment, 50 serum did not destroy 1 virus.
The goat then received 2 cc. 1 in 10 fixed virus . daily for .10 days, 2 grammes fresh brain
substance.
37 days after, 10 serum did not destroy 1 virus.
50
19
did
„
1 „
The goat then received 3 cc. 1 in 10 fixed virus daily for 10 days, 3 grammes of fresh brain
substance.
25 days after the end. 25 serum did not destroy 1 virus.
"
"
50 "
did
" 1 "
Goa t B r ecei ved i n al l dur i ng a per i od of f our mont hs 6 .35 gr ammes of f i xed vi r us, 1/ 4340
of its body weight. It was then bled and its serum used. for various experiments since it was the
best available at the time, though not powerfully antirabic. The immunisation of this animal
was not proceeded with as it was required for the preparation of an antisheep hæmolytic serum,,
a function it performed to perfection.