8
The following table shows the effect of each of these three strains as regards the
length of the incubation period and the duration of the disease when inoculated
subdurally:—
Animal inoculated
subdurally.
Incubation
period in days.
Death
Days.
Virus used.
Guinea pig ..
..
..
Rabbit ..
..
..
..
Monkey
5 to 6
6
9
7 to 8
8 to 9
11
Laboratory rabbit virus.
,,
Guinea pig ..
..
..
Rabbit ..
..
..
..
Monkey
5
5
5 to 7
6 to 7
6
10
Guinea pig virus.
Guinea pig ..
..
..
Rabbit ..
..
..
Monkey
10
8
11
1 0 ½
2
131;
1 1 ½
Dog virus
It appears from the table that dog street virus passed through 29 guinea pigs is more
rapid in its action than dog street virus passed through 248 rabbits or than dog street
virus passed through 19 dogs. It must, however, be remembered that a different strain
was used for each series and they might have differed in activity in the first place.
In each case the virus used was fixed, i.e., the rabbit strain had an incubation of
6 days in rabbits, the guinea pig virus, an incubation of 5 days in guinea pigs and the
dog virus, an incubation of 9 days in dogs.
There was no difference in virulence in the three strains; they all killed surely,
but they differed in activity, the dog strain being the least active. As we have shown
before (Bulletin 1, page 16), rabies does not die out when inoculated subdurally into a
succession of dogs but becomes fixed. If ordinary street dogs be used for the series, a
certain number of passages will fail owing to the insusceptibility of the subjects. One
concludes therefore that dogs are less susceptible to rabies than either rabbits or
guinea pigs, and probably the virus they provide is somewhat less active than that
obtained from rabbits and guinea pigs, and, probably, also rats. Apparently the only
reason why rabies does not spread in nature amongst such animals as rabbits or guinea
pigs is because it is not their habit to bite, as it is the habit of dogs, and rabies, if
introduced, would speedily die out in consequence. The virus finds its way to the
salivary glands of guinea pigs just as it does in dogs.
4.—To ascertain if protective inoculations of fixed virus are of more value
round the site of infection with street virus than at a distance.
(1) Six guinea pigs were inoculated subcutaneously in the abdomen with first pas-
sage street virus brain. On the next day protective subcutaneous injections with fixed
virus were begun. In all, fourteen injections, amounting to 1/10,000 of the animal's
weight of fresh fixed virus, were given in a circle round the point infected with street
virus.
Three of the six survived. Of the remaining three—
No. 84 died. on 14th day.
1 5 t h "
1 7 t h "
No. 84 showed no Negri bodies : no sub-inoculation made.
No. 115
a guinea pig inoculated subdurally with its
brain showed Negri bodies to 3µ in hippocampus and to 6 µ in cerebellum.
No. 181 showed tiny Negri bodies : no sub-inoculation made.
As we have shown elsewhere (page 1), subcutaneous inoculation of street virus brain
substance in guinea pigs in a large proportion of cases does not produce Negri bodies
in the brain, yet these bodies may reappear if subdural passages be made from the
brain of the animals which have succumbed to subcutaneous inoculation. The fact
that large and typical Negri bodies were absent from the brains of guinea pigs 84, 115