J. F. SHIRLAW 357
Transmission experiments : Material—Loralai outbreak
(The emulsion used was prepared from the brain cortex (parietal area) in
all three cases and 0.1 c.c. inoculated subdurally)
—
Rabbit 161 . . . . . .
Rabbit 162 . . . . . .
Rabbit 168 . . . . . .
Guinea pig 163 . . . . . .
Guinea pig 164 . . . . . .
Guinea pig 165 . . . . . .
Source of inoculum
Horse C-318 . .
Horse A-40 . .
Horse A-84 . .
Do. . .
Do. . .
Do. . .
Date
of
inoculation
13-12-34
13-12-34
18-12-34
17-12-34
17-12-34
17-12-34
Period
observed
1-6-35
25-12-35
1-6-35
7-1-35
2-1-35
(17 days).
9-1-35
(24 days).
Result
Lived.
Died—E. E.
Lived.
Died—E. E.
Do.
Do.
It will be seen from this group of experiments that the results of animal
transmission experiments appear to vary directly with the type of disease,
i.e. when the material used for inoculation is derived from peracute cases
(as at Multan) it appears more virulent. A certain proportion of rabbits
die (46 per cent) within an average of four and a half days. When the material
used is from a mild outbreak, (as at Loralai), one out of three rabbits die with
an extended interval between inoculation and death. In this case, the
number of rabbits inoculated was too small to warrant any far-reaching con-
clusions, although the statement appears capable of such an interpretation.
When the material used is from chronic cases (as at Jullundur), no rabbits die.
The observations are enhanced in the results of Guinea-pigs inoculations.
Following inoculations with the Multan material, the interval between in-
oculation and death averaged three days ; with the Jullundur material, twenty-
eight days ; and with the Loralai material twenty-one days.
It must be conceded that guinea-pigs are the animals of choice in such
transmission experiments. Subdural inoculation invariably results in death
with the production of classic lesions, not only in the central nervous system
but in the kidney as well.
The second point of importance that emerges from a study of these
results is that filtered as well as unfiltered material is capable of initiating
these lesions. This fact, taken in conjunction with the fact that no organisms
(except in a very few cases Streptococcus melanogenes) could be isolated either
from the material used for the inoculation or from the brains of animals
dying from the inoculation, points very strongly to the existence of a filterable
virus. In fact, there can be no alternative explanation.
Tentatively accepting this postulate, is it possible to prove the trans-
mission of such a virus indefinitely through a series of susceptible animals ?
The following experiment supplies the answer to this question.
In this experiment it was decided to use an alternative inoculation
route as some criticism had been levelled against the subdural brain emulsion
inoculation. This modification lay in the inoculation of white mice by the
intranasal insufflation of brain emulsion prepared in the same fashion as
previously used in the subdural inoculation. It is generally believed that
the naso-pharynx is the atrium in diseases of the poliomyelitis group and its
adoption appeared rational. Moreover, the preliminary experiments ap-
peared to indicate a peculiar susceptibility of small rodents to the infection.
E