J. F. SHIRLAW 365
distribution and one would be entitled to believe, therefore, that the distri-
bution of the virus corresponds to the distribution of the lesions.
Yet, so far as the results recorded in the text can be considered conclusive,
Guinea-pigs are invariably susceptible to subdural inoculation of brain sus-
pensions and filtrates, thus proving a distribution of the virus, not necessarily
uniform, throughout the brain. The probable explanation is that Guinea-
pigs are much more suceptible to the virus than rabbits. In the two inocula-
tions performed on the horse, this animal appeared particularly susceptible
and it would appear, therefore, that animal host susceptibility is a variant
factor. Hurst has shown, for example, that the monkey alone is susceptible
to the virus of anterior poliomyelitis and so strict is the host specificity, that
the Old World monkey is alone susceptible.
Variations in the strains and virulence of strains is another factor that
must be reckoned with. Kumri lesions are usually of a mild degree, and it
is possible, therefore, that the strain responsible for the initiation of the lesions
is of a mild degree of virulence. It would be as correct to argue, however,
that in Kumri enzootic areas the majority of animals have acquired some
degree of immunity through exposure to latent infection, an observation
that is supported by the fact that, in such areas, acute"explosive " cases of
the disease are not rare.
The work of Macalister on Kumri is a classic. It would be out of place
to criticise it too severely but it must be remembered that this author was
writing at a time when the knowledge of neurotropic virus diseases was in
its infancy. World-wide research has illumined many obscurities.
Macalister defines Kumri as a combined diffuse sclerosis and central
poliomyelitis of the horse, with demyelination of the nerve tracts. He states,
that the title chosen is not free from objections, as he was uncertain whether
sclerosis was a primary or secondary lesion. The writer has been unable to
confirm Macalister's findings that Kumari is a demyelinating disease with
secondary sclerosis. A large number of spinal cords both from cases of equine
encephalomyelitis and those designated Kumri have been examined by Busch's
modification of the Marchi method, with entirely negative results. These
were selected from recent, acute cases of the disease and it is considered that
the lesions described by Macalister were probably secondary, dependent on
extensive neuron degeneration, although even in chronic cases of Kumri,
these lesions could not be determined by the writer. Demyelination is not
a primary lesion of neurotropic virus infections. ' A point worthy of emphasis
is that these neurotropic viruses are not responsible for direct damage to the
myelin sheaths : when nerve cells are destroyed, the usual type of Wallerian
degeneration ensues in the corresponding nerves and tracts, but a primary
attack on the myelin is characteristic of quite another type of encephalitis '
[Hurst].
If a type of encephalitis of different features from equine encephalomye-
litis (or Kumri) exists in India, it has not made itself apparent.
CONCLUSIONS
1. Equine encephalomyelitis, of a type strictly comparable with that
existing in Western countries, exists in India.