352
Equine Encephalomyelitis in India
distribution of these lesions is irregular throughout the brain, relatively
slightly affected areas existing alongside of areas in which the changes are
expressed in maximum degree, even in adjacent areas of the parietal cortex.
In the cord, there is no particular localisation of this process. The dorsal
and ventral horns are equally affected, and the lesion is, therefore, unlike
that of anterior poliomyelitis in which the anterior horn is alone affected.
In no case has it been possible to demonstrate the presence of specific
inclusion bodies, whether intranuclear or cytoplasmic, in the nerve cells of
Ammon's horn, which is a selective site of occurrence [Nicolau and Galloway.]
Bouin was used as a routine fixative, on account of its rapid penetration.
According to certain observers [Hurst], sublimate fixed material is to be
preferred in examining for inclusion bodies and this observation coincides
with the writer's later experiences in the examination of nerve tissues for
Negri bodies. The routine stain used was Mann, but the panoptic method,
May-Grunwald-Giemsa and Pappenheim, gave equally negative results.
It appears, therefore, at the moment, that ' inclusion bodies ' are not a specific
feature of the Indian form of equine encephalomyelitis and it is this feature
which promptly distinguishes it from ' Borna disease'.
The blood vessels, especially the arterioles, of the brain and cord are
affected with a chronic, proliferative type of inflammation extending through
all coats and leading to a narrowing of the lumen. The gross thickening
of the blood vessels is a characteristic lesion. One would expect, in such
lesions, to find thrombosis fairly frequent, but this lesion has never been
noted and areas of infraction with secondary softening (colliquative necrosis)
are certainly absent. The veins are abnormally distended and over dilata-
tion tends to spontaneous rupture with considerable haemorrhage. It is not
unusual to find, especially in the vessels of the pia-arachnoid, an extensive
area of venous haemorrhage surrounding the homonymous artery and, in the
cord, effecting a mechanical separation of the dorsal nerve ganglia.
The kidney lesion consists, in early cases, of marked haemorrhage between
the tubules, which themselves are perfectly normal, although they contain
a considerable quantity of blood. Rupture of the capillaries of the glo-
merular tuft is frequent. This lesion appears to depend on a primary sclerosis
of all branches of the arterial supply of the kidney. It is interesting to note
that Nicolau and Galloway encountered a similar lesion in the kidneys of
inoculated rabbits. " The condition may be described as renal congestion,
not a true nephritis ", and they consider it to originate from a compression
of blood vessels. In cases which have survived for a long time, there is a
marked tendency for an interstitial change to supervene although haemor-
rhages are still prominent. Perivascular infiltration is frequently seen around
the small cortical vessels. Similar changes affecting the blood vessels may-
be seen in the spleen and liver and, less frequently, in the lungs, and haemor-
rhage in these organs has undoubtedly a similar origin to that noted in the
kidney.
VII.—THE SEARCH FOR A NEUROTROPIC VIRUS
Mention has been made, in a preliminary note, of efforts to determine the
etiological factor in this disease. It has long been an impression in India