12 BULLETIN 65, U. S. DEPARTMENT OF AGRICULTURE. 
throughout the carcass may show a pronounced icteric appearance 
in certain cases. On removing the bones of the skull the brain 
appears to be normal macroscopically in a few instances, but in most 
cases the ves and capillaries of the meninges of the cerebrum, cere- 
bellum, and occasionally the medulla are distinctly dilated and 
engorged, and in a few cases there are pronounced lesions of a lepto- 
meningitis. An excessive amount of cerebrospmal fluid is present 
in most of the cases. On the floor of the lateral ventricles of several 
brains there was noted a slight softening due to hemorrhages into the 
brain substance. There is always an abundance of fluid in the sub- 
arachnoid spaces, ventricles, and at the base of the brain, usually of 
the color of diabetic urme, and contaming a limited amount of floceculi, 
but in a few cases it was slightly blood tinged. The spinal cord was 
not found mvolved in the few cases examined. 
A comparative microscopic examimation of the brains of horses 
which died in Kansas, New Jersey, Maryland, and Virginia this year 
with those of horses from previous outbreaks showed the same char- 
acteristic perivascular round-cell infiltration, especially in the olfac- 
tory lobe and the hippocampus. The pia mater showed an increased 
amount of connective tissue with dense round-cell infiltration which 
extended into the adjacent cortical portion of the cerebrum. The 
capillary blood vessels were engorged with cells and their walls were 
greatly infiltrated. Limited areas of leucocytic infiltration and small 
hemorrhages in the brain tissue were not infrequently observed. No 
cellular inclusions in the ganglionic cells were detected after pro- 
longed examination. 
TREATMENT. 
One attack of the disease does not confer immunity. Horses have 
been observed which have recovered from two attacks, and still 
others that recovered from the first but died as a result of the second 
attack. 
Inasmuch as a natural immunity does not appear after an attack 
of cerebrospinal meningitis, it might be anticipated that serum of 
recovered cases would possess neither curative nor prophylactic 
qualities. Nevertheless, experiments were made along these lines 
vith serum from recovered cases, but without any positive results. 
Similar investigations have been conducted by others in Europe with 
precisely the same results. With the tendency of the disease to 
produce pathological lesions in the central nervous system, it seems 
scarcely imaginable that a medicinal remedy will be found to heal 
these foci, and even where recovery takes place there is likely to 
remain some considerable disturbance in the functions, as blindness, 
partial paralysis, dumbness, etc. Indeed, when the disease once 
becomes established in an animal, drugs seem to lese their physio- 
