12 BULLETIN 65, U. S. DEPARTMENT OF AGEICULTURE. 



throughout the carcass may show a pronounced icteric appearance 

 in certain cases. On removing the bones of the skull the bram 

 appears to be noiTiial macroscopically in a few instances, but in most 

 cases the veins and capillaries of the meninges of the cerebrum, cere- 

 bellum, and occasionally the medulla are distinctly dilated nnd 

 engorged, and in. a few cases there are pronounced lesions of a lepto- 

 meningitis. An excessive amount of cerebrospinal fluid is present 

 in most of the cases. On the floor of the lateral ventricles of several 

 brains there was noted a slight softenmg 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 urine, and containing a limited amount of flocculi, 

 but m a few cases it was slightly blood tinged. The spinal cord was 

 not found involved in the few cases examined. 



A comparative microscopic examination 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 comiective tissue with dense round-cell infiltration which 

 extended mto the adjacent cortical portion of the cerebrum. The 

 capillary blood vessels were. engorged with cells and their walls were 

 greatly uifiltrated. Limited areas of leucocytic infiltration and small 

 hemoiThages 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 mimunity. 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 natm'al 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 

 with serum from recovered cases, but without any positive results. 

 Similar investigations have been conducted l)y 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 imaginal)le 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 lose their physio- 



