464 MENINGITIS IN HORSES 
substance of the brain and spinal cord shows similar infiltrations widely 
diffused. The infiltrating cells are chiefly lymphocytes—1. e., they 
are for the most part derived from the vessels.” 
Jcest described special bodies termed ‘‘nuclear inclusions” which 
can as a rule be demonstrated “‘in the olfactory convolution and in 
the large polymorphic ganglion cells of Ammon’s horn.” These 
bodies are not found in any other disease, and are said, when present, 
to be diagnostic of ““Borna sickness.”’ But ‘in individual cases they 
Fic. 109. OLFAcTORY TRACT. (a) DIFFUSE INTERSTITIAL INFILTRATION, (b) PERI- 
VASCULAR INFILTRATION. x 90 (after Udall). 
bear no relationship, either as to size or number or as to localization, 
to the inflammatory infiltration.” 
The inflammatory process is most marked in the olfactory bulb 
and olfactory convolution, and next to these in the caudate nucleus 
and “Ammon’s horn.” It is believed that it commences in the olfac- 
tory lobe, and then extends to other parts, also that the meningitis 
occurs subsequently to the encephalitis. 
Udall found that “the inflammatory infiltrates are undoubtedly due 
to the local effect of the virus. Inconsidering the possible effect of an 
actual poison one seeks for the cause in the vicinity of the infiltrates. 
