MENINGO-ENCEPHALITIS 439 



when one exists the other is present at least to some extent. 

 Furthermore, the treatment is essentially the same. 



Etiology. Meningo-encephalitis is caused by practically 

 the same factors that produce hyperemia of the brain. 

 These are: Violent exercise, excitement, blows or concus- 

 sions on the head. Excessive heat, direct sunlight, etc., are 

 thermic causes. 



Infectious diseases, as rabies and distemper, are at times 

 accompanied by meningo-encephalitis as are suppurative dis- 

 eases of the auditory canal (otitis) frequently seen in the rab- 

 bit and occasionally in the dog. Other causes are metastatic 

 emboli from infected internal organs as the uterus, lungs, 

 heart (endocarditis) and mammary glands (tumors). 



Pathology. In meningo-encephalitis lesions of various 

 size and character may be seen, depending upon the cause, 

 and may be formed anywhere in the brain or on the mem- 

 branes. There may be numerous inflammatory areas or 

 perhaps only one. Usually hemorrhagic, circumscribed or 

 diffuse areas are noted either on or within the hemisphere, 

 or on the cerebral membranes. The color of the areas varies 

 from a dark brown to a greenish-yellow, depending on the 

 age of the lesion. In those cases caused by metastatic 

 emboli, suppurative areas may be found in any part of 

 the brain and are usually multiple. 



Symptoms. As in hyperemia of the brain, there are symp- 

 toms of psychic or motor disturbance, or both. Early there 

 is restlessness and timidity, and the dog may howl or bark 

 continuously. If unrestrained the animal will run or wander 

 about in an aimless manner and frequently run against 

 objects. The head is hot, visible mucous membranes con- 

 gested, and the eyes have a vacant, staring expression. The 

 pupils may show unilateral contraction or dilatation. While 

 most text-books state that the pupils are contracted, the 

 writer has observed that in most cases they are either dilated 

 or unequal. 



In severe cases of meningo-encephalitis, spasms and 

 convulsions, followed by unconsciousness, are observed. 

 The animal may gradually recover consciousness, or may 

 die in one of these attacks. When the inflammatory areas 



