6.')8 Acute X()ii-j»uruleiit Eueeplialitis. 



The most recent iiivestig-ation indicates that in many cases there 

 are grounds for connecting the disease with influenza, but one 

 cannot generalize regarding this, because the occurrence of dis- 

 eases that are similar from the point of view of pathological 

 anatomy in the other species — cattle, sheep and dogs — cannot 

 be placed in comparison with it. In the contagious outl)reaks 

 recorded by Buckley & MacCallum no cause could be found 

 either culturally or histologically. The cause was also unknown 

 in the cases recorded by Friedberger, Thomassen, Lesbre & 

 Forgeot, Marek, in the horse, Arloing in the ass, Vatli and 

 Hamoir in cattle. Montane, Hamoir, Nesmeloff, Desoubry and 

 Marek in the dog. 



In the dog there can be no doubt that the most frequent 

 cause is distemper, the encephalitis appearing at the same time 

 as other symptoms or after their disappearance. Whether the 

 virus of distemper is itself the cause or whether it prepares the 

 ground for a subsequent infection or intoxication is not yet 

 decided, but the probability is that it is the virus itself or some 

 toxin elaborated by it. 



The socalled Borna disease should probably in certain cases 

 be considered principally, if not entirely, as a non-hen:::^ :;ic 

 inflammation of the brain and spinal cord. 



The non-hemorrhagic encephalitis occurring in rabies has 

 long been known and will not be further referred to here (see 

 Vol. I). 



In no single case has the sun been proved to be the cause 

 of encephalitis (sunstroke), but a priori the possibility of such 

 an effect being due to chemical effects produced by the rays is 

 not excluded. In this case, as in many skin diseases, the rays 

 of the sun should be considered rather as predisposing causes. 



It is probable that certain foodstuffs exert only a predis- 

 posing action. Many authors have considered the legiuninosa? 

 as direct causes of encephalitis. As a matter of fact there are 

 no grounds for the belief that many foodstuffs are capable of 

 setting up an inflammatory process in the brain in a manner 

 similar to the skin rashes caused by foods in association with 

 certain determining factors. The presence of certain nervous 

 symptoms is not always demonstrable, because there may be 

 simply functional disturbance. Butler observed a non-hem- 

 orrhagic encephalitis in horses by feeding them on damaged 

 rye and claimed to have produced it experimentally. 



Overexertion which in many cases is followed by encepha- 

 litis is no doubt only a predisposing cause. 



Anatomical Changes. Lesions may be found in any part of 

 the brain, the liemisplieres, basal ganglia, the peduncles, cere- 

 bellum, or its peduncles, the medulla, the gray or white matter. 

 In the fore brain it is usually the gray matter that is involved 

 (Dexler). As a rule there are numerous inflammatory centers 

 scattered over the brain, but occasionally only a single center is 



