Occurrence. Etiology. 637 



Montane Desoubry and Nesmeloff. The eases of cerebral apoplexy in 

 cattle recorded by Vath in 1892 were apparently in reality cases of 

 encephalitis. More recently Dexler (1899, 1903, 1904) described a dif- 

 fuse hemorrhagic inflammation of the brain substance in cases of so- 

 called "blind staggers" and other diseases in the horse. He has given 

 a very clear account of the disease from a clinical point of view and 

 also of the pathological anatomy. A contagious hemorrhagic encephali- 

 tis was observed by Buckley & MacCallum in Maryland (North America) 

 in 1900. Cases of acute encephalitis have also been recorded by Lesbre 

 & Forgeot, also by Marek. The communications by Kolesnikotf, Brusso 

 & Galli-Valerio, Dexler, Nissel, Lienaux, Marek, Marchand, Petit & 

 Coquot, and Pecard, regarding encephalitis in cases of influenza, must 

 be mentioned. 



Occurrence. In all probability all the domesticated ani- 

 mals are likely to be attacked, altliougli up to the present cases 

 have been recorded in horses, cattle, dogs and sheep. From 

 these records it appears that the horse and the dog- are most 

 frequently affected. Even the non-specific form of the disease 

 may sometimes become contagions. 



71:l:^^ogy. The nature of the inflammatory processes in- 

 volving the brain substance indicate that non-purulent encepha- 

 litis is certainly due to an infection or a bacterial intoxica- 

 tion (post-infectious encephalitis, Dexler). The infective ma- 

 terial cannot always be detected in the brain tissue, although in 

 given cases no doubt exists as to the infectious nature of the 

 disease. This may be due either to the disappearance of the 

 infective material after the inflammation has set in or to the 

 fact that its action is more accentuated on other organs. As 

 already mentioned bacteria occur with great constancy in the 

 brain in infections of a general nature (see page 598). 



According to Dexler and others there is not rarely in cases 

 of influenza in the horse a non-purulent, hemorrhagic diffuse 

 encephalitis, similar lesions being simultaneously present in the 

 spinal cord. Encephalitis, as a rule, sets in during an attack 

 of pneumonia or severe catarrhal influenza, but in some cases 

 only after the disappearance of the symptoms of these diseases. 

 The striking s^Tnptoms of cerebral disturbance wdiich occur in 

 many outbreaks are often due to an insignificant diffuse en- 

 cephalitis. 



The cause of the inflammation of the brain which in some 

 cases is hemorrhagic and in others resembles influenza enceph- 

 alitis as described by Dexler in blind staggers and more recently 

 in horses dead of other acute diseases of the brain is not yet 

 known. Here infection of an unknow^n nature must be ac- 

 cepted. According to Dexler it may be derived from the lungs, 

 intestines, or other organs, and it is not necessary to demon- 

 strate the cause of the condition in the brain, because it may 

 produce its effects only through toxins circulating in the blood 

 or it may meanwhile have disappeared from the diseased tissue. 



