c 



SECTI.ON XV 



DISEASES OF THE NERVOUS SYSTEM 



Encephalitis 

 LINICALLY, it is almost impossible to differ- 



entiate between inflammation of the brain sub- 

 stance and inflammation of its coverings, since the 

 symptoms are essentially the same, and also because 

 when one is affected the others are also. 



It is most convenient to subdivide brain inflarn- 

 mations into the acute and subacute forms. Under 

 the former are included all rapidly progressing cases, 

 with extreme symptoms of cerebral inflammation — 

 that is, excitement — and under the second, those 

 which present signs of depression and are slower in 

 their course. 



However, it must be remembered that transitions 

 and intermediate stages occur between the two form.s 

 and that therefore no strict boundary can be set 

 between them. The following brain diseases may 

 occur with symptoms of acute encephalitis — hyper- 

 emia of the brain, pachymeningitis, leptomeningitis, 

 encephalitis, emboli, and abscesses. 



Subacute encephalitis may occur as a sequel to 

 the acute form, from poisoning from food stuffs, and 

 as a result of toxemia during the course of an infec- 

 tious disease. 



Cause. — Exposure to an excessively high tem- 

 perature, overexertion, parasites, new growths, em- 

 boli, thrombosis, skull traumatisms, otitis media, 

 septicemia, and pyemia all cause disease of the en- 

 cephalon or the meninges, or both. 



Symptoms. — There are generally premonitory signs 

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