426 DISEASF:S OF THE NERVOUS SYSTEM. 



corpora striata and optic thalami, and the brain-tissue imme- 

 diately surrounding. 



If there is not a fatal termination of the hemorrhage, in a 

 short time the clot undergoes complete liquefaction, and, hav- 

 ing been surrounded by a fibrous-tissue capsule, a sort of cyst 

 results ; or later there may be simply a pigmented scar to 

 mark the site of the hemorrhage. 



Secondary degeneration of the direct and crossed pyramidal 

 tracts results, when, as is often the case, the hemorrhage has 

 occurred in the region of the internal capsule; due, it is sup- 

 posed, to the separation of these motor-nerve fibres from their 

 trophic centres. 



INFLAMMATION. 



Acute inflammation of the brain encephalitis may occur 

 in the course of various acute infectious diseases, as typhoid 

 fever, septicaemia, and influenza. The condition is character- 

 ized by the formation of localized areas of softening, which are 

 red or yellow in color, according to the amount of extra vasa ted 

 blood present. 



Microscopically, in these areas, and also in others where 

 softening is not yet manifest, the bloodvessels are dilated, 

 engorged with blood, and surrounded with migrated leuko- 

 cytes. The ganglion-cells and nerve-fibres undergo a granular 

 and fatty degeneration. In the centre of the area the neurog- 

 lia undergoes a similar change ; at the periphery, however, 

 may be noted the formation of new neuroglia cells and fibres. 



Suppurative inflammation of the brain is most frequently 

 associated with a similar inflammation of the meninges. The 

 condition may also occur in the course of pyaemia, ulcerative 

 endocarditis, and other septic processes; and in influenza, pneu- 

 monia, and other infectious diseases ; or it may follow direct 

 injury, or septic inflammation of the bones of the skull. 



The abscess-formations which characterize this condition 

 may be quite small, or large enough to contain, in one case, 

 as much as four hundred cubic centimetres of pus. In a large 

 proportion of cases the abscess is solitary ; multiple abscesses 

 are generally metastatic. 



Chronic inflammation of the brain is characterized, like 

 chronic inflammation of other organs, by an increase of the 



