INFLAMMATION OF THE BRAIN ENCEPHALITIS. 255 



pus-cells ; abscesses are formed, which, besides the usual constituents 

 of pus, often contain some remains of disintegrated brain-substance. 

 Cerebral abscesses are either surrounded by brain-substance softened by 

 extension of inflammation to tne surrounding parts, or by newly-formed 

 connective tissue ; in the latter case they are said to be capsulated. 



Encephalitis is a rare disease, and is not induced by the causes 

 which usually excite inflammation in other organs. 1. The most fre- 

 quent form is traumatic encephalitis ; it results not only from direct in- 

 juries affecting the brain after the skull is opened, but there are nu- 

 merous cases where the cranium has remained uninjured, and where 

 there was apparently only slight contusion. It is most probable that 

 in such cases the brain has been bruised by the vibrating cranium, and 

 some small vessels have been ruptured and ecchymoses formed. It 

 also appears as" if the small extravasations of blood occasionally in- 

 duce no symptoms at first, but excite inflammation in the surround- 

 ing parts, and thus subsequently cause encephalitis. At least, the 

 first signs of the inflammation are occasionally not observed till long 

 after the injury. Among the cases of traumatic origin we must in- 

 clude those where breaking down of the brain by an extensive extrav- 

 asation of blood has caused inflammation in the vicinity. 2. In other 

 cases the encephalitis depends on the irritation of the brain from neo- 

 plasia and necrosed spots. 3. Among the most frequent causes of en- 

 cephalitis are diseases of the cranial bones, especially of the petrous 

 bone. As we shall hereafter show, the presence of an otorrhcea may 

 decide .the question between an abscess of the brain and a tumor. 

 Cases are also known where caries of a superior maxillary extended to 

 the brain and caused encephalitis. I remember a clergyman in Mag- 

 deburg who died of abscess of the brain a few years after a large por- 

 tion of the upper jaw had been exsected on account of extensive ca- 

 ries. 4. Occasionally the disease occurs in the course of acute and 

 chronic infectious diseases, such as pyaemia, glanders, typhus, etc., 

 without our being able to give any plausible explanation for it. 5. 

 Lastly, but rarely, encephalitis occurs without any known cause in 

 persons previously healthy. 



ANATOMICAL APPEARANCES. This disease never attacks the entire 

 brain ; it is always confined to certain points. The size of these spots 

 varies from that of a bean to that of a fist, or larger. They are usually 

 of an irregular spherical shape. Ordinarily there is only one, but 

 sometimes there are several. They may be located either in the cere- 

 brum or cerebellum ; they are most frequently in the gray substance 

 and very near the surface, if they do not quite reach it. In the com- 

 mencement of the disease at the affected parts, we find the brain-sub- 

 stance swollen, infiltrated, softened, and pointed with red spots from 



